c© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim10.1002/14356007.a28 103

Waxes 1

Waxes

Uwe Wolfmeier, Hoechst Aktiengesellschaft, Werk Gersthofen, Augsburg, Federal Republic of Germany(Chap. 1)

Hans Schmidt, Hoechst Aktiengesellschaft, Werk Gersthofen, Augsburg, Federal Republic of Germany(Chap. 2)

Franz-Leo Heinrichs, Hoechst Aktiengesellschaft, Werk Gersthofen, Augsburg, Federal Republic ofGermany (Chap. 3)

Georg Michalczyk, DEA Mineralol AG, Hamburg, Federal Republic of Germany (Chap. 4, Chap. 7 in part)

Wolfgang Payer, Hoechst Aktiengesellschaft, Werk Ruhrchemie, Oberhausen, Federal Republic of Germany(Chap. 5)

Wolfram Dietsche, BASF Aktiengesellschaft, Ludwigshafen, Federal Republic of Germany (Sections 6.1.1,6.1.2, and 6.1.4)

Klaus Boehlke, BASF Aktiengesellschaft, Ludwigshafen, Federal Republic of Germany (Sections 6.1.1,6.1.2, and 6.1.4)

Gerd Hohner, Hoechst Aktiengesellschaft, Werk Gersthofen, Augsburg, Federal Republic of Germany(Sections 6.1.3, 6.1.5, 6.2, and 6.3)

Josef Wildgruber, Hoechst Aktiengesellschaft, Werk Gersthofen, Augsburg, Federal Republic of Germany(Chap. 7)

1. Introduction . . . . . . . . . . . . . . 31.1. History of Waxes and Their

Applications . . . . . . . . . . . . . . 31.2. Definition . . . . . . . . . . . . . . . . 41.3. Classification . . . . . . . . . . . . . 41.4. Properties and Uses . . . . . . . . . 61.5. World Market Volume for Waxes 71.6. International Wax Organizations 82. Recent Natural Waxes . . . . . . . 82.1. Introduction . . . . . . . . . . . . . . 82.2. Vegetable Waxes . . . . . . . . . . . 92.2.1. Carnauba Wax . . . . . . . . . . . . . 92.2.2. Candelilla Wax . . . . . . . . . . . . . 122.2.3. Ouricury Wax . . . . . . . . . . . . . . 142.2.4. Sugarcane Wax . . . . . . . . . . . . . 142.2.5. Retamo Wax . . . . . . . . . . . . . . 152.2.6. Jojoba Oil . . . . . . . . . . . . . . . . 162.2.7. Other Vegetable Waxes . . . . . . . . 172.3. Animal Waxes . . . . . . . . . . . . . 172.3.1. Beeswax . . . . . . . . . . . . . . . . . 172.3.2. Other Insect Waxes . . . . . . . . . . 202.3.3. Wool Wax . . . . . . . . . . . . . . . . 213. Montan Wax . . . . . . . . . . . . . . 213.1. Formation and Occurrence . . . . 213.2. Extraction . . . . . . . . . . . . . . . 213.3. Properties and Composition . . . . 223.4. Refining and Derivatization . . . . 233.4.1. Deresinification . . . . . . . . . . . . 23

3.4.2. Bleaching . . . . . . . . . . . . . . . . 233.4.3. Derivatization . . . . . . . . . . . . . . 243.5. Uses and Economic Aspects . . . . 254. Petroleum Waxes . . . . . . . . . . . 264.1. Introduction . . . . . . . . . . . . . . 264.2. Macrocrystalline Waxes (Paraffin

Waxes) . . . . . . . . . . . . . . . . . . 264.2.1. Chemical Composition and General

Properties . . . . . . . . . . . . . . . . 264.2.2. Division into Product Classes . . . . 274.2.3. Occurrence of Raw Materials and

Processing . . . . . . . . . . . . . . . . 304.2.3.1. Dewaxing Lubricating Oil

Distillates . . . . . . . . . . . . . . . . 304.2.3.2. Deoiling Slack Waxes . . . . . . . . . 314.2.3.3. Refining Deoiled Slack Waxes . . . 334.2.4. Storage, Transportation,

Commercial Forms, and Producers 344.2.5. Quality Specifications and Analysis 354.2.6. Uses . . . . . . . . . . . . . . . . . . . 374.3. Microcrystalline Waxes

(Microwaxes) . . . . . . . . . . . . . 384.3.1. Chemical Composition and General

Properties . . . . . . . . . . . . . . . . 384.3.2. Division into Product Classes . . . . 384.3.3. Occurrence of Raw Materials and

Processing . . . . . . . . . . . . . . . . 394.3.4. Commercial Products and Producers 41

2 Waxes

4.3.5. Quality Specifications and Analysis 414.3.6. Uses . . . . . . . . . . . . . . . . . . . 424.4. Legal Aspects . . . . . . . . . . . . . 434.5. Ecology . . . . . . . . . . . . . . . . . 434.6. Economic Aspects . . . . . . . . . . 444.7. Candles . . . . . . . . . . . . . . . . . 445. Fischer –Tropsch Paraffins . . . . 456. Polyolefin Waxes . . . . . . . . . . . 466.1. Production and Properties . . . . . 466.1.1. Polyethylene Waxes by

High-Pressure Polymerization . . . 466.1.1.1. Production . . . . . . . . . . . . . . . . 476.1.1.2. Properties . . . . . . . . . . . . . . . . 496.1.2. Copolymeric Polyethylene Waxes

by High-Pressure Polymerization . 49

6.1.3. Polyolefin Waxes by Ziegler –NattaPolymerization . . . . . . . . . . . . . 50

6.1.3.1. Production . . . . . . . . . . . . . . . . 516.1.3.2. Properties . . . . . . . . . . . . . . . . 516.1.4. Degradation Polyolefin Waxes . . . 526.1.4.1. Production . . . . . . . . . . . . . . . . 526.1.4.2. Properties . . . . . . . . . . . . . . . . 546.1.5. Polar Polyolefin Waxes . . . . . . . . 546.2. Uses . . . . . . . . . . . . . . . . . . . 556.2.1. Nonpolar Polyolefin Waxes . . . . . 556.2.2. Polar Polyolefin Waxes . . . . . . . . 566.3. Economic Importance . . . . . . . . 567. Toxicology . . . . . . . . . . . . . . . 578. References . . . . . . . . . . . . . . . 59

1. Introduction

Waxes are among the oldest worked materialsused by humans. Their value as versatile con-struction materials (“man’s first plastic”) wasdiscovered very early. Today, waxes are usedmostly as additives and active substances. Theuse of waxes is expected to increase in the futurebecause of their generally favorable toxicologi-cal and ecological properties.

The historic prototype of all waxes isbeeswax. Since it could be obtained with rel-atively little effort, it was popular in antiquity,and even now the term wax is occasionally usedin everyday speech as a synonym for beeswax.However, the scientific and commercial defini-tion of wax covers a much wider area.

1.1. History of Waxes and TheirApplications

Utilization of waxes was probably begun in pre-historic times, but because of their transitory na-ture, no definite archaeological evidence exists.Thus, the utilization of wax and related sub-stances in mummification and as protective cov-erings in ancient Egypt (from ca. 3000 b.c.) re-presents the earliest scientific proof of the use ofwaxes.Ancientwritten documents containmanyindications that waxes found many different ap-plications. The most well known is the story ofDaedalus and Icarus, who used wax as an ad-hesive to make wings by attaching feathers toeach other. In antiquity, wax was used as a raw

material for modeling, in the production of cast-ing molds, as a pigment carrier, and for surfaceprotection.

In colonial times, hitherto unknown waxes,such as carnauba, candelilla, and Chinese insectwax, were introduced in Europe. From the oc-currence of wax, Columbus inferred the richesof the Caribbean islands: “Where there is wax,there are also thousands of other things” [1].

For a long time, not much was known aboutthe chemical nature of wax. Only in the 18thcentury did the discovery occur that beeswax isan animal secretion and not a plant product col-lected by bees. Wax research was establishedas a scientific discipline in 1823 [2]. It becamepart of the new research area of soaps, oils, fats,and waxes. The real breakthrough of wax as animportant raw material, in terms of quantity aswell, occurred at the beginning of the IndustrialRevolution. Ozocerite (fossil wax) was minedand refined to give ceresin (1875), montan waxwas obtained from Eocene lignite (1897), andparaffin waxes were obtained from crude pe-troleum. In 1935 the first fully synthetic waxeswere produced by the Fischer – Tropsch process.Polyethylene wax has been synthesized by thehigh pressure process since 1939, and becameavailable by the low-pressure Ziegler process af-ter 1953. On a laboratory scale polyolefin waxescan also be synthesized by using modern metal-locene catalysts.

Degradation processes for the production ofwaxes,which start fromhighmolarmass plastics(mainly polypropylene), have also achieved acertain degree of importance. Finally, lowmolar

Waxes 3

mass substances, which would otherwise haveto be disposed of in plastics production, can beprocessed or refined to give industrially utiliz-able waxes.

A large and still increasing number of naturaland synthetic waxes and related substances ex-ists, as well as applications for these materials.No decrease in overall demand is apparent, sowaxes are likely to remain important during thecoming decades. The history of waxes has beendescribed in great detail in [3].

1.2. Definition

No generally accepted definition exists for theterm wax. All attempts to formulate a precise,comprehensive, and scientifically verifiable def-inition of wax must take the large number ofwaxlike products and the chemical complex-ity of individual types into account. Neverthe-less, use of the term wax for different chemicalspecies with common properties is still reason-able.

Typically waxes do not consist of a singlechemical compound, but are often very com-plex mixtures. Being oligomers or polymers inmany cases, the components differ in their molarmass, molar mass distribution, or in the degreeof side-chain branching. Functional groups (e.g.,carboxyl, alcohol, ester, keto, and amide groups)can be detected in waxes, sometimes several dif-ferent groups.

The academic definition still quoted in chem-istry text books – that waxes are esters oflong-chain carboxylic acids with long-chainalcohols – is no longer useful. It applies fairlywell only to some classical waxes, such asbeeswax; others (e.g., petroleum waxes) do notfall in this category. Today, physical and tech-nical definitions are preferred. Several attemptswere made to differentiate between waxes andother classes of substance, particularly fats,resins, and high molar mass polymers, by usingseveral criteria. These primarily physical defi-nitions are to some extent arbitrary and are notgeneralled accepted. Waxes can also be classi-fied according to their applications.

Probably the most conclusive definition hasbeen drawn up in Europe by the DeutscheGesellschaft fur Fettwissenschaft (DGF, Ger-man Association for Fat Science). It was used in

modified form in the customs tariff of the Euro-peanUnion [4], [5]. According to this definition,waxes must have:

1) A drop point (mp) >40 ◦C2) Their melt viscosity must not exceed

10 000mPa · s at 10 ◦C above the drop point3) They should be polishable under slight

pressure and have a strongly temperature-dependent consistency and solubility

4) At 20 ◦C they must be kneadable or hard tobrittle, coarse to finely crystalline, transpar-ent to opaque, but not glassy, or highly vis-cous or liquid

5) Above 40 ◦C they should melt withoutdecomposition

6) Above the mp the viscosity should exhibita strongly negative temperature dependenceand the liquid should not tend to stringiness

7) Waxes should normally melt between ca. 50and 90 ◦C (in exceptional cases up to 200 ◦C)

8) Waxes generally burn with a sooting flameafter ignition

9) Waxes can form pastes or gels and are poorconductors of heat and electricity (i.e., theyare thermal and electrical insulators).

In the case of higher molar mass polyolefinwaxes, differentiating between a wax and a ther-moplastic polymer is sometimes difficult. Thisdifferentiation is particularly important for ap-plications where a food approval is essential(FDA, EC,MITI in Japan, etc.). In case of doubt,relevant national regulations must be consulted.

1.3. Classification

Waxes can be classified according to various cri-teria such as origin; chemical, physical, and en-gineering properties; or applications (see Sec-tion 1.2). The primary differentiation is usuallymade according to origin or occurrence and syn-thesis. A proposal for a classification is shown inFigure 1. Here, waxes are divided into two maingroups: natural and synthetic. Natural waxes ex-hibit their wax character without chemical treat-ment, whereas synthetic waxes generally ac-quire their waxy nature in the course of synthe-sis. There are no clear borderlines.

4 Waxes

Figure 1. Classification of waxes

Natural waxes are formed through bio-chemical processes and are products of animalor plant metabolism. Natural waxes formed inearlier geological periods are known as fossilwaxes. All petroleum, lignite (montan wax), andpeat waxes belong to this largest category. Fos-sil waxes occur predominantly as minor com-ponents of oil, coal, and peat. Some depositswith a high wax content were formed by sedi-mentation.Ozocerite separated from oil, and py-ropissite, one of the few organic minerals, is amixture of montan wax and resins. Whereas pe-troleum waxes are predominantly nonpolar hy-drocarbons, lignite and peat waxes consist ofoxygen-containing compounds.

Biological wax synthesis is still taking placein nature. Many plants, particularly carnaubapalm, and animals –most importantly insects,such as bees – produce waxes. These are knownas nonfossil or recent natural waxes. Naturalwaxes are seldomused industrially in their origi-nal form.They are generally converted intomod-

ified natural waxes by refining, e.g., by distil-lation, or extraction. Chemical processes, suchas hydrogenation, bleaching, and oxidation, canalso be used. Physical and chemical treatmentcan be combined; the objective of all these pro-cesses is to obtain a wax that is as pure as pos-sible.

Partially Synthetic Waxes. If naturalwaxesor waxlike materials are modified by chemi-cal reactions such as esterification, amidation,or neutralization of acidic waxes (with aqueousalkali or alkaline-earth metal hydroxides), par-tially synthetic waxes are obtained. These canbe tailored to particular applications. In esteri-fied waxes the relationship to natural waxes isstill easily recognizable. For example, naturalmontan waxes, which consist mainly of estersof long-chain acids with long-chain alcohols,can be converted into acid waxes by cleavage ofthe esters and oxidation of the alcohols. Subse-quent reaction with dihydric alcohols gives es-

Waxes 5

ters that have chemical structures comparableto those of the starting materials. Amide waxesdo not occur naturally to any significant extent.This group consists of reaction products of fattyacids with ammonia, amines, and diamines. Anindustrially important amide wax is distearoylethylenediamine.

Alcohol waxes (lanette waxes) also belong tothe partially synthetic waxes. They are mixturesof long-chain alcohols that are optimized fortheir main area of use, in ointments and creamsfor pharmaceuticals and cosmetics, by the addi-tion of fatty acid esters and emulsifiers. Alcoholwaxes can also be used for industrial emulsionswith good long-term stability.

Wool wax (lanolin) is obtained in crude formfrom sheep’s wool. It is refined by chemical andadsorptive bleaching, and sometimes by subse-quent hydrogenation or separation of the acidicfractions after hydrolysis.Wool wax is amixtureof esters, some being derived from branched orcyclic waxy or fatty acids and alcohols.

Fully synthetic waxes were developed onlyin the 20th century. Lowmolar mass compoundsare used as starting materials. The products canbe waxes in the narrower sense of the defini-tion (see Section 1.2), or substances with onlypartial wax character. The two main groups offully synthetic waxes are the Fischer – Tropschand the polyolefin waxes. These waxes can beclassified according to the starting material usedfor production (C1 or C2 chemistry).

C1 Building Blocks. The Fischer – Tropsch(FT) synthesis is described elsewhere in detail(→Coal Liquefaction, Chap. 2.2.). The oldestFTvariant is theARGEprocess (Arbeitsgemein-schaft Ruhrchemie – Lurgi). Synthesis gas is ob-tained by reaction of steam with carbon (→GasProduction, Chap. 4.) and is then converted cat-alytically into a broad spectrum of saturated andunsaturated hydrocarbons. Among these prod-ucts are the Fischer – Tropsch waxes. They arecharacterized by low branching of the hydrocar-bon chain and a narrowmolar mass distribution.They are relatively hard products. The ARGEprocess has been used commercially by SASOLin the Republic of South Africa.

Besides carbon, natural gas can also be usedas a raw material for C1 syntheses. The ShellMiddleDistillate Synthesis (SMDS) process uti-lizes synthesis gas produced by steam reform-

ing of natural gas [6]. Fischer – Tropsch waxfractions are produced and marketed at the newSMDS plant in Bintulu (Sarawak/Malaysia).This process is a variant of the classical FT pro-cess and employs specially developed catalysts.

Polyolefin waxes are, in most cases, prod-ucts of C2 or C3 chemistry. Low molarmass α-olefins, usually ethylene, are poly-merized. The other route to polyethylenewaxes – thermomechanical degradation of poly-ethylene plastic – is now of minor importance.The two most important production processesare the high-pressure and the Ziegler processes.More recently, polyolefin waxes have also beensynthesized by using modern metallocene cata-lysts.

Polyolefin waxes can be homopolymers orcopolymers of C2, C3, C4 (ethylene, propene,and butene), or higher α-olefins. Polypropylene(PP) waxes are produced by the Ziegler processor by thermomechanical degradation of polypro-pylene plastic. Polypropylene waxes are gener-ally partially crystalline. In addition, predomi-nantly amorphous and atactic low molar masspolypropylene (APO or APAO) with a waxlikecharacter is now produced and marketed by sev-eral companies. Besides this deliberate produc-tion, atactic PP (APP) is still produced as a by-product of PP plastics.

All FT and polyolefin waxes are nonpolar.Polar waxes are obtained by subsequent reac-tions, such as oxidation by air or grafting (e.g.,with maleic anhydride), optionally followed byneutralization to metallic soaps, esterification,or amide formation. Polar polyolefin waxes arealso accessible via direct copolymerization oraddition reactions (e.g., of olefins with unsatu-rated carboxylic acids or esters).

Aconsiderable proportionof industrially pro-cessed waxes is used not in pure form but as waxcompounds. For example, the viscosity and mpof paraffin waxes can be increased to the desireddegree by mixing with polyolefin waxes.

1.4. Properties and Uses

The number of possible and actual uses of waxesis extraordinarily high. The physical and chem-ical properties of various types of wax can becombined fairly freely through mixtures andpreparations. Therefore, waxes are represented

6 Waxes

in almost all possible areas of use, although todiffering extents. Any selection of applicationsthus has to be somewhat arbitrary.

For the user, the application-oriented func-tion of the wax is important, not so much itschemical structure. The latter is defined pri-marily by the characteristic hydrocarbon chain,the basic building block of almost all waxes.It imparts hydrophobing properties to waxes.The carbon chain length of fatlike waxes isn = 16 – 18 (e.g., amide wax); for esterified andparaffinwaxes, n = 20 – 60; and for polyethylenewaxes, less than hundred to several thousand.Besides the chain length itself (and thus the mo-lar mass), molar mass distribution and degreeof branching also affect the properties of waxes.Themelting and softening points,melt viscosity,and degree of hardness increase with increasingchain length. High degrees of branching lowerthe mp and the hardness. Polar groups, such ascarboxyl, ester, and amide groups, strengthenintermolecular forces and generally raise thempand hardness.

Particular features of many waxes are theirgood absorption capacities and their ability tobind solvents. Hot wax solutions form stable,homogeneous pastes on cooling. These can beapplied to surfaces and polished after evapora-tion of the solvent. The resulting wax films areshiny or glossy, hard, and resistant tomechanicalstress.

When a suitable emulsifier is added, polarwaxes can form fine stable dispersions in water.Mixed aqueous – organic emulsions can also beproduced. These mostly stable dispersions andemulsions are used for surface protection. Afterapplication, the wax-containing phase dries anda protective, sometimes even glossy, coating isformed.

In addition to surface protection, hydrophob-ing, and gloss-giving, other functions of waxesinclude surface protection, hydrophobing, gloss-giving, matting, mold releasing, lubricating,binding, imparting compatibility or flexibil-ity, regulating viscosity, adjusting consistency,emulsifying, dispersing, and adjusting droppoints. Waxes are also used as combustible andilluminating materials.

For special applications only a few –frequently only one – of these functions are im-portant. Some occasionally opposite effects arenoteworthy: wax gives polish and gloss to var-

ious surfaces but has a matting effect as an ad-ditive in paints and coatings. Waxes are used asbinders in master batches but as release agentsin molding plastics. Table 1 gives some idea ofthe versatility of waxes but does not claim to becomplete. For the specific suitability of waxesto individual applications, monographs, com-panybrochures, and prospectuses should be con-sulted.

Table 1. Branches of industry in which waxes are used

Branch Examples of applications

Adhesives, hot melts viscosity regulation, lubricants,surface hardening

Building modification of bitumen, antigraffititreatment

Candles fuel, drop point regulationCeramics and metal binders for sinteringCosmetics binders and consistency regulators

for ointments, pastes, creams,lipsticks

Electrical and electronicsindustries

release agents, insulating materials,etching bases

Explosives stabilizationFoods citrus fruit and cheese coating,

chewing gum base, confectioneryMatches, pyrotechnics impregnation, fuelMedicine andpharmaceuticals

molding and release agents indental laboratories, retardants,surface hardening of pills

Office equipment dispersing agents and binders forcarbon paper and selfduplicatingpaper; antioffset for toners forphotocopiers

Paints and coatings matting, surface protectionPaper and cardboard surface hardeningPlastics lubricants (PVC∗), release agents

(PA∗∗), pigment carriers(masterbatch)

Polishes surface protection of leather, floors,cars

Printing inks improvement of rub resistance, slipRecycling compatibilizingRubber industry release agents enhancing rigidity,

surface hardening

∗ PVC= poly(vinyl choride).∗∗ PA= polyamide.

1.5. World Market Volume for Waxes

No reliable global capacity or production dataare available for waxes. The main reasons forthis are the many types of wax and the difficul-ties in differentiating among them; the compar-atively low transparency of the market; and thedependence of wax production on external fac-tors, such as crude petroleum consumption andannual harvest of natural waxes. Some statistical

Waxes 7

data exist for certain markets (e.g., the UnitedStates [7]). Thus, the following figures can beregarded only as rough indications, with a cor-respondingly large degree of fluctuation, of themagnitude of annual worldwide wax consump-tion data:

Paraffin waxes, including microcrystallinewaxes

3 000 000 t/a

Polyolefin waxes including oxidates andcopolymers

200 000 t/a

Fischer – Tropsch waxes 100 000 t/aAmide wax 50 000 t/aMontan wax including crude montan wax 25 000 t/aCarnauba wax 15 000 t/aBeeswax 10 000 t/aCandelilla and other plant waxes 3 000 t/a

Forecasts for future market development an-ticipate positive growth factors. Specialties, suchas special waxes or compounds for critical ap-plications (e.g., in the electrical, electronics, orceramics industries), will probably profit morefrom this development than waxes, that are tendto be continuously replaced in their applications.The decreasing demand forwaxes in the packag-ing sector, for example, is becoming noticeable.The proportion ofwaxes used in someother clas-sical applications (e.g., carbon paper) is contin-ually declining. However, waxes generally havefavorable ecological and toxicological proper-ties, in addition to the variety of applications de-scribed, so their market chances may outweighthe risks in the long term.

1.6. International Wax Organizations

In Europe the interests of all wax producers havebeen represented by the European Wax Federa-tion since 1979 (EWF, Avenue van Nieuwen-huyse 4, Brussels, Belgium). The EWF is amember of the Conseil Europeen des Federa-tions de l’Industrie Chimique (CEFIC) and isopen to all European wax producers and someoutside Europe. It represents the interests of itsmembers, with regard to both technical ques-tions such as specifications and legal matters re-ferring in particular to the European Union. Inother regions, no organizations exist that coverthe entire wax spectrum.

2. Recent Natural Waxes

2.1. Introduction

Many plant and animal organisms producewaxes with extraordinarily complex composi-tions. The main components are usually thosethat correspond to the classical definition ofwaxes – i.e., esters of long-chain aliphatic al-cohols and acids, which belong to homolo-gous series in the ca. C16 –C36 (predominantlyC22 –C36) range, those with an even numberof carbon atoms predominating. Recent nat-ural waxes also contain smaller quantities ofesters derived from acids and alcohols withan uneven number of carbon atoms as wellas bifunctional components such as diols, hy-droxycarboxylic, and dicarboxylic acids. Nat-ural waxes contain very small proportions ofbranched carboxylic acids, mainly those withω-methyl branching. Aromatic acids, such ascinnamic, 4-hydroxycinnamic, and ferulic (4-hydroxy-3-methoxycinnamic) acids, have alsobeen found in some waxes. Because of the pres-ence of bifunctional components, natural waxescan contain not only the simple, classical waxesters, but also oligoesters with two or more es-ter functions and other functional groups in themolecule.

Free acids and alcohols are present in nat-ural waxes in widely varying quantities. Theyare generally identical to those present as estercomponents.

Homologous n-alkanes in the ca. C15 –C37range, mainly those with an uneven numberof carbon atoms, are also components of natu-ral waxes in proportions of 1 – 50%. Branched-chain and olefinic hydrocarbons are present ininsignificant quantities. Glycerides (fats), phy-tosterols, terpenes, resins, long-chain carbon-yl compounds, and flower pigments are alsopresent in very small proportions. Because ofthe complexmixtures involved and the relativelysimple analysis techniques of earlier years, theinconsistency of literature data on the composi-tion of natural waxes is understandable.

Modern analytical instruments are requiredfor complete analysis of a natural wax. High-temperature capillary GC, possibly coupled to amass spectrometer, is a suitable the best analyt-ical method.

8 Waxes

Beeswax and carnauba and candelilla waxeshave a total annual market volume of ca. 28 000 tworldwide. These are economically themost im-portant natural waxes [8].

Among the large number of other knownwaxes, ouricury, esparto, bamboo, and Japanwax (actually a special vegetable tallow) are ofregional or local importance. Their availabilityis estimated to be 3000 – 4000 t/a [8], [9].

In all areas of application for waxes, recentnatural waxes are nowmostly used together withmodified fossil and synthetic waxes. Applica-tions include preparations for cleaning, polish-ing, and preserving floors, furniture, and carbodywork surfaces; the candle industry; craftwork; production of pharmaceuticals, cosmet-ics, and confectionery (observing appropriate le-gal approval); metal and ceramic sintering tech-nology; coating techniques; the paint and coat-ing industries; and the production of carbon pa-per compounds. The latter, which was importantin terms of quantity, has been replaced almostcompletely by new duplicating processes. De-spite the market recession this has caused [10],an annual growth of ca. 4% is expected in theU.S.market for natural and syntheticwaxes [11].

Special, ion-free or low-ion natural wax raf-finates have also been used in electronics.

In his standard bookTheChemistry andTech-nology of Waxes, A. J.Warth included a com-prehensive chapter on all known recent naturalwaxes. The second edition of the book was pub-lished in 1956 and is currently out of print [12].

2.2. Vegetable Waxes

In contact with the environment, plants form acompressed epidermis on their surfaces by de-positing secondary layers of cellulose, except inthe case of inflorescence [13]. This mechanicalreinforcement is supplemented by deposition ofcutin in the outer epidermal layers and an outercoating of cutin (cuticula) to regulate water con-tent. As a result of climatic conditions, manyplants in tropical regions also store waxes in cu-tinized membrane layers in the cuticula as anadditional protection against evaporation of wa-ter. In many cases, waxes exude outward andform wax coatings, which can be up to severalmillimeters thick. Xerophytes, plants found inexceptionally arid regions, are however not thegreatest wax producers [14]. Specific soil types,

temperature, dry periods, and heavy rainfall, aswell as temporal changes in these, are respon-sible for enhanced wax formation. Vegetablewaxes can be classified according to their originas deciduous and coniferous tree waxes, shruband herbwaxes, and grass and flowerwaxes, andwithin these groups into leaf, needle, stem, androot waxes; bark and skin waxes; and seed andfruit waxes.

2.2.1. Carnauba Wax

The leaf wax of the carnauba palm is by far themost important recent vegetable wax both eco-nomically and with regard to applications [12],[13], [15], [16]. The carnauba palm is a fan palmfound mainly in Brazil and given the botani-cal name Copernicia cerifera by v.Martius in1819 in honor of the astronomer Copernicus.It was apostrophized as the life tree of Brazil byv. Humboldt.

History. The existence of carnauba wax wasfirst reported in 1648 [17], and some data con-cerning its composition were published in 1811in Transactions of the Royal Society, London.

In 1836 the Brazilian Macedo arranged forchemical investigations to be carried out oncarnauba wax at the Sorbonne in Paris. Hebegan small-scale extraction and purificationof carnauba wax in 1856. In 1862, 1280 t ofcarnauba wax was exported from Brazil.

Occurrence and Isolation. The carnaubapalm occurs mainly in north eastern Brazil inthe provinces of Bahia, Rio Grande do Norte,Paraiba, Pernambuco, and particularly Cearaand Piaui, where there is a total stand of ca.90×106 palms in a surface area of 106 km2

[18], [19]. Smaller areas exist in southern Brazil,northern Argentina, Paraguay, and Bolivia. Dif-ferent climatic conditions in other tropical andsubtropical countries, in which carnauba palmswere planted as an experiment, allow satisfac-tory growth but markedly reduced formation ofwax deposits on the leaves.

The palms grow to a height of 6 – 12m, oc-casionally to 20m, and are said to achieve alifetime of up to 200 years. When the palm hasreached an age of ca. eight years, one leaf givesa wax yield of 5 – 7 g, which is worth harvesting.The annual yield of wax per palm is ca. 150 g.

Waxes 9

To isolate the wax, ca. 20 – 30 leaves at dif-ferent stages of development are removed fromeach palm twice a year (September and Decem-ber) [12].

The unopened heart leaves, of which only afew are removed per palm, carry particularlylight-colored wax (prime yellow). Wax on theouter palm leaves is yellow, gray-green, or gray-brown, depending on climatic conditions duringthe vegetation period and on leaf age.

After drying the leaves in the sun or on steam-heated racks, the wax is chipped off manuallyor nowadays mostly by machine. The primarypurification process involves melting over waterand gives a crude wax that can be purified fur-ther by centrifugation, filtration with additives,or solvent extraction. Additional bleaching withhydrogen peroxide is also carried out.

The central ribs are often removed from theleaves before drying. The dried leaves are thenchopped and the chips separated by air classi-fication to give a mixture of ca. 60% wax and40% chopped plant, which is stirred with wa-ter and oxalic acid to form a paste. The latter isheated to its boiling point and pressed througha filter while hot. Centrifugation of the filtrategives virtually anhydrous wax. The remainingwax is extracted from the dried filter cake withaliphatic hydrocarbons (e.g., heptane).

The crude product is normally supplied inlumps that are obtained by breaking up the waxblocks into which the melt was cast. Carnaubawax is also sold now in other forms.

Types. Internationally recognized classifica-tions and specifications for genuine, unfalsifiedtypes of carnauba wax were worked out by theAmericanWax Importers and Refiners Associa-tion according to established methods of deter-mination [20].

The classification used in Brazil, shown inTable 2, has been valid worldwide since the be-ginning of the 1980s.

The highest-value type, T 1, is a prime yellowwax purified by filtration. To obtain T 3, suit-able crude waxes (colored) are filtered and thenbleached with hydrogen peroxide. The T 4 waxis exported predominantly in the form of cen-trifuged or filtered variants.

Chemically refined or derivatized carnaubawaxes are no longer available commercially be-cause of lack of demand [8]. Chemical refining

processes, such as heatingwith alkali in the pres-ence of paraffins, gave carnauba wax residues inaddition to the corresponding raffinates [21–27].Where these processes are used, they account for<1% of the total volume of carnauba wax.

Properties. Carnaubawax is one of the hard-est and highest-melting natural waxes. Becauseof its fine crystalline structure, its fracture edgesare smooth and have a macroscopically homo-geneous structure. At room temperature the waxhas a weakly aromatic odor and a characteristichaylike scent (similar to coumarin) in themoltenstate [28]. Carnauba wax is compatible with al-most all natural and synthetic waxes and a num-ber of natural and synthetic resins. It is readilysoluble in most nonpolar solvents on warming[12] and is miscible with them in all proportionsabove its mp. On cooling, the wax precipitatesfrom solution to form a solid paste. Carnaubawax is only partially soluble in polar solvents,even onwarming, and is generally sparingly sol-uble at room temperature (0.15 – 0.6%) [12].

Melting, solidification, and drop points aswell as hardness of other waxes increase onaddition of small quantities of carnauba wax.With paraffins, the addition of carnauba waxsuppresses their tendency toward coarse crys-tallinity and reduces possible tack in the case ofsoft waxes.

Composition. Many analyses of carnaubawax has been carried out, with conflicting re-sults [12], [14], [15]. According to a thoroughinvestigation, carnauba wax prime yellow (T 1)has the composition given below [29]:

Aliphatic esters 40.0wt%Diesters of 4-hydroxycinnamicacid

21.0wt%

Esters of ω-hydroxycarboxylicacids

13.0wt%

Free alcohols 12.0wt%Diesters of 4-methoxycinnamicacid

7.0wt%

Free aliphatic acids 4.0wt%Free aromatic acids 1.0wt%Hydrocarbons (paraffins) 1.0wt%Free ω-hydroxycarboxylic acids 0.5wt%Triterpene diols 0.5wt%Unsaponifiable components 56.4wt%Saponifiable components 39.2wt%Aromatics and/or resins 4.4wt%

The aliphatic esters contain monocarboxylicacids of average chain length C26 and mono-

10 Waxes

Table 2. Carnauba wax types and specifications

Characteristic T 1 (primeyellow)

T 3 (fattygray/light)

T 4 (fattygray/crude)

T 4 (fattygray/centrifuged)

T 4 (fatty gray/filtered)

Minimum mp, ◦C 83.0 82.5 82.5 82.5 82.5Minimum flash point, ◦C 310 299 299 299 299Moisture content, % 0 0 2.0 (max.) 1.0 (max.) 0.1 (max.)Minimum acid number, mgKOH/g 2 4 4 4 4Maximum acid number, mgKOH/g 6 10 10 10 10Minimum saponification number,mgKOH/g

78 78 78 78 78

Maximum saponification number,mgKOH/g

88 88 88 88 88

Ester number, mgKOH/g 75 – 85 75 – 85 75 – 85 75 – 85 75 – 85Maximum ash content, % 0.04 0.15 0.20 0.20 0.10Solidification point, ◦C 80 79 79 79 79Drop point, ◦C 84 83 83 83 83Minimum particle size, mesh 95 95 95 95 95

hydric alcohols of average chain length C32.The ω-hydroxyesters contained are mixtures ofca. 90% esters of ω-hydroxyacids (C26) andmonohydric alcohols (C32) and 10% estersof monocarboxylic acids (C28) and α,ω-diols(C30).

Table 3. Chain-length distributions for straight-chain monocarbox-ylic acids and monohydric alcohols, and paraffins in carnauba wax

Chain length(C-number)

Acids∗, %(approx.)∗∗

Alcohols∗, %(approx.)∗∗

Paraffins∗, %(approx.)∗∗

16 2.018 3.020 8.5 0.421 0.522 7.5 0.5 0.723 1.324 23.2 0.7 1.625 2.626 10.5 0.5 3.527 8.728 16.5 2.0 5.429 13.130 5.5 10.6 13.931 29.332 2.0 60.8 9.633 7.334 0.5 16.4 1.535 0.336 0.6 0.4

∗ Values based on 100% total acid, total alcohols, and totalparaffins in each case (deviations from 100%= sum of allother acids and alcohols).∗∗ Approximate.

Esters containing 4-hydroxy- and 4-methoxycinnamic acids are present mainly asoligomers and polymers. The monomer units ofthese are diesters of the above-named cinnamic

acids with mono- and polyhydric alcohols andω-hydroxycarboxylic acids.

The free alcohols are similar in compositionto those in aliphatic esters. The wax also con-tains a small proportion of secondary alcohols.

The even-numbered n-monocarboxylicacids, n-monohydric alcohols, and n-alkanespresent in all carnauba wax types have typi-cal, distinctive chain-length distributions (seeTable 3).

The important difference between Type 1carnauba wax and the other types is that the lat-ter contain no triterpenediols and the esters of4-hydroxy- and 4-methoxycinnamic acids havehigher degrees of polymerization comparedwithType 1. This may be attributed partly to differ-ences in climate but also to the fact that Type 1is harvested from genetically younger leaves,whereas the others come from older leaves thathave been exposed to more sunshine.

Uses.T 4 Variants. The wide use of carnauba wax

in the production of preserving and cleans-ing agents for floors (floor polishes, ionogenicand nonionogenic day-bright emulsions, wipingwaxes and cleaners, sealing emulsions, spraycleaners, etc.); and polishes for furniture, cars,and shoes (solvent –water or straight solventproducts) is based on its ability to form pastesand glossy and repolishable films and its abil-ity to be dispersed. In this classical area a largeproportion of T 4 variants of carnauba wax areused.

Waxes 11

Type 1 carnauba wax and some of Type 3(after absorptive purification to remove perox-ide components arising from hydrogen perox-ide bleaching) are approved for use in the phar-maceutical industry (e.g., as polishes for pills)and the cosmetics industry (as lipsticks and lipsalves).

In the food sector, T 1 and T 3waxes are usedas release agents for bakery and confectioneryproducts and as additives in chewing gum pro-duction.

In polymer processing, carnauba wax is usedin release agent preparations and, to a small ex-tent, as a lubricant. The varnish industry usescarnauba wax as an additive in the interior coat-ing of food containers [8].

In the leather industry, carnauba wax is usedfor cutting waxes, cleaning waxes, and edginginks. It is also approved for coating citrus fruit.

Economic Aspects. About 10 000 –16 000 t/a carnauba wax is available worldwide,of which ca. one-fifth is Type 1. Brazil, the soleexporter, supplies mainly Europe (ca. 2000 t/a),the United States (3000 – 4000 t/a), and Japan[8]. About 3000 – 3500 t/a is for indigenous sup-ply.

Carnauba wax consumption in the UnitedStates decreased markedly from 1955 to 1976and then remained constant [9]. Brazil is increas-ingly exporting purified or bleached products inflaked form to achieve higher prices. Harvests,exports, and price structuring are subject to gov-ernment control.

Waxes with Similar Compositions. Coper-nicia australis, a palm that produces large quan-tities of leaf wax, is found in Paraguay andaround its border with Argentina (Gran Chaco).It is similar to Copernicia cerifera in many re-spects. A few small factories for isolating thispalm wax are said to have been erected since1945 [30].

The Brazilian cauacu bush, found mainly inPara province and by the upper Amazon, pro-duces a wax that is said to be similar to carnaubawax in chemical composition. However, thewaxis isolated only sporadically and to a limited ex-tent [31].

2.2.2. Candelilla Wax

Occurrence and Isolation. The climaticconditions of the semideserts in southern Cal-ifornia, Arizona, south western Texas, northernMexico, and parts of Central and South Amer-ica favor enhanced wax formation in Euphor-bia ( E. cerifera, E. antisyphilitica) and Pedilan-thus ( P. pavonis, P. aphyllus) species. The waxdeposited on the stalks and leaf stems of theseplants, which grow as bushes or shrubs, is knownas candelilla wax [12], [14], [32], [33].

Numerous and dense stands of these plantsare foundmainly in northernMexico in the statesof Chihuahua, Coahuila, Durango, Nuevo Leon,SanLuis Potosi, Tamaulipas, andZacatecas overa total area of more than 100 000 km2. These arethe only areas in which candelilla wax is ob-tained [34].

In manual harvesting the plants are pulledout, leaving most of the root system in the soil.Together with scattered seeds, roots remainingpartially in the soil guarantee the growth of newstands, which takes several years.

In collecting and processing locations, plantmaterial is boiled with ca. 0.2% sulfuric acidin open vessels, which are heated using alreadydewaxed and dried stalks. Metal grids keep theplants under the surface of the liquid, and ad-dition of sulfuric acid inhibits emulsification ofthewax. The latter collects inmolten formon thesurface of the liquid. After the wax is skimmedoff into open vats or barrels, it solidifies to formthe crude wax known as cerote. Yields based onplant material are 3 – 4%.

Wax from outer areas of the solidified waxblocks is removedwith impurities that have con-centrated there and is subjected to the boilingprocess again. The remainder of the wax is pu-rified in a central refinery located in Saltillo bymelting with sulfuric acid and filtering in filterpresses. The crude wax broken down into lumpsis the Mexican commercial product (MexicanStandard Grade Candelilla Wax).

Candelilla wax raffinates are obtained fromcrude wax by adsorptive purification or hydro-gen peroxide bleaching. They are produced andsold in the United States and Europe. The prop-erties of these products, apart from color, areidentical to those of crude candelilla wax.

Following the transfer of Mexican candelillawax production from state monopoly to private

12 Waxes

enterprise, candelilla wax raffinates produced inMexico will also be put on the market [8].

By deresinification and subsequent oxidativechromic acid bleaching, products that are almostwhite can be obtained. Because of the high priceof genuine wax, these processes have no practi-cal importance.

Properties and Composition. Candelillawax is a hard, brittle wax that is very similar tocarnauba wax with regard to solubility in polarand nonpolar organic solvents. A large propor-tion of the resin present in the wax can be ex-tracted at room temperature with hot 70% etha-nol, acetone, or low-boiling, chlorinated organicsolvents.

The physical and chemical properties, thecolor (brown – brownish yellow – pale yellow),and the degree of purity vary depending on cli-mate, time of harvest, region, and age of har-vested plants. The recognized specification forgenuine crude candelilla wax is given in the fol-lowing [34].

mp 68.5 – 72.5 ◦CRefractive index 1.4550 – 1.4611d 154 0.950 – 0.990

Acid number 12 – 22mgKOH/gSaponification number 43 – 65mgKOH/gHydrocarbon content 30.6 – 45.6%Total acid content 20.6 – 29.0%Color amberFlash point 235.4 – 248.4 ◦CComponents insoluble inxylene/toluene (1 : 1)

0.0 – 0.1%

The data agree with those previously laiddown by the American Wax Importers and Re-finers Association for prime crude candelillawax [20].

The average composition of candelilla waxgives below is derived from the large number ofvalues found in the literature.

Hydrocarbons (ca. 98% paraffins + 2%alkenes)

42.0wt%

Wax+ resin + sitosteroyl esters 39.0wt%Lactones 6.0wt%Free wax and resin acids 8.0wt%Free wax and resin alcohols (terpenealcohols)

5.0wt%

Saponifiable components 23.0 – 29.0wt%Unsaponifiable components 71.0 – 77.0wt%

Candelilla wax differs fundamentally fromcarnauba wax in its high hydrocarbon content of

45% (max.) and resin content of 20%.Whereascarnauba wax contains>80%wax according tothe classical chemical definition, candelilla waxconsists of <35% of these components.

As in all natural waxes, in candelilla wax theparaffins and wax acids or alcohols with even-numbered carbon chains have typical and dis-tinctive chain-length distributions (Table 4).

Table 4. Chain-length distribution of even-numbered carboxylicacids and alcohols, and paraffins in candelilla wax

Chainlength(C-number)

Acids∗, %(approx.)∗∗

Alcohols∗, %(approx.)∗∗

Paraffins∗, %(approx.)∗∗

22 0.32324 0.12526 0.3 2.4 0.127 0.228 3.2 17.4 0.529 5.630 36.4 58.0 1.331 80.032 48.6 19.0 1.833 9.034 8.0 0.2

∗ Values based on resin-free total acid, total alcohol, and totalparaffin (deviations from 100%= sum of all other acids,alcohols, and hydrocarbons).∗∗ Approximate.

Uses. Candelilla wax is used in classicalcleaning preparations and polishes (e.g., as acomponent of shoe and other leather polishes)and in furniture, car, and floor polishes. Be-cause of its particular composition, this wax canbe used in the applications only in combinationwith other suitable natural and synthetic waxes.Its use in floor polish is very limited because thehigh resin content leads to increased dirt pickup.

Candelilla wax is also used in the productionof candles, coatings for paper and cardboard,hotmelt adhesives, and in polymer processing.

It is also approved for use in the cosmetics,pharmaceutical, and food industries. The mainuse of candelilla wax, principally in the UnitedStates and Europe, is by the cosmetics industryin the production of lipstick. Here, propertiessuch as outstanding framework formation withcastor oil, gloss, and uniform shrinkage on cool-ing (very good demolding after casting lipsticks)are very important [8]. Candelilla wax is also

Waxes 13

used as a polish for pills and in the productionof chewing gum and confectionery.

Economic Aspects. For nomadic peasants inthe areas of Mexico mentioned, proceeds fromthe candelilla harvest were an important partof their income for a long time. Because ofcontinuing improvements in infrastructure, theuneconomical isolation of candelilla wax hasdecreased since 1950 and been replaced in-creasingly by agricultural production. Exportsto the main consumer, the United States, fellfrom 2500 t in 1950 [14] to 1800 t in 1974 [33],1100 t in 1980, and ca. 310 t in 1992 [35]. About800 – 1000 t of candelilla wax is available on theworld market, of which ca. 200 t is consumed inEurope [8].

In the United States, demand for candelillawax is increasing because of the shift of usefrom classical areas to those of foods, cosmet-ics, and pharmaceuticals [35]. Privatization ofcandelilla wax isolation in Mexico and effortsto produce raffinates there will probably lead togreater availability of these waxes.

2.2.3. Ouricury Wax

Occurrence and Isolation. Ouricury wax isdeposited on the leaf stems of feather palms (Syagros coronata), which grow mainly in theBrazilian state of Bahia. There it is also knownas urucury, licuri, aricuri, nicuri, and coqueiro.

The isolation process for ouricurywax is verysimilar to that used for carnauba wax, but it ismade more difficult by strong adhesion of thewax to the plant, and mechanical scratching orscraping off is necessary. The annual yield perpalm is ca. 1 kg of crude wax.

Preliminary purification involves meltingcrude wax in hot water and filtering the meltthrough filter cloths or suitable sieves [12], [14],[36]. Additional purification in filter presses isused to obtainUSAPure Refined wax. The crudewax is sold in lumps (Brazilian Crude).

Properties and Composition. Ouricurywax resembles carnauba wax very closely withregard to its hardness, gloss, solubility in po-lar and nonpolar solvents, and hardening capac-ity when used in combination with soft waxes.Its color is somewhat darker than that of dark

carnauba wax types. The mp is 82.5 ◦C. Themost important properties for genuine commer-cial products have been established [20]. Thor-ough investigation of ouricury wax gave the fol-lowing composition [37]:

Simple aliphatic esters 23.5wt%Monoesters of hydroxycarboxylic acids 22.4wt%Diesters of hydroxycarboxylic acids 17.2wt%Acidic hydroxypolyesters 5.4wt%Free acids 8.7wt%Free alcohols 3.0wt%Resins 14.8wt%Water 1.4wt%Ash 0.4wt%

Alkaline saponification of ouricury waxyields varying quantities of total acids(69 – 74%) and unsaponifiable components(26 – 31%), as usual in the case of naturalwaxes.Despite these facts, ouricurywax, like other veg-etable waxes, can be characterized definitely bythe chainlength distributions of its n-paraffinand acids and alcohol components.

Uses and Importance. Ouricury wax waspreviously used in floor and shoe polishes andin carbon paper coloring agents, instead ofcarnauba wax, mainly because of its low price.As a result of increasing price, the importanceof ouricury wax has decreased sharply. Accord-ing to Brazilian statistics, 39 t was exported in1980. In 1991 the consumption in the UnitedStates was ca. 4.5 t/a [38].

2.2.4. Sugarcane Wax

Occurrence and Isolation. Sugarcane waxis formed as a powdery, pale to dark yellowdeposit on sugarcane stalks (particularly in thethickened nodes) in quantities of 0.1 – 0.25%based on cane weight, depending on countryof origin. The main sugarcane-growing coun-tries are India (ca. 96×106 t/a), Brazil (ca.80×106 t/a), and Cuba (ca. 40×106 t/a).

Sugarcane wax is generally extracted fromthe dried filter cake (ca. 1% based on sugar-cane) [12] formed during sugarcane processingby using alcohols, carbon disulfide, carbon tetra-chloride, or aromatic and aliphatic hydrocarbons[39].

14 Waxes

The crude wax content of the filter cake(in weight percent) varies between the follow-ing limits, depending on sugarcane origin andmethod of processing:

India 8.0 – 18.0wt%Louisiana 4.4 – 17.9wt%Puerto Rico 12.0 – 14.0wt%Hawaii 9.6 – 11.0wt%Philippines 10.5 – 11.0wt%Cuba 12.4 – 22.0wt%Java 5.0 – 15.0wt%Republic of South Africa 6.9 – 14.6wt%Argentina 11.9 – 15.5wt%Brazil 8.9 – 17.8wt%

Crude wax can be freed frommost glycerides(fats and oils) by treatment with acetone, methylethyl ketone, methanol, ethanol, 1-propanol andisopropanol, 1-butanol, or ethyl acetate. In a sub-sequent recrystallization step, preferably in iso-propanol, resinous and colored components canbe removed. Further treatment with bleachingearths or oxidative bleaching of the wax meltwith air gives waxes ready for use in a varietyof applications. Bleaching processes for prepuri-fiedwax using potassium chlorate – sulfuric acidor chromic acid – sulfuric acid would be effec-tive but are not used for cost reasons.

Properties and Composition. Crude sug-arcane wax is a black-brown to green-brownsemisolid with an unpleasant, rancid odor.

Semi- and completely purified products arebrown- to yellow-colored hard waxes, whosecharacteristics vary considerably.Melting pointsof 68 – 81 ◦C, acid numbers of 7 – 22mgKOH/gsaponification numbers of 32 – 65mgKOH/gand proportions of unsaponifiable material of52 – 62% have been published in the literature.The following values are typical for a semiraffi-nate [12]:

Wax esters (aliphatic and sterol esters) 78 – 82wt%Free fatty and wax acids ca. 14wt%Free alcohols (wax alcohols and sterols) 6 – 7wt%Hydrocarbons 3 – 5wt%

On comparing crude wax with a raffinatesample [40] in terms of chain-length distribu-tions of the even-numbered acids and wax al-cohols and of the paraffins, characteristic differ-ences can be seen, particularly with the acids.

Importance and Uses. From an estimatedannual worldwide harvest of ca. 510×106 t ofsugarcane, ca. 5.1×106 t/a of dry filter cake ma-terial is theoretically obtained. From this, ca.510 000 t of crude sugarcane wax could be ex-tracted, given an averagewax content of ca. 10%in the filter cake. If refining losses are assumedto be 50%, ca. 255 000 t of sugarcane wax raf-finate per year remains theoretically availableworldwide.

In the past, many attempts have been madeto produce crude sugarcane wax on an industrialscale. As early as 1841, isolation of thewax fromfilter cakeswas begun, and in 1909 a correspond-ing extraction process was patented.

Around 1916, crude sugarcane wax was ex-tracted as a commercial product in South Africaand Java. In 1958 the wax was produced in twoCuban and one Australian plant. However, in1960, production in Australia was halted andonly one plant was still operating in Cuba [39].In India, an extraction plant is thought to havebeen operating continuously since 1950 [39].This plant is attached to a sugar refinery witha daily throughput of 1200 t of sugarcane.

Difficulties resulting from the necessary cen-tralization of production locations, the necessar-ily rapid and complete drying of large quanti-ties of filter cake material (which has a tendencyto ferment), and last, but not least, the increas-ing costs of extraction havemade sugarcanewaxraffinate incapable of competing with carnaubawax on the world market in terms of price. Con-sequently, sugarcane wax raffinates have onlyregional importance.

In producer countries, crude sugarcane waxcan be used in floor and shoe polishes, carbonpaper production, impregnating agents, and pro-duction of wax compounds.

2.2.5. Retamo Wax

Occurrence and Isolation. In arid areas ofArgentina, Bulnesia retama grows wild as treesand shrubs. Branches and twigs are coated witha wax deposit that can be collected mechani-cally after drying the plant material harvested insummer. The crude wax is purified by meltingwith dilute sulfuric acid and subsequent filtra-tion through cloths. It is sold exclusively on thehome market as retamo wax [12].

Waxes 15

Properties and Composition. Retamo waxis a light to medium brown, odorless, hard wax.It is very similar to other vegetable waxes, suchas carnauba wax, with regard to its solubility inpolar and nonpolar organic solvents.

Data found in the literature, such as mp(76 – 78 ◦C), acid number (ca. 49mgKOH/g),saponification number (ca. 87mgKOH/g), pro-portion of hydrocarbons (15 – 25%), and con-tent of unsaponifiable components (38 – 42%),characterize the wax less precisely than the typi-cal chain-length distributions of even-numberedwax acids and alcohols and of paraffins [40].

Uses and Importance. With a decreasingannual production of several hundred tonnes(1975, ca. 500 t/a), retamo wax is of limited im-portance on the Argentinian market. It is usedfor floor, car, and shoe polishes and in the pro-duction of colored polishing inks.

2.2.6. Jojoba Oil

According to the DGF definition, jojoba oil isnot a wax. However, its chemical compositionallows it to be classified as a “liquid wax” in thesense of the classical definition of waxes.

Occurrence and Isolation. The jojoba bush(Simmondsia chinensis = Simmondsia califor-nica =Buxus chinensis) grows wild over an areaof ca. 250 000 km2, most of which lies in theSonora desert. The population density variesfrom a few to 500 plants per hectare. In certainareas, millions of jojoba bushes can be found.

The bushes carry fruit capsules that can con-tain one to three nuts of differing sizes. The yieldfrom the harvest of wild jojoba bushes can rangefrom a few nuts to 14 kg of nuts per plant. Theaverage yield is ca. 1.8 kg per bush.

The nuts contain 50 – 60wt% oil, whichcan be extracted almost completely from thedeshelled, granulated fruit. Around 35 – 40% ofa particularly high-value oil is obtained by coldpressing and a further 15 – 20%of a lower-valueoil by extraction of the pressed cake. The oil ispurified by simple filtration [41].

Properties and Composition. Jojoba oil is avirtually colorless to golden yellow, odorless,

unsaturated oil, for which the most importantcharacteristics are as follows:

mp 6.8 – 7.0 ◦CAcid number 2mgKOH/gSaponification number 92mgKOH/gIodine number 82 g I2/100 g

A highly crystalline, relatively hard waxis obtained from jojoba oil by hydrogenation.Saponification of the oil gives 51% unsaponifi-able material and 52% total acid.

Jojoba oil has the following compositionwithregard to substance groups:

Wax esters ca. 97.0wt%Free alcohols ca. 1.1wt%Free acids ca. 1.0wt%Sterols ca. 0.9wt%

Unlike other vegetable waxes, the acidsand alcohols in jojoba oil are monounsat-urated, straight-chain representatives of thechain-length range C16 –C24. Among the acidsthe C18 (ca. 12.5% of the total acids), C20 (ca.67% of the total), and C22 components (ca.14.5% of the total) predominate, and among thealcohols, the C20 (ca. 48% of the unsaponifiablecomponents) and C22 components (ca. 41% ofthe unsaponifiable components). With this un-usual composition, jojoba oil is very similar tosperm oil contained in the skull a bone of thesperm whale.

Uses and Importance. An extraordinarilyhigh market demand exists for a sperm oil sub-stitute, which can be satisfied to a great extentby jojoba oil. This demand is a result of theworldwide prohibition of whaling, even thoughthe latter is not obeyed by all countries.

The first experimental jojoba plantationswere begun in theUnited States (Arizona, Texas,andCalifornia) to effect infrastructural improve-ments. Many other jojoba oil plantations werestarted in Mexico, Argentina, Australia, Brazil,Africa, Egypt, Israel, and countries whose cli-matic conditions allowed desert farming.

Because management of these plantations isdifficult and the time required to achieve eco-nomical harvests is relatively long (eight toten years), jojoba oil is available in insufficientquantities at a very high price. Its use is there-fore limited to cosmetics and pharmaceuticals.As soon as reliable quantities can be supplied at

16 Waxes

acceptable prices, jojoba oil may attract extraor-dinarily great interest as a raw material, particu-larly in the production of high-performance lu-bricants and in modified form in plasticizers andstabilizers.Hydrogenated jojoba oil, which cor-responds to fatty esters such as stearyl stearate inits properties, will remain noncompetitive withthese esters in terms of price and will thereforenot achieve market importance.

2.2.7. Other Vegetable Waxes

Many other vegetable waxes are known, and thecomposition of some of them has been inves-tigated [12]. However, they are either of verylimited local importance or of purely academicinterest. These waxes include:

Caranday waxRaffia waxColumbia waxEsparto waxAlfalfa waxBamboo waxHemp waxDouglas fir waxCork waxSisal waxFlax waxCotton waxDammar waxCereal waxTea waxCoffee waxRice waxOcatilla waxOleander wax∗ Palm waxes

Japan tallow wax, which is available com-mercially, fulfills some application-oriented cri-teria as a wax but, because of its chemical na-ture, is a vegetable tallow and thus belongs to thegroup of other tallows such as myrica, bayberry,ucuhuba, Borneo, Malabar, and illipe.

2.3. Animal Waxes

Animal waxes are obtained mainly from bees(Apoidae), particularly the honeybee (Apidae),stingless bee (Meliponinae), and bumblebee

(Bombinae). Some scale insects (Coccidae) alsoproduce waxes.

Waxes obtained from land mammals (sheep,goats, llamas, and dromedaries) and marine ani-mals, as well as those of microbiological origin,are also known.

2.3.1. Beeswax

Beeswax is the oldest natural wax used by hu-mans and still the most important animal wax.

Occurrence. Beeswax is an end product ofthe metabolism of a honeybee class ( Apis mel-lifica, A. carnica), which belongs to the Apisgenus. This species of honeybee is found world-wide and domesticated to a high degree. Wax issecreted from the wax glands in the lowest ab-dominal segments of the worker bee as white,slightly transparent flakes (virgin wax). Fromthere it is taken to jaw, plasticized by chewing,and then used in this form as a building materialfor incubating combs and honeycombs.

If plenty of food is available and honey pro-duction is increasing, the wax glands are stim-ulated to enhance production for building newhoneycombs. If the beekeeper makes preformedhoneycombs available to the bees, honey pro-duction is increased [13], [36], [42], [43].

A bee population of ca. 30 000 worker beesproduces ca. 270 g of wax from 3 kg of sugar or3.6 kg of honey in one-fifth of a generation – ca.50 d. A bee population consumes ca. 50 kg ofpollen and 62 kg of honey per year.

Beeswax is produced in almost all countriesof the world. In Europe, wax produced in a par-ticular country is consumed there and supple-mented by imports. Suppliers are African coun-tries, such as Tunisia, Morocco, Kenya, Tanza-nia, Zambia, and the Central African Republic.NorthAmerica,Australia,NewZealand,Russia,and the People’s Republic of China also exportbeeswax.

Isolation. Toobtainwax, the combs are freedfrom honey as far as possible by centrifuging.Then the wax is isolated either thermally by us-ing sunlight or with boiling water. Particularlyheavy impurities become enriched in the aque-ous phase. Insoluble impurities remaining in thewax melt can be removed by filtration through

Waxes 17

a fine mesh sieve of filter cloths, or by pressurefiltration or centrifuging.

Colored, wax-soluble impurities can often beremoved by treating the wax melt with acti-vated carbon, aluminum ormagnesium silicates,or other bleaching earths. As in pressure filtra-tion and centrifugation,wax-containing residuesare formed from which lower-quality waxes canbe isolated by solvent extraction. The oldestmethod of lightening the color, which is saidto have been practiced in 1000 b.c., involvesbleaching beeswax, that has been processed tothin strips or shavings (large surface), in air andsunshine.

In the aforementioned purification processes,beeswax remains chemically unchanged and itscharacteristic, honeylike odor is retained. Thesuccess of the process depends mainly on thesource of the beeswax.

Posttreatment of beeswax is now limited towashing with water or adsorptive purificationwith bleaching or diatomaceous earths. Bleach-ing with hydrogen peroxide is used out becauseperoxy compounds are formed [8].

If the process is carried out skillfully, chem-ical bleaching processes, such as refining withchromic acid – sulfuric acid, give very light,almost chemically unchanged products, whichhave lost the aromatic odor of the starting ma-terial. However, these processes are not em-ployed. The same holds true for those involvingmild bleaching with permanganate and sulfuricacid or the use of chlorine-containing bleachingagents such as chlorine bleach, sodium chlorite,and chloramine. The latter givewaxes that do nothave stable colors and often contain chlorine.

Beeswax is sometimes derivatized by ethoxy-lation or esterification. The products obtained donot have any market importance.

Properties. Crude, mechanically purifiedbeeswax contains, besides wax, flower andpollen pigments and propolis resin, which actsas a cement in honeycomb construction. There-fore, depending on the source, the wax can havea yellow, orange, or dark brown color.

Beeswax ismoderately hard. It becomes plas-tic and kneadable on warming in the hands,without sticking. It has a noncrystalline, finelygrained fracture pattern. On cutting, matt sur-faces are produced. Beeswax has a honeylikeodor that intensifies on melting. It is moderately

soluble in polar and nonpolar organic solventsin the cold, and completely soluble when heatedto its boiling point.

Chemically bleached beeswaxes are cream toivory in color and practically odorless and taste-less. They have a somewhat harder and morebrittle consistency than chemically untreatedproducts.

The following limiting values have been es-tablished for the properties of mechanically pu-rified and bleached beeswax [20]:

mp 62 – 65 ◦CAcid number 17 – 24mgKOH/gEster number 72 – 79mgKOH/gEster number/acid number 3.3 – 4.2Saponification turbidity point 65 ◦C

Extensive investigations show that propertiesvary even among waxes from the same source[44].

Composition. The following values aregiven in the literature for the approximate com-position of beeswax with regard to wax classes:

Wax esters 70 – 80%Free acids 10 – 15%Paraffins 10 – 20%

Alkenes, isoparaffins, cholesteryl esters, andpollen pigments are present in minor amounts[12], [45].

Since the typical data for beeswax vary bet-ween relatively wide limits, misrepresentationof beeswax is difficult to detect by using thesedata [46]. A large number of publications existon the analysis of beeswax [47]. Beeswax can beseparated into the various substance classes bychromatographic methods [48–53]. Beeswax ofdifferent origin has been shown to have similarcomposition.

Comparative GC studies, in which ca. 65%of the waxes investigated are analyzed (residuesmostly involatile di- and triesters), also showgreat similarity among beeswax of widely vary-ing origin [54] (see Table 5).

Parallel GC investigations on a genuinebeeswax sample and the same sample afterhydrolysis and silylation show that C22 –C36wax acids are present predominantly as the freeacid, while all C12 –C20 fatty acids are esterified[54].

18 Waxes

Table 5. Composition of beeswax of different origins ∗[54]

Components Eastern Switzerland Brazil China Canada Czech Republic

Hydrocarbons, % 14 15 16 14 13Fatty (wax) acids, % 12 14 9 (8) – 12 13Fatty alcohols, % 1 1 1 1Palmitates, % 22 20 24

35∗∗ 31∗∗Oleates, % 4 3 5Hydroxymonoesters, % 12 12 11 (4) – 8 13Total, % 65 65 66 (62) – 70 70

∗ Values in parantheses were found only in a few cases.∗∗ Palmitates and oleates.

Gas chromatography of hydrolyzed and sily-lated beeswax allows a total analysis in which95% of its components can be identified [54](Table 6).

Table 6. Percentages of individual substance classed in a hydrolyzedwax sample from the honeybee Apis mellifica (Switzerland) [54]

Chain length(C-number)

Hydrocarbons Fatty acids Hydroxyfatty acids

Fattyalcohols

16 17.98 11.601718 2.44 0.711920 0.152122 0.33 1.66 0.1223 0.2524 0.10 4.94 0.59 5.5925 0.5826 0.11 1.75 1.38 3.3727 4.4228 0.08 1.78 0.10 4.3729 2.6430 0.07 1.58 9.5831 3.2732 1.05 7.9833 2.2434 0.94 0.8835 0.1236 0.08Total 14.23 33.02 16.04 31.89

Studies using GC show that a spectrum ofwax samples from Apis mellifica has the samecharacteristic composition independent of thebreed of bee. Small differences exist only in thepercentage of individual components and sub-stance classes, so that in general the followingranges of composition are correct for variousclasses of substance [54]:

Hydrocarbons 13 – 16%Fatty acids 30 – 35%Palmitic acid 15 – 20%Hydroxy fatty acids 13 – 17%

Fatty alcohols 30 – 35%Other substances 4 – 8%

The remaining substances are present mainlyin concentrations of <0.05%.

By using these facts, beeswax misrepre-sentation can be detected by a correspondingtotal analysis of the wax even in the presenceof small quantities of blending materials [54].

Uses. Beeswax, mainly the yellow variety, isone of the raw materials used in the produc-tion of household candles, expensive decora-tive candles, and candles for religious purposes.For the latter, the Roman Catholic Church pre-scribes a minimum beeswax content of 10%.Beeswax is also used for artistic and handicraftpurposes (waxflowers,wax sculptures, painting,and batik). Most bleached and purified beeswaxis used in cosmetics and pharmaceuticals (toregulate the consistency of lipsticks, creams,ointments, and suppositories) and in the foodsector (as a release agent and a polish in con-fectionery production). Its use in these areas isfavored by corresponding licensing regulations.

A significant proportion of beeswax, ca. 40%of the total market volume, is sold back to bee-keepers for the production of synthetic hon-eycombs, in which blends with paraffins andceresin, which are not allowed for pharmaceuti-cals, are often used.

Economic Aspects. From the worldwidehoney production figures for 1976, produc-tion of 11 000 – 19 000 t of beeswax was esti-

Waxes 19

mated.Whether the quantities used in the candleand beekeeping industries were included in theworldwide consumption figure of ca. 10 000 t for1981, is not known. At that time, total importsfor the Federal Republic of Germany amountedto 1000 t.

At present (1994), ca. 15 000 t of beeswax isavailable on the world market. Ca. 6000 t is usedin industry, and ca. 4000 t is sold back to bee-keepers [8].

The annual availability of beeswax dependsstrongly on climatic variations in exporter coun-tries and bee diseases that break out occasion-ally. In 1993, for example, a marked drop in ex-ports from the United States occurred becauseof catastrophic weather conditions in the Mis-sissippi area [8].

2.3.2. Other Insect Waxes

The following waxes are not market productsand only in some cases have limited regionalimportance in the countries of origin.

Ghedda Wax. Ghedda wax is produced bysome types of wild bee bound in Asia (Apisindica, A. florea, A. dorsata). It was formerlyexported as such but more frequently now isblended with beeswax from the East Indies.

Ghedda wax has a yellow-brown colorand varying characteristic data (e.g., acidnumber 4 – 11mgKOH/g, saponificationnumber 86 – 130mgKOH/g, iodine number5 – 11 g I2/100 g, mp 60 – 66 ◦C). It has a con-sistency similar to beeswax with a fatty feel,which can be attributed to its glyceride content.Gheddawax consists of ca. 78 – 80%wax esters,4% glycerides (fats), 5 – 6% free acids, 8 – 9%hydrocarbons, and 1 – 2% partly resinous im-purities [12].

Among the acids are 7- and 16-hydroxypalmitic acids and 7,16-dihy-droxymargaric acid, which can be used foridentification of ghedda wax or other beeswaxesblended with ghedda wax in modern umpire as-says.

Shellac Wax. The resinous exudate of thescale insect Laccifer lacca (formerly Tachardialacca) of the Coccidae family is an impor-tant commercial product, known as shellac

(→Resins, Natural, Chap. 4.19.). Shellac con-tains 4 – 5% wax, which can be obtained bytreatment with dilute soda solution or 90 – 95%ethanol (spirit extraction) as an insoluble com-ponent.

Shellac wax is a hard, yellow to brown prod-uct. Very light, bleached types are also known.The widely varying data found in the literature(e.g., acid number 12 – 24mgKOH/g, saponifi-cation number 63 – 126mgKOH/g, iodine num-ber 6 – 9 g I2/100 g, solidifying point 58 – 80 ◦C)may be attributed to the different sources of shel-lac and different methods of extraction and post-treatment of the wax component. Thus, the com-position with regard to substance classes alsovaries as follows [12]:

Wax esters 70 – 82%Free acids 10 – 24%Free alcohols <1%Hydrocarbons 1 – 6%Shellac 1 – 4%

Investigations [55] of bleached shellac waxesshow that the total acid content of the wax,similar to that of beeswax, consists essentiallyof a mixture of even-numbered fatty acids(C12 –C18, 21 – 26% of the total acid) andwaxyacids (C28 –C34, mainly C32 and C34). A sig-nificant component is trihydroxypalmitic acid(aleuritic acid), even though it occurs only inquantities of 0.5 – 1.0%. Among the alcohols(C28 –C32) the C28 component predominates(62 – 65% of the total alcohol). The main hy-drocarbon components are paraffins with 27, 29,and 31 carbon atoms.

Chinese Insect Wax. The East Asian waxscale insect ( Ericerus pela, subgenus Lecani-inae, family Coccidae) secretes a wax on thetwigs and leaves of trees and shrubs on which itis a parasite. The wax can be extracted by melt-ing with hot water. It is hard, brittle, crystalline,and odorless, with a light color, and consists of95 – 97% wax esters, 0.5 – 1.0% free acids, and2 – 3% hydrocarbons [12]. The high proportionof wax esters is significant. The East Indian waxscale insect ( Ceroplastes ceriferus) is said toproduce a wax similar to beeswax in composi-tion [12].

20 Waxes

2.3.3. Wool Wax

Sheep secrete a substance from their sebaceousglands to protect the epidermis and the woolfrom adverse weather conditions and from theirown acidic perspiration. This substance is in-correctly referred to in the literature as wool fat.Because of its chemical composition it shoulddefinitely be classified as a wax.

Woolwax is obtained in emulsified form fromraw wool by machine washing with soap liquor.Extractionofwoolwith suitable organic solventsis not employed because it would lead to com-plete degreasing of the wool and thus make itnonelastic.

Many processes exist for obtaining crudewool wax from the emulsion, some of thempatented [36]. Wax is first precipitated alongwith the acids of the soap solution by additionof sulfuric acid. The fatty acids remain in thecrude product regardless of whether the precip-itates are pressed out, centrifuged, or extractedwith solvents. They can be removed almost com-pletely by dissolving the crude product (e.g., inhexane) and subsequent extraction with a mix-ture of alcohol and dilute aqueous sodium hy-droxide. Further purification steps (e.g., bleach-ing with hydrogen peroxide in the presence ofphosphoric acid [56]) give neutral wool wax,which is usually treated subsequently with ad-sorbents such as bleaching earth or activated car-bon and sold in a highly pure form as Adepslanae.

Crude wool wax is a greasy, glutinuous,brown-yellow to brown-black substance with apenetrating goatlike odor (mp 34 – 38 ◦C). Neu-tral wool wax is yellow to light brown in color(mp 38 – 42 ◦C), with a milder odor, whereasAdeps lanae is a pale yellow, almost odorlesssubstance (mp 40 – 42 ◦C).

The composition of wool wax varies depend-ing on the origin of the wool, breed of sheep,climatic conditions, farming method, and typeof pasture.

Wool wax usually consists of a mixture ofca. 48% wax esters, 33% sterol esters, 6%free sterols, 3.5% free acids, 6% lactones, and1 – 2% hydrocarbons [12]. The low mp and ap-pearance of wool wax may be attributed to thehigh proportion of branched acids.

Uses. Wool wax is used mainly as the crudeproduct, as neutralwoolwax, or as hydrogenatedneutral woolwax and in the formofwoolwax al-cohols (obtainable by hydrolysis) in leather pol-ishes, cosmetics (e.g., creams, baby-care prod-ucts, and toilet soap), pharmaceuticals (e.g.,plasters, ointments, and suppositories), and lu-bricants. The purified, commercial product isknown as wool wax or lanolin.

3. Montan Wax

3.1. Formation and Occurrence

Montan wax is a vegetable fossil wax. It formspart of the extractable, bituminous componentsof lignite and peat. The composition of bitumendepends on the carbonized plant material andon the geology and conditions of the deposit.The main components of bitumen are waxes,resins, asphaltenes, and dark residues. If the pro-portion of wax is >60%, the bitumen is gen-erally known as crude montan wax. Prerequi-sites for formation of this wax were the sameor similar to those now necessary for forma-tion of recent natural waxes (e.g., carnauba wax[57–60]). Lignite, which originates from plantmaterial of the Eocene period, has a high andeconomically utilizable proportion of wax com-ponents. Deposits of lignite, which are used forwax extraction, are foundmainly in eastern Ger-many (Roblingen), Ukraine (Alexandrija), Rus-sia (Baschkiren), the United States (California),and China. Other deposits are of only local im-portance or are not even exploited. The largestcrude montan wax producers are the Montan-werkeRomonta inRoblingen (Germany) and theAmerican Lignite Co. in the United States.

3.2. Extraction

The most economically important bitumen-richlignite deposits are found in the area around thecity of Halle in Germany. An industrial processfor extracting montan wax from this type of coalwas based on investigations bei Riebeck. Theoriginal patent [61], [62] for this process, pub-lished in 1880, describes how montan wax canbe obtained by solvent extraction. In 1900 theproduction ofmontanwaxwas begun inVolpke,and later in other locations.Romonta inAmsdorf

Waxes 21

[62] is currently the most important productionsite. There, lignite with a bitumen content bet-ween 10 and 20% is used for industrial extrac-tion of montan wax. The process used involvesthe following steps: size reduction, drying, ex-traction, evaporation of the extract, and formu-lation [57], [60]. The yield and composition ofthe extract are determined by coal quality (clayand mineral content); physical parameters suchas water content, particle size, and particle-sizedistribution; and properties of the solvent.

Granulating and Drying. Run-of-mine,pit-wet lignite contains ca. 50% water. Beforeextraction it is ground in roll mills and dried toa residual moisture level of ca. 15% in steamheated tubular dryers. The particle-size distri-bution is ca. 7% >8mm, 75% 1 – 8mm, and18% fines.

Lignite Extraction and Wax Production.Various machines such as band, chamber,carousel, or bucket chain conveyor extractors areused for extraction. Many solvents and solventmixtures have been tested and used to extractwax from lignite. They include aliphatic, aro-matic, and unsaturated hydrocarbons and hy-drocarbon mixtures, mono- and polyhydric al-cohols, ketones, esters, ethers, and mixtures ofhydrocarbons and alcohols. The yield of ex-tract is highest when polar solvents (e.g., etha-nol) or solvent mixtures (e.g., ethanol – toluene)are used. However, the extract then containsa high proportion of polar substances, such asresin acids, sterols, triterpenes, or dark residues,and only a small proportion of wax. With hy-drocarbons the overall yield is lower, but theproportion of wax in the extract is significantlyhigher. In industry, only hydrocarbons or hydro-carbonmixtures are therefore used (e.g., tolueneat Romonta in Roblingen). Mixtures of aromaticand aliphatic hydrocarbons and naphthenic ben-zine are used by other producers.

If toluene is used, extraction is carried outat 85 ◦C. After extraction, the solvent containsca. 8 – 10% dissolved crude montan wax. Themixture is worked up in a three-stage distilla-tion. The bitumen content is increased to 50%in a continuous evaporator and then to 90% ina circulation evaporator. The remaining solventis removed by blowing in steam directly or in afalling-filmvaporizer. Thewaxmelt is pelletized

or poured into molds. The extracted coal gran-ulates are freed from solvent by steam strippingand used for electricity production in a powerstation. The toluene –water mixture is workedup, and toluene is recycled to the extraction pro-cess.

3.3. Properties and Composition

Crude montan wax is a black-brown, hard, brit-tle product with a conchoidal fracture pattern.It cannot be scratched by fingernails at roomtemperature. Crude montan wax has a penetrat-ing terpene-like odor, which becomes very in-tense on melting. The wax is soluble in manyorganic solvents, particularly aromatic or chlo-rinated hydrocarbons, even on moderate heat-ing. Crude montan wax consists of a mixture ofwax acids, wax esters, resins, asphaltenes, anddark residues. The ester and acid componentscan be saponified and emulsified by treatmentwith aqueous alkali [57], [59], [60]. The waxesform the crystalline component of montan wax.They effect the relatively sharp transition fromsolid to liquid state and vice versa. The resinsand asphaltenes have a more amorphous natureand exhibit glassy behavior. The qualitative andquantitative composition of crude montan waxis determined by the carbonized plants, extent ofcarbonization, the solvent, and extraction condi-tions.

A typical crude montan wax contains ca.:

Wax acids 35%Wax alcohols 20%Hydroxycarboxylic acids 10%Dicarboxylic acids 3%Wax ketones 1%Hydrocarbons 2%Resin acids 15%Sterols 10%Dark residues 4%

Characteristic properties are:

Acid number 20 – 40mg KOH/gSaponification number 70 – 120mg KOH/gIodine number 30 – 45 g I2/100 gDrop point ca. 85 ◦CDensity (100 ◦C) ca. 0.86 g/cm3

Thermal expansion (20 – 100 ◦C) 18%

22 Waxes

Wax Components. Crude montan wax con-tains 70 – 75% waxlike components, of whichthe following have been isolated:

Straight-chain carboxylic acids C16 –C34

Straight-chain alcohols C18 –C34

Straight-chain ω-hydroxycarboxylic acids C16 –C32

Straight-chain 2-hydroxycarboxylic acids C16 –C32

Straight-chain ω-dicarboxylic acids C22 –C32

Esters of C16 –C34 carboxylic acids andC18 –C34 alcoholsStraight-chain aliphatic hydrocarbons C25 –C33

These compounds form homologous series,in which chain lengths in the range of C28 –C30predominate. The chain-length distribution forstraight-chain carboxylic acids and alcoholsfound by GC analysis is shown in Figure 2.

Resins and Dark Residues. Besides thewax components, crude montan wax also con-tains ca. 25 – 30% resins and dark residues. Thequantity and composition of these componentsare determined mainly by the properties of thelignite, the extraction solvent, and the extrac-tion temperature. The resin can be removedfrom crude montan wax by exhaustive extrac-tion with methanol. In industry, this method isnot used to determine resin content because itis expensive and time-consuming. Instead, theproportion of soluble compounds (i.e., resins) isdetermined by a standardized procedure such assolubility in acetone or in a toluene – ethanol orbenzene – ethanol mixture. The resin is charac-terized by its chemical and physical properties,of which the following are typical:

Drop point ca. 75 ◦CAcid number ca. 33mg KOH/gSaponification number ca. 75mg KOH/gOH number ca. 70mg KOH/gIodine number ca. 90 g I2/100 gSulfur content ca. 2 – 2.5%

Determination of all individual componentsin resin extracts has not yet proved possible.However, substance classes and typical com-pounds in these classes have been identified:e.g., triterpenes such as betulinol, sterols, diter-penoid acids and their esters, and diterpenoidalcohols and their esters.

3.4. Refining and Derivatization

Because of its dark color and its resin content,which sometimes lead to problems, direct use ofcrude montan wax is limited. For most applica-tions the wax must be refined. Refining involvesthree steps: extractive deresinification, oxidativebleaching, and subsequent derivatization [57–60], [63].

3.4.1. Deresinification

The resin components of the crude wax are sol-uble in many solvents even at low temperature(10 – 20 ◦C). Treatment of pulverized crude waxwith methylene chloride, ethyl acetate, or meth-anol reduces the resin content to 5 – 10%. Othersolvents, such as ketones, ethers, hydrocarbons,mixtures of alcohols and aromatics, liquid SO2or supercritical CO2, can be used but have notachieved industrial importance. After removalof the solvent, the extracted resin contains ca.10 – 20%wax. Deresinified wax can be used di-rectly or as amixturewith otherwax componentsfor various applications. Such products are soldby Romonta, Amsdorf, and the American Lig-niteCo.Most deresinified crudewax is subjectedto oxidative bleaching.

3.4.2. Bleaching

A purification process for the crude wax wassought very early on. Of the many processes in-vestigated, only three have actually been used inproduction [57], [60], [64–67].

Distillation was the first method for obtain-ing light, hard waxes from crude montan wax.The crude wax was heated to 420 ◦C in stillsand thus partially cracked. The distillate there-fore consisted of 50 – 80% hydrocarbons and20 – 50% wax acids. The hydrocarbons wereremoved in a further workup step, leaving themontan wax acids.

Oxidation with Nitric and Sulfuric Acids.In this process, paraffin had to be added as adiluting agent. The resin was precipitated asthe nitroresin and removed. The dark residues

Waxes 23

Figure 2. Chain-length distribution of acids and alcohols in montan wax

were coked and the wax acids extracted fromthis coke. However, the wax still had a certainamount of dark residues and nitrate-containingproducts.

Oxidation with Chromic Acid or Chro-mates in Sulfuric Acid. In processes describedthus far, the wax is damaged considerably andthe chainlength distributions of its constituentsare altered. Oxidative bleaching with aqueouschromic – sulfuric acid mixtures, developed byI.G. Farben, is much more suitable. The start-ing material is deresinified crude montan wax.The resin components and dark residues are ox-idized to carbon dioxide or low molar mass,water-soluble compounds in a multistage oxida-tion process. The wax esters are simultaneouslyhydrolyzed; the wax alcohols formed are oxi-dized to wax acids; and the hydroxycarboxylicacids are oxidized to dicarboxylic acids. Someesters remain unaltered.

where n is an even number between 24 and 32.A mixture of light wax acids, which are very

similar in chain-length distribution to the crudewax, is obtained in a yield of 80 – 85% based oncrude wax. Minor components of the mixtureare unchanged esters and long-chain dicarbox-ylic acids. The spent oxidizing agent is removed

and worked up, and the bleached wax is freedfrom residual chromium salts in a subsequentstep.

Depending on the quantity of chromic acid,the acid number of the bleached wax is between100 and 135mg KOH/g. Oxidation can be per-formed batchwise or continuously. In the Ger-sthofen process used by Hoechst, the oxidizingagent is regenerated electrochemically. BASF,Volpke, and other producers use the spent oxi-dizing agent in an associated plant for the pro-duction of chromium-containing tanning agents.

Development is still being carried out on re-fining processes [68] such as alkaline dehydro-genating oxidation with anhydrous alkali hy-droxide. Apparently, these processes have notbeen used in industry up to now. An overviewof the current processes used for extraction andrefining of montan wax is given in Figure 3.

3.4.3. Derivatization

Reconstruction of the original wax structure isattempted by treating the wax acids obtainedwith dihydric alcohols or Ca(OH)2. By varyingthe proportions of free acid and soap and the de-gree of esterification, the reaction can be carriedout in such a way that the products formed areoptimized for a particular application [57], [64],[65], [69].

CH3−(CH2)n−COOH+HOCH2−CH2OH→CH3−(CH2)n−COO−CH2−CH2−OR

R=H or CH3−(CH2)n−CO−CH3−(CH2)n−COOH+Ca(OH)2 →

(CH3−(CH2)n−COO)−2 Ca2+

24 Waxes

Figure 3. Flow sheet for extraction and refining of montan waxes

The most important products in this seriesare the esters of ethylene glycol (e.g., HoechstWaxE or Hoechst WaxKSL) and mixtures ofesters of 1,3-butanediol with calciummontanate(e.g.,HoechstWaxOP).Broad variation in prop-erties can be achieved by using tri- and polyhy-dric alcohols, aromatic alcohols, aminoalcohols,and ethoxylated or fluorinated alcohols. Reac-tive waxes can be produced from partial estersof polyols by treatment with dicarboxylic acids,isocyanates, epoxides, or unsaturated carboxylicacids.

These waxes exhibit interesting propertiesand have been produced and used for specialapplications. If the reaction is not stopped at thereactive wax stage and a suitable stoichiometryis chosen, oligomeric waxes are produced.

3.5. Uses and Economic Aspects

Montan wax acid and its derivatives are versa-tile materials [64] , [65], [69–71]. They are usedin the form of flakes, powders, pastes with sol-

vents, or aqueous emulsions. The main areas ofuse are in polishes for floors, cars, and leather; inplastics processing as lubricants, release agents,and nucleating agents; in the paper and buildingindustries; and in wood and metal processing.Montan wax derivatives are also used in smallquantities in pharmaceutical formulations; cos-metics; and the production of adhesives, resins,and office equipment. In addition to their tech-nical properties, the low toxicity of montan waxderivatives and the fact that BGA or FDA ap-proval has already been granted for some deriva-tives are important criteria favoring their use.

Production figure of montan wax for 1994are given below, together with a breakdown ofmontan wax consumption in different applica-tion areas:

Crude montan waxRomonta ca. 19 000 t/aAlpco ca. 2 500 t/aUkraine ca. 1 500 t/aChina ca. 1 000 t/aBleached montan waxesHoechst Gersthofen ca. 11 000 t/aVolpker Montanwachs ca. 3 500 t/aChina ca. 500 t/aPoland <500 t/aCzechia <500 t/aApplication areasPlastics, lubricant ca. 7 000 t/aPolishes, coatings ca. 5 500 t/aTechnical applications ca. 2 500 t/a

Waxes 25

Table 7. Classification of waxes from crude petroleum

Origin

light, medium, heavy lubricating oil distillates residues from vacuumdistillation

crude oil

Group (macrocrystalline) paraffin waxes microcrystalline waxes(microwaxes)

settling waxes

Subgroup paraffin waxes intermediate waxes residue waxes pipe waxestank bottom waxes

Crude products crude waxes (slack waxes) petrolatum raw waxesDeoiled and refinedproducts

scale waxes deoiled slack waxes filtered (decolorized)waxes fully refined waxes

plastic microwaxes hard microwaxes

Side products fromdeoiling

soft waxes soft petrolatum (microwaxslacks)

4. Petroleum Waxes

4.1. Introduction

The quantity of waxes obtained from crude pe-troleum has increased continuously for two rea-sons: (1) the demand for lubricating oils withlow pour points and (2) the large proportion ofparaffinic crudes in total crude oil productionthat have to be dewaxed for the production oflubricating oils. This development has increasedthe need to find more industrial applications forpetroleum waxes. When the processing of lubri-cating oil began in the second half of the 19thcentury, waxeswere still inconvenient side prod-ucts. Since then, worldwide consumption of pe-troleum waxes has increased to 3×106 t/a. Thisconsumption corresponds to more than 95% ofthe waxes of all types produced worldwide. De-pending on their natural occurrence and theircrystallinity, petroleum waxes are divided into:

1) Macrocrystalline waxes (paraffin waxes)2) Microcrystalline waxes (microwaxes)

Table 7 gives a detailed classification ofparaffin and microcrystalline waxes based onorigin and method of refining [80].

Paraffin waxes are obtained from light andmiddle lubricating oil cuts of vacuum distilla-tion. Paraffin waxes also include waxes fromheavy lubricating oil distillates, which are inter-mediates between macrocrystalline and micro-crystalline waxes with regard to structure andcomposition (intermediate waxes).

Microcrystalline waxes originate from vac-uum residues and from the sediments of paraf-finic crude oil (settling waxes). Waxes that areliquid at room temperature are mostly contained

in diesel oil or gas oil fractions (→Heating Oils,→Aviation Turbine Fuels) and can be isolatedfrom them. These are not dealt with here.

4.2. Macrocrystalline Waxes (ParaffinWaxes)

4.2.1. Chemical Composition and GeneralProperties

Chemical Composition. Paraffin waxesconsist predominantly of mixtures of straight-chain alkanes in a typical distribution of thehomologous series whose molar masses dependon the boiling range of the lubricating oil distil-late from which they are obtained. Long-chain,weakly branched isoalkanes are present in amuch lower proportion, along with a very smallfraction of monocyclic alkanes.

The intermediate waxes have a similar com-position, but the molar masses of the n- andisoalkanes are higher. Intermediate waxes con-tain a higher proportion of cycloalkanes andisoalkanes; the latter more strongly branchedthan those in paraffin waxes.

According to the European Wax Federation(EWF), paraffin waxes have a C-number distri-bution of n-alkanes from18 to 45 and a total con-tent of iso- and cycloalkanes of 0 – 40%. Typicaldata for the intermediate waxes are an n-alkaneC-number of 22 to 60 and a total content of iso-and cycloparaffins of 30 – 60%.

General Physical Properties. Paraffinwaxes are insoluble in water and sparinglysoluble in low molar mass aliphatic alcoholsand ethers. They are more soluble in ketones,

26 Waxes

chlorohydrocarbons, petroleum spirit, solventnaphtha, benzene, toluene, xylene, and higheraromatics, especially at elevated temperature.The solubility decreases markedly with increas-ing molar mass (higher melting point) of thewaxes.

Chemical Properties. Paraffin waxes areextremely unreactive under normal conditions.Oxidation reactions occur only at elevated tem-peratures (e.g., on storage and processing above100 ◦C), particularly in the presence of oxy-gen and catalytically active metals. These re-actions can be recognized from the burnt odorproduced and the yellow to brown colorationof the waxes. Nevertheless, under certain ther-mally and catalytically controlled conditions,these waxes can undergo chemical reactionssuch as chlorination (→Chlorinated Hydrocar-bons, Chap. 7.3.), oxidation, dehydrogenation,and cracking (→Oil Refining, Chap. 3.6.3.2.,→Oil Refining, Chap. 3.6.4.), of which chlori-nation and cracking are important in industry.

4.2.2. Division into Product Classes

Depending on the degree of refining, paraffinwaxes are divided into the following productclasses:

1) Crude waxes, also known as slack waxes2) Slack wax raffinates (scale waxes)3) Deoiled slack waxes4) Soft waxes5) Semirefined waxes6) Filtered (decolorized) waxes7) Fully refined waxes

Table 8 gives an overview of the change inphysical characteristics with degree of refining.

Crude waxes (slack waxes) [64742-61-6]consist of a mixture of alkanes, which can besolid, semisolid, or liquid at room tempera-ture; alkyl-substituted cyclopentanes and cyclo-hexanes (naphthenes); and alkyl-substituted aro-matics. They also contain, as impurities, the typ-ical contents of the lubricating oil cuts fromwhich they originate, such as asphaltenes, resins,olefins, and sulfur and nitrogen compounds. Theoil content of slack waxes is usually between 5and 12%, but can be as high as 25%.

n-Paraffins and isoparaffins predominate inslackwaxes in termsof quantity; both are presentin continuously distributed homologous series.The chain-length spectrum (C-number distribu-tion) is determined from the width of the boil-ing range, the distribution maximum (C-numbermaximum) from the boiling level of the lubri-cating oil fraction. In isoparaffins, compoundswith terminalmethyl branches predominate, fol-lowed by other methyl-substituted alkanes. Theconcentration of these compounds decreases asthe branching point moves toward the mid-dle of the chain. Other components are com-pounds with terminal ethyl branches and mul-tiply branched structures, which can be detectedonly in slack waxes from heavy vacuum distil-lates [81], [82].

Table 9 shows the composition of some slackwaxes as a function of origin.

Physical Properties. Depending on the ori-gin and production process, slack waxes arelight- to dark-brown, soft, unctuous to semisolidmaterials without a clear crystal structure be-cause of their high oil and soft wax content. Thecongealing points lie between 35 and 65 ◦C; thedrop points, between 35 and 68 ◦C; the needlepenetration at 25 ◦C (a reciprocal measure of thehardness) is between 40 and 80 (at greater oilcontent, even higher); the viscosities at 100 ◦Care between 3 and 10mm2/s; the densities at70 ◦C, between 775 and 815 kg/m3; and the flashpoints between 190 and 250 ◦C.

Scale Waxes. Normally being physi-cally decolorized slack waxes, scale waxes[90669-78-6] essentially have the same com-position as the raw materials from which theyare obtained. Only the dark material contentsof the slack waxes (asphaltenes and resins) areremoved by the decolorization process, and thecontent of alkylaromatics, and of sulfur and ni-trogen compounds, is reduced. In physical prop-erties, scale waxes are similar to slack waxes.Decolorization renders the products white topale yellow.

Deoiled Slack Waxes (Crude HardWaxes, Raw Waxes). In deoiled slack waxes[8002-74-2] the predominant proportion of thehydrocarbons that are liquid (oils) under nor-mal conditions, and a certain proportion of the

Waxes 27

Table 8. Variation in physical data with degree of refining of paraffin wax (starting material : slack wax from a medium machine oil)

Characteristics Slack wax Deoiled wax Filtered (decolorized) wax Fully refined wax

Congealing point, ◦C 59 62 62 62Needle penetration, 0.1mmat 25 ◦C 57 18 18 17at 30 ◦C 80 26 26 25at 35 ◦C 105 36 36 36

Oil content, % 9.9 0.5 0.5 0.4Viscosity (at 100 ◦C), mm2/s 6.8 6.1 6.0 5.8Color brown brown whitish whiteFluorescence very strong weak none

Table 9. Composition of slack waxes from various lubricating oil distillates of the same origin (80% Arabian, 10% German, and 10%Norwegian crude oil)

Characteristic Slack waxes from

Heavy spindle oil Light machine oil Medium machine oil Heavy machine oil

Congealing point, ◦C 47 50 58 62Oil content, % 9.5 9.0 9.8 8.0n-Paraffin content, % 73 58 52 39C-number range 16 – 36 19 – 43 21 – 48 22 – 58C-number max. 24 29 34 41Cmax content, % 17 14 10 8

semisolid ones (softwaxes), have been removed.Liquid and semisolid waxes consist mainlyof low molar mass n- and isoparaffins and ofisoparaffins with centrally located and stronglybranched side chains, as well as naphthenesand alkylaromatics. Therefore, in deoiled slackwaxes the n- and weakly branched isoparaffinsare enriched. By removal of the low molar massportion a narrowerC-number range results alongwith a more pronounced C-number maximum.

Table 10 shows these relationships with twowaxes from heavy spindle oil and medium ma-chine oil used as examples.

Physical Properties. In structure and consis-tency, deoiled slack waxes are coarse to mediumcrystalline, brittle to weakly plastic and depend-ing on the degree of deoiling, hard to very hard.These waxes are light to dark brown and darkenon heating. The congealing points are between48 and 72 ◦C; the drop points between 48 and75 ◦C; and the needle penetrations at 25 ◦C bet-ween 10 and 30. At the same degree of deoiling,the course of the penetration – temperature curve(increase in penetration in the penetrogram [83]essentially depends on the origin of the waxes(Fig. 4).

Figure 4. Variation of needle penetration with temperaturefor deoiled slack waxes of different originsa) From heavy spindle oil (North Sea); b) From light ma-chine oil (North Sea); c) From heavy machine oil (NorthSea); d) Wax from Indonesia

Crude soft waxes [64742-67-2] are some-times known as foot oils (see Section 4.2.3.2)and are formed in the deoiling of slack waxes.They consist predominantly of low molar mass

28 Waxes

Table 10. Composition of deoiled slack waxes from two lubricating oil distillates (origin – see Table )

Characteristic Slack wax∗ Deoiled Slack wax∗∗ Deoiled

Congealing point, ◦C 47 50 58 67Oil content, % 9.5 0.3 9.8 0.4n-Paraffin content, % 73 84 52 64C-number range 16 – 36 19 – 36 21 – 48 23 – 48C-number max. 24 24 34 34Cmax content, % 17 19 10 11

∗ From heavy spindle oil.∗∗ From medium machine oil.

n-paraffins and strongly branched isoparaffins;higher molar mass, weakly branched isoparaf-fins; naphthenes; and alkylaromatics. The n-paraffin content of soft waxes is generally<25wt%.

Softwaxes are very soft, unctuous to inhomo-geneous materials at room temperature becauseof their high oil content, which can be 30wt%orgreater. The oil is included in voids of the crys-tal lattice of the solid hydrocarbons. Soft waxeshave a light- to dark-brown color and congeal-ing points <40 ◦C. Their viscosities at 100 ◦Care between 3 and 12mm2/s; their flash points,between 180 and 220 ◦C.

Semi-refined, filtered (decolorized), andfully refined waxes are similar to deoiled slackwaxes in the composition of their main compo-nents. Through refining they are freed frommorehighly condensed alkylaromatics and naph-thenes, olefins, and sulfur and nitrogen com-pounds. Depending on the origin, their con-tent of n-paraffins varies between 92wt% (East-Asian waxes) and 45wt% (waxes from heavymachine oil distillates of German origin). Thecomposition of the refined waxes is determinednot only by the origin of the crude (Table 11), butalso by the boiling range of the starting distillate.As the boiling ranges of the lubricating oils rise,the molar masses of the hydrocarbons containedin waxes obtained from them increase. The con-centration ratio of iso- and cycloparaffins to n-paraffins also increases. Thus, for example, a re-fined wax from Tuismasy (Ural) crudes contains81.6% n-paraffins with an average molar massof 360 g/mol (averageC-number 25.7) and 9.3%isoparaffins (average molar mass 384 g/mol; av-erage C-number 27.4). The naphthenes (9.1%)consist of 81.5% monocyclic and 15.5% bi-cyclic alkanes (average C-number 28.9) [84].

Table 11. Composition of fully refined waxes (congealing point62 ◦C in each case) from different origins

Characteristic Wax from machine oil distillate

Saudi Arabia Russia East Asia

Congealingpoint, ◦C

62 62 62

Oil content, % 0.3 0.6 0.2n-Paraffincontent, %

52 78 92

C-numberrange

23 – 48 23 – 41 25 – 38

C-number max. 34 32 30Cmax content,%

10 14 21

Physical Properties. Waxes in this group dif-fer fromdeoiled slackwaxes and fromeachotherin their residual oil content and, thus, in hard-ness, color, and color stability.

Semirefined waxes have an oil content of1.5 – 3%, and the needle penetration at 25 ◦Ccan be 20 – 60. They are somewhat plastic andkneadable, colorless to white, have good colorstability under light, and are virtually odorlessand tasteless.

Filtered (decolorized) waxes have an oilcontent of 1.5% (max.) and a needle penetrationat 25 ◦C of 10 – 26. They have a whitish colorand are relatively color stable and generallyodorless.

Fully refined waxes (oil content and penetra-tion similar to decolorized waxes) are crys-talline, no longer kneadable, pure white, trans-parent to slightly opaque, color stable, light-resistant, odorless, and tasteless. They fulfill pu-rity criteria for the production of packaging ma-terials for foods and for the formulation of cos-metics and pharmaceuticals. Detailed informa-tion on the chemical composition of fully refinedwaxes and methods for their analytical determi-nation can be found in the CONCAWE report[85].

Waxes 29

Figure 5. Process schematic for the production of paraffin waxes

According to a more recent definition, fullyrefinedwax products are those that fulfill variousnational purity requirements (see Section 4.2.5).The oil content, whichwas once limited to 0.5%(max.), is no longer a criterion since the oils con-tained in the wax also consist of n- and isoparaf-fins of the required purity. Depending on the lit-erature, the oil content of fully refinedwaxes canbe 1.5% (max.) [86] or 2.0% (max.) [87].

4.2.3. Occurrence of Raw Materials andProcessing

Paraffin waxes are contained in crude petroleumand are obtained during oil refining. Dependingon the source of the petroleum, the content ofsolid waxes can vary between 2% (Rumanianorigin) and 30% (Indonesian origin); generally,however, it is between 3 and 15% in crude pe-troleum from the main production areas.

Because of their higher molar masses andthus higher boiling ranges, waxes become en-riched in the residues from atmospheric distilla-tion (long residues). In processing the residues

to lubricating oils, waxes are obtained in all frac-tions of the vacuum distillation. Because of theirpoor solubility, they give rise to the high pourpoints of the basic oils and must therefore beremoved. The yields of wax vary depending onthe origin and quality requirements of the oils.For a wax content of crude petroleum of ca. 5%,8 – 18% solid waxes in the individual lubricat-ing oil fractions can be expected.

Slack waxes are produced in the dewaxingof lubricating oil distillates (→Lubricants andRelated Products). The type of process used andprocess parameters used are according to the de-sired quality of the lubricating oils.

The process steps necessary for the produc-tion of refined waxes are shown in Figure 5.

4.2.3.1. Dewaxing Lubricating Oil Distillates

The principle of dewaxing lubricating oil distil-lates is based on the different crystallization tem-peratures of straight-chain and weakly branchedparaffins and the oil phase. The wax-containing

30 Waxes

Figure 6. Dewaxing of lubricating oil distillatesa) Scraping chiller; b) Cooler; c) Vacuum rotating filter; d) Solvent recovery

solvent-neutral oils (i.e., the raffinates from sol-vent refining) are mixed with suitable solventssuch as propane, naphtha, chlorohydrocarbons,ketones, or (most frequently) a toluene –methylethyl ketone mixture. The oil – solvent mixtureis subsequently warmed to obtain a homoge-neous solution and then cooled continuously inscraping chillers to obtain the wax crystals ina loose suspension. In the subsequent filtration,crystallized wax is separated in vacuum rotaryfilters, and washed with fresh solvent; the low-wax solvent-neutral oil is then freed from thesolvent by distillation. The solvent-containingwax is either separated from the solvent by dis-tillation if it is to be obtained as such or feddirectly into the deoiling process for productionof hard waxes.

Process conditions are controlled in such awax that high throughput rates (i.e., short filtra-tion times) and as low an oil content of the slackwaxes as possible are achieved [88].

The selectivity of the dewaxing process iscontrolled by the cooling temperature in thescraping chiller and by the oil – solvent ratio.For common lubricating oil fractions the cool-ing temperature is between −50 and −20 ◦C atoil yields of 65 – 85%. The most important pro-cess parameter is the targeted pour point of thedewaxed oil. Figure 6 shows a typical dewaxingprocess.

In dewaxing, all hydrocarbons with crystal-lization temperatures above the chosen cool-

ing temperature are removed. n-Paraffins arethus almost completely separated, along witha suitable fraction of the long-chain, weaklybranched isoparaffins. Even under optimum fil-tration and washing conditions, impurities con-sisting of highly branched isoparaffins and cy-cloparaffins are present in slack waxes, thus giv-ing rise to their oil content [89].

A second process for producing lubricatingoils with the required low-temperature proper-ties is catalytic dewaxing. n-Paraffins are pref-erentially cracked on zeolite catalysts to givelow molar mass hydrocarbons. Wax thus can-not be obtained from this process. Catalytic de-waxing is said to be very selective in the caseof heavy distillates, whereas in light distillatesthe branched paraffins also react (loss of yield).Since no solvents are used in this process it doesnot require solvent recovery and is therefore en-vironmentally friendly [90].

4.2.3.2. Deoiling Slack Waxes

Refining slackwaxes begins with deoiling to ob-tain harder, higher-value products (hard waxes).The two main processes are solvent and sweatdeoiling. The oils produced as byproducts,which contain a higher or lower proportion ofsoft waxes, are known as foot oils or soft waxes,depending on the consistency and the processused.

Waxes 31

Solvent deoiling is themost commonly usedprocess, involving one of three possible tech-niques: pulping, crystallization, or spray deoil-ing. Starting materials for all deoiling processesare either molten slack waxes (if deoiling is car-ried out in a location other than that of slackwax production) or slack wax – solvent mix-tures, formed in dewaxing lubricating oil dis-tillates (see Table 12).

Slack waxes from spindle oils to heavy ma-chine oils, and to some extent petroleum as well(see Section 4.3), can be deoiled by the threesolvent deoiling methods. The yields of deoiledslack waxes depend on their origin, the processused, and the degree of deoiling. Yields are bet-ween 80% for spindle oil distillates and ca. 60%for heavy machine oil distillates, based on theslack wax used.

Pulping Process. The inhomogeneous mix-ture of crystallized wax, oil, and solvent is di-luted or repulped by addition of the same sol-vent or a solventmixture (normally by using partof the wash filtrates produced later). The oils,soft waxes, and part of the low molar mass hardwaxes thus dissolve. The pulp is cooled withstirring in scraping chillers, and the temperatureis adjusted to that necessary for the desired de-gree of deoiling. Hard waxes, which are partlyundissolved and have partly recrystallized, areremoved on vacuum rotary filters and washedwith solvent; the solvent is subsequently dis-tilled off.

The quality of the hard waxes produced isdetermined by the deoiling temperature and thequantity of solvent used. With a 1,2-dichloro-ethane –methylene chloride mixture as solvent(Edeleanu Process), for example, typical deoil-ing temperatures are −10 ◦C for slack waxesfrom heavy spindle oil, −5 ◦C for those froma light machine oil, and +15 ◦C for those frommedium to heavy machine oil.

Crystallization Process. The molten slackwax or solvent-containing wax crystallizatefrom the dewaxing process is dissolved com-pletely, or almost completely, in solvents bywarming, and the mixture is cooled to a giventemperature in one or several steps, dependingon the desired degree of deoiling. The tempera-ture is chosen such that only the hard wax crys-

tallizes. The crystallizate is filtered and washed,and the solvent is removed by distillation.

In both the pulping and the crystallizationprocesses, technical problems arise in attempt-ing to produce readily filterable hard wax crys-tals that allow high filtration capacity with goodwashability. These problems can be solved invarious ways: e.g., through the nature and quan-tity of the solvent; the construction of the crys-tallization apparatus; successive solvent dosingduring cooling; addition of cold solvent to thewarm, intensively stirred wax – solvent mixture[91]; and use of filter aids [88]. Other improve-ments have been brought about by the develop-ment of economical cooling and filtration sy-sems [92].

Spray Deoiling. Molten slack wax issprayed into a countercurrent of cold air, andprecipitated wax particles are washed with sol-vents inmixerswhereby the oil is largely diluted.After settling the washed wax particles are cen-trifuged and washed, and the adhering solventis distilled off. The washing temperature is bet-ween 5 and 15 ◦C [93].

Sweat Deoiling. Molten slack wax ischarged to chambers equipped with sieve bot-toms and heating coils. The wax is solidi-fied by cooling and then warmed very slowly.The oil – and, at higher temperatures, the low-melting soft waxes, as well – sweat from thewaxblock and run through the perforated bottom(run-off slack wax). At the end of the processthe remaining hard wax is melted to remove itfrom the sweating chamber.

No new plants are being built for this classi-cal deoiling process because of the low selectiv-ity (poor yields of hard wax), time-consumingwarmup, need to use a batch process, and inap-plicability of the method to strongly oil-bindingslack waxes from medium and heavy machineoil distillates. In existing plants an attempt isbeing made to improve yields of hard waxes bypartially recycling the run-off slack [94].

Overview of Processes inCurrentUse. Thedeoiling processes most widely used in industryare listed in Table 12.

Of the deoiling plants operating in Germany,half employ solvent deoiling (using mainly theEdeleanu dichloroethane –methylene chloride

32 Waxes

Table 12. Processes for deoiling slack waxes [95]

Company Process Solvent Starting material

Exxon crystallization process (Dilchilldeoiling)

methyl ethyl ketone –methyl isobutylketone (or – toluene)

slack wax – solvent mixture∗

Edeleanu pulping process (Di-Me deoiling) 1,2-dichloroethane –methylene chloride slack wax – solvent mixture∗Edeleanu spray deoiling 1,2-dichloroethane slack waxTexaco pulp process (one- and two-step) benzene (or benzene – toluene) slack wax – solvent mixture∗Texaco crystallization process (wax

fractionation)methyl ethyl ketone slack wax and slack wax – solvent

mixture∗Union oil crystallization process water-saturated methyl isobutyl ketone slack wax

sweat deoiling slack wax

∗ From the dewaxing step.

process) and the others use spray deoiling (Ede-leanu) and sweat deoiling.

In the United States, more than 90% ofthe existing plants use solvent deoiling. Themost common solvents are methyl ethyl ketoneand methyl ethyl ketone – aromatics mixtures.Propane and methyl isobutyl ketone are alsoused.

4.2.3.3. Refining Deoiled Slack Waxes

Deoiled slack waxes whose maximum oil con-tent is 0.5%, 0.5 – 1.5%, or 2 – 3%, dependingon the use anticipated, still contain impuritiesand are mostly dark in color. To improve theirquality they are purified further by adsorbents(decolorizing) or chemically. The choice of re-fining process depends on economic factors andthe quality of raffinates required. Process com-binations have also been introduced into indus-try. The preferred process in new plants is hy-drotreating.

Refining with adsorbents (decolorizing)(→Lubricants andRelated Products) can be per-formed batchwise, semicontinuously, or contin-uously. The decolorizing temperature can be bet-ween 70 and 120 ◦C, depending on starting ma-terial.

In batch decolorizing, molten wax is stirredin heated vessels with decolorizing clays (chem-ically activated clays, bentonite, bauxite) in oneormore steps until the desired lightening of coloris achieved. The used clay is removed in heatedfilter presses and thermally regenerated.

Percolation Process. In the percolation pro-cess, molten wax flows downward through atower containing 10 – 50 t of decolorizing clay,

depending on plant size. After the clay has beenexhausted, the wax flow is stopped; wax adher-ing to the clay is washed off with naphtha; theremaining solvent is driven off with steam; andthe clay is burnt off in a separate tower, activated,and reused [96].

The semicontinuous decolorizing process op-erateswith two or three percolator towers, whichare in different phases of the adsorption cy-cle. While the adsorption process occurs in onetower, in the others the used decolorizing clay iswashed, stripped, removed for regeneration, andreplaced by new activated clay.

In the continuous process the regeneratedclay flows downward through the adsorptiontower in countercurrent to the molten wax. Theloaded clay passes in the form of a sludge to awashing tower where adsorbed wax is extractedwith naphtha and then to a second tower wherenaphtha is driven offwich steam.The clay is thenburnt off in a rotary kiln, activated, and fed backto the top of the adsorption tower after cooling[97].

The decolorized waxes are then stripped withsteam in packed columns at 110 – 170 ◦C, ei-ther under vacuum (0.6 – 1.6 kPa), under re-duced pressure (up to 80 kPa), or under pressure(up to 0.8MPa) to remove odorous substances.The weight ratio of steam to wax varies between0.5 : 1 and 1 : 1 at detention times up to 15min.To improve the aging resistance of the waxes,apparatus with aluminum or stainless steel lin-ing is recommended for stripping [98].

Depending on the starting material, the waxqualities listed in Table 13 are obtained by thedecolorizing process.

The quantity of decolorizing clay requireddepends on the origin and desired quality of

Waxes 33

the waxes and is normally between 2 and 4%.Refining with adsorbents removes dark sub-stances, condensed alkyl aromatics, compoundscontaining hetero atoms, and metallic impuri-ties.

Nevertheless, producing fully refined waxesfulfilling all of the purity requirements (see Sec-tion 4.2.5) by adsorption is possible only usingextremely complex processes (multistage de-colorizing) and large quantities of decolorizingclay, particularly in the case of the high molarmass wax fractions. To produce these types ofhigh-purity waxes, chemical refining is the pro-cess of choice.

Table 13.Wax qualities obtained by decolorization

Starting material Oil content, % Decolorized product

Slack wax >3 scale waxDeoiled slack wax 1.5 – 3 semirefined waxDeoiled slack wax 1.5 (max.) filtered wax

[64742-43-4]

Chemical Refining. Concentrated sulfuricacid, fuming sulfuric acid (oleum), or hydrogenis used as chemical refining agent.

Sulfuric acid refining can only be carried outbatchwise because of the slow separation ofthe wax and acid sludge phases. Molten wax ismixed with sulfuric acid at 80 – 140 ◦C for sometime (between 0.5 and 2 h, depending on the ori-gin of the wax). After separation of the heav-ier acid sludge, the wax is washed with alkali,treated with decolorizing clay, and stripped withsteam to remove the last residues of impuritiesand odorous substances.

All compounds that react chemically with theaggressive acid, such as unsaturated aliphaticand aromatic hydrocarbons, metal compounds,and those containing hetero atoms, are removedby sulfuric acid refining. Labile quaternary car-bon atoms are also attacked, with bond cleavageand formation of aliphatic sulfonic acids.

The process can be optimized by variationof the number of reaction steps, degree of acid-ity, reaction temperature, ratio of wax to acidused, reaction time, and intensity of mixing. Thehigher the average molar mass of the wax frac-tion, the slower is the separation between thewax and the acid sludge phase.

The process has several disadvantages suchas the necessity for batch operations, poor yields

of raffinates, formation of polluting byproducts,and waste gas and corrosion problems. For thesereasons, almost all new plants are based on hy-drotreating.

Hydrotreating (Fig. 7). Deoiled slack wax isheated to the required temperature together withfresh and recycyled hydrogen in the preheater(b) and passed over a sulfur-resistant fixed-bedcatalyst (c). After cooling, the reaction mixtureand hydrogen are separated in the high-pres-sure gas separator (d), and hydrogen is recycledinto the process. After depressurizing in the low-pressure gas separator (e), the wax passes intothe stripper (f), where all the light crack prod-ucts, odorous substances, and reaction gases arestripped off completely with compressed steamunder vacuum. The wax is subsequently driedwith nitrogen (g). A combination of metals fromgroups 6 and 10 on an inert carrier is gener-ally used as the catalyst (e.g., nickel – tungstenor nickel –molybdenum on neutral aluminumoxide).

Reaction conditions can vary within widelimits, depending on starting material, degreeof refining required, and composition of thecatalyst – e.g., between 200 and 350 ◦C, 20 and200 bar, and throughputs of 0.2 – 0.81 L of waxper liter of catalyst and hour. Yields are almost100%, based on starting wax [99], [100].

Under the severe reaction conditions ofhigh-pressure hydrogenation, all aromatic com-pounds are hydrogenated to naphthenes, all darksubstances are decomposed, and all sulfur andnitrogen atoms are removed as hydrogen sul-fide and ammonia. Metallic impurities becomebonded to the catalyst.

The process can be used to refine all classesof wax (paraffin waxes, intermediate waxes, andmicrowaxes).

4.2.4. Storage, Transportation, CommercialForms, and Producers

Paraffin waxes are transported in liquid form(molten) in road tank trucks, rail tankers, orliquid containers. Solid waxes are marketed inslabs in small and large cartons and sacks, andas pastilles, flakes, and powder in sacks or bigbags. They are also supplied in fiberboard andsteel drums and in molded cartons.

34 Waxes

Figure 7. Two-step hydrotreating of waxesa) Deaerator; b) Preheater; c) Reactors; d) High-pressure gas separator; e) Low-pressure gas separator; f) Stripper; g) Vacuumdryer; h) Filter

Even refined waxes can become yellow ordecompose to form odorous substances on pro-longed heating, particularly in the presence ofair or catalytically active metals. On storage,transportation, and processing, the waxes aretherefore preferably heated in vessels, fittedwithwarm water equipment, and the containers andpiping arewell insulated. Storage tanks are oftenblanketed with inert gas. In some cases, antioxi-dants are added to fully refined waxes in quanti-ties up to 0.01%. Deoiled and refined waxes aredifferentiated according to melting range (gra-dation). Some examples of commercial waxesare given below.

Europe United States

(Melting gradation in ◦C) (AMP∗ gradation in ◦F)48/50 120 – 12250/52 122 – 12452/54 126 – 13054/56 130 – 13256/58 132 – 13458/60 134 – 13660/62 136 – 14062/64 143 – 145

∗AMP=American Paraffin Wax

Important producers of paraffin waxes in-clude: Shell (United Kingdom, United States,Germany), Texaco (United States), BP (France,Germany), Mobil (United States, United King-dom), Lutzendorf (Germany), DEA (Germany),

Wintershall (Germany), CFP (France), Total(France), Empetrol (Spain), Petrogal (Portugal).In Germany, for example, the companies eitherprocess the waxes to refined waxes (DEA, Win-tershall) themselves or sell them to wax refiner-ies (H.O. Schumann).Waxes are sold mostly byDEA, H.O. Schumann, and Wintershall.

4.2.5. Quality Specifications and Analysis

The quality specifications of paraffin waxes aredetermined mainly by their uses. They are dif-ferentiated in terms of physical characteristics,chemical composition, purity requirements, andapplication properties. The following standardspecifications have been published for waxesthat come in contact with foods:

1) Food andDrugAdministration:Code of Fed-eral Regulations (United States) [101]

2) FAO Food and Nutrition Paper (EC) [102]3) Specifications of the European Wax Federa-

tion (EC) [86]4) Kunststoffe im Lebensmittelverkehr (Plas-

tics which come into contact with foods,Recommendations of the German BGA)[103]

5) Hydrocarbons in Food Regulations (UnitedKingdom) [104]

For waxes in cosmetic and pharmaceuticalpreparations, standards are found in the fol-lowing publications: DAB (Germany), Codes

Waxes 35

Francais (CF) (France), B.P. (United King-dom), ISCIMonograph (Japan), U.S. Formulary(United States), and CTFA International Cos-metics Ingredient Dictionary (United States).

The most common test standards for the de-termination of physical data are summarized inTable 14. The most important test standards fordetermining chemical composition can be foundin Table 15. Some examples of important testmethods for determination of the purity ofwaxesare listed below:

Fluorescence 49th communicationof the BGA

Alkali- or acid-reacting substances DAB, B.P., U.S.P.Behavior toward sulfuric acid DAB, BGA, CF,

U.S.P.Presence of polycyclic aromatics DAB, BGA, FDA

Table 14. Standardized test methods for determination of physicaldata

Determination Method

mp (cooling curve), ◦C DIN ISO3841 ASTM D87Congealing point, ◦C DIN ISO2207 ASTM D938Needle penetration,0.1mm

DIN51 579 ASTM D1321

Oil content, % DIN ISO2908 ASTM D721Viscosity, mm2/s DIN 51 562/T1 ASTM D445Density, kg/m3 DIN51 757 ASTM D1298Refractive index DIN 51 423/T2 ASTM D1747ColorASTM color index DIN ISO2049 ASTM D1500Lovibond color IP∗ 17Saybolt color DIN 51 411 ASTM D156

Odor ASTM D1833

∗ IP = Institute of Petroleum, United Kingdom.

Table 15. Standardized test methods for determining chemical com-position

Determination Method

Ash content, % DIN EN7 ASTM D482Sulfur content, ppm DIN 51 400/T7 ASTM D2622Heavy metal content (As,Cr, Cd, Pb), ppm

XRF a analysis

C-number distribution DGF b M-V9 EWF c methodC-number max. DGF b M-V9 IP d draftn-Paraffin content, % DGF b M-V9 ASTM draft

a XRF=X-ray fluorescence spectromety.b DGF Einheitsmethoden der Deutschen Gesellschaft furFettwissenschaften [Standardized methods of the DeutscheGesellschaft fur Fettwissenschaften (German Fat association)].c EWF=European Wax Federation.d IP = Institute of Petroleum, United Kingdom.

A looseleaf collection of national and inter-national purity regulations for waxes has beenissued by the European Wax Federation and issupplemented continuously [105].

Some of the methods cited are basic testprocedures for gaining accreditation accord-ing to the series of standards DINEN45 000and the regulations of the Deutsche Akkred-itierungsstelle Mineralol GmbH (DASMIN).With accreditation, DASMIN recognizes thecompetence of testing laboratories to test thequality of waxes.

The determination of application propertiesis described mostly in in-house methods and in-cludes, for example, oil binding properties, con-traction, polishability, abrasion resistance, sol-vent retention, blocking point, steam permeabil-ity, flexibility, extendability, and color stability.Melting and congealing characteristics and la-tent heats are determined by using differentialthermoanalysis [standardized DGF method M-III 14 (1989); ASTM-D4419-84].

Special analytical methods have been devel-oped to determine the chemical composition ofparaffin waxes.

The content of n- and isoparaffins is de-termined most accurately by using computer-supported high-temperature gas chromatogra-phy [106], [107]. Here, the DGF methodM-V9(1988) is the universal standard. This method al-lows not only sufficient separation of the n- andisoparaffin signals (depending on the columnlength and injector temperature, waxes up to aC-number of ca. 80 can be determined quantita-tively), but also determination of the C-numberdistribution and position of the C-number max-imum.

The determination of n- and isoparaffins us-ing urea adduct formation and molecular sieveadsorption has been shown to be a nonquantita-tive separation method. Only enrichment of then-paraffins results. This, however, clearly dimin-ishes with increasing molar mass and complex-ity of the waxes investigated [108].

For individual analysis of the different, paraf-finic substance groups, coupled GC–MS andGC–NMR methods have been described [85],[109].

The determination of individual polycyclicaromatic hydrocarbons in waxes is currentlypossible into the µg/kg (ppb) region [85], [110],[111].

36 Waxes

Table 16. Uses of paraffin waxes worldwide, 1992 (in 1000 t)

Use United States Asia Western Europe of which Germany

Candles and decorativemodeling

100 450 230 55

Paper, cardboard, wood 450 220 120 25Hot melt adhesives 60 20 20 10Rubber and cables 40 20 30 10Industrial products 50 30 50Pharmaceuticals andcosmetics

20 30 10

Other uses 130 130 40 50∗∗ Including industrial products, pharmaceuticals and cosmetics

4.2.6. Uses

Paraffin waxes are used in very different fieldsof industry. They not only are used as such,but are also important components of wax com-pounds (i.e., mixtures of paraffin waxes withotherwaxes, plastics, resins, etc.). The consump-tion figures listed in Table 16 cover the most im-portant areas of use.

Slack waxes that are not processed further torefined waxes or subjected to dehydrogenationor cracking processes – for example, to give α-olefins (→Hydrocarbons, Chap. 2.1.2.1.) – areused mostly in the wood and mineral oil pro-cessing industries.

Wood processing requires slack waxes, eithermolten or in the form of emulsions, mainly forthe production of particle board and fiberboard.In the United States the production of artificiallogs for barbecues and fires is also important.

In the mineral oil processing industry, slackwaxes are used to produce petroleum jellies,wire-drawing agents, lubricants, spray emul-sions, and anticorrosives.

In addition to wax industry products with awide area of applications, slack waxes are alsoused to produce chlorinated paraffins (→Chlo-rinated Hydrocarbons, Chap. 7.3.), papers andcardboards for technical uses, cable cover-ings, solid anticorrosives, fire lighters, and waxtorches.

Soft waxes have only a limited market inthe production of industrial petroleum jelliesand emulsions (wood and building industry),torches, and fire lighters and for condition-ing fertilizers. The deoiling of soft waxes

gives highly plastic and extendable products(isowaxes).

RefinedWaxes [ScaleWaxes, Filtered (De-colorized), Semi- and Fully Refined Waxes].In Germany the producers of candles and waxgoods (pictures, sculptures, ornaments) are themain users of refined waxes, which can be pro-cessed by all common production methods forcandles (molding, drawing, extrusion molding,and powder compressing). In terms of quantity,paraffin wax is the most important raw materialfor the candle industry.

The second most important consumer of re-fined waxes is the wax industry, which requiresparaffin waxes as an important raw material forcompounding wax products for the most widelyvarying applications.

In the paper, cardboard, and packaging indus-tries, refinedwaxes are used in the form of emul-sions for paper sizing as antifoams in the produc-tion of paper, cardboard, and corrugated card-board; and as impregnating and coating waxesfor paper and packaging materials [112].

The viscosity of heat-sealwaxes and hot-meltadhesives is adjusted with paraffin waxes. Inrubber articles, tires, and solid cable coverings,waxes act as external lubricants/plasticizers,mold-release agents, and rapidly migrating pro-tection agents of rubber against sunlight. Theyare therefore used predominantly for staticallystressed rubber articles (profiles, gaskets, lin-ings, and cable jackets).

Other important applications are in cleansersand polishes (→Cleansing Agents, Chap. 1.4.;→Shoe Polishes, Chap. 3.1.); cosmetics(creams, ointments, lipsticks); matches; plastics

Waxes 37

(external lubricants); office papers; and water-proof textiles (dry impregnation).

In the United States, by far the greatestproportion of refined waxes is used for paperand cardboard finishing, mainly for deep-freezepackaging and wrapping for meat, candy, andflowers; paper cups; yogurt and soft cheese pots;and corrugated cardboard [113].

In the former Soviet Union, refined waxesstill play an important role in the production ofsynthetic fatty acids via catalytic oxidation pro-cesses (→Fatty Acids, Chap. 4.1.). Fatty acidsare mainly used in the soap industry.

4.3. Microcrystalline Waxes(Microwaxes)

4.3.1. Chemical Composition and GeneralProperties

Like paraffin waxes, microcrystalline waxesconsist of a mixture of saturated hydrocarbonsthat are predominantly solid at room tempera-ture, such as n- and isoalkanes, naphthenes, andalkyl- and naphthene-substituted aromatics. Un-like paraffin waxes, isoparaffins and naphtheniccompounds predominate here. The microcrys-talline structure can be explained by the pres-ence of strongly branched isoparaffins and naph-thenes, which inhibit crystallization.

General Physical Properties. Microcrys-talline waxes are insoluble in water and mostorganic solvents at room temperature. They aremoderately to readily soluble in solvents such aschlorohydrocarbons, benzene, toluene, xylene,solvent naphtha, and turpentine oil, especiallyat elevated temperature. Solubility decreasesmarkedly as molar mass increases. Solventsand oils are retained very strongly by micro-crystalline waxes and therefore evaporate veryslowly. The quality of some consumer products,such as petroleum jellies or floor and shoe pol-ish, is determined by this retention capacity ofmicrowaxes.

Chemical Properties. Microwaxes aremorereactive than paraffin waxes because of thehigher concentration of complex branched hy-drocarbons with tertiary and quaternary carbonatoms. These C−C bonds are not very thermally

stable (i.e. thewaxes darken and resinify) onpro-longed heating. In addition, they form black tar-like substances on contactwith aggressive chem-icals such as concentrated sulfuric acid or anti-mony pentachloride.

The reaction of microwaxes with oxygen atelevated temperature and in the presence of cat-alytically acting heavy-metal soaps is used forthe production of oxidized microwaxes.

4.3.2. Division into Product Classes

Depending on the degree of refining, mi-crowaxes are divided into the following classes:

1) Bright stock slack waxes (petrolatum)2) Plastic microwaxes3) Hard microwaxes

Table 17 and Figure 8 show some typicalcharacteristics of microwaxes.

Figure 8. Variation of needle penetration with temperaturefor various microwaxes compared with a paraffin waxa) Bright stock slack wax; b) Plastic microwax; c) Hardmicrowax; d) Paraffin wax 60/62

Bright stock slack waxes (petrolatum)constitute themost complexmixture in the groupof microcrystalline waxes. The molar massesof the hydrocarbons can be between 320 and1200 g/mol. The n-alkane content is seldom>10%. Asphaltenes, hydrocarbon resins, andsulfur, nitrogen, and oxygen compounds arepresent as impurities. The oil content is nor-mally between 3 and 15%, but it can be ashigh as 30%. Bright stock slack waxes are white

38 Waxes

Table 17. Typical physical characteristics of microwaxes

Characteristic Bright stock slack wax Plastic microwax Hard microwax

Congealing point, ◦C 67 72 75 87Drop point, ◦C 76 78 80 91Needle penetration, 0.1mmat 25 ◦C 65 30 28 8at 40 ◦C 140 85 66 18

Oil content, % 3.8 1.8 1.6 0.4Viscosity (at 100 ◦C), mm2/s 18.7 15.7 14.9 16.2Refractive index (at 100 ◦C) 1.4505 1.4458 1.4412 1.4410Color dark brown yellow white white

or yellow to dark brown, greasy to softly plas-tic, unctuous, smooth products with a typicalodor, depending on the refining process. Theyhave a very good oil-staining capacity, and somegrades have a pronounced stickiness. The con-gealing points are between 60 and 75 ◦C; thedrop points between 62 and 80 ◦C; and the hard-ness (needle penetration at 25 ◦C), between 45and 160, depending on the oil content. Theviscosities (10 – 30mm2/s at 100 ◦C), densities(810 – 860 kg/m3 at 80 ◦C), and flash points(290 – 320 ◦C) are clearly higher than those ofparaffin waxes.

Plastic Microwaxes. In plastic microwaxesthe highermolarmass n- and isoparaffins and theweakly branched isoparaffins and naphthenesare enriched compared with the petrolatum fromwhich they are obtained by deoiling. Molarmasses are between 450 and 1200 g/mol. Then-paraffin content can be as high as 40%. De-pending on the degree of refining the impuritiespresent in petrolatum are removed completelyor to a great extent. The oil content is usuallybetween 1.5 and 5%.

The plastic microwaxes, although relativelyhard, are definitely plastic, readilymoldable, andkneadable. The plasticity is due to the presenceof very long carbon chains in the n-paraffinsand terminally branched isoparaffins. Thewaxesfeel dry to slightly adhesive, and are sold aswhite to brown products. Congealing points are65 – 80 ◦C, and the hardness (needle penetrationat 25 ◦C) is 10 to 60. Highly refinedmicrowaxesare odorless and tasteless.

Hard microwaxes also essentially consist ofhigh molar mass alkanes (predominantly n-alkanes and isoalkanes with short side chainsstatistically distributed over the main carbon

chain) and naphthenes. Average molar massesare between ca. 500 and 1200 g/mol. Thus, forexample, a refined, hard microwax of NorthAmerican origin contains 89% nonpolar hydro-carbons (n-, iso-, and cycloparaffins) and hasan average C-number of 48 [85]. The n-paraffincontent can be as high as 70%.

The extremely microcrystalline to almostamorphous structure of hard microwaxes is as-sociatedwith the formation of supercooledmeltsduring the setting process.

The waxes are tough and hard, barely ductileand weakly adhesive. Depending on the degreeof refining, hard white, yellow and brown mi-crowaxes are on the market, the white to paleyellow products being of highest purity. Theysolidify between 80 and 94 ◦C. The needle pen-etration at 25 ◦C is <10. The hardness of hardwaxes decreases only slightly with temperatureuntil close to their softening point (Fig. 8).

4.3.3. Occurrence of Raw Materials andProcessing

Like paraffin waxes, microwaxes are compo-nents of crude petroleum. Because of their highmolar masses, and thus high boiling range andpoor solubility, they either are enriched in thevacuum residues (short residues) from lubricat-ing oil distillation (residual waxes) or separateduring the transportation and storage of crudeoils (settling waxes). Settling waxes form pastyto solid deposits on the walls of pump tubesand pipelines and on the bottom of storage tanks(pipe and tank bottom waxes). Vacuum residuesand pipe and tank bottom waxes are the raw ma-terials for recovery of microcrystalline waxes.

Waxes 39

Figure 9. Process schematic for the production of microwaxes

Figure 9 shows schematically the processsteps involved in the production of microcrys-talline waxes.

In the United States, the most importantproducer country for microwaxes, the vacuumresidues are subjected to deasphalting, refining,and dewaxing to produce high-value bright stockoils. Bright stock slack waxes (petrolatum) areproduced in the process as economically im-portant byproducts. However, only in the rarestcases they are processed further to microwaxesin the lube oil refineries themselves. Petrolatumis either marketed directly or used, for exam-ple, for the production of petroleum jellies. Forfurther processing it is sold to companies spe-cializing in the production of microwaxes. Thesame companies also process settlingwaxes pur-chased from oil companies.

Deasphalting is the first step in the pro-cessing of tank bottom waxes, pipe waxes, andresidues, which have been freed from water,mechanical impurities, and volatile components.When propane is used as the deasphalting agent,considerable proportions of resins, polycyclicaromatics, and nitrogen and sulfur compoundsare removed. To improve the selectivity with aslow a propane throughput as possible, rotatingdisk contactors are now used instead of packedor sieve bottom columns (→Lubricants and Re-lated Products). In addition, the extraction pro-cess is carried out in two steps [114].

Deasphalting of residues is followed by sol-vent extraction and dewaxing. The productsformed here are the bright stock oils and brightstock slack waxes (petrolatum).

Deoiling. The crude and bright stock slackwaxes thus obtained are deoiled by fractional

40 Waxes

crystallization (see page 32) if they are to beprocessed further to microwaxes. Preferred sol-vents are methyl ethyl ketone and methyl iso-butyl ketone, often as a mixture with benzene ortoluene. Propane and naphtha, frequently usedearlier, have become less important because oftheir low selectivity.

The crudewaxes (deasphalted settlingwaxes)and bright stock slack waxes are mixed eithermolten or as a pulp (if the deoiling is to fol-low immediately after dewaxing the brightstockoils), without isolation of the slack wax withfresh, warm solvents and warmed until onlythe less soluble (high molar mass) waxes re-main undissolved. These waxes are then fil-tered, washed, and freed from solvent (hard mi-crowax fraction). To obtain plastic microwaxesthe filtrate is cooled further. The properties ofreprecipitated and refiltered waxes are deter-mined by the filter temperature. The low molarmass, very plastic, and soft microwax foot oils[64742-67-2] remains in the filtrate. If the hardmicrowaxes are not extracted, a one-step crystal-lization process is sufficient for obtaining plasticmicrowaxes.

Deoiled microwaxes are still dark yellow todark brown and not completely odorless, so theymust subsequently be refined to satisfy a broadapplication range.

Refining. Refining is carried out either withadsorbents (decolorizing) or with hydrogen (hy-drotreating). Refining with concentrated sulfu-ric acid, which is possible in principle, has notbecome important economically because of thehigh loss of material.

For refining microwaxes with adsorbents,the same process principles apply as for decol-orizing paraffin wax (see page 33). Since mi-crowaxes are more difficult to decolorize thanparaffin waxes, countercurrent percolation isused predominantly. Here, the wax melt contin-ually comes in contact with fresh decolorizingclay [115]. Bauxite is also frequently used as adecolorizing agent.

Hydrotreating is carried out as described forparaffin waxes, in one or two steps in reactorspackedwith sulfur-resistant, heavy-metal-dopedmixed catalysts (see page 34). Reaction condi-tions are ca. 350 ◦C and 150 bar, depending onthe properties of the catalyst, at a space veloc-ity of 0.3 L of wax per liter of catalyst and hour.

Hydrogenated products are treated further by ad-sorptive decolorizing or stripping to completelyremove odorous materials and volatile compo-nents.

In the United States, a whole range of mi-crowaxes is produced according to the processeddescribed. Products differ in their congealingpoint, drop point, hardness, viscosity, and color.They are sold in the liquid (molten) form and assolids in the form of slabs, pellets, and powder.

4.3.4. Commercial Products and Producers

Table 18 shows the most important producers ofmicrowaxes in the United States and the corre-sponding commercial products.

Table 18. Producers of microwaxes in the United States and com-mercial products

Producer Production site Commercial products

Bareco Div. ofPetrolite Corp.

Kilgore, Tex.Barnsdale, Okla.

Petrolite Crown, BeSquare, Mekon,Stawax, Cardis,Victory, Ultraflex

Mobil Oil Co. Beaumont, Tex.Paulsboro, N.J.

Wax Rex, Mobilwax

Quaker State OilRef. Corp.

Emlenton, Pa.Farmers Valley, Pa.Newell, W.V.

Microwax, Superflex

Shell Oil Co. Deer Park, Tex.Wood River, Ill.

Shellwax

Sun Oil Co. Tulsa, Okla. Sunoco Wax, SunoliteWitco Chem. Corp. Bradford, Pa. Multiwax

In Europe, H.O. Schumann (Germany), Mo-bil (United Kingdom), CFR/Total, Mobil, andBP (France), Shell and Witco (Holland), Repsol(Spain), and Petrogal (Portugal), for example,produce microwaxes by deoiling bright stockslack waxes.

4.3.5. Quality Specifications and Analysis

The quality required depends on the industrialuse. In principle, the specifications given forparaffin waxes apply here.

Basic product specifications can be found inthe following sources:

1) Food andDrugAdministration;Code of Fed-eral Regulations (United States) [101]

2) European Wax Federation (EC) [86]

Waxes 41

3) Kunststoffe im Lebensmittelverkehr;Empfehlungen des Bundesgesundheit-samtes Deutschland (Plastics for Contactwith Foods; Recommendations of the Fed-eral Health Authority, Germany) [103]

The EWF specifies microwaxes for use inpackaging materials for foods, as shown in Ta-ble 19.

Table 19.Microwaxes for food packaging

Determination Method Specification

Congealing point, ◦C DIN ISO2207ASTM D938

65 (min.)

Needle penetration, 0.1mm DIN51 579 ASTMD1321

<50

Extractables, % ASTM D721 2.5 (max.)Viscosity at 100 ◦C, mm2/s DIN 51 562/T1

ASTM D445>13

Density at 100 ◦C, kg/m3 DIN51 757 ASTMD1298

790 – 840

Refractive index at 100 ◦C DIN51 423/T2ASTM D1747

1.430 – 1.450

Color DIN ISO2049ASTM D1500

2.0 (max.)

Odor ASTM D1833 weakAsh content, % DIN EN7 ASTM

D482<0.05

Sulfur content, ppm DIN 51 400/T7ASTM D2622

<300 a

<4000 b

Heavy-metal content (As,Cd, Cr, Pb), ppm

XRF analysis c <1

C-number distribution ofn-paraffins

DGF M-V9 (88)IP 372-85

23 – 85

Non-n-paraffin content, % DGF M-V9 (88) 25 – 75UV-Absorption $ 172.886 FDAat 280 – 289mm 0.15 (max.)at 290 – 299mm 0.12 (max.)at 300 – 359mm 0.08 (max.)at 360 – 400mm 0.02 (max.)

a Hydrotreated.b Refined with sulfuric acid/decolorizing clay.c XRF=X-ray fluorescence spectrometry.

In the use of microwaxes to produce foodpackaging materials, and cheese and chewinggum waxes, purity and physiological nontoxic-ity are particularly important. For microwaxesthe absence of specific polycyclic aromatics isrequired. These substances can occur as impu-rities in insufficiently refined waxes, and someof them have been found to be carcinogenic.Polycyclic aromatics can be detected by UV ex-tinction after a special enrichment process (de-tection limit in microwaxes 10−7 g per gram ofwax substance). Microwaxes have been shownto be toxicologically and physiologically harm-less in extensive animal experiments, when UV

adsorption values specified according to test reg-ulations of the FDA [101] and theBGA [103] arenot exceeded.

The physical characteristics of microwaxesare determined according to the same stan-dardized methods used for paraffin waxes (seeTable 14). In addition, some special analyticalmethods have been introduced, for example:

Determination of gloss andgloss stability

ASTMD2895

Determination of blocking point ASTMD3234Determination of sealingstability

TAPPI [Tech. Assoc. Pulp &Paper Ind. (United States)]T 642

Determination of water vaporpermeability

ASTMD988

DIN 53 413Determination of specificpenetration resistance

DIN 53 482

Determination of dielectric lossfactor

DIN 53 483

Oil-binding capacity, adhesiveness, and lightstability are additional quality factors.

4.3.6. Uses

Bright Stock Slack Waxes. The greatestproportion of bright stock slack waxes is pro-cessed further to microwaxes. Important con-sumers are the wax-producing industry, whichrequires crude and refined bright stock slackwaxes for compounding adhesive waxes, cheesewaxes, chewing gum base, cosmetic prepara-tions, sealing and cable compounds, impregnat-ing insulating materials and pesticide sprays;and the mineral oil processing industry, whichproduces anticorrosives, cavity and underfloorprotection agents for motor vehicles, and petro-leum jellies. Other uses include the productionof artificial fire logs and oxidized petrolatum,which is suitable for the formulation of rustpreventives.

Oxidized petrolatum and microwaxes aremainly produced industrially in the UnitedStates. Air at normal or at slight overpressureis blown through the wax, which is heated to150 – 180 ◦C until the desired degree of ox-idation is reached. Darkening of the wax isavoided by adding fresh wax to the reactionzone. Oxidized microwaxes are specified andtraded according to their melting range and de-gree of oxidation (expressed in terms of acid

42 Waxes

and saponification numbers). The acid and estergroups, which are distributed statistically overthe hydrocarbon chains, can be reacted with in-organic and organic bases to form soaps that canbe dispersed in water (emulsified waxes). Thesecompounds also impart to the oxidized waxesan excellent adhesion to metals.

Plastic Microwaxes. The main consumer ofplastic microwaxes is the wax industry. Plas-tic microwaxes are added to wax compoundsthat require either pronounced plastic or oil- andsolvent-staining properties for their industrialapplications.

Typical applications include the following:

1) Paper and cardboard coating for packagingmeat and sausage products, cereals, bread,candy, ice cream, cookies, yogurt, and frozenfood

2) External lubricant (sliding) for extrusion ofplastics

3) Formulation of cheese waxes and chewinggum bases

4) Decorative for candles, production of waxpictures and sculptures

5) Polishes and grinding agents6) Lost wax casting and dental compounds7) Foam regulators for detergents8) Protectives against crack formation in tires

and rubber articles (sun-proof waxes) [116]9) Additives for explosives and propellant ma-

terials.

Hard microwaxes have numerous applica-tions based on their highmelting points and greathardness; favorable hardness – temperature be-havior; and good solvent retention. They areused as release agents for pressing plastics andfiberboard, in the production of ceramic articlesand in molding polyurethane foam, in solvent-containing cleansing agents, in grinding and pol-ishing pastes, and flat varnishes and paints.

The Committee on Toxicity (COT) in theUnited Kingdom has recommended that onlyhard microwaxes be approved for use in the pro-duction of cheese waxes, poultry defeatheringcompounds, and chewing gum [117].

On an industrial scale, hard microwaxes areoxidized to an acid number of 30 and are usedin this form to produce emulsions (polishes andrelease agents) and as additives for paints and

coatings, printing inks, and office transfer pa-pers.

4.4. Legal Aspects

Apart from environmental effects, petroleumwaxes can be absorbed by the human organismvia foods (paraffins either are contained in themnaturally, have been added to them, or have mi-grated there from the packagingmaterials), fromchewing gum (only on swallowing or the simul-taneous consumption of fat-solubilizing choco-lates), and through the use of lipstick. To protecthuman health, national and international regula-tions and recommendations have been enactedto limit the oral consumption of waxes.

The use of waxes in packaging materials issubject ofEEC legislation [118]. In the appendixlists (lists of additives), waxes are permitted,provided that specific migration limits of 0.3mgper kilogram food for waxes treated with sulfu-ric acid or decolorizing clay and 3mg per kilo-gram for high-pressure hydrotreated waxes arenot exceeded.

Extensive literature on themigration of paraf-fins into foods has been published [119–122].

The permitted paraffins must correspond topublished specifications (see Section 4.2.5).

In Germany the addition of petroleum waxesto food and animal feed is not allowed. The useof waxes as cheese coatings and in chewing gumis controlled by supplementary regulations.

In the United Kingdom the Ministry of Agri-culture, Fisheries, and Food (MAFF) proposesa prohibition of petroleum waxes as food addi-tives in England, Scotland, and Northern Ireland[117]. Only specified microwaxes may still beadded to foods for a limited period.

In the United States, not indication has beengiven of any intention to ban paraffins in food.

4.5. Ecology

Paraffin and microcrystalline waxes are insol-uble in water and can be separated as solids,together with sludge, in oil separators andsewage treatment plants. In the German cat-alogue of substances that are hazardous towater, they are therefore listed in water haz-ard class 0 (Wassergefahrdungsklasse, WGK0).

Waxes 43

Since paraffins have a water solubility of< 1µg/L, they have no toxic effects on aquaticorganisms. Used paraffin-containing packagingmaterials can be combusted without any prob-lem in waste incineration plants. No pollutingsubstances are formed, and the high calorificvalue of the paraffins improves the energy bal-ance of the plants.

The biodegradability of petroleumwaxes sat-isfies OECD guideline 301B (1981) [123].Withthe exception of microwaxes, biodegradabili-ties of more than 60% after 28 d were mea-sured. Bacterial degradationmechanisms are de-scribed in [124]. According to this, paraffin-con-taining packaging materials can also be com-posted [125–127]. No substances that are toxicor hazardous to groundwater are formed.

The biodegradation of waxes under anaero-bic conditions (covered landfills) proceedsmuchmore slowly.

A large number of investigations have beencarried out on the recycling of used wax-containing packaging materials. The water-insoluble, hydrophobic petroleum wax tends toform particles in the paper mills and give rise toblockages in the sizing equipment [128].

In Europe, ca. 20×106 t of waste paper wasrecycled as a raw material for paper productionin 1991. This figure includes 0.35×106 t of wax-containing paper and cardboard with averagewax content of 12%. Assuming an even distri-bution, this gives a wax content of 0.21%wax inwastepaper [129]. The practice has shown that inmodern wastepaper processing plants, wax-con-taining packagingmaterials do not interferewiththedilutionprocess,but nearly increase thequan-tity of waste products. These waste products canbe used to produce water-resistant cardbord.

4.6. Economic Aspects

In 1992, 9.5×105 t of paraffin and microcrys-talline waxes were produced in the UnitedStates, 8×105 t in Asia, 6.5×105 t in WesternEurope, 2.6×105 t in Germany alone, 2.0×105 tin Eastern Europe. and 4.0×105 t in the rest ofthe world.

In industrialized countries, a stagnation(probably a decrease) in petroleum wax produc-tion is anticipated for the coming years, inde-pendent of the growth in demand. This is be-

cause of the further development of car engineand tribology technology (reduced specific lu-bricant consumption and longer periods betweenoil changes), an increase in the proportion of par-tially or fully synthetic and biodegradable lubri-cants, the recycling of used oils, and the closingdown of excess capacity in distillation plants de-spite an increase in the number ofmotor vehiclesand the distances traveled [130].

However, in Asia, particularly China andMalaysia, an increase in wax production to1.5×106 t in 2000 is predicted, because thesewaxes can be inexpensively produced from in-digenouswax-rich crude petroleumby direct de-waxing. According to careful estimates, world-wide petroleum wax production will be ca.3.8×106 t in 2000 (40% in Asia, 25% in theUnited States, 17% in Western Europe).

The worldwide consumption of petroleumwaxes was ca. 2.8×106 t in 1992, of which (inmillion tonnes) 0.5 was in Western Europe, 0.2in Eastern Europe, 0.85 in the United States, and0.9 in Asia.

4.7. Candles

According to German commercial qualityclass RAL040A2 (Issue 02/1993), candles aresources of heat and light and consist of a wickand a solid combustiblematerial surrounding thewick. Therefore tea lights, lights for graveyards,and oil lamps are also included in this category.

The first candles have been traced to shortlyafter the birth of Christ. With Christianity, andlater with the rise of principalities and the up-per middle class, the use of candles developedrapidly. Whereas initially, tow wicks, beeswax,tallow, and spermaceti were used for candle pro-duction, from the 19th century onward the useof cotton wicks, petroleumwax, and stearin per-mitted the problem-free handling of candles.

Today, refined (petroleum) wax is the mainraw material used in candle production. Can-dles are also made from stearin, beeswax, com-posites (mixtures of various waxes), and ceresin(mixtures of paraffin and hard waxes). Candlesare dyed with wax-soluble organic aniline dyes(full dyeing), organic pigments, and (less often)natural pigments (dip dyeing). Fashionable can-dles with a colored dipping-paint coating arealso available. Wicks consist of twisted cotton

44 Waxes

threads and are sold as round or flat wicks of dif-ferent strengths. The wicks are twisted and pre-pared so as to guarantee uniform burning, goodwick curling position, and good suction capac-ity for the molten combustible material and toprevent afterglow of the wick once the candlehas been extinguished. Candles are sometimesperfumed.

A range ofmechanical and hand-worked pro-cesses exist for industrial production of candles.In the drawing process a candle strand is pro-duced by passing the wick several times throughthe hot wax bath. The strand then passes onto thecutting machine, where it is cut to the desiredlength of the candle. With continuously oper-ating candle-drawing machines, production ofmore than 10 000 candles per hour is possible. Inthe molding process, molten wax is poured intomolds, in the middle of which the wicks are heldtaut.Moldingmachines are available in differentsizes. Modern rotating molding machines havean hourly capacity up to 10 000 candles. Thepowder pressing process uses powdered wax asthe starting material, which is either molded to-gether with the wick in an extruder to form acandle strand or pressed into molds in a stamppress. At the same time, the wick is introducedwith a tubular needle. Another process exists,known as the dunking process. Here, the wick isdipped repeatedly into molten wax.

Blank candles are made pointed by usingmilling cutters and are coated with dyed dip-coating material if necessary.

The quality control of candles involves, forexample, determining their weight and dimen-sions, burning period, and burning properties (nodrips or soot). The production of candles in Ger-many (East and West) was 80 000 t in 1988, and17 000 t were imported. Thus, with an export of22 000 t, a total of 75 000 t was consumedwithinGermany.

5. Fischer –Tropsch Paraffins

Production. The sole producer ofFischer – Tropsch paraffins is South AfricanCoal, Oil and Gas (SASOL) in the Republic ofSouth Africa (→Coal Liquefaction, Chap. 2.2.).The formerly used ARGE (Ruhrchemie/Lurgiconsortium) process, which employed iron cat-alysts arranged as a fixed bed in multitubular

flow reactors, was changed to the SASOL slurrybed proces (SSBP), which afforded consider-able cost savings. Production capacity has beendoubled [131].

In the slurry or bubble column reactor,finely divided iron catalyst (average particle size50µm) is suspended in a Fischer – Tropsch waxwith low viscosity at the reaction temperature,and synthesis gas (a mixture of carbon monox-ide and hydrogen) is bubbled through. At re-action temperatures of 220 – 240 ◦C and pres-sures around 2MPa, n-alkanes and n-alkenes areformed preferentially,with up to 40%crudewaxin the synthesis product.

Crude wax is separated from the otherproducts of synthesis by fractional conden-sation. The low-boiling constituents (gasolineand diesel fuel) are removed by distillationunder atmospheric pressure, followed by vac-uum distillation to separate the soft waxes. Be-sides n-alkanes, distillation bottoms also containalkenes, hydrocarbons with hydroxyl and car-bonyl groups, and colored components. For pu-rification and stabilization, the bottom productsare subjected to a hydrofining step employing anickel catalyst to yield a white hard wax that ispractically free of alkenes, aromatics, functionalhydrocarbons, and sulfur compounds.

Soft waxes are also subjected to hydrogen-ation.

Properties. Fischer – Tropsch waxes consistessentially of n-paraffins with chain lengths bet-ween 20 and 50 carbon atoms. Products with anaverage molar mass of 400 g/mol are marketedas soft, and those with an average molar massof 700 g/mol as hard waxes. The paraffins havea fine crystalline structure and, because of thenarrow molar mass distribution, a small meltingrange and very low melt viscosities. Congeal-ing point, density, and hardness increasewith in-creasing mean molar mass. The low molar masscompared with polyolefin waxes is the reasonfor a certain displaceability of the crystal layersrelative to each other and, associated with this,the polishability.

Synthetic paraffins are fully compatible withrefined waxes, polyolefin waxes, and most veg-etable waxes. They are soluble at elevated tem-perature in the usual wax solvents (e.g., naph-tha, turpentine, and toluene) to give clear solu-tions. Addition of 10 – 20% synthetic paraffin

Waxes 45

to other waxes increases their congealing pointand hardness without significantly influencingmelt viscosity. In wax pastes, the tendency ofFischer – Tropsch waxes to form microcrystalsincreases solvent retention. Some typical datafor Fischer – Tropsch waxes are listed in Ta-ble 20.

Table 20.Typical properties of Fischer – Tropsch soft andhard paraf-fins

Characteristic Sasol WaxM Sasol WaxH2Vestowax SP 1002

Drop point, ◦C 106 – 112Needle penetration,0.1mm

1 – 3

Color white whiteMolar mass, g/mol 400 700Density (at 23 ◦C), g/cm3 0.94 0.94Viscosity (120 ◦C), mPa · s <20 <20

Uses. Fischer – Tropsch waxes are used inplastics processing as lubricants for poly(vinylchloride) and polystyrene, as well as mold-release agents; asmelting point improvers, hard-eners, and viscosity reducers in hot melts andcandles; and, because of their good polishabil-ity, for the production of cleaning agents andpolishes.

Micronized waxes improve the abrasion re-sistance of paints and printing inks.

Oxidized waxes containing fatty acids andfatty acid esters are produced from syntheticparaffin by oxidation and partial saponification.Major areas of application are as mold-releaseagents in plastics processing, in polishes andcleaning agents, and as auxiliaries in the textileand paper industries.

Trade Names. Fischer – Tropsch waxes aremarketed, e.g., as Sasol Wax (Sasol MarketingCo., Johannesburg, South Africa) and VestowaxSH/SP (Huls AG, Marl, Germany).

6. Polyolefin Waxes

6.1. Production and Properties

6.1.1. Polyethylene Waxes by High-PressurePolymerization

High-pressure polyethylene (PE) waxes are pro-duced, like high-pressure polyethylene plastic,

at high pressure and elevated temperature in thepresence of radical formers. As waxes, their mo-lar masses are considerably lower than those ofplastics. The molar mass range is adjusted dur-ing polymerization by the addition of regulators.

High-pressure polyethylene waxes are par-tially crystalline and therefore consist mainlyof branched molecular chains in which shorterside chains, such as ethyl and butyl, predomi-nate. They generally have low densities (low-density polyethylenewaxes, LDPEwaxes). Lessbranched polyethylene waxes with higher crys-tallinity and density (high-density polyethylenewaxes, HDPE waxes) can be produced by in-creasing the pressure.

High-pressure polyethylene waxes with mo-lar masses between 3000 and 20 000 g/mol[weight-averagemolar mass Mw, determined bygel permeation chromatography (GPC)] domi-nate the market.

The development of high-pressure PE waxesproceeded in parallel to that of LDPE plastics(→Polyolefins, Chap. 1.1.). In 1939, waxlikeethylene polymers were formed by using a vari-ant of the ICI high-pressure polymerization pro-cess [133]. Industrial production of high-pres-sure ethylene waxes was started in the 1940s[134], [135]. Parallel to this, the technology ofthermal depolymerization – the thermal degra-dation of polyethylene plastics to polyethylenewaxes –was developed (see Section 6.1.4).

With the rapid growth of petrochemistry andthe expansion of polyethylene plant capacities,the economic importance of PE waxes also in-creased rapidly. Waxes with very versatile prop-erty profiles could be synthesized by varying thedensity and molar mass of the homopolymersand functionalizing polyethylene by copolymer-ization with various monomers (e.g., vinyl ac-etate or acrylic acid) or by melt oxidation.

Because PE waxes are rather inexpensive,have improved applicability and consistency inquality, and are in constant supply they have dis-placed expensive natural waxes (e.g., carnaubaand montan waxes) in many areas.

The high-pressure process is not applicablefor production of polypropylene waxes, becauseonly soft or oily products can be obtained. Thesewaxes are therefore produced by the Zieglerprocess (see Section 6.1.3) or by depolymer-ization of high-density polypropylene (see Sec-tion 6.1.4).

46 Waxes

6.1.1.1. Production

The technology involved in the production ofhigh-pressure PE waxes (see Fig. 10) is analo-gous to that used for high-pressure polyethylene(→Polyolefins, Chap. 1.5.1.). The only differ-ences are in the product finishingprocess.Unlikeviscous plastic melts, which must be granulatedunderwater in granulators, for example, the mo-bile wax melt can be converted into powder byspraying or into granules by using dicers.

The reaction vessels are stirred autoclaves ortubular reactors (→Polyolefins, Chap. 1.5.1.1.,→Polyolefins, Chap. 1.5.1.2.), the design ofwhich can vary considerably.

Reaction Mechanism. The high-pressurepolymerization of ethylene is a highly exother-mic radical chain reaction (→Plastics, Gen-eral Survey, Chap. 3.3.2.), which is initiatedby reaction of ethylene with radicals formedby decomposition of an initiator [136]. Chainpropagation occurs through addition of furtherethylene units. Chain growth is terminated, forexample, by reaction with a regulator moleculesuch as propene:

R−CH2CH2 +CH2 =CH−CH3 →R−CH=CH2 +CH3−CH−CH3

Polymerization is terminated by recombinationor disproportionation of two macroradicals:

Long-chain branching occurs by intermolec-ular chain-transfer reactions:

A particular feature of polyethylenewax syn-thesis by the high-pressure process is the in-creased formation of short ethyl and butyl sidechains. These are formed by intramolecular rad-ical transfer:

At the high pressures necessary for polymer-ization, ethylene is in a supercritical state. Poly-merization therefore takes place in a one-phasesystem. After leaving the reactor, the reactionmixture is decompressed in high- or low-pres-sure separators, and unreacted ethylene evapo-rates. The wax remains as a melt and ethylene isrecycled.

Reaction Conditions. The structure, molarmass, and thus properties of polyethylene waxare determined mainly by reaction pressure, re-action temperature, type and quantity of initiatorand molar mass regulator, and reactor type andgeometry [137–141].

In the homo- and copolymerization ofethylene the reaction pressure is usually150 – 320MPa. Somewhat lower pressures areused in autoclaves than in tubular reactors. Otherprocess variants involve much lower pressuresof 70MPa (max.) with isopropanol as the molarmass regulator [139], [140].

Higher pressure favors chain propagationand thus leads to very short residence times inthe reactor. It also inhibits chain-transfer reac-tions so that with increasing pressure the de-gree of branching decreases and the density,crystallinity, hardness, andmp increase. In tubu-lar reactors, rising pressure increases the poly-mer yield, whereas in autoclaves this effect issmaller.

For homopolymerizaion the reaction tem-perature is 200 – 350 ◦C and for copolymeriza-tion 200 – 300 ◦C. High reaction temperature fa-vors chain-transfer reactions. For this reason thepolyethylene waxes formed have many short-chain and only a few long-chain branches [142]and thus low densities. Higher-density waxeswith lower degrees of branching are formed atlower reaction temperature.

Organic peroxides andmolecular oxygen (thelatter exclusively in tubular reactors) are usedas initiators. They decompose into radicals un-

Waxes 47

Figure 10. Schematic of production of polyethylene waxes by the high-pressure process in stirred autoclavesa) Precompressor; b) Postcompressor; c) Autoclave reactor; d) High-pressure separator; e) Low-pressure separator

der polymerization conditions.To ensure that theperoxides aremetered reproducibly, they are dis-solved in organic solvents.

Hydrogen and almost all organic compoundscan act asmolarmass regulators (chain termina-tors). Hydrogen, lower alkanes (e.g., propane),lower alkenes (e.g., propene or butene), alkylaromatics, lower aldehydes (e.g., propionalde-hyde), and lower alcohols (e.g., isopropanol) ormixtures of these substances are mainly em-ployed. The concentration and reactivity of theseregulators determine the average molar mass,the degree of branching, and thus the densityof polyethylene wax. The activity of the regu-lator increases with increasing temperature anddecreases with increasing pressure [136].

Reactor type and geometry also signifi-cantly influence polymer structure and prop-erties. Because of the backmixing occurringin autoclaves, spherical molecules with manylong-chain branches are predominantly formed.In tubular reactorswith plug flow, long, straightmolecules with little long-chain branching pre-dominate [143]. High-density, highly crystallinepolyethylene waxes can therefore be producedonly in tubular reactors.

Just as the geometries of the autoclave andthe tubular reactor differ, so do operating proce-

dures. In the case of autoclaves the initiator so-lution and the molar mass regulator are chargeddirectly to the preheated pressurized vessel byusing high-pressure pumps. In tubular reactorsthe initiator (e.g., air) and the molar mass reg-ulator are added to the reaction mixture beforethe compression stage or at the entrance to thereactor. With autoclaves, comonomers can becharged to different parts of the reaction vessel(see Fig. 10).

Product Finishing. Shaping of the moltenpolyethylene can be performed directly after re-moval of gaseous products in high- and low-pressure separators and subsequent fine de-gassing and filtration. Since nometal-containingcatalysts are used in high-pressure polymeriza-tion of ethylene, no catalyst removal is neces-sary. Low molar mass fragments and residuesof the initiator and molar mass regulator evapo-rate mainly in the separators. Only an extremelysmall proportion is incorporated into the poly-mer.

Granules can be produced by using stripdicers. The wax melt flows in thin strips on acontinuous, water-cooled metal band and, aftersolidification, is chopped with a rotating knife.Pastilles can be obtained by metered dripping of

48 Waxes

the melt from a distributor head onto this typeof cooling band.

A particular characteristic of wax melts istheir low melt viscosity. Thus, spraying the meltto form powders of spherical particles is alsopossible. By using special nozzle arrangements(binary nozzles) with nitrogen as the atomizinggas, micronized waxes (very fine powders) withparticle sizes in the micrometer range can beproduced.

Powders and micronized waxes can also beobtained by grinding granules in jet mills. Withsoft or very viscoelastic waxes, cooling with dryice or liquid nitrogen is necessary. Coarse parti-cles must be removed by subsequent classifica-tion.

Like all organic dusts (e.g., coal or flour), waxpowders, and particularlymicronizedwaxes, arehighly susceptible to dust explosions. Appropri-ate safety precautions must be taken during pro-cessing, in particular grounding all installationsto avoid spark formation through electrostaticcharge buildup.

6.1.1.2. Properties

The transition from polyethylene plastic to poly-ethylene wax is flexible. If the molar mass islowered, the thermoplastic materials is grad-ually changed to a wax. The DGF definitionof wax (see Section 1.2) gives an approximateboundary: For waxes, an upper limit to the meltviscosity of ca. 20 000mm2/s at 120 ◦C is de-fined, which corresponds to an average molarmass (weight-average molar mass Mw) of ca.37 000 g/mol.

The properties of polyethylene waxes are de-termined strongly by Mw as a measure of the av-erage chain length and by the degree of branch-ing as a measure of the shape of the molecules.Melt viscosity increases with increasing molarmass. Crystallinity, hardness, mp, and solidifi-cation point increase as the degree of branch-ing decreases. These data are important forapplication-oriented properties.

The molar mass can be determined by GPC.This method gives the weight-average (Mw) andthe number-average (Mn) molar mass. The ra-tio Mw/Mn is a measure of molar mass distri-bution and is known as the polydispersity index(→Polymerization Processes, Chap. 2.1.1.). For

high-pressure polyethylenewaxes currently pro-duced, this value lies between 2.0 and 2.5. Thewaxes have a much narrower molar mass dis-tribution than high-pressure polyethylene, forwhich the values are 3 – 8 (tubular reactor) and12 – 16 (autoclave) [136].

Table 21 gives a series of structure and prop-erty data for three high-pressure polyethylenewaxeswith increasingdensity from twodifferentproducers (some of this represents unpublisheddata supplied by the authors).

The following conclusions canbedrawn fromthese data:

1) The degree of branching is generally lowwith ca. ten branches (max.) per molecule.The side chains are mostly ethyl and butylgroups with a very small proportion of long-chain branches [144–146].

2) The density, crystallinity, hardness, solid-ification point, and drop point increaseas degree of branching decreases [147].All density-dependent properties vary cor-respondingly.

3) High-pressure PE waxes contain a smallproportion of double bonds, whose dis-tribution in the macromolecule dependson the production process, as the largedifferences between the levels of cen-tral double bonds show. The formationof double bonds is attributed to de-polymerization of chain radicals at highreaction temperature [136], [148], e.g.:

High-density polyethylene waxes are color-less, white to transparent and form clear melts.Like other waxes, they dissolve in nonpolar sol-vents (e.g., aliphatic, aromatic, and chlorinatedhydrocarbons) on heating and generally crystal-lize as very fine particles on cooling. Dependingon the type and concentration of the wax, theythen form mobile dispersions or paste-like gels,which frequently exhibit thixotropic properties.

6.1.2. Copolymeric Polyethylene Waxes byHigh-Pressure Polymerization(→Polyolefins, Chap. 1.5.1.3.)

In the high-pressure process, many othermonomers can copolymerize with ethylene giv-

Waxes 49

Table 21. Structure and properties of high-pressure polyethylene waxes A –C and D–F from two different producers

Characteristic A B C D E F

Density (23 ◦C), g/cm3 (DGF-M-III 2a) 0.92 0.92 0.945 0.92 0.92 0.94CH3 per 1000 C atoms 26 22 17 32 23 20Branches per molecule 3.4 1.8 1.0 3.7 1.9 1.8Crystallinity (from IR data), % 54 59 67 52 62 64Central double bonds per 1000 C atoms 0.1 0.4 0.4 0 0 0Terminal double bonds per 1000 C atoms 0.1 0.1 0 1.3 1.2 1.3Side-chain double bonds per 1000 C atoms 0.6 0.4 0.2 0.9 0.5 0.4Ball indentation hardness (23 ◦C), bar (DGF-M-III 9a) 200 370 550 314 413 482Solidification point, ◦C (DGF-M-III 4a) 96 99 106 93 101 104Drop point, ◦C (DGF-M-III 3) 106 112 116 106 111 113Melt viscosity (120 ◦C), mm2/s (DGF-M-III 8) 1310 1160 1200 780 925 890Weight-average molar mass Mw , g/mol 6140 5930 6000 5200 5500 5500Number average molar mass Mn, g/mol 2920 2390 2440 2490 2380 2660Mw /Mn (polydispersity index) 2.1 2.5 2.5 2.1 2.3 2.1

ing rise to considerable changes in product prop-erties [139], [141]. For copolymerization, au-toclaves with their intensive mixing, constanttemperature, and consequently stable reactionprocess are particularly suitable. In industry,vinyl acetate and acrylic acid are used mainly ascomonomers, giving waxes with higher polar-ity and lower crystallinity. Here also, the degreeof branching decreases with increasing pressureand decreasing temperature. Density, mp, andhardness increase accordingly.

Table 22 gives characteristic data for two im-portant copolymeric high-pressure polyethylenewaxes with vinyl acetate and acrylic acid ascomonomers.

Table 22. Physical and chemical data for copolymeric high-pressurepolyethylene waxes

Characteristic Ethylene – vinylacetatecopolymer wax

Ethylene –acrylic acidcopolymerwax

Weight-average molar mass Mw ,g/mol

ca. 6800 ca. 6100

Number-average molar massMn, g/mol

3000 3000

Melt viscosity (120 ◦C), mm2/s(DGF-M-III 8)

2000 1300

Solidification point, ◦C(DGF-M-III 4a)

85 93

Drop point, ◦C (DGF-M-III 3) 96 102Ball indentation hardness(120 ◦C), bar (DGF-M-III 9a)

120 410

Acid number, mg KOH/g 45Vinyl acetate content, % 10

Ethylene – vinyl acetate copolymer is a rela-tively polar but nevertheless hydrophobic waxthat can be dispersed in organic solvents partic-

ularly well. It is used as an additive in metallicautomotive paints, as a dispersing agent in pig-ment concentrates, and as a component of hotmelts.

Ethylene – acrylic acid copolymer is suitablefor aqueous systems because it can be emulsi-fied readily and is chemically and thermally in-tensive. Its emulsions are usedmainly inmodernfloor polishes and mold-release agents.

6.1.3. Polyolefin Waxes by Ziegler –NattaPolymerization

Like high molar mass polyethylene plastics, PEwaxes can be produced by the Ziegler low-pressure process using organometallic catalysts(→Polyolefins, Chap. 1.5.2.), in addition to theradical process at high pressure and temperature.Like high-density polyethylene, Ziegler waxeshave a mainly linear molecular structure. Theycan contain short side chains but not long oneslike high-pressure polyethylene waxes.

For direct synthesis of polymer waxesfrom propylene or higher α-olefins, onlythe Ziegler –Natta process is suitable(→Polyolefins, Chap. 2.5.).

Ziegler PE waxes currently on the mar-ket have a molar mass between 800 and8000 g/mol (Mn). They thus bridge the gap bet-ween Fischer – Tropsch and paraffin waxes andHDPE thermoplastics. Besides controlling chainlength, the polymerization process allows ad-justment of the degree of crystallinity so thatboth hard – brittle, high-melting products and

50 Waxes

softer, flexible products with low melting pointscan be obtained.

The soluble, soft wax fractions inevitablyproduced in the suspension process for HDPEare more similar to paraffin waxes than to PEwaxes because of their low molar masses. Fornormal hard wax applications, they can be usedonly after processing by distillation or extraction[149].

6.1.3.1. Production

For the production of Ziegler –Natta polyolefinwaxes, Ziegler catalysts that give polymers withlow average chain lengths and narrow chain-length distributions, and are sufficiently activeunder the special conditions of wax synthe-sis, are particularly suitable. The low degree ofpolymerization typical of waxes is achieved bycarrying out polymerization in the presence ofhydrogen as a molar mass regulator at com-paratively high temperature (usually between100 and 200 ◦C, sometimes even higher) [150–154]. Aliphatic hydrocarbons are used as reac-tion medium. Because of the high reaction tem-perature the waxes are formed in solution (solu-tion polymerization). If the product viscosity issufficiently low the molten polymer formed canitself function as the solvent (bulk polymeriza-tion) [155], [156]. Unlike modern HDPE pro-cesses in which the catalyst is not removed, inthe case of wax synthesis the catalyst must usu-ally be decomposed and filtered off [157], [158].This applies at least to the heterogeneous tita-nium catalysts still used today (see below) andis necessary because waxes have higher purityrequirements than PE plastics as a consequenceof the applications for which they are used. Afterthe solvent has been distilled off, the waxmelt isshaped (e.g., by spraying or pastille formation).

Catalyst Systems. Classical Ziegler cata-lysts, consisting of titanium tetrachloride andalkylaluminum compounds, can be used for waxsynthesis, but their activity is low [155], [156],[159–161]. The degree of branching and thusalso the density, drop point, and hardness canbe adjusted by copolymerization, by the specialtype of catalyst preparation [160], and by vary-ing the polymerization temperature [155], [161].

The state of the art for production of PEhomo- and copolymer waxes involves, as inplastics production, the use of supported cata-lysts, which contain titanium atoms as the ac-tive species and magnesium compounds as thecarrier material (→Polyolefins, Chap. 1.3.2.2.).Catalysts derived from titanium tetrachlorideand magnesium chloride, oxide, hydroxide[151–154], or alkoxide [150], for example, aresuitable.

Catalysts based on Ti –Mg compounds canalso be used in the production of polypropyl-ene waxes. Through an appropriate choice ofcatalyst, the degree of crystallinity (isotactic-ity) (→Polyolefins, Chap. 2.2.) can be variedwithin wide limits and thus adapted to a par-ticular application. Flexible products with aver-age crystallinity can be obtained [162]. Highlycrystalline polypropylenewaxes cannowbepro-duced economically by using stereoregulatingsilanes as additional catalyst components [163],[164]. Formerly, these waxes could be producedonly by thermal degradation of high molar masspolypropylene (Section 6.1.4).

Indications are that the homogeneousmetallocene – alumoxane catalyst systems[165], [166], which became known at the endof the 1970s and nowadays are used for plasticssynthesis in industry, will also become impor-tant in wax synthesis. Since the 1980s, manypatent applications have appeared in this field,relating to both PE [167–172] and PP [173–175]waxes. Metallocene catalysts have a number ofadvantages compared with titanium catalysts.They are more active and can thus be employedin lower quantities, so catalyst removal is notnecessary. Polymerization can occur at lowertemperature, and the process is therefore moreeconomical. Above all, the specific polymeriza-tion properties and great structural variabilityof metallocene systems are likely to give poly-olefin waxes with optimized or completely newproperty profiles.

6.1.3.2. Properties

Themost importantmolecular structure parame-ters, which determine the macroscopic propertyprofile of PE waxes, are the average molar mass(average chain length) and the degree of branch-ing. Melt viscosity rises exponentially with in-

Waxes 51

creasing molar mass (Fig. 11). Unbranched, ho-mopolymeric PE waxes have a high degree ofcrystallinity as a result of their undistorted lin-earmolecular structure. They are brittle and hard(needle penetration numbers <1) and have highdensities and melting points (up to ca. 127 ◦C).These products can be obtained only by Zieglerpolymerization. Radical polymerization alwaysgives branched waxes.

Figure 11. Relationship between average molar mass Mwand melt viscosity for PE waxes

By using 1-alkenes (generally propene) ascopolymers, defects can be introduced intothe polymer chain in the form of short-chainbranches, which lead to a decrease in crys-tallinity. The density, hardness, drop point, andheat of fusion are also decreased, while flexibil-ity and plasticity increase.

In Table 23, some important physical prop-erties of typical commercially available Zieglerpolyolefin waxes are compared.

Ziegler waxes are colorless and odorless andform clear, transparent melts with high ther-mostability. Like most other waxes, they are sol-uble on warming in nonpolar aliphatic and aro-matic solvents without leaving a residue, and oncooling often crystallize out as pastes. Commer-cial products have a melt viscosity range fromca. 10 to 30 000mPa · s (at 140 ◦C). Their den-sities are between 0.92 and 0.97 g/cm3.

6.1.4. Degradation Polyolefin Waxes

By heating in the absence of air, the molecu-lar chain of high molar mass polyolefins canbe cleaved into smaller molecules with wax-like character. The starting materials are usu-ally low- and high-density polyethylene, isotac-tic polypropylene, and polybutene. The produc-

tion capacities of degradation polyolefin waxeshave diminished since ca. 1980 in favor of thebuilt products (see Sections 6.1.1, 6.1.2, 6.1.3).While the proportion of degradation PE waxeshas diminished, that of PP waxes has increased.Despite the relatively unfavorable energy bal-ance of the degradation process, it is still usedbecause of its technological simplicity and, forPEwaxes, occupies third placewith regard to theproduction quantity after the high-pressure andlow-pressure PE waxes. The degradation pro-cess was developed approximately in parallel tohigh-pressure polymerization [176–178].

6.1.4.1. Production

Polyethylene is a thermally stable polymerichydrocarbon. In the absence of oxyen it canwithstand temperatures up to ca. 290 ◦C [179].At higher temperature, thermal degradation be-gins with a decrease in the molar mass; from400 ◦C, degradation occurs with high rate andyield [179]. The cleavage products consist al-most exclusively of a wax fraction with a mo-lar mass distribution that is barely wider thanthat of high-pressurePEwaxes. Low-boiling andgaseous crack products are formed only in smallquantities. Individual process steps are shown inFigure 12.

Figure 12. Process schematic for the production of degra-dation polyolefin waxes

52 Waxes

Table 23. Structure and properties of typical commercial Ziegler polyolefin waxes

A B C D EEthylenehomopolymer wax

Ethylenecopolymer wax

Ethylenehomopolymer wax

Ethylenehomopolymer wax

Propylenehomopolymer wax

Number-average molar mass Mn,g/mol (GPC)

1600 2200 850 5000 3000

Weight-average molar mass Mw ,g/mol (GPC)

4800 6300 920 17 000 18 000

Molar mass distribution(Mw /Mn)

3.0 2.9 1.1 3.4 6.0

Density (23 ◦C), g/cm3

(DGF-M-III 2a)0.97 0.93 0.96 0.97 0.88

Heat of fusion, J/g (DSC) 240 120 230 200 60Viscosity (140 ◦C), mPa · s 400 600 10 25 000 1700∗Drop point, ◦C (DGF-M-III 3) 125 118 107 135∗∗ 158∗∗Needle penetration, 0.1mm(DGF-M-III 9b)

<1 3 2 <1 <1

∗ Temperature of measurement 170 ◦C.∗∗ Softening point ring/ball (DGF-M-III 13).

The starting materials for thermal degrada-tion to polyolefin waxes are LDPE and HDPE[180] and HD polypropylene [181–184]. Degra-dation of copolymeric polyolefins [185] andpolybutenes [186] has also been described buthas not achieved great economic importance.

In the industrial process [180], polyolefin pel-lets are melted under nitrogen in a single-screwextruder and extruded into a steel tube heatedto ca. 400 ◦C. The residence time is 15 – 30min.The product is then cooled by evaporative cool-ing in ca. 5min to <250 ◦C. It is freed fromlow molar mass components by degassing ina separator. The product can then be finishedas described for high-pressure PE wax (Sec-tion 6.1.4.1).

The degree of branching of degradationwaxes formed, and thus all structure-dependentproperties such as crystallinity, density, hard-ness, and mp, are controlled by the choice ofstarting material (LDPE or HDPE, stabilizerfree). The average molar mass depends on res-idence time in the hot-tube reactor and the av-erage molar mass of the starting material. Thedegradation temperature affects mainly the re-action time and thus the throughput rate.

Batchwise, thermal degradation in autoclaveshas also been described [182], [185]. It is per-formed in certain cases in the presence of hy-drogen and hydrogenation catalysts to saturatedouble bonds formed on chain cleavage [176].

Like other polyethylene waxes, degradationwaxes can be modified by air oxidation and thus

rendered emulsifiable (see Section 6.1.5). Pre-liminary hydrogenation of double bonds can benecessary to avoid cross-linking reactions dur-ing oxidation.

Because of their double bonds, degradationwaxes are particularly suited to grafting withunsaturated carboxylic acids (e.g., with maleicanhydride [187], [188]).

Little information is available in the litera-ture on the mechanism of thermal degradationof polyolefins to formwaxes [179]. Presumably,radicals form from the few oxygen-containinggroups in the polyolefin and initiate a radicalchain reaction, in which the chain is cleavedthrough radical transfer and a double bond isformed:

Since tertiary hydrogen atoms are particu-larly susceptible to radical transfer, the degra-dation reaction begins at the carbon atoms ofthe branches, to form fragments containing side-

Waxes 53

chain double bonds. Only later are linear chainscleaved, to form central and terminal doublebonds.

6.1.4.2. Properties

In Table 24, properties (in some cases unpub-lished results supplied by the authors) of threedegradation and three high-pressure polyethyl-ene waxes, with about the same average mo-lar mass to decreasing branching and increasingdensity, are compared. The two types of waxcan be seen not to differ significantly. For both,the same relationships are valid between mo-lar mass and melt viscosity and between degreeof branching and density, crystallinity, hardness,and solidification and drop points. The width ofthe averagemolarmass distribution (polydisper-sity) is also comparable. A significant differenceis that degradation polyethylene waxes containconsiderably more double bonds than compara-ble polyethylenewaxes formed by high-pressurepolymerization. Determination of the type andlevel of double bonds from the IR spectrum cantherefore be used for analytical identification ofdegradation polyethylene waxes. The technicalproperties are affected only slightly by doublebonds.

Compared with degradation polyethylenewaxes, degradation polypropylene waxes usu-ally have extremely high melting points andhardness because they are produced from highlycrystalline, isotactic high-density polypropyl-ene. Some characteristics of a relatively lowmolar mass degradation polypropylene wax arelisted below:

mp (DSC) 130 – 160 ◦CBall indentation hardness (23 ◦C)(DGF-M-III 9a)

500 – 1900 bar

Melt viscosity (200 ◦C)(DGF-M-III 8)

800 – 1900m2/s

Weight-average molar mass (GPC,standard: PP)

17 000 – 37 000 g/mol

Degradation polyolefin waxes are colorless,white to transparent, and form clear melts. Onwarming, they dissolve in nonpolar solventssuch as aliphatic, aromatic, and chlorinated hy-drocarbons, and on cooling, they crystallize asdispersions or gels (pastes).

6.1.5. Polar Polyolefin Waxes

Polar polyolefin waxes generally contain car-boxyl and ester groups, which give them specialtechnical properties, in particular emulsifiabil-ity in aqueous media. They can be produced bya variety of methods:

1) Oxidationof nonpolarPEwaxes (melt oxida-tion) or PE plastics (oxidative degradation)with air

2) Radical high-pressure polymerization of eth-ylene with oxygen-containing comonomers(acrylic acid, acrylates, vinyl acetate, etc.)(see Section 6.1.1.1)

3) Radical grafting of polar unsaturatedmonomers onto nonpolar PE and PP waxes

To a great extent, PE waxes are convertedintowax oxidates by treatmentwith atmosphericoxygen in the melt at ca. 150 – 160 ◦C [189–191].Oxygen functions (carboxyl, ester, carbon-yl, hydroxyl groups, etc.) are introduced into thewax molecule by complex mechanisms involv-ing peroxy intermediates and chain-shorteningreactions [192]. The usual commercial productswith acid numbers between 25 and 30mg ofKOH per gram contain ca. 3 – 4wt% oxygen,mainly in the form of carboxyl and ester groups.

Oxidation of the molten wax is limited towaxes whose molar mass is not too high. In thecase of longer-chain startingmaterials, intensivedispersion of air in the melt, which is necessaryfor the reaction to run smoothly, is inhibited bythe melt’s high viscosity. In this case, waxes canbe oxidized in inert dispersion agents. Since a(statistical) chain cleavage is always associatedwith oxidation (i.e., a lowering of molar mass),PE plastics can also be converted into a polarwax by this route (oxidative degradation). Forexample,molten polyethylene in an aqueous dis-persion canbe converted into emulsifiablewaxesby passing in air at 130 – 160 ◦C with intensivestirring. These waxes are harder and have higherdrop points than the usual melt oxidates withthe same acid number because of their relativelyhighmolarmasses [193]. The reaction can be ac-celerated by addition of peroxides. High-densitypolyethylene gives hard brittle products. Tough,flexible waxes, which can be used as antislipcomponents of floor polishes, can be obtainedfrom LDPE containing vinyl acetate [194].

54 Waxes

Table 24. Characteristics of three degradation and three high-pressure polyethylene waxes

Characteristic Degradation PE wax High-pressure PE wax

G H I A B C

Density (23 ◦C), g/cm3 (DGF-M-III 2a) 0.92 0.93 0.95 0.92 0.93 0.945CH3 per 1000 C atoms 32 16 8 26 22 17Branches per molecule 3.5 0.5 0 3.4 1.8 1.0Crystallinity (from IR data), % 43 63 74 54 59 67Central double bonds per 1000 C atoms 1.2 1.5 2.0 0.1 0.4 0.4Terminal double bonds per 1000 C atoms 3.3 2.6 2.6 0.1 0.1 0Side-chain double bonds per 1000 C atoms 1.7 1.1 0.5 0.6 0.4 0.2Ball indentation hardness (23 ◦C), bar(DGF-M-III 9a)

450 500 600 200 370 550

Solidification point, ◦C (DGF-M-III 4a) 96 100 110 96 99 106Drop point, ◦C (DGF-M-III 3) 105 112 121 106 112 116Melt viscosity (120 ◦C), mm2/s (DGF-M-III 8) 930 1230 1300 1310 1160 1200Weight-average molar mass Mw , g/mol 5400 6040 6100 6140 5930 6000Number average molar mass Mn, g/mol 2400 2160 2440 2920 2390 2440Mw /Mn (polydispersity index) 2.3 2.8 2.5 2.1 2.5 2.5

Table 25. Properties of typical commercial oxidized polyolefin waxes

Characteristic A B C D E

Raw material high-pressure PEwax

Ziegler PE wax HDPE HDPE ethyl-ene – vinylacetatecopolymer

Acid number, mg KOH/g (DGF-M-IV 2) 22 18 16 60 21Saponification number, mg KOH/g(DGF-M-IV 2)

50 38 103 80

Viscosity (120 ◦C), mPa · s 400 200 8500 (150 ◦C) 300 3000Drop point, ◦C (DGF-M-III 3) 100 116 140 111 100Needle penetration, 0.1mm(DGF-M-III 9b)

5 5 <0.5 1 2

Density, g/cm3 (DGF-M-III 2a) 0.96 0.98 0.98 1.02 0.96

Oxidative degradation of polyethylene canalso be carried out as a gas – solid reaction. Inthis case, no dispersing agent is required. Air,oxygen-enriched air, or pure oxygen in the pres-ence of radical initiators is reacted with the sub-strate in powder form a few degrees below thesoftening point [195–198]. Because a low tem-perature (<130 ◦C) must be maintained, the ox-idation period is comparatively long. For exam-ple, it requires at least 20 h to achieve acid num-bers of 25 – 30mg of KOH per gram. Use ofair – ozone mixtures as the oxidizing agent hasalso been described [199], [200]. Another pro-cess variant involves oxidation of polyethylenepowder with air in aqueous suspension underpressure [201]. The properties of some repre-sentative commercial wax and plastic oxidatesare given in Table 25.

Oxidized PE waxes can be modified fur-ther by esterification [202], amidation [203–205], saponification, and other derivatization re-

actions [206] and thus adapted to special tech-nical requirements.

Polyolefin waxes can also be converted intoemulsifiable products by grafting unsaturatedpolar compounds (maleic anhydride, etc.) [161],[207–210]. For polypropylene wax [211–213],this is the only method of introducing oxygenfunctions that is used in practice, since air oxi-dation would lead to low molar mass, colored,soft degradation products.

6.2. Uses

6.2.1. Nonpolar Polyolefin Waxes

Polyolefin waxes are used in widely differingapplications, mostly as auxiliaries in productsand production processes. The areas of use ofhigh-pressure, Ziegler, and degradation waxesoverlap extensively. More details can be found

Waxes 55

in leaflets and brochures of various productioncompanies. Important areas of use include thefollowing:

1) In Additive and Pigment Master batches.PE and PP waxes are carrier materials andbinders in concentrates used as plastics ad-ditive and for coloration of plastics.

2) As Additives to Improve Rub Resistance andas Slip Agents [214]. PE waxes are incorpo-rated into printing inks after micronizing bymilling or spraying, or in the form of disper-sions.

3) In Paints and Coatings, PE waxes are usedfor matting effects and to increase resistanceto scratching [215], [216].

4) In Plastics Processing, PE waxes are used aslubricants and release agents in molding.

5) In Polishes. PE waxes are components ofheat-resistant pastes for floor, shoe, and carpolishes.

6) In Hotmelt Coatings. PE and PP waxes areheat-sealable components of coatings andadhesives for paper and metal sheeting be-cause they improve insulation, gloss proper-ties) and heat resistance.

7) ForCorrosionProtection. PEwaxes are usedas hydrophobing components for temporarycorrosion protection of motor vehicles, ma-chines, and instruments.

8) Photocopying. PE and highly crystalline PPwaxes are used in toner preparations for pho-tocopying machines.

9) In the Rubber Industry, PE waxes are usedas release agents in processing.

Also, PE and PP waxes are used as compo-nents of insulating compounds, as carriers andbinders for mechanically and chemically react-ing self-duplicating paper and wax crayons, tocoat granular fertilizer, and to increase the heatresistance of candles.

6.2.2. Polar Polyolefin Waxes

Polar polyolefin waxes are used mainly in theform of aqueous emulsions (dispersions). De-pending on the nature of the emulsifier systemused, nonionic, nonionic – ionic, anionic, andcationic formulations can be produced. Emul-sions are produced by mixing molten waxes andemulsifierswith hotwater.On rapid coolingwith

intensive stirring,wax droplets solidify and formstable, finely divided dispersions. High-meltingwaxes must be emulsified under pressure. Afterthe emulsion is applied, water evaporates andleaves a homogeneous wax film, often with ahigh gloss, on the treated surface. This effect isused in floor polishes where polar waxes are ap-plied in combination with acrylate- and styrene-based polymer dispersions. Waxes obtained byoxidative degradation of plastics are primarilyused in this area because they form harder-wearing films due to their greater hardness thanlower molar mass melt oxidates. Polyethylenewax emulsions are also used as leather and shoepolishes and in many other areas of industry. Intextiles, they are used for wash andwear finishesand to improve sewing properties. They are usedas hydrophobing agents in paint dispersions, asrelease agents in the building industry, and insurface finishing of paper products. Citrus fruitis provided with a glossy surface and protectedfrom drying out through the application of waxfilms [217]. In the plastics processing industry,polar PEwaxes are used as lubricants and releaseagents.

6.3. Economic Importance

As indispensable additives with a secure rawmaterial supply and broad application potential,polyolefin waxes play an important role, mainlyin the industrial, but also in the consumermarketsectors.

The quantity of polyolefin waxes annuallyconsumed worldwide is ca. 200 000 t (1995),including oxidized and grafted products. High-pressure waxes (PE and polar copolymers) ac-count for ca. 70%. The remainder consists es-sentially of Ziegler products (PE, PP). Degra-dation waxes (mainly PP) are less important interms of quantity.

Ca. 12 000 t of polar waxes are producedworldwide by oxidative degradation of PE plas-tics.

The main consumers of nonpolar polyolefinwaxes are the producers of pigment concentratesand of plastic and rubber articles, as well as thepaint and printing ink industry. Polar waxes areused mainly in the form of emulsions in the tex-tile, polish, and paper industries.

56 Waxes

Producers and Trade Names.High-Pressure Waxes. Allied-Signal, United

States (A-C Polyethylene). Eastman Kodak,United States ( EpoleneWax). BASF,Germany (Polyethylenwachs BASF, Luwax). Leuna, Ger-many ( LE-Wachs).

Ziegler Waxes. Hoechst, Germany (Hoechst-Wachs). Mitsui Petrochemical Ind., Japan ( Hi-wax). Huls, Germany ( Vestowax). Petrolite,United States ( Polywax).

Degradation Waxes. Sanyo Chemical Indus-tries, Japan ( Viscol, Youmex). Mitsui Petro-chemical Ind., Japan ( NP-Types). Lion Chemi-cal, Korea ( L-C Wax). Eastman Kodak, UnitedStates ( Epolene). Ceralit, Brazil ( Cerit Poly).

7. Toxicology

On the basis of experience accumulated overthousands of years, waxes are generally con-sidered harmless, nontoxic, environmentallyfriendly products. The results of scientific tox-icological and ecotoxicological tests on naturalwaxes, montan waxes, polyethylene waxes, andother wax products generally support this.

Natural Waxes. From the group of animaland vegetable waxes, carnauba wax was sub-jected to toxicological tests. In a two-generationfeeding experiment, 1% wax (max.) based onthe feed, was administered first to pregnant ratsand then to their first-generation offspring over aperiod of 90 d. The results gave no indication ofdose-dependent effects in the rats treated com-pared to the untreated control group [218].

Montan Waxes and Their Derivatives.The toxicological properties of acid, ester, andpartially saponified ester waxes (partially neu-tralized with calcium hydroxide) derived frommontan wax are determined mainly by the in-digestibility of the products, as in the case ofnatural waxes. Besides determining acute oraltoxicity, extensive feeding experiments on ratsand dogs over periods of 90 d, 140 d, and 2 ahave been carried out with montan wax deriva-tives [219]. The LD50 values are >15 000 and20 000mg per kilogram of body weight, respec-tively. According to the usual classification,these products are considered practically non-toxic and harmless [220].

Long-term feeding experiments led to nomacroscopically or microscopically recogniz-able toxicological damage to the animals, even atvery high dosages of 5% in the feed (Table 26).

Dermatological examination of montan waxderivatives in the percutaneous test and themucous membrane test on rabbits (Hoechstwaxes S, E, and OP) did not lead to any irritationof the skin or mucous membranes.

In the Ames mutagenicity test with andwithout external metabolic activation, a mon-tanic acid – ethylene glycol ester wax (Hoechstwax E) did not show any mutagenicity (testeddosages 4 – 5000µg per plate) [221].

The ecotoxicological behavior of montanwaxes is attributed to their water insolubility.Mixtures with water are attacked very slowlyby microorganisms and cause no perceptible bi-ological oxygen demand (BOD) in water bod-ies and sewage treatment plants. The waxesare separated from wastewater as ballast ma-terials together with sludge. In the determina-tion of biodegradability according to OECD testmethod 302B (static test/Zahn –Wellens test),the finely dispersed montan wax derivatives inwastewater show good elimination of chemi-cal oxygen demand (→Ecology and Exotoxi-cology). They are separated with sludge and arenontoxic to fish and bacteria.

In the case of wax emulsions, when the usualtest methods for determination of COD andBOD are used, a very slow oxygen consumptioncan be detected, which is higher than the oxygendemand of the emulsifiers [219]. In wastewater,these emulsions break up as a result of great di-lution, altered pH, and the presence of calciumand magnesium ions. The findings described forpure wax –water mixtures also apply to the ag-glomerates formed.

Polyolefin Waxes. Polyethylene waxes, ox-idized polyethylene waxes, and polypropylenewaxes are similar to those based on montan waxand natural waxeswith regard to toxicology. TheLD50 values for rats are >5000 and 15 000mgper kilogram of body weight, respectively. Ina long-term toxicity test (a 9-month feeding ex-periment on rats), polyethylenewaxes caused notoxic damage to the animals even at the highestdosage of 8.5% in the feed. In a 90-d feeding ex-periment on rats, oxidized polyethylene wax upto acid numbers 70 in dosages of 0.2, 1, 1.6, and

Waxes 57

Table 26. Acute oral, subchronic, and chronic toxicity of montan wax derivatives

Wax Chemicalcomposition

Acute oral toxicity,LD50, mg/kg

Subchronic toxicity,90-d no-effect level∗,mg/kg

Subchronic toxicity,140-d no-effectlevel∗, mg/kg

Chronic toxicity, 2-ano-effect level∗,mg/kg

Acid wax (Hoechstwax S)

montanic acidC16 –C36

>15.000 (rat)

Ester wax (Hoechstwax E)

esters of montanicacid with ethanediol

>20 000 (mouse) 50 000 (dog) 50 000 (rat)

Ester wax (HoechstwaxKPS)

esters of montanicacid with ethanedioland 1,3-butanediol

>15 000 (rat) 50 000 (dog) 50 000 (rat)

Ester wax(HostalubWE4)

esters of montanicacid with glycerol

50 000 (rat)

Partially saponifiedester wax (HoechstwaxOP)

esters of montanicacid with1,3-butanediol andcalcium salts ofmontanic acid

>20 000 (mouse) 50 000 (dog) 50 000 (rat)

∗ Proportion by weight in the feed.

5% in the feed produced no adverse effects in theanimals.Histopathological tests showednomor-phologically recognizable damage or changescaused by the waxes. No accumulation was ob-served in tissues, liver, or lymph glands. Fat andiron metabolism and spermatogenesis and oo-genesis were unaffected (Table 27) [219]. Prac-tically no negative effects were found in derma-tological tests on rabbits. Polyethylene waxesand oxidized polyethylenewax show goodCODelimination under sewage treatment plant condi-tions and no toxicity to fish or bacteria.

Paraffins and Microwaxes. Petroleumwaxes have been used for decades as food ad-ditives, as wax coatings for cheese, in chew-ing gum, for upgrading food packaging, and incosmetics and pharmaceutical products, with-out damaging human health. The toxicologicalproperties of paraffins andmicrowaxes extractedfrom crude petroleum depend essentially ontheir composition and purity, particularly theirresidual aromatics content.

In a study of the toxicity of petroleumwaxes,rats were fed with several paraffin products for2 years. At a dosage of 10% wax in the feed, notoxicological or carcinogenic effects were ob-served. Even on repeated application of petro-leum waxes to the skin of mice and rabbits, nocarcinogenic effects were detected [222].

Toxicological tests have been carried outwithparaffins and microwaxes are mainly 90-d feed-ing experiments on rats. In these, varying tox-icological effects were observed. For low mo-lar mass paraffins, accumulation in the tissues

and increased organ weights of the liver, kidney,spleen and lymph glands were observed. Themost important histopathological findings weregranulomata in the liver and histiocytosis in thelymph glands. These effects were not foundwithhigh molar mass waxes.

No toxic effects were found at a dose of0.6mg per kilogram of body weight and day forlow molar mass paraffins (C-number maximum25) and 1.8 g per kilogram of body weight perday for high molar mass paraffin (microwaxes,C-number maximum 42).

The latest results are published in BIBRA re-ports [223], [224], CONCAWE reports [225],and reports of the Toxicology Forum [226],[227].

Amide Waxes. The most well knownamide wax, bis(stearoyl)- bis(palmitoyl)ethyl-enediamide, has an LD50 of >20 000mg/kg(mouse). In determination of the chronic toxicityin a 2-a feeding experiment on rats, a non-effectlevel of 5% in the feed was established [218].

Approval for Food Contact. On the basisof their low toxicity, a range of natural waxes,montan wax derivatives, amide waxes, poly-ethylene waxes, paraffins, and microcrystallinewaxes have been approved for food contact bythe health authorities ofmany countries [e.g., theGerman BgVV (formerly BGA), the U.S. FDA,and in Australia and Japan]. The products arealso contained in the draft version of the EC ad-ditives list (Synoptic Document no. 7 of May,15, 1994). Some of the waxes are approved in

58 Waxes

Table 27. Acute oral, subchronic, and chronic toxicity of polyolefin waxes

Wax Acute oral toxicity, LD50,mg/kg

Subchronic toxicity, 90-d(rat) no-effect level∗, mg/kg

Subchronic toxicity,9-month (rat) no-effectlevel∗, mg/kg

Polyethylene wax (Hoechst wax PE 520) >15 000 85 000Polyethylene wax oxidates(Hoechst wax PED121) 16 000(Hoechst wax PED522/PED136) >15 000 50 000

Polypropylene wax (Hoechst wax PP 230) >5000

∗ Proportion by weight in the feed.

the European Directives 95/2/EC and 95/3/ECfor food contact.

Registration According toEINECS/TSCA/AICS/DSL. Waxes are regis-tered under the CAS numbers given in Table 28in the European Inventory of Existing ChemicalSubstances (EINECS), the TSCA inventory inthe United States, the Australian AICS inven-tory, and the Canadian DSL inventory.

Table 28. Registration according to EINECS, TSCA, AICS, DSL

Type of wax CAS registry no.

Natural waxesBeeswax [8012-89-3]Carnauba wax [8015-86-9]Candelilla wax [8006-44-8]

Waxes based on montan waxMontan wax fatty acids [68476-03-9]Ethylene esters of montan wax fatty acids [73138-45-1]1-Methyl-1,3-propanediyl esters of montan

wax fatty acids[73138-44-0]

Calcium salts of montan wax fatty acids [68308-22-5]Montan wax glycerides [68476-38-0]Montan wax (crude montan wax) [8002-53-7]

Polyolefin waxesPolyethylene wax [9002-88-4]∗Ethylene [74-85-1]Polypropylene wax [9003-07-0]∗Propylene [115-07-1]Polyethylene wax oxidates [68441-17-8]∗

Petroleum waxesParaffin and hydrocarbon waxes [8002-74-2]Microcrystalline waxes [63231-60-7]

Amide waxN,N′-Ethylenedistearamide [110-30-5]

∗ In EINECS, polymers are registered only under the CASregistry no. of the monomer.

Waxes are not in theMAK value list for 1995.

LabelingAccording toGefStoffV,ChemG,and ECGuidelines. If they are pure and are notin the form of preparations with components

for which labeling is compulsory (e.g., emul-sifiers), waxes do not have to be labeled ac-cording to GefStoffV (October 26, 1993), theChemG, Technische Regeln fur Gefahrstoffe(technical regulations governing hazardous sub-stances, TRGS) 200, and the EC Guideline67/548/EC and adaptations and amendments.

Status According to OSHA. Paraffins areregulated by OSHA. Labeling is prescribed onpackaging of paraffins (right-to-know label), inwhichwarning of paraffin vapors is given. Paraf-fin vapors are classified as eye and respiratoryirritants; they have the following exposure lim-its:

OSHA-PEL 2mg/m3

ACGIH-TLV 2mg/m3

Other waxes are not regulated by OSHA.

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Waxes 59

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