amino and furon resin

Amino and Furan Resins

Christopher C. Ibeh

INTRODUCTION

The amino and finan resins are grouped together primarily because they are versions of phenolic resins that complement and supplement phenolic resins. They are also relatively low-volume consumption resins. The light- colored aminos were originally introduced to expand the market share of phenolic-type products. Phenolic resins occur only in dark, opaque colors and can therefore be used only to manufacture dark-colored products.

Amino resins are thermosetting plastic materials that are produced by the reaction between amino group (NH&bearing compounds (such as aniline, guanamines, urea, melamines, thiourea, ethylene urea, and sulfonamide) and formaldehyde. The two most popular and viable aminos, urea-formaldehyde and melamine-formaldehyde resins, are the ammos of interest in this chapter.

Furan resins, on the other hand, are produced by the reaction between phenols and fumns [such as fLrf%ral (aldehyde), and finfural derivatives]. Th- ey are used in place of formaldehyde in the conventional production of phenolic resins.

Work with urea and urea-formaldehyde resins may have begun as early as the 1880s in France and Germany by Einhorn, Holzer, and Goldsch- midt et al. H. John and F. Pollack introduced them commercially into the U.S.

72

Amino and Furan Resins 73

in 1928.[‘-‘1 Companies manufacturing urea-formaldehyde resins include American Cyanamid, Reichhold Chemicals, and Allied Corp.

The melamine-formaldehyde resins were brought into the market in 1935. In addition to their light-coloredness, they exhibit enhanced water and heat resistance. These resins have completely replaced thiourea-formaldehyde resins, which were also produced in the 1930s. American Cyanamid Company is the major producer of melamine-formaldehyde resins having begun the first commercial manufacture in the U.S. in 1939. Other companies producing these resins are Fiberite Corp., Ciba-Geigy Corp., and Allied Corp.

Furan resins are relatively recent inventions. The Rufurals and furfmal derivatives on which they are based were first produced by Quaker Oats Company after World War I. Other companies producing furan resins include Furan Division of Ashland Chemical and M&T Chemical. Ashland Chemical also produces urea and melamine-formaldehyde resins.

RAW MATERIALS

Urea (NH,CONH,) and formaldehyde (CH,O) are the raw materials of urea-formaldehyde resins. Melamine (C,N,(NH,),) and formaldehyde are the raw materials for melamine-formaldehyde resins. For fixan resins, the raw materials are fixf%ral and its derivatives and phenol.

Urea

Urea, a white crystalline solid, is a diamide of carbonic acid. Wohler’s work in 1824 in urea synthesis marks a cornerstone in the connection between the chemistry of living and inanimate matter. Wohler’s process for synthesiz- ing urea involved the molecular rearrangement of ammonium cyanate.c61

Urea is synthesized from the high pressure reaction between carbon dioxide and ammonia:

74 Handbook of Thermoset Plastics

2NH, + CO, 150-200°C NH,2COHN, + H,O _)

1400-1500 psi

Ammonia + carbon dioxide + Urea + Water

Melamine

Melamine is the triamide of cyanuric acid (2,4,6-triamino-1,3,5-tria- zinc). In the Ciba Geigy process patented in 1936, calcium cyanamide is con- verted to cyanamide, and the cyanamide is reacted with ammonia under pressure to yield melaminers] (Figure 3-l).

Amino and Fur-an Resins 75

Furans

The term furans refers to &rt%ral (aldehydes) and furfnral derivatives such as fM%ral alcohol, furan, tetrahydroIman, and tetrahydrofurfural alcoh- 01[‘1[*1 (Figure 3-2).

Furmtal is a thermally stable, amber-colored aldehyde that occurs in liquid form. It is synthesized by the acid hydrolysis and steam distillation of agricultural byproducts such as corn cobs, rice hulls, oat hulls, and sugar cane bagase.

Furtural alcohol (FA) is a pale yellow, water soluble liquid produced by the hydrogenation of fnrfnral.

Furan is a colorless, cyclic, dienic ether produced from the decarbony- lation of I%rI$ral using a noble metal catalyst such as palladium on charcoal.

Tetrahydrotumn (THF) is a colorless, cyclic ether produced from the hydrogenation of I&m.

Tetrahydrofbrfixyl alcohol (THFA) is a colorless, water-miscible, bio- degradable primary alcohol produced commercially by the vapor-phase hydrogenation of tnrhuyl alcohol using a nickel or copper catalyst. FA, THF, and THFA are registered trademarks of QO Chemicals, Inc., a subsidiary of Great Lakes Chemical Corporation, West Lafayette, IN.

Furfural Furfuryl Alcoho 1

Furan Tetrahydro- Furfuryl Alcoho 1

Figure 3-2: Structure of Furans


AMINO RESINS

Chemistry and Resinification

Urea-Formaldehyde Resins. The resinification process for urea- formaldehyde occurs in two main stages, addition or methylolation and condensation. In the methylolation step, urea and formaldehyde are reacted under controlled conditions using an alkaline catalyst. Typically, the methylolation step is carried out at a pH of about 8.0. The methylolation stage usually results ts in a mixture of metbylolated species, monomethylol urea, and dimethylol urea and trimethylol urea.

NH,CONH, + CH,O pH=8 +

urea + formaldehyde

NH,CONHCH,OH + CH,O pH=8 _)

HOCH@lXONHCH,OH + CH,OH pH=8.0 +

NH,CONHCH,OH

monomethylol urea

HOCHmCONHCH,OH

dimethylol urea

(HOCH,),NCONHCH,OH

trimethylol urea

The urea methylolation reaction is controlled such that 1 mole of urea combines with 2 moles of formaldehyde to yield dimethylol urea predominantly. t’-‘] The second phase of the resinification process involves the condensation of the methylolated species in the presence of an acid catalyst, which when carried to completion, results in a fully cured, infusible resin with methylene linkages. The condensation reaction proceeds to a predetermined


end point, and the resin intermediate is cooled. The resin intermediate is stabilized by adjusting the pH to about 7.0 to 8.0. The condensation of the methylolated species is equivalent to 2 moles of urea reacting with 1 mole of formaldehyde to form urea-formaldehyde resin.

2NH,CONH, + CH,O + NH,CONH-CH,-NHCONH, + H,O

urea + formaldehyde urea-formaldehyde + water

Melamine-Formaldehyde Resins. The reaction of melamine and formaldehyde occurs more readily and completely than that of urea and formaldehyde. Up to 6 moles of formaldehyde can be combined with 1 mole of melamine to produce hexamethylol melamine. The trimethylol melamine is most common, however. The melamine-formaldehyde resins are more water and heat resistant than the urea-formaldehyde resins (Figures 3-3a and 3-3b).

The final form of the amino resin produced depends on such factors as reaction temperature, pH control, reactant ratio, and degree of polymerization. These factors are varied to achieve the forms suitable for various end- uses such as:

(1) Adhesives and bonding resins. (2) Crosslinking agents for coating resins.

(3) Laminating resins.

(4) Molding resins.

r-4’ \‘N N’ 94 II I + 3cH20 -->

rw2Af \ ” d, NH2

MiCH20H~C,N~ MiCH2oH

Melamine Trimethylol-Melamine

Figure 3-3a: Structure of Trimethylol Melamine

78 Handbook of E’zermoset Plastics

cH2oH cH2oH

N-l2 ‘N’ I I

,4-I c

N’ +N II I +- -’

-\ II 1 /cH2oH

N/C\//CNN clt2oH/ N VliH2OH

Melamine Hexamethylol+elamine

Figure 3-3b: Structure of Hexamethylol Melamine

Adhesive and Bonding Resins

Urea-formaldehyde and melamine-formaldehyde resins, usually in the liquid or spray-dried forms, are used as adhesives. Though the melamine-formaldehyde resins are more water and heat resistant and give more durable adhesives and bonding resins than the urea-formaldehyde resins, their higher costs limit their use.

Their durability and water-resistant characteristics promote the use of melamine-formaldehyde resins in outdoor and marine applications. The light colored amino resins are attractive for decorative plywood veneers without encountering the associated problem of discoloration caused by resin bleed- through. Typically, the adhesive and bonding resins have urea:formaldehyde ratios of 1:1.5 to 2.0 and a melamine:formaldehyde ratio of 1:3.0. The react- ions are carried out at a pH of 7.5 to 8.0 and at reflux for up to 8 hours until 50 to 60% solid composition is attained. The pH is lowered as viscosity is increased; the reaction is then stopped and the resin is stabilized using caustic


soda by raising the pH to 8.0. The typical formulation of adhesive resins is about 15% resin, woodtlour, pecan, and walnut shells are the common fillers. Acid catalysts are favored in adhesive and bonding amino resins.

The processing or pressing conditions for amino resins are typically 70’ and 200 psi (cold pressing) for up to 24 hours. Melamine-formaldehyde resins can be cured or pressed without a catalyst but only at a higher processing temperature (hot pressing).

Amino resin adhesives are typically applied in the bonding of wood. The bonding strength of aminos is most effective with heat and pressure for wood particles of the 40 to 80 mesh range. Hot pressing causes the amino resins to seep through the pores of the wood core and polymerize (crosslink) inside the wood. This crosslinking binds the wood together, resulting in a structure that is stronger and more moisture resistant than the original wood. Some amino resin-based adhesives are made from blends of urea and melamine resins. The American Cyanamid Company’s Melurac resin is a co-spray dried melamine-urea-formaldehyde adhesive in a free-flowing powdered form designed for exterior waterproofing applications.

Coating Resins

Amino resins serve as crosslinking agents for hydroxyl, carboxyl, and amide functional polymers such as acrylics, polyesters, epoxies, and alkyds. Liquid amino coating resins are produced by reacting the initial methylolated species, dimethylol urea and hexamethylol-melamine, with either n-butanol or methanol. This step results in an amino resin that is more soluble in and compatible with the coating resins. The increased compatibility enhances the ether exchange reaction between the amino resins and the reactive sites of the coating polymers to produce coating films with a very high degree of crosslinking.

Urea-formaldehyde coating resins cure more rapidly but have lower moisture resistance than melamine-formaldehyde coating resins. In general, melamine-based coating resins have better overall performance, but, again, their higher costs limit their use. It is common to use a combination of urea/ melamine-based resins to achieve the right balance of properties, costs, and performance.


Beetle, Cymel, and Melmac are trade names of American Cyanamid Company’s liquid coating resins.t’“l

The Beetle grades are butylated and iso-butylated urea-formaldehyde resins with low-temperature cure characteristics, very good substrateiintercoat adhesiveness, and low cost. These urea-formaldehyde coating resins are compatible with hydroxy&aring polymers such as amine-catalyzed epoxy resins, oil-alkyd resins, epoxy-ester resins, cellulosics, and conversion varnishes.

The Cymel grades are either methylated or butylated melamine-formaldehyde resins with UV-resistance, chemical resistance, exterior durability, fast-cure characteristics, and very good adhesiveness. These melamine-formaldehyde coating resins exhibit compatibility for a wide range of resin types with thio, hydroxyl, carboxyl, and amide functional groups such as alkyd and polyester resins, epoxy resins, acrylics, vinyl polymers, and cellulosics. (Com- patible cellulosics include ethyl cellulose, hydroxyethyl cellulose, nitrocell- ulose, and carboxylated cell&se derivatives.) They are also good wetting and dispersing agents for carbon black and organic pigments. Some Cymel resins require the presence of strong acid catalysts for effectiveness and a high degree of crosslinking. P-toluene sulfonic acid is the most popular catalyst used with Cymel resins. The other catalysts are dodecylbenzene sulfonic acid, oxalic acid, maleic acid, hexamic acid, and metal salts. Metal salts like magnesium bromide (MgBr,), aluminum nitrate (Al(NO,),), and zinc nitrate (Zn(NO,),) are used to achieve hardness and solvent resistance, but they cause discoloration and low gloss.

Laminating Resins

Amino laminating resins are predominantly melamine-formaldehyde resins based. Typically, 1 mole of melamine reacts with 2 moles of formaldehyde at a pH of 8 to 10 to achieve a 50 to 65% solids resin. Catalysts and plasticizers are usually added to enhance cure and flexibility. Melamine-formaldehyde laminating resins have characteristic hardness, clarity, stain resistance, and UV-resistance. Spray drying is sometimes used to achieve long shelf life.

The methylolated melamine-formaldehyde resins form stable cationic colloids in the presence of such acids as carboxylics. The colloidal melamine

Amino and Furan Resins 8 1

resins impregnate and form strong ionic bonds with cellulose fibers (paper) in water dispersions, [‘I with a consequent increase in wet tensile strength. The degree of impregnation is enhanced by using water dispersions containing 0.5 to 1 .O percent of alcohol as a surfactant. The alcohol surfactant reduces the surface tension of the resin solution and increases fiber wettability. Typical colloid composition is of the melamine resin-acid-water ratio of 1: 1:6.5 by weight.

Saturation of the fiber material with the resin typically involves the free-turning-roll-pulling of fiber material through a resin solution bath. The resin-saturated web is then drawn to the dryer. The resin concentration, pulling speed, and residence time of the fiber in the bath influence the rate of impregnation. The dryer and drying process are an integral part of the laminating process. The drying process helps to evaporate the resin solvent and enhance the degree of resin polymerization.

Amino Molding Resins

Granule and powder forms of urea-formaldehyde and melamine-formaldehyde resins are used in molding resins. Their characteristic clarity prom- otes their use in a variety of colored products. Amino molding compounds are commonly formulated with fillers for strength and dimensional stability. Chemically purified alpha cellulose fibers are the most popular fillers for amino molding resins. The other tillers are talc, mica, glass fibers, chopped cotton flock, and wood flour.

Common mole ratios of urea or melamine to formaldehyde in amino resins are 2:3 and 3:4. The resinification process is carried beyond the point of water solubility, and then the resin-tiller mixture is heated at controlled humidity conditions. The resin-to-filler ratio, filler type, catalyst type, and degree of polymerization are varied to achieve different molding properties.

Compression transfer methods for processing and injection (screw and cold manifold) molding are the major amino molding resins. Molding temp- eratures are 260°-340’F for urea-formaldehyde resins and 260°-360’F for melamine-formaldehyde resins. Compression molding pressures of 2000 to 8000 psi are common for amino resins. Processing is enhanced by the presence of an acid catalyst such as phthalic anhydride and an inhibitor such as


hexamethylenetetramine (“HEXA”). Small amounts of the inhibitor help to stabilize the molding resin during storage and prior to molding, and to control the cure rate during molding.

FURAN RESINS

Chemistry and Resinification of Furan Resins Hw1[81

Furfuryl alcohol-based resins are the most important industrial furan resins in terms of usage and volume. [‘I The final cross-linked products exhibit outstanding properties and characteristics.

Furfural replaces formaldehyde in the conventional production of phenolic resins. It reacts easily with phenol in the presence of an alkaline catalyst to form a novolac phenol-furfural resin. (Novolac phenolic resin requ- ires an acid catalyst.)

Furfuryl alcohol readily resinilies or homopolymerizes in the presence of an acid catalyst [such as mineral acids, organic acids, Lewis acids (boron halides, e.g., BF,), and acyl halides] to produce liquid linear chains (oligo- mers). These chains consist primarily of dimers and trimers that have methylene linkages between the furan rings.

The process essentially is a methylolation involving the condensation of the methyl01 group of one furfury alcohol molecule with another molecule at the fifth position (Figure 3-4). The furfury alcohol resinification process is highly exothermic; the necessary temperature control is accomplished by cooling via either reflux or an external cooling fluid. The process is carried to a predetermined viscosity end point, and the reaction is stopped by adjusting the pH to between 5 and 8. The resulting liquid resin has a shelf life of more than 6 months. Furfuiyl alcohol also undergoes copolymerization with aldehydes such as formaldehyde and furfural, and with phenols and urea in the presence of an aldehyde.


Figure 3-4: Resinification Reaction of Furfuryl Alcohol

These furfnryl alcohol resins cross link (cure) in the presence of a strong acid catalyst via condensation. The terminal methyl01 group of one linear chain (Figure 3-4) joins with the methylene bridge of another chain to form a three-dimensional network structure (Figure 3-5).

Figure 3-5: Crosslinking of Fmliuyl Alcohol to Form 3-D Network Structure

PROPERTIES OF AMINO AND FURAN RESINS

The amino and fiuan resins, previously mentioned, were originally introduced to complement the phenolic resins and, as such, have comparable, but sometimes better, properties than the phenolic resins Table 3- 1. The characteristic light colors of these resins imply that they can be used in various colored products.

Ammo resins are generally stronger than phenolic resins. Cellulose- filled ammo resins have a tensile strength of about 5000 to 13,000 psi compared to 5000 to 9000 psi for cellulose-filled phenolic resins.

Melamine-formaldehyde resins have higher water and heat resistances than either phenolic resins or urea-formaldehyde resins.


Figure 3-6: Light colored amino resins-based coasters compared to dark colored phenolic resins-based coasters. The coasters were compression molded by students of Professor Robert Susnik’s plastic processing laboratory class at Pit&burg State University, Pittsburg, Kansas. The coasters were tested for arc resistance using a Beckman arc tester housed in the plastics testing laboratory. Melamine-formaldehyde resin has higher arc resistance than phenol-formaldehyde and urea-formaldehyde resins.


Figure 3-7: Fabricated items made from particleboard. Particleboard has superior structural strength and is somewhat less expensive than medium- density fiberboard. (Courtesy of Weyerhaeuser)


Applications of Amino and Furan Resins p1[21[511’-111

Trends in the consumption of amino resins are presented in Tables 3-2 through 3-5. The five major areas of amino resins application are adhesive and bonding, coatings, molded parts, plywood, and laminates. Adhesive and bonding is the largest market for amino and furan resins. Another major use of furan resins is as binders in core moldings and friction materials.

Adhesive and Bonding

Amino resins totaling 1.44 billion pounds were consumed in 1993 through adhesive and bonding applications (Table 3-2), mainly fibrous and granulated wood products (composite wood materials other than plywood). The major amino and fnran resins used to bond wood products are urea-formaldehyde resin, melamine-formaldehyde resin, melamine-urea copolymer resins, and turf&y1 alcohol-modified urea-formaldehyde resins.

Composite wood materials or composition boards, such as fiberboard, particleboard, waferboard, and oriented strandboard (OSB), account for more than 70% of the amino and furan resins adhesive and bonding market. Other uses include boat hulls, flush doors, fwniture, bag seam pastes, glass and mineral fiber mats, foundry sand cores (lost cores and molds), coated abrasive paper (emery), orthopedic casts and bandages, urea-formaldehyde foams, furan-polymer concrete, and general assembly bonding. American Cyanamid’s Melurac-400 resin achieves high-frequency bonding of truck and railroad flooring, laminated timber bonds, and millwork. It is also used for water-proof bonding of exterior doors and curved plywood.


Table 3-l : Properties of Amino (Urea, Melamine, Furan) Molding Compounds

Urea Melamine formaldehyde

” .m .- _

ti

% ASTM Alpha Glass test cellulo¶e- CellUlO6e- fiber-

Properties method filled filled reinlorced

1 Melhog lemperal”re. ‘C. Thermoset Thermosel rhrrrrosrl 1, (cryslalllnr)

g 1, (amorphous)

._ 2. Processtog lemperalure range. ‘F C. 275.350 C 260-370 c 260.350

2: IC = compressaon: T = Iranrler: I 290-320 I ZOO-340

: I m,ec,~on: E ex,rus8on, = = 1 270-300 T. 300

0 3 Molding pressure range. IO’ p s I. 2.20 6-20 2-6

& 4 Compressson ,ilteo 2 2-3 0 2.1-3 I 5. IO

5 Mold (knear) shrmkage, r./ln. 0955 0.006-0.014 0.005-0.015 0001-0006

6 Tensile strength at break. p s.i.

,%-I”. Iheck specmw,“,

I5 Hard”.%, Rockwelt 0765 t.4110.120 t.4115.125 Ml I5

Shore/Barcol 02240/ 02563

16 Coel 01 knear thermal exyanrton. 0696 22-36 40.45 15-26 10-e I” A” /‘C

- -___ z I? Oalleclton 264 I I ,emprral”,a p 0646 260-290 350-390 37,.400 E under tla.uraI lo.,*. “F

G -___

66pst 0646

f. __- I6 lhe,m.al conduclwly. 10.‘can -cm / c,,r-- 7 10 6.5-10 10.11 5

WC -cm z-“C


Table 3-l : Properties of Amino (Urea, Melamine, Furan) Molding Compounds (Continued)

Reprinted by permission of Modem Plastics Encyclopedia, McGraw-Hill, Inc.

Am

ino and Furan R

esins 89


Table 3-3: Trends in Amino (Urea-Formaldehyde and Melamine-

I

Formaldehyde) Coating Resins Consumption (106 Ib/yr)1511”1

Amino Coating Resins

Year

I 1987 111 87 I 24

I 1991 92 55 I 24

1992

t- 1993

Protective

35

84

90

103

111

100

104

138 50 19

147 __ I __

~ Paper Treatment Textile Treatment

33 I 31

c

57 I 34

Medium density fiberboard (MDF) and particleboard are the largest application areas for the adhesive and bonding market. (For more detailed inf- ormation concerning the composition of MDF, particleboard, and other composition boards, refer to the preceding section on Adhesive and Bonding Resins and the Chapter 2, Phenol-Formaldehyde Resins.) Particleboard is wood bas-


ed, whereas fiberboard is paper based, but both find major use in interior applications, mainly due to the low moisture resistance of urea-formaldehyde resin. Outdoor application types are generally based on melamine-type amino resins.

The waferboard and oriented strandboard markets are dominated by phenolic resin-type adhesives, designed mainly for exterior (outdoor) and structural applications.

Polymer concrete typically has a composition of about 10% resin and 90% aggregate. The aggregate is made up of 50% pea gravel, 35% fine sand, and 15% fly ash. Due to its chemical resistance, it is mainly used for man- holes, road repairs, seamless flooring, and corrosion-resistant bricks.

Table 3-4: Trends in Urea-Formaldehyde Molding Resins Consumption

1989 49.3 3.3 1.6 54.2

1990 50.7 3.8 0.8 55.3

1991 49.6 3.4 0.8 53.8

1992 52 3.4 1.2 56.6

1993 54 3 1.5 58.5


Table 3-5: Trends in Melamine Molding Resins Consumption

Furfkyl alcohol resin binder is used primarily for foundry sand cores and molds.

Coatings. Amino resin coatings have three principal applications: protective coatings, paper treatment, and textile treatment (Table 3-3). The protective coating applications predominate, with about 47 million pounds of amino resins used in 1993.

Protective coatings. Alkylated (butanolated and methylolated) amino resins are used mainly as crosslinking agents for protective coating resins such as acrylics, alkyds, epoxies, and polyesters. Butanolated amino


resins dominate the coating market, but methylolated melamine-formaldehyde resins are preferred for moisture-resistant, chemical-resistant, high-solids, outdoor coating systems in automotive topcoats, beverage cans, appliances, metal decorating, and prefabricated metals. Urea-formaldehyde resin-based coatings are typically used for the indoor coating of metals and wood. Urea- formaldehyde resins are also used, for instance, in carborundum-based abrasive, and fiber glass insulation coatings. Floor finishes based on urea-formaldehyde/epoxy copolymers are also common.

Textile treatment and coating. Wool, cotton, and other cellulosic textiles resist creasing by being impregnated with, typically, low molecular weight, highly methylolated resins (especially dimethylolated resins). About a 10 to 15% resin solid solution, with aluminum acetate or formic acid added, is used to impregnate alkaline fabric. The impregnated fabric is squeezed and pressed to twice its dry weight, and then dried and cured at about 140- 160 o C for 2 minutes. Textile treatment and coating enhance strength, minimize shrinkage, and impart chlorine resistance, abrasion and wear resistance, mil- dew proofing, and wash and wear (permanent press) characteristics.

Paper treatment and coating. Enhancing strength is the major reason for impregnating paper with resin. Sulfate pulp paper, Krafi paper, and unbleached sulfite cellulose paper are impregnated with amino resins typically at a pH of about 4 to 5. Urea-formaldehyde is the most commonly used amino resin, but melamine-based resins are used more for unbleached sulfite cellulose paper. Resin-impregnated Kraft paper is used for making bags, printing paper, and towel paper. Other paper products include shrinkage-free sheets from urea-formaldehyde-impregnated cellulose pulp and water-proof corru- gated cardboard.

Laminating. Plywood, which by definition of being a sandwich-type construction is a laminate but is never categorized as such, commands more usage of amino resins than all other laminates combined. Sixty-one million pounds of amino resins were used in plywood applications in 1993 compared to 38 million pounds for other laminates. These amino mainly urea-formaldehyde based resins, are typically used for interior applications.

The use of amino resins in plywood is relatively small compared to phenolic resins. The resins, with 1.55 billion pounds of phenolic resins used in plywood in 1993, dominated the market. Phenolic resins-based plywood is used for exterior applications, hence its domination of the plywood market.

94 Handbook of l%ermoset Plastics

Melamine resins, which dominate the amino resins laminates market are used more for decorative than for electrical and industrial purposes. Amino-m&s laminates are paper, cloth, veneers (wood) and glass (cloth and mat) based, sandwich-type constructions with high percentages amino resins. Stacks of heat-cured sheets are pressed together to produce laminates having the desired chara&ristics. Decorative laminates are used mainly for furniture construction kitchen counter tops, cabinets, and vertical wall surfaces. Indus- trial laminates are used for printed circuit boards, electrical panels, welding torch electrode insulators, and electrical switch gears. Other laminate applications include light reflectors and di&sers, refrigerator breaker strips, and name plates.

Molding. Eighty million pounds of amino molding compounds were used in 1993 (Table 3-2). About 73% were urea-type resins (Tables 3-4 and 3-5), due mainly to the higher costs of melamine resins (in spite of their better properties). The major areas of amino molding resins application are electrical, closures, housewares, buttons, and sanitaryware.

Alpha celhtlose-filled melamine molding resins are used to make hou- seware such as dinnerware (dishes, cups), ash trays, utensil handles, knobs, appliance components, control buttons, and sanitaryware such as toilet seats and bowl, and shaver housing.

Alpha cellulose-filled urea molding resins are used to make electrical wiring devices, such as circuit breakers, receptacles, electric blanket control housings, toothpaste tube housing, and knob handles.

Woodflour-tilled melamine molding resins are used for industrial electrical parts and military specifications. Glass- and mineral-filled melamine resins are also used for military specifications.

Miscellaneous. Filled urea resins, which can develop a dielectric strength of up to 1500 V/mm and electrical resistances of up to lOI ohm/cm, are used for electrical insulation.

Urea formaldehyde foam is used as artificial soil to grow plants and grass (plastoponics l/m introduced by Baumamr in 1967).r’21 Urea foam is also used in road construction projects to protect loose soil by growing grass in it such as for freeway abutments.


Modified urea resins are being used in glass mat shingles to replace tarpaper shingles. Glass mat shingles have higher resistance than tarpaper shingles and an improved fire risk insurance rating.

Melamine resins-based plywood and particleboard forms are used for concrete pouring.

Melamine resins-impregnated slag cotton is used in acoustic tiles for sound and fire-resistant insulation.

Furfuryl alcohol resin is used as a nonreactive diluent for epoxy resins. It is also the bonding material for corrosion-resistant fiberglass rein- forced plastic, which has excellent resistance to heat distortion and flame spread. This plastic is used in process piping, underground sewer, tanks, vats, ducts, and reaction vessels.

Furfuryl alcohol-impregnated graphite is used in nuclear reactors owing to its low permeability.

Furfmal and fin-fural-phenolic molding compounds are used for TV cabinets because of their long flow and chemical resistance characteristics.

Trade Name Beetle Chem-Rez C ymel Fabrez Melamine Melatine Mehnac Mehuac Permalite Plaskon Plaspreg QuaCorr

TRADE NAMES Type of Resin U/F FlNail

U/F

U/FandM/F Fl.lIaIl Furan

U/F - urea-formaldehyde M/F - melamine-formaldehyde

Company. American Cyanamid Ashland Chemical American Cyanamid Reichold Chemicals Fiberite Ciba-Geigy Corp. American Cyanamid American Cyanamid Ciba-Geigy Corp. Allied Corp. FuraneDivM&TChemical QO Chemicals, Inc.


REFERENCES

1.

2.

3.

8.

9.

10.

11.

12.

Blais, F.J., Amino Resins, Reinhold Publishing Corporation, New York, p 3, (1959). Meyer, B., Urea-Formaldehyde Resins, Addison-Wesley Publishing Com- pany, Inc., Reading, MA, p 4, (1979). Dick, S.J., Compounding Materials for the Polymer Industries: A Concise Guide to Polymers, Rubbers, Adhesives, and Coatings, Noyes Publications, Park Ridge, NJ, p 3, (1984). Richardson, T.L., Industrial Plastics: Theory and Applications, 2nd edition, Delmar Publishers, Inc., Albany, NY, p 2 10, ( 1989). Wooten, A.L., Urea, Melamine, and Furan Resins, Forest Products Utiliza- tion Laboratory, Mississippi State University, (1986). Gilman, H., Organic Chemistry: An Advanced Treatise, Vol. I, 2nd edition, John Wiley and Sons, Inc. New York, p 967, (1947). McKillip, W.J., Furan andDerivatives, QO Chemicals, Inc., West Lafayette, IN (reprint f?om Ulhnan’s Encyclopedia oflndustrial Chemistry, Vol. Al 2) VCH, New York, N.Y. p 119, (1989). Othmer, R., Furan Derivatives, QO Chemicals, Inc., West Lafayette, IN (reprint from Encyclopedia of Chemical Technology, Vol. II, 3rd edition, John Wiley & Sons, Inc. 1980), p 499, New York Schupp, R.J., Amino,Modem Plastics Encyclopedia, McGraw-Hill, Inc., New York, N.Y. p 17, (1986-1987). Cymel and Beetle-Conventional Butylated Amino Resins, American Cyan- amid Company, Charlotte, NC. U.S. Resins Sales by Process and Market, Modem Plastics, January issues p 57-67, (1984-1994). Meyer, B., Urea-Formaldehyde Resins, Adison-Wesley Publishing Comp- any, Inc., Reading, MA, p 207, (1979).

amino and furon resin

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