PAPER

Papermaking: Past & Present Paper identifies a broad range of products which are formed by bonding of many small discrete cellulosic or synthetic fibers into a sheet. The word “paper” is derived from the Egyptian word “papyrus:’ a material which is formed by matting sliced strips of reed together. However, the first production of true paper, a sheet comprised of small individual fibers, is credited to the Chinese in the year 105 A.D.

Early papermaking involved the reduc- tion of bark or grass to a fibrous pulp by beating it in a stone mortar. Water was added to create a pulp slurry which was in turn poured into a mould with a porous bottom which allowed the water to drain away. The newly formed sheet was then dried in the sun.

Papermaking proceeded in this manner for many centuries. Production, done totally by hand, was very small, but so was demand. However, with Gutenberg’s inven- tion of printing with movable type in 1447, the demand for paper soared. Handforming methods quickly proved inadequate, and a shortage of rags, a prime component of paper at that time, further limited production.

Neither problem was resolved until the early 19th century. In 1799 the prototype of today’s fourdrinier machine was invented by a Frenchman named Nicholas Robert. Its

N DUSTRY BASICS

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name is derived from two brothers named Fourdrinier who financed its development. The fourdrinier, however greatly refined, has not changed in principle since then.

Early papermakers had found naturally occurring, relatively pure cellulose fibers in the inner bark of certain trees and in cotton. However, it wasn’t until the 1830’s that

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Anselm Payen, a French chemist, identified cellulose as a separate component of wood. With this discovery, only a few years passed before wood was being pulped for use in papermaking. Thus, the modern paper- making industry was born.

Paper is made, to a greater or lesser extent, in nearly every country in the world. The United States, the leader in productive capacity, has the largest concentration of mills, equipment, and buying power in the world. Pulp and paper is the ninth largest industry in the US.

Paper is made from hundreds of different species of hardwood and softwood trees. Many factors, such as age and climate, affect the nature and composition of wood species.

Mod fiber is the primary raw material; but other fibers, including synthetics, are used in some grades. Many different chemicals are used for both the pulping and manufac- turing processes and as additives required as dyes and fillers and strengthening agents.

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And water in very large quantities must be available for the manufacture of paper.

Energy consumption is enormous in every phase of papermaking from transpor- tation of the raw material to the mill, through the manufacturing phase, and end- ing with transport of the finished product to the consumer. Since the petroleum price increases of the 1970s, most mills have installed additional power boilers to produce energy from woodwaste, spent chemicals, coal and sources other than oil.

References For further reading about the history of pulping and papermaking:

Bureau, William E-Milestones in Papermaking. Pittsburgh, Graphic A r t s Pch. Foundation, 1981.

Hunter, Dard-Papermaking through Eighteen Centuries. New York, W.E. Rudge, 1930.

Hunter, Dard-Papermaking: The History and Qch- niques of an Ancient Craft, 1st Ed., New York, A.A. Knopf, 1943.

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PAPER INDUSTRY BASICS

The Process

k l d in pul$.ng. The more refined the pulp must be, the more involved and costly the method of pulping. For example, kraft paper and linerboard do not require nearly the amount of chemicals as that required for white text paper, nor do they require refining and washing.

Mechanical pulping involves grinding a whole log to a pulpy mass by abrasion. With the refiner mechanical method, wood chips are steam-softened or partially decomposed with chemical solutions.

In the chemical process, chips are loaded into a digester and “cooked” in a liquor with chemicals to remove lignin and other nod- brous impurities. The wood fibers separate when the cooked chips are “blown” from the digester. The unwanted nonfibrous resi- due is then drained off. After a series of washing and bleaching stages, the fibers are passed through refiners which fiay them for better bonding in the forming process.

PAPER FORMATION Whatever pulping method is used, the next step is to form the slurry into the desired type of paper. After all bleaching, washing and refining is accomplished, and required chemicals are added, the slurry is pumped into a headbox. From the headbox the slurry is introduced onto the wire mesh of the fourdrinier machine.

The greater the quantity of slurry released from the headbox, the thicker will be the resulting paper. As the wire moves along, water drains through the wire mesh allowing the fibers to mat and interlace and form the sheet of paper.

Another important factor in paper formation is the speed of the fourdrinier machine. A mill measures its success in terms of saleable output. The faster the paper is produced, the more profitable the mill will be.

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Mills strive to attain maximum speed possible while preserving the quality of the sheet. Linerboard, for example, requires strength characteristics that must be main- tained. In contrast, newsprint permits higher speed formation since the quality and strength criteria are less critical.

After the paper travels the fid length of the fourdrinier, it leaves the wire and enters the press section for further dewatering. The fourdrinier wire, in the meantime, continues its loop.

7W.n Wire Formers The twin wire machine is a recent innovation which is gaining popularity. The traditional fourdrinier is essentially a two-dimensional unit measured in width and length. The twin wire machine, on the other hand, &three dimensional. Twin wire machines can be either vertical or horizontal in design.

In the vertical twin wire machine, the pulp sluny emerges under pressure fiom the headbox into a vertical upward flow. Two separate loops of wire mesh come together at a forming nip, and the sluny enters at that point. Drainage begins immediately with water leaving the wires in both directions. After the paper web has completed the short forming distance; it travels along the second wire and, as with the fourdrhier, is picked up by a felt and carried into the press section for further dewatering.

The operating speed of the twin wire machine is well in excess of the fourdrinier. In tissue production, speeds of 6,000 feet per minute have been reached, with an even higher potential.

Drying As the paper web is carried on a moving felt into the press section, it is compressed and more water is squeezed out. Then it enters a long series of dryers. It continues through this section of steamheated cylinders to the calender stacks where it is pressed and smoothed. The finished paper is then wound onto a large roll.

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I PAPER INDUSTRY BASICS

FINISHING & CONVERTING The finished roll of paper must be processed further into different sizes and forms to fill the requirements of various end users.

Coating Not all papers are coated, but there is a great demand for paper with a smooth printing surface. Most printing processes produce better results on coated papers; and for four color work, coated stock is essential.

Coatings add opacity and brightness a reflective whiteness to the paper. In printing papers, coated stock comes in three principal forms: glossy, dull and matte. Glossy stock is just that, shiny, and is what many people think of when the term “coated” is used. However, dull coated is ideal for books where the elimination of light glare is important. Matte coated is similar to dull but also has a “tooth” in it. Matte is a popular artists’ paper.

Although some lower grade publication stocks are coated in an added process in the dryer section, higher grades are usually manufactured as a separate operation off the machine. Air knife and blade are the two popular methods of applying coatings. In the air knife process, a jet of air serves as a blade to remove the excess of freshly-applied coating material. In blade coating, a flexible blade is set at an angle to accomplish this. Coatings can be applied on one or both sides of the paper.

Calendering Calendering involves passing the paper through a series of polished steel rollers to

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smooth it before winding it onto a roll. The I L smoother the paper desired, the more rollers

the paper passes through. Smoother finish ~

paper will have less bulk for its basis weight than a vellum finish product. Winding and Sheeting I

Winding the paper onto a roll is just about the last step of the manufacturing process after it has been coated and calendered or otherwise processed. The width of the reel will correspond to the width of the four- drinier. This reel will then typically pass through a rewinder and slit into smaller rolls.

These rolls may go directly to the end user, or they may be converted into sheets. Paper merchants stock many types of paper in standard sheet sizes for the large printing market.

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End Products Hundreds of different types of paper are used today for commercial, industrial and domestic applications. They range from the h e s t printing papers to panelboard. Nearly 7 8 - d o n tons of paper and paperboard were produced in the United States in the past year. The following covers some of the more common types.

TISSUE Soft tissue includes paper toweling, bath- room and facial tissue, and wrapping tissue for domestic, industrial, hospital and institu- tional use.

NEWSPRINT Newsprint is the most economical type of printing paper which can be purchased and used to transmit a printed message. It has a

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groundwood fhnish with a small additional amount of chemical pulp to provide neces- sary strength. A growing percentage of newsprint is produced using recycled paper.

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Representing more than half of the total commercial and industrial categories of paper produced in the U.S., printing and writing papers refer to a large segment of products. This includes coated and uncoated groundwood, coated and uncoated free sheets, wood or cotton fiber content bond, ledger, copier, and many other papers which serve as a medium for the printed word.

WRAPPING PAPER Wrapping paper comes in a wide variety of forms for business, industrial and consumer use. One of the most common is the brown kraft paper used in mailing paper and consumer grocery bags. Envelopes, gum- med sealing tapes, insulation, abrasive papers and coated food wrappings are a few of the many other uses.

PAPERBOARD There are three principal grades of paper- board: boxboard, containerboard and specialties. Paperboard has a variety of uses in packaging, shipping, building construc- tion and manufacturing.

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PAPER INDUSTRY BASICS

Recycling and Recycled Paper Paper recycling has assumed a growing role in fiber supply as solid waste management has reached crisis proportions in the United States as well as the rest of the world. Over

~ 30 states haveenacted legislation requiring state agencies to purchase recycled paper. Many states have also legislated or are in the process of legislating minimum recycled fiber content in newsprint.

In 1989 27.6 million tons of wastepaper were collected for recycling in the U.S. Of that amount, 21.3 million tons were used as raw material to make paper and paperboard with the remainder being exported to other countries for recycling.

Of the 600 paper and board mills in the United States, about one third of them depend almost exclusively on wastepaper as their raw material while most of the others use between 10% and 35%. Last year over 32% of all the paper consumed in the U.S. was collected for recycling, and the industry has set a goal for 1995 to recycle 40% of all paper. Wastepaper is the fastest growing raw material for papermaking not only in the U.S., but also in the world. The U.S. is the only exporting country of any magnitude.

Wrldwide the use of recycled fiber is expected to grow from nearly 75 d o n tons in 1988 to 100 million tons in 1996 and reach 130 million tons by 2001. The use of recycled fiber in newsprint will continue to grow in western Europe, Japan and eastern Asia; and there will be major changes in newsprint production in the U.S. as a result of current and expected legislation.

*Information in this section was extracted from articles by J. Rodney Edwards, A.P.I., in the August 1990 issue of Tdppi Journal and by Esko Uutela, Jaakko Poyry> and Norman Black, in the July 1990 issue of Xippi Journal.

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No significant use of wastepaper is foreseen in lightweight coated papers due to ongoing brightness and printability prob- lems. Use of wastepaper is already high in tissue grades and will increase and be found in a wider range of these grades. Recycled fiber is already well established in carton- board grades.

The accelerated growth in wastepaper use will be accompanied by similar accelera- tion in the demand for wastepaper process- ing equipment and chemicals. Presently, about 11 million tons of wastepaper are deinked annually worldwide. By 2001 this figure will have increased to over 30 million tons. The demand for deinkhg chemicals will grow at a rate of 8-10% yearly and will be almost three times higher in 2001 than in 1988.

In the immediate future wastepaper use will grow twice as fast as the use of virgin fiber. Overall global demand for paper and board will continue to grow strongly so virgin fiber demands will also grow.

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T A P P I J O U R N A L I MiU Operations Integrated pulping and papermaking mills are highly complex operations requiring expertise from many different disciplines. There are four major functional areas into which the operation of the integrated mill falls: production, technical, plant engineer- ing, and research and development. There is typically a manager in charge of each of these areas with superintendents in charge of the major operations of each contributing function.

PRODUCTION DEPARTMENT Production is the heart of the mill’s opera- tion. The production department sees that wood chips are pulped and paper is made. Rchnical, engineering and RGtD all vital to the mill‘s operation serve or relate to the needs of production. Production typically consists of the wood department, the pulp mill, the power and recovery units, the paper mill, the finishing department, and the coat- ing system for certain grades of paper. (Coat- ing formulation, because it is closely related

to product development, is usually the responsibility of RGtD.)

wood Department The woodyard superintendent and his staff are responsible for the receipt and storage of logs, barking and chipping, and chip handling and storage. The wood department provides a ready supply of chips of desired specification to the pulp mill.

Pulp Mill The pulp mill superintendent oversees the conversion of wood from its raw state to a liquid slurry of bleached fibers. He and his staff are in charge of the digesters, washing, screening, bleaching and pulp storage.

There are a number of methods for reducing wood to its “pulped” state. Most typically it is “cooked” with various chemi- cals in a large digester then washed and screened for dirt and other impurities. The pulp is then processed through one or more bleach sequences to remove lignin and other impurities. The bleached pulp is then stored in holding tanks to await transport to the stock preparation area.

Paper Mill The paper mill superintendent is responsible for stock preparation, and operation of paper machines and dryers. In larger mills these are usually assistant superintendents, each in charge of one or two paper machines and one in charge of stock preparation.

The paper mill consists of a sequence of machines which transforms the liquid pulp into a dry roll of paper. Pulp stock, which is prepared by adding various chemicals to the bleached pulp slurry, is poured onto one of several forming wire systems where most of

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the process water is removed. The remaining web of fibers is then transferred to a number of drymg rolls where remaining moisture is removed. The resulting paper is then calen- dered (or pressed) and wound onto a roll.

Power and Recovery pulp and paper is the second most energy- intensive industry in the United States. Purchasing power and water, using waste materials and recovering substances for re-use are extremely important to the profitability of a mill. In some mills these functions fall into a separate department. In others, recovery and recausticizing are the responsibility of the pulp mill, with power and utilities being part of plant engineering.

Power and recovery superintendents are responsible for power boilers, recovery boil- ers, recausticizing, liquor preparation, and utilities including electricity, water, steam and compressed air.

Finishing The finishing department is responsible for rewinding, supercalendering, wrapping, cutting and trimming, packaging and ship- ping. Coating, $required, takes place in this department; but the coating superintendent typically reports to the production manager. In small mills, one person oversees these functions. In larger, more complex mills, assistant superintendents and supervisors are in charge of each of these areas.

1: PAPER INDUSTRY BASICS

TECHNICAL DEPARTMENT The technical director is responsible for process improvement, process and quality monitoring and compliance with environ- mental regulations, and the technical staff is comprised of people in charge of each of these areas. The technical department is involved in all stages of production and thus makes sigtllficant contributions to buying decisions relating to new equipment and process changes which affect operations.

Process Engineering In smaller mills, individual process engineers are assigned to the wood department, pulp mill and paper mill areas. In larger opera- tions, groups of engineers and their leaders would be responsible for these areas.

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PLANT ENGINEERING DEPARTMENT Plant engineering includes responsibility for physical plant facilities and maintenance of those facilities. One individual, usually the plant engineer, oversees this department.

Design Design includes design and development and project engineering. Desigdproject engineers usually specialize in different areas of production. There are usually project group leaders who report to the plant engineer.

Maintenance Maintenance includes mechanical, electrical, instrument and general maintenance.

Process Control Quality analysis and control of the pulping and papermaking process is the responsibil- ity of the process control department. This includes instrumentation and monitoring equipment. In larger mills there will be groups for each of these functions. Shift chemists and testing supervisors usually report to the process control superintendent.

Environmental Control Environmental regulations have com- pounded in recent years, and all mills must now comply with many strict requirements. In large mills the environmental finction includes groups responsible for air quality monitoring, effluent treatment, plant opera- tions and, sometimes, noise monitoring.

Pipefitters, welders, millwrights, electricians, carpenters, painters and janitors all fall under this important category.

RESEARCH &DEVELOPMENT In most major paper companies, research and development is centralized. These cor- porate research centers include laboratory and pilot plant equipment to simulate the processes in each of a company’s mills. In most cases evaluation of new (revolutionary) equipment and processes is corporate research’s responsibility. Evaluation of improved (evolutionary) equipment or processes may rest with corporate RGrD, be assigned to the individual mill’s technical department, or be shared by both groups.

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I PAPER I N DUSTRY BAS I CS

The Buying Process

REACHING THE INFLUENCES

BUYING

In 1990 U.S. paper industry spent over $17 billion* on mill operating equipment and services. About half of this amount was spent on manufacturing equipment. Expenditures for equipment not directly used in the manufacturing process, such as process automation controls, pollution control equipment, power or other types, are not included in this figure.

There are 800 pulp, paper and paper- board mills in the United States. Competition to reach the buying influences within them is intense, and marketers must carefully tailor their selling efforts to do this effectively.

Because pulping and papermaking are complex, interrelated operations, a change in one segment of the process can have rami- fications throughout the remainder of the operation. Therefore, a company which is marketing an innovative process, or piece of equipment to the pulp mill operations team most likely will be concerned with other groups. It may need to work with the opera- tors of the paper machine, the coater, and the process control equipment; the technical director; and the maintenance manager. And, if the installation requires a capital expenditure, the seller must not only be concerned with the immediate supervisors and managers, but also managers or vice presidents several layers higher as well as long-range development planners.

Much buying in paper mills is done by a committee comprised of representatives from many parts of the mill. The following brief overview of mill operations is designed to give the newcomer to the paper industry some understanding of why this is so.

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PURCHASING INFLUENCES The buying process for goods and services purchased by the pulp and paper industry may be very simple or relatively complex, depending on the nature of what is being bought. Very few people may be involved in a commodity purchase, whereas a purchas- ing committee representing all phases of mill operations may be involved in the purchase of a major process control system.

Strictly speaking, a commodity product has no differentiation from others of its kind. That is, oxygen is oxygen no matter where

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*American Paper Institute

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you buy it. Commodities are bought for what they are. Conversely, specialties are bought for what they do. A specialty product usu- ally has a direct effect on the outcome of the manufacturing process, may interact with other products used in the process, and may have services and other extras included with it.

The distinction between commodities and specialties is not always clear-cut. Corn- starch, for example, may be considered a commodity in some respects. However, it may be converted to a variety of forms, each of which may have different applications which require technical service support. In these cases, the commodity becomes a specialty chemical.

Purchasing Agents In general, the purchasing agent is the primary decision maker in placing orders for commodity materials and storeroom supply items (valves, batteries, pipe, etc.) . The pur- chasing agent’s concerns are getting the best price and on-time delivery. The purchasing agent plays a smaller role in the purchase of specialties where operating and technical personnel have the major decision making responsibility.

Buying Influence Various operations and technical people become involved in the decision on buying specialty items-particularly large, expensive ones. A way to identify these buying influ- ences is to look at the organization of a mill. A large, integrated mill has a very compli- cated organizational structure. It is possible

to look within a mill and, based upon its complexity and size, make some judgments about who is likely to be buying what.

M d t i - w Companies The larger the company, the more compli- cated the management structure. Resident mill managers usually report to a corporate vice president of manufacturing. In larger companies, mills may be grouped by paper grade and headed by a corporate executive in charge of that group. Such companies often centralize many of their buying functions to gain the economics of volume purchases. Thus, another dimension is added to the marketing scenario.

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ORGANIZATIONAL STRUCTURE OF AN INTEGRATED MILL

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T A P P I J O U R N A L I CAPI'IIAL EXPENDITURES More often than not, there are many Merent primary and secondary buying influences involved in a capital equipment purchase. As an example, consider the case of the purchase of a coater or other new type of surface sizing device to replace a con- ventional size press in the paper machine. Operating management, including the paper mill superintendent, production manager, and mill manager are concerned about potential runnability problems, effect on machine efficiency, production capability, ease of operation, effect on paper quality, and other operating variables. The division general manager, manufacturing vice president, and other corporate managers are concerned about equipment costs, required downtime for installation, overall cost, return-on- investment, and payback period.

Plant engineering is concerned about how the new equipment will fit with existing equipment, the space required, downtime required for installation, requirements for utilities (electricity, water, compressed air), ease of maintenance and the potential to reuse existing parts in the new equipment. Corporate engineering, or a consulting engineer, will be concerned about overall project cost, utility requirements, foundation and building modification requirements, and the potential impact on other capital projects at the same mill. The and/or technical department is concerned about the capa- bility of the new device to facilitate the production of new grades, effect on quality

parameters of existing grades and the requirement to reformulate surface sizes and/or coatings.

Marketing management is concerned about the capability of a new device to make existing grades without compromising quality as well as the capability to expand the current grade line or make entirely new grades on an existing machine. At various times during the process leading up to a deci- sion to buy a particular piece of equipment, each of the above groups will have its input with its amount of influence on the final buying decision varying case by case.

The buying process could start with any of the foregoing groups. For example, marketing or product development could recognize the opportunity to sell more profitable paper if the capability of the existing machine is expanded. General management could recognize that the machine is not currently making a profit contribution adequate to justify its existence necessitating a decision to find a way to increase profit contribution or shut the machine down. The superintendent could look at the new device as a potential means to increase production or reduce downtime. The technical department could see it as a way to improve quality or make a more consistent product.

An analog could be drawn for other types of capital equipment with the role of groups such as marketing and product development lessening if the equipment

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would not result in a change in end product. For example, the decision to buy a new barking drum or chipper would have only minimal involvement from groups other than the woodyard superintendent, pulp mill superintendent, engineering and executive management unless it would be expected to cause a significant difference in pulp quality.

OPERATING SUPPLIES Buying decisions on maintenance replace- ment items, such as machine clothing, are made typically by the people running the machinery. Chemical raw materials and specialty chemical additives start to become more complex. Consider a pulp mill defoamer. The pulp mill super- intendent looks at it as a means to control foam on the brown stock washers and is concerned primarily with its performance as a defoamer at a minimum cost-per-ton addition rate. The technical department is concerned with the potential interaction of the defoamer with other additives used later in the process. (E .g., will it affect retention, sizing, or deposit control on the paper machine? Is it FDA-approved?) As the complexity of the grades made at a given mill increases, the potential for inter- reaction among additives at various stages of the process increases exponentially. The operating superintendent considering the use of an additive such as a felt conditioner must have it screened and tested for compatibility by the technical department.

Raw materials and additives used in coatings are even more complex. Efficacy in the coating formulation and in the coated

I PAPER INDUSTRY BASICS

sheet along with the potential effect on other components in the formulation must be determined by RGtD. In addition, the potential effects of recycled coated broke must be determined.

In summary who is involved in the buying process for a given product is deter- mined by: 1. The potential effect of the product on the

end product properties of the pulp or paper being produced;

2. The degree to which the product invades the process and its potential for inter- reaction with other raw materials and additives.

NEED FOR MULTI-LEVEL SELLING - The variety of people involved in the buying process for different products makes it necessary to sell the same product or service to different people in an individual mill organization. In the case of big ticket capital equipment, it is usually also necessary to make the same sale to people in corporate management, corporate engineering, and RGrD, and, perhaps, outside consultants working with the given mill.

Each of these groups of people has need for information relative to their own particular scope of interest.

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References Marketing to the F'ulp and Paper Industry, WPI, 1985. Saltman, David-Pulp and Paper Primer, TAPPI, 1983. Whitney, Roy P.-The Story of Paper, TAPPI, 1984.

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Newer technologies

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NONWOVENS What is a nonwoven? Because there are so many different configurations of non- wovens, a simple definition is inappropriate, if not impossible. However, nonwovens are manufactured as sheets, webs or bat& of directionally or randomly oriented fibers which are bonded together. Nonwoven fibers can be natural or man-made.

History Although the first commercial production occurred in 1853 with the carded nonwovens machines, nonwoven-like materials have long existed in nature. Spider webs and cocoons have close similarity to spunbonded nonwovens.

be low melting, high melting or not melt at all. They can be stiff or flexible, absorbent or repellent, weak or strong.

Although most nonwoven materials are constructed of manufactured fibers, natural fibers are preferable for some applications. Jute is commonly used for carpet backing and automobile insulation, and fluff made from wood pulp is used in the inner portion of diapers for its absorbency.

The principal manufactured fiber being used is polyester because of its low cost, high strength, resilience and whiteness retention. Common uses include interfacing, bunting, window shades, diaper cover stock and computer floppy disk covers.

Polypropylene is gaining in popularity as a nonwovens fiber. It is extremely low in cost and has properties similar to polyester. m i c a l uses include diaper cover stock, geotextiles, filters, oil spill scavenging devices, linens and indoor-outdoor carpets. Polyethylene, a similar fiber, is often used in hang tags, mailing envelopes and work

Many other manufactured fibers are used in nonwovens. Acrylic fibers are favored for their chemical resistance; and nylon, toughness and resilience. In addition to the various forms of nylon, glass, metallic and ceramic fibers are also used for applica- tions requiring unusual properties.

clothing.

Fibers Used in Nonwovens Fibers used in nonwovens can be natural or synthetic and can vary in length from one millimeter to a continuous strand. They can

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Manufacturing Methods Four basic manufacturing methods apply to nonwoven webs: carding, air-laying, wet- laying, and the spunbonded process.

CARDING This is a dry-laying method which is based on the yarn manufacturing process. In this case, though, instead of condensing the fibers into a single strand, the M width of the fiber web is maintained. Multiple layers of the carded webs are then combined in a unidirectional pattern and then bonded chemic ally, mechanically or thermally. Carded nonwovens have a wide range of applications including geotextiles, interfac- ing, indoor-outdoor carpeting, synthetic shoe leather, blankets, paper making felts and many other products.

AIR-LAYING Another dry-laid method is air-laying. In this method air is used to transport and form a batt of fiber in a random pattern. A stream of air carries the fibers to a vacuum condens- ing belt or drum. In either carding or air lay- ing almost any generic type fibers can be used either alone or in combination. Air-laid webs tend to be lofty and porous which makes them useful for filters, fiberfill, padding, wipes and other uses.

WET-L AYING The wet-laying process was developed from the paper manufacturing process and uses an inclined wire rather than the flat tabled fourdrinier. Wter is removed mechanically by gravity, foils or table rolls and pressure. The web is then passed over a heated section to remove excess moisture. The long fibers used in wet-laying create an end product

I PAPER INDUSTRY BASICS

ideal for use in automotive oil and air filters, milk filters, tea bags, bunting, hang tags, roofing shingles and electrical insulation.

SPUNBONDED PROCESS The spunbonded process combines fiber for- mation and web formation. The most com- mon method of manufacture uses molten polymer forced through spinnerettes. The fibers are spun and then drawn and oriented and deposited uniformly on a moving screen, densified, and bonded. Most spun- bondeds are melt-spun and thermally bonded. End uses include geotextiles, bail- ing, filter fabrics, work clothing, wallpaper and other products.

The melt blown process, a variation of the spun bonded process, uses a high- velocity air jet which blows random lengths of fibers against a firming drum or screen. The resulting mat formed from these ultra fine fibers has excellent filtration and insu- lating properties. Melt blown fabrics are commonly used as insulation in outdoor apparel, filters and wipes.

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T A P P I J O U R N A L I Bonding The fibrous network within the nonwoven web must be bonded to achieve adequate functional strength. Four methods can be used: inherent bonding, thermal bonding, mechanical bonding and chemical bonding.

INHERENT BONDING A web is said to be inherently bonded when no Wher bonding is needed after the web has been formed. Inherent bonding accounts for a very small proportion of all nonwovens so the process is of limited importance.

THERMAL BONDING Although accounting for only 5 % of all non- wovens, thermal bonding is growing in importance. Most of the synthetic fibers used in nonwovens today are easily bonded by the application of heat.

MECHANICAL BONDING Mechanical bonding is used on more than 40% of all nonwovens. There are several techniques in common use.

Needle punching Neede punching relies on the use of barbed needles which are “punched” through the fabric to entangle the fibers. Products made by this method include papermaking felts, indoor-outdoor carpets, blankets, padding and synthetic leather.

Stitch-through process The stitch-through process uses machines which can form fabrics from yarns alone. They can also stitch nonwoven webs from yarns or create pile fabrics formed by yarns.

End uses for these fabrics vary considerably and include drapery, upholstery, apparel, carpeting and toweling.

Spunlaced process Also known as the hydroentanglement process, the spunlaced process starts with a carded web that is carried by a belt under multiple water jets. Fine, high-pressure water jets cause the fibers to migrate and entangle with one another. Resultant fabrics can have numerous patterns. spunlaced fab- rics are used for headrest covers on planes, medical gauze, wipes and table linens.

CHEMICAL BONDING Chemical bonding is accomplished with either solvents or binders.

Solvents In this method fibers are bonded together as they come into contact with one another after the fibers’ outer surface is softened. Calendering is often done to increase the degree of bonding.

Binders More commonly, nonwovens are bonded with adhesive-like binders. They can be applied by spraying, saturation, coating, foam or printing, depending on the product. The type of binder and method of applica- tion substantially alters the performance characteristics of the nonwovens.

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Finishing Nonwovens can be finished chemically, mechanically, and with a high-energy process.

CHEMICAL FINISHING The principal chemical finishing treatment is dyeing and printing to achieve a certain color or pattern. Product sterilization is also frequently done for items used for medical applications. Flame retardants, water repellents, mildew proofers and bactericides are other examples of chemical finishing processes.

MECHANICAL FINISHING Calendering, embossing, brushing and compacting are some of the more com- mon finishing techniques. Compacting is by far the most important and can be accomplished by creping with a doctor blade or one of several other patented processes. Compaction increases stretchability, toughness and softness and is often used for linens, wipes and similar products.

HIGH ENERGY FINISHING Examples of high energy finishing include singeing, ultrasonic welding and sterilization, with sterilization with dry heat, steam or radiation being the most important.

Diversity of Uses Their economical cost and diverse proper- ties, make applications and end uses for nonwovens essentially limitless. Disposable

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products have received the greatest attention, but durable nonwovens are achieving greater prominence.

Disposable products include diapers, sanitary napkins, wipes, surgical gowns, drapes, packs, sponges, gauze, barrier packaging, filters, towelettes, dust cloths, hang tags, napkins, work clothes, and many other such products.

The long and sometimes permanent life span of durable nonwovens make them excellent for many hard use applications. Papermaking felts, geotextiles, automotive fabrics, gaskets, carpets, carpet backing and roofing shingles are a few examples.

Nonwoven products increasing in importance include air laid, stitch-through, spunlaced, spunbonded, melt-blown ther- mally bonded, and wet laid nonwovens. Because of their wide range of properties, nonwovens have been used to replace many existing products while at the same time new applications are being developed.

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The foregoing article about nonwovens is a condensation of “Nonwovens: the state of the art:’ J. Robert Wagner, Zdppijournal, April 1988, pp. 115-121.

FLEXIBLE PACKAGING Another volume end user of paper is the flexible packaging industry. Difficult to clearly define because of the many different combinations of materials used, flexible packaging cuts across the paper, plastics, aluminum and container industries. End use applications range from hygienic packaging for foods and medical supplies to bags for garden fertilizer to soft drink containers.

Materials Nearly all flexible packaging incorporates some form of plastic. Plastic films and foils are laminated together with paper in a variety of combinations to produce end products with a variety of desired properties. Moisture-proofing, abrasion-resistance, temperature-resistance, opacity, grease- proofing, physical strength and, of course, flexibility, are some common ones. In other cases films are extruded and formed into appropriate shapes and sizes of pack- ages. Various forms of polyethylene and polypropylene, thermoplastic urethane, nylon and other synthetic materials are used alone or in combination to produce many products.

Thermoplastic adhesives are used in many packaging applications. Such adhesives are developed for their heat resk- tances, resilience in frigid temperatures, moisture or oil repellence, or other charac- teristics. Special formula inks, solvents, resins and primers are also key elements in the manufacture of many packages.

Fragmented Industry Although major producers of paper, petrochemicals and aluminum provide the raw materials used in flexible packaging, much of the actual production of the packaging is fragmented across a diversity of hundreds of manufacturers. Many of the larger ones have integrated their operations from the production of raw materials to the conversion of bags, printed rolls and sheets, coating, laminating or coextruding operations. Smaller companies are often engaged in the conversion of packaging material by laminating, coating, printing, waxing, or othenvise fabricating to produce wraps, bags and other packages as well as shrink or stretch film and roll stock. In addition, many end users of flexible packaging materials now have developed their own in-house converting operations. Although flexible packaging has replaced paper for some applications, e.g., plastic grocery sacks, it has opened new applications for paper, too. Laminated with film or foil, paper is an essential component in many food, medical and consumer product packages.

As new improved formulations offer an increasing diversity of features, manufacturers will receive even wider acceptance of their products. With society seeking ever higher levels of convenience in foods and other products, the fUture of flexible packaging is assured.

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Papermaking miOM THE FOREST To THE FINISHED PRODUCT- THE PROCESS SIMPLIFIED

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