PAPER NDUSTRY BASICS

Papermaking: Past & Present r 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. name is derived from two brothers named Neither problem was resolved until the Fourdrinier who financed its development. early 19th century. In 1799 the prototype of The fourdrinier, however greatly refined, has today’s fourdrinier machine was invented by not changed in principle since then. a Frenchman named Nicholas Robert. Its 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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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, Anselm Payen, a French chemist, identified coal and sources other than oil. 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 References world. Pulp and paper is the ninth largest For further reading about the history of pulping and industry in the US. papermaking: Paper is made from hundreds of different Bureau, William E-Milestones in Papermaking. species of hardwood and softwood trees. Pittsburgh, Graphic Arts Pch. Foundation, 1981. Many factors, such as age and climate, affect Hunter, Dard-Papermaking through Eighteen the nature and composition of wood species. Centuries. New York, W.E. Rudge, 1930. Mod fiber is the primary raw material; Hunter, Dard-Papermaking: The History and Qch- but other fibers, including synthetics, are used niques of an Ancient Craft, 1st Ed., New York, A.A. in some grades. Many different chemicals Knopf, 1943. are used for both the pulping and manufac- turing processes and as additives required as dyes and fillers and strengthening agents.

3 PAPER INDUSTRY BASICS

The Process

kld 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. The greater the quantity of slurry released from the headbox, the thicker will PAPER FORMATION be the resulting paper. As the wire moves Whatever pulping method is used, the next along, water drains through the wire mesh step is to form the slurry into the desired allowing the fibers to mat and interlace and type of paper. After all bleaching, washing form the sheet of paper. and refining is accomplished, and required Another important factor in paper chemicals are added, the slurry is pumped formation is the speed of the fourdrinier into a headbox. From the headbox the slurry machine. A mill measures its success in is introduced onto the wire mesh of the terms of saleable output. The faster the fourdrinier machine. paper is produced, the more profitable the mill will be.

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7W.nWire 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.

Mills strive to attain maximum speed Drying possible while preserving the quality of the As the paper web is carried on a moving felt sheet. Linerboard, for example, requires into the press section, it is compressed and strength characteristics that must be main- more water is squeezed out. Then it enters a tained. In contrast, newsprint permits long series of dryers. It continues through higher speed formation since the quality and this section of steamheated cylinders to the strength criteria are less critical. calender stacks where it is pressed and After the paper travels the fid length of smoothed. The finished paper is then wound the fourdrinier, it leaves the wire and enters onto a large roll. the press section for further dewatering. The fourdrinier wire, in the meantime, continues its loop.

5 PAPER INDUSTRY BASICS I

FINISHING & CONVERTING r The finished roll of paper must be processed smooth it before winding it onto a roll. The I further into different sizes and forms to fill smoother the paper desired, the more rollers L

the requirements of various end users. the paper passes through. Smoother finish ~ paper will have less bulk for its basis weight Coating than a vellum finish product. Not all papers are coated, but there is a great Winding and Sheeting I demand for paper with a smooth printing surface. Most printing processes produce Winding the paper onto a roll is just about better results on coated papers; and for four the last step of the manufacturing process color work, coated stock is essential. after it has been coated and calendered or Coatings add opacity and brightness a otherwise processed. The width of the reel reflective whiteness to the paper. In printing will correspond to the width of the four- papers, coated stock comes in three principal drinier. This reel will then typically pass forms: glossy, dull and matte. Glossy stock through a rewinder and slit into smaller rolls. is just that, shiny, and is what many people These rolls may go directly to the end think of when the term “coated” is used. user, or they may be converted into sheets. However, dull coated is ideal for books where Paper merchants stock many types of paper the elimination of light glare is important. in standard sheet sizes for the large printing Matte coated is similar to dull but also has a market. “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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End Products Hundreds of different types of paper are groundwood fhnish with a small additional used today for commercial, industrial and amount of chemical pulp to provide neces- domestic applications. They range from the sary strength. A growing percentage of hest printing papers to panelboard. Nearly newsprint is produced using recycled paper.

78-don tons of paper and paperboard ~ ~ were produced in the United States in the P"GA"G past year. The following covers some of the Representing more than half of the total more common types. commercial and industrial categories of paper produced in the U.S., printing and TISSUE writing papers refer to a large segment of Soft tissue includes paper toweling, bath- products. This includes coated and uncoated room and facial tissue, and wrapping tissue groundwood, coated and uncoated free for domestic, industrial, hospital and institu- sheets, wood or cotton fiber content bond, tional use. ledger, copier, and many other papers which serve as a medium for the printed word. NEWSPRINT Newsprint is the most economical type of WRAPPING PAPER printing paper which can be purchased and Wrapping paper comes in a wide variety of used to transmit a printed message. It has a 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.

7 PAPER INDUSTRY BASICS

Recycling and Recycled Paper Paper recycling has assumed a growing role No significant use of wastepaper is in fiber supply as solid waste management foreseen in lightweight coated papers due to has reached crisis proportions in the United ongoing brightness and printability prob- ~ States as well as the rest of the world. Over lems. Use of wastepaper is already high in

~ 30 states haveenacted legislation requiring tissue grades and will increase and be found state agencies to purchase recycled paper. in a wider range of these grades. Recycled ~ Many states have also legislated or are in the fiber is already well established in carton- process of legislating minimum recycled board grades. fiber content in newsprint. The accelerated growth in wastepaper I In 1989 27.6 million tons of wastepaper use will be accompanied by similar accelera- were collected for recycling in the U.S. Of tion in the demand for wastepaper process- that amount, 21.3 million tons were used as ing equipment and chemicals. Presently, raw material to make paper and paperboard about 11 million tons of wastepaper are with the remainder being exported to other deinked annually worldwide. By 2001 this countries for recycling. figure will have increased to over 30 million Of the 600 paper and board mills in the tons. The demand for deinkhg chemicals United States, about one third of them will grow at a rate of 8-10%yearly and will depend almost exclusively on wastepaper as be almost three times higher in 2001 than their raw material while most of the others in 1988. use between 10%and 35%.Last year over In the immediate future wastepaper use 32% of all the paper consumed in the U.S. will grow twice as fast as the use of virgin was collected for recycling, and the industry fiber. Overall global demand for paper and has set a goal for 1995 to recycle 40% of all board will continue to grow strongly so paper. Wastepaper is the fastest growing virgin fiber demands will also grow. 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 dontons 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.

*Informationin 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. 8 I TAPPI JOURNAL MiU Operations Integrated pulping and papermaking mills to product development, is usually the are highly complex operations requiring responsibility of RGtD.) expertise from many different disciplines. There are four major functional areas into wood Department which the operation of the integrated mill The woodyard superintendent and his staff falls: production, technical, plant engineer- are responsible for the receipt and storage of ing, and research and development. There is logs, barking and chipping, and chip typically a manager in charge of each of handling and storage. The wood department these areas with superintendents in charge provides a ready supply of chips of desired of the major operations of each contributing specification to the pulp mill. function. Pulp Mill PRODUCTION DEPARTMENT The pulp mill superintendent oversees the Production is the heart of the mill’s opera- conversion of wood from its raw state to a tion. The production department sees that liquid slurry of bleached fibers. He and his wood chips are pulped and paper is made. staff are in charge of the digesters, washing, Rchnical, engineering and RGtD all vital to screening, bleaching and pulp storage. the mill‘s operation serve or relate to the There are a number of methods for needs of production. Production typically reducing wood to its “pulped” state. Most consists of the wood department, the pulp typically it is “cooked” with various chemi- mill, the power and recovery units, the paper cals in a large digester then washed and mill, the finishing department, and the coat- screened for dirt and other impurities. The ing system for certain grades of paper. (Coat- pulp is then processed through one or more ing formulation, because it is closely related 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 9 PAPER INDUSTRY BASICS 1:

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- TECHNICAL DEPARTMENT ers, recausticizing, liquor preparation, and The technical director is responsible for utilities including electricity, water, steam process improvement, process and quality and compressed air. monitoring and compliance with environ- mental regulations, and the technical staff is Finishing comprised of people in charge of each of The finishing department is responsible for these areas. The technical department is rewinding, supercalendering, wrapping, involved in all stages of production and thus cutting and trimming, packaging and ship- makes sigtllficant contributions to buying ping. Coating, $required, takes place in this decisions relating to new equipment and department; but the coating superintendent process changes which affect operations. typically reports to the production manager. In small mills, one person oversees these Process Engineering functions. In larger, more complex mills, In smaller mills, individual process engineers assistant superintendents and supervisors are assigned to the wood department, pulp are in charge of each of these areas. mill and paper mill areas. In larger opera- tions, groups of engineers and their leaders would be responsible for these areas.

10 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. Pipefitters, welders, millwrights, electricians, Process Control carpenters, painters and janitors all fall Quality analysis and control of the pulping under this important category. and papermaking process is the responsibil- ity of the process control department. This RESEARCH &DEVELOPMENT includes instrumentation and monitoring In most major paper companies, research equipment. In larger mills there will be and development is centralized. These cor- groups for each of these functions. Shift porate research centers include laboratory chemists and testing supervisors usually and pilot plant equipment to simulate the report to the process control superintendent. processes in each of a company’s mills. In most cases evaluation of new (revolutionary) Environmental Control equipment and processes is corporate Environmental regulations have com- research’s responsibility. Evaluation of pounded in recent years, and all mills must improved (evolutionary) equipment or now comply with many strict requirements. processes may rest with corporate RGrD, be In large mills the environmental finction assigned to the individual mill’s technical includes groups responsible for air quality department, or be shared by both groups. monitoring, effluent treatment, plant opera- tions and, sometimes, noise monitoring.

11 PAPER IN DUSTRY BAS ICS I The Buying Process 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 REACHING THE BUYING to give the newcomer to the paper industry , INFLUENCES some understanding of why this is so. In 1990 U.S. paper industry spent over $17 billion* on mill operating equipment and PURCHASING INFLUENCES services. About half of this amount was The buying process for goods and services

spent on manufacturing equipment. purchased by the pulp and paper industry ~ Expenditures for equipment not directly may be very simple or relatively complex, used in the manufacturing process, such as depending on the nature of what is being process automation controls, pollution bought. Very few people may be involved in control equipment, power or other types, are a commodity purchase, whereas a purchas- not included in this figure. ing committee representing all phases of mill There are 800 pulp, paper and paper- operations may be involved in the purchase ~ board mills in the United States. Competition of a major process control system. to reach the buying influences within them is Strictly speaking, a commodity product intense, and marketers must carefully tailor has no differentiation from others of its kind. their selling efforts to do this effectively. That is, oxygen is oxygen no matter where

*American Paper Institute

12 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- to look within a mill and, based upon its chasing agent’s concerns are getting the best complexity and size, make some judgments price and on-time delivery. The purchasing about who is likely to be buying what. agent plays a smaller role in the purchase of specialties where operating and technical Mdti-wCompanies personnel have the major decision making The larger the company, the more compli- responsibility. cated the management structure. Resident mill managers usually report to a corporate Buying Influence vice president of manufacturing. In larger Various operations and technical people companies, mills may be grouped by paper become involved in the decision on buying grade and headed by a corporate executive specialty items-particularly large, expensive in charge of that group. Such companies ones. A way to identify these buying influ- often centralize many of their buying ences is to look at the organization of a mill. functions to gain the economics of volume A large, integrated mill has a very compli- purchases. Thus, another dimension is cated organizational structure. It is possible added to the marketing scenario.

13 PAPER INDUSTRY BASICS I ORGANIZATIONAL STRUCTURE OF AN INTEGRATED MILL

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CAPI'IIAL EXPENDITURES More often than not, there are many Merent parameters of existing grades and the primary and secondary buying influences requirement to reformulate surface sizes involved in a capital equipment purchase. and/or coatings. As an example, consider the case of the Marketing management is concerned purchase of a coater or other new type of about the capability of a new device to make surface sizing device to replace a con- existing grades without compromising ventional size press in the paper machine. quality as well as the capability to expand Operating management, including the paper the current grade line or make entirely new mill superintendent, production manager, grades on an existing machine. At various and mill manager are concerned about times during the process leading up to a deci- potential runnability problems, effect on sion to buy a particular piece of equipment, machine efficiency, production capability, each of the above groups will have its input ease of operation, effect on paper quality, with its amount of influence on the final and other operating variables. The division buying decision varying case by case. general manager, manufacturing vice The buying process could start with any president, and other corporate managers are of the foregoing groups. For example, concerned about equipment costs, required marketing or product development could downtime for installation, overall cost, recognize the opportunity to sell more return-on- investment, and payback period. profitable paper if the capability of the Plant engineering is concerned about existing machine is expanded. General how the new equipment will fit with existing management could recognize that the equipment, the space required, downtime machine is not currently making a profit required for installation, requirements for contribution adequate to justify its existence utilities (electricity, water, compressed air), necessitating a decision to find a way to ease of maintenance and the potential to increase profit contribution or shut the reuse existing parts in the new equipment. machine down. The superintendent could Corporate engineering, or a consulting look at the new device as a potential means engineer, will be concerned about overall to increase production or reduce downtime. project cost, utility requirements, foundation The technical department could see it as a and building modification requirements, and way to improve quality or make a more the potential impact on other capital projects consistent product. at the same mill. The and/or technical An analog could be drawn for other department is concerned about the capa- types of capital equipment with the role of bility of the new device to facilitate the groups such as marketing and product production of new grades, effect on quality development lessening if the equipment

15 PAPER INDUSTRY BASICS I

would not result in a change in end product. sheet along with the potential effect on other For example, the decision to buy a new components in the formulation must be barking drum or chipper would have only determined by RGtD. In addition, the minimal involvement from groups other potential effects of recycled coated broke than the woodyard superintendent, pulp mill must be determined. superintendent, engineering and executive In summary who is involved in the management unless it would be expected to buying process for a given product is deter- cause a significant difference in pulp quality. mined by: 1. The potential effect of the product on the OPERATING SUPPLIES end product properties of the pulp or Buying decisions on maintenance replace- paper being produced; ment items, such as machine clothing, are 2. The degree to which the product invades made typically by the people running the the process and its potential for inter- machinery. Chemical raw materials and reaction with other raw materials and specialty chemical additives start to additives. become more complex. Consider a pulp mill defoamer. The pulp mill super- NEED FOR MULTI-LEVEL SELLING - intendent looks at it as a means to The variety of people involved in the buying control foam on the brown stock washers process for different products makes it and is concerned primarily with its necessary to sell the same product or service performance as a defoamer at a minimum to different people in an individual mill cost-per-ton addition rate. The technical organization. In the case of big ticket capital department is concerned with the potential equipment, it is usually also necessary to interaction of the defoamer with other make the same sale to people in corporate additives used later in the process. (E .g., will management, corporate engineering, and it affect retention, sizing, or deposit control RGrD, and, perhaps, outside consultants on the paper machine? Is it FDA-approved?) working with the given mill. As the complexity of the grades made at a Each of these groups of people has need ~ given mill increases, the potential for inter- for information relative to their own reaction among additives at various stages particular scope of interest. 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. References Raw materials and additives used in Marketing to the F'ulp and Paper Industry, WPI, 1985. coatings are even more complex. Efficacy in Saltman, David-Pulp and Paper Primer, TAPPI, 1983. the coating formulation and in the coated Whitney, Roy P.-The Story of Paper, TAPPI, 1984. I TAPPI JOURNAL Newer technologies 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. NONWOVENS Polypropylene is gaining in popularity What is a nonwoven? Because there are so as a nonwovens fiber. It is extremely low in many different configurations of non- cost and has properties similar to polyester. wovens, a simple definition is inappropriate, mical uses include diaper cover stock, if not impossible. However, nonwovens are geotextiles, filters, oil spill scavenging manufactured as sheets, webs or bat& of devices, linens and indoor-outdoor carpets. directionally or randomly oriented fibers Polyethylene, a similar fiber, is often used in which are bonded together. Nonwoven fibers hang tags, mailing envelopes and work can be natural or man-made. clothing. Many other manufactured fibers are History used in nonwovens. Acrylic fibers are Although the first commercial production favored for their chemical resistance; and occurred in 1853 with the carded nonwovens nylon, toughness and resilience. In addition machines, nonwoven-like materials have to the various forms of nylon, glass, metallic long existed in nature. Spider webs and and ceramic fibers are also used for applica- cocoons have close similarity to spunbonded tions requiring unusual properties. nonwovens. 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

17 PAPER INDUSTRY BASICS I

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 ideal for use in automotive oil and air filters, shoe leather, blankets, paper making felts milk filters, tea bags, bunting, hang tags, - and many other products. roofing shingles and electrical insulation. AIR-LAYING SPUNBONDED PROCESS Another dry-laid method is air-laying. In The spunbonded process combines fiber for- this method air is used to transport and form mation and web formation. The most com- a batt of fiber in a random pattern. A stream mon method of manufacture uses molten of air carries the fibers to a vacuum condens- polymer forced through spinnerettes. The ing belt or drum. In either carding or air lay- fibers are spun and then drawn and oriented ing almost any generic type fibers can be and deposited uniformly on a moving used either alone or in combination. Air-laid screen, densified, and bonded. Most spun- webs tend to be lofty and porous which bondeds are melt-spun and thermally ~~ makes them useful for filters, fiberfill, bonded. End uses include geotextiles, bail- padding, wipes and other uses. ing, filter fabrics, work clothing, wallpaper and other products. WET-L AYING The melt blown process, a variation of __ The wet-laying process was developed from the spun bonded process, uses a high- the paper manufacturing process and uses velocity air jet which blows random lengths an inclined wire rather than the flat tabled of fibers against a firming drum or screen. - fourdrinier. Wter is removed mechanically The resulting mat formed from these ultra by gravity, foils or table rolls and pressure. fine fibers has excellent filtration and insu- The web is then passed over a heated section lating properties. Melt blown fabrics are to remove excess moisture. The long fibers commonly used as insulation in outdoor used in wet-laying create an end product apparel, filters and wipes. I TAPPI JOURNAL

Bonding The fibrous network within the nonwoven End uses for these fabrics vary considerably web must be bonded to achieve adequate and include drapery, upholstery, apparel, functional strength. Four methods can be carpeting and toweling. used: inherent bonding, thermal bonding, mechanical bonding and chemical bonding. Spunlaced process Also known as the hydroentanglement INHERENT BONDING process, the spunlaced process starts with a A web is said to be inherently bonded when carded web that is carried by a belt under no Wher bonding is needed after the web multiple water jets. Fine, high-pressure has been formed. Inherent bonding water jets cause the fibers to migrate and accounts for a very small proportion of all entangle with one another. Resultant fabrics nonwovens so the process is of limited can have numerous patterns. spunlaced fab- importance. rics are used for headrest covers on planes, medical gauze, wipes and table linens. THERMAL BONDING Although accounting for only 5% of all non- CHEMICAL BONDING wovens, thermal bonding is growing in Chemical bonding is accomplished with importance. Most of the synthetic fibers either solvents or binders. used in nonwovens today are easily bonded by the application of heat. Solvents In this method fibers are bonded together as MECHANICAL BONDING they come into contact with one another Mechanical bonding is used on more than after the fibers’ outer surface is softened. 40% of all nonwovens. There are several Calendering is often done to increase the techniques in common use. degree of bonding. Needle punching Binders Neede punching relies on the use of barbed More commonly, nonwovens are bonded needles which are “punched” through the with adhesive-like binders. They can be fabric to entangle the fibers. Products made applied by spraying, saturation, coating, by this method include papermaking felts, foam or printing, depending on the product. indoor-outdoor carpets, blankets, padding The type of binder and method of applica- and synthetic leather. tion substantially alters the performance characteristics of the nonwovens. 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.

19 PAPER INDUSTRY BASICS I

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. products have received the greatest MECHANICAL FINISHING attention, but durable nonwovens are Calendering, embossing, brushing and achieving greater prominence. compacting are some of the more com- Disposable products include diapers, __~ mon finishing techniques. Compacting is by sanitary napkins, wipes, surgical gowns, far the most important and can be drapes, packs, sponges, gauze, barrier accomplished by creping with a doctor blade packaging, filters, towelettes, dust cloths, or one of several other patented processes. hang tags, napkins, work clothes, and many Compaction increases stretchability, other such products. toughness and softness and is often used for The long and sometimes permanent life linens, wipes and similar products. span of durable nonwovens make them excellent for many hard use applications. HIGH ENERGY FINISHING Papermaking felts, geotextiles, automotive Examples of high energy finishing include fabrics, gaskets, carpets, carpet backing and singeing, ultrasonic welding and sterilization, roofing shingles are a few examples. with sterilization with dry heat, steam or Nonwoven products increasing in radiation being the most important. importance include air laid, stitch-through, spunlaced, spunbonded, melt-blown ther- Diversity of Uses mally bonded, and wet laid nonwovens. ___ Their economical cost and diverse proper- Because of their wide range of properties, ties, make applications and end uses for nonwovens have been used to replace many ~ nonwovens essentially limitless. Disposable existing products while at the same time - new applications are being developed.

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 Fragmented Industry Another volume end user of paper is the Although major producers of paper, flexible packaging industry. Difficult to petrochemicals and aluminum provide the clearly define because of the many different raw materials used in flexible packaging, combinations of materials used, flexible much of the actual production of the packaging cuts across the paper, plastics, packaging is fragmented across a diversity aluminum and container industries. End use of hundreds of manufacturers. Many of the applications range from hygienic packaging larger ones have integrated their operations for foods and medical supplies to bags for from the production of raw materials to garden fertilizer to soft drink containers. the conversion of bags, printed rolls and sheets, coating, laminating or coextruding Materials operations. Smaller companies are often Nearly all flexible packaging incorporates engaged in the conversion of packaging some form of plastic. Plastic films and foils material by laminating, coating, printing, are laminated together with paper in a waxing, or othenvise fabricating to produce variety of combinations to produce end wraps, bags and other packages as well products with a variety of desired properties. as shrink or stretch film and roll stock. Moisture-proofing, abrasion-resistance, In addition, many end users of flexible temperature-resistance, opacity, grease- packaging materials now have developed proofing, physical strength and, of course, their own in-house converting operations. flexibility, are some common ones. In other Although flexible packaging has replaced cases films are extruded and formed paper for some applications, e.g., plastic into appropriate shapes and sizes of pack- grocery sacks, it has opened new applications ages. Various forms of polyethylene and for paper, too. Laminated with film or foil, polypropylene, thermoplastic urethane, paper is an essential component in many nylon and other synthetic materials are food, medical and consumer product packages. used alone or in combination to produce As new improved formulations offer an many products. increasing diversity of features, manufacturers Thermoplastic adhesives are used will receive even wider acceptance of their in many packaging applications. Such products. With society seeking ever higher adhesives are developed for their heat resk- levels of convenience in foods and other tances, resilience in frigid temperatures, products, the fUture of flexible packaging moisture or oil repellence, or other charac- is assured. teristics. Special formula inks, solvents, resins and primers are also key elements in the manufacture of many packages.

21 PAPER INDUSTRY BASICS I Papermaking miOM THE FOREST To THE FINISHED PRODUCT- THE PROCESS SIMPLIFIED

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