TECHNOLOGY
Hybrid processes spawn throwaway fabrics Modified textile- and papermaking techniques used in producing disposables to meet growing demand When lab coats get dirty, maybe they ought to be thrown away. And for that matter, why not throw away overalls, coats, dresses, masks, surgical gowns, or any of the numerous other service items used in homes, hospitals, or industry, Why not indeed, if it costs more to clean them than to buy new ones. That, at least, is the key underlying rationale for the growing push behind man-made, nonwoven fabrics referred to, logically enough, as "disposables." What is a disposable? Though paper dresses and gowns (and even bikinis) have received much of the publicity, disposable fabrics are made from practically all of the natural and manmade fibers. These include cellulose, nylon, polyester, rayon, acrylics, and olefins, as well as paper. The industry represents a cross fertilization of technologies from the chemical, paper, plastic, and textile sectors. According to Martin M. Scher, director of corporate planning and development, Erving Paper Mills, it is an industry which is substituting sophisticated technology for multiphase manufacturing. Those involved in bringing disposable products to the consumer include web-material makers, converters, marketers, distributors, and equipment manufacturers and involvement grows as companies continue to commit added resources to meet growing disposables potential. The basic structure of disposable nonwoven fabrics is formed by processing suitable fibers using machines which are normally used, at some stage, in making textiles (dry process); or by processing a dispersed fiber slurry on equipment used in papermaking (wet process). A third process results from modifying and combining the wet and dry methods. In most variations of any of these process types (Du Pont's Spunbonded process being one notable exception) various chemicals are used to impart absorbancy, moisture repellency, flame retardancy, softness, strength, and other properties. Wet process. In this method, blends of wood pulp or cellulose and synthetic fibers are dispersed in water and cast on a paper machine. Or, in some cases, a dispersed fiber slurry is brought to a large perforated cylinder 42 C&EN JUNE 3, 1968
NYLON BOBBINS. Kimberly-Clark's creel room houses the bobbins from which strands of thread are fed to a machine that cross-lays them without weaving. This thread grid is then sandwiched between layers of tissue to form scrim-reinforced material for use in paper fabrics
which, by rotating, brings the fiber onto its surface in web formation. A vacuum formed on the inside of the cylinder removes excess liquid from the web material. The fibrous web is then taken off the cylinder and sent through a press to remove more moisture. After this it goes through a series of dry drums where temperatures of about 175° F. complete the drying process. Bonding can be accomplished by either adding an adhesive initially to the slurry to give integrity to the wet web, or adding it later after the web is formed into a sheet. In some instances the bonding agent is added to the sheet just prior to cutting and processing. Synthetics used can be either fine or coarse denier fibers which are longer and more regular than the wood pulp fibers. They give tensile and tear strength, drape, hand, flexibility, and bursting strength to the nonwoven product. Paper machines used in wet processing (such as the inclined wire Fourdrinier and the Rotoformer), must be slowed from the speeds normal to paper service (300 to 1000 feet per minute) to 60 to 120 feet per minute for making fabrics. A wet-web nonwoven which has appeared in the apparel market is Hollingsworth & Vose's Hovolon. Hovolon is 7 5 % cellulose and 2 5 % synthetic (such as nylon or dacron),
held together with an acrylic adhesive binder. Dry process. In this technique a mass of synthetic staple fibers is opened up, separated, and straightened by means of air (fluffing action) and/or fine wires, then arranged in web formation on textile equipment. Types of equipment used include cotton cards, garnets, and rando webbers (the last of which was developed by the Curlator Corp.). In one kind of dry operation, three lap rolls of a material, such as Avisco rayon staple—arranged in web in a cotton card machine—are simultaneously drawn out and laid on top of each other in the rando web machine. From here, the layered web goes to a binder bath containing an adhesive used to hold the fibers and layers together. After drying, the bonded nonwoven is rolled, now ready for cutting and related fabric processing. Product examples include: Kimberly-Stevens' Bondaire, a rando web low-density, high-loft material of rayon, nylon, polyester, or modacrylic fibers; Chicel, a cellulose-reinforced fabric made of paper and cotton by Chicopee Mills, Inc.; and Lowndex, made by Lowndes Products of 100% rayon fibers laid unidirectionally in lengths of l 1 / 2 to 3 inches. In Du Pont's Spunbonded process synthetic fibers are spun in a conventional fashion, then formed into a sheet or web and bonded into position.
Many U.S. companies, including American Viscose, Scott Paper, Kendall, Du Pont, and KimberlyClark are vying for an advantageous position in the disposables market —one which may reach the $1 billion per year level within the next five years. Even this estimate, says Harry Neilson, industrial merchandiser (fiber operations) of FMC's Avisco division, may prove to be a drop in the bucket when increased laundry and rental costs and other factors cause the throwaway concept to really catch hold.
LAP ROLL. Avisco uses curlator machines such as the one in this picture to draw out and lay three "lap" rolls of rayon staple on top of each other. The layered web then goes to a binder bath where adhesive is applied. After drying the bonded nonwoven material is rolled
When polyester fibers are used the product is called Reemay. Reemay is a randomly arranged sheet of continuous filaments containing no fillers, paper, or binders. The webs are bonded primarily at filament crossovers by heat and pressure. No chemicals are used. Another Spunbonded Du Pont product is Tyvek, made from linear polyethylene fibers. Kendall Co., a pioneer in disposables, also has a chemical-free fabric in its product line. Weblox by name, it utilizes a mechanical entanglement of the fibers instead of chemical binders. Combination process. Reinforced paper nonwovens of sandwich construction can be made by combining the wet and dry methods. An example is Scott Paper Co.'s Dura-Weve, made of two sheets of tissuelike paper (100% bleached pulp stock) reinforced with rayon scrim between the layers. Rayon scrim is a loose nonwoven mesh of filaments arranged in a grid. Another type of scrim-reinforced material (SRM) is that which is made by Kimberly-Clark—marketed by Kimberly-Stevens Corp.—under the tradename Kaycel. According to Kimberly-Clark's vice president and general manager for commercial products, William G. Wilson, the process for SRM begins in a "creel" room, with racks of bobbins of nylon filament yarn.
The nylon strands feed through spaced perforations in a panel at the head of a "nonweaving" machine, then over a roller where they pick up a phenolic resin adhesive. Next, Mr. Wilson explains, the strands pass through a cross-layer, where half of them—routed through a rotating drum—are laid at a right angle to the direction of the machine, without weaving. The tacky adhesive bonds the strands, forming a gauzelike scrim. Then, rolls of double-layer facial quality tissue—above and beneath the trimmed scrim "sheet," ahead of the cross-layer—unwind in the machine direction, forming a five-layer lamination with the cross-laid scrim in the middle. This sandwich then passes through a series of compression and dryer rolls which set the adhesive, bonding the scrim to its outer laminations of tissue. Strength and other properties of the fabric may be altered by changing the spacing between the nylon strands or by using higher or lower denier fibers. Ravon, cotton, glass, or acrylic fibers may be used instead of nylon. SRM (Kaycel), like other nonwovens, can be cut, sewn, printed, and grommeted in about the same way as comparable weights of woven cloth. It is used to make "paper" dresses and for a variety of disposable garments and products for institutional-industrial use.
Current uses for disposable fabrics range from pup tents and sleeping bags to high-fashion evening gowns. In spite of the wide end-use potential, industry spokesmen pointed out to C&EN's Jim Haskins that the largest potential markets for disposables are hospitals and industry. In these areas current penetration is on the order of 1 to 5 % . However, interest is building and nonwoven makers are optimistic about future prospects. One thing is certain, it will take an all out, unified effort by this fledgling industry to gain deeper market penetration. The reason, says Avisco's Harry Neilson, is that no one company or given industry can expect to cope with the entire world of disposable soft goods by itself. Apparently this feeling is general because a disposable products communications center has come into being. Last month the Disposables Association was born with a nucleus of 27 charter member companies (C&EN, April 22, page 17). As of this month the membership exceeds 60. The objective of the association, says Donald C. Uehlein, industrial products manager for nonwovens at the Kendall Co., is to provide members the means to become acquainted with all sides of the new industry so that informed decisions can be made on the direction of its business.
JUNE 3, 1968 C&EN
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