|Textile World looks at several natural and man-made fibers and their uses in nonwovens applications. |
Janet Bealer Rodie, Managing Editor
The nonwovens industry makes use of a wide range of textile fibers. Functional properties may be inherent or engineered into both natural and man-made fibers to make them appropriate for various applications. This article highlights a few well-established fibers as well as some newer fiber entries into the nonwovens marketplace and mentions the manufacturing processes used.
Natural And Renewable Fibers
In consideration of the increasing demand for ever-more environmentally sustainable products and processes, natural and biobased fibers are good choices for certain nonwoven products because they are biodegradable and compostable as well as being produced from renewable resources. And while recycling generally is a consideration related to the sustainability of man-made fibers, natural- and renewable-fiber-based materials also can be recycled for certain nonwoven applications.
Cotton is used in nonwoven hygiene products including wipes, feminine hygiene products, diapers and adult incontinence products. It is soft, comfortable, hypoallergenic and naturally absorbent; and has greater wet strength than dry. Most hygiene products are spunlaced; but cotton also may be needlepunched for wipes such as decontamination wipes, and also in its relatively unprocessed raw state for oil absorption, such as cotton boom used in the recent Gulf of Mexico oil spill cleanup efforts.
"With respect to nonwoven fibers, cotton is a recent trend and is continuing to grow at a surprisingly healthy rate," said Janet O'Regan, director of strategic initiatives, Cotton Incorporated, Cary, N.C., a marketing and R&D company promoting upland cotton. She listed several reasons including the aforementioned trend toward sustainability; the growth of the wipes market over the last 10 years; the development and growth of spunlacing technology; pricing; performance and consumer appeal; and health- and well-being-related features, especially for hygiene applications.
O'Regan went on to talk about the needlepunched oil-absorbing cotton boom that played a role in the Gulf cleanup. "This is a really cool newer direction," she said. "Bleached and scoured cotton took off for wipes and hygiene, but over past two years, we've also been working with raw fiber that hasn't been processed except for mechanical cleaning. That fiber is naturally oleophilic and hydrophobic. It's Mother Nature's way of preventing the fiber from biodegrading in the field while it's growing because it has oils and pectins on it that protect it from the elements."
Viscose And Lyocell
Regenerated cellulosic fibers such as viscose and lyocell also have nonwoven hygiene, wipes and incontinence applications, for virtually the same reasons that make cotton suitable for those uses, but also because their production conditions are not conducive for microbial growth -- an advantage as well for many other applications. Technical applications include electrical insulation, automotive and filtration; as well as medical drapes, swabs and wound dressings. Nonwoven processes used include spunlace, needlepunch and chemical bonding.
Austria-based Lenzing AG offers Lenzing Viscose® -- whose production technology includes the recycling or sale of the chemical and waste products produced in the process -- and Tencel® and Lenzing Lyocell® -- both produced in a closed-loop process that uses no harmful chemicals -- for various nonwoven applications noted above. The company reports it can customize the fiber to suit a particular application -- for example, by adding a finish to facilitate high-speed carding, improving the absorbency for a feminine hygiene product, or enhancing the purity of fiber used in electrical insulation products.
In the filtration arena, Lenzing Viscose has long been used in food and beverage applications; while Tencel, with its tendency to fibrillate, is being promoted for automotive fuel and oil filters, cigarette filters, and industrial air and liquid process filters. Lenzing reports Tencel's properties include significantly increased wet strength and low linting in addition to the absorbency, softness and breathability that are inherent in both Lenzing Viscose and Tencel. The company also notes that its customized Tencel Short Cut fibers offer a flushable solution for wipes, and its Tencel Tow can be cut and converted by downstream users for various specialty products and applications.
Viscose, Tencel and lyocell are spunlaced for hygiene, wipes and other personal care products, as well as for gauzes and face masks. They may be blended with polyamide or polyester into spunlaced coating substrates, such as for artificial leather. Low-linting lyocell and Tencel also can be used for clean room wipes. Needlepunched viscose, Tencel and lyocell, alone or in blends, have applications in hygiene and medical products, wipes, coating substrates and artificial leather. Chemical bonding applications include medical drape, food contact, interlining and household wipes. Lenzing reports chemically bonded nonwovens made with Tencel and Lenzing Lyocell can offer added strength or lighter weight; and when binder levels are reduced, they can offer increased absorbency.
Polylactide (PLA) biopolymers offer a renewable and biodegradable or recyclable alternative to petrochemical-based fibers. Applications include spunlaced wipes and hygiene products, in which PLA may be blended with cotton or viscose; agricultural textiles that may be tilled under at the end of a growing season; needlepunched carpet and automotive products; spunbond filtration and geotextile products as well as teabags and other such products; and meltblown filtration products.
NatureWorks LLC, Minnetonka, Minn., produces PLA under the Ingeo™ brand. According to Robert Green, the company's Americas director, Fibers and Nonwovens, the fiber offers opportunities to meet market needs and is competitive price-wise with incumbent fibers.
"We think that, in general, the hygiene space is a very good fit for our materials. A lot of wipes already have natural components, such as viscose and cotton, and Ingeo is a great complement. Essentially, it offers a thermoplastic that has natural origins and very good environmental credentials," Green said, adding that using Ingeo in a blend with cotton or viscose allows producers to improve the sustainability of their products.
PLA also has inherent flammability characteristics, Green noted. It is difficult to start burning and generates little smoke, he said; and its self-extinguish time is significantly shorter than polyester or cotton. It also is inherently ultraviolet-transparent, moisture-wicking and hypoallergenic; and has low odor retention. These properties can be further improved using topical treatments or additives.
Man-made fibers are used in many of the same applications as natural and renewable fibers, and sometimes are blended with those fibers to provide enhanced function in a product.
Polyester staple fiber (PSF) has applications in spunlaced products including wipes and hygiene as well as medical/surgical gowns, masks, drapes and such; needlepunched filtration, automotive and industrial products; airlaid filtration products; and resin bond and thermal bond products. There is also significant growth in spunbond applications using polyester resin. Specific functionalities, such as antimicrobial properties for filtration applications or moisture management for wipes, can be integrated into the polymer.
According to Wayne Proctor, senior manager of sales, nonwovens, for Charlotte-based PSF manufacturer DAK Americas LLC, spunlace comprises the biggest part of the nonwovens market where polyester is concerned. "DAK's key to success in this market is that it is dedicated to fiber design to deliver functionality," he said. "For example, we design the proper crimp, finish or heat set that delivers the functionality the customer desires, depending on the intended application."In addition, DAK Americas' Steripur®AM silver-based antimicrobial fiber has filtration applications, and Delcron® Hydrotec moisture-management fiber has applications in wipes and also some filtration. These functionalities are integrated permanently into the fiber rather than applied as topical treatments, said Ricky Lane, the company's manager, public affairs, trade relations and communications.
Polypropylene And Bicomponent Fibers
Polypropylene (PP) is used in diaper, baby wipe, filtration, automotive, geosynthetics, furniture backing, construction, insulation and acoustics applications, among others. Because of its low specific gravity, it may replace other fibers to reduce basis weight and system cost; but modifying the fiber's surface may also provide alternatives to replace other PP fibers in certain applications, according to John Wolhar, hygiene sales manager, Americas, for Duluth, Ga.-based polyolefin fiber manufacturer FiberVisions Corp. Nonwoven processes used include spunlace, carded thermal bond, needlepunch and spunbond.
Wohlar said PP doesn't necessarily compete with other fibers in the nonwovens arena. "We're competing with alternate technologies or other forms of PP, offering finer fibers, shapes or modified surface characteristics like finish that allow people to use a staple-based nonwoven to replace a spunbond nonwoven, for example," he explained. The fibers can be treated to make them hydrophilic or hydrophobic. Wohlar also mentioned botanical finishes -- such as chamomile, green tea and aloe -- and vitamin E, noting they may offer benefits in certain applications.
FiberVisions recently has introduced fine-titer shaped polyolefin fibers for nonwovens markets. The company reports these fibers can improve fabric uniformity, coverage and fabric opacity; and also provide loft and enhanced softness.
Bicomponent fibers also may be used in nonwoven applications. FiberVisions' sister company ES FiberVisions manufactures bicomponent fibers for hygiene, cosmetics, filtration, medical, industrial and agricultural applications. These might be biodegradable, or have a PP or polyester core and a PP or polyethylene sheath; or they may be based on specialized polymers. They often are used in low-level blends to bind other fibers. Processes include thermal bond, carded through air, airlaid, wetlaid, carded needlepunch and carded spunlace. Teabags and wipes are two wetlaid applications using short cut fibers. Airlaid nonwovens using bicomponent fibers are used primarily for baby wet wipes, industrial oil absorbent pads and feminine hygiene product components.
Post-industrial and post-consumer recycled fiber also is used in nonwoven products and provides the added advantage of giving textile waste another life instead of having it end up in a landfill.
Leigh Fibers Inc., Wellford, S.C., reprocesses post-industrial fabric waste made with both natural and man-made fibers into shoddy for use in a wide range of nonwoven and other under-the-surface applications as well as for remelting and spinning applications. The company's SafeLeigh™ flame-retardant (FR) aramid fiber recycled from post-industrial clippings can provide inherent FR properties for needlepunched and airlaid nonwoven furniture, mattress and automotive applications, according to George Martin, the company's executive vice president of sales and marketing. Denim may be turned into carpet pads or insulation. Cotton, rayon, acetate, PP, acrylic and other textile waste can be used in many under-the-surface applications as well as wet wipes. Besides needlepunch, processes include airlaid, thermal bond, garnetting and other pad-making processes.
Cotton Incorporated's O'Regan also mentioned initiatives for recycling post-industrial and post-consumer cotton textiles. Strateline Industries LLC, Rogers, Ark., makes wet wipe substrates from fiber recycled from fabric cuttings supplied by T-shirt factories in China. In another project, Cotton Incorporated has partnered with Bonded Logic Inc., Chandler, Ariz., to collect blue jeans for reprocessing into insulation that is donated for use in houses built by Habitat for Humanity. The insulation and other building products made using reprocessed post-industrial cotton and other cellulose materials also are available through retail channels.
Post-consumer recycled fibers such as PLA or polyester can be used in any application -- nonwoven or other -- that uses virgin fiber.
While PLA is biodegradable and can be composted, it also can be recycled in a closed-loop system, as was the needlepunched carpet made with Ingeo fibers that was installed at the site of the United Nations Climate Change Conference, held in December 2009 in Copenhagen, Denmark.
"At the end of its useful life, PLA can be hydrolized back to lactic acid very easily and economically," NatureWorks' Green said. "This chemical recycling potentially will alleviate issues of cleaning and contamination."
DAK Americas has partnered with Dalton, Ga.-based carpet manufacturer Shaw Industries Inc. to establish a joint venture in Fayetteville, N.C. -- Clear Path Recycling LLC -- to recycle post-consumer polyethylene terephthalate (PET) bottles into Recycled PET (RPET) flake of a high and consistent quality that will be used by both companies to process into fiber.
"We now have the foundation to include recycled content in our product and will strive to meet our customers' requirements to incorporate the product into endstream uses," DAK Americas' Lane said. The fiber will be available for all applicable end-uses including nonwovens.