Versatility, flexibility and efficiency are the most notable benefits that synthetic fibers can deliver to nonwovens. These benefits allow synthetic fibers to be applied in nearly every market for nonwovens, including hygiene, medical, filtration, automotives, wipes, artificial leather and bedding. Because they can be engineered, synthetic fibers also work well in a variety of nonwovens technologies such as airlaid, carded, thermal bonded, needlepunched and spunlaced. Furthermore, synthetic fibers can be easily dyed and chemically finished.
Polyester has remained one of the most popular synthetic fibers in nonwovens, because of its versatility in a wide range of end uses. Most recently, polyester has found a place in the hygiene market, especially in baby diapers, feminine hygiene products and adult incontinence items and wipes. “Polyester in diaper acquisition/distribution layers provides increased moisture-management properties and strength,” explained Robert Usher, business director of Wellman Incorporated, Shrewsbury, NJ. “Polyester additionally will prevent gel blockage and fluff pulp from collapsing in these products. It helps move fluid to absorbent layers in the diapers that contain superabsorbents. In wipes, polyester fiber provides increased fiber strength and stability. Because of polyester’s overall functionality and performance, manufacturers are steering toward using it in the hygiene market.”
Although polyester is more expensive than wood pulp and superabsorbent fibers, its functionality is important to the overall product. Natural-based fibers, such as wood pulp, serve more as an inexpensive filler and absorbent fiber, while polyester is more technical.
“Polyester staple fiber is one of the most rapidly growing fibers due to its cost effectiveness, turnkey technology and ease of processability and care,” said Horst Lehmbach, business segment manager of nonwovens at DuPont Sabanci Polyester GmbH (Dupont SA), Hamm, Germany. “Almost all end uses can use polyester because it does not have limitations. Polyester fibers can be produced with different deniers, cut lengths and cross sections.”
Additionally, polyester can have a range of luster options, such as bright or semi-dull. This can help improve the stress-strain behavior of nonwovens, particularly in thermal bonded and spunlaced nonwovens, according to Suthida Archadech, key account manager of Bangkok-based polyester fiber supplier, Tuntex Thailand, “Polyester fibers offer the opposite of what a cotton fiber can offer because they have higher elongation properties,” he explained. “Furthermore, these fibers provide permanent hydrophilic properties, which is ideal for hygiene disposable products.”
In addition to polyester, other synthetic fiber types making strides in nonwovens include polyolefin and polypropylene. These fibers offer the much sought-after balance of high performance and low cost, making them attractive to many markets.
“Polypropylene fibers will continue to grow in different applications and markets, such as filtration, as they become more advanced, more refined and more application-focused,” opined Erik Gammelgaard, marketing manager at FiberVisions, Varde, Denmark.
Lenzing AG manufactures cellulose staple fibers for nonwovens in the hygiene, medical, cosmetic,
household and automotives markets.
Wanted: Specialty Markets
Synthetic fibers are already well established in several end use markets for nonwovens, such as filtration, hygiene and artificial leather. Polyester fibers are also establishing a niche for themselves in the home furnishings and do-it-yourself (DIY) markets such as wallpaper. Using polyester staple fibers in nonwoven wallpaper can offer increased strength. “Anyone dealing with wallpaper professionally knows nonwovens are considered to be a synonym for wallpaper with attributes, including strength and dimensional stability,” Mr. Lehmbach explained. “In comparison to traditional wallpaper, nonwoven products are produced on modified papermaking or specialty equipment for wetlaid fabrics. This is capable of processing longer, stronger fibers, compared to pure cellulose pulp.”
DuPont’s Dacron polyester fiber is currently used as a reinforcement material in wallpaper with more advantages during installation. These include no paste dwell time, immediate adhesion and dimensional stability when wet. Additionally, the stability and opacity of polyester nonwovens in wallpaper can help disguise cracks and seams.
“During the past 18 months, the demand for polypropylene non-foaming fibers has increased significantly in water filtration media,” said Geoff Rostron, sales manager of Drake Extrusion, Bradford, West Yorkshire, U.K. “These non-foaming fibers are formed by using a dref spinning system, where the fibers are spun into yarns and then wound into a cartridge. Thousands of tons of our polypropylene are now being applied in water filtration media.”
The rise of these more specific applications has synthetic fiber manufacturers using newer, more innovative technologies to improve the final product. Experimenting with fiber selection and newer converting and bonding techniques has become an essential part of the production process.
Polyester fibers are gaining ground in diapers, where they aid in transporting liquid.
Manufacturers have been relying on bicomponent and multicomponent technologies to expand synthetic fibers’ presence in nonwovens markets. As end product demands become more stringent, fiber suppliers must also do their part to choose the best fiber combinations for these newer technologies.
“As technology continues to improve, fiber blends are becoming more commonplace,” explained Paul Latten, nonwovens and industrial staple business director of KoSa, Houston, TX. “KoSa offers pre-blended fibers that give manufacturers enhanced synergistic properties while reducing the cost, time and effects of blending internally. Our polyester fibers have achieved success in blends with glass and carbon-based fibers in a range of markets such as geotextiles, construction, industrial and automotives.”
Bicomponent fibers allow nonwoven manufacturers to have the ‘best of both worlds.’ For example, using a bicomponent fiber can allow customers to get an environmentally friendly binder solution by combining the benefits of a polyethylene and a polypropylene reinforcing fiber, in one product. This eliminates the need for latex spray bonding.
“Bicomponent fibers are engineered to deliver enhanced adhesion using various bonding temperatures, with a range of other fibers, including wood pulp, rayon, polyolefin, glass, cotton, nylon and wool,” said KoSa’s Mr. Latten. “This yields increased strength, resiliency, improved absorbency and flexible design options such as embossing.”
Aware of the impact that fiber selection has on a nonwoven web, manufacturers are experimenting with different ways to engineer the fiber. For example in a spunlaced web for hygiene applications, the fiber must be finished so that it can provide permanent hydrophilic properties. Likewise, a low-melt polypropylene fiber will often be selected if the web will be thermal bonded, as these products require both a higher and a lower melting fiber for more uniform bonding. A more uniformly bonded product allows bulk.
Despite the increasing importance of fiber selection and technology, cost dictates new trends in the synthetic fiber market. With the prices for wood pulp, superabsorbent fibers and cellulose less expensive than other fibers, manufacturers are discovering that these fibers, depending on the bonding technology used, can produce the same qualities as more expensive fibers. One such fiber is polyacrylate, which is found in superabsorbents (SAP) powders. When applied in hygiene applications, these fibers provide more liquid absorption and thinness. For Technical Absorbents, Grimsby, U.K., polyacrylate is the only fiber in its Oasis superabsorbents, which are used in feminine hygiene products and food trays.
Nonwovens made of polyester fibers will continue to grow in the automotive market because of their ability to be easily molded.
“The demand in hygiene products is for less bulk and more thinness,” explained David Hill, business development manager of Technical Absorbents. “Because of this, fibers such as wood pulp and polyacrylate will gain ground as the fiber of choice for nonwovens, especially in airlaid products. As airlaid technology continues to grow in the baby diaper and feminine hygiene markets, traditional fibers will be considered too costly for airlaid applications. However, by using cellulose or fluff pulp fibers with the airlaid process the same results are achieved as using rayon with a carding technology, which are more expensive. In order to have higher profit margins in the synthetic fiber market, it is important to choose fibers that will match the converting and bonding technologies.”
Manufacturers are also switching to cellulose and wood pulp fibers within the wipes market. As this market continues to boom worldwide, several areas within this market might face the threat of becoming a commodity. Manufacturers are responding to these possibilities by switching to low-cost fibers, such as cellulose, in place of more expensive carded fibers. “The traditional ways that wipes have been made, which have included carding, are being ‘attacked’ right now by airlaid and spunlace technologies,” Mr. Hill said. “The only setback for airlaid is the cost of the equipment. However, it will only be a matter of time until manufacturers will be able to buy airlaid machinery to make core material for hygiene products.”
In the meantime, cellulose and fluff pulp will continue to penetrate the wipes market because of their low cost and high absorbency. These attributes will allow these materials to expand more into end products. Tencel, Flemington, NJ, manufactures Lyocell fiber, which is a man-made fiber from a natural cellulose polymer, for wipes and other key markets. Lyocell is ideal for wipes because of its purity, high dry and wet strength, stability and absorbency, according to executives.
uses polyacrylate fibers, which are derived from superabsorbents, to manufacture its Oasis fiber.
“Notable successes to date for Lyocell have been in spunlaced, wetlaid and needlepunched fabrics for wipes, filtration and artificial leather substrates,” said Nick Hrinko, nonwovens business director of Tencel. “Cellulosic fibers will increase marketshare in areas where their key attributes are critical to the final product.”
For cellulose to continue gaining marketshare in the wipes and hygiene markets, manufacturers are using it in combination with other fibers so the nonwoven web can hold up to the higher line speeds and other machinery advancements coming onstream.
“On one hand, cellulose will need to cope with increasing line speeds, and on the other, it will need to supply specialty fibers with new properties,” explained Heinrich Jakob, marketing and sales director for nonwovens at Lenzing, Austria-based Lenzing AG. In response to this, cellulose is being combined with polyester for spunlaced wet wipes. This creates material that is soft yet strong enough for higher line speeds and bonding processes.
Viscose fibers, derived from wood pulp, are replacing cotton in hygiene applications.
As new machinery and technological advancements continue to grow in the nonwovens industry, nonwovens manufacturers are also examining new geographical areas for possible expansion. Asia’s large population has attracted nonwovens manufacturers to this area. As this move continues to escalate, it will spur additional competition among fiber suppliers in North America and Europe, leading to a tougher fight to gain marketshare.
“Manufacturers have to remember that the fiber industry is global,” stressed FiberVisions’ Mr. Gammelgaard. “China and India especially have a huge capacity of man-made fibers. I think other fiber manufacturers will be facing tough competition from the Asia-Pacific region. This will force manufacturers to find new ways of competing including speeding up product development, working more closely with customers and forming alliances throughout the value chain.”