Lyocell is a regenerated cellulose fiber made from dissolving pulp (bleached wood pulp). It was first manufactured in 1987 by Courtaulds Fibres UK at their pilot plant S25. As of 2010 it is manufactured by Lenzing AG of Lenzing, Austria, under the brand name "Lyocell by Lenzing", and under the brand name Tencel by the Tencel group, now owned by Lenzing AG[1].
The US Federal Trade Commission defines Lyocell as "a cellulose fabric that is obtained by an organic solvent spinning process". It classifies the fibre as a sub-category of rayon.
The fiber is used to make textiles for clothing and other purposes.
Contents |
Lyocell was introduced to consumers in 1991 and originally marketed as a type of Rayon. Lyocell shares many properties with other cellulosic fibers such as cotton, linen, ramie and rayon. Some main characteristics of lyocell fibers are that it is soft, absorbent, very strong when wet or dry, and resistant to wrinkles; it can be machine- or hand-washed or drycleaned, it drapes well, and it can be dyed many colors, as well as simulating a variety of textures like suede, leather, or silk.[2]
Lyocell is created through a process called solvent spinning. The wood pulp is dissolved in N-Methylmorpholine N-oxide, creating a solution called "dope." The dope is then pushed through a spinneret to form the individual fibers. After the dope has been spun into lyocell fibers, it is washed and the chemicals are retrieved from the water, purified, and recycled. (Kadolph, Sara, and Anna Langford. Textiles:Ninth Edition. Prentice Hall. 2002.) Since there is little by product, this process is labelled as relatively eco-friendly. However, it uses a substantial amount of energy and the solvent is a by-product of petrol production.
Preparing the wood pulp The hardwood trees grown for lyocell production are harvested by loggers and trucked to the mill. At the mill, the trees are cut to 20 ft (6.1m) lengths and debarked by high-pressure jets of water. Next, the logs are fed into a chipper, a machine that chops them into squares little bigger than postage stamps. Mill workers load the chips into a vat of chemical digesters that soften them into a wet pulp. This pulp is washed with water, and may be bleached. Then, it is dried in a huge sheet, and mill workers roll it onto spools. The sheet of cellulose has the consistency of thick posterboard paper. The roll of cellulose is enormous, weighing some 500 lb (227 kg).
Dissolving the cellulose At the lyocell mill, workers unroll several spools of cellulose and break them into one inch squares. The workers then load these squares into a heated, pressurized vessel filled with amine oxide.
Filtering After a short time soaking in the solvent, the cellulose dissolves into a clear solution. It is pumped out through a filter, to insure that all the chips are dissolved.
Spinning Next, the solution is pumped through spinnerets. These are devices used with a variety of manmade fibers. Something like a showerhead, the spinneret is pierced with small holes, and when the cellulose is forced through it, long strands of fiber come out. The fibers are then immersed in another solution of amine oxide, diluted this time. This sets the fiber strands. Then, they are washed with de-mineralized water.
Drying and finishing
The lyocell fiber next passes to a drying area, where the water is evaporated from it. The strands at this point pass to a finishing area, where a lubricant is applied. This may be a soap or silicone or other agent, depending on the future use of the fiber. This step is basically a detangler, making the future steps of carding and spinning into yarn easier.
Final steps The dried, finished fibers are at this stage in a form called tow. Tow is a large untwisted bundle of continuous length filaments. The bundles of tow are taken to a crimper, a machine which compresses the fiber, giving it texture and bulk. The crimped fiber is carded by mechanical carders, which perform an action like combing, to separate and order the strands. The carded strands are cut and baled for shipment to a fabric mill. The entire manufacturing process, from unrolling the raw cellulose to baling the fiber, takes only about two hours. After this, the lyocell may be processed in a wide assortment of ways. It may be spun with another fiber, such as cotton or wool. The yarn can be woven or knit like any other fabric, and given a variety of finishes, from soft and suede-like to silky.
Recovery of the solvent The amine oxide used to dissolve the cellulose and set the fiber after spinning is recovered and re-used in the manufacturing process. The dilute solution is evaporated, removing the water, and the amine oxide is routed for re-use in the pressurized vessel in step 2. Ninety-nine percent of the amine oxide is recoverable in the typical lyocell manufacturing process.
Currently Lyocell is more expensive to produce than cotton or rayon, but is included in many everyday items. Staple fibres are used in apparel items such as denim, chino, underwear and other casual wear clothing, and towels. Filament fibers are used in items that have a silkier appearance such as women’s clothing and men’s dress shirts. Lyocell can be blended with a variety of other fibers such as silk, cotton, rayon, polyester, linen, nylon, and wool. Lyocell is also used in conveyor belts, specialty papers and medical dressings. (Textiles, Kadolph & Langford). Tencel is also used for making baby diaper wipes - Costco/Kirkland is one brand that uses the material.
Lyocel is manufactured by Lenzing in Mobile, Alabama, USA, in Grimsby, England, and in Heiligenkreuz, Burgenland, Austria.
|
|||||||||||||||||||||
   | Federal Trade Commission webpage on textiles - Textile, Wool, Fur, Apparel and Leather Matters |
| | OSU fact sheet - Lyocell - One Fiber, Many Faces, HYG-5572-99 |
| | A site advocating the use of lyocell as an eco-friendly textile - Lyocell - Information, News and Links |
|
|
Wikis
Quiz
Map
Search
