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Lyocell is a semi-synthetic fibre used to make textiles for clothing and other purposes. It is a form of regenerated cellulose made by dissolving pulp and dry jet-wet spinning. Unlike
rayon Rayon, also called viscose and commercialised in some countries as sabra silk or cactus silk, is a semi-synthetic fiber made from natural sources of regenerated cellulose fiber, cellulose, such as wood and related agricultural products. It has t ...
, which is made by the more common
viscose Rayon, also called viscose and commercialised in some countries as sabra silk or cactus silk, is a semi-synthetic fiber made from natural sources of regenerated cellulose, such as wood and related agricultural products. It has the same molecula ...
processes, Lyocell production does not use
carbon disulfide Carbon disulfide (also spelled as carbon disulphide) is an inorganic compound with the chemical formula and structure . It is also considered as the anhydride of thiocarbonic acid. It is a colorless, flammable, neurotoxic liquid that is used as ...
, which is toxic to workers and the environment. Lyocell was originally trademarked as Tencel in 1982. "Lyocell" has become a genericised trademark used to refer to the Lyocell process for making cellulose fibres. The U.S.
Federal Trade Commission The Federal Trade Commission (FTC) is an independent agency of the United States government whose principal mission is the enforcement of civil (non-criminal) United States antitrust law, antitrust law and the promotion of consumer protection. It ...
defines Lyocell as "a fiber composed of cellulose precipitated from an organic solution in which no substitution of the
hydroxy group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...
s takes place, and no chemical intermediates are formed". It classifies the fibre as a sub-category of rayon.


Names

Other trademarked names for Lyocell fibres are Tencel ( Lenzing AG), Newcell (
Akzo Nobel Akzo Nobel N.V., stylised as AkzoNobel, is a Dutch multinational company which creates paints and performance coatings for both industry and consumers worldwide. Headquartered in Amsterdam, the company has activities in more than 150 countries ...
), and Seacell (Zimmer AG). The Aditya Birla Group also sells it under the brand name Excel. There are other manufacturers like Sateri which sell their product under generic name Lyocell


History

The development of Tencel was motivated by environmental concerns; researchers sought to manufacture rayon by means less harmful than the
viscose Rayon, also called viscose and commercialised in some countries as sabra silk or cactus silk, is a semi-synthetic fiber made from natural sources of regenerated cellulose, such as wood and related agricultural products. It has the same molecula ...
method. The Lyocell process was developed in 1972 by a team at the now defunct American Enka fibres facility at Enka, North Carolina. In 2003, the
American Association of Textile Chemists and Colorists AATCC—the American Association of Textile Chemists and Colorists— is a 501(c)(6) not-for-profit professional association that provides test method development, quality control materials, educational development, and networking for textile an ...
(AATCC) awarded Neal E. Franks their Henry E. Millson Award for Invention for Lyocell. In 1966–1968, D. L. Johnson of Eastman Kodak Inc. studied NMMO solutions. From 1969 to 1979, American Enka tried unsuccessfully to commercialise the process. The operating name for the fibre inside the Enka organisation was "Newcell", and the development was carried through a pilot plant scale before the work was stopped. The basic process of dissolving cellulose in NMMO was first described in a 1981 patent by Mcorsley for Akzona Incorporated (the holding company of Akzo). In the 1980s the patent was licensed by
Akzo Akzo Nobel N.V., stylised as AkzoNobel, is a Dutch multinational company which creates paints and performance coatings for both industry and consumers worldwide. Headquartered in Amsterdam, the company has activities in more than 150 countries ...
to Courtaulds and Lenzing. The
fibre Fiber (spelled fibre in British English; from ) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorp ...
was developed by
Courtaulds Courtaulds was a United Kingdom-based manufacturer of fabric, clothing, artificial fibres, and chemicals. It was established in 1794 and became the world's leading man-made fibre production company before being broken up in 1990 into Courtauld ...
Fibres under the brand name "Tencel" in the 1980s. In 1982, a 100-kg/week pilot plant was built in Coventry, UK, and production increased tenfold (to a ton/week) in 1984. In 1988, a 25-ton/week semi-commercial production line opened at the Grimsby, UK, pilot plant. The process was first commercialised at Courtaulds' rayon factories at
Mobile, Alabama Mobile ( , ) is a city and the county seat of Mobile County, Alabama, United States. The population was 187,041 at the 2020 United States census, 2020 census. After a successful vote to annex areas west of the city limits in July 2023, Mobil ...
(1990), and at the Grimsby plant (1998). In January 1993, the Mobile Tencel plant reached full production levels of 20,000 tons per year, by which time Courtaulds had spent £100 million and 10 years on Tencel development. Tencel revenues for 1993 were estimated as likely to be £50 million. The second plant in Mobile was planned. By 2004, production had quadrupled to 80,000 tons. Lenzing began a pilot plant in 1990, and commercial production in 1997, with 12 metric tonnes/year made in a plant in Heiligenkreuz im Lafnitztal, Austria. When an explosion hit the plant in 2003 it was producing 20,000 tonnes/year, and planning to double capacity by the end of the year. In 2004 Lenzing was producing 40,000
ton Ton is any of several units of measure of mass, volume or force. It has a long history and has acquired several meanings and uses. As a unit of mass, ''ton'' can mean: * the '' long ton'', which is * the ''tonne'', also called the ''metric ...
s 'sic'', probably metric tonnes In 1998, Lenzing and Courtaulds reached a patent dispute settlement. In 1998, Courtaulds was acquired by competitor
Akzo Nobel Akzo Nobel N.V., stylised as AkzoNobel, is a Dutch multinational company which creates paints and performance coatings for both industry and consumers worldwide. Headquartered in Amsterdam, the company has activities in more than 150 countries ...
, who combined the Tencel division with other fibre divisions under the Accordis banner, then sold them to private equity firm CVC Partners. In 2000, CVC sold the Tencel division to Lenzing AG, who combined it with their "Lenzing Lyocell" business, but maintained the brand name Tencel. They took over the plants in Mobile and Grimsby, and by 2015 was the largest Lyocell producer at 130,000 tonnes/year.


Uses

It is used in many everyday fabrics. Staple fibres are used in clothes such as
denim Denim is a sturdy cotton warp-faced textile in which the weft passes under two or more Warp (weaving), warp threads. This twill weave produces a diagonal ribbing that distinguishes it from cotton duck. Denim, as it is recognized today, was f ...
, chino, underwear, casual wear, and towels. Filament fibres, which are generally longer and smoother than staple fibres, are used in items that have a silkier appearance such as women's clothing and men's
dress shirt A dress shirt, button shirt, button-front, button-front shirt, or button-up shirt is a garment with a Collar (clothing), collar and a full-length opening at the front, which is fastened using buttons or shirt studs. A button-down or button-down ...
s. Lyocell may be blended with a variety of other fibres such as
silk Silk is a natural fiber, natural protein fiber, some forms of which can be weaving, woven into textiles. The protein fiber of silk is composed mainly of fibroin and is most commonly produced by certain insect larvae to form cocoon (silk), c ...
, cotton, rayon, polyester,
linen Linen () is a textile made from the fibers of the flax plant. Linen is very strong and absorbent, and it dries faster than cotton. Because of these properties, linen is comfortable to wear in hot weather and is valued for use in garments. Lin ...
,
nylon Nylon is a family of synthetic polymers characterised by amide linkages, typically connecting aliphatic or Polyamide#Classification, semi-aromatic groups. Nylons are generally brownish in color and can possess a soft texture, with some varieti ...
, and
wool Wool is the textile fiber obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have some properties similar to animal w ...
. When mixed with other fibres, the resulting fabric is much stronger and more resistant to wear, tear, and pilling. Lyocell also is used in conveyor belts, speciality
paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, Textile, rags, poaceae, grasses, Feces#Other uses, herbivore dung, or other vegetable sources in water. Once the water is dra ...
s, and medical dressings.


Properties

Lyocell shares many properties with other fibres such as
cotton Cotton (), first recorded in ancient India, is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure ...
,
linen Linen () is a textile made from the fibers of the flax plant. Linen is very strong and absorbent, and it dries faster than cotton. Because of these properties, linen is comfortable to wear in hot weather and is valued for use in garments. Lin ...
,
silk Silk is a natural fiber, natural protein fiber, some forms of which can be weaving, woven into textiles. The protein fiber of silk is composed mainly of fibroin and is most commonly produced by certain insect larvae to form cocoon (silk), c ...
,
ramie Ramie (pronounced: , ; from Malay ), ''Boehmeria nivea'', is a flowering plant in the nettle family Urticaceae, native to eastern Asia. It is an herbaceous perennial growing to tall;
,
hemp Hemp, or industrial hemp, is a plant in the botanical class of ''Cannabis sativa'' cultivars grown specifically for industrial and consumable use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest ...
, and
viscose rayon Rayon, also called viscose and commercialised in some countries as sabra silk or cactus silk, is a semi-synthetic fiber made from natural sources of regenerated cellulose, such as wood and related agricultural products. It has the same molecula ...
(to which it is very closely related chemically). Lyocell is 50% more absorbent than cotton, and has a longer wicking distance compared to modal fabrics of a similar weave. Compared to cotton, consumers often say Lyocell fibres feel softer and "airier", due to their better ability to wick moisture. Industry claims of higher resistance to wrinkling are as yet unsupported. Lyocell fabric may be machine washed or dry cleaned. It drapes well and may be dyed many colours, needing slightly less dye than cotton to achieve the same depth of colour.


Manufacturing process

The Lyocell process uses a direct solvent rather than indirect dissolution such as the xanthation-regeneration route in the viscose process. Lyocell fibre is produced from dissolving pulp, which contains
cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...
in high purity with little
hemicellulose A hemicellulose (also known as polyose) is one of a number of heteropolymers (matrix polysaccharides), such as arabinoxylans, present along with cellulose in almost all embryophyte, terrestrial plant cell walls. Cellulose is crystalline, strong, an ...
and no
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidit ...
. Hardwood logs (such as
oak An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...
and
birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' contains 3 ...
) are chipped into squares about the size of postage stamps. The chips are digested chemically, either with the prehydrolysis-
kraft process The kraft process (also known as kraft pulping or sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibres, the main component of paper. The kraft process involves treatment of wood chip ...
or with
sulfite process The sulfite process produces wood pulp that is almost pure cellulose fibers by treating wood chips with solutions of sulfite and bisulfite ions. These chemicals cleave the bonds between the cellulose and lignin components of the lignocellulose. A ...
, to remove the
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidit ...
and hemicellulose. The pulp is bleached to remove the remaining traces of lignin, dried into a continuous sheet and rolled onto spools. The pulp has the consistency of thick posterboard paper and is delivered in rolls weighing some 500 lb (230 kg). : At the Lyocell mill, rolls of pulp are broken into one-inch squares and dissolved in ''N''-methylmorpholine ''N''-oxide (NMMO), giving a solution called "dope". The filtered cellulose solution is then pumped through
spinnerets A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and ar ...
, devices used with a variety of synthetic fibres. The spinneret is pierced with small holes rather like a shower head; when the solution is forced through it, continuous strands of filament come out. The fibres are drawn in air to align the cellulose molecules, giving the Lyocell fibres its characteristic high strength. The fibres are then immersed into a water bath, where desolvation of the cellulose sets the fibre strands. The bath contains some dilute
amine oxide In chemistry, an amine oxide, also known as an amine ''N''-oxide or simply ''N''-oxide, is a chemical compound that has the chemical formula . It contains a nitrogen-oxygen coordinate covalent bond with three additional hydrogen and/or substitue ...
in a steady state concentration. Then the fibres are washed with demineralised water. Next, the Lyocell fibre passes to a drying area, where the water is evaporated from it. Manufacture then follows the same route as with other kinds of fibres such as viscose. The strands pass to a finishing area, where a lubricant, which may be a soap or silicone or other agents, depending on the future use of the fibre, is applied. This step is a detangler, prior to carding and spinning into yarn. At this stage, the dried, finished fibres are in a form called tow, a large, untwisted bundle of continuous lengths of filament. The bundles of tow are taken to a crimper, a machine that compresses the fibre, giving it texture and bulk. The crimped fibre is then carded by mechanical carders, which perform a combing action to separate and order the strands. The carded strands are then cut and baled for shipment to a fabric mill. The entire manufacturing process, from unrolling the raw cellulose to baling the fibre, takes roughly two hours. After this, the Lyocell may be processed in many ways. It may be spun with another fibre, such as cotton or wool. The resulting yarn can be woven or knitted like any other fabric, and may be given a variety of finishes, from soft and suede-like to silky. The
amine oxide In chemistry, an amine oxide, also known as an amine ''N''-oxide or simply ''N''-oxide, is a chemical compound that has the chemical formula . It contains a nitrogen-oxygen coordinate covalent bond with three additional hydrogen and/or substitue ...
used to dissolve the cellulose and set the fibre after spinning (NMMO) is recycled. Typically, 99 per cent of the amine oxide is recovered. NMMO biodegrades without producing harmful products. Since there is little waste product, this process is relatively eco-friendly, though it is energy-intensive.


Future research

Lyocell's lack of antibacterial properties limits its uses in the medical field. Due to its biodegradability, low toxicity, and comfort, Lyocell would become a useful material for antibacterial garments. Several approaches have been tested to introduce antibacterial capabilities. Three general approaches have been studied to achieve this: physical blending, chemical reaction, and post-treatment. Physical blending methods introduce antibacterial agents into the spinning dope. In chemical reaction methods, antibacterial additives are crosslinked into the Lyocell fibres and therefore giving antimicrobial properties. In post-treatment methods, antibacterial additives are being deposited on Lyocell fibre surfaces through physical coating, padding, or impregnation processes. Physical blending and post-treatment methods appear to be the most promising for large-scale manufacturing. Careful consideration of cost, preparation time, and antibacterial effectiveness is required to select the best method. Creating successful modification of Lyocell fibres to enhance antibacterial properties would allow to manufacture products for health care (such as lab coats, caps, gowns), hygiene products (scrubs, sanitary napkins), and clothing (socks, underwear).


See also

*
Modal (textile) Rayon, also called viscose and commercialised in some countries as sabra silk or cactus silk, is a semi-synthetic fiber made from natural sources of regenerated cellulose, such as wood and related agricultural products. It has the same molecul ...


References


Sources

* *


Further reading

* {{Fibers Cellulose Synthetic fibers