Rayon, also called viscose [1] and commercialised in some countries as sabra silk or cactus silk, [2] is a semi-synthetic fiber [3] made from natural sources of regenerated cellulose, such as wood and related agricultural products. [4] It has the same molecular structure as cellulose. Many types and grades of viscose fibers and films exist. Some imitate the feel and texture of natural fibers such as silk, wool, cotton, and linen. The types that resemble silk are often called artificial silk. It can be woven or knit to make textiles for clothing and other purposes. [5]
Rayon production involves solubilizing cellulose to allow turning the fibers into required form. Three common solubilization methods are:
French scientist and industrialist Hilaire de Chardonnet (1838–1924) invented the first artificial textile fiber, artificial silk. [11]
Swiss chemist Matthias Eduard Schweizer (1818–1860) discovered that cellulose dissolved in tetraamminecopper dihydroxide. Max Fremery and Johann Urban developed a method to produce carbon fibers for use in light bulbs in 1897. [12] Production of cuprammonium rayon for textiles started in 1899 in the Vereinigte Glanzstoff Fabriken AG in Oberbruch (near Aachen).[ citation needed ] [13] Improvement by J. P. Bemberg AG in 1904 made the artificial silk a product comparable to real silk. [14] [15]
English chemist Charles Frederick Cross and his collaborators, Edward John Bevan and Clayton Beadle, patented their artificial silk in 1894. They named it "viscose" because its production involved the intermediacy of a highly viscous solution. Cross and Bevan took out British Patent No. 8,700, "Improvements in Dissolving Cellulose and Allied Compounds" in May, 1892. [16] In 1893, they formed the Viscose Syndicate to grant licences and, in 1896, formed the British Viscoid Co. Ltd. [11] [17]
The first commercial viscose rayon was produced by the UK company Courtaulds Fibres in November 1905. [18] Courtaulds formed an American division, American Viscose (later known as Avtex Fibers), to produce their formulation in the US in 1910. [19] The name "rayon" was adopted in 1924[ citation needed ], with "viscose" being used for the viscous organic liquid used to make both rayon and cellophane. In Europe, though, the fabric itself became known as "viscose", which has been ruled an acceptable alternative term for rayon by the US Federal Trade Commission (FTC).[ citation needed ]
Rayon was produced only as a filament fiber until the 1930s, when methods were developed to utilize "broken waste rayon" as staple fiber.[ citation needed ]
Manufacturers' search for a less environmentally-harmful process for making Rayon led to the development of the lyocell method for producing Rayon. [20] The lyocell process was developed in 1972 by a team at the now defunct American Enka fibers facility at Enka, North Carolina.[ citation needed ] In 2003, the American Association of Textile Chemists and Colorists (AATCC) awarded Neal E. Franks their Henry E. Millson Award for Invention for lyocell. [21] In 1966–1968, D. L. Johnson of Eastman Kodak Inc. studied NMMO solutions. In the decade 1969 to 1979, American Enka tried unsuccessfully to commercialize the process. [20] The operating name for the fibre inside the Enka organization was "Newcell", and the development was carried through 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 [20] [22] (the holding company of Akzo). In the 1980s the patent was licensed by Akzo to Courtaulds and Lenzing. [23] The fibre was developed by Courtaulds Fibres under the brand name "Tencel" in the 1980s. In 1982, a 100 kg/week pilot plant was built in Coventry, UK, and production was 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. [24] [20] The process was first[ citation needed ] commercialized at Courtaulds' rayon factories at Mobile, Alabama [25] (1990[ citation needed ]), and at the Grimsby plant (1998)[ citation needed ]. 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. A second plant in Mobile was planned. [25] By 2004, production had quadrupled to 80,000 tons. [23]
Lenzing began a pilot plant in 1990, [20] and commercial production in 1997, with 12 metric tonnes/year made in a plant in Heiligenkreuz im Lafnitztal, Austria. [20] [23] 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. [26] In 2004 Lenzing was producing 40,000 tons [sic, probably metric tonnes]. [23] In 1998, Lenzing and Courtaulds reached a patent dispute settlement. [23]
In 1998 Courtaulds was acquired by competitor Akzo Nobel, [27] which 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, which combined it with their "Lenzing Lyocell" business, but maintained the brand name Tencel. [23] It took over the plants in Mobile and Grimsby, and by 2015 were the largest lyocell producer at 130,000 tonnes/year. [20]
Rayon is produced by dissolving cellulose, then converting this solution back to insoluble fibrous cellulose. Various processes have been developed for this regeneration. The most common methods for creating rayon are the cuprammonium method, the viscose method, and the lyocell process. The first two methods have been practiced for more than a century.
Cuprammonium rayon has properties similar to viscose; however, during its production, the cellulose is combined with copper and ammonia (Schweizer's reagent). Due to the detrimental environmental effects of this production method, cuprammonium rayon is no longer being produced in the United States. [28] The process has been described as obsolete, [6] but cuprammonium rayon is still made by one company in Japan. [29] [ better source needed ]
Tetraamminecopper(II) sulfate is also used as a solvent.
The viscose process builds on the reaction of cellulose with a strong base, followed by treatment of that solution with carbon disulfide to give a xanthate derivative. The xanthate is then converted back to a cellulose fiber in a subsequent step.
The viscose method can use wood as a source of cellulose, whereas other routes to rayon require lignin-free cellulose as a starting material. The use of woody sources of cellulose makes viscose cheaper, so it was traditionally used on a larger scale than the other methods. On the other hand, the original viscose process generates large amounts of contaminated wastewater. Newer technologies use less water and have improved the quality of the wastewater.
The raw material for viscose is primarily wood pulp (sometimes bamboo pulp), which is chemically converted into a soluble compound. It is then dissolved and forced through a spinneret to produce filaments, which are chemically solidified, resulting in fibers of nearly pure cellulose. [30] Unless the chemicals are handled carefully, workers can be seriously harmed by the carbon disulfide used to manufacture most rayon. [31] [32]
To prepare viscose, pulp is treated with aqueous sodium hydroxide (typically 16–19% by mass) to form "alkali cellulose", which has the approximate formula [C6H9O4−ONa]n. This material is allowed to depolymerize to an extent. The rate of depolymerization (ripening or maturing) depends on temperature and is affected by the presence of various inorganic additives, such as metal oxides and hydroxides. Air also affects the ripening process, since oxygen causes depolymerization. The alkali cellulose is then treated with carbon disulfide to form sodium cellulose xanthate: [5]
Rayon fiber is produced from the ripened solutions by treatment with a mineral acid, such as sulfuric acid. In this step, the xanthate groups are hydrolyzed to regenerate cellulose and carbon disulfide:
Aside from regenerated cellulose, acidification gives hydrogen sulfide (H2S), sulfur, and carbon disulfide. The thread made from the regenerated cellulose is washed to remove residual acid. The sulfur is then removed by the addition of sodium sulfide solution, and impurities are oxidized by bleaching with sodium hypochlorite solution or hydrogen peroxide solution. [17]
Production begins with processed cellulose obtained from wood pulp and plant fibers. The cellulose content in the pulp should be around 87–97%.
The steps: [30]
The lyocell process relies on dissolution of cellulose products in a solvent, N-methyl morpholine N-oxide (NMMO).
The process starts with cellulose and involves dry jet-wet spinning. It was developed at the now defunct American Enka Company and Courtaulds Fibres. Lenzing's Tencel is an example of a lyocell fiber. [14] Unlike the viscose process, the lycocell process does not use highly toxic carbon disulfide. [9] [10] "Lyocell" has become a genericized trademark, used to refer to the lyocell process for making cellulose fibers. [10]
As of 2018 [update] , the lyocell process is not widely used, because it is still more expensive than the viscose process. [10] [9]
Rayon is a versatile fiber and is widely claimed to have the same comfort properties as natural fibers, although the drape and slipperiness of rayon textiles are often more like nylon. It can imitate the feel and texture of silk, wool, cotton, and linen. The fibers are easily dyed in a wide range of colors. Rayon fabrics are soft, smooth, cool, comfortable, and highly absorbent, but they do not always insulate body heat, making them ideal for use in hot and humid climates, although also making their "hand" (feel) cool and sometimes almost slimy to the touch. [33]
The durability and appearance retention of regular viscose rayons are low, especially when wet; also, rayon has the lowest elastic recovery of any fiber. However, HWM rayon (high-wet-modulus rayon) is much stronger and exhibits higher durability and appearance retention. Recommended care for regular viscose rayon is dry-cleaning only. HWM rayon can be machine-washed. [34]
Regular rayon has lengthwise lines called striations and its cross-section is an indented circular shape. The cross-sections of HWM and cupra rayon are rounder. Filament rayon yarns vary from 80 to 980 filaments per yarn and vary in size from 40 to 5000 denier. Staple fibers range from 1.5 to 15 denier and are mechanically or chemically crimped. Rayon fibers are naturally very bright, but the addition of delustering pigments cuts down on this natural brightness. [34]
The physical properties of rayon remained unchanged until the development of high-tenacity rayon in the 1940s. Further research and development led to high-wet-modulus rayon (HWM rayon) in the 1950s. [34] Research in the UK was centred on the government-funded British Rayon Research Association.
High-tenacity rayon is another modified version of viscose that has almost twice the strength of HWM. This type of rayon is typically used for industrial purposes such as tire cord. [28]
Industrial applications of rayon emerged around 1935. Substituting cotton fiber in tires and belts, industrial types of rayon developed a totally different set of properties, amongst which tensile strength and elastic modulus were paramount.
Modal is a genericized trademark of Lenzing AG, used for (viscose) rayon which is stretched as it is made, aligning the molecules along the fibers. Two forms are available: "polynosics" and "high wet modulus" (HWM). [35] [36] [ better source needed ]High-wet-modulus rayon is a modified version of viscose that is stronger when wet. It can be mercerized like cotton. HWM rayons are also known as "polynosic".[ contradictory ] Polynosic fibers are dimensionally stable and do not shrink or get pulled out of shape when wet like many rayons. They are also wear-resistant and strong while maintaining a soft, silky feel. They are sometimes identified by the trade name Modal. [28] Modal is used alone or with other fibers (often cotton or spandex) in clothing and household items like pajamas, underwear, bathrobes, towels, and bedsheets. Modal can be tumble-dried without damage. [37] The fabric has been known to pill less than cotton due to fiber properties and lower surface friction. [36] The trademarked Modal is made by spinning beech-tree cellulose and is considered a more eco-friendly alternative to cotton, as the production process uses on average 10–20 times less water. [38]
In 2018, viscose fiber production in the world was approximately 5.8 million tons, and China was the largest producer with about 65% of total global production. [39] Trade names are used within the rayon industry to label the type of rayon in the product. Viscose rayon was first produced in Coventry, England in 1905 by Courtaulds.
Bemberg is a trade name for cuprammonium rayon developed by J. P. Bemberg. Bemberg performs much like viscose but has a smaller diameter and comes closest to silk in feel. Bemberg is now only produced in Japan. [29] The fibers are finer than viscose rayon. [15] [ failed verification ]
Modal and Tencel are widely used forms of rayon produced by Lenzing AG. Tencel, generic name lyocell, is made by a slightly different solvent recovery process, and is considered a different fiber by the US FTC. Tencel lyocell was first produced commercially by Courtaulds' Grimsby plant in England. The process, which dissolves cellulose without a chemical reaction, was developed by Courtaulds Research.
Birla Cellulose is also a volume manufacturer of rayon. They have plants located in India, Indonesia and China.
Accordis was a major manufacturer of cellulose-based fibers and yarns. Production facilities can be found throughout Europe, the U.S. and Brazil. [40]
Visil rayon and HOPE FR are flame retardant forms of viscose that have silica embedded in the fiber during manufacturing.
North American Rayon Corporation of Tennessee produced viscose rayon until its closure in the year 2000. [41] [42]
Indonesia is one of the largest producers of rayon in the world, and Asia Pacific Rayon (APR) of the country has an annual production capacity of 0.24 million tons. [43]
The biodegradability of various fibers in soil burial and sewage sludge was evaluated by Korean researchers. Rayon was found to be more biodegradable than cotton, and cotton more than acetate. The more water-repellent the rayon-based fabric, the more slowly it will decompose. [44] Subsequent experiments have shown that wood-based fibres, like Lyocell, biodegrade much more readily than polyester. [45] Silverfish—like the firebrat—can eat rayon, but damage was found to be minor, potentially due to the heavy, slick texture of the tested rayon. [46] Another study states that "artificial silk [...] [was] readily eaten" by the grey silverfish. [47]
A 2014 ocean survey found that rayon contributed to 56.9% of the total fibers found in deep ocean areas, the rest being polyester, polyamides, acetate and acrylic. [48] A 2016 study found a discrepancy in the ability to identify natural fibers in a marine environment via Fourier transform infrared spectroscopy. [49] Later research of oceanic microfibers instead found cotton being the most frequent match (50% of all fibers), followed by other cellulosic fibers at 29.5% (e.g., rayon/viscose, linen, jute, kenaf, hemp, etc.). [50] Further analysis of the specific contribution of rayon to ocean fibers was not performed due to the difficulty in distinguishing between natural and man-made cellulosic fibers using FTIR spectra.
For several years, there have been concerns about links between rayon manufacturers and deforestation. As a result of these concerns, FSC and PEFC came on the same platform with CanopyPlanet to focus on these issues. CanopyPlanet subsequently started publishing a yearly Hot Button report, which puts all the man-made cellulosics manufacturers globally on the same scoring platform. The scoring from the 2020 report scores all such manufacturers on a scale of 35, the highest scores having been achieved by Birla Cellulose (33) and Lenzing (30.5).
Carbon disulfide is highly toxic. [51] It is well documented to have seriously harmed the health of rayon workers in developed countries, and emissions may also harm the health of people living near rayon plants [51] and their livestock. [52] Rates of disability in modern factories (mainly in China, Indonesia, and India) are unknown. [32] [7] This has raised ethical concerns over viscose rayon production. [8] [7] [9] [31] As of 2016 [update] , production facilities located in developing countries generally do not provide environmental or worker safety data. [53]
Most global carbon disulfide emissions come from rayon production, as of 2008. [54] As of 2004 [update] , about 250 g of carbon disulfide is emitted per kilogram of rayon produced. [55]
Control technologies have enabled improved collection of carbon disulfide and reuse of it, resulting in a lower emissions of carbon disulfide. [5] These have not always been implemented in places where it was not legally required and profitable. [52]
Carbon disulfide is volatile and is lost before the rayon gets to the consumer; the rayon itself is basically pure cellulose. [31]
Studies from the 1930s show that 30% of American rayon workers experienced significant health impacts due to carbon disulfide exposure. Courtaulds worked hard to prevent this information being published in Britain. [8]
During the Second World War, political prisoners in Nazi Germany were made to work in appalling conditions at the Phrix rayon factory in Krefeld. [56] Nazis used forced labour to produce rayon across occupied Europe. [8]
In the 1990s, viscose rayon producers faced lawsuits for negligent environmental pollution. Emissions abatement technologies had been consistently used. Carbon-bed recovery, for instance, which reduces emissions by about 90%, was used in Europe, but not in the US, by Courtaulds. [52] Pollution control and worker safety started to become cost-limiting factors in production.
Japan has reduced carbon disulfide emissions per kilogram of viscose rayon produced (by about 16% per year), but in other rayon-producing countries, including China, emissions are uncontrolled. Rayon production is steady or decreasing except in China, where it is increasing, as of 2004 [update] . [55]
Rayon production has largely moved to the developing world, especially China, Indonesia and India. [7] [8] Rates of disability in these factories are unknown, as of 2016 [update] , [32] [7] and concerns for worker safety continue. [53]
Studies have found the production of rayon can be harmful to the health of factory workers. [57] [58] Workers in factories utilizing the viscose process may be exposed to high levels of carbon disulfide, which can cause coronary heart disease, retinal damage, behavioral changes, impaired motor function, and various fertility and hormonal effects. [59]
Related materials are not regenerated cellulose, but esters of cellulose. [60] [61]
Nitrocellulose is a derivative of cellulose that is soluble in organic solvents. It is mainly used as an explosive or as a lacquer. Many early plastics, including celluloid, were made from nitrocellulose.
Cellulose acetate shares many traits with viscose rayon and was formerly considered the same textile. However, rayon resists heat, while acetate is prone to melting. Acetate must be laundered with care either by hand-washing or dry cleaning, and acetate garments disintegrate when heated in a tumble dryer. [62] [63] The two fabrics are now required to be listed distinctly on USA garment labels. [64]
Cellophane is generally made by the viscose process, but dried into sheets instead of fibers.
Cellulose is an organic compound with the formula (C
6H
10O
5)
n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall of green plants, many forms of algae and the oomycetes. Some species of bacteria secrete it to form biofilms. Cellulose is the most abundant organic polymer on Earth. The cellulose content of cotton fibre is 90%, that of wood is 40–50%, and that of dried hemp is approximately 57%.
Fiber 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 incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene.
Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria, and liquid water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated with nitrocellulose lacquer to prevent this.
Carbon disulfide is an inorganic compound with the chemical formula CS2 and structure S=C=S. It is also considered as the anhydride of thiocarbonic acid. It is a colorless, flammable, neurotoxic liquid that is used as a building block in organic synthesis. Pure carbon disulfide has a pleasant, ether- or chloroform-like odor, but commercial samples are usually yellowish and are typically contaminated with foul-smelling impurities.
Synthetic fibers or synthetic fibres are fibers made by humans through chemical synthesis, as opposed to natural fibers that are directly derived from living organisms, such as plants or fur from animals. They are the result of extensive research by scientists to replicate naturally occurring animal and plant fibers. In general, synthetic fibers are created by extruding fiber-forming materials through spinnerets, forming a fiber. These are called synthetic or artificial fibers. The word polymer comes from a Greek prefix "poly" which means "many" and suffix "mer" which means "single units"..
Lyocell is a semi-synthetic fiber 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 made by the more common viscose processes, Lyocell production does not use carbon disulfide, which is toxic to workers and the environment. Lyocell was originally trademarked as Tencel in 1982.
The Lenzing Group is an international group with its headquarters in Lenzing, Austria, and production sites in all major markets. Lenzing produces wood-based viscose fibers, modal fibers, lyocell fibers and filament yarn, which are used in the textile industry — in clothing, home textiles and technical textiles — as well as in the nonwovens industry. In addition, the company is active in mechanical and plant engineering. The Lenzing Group markets its products under the brand names TENCEL, VEOCEL, LENZING ECOVERO and LENZING.
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 Courtaulds plc and Courtaulds Textiles Ltd.
Bamboo textile is any cloth, yarn or clothing made from bamboo fibres. While bamboo was historically used only for structural elements, such as bustles and the ribs of corsets, in recent years various technologies have been developed that allow bamboo fibre to be used for a wide range of textile and fashion applications.
Dissolving pulp, also called dissolving cellulose, is bleached wood pulp or cotton linters that has a high cellulose content. It has special properties including a high level of brightness and uniform molecular-weight distribution. This pulp is manufactured for uses that require a high chemical purity, and particularly low hemicellulose content, since the chemically similar hemicellulose can interfere with subsequent processes. Dissolving pulp is so named because it is not made into paper, but dissolved either in a solvent or by derivatization into a homogeneous solution, which makes it completely chemically accessible and removes any remaining fibrous structure. Once dissolved, it can be spun into textile fibers, or chemically reacted to produce derivatized celluloses, such cellulose triacetate, a plastic-like material formed into fibers or films, or cellulose ethers such as methyl cellulose, used as a thickener.
Many clothing materials have been used to make garments throughout history. Grasses, furs and much more complex and exotic materials have been used. Cultures near the Arctic Circle, make their wardrobes out of processed furs and skins. Different cultures have added cloth to leather and skins as a way to replace real leather. A wide range of fibers, including natural, cellulose, and synthetic fibers, can be used to weave or knit cloth. From natural fibers like cotton and silk to synthetic ones like polyester and nylon, most certainly reflects culture.
Cellulose fibers are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants, or from other plant-based material. In addition to cellulose, the fibers may also contain hemicellulose and lignin, with different percentages of these components altering the mechanical properties of the fibers.
Oberbruch Industry Park, is a former 110-hectare (270-acre) site of Akzo Nobel in Heinsberg, Germany's most western district, near the Dutch border. It was founded in 1891 as a location for fiber industries. It is the birthplace of the German rayon and man-made fiber industry. Today, it is a diversified multi-user site, hosting companies from fields of industry such as high-performance fibers and energy technologies as well as from industrial biotechnology. Oberbruch Industry Park is the competency center for carbon (fiber) technology in North Rhine-Westphalia (NRW). Since 2000, the industry park has been operated by the Dutch energy company Nuon, the first independent industrial park operator not to come from the chemical industry. Since January 7, 2009 N.V. Nuon Energy has been part of Vattenfall.
Cuprammonium rayon is a rayon fiber made from cellulose dissolved in a cuprammonium solution, Schweizer's reagent.
Devoré is a fabric technique particularly used on velvets, where a mixed-fibre material undergoes a chemical process to dissolve the cellulose fibres to create a semi-transparent pattern against more solidly woven fabric. The same technique can also be applied to textiles other than velvet, such as lace or the fabrics in burnout t-shirts.
Green textiles are fabrics or fibres produced to replace environmentally harmful textiles and minimise the ecological impact. Green textiles are part of the sustainable fashion and eco-friendly trends, providing alternatives to the otherwise pollution-heavy products of conventional textile industry, which is deemed the most ecologically damaging industry.
Vereinigte Glanzstoff-Fabriken was a German manufacturer of artificial fiber founded in 1899 that became one of the leading European producers of rayon.
Max Fremery was a German chemist and industrialist. He was one of the founders of the Vereinigte Glanzstoff-Fabriken (VGF) in 1899. VGF became a major manufacturer of artificial fibers.
J. P. Bemberg was a German rayon manufacturer that produced an unusually fine artificial fiber which became known as Bemberg®. J. P. Bemberg came under the control of Vereinigte Glanzstoff-Fabriken and eventually disappeared after a series of mergers and divestitures, but Bemberg™ rayon was still being produced in 2015 by Asahi in Japan,
Red Scar Works was built in 1939 by Courtaulds and produced continuous filament viscose rayon. It was located in Ribbleton, Preston, off Longridge Road. The closure of the works was announced in November 1979 and the issue raised in the UK Parliament House of Commons by the constituency MP. At the time of closure, approximately 2,600 people were employed there, but there were approximately 4,000 at its peak. It was at one time the largest rayon producing site in Britain. Two main products were manufactured: one being tyre yarn made by a process known as CSPT, trademarked Tenasco, in two principle deniers; the other being a general-purpose textile yarn called Bright. A range of deniers of this were produced; pigmented variants in a wide range of colours were trademarked Duracol. At the time of closure, one reason given by management for the closure was the rising popularity of steel belt radial tyres, thus reducing demand for viscose tyre yarn.
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