Viscose: Difference between revisions
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{{Distinguish|Viscous}} |
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'''Viscose''' is a type of [[rayon]] fiber that is made from natural sources such as wood and agricultural products that are regenerated as [[cellulose fiber]]. The molecular structure of natural cellulose is preserved in the process. The many types and grades of viscose fibers can imitate the feel and texture of [[Natural fiber|natural fibers]] such as [[silk]], [[wool]], [[cotton]], and [[linen]]. The types that resemble silk are often called [[Art silk|artificial silk]]. The fibre is used to make textiles for clothing and other purposes.<ref>{{Ullmann | first1=Hans | last1=Krässig | first2=Josef | last2=Schurz | first3=Robert G. | last3=Steadman | first4=Karl | last4=Schliefer | first5= Wilhelm |last5=Albrecht|first6=Marc | last6=Mohring | first7=Harald | last7=Schlosser | title=Cellulose | year=2002 | doi=10.1002/14356007.a05_375.pub2}}</ref> |
'''Viscose''' is a type of [[rayon]] fiber that is made from natural sources such as wood and agricultural products that are regenerated as [[cellulose fiber]]. The molecular structure of natural cellulose is preserved in the process. The many types and grades of viscose fibers can imitate the feel and texture of [[Natural fiber|natural fibers]] such as [[silk]], [[wool]], [[cotton]], and [[linen]]. The types that resemble silk are often called [[Art silk|artificial silk]]. The fibre is used to make textiles for clothing and other purposes.<ref name=Ull>{{Ullmann | first1=Hans | last1=Krässig | first2=Josef | last2=Schurz | first3=Robert G. | last3=Steadman | first4=Karl | last4=Schliefer | first5= Wilhelm |last5=Albrecht|first6=Marc | last6=Mohring | first7=Harald | last7=Schlosser | title=Cellulose | year=2002 | doi=10.1002/14356007.a05_375.pub2}}</ref> |
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Rayon is manufactured from naturally occurring cellulose; hence, it is not considered to be synthetic. Technically, the term [[synthetic fiber]] is reserved for [[Total synthesis|fully synthetic]] fibers made from synthetic polymers. In manufacturing terms, rayon is classified as "a fiber formed by regenerating natural materials into a usable form"{{Citation needed|date=February 2020}}. Specific types of rayon include viscose, [[Modal (textile)|Modal]] (a trade name for high-wet-modulus rayon) and [[lyocell]] (more exactly a ''production process''; the manufactured product is known as Tencel), each of which differs in the manufacturing process and the properties of the finished product. |
Rayon is manufactured from naturally occurring cellulose; hence, it is not considered to be synthetic. Technically, the term [[synthetic fiber]] is reserved for [[Total synthesis|fully synthetic]] fibers made from synthetic polymers. In manufacturing terms, rayon is classified as "a fiber formed by regenerating natural materials into a usable form"{{Citation needed|date=February 2020}}. Specific types of rayon include viscose, [[Modal (textile)|Modal]] (a trade name for high-wet-modulus rayon) and [[lyocell]] (more exactly a ''production process''; the manufactured product is known as Tencel), each of which differs in the manufacturing process and the properties of the finished product. |
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Viscose rayon is a fiber of regenerated cellulose; its molecular structure is that of cellulose in [[cotton]] and many other plants such as soy, bamboo, and sugar cane. Cellulose is a linear polymer of β-D-glucose units with the empirical formula (C<sub>6</sub>H<sub>10</sub>O<sub>5</sub>)<sub>{{mvar|n}}</sub>.<ref name="Ullmann's Encyclopedia of Industrial Chemistry">{{cite book|last=Booth|first=Gerald|title=Dyes, General Survey|year=2000|publisher=Wiley-VCH |doi=10.1002/14356007.a09_073}}</ref> To prepare viscose, dissolving pulp is treated with aqueous sodium hydroxide (typically 16-19% [[w/w]]) to form "alkali cellulose", which has the approximate formula [C<sub>6</sub>H<sub>9</sub>O<sub>4</sub>-ONa]<sub>{{mvar|n}}</sub>. This 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]].<ref name="Wheeler 1928">{{cite book|last=Wheeler|first=Edward|title=The Manufacture of Artificial Silk With Special Reference to the Viscose Process|year=1928|publisher=D. Van Nostrand company|location=New York}}</ref> |
Viscose rayon is a fiber of regenerated cellulose; its molecular structure is that of cellulose in [[cotton]] and many other plants such as soy, bamboo, and sugar cane. Cellulose is a linear polymer of β-D-glucose units with the empirical formula (C<sub>6</sub>H<sub>10</sub>O<sub>5</sub>)<sub>{{mvar|n}}</sub>.<ref name="Ullmann's Encyclopedia of Industrial Chemistry">{{cite book|last=Booth|first=Gerald|title=Dyes, General Survey|year=2000|publisher=Wiley-VCH |doi=10.1002/14356007.a09_073}}</ref> To prepare viscose, dissolving pulp is treated with aqueous sodium hydroxide (typically 16-19% [[w/w]]) to form "alkali cellulose", which has the approximate formula [C<sub>6</sub>H<sub>9</sub>O<sub>4</sub>-ONa]<sub>{{mvar|n}}</sub>. This 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]].<ref name="Wheeler 1928">{{cite book|last=Wheeler|first=Edward|title=The Manufacture of Artificial Silk With Special Reference to the Viscose Process|year=1928|publisher=D. Van Nostrand company|location=New York}}</ref> |
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:[C<sub>6</sub>H<sub> |
:[C<sub>6</sub>H<sub>5</sub>(OH)<sub>4</sub>-ONa]<sub>{{mvar|n}}</sub> + {{mvar|n}}[[Carbon disulfide|CS<sub>2</sub>]] → [C<sub>6</sub>H<sub>5</sub>(OH)<sub>4</sub>-OCS<sub>2</sub>Na]<sub>{{mvar|n}}</sub> |
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The higher the ratio of cellulose to combined sulfur, the lower the solubility of the cellulose xanthate. The xanthate is dissolved in aqueous sodium hydroxide (typically 2-5% w/w). The solution's viscosity is determined by the extent of depolymerization of the alkali cellulose. |
The higher the ratio of cellulose to combined sulfur, the lower the solubility of the cellulose xanthate. The xanthate is dissolved in aqueous sodium hydroxide (typically 2-5% w/w). The solution's viscosity is determined by the extent of depolymerization of the alkali cellulose. |
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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 |
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. |
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:[C<sub>6</sub>H<sub> |
:[C<sub>6</sub>H<sub>5</sub>(OH)<sub>4</sub>-OCS<sub>2</sub>Na]<sub>2{{mvar|n}}</sub> + {{mvar|n}}H<sub>2</sub>SO<sub>4</sub> → [C<sub>6</sub>H<sub>5</sub>(OH)<sub>4</sub>-OH]<sub>2{{mvar|n}}</sub> +2{{mvar|n}}CS<sub>2</sub> + {{mvar|n}}Na<sub>2</sub>SO<sub>4</sub> |
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:H<sub>2</sub>COS<sub>2</sub> → H<sub>2</sub>O + CS<sub>2</sub> |
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Aside from regenerated cellulose, acidification gives hydrogen sulfide (H<sub>2</sub>S), 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.<ref name="Wheeler 1928" /> |
Aside from regenerated cellulose, acidification gives hydrogen sulfide (H<sub>2</sub>S), 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.<ref name="Wheeler 1928" /> |
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=== Pollution=== |
=== Pollution=== |
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{{See also|Rayon#Environment and sustainability}} |
{{See also|Rayon#Environment and sustainability}} |
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Because [[carbon disulfide]] is highly toxic, its use on a large scale demands care. Historically, however, several incidents have resulted in many poisonings. With production facilities often located in developing countries, concerns for worker safety continue.<ref name="FakeSilk">{{cite book|author=Paul David Blanc|title=Fake Silk The Lethal History of Viscose Rayon|publisher=Yale University Press|year=2016|pages=325|isbn=9780300204667}}</ref> Newer control technologies have enabled improved collection of carbon disulfide and reuse of it, resulting in a lower emissions of carbon disulfide. |
Because [[carbon disulfide]] is highly toxic, its use on a large scale demands care. Historically, however, several incidents have resulted in many poisonings. With production facilities often located in developing countries, concerns for worker safety continue.<ref name="FakeSilk">{{cite book|author=Paul David Blanc|title=Fake Silk The Lethal History of Viscose Rayon|publisher=Yale University Press|year=2016|pages=325|isbn=9780300204667}}</ref> Newer control technologies have enabled improved collection of carbon disulfide and reuse of it, resulting in a lower emissions of carbon disulfide.<ref name=Ull/> |
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Viscose or rayon may also be manufactured using the [[Lyocell]] process, which uses [[N-Methylmorpholine N-oxide|N-methylmorpholine N-oxide]] as the solvent to dissolve the cellulose. NMO is more expensive that carbon disulfide, such that losses during processing must be minimized. |
Viscose or rayon may also be manufactured using the [[Lyocell]] process, which uses [[N-Methylmorpholine N-oxide|N-methylmorpholine N-oxide]] (NMO) as the solvent to dissolve the cellulose. NMO is more expensive that carbon disulfide, such that losses during processing must be minimized. |
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== History == |
== History == |
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Revision as of 14:08, 9 August 2020
Viscose is a type of rayon fiber that is made from natural sources such as wood and agricultural products that are regenerated as cellulose fiber. The molecular structure of natural cellulose is preserved in the process. The many types and grades of viscose fibers can 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. The fibre is used to make textiles for clothing and other purposes.[1]
Rayon is manufactured from naturally occurring cellulose; hence, it is not considered to be synthetic. Technically, the term synthetic fiber is reserved for fully synthetic fibers made from synthetic polymers. In manufacturing terms, rayon is classified as "a fiber formed by regenerating natural materials into a usable form"[citation needed]. Specific types of rayon include viscose, Modal (a trade name for high-wet-modulus rayon) and lyocell (more exactly a production process; the manufactured product is known as Tencel), each of which differs in the manufacturing process and the properties of the finished product.
Viscose can mean:
- A viscous solution of cellulose
- A synonym of rayon
- A specific term for viscose rayon — rayon made using the viscose (cellulose xanthate) process
The viscose fiber is made from dissolving wood pulp and regenerating it in the form of fibers. Pulp made from wood or bamboo is the most common raw material for making viscose. Viscose process dissolves cellulose pulp with aqueous sodium hydroxide in the presence of carbon disulfide. This viscous solution bears the name viscose. The cellulose solution is used to spin the viscose or the rayon fiber. Viscose rayon fiber is a soft fiber commonly used in dresses, linings, shirts, shorts, coats, jackets, and other outerwear. It is also used in industrial yarns, tyre cord, upholstery and carpets, to make disposable wipes, cleaning cloths and in the casting of cellophane.
Manufacture
Viscose rayon is a fiber of regenerated cellulose; its molecular structure is that of cellulose in cotton and many other plants such as soy, bamboo, and sugar cane. Cellulose is a linear polymer of β-D-glucose units with the empirical formula (C6H10O5)n.[3] To prepare viscose, dissolving pulp is treated with aqueous sodium hydroxide (typically 16-19% w/w) to form "alkali cellulose", which has the approximate formula [C6H9O4-ONa]n. This 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.[4]
- [C6H5(OH)4-ONa]n + nCS2 → [C6H5(OH)4-OCS2Na]n
The higher the ratio of cellulose to combined sulfur, the lower the solubility of the cellulose xanthate. The xanthate is dissolved in aqueous sodium hydroxide (typically 2-5% w/w). The solution's viscosity is determined by the extent of depolymerization of the alkali cellulose.
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.
- [C6H5(OH)4-OCS2Na]2n + nH2SO4 → [C6H5(OH)4-OH]2n +2nCS2 + nNa2SO4
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.[4]
Pollution
Because carbon disulfide is highly toxic, its use on a large scale demands care. Historically, however, several incidents have resulted in many poisonings. With production facilities often located in developing countries, concerns for worker safety continue.[5] Newer control technologies have enabled improved collection of carbon disulfide and reuse of it, resulting in a lower emissions of carbon disulfide.[1]
Viscose or rayon may also be manufactured using the Lyocell process, which uses N-methylmorpholine N-oxide (NMO) as the solvent to dissolve the cellulose. NMO is more expensive that carbon disulfide, such that losses during processing must be minimized.
History
French scientist and industrialist Hilaire de Chardonnet (1838–1924), inventor of the first artificial textile fiber, artificial silk, created viscose.[6] British scientists Charles Frederick Cross and Edward John Bevan took out British Patent No. 8,700, "Improvements in Dissolving Cellulose and Allied Compounds" in May, 1892.[7] In 1893 they formed the Viscose Syndicate to grant licences, and in 1896 formed the British Viscoid Co. Ltd. to exploit the process.[6]
Products made from viscose
References
- ^ a b Krässig, Hans; Schurz, Josef; Steadman, Robert G.; Schliefer, Karl; Albrecht, Wilhelm; Mohring, Marc; Schlosser, Harald (2002). "Cellulose". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_375.pub2. ISBN 978-3527306732.
- ^ Siegfried Hauptmann: Organische Chemie, 2. durchgesehene Auflage, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1985, S. 652, ISBN 3-342-00280-8.
- ^ Booth, Gerald (2000). Dyes, General Survey. Wiley-VCH. doi:10.1002/14356007.a09_073.
- ^ a b Wheeler, Edward (1928). The Manufacture of Artificial Silk With Special Reference to the Viscose Process. New York: D. Van Nostrand company.
- ^ Paul David Blanc (2016). Fake Silk The Lethal History of Viscose Rayon. Yale University Press. p. 325. ISBN 9780300204667.
- ^ a b Woodings, Calvin R. "A Brief History of Regenerated Cellulosic Fibres". Woodings Consulting Ltd. Retrieved 26 May 2012.
- ^ Day, Lance; Ian McNeil (1998). Biographical Dictionary of the History of Technology. Taylor & Francis. p. 113. ISBN 0-415-19399-0.
External links
Definitions from Wiktionary
Media from Commons
Data from Wikidata
- "Viscose". Plastiquarian.com. Archived from the original on 2008-06-25.
- What Is Viscose? from Barnhardt Natural Fibers
- viscose fibre