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Rayon

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+#REDIRECT [[Rayon]]
-{{Distinguish|viscous}}
-'''Viscose''' is a [[Semisynthesis|semi-synthetic]] fiber. "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 process [[dissolving pulp|dissolves 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 rayon fiber, which may also be called viscose. 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 cleaning cloths and in the casting of [[cellophane]].
-== Manufacture ==
-[[File:Xanthogenate Cellulose Structural Formula V1.svg|300px|thumb|Cellulose is treated with alkali and carbon disulfide to yield viscose.]]
-[[File:Xanthogenate Cellulose Acid Hydrolysis V1.svg|300px|thumb|Rayon fiber is produced from the ripened viscose solutions by treatment with a mineral acid, such as sulfuric acid.<ref name=Hauptmann>[[Siegfried Hauptmann]]: ''Organische Chemie'', 2. durchgesehene Auflage, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1985, S.&nbsp;652, {{ISBN|3-342-00280-8}}.</ref>]]
-Viscose rayon is a fiber of regenerated cellulose; it is structurally similar to [[cotton]] but may be produced from a variety of 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>. 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>
-:[C<sub>6</sub>H<sub>9</sub>O<sub>4</sub>-ONa]<sub>{{mvar|n}}</sub>  +  {{mvar|n}}[[Carbon disulfide|CS<sub>2</sub>]]   →   [C<sub>6</sub>H<sub>9</sub>O<sub>4</sub>-OCS<sub>2</sub>Na]<sub>{{mvar|n}}</sub>
-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) and allowed to depolymerize to a desired extent, indicated by the solution's viscosity. The rate of depolymerization (ripening or maturing) depends on temperature and is affected by the presence of various inorganic and organic additives, such as metal oxides and hydroxides.<ref name="Wheeler 1928" /> Air also affects the ripening process since oxygen causes depolymerization.<ref>{{cite journal|last=Bartell|first=F. E.|author2=Cowling, Hale |title=Depolymermiation of Cellulose in Viscose Production|journal=Industrial & Engineering Chemistry|date=1 May 1942|volume=34|issue=5|pages=607–612|doi=10.1021/ie50389a017}}</ref>
-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 release dithiocarbonic acid that later decomposes to carbon disulfide and water:<ref name="Wyss 1043–1045">{{cite journal|last=Wyss|first=George de|title=The Ripening of Viscose.|journal=Industrial & Engineering Chemistry|date=1 October 1925|volume=17|issue=10|pages=1043–1045|doi=10.1021/ie50190a018}}</ref>
-:[C<sub>6</sub>H<sub>9</sub>O<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>9</sub>O<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>
-:H<sub>2</sub>COS<sub>2</sub>   →   H<sub>2</sub>O  +  CS<sub>2</sub>
-Aside from regenerated cellulose, acidification gives hydrogen sulfide(H<sup>2</sup>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.<ref name="Wheeler 1928" />
-=== Pollution===
-{{see also|Rayon#Manufacturing health hazards}}
-Highly toxic [[carbon disulfide]] is used in the production of viscose. It is carefully recovered in the manufacturing process.  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>
-== History ==
-{{See also|Rayon#Viscose method}}
-French scientist and industrialist [[Hilaire de Chardonnet]] (1838–1924)—who invented the first artificial textile fiber, ''artificial silk''—created viscose.<ref name="crw-bhrcf" /> 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.<ref name=bdht>{{cite book|last=Day|first=Lance|title=Biographical Dictionary of the History of Technology|year=1998|publisher=Taylor & Francis|isbn=0-415-19399-0|pages=113|author2=Ian McNeil }}</ref> In 1893 they formed the Viscose Syndicate to grant licences, and in 1896 formed the British Viscoid Co. Ltd. to exploit the process.<ref name=crw-bhrcf>{{cite web|last=Woodings|first=Calvin R.|title=A Brief History of Regenerated Cellulosic Fibres|url=http://www.nonwoven.co.uk/reports/History%20of%20Cellulosics.html|publisher=WOODINGS CONSULTING LTD.|accessdate=26 May 2012}}</ref>
-The use of viscose is declining. Instead, rayon may be manufactured using the [[Lyocell]] process, which uses [[N-Methylmorpholine N-oxide|N-methylmorpholine N-oxide]] as the solvent and produces little waste product, making it relatively eco-friendly.<ref>{{Cite journal|last=Dawson|first=Tim|year=2011|title=Progress towards a greener textile industry|doi=10.1111/j.1478-4408.2011.00346.x|journal=Coloration Technology|volume=128|pages=1–8}}</ref>
-== Products made from viscose ==
-* [[Art silk]]
-* [[Cellophane]]
-* [[Rayon]]
-* [[Casing_(sausage)#Cellulose|Sausage casings]]<!--Fact. I might be able to dig up at least one UK and one US company that makes/made them.-->
-* [[Velvet|Synthetic velvet]]
-== References ==
-{{reflist|2}}
-== External links ==
-{{Sister project links||b=no|commons=Category:Viscose |d= Q182045|m=no |mw=no |n=no |q= no|s= no |species=no |species_author=no |v= no |voy=no |wikt=viscose }}
-* {{cite web| title= Viscose| url= http://www.plastiquarian.com/viscose.htm | archiveurl= https://web.archive.org/web/20080625080322/http://www.plastiquarian.com/viscose.htm | work= Plastiquarian.com | archivedate= 2008-06-25}}
-* [https://www.barnhardtcotton.net/blog/q-and-a-what-is-viscose/ What Is Viscose? from Barnhardt Natural Fibers]
-[[Category:Synthetic fibers]]
-[[Category:Cellulose]]