Manufacture Viscose

cellulose treated alkali , carbon disulfide yield viscose.



rayon fiber produced ripened viscose solutions treatment mineral acid, such sulfuric acid.

viscose rayon fiber of regenerated cellulose; structurally similar cotton may produced variety of plants such soy, bamboo, , sugar cane. cellulose linear polymer of β-d-glucose units empirical formula (c6h10o5)n. prepare viscose, dissolving pulp treated aqueous sodium hydroxide (typically 16-19% w/w) form alkali cellulose, has approximate formula [c6h9o4-ona]n. alkali cellulose treated carbon disulfide form sodium cellulose xanthate.

[c6h9o4-ona]n + ncs2 → [c6h9o4-ocs2na]n

the higher ratio of cellulose combined sulfur, lower solubility of cellulose xanthate. xanthate dissolved in aqueous sodium hydroxide (typically 2-5% w/w) , allowed depolymerize desired extent, indicated solution s viscosity. rate of depolymerization (ripening or maturing) depends on temperature , affected presence of various inorganic , organic additives, such metal oxides , hydroxides. air affects ripening process since oxygen causes depolymerization.

rayon fiber produced ripened solutions treatment mineral acid, such sulfuric acid. in step, xanthate groups hydrolyzed regenerate cellulose , release dithiocarbonic acid later decomposes carbon disulfide , water:

[c6h9o4-ocs2na]2n + nh2so4 → [c6h9o4-oh]2n +2ncs2 + nna2so4


h2cos2 → h2o + cs2

aside regenerated cellulose, acidification gives hydrogen sulfide, sulfur, , carbon disulfide. thread made regenerated cellulose washed remove residual acid. sulfur removed addition of sodium sulfide solution , impurities oxidized bleaching sodium hypochlorite solution.

pollution

highly toxic carbon disulfide used in production of viscose. recovered in manufacturing process. historically, however, several incidents have resulted in many poisonings. production facilities located in developing countries, concerns worker safety continue.