GB356012A - Improvements relating to the manufacture of cellulose esters - Google Patents

Abstract

Carboxylates.-In the hydrolysis of cellulose esters, an alcohol, e.g. methyl or ethyl, is added to the esterification mixture in excess of the amount theoretically necessary to esterify the residual organic acid, the ester being maintained in solution by a suitable organic liquid e.g. ethylene chloride, chloroform or tetrachlorethane. The residual acid is thereby readily separated. The amount of acid may be reduced by esterifying in presence of a solvent such as ethylene chloride, as described in Specification 351,118; or the solvent may be added after the esterification step. In an example, to 100 lbs. cotton linters is added 100 lbs. glacial acetic acid and 700 lbs. of ethylene chloride, the mixture being heated to 150 DEG F. for about 4 hours and then cooled to 65 DEG F.; 300 lbs. of 85 per cent acetic anhydride and 400 ccs. of sulphuric acid and 1350 ccs. of commercial liquid phosphoric acid are then added and the mixture is allowed to acetylate at a temperature of 45-100 DEG F. When a homogeneous, clear dope is obtained, 350 lbs. of ethyl alcohol is slowly added while stirring. The mixture is maintained at 100 DEG F. until acetone-solubility is obtained, usually about one week, after which it is poured through a header into boiling water and the vapours so produced are passed through a condenser. The condensate which consists of ethylene chloride, ethyl acetate, ethyl alcohol and water, is separated by fractional distillation. The proportions of acetic acid, ethylene chloride and acetic anhydride may be those given in Specification 351,118. The invention is applicable to cellulose propionate or other acylates.