GB539156A - Improvements in or relating to the production of cellulose esters - Google Patents

Abstract

539,156. Cellulose esters. BRITISH CELANESE, Ltd. Feb. 28, 1940, No. 3704. Convention date, Feb. 28, 1939. [Class 2 (ii)] To the primary solution containing an organic ester of cellulose, the excess anhydride employed in the esterification, and an acid catalyst comprising sulphuric acid or a derivative thereof, there is added an amount of water just sufficient to convert the anhydride to acid, a further amount of water corresponding to 6-12 per cent. of the weight of cellulose ester in the primary solution and a halide of a polyvalent metal in amount at least equivalent to the acid catalyst. The cellulose ester is' allowed to ripen at a low temperature and is then precipitated from the solution. The precipitated product is obtained in a fibrous condition. The process enables cellulose esters of high acyl content, e.g. cellulose acetates of acetyl value above 55 per cent, and capable of being dissolved completely in acetone, to be obtained. The temperature of ripening may be 18‹-30‹C. The process is applicable to the production of cellulose acetate, propionate, butyrate, acetopropionate, or other cellulose ester. The products obtained have high heat stability and are resistant to de-lustring agents. Films made from the cellulose esters have a high resistance to blushing, distortion, and cockling. Fabrics may be dyed at elevated temperatures without loss of lustre. The Specification as open to inspection under Sect. 91 comprises also ripening processes in which the polyvalent metal halide is omitted, and in which the range of water added in addition to that required for conversion of the anhydride is 3.6-28.8 per cent of the weight of cellulose ester. This subject-matter does not appear in the Specification as accepted.