GB521884A - Improvements in or relating to the manufacture of cellulose esters - Google Patents

Abstract

521,884. Cellulose esters. I.G. FARBENINDUSTRIE AKT.-GES. Nov. 30, 1938, No. 34943. Convention date, Dec. 1, 1937. [Class 2 (ii)] Cellulose esters of high clarity are prepared by incorporating perchloric acid with cellulose ester solutions, prepared in the presence of sulphuric acid, shortly before esterification is complete ; alternatively, after esterification is complete, hydrolysis of such esters is carried out in the presence of perchloric acid. The two methods may be combined, for example, by adding a portion of the perchloric acid to the esterification solution shortly before esterification is complete, and a further portion before hydrolysis begins. In an example, cellulose is acetylated with a reaction mixture containing acetic anhydride, methylene chloride and sulphuric acid. After adding water to destroy excess of acetic anhydride, hydrolysis is effected by adding aqueous perchloric acid. In another example, cotton linters, pretreated with acetic acid, are acetylated in a mixture comprising acetic anhydride, methylene chloride and sulphuric acid, and shortly before esterification is complete, perchloric acid is added. The solution may be worked up, if desired after hydrolysis. In a further example, cotton linters, pretreated with acetic acid, are esterified with a mixture consisting of ethylene chloride, acetic anhydride, butyric acid and sulphuric acid. During the reaction perchloric acid is added and the esterification completed. The product may be worked up directly or hydrolyzed after addition of more perchloric acid. Specifications 337,366, [Class 2 (ii)], and 403,554 are referred to.