GB540147A - Improvements in cellulose esters - Google Patents

Abstract

540,147. Cellulose esters ; artificial filaments &c. BRITISH CELANESE, Ltd. April 5, 1940, No. 6218. Convention date, April 6, 1939. [Class 2 (ii)] In the production of a cellulose ester of an organic carboxylic acid, there is added to the primary esterification solution, for the purpose of improving its stability, an organic acid having a dissociation constant of at least 1.55 x 10<SP>-3</SP>. The treated solution may be used for the production of filaments, foils, films, and other products. An acid anhydride may be used as esterifying agent and a catalyst such as sulphuric acid, zinc chloride, acid sulphates, or mixtures of sulphuric and phosphoric acids may be present during esterification. In addition to the organic acid, there may also be added to the primary*esterification solution water or other hydrolysing agent just sufficient to hydrolyse any excess of acid anhydride. The organic acid which is added may be monochloracetic, trichloracetic, or oxalic acid. Since the tendency towards gelation is reduced in the treated solutions, the proportion of catalyst employed in the esterification may be reduced, e.g. sulphuric acid in amount 0.5 per cent based on the weight of cellulose may be used. In an example, cellulose is acetylated with a mixture of acetic acid, acetic anhydride, and sulphuric acid, and at the end of the re-action sufficient water is added to hydrolyse excess anhydride. Oxalic acid in amount 5-10 per cent of the acetylation solution is added. The solution may then be stored for several months. It may be wet spun into filaments, foils, and the like. The process is applicable to the production of cellulose acetate, propionate, butyrate, and other cellulose esters and mixed esters.