GB446949A - Improvements in or relating to the production of esters of cellulose - Google Patents

Abstract

Stable organic esters of cellulose are obtained by acting on cellulose with an esterification medium containing the appropriate anhydride, the corresponding acid in amount at least sufficient to dissolve all the cellulose ester produced, less than 10 per cent of sulphur-containing catalyst, based on the weight of cellulose, and as catalyst aid at least 2 per cent of a hydrogen halide. The catalyst may be sulphuric acid and the catalyst aid may be hydrochloric acid, or zinc, aluminium, or sodium halides together with hydrogen halide. The cellulose esters may be ripened in the presence of hydrochloric acid, aluminium, tin, or zinc chlorides. The esterification solutions may be used directly for the production of articles or the ester may be precipitated with water and redissolved. In an example, cotton linters are pretreated with acetic anhydride, glacial acetic acid, zinc chloride, and a very small proportion of sulphuric acid. The mixture is added to a further quantity of acetic anhydride, acetic acid, and sulphuric acid. The temperature is regulated by cooling means, and aqueous hydrochloric acid is added during esterification. Water is added and the solution is subjected to ripening for several days. The viscosity of the product may be reduced by raising the temperature of esterification. The products may be used for the production of artificial filaments or lacquers. Specification 446,723 is referred to. The Specification as open to inspection under Sect. 91 comprises also the use of other halogen-containing acids or salts of such acids as catalyst aids. In an example, cellulose is pretreated with acetic anhydride, acetic acid, and sulphuric acid, and then esterified after adding further quantities of acetic anhydride, acetic acid, sulphuric acid, and aluminium chloride. The solution is ripened after the addition of dilute hydrochloric acid. This subject-matter does not appear in the Specification as accepted.