GB531014A - Improvements in or relating to the manufacture of cellulose derivatives - Google Patents

Abstract

531,014. Cellulose esters. BRITISH CELANESE, Ltd., (Celanese Corporation of America). July 8, 1939, No. 19953. [Class 2 (ii)] A primary organic acid ester of cellulose obtained by treating cellulose with an organic acid anhydride in a hydrophile solvent for the primary ester using sulphuric acid as catalyst is converted into a secondary ester by adjusting the amount of sulphuric acid and incorporating such an amount of water in the esterification solution that a medium is obtained containing sulphuric acid in amount equal to 4-10 per cent. of the weight of the cellulose employed as starting material and 8-12 per cent. of the water present, and part of the desired ripening is effected at a temperature of 40-80‹C. More water is then incorporated so as to bring the ratio of sulphuric acid to water below that existing at the commencement of ripening, and further ripening is allowed to take place at 40-80‹C. The process is applicable to the production of cellulose acetate, propionate, butyrate or other ester. If the sulphuric acid employed for esterification is higher than that required for ripening the excess may be neutralized e.g. with magnesium carbonate or sodium acetate. The hydrophile solvent may be a lower fatty acid. In an example, cotton linters are acetylated with a solution containing acetic acid, acetic anhydride, and sulphuric acid. On completion of acetylation, water is added to destroy the excess of acetic anhydride, and part of the sulphuric acid is neutralized with magnesium carbonate. A further quantity of water is added. The mixture is stirred and maintained at about 60‹C. After some hours a diluted solution of acetic acid is added and the mixture is again stirred for a few hours at 60‹C. The ripened cellulose acetate is then precipitated by adding a large quantity of water. It may be used in the manufacture of actificial filaments, films, lacquers, and other products.