GB676232A - Improvements in and relating to the production of cellulose esters - Google Patents

Abstract

Secondary cellulose organic acid esters are produced by esterifying cellulose with a fatty acid anhydride in the presence of an esterification catalyst and methylene chloride to form a cellulose triester solution containing 50-60 per cent methylene chloride and then adding water and sulphuric acid and allowing hydrolysis to proceed until the triester is converted to a secondary ester, methylene chloride being removed, e.g. by distillation from the solution before or during hydrolysis until its content is reduced to 30-45 per cent based on the weight of the original solution. Preferably 45-60 per cent of the total weight of methylene chloride is removed from the solution. Hydrolysis may be effected in two stages by first reducing the acyl content of the ester to about 59 per cent under pressure and then completing the hydrolysis at atmospheric pressure. Examples are given of the acetylation of cellulose with acetic anhydride in the presence of acetic acid, methylene chloride and sulphuric acid as catalyst at below 50 DEG C., to produce the triacetate solution, hydrolysis being then effected after the addition of aqueous sulphuric acid and removal of the methylene chloride being effected in one case before and in another case during the hydrolysis. The process is also applicable to the production of cellulose acetate-butyrate and cellulose butyrate.