GB616132A - Improvements in the production of cellulose derivatives - Google Patents

Abstract

A process for the production of cellulose esters of increased acyl content comprises heating a mixture of a partially hydrolysed organic acid ester of cellulose and an organic acid anhydride dissolved in an organic solvent medium free from catalyst. The product is precipitated from solution in fibrous form and is relatively easily washed and dried. It possesses a degree of stability substantially greater than the hydrolysed cellulose ester from which it is prepared. The further esterification may be halted at any point short of the tri-ester. Esters which may be thus prepared include cellulose acetate, propionate, butyrate (including the triacetate, tri-propionate, tri-butyrate) and fully esterified mixed esters such as cellulose acetate-propionate, acetate-butyrate, acetate-stearate, acetate-laurate, acetate-crotonate and butyrate-crotonate. The hydrolysed ester (1 part by weight) may be dissolved in 3-10 parts by weight of organic acid and 0.1 to 2.0 parts of the anhydride added, depending on the degree of esterification desired, and heated from 60 DEG C. to 100 DEG C. or more for 6-200 hours. In an example 10 parts by weight of cellulose acetate of acetyl value 49 per cent (as acetic acid) are dissolved in 40 parts glacial acetic acid and 5 parts acetic anhydride added. Reaction is allowed to take place at 70 DEG C. for 24 hours. The ester is precipitated by addition of water, and has an acetyl value of 54.9 per cent.