GB574106A - Improvements in or relating to the production of organic acid esters of cellulose - Google Patents

Abstract

Organic acid esters of cellulose containing sulphuric acid radicles are stabilized by incorporating with a ripened esterification solution containing water and more than 2 per cent of free sulphuric acid, based on the weight of the original cellulose, an amount of neutralising agent sufficient to reduce the sulphuric acid content to between 0.5 and 2 per cent and allowing the solution to stand until the desired degree of stabilization has been effected. The process is applicable to cellulose esters such as the acetate, propionate, butyrate, laurate, acetate-propionate, acetate-butyrate, acetate-stearate, or to ether-esters such as ethyl-cellulose-acetate, ethyl-cellulose-propionate and ethyl-cellulose-stearate. The ester is hydrolysed and the proportion of free sulphuric acid in the solution adjusted by neutralisation with, for example, magnesium acetate or carbonate, aluminium hydroxide or acetate, zinc oxide or acetate, or other salts of magnesium, aluminium or zinc. The proportion of water present in the solution may also be reduced by the addition of acetic or other anhydride or by the addition of a suitable salt, e.g. anhydrous magnesium sulphate which forms a hydrate insoluble in the solution, or the salt may be formed in the solution by the addition of, e.g., magnesium acetate and sulphuric acid. If necessary, the proportion of water present in the solution may be increased by the addition of more water or dilute acid. The solution is then allowed to stand, if desired, at raised temperature until the desired degree of stabilization is obtained. Examples are given, in one of which cotton linters are esterified with a mixture of aceticanhydride, p acetic acid and sulphuric acid. Excess anhydride is then removed by the addition of excess aqueous acetic acid and the solution ripened. An aqueous solution of magnesium acetate is then added to reduce the amount of free sulphuric acid to the desired amount and increase the amount of water. The solution is heated to 70 DEG C. for one hour, after which the stabilized ester is precipitated and washed. Specification 524,634 is referred to.