GB627861A - Improvements in the production of cellulose esters of organic acids - Google Patents

Abstract

A process for the production of stable primary organic acid esters of cellulose comprises reacting cellulose and an organic acid anhydride in the presence of an inorganic acid catalyst and of a solvent for the primary ester, neutralising the catalyst present and heating the solution of the ester while it still contains substantially no water until the ester has the required stability. Secondary esters of improved stability may also be produced by hydrolysing the stabilized primary esters with water. The catalyst is neutralized by the addition of magnesium, zinc, aluminium, calcium, barium or strontium acetate or barium or strontium oxide or hydroxide. Sodium salts should be avoided. The amount of water added with the neutralizing agent or that produced by neutralization should not be sufficient to hydrolyse the acid anhydride present, and if this anhydride is hydrolysed, more should be added to ensure an excess. The stabilization is carried out by heating at from 85 DEG to 130 DEG C. for 30 to 1 hours. After stabilization the primary ester may be precipitated as a p soft white fibre by the addition of water, washed and dried. In the production of stable secondary esters from the stabilized primary esters of the invention, water in amount equal to 45 to 150 per cent of the weight of the original cellulose is added and the hydrolysis conducted at a temperature of 80 DEG to 130 DEG C. for 100 to 2 hours or until the desired solubility characteristics or acetyl value is reached. The ester is precipitated with water, washed and dried. The process is applicable to the production of highly stable cellulose acetate, propionate, butyrate, and mixed esters such as cellulose acetate-propionate, and acetate-butyrate. In an example 100 parts by weight of cotton are pretreated for 6 hours at 20 DEG C. with sulphuric acid and acetic acid, entered into an acetyliser containing 350 parts of acetic anhydride, 400 parts of acetic acid and 15 parts of sulphuric acid (all parts by weight). After completion of the acetylation, the sulphuric acid is neutralized by addition of magnesium acetate and the neutralized primary solution heated to 90 DEG C. for 24 hours. The stabilized ester is precipitated with water, washed and dried.