GB344151A - Manufacture of cellulose esters - Google Patents

Abstract

Cellulose is hydrated by means of nitric acid and is then heated with an aliphatic acid at 100-170 DEG C. without a catalyst until substantially 2 1/2 -3 molecular proportions of the fatty acid have been combined with an amount of cellulose corresponding with 24 carbon atoms. Any of the usual forms of cellulose material such as cotton, cotton linters, rag stock, or wood pulp may be employed, and the material may be preliminarily bleached or treated with alkali. In an example cotton linters are treated in a bath of nitric acid of 68 per cent strength at room temperature for 1 hour. The material is separated from the acid, washed with water and the latter is removed by treatment with alcohol or benzol. The dry hydrated material is then heated with a fatty acid such as acetic, propionic, butyric, valeric, caproic, or heptylic acid. The wet hydrated material may be heated with a fatty acid if desired. When the dry material is boiled with glacial acetic acid for 150 to 200 hours, from 13 to 15 per cent of acetyl is introduced into the cellulose molecule. Similar treatment of non-hydrated cellulose results in the introduction of only 6-8 per cent of acetyl. Other processes are also referred to in which cellulose precipitated from cuprammonium solution, or regenerated from cellulose xanthate, or obtained by saponification of cellulose nitrate, or which has been mercerized with strong caustic soda, is boiled with acetic acid. The partially esterified material may be further esterified with the aid of a small proportion of acid anhydride and a catalyst milder than sulphuric acid.