GB403646A - Improvements in acidylation - Google Patents

Abstract

Unsubstituted polymeric hydroxy compounds, particularly cellulose, are acidylated with anhydrides of benzoic acid or its homologues, or with halogen (e.g. chlorine) or nitro substitution derivatives thereof. Other polymeric hydroxy compounds are starches, dextrin, and polyvinyl alcohol. Polymeric hydroxy compounds partially esterified with the aromatic radicle may be subjected to further esterification to introduce aliphatic acid radicles and/or to etherification to introduce ether radicles. Mixed esters or ether-esters of cellulose containing aromatic acid radicles and also acetic or other lower aliphatic acid radicles and/or ether radicles are particularly useful. The cellulosic material, e.g. cotton linters, or wood pulp purified by the process of Specification 249,173, [Class 2 (ii), Cellulose &c.], may be acidylated so that the ester is obtained in solution, or fabrics or other textile materials may be esterified without losing their fibrous structure, such esterification being either uniform or local. Esterification may be carried out at elevated temperatures without catalysts, but acid or alkaline catalysts may be employed. When mixed esters or ether-esters are produced, the introduction of the lower ester or ether group takes place simultaneously with or after the benzoylation or other acidylation characteristic of the invention for example, the cellulose material may be simultaneously treated in the presence of alkali with the aromatic acid anhydride and an alkylating agent, e.g. dimethyl sulphate, to produce a mixed ether-ester, or the cellulose, preferably pretreated with acetic acid, may be introduced into a medium of acetic acid containing benzoic anhydride and catalyst, and when the reaction is completed, acetic anhydride introduced. Further treatments to remove combined catalyst or change the solubility characteristics of the products may be carried out in the usual manner. The products may be employed in the production of filaments, films, plastics, electric insulation, and the like. Examples are given of the production of cellulose benzoate in solution, and of cellulose benzoate in the fibrous form. In the latter case, the cellulose fibres are given modified dyeing properties. Specifications 263,938, [Class 2 (ii), Cellulose &c.], and 403,645 also are referred to.