GB399508A - Improvements in cellulosic materials - Google Patents

Abstract

Cellulosic materials are subjected to treatment with sulphur dioxide in proportions of at least 40 per cent of the weight of the cellulosic materials at ordinary temperature for a substantial period of time, i.e. of the order of an hour or more, or at increased temperatures. The starting material may be cotton or wood pulps, particularly those which have undergone a preliminary treatment with alkali. The sulphur dioxide may be employed in the gaseous or liquid form, or may be dissolved in a liquid medium, for example, a lower fatty acid. There may be present also inert diluents such as toluene and benzene, or constituents of a subsequent esterification mixture, for example, p acetic anhydride, or sulphuric acid or other catalyst. The sulphur dioxide may or may not be removed prior to esterification or etherification of the cellulose, and in the latter case, chlorine may be introduced into the mixture to form sulphuryl chloride, which acts as the catalyst in a subsequent esterification. The following examples are given:--(1) Wood pulp treated by the process of Specification 249,173, [Class 2 (ii), Cellulose &c.], is heated for 1 to 2 hours at 50 DEG -60 DEG C. with glacial acetic acid and sulphur dioxide (50 per cent of the weight of the cellulose); After cooling, acetic acid, acetic anhydride and chlorine are introduced to effect acetylation. (2) Moistened cotton linters are allowed to stand for 2-3 hours at ordinary temperatures with 60 per cent of liquid sulphur dioxide, and then introduced into a mixture of acetic acid, acetic anhydride, and sulphuric acid. (3) Cotton linters are pretreated with sulphur dioxide (100 per cent of the weight of the cellulose) and acetic acid at 30 DEG C. After 2-3 hours the sulphur dioxide is removed, and the pretreated cellulose acetylated in a mixture comprising acetic acid, benzol, acetic anhydride, and sulphuric acid. Specifications 20977/11, 20852/12, 6463/15, 14101/15, 100,009, 101,555, 164,374, 164,375, 164,377, 207,562, 277,721, 300,140, 309,201, 312,095, 312,096, 312,098, 315,278, 326,515, [all in Class 2 (ii), Cellulose &c.], and 395,707 also are referred to.