GB350417A - Improvements in processes for changing the solubility of cellulose acetate - Google Patents

Abstract

Cellulose acetate is hydrolysed in the presence of a large excess of solvent at a comparatively low temperature and in the presence of sulphuric acid not exceeding 0,6 per cent of the weight of the bath. Another acid catalyst can be substituted for the sulphuric acid in a corresponding percentage according to its catalytic activity as compared with that of sulphuric acid, the corresponding figures being given for sulphuric acid, phosphoric acid, thionyl chloride, and p-toluene-sulphochloride. In examples, to a solution of 80 parts by weight of cellulose triacetate in 500 parts of acetic acid is added 1 part of sulphuric acid, 3 parts of phosphoric acid, 37 parts of water, and 60 parts of glacial acetic acid, and the mixture is allowed to stand at 70 DEG F., 80 DEG F., 90 DEG F., or 100 DEG F. The acetyl content of the triacetate falls steadily from 44,8 per cent to about 34 per cent. In a further example cellulose acetate soluble in chloroform is hydrolysed, using sulphuric acid only as catalyst. Specification 292,398, [Class 2 (ii), Cellulose &c.], is referred to. The Specification as open to inspection under Sect. 91 (3) (a) specifies a mineral acid catalyst from 0,1 per cent to not more than 1,0 per cent and other catalysts such as phenolsulphonic acid, acid sulphites, and sulphur chlorides in the ratio of their catalytic reactivities; it refers also to the use of a mixture of sulphuric and phosphoric acid in the pretreatment, acetylation, and hydrolysis stages. This subject-matter does not appear in the Specification as accepted.