GB478716A - Process for the manufacture of highly acetylated cellulose - Google Patents

Abstract

For the manufacture of fibrous cellulose acetates by heterogeneous acetylation there is employed as a catalyst a mixture of perchloric and sulphuric acids without any metallic salt; the cellulose is either not subjected to pretreatment or is pretreated in the absence of any mineral acid, for example, with acetic acid alone. Relative proportions of perchloric acid to sulphuric acid of 5 : 1 may be used, although proportions of sulphuric acid of less than 5 per cent, for example, of 1--2 per cent, are effective. Acetates produced with these low proportions of sulphuric acid are stabilized by simple washing with cold water. A mixed catalyst as above may be used in the acetylation process described in Specification 464,843. In examples, bleached linters are pretreated with glacial acetic acid, and to the mixture is added a pre-cooled acetylation mixture consisting of acetic anhydride, acetic acid, perchloric and sulphuric acids, and ether, ethyl acetate or benzene as non-solvents, the temperature of the mixture being -9 to -14 DEG C. Specification 405,825 also is referred to.