GB483485A - An improved process for producing mixed cellulosic esters - Google Patents

Abstract

Mixed esters of cellulose are obtained by digesting an ester containing sulphuric acid residues as derived from the catalyst used for the esterification of such ester, with a liquid comprising at least one substance which contains at least one radicle of the kind to be introduced and chosen from fatty acids, esters of fatty acids and substitution derivatives thereof, the conditions of the digestion being such that the sulphuric acid residues are retained in sufficient quantities in the ester and that the latter is maintained throughout in the swollen condition. If desired, further quantities of catalyst may be added to the digestion liquid; and the latter may also contain a diluent. The cellulose ester to be treated may be prepared by the heterogeneous or homogeneous method. After the production of the mixed ester, sulphuric acid residues remaining therein are removed as by repeated treatment with water or other appropriate stabilizing agent. In an example, cellulose acetate prepared by the heterogeneous method is washed with benzene and ethyl acetate, then digested with ethyl butyrate to produce the desired cellulose acetate butyrate, which is finally stabilized by repeated treatment with ethyl acetate. Specifications 338,201, 338,202, [both in Class 2 (ii)], 360,058, 411,260, and 468,880 are referred to.