Patent GB-325231-A (GB)
Title: Improvements in the manufacture of cellulose esters
IPC: C08B3/00
Filed: 1928-08-13
Abstract: 325,231. Dreyfus, K. Aug., 13, 1928. Divided on 325,224. Cellulose carboxylates; preparatory treatment of cellulose.-Cellulose esters of fatty acids, particularly cedlulase acetate, butyrate or propionate, are prepared by a combined process of pretreating cellulosic materials with organic acids and thereafter esterifying in suspension in organic media containing a non-solvent for the cellulose ester in which water is soluble or with it is miscible to an appreciable extent. Suitable non- solvents comprise ether, methyl acetate, ethyl acetate, other esters, or acetone or mixtures of ether or like liquids with benzol or the like. As esterifying agents there may be used anhydrides or other agents, such as acid chlorides. The cellulosic materials which may be employed comprise cotton or other cellulose or near conversion products thereof. Wood pulps or bamboo, esparto or other cellulosic materials containing encrusting matters and from which the lignin, pentosan, and like constituents have been substantially removed, as for example in sulphite pulp, soda pulp, or sulphate pulp may be employed, but are preferably subjected to an alkaline purifying treatment as described in Specification 249,173. The process may be applied to fibres, yarns, fabrics or the like, for example of cotton or other natural cellulosic materials, or of viscose or other regenerated cellulosic artificial fibres. The cellulosic materials may be pretreated with large or small quantities of organic acids in concentrated or dilute form or with the vapours of such acids as described in Specification 263,938. If desired sulphuric acid or other catalysts may be incorporated in the organic acid employed in the pretreatment or alternatively the cellulosic materials may be subjected to the combined action of organic acids and of hydrochloric acid or other hydrohalide acids or chlorides or other halides or mixtures thereof as described in Specfication 312,098. Further the cellulosic materials may be treated with pretreating agents mixed with the medium to be employed in the subsequent esterification, for example with a mixture of ether and glacial or dilute acetic acid. The esterification in suspension may, if desired, be effected in presence of a solvent, for example acetic acid, or solvents for the ester produced. Any desired catalysts, for example sulphuric acid or organically substituted sulphuric acids, such as benzene sulphonic acid, or bisulphates, for example sodium bisulphates, phosphoric acid, sulphuryl chloride, or the catalysts described in Specifications 308,322, 308.323, 309,201, 311,790, 312,095, and 312,096, may be employed. Esterinoation may be effected, for example, at the boiling point of the ether or other non- solvent under a reflux condenser. In examples, cotton linters are soaked in a mixture of glacial acetic acid and sulphuric acid and then esterified by adding the whole to a mixture of ether and acetic anhydride or alternatively a mixture of acetic acid and ether is used and acetic anhydride then added; cotton linters are pretreated with formic acid as liquid or vapour and after removal of substantially the whole of the formic acid, the pretreated cellulose is esterified after adding to a mixture of ether, acetic anhydride, and sulphuric acid; cellulose is soaked in glacial acetic acid and then esterified after adding to a mixture of ether, acetic anhydride, and sulphuric acid. Specifications 207,562 and 325,224 also are referred to.