Patent GB-342740-A (GB)
Title: Improvements in or relating to the manufacture of cellulose esters and of articles made therefrom
IPC: C08B3/02
Filed: 1929-08-02
Abstract: Cellulosic material is esterified by means of fatty acid anhydrides in the presence of a catalyst comprising a hydrohalide acid mixed with one or more halides of iron, manganese, cobalt, nickel, or copper, either or both of the components of the mixed catalyst being present in a proportion of under 2 per cent on the weight of the cellulose.  As initial materials in the process are mentioned cotton, or other cellulose or near conversion products, wood pulps, &c. Fibres or fabrics of cotton, or viscose, or other regenerated cellulosic artificial fibres may also be employed. The starting material is preferably subjected to a pretreatment before the esterification, and the following are referred to as being particularly suitable: pretreatment with organic acids, as described, for example, in Specification 263,938, [Class 2 (ii), Cellulose &c.], pretreatment with hydrohalide acids, or halides of iron, tin, cobalt, nickel, manganese or copper, or mixtures thereof, as described in Specification 312,098, [Class 2 (ii), Cellulose &c.].  Chemical wood pulps are preferably subjected to an alkaline purifying treatment, followed by a treatment with organic acids as described in Specification 249,173, [Class 2 (ii), Cellulose &c.], or followed by a pretreatment with hydrohalide acids and/or halide salts and/or organic acids according to the process of Specification 312,098, [Class 2 (ii), Cellulose &c.].  In a modification of the process, the hydrohalide acid may be employed in conjunction with the halide salt during a part only of the esterification.  For example, the hydrohalide acid may be wholly or partly neutralized during the later stages of the esterification, either by the addition of ferric oxide or hydroxide, or of a suitable neutralizing agent not containing iron or other metal catalyst.  In such a two-stage process, the temperature may vary with each stage.  The secondary treatment, or ripening, for the purpose of changing the solubility of the product, may be carried out in the presence of the catalyst used for the esterification, but other ripening agents may be added. In examples, (1) cotton linters pretreated with formic acid, are esterified by means of acetic anhydride in the presence of acetic acid and a catalyst comprising 15 per cent ferric chloride and 1 per cent hydrochloric acid.  (2) Cotton linters are pretreated with glacial acetic acid and hydrochloric acid, and afterwards is esterified by means of acetic anhydride in the presence of glacial acetic acid which contains 1,5 per cent of ferric chloride calculated on the cellulose.  (3) Cotton linters, pretreated as in example (1) are acetylated in the presence of 20 per cent ferric chloride and 5 per cent hydrochloric acid.  After 2 hours, 5 per cent of freshly precipitated ferric hydroxide are added and the reaction carried to completion.  The products may be used for the production of artificial silk, fibres, films, moulding powders, thermoplastic masses, &c.  Specifications 264,937, 314,918, 316,160, [all in Class 2 (ii), Cellulose &c.], 342,738, and 342,739, also are referred to.