Patent GB-325822-A (GB)
Title: Improvements in the manufacture of cellulose esters
IPC: C08B3/00
Filed: 1928-11-21
Abstract: 325,822. Dreyfus, H. Nov. 21, 1928. Collulose carboxylates; preparatory treatment of cellulose.-Cellulose carboxylates are prepared by treating cellulose or its conversion products, or derivatives containing one or more hydroxyl groups, with an organic acid anhydride in the presence of a tertiary organic base; the reaction is effected at a temperature above 100‹ C., or alternatively, or additionally, the cellulosic material is pretreated with a tertiary organic base at a temperature above 100‹ C. The initial cellulosic material may be cellulose that has been pretreated with alkalies and organic acids in turn, as described in Specification 249,173, or with organic and/or inorganic acids, as described in Specifications 263,938 and 312,098, the inorganic acids being removed before esterification. The organic base should preferably boil above 100‹ C., although bases of lower boiling point may be used in conjunction with organic diluents; suitable bases are pyridine, N-alkyl or -aryl piperidines, dialkyl anilines or naphthylamines or their homologues, hexahydrodialkyl anilines and their homologues, dimethyl-n-hexylamine, and isoamyldiethylamine. The pretreatment with the bases may be effected under reflux or under pressure or with the vapour of the reagent. The esterification may be conducted in the presence of solvents for the esters and/or non-solvent diluents, such as toluene, xylene, or chlorobenzenes, or the reagents may be used in the vapour state. Esterification in the presence of diluents or with vaporous reagents may be applied tu cotton or regenerated cellulose fibres or fabrics. Mixed esters may be prepared by employing two or more anhydrides together or successively, or by starting from a partly esterified cellulose. The esters prepared as described above may be further eaterified in the presence of sulphuric or other mineral acid, acid salts such as bisulphates, or salt such as zinc or ferric chloride, containing a mineral acid radicle and having an acid reaction; such further esterification may be effected as described in Specifications 207,562, 308,322, 308,323, 309,201, 312,095 and 312,096. The solubility properties of esters produced in any of the ways described above may be changed by subjecting the esters to secondary treatment either in the esterification solutions or after separation therefrom. Such treatment may comprise the addition of inorganic or organic acids, acid salts, or mineral acid salts of organic bases, preferably after the excess of anhydride has been decomposed by addition of water in excess or of lactic acid, alcohols, &c. The secondary treatment may be applied to the ester suspended in ether, &c. as described in Specification 325,224. A further secondary treatment applicable to the esters produced with an organic acid anhydride in the presence of an organic base consists in heating the ester with an organic base, such as those specified above, with or without water and/or an organic acid and/or a solvent or non- solvent diluent. This treatment may be applied without intermediate separation of the estsr. The esters obtained as described above, with or without secondary treatment, mav be used for the customary purposes. According to the examples, (1) viscose fibres are boiled under reflux for 5-15 hours with acetic anhydride and dinxethyl-n-hexylamine; the product may be converted into a triacetate by known methods, or by continuing the boiling for 1-3 days; (2) cotton linters are boiled under reflux with dimethyl-nhexylamine, acetic anhydride is run in, and acetylation is effected as described in example 1; (3) sulphite pulp is boiled with caustic soda solution of 0.25-2.5 per cent strength, pressed, washed, heated with glacial acetic acid, hydroextracted, and treated with air; it is then heated under pressure at 150-170‹ C. with acetic anhydride and methylpiperidine ; (4) cotton linters are boiled under reflux with acetic anhydride and dimethyl-n-hexylamine, and the product, after hydro-extracting, is further acetylated in known manner; (5) the reaction mixtures obtained in examples 1-3 are heated with a mixture of acetic and hydrochloric acids or (6) boiled under reflux with the acid. The manufacture of cellulose propionates and butyrates is referred to.