GB343521A - Improvements in or relating to the manufacture of cellulose ethers - Google Patents

Abstract

Cellulose ethers of hydroxy carboxylic acids, which are soluble in organic solvents, are produced by effecting etherification of cellulose with halogenated organic acids or their derivatives, used in such proportions as will introduce more than one ether group into the cellulose molecule in presence of sufficient caustic alkali to form with any water present a solution of concentration at least 40 per cent strength. The caustic alkali may be present in a quantity exceeding 3 times the weight of any water present. Etherifying agents mentioned are chloracetic acid including its salts and esters, chlorpropionic acid, chlormalonic acid, and chlorsuccinic acid. As initial materials for the reaction there may be used cotton, or the near conversion products of cellulose, wood pulps, or cellulose derivatives containing free hydroxy groups, such as cellulose which is not fully etherified. In carrying out the etherification, the cellulose is kneaded with a concentrated solution of caustic alkali, or is moistened with the required amount of water (preferably less than 4 times the weight of the cellulose) and then kneaded with solid caustic alkali; the water may be wholly or partly replaced by an alcohol. The process of etherification, which may be carried out in the presence of a diluent such as alcohol, benzene, or toluene, is preferably conducted in stages, fresh caustic alkali, or etherifying agent, or both, being added at each stage. Substances which bind water by chemical reaction, e.g. lime, and also catalysts such as copper powder, or copper salts or hydroxides may be added. If desired, the free carboxylic acid groups in the products may be esterified, for example, by treating the sodium salt with an alkyl halide, dialkyl sulphate, or an aralkyl halide. According to examples, (1) cotton or purified wood pulp is kneaded with caustic soda solution and caustic soda, and then treated with chloracetic acid for about 6 hours, after which time more caustic soda and chloracetic acid is added and the reaction carried to completion. The cellulose glycollic acid which is separated by adding hydrochloric acid and alcohol, is soluble in cold dilute alkali, acetone, acetic acid, formic acid, and chloracetic acid; (2) Cotton or wood pulp is kneaded with caustic soda solution, quick lime, and powdered caustic soda, preferably in the presence of benzene or other diluent. Chloracetic acid is then added in two or more stages as in example (1), the product is isolated from the benzene &c., and separated as before. (3) The product of examples (1) and (2) is treated with caustic soda and dimethyl sulphate in two successive stages, the cellulose glycollic acid methyl ester thus produced being soluble in acetone, acetic acid, and chloracetic acid. The products may be employed in the production of moulded articles, films, artificial filaments, ribbons and the like, and may also be used as sizes for finishing agents for textile materials; in coating compositions; as protective colloids; and as thickening agents in textile printing. In the manufacture of artificial filaments, films, &c., the cellulose ethers may be used in conjunction with cellulose acetate or other water-resistant substitution derivative of cellulose. Specifications 187,639, [Class 2 (ii), Cellulose &c.], and 244,143, [Class 15 (ii), Dyeing, Processes &c. for], are referred to.