GB546026A - Improvements in or relating to the manufacture of water-soluble salts of water-insoluble cellulose hydroxy fatty acid ethers, and of the corresponding cellulose hydroxy fatty acid ethers - Google Patents

Abstract

546,026. Cellulose ethers. HOUGHTON, A. A., LUCKHURST, K., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Dec. 20, 1940, No. 17932. [Class 2 (ii)] A water-insoluble cellulose hydroxy fatty acid is isolated from an etherification reaction mixture, which includes a water-soluble alkali metal salt of the cellulose ether in fibrous form and other products of the etherification reaction, by adding to the mixture an excess of an acid capable of liberating the cellulose hydroxy fatty acid, the concentration and amount of the acid being such that the fibrous condition of the cellulose ether is retained throughout its addition, if desired, with the assistance of a non- solvent water-miscible organic liquid, and then purifying the resultant fibrous cellulose hydroxy fatty acid by extracting it with water. The product may be converted into a water-soluble salt without losing its fibrous form by mixing it with a base or a salt of a volatile acid in the presence of a medium containing a sufficient proportion of a volatile organic water-miscible liquid, e.g. alcohol, which is not a solvent for the cellulose ether. Preparations which dissolve in water to form solutions of predetermined pH may be obtained by controlling the extent of conversion of the fibrous cellulose ether into its salts. When converting the ether into a watersoluble salt there may be added a larger quantity of base than that necessary for complete conversion, and the excess may be converted into another salt before evaporating the volatile organic medium. To minimize swelling of the fibrous alkali metal salt of the cellulose ether the etherification mixture may contain alkali metal chlorides, anhydrous sodium carbonate or sulphate, ethyl alcohol, or acetone. The acid used for liberating the cellulose hydroxy fatty acid in the etherification reaction mixture may be sulphuric, nitric, phosphoric, or hydrochloric acid. In the case of sulphuric acid, the concentration of the acid solution added may be 60-80 per cent. Such a concentration avoids swelling of the water-soluble salt due to water introduced with the acid and also avoids loss of the fibrous form of the cellulose carboxylic ether as the result of any excess sulphuric acid after the conversion is complete. The purified cellulose ether may be converted into a salt by a solution of sodium, potassium, or lithium hydroxide, carbonate, or acetate, or ammonia, ammonium carbonate or acetate. The watersoluble salts of the cellulose hydroxy fatty acids are useful as emulsifying or dispersing agents. The viscosity characteristics may be permanently reduced by heating the cellulose ethers in acid or salt form and in dissolved or undissolved state. For the production of cellulose glycollic acid the etherifying agent may be sodium chloracetate.