GB623276A - Preparation of carboxyalkyl ethers of cellulose - Google Patents

Abstract

A carboxyalkyl ether of cellulose is obtained by subjecting cellulose to the action of a carboxyalkyl halide in presence of strong alkali and in presence of sufficient isopropyl alcohol or tert.-butyl alcohol to maintain the cellulose ether formed in a solid undissolved state throughout the reaction. The product is readily obtained from the reaction medium by draining off or centrifuging off the liquid and washing. The proportion of alcohol used may be 5-50 parts for each part of cellulose. The ratio of alcohol to water in the reaction system is preferably greater than 1.5 parts of alcohol to one part of water. The ethrrifying agent may be chloracetic, chlorpropionic, or chlorbutyric acid, or a sodium, or potassium salt thereof, or a corresponding bromine or iodine compound. In an example, purified cotton linters are immersed in tertiary butyl alcohol and the resulting slurry is vigorously stirred while caustic soda solution of 30 per cent strength is slowly added. Agitation is continued and the temperature is gradually reduced from about 30 DEG to 17 DEG C. Solid monochloracetic acid is slowly added and the mixture is heated to 55 DEG C. The reaction product remains fibrous and similar in appearance to the original shredded linters. The liquid is drained from the fibrous product which is then stirred with aqueous methanol, neutralized with acetic acid, drained, washed with aqueous methanol, and then dried. The final product is soluble in water. The reaction is preferably carried out with 0.01-3.0 parts of etherifying agent per part of cellulose. Preferably there are 0.5-1.0 mols. of etherifying agent per mol. of free alkali. The alkali may be present in the ratio of 0.1-2.0 parts per part of cellulose. Etherification may be effected at 25-100 DEG C.