GB546647A - Improvements in or relating to the production of alkali cellulose and cellulose derivatives - Google Patents

Abstract

546,647. Cellulose derivatives. DREYFUS, H. Jan. 22, 1941, Nos. 856 and 4354. [Class 2 (ii)] Alkali-cellulose is obtained by impregnating cellulose with an aqueous alkali solution and subjecting the impregnated cellulose to azeotropic distillation to remove water. The alkali-cellulose may be used for the production of cellulose ethers or viscose. The distillation is preferably carried out in the absence of oxygen, e.g. in an atmosphere of nitrogen or other inert atmosphere. It may be carried out under low pressure. A water-immiscible azeotroping liquid which is also suitable as diluent in the etherification process may be used, e.g. benzene or toluene. Such a liquid may be separated from the water present in the condensate and then returned to the distillation apparatus. Cotton linters or wood-pulp is immersed in caustic soda solution, the excess of alkali solution is removed by centrifuging, and the mass is then subjected to azeotropic distillation. The concentration of the solution and the degree of expression are preferably so chosen that the molecular ratio of alkali to cellulose in the alkali-cellulose is between 3 and 5 to 1. The whole or part only of the water may be removed by distillation. For the etherification, ethyl chloride or diethyl sulphate may be used, preferably in presence of a diluent. Ethyl chloride may be used in large excess so that it acts not only as etherifying agent but also as diluent. Etherification may be carried out at elevated temperature.