GB543596A - Improvements in or relating to the manufacture of cellulose ethers - Google Patents

Abstract

543,596. Cellulose derivatives. DREYFUS, H. Sept. 3, 1940, No. 13779. [Class 2 (ii)] Cellulose ethers are obtained by impregnating cellulose with a substantially saturated solution of a caustic alkali, incorporating further alkali and raising the temperature sufficiently to bring the alkali into solution, and subjecting the cellulose to etherification. An aqueous solution of caustic soda or potash may be used and further quantities of alkali may be added in one or more stages. Incorporation of further alkali may be effected prior to etherification but the alkali is preferably added in stages during etherification. Alkyl chlorides, dialkyl sulphates sodium alkyl sulphates, or aralkylating agents may be used. One mol of cellulose may be impregnated with about 4 mols of caustic soda in the form of a 50 per cent. solution and then about 1-2 molecular equivalents of etherifying agent may be added, the temperature being maintained at 35-55‹C. A further quantity of powdered caustic soda is then added and the temperature is raised to 70-80‹C. to bring the soda into solution. Further quantities of etherifying agent and powdered caustic soda are added and the temperature is raised to 90- 100‹C. to bring the soda into solution. The reaction may be carried out in presence of an inert diluent such as benzene, toluene, or xylene. Instead of adding further quantities of caustic soda as such during the reaction, there may be added metallic sodium which reacts with the water present to form caustic soda. The etherifying agent used may be soluble in the benzene or other inert diluent, e.g. it may be a salt of ethyl or other alkyl sulphuric acid with an organic base of high molecular weight, e.g. diethyl cyclohexylamine or tricyclohexylamine.