GB734924A - Improvements in or relating to modified ethyl cellulose and its method of preparation - Google Patents

Abstract

Alkali cellulose is reacted with ethylene oxide at 20-80 DEG C., preferably in a system in which the ratio by weight of sodium hydroxide: cellulose is between 0.25 : 1 and 0.5 : 1 and the water: cellulose ratio is between 0.7 : 1 and 2 : 1, to give a degree of substitution between 0.3 and 0.9 mols per anhydroglucose unit, and the hydroxyethyl cellulose so produced is reacted with excess ethyl chloride at 95-160 DEG C., in a system in which the sodium hydroxide: hydroxyethyl cellulose ratio is between 2 : 1 and 10 : 1 by weight and the water: hydroxyethyl cellulose ratio is between 1 : 1 and 8 :1, to give an ethoxyl degree of substitution of 2.6 to 2.9. The ethyl-oxyethyl cellulose produced has a high aliphatic hydrocarbon tolerance. The ethyl chloride required for the second step of the process may be present during the first step, along with the ethylene oxide, but the temperature and alkali concentration are such that no ethylation takes place. The second step may be carried out by increasing the alkali concentration by adding strong caustic soda solution, or dilute caustic soda together with solid caustic soda, to give the required ratios between caustic soda, water and hydroxyethyl cellulose, and then raising the temperature. Since alkali is consumed in the second step it is preferred to add caustic soda gradually, during the course of the reaction, and the ethyl chloride also may be added gradually, at about the rate at which it is consumed. In an example, 400 parts of chemical cellulose are steeped in excess 20 per cent sodium hydroxide for 1 hour and pressed to a weight of 1344 parts. The alkali cellulose is shredded and then agitated in an autoclave with 120 parts of ethylene oxide, 136 parts of diethyl ether and 1600 parts of ethyl chloride for 5 hours at 60 DEG C. The product has a hydroxyethyl degree of substitution of 0.38. Then 2090 parts of 49.7 per cent sodium hydroxide, 976 parts of sodium hydroxide pellets and 80 parts of ether are added to the autoclave and the mixture is agitated for 5 hours at 130 DEG C., whereby 2.64 ethoxyl groups are introduced per anhydroglucose unit. The reaction mixture is neutralized with acetic acid, wet milled and washed free of salts, and the resulting ethyl oxyethyl cellulose is dried.