GB782842A - Improved process for producing hydroxyethoxycellulose - Google Patents

Abstract

Hydroxyethyl cellulose is continuously produced by forcing an aqueous solution of sodium hydroxide through a continuously travelling continuous sheet of dry cellulose pulp, removing excess sodium hydroxide solution from the sheet, and passing ethylene oxide through the moving sheet to substitute 2-8 per cent, advantageously about 3-5 per cent, by weight of ethylene oxide, based on the weight of the cellulose, the resulting hydroxy-ethyl cellulose being substantially completely soluble in 2-10 per cent aqueous sodium hydroxide solution at 0 DEG C., but practically insoluble in water. The concentration of the sodium hydroxide solution may be 10 to 50 per cent, e.g. 20 per cent, and the alkalized cellulose pulp sheet may contain about 36 per cent of cellulose and 17.5 per cent of sodium hydroxide. The hydroxyethyl cellulose may be used to prepare aqueous solutions containing 4-15 per cent of hydroxyethyl cellulose of D.P. 200-600 and 2-10 per cent of caustic soda, e.g. a solution containing 8 per cent of the cellulose ether and 7 per cent of the alkali. The solutions may be extruded at 25-65 DEG C. into aqueous coagulating baths containing 4-15 per cent of sulphuric acid, 13-25 per cent of sodium sulphate and 0-15 per cent of zinc sulphate to form filaments or films. In the example, a 20 per cent aqueous solution of sodium hydroxide is forced through a continuous travelling sheet of cellulose and the sheet is then led into a chamber in which ethylene oxide gas is forced through it at about 40 DEG C. by contacting one side of the sheet with the gas and the other with a vacuum to etherify the sheet uniformly with formation of a hydroxyethyl cellulose in which 3 per cent of ethylene oxide, based on cellulose, is substituted.