Patent GB-164374-A (GB)
Title: Improvements in or relating to the manufacture of cellulose derivatives
IPC: C08B11/02
Filed: 1919-09-01
Abstract: Alkyl ethers of cellulose, more particularly ethyl and methyl ethers, are prepared by treating cellulose or its near conversion products not soluble in alkali, such as mercerized cellulose, with a suitable alkylating-agent in the presence of alkali, under such conditions that (1) the quantity of water present or added, disregarding water formed during the process, is at no stage of the etherification greater than about four times the weight of cellulose, and preferably not in greater amount than about one-half and one and a half times this weight, or it may even be as low as the natural humidity content of the cellulose, and (2) the total quantity of alkali is at least equal to and preferably exceeds by 8-19 or more times the weight of water present or added. The ethers so obtained are characterized by their insolubility in hot or cold water and by the fact that they are not precipitated from alcoholic solution by alcoholic solutions of alkali; and the same properties hold in the case of the intermediately-formed partly-etherified ethers. The requisite quantities of water and alkali are added prior to the alkylating process or partly or entirely during the process, either continuously or by stages; and the alkylating agent is introduced all at once or continuously or in stages, but preferably in such a manner that an excess of alkali is always present. For making highly ethylated ethers it is necessary to employ relatively to one molecular equivalent of cellulose, C6H10O5, 8-20 molecules of alkali and 5-9 molecules of diethyl sulphate. The temperature of the reaction varies according to the akylating agent selected etc.; in the case of diethyl sulphate, the temperature may be between room temperature, or even lower, and 80 DEG C., but preferably below 55 DEG C.; with dimethyl sulphate, it is preferred to keep the temperature at 0 DEG  C. or even lower; and in the case of alkyl halides the temperature is preferably raised to between 50-80 DEG  C.  The reaction is accelerated by the addition of contact substances such as powdered copper or copper salts or hydroxides.  It is advantageous to carry out the reaction in the presence of liquid diluents such as benzol, which do not themselves suffer etherification, since such addition facilitates mixing and renders the reaction more uniform.  In examples, one molecular equivalent of cellulose &c. is kneaded with four molecules of caustic soda and an equal weight of water, and 1-2 molecules of diethyl sulphate are added while maintaining the temperature at 40-55 DEG  C. or between ordinary temperature and 30 DEG  C., with subsequent additions of 4-6 molecules of powdered caustic soda and 2-3 molecules of diethyl sulphate, and 4-6 molecules of caustic soda and 2-2 1/2 molecules of diethyl sulphate, the products being eventually separated and washed with water; one molecular equivalent of cellulose &c. is impregnated with an equal weight of water, kneaded with 4 molecules of caustic soda and 1 1/2 molecules of diethyl sulphate added while keeping the mixtures at a temperature of 40 DEG  C., with subsequent additions at intervals of caustic soda and diethyl sulphate until a total of 12-18 molecules of the former and 6-8 1/2 molecules of the latter have been added; one molecular equivalent of cellulose &c. is impregnated with 20 per cent caustic soda, and, after standing, squeezed or centrifuged until the mass contains an amount of water equal to the weight of cellulose, whereupon 4 1/4 molecules of caustic soda are added, and the process continued as in the first example above; one molecular equivalent of cellulose &c. is treated with a 50 per cent solution of 4 molecules of caustic soda, the mass thoroughly kneaded, then 2 molecules of dimethyl sulphate are added while maintaining the temperature at -5 to -10 DEG  C., and subsequently 4-6 molecules of caustic soda and 2-3 molecules of dimethyl sulphate, and 4-8 molecules of caustic soda, and 2-3 1/2 molecules of dimethyl sulphate; and in these examples the diethyl and dimethyl sulphate may be introduced as a solution in an equal weight of benzol.  By employing mixtures of different alkylating agents, mixed ethers may be obtained; or the cellulose may be partly etherified while employing one or more alkylating agents and then further etherified with another or others. The ethers obtained according to the above process may be employed in the manufacture of films, artificial filaments, celluloid-like masses, electric insulating-materials, varnishes, dopes, and coating materials.  Specifications 12854/12 and 6035/13 are referred to.