Patent GB-187639-A (GB)
Title: Improvements in or relating to the manufacture of cellulose derivatives
IPC: C08B11/02
Filed: 1921-04-19
Abstract: Relates to the manufacture of cellulose ethers as described in Specifications 164,374, 164,375, and 164,377.  According to the present invention, the quantity of water present during the etherification is reduced by the addition of agents capable of binding water by chemical combination, to the proportion specified in the prior Specifications, that is, to an amount not exceeding four times the weight of cellulose taken, but preferably to an amount between nil to about one-half of the weight of the cellulose; the amount of caustic alkali or other base used in the etherification is at least equal to and preferably exceeds in the ratio of 3 : 1 to 19 : 1 or more the weight of water present or added.  By the use of such water-binding agents, the alkali is more firmly seated on or united to the cellulose, and the etherification may be carried out with reduced quantities, even down to theoretical quantities, of alkali and etherifying-agent. Suitable water-binding agents are the oxides of the alkali and alkaline earth metals, the hydrides of calcium and magnesium, the metals, calcium, barium and sodium, and sodamide and sodium ethylate powder.  The compounds formed by the union of the water-binding agent with the water present may constitute in part or wholly the alkali or base necessary for the etherification; the hydroxides of the alkaline earth metals may be employed as the base, but with these, being weaker, the etherification may be conducted at temperatures higher than those necessary with the caustic alkalies. In order better to control the temperature during the removal of the water, the water-binding agents are preferably incorporated in the presence of diluents or solvents such as benzol, toluol, carbon tetrachloride, ether, ligroin, or benzene, and the mixture is strongly cooled; the solvents or diluents may also be employed during the etherifications.  The initial material is either cellulose or a near conversion product insoluble in dilute alkali at ordinary temperatures, or alkali-soluble cellulose derivatives from which such alkali-insoluble cellulose or conversion products may be reconstituted, or such reconstituted products themselves.  For examples, cellulose impregnated with water is kneaded with sodium oxide either alone or with an addition of caustic soda and preferably in the presence of a diluent such as benzol, while cooling strongly, and to the mass which contains either no water or a very reduced quantity, diethyl sulphate is added, the temperature being maintained at 60-80 DEG  C., or even at ordinary temperature or lower; instead of diethyl sulphate the corresponding methyl ester may be used, the temperature in this instance being maintained at 0 DEG  C. or lower, for example, at 5 DEG  C. to 10 DEG  C.; cellulose impregnated with water and caustic soda is kneaded with calcium oxide, preferably in the presence of benzol, &c., while strongly cooling, and the esterification is effected by the addition of diethyl sulphate with or without the addition of a further quantity of solid caustic soda, the temperature in this instance being between 60 DEG  C. and 130 DEG C.  Alternatively, the water-binding agents may be added partly or entirely during the etherification.  Specifications 12854/12 and 6035/13 also are referred to.