GB519907A - Improvements in or relating to the production of cellulose ethers - Google Patents

Abstract

519,907. -Cellulose ethers. DU PONT DE NEMOURS & CO., E. I., MAXWELL, R. W. Oct. 7, 1938, No. 29161. [Class 2 (ii)] Cellulose is converted into cellulose ethers of low degree of etherification insoluble in organic solvents and in water, by uniformly wetting the cellulose with a caustic alkaline solution of less than mercerising strength containing a substantially non-volatile etherifying agent dissolved in it, and evaporating the solvent from the reaction mass until it feels dry to the touch, and then maintaining the mass at a suitable temperature until the etherification is completed. After removing the solvent the reaction mixture may be further heated. Sodium methyl sulphate, sodium ethyl sulphate, sodium chloroacetate, glycerol mono-chlorohydrin, or benzyl chloride may be used as etherifying agent. Steeping may be effected in the cold or at raised temperature. The amount of steeping liquor left after the excess has been removed may amount to as much as that which will not drain freely from the cellulose by gravity without external pressure. The steeped cellulose may be pressed to contain only a small steeping liquor, prior to the evaporation step. The solvent may be evaporated by passing the impregnated cellulose over hot drying rolls or through a drying column. The material treated may be in the form of a continuous web or sheet. Long fibre cotton, yarn, or woven goods may' be treated so as to modify their dyeing, lustre, wetting, or other properties. The products may be used for making other cellulose derivatives, or if they are capable of being dissolved in aqueous alkaline solutions, they may be used in the production of filaments, films, sizes, coatings, or fixing agents for pigments. The impregnating solution may be aqueous or alcoholic. The,amount,of caustic alkali in the etherification mixture may be equivalent to that of the etherifying agent or less. Wetting agents such as the sodium salts of acids derived from alcohols made by reduction of carbon monoxide catalytically under pressure may be used in the steeping solution. Products may be obtained which are soluble in dilute caustic soda solution after cooling to below 0‹ C. In an example, sulphite pulp is subjected to mercerisation and steeped in a solution of caustic soda and sodium methyl sulphate. After steeping, the sheets are pressed and then heated in a current of air until dry. They are placed in a container and after displacing the air by nitrogen, they are allowed to age for a few days at 60‹ C. The sheets are then washed with cold water and then formed into a slurry with caustic soda solution. On cooling to below 0‹ C., a viscous solution is obtained. The cellulose ethers obtained by the process may be subjected to xanthation, and the cellulose ether xanthates may be converted into filaments.