GB686001A - Improvements in the manufacture of carboxymethyl cellulose - Google Patents

Abstract

Carboxymethyl cellulose is prepared by immersing cellulose in 15-33 per cent caustic soda solution at a temperature above 50 DEG C., preferably 75-85 DEG C., pressing the impregnated product until the molecular ratio of NaOH to cellulose (C6H10O5), in the pressed product, as determined by analysis, is between 2.0 and 3.1, mixing chloracetic acid or sodium chloracetate with the alkali cellulose so obtained and kneading the mixture at a temperature below 25 DEG C. Preferably 0.65-1.25 molecular proportions of chloracetic acid or sodium chloracetate are employed for each molecular proportion of cellulose (C6H10O5). The chloracetic acid or sodium chloracetate is preferably added in stages to the mixture as the reaction proceeds and the alkali cellulose is preferably given a pre-kneading prior to the first addition. The product may be purified by neutralizing the remaining caustic soda with carbon dioxide or hydrogen chloride. Alternatively, the caustic soda may be washed out with 75-85 per cent aqueous methanol or ethanol. Examples are given in which the temperature of the aqueous caustic soda is 80 DEG C., and kneading is effected at 15-20 DEG C.