HOMOGENEOUS ACETYLATION OF CELLULOSE DISSOLVED IN DIMETHYL SULFOXIDE-FORMALDEHYDE SYSTEM

Bleached sulfite pulp was dissolved with formaldehyde in dimethyl sulfoxide, and the optimum condition was determined in terms of sufficient dissolution and prevention of degradation of cellulose. Homogeneous acetylation of the cellulose dissolved was examined, and the cellulose acetates witl a degree of substitution up to 2.4 were obtained in recovery yield ca. 80%. The preparation of the cellulose acetate with a degree of substitution close to 3.0 was inferred to be difficult with the present method. The cellulose acetates with a degree of substitution 2.0-2.4 was found to be easily soluble in ethyleneglycol monomethyl ether and ethyl lactate, and practically soluble in acetone. The solubility of the cellulose acetate was found to be slightly poorer than that of partially saponified cellulose acetate with a similar degree of substitution, prepared from cellulose triacetate, suggesting that the degree of polymerization of the acetate was higher than that of the partially saponified one. The cellulose acetate film prepared from the ethyleneglycol monomethyl ether solution was slightly yellowish transparent, and brittle, but was hard and had rather high tensile strength. The results indicate that the cellulose acetate obtained with the present method may have a possibility for commercial application.