Manufacture of Dissolving Sulfate Pulp by Xylenesulfonate Prehydrolysis(1)

Abstract

Beech wood chips prehydrolyzed with an aqueous solution of xylene-sulfonate and water were cooked by sulfate pulping process, and the rates of dissolution of main wood constituents and the properties of pulps thus obtained were compared. The results are as follows : (1) If a 25% xylenesulfonate solution (pH 6.1) are used, 120 minutes prehydrolysis at 160deg;C gives a better effect on the succeeding sulfate cooking than 80 minutes and 160 minutes prehydrolyses.(2) The xylenesulfonate prehydrolysis gives a better effect on the succeeding sulfate cooking than the water prehydrolysis. In the former the rate of delignification is greater and less cellulose is decomposed during sulfate cooking. However the rates of dissolution of pentosan from chips prehydrolyzed in the two methods are nearly equal during sulfate cooking.(3) The facts, given above, indicates that the xylenesulfonate prehydrolysis tends to shorten the time of sulfate cooking, and gives pulp of high α-cellulose content at higher yield. The distribution of polymerization degrees of cellulose in pulp, prepared by the xylenesulfonate prehydrolysis, is more homogeneous, too.(4) Though the experiments of bleaching and purification of unbleached pulp have not been carried out, it may be expected that the xylene-sulfonate prehydrolysis gives more bleachable pulp than the water prehydrolysis at same pulp yield. By the xylenesulfonate prehydrolysis, the preparation of pulp where α-cellulose content is not less than 97% may be also expected without special treatment of purification.