Research On Reactivity Improvement And Mechanism Of Dissolving Pulp

The quantity demanded of dissolving pulp especially with high reactivity are moreand more recently. But the dissolving pulp has some limitations such as nonuniform ofpolymerization degree and low reactivity. The new raw material and dissolving pulpwith high reactivity have attracted more and more attention. In this paper, the dissolvingpulp was prepared from bamboo and poplar slab through changing the originalproduction process; the methods of beating and biological were researched to improvethe reactivity of dissolving pulp and mechanism were also researched. The mainconclusion are as followings:(1) The dissolving pulp of bamboo were prepared with the pre-hydrolysis, kraftcooking and Op-H-P three stage bleaching process. The optimum process conditions ofpre-hydrolysis were obtained as followings: the liquid ratio of1:8, the highesttemperature of160±2℃, time of2h, H2SO4dosage of1.0%. The better conditions ofkraft cooking were165±2℃, the liquid ratio of1:4and time of2h. During kraft cooking,lignin was removed largely and viscosity was decreased further. The brightness of pulpis85.6%ISO by Op-H-P multistage. Basing on the above process conditions, thedissolving pulp with96.49%alpha cellulose,4.32%pentosan,502.35degree ofpolymerization,240.9s reactivity and71.16%crystallization index.(2) The dissolving pulp of poplar slab with high reactivity were prepared with thepre-hydrolysis, kraft cooking and Op-Q-P three stage bleaching process. The optimumprocess conditions of pre-hydrolysis were obtained as followings: the liquid ratio of1:6,the highest temperature of160±2℃, time of2h, H2SO4dosage of1.0%. The betterconditions of kraft cooking were165±2℃, the liquid ratio of1:4and time of2h. Duringkraft cooking, lignin was removed largely and viscosity was decreased further. Thebrightness of pulp is more than85%ISO by Op-Q-P multistage. Basing on the aboveprocess conditions, the dissolving pulp with95.13%alpha cellulose,3.73%pentosan,488.84degree of polymerization,7.7s reactivity and68.13%crystallization index.(3) The reactivity of bamboo dissolving pulp were improved with a certain extentbeating, and the improvement of reactivity were most obvious with47°SR beatingdegree, now the reactivity reached128.0s. But the reactivity of poplar slab dissolvingpulp were improved with beating had no positive effect, on the contrary, the reactivityafter beating were bad. The improvement of reactivity through beating were achievedwith changing the form of the fiber. (4) The reactivity of bamboo dissolving pulp were improved with acidic xylanasetreatment, and the improvement of reactivity were most obvious when the dosage was1.0IU/g, now the reactivity reached4.43s. But the reactivity of poplar slab dissolvingpulp were improved with acidic xylanase treatment had no positive effect, on thecontrary, the reactivity after acidic xylanase treatment were bad. The improvement ofreactivity through acidic xylanase treatment were achieved with hemicellulosedegradation and changing the form of the fiber.