Converting Bleaching Softwood Kraft Pulp Into Dissolving Pulp For Viscose Process

Dissolving pulp was commonly used for the production of cellulose derivatives and regenerated cellulose, which were required to have a high cellulose content, low levels of hemicelluloses, lignin, extractives, and minerals, a uniform molecular weight distribution and high cellulose reactivity.The demand of biomass fiber, which could replace the synthetic fiber, increased with the shortage of oil resources and higher requirement of special cellulose.The cotton, wood, and hemp were mainly raw material for production process of dissolving pulp using.the method of sulphite, pre-kraft or Soda-AQ. However the supply of cotton and hemp were limite, and the production process using wood was complicated. Converting commercial paper-grade pulp into dissolving pulp using chemical treatment and enzymatic treatment, could broaden the resource of raw materials of dissolving pulp production, and increase the added value of paper-gade pulp.The effect of various chemical pre-treatment and enzymatic treatment on the increase of a-celluloses content of paper-grade bleached kraft softwood pulp was investigated this paper. It was observed that9%NaOH treatment could increase the a-cellulose content and cellulose reactivity obviously. And both of6%NaOH+3%H2O2treatment and1%H2SO4treatment could decrease the pulp viscosity evidently, decreased by40.0%and45.3%respectively, compared with that of the raw pulp. Moreover,9%NaOH treatment and1%H2SO4treatment both could increase the cellulose reactivity apparently, which was higher than that of untreated pulp with63.7%and74.7%respectively. The xylanase treatmnet, laccase treatment and xylanase mixing with laccase treatment could increase the a-cellulose content to a certain degree, however, the effectiveness on removing of hemicelluloses was lower than that of9%NaOH treatment.The effects of cellulase treatment and glucanase treatment on increasing of the cellulose reactivity and decreasing of the pulp viscosity was also investigated. The result showed that both cellulase treatment and glucanase treatment could increase the cellulose reactivity, but the effectiveness of glucanase treatment on reactivity was much lower than that of cellulase treatment. The reactivity reached to70.0%, which was higher than dissolving pulp, at the enzyme dosage of300IU/g.Combination of the chemical treatment and cellulase treatment on the basic of the above research was included in this paper. Both the treatment sequence of chemical treatment and cellulase treatment and the effects of different ratio of NaOH to H2O2on pulp component and properties were investigated. It was illustrated that the sutiable sequence for converting paper-grade pulp into dissolving pulp was enzyme treatment followed by chemical treatments. When the ratio of NaOH:H2O2was10:1, the a-cellulose content was88.2%, the cellulose reactivity increased to68.4%and the viscosity decreased to536.3mL/g, which reached the requirements of dissolving pulp.