Dissolving pulps from enzyme treated kraft pulps for viscose application

The purpose of this study was to illuminate enzymatic treatments as process steps for the efficient conversion of paper-grade pulps to dissolving pulps in terms of process economics. The challenge of pulp refinement comprises the selective removal of hemicelluloses and the precise adjustment of the pulp viscosity, while maintaining the reactivity of the pulp as required for viscose application. A commercial oxygen-delignified E. globulus paper-grade kraft pulp was subjected to xylanase (X) pre-treatment combined with cold caustic extraction (CCE) at reduced alkali concentration and to endoglucanase (EG) posttreatment after TCF-bleaching. The xylanase pre-treated pulp showed increased reactivity towards xanthation and high viscose dope quality in terms of particle content in comparison to the pulp after cold caustic extraction at elevated alkali concentration. The dependence of cellulose chain scission upon endoglucanase treatment on certain pulp qualities was analyzed in detail, and this allowed precise viscosity reduction as well as reactivity increase. The qualities of the spun fibers from the differently treated pulps were very similar to those viscose fibers from commercial dissolving pulps.