Patent ID: 6057438
Filing Date: 2000-05-02
Classification: C08B,D21C

Abstract:
Process for the co-production of dissolving-grade pulp and xylan by the steps comprising:(1) intimately contacting a paper-grade, hardwood, kraft or soda pulp with aqueous sodium hydroxide solution at a temperature of about 50 to 100.degree. C.;(2) subjecting the slurry resulting from step (1) to liquid/solid separation and removing sodium hydroxide from the solid material separated;(3) intimately contacting the solid material obtained from step 2 with a solution of a xylanase enzyme;(4) subjecting the slurry resulting from step (3) to liquid/solid separation;(5) intimately contacting the solid material obtained from step (4) with aqueous sodium hydroxide solution at a temperature of about 50 to 100.degree. C.;(6) subjecting the slurry resulting from step (5) to liquid/solid separation and removing sodium hydroxide from the solid material separated to obtain dissolving-grade pulp; and(7) combining the liquids of steps (2) and/or (6) with one or more C.sub.1 -C.sub.4 alkanols to effect precipitation of xylan from the liquids and subjecting the resulting mixture to liquid/solid separation to recover xylan.wherein the paper-grade pulp comprises about 75 to 84 weight percent cellulose, about 15 to 22 weight percent xylans, and about 0.3-3 weight percent mannans; and the dissolving-grade pulp comprises about 97 to 98.5 weight percent cellulose, 0.5 to 3 weight percent xylans, and about 0.1 to 0.5 weight percent mannans.