Process for production of bleached pulp

摘要

Provided is a process for producing bleached pulp, including subjecting unbleached pulp, which is obtained by cooking a lignocellulose substance, to alkali-oxygen bleaching treatment and then subjecting the alkali-oxygen bleached pulp to chlorine-free bleaching treatment including chlorine dioxide treatment, wherein in at least one chlorine dioxide treatment stage in which the chlorine dioxide treatment is performed, monopersulfuric acid is used in combination. The amount of chlorine dioxide to be used is reduced and the color reversion resistance of the bleached pulp is improved by this process.

主权项

1. A process for producing bleached pulp, comprising:
subjecting unbleached pulp, which is obtained by cooking a lignocellulose substance, to alkali-oxygen bleaching treatment; and then subjecting the alkali-oxygen bleached pulp to elemental-chlorine-free bleaching treatment including a chlorine dioxide treatment, wherein monopersulfuric acid is added during the chlorine dioxide treatment, and the addition comprises: adding monopersulfuric acid in an initial stage of the chlorine dioxide treatment after the akali-oxygen bleaching treatment with an addition rate of from 0.1 to 1% by mass, at a treatment pH of from 2.5 to 3.5, a treatment time of from 30 to 120 minutes and a treatment temperature of 60° C. to 80° C.; or adding monopersulfuric acid in a final stage of the chlorine dioxide treatment after the alkali-oxygen bleaching treatment with an addition rate of from 0.1 to 1% by mass, at a treatment pH of from 4.0 to 5.5, a treatment time of from 30 to 120 minutes and a treatment temperature of from 60° C. to 80° C., and wherein the monopersulfuric acid is prepared by mixing sulfuric acid and hydrogen peroxide in a mixing ratio by mole of sulfuric acid to hydrogen peroxide of from 2/1 to 4/1.