Patent ID: 8268123

Claim:
A method for producing bleached pulp, comprising processing unbleached pulp containing hexeneuronic acid, obtained by cooking a lignocellulose substance, by alkali-oxygen bleaching, followed by treatment with peroxomonosulfuric acid at a pH of from 2 to 3.3 and at a temperature of from 40° to 70° C. so as to decompose the hexeneuronic acid, whereby amount of the hexeneuronic acid in the pulp is reduced, the peroxomonosulfuric acid having been prepared by mixing sulfuric acid and hydrogen peroxide in a mixing ratio by mole of sulfuric acid to hydrogen peroxide in a range of from 2/1 to 4/1, and thereafter by multistage elementary chlorine-free bleaching treatment starting from chlorine dioxide treatment.