Patent ID: 8246780
Filing Date: 2012-08-21
Classification: D21C,D21H

Abstract:
1. A method of preparing a treated bleached pulp material having enhanced brightness and enhanced resistance to thermal yellowing comprising: i) providing bleached pulp material consisting essentially of bleached kraft pulp with a R457 ISO brightness at least about 86.64; and ii) contacting the bleached pulp material in a papermaking or tissue making process with about 0.005 to about 0.08 weight percent, based on oven-dried pulp material of one or more reducing agents wherein the reducing agents are added to the bleached pulp material (a) in a blending or transfer chest; (b) before or after the cleaners; (c) before or after the fan pump to the paper machine headbox; (d) to the paper machine white water; (e) to the silo or save all; (f) in the press section; or (g) in the curl control unit, wherein the reducing agents are selected from the group consisting of sulfites, bisulfites, metabisulfites (pyrosulfites), and dithionites (hydrosulfites) wherein said bisulfites are selected from monobasic metal salts of sulfurous acid and said sulfites are selected from dibasic metal salts of sulfurous acid.