Patent ID: 6743332
Filing Date: 2004-06-01
Classification: D21C,D21D

Abstract:
A method of brightening mechanical pulp, comprising the steps of:providing cellulosic materials derived from softwood or hardwood trees, said materials having an initial brightness level, introducing the cellulosic materials to a refining system for conversion to a pulp, providing a bleaching liquor to the refining system, wherein the liquor comprises hydrogen peroxide and alkali, wherein the alkali comprises at least one of Mg(OH)2 and Na2CO3, or a combination thereof; holding the pulp and the bleaching liquor at a temperature in the range of about 85Â° C. to about 160Â° C. for a time of about 2 to about 180 minutes; and increasing the brightness of the pulp at least to a brightness level which can be obtained if 100% of the alkali is NaOH and the pulp and bleaching liquor are held at about the same time and temperature conditions.