Patent ID: 7368036
Filing Date: 2008-05-06
Classification: D21C

Abstract:
1. A method of bleaching chemical pulp comprising the steps of: a) treating chemical pulp in a first chlorine dioxide bleaching stage and then washing the pulp with a first water wash to produce a partially bleached pulp; b) treating said partially bleached pulp with a xylanase directly subsequent to said first chlorine dioxide bleaching stage and said first water wash to hydrolyze xylan present in said partially bleached pulp, and then washing the pulp with a second water wash to produce an enzymatically treated pulp, wherein said treating is carried out at a pH of between about 3 and about 8; and c) treating said enzymatically treated pulp to a second chlorine dioxide bleaching stage directly subsequent to the xylanase treatment stage and said second water wash (step b).