Patent ID: 6923887
Filing Date: 2005-08-02
Classification: D21B,D21C,Y02W

Abstract:
1. A method for hydrogen peroxide bleaching a lignocellulosic pulp comprising lignin and hemicelluloses, the lignin having chromophoric groups which imparts color thereto, the method comprising: providing a lignocellulosic pulp sample for bleaching, the lignocellulosic pulp sample stemming from a pulp producing process; providing a bleaching liquor comprising water and an organic component selected from the group consisting of methanol, ethanol and dioxane, the water and the organic component comprising solvent components constituting a bleaching medium; dissolving within the bleaching liquor at least a basic agent and at least a bleaching agent comprising hydrogen peroxide; and subjecting the lignocellulosic pulp sample to the bleaching liquor containing the at least a basic agent and the at least a bleaching agent comprising hydrogen peroxide, for a predefined amount of time at predefined bleaching conditions; wherein the organic component amounts to at least 5% in weight of the bleaching medium and is selected for reducing the dissolution of hemicelluloses and at the same time increasing at least one of the dissolution of lignin and the accessibility of the chromophoric groups to the at least a bleaching agent relative to a bleaching medium absent the at least an organic component.