METHOD FOR PRODUCTION OF BLEACHED WOOD-FIBROUS MATERIAL

摘要

The invention relates to a method for producing bleached wood fibre material, comprising the following steps: a) delaminating wood particles, that are large and optionally pre-treated with chemicals and/or water, into modified wood particles; b) grinding the modified wood particles produced in step a) in one or a number of refiners; c) and optionally treating the material produced in step b) with oxidative or reductive bleaching agents. The method is characterised in that step a) and/or step b) are carried out in the presence of a composition Z, said composition Z containing one or a number of the following components (Z1) to (Z3): a salt of dithionous acid H2S2O4 (Z1); a compound (Z2) that generates the dithionous acid or a derivate of the dithionous acid; a salt of sulphurous acid (sulphite) plus sodium tetrahydridoborate (Z3); and optionally additives (Z4).