Enhanced dithionite bleaching
AssigneeHoechst Celanese Corporation
InventorsS. Allen Grimsley, James C. Robinson, Mark A. Schroeder
Life of this patent
Estimating the term…
Abstract
Compositions and a method are disclosed for minimizing brightness reversion of chromophore-containing wood pulps, especially low-cellulose wood pulps, such as groundwood and thermomechanical pulps, which have been reductively bleached or bleached with hydrogen peroxide. Ascorbic acid and palmitoyl ascorbate are particularly effective for preventing such reversion at low levels.
Claims10
A method for minimizing brightness reversion of bleached high yield wood pulps containing chromophores, comprising the addition of a furanone to said pulps at 0.1% to 5% by weight, based on the weight of dry pulp, to obtain increased retention of brightness gains created by bleaching wherein said bleaching is reductive bleaching or peroxide oxidative bleaching, said furanone being added before, during, or after said bleaching if said furanone is water insoluble or after substantial dewatering of said pulps if said furanone is water soluble, said furanone being selected from the group consisting of compounds having the formula, 3,4-dihydroxy-2(5H)-furanone, and the following structural formula:
- ##STR5## wherein X is O, S, N, Si, C, Z is a whole number from 0-2, R.sub.1 is hydrogen or an alkyl having 1-5 carbon atoms, and R.sub.2 and/or R.sub.3 is any substituent that does not attack the furanone ring.
Dependencies are inferred from the claim text.