High consistency peroxide bleaching
US4938842A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 23, 1989 |
| Grant date | Jul 3, 1990 |
| Priority date | — |
| Expiry date | Feb 23, 2009 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/163
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
A process is provided for the bleaching of wood pulp with hydrogen or sodium peroxide. The process includes the steps of adding to a wood pulp a bleach liquor having an effective amount of hydrogen or sodium peroxide bleaching agent and, by weight of the diluted wood pulp, 0.5 to 6% sodium hydroxide, 0 to 5% sodium silicate, 0 to 1%, preferably 0.02 to 0.05%, magnesium sulphate, and a chelating agent in an amount sufficient to sequester heavy metal ions in the pulp, to produce a pulp consistency of 1 to 16% at a temperature in the range of the bleach liquor freezing point to 25.degree. C., uniformly mixing the bleach liquor with the wood pulp, and immediately thickening the diluted wood pulp to a consistency in the range of 20 to 70% for bleaching of the thickened wood pulp. The wood pulp can be subjected to a preliminary treatment by the addition of a chelating agent in an amount sufficient to sequester chelatable heavy metals including manganese at a pulp consistency of 1 to 10%, and dewatering said pulp to a consistency of 20 to 70% to remove the sequestered manganese to less than 10 ppm.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.