Non-chlorine bleaching of kraft pulp
US5691193A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 23, 1994 |
| Grant date | Nov 25, 1997 |
| Priority date | — |
| Expiry date | Jun 23, 2014 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S435/911
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
A process for the bleaching of kraft pulps with non-chlorine chemicals, employing a sequential reaction of oxidative enzymes and hydrogen peroxide. The kraft pulp can be from conventional or extended pulping, or from an oxygen delignification step. The enzyme reaction is monitored by methanol release which results from the demethylation of lignin. The process essentially comprises three steps. The first step is the oxidation of kraft pulp either with manganese peroxidase enzyme in the presence of Mn(II) salts, hydrogen peroxide and chelator, or with laccase enzyme preferably in the presence of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), or a combination of both enzymes in a crude mixture as typically produced by certain fungi. The Mn(II) salts and chelator may already be present in sufficient amount in the pulp. This first step is performed at an acidic pH, and moderate temperatures for a period of time between 30 and 240 minutes. The two subsequent steps are the chelation of metals in the pulp and the alkaline hydrogen peroxide treatment.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.