Process for bleaching lignocellulosic matter
US4812206A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 22, 1987 |
| Grant date | Mar 14, 1989 |
| Priority date | — |
| Expiry date | Sep 22, 2007 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/1057
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
A process for bleaching a lignocellulosic matter in the form of a mechanical, thermomechanical, chemicomechanical or chemicothermomechanical papermaking pulp, or of wood chips while being converted into one of these pulp types by processing in a machine consisting essentially of two interpenetrating spiral surfaces wound around parallel shafts driven in synchronous rotation in the same direction inside a barrel which encloses them, and determining between upstream and downstream in the direction of forward travel of the matter a series of zones for drawing and braking the matter, which comprises combining a bleaching treatment using a reducing agent and a bleaching treatment using an oxidizing agent, characterized in that, after pretreatment using at least one metal-complexing or sequestering agent, the lignocellulosic matter undergoes a washing operation with an efficiency greater than 96% before undergoing in succession a bleaching treatment using a reducing agent at a pH of between about 8 and 12, a washing operation to remove the reducing agent and a bleaching treatment using an oxidizing agent.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.