Bleaching of deinked paper/wood pulp
US5449436A · kind A · utility
5Cited by
5References
6Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Mar 1, 1993 |
| Grant date | Sep 12, 1995 |
| Priority date | — |
| Expiry date | Mar 1, 2013 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02W30/64
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
Deinked paper/wood pulps are improvedly bleached to high levels of whiteness by conjointly treating such pulps with a sulfite bleaching agent, e.g., Na.sub.2 SO.sub.3, NaHSO.sub.3 or mixture thereof, or SO.sub.2 and NaOH, and a reducing agent more electronegative than the sulfite ion, e.g., thiourea dioxide, sodium borohydride or sodium dithionite, in a reaction medium having an initial pH ranging from 6 to 12, advantageously followed by washing sulfite and reducing agent values from the bleached pulp and then treating the washed pulp with hydrogen peroxide in an aqueous alkaline medium.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.