Modified digestion of paper pulp followed by ozone bleaching
US5328564A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 18, 1992 |
| Grant date | Jul 12, 1994 |
| Priority date | — |
| Expiry date | Feb 18, 2012 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/163
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
Kraft pulp is bleached to a brightness of about 90 CPPA or greater, without the use of chlorinated organic compounds that has commercially acceptable strength properties. During production of the kraft pulp it is subjected to extended delignification, by adding kraft white liquor to a first recirculation loop in the digester, and/or a second, wash, recirculation loop in the digester; or by conventional pulping followed by two oxygen stages, with washing between the stages. The extended delignification pulp is then subjected to ozone bleaching, with an ozone dosage of less than 1.0% (preferably less than about 0.5%). The ozone bleaching sequence may be a (ZE)P(ZE)P sequence.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.