Method of bleaching pulp with chlorine-free chemicals wherein a complexing agent is added immediately after an ozone bleach stage
US6010594A · kind A · utility
32Cited by
11References
37Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Sep 15, 1997 |
| Grant date | Jan 4, 2000 |
| Priority date | — |
| Expiry date | Sep 15, 2017 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/163
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
Kraft pulp is bleached to an acceptable brightness (e.g. 86 ISO or more) without using chlorinated organic compounds, yet the strength of the produced pulp remains commercially acceptable. In the manufacture of pulp, the pulp which is cooked and oxygen delignified to a kappa number of 14 or less, and then is bleached with ozone at a medium consistency. After the ozone treatment, heavy metals are removed from the pulp, and then the pulp is led to oxygen and/or peroxide treatment, which is followed by a second ozone bleaching stage. The sequence (ZT) (EOP) (ZP) is preferred.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.