Environmentally improved process for bleaching lignocellulosic materials with oxygen, ozone and chlorine dioxide
US5296099A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 28, 1992 |
| Grant date | Mar 22, 1994 |
| Priority date | — |
| Expiry date | Aug 28, 2012 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/1057
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
A process for delignifying and bleaching a lignocellulosic pulp without the use of elemental chlorine by partially delignifying the pulp to a K No. of about 10 or less and a viscosity of greater than about 13 cps; and further delignifying the partially delignified pulp with an effective amount of ozone for a sufficient time to obtain a substantially delignified pulp having a K No. of about 5 or less, a viscosity of greater than about 10, and a GE brightness of at least about 50%. The substantially delignified pulp may be brightened by the addition of a bleaching agent such as chlorine dioxide or a peroxide to obtain a final product having a GE brightness of at least about 65%, preferably above 70% to as high as 90%. Because of the absence of elemental chlorine in this sequence, filtrate from all stages but the chlorine dioxide stage (if used) can be recovered without sewering. Major environmental improvements are thus achieved.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.