Bleaching cellulose pulp having cleanliness which varies significantly over time using at least two different bleaching stages and bleaching chemicals
US6153300A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 18, 1994 |
| Grant date | Nov 28, 2000 |
| Priority date | — |
| Expiry date | Apr 18, 2014 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/2978
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
Recycled paper pulp having at least two different types of paper which consume widely different amounts of bleaching chemical, or mixed hardwood and soft-wood pulps, are treated in a manner that enhances distribution and redistribution of bleaching chemical to enhance uniformity of the bleaching treatment. The pulp is intensely mixed to provide a homogenous mixture of fibrous material and bleaching chemical, and then is continuously or intermittently subjected to mechanical action (such as in low intensity mixers, or by agitating pulp in a retention tank) of sufficient intensity and duration so as to enhance distribution and redistribution of a bleaching chemical. Also, recycled pulp will have cleanliness which varies significantly over time, and this is accommodated by sensing at least one of the brightness, color, or lignin content (e.g. all three) of the pulp prior to treatment in a first bleaching stage, controlling the quantity of first bleaching chemical added to the first stage in response to at least one of the brightness, color, or lignin content sensing to achieve a target brightness increase for the first stage, and then repeating the sensing and quantity control steps f…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.