US4029543A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Mechanically freeing wood fibers in the presence of spent peroxide bleaching liquor
Assignee: Mo och Domsjo AB
•
Filing: 1976-05-28
•
Granted: 1977-06-14
•
Expires: 1996-05-28
Abstract
Abstract A process for the preparation of a cellulose pulp by mechanically freeing wood fibers in a grinder to form a fibrous pulp and bleaching the fibrous pulp with a peroxide-containing bleaching agent, as the only bleaching agent, in a peroxide bleaching stage, the mechanical freeing of the fibers being carried out in the presence of a spent liquor from the peroxide bleaching stage have a pH of 7 to 9.
Inventors
- 👤 Jonas Arne Ingvar Lindahl
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:40
CPC Classifications
D; D21; D21B; D21B1/00; D21B1/04; D21B1/12; D21B1/14; D21B1/16; D21C; D21C9/00; D21C9/10; D21C9/1005
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
90 words
In the process for the preparation of a cellulose pulp by mechanically freeing wood fibers in a grinder to form a fibrous pulp, and bleaching the fibrous pulp in a peroxide bleaching stage by adding a peroxide-containing bleaching agent, as the only bleaching agent, to said fibrous pulp the improvement which comprises mechanically freeing the wood fibers in a separate step preliminary to said bleaching, in the presence of only spent bleaching liquor from said peroxide bleaching stage, said liquor having a pH within the range from 7 to 9.
Claim 2
Dependent Claim
90 words
In the process for the preparation of a cellulose pulp by mechanically freeing wood fibers in a grinder to form a fibrous pulp, and bleaching the fibrous pulp in a peroxide bleaching stage by adding a peroxide-containing bleaching agent, as the only bleaching agent, to said fibrous pulp the improvement which comprises mechanically freeing the wood fibers in a separate step preliminary to said bleaching, in the presence of only spent bleaching liquor from said peroxide bleaching stage, said liquor having a pH within the range from 7 to 9.
Claim 3
Dependent Claim
14 words
The process of claim 1, in which the peroxide-containing bleaching agent is hydrogen peroxide.
Claim 4
Dependent Claim
17 words
The process of claim 2, in which the pH of the spent liquor is higher than 7.5.
Claim 5
Dependent Claim
18 words
The process of claim 3, in which the pH of the spent liquor is 8 to 9 .
Claim 6
Dependent Claim
31 words
The process of claim 1, in which one part of the spent liquor also is added to the fibrous pulp after the grinder but before the addition of the bleaching agent.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-06-13 | 1980-12-13 | 1981-06-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-06-13 | 1984-12-13 | 1985-06-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-06-13 | 1988-12-13 | 1989-06-14 | $7700.00 | Window Closed / Lapsed |