US4718980A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interstage treatment of mechanical pulp
Assignee: North Pacific Paper Co LLC
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Filing: 1985-12-30
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Granted: 1988-01-12
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Expires: 2005-12-30
Abstract
Abstract A two-stage pulp refining system in which the fibrous material from the first stage refiner is in contact with an alkaline bleaching solution between refining stages at a temperature of 32 DEG -96 DEG C. and at a consistency of 15-25% on an oven dry basis. The material is then diluted and then pressed to a consistency of at least 20% and passes through the second stage refiner.
Inventors
- 👤 Leonard E. Lowrie
- 👤 William L. Duncan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:47
CPC Classifications
D; D21; D21B; D21B1/00; D21B1/04; D21B1/12; D21B1/14; D21B1/16; D21C; D21C9/00; D21C9/10; D21C9/16; D21C9/163
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
99 words
A process for improving the physical properties of two-stage refiner pulp consisting essentially of refining wood chips in a first stage of refining to form fibers and fiber bundles, soaking said fibers and fiber bundles in an alkaline peroxide bleach at a temperature of 32°-96° C., at a consistency in the range of 15-25% for from 30-120 minutes, decreasing the consistency of said fibers and fiber bundles to below 15%, increasing the consistency of said fibers and fiber bundles to a consistency of at least 20%, refining said latter fibers and fiber bundles in a second stage of refining.
Claim 2
Dependent Claim
99 words
A process for improving the physical properties of two-stage refiner pulp consisting essentially of refining wood chips in a first stage of refining to form fibers and fiber bundles, soaking said fibers and fiber bundles in an alkaline peroxide bleach at a temperature of 32°-96° C., at a consistency in the range of 15-25% for from 30-120 minutes, decreasing the consistency of said fibers and fiber bundles to below 15%, increasing the consistency of said fibers and fiber bundles to a consistency of at least 20%, refining said latter fibers and fiber bundles in a second stage of refining.
Claim 3
Dependent Claim
15 words
The process of claim 1 in which said first stage of refining is under pressure.
Claim 4
Dependent Claim
14 words
The process of claim 1 in which said first stage is heated by steam.
Claim 5
Dependent Claim
13 words
The process of claim 1 in which said consistency is decreased to 3-6%.
Claim 6
Dependent Claim
15 words
The process of claim 1 in which said consistency is increased to at least 25%.
References Cited (Backward Citations)
US4279694A
Cited
CA1145107A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-01-11 | 1991-07-13 | 1992-01-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-01-11 | 1995-07-13 | 1996-01-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-01-11 | 1999-07-13 | 2000-01-12 | $7700.00 | Window Closed / Lapsed |