Patent US4444621A successfully refreshed from Google Patents.
US4444621A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process and apparatus for the deresination and brightness improvement of cellulose pulp
Assignee: Mo och Domsjo AB
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Filing: 1981-12-03
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Granted: 1984-04-24
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Expires: 2001-12-03
Abstract
Abstract A process and apparatus are provided for the deresination and brightness improvement of cellulose pulp, by adjusting the pulp concentration to within the range from about 15 to about 35%; adding sufficient alkali to the pulp to bring the amount of alkali, calculated as NaOH, within the range from about 0.5 to about 17 g/kg of water accompanying the pulp; adding sufficient oxidizing bleaching agent to the pulp to bring the amount of oxidizing bleaching agent to within the range from about 0.2 to about 22 g/kg of water; subjecting the pulp to a mild, mechanical working in the bite of twin interdigitated rotating screws at an energy input of from 8 to 100 kWh per ton of pulp; removing and reacting the pulp with the added alkali and bleaching agent for from about 0.1 to about 5 hours; and then washing out dissolved resin from the pulp.
Inventors
- 👤 Jonas A. I. Lindahl
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:07
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/08
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
152 words
A process for reducing the resin content of bleached and unbleached cellulose pulps while improving their brightness, which comprises adjusting the pulp concentration to within the range from about 15 to about 35%; mixing the cellulose pulp with alkali in a sufficient amount to adjust the amount of alkali, calculated as NaOH, within the range from about 0.5 to about 17 g/kg of water; adding sufficient oxidizing bleaching agent to the pulp to bring the amount of oxidizing bleaching agent to within the range from about 0.2 to about 22 g/kg of water; subjecting the pulp to a mild mechanical treatment in the bite of twin interdigitated rotating screws at an input energy of from 8 to 100 kWh per ton of pulp; and then removing and reacting the cellulose pulp at substantially the same pulp consistency with the added alkali and bleaching agent for from about 0.1 to about 5 hours.
Claim 2
Dependent Claim
152 words
A process for reducing the resin content of bleached and unbleached cellulose pulps while improving their brightness, which comprises adjusting the pulp concentration to within the range from about 15 to about 35%; mixing the cellulose pulp with alkali in a sufficient amount to adjust the amount of alkali, calculated as NaOH, within the range from about 0.5 to about 17 g/kg of water; adding sufficient oxidizing bleaching agent to the pulp to bring the amount of oxidizing bleaching agent to within the range from about 0.2 to about 22 g/kg of water; subjecting the pulp to a mild mechanical treatment in the bite of twin interdigitated rotating screws at an input energy of from 8 to 100 kWh per ton of pulp; and then removing and reacting the cellulose pulp at substantially the same pulp consistency with the added alkali and bleaching agent for from about 0.1 to about 5 hours.
Claim 3
Dependent Claim
24 words
A process according to claim 1 in which the oxidizing bleaching agent is added in an amount of from 0.3 to 11 g/kg water.
Claim 4
Dependent Claim
17 words
A process according to claim 1 in which the oxidizing bleaching agent is a peroxide bleaching agent.
Claim 5
Dependent Claim
17 words
A process according to claim 1 in which the oxidizing bleaching agent is a hypochlorite bleaching agent.
Claim 6
Dependent Claim
13 words
A process according to claim 1 in which the alkali is sodium hydroxide.
Claim 7
Dependent Claim
23 words
A process according to claim 1 in which the pulp consistency is adjusted to within the range from about 19 to about 29%.
Claim 8
Dependent Claim
21 words
A process according to claim 1 in which the input energy is from 10 to 75 kWh per ton of pulp.
Claim 9
Dependent Claim
13 words
A process according to claim 1 in which the cellulose pulp is bleached.
Claim 10
Dependent Claim
13 words
A process according to claim 1 in which the cellulose pulp is unbleached.
Claim 11
Dependent Claim
48 words
A process according to claim 1 in which the cellulose pulp is held for a short time after adjusting pulp concentration and before the mild mechanical working; and the alkali and oxidizing bleaching agent are added during the adjustment of the pulp concentration and during the holding time.
Claim 12
Dependent Claim
15 words
A process according to claim 10 in which steam is added during the holding time.
Claim 13
Dependent Claim
23 words
A process according to claim 10 in which during the short holding time the cellulose pulp is transported to the mild mechanical working.
Claim 14
Dependent Claim
17 words
A process according to claim 10 in which the holding time is from two to ten seconds.
Claim 15
Dependent Claim
32 words
A process according to claim 1 in which in addition to alkali and bleaching agent at least one member selected from the group consisting of surface-active agents and complex-forming agents is added.
Claim 16
Dependent Claim
20 words
A process according to claim 1 in which the pulp is reacted with oxygen gas during the reaction with alkali.
Claim 17
Dependent Claim
39 words
A process according to claim 1 in which the cellulose pulp is unbleached chemical cellulose pulp from which spent pulp liquor has been washed out in a washing stage at a washed pulp concentration of from 4 to 6%.
Claim 18
Dependent Claim
27 words
A process according to claim 1 in which cellulose pulp is screened cellulose pulp diluted to a pulp concentration of from 0.5 to 3% during the screening.
Claim 19
Dependent Claim
37 words
A process according to claim 1 in which the pulp is bleached in a mild delignifying bleaching with a bleaching agent selected from the group consisting of chlorine and chlorine dioxide before or after applying the process.
Claim 20
Dependent Claim
36 words
A process according to claim 1, in which the pulp is bleached with a peroxide bleaching agent selected from the group consisting of hydrogen peroxide, sodium peroxide and peracetic acid before or after applying the process.
Claim 21
Dependent Claim
35 words
A process according to claim 1 in which the alkali added is selected from the group consisting of sodium hydroxide, potassium hydroxide, oxidized white liquor, green liquor, and sodium carbonate in admixture with sodium hydroxide.
References Cited (Backward Citations)
CA902306A
Cited
US4294653A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-04-24 | 1987-10-24 | 1988-04-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-04-24 | 1991-10-24 | 1992-04-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-04-24 | 1995-10-24 | 1996-04-24 | $7700.00 | Window Closed / Lapsed |