Patent US3622444A successfully refreshed from Google Patents.
US3622444A
Expired / Lapsed
US
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Pulp bleaching process
Assignee: PPG Architectural Coatings Canada Inc
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Filing: 1970-03-25
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Granted: 1971-11-23
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Expires: 1990-03-25
Abstract
Abstract A process for bleaching sulfate or sulfite wood pulp having as the first three steps; chlorination, caustic extraction and chlorination; the pulp in the chlorination steps being pretreated with ammonia or an ammonium salt. Additional process steps may follow. The process provides wood pulp bleached to a highbrightness level at relatively low chemical cost while avoiding severe degradation of the pulp.
Inventors
- 👤 Douglas Haig Andrews
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 17:15
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/10; D21C9/12; D21C9/14; D21C9/144
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
21 words
A process as claimed in claim 1 wherein the wood pulp is washed with water at the completion of each step.
Claim 2
Dependent Claim
12 words
treating the chlorine-treated wood pulp in aqueous suspension with alkali base; and
Claim 3
Dependent Claim
40 words
treating the alkali-treated wood pulp in aqueous suspension initially with 0.3 percent to 0.5 percent by weight of ammonia or an ammonium salt and sequentially with sufficient chlorine to provide residual chlorine of at least 0.1 percent on the pulp.
Claim 4
Dependent Claim
43 words
A process as claimed in claim 1 wherein the three initial steps are followed by additional steps comprising a. treating the chlorine-treated wood pulp in aqueous suspension with alkali base, and b. treating the alkali-treated wood pulp in aqueous suspension with chlorine dioxide.
Claim 5
Dependent Claim
23 words
A process as claimed in claim 3 wherein the wood pulp is washed with water at the completion of steps (a) and (b).
Claim 6
Dependent Claim
19 words
A process as claImed in claim 3 wherein alkali base is employed as an additional reagent in step (b).
Claim 7
Dependent Claim
36 words
A process as claimed in claim 1 wherein the treatment with chlorine in step (1) is carried out at 10* C. to 40* C. temperature at a wood pulp consistency of 2 percent to 5 percent.
Claim 8
Dependent Claim
36 words
A process as claimed in claim 1 wherein the treatment with chlorine in step (3) is carried out at 20* C. to 60* C. temperature at a wood pulp consistency of 2 percent to 15 percent.
Claim 9
Dependent Claim
55 words
A process as claimed in claim 1 wherein the three initial steps are followed by additional steps comprising a. treating the chlorine-treated wood pulp in aqueous suspension with alkaline hypochlorite, b. treating the hypochlorite-treated wood pulp in aqueous suspension with alkali base, and c. treating the alkali-treated wood pulp in aqueous suspension with chlorine dioxide.
Claim 10
Dependent Claim
43 words
A process as claimed in claim 1 wherein the three initial steps are followed by additional steps comprising a. treating the chlorine-treated wood pulp with hydrogen peroxide or alkali peroxide, and b. treating the peroxide-treated wood pulp in aqueous suspension with chlorine dioxide.
References Cited (Backward Citations)
US1801876A
Cited
US1787395A
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US1957938A
Cited
US2587064A
Cited
US3020197A
Cited
US3020196A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-22 | 1975-05-24 | 1975-11-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-22 | 1979-05-24 | 1979-11-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-22 | 1983-05-24 | 1983-11-23 | $7700.00 | Window Closed / Lapsed |