US3962030A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bleaching wood pulp with sodium hydrosulfite in the presence of hexamethylenetetramine
Assignee: Ventron Corp
•
Filing: 1975-04-18
•
Granted: 1976-06-08
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Expires: 1995-04-18
Abstract
Abstract A process for bleaching wood pulp with sodium hydrosulfite in the presence of at least 2 weight percent of hexamethylenetetramine based upon the weight of sodium hydrosulfite.
Inventors
- 👤 Edward A. Sullivan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 21:58
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/10; D21C9/1084; D21C9/1089
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
76 words
In a process for bleaching wood pulp with sodium hydrosulfite under anaerobic conditions at a temperature between about 90°F and 180°F and at a pH of between about 4.0 and 7.0, the improvement which comprises conducting the bleaching in the presence of at least about 2 weight percent hexamethylenetetramine based upon the weight of sodium hydrosulfite, said weight percent of hexamethylenetetramine being effective to prevent formation of hydrogen sulfide during sodium hydrosulfite bleaching of wood pulp.
Claim 2
Dependent Claim
76 words
In a process for bleaching wood pulp with sodium hydrosulfite under anaerobic conditions at a temperature between about 90°F and 180°F and at a pH of between about 4.0 and 7.0, the improvement which comprises conducting the bleaching in the presence of at least about 2 weight percent hexamethylenetetramine based upon the weight of sodium hydrosulfite, said weight percent of hexamethylenetetramine being effective to prevent formation of hydrogen sulfide during sodium hydrosulfite bleaching of wood pulp.
Claim 3
Dependent Claim
29 words
The process of claim 1 wherein the bleaching is conducted in the presence of between about 5 and 25 weight percent hexamethylenetetramine based upon the weight of sodium hydrosulfite.
Claim 4
Dependent Claim
32 words
The process of claim 1 wherein, prior to the bleaching step, the sodium hydrosulfite is formed by reacting aqueous sodium bisulfite and sodium borohydride at a pH between about 6 and 7.
Claim 5
Dependent Claim
32 words
The process of claim 2 wherein, prior to the bleaching step, the sodium hydrosulfite is formed by reacting aqueous sodium bisulfite and sodium borohydride at a pH between about 6 and 7.
Claim 6
Dependent Claim
20 words
The process of claim 1 wherein a mixture of the sodium hydrosulfite and hexamethylenetetramine is added to the wood pulp.
Claim 7
Dependent Claim
20 words
The process of claim 2 wherein a mixture of the sodium hydrosulfite and hexamethylenetetramine is added to the wood pulp.
References Cited (Backward Citations)
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Cited
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Cited
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Cited
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Cited
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Cited
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Cited
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Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-06-08 | 1979-12-08 | 1980-06-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-06-08 | 1983-12-08 | 1984-06-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-06-08 | 1987-12-08 | 1988-06-08 | $7700.00 | Window Closed / Lapsed |