US4244777A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bleaching stilbene yellow dyed wood pulp
Assignee: Weyerhaeuser Co
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Filing: 1979-11-07
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Granted: 1981-01-13
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Expires: 1999-11-07
Abstract
Abstract Chlorine dioxide is a specific bleaching agent for stilbene yellow dye which has been used to dye paper stock. Chlorine dioxide may be used in amounts as low as 0.25% based on the oven dry weight of the pulp fiber.
Inventors
- 👤 Maharaj K. Gupta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 15:07
CPC Classifications
D; D21; D21C; D21C5/00; D21C5/02; D21C9/00; D21C9/10; D21C9/12; D21C9/14; Y; Y02; Y02W; Y02W30/00; Y02W30/50; Y02W30/64
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
62 words
A process for bleaching stilbene yellow dyed wood pulp said dye not being bleachable by ozone, oxygen, hydrogen peroxide, chlorine or hypochlorite, comprising repulping stilbene yellow dyed paper in water to form an aqueous slurry of stilbene yellow dyed wood pulp, treating said slurry with chlorine dioxide in an amount sufficient to bleach and remove the yellow color of said wood pulp.
Claim 2
Dependent Claim
62 words
A process for bleaching stilbene yellow dyed wood pulp said dye not being bleachable by ozone, oxygen, hydrogen peroxide, chlorine or hypochlorite, comprising repulping stilbene yellow dyed paper in water to form an aqueous slurry of stilbene yellow dyed wood pulp, treating said slurry with chlorine dioxide in an amount sufficient to bleach and remove the yellow color of said wood pulp.
Claim 3
Dependent Claim
27 words
The process of claim 1 in which said chlorine dioxide is used in an amount of up to 4% of the oven-dry weight of said wood pulp.
Claim 4
Dependent Claim
28 words
The process of claim 1 in which said chlorine dioxide is used in an amount of up to 2% of the oven dry weight of said wood pulp.
Claim 5
Dependent Claim
27 words
The process of claim 1 in which said chlorine dioxide is used in an amount of up to 1% of the oven-dry weight of said wood pulp.
Claim 6
Dependent Claim
27 words
The process of claim 1 in which said chlorine dioxide is used in an amount of up to 0.5% of the oven-dry weight of said wood pulp.
Claim 7
Dependent Claim
27 words
The process of claim 1 in which said chlorine dioxide is used in an amount of at least 0.25% of the oven-dry weight of said wood pulp.
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) | 1984-01-13 | 1984-07-14 | 1985-01-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-01-13 | 1988-07-14 | 1989-01-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-01-13 | 1992-07-14 | 1993-01-13 | $7700.00 | Window Closed / Lapsed |