Patent US4956048A successfully refreshed from Google Patents.
US4956048A
Expired / Lapsed
US
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Method of alcohol washing brownstock pulp prior to a chlorination bleaching stage
Assignee: Westvaco Corp
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Filing: 1989-04-17
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Granted: 1990-09-11
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Expires: 2009-04-17
Abstract
Abstract In the method of chemical pulping of wood including a chlorination stage pulp bleaching step followed by alkaline extraction, a method of reducing the amount of dioxins and furans produced thereby is disclosed wherein the brownstock pulp is first washed with alcohol prior to bleaching.
Inventors
- 👤 Ronnie G. Hise
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 14:45
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/10; D21C9/12; D21C9/14; D21C9/02
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
82 words
An improved method of chemical pulping and bleaching comprising bleaching brownstock chemical pulp with a chlorination stage followed by a lignin extraction stage and producing an amount of chlorinated dioxins and furans as a by-product of the bleaching, wherein the improvement comprises reducing the amount of chlorinated dioxins and furans up to at least 80% by washing the pulp with alcohol prior to the chlorination bleaching stage, wherein the alcohol washing does not significantly change the Kappa No. of the chemical pulp.
Claim 2
Dependent Claim
82 words
An improved method of chemical pulping and bleaching comprising bleaching brownstock chemical pulp with a chlorination stage followed by a lignin extraction stage and producing an amount of chlorinated dioxins and furans as a by-product of the bleaching, wherein the improvement comprises reducing the amount of chlorinated dioxins and furans up to at least 80% by washing the pulp with alcohol prior to the chlorination bleaching stage, wherein the alcohol washing does not significantly change the Kappa No. of the chemical pulp.
Claim 3
Dependent Claim
27 words
The improved method of claim 1 wherein the pulp is softwood pulp and the chlorination stage includes subjecting the pulp to combinations of chlorine dioxide and chlorine.
Claim 4
Dependent Claim
21 words
The method of claim 2 wherein the alcohol is selected from the group consisting of methanol, ethanol, propanol, isopropanol, and octanol.
Claim 5
Dependent Claim
10 words
The method of claim 3 wherein the alcohol is ethanol.
References Cited (Backward Citations)
US2042705A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-09-10 | 1994-03-12 | 1994-09-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-09-10 | 1998-03-12 | 1998-09-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-09-10 | 2002-03-12 | 2002-09-11 | $7700.00 | Window Closed / Lapsed |