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US4270914A
Expired / Lapsed
US
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Process for controlling hemicellulose concentration during the mercerization of cellulose
Assignee: Borregaard Industries Ltd
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Filing: 1979-10-26
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Granted: 1981-06-02
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Expires: 1999-10-26
Abstract
Abstract The disadvantages stemming from a high content of hemicellulose in recirculated sodium hydroxide solutions used for the mercerization of cellulose in the preparation of viscose are reduced or eliminated by subjecting at least a part of the spent sodium hydroxide solution to an ultrafiltration process to remove part or all of the hemicellulose therein. The filtered sodium hydroxide liquor is supplied with make-up sodium hydroxide and is returned to the mercerization step.
Inventors
- 👤 Birger Dahl
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 19:50
CPC Classifications
B; B01; B01D; B01D61/00; B01D61/14; B01D61/145; D; D06; D06M; D06M11/00; D06M11/32; D06M11/36; D06M11/38
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
75 words
A continuous process for the mercerization of cellulose, comprising (a) treating cellulose with a strong aqueous solution of sodium hydroxide; (b) removing the excess liquor containing dissolved hemicellulose; (c) passing said liquor through ultrafiltration to remove all or part of the dissolved hemicellulose; and (d) returning the portion of the sodium hydroxide liquor depleted of dissolved hemicellulose to treatment step (a) and removing for other uses the ultrafiltrate portion which is high in hemicellulose content.
Claim 2
Dependent Claim
75 words
A continuous process for the mercerization of cellulose, comprising (a) treating cellulose with a strong aqueous solution of sodium hydroxide; (b) removing the excess liquor containing dissolved hemicellulose; (c) passing said liquor through ultrafiltration to remove all or part of the dissolved hemicellulose; and (d) returning the portion of the sodium hydroxide liquor depleted of dissolved hemicellulose to treatment step (a) and removing for other uses the ultrafiltrate portion which is high in hemicellulose content.
Claim 3
Dependent Claim
24 words
The process of claim 1, wherein the ultrafiltration is carried out using an alkali-resistant membrane having a molecular weight separating limit of about 10,000.
Claim 4
Dependent Claim
44 words
The process of claim 1 or 2, wherein the hemicellulose content of the treatment solution of step (a) is controlled by bleeding off a predetermined amount of said excess hemicellulose-containing liquor before step (c) without ultrafiltration and returning said liquor to treatment step (a).
Claim 5
Dependent Claim
23 words
The process of claim 1 or 2 wherein said ultrafiltrate high in hemicellulose content is used to dissolve cellulose xanthogenate in preparing viscose.
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) | 1984-06-01 | 1984-12-01 | 1985-06-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-06-01 | 1988-12-01 | 1989-06-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-06-01 | 1992-12-01 | 1993-06-02 | $7700.00 | Window Closed / Lapsed |