Patent US4941943A successfully refreshed from Google Patents.
US4941943A
Expired / Lapsed
US
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Process for preparing sodium carboxy-methyl cellulose
Assignee: Metsa Board Oyj
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Filing: 1988-01-27
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Granted: 1990-07-17
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Expires: 2008-01-27
Abstract
Abstract The invention relates to a method and an equipment for preparing NaCMC, in which (a) cellulose is slushed in the reaction medium until a consistency of c. 5-15%, preferably 5-10%, (b) the fibre suspension obtained in step (a) is thickened to a consistency of c. 20-35% and (c) the pulp containing reaction medium obtained in the second step is homogenized by means of a screw conveyor having a screw pitch which decreases from an inlet opening thereof towards an outlet opening thereof, in order to increase the reactivity, whereby a mercerization activating the cellulose is carried out after step (b) and/or (c), and the cellulose thus pretreated is etherified in a manner known per se.
Inventors
- 👤 Kari Edelman
- 👤 Torsten Lindroos
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 16:28
CPC Classifications
C; C08; C08B; C08B17/00; C08B17/06; C08B11/00; C08B11/02; C08B11/04; C08B11/10; C08B11/12
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
112 words
A process for preparing sodium carboxy-methyl cellulose, comprising: (a) conducting a pretreatment which includes: (i) slushing cellulose into a reaction medium until a fiber suspension having a consistency of about 5 to 15 percent is achieved; (ii) thereafter thickening said fiber suspension until a pulp-containing reaction medium having a consistency of about 20 to 35 percent is achieved; (iii) thereafter homogenizing said pulp-containing reaction medium using a screw conveyor having a screw pitch which decreases from an inlet opening thereof towards an outlet opening thereof, and thereby increasing the reactivity of said pulp; and (iv) after conducting step (ii), mercerizing said pulp, thereby activating cellulose therein; and (b) etherifying said activated cellulose.
Claim 2
Dependent Claim
112 words
A process for preparing sodium carboxy-methyl cellulose, comprising: (a) conducting a pretreatment which includes: (i) slushing cellulose into a reaction medium until a fiber suspension having a consistency of about 5 to 15 percent is achieved; (ii) thereafter thickening said fiber suspension until a pulp-containing reaction medium having a consistency of about 20 to 35 percent is achieved; (iii) thereafter homogenizing said pulp-containing reaction medium using a screw conveyor having a screw pitch which decreases from an inlet opening thereof towards an outlet opening thereof, and thereby increasing the reactivity of said pulp; and (iv) after conducting step (ii), mercerizing said pulp, thereby activating cellulose therein; and (b) etherifying said activated cellulose.
Claim 3
Dependent Claim
28 words
The process of claim 1, wherein: said step of slushing is carried out until a fiber suspension having a consistency of about 5 to 10 percent is achieved.
Claim 4
Dependent Claim
31 words
The process of claim 1, wherein: the mercerization of step (iv) is conducted in two stages, including a premercerization conducted after step (ii), and a main mercerization conducted after step (iii).
Claim 5
Dependent Claim
16 words
The process of claim 1, comprising: consuming about 40 kwh/t of cellulose in conducting step (iii).
Claim 6
Dependent Claim
30 words
The process of claim 1, further comprising: removing reaction medium in step (ii) and recycling at least some of said removed reaction medium to step (i) for slushing said cellulose.
Claim 7
Dependent Claim
11 words
The process of claim 1, wherein: said reaction medium is ethanol.
Claim 8
Dependent Claim
20 words
The process of claim 1, wherein: in step (i), said cellulose is slushed into said reaction medium using a pulper.
Claim 9
Dependent Claim
20 words
The process of claim 1, wherein: in step (ii), said thickening is carried out using a continuously fed screw press.
Claim 10
Dependent Claim
18 words
The process of claim 1, wherein: in step (b), the activated cellulose is kneaded in a kneader-type reactor.
References Cited (Backward Citations)
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US4444621A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-07-16 | 1994-01-15 | 1994-07-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-07-16 | 1998-01-15 | 1998-07-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-07-16 | 2002-01-15 | 2002-07-17 | $7700.00 | Window Closed / Lapsed |