US4581446A
Expired / Lapsed
US
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Purification of cellulose ethers
Assignee: Dow Chemical Co
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Filing: 1985-03-15
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Granted: 1986-04-08
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Expires: 2005-03-15
Abstract
Abstract Impurities in cellulose ether compositions are removed by providing a functionally effective thickness of a cellulose ether composition to a filtration device, and contacting the thickness, in a manner such that substantial thickness is maintained with at least one extracting solution in which the impurities in the cellulose ether are soluble such that a gradient impurity concentration is formed. High purity cellulose ethers are prepared, without experiencing large product losses.
Inventors
- 👤 Gary J. Schulz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 00:01
CPC Classifications
C; C08; C08B; C08B11/00; C08B11/20
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
111 words
A process for removing solvent-soluble impurities from a cellulose ether composition, said process comprising (a) providing a functionally effective thickness of said cellulose ether composition in a filtration device, (b) contacting said cellulose ether composition with an extracting solution comprising a solvent for said impurities, in a manner such that said extracting solution can migrate through said thickness of the cellulose ether composition and through said filtration device, and (c) allowing said extracting solution to migrate through said thickness of the cellulose ether composition, such that (1) substantial thickness of the cellulose ether composition is maintained in the filtration device, and (2) a gradient impurity concentration is effected through the thickness.
Claim 2
Dependent Claim
111 words
A process for removing solvent-soluble impurities from a cellulose ether composition, said process comprising (a) providing a functionally effective thickness of said cellulose ether composition in a filtration device, (b) contacting said cellulose ether composition with an extracting solution comprising a solvent for said impurities, in a manner such that said extracting solution can migrate through said thickness of the cellulose ether composition and through said filtration device, and (c) allowing said extracting solution to migrate through said thickness of the cellulose ether composition, such that (1) substantial thickness of the cellulose ether composition is maintained in the filtration device, and (2) a gradient impurity concentration is effected through the thickness.
Claim 3
Dependent Claim
14 words
The process of claim 1, wherein the cellulose ether is a water-soluble cellulose ether.
Claim 4
Dependent Claim
11 words
The process of claim 2, wherein the impurities comprise sodium chloride.
Claim 5
Dependent Claim
18 words
The process of claim 3, wherein the extracting solution can insolubilize a portion of the cellulose ether composition.
Claim 6
Dependent Claim
15 words
The process of claim 4, wherein the extracting solution is an aqueous sodium chloride solution.
Claim 7
Dependent Claim
13 words
The process of claim 3, wherein the cellulose ether is hydroxypropyl methylcellulose ether.
Claim 8
Dependent Claim
32 words
The process of claim 6, wherein the hydroxypropyl methylcellulose has a hydroxypropoxyl molar substitution from about 0.1 to about 0.35, and a methoxyl degree of substitution from about 1.1 to about 1.65.
Claim 9
Dependent Claim
23 words
The process of claim 7, wherein the cellulose ether has a viscosity as a 2 percent solution of less than about 10,000 cps.
Claim 10
Dependent Claim
14 words
The process of claim 1, wherein the filtration device comprises a vertical cylindrical tank.
Claim 11
Dependent Claim
15 words
The process of claim 9, wherein the filtration device comprises a means for controlling temperature.
Claim 12
Dependent Claim
15 words
The process of claim 10, wherein the filtration device comprises a means for controlling pressure.
Claim 13
Dependent Claim
18 words
The process of claim 1, wherein the extracting solution can insolubilize a portion of the cellulose ether composition.
Claim 14
Dependent Claim
47 words
The process of claim 1, further comprising the steps of (d) slurrying the cellulose ether composition with a solution comprising a solvent for said impurities; (e) removing the cellulose ether composition slurry from said filtration device, and (f) isolating the cellulose ether composition from said slurry solution.
Claim 15
Dependent Claim
11 words
The process of claim 13, wherein the slurry solution comprises water.
Claim 16
Dependent Claim
16 words
The process of claim 1, wherein (b) and (c) are repeated employing a second extracting solution.
Claim 17
Dependent Claim
14 words
The process of claim 15, wherein the cellulose ether is a water-soluble cellulose ether.
Claim 18
Dependent Claim
22 words
The process of claim 16, wherein the cellulose ether has a viscosity as a 2 percent solution less than about 10,000 cps.
Claim 19
Dependent Claim
17 words
The process of claim 15, wherein the extracting solution and the second extracting solution are aqueous solutions.
Claim 20
Dependent Claim
22 words
The process of claim 18, wherein the extracting solution and second extracting solution can insolubilize a portion of the cellulose ether composition.
Claim 21
Dependent Claim
20 words
The process of claim 19, wherein the extracting solution and the second extracting solution contain an amount of the impurities.
Claim 22
Dependent Claim
20 words
The process of claim 20, wherein the second extracting solution contains a lesser concentration of impurities than the extracting solution.
Claim 23
Dependent Claim
11 words
The process of claim 21, wherein the impurities comprise sodium chloride.
Claim 24
Dependent Claim
14 words
The process of claim 22, wherein the cellulose ether is a water-soluble cellulose ether.
Claim 25
Dependent Claim
14 words
The process of claim 23, wherein the cellulose ether is a hydroxypropyl methylcellulose ether.
Claim 26
Dependent Claim
32 words
The process of claim 24, wherein the cellulose ether has a hydroxypropoxyl molar substitution from about 0.1 to about 0.35, and a methoxyl degree of substitution from about 1.1 to about 1.65.
Claim 27
Dependent Claim
23 words
The process of claim 25, wherein the cellulose ether has a viscosity as a 2 percent solution of less than about 10,000 cps.
Claim 28
Dependent Claim
25 words
The process of claim 26, wherein the filtration device comprises a vertical cylindrical tank, a means for controlling temperature, and a means for controlling pressure.
Claim 29
Dependent Claim
32 words
The process of claim 27, wherein the cellulose ether composition is provided to the filtration device as a slurry, and which slurry solution is removed after providing said composition to said device.
Claim 30
Dependent Claim
15 words
The process of claim 28, wherein the slurry solution contains an amount of the impurities.
Claim 31
Dependent Claim
19 words
The process of claim 29, wherein the slurry solution contains a greater amount of impurities than the extracting solution.
Claim 32
Dependent Claim
65 words
The process of claim 30, further comprising the steps of (d) slurrying the thickness of cellulose ether composition with water, or a solution containing impurities at a concentration about equal to or less than the impurity concentration contained in the second extracting solution, (e) removing the cellulose ether composition slurry from said filtration device, and (f) isolating the cellulose ether solution from said slurry solution.
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) | 1989-04-07 | 1989-10-07 | 1990-04-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-04-07 | 1993-10-07 | 1994-04-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-04-07 | 1997-10-07 | 1998-04-08 | $7700.00 | Window Closed / Lapsed |