US4859339A
Expired / Lapsed
US
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Microporous membranes of syndiotactic vinylaromatic polymers
Assignee: Dow Chemical Co
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Filing: 1988-02-11
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Granted: 1989-08-22
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Expires: 2008-02-11
Abstract
Abstract Microporous, asymmetric membranes comprising syndiotactic vinylaromatic polymers having utility as membranes for ultrafiltration or reverse osmosis and a process for their production.
Inventors
- 👤 Ritchie A. Wessling
- 👤 Chieh-Chun Chau
- 👤 Alan F. Burmester
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 17:52
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/28
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
9 words
A microporous, asymmetric membrane comprising a syndiotactic vinylaromatic polymer.
Claim 2
Dependent Claim
9 words
A microporous, asymmetric membrane comprising a syndiotactic vinylaromatic polymer.
Claim 3
Dependent Claim
10 words
A crystalline, microporous, asymmetric membrane comprising a syndiotactic vinylaromatic polymer.
Claim 4
Dependent Claim
10 words
A crystalline, microporous, asymmetric membrane comprising a syndiotactic vinylaromatic polymer.
Claim 5
Dependent Claim
11 words
An oriented crystalline, microporous, asymmetric membrane comprising a syndiotactic vinylaromatic polymer.
Claim 6
Dependent Claim
11 words
An oriented crystalline, microporous, asymmetric membrane comprising a syndiotactic vinylaromatic polymer.
Claim 7
Dependent Claim
96 words
A process for preparing an asymmetric, microporous membrane comprising a syndiotactic vinylaromatic polymer comprising: (a) forming a solution comprising a syndiotactic vinylaromatic polymer and a polar aprotic solvent at a elevated temperature; (b) supercooling the solution so as to retain the syndiotactic vinylaromatic polymer in solution; (c) forming the solution into a membrane; (d) inducing phase separation and pore formation by contacting the membrane with a substance that is miscible with the polar aprotic solvent but is a nonsolvent for the syndiotactic vinylaromatic polymer so as to result in the formation of an asymmetric, microporous membrane.
Claim 8
Dependent Claim
96 words
A process for preparing an asymmetric, microporous membrane comprising a syndiotactic vinylaromatic polymer comprising: (a) forming a solution comprising a syndiotactic vinylaromatic polymer and a polar aprotic solvent at a elevated temperature; (b) supercooling the solution so as to retain the syndiotactic vinylaromatic polymer in solution; (c) forming the solution into a membrane; (d) inducing phase separation and pore formation by contacting the membrane with a substance that is miscible with the polar aprotic solvent but is a nonsolvent for the syndiotactic vinylaromatic polymer so as to result in the formation of an asymmetric, microporous membrane.
Claim 9
Dependent Claim
22 words
A process according to claim 4 wherein the polar, aprotic solvent is a C 1-4 alkyl, cycloalkyl, aryl or alkaryl N-substituted pyrrolidone.
Claim 10
Dependent Claim
21 words
A process according to claim 4 wherein the polar, aprotic solvent is selected from the group consisting of N-cyclohexyl-2-pyrrolidone and N-methyl-2-pyrrolidone.
Claim 11
Dependent Claim
15 words
A process according to claim 4 wherein the membrane is leached with the contacting substance.
Claim 12
Dependent Claim
12 words
A process according to claim 7 wherein the contacting substance is water.
Claim 13
Dependent Claim
31 words
A process according to claim 4 wherein crystal formation is induced in the membrane by heating the membrane to a temperature above the glass transition temperature of the syndiotactic vinylaromatic polymer.
Claim 14
Dependent Claim
16 words
A process according to claim 9 wherein the syndiotactic vinylaromatic polymer has an oriented molecular structure.
Claim 15
Dependent Claim
23 words
A process according to claim 10 wherein the polymer is oriented by uniaxial or biaxial stretching the membrane while at an orientable temperature.
Claim 16
Dependent Claim
14 words
A process according to claim 4 wherein the syndiotactic vinylaromatic polymer is syndiotactic polystyrene.
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) | 1992-08-21 | 1993-02-20 | 1993-08-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-08-21 | 1997-02-20 | 1997-08-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-08-21 | 2001-02-20 | 2001-08-22 | $7700.00 | Window Closed / Lapsed |