US4764320A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for preparing semipermeable membrane compositions
Assignee: Dow Chemical Co
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Filing: 1987-06-12
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Granted: 1988-08-16
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Expires: 2007-06-12
Abstract
Abstract Semipermeable membranes with improved permeation flux are prepared by contacting a glassy polymer in the form of a hollow fiber or film with a solvent in which the polymer swells at conditions which permit the swelling solvent to diffuse into the glassy polymer and then stretching the swollen polymer in an amount sufficient to cause visible stress whitening.
Inventors
- 👤 Chieh-Chun Chau
- 👤 Lu H. Tung
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 21:34
CPC Classifications
D; D01; D01D; D01D5/00; D01D5/24; B; B01; B01D; B01D67/00; B01D67/0002; B01D67/0023; B01D67/0025; B01D67/0027; B29; B29C; B29C55/00; B29C55/02; B29C55/04; B29C55/10; B29C55/12; C; C08; C08J; C08J7/00; C08J7/02; B29K; B29K2105/00; B29K2105/04; B29K2105/24; B29K2995/00; B29K2995/0037; B29K2995/0039; B29K2995/0065
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
82 words
A method for preparing semipermeable membrane compositions comprising the steps of (a) contacting a glassy polymer in the form of a hollow fiber or film with a solvent in which the polymer swells at conditions to permit the swelling solvent to diffuse into the glassy polymer and cause the polymer to increase in at least one dimension by 5 percent; and then (b) stretching the swollen polymer in at least one major direction in an amount sufficient to cause visible stress whitening.
Claim 2
Independent Claim
82 words
A method for preparing semipermeable membrane compositions comprising the steps of (a) contacting a glassy polymer in the form of a hollow fiber or film with a solvent in which the polymer swells at conditions to permit the swelling solvent to diffuse into the glassy polymer and cause the polymer to increase in at least one dimension by 5 percent; and then (b) stretching the swollen polymer in at least one major direction in an amount sufficient to cause visible stress whitening.
Claim 3
Dependent Claim
23 words
The method of claim 1 wherein the glassy polymer is selected from the group consisting of polysulfone, polyethersulfone, polycarbonate, polymethylmethacrylate, polyarylate and polyvinylchloride.
Claim 4
Dependent Claim
19 words
The method of claim 2 wherein the glassy polymer is selected from the group consisting of polycarbonate and polysulfone.
Claim 5
Dependent Claim
24 words
The method of claim 1 wherein the glassy polymer is crosslinked to a degree effective to increase the tensile strength of the semipermeable membrane.
Claim 6
Dependent Claim
41 words
The method of claim 4 wherein the solvent is selected from the group consisting of saturated aliphatic hydrocarbons having less than 10 carbon atoms, ketones having less than 10 carbon atoms, alcohols having less than 10 carbon atoms, and mixtures thereof.
Claim 7
Dependent Claim
21 words
The method of claim 1 wherein the swelling solvent increases the thickness of the glassy polymer by at least 5 percent.
Claim 8
Dependent Claim
14 words
The method of claim 1 further comprising the step of annealing the finished membrane.
Claim 9
Dependent Claim
56 words
The process of claim 1 wherein the membrane exhibits at least a twofold increase in permeation flux relative to the flux exhibited by the glassy polymer prior to treatment while maintaining a ratio of permeation flux for oxygen to nitrogen of at least 90 percent of the ratio achieved by the glassy polymer prior to treatment.
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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) | 1991-08-16 | 1992-02-15 | 1992-08-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-08-16 | 1996-02-15 | 1996-08-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-08-16 | 2000-02-15 | 2000-08-16 | $7700.00 | Window Closed / Lapsed |