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US4775703A
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Process for preparing microporous polyvinylidene fluoride membranes
Assignee: IONICS INCORPORATED 65 GROVE STREET WATERTOWN MASSACHUSETTS 02172
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Filing: 1988-02-22
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Granted: 1988-10-04
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Expires: 2008-02-22
Abstract
Abstract A process for preparing assymetric polyvinylidene fluoride microporous membranes using novel pore forming agents of an ammonium salt which is a non-solvent for the polymeric casting solution; such agents for example being ammonium hydroxide, ammonium chloride and the like.
Inventors
- 👤 Thomas J. Susa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:27
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/26; B; B01; B01D; B01D67/00; B01D67/0002; B01D67/0009; B01D67/0011; B01D71/00; B01D71/06; B01D71/30; B01D71/32; B01D71/34; C08J9/28; C08J2327/00; C08J2327/02; C08J2327/12; C08J2327/16
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
76 words
A casting solution adapted to be partially evaporated to form a film for subsequent conversion into a microporous membrane by leaching, said casting solution comprising about 14-21 wt. % of vinylidene fluoride polymer, 79-86 wt. % of a polar solvent capable of dissolving said polymer and between about 0.05-500 parts per million of a pore forming agent selected from the group consisting of ammonium hydroxide, ammonium acetate, ammonium bifluoride, ammonium carbonate, ammonium chloride and ammonium thiocyanate.
Claim 2
Dependent Claim
76 words
A casting solution adapted to be partially evaporated to form a film for subsequent conversion into a microporous membrane by leaching, said casting solution comprising about 14-21 wt. % of vinylidene fluoride polymer, 79-86 wt. % of a polar solvent capable of dissolving said polymer and between about 0.05-500 parts per million of a pore forming agent selected from the group consisting of ammonium hydroxide, ammonium acetate, ammonium bifluoride, ammonium carbonate, ammonium chloride and ammonium thiocyanate.
Claim 3
Dependent Claim
34 words
The casting solution of claim 1 wherein the solvent is selected from the group consisting of dimethyl acetamide, dimethyl formamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, diethyl acetamide, triethyl phosphate, hexamethly phosphoramide, propylene carbonate, tetramethylurea and acetone.
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) | 1991-10-04 | 1992-04-04 | 1992-10-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-10-04 | 1996-04-04 | 1996-10-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-10-04 | 2000-04-04 | 2000-10-04 | $7700.00 | Window Closed / Lapsed |