US4248913A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for preparing a membrane
Assignee: Kovalus Separation Solutions LLC
•
Filing: 1979-05-24
•
Granted: 1981-02-03
•
Expires: 1999-05-24
Abstract
Abstract A process for preparing a microporous polymeric membrane, which process comprises preparing a polymer-casting solution, casting a thin film of the casting solution on a support base, allowing partial evaporation of the solvent from the cast film for a predetermined period of time and contacting the partially evaporated cast film with the microporous leaching liquid to provide a membrane, the improvement which comprises: providing a casting solution which comprises a vinylidene fluoride polymer and from about 35 to about 85% by weight of a vinyl acetate polymer; and hydrolyzing the acetate polymer after the leaching step to convert the acetate groups to hydroxyl groups, to provide an improved membrane having good mechanical strength and hydrophilic properties.
Inventors
- 👤 Stephen Z. Jakabhazy
- 👤 Leos J. Zeman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 18:53
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/30; B01D71/32; B01D71/34; B01D67/00; B01D67/0081; B01D67/0093; B01D67/00931; B01D71/38; B01D71/381; B01D71/383
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
123 words
In a process for preparing a microporous polymeric membrane, which process comprises preparing a membrane-casting solution, casting a thin film of the casting solution on a support base, allowing partial evaporation of the solvent from the cast film for a predetermined period of time and contacting the partially evaporated cast film with a leaching liquid to provide the microporous membrane, the improvement which comprises: (a) providing a casting solution which comprises a vinylidene fluoride polymer and from about 35 to about 85 weight percent per total polymer of a vinyl acetate polymer; and (b) hydrolyzing the vinyl acetate polymer in the leached membrane to convert the acetate groups to hydroxyl groups and provide an improved membrane having good mechanical strength and hydrophilic properties.
Claim 2
Dependent Claim
123 words
In a process for preparing a microporous polymeric membrane, which process comprises preparing a membrane-casting solution, casting a thin film of the casting solution on a support base, allowing partial evaporation of the solvent from the cast film for a predetermined period of time and contacting the partially evaporated cast film with a leaching liquid to provide the microporous membrane, the improvement which comprises: (a) providing a casting solution which comprises a vinylidene fluoride polymer and from about 35 to about 85 weight percent per total polymer of a vinyl acetate polymer; and (b) hydrolyzing the vinyl acetate polymer in the leached membrane to convert the acetate groups to hydroxyl groups and provide an improved membrane having good mechanical strength and hydrophilic properties.
Claim 3
Dependent Claim
27 words
The process of claim 1 wherein the vinylidene fluoride polymer is a substantially regular and linear vinylidene fluoride polymer having a high content of a crystalline phase.
Claim 4
Dependent Claim
23 words
The process of claim 1 wherein the vinyl acetate polymer is polyvinyl acetate having a molecular weight of more than about 1,000,000 daltons.
Claim 5
Dependent Claim
29 words
The process of claim 1 wherein the casting solution comprises a polar solvent selected from the group consisting of dimethyl acetamide, dimethyl formamide, N-methyl pyrrolidone, dimethyl sulfoxide and acetone.
Claim 6
Dependent Claim
30 words
The process of claim 1 wherein the casting solution comprises a solvent and a diluent, and wherein the diluent is selected from the group consisting of triethyl phosphate and sulfolane.
Claim 7
Dependent Claim
21 words
The process of claim 1 wherein the casting solution comprises dimethyl formamide as a solvent and triethyl phosphate as a diluent.
Claim 8
Dependent Claim
20 words
The process of claim 1 wherein the casting solution comprises N-methyl pyrrolidone as a solvent and sulfolane as a diluent.
Claim 9
Dependent Claim
22 words
The process of claim 1 wherein the casting solution is cast in a thin film onto a porous and fibrous support base.
Claim 10
Dependent Claim
24 words
The process of claim 1 wherein the film is cast in a thickness of about 5 to 50 mils on a porous support base.
Claim 11
Dependent Claim
23 words
The process of claim 1 wherein the film is hydrolyzed by contacting the membrane with sulfuric acid under hydrolyzing time and temperature conditions.
Claim 12
Dependent Claim
43 words
The process of claim 1 wherein the time of exposure to air of the film is between about 1 and 60 seconds, and wherein the temperature of the leaching liquid is between about 40° to 80° C. and the leaching liquid is water.
Claim 13
Dependent Claim
20 words
The process of claim 1 wherein the casting solution comprises acetone as a solvent and triethyl phosphate as a diluent.
Claim 14
Dependent Claim
23 words
The process of claim 1 wherein the casting solution comprises from about 60 to 80 percent by weight of a vinyl acetate polymer.
Claim 15
Dependent Claim
20 words
The process of claim 1 wherein the casting solution comprises from about 10 to 30% by weight of the polymer.
Claim 16
Dependent Claim
22 words
The process of claim 1 wherein the leaching liquid comprises water and the leaching temperature is from about 40° to 80° C.
Claim 17
Dependent Claim
25 words
The process of claim 1 which comprises hydrolyzing substantially all of the vinyl acetate polymer to convert all of the vinyl acetate to vinyl alcohol.
Claim 18
Dependent Claim
21 words
The process of claim 1 which comprises hydrolyzing the leached membrane by a nonaqueous sodium methanolate-catalyzed methanolysis of the vinyl acetate.
Claim 19
Dependent Claim
19 words
The process of claim 1 which comprises hydrolyzing the leached membrane by an aqueous acid or base-catalyzed hydrolysis reaction.
Claim 20
Dependent Claim
45 words
The process of claim 1 wherein the vinyl acetate polymer is polyvinyl acetate having a molecular weight of more than about 1,000,000 daltons and the vinylidene fluoride polymer is a substantially regular and linear vinylidene fluoride polymer having a high content of a crystalline phase.
Claim 21
Dependent Claim
22 words
The process of claim 1 which includes grafting vinyl monomers onto the membrane by reaction with the hydroxyl groups of the membrane.
Claim 22
Dependent Claim
21 words
The process of claim 20 which includes the reaction of styrene sulfonic acid monomers with the hydroxyl groups of the membrane.
Claim 23
Dependent Claim
164 words
In a process for preparing a microporous polymeric membrane, which process comprises preparing a membrane-casting solution, casting a thin film of the casting solution on a support base, allowing partial evaporation of the solvent from the cast film for a predetermined period of time and contacting the partially evaporated cast film with a leaching liquid to provide the microporous membrane, the improvement which comprises: (a) providing a casting solution which comprises an aprotic polar solvent and a diluent, a vinylidene fluoride polymer substantially regular and linear in structure with a high content of a crystalline phase, and from about 35 to 85 weight percent per total polymer of a vinyl acetate polymer having a molecular weight of over about 1,000,000 daltons; and (b) hydrolyzing the vinyl acetate polymer in the leached membrane by contacting the membrane with a hydrolyzing acid to provide an improved membrane containing a vinylidene fluoride polymer and a vinyl alcohol polymer, the membrane having good mechanical strength and hydrophilic properties.
Claim 24
Dependent Claim
164 words
In a process for preparing a microporous polymeric membrane, which process comprises preparing a membrane-casting solution, casting a thin film of the casting solution on a support base, allowing partial evaporation of the solvent from the cast film for a predetermined period of time and contacting the partially evaporated cast film with a leaching liquid to provide the microporous membrane, the improvement which comprises: (a) providing a casting solution which comprises an aprotic polar solvent and a diluent, a vinylidene fluoride polymer substantially regular and linear in structure with a high content of a crystalline phase, and from about 35 to 85 weight percent per total polymer of a vinyl acetate polymer having a molecular weight of over about 1,000,000 daltons; and (b) hydrolyzing the vinyl acetate polymer in the leached membrane by contacting the membrane with a hydrolyzing acid to provide an improved membrane containing a vinylidene fluoride polymer and a vinyl alcohol polymer, the membrane having good mechanical strength and hydrophilic properties.
References Cited (Backward Citations)
US3247133A
Cited
US2884387A
Cited
US3216882A
Cited
US3194727A
Cited
US3276996A
Cited
US3615024A
Cited
US3750735A
Cited
US3951621A
Cited
US4113912A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-02-03 | 1984-08-04 | 1985-02-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-02-03 | 1988-08-04 | 1989-02-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-02-03 | 1992-08-04 | 1993-02-03 | $7700.00 | Window Closed / Lapsed |