US4089759A
Expired / Lapsed
US
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Method for improving selectivity of membranes used in chlor-alkali cells
Assignee: BASF Corp
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Filing: 1976-10-04
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Granted: 1978-05-16
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Expires: 1996-10-04
Abstract
Abstract Membranes for use in chlor-alkali cells, made of a copolymer of tetrafluoroethylene and sulfonylfluoride perfluorovinyl ether, have their selectivity improved, with resulting substantial decrease in consumption of electric power per mole of sodium hydroxide produced, by being heat-treated at 100 to 275° Centigrade for several hours to four minutes. The current efficiency is substantially increased, and the power consumption, per unit of sodium hydroxide produced, is usually decreased by about 10 percent or more.
Inventors
- 👤 Michael Krumpelt
- 👤 Stanley Tariho Hirozawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 15:05
CPC Classifications
C; C08; C08J; C08J5/00; C08J5/20; C08J5/22; C08J5/2287; C08J5/2293; C08J2327/00; C08J2327/02; C08J2327/12; C08J2327/18; C08J2371/00; C08J2371/08; C08J2371/10; C08J2371/12
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
81 words
A method for improving the selectivity of a membrane consisting of copolymerized polytetrafluoroethylene and sulfonated perfluorinated polyvinyl ether in the salt or fill acid form, having an equivalent weight number of approximately 1000 to 1500 and a thickness of approximately 0.1 to 0.5 millimeters, said method comprising the step of thermally treating in a non-aqueous environment said membrane prior to use by subjecting it to a temperature of 100° to 275° Centigrade for a period of several hours to 4 minutes.
Claim 2
Independent Claim
81 words
A method for improving the selectivity of a membrane consisting of copolymerized polytetrafluoroethylene and sulfonated perfluorinated polyvinyl ether in the salt or fill acid form, having an equivalent weight number of approximately 1000 to 1500 and a thickness of approximately 0.1 to 0.5 millimeters, said method comprising the step of thermally treating in a non-aqueous environment said membrane prior to use by subjecting it to a temperature of 100° to 275° Centigrade for a period of several hours to 4 minutes.
Claim 3
Dependent Claim
27 words
A method as defined in claim 1 wherein during said step said membrane is subjected to a substantial pressure of up to 9.76 kilograms per square centimeter.
Claim 4
Dependent Claim
33 words
A method as defined in claim 2, wherein said step of thermally treating said membrane is conducted at a temperature of 175° to 225° Centigrade for a time of 5 to 12 minutes.
Claim 5
Dependent Claim
34 words
A method as defined in claim 1, wherein said step of thermally treating said membrane is conducted at a temperature of 175° to 225° Centigrade for a time of 3 hours to 1/2 hour.
Claim 6
Dependent Claim
18 words
A method as defined in claim 1, wherein said membrane has a thickness of 0.1 to 0.25 millimeters.
Claim 7
Dependent Claim
9 words
A membrane made by the method of claim 1.
Claim 8
Dependent Claim
104 words
In a method of electrolyzing an alkali-metal halide by subjecting an aqueous solution of said halide to electrolysis in a cell having anode and cathode compartments separated by membrane members consisting of copolymerized tetrafluoroethylene and sulfonated perfluorinated vinyl ether, in the salt or free acid form, having an equivalent weight number of approximately 1000 to 1500 and a thickness of approximately 0.1 to 0.25 millimeters, the improvement which consists in the step of thermally treating in a non-aqueous environment said membrane prior to use in said cell at a temperature of 100° to 275° Centigrade for a period of several hours to 4 minutes.
Claim 9
Dependent Claim
104 words
In a method of electrolyzing an alkali-metal halide by subjecting an aqueous solution of said halide to electrolysis in a cell having anode and cathode compartments separated by membrane members consisting of copolymerized tetrafluoroethylene and sulfonated perfluorinated vinyl ether, in the salt or free acid form, having an equivalent weight number of approximately 1000 to 1500 and a thickness of approximately 0.1 to 0.25 millimeters, the improvement which consists in the step of thermally treating in a non-aqueous environment said membrane prior to use in said cell at a temperature of 100° to 275° Centigrade for a period of several hours to 4 minutes.
Claim 10
Dependent Claim
26 words
An improvement as defined in claim 7, wherein during said step said membrane is subjected to a pressure of up to 9.76 kilograms per square centimeter.
Claim 11
Dependent Claim
33 words
An improvement as defined in claim 8, wherein said step of thermally treating said membrane is conducted at a temperature of 175° to 225° Centigrade for a time of 5 to 12 minutes.
Claim 12
Dependent Claim
34 words
An improvement as defined in claim 7, wherein said step of thermally treating said membrane is conducted at a temperature of 175° to 225° Centigrade for a time of 3 hours to 1/2 hour.
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) | 1981-05-15 | 1981-11-14 | 1982-05-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-05-15 | 1985-11-14 | 1986-05-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-05-15 | 1989-11-14 | 1990-05-16 | $7700.00 | Window Closed / Lapsed |