US4681605A
Expired / Lapsed
US
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Anisotropic membranes for gas separation
Assignee: Amersham Biosciences Membrane Separations Corp
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Filing: 1985-06-27
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Granted: 1987-07-21
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Expires: 2005-06-27
Abstract
Abstract A gas separation membrane has a dense separating layer about 10,000 Angstroms or less thick and a porous support layer 10 to 400 microns thick that is an integral unit with gradually and continuously decreasing pore size from the base of the support layer to the surface of the thin separating layer and is made from a casting solution comprising ethyl cellulose and ethyl cellulose-based blends, typically greater than 47.5 ethoxyl content ethyl cellulose blended with compatible second polymers, such as nitrocellulose. The polymer content of the casting solution is from about 10% to about 35% by weight of the total solution with up to about 50% of this polymer weight a compatible second polymer to the ethyl cellulose in a volatile solvent such as isopropanol, methylacetate, methanol, ethanol, and acetone. Typical nonsolvents for the casting solutions include water and formamide. The casting solution is cast in air from about zero to 10 seconds to allow the volatile solvent to evaporate and then quenched in a coagulation bath, typically water, at a temperature of 7°-25° C. and then air dried at ambient temperature, typically 10°-30° C.
Inventors
- 👤 Arye Z. Gollan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 17:26
CPC Classifications
D; D01; D01D; D01D5/00; D01D5/24; B; B01; B01D; B01D67/00; B01D67/0002; B01D67/0009; B01D67/00091; B01D69/00; B01D69/02; B01D69/08; B01D69/12; B01D71/00; B01D71/06; B01D71/08; B01D71/12; B01D71/22; B01D2323/00; B01D2323/08; B01D2323/081; B01D2323/12; B01D2325/00; B01D2325/02; B01D2325/022; Y; Y10; Y10S; Y10S264/00; Y10S264/14
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
151 words
A method of making anisotropic membranes for gas separation which method includes the steps of, forming a casting solution having a base polymer of ethyl cellulose with at least substantially 2.2 ethoxyl groups per anhydroglucose unit and a nonsolvent compatible with said base polymer in a solvent system including at least one solvent having relatively high volatility with a low boiling point below 100° C., casting a membrane precursor with said casting solution, exposing said cast membrane precursor to air for a short time interval significantly less than a minute to cause sufficient solvent loss to form an integral skin layer, and then immersing the cast membrane precursor into a leaching agent that dissolves said nonsolvent but not said base polymer sufficiently long to dissolve said nonsolvent and form an anisotropic membrane with pores and an integral, essentially imperfection-free separating skin layer comprising said ethyl cellulose, and then drying said membrane.
Claim 2
Independent Claim
151 words
A method of making anisotropic membranes for gas separation which method includes the steps of, forming a casting solution having a base polymer of ethyl cellulose with at least substantially 2.2 ethoxyl groups per anhydroglucose unit and a nonsolvent compatible with said base polymer in a solvent system including at least one solvent having relatively high volatility with a low boiling point below 100° C., casting a membrane precursor with said casting solution, exposing said cast membrane precursor to air for a short time interval significantly less than a minute to cause sufficient solvent loss to form an integral skin layer, and then immersing the cast membrane precursor into a leaching agent that dissolves said nonsolvent but not said base polymer sufficiently long to dissolve said nonsolvent and form an anisotropic membrane with pores and an integral, essentially imperfection-free separating skin layer comprising said ethyl cellulose, and then drying said membrane.
Claim 3
Dependent Claim
20 words
A method in accordance with claim 1 wherein said casting solution contains about 10% to 35% by weight of polymer.
Claim 4
Dependent Claim
20 words
A method in accordance with claim 2 wherein said casting solution contains about 14% to 25% by weight of polymer.
Claim 5
Dependent Claim
19 words
A method in accordance with claim 2 wherein said base polymer has an ethoxyl content of at least 45%.
Claim 6
Dependent Claim
20 words
A method in accordance with claim 4 wherein said base polymer has an ethoxyl content within the range of 4.75-52%.
Claim 7
Dependent Claim
21 words
A method in accordance with claim 4 wherein said nonsolvent is 10% to about 50% by weight of said casting solution.
Claim 8
Dependent Claim
28 words
A method in accordance with claim 2 wherein the degree of substitution of ethoxyl for the hydroxyl groups of said ethyl cellulose polymeric material is at least 2.25.
Claim 9
Dependent Claim
20 words
A method in accordance with claim 7 wherein said degree of substitution is within the range of 2.42 to 3.0.
Claim 10
Dependent Claim
91 words
A method in accordance with claim 1 and further including the steps of spinning said casting solution to form a hollow filament having a bore, injecting a fluid into said bore, exposing the outside of the fiber to an environment that induces solvent evaporation and formation of the integral gas separating thin layer for a time interval within the range just above zero to about 10 seconds, immersing the fiber in a coagulating medium for a time at least sufficient to insure solidification of the filament, and then drying the filament.
Claim 11
Dependent Claim
13 words
A method in accordance with claim 1 wherein said casting solution includes nitrocellulose.
Claim 12
Dependent Claim
32 words
A method in accordance with claim 1 wherein the at least one solvent of relatively high volatility is a solvent from the group consisting of isopropanol, methyl acetate, methanol, ethanol, and acetone.
Claim 13
Dependent Claim
23 words
A method in accordance with claim 11 wherein the nonsolvent in said casting solutin is from the group consisting of water and formamide.
Claim 14
Dependent Claim
23 words
A method in accordance with claim 1 wherein the nonsolvent in said casting solution is from the group consisting of water and formamide.
Claim 15
Dependent Claim
28 words
An anisotropic membrane with pores and an integral essentially imperfection-free separating skin layer for gas separation comprising ethyl cellulose made in accordance with the method of claim 1.
Claim 16
Dependent Claim
40 words
A membrane and made in accordance with the method of claim 1 formed from a casting solution comprising ethyl cellulose with a porous substrate coated with an anisotropic porous membrane of thickness significantly less than that of said porous substrate.
Claim 17
Dependent Claim
18 words
A membrane in accordance with claim 15 wherein said coating is formed of an anisotropic ethyl cellulose-based membrane.
Claim 18
Dependent Claim
38 words
A membrane in accordance with claim 16 wherein the thickness of said anisotropic membrane coating is less than of the order of 10,000 Angstroms and that of said porous substrate is within the range of substantially 10-400 microns.
Claim 19
Dependent Claim
38 words
A membrane in accordance with claim 15 wherein the thickness of said anisotropic membrane coating is less than of the order of 10,000 Angstroms and that of said porous substrate is within the range of substantially 10-400 microns.
Claim 20
Dependent Claim
28 words
A dense ethyl cellulose membrane and made in accordance with the method of claim 1 formed from a casting solution having an ethyoxyl content of at least 47.5%.
Claim 21
Dependent Claim
27 words
A dense ethyl cellulose membrane in accordance with claim 19 having a porous substrate formed with a coating of thickness significantly less than that of said substrate.
Claim 22
Dependent Claim
20 words
A dense ethyl cellulose membrane in accordance with claim 19 wherein said dense ethyl cellulose membrane is a thin coating.
Claim 23
Dependent Claim
26 words
A dense ethyl cellulose membrane in accordance with claim 21 wherein the thickness of said thin coating is less than of the order of 10,000 Angstroms.
Claim 24
Dependent Claim
19 words
A dense ethyl cellulose membrane in accordance with claim 19 wherein said dense ethyl cellulose membrane is a substrate.
Claim 25
Dependent Claim
24 words
A dense ethyl cellulose membrane in accordance with claim 23 wherein the thickness of said substrate is within the range of substantially 10-400 microns.
Claim 26
Dependent Claim
20 words
A dense ethyl cellulose membrane in accordance with claim 19 wherein said dense ethyl cellulose membrane is a self-standing sheet.
Claim 27
Dependent Claim
20 words
A dense ethyl cellulose membrane in accordance with claim 19 wherein said dense ethyl cellulose membrane is a hollow fiber.
Claim 28
Dependent Claim
24 words
A method in accordance with claim 1 wherein said casting solution includes a second polymer compatible with said base polymer in said casting solution.
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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) | 1990-07-20 | 1991-01-19 | 1991-07-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-07-20 | 1995-01-19 | 1995-07-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-07-20 | 1999-01-19 | 1999-07-21 | $7700.00 | Window Closed / Lapsed |