Patent US4990165A successfully refreshed from Google Patents.
US4990165A
Expired / Lapsed
US
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Permeable membranes for enhanced gas separation
Assignee: Praxair Technology Inc
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Filing: 1989-09-27
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Granted: 1991-02-05
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Expires: 2009-09-27
Abstract
Abstract Composite membranes are prepared by depositing a separation layer on an asymmetric support layer. The separation layer has a selectivity equal to or greater than that of the material of the asymmetric support layer for a desired gas separation. The support layer is desirable produced in non-asymmetric form, and exposed to an elevated temperature approaching the glass transition temperature of the support layer material under non-swelling conditions to modify the structure thereof to create asymmetry therein, before or after the deposition of the separation layer, and to increase its compaction resistance and collapse pressure. Such desirable properties are conveniently achieved on a repeatable basis, enhancing the uniformity and reliability of the treated support layer and of composite membranes produced therefrom, for use in gas separation operations.
Inventors
- 👤 Benjamin Bikson
- 👤 James E. Miller
- 👤 Joyce K. Nelson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 13:37
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0081; B01D67/0083; B01D53/00; B01D53/22; B01D53/228; B01D69/00; B01D69/12
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
169 words
An asymmetric membrane having enhanced gas separation characteristics comprising a relatively thin dense semipermeable skin region and a less dense, porous non-selective support region that serves to preclude the collapse of the skin region under pressure, said skin region being capable of selectively permeating a more readily permeable component of a feed mixture to be separated at a desirably high permeation rate, said membrane having washed and dried, and having been exposed in essentially dry form to an elevated temperature of from about 15° C. to about 1° C. less than the glass transition temperature of the membrane material under non-swelling conditions for a period of time sufficient to modify the membrane structure to create asymmetry therein and to increase its compaction resistance and collapse pressure, whereby said asymmetric membrane exhibits enhanced selectivity and permeability characteristics, and advantageous combinations of selectivity and permeability, together with desirable compaction resistance and collapse pressure, on a repeatable basis, enhancing the uniformity and reliability of the membrane for use in gas separation operations.
Claim 2
Dependent Claim
169 words
An asymmetric membrane having enhanced gas separation characteristics comprising a relatively thin dense semipermeable skin region and a less dense, porous non-selective support region that serves to preclude the collapse of the skin region under pressure, said skin region being capable of selectively permeating a more readily permeable component of a feed mixture to be separated at a desirably high permeation rate, said membrane having washed and dried, and having been exposed in essentially dry form to an elevated temperature of from about 15° C. to about 1° C. less than the glass transition temperature of the membrane material under non-swelling conditions for a period of time sufficient to modify the membrane structure to create asymmetry therein and to increase its compaction resistance and collapse pressure, whereby said asymmetric membrane exhibits enhanced selectivity and permeability characteristics, and advantageous combinations of selectivity and permeability, together with desirable compaction resistance and collapse pressure, on a repeatable basis, enhancing the uniformity and reliability of the membrane for use in gas separation operations.
Claim 3
Dependent Claim
12 words
The membrane of claim 1 in which the membrane material comprises polysulfone.
Claim 4
Dependent Claim
14 words
The membrane of claim 1 in which said desired form comprises hollow fiber form.
Claim 5
Dependent Claim
15 words
The membrane of claim 1 in which said non-swelling conditions comprise a heated gas atmosphere.
Claim 6
Dependent Claim
16 words
The membrane of claim 1 in which said heated gas atmosphere comprises hot, essentially dry air.
Claim 7
Dependent Claim
38 words
The membrane of claim 1 in which said non swelling conditions comprise a bath of non-swelling liquid, the exposure of said membrane thereto being for a period of time not sufficient to cause the collapse of said membrane.
Claim 8
Dependent Claim
111 words
In the process of preparing a polymeric membrane capable of selectively permeating a more readily permeable component of a feed gas mixture in which said membrane is produced in a desired porous form, washed and dried, the improvement comprising exposing said membrane in essentially dry form to an elevated temperature of from about 15° C. to about 1° C. less than the glass transition temperature of the membrane material under non-swelling conditions for a period of time sufficient to modify the membrane structure to form asymmetry therein, with increased compaction resistance and collapse pressure, whereby the uniformity and reliability of the treated membrane is enhanced for use in gas separation operations.
Claim 9
Dependent Claim
111 words
In the process of preparing a polymeric membrane capable of selectively permeating a more readily permeable component of a feed gas mixture in which said membrane is produced in a desired porous form, washed and dried, the improvement comprising exposing said membrane in essentially dry form to an elevated temperature of from about 15° C. to about 1° C. less than the glass transition temperature of the membrane material under non-swelling conditions for a period of time sufficient to modify the membrane structure to form asymmetry therein, with increased compaction resistance and collapse pressure, whereby the uniformity and reliability of the treated membrane is enhanced for use in gas separation operations.
Claim 10
Dependent Claim
16 words
The process of claim 7 in which said non swelling conditions comprise a heated gas atmosphere.
Claim 11
Dependent Claim
27 words
The process of claim 8 in which the membrane is exposed to said elevated temperature for a period of from about 5 seconds to about 5 minutes.
Claim 12
Dependent Claim
20 words
The process of claim 9 in which said period of time is from about 30 seconds to about 4 minutes.
Claim 13
Dependent Claim
12 words
The process of claim 7 in which said polymeric membrane comprises polysulfone.
Claim 14
Dependent Claim
16 words
The process of claim 7 in which said heated gas atmosphere comprises hot, essentially dry air.
Claim 15
Dependent Claim
43 words
The process of claim 7 in which the membrane is exposed to said elevated temperature under non-swelling conditions by passing the membrane through a bath of non swelling liquid for a period of time not sufficient to cause the collapse of said membrane.
Claim 16
Dependent Claim
21 words
The process of claim 3 in which said non-swelling liquid comprises silicone oil, and including washing and drying the treated membrane.
Claim 17
Dependent Claim
15 words
The process of claim 14 in which said treated membrane is in hollow fiber form.
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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) | 1994-02-04 | 1994-08-06 | 1995-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-02-04 | 1998-08-06 | 1999-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-02-04 | 2002-08-06 | 2003-02-05 | $7700.00 | Window Closed / Lapsed |