EP0266204A2
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EP
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Pressure dependent anisotropic transport membrane system
Assignee: Kingston Technologies Inc
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Filing: 1987-10-29
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Granted: —
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Expires: 2007-10-29
Abstract
Abstract Pressure-dependent anisotropic behavior is provided by a size selective separation membrane system comprising at least two successive porous layers. The first layer comprises a soft, elastic, effectively porous material, and the second layer comprises a substantially rigid porous material. When positive pressure presses the first layer against the second layer, the second layer serves as a rigid support for the first layer, and the first layer is compressible to reduce its effective pore size. The first layer material is characterized by: a) a durometer hardness lower than about 50 (Shore A) and an effective pore size between about 0.001 micron and 0.1 micron when the material is in an unstressed condition; b) sufficient compressibility that, when a pressure differential of 500 psi is applied across its thickness, the first layer reversibly compresses at least 10%, thereby reducing its effective pore size; c) sufficient compressibility, that, when a pressure differential of 100 psi is applied across the thickness of the system, the effective flow rate is reduced by a factor of at least 20 compared to the flow rate when 100 psi is exerted in the opposite direction. A substance can be separated from a liquid mixture using the membrane system, by: positioning the second layer of the membrane system in contact with the mixture; exerting pressure on the mixture to force liquid with the substance first through the pores of the rigid layer and then through the pores of the soft layer of the membrane system; and reversing the flow through the membrane system by exerting pressure on the resulting filtrate, in a manner to compress the soft material sufficiently to reduce the pore size to prevent passage of the substance. The membrane system is manufactured by coagulating the layers from polymers in solution.
Inventors
- 👤 Yatin B. Thakore
- 👤 Karen L. Swanson
- 👤 Vladimir A. Stoy
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 10:03
CPC Classifications
A; A61; A61K; A61K9/00; A61K9/20; A61K9/28; A61K9/2806; A61K9/2833; A61K9/284; B; B01; B01D; B01D61/00; B01D61/14; B01D61/149; B01D69/00; B01D69/02; B01D69/12; B01D69/1214
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
126 words
Pressure-dependent anisotropic-transport membrane system comprising: (a) a first layer of soft elastic reversibly compressible and effectively porous material, and (b) a second layer of rigid effectively porous material, whereby when a pressure differential is applied across said membrane system with a higher pressure exerted against said first layer, said first layer is reversibly compressed against said second layer to reversibly reduce the pore size of said first layer, when said pressure differential is reduced said first layer decompresses from said second layer increasing the pore size of said first layer, and when said pressure differential is reversed with a lower pressure exerted against said first layer said first layer reversibly expands away from second layer to further increase the effective pore size of said first layer.
Claim 2
Dependent Claim
126 words
Pressure-dependent anisotropic-transport membrane system comprising: (a) a first layer of soft elastic reversibly compressible and effectively porous material, and (b) a second layer of rigid effectively porous material, whereby when a pressure differential is applied across said membrane system with a higher pressure exerted against said first layer, said first layer is reversibly compressed against said second layer to reversibly reduce the pore size of said first layer, when said pressure differential is reduced said first layer decompresses from said second layer increasing the pore size of said first layer, and when said pressure differential is reversed with a lower pressure exerted against said first layer said first layer reversibly expands away from second layer to further increase the effective pore size of said first layer.
Claim 3
Dependent Claim
61 words
The pressure-dependent anisotropic-transport membrane system of claim 1, wherein when a pressure differential of between about 100 psi to about 500 psi is applied across said membrane system with the higher pressure exerted on said first layer, said first layer is reversibly compressed against said second layer by at least 10% to reduce the effective pore size of said first layer.
Claim 4
Dependent Claim
70 words
The pressure-dependent anisotropic-transport membrane system of claim 1 or 2, wherein when said pressure differential is 100 psi with the higher pressure being exerted on said first layer, said flow rate through the membrane system is reduced by a factor of at least 20 as compared with the flow rate that results when said 100 psi pressure differential is reversed and said higher pressure is exerted against said second layer.
Claim 5
Dependent Claim
50 words
The pressure-dependent anisotropic-transport membrane system of claim 1, 2 or 3, wherein said first layer has a durometer hardness less than about 50 (Shore A) and an effective pore size ranging from about 0.001 microns to about 0.1 microns when there is no pressure gradient acting across said first layer.
Claim 6
Dependent Claim
62 words
The pressure-dependent anisotropic-transport membrane system of any one of the preceding claims, wherein the first layer is characterised by an effective pore size suitable for microfiltration when a higher pressure is applied to the second layer and an effective pore size suitable for ultrafiltration when a higher pressure is applied to the first layer compressing the first layer against the second layer.
Claim 7
Dependent Claim
29 words
The pressure-dependent anisotropic-transport membrane system of any one of the preceding claims, wherein the second layer is characterised by a durometer hardness of at least about 60 (Shore A).
Claim 8
Dependent Claim
41 words
The pressure-dependent anisotropic-transport membrane system of any one of the preceding claims, wherein in the region adjacent the first layer, the second layer is characterised by an average pore size in the range from about 0.01 microns to about 200 microns.
Claim 9
Dependent Claim
19 words
The pressure-dependent anisotropic-transport membrane system of any one of the preceding claims, wherein said first layer comprises a hydrogel.
Claim 10
Dependent Claim
21 words
The pressure-dependent anisotropic-transport membrane system of claim 8, wherein said hydrogel has a water content of at least 30% by weight.
Claim 11
Dependent Claim
28 words
The pressure-dependent anisotropic-transport membrane system of any one of the preceding claims, wherein said first layer comprises a co-polymer which is the hydrolysis product of acrylonitrile and polyacrylonitrile.
Claim 12
Dependent Claim
19 words
The pressure-dependent anisotropic-transport membrane system of any one of the preceding claims, wherein the second layer comprises 85-100% polyacrylonitrile.
Claim 13
Dependent Claim
42 words
The pressure-dependent anisotropic-transport membrane system of any one of the preceding claims, wherein the first layer is asymmetrically porous, the pores of the first layer being smallest in a thin layer on the side of the soft material opposite the second layer.
Claim 14
Dependent Claim
22 words
The pressure-dependent anisotropic-transport membrane system of any one of the preceding claims, wherein the first and second layer comprise an integral unit.
Claim 15
Dependent Claim
28 words
The pressure-dependent anisotropic-transport membrane system of any one of the preceding claims, further comprising an external supporting mesh having openings substantially larger than the pores of the layers.
Claim 16
Independent Claim
255 words
A method of separating a substance from a fluid mixture by using a pressure-dependent anisotropic-transport membrane system, comprising the steps of: (a) positioning said fluid mixture in contact with a rigid layer of an effectively porous component of said pressure-dependent anisotropic-transport membrane system; (b) exerting a pressure gradient across said pressure-dependent anisotropic-transport membrane system whereby: (i) said pressure gradient causing a higher pressure to act against said rigid layer to force said fluid containing said substance through said rigid layer; (ii) said pressure gradient causing a lower pressure on the other side of said rigid layer, said pressure gradient acting on a soft elastic layer of reversibly compressible and effectively porous component of said pressure-dependent anisotropic-transport membrane system, said pressure gradient causing said soft elastic layer to reversibly expand away from said rigid layer to increase the effective pore size of the soft elastic layer and allow the fluid containing the substance to pass through the soft elastic layer, (c) reversing the pressure gradient across the pressure-dependent anisotripic-transport membrane system whereby: said reversed pressure gradient causing a higher pressure to be exerted against the elastic layer, said reversed pressure gradient reversibly compresses the soft elastic layer against the rigid layer thereby reducing the effective pore size of the soft elastic layer sufficiently to allow the passage of the fluid through the soft elastic layer and then through the rigid layer, but preventing the passage of the substance through the soft elastic layer, whereby the substance is retained on the side of the soft elastic layer.
Claim 17
Independent Claim
255 words
A method of separating a substance from a fluid mixture by using a pressure-dependent anisotropic-transport membrane system, comprising the steps of: (a) positioning said fluid mixture in contact with a rigid layer of an effectively porous component of said pressure-dependent anisotropic-transport membrane system; (b) exerting a pressure gradient across said pressure-dependent anisotropic-transport membrane system whereby: (i) said pressure gradient causing a higher pressure to act against said rigid layer to force said fluid containing said substance through said rigid layer; (ii) said pressure gradient causing a lower pressure on the other side of said rigid layer, said pressure gradient acting on a soft elastic layer of reversibly compressible and effectively porous component of said pressure-dependent anisotropic-transport membrane system, said pressure gradient causing said soft elastic layer to reversibly expand away from said rigid layer to increase the effective pore size of the soft elastic layer and allow the fluid containing the substance to pass through the soft elastic layer, (c) reversing the pressure gradient across the pressure-dependent anisotripic-transport membrane system whereby: said reversed pressure gradient causing a higher pressure to be exerted against the elastic layer, said reversed pressure gradient reversibly compresses the soft elastic layer against the rigid layer thereby reducing the effective pore size of the soft elastic layer sufficiently to allow the passage of the fluid through the soft elastic layer and then through the rigid layer, but preventing the passage of the substance through the soft elastic layer, whereby the substance is retained on the side of the soft elastic layer.
Claim 18
Dependent Claim
59 words
The method of claim 15, whereby step (c) of reversing said pressure gradient further includes controlling said pressure gradient exerted across the soft elastic layer to a predetermined range which maintains an effective pore size in the soft elastic layer and prevents the passage of said substance through the soft elastic layer but allows passage of any other substance.
Claim 19
Dependent Claim
37 words
The method of claim 15 or 16, wherein said mixture includes a second substance too large to pass through the membrane system in either direction, whereby said method effectively separates said first substance from said second substance.
Claim 20
Dependent Claim
80 words
The method of claim 15, 16 or 17, wherein the pressure gradient across said pressure-dependent anisotropic-transport membrane system is periodically reversed, whereby during application of a higher pressure to said soft elastic layer said fluid flowing through said pressure-dependent anisotropic-transport membrane system disrupts the build-up substance on said rigid layer, and whereby during application of higher pressure to said rigid layer said fluid flowing through said pressure-dependent anisotropic-transport membrane system disrupts the build-up of substance on said soft elastic layer.
Claim 21
Independent Claim
88 words
A method for manufacturing pressure-dependent anisotropic-transport membrane system having a rigid substantially porous polymeric layer interfacing with a soft elastic substantially porous reversibly compressible polymeric layer, comprising the steps of: (a) dissolving soft elastic polymer and a rigid polymer in solvent, (b) coagulating said polymers by contacting the solution with a fluid bath in which one of the polymers is more soluble than the other polymer, whereby the first, less soluble polymer coagulates as a first layer, and a second more soluble polymer coagulates as a second layer.
Claim 22
Independent Claim
88 words
A method for manufacturing pressure-dependent anisotropic-transport membrane system having a rigid substantially porous polymeric layer interfacing with a soft elastic substantially porous reversibly compressible polymeric layer, comprising the steps of: (a) dissolving soft elastic polymer and a rigid polymer in solvent, (b) coagulating said polymers by contacting the solution with a fluid bath in which one of the polymers is more soluble than the other polymer, whereby the first, less soluble polymer coagulates as a first layer, and a second more soluble polymer coagulates as a second layer.
Claim 23
Independent Claim
13 words
The method of claims 19, wherein said fluid bath is an aqueous fluid.
Claim 24
Dependent Claim
28 words
The method of claim 19 or 20, wherein the layers are coagulated by spreading the solution on a substrate and then contacting the substrate with said fluid bath.
Claim 25
Dependent Claim
87 words
The method of claim 19, 20 or 21, further comprising the steps of: (a) dissolving said first polymer in a first solution, (b) dissolving said second polymer in a second solution, (c) spreading the first solution on a substrate and coagulating the first solution with a non-solvent of said first polymer to form a first layer, (d) spreading the second solution on the first layer and coagulating the second solution with a non-solvent of said second polymer to form adhering layers of the first and second polymers.
References Cited (Backward Citations)
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