US5006247A — Asymmetric porous polyamide membranes

Claim 1

Independent Claim 144 words

An asymmetric, porous polyamide membrane permeable to fluid flow comprising: (A) a porous skin layer, and (B) adjacent to the skin layer, an integral, porous support layer having at least one region comprising a network of substantially parallel, hollow tube-like structures, each of the tube-like structures being oriented such that the longitudinal dimension of each tube-like structure is essentially perpendicular to the skin layer; wherein: the skin layer is relatively thin and dense compared to the support layer, the pore diameters in the skin layer are relatively small compared to the diameters of the tube-like structures in the support layer, in membranes having support layers with more than one region, the cross-sectional area of the tube-like structures is larger in regions located farther from the skin layer, and the polyamide is an aliphatic polyamide having a glass transition temperature of less than 200° C.

Claim 2

Dependent Claim 144 words

An asymmetric, porous polyamide membrane permeable to fluid flow comprising: (A) a porous skin layer, and (B) adjacent to the skin layer, an integral, porous support layer having at least one region comprising a network of substantially parallel, hollow tube-like structures, each of the tube-like structures being oriented such that the longitudinal dimension of each tube-like structure is essentially perpendicular to the skin layer; wherein: the skin layer is relatively thin and dense compared to the support layer, the pore diameters in the skin layer are relatively small compared to the diameters of the tube-like structures in the support layer, in membranes having support layers with more than one region, the cross-sectional area of the tube-like structures is larger in regions located farther from the skin layer, and the polyamide is an aliphatic polyamide having a glass transition temperature of less than 200° C.

Claim 3

Dependent Claim 23 words

The membrane of claim 1 wherein each tube-like structure in a particular region of the support layer has approximately the same cross-sectional area.

Claim 4

Dependent Claim 12 words

The membrane of claim 1 having an asymmetric ratio greater than 10.

Claim 5

Dependent Claim 19 words

The membrane of claim 1 having an average pore diameter in the skin layer of 0.001 to 10 μm.

Claim 6

Dependent Claim 95 words

The membrane of claim 1 wherein the polyamide is selected from the group consisting of (A) polyamides having the formulas: ##STR2## wherein each R group may be independently selected from the group consisting of H, and alkyl groups having 1 to 4 carbon atoms, and each R 1 and R 2 or R 3 group may be independently selected from the group consisting of linear or branched aliphatic or cycloaliphatic moieties or combinations thereof, wherein said R 1 , R 2 , and R 3 groups can also contain hetero atoms, or (B) blends thereof.

Claim 7

Dependent Claim 44 words

The membrane of claim 5 wherein all R 1 groups in any particular polymer (I) are the same, and all R 2 groups in any particular polymer (I) are the same, and all R 3 groups in any particular polymer (II) are the same.

Claim 8

Dependent Claim 22 words

The membrane of claim 5 wherein R 1 , R 2 and R 3 groups contain from 1 to 12 carbon atoms.

Claim 9

Dependent Claim 26 words

The membrane of claim 1 wherein the polyamide is selected from the group consisting of nylon 6, nylon 6,6, nylon 6,9, copolymers thereof, and blends thereof.

Claim 10

Dependent Claim 17 words

The membrane of claim 1 having an air flux rate of 2.5 to 75 L/kPa(sec)m 2 .

Claim 11

Dependent Claim 11 words

The membrane of claim 1 in the form of a sheet.

Claim 12

Dependent Claim 12 words

The membrane of claim 1 in the form of a hollow fiber.

Claim 13

Dependent Claim 20 words

A supported asymmetric membrane comprising the membrane of claim 1 and a preformed, porous, support layer having two parallel surfaces.

Claim 14

Dependent Claim 22 words

The membrane of claim 12 wherein the support layer is selected from the group consisting of non-woven web, woven cloth and paper.

Claim 15

Dependent Claim 16 words

The membrane of claim 12 wherein the non-woven web is a spun-bonded, nylon 6,6 non-woven web.

Claim 16

Dependent Claim 86 words

The membrane of claim 1 prepared by a process comprising the steps of: (A) preparing a casting solution comprising an aliphatic polyamide, having a glass transition temperature less than 200° C., dissolved in an alcohol/salt solution; (B) coating a film of preselected thickness of the casting solution onto the surface of a casting substrate; (C) exposing the resulting film to a non-solvent liquid bath thereby precipitating the polyamide and forming the porous, asymmetric polyamide membrane; and (D) recovering the membrane from the bath and drying it.

Claim 17

Dependent Claim 42 words

The membrane of claim 15 wherein the process of preparing the membrane further comprises a step after step (B) and before step (C) in which the film of casting solution is exposed to air for a period of up to 120 seconds.

Claim 18

Dependent Claim 18 words

The membrane of claim 15 wherein said alcohol is a lower alkanol or a blend of lower alkanols.

Claim 19

Dependent Claim 32 words

The membrane of claim 17 wherein said alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, and mixtures of ethanol and methanol, ethanol and propanol, and methanol and propanol.

Claim 20

Dependent Claim 34 words

The membrane of claim 15 wherein the salt is selected from the group consisting of anhydrous calcium chloride, calcium chloride dihydrate, calcium iodide tetrahydrate, calcium nitrate tetrahydrate, calcium salicylate, lithium chloride and blends thereof.

Claim 21

Dependent Claim 29 words

The membrane of claim 15 wherein the casting solution comprises 10 to 50 weight percent salt, 47 to 76 weight percent alcohol, and 3 to 14 weight percent polyamide.

Claim 22

Dependent Claim 105 words

The membrane of claim 12 prepared by a process comprising the steps of: (A) preparing a casting solution comprising an aliphatic polyamide, having a glass transition temperature less than 200° C., dissolved in an alcohol/salt solution; (B) coating a film of preselected thickness of the casting solution onto one or both parallel surfaces the porous, preformed support; (C) placing the coated, preformed support on a casting substrate; (D) immersing the coated, preformed support and casting substrate in a non-solvent liquid bath thereby precipitating the polyamide and forming the supported, porous, asymmetric polyamide membrane; and (E) recovering the supported membrane from the bath and drying it.

Claim 23

Dependent Claim 41 words

The membrane of claim 21 wherein the process of preparing the membrane further comprises a step after step (C) and before step (D) in which the coated, preformed support is exposed to air for a period of up to 120 seconds.

Claim 24

Dependent Claim 23 words

The membrane of claim 21 wherein the porous preformed support is selected form the group consisting of non-woven webs, woven fabrics, and paper.

Claim 25

Dependent Claim 83 words

The membrane of claim 11 prepared by a process comprising the steps of: (A) preparing a casting solution comprising an aliphatic polyamide, having a glass transition temperature less than 200° C., dissolved in an alcohol/salt solution; (B) extruding a hollow fiber of the casting solution through an annular die; (C) immersing the resulting fiber in a non-solvent liquid bath thereby precipitating the polyamide and forming the porous, asymmetric, polyamide, hollow fiber membrane; and (D) recovering the membrane from the bath and drying it.

Claim 26

Dependent Claim 42 words

The membrane of claim 24 wherein the process of preparing the membrane further comprises a step after step (B) and before step (C) in which the fiber of casting solution is exposed to air for a period of up to 120 seconds.

Claim 27

Dependent Claim 85 words

A process for making a porous asymmetric membrane comprising the steps of: (A) preparing a casting solution comprising an aliphatic polyamide, having a glass transition temperature less than 200° C., dissolved in an alcohol/salt solution; (B) coating a film of preselected thickness of the casting solution onto the surface of a casting substrate; (C) exposing the resulting film to a non-solvent liquid bath thereby precipitating the polyamide and forming the porous, asymmetric polyamide membrane; and (D) recovering the membrane from the bath and drying it.

Claim 28

Dependent Claim 85 words

A process for making a porous asymmetric membrane comprising the steps of: (A) preparing a casting solution comprising an aliphatic polyamide, having a glass transition temperature less than 200° C., dissolved in an alcohol/salt solution; (B) coating a film of preselected thickness of the casting solution onto the surface of a casting substrate; (C) exposing the resulting film to a non-solvent liquid bath thereby precipitating the polyamide and forming the porous, asymmetric polyamide membrane; and (D) recovering the membrane from the bath and drying it.

Claim 29

Dependent Claim 35 words

The process of claim 26 further comprising a step after step (B) and before step (C) in which the film of casting solution is exposed to air for a period of up to 120 seconds.

Claim 30

Dependent Claim 106 words

A process for preparing a supported, porous asymmetric membrane comprising the steps of: (A) preparing a casting solution comprising an aliphatic polyamide, having a glass transition temperature less than 200° C., dissolved in an alcohol/salt solution; (B) coating a film of preselected thickness of the casting solution onto one or both parallel surfaces of a porous, preformed support; (C) placing the coated, preformed support on a casting substrate; (D) immersing the coated, preformed support and casting substrate in a non-solvent liquid bath thereby precipitating the polyamide and forming the supported, porous, asymmetric polyamide membrane; and (E) recovering the supported membrane from the bath and drying it.

Claim 31

Dependent Claim 106 words

A process for preparing a supported, porous asymmetric membrane comprising the steps of: (A) preparing a casting solution comprising an aliphatic polyamide, having a glass transition temperature less than 200° C., dissolved in an alcohol/salt solution; (B) coating a film of preselected thickness of the casting solution onto one or both parallel surfaces of a porous, preformed support; (C) placing the coated, preformed support on a casting substrate; (D) immersing the coated, preformed support and casting substrate in a non-solvent liquid bath thereby precipitating the polyamide and forming the supported, porous, asymmetric polyamide membrane; and (E) recovering the supported membrane from the bath and drying it.

Claim 32

Dependent Claim 34 words

The process of claim 28 further comprising a step after step (C) and before step (D) in which the coated, preformed support is exposed to air for a period of up to 120 seconds.

Claim 33

Dependent Claim 84 words

A process of preparing a porous, asymmetric hollow fiber member comprising the steps of: (A) preparing a casting solution comprising an aliphatic polyamide, having a glass transition temperature less than 200° C., dissolved in an alcohol/salt solution; (B) extruding a hollow fiber of the casting solution through an annular die; (C) immersing the resulting fiber in a non-solvent liquid bath thereby precipitating the polyamide and forming the porous, asymmetric, polyamide, hollow fiber membrane; and (D) recovering the membrane from the bath and drying it.

Claim 34

Dependent Claim 84 words

A process of preparing a porous, asymmetric hollow fiber member comprising the steps of: (A) preparing a casting solution comprising an aliphatic polyamide, having a glass transition temperature less than 200° C., dissolved in an alcohol/salt solution; (B) extruding a hollow fiber of the casting solution through an annular die; (C) immersing the resulting fiber in a non-solvent liquid bath thereby precipitating the polyamide and forming the porous, asymmetric, polyamide, hollow fiber membrane; and (D) recovering the membrane from the bath and drying it.

Claim 35

Dependent Claim 35 words

The process of claim 30 further comprising a step after step (B) and before step (C) in which the fiber of casting solution is exposed to air for a period of up to 20 seconds.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1994-04-08	1994-10-08	1995-04-09	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1998-04-08	1998-10-08	1999-04-09	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2002-04-08	2002-10-08	2003-04-09	$7700.00	Window Closed / Lapsed

Asymmetric porous polyamide membranes

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