Composite membranes for fluid separations

Claim 2

A composite separation membrane comprising a two-layer composite of a support membrane layer and a permselective membrane layer, said composite separation membrane being prepared by a process comprising: (a) providing a support membrane layer characterized by permeation rates P 1 (A) /l 1 respectively of components A and B of a fluid mixture, wherein l 1 is the thickness of the support membrane layer and P 1 (A) and P 1 (B) are the permeabilities to components A and B; (b) providing a permselective material characterized by permeabilities P 2 (A) and P 2 (B) respectively to said components A and B, and by intrinsic selectivity α; (c) determining an appropriate selectivity α A/B for said composite separation membrane for component A over component B; (d) determining a thickness l 2 for said permselective membrane layer which satisfies the relationship: ##EQU10## (e) coating said support membrane layer with said permselective material to create a permselective membrane layer of thickness l 2 .

Claim 3

The composite separation membrane of claim 1, wherein α A/B is at least 70% of the intrinsic selectivity α of said permselective material.

Claim 4

The composite separation membrane of claim 1, wherein said intrinsic selectivity α of said permselective material is at least 10.

Claim 5

The composite separation membrane of claim 1, wherein said support membrane layer is made from a polymer chosen from the group consisting of polysulfone, polyimides, polyamides, polyetherimide, polyvinylidene fluoride, polyethylene, polypropylene, polyethersulfone and polytetrafluoroethylene.

Claim 6

The composite separation membrane of claim 1, wherein said permselective material is chosen from the group consisting of silicone rubber, chlorosulfonated polyethylene, polysilicone-carbonate copolymers, fluoroelastomers, plasticized polyvinylchloride, polyurethane, polybutadiene, polystyrene-butadiene copolymers, styrene/butadiene/styrene block copolymers, polyacetylene, substituted polyacetylene, polyether/polyamide block copolymers, polymethylpentene, ethylcellulose and cellulose acetates.

Claim 7

A composite separation membrane comprising a two-layer composite of a support membrane layer and a permselective membrane layer, said composite separation membrane being prepared by a process comprising: (a) providing a support membrane layer characterized by permeation rates P 1 (A) /l 1 and P 1 (B) /l 1 respectively of components A and B of a fluid mixture, wherein l 1 is the thickness of the support membrane layer and P 1 (A) and P 1 (B) are the permeabilities to components A and B; (b) providing a permselective material characterized by permeabilities P 2 (A) and P 2 (B) respectively to said components A and B, and by intrinsic selectivity α; (c) determining an appropriate thickness l 2 for said permselective membrane layer; (d) determining a selectivity α A/B for said composite separation membrane for component A over component B, which selectivity satisfies the relationship: ##EQU11## (e) coating said support membrane layer with said permselective material to create a composite separation membrane characterized by selectivity α A/B .

Claim 8

A composite separation membrane comprising a two-layer composite of a support membrane layer and a permselective membrane layer, said composite separation membrane being prepared by a process comprising: (a) providing a support membrane layer characterized by permeation rates P 1 (A) /l 1 and P 1 (B) /l 1 respectively of components A and B of a fluid mixture, wherein l 1 is the thickness of the support membrane layer and P 1 (A) and P 1 (B) are the permeabilities to components A and B; (b) providing a permselective material characterized by permeabilities P 2 (A) and P 2 (B) respectively to said components A and B, and by intrinsic selectivity α; (c) determining an appropriate thickness l 2 for said permselective membrane layer; (d) determining a selectivity α A/B for said composite separation membrane for component A over component B, which selectivity satisfies the relationship: ##EQU11## (e) coating said support membrane layer with said permselective material to create a composite separation membrane characterized by selectivity α A/B .

Claim 9

The composite separation membrane of claim 6, wherein α A/B is at least 70% of the intrinsic selectivity α of said permselective material.

Claim 10

The composite separation membrane of claim 6, wherein said intrinsic selectivity α of said permselective material is at least 10.

Claim 11

The composite separation membrane of claim 6, wherein said support membrane layer is made from a polymer chosen from the group consisting of polysulfone, polyimides, polyamides, polyetherimide, polyvinylidene fluoride, polyethylene, polypropylene, polyethersulfone and polytetrafluoroethylene.

Claim 12

The composite separation membrane of claim 6, wherein said permselective material is chosen from the group consisting of silicone rubber, chlorosulfonated polyethylene, polysilicone-carbonate copolymers, fluoroelastomers, plasticized polyvinylchloride, polyurethane, polybutadiene, polystyrene-butadiene copolymers, styrene/butadiene/styrene block copolymers, polyacetylene, substituted polyacetylene, polyether/polyamide block copolymers, polymethylpentene, ethylcellulose and cellulose acetates.

Claim 13

A composite separation membrane comprising a two-layer composite of a support membrane layer and a permselective membrane layer, said composite separation membrane being prepared by a process comprising: (a) providing a permselective material characterized by permeabilities P 2 (A) and P 2 (B) respectively to components A and B of a fluid mixture and by intrinsic selectivity α; (b) determining an appropriate thickness l 2 for said permselective membrane layer; (c) determining an appropriate selectivity α A/B for said composite separation membrane for said component A over said component B; (d) determining the value of R which satisfies the equation: ##EQU12## wherein R is the ratio l 2 /P 2 (A) /l 1 /P 1 (A), l 1 is the thickness of the support membrane layer, and P 1 (A) is the permeability of the support membrane layer to said component A; (e) determining the permeation rate P 1 (A) /l 1 of said support membrane layer from the value of R that has been determined in step (d); (f) providing a support membrane layer characterized by permeation rate P 1 (A) /l 1 ; (g) coating said support membrane layer with said permselective material to create a composite separation membrane characterized by selectivity α A/B and permselective membrane layer thickness l 2 .

Claim 14

A composite separation membrane comprising a two-layer composite of a support membrane layer and a permselective membrane layer, said composite separation membrane being prepared by a process comprising: (a) providing a permselective material characterized by permeabilities P 2 (A) and P 2 (B) respectively to components A and B of a fluid mixture and by intrinsic selectivity α; (b) determining an appropriate thickness l 2 for said permselective membrane layer; (c) determining an appropriate selectivity α A/B for said composite separation membrane for said component A over said component B; (d) determining the value of R which satisfies the equation: ##EQU12## wherein R is the ratio l 2 /P 2 (A) /l 1 /P 1 (A), l 1 is the thickness of the support membrane layer, and P 1 (A) is the permeability of the support membrane layer to said component A; (e) determining the permeation rate P 1 (A) /l 1 of said support membrane layer from the value of R that has been determined in step (d); (f) providing a support membrane layer characterized by permeation rate P 1 (A) /l 1 ; (g) coating said support membrane layer with said permselective material to create a composite separation membrane characterized by selectivity α A/B and permselective membrane layer thickness l 2 .

Claim 15

The composite separation membrane of claim 11, wherein α A/B is at least 70% of the intrinsic selectivity α of said permselective material.

Claim 16

The composite separation membrane of claim 11, wherein said intrinsic selectivity α of said permselective material is at least 10.

Claim 17

The composite separation membrane of claim 11, wherein said support membrane layer is made from a polymer chosen from the group consisting of polysulfone, polyimides, polyamides, polyetherimide, polyvinylidene fluoride, polyethylene, polypropylene, polyethersulfone and polytetrafluoroethylene.

Claim 18

The composite separation membrane of claim 11, wherein said permselective material is chosen from the group consisting of silicone rubber, chlorosulfonated polyethylene, polysilicone-carbonate copolymers, fluoroelastomers, plasticized polyvinylchloride, polyurethane, polybutadiene, polystyrene-butadiene copolymers, styrene/butadiene/styrene block copolymers, polyacetylene, substituted polyacetylene, polyether/polyamide block copolymers, polymethylpentene, ethylcellulose and cellulose acetates.