Reverse osmosis membrane and process for making the same

Claim 2

A reverse osmosis membrane including an active layer and a physical support for the active layer in which the improvement comprises: the active layer consisting essentially of a continuous, non-porous, uniform film of an organic, film-forming polymer which is substantially inert in the presence of an oxidizing agent having a sufficient oxidizing potential to serve as a sterilizing agent, said film being from about 50 to about 1500°A thick and being capable of dissolving an amount of water equal to at least two percent by weight of the weight of the film.

Claim 3

A membrane as claimed in claim 1 wherein: said membrane includes a continuous, non-porous layer of an irreversible hydrogel composition containing at least one hydrogel-forming polymer and water, said hydrogel layer being located between said support and said active layer.

Claim 4

A membrane as claimed in claim 2 wherein: said hydrogel layer is from about 0.1 to about 5 microns thick when dry, said hydrogel forming polymer is capable of absorbing an amount of water equal to at least 150 percent of its own weight, said polymer in said hydrogel layer being present in the form of swollen polymer coils of polymer chains of a molecular weight of from about 30,000 to about 5,000,000.

Claim 5

A membrane as claimed in claim 2 wherein: said hydrogel layer is from about 2 to about 3 microns thick when dry, said polymer in said hydrogel layer is capable of absorbing an amount of water equal to at least 15 times the weight of said hydrogel forming polymer and is incapable of absorbing an amount of water in excess of about 200 times of its own weight, said hydrogel forming polymer in said hydrogel layer is present in the form of swollen polymer coils of polymer chains of the molecular weight of from about 500,000 to about 3,000,000.

Claim 6

A membrane as claimed in claim 1 wherein: said film-forming polymer is a polymer selected from the group consisting of hydrophilic, partially hydrolyzed polyvinyl ester, epoxy and phenolic polymers.

Claim 7

A membrane as claimed in claim 5 wherein: said film-forming polymer is capable of dissolving an amount of water equal to from about 2 to about 20 percent of its own weight, and said film is from about 50 0 A to about 1500°A thick.

Claim 8

A membrane as claimed in claim 5 wherein: said film-forming polymer is capable of dissolving an amount of water equal to from about 5 to about 15 percent of its own weight, and said film is from about 200°A to about 500°A thick.

Claim 9

A membrane as claimed in claim 1 wherein: said membrane includes a continuous, non-porous layer of a thermally irreversible hydrogel composition containing at least one hydrogel-forming polymer and water, said hydrogel layer being located between said support and said active layer, said film-forming polymer is a polymer selected from the group consisting of hydrophilic epoxy and phenolic polymers.

Claim 10

A membrane as claimed in claim 8 wherein: said hydrogel layer is from about 0.1 to about 5 microns thick, said hydrogel forming polymer is capable of absorbing an amount of water equal to at least 150 percent of its own weight, said polymer in said hydrogel layer being present in the form of swollen polymer coils of polymer chains of a molecular weight of from about 30,000 to about 5,000,000, said film-forming polymer is capable of dissolving an amount of water equal to from about 2 to about 20 percent of its own weight, and said film is from about 50°A to about 1500°A thick.

Claim 11

A membrane as claimed in claim 8 wherein: said hydrogel layer is from about 1.5 to about 5 microns thick, said polymer in said hydrogel layer is capable of absorbing an amount of water equal to at least 15 times the weight of said hydrogel forming polymer and is incapable of absorbing an amount of water in excess of about 200 times of its own weight, said hydrogel forming polymer in said hydrogel layer is present in the form of swollen polymer coils of polymer chains of the molecular weight of from about 500,000 to about 3,000,000, said film-forming polymer is capable of dissolving an amount of water equal to from about 5 to about 15 percent of its own weight, said film is from about 200 0 A to about 500°A thick.

Claim 12

A membrane as claimed in claim 2 or 5 wherein: said support is a porous asymmetric member having a porous surface in contact with said hydrogel layer, the porosity of said asymmetric member increasing in accordance with the distance away from said hydrogel layer.

Claim 13

'12. A membrane as claimed in claim 11 wherein: from about 10 to about 30 percent of the surface of said support in contact with said hydrogel layer is open and from about 70 to about 95 percent of the surface of said support remote from said hydrogel layer is open.

Claim 14

A membrane as claimed in claim 11 wherein: the pores within said porous surface in contact with said hydrogel layer are at least about 0.05 microns in diameter and are no greater than about 0.5 microns in diameter, said pores in said surface in contact with said hydrogel layer being substantially free from material from within said hydrogel layer.

Claim 15

A membrane as claimed in claim 11 wherein: said support is formed of a polymer having a glass transition temperature above about 130°C and is from about 40 to about 120 microns thick.

Claim 16

A membrane as claimed in claim 1 wherein: said membrane includes a continuous, non-porous layer of a thermally irreversible hydrogel composition containing at least one hydrogel-forming polymer and water, said hydrogel layer being located between said support and said active layer, said hydrogel layer is from about 0.1 to about 5 microns thick when dry, said hydrogel forming polymer is capable of absorbing an amount of water equal to at least 150 percent of its own weight, said polymer in said hydrogel layer being present in the form of swollen polymer coils of polymer chains of a molecular weight of from about 30,000 to about 5,000,000, said film-forming polymer is a polymer selected from the group consisting of hydrophilic, partially hydrolyzed polyvinyl ester, epoxy and phenolic polymers, said film-forming polymer is capable of dissolving an amount of water equal to from about 2 to about 20 percent of its own weight, said support is a porous asymmetric member having a porous surface in contact with said hydrogel layer, the porosity of said asymmetric member increasing in accordance with the distance away from said hydrogel layer, from about 10 to about 30 percent of the surface of said support in contact with said hydrogel layer is open and from about 70 to about 95 percent of the surface of said support remote from said hydrogel layer is open, the pores within said porous surface in contact with said hydrogel layer are at least about 0.05 microns in diameter and are no greater than about 0.5 microns in diameter, said pores in said surface in contact with said hydrogel layer being substantially free from material from within said hydrogel layer.

Claim 17

A membrane-as claimed in claim 1 wherein: said membrane includes a continuous, non-porous layer of a thermally irreversible hydrogel composition containing at least one hydrogel-forming polymer and water, said hydrogel layer being located between said support and said active layer, said hydrogel layer is from about 2 to about 3 microns thick when dry, said polymer in said hydrogel layer is capable of absorbing an amount of water equal to at least 15 times the weight of said hydrogel-forming polymer and is incapable of absorbing an amount of water in excess of about 200 times of its own weight, said hydrogel-forming polymer in said hydrogel layer is present in the form of swollen polymer coils of polymer chains of the molecular weight of from about 500,000 to about 3,000,000, said film-forming polymer is a polymer selected from the group consisting of hydrophilic, partially hydrolyzed polyvinyl ester, epoxy and phenolic polymers, said film-forming polymer is capable of dissolving an amount of water equal to from about 5 to about 15 percent of its own weight, said film is from about 200 0 to about 5000A thick, said support is a porous asymmetric member having a porous surface in contact with said hydrogel layer, the porosity of said asymmetric member increasing in accordance with the distance away from said hydrogel layer, from about 10 to about 30 percent of the surface of said support in contact with said hydrogel layer is open and from about 90 to about 95 percent of the surface of said support remote from said hydrogel layer is open, the pores within-said porous surface in contact with said hydrogel layer are at least about 0.5 microns in diameter and are no greater than about 5 microns in diameter, said pores in said surface in contact with said hydrogel layer being substantially free from material from within said hydrogel layer.

Claim 18

A membrane as claimed in claim 16 or 17 wherein: said polymer coils are cross-linked within said hydrogel composition.

Claim 19

A membrane as claimed in claim 16 or 17 wherein: said support is a polymer support, said polymer coils are cross-linked to one another, to said support and to said active layer.

Claim 20

A membrane as claimed in claim 16 or 17 wherein: said support is formed of a polymer having a glass transition temperature above about 130°C., is from about 40 to about 120 microns thick.

Claim 21

A membrane as claimed in claims 16 or 17 wherein: said support is a polymer support, said polymer coils are cross-linked to one another, to said support.and to-said active layer, said support is .formed of a polymer having a glass transition temperature above about 130°C., is from about 40 to about 120 microns thick.

Claim 22

, 21. A reverse osmosis membrane including an active layer and a physical support for said active layer in which the improvement comprises: said membrane including a continuous, non-porous layer of an irreversible hydrogel composition containing at least one hydrogel-forming polymer and water, said hydrogel layer being located between said support and said active layer.

Claim 23

, 21. A reverse osmosis membrane including an active layer and a physical support for said active layer in which the improvement comprises: said membrane including a continuous, non-porous layer of an irreversible hydrogel composition containing at least one hydrogel-forming polymer and water, said hydrogel layer being located between said support and said active layer.

Claim 24

A reverse osmosis membrane as claimed in claim 21 wherein: the active layer consisting essentially of a continuous, non-porous, uniform film of an organic, film-forming polymer which is substantially inert in the presence of an oxidizing agent having a sufficient oxidizing potential to serve as a sterilizing agent, said film being from about 50 0 A to about 1500°A thick and being capable of dissolving an amount of water equal to at least two percent by weight of the weight of the film.

Claim 25

A reverse osmosis membrane as claimed in claim 21 wherein: said film-forming polymer is a polymer selected from the group consisting of hydrophilic epoxy and phenolic polymers, said film-forming polymer is capable of dissolving an amount of water equal to from about 2 to about 20 percent of its own weight, and said film is from about 50°A to about 1500°A thick.

Claim 26

A reverse osmosis membrane as claimed in claim 21 wherein: said film-forming polymer is a polymer selected from the group consisting of hydrophilic, partially hydrolyzed polyvinyl esters, epoxy and phenolic polymers, said film-forming polymer is capable of dissolving an amount of water equal to from about 5 to about 15 percent of its own weight, and said film is from about 200 0 A to about 500°A thick.

Claim 27

A reverse osmosis membrane as claimed in claim 21, 22, 23 or 24 wherein: said hydrogel layer is from about 0.1 to about 5 microns thick when dry, said hydrogel forming polymer is capable of absorbing an amount of water equal to at least 150 percent of its own weight, said polymer in said hydrogel layer being present in the form of swollen polymer coils of polymer chains of a molecular weight of from about 30,000 to about 5,000,000.

Claim 28

A reverse osmosis membrane as claimed in claims 21, 22, 23 or 24 wherein: said hydrogel layer is from about 2 to about 3 microns thick when dry, said polymer in said hydrogel layer is capable of absorbing an amount of water equal to at least 15 times the weight of said hydrogel forming polymer and is incapable of absorbing an amount of water in excess of about 200 times of its own weight, said hydrogel forming polymer in said hydrogel layer is present in the form of swollen polymer coils of polymer chains of the molecular weight of from about 500,000 to about 3,000,000.

Claim 29

A process of producing a reverse osmosis membrane in which an active layer capable of dissolving water is located on a surface of a porous support in which the improvement comprises: applying to said surface of said porous support a water containing solution of prepolymer chains capable of reacting so as to form an active layer, thereafter concurrently reducing the solvent content of this solution and reacting said prepolymer chains so as to form said active layer, the viscosity of said solution, the time and manner of said contact of said solution with said surface, and the rate and conditions of said solvent removal being such that said active layer is formed on said surface of said support without penetration of said active layer into the pores of said support to any extent sufficient to detrimentally affect the ability of water to flow through said support.

Claim 30

A process of producing a reverse osmosis membrane in which an active layer capable of dissolving water is located on a surface of a porous support in which the improvement comprises: applying to said surface of said porous support a water containing solution of prepolymer chains capable of reacting so as to form an active layer, thereafter concurrently reducing the solvent content of this solution and reacting said prepolymer chains so as to form said active layer, the viscosity of said solution, the time and manner of said contact of said solution with said surface, and the rate and conditions of said solvent removal being such that said active layer is formed on said surface of said support without penetration of said active layer into the pores of said support to any extent sufficient to detrimentally affect the ability of water to flow through said support.

Claim 31

A process as claimed in claim 27 wherein: said solution is sufficiently dilute so that there is substantially no chance of said prepolymer chains reacting until the solvent content of said solution is reduced.

Claim 32

A process as claimed in claim 27 wherein: said polymer chains are capable of reacting to form a polymer selected from the group consisting of epoxy and phenolic polymers.

Claim 33

A process of producing a reverse osmosis membrane which comprises: forming a porous, sheet-like support layer which is sufficiently porous so that water can pass through said support layer, forming a continuous hydrogel layer upon a surface of said support layer in such a manner that the pores of said support layer are sufficiently free from the presence of material from within said hydrogel layer so that fluid flow through the pores of said support layer is not detrimentally affected by the presence of said material within said pores, and forming a continuous active layer capable of dissolving water so as to segregate the dissolved water from other materials in the solution being purified on the surface of said hydrogel layer remote from said support layer.

Claim 34

A process of producing a reverse osmosis membrane which comprises: forming a porous, sheet-like support layer which is sufficiently porous so that water can pass through said support layer, forming a continuous hydrogel layer upon a surface of said support layer in such a manner that the pores of said support layer are sufficiently free from the presence of material from within said hydrogel layer so that fluid flow through the pores of said support layer is not detrimentally affected by the presence of said material within said pores, and forming a continuous active layer capable of dissolving water so as to segregate the dissolved water from other materials in the solution being purified on the surface of said hydrogel layer remote from said support layer.

Claim 35

A process as claimed in claim 30 wherein: all of said layers are formed of polymer compositions, and the formation of at least one of said layers includes the step of cross-linking said one of said layers with an adjacent layer during the formation of said one of said layers.

Claim 36

A process as claimed in claim 30 wherein: said hydrogel layer and said active layer are concurrently formed by applying to a surface of said support layer a solution containing both swollen hydrogel polymer coils and materials necessary for the production of said active layer and then heating so as to volatilize the solvent from said solution and so as to concurrently produce said hydrogel and active layers by entropic separation.