Multi-layer filter membrane

Claim 2

A MULTIPLE LAYER FILTER MEMBRANE COMPRISING: A. AN OSMOTIC SKIN COMPOSED OF AT LEAST ONE CLOSED CONTINUOUS FILM ABOUT 0.05 TO ABOUT 0.1 UM THICK OF A SELECTIVELY PERMEABLE HIGH POLYMER SELECTED FROM THE GROUP CONSISTING OF AN INELASTIC SELECTIVELY PERMEABLE HIGH POLYMER, AN ELASTIC SELECTIVELY PERMEABLE HIGH POLYMER AND AN ELASTIFIED SELECTIVELY PERMEABLE HIGH POLYMER; AND B. A POROUS BASE CONTAINING FINELY DIVIDED FILLER MATERIAL THEREIN, BASE COMPOSED OF A GEL FILM WHICH SWELLS IN CONTACT WITH AND IS INSOLUBLE IN WATER, THE GEL LAYER BACKED BY A RELATIVELY THICKER CELLULOSE ACETATE SPONGE LAYER IMPREGNATED ON THE SIDE REMOTE FROM BOTH THE GEL LAYER AND OSMOTIC SKIN (A) HAVING A PORE SIZE WHICH IN CREASES CONTINUOUSLY FROM THE GEL THROUGH OUT THE SPONGE LAYER TO THE BACK THEREOF.

Claim 3

A membrane according to claim 1 wherein the selectively permeable high polymer has a co-efficient of linear thermal expansion between 5 and 8 . 10 5 (degrees 1).

Claim 4

A membrane according to claim 1 wherein the continuous film is bound by secondary valence bonds.

Claim 5

A membrane according to claim 1 wherein the continuous film is bound by primary valence bonds.

Claim 6

A membrane according to claim 1 wherein the inelastic selectivity permeable high polymer is selected from the group consisting of a phenoxy resin, polyvinyl chloride, polyvinyl fluoride, a polysulphone, cellulose triacetate, a polyacrylate and a polyamide.

Claim 7

A membrane according to claim 1 wherein the elastic selectively permeable high polymeR is selected from the group consisting of natural rubber, silicone rubber and synthetic rubber.

Claim 8

A membrane according to claim 6 wherein the continuous film rests on a gel layer consisting of a material selected from the group consisting of alginic acid, an agar-agar/formaldehyde reaction product, and a gelatine/formaldehyde reaction product and the supporting base consists exclusively of a sponge layer comprising cellulose acetate having a 31.5 percent acetyl content and filler materials.

Claim 9

A membrane according to claim 6 wherein the continuous film rests on a gel layer consisting of a material selected from the group consisting of alginic acid, an agar-agar/formaldehyde reaction product, and a gelatine/formaldehyde reaction product, the supporting base consists exclusively of a sponge layer comprising cellulose acetate having a 31.5 percent acetyl content and filler materials and the sponge layer is reinforced with a fabric of a material selected from the group consisting of glass, fully synthetic fibres, graphite fibres and stainless metal fibres.

Claim 10

A membrane according to claim 1 wherein the elastified selectively permeable high polymer is composed of inelastic high polymer blended with a material selected from the group consisting of polyurethane, polymeric plasticizer, silicone rubber, natural rubber and synthetic rubber to elastify same.

Claim 11

A membrane according to claim 1 wherein at least one supplementary layer is provided between the continuous film and the supporting base.

Claim 12

A membrane according to claim 10 wherein the supplementary layer consists of a reaction product of formaldehyde with a material selected from the group consisting of gelatine and agar-agar.

Claim 13

A membrane according to claim 10 wherein the supplementary layer is a material selected from the group consisting of alginic acid, cellulose triacetate and a polyamide soluble in alcohol.

Claim 14

A membrane according to claim 1 wherein the supporting base consists of a gel film about 20 Mu m thick having a pore size below 100 A backed by a sponge layer of cellulose acetate about 130 Mu m thick and having a pore size of about 2500 to 4000 A which increases continuously from the gel through the sponge layer to the back.

Claim 15

A membrane according to claim 16 wherein the cellulose acetate has an acetyl content of 31.5 percent.

Claim 16

A membrane according to claim 1 wherein the finely-divided filler material of the supporting base is a material selected from the group consisting of TiO2, quartz, Al2O3, powdered pumice, bentonite, graphite, talc, glass fibres and pyrogenic highly disperse silica.

Claim 17

A membrane according to claim 1 wherein the supporting base is reinforced by the incorporation of a fabric of a material selected from the group consisting of glass, fully synthetic fibres, graphite fibres and stainless metal fibres.

Claim 18

A membrane according to claim 1 wherein the back of the supporting base having the sponge structure is impregnated with a material selected from the group consisting of glycerine, polyvinyl methyl ether and polyacrylic acid.

Claim 19

A membrane according to claim 1 wherein the continuous film rests on a supplementary layer consisting of an alcohol-soluble polyamide having a water absorption capacity of 2.4 percent, backed by a supplementary layer of cellulose triacetate underneath which is the supporting base of cellulose acetate.

Claim 20

A membrane according to claim 1 wherein the continuous film consists of an elastic selectively permeable high polymer, and rests on a supplementary layer consisting of an alcohol-soluble polyamide having a water absorption capacity of 2.4 percent, backed by a supplementary layer of cellulose triacetate underneath which is the supporting base, the supporting base consisting of hydrated cellulose, and a layer of polyisocyamate bound by polyaddition being interposed between the continuous film and the supporting base.

Claim 21

A membrane accoRding to claim 19 wherein the polyisocyanate layer consists of triphenylmethane-4, 4'', 4''''-triisocyanate.

Claim 22

A membrane according to claim 1 wherein a layer of polyioscyanate bound by polyaddition is interposed between the continuous elastified selectively permeable high polymer film and the support base.

Claim 23

A membrane according to claim 1 wherein a layer of triphenylmethane-4, 4'', 4''''-triisocyanate bound by polyaddition is interposed between the continuous elastified selectively permeable high polymer film and the support base.

Claim 24

A membrane according to claim 1 wherein the porous supporting base is about 100 to about 150 Mu m in thickness.

Claim 25

A membrane according to claim 1 wherein said filler material is present in the supporting base to the extent of about 20 to about 30 percent of the solids present in the layer.

Claim 28

A method according to claim 25 wherein the watered supporting base of cellulose acetate is hydrolysed and thus converted to a supporting base of hydrated cellulose by treating the same with an alcoholic KOH at room temperature for 1 to 10 minutes.

Claim 29

A method according to claim 26 wherein a solvent selected from the group consisting of ethyl acetate and methyl isobutyl ketone is poured over the gel side of the impregnated and dried supporting base, the resultant film being dried for 1 to 3 minutes, a second very thin film of cellulose triacetate is then applied to the dried film and a very thin third film of a polyamide soluble in a water and alcohol mixture and having an absorption capacity for water of 2.4 percent is applied to the second film and also dried, and a phenoxy resin in the form of an 0.5 percent by weight solution in ethyl glycol acetate is applied in film form and dried.

Claim 30

A method according to claim 26 wherein a solvent selected from the group consisting of ethyl acetate and methyl isobutyl ketone is poured over the gel side of the impregnated and dried supporting base, the resultant film being dried for 1 to 3 minutes, a second very thin film of cellulose triacetate is then applied to the dried film and a very thin third film of a polyamide soluble in a water and alcohol mixture and having an absorption capacity for water of 2.4 percent is applied to the second film and also dried, a phenoxy resin in the form of an 0.5 percent by weight solution in ethyl glycol acetate is applied in film form and dried, the high polymer forming the desalination layer proper is dissolved in a non-aqueous solvent, and the process of pouring is performed when relative humidity is negligibly low.

Claim 31

A method according to claim 26 wherein the impregnated and dried supporting base of cellulose hydrate is provided on its gel side with a coating of a 1 percent by weight solution of triphenylmethane-4, 4'', 4''''-triisocyanate in methylene chloride and submitted to a warm air treatment at 50*C for 2 minutes, and an inelastic layer of a phenoxy resin is then formed from an 0.5 percent by weight solution of the phenoxy resin in ethyl glycol acetate and the resultant membrane dried.

Claim 32

A method according to claim 26 wherein a solvent selected from the group consisting of ethyl acetate and methylisobutyl ketone is poured over the gel side of the impregnated and dried supporting base, the resultant film being dried for 1 to 3 minutes, a second very thin film of cellulose triacetate is then applied to the dried film and a very thin third film of a polyamide soluble in a water and alcohol mixture and having an absorption capacity for water of 2.4 percent is applied to the second film and also dried, a phenoxy resin in the form of an 0.5 percent by weight solution in ethyl glycol acetate is applied in film form and dried, the solution for forming the supporting base, having been poured, is at once immersed in water without a residence time in air, the resultant supporting base is impregnated on one side, dried and coated with a gel substance consisting of an agar-agar/formaldehyde reaction product, and, when the gel has been dried in warm air at 50*C for 2 minutes an elastic layer of a material selected from the group consisting of natural rubber, butadiene/acrylonitrile rubber and silicone rubber is applied and the resultant layer dried at a temperature between room temperature and 60*C.

Claim 33

A method according to claim 26 wherein a solvent selected from the group consisting of ethyl acetate and methyl isobutyl ketone is poured over the gel side of the impregnated and dried supporting base, the resultant film being dried for 1 to 3 minutes, a second very thin film of cellulose triacetate is then applied to the dried film and a very thin third film of a polyamide soluble in a water and alcohol mixture and having an absorption capacity for water of 2.4 percent is applied to the second film and also dried, a phenoxy resin in the form of an 0.5 percent by weight solution in ethyl glycol acetate is applied in film form and dried, the high polymer forming the desalination layer proper is dissolved in a non-aqueous solvent, the process of pouring is performed when relative humidity is negligibly low, the solution for forming the supporting base, having been poured, is at once immersed in water without a residence time in air, the resultant supporting base is impregnated on one side, dried and coated with a gel substance consisting of an agar-agar/formaldehyde reaction product, and, when the gel has been dried in warm air at 50*C for 2 minutes an elastic layer of a material selected from the group consisting of natural rubber, butadiene/acrylonitrile rubber and silicone rubber is applied and the resultant layer dried at a temperature between room temperature and 60*C.

Claim 34

A method according to claim 25 wherein the impregnated layer forming the supporting base is dried for a few minutes with hot air at 100*C, the dried layer is then coated with a 1 percent by weight solution of triphenylmethane-4, 4'', 4''''-triisocyanate in methylene chloride and an 0.5 percent by weight solution of natural rubber in petrol is applied and the coated membrane is dried with hot air at a temperature between 80* and 110*C.

Claim 35

A method according to claim 25 wherein the impregnated lAyer forming the supporting base is dried for a few minutes with hot air at 100*C, the dried layer is then coated with a 1 percent by weight solution of triphenylmethane-4, 4'', 4''''-triisocyanate in methylene chloride and an 0.5 percent by weight solution of a butadiene/acrylonitrile rubber in methyle chloride is applied and the coated membrane is dried with hot air at a temperature between 80* and 110*C.

Claim 36

A method according to claim 25 wherein the impregnated layer forming the supporting base is dried for a few minutes with hot air at 100*C, the dried layer is then coated with a composition having the following formulation:

Claim 37

A multilayer filter membrane suitable for use in reverse osmosis, hyperfiltrations and other such separation processes, said membrane comprising: a. an osmotic skin composed of at least one closed, continuous film about 0.05 to about 0.1 Mu m thick of an inelastic, elastic or elastified selectively permeable high polymer; and b. a porous base layer containing about 20 to about 30 percent, calculated on the solids content, of a finely divided filler material therein, the base composed of a gel film which swells in contact with and is insoluble in water and backed by a relatively thicker cellulose acetate sponge layer about 100 to about 150 Mu m in thickness having a pore size of about 2500 to 4000 A increasing continuously from the gel through the sponge layer to the back and impregnated on the side remote from both the gel layer and osmotic skin (a).

Claim 38

A multilayer filter membrane suitable for use in reverse osmosis, hyperfiltrations and other such separation processes, said membrane comprising: a. an osmotic skin composed of at least one closed, continuous film about 0.05 to about 0.1 Mu m thick of an inelastic, elastic or elastified selectively permeable high polymer; and b. a porous base layer containing about 20 to about 30 percent, calculated on the solids content, of a finely divided filler material therein, the base composed of a gel film which swells in contact with and is insoluble in water and backed by a relatively thicker cellulose acetate sponge layer about 100 to about 150 Mu m in thickness having a pore size of about 2500 to 4000 A increasing continuously from the gel through the sponge layer to the back and impregnated on the side remote from both the gel layer and osmotic skin (a).