US4900449A — Filtration membranes and method of making the same

Claim 1

Independent Claim 70 words

A microporous membrane comprising a polymer which in bulk form is hydrophobic and has an equilibrium water absorption ranging from about 2% to about 4% and which is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 2

Dependent Claim 70 words

A microporous membrane comprising a polymer which in bulk form is hydrophobic and has an equilibrium water absorption ranging from about 2% to about 4% and which is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 3

Dependent Claim 15 words

The membrane of claim 1 wherein said polymer additive is selected from polyethyleneglycol and polyvinylpyrrolidone.

Claim 4

Dependent Claim 15 words

The membrane of claim 1 wherein said hydrophobic polymer is selected from polyethersulfones and polyimides.

Claim 5

Dependent Claim 12 words

The membrane of claim 1 wherein said hydrophobic polymer is a polyamide-imide.

Claim 6

Dependent Claim 80 words

A microporous membrane comprising a polyethersulfone polymer of the general formula ##STR8## which in bulk is hydrophobic and has an equilibrium water absorption of about 2% to about 4% and polyvinylpyrrolidone in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions, said membrane being further characterized by remaining hydrophilic after extraction with isopropanol.

Claim 7

Dependent Claim 80 words

A microporous membrane comprising a polyethersulfone polymer of the general formula ##STR8## which in bulk is hydrophobic and has an equilibrium water absorption of about 2% to about 4% and polyvinylpyrrolidone in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions, said membrane being further characterized by remaining hydrophilic after extraction with isopropanol.

Claim 8

Dependent Claim 69 words

A microporous membrane comprising a polyamide-imide polymer which is hydrophobic in bulk form and has an equilibrium water absorption of about 2% to about 4% and is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 9

Dependent Claim 69 words

A microporous membrane comprising a polyamide-imide polymer which is hydrophobic in bulk form and has an equilibrium water absorption of about 2% to about 4% and is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 10

Dependent Claim 75 words

A microporous membrane comprising a polyimide polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4% and which is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, said membrane being further characterized by having a pore size such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 11

Dependent Claim 75 words

A microporous membrane comprising a polyimide polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4% and which is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, said membrane being further characterized by having a pore size such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 12

Dependent Claim 102 words

A microporous membrane comprising a polyimide polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4% and which is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, said polymer having the general formula ##STR9## where 10% to 90% of the R groups are ##STR10## and the remaining R groups are ##STR11## said membrane being further characterized by being hydrophilic and having a pore size range such that the membrane does not retain or reject dissolved proteins or salts from feed solutions.

Claim 13

Dependent Claim 102 words

A microporous membrane comprising a polyimide polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4% and which is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, said polymer having the general formula ##STR9## where 10% to 90% of the R groups are ##STR10## and the remaining R groups are ##STR11## said membrane being further characterized by being hydrophilic and having a pore size range such that the membrane does not retain or reject dissolved proteins or salts from feed solutions.

Claim 14

Dependent Claim 85 words

A microporous membrane comprising a polyamide-imide polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4% and which is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, said polymers having the general formula ##STR12## where R is aromatic, the membrane being further characterized by a pore size range such that the membrane does not retain or reject dissolved proteins or salts from feed solutions.

Claim 15

Dependent Claim 85 words

A microporous membrane comprising a polyamide-imide polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4% and which is blended with a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, said polymers having the general formula ##STR12## where R is aromatic, the membrane being further characterized by a pore size range such that the membrane does not retain or reject dissolved proteins or salts from feed solutions.

Claim 16

Independent Claim 115 words

A method of producing a microporous, inherently water wettable dry membrane, comprising: (a) dissolving in a polar aprotic solvent a polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%; (b) adding a pore forming agent to the solution; (c) blending with the solution a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions; (d) casting the solution in a thin layer; (e) humidifying the solution sufficiently to precipitate the membrane; and (f) drying the membrane.

Claim 17

Independent Claim 115 words

A method of producing a microporous, inherently water wettable dry membrane, comprising: (a) dissolving in a polar aprotic solvent a polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%; (b) adding a pore forming agent to the solution; (c) blending with the solution a polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions; (d) casting the solution in a thin layer; (e) humidifying the solution sufficiently to precipitate the membrane; and (f) drying the membrane.

Claim 18

Dependent Claim 19 words

The method of claim 10 wherein the polymer additive blended with the solution is selected from polyvinylpyrrolidone and polyethyleneglycol.

Claim 19

Independent Claim 104 words

A method of producing a microporous, inherently water wettable dry membrane, comprising: (a) dissolving in a polar aprotic solvent a polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%; (b) adding polyethyleneglycol to the solution in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions; (c) casting the solution in a thin layer; (d) humidifying the solution sufficiently to precipitate the membrane; and (e) drying the membrane.

Claim 20

Independent Claim 104 words

A method of producing a microporous, inherently water wettable dry membrane, comprising: (a) dissolving in a polar aprotic solvent a polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%; (b) adding polyethyleneglycol to the solution in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions; (c) casting the solution in a thin layer; (d) humidifying the solution sufficiently to precipitate the membrane; and (e) drying the membrane.

Claim 21

Dependent Claim 12 words

The method of claim 12 further comprising incorporating polyvinylpyrrolidone into the solution.

Claim 22

Dependent Claim 19 words

The method of claim 12 wherein the hydrophobic polymer dissolved in the solvent is selected from polyethersulfones and polyimides.

Claim 23

Dependent Claim 46 words

The method of claim 14 wherein the hydrophobic polymer dissolved in the solvent is a polyethersulfone of the general formula ##STR13## or a polyimide of the general formula ##STR14## where 10% to 90% of the R groups are ##STR15## and the remaining R groups are ##STR16##

Claim 24

Dependent Claim 16 words

The method of claim 12 wherein the hydrophobic polymer dissolved in the solvent is a polyamide-imide.

Claim 25

Dependent Claim 29 words

The method of claim 16 wherein the hydrophobic polymer dissolved in the solvent is selected from a polyimide of the following general formula ##STR17## where R is generally aromatic.

Claim 26

Independent Claim 112 words

A method of making a microporous, inherently water wettable dry membrane, comprising: (a) dissolving in a polar aprotic solvent a polyethersulfone polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said polymer having the general formula ##STR18## (b) adding polyethyleneglycol to the solution in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions; (c) casting the solution in a thin layer; (d) humidifying the solution sufficiently to precipitate the membrane; and (e) drying the membrane.

Claim 27

Independent Claim 112 words

A method of making a microporous, inherently water wettable dry membrane, comprising: (a) dissolving in a polar aprotic solvent a polyethersulfone polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said polymer having the general formula ##STR18## (b) adding polyethyleneglycol to the solution in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions; (c) casting the solution in a thin layer; (d) humidifying the solution sufficiently to precipitate the membrane; and (e) drying the membrane.

Claim 28

Dependent Claim 12 words

The method of claim 18 further comprising incorporating polyvinylpyrrolidone into the solution.

Claim 29

Independent Claim 118 words

A method of making a microporous inherently wettable dry membrane, comprising: (a) dissolving in a polar aprotic solvent a polyamide-imide polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said polymer having the general formula ##STR19## where R comprises an aromatic group; (b) adding polyethylene glycol to the solution in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions, (c) casting the solution in a thin layer; (d) humidifying the solution sufficiently to precipitate the membrane; and (e) drying the membrane.

Claim 30

Independent Claim 118 words

A method of making a microporous inherently wettable dry membrane, comprising: (a) dissolving in a polar aprotic solvent a polyamide-imide polymer which in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said polymer having the general formula ##STR19## where R comprises an aromatic group; (b) adding polyethylene glycol to the solution in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions, (c) casting the solution in a thin layer; (d) humidifying the solution sufficiently to precipitate the membrane; and (e) drying the membrane.

Claim 31

Dependent Claim 90 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polymer and a polymer additive, which polymer in bulk form is hydrophobic and has a water absorption equilibrium ranging from about 2% to about 4%, the polymer additive in the membrane being in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 32

Dependent Claim 90 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polymer and a polymer additive, which polymer in bulk form is hydrophobic and has a water absorption equilibrium ranging from about 2% to about 4%, the polymer additive in the membrane being in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 33

Dependent Claim 10 words

The process of claim 21 wherein said matter is bacteria.

Claim 34

Dependent Claim 11 words

The process of claim 21 wherein said matter is particulate matter.

Claim 35

Dependent Claim 12 words

The process of claim 21 wherein said solution is an aqueous solution.

Claim 36

Dependent Claim 104 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polyethersulfone polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said membrane having a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions, the polymer having the general formula ##STR20## said polymer additive comprising polyvinylpyrrolidone in an amount effective to make the membrane inherently water wettable when dried, said membrane remaining inherently wettable after extraction with isopropanol.

Claim 37

Dependent Claim 104 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polyethersulfone polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said membrane having a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions, the polymer having the general formula ##STR20## said polymer additive comprising polyvinylpyrrolidone in an amount effective to make the membrane inherently water wettable when dried, said membrane remaining inherently wettable after extraction with isopropanol.

Claim 38

Dependent Claim 10 words

The process of claim 25 wherein said matter is bacteria.

Claim 39

Dependent Claim 11 words

The process of claim 25 wherein said matter is particulate matter.

Claim 40

Dependent Claim 12 words

The process of claim 25 wherein said solution is an aqueous solution.

Claim 41

Dependent Claim 88 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polyamide-imide polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said polymer additive being present in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 42

Dependent Claim 88 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polyamide-imide polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said polymer additive being present in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 43

Dependent Claim 10 words

The process of claim 29 wherein said matter is bacteria.

Claim 44

Dependent Claim 11 words

The process of claim 29 wherein said matter is particulate matter.

Claim 45

Dependent Claim 12 words

The process of claim 29 wherein said solution is an aqueous solution.

Claim 46

Dependent Claim 88 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polyimide polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said polymer additive being present in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 47

Dependent Claim 88 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polyimide polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, said polymer additive being present in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 48

Dependent Claim 10 words

The process of claim 33 wherein said matter is bacteria.

Claim 49

Dependent Claim 11 words

The process of claim 33 wherein said matter is particulate matter.

Claim 50

Dependent Claim 12 words

The process of claim 33 wherein said solution is an aqueous solution.

Claim 51

Dependent Claim 110 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polyimide polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, the polymer having the general formula ##STR21## where 10% to 90% of R is ##STR22## and the remaining R groups are ##STR23## said polymer additive being present in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 52

Dependent Claim 110 words

A process for filtering matter from a solution comprising flowing said solution through a microporous, inherently water wettable membrane comprising a polyimide polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, the polymer having the general formula ##STR21## where 10% to 90% of R is ##STR22## and the remaining R groups are ##STR23## said polymer additive being present in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 53

Dependent Claim 10 words

The process of claim 37 wherein said matter is bacteria.

Claim 54

Dependent Claim 11 words

The process of claim 37 wherein said matter is particulate matter.

Claim 55

Dependent Claim 12 words

The process of claim 37 wherein said solution is an aqueous solution.

Claim 56

Dependent Claim 80 words

A dry filter comprising an inherently water wettable, microporous membrane comprising a polyethersulfone polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, the polymer additive comprising polyethylene glycol in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions;

Claim 57

Dependent Claim 80 words

A dry filter comprising an inherently water wettable, microporous membrane comprising a polyethersulfone polymer and a polymer additive, which polymer in bulk form is hydrophobic and has an equilibrium water absorption of about 2% to about 4%, the polymer additive comprising polyethylene glycol in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions;

Claim 58

Dependent Claim 84 words

A microporous, inherently water wettable dry membrane comprising a polymer and a polymer additive which polymer is hydrophobic in bulk form and has an equilibrium water absorption of about 2% to about 4%, said polymer additive being blended in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions, said polymer additive being selected from polyethyleneglycol and polyvinylpyrrolidone.

Claim 59

Dependent Claim 84 words

A microporous, inherently water wettable dry membrane comprising a polymer and a polymer additive which polymer is hydrophobic in bulk form and has an equilibrium water absorption of about 2% to about 4%, said polymer additive being blended in an amount effective to make the membrane when formed and dried inherently water wettable, with a pore size range such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions, said polymer additive being selected from polyethyleneglycol and polyvinylpyrrolidone.

Claim 60

Dependent Claim 79 words

A microporous, inherently water wettable dry membrane comprising a polymer which is hydrophobic in bulk form and has an equilibrium water absorption ranging from about 2% to 4% and which is blended with polyvinylpyrrolidone polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, the pore size range of said formed and dried membrane being such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 61

Dependent Claim 79 words

A microporous, inherently water wettable dry membrane comprising a polymer which is hydrophobic in bulk form and has an equilibrium water absorption ranging from about 2% to 4% and which is blended with polyvinylpyrrolidone polymer additive in an amount effective to make the membrane when formed and dried inherently water wettable, the pore size range of said formed and dried membrane being such that the membrane does not retain or reject dissolved proteins or salts from aqueous feed solutions.

Claim 62

Dependent Claim 12 words

The membrane of claim 43 wherein said hydrophobic polymer is a polyethersulfone.

Claim 63

Dependent Claim 22 words

The membrane of claim 44 wherein polyvinylpyrrolidine is incorporated into the membrane in an amount less than 1% of the polyethersulfone weight.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-02-12	1993-08-14	1994-02-13	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-02-12	1997-08-14	1998-02-13	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-02-12	2001-08-14	2002-02-13	$7700.00	Window Closed / Lapsed

Filtration membranes and method of making the same

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