Microporous membranes of ultrahigh molecular weight polyethylene

Claim 2

A microporous UHMW-PE membrane having microporosity and permeability sufficient to provide a water flow rate above the curve of FIG. 5 at a methanol bubble point plotted thereon.

Claim 3

A microporous membrane of claim 1 having a tensile strength above about 500 psi, a melting point above about 132° C., and an elongation at break above about 100%.

Claim 4

A UHMW-PE microporous membrane of claim 2 comprising a filtration medium.

Claim 5

A microporous UHMW-PE membrane of claim 1 having a lacy-type open structure.

Claim 6

A microporous UHMW-PE membrane of claim 1 having a cellular structure.

Claim 7

A water-resistant breathable microporous membrane formed from UHMW-PE and having microporosity and permeability sufficient to provide an air flow rate of at least 0.1 lit/min/cm 2 at differential pressure equal to 10 psi, a minimum water intrusion pressure of about 2 psi and a water flow rate above the curve of FIG. 5 at a methanol bubble point plotted thereon.

Claim 8

A water-resistant breathable microporous membrane formed from UHMW-PE and having microporosity and permeability sufficient to provide an air flow rate of at least 0.1 lit/min/cm 2 at differential pressure equal to 10 psi, a minimum water intrusion pressure of about 2 psi and a water flow rate above the curve of FIG. 5 at a methanol bubble point plotted thereon.

Claim 9

A water-resistant breathable microporous membrane of claim 6 additionally having a tensile strength above about 500 psi, an elongation at break above about 100% and a melting point above about 132° C.

Claim 10

A microporous ultra-high molecular weight polyolefin membrane produced by a method comprising: a. forming a mixture comprising an ultra-high molecular weight polyolefin and a porogen; b. heating the mixture to an elevated temperature to produce a solution of ultra-high molecular weight polyolefin and porogen; c. extruding the solution of ultra-high molecular weight polyolefin and porogen through a forming die under moderate shear sufficient to enable the employment of conventional extrusion equipment and/or techniques to thereby form a membrane; d. cooling the membrane sufficiently to cause phase separation resulting in a polymer-rich, porogen-poor phase and a polymer poor, porogen-rich phase in said membrane; e. creating a microporous structure in the membrane by removing porogen from said membrane; and f. drying the microporous membrane under restraint to minimize collapse of the microporous structure.

Claim 11

A microporous ultra-high molecular weight polyolefin membrane produced by a method comprising: a. forming a mixture comprising an ultra-high molecular weight polyolefin and a porogen; b. heating the mixture to an elevated temperature to produce a solution of ultra-high molecular weight polyolefin and porogen; c. extruding the solution of ultra-high molecular weight polyolefin and porogen through a forming die under moderate shear sufficient to enable the employment of conventional extrusion equipment and/or techniques to thereby form a membrane; d. cooling the membrane sufficiently to cause phase separation resulting in a polymer-rich, porogen-poor phase and a polymer poor, porogen-rich phase in said membrane; e. creating a microporous structure in the membrane by removing porogen from said membrane; and f. drying the microporous membrane under restraint to minimize collapse of the microporous structure.

Claim 12

A microporous membrane produced by a method including the steps of: a. forming a mixture comprising UHMW-PE and a porogen; b. heating the mixture to an elevated temperature to produce a solution of UHMW-PE and porogen; c. extruding the solution of UHMW-PE and porogen through a forming die under moderate shear sufficient to enable the employment of conventional extrusion equipment and/or techniques to thereby form a membrane; d. cooling the membrane sufficiently to cause phase separation resulting in a polymer-rich, porogen-poor phase and a polymer-poor, porogen-rich phase in said membrane; e. creating a microporous structure in the membrane by removing porogen from said membrane; f. drying the microporous membrane under restraint to minimize collapse of the microporous structure.

Claim 13

A microporous membrane produced by a method including the steps of: a. forming a mixture comprising UHMW-PE and a porogen; b. heating the mixture to an elevated temperature to produce a solution of UHMW-PE and porogen; c. extruding the solution of UHMW-PE and porogen through a forming die under moderate shear sufficient to enable the employment of conventional extrusion equipment and/or techniques to thereby form a membrane; d. cooling the membrane sufficiently to cause phase separation resulting in a polymer-rich, porogen-poor phase and a polymer-poor, porogen-rich phase in said membrane; e. creating a microporous structure in the membrane by removing porogen from said membrane; f. drying the microporous membrane under restraint to minimize collapse of the microporous structure.

Claim 14

A microporous membrane of claim 9 wherein said UHMW-PE has a weight average molecular weight of at least 1,000,000.

Claim 15

A microporous membrane of claim 10, wherein said membrane is formed by extruding the solution through a slot die.

Claim 16

A microporous membrane of claim 10 wherein said membrane is formed by extruding the solution through a blown film die.

Claim 17

A microporous membrane of claim 10 wherein said membrane is formed by extruding the solution through a hollow fiber die.

Claim 18

A microporous membrane of claim 10 wherein said UHMW-PE is present in the mixture of UHMW-PE and porogen in an amount of from about 2% to about 20%, by weight, based upon UHMW-PE and porogen.

Claim 19

A microporous membrane of claim 14 wherein said porogen comprises mineral oil.

Claim 20

A microporous membrane of claim 15 wherein said membrane is restrained during extraction.

Claim 21

A microporous membrane of claim 9 wherein said UHMW-PE has an intrinsic viscosity of at least about 8.

Claim 22

A microporous membrane of claim 9 wherein said membrane is restrained during extraction.