# US 8,540,801 B2 · Microporous membrane and method for forming

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- Number: US 8,540,801 B2
- Document ID: US8540801B2
- Status: Granted
- Kind: B2
- Application number: 13/129,145
- Filed: 2009-10-22
- Published: 2011-09-22
- Granted: 2013-09-24
- Earliest claimed: 2008-11-21
- Assignees: 3M Innovative Properties Company
- Applicants: Ilyess H. Romdhane; Mikhail S. Mezhirov
- Inventors: Ilyess H. Romdhane; Mikhail S. Mezhirov
- Web page: https://patentgrep.com/patent/US8540801B2

## CPC

- B01D 71/08: Polysaccharides
- B01D 67/0013: {Casting processes}
- B01D 69/02: characterised by their properties
- B01D 69/1213: {Laminated layers}
- B01D 71/301: {Polyvinylchloride}
- B01D 71/56: Polyamides, e.g. polyester-amides
- B01D 71/643: {Polyether-imides}
- B01D 71/68: Polysulfones; Polyethersulfones
- B01D 2325/02834: more than 0.1 and up to 1 µm
- Y10T 428/249953: Composite having voids in a component [e.g., porous, cellular, etc.]
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The present disclosure describes a method for forming microporous membranes. More specifically, vapor induced phase separation techniques are used for forming multizone microporous membranes having improved material throughput.

## Claims

### Claim 1

A method for forming a microporous membrane comprising:
casting a plurality of dope formulations on a support to provide a multilayer sheet having a first major surface;
exposing the multilayer sheet to a first relative humidity level such that water vapor diffuses into the first major surface;
exposing the multilayer sheet to a second relative humidity level such that additional water vapor diffuses into the multilayer sheet effecting a phase separation to provide the microporous membrane, wherein the second relative humidity level is greater than the first relative humidity level;
washing the microporous membrane; and
drying the microporous membrane.

### Claim 2 (depends on 1)

The method of claim 1, wherein casting a plurality of dope formulations comprises casting a first dope formulation and a second dope formulation to provide the multilayer sheet.

### Claim 3 (depends on 2)

The method of claim 2, wherein the first dope formulation is the same formulation as the second dope formulation.

### Claim 4 (depends on 1)

The method of claim 1, further comprising formulating the plurality of dope formulations, each of the plurality of dope formulations comprising a polymeric material, an adjuvant and a solvent.

### Claim 5 (depends on 4)

The method of claim 4, wherein the polymeric material in each of the plurality of dope formulations is selected from the group consisting of polyethersulfones, polyetherimides, nylons, polyimides, polyamides, polysulfones, polyarylsulphones, polyvinyl chloride, polyalkylene terephthalates, polycarbonates, polyolefins, cellulosics, polystyrenes, acrylic polymers, methacrylic polymers, copolymers of acrylic or methacrylic polymers, and combinations thereof.

### Claim 6 (depends on 4)

The method of claim 4, wherein the adjuvant comprises a poly(alkylene glycol), a polyether, or combinations thereof.

### Claim 7 (depends on 6)

The method of claim 6, wherein the poly(alkylene glycol) is poly(ethylene glycol).

### Claim 8 (depends on 4)

The method of claim 4, wherein a concentration of the adjuvant of the first dope formulation and the second dope formulation independently is in a range from about 60 to about 70 weight percent based on the total weight of the dope formulation.

### Claim 9 (depends on 4)

The method of claim 4, wherein a concentration of polymeric material of the second dope formulation is greater than a concentration of polymeric material of the first dope formulation.

### Claim 10 (depends on 4)

The method of claim 4, wherein the concentration of polymeric material of the first dope formulation and the second dope formulation independently is in a range from about 5 to about 15 weight percent based on the total weight of the dope formulation.

### Claim 11 (depends on 1)

The method of claim 1, wherein the second relative humidity level is at least 5 percent greater than the first relative humidity level.

### Claim 12 (depends on 11)

The method of claim 11, wherein the first relative humidity level is in a range from about 45 to about 55 percent and the second relative humidity level is in a range from about 60 to about 80 percent.

### Claim 13 (depends on 1)

The method of claim 1, wherein exposing the multilayer sheet further comprises exposing the multilayer sheet to an intermediate humidity level.

### Claim 14 (depends on 13)

The method of claim 13, wherein the intermediate humidity level is intermediate to the first relative humidity level and to the second relative humidity level.