# US 5,708,040 A · Method for preparing porous membranes utilizing water or organic vapor adsorption

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- Number: US 5,708,040 A
- Document ID: US5708040A
- Status: Granted
- Kind: A
- Application number: 08/654,731
- Filed: 1996-05-29
- Granted: 1998-01-13
- Earliest claimed: 1995-10-28
- Assignees: Korea Institute of Science and Technology
- Inventors: Jae Min Hong; Seong Ryong Ha; Hyun Chae Park; Yong Soo Kang; Kyu Hong Ahn
- Web page: https://patentgrep.com/patent/US5708040A

## CPC

- C08J 9/28: by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
- B01D 67/0013: {Casting processes}
- B01D 69/02: characterised by their properties
- B01D 2323/12: Specific ratios of components used
- B01D 2325/022: Asymmetric membranes
- B01D 2325/20: Specific permeability or cut-off range
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- 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)

## Abstract

The present invention describes a method for preparing an asymmetric porous membrane by a dry-wet phase inversion method, which comprises contacting a cast or spun polymer solution with water or organic vapor prior to immersing into the non-solvent precipitation medium, whereby said water or organic vapor is adsorbed onto the cast or spun polymer solution. Higher permeability and excellent rejection ability can be obtained, due to the high porosity and uniform pore size of said membranes according to the present invention.

## Claims

### Claim 1

A method for preparing an asymmetric porous membrane by a dry-wet phase inversion process, comprising bringing a cast or spun polymer solution into contact with a gas containing water vapor or organic vapor prior to immersing the cast or spun polymer solution into a non-solvent precipitation medium, whereby said water vapor or organic vapor is adsorbed onto said polymer solution.

### Claim 2 (depends on 1)

The method according to claim 1, wherein said polymer solution is composed of at least one polymer selected from the group consisting of polysulfone, polyethersulfone, polyamide, polyimide, polyetherimide, polyolefin, polycarbonate, polyphenyleneoxide, polyvinylidene fluoride, polyacrylonitrile, cellulose, and their derivatives.

### Claim 3 (depends on 1)

The method according to claim 1, wherein said polymer solution contains at least one solvent selected from the group consisting of N-methyl pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, dioxane, methylene chloride, methyl acetate, ethyl acetate, and chloroform, and co-solvent thereof.

### Claim 4 (depends on 1)

The method according to claim 1, wherein said organic vapor is vapor of a non-solvent or a solvent, or a mixture thereof, which sparingly dissolves the membrane forming polymer.

### Claim 5 (depends on 4)

The method according to claim 4, wherein said organic vapor is vapor of at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and t-butanol.

### Claim 6 (depends on 1)

The method according to claim 1, wherein said gas contains water vapor.

### Claim 7 (depends on 1)

The method according to claim 1, wherein said gas contains an organic vapor.