Microporous membrane made of non-crystalline polymers and method of producing the same

• US 5,746,916 A
• Filed: 01/25/1995
• Issued: 05/05/1998
• Est. Priority Date: 01/26/1994
• Status: Expired due to Term

• Current Assignee: Mitsubishi Rayon Company Limited (Mitsubishi Chemical Holdings Corporation)
• Original Assignee: Mitsubishi Rayon Company Limited (Mitsubishi Chemical Holdings Corporation)
• Inventors: Kawai, Miho, Koyanagi, Seiya, Kamo, Jun
• Primary Examiner(s): FORTUNA, ANA M
• Application Number:
  US08/377,706
• Time in Patent Office: 1,196 Days
• Field of Search: 264/41, 264/49, 210/500.41, 210/500.23, 210/500.39, 210/500.35
• US Class Current: 210/500.23
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2323/30 Cross-linking
• CPC Class Codes: B01D 2325/36 Hydrophilic membranes
• CPC Class Codes: B01D 67/0027 by stretching
• CPC Class Codes: B01D 67/003 by selective elimination of components, e.g. by leaching
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 71/64 Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
• CPC Class Codes: B01D 71/641 Polyamide-imides
• CPC Class Codes: B01D 71/643 Polyether-imides
• CPC Class Codes: B01D 71/68 Polysulfones; Polyethersulfones

Abstract

A microporous membrane made of a non-crystalline polymer having, within its wall, microfibrils and slit-like micropores which are oriented in the lengthwise direction of the membrane, said slit-like micropores communicating from one surface to the other surface of the membrane, and forming a stacked construction. This membrane has a high flux value of AFR and WFR, excellent heat-, solvent-, and pressure-resistance, and a high mechanical strength, and does not contain any undesirable materials which eluate during use. This membrane is thus useful as a multi-purpose separation membrane, such as for medical uses, food industries, purification of water or air, and the separation of hot liquids.

Claims

1. A method of producing a microporous membrane made of a non-crystalline polymer having, within its wall, microfibrils and slit-like micropores which are oriented in the lengthwise direction of the membrane, wherein said slit-like micropores communicate from one surface to the other surface of the membrane, and form a stacked construction, and said non-crystalline polymer is at least one selected from the group consisting of polysulfone, polyimide, polyarylate, polycarbonate, polyphenylene oxide, polystyrene. polymethylmethacrylate, and copolymers thereof, said method comprising the steps of:

(1) mixing 40 to 95 wt. % of a non-crystalline polymer and 60 to 5 wt. % of fine particles having an average particle size of from 0.01 to 10 μ

m to make a mixed composition,

(2) making a precursor from the mixed composition; and

(3) stretching the precursor at a deformation rate of not less than 200 %/min.

2. A method of producing a microporous membrane according to claim 1, wherein a heat-setting step is further conducted after the stretching step.

3. A microporous membrane produced by the method of claim 2.

4. A microporous membrane produced by the method of claim 1.

5. A method according to claim 1, wherein in step (2) the precursor to said microporous membrane is formed at a temperature from the glass transition temperature (Tg) of said non-crystalline polymer to a temperature of Tg+200°

C.

6. A method according to claim 1, wherein said fine particles have an average particle size of 0.1 to 5μ

.

7. A method according to claim 1, wherein said fine particles have an average particle size of 60 to 15 wt %.

12. A method according to claims 1 or 8, wherein said fine particles are comprised of at least one member selected from the group consisting of crosslinked silicone resin, surface-treated calcium carbonate, calcium oxide, silica, alumina, aluminum sulfate, barium sulfate, talc, clay, titanium dioxide, a crosslinked polystyrene resin, a melamine resin, a methylmethacryalte resin, a crosslinked rubber and a benzoguanamine resin.

13. A method according to claims 1 or 8, wherein said fine particles are extractable from said membrane by an aqueous extraction agent.

8. A method of producing a microporous hollow fiber membrane comprising the steps of:

(1) mixing 40 to 95 wt. % of at least one non-crystalline polymer selected from the group consisting of polysulfone. polyimide, polyarylate, polycarbonate, polyphenylene oxide, polystyrene. polymethylmethacrylate, and copolymers thereof and 60 to 5 wt. % of fine particles having an average particle size of from 0.01 to 10 μ

m to make a mixed composition;

(2) spinning the mixed composition through a nozzle to make a hollow fiber precursor;

(3) stretching the hollow fiber precursor at a deformation rate of not less than 200 %/min.

9. A method of producing a microporous hollow fiber membrane according to claim 8, wherein a heat-setting step is further conducted after the stretching step.

10. A microporous hollow fiber membrane produced by the method of claim 9.

11. A microporous hollow fiber membrane produced by the method of claim 8.