MEMBRANE-FORMING DOPE FOR NON-SOLVENT INDUCED PHASE SEPARATION METHODS, AND A METHOD FOR PRODUCING A POROUS HOLLOW FIBER MEMBRANE USING THE SAME

Abstract

A membrane-forming dope for non-solvent induced phase separation methods, the membrane-forming dope comprising 15 to 40 wt. % of polysulfone-based resin, 5 to 60 wt. % of polyvinylpyrrolidone, and 0.1 to 10 wt. % of polyoxyethylene sorbitan fatty acid ester, all of which are dissolved in a water-soluble organic solvent solution. A porous hollow fiber membrane is produced by spinning the membrane-forming dope by a non-solvent induced phase separation method using an aqueous liquid as a core liquid. The obtained high-performance porous hollow fiber membrane can be used as a water vapor permeable membrane used in fuel cells, because its water vapor permeability is not significantly reduced even after use in a high temperature environment such as, for example, 100 to 120? C.

Claims

1. A membrane-forming dope for non-solvent induced phase separation methods, the membrane-forming dope comprising 15 to 30 wt. % of polyphenylsulfone resin, 15 to 40 wt. % of polyvinylpyrrolidone, and 0.5 to 5 wt. % of polyoxyethylene sorbitan fatty acid ester, all of which are dissolved in a water-soluble organic solvent solution.

2. (canceled)

3. The membrane-forming dope for non-solvent induced phase separation methods according to claim 1, wherein the polyoxyethylene sorbitan fatty acid ester is polyoxyethylene sorbitan monolaurate.

4. (canceled)

5. The membrane-forming dope for non-solvent induced phase separation methods according to claim 1, 2, or 3, wherein the membrane-forming dope is free from inorganic particles.

6. A method for producing a porous hollow fiber membrane, the method comprising spinning the membrane-forming dope for non-solvent induced phase separation methods according to claim 1, by a non-solvent induced phase separation method using a double circular nozzle and using an aqueous liquid as a core liquid.

7. A water vapor permeable membrane, which is produced by the method for producing according to claim 6.

8. The water vapor permeable membrane according to claim 7, which is used as humidifying membranes for fuel cells.

9. The water vapor permeable membrane according to claim 8, which is used in a high temperature environment of 100 to 120? C.

10. The membrane-forming dope for non-solvent induced phase separation methods according to claim 3, wherein the membrane-forming dope is free from inorganic particles.

11. A method for producing a porous hollow fiber membrane, the method comprising spinning the membrane-forming dope for non-solvent induced phase separation methods according to claim 3, by a non-solvent induced phase separation method using a double circular nozzle and using an aqueous liquid as a core liquid.

Description

EXAMPLES

[0027] The following describes the present invention with reference to Examples.

Example

[0028] A membrane-forming dope being homogeneous at room temperature was prepared. The membrane-forming dope comprised 20 parts by weight of polyphenylsulfone resin (RADEL R-5000, produced by Solvay Specialty Polymers), 15 parts by weight of polyvinylpyrrolidone (K-30, produced by Junsei Chemical Co. Ltd.), 1 part by weight of polyoxyethylene sorbitan monolaurate (Tween 20, produced by Kanto Chemical Co., Ltd.), and 64 parts by weight of dimethylacetamide.

[0029] Dry-wet spinning was performed by extruding the prepared membrane-forming dope into a water coagulation bath using a spinning nozzle having a double circular structure and using water as a core liquid. Then, washing was carried out in pressurized water at 121? C. for 1 hour, followed by drying in an oven at 60? C., thereby obtaining a porous polyphenylsulfone resin hollow fiber membrane having an outer diameter of 1,000 ?m and an inner diameter of 700 ?m.

[0030] The obtained porous polyphenylsulfone resin hollow fiber membrane was measured for water vapor permeation rate, pure water permeation rate, and air permeation rate.

[0031] Water vapor permeation rate: A both end-opened type hollow fiber membrane module was produced by using 3 hollow fiber membranes having an effective length of 17 cm. Humidified air at an RH of 90% was supplied from the outside of the membrane, and dry air was supplied in the inside of the membrane. The amount of water vapor permeation per time was measured, and converted into the amount of air permeation per unit membrane area, unit time, water vapor partial pressure difference between the outside and inside of the membrane, and 1 MPa.

[0032] Pure water permeation rate: Using a both end-opened type hollow fiber membrane module having an effective length of 15 cm, pure water was used as raw water and filtered from the inside of the hollow fiber membrane to the outside (internal pressure filtration) under conditions in which the temperature was 25? C. and the pressure was 1 MPa. The amount of water permeation per time was measured, and converted into the amount of water permeation per unit membrane area, unit time, and 1 MPa.

[0033] Air permeation rate: Using a module prepared by forming a hollow fiber membrane having an effective length of 15 cm into a loop shape, and fixing the both ends of the loop to a glass tube, air at a temperature of 25? C. and a pressure of 50 kPa was applied from the inside of the membrane to the outside. The amount of air permeation per time was measured, and converted into the amount of air permeation per unit membrane area, unit time, and 1 MPa.

Comparative Example 1

[0034] In the Example, polyoxyethylene sorbitan monolaurate was not used, and the amount of dimethylacetamide was changed to 65 parts by weight.

Comparative Example 2

[0035] In the Example, polyvinylpyrrolidone was not used, the amount of polyoxyethylene sorbitan monolaurate was changed to 15 parts by weight, and the amount of dimethylacetamide was changed to 65 parts by weight, respectively.

[0036] Table below shows the results obtained in the above Example and Comparative Examples.

TABLE-US-00001 TABLE Comp. Comp. Measurement item Example Ex. 1 Ex. 2 Water vapor permeation rate (g/cm.sup.2/ minute/MPa) After membrane formation (90? C.) 0.282 0.280 0.290 After retention at 120? C. for 50 hours 0.273 0.241 0.260 Performance reduction rate (%) 3 14 10 Pure water permeation rate (ml/cm.sup.2/hour/ 0.0 0.0 0.0 MPa) Air permeation rate (ml/cm.sup.2/minute/MPa) 0.0 0.0 0.0

INDUSTRIAL APPLICABILITY

[0037] The porous hollow fiber membrane according to the present invention can be effectively used as a water vapor permeable membrane used in fuel cells, or the like, because its water vapor permeability is not significantly reduced even after use in a high temperature environment such as 100 to 120? C.