Hydrophilic hollow fiber ultrafiltration membranes that include a hydrophobic polymer and a method of making these membranes

• US 6,596,167 B2
• Filed: 03/26/2001
• Issued: 07/22/2003
• Est. Priority Date: 03/26/2001
• Status: Expired due to Fees

• Current Assignee: Koch Membrane Systems, Inc. (KOCH Industries Incorporated)
• Original Assignee: Koch Membrane Systems, Inc. (KOCH Industries Incorporated)
• Inventors: Ji, Jiang, Mehta, Mahesh J., Dicecca, Candeloro
• Primary Examiner(s): FORTUNA, ANA M
• Application Number:
  US09/817,889
• Publication Number:
  US 20030015466A1
• Time in Patent Office: 848 Days
• Field of Search: 210/500.36, 210/500.41, 210/500.42, 210/500.27, 210/490, 210/500.23, 264/41, 264/48, 264/49, 264/177.14, 427/244, 427/245
• US Class Current: 210/500.42
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2323/30 Cross-linking
• CPC Class Codes: B01D 2325/20 Specific permeability or cut-off range
• CPC Class Codes: B01D 2325/36 Hydrophilic membranes
• CPC Class Codes: B01D 67/00113 Pretreatment of the casting solutions, e.g. thermal treatment or ageing
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 71/34 Polyvinylidene fluoride

Abstract

A hydrophilic membrane that includes a hydrophobic polymer and a water-soluble polymer-metal complex is provided. This membrane is made by heating a mixture of a hydrophobic polymer, a metal compound, and a water-soluble polymer. The water-soluble polymer forms complexes with the metal compound and homogeneously entangles with the dissolved hydrophobic polymer to form a viscous dope. The dope is extruded through an annular orifice to form a hollow fiber. The fiber is put in an environment having a controlled humidity so that it becomes partially solidified, and then, the fiber is put in a coagulation bath. The hollow fiber is formed by phase inversion in the coagulation bath and is collected using a take-up wheel that is partially immersed in a leaching bath.

Claims

1. A hydrophilic hollow fiber membrane comprising:

a hydrophobic polymer; and

a water-soluble polymer transition metal complex entangled with said hydrophobic polymer, wherein said water-soluble polymer is selected from the group consisting of polyvinylpyrrolidone, polyvinylpyrridine, and combinations thereof.

2. The membrane of claim 1, wherein said membrane has a tensile strength of about 200 to 700 psi.

3. The membrane of claim 1, wherein said membrane has a water flux of about 100 to 1500 gfd at about 40 psi.

4. The membrane of claim 1, wherein said membrane has a rejection towards a 150 k Dextran molecular weight marker ranging from about 5% to 99.9%.

5. The membrane of claim 1, wherein said hydrophobic polymer is a synthetic polymer capable of forming a film or fiber and is selected from the group consisting of polyvinylidene fluoride, polyetherketone, polypropylene, polyethylene, and combinations thereof.

6. The membrane of claim 1, wherein said membrane is comprised of polyvinylidene fluoride and a polyvinylpyrrolidone and iron complex.

7. The membrane of claim 1, wherein said membrane is an ultrafiltration membrane.

8. The membrane of claim 1, wherein said water-soluble polymeric component is permanently anchored in said hydrophobic polymer membrane matrix.

9. The membrane of claim 1, wherein said water-soluble polymeric component cannot be washed out of said membrane matrix with water or bleach comprised of 12.5% sodium hypochlorite.

10. A method of making a hydrophilic hollow fiber membrane, comprising:

mixing a hydrophobic polymer and a solvent to form a mixture;

heating said mixture to form a solution;

adding a transition metal compound and a water-soluble polymer is selected from the group consisting of polyvinylpyrrolidone, polyvinylpyrridine, and combinations thereof to said solution;

heating and mixing said solution, wherein said water-soluble polymer forms complexes with said transition metal containing compound and homogeneously entangles with said dissolved hydrophobic polymer to form a viscous dope; and

extruding said dope through an annular orifice to form a hollow fiber.

11. The method of claim 10, further comprising:

feeding said fiber into a coagulation bath, wherein said fiber is formed by phase inversion in said coagulation bath.

12. The method of claim 11, further comprising:

feeding said fiber through an environment having a controlled humidity so that said fiber becomes partially solidified before said fiber enters said coagulation bath.

13. The method of claim 11, further comprising:

collecting said hollow fiber with a take-up wheel partially immersed in a leaching bath.

14. The method of claim 13, wherein said leaching bath is comprised of a nonsolvent and has a temperature of about 0.1 to 100°

C.

15. The method of claim 13, wherein said hollow fiber is formed at a rate of about 5 to 300 ft/min.

16. The method of claim 11, wherein said coagulation bath is comprised of about 0% to 60% v/v of said solvent and is at a temperature of 0 to 100°

C.

17. The method of claim 10, wherein said heating steps (b) and (d) take place at a temperature from 0°

C. to the boiling point of the solvent, allowing said dope to be mixed under the reflux of the solvent.

18. The method of claim 10, wherein said viscous dope has a viscosity of about 100 to 600,000 centipoise (cp) at about 25°

C.

19. The method of claim 10, wherein said environment has a relative humidity of 0 to 100% and a temperature range from 0 to 100°

C.

20. The method of claim 19, wherein said humidity is provided by a column having a waterfall at the interior surface of said column and wherein said column maintains between about 50 to 100% relative humidity at various temperatures.

21. The method of claim 10, wherein said solvent is a polar solvent.

22. The method of claim 21, wherein said polar solvent is selected from the group consisting at dimethyl acetamide, N-methyl pyrrolidone, dimethyl formamide, dimethylsulfone, trialkylphosphate, and combinations thereof.

23. The method of claim 10, wherein said metal containing compound is comprised of an electron acceptor that is capable of forming complexes with a variety of ligands.