Poly(ethylene chlorotrifluoroethylene) membranes

• US 7,632,439 B2
• Filed: 01/31/2007
• Issued: 12/15/2009
• Est. Priority Date: 02/12/2002
• Status: Expired due to Fees

• Current Assignee: Evoqua Water Technologies LLC
• Original Assignee: Siemen Water Technologies Corporation (Siemens AG)
• Inventors: Muller, Heinz-Joachim, Mullette, Daniel
• Primary Examiner(s): Fortuna; Ana M
• Application Number:
  US11/700,625
• Publication Number:
  US 20070216057A1
• Time in Patent Office: 1,049 Days
• Field of Search: 210/500.27, 210/500.36, 210/500.23, 210/502.1, 521/50, 521/90, 264/41, 264/49, 264/127, 264/213, 264/512, 264/514, 264/515, 264/171.17, 264/171.26, 264/173.13, 264/173.16, 264/48, 428/308.4
• US Class Current: 264/41
• CPC Class Codes: B01D 2323/08 Specific temperatures applied
• CPC Class Codes: B01D 2323/081 Heating
• CPC Class Codes: B01D 2323/18 Pore-control agents or pore formers
• CPC Class Codes: B01D 2323/22 Specific non-solvents or non-solvent system
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 2325/0231 Dense layers being placed on the outer side of the cross-section
• CPC Class Codes: B01D 2325/20 Specific permeability or cut-off range
• CPC Class Codes: B01D 2325/36 Hydrophilic membranes
• CPC Class Codes: B01D 2325/38 Hydrophobic membranes
• CPC Class Codes: B01D 67/0018 Thermally induced processes [TIPS]
• 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 67/0031 by elimination of at least one of the blocks of a block copolymer
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 71/32 containing fluorine atoms
• CPC Class Codes: B29C 67/202 comprising elimination of a solid or a liquid ingredient
• CPC Class Codes: D01D 5/24 with a hollow structure; Spinnerette packs therefor D01D5/38 takes precedence; producing tubes of plastic material B29D; addition of agents forming hollow filaments D01F1/08
• CPC Class Codes: Y10T 428/249958 Void-containing component is synthetic resin or natural rubbers

Abstract

Porous polymeric membranes including HALAR® (poly(ethylene chlorotrifluoroethylene)) and related compounds and the methods of production thereof which avoid the use of toxic solvents. Preferred solvents, coating agents and pore forming agents are citric acid ethyl ester or glycerol triacetate. The membranes may be in the form of a hollow fiber or flat sheet, and may include other agents to modify the properties of the membranes, such as the hydrophilic/hydrophilic balance. Leachable agents may also be incorporated into the membranes.

Claims

1. A method of forming a membrane comprising casting a membrane from a solution at a temperature greater than 200°

C. consisting essentially of poly(ethylene chlorotrifluoroethylene) and at least one solvent selected from the group consisting of a compound according to formula I and formula II;

2. The method of claim 1, wherein the solvent according to formula I is citric acid ethyl ether.

3. The method of claim 1, wherein the solvent according to formula II is glycerol triacetate.

4. The method of claim 1, further comprising inducing a phase separation of poly(ethylene chlorotrifluoroethylene) and the solvent.

5. The method of claim 4, further comprising contacting a first surface with a lumen forming fluid.

6. The method of claim 5, wherein the act of contacting a first surface with the lumen forming fluid comprises contacting the surface with diethylene glycol.

7. The method of claim 5, further comprising contacting a second surface with a coating fluid.

8. The method of claim 7, wherein the act of contacting the second surface with the coating fluid comprises contacting the surface with a fluid selected from the group consisting of glycerol triacetate, citric acid ethyl ester, diethylene glycol, and mixtures thereof.

9. The method of claim 4, further comprising removing the solvent from the membrane.

10. The method of claim 4 wherein R₁, R₂, and R₃are selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, and hexyl.

11. A method of forming a hollow fiber membrane comprising:

forming a blend at a temperature greater than 200°

C. consisting essentially of poly(ethylene chlorotrifluoroethylene) and at least one solvent selected from the group consisting of a compound according to formula I and formula II;

12. The method of claim 11, wherein the solvent according to formula I is citric acid ethyl ether.

13. The method of claim 11, wherein the solvent according to formula II is glycerol triacetate.

14. The method of claim 11, wherein the blend comprises about 14-25% poly(ethylene chlorotrifluoroethylene).

15. The method of claim 11, further comprising an act of contacting a second surface of the hollow fiber shape with a coating fluid.

16. The method of claim 15, wherein the coating fluid is selected from the group consisting of glycerol triacetate, citric acid ethyl ester, diethylene glycol, and mixtures thereof.

17. The method of claim 11, wherein the lumen forming fluid comprises diethylene glycol.

18. The method of claim 11, wherein the blend further comprises a solid pore forming agent.

19. The method of claim 18, further comprising an act of removing the pore forming agent from the hollow fiber with a leachant.

20. The method of claim 19, wherein the leachant comprises a caustic solution.

21. The method of claim 18, wherein the pore forming agent is an inorganic solid with a particle size of less than 1 micron.

22. The method of claim 18, wherein the pore forming agent comprises silica.

23. The method of claim 22, further comprising an act of preparing from the blend, a dope comprising from about 3 weight percent to about 9 weight percent silica.

24. A method of preparing a porous polymeric material comprising:

heating a mixture to a temperature greater than 200°

C. to form a solution consisting essentially of poly(ethylene chlorotrifluoroethylene) and at least one solvent selected from the group consisting of a compound according to formula I and formula II;

25. The method of claim 24, wherein R₁, R₂, and R₃, are selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl and hexyl.