Membrane post treatment

• US 7,662,212 B2
• Filed: 07/08/2004
• Issued: 02/16/2010
• Est. Priority Date: 07/08/2003
• Status: Expired due to Fees

• Current Assignee: Evoqua Water Technologies LLC
• Original Assignee: Siemen Water Technologies Corporation (Siemens AG)
• Inventors: Mullette, Daniel, Patel, Neeta, Muller, Joachim
• Primary Examiner(s): Greene; Jason M
• Application Number:
  US10/564,024
• Publication Number:
  US 20060157404A1
• Time in Patent Office: 2,049 Days
• Field of Search: 96/4, 96/11, 96/12, 96/13, 96/14, 95/95, 95/45, 95/50, 95/52, 95/54, 210/490, 210/640, 210/650, 210/651, 210/652, 210/653, 210/654, 210/500.21, 210/500.27, 210/500.28, 210/500.42, 427/244, 427/245, 427/331, 427/430.1, 555/24, 55D/IG.5
• US Class Current: 95/45
• CPC Class Codes: B01D 2323/02 Hydrophilization
• CPC Class Codes: B01D 2323/10 Specific pressure applied
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2323/283 Reducing the pores
• CPC Class Codes: B01D 2323/30 Cross-linking
• CPC Class Codes: B01D 2323/34 Use of radiation
• CPC Class Codes: B01D 67/0011 Casting solutions therefor
• CPC Class Codes: B01D 67/00111 Polymer pretreatment in the casting solutions
• CPC Class Codes: B01D 67/0018 Thermally induced processes [TIPS]
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: B01D 67/009 with wave-energy, particle-radiation or plasma
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 71/26 Polyalkenes
• CPC Class Codes: B01D 71/262 Polypropylene
• CPC Class Codes: B01D 71/32 containing fluorine atoms
• CPC Class Codes: B01D 71/34 Polyvinylidene fluoride
• CPC Class Codes: Y10S 55/05 Methods of making filter

Abstract

The invention relates to polymeric ultrafiltration or microfiltration membranes of, for instance, Halar, PVDF or PP, incorporating PVME or vinyl methyl ether monomers. The PVME may be present as a coating on the membrane or dispersed throughout the membrane or both. The membranes are preferably hydrophilic with a highly asymmetric structure with a reduced pore size and/or absence of macrovoids as a result of the addition of PVME. The PVME maybe cross-linked. The invention also relates to methods of hydrophilising membranes and/or preparing hydrophilic membranes via thermal or diffusion induced phase separation processed.

Claims

1. A polymeric ultra or microfiltration membrane incorporating PVME wherein the PVME is incorporated in the membrane as a homogeneous or heterogeneous dispersion throughout the membrane and the PVME is present as a coating on the membrane.

2. A polymeric ultra or microfiltration membrane according to claim 1 wherein the PVME is present as a coating on the membrane and is incorporated in the membrane as a homogeneous dispersion throughout the membrane.

3. A membrane according to claim 1 wherein the polymeric ultra or microfiltration membrane includes one or more of Halar, PVDF or PP.

4. A membrane according to claim 1 which is hydrophilic.

5. A membrane according to claim 1 which has an asymmetric structure.

6. A membrane according to claim 1 having reduced pore size as a result of the addition of PVME.

7. A membrane according to claim 1 substantially free from macrovoids.

8. A membrane according to claim 1 including cross linked PVME.

9. A polymeric ultra or microfiltration membrane incorporating adsorbed PVME and embedded PVME and wherein adsorbed PVME is cross-linked with embedded PVME.

10. A polymeric ultra or microfiltration membrane according to claim 9 containing PVDF and PVME in a ratio of 0.1:

24 to 0.5 to 24.

11. A polymeric ultra or microfiltration membrane according to claim 9 containing 0.4 to 30 wt % PVME.

12. A polymeric ultra or microfiltration according to claim 9 which on soaking for 8 hours produces a detectable quantity of PVME.

13. A polymeric ultra or microfiltration membrane according to claim 9 containing PVME which on soaking for 48 hours produces a leachate having at least 5 ppm PVME.

14. A hydrophobic polymeric ultra or microfiltration membrane according to claim 9 rendered hydrophilic by contacting the membrane with an aqueous or alcoholic solution of PVME with a concentration 0.05 to 5 wt %.

15. A method of hydrophilising a membrane prepared from a polymeric material, said method including the step of contacting said polymeric material with a compatible at least partially water soluble copolymer containing vinylmethyl ether monomer and at least one other co-monomer.

16. A method according to 15 wherein the vinylmethyl ether monomer is present in an amount of at least 50 mole % of the polymeric hydrophilising agent.

45. A method according to claim 16 wherein PVME is incorporated in the membrane dope and formed into a membrane, and wherein said membrane is further treated with PVME.

46. A method according to claim 16 wherein the membrane is treated to cross-link incorporated and/or adsorbed PVME.

47. A method according to claims 46 wherein the method of cross linking is e-beam.

17. A method according to 15 wherein the co-monomer is selected from the group consisting of:

co-polymerisable acrylate monomers and copolymerisable vinyl monomers.

18. A method of modifying the hydrophobic/hydrophilic balance of a polymer membrane prepared from a polymeric material, said method including the step of contacting said polymeric material with polyinylmethyl ether (PVML) to produce a modified polymeric membrane wherein the polymeric membrane is an ultrafiltration membrane or a microfiltration membrane.

19. A method according to claim 18 wherein the polymeric membrane is coated with PVME.

20. A method according to claim 18 wherein the polymeric material is a hydrophobic polymer and hydrophobic/hydrophilic balance of the polymer is modified to provide a hydrophilic modified polymeric membrane.

21. A method according to claim 18 wherein the polymeric material is poly(vinylidene fluoride) (PVDF), poly(ethylene-chlorotrifluoroethylene) (Halar) and poly(propylene)(PP) or mixtures thereof.

22. A method according to claim 18 wherein the polymeric material is a formed membrane treated with a solution of PVME at a concentration and for a time sufficient to allow PVME saturation of said membrane to take place.

23. A method according to claim 22 wherein the polymeric material is post treated by soaking in a solution of PVME in ethanol.

24. A method according to claim 23 wherein the polymeric material is post treated by soaking in a solution of PVME in water.

25. A method according to claim 18 wherein the concentration of PVME is less than 10%.

26. A method according to claim 25 wherein the concentration of PVME is greater than 0.1%.

27. A method according to claim 18 wherein treatment with PVME takes place for between 5 minutes and 16 hours.

28. A method according to claim 27 wherein treatment with a solution of PVME is followed by a rinsing stage to remove unbound PVME.

29. A method according to claim 18 wherein the polymeric material is treated with PVME b means of adding PVME to membrane dope prior to casting.

30. A method according to claim 29 wherein the membrane dope is cast via a thermally induced phase separation process.

31. A method according to claim 30 wherein the membrane dope includes PVME in an amount up to 1 wt %.

32. A method according to claim 31 wherein the membrane dope is cast via a diffusion induced phase separation process.

33. A method according to claim 32 wherein the membrane dope includes PVME in an amount higher than 1 wt %.

34. A method according to claim 32 wherein the PVME is dissolved in a polymer dope/solvent/non-solvent mixture.

35. A method according to claim 34 wherein the solvent/non-solvent mixture includes a PVME solvent and PVME non-solvent.

36. A method according to claim 34 wherein the PVME solvent possesses weak polarity.

37. A method according to claim 34 wherein the PVME solvent is glyceroltriacteate.

38. A method according to claim 35 wherein the PVME non-solvent is strongly polar.

39. A method according to claim 38 wherein the PVME non-solvent is diethylene, glycol, triethylene glycol, 1,4-butanediol or mixtures thereof.

40. A method according to claim 35 herein the solvent mixture includes from 40-60% non-solvent.

41. A method according to claim 40 wherein the solvent mixture includes PVME in amount of 0.1-2 wt %.

42. A method according to claim 32 herein the method of casting is a TIPS process further including treatment with a coating solution.

43. A method according to claim 32 wherein the method of casting is a TIPS process further including treatment with a coating solution which contains a solvent and a non-solvent.

44. A method according to claim 39 wherein the process is a DIPS process where N-methylpyrrolidone is present as a solvent, and water is present as non-solvent.