Method of forming an asymmetric membrane

Patent metadata

Field	Value
Publication number	US-9751050-B2
Application number	US-99765809-A
Country	US
Kind code	B2
Filing date	May 13, 2009
Priority date	Jun 30, 2008
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

The present disclosure provides methods for forming asymmetric membranes. More specifically, methods are provided for applying a polymerizable species to a porous substrate for forming a coated porous substrate. The coated porous substrate is exposed to an ultraviolet radiation source having a peak emission wavelength less than 340 nm to polymerize the polymerizable species forming a polymerized material retained within the porous substrate so that the concentration of polymerized material is greater at the first major surface than at the second major surface.

First claim

What is claimed is:

1. A method of forming an asymmetric membrane comprising:
providing a porous substrate having a first major surface and a second major surface;
applying a polymerizable composition to the porous substrate providing a coated porous substrate, the polymerizable composition comprising
i) at least one polymerizable species; and
ii) at least one photoinitiator; and

exposing the coated porous substrate to an ultraviolet radiation source having a peak emission wavelength less than 340 nm to polymerize the polymerizable species, wherein the photoinitiator residing at the first major surface is exposed to a greater peak irradiance of ultraviolet radiation than the photoinitiator residing further into the thickness of the porous substrate thus reducing the amount of polymerization within the pores of the substrate through the thickness of the substrate, thereby providing an asymmetric membrane, the asymmetric membrane having a polymerized material retained within the porous substrate, the polymerized material having a concentration greater at the first major surface than at the second major surface.

2. The method of claim 1 , further comprising washing the asymmetric membrane after exposing to an ultraviolet radiation source having a peak emission wavelength less than 340 nm.

3. The method of claim 1 , wherein the porous substrate is microporous.

4. The method of claim 1 , wherein the porous substrate comprises a microporous, thermally-induced phase separation membrane.

5. The method of claim 1 , wherein the porous substrate is hydrophilic.

6. The method of claim 1 , wherein the porous substrate is hydrophobic.

7. The method of claim 1 , wherein the porous substrate comprises a film, a nonwoven web, a woven web, a fiber, or combinations thereof.

8. The method of claim 7 , wherein the porous substrate further comprises a particulate.

9. The method of claim 7 , wherein the fiber is a hollow fiber.

10. The method of claim 1 , wherein the porous substrate comprises polyolefins, polyamides, fluorinated polymers, poly(ether)sulfones, cellulosics, poly(ether)imides, polyacrylonitriles, polyvinyl chlorides, ceramics, or combinations thereof.

11. The method of claim 10 , wherein the porous substrate comprises polyolefins.

12. The method of claim 11 , wherein the polyolefins comprise polyethylene or polypropylene.

13. The method of claim 10 , wherein the porous substrate comprises polyamides.

14. The method of claim 13 , wherein the polyamides comprise nylon 6,6.

15. The method of claim 1 , wherein applying comprises die coating, roll coating, dip coating, spray coating, curtain coating, slide coating or combinations thereof.

16. The method of claim 1 , wherein applying the polymerizable composition comprises immersing or saturating the porous substrate.

17. The method of claim 1 , wherein applying the polymerizable composition comprises immersing or saturating a portion of the thickness of the porous substrate to at least one micrometer from the first major surface.

18. The method of claim 1 , wherein at least one of the polymerizable species comprises acrylates, (meth)acrylates, (meth)acrylamides, styrenics, allylics, vinyl ethers, or combinations thereof.

19. The method of claim 18 , wherein at least one of the polymerizable species comprises an ionic group.

20. The method of claim 19 , wherein the ionic group comprises a sulfonic acid or a sulfonic acid salt.

21. The method of claim 19 , wherein the ionic group comprises an amine or a quaternary ammonium salt.

22. The method of claim 19 , wherein the ionic group comprises a carboxylic acid or a carboxylic acid salt.

23. The method of claim 19 , wherein the ionic group comprises a phosphonic acid or a phosphonic acid salt.

24. The method of claim 19 , wherein the ionic group is positively charged, negatively charged, or combinations thereof.

25. The method of claim 1 , wherein the polymerizable composition further comprises a solvent.

26. The method of claim 1 , wherein exposing the coated porous substrate comprises providing an inert environment.

27. The method of claim 1 , wherein the ultraviolet radiation source having a peak emission less than 340 nm is a narrow bandwidth ultraviolet radiation source.

28. The method of claim 27 , wherein the ultraviolet radiation source comprises monochromatic radiation sources, fluorescent radiation sources or combinations thereof.

29. The method of claim 1 , wherein the ultraviolet radiation source comprises a plurality of monochromatic radiation sources.

30. The method of claim 29 , wherein the plurality of monochromatic radiation sources comprises excimer lamp sources, low pressure mercury lamp sources, light emitting diodes, laser sources, or combinations thereof.

31. The method of claim 1 , where the ultraviolet radiation source comprises a plurality of fluorescent radiation sources.

32. The method of claim 1 , wherein the ultraviolet radiation source comprises a peak emission wavelength in a range of about 140 nm to about 320 nm.

33. The method of claim 1 , wherein the ultraviolet radiation source comprises a peak emission wavelength in a range of about 200 nm to about 300 nm.

34. The method of claim 1 , wherein the first major surface of the asymmetric membrane is hydrophilic, and the second major surface of the asymmetric membrane is hydrophobic.

35. The method of claim 1 , wherein the first major surface of the asymmetric membrane is hydrophobic, and the second major surface of the asymmetric membrane is hydrophilic.

36. The method of claim 1 , further comprising positioning the coated porous substrate between a transparent first layer and a second layer to form a multilayer structure, the transparent first layer positioned adjacent to the first major surface and the second layer positioned adjacent to the second major surface, the transparent first layer nearest the ultraviolet radiation source, wherein the transparent first layer and the second layer comprise continuous sheets of materials, wherein the transparent first layer and the second layer provide protection to the membrane from exposure to oxygen, and wherein exposing the coated porous substrate to the ultraviolet radiation source having a peak emission wavelength less than 340 nm comprises exposing the multilayer structure to ultraviolet radiation.

37. The method of claim 36 , further comprising removing the transparent first layer and the second layer from the multilayer structure after treating the coated porous substrate with the ultraviolet radiation source having a peak emission wavelength less than 340 nm.

38. A method of claim 1 , wherein the polymerizable composition further comprises a crosslinker.

Assignees

• Zhou Jinsheng
• Hester Jonathan F
• Dehn Derek J
• Meehan Daniel P
• Wright Robin E
• 3M Innovative Properties Co

Inventors

• Zhou Jinsheng
• Hester Jonathan F
• Dehn Derek J
• Meehan Daniel P
• Wright Robin E

Classifications

• B01D2325/14

  Membrane materials having negatively charged functional groups · CPC title

• Y10T428/24942

  including components having same physical characteristic in differing degree · CPC title

• B01D2323/30

  Cross-linking · CPC title

• B01D2323/345

  UV-treatment · CPC title

• B01D67/0006

  by chemical reactions (in-situ polymerisation, polycondensation, cross-linking or reaction for manufacturing composite membranes B01D69/125) · CPC title