Hydrophobic membranes

• US 4,954,256 A
• Filed: 05/15/1989
• Issued: 09/04/1990
• Est. Priority Date: 05/15/1989
• Status: Expired due to Term

• Current Assignee: Pall Corporation (Danaher Corporation)
• Original Assignee: Pall Corporation (Danaher Corporation)
• Inventors: Degen, Peter J., Rothman, Isaac, Gsell, Thomas C.
• Primary Examiner(s): Foelak, Morton
• Application Number:
  US07/351,219
• Time in Patent Office: 477 Days
• Field of Search: 525/276, 525/426, 525/445, 525/455, 525/535, 521/53, 521/134, 521/137, 521/138, 210/490
• US Class Current: 210/490
• CPC Class Codes: B01D 19/0031 by filtration
• CPC Class Codes: B01D 67/0093 Chemical modification
• CPC Class Codes: B01D 67/00931 by introduction of specific groups after membrane formation, e.g. by grafting
• CPC Class Codes: C08J 9/405 with polymerisable compounds

Abstract

A hydrophobic polymeric microporous membrane having a CWST of less than about 28 dynes/cm is obtained by forming a (co)polymer of a fluorine-containing ethylenically unsaturated monomer that is permanently chemically bonded to a microporous membrane substrate.

Claims

1. A microporous polymeric membrane having pores with diameters of about 0.05 μ

m or greater and a CWST less than about 28 dynes/cm comprising a microporous polymeric membrane substrate and, permanently chemically bonded to all portions of the surface thereof, a superstrate fluoropolymer formed from a monomer containing an ethylenically unsaturated group and a fluoroalkyl group.

2. A microporous polymeric membrane according to claim 1 in which the monomer comprises a perfluoroalkyl group.

3. A microporous polymeric membrane according to claim 2 in which the monomer is selected from the group consisting of perfluoroalkanesulfonamidoethyl acrylates and perfluoroalkanesulfonamidoethyl methacrylates.

4. A microporous polymeric membrane according to claim 1 in which the polymer from which the substrate membrane is made is selected from the group consisting of polyamides, polyolefins, and fluorine-containing polymers.

5. A microporous polymeric membrane according to claim 4 in which the substrate membrane is made from a polyamide.

6. A microporous polymeric membrane according to claim 4 in which the substrate membrane is made from poly(vinylidene fluoride).

7. A microporous polymeric membrane according to claim 1 in which the superstrate fluoropolymer is a copolymer of a non-fluorine-containing monomer and the monomer containing an ethylenically unsaturated group and a fluoroalkyl group.

8. A microporous polymeric membrane according to claim 7 in which the non-fluorine-containing monomer is an ethylenically unsaturated monomer which contains a polar functional group.

9. A microporous polymeric membrane according to claim 8 in which the ethylenically unsaturated monomer is selected from the group consisting of unsaturated acids and esters of such acids.

10. A microporous polymeric membrane according to claim 9 in which the ethylenically unsaturated monomer is selected from esters of acrylic and methacrylic acids with a C₁ -C₁₈ alcohol.

14. The membrane of claim 1 wherein the monomer is selected from the group consisting of perfluoroalkyl acrylates, perfluoroalkyl methacrylates, and polyfluoroalkyl acrylamides.

15. The membrane of claim 14 wherein the monomer contains a perfluoroalkyl group having a carbon chain from about 4 to about 13 atoms long.

16. The membrane of claim 14 wherein the perfluoroalkyl acrylate is a fluoroalkanesulfonamidoethyl acrylate.

17. The membrane of claim 16 wherein the fluoroalkanesulfonamido ethyl acrylate is 2-(N-ethylperfluorooctanesulfonamido) ethyl acrylate.

18. The membrane of claim 14 wherein the perfluoroalkyl methacrylate is a fluoroalkanesulfonamidoethyl methacrylate.

11. A microporous polymeric membrane having pores with diameters of about 0.05 μ

m or greater and a CWST less than about 28 dynes/cm comprising a microporous, fluoropolymeric membrane substrate and, permanently chemically bonded to all portions of the surface thereof, a superstrate which is a copolymer of a non-fluorine-containing ethylenically unsaturated monomer and a monomer having an ethylenically unsaturated group and a perfluoroalkyl group.

12. A microporous polymeric membrane having pores with diameters of about 0.05 μ

m or greater and a CWST less than about 28 dynes/cm comprising a microporous polymeric membrane substrate and, permanently chemically bonded to all surfaces thereof, a fluoropolymer formed from a monomer containing an ethylenically unsaturated group and a fluoroalkyl group, said membrane having an air flow resistance that does not differ significantly from the air flow resistance of the ungrafted microporous polymeric membrane substrate.

13. A microporous polymeric membrane having pores with diameters of about 0.05 μ

m or greater and a CWST less than about 28 dynes/cm comprising a microporous polymeric membrane substrate and, permanently chemically bonded to all surfaces thereof, a fluoropolymer formed from a monomer containing an ethylenically unsaturated group and a fluoroalkyl group, said microporous polymeric membrane retaining from an essentially unchanged CWST after exposure to trichlorotrifluoroethane.