Porous Composite Membrane

• US 20120061314A1
• Filed: 04/12/2010
• Published: 03/15/2012
• Est. Priority Date: 04/13/2009
• Status: Active Grant

• Current Assignee: Entegris Incorporated
• Original Assignee: Entegris Incorporated
• Inventors: Choi, Wai-ming, Kataoka, Kiminori
• Granted Patent: US 9,457,322 B2
• Time in Patent Office: Days
• US Class Current: 210/490
• CPC Class Codes: B01D 2323/39 Electrospinning
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: B01D 69/1216 Three or more layers

Abstract

Embodiments of the invention include a liquid filter member that includes a layer of polymeric nano fibers overlying a microporous membrane. A pressure drop of the filter member is substantially the same, or is less than, a pressure drop of the microporous membrane and the filter member has a particle retention in the presence of surfactant that is greater than the particle retention of the microporous membrane alone under the same test conditions.

Claims

1. A filter member comprising:

a layer of polymeric nano fibers overlying a microporous membrane, a liquid pressure drop of the filter member in a test liquid is substantially the same as a liquid pressure drop of the microporous membrane in the test liquid, the filter member has a particle retention under sieving conditions for test particles that is greater than a particle retention under sieving conditions of the microporous membrane for the test particles.

2. The filter member of claim 1 further including a porous support, said layer of polymeric nano fibers overlying the microporous membrane is between the porous support and the microporous membrane.

3. The filter member of claim 1 where the test particles are between 20 nanometers and 30 nanometers in diameter and the test liquid comprises between 0.1% (wt/wt) to 0.3% (wt/wt) surfactant in the test liquid.

4. The filter member of claim 1 where the microporous membrane has a size rating of between 0.001 microns and 0.05 microns.

5. The filter member of claim 4 further comprising a first support layer overlying the nanofiber layer and a second nanofiber layer overlying the first support layer.

6. The filter member of claim 1 where the microporous membrane is an asymmetric microporous membrane.

7. The filter member of claim 5 where the microporous membrane is an asymmetric microporous membrane.

13. The liquid filter member of claim 6 where the monolayer coverage is between 10% and 30%.

8. A filter member comprising a microporous membrane having size rating and a nanofiber layer overlying a surface of the microporous membrane, said nanofiber layer has a size rating that is the same or larger than the size rating of the microporous membrane, said microporous membrane has a bubble point greater than 0.206 MPa and an IPA Flow time greater than 500 seconds for 500 milliliters of isopropyl alcohol at a pressure of 0.10 MPa and temperature of 21°

C.,

the filter member further comprises a non-woven support overlying the nanofiber layer, the nano fibers comprising said nanofiber layer have a diameter in a range of 50 nanometers to 200 nanometers, the nanofiber layer is characterized by an isopropyl alcohol (IPA) flow time of 20 seconds to 200 seconds for 500 milliliters of IPA at a pressure of 0.10 MPa and temperature of 21°

C.;

a filter member IPA flow time that is no greater than 100 seconds more than the IPA flow time of the microporous membrane for 500 milliters of IPA at a pressure of 0.10 MPa and temperature of 21°

C.; and

a liquid particle retention for said filter member for approximately 25 nanometer fluorescent polystyrene latex beads in a test liquid, at test particle coverage on the filter member of between 1% monolayer coverage to 30% monolayer coverage, said test liquid comprises a surfactant between 0.1% (wt/wt) to 0.3% (wt/wt), the liquid particle retention for said filter member is substantially the same or is greater than a liquid particle retention of the microporous membrane for the 25 nanometer fluorescent polystyrene latex beads under the same conditions.

9. The filter member of claim 8 where the microporous membrane has a size rating of less than 0.1 micron.

10. The filter member of claim 8 where the size rating of the microporous membrane is between 0.001 microns to 0.05 microns.

11. The filter member of claim 8 where the microporous membrane is made from ultra high molecular weight polyethylene, the nanofiber layer is nylon, and the non-woven support is nylon.

12. The filter member of claim 8 where the microporous membrane is an asymmetric microporous membrane.

14. A filter member comprising:

a microporous membrane having a size rating and an isopropyl alcohol bubble point greater than 206,000 Pa, said microporous membrane has an IPA Flow time of greater than 500 seconds for 500 milliliters of isopropyl alcohol at a pressure of 0.10 MPa and temperature of 21°

C.,

the filter member further comprises a non-woven support with a nanofiber layer on a surface of the non-woven support, the nanofiber layer has a size rating that is the same or larger than the size rating of the microporous membrane, said nano fiber layer comprising one or more nanofibers;

the filter member has a liquid pressure drop for a liquid feed solution, said liquid feed solution is 0.1% (w/w) Triton X-IOO in water at a flow rate of 30 milliliters/minute at room temperature, where the liquid pressure drop is between 0% and 15% less than the pressure drop of the microporous membrane in the liquid feed solution; and

a liquid particle retention of the filter member for approximately 25 nanometer fluorescent polystyrene latex beads in a test liquid, said retention at 1% monolayer coverage to 5% monolayer bead coverage with 0.3 wt % sodium dodecylsulfate surfactant in said test liquid, said liquid particle retention of the filter member is substantially the same or is greater than a liquid particle retention of the microporous membrane for the same 25 nanometer fluorescent polystyrene latex beads in the test liquid.

15. The filter member of claim 14 where the nano fiber layer is interposed between the non-woven support and the microporous membrane.

16. The filter member of claim 14 where the nanofibers have a diameter of 200 nanometers or less.

17. The filter member of claim 14 where the microporous membrane has an asymmetric pore structure and a size rating of 0.05 microns or less.

18. The filter member of claim 14 where the nano fiber comprises nylon 6.

19. The filter member of claim 18 where the nano fiber layer has a base weight of between 1 gram per meter squared and 3 grams per meter squared.

20. The filter member of claim 19 where the nano fiber layer on the nonwoven support has a thickness of between 2 microns and 10 microns.