Hydrophobic membrane materials for filter venting applications

• US 6,811,696 B2
• Filed: 04/12/2002
• Issued: 11/02/2004
• Est. Priority Date: 04/12/2002
• Status: Expired due to Term

• Current Assignee: Cytiva (Danaher Corporation)
• Original Assignee: Pall Corporation (Danaher Corporation)
• Inventors: Rudolph, James E. Jr., McDonogh, Richard, Wang, I-fan
• Primary Examiner(s): FORTUNA, ANA M
• Application Number:
  US10/123,074
• Publication Number:
  US 20030192826A1
• Time in Patent Office: 935 Days
• Field of Search: 210/500.36, 210/500.22, 210/500.42, 210/500.23, 210/500.27, 96/4, 264/41, 264/650
• US Class Current: 210/500.36
• CPC Class Codes: B01D 19/0031 by filtration
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2323/38 Graft polymerization
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 67/0011 Casting solutions therefor
• CPC Class Codes: B01D 67/00113 Pretreatment of the casting solutions, e.g. thermal treatment or ageing
• CPC Class Codes: B01D 67/0013 Casting processes
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 71/32 containing fluorine atoms
• CPC Class Codes: B01D 71/36 Polytetrafluoroethene

Abstract

The present invention relates to filtration media having both hydrophobic (water-repellent) properties. The filtration media are produced using a fluorothermoplastic material, such as a terpolymer of tetrafluoroethylene, vinylidene fluoride, and hexafluoropropylene. The invention also relates to methods of preparing such filtration media using casting solution phase inversion.

Claims

1. A flat sheet membrane, the membrane cast from a dope comprising a solvent and a terpolymer of tetrafluoroethylene, vinylidene fluoride, and hexafluoropropylene, the membrane having a first porous face having a first average pore diameter, a second porous face having a second average pore diameter, and a porous supporting structure therebetween wherein the supporting structure comprises a reticulated network of flow channels, and wherein the porous faces and the porous supporting structure comprise a network of structural surfaces capable of contacting a filter stream.

2. The membrane of claim 1, wherein the membrane comprises an isotropic membrane.

3. The membrane of claim 1, wherein the first and second average pore diameters have an asymmetry of at least about 2:

1.

4. The membrane of claim 1, wherein the first and second average pore diameters have an asymmetry of at least about 5:

1.

5. The membrane of claim 1, wherein the first and second average pore diameters have an asymmetry of at least about 10:

1.

6. The membrane of claim 1, wherein the first and second average pore diameters have an asymmetry of at least about 20:

1.

7. The membrane of claim 1, wherein the dope comprises a dispersion of the terpolymer in the solvent.

8. The membrane of claim 1, wherein the dope comprises a homogeneous solution of the terpolymer in the solvent.