PTFE/PFSA BLENDED MEMBRANE

Abstract

A porous membrane comprising PTFE blended with PFSA is disclosed.

Claims

1. A porous membrane comprising PTFE blended with perfluorosulfonic acid (PFSA), wherein the membrane has a CWST of at least about 27 dynes/cm (about 2710.sup.5 N/cm).

2. The porous membrane of claim 1, having a CWST of at least about 30 dynes/cm (about 3010.sup.5 N/cm).

3. A method for filtering a metal-containing fluid, the method comprising passing a metal-containing fluid through a porous membrane comprising PTFE blended with perfluorosulfonic acid (PFSA), wherein the membrane has a CWST of at least about 27 dynes/cm (about 2710.sup.5 N/cm).

4. The method of claim 3, wherein the metal-containing fluid is a fluid used in the electronics industry.

5. The method of claim 3, comprising removing Group 2 metals and/or transition metals from the metal-containing fluid.

6. A method for filtering a SPM fluid, the method comprising passing the SPM fluid through a porous membrane comprising PTFE blended with perfluorosulfonic acid (PFSA), wherein the membrane has a CWST of at least about 30 dynes/cm (about 3010.sup.5 N/cm).

7. The method of claim 6, comprising removing metal from the fluid.

8. The method of claim 7, comprising removing Group 2 metals and/or transition metals from the metal-containing fluid.

9. A method of making a porous membrane, the method comprising combining PTFE resin with perfluorosulfonic acid (PFSA), optionally also including a lubricant; forming a tape; stretching the tape to produce a porous membrane; and, soaking the porous membrane in isopropyl alcohol (IPA).

10. The method of claim 9, further comprising drying the membrane. Please add the following claim:

11. The method of claim 4, comprising removing Group 2 metals and/or transition metals from the metal-containing fluid.

Description

EXAMPLE 1

[0036] This example demonstrates a method of preparing membranes blended with different concentrations of PFSA according to embodiments of the invention.

[0037] PTFE resin is mixed with 15 phr lubricant (EXXOL D80) and PFSA additive at concentrations of 5 phr, 10 phr, and 20 phr (24% w/w; AQUIVION PFSA 24; D83-24B Solvay Plastics), for 20 minutes and equilibrated for 12 hours.

[0038] Billets are formed by pressuring the mixture twice at 20 bars for 55 seconds, and equilibrated for 12 hours at room temperature.

[0039] Extrusion is performed at 26 mm gap size, maximum pressure and constant temperature of 55 C. resulting in tube-shaped PTFE tapes. The tubes are cut open along the central axis and re-rolled around a pipette, resulting in new billets. The billets are re-extruded with same conditions as used during first extrusion process.

[0040] Calendaring is performed at room temperature to a resulting tape thicknesses of 9-10 mils with 44 inch in length and width dimensions. Tapes are dried at 125 C. for 1 hour. Tapes are stretched such that stretch ratios of both machine direction (MD) and transverse direction (TD) ratios are 1.5 and 3.0, at 300%/sec stretch rate. The temperature in the stretch oven is set to 150 C., and annealing is conducted in the annealing oven at 350 C. for 5 seconds.

[0041] Membranes are soaked for 5 days in 1:1 isopropyl alcohol (IPA):deionized (DI) water.

[0042] The membrane with the highest PFSA concentration (20 phr) is challenged in static mode with sulfuric perioxide mixture (SPM) at 140 C. for 3 hours.

[0043] Membranes are washed in DI water overnight and dried (including the SPM challenged membrane) at 160 C. for 10 min.

[0044] The results (compared to an untreated (control) PTFE membrane without blending with PFSA) are as follows:

TABLE-US-00001 membrane CWST range (dynes/cm.sup.2) Control PTFE, no PFSA 25-27 PFSA content 5 phr (w/w) 31-33 PFSA content 10 phr (w/w) 31-33 PFSA content 20 phr (w/w) 31-33 After IPA:DI soak (PFSA 5 phr) 31-35 After IPA:DI soak (PFSA 20 phr) 35-41 After static SPM challenge (PFSA 20 phr) 35-41

[0045] This example shows CWST is stably increased, providing non-dewetting membranes, even after exposure to SPM, in accordance with an embodiment of the invention.

[0046] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0047] The use of the terms a and an and the and at least one and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term at least one followed by a list of one or more items (for example, at least one of A and B) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0048] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.