Amorphous fluoropolymer film

Abstract

A porous membrane is provided comprising layers (A), (B), and (C) in an ACB orientation, wherein layer (A) comprises an amorphous fluoropolymer, layer (B) comprises a symmetric fluoropolymer membrane or an asymmetric fluoropolymer membrane, and layer (C) comprises a composite fluoropolymer comprising (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer membrane or an asymmetric fluoropolymer membrane. A method for producing and using the porous membrane is also provided.

Description

[Background technology]

[0001]

[0001] For example, conventional methods for manufacturing PTFE films by extrusion, heating, stretching, and / or calendering can be energy-intensive and unsuitable for achieving films with desired pore size, chemical stability, nitrogen flux, and cleanliness. Therefore, there is a continuous need to develop finer, faster, and cleaner PTFE films (e.g., stretched PTFE films), particularly for filtration in microelectronics applications.

[0002]

[0002] These and other advantages of the present invention will become apparent from the following description. [Overview of the project]

[0003]

[0003] The present invention relates to a porous membrane comprising layer (A), layer (B), and layer (C) in an ACB orientation, Layer (A) contains an amorphous fluoropolymer, Layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. Layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. To provide a porous membrane.

[0004]

[0004] The present invention also relates to a porous membrane comprising layer (A), layer (B), and layer (C) in a BCACB orientation, Each layer (A) contains an amorphous fluoropolymer. Each layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. Each layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. To provide a porous membrane.

[0005]

[0005] The present invention also relates to a method for producing a porous membrane, (i) A step of casting a solution containing an amorphous fluoropolymer resin onto a first surface of a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film, (ii) Applying pressure to a second surface of a symmetric fluoropolymer film or an asymmetric fluoropolymer film, thereby drawing at least a portion of the solution containing the amorphous fluoropolymer into the symmetric fluoropolymer film or the asymmetric fluoropolymer film, (iii) A porous membrane comprising layers (A), (B), and (C) in an ACB orientation obtained by inverting a solution containing an amorphous fluoropolymer resin, a. Layer (A) contains an amorphous fluoropolymer, b. Layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. c. Layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. The steps include forming a porous membrane and This provides a method that includes this.

[0006]

[0006] The present invention also relates to a method for producing a porous membrane, (i) casting a solution containing an amorphous fluoropolymer resin onto a first surface of a first symmetric fluoropolymer film or a first asymmetric fluoropolymer film, (ii) The step of applying the first surface of the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film onto the casting solution, (iii) Applying pressure to the second surface of the first symmetric fluoropolymer film or the first asymmetric fluoropolymer film and / or the second surface of the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film, thereby drawing at least a portion of the solution containing the amorphous fluoropolymer into the first symmetric fluoropolymer film or the first asymmetric fluoropolymer film and / or the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film, (iv) A porous membrane comprising layers (A), (B), and (C) in a BCACB orientation obtained by inverting the phase of a solution containing an amorphous fluoropolymer resin, a. Layer (A) contains an amorphous fluoropolymer, b. Layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. c. Layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. The steps include forming a porous membrane and This provides a method that includes this.

[0007]

[0007] The present invention further provides a method for processing a contaminated fluid, comprising the step of passing at least a portion of the contaminated fluid through a porous membrane as described herein, and a method for recovering material from a fluid, comprising the step of passing at least a portion of the fluid through a porous membrane so as to retain at least a portion of the material on the porous membrane as described herein. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram illustrating an exemplary method for preparing the porous membrane described herein by applying pressure through a vacuum. [Figure 2] This is a scanning electron microscope (SEM) image of the porous membrane prepared in Example 1, with a field of view of 12 μm. [Figure 3A] These are scanning electron microscope (SEM) images of the porous membrane prepared in Example 1, with a field of view of 55.5 μm, showing (A) an amorphous fluoropolymer layer, (C) a composite layer, and (B) an asymmetric fluoropolymer film layer. [Figure 3B] These are scanning electron microscope (SEM) images of the porous membrane prepared in Example 1, with a field of view of 55.5 μm, showing (A) an amorphous fluoropolymer layer, (C) a composite layer, and (B) an asymmetric fluoropolymer film layer. [Figure 3C](A) shows an amorphous fluoropolymer layer, (C) shows a composite layer, and (B) shows an asymmetric fluoropolymer membrane layer. It is a scanning electron microscope (SEM) image of a porous membrane prepared in Example 1 with a field of view of 55.5 μm. [Figure 3D] (A) shows an amorphous fluoropolymer layer, (C) shows a composite layer, and (B) shows an asymmetric fluoropolymer membrane layer. It is a scanning electron microscope (SEM) image of a porous membrane prepared in Example 1 with a field of view of 55.5 μm. [Figure 4] It is a graph showing the average flow pore (MFP) diameter and the N2 flux at 100 psi (lpm / cm2) of the porous membrane prepared in Example 1. [Figure 5] It is a schematic diagram showing an exemplary method for preparing the porous membrane described herein by applying pressure through a Mayer bar. [Figure 6] It is a scanning electron microscope (SEM) image of a porous membrane prepared in Example 2 with a field of view of 277 μm. [Figure 7A] (A) shows an amorphous fluoropolymer layer, (C) shows a composite layer, and (B) shows an asymmetric fluoropolymer membrane layer. It is a scanning electron microscope (SEM) image of a porous membrane prepared in Example 2 with a field of view of 111 μm. [Figure 7B] (A) shows an amorphous fluoropolymer layer, (C) shows a composite layer, and (B) shows an asymmetric fluoropolymer membrane layer. It is a scanning electron microscope (SEM) image of a porous membrane prepared in Example 2 with a field of view of 55.5 μm. [Figure 7C] (A) shows an amorphous fluoropolymer layer, (C) shows a composite layer, and (B) shows an asymmetric fluoropolymer membrane layer. It is a scanning electron microscope (SEM) image of a porous membrane prepared in Example 2 with a field of view of 27.7 μm. [Figure 7D] (A) shows an amorphous fluoropolymer layer, (C) shows a composite layer, and (B) shows an asymmetric fluoropolymer membrane layer. It is a scanning electron microscope (SEM) image of a porous membrane prepared in Example 2 with a field of view of 13.9 μm. [Figure 8]A graph showing the mean flow pore (MFP) diameter and N2 flux at 100 psi (lpm / cm2) of the porous membrane prepared in Example 2. [Figure 9] A graph showing the mean flow pore (MFP) diameter and N2 flux at 100 psi (lpm / cm2) of the porous membrane prepared in Example 3.

Mode for Carrying Out the Invention

[0009]

[0017] The present invention provides a porous membrane comprising layer (A), layer (B), and layer (C) in an A-C-B orientation, where layer (A) contains an amorphous fluoropolymer, layer (B) contains a symmetric fluoropolymer membrane or an asymmetric fluoropolymer membrane, and layer (C) contains a composite fluoropolymer comprising (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer membrane or an asymmetric fluoropolymer membrane. The porous membrane is provided.

[0010]

[0018] In some embodiments, the present invention provides a porous membrane comprising layer (A), layer (B), and layer (C) in a B-C-A-C-B orientation, each layer (A) contains an amorphous fluoropolymer, each layer (B) contains a symmetric fluoropolymer membrane or an asymmetric fluoropolymer membrane, and each layer (C) contains a composite fluoropolymer comprising (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer membrane or an asymmetric fluoropolymer membrane. The porous membrane is provided.

[0011]

[0019] The porous membrane comprises a layer (A) containing an amorphous fluoropolymer. As used herein, the term “amorphous fluoropolymer” refers to a fluorinated (e.g., perfluorinated) polymer that lacks crystallinity. The amorphous fluoropolymer may be any suitable fluorinated (e.g., perfluorinated) polymer that lacks crystallinity. For example, the amorphous fluoropolymer may be a homopolymer, or preferably a copolymer containing two or more monomers (e.g., three monomers, four monomers, five monomers, or more monomers).

[0012]

[0020] Examples of suitable amorphous fluoropolymer monomers include fluorinated olefin monomers such as tetrafluoroethylene ("TFE"), vinylidene fluoride, and hexafluoropropylene, as well as fluorinated functional monomers such as perfluoroalkyl vinyl ethers, perfluoroesters, perfluorosulfonyl fluorides, and perfluorodioxoles. In some embodiments, the amorphous fluoropolymer includes an ether group, a dioxole group, or a combination thereof. In certain embodiments, the amorphous fluoropolymer includes at least one tetrafluoroethylene unit and at least one fluorinated ether unit, a fluorinated dioxole unit, or a combination thereof. A preferred amorphous fluoropolymer is a copolymer of tetrafluoroethylene and perfluorodioxole. Exemplary perfluorodioxoles include perfluoro-1,3-dioxole and perfluoro-2,2-dimethyl-1,3-dioxole ("PDD"). Therefore, in other embodiments, the amorphous fluoropolymer is a copolymer of PDD and one or more comonomers selected from TFE, vinylidene fluoride, and hexafluoropropylene. A particular example of an amorphous fluoropolymer suitable for preparing the porous membrane of the present invention is a copolymer of PDD and TFE.

[0013]

[0021] In some embodiments, the amorphous fluoropolymer layer (A) is prepared from an amorphous fluoropolymer resin selected from CHEMOURS® Teflon AF resin (e.g., CHEMOURS® TEFLON® AF1600 or CHEMOURS® TEFLON® AF2400), Asahi Glass Company CYTOP® resin, Solvay HYFLON® resin, or a combination thereof.

[0014]

[0022] Layer (A) containing an amorphous fluoropolymer may be cast from a casting solution containing the amorphous fluoropolymer described herein and one or more solvents and / or non-solvents. Exemplary solvents / non-solvents include halogenated solvents, e.g., fluorocarbons (e.g., perfluorocarbons) or solvents from the 3M™ NOVEC™ series (e.g., 3M™ NOVEC™ 7500), GENESOLV™ 2000 (1,1-dichloro-1-fluoroethane) from Allied Signal, Inc., and FC-43 (perfluoroC) from 3M™. 12 Examples include, but are not limited to, alkanes, ECTFE® oil (ethylene-chlorotrifluoroethylene copolymer) manufactured by Halocarbon Co. (River Edge, New Jersey), CHEMOURS® OPTEON® series, SOLVAY® SOLKANE® series, acetone, ethanol, isopropanol, diethyl ether, ethyl acetate, tetrahydrofuran, and combinations thereof.

[0015]

[0023] The porous membrane comprises a layer (B) containing a symmetrical fluoropolymer membrane or an asymmetrical fluoropolymer membrane, i.e., a symmetrical (e.g., isotropic) fluoropolymer and an asymmetrical (e.g., anisotropic) fluoropolymer porous (e.g., microporous) membrane. As used herein, the term “symmetrical fluoropolymer membrane” refers to a fluoropolymer membrane having a pore structure (e.g., mean pore diameter) that is substantially the same throughout the membrane, i.e., from one surface to the other. As used herein, the term “asymmetrical fluoropolymer membrane” refers to a fluoropolymer membrane having a pore structure (e.g., mean pore diameter) that varies throughout the membrane, typically, (i) a pore structure in which the diameter increases from one surface of the membrane to the other, or (ii) a pore structure having an hourglass shape in which the pore diameter decreases at a point within the thickness of the membrane and increases at the opposing surface.

[0016]

[0024] In some embodiments, the symmetrical or asymmetrical fluoropolymer membrane comprises polytetrafluoroethylene (PTFE). In some embodiments, the polytetrafluoroethylene (PTFE) is stretched polytetrafluoroethylene (ePTFE), such as a stretched PTFE membrane like an EMFLON membrane. The symmetrical or asymmetrical fluoropolymer membrane of layer (B) may have any suitable pore structure, e.g., pore diameter (e.g., demonstrated by bubble points, or by KL as described in, for example, U.S. Patent No. 4,340,479, or demonstrated by capillary condensation flow porometry), mean flow pore (MFP) diameter (e.g., characterized using a porometer, e.g., one available under the trademarks of Porvair Porometer (Porvair plc, Norfolk, UK) or POROLUX (Porometer.com, Belgium)), pore evaluation, pore diameter (e.g., characterized using a modified OSU F2 test as described in, for example, U.S. Patent No. 4,925,572), or removal evaluation medium.

[0017]

[0025] The symmetrical or asymmetrical fluoropolymer film of layer (B) can be prepared by methods known to those skilled in the art. For example, see U.S. Patent Nos. 3,953,566, 4,187,390, and 3,962,153, which describe several methods for preparing porous PTFE films. For example, the symmetrical or asymmetrical fluoropolymer film of layer (B) can be prepared from a paste-forming fluoropolymer such as a fine fluoropolymer. A blend or preform containing a fine PTFE resin, e.g., ASTM D 4895 Type I, Grade 3, and an extrusion aid (or lubricant) is prepared by techniques known to those skilled in the art, e.g., compression molding. Fine PTFE resins are available from Asahi Glass Fluoropolymers in Bayonne, New Jersey. Examples of extrusion aids include liquid hydrocarbons, such as solvent naphtha and white oil; aromatic hydrocarbons, alcohols, ketones, esters; oils, such as mineral oil; hydrofluorocarbons, such as Freon® 134a; and water, such as water containing surfactants. The preform is then formed into articles such as sheets by, for example, pressing or rolling.

[0018]

[0026] The resulting sheet can be pressed, rolled, or calendered between driven rolls to a desired thickness, typically from about 2 mils (about 50 μm) or less to about 14 mils (about 350 μm) or more, for example. The resulting (unsintered) sheet is then expanded by stretching it in one, two, three, or more directions. For example, uniaxial or biaxial stretching may be performed. Stretching generates a microstructure containing nodes and fibrils. While the stretched sheet is in the stretched state, heating causes the film to amorphous lock. Heat sintersects the film. Sintering may be complete or partial. The amorphous lock process stabilizes the nodes. The amorphous-locked film is cooled to ambient temperature. Expansion (stretching) and sintering can also be performed simultaneously. See, for example, U.S. Patents 4,761,754, 4,714,748, and 4,760,012. The expanded sintered film can expand further at a temperature higher than the crystalline melting temperature of the highest melting point PTFE present, and can be stretched in a direction perpendicular or perpendicular to the direction of the first stretch performed at a temperature lower than the melting temperature of PTFE. See, for example, U.S. Patent No. 5,814,405. Extrusion aids can be removed before, during, or preferably after stretching.

[0019]

[0027] The symmetric or asymmetric fluoropolymer film of layer (B) preferably has a microstructure characterized by nodes and fibrils. Depending on the preparation method, the direction, size, and shape of the nodes may change, and the thickness, direction, length, and orientation of the fibrils may change. For example, when the symmetric or asymmetric fluoropolymer film of layer (B) is produced by uniaxial expansion, the nodes are elongated, and the long axis of the nodes is oriented approximately perpendicular to the expansion direction. The fibrils interconnecting the nodes are approximately parallel to the expansion direction. Biaxial and triaxial expansion can orient the fibrils in two or three directions, which can result in changes in the distribution, size, and shape of the nodes.

[0020]

[0028] The fibrils of the symmetric or asymmetric fluoropolymer film of layer (B) are, in some embodiments, substantially thin or have a narrow cross-section or diameter. The nodes may vary in size, e.g., diameter, from about 400 μm to about 0.05 μm, depending on the conditions used in manufacturing, for example, during expansion. The nodes may include aggregates of smaller nodes.

[0021]

[0029] Therefore, layer (B) can have any suitable average flow pore diameter (for example, as characterized using a porometer, e.g., one available under the trademarks of Porvair Porometer (Porvair plc, Norfolk, UK) or POROLUX (Porometer.com, Belgium)). For example, layer (B) can have an average flow pore diameter of 50 nm or more, e.g., 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, or 100 nm or more. Alternatively or additionally, layer (B) can have an average flow pore diameter of 1 μm or less, e.g., 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less. Therefore, layer (B) can have an average flow pore diameter bounded by any two of the aforementioned endpoints. For example, layer (B) has the following thicknesses: 50nm~1μm, 50nm~500nm, 50nm~400nm, 50nm~300nm, 50nm~200nm, 50nm~100nm, 60nm~1μm, 60nm~500nm, 60nm~400nm, 60nm~300nm, 60nm~200nm, 60nm~100nm, 70nm~1μm, 70nm~500nm, 70nm~400nm, 70nm~300nm, 70nm~200nm, 70nm~100nm, and 80nm~1μm. The average flow pore diameter can be 80nm~500nm, 80nm~400nm, 80nm~300nm, 80nm~200nm, 80nm~100nm, 90nm~1μm, 90nm~500nm, 90nm~400nm, 90nm~300nm, 90nm~200nm, 90nm~100nm, 100nm~1μm, 100nm~500nm, 100nm~400nm, 100nm~300nm, 100nm~200nm, or 100nm~100nm. In some embodiments, layer (B) has an average flow pore diameter of 60nm~500nm or an average flow pore diameter of 60nm~200nm. In a particular embodiment, layer (B) has an average flow pore diameter of 60nm~100nm.

[0022]

[0030] The porous membrane comprises a layer (C) containing (i) an amorphous fluoropolymer and (ii) a composite fluoropolymer including a symmetrical or asymmetrical fluoropolymer membrane. As used herein, the term “composite” means a mixture of (i) the amorphous fluoropolymer described herein and (ii) the symmetrical or asymmetrical fluoropolymer membrane (e.g., the porous membrane of layer (B)) described herein. For example, the composite can be formed by inverting the phase of a solution (e.g., a casting solution) containing an amorphous fluoropolymer resin incorporated into a symmetrical or asymmetrical fluoropolymer membrane by the method described herein.

[0023]

[0031] The porous membrane comprises layers (A), (B), and (C) in an ACB orientation. For example, the porous membrane may have orientations such as ACB, BCACB, ACBCACB, or BCACBCACB. In some embodiments, the porous membrane comprises layers (A), (B), and (C) in a BCACB orientation.

[0024]

[0032] The porous membrane can have any suitable thickness. Therefore, the porous membrane can have an average thickness of 5 microns or more, for example, 10 microns or more, 25 microns or more, 50 microns or more, or 100 microns or more. Alternatively or additionally, the porous membrane can have an average thickness of 5000 microns or less, for example, 2000 microns or less, 1000 microns or less, 500 microns or less, 250 microns or less, 200 microns or less, or 100 microns or less. Therefore, the porous membrane can have an average thickness bounded by any two of the aforementioned endpoints. For example, porous membranes include those with a thickness of 5 microns to 5000 microns, 5 microns to 2000 microns, 5 microns to 1000 microns, 5 microns to 500 microns, 5 microns to 250 microns, 5 microns to 200 microns, 5 microns to 100 microns, 10 microns to 5000 microns, 10 microns to 200 microns, 10 microns to 1000 microns, 10 microns to 500 microns, 10 microns to 250 microns, 10 microns to 200 microns, 10 microns to 100 microns, 25 microns to 5000 microns, 25 microns to 2000 microns, 25 microns to 1000 microns, and 25 microns to 5 The porous membrane can have an average thickness of 00 microns, 25 to 250 microns, 25 to 200 microns, 25 to 100 microns, 50 to 5000 microns, 50 to 2000 microns, 50 to 1000 microns, 50 to 500 microns, 50 to 250 microns, 50 to 200 microns, 50 to 100 microns, 100 to 5000 microns, 100 to 2000 microns, 100 to 1000 microns, 100 to 500 microns, 100 to 250 microns, or 100 to 200 microns. In some embodiments, the porous membrane has an average thickness of 25 to 1000 microns. In a particular embodiment, the porous membrane has an average thickness of 25 to 500 microns. In a preferred embodiment, the porous membrane has an average thickness of 25 to 250 microns.

[0025]

[0033] A porous membrane can have any suitable average flow pore diameter (for example, as characterized using a porometer, e.g., one available under the trademarks of Porvair Porometer (Porvair plc, Norfolk, UK) or POROLUX (Porometer.com, Belgium)). For example, a porous membrane can have an average flow pore diameter of 5 nm or more, e.g., 10 nm or more, 20 nm or more, 30 nm or more, or 40 nm or more. Alternatively or additionally, a porous membrane can have an average flow pore diameter of 80 nm or less, e.g., 70 nm or less, 60 nm or less, 50 nm or less, or 40 nm or less. Thus, a porous membrane can have an average flow pore diameter bounded by any two of the aforementioned endpoints. For example, a porous film can have an average flow pore diameter of 5nm-80nm, 5nm-70nm, 5nm-60nm, 5nm-50nm, 5nm-40nm, 10nm-80nm, 10nm-70nm, 10nm-60nm, 10nm-50nm, 10nm-40nm, 20nm-80nm, 20nm-70nm, 20nm-60nm, 20nm-50nm, 20nm-40nm, 30nm-80nm, 30nm-70nm, 30nm-60nm, 30nm-50nm, 30nm-40nm, 40nm-80nm, 40nm-70nm, 40nm-60nm, or 40nm-50nm. In some embodiments, the porous film has an average flow pore diameter of 10nm-60nm. In a particular embodiment, the porous film has an average flow pore diameter of 20nm-60nm. In a preferred embodiment, the porous membrane has an average flow pore diameter of 20 nm to 40 nm.

[0026]

[0034] In some embodiments, layer (C) has an average pore diameter smaller than that of layer (B) (e.g., as characterized using a scanning electron microscope). While we do not wish to be bound by any particular theory, as described herein, the average pore diameter of the composite obtained by drawing at least a portion of a solution containing an amorphous fluoropolymer into a symmetric or asymmetric fluoropolymer film is considered to be smaller than that of the symmetric or asymmetric fluoropolymer film. Alternatively or additionally, layer (C) may have an average pore diameter that increases from the side in contact with layer (A) to the side in contact with layer (B) (e.g., as characterized using a scanning electron microscope). While we do not wish to be bound by any particular theory, as described herein, by drawing at least a portion of a solution containing an amorphous fluoropolymer into a symmetric or asymmetric fluoropolymer film, the concentration of the amorphous fluoropolymer in the composite layer (C) is considered to decrease from the side in contact with layer (A) to the side in contact with layer (B), and thus the average pore size is considered to increase from the side in contact with layer (A) to the side in contact with layer (B). Alternatively or additionally, layer (B) may have an average pore size that increases from the side in contact with layer (C) to the surface of the porous film (e.g., as characterized using a scanning electron microscope).

[0027]

[0035] In some embodiments, the porous membrane of the present invention has desirable surface properties that are little to no fouling and / or allow for rapid membrane cleaning. Furthermore, the porous membrane of the present invention can have solvent resistance, chemical resistance, and heat resistance. In certain embodiments, the porous membrane is free of leachate or substantially free of leachate. Therefore, the purity of the processing fluid using the porous membrane is not impaired.

[0028]

[0036] The present invention also provides a method for producing a porous membrane (for example, a porous membrane comprising layer (A), layer (B), and layer (C) as described herein).

[0029]

[0037] In some embodiments, this method (i) A step of casting a solution containing an amorphous fluoropolymer resin onto a first surface of a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film, (ii) Applying pressure to a second surface of a symmetric fluoropolymer film or an asymmetric fluoropolymer film, thereby drawing at least a portion of the solution containing the amorphous fluoropolymer into the symmetric fluoropolymer film or the asymmetric fluoropolymer film, (iii) A porous membrane comprising layers (A), (B), and (C) in an ACB orientation obtained by inverting a solution containing an amorphous fluoropolymer resin, a. Layer (A) contains an amorphous fluoropolymer, b. Layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. c. Layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. The steps include forming a porous membrane and Includes.

[0030]

[0038] In some embodiments, this method (i) casting a solution containing an amorphous fluoropolymer resin onto a first surface of a first symmetric fluoropolymer film or a first asymmetric fluoropolymer film, (ii) The step of applying the first surface of the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film onto the casting solution, (iii) Applying pressure to the second surface of the first symmetric fluoropolymer film or the first asymmetric fluoropolymer film and / or the second surface of the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film, thereby drawing at least a portion of the solution containing the amorphous fluoropolymer into the first symmetric fluoropolymer film or the first asymmetric fluoropolymer film and / or the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film, (iv) A porous membrane comprising layers (A), (B), and (C) in a BCACB orientation obtained by inverting the phase of a solution containing an amorphous fluoropolymer resin, a. Layer (A) contains an amorphous fluoropolymer, b. Layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. c. Layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. The steps include forming a porous membrane and Includes.

[0031]

[0039] This method comprises the step of casting a solution containing an amorphous fluoropolymer resin onto the surface of a symmetrical or asymmetrical fluoropolymer film. In some embodiments, the solution containing the amorphous fluoropolymer further comprises one or more solvents and / or non-solvents. Exemplary solvents / non-solvents include halogenated solvents, e.g., fluorocarbons (e.g., perfluorocarbons) or solvents from the 3M™ NOVEC™ series (e.g., 3M™ NOVEC™ 7500), GENESOLV™ 2000 (1,1-dichloro-1-fluoroethane) from Allied Signal, Inc., and FC-43 (perfluoroC) from 3M™. 12 Examples include, but are not limited to, ECTFE® oil (ethylene-chlorotrifluoroethylene copolymer) manufactured by Halocarbon Co. (River Edge, New Jersey), CHEMOURS® OPTEON® series, SOLVAY® SOLKANE® series, acetone, ethanol, isopropanol, diethyl ether, ethyl acetate, tetrahydrofuran, and combinations thereof. In certain embodiments, the solution containing the amorphous fluoropolymer resin comprises a halogenated solvent, acetone, ethanol, isopropanol, diethyl ether, ethyl acetate, tetrahydrofuran, or a combination thereof.

[0032]

[0040] A method for producing a porous membrane includes the step of applying pressure to the surface of a symmetric or asymmetric fluoropolymer membrane to draw at least a portion of a solution containing an amorphous fluoropolymer into the symmetric or asymmetric fluoropolymer membrane. The pressure can be applied by any suitable means, as long as at least a portion of the solution containing the amorphous fluoropolymer is drawn into the symmetric or asymmetric fluoropolymer membrane. In some embodiments, the pressure is applied by vacuum, a Meyer bar, a slot die, a doctor blade, an air blade, or a combination thereof.

[0033]

[0041] A method for producing a porous membrane includes the step of inverting the phase of a solution containing an amorphous fluoropolymer resin to form a porous membrane comprising layers (A), (B), and (C). Phase inversion can be carried out by any suitable method. For example, phase inversion can be carried out by precipitation from the gas phase, precipitation by controlled evaporation, thermally induced phase separation, or immersion precipitation.

[0034]

[0042] All other aspects of methods for producing porous membranes (for example, porous membranes comprising layers (A), (B), and (C) as described herein), such as amorphous fluoropolymers, symmetric fluoropolymer membranes, asymmetric fluoropolymer membranes, and composite fluoropolymers, are as described herein with respect to porous membranes.

[0035]

[0043] The present invention further provides a method for processing a contaminated fluid, comprising the step of passing at least a portion of the contaminated fluid through a porous membrane as described herein, and a method for recovering material from a fluid, comprising the step of passing at least a portion of the fluid through a porous membrane as described herein, such that at least a portion of the material is retained on the porous membrane.

[0036]

[0044] In some embodiments, the fluid (e.g., the contaminated fluid) is corrosive and may have a high temperature (e.g., above 50°C, above 100°C, or above 150°C). For example, the fluid may contain a strong acid (e.g., sulfuric acid or hydrofluoric acid), a strong base (e.g., sodium hydroxide or potassium hydroxide), or a strong oxidizing agent (e.g., a peroxide such as hydrogen peroxide). Exemplary fluids that may be corrosive include, but are not limited to, etching fluids used in the electronics industry or other lithography-based processes. In this regard, the etching fluid can be passed through a porous membrane described herein to remove or separate contaminants such as metals, polymers, ceramic particles, or other etching particles.

[0037]

[0045] In some embodiments, the fluid (e.g., the contaminated fluid) is a biological composition. For example, the biological composition can be passed through a porous membrane as described herein to remove or separate biological materials such as, for example, biopolymers (e.g., glycopolymers, cellulosinic polymers, etc.), lipids (e.g., lipid vesicles, micelles, liposomes, etc.), carbohydrates (e.g., sugars, starches, cellulose, glycogen, etc.), peptides (e.g., polypeptides, proteins, peptide mimes, glycopeptides, etc.), antibody constructs (e.g., antibodies, antibody derivatives (including Fc fusions, Fab fragments, and scFv), etc.), nucleotides (e.g., RNA, DNA, antisense, siRNA, aptamers, etc.), bacteria, viruses, or any combination thereof. In some embodiments, the biomaterial includes lentiviruses, AAV capsids, or plasmid DNA, and other biological contaminants from the fluid.

[0038]

[0046] The nature of this disclosure The embodiments of the present invention described herein, including those of the embodiments, may be useful on their own or in combination with one or more other embodiments. Without limiting the foregoing description, certain non-limiting embodiments of this disclosure, numbered 1 to 24, are provided below. As will be apparent to those skilled in the art upon reading this disclosure, each of the individually numbered embodiments may be used with or combined with any preceding or succeeding individually numbered embodiment. This is intended to support all such combinations of embodiments, and is not limited to the combinations of embodiments expressly provided below.

[0039]

[0047] (1) In embodiment (1), a porous membrane comprising layers (A), (B), and (C) in an ACB orientation, Layer (A) contains an amorphous fluoropolymer, Layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. Layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. A porous membrane is presented.

[0040]

[0048] (2) In embodiment (2), a porous membrane comprising layers (A), (B), and (C) in a BCACB orientation, Each layer (A) contains an amorphous fluoropolymer. Each layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. Each layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. A porous membrane is presented.

[0041]

[0049] (3) Embodiment (3) presents a porous membrane according to Embodiment (1) or Embodiment (2), wherein layer (C) has an average pore diameter smaller than the average pore diameter of layer (B).

[0042]

[0050] (4) In embodiment (4), one of the porous membranes of embodiments (1) to (3) is presented, wherein layer (C) has an average pore diameter that increases from the side in contact with layer (A) to the side in contact with layer (B).

[0043]

[0051] (5) In embodiment (5), one of the porous membranes of embodiments (1) to (4) is presented, wherein the amorphous fluoropolymer contains an ether group, a dioxole group, or a combination thereof.

[0044]

[0052] (6) Embodiment (6) presents a porous membrane according to any one of embodiments (1) to (5), wherein the amorphous fluoropolymer comprises at least one tetrafluoroethylene unit and at least one fluorinated ether unit, a fluorinated dioxole unit, or a combination thereof.

[0045]

[0053] (7) In embodiment (7), a porous membrane is presented which is one of embodiments (1) to (6), wherein the symmetric fluoropolymer membrane or asymmetric polymer membrane contains polytetrafluoroethylene (PTFE).

[0046]

[0054] (8) In embodiment (8), a porous membrane of embodiment (7) is presented in which polytetrafluoroethylene (PTFE) is stretched polytetrafluoroethylene (ePTFE).

[0047]

[0055] (9) In embodiment (9), a porous membrane is presented in which layer (B) has an average flow pore diameter of 60 nm to 500 nm, one of the embodiments (1) to (8).

[0048]

[0056] (10) In embodiment (10), one of the porous membranes of embodiments (1) to (8) is presented, wherein layer (B) has an average flow pore diameter of 60 nm to 200 nm.

[0049]

[0057] (11) In embodiment (11), one of the porous membranes of embodiments (1) to (8) is presented, wherein layer (B) has an average flow pore diameter of 60 nm to 100 nm.

[0050]

[0058] (12) In embodiment (12), one of the porous membranes of embodiments (1) to (11) is presented, having an average flow pore diameter of 10 nm to 60 nm.

[0051]

[0059] (13) In embodiment (13), one of the porous membranes of embodiments (1) to (11) is presented, having an average flow pore diameter of 20 nm to 60 nm.

[0052]

[0060] (14) In embodiment (14), one of the porous membranes of embodiments (1) to (11) is presented, having an average flow pore diameter of 20 nm to 40 nm.

[0053]

[0061] (15) In embodiment (15), one of the porous membranes of embodiments (1) to (14) is presented, having an average thickness of 5 microns to 1000 microns.

[0054]

[0062] (16) In embodiment (16), one of the porous membranes of embodiments (1) to (14) is presented, having an average thickness of 25 microns to 500 microns.

[0055]

[0063] (17) In embodiment (17), one of the porous membranes of embodiments (1) to (14) is presented, having an average thickness of 25 microns to 250 microns.

[0056]

[0064] (18) Embodiment (18) describes a method for producing a porous membrane, (i) A step of casting a solution containing an amorphous fluoropolymer resin onto a first surface of a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film, (ii) Applying pressure to a second surface of a symmetric fluoropolymer film or an asymmetric fluoropolymer film, thereby drawing at least a portion of the solution containing the amorphous fluoropolymer into the symmetric fluoropolymer film or the asymmetric fluoropolymer film, (iii) A porous membrane comprising layers (A), (B), and (C) in an ACB orientation obtained by inverting a solution containing an amorphous fluoropolymer resin, a. Layer (A) contains an amorphous fluoropolymer, b. Layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. c. Layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. The steps include forming a porous membrane and A method including this is presented.

[0057]

[0065] (19) Embodiment (19) describes a method for producing a porous membrane, (i) casting a solution containing an amorphous fluoropolymer resin onto a first surface of a first symmetric fluoropolymer film or a first asymmetric fluoropolymer film, (ii) The step of applying the first surface of the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film onto the casting solution, (iii) Applying pressure to the second surface of the first symmetric fluoropolymer film or the first asymmetric fluoropolymer film and / or the second surface of the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film, thereby drawing at least a portion of the solution containing the amorphous fluoropolymer into the first symmetric fluoropolymer film or the first asymmetric fluoropolymer film and / or the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film, (iv) A porous membrane comprising layers (A), (B), and (C) in a BCACB orientation obtained by inverting the phase of a solution containing an amorphous fluoropolymer resin, a. Layer (A) contains an amorphous fluoropolymer, b. Layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. c. Layer (C) comprises a composite fluoropolymer including (i) an amorphous fluoropolymer and (ii) a symmetric fluoropolymer film or an asymmetric fluoropolymer film. The steps include forming a porous membrane and A method including this is presented.

[0058]

[0066] (20) Embodiment (20) presents the method of Embodiment (18) or Embodiment (19), wherein pressure is applied by vacuum, Meyer bar, slot die, doctor blade, air blade, or a combination thereof.

[0059]

[0067] (21) In embodiment (21), one of the methods of embodiments (18) to (20) is presented, wherein the solution containing the amorphous fluoropolymer resin contains a halogenating solvent, acetone, ethanol, isopropanol, diethyl ether, ethyl acetate, tetrahydrofuran, or a combination thereof.

[0060]

[0068] (22) Embodiment (22) presents a method for treating a contaminated fluid, comprising the step of passing at least a portion of the contaminated fluid through one of the porous membranes of Embodiments (1) to (17).

[0061]

[0069] (23) Embodiment (23) presents the method of Embodiment (22) in which the contaminated fluid is corrosive.

[0062]

[0070] (24) Embodiment (24) presents a method for recovering material from a fluid, comprising the step of passing at least a portion of the fluid through a porous membrane such that at least a portion of the material is retained on any one of the porous membranes of Embodiments (1) to (17).

[0063]

[0071] Examples These following embodiments further illustrate the present invention, but should not be construed as limiting its scope.

[0064]

[0072] Example 1 This example demonstrates the preparation of porous membranes, including amorphous fluoropolymers, composites, and asymmetric fluoropolymer membranes, as described herein, by applying pressure through a vacuum, as shown in Figure 1.

[0065]

[0073] A polymer blend containing CHEMOURS® TEFLON® AF1600 fluoropolymer (0.4 g) and 3M® NOVEC® 7500 fluorocarbon solvent (9.6 g) was prepared, incubated at 60°C for 24 hours, and then equilibrated at 20°C.

[0066]

[0074] A strip (3 inches wide x 8 inches long) of asymmetrically stretched polytetrafluoroethylene (ePTFE) film (0.2 microns, commercially available from Sumitomo®) was placed on a flatbed casting mill with a linear velocity of 40 mm / second. A stainless steel Meyer bar (4 mil rating) was placed on the leading edge of the ePTFE film support. Three grams of amorphous fluoropolymer blend were poured across the ePTFE support, just downstream of the Meyer bar, to initiate casting. Once the Meyer bar had completely crossed the ePTFE support, the amorphous fluoropolymer blend / ePTFE structure was removed and placed on a glass frit (2 inches in diameter) mounted on a triangular suction bottle connected to a vacuum source (700 mmHg). Vacuum was applied for 5 seconds, then the structure was removed and immersed in a 20°C acetone bath for 2 minutes to invert the phase. The newly formed film was then removed, immersed in a 20°C isopropyl alcohol bath for 2 minutes, subsequently removed, and dried in air under ambient conditions.

[0067]

[0075] Scanning electron microscope (SEM) images of the obtained porous membrane were taken and are shown in Figures 2 and 3A to 3D. As is clear from the results shown in Figures 3A to 3D, there are three distinguishable layers, from top to bottom, including an amorphous fluoropolymer layer (A), a composite layer (C), and an asymmetric fluoropolymer membrane layer (B).

[0068]

[0076] To demonstrate that the porous membranes prepared in this example have a reduced average pore diameter compared to porous membranes prepared without vacuum, the average flow pore (MFP) diameter was measured. An independent control membrane (master control) prepared immediately before the vacuum experiment, two controls (Vac1 control and Vac2 control) taken from outside the vacuum-exposed membrane region, and test membranes (Vac1 and Vac2) from two different vacuum-exposed regions were exposed to nitrogen flux at 100 psi (689.5 kPa). The results are shown in Figure 4.

[0069]

[0077] As is clear from the results shown in Figure 4, the test film was 100 psi (lpm / cm²). 2 At approximately 10N2 flux, the MFP diameter was approximately 40-60 nm, while the two controls that were not subjected to vacuum measured at 100 psi (lpm / cm²). 2 At approximately 20 N2 flux, the MFP diameter was approximately 80 nm. Similarly, the master control had a diameter of approximately 100 psi (lpm / cm²). 2 At approximately 35N2 flux, the MFP diameter was approximately 100 nm. These results indicate that applying pressure through a vacuum reduced the average flow pore diameter of the porous membrane by approximately 25-50%.

[0070]

[0078] Example 2 This example demonstrates the preparation of porous membranes, including amorphous fluoropolymers, composites, and asymmetric fluoropolymer membranes, as described herein, by applying pressure through a Meyer bar, as shown in Figure 5.

[0079] A polymer blend containing CHEMOURS® TEFLON® AF2400 fluoropolymer (0.15 g) and 3M® NOVEC® 7500 fluorocarbon solvent (9.85 g) was prepared, incubated at 60°C for 24 hours, and then equilibrated at 20°C.

[0071]

[0080] Two strips (3 inches wide x 8 inches long) of asymmetrically stretched polytetrafluoroethylene (ePTFE) film (0.2 microns, commercially available from Sumitomo®) were stacked on a flatbed casting mill with a linear velocity of 40 mm / second. A stainless steel Meyer bar (4 mil rating) was placed on the leading edges of the two ePTFE film layers. The distal end of the upper (topmost) layer of the ePTFE film was peeled away from the bottom layer and returned to the position of the Meyer bar, thereby exposing the interface between the upper and lower ePTFE. Three grams of amorphous fluoropolymer blend were poured across the exposed bottom ePTFE layer, just downstream of the Meyer bar, and casting was initiated. Once the Meyer bar had completely traversed the ePTFE support, thereby compressing the upper ePTFE layer onto the lower ePTFE layer, the amorphous fluoropolymer blend / ePTFE structure was removed and inverted in an acetone bath at 20°C for 2 minutes. Subsequently, the newly formed film was removed, immersed in an isopropyl alcohol bath at 20°C for 2 minutes, and then removed and dried in air under ambient conditions.

[0072]

[0081] Scanning electron microscope (SEM) images of the obtained porous membrane were taken and are provided in Figures 6 and 7A to 7D. As is clear from the results shown in Figures 7A to 7D, there are five distinguishable layers, from top to bottom, including an asymmetric fluoropolymer membrane layer (B), a composite layer (C), an amorphous fluoropolymer layer (A), a composite layer (C), and an asymmetric fluoropolymer membrane layer (B).

[0073]

[0082] To demonstrate that the porous membranes prepared by this embodiment have a reduced average pore diameter compared to porous membranes prepared without compression through the upper PTFE layer, the average flow pore (MFP) diameter was measured. A sample-placed control membrane (i.e., without compression through the upper PTFE layer) and a test membrane, both containing a single amorphous fluoropolymer layer cast onto an asymmetric ePTFE support unaffected by further downstream influences, were exposed to nitrogen flux at 100 psi (689.5 kPa) under identical conditions. The results are shown in Figure 8.

[0074]

[0083] As is clear from the results shown in Figure 8, the test film was 100 psi (lpm / cm²). 2 ) has an MFP diameter of approximately 30 nm at a flux of approximately 5N2, while the reference film has a flux of 100 psi (lpm / cm²). 2 At approximately 30N2 flux, the MFP diameter was approximately 80 nm. These results indicate that applying pressure through the Meyer bar and the upper ePTFE layer reduced the average flow pore diameter of the porous membrane by approximately 60% compared to the control membrane.

[0075]

[0084] Example 3 This example demonstrates the preparation of porous membranes, including amorphous fluoropolymers, composites, and symmetrical fluoropolymer membranes, as described herein, by applying pressure through a Meyer bar, as shown in Figure 5.

[0076]

[0085] A polymer blend containing CHEMOURS® TEFLON® AF2400 fluoropolymer (0.15 g) and 3M® NOVEC® 7500 fluorocarbon solvent (9.85 g) was prepared, incubated at 60°C for 24 hours, and then equilibrated at 20°C.

[0077]

[0086] Two strips (width 3 inches × length 8 inches) of symmetrically extended polytetrafluoroethylene (ePTFE) membrane (0.45 micron, commercially available from Sumitomo®) were overlaid on a flat-bed casting machine having a linear velocity of 40 mm / second. A stainless steel Mayer bar (4 mil rating) was placed on top of the leading edge of the two ePTFE membrane layers. The distal end of the upper (top) layer of the ePTFE membrane was peeled from the bottom layer and returned to the position of the Mayer bar, thereby exposing the interface between the upper ePTFE and the lower ePTFE. 3 grams of an amorphous fluoropolymer blend was poured immediately downstream of the Mayer bar across the exposed bottom ePTFE layer and casting was initiated. When the Mayer bar completely traversed the ePTFE support, thereby compressing the upper ePTFE layer onto the lower ePTFE layer, the amorphous fluoropolymer blend / ePTFE structure was removed and placed in an acetone bath for 2 minutes of phase inversion at 20 °C. Thereafter, the newly formed membrane was removed, immersed in an isopropyl alcohol bath at 20 °C for 2 minutes, and subsequently removed and dried in air under ambient conditions.

[0078]

[0087] To demonstrate that the porous membrane prepared by this example has a reduced average pore diameter compared to a porous membrane prepared without compression through the upper PTFE layer, the mean flow pore (MFP) diameter was measured. A sample placement control membrane (i.e., without compression through the upper PTFE layer) and a test membrane comprising a single amorphous fluoropolymer layer cast on a symmetric ePTFE support under the same conditions but not subject to further downstream effects were exposed to nitrogen flux at (689.5 kPa). The results are shown in FIG. 9.

[0079]

[0088] As is apparent from the results shown in FIG. 9, the test membrane has an MFP diameter of approximately 60 nm at a nitrogen flux of about 5 N2 at 100 psi (lpm / cm 2 ) while the placement control membrane has an MFP diameter of about 60 nm at a nitrogen flux of about 5 N2 at 100 psi (lpm / cm 2At a flux of approximately 25-30 N2, the MFP diameter was approximately 80-100 nm. These results indicate that applying pressure through the Meyer bar and the upper ePTFE layer reduced the average flow pore diameter of the porous membrane by approximately 30% compared to the control membrane.

[0080]

[0089] All references cited herein, including publications, patent applications, and patents, are incorporated herein by reference to the same extent as if they were included herein in their entirety, provided that each reference is individually and specifically indicated as being incorporated herein by reference.

[0081]

[0090] In the context describing the present invention (in particular in the context of the following claims), the terms “a,” “an,” “the,” and “at least one,” as well as similar references, should be interpreted as encompassing both singular and plural, unless otherwise indicated herein or unless clearly inconsistent with the context. The use of the term “at least one” followed by a list of one or more items (e.g., “at least one of A and B”) should be interpreted as meaning one item (A or B) selected from the enumerated items or any combination of two or more enumerated items (A and B), unless otherwise indicated herein or unless clearly inconsistent with the context. The terms “equip,” “have,” “include,” and “incorporate” should be interpreted as open-ended terms (i.e., “include, but not limited to”) unless otherwise indicated herein. The descriptions of ranges of values ​​herein are intended merely as a simple way to refer individually to each distinct value that falls within that range, unless otherwise indicated herein, and each distinct value is incorporated herein as if it were individually described herein. All methods described herein may be performed in any suitable order unless otherwise indicated herein or unless it is clearly inconsistent with the context. Any use of any examples or illustrative language provided herein (e.g., "etc.") is intended solely to better illustrate the invention and does not imply any limitation of the scope of the invention unless otherwise specified in the claims of this application. Nothing in this specification should be construed as indicating that any non-claimed element is essential to the practice of the invention.

[0082]

[0091] Preferred embodiments of the present invention, including the best modes known to the inventors for carrying out the invention, are described herein. Modifications of these preferred embodiments may become apparent to those skilled in the art by reading the foregoing description. The inventors expect that those skilled in the art will appropriately use such modifications, and they intend that the invention may be carried out in ways other than those specifically described herein. Accordingly, the invention includes all modifications and equivalents of the subject matter described in the claims appended herein, as permitted by applicable law. Furthermore, unless otherwise indicated herein, or unless clearly inconsistent with the context, any combination of any possible modifications of the elements described herein is incorporated into the invention.

Claims

1. A porous membrane comprising layers (A), (B), and (C) in an A-C-B orientation, The aforementioned layer (A) comprises an amorphous fluoropolymer, The aforementioned layer (B) includes a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film. The layer (C) comprises (i) the amorphous fluoropolymer and (ii) a composite fluoropolymer including the symmetric fluoropolymer film or the asymmetric fluoropolymer film. Porous membrane.

2. The porous membrane according to claim 1, comprising the layer (A), the layer (B), and the layer (C) in a B-C-A-C-B orientation.

3. The porous membrane according to claim 1 or 2, wherein the layer (C) has an average pore diameter smaller than the average pore diameter of the layer (B).

4. The porous membrane according to any one of claims 1 to 3, wherein the layer (C) has an average pore diameter that increases from the side in contact with the layer (A) to the side in contact with the layer (B).

5. The porous membrane according to any one of claims 1 to 4, wherein the amorphous fluoropolymer comprises an ether group, a dioxol group, or a combination thereof.

6. The porous membrane according to any one of claims 1 to 5, wherein the amorphous fluoropolymer comprises at least one tetrafluoroethylene unit and at least one fluorinated ether unit, a fluorinated dioxole unit, or a combination thereof.

7. The porous membrane according to any one of claims 1 to 6, wherein the symmetric fluoropolymer membrane or the asymmetric polymer membrane contains polytetrafluoroethylene (PTFE).

8. The porous membrane according to claim 7, wherein the polytetrafluoroethylene (PTFE) is stretched polytetrafluoroethylene (ePTFE).

9. The porous membrane according to any one of claims 1 to 8, wherein the layer (B) has an average flow pore diameter of 60 nm to 500 nm.

10. The porous membrane according to any one of claims 1 to 8, wherein the layer (B) has an average flow pore diameter of 60 nm to 200 nm.

11. A porous membrane according to any one of claims 1 to 10, having an average flow pore diameter of 10 nm to 60 nm.

12. A porous membrane according to any one of claims 1 to 10, having an average flow pore diameter of 20 nm to 60 nm.

13. A porous membrane according to any one of claims 1 to 12, having an average thickness of 5 microns to 1000 microns.

14. A porous membrane according to any one of claims 1 to 12, having an average thickness of 25 microns to 500 microns.

15. A method for producing a porous membrane, (iv) The step of casting a solution containing an amorphous fluoropolymer resin onto the first surface of a symmetrical fluoropolymer film or an asymmetrical fluoropolymer film, (v) Applying pressure to the second surface of the symmetric fluoropolymer film or the asymmetric fluoropolymer film, thereby drawing at least a portion of the solution containing the amorphous fluoropolymer into the symmetric fluoropolymer film or the asymmetric fluoropolymer film, (vi) The solution containing the amorphous fluoropolymer resin is reversed to obtain a porous membrane comprising layer (A), layer (B), and layer (C) in an A-C-B orientation, a. The layer (A) comprises the amorphous fluoropolymer, b. The layer (B) includes the symmetric fluoropolymer film or the asymmetric fluoropolymer film, c. The layer (C) comprises (i) the amorphous fluoropolymer and (ii) a composite fluoropolymer including the symmetric fluoropolymer film or the asymmetric fluoropolymer film. The steps of forming a porous membrane and A method that includes this.

16. A method for producing a porous membrane, (v) The step of casting a solution containing an amorphous fluoropolymer resin onto the first surface of a first symmetric fluoropolymer film or a first asymmetric fluoropolymer film, (vi) Applying the first surface of the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film onto the casting solution, (vii) Applying pressure to the second surface of the first symmetric fluoropolymer film or the first asymmetric fluoropolymer film and / or the second surface of the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film, thereby drawing at least a portion of the solution containing the amorphous fluoropolymer into the first symmetric fluoropolymer film or the first asymmetric fluoropolymer film and / or the second symmetric fluoropolymer film or the second asymmetric fluoropolymer film; (viii) The solution containing the amorphous fluoropolymer resin is reversed to obtain a porous membrane comprising layers (A), (B), and (C) in a B-C-A-C-B orientation, a. The layer (A) comprises the amorphous fluoropolymer, b. The layer (B) includes the symmetric fluoropolymer film or the asymmetric fluoropolymer film, c. The layer (C) comprises (i) the amorphous fluoropolymer and (ii) a composite fluoropolymer including the symmetric fluoropolymer film or the asymmetric fluoropolymer film. The steps of forming a porous membrane and A method that includes this.

17. The method according to claim 15, wherein the pressure is applied by a vacuum, a Meyer bar, a slot die, a doctor blade, an air blade, or a combination thereof.

18. The method according to claim 16, wherein the pressure is applied by a vacuum, a Meyer bar, a slot die, a doctor blade, an air blade, or a combination thereof.

19. A method for treating a contaminated fluid, comprising the step of passing at least a portion of the contaminated fluid through a porous membrane according to any one of claims 1 to 14.

20. A method for recovering material from a fluid, comprising the step of passing at least a portion of the fluid through a porous membrane such that at least a portion of the material is retained on the porous membrane according to any one of claims 1 to 14.

Images