PFAS-free coated track etched membrane

Abstract

The present invention relates to a film comprising a track-etched membrane substrate containing pores and a coating on at least one surface of the track-etched membrane substrate, wherein the coating is free of perfluoroalkyl compounds and polyfluoroalkyl compounds. The film of the invention provides hydrophobic and even oleophobic properties.

Description

[Technical Field]

[0001] The present invention relates to a film comprising a track-etched membrane substrate containing pores and a coating on at least one surface of the track-etched membrane substrate, wherein the coating is free of perfluoroalkyl compounds and polyfluoroalkyl compounds. The film of the invention provides hydrophobic and even oleophobic properties. [Background technology]

[0002] Background of the Invention The fabrication of "classic" track-etched membranes (TEMs) involves high-energy heavy ion irradiation of a polymer foil, followed by, for example, activation of latent tracks with UV light, and then etching. The fabrication of TEMs, which are now commercially available in considerable quantities, focuses on delivering through-pores that penetrate throughout the entire thickness of the film and whose pores have the highest possible uniformity in pore size and pore density throughout the entire film of several hundred square meters.

[0003] Track-etched membranes (TEMs) are commonly used in a variety of industries, including mobility applications, biotechnology, pharmaceuticals, and water treatment. They are made of thin polymer films and contain pores that are only visible under a microscope.

[0004] Currently, all hydrophobic track-etched membranes on the market are coated with PFAS coating (e.g., EP 2583733 B1; EP 2683176 B1).

[0005] When coated with C6 or C8 PFAS coating (perfluoroalkyl and polyfluoroalkyl substances = PFAS), truck etched membranes can achieve reasonable airflow in combination with highly hydrophobic and highly oleophobic grades, enabling many ventilation and filtration applications, including critical safety applications such as ventilation for electronic control units or headlights in automobiles.

[0006] Chemicals in the PFAS family are currently under close scrutiny from various regulatory authorities, including the European Chemicals Agency (ECHA) in the EU and the Environmental Protection Agency (EPA) in the United States, primarily due to the known and suspected carcinogenic characteristics of some PFAS or their precursors, or due to chemical releases during the manufacture or decomposition of PFAS. C8 PFAS is even banned today for environmental reasons.

[0007] In other words, there is a need for new, environmentally friendly track-etched membranes. [Overview of the project]

[0008] According to the present invention, this problem is solved by providing a film comprising a track-etched membrane substrate containing pores and a coating on at least one surface of the track-etched membrane substrate, wherein the coating does not contain perfluoroalkyl compounds or polyfluoroalkyl compounds.

[0009] The invention relates to a preferably 100% PFAS-free hydrophobic and reasonably oleophobic track-etched membrane having a PFAS-free coating, which is a polymer film containing uniformly distributed, microscopically visible, substantially cylindrical pores of equal size, as in conventional track-etched membranes, i.e., track-etched membrane substrates, typically made of PET, PC, PEN, PI, or PEEK. However, it has one of several unique PFAS-free coatings that gives it hydrophobic and reasonably oleophobic capabilities. The PFAS-free coating is a thin layer of polymer material deposited on the surface of the film using the specialized techniques described herein.

[0010] Another aspect of the invention relates to a method for depositing a PFAS-free hydrophobic coating on a track-etched membrane substrate. [Modes for carrying out the invention]

[0011] Detailed explanation The invention presented herein describes a novel type of film comprising a track-etched membrane substrate containing pores and a coating on at least one surface of the track-etched membrane substrate, wherein the coating does not contain perfluoroalkyl compounds or polyfluoroalkyl compounds.

[0012] Track etching is a well-known technique to those skilled in the art. Exemplary methods for producing track-etched membranes are described in publications listed herein or in patent documents such as US 3612871 B2, DD-AP 235923 and DE 19536033 A1. The essence of the technique lies in the irradiation of a thin polymer film with high-energy charged particles (ions, protons, alpha particles, etc.) or fragments of heavy nuclear fission (argon, krypton, xenon, uranium, etc.), resulting in the radiolysis of the polymer and the formation of damaged channels (i.e., so-called "tracks") in the material. During further etching of the irradiated film with solutions of alkalis, acids, oxidizing agents, and other chemical reagents, fragments of the material are washed away from the tracks and regular through-pores are formed (P. Apel, Radiation Measurements 34(1), 559-566, 2001).

[0013] The material of the track-etched membrane substrate, i.e., the polymer film, preferably contains at least one of a hydrolyzable polymer and an oxidatively destructive polymer. Preferably, it is selected from polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), polyether ether ketone (PEEK), and other polymers or composite materials having similar properties. Polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), and polyether ether ketone (PEEK) are particularly preferred. Polyethylene terephthalate (PET) is most preferred.

[0014] The thickness of the track-etched membrane substrate is not particularly limited. The thickness can be adapted and selected according to the intended use. For example, thicker membranes may provide improved water penetration pressure (WEP) and, in particular, improve the long-term WEP performance of the membrane. This effect is supported by experimental data provided herein. Water penetration pressure is the minimum pressure required to push water through the largest opening of a dry, hydrophobic membrane. Thinner membranes may be used as long as they are adequately supported. Preferably, the thickness is in the range of 3 to 200 μm, most preferably 20 to 75 μm.

[0015] The films and, in particular, coatings of the invention do not comprise perfluoroalkyl compounds and polyfluoroalkyl compounds (PFAS), i.e., are essentially PFAS-free.

[0016] Perfluoroalkyl and polyfluoroalkyl compounds are synthetic organofluorine chemical compounds having multiple fluorine atoms attached to an alkyl chain. The initial definition, since 2011, was that they have at least one perfluoroalkyl moiety, -C n F 2n+1 -It was required to contain (Buck et al. “Perfluoroalkyl and polyfluoroalkyl substances in the environment: terminology, classification, and origins”. Integrated Environmental Assessment and Management. 7(4):513-41, 2011).

[0017] In 2021, the Organization for Economic Cooperation and Development (OECD) expanded its terminology, stating that "PFAS are defined as fluorinated substances containing at least one fully fluorinated methyl or methylene carbon atom (without any H / Cl / Br / I atoms attached to it), i.e., any chemical substance having at least a perfluoromethyl group (-CF3) or a perfluoromethylene group (-CF2-), with some notable exceptions, is a PFAS."

[0018] In this specification, the OECD definition shall apply. Within the meaning of the present invention, that is, any chemical substance having at least a perfluoromethyl group (-CF3) or a perfluoromethylene group (-CF2-) is a PFAS.

[0019] In particular, the films and especially the coatings of the invention do not contain PFAS compounds having eight carbon atoms (such as PFOA by REACH, perfluorooctanoic acid, and PFOA-related compounds, C8) and / or having six carbon atoms (such as PFHxS by REACH, perfluorohexanesulfonic acid or PFHxA, perfluorohexanoic acid, and related compounds, C6). Of course, it is preferable that the films of the invention do not contain C6 and C8 PFAS or any other PFAS.

[0020] Furthermore, the film of the invention excludes perfluorocarboxylic acids having 9 to 14 carbon atoms, such as perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA), or perfluorotetradecanoic acid (PFTeDA).

[0021] According to a preferred embodiment, the film and, in particular, the coating of the invention are 100% free of any PFAS.

[0022] The pores of the track-etched membrane substrate extend in the thickness direction through the track-etched membrane substrate such that the track-etched membrane substrate has openings corresponding to a number of through-holes. Preferably, the pores have a constant cross-sectional shape and extend linearly through the track-etched membrane substrate. The direction of the pores within the membrane can be adjusted within an angle in the range of 0° to 60°, preferably 30° to 50° (measured from a perpendicular line perpendicular to the surface of the membrane) during the irradiation process.

[0023] Each of the pores preferably has a size of from 0.1 to 20 μm, more preferably from 0.1 to 10 μm, particularly from 0.15 to 1.0 μm. According to the invention, the "size" of the pores means the diameter of a circle having an area equal to the cross-sectional area of the through-hole. As known to those skilled in the art, the size of the pores can be adjusted by the etching time or the concentration of the etching treatment liquid.

[0024] Preferably, the size of the pores is also preferably highly uniform and homogeneous over the membrane substrate region, and in a particularly preferred embodiment of the invention, the standard deviation of the size of the pores varies between 0% and 10%, preferably between 0% and 5%, most preferably between 0% and 3%.

[0025] The shape of the pores is not limited, but the pores are preferably conical, semi-cylindrical, substantially cylindrical and / or cylindrical in shape. Preferably, the pores are of a uniform shape, particularly of a uniform shape and size.

[0026] According to a preferred embodiment, the track-etched membrane substrate contains substantially cylindrical pores of equal size that are uniformly distributed and only visible under a microscope.

[0027] The pores preferably have a density of 1,000 to 1×10 2 per cm 10 preferably 1×10 2 to 8×10 6 per cm 8The pores are uniformly distributed within a specific range, within certain limitations. The pore density is set during the irradiation process, for example, depending on the amount of ions applied during ion beam irradiation. The pore size and therefore the pores can be adjusted during etching.

[0028] Preferably, the pore density is also preferably highly uniform and homogeneous across the film substrate region, and in a particularly preferred embodiment of the invention, the standard deviation of the pore density varies between 0% and 10%, preferably between 0% and 5%, and most preferably between 0% and 3%.

[0029] A PFAS-free coating is provided on at least one surface of the track-etched membrane substrate. It is preferable that it be provided on both surfaces and inside the pores, but the coating may also be provided on one surface of the track-etched membrane substrate and / or over a portion of the length of the pores.

[0030] The coating may coat only the outer surface of the track-etched membrane substrate and the walls or outer surfaces of the pores within the substrate. According to a preferred embodiment, the coating covers both the surface and the pores of the film substrate.

[0031] According to the preferred embodiment, the coating is thinner than the pore radius.

[0032] According to a preferred embodiment, the coating is based on an acrylic copolymer or alkyl urethane, i.e., an acrylic copolymer or alkyl polyurethane.

[0033] Acrylic copolymers are particularly preferred. The term "acrylic copolymer" is well understood by those skilled in the art. Generally, an acrylic polymer or acrylate polymer (also known as acrylic or polyacrylate) is any of a group of polymers prepared from acrylate monomers, where an acrylic copolymer is a polymer derived from more than one monomer, i.e., another monomer in addition to (beside) an acrylate monomer such as methacrylic acid.

[0034] Examples of preferred acrylic polymers are polymethyl methacrylate, poly(2-ethylhexyl acrylate), poly(tert-butyl acrylate), poly(styrene-co-methyl methacrylate), poly(butyl acrylate-co-methyl methacrylate), poly(acrylonitrile -co-butyl acrylate), poly(2-ethylhexyl acrylate-co-butyl acrylate) and similar polymers having the general structure, i.e., polyacrylate:

[0035]

Chemical formula

[0036] and similar polymers having the same.

[0037] As understood by those skilled in the art, "polyurethane" refers to a class of polymers composed of organic units linked by carbamate (urethane) linkages. In contrast to other common polymers such as polyethylene and polystyrene, polyurethanes can be manufactured from a wide range of starting materials.

[0038] <0000l39>Examples of preferred polyurethanes are alkyl urethanes having R1, R2 as C n H n+2 as shown in the figure below

[0039]

Chemical formula

[0040] That is the case.

[0041] According to a preferred embodiment, the coating is: A) A dispersion of paraffin wax (a mixture of various saturated CnH2n+2 (where n is an integer, preferably 18-70), e.g., petrolatum, ceresin), acrylic copolymer, and aromatic aliphatic ether alcohol or B) Provided by applying a dispersion of alkyl urethane and aromatic aliphatic ether alcohol, and subsequently curing it. A dispersion of paraffin wax and acrylic copolymer is particularly preferred.

[0042] The dispersion may contain additional crosslinking agents, particularly dispersions of dimethylpyrazole-blocked polyisocyanates.

[0043] In a more preferred embodiment, an ethoxylated aliphatic alcohol is added to the dispersion.

[0044] In this specification, particularly preferred PFAS-free coatings are: 1) Dispersions of paraffin wax and acrylic copolymers with or without additional crosslinking agents, such as dispersions of dimethylpyrazole-blocked polyisocyanates with or without ethoxylated aliphatic alcohols and aromatic aliphatic ether alcohols. example Phobotex R-Ace, along with Phobol Extender UXN and Invadine PBN from Huntsman Textile Effects / Archroma, or 2) Dispersions of alkyl urethanes with or without additional crosslinking agents, such as dispersions of dimethylpyrazole-blocked polyisocyanates with or without ethoxylated aliphatic alcohols and aromatic aliphatic ether alcohols. exampleZelans R3 (Chemours) along with Phobol Extender UXN and Invadine PBN (both from Huntsman Textile Effects / Archroma), or 3) Any different dispersions, either as standalone coating solutions or in any mixture: a) Modified fats based on palm oil derivatives, preferably with or without additional crosslinking agents, wherein the crosslinking agent is preferably based on polyisocyanates, and more particularly on dimethylpyrazole-blocked polyisocyanates. b) Acrylic copolymers, particularly those based on ethoxylated alcohols and alkyl acrylates. c) Paraffin-zirconium salt composition Examples: Texaphob HFF-C;HFF;HFF-PZ; or 4) A solution of polyolefin in a suitable solvent with or without additional crosslinking agents, e.g., an ethoxylated aliphatic alcohol having an acrylic copolymer in isopropanol. Provided by [company name].

[0045] As used herein, "aromatic aliphatic" refers to compounds that are essentially aliphatic and contain one or more aryl groups.

[0046] The PFAS-free coating and track-etched membrane combinations described (e.g., PET, PC, PEN, PI, or PEEK base materials) are designed to provide a novel and unique family of membranes that offer superior hydrophobicity and reasonable oleophobicity, PFAS-free films as an environmentally friendly alternative to conventional PFAS-coated track-etched membranes and even expanded polytetrafluoroethylene (ePTFE) in non-essential applications.

[0047] The unique combination of the track-etched membrane substrate and the proposed PFAS-free coating results in reduced environmental impact: the absence of PFAS in the manufacture, use, or degradation of the film, along with comparable hydrophobic and reasonable oleophobic properties.

[0048] Further aspects of the present invention include the step: (a) To provide a track-etched membrane substrate, (b) - Dispersion of paraffin wax, acrylic copolymer and aromatic aliphatic ether alcohol or - Dispersion of alkyl urethane and aromatic aliphatic ether alcohol or - A solution of polyolefin in a suitable solvent Applying, and (c) To cure and / or dry This relates to a method for depositing a coating that is essentially PFAS-free, including, on a track-etched membrane substrate.

[0049] The coatings and track-etched membrane substrates provided are as described above in this specification.

[0050] In step (b), the application of the dispersion or solution may be by a dip coating, spray coating or plasma coating procedure, preferably by a dip coating procedure.

[0051] In a preferred embodiment, the dispersion or solution obtained in step (b) may contain an additional crosslinking agent, particularly a dispersion of dimethylpyrazole block polyisocyanate. The addition of an ethoxylated aliphatic alcohol may also be preferred. In a particularly preferred embodiment, a dispersion of dimethylpyrazole block polyisocyanate and an ethoxylated aliphatic alcohol is added.

[0052] In an optional step (d), the film provided according to step (c) can be laminated onto a PFAS-free nonwoven fabric substrate, which may be made of a further carrier film or, for example, kernmantle fibers. One example may be a PET+CoPET kernmantle nonwoven fabric.

[0053] In other words, according to a further embodiment, the invention relates to structures such as membranes, including the track-etched membrane substrate and coating described herein, and further carriers such as polymer films or nonwoven fabric substrates.

[0054] The proposed unique combination of track-etched membrane substrates and PFAS-free coatings provides a wide range of 100% PFAS-free track-etched membranes with superior hydrophobicity and reasonably oleophobicity, which were previously unavailable on the market.

[0055] The proposed PFAS-free truck-etched membrane aims to reduce PFAS release into the environment due to the manufacturing, use, and end-of-life of conventional PFAS-coated truck-etched membranes and ePTFE. This patent application discloses a unique combination of these with significant potential in a variety of industries, including consumer electronics, mobility, automotive lighting, electronic control units, battery technology, biotechnology, pharmaceuticals, and water treatment.

[0056] Further aspects of the invention relate to the use of the films and structures of the invention in oil-repellent and water-repellent fabrics, and in industrial polymers for specific films or sealants, for implantable medical devices, photographic coatings, and photolithography processes.

[0057] Much of the above description of preferred embodiments will be apparent to those skilled in the art as applicable to specific situations and, in particular, to the general use of films. Adaptations and modifications of such preferred embodiments may be necessary and advantageous for specific applications as well as for other possible uses. Such adaptations and modifications can be readily made by those skilled in the art based on their own knowledge and the overall information provided herein.

[0058] The invention is further illustrated by the following figures and embodiments, but these are not intended to limit the scope of the invention as defined by the attached claims. [Brief explanation of the drawing]

[0059] figure [Figure 1] Figure 1 is a graph illustrating the effect of film thickness [μm] on long-term L-WEP [mbar]. [Figure 2] Figure 2 is a graph illustrating the effect of film thickness [μm] on short-term S-WEP [mbar]. [Figure 3] Figure 3 is a graph illustrating the effect of the L-WEP / S-WEP ratio on film thickness [μm]. [Figure 4] Figure 4 is a graph illustrating the airflow rate, which depends on (A) the film thickness and (B) the pore size. [Figure 5] Figure 5 is a graph illustrating the effect of pore size [μm] on S-WEP [mbar]. [Examples]

[0060] 1. Effect of PFAS-free coatings on WEP Oxyphen 20.IC00.507.502 Track Etched Membrane (50×10 6 pore size / cm 2The 35 μm PET, with a pore diameter (bubble point) of approximately 0.5 μm, combined with its conventional PFAS coating, has a short-term water intrusion pressure (S-WEP) of approximately 2 bar and an oleophobicity grade of 6.5 on the AATCC 118 test. The AATCC 118 test is known to those skilled in the art.

[0061] The same film having the new PFAS-free coatings 1, 2, or 3 proposed above has an oleophobic grade of 1.5 on S-WEP and AATCC 118 with a reduction of approximately 20%, and liquids for grades 3-5 exhibit long-term stable "C-type" droplets, which is also impressive water-repellent performance.

[0062] 2. Effect of film thickness on WEP To demonstrate the effect of membrane thickness on water intrusion pressure, specific long-term water intrusion pressures (pL-WEP) were recorded so that 50% of the samples were still OK after 10 minutes. Membranes with almost the same minimum pore size (by the bubble point test method) in the range of approximately 0.4 μm were measured with thicknesses of 23 μm, 36 μm, and 50 μm, and with pore sizes of 50-100 MIO / cm². 2 The selection was made based on the following criteria. The results clearly show a dependency: "Thicker films provide longer-term protection against water penetration" (Figure 1). The effect is strong, with pL-WEP increasing by almost 5 times when the thickness doubles.

[0063] p L-WEP is one method for characterizing the hydrophobicity of a membrane, measured by "applying pressure, holding it, and observing it." Another, faster method for characterizing hydrophobicity, which is often used in practice, is to gradually increase the water pressure until leakage occurs (p S-WEP or s-WEP, or "increase pressure until the membrane leaks"). This measurement is valuable for estimating short-term, rapid loading on the membrane. The membranes selected for the examples did not show a dependence of s-WEP versus thickness, as in the case of p-LWEP versus thickness, and were all approximately 2 bar at s-WEP (Figure 2).

[0064] The ratio of p L-WEP to p S-WEP is still significantly affected by thickness, with the influence of L-WEP thickness being stronger (Figure 3).

[0065] The airflow rate for the selected samples was 4.5–9 L / min / cm² / bar, without any apparent trend with respect to thickness or pore size (Figure 4).

[0066] There is a small decrease in s-WEP with respect to pore size, but this effect is not as strong as the effect of thickness on p-L-WEP (Figure 5).

[0067] As a result, the observed effect of thickness on pL-WEP is the primary effect in the presented sample dataset, and it is suggested that the movement toward thicker films allows for longer-term protection against water intrusion.

Claims

1. A film comprising a track-etched membrane substrate containing pores and a coating on at least one surface of the track-etched membrane substrate, wherein the coating does not contain perfluoroalkyl compounds or polyfluoroalkyl compounds.

2. The film according to claim 1, wherein the material of the track-etched membrane substrate is selected from polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), polyetheretherketone (PEEK), and other polymers having similar properties, preferably PET or PC.

3. The film according to claim 1 or 2, wherein the track-etched membrane substrate includes uniformly distributed, substantially cylindrical pores of equal size.

4. The film according to any one of claims 1 to 3, wherein the outer surface of the track-etched membrane substrate and the walls of the pores in the substrate are coated.

5. The film according to any one of claims 1 to 4, wherein the coating is thinner than the pore radius.

6. The film according to any one of claims 1 to 5, wherein the pore size is 0.1 to 20 μm, preferably 0.1 to 10 μm, and particularly 0.15 to 1.0 μm.

7. Track etched membrane base material, 1 cm ２ 1,000 to 1 x 10 １０ A number of pores, preferably 1 cm ２ 1 x 10 ６ from 8 x 10 ８ A membrane according to any one of claims 1 to 6, having a number of pores.

8. The film according to any one of claims 1 to 7, wherein the coating does not contain 100% perfluoroalkyl compounds and polyfluoroalkyl compounds.

9. The film according to any one of claims 1 to 8, wherein the coating is provided by applying a dispersion of paraffin wax, an acrylic copolymer, and an aralphatic ether alcohol, or a dispersion of alkyl urethane and an aralphatic ether alcohol, preferably a dispersion of paraffin wax and an acrylic copolymer, and subsequently curing it.

10. The membrane according to claim 9, wherein the dispersion comprises an additional crosslinking agent, particularly a dispersion of dimethylpyrazole block polyisocyanate.

11. The film according to claim 9 or 10, wherein an ethoxylated aliphatic alcohol is added.

12. The film according to any one of claims 1 to 8, wherein the coating is provided by applying a solution of polyolefin in a suitable solvent, with or without an additional crosslinking agent.

13. Process: (a) To provide a track-etched membrane substrate; (b) a. A dispersion of paraffin wax, acrylic copolymer, and aromatic aliphatic ether alcohol; or b. Dispersion of alkyl urethane and aromatic aliphatic ether alcohol; or c. i) Modified fats, preferably based on palm oil derivatives, with or without additional crosslinking agents. ii) Acrylic copolymers, particularly those based on ethoxylated alcohols and alkyl acrylates, iii) Paraffin zirconium salt composition or iv) Any mixture of them A dispersion based on; or d. A solution of polyolefin in a suitable solvent, with or without additional crosslinking agents. Applying the principle; and (c) To cure and / or dry A method for depositing a coating that is essentially PFAS-free, including the coating itself, on a track-etched membrane substrate.

14. A structure comprising a film according to any one of claims 1 to 12, and a further carrier such as a polymer film or a nonwoven fabric substrate.

15. Use of a film according to any one of claims 1 to 12 or a structure according to claim 14 in consumer and industrial electronic protection, oil-repellent and water-repellent fabrics, and industrial polymers for specific films or sealants, for implantable medical devices, photographic coatings, and photolithography processes.

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