Track-etched membranes coated with PFAS-free coating, method for depositing an essentially PFAS-free coating, structure and use.

Description

1 / 13 “PFAS-FREE COATED TRACK-ETCHED MEMBRANES, METHOD FOR DEPOSITING AN ESSENTIALLY PFAS-FREE COATING OF PFAS, STRUCTURE AND USE

[001] The present invention relates to membranes comprising a track-etched type membrane substrate comprising pores and a coating on at least one surface of the track-etched type membrane substrate, wherein the coating does not comprise perfluoroalkyl and polyfluoroalkyl compounds. The membranes of the invention provide hydrophobic and even oleophobic capabilities. BACKGROUND OF THE INVENTION

[002] The production of classic track-etched membranes (TEMs) involves irradiating polymer sheets with highly energetic heavy ions followed by activation of latent tracks, for example by UV light, as well as subsequent etching treatment. TEM production, which is currently commercially available in significant volumes, focuses on providing pass-through pores that penetrate the entire thickness of a membrane and whose pores have the greatest possible homogeneity of pore sizes and densities across hundreds of square meters of membrane.

[003] Beam-etched membranes (TEMs) are commonly used in various sectors, including mobility, biotechnology, pharmaceuticals, and water treatment applications. They are produced from thin polymer films and contain microscopic pores.

[004] Currently, all track-etched hydrophobic membranes on the market are coated with PFAS coatings (e.g., documents no. EP 2 583 733 B1; EP 2 683 176 B1).

[005] When coated with a C6 or C8 PFAS coating (perfluoroalkyl and polyfluoroalkyl substances = PFAS), track-etched membranes can achieve reasonable airflow rates in combination with high hydrophobicity and high degrees of oleophobicity, enabling many ventilation and filtration applications. Petition 870250091442, dated 07 / 10 / 2025, page 86 / 100 2 / 13 including critical safety applications, such as ventilation for electronic control units or headlights in cars.

[006] The PFAS family of chemicals is currently under intense scrutiny from several regulatory agencies, including the European Chemicals Agency (ECHA) in the EU and the Environmental Protection Agency (EPA) in the US, primarily due to known and suspected carcinogenic characteristics of some PFASs or their precursors, or due to chemical releases during the production or decomposition of PFAS. C8 PFAS are even banned today for environmental reasons.

[007] Thus, there is a need for new environmentally friendly track-etched membranes. SUMMARY OF THE INVENTION

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

[009] The inventive membrane, preferably 100% hydrophobic and reasonably oleophobic, PFAS-free, with a PFAS-free coating, is produced from a polymer film, typically PET, PC, PEN, PI or PEEK, containing microscopic, almost cylindrical pores of equal size homogeneously distributed, as in traditional track-etched membranes, i.e., the track-etched membrane substrate. However, it has one of several unique PFAS-free coatings that give it hydrophobic and reasonably oleophobic capabilities. The PFAS-free coating is a thin layer of a polymeric material that is deposited on the membrane surface using a specialized technique, as described in this document.

[010] Another aspect of the invention relates to a method for depositing a PFAS-free hydrophobic coating onto a track-type membrane substrate. Petition 870250091442, dated 07 / 10 / 2025, p. 87 / 100 3 / 13 etched. DETAILED DESCRIPTION

[011] The invention presented here describes a new type of membranes comprising a track-etched type membrane substrate comprising pores and a coating on at least one surface of the track-etched type membrane substrate, wherein the coating does not comprise perfluoroalkyl and polyfluoroalkyl compounds.

[012] Track-etching is a technique well known to those skilled in the art. Exemplary methods for producing track-etched membranes are described in the publications listed herein or in patent documents such as US Nos. 3,612,871 B2, DD-AP 235923 and DE 195 36,033 A1. The essence of the technology lies in the irradiation of thin polymer films by high-energy charged particles (ions, protons, α particles, etc.) or with fission fragments of heavy nuclei (argon, krypton, xenon, uranium, etc.), resulting in the radiative degradation of macromolecules and the formation of damaged channels (i.e., so-called tracks) in the material. During subsequent corrosion of films irradiated with solutions of alkalis, acids, oxidants and other chemical reagents, fragments of material are washed away from the tracks and a regular porosity is formed (P. Apel, Radiation Measurements 34(1), 559-566, 2001).

[013] The substrate material of the track-etched membrane, i.e., a polymer film, preferably contains at least one hydrolyzable polymer and one oxidatively destructible 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 with similar properties. Polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), and polyether ether ketone (PEEK) are particularly preferred. Polyethylene terephthalate (PET) is the most preferred.

[014] The thickness of the track-etched membrane substrate is not Petition 870250091442, dated 07 / 10 / 2025, page 88 / 100 4 / 13 particularly limited. The thickness can be adapted and chosen according to the intended use. For example, thicker membranes can provide an enhanced water inlet pressure (WEP) and, in particular, improve the long-term WEP performance of a membrane. This effect is supported by experimental data provided in this document. The water inlet pressure is the minimum pressure required to force water through the largest opening of a dry hydrophobic membrane. Thinner membranes can be used provided they are sufficiently supported. Preferably, the thickness is in the range of 3-200 µm, preferably 20-75 µm.

[015] The membranes of the invention and, in particular, the coating do not comprise perfluoroalkyl and polyfluoroalkyl compounds (PFAS), that is, they are essentially PFAS-free.

[016] Perfluoroalkyl and polyfluoroalkyl compounds are synthetic organofluorinated chemical compounds that have multiple fluorine atoms bonded to an alkyl chain. An initial definition, from 2011, required that they contain at least one perfluoroalkyl chemical moiety, -CnF2n+1- (Buck et al. Perfluoroalkyl and polyfluoroalkyl substances in the environment: terminology, classification, and origins. Avaliação e Gestão Ambiental Integrada. 7 (4): 513-41, 2011).

[017] As of 2021, the Organisation for Cooperation and Development The Economic Commission for Europe (OECD) expanded its terminology, stating that PFASs are defined as fluorinated substances containing at least one fully fluorinated methyl or methylene carbon atom (free of any H / Cl / Br / I atoms bonded to it), that is, with some notable exceptions, any chemical with at least one perfluorinated methyl group (-CF3) or one perfluorinated methylene group (-CF2-) is a PFAS.

[018] In this document, the OECD definition shall be followed. For the purposes of this invention, that is, any chemical with at least one perfluorinated methyl group (-CF3) or one perfluorinated methylene group (-CF2-) is a PFAS.

[019] In particular, the membranes of the invention, and especially the coating, Petition 870250091442, dated 07 / 10 / 2025, p. 89 / 100 5 / 13 do not include PFAS compounds with 8 carbon atoms (C8, such as PFOA, perfluorooctanoic acid and PFOA-related compounds, according to REACH) and / or 6 carbon atoms (C6, such as PFHxS, perfluorohexanesulfonic acid or PFHxA, perfluorohexanoic acid and related compounds, according to REACH). Obviously, it is preferable that the membrane of the invention be free of C6 and C8 PFAS or any other PFAS.

[020] Also, perfluorinated carboxylic acids with nine to fourteen carbon atoms, such as perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA) or perfluorotetradecanoic acid (PFTeDA), should not be included in the inventive membrane.

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

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

[023] Each of the pores preferably has a size of 0.1 to 20 pm, more preferably 0.1 to 10 pm, in particular 0.15 to 1.0 pm. According to the invention, the size of a pore means the diameter of a circle with an area equal to the cross-sectional area of ​​the passing pore. As is known to those skilled in the art, the sizes of the pores can be adjusted by the etching time or by the concentration of an etching treatment liquid.

[024] Preferably, the pore size is also, preferably, Petition 870250091442, dated 07 / 10 / 2025, pages 90 / 100 6 / 13 highly uniform and homogeneous over the membrane substrate area and, in particularly preferred embodiments of the invention, the standard deviation of the pore size ranges between 0% and 10%, preferably between 0% and 5%, most preferably between 0% and 3%.

[025] The shape of the pores is not limited, but the pores are preferably conical, semi-cylindrical, almost cylindrical and / or cylindrical in shape. Preferably, the pores are of uniform shape, in particular, of uniform shape and size.

[026] According to a preferred embodiment, the track-etched type membrane substrate comprises homogeneously distributed nearly cylindrical microscopic pores of equal size.

[027] The pores are preferably distributed uniformly, so that the density of the plurality of passing pores falls within specific limits included in a range of 1000 to 1 x 1010 pores per cm2, preferably 1 x 106 to 8 x 108 pores per cm2. The pore densities are defined in the irradiation step, for example, depending on the amount of ions applied at the time of ion beam irradiation. The pore sizes and therefore the porosity can be adjusted during recording.

[028] Preferably, the pore density is also highly uniform and homogeneous over the membrane substrate area and, in particularly preferred embodiments of the invention, the standard deviation of the pore density ranges between 0% and 10%, preferably between 0% and 5%, and most preferably between 0% and 3%.

[029] The PFAS-free coating is provided on at least one surface of the track-etched membrane substrate. Although it is preferable that it be applied to both surfaces and within the pores, the coating may also be applied to one surface and possibly part of the pore length of the track-etched membrane substrate.

[030] The coating can cover the outer surface of the track-etched membrane substrate and the pore walls in the substrate or just the surface. Petition 870250091442, dated 07 / 10 / 2025, page 91 / 100 7 / 13 external. According to a preferred embodiment, the coating covers both the surfaces and the pores of the membrane substrate.

[031] According to preferred embodiments, the coating is thinner than the pore radius.

[032] According to the preferred embodiments, the coating is based on an acrylic or alkyl urethane copolymer, that is, an acrylic copolymer or alkyl polyurethane.

[033] Acrylic copolymers are particularly preferred. The term “acrylic copolymer” is well understood by a person skilled in the art. In general, an acrylic polymer or acrylate polymer (also known as acrylic or polyacrylate) is any one of a group of polymers prepared from acrylate monomers, wherein an acrylic copolymer is a polymer derived from more than one species of monomer, that is, one more species of monomer besides the acrylate monomer, such as methacrylic acid.

[034] 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(acrylnitril-co-butyl acrylate), poly(2-ethylhexyl acrylate-co-butyl acrylate and similar polymers with the general structure, i.e., polyacrylates:

[035] As understood by a person skilled in the art, polyurethane refers to a class of polymers composed of organic units linked by carbamate (urethane) bonds. In contrast to other common polymers, such as polyethylene and polystyrene, polyurethane can be produced from a wide range of starting materials. Petition 870250091442, dated 07 / 10 / 2025, page 92 / 100 8 / 13

[036] Examples of preferred polyurethanes are alkylethanes (image below) with R1, R2 as CnHn+2.

[037] According to a preferred embodiment, the coating is provided by applying: A) a dispersion of paraffin wax (a mixture of several saturated CnH2n+2 compounds (n being an integer, preferably 18-70), for example, petrolatum, ceresin), acrylic copolymer and an oralis ether alcohol or B) a dispersion of alkyl urethane alcohol and an araphate ether, and subsequent curing.

[038] A dispersion of paraffin wax and acrylic copolymer is particularly preferred.

[039] The dispersion may comprise an additional crosslinker, in particular a dimethylpyrazole-blocked polyisocyanate dispersion.

[040] According to other preferred embodiments, ethoxylated fatty alcohol is added to the dispersion.

[041] In this document, particularly preferred PFAS-free coatings are provided by: 1) a dispersion of paraffin wax and acrylic copolymer with or without an additional crosslinker, such as a dispersion of a dimethylpyrazole-blocked polyisocyanate with or without the addition of ethoxylated fatty alcohol and an araliphatic ether alcohol; Example: Phobotex R-Ace, along with Phobol Extender UXN and Invadine PBN, from Huntsman Textile Effects / Archroma, or 2) an alkylated urethane dispersion with or without an additional crosslinker, such as a dimethylpyrazole-blocked polyisocyanate dispersion with or without the addition of ethoxylated fatty alcohol and an araliphatic ether alcohol; Example: Zelans R3 (Chemours) together with Phobol Extender UXN and Petition 870250091442, dated 07 / 10 / 2025, p. 93 / 100 9 / 13 Invadine PBN (both from Huntsman Textile Effects / Archroma), or 3) Different dispersions, either as a standalone coating solution or in any mixture: a) Modified fats, preferably based on a palm oil derivative with or without an additional crosslinker, wherein the crosslinker is preferably based on polyisocyanate, in particular based on a polyisocyanate blocked by dimethylpyrazole, b) acrylic copolymer, in particular based on ethoxylated alcohol and alkyl acrylate, c) composition of the zirconium salt in paraffin; Examples: Texaphob HFF-C; HFF; HFF-PZ; or 4) Polyolefin solutions in suitable solvents, with or without additional crosslinking, for example, ethoxylated fatty alcohol with acrylic copolymer in isopropanol.

[042] Aralphatic, as used in this document, refers to an essentially aliphatic compound containing one or more aryl groups.

[043] The combinations of PFAS-free coatings and mat-etched membranes (e.g., PET, PC, PEN, PI or PEEK base material) described are designed to provide excellent PFAS-free hydrophobic and reasonably oleophobic membranes as a unique new family of membranes that is an environmentally friendly alternative to common PFAS-coated mat-etched membranes as well as expanded polytetrafluoroethylene (ePTFE) in non-essential applications.

[044] The unique combination of the track-etched type membrane substrate and the proposed PFAS-free coating results in reduced environmental impact: No PFAS in the production, use or decomposition of the membrane, along with comparable hydrophobic performance and reasonable oleophobic performance.

[045] Another aspect of the present invention relates to a method for depositing an essentially PFAS-free coating onto a substrate of Petition 870250091442, dated 07 / 10 / 2025, page 94 / 100 10 / 13 track-etched type membrane, which comprises the following steps: (a) provide a track-etched type membrane substrate, (b) apply - a dispersion of paraffin wax, acrylic copolymer and oralphatic ether alcohol or - a dispersion of alkyl urethane and araphatic ether alcohol or - a solution of polyolefins in suitable solvents, and (c) cure and / or dry.

[046] The supplied coating, as well as the track-etched type membrane substrate, are as described above.

[047] In step (b), the application of a dispersion or solution can be done by immersion coating, spray coating or plasma coating procedures, preferably by immersion coating procedure.

[048] According to preferred embodiments, the dispersions or solutions according to step (b) may comprise an additional crosslinker, in particular a dispersion of a dimethylpyrazole-blocked polyisocyanate. It may also be preferable to add ethoxylated fatty alcohol. According to a particularly preferred embodiment, a dispersion of a dimethylpyrazole-blocked polyisocyanate and ethoxylated fatty alcohol is added.

[049] In an optional step (d), the membrane provided according to step (c) can be laminated to an additional support film or to a PFAS-free nonwoven substrate, for example, made of kernmantle fibers. An example could be a PET+CoPET kernmantle nonwoven.

[050] Thus, according to another aspect, the invention relates to a structure, such as a membrane, comprising the track-etched type membrane substrate and the coating as described herein and another support, such as a polymer film or a nonwoven substrate.

[051] The proposed unique combinations of membrane substrate type Petition 870250091442, dated 07 / 10 / 2025, p. 95 / 100 11 / 13 track-etched and PFAS-free coatings offer a range of excellent, hydrophobic, and reasonably oleophobic 100% PFAS-free track-etched membranes that were previously unavailable on the market.

[052] The proposed PFAS-free track-etched membranes aim to reduce PFAS releases to the environment due to the production, use, and end-of-life of traditional PFAS-coated track-etched membranes, as well as ePTFE. This patent application discloses these unique combinations, which have significant potential in various sectors, including consumer electronics, mobility, automotive lighting, electronic control units, battery technology, biotechnology, pharmaceuticals, and water treatment.

[053] Another aspect of the invention relates to the use of the innovative membranes and structures in implantable medical devices, photographic coatings and for photolithographic processes, oil and water repellent textiles and industrial polymers for specific membranes or sealants.

[054] It will be evident to the qualified person that many of the above explanations about preferred embodiments apply to specific circumstances and, especially, to the general use of the membrane. For other possible uses, but also for specific applications, adaptations and variations of such preferred embodiments may be necessary and advantageous. Such adaptations and variations can be easily made by a person skilled in the art based on their knowledge and the general information provided herein.

[055] The invention will be illustrated by the following Figures and Examples, which are not intended to limit the scope of the invention as defined by the appended claims. FIGURES Figure 1 is a graph illustrating the effect of membrane thickness [m] on long-term L-WEP [mbar]; Figure 2 is a graph illustrating the effect of membrane thickness [m] on short-term S-WEP [mbar]; Figure 3 is a graph illustrating the effect of membrane thickness ^m] Petition 870250091442, dated 07 / 10 / 2025, page 96 / 100 12 / 13 in the L-WEP / S-WEP ratio; Figure 4 is a graph illustrating the airflow rate as a function of membrane thickness (A) and pore size (B); and Figure 5 is a graph illustrating the effect of pore size [m] on SWEP [mbar]. EXAMPLES 1. EFFECT OF PFAS-FREE COATING ON WEP

[056] The Oxyphen 20.IC00.507.502 track-etched membrane (35 µm PET, with 50 x 10⁶ pores / cm² and approximately 0.5 µm pore diameter (Bubble Point)) has, in combination with its usual PFAS coating, approximately 2 bar short-term water inlet pressure (S-WEP) and an oleophobic grade of 6.5 in the AATCC 118 test. The AATCC 118 test is known to those skilled in the art.

[057] The same membrane with a new PFAS-free coating 1, 2 or 3, as proposed above, has about 20% less S-WEP and an oleophobic grade of 1.5 in the AATCC 118 test, with liquids to grade 3-5 which shows long-term stable Type C droplets, which is also an impressive repellency performance. 2. EFFECT OF MEMBRANE THICKNESS ON WEP

[058] To demonstrate the effect of membrane thickness on water inlet pressure, a specific long-term water inlet pressure (p LWEP) was recorded, such that 50% of the samples were still OK after 10 minutes. Membranes with approximately the same minimum pore sizes within a range of about 0.4 µm (according to the bubble point test method) were selected with thicknesses of 23 µm, 36 µm, and 50 µm and 50–100 MiO pores / cm². The results clearly show the dependence of thicker membranes on providing more protection against long-term water inlet (Figure 1). The effect is strong, with almost a 5x increase in p L-WEP with a 2x increase in thickness.

[059] p L-WEP is a way of characterizing the water repellency of a membrane, measured as applying pressure, holding, and observing. Another more Petition 870250091442, dated 07 / 10 / 2025, page 97 / 100 A quick way to characterize water repellency that is frequently used in practice is to gradually increase the water pressure until leakage occurs (p-S-WEP or s-WEP, or increasing the pressure until the membrane leaks). This measurement is valuable for estimating a short-term rapid load on the membrane. The membranes that were selected for the example do not show an s-WEP vs. thickness dependence, as in the case of p-LWEP vs. thickness, and are all around 2 bar in s-WEP (Figure 2).

[060] The p L-WEP / p S-WEP ratio is still significantly influenced by thickness, showing that the effect of L-WEP thickness is stronger (Figure 3).

[061] The air flow rate is 4.5-9 L / min / cm2 / bar for the selected samples, with no clear trend with thickness or pore size (Figure 4).

[062] There is a slight reduction in s-WEP with pore size, but this effect is not as strong as the effect of thickness on p L-WEP (Figure 5).

[063] Consequently, the observed effect of thickness on p L-WEP is the main effect in the sample dataset presented and shows that moving towards thicker membranes allows for more long-term protection against water ingress. Petition 870250091442, dated 07 / 10 / 2025, pages 98 / 100

Claims

1 / 3 CLAIMS 1. Membrane characterized by comprising a track-etched type membrane substrate comprising pores and a coating on at least one surface of the track-etched type membrane substrate, wherein the coating does not comprise perfluoroalkyl and polyfluoroalkyl compounds.

2. Membrane, according to claim 1, characterized in that the track-etched membrane substrate material is selected from polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), polyether ether ketone (PEEK) and other polymers with similar properties, preferably PET or PC.

3. Membrane, according to claim 1 or 2, characterized in that the track-etched membrane substrate comprises homogeneously distributed quasi-cylindrical pores of equal size.

4. Membrane, according to any one of claims 1 to 3, characterized in that the outer surface of the tracketched membrane substrate and the pore walls in the substrate are coated.

5. Membrane, according to any one of claims 1 to 4, characterized in that the coating is thinner than the pore radius.

6. Membrane, according to any one of claims 1 to 5, characterized in that the pore size is from 0.1 to 20 μm, preferably 0.1 to 10 μm, in particular 0.15 to 1.0 μm.

7. Membrane, according to any one of claims 1 to 6, characterized in that the track-etched membrane substrate has from 1000 to 1 x 1010 pores per cm2, preferably from 1 x 106 to 8 x 108 pores per cm2.

8. Membrane, according to any one of claims 1 to 7, characterized in that the coating is 100% free of perfluoroalkyl and polyfluoroalkyl compounds.

9. Membrane, according to any one of claims 1 to 8, characterized in that the coating is provided by applying a dispersion of paraffin wax, acrylic copolymer and oralphatic ether alcohol or a dispersion of alkyl urethane and oralphatic ether alcohol, preferably a dispersion of paraffin wax and acrylic copolymer and subsequent curing.

10. Membrane, according to claim 9, characterized in that the dispersion comprises an additional crosslinker, in particular a dimethylpyrazole-blocked polyisocyanate dispersion.

11. Membrane, according to claim 9 or 10, characterized by having ethoxylated fatty alcohol added to it.

12. Membrane, according to any one of claims 1 to 8, characterized in that the coating is provided by applying a solution of polyolefins in suitable solvents with or without additional crosslinking.

13. Method for depositing an essentially PFAS-free coating on a track-etched membrane substrate characterized by comprising the steps: (a) providing a track-etched membrane substrate, (b) applying a. a dispersion of paraffin wax, acrylic copolymer and aralphatic ether alcohol; or b. a dispersion of alkyl urethane alcohol and aralphatic ether; or c. a dispersion based on i) modified fats, preferably based on a palm oil derivative, with or without additional crosslinker, ii) acrylic copolymer, in particular based on ethoxylated alcohol and alkyl acrylate, iii) zirconium salt composition in paraffin or iv) any mixture thereof; or d. a solution of polyolefins in suitable solvents, with or without additional crosslinker; and Petition 870250091442, dated 07 / 10 / 2025, p. 79 / 100 3 / 3 (c) cure and / or dry.

14. Structure characterized by comprising a membrane, as defined in any one of claims 1 to 12, and another support, such as a polymer film or a nonwoven substrate.

15. Use of a membrane, as defined in any one of claims 1 to 12, or of a structure, as defined in claim 14, characterized by being intended for implantable medical devices, photographic coatings and for photolithographic processes, consumer and industrial electronic protection, oil and water repellent textiles and industrial polymers for specific membranes or sealants. Petition 870250091442, dated 07 / 10 / 2025, pp. 80 / 100

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