Porous PTFE article with hydrophilic coating

Abstract

A porous ePTFE article coated with a hydrophilic coating is provided. The coating may be modified by covalent modification of the PVOH coating. The covalent modification may include grafting small molecules, polymers to or from a PVOH backbone, modifying PVAc precursors of PVOH, cross-linking polymers via thermal or photochemistry, cross-linking polymers with a multifunctional cross-linking agent, and the like, and combinations thereof.

Description

Cross-references to related applications

[0001] This application claims the benefit of US 63 / 521,073, filed June 14, 2023; US 63 / 521,076, filed June 14, 2023; and US 63 / 521,065, filed June 14, 2023, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0002] This disclosure relates to porous articles made of PTFE and including a hydrophilic coating. This disclosure further relates to porous articles made of ePTFE and including a hydrophilic coating containing PVOH and / or chemically modified PVOH. Summary of the Invention

[0003] Porous ePTFE articles coated with a hydrophilic coating are provided.

[0004] According to embodiments, the coating is modified by utilizing compositions and / or methods that allow for alteration of the film's properties as needed. For example, a hydrophilic PVOH coating can be applied in a manner that allows for control and variation of thickness, morphology, wetting properties, polymer crystallinity, etc.

[0005] According to an embodiment, the coating comprises an interpenetrating polymer network of PVOH and a second polymer. The second polymer may include one or more of polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), or polyethylene glycol.

[0006] According to an embodiment, the coating comprises a first layer of poly(vinyl alcohol) and a second layer on the first layer comprising one or more of polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), or polyethylene glycol.

[0007] According to an embodiment, the coating comprises a first layer of poly(vinyl alcohol) and a second layer on the first layer containing a water-insoluble polymer.

[0008] According to embodiments, the coating is modified by modifying the PVOH in the coating composition or by modifying the PVOH in the coating (after the coating composition has been applied to a porous substrate). Such modification may include covalent modification of the PVOH coating. Covalent modification may include grafting small molecules or polymers onto or from the PVOH backbone, modifying PVAc precursors of PVOH, thermally or photochemically crosslinking polymers, crosslinking polymers with multifunctional crosslinking agents, and combinations thereof.

[0009] According to an embodiment, the coating comprises an interpenetrating polymer network of PVOH and a second polymer. The second polymer may include one or more of polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), or polyethylene glycol.

[0010] According to an embodiment, the coating comprises a first layer of poly(vinyl alcohol) and a second layer on the first layer comprising one or more of polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), or polyethylene glycol.

[0011] According to an embodiment, the coating comprises a first layer of poly(vinyl alcohol) and a second layer on the first layer containing a water-insoluble polymer. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a porous article according to an embodiment of the present disclosure.

[0013] Figure 2 It is to contain Figure 1 A schematic diagram of a porous filter. definition

[0014] Unless otherwise specified, all scientific and technical terms used herein have their common meaning in the art. The definitions provided herein are intended to aid in understanding certain terms that are frequently used herein and are not intended to limit the scope of this disclosure.

[0015] Unless otherwise specified, the terms "polymer" and "polymer material" include, but are not limited to, organic homopolymers, copolymers such as block, graft, random and alternating copolymers, terpolymers, and their blends and modifications. The term "polymer" further includes different polymer architectures such as linear, branched, bottle-brush, dendritic macromolecules, etc. Furthermore, unless otherwise specifically limited, the term "polymer" should include all possible geometric configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic, and atactic symmetries.

[0016] The terms “formed from,” “polymerized from,” and “grafted from” are open-ended and may include other components that may not be explicitly described relative to the main body formed or polymerized from the said component. For example, a polymer formed or polymerized from one or more monomers may contain end-capping groups or other groups not explicitly mentioned.

[0017] The term "grafting" refers to a technique in which a formed polymer is covalently attached to a surface or another polymer (as the case may be).

[0018] The term "graft-self" refers to a polymerization technique in which polymer chains are grown from a surface or another polymer. Graft-self methods can involve surface polymerization functionalized from an initiator. Polymers prepared by graft-self methods can grow one monomer at a time.

[0019] As used herein, the term "hydrophilic" can be understood as having the meaning of "preferring to mix with water, dissolve in water, or be wetted by water," and can be understood as having the opposite meaning to "hydrophobic." Hydrophobic materials are defined as materials with a water contact angle greater than 90°, while hydrophilic materials are defined as materials with a water contact angle less than 90°. Hydrophilicity can be measured by using the ASTM D7334-08R22 test method or by measuring the water contact angle of a material using an automated contact angle tester and the ASTM D5725-99 test method.

[0020] The term “about” is used here in conjunction with numerical values ​​to include normal variation in the measured values ​​as would be expected by those skilled in the art, and should be understood to have the same meaning as “approximately” and to cover a typical range of error, such as ±5% of the value.

[0021] Terms such as “a / an” and “the / described” are not intended to refer to singular entities only, but rather to include general categories that can be described using specific examples.

[0022] The terms “an,” “a,” and “the / described” are used interchangeably with the term “at least one / a kind.” The phrases “at least one / a kind of…” and “including at least one / a kind of…” preceding the list refer to any one item in the list and any combination of two or more items in the list.

[0023] As used herein, the term “or” is generally used in its usual sense, including “and / or”, unless the context clearly indicates otherwise. The term “and / or” means one or all of the listed elements or a combination of any two or more of the listed elements.

[0024] A range of values ​​described by its endpoints includes all numbers falling within that range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc., or 10 or less includes 10, 9.4, 7.6, 5, 4.3, 2.9, 1.62, 0.3, etc.). If the range of values ​​is "up to" or "at least" a specific value, then that value is included within that range.

[0025] As used herein, terms such as “have / having,” “include / including,” and “comprise / comprising” are used in their open-ended sense and generally mean “including but not limited to.” It should be understood that the terms “substantially composed of,” “consisting of,” etc., are included within “comprising.” As used herein, when referring to compositions, products, methods, etc., “substantially composed of” means that the components of the composition, product, method, etc., are limited to the listed components and any other components that do not materially affect one or more essential and novel characteristics of the composition, product, method, etc.

[0026] The terms "preferred" and "ideally" refer to embodiments that may provide certain benefits in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are not available and is not intended to exclude other embodiments from the scope of this disclosure, including the claims.

[0027] For clarity, any directions such as “top,” “bottom,” “left,” “right,” “upper,” “lower,” and other directions and orientations mentioned herein are described with reference to the accompanying drawings and are not intended to limit the actual device or system or the use of such device or system. The device or system described herein can be used in multiple directions and orientations. Detailed Implementation

[0028] This disclosure relates to applying a hydrophilic coating to porous ePTFE articles. Expanded polytetrafluoroethylene (“ePTFE”) is manufactured using a stretching process. ePTFE is porous and can be used to provide porous membranes. Such porous membranes can be used as filter media, separator films, semi-permeable barriers, etc. ePTFE can form one or more filter media layers and can be used in filters for air and solvent purification. However, the strong hydrophobicity of ePTFE may degrade its performance when used in contact with water.

[0029] Polytetrafluoroethylene (PTFE) is a valuable material with wide applications across various industries. PTFE's hydrophobicity and low surface energy pose challenges in certain applications, particularly when surface wetting is required. Attempts to improve the hydrophilicity of PTFE materials have included grafting acrylic acid, 4-vinylpyridine, and N-vinylpyrrolidone onto PTFE via ionizing radiation-induced or catalytic polymerization. However, this method does not achieve uniform hydrophilicity because the graft copolymerization occurs only on the surface layer of PTFE and does not extend into the interior of the material. To overcome this problem and extend the graft polymerization into the interior of porous PTFE, surfactant impregnation and etching are employed. However, non-uniform hydrophilicity still exists at smaller pore sizes.

[0030] The hydrophilicity of PTFE materials is particularly desirable for providing porous membranes used in applications where wetting of the membrane is desired. Such applications include membrane filters, ultrafiltration membranes, dialysis membranes, and reverse osmosis membranes. Excellent mechanical properties and good permeability are desirable characteristics for hydrophilic polymer membranes used in similar applications.

[0031] Forming hydrophilic surfaces on ePTFE membranes presents challenges. Modifying the surface of ePTFE to make it easily wettable for use in filtration applications in the food, beverage, and pharmaceutical industries is highly desirable.

[0032] PTFE is known to be hydrophobic and has low surface energy due to the high density of fluorine on its surface, resulting in low surface energy. This low surface energy makes it difficult to modify PTFE by applying coatings, as most materials do not adhere to the PTFE surface. In some cases, it is desirable to provide PTFE articles with hydrophilic surfaces. In other cases, it is desirable to provide PTFE articles with water-wettable surfaces. Such hydrophilic and wettable surfaces can be achieved by applying a hydrophilic coating containing poly(vinyl alcohol) (“PVOH”) to the surface of PTFE. Such hydrophilic and wettable surfaces can be further achieved by applying a hydrophilic coating containing PVOH to porous ePTFE.

[0033] This disclosure relates to improvements to hydrophilically coated ePTFE articles, including hydrophilically coated ePTFE membranes, films, and filter media. According to an embodiment, the ePTFE article comprises a porous ePTFE substrate coated with a coating composition containing PVOH.

[0034] Typically, PVOH can be applied to a porous substrate (e.g., a porous ePTFE membrane or diaphragm) by applying PVOH in an aqueous solution, thereby creating a PVOH film on the porous substrate. The solution can optionally be removed, although removal is not necessary for forming a PVOH coating on the PTFE. The PVOH can then be crosslinked. For example, the porous substrate can be coated by immersing, dip-coating, spraying, printing, or brushing a coating composition onto it. The porous substrate can be pre-wetted before coating. The coated substrate can be rinsed after coating. The coating composition can be dried and / or cured onto the porous substrate. In one exemplary embodiment, the porous substrate is pre-wetted using water or an aqueous solvent composition or a water-miscible solvent (such as acetone, ethanol, or isopropanol). The solvent can be replaced with water. The substrate (still wetted with water) can be placed in contact with a water bath containing the coating composition.

[0035] The concentration of PVOH in the aqueous solution can be 0.1 wt% or greater, 0.2 wt% or greater, 0.5 wt% or greater, 1 wt% or greater, 2 wt% or greater, 3 wt% or greater, 4 wt% or greater, or 5 wt% or greater. The concentration of PVOH in the aqueous solution can be 20 wt% or less, 10 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, or 2 wt% or less. The hydrolysis rate of PVOH can be 88% or greater, 90% or greater, 95% or greater, 98% or greater, or 99% or greater. The molecular weight of PVOH can be 50 kDa or greater, 75 kDa or greater, or 80 kDa or greater. The molecular weight of PVOH can be 120 kDa or less, 100 kDa or less, or 90 kDa or less. In some embodiments, the PVOH is 99% or more hydrolyzed, has a molecular weight of 80 kDa to 90 kDa, and is contained in water at a concentration of 1.5 wt% to 2.5 wt%.

[0036] For example, the substrate can be placed in a water bath containing 1-2 wt% of fully (99%) hydrolyzed poly(vinyl alcohol) for at least 2 minutes. The water bath can be at or above room temperature. Room temperature should be understood as a temperature of about 20°C to 26°C. The substrate can then be rinsed. A crosslinking composition containing a crosslinking agent suitable for crosslinking coating compositions (e.g., PVOH) can be applied to the substrate. In some embodiments, the substrate can be rinsed with water and immersed in an aqueous solution of glutaraldehyde and H2SO4 at an elevated temperature. For example, the substrate can be immersed in an aqueous solution of 2 mM to 8 mM (e.g., about 5 mM) glutaraldehyde and 0.1 M to 0.5 M (e.g., about 0.25 M) H2SO4 at a temperature of 40°C to 80°C (e.g., about 60°C) for 1 minute to 5 minutes (e.g., about 2 minutes).

[0037] The coating composition can at least partially penetrate a porous substrate, such that the inner surface (e.g., the surface of a single fiber or the surface of a pore) is coated. In some embodiments, the coating composition fully penetrates the porous substrate, such that both the main surface and the inner surface are coated. According to embodiments, the coatings disclosed herein can be characterized as conformal. As used herein, the term "conformal" means a coating that conforms to the surface profile of the substrate, regardless of surface roughness or defects, such that the coating is present across the entire surface.

[0038] According to embodiments, the coating can be modified by modifying the PVOH in the coating composition or by modifying the PVOH in the coating (after the coating composition has been applied to a porous substrate). Such modifications can be applied to alter the polymer surface and its mechanical properties. These modifications can include covalent modification of the PVOH coating. Covalent modification can include grafting small molecules or polymers onto or from the PVOH backbone via thermal annealing or photochemical crosslinking, and combinations thereof. Such polymers will have a different chemical composition than the unmodified PVOH coating.

[0039] In some embodiments, the PVOH coating is modified by grafting a biomolecule onto it. This can improve the biocompatibility of the resulting coated porous article. Examples of such biomolecules include amino acids, peptides, proteins, sugars, polysaccharides, oligosaccharides, etc. In some embodiments, the PVOH coating is modified by grafting starch, chitosan, cellulose, gelatin, heparin, synthetic peptides, or combinations of two or more thereof onto the PVOH. Coupling can be performed using known coupling chemistry. In some embodiments, the PVOH is coupled via glutaraldehyde, dicyclohexylcarbodiimide, carbonyl diimide, or other carbodiimide chemicals, disuccinimide carbonate, epichlorohydrin, or other suitable coupling agents. Grafting may involve contacting the PVOH with the biomolecule of interest and the coupling agent. The biomolecule to be coupled to the PVOH may be included in a ratio of 0.1 wt% to 100 wt% based on the weight of the PVOH. Furthermore, modified PVOH containing appropriate functional groups can be further reacted with biomolecules of interest containing maleimide derivatives, iodoacetamide derivatives, alkyne-azide chemical derivatives, thiol-ene chemical derivatives, thiol-alkyne chemical derivatives, isocyanate derivatives, etc. (including other reactive group derivatives referred to as click chemistry or covalent bioconjugation techniques) to increase biocompatibility. Methods for forming coated articles may include covalently coupling a biomolecule with poly(vinyl alcohol), wherein the biomolecule has a first reactive stem and the poly(vinyl alcohol) has a second reactive stem, and wherein the first and second reactive stems cooperate and react in the bioconjugation reaction.

[0040] In some embodiments, the PVOH coating is modified by grafting oligomers and / or polymers onto the PVOH coating. The PVOH coating is further modified by attaching a second fully formed polymer to the PVOH. The second polymer may be a hydrophilic polymer with a molecular weight of 500 Da to 100 kDa. The second polymer can be grafted onto the PVOH backbone using known grafting chemicals. Exemplary grafting techniques include coupling via glutaraldehyde, dicyclohexylcarbodiimide or other carbodiimide chemicals, carbonyl diimidazole, disuccinimide carbonate, epichlorohydrin, or other suitable coupling agents. Grafting may involve contacting the PVOH with the second polymer and the coupling agent. Furthermore, the functionalized PVOH can be further reacted with modified hydrophilic polymers of interest containing one or more reactive stems, such as maleimide derivatives, iodoacetamide derivatives, alkyne-azide chemical derivatives, thiol-ene chemical derivatives, thiol-alkyne chemical derivatives, isocyanate derivatives, N-hydroxysuccinimide esters (NHS), etc. (including other reactive group derivatives referred to as click chemistry or conjugation techniques)). Examples of polymers to be grafted include polyethylene glycol (PEG), linear polyethyleneimine (PEI), polyallyl alcohol (PAlA), polyacrylic acid (PAA), sodium polyacrylate (PAANa), and poly(2-hydroxyethyl methacrylate) (PHEMA).

[0041] In some embodiments, the PVOH coating is modified by grafting polymers and / or oligomers onto the PVOH coating via grafting-from techniques such as surface-initiated polymerization. Grafting-from polymerization can be accomplished using suitable techniques such as addition polymerization or condensation polymerization. Examples of addition polymerization techniques include radical polymerization, such as atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization; anionic polymerization; and cationic polymerization. In some embodiments, where the polymer is grafted onto a supporting substrate or a polymer already on the substrate, an initiator is first coupled to the supporting substrate or the polymer already on the substrate (e.g., via OH groups on the supporting substrate or the polymer). Hydrophilic polymers (e.g., PEG, polyglycidyl ether, polylactide, polycarbonate having 100 or fewer, 80 or fewer, 60 or fewer, 40 or fewer, or 20 or fewer repeating units, and 4 or more, 6 or more, 10 or more, 15 or more, or 20 or more repeating units) can be grafted from PVOH via acid- or base-catalyzed ring-opening polymerization using ring-opening polymerization of ethylene oxide, other cyclic ethers, cyclic esters, or cyclic carbonate derivatives. Hydrophilic acrylate derivatives (e.g., polyacrylic acid (PAA), sodium polyacrylate (PAANa), poly(2-hydroxyethyl methacrylate) (PHEMA) having repeating units of N = 1-100) can be grafted from PVOH polymers by PVOH modification with an atom transfer radical polymerization (ATRP) initiator (e.g., α-haloester derivatives, or other common ATRP initiators). Hydrophilic acrylate derivatives can also be grafted from PVOH polymers by modifying PVOH with reversible addition-fragmentation chain transfer polymerization (RAFT) initiators (dithiocarbonyl derivatives, thiocarbonyl thio derivatives, or other common chain transfer agents (CTA)).

[0042] In some embodiments, the PVOH is crosslinked via a dialdehyde catalyzed by a photoacid. The dialdehyde (e.g., glutaraldehyde, terephthalaldehyde, o-phthalaldehyde, or glyoxal) can be used as a crosslinking agent at 0.1-20 wt% in a solution containing PVOH, the dialdehyde, a solvent (water, ethanol, isopropanol, DMF, DMSO, etc.), and a photoacid catalyst (triphenylsulfonium trifluoromethanesulfonate or other common photoacids). The composition can be applied to a porous substrate and irradiated with UV light. Irradiation with UV light initiates acid-catalyzed crosslinking. Specific wavelengths of UV light can be selected based on the photoacid catalyst. For example, a wavelength of 233 nm can be used for triphenylsulfonium trifluoromethanesulfonate, or other wavelengths for various photoacids.

[0043] In some embodiments, the PVOH coating is modified by incorporating other groups that are more easily crosslinked into the PVOH. The PVOH polymer can be modified to include readily crosslinkable functional groups before deposition onto a porous substrate. The crosslinkable functional groups can be more easily crosslinked than the PVOH itself. For example, the PVOH can be reacted in a solution of 1-20 wt% allyl glycidyl ether, propargyl glycidyl ether, acryloyl chloride derivative, or other activated acrylate derivative in a selected solvent (e.g., water, ethanol, isopropanol, DMF, DMSO) to place allyl, propargyl, diacrylic acid, or acrylate functional groups onto the polymer. These functional groups can then be crosslinked via UV light, thermal annealing, or chemical additives (such as dithiols, diazides, diamines, or diols). The resulting porous article may include a porous ePTFE substrate and a coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol) comprising crosslinked allyl, propargyl, diacrylidine, acrylate functional groups, or combinations thereof.

[0044] PVOH is typically prepared industrially by hydrolyzing polyvinyl acetate (“PVAc”). In some embodiments, the PVOH coating is modified by incorporating other groups that can be more easily crosslinked into the PVOH precursor before hydrolyzing PVAc to PVOH. Prior to hydrolysis, a monomer containing a group that can be easily crosslinked can be added to the polymerization solution of PVAc to produce a copolymer of PVAc and a comonomer containing a functional stem. The PVAc content in the copolymer can be 90 to 99 mol-%, and the comonomer content can be 1 mol-% to 10 mol-%. Functional groups (such as cyclic ethers or allyl groups) can be incorporated, respectively, via copolymerization with glycidyl methacrylate or allyl methacrylate. Other functional groups can be incorporated by copolymerization with acrylate derivatives or other activated vinyl monomers containing aldehydes, alkynes, alkenes, alkyl halides, diacylidine, cyclic ethers, cyclic esters, or other reactive functional groups. The resulting porous article may include a porous ePTFE substrate and a coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol) comprising crosslinked allyl, propargyl, diacrylidine, acrylate functional groups, or combinations thereof.

[0045] In some embodiments, the PVOH coating is modified by crosslinking the PVOH with a crosslinking agent having more than two reactive groups per crosslinking agent. Instead of the typically used bifunctional crosslinking agents, trifunctional (or more advanced) crosslinking agents can be used to crosslink the PVOH to increase the crosslinking density of the resulting coating, increase thermal stability, and / or increase antioxidant properties. For example, in the crosslinking of acid-catalyzed polymers, a trifunctional aldehyde (such as 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde) can be used instead of glutaraldehyde. Alternatively, triglycidyl ether crosslinking agents (such as trimethylolpropane triglycidyl ether or trimethylolpropane triglycidyl ether) can be used as trifunctional crosslinking agents through acid- or base-promoted ring-opening. Other examples of crosslinking agents include small molecules or oligomers containing more than two reactive functional groups (such as aldehydes, cyclic ethers, cyclic esters, or alkyl halides). Alternatively, PVOH can be modified to include crosslinkable functional groups (e.g., allyl, propargyl, or acrylate functional groups) to form modified PVOH, and the modified PVOH can be crosslinked with trithiol, tetrathiol, or elemental sulfur via photo-initiated chemical or thermal annealing. Modified PVOH containing acrylate functional groups can be crosslinked by thermal annealing of small molecules or oligomers containing more than two amine groups (such as tris(2-aminoethyl)amine, diethylenetriamine, linear polyethyleneimine, or branched polyethyleneimine).

[0046] According to embodiments, coatings can be modified using compositions and / or methods that allow for alteration of the film's properties as needed. For example, hydrophilic PVOH coatings can be applied in a manner that allows for control and variation of thickness, morphology, wetting properties, polymer crystallinity, etc.

[0047] According to an embodiment, the coating is prepared by depositing PVOH as a coating composition containing large macromolecular aggregates of PVOH. A typical PVOH coating composition contains PVOH with a molecular weight of about 80 kDa to 90 kDa. The macromolecular aggregates may contain multiple individual PVOH chains and have a molecular weight of 250 kDa or greater, or 300 kDa or greater. Coatings containing macromolecular aggregates of PVOH can exhibit enhanced wettability. The deposition of macromolecular aggregates can be achieved in at least two ways. A first method involves exposing an ePTFE substrate to a PVOH solution at a concentration higher than the critical entanglement concentration of PVOH, which can produce a coating with co-adsorption of individual chains and entangled macromolecular aggregates. The critical entanglement concentration of PVOH in water is estimated to be about 0.2 M, as measured by the number of individual repeating units of vinyl alcohol. To generate macromolecular aggregates in the coating, the molecular weight distribution of the PVOH polymer chains can be between 10 kDa and 300 kDa. A second method to achieve macromolecular aggregates in the coating involves exposing the ePTFE membrane to a PVOH solution containing individual polymer chains with a molecular weight of 300 kDa or greater. These extremely high molecular weight chains can be deposited as microparticles rather than morphologically smooth membranes.

[0048] According to an embodiment, the coating is prepared by contacting an ePTFE porous substrate with a coating composition containing PVOH at a temperature range of 40°C to 55°C. The coating composition may contain PVOH and water. The concentration of PVOH in the coating composition may be from about 1 wt% to 10 wt%. The coating may be applied by any suitable method, such as dip coating. The coating composition may be heated to a desired temperature range of 40°C to 55°C. The heated coating composition may be applied to the substrate, for example, by immersing the substrate in the heated coating composition. The immersion time may be 1 min or longer, 1.5 min or longer, 2 min or longer, 5 min or longer, or 10 min or longer. The immersion time may be 1 hour or less, 30 minutes or less, 20 minutes or less, 15 minutes or less, 10 minutes or less, 5 minutes or less, 3 minutes or less, or 2 minutes or less. The immersion time may be from 1 min to 1 hour, or from 1 min to 5 min. The coating composition may also contain adsorbent structure modifiers (such as salts and surfactants), as discussed further below.

[0049] According to embodiments, coatings are prepared by including one or more of a liquid-dissociating additive, a lyophilic additive, or a zwitterionic additive in the coating composition. Such liquid-dissociating, lyophilic, and zwitterionic additives can be salts or other suitable compounds. Including one or more of these additives allows for improved control over the PVOH membrane structure. Examples of lyophilic agents include ammonium sulfate, tert-butanol, and trehalose. Examples of liquid-dissociating agents include sodium thiocyanate, guanidine chloride, and n-butanol. Examples of zwitterionic agents include phosphatidylcholine. The coating composition may contain one or more additives at concentrations of 0.01 mol / L or greater, up to a maximum of 2 mol / L.

[0050] According to embodiments, a coating is prepared by applying PVOH in two or more coating steps, wherein at least one of the process parameters is changed from a first step to a second step or a subsequent step. Process parameters that can vary between steps include temperature, additives (e.g., liquid-ionizing additives, lyophilic additives, or zwitterionic additives), the molecular weight distribution of the PVOH, the degree of hydrolysis of the PVOH, and the use of surfactants in the coating composition. One or more of the process parameters can be changed simultaneously. In one exemplary embodiment, the PVOH coating is applied in two steps, wherein in the first step, a coating composition containing PVOH with a high molecular weight distribution of 90 kDa to 185 kDa is deposited at 80°C, followed by a second deposition at 20°C of PVOH with a narrower molecular weight distribution of 80 kDa to 90 kDa. In another exemplary embodiment, the PVOH coating is applied in two steps, wherein in both steps, the PVOH has a molecular weight distribution of 80 kDa to 90 kDa at 20°C, but the coating composition in the first step contains 2 M NaCl, and the coating composition in the second step contains 0.1 M NaSCN (sodium thiocyanate).

[0051] According to the embodiments, coatings are prepared by reversibly co-adsorbing a surfactant with PVOH to generate a PVOH film with enhanced wettability and stability. Examples of suitable surfactants that can be used include anionic surfactants such as sodium dodecyl sulfate (i.e., sodium lauryl sulfate); and nonionic surfactants such as sorbitan monooleate (e.g., SPAN 80). ® ), polyethylene glycol dehydrated sorbitan monolaurate (such as TWEEN 20) ® ), or polyoxyethylene-polyoxypropylene block copolymers (such as PLURONIC ), ®(F127); or a combination of two or more thereof. The surfactant may be included in the coating composition at a concentration of 0.5 wt% or greater, 1 wt% or greater, 1.5 wt% or greater, or 2 wt% or greater. The surfactant may be included in the coating composition at a concentration of 5 wt% or less, 4 wt% or less, 3 wt% or less, or 2 wt% or less. Multiple surfactants may be combined in the coating composition.

[0052] According to embodiments, the coating is prepared by depositing two or more different grades of PVOH onto a substrate. The different grades of PVOH may include PVOH with different molecular weight distributions, different degrees of hydrolysis, and different concentrations. In an exemplary embodiment, the coating composition (applied in a single step) comprises a first concentration of PVOH having a degree of hydrolysis of 85% and a molecular weight of 80 kDa to 90 kDa, and a second concentration of PVOH having a degree of hydrolysis of 99% (or higher) and a molecular weight of 80 kDa to 140 kDa. The first concentration may be lower than the second concentration. For example, the first concentration may be about 0.1 wt-%, and the second concentration may be about 5 wt-%.

[0053] According to embodiments, the coating can be modified by including different second polymers in the PVOH coating. For example, a coating composition can be prepared such that an interpenetrating polymer network (“IPN”) is formed. An IPN is a polymer network comprising two or more polymers that are at least partially interwoven at the polymer scale but are not covalently bonded to each other. The polymers of an IPN typically cannot separate from each other unless chemical bonds are broken. Alternatively, another polymer can be added as a second coating to the PVOH coating. According to embodiments, one or more additional polymers, oligomers, or small molecules are mixed into or layered on top of the PVOH layer. The additional polymers, oligomers, or small molecules can adhere to or entangle with the PVOH, but are not covalently bonded to the PVOH. The second polymer can be added, for example, by using a saturation coating technique (such as dip coating or spray coating) to saturate the PVOH-coated ePTFE substrate with a second polymer carried by a fluid. The carrier fluid can then be removed by drying. Applying the second polymer can form a second conformal coating on the first PVOH coating.

[0054] According to an embodiment, a solution of PVOH and another polymer is applied to an ePTFE substrate. The second polymer may be a polymer that does not have an inherent affinity for or binding ability to ePTFE. PVOH adsorbs onto the ePTFE and traps the second polymer through non-covalent entanglement, thereby forming an interpenetrating polymer network. The entanglement may involve hydrogen bonding or be inherently mechanical. According to an embodiment, the entanglement is sufficient to permanently trap the second polymer within the structure of the PVOH coating. The second polymer can be selected to provide desired properties, such as adding hydrophilicity, mechanical strength, biocompatibility, or charge to the coating. The coating can optionally be applied in a two-step process, wherein PVOH is first deposited and then exposed to a high concentration of the second polymer. The second polymer can be selected and sufficient time can be allowed for rearrangement, allowing diffusion to occur and the second polymer to embed within the adsorbed PVOH membrane.

[0055] IPNs can also be prepared by polymerizing and / or crosslinking a second network within a first network. For example, one of the two polymeric components of an IPN (e.g., the second polymer) can be started as a monomer crosslinked within a network of another polymer (e.g., PVOH).

[0056] Examples of second polymers that can be used to form an IPN with PVOH include polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), poly(4-vinylpyridine), poly(vinylpyrrolidone), and polyethylene glycol. The PVOH used in the coating composition can have a higher molecular weight than is typically used in the preparation of PVOH coatings. That is, the PVOH can have a molecular weight greater than 90 kDa. The coating composition may contain PVOH and one or more of polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), poly(4-vinylpyridine), poly(vinylpyrrolidone), or polyethylene glycol. The resulting coating may contain PVOH and one or more of polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), poly(4-vinylpyridine), poly(vinylpyrrolidone), or polyethylene glycol in an interpenetrating polymer network.

[0057] According to an embodiment, the PVOH coating is modified by applying a second polymer to the PVOH coating, wherein the second polymer is able to adhere firmly to the PVOH. The coating can be applied in two steps, wherein the first step involves contacting a porous ePTFE substrate with a first coating composition containing PVOH, and then contacting the substrate with a second coating composition containing the second polymer. The second polymer may include, for example, polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), or polyethylene glycol. The resulting coating may include a first layer of poly(vinyl alcohol) and a second layer on the first layer containing one or more of polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), or polyethylene glycol.

[0058] In some embodiments, a second polymer is applied as a second coating onto the PVOH coating. The deposition of the PVOH coating may be followed by the deposition of a second coating of at least one water-insoluble polymer by removing the carrier liquid containing the second polymer. Examples of suitable polymers include poly(2-hydroxyethyl methacrylate) and poly(hydroxypropyl methacrylate). The water-insoluble polymer can also be achieved by applying a polymer that is water-soluble prior to application and crosslinking and can become water-insoluble upon crosslinking. Examples of water-soluble polymers that can become water-insoluble after crosslinking are poly(lactic-co-glycolic acid) and poly(ethyleneimine). In an exemplary embodiment, PVOH is coated onto an ePTFE substrate, and the solution is subsequently removed to leave a residual PVOH film on the ePTFE. The coated substrate is then contacted with a solution of poly(lactic-co-glycolic acid) in tetrahydrofuran to form a second coating. In another example, the second polymer is poly(ethyleneimine) with a formaldehyde crosslinking agent in methanol. The methanol is evaporated, and crosslinking occurs at 90°C for 10 minutes. In another example, poly(2-hydroxyethyl methacrylate) is deposited from isopropanol and the isopropanol is evaporated.

[0059] Now for reference Figure 1 and Figure 2 This disclosure describes a coated porous article 10. The coated porous article 10 can be used as a filter medium. This disclosure further describes a filter 200 including the coated porous article 10 (e.g., a filter medium), a method of manufacturing the coated porous article 10, and a method of using the coated porous article 10 (e.g., a filter medium). It should be noted that although the figures show a coated filter medium, the methods of this disclosure can also be used to apply a coating to the surface of other articles. In particular, the methods of this disclosure can be used to apply a coating to articles containing ePTFE, which include porous surfaces that can benefit from a hydrophilic coating.

[0060] like Figure 1 As schematically illustrated, the coated porous article 10 disclosed herein typically comprises a porous substrate 20 coated with a coating 40 comprising a hydrophobic coating composition 41. The coating may be present on the main surfaces 1, 2 of the porous substrate 20 and also on the surfaces of the pores. Although the coating 40 is... Figure 1 The porous substrate 20 is shown as a solid layer, but coating 40 can at least partially coat the surfaces of the fibers and pores of the porous substrate 20. That is, coating 40 can form a conformal coating on the porous substrate 20. The porous substrate can have a thickness T20, and coating 40 can have a thickness T40.

[0061] Figure 2 The filter 200 is shown. The filter 200 may include a housing 220 having an interior 221, an inlet 201, and an outlet 202. A filter medium 210 made of or comprising a coated porous article is disposed within the interior 221 or the housing 220.

[0062] Porous substrates can be supplied as thin films or membranes. Porous substrates can have any thickness suitable for their intended purpose. Porous substrates can have thicknesses of 0.1 μm or greater, 0.5 μm or greater, 1 μm or greater, 5 μm or greater, 10 μm or greater, or 100 μm or greater. Porous substrates can have thicknesses of 5 mm or less, 2 mm or less, 1 mm or less, 500 µm or less, 200 µm or less, 100 µm or less, 50 µm or less, 25 µm or less, 10 µm or less, 5 µm or less, 2 µm or less, or 1 µm or less.

[0063] According to an embodiment, the coating forms a very thin layer on a porous substrate. Preferably, the coating is thin enough not to clog the pores of the porous substrate. The coating may have a thickness of 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, 50 nm or less, 20 nm or less, 10 nm or less, or 5 nm or less. The coating may have a thickness of 0.5 nm or greater.

[0064] The coated porous substrate can have an average pore size of 1 mm or less, 100 µm or less, 10 µm or less, 1 µm or less, 0.6 µm or less, 0.5 µm or less, 0.4 µm or less, 0.3 µm or less, 0.2 µm or less, 0.1 µm or less, or 0.01 µm or less. The porous substrate can also have an average pore size of 1 nm or greater, 5 nm or greater, 10 nm or greater, 0.1 μm or greater, 1 μm or greater, 10 μm or greater, or 100 µm or greater. The average pore size of the porous substrate can range from 1 nm to 1 mm, 1 nm to 1 μm, 1 nm to 0.5 μm, 0.1 μm to 0.6 μm, 1 μm to 1 mm, or 100 μm to 1 mm. A method for measuring pore size is described in ASTM D6767-21.

[0065] The permeability of porous substrates or coated porous articles can be measured by measuring their Frazier permeability using a Frazier permeability tester available from Frazier Precision Instrument Co. Inc., Gaithersburg, Maryland, as described in ASTM D737-18. The Frazier permeability is measured in units of 1 cfm / ft at a 0.5-inch water pressure drop. 2 This is equivalent to 0.5 cm at 125 Pa. 3 / s / cm 2 In some embodiments, the coated porous article 10 (e.g., a filter medium) has a diameter of 0.02 cm. 3 / s / cm 2 Or larger, 0.05 cm 3 / s / cm 2 Or larger, 0.1 cm 3 / s / cm 2 Or larger, 0.2 cm 3 / s / cm 2 Or larger, 0.3 cm 3 / s / cm 2 Or larger, or 0.5 cm 3 / s / cm 2 Or even higher permeability. The permeability of the coated porous article 10 (e.g., filter media) can be 2 cm⁻¹. 3 / s / cm 2 Or smaller, 1.5 cm 3 / s / cm 2 Or smaller, 1.0 cm 3 / s / cm 2Or smaller, or 0.8 cm 3 / s / cm 2 Or smaller.

[0066] Compared to uncoated ePTFE membranes, coated porous articles exhibit improved wettability. According to embodiments, coated porous articles include a coating that makes the article wettable with water. As used herein, the term "wettable" means a material that allows fluid to diffuse uniformly across its surface. In the case of porous wettable materials, fluid will penetrate into the material and diffuse throughout the material (including into the pores). The wettability of the material can be measured using the ASTM D7334-08R22 test method. Example

[0067] The following is a list of various embodiments disclosed herein.

[0068] Example 1 is a porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises macromolecular aggregates of poly(vinyl alcohol).

[0069] Example 2 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol), The method includes: Preparation of coating compositions comprising an aqueous solution of poly(vinyl alcohol); The coating composition was heated to a temperature of 40°C to 55°C; and A porous substrate is immersed in a heated coating composition.

[0070] Example 3 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol), The method includes: A coating composition is prepared comprising an aqueous solution of poly(vinyl alcohol) and one or more additives, including a liquid-free additive, a lyophilic additive, or an amphoteric additive; and The porous substrate is immersed in the coating composition.

[0071] Example 4 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol), The method includes: Prepare a first coating composition and a second coating composition, each of the first and second coating compositions comprising an aqueous solution of poly(vinyl alcohol), wherein one or more of the following factors—temperature, incorporation of additives, molecular weight distribution of poly(vinyl alcohol), degree of hydrolysis of poly(vinyl alcohol), or combinations thereof—are different between the first and second coating compositions; and The porous substrate is immersed in the first coating composition and the second coating composition.

[0072] Example 5 is the method as described in any one of Examples 2 to 4, wherein the aqueous solution contains 0.1 wt% or more, 0.2 wt% or more, 0.5 wt% or more, 1 wt% or more, 2 wt% or more, 3 wt% or more, 4 wt% or more, or 5 wt% or more of poly(vinyl alcohol).

[0073] Example 6 is the method as described in any one of Examples 2 to 5, wherein the aqueous solution contains 20 wt% or less, 10 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, or 2 wt% or less of poly(vinyl alcohol).

[0074] Example 7 is the method as described in any one of Examples 2 to 6, wherein the poly(vinyl alcohol) in the aqueous solution has a hydrolysis rate of 88% or greater, 90% or greater, 95% or greater, 98% or greater, or 99% or greater.

[0075] Example 8 is the method as described in any one of Examples 2 to 7, wherein the poly(vinyl alcohol) in the aqueous solution has a molecular weight of 50 kDa or greater, 75 kDa or greater, or 80 kDa or greater.

[0076] Example 9 is the method as described in any one of Examples 2 to 8, wherein the poly(vinyl alcohol) in the aqueous solution has a molecular weight of 120 kDa or less, 100 kDa or less, or 90 kDa or less.

[0077] Example 10 is the method as described in any one of Examples 2 to 9, wherein the poly(vinyl alcohol) in the aqueous solution is 99% or more hydrolyzed, has a molecular weight of 80 kDa to 90 kDa, and has a concentration of 1.5 wt% to 2.5 wt%.

[0078] Example 11 is a method as described in any one of Examples 2 to 10, wherein the method comprises placing the substrate in a water bath containing 1-2 wt% of fully (99%) hydrolyzed poly(vinyl alcohol) for at least 2 minutes.

[0079] Example 12 is the method as described in Example 11, wherein the water bath is at a temperature of about 20°C to 26°C.

[0080] Example 13 is the method as described in Example 11 or 12, the method further comprising rinsing the substrate, optionally rinsing the substrate with water.

[0081] Example 14 is a method as described in any one of Examples 11 to 13, the method further comprising contacting a substrate with a crosslinking composition containing a crosslinking agent suitable for a crosslinking coating composition.

[0082] Example 15 is the method as described in Example 14, wherein the crosslinking composition comprises an aqueous solution of glutaraldehyde and H2SO4.

[0083] Example 16 is the method as described in Example 14, wherein the substrate is immersed in an aqueous solution of 2 mM to 8 mM (optionally, about 60°C) glutaraldehyde and 0.1 M to 0.5 M (optionally, about 0.25 M) H2SO4 for 1 minute to 5 minutes (optionally, about 2 minutes) at a temperature of 40°C to 80°C (optionally, about 60°C).

[0084] Example 17 is a porous article manufactured by any one of Examples 2 to 17.

[0085] Example 18 is a porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises an interpenetrating polymer network of PVOH and a second polymer, wherein the second polymer optionally comprises one or more of polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), poly(4-vinylpyridine), poly(vinylpyrrolidone), or polyethylene glycol.

[0086] Example 19 is a porous article comprising: Porous substrates containing ePTFE; and The coating disposed on the porous substrate includes a first layer comprising poly(vinyl alcohol) and a second layer disposed on the first layer comprising one or more of polyacrylic acid, poly(2-ethyl-2-oxazoline), poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), poly(4-vinylpyridine), poly(vinylpyrrolidone), or polyethylene glycol.

[0087] Example 20 is a porous article comprising: Porous substrates containing ePTFE; and A first coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol); and A second coating is disposed on the first coating, the second coating comprising a water-insoluble polymer.

[0088] Example 21 is a porous article as described in Example 20, wherein the water-insoluble polymer comprises poly(2-hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate), or a combination thereof.

[0089] Example 22 is a porous article as described in Example 21, wherein the water-insoluble polymer is formed by crosslinking a water-soluble polymer.

[0090] Example 23 is a porous article as described in Example 22, wherein the water-soluble polymer comprises poly(lactic acid-co-glycolic acid), poly(ethyleneimine), or a combination thereof.

[0091] Example 24 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol), The method includes: A first coating composition is applied to a porous substrate, the first coating composition comprising an aqueous solution containing poly(vinyl alcohol); The aqueous solution is removed, leaving a poly(vinyl alcohol) film on the substrate; and A second coating composition is applied to the poly(vinyl alcohol) film, the second coating composition comprising a solution of poly(lactic acid-co-glycolic acid) in tetrahydrofuran.

[0092] Example 25 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol), The method includes: A first coating composition is applied to a porous substrate, the first coating composition comprising an aqueous solution containing poly(vinyl alcohol); Remove the aqueous solution and leave a poly(vinyl alcohol) film on the substrate; A second coating composition is applied to the poly(vinyl alcohol) film, the second coating composition comprising a poly(ethyleneimine) having a formaldehyde crosslinking agent in methanol; and The methanol is evaporated at an elevated temperature to achieve crosslinking of the poly(ethyleneimine).

[0093] Example 26 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol), The method includes: A first coating composition is applied to a porous substrate, the first coating composition comprising an aqueous solution containing poly(vinyl alcohol); Remove the aqueous solution and leave a poly(vinyl alcohol) film on the substrate; A second coating composition is applied to the poly(vinyl alcohol) film, the second coating composition comprising poly(2-hydroxyethyl methacrylate) in isopropanol; and Evaporate the isopropanol.

[0094] Example 27 is a porous article manufactured by the method described in any one of Examples 24 to 26.

[0095] Example 28 is a porous article or method as described in any one of Examples 18 to 27, wherein the first coating and the second coating form an interpenetrating polymer network (“IPN”).

[0096] Example 29 is a porous article as described in any one of Examples 18 to 28, wherein the poly(vinyl alcohol) has a molecular weight of 80 kDa or greater, 90 kDa or greater, or 100 kDa or greater.

[0097] Example 30 is a porous article as described in any one of Examples 18 to 29, wherein the poly(vinyl alcohol) in the aqueous solution has a molecular weight of 300 kDa or less, 200 kDa or less, or 150 kDa or less.

[0098] Example 31 is a porous article comprising: Porous substrates containing ePTFE; and The coating disposed on the porous substrate comprises poly(vinyl alcohol) and one or more surfactants.

[0099] Example 32 is a porous article as described in Example 31, wherein the one or more surfactants include anionic surfactants or nonionic surfactants.

[0100] Example 33 is a porous article as described in Example 31, wherein the one or more surfactants include sodium dodecyl sulfate, sorbitan monooleate, polyethylene glycol sorbitan monolaurate, or polyoxyethylene-polyoxypropylene block copolymer, or a combination of two or more thereof.

[0101] Example 34 is a porous article as described in any one of Examples 31 to 33, wherein the coating is formed by a coating composition comprising a surfactant at a concentration of 0.5 wt% or greater, 1 wt% or greater, 1.5 wt% or greater, or 2 wt% or greater.

[0102] Example 35 is a porous article as described in any one of Examples 31 to 34, wherein the coating is formed by a coating composition comprising a surfactant at a concentration of 5 wt% or less, 4 wt% or less, 3 wt% or less, or 2 wt% or less.

[0103] Example 36 is a porous article as described in any one of Examples 31 to 35, wherein the first poly(vinyl alcohol) has a first molecular weight and a first degree of hydrolysis, and the coating further comprises a second poly(vinyl alcohol) having a second molecular weight and a second degree of hydrolysis.

[0104] Example 37 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises a first poly(vinyl alcohol) and one or more surfactants. The method includes: In a first coating step, a first coating composition comprising an aqueous solution containing poly(vinyl alcohol) is applied to the porous substrate, and the first coating step is performed using a first set of coating parameters, including temperature, molecular weight distribution of poly(vinyl alcohol), degree of hydrolysis of poly(vinyl alcohol), optional presence of additives, and optional presence and composition of surfactants; and In a second coating step, a second coating composition is applied to the first coating composition, the second coating composition comprising an aqueous solution containing poly(vinyl alcohol), and the second coating step is performed using a second set of coating parameters, the second set of coating parameters including temperature, molecular weight distribution of poly(vinyl alcohol), degree of hydrolysis of poly(vinyl alcohol), optional presence of additives, and optional presence and composition of surfactants, wherein at least one of these coating parameters differs from the first set of coating parameters, and wherein at least one of the first coating composition and the second coating composition contains a surfactant; and Dry the coating.

[0105] Example 38 is the method as described in Example 37, the method comprising removing water from the aqueous solution after the first coating step and before the second coating step.

[0106] Example 39 is the method as described in Example 37 or 38, wherein the surfactant comprises anionic surfactant or nonionic surfactant.

[0107] Example 40 is the method as described in any one of Examples 37 to 39, wherein the surfactant comprises sodium dodecyl sulfate, sorbitan monooleate, polyethylene glycol sorbitan monolaurate, or polyoxyethylene-polyoxypropylene block copolymer, or a combination of two or more thereof.

[0108] Example 41 is the method as described in any one of Examples 37 to 40, wherein the first coating composition, the second coating composition, or both contain a surfactant at a concentration of 0.5 wt% or greater, 1 wt% or greater, 1.5 wt% or greater, or 2 wt% or greater.

[0109] Example 42 is a method as described in any one of Examples 37 to 41, wherein the first coating composition, the second coating composition, or both contain a surfactant at a concentration of 5 wt% or less, 4 wt% or less, 3 wt% or less, or 2 wt% or less.

[0110] Example 43 is a method as described in any one of Examples 37 to 42, wherein the first coating composition comprises a first poly(vinyl alcohol) having a first molecular weight, and the second coating composition comprises a second poly(vinyl alcohol) having a second molecular weight different from the first molecular weight.

[0111] Example 44 is a method as described in any one of Examples 37 to 43, wherein the first coating composition comprises a first poly(vinyl alcohol) having a first degree of hydrolysis, and the second coating composition comprises a second poly(vinyl alcohol) having a second degree of hydrolysis different from the first degree of hydrolysis.

[0112] Example 45 is a porous article comprising: Porous substrates containing ePTFE; and The coating disposed on the porous substrate comprises a first poly(vinyl alcohol) having a first molecular weight and a first degree of hydrolysis, and a second poly(vinyl alcohol) having a second molecular weight and a second degree of hydrolysis.

[0113] Example 46 is a porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol) and biomolecules covalently attached to the poly(vinyl alcohol).

[0114] Example 47 is a porous article as described in Example 46, wherein the biomolecule includes amino acids, polypeptides, sugars, or polysaccharides.

[0115] Example 48 is a porous article as described in Example 46 or 47, wherein the biomolecule comprises a first reactive stem and the poly(vinyl alcohol) comprises a second reactive stem, and wherein the first reactive stem and the second reactive stem cooperate and react in a bioconjugation reaction.

[0116] Example 49 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol) and biomolecules covalently attached to the poly(vinyl alcohol). The method includes: A coating composition comprising poly(vinyl alcohol) and biomolecules is applied to the porous substrate; and The biomolecule was covalently coupled to the poly(vinyl alcohol).

[0117] Example 50 is the method described in Example 49, wherein the biomolecule and the poly(vinyl alcohol) react in a bioconjugation reaction.

[0118] Example 51 is a porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol) and a second polymer grafted onto the poly(vinyl alcohol).

[0119] Example 52 is a porous article as described in Example 51, wherein the second polymer comprises polyethylene glycol (PEG), linear polyethyleneimine (PEI), polyallyl alcohol (PAlA), polyacrylic acid (PAA), sodium polyacrylate (PAANa), poly(2-hydroxyethyl methacrylate) (PHEMA), or any combination thereof.

[0120] Example 53 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol) and a second polymer grafted onto the poly(vinyl alcohol). The method includes: A coating composition comprising the poly(vinyl alcohol) and the second polymer is applied to the porous substrate; and The second polymer is covalently coupled to the poly(vinyl alcohol) to form the porous article.

[0121] Example 54 is the method as described in Example 53, wherein covalently coupling the second polymer to the poly(vinyl alcohol) includes reacting the coupling agent with the poly(vinyl alcohol) and the second polymer.

[0122] Example 55 is the method as described in Example 53 or 54, wherein the coupling agent comprises glutaraldehyde, carbodiimide (optionally dicyclohexylcarbodiimide), carbonyl diimidazole, disuccinimide carbonate, epichlorohydrin, or a combination of two or more thereof.

[0123] Example 56 is the method as described in any one of Examples 53 to 55, wherein the second polymer comprises polyethylene glycol (PEG), linear polyethyleneimine (PEI), polyallyl alcohol (PAlA), polyacrylic acid (PAA), sodium polyacrylate (PAANa), poly(2-hydroxyethyl methacrylate) (PHEMA), or a combination of two or more thereof.

[0124] Example 57 is the method as described in Example 53, wherein the poly(vinyl alcohol) comprises a modified poly(vinyl alcohol) containing functional groups, and the method further comprises reacting the functional groups with a modified hydrophilic polymer comprising maleimide, iodoacetamide, alkyne, azide, thiol-ene, thiol-alkyne, isocyanate, or combinations thereof.

[0125] Example 58 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol) and a second polymer grafted from the poly(vinyl alcohol). The method includes: The second polymer is grafted onto the poly(vinyl alcohol) to form a copolymer; and A coating composition comprising the copolymer is applied to the porous substrate.

[0126] Example 59 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol) and a second polymer grafted from the poly(vinyl alcohol). The method includes: A coating composition comprising poly(vinyl alcohol), one or more monomers, and an initiator is applied to the porous substrate; and Poly(vinyl alcohol) is polymerized with one or more monomers to form copolymers.

[0127] Example 60 is the method described in Example 58 or 59, wherein the graft self-polymerization is carried out using a ring-opening polymerization, an atom transfer radical polymerization (ATRP) initiator, or a reversible addition-fragmentation chain transfer polymerization (RAFT) initiator.

[0128] Example 61 is a method as described in any one of Examples 58 to 60, wherein the second polymer comprises a hydrophilic polymer containing 100 or fewer repeating units.

[0129] Example 62 is the method as described in any one of Examples 58 to 61, wherein the second polymer comprises polyethylene glycol (PEG), polyglycerol ether, polylactide, polycarbonate, polyacrylic acid (PAA), sodium polyacrylate (PAANa), poly(2-hydroxyethyl methacrylate) (PHEMA), or a combination of two or more thereof.

[0130] Example 63 is a method as described in any one of Examples 53 to 62, wherein the second polymer comprises 4 or more, 6 or more, 10 or more, 15 or more, or 20 or more repeating units.

[0131] Example 64 is the method as described in any one of Examples 53 to 63, wherein the second polymer comprises 100 or fewer, 80 or fewer, 60 or fewer, 40 or fewer, or 20 or fewer repeating units.

[0132] Example 65 is a porous article manufactured by the method described in any one of Examples 53 to 64.

[0133] Example 66 is a method for forming a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate, the coating comprising cross-linked poly(vinyl alcohol), The method includes: Poly(vinyl alcohol) is exposed to a crosslinking solution to crosslink the poly(vinyl alcohol), the crosslinking solution containing a crosslinking agent and a photoacid catalyst; and Irradiate the poly(vinyl alcohol) with ultraviolet light.

[0134] Example 67 is the method as described in Example 66, wherein the crosslinking agent comprises a dialdehyde, optionally comprising glutaraldehyde, terephthalaldehyde, o-phthalaldehyde, glyoxal, or a combination of two or more thereof.

[0135] Example 68 is a porous article manufactured by the method described in Example 66 or 67.

[0136] Example 69 is a porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol), the poly(vinyl alcohol) comprising crosslinked allyl, propargyl, diacrylidine, acrylate functional groups, or combinations thereof.

[0137] Example 70 is a method for preparing a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol), the poly(vinyl alcohol) comprising crosslinked allyl, propargyl, diaziridine, acrylate functional groups, or combinations thereof. The method includes: A coating composition containing poly(vinyl alcohol) is applied to the porous substrate; The poly(vinyl alcohol) is contacted with a solution containing one or more of the functional groups selected from allyl, propargyl, diaziridine, and acrylate; and Crosslinking one or more of the allyl, propargyl, diacrylidine, and acrylate functional groups.

[0138] Example 71 is a method for preparing a porous article, the porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol), the poly(vinyl alcohol) comprising crosslinked allyl, propargyl, diaziridine, acrylate functional groups, or combinations thereof. The method includes: Modified poly(vinyl acetate) was prepared by solution polymerization of vinyl acetate and monomers containing crosslinkable functional stems. The modified poly(vinyl acetate) was hydrolyzed to prepare modified poly(vinyl alcohol); The coating composition comprising the modified poly(vinyl alcohol) is applied to the porous substrate; and Crosslink the crosslinkable functional stem.

[0139] Example 72 is a porous article comprising: Porous substrates containing ePTFE; and A coating disposed on the porous substrate comprises poly(vinyl alcohol) crosslinked with a crosslinking agent containing more than two reactive groups per crosslinking agent.

[0140] Example 73 is a method for preparing a porous article as described in Example 40, the method comprising: A coating composition containing poly(vinyl alcohol) is applied to the porous substrate; and The poly(vinyl alcohol) is crosslinked using a crosslinking agent that contains more than two reactive groups per crosslinking agent.

[0141] Example 74 is the method as described in Example 73, wherein the poly(vinyl alcohol) is first modified to include crosslinkable functional groups (optionally including allyl, propargyl, or acrylate functional groups) to form modified poly(vinyl alcohol), and the modified poly(vinyl alcohol) is crosslinked.

[0142] Example 75 is the method as described in Example 73 or 74, wherein the crosslinking is performed via photoinitiated chemistry or thermal annealing.

[0143] Example 76 is a porous article or method as described in Example 72 or 73, wherein the crosslinking agent comprises a trifunctional aldehyde, such as 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde; a triglycidyl ether, such as trimethylolpropane triglycidyl ether or trimethylolpropane triglycidyl ether; or a small molecule or oligomer containing more than two reactive functional groups selected from aldehydes, cyclic ethers, cyclic esters, and alkyl halides.

[0144] Example 77 is a porous article or method as described in any of the preceding examples, wherein the porous substrate is a fibrous article.

[0145] Example 78 is a porous article or method as described in any of the foregoing examples, wherein the porous substrate is a thin film or a diaphragm.

[0146] Example 79 is a porous article or method as described in any of the preceding examples, wherein the coating is a conformal coating.

[0147] Example 80 is a porous article or method as described in any of the preceding examples, wherein the porous substrate has an average pore size in the range of 1 nm to 1 mm, 1 nm to 1 μm, 1 nm to 0.5 μm, 0.1 μm to 0.6 μm, 1 μm to 1 mm, or 100 μm to 1 mm. The pore size can be measured according to ASTM D6767-21.

[0148] Example 81 is a porous article or method as described in any of the preceding examples, wherein the coated porous substrate has an average pore size of 1 mm or less, 100 µm or less, 10 µm or less, 1 µm or less, 0.6 µm or less, 0.5 µm or less, 0.4 µm or less, 0.3 µm or less, 0.2 µm or less, 0.1 µm or less, or 0.01 µm or less. The pore size can be measured according to ASTM D6767-21.

[0149] Example 82 is a porous article or method as described in any of the foregoing examples, wherein the coated porous substrate has a density of 0.02 cm. 3 / s / cm 2 Or larger, 0.05 cm 3 / s / cm 2 Or larger, 0.1 cm 3 / s / cm 2 Or larger, 0.2cm 3 / s / cm 2 Or larger, 0.3 cm 3 / s / cm 2 Or larger, or 0.5cm 3 / s / cm 2 Or a higher permeability. Permeability can be Fraser permeability as measured according to ASTM D737-18.

[0150] Example 83 is a porous article or method as described in any of the foregoing examples, wherein the coated porous substrate has a diameter of 2 cm. 3 / s / cm 2 Or smaller, 1.5 cm 3 / s / cm 2 Or smaller, 1.0 cm 3 / s / cm 2 Or smaller, or 0.8 cm 3 / s / cm 2 Or even lower permeability. Permeability can be Fraser permeability as measured according to ASTM D737-18.

[0151] Example 84 is a porous article or method as described in any of the foregoing examples, wherein the coated porous article has a porous diameter of 0.02 cm. 3 / s / cm 2 Or larger, 0.05 cm 3 / s / cm 2 Or larger, 0.1 cm 3 / s / cm 2 Or larger, 0.2cm 3 / s / cm 2 Or larger, 0.3 cm 3 / s / cm 2 Or larger, or 0.5 cm 3 / s / cm 2 Or a higher permeability. Permeability can be Fraser permeability as measured according to ASTM D737-18.

[0152] Example 85 is a porous article or method as described in any of the foregoing examples, wherein the coated porous article has a diameter of 2 cm. 3 / s / cm 2 Or smaller, 1.5 cm 3 / s / cm 2 Or smaller, 1.0 cm 3 / s / cm 2 Or smaller, or 0.8 cm 3 / s / cm 2 Or even lower permeability. Permeability can be Fraser permeability as measured according to ASTM D737-18.

[0153] Example 86 is a porous article or method as described in any of the preceding examples, wherein the porous substrate has a thickness of 0.1 μm or greater, 0.5 μm or greater, 1 μm or greater, 5 μm or greater, 10 μm or greater, or 100 μm or greater.

[0154] Example 87 is a porous article or method as described in any of the preceding examples, wherein the porous substrate has a thickness of 5 mm or less, 2 mm or less, 1 mm or less, 500 µm or less, 200 µm or less, 100 µm or less, 50 µm or less, 25 µm or less, 10 µm or less, 5 µm or less, 2 µm or less, or 1 µm or less.

[0155] Example 88 is a porous article or method as described in any of the preceding examples, wherein the coating has a thickness of 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, 50 nm or less, 20 nm or less, 10 nm or less, or 5 nm or less.

[0156] Example 89 is a porous article or method as described in any of the foregoing examples, wherein the coating has a thickness of 0.5 nm or greater.

[0157] Example 89 is a filter comprising a housing having an interior, an inlet, and an outlet, and a filter medium disposed within the interior of the housing and comprising a porous article as described in any of the preceding examples. Example

[0158] A porous ePTFE membrane was treated to have a hydrophilic coating. The ePTFE membrane had a thickness of approximately 150-200 μm and a pore size of 1-5 μm. The ePTFE membrane was immersed in an isopropanol bath for 10 minutes. While the ePTFE membrane was still wetted by isopropanol, it was then immersed in a DI water bath for another 10 minutes. Finally, the membrane was transferred to a bath containing 2 wt% polyvinyl alcohol in water for 10 minutes. The membrane was then dried in an oven at 150°C for 10 minutes. It was confirmed that the membrane was completely wettable by water after drying, with the pore size maintained at 1-5 μm and a final thickness of 90-150 μm.

[0159] All references and publications cited herein are expressly incorporated in their entirety by citation, unless they may directly contradict this disclosure. While specific embodiments have been illustrated and described herein, those skilled in the art will understand that various alternative and / or equivalent implementations may be used instead of the specific embodiments shown and described without departing from the scope of this disclosure. It should be understood that this disclosure is not intended to be unduly limited by the illustrative embodiments and examples set forth herein, and such examples and examples are presented by way of example only, while the scope of this disclosure is intended to be limited only by the claims set forth herein.

Claims

1. A porous article comprising: a porous substrate comprising ePTFE; and a coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol) and a biomolecule covalently attached to the poly(vinyl alcohol), optionally wherein the biomolecule comprises an amino acid, a polypeptide, a sugar, a polysaccharide.

2. A method of forming the article of claim 1, the method comprising: covalently coupling the biomolecule to the poly(vinyl alcohol) to form the porous article, optionally wherein the biomolecule and the poly(vinyl alcohol) are reacted in a bioconjugation reaction.

3. A porous article comprising: a porous substrate comprising ePTFE; and a coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol) and a second polymer grafted to the poly(vinyl alcohol), optionally wherein the second polymer comprises polyethylene glycol (PEG), linear polyethylenimine (PEI), polyallyl alcohol (PAlA), polyacrylic acid (PAA), polyacrylic acid sodium salt (PAANa), poly(2-hydroxyethyl methacrylate) (PHEMA), or any combination thereof.

4. A method of forming the article of claim 3, the method comprising: covalently coupling the second polymer to poly(vinyl alcohol) to form the porous article, optionally wherein the covalently coupling the second polymer comprises reacting a coupling agent with the poly(vinyl alcohol) and the second polymer.

5. A method of forming a porous article, the porous article comprising: a porous substrate comprising ePTFE; and a coating disposed on the porous substrate, the coating comprising crosslinked poly(vinyl alcohol), the method comprising: exposing the poly(vinyl alcohol) to a crosslinking solution to crosslink the poly(vinyl alcohol), the crosslinking solution comprising a crosslinking agent and a photoacid catalyst; and irradiating the poly(vinyl alcohol) with ultraviolet light.

6. A porous article comprising: a porous substrate comprising ePTFE; and a coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol), the poly(vinyl alcohol) comprising crosslinked allyl, propargyl, bis-aziridinyl groups, acrylate functional groups, or a combination of two or more thereof.

7. A method of making the porous article of claim 6, the method comprising: applying a coating composition comprising poly(vinyl alcohol) to the porous substrate; contacting the poly(vinyl alcohol) with a solution comprising one or more of allyl, propargyl, bis-aziridinyl groups, and acrylate functional groups; and crosslinking one or more of the allyl, propargyl, bis-aziridinyl groups, and acrylate functional groups.

8. A method of making the porous article of claim 6, the method comprising: preparing a modified poly(vinyl acetate) by polymerizing a solution of vinyl acetate and a monomer comprising crosslinkable functional handles; hydrolyzing the modified poly(vinyl acetate) to prepare a modified poly(vinyl alcohol); applying a coating composition comprising the modified poly(vinyl alcohol) to the porous substrate; and crosslinking the crosslinkable functional handles.

9. A porous article comprising: a porous substrate comprising ePTFE; and a coating disposed on the porous substrate, the coating comprising poly(vinyl alcohol) crosslinked with a crosslinker comprising more than two reactive groups per crosslinker.

10. A method of making the porous article of claim 9, the method comprising: applying a coating composition comprising poly(vinyl alcohol) to the porous substrate; and crosslinking the poly(vinyl alcohol) using a crosslinker comprising more than two reactive groups per crosslinker.

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