Acid-resistant filter media

Abstract

To provide certain membranes useful in the filtration of liquids and the removal of various contaminants in the liquids.SOLUTION: A composite porous filter membrane comprises: a porous hydrophobic polymeric filter material having a coating thereon, where the coating is of a polyamide polymer which is soluble in a blend of formic acid and dichloromethane.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a composite filter material or membrane comprising a porous polymeric filter coated with a layer comprising certain polyamide polymers. [Background technology]

[0002] Filter products are essential tools in modern industry used to remove undesirable materials from useful fluid streams. Useful fluids treated using filters include water, liquid industrial solvents and process fluids, industrial gases used for manufacturing or processing (e.g., in semiconductor manufacturing), and liquids having medical or pharmaceutical uses. Undesirable materials removed from fluids include impurities and contaminants such as particles, microorganisms, and dissolved chemical species. Specific examples of filter applications include use with liquid materials for semiconductor and microelectronic device manufacturing.

[0003] To perform the filtering function, the filter includes a filter membrane, which serves to remove undesirable materials from the fluid passing through it. The filter membrane may be in the form of a flat sheet, which may be wound (e.g., spirally), flat, pleated, or disk-shaped, as appropriate. Alternatively, the filter membrane may be in the form of hollow fibers. The filter membrane may be contained within a housing or otherwise supported such that the fluid being filtered enters through a filtration inlet and must pass through the filter membrane before passing through a filtration outlet.

[0004] Filter membranes can be constructed from porous structures with average pore sizes that can be selected based on the application of the filter, i.e., the type of filtration performed by the filter. Typical pore sizes are in the micron or submicron range, such as from about 0.001 micron to about 10 microns. Membranes with average pore sizes of about 0.001 to about 0.05 microns are sometimes classified as ultrafilter membranes. Membranes with pore sizes between about 0.05 and 10 microns are sometimes referred to as microporous membranes.

[0005] Filter membranes with pore sizes in the micron or submicron range can be effective in removing undesirable materials from a fluid stream by either sieving or non-sieving mechanisms, or both. Sieving mechanisms are a form of filtration that removes particles from a liquid stream by mechanically retaining them on the surface of the filter membrane, which mechanically interferes with the movement of the particles and acts to retain them in the filter, mechanically impeding the flow of the particles through the filter. Typically, the particles can be larger than the pores of the filter. "Non-sieving" filtration mechanisms are forms of filtration in which the filter membrane retains suspended particles or dissolved materials contained in the fluid stream passing through the filter membrane in a non-mechanical manner, for example, an electrostatic mechanism that electrostatically attaches and retains particulate matter or dissolved impurities to the filter surface and removes them from the fluid stream, the particles may be dissolved or solid with a particle size smaller than the pores of the filter material.

[0006] Removal of ionic materials, such as dissolved anions or cations, from solutions is important in many industries, such as the microelectronics industry, where extremely low concentrations of ionic contaminants and particles can adversely affect the quality and performance of microprocessors and memory devices. The ability to make positive and negative photoresists with low levels of metal ion contaminants, or to deliver isopropyl alcohol used in Maragoni drying for wafer cleaning with low parts per billion or parts per trillion levels of metal ion contaminants, is highly desirable and are just two examples of the need for contamination prevention in semiconductor manufacturing. Colloidal particles, which can be positively or negatively charged depending on the chemistry of the colloid and the pH of the solution, can also contaminate processing fluids and need to be removed. Microporous filter membranes made of polymeric materials that attract dissolved ionic materials can remove the dissolved ionic materials by a non-sieving filtration mechanism. Examples of such microporous membranes are made from chemically inert low surface energy polymers such as ultra-high molecular weight polyethylene ("UPE"), polytetrafluoroethylene, nylon, and the like. Due to the ability of nylon to be formed into filter membranes exhibiting high permeability and due to the excellent non-sieving filtration behavior of nylon, nylon filter membranes are used in a variety of different filtration applications, particularly in the semiconductor processing industry. However, due to the hydrolytic instability of the amide bond, many commercially available nylon filter membranes are not suitable for applications in which the membrane is exposed to strong acids, and similarly, such nylon filter membranes cannot be washed with acidic solutions. Summary of the Invention

[0007] The field of microelectronic device processing requires steady improvements in processing materials and methods to sustain the parallel steady improvement in microelectronic device performance (e.g., speed and reliability). Opportunities exist to improve microelectronic device manufacturing in all aspects of the manufacturing process, including methods and systems for filtering liquid materials.

[0008] In microelectronic device fabrication, a wide variety of different liquid materials are used as process solvents, cleaning agents, and other processing solutions. Many, if not most, of these materials are used at extremely high levels of purity. As an example, the liquid materials (e.g., solvents) used in photolithographic processing of microelectronic devices must be of extremely high purity. Specific examples of liquids used in microelectronic device fabrication include spin-on-glass (SOG) technology, back surface antireflective coating (BARC) methods, and processing solutions for photolithography. Some of these liquid materials are acidic. In order to provide these liquid materials at a high level of purity for use in microelectronic device fabrication, the filtration system must be highly effective at removing various contaminants and impurities from the liquid and must be stable (i.e., do not decompose or introduce contaminants) in the presence of the liquid material (e.g., acidic material) being filtered.

[0009] In a first embodiment, the porous composite filter membrane comprises a porous hydrophobic polymeric filter material having a coating thereon, the coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane.

[0010] In a second aspect, the porous polymer membrane comprises a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane. Such membranes can be prepared using known air casting techniques to provide polyamide or nylon membranes that exhibit superior acid stability compared to polyamide membranes prepared from nylon 6 or nylon 6,6. In one embodiment, the membranes of this second aspect are prepared from nylon 11 and / or nylon 12.

[0011] In a third embodiment, there is provided a porous hydrophobic polymeric filter membrane having thereon a polyamide coating as a first coating, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, thereby providing a polyamide coated membrane, said polyamide coated membrane having thereon a second coating that is a free radical reaction product of (i) at least one crosslinker and (ii) at least one monomer in the presence of a photoinitiator.

[0012] In a fourth embodiment, a porous filter membrane comprises a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, and the membrane is then coated with the free radical reaction product of (i) at least one crosslinker and (ii) at least one acrylamide monomer in the presence of a photoinitiator.

[0013] In a fifth aspect, (a) a porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, said membrane having grafted thereon pendant hydrophilic groups selected from hydroxyl groups, amine groups, carboxylic acid groups, or combinations thereof, and pendant ionic groups different from the pendant hydrophilic groups; (b) A porous composite filter membrane comprising a porous hydrophobic polymeric filter membrane having coated thereon a coating, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, thereby providing a polyamide-coated membrane, which is thereafter grafted with (i) pendant hydrophilic groups selected from hydroxyl groups, amine groups, carboxylic acid groups or combinations thereof, and (ii) pendant ionic groups different from the pendant hydrophilic groups.

[0014] In another aspect, the present disclosure provides a method for preparing a filter membrane of aspects 1 to 5. In another aspect, the present disclosure provides a method for removing impurities from a liquid, comprising contacting the liquid with a membrane of the present disclosure.

[0015] All filter membranes, such as the lower porous hydrophobic membrane used as starting material in the polyamide membrane of the second aspect, the first aspect, the third aspect, the fourth aspect and the second embodiment (b) of the fifth aspect, can be prepared from the underlying polymer composition using known methods such as air casting. See, for example, U.S. Pat. No. 7,891,500 and the references cited therein, which are incorporated herein by reference. Alternatively, the lower filter membrane can be prepared by known methods such as phase inversion, interfacial polymerization, stretching, track etching and electrospinning. See, for example, BSLalia et al., Desalination 326 (2013) 77-95 and P. van de Witte, et al., Journal of Membrane Science 117 (1996) 1-31.

[0016] The present disclosure may be more fully understood in consideration of the following description of various exemplary embodiments in conjunction with the accompanying drawings. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 (schematic and not necessarily to scale) illustrates one example of a filter product as described herein. [Diagram 2] 2 is a simplified diagram of a polyamide coated porous filter membrane. As described below, the polyamide coating and / or the cured coating does not necessarily form a continuous coating on the base membrane as shown. [Diagram 3] 3 is a comparison of the stability of UPE membranes coated with nylon 6, nylon 11, and nylon 12. Each bar on the left represents initial data, and each bar on the right represents data after a 99% formic acid wash. This data demonstrates the superior acid stability of representative membranes of the present disclosure, particularly the membrane of the second embodiment, as described below. [Figure 4]Figure 4 is a graphical representation of the surface tension of mixtures of methanol and water at 20° C. The surface tension (nM / m at 20° C.) is plotted against the mass (%) of methanol in water. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] While the present disclosure is susceptible to various modifications and alternative forms, details of which have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the specific exemplary embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.

[0019] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates to the contrary. As used in this specification and the appended claims, the term "or" is generally used in its sense including "and / or" unless the content clearly dictates to the contrary.

[0020] The term "about" generally refers to a range of numbers that are considered equivalent to a stated value (e.g., having the same function or result). In many instances, the term "about" may include numbers that are rounded to the nearest significant figure.

[0021] Numerical ranges expressed using endpoints include all numbers subsumed within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

[0022] As noted above, in a first aspect, the porous composite filter membrane comprises a porous hydrophobic polymeric filter membrane having a coating thereon, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane. In one embodiment, the mixture of formic acid and dichloromethane is a 1:1 (volume:volume) mixture. In one embodiment of this aspect, the polyamide is a polyamide having the general repeating unit -[(CH2) x C(O)NH] n -, where x is an integer between about 8 and 12, and n represents the number of repeat units in the polyamide polymer. In one embodiment, the polyamide polymer is selected from nylon 11 and nylon 12, or mixtures thereof. In one embodiment, the membrane has a bubble point between about 20 and 200 psi, as measured using ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C., and / or the membrane has a viscosity between about 1 and about 30 μg / cm. 2 Ponceau S dye binding capacity between about 1 and about 30 μg / cm 2 In one embodiment, the membrane has an isopropanol flow time, measured at 14.2 psi, of about 150 to about 20,000 seconds / 500 mL.

[0023] In this first embodiment, a composite membrane starting with a porous hydrophobic filter membrane, such as one composed of ultra-high molecular weight polyethylene ("UPE"), is treated with a solution of polyamide polymer in a mixture of formic acid and dichloromethane. Once the membrane is coated, it is transferred to a vessel containing a solution comprising water. The resulting membrane is then subjected to one or more washing steps, including passing through a vessel of aqueous and lower alcohol (e.g., C1-C4 alcohol) washes. Upon drying, this process provides the composite membrane of the first embodiment. As shown in FIG. 4, the exemplary membrane of the first embodiment of the present disclosure exhibited superior acid stability when compared to a similar membrane prepared using nylon 6.

[0024] In certain embodiments, the surface energy is greater than 30 dynes / cm, from about 30 to about 100 dynes / cm, or from about 30 to about 85 dynes / cm, or from about 30 to about 65 dynes / cm.

[0025] As noted above, in a second aspect, the present disclosure provides a porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane. In one embodiment, the mixture of formic acid and dichloromethane is a 1:1 (volume:volume) mixture. Such membranes can be prepared by dissolving such polyamides in a mixture of formic acid and dichloromethane to form a polyamide solution, which is then subjected to known air casting techniques to provide a novel polyamide membrane with significantly improved acid stability over similar nylon membranes comprising nylon 6 or nylon 6,6. In one embodiment, the polyamides of this aspect are comprised of the common repeating unit -[(CH2) x C(O)NH] n -, where x is an integer between about 8 and 12, and n represents the number of repeat units in the polyamide polymer. In one embodiment, the polyamide polymer is selected from nylon 11 and nylon 12, or mixtures thereof. In one embodiment, the membrane has a bubble point between about 20 and about 200 psi, and / or a viscosity between about 1 and about 100 μg / cm, as measured using ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C. 2 Ponceau S dye binding capacity between about 1 and about 100 μg / cm 2 In one embodiment, the membrane has an isopropanol flow time, measured at 14.2 psi, of about 150 to about 20,000 seconds / 500 mL.

[0026] In certain embodiments, the surface energy is greater than 30 dynes / cm, from about 30 to about 100 dynes / cm, or from about 30 to about 85 dynes / cm, or from about 30 to about 65 dynes / cm.

[0027] As noted above, in a third aspect, a porous composite filter membrane comprises a porous hydrophobic polymeric filter membrane having a polyamide coating thereon, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, thereby providing a polyamide-coated membrane, which is then coated with a free radical reaction product of (i) at least one crosslinker and (ii) at least one monomer in the presence of a photoinitiator. In one embodiment of this aspect of the disclosure, the polyamide is a polyamide having repeating units -[(CH2) x C(O)NH] n -, where x is an integer between about 8 and 12, and n represents the number of repeat units in the polyamide polymer. In one embodiment, the polyamide polymer is selected from nylon 11 and nylon 12, or mixtures thereof. In this aspect, the crosslinker and monomer (as discussed more fully below) are not grafted onto the surface of the polyamide coated hydrophobic membrane, but rather are polymerized at or near the surface of the membrane to form an additional partial coating thereon. In one embodiment, the membrane has a bubble point between about 20 and about 200 psi, as measured using ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C., and / or the membrane has a hydrophobicity between about 1 and about 30 μg / cm 2 Ponceau S dye binding capacity between about 1 and about 30 μg / cm 2 In one embodiment, the membrane has an isopropanol flow time, measured at 14.2 psi, of about 150 to about 20,000 seconds / 500 mL.

[0028] In this third aspect of the disclosure, a composite membrane starting from a porous hydrophobic filter membrane, such as one composed of ultra-high molecular weight polyethylene, is treated with a solution of such a polyamide polymer, for example in a mixture of formic acid and dichloromethane in a 50 / 50 ratio (by volume). Once the membrane is coated, it is transferred to a mixing vessel containing an aqueous solution comprising (i) at least one crosslinker, (ii) at least one monomer, and (iii) at least one photoinitiator, hereinafter referred to as the "monomer solution". The thus coated membrane may then be subjected to UV light to initiate free radical polymerization at or near the surface of the polyamide coating with (i) at least one crosslinker and (ii) at least one charged acrylamide monomer. The resulting membrane is then subjected to one or more washing steps, including passing through a washing vessel of aqueous and lower alcohol (e.g., C1-C4 alkanol). Once dried, this process gives the composite membrane of this third aspect of the disclosure.

[0029] In certain embodiments, the surface energy is greater than 30 dynes / cm, from about 30 to about 100 dynes / cm, or from about 30 to about 85 dynes / cm, or from about 30 to about 65 dynes / cm.

[0030] In this third aspect of the disclosure, the crosslinker is a non-charged difunctional (i.e., having two carbon-carbon double bonds) vinyl, acrylic or methacrylic monomeric species, optionally with amide functionality. Non-limiting examples of such crosslinkers include methylene bis(acrylamide), tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, divinyl sulfone, divinyl benzene, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione 98%, and ethylene glycol divinyl ether.

[0031] The monomers referred to herein are of the vinyl, acrylic or methacrylic type, either charged or uncharged.

[0032] Non-limiting examples of positively charged monomers that can be used in embodiments of the present disclosure include 2-(dimethylamino)ethyl hydrochloride acrylate, [2-(acryloyloxy)ethyl]trimethylammonium chloride, 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl)methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl ... Examples of the monomers that may be used include, but are not limited to, acrylamidopropyl trimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl) methacrylamide hydrochloride, N-(3-aminopropyl) methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride, and vinylbenzyltrimethylammonium chloride. In certain embodiments, the positively charged monomer comprises acrylamidopropyl trimethylammonium chloride (APTAC). It should be understood that some of the positively charged monomers listed above contain quaternary ammonium groups and are naturally charged, whereas other positively charged monomers, such as those containing primary, secondary, and tertiary amines, are adjusted to generate a charge by treatment with an acid. Monomers that can be positively charged naturally or by treatment can be polymerized and crosslinked with a crosslinking agent to form a coating on the porous membrane.

[0033] Examples of negatively charged monomers that can be used include, but are not limited to, 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl acrylate potassium salt, 2-propylacrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethyl maleate, 3-sulfopropyl methacrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid, and vinylphosphonic acid, either individually or in combination of two or more of the following. In certain embodiments, the negatively charged monomer comprises a sulfonic acid moiety. It should be understood that some of the negatively charged monomers listed above contain strong acid groups and are naturally charged, while other negatively charged monomers, including weak acids, are adjusted to generate a charge by treatment with base. Monomers that are naturally or by process negatively charged can be polymerized and crosslinked with a crosslinking agent to form a coating on a porous membrane that is negatively charged in an organic solvent.

[0034] Examples of neutral monomers that can be used include, but are not limited to, acrylamide, N,N-dimethylacrylamide, N-(hydroxyethyl)acrylamide, diacetone acrylamide, N-[tris(hydroxymethyl)methyl]acrylamide, N-(isobutoxymethyl)acrylamide, N-(3-methoxypropyl)acrylamide, 7-[4-(trifluoromethyl)coumarin]acrylamide, N-isopropylacrylamide, 2-(dimethylamino)ethyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, ethyl acrylate, 2-hydroxyethyl acrylate, butyl acrylate, ethylene glycol methyl ether acrylate, 4-hydroxybutyl acrylate, hydroxypropyl acrylate, 4-acetoxyphenethyl acrylate, benzyl acrylate, 1-vinyl-2-pyrrolidinone, vinyl acetate, ethyl vinyl ether, vinyl 4-tert-butylbenzoate, and phenyl vinyl sulfone.

[0035] In one embodiment, the photoinitiator is selected from those recognized as type I photoinitiators. Without wishing to be bound by theory, type I photoinitiators undergo unimolecular bond cleavage to generate free radicals when irradiated. Examples of suitable initiators include various persulfates such as sodium persulfate and potassium persulfate, 1-hydroxycyclohexyl phenyl ketone, sold under the trademark Irgacure 2959 (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone), and benzoyl peroxide.

[0036] The amount of photoinitiator in the monomer solution can be any amount (i.e., concentration) high enough to affect the desired free radical reaction between the crosslinker and the monomer. Examples of useful amounts of photoinitiator in the monomer solution can range from up to 1 weight percent, such as from 0.1 or 0.5 to 4.5 weight percent, or from 1 or 2 to 3 or 4 weight percent.

[0037] The type of solvent used for the monomer solution can be any that is effective to allow the monomer solution to dissolve and deliver a useful amount of monomer to the surface of the hydrophilic polymer. A preferred solvent for the monomer solution is water or water with the addition of an organic solvent. The solvent can include an organic solvent, water, or both. Examples of organic solvents include alcohols, especially lower alcohols (e.g., C1-C6 alcohols), with isopropanol, methanol, and hexylene glycol being useful examples. The particular solvent used for a particular process, monomer solution, and monomer can be based on factors such as the type and amount of monomer in the monomer solution, the type of hydrophilic polymer, and other factors. In a solvent that contains both water and an organic solvent, the organic solvent can be included in any amount, for example, less than 90, 75, 50, 40, 30, 20, or 10% by weight. As an example, a useful solvent composition can contain 1-10% by weight hexylene glycol in water. In one embodiment, the water is deionized water.

[0038] The amount of monomer in the monomer solution, in one embodiment, is about 0.5-5 wt % based on the weight of the solution. The amount of crosslinker in the monomer solution, in one embodiment, is about 0.25-3.0 wt % based on the total weight of the monomer solution. In one embodiment, the relative amounts of monomer and crosslinker utilized, together with the relative coverage of such final crosslinked or free radical polymerized coating (on the polyamide coated hydrophobic membrane), are such that the overall, i.e., resulting membrane, has a surface energy of about 30-85 dynes / cm.

[0039] After the monomer solution has been effectively contacted or coated onto the polyamide-coated underlying porous hydrophobic membrane, the resulting membrane is exposed to electromagnetic radiation, typically in the ultraviolet portion of the spectrum, or another energy source effective to cause the photoinitiator to initiate free radical polymerization of the crosslinker and monomer.

[0040] As stated above, in a fourth aspect, the present disclosure provides a porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, the membrane being subsequently coated with a free radical reaction product of (i) at least one crosslinker and (ii) at least one monomer in the presence of a photoinitiator. Such a membrane can be prepared using the membrane of the first aspect as the starting material, followed by the acrylic coating step described above in the third aspect.

[0041] In certain embodiments, the surface energy is greater than about 30 dynes / cm, from about 30 to about 100 dynes / cm, or from about 30 to about 85 dynes / cm, or from about 30 to about 65 dynes / cm.

[0042] In some embodiments, the film has a bubble point of between about 20 and about 200 psi when measured using ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C., and / or the film has a viscosity of between about 1 and about 30 μg / cm 2 Ponceau S dye binding capacity between about 1 and about 30 μg / cm 2 In one embodiment, the membrane has an isopropanol flow time, measured at 14.2 psi, of about 150 to about 20,000 seconds / 500 mL.

[0043] As noted above, in a fifth aspect, the present disclosure provides a porous membrane having a pendant ionic moiety. In particular, in this aspect, the present disclosure provides two embodiments: a. a porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, said membrane being grafted with pendant hydrophilic groups selected from hydroxyl groups, amine groups, carboxyl groups or combinations thereof, and pendant ionic groups different from the pendant hydrophilic groups; b. A porous composite filter membrane comprising a porous hydrophobic polymeric filter membrane having a coating thereon, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, thereby providing a polyamide coated membrane, which is thereafter grafted with pendant hydrophilic groups selected from hydroxyl groups, amine groups, carboxylic acid groups or combinations thereof, and pendant ionic groups different from the pendant hydrophilic groups. to provide.

[0044] In one embodiment of this fifth aspect of the disclosure, the polyamide comprises the general repeat unit -[(CH) x C(O)NH] n where x is an integer from about 8 to 12 and n represents the number of repeat units in the polyamide polymer. In one embodiment, the polyamide polymer is selected from nylon 11 and nylon 12 or mixtures thereof.

[0045] In this fifth aspect of the disclosure, embodiment a., a method for preparing such a membrane comprises: a. contacting the membrane of the second embodiment with a photoinitiator solution comprising a solvent and a photoinitiator to deposit the photoinitiator on the surface of the polyamide polymer; b. after contacting the surface with the photoinitiator solution to place a photoinitiator on the surface, contacting the surface with a monomer solution comprising a charged monomer, the charged monomer comprising an ionic group; c. exposing the surface to electromagnetic radiation to graft ionic groups onto the polyamide polymer; Includes.

[0046] In this embodiment a., the membrane is therefore a polyamide soluble in a mixture of formic acid and dichloromethane (e.g., a 1:1, volume:volume mixture), in one embodiment selected from nylon 11 and nylon 12, and coated with the free radical reaction product of a crosslinker and acrylamide monomer as described in the third aspect above.

[0047] In some embodiments, the film has a bubble point of between about 20 and about 200 psi when measured using ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C., and / or the film has a viscosity of between about 1 and about 300 μg / cm 2 Ponceau S dye binding capacity between about 1 and about 300 μg / cm 2 In one embodiment, the membrane has an isopropanol flow time, measured at 14.2 psi, of about 150 to about 20,000 seconds / 500 mL.

[0048] In a fifth aspect, embodiment b., there is provided a method for preparing such a membrane, comprising the steps of: a. contacting the membrane of the first embodiment with a photoinitiator solution comprising a solvent and a photoinitiator to deposit a photoinitiator on the surface of the polyamide polymer; b. after contacting the surface with the photoinitiator solution to place a photoinitiator on the surface, contacting the surface with a monomer solution comprising a charged monomer, the charged monomer comprising an ionic group; c. exposing the surface to electromagnetic radiation to graft ionic groups onto the polyamide polymer; Includes.

[0049] In this embodiment b., the membrane is therefore a porous hydrophilic polymer membrane, e.g. ultra-high molecular weight polyethylene, coated with a polyamide soluble in a mixture of formic acid and dichloromethane (e.g., in a 50 / 50 ratio (by volume)), which polyamide is in one embodiment selected from nylon 11 and nylon 12, and then grafted with certain pendant ionic groups.

[0050] In some embodiments, the film has a bubble point of between about 20 and about 200 psi when measured using ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C., and / or the film has a viscosity of between about 1 and about 300 μg / cm 2Ponceau S dye binding capacity between about 1 and about 300 μg / cm 2 In one embodiment, the membrane has an isopropanol flow time, measured at 14.2 psi, of about 150 to about 20,000 seconds / 500 mL.

[0051] With respect to this fifth aspect, Applicant has determined that chemically attaching charged ("ionic") chemical groups to hydrophilic polymers by certain chemical grafting techniques, including the use of photoinitiators, entails certain specific technical challenges. Many of these techniques involve contacting a polymer surface with a solution containing a charged reactive compound (e.g., a "charged monomer") and a photoinitiator, and then exposing the polymer and solution to electromagnetic radiation. The charged monomer contains a reactive moiety (e.g., an unsaturated moiety) and a charged chemical group that is chemically bonded to the polymer. When the solution containing the charged monomer, polymer, and photoinitiator is exposed to radiation, the photoinitiator initiates a chemical reaction between the unsaturated moiety and the hydrophilic polymer. Through this reaction, the unsaturated moiety becomes chemically bonded to the polymer, i.e., "grafted" to the polymer.

[0052] In this fifth aspect, the ionic group can be any group. The pendant ionic group is different from the pendant hydrophilic group. In certain embodiments where the hydrophilic polymer is included in a filter membrane, the ionic group can be effective in improving the filtration performance of the filter membrane, particularly the non-sieving filtration performance of the filter membrane. Examples of ionic groups that can be included on the described hydrophilic polymers, particularly on the hydrophilic polymers included in the filter membrane, include cationic nitrogen-containing ionic groups, anionic sulfur-containing ionic groups and anionic phosphorus-containing ionic groups, including their chemical counterparts (e.g., salts or acids). As a specific example, the pendant ionic group can be a cationic nitrogen-containing cyclic aromatic group, a cationic imidazole or cationic amine, or an anionic phosphonic acid group or an anionic sulfonic acid group.

[0053] When these techniques are used to deposit charged monomers onto hydrophilic polymers, certain technical challenges exist. Typical photoinitiators (e.g., benzophenone and benzophenone derivatives) are hydrophobic and are not inherently attracted to the hydrophilic surface of the hydrophilic polymer. The resulting challenge is to place an effective amount of the hydrophobic photoinitiator on the surface of the hydrophilic polymer.

[0054] Disclosed herein is a technique that allows a charged monomer to be chemically bonded, i.e., grafted, to a hydrophilic polymer or an article made from a hydrophilic polymer, including but not limited to a porous filter membrane. The technique generally involves placing a photoinitiator on the surface of a hydrophilic polymer; then placing a charged monomer on the surface; and then exposing the photoinitiator and the charged monomer present on the surface of the hydrophilic polymer to radiation. The radiation causes the photoinitiator to initiate a reaction between the unsaturated moiety and the hydrophilic polymer, whereby the unsaturated moiety is chemically bonded, i.e., "grafted," to the polymer, and the resulting hydrophilic polymer contains a charged (ionic) chemical group that is chemically bonded to the hydrophilic polymer via a covalent chemical bond.

[0055] A more specific example of this method involves grafting ionic groups onto a porous filter membrane (e.g., a hydrophilic porous filter membrane) that has been made to include a hydrophilic polymer. The method involves chemically bonding charged chemical groups of charged monomers to the hydrophilic polymer surface of the filter membrane, which in some embodiments includes the interior pore surfaces of the membrane. The method can include contacting the filter membrane with a photoinitiator solution containing a solvent and a photoinitiator to deposit a photoinitiator on the surface of the hydrophilic polymer, including the interior pore surfaces; optionally removing excess photoinitiator solution from the surface, for example by rinsing (with water), drying (solvent evaporation), or both rinsing and drying; depositing a charged monomer on the surface after contacting the surface with the photoinitiator solution, and optionally after removing excess photoinitiator solution from the surface; and exposing the surface (having the photoinitiator and charged monomer) to electromagnetic radiation to react with the hydrophilic polymer and chemically bond the charged monomer to the hydrophilic polymer via a covalent chemical bond, i.e., grafted to the hydrophilic polymer.

[0056] In comparison with certain previous grafting methods, the present invention involves the use of a hydrophobic photoinitiator to chemically attach charged (ionic) chemical groups to a polymer that is hydrophilic. As used herein, the term "hydrophilic" to describe a hydrophilic polymer refers to a polymer that attracts water molecules due to the presence of a sufficient amount of hydrophilic pendant functional groups attached to the polymer backbone, such as hydroxyl (-OH) groups, carboxyl groups (-COOH), amino groups, (-NH2), or similar functional groups attached to the polymer backbone. In some embodiments, the pendant hydrophilic groups are selected from the group consisting of hydroxyl groups, amine groups, carboxylic acid groups, or combinations thereof. When the hydrophilic polymer is formed into a porous filter membrane, these hydrophilic groups help absorb water onto the porous filter membrane.

[0057] According to the method described for this fifth embodiment, a photoinitiator is placed on the surface of a hydrophilic polymer, for example, on the surface of a porous filter membrane or other article that contains a hydrophilic polymer. The photoinitiator can be dissolved in a solvent by a preferred technique to form a photoinitiator solution that is then applied to the hydrophilic polymer to place the photoinitiator on the surface. The photoinitiator can be dissolved in a liquid solvent, which can be water, an organic solvent, or a combination of an organic solvent and water, to form a photoinitiator solution. The photoinitiator solution is then contacted with the polymer by any useful method, such as spraying, dipping, soaking, adsorption, etc.

[0058] The solvent of the photoinitiator solution can be any solvent that is effective for dissolving the photoinitiator and delivering the photoinitiator to the surface of the hydrophilic polymer, for example, to the surface of a hydrophilic porous polymer membrane. In the case of a polymer that is hydrophilic and a photoinitiator that is hydrophobic, the solvent must be compatible with each of these two components in order to successfully contact the hydrophobic photoinitiator, desirably in large quantities, with the surface of the hydrophilic polymer, including contact with the interior pores of a filter membrane made of a hydrophilic polymer. To achieve this, the solvent of the exemplary photoinitiator solution as described may contain at least some amount of water while still being able to dissolve a useful amount of the photoinitiator. Including water as part of the photoinitiator solvent may be effective in making the solvent more polar, which may make the delivery (e.g., precipitation) of the hydrophobic photoinitiator from the solvent onto the hydrophilic polymer more efficient. Additionally, water may improve the web transport of the membrane during processing, since exposing a hydrophilic polymer, such as nylon, to a more concentrated, e.g., pure, organic solvent may tend to cause deformation of the polymer membrane during handling.

[0059] The term "solvent" refers to any liquid that is effective to contain a useful amount of dissolved photoinitiator and allows the liquid to carry the dissolved photoinitiator to the surface of the hydrophilic polymer or an article made to contain the hydrophilic polymer, such as a polymeric filter membrane, including the interior pore surfaces. The solvent can include an organic solvent, water, or both. Examples of organic solvents include alcohols, especially lower alcohols (C1-C4 alcohols), with isopropanol and methanol being useful examples.

[0060] Exemplary solvents for the photoinitiator solution include, consist of, or consist essentially of a mixture of an organic solvent and water, such as a mixture of water and a lower (C1-C4) alcohol, such as a mixture of methanol and water or a mixture of isopropanol and water. A combination of a lower alcohol, such as isopropanol or methanol, with water can be particularly effective in dissolving a hydrophobic initiator, such as benzophenone (or a derivative thereof), yet is very effective in wetting the surface of a hydrophilic polymer, such as the surface (including the interior pore surface) of a porous filter membrane made of a hydrophilic polymer. The effectiveness of these solvent mixtures to dissolve a hydrophobic photoinitiator (e.g., benzophenone or a derivative thereof) and wet a hydrophilic substrate can enable the solvent mixture to be used to effectively deliver a useful amount of hydrophobic photoinitiator onto the surface of a hydrophilic polymer, including the interior pore surface of a porous hydrophilic filter membrane. The relative amounts of organic solvent (e.g., a lower alcohol such as methanol, isopropanol, or a mixture thereof) and water in the solvent can be any effective amount, for example, the ratio of water:organic solvent (weight:weight) can be in the range of 10:90 to 90:10, 20:80 to 80:20, e.g., 30:70 to 70:30, or 40:60 to 60:40.

[0061] In this fifth embodiment, the photoinitiator can be any photoinitiator that effectively responds to radiation (e.g., ultraviolet light) to initiate the reaction between the reactive group of the charged monomer and the hydrophilic polymer described herein. Examples include photoinitiators known in the chemical arts as "Type II" photoinitiators. Known useful examples of Type II photoinitiators include benzophenone and benzophenone derivatives.

[0062] The amount of photoinitiator in the photoinitiator solution can be any amount (concentration) high enough to allow the photoinitiator solution to deliver a desired, useful or maximum amount of photoinitiator to the hydrophilic polymer surface. The amount and method of application should be sufficient to place an amount of photoinitiator on the polymer surface that is desirably effective to react a large amount of charged monomer with the polymer surface. Examples of useful amounts of photoinitiator in the photoinitiator solution can range up to 5 weight percent, for example, from 0.1 or 0.5 to 4.5 weight percent, or from 1 or 2 to 3 or 4 weight percent.

[0063] The photoinitiator solution can be applied to the surface of the hydrophilic polymer by any useful technique, such as by spraying the photoinitiator solution onto the hydrophilic polymer, dipping or soaking the hydrophilic polymer in the photoinitiator solution, etc. Desirably, the entire surface of the article comprising the hydrophilic polymer, including, for example, all the internal surfaces of a porous filter membrane, can be contacted with the photoinitiator solution and wetted by the photoinitiator solution. If necessary, the applying step can include manipulation of the hydrophilic polymer or the article comprising the hydrophilic polymer, for example, by stretching or squeezing the porous filter material to wet all the surfaces of the porous filter material. In some embodiments, the photoinitiator solution comprises 0.1 to 2 weight percent benzophenone or a benzophenone derivative, water, and one or more of isopropanol and methanol. In some embodiments, the photoinitiator solution comprises 20 to 80 parts by weight isopropanol and 80 to 20 parts by weight percent isopropanol, based on 100 parts by weight total isopropanol and water.

[0064] Then, if desired, a portion of the photoinitiator solution present on the surface of the hydrophilic polymer surface can be removed, but still effectively leave a desired amount of photoinitiator solution on the surface. The photoinitiator solution can be present in excess of the amount required, but the excess amount can be removed by any one or more techniques of mechanical removal. In the case of a porous filter membrane, examples of techniques for removing excess photoinitiator solution include squeezing the filter membrane dry, squeezing, folding or stretching using mechanical force or pressure such as a roller, rinsing with a spray or water bath (e.g., with deionized water), or evaporating the solvent from the photoinitiator solution present on the hydrophilic polymer surface by one or more of the use of air flow or heat, such as by the use of a fan or "air knife" dryer, heat, or a combination thereof.

[0065] According to one optional step of removing excess photoinitiator solution, the hydrophilic polymer, such as a porous hydrophilic filter membrane, containing the photoinitiator solution in contact with its surface can be rinsed using water, such as deionized water. The rinsing step can be carried out by any useful technique, such as by spraying the rinsing (e.g., deionized) water onto the hydrophilic polymer, by dipping or soaking the hydrophilic polymer in water (e.g., deionized water), etc., thereby removing at least a portion of the excess photoinitiator solution (including its organic solvent) from the hydrophilic polymer surface. The rinsing step should allow a useful amount of photoinitiator to remain on the surface of the hydrophilic polymer, and preferably a reduced amount of solvent from the photoinitiator solution remains on the surface.

[0066] In a different optional step of removing a portion of the photoinitiator solution from the surface of the hydrophilic monomer, which may be optionally performed after the rinsing step or the mechanical drying step or both, the hydrophilic polymer (e.g., a porous hydrophilic filter membrane) having the photoinitiator solution in contact with its surface can be treated to remove the solvent of the photoinitiator solution by drying the solvent by evaporation, leaving a concentrated amount of photoinitiator on the hydrophilic polymer surface. This type of drying step to evaporate the solvent of the photoinitiator solution on the surface of the hydrophilic polymer can be performed by applying heat to the photoinitiator solution, by passing a stream of air or another gaseous fluid through the photoinitiator solution, or by allowing the solvent to evaporate from the photoinitiator solution by leaving it in air at ambient conditions, e.g., room temperature, for a time effective to evaporate the desired portion of the solvent of the photoinitiator solution. Desirably, a significant portion of the solvent, e.g., at least 40, 50, 70 or 90% by weight, can be evaporated and removed from the photoinitiator solution. As a result, a concentrated amount of photoinitiator remains on the surface of the hydrophilic polymer, preferably in a fairly uniform distribution throughout the surface, including, for example, the interior pores of a porous filtration membrane.

[0067] Optionally, if desired, after the drying step, the hydrophilic polymer having the photoinitiator present on its surface can be rewetted with water, e.g., deionized water, such as by spraying deionized water onto the hydrophilic polymer, by immersing the hydrophilic polymer in deionized water, or by any other technique that is effective to rewet the photoinitiator without removing the photoinitiator from the surface of the hydrophilic polymer.

[0068] According to the method described in this fifth aspect, after disposing the photoinitiator on the surface of the hydrophilic polymer (with optional drying or wetting steps), the next step can be disposing a charged monomer on the surface in combination with the photoinitiator. The charged monomer can be disposed on the surface on which the photoinitiator has been previously disposed by any useful technique, useful examples include contacting the surface with a monomer solution containing the charged monomer dissolved in a solvent. Specific examples of these techniques include spraying, dipping, soaking, adsorption, etc. After the charged monomer has been successfully disposed on the surface with the photoinitiator, the surface (with the photoinitiator and the charged monomer) is exposed to radiation to initiate a chemical reaction that chemically bonds the charged monomer to the hydrophilic polymer (through a covalent chemical bond), a process often referred to as chemical "grafting".

[0069] In this fifth embodiment, the charged monomer can be a reactive compound that includes a reactive moiety, such as an unsaturated moiety (e.g., vinyl, acrylate, methacrylate, etc.) and an ionic moiety, which can be anionic or cationic.

[0070] Examples of suitable cationic charged monomers include acrylate, methacrylate, acrylamide, methacrylamide, amine (e.g., primary amine, secondary amine, tertiary amine, and quaternary amine), and vinyl types with quaternary ammonium, imidazolium, phosphonium, guanidinium, sulfonium, or pyridinium functional groups. Examples of suitable acrylate monomers include 2-(dimethylamino)ethyl hydrochloride acrylate and [2-(acryloyloxy)ethyl]trimethylammonium chloride. Examples of suitable methacrylate monomers include 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl)methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, and [2-(methacryloyloxy)ethyl]trimethylammonium chloride. Examples of suitable acrylamide monomers include acrylamidopropyltrimethylammonium chloride. Examples of suitable methacrylamide monomers include 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl) methacrylamide hydrochloride and N-(3-aminopropyl)-methacrylamide hydrochloride.Other suitable monomers include diallyldimethylammonium chloride, allylamine hydrochloride, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride and vinylbenzyltrimethylammonium chloride.

[0071] Suitable anionic monomers include acrylate, methacrylate, acrylamide, methacrylamide, and vinyl types with sulfonic acid, carboxylic acid, phosphonic acid, or phosphoric acid functional groups. Examples of suitable acrylate monomers include 2-ethylacrylic acid, acrylic acid, 2-carboxyethylacrylate, 3-sulfopropylacrylate potassium salt, 2-propylacrylic acid, and 2-(trifluoromethyl)acrylic acid. Examples of suitable methacrylate monomers include methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethylmaleate, and 3-sulfopropylmethacrylate potassium salt. An example of a suitable acrylamide monomer is 2-acrylamido-2-methyl-1-propanesulfonic acid. An example of a suitable methacrylamide monomer is 3-methacrylamidophenylboronic acid. Other suitable monomers include vinylsulfonic acid (or vinylsulfonic acid sodium salt) and vinylphosphonic acid (and its salts).

[0072] Other suitable monomers are N-(hydroxymethyl)acrylamide (HMAD), (3-acrylamidopropyl)trimethylammonium chloride (APTAC) and (vinylbenzyl)trimethylammonium chloride (VBTAC).

[0073] The type of solvent used for the monomer solution in this fifth aspect can be any that is effective to allow the monomer solution to dissolve and deliver a useful amount of charged monomer to the surface of the hydrophilic polymer. A preferred solvent for the monomer solution is water or water with the addition of an organic solvent. The solvent can include an organic solvent, water, or both. Examples of organic solvents include alcohols, especially lower alcohols (C1-C6 alcohols), with isopropanol, methanol, and hexylene glycol being useful examples. The particular solvent used for the particular process, monomer solution, and charged monomer can be based on factors such as the type and amount of charged monomer in the monomer solution, the type of hydrophilic polymer, and other factors. In a solvent that contains both water and an organic solvent, the organic solvent can be included in any amount, for example, less than 90, 75, 50, 40, 30, 20, or 10% by weight. As an example, a useful solvent composition can contain 1-10% by weight hexylene glycol in water.

[0074] The amount of charged monomer in the monomer solution can be any amount (concentration) high enough to allow the monomer solution to deliver a desired, useful or maximum amount of charged monomer to the hydrophilic polymer surface. The amount of monomer solution, the concentration of charged monomer in the monomer solution, and the method used to apply the monomer solution to the hydrophilic polymer should desirably be sufficient to place an amount of charged monomer on the polymer surface that is effective to react a large amount of the charged monomer with the hydrophilic polymer surface. Examples of useful amounts of monomer in the monomer solution can range up to 5 or 10 weight percent, for example, from 0.5 to 5 weight percent, or from 1 or 2 to 3 or 4 weight percent. In some embodiments, the charged monomer comprises vinyl imidazole, 2-acrylamido-2-methylpropanesulfonic acid, (3-acrylamidopropyl)trimethylammonium chloride, vinylsulfonic acid, vinylphosphonic acid, acrylic acid, (vinylbenzyl)trimethylammonium chloride, or polydiallyldimethylammonium chloride. In some embodiments, the monomer solution comprises 0.5-10 wt % charged monomer dissolved in 90-99.5 wt % deionized water, based on the total weight of the monomer solution.

[0075] After the monomer solution has been effectively delivered to the surface of the hydrophilic polymer (including the photoinitiator pre-disposed thereon), the hydrophilic polymer (with the photoinitiator and charged monomers on its surface) is exposed to electromagnetic radiation, typically in the ultraviolet portion of the spectrum, or another energy source effective to cause the photoinitiator to initiate a chemical reaction in which the reactive moieties on the charged monomers react with and chemically (covalently) bond to the hydrophilic polymer.

[0076] The amount of ionic groups that can be attached to the hydrophilic polymer, described in terms of the amount of hydrophilic monomer or reactive monomer chemically bonded to a filter material containing a hydrophilic monomer, can be any useful amount, for example, an amount effective to increase the non-sieving filtration function of the hydrophilic filter membrane to which the ionic groups are attached. Preferably, the presence and amount of pendant ionic groups does not result in a substantial or unacceptable level of detrimental effect on other properties of the filter membrane, such as flow properties.

[0077] For example, hydrophilic polymers to which ionic groups have been chemically attached by use of grafting techniques involving photoinitiators, articles or compositions containing these polymers, such as filter membranes made with the polymers, may (although not preferred) contain very small but analytically detectable (residual) amounts of photoinitiators.

[0078] As mentioned above, the present disclosure provides a composite membrane that is useful as a filter material for removing impurities from various fluids.Due to the nature of the process, in various aspects of the present disclosure, the polyamide coating applied to the hydrophobic filter material or membrane does not completely cover or encapsulate the hydrophobic filter material or membrane, but rather forms a semi-continuous or partial coating on the underlying membrane.Similarly, in the third and fourth aspects of the present disclosure, where free radical polymerization is carried out in the presence of a polyamide-coated membrane or nylon membrane, the resulting cured or crosslinked polymer coating does not completely cover or encapsulate the surface of the underlying membrane, but also forms a semi-continuous or partial coating on the nylon membrane or the porous hydrophobic membrane structure coated with polyamide.

[0079] In certain embodiments, the lower hydrophobic porous polymeric filter material is formed from a polymeric material, a mixture of different polymeric materials, or polymeric and non-polymeric materials. The polymeric materials forming the filter can be crosslinked together to provide a filter structure with a desired degree of integrity.

[0080] The polymeric material that can be used to form the lower porous filter membrane of the present disclosure is a hydrophobic polymer. In some embodiments, the filter membrane comprises a polyolefin or a halogenated polymer. Exemplary polyolefins include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polybutene (PB), polyisobutylene (PIB), and copolymers of two or more of ethylene, propylene, and butylene. In further specific embodiments, the filter material comprises ultra-high molecular weight polyethylene (UPE). UPE filter materials, such as UPE membranes, typically have a molecular weight of about 1×10 6 More than daltons (Da), e.g., about 1 × 10 6 ~9×10 6 Da, or 1.5 × 10 6 ~9×10 6 It is formed from resins having molecular weights (viscosity average molecular weight) in the Da range. Crosslinking between polyolefin polymers such as polyethylene can be promoted by the use of heat or crosslinking chemicals such as peroxides (e.g., dicumyl peroxide or di-tert-butyl peroxide), silanes (e.g., trimethoxyvinylsilane) or azoester compounds (e.g., 2,2'-azo-bis(2-acetoxy-propane). Exemplary halogenated polymers include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), fluorinated ethylene polymers (FEP), polyhexafluoropropylene and polyvinylidene fluoride (PVDF).

[0081] In other embodiments, the filter material includes a polymer selected from polyimide, polysulfone, polyethersulfone, polyarylsulfone polyamide, polyacrylate, polyester, polyamideimide, cellulose, cellulose ester, polycarbonate, or combinations thereof.

[0082] In another embodiment, the lower hydrophobic porous filter membrane can be selected from commercially available hydrophobic membranes such as those prepared from ultra-high molecular weight polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride, polyarylsulfone, and the like.

[0083] Typically, the lower porous filter membrane is asymmetric. In one example of an asymmetric membrane, the pore size of one side and region of the membrane is larger than the pore size of the opposite side and region. In another example, there may be an asymmetric structure (e.g., hourglass shape) in which the pore size of the central region of the membrane is smaller than either side, while the pore size of the opposite side (and region) of the membrane is larger. In another version, the microporous membrane can have an essentially symmetric pore structure (substantially the same pore size across the thickness of the membrane) throughout its thickness.

[0084] The polyamide polymers referred to above, also commonly known as "nylons", are typically understood to include copolymers and terpolymers having repeating amide groups in the polymer backbone. In general, nylon and polyamide resins include copolymers of diamines and dicarboxylic acids.

[0085] Polyamides useful in the practice of the present disclosure are soluble in mixtures of formic acid and dichloromethane. In one embodiment of such a mixture, the amount of formic acid varies from about 25% to about 75% by volume and the amount of dichloromethane varies from about 75% to about 25% by volume. In one embodiment, the mixture comprises about 50% by volume formic acid and about 50% by volume dichloromethane. In one embodiment, polyamides useful in the present disclosure have the general formula -[(CH2) x C(O)NH] n-, where x is an integer between about 8 and 12, and n represents the number of repeat units in the polyamide structure. Within this embodiment is the resin known as Nylon 11 (CAS Number 9012-03-07). Nylon 11 is commercially available from Arkema under the trademark Rilsan® Polyamide 11. Nylon 11 can be produced by polymerization of 11-aminoundecanoic acid. Also within this embodiment is the commercially available polyamide known as Nylon 12, where x is 11 in the above formula. Nylon 12 can be made from ω-aminolauric acid or laurolactam monomers, each of which has 12 carbon atoms (CAS Number 24937-16-4).

[0086] In certain embodiments of the present disclosure, the polyamides are those commonly referred to as nylon 11 and nylon 12. Such nylon polymers are available in a variety of grades that vary with respect to molecular weight, density, modulus, and melting point. All such polyamides are soluble in the formic acid / dichloromethane mixture described above, but are generally considered to be insoluble in aqueous solutions. Such polyamides are utilized as dilute solutions in the formic acid / dichloromethane mixture. In one embodiment, the polyamides are utilized at a concentration of about 1-4% by weight in a 50 / 50 (volume %) mixture of formic acid and dichloromethane.

[0087] In various examples of the methods and articles of the present disclosure, the membrane of the present disclosure may be included in a porous filter membrane. As used herein, a "porous filter membrane" is a porous solid that contains porous (e.g., microporous) interconnected passages that extend from one surface of the membrane to the opposite surface of the membrane. The passages generally provide a tortuous tunnel or path through which the liquid being filtered must pass. Any particles contained in this liquid that are larger than the pores are prevented from entering the microporous membrane or are trapped within the pores of the microporous membrane (i.e., are removed by a sieving-type filtration mechanism) as the fluid containing these particles passes through the microporous membrane. Particles smaller than the pores can also be trapped or absorbed on the pore structure and removed, for example, by a non-sieving filtration mechanism. The liquid and possibly a reduced amount of particles or dissolved materials pass through the microporous membrane.

[0088] The exemplary porous polymeric filter membranes described herein for various embodiments can be characterized by physical characteristics including pore size, bubble point, and porosity.

[0089] Porous polymeric filter membranes may have any pore size that allows the filter membrane to be effective to function as a filter membrane, including pores of a size (average pore size) that may be considered, for example, a microporous filter membrane or an ultrafilter membrane, as described herein. Examples of useful or preferred porous membranes may have an average pore size ranging from about 0.001 microns to about 1 or 2 microns, e.g., 0.01 to 0.8 microns, with the pore size being selected based on one or more factors including the particle size or type of impurity to be removed, the pressure and pressure drop requirements, and the viscosity requirements of the liquid being processed by the filter. Ultrafilter membranes may have an average pore size ranging from 0.001 microns to about 0.05 microns. Pore size is often reported as the average pore size of the porous material, which may be measured by known techniques such as mercury porosimetry (MP), scanning electron microscopy (SEM), liquid displacement (LLDP) or atomic force microscopy (AFM).

[0090] Bubble point is also a known characteristic of porous membranes. According to the bubble point test method, a sample of a porous polymeric filter membrane is immersed in a liquid having a known surface tension, wetted with a liquid having a known surface tension, and a gas pressure is applied to one side of the sample. The gas pressure is gradually increased. The minimum pressure at which gas will flow through the sample is called the bubble point. To determine the bubble point of a porous material, a sample of the porous material is immersed in ethoxy-nonafluorobutane HFE7200 (available from 3M) at a temperature of 20 to 25 degrees Celsius (e.g., 22 degrees Celsius) and wetted with ethoxy-nonafluorobutane HFE7200. Gas pressure is applied to one side of the sample by using compressed air, and the gas pressure is gradually increased. The minimum pressure at which gas will flow through the sample is called the bubble point. Examples of useful bubble points of porous polymeric filter membranes useful or preferred according to the present specification, measured using the procedure described above, can range from about 20 to about 200 psi. The porous polymeric filter layer described can have any porosity that allows the porous polymeric filter layer to be effective as described herein.Exemplary porous polymeric filter layers can have relatively high porosity, for example, at least 60, 70 or 80% porosity.As used herein, and in the technical field of porous bodies, the "porosity" of a porous body (sometimes referred to as porosity) is a measure of the void (i.e., "empty") space within the porous body as a percentage of the total volume of the porous body, and is calculated as the ratio of the volume of the voids of the porous body to the total volume of the porous body.A porous body with a porosity of 0% is completely solid.

[0091] The described porous polymeric filter membranes may be in the form of sheets or hollow fibers having any useful thickness, for example, a thickness ranging from 5 to 100 microns, for example from 10 or 20 to 50 or 80 microns.

[0092] The filter membranes herein may be useful in any type of industrial or life science process that requires high purity liquid materials as input. Non-limiting examples of such processes include processes for making microelectronic or semiconductor devices, a specific example of which is a method for filtering liquid processing materials (e.g., solvents or solvent-containing liquids) used for semiconductor photolithography. Examples of contaminants present in processing liquids or solvents used to make microelectronic or semiconductor devices may include metal ions dissolved in the liquid, solid particulate matter suspended in the liquid, and gelled or solidified materials present in the liquid (e.g., produced during photolithography).

[0093] The filter membrane can be useful for removing dissolved or suspended contaminants or impurities from liquids flowing through the coated filter membrane, either by sieving or non-sieving mechanisms, preferably by both combined non-sieving and sieving mechanisms. In the case of the second, third and fourth aspects of the present disclosure, the lower porous hydrophobic filter membrane itself (before conversion to the composite filter membrane of the present disclosure) can exhibit effective sieving and non-sieving filtration properties, as well as desirable flow properties. The composite filter membrane of the present disclosure can exhibit equivalent sieving filtration properties, useful or equivalent (not excessively reduced) flow properties, and improved (e.g., substantially improved) non-sieving filtration properties, compared to the lower hydrophobic polymeric membrane utilized as the starting material.

[0094] Specific examples of the described filter membranes can be used to purify liquid chemicals used or useful in semiconductor or microelectronic manufacturing applications, for example, to filter liquid solvents or other process fluids used in semiconductor photolithography processes. Some specific non-limiting examples of solvents that can be filtered using the described filter membranes include n-butyl acetate (nBA), isopropyl alcohol (IPA), 2-ethoxyethyl acetate (2EEA), xylene, cyclohexanone, ethyl lactate, methyl isobutyl carbinol (MIBC), methyl isobutyl ketone (MIBK), isoamyl acetate, undecane, propylene glycol methyl ether (PGME) and propylene glycol monomethyl ether acetate (PGMEA), and a mixture of propylene glycol monomethyl ether (PGME) and PGMEA (7:3). The exemplary filter membranes described may be effective in removing metals from solvents containing water, amines, or both, such as bases and aqueous bases, such as NH4OH, tetramethylammonium hydroxide (TMAH), and equivalent solutions that may optionally contain water. In some embodiments, a liquid containing a solvent selected from tetramethylammonium hydroxide (TMAH) or NH4OH is passed through a filter having a membrane described herein to remove metals from the solvent. In some embodiments, passing the solvent-containing liquid through the membrane to remove metals from the solvent-containing liquid results in a reduction in the concentration of the metal in the solvent-containing liquid.

[0095] The filter membrane of the present disclosure can also be characterized with respect to the dye-binding capacity of the filter membrane. Specifically, charged dyes can be bound to the surface of the filter membrane. The amount of dye that can be bound to the filter membrane can be quantitatively measured by spectroscopy based on the difference in the measured absorption readings of the membrane at the absorption frequency of the dye. Dye-binding capacity can also be evaluated by using negatively charged dyes and by using positively charged dyes.

[0096] Furthermore, the filter membrane as described can be characterized by the flow rate or flux of liquid flow through the filter membrane. The flow rate must be high enough to allow the filter membrane to be efficient and effective in filtering the flow of fluid through the filter membrane. The flow rate, or, alternatively, the resistance to the flow of liquid through the filter membrane, can be measured in terms of flow rate or flow time. The filter membranes described herein can have relatively low flow times and excellent filtration performance (e.g., as measured by particle retention, dye binding capacity, or both), preferably in combination with a relatively high bubble point. An example of a useful or preferred isopropanol flow time can be less than about 20,000 seconds / 500 mL, such as less than about 4,000 or 2,000 seconds / 500 mL.

[0097] The membrane isopropanol (IPA) flow time reported herein is 13.8 cm for 500 ml of IPA fluid at 14.2 psi and a temperature of 21 degrees Celsius. 2 The time required for a substance to pass through a membrane having an effective surface area of ​​100 μm is determined.

[0098] In some embodiments, the composite membranes described herein can have flow times that are approximately equal to or greater than those of the same filter membrane that does not contain the polyamide coating and the co-reacted crosslinker / monomer coating. In other words, creating a composite membrane from an underlying porous hydrophobic filter membrane does not have a substantial adverse effect on the flow properties of the filter membrane, and may even improve the filtration function of the filter membrane, particularly the non-sieving filtration function of the membrane, as measured, for example, by dye binding capacity, particle retention, or both, depending on the pore size.

[0099] The water flow time of the membrane can be determined by cutting the membrane into a 47 mm disk, wetting it with water, and then placing the disk in a filter holder attached to a reservoir for holding a fixed amount of water. The reservoir is connected to a pressure regulator. Water is allowed to flow through the membrane under a differential pressure of 14.2 psi (pounds per square inch). After equilibrium is reached, the time it takes for 500 ml of water to flow through the membrane is recorded.

[0100] In some embodiments, the composite membrane of the present disclosure can have a flow time that is approximately equal to and not significantly greater than that of the same filter membrane that does not contain the polyamide coating (second aspect) and the crosslinker / charged acrylamide monomer coating (third aspect) that is reacted together, or the composite membrane of the fourth aspect, embodiment II. In other words, making a composite membrane from a lower porous hydrophobic filter membrane does not have a substantial adverse effect on the flow properties of the filter membrane, and can still improve the filtration function of the filter membrane, in particular the non-sieving filtration function of the membrane, as measured, for example, by dye binding capacity, particle retention, or both. According to some filter membranes, the measured flow time of the filter membrane of the present disclosure can be different (e.g., greater) than the flow time of the lower hydrophobic porous filter membrane by 30% or 20% or less, for example, 10%, 5, or 3% or less.

[0101] The described filter membranes can be included in a larger filter structure, such as a multi-layer filter assembly or filter cartridge used in a filtration system. The filtration system places the filter membrane in a filter housing, for example as part of a multi-layer filter assembly or as part of a filter cartridge, to expose the filter membrane to the flow path of the liquid chemical so that at least a portion of the liquid chemical flow passes through the filter membrane, so that the filter membrane removes a certain amount of impurities or contaminants from the liquid chemical. The structure of the multi-layer filter assembly or filter cartridge can include one or more of a variety of additional materials and structures that support the composite filter membrane in the filter assembly or filter cartridge to allow fluid to flow from the filter inlet through the composite membrane (including the filter layer) and through the filter outlet, thereby passing the composite filter membrane as it passes through the filter. The filter membrane supported by the filter assembly or filter cartridge can be any useful shape, such as a pleated cylinder, a cylindrical pad, one or more non-pleated (flat) cylindrical sheets, a pleated sheet, among others.

[0102] An example of a filter structure comprising a filter membrane in the form of a pleated cylinder can be made to include the following components: a rigid or semi-rigid core that supports the coated pleated cylindrical filter membrane at the inner opening of the coated pleated cylindrical filter membrane; a rigid or semi-rigid cage that supports or surrounds the outside of the coated pleated cylindrical filter membrane at the outside of the filter membrane; optional end pieces or "packs" located at each of the two opposite ends of the coated pleated cylindrical filter membrane; a filter housing that includes an inlet and an outlet, any of which may be included in the filter structure but may not be required. The filter housing can be of any useful desired size, shape and material, and can preferably be made from a suitable polymeric material.

[0103] The following detailed description should be read with reference to the drawings, in which like elements in different drawings are numbered the same. The detailed description and drawings, which are not necessarily to scale, depict exemplary embodiments and are not intended to limit the scope of the present disclosure. The illustrated exemplary embodiments are intended as examples only. Selected features of any exemplary embodiment may be incorporated into additional embodiments, unless expressly stated to the contrary.

[0104] As an example, FIG. 1 shows a filter component 30 produced from a pleated cylindrical component 10 and an end piece 22 along with other optional components. The cylindrical component 10 includes a filter membrane 12 and is pleated as described herein. The end piece 22 is attached (e.g., "stuffed") to one end of the cylindrical filter component 10. The end piece 22 can be preferably made of a melt-processable polymeric material. A core (not shown) can be disposed in the inner opening 24 of the pleated cylindrical component 10, and a cage (not shown) can be disposed around the outside of the pleated cylindrical component 10. A second end piece (not shown) can be attached ("stuffed") to a second end of the pleated cylindrical component 30. The resulting pleated cylindrical component 30 with two opposing stuffed ends and the optional core and cage can then be placed into a filter housing including an inlet and an outlet, configured such that all of the fluid entering the inlet must pass through the filter membrane 12 before exiting the filter at the outlet. EXAMPLES

[0105] Porosity Measurement Bubble Point The porosimetry bubble point test method measures the pressure required to push air through the wetted pores of a membrane. The bubble point test is a well-known method for determining the pore size of a membrane. To determine the bubble point of a porous material, a sample of the porous material is immersed in ethoxy-nonafluorobutane HFE7200 (available from 3M) at a temperature of 20-25 degrees Celsius (e.g., 22 degrees Celsius) and wetted with ethoxy-nonafluorobutane HFE7200. Gas pressure is applied to one side of the sample by using compressed air, and the gas pressure is gradually increased. The minimum pressure at which gas will flow through the sample is called the bubble point.

[0106] As used herein, the "surface energy" (surface free energy) of a surface is considered to be equal to the surface tension of the highest surface tension liquid that wets the surface within 2 seconds of contact (see Example 6, Surface Energy Measurements) (also called the "Wetting Liquid Surface Tension" test or "Standard Liquid" test), and generally corresponds to the relative hydrophobicity / hydrophilicity of the surface. In some embodiments, the membrane has a surface energy of greater than about 30 dynes / centimeter, measured as the surface tension of the highest surface tension liquid that wets the surface within 2 seconds, as described in Example 6.

[0107] Example 1: Preparation of 3% nylon 11 in a mixture of formic acid and dichloromethane. A mixture containing 3 wt% nylon 11 was prepared using the following method. First, a 1:1 volume ratio of ≥96% formic acid (Sigma-Aldrich) and dichloromethane (Sigma-Aldrich) was prepared by slowly adding 500 mL of ≥96% formic acid to 500 mL of dichloromethane, and the solution was stirred at room temperature. Next, 30 grams of nylon 11 (Sigma-Aldrich) was added to 970 grams of a 1:1 volume ratio mixture of formic acid and dichloromethane. The resulting mixture was gently stirred for 16 hours to obtain a homogenous solution of 3 wt% nylon 11 in a 1:1 mixture of formic acid and dichloromethane.

[0108] Example 2: Preparation of Asymmetric 3 nm UPE Membrane Coated with Nylon 11 Similar to Example 1, a 3 wt% solution of nylon 11 in a 1:1 mixture of formic acid and dichloromethane was prepared. A sheet of Asymmetric 3 nm UPE Membrane (Entegris) was placed on a sheet of polyethylene and an excess of 3 wt% nylon 11 solution was dropped onto the membrane and immediately covered with the polyethylene sheet. Excess solution was removed from the membrane by firmly rolling a rubber roller over the polyethylene sandwich laid flat on a table. It was observed that the membrane turned slightly transparent, indicating that the membrane was wetted with and absorbed the coating solution. The membrane sheet was removed from the polyethylene sandwich, restrained in a frame and allowed to dry at room temperature. Prior to coating with nylon 11, the Asymmetric 3 nm UPE Membrane was 95 um thick, had an IPA flow time of 4080 sec / 500 mL, an ethoxy-nonafluorobutane HFE7200 average bubble point of 92 psi, a surface energy of 30 dynes / cm and a surface area of ​​0.0 μg / cm. 2 The resulting film after coating with nylon 11 was 95um thick, had an IPA flow time of 5730sec / 500mL, an HFE average bubble point of 100psi, a surface energy of 48dynes / cm, and a Ponceau S dye binding capacity of 9.1μg / cm 2 The increase in flow time, bubble point, surface energy and Ponceau S dye binding capacity indicates that the membrane was coated with nylon 11.

[0109] Example 3: Preparation of Asymmetric 3 nm UPE Membrane Coated with Nylon 12 Similar to Example 1, a 3 wt% solution of nylon 12 in a 1:1 mixture of formic acid and dichloromethane was prepared. A sheet of Asymmetric 3 nm UPE Membrane (Entegris) was placed on a sheet of polyethylene and an excess of 3 wt% nylon 12 solution was dropped onto the membrane and immediately covered with the polyethylene sheet. Excess solution was removed from the membrane by rolling a rubber roller firmly over the polyethylene sandwich laid flat on a table. It was observed that the membrane turned slightly transparent, indicating that the membrane was wetted with and absorbed the coating solution. The membrane sheet was removed from the polyethylene sandwich, restrained in a frame and allowed to dry at room temperature. Prior to coating with nylon 12, the Asymmetric 3 nm UPE Membrane was 95 um thick, had an IPA flow time of 4080 sec / 500 mL, an ethoxy-nonafluorobutane HFE7200 average bubble point of 92 psi, a surface energy of 30 dynes / cm and a surface area of ​​0.0 μg / cm. 2 The resulting film after coating with nylon 12 was 95um thick, had an IPA flow time of 4330sec / 500mL, an ethoxy-nonafluorobutane HFE7200 average bubble point of 98psi, a surface energy of 45dynes / cm, and a Ponceau S dye binding capacity of 4.9μg / cm. 2 The increase in flow time, bubble point, surface energy and Ponceau S dye binding capacity indicates that the membrane was coated with nylon 12.

[0110] Example 4: Coating Stability for Nylon 12 Coated UPE Compared to Nylon 6 Coated UPE A 3 nm UPE membrane coated with nylon 12 was prepared as in Example 2. A 3 nm UPE membrane coated with nylon 6 was prepared as in Example 2, except that the nylon was nylon 6 (Sigma-Aldrich) and the solvent consisted only of ≥96% formic acid. To evaluate the acid stability of the coating, the resulting membrane was exposed to ≥96% formic acid by rotating for 24 hours. After 24 hours of exposure to ≥96% formic acid, the treated membrane was rinsed with deionized water until a stable pH was obtained. The stability of the coating was evaluated by Fourier transform infrared spectroscopy (FTIR) to compare the nylon / UPE peak ratios initially and after exposure to formic acid. The nylon 6 coated UPE membrane lost 90.2% of its nylon coating as determined by FTIR analysis, whereas the nylon 12 coated UPE membrane lost 0.0% of its nylon 12 coating. This data suggests that the nylon 12 coated UPE membrane exhibits improved stability against acid exposure compared to the nylon 6 coated UPE membrane.

[0111] Example 5: Preparation of nylon 11 membrane from formic acid and dichloromethane solvent system A 6 wt% solution of nylon 11 in a 1:1 mixture of formic acid and dichloromethane was prepared similar to Example 1. The solution was cast onto a glass plate using a film applicator set at a thickness of 400 um. The cast nylon 11 / formic acid / dichloromethane film was allowed to evaporate at room temperature. This resulted in a white sheet of nylon 11 membrane that was easily separated from the glass plate. The resulting nylon 11 membrane was determined to have an IPA average bubble point of 17.2 psi and an IPA flow time of 550 sec / 500 mL.

[0112] Example 6 - Surface Energy Measurements A liquid will wet a porous polymer membrane if the surface tension of the liquid is less than the surface free energy of the membrane. In the present disclosure, a porous membrane is wetted by a liquid when the membrane is placed in contact with the liquid with the highest surface tension in a series of inert (standard) liquids, and the membrane spontaneously wicks the liquid within 2 seconds without the application of external pressure.

[0113] In a representative example, a series of inert (standard) liquids were prepared by mixing methanol and water in different mass ratios. The surface tensions of the resulting liquids are shown in Figure 4 (plotted using surface tension data published in Lange's Handbook of Chemistry 11th edition).

[0114] Aspects of the Disclosure In a first aspect, the present disclosure provides a composite porous filter membrane comprising: a porous hydrophobic polymeric filter material having a coating thereon, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane; A composite porous filter membrane is provided.

[0115] In a second aspect, the present disclosure provides a method for producing a polyamide polymer having the formula -[(CH) x C(O)NH] n -, where x is an integer from about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

[0116] In a third aspect, the present disclosure provides the membrane of the first or second aspect, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

[0117] In a fourth aspect, the present disclosure provides a method for producing a membrane comprising the steps of: (i) a surface energy of about 20 to about 100 dynes / cm; (ii) isopropanol flow times of about 150 to about 20,000 seconds / 500 mL, measured at 14.2 psi; (iii) a bubble point of about 20 to about 200 psi when measured using an ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C.; and (iv) about 1 and about 30 μg / cm 2 Ponceau S dye binding capacity between about 1 and about 30 μg / cm 2 Methylene blue dye binding capacity (MB DBC) The membrane of any one of the first three aspects is provided, having

[0118] In a fifth aspect, the disclosure provides the membrane of any one of the first four aspects, wherein the hydrophobic polymer filter membrane is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride, and polyarylsulfone.

[0119] In a sixth aspect, the present disclosure provides the membrane of any one of the first five aspects, wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene).

[0120] In a seventh aspect, the present disclosure provides a porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane.

[0121] In an eighth aspect, the present disclosure provides a polyamide polymer having the formula -[(CH2) x C(O)NH] n -, where x is an integer from about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

[0122] In a ninth aspect, the present disclosure provides the membrane of any of the seventh to eighth aspects, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

[0123] In a tenth aspect, the present disclosure provides a method for producing a membrane comprising the steps of: Isopropanol flow times of about 150 to about 20,000 seconds / 500 mL measured at 14.2 psi and Bubble point of about 20 to about 200 psi when measured using ethoxy-nonafluorobutane HFE7200 at a temperature of about 22°C The membrane of any one of the first to ninth aspects is provided, having

[0124] In an eleventh aspect, the present disclosure provides a method for producing a membrane comprising the steps of: Approximately 1 and approximately 100 μg / cm 2 Ponceau S dye binding capacity between about 1 and about 100 μg / cm 2 Methylene blue dye binding capacity (MB DBC) The membrane of any of the seventh to tenth aspects is provided, having

[0125] In a twelfth aspect, the disclosure provides a porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, the membrane being subsequently coated with a free radical reaction product of (i) at least one crosslinker and (ii) at least one monomer in the presence of a photoinitiator.

[0126] In a thirteenth aspect, the present disclosure provides a polyamide polymer having the formula -[(CH2) x C(O)NH] n -, where x is an integer from about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

[0127] In a fourteenth aspect, the present disclosure provides the membrane of the twelfth or thirteenth aspect, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

[0128] In a fifteenth aspect, the present disclosure provides a method for producing a membrane comprising the steps of: (i) a surface energy of about 30 to about 100 dynes / cm; (ii) isopropanol flow times of about 150 to about 20,000 seconds / 500 mL, measured at 14.2 psi; (iii) a bubble point of about 20 to about 200 psi when measured using an ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C.; and (iv) about 1 and 30 μg / cm 2 Ponceau S dye binding capacity between about 1 and about 30 μg / cm 2 Methylene blue dye binding capacity (MB DBC) The membrane of the twelfth to fourteenth aspects is provided, having

[0129] In a sixteenth aspect, the present disclosure provides the membrane of any of the twelfth to fifteenth aspects, wherein the crosslinker is selected from methylene bis(acrylamide), tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, divinyl sulfone, divinyl benzene, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and ethylene glycol divinyl ether.

[0130] In a seventeenth aspect, the present disclosure provides a process for the preparation of a polymerizable compound comprising the steps of: a) preparing a polymerizable compound having a structure in which the monomer is selected from the group consisting of 2-(dimethylamino)ethyl hydrochloride acrylate, [2-(acryloyloxy)ethyl]trimethylammonium chloride, 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl) methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyl trimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl) methacrylamide hydrochloride, N-(3-aminopropyl) methacrylamide hydrochloride, diallyldimethylammonium chloride, a and n is 0, 1 or 2. The membrane of any of the twelfth to fifteenth aspects is provided, wherein the reactive group is selected from: disodium acrylate, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride, vinylbenzyltrimethylammonium chloride and acrylamidopropyltrimethylammonium chloride, 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl acrylate potassium salt, 2-propylacrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethyl maleate, 3-sulfopropyl methacrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid, and vinylphosphonic acid.

[0131] In an eighteenth aspect, the present disclosure provides the membrane of any of the twelfth to fifteenth aspects, wherein the monomer is selected from 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl acrylate potassium salt, 2-propylacrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethyl maleate, 3-sulfopropyl methacrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid, and vinylphosphonic acid.

[0132] In a nineteenth aspect, the present disclosure provides the membrane of any one of the twelfth to fifteenth aspects, wherein the monomer is selected from acrylamide, N,N-dimethylacrylamide, N-(hydroxyethyl)acrylamide, diacetone acrylamide, N-[tris(hydroxymethyl)methyl]acrylamide, N-(isobutoxymethyl)acrylamide, N-(3-methoxypropyl)acrylamide, 7-[4-(trifluoromethyl)coumarin]acrylamide, N-isopropylacrylamide, 2-(dimethylamino)ethyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, ethyl acrylate, 2-hydroxyethyl acrylate, butyl acrylate, ethylene glycol methyl ether acrylate, 4-hydroxybutyl acrylate, hydroxypropyl acrylate, 4-acetoxyphenethyl acrylate, benzyl acrylate, 1-vinyl-2-pyrrolidinone, vinyl acetate, ethyl vinyl ether, vinyl 4-tert-butylbenzoate, and phenyl vinyl sulfone.

[0133] In a twentieth aspect, the present disclosure provides a porous hydrophobic polymeric filter membrane having coated thereon as a first coating a polyamide coating, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, thereby providing a polyamide coated membrane, said polyamide coated membrane having thereon a second coating that is a free radical reaction product of (i) at least one crosslinker and (ii) at least one monomer in the presence of a photoinitiator.

[0134] In a twenty-first aspect, the present disclosure provides a polyamide polymer having the formula -[(CH2) x C(O)NH] n -, where x is an integer from about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

[0135] In a twenty-second aspect, the present disclosure provides the membrane of the twentieth aspect, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

[0136] In a twenty-third aspect, the present disclosure provides a method for producing a membrane comprising the steps of: (i) a surface energy of about 30 to about 100 dynes / cm; (ii) isopropanol flow times of about 150 to about 20,000 seconds / 500 mL, measured at 14.2 psi; (iii) a bubble point of about 20 to about 200 psi when measured using an ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C.; and (iv) about 1 and about 30 μg / cm 2 Ponceau S dye binding capacity between about 1 and about 30 μg / cm 2 Methylene blue dye binding capacity (MB DBC) The membrane of the twentieth or twenty-first aspect is provided, having

[0137] In a twenty-fourth aspect, the present disclosure provides the membrane of the twentieth, twenty-first, twenty-second or twenty-third aspects, wherein the hydrophobic polymer filter membrane is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride and polyarylsulfone.

[0138] In a twenty-fifth aspect, the present disclosure provides the membrane of any one of the twentieth to twenty-fourth aspects, wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene).

[0139] In a twenty-sixth aspect, the present disclosure provides the membrane of any one of the twentieth to twenty-fifth aspects, wherein the crosslinker is selected from methylene bis(acrylamide), tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, divinyl sulfone, divinyl benzene, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and ethylene glycol divinyl ether.

[0140] In a twenty-seventh aspect, the present disclosure provides a process for the preparation of a methacrylic acid ester copolymer comprising the monomer selected from the group consisting of 2-(dimethylamino)ethyl hydrochloride acrylate, [2-(acryloyloxy)ethyl]trimethylammonium chloride, 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl) methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyl trimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl) methacrylamide hydrochloride, N-(3-aminopropyl) methacrylamide hydrochloride, diallyldimethylammonium chloride, acrylamidopropyl tri ... and the like. The membrane of any one of the twentieth to twenty-sixth aspects is provided, wherein the reactive group is selected from among vinyl amine hydrochloride, vinyl imidazolium hydrochloride, vinyl pyridinium hydrochloride, vinyl benzyl trimethyl ammonium chloride and acrylamidopropyl trimethyl ammonium chloride, 2-ethyl acrylic acid, acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl acrylate potassium salt, 2-propyl acrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethyl maleate, 3-sulfopropyl methacrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinyl sulfonic acid, and vinyl phosphonic acid.

[0141] In a twenty-eighth aspect, the present disclosure provides the membrane of any one of the twentieth to twenty-sixth aspects, wherein the monomer is selected from 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl acrylate potassium salt, 2-propylacrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethyl maleate, 3-sulfopropyl methacrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid, and vinylphosphonic acid.

[0142] In a twenty-ninth aspect, the present disclosure provides the membrane of any one of the twentieth to twenty-sixth aspects, wherein the monomer is selected from acrylamide, N,N-dimethylacrylamide, N-(hydroxyethyl)acrylamide, diacetone acrylamide, N-[tris(hydroxymethyl)methyl]acrylamide, N-(isobutoxymethyl)acrylamide, N-(3-methoxypropyl)acrylamide, 7-[4-(trifluoromethyl)coumarin]acrylamide, N-isopropylacrylamide, 2-(dimethylamino)ethyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, ethyl acrylate, 2-hydroxyethyl acrylate, butyl acrylate, ethylene glycol methyl ether acrylate, 4-hydroxybutyl acrylate, hydroxypropyl acrylate, 4-acetoxyphenethyl acrylate, benzyl acrylate, 1-vinyl-2-pyrrolidinone, vinyl acetate, ethyl vinyl ether, vinyl 4-tert-butylbenzoate, and phenyl vinyl sulfone.

[0143] In a thirtieth aspect, the disclosure provides a porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, said membrane grafted with pendant hydrophilic groups selected from hydroxyl groups, amine groups, carboxylic acid groups or combinations thereof, and pendant ionic groups different from the pendant hydrophilic groups.

[0144] In a thirty-first aspect, the present disclosure provides a porous composite filter membrane comprising a porous hydrophobic polymeric filter membrane having coated thereon a coating, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, thereby providing a polyamide coated membrane, which is subsequently grafted with pendant hydrophilic groups selected from hydroxyl groups, amine groups, carboxylic acid groups or combinations thereof, and pendant ionic groups different from the pendant hydrophilic groups.

[0145] In a thirty-second embodiment, the present disclosure provides a polyamide polymer having the formula -[(CH2) x C(O)NH] n -, wherein x is an integer of about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

[0146] In a thirty-third aspect, the present disclosure provides the membrane of the thirtieth or thirty-first aspect, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

[0147] In a thirty-fourth aspect, the present disclosure provides a method for the preparation of a medicament for the treatment of a cancer, comprising the steps of: a. Surface energy of about 30 to about 100 dynes / cm; b. Isopropanol flow times of about 150 to about 20,000 seconds / 500 mL measured at 14.2 psi; c. a bubble point of about 20 to about 200 psi when measured using ethoxy-nonafluorobutane HFE7200 at a temperature of about 22° C.; and d. Approximately 1 and approximately 300 μg / cm 2 Ponceau S dye binding capacity between about 1 and about 300 μg / cm 2 Methylene blue dye binding capacity (MB DBC) The membrane of the 30th or 31st aspect is provided, having

[0148] In a thirty-fifth aspect, the present disclosure provides the membrane of the thirty-first aspect, wherein the hydrophobic polymeric filter material is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride, and polyarylsulfone.

[0149] In a thirty-sixth aspect, the present disclosure provides the membrane of the thirty-first aspect, wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene).

[0150] In a thirty-seventh aspect, the present disclosure provides a method for preparing a composite porous filter membrane of any one of the first to sixth aspects, comprising: a. dissolving a polyamide polymer in a mixture of formic acid and dichloromethane to form a polyamide solution; b. contacting a porous hydrophobic polymeric filter material with the polyamide solution to provide a polyamide-coated membrane; c. immersing the polyamide coated membrane in an aqueous solution comprising water; d. rinsing the polyamide coated membrane with C1-C4 alcohols and water; e. drying the polyamide coated membrane; The present invention provides a method comprising:

[0151] In a thirty-eighth aspect, the present disclosure provides the method of the thirty-seventh aspect, wherein the polyamide is selected from nylon 11 and nylon 12.

[0152] In a thirty-ninth aspect, the present disclosure provides a method for preparing a composite porous filter membrane of any one of the twelfth to twenty-first aspects, comprising: i. dissolving a hydrophilic polyamide polymer in a mixture of formic acid and dichloromethane to form a polyamide solution; ii. contacting a porous hydrophobic polymeric filter material with the polyamide solution to provide a polyamide-coated membrane; iii. immersing the polyamide coated membrane in an aqueous bath solution comprising water, at least one crosslinking agent, at least one monomer, and at least one photoinitiator; iv. removing the resulting film from the bath and exposing it to ultraviolet radiation; and then v. rinsing the polyamide-coated membrane with C1-C4 alcohol and water; vi. drying the composite porous filter membrane; The present invention provides a method comprising:

[0153] In a fortieth aspect, the present disclosure provides the method of the thirty-ninth aspect, wherein the polyamide is selected from nylon 11 and nylon 12.

[0154] In a forty-first aspect, the present disclosure provides a method for preparing the composite membrane of the thirty-first aspect, comprising: contacting the membrane of the first embodiment with a photoinitiator solution comprising a solvent and a photoinitiator to deposit a photoinitiator on a surface of the polyamide polymer; after contacting the surface with the photoinitiator solution to dispose a photoinitiator on the surface, contacting the surface with a monomer solution comprising a charged monomer, the charged monomer comprising an ionic group; exposing the surface to electromagnetic radiation to graft ionic groups onto the polyamide polymer; The present invention provides a method comprising:

[0155] In a forty-second embodiment, the present disclosure provides a method for preparing the composite porous filter membrane of the thirtieth embodiment, comprising: contacting the membrane of the seventh embodiment with a photoinitiator solution comprising a solvent and a photoinitiator to deposit a photoinitiator on the surface of the polyamide polymer; after contacting the surface with the photoinitiator solution to dispose a photoinitiator on the surface, contacting the surface with a monomer solution comprising a charged monomer, the charged monomer comprising an ionic group; exposing the surface to electromagnetic radiation to graft ionic groups onto the polyamide polymer; The present invention provides a method comprising:

[0156] In a forty-third aspect, the present disclosure provides a method for preparing the membrane of the twelfth aspect, comprising: i. immersing the membrane of the seventh embodiment in an aqueous bath solution comprising water, at least one crosslinking agent, at least one monomer, and at least one photoinitiator; ii. removing the resulting film from the bath and exposing it to ultraviolet radiation; and then iii. rinsing the membrane with C1-C4 alcohol and water and drying the membrane; The present invention provides a method comprising:

[0157] In a forty-fourth aspect, the present disclosure provides a method for removing impurities from a liquid, the method comprising contacting the liquid with a membrane of any one of the first to thirty-sixth aspects.

[0158] In a forty-fifth aspect, the present disclosure provides a filter comprising the membrane of any one of the first to sixth aspects.

[0159] In a forty-sixth aspect, the present disclosure provides a filter comprising the membrane of any one of the seventh to eleventh aspects.

[0160] In a forty-seventh aspect, the present disclosure provides a filter comprising the membrane of any one of the twelfth to twenty-first aspects.

[0161] In a forty-eighth aspect, the present disclosure provides a filter comprising the membrane of any one of the twenty-second to twenty-ninth aspects.

[0162] In a forty-ninth aspect, the present disclosure provides a filter comprising the membrane of the thirtieth aspect.

[0163] In a fiftieth aspect, the present disclosure provides a filter comprising the membrane of the thirty-first aspect.

[0164] Having thus described some exemplary embodiments of the present disclosure, those skilled in the art will readily appreciate that still other embodiments may be made and used within the scope of the claims appended hereto. Many advantages of the present disclosure covered by this document have been set forth in the foregoing description. It will be understood, however, that the present disclosure is in many respects merely illustrative. Changes may be made in detail without departing from the scope of the present disclosure. The scope of the present disclosure is, of course, to be defined in the language in which the appended claims are expressed.

Claims

1. 1. A composite porous filter membrane comprising: a porous hydrophobic polymeric filter material having a coating thereon, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane; Composite porous filter membrane.

2. The polyamide polymer has the formula -[(CH ２ ) ｘ C(O)NH] ｎ 2. The membrane of claim 1, having a repeat unit structure of: -, where x is an integer from about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

3. 3. The membrane of claim 1 or 2, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

4. The membrane has the following properties: (i) a surface energy of about 20 to about 100 dynes / cm; (ii) an isopropanol flow time of about 150 to about 20,000 seconds / 500 mL measured at 14.2 psi; (iii) a bubble point of about 20 to about 200 psi, as measured using an ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.; and (iv) about 1 and about 30 μg / cm ２ Ponceau S dye binding capacity between about 1 and about 30 μg / cm ２ Methylene blue dye binding capacity (MB DBC) The membrane according to any one of claims 1 to 3, having

5. 5. The membrane of any one of claims 1 to 4, wherein the hydrophobic polymeric filter membrane is selected from density polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride and polyarylsulfone.

6. 6. The membrane of claim 5, wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene).

7. A porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane.

8. The polyamide polymer has the formula -[(CH ２ ) ｘ C(O)NH] ｎ 8. The membrane of claim 7, having a repeat unit structure of: -, where x is an integer from about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

9. 9. The membrane of claim 7 or 8, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

10. The membrane has the following properties: an isopropanol flow time of about 150-20,000 seconds / 500 mL measured at 14.2 psi; and A bubble point of about 20 to about 200 psi when measured using an ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.

10. The membrane of claim 7, having the formula:

11. The membrane has the following properties: About 1 and about 100 μg / cm ２ Ponceau S dye binding capacity between about 1 and about 100 μg / cm ２ Methylene blue dye binding capacity (MB DBC) The membrane according to any one of claims 7 to 10, having

12. 1. A porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, the membrane being subsequently coated with a free radical reaction product of (i) at least one crosslinker and (ii) at least one monomer in the presence of a photoinitiator.

13. The polyamide polymer has the formula -[(CH ２ ) ｘ C(O)NH] ｎ 13. The membrane of claim 12, having a repeat unit structure of: -, where x is an integer from about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

14. 14. The membrane of claim 12 or 13, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

15. The membrane has the following properties: (i) a surface energy of about 30 to about 100 dynes / cm; (ii) an isopropanol flow time of about 150 to about 20,000 seconds / 500 mL measured at 14.2 psi; (iii) a bubble point of about 20 to about 200 psi, as measured using an ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.; and (iv) about 1 and 30 μg / cm ２ Ponceau S dye binding capacity between about 1 and about 30 μg / cm ２ Methylene blue dye binding capacity (MB DBC) The membrane according to any one of claims 12 to 14, having the following structure:

16. 16. The membrane according to any one of claims 12 to 15, wherein the crosslinking agent is selected from methylene bis(acrylamide), tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, divinyl sulfone, divinyl benzene, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and ethylene glycol divinyl ether.

17. The monomer is 2-(dimethylamino)ethyl hydrochloride acrylate, [2-(acryloyloxy)ethyl]trimethylammonium chloride, 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl)methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyltrimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl)methacrylamide hydrochloride, N-(3-aminopropyl)methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride 17. The membrane according to any one of claims 12 to 16, wherein the acrylic acid is selected from the group consisting of acrylic acid, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride, vinylbenzyltrimethylammonium chloride and acrylamidopropyltrimethylammonium chloride, 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl acrylate potassium salt, 2-propylacrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethyl maleate, 3-sulfopropyl methacrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid and vinylphosphonic acid.

18. 18. The membrane of any one of claims 12 to 17, wherein the monomer is selected from 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl acrylate potassium salt, 2-propylacrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethyl maleate, 3-sulfopropyl methacrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid and vinylphosphonic acid.

19. 19. The membrane of any one of claims 12 to 18, wherein the monomer is selected from acrylamide, N,N-dimethylacrylamide, N-(hydroxyethyl)acrylamide, diacetone acrylamide, N-[tris(hydroxymethyl)methyl]acrylamide, N-(isobutoxymethyl)acrylamide, N-(3-methoxypropyl)acrylamide, 7-[4-(trifluoromethyl)coumarin]acrylamide, N-isopropylacrylamide, 2-(dimethylamino)ethyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, ethyl acrylate, 2-hydroxyethyl acrylate, butyl acrylate, ethylene glycol methyl ether acrylate, 4-hydroxybutyl acrylate, hydroxypropyl acrylate, 4-acetoxyphenethyl acrylate, benzyl acrylate, 1-vinyl-2-pyrrolidinone, vinyl acetate, ethyl vinyl ether, vinyl 4-tert-butyl benzoate and phenyl vinyl sulfone.

20. 1. A porous hydrophobic polymeric filter membrane having coated thereon a polyamide coating as a first coating, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, thereby providing a polyamide coated membrane, said polyamide coated membrane having thereon a second coating that is the free radical reaction product of (i) at least one crosslinker and (ii) at least one monomer in the presence of a photoinitiator.

21. The polyamide polymer has the formula -[(CH ２ ) ｘ C(O)NH] ｎ 21. The membrane of claim 20, having a repeat unit structure of: -, where x is an integer from about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

22. 22. The membrane of claim 20 or 21, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

23. The membrane has the following properties: (i) a surface energy of about 30 to about 100 dynes / cm; (ii) an isopropanol flow time of about 150 to about 20,000 seconds / 500 mL measured at 14.2 psi; (iii) a bubble point of about 20 to about 200 psi, as measured using an ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.; and (iv) about 1 and about 30 μg / cm ２ Ponceau S dye binding capacity between about 1 and about 30 μg / cm ２ Methylene blue dye binding capacity (MB DBC) 23. The membrane of any one of claims 20 to 22, having

24. 24. The membrane of any one of claims 20 to 23, wherein the hydrophobic polymeric filter membrane is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride and polyarylsulfone.

25. 25. The membrane of claim 24, wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene).

26. 26. The membrane of any one of claims 20 to 25, wherein the crosslinking agent is selected from methylene bis(acrylamide), tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, divinyl sulfone, divinyl benzene, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and ethylene glycol divinyl ether.

27. The monomer is 2-(dimethylamino)ethyl hydrochloride acrylate, [2-(acryloyloxy)ethyl]trimethylammonium chloride, 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl)methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyltrimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl)methacrylamide hydrochloride, N-(3-aminopropyl)methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride 27. The membrane according to any one of claims 20 to 26, wherein the acrylic acid is selected from the group consisting of acrylic acid, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride, vinylbenzyltrimethylammonium chloride and acrylamidopropyltrimethylammonium chloride, 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl acrylate potassium salt, 2-propylacrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethyl maleate, 3-sulfopropyl methacrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid and vinylphosphonic acid.

28. 28. The membrane of any one of claims 20 to 27, wherein the monomer is selected from 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl acrylate potassium salt, 2-propylacrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, 2-methyl-2-propene-1-sulfonic acid sodium salt, mono-2-(methacryloyloxy)ethyl maleate, 3-sulfopropyl methacrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid and vinylphosphonic acid.

29. 29. The membrane of any one of claims 20 to 28, wherein the monomer is selected from acrylamide, N,N-dimethylacrylamide, N-(hydroxyethyl)acrylamide, diacetoneacrylamide, N-[tris(hydroxymethyl)methyl]acrylamide, N-(isobutoxymethyl)acrylamide, N-(3-methoxypropyl)acrylamide, 7-[4-(trifluoromethyl)coumarin]acrylamide, N-isopropylacrylamide, 2-(dimethylamino)ethyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, ethyl acrylate, 2-hydroxyethyl acrylate, butyl acrylate, ethylene glycol methyl ether acrylate, 4-hydroxybutyl acrylate, hydroxypropyl acrylate, 4-acetoxyphenethyl acrylate, benzyl acrylate, 1-vinyl-2-pyrrolidinone, vinyl acetate, ethyl vinyl ether, vinyl 4-tert-butyl benzoate and phenyl vinyl sulfone.

30. 1. A porous filter membrane comprising a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, said membrane being grafted with pendant hydrophilic groups selected from hydroxyl groups, amine groups, carboxylic acid groups or combinations thereof, and pendant ionic groups different from the pendant hydrophilic groups.

31. 1. A porous composite filter membrane comprising a porous hydrophobic polymeric filter membrane having a coating thereon, said coating being a polyamide polymer that is soluble in a mixture of formic acid and dichloromethane, thereby providing a polyamide coated membrane, which is subsequently grafted with pendant hydrophilic groups selected from hydroxyl groups, amine groups, carboxylic acid groups or combinations thereof, and pendant ionic groups different from the pendant hydrophilic groups.

32. The polyamide polymer has the formula -[(CH ２ ) ｘ C(O)NH] ｎ 32. The membrane of claim 30 or 31, having a repeat unit structure of: -, where x is an integer from about 8 to 12, and n represents the number of repeat units in the polyamide polymer.

33. 33. The membrane of any one of claims 30 to 32, wherein the polyamide polymer is selected from nylon 11 and nylon 12.

34. The following characteristics: a. a surface energy of about 30 to about 100 dynes / cm; b. an isopropanol flow time of about 150 to about 20,000 seconds / 500 mL measured at 14.2 psi; c. a bubble point of about 20 to about 200 psi when measured using an ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.; and d. Between about 1 and about 300 μg / cm ２ Ponceau S dye binding capacity between about 1 and about 300 μg / cm ２ Methylene blue dye binding capacity (MB DBC) 34. The membrane of any one of claims 30 to 33, having the following structure:

35. 32. The membrane of claim 31 , wherein the hydrophobic polymeric filter material is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride, and polyarylsulfone.

36. 32. The membrane of claim 31 , wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene).

37. 38. A method for removing impurities from a liquid comprising contacting the liquid with the membrane of any one of claims 1 to 37.

38. A filter comprising a membrane according to any one of claims 1 to 6.

39. A filter comprising a membrane according to any one of claims 7 to 11.

40. A filter comprising a membrane according to any one of claims 12 to 19.

41. A filter comprising a membrane according to any one of claims 20 to 29.

42. A filter comprising the membrane of claim 30.

43. A filter comprising the membrane of claim 31.

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