JP2024138302A - Composite Filter Material - Google Patents

Abstract

A composite membrane useful for removing various impurities from liquids is provided. In one embodiment, the composite membrane includes a hydrophobic polymer having a polyamide coated thereon, and in another embodiment, such composite membrane has certain acrylic polymers coated thereon. The composite membranes are useful in removing various impurities in liquids such as those encountered in industrial and life science processes.Selected Figure 2

Description

The present disclosure relates to a composite filter material or membrane that includes a porous polymeric filter coated with a layer that includes a polyamide polymer.

Filter products are essential tools in modern industry used to remove undesirable materials from useful fluid streams. Useful fluids that are 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 with medical or pharmaceutical applications. 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.

To perform the filtration 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 desired. Alternatively, the filter membrane may be in the form of hollow fibers. The filter membrane may be contained or otherwise supported within a housing such that the fluid being filtered enters through a filtration inlet and must pass through the filter membrane before passing through a filtration outlet.

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 microns 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.

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 mode of filtration that removes particles from a liquid stream by mechanically retaining them on the surface of the filter membrane, which acts to mechanically interfere with the movement of the particles and retain them within 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 modes 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-exclusively mechanical manner, such as electrostatic mechanisms that electrostatically attach and retain particulate matter or dissolved impurities to the filter surface and remove them from the fluid stream, where the particles may be dissolved or solid with a particle size smaller than the pores of the filter material.

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, and the like. Due to the ability of nylon to be formed into highly permeable filter membranes and due to the excellent sieving and non-sieving filtration behavior of nylon, specifically, nylon filter membranes are used in a variety of different filtration applications in the semiconductor processing industry.

The field of microelectronic device processing requires steady improvements in processing materials and methods to sustain parallel steady improvements 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.

In microelectronic device processing, 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 processing 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 processing, 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.

In one embodiment, the composite porous filter membrane comprises:
a porous hydrophobic polymeric filter material having a coating thereon, said coating being a polyamide polymer that is soluble in formic acid;
(i) a surface energy greater than about 30 dynes/cm;
(ii) having an isopropanol flow rate time, measured at 14.2 psi, of about 150 to about 20,000 seconds/500 mL.

The inventors believe that the polyamide coating formed on the surface of the porous hydrophobic polymeric filter material is a porous coating, thereby providing a substantially greater surface area to the polyamide coating surface. When a formic acid solution of the polyamide described herein is placed on a glass plate and the solvent is allowed to evaporate, the film so formed is opaque, thus indicating that a porous film, rather than a non-porous film, is formed on the hydrophobic surface. This feature is therefore believed to provide improved non-sieving filtration performance.

In a second aspect, a composite porous filter membrane comprises a porous hydrophobic polymeric filter membrane having a polyamide coating thereon as a first coating, the polyamide being soluble in formic acid, thereby providing a polyamide-coated membrane, the membrane having a second coating thereon 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.

In another aspect, disclosed herein is a method for removing impurities from a liquid, the method comprising contacting the liquid with a composite membrane described herein.

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

FIG. 1 (schematic and not necessarily to scale) illustrates one example of a filter product as described herein. 2 is a simplified diagram of a polyamide coated porous filter membrane, showing a base membrane (a hydrophobic polymeric filter membrane) onto which the polyamide is coated. As will be described below, the polyamide coating does not necessarily form a continuous coating on the base membrane as shown. 3 is a graphical representation of the surface tension of mixtures of methanol and water at 20° C. Surface tension (nM/m at 20° C.) is plotted against the mass (%) of methanol in water.

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.

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.

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.

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

As described above, in a first aspect, the composite porous filter membrane comprises:
a porous hydrophobic polymeric filter material having a coating thereon, said coating being a polyamide polymer that is soluble in formic acid;
i. a surface energy of greater than about 30 dynes/cm; and ii. an isopropanol flow rate time of about 150 to about 20,000 seconds/500 mL, measured at 14.2 psi.

In some embodiments, the surface energy is about 30 to about 100 dynes/cm, about 30 to about 85 dynes/cm, or about 30 to about 65 dynes/cm.

In some embodiments, the membrane has a bubble point of about 20-200 psi when measured using an HFE 7200 at a temperature of about 22° C. and/or the membrane has a Ponceau S dye binding capacity of between about 1 and about 10 μg/cm ² and a Methylene Blue dye binding capacity (MB DBC) of between about 1 and about 10 μg/cm ^2. In some embodiments, the membrane has a Ponceau S dye binding capacity of about 8 to about 10 μg/cm ² , and in other embodiments, the membrane has a Ponceau S dye binding capacity of about 9.2 μg/cm ² .

In some embodiments, the flow rate of isopropanol is about 6,000 to about 10,000 seconds/500 mL, and in other embodiments, about 8,000 seconds/500 mL.

As noted above, the composite membranes described herein are useful as filtration media for removing impurities from a variety of fluids. In certain embodiments of the first and second aspects, the polyamide coating applied to the hydrophobic filter media or membrane does not completely cover or encapsulate the hydrophobic filter media or membrane, but rather forms a semi-continuous or partial coating on the underlying porous hydrophobic membrane. Similarly, in the second aspect, where free radical polymerization is carried out in the presence of a polyamide-coated membrane, the resulting cured or crosslinked polymer coating, in certain embodiments, does not completely cover or encapsulate the membrane surface, but also forms a semi-continuous or partial coating on the polyamide-coated porous hydrophobic membrane structure.

In some 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.

The polymeric materials that can be used to form the lower porous filter membrane of the present disclosure are hydrophobic polymers that in some embodiments have a surface energy of less than about 40 dynes/cm. In some embodiments, the filter hydrophobic polymer 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 more specific embodiments, the filter material comprises ultra-high molecular weight polyethylene (UPE). UPE filter materials, such as UPE membranes, are typically formed from resins having a molecular weight (viscosity average molecular weight) greater than about 1×10 ⁶ Daltons (Da), for example in the range of about 1×10 ⁶ to 9×10 ⁶ Da, or 1.5×10 ⁶ to 9×10 ⁶ Da. 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 polymer (FEP), polyhexafluoropropylene, and polyvinylidene fluoride (PVDF).

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.

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, etc.

The composite membrane, starting with a porous hydrophobic filter membrane such as one composed of ultra-high molecular weight polyethylene, is treated with a solution of polyamide polymer in formic acid, for example. Once the membrane is coated, it is transferred to a mixing vessel containing an aqueous solution including water. The resulting membrane is then subjected to one or more washing steps including passing through washing vessels of aqueous and lower alcohols. Once dried, this process provides the composite membrane of the first aspect. In one embodiment, the washing steps include two successive vessels containing water and a vessel containing a lower, e.g., _C1 - _C4 alcohol, between the two successive vessels of water.

Alternatively, in the second embodiment mentioned above, 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 polyamide polymer, for example in formic acid. Once the membrane is coated, it is transferred to a mixing vessel containing an aqueous solution comprising (i) at least one crosslinking agent, (ii) at least one monomer, and (iii) at least one photoinitiator, hereinafter referred to as "monomer solution". The membrane thus coated can then be subjected to UV light to initiate free radical polymerization at the surface of the polyamide coating with (i) at least one crosslinking agent and (ii) at least one monomer. The resulting membrane is then subjected to one or more washing steps, including passing through aqueous and lower alcohol washing vessels. Once dried, this process gives the composite membrane of the second embodiment.

In certain embodiments, the composite membrane of this second aspect has the following properties:
(i) an isopropanol flow rate time of about 150-20,000 seconds/500 mL measured at 14.2 psi;
(ii) having a bubble point of about 20-200 psi when measured using an ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.; and (iii) having a Ponceau S dye binding capacity of between about 1 and 30 μg/ ^cm2 and a Methylene Blue dye binding capacity (MB DBC) of between about 1 and 30 μg/ ^cm2 .
has.

In some embodiments, the surface energy is greater than 30 dynes/cm, about 30-100 dynes/cm, or about 30-85 dynes/cm, or about 30-65 dynes/cm.

The polyamide polymers referred to above, also commonly known as "nylons", are typically understood to include copolymers and terpolymers that contain repeating amide groups in the polymer backbone. In general, nylon and polyamide resins include copolymers of diamines and dicarboxylic acids, or homopolymers of lactams and amino acids. In certain embodiments, nylons for use in the manufacture of the filter membranes described herein include copolymers of hexamethylenediamine and adipic acid (nylon 6,6), copolymers of hexamethylenediamine and sebacic acid (nylon 610), homopolymers of polycaprolactam (nylon 6), and copolymers of tetramethylenediamine and adipic acid (nylon 46). Nylon polymers are available in a wide range of grades that vary considerably in terms of molecular weight and in other properties, ranging from about 15,000 to about 42,000 (number average molecular weight). All such polyamides, as contemplated herein, are soluble in formic acid, but are generally insoluble in aqueous solutions. Such polyamides are utilized as dilute solutions in formic acid. In one embodiment, the polyamide is utilized at a concentration of about 1-4% by weight in formic acid.

The above crosslinkers are uncharged 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, divinylbenzene, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione 98%, and ethylene glycol divinyl ether.

The monomers referred to herein are charged or uncharged vinyl, acrylic or methacrylic monomer species.

Non-limiting examples of positively charged monomers that can be used in embodiments of the present disclosure include, individually or in combination of two or more of the following, 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-(meth Examples of 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, either naturally or by treatment, can be polymerized and crosslinked with a crosslinking agent to form a coating on the porous membrane.

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 a base. Monomers that are naturally or processed 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.

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.

The photoinitiator, in one embodiment, 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 upon irradiation. Examples of suitable initiators include various persulfates such as sodium and potassium persulfate, 1-hydroxycyclohexyl phenyl ketone, sold under the trademark Irgacure 2959 (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone), and benzoyl peroxide.

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 up to 1 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.

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.

The amount of monomer in the monomer solution is, in one embodiment, about 0.5-5 wt. % based on the weight of the solution. The amount of crosslinker in the monomer solution is, in one embodiment, 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, along 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.

After the monomer solution has been effectively exposed 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 a chemical reaction that causes the reactive moieties of the monomer to react with the crosslinker and become chemically (covalently) bonded to the crosslinker.

In various examples of the methods and articles described herein, the composite membranes described herein can 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 the 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., 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 onto 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.

The exemplary porous polymeric filter membranes described herein (considered either before or after a surface coating step thereon) can be characterized by physical characteristics including pore size, bubble point, and porosity.

Porous polymeric filter membranes may have any pore size that allows the filter membrane to be effective in functioning 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).

Bubble point is also a known characteristic of porous membranes. With 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 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 HFE 7200 (available from 3M) at a temperature of 20-25 degrees Celsius (e.g., 22 degrees Celsius) and wetted with ethoxy-nonafluorobutane HFE 7200. 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 for the porous polymeric filter membranes useful or preferred according to the present specification, as measured using the above procedure, can be in the range of 5 to 200 psi, for example, in the range of 20 to 200 psi.

The described porous polymeric filter layers can have any porosity that allows the porous polymeric filter layers to be effective as described herein. Exemplary porous polymeric filter layers can have a relatively high porosity, for example, at least 60, 70 or 80% porosity. As used herein, and in the art of porous bodies, the "porosity" of a porous body (sometimes called 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, calculated as the ratio of the volume of the voids in the porous body to the total volume of the porous body. A porous body with a porosity of 0% is completely solid.

The described porous polymeric filter membranes can 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.

The described filter membranes may be useful for filtering liquids to remove undesirable materials (e.g., contaminants or impurities) from the liquid to produce a high purity liquid that can be used as an industrial process material. The filter membranes may be useful for removing dissolved or suspended contaminants or impurities from a liquid flowing through the coated filter membrane, either by sieving or non-sieving mechanisms, and preferably by both combined non-sieving and sieving mechanisms. The lower porous hydrophobic filter membrane itself (before conversion to a composite hydrophobic filter membrane described herein) may exhibit effective sieving and non-sieving filtration properties, as well as desirable flow properties. The composite filter membranes described herein may exhibit at least equivalent sieving filtration properties, useful or equivalent (not unduly reduced) flow properties, and improved (e.g., substantially improved) non-sieving filtration properties, as compared to the lower hydrophobic polymeric membrane utilized as the starting material.

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).

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 NH ₄ OH, 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 NH ₄ OH is passed through a filter having a membrane described herein to remove metals from the solvent. In some aspects, passing the solvent-containing liquid through the membrane to remove metals from the solvent-containing liquid results in a reduction in the concentration of metals in the solvent-containing liquid.

The composite filter membranes described herein can also be characterized with respect to the dye-binding capacity of the filter membrane. Specifically, a charged dye 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 be assessed by the use of negatively charged dyes and also by the use of positively charged dyes.

The composite filter membrane of the first aspect may in certain embodiments have a dye binding capacity for methylene blue dye of at least 1 microgram per square centimeter of filter membrane (μg/cm ² ), e.g., greater than 1 or 10 μg/cm ² ; alternatively or in addition, the coated filter membranes described may have a dye binding capacity for Ponceau S dye that is about 1-10 μg/cm ² , e.g., greater than 1-10 or about 5 μg/cm ² , and a methylene blue dye (MB DBC) binding capacity between 1 and 10 μg/cm ² .

The composite filter membrane of the second aspect may, in certain embodiments, have a dye-binding capacity for methylene blue dye of at least 1 microgram per square centimeter (μg/ ^cm2 ) of filter membrane, e.g., greater than 1, 10, 100 or 500 μg/ ^cm2 ; alternatively or in addition, the coated filter membranes described may have a dye-binding capacity for Ponceau S dye of at least 1 μg/ ^cm2 , e.g., greater than 1, 10, 100 or 500 μg/ ^cm2 .

Additionally, filter membranes 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. Flow rate, or alternatively considered, resistance to liquid flow 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. Examples of useful or preferred isopropanol flow times can be less than about 20,000 seconds/500 mL, such as less than about 4,000 or 2,000 seconds/500 mL.

The membrane isopropanol (IPA) flux times reported herein are determined by measuring the time it takes for 500 ml of isopropyl alcohol (IPA) fluid to pass through a membrane with an effective surface area of 13.8 ^cm2 at 14.2 psi and a temperature of 21 degrees Celsius.

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 characteristics of the filter membrane, and may still 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.

The described filter membranes can be included within 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, such 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 within 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 through the composite filter membrane as it passes through the filter. The filter membrane supported by the filter assembly or filter cartridge can be of any useful shape, such as a pleated cylinder, a cylindrical pad, one or more non-pleated (flat) cylindrical sheets, pleated sheets, among others.

An example of a filter structure including 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 opposing 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.

The detailed description and drawings, which are not necessarily to scale, depict exemplary embodiments and are not intended to limit the scope of the embodiments described herein. The exemplary aspects shown are intended as examples only. Selected features of any exemplary aspect may be incorporated in additional aspects unless expressly stated to the contrary.

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 outer periphery 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 in a filter housing including an inlet and an outlet, and configured such that all of the fluid entering the inlet must pass through the filter membrane 12 before exiting the filter at the outlet.

を使用して粒子保持率を計算する。 "Particle retention" or "coverage" refers to the percentage of the number of particles that can be removed from a fluid stream by a membrane disposed in the fluid path of the fluid stream. Particle retention determined according to the following procedure is referred to as the "Particle Retention Test." An aqueous feed solution of 0.1% Triton X-100 with a pH of about 5 containing 8 ppb polystyrene particles with a diameter of 25 nm (available from Duke Scientific G25B) and 0.5 M NaCl is prepared. The particle retention of a 47 mm membrane disk can be measured by passing a sufficient amount of the aqueous feed solution to achieve a monolayer coverage of 1% through the membrane at a constant flow rate of 7 mL/min and collecting the filtrate. Particle retention can be determined for different monolayer percentages such as 0.5%, 1%, 2%, 3%, 4% or 5%. To accurately determine particle retention, the process is calibrated to determine the concentration of polystyrene particles in the feed stream that do not pass through the membrane. The concentration of polystyrene particles in the filtrate and the feed stream can be calculated from the absorbance of the filtrate using a fluorescence spectrophotometer.

Calculate the particle retention using:

式中
ａ＝有効膜表面積（ｍｍ^２）
ｄ_ｐ＝粒子の直径（ｍｍ）
ｎ＝％単層 The number (#) of particles required to achieve 1% monolayer coverage can be calculated from the following formula:

Where a = effective membrane surface area (mm ² )
_dp = particle diameter (mm)
n = % monolayer

In some embodiments, the membranes disclosed herein have a particle retention as determined by a 1% monolayer particle retention test in the ranges of about 75% to about 100%, about 75% to about 99%, about 75% to about 95%, about 75% to about 90%, about 80% to about 100%, about 80% to about 99%, about 80% to about 95%, about 80% to about 90%, about 85% to about 100%, about 85% to about 99%, about 85% to about 95%, about 85% to about 90%, about 90% to about 100%, about 90% to about 99%, about 90% to about 95%, and all ranges and subranges therebetween. In some embodiments, the membranes disclosed herein have a particle retention as determined by a 3% monolayer particle retention test in the ranges of about 70% to about 100%, about 70% to about 99%, about 70% to about 95%, about 70% to about 90%, about 75% to about 100%, about 75% to about 99%, about 75% to about 95%, about 75% to about 90%, about 80% to about 100%, about 80% to about 99%, about 80% to about 95%, about 80% to about 90%, about 85% to about 100%, about 85% to about 99%, about 85% to about 95%, about 85% to about 90%, about 90% to about 100%, about 90% to about 99%, about 90% to about 95%, and all ranges and subranges therebetween.

Porosimetry 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 and wetted with ethoxy-nonafluorobutane HFE 7200 (available from 3M) at a temperature of 20-25 degrees Celsius (e.g., 22 degrees Celsius). 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.

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 3, 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 3.

Example 1 - Preparation of Asymmetric 5 nm UPE Membrane Coated with Nylon 6 A coating solution of 3 wt% nylon 6 was prepared by dissolving 3 g of nylon 6 resin in 77 g of 98% formic acid and 20 g of isopropanol. A 47 mm disk of asymmetric 5 nm UPE membrane was wetted with the coating solution for 10 seconds. The membrane disk was removed from the nylon 6 solution and placed between two polyethylene sheets. Excess solution was removed from the membrane by rolling a rubber roller over the polyethylene sandwich laid flat on a table. The membrane disk was removed from the sandwich and immediately placed in a deionized water solution where it was immersed for 2 minutes to allow the nylon to phase separate into an asymmetric 5 nm UPE membrane. The membrane disk was removed from the DI water solution and immediately immersed in a 100% methanol solution for 2 minutes. The membrane was restrained in a holder and placed in an oven set at 60°C for 10 minutes. Prior to coating with nylon 6, the asymmetric 5 nm UPE membrane had an HFE average bubble point of 112 psi, an IPA flow time of 4,234 sec/500 mL, a thickness of 55 um and a Ponceau S dye binding capacity of 0.0 ug/ ^cm2 . The resulting nylon 6 coated UPE membrane had an ethoxy-nonafluorobutane HFE 7200 average bubble point of 114 psi, an IPA flow time of 5,264 sec/500 mL, a thickness of 54 um and a Ponceau S dye binding capacity of 2.5 ug/ ^cm2 .

Example 2: Retention of Nylon 6 Coated UPE Membranes 47 mm discs of asymmetric 3 nm, 5 nm and 10 nm UPE membranes were coated with a 3 wt % nylon 6 solution as described in Example 1. The particle retention test described above was then measured for the coated and uncoated 3 nm, 5 nm and 10 nm UPE membranes, and the results are shown in Table 1 below.
Table 1

As can be seen from the table, coating with 3 nm, 5 nm and 10 nm UPE films improved particle retention at each monolayer percentage compared to uncoated 3 nm, 5 nm and 10 nm UPE films.

Example 2 - Preparation of Asymmetric 5 nm UPE Membrane Coated with Nylon 6 and UV Cured Monomer Coating A coating solution of 3 wt% nylon 6 was prepared by dissolving 3 g of nylon 6 resin in 77 g of 98% formic acid and 20 g of isopropanol. A 47 mm disk of asymmetric 5 nm UPE membrane was wetted with the coating solution for 10 seconds. The membrane disk was removed from the nylon 6 solution and placed between two polyethylene sheets. Excess solution was removed from the membrane by rolling a rubber roller over the polyethylene sandwich laid flat on a table. The membrane disk was removed from between the polyethylene sheets and immediately placed in a deionized water solution where it was immersed for 2 minutes to phase separate the nylon into an asymmetric 5 nm UPE membrane. The membrane disk was removed from the DI water solution and immediately immersed in a monomer solution containing 0.2% Irgacure 2959, 0.2% MBAM (N,N'-methylenebis(acrylamide)), 0.5% APTAC ((3-acrylamidopropyl)trimethylammonium chloride solution, available from Sigma-Aldrich), and 5% methanol. The membrane disk was removed from the monomer solution and placed between two polyethylene sheets. Excess solution was removed from the membrane by rolling a rubber roller over the polyethylene sandwich, which was laid flat on a table. The polyethylene sandwich was then taped to a transport unit that carried the assembly through a Fusion Systems broadband UV exposure lab unit emitting at wavelengths from 200 nm to 600 nm. The time of exposure is controlled by the speed at which the assembly moves through the UV unit. In this example, the assembly moved through the UV chamber at 10 feet/min. After UV exposure, the membrane disc was removed from between the polyethylene sandwich and immediately placed in a 100% methanol solution for 2 minutes. The membrane was restrained in a holder and placed in an oven set at 60°C for 10 minutes. Prior to coating with nylon 6, the asymmetric 5 nm UPE membrane had an ethoxy-nonafluorobutane HFE 7200 average bubble point of 112 psi, an IPA flow time of 4,234 sec/500 mL, a thickness of 55 um and a Ponceau S dye binding capacity of 0.0 ug/ ^cm2 . The resulting nylon 6 coated and UV cured monomeric UPE membrane had an HFE average bubble point of 114 psi, an IPA flow time of 10,278 sec/500 mL, a thickness of 53 um and a Ponceau S dye binding capacity of 6.5 ug/ ^cm2 .

Example 3 - 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 this 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.

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 3 (plotted using surface tension data published in Lange's Handbook of Chemistry, 11th edition).

A 47 mm disk of the membrane prepared according to Example 1 was placed in contact with the inert liquids in a beaker, one liquid at a time. For each liquid, the amount of time required for the membrane to spontaneously wick up the liquid was recorded. The liquids of 58% methanol with a surface tension of 30.32 mN/m and 22% methanol with a surface tension of 47.86 mN/m were the highest surface tension liquids that wetted the UPE and UPE coated membranes, respectively, within 2 seconds.

A 47 mm disk of the membrane prepared according to Example 2 was placed in contact with the inert liquids in a beaker, one liquid at a time. For each liquid, the amount of time required for the membrane to spontaneously wick up the liquid was recorded. The liquids of 58% methanol with a surface tension of 30.32 mN/m and 16% methanol with a surface tension of 51.83 mN/m were the highest surface tension liquids that wetted the UPE and UPE coated membranes, respectively, within 2 seconds.

Example 4 - Reduction of Metals in PGMEA by Nylon Membranes, Asymmetric 5 nm UPE Membranes Coated with Nylon 6, and Asymmetric 5 nm UPE Membranes Coated with Nylon 6 and a UV-cured Monomer Coating This example demonstrates the ability of 5 nm asymmetric UPE membranes coated with nylon 6 or nylon 6 and a UV-cured monomer to reduce metals in PGMEA during filtration. Metal reduction performance is compared to a nylon 6 membrane with a 5 nm pore size.

Nylon 6 coated UPE membranes were prepared and cut into 47 mm membrane strips using a method similar to that of Examples 1 and 2. The membrane strips were conditioned and mounted in a clean 47 mm Filter Assembly (Savillex) by washing several times with 0.35% HCl followed by deionized water. The membrane and filter assembly were flushed with Isopropanol Gigabit (KMG) followed by PGMEA. As a control sample, a 5 nm nylon 6 membrane was also prepared and conditioned using the same method and mounted in the filter assembly. CONOSTAN Oil Analysis Standard S-21 (SCP Science) was added to the application solvent PGMEA with a target concentration of 13.59 ppb total metals. To determine filtration metal removal efficiency, the metal spiked applied solvent was passed through the corresponding 47 mm filter assembly containing each filter at 10 mL/min and the filtrate was collected into clean PFA jars at 50, 100 and 150 mL. ICP-MS was used to determine the metal concentrations of the metal spiked applied solvent and each filtrate sample. The results are tabulated in Table 4.1: Metal Reduction in PGMEA. The results show that the 5 nm nylon 6 membrane can reduce total metals from 13.59 ppb to 4.79 ppb after 150 mL, the Asymmetric 5 nm UPE membrane coated with nylon 6 can reduce total metals from 13.59 ppb to 5.43 ppb after 150 mL, and the Asymmetric 5 nm UPE membrane coated with nylon 6 and a UV cured monomer coating can reduce total metals from 13.59 ppb to 3.26 ppb after 150 mL.
Table 4.1: Metals Reduction in PGMEA

The results show that the nylon 6 coated UPE membranes generally have better metal removal than the nylon 6 control membrane, and that the nylon 6 and UV cured monomer coated UPE membranes have better metal removal than both the nylon 6 control membrane and the nylon 6 coated UPE membrane.

Aspects of the Disclosure In a first aspect, the 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 formic acid;
A composite porous filter membrane is provided having: i. a surface energy greater than about 30 dynes/cm; and ii. an isopropanol flux time, measured at 14.2 psi, of about 150 to about 20,000 seconds/500 mL.

In a second 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 formic acid;
a surface energy greater than about 30 dynes/cm; and ii. a 3% monolayer particle retention in the range of about 70% to about 100%.

In a third aspect, the present disclosure provides a filter membrane of the first or second aspect, wherein the membrane has a particle retention rate at 3% monolayer in the range of about 80% to about 100%.

In a fourth aspect, the present disclosure provides a filter membrane according to any one of the first to third aspects, wherein the membrane has a bubble point of about 20 to about 200 psi when measured using ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22°C.

In a fifth aspect, the present disclosure provides a filter membrane of any of the first to fourth aspects, wherein said membrane has a Ponceau S dye binding capacity of between about 1 and about 10 μg/ ^cm2 and a Methylene Blue dye binding capacity (MB DBC) of between about 1 and about 10 μg/ ^cm2 .

In a sixth aspect, the present disclosure provides a filter membrane of any of the first to fifth aspects, wherein the hydrophobic polymeric filter material is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride, and polyarylsulfone.

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

In an eighth aspect, the present disclosure provides a filter membrane of any of the first to seventh aspects, having a surface energy of about 30 to about 100 dynes/cm.

In a ninth aspect, the present disclosure provides a filter membrane according to any one of the first to eighth aspects, wherein the polyamide polymer is composed of at least one of: (i) a copolymer of hexamethylenediamine and adipic acid; (ii) a homopolymer of polycaprolactam; (iii) a copolymer of hexamethylenediamine and sebacic acid; and (iv) a copolymer of tetramethylenediamine and adipic acid.

In a tenth aspect, the present disclosure provides a filter membrane of any of the first to ninth aspects, wherein the polyamide polymer has a number average molecular weight of about 15,000 to about 42,000 daltons.

In an eleventh aspect, the present disclosure provides a method for producing a membrane comprising the steps of:
(i) having a bubble point of about 50 to 150 psi when measured using an ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.;
(ii) an isopropanol flow rate time of about 6,000 to about 10,000 seconds/500 mL measured at 14.2 psi; and (iii) a Ponceau S dye binding capacity of about 8 to about 10 μg/ ^cm2 and a Methylene Blue dye (MB DBC) binding capacity of between 1 and 100 μg/ ^cm2 . The filter membrane of any of the first to tenth aspects is provided.

In a twelfth aspect, the present disclosure provides a composite porous filter membrane comprising a porous hydrophobic polymeric filter membrane having a polyamide coating thereon as a first coating, the polyamide being soluble in formic acid, thereby providing a polyamide-coated membrane, the polyamide-coated membrane having a second coating thereon 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.

In a thirteenth aspect, the present disclosure provides the membrane of the twelfth aspect, wherein the hydrophobic polymeric filter material is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride, and polyarylsulfone.

In a fourteenth aspect, the present disclosure provides a membrane of the twelfth or thirteenth aspects, wherein the membrane has a particle retention at 3% monolayer in the range of about 70% to about 100% or in the range of about 80% to about 100%.

In a fifteenth aspect, the present disclosure provides a film of any one of the twelfth to fourteenth aspects, having a surface energy of about 30 to about 85 dynes/cm.

In a sixteenth aspect, the present disclosure provides the membrane of any of the twelfth to fifteenth aspects, wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene).

In a seventeenth aspect, the present disclosure provides a method for producing a membrane comprising the steps of:
(i) having an isopropanol flow rate time of about 150 to about 20,000 seconds/500 mL, measured at 14.2 psi;
(ii) having 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
(iii) having a Ponceau S dye binding capacity of between about 1 and about 30 μg/ ^cm2 and a Methylene Blue dye binding capacity (MB DBC) of between about 1 and about 30 μg/ ^cm2 ;
A membrane according to any of the twelfth to seventeenth aspects is provided.

In an eighteenth aspect, the present disclosure provides the membrane of any one of the twelfth to seventeenth aspects, wherein the polyamide is composed of at least one of: (i) a copolymer of hexamethylenediamine and adipic acid; (ii) a homopolymer of polycaprolactam; (iii) a copolymer of hexamethylenediamine and sebacic acid; and (iv) a copolymer of tetramethylenediamine and adipic acid.

In a nineteenth aspect, the present disclosure provides the membrane of any one of the twelfth to nineteenth aspects, wherein the polyamide polymer has a number average molecular weight of about 15,000 to about 42,000 daltons.

In a twentieth aspect, the present disclosure provides the membrane of any one of the twelfth to nineteenth aspects, 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.

In a twenty-first aspect, the present disclosure provides a method for producing a polymerizable composition comprising the steps of: 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, aryl The membrane according to any one of the twelfth to twentieth aspects is selected from vinylamine hydrochloride, 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.

In a twenty-second aspect, the present disclosure provides a membrane according to any one of the twelfth to twenty-first 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.

In a twenty-third aspect, the present disclosure provides the membrane of any one of the twelfth to twenty-second 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-butyl benzoate, and phenyl vinyl sulfone.

In a twenty-fourth aspect, the present disclosure provides a method for preparing the composite porous filter membrane of any one of the first to ninth aspects, comprising:
a. dissolving a polyamide polymer in formic acid 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 a solution comprising water;
d. rinsing the polyamide coated membrane with a _C1 - _C4 alcohol and water;
e. drying the polyamide coated membrane.

In a twenty-fifth aspect, the present disclosure provides a method for preparing the composite porous filter membrane of any one of the tenth to twentieth aspects, comprising:
a. dissolving a hydrophilic polyamide polymer in formic acid 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 a monomer solution comprising water, at least one crosslinking agent, at least one monomer, and at least one photoinitiator;
d. removing the resulting film from the bath and exposing it to ultraviolet radiation, and then
e. rinsing the polyamide coated membrane in a rinse bath comprising a solvent selected from water and a _C1 - _C4 alcohol;
f. drying the composite porous filter membrane;
The present invention provides a method comprising:

In a twenty-sixth aspect, the present disclosure provides a method for removing impurities from a liquid, the method comprising contacting the liquid with a composite membrane of any one of the first to nineteenth aspects.

In a twenty-seventh aspect, the present disclosure provides the method of the twenty-sixth aspect, wherein the impurities are selected from one or more metal or metalloid ions.

In a twenty-eighth aspect, the present disclosure provides the method of the twenty-seventh aspect, wherein the impurities are selected from one or more ions of lithium, boron, sodium, magnesium, aluminum, potassium, calcium, titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, molybdenum, silver, cadmium, tin, barium, and lead.

In a twenty-ninth aspect, the present disclosure provides a filter comprising a membrane according to any one of the first to eleventh aspects.

In a thirtieth aspect, the present disclosure provides a filter comprising a membrane according to any one of the twelfth to twenty-third aspects.

Having thus described several illustrative aspects of the present disclosure, those skilled in the art will readily appreciate that still other aspects 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 (40)

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 formic acid;
a composite porous filter membrane having an isopropanol flow time, measured at 14.2 psi, of from about 150 to about 20,000 seconds/500 mL; The membrane of claim 1, wherein the membrane has a particle retention rate at 3% monolayer in the range of about 70% to about 100%. The membrane of claim 2, wherein the membrane has a particle retention rate at 3% monolayer in the range of about 80% to about 100%. The membrane of any one of claims 1 to 3, wherein the membrane has a bubble point of about 20 to about 200 psi when measured using ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22°C. 5. The membrane of any one of claims 1 to 4, wherein the membrane has a Ponceau S dye binding capacity of between about 1 and about 10 μg/ ^cm2 and a Methylene Blue dye binding capacity (MB DBC) of between about 1 and about 10 μg/ ^cm2 . The membrane of any one of claims 1 to 5, wherein the hydrophobic polymeric filter material is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride and polyarylsulfone. The membrane of any one of claims 1 to 6, wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene). The film according to any one of claims 1 to 7, having a surface energy of about 30 to about 100 dynes/cm. The membrane according to any one of claims 1 to 8, wherein the polyamide polymer is composed of at least one of: (i) a copolymer of hexamethylenediamine and adipic acid; (ii) a homopolymer of polycaprolactam; (iii) a copolymer of hexamethylenediamine and sebacic acid; and (iv) a copolymer of tetramethylenediamine and adipic acid. The membrane of any one of claims 1 to 9, wherein the polyamide polymer has a number average molecular weight of about 15,000 to about 42,000 daltons. The membrane,
(i) a bubble point of about 50 to about 150 psi, as measured using an ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.;
(ii) an isopropanol flow time of about 6,000 to about 10,000 seconds/500 mL measured at 14.2 psi; and (iii) a Ponceau S dye binding capacity of about 8 to about 10 μg/ ^cm2 and a Methylene Blue dye (MB DBC) binding capacity of between 1 and 100 μg/ ^cm2 . A composite porous filter membrane comprising a porous hydrophobic polymeric filter membrane having a polyamide coating coated thereon as a first coating, the polyamide being soluble in formic acid, thereby providing a polyamide-coated membrane, the polyamide-coated membrane having a second coating thereon 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. The membrane of claim 12, wherein the hydrophobic polymeric filter material is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride, and polyarylsulfone. The film according to claim 12 or 13, having a surface energy of about 30 to about 85 dynes/cm. The membrane of any one of claims 12 to 14, wherein the membrane has a particle retention rate at 3% monolayer in the range of about 70% to about 100%. The membrane of claim 15, wherein the membrane has a particle retention rate at 3% monolayer in the range of about 80% to about 100%. The membrane of any one of claims 12 to 16, wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene). The membrane,
(i) having an isopropanol flow time, measured at 14.2 psi, of about 150 to about 20,000 seconds/500 mL;
(ii) having 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 (iii) having a Ponceau S dye binding capacity of between about 1 and about 30 μg/ ^cm2 and a Methylene Blue dye binding capacity (MB DBC) of between about 1 and about 30 μg/ ^cm2 .
18. A membrane according to any one of claims 12 to 17. The membrane of any one of claims 12 to 18, wherein the polyamide is composed of at least one of: (i) a copolymer of hexamethylenediamine and adipic acid; (ii) a homopolymer of polycaprolactam; (iii) a copolymer of hexamethylenediamine and sebacic acid; and (iv) a copolymer of tetramethylenediamine and adipic acid. The membrane according to any one of claims 12 to 19, wherein the hydrophilic polyamide polymer has a number average molecular weight of about 15,000 to about 42,000 daltons. The membrane according to any one of claims 12 to 20, 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. 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, acrylamidopropyl trimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl) methacrylamide hydrochloride, N-(3-aminopropyl) methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride The membrane according to any one of claims 12 to 21, wherein the acrylic acid is selected from 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. The membrane according to any one of claims 12 to 22, 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. 24. The membrane according to any one of claims 12 to 23, 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. 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 formic acid;
a surface energy greater than about 30 dynes/cm; and a 3% monolayer particle retention in the range of about 70% to about 100%. The membrane of claim 25, wherein the membrane has a particle retention rate at 3% monolayer in the range of about 80% to about 100%. The membrane of claim 25 or 26, wherein the membrane has a bubble point of about 20 to about 200 psi when measured using ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22°C. 28. The membrane of any one of claims 25 to 27, wherein the membrane has a Ponceau S dye binding capacity of between about 1 and about 10 μg/ ^cm2 and a Methylene Blue dye binding capacity (MB DBC) of between about 1 and about 10 μg/ ^cm2 . 29. The membrane of any one of claims 25 to 28, wherein the hydrophobic polymeric filter material is selected from polyethylene, polypropylene, polycarbonate, poly(tetrafluoroethylene), polyvinylidene fluoride and polyarylsulfone. 30. The membrane of any one of claims 25 to 29, wherein the hydrophobic polymeric filter material is selected from ultra-high molecular weight polyethylene and poly(tetrafluoroethylene). The film according to any one of claims 25 to 30, having a surface energy of about 30 to about 100 dynes/cm. 32. The membrane of any one of claims 25 to 31, wherein the polyamide polymer is composed of at least one of: (i) a copolymer of hexamethylenediamine and adipic acid; (ii) a homopolymer of polycaprolactam; (iii) a copolymer of hexamethylenediamine and sebacic acid; and (iv) a copolymer of tetramethylenediamine and adipic acid. The membrane of any one of claims 25 to 32, wherein the polyamide polymer has a number average molecular weight of about 15,000 to about 42,000 daltons. The membrane,
(iv) a bubble point of about 50 to about 150 psi, as measured using an ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.;
(v) an isopropanol flow time of about 6,000 to about 10,000 seconds/500 mL measured at 14.2 psi; and (vi) a Ponceau S dye binding capacity of about 8 to about 10 μg/ ^cm2 and a Methylene Blue dye (MB DBC) binding capacity of between 1 and 100 μg/ ^cm2 . A method for preparing a composite porous filter membrane according to any one of claims 1 to 11 or 25 to 34, comprising the steps of:
a. dissolving a polyamide polymer in formic acid 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 a solution comprising water;
d. rinsing the polyamide coated membrane with a _C1 - _C4 alcohol and water;
e. drying the polyamide coated membrane. 25. A method for preparing a composite porous filter membrane according to any one of claims 12 to 24, comprising the steps of:
a. dissolving a hydrophilic polyamide polymer in formic acid 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 a monomer solution comprising water, at least one crosslinking agent, at least one monomer, and at least one photoinitiator;
d. removing the resulting film from the bath and applying ultraviolet radiation, followed by
e. rinsing the polyamide coated membrane in a rinse bath comprising a solvent selected from water and a _C1 - _C4 alcohol;
f. drying the composite porous filter membrane;
A method comprising: A method for removing impurities from a liquid, comprising contacting the liquid with a composite membrane according to any one of claims 1 to 34. The method of claim 37, wherein the impurities are selected from one or more metal or metalloid ions. The method of claim 38, wherein the impurities are selected from one or more ions of lithium, boron, sodium, magnesium, aluminum, potassium, calcium, titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, molybdenum, silver, cadmium, tin, barium, and lead. A filter comprising a membrane according to any one of claims 1 to 34.

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