Patent Description:
Membranes have been used to remove metal contaminants from liquids in industries such as the micro-electronic industry. For instance, photoresist solutions with ultra low levels of metal ion contaminants are desirable for low wafer defectivity and higher yields during high volume manufacturing of integrated circuits. Cation exchange membranes (i.e. negatively charged membranes) are the industry standard for removing such metal contamination from photoresist solutions used in the production of microchips.

To remove metal contaminants, negatively charged membranes such as described in examples in <CIT> and publication METAL ION REMOVAL FROM PHOTORESIST SOLVENTS (Microlithography Conference) have described the removal of metal contaminants from organic solvents or mixed solvents. Most or many other membrane technologies target removing metals from aqueous solvent, not organic solvents, and or the membranes have not been modified with positive charge i.e. anion exchange membrane. See for example references such as <CIT>. <CIT> also deals with a method of removing metal contaminants from liquids.

Negatively charged or cation exchange membranes provide a way to remove metal contaminants from organic solvents due to favorable electrostatic interactions between opposite charges on membrane and metal contaminants. As discussed above, photoresist solutions with ultra low levels of metal ion contaminants are wanted for low wafer defectivity and higher yields for manufacturing integrated circuits. Existing cation exchange membranes however, are limited in their applicability to purify organic solvents and remove metal contaminants. More specifically they are limited in removing metal contaminants from water immiscible organic solvents due to limited selectivity.

Thus, need still exists for a device, membrane, and method of removing metal contaminants from organic solvents and specific types of organic solvents such as organic solvents used for photoresist and water immiscible organic solvents. Moreover, need still exists for materials that enable the removal of metal contaminants from organic liquids in general and specific types of organic solvents such as water immiscible organic solvents and organic solvents used for photoresist.

The embodiments disclosed herein meet these and other needs by providing materials and methods of removing metal contaminants from organic liquids and specifically, water immiscible organic liquids.

The present invention is defined by the claims appended hereto.

In the following description, it is understood that terms such as "top," "bottom," "outward," "inward," and the like are words of convenience and are not to be construed as limiting terms. Reference will now be made in detail to exemplary embodiments of the disclosure, which are illustrated in the accompanying figures and examples. Referring to the drawings in general, it will be understood that the illustrations are for the purpose of describing a particular embodiments of the disclosure and are not intended to limit the same.

Whenever a particular embodiment of the disclosure is said to comprise or consist of at least one element of a group and combinations thereof, it is understood that the embodiment may comprise or consist of any of the elements of the group, either individually or in combination with any of the other elements of that group. Furthermore, when any variable occurs more than one time in any constituent or in a formula, its definition on each occurrence is independent of its definition at every other occurrence. Also, combinations of substituents and/or variables are permissible only if such combinations result in stable compounds.

An embodiment of the disclosure includes a filter device and a method of removing metal contaminants from an organic liquid by passing the organic liquid through a coated porous polymeric membrane. As shown in <FIG>, the porous polymeric membrane <NUM> includes a coating <NUM> having one or more polymerized monomers <NUM> with a charge in the organic liquid that are cross-linked by a cross-linker <NUM>. The organic liquid has a lower concentration of the metal contaminants after passing through the coated porous membrane. The coated porous membrane could be placed in a filter housing.

<FIG> illustrates a filter device <NUM> which has a coated porous polymeric membrane <NUM> secured to a filter housing <NUM>, the filter housing has a liquid inlet <NUM> and a liquid outlet <NUM>. The porous polymeric membrane <NUM> includes a coating <NUM> having one or more polymerized monomers with a charge in the organic liquid that are cross-linked by a cross-linker.

<FIG> illustrates a filter device <NUM> which has at least two coated porous polymeric membranes <NUM> and <NUM> secured to a filter housing <NUM>, the filter housing has a liquid inlet <NUM> and a liquid outlet <NUM>. The porous polymeric membrane <NUM> includes a coating <NUM> having one or more polymerized monomers with a charge in the organic liquid that are cross-linked by a cross-linker and the porous polymeric membrane <NUM> includes a coating <NUM> having one or more polymerized monomers with a charge in the organic liquid that are cross-linked by a cross-linker.

In a particular embodiment, the organic liquid includes organic liquid used for photoresist or a photoresist composition. In another embodiment, the organic liquid is immiscible with water. In some versions, use of the term "metal" shall be understood to have the same meaning as the respective metal ion or a component of an ion complex unless stated otherwise. It should be appreciated that the metal also includes the reaction product of one or more ions with each other and the reaction product of the one or more metal ions and one or more solvents with each other. Metal contaminant is the presence of unwanted metals in an environment or material such liquid, making something less pure or suitable for intended purpose. In some versions, use of the term "metal" shall be understood to have the same meaning as the respective metal ion as a component of the ion complex unless stated otherwise. Metal contaminant can refer to neutral, negatively charged, or positively charged metal species and combinations thereof which may be present at equilibrium.

It should be appreciated that the methods of the disclosure include removing metal contaminants with various types of porous membranes and is not limited by the type membrane <NUM>. Examples of porous membranes such as <NUM> or <NUM> can include but not limited to, polyethylene containing membranes, polysulfone containing membranes, polyether sulfone containing membranes, polyarylsulfone containing membranes, and PTFE membranes, either individually or in combinations of two or more thereof. A particular embodiment includes membranes comprising a polyolefin. Suitable polyolefins include, but are not limited to, polyethylene, high density polyethylene, ultra-high molecular weight polyethylene, and combinations of these. Suitable halocarbon polymers include, but not limited to, polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF), either individually or in combinations of two or more thereof. In a particular embodiment, the porous polymeric membrane includes a polyethylene based membrane referred to as ultra-high molecular weight polyethylene (UPE). UPE membranes are typically formed from a resin having a molecular weight greater than about <NUM>,<NUM>,<NUM> Daltons. In some embodiments the molecular weight of the UPE is in a range from about <NUM>,<NUM>,<NUM> Daltons to about <NUM>,<NUM>,<NUM> Daltons. In another embodiment, the molecular weight of the polyethylene membrane is in a range from about <NUM>,<NUM>,<NUM> Daltons to about <NUM>,<NUM>,<NUM> Daltons. In a particular embodiment, the molecular weight of the polyethylene membrane is in a range from about <NUM>,<NUM>,<NUM> Daltons to about <NUM>,<NUM>,<NUM> Daltons. In some instances, the porous polymeric membrane can have a bubble point between about <NUM> psi and <NUM> psi, when ethoxy-nonafluorobutane (or HFE-<NUM>) is used as the wetting solvent. In one instance the porous polymeric membrane can be a polyethylene based membrane. It should be appreciated that although examples and embodiments herein are described with reference to UPE, the principles are not limited to polyethylene membranes. A person of ordinary skill in the art will also appreciate the porous polymeric membrane can be made of other suitable polymeric substances that include one or more polymerized monomers which are cross-linked to each other with cross linkers.

The porous polymeric membrane <NUM> can be any suitable porous membrane, which can be structurally amorphous, crystalline, or any suitable morphologic combination thereof. The porous polymeric membrane can be made of any suitable polymer such as, for example, polyolefins (including fluorinated polyolefins), polyamides, polyacrylates, polyesters, nylons, polysulfones (PS), polyethersulfones (PES), celluloses, polycarbonates, single polymers, copolymers, composites, and combinations thereof. The UPE membranes described herein can have a variety of geometric configurations, such as a flat sheet, a corrugated sheet, a pleated sheet, and a hollow fiber, among others. The porous polymeric membrane can have a pore structure that can be isotropic or anisotropic, skinned or unskinned, symmetric or asymmetric, any combination of these or can be a composite membrane including one or more retentive layers and one or more support layers. Furthermore, the coated porous membrane can be supported or unsupported by webs, nets, and cages, among others.

As shown in <FIG>, which is schematic of a membrane <NUM> used for removing metal contaminants, the porous polymeric membrane includes a coating <NUM> having one or more polymerized monomers <NUM> with a positive charge in a organic liquid. The coating <NUM> includes an organic backbone formed from the polymerized monomers. The coating <NUM> can include a crosslinker <NUM> and a monomer <NUM> or a co-polymer <NUM>. In some embodiments the monomers have groups like alkyl ammonium groups that are positively charged in an organic solvent. It should be appreciated the plurality of polymerized monomers may differ from each other or may be the same with respect to various characteristic. Polymerization and cross-linking of the polymerizable monomer onto the porous membrane <NUM> substrate is effected so at least a portion and upto the entire surface of the porous membrane <NUM>, including the inner pore surfaces of the porous membrane, is modified with a cross-linked polymer. It should be understood that the disclosure encompasses coating the porous membrane with as much of the surface of the membrane as desired, from greater than <NUM>% to <NUM>%, with cross-linked polymer composition.

In other embodiments of the coated porous polymeric membrane grafting can be used to modify the porous membrane and bond the polymerized monomer, co-polymer, cross-linker or a combination of these directly to the porous membrane material. In some other embodiments, a combination of techniques such as a portion is cross-linked and a portion is grafted can be used. Embodiments also encompass cross-linking a grafted portion. The cross-linking and grafting techniques encompass coating as much of the surface of the porous membrane as desired from greater than <NUM>% to <NUM>%.

Monomers <NUM> with a positive charge in an organic liquid used in the coating <NUM> in embodiments of the disclosure include, but are not limited to, <NUM>-(dimethylamino)ethyl hydrochloride acrylate, [<NUM>-(acryloyloxy)ethyl] trimethylammonium chloride, <NUM>-aminoethyl methacrylate hydrochloride, N-(<NUM>-aminopropyl) methacrylate hydrochloride, <NUM>-(dimethylamino)ethyl methacrylate hydrochloride, [<NUM>-(methacryloylamino)propyl]trimethylammonium chloride solution, [<NUM>-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyl trimethylammonium chloride, <NUM>-aminoethyl methacrylamide hydrochloride, N-(<NUM>-aminoethyl) methacrylamide hydrochloride, N-(<NUM>-aminopropyl)-methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride, vinyl imidazolium hydrochloride, vinyl pyridinium hydrochloride, and vinyl benzyl trimethyl ammonium chloride, either individually or in combinations of two or more thereof. In a particular embodiment, the monomer with positive charge includes acrylamido propyl trimethylammonium chloride (APTAC). It should be appreciated that some monomers <NUM> with a positive charge listed above, comprise a quaternary ammonium group and are naturally charged in organic solvent while other monomers with a positive charge such as comprising primary, secondary and tertiary amines are adjusted to create charge by treatment with an acid. Monomers which can be positively charged in an organic solvent, either naturally or by treatment, can be polymerized and cross-linked with a cross-linker to form a coating on the porous membrane that is also positively charged when in contact with an organic solvent.

In an embodiment illustrated in <FIG>, the coating <NUM> on the porous polymeric membrane <NUM> includes a plurality of polymerized monomers <NUM> with a positive charge. It should be appreciated that embodiments of the disclosure can include a plurality of polymerized monomers <NUM> with a positive charge which differ from each other (co-polymer) or are the same (homo-polymer). In an embodiment, some of the pluralities of polymerized monomers with a positive charge are the same. In another particular embodiment, some of the plurality of polymerized monomers with a positive charge differ from each other. The plurality of polymerized monomers with a positive charge may have one or more characteristics which differ from each other or are similar. As shown in <FIG>, in a particular embodiment of the coating <NUM>, one or more of the polymerized monomers are different from each other and form a co-polymer <NUM> with positive charges that are cross-linked with a cross-linker <NUM> to other polymerized monomers.

Monomers <NUM> with negative charges in an organic liquid used in the coating <NUM> include, but are not limited to, <NUM>-ethylacrylic acid, acrylic acid, <NUM>-carboxyethyl acrylate, <NUM>-sulfopropyl acrylate potassium salt, <NUM>-propyl acrylic acid, <NUM>-(trifluoromethyl)acrylic acid, methacrylic acid, <NUM>-methyl-<NUM>-propene-<NUM>-sulfonic acid sodium salt, mono-<NUM>-(methacryloyloxy)ethyl maleate, <NUM>-sulfopropyl methacrylate potassium salt, <NUM>-acrylamido-<NUM>-methyl-<NUM>-propanesulfonic acid, <NUM>-methacrylamido phenyl boronic acid, vinyl sulfonic acid, and vinyl phosphonic acid, either individually or combinations of two or more thereof. In a particular embodiment, the monomer with negative charge includes sulfonic acid. It should be appreciated that some monomers with a negative charge listed above, comprise a strong acid group and are naturally charged in organic solvent while other monomers with a negative charge comprising weak acids are adjusted to create charge by treatment with base. Monomers which are negatively charged in an organic solvent, either naturally or by treatment can be polymerized and cross-linked with a cross-linker <NUM> to form a coating on a porous membrane that is negatively charged in an organic solvent.

In an embodiment, the coating has a plurality of polymerized monomers <NUM> with negative charges. It should be appreciated that embodiments of the disclosure can include those with a plurality of monomers with negative charges which differ from each other or are the same. In an embodiment, the plurality of monomers with negative charges are the same. In another particular embodiment, the plurality of monomers with negative charges differ from each other. The plurality of monomers with negative charges may have one or more characteristics which differ from each other or are similar. As shown in <FIG> schematic membrane, in an embodiment of the coating, the one or more polymerized monomers <NUM> with negative charges that are cross-linked to other one or more polymerized monomers with negative charges. The coating <NUM> includes a combination of polymerized monomers which are positively charged and negative charged that are cross-linked on the same membrane or respectively on separate membranes. In another embodiment, a porous polymeric membrane includes polymerized monomers <NUM> with positive charge that are cross-linked and another separate porous polymeric membrane includes polymerized monomers <NUM> with negative charges that are cross-linked. In another embodiment, the coating <NUM> with polymerized monomers having positive and negative charges are cross-linked and on the same porous polymeric membrane. In still other embodiments, the coating with polymerized monomers which are cross-linked includes monomers that are zwitterionic and have both positive and negative charges on the same monomer in an organic liquid.

A zwitterionic monomer has both a positive and negative charge in the same monomeric backbone. Non-limiting examples of zwitterionic monomers that can be polymerized and cross-linked on surfaces of a membrane include [<NUM>-(Methacryloylamino)propyl]dimethyl(<NUM>-sulfopropyl)ammonium hydroxide; [<NUM>-(Methacryloyloxy)ethyl]dimethyl-(<NUM>-sulfopropyl)ammonium hydroxide; <NUM>-(Methacryloyloxy)ethyl <NUM>-(Trimethylammonio)ethyl Phosphate; <NUM>-(<NUM>-Sulfopropyl)-<NUM>-vinylpyridinium hydroxide; and combinations of these.

It should also be appreciated that methods of the disclosure include removing metal contaminants from a range of organic liquids, which can be liquids, either individually or in combinations of two or more thereof. Non limiting examples of organic liquids include cyclohexanone, isopentyl ether, PGMEA, Methyl isobutyl carbinol, N-butyl acetate, Methyl-<NUM>-hydroxyisobutyrate, and a mixed solution of propylene glycol monomethyl ether (PGME) and PGMEA (<NUM>:<NUM> mixing ratio surface tension of <NUM> mN/m), and either individually or in combinations of two or more thereof. A particular embodiment includes organic liquids which are immiscible with water such as but not limited to cyclohexanone and PGMEA. In an embodiment, immiscible with water means soluble in water up to at <NUM> per <NUM> water.

An embodiment of the disclosure includes removing metal contaminants from a combination of a plurality of organic liquids which differ from each other. A particular embodiment includes solvents used for photoresist. Examples of solvents used in photoresist include liquids such as but not limited to methyl-amyl ketone, ethyl-<NUM>-ethoxypropionate, propylene glycol methyletheracetate, methanol, and ethyl lactate, either individually or in combinations of two or more thereof.

The methods of the disclosure are not limited by a sequence or frequency or order of various acts or steps unless specified and may be repeated as desired.

Another embodiment includes removing metal contaminants from an organic liquid by passing an organic liquid through a plurality of porous polymeric membranes. In a particular embodiment, the first porous polymeric membrane includes a coating having a cross-linked polymerized monomer with a positive charge. The second porous polymeric membrane includes a coating having a cross-linked polymerized monomer with a negative charge. The organic liquid has a lower concentration of the metal contaminants after passing through the porous polymeric membranes. In a particular embodiment, the organic liquid includes liquids used for photoresist.

As discussed, the method is not limited by a sequence or order unless specified and may be repeated as desired. In another embodiment, the membrane with cross-linked monomers with negative charges is first membrane, and the membrane with the cross-linked monomers with positive charges is the second membrane. Furthermore, a combination of polymerized monomers <NUM> with positive and negative charges can be coated on the porous polymeric membrane <NUM>. In another embodiment, the coating <NUM> with polymerized monomers <NUM> having positive and negative charges are on the same membrane <NUM>. In an embodiment, the first membrane in a two layer membrane stack can include a coating <NUM> with polymerized monomers <NUM> having positive and negative charges on the same membrane <NUM>. In another embodiment, the second membrane in a two layer membrane stack can include a coating <NUM> with polymerized monomers having positive and negative charge on the same membrane <NUM>. As discussed, sequence or frequency or order may be altered unless specified. It should be appreciated that the first and second membranes <NUM> may effectively remove metal contaminants which differ from each other or at differing efficiency.

Another embodiment includes a method of removing metal contaminants from an organic liquid by passing an organic liquid through a porous polymeric membrane <NUM> having a plurality of layers. The porous polymeric membrane includes first layer and second layer. The first layer includes a coating <NUM> having one or more cross-linked polymerized monomers <NUM> with a positive charge. The second layer includes a coating having one or more cross-linked polymerized monomers <NUM> with a negative charge. The organic liquid has a lower concentration of the metal contaminants after passing thru the porous polymeric membrane <NUM>. In a particular embodiment, the organic liquid includes liquids used for photoresist. A combination of polymerized monomers with positive and negative charges can be coated on the layers of the polymeric membrane <NUM>. It should be appreciated that different layers of a membrane <NUM> and in a device <NUM> may effectively remove metal contaminants which differ from each other or at differing efficiency.

In an embodiment, metal contaminants removed include such as but are not limited to Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Mo, Ag, Cd, Sn, Ba, and Pb, either individually or in combinations of two or more therof. In another embodiment, metal contaminants are removed such as Al, Ca, Cr, Cu, Fe, Pb, Mg, Mn, Ni, K, Na, Sn, Ti, and Zn, either individually or in combinations of two or more therof. In a particular embodiment, metal contaminants are removed such as Fe, Ni, Cr, Cu, and Al, either individually or in combinations of two or more thereof. In an embodiment, metal contaminants are removed such as Fe, Ni, and Cr, either individually or in combinations of two or more thereof. In an embodiment, metal contaminant removal efficiency of metals, such as Al, Ca, Cr, Cu, Fe, Pb, Mg, Mn, Ni, K, Na, Sn, Ti, and Zn combined, from water immiscible organic liquid after passing the water immiscible organic liquid thru the porous membrane is about <NUM>% for removing metal contaminants from organic liquid immiscible with water. In the examples provided infra, a device with <NUM><NUM> membrane area was challenged with <NUM> of solution of respective liquid. In a particular embodiment, metal contaminant removal efficiency is about <NUM>%, <NUM>%, <NUM>%, <NUM>, <NUM>%, and <NUM>% and <NUM>% as detailed in Table <NUM> infra. In other words, the metal contaminant concentration in the organic liquid feed stream for one or more of the metal species listed above is reduced after passing through one or more of the coated porous membranes by about <NUM>%, <NUM>%, <NUM>%, <NUM>, <NUM>%, and <NUM>% and <NUM>% of the initial feed concentration. In some embodiments the metal contaminant concentration in the organic liquid feed stream is <NUM> parts per billion (ppb v/v) or less and the metal contaminant removal is measured by passing the organic liquid feed stream through a device including <NUM><NUM> of coated porous membrane as described herein at a flow rate of <NUM> milliliters per minute (ml/min) and measuring the treated effluent organic liquid.

In an embodiment, the total concentration of metal contaminants in the organic liquid after passing thru the porous membrane is less than <NUM> ppb v/v. In another embodiment, the concentration of total metal contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppb v/v. In a particular embodiment, concentration of total metal contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppb v/v. In other embodiments, concentration of total metal contaminants is less than about <NUM> ppb v/v, less than about <NUM> ppb v/v, less than about <NUM> ppb v/v, less than about <NUM> ppb v/v, less than about <NUM> ppb v/v, less than about <NUM> ppb v/v, less than about <NUM> ppb v/v, and less than about <NUM> ppb v/v. In some embodiments the organic liquid is water immiscible.

In a particular embodiment, metal contaminant removal efficiency of Fe contaminants from the organic liquid after passing through a device with a <NUM><NUM> sample of the coated cross-linked monomer on a porous membrane is at least <NUM>% [after <NUM> liquid treated by the device] for removing metal contaminants from organic liquid. In another embodiment, Fe contaminant removal efficiency is about <NUM>%, <NUM>%, <NUM>%, <NUM>, <NUM>%, and <NUM>% and <NUM>%. In an embodiment, the concentration of Fe contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> parts per billion by volume (ppbv/v). In another embodiment, the concentration of Fe contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppbv/v. In a particular embodiment, the concentration of Fe contaminants in the organic liquid after passing thru the porous membrane is about <NUM> ppb. In other embodiments, concentration of Fe contaminants is less than about <NUM> ppbv/v and less than about <NUM> ppbv/v. In some embodiments, the organic liquid is water immiscible.

In another particular embodiment, metal contaminant removal efficiency of Ni contaminants from organic liquid after passing through a device with a <NUM><NUM> sample of the coated cross-linked monomer on a porous membrane is at least <NUM>% [after <NUM> liquid treated by the device] for removing metal contaminants from organic liquid. In other embodiments, Ni contaminant removal efficiency is about <NUM>%, <NUM>%, <NUM>%, <NUM>, <NUM>%, and <NUM>% and <NUM>%. In an embodiment, the concentration of Ni contaminants in the organic liquid after passing thru the porous membrane is about <NUM> ppb v/v. In another embodiment, the concentration of Ni contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppb v/v. In a particular embodiment, the concentration of Ni contaminants in the organic liquid after passing thru the porous membrane is about <NUM> ppb v/v. In other embodiments, concentration of Ni contaminants is less than about <NUM> ppbv/v and less about <NUM> ppb v/v. In some embodiments, the organic liquid is water immiscible.

In yet another embodiment, metal contaminant removal efficiency of Cr from organic liquid after passing through a device with a <NUM><NUM> sample of the coated cross-linked monomer on a porous membrane is at least <NUM>% [after <NUM> liquid treated by the device] for removing metal contaminants from organic liquid. In another embodiment, Cr contaminant removal efficiency is about <NUM>%, <NUM>%, <NUM>%, <NUM>, <NUM>%, and <NUM>% and <NUM>%. In an embodiment, the concentration of Cr contaminants in the organic liquid after passing thru the porous membrane is about <NUM> ppb v/v. In another embodiment, the concentration of Cr contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppb v/v. In a particular embodiment, the concentration of Cr contaminants in the organic liquid after passing thru the porous membrane is about <NUM> ppb v/v. In other embodiments, concentration of Cr contaminants is less than about <NUM> ppb v/v, less than about <NUM> ppb v/v, and less than about <NUM> ppb v/v. In some embodiments, the organic liquid is water immiscible.

In yet another embodiment, metal contaminant removal efficiency of Al from organic liquid after passing through a device with a <NUM><NUM> sample of the coated cross-linked monomer on a porous membrane is at least <NUM>% [after <NUM> liquid treated by the device] for removing metal contaminants from organic liquid. In other embodiment, Al contaminant removal efficiency is about <NUM>%, <NUM>%, <NUM>%, <NUM>, <NUM>%, and <NUM>% and <NUM>%. In an embodiment, the concentration of Al contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppb v/v. In another embodiment, the concentration of Al contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppb v/v. In a particular embodiment, the concentration of Al contaminants in the organic liquid after passing thru the porous membrane is about <NUM> ppb v/v. In some embodiments the organic liquid is water immiscible.

In another embodiment, metal contaminant removal efficiency of Cu from the organic liquid after passing through a device with a <NUM><NUM> sample of the coated cross-linked monomer on a porous membrane is at least <NUM>% [after <NUM> liquid treated by the device] for removing metal contaminants from organic liquid. In other embodiments, Cu contaminant removal efficiency is about <NUM>%, <NUM>%, <NUM>%, <NUM>, <NUM>%, and <NUM>% and <NUM>%. In a particular embodiment, the concentration of Cu contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppb v/v. In another embodiment, the concentration of Cu contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppb v/v. In a particular embodiment, the concentration of Cu contaminants in the organic liquid after passing thru the porous membrane is less than about <NUM> ppb v/v.

The amount of negatively charged groups in the coatings on the porous polymeric membranes in embodiments of the disclosure is related to the amount of methylene blue dye (available from Sigma) that binds to the membrane. To determine the methylene blue dye binding capacity by a membrane sample, a <NUM> diameter sample of the coated membrane can be soaked in a beaker containing a solution containing <NUM> weight% of the dye for <NUM> minutes with continuous mixing at room temperature. The membrane disk can then be then removed and the absorbance of the dye solution measured using a Cary spectrophotometer (Agilent Technologies) operating at a wavelength of <NUM> nanometers (nm) and compared to the absorbance of starting solution (before membrane soaking). Since the dye is cationic in nature it bound to the negatively charged membrane. In embodiments of porous polymeric membranes comprising cross-linked polymerized negatively charged monomers, the methylene blue dye binding can range from <NUM>µg/cm<NUM> to <NUM>µg/cm<NUM>.

The amount of positively charged groups in the coatings on the porous polymeric membranes in embodiments of the disclosure is related to the amount of Ponceau-S dye (available from Sigma) dye that binds to the membrane. To determine the Ponceau-S dye binding capacity by a membrane sample, a <NUM> diameter sample of the coated membrane can be soaked in a beaker containing <NUM> weight% Ponceau-S dye (Sigma) for <NUM> minutes with continuous mixing at room temperature. The membrane disk can then be removed and the absorbance of the dye solution measured using a Cary spectrophotometer (Agilent Technologies) operating at a wavelength of <NUM> and compared to the absorbance of starting solution (before membrane soaking). Because the dye is anionic in nature, the dye is bound to the positively charged membrane. In embodiments of porous polymeric membranes comprising cross-linked polymerized positively charge monomers, the Ponceau-S dye binding can range from <NUM>µg/cm<NUM> to <NUM>µg/cm<NUM>.

The charge density of the porous polymeric membranes comprising cross-linked polymerized negatively charge monomers can be determined by titration of HCl conditioned membrane samples with <NUM> NaOH as described herein. The charge density of the negatively charged membrane in embodiments of the disclosure may range from about <NUM> to about <NUM> meq/m<NUM>. In some embodiments, the negatively charged membrane can have a charge density as determined by the above titration procedure of from about <NUM> meq/m<NUM>to <NUM> meq/m<NUM>; in other embodiments the charge density can range from <NUM> meq/m<NUM> to <NUM> meq/m<NUM>; from <NUM> meq/m<NUM> to <NUM> meq/m<NUM>; from <NUM> meq/m<NUM> to 12meq/m<NUM>; and from <NUM> meq/m<NUM> to <NUM> meq/m<NUM>. Higher charge densities provide greater contaminant binding capacity.

The charge density of the porous polymeric membranes comprising cross-linked polymerized positively charge monomers can be determined by titration of NaOH conditioned membrane samples with <NUM> HCl as described herein. The charge density of the positively charged membrane in embodiments of the disclosure may range from about <NUM> meq/m<NUM> to about <NUM> meq/m<NUM>. In some embodiments, the positively charged membrane can have a charge density as determined by this titration procedure can range from about <NUM> meq/m<NUM> to <NUM> meq/m<NUM>; in other embodiments the charge density can range from: <NUM> meq/m<NUM> to <NUM> meq/m<NUM>; from <NUM> meq/m<NUM> to <NUM> meq/m<NUM>; from <NUM> meq/m<NUM> to 12meq/m<NUM>; from <NUM> meq/m<NUM> to <NUM> meq/m<NUM>; from <NUM> meq/m<NUM> to 7meq/m<NUM>; and from <NUM> meq/m<NUM> to <NUM> meq/m<NUM>. Higher charge densities provide greater contaminant binding capacity.

It should be appreciated that first and second coated porous polymeric membranes as disclosed herein and a device containing these may effectively remove metal contaminants which differ from each other. In some embodiments the organic liquid is water immiscible.

Another embodiment of the disclosure provides a filtration device <NUM> as shown in <FIG>. The filtration device <NUM> includes a filter incorporating a porous polymeric membrane <NUM>. The porous polymeric membrane <NUM> includes a coating having a cross-linked polymerized monomer with a charge. Embodiments of the filtration device include coated porous polymeric membranes with positively charged monomers, negatively charged monomers, those with positively charged monomer and negatively charged monomers mixed together, those with zwitterionic monomers, and those that combine one or more charged monomers on two or more separate porous polymeric membrane layers (see <FIG> and device <NUM>). In an embodiment, organic liquid has a lower concentration of metal contaminants after passing through the porous membrane. In a particular embodiment, the organic liquid includes water immiscible organic liquid. In another particular embodiment, the organic liquid includes organic liquid used for photoresist.

Another embodiment of the filtration device <NUM> includes a filter as shown in <FIG> incorporating a plurality of membranes <NUM> and <NUM>. A first porous polymeric membrane <NUM> includes a coating <NUM> having a cross-linked polymerized monomer with a positive charge. A second porous polymeric membrane <NUM> includes a coating <NUM> having a cross-linked polymerized monomer with a negative charge. In an embodiment, organic liquid has a lower concentration of metal contaminants after passing through the porous membrane. In a particular embodiment, the organic liquid includes water immiscible organic liquid. In another particular embodiment, the organic liquid includes organic liquid used for photoresist.

As discussed, embodiments are not limited by a sequence or order unless specified and may be repeated as desired. In another embodiment, the membrane with cross-linked monomers with negative charges is first membrane, and the membrane with the cross-linked monomers with positive charges is the second membrane. Furthermore, a combination of polymerized monomers <NUM> with positive and negative charges can be coated on the polymeric membrane <NUM>. It should be appreciated that the first and second membranes <NUM> may effectively remove metal contaminants which differ from each other or at differing efficiency.

Another embodiment of the filtration device <NUM> includes a filter incorporating one or more polymeric porous membranes <NUM>, and <NUM>. In the illustrated and non-limiting embodiment in <FIG>, the device <NUM> has porous polymeric membrane including a first layer <NUM> and second layer <NUM>. The first layer includes a coating <NUM> having one or more cross-linked polymerized monomers with a positive charge. The second layer includes a coating <NUM> having one or more cross-linked polymerized monomers with a negative charge. The organic liquid has a lower concentration of the metal contaminants after passing through the coated porous polymeric membranes <NUM> and <NUM>. In a particular embodiment, the organic liquid includes a liquid used for photoresist. A combination of polymerized monomers with positive and negative charges can be coated on the layers of the polymeric membrane <NUM>. It should be appreciated that different layers of a membrane in the device <NUM> may effectively remove metal contaminants which differ from each other or at differing efficiency. Order of the layers does not matter and is not restricted unless specified.

As discussed supra, monomers with positive charges include <NUM>-(dimethylamino)ethyl hydrochloride acrylate, [<NUM>-(acryloyloxy)ethyl] trimethylammonium chloride, <NUM>-aminoethyl methacrylate hydrochloride, N-(<NUM>-aminopropyl) methacrylate hydrochloride, <NUM>-(dimethylamino)ethyl methacrylate hydrochloride, [<NUM>-(methacryloylamino)propyl]trimethylammonium chloride solution, [<NUM>-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyl trimethylammonium chloride, <NUM>-aminoethyl methacrylamide hydrochloride, N-(<NUM>-aminoethyl) methacrylamide hydrochloride, N-(<NUM>-aminopropyl)-methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride, vinyl imidazolium hydrochloride, vinyl pyridinium hydrochloride, and vinyl benzyl trimethyl ammonium chloride, either individually or in combinations of two or more thereof.

In a particular embodiment, the monomer with positive charge that can be used in a coating includes acrylamido propyl trimethylammonium chloride (APTAC).

In an embodiment, the coating <NUM> includes a plurality of polymerized monomers with positive charges. It should be appreciated that embodiments of the disclosure include a plurality of polymerized monomers with positive charges which differ from each other or are the same. In an embodiment, some of the plurality of polymerized monomers <NUM> with positive charges are the same. In another particular embodiment, some of the plurality of polymerized monomer with positive charges differ from each other. The plurality of polymerized monomers <NUM> with positive charges may have one or more characteristics which differ from each other or are similar. As shown in <FIG>, in a particular embodiment, one or more monomers with positive charges can be cross-linked to other one or more monomers.

As also discussed supra, monomers with negative charges include <NUM>-ethylacrylic acid, acrylic acid, <NUM>-carboxyethyl acrylate, <NUM>-sulfopropyl acrylate potassium salt, <NUM>-propyl acrylic acid, <NUM>-(trifluoromethyl)acrylic acid, methacrylic acid, <NUM>-methyl-<NUM>-propene-<NUM>-sulfonic acid sodium salt, mono-<NUM>-(methacryloyloxy)ethyl maleate, <NUM>-sulfopropyl methacrylate potassium salt, <NUM>-acrylamido-<NUM>-methyl-<NUM>-propanesulfonic acid, <NUM>-methacrylamido phenyl boronic acid, vinyl sulfonic acid, and vinyl phosphonic acid, either individually or combinations of two or more thereof.

In a particular embodiment, the monomer with negative charge that can be used in a coating includes vinyl sulfonic acid or a salt thereof.

In an embodiment, the plurality of polymerized monomers <NUM> includes monomers with negative charges. It should be appreciated that embodiments of the disclosure include a plurality of polymerized monomers <NUM> with negative charges which differ from each other or are the same. In an embodiment, the plurality of monomers polymerized with negative charges are the same. In another particular embodiment, the plurality of polymerized monomers <NUM> with negative charges differ from each other. The plurality of polymerized monomers <NUM> with negative charges may have one or more characteristics which differ from each other or are similar. Monomers with negative charges can be cross-linked to other monomers with other charges or same charges.

In an embodiment, the plurality of polymerized monomers include zwitterionic monomers. Polymerized zwitterionic monomers <NUM> can be cross-linked or grafted to the porous polymeric membrane <NUM>. It should be appreciated that embodiments of the disclosure include a plurality of polymerized zwitterionic monomers <NUM> which differ from each other or are the same. In an embodiment, the plurality of zwitterionic polymerized monomers are the same. In another particular embodiment, the plurality of polymerized zwitterionic monomers <NUM> differ from each other. The plurality of polymerized zwitterionic monomers <NUM> may have one or more characteristics which differ from each other or are similar.

A zwitterionic monomer has both a positive and negative charge in the same monomeric backbone. Examples of zwitterionic monomers that can be grafted or cross-linked to the porous polymeric membrane in embodiments of the disclosure include [<NUM>-(Methacryloylamino)propyl]dimethyl(<NUM>-sulfopropyl)ammonium hydroxide; [<NUM>-(Methacryloyloxy)ethyl]dimethyl-(<NUM>-sulfopropyl)ammonium hydroxide; <NUM>-(Methacryloyloxy)ethyl <NUM>-(Trimethylammonio)ethyl Phosphate; and <NUM>-(<NUM>-Sulfopropyl)-<NUM>-vinylpyridinium hydroxide either individually or combinations of two or more thereof.

For illustration and not limitation, polymerization and cross-linking of the polymerizable monomer onto the porous membrane <NUM> substrate can be effected so that a select portion or the entire surface of the porous membrane <NUM>, including the inner surfaces of the porous membrane, is modified with a cross-linked polymer. It should be understood that various embodiments of the coated porous polymeric membrane encompasses cross-linking as much of the surface of the membrane as desired from greater than <NUM>% to <NUM>%. It should also be understood that embodiments also encompass other technique such as grafting and a combination of techniques such as a portion is cross-linked and a portion is grafted. Embodiments also encompass cross-linking a grafted portion.

A reagent bath comprised of: (<NUM>) at least one polymerizable monomer which is ethylenically unsaturated and has at least one charged monomer group, (<NUM>) a polymerization initiator, if needed, and (<NUM>) a cross-linking agent in a polar solvent such as a water soluble solvent for these three constituents, is contacted with the porous polymeric membrane substrate under conditions to effect polymerization and crosslinking of the monomer and deposition of the resulting cross-linked polymer onto the porous polymeric membrane substrate. Even though the solvent is a polar solvent, the requisite degree of membrane surface modification may be and is obtained. When the monomer is di-functional or has higher functionality, an additional cross-linking agent is not needed but may be used. Representative suitable polar solvents include solvents having a dielectric constant above <NUM> at room temperature such as polyols including <NUM>-methyl-<NUM>,<NUM>-pentanediol, <NUM>,<NUM> pentanedione, glycerine or <NUM>,<NUM>'-thiodiethanol; amides such as formamide, dimethyl formamide, dimethyl acetamide; alcohols such as methanol, or the like; and nitro substituted aromatic compounds including nitrobenzene, <NUM>- furaldehyde, acetonitrile, <NUM>-methyl pyrrolidone or the like. The particular solvent is chosen to solublize the cross-linking agent, the monomer and the initiator, if present.

Suitable initiators and cross-linking agents for the monomers described above can be used. For example, when utilizing charged alkyl groups as the polymerizable monomer, suitable photopolymerization initiators include benzophenone, <NUM>-(<NUM>-hyroxyethoxy)phenyl-(<NUM>-hydroxy-<NUM>-propyl) ketone, azoisopropane or <NUM>,<NUM>-dimethoxy-<NUM>-phenylacetophenone or the like. Suitable thermal initiators include organic peroxides such as dibenzoyl peroxide, t-butylhydroperoxide, cumylperoxide or t-butyl perbenzoate or the like and azo compounds such as azobisisobutyronitrile (AIBN) or <NUM>,<NUM>,'-azobis(<NUM>-cyanovaleric acid) or the like. Representative suitable cross-linking agents include <NUM>,<NUM>-hexanediol diacrylate, tetraethylene glycol diacrylate; <NUM>,<NUM>,<NUM>-trimethylolpropane triacrylate or the like; N, N'-methylene bisacrylamide or the like, either individually or combinations of two or more thereof.

Generally, the polymerizable monomer is present in the reactant solution at a concentration between about <NUM>% and about <NUM>%, preferably between about <NUM>% and about <NUM>% based upon the weight of the total solution. The cross-linking agent is present in an amount of between about <NUM>% and about <NUM>% by weight, based upon the weight of the polymerizable monomer. Greater amounts of cross-linking agents can be used. The polymerization initiator is present in an amount of between about <NUM>% and about <NUM>% by weight, based upon the weight of the polymerizable monomer. As noted above, the cross-linking agent can be utilized without the monomer and thereby functions as the polymerizable monomer.

Polymerization and cross-linking is effected by exposing the monomer reaction system to ultraviolet (UV) light, thermal sources or ionizing radiation. The polymerization and crosslinking is effected in an environment where oxygen does not inhibit polymerization or crosslinking. The process is conveniently effected by dipping the membrane substrate in the solution containing the monomer, crosslinking agent, and the initiator, sandwiching the membrane between two ultraviolet light transparent sheets, such as polyethylene, or in a blanket of an inert gas such as nitrogen and exposing to UV light. The process can be effected continuously and the desired cross-linked coating is formed after UV exposure is initiated. By controlling the reactant concentrations and UV exposure, as set forth above, a composite membrane is produced which is nonplugged and has essentially the same porous configuration as the membrane substrate.

The porosimetry bubble point test method measures the pressure required to push air through the wet pores of a membrane. Generally the higher the pressure, the smaller the pore size of the membrane. The test was performed by mounting a <NUM> disk of a dry membrane sample in a holder with the tight side (e.g., having smaller pores in an asymmetric membrane) of the membrane facing down. The holder is designed in a way to allow the operator to place a small volume of liquid on the upstream side of the membrane. The dry air flow rate of the membrane is measured first by increasing the air pressure on the upstream side of the membrane to <NUM> psi. The pressure is then released back to atmospheric pressure and a small volume of isopropyl alcohol. (IPA) (Sigma, USA) is placed on the upstream side of the membrane to wet the membrane. The wet air flow rate is then measured by increasing the pressure again to <NUM> psi. The bubble point of the membrane is measured from the pressure required to displace IPA from the pores of the IPA-wet membrane. This critical pressure point is defined as the pressure at which a first non-linear increase of wet air flow is detected by the flow meter. The range of observed IPA bubble point for porous membranes used in this application was <NUM>-<NUM> pounds per square inch (psi).

Membrane IPA flow time was determined by cutting membranes into <NUM> disks and wetting with IPA before placing the disk in a filter holder with a reservoir for holding a volume of IPA. The reservoir is connected to a pressure regulator. IPA was flowed through the membrane under <NUM> psi (pounds per square inch) differential pressure. After equilibrium was achieved, the time for <NUM> of IPA to flow through the membrane was recorded.

<FIG> is a schematic of diagram of a testing line for removing metals from an organic liquid in accordance with an embodiment of the disclosure. The testing line can include a pressure reducing valve <NUM> in-line with a gas purifier and or particle filter <NUM> to purify the gas used to pressure dispense test organic liquid <NUM> contained in pressure vessel <NUM>. The test organic liquid <NUM> can be spiked with a metals standard like CONOSTAN S-<NUM> Standard (SCP science, oil based <NUM> metal standard, <NUM> ppm total concentration) to create the metals challenge in the liquid <NUM>. The volume and flow rate of the spiked organic liquid can be determined using flow meter <NUM> and by collection of filtrate <NUM> after passing through one or more test coated porous polymeric membranes in membrane test holder or disposable filter <NUM>. The method is not limited by the order or frequency of the steps unless expressly noted. It should be appreciated method includes repeating steps at desired frequency and intervals unless specified.

Fill the tank with the feed (challenge) solution of organic liquid.

Pump challenge solution of organic liquid through the device at <NUM>/min flow rate for <NUM>. Collect filtrate.

Measure metal concentration of the feed and filtrate solutions of the organic liquid using atomic absorption spectroscopy or ICP-MS. Calculate metal removal efficiency by comparing metal concentration before and after passing the organic liquid through the coated porous membrane.

The following examples illustrate the invention. Only those examples falling within the scope of the claims are examples of the invention.

This example demonstrates the preparation of surface modification solution which includes monomers with negative charges as well as a radical initiator i.e. materials to form coating.

In a representative experiment, a solution was made which includes: <NUM> % Irgacur <NUM>; <NUM>% Methanol, <NUM>%Vinyl sulfonic acid salt( N-SVN-<NUM>); <NUM>% Dimethyl acrylamide ( DMAm), <NUM>% Acrylamido methyl Propane sulfonic acid (AMPS), <NUM>% methylene bis acrylamide (MBAm) cross linker, <NUM>% water.

This example demonstrates the preparation of surface modification solution containing monomers with positive charges, as well as a radical initiator i.e. materials to form coating.

In a representative experiment, a solution was made containing: <NUM>% Irgacure <NUM>, <NUM>% Methanol <NUM>% Acrylamido propyl trimethylammonium Chloride( APTAC), <NUM>% Dimethyl acrylamide ( DMAm) and <NUM>% methylene bis acrylamide ( MB Am) cross linker, <NUM>% water.

This example demonstrates how a polyethylene membrane is surface modified with a coating having polymerized monomer with negative charges.

In a representative experiment, <NUM> disk of UPE porous membrane (<NUM> psi average mean bubble point in IPA, Entegris, Inc. ) was wet with IPA solution for <NUM> sec. An exchange solution comprising <NUM> % hexylene glycol and <NUM> %water was used to rinse the membrane and remove IPA. The porous membrane disk was then introduced into the surface modification solutions described in Example <NUM>. The dish was covered and the porous membrane was soaked in the solution for <NUM> minutes. The porous membrane disk was removed and placed between <NUM> mil polyethylene sheets. The excess solution was removed by rolling a rubber roller over the polyethylene/membrane disk/polyethylene sandwich as it lays flat on a table. The polyethylene sandwich was then taped to a transport unit which conveyed the assembly through a Fusion Systems broadband UV exposure lab unit emitting at wavelengths from <NUM> to <NUM>. Time of exposure was controlled by how fast the assembly moves through the UV unit. In this example, the assembly moved through the UV chamber at <NUM> feet per minute. After emerging from the UV unit, the membrane was removed from the sandwich and immediately placed in DI water, where it was washed by swirling for <NUM> minutes. Next, the treated membrane sample was washed in methanol for <NUM> minutes. Following this washing procedure the membrane was dried on a holder in an oven operating at <NUM> for <NUM>. IPA flow time of the membrane modified as described above was <NUM> sec.

This example demonstrates how a polyethylene membrane is surface modified to with coating having polymerized monomer with positive charge.

In a representative experiment, <NUM> disk of UPE membrane (<NUM> psi average mean bubble point in IPA, Entegris, Inc. ) was wet with IPA solution for <NUM> sec. An exchange solution comprising <NUM> % hexylene glycol and <NUM> %water was used to rinse the membrane and remove IPA. The membrane disk was then introduced into the surface modification solution described in Example <NUM>. The dish was covered and the membrane was soaked in the solution for <NUM> minutes. The membrane disk was removed and placed between <NUM> mil polyethylene sheets. The excess solution was removed by rolling a rubber roller over the polyethylene/membrane disk/polyethylene sandwich as it lays flat on a table. The polyethylene sandwich was then taped to a transport unit which conveyed the assembly through a Fusion Systems broadband UV exposure lab unit emitting at wavelengths from <NUM> to <NUM>. Time of exposure was controlled by how fast the assembly moves through the UV unit. In this example, the assembly moved through the UV chamber at <NUM> feet per minute. After emerging from the UV unit, the membrane was removed from the sandwich and immediately placed in DI water; where the membrane was washed by swirling for <NUM> minutes. Next, the treated membrane sample was washed in methanol for <NUM> minutes. Following this washing procedure the membrane was dried on a holder in an oven operating at <NUM> for <NUM>. The IPA flow time of the membrane modified as described above was <NUM> sec.

This example illustrates how the dye binding capacity of the membrane modified according to Example <NUM> was determined.

To confirm that the process of Example <NUM> resulted in a negatively charged UPE membrane the following experiment was carried out: The dry <NUM> disk membrane of Example <NUM> was placed in a beaker containing <NUM> weight% Methylene blue dye (Sigma). The beaker was covered and the membrane was soaked for <NUM> minutes with continuous mixing at room temperature. The membrane disk was then removed and the absorbance of the dye solution was measured using a Cary spectrophotometer (Agilent Technologies) operating at <NUM> and compared to the absorbance of starting solution (before membrane soaking). Since the dye is cationic in nature it bound to the negatively charged membrane with an average dye binding capacity measured in micrograms (µg) per centimeter squared of <NUM>µg/cm<NUM>. The calibration curve depicted in <FIG> was used to convert dye solution absorbance data to weight% and finally mass of dye bound per membrane unit area.

The absorbance of <NUM> dye solutions with known concentrations was determined using a Cary Spectrophotometer at <NUM> wavelength and used to obtain a calibration curve. The slope of the curve was used to convert the absorbance of the dye solution before and after soaking the membrane to weight% and finally mass of dye bound per membrane unit area.

To confirm that the process of Example <NUM> resulted in a positively charged UPE membrane the following experiment was carried out: The dry <NUM> disk membrane of Example <NUM> was placed in a beaker containing <NUM> weight% Ponceau-S dye (Sigma). The beaker was covered and the membrane was soaked for <NUM> minutes with continuous mixing at room temperature. The membrane disk was then removed and the absorbance of the dye solution was measured using a Cary spectrophotometer (Agilent Technologies) operating at <NUM> and compared to the absorbance of starting solution (before membrane soaking). Because the dye is anionic in nature, the dye is bound to the positively charged membrane with an average dye binding capacity measured in micrograms (µg) per centimeter squared of 54µg/cm<NUM>. The calibration curve depicted in <FIG> was used to convert dye solution absorbance data to weight% and finally mass of dye bound per membrane unit area.

This example illustrates the metal removal efficiency in cyclohexanone of a device comprising membrane prepared as described in Example <NUM>.

A device was made comprising <NUM><NUM> of the membrane prepared according to Example <NUM>. The device was connected to a testing line and challenged with cyclohexanone feed solution as described in the general metal removal test procedure section. A challenge solution was prepared by spiking <NUM> of CONOSTAN S-<NUM> Standard (SCP science, oil based <NUM> metal standard, <NUM> ppm total concentration) into <NUM> of cyclohexanone solution (Sigma). Resulting metal concentration in the challenge solution was determined using ICP-MS and is depicted in Table1. The concentration of metals decreased significantly, after filtration through the positively charged membrane device. Removal efficiency ranged from <NUM> to <NUM>% depending on metal type.

This example illustrates the metal removal efficiency in Cyclohexanone of a device comprising membrane prepared as described in Example <NUM>.

A device was made comprising <NUM><NUM> of the membrane prepared according to Example <NUM>. The device was connected to a testing line and challenged with cyclohexanone feed solution as described in the general metal removal test procedure section. A challenge solution was prepared by spiking <NUM> of CONOSTAN S-<NUM> Standard (SCP science, oil based <NUM> metal standard, <NUM> ppm total concentration) into <NUM> of cyclohexanone solution (Sigma). Resulting metal concentration in the challenge solution was determined using ICP-MS and is depicted in Table <NUM>. The concentration of metals decreased after filtration through the negatively charged membrane device. Removal efficiency ranged from <NUM> to <NUM>% depending on metal type.

This example illustrates the improved metal removal efficiency in cyclohexanone when an embodiment of a device with a positively charged membrane is used instead of a device with a negatively charged membrane. Common metals present in cyclohexanone solution according to Example <NUM> and Example <NUM>, were plotted in <FIG> to demonstrate the surprising superior metal removal efficiency of positively charged membrane device (black bars) e.g. <NUM> in comparison to negatively charged membrane device (gray bars) e.g. <NUM> for the elements Na, Mg, Al, Fe, Ti, Cr, Ni, Cu, Ag, Sn, and Pb.

<FIG> is a comparative graph of removing metal contaminants from cyclohexanone with an embodiment of positively charged membrane device <NUM> vs. a negatively charged membrane device and comparatively shows the difference in removing metal contaminants from liquids that are miscible with and not miscible with water. <FIG> demonstrates the method, membrane and device unexpectedly and efficiently remove metal contaminants from water immiscible organic liquid by at least <NUM>% after passing the water immiscible organic liquid thru the porous membrane.

Charge density determination of negatively Charged <NUM> micron (µm) bubble point pore size rated UPE Membrane prepared as described in Example <NUM>.

Six <NUM> diameter membrane coupons were cut from a cross section of a negatively charged <NUM> UPE membrane. The membranes were prewet with IPA and exchanged into water. The wetted membrane were conditioned by dipping into <NUM> N HCl followed by submerging in <NUM> of <NUM> N HCl for <NUM> minutes with stirring. The HCl conditioned membrane were repeatedly washed in fresh <NUM> deionized water until the pH of the deionized water wash stabilized at pH of +/- <NUM> relative to the fresh (not exposed to membrane) deionized water reading. The membranes were then placed in <NUM> of <NUM> NaCl and stirred for <NUM> minutes and the membranes were removed and discarded. The <NUM> of <NUM> NaCl that was exposed to the membrane had a pH of <NUM>. The solution was titrated with <NUM> NaOH and the volume of NaOH to reach pH <NUM> was recorded. The charge density of the negatively charged membrane was determined to be <NUM> meq/m<NUM>. For comparison, an unmodified <NUM> UPE membrane was run as a control and the charge density was determined to be <NUM> meq/m<NUM>. Although the charge density of the negatively charged membrane was determined to be <NUM> meq/m<NUM>, the charge density of the negatively charged membrane may range from about <NUM> to about <NUM> meq/m<NUM>. In an embodiment, the negatively charged membrane has a charge density from about <NUM> meq/m<NUM>to <NUM> meq/m<NUM>, <NUM> meq/m<NUM> to <NUM> meq/m<NUM>, <NUM> meq/m<NUM> to <NUM> meq/m<NUM>, <NUM> meq/m<NUM> to 12meq/m<NUM>, and <NUM> meq/m<NUM> to <NUM> meq/m<NUM>.

Charge density determination of positively Charged <NUM> UPE Membrane prepared as described in Example <NUM>. Six <NUM> diameter membrane coupons were cut from a cross section of a positively charged <NUM> rated UPE membrane. The membranes were prewet with IPA and exchanged into water. The wetted membrane were conditioned by dipping into <NUM> N NaOH followed by submerging in <NUM> of <NUM> N NaOH for <NUM> minutes with stirring. The NaOH conditioned membrane were repeatedly washed in fresh <NUM> deionized water until the pH of the deionized water wash stabilized at pH of +/- <NUM> relative to the fresh (not exposed to membrane) deionized water reading. The membranes were then placed in <NUM> of <NUM> NaCl and stirred for <NUM> minutes and the membranes were removed and discarded. The <NUM> of <NUM> NaCl that was exposed to the membrane had a pH of <NUM>. The solution was titrated with <NUM> HCl and the volume of HCl to reach pH <NUM> was recorded. The charge density of the positively charged membrane was determined to be <NUM> meq/m2. An unmodified <NUM> UPE membrane was run as a control and the charge density was determined to be <NUM> meq/m2. Although the charge density of the positively charged membrane was determined to be <NUM> meq/m<NUM>, the charge density of the positively charged membrane may range from about <NUM> meq/m<NUM> to about <NUM> meq/m<NUM>. In an embodiment, the positively charged membrane has a charge density from about <NUM> meq/m<NUM> to <NUM> meq/m<NUM>, <NUM> meq/m<NUM> to <NUM> meq/m<NUM>, <NUM> meq/m<NUM> to <NUM> meq/m<NUM>, <NUM> meq/m<NUM> to 12meq/m<NUM>, <NUM> meq/m<NUM> to <NUM> meq/m<NUM>, <NUM> meq/m<NUM> to 7meq/m<NUM>, and <NUM> meq/m<NUM> to <NUM> meq/m<NUM>.

Thus, embodiments of the disclosure include membranes with specific charge density and method of making such membranes with a given charge density. The charge density is not limited to the particular value such as <NUM> meq/m<NUM>, <NUM> meq/m<NUM>, <NUM> meq/m<NUM>, but for illustration and not limitation of making positively charged membranes with charge density.

Positively and Negatively charged <NUM> UPE membranes were prepared using a method similar to Example <NUM> and Example <NUM> and cut into <NUM> membrane coupons. These membrane coupons were conditioned by washing several times with <NUM>% HCl followed by soaking in <NUM>% HCl overnight and equilibrated with deionized water. For each sample, one <NUM> membrane coupon was secured into a clean PFA <NUM> Single Stage Filter Assembly (Savillex). The membrane and filter assembly were flushed with IPA followed by application solvent. The application solvents include Cyclohexanone, a PGME (propylene glycol monomethyl ether ) composition, a PGME/PGMEA thinner, PGMEA (propylene glycol monomethyl ether acetate ), and a PGMEA/HBM (methyl <NUM>-hydroxy-<NUM>-methyl propionate)/EL (ethyl lactate) mixture. The application solvents were spiked with CONOSTAN Oil Analysis Standard S-<NUM> (SCP Science) at a target concentration of <NUM> ppb of each metal. To determine the filtration metal removal efficiency the metal spiked application solvents were passed through the corresponding <NUM> filter assembly containing each filter at <NUM>/min and the filtrate was collected into a clean PFAjar at <NUM>, <NUM>, and <NUM>. The metal concentration for the metal spiked application solvent and each filtrate sample was determined using ICP-MS. The results are depicted in Total Metals Removal (%) in Table <NUM> and Individual Metal Removal % at <NUM> Filtration in <FIG> (PGMEA), <FIG> (PGMEA/HBM/EL), <FIG> (Cyclohexanone), <FIG> (PGME/PGMEA thinner), and <FIG> (PGME).

This example demonstrates the ability for two layer format coated membrane materials to reduce metals in solvents. Positively and Negatively charged <NUM> UPE membranes were prepared using a method similar to Example <NUM> and Example <NUM> and cut into <NUM> membrane coupons. These membrane coupons were conditioned by washing several times with <NUM>% HCl followed by soaking in <NUM>% HCl overnight and equilibrated with deionized water. For each sample, two <NUM> membrane coupons were layered on top of each other and secured into a clean <NUM> Filter Assembly (Savillex) resulting in a two layer filter. The membrane and filter assembly were flushed with IPA followed by application solvent. The application solvents include Cyclohexanone, and PGME thinner. The application solvents were spiked with CONOSTAN Oil Analysis Standard S-<NUM> (SCP Science) at a target concentration of <NUM> ppb of each metal. To determine the filtration metal removal efficiency the metal spiked application solvents were passed through the corresponding <NUM> dual layer filter assembly containing each filter at <NUM>/min and the filtrate was collected into a clean PFA jar at <NUM>, <NUM>, and <NUM>. The metal concentration for the metal spiked application solvent and each filtrate sample was determined using ICP-MS. The results are depicted in Total Metals Removal (%) in Table <NUM> and Individual Metal Removal % at <NUM> Filtration in <FIG> (cyclohexanone), and <FIG> (PGME).

This example demonstrates the ability for coated membrane materials to reduce metals in solvents under static soaking conditions. Positively and Negatively charged <NUM> UPE membranes were prepared using a method similar to Example <NUM> and Example <NUM> and cut into <NUM> membrane coupons. These membrane coupons were conditioned by washing several times with <NUM>% HCl followed by soaking in <NUM>% HCl overnight, equilibrated with deionized water, and allowed to dry at room temperature. The application solvents include Cyclohexanone, PGME, PGME/PGMEA THINNER, PGMEA, and a PGMEA/HBM/EL THINNER. The application solvents were spiked with CONOSTAN Oil Analysis Standard S-<NUM> (SCP Science) at a target concentration of <NUM> ppb of each metal. To determine the static soak metal removal efficiency <NUM> of the metal spiked application solvents were placed in a PFA jar with the conditioned and dried <NUM> membrane coupons. The PFA jar containing the metal spiked application solvents and membrane coupons were rotated for <NUM> hours. After <NUM> hours the membrane coupons were removed. The metal concentration for the metal spiked application solvent and each solvent membrane supernatant sample was determined using ICP-MS. The results are provided in % Removal in Table <NUM>.

This example demonstrates the preparation of surface modification solution which includes individual monomers with positive and negative charges as well as a cross linker and a radical initiator i.e. materials to form coating.

In a representative experiment, a solution was made which includes <NUM> % Irgacur <NUM>; <NUM>% Methanol, <NUM> % Acrylamido methyl Propane sulfonic acid (AMPS), <NUM>% Acrylamido propyl trimethylammonium Chloride (APTAC), <NUM> % methylene bis acrylamide (MBAm) cross linker, <NUM>% water.

This example demonstrates how a polyethylene membrane is surface modified with coating having polymerized monomers with both positive and negative charges.

In a representative experiment, <NUM> disk of UPE membrane (<NUM> psi average mean bubble point in IPA, Entegris, Inc. ) was wet with IPA solution for <NUM> sec. An exchange solution comprising <NUM> % hexylene glycol and <NUM> % water was used to rinse the membrane and remove IPA. The membrane disk was then introduced into the solution from Example <NUM>. The dish was covered and the membrane was soaked in the solution for <NUM> seconds. The membrane disk was removed and placed between polyethylene sheets. The excess solution is removed by rolling a rubber roller over the polyethylene/membrane disk/polyethylene sandwich as it lays flat on a table. The polyethylene sandwich was then taped to a transport unit which conveyed the assembly through a Fusion Systems broadband UV exposure lab unit emitting at wavelengths from <NUM> to <NUM>. Time of exposure is controlled by how fast the assembly moves through the UV unit. In this example, the assembly moved through the UV chamber at <NUM> feet per minute. After emerging from the UV unit, the membrane was removed from the sandwich and immediately placed in DI water, where it was washed by swirling for <NUM> minutes. Next, the treated membrane sample was washed in methanol for <NUM> minutes. Following this washing procedure the membrane was dried on a holder in an oven operating at <NUM> for <NUM>.

Single Layer Mixed charged <NUM> UPE membranes were prepared using a method similar to Example <NUM> and cut into <NUM> membrane coupons. These membrane coupons were conditioned by washing several times with <NUM>% HCl followed by soaking in <NUM>% HCl overnight and equilibrated with deionized water. For each sample, one <NUM> membrane coupon was secured into a clean PFA <NUM> Single Stage Filter Assembly (Savillex). The membrane and filter assembly were flushed with IPA followed by application solvent. The application solvent was PGME based thinner. The application solvents were spiked with CONOSTAN Oil Analysis Standard S-<NUM> (SCP Science) at a target concentration of <NUM> ppb of each metal. To determine the filtration metal removal efficiency the metal spiked application solvents were passed through the corresponding <NUM> filter assembly containing each filter at <NUM>/min and the filtrate was collected into a clean PFA jar at <NUM>, <NUM>, and <NUM>. The metal concentration for the metal spiked application solvent and each filtrate sample was determined using ICP-MS. The results are depicted with a comparison to single charged membranes prepared with a similar method in Total Metals Removal (%) in Table <NUM> and Individual Metal Removal % at <NUM> Filtration in <FIG> (PGME). The mixed charge membrane shows improvements in Total Metal Removal when compared to either the positively or negatively single charge membrane. The mixed charged membrane shows improved Individual Metal Removal for at least B, Al, Ti, Mn, Fe, Ni, Sn, when compared to either the positively or negatively single charge membrane.

<NUM> disks of UHMWPE membrane (<NUM> psi HFE bubble point) were wet in <NUM> wt% benzophenone / IPA solution for <NUM> sec. A grafting monomer solution was made containing <NUM>% dimethylacrylamide (DMAM, Sigma) and <NUM>% of <NUM>-acrylamido-<NUM>-methylpropane sulfonic acid (AMPS, Sigma), <NUM>% N,N'-methylenebisacrylamide (MBAM), <NUM>% Sodium Sulfate, and <NUM>% sodium persulfate dissolved in water. The grafting monomer solution was placed in a dish and the Benzophenone wetted membrane was introduced into the solution. The dish was covered and the membrane was soaked for <NUM> minutes. The membrane disk was removed and placed between polyethylene sheets. The excess solution is removed by rolling a rubber roller over the polyethylene/membrane disks/polyethylene sandwich as it lays flat on a table. The polyethylene sandwich is then taped to a transport unit which conveys the assembly through a Fusion Systems broadband UV exposure lab unit emitting at wavelengths from <NUM> to <NUM>. Time of exposure is controlled by how fast the assembly moves through the UV unit. In this example, the assembly moved through the UV chamber at <NUM> feet per minute. After emerging from the UV unit, the membrane was removed from the sandwich and immediately placed in DI water, where it was washed by swirling for <NUM> minutes. Next, it was washed in methanol for <NUM> minutes. Following this washing procedure the membrane was dried on a holder in an oven operating at <NUM> for <NUM>. The resulting membrane had a negative charge which was confirmed with its ability to bind methylene blue dye.

<NUM> disks of UHMWPE membrane (<NUM> psi HFE bubble point) were wet in <NUM> wt% benzophenone / IPA solution for <NUM> sec. A grafting monomer solution was made containing <NUM>% dimethylacrylamide (DMAM, Sigma) and <NUM>% of acrylamido propyl trimethylammonium chloride (APTAC, Sigma), <NUM>% N,N'-methylenebisacrylamide (MBAM), <NUM>% Sodium Sulfate, and <NUM>% sodium persulfate dissolved in water. The grafting monomer solution was placed in a dish and the Benzophenone wetted membrane was introduced into the solution. The dish was covered and the membrane was soaked for <NUM> minutes. The membrane disk was removed and placed between polyethylene sheets. The excess solution is removed by rolling a rubber roller over the polyethylene/membrane disks/polyethylene sandwich as it lays flat on a table. The polyethylene sandwich is then taped to a transport unit which conveys the assembly through a Fusion Systems broadband UV exposure lab unit emitting at wavelengths from <NUM> to <NUM>. Time of exposure is controlled by how fast the assembly moves through the UV unit. In this example, the assembly moved through the UV chamber at <NUM> feet per minute. After emerging from the UV unit, the membrane was removed from the sandwich and immediately placed in DI water, where it was washed by swirling for <NUM> minutes. Next, it was washed in methanol for <NUM> minutes. Following this washing procedure the membrane was dried on a holder in an oven operating at <NUM> for <NUM>. The resulting membrane had a positive charge which was confirmed with its ability to bind Ponceau S dye.

Positively and Negatively charged UPE membranes were prepared using a grafting method similar to examples <NUM> and <NUM> and cut into <NUM> membrane coupons. These membrane coupons were conditioned by washing several times with <NUM>% HCl followed by soaking in <NUM>% HCl overnight and equilibrated with deionized water. For each sample, one <NUM> membrane coupon was secured into a clean PFA <NUM> Single Stage Filter Assembly (Savillex). For another sample one of each positively and negatively charged <NUM> coupon was secured into a clean PFA <NUM> Single Stage Filter Assembly. For another sample one unmodified membrane was secured into a clean PFA <NUM> Single Stage Filter Assembly. The membranes and filter assembly were flushed with IPA followed by application solvent. The application solvent was microelectronics grade PGMEA. The application solvent was spiked with CONOSTAN Oil Analysis Standard S-<NUM> (SCP Science) at a target concentration of <NUM> ppb of each metal. To determine the filtration metal removal efficiency the metal spiked application solvents were passed through the corresponding <NUM> filter assembly containing each filter at <NUM>/min and the filtrate was collected into a clean PFA jar at <NUM>, <NUM>, and <NUM>. The metal concentration for the metal spiked application solvent and each filtrate sample was determined using ICP-MS. The results are depicted in Total Metals Removal (%) in <FIG> (PGMEA).

Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative or qualitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term such as "about" or numerical ranges is not to be limited to a specified precise value, and may include values that differ from the specified value. Furthermore, "removing or reducing metal contaminants" may be used in combination with a term, and include a varying amount of metal ion removal and is not to be limited to a specified precise value, and may include values that differ from a specified value.

Claim 1:
A method of removing metal contaminants from an organic liquid used for photoresist, the method comprising: passing the organic liquid through a porous polymeric membrane comprising a coating: said coating comprises a combination of polymerized monomers which are positively charged and negatively charged in the organic liquid, that are cross-linked on the porous polymeric membrane; and, removing metals contaminants from the organic liquid wherein the organic liquid has a lower concentration of the metal contaminants after passing through the porous membrane;
wherein the monomer with a positive charge is selected from a group consisting of <NUM>-(dimethylamino)ethyl hydrochloride acrylate, [<NUM>-(acryloyloxy)ethyl] trimethylammonium chloride, <NUM>-aminoethyl methacrylate hydrochloride, N-(<NUM>-aminopropyl) methacrylate hydrochloride, <NUM>-(dimethylamino)ethyl methacrylate hydrochloride, [<NUM>-(methacryloylamino)propyl]trimethylammonium chloride solution, [<NUM>-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyl trimethylammonium chloride, <NUM>-aminoethyl methacrylamide hydrochloride, N-(<NUM>-aminoethyl) methacrylamide hydrochloride, N-(<NUM>-aminopropyl)-methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride, vinyl imidazolium hydrochloride, vinyl pyridinium hydrochloride, and vinyl benzyl trimethyl ammonium chloride; and
wherein the monomer with a negative charge is selected from a group consisting of <NUM>-ethylacrylic acid, acrylic acid, <NUM>-carboxyethyl acrylate, <NUM>-sulfopropyl acrylate potassium salt, <NUM>-propyl acrylic acid, <NUM>-(trifluoromethyl)acrylic acid, methacrylic acid, <NUM>-methyl-<NUM>-propene-<NUM>-sulfonic acid sodium salt, mono-<NUM>-(methacryloyloxy)ethyl maleate, and <NUM>-sulfopropyl methacrylate potassium salt, <NUM>-acrylamido-<NUM>-methyl-<NUM>-propanesulfonic acid, <NUM>-methacrylamido phenyl boronic acid, vinyl sulfonic acid, and vinyl phosphonic acid.