Processed microporous membrane

Abstract

A method for treating the surface of a microporous membrane, comprising the steps of contacting the membrane with a treatment composition to form a silane-treated membrane; subjecting the silane-treated membrane to conditions sufficient to effect condensation between a filler in the membrane and an acrylic polymer in the treatment composition; contacting the silane-treated membrane with an amine-functional polysaccharide dispersed in an acidic aqueous medium to form a polysaccharide-treated membrane; contacting the polysaccharide-treated membrane with an aqueous acid; and contacting the polysaccharide-treated membrane with an amine-functional alkoxysilane to form a hydrogel layer on the membrane. Also provided is a method for treating a filtration device comprising a microporous membrane and an acid-functional acrylic layer on the membrane. The present invention further relates to a treated microporous membrane comprising a microporous membrane, an acrylic layer on the microporous membrane, and a hydrogel layer on at least one surface of the acrylic layer.

Description

Background Art

[0001] Cross - reference to related applications The present disclosure relates to a method for treating the surface of a microporous membrane and the treated microporous membrane. The present disclosure also relates to a method for treating a filtration device and the treated filtration device.

[0002] In the United States, billions of gallons of co - produced water are pumped annually by oil and gas wells. The natural “oil” from the wells is actually a multiphase emulsion of oil, water, and gas. Generally, all three fluids are found in all hydrocarbon wells and well effluents. For example, bilge water contains high hydrocarbon concentrations with a wide range of carbon numbers. Bilge water is often a mixture of cleaning chemicals, rust, sewage, boiler water chemicals, lubricating and hydraulic oils, foaming liquids, domestic wastewater, metals, soot, bacteria, dust, etc.

[0003] Due to its value and environmental concerns, oil needs to be separated from these effluents. This is usually done through gravity sedimentation in large tanks, which requires capital and significant space that is not always available on - site. Gas is easily separated in mechanical separators or by depressurization in storage vessels. In the case of heavy oils and many emulsified fluid systems, the raw fluid is heated to change the density of the oil and water by heating the light components and essentially agitating their molecular structures so that these fluids can be more easily separated. Then, water is a by - product.

[0004] The filled microporous membrane is known to be a low-cost, efficient, and environmentally friendly separation medium for the separation of oil from produced water such as bilge water and the other effluents described above. However, like most filtration media, over time, the filtration membrane can become contaminated with residual oil and other contaminants. Such contamination can reduce the flux rate and thus the efficiency of the filter device. It would be desirable to provide a microporous membrane for use as a long-life filtration medium capable of operating at high pressure with improved antifouling properties and good oil retention while maintaining a high flux rate.

Summary of the Invention

[0005] A method for treating the surface of a microporous membrane is provided, the membrane comprising an organic thermoplastic matrix, micronized particulate substantially water-insoluble inorganic fillers distributed throughout the matrix, and an interconnected pore network communicating throughout the microporous membrane. The method comprises, in sequence: (1) contacting at least one surface of the membrane with a treatment composition to form a silane-treated membrane, the treatment composition comprising (a) an acrylic polymer prepared from a mixture of vinyl monomers comprising (i) a (meth)acrylic acid monomer and (ii) a silane-functional acrylic monomer, and (b) a base, wherein the acrylic polymer is in contact with the fillers present in the matrix; (2) subjecting the silane-treated membrane formed in (1) to conditions sufficient to effect a condensation reaction between the fillers and the acrylic polymer; (3) contacting at least one surface of the silane-treated membrane with a dispersion comprising an amine-functional polysaccharide dispersed in an aqueous medium containing an organic acid to form a polysaccharide-treated membrane; (4) contacting at least one surface of the polysaccharide-treated membrane formed in (3) with an aqueous acid; and (5) contacting the polysaccharide-treated membrane with an amine-functional alkoxysilane to form a polysaccharide hydrogel layer on the membrane. Also provided is a treated microporous membrane prepared by the method.

[0006] A filtration device is provided, and in addition, a method for treating a filtration device including a microporous membrane is provided. The microporous membrane includes an organic thermoplastic matrix, micronized particulate substantially water-insoluble inorganic fillers distributed throughout the matrix, an interconnected pore network communicating throughout the microporous membrane, and an acid-functional acrylic layer on at least one surface of the microporous membrane. The acid-functional acrylic layer is bonded to the filler via a siloxane functional group. The method sequentially includes: (1) contacting at least one surface of the acid-functional acrylic layer on the microporous membrane with a dispersion containing an amine-functional polysaccharide dispersed in an aqueous medium containing an organic acid to form a polysaccharide-treated membrane; (2) contacting at least one surface of the polysaccharide-treated membrane formed in (1) with an aqueous acid; and (3) contacting the polysaccharide-treated membrane with an amine-functional alkoxysilane to form a polysaccharide hydrogel layer on the membrane. The present disclosure also targets a treated filtration device prepared by this method.

[0007] The present disclosure further targets a treated microporous membrane including: (1) a microporous membrane including an organic thermoplastic matrix, micronized particulate substantially water-insoluble inorganic fillers distributed throughout the matrix, and an interconnected pore network communicating throughout the microporous membrane; (2) an acrylic layer on at least one surface of the microporous membrane, wherein the acrylic layer is bonded to the filler via a siloxane functional group; and (3) a hydrogel layer on at least one surface of the acrylic layer, wherein the hydrogel layer is formed from an amine-functional polysaccharide and an amine-functional alkoxysilane.

Embodiments for Carrying Out the Invention

[0008] For the purposes of the following detailed description, it is to be understood that various alternative variations and orders of steps are envisioned, unless explicitly specified to the contrary. Further, except in the case of any examples otherwise or unless otherwise indicated, all numbers expressing amounts of ingredients, for example, used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter should be construed in light of the reported significant digits and by applying ordinary rounding techniques.

[0009] The numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, but the numerical values set forth in the specific examples are reported as precisely as possible. Nevertheless, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0010] Also, it is to be understood that any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0011] Unless otherwise specified in this application, the use of the singular form includes the plural, and the plural includes the singular. Further, in this application, the use of "a" or "an" means "at least one" unless otherwise specified. For example, "a" additive, "a" silica, etc. refer to one or more than one of these items. Also, as used herein, the term "polymer" is intended to refer to both prepolymers, oligomers, and both homopolymers and copolymers. The term "resin" is used interchangeably with "polymer".

[0012] As used herein, the transitional phrase "comprising" (and other equivalent terms, such as "containing" and "including") is "non-limiting" and is used with respect to compositions, methods, and their respective components (plural or singular) that are non-limiting while being essential and including unspecified things. The term "consisting essentially of" refers to the components (plural or singular) required for a given embodiment and allows for the presence of components (plural or singular) that do not substantially affect the characteristics or functional features (plural or singular) of that embodiment. The term "consisting of" refers to compositions and methods that exclude any other components not described in the description of that embodiment. Further, nevertheless, the term "comprising" includes the more narrow terms "consisting essentially of" and "consisting of".

[0013] The present disclosure is directed to a method for treating the surface of a microporous membrane, the membrane comprising an organic thermoplastic matrix, micronized particulate substantially water-insoluble inorganic fillers distributed throughout the matrix, and an interconnected pore network communicating throughout the microporous membrane. The method comprises the following steps: (1) contacting at least one surface of the membrane with a treatment composition to form a silane-treated membrane, the treatment composition comprising: (a) an acrylic polymer prepared from a mixture of vinyl monomers comprising (i) a (meth)acrylic acid monomer and (ii) a silane-functional acrylic monomer, and (b) a base in an amount sufficient to achieve at least 100% neutralization of the meth(acrylic) acid monomer, the acrylic polymer being in contact with the fillers present in the matrix; (2) subjecting the silane-treated membrane formed in (1) to conditions sufficient to effect a condensation reaction between the fillers and the acrylic polymer; (3) contacting at least one surface of the silane-treated membrane with a dispersion comprising an amine-functional polysaccharide dispersed in an aqueous medium containing an organic acid to form a polysaccharide-treated membrane; (4) contacting at least one surface of the polysaccharide-treated membrane formed in (3) with an aqueous acid; and (5) contacting the polysaccharide-treated membrane with an amine-functional alkoxysilane to form a polysaccharide hydrogel layer on the membrane.

[0014] As used herein, "microporous material" or "microporous membrane" or "microporous sheet" means a material having an interconnected pore network, without treatment, coating, printing ink, impregnating agent, and on a pre-bonded basis, the pores having a volume average diameter in the range of 0.001 to 1.0 micrometers as determined as described below and constituting at least 5 volume percent of the microporous material considered below in this specification.

[0015] The organic thermoplastic matrix can include any of several known polymers known in the art, typically polyolefin-based materials. For example, the organic thermoplastic matrix can include polyolefins, polyether ketones, polyvinylidene fluoride (PVDF), polysulfones, and / or polyether sulfones. In some cases, different polymers derived from at least one ethylenically unsaturated monomer can be used in combination with polyolefin-based polymers. Suitable examples of such polyolefin-based polymers include, but are not limited to, polymers derived from ethylene, propylene, and / or butene such as polyethylene, polypropylene, and polybutene. Also suitable are high-density and / or ultra-high molecular weight polyolefins known and defined in the art such as high-density polyethylene (HDPE). The polyolefin matrix can also include copolymers, for example, copolymers of ethylene and butene, or copolymers of ethylene and propylene. It should be noted that the phrase "and / or" when used in a list is intended to encompass alternative examples including each individual component in the list, and any combination of components. For example, the list "A, B, and / or C" is intended to encompass seven separate examples including A, or B, or C, or A + B, or A + C, or B + C, or A + B + C.

[0016] Non-limiting examples of ultra-high molecular weight (UHMW) polyolefins can include essentially linear UHMW polyethylene (PE) or polypropylene (PP). Since UHMW polyolefins do not have an infinite molecular weight, they are technically classified as thermoplastic materials.

[0017] Ultra-high molecular weight polypropylene can include essentially linear ultra-high molecular weight isotactic polypropylene. Often, the degree of isotacticity of such polymers is at least 95 percent, for example, at least 98 percent.

[0018] There is no specific limitation on the upper limit of the intrinsic viscosity of UHMW polyethylene. However, in one non-limiting example, the intrinsic viscosity can range from at least 6 deciliters / gram, or at least 7 deciliters / gram, or at least 18 deciliters / gram up to a maximum of 50 deciliters / gram, or a maximum of 45 deciliters / gram, or a maximum of 18 deciliters / gram, or a maximum of 16 deciliters / gram. Thus, the intrinsic viscosity of UHMW can be, for example, in the range of 6 - 50 deciliters / gram, or 6 - 45 deciliters / gram, or 6 - 18 deciliters / gram, or 6 - 16 deciliters / gram, or 7 - 50 deciliters / gram, or 7 - 45 deciliters / gram, or 7 - 18 deciliters / gram, or 7 - 16 deciliters / gram, or 18 - 50 deciliters / gram, or 18 - 45 deciliters / gram.

[0019] For the purposes of the present disclosure, the intrinsic viscosity is determined by extrapolating the reduced viscosity or intrinsic viscosity of several dilute solutions of UHMW polyolefin to zero concentration, where the solvent is freshly distilled decahydronaphthalene to which 0.2 weight percent of 3,5 - di - tert - butyl - 4 - hydroxyphenyl phosphite, neopentanetetrayl ester [CAS Registry Number 6683 - 19 - 8] has been added. The reduced viscosity or intrinsic viscosity of UHMW polyolefin is confirmed from the relative viscosity obtained at 135 °C using an Ubbelohde No.1 viscometer in accordance with the general procedure of ASTM D 4020 - 81, except that several dilute solutions of different concentrations are employed.

[0020] The nominal molecular weight of UHMW polyethylene is empirically related to the intrinsic viscosity of the polymer by the following equation: M = 5.37×10 4 [η] 1.37 where M is the nominal molecular weight and [η] is the intrinsic viscosity of UHMW polyethylene expressed in deciliters / gram. Similarly, the nominal molecular weight of UHMW polypropylene is empirically related to the intrinsic viscosity of the polymer by the following equation: M = 8.88×10 4 [η] 1.25 Wherein, M is the nominal molecular weight, and [η] is the intrinsic viscosity of UHMW polypropylene expressed in deciliters / gram.

[0021] Mixtures of substantially linear ultra-high molecular weight polyethylene and low molecular weight polyethylene can be used. For example, the UHMW polyethylene can have an intrinsic viscosity of at least 10 deciliters / gram, and the low molecular weight polyethylene can have an ASTM D 1238-86 Condition E melt index of less than 25 grams / 10 minutes, such as less than 50 grams / 10 minutes, for example less than 15 grams / 10 minutes, and an ASTM D 1238-86 Condition F melt index of at least 0.1 grams / 10 minutes, such as at least 0.1 grams / 10 minutes, for example 0.5 grams / 10 minutes. The amount of UHMW polyethylene used in this example (as a weight percentage) is described in column 1, lines 52 to column 2, line 18 of U.S. Patent No. 5,196,262, the disclosure of which is incorporated herein by reference. More specifically, the weight percentage of UHMW polyethylene used is described in relation to Figure 6 of U.S. Patent No. 5,196,262, that is, with respect to the polygons ABCDEF, GHCI, or JHCK in Figure 6, which figure is incorporated herein by reference. For example, the weight percentage of ultra-high molecular weight polyethylene in the total polyethylene of the matrix can range from 3 to 60 weight percent, such as 10 to 48 weight percent.

[0022] The nominal molecular weight of low molecular weight polyethylene (LMWPE) is lower than that of UHMW polyethylene. LMWPE is a thermoplastic material and many different types are known. One method of classification is by density expressed in grams / cubic centimeter and rounded to the third decimal place according to ASTM D 1248-84 (reapproved in 1989). Non-limiting examples of density are found in the following table.

Table 1

[0023] UHMWPE and LMWPE can together constitute at least 65 weight percent, for example at least 85 weight percent, of the polyolefin polymer of the microporous material. Also, UHMWPE and LMWPE can together constitute substantially 100 weight percent of the polyolefin polymer of the microporous material. In some examples, UHMWPE can constitute substantially 100 weight percent (e.g., at least 99 weight percent) of the polyolefin polymer of the microporous material.

[0024] Typically, the organic thermoplastic matrix can include polyolefins, including ultra-high molecular weight polyethylene, ultra-high molecular weight polypropylene, high density polyethylene, high density polypropylene, or mixtures thereof.

[0025] If desired, other thermoplastic organic polymers can also be present in the matrix of the microporous material, provided that their presence does not substantially affect the properties of the microporous material substrate in an adverse manner. The amount of other thermoplastic polymers that can be present depends on the nature of such polymers. Non-limiting examples of thermoplastic organic polymers that can optionally be present in the matrix of the microporous material include low density polyethylene, high density polyethylene, poly(tetrafluoroethylene), polypropylene, copolymers of ethylene and propylene, copolymers of ethylene and acrylic acid, or copolymers of ethylene and methacrylic acid. If desired, all or some of the carboxyl groups of the carboxyl-containing copolymer can be neutralized with sodium, zinc, or the like. Generally, the microporous material includes at least 70 weight percent of UHMW polyolefin based on the weight of the matrix. In non-limiting examples, the other thermoplastic organic polymers described above are substantially absent from the matrix of the microporous material.

[0026] The microporous membrane further comprises a micronized particulate and substantially water-insoluble inorganic filler distributed throughout the matrix.

[0027] The inorganic filler can include any of several inorganic fillers known in the art, provided that the filler is capable of undergoing a condensation reaction with an acrylic polymer present in the treatment composition applied to the membrane in (1). The filler should be micronized and substantially water-insoluble in order to allow for a uniform distribution throughout the polyolefin-based polymer matrix during the manufacture of the microporous material. Generally, the inorganic filler is selected from the group consisting of silica, alumina, calcium oxide, zinc oxide, magnesium oxide, titanium oxide, zirconium oxide, and mixtures thereof.

[0028] The micronized and substantially water-insoluble filler can be in the form of ultimate particles, aggregates of ultimate particles, or a combination of both. At least 90 weight percent of the filler used in preparing the microporous material has a total particle size in the range of 5 to 40 micrometers as determined by use of a Beckman Coulter laser diffraction particle size instrument LS 13320 in accordance with the manufacturer's instructions. This apparatus generally uses a laser having a wavelength of 750 nm to size particles having diameters from 0.04 mm to 2000 mm and is capable of measuring particle diameters as small as about 0.04 microns. The particles scatter light in a pattern determined by their size, and an array of photodetectors detects and measures the scattered light. The photodetectors are scanned and their output is converted to digital values that are transmitted to a computer for calculation. Typically, at least 90 weight percent of the filler has a total particle size in the range of 10 to 30 micrometers. The size of the filler aggregates can be reduced during the processing of the components used to prepare the microporous material. Thus, the distribution of the total particle size in the microporous material can be smaller than that of the raw filler itself.

[0029] As described above, the filler particles are substantially water-insoluble and may also be substantially insoluble in any organic processing fluid used to prepare the microporous material. In other words, the composition of the filler particles promotes retention of the filler in the microporous material.

[0030] In addition to the filler, other micronized particulate and substantially water-insoluble materials may also be employed as necessary. Non-limiting examples of such optional materials can include carbon black, charcoal, graphite, iron oxide, copper oxide, antimony oxide, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, calcium carbonate, or magnesium carbonate. In one non-limiting example, silica and any one or more of the aforementioned optional filler materials can include the filler.

[0031] The filler typically has a large surface area that enables it to carry the majority of the processing plasticizer used for the filler to form the microporous material. The surface area of the filler particles, determined by the Brunauer, Emmett, Teller (BET) method according to ASTM C 819-77 using nitrogen as the adsorbate and corrected by degassing the system and sample at 130 °C for 1 hour, can be at least 20 square meters per gram or at least 25 square meters per gram to a maximum of 900 square meters per gram or a maximum of 850 square meters per gram, for example, in the range of 20 to 900 square meters per gram, or 20 to 850 square meters per gram, or 25 to 900 square meters per gram, or 25 to 850 square meters per gram. Prior to nitrogen adsorption, the filler sample is dried by heating at 160 °C for 1 hour in flowing nitrogen (PS).

[0032] In certain examples, the inorganic filler includes silica, such as precipitated silica, silica gel, or fumed silica.

[0033] Silica gel is generally produced commercially by acidifying an aqueous solution of a soluble metal silicate, such as sodium silicate, at low pH with an acid. The acid employed is generally a strong mineral acid such as sulfuric acid or hydrochloric acid, although carbon dioxide can also be used. Since there is essentially no density difference between the gel phase and the surrounding liquid phase while the viscosity is low, the gel phase does not sediment, i.e., does not precipitate. Thus, silica gel can be described as a coherent and rigid three-dimensional network formed by the precipitation of non-sedimenting continuous particles of colloidal amorphous silica. The state of subdivision ranges from large solid masses to ultrafine particles, and the degree of hydration ranges from almost anhydrous silica to soft gelatinous masses containing up to about 100 parts by weight of water per part by weight of silica.

[0034] Precipitated silica is generally produced commercially by combining an aqueous solution of a soluble metal silicate, usually an alkali metal silicate such as sodium silicate, and an acid such that colloidal silica particles grow in a weakly alkaline solution and are coagulated by the alkali metal ions of the resulting soluble alkali metal salt. A variety of acids, including but not limited to mineral acids, can be used. Non-limiting examples of acids that can be used include hydrochloric acid and sulfuric acid, although carbon dioxide can also be used to produce precipitated silica. In the absence of a coagulant, silica does not precipitate from a solution at any pH. In non-limiting examples, the coagulant used to effect the precipitation of silica can be the soluble alkali metal salt formed during the formation of the colloidal silica particles, or an added electrolyte such as a soluble inorganic or organic salt, or a combination of both.

[0035] Precipitated silica can be described as a precipitate aggregate of colloidal amorphous silica ultimate particles that did not exist as a macroscopic gel at any point during preparation. The size and degree of hydration of the aggregates can vary widely. Precipitated silica powder differs from ground silica gel in that the precipitated silica powder generally has a more open structure, i.e., a higher specific pore volume, than silica gel. However, the specific surface area of precipitated silica, measured by the Brunauer, Emmet, Teller (BET) method using nitrogen as the adsorbate, is often smaller than that of silica gel.

[0036] Many different precipitated silicas can be employed as fillers used to prepare microporous materials. Precipitated silicas are well-known commercial materials, and the processes for producing them are described in detail in many U.S. patents, including U.S. Patent Nos. 2,940,830 and 4,681,750. The average ultimate particle size of the precipitated silica used (regardless of whether the ultimate particles are aggregated) is generally less than 0.1 micrometer, e.g., less than 0.05 micrometer, or less than 0.03 micrometer, as determined by transmission electron microscopy. Non-limiting examples of suitable precipitated silicas include those sold under the trademark HI-SIL by PPG (Pittsburgh, PA).

[0037] The inorganic filler particles can constitute at least 10 weight percent, or at least 25 weight percent, or at least 30 weight percent, or at least 40 weight percent, or at least 50 weight percent, or at least 60 weight percent of the microporous membrane, and up to 90 weight percent, or up to 85 weight percent. For example, such filler particles can constitute 25 to 90 weight percent, or 25 to 85 weight percent, or 30 to 90 weight percent, or 30 to 85 weight percent, or 40 to 90 weight percent, or 40 to 85 weight percent, or 50 to 90 weight percent, or 50 to 85 weight percent, or 60 to 90 weight percent, or 60 to 85 weight percent of the microporous membrane. The filler is typically present in the microporous membrane in an amount in the range of 50 weight percent to 85 weight percent of the microporous membrane. Often, the weight ratio of filler to polyolefin in the microporous material is in the range of 0.5:1 to 10:1, such as 1.7:1 to 3.5:1. Alternatively, the weight ratio of filler to polyolefin in the microporous material can be greater than 4:1. It is contemplated that such levels of filler can be employed because higher levels of filler provide a greater surface area available for condensation reactions with the treatment composition.

[0038] The microporous material used in the disclosed membranes further includes an interconnected pore network that communicates throughout the microporous material.

[0039] Without treatment, coating, or impregnating agent, such pores can constitute at least 5 volume percent, or at least 15 volume percent, or at least 20 volume percent, or at least 25 volume percent, or at least 35 volume percent, or at least 45 volume percent, and up to 95 volume percent, or up to 75 volume percent. Thus, the pores can constitute 5 - 95 volume percent, or 15 - 95 volume percent, or 20 - 95 volume percent, or 25 - 95 volume percent, or 35 - 95 volume percent, or 45 - 95 volume percent, or 5 - 70 volume percent, or 15 - 70 volume percent, or 20 - 70 volume percent, or 25 - 70 volume percent, or 35 - 70 volume percent, or 45 - 70 volume percent of the microporous material. Often, the pores contain at least 35 volume percent, or even at least 45 volume percent of the microporous material. Such high porosity provides a larger surface area throughout the microporous material, which in turn promotes the removal of contaminants from fluid flow and a higher flux rate of fluid flow through the membrane.

[0040] As used herein and in the claims, the porosity of a microporous material, expressed as volume percent (also known as void volume), is determined according to the following equation: Porosity = 100[1 - d1 / d2] Where d1 is the density of the sample, determined from the sample weight and sample volume confirmed from measurement of the sample dimensions, and d2 is the density of the solid portion of the sample, determined from the sample weight and the volume of the solid portion of the sample. The volume of the solid portion of the sample is determined using a Quantachrome Stereopycnometer (Quantachrome Corporation (Boynton Beach, FL)) according to the attached operating manual.

[0041] Porosity can also be measured using a Gurley Densometer, Model 4340, manufactured by GPI Gurley Precision Instruments (Troy, NY). The reported porosity value is a measure of the velocity of air flow through the sample or its resistance to air flow through the sample. The unit of measurement for this method is the "Gurley second" and represents the time in seconds to pass 100 cc of air through a 1 square inch area using a pressure differential of 4.88 inches of water. Lower values are equivalent to less air flow resistance (more air can pass freely). The measurement is completed using the procedure described in the manual for the MODEL 4340 Automatic Densometer.

[0042] The volume average diameter of the pores in the microporous material can be determined by mercury porosimetry using an Autopore III porosimeter (Micromeritics, Inc. (Norcross, GA)) according to the attached operating manual. The volume average pore radius for a single scan is determined automatically by the porosimeter. When operating the porosimeter, the scan is performed within the high pressure range (138 absolute kilopascals to 227 absolute megapascals). If approximately 2 percent or less of the total intrusion volume occurs at the lower limit of the high pressure range (138 to 250 absolute kilopascals), the volume average pore diameter is determined as twice the volume average pore radius determined by the porosimeter. Alternatively, an additional scan is performed within the low pressure range (7 to 165 absolute kilopascals) and the volume average pore diameter is calculated according to the following equation: d = 2[v1r1 / w1 + v2r2 / w2] / [v1 / w1 + v2 / w2] where d is the volume average pore diameter, v1 is the total volume of mercury intruded within the high pressure range, v2 is the total volume of mercury intruded within the low pressure range, r1 is the volume average pore radius determined from the high pressure scan, r2 is the volume average pore radius determined from the low pressure scan, w1 is the weight of the sample that received the high pressure scan, and w2 is the weight of the sample that received the low pressure scan.

[0043] In the process of determining the volume-average pore diameter of the above procedure, the maximum pore radius detected may be noted. This is determined from the low-pressure range scan when performed, or alternatively, from the high-pressure range scan. The maximum pore diameter is twice the maximum pore radius. Since some generation or processing steps, such as coating processes, printing processes, impregnation processes, and / or bonding processes, can result in the filling of at least some of the pores of the microporous material, and since some of these processes irreversibly compress the microporous material, the parameters regarding porosity, the volume-average diameter of the pores, and the maximum pore oversize are determined for the microporous material prior to the application of one or more of such generation or processing steps.

[0044] To prepare the disclosed microporous material, a filler, an organic thermoplastic matrix such as a polyolefin polymer (typically in solid form such as powder or pellets), a processing plasticizer, and small amounts of lubricant and antioxidant are mixed until a substantially homogeneous mixture is obtained. The weight ratio of filler to polymer employed in forming the mixture is essentially the same as the weight ratio of the resulting microporous material substrate. The mixture, along with additional processing plasticizer, is introduced into the heated barrel of a screw extruder. The extruder is fitted with a die such as a sheet die to form the desired final shape.

[0045] In an exemplary manufacturing process, when the material is formed into a sheet or film, the continuous sheet or film formed by the die is transferred to a pair of heated calendar rolls that act in concert to form a continuous sheet of lesser thickness than the continuous sheet emerging from the die. The final thickness can depend on the desired end use. The microporous material can have a thickness in the range of 0.7 to 18 mils (17.8 to 457.2 microns), such as 0.7 to 15 mils (17.8 to 381 microns), or 1 to 10 mils (25.4 to 254 microns), or 5 to 10 mils (127 to 254 microns).

[0046] Optionally, the sheet emerging from the calendar roll can then be stretched in at least one stretching direction exceeding the elastic limit. The stretching can alternatively be carried out a plurality of times during or immediately after emerging from the sheet die, or during calendar processing, or during the manufacturing process. The stretching can be carried out before extraction, after extraction, or both. In addition, the stretching can be carried out during the application of the pretreatment composition and / or the treatment composition described in more detail below. The stretched microporous material substrate can be produced by stretching the intermediate product in at least one stretching direction exceeding the elastic limit. Usually, the stretching ratio is at least 1.2. In many cases, the stretching ratio is at least 1.5. Usually, it is at least 2. Frequently, the stretching ratio is in the range of 1.2 to 15. Often, the stretching ratio is in the range of 1.5 to 10. Usually, the stretching ratio is in the range of 2 to 6.

[0047] The temperature at which stretching is achieved can vary widely. Stretching can be achieved at ambient room temperature, but usually, elevated temperatures are employed. The intermediate product can be heated by any of a variety of techniques before, during, and / or after stretching. Examples of these techniques include radiative heating such as that provided by an electrically heated or infrared heater by gas combustion, convective heating such as that provided by recirculating hot air, and conductive heating such as that provided by contact with a heated roll. The temperature measured for temperature control purposes can vary depending on the equipment used and personal preference. For example, the temperature measuring device can be the surface temperature of the infrared heater, the temperature inside the infrared heater, the air temperature at a point between the infrared heater and the intermediate product, the temperature of the circulating hot air at a point within the equipment, the temperature of the hot air entering or exiting the equipment, the surface temperature of the roll used in the stretching process, the temperature of the heat transfer fluid entering or exiting such a roll, or the film surface temperature that can be arranged to be checked. Generally, one or more temperatures, if present, are controlled such that the intermediate product is stretched substantially evenly so that the variation in the film thickness of the stretched microporous material is within acceptable limits and the amount of stretched microporous material outside those limits is acceptably low. The temperature used for control purposes depends on the nature of the equipment used, the location of the temperature measuring device, and the identity of the substance or object whose temperature is being measured, so it will be apparent that it may or may not be close to the temperature of the intermediate product itself.

[0048] Taking into account the location of the heating device and the line speed typically employed during stretching, a variable temperature gradient may or may not exist through the thickness of the intermediate product. Also, due to such line speed, it is not feasible to measure these temperature gradients. The existence of a variable temperature gradient makes it unreasonable to refer to a single film temperature when they occur. Therefore, the film surface temperature that can be measured is most often used to characterize the thermal conditions of the intermediate product.

[0049] The film surface temperature at which stretching is achieved can vary widely, but generally, they are such that the intermediate product is stretched substantially evenly, as described above. In most cases, the film surface temperature during stretching is within the range of 20°C to 220°C. Often, such temperatures are within the range of 50°C to 200°C, such as 75°C to 180°C.

[0050] Stretching can be achieved in a single step or multiple steps, as desired. For example, if the intermediate product is stretched in a single direction (uniaxial stretching), the stretching can be achieved by a single stretching step or a series of stretching steps until the desired final stretch ratio is obtained. Similarly, if the intermediate product is stretched in two directions (biaxial stretching), the stretching can be performed by a single biaxial stretching step or a series of biaxial stretching steps until the desired final stretch ratio is obtained. Biaxial stretching can also be achieved by one of a series of more uniaxial stretching steps in one direction and one or more uniaxial stretching steps in another direction. The biaxial stretching step in which the intermediate product is stretched simultaneously in two directions, and the uniaxial stretching steps can be performed in any order in sequence. Stretching in more than two directions is within the contemplated scope. It can be seen that there are a very large number of various permutations of steps. Other steps such as cooling, heating, sintering, annealing, winding, unwinding, etc. can be included in the overall process as needed and as desired.

[0051] Various types of stretching devices are well-known and can be used to achieve stretching of intermediate products. Uniaxial stretching is typically achieved by stretching between two rollers, where the second or downstream roller rotates at a peripheral speed faster than the first or upstream roller. Uniaxial stretching can also be achieved on a standard drawframe. Biaxial stretching can be achieved by stretching simultaneously in two different directions on a drawframe. However, more commonly, biaxial stretching is achieved either by first uniaxially stretching between two differentially rotating rollers as described above and then uniaxially stretching in a different direction using a drawframe, or by using a drawframe to perform biaxial stretching. The most common type of biaxial stretching is when the two stretching directions are approximately perpendicular to each other. In most cases where a continuous sheet is being stretched, one stretching direction is at least approximately parallel to the long axis (machine direction) of the sheet, and the other stretching direction is at least approximately perpendicular to the machine direction and lies within the plane of the sheet (the cross direction).

[0052] Stretching the sheet prior to extraction of the processing plasticizer allows for a thinner film with larger pore diameters than conventionally processed microporous materials. Also, stretching of the sheet prior to extraction of the processing plasticizer is thought to minimize post-processing heat shrinkage. It should be noted that stretching of the microporous membrane can occur at any point before, during, or after application of the pretreatment composition (described below herein) and / or before, during, or after application of the treatment composition. Stretching of the microporous membrane can occur one or more times during the processing process.

[0053] The product moves to a first extraction zone where the processing plasticizer is substantially removed by extraction with an organic liquid which is a good solvent for the processing plasticizer, a poor solvent for the organic polymer and more volatile than the processing plasticizer. Usually but not necessarily, both the processing plasticizer and the organic extractant are substantially immiscible with water. The product then moves to a second extraction zone where the residual organic extractant is substantially removed by vapor and / or water. The product then passes through a forced air dryer for substantial removal of residual water and residual organic extractant. From the dryer, the microporous material can be passed to a take-up roll when it is in the form of a sheet.

[0054] The processing plasticizer has little solvating effect on the thermoplastic organic polymer at 60 °C, only a moderate solvating effect at elevated temperatures of about 100 °C and a significant solvating effect at elevated temperatures of about 200 °C. It is liquid at room temperature and is usually a processing oil such as paraffinic oil, naphthenic oil or aromatic oil. Suitable processing oils include those meeting the requirements of ASTM D 2226 - 82, Types 103 and 104. Oils having a pour point of less than 22 °C or less than 10 °C according to ASTM D 97 - 66 (reapproved 1978) are most frequently used. Examples of suitable oils are SHELLFLEX 412 and SHELLFLEX 371 oils (Shell Oil Co., Houston, TX), which are solvent refined and hydrotreated oils derived from naphthenic crude oil. Other materials including phthalate ester plasticizers such as dibutyl phthalate, bis(2-ethylhexyl) phthalate, diisodecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate and ditridecyl phthalate are expected to function satisfactorily as processing plasticizers.

[0055] There are many organic extracts that can be used in the process of manufacturing microporous membranes. Examples of suitable organic extracts include, but are not limited to, 1,1,2-trichloroethylene, perchloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, methylene chloride, chloroform, 1,1,2-trichloro-1,2,2-trifluoroethane, isopropyl alcohol, diethyl ether, acetone, hexane, heptane, and toluene. One or more azeotropic mixtures of halogenated hydrocarbons selected from trans-1,2-dichloroethylene, 1,1,1,2,2,3,4,5,5,5-decafluoropentane, and / or 1,1,1,3,3-pentafluorobutane can also be employed. Such materials are commercially available as VERTREL MCA (1,1,1,2,2,3,4,5,5,5-dihydrodecafluoropentane and trans-1,2-dichloroethylene: 62% / 38% binary azeotropic mixture), as well as VERTREL CCA (1,1,1,2,2,3,4,5,5,5-dihydrodecafluoropentane, 1,1,1,3,3-pentafluorobutane, and trans-1,2-dichloroethylene: 33% / 28% / 39% ternary azeotropic mixture), VERTREL SDG (80 - 83% trans-1,2-dichloroethylene, 17 - 20% hydrofluorocarbon mixture), all of which are available from MicroCare Corporation (New Britain, CT).

[0056] In the process described above for producing the microporous membrane, extrusion and calendaring are facilitated when the filler carries most of the processing plasticizer. The volume of filler particles for absorbing and holding the processing plasticizer is a function of the surface area of the filler. Thus, the filler typically has a large surface area, as considered above. Since it is desirable to substantially retain the filler in the microporous material substrate, when the microporous material substrate is produced by the above process, the filler should be substantially insoluble in the processing plasticizer and substantially insoluble in the organic extractant. The residual processing plasticizer content is usually less than 15 weight percent of the resulting microporous material, which can be further reduced to levels such as less than 5 weight percent by additional extraction using the same or different organic extractants. The resulting microporous material can be further processed according to the desired application.

[0057] As described above, a method for treating the surface of a (the above-described) microporous membrane includes the step of contacting at least one surface of the membrane with a treatment composition comprising: (1) an acrylic polymer prepared from a mixture of vinyl monomers comprising (a)(i) a (meth)acrylic acid monomer and (ii) a silane-functional acrylic monomer, and optionally, (b) a base. Additionally, the acrylic polymer is in contact with the filler present in the matrix. The method further includes the step of (2) subjecting the membrane of (1) to conditions sufficient to effect a condensation reaction between the inorganic filler and the acrylic polymer of the treatment composition.

[0058] A treatment composition for treating the surface of a microporous membrane comprises (a) an acrylic polymer and optionally, (b) a base. The treatment composition may further comprise at least one of (c) poly(N-vinylpyrrolidone) or polyoxazoline.

[0059] The treatment composition can be a solution in which the components of the treatment composition (for example, acrylic polymer (a), base (b) as required, and optionally at least one of poly(N-vinylpyrrolidone) or polyoxazoline (c)) are dissolved in a solvent such as an alkyl alcohol or a volatile ketone. Particularly preferred solvents include those having a boiling point lower than 120°C, and examples include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, acetone, methyl ethyl ketone, and methyl isobutyl ketone. Note that when the solution is not aqueous, the base (b) is typically not necessary.

[0060] Alternatively, the treatment composition can be an aqueous treatment composition in which the components of the treatment composition (e.g., acrylic polymer (a), base (b), and optionally at least one of poly(N-vinylpyrrolidone) or polyoxazoline (c)) are dispersed in an aqueous medium. When present, the base is typically used in an amount sufficient to achieve at least 100% neutralization of the (meth)acrylic acid monomer. As used herein, "aqueous medium" refers to a liquid medium that contains at least 50% by weight of water, based on the total weight of the liquid medium. Such an aqueous liquid medium can contain, for example, at least 60% by weight of water, or at least 70% by weight of water, or at least 80% by weight of water, or at least 90% by weight of water, or at least 95% by weight of water, or 100% by weight of water, based on the total weight of the liquid medium. When present, the solvent that constitutes less than 50% by weight of the liquid medium includes an organic solvent. Non-limiting examples of suitable organic solvents include polar organic solvents. By definition, a molecule can be "polar" if there is an unequal sharing of electrons between the two atoms of a diatomic molecule or due to an asymmetric arrangement of polar bonds in a more complex molecule such that an overall dipole exists in the molecule. Examples of polar solvents include protic organic solvents such as glycols, alcohols, glycol ether alcohols, volatile ketones, glycol diethers, esters, and diesters. Other non-limiting examples of organic solvents include aromatic and aliphatic hydrocarbons. The treatment composition can have a pH > 7.

[0061] The acrylic polymer (a) can be prepared from a mixture of vinyl monomers. The vinyl monomers usually include (i) (meth)acrylic acid monomers and (ii) silane-functional acrylic monomers. The vinyl monomers may include (iii) N-vinylpyrrolidone. The (meth)acrylic acid monomer (i) may be present in an amount of at least 2 wt%, or at least 5 wt%, and at most 20 wt%, or at most 10 wt% based on the total weight of the vinyl monomers, for example, in an amount of 2-20 wt%, or 5-20 wt%, or 2-10 wt%, or 5-10 wt%. The silane-functional acrylic monomer (ii) may be present in an amount of at least 10 wt%, or at least 20 wt%, or at least 40 wt%, and at most 80 wt%, or at most 70 wt%, or at most 60 wt%, or at most 55 wt% based on the total weight of the vinyl monomers, for example, in an amount of 10-80 wt%, or 10-70 wt%, or 10-60 wt%, or 10-55 wt%, or 20-80 wt%, or 20-70 wt%, or 20-60 wt%, or 20-55 wt%, or 40-80 wt%, or 40-70 wt%, or 40-60 wt%, or 40-55 wt%. N-vinylpyrrolidone (iii), if present, may be present in an amount of at least 1 wt%, or at least 5 wt%, and at most 60 wt%, or at most 40 wt%, or at most 25 wt%, or at most 15 wt% based on the total weight of the vinyl monomers, for example, in an amount of 1-60 wt%, or 1-40 wt%, or 1-25 wt%, or 1-15 wt%, or 5-60 wt%, or 5-40 wt%, or 5-25 wt%, or 5-15 wt%.

[0062] Other vinyl monomers may be present to prepare the acrylic polymer (a), and non-limiting examples include, as necessary, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypropyl (meth)acrylate, styrene, acrylamide, alkyl-substituted acrylamide, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, substituted styrene, maleic anhydride, or combinations thereof.

[0063] As used herein, the term "acrylic" polymer refers to polymers well known to those skilled in the art resulting from the polymerization of one or more ethylenically unsaturated polymerizable materials. Suitable acrylic polymers for use can be made by any of a variety of methods, as will be understood by those skilled in the art. In certain examples, such acrylic polymers are made by the addition polymerization of different unsaturated polymerizable materials, at least one of which is (ii) a silane-functional acrylic monomer. The result of such polymerization is an acrylic polymer containing a hydrolyzable silane functional group. Examples of hydrolyzable silane groups include, but are not limited to, groups having the structure Si-Xn, where n is an integer having a value in the range of 1 to 3 and X is selected from chlorine, bromine, iodine, alkoxy esters, and / or acyloxy esters.

[0064] (Meth)acrylic acid monomer (i) may include acrylic acid, methacrylic acid, or combinations thereof.

[0065] Non-limiting examples of the silane-functional acrylic monomer (ii) include ethylenically unsaturated alkoxysilanes and ethylenically unsaturated acyloxysilanes. More specific examples thereof include acrylate alkoxysilanes such as gamma-acryloxypropyltrimethoxysilane and gamma-acryloxypropyltriethoxysilane, and methacrylate alkoxysilanes such as gamma-methacryloxypropyltrimethoxysilane, gamma-methacryloxypropyltriethoxysilane, and gamma-methacryloxypropyltris(2-methoxyethoxy)silane. Examples of acyloxysilanes include acrylate acetoxysilanes, methacrylate acetoxysilanes, and ethylenically unsaturated acetoxysilanes such as acrylatopropyltriacetoxysilane and methacrylatopropyltriacetoxysilane. In certain instances, it may be desirable to utilize monomers that, upon addition polymerization, result in an acrylic polymer in which the Si atom of the resulting hydrolyzable silyl group is separated from the polymer backbone by at least two atoms. One non-limiting commercially available example of a suitable (ii) silane-functional acrylic monomer is SILQUEST A-174 available from Momentive Performance Materials (Waterford, NY).

[0066] The acrylic polymer (a) may have a weight average molecular weight (M w , g / mol or Da) of at least 10,000 Da, or at least 12,000 Da, and up to 35,000, such as up to 30,000, or up to 25,000, or up to 20,000, or up to 16,000, or up to 15,000 Da. Thus, M wcan range from 10,000 to 35,000, or 10,000 to 30,000, or 10,000 to 25,000, or 10,000 to 20,000, or 10,000 to 16,000, or 10,000 to 15,000, or 12,000 to 35,000, or 12,000 to 30,000, or 12,000 to 25,000, or 12,000 to 20,000, 12,000 to 16,000, or 12,000 to 15,000 Da. As used herein, M w is measured by gel permeation chromatography using a polystyrene standard in accordance with ASTM D6579-11 (gel permeation chromatography used to characterize polymer samples is performed using a Waters 2695 separation module equipped with a Waters 2414 differential refractometer (RI detector), tetrahydrofuran (THF) is used as the eluent at a flow rate of 1 ml / min, two PLgel Mixed-C (300×7.5 mm) columns are used for separation, and the M of the polymer sample w can be measured by gel permeation chromatography against a linear polystyrene standard of 800 to 900,000 Da).

[0067] Acrylic polymer (a) can come into contact with the filler present in the matrix when the treatment composition is applied to the microporous membrane so that the membrane can be subjected to conditions sufficient to cause a condensation reaction between the filler and acrylic polymer (a).

[0068] In some non-limiting examples, acrylic polymer (a) can constitute 90 to 100% by weight of the solids in the treatment composition.

[0069] Base (b) may include any compound capable of neutralizing the (meth)acrylic acid monomer (a). Base (b) may be included in an amount sufficient to at least partially neutralize the (meth)acrylic acid monomer (i). For example, base (b) may be included in an amount sufficient to neutralize at least 50%, or at least 75%, or at least 100% of the (meth)acrylic acid monomer. For example, base (b) may be included in an amount sufficient to neutralize up to 250%, or up to 300%, or up to 400% of the (meth)acrylic acid monomer (i). Base (b) may be included in the treatment composition in an amount sufficient to achieve 100% to 300% neutralization of the (meth)acrylic acid monomer (i), for example, 110 to 250%, or for example, 150% to 200%.

[0070] Non-limiting examples of base (b) include amines (e.g., dimethylethanolamine, dibutylamine, diisopropylamine, amine-functional alkoxysilanes), sodium hydroxide, ammonium hydroxide, etc. The amine may include a tertiary amine. a Ammonium hydroxide, dimethylethanolamine, dibutylamine, and diisopropylamine are particularly preferred.

[0071] Optional poly(N-vinylpyrrolidone) or polyoxazoline (c) may include polyalkyloxazolines such as poly(2-ethyl-2-oxazoline), poly(2-methyl-2-oxazoline), and poly(2-methyl / ethyl-2-oxazoline), and / or poly(N-vinylpyrrolidone).

[0072] In some non-limiting examples, poly(N-vinylpyrrolidone) or polyoxazoline (c) may constitute 1 to 20 wt% of the solids in the treatment composition.

[0073] Before contacting the treatment composition with at least one surface of the microporous membrane, the microporous membrane can be pretreated with a pretreatment composition. The surface of the microporous membrane can be pretreated by contacting it with a hydrophilic polymer. "Hydrophilic" means that the polymer has polar characteristics and has a tendency to interact with, be miscible with, or be dissolved by water and other polar substances. The hydrophilic polymer (c) includes polyalkyl oxazolines such as poly(2-ethyl-2-oxazoline), poly(2-methyl-2-oxazoline), and poly(2-methyl / ethyl-2-oxazoline), triblock copolymers based on poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol), polyethyleneimine, polyamide, oxidized polyethylene or its derivatives, polyethylene oxide, polyethylene glycol, poly(N-vinylpyrrolidone), polyacrylic acid, polymethacrylic acid, polyethylene glycol derivatives, polypropylene oxide or its derivatives, copolymers of polyethylene glycol and polyethylene oxide, polyvinyl alcohol, vinyl acetate, cellulose or its derivatives, polyimide, collagen, polypeptides, hydrogels such as guar and pectin, polypeptides, poly(meth)acrylates such as poly(2-hydroxyethyl methacrylate), poly(meth)acrylamide, polysaccharides such as chitosan, poly(phosphorylcholine) derivatives, zwitterionic polymers such as polysulfobetaine and polycarboxybetaine, or any of the hydrophilic polymers from paragraph

[0090] of US Patent Application No. 2014 / 0069862, including one or more of polyethyleneimine. The pretreated microporous membrane can be dried before contacting it with the treatment composition, or the treatment composition can be contacted covering the surface wet from the pretreatment. In some non-limiting examples, the surface of the microporous membrane can be contacted with a hydrophilic polymer after being contacted with the treatment composition such that the hydrophilic polymer is used as a post-treatment composition. This can be in addition to or in place of using a hydrophilic polymer as the pretreatment composition.

[0074] The pretreatment composition and / or the treatment composition can be brought into contact with at least one surface of the microporous membrane by any coating means known in the art. For example, the treatment composition can be applied to at least one surface of the microporous membrane by impregnation, spraying, dipping, and / or flowing, or by a specific coating technique. The treatment composition can be applied after plasticizer extraction and after any of the aforementioned stretching steps, during, or before. Alternatively, stretching can be delayed until after application of the treatment composition.

[0075] The treatment composition can be applied covering a dry or pre-wetted membrane.

[0076] When the treatment composition is applied to at least one surface of the microporous membrane in (1), a silane-treated membrane is formed. Then, the silane-treated membrane in (1) is subjected to conditions sufficient to bring about a condensation reaction between the inorganic filler (e.g., functional groups present on its surface) and the acrylic polymer (a) via silane groups present from the silane-functional acrylic monomer (ii) residues. Such reaction conditions will be considered in more detail below in this specification.

[0077] The conditions sufficient to bring about the condensation reaction in (2) can include drying as described hereinafter. The conditions sufficient to bring about the condensation reaction in (2) can include adjusting the pH to the range of 4 to 7, such as by rinsing the membrane with water (e.g., deionized or distilled water) or dilute aqueous acid.

[0078] Furthermore, the treatment composition can be applied in multiple steps. That is, the microporous membrane can be contacted with one or more applications of the treatment composition(s) in (1). Further, the treatment compositions applied in such multi-step applications can be the same or different compositions, provided that each composition contains at least one acrylic polymer (a). Also, any of the aforementioned treatment compositions suitable for application to the microporous membrane of (1) by the disclosed method can further contain at least one nonionic surfactant and / or anionic surfactant and / or rheology modifier, as described immediately below.

[0079] Non-limiting examples of suitable anionic surfactants for use in the treatment compositions used in the disclosed method include sodium stearate, ammonium stearate, ammonium coconut fatty acid, sodium laurate, sodium cocyl sarcosinate, sodium lauroyl sarcosinate, sodium tallow soap, sodium coconut soap, sodium myristoyl sarcosinate, sodium dioctyl sulfosuccinate, or some combination thereof, but are not limited thereto.

[0080] The rheology modifier can be essentially pseudoplastic or thixotropic. Non-limiting examples of suitable rheology modifiers for use in the treatment compositions used in the disclosed method include cationic quaternary amine compounds combined with propylene glycol (such as DISPERSOGEN SPS manufactured by Clariant (Muttenz, Switzerland)), aqueous dispersions of acrylic copolymers (such as RHEOTECH 4800 manufactured by Arkema Group (Colombes, France)), anionic aqueous solutions of sodium polyacrylate (such as ALCOGUM 296-W manufactured by AkzoNobel (Amsterdam, Netherlands)), or some combination thereof, but are not limited thereto.

[0081] Non-limiting examples of suitable nonionic surfactants for use in the treatment compositions used in the disclosed methods include polyalkylene oxide alkyl ethers, where the alkyl group can be straight-chain or branched and have a chain length of C6-C22; polyalkylene oxide alkyl esters, where the alkyl group can be straight-chain or branched and have a chain length of C6-C22; organic amines having a straight-chain or branched C6-C22 carbon chain of the general formula R*NR′R″, where R* can be C8-C22 alkyl and R′ and R″ can each independently be H or C1-C4 alkyl, such that the molecule is substantially soluble or substantially emulsifiable in water, for example, octadecylamine; tertiary amines having a C6-C22 carbon chain; polyethyleneimine; polyacrylamide; glycols and alcohols having a straight-chain or branched C6-C22 alkyl capable of forming an ester bond (-SiOC-); polyvinyl alcohol; and mixtures thereof, but are not limited thereto.

[0082] Nonionic surfactants can also be selected from polyalkylene oxide ethers such as polypropylene oxide ether or polyethylene oxide ether, for example, but not limited to, hexaethylene glycol monododecyl ether, hexaethylene glycol monohexadecyl ether, hexaethylene glycol monotetradecyl ether, hexaethylene glycol monooctadecyl ether, heptaethylene glycol monododecyl ether, heptaethylene glycol monohexadecyl ether, heptaethylene glycol monotetradecyl ether, heptaethylene glycol monooctadecyl ether, nonaethylene glycol monododecyl ether, octaethylene glycol monododecyl ether, polyalkylene oxide esters such as polypropylene oxide ester or polyethylene oxide ester, for example, but not limited to, hexaethylene glycol monododecyl ester, hexaethylene glycol monohexadecyl ester, hexaethylene glycol monotetradecyl ester, hexaethylene glycol monooctadecyl ester, heptaethylene glycol monododecyl ester, heptaethylene glycol monohexadecyl ester, heptaethylene glycol monotetradecyl ester, heptaethylene glycol monooctadecyl ester, nonaethylene glycol monododecyl ester, octaethylene glycol monododecyl ester, polysorbate esters such as polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan dipalmitate, polyoxyethylene sorbitan dioleate, polyoxyethylene sorbitan distearate, polyoxyethylene sorbitan monopalmitate monooleate and other polyoxyethylene sorbitan difatty acid esters, not limited to, polyoxyethylene sorbitan tristearate and other polyoxyethylene sorbitan trifatty acid esters, or mixtures thereof.

[0083] In certain examples, the treatment composition can include nonionic surfactants selected from poly(ethylene glycol)-based block copolymers, such as block copolymers of poly(propylene glycol) and poly(ethylene glycol) (such as the triblock copolymer PLURONIC 17R2 commercially available from BASF Corporation (Ludwigshafen, Germany)), cetylstearyl alcohol, polyethylene glycol and its derivatives, such as polyoxyethylene octyl phenyl ether, polyalkyl glycol, cetyl alcohol, cocamidomono or diethanolamine, decyl glucoside, octylphenoxypolyethoxyethanol, isocetyl alcohol, lauryl glucoside, monolaurin, fatty alcohol polyglycol ether, polyglycol ether, polyethylene glycol derivatives of mono- or diglycerides, mono- and polyglycerol derivatives, such as polyglycerol polyricinoleate, sorbitan esters, polysorbates, and polyethylene oxide. Mixtures of any of the aforementioned nonionic surfactants can be used.

[0084] As discussed above, the method for treating the surface of the filled microporous membrane further includes the step of subjecting the membrane of (2)(1) to conditions sufficient to effect a condensation reaction between the inorganic filler and the silane-functional polyamine compound.

[0085] In the “wet method,” the treatment composition is applied to one or more surfaces of the microporous membrane and rinsed with water to effect a condensation reaction between the inorganic filler and (a) an acrylic polymer. The wet method can be effectively used to treat microporous membranes in the form of sheets or when the microporous membrane is a component of an existing or prefabricated separation device, such as a hollow fiber filter membrane component, a tubular device, a spiral wound or pleated filter device, or a separation membrane as a component of a battery (e.g., a battery separator). The sheet can be pre-wetted or dried prior to treatment with the treatment composition.

[0086] In the "dry method" that brings about the condensation reaction in step (2) of the disclosed method, the condensation reaction between the inorganic filler and (a) the acrylic polymer is brought about by drying the membrane. The dry method can be used when the base (b) has a vapor pressure of ≥ 1 Pa. The dry method is particularly useful for the treatment of microporous membranes in the form of sheets. The dry method can be initiated on the microporous membrane before any stretching, or after stretching in the machine direction and before stretching in the transverse direction, or the dry method can be initiated on a microporous membrane that has already been biaxially stretched. Also, when the dry method is employed, the microporous membrane can be stretched during the drying / heating step in addition to, or instead of, the stretching prior to treatment with the treatment composition. It should be noted that during the application of the treatment composition in the dry method, the microporous membrane to which each treatment composition is applied should be dimensionally stable and held during the said application and drying steps. Further, during the drying / heating step of the dry method, the membrane is typically held under tension to prevent / minimize shrinkage, whether or not stretching is occurring simultaneously.

[0087] The drying temperature for bringing about the condensation reaction can occur within a temperature range of at least 20 °C to a maximum of 145 °C, or a maximum of 120 °C, or a maximum of 100 °C, or a maximum of 95 °C. Exemplary temperature ranges include 20 °C to 145 °C, 20 °C to 120 °C, 20 °C to 100 °C, and 20 °C to 95 °C.

[0088] In certain examples of the method, at this point, the membrane resulting from step (2) can be formed into a filtration device such as a hollow fiber, a tubular device, a spiral wound filtration device, or a pleated filtration device, which can be in the form of a filtration cartridge depending on the intended use. Alternatively, the membrane can be formed into a filtration device after any subsequent treatment steps.

[0089] This method further includes the step of contacting at least one surface of the (3) silane-treated film with a dispersion containing an amine-functional polysaccharide dispersed in an aqueous medium containing an organic acid to form a polysaccharide-treated film. Typically, the silane-treated film is immersed in the dispersion, and / or the dispersion can be passed (once) or circulated (multiple times) through the film at ambient temperature for about 15 to 30 minutes. "Ambient temperature" means the surrounding temperature without the application of heat or other energy. Usually, the ambient temperature is in the range of 60 to 90°F (15.6 to 32.2°C), such as a typical room temperature of 72°F (22.2°C).

[0090] Examples of amine-functional polysaccharides include polygalactosamine, polymannosamine, polyfructosamine, polyglucosamine, etc. Common polyglucosamines include poly-D-glucosamine and chitosan, which is a partially deacetylated poly-N-acetyl-D-glucosamine derived from the shells of crustaceans (note: more than 60% deacetylation is most preferred). To the extent that the polysaccharide is soluble in the acidic solution, the amine-functional polysaccharide can be present in the dispersion in an amount of at least 0.25 weight percent, or at least 0.50 weight percent, or at least 0.75 weight percent, and up to 15 weight percent, or up to 10 weight percent, or up to 5 weight percent based on the total weight of the dispersion.

[0091] Examples of organic acids that can be used in the aqueous medium include formic acid, acetic acid, lactic acid, benzoic acid, propanoic acid, etc. Mixtures of acids can also be used. The pH of the dispersion is adjusted with the organic acid to be below 6.5, such as a pH of 1 to 6.

[0092] Next, at least one surface of the polysaccharide-treated film formed in (3) is contacted with (4) an aqueous acid, which at least partially neutralizes the amine functional groups on the polysaccharide (thus forming an ammonium base), and subsequently with (5) an amine-functional alkoxysilane to form a polysaccharide hydrogel layer on the film. In each of these steps, again, the film can be immersed and / or the relevant treatment solution can be passed or circulated through the film at ambient temperature.

[0093] The aqueous acid for use in step (4) can be organic or inorganic, and typically the aqueous acid includes an inorganic acid such as boric acid, sulfuric acid, or phosphoric acid. A mixture of acids can also be used. The acid can form an ammonium salt on the amine groups present on the polysaccharide and can have two or more protons capable of forming a loosely cross-linked network (not bound by theory).

[0094] Examples of the amine-functional alkoxysilane include aminopropyltriethoxysilane, aminopropyltrimethoxysilane, aminobutyltriethoxysilane, aminobutyltrimethoxysilane, aminophenyltrimethoxysilane, 3-aminopropyltris (methoxyethoxyethoxy) silane, 11-aminoundecyltriethoxysilane, 2-(4-pyridylethyl)triethoxysilane, aminopropylsilanetriol, 3-(m-aminophenoxy)propyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyldimethylethoxysilane, or a combination thereof. The amine-functional alkoxysilane may include polyaminosilane. Non-limiting examples of the polyaminosilane include N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyl-silanetriol, N-(2aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, diethylmethyltriethoxysilane, N,N-diethyl-3-aminopropyl)trimethoxysilane, 3-(N-styrylmethyl-2-aminoethylamino)propyltrimethoxysilane hydrochloride, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride, N-(trimethoxysilylethyl)benzyl-N,N,N-trimethylammonium chloride, trimethoxysilylpropyl-modified (polyethyleneimine), or a combination thereof.

[0095] Alternatively, the amine-functional alkoxysilane may comprise a reaction product of (i) a polyamine having at least one primary amino group and / or at least one secondary amino group, and (ii) an epoxy-functional silane. In this example, the polyamine (i) used to form the amine-functional alkoxysilane may include polyethyleneimine, N-(3-aminopropyl)-1,4-butanediamine, N,N'-bis(3-aminopropyl)-1,4-butanediamine, N-(3-aminopropyl)-N'-[3-[(3-aminopropyl)amino]propyl]propane-1,3-diamine, 1,13-diamino-5,9-diazatridecane, triethylenetetramine, diethylenetriamine, and / or 1-(2-aminoethyl)piperazine. Suitable epoxy-functional silanes for use as the epoxy-functional silane (ii) may be any of those selected from the group consisting of diepoxy-functional silanes, epoxycyclohexylsilanes, epoxycyclohexylalkylsilanes, glycidoxyalkylsilanes, and mixtures thereof. Specific examples of the epoxy-functional silane (ii) used to form the amine-functional alkoxysilane may include (3-glycidoxypropyl)trialkoxysilane, (3-glycidoxypropyl)bis(trimethylsiloxy)methylsilane, (3-glycidoxypropyl)dimethylethoxysilane, and / or (3-glycidoxypropyl)methyldiethoxysilane.

[0096] The reaction of a polyamine with an epoxy-functional silane containing at least one condensable or hydrolyzable group can be carried out "without containing other substances" or in the presence of a solvent. The reaction of a polyamine with an epoxy-functional silane can be carried out in a polar solvent. Some non-limiting examples of suitable polar solvents that can be used include those disclosed above, in particular, water or alcohols such as C1-C6 alcohols, or a mixture of water and one or more of C1-C6 alcohols. Such suitable C1-C6 alcohols can be any of those selected from the group consisting of methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 1-hexanol, and mixtures thereof. Acids such as acetic acid, hydrochloric acid, sulfuric acid, nitric acid, carbonic acid, lactic acid, citric acid, phosphoric acid, and / or oxalic acid can be present to assist in the dissolution of the polyamine. The acid can be present in the reaction mixture in an amount greater than 0 weight percent, or at least 1 weight percent, and up to 10 weight percent, or up to 5 weight percent, or up to 2 weight percent, based on the total weight of the reaction mixture. For example, the acid can be present in the reaction mixture in an amount of greater than 0 to up to 10 percent, or greater than 0 to up to 5 percent, or greater than 0 to up to 2 percent, or 1 to 10 percent, or 1 to 5 percent, or 1 to 2 percent. This solution can be used as a treatment composition containing a silane-functional polyamine, or a portion of the solvent can be removed, for example, by stripping or distillation techniques as is well known in the art. Also, the reaction of a polyamine with an epoxy-functional silane can be achieved by heating. The exact reaction temperature depends on various factors including the specific reactants selected and the type of solvent used. However, the temperature generally ranges from ambient temperature to 90 °C, and the reaction time can be several hours, such as up to 5 hours, for example, 0.5 hours to 2 hours.

[0097] Typically, the molar ratio of the sum of the primary and secondary amino groups present in the polyamine (i) to the epoxy groups present in the epoxy-functional silane (ii) is in the range of 1:1 to 100:1, such as 3:1 to 50:1, or 4:1 to 40:1, or 6:1 to 25:1.

[0098] Amine-functional alkoxysilanes often include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-(trimethoxysilylpropyl)diethylenetriamine, trimethoxysilylpropyl-modified (polyethyleneimine), and / or dimethoxysilylmethylpropyl-modified (polyethyleneimine).

[0099] Amine-functional alkoxysilanes can be combined with surfactants, particularly nonionic surfactants. Suitable examples include those mentioned above.

[0100] Steps (4) and (5) are thought to enable the formation of a polysaccharide hydrogel layer on the membrane. As used herein, "hydrogel" is a water-insoluble three-dimensional network of physically or chemically bonded polymer chains that can trap water in the intermolecular spaces. Typically, the treated microporous membrane is kept moist during and after treatment and storage, such as by filling it with an aqueous solution, to prevent the decomposition of the hydrogel on the membrane surface.

[0101] The present disclosure further relates to a method for treating a filtration device, the filtration device comprising a microporous membrane, the microporous membrane comprising an organic thermoplastic matrix, micronized particulate substantially water-insoluble inorganic fillers distributed throughout the matrix, an interconnected pore network communicating throughout the microporous membrane, and an acid-functional acrylic layer on at least one surface of the microporous membrane, the acid-functional acrylic layer being bonded to the filler via siloxane functional groups. Examples of suitable filtration devices can be formed from a microporous membrane treated according to steps (1) and (2) in the method described above. Typical filtration devices are usually in the form of hollow fibers, tubular devices, spiral wound filtration devices, or pleated filtration devices housed within a cartridge.

[0102] In a method for treating a filtration device of the present disclosure, (1) at least one surface of the acid-functional acrylic layer on the microporous membrane is contacted with a dispersion comprising an amine-functional polysaccharide dispersed in an aqueous medium containing an organic acid to form a polysaccharide-treated membrane. Such a dispersion can comprise any of those disclosed above.

[0103] Subsequently, at least one surface of the polysaccharide-treated membrane formed in (1) is contacted with (2) an aqueous acid and then (3) an amine-functional alkoxysilane to form a polysaccharide hydrogel layer on the membrane. The aqueous acid for use in step (2) can be organic or inorganic and usually comprises an inorganic acid as described above. Similarly, the amine-functional alkoxysilane used in step (3) often comprises 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-trimethoxysilylpropyl)diethylenetriamine, trimethoxysilylpropyl-modified (polyethyleneimine), and / or dimethoxysilylmethylpropyl-modified (polyethyleneimine).

[0104] Alternatively, the amine-functional alkoxysilane can include a reaction product of (i) a polyamine having at least one primary amino group and / or at least one secondary amino group, and (ii) an epoxy-functional silane. Examples of the polyamine (i) and the epoxy-functional silane (ii) used to form the amine-functional alkoxysilane include any of those disclosed above.

[0105] Steps (1) to (3) of the method for treating the filtration device can each be carried out in a similar manner to those described above for the similar process steps in the method for treating the surface of the microporous membrane. Again, the membrane on the treated filtration device is usually kept wet after treatment and during storage to prevent the decomposition of the hydrogel on the membrane surface.

[0106] The present disclosure further relates to a treated microporous membrane comprising: (1) an organic thermoplastic matrix, micronized particulate and substantially water-insoluble inorganic fillers distributed throughout the matrix, and an interconnected pore network communicating throughout the microporous membrane; (2) an acrylic layer on at least one surface of the microporous membrane, wherein the acrylic layer is bonded to the filler via a siloxane functional group; and (3) a hydrogel layer on at least one surface of the acrylic layer, wherein the hydrogel layer is formed from an amine-functional polysaccharide and an amine-functional alkoxysilane. The treated microporous membrane can be in the form of a sheet and / or a component of a filtration device such as a hollow fiber, a tubular device, a spiral wound filtration device, or a pleated filtration device, depending on the intended application, and / or can be within a cartridge. The treated microporous membrane can be prepared, for example, using the method described above.

[0107] The microporous membrane (1) typically includes any of those described above. For example, the organic thermoplastic matrix may include polyacrylonitrile, cellulose nitrate, polycarbonate, cellulose acetate, polytetrafluoroethylene (PTFE), polyamide, polyolefin, polyether ketone, polyvinylidene fluoride (PVDF), polysulfone, and / or polyethersulfone, while the filler may include silica, alumina, calcium oxide, zinc oxide, magnesium oxide, titanium oxide, and / or zirconium oxide. The microporous membrane (1) often includes a polyolefin-based matrix and a silica filler.

[0108] The acrylic layer (2) can be formed from a mixture of vinyl monomers including (i) a (meth)acrylic acid monomer and (ii) a silane-functional acrylic monomer. Monomers (i) and (ii) can be any of those disclosed above. In a specific example, the mixture of vinyl monomers used to form the acrylic layer (2) further includes (iii) N-vinylpyrrolidone.

[0109] As described above, the treated microporous membrane further includes a hydrogel layer (3) on at least one surface of the acrylic layer. The hydrogel layer is formed from an amine-functional polysaccharide and an amine-functional alkoxysilane such as those described above (the amine group can be previously converted to an ammonium base). The hydrogel layer can be formed using any of the amine-functional polysaccharides and amine-functional alkoxysilanes disclosed above.

[0110] When used for oil-water separation applications, the treated membranes of the present disclosure, as well as the treated membranes and filtration devices prepared by the disclosed methods, have been found to exhibit a longer practical durability, as demonstrated by a reduction in fouling, an improvement in flux rate over time, and robustness to cleaning procedures, compared to equivalent untreated membranes. Such membranes can also exhibit higher oil retention, particularly under high operating pressures, i.e., pressures above 30 psi, or above 40 psi, and pressures above 15 psi such as up to a maximum of 100 psi.

[0111] The following examples are intended to further illustrate and demonstrate the membranes and treatment methods described herein. It is understood that the disclosure herein is not necessarily limited to the examples described in this section. Components described elsewhere in this document as suitable alternative materials for use but not demonstrated in the following examples are expected to provide results comparable to their demonstrated counterparts. Unless otherwise indicated, all parts are by weight.

Examples

[0112] Part 1: Methods for Generating and Treating Membranes Extruded sheets were prepared according to Example M-2 of US10,888,821(A1) and used as the substrate for all of the following examples.

[0113] Part 1. Preparation of Treatment Compositions Part 1a. Preparation of Acrylic Polymer Dispersions: Acrylic polymers were prepared from the following components listed in Table 1.

[0114] Charge A was placed into a four-neck round-bottom flask equipped with a condenser, nitrogen adapter, mechanical stirrer, and addition funnel, and the reactants were heated to 80 °C under a nitrogen blanket while stirring. Next, Charges B and C were added simultaneously over 3 hours at reflux, and then held at reflux for an additional 2 hours. Next, Charge D was added over 30 minutes at 80 °C. The reaction mixture was held at 80 °C for an additional 2 hours. The clear solution was then cooled to 50 °C and poured into Charge E while stirring over 15 minutes. The solution was stirred for 30 minutes and then filtered through a 100 micron mesh filter bag. The solids content was checked by heating the sample in an oven at 110 °C for 1 hour (10.36% solids). [Table 2]

[0115] Section 1b. Acrylic treatment solution A polyethylene beaker equipped with an air-driven paddle stirrer was charged with water and 2-butoxyethanol according to the amounts in Table 2. After stirring for 5 minutes, the acrylic polymer dispersion from Section 1a was added slowly to yield a solution with a pH of 9 - 10. [Table 3]

[0116] Section 1c. Preparation of polysaccharide treatment solution: A 1 wt% solution of chitosan (derived from shrimp shells, ≥75% deacetylated) in 2% acetic acid was prepared by stirring until the solid was completely dissolved.

[0117] Section 1d. Preparation of amine-functional alkoxysilane treatment solution A polyethylene beaker equipped with an air-driven paddle stirrer was charged with cold water and stirred to generate a vortex of about 1 inch. A specified amount of poly(2-ethyl-2-oxazoline) was added and stirred for 4 hours. 2-Butoxyethanol and a surfactant were added and the solution was stirred for an additional 30 minutes. Then, 3-aminopropyltriethoxysilane was added and the solution was stirred for 15 minutes. A trimethoxysilylpropyl polyethyleneimine solution was added to the main mixing vessel and stirred for at least 5 minutes before use.

Table 4

[0118] Part 2. Treatment of the membrane Example 1 Step 1. A sheet of microporous membrane was cut to approximately 10.5 inches × 10.5 inches and clamped to the outer perimeter of a 12-inch × 12-inch metal frame using 1-inch binder clips. The solution from Part 1b was applied sufficiently to yield a target coating weight of 281 g / m 2 The sample in the frame was placed in an oven set at 95 °C for 10 minutes. The assembly was then cooled to room temperature.

[0119] Step 2. Apply the chitosan solution of Part 1c until the liquid is no longer absorbed by the membrane as evidenced by the stationary liquid on the surface, then wipe it off, followed by a 15-minute holding time in a sealed plastic bag. The treated membrane was kept wet in the bag until the next step.

[0120] Step 3. Place the membrane from Step 2 into 2.5% H2SO4 for 30 minutes, then raise it with water. Next, put the membrane into a sealed plastic bag and keep it wet until the next step.

[0121] Step 4. Completely immerse the membrane from Step 3 in the amine-functionalized silane solution prepared in Part 1d. The membrane was left immersed for 15 minutes and then raised with water. Next, put the membrane into a sealed plastic bag and keep it wet in the bag for testing.

[0122] Comparative Example CE-2: Prepare a sheet of the microporous membrane and subject it to Step 1 of Example 1 to provide a silane (acrylic)-treated membrane.

[0123] Comparative Example CE-3 Leave the sheet of the microporous membrane untreated and use it as Comparative Example CE-3.

[0124] Part 3: Performance Testing of the Membrane Water Flux: The water flux was tested using a Sterlitech filter holder with a membrane area of 90 cm 2 Load 1 liter of water into the Sterlitech unit equipped with the membrane and seal it. Set the air pressure to 50 psi and record the time required for 1 liter of water to pass through the membrane. Calculate the corresponding water flux.

[0125] Oil resistance: The membrane wetted with the target water was removed from the above water flux testing equipment and immediately evaluated for oil resistance. Using a disposable dropper, 3 drops of oil were placed on the membrane surface. All 3 drops were left as they were for about 1 minute and then wiped off using a paper wipe. If the oil droplets penetrated the membrane and left a stain, the result was given an evaluation of 1. If most of the oil droplets remained on the surface but clearly stained the membrane, the result was given an evaluation of 2. If the oil droplets remained on the surface, did not penetrate the membrane, and / or slightly stained the surface, the result was given an evaluation of 3.

[0126] Oil absorption test: A 2 cm × 2 cm specimen of the membrane was completed by immersing it in 100% crude oil for 24 hours. The sample was then removed from the oil bath and all excess oil was wiped off the surface. The resulting sample was placed in a beaker filled with 100 ml of hexane, immersed for 5 minutes, and then removed. The corresponding oil concentration during hexane immersion was determined using a TD-3100 manufactured by Turner Design hydrocarbon Instruments.

[0127] Water / oil extrusion pressure test: A 50 / 50 volume blend of 200 ml of water and Texas Crude (purchased from Texas Crude) was used for the test along with a Sterlitech filter holder having a membrane area of 90 cm 2 Once the Sterlitech unit was fully attached and loaded, the test was started at a pressure of 5 psi and then the pressure was increased in 0.5 psi increments every 5 minutes. The pressures at which water and then oil passed through the membrane were recorded. The difference between these two pressures is recorded in Table 5 as ΔP oil-water. A larger ΔP corresponds to a wider range of operable pressures where oil is less likely to pass through as a contaminant to the permeate.

Table 5

[0128] A higher delta P is better for high-pressure applications.

[0129] While specific embodiments of the invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that many modifications in the details of the invention may be made without departing from the invention as defined in the appended claims.

Claims

1. A microporous membrane comprising an organic thermoplastic matrix, micronized particulate substantially water-insoluble inorganic fillers distributed throughout the matrix, and an interconnected pore network communicating throughout the microporous membrane, a method for treating the surface of the microporous membrane, comprising, in order: (1) contacting at least one surface of the microporous membrane with a treatment composition to form a silane-treated membrane, said treatment composition comprising: (a) (i) a mixture of vinyl monomers comprising a (meth)acrylic acid monomer and (ii) a silane-functional acrylic monomer, an acrylic polymer prepared therefrom, (b) optionally, a base, and said acrylic polymer being in contact with said fillers present in said matrix, the step; (2) subjecting the silane-treated membrane formed in (1) to conditions sufficient to effect a condensation reaction between said filler and said acrylic polymer; (3) contacting at least one surface of the silane-treated membrane with a dispersion comprising an amine-functional polysaccharide dispersed in an aqueous medium containing an organic acid to form a polysaccharide-treated membrane; (4) contacting at least one surface of the polysaccharide-treated membrane formed in (3) with an aqueous acid; (5) contacting the polysaccharide-treated membrane with an amine-functional alkoxysilane to form a polysaccharide hydrogel layer on said membrane. A method comprising.

2. The method according to claim 1, wherein the organic thermoplastic matrix comprises polyacrylonitrile, cellulose nitrate, polycarbonate, cellulose acetate, polytetrafluoroethylene (PTFE), polyamide, polyolefin, polyether ketone, polyvinylidene fluoride (PVDF), polysulfone, and / or polyethersulfone.

3. The method according to any one of the preceding claims, further comprising, prior to step (3), assembling the membrane of step (2) into a hollow fiber, tubular device, spiral wound filtration device, or pleated filtration device.

4. The method according to any one of the preceding claims, wherein the mixture of vinyl monomers further comprises (iii) N-vinylpyrrolidone.

5. The method according to any one of the preceding claims, wherein the treatment composition of step (1) further comprises at least one of (c) poly (N-vinylpyrrolidone) or polyoxazoline.

6. The method according to any one of the preceding claims, wherein the base contains an amine. **Claim 7** The method according to claim 6, wherein the amine contains a tertiary amine. **Claim 8** The acrylic polymer has a weight average molecular weight (M ｗ ) of up to 35,000 Da, or up to 30,000 Da, or up to 25,000 Da, or up to 20,000 Da, or up to 16,000 Da, or up to 15,000 Da, according to any one of the preceding claims. **Claim 9** The method according to any one of the preceding claims, wherein the filler is selected from the group consisting of silica, alumina, calcium oxide, zinc oxide, magnesium oxide, titanium oxide, zirconium oxide, and mixtures thereof. **Claim 10** The method according to any one of the preceding claims, wherein the filler contains silica. **Claim 11** The method according to any one of the preceding claims, wherein the step of subjecting the silane-treated film formed in (1) to conditions sufficient to effect a condensation reaction between the filler and the acrylic polymer includes the step of drying the film in step (2). **Claim 12** The method according to claim 11, wherein the drying step occurs at a temperature in the range of 20°C to 145°C, or 20°C to 120°C, or 20°C to 100°C, or 20°C to 95°C. **Claim 13** The method according to any one of claims 1 to 10, wherein the step of subjecting the silane-treated film formed in (1) to conditions sufficient to effect a condensation reaction between the filler and the acrylic polymer includes the step of adjusting the pH to a range of 4 to 7 in step (2). **Claim 14** The method according to any one of the preceding claims, wherein the base is included in an amount sufficient to neutralize at least 75% of the acid functional groups on the (meth)acrylic acid monomer. **Claim 15** The method according to any one of the preceding claims, wherein the amine-functional polysaccharide contains polyglucosamine. **Claim 16** The method according to any one of the preceding claims, wherein the organic acid used in step (3) contains formic acid, acetic acid, lactic acid, benzoic acid, and / or propanoic acid. **Claim 17** The method according to any one of the preceding claims, wherein the aqueous acid used in step (4) contains sulfuric acid, phosphoric acid, and / or boric acid. **Claim 18** The method according to any one of the preceding claims, wherein the amine-functional alkoxysilane contains 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-trimethoxysilylpropyldiethylenetriamine, trimethoxysilylpropyl-modified (polyethyleneimine), and / or dimethoxysilylmethylpropyl-modified (polyethyleneimine). **Claim 19** The method according to any one of claims 1 to 17, wherein the amine-functional alkoxysilane comprises a reaction product of (i) a polyamine having at least one primary amino group and / or at least one secondary amino group, and (ii) an epoxy-functional silane.

20. The method according to claim 19, wherein the polyamine (i) comprises polyethyleneimine, N-(3-aminopropyl)-1,4-butanediamine, N,N'-bis(3-aminopropyl)-1,4-butanediamine, N-(3-aminopropyl)-N'-[3-[(3-aminopropyl)amino]propyl]propane-1,3-diamine, 1,13-diamino-5,9-diazatridecane, triethylenetetraamine, diethylenetriamine, and / or 1-(2-aminoethyl)piperazine.

21. The method according to claim 19 or 20, wherein the epoxy-functional silane (ii) comprises (3-glycidoxypropyl)trialkoxysilane, (3-glycidoxypropyl)bis(trimethylsiloxy)methylsilane, (3-glycidoxypropyl)dimethylethoxysilane, and / or (3-glycidoxypropyl)methyldiethoxysilane.

22. A treated microporous membrane prepared by the method according to any one of the preceding claims.

23. The treated microporous membrane according to claim 22, wherein the membrane in contact with the treatment composition is in the form of a sheet.

24. A method for treating a filtration device, wherein the filtration device comprises a microporous membrane, the microporous membrane comprising an organic thermoplastic matrix, micronized particulate substantially water-insoluble inorganic filler distributed throughout the matrix, an interconnected pore network communicating throughout the microporous membrane, and an acid-functional acrylic layer on at least one surface of the microporous membrane, the acid-functional acrylic layer being bonded to the filler via a siloxane functional group, the method comprising, in sequence: (1) contacting at least one surface of the acid-functional acrylic layer on the microporous membrane with a dispersion comprising an amine-functional polysaccharide dispersed in an aqueous medium containing an organic acid to form a polysaccharide-treated membrane; (2) contacting at least one surface of the polysaccharide-treated membrane formed in (1) with an aqueous acid. (3) contacting the polysaccharide-treated membrane with an amine-functional alkoxysilane to form a polysaccharide hydrogel layer on the membrane; a method comprising.

25. The method according to claim 24, wherein the organic thermoplastic matrix comprises a polyolefin, a polyether ketone, a polyvinylidene fluoride (PVDF), a polysulfone, and / or a polyether sulfone.

26. The method according to claim 24 or 25, wherein the filtration device is in the form of a hollow fiber, a tubular device, a spiral wound filtration device, or a pleated filtration device.

27. The method according to any one of claims 24 to 26, wherein the filler is selected from the group consisting of silica, alumina, calcium oxide, zinc oxide, magnesium oxide, titanium oxide, zirconium oxide, and mixtures thereof.

28. The method according to any one of claims 24 to 27, wherein the filler comprises silica.

29. The method according to any one of claims 24 to 28, wherein the amine-functional polysaccharide comprises polyglucosamine.

30. The method according to any one of claims 24 to 29, wherein the organic acid used in step (1) comprises formic acid, acetic acid, lactic acid, benzoic acid, and / or propanoic acid.

31. The method according to any one of claims 24 to 30, wherein the aqueous acid used in step (2) comprises sulfuric acid, phosphoric acid, and / or boric acid.

32. The method according to any one of claims 24 to 31, wherein the amine-functional alkoxysilane comprises 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-trimethoxysilylpropyl)diethylenetriamine, trimethoxysilylpropyl-modified (polyethyleneimine), and / or dimethoxysilylmethylpropyl-modified (polyethyleneimine).

33. The method according to any one of claims 24 to 31, wherein the amine-functional alkoxysilane comprises a reaction product of (i) a polyamine having at least one primary amino group and / or at least one secondary amino group, and (ii) an epoxy-functional silane.

34. The method according to claim 33, wherein the polyamine (i) comprises polyethyleneimine, N-(3-aminopropyl)-1,4-butanediamine, N,N'-bis(3-aminopropyl)-1,4-butanediamine, N-(3-aminopropyl)-N'-[3-[(3-aminopropyl)amino]propyl]propane-1,3-diamine, 1,13-diamino-5,9-diazatridecane, triethylenetetramine, diethylenetriamine, and / or 1-(2-aminoethyl)piperazine.

35. The method according to claim 33 or 34, wherein the epoxy-functional silane (ii) comprises (3-glycidoxypropyl)trialkoxysilane, (3-glycidoxypropyl)bis(trimethylsiloxy)methylsilane, (3-glycidoxypropyl)dimethylethoxysilane, and / or (3-glycidoxypropyl)methyldiethoxysilane.

36. A processed filtration device prepared by the method according to any one of claims 24 to 35.

37. A processed microporous membrane, comprising: (1) a microporous membrane comprising an organic thermoplastic matrix, micronized particulate substantially water-insoluble inorganic fillers distributed throughout the matrix, and an interconnected pore network communicating throughout the microporous membrane; (2) an acrylic layer on at least one surface of the microporous membrane, wherein the acrylic layer is bonded to the filler via a siloxane functional group; (3) a hydrogel layer on at least one surface of the acrylic layer, wherein the hydrogel layer is formed from an amine-functional polysaccharide and an amine-functional alkoxysilane.

38. The processed microporous membrane according to claim 37, wherein the organic thermoplastic matrix comprises a polyolefin, a polyether ketone, polyvinylidene fluoride (PVDF), a polysulfone, and / or a polyethersulfone.

39. The processed microporous membrane according to claim 37 or 38, wherein the filler is selected from the group consisting of silica, alumina, calcium oxide, zinc oxide, magnesium oxide, titanium oxide, zirconium oxide, and mixtures thereof.

40. The treated microporous membrane according to any one of claims 37 to 39, wherein the acrylic layer is formed from a mixture of vinyl monomers comprising (i) a (meth)acrylic acid monomer and (ii) a silane-functional acrylic monomer.

41. The treated microporous membrane according to claim 40, wherein the mixture of vinyl monomers further comprises (iii) N-vinylpyrrolidone.

42. The treated microporous membrane according to any one of claims 37 to 41, wherein the amine-functional polysaccharide comprises polyglucosamine.

43. The treated microporous membrane according to any one of claims 37 to 42, wherein the amine-functional alkoxysilane comprises 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-trimethoxysilylpropyl)diethylenetriamine, trimethoxysilylpropyl-modified (polyethyleneimine), and / or dimethoxysilylmethylpropyl-modified (polyethyleneimine).

44. The treated microporous membrane according to any one of claims 37 to 42, wherein the amine-functional alkoxysilane comprises a reaction product of (i) a polyamine having at least one primary amino group and / or at least one secondary amino group and (ii) an epoxy-functional silane.

45. The treated microporous membrane according to claim 44, wherein the polyamine (i) comprises polyethyleneimine, N-(3-aminopropyl)-1,4-butanediamine, N,N'-bis(3-aminopropyl)-1,4-butanediamine, N-(3-aminopropyl)-N'-[3-[(3-aminopropyl)amino]propyl]propane-1,3-diamine, 1,13-diamino-5,9-diazatridecane, triethylenetetraamine, diethylenetriamine, and / or 1-(2-aminoethyl)piperazine.

46. The treated microporous membrane according to claim 44, wherein the epoxy-functional silane (ii) comprises (3-glycidoxypropyl)trialkoxysilane, (3-glycidoxypropyl)bis(trimethylsiloxy)methylsilane, (3-glycidoxypropyl)dimethylethoxysilane, and / or (3-glycidoxypropyl)methyldiethoxysilane.

47. The processed microporous membrane according to any one of claims 37 to 46, wherein the membrane is a component of a hollow fiber filtration device, a tubular filtration device, a spiral wound filtration device, or a pleated filtration device.

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