BR112019010028B1 - METHOD FOR TREATMENT OF A SURFACE OF A MICROPOROUS MEMBRANE AND TREATED MICROPOROUS MEMBRANE - Google Patents

Abstract

The present invention is directed to a method for treating a surface of a filled microporous membrane. The microporous membrane includes a polyolefin matrix, the inorganic charge distributed through the matrix, and a network of interconnected pores across the membrane. The method includes sequentially (1) contacting at least one surface of the membrane with a treatment composition of a silane functional polyamine compound having at least one alkoxy silane group such that the silane functional polyamine compound is in intimate contact with the filler present in the matrix; and (2) subjecting the membrane of (1) to conditions sufficient to effect a condensation reaction between the inorganic filler and the silane-functional polyamine compound. Treated membranes are also provided.

Description

field of invention

[0001] The present invention relates to methods for treating microporous membranes useful as a filter medium and adsorption medium, and to microporous membranes prepared by the methods.

Background of the invention

[0002] According to the Department of Energy, 21 billion gallons of water by-products are entrained by oil and gas wells each year in the United States. The natural “oil” from a well is actually a multiphase oil/gas/water fluid. Generally, all three fluids are found in every hydrocarbon well and well effluent.

[0003] Due to its values and because of environmental problems, the aeolus needs to be separated from this effluent. This is usually done by gravitational settling in large tanks, which require capital and significant space that is not always available on site. The gas is easily separated in a mechanical separator or by pressure reduction inside a storage vessel. In the case of heavy oils and many emulsified fluid systems, the raw fluids are heated to change the density of the oil and water by heating lighter extremes and essentially agitating their molecular structures so that these fluids can separate more easily. Water is then a by-product.

[0004] Microporous filled membranes are known to be low cost, efficient, and environmentally friendly separation means for separating aeolian from water by-products as mentioned above. However, as with most filtration media, over a period of time the filtration membranes can become soiled with residual oil and other contaminants. Such soiling can slow flow rates and thus reduce the efficiency of filter devices. Thus, it would be desirable to provide a microporous membrane for use as an extended life filter medium having improved anti-fouling properties while maintaining a high flow rate. Methods for treating filled microporous membranes as described and claimed herein provide such improved anti-fouling properties.

Summary of the invention

[0005] The present invention is directed to a method for treating a surface of a filled microporous membrane. The microporous membrane comprises a finely divided, particulate, polyolefin polymeric matrix, a substantially water-insoluble inorganic filler distributed throughout the matrix, and a network of interconnected pores communicating through the microporous membrane. The method further comprises (1) contacting at least one surface of the membrane with a treatment composition comprising a silane functional polyamine compound having at least one alkoxy silane group, the silane functional polyamine compound being in intimate contact with the charge present on the headquarters; and (2) subjecting the membrane of (1) to conditions sufficient to effect a condensation reaction between the inorganic filler and the silane-functional polyamine compound.

[0006] The present invention is also directed to treated microporous membranes prepared by the various claimed methods.

Detailed description of the invention

[0007] Any other working examples, or where otherwise indicated, all numbers expressing amounts of ingredients, reaction conditions, and so used in the report and claims shall be understood to be modified in all examples by the term "about" . Consequently, unless otherwise indicated, the numerical parameters represented in the report below and in the appended claims are approximations that may vary depending on the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the patent application to the doctrine of equivalents, for the scope of the claims, each numerical parameter must at least be constructed in light of the reported number of significant digits and by the application of ordinary rounding techniques.

[0008] Notwithstanding, those numerical ranges and parameters represented in the broad scope of the invention are approximations, the numerical values represented in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in its respective test measurements.

[0009] Furthermore, it should be understood that any numerical range quoted here is intended to include all subranges subsumed here. For example, a range of “1 to 10” is intended to include all subranges between (and including) the quoted minimum value of 1 and the quoted maximum value of 10, i.e., having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0010] As used in this report and the appended claims, the articles “a”, “an”, and “the”, “the” include reference to the plural unless expressly and unambiguously limited to a reference.

[0011] The various embodiments and examples of the present invention as presented herein are each understood to be non-limiting with respect to the scope of the invention.

[0012] The present invention is directed to a method for treating a surface of a filled microporous membrane. The microporous membrane comprises a finely divided, polyolefin polymeric matrix, particulate, substantially water-insoluble inorganic filler distributed throughout the matrix, and a network of interconnected, communicating pores across the microporous membrane. The method comprises sequentially (1) contacting at least one surface of the membrane with a treatment composition comprising a silane functional polyamine compound having at least one alkoxy silane group, the silane functional polyamine compound being in intimate contact with the charge present in the matrix ; and (2) subjecting the membrane 91) to conditions sufficient to effect a condensation reaction between the inorganic filler and the silane-functional polyamine compound.

[0013] As used herein, “microporous material” or “microporous membrane” or “microporous sheet” means a material having a network of interconnecting pores, being that under free treatment, free coating, free ink printing, free impregnation, and pre-bonding base, the pores having a volume average diameter ranging from 0.001 to 1.0 micrometers, and constitute at least 5 percent by volume of the microporous material as discussed hereinbelow.

[0014] The polyolefin polymeric matrix can comprise any of a number of polyolefin materials known in the prior art. In some examples, a different polymer derived from at least one ethylenically unsaturated monomer can be used in combination with the polyolefinic polymers. Suitable examples of such polyolefin polymers may include, but are not limited to, polymers derived from ethylene, propylene, and/or butene, such as polyethylene, polypropylene, and polybutene. Ultra-high molecular weight and/or high density polyolefins, such as high density polyethylene, are also suitable. The polyolefin matrix may also comprise a copolymer, for example an ethylene butene copolymer or an ethylene propylene copolymer.

[0015] Non-limiting examples of ultra-high molecular weight (UHMW) polyolefins can essentially include essentially linear UHMW polyethylenes (PE) or polypropylene (PP). To the extent that UHMW polyolefins are not thermosetting polymers having an infinite molecular weight, they are technically classified as thermoplastic materials.

[0016] The ultra-high molecular weight polypropylene may comprise essentially linear isotactic ultra-high molecular weight polypropylene. Often, the degree of isotacticity of such polymers is at least 95 percent, for example at least 98 percent.

[0017] Although there is no particular restriction on the upper limit of the intrinsic viscosity of UHMW polyethylene, in a non-limiting example, the intrinsic viscosity may range from 18 to 39 deciliters/gram, for example, from 18 to 32 deciliters/gram . While there is no particular restriction on the upper limit of the intrinsic viscosity of UHMW polypropylene, in a non-limiting example, the intrinsic viscosity can range from 6 to 18 deciliters/gram, for example from 7 to 16 deciliters/gram.

[0018] For the purpose of the present invention, the intrinsic viscosity is determined by extrapolation to zero concentration of the reduced viscosities or the inherent viscosities of various dilute solutions of UHMW polyolefins where the solvent is freshly distilled decahydronaphthalene to which 0.2 percent in weight, 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid, neopentanetetrayl ester [CAS Registry No. 6683-19-8] was added. The reduced viscosities or inherent viscosities of UHMW polyolefins are determined from the relative viscosities obtained at 135°C using an Ubbelohde No. 1 viscometer according to the general procedures of ASTM D4020-81, except that several dilute solutions of different concentrations are employees.

[0019] The nominal molecular weight of UHMW polyethylene is empirically related to the intrinsic viscosity of the polymer according to the following equation: M=5.37 x 104 [ή]1-37 where M is the nominal molecular weight and [ή] 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 according to the following equation: M=8.88 x 104 [ή]1-25 where M is the molecular weight and [ή] is the intrinsic viscosity of UHMW polypropylene expressed in deciliters/gram.

[0020] A mixture of substantially linear ultra-high molecular weight and lower molecular weight polyethylene can be used. In certain embodiments, the UHMW polyethylene has an intrinsic viscosity of at least 10 deciliters/gram, and the lower molecular weight polyethylene has an ASTM D 1238086, Condition E, on melt index less than 50 grams/10 minutes, for example, less than 25 grams/10 minutes, such as less than 15 grams/10 minutes, and an ASTM D 1238-86, Condition F on a melt index of at least 0.1 grams/10 minutes, e.g., at least 0, 5 grams/10 minutes, such as at least 1.0 grams/10 minutes. The amount of UHMW polyethylene used (as a weight percent) in this embodiment is described in column 1, line 52 to column 2, line 18 of US Patent 5,196,262, the description of which is incorporated herein by reference. More particularly, the percentage by weight of UHMW polyethylene used is described in relation to Figure 6 of US Patent 5,196,262; named, with reference to the polygons ABCDEF, GHCI or JHCK of Figure 6, which figure is incorporated herein by reference.

[0021] The nominal molecular weight of lower molecular weight polyethylene (LMWPE) is less 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 centimeters and rounded to the nearest thousandth, in accordance with ASTM D 1248-84 (re-approved in 1989). Non-limiting examples of densities are found in the following table.

[0022] Any or all of the polyethylenes listed in the above table can be used as the LMWPE in the matrix of the microporous material. HDPE can be used because it can be more linear than MDPE or LDPE. The processes for preparing the various LMWPE are well known and well documented. They include the high pressure process, the Phillips Petroleum Company process, the Standard Oil Company (Indiana) process, and the Ziegler process. ASTM D 1238-86, Condition E (ie, 190°C, and 2.16 kilograms of load) on the LMWPE melt index is less than about 50 grams/10 minutes. Often, the melt index in the E condition is less than about 25 grams/10 minutes. The E condition of the melt index can be less than about 15 grams/10 minutes. ASTM D1238-86, in condition F (i.e., 190°C and 21.6 kilogram load) in LMWPE melt index is at least 0.1 gram/10 minutes. In many cases, the condition F melt index is at least 0.5 grams/10 minutes, such as at least 1.0 grams/10 minutes.

[0023] UHMWPE and LMWPE may further constitute at least 65 weight percent, for example at least 85 weight percent, of the polyolefin polymer of the microporous material. Furthermore, UHMWPE and LMWPE together can constitute substantially 100 percent by weight of the polyolefin polymer of the microporous material.

[0024] Typically, the polyolefin polymeric matrix may comprise a polyolefin comprising 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 may also be present in the matrix of the microporous material providing that their presence does not materially affect the properties of the microporous material substrate in an adverse manner. The amount of other thermoplastic polymers that may be present depends on the nature of such polymers. Non-limiting examples of thermoplastic organic polymers that may optionally be present in the matrix of the microporous material include low density polyethylene, high density polyethylene, poly(tetrafluoroethylene), polypropylene, ethylene and propylene copolymers, ethylene acrylic acid copolymers, and copolymers of ethylene and methacrylic acid. If desired, all or a portion of the carboxyl groups of carboxyl-containing copolymers can be neutralized with sodium, zinc, or the like. Generally, the microporous material will comprise at least 70 weight percent UHMW polyolefins, based on the weight of the matrix. In a non-limiting embodiment, the thermoplastic organic polymer described above is substantially absent from the microporous material matrix.

[0026] The microporous membranes of the present invention further comprise particulate, finely divided, substantially water-insoluble inorganic fillers distributed throughout the matrix.

[0027] The inorganic filler can include any of a number of inorganic fillers known in the art, providing that the filler is capable of imparting a condensation reaction with the silane present in the treatment composition comprising a silane functional polyamine compound that is applied to the membrane at (1). The filler must be finely divided and substantially insoluble in water to allow uniform distribution throughout the polyolefin polymeric matrix during fabrication 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 substantially water-insoluble, finely divided filler may be in the form of final particles, aggregates of final particles, or a combination of both. At least about 90 percent by weight of the filler used in preparing the microporous material has coarse particle sizes in the range of 5 to about 40 micrometers, as determined using a Beckman Laser Diffraction Particle Sizer Instrument, LS230 Coulton, capable of measuring particle diameters as small as 0.04 microns. Typically, at least 90 percent by weight of the filler having coarse particle sizes in the range of 10 to 30 micrometers. The sizes of the filler agglomerates can be reduced during the processing of ingredients used to prepare the microporous material. Consequently, the size distribution of coarse particles in the microporous material may be smaller than in the bulk filler itself.

[0029] As previously mentioned, the filler particles are substantially insoluble, and may also be substantially insoluble in any organic processing liquid used to prepare the microporous material. This may facilitate charge retention in the microporous material.

[0030] In addition to fillers, other finely divided particulates substantially insoluble in water can optionally be employed. Non-limiting examples of such optional materials may include carbon black, carbon, graphite, iron oxide, copper oxide, antimony oxide, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, calcium carbonate, and magnesium carbonate. In a non-limiting embodiment, silica and any of the aforementioned optional fillers can comprise the filler.

[0031] The filler typically has a high surface area allowing the filler to carry much of the processing plasticizer used to form the microporous material. High surface area charges are very small particle size materials, materials that have a high degree of porosity, or materials that exhibit both characteristics. The surface area of the filler particles can vary from 20 to 900 square meters per gram, for example, from 25 to 850 square meters per gram, as determined by the Brunauer, Emmett, Teller (BET) method, according to ASTM C 819-77 using nitrogen as the adsorbate, but modified by degassing the system and the sample for one hour at 130°C. Prior to nitrogen sorption, the batch samples are dried by heating at 160°C in flowing nitrogen (OS) for 1 hour.

[0032] In a particular embodiment of the present invention, the inorganic filler comprises silica, for example, precipitated silica, silica gel, or fumed silica.

[0033] Silica gel is generally produced commercially by acidifying an aqueous solution of a soluble metal silicate, for example sodium silicate at low pH with acid. The acid employed is usually a strong mineral acid, such as sulfuric acid or hydrochloric acid, although carbon dioxide can be used. However, as there is essentially no difference in density between the gel phase and the surrounding liquid phase as long as the viscosity is low, the gel phase does not decrease, i.e. does not precipitate. Consequently, silica gel can be described as an unprecipitated, coherent, rigid, three-dimensional network of continuous colloidal amorphous silica particles. The state of subdivision ranges from large, solid masses to sub-microscopic particles, and the degree of hydration from anhydrous silica to soft gelatinous masses containing on the order of 100 parts of water per part of silica by weight.

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

[0035] Precipitated silica can be described as precipitated aggregates of final colloidal amorphous silica particles which do not have any point existing as macroscopic gel during preparation. Aggregate sizes and degree of hydration can vary widely. Precipitated silica powder differs from silica gel that has been pulverized in that precipitated silica powder generally has a more open structure, that is, a more specific pore volume. However, the specific surface area of precipitated silica, as measured by the Brunauer, Emmet, Teller (BET) method using nitrogen as the adsorbate, is often less than that of silica gel.

[0036] Many different precipitated silicas can be employed as the filler used to prepare the microporous material. Precipitated silicas are well known commercial materials, and processes for making them are described in detail in many US patents, including Patent Nos.: US 2,940,830; 2,940,830; and 4,681,750. The final average particle size (regardless of whether or not the final particles are agglomerated) of used precipitated silicas is generally less than 0.1 micrometer, i.e. 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 Industries, Inc.

[0037] The inorganic filler particles can constitute from 10 to 90 percent by weight of the microporous membrane. For example, such filler particles can constitute from 25 to 90 percent by weight of the microporous membrane, such as from 30 percent to 90 percent by weight of the microporous membrane, or from 40 to 90 percent by weight of the microporous membrane, or from 50 to 90 percent by weight of the microporous membrane, and further from 60 percent to 90 percent by weight of the microporous membrane. Filler is typically present in the microporous membrane of the present invention in an amount ranging from 50 percent to about 85 percent by weight of the microporous membrane. Often, the weight ratio of filler to polyolefins in the microporous material ranges from 0.5:1 to 10:1, such as 1.7:1 to 3.5:1. Alternatively, the weight ratio of filler to polyolefins in the microporous material can be greater than 4:1. It is contemplated that higher levels of charge could be employed, as charge levels could provide greater surface area available for condensation reactions with the treatment compositions.

[0038] The microporous material used in the membrane of the present invention further comprises a network of interconnected pores communicating through the microporous material.

[0039] On a free treatment, free coating, or impregnating free base, such pores may comprise at least 5 percent by volume, for example, from at least 5 to 95 percent by volume, or from at least at least 15 to 95 percent by volume, or at least 20 to 95 percent by volume, or at least 25 to 95 percent by volume, or from 35 to 70 percent by volume of the microporous material. Often, the pore comprises at least 35 percent by volume, or even at least 45 percent by volume, of the microporous material. Such high porosities provide for greater surface area across the microporous material, which in turn facilitates removal of contaminants from a fluid stream and increased flow rates of a fluid stream across the membrane.

[0040] As used herein and in the claims, the porosity (also known as void volume) of the microporous material, expressed as a percentage by volume, is determined according to the following equation: Porosity = 100[1-d1/d2] where d1 is the density of the sample, which is determined from the weight of the sample and the volume of the sample as determined from measurements of the dimensions of the sample, and d1 is the density of the solid portion of the sample, which is determined from the weight of the sample 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 Corp.) in accordance with the accompanying operating manual.

[0041] Porosity can also be measured using a Gurley Densometer, Model 4340, manufactured by GPI Gurley Precision Instruments of Troy, New York. Reported porosity values are a measure of the rate of air flow through a sample or its resistance to an air flow through the sample. The unit of measurement for this method is a "Gurely second" and represents the time in seconds to pass 100 cm3(cc) of air through an area of 6.45 cm2 (1 square inch) using a differential pressure of 12.39 cm (4.88 inches) of water. Smaller values equate to less airflow resistance (more air is allowed to pass freely). For the purposes of the present invention, measurements are completed using the procedure listed in the manual for the Model 4340 Automatic Hydrometer.

[0042] The mean pore volume diameter of the microporous material can be determined by mercury porosimetry using an Autopore III porosimeter (Micrometers, Inc.) according to the accompanying operating manual. The volume average pore radius for a single scan is automatically determined by the porosimeter. In porosimeter operation, a sweep is made in the high pressure range (from 138 absolute kilopascals to 227 absolute megapascals). If approximately 2 percent or less of the total introduced volume occurs in the low portion (from 138 to 250 Kilopascal absolute) of the high pressure range, the volume mean pore diameter is taken as twice the volume mean pore radius determined by the porosimeter. Otherwise, an additional scan is performed in the low pressure range (from 7 to 165 Kilopascal absolute) and the volume-average pore diameter is calculated according to the equation: d = 2 [v1r1/w1 + v2r2/w2] / [v1/w1 + v2/w2] where d is the average volume pore diameter, v1 is the total volume of mercury introduced into the high pressure range, v2 is the total volume of mercury introduced into the low pressure range, r1 is the volume mean pore radius determined from the high pressure scan, r2 is the volume mean pore radius determined from the high pressure scan, w1 is the weight of the sample subjected to the high pressure scan, and w2 is the weight of the sample subjected to the low pressure scan.

[0043] In the course of determining the volume-average pore diameter of the above procedure, the maximum detected pore radius is sometimes observed. This is taken from the low pressure range sweep, if run; otherwise it is taken from the high pressure range sweep. The maximum pore diameter is twice the maximum pore radius. Insofar as some production or treatment steps, e.g. coating processes, printing processes, impregnation processes or treatment steps, e.g. 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 comprise the microporous material, the parameters on the respective porosity, mean pore volume diameter, and maximum pore diameter are determined for the microporous material prior to application of one or more of such production or treatment steps.

[0044] To prepare the microporous materials of the present invention, filler, polyolefin polymer (typically in solid form such as powder or pellets), plasticizer processing, and minimal amounts of lubricant and antioxidants are mixed until a substantially uniform mixture is obtained . The weight ratio of filler to polymer employed in forming the mixture is essentially the same as that of the microporous substrate material to be produced. The mixture, along with additional processing plasticizer is introduced into the heated barrel of a screw extruder. Attached to the extruder is a die, such as a lamination die, to form the final desired shape.

[0045] In an exemplary manufacturing process, when the material is formed into a sheet or film, a continuous sheet or film formed by a mold is followed by a pair of heated calender rolls acting cooperatively to form a continuous sheet of smaller thickness than the continuous sheet coming out of the mold. Final thickness may depend on desired end-use application. The microporous material can have a thickness ranging from 0.7 to 18 mil (17.9 to 457.2 microns), such as 0.7 to 15 mil (17.8 to 381 microns), or 1 to 10 mil (25 .4 to 254 microns) or 5 to 10 mil (127 to 254 microns), and demonstrates a bubble point of 1 to 80 psi based on ethanol.

[0046] Optionally, the blade coming out of the calender rolls can then be stretched in at least one stretching direction above the elastic limit. Stretching may alternatively occur during or immediately after exiting the rolling die or during calendering, or multiple periods during the manufacturing process. Stretching can occur before extraction, after extraction, or both. Additionally, stretching can occur during application of the first and/or second treatment composition, described in more detail below. The drawn microporous material substrate can be produced by stretching the intermediate product in at least one stretching direction above the elastic limit. Usually, the stretch ratio is at least about 1.2. In many cases, the stretch ratio is at least about 1.5. Preferably, it is at least about 2. Often, the stretch ratio is in the range of about 1.2 to about 1.5. Often, the stretch ratio is in the range of about 1.5 to about 10. Usually, the stretch ratio is in the range of about 2 to about 6.

[0047] The temperature at which stretching is followed can vary widely. Stretching can be accomplished at about room temperature, but usually elevated temperatures are employed. The intermediate product can be heated by any of a wide variety of techniques before, during, and/or after drawing. Examples of these techniques include radioactive heating, such as that provided by electrically heated heaters or gas-fired infrared heaters; convective heating, such as that provided by recirculating heated air; and conductive heating, such as that provided by contact with heated rollers. The temperature that is measured for the purpose of temperature control may vary depending on the instrument used and personal preference. For example, temperature measuring devices can be placed to determine the temperature of the surfaces of infrared heaters, the interior of infrared heaters, the air temperature of points between the infrared heaters and the intermediate product, the temperatures of hot air circulating in the points within the apparatus, the temperature of hot air entering or leaving the apparatus, the surface temperature of rollers used in the drawing process, the temperature of heat transfer fluid entering or leaving such rollers, or film surface temperatures. In general, the temperature or temperatures are controlled so that the intermediate product is drawn uniformly so that variations, if any, in the film thickness of the drawn microporous material are within acceptable limits and so that approximately stretched out of bounds those are acceptably smaller. It will be apparent that the temperatures used for the purpose of control may or may not be closed to those of the intermediate products thereof, since it depends on the nature of the apparatus used, the locations of the devices measuring the temperature, and the identities of the substances or objects whose temperatures are being measured.

[0048] In view of the locations of the heating devices and the line speed usually employed during drawing, temperature variation gradients may or may not be present across the thickness of the intermediate product. Furthermore, due to such line speeds, it is impractical to measure these temperature gradients. The presence of temperature variation gradients, when they occur, makes it unreasonable to refer to a singular film temperature. Consequently, film surface temperatures, which can be measured, are best used to characterize the thermal condition of the intermediate product.

[0049] These are ordinarily about the same across the width of the intermediate product during drawing, although it may be intentionally varied, as for example, to compensate for the intermediate products having a wedge-shaped cross-section of the blade. The surface temperature of the film along the length of the blade can be about the same or it can be different during stretching.

[0050] The surface temperature of the film at which stretching is accompanied can vary widely, but in general they are such that the intermediate product is uniformly stretched, as explained above. In many cases, surface temperatures of the film during stretching are in the range of about 20°C to about 220°C. Often, such temperatures are in the range of about 50°C to about 200°C. From about 75°C to about 180° is preferred.

[0051] The stretching can be accomplished in a single step or a plurality of steps as desired. For example, when the intermediate product must be drawn in a single direction (uniaxial drawing), the drawing may be accompanied by a drawing step or a sequence of drawing steps until the desired final draw ratio is achieved. Similarly, when the intermediate product must be stretched in two directions (biaxial stretching), the stretching can be conducted by a single biaxial stretching step or a sequence of biaxial stretching steps until the desired final stretch ratios are achieved. Biaxial stretching may also be accompanied by a sequence of one or more uniaxial stretching steps in one direction and one or more uniaxial stretching steps in another direction. The biaxial drawing steps where the intermediate product is drawn simultaneously in two directions and the uniaxial drawing steps can be conducted in sequence in any order. Stretching in more than two directions is within contemplation. It can be seen that the various exchanges of steps are quite numerous. Other steps, such as cooling, heating, sintering, annealing, winding, non-coiling, and the like, can optionally be included in the completed processes as desired.

[0052] Various types of stretching apparatus are well known and can be used to accompany the stretching of the intermediate product. Uniaxial stretching is usually accompanied by stretching between two rollers, with the second or downstream roller rotating at a greater peripheral speed than the first or downstream roller. Uniaxial stretching can also be accomplished on a standard tensioning machine. Biaxial stretching can be accompanied by simultaneous stretching in two different directions on the tensioning machine. More commonly, however, biaxial stretching is accompanied by the first uniaxial stretching between two differently rotating rollers as described above, followed by either uniaxial stretching in a different direction using a tensioning machine or biaxially stretching using a tensioning machine. The most common type of biaxial stretch is where the two stretch directions are at approximately right angles to each other. In many cases where the blade is still being stretched, one direction of stretch is at least approximately parallel to the major axis of the blade (machine direction) and the other direction of stretch is at least approximately perpendicular to the machine direction and is in the plane. of the blade (transverse direction).

[0053] The stretching of the blades before the extraction of the plasticizer processing allows thinner films with larger pore sizes than in conventionally processed microporous materials. It is also believed that stretching the blades prior to extraction from plasticizer processing minimizes thermal reduction after processing. It should also be noted that stretching of the microporous membrane may be conducted at any point prior to, during, or subsequent to application of the first treatment composition (as described below), and/or prior to, during, or subsequent to application of the second treatment composition. Stretching of the microporous membrane can occur once or multiple times during the treatment process.

[0054] The product passes through 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 extraction liquid are substantially immiscible with water. The product then passes through a second extraction zone where residual organic extraction liquid is substantially removed by steam and/or water. The product is then passed through a forced air dryer to remove substantial residual water and remaining residual organic extraction liquid. From the dryer, the microporous material can be passed through a take-up roller, when it is in the form of a sheet.

[0055] The processing plasticizer has little resolving effect on the thermoplastic organic polymer at 60°C, only a moderate resolving effect at elevated temperatures in the order of about 100°C, and a significant resolving effect at elevated temperatures in the order of about 200°C. It is a liquid at room temperature and usually it is a processing oil, such as paraffinic oil, naphthenic oil, or aromatic oil. Suitable process oils include those meeting the requirements of ASTM D 2226-82, Types 103 and 104. Those oils that have a poor point of less than 22°C, or less than 10°C, in accordance with ASTM D 97-66 (reapproved 1978), are used more frequently. Examples of suitable oils include Shellflex® 412 and Shellflex® 371 oil (Shell Oil Co.), which are solvent refined and hydrotreated oils derived from that crude naphthenic. It is expected that other materials, including the phthalate ester plasticizer, such as dibutyl phthalate, bis(2-ethylhexyl)phthalate, diisodecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, and ditridecyl phthalate will function satisfactorily as a processing plasticizer.

[0056] There are many organic extraction liquids that can be used in the microporous membrane manufacturing process. Examples of suitable organic extraction liquids include, but are not limited to, 1,1,2-trichlorethylene; perchlorethylene; 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 halogenated hydrocarbon azeotropes selected from trans-1,2-dichloroethylene, 1,1,1,2,2,3,4,555-decafluoropentane, and/or 1,1,1,3,3-pentaflorobutane also can be employed. Such materials are commercially available as VERTREL, TM. MCA (a binary azeotrope of 1,1,1,2,2,3-4,5,5,5-dihydrodecafluoropentane and trans-1,2-dichloroethylene: 62%/38%) and VERTREL.TM. CCA (a ternary azeotrope of 1,1,1,2,2,3,4,5,5,5-dihydrodecafluoropethane, 1,1,1,2,3-pentaflorbutane, and trans-1,2-dichloroethylene: 33 %/28%/39%); Vertrel.TM.SDG (80-83% trans-1,2-dichloroethylene, 17-20% hydrofluorocarbon blend) all available from MicroCAre Corporation.

[0057] In the above-described process for producing microporous membrane, extrusion and calendering are facilitated when the filler carries a lot of the processing plasticizer. The ability of the filler particles to absorb and hold the processing plasticizer is a function of the surface area of the filler. Therefore, the filler typically has a high surface area as discussed above. Insofar as it is desirable to essentially retain the filler in the microporous material substrate, the filler must be substantially insoluble in the processing plasticizer and substantially insoluble in the organic extraction liquid when the microporous material substrate is produced by the above process. Residual processing plasticizer content is usually less than 15 weight percent of the resulting microporous material and this can be reduced further to levels, such as less than 5 weight percent, by further extractions using the same or an extraction liquid. different organic. The resulting microporous materials can be further processed depending on the desired application.

[0058] As previously mentioned, the method for treating a surface of a microporous membrane (as described herein), comprises sequentially (1) contacting at least one surface of the membrane with a treatment composition comprising a silane functional polyamine compound having at least one alkoxysilane group, whereby the silane-functional polyamine compound is in intimate contact with the inorganic filler present in the matrix; and (2) subjecting the membrane of (1) to conditions sufficient to effect a condensation reaction between the inorganic filler and the silane groups of the silane functional polyamine compound. As used herein, in the report and in the claims, with respect to the silane-functional polyamine compound applied in (1), by "polyamine" is meant a compound having at least three amino groups.

[0059] Generally, the silane-functional polyamine compound present in the treatment composition comprises a silane-functional derivative of an amine-containing compound selected from the group consisting of polyethyleneimine, amino group-containing polysaccharides, N-(3-aminopropyl)-1, 4-butanediamino, N,N'-bis(3-aminopropyl)-1,4-butanediamino, N-(3-aminopropyl)-N'-[3-[(3-aminopropyl)amiono]propyl]propane-1, 3-diamine, 1,13-diamino-5,9-diazatridecane, triethylene tetraamine, diethylene triamine, 1-(2-aminoethyl)piperazine, and mixtures thereof. In a particular embodiment of the present invention, the silane-functional amino group-containing polysaccharides comprise a silane-functional polyglucososamine. Suitable silane functional polyamines may also include, for example, 3-(trimethoxysilylpropyl)diethylenetriamine, trimethoxysilylpropyl-modified (polyethyleneimine), and dimethoxysilylmethylpropyl-modified (polyethyleneimine), all of which are commercially available from Gelest, Inc.

[0060] The silane functional polyamine compound may comprise the reaction product of (i) a polyamine having at least one primary amino group and/or at least one secondary amino group with (ii) an epoxy functional silane. Polyamines suitable for use as polyamine (i) may include, but are not limited to, any of the polyamines mentioned immediately above, as well as mixtures thereof. Epoxy functional silanes suitable for use as the epoxy functional silane (ii) may be any of those selected from the group consisting of di-epoxy-functional silanes, epoxy cyclohexyl silanes, cyclohexylalkyl epoxy silane, glycidoxyalkyl silanes, and mixtures thereof. In a particular embodiment of the present invention, the epoxysilane compound (ii) comprises a glycidoxyalkyl silane selected from the group consisting of (3-glycidoxyproyl)trialkoxysilane, (3-glycidoxypropyl)bis(trimethylsiloxy)methylsilane, (3-glycidoxyproyl) ) dimethylethoxysilane, (3-glycidoxypropyl)methyldiethoxysilane, and mixtures thereof.

[0061] The reaction of a polyamine with an epoxy-functional silane containing at least one condensable or hydrolyzable group can be carried out “near” 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 water or alcohol, such as any of the C1 to C6 alcohols described in detail herein below, or mixtures of water and one or more of the C1 to C6 alcohols. An acid, such as any of those described in detail hereinbelow, may be present to aid dissolution of the polyamine. The acid can be present in an amount greater than 0 up to and including 10 percent, such as greater than 0 up to and including 5 percent, or from 1 to 2 percent. This solution can be used as the treatment composition comprising a silane functional polyamine, or a portion of the solvent can be removed, for example, by stripping or distillation techniques as are well known in the art. Furthermore, the reaction of a polyamine with an epoxy-functional silane can be achieved via heating. The exact reaction temperature depends on a variety of factors, including the specific reagents selected and the type of solvent used. Temperatures, however, generally range from room temperature to 90°C and reaction times can be several hours, such as up to 5 hours, for example, from 0.5 hour to 2 hours.

[0062] 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) varies from 1:1 to 10:1, such as from 3: 1 to 50:1, or 4:1 to 40:1, or 6:1 to 25:1.

[0063] The treatment composition applied to the membrane in step (1) of the method of the present invention may further comprise a functional monoamine silane, such as any of those known in the art. For example, the treatment composition may comprise a silane-functional monoamine selected from the group consisting of aminopropyltriethoxysilane, aminopropyltrimethoxysilane, aminobutyltriethoxysilane, aminobutyltrimethoxysilane, aminophenyltrimethoxysilane, 3-aminopropyltris(methoxyethoxyethoxy)silane, 11-aminoundecyltriethoxysilane, 2-(4-pyridylethyl) triethoxysilane, aminopropylsilanetriol, 3-(m-aminophenoxy)propyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropylmethyldiethoxysilane silane, 3-aminopropyldimethylethoxysilane, and mixtures thereof.

[0064] The treatment composition may be in the form of an aqueous composition. The aqueous treatment composition may be an acidic aqueous composition or a basic aqueous composition. Additionally, the treatment composition can also include a C1 to C6 alcohol, either alone (as the sole solvent) or in combination with water. Said suitable C1 to C6 alcohol may be any of those selected from the group consisting of methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 1-hexanol, and mixtures thereof.

[0065] Suitable acids for use in preparing the aqueous acid treatment composition may include, but are not limited to, those selected from the group consisting of acetic acid, hydrochloric acid, sulfuric acid, nitric acid, carbonic acid, lactic acid , citric acid, phosphoric acid, oxalic acid, and mixtures thereof. Suitable bases for use in preparing the aqueous base treatment composition may include, but are not limited to, a base selected from the group consisting of ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and mixtures thereof.

[0066] As mentioned above, the treatment composition applied to the microporous membrane in the method of the present invention may also comprise an alcohol, either as a sole solvent or in combination with water.

[0067] The treatment composition can be applied to the microporous membrane by any means of application known in the art. For example, the treatment composition can be applied to at least one surface of the microporous membrane by dipping, spraying, dipping, and/or pouring or certain application techniques. The treatment composition can be applied after plasticizer extraction and either before, during, or after any of the previously described stretching steps. Alternatively, stretching can be delayed until application of the treatment composition. During the application of the treatment composition to at least the surface of the microporous membrane in (1), the membrane of (1) is (2) subjected to conditions sufficient to effect a condensation reaction between the functional groups present on the surface of the filler inorganic compound and the silane groups of the silane-functional polyamine compound. Such reaction conditions will be discussed in more detail here below.

[0068] Additionally, the treatment composition can be applied in multiple steps. That is, the microporous membrane can be contacted at (1) with one or more applications of the treatment composition. Furthermore, the treatment compositions applied in such multi-step applications can be the same or different compositions, providing each composition comprises at least one silane functional polyamine compound. It should be noted that any of the previously described treatment compositions suitable for application to the microporous membrane of (1) according to the method of the present invention may further comprise at least one non-ionic surfactant as described immediately below, as well as a polyalkylene of oxazoline such as oxazoline polyethylene.

[0069] Non-limiting examples of non-ionic surfactants suitable for use in the treatment composition used in the method of the present invention may include, but are not limited to, polyalkylene oxide alkyl esters, wherein the alkyl group may be straight chain or branched having a chain length of from C6 to C22; polyalkylene oxide alkyl esters, the alkyl group being straight or branched chain having a chain length of from C6 to C22; organic amines with straight or branched carbon chains from C6 to C22 having the general formula R*NR1'R", where R* may be C6 to C22 alkyl and R' and R" may each independently be H or alkyl C1 to C4, such as the molecule may be substantially soluble or substantially emulsifiable in water, for example, octadecylamine; tertiary amines with carbon chains from C6 to C22; polyethyleneimines, polyacrylamides; C6 to C22 straight chain or branched alkyl glycols and alcohols that can form ester linkages (--SiOC--), polyvinyl alcohol, and mixtures thereof.

[0070] The non-ionic surfactant can also be chosen from polyalkylene oxide ethers such as polypropylene oxide ethers and polyethylene oxide ethers, such as but not limited to hexaethylene glycol monododecylether, hexaethylene glycol monohexadecylether, monotetradecylether hexaethylene glycol, hexaethylene glycol monooctadecylether, heptaethylene glycol monododecylether, heptaethylene glycol monohexadecylether, heptaethylene glycol monotetradecylether, heptaethylene glycol monooctadecylether, nonaethylene glycol monododecylether, octaethylene glycol monododecylether, esters of polyalkylene oxide, for example, esters of polypropylene oxide and polyethylene oxide esters, such as, but not limited to, hexaethylene glycol monododecylester, hexaethylene glycol monohexadecylester, hexaethylene glycol monotetradecylester, hexaethylene glycol monooctadecylester, heptaethylene glycol monododecylester, heptaethylene glycol monohexadecylester, heptaethylene glycol monotetradecylester, heptaethylene glycol monooctadecylester heptaethylene glycol, nonaethylene glycol monododecylester, octaethylene glycol monododecylester, polysorbate esters such as polyoxyethylene mono sorbitan fatty acid esters, including but not limited to polyoxyethylene mono sorbitan palmitate, polyoxyethylene mono sorbitan oleate, polyoxyethylene mono sorbitan stearate, di acid esters -polyoxyethylene sorbitan fatty acid, such as polyoxyethylene sorbitan dipalmitate, polyoxyethylene sorbitan dioleate, polyoxyethylene sorbitan distearate, polyoxyethylene sorbitan monopalmitate monooleate, polyoxyethylene sorbitan tri-fatty acid esters, such as, but not limited to, polyoxyethylene sorbitan tristearate, and mixtures thereof.

[0071] In a particular embodiment, the treatment composition used in the method of the present invention may comprise a nonionic surfactant selected from block copolymer based on poly(ethylene glycol), for example, poly(ethylene glycol) block copolymers. propylene glycol) and poly(ethylene glycol), (such as PLURONIC® 17r2 triblock copolymer which is commercially available from BASF Corporation); cetylstearyl alcohol; polyethylene glycol and derivatives thereof, for example, polyoxyethylene octyl phenyl ether; polyalkyl glycols; cetyl alcohol; cocamide mono- or di-ethanolamine; decyl glycoside; octylphenoxypolyethoxyethanol; isocetyl alcohol; lauryl glucoside; monolaurin, polyglycol fatty alcohol ethers; polyglycol ethers; polyethylene glycol derivatives of mono- or diglycerides; mono- and polyglycerol derivatives, for example polyglycerol polyricinoleate, sorbitan esters; polysorbate and oxidized polyethylene. Mixtures of any of the aforementioned non-ionic surfactants can be used.

[0072] As discussed above, the method for treating a surface of a filled microporous membrane according to the present invention further comprises (2) subjecting the membrane of (1) to conditions sufficient to effect a condensation reaction between the inorganic filler and the silane functional polyamine compound. In the "wet method", the aqueous acid treating composition or aqueous base treating composition (as the case may be) may be applied to one or more surfaces of the microporous membrane as described above, or the acid treating composition Aqueous or aqueous basic treatment composition can be passed through the microporous membrane under high pressure so as to effect the condensation reaction between the inorganic filler and the silane functional polyamine compound. In this wet method, the condensation reaction in (2) can be carried out at room temperature. The wet method can be used effectively to treat or recover/clean a microporous membrane that is in the form of a sheet or when the microporous membrane is a component of a prefabricated or existing separation device, such as the load from a spiral or pleated wound filter device, or a pleated separation membrane, or a separation membrane as a component of a battery (i.e., a battery separator).

[0073] In the “dry method” of carrying out the condensation reaction in step (2) of the method of the present invention, the condensation reaction between the inorganic filler and the silane-functional polyamine compound is carried out by exposing the microporous membrane treated with (1) at elevated temperatures. The temperature generally ranges from 50°C to 145°C. such temperatures are sufficient to effect at least one condensation reaction in (2). The dry method is particularly useful for treating microporous membranes in the form of a sheet. The dry method can be started on a microporous membrane before any stretching, or after stretching in the machine direction and before a stretching in the transverse direction, or the dry method can be started on a microporous membrane that has already passed through a biaxial stretch. Furthermore, when the dry method is employed, the microporous membrane can be stretched during the drying/heating step in addition to or instead of stretching prior to treatment with the treatment composition. During the application of the treatment composition in the dry method, it must be observed that the microporous membrane to which the respective treatment composition is applied must be kept dimensionally stable during said application. Additionally, during the dry method, drying/heating steps, the membrane is typically kept under tension in order to prevent/minimize shrinkage, with respect to whether stretching is occurring simultaneously.

[0074] It should be noted here that wet and dry method steps can be combined if desired. That is, the condensation reaction can be carried out by applying an aqueous treatment composition (either an aqueous acidic composition or an aqueous basic composition) at room temperature, then the membrane treated so far can be subjected to the elevated temperature, or vice versa. -versa.

[0075] The present invention also provides microporous membranes prepared by any of the various methods described above.

[0076] The methods for treating a surface of a microporous membrane filled according to the present invention differ significantly from this known method, where conventional hydrophilic coatings are applied to the surface of the microporous membrane. In the methods of the present invention, the components of the treatment composition chemically interact with the inorganic filler on all surfaces in and on the membrane, including within the pores. The components are reacted via condensation to form a permanent surface that imparts hydrophilic character over the entire membrane, including pore surfaces without pore occlusion. Such methods result in the treatment being bound to the membrane surface and the interior of the pores via covalent interaction with the inorganic filler particles. Thus, the treatment is not removed by normal chemical or physical use (for example, by wiping with a basic cleaning solution). It has been observed that, when used in oil-water separation applications, membranes prepared by the methods of the present invention exhibit a longer practical lifespan as evidenced by decreased fouling, improved flow rates over extended periods of time, and robustness against cleaning procedures when compared to an equivalent, untreated membrane. Such membranes may also demonstrate lesser shrinkage (ie, the membranes maintain pore integrity) when compared to an equivalent untreated membrane. This is particularly true for the membranes of the present invention, which are prepared using the dry method as mentioned above.

[0077] The present invention is more particularly described in the examples which follow which are intended to be illustrative only, as various modifications and variations herein will be apparent to those skilled in the art.

Examples Part 1: Substrate Preparation

[0078] The membrane was prepared according to Example 4 in Publication US 2013/0228529 A1. The extruded sheet was then stretched in both machine and transverse directions. Stretching in the machine direction was performed at 270°F with a slow draw roller set at 15 FPM and a fast draw roll set at 28 FPM. Drawing in the transverse direction was performed at 270°F and a draw ratio of 2 to 1.

[0079] For all examples and comparative examples described below, a sheet of microporous membrane prepared above was cut to approximately 7” x 7” and attached to the outer perimeter of a 5” x 5” square metal frame fabricated from metal 3/4” stock square tubular stock, with excess slack removed. The blade-mounted frame was placed on a flat counter, with the blade continuous or top side facing. This guideline was maintained through each of the treatment steps.

Part 2: Preparation of Treatment Solutions Part 2.1 - Silane Functional Polyamine Solutions

[0080] For each solution, the water and/or 2-propanol shown in Table 1 were added to a polyethylene beaker fitted with an air-powered paddle stirrer. To this was added the indicated amount of silane functional polyamine. The mixture was stirred for a minimum of 30 minutes before using in Part 3. Table 1 1 Trimethoxysilylpropylpolyethyleneimine: A 50% solution in isopropyl alcohol, sold under product code SSP-060 by Gelest, Inc. 2 Trimethoxysilylpropyldiethylenetriamine was purchased from Gelest, Inc.

Part 2.2 - In-situ produced silane functional polyamine solutions:

[0081] The ingredients listed in Table 2 below were added to a polyethylene beaker fitted with an air-powered paddle stirrer. After addition of both chitosan and poly(ethyleneimine), the mixture was stirred for at least two hours until the materials were completely dissolved. After the siloxane was added, each mixture was heated to 80°C and stirred for 60 minutes. The surfactant was added to the chitosan solution and stirred for an additional 15 minutes. The solutions were cooled to room temperature before use. Both solutions had a pH measurement between 8 and 9. Table 2 Treatment Compositions for In-Situ Functional Silane Polyamines 1 Branched polyethyleneimine with reported average Mn of 10,000 and Mw of 25,000 purchased from Sigma-Aldrich under product number 408727. 2 A block copolymer surfactant, available from BASF Corporation.

Part 3 - Sample preparation

[0082] Dry Process: The treatment solution, as listed in Table 3 below, was liberally applied to an upper side of the slide using a disposable dropper until the liquid was clearly wetted across the slide, as determined by observing transparency slide constant while adding more solution. Full application of solution and moisture through required approximately one minute to complete. Excess free liquid was gently wiped from all membrane surfaces. The treated membranes were then post-treated by heating in a forced air oven set at 130°C for 15 minutes. Then, the structured membrane was placed on top of the counter with the upper side of the slide facing and allowed to cool to room temperature before testing. Table 3 Examples of dry process

[0083] Wet process: the treatment solution, as designated in Table 4 below, was applied in the same manner as above. Excess free liquid was gently wiped off the entire surface of the membrane and the structured membrane was placed in a rigid plastic bag with air for 15 minutes to prevent evaporation. Treated membranes were kept moist in the pouch until testing. Table 4 Solution formulations for the single solution treated wet processed examples

[0084] Multi-Step Process: The treatment solution, as listed in Table 5 below, was first applied in the same manner as above. Any excess free liquid was gently wiped off the entire surface of the membrane and the framework membrane was placed in a tight plastic air bag for 15 minutes to prevent evaporation. The array was then removed from the pouch, and the membrane was then treated with a 0.25% or 0.50% chitosan solution prepared in 1% (by weight) aqueous acetic acid until the longest unabsorbed liquid within the pouch was removed. membrane, as evidenced by stable liquid on the surface, which was then cleaned and followed for an exact 15 minutes in a tight plastic bag with air between each step. Two of the examples were further treated with a glutaraldehyde solution in the same manner. Membranes were kept moist in the bag until testing. Table 5 Solution formulations for examples treated with multiple solutions

[0085] CE-17 used the membrane prepared in part 1 without further treatment.

[0086] Comparative Example (CE) 18 used a hydrophilic coating solution of 6g SELVOL® 325 polyvinyl alcohol (supplied by Sekisui Specialty Chemicals America) in 294g cold water. This coating solution was liberally applied to the top side of the membrane described in Part 1 using a disposable dropper until the transparency was unchanged with the additional solution. Any excess free liquid was gently wiped from the surface of the membrane. The membrane was then post-treated with heating in a forced air oven set at 105°C for 15 minutes.

[0087] CE-19 used a hydrophilic coating solution prepared according to Part III, example A, in Publication US 2014/0069862 A1, but using 10g of the polyethyloxazoline in the formulation. This coating solution was applied to the membrane described in Part I in the same manner as above. Any excess free liquid was gently wiped from the surface of the membrane. The membranes were then post-treated with heating in a forced air oven set at 105°C for 15 minutes.

Part 4 - Physical Properties of the treated membranes:

[0088] The membranes prepared in Part 3 were tested for the physical properties described below.

[0089] Gurely: This test was performed only on dry membrane samples. Porosity was determined using a Gurely precision densometer, model 4340, manufactured by GPI Gurley Precision Instruments of Troy, NY. The test area was 6.45 cm2 (1 square inch) and the result reported as Gurley per seconds per 100 cm3(cc) of air.

[0090] Contact Angle: Was measured on a VCA 2500Xe video contact angle system, available from AST Products, Inc. using 1 microliter of ultrapure water. Contact angles were measured on dry process samples only.

[0091] Wet/dry shrinkage test: coupons from 8 cm x 8 cm samples of the treated materials were used. For the wet treatment samples, the coupons were cut from the finished membrane and allowed to humidify at room temperature overnight. Dry treatment samples were soaked in deionized water for one hour. Those with water contact angles greater than 10 were pre-moistened with a 50/50 water/isopropyl alcohol solution then rinsed with and soaked for one hour in deionized water. After soaking, the samples were removed from the water bath and air-dried at room temperature overnight. The resulting samples were measured 3 times in both the transverse (CD) and machine (MD) directions, the values averaged, and the shrinkage calculated and reported as a percentage of the pre-wet sample coupons in Table 7. water contact and Gurley were only relevant on wet process samples. Table 7 Physical Properties of Examples and Comparative Examples

Part - Performance Test of Treated Membranes

[0092] Each of the prepared membranes of Part 3 was tested for the following performance properties.

[0093] Water flow: Water flow was tested with a Sterlitech filter retainer with a membrane area of 90 cm2. The membrane fitted Sterlitech unit was filled with 1 liter of water and sealed. The air pressure was set to 50 psi and the time required for a 1 liter amount of water to pass through the membrane was recorded. The corresponding water flow was calculated.

[0094] Oil resistance: The water-wetted membrane of interest was removed from the above water flow test equipment and immediately evaluated for oil resistance. Three drops of oil were placed on the surface of the membrane using a disposable dropper. All three drops were allowed to remain undisturbed for approximately one minute, then wiped off using a tissue. If the oil droplet penetrated and stained the membrane, the result was given as a rating of 1. If the oil droplet remained mostly on the surface, but clearly staining the membrane, the result was given as a rating of 2. If the oil drop remained on the surface, did not penetrate the membrane and/or only slightly stained the surface, the result was given at a rate of 3.

[0095] Oil absorption test: A 2 cm x 2 cm coupon membrane was completely submerged in 100% crude oil for 24 hours. The sample was then removed from the water bath and all excess oil wiped from the surface. The resulting sample was placed in a beaker filled with 100 ml of hexane, allowed to soak for 5 minutes, and then removed. The corresponding oil concentration in the soaked hex was determined with a Turner Design Hydrocarbon Instruments TD-3100.

[0096] Water/oil extrusion pressure test: an amount of 200 ml of a 50/50 volume mixture of water and Texas crude oil (purchased from Texas Crude) was used for the test along with a Sterlitech filter retainer with a membrane area of 90 cm2. Once the Sterlitech unit was fully adjusted and charged, the test was started at a pressure of 5 psi and then the pressure was increased 2.5 psi at a time every 10 minutes. The pressure at which water and then oil passed through the membrane was recorded. The difference between these two pressures was recorded in Table 8 as ΔP oil-water. The performance result shown in Table 7 below illustrates that microporous membranes prepared by the methods of the present invention demonstrate greater oil resistance and lower oil absorption than other hydrophilic coatings known in the art (Comparative Examples). Low ΔP values (less than or equal to 5 psi) directly correlate to oil-contaminated permeate in practical use. Table 8 Performance of treated membranes 1 ΔP not measured due to too low flow.

Part 6 - Treatment and test of manufactured filtration cartridge:

[0097] The membrane described in Part 1 was arranged in two industrial standard size 1812 spiral cartridges with a single sheet design. The cartridge each contained 3.5 square feet of active membrane area with an end feed gap of 35 mil (899 microns). One of these cartridges was left untreated and the other was treated as follows. The cartridge treatment system comprised an ARO double diaphragm pump, valves, piping, fittings, pressure and flow gauges positioned in a basic secondary compartment with dimensions of 24” x 18”. The widest point of the arrangement was 24”. The system was designed to circulate liquids under pressure through an 1812 cartridge. One liter of treatment solution B was pumped through the cartridge for 1 minute at a peak pressure of 20 psi, held in the cartridge for 15 minutes, and drained by gravity. . After this procedure, one liter of each of the solutions described in Table 5, Example 15, was pumped through the cartridge for 5 minutes at a peak pressure of 20 psi, held in the cartridge for 15 minutes, then drained by gravity. The cartridge was finally treated with one liter of water for 15 minutes under continuous pumping before testing.

[0098] The treated cartridge and the untreated cartridge were each arranged in an 1812 RO membrane housing with a 0.63 cm (x4 inch) port at the feed inlet. A salt/oil/water mixture designed to simulate produced water was used for the test, the composition of which is detailed in Table 9. Table 9 Salt/oil/water formulation

[0099] The salt/oil/water solution was pumped through each of the test cartridges at a feed rate of 11.36 liters/minute (3 gallons/minute). The feed return and permeate were directed back into the original source vessel and the feed pressure, flow and temperature were each recorded over time. An addition of 300 ppm of oil was added every 8 hours throughout the test to simulate constant usage conditions. Permeate flux rate was recorded over time and reported as GFD (litres/meter2/day)((Gal/sq.ft/day)). The results are shown graphically in Figure 1.

[0100] The test results presented in plot 1 above, illustrates the reduction of soiling of a membrane prepared by the methods of the present invention (incorporated as a component in a filter cartridge) compared to an untreated membrane (incorporated as a component in an analog filter cartridge). This reduced soiling contributes significantly to longer cartridge life.

[0101] Although particular embodiments of this invention have been described above, for the purpose of illustration, it will be apparent to a person skilled in the art that numerous variations of the details of the present invention can be made without departing from the scope of protection of the invention, as defined in the attached claims.

Claims (16)

1. Method for treating a surface of a microporous membrane, comprising a polyolefin polymeric matrix, said polyolefin polymeric matrix consisting essentially of a polyolefin selected from the group consisting of ultra-high molecular weight polyethylene, ultra-high molecular weight polypropylene ultra-high, high-density polyethylene, high-density polypropylene, and blends thereof; - a finely divided particulate, substantially water-insoluble inorganic filler distributed throughout the polyolefin polymeric matrix, the inorganic filler being selected from the group consisting of silica, alumina, calcium oxide, zinc oxide, magnesium oxide, zinc oxide titanium, zirconium oxide, and mixtures thereof; and - a network of interconnected pores communicating through the microporous membrane, said method being characterized in that it comprises in sequence: (1) contacting at least one surface of the membrane with a treatment composition comprising a silane-functional polyamine compound having at least one alkoxysilane group, wherein the treatment composition comprises (i) an aqueous acidic composition, or (i) a basic aqueous composition, such that the silane-functional polyamine compound is in intimate contact with the charge present in the polyolefin polymeric matrix ; and (2) effecting a condensation reaction between the inorganic filler that is distributed through the polyolefin polymeric matrix and the silane-functional polyamine compound by subjecting the membrane of (1) to room temperature for a time sufficient to effect a condensation reaction between the filler inorganic filler and the silane functional polyamine compound and/or (i) subjecting the membrane of (1) to temperatures ranging from 50°C to 145°C to effect a condensation reaction between the inorganic filler and the silane functional polyamine compound. 2. Method according to claim 1, characterized in that the silane-functional polyamine compound comprises a silane-functional derivative of an amine-containing compound selected from the group consisting of polyethyleneimine, amino group-containing polysaccharide, 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, triethylene tetraamine, diethylene triamine, 1-(2-aminoethyl)piperazine, and mixtures thereof. 3. Method according to claim 2, characterized in that the silane-functional polyamine compound comprises a polysaccharide containing the silane-functional amino group comprises a silane-functional polyglucososamine. 4. Method according to claim 1, characterized in that the silane-functional polyamine is selected from the group consisting of 3-trimethoxysilylpropyl)diethylenetriamine, modified trimethoxysilylpropyl (polyethyleneimine), modified dimethoxysilylmethylpropyl (polyethyleneimine), and mixtures thereof. 5. Method according to claim 1, characterized in that the silane-functional polyamine compound comprises the reaction product of (i) a polyamine having at least one primary amino group and/or at least one secondary amino group with (ii ) an epoxy-functional silane. 6. Method according to claim 5, characterized in that the polyamine (i) is selected from the group consisting of polyglucosamine, polyethyleneimine, triethylene tetraamine, diethylene triamine, 1-(2-aminoethyl)piperazine, and mixtures of the same. 7. Method according to claim 5, characterized in that the epoxy functional silane (ii) is selected from the group consisting of di-epoxy functional silanes, epoxy cyclohexyl silanes, cyclohexylalkyl epoxy silanes, glycidoxyalkyl silanes, and mixtures thereof . 8. Method according to claim 7, characterized in that the epoxy silane compound is a glycidoxyalkyl silane selected from the group consisting of (3-glycidoxypropyl)trialkoxysilane, (3-glycidoxypropyl)bis (trimethylsiloxy)methylsilane, (3 -glycidoxypropyl)dimethylethoxysilane, (3-glycidoxypropyl)methyldiethoxysilane, and mixtures thereof. 9. Method, according to claim 5, characterized in that 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 functional epoxy silane (ii) varies from 1:1 to 10 :1. 10. Method according to claim 1, characterized in that the inorganic filler comprises silica. 11. Method, according to claim 1, characterized in that the treatment composition further comprises a functional monoamine silane selected from the group consisting of aminopropyltriethoxysilane, aminopropyltrimethoxysilane, aminobutyltriethoxysilane, aminobutyltrimethoxysilane, aminophenyltrimethoxysilane, 3-aminopropyltris(methoxyethoxyethoxy)silane, 11-aminoundecyltriethoxysilane, 2-(4-pyridyethyl)triethoxysilane, aminopropylsilanetriol, 3-(m-aminophenoxy)propyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyldimethylethoxysilane, and mixtures thereof. 12. Method according to claim 1, characterized in that the treatment composition further comprises a C1 to C6 alcohol. 13. Method according to claim 12, characterized in that the alcohol is selected from methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 1-hexanol, and mixtures thereof. 14. Treated microporous membrane, characterized in that it is prepared by the method as defined in claim 1. 15. Treated microporous membrane, prepared from the method as defined in claim 1, characterized in that the treated membrane is a component of a separation device. 16. Treated microporous membrane, prepared by the method as defined in claim 1, characterized in that the treated membrane is in the form of a blade.