Filters for microprocessing or semiconductor processing fluids and methods of using the same

Abstract

This invention describes a filter and a filtration product comprising a microporous membrane for filtration, wherein at least one layer of the membrane has an average pore size of less than 0.035 micrometers; the filter or filtration product and the membrane thereof can be used in an ultrafiltration or nanofiltration process, such as for processing fluids in microelectronics or semiconductors.

Description

Technical Field

[0001] This application relates to filters and filtration products for processing microelectronic or semiconductor fluids and comprising dry membranes suitable for use in filtration processes, as well as methods of using such filtration products. These processes may involve ultrafiltration or nanofiltration. Prior Technology

[0002] Filters with polymer microporous membranes are used in a variety of applications to remove unwanted materials from a useful fluid flow. Many gaseous and liquid fluids in industry are treated using filters, including ambient air, drinking water, fuels, liquid industrial solvents and processing fluids, industrial gases used in manufacturing or processing, liquids for medical or pharmaceutical purposes, and solvents and processing fluids used in microprocessor and semiconductor manufacturing.

[0003] Non-desired materials removed by the fluid include impurities and contaminants such as particles, microorganisms, and dissolved chemical species. Specific examples of impurity removal applications of filtration membranes include their use in the pharmaceutical industry to remove particles or bacteria from therapeutic solutions, treating ultrapure aqueous and organic solvent solutions for microelectronic processing, and their use in air and water purification processes. Nanofiltration and / or ultrafiltration are commonly used in these processes. Membranes used in nanofiltration and ultrafiltration are expected to exhibit one or more of the following properties: mechanical stability, dimensional stability, flow rate suitable for commercial use, low contaminant levels, etc. Improvements in any or all of these properties are desired. Summary of the Invention

[0004] This document describes filtration products and microporous membranes used for filtration, such as filters or filtration products for handling fluids in microelectronics or semiconductor processes. In some embodiments, at least one layer of the membrane (referred to as a "dense layer") has an average pore size of less than 0.035 micrometers and a thickness of less than 14 micrometers. In some embodiments, the average pore size of the dense layer may be less than 0.03 micrometers, less than 0.025 micrometers, or less than 0.020 micrometers. In some preferred embodiments, the average pore size of the dense layer may range from about 0.010 micrometers to about 0.020 micrometers. In some embodiments, the average pore size of the dense layer may be less than 0.035 micrometers and the thickness of the dense layer may be less than 12 micrometers. In some embodiments, the average pore size of the dense layer may be less than 0.035 micrometers and the thickness of the layer may be less than 10 micrometers. The average pore size can be measured using an Aquapore device available from PMI (Porous Materials Corporation). The average pore size is expressed in micrometers or μm.

[0005] In some embodiments, the dense layer may be a polypropylene layer, while in other embodiments the dense layer may be a polyethylene layer.

[0006] In some of the embodiments described above, the membrane may be a single-layer membrane, a double-layer membrane, a triple-layer membrane, or a multilayer membrane. Such double-layer, triple-layer, or multilayer membranes may be formed by laminating two or more layers, co-extruding two or more layers, or a combination of lamination and extrusion steps.

[0007] In some embodiments described above, the membrane may be a three-layer membrane comprising a polypropylene layer, a polyethylene layer, and a polypropylene layer in sequence.

[0008] In some of the embodiments described above, the thickness of the film is less than 14 micrometers, less than 12 micrometers, or less than 10 micrometers.

[0009] In some embodiments, the film is translucent or transparent. In some embodiments, the film may have a blue hue and be translucent or transparent.

[0010] In some of the embodiments described above, the shrinkage rate of the membrane at 90°C for 1 hour is less than 25%, less than 20%, less than 15%, less than 10%, or less than 5%.

[0011] In some embodiments described above, the membrane has a flow time ranging from 400 seconds to 40,000 seconds. The flow time can be measured using isopropanol (IPA), wherein the flow time is the time it takes for 500 ml of isopropanol to flow through a 47 mm disk of the membrane having an area of ​​12.5 cm² at a temperature of 21°C and a pressure of 0.1 MPa.

[0012] In some embodiments, the membrane may be hydrophilically treated or coated on at least one side. This can improve filtration efficiency when removing contaminants from a liquid containing water or ethanol.

[0013] In some embodiments, the membrane can be treated to improve its filtration efficiency, particularly its non-sieving filtration efficiency. A porous membrane can remove contaminants from a fluid via either a sieving mechanism or a non-sieving mechanism. By a sieving mechanism, contaminants (e.g., particles) larger than a pore of the membrane are mechanically prevented from passing through the membrane, are trapped within the membrane, and are removed from the fluid flowing through the membrane. By a non-sieving mechanism, impurities smaller than a pore of the membrane are adsorbed onto the membrane surface via a chemical or electrostatic interaction, held within the membrane, and removed from the fluid flowing through the membrane. A membrane as described can be modified or treated to add chemical species to the surface of the membrane pores, including at the surface of the internal pores where contaminants are adsorbed via an electrostatic or chemical interaction. These chemical species can be added to the membrane surface by coating the surface with a coating containing chemical species effective in improving the non-sieving filtration efficiency of the membrane. The coating can be applied to the surface and, where appropriate, cross-linked after application. Other methods may be used to chemically attach chemical species to the polymer of the membrane, such as by grafting them onto the polymer of the membrane.

[0014] In another embodiment, an ultrafiltration or nanofiltration process is described. One step of this process involves filtering a fluid (e.g., a solvent useful in microelectronics and semiconductor processing) through a membrane, which may be contained in a filtration product described herein.

[0015] In another embodiment, a filtration product is described, comprising a treated or modified membrane as described, wherein the membrane is contained in a frame or a housing or supported by a frame or a housing.

[0016] In another embodiment, the present invention relates to a filter or filtration product for processing fluids in microelectronics or semiconductors. The filtration product comprises: a housing having an inlet and an outlet; and a multilayer microporous membrane supported between the inlet and the outlet. The multilayer microporous membrane comprises: a first polyolefin layer and a second polyolefin layer. The second polyolefin layer comprises uniaxially oriented micropores having an average pore size of less than 0.035 micrometers.

[0017] In another embodiment, the invention relates to a method of using a filter or filtration product as described above by passing a liquid fluid through the filter membrane of the filter or filtration product to remove an impurity or contaminant from the liquid fluid. Simple Explanation of the Diagram

[0018] Figure 1 shows a SEM image of one of the dry microporous membranes used in a filter or filtration product as described herein.

[0019] Figure 2 is a diagram of one of the membranes used in a filter or filtration product as described.

[0020] Figure 3 is a diagram of one of the membranes used in a filter or filtration product as described.

[0021] Figure 4 shows an example of a filter product (filter cartridge) as described.

[0022] Figure 5 shows an example of a filter product as described. Implementation

[0023] The subject matter of this invention is specifically described herein to satisfy legal requirements. However, this description itself is not intended to limit the scope of this patent. Rather, the inventors have considered that the claimed subject matter may also be embodied in other ways to include different steps or combinations of steps similar to those described in this document in conjunction with other current or future techniques. Furthermore, although the term "step" may be used herein to mean different elements of the method employed, such term should not be construed as implying any particular order among or between the steps disclosed herein unless the order of the individual steps is explicitly described.

[0024] Therefore, the embodiments described herein can be more readily understood by referring to the following detailed description, examples, and figures. However, the elements, devices, and methods described herein are not limited to the specific embodiments presented in the detailed description, examples, and figures. It should be understood that the exemplary embodiments herein merely illustrate the principles of the invention. Numerous modifications and adaptations will readily become apparent to those skilled in the art without departing from the spirit and scope of the invention.

[0025] Furthermore, all ranges disclosed herein should be understood to encompass any and all subranges contained herein. For example, a specified range "1.0 to 10.0" should be considered to include any and all subranges that begin with a minimum value of 1.0 or greater and end with a maximum value of 10.0 or less, such as 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9.

[0026] Unless otherwise expressly stated, all ranges disclosed herein shall also be considered to include the endpoints of the range. For example, a range such as “between 5 and 10”, “5 to 10”, or “5-10” shall generally be considered to include the endpoints 5 and 10.

[0027] Furthermore, when the phrase "Gundam" is used in conjunction with a quantity or number, it should be understood that the quantity is at least a detectable measure or number. For example, a material existing in a quantity specified by "Gundam" can exist from a detectable measure and Gundam includes the specified quantity.

[0028] Additionally, in any of the disclosed embodiments, the terms “substantially,” “approximately,” and “about” may be replaced with “within [a percentage] of the specified content,” where the percentage includes 0.1%, 1%, 5%, and 10%.

[0029] The following describes useful filtration membranes (or "filter membranes") in filters and filtration products (such as filter cartridges containing modified or treated filter membranes), and methods for using filtration membranes and filtration products to filter a liquid fluid. Filtration membranes include microporous polyolefin membranes, membranes composed of microporous polyolefin membranes, or membranes essentially composed of microporous polyolefin membranes, which are effective for filtering liquid fluids (removing contaminants from the liquid fluid), including liquid fluids used in processes for manufacturing microelectronic or semiconductor devices, sometimes referred to as "microelectronic or semiconductor processing fluids." These membranes exhibit useful flow properties of a liquid passing through the membrane (e.g., flow rate, flow time, bubble point) along with effective particle removal properties (e.g., retention rate of particles of various sizes) to provide the membrane with high filtration efficiency.

[0030] Filter membranes and filtration products containing filter membranes (including filter components, such as filter cartridges) can be used in methods of filtering a liquid chemical material to remove unwanted materials (contaminants, impurities) from the liquid chemical material, especially for producing a high-purity liquid chemical material useful for performing a process during the manufacture of microelectronic or semiconductor devices. Examples of filters and filtration products include those used in or useful in a step of processing a semiconductor or microelectronic device (e.g., a microelectronic substrate or a semiconductor substrate) to remove contaminants or impurities from a liquid chemical, such as a liquid solvent or other process liquid used in a filtration method, including: semiconductor photolithography, a wet etching or cleaning step, a method for forming spin-on glass (SOG) or a back-side anti-reflective coating (BARC) method, etc.

[0031] Some specific, non-limiting examples of liquid chemical materials that can be filtered using a filter membrane or filter product as described include: n-butyl acetate (nBA), isopropanol (IPA), 2-ethoxyethyl acetate (2EEA), cyclohexanone, ethyl lactate, γ-butyrolactone, hexamethyldisilazane, methyl 2-hydroxyisobutyrate, methyl isobutyl methanol (MIBC), n-butyl acetate, methyl isobutyl ketone (MIBK), isoamyl acetate, propylene glycol monoethyl ether, propylene glycol methyl ether (PGME), 2-heptanone, and propylene glycol monomethyl ether acetate (PGMEA).

[0032] A membrane as described herein contains at least one layer which may be referred to as a "dense" layer or a "retaining" layer, comprising a polyolefin polymer and containing pores with an average pore size of less than 0.035 micrometers, wherein such pores are elongated pores with an aspect ratio greater than one of 1.0, 1.2, 1.5, 2.0 or 3.0, which is attributed to the uniaxial stretching or tension of the membrane system (uniaxial, as opposed to biaxial).

[0033] The membrane forms an open structure containing pores that are distributed throughout and across the thickness of the membrane (which includes multiple layers of the membrane) and are configured to have different pore sizes and different average pore sizes at different portions of the membrane (i.e., at different "layers" of the membrane).

[0034] The example membrane comprises multiple layers, including: a first layer (sometimes referred to as a "dense" layer or a "retention" layer) containing relatively small pores; and a second layer (an "open" layer or a "support" layer) containing relatively larger pores compared to the dense layer. The dense layer has smaller pores, higher retention properties, and exhibits higher flow resistance through the membrane due to the smaller pores. The dense layer exhibits higher flow resistance relative to the open layer and inhibits liquid flow through the filter membrane to a greater extent than an open layer. An open layer has relatively larger pores, lower retention properties, resulting in lower flow resistance (relative to the dense layer) and allowing liquid flow to pass through the other layer of the filter membrane at a relatively higher rate.

[0035] A uniformly dense layer of a membrane acts as a retention portion of the membrane and is responsible for physically retaining (capturing) and removing particles or impurities from the fluid as it passes through the membrane's pores. The dense layer can effectively act as a retention portion of the membrane without being excessively or extremely thick. A relatively thin uniformly dense layer will introduce a relatively reduced resistance to liquid flow through the membrane and is therefore potentially advantageous by allowing for higher flow rates. Accordingly, the porous membrane described can be fabricated to include a uniformly dense layer that is relatively thin (having a smaller thickness) compared to the thickness of the membrane's open layer.

[0036] One of the open layers of the membrane serves to support the dense layer and, ideally, does not significantly restrict liquid flow through the membrane. The average pore size of the open layer will be larger than the average pore size of the dense layer.

[0037] The pore size of a multilayer membrane may vary in different layers of the membrane, with the pores in a uniform dense layer being smaller than those in an open layer. The pores in different layers of a membrane may have different average sizes to provide a combination of useful filtration properties (e.g., as measured by retention rate) and desired flow properties (e.g., as measured by flow time). The average pore size of an example membrane may fall within a range sometimes classified as “micropore,” “ultrapore,” or “nanopore”; for the purposes of this description and the claims of this invention, the term “micropore” is sometimes used to refer to pores within any of these size ranges, including micropore and submicropore sizes, as a way of distinguishing them from materials with larger pore sizes, i.e., from materials considered “macropores.”

[0038] According to the example membrane, the average pore size of one of the dense layers may be less than 0.035 micrometers, less than 0.03 micrometers, less than 0.025 micrometers, or less than 0.020 micrometers, for example, in the range from about 0.010 micrometers to about 0.020 micrometers. According to the example membrane, the average pore size of one of the open layers may be within the same range or larger, but will be larger than the pore size of the dense layer. For example, the average pore size of one of the open layers may be at least 0.010 micrometers, at least 0.020 micrometers, or at least 0.030 micrometers, for example, in the range from about 0.010 micrometers to about 0.20 micrometers.

[0039] The pore size of a membrane can be measured directly or indirectly using known techniques. For example, the average pore size of a uniform dense layer can be measured by correlating it with a measured bubble point of a membrane or membrane layer, or by using BP or liquid-liquid porosity measurement techniques. The average pore size of an open layer can be measured using surface scanning electron microscopy (SEM).

[0040] The example membrane comprises a uniform dense layer having a thickness less than that of an open layer, for example based on the fact that the dense layer is prepared to contain a lower amount of polymer (based on mass or volume per unit area) compared to the amount of polymer in the open layer. The example thickness of the uniform dense layer can be less than 14 micrometers, for example as described elsewhere herein.

[0041] An example of a single membrane (e.g., all (two, three, four, etc.) polyolefin layers of a single membrane) may have a total thickness of less than 20 micrometers, as described elsewhere in this document.

[0042] Example membranes may include polyolefin layers, be composed of polyolefin layers, or be essentially composed of polyolefin layers, such polyolefin layers comprising: a single polyolefin layer which is only a uniform dense layer without additional polyolefin layers; two polyolefin layers which each comprise only a uniform dense layer without additional polyolefin layers and an open layer; or three polyolefin layers which each comprise only a uniform dense layer without additional polyolefin layers and two open layers, wherein the dense layer is located between the two open layers.

[0043] A multilayer film comprising a dense polyolefin layer and one or more open polyolefin layers may include a dense layer containing polypropylene and one or two open layers containing polyethylene (including the dense layer and the one or two open layers, consisting of the dense layer and the one or two open layers, or essentially consisting of the dense layer and the one or two open layers). Alternatively, a multilayer film may include a dense polyolefin layer and one or more open polyolefin layers, comprising a dense layer containing polyethylene and one or two open layers containing polyethylene (including the dense layer and the one or two open layers, consisting of the dense layer and the one or two open layers, or essentially consisting of the dense layer and the one or two open layers).

[0044] An example dense layer may contain polypropylene (including polypropylene, essentially composed of polypropylene, or composed of polypropylene) and may be referred to as a "polypropylene layer" or a "polypropylene-containing layer". Based on the total weight of the polymer in the dense layer, the example dense layer may contain at least 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, 98 wt%, or 99 wt% of polypropylene polymer (homogene or copolymer).

[0045] An example dense layer may contain polyethylene (including polyethylene, essentially composed of polyethylene, or composed of polyethylene) and may be referred to as a "polyethylene layer" or a "polyethylene-containing layer". Based on the total weight of the polymer in the dense layer, the example dense layer may contain at least 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, 98 wt%, or 99 wt% of polyethylene polymer (homopolymer or copolymer).

[0046] An example open layer may contain polypropylene (including polypropylene, essentially composed of polypropylene, or composed of polypropylene) and may be referred to as a "polypropylene layer" or a "polypropylene-containing layer". Based on the total polymer in the dense layer, the example open layer may contain at least 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, 98 wt%, or 99 wt% of polypropylene polymer (homogene or copolymer).

[0047] An example open layer may contain polyethylene (including polyethylene, essentially composed of polyethylene, or composed of polyethylene) and may be referred to as a "polyethylene layer" or a "polyethylene-containing layer". Based on the total polymer in the dense layer, the example open layer may contain at least 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, 98 wt%, or 99 wt% of polyethylene polymer (homogeneity or copolymer).

[0048] The term "polypropylene" refers to a polymer that has a molecular structure that partially or substantially has one of the repeating -CH-CH(CH 3)- units. Polypropylene can be produced by reacting a monomer composition containing monomers, including propylene monomers, or composed of or substantially composed of propylene monomers. Therefore, a polypropylene polymer can be a polypropylene homopolymer prepared by reacting monomers composed of or substantially composed of propylene monomers. Alternatively, the polypropylene polymer may be a polypropylene copolymer prepared by reacting propylene with one of the following combinations of propylene monomers (which contain propylene monomers, consist of propylene monomers, or are essentially composed of propylene monomers) together with another type of monomer (such as another α-olefin monomer, for example, ethylene, butene, hexene, or octane, or a combination thereof); for the polypropylene copolymer, the amount of propylene monomer used to produce the copolymer relative to the non-propylene monomers may be any useful amount, such as an amount of propylene monomer of at least 50%, 60%, 70%, 80%, 90%, 95%, or 99% (by weight) of the total weight of all monomers (propylene monomers and non-propylene monomers) in a monomer composition used to prepare the propylene copolymer.

[0049] The term "polyethylene" refers to a polymer that has a linear molecular structure having partially or substantially one of the repeating -CH2-CH2- units. Polyethylene can be produced by reacting a monomer composition containing monomers, including ethylene monomers, monomers composed of ethylene monomers, or monomers substantially composed of ethylene monomers. Thus, a polyethylene polymer can be a polyethylene homopolymer prepared by reacting monomers composed of ethylene monomers or monomers substantially composed of ethylene monomers. Alternatively, a polyethylene polymer can be a polyethylene copolymer prepared by reacting a combination of ethylene and non-ethylene monomers (which may contain ethylene monomers, monomers composed of ethylene monomers, or monomers substantially composed of ethylene monomers) together with another type of monomer (such as another α-olefin monomer, for example, butene, hexene, or octane, or a combination thereof); for a polyethylene copolymer, the amount of ethylene monomer used to produce the copolymer relative to the non-ethylene monomers can be any useful amount, such as at least 50%, 60%, 70%, 80%, 90%, 95%, or 99% (by weight) of ethylene monomers in a monomer composition used to prepare the ethylene copolymer.

[0050] As used herein, a composition described as "essentially consisting of a particular component or a combination of designated components" (e.g., a monomeric composition or polymeric composition of a film layer) is a composition containing that component or combination of designated components and not exceeding a small or insignificant amount of other materials (e.g., not exceeding 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, 0.1 wt%, or 0.05 wt%). A monomeric composition or polymeric layer of a film described as containing a monomer or polymer "essentially consisting of ethylene monomer, propylene monomer, ethylene polymer, propylene polymer, or the like" is a monomeric or polymeric composition containing ethylene or propylene monomer or ethylene or propylene polymer (including copolymers as described) and not exceeding a small or insignificant amount of other materials (e.g., not exceeding 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, 0.1 wt%, or 0.05 wt%).

[0051] This membrane is a type known as a "dry" microporous membrane. In some embodiments, at least one layer of the membrane is a uniformly dense layer having an average pore size of less than 0.035 micrometers and a thickness of less than 14 micrometers, less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer. In some embodiments, at least one dense layer of the membrane has an average pore size of less than 0.030 micrometers and a thickness of less than 14 micrometers, less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer. In some embodiments, at least one dense layer of the membrane has an average pore size of less than 0.025 micrometers and a thickness of less than 14 micrometers, less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer. In some embodiments, at least one dense layer of the membrane has an average pore size of less than 0.020 micrometers and a thickness of less than 14 micrometers, less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer. In some embodiments, at least one layer of the membrane has an average pore size of less than 0.015 micrometers and a thickness of less than 14 micrometers, less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer. In some embodiments, at least one dense layer of the membrane has an average pore size of less than 0.010 micrometers and a thickness of less than 14 micrometers, less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer. In some embodiments, at least one layer of the membrane has an average pore size of less than 0.005 micrometers and a thickness of less than 14 micrometers, less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer.In some preferred embodiments, at least one dense layer of the membrane has an average pore size from about 0.010 micrometers to about 0.020 micrometers and a thickness of less than 14 micrometers, less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer.

[0052] In some embodiments described above, at least one dense layer may be a uniform dense layer comprising polypropylene, i.e., a polypropylene-containing layer. In some embodiments described above, at least one layer may be a uniform dense layer comprising polyethylene, i.e., a polyethylene-containing layer.

[0053] In some embodiments described above, the membrane may be a single-layer membrane, a bilayer membrane, a trilayer membrane, or a multilayer membrane, any of which includes at least one dense layer as described. A multilayer membrane may have four or more layers. Bilayer, trilayer, or multilayer membranes may be formed by laminating two or more layers, co-extruding two or more layers, or a combination of lamination and extrusion steps.

[0054] In some embodiments, the membrane may have a total thickness of less than 20 micrometers, less than 19 micrometers, less than 18 micrometers, less than 17 micrometers, less than 16 micrometers, less than 15 micrometers, less than 14 micrometers, less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer.

[0055] For example, in one embodiment, the membrane may be a monolayer membrane, wherein at least one layer of the membrane has an average pore size of less than 0.035 micrometers (preferably between 0.010 micrometers and 0.020 micrometers), a thickness of 7 micrometers or less, and the total membrane thickness is 7 micrometers or less. An alternative membrane may be a bilayer membrane, wherein at least one layer of such membrane is a dense polyolefin layer having an average pore size of less than 0.035 micrometers (preferably between about 0.010 micrometers and 0.020 micrometers) and a thickness of approximately 4 micrometers, and the total membrane thickness is approximately 8 micrometers.

[0056] In some embodiments described herein, the membrane may be a three-layer membrane comprising, consisting of, or essentially consisting of the following: a polypropylene-containing layer as an open layer, a polyethylene-containing layer as a uniformly dense layer, and a second polypropylene-containing layer as a second open layer. In some embodiments described above, the membrane may be a three-layer membrane comprising, consisting of, or essentially consisting of the following: a polyethylene-containing layer as an open layer, a polypropylene-containing layer as a uniformly dense layer, and a second polyethylene-containing layer as a second open layer. The polypropylene-containing layer may be a single layer comprising, consisting of, or essentially consisting of the following: a polypropylene homopolymer, a copolymer, or a combination thereof. The polyethylene-containing layer may comprise, consist of, or essentially consist of the following: a polyethylene homopolymer, a copolymer, or a combination thereof.

[0057] As understood by those skilled in the art, a dry membrane is a membrane formed without the use of solvents or oils to form pores. In some embodiments, membranes formed using particulate pore-forming agents may also be excluded from dry membranes. Such excluded membranes may include β-nucleated biaxially oriented polypropylene (BNBOPP) membranes.

[0058] Dry membranes exhibit a distinctly uniform pore structure recognizable to those skilled in the art. See, for example, Figure 1, which illustrates a uniaxially stretched dry membrane. As can be seen from Figure 1, dry membranes have elongated or slit-shaped pores. The pore size of a biaxially stretched dry membrane may be too large for applications in ultrafiltration or nanofiltration.

[0059] Typically, one procedure for preparing a dry membrane may include the steps of: extruding a thermoplastic polyolefin polymer resin (e.g., containing at least 95% or 99% polymer when the polymer resin contains less than 5% or 1% solvent by weight) to form a non-porous precursor, and then stretching the precursor in a manner that would cause pore formation. The membrane described may be prepared by stretching the precursor in a unidirectional direction (e.g., uniaxial rather than biaxial) to form uniaxially oriented pores having an aspect ratio (length dimension: width dimension) greater than 1.0 (e.g., at least 1.2, 1.5, 2.0, or 3.0).

[0060] Referring to Figure 2, a bilayer membrane having a single compact layer and a single open layer is illustrated. As shown, membrane 120 includes an open layer 122 and a compact layer 124. The compact layer 124 comprises polypropylene, is composed of polypropylene, or is essentially composed of polypropylene, which may be a polypropylene homopolymer or a polypropylene copolymer. The open layer 122 comprises polyethylene, is composed of polyethylene, or is essentially composed of polyethylene, which may be a polyethylene homopolymer or a polyethylene copolymer. Alternatively, the compact layer 124 may comprise polyethylene, is composed of polyethylene, or is essentially composed of polyethylene, which may be a polyethylene homopolymer or a polyethylene copolymer, and the open layer 122 may comprise polypropylene, is composed of polypropylene, or is essentially composed of polypropylene, which may be a polypropylene homopolymer or a polypropylene copolymer. The compact layer 124 may have a thickness of no more than 14 micrometers and an average pore size of no more than 0.035 micrometers, wherein the pores are uniaxially oriented and have an aspect ratio greater than one of 1.0, 1.2, 1.5, 2.0, or 3.0. The open layer 122 may have a thickness of no more than 19 micrometers, or a thickness in the range of 6 micrometers to 19 micrometers or in the range of 5 micrometers to 18 micrometers, and an average pore size of at least 0.010 micrometers (in the range of 0.010 micrometers to 0.20 micrometers). The membrane 120 may have a total thickness of less than 20 micrometers and comprises two layers.

[0061] One method to improve filtration efficiency, particularly non-sieving efficiency, is to coat, treat, or chemically modify one or more layers of a membrane. For example, a membrane may be modified or treated to add chemical species to the surface of the membrane pores, including at the surface of the internal pores where contaminants are adsorbed by an electrostatic or chemical interaction.

[0062] According to a specific example method, such chemical species can be added to a membrane surface by coating it with a coating containing chemical species effective for improving non-sieving filtration efficiency. The coating can be applied to the surface and, if applicable, crosslinked after application. As an example, a polymer having ionic groups can be coated onto the membrane and crosslinked thereon, as described in U.S. Patent 11,731,085, the entire contents of which are incorporated herein by reference. As another example, a polymer having ionic groups can be coated onto the membrane without crosslinking, as described in U.S. Patent 11,413,586, the entire contents of which are incorporated herein by reference.

[0063] Other methods may be used to chemically attach (e.g., graft) chemical species onto the polymer of the membrane. See, for example, U.S. Patent 10,892,620, the entire contents of which are incorporated herein by reference.

[0064] Referring to Figure 3, a three-layer membrane having a single dense layer and two open layers is illustrated, with an open layer on each side of the dense layer. As illustrated, membrane 130 sequentially comprises: an open layer 132, a dense layer 134, and an open layer 136. The dense layer 134 comprises polypropylene, is composed of polypropylene, or is essentially composed of polypropylene, which may be a polypropylene homopolymer or a polypropylene copolymer. Each of open layers 132 and 136 independently comprises polyethylene, is composed of polyethylene, or is essentially composed of polyethylene, which may be a polyethylene homopolymer or a polyethylene copolymer. Alternatively, the dense layer 134 may comprise polyethylene, is composed of polyethylene, or is essentially composed of polyethylene, which may be a polyethylene homopolymer or a polyethylene copolymer, and each of open layers 132 and 136 may independently comprise polypropylene, is composed of polypropylene, or is essentially composed of polypropylene, which may be a polypropylene homopolymer or a polypropylene copolymer. The dense layer 134 may have a thickness of no more than 14 micrometers and an average pore size of no more than 0.035 micrometers, wherein the pores are uniaxially oriented and have an aspect ratio greater than 1.0, 1.2, 1.5, 2.0, or 3.0. Each of the open layers 140 and 160 may independently have a thickness in the range of 3 micrometers to 9.5 micrometers or a thickness in the range of 2 micrometers to 8.5 micrometers and an average pore size of at least 0.010 micrometers (an average pore size in the range of 0.010 micrometers to 0.20 micrometers). The membrane 130 may have a total thickness of less than 20 micrometers and comprises all three layers.

[0065] In some embodiments described above, the membrane shrinkage rate at 90°C for 1 hour is less than 25%, less than 20%, less than 15%, less than 10%, or less than 5%, less than 4%, less than 3%, less than 2%, or less than 1%. A low shrinkage rate indicates high dimensional stability, which is crucial. Shrinkage during filtration applications or during filter assembly can cause the membrane to tear, rupture, or alter other properties, rendering its performance insufficient and / or unpredictable. The shrinkage rate is measured by placing the membrane (L1) unrestricted in a 90°C oven for 1 hour, measuring the membrane (L2) after it has been in the oven, and calculating the shrinkage rate using Formula 1. (1)

[0066] The characteristics of a membrane as described may include (in addition to having an open layer and a uniform dense layer as described) features such as porosity, bubble point, flow time, and retention.

[0067] A membrane may be characterized by a bubble point (e.g., the average bubble point) that is related to the pore size of the membrane or a layer of the membrane, a known property of porous filtration membranes. The bubble point corresponds to the pore size, which may correspond to filtration efficiency, such as that measured by retention rate. A smaller pore size may be associated with a higher bubble point and generally with better filtration efficiency (higher retention rate). However, a higher bubble point is also generally associated with relatively higher flow resistance and a longer flow time (for a given pressure drop, higher flow resistance and a lower flow rate). The example filtration membranes described herein may exhibit a combination of a relatively high bubble point, good filtration efficiency, and a useful flow level (e.g., a flow rate or "flow time" that allows the filtration membrane to be used in a commercial filtration process).

[0068] A method for determining the bubble point of a porous material involves immersing a sample of the porous material in a liquid with a known surface tension to wet it, and applying a pressure to one side of the sample. The pressure is gradually increased. For the purposes of this description, unless otherwise stated, the measured bubble point refers to the "average bubble point," which is the opposite of the "initial bubble point." An average bubble point is measured as the average pressure between an initial bubble point and a condition of a dry film. The initial bubble point is the pressure at which the first bubble passes through the film. These terms are well known in the field of porous membranes.

[0069] Examples of useful bubble points of a porous filter membrane measured using a test method described in the examples below may be at least 50, 80, 90, 100 or 120 psi or greater (e.g., up to 200 or 300 psi), while the membrane also exhibits useful properties of flow time and retention as described elsewhere in this document (measured using an HFE-7200 (3M) at a temperature of 22 degrees Celsius).

[0070] A membrane as described can exhibit an effective level of resistance to liquid flow through it, along with a desired bubble point and filtration efficiency. Resistance to liquid flow through the membrane can be measured based on flow rate or flow time (which is the inverse of flow rate). A membrane as described preferably has a useful or relatively low flow time, preferably along with a relatively high bubble point and good filtration efficiency.

[0071] The flow time of a membrane can be measured using various techniques and fluids (including isopropanol). Example membranes may have a flow time equal to or greater than 400 seconds, as measured using IPA, for example, from about 400 seconds to about 40,000 seconds, 500 seconds to about 40,000 seconds, 600 seconds to about 40,000 seconds, 700 seconds to about 40,000 seconds, 800 seconds to about 40,000 seconds, 900 seconds to about 40,000 seconds, 1,000 seconds to about 40,000 seconds, 2,000 seconds to about 40,000 seconds, 3,000 seconds to about 40,000 seconds, 4,000 seconds to about 40,000 seconds, and 5,000 seconds to about 40,000 seconds. The range of 0 seconds, 6,000 seconds to about 40,000 seconds, 7,000 seconds to about 40,000 seconds, 8,000 seconds to about 40,000 seconds, 9,000 seconds to about 40,000 seconds, 10,000 seconds to about 40,000 seconds, and within the range of 11,000 seconds to about 40,000 seconds, 17,000 seconds to about 40,000 seconds, 20,000 seconds to about 40,000 seconds, 25,000 seconds to about 40,000 seconds, 30,000 seconds to about 40,000 seconds, or 35,000 seconds to about 40,000 seconds. The flow time can be the flow time using IPA (isopropanol), wherein the flow time is the time for 500 ml of isopropanol (IPA) to flow through a 47 mm disk of the membrane with an area of ​​12.5 cm² at a temperature of 21°C and a pressure of 0.1 MPa.

[0072] The effectiveness of a filter membrane used to remove unwanted materials (i.e., "contaminants") from a liquid can be measured in one manner as "retention rate". Regarding the effectiveness of a filter membrane (e.g., a filter membrane as described), retention rate generally refers to the total amount of one impurity removed from a liquid containing impurities relative to the total amount of impurities in the liquid before the liquid is passed through the filter membrane (actually or during a performance test). Therefore, the "retention rate" value of a filter membrane is a percentage, wherein a filter with a higher retention rate value (a higher percentage) is relatively more effective in removing particles from a liquid, and a filter with a lower retention rate value (a lower percentage) is relatively less effective in removing particles from a liquid. Membranes prepared according to the exemplary methods described herein can exhibit filtration performance (e.g., measured by retention rate) at least comparable to commercially available filter membranes prepared from comparable materials (e.g., polyolefins) having comparable, nearly comparable, or somewhat similar thicknesses, and flow properties (e.g., measured by flow time) and bubble points within a comparable range. For example, the disclosed membrane and the disclosed filter product including such membrane may have a retention rate value of not less than 20%, not less than 25%, not less than 30%, not less than 35%, not less than 40%, not less than 45%, not less than 50%, not less than 55%, not less than 60%, not less than 65%, not less than 70%, not less than 75%, not less than 80%, not less than 85%, not less than 90%, not less than 95%, or not less than 99% (e.g., as measured by G25 1% monolayer particle loading).

[0073] In specific instances, the membrane described herein may exhibit a useful or improved combination of a liquid's bubble point (average bubble point) and flow properties (e.g., as measured by flow time). Compared to comparable microporous polyolefin filtration membranes, the useful or preferred membrane described herein may have a higher bubble point for a similar flow time, which is a desired combination. Within a range of bubble points relative to flow time, the example membranes may exhibit a higher bubble point for an equal flow time, or in other words, a reduced (improved) flow time at the same bubble point. Example membranes may exhibit flow time and bubble point properties such as: a flow time of less than 2000 seconds and an average bubble point of 75 psi or higher; a flow time of less than 3000 seconds and an average bubble point of 100 psi or higher; a flow time of less than 5000 seconds and an average bubble point of 125 psi or higher; or a flow time of less than 8000 seconds and an average bubble point of 150 psi or higher; wherein: flow time is defined herein, and bubble point is an average bubble point measured at room temperature using an HFE-7200 liquid fluid. These membranes also exhibit a useful filtration level as measured by "retention rate," for example, filtration efficiency within a range comparable to other polyolefin filter membranes of comparable thickness.

[0074] According to another preferred embodiment, the example membranes described may exhibit flow time and bubble point properties such as: a flow time of less than 1500 seconds and an average bubble point of 75 psi or higher; a flow time of less than 2500 seconds and an average bubble point of 100 psi or higher; a flow time of less than 4000 seconds and an average bubble point of 125 psi or higher; a flow time of less than 6000 seconds and an average bubble point of 150 psi or higher; and a flow time of less than 8000 seconds and an average bubble point of 175 psi or higher. These membranes also exhibit a useful filtration level as measured by "retention rate," for example, filtration efficiency within a range comparable to other polyethylene filters of comparable thickness.

[0075] A filter membrane may be contained within a larger filtration product (such as a filter housing or filter cartridge), the larger filtration product including any structure supporting the membrane to allow liquid fluid to flow through the membrane from one inlet side and exit from one outlet side. The housing includes: an inlet on one side of the supported membrane, allowing fluid to enter the housing on one upstream side of the membrane while the membrane is supported by the housing; and an outlet on a second side of the membrane, allowing fluid passing through the membrane to exit the membrane on one downstream side while the membrane is supported by the housing. The terms "inlet" and "outlet" may refer to a specific structure, such as a defined opening or defined conduit (tube, pipe, or engagement thereof) of a housing or a component of a housing (e.g., a support frame, a core, a cage, or the like), or may refer to a space (an "inlet space" or an "outlet space") located on either side (upstream and downstream) of the membrane when the membrane is supported by the housing, which allows fluid flow to enter and exit the housing and through the membrane. The terms "inlet" and "outlet" may also more generally refer to spaces on either side of the membrane that together allow fluid flow to enter the membrane on an upstream or inlet side, then through the membrane, and exit the membrane on an outlet or downstream side.

[0076] The housing includes a membrane supported within a larger filtration system to allow fluid flow through the membrane within the housing, particularly a filtration system supplying filtered liquid chemicals to a tool or process used in the manufacture of microelectronic or semiconductor devices. The filtration system places a filter membrane (e.g., as part of a filter, filter housing, or filter cartridge) in a flow path of a liquid chemical such that the liquid chemical flows through the filter membrane, enabling the filter membrane to remove impurities or contaminants from the liquid chemical. The filtration product or housing may include one or more additional materials and structures supporting the filter membrane within the filter, such that fluid flows from a filter inlet, through the filter membrane, and through a filter outlet, thereby passing through the filter membrane as it passes through the filtration product. The filter membrane supported by the filtration structure can be of any useful shape, such as a pleated cylinder, a cylindrical pad, one or more non-pleated (flat) cylindrical sheets, a pleated sheet, etc.

[0077] An example of a filter structure (e.g., a housing) comprising a filter membrane in the form of a pleated cylinder can be prepared to include any of the following components, any of which may be included in a filter product but may not be necessary: ​​a rigid or semi-rigid core supporting the pleated cylindrical coated filter membrane on its inner side (inlet or outlet); a rigid or semi-rigid cage supporting or surrounding the outer side (outlet or inlet) of the pleated cylindrical filter membrane; and optional end pieces or "pucks" located at each of the two opposite ends of the pleated cylindrical filter membrane. Regarding a housing in the form of a filter cartridge, the cartridge is considered to have an inlet on one side of the filter membrane and an outlet on the opposite side of the filter membrane; depending on the direction of fluid flow through the membrane, an inlet or an outlet may be on either side of the membrane.

[0078] A filter housing may also include an inlet, outlet, or both in the form of a conduit, pipe, tube, or other fluid flow channel, adapted to be connected via one or more auxiliary fluid conduits to receive a liquid fluid from a fluid supplier at a first side (an inlet side) of a filter membrane, such that the fluid flows through the membrane within the housing and from a second side (an outlet side) of the filter membrane, and then through the outlet to a fluid destination, which may be a tool for processing semiconductor or microelectronic devices. The filter housing may have any useful and desired size, shape, and material, and is preferably made of a suitable polymeric material.

[0079] As an example, Figure 4 shows a filter product (replaceable filter cartridge) 230, which is a product of a pleated cylindrical assembly 210 and an end piece 222, along with other optional components. The cylindrical assembly 210 includes a pleated filter membrane 212 as described herein. The end piece 222 is attached (e.g., "sealed") to one end of the cylindrical filter assembly 210. The end piece 222 may preferably be made of a melt-processable polymeric material. A core (not shown) may be placed at an internal opening or space "entrance" 224 of the pleated cylindrical assembly 210, and a cage (not shown) may be placed around an external opening or space ("exit") of the pleated cylindrical assembly 210. The filter cartridge includes an inlet and an outlet (e.g., at a core, cage, or other support structure) on both the inlet (upstream) and outlet (downstream) sides of the membrane, wherein the positions of the inlet and outlet depend on the direction of fluid flow through the fluid membrane while the filter cartridge 230 is mounted within a housing (which may also have an inlet and an outlet). A second end piece (not shown) may be attached ("sealed") to a second end of the pleated cylindrical assembly 210. The resulting pleated cylindrical filter membrane, contained in a replaceable filter cartridge 230 having two opposing sealed ends and optional cores and cages, can then be placed in a larger (secondary) filter housing, which includes an upstream housing inlet for receiving fluid into the filter membrane and a downstream housing outlet for discharging fluid that has passed through the filter membrane, and the downstream housing outlet is configured such that a certain amount of fluid entering the housing at the housing inlet must pass through the filter membrane 212 before leaving the filter housing at the housing outlet.

[0080] Referring to Figure 5, the example filter product 250 includes a housing containing a replaceable filter cartridge 230. The filter product 250 includes a dual-component housing containing a filter cup 252, one open end of which is attached to a base 254. Optionally, the filter cup can be removably engaged with the base 254 to allow the filter cup 252 to be separated from the base 254 to allow a removable filter cartridge 230 to be placed into or removed from the housing. The assembled housing includes an inlet 256, an inlet space 260 on the inner side of one of the filter cartridges 230, an outlet space 262 between the filter cartridge 230 and the filter cup 252, and an outlet 258. The removable filter cartridge 230 is positioned inside one of the filter cups 252, allowing liquid to flow into the inlet 256, into the inlet space 260, then through the filter assembly 212 of the filter cartridge 230, into the outlet space 262, and then out of the filtered product 250 through the outlet 258.

[0081] A filter housing or related component (e.g., gasket, fitting) may have any useful and desired size, shape, and material. Examples of housings and components may be made of fluorinated or non-fluorinated polymers, such as nylon, polyethylene, or fluorinated polymers such as poly(tetrafluoroethylene-co-perfluoro(alkyl vinyl ether)), TEFLON® perfluoroalkoxyalkylene (PFA), perfluoromethylalkoxy (MFA), or another suitable fluoropolymer (e.g., a perfluoropolymer).

[0082] A membrane assembly as described, or a filter or filter assembly containing a membrane assembly, can be useful in a method of filtering a liquid chemical to purify or remove unwanted materials (contaminants) from the liquid chemical, particularly for the production of a high-purity liquid chemical useful for an industrial process requiring a liquid chemical input with a very high purity level. Typically, the liquid chemical can be any of a variety of useful commercial liquid chemicals of any type useful in any industrial or commercial application. Specific examples of the membrane assemblies and filter products described can be used to purify a liquid chemical used in a semiconductor or microelectronics manufacturing application, such as for filtering a liquid solvent or other process solution used in a semiconductor photolithography process, a wet etching or cleaning step, a method for forming spin-coated glass (SOG), or a back-side anti-reflective coating (BARC) process.

[0083] Some specific, non-limiting examples of solvents (including cleaning solutions) that can be used for filtration by a membrane assembly as described include: n-butyl acetate (nBA), isopropanol (IPA), 2-ethoxyethyl acetate (2EEA), xylene, cyclohexanone, ethyl lactate, methyl isobutyl methanol (MIBC), methyl isobutyl ketone (MIBK), isoamyl acetate, undecane, propylene glycol methyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), or mixtures thereof, such as a mixture of PGME and PGMEA; or concentrated or dilute ammonium hydroxide, hydrogen peroxide, hydrochloric acid, HF, sulfuric acid, another peroxide solution, or combinations thereof, such as a combination of ammonium hydroxide and hydrogen peroxide or a combination of hydrochloric acid and hydrogen peroxide. Example

[0084] Example 1 is a dry-process single-layer polypropylene membrane with a total thickness of 7 micrometers.

[0085] Example 2 is a dry-process three-layer membrane comprising three polypropylene-containing layers with a total thickness of 6 micrometers. The thickness of the polypropylene-containing layer with the smallest pore size is approximately 2 micrometers, and the pore size is 22 nm.

[0086] Example 3 is a dry membrane with a pore size of 20 nm.

[0087] Comparative Example 1 is a dry-processed single-layer polypropylene film with a total thickness of 7 micrometers.

[0088] Comparative Example 2 is a dry-process three-layer membrane comprising, in sequence, a polypropylene layer, a polyethylene layer, and a polypropylene layer. The total thickness of the membrane is 20 micrometers, of which the thickness of the PP layers is 14 micrometers. The polypropylene layers have an average pore size of 35 nm. nature unit Example 1 Example 2 Example 3 Comparison Example 1 Comparison Example 2 Basis weight g / m 2 3.6 3.1 <5 3.3 3.5 MD shrinkage rate, 90°C % 3 4 <5 17 1 thickness μm 7 6 Less than 10 7 7 confinement layer aperture nm twenty three twenty two Between 10 nm and 20 nm twenty three 40

[0089] Comparative Example 2 has the problem of pores that are too large for nanofiltration or ultrafiltration processes. Comparative Example 1 has a high shrinkage rate, which makes it unsuitable for use due to its low dimensional stability. Shrinkage of the membrane during application or assembly may cause it to tear, rupture, or alter other properties, making its performance insufficient and / or unpredictable. Examples 1 and 2 have high dimensional stability (e.g., low shrinkage rate) and sufficiently small pores for nanofiltration or ultrafiltration processes (including the filtration of gases or liquids).

[0090] 120: Membrane 122: Open layer 124: Compact layer 130: Membrane 132: Open layer 134: Dense layer 136: Open layer 210: Pleated cylindrical assembly / cylindrical filter assembly 212: Filter membrane / filter assembly 222: End device 224: Internal openings or spatial "entrances" 230: Filtration products (replaceable filter cartridges) / filter cartridges / removable filter cartridges 250: Filtration products 252: Filter Cup 254: Base 256: Entrance 258: Exports 260: Entrance Space 262: Export Space

Claims

1. A filtration product for processing fluids used in microelectronics or semiconductor processing, comprising: A housing having an inlet and an outlet, wherein a multilayer microporous membrane, disposed between the inlet and the outlet, is subjected to a uniaxial stretching dry process. The multilayer microporous membrane comprises: a first polyolefin layer and a second polyolefin layer including uniaxially oriented micropores having an average pore size of less than 0.035 micrometers; wherein the filtration product is characterized by having an average bubble point of at least 50 psi, at least 80 psi, at least 90 psi, at least 100 psi, or at least 120 psi, as measured at room temperature using an HFE-7200 liquid fluid analyzer; wherein the multilayer microporous membrane has a total thickness of not more than 20 micrometers; wherein the thickness of the second polyolefin layer is less than 14 micrometers; and wherein the first polyolefin layer includes micropores having a pore size greater than the average pore size of the uniaxially oriented micropores of the second polyolefin layer.

2. The filter product as requested in item 1, having an average bubble point of up to 200 psi or up to 300 psi.

3. The filter product of claim 1 or 2, wherein the micropores have an average aspect ratio greater than 1.0, greater than 1.2, greater than 1.5, greater than 2.0 or greater than 3.

0.

4. As in the filter product of claim 1 or 2, the multilayer microporous membrane comprises: The first polyolefin layer, the second polyolefin layer, and the third polyolefin layer; wherein the first polyolefin layer and the third polyolefin layer each comprise polyethylene, and the second polyolefin layer comprises polypropylene.

5. As in request item 1 or 2, the multilayer microporous membrane comprises: The first polyolefin layer, the second polyolefin layer, and the third polyolefin layer; wherein the first polyolefin layer and the third polyolefin layer each comprise polypropylene, and the second polyolefin layer comprises polyethylene.

6. The filter product as claimed in item 1 or 2, wherein the second polyolefin layer comprises: At least 90% by weight of polypropylene or at least 95% by weight of polypropylene based on the total weight of the second polyolefin layer; or at least 90% by weight of polyethylene or at least 95% by weight of polyethylene based on the total weight of the second polyolefin layer.

7. The filter product as claimed in item 1 or 2, wherein the second polyolefin layer has a thickness of less than 13 micrometers, less than 12 micrometers, less than 11 micrometers, less than 10 micrometers, less than 9 micrometers, less than 8 micrometers, less than 7 micrometers, less than 6 micrometers, less than 5 micrometers, less than 4 micrometers, less than 3 micrometers, less than 2 micrometers, or less than 1 micrometer.

8. The filter product as claimed in claim 1 or 2, wherein the first polyolefin layer comprises at least 60% by weight of polyolefin based on the total weight of the first polyolefin layer.

9. The filter product as claimed in item 1 or 2, wherein the average pore size of the uniaxially oriented micropores of the second polyolefin layer is less than 0.030 micrometers, less than 0.025 micrometers, or less than 0.020 micrometers.

10. The filter product of claim 1 or 2, wherein the uniaxially oriented micropores of the second polyolefin layer have an average pore size in the range of about 0.010 micrometers to about 0.020 micrometers.

11. The filter product as requested in item 1 or 2, wherein the shrinkage rate of the multilayer microporous membrane is less than 25% at 90°C for 1 hour.

12. The filter product as requested in item 1 or 2, wherein the total thickness is not greater than 14 micrometers, not greater than 13 micrometers, not greater than 12 micrometers, not greater than 11 micrometers, not greater than 10 micrometers, not greater than 9 micrometers, not greater than 8 micrometers, not greater than 7 micrometers, not greater than 6 micrometers, not greater than 5 micrometers, not greater than 4 micrometers, not greater than 3 micrometers, not greater than 2 micrometers or not greater than 1 micrometer.

13. The filter product as claimed in item 1 or 2, which demonstrates a measured flow time in the range of 400 seconds to 40,000 seconds, measured using isopropanol, wherein the flow time is the time for 500 ml of isopropanol to flow through a 47 mm disk of the membrane having an area of ​​12.5 cm² at a temperature of 21 degrees Celsius and a pressure of 0.1 MPa.

14. The filter product as requested in item 1 or 2, wherein the filter product has a retention rate of not less than 20%, not less than 25%, not less than 30%, not less than 35%, not less than 40%, not less than 45%, not less than 50%, not less than 55%, not less than 60%, not less than 65%, not less than 70%, not less than 75%, not less than 80%, not less than 85%, not less than 90%, not less than 95%, or not less than 99%.

15. The filter product as requested in item 1 or 2, wherein the multilayer microporous membrane is a flat sheet, a rolled-up sheet, or a pleated sheet.

16. The filter product as requested in item 1 or 2, wherein the multilayer microporous membrane is a pleated cylinder.

17. The filter product as requested in item 1 or 2, includes: The housing surrounds the membrane, has a housing inlet that allows fluid to flow into the housing and into an inlet space, and a housing outlet that allows the fluid to flow out of the housing after the fluid has passed through the membrane.

18. The filter product of claim 1 or 2, comprising a frame and the multilayer microporous membrane supported by the frame, wherein an inlet is on one side of the filter membrane and an outlet is on a second side of the filter membrane.

19. The filter product as requested in item 1 or 2, wherein the filter product is a replaceable filter cartridge.

20. The filter product of claim 1 or 2, wherein the multilayer microporous membrane is modified by at least one of coating, washing, extraction, molding, shaping, folding, winding, pleating and forming into a pleated cylinder.

21. A method of using a filter product as claimed in any one of claims 1 to 20, the method comprising passing a fluid through a filter membrane.

22. The method of claim 21, wherein the fluid comprises n-butyl acetate (nBA), isopropanol (IPA), 2-ethoxyethyl acetate (2EEA), xylene, cyclohexanone, ethyl lactate, methyl isobutyl methanol (MIBC), methyl isobutyl ketone (MIBK), isoamyl acetate, propylene glycol methyl ether (PGME or (2-methoxy-1-methylethyl acetate)), propylene glycol monomethyl ether acetate (PGMEA), propylene glycol ethyl ether (PGEE), NMP (1-methyl-2-pyrrolidone), γ-butyl lactone, dimethyl ether, dibutyl ether, toluene, concentrated ammonium hydroxide, dilute ammonium hydroxide, hydrogen peroxide, another peroxide solution, hydrochloric acid, hydrofluoric acid, sulfuric acid, or any mixture thereof.

23. The method of claim 21 or 22, wherein the fluid, after passing through the filter membrane, is characterized by including a reduced amount of one contaminant compared to before passing through the filter membrane.

24. The method of claim 23, wherein the pollutant is reduced by not less than 20%, not less than 25%, not less than 30%, not less than 35%, not less than 40%, not less than 45%, not less than 50%, not less than 55%, not less than 60%, not less than 65%, not less than 70%, not less than 75%, not less than 80%, not less than 85%, not less than 90%, not less than 95%, or not less than 99%.

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