Composite hollow fibers and related methods and products

Abstract

The present disclosure relates to composite hollow fibers and related methods and products. Composite hollow fiber filter membranes comprising a porous polymeric hollow fiber support and a filtration layer are described; methods of making the composite hollow fibers and using the composite hollow fibers as filter membranes; methods of making filter assemblies or filters from the composite hollow fibers; and filter assemblies and filters containing the composite hollow fibers as filter membranes.

Description

[0001] Information related to divisional application

[0002] This application is a divisional application of Chinese invention patent application No. 202010176737.4, filed on March 13, 2020, entitled "Composite Hollow Fiber and Related Methods and Products". Technical Field

[0003] The following description relates to composite hollow fibers suitable for use as filter membranes and comprising a porous polymeric hollow fiber support and a filter layer; methods for manufacturing said composite hollow fibers and using said composite hollow fibers as filter membranes; methods for manufacturing filter assemblies or filters from said composite hollow fibers; and filter assemblies and filters containing said composite hollow fibers as filter membranes. Background Technology

[0004] The primary application of filter membranes is the removal of unwanted materials from useful fluid streams. Filters are used to treat many gaseous and liquid fluids in industry, including ambient air, drinking water, liquid industrial solvents and processing fluids, industrial gases used in manufacturing or processing (e.g., in semiconductor manufacturing), and liquids with medical or pharmaceutical uses. Unwanted materials removed from the fluids include impurities and contaminants such as particles, microorganisms, and dissolved chemical species. Specific examples of impurity removal applications of filter membranes include their use in the pharmaceutical industry to remove particles or bacteria from therapeutic solutions, in treating ultrapure aqueous and organic solvent solutions used in microelectronics and semiconductor processing, and in air and water purification processes.

[0005] To perform filtration, filter products include a filter membrane responsible for removing unwanted materials from the fluid. Depending on the requirements, the filter membrane may be in sheet form, or it may be wound (e.g., spiral-shaped), pleated, etc. Alternatively, the filter membrane may be in the form of hollow fibers. The filter membrane may be contained within a housing containing an inlet and an outlet, such that the fluid to be filtered enters through the inlet and passes through the filter membrane before passing through the outlet.

[0006] Undesirable materials in a fluid are removed from the fluid by being captured mechanically or electrostatically by a filter membrane, for example, by sieving or “non-sieving” mechanisms, or both. A sieving mechanism is a filtration mode that removes particles from a liquid flow by retaining particles at the membrane pores through mechanical disturbance caused by particle movement. In this mechanism, at least one particle size is larger than the pore size. A “non-sieving” filtration mechanism is a filtration mode that mechanically retains suspended particles or dissolved materials contained in the liquid flowing through the filter membrane, for example, by incorporating an electrostatic mechanism that electrostatically attracts and retains particles or dissolved materials to and from the outer or inner surface of the filter membrane (depth filtration).

[0007] Filter membranes can be composed of porous polymeric membranes whose average pore size can be selected based on the intended use of the filter (i.e., the type of filtration performed using the filter). Typical pore sizes are in the micrometer or submicrometer range, for example, from about 0.001 micrometers to about 10 micrometers. Generally, membranes with an average pore size of about 0.001 to about 0.05 micrometers are classified as ultrafiltration membranes. Sometimes membranes with pore sizes between about 0.05 and 10 micrometers are classified as microporous membranes.

[0008] For commercial applications, filter membranes should be of a type that can be efficiently manufactured and assembled into filter products. The membrane must be efficiently produced and must possess mechanical properties (e.g., strength and flexibility) that allow it to withstand assembly into filter cartridges or filter forms. In addition to mechanical properties, the membrane should have suitable chemical functionalities and microstructures for high-performance filtration. In some applications, more than one chemical functionality, microstructure, or pore size is required to achieve high filtration performance. Therefore, composite membranes with at least two or more chemical functionalities are suitable for this purpose.

[0009] Various polymers have been identified that can be formed into porous hollow fiber filter membranes using techniques such as thermally induced phase inversion (TIPS) or non-solvent-induced phase inversion (NIPS). Similarly, various techniques and apparatuses have been developed for assembling hollow fiber filter membranes into final filtration products within a housing. See, for example, WO 2017 / 007683 and US 5,695,702, the entire contents of which are incorporated herein by reference.

[0010] For commercial applications, filter membranes must also exhibit effective and reliable filtration functionality, such as the ability to efficiently remove high volumes of impurities from a continuous flow of fluid passing through the membrane. Filtration performance is typically evaluated using two parameters: flux and retention rate. Flux assesses the rate at which fluid flows through the filter or membrane and must be high enough to reflect the possibility of high flow levels through the filter, thus making the filter economically viable. Retention rate generally refers to the amount of impurities removed (in percentage) from the fluid flow passing through the filter and is an indicator of filter efficiency. Both membrane flux and retention rate are significantly dependent on the membrane microstructure and pore size, and are typically measured by the bubble point. At the cost of lower flux, membranes with smaller pores have higher bubble points and better sieving retention capacity (assuming the same membrane shape and thickness); assuming the same membrane shape and thickness, larger pore sizes correspond to lower bubble points and lower sieving retention rates but higher flux. The non-sieving retention capacity of a membrane is a more complex characteristic that, in addition to membrane microstructure and pore size, depends on membrane surface properties (e.g., charge).

[0011] One area of ​​significant commercial interest in membrane filtration is the removal of contaminants from photoresist solutions in the semiconductor industry. As the semiconductor industry moves towards smaller nodes, contamination becomes more critical, as even smaller contaminants can cause defects in wafer products and significantly reduce production yields. Contaminants in photoresist fluids can include gels, ions, or nanoparticles with organic or inorganic properties. Among the two common geometries of membranes, hollow fiber membranes are of particular interest for contaminant removal applications because the outside-to-inflow configuration of hollow fiber devices potentially offers faster throughput times compared to devices made from flat sheet membranes. Transmission time is the time required for the particle count in the liquid to pass through the filter and reach the baseline. The potentially better throughput time of hollow fiber devices is because the cavities of the hollow fibers are not exposed to environmental contaminants such as dust and particles during membrane processing, handling, and device manufacturing, and are therefore more likely to be cleaner. Better device integrity compared to pleated flat sheet membranes is another potential advantage of hollow fiber devices, as pleating operations can introduce defects at or near the pleated tips of the membrane, especially when the membrane material is a brittle polymer.

[0012] Due to the nature of organic solvents used in photolithography applications (e.g., cyclohexanone, n-butyl acetate, PGME, and PGMEA), the chemical compatibility of membranes with these solvents is a limiting factor in the selection of membrane materials for these applications. Therefore, solvent-compatible polymers containing polyethylene and nylon have been considered for the preparation of the hollow membranes used in this application. However, there are key limitations associated with these membranes used to meet the high requirements for contaminant removal in the semiconductor industry. The pore size of polyethylene hollow fiber membranes (which are produced by the TIPS process) is typically limited to a pore size greater than 40 nm. This limitation is partly due to the phase separation nature of polyethylene solutions and partly due to the process limitations of rapidly cooling the extruded fibers. For similar reasons, the degree of asymmetry achievable in the microstructure of TIPS-treated membranes is generally lower than that of NIPS-treated membranes. Therefore, TIPS-treated membranes typically have a poorer flux-bubbling point balance compared to NIPS-treated membranes. Furthermore, the non-polar nature of polyethylene polymers results in limited non-sieving (polar) retention capacity of polyethylene compared to highly polar polymers such as nylon. Unlike polyethylene, nylon membranes exhibit extremely high non-sieve retention rates due to its polar and electrostatic properties, and these membranes can be processed using NIPS and TIPS processes. However, the slow phase separation nature of nylon in the NIPS process makes it difficult to manufacture high-BP (small pore size) membranes with good flux. On the other hand, TIPS treatment of nylon has similar limitations to TIPS-treated polyethylene membranes. In general, improved filter membranes are needed that meet the criteria of solvent compatibility, high retention rates, and good flux. Summary of the Invention

[0013] The following description relates to novel composite hollow fiber membranes for the efficient removal of contaminants from photoresist solutions in semiconductor manufacturing processes, and the processes for manufacturing these composite hollow fibers. The membranes uniquely combine desired sieving properties with strong non-sieving properties (e.g., electrostatic, affinity, photophobic) to achieve high particle retention and high throughput. The composite hollow fibers of this invention also possess good mechanical properties for use in manipulation, device fabrication, and pressure-driven applications.

[0014] The fabrication of composite membranes is a suitable method for tuning membrane properties to achieve high flux, high retention, good mechanical properties, and reasonable cost. For example, a combination of high flux, high retention, and good mechanical properties can be achieved by fabricating a thin layer (close layer) with smaller pore sizes on a thicker layer (support layer) with larger pore sizes. In this configuration, the high flow resistance of the close layer is minimized by reducing its thickness, while the desired membrane mechanical strength is achieved by using a thicker support layer with minimal flow resistance due to the larger pore sizes. Sometimes, the composite membrane concept can be used to reduce the cost of membranes made from expensive polymers by fabricating a thin layer of functional, expensive polymers on a thicker support layer. Another applicable application of composite membranes is when layers with different functionalities are needed within a single membrane for desired separation.

[0015] Several types of composite hollow fiber development have been reported. Early development of these membranes aimed to facilitate gas separation applications by coating a dense polymer layer onto the outer surface of a microporous hollow fiber support. The process for manufacturing these membranes involves coating the outer surface of the microporous hollow fiber with a polymer solution, followed by an annealing step to evaporate the solvent from the coating solution and create a dense, non-porous layer on the outer surface of the hollow fiber. Another example of a method for manufacturing composite membranes involves co-spinning two different polymer solutions into a condensation bath using a dual-pore spinneret to form a bilayer membrane. A major limitation of this method is the difficulty in independently tuning the properties of each layer, as phase separation in one layer affects the rate of phase separation in the other layers, thus influencing their properties. Similarly, it is sometimes impossible or extremely complex to manufacture a bilayer hollow fiber membrane where one layer is from a NIPS-processable polymer and the other from a TIPS-processable polymer. For example, to manufacture polyethylene (PE)-polyethersulfone (PESU) composite hollow fibers by this method, the high temperature (approximately 150°C) of the polyethylene solution required for TIPS treatment increases the spinneret temperature and subsequently the treatment temperature of the PESU solution. This can negatively impact phase separation in the polyethersulfone layer, as PES polymer solutions tend to undergo phase separation at high temperatures. Therefore, the PES solution may undergo phase separation inside the spinneret before entering the condensation bath. This phenomenon may hinder optimal control of the PES layer properties.

[0016] The applicant has now discovered a novel hollow fiber filter membrane structure that exhibits useful or advantageous filtration performance characteristics, including high flux, relatively high bubble point (small pore size), and good retention. The performance is better than or shows a significant improvement over previous and current commercial hollow fiber filter membrane products.

[0017] As described herein, hollow fiber filter membranes are fabricated in a composite form. The composite comprises a porous polymeric hollow fiber support, wherein a porous filter layer is disposed on the hollow fiber support. The hollow fiber support acts as a support structure on which the filter layer is disposed. The hollow fiber support may also be able to act as a filter, but does not need to act as a filter to remove unwanted materials from the liquid flow passing through the composite hollow fiber membrane. Depending on the type and size of the unwanted materials (contaminants) removed from the fluid passing through the composite filter membrane and depending on the physical properties (e.g., pore size) and chemical composition of the hollow fiber support, the hollow fiber support can effectively remove unwanted materials by sieving or non-sieving mechanisms. Alternatively, the hollow fiber support is not required to provide significant filtration effect, and most of the filtration performance of the composite can be provided by the filter layer.

[0018] The filter layer is porous and performs a filtration function, i.e., removing unwanted materials from the liquid flow passing through the composite hollow fiber membrane. The filter layer may preferably be in the form of a thin, porous layer of filter layer polymer located on the outer side of the hollow fiber support. The porous hollow fiber support comprises a porous matrix extending through the thickness of the hollow fiber support. Therefore, the composite comprises a hollow fiber support layer and a filter layer.

[0019] In some embodiments, the hollow fiber support may have relatively larger pores than the filter layer and may be relatively thicker than the filter layer. In these example composites, the relatively larger pore size of the larger (thicker) hollow fiber support results in a lower level of flow resistance through the hollow fiber support (and greater flowability at lower flow times) compared to a similar support with smaller pores. A thinner filter layer with relatively smaller pores acts efficiently as a filter to remove unwanted materials from the fluid flow, but because of its relatively thinness, it still allows a useful or advantageous high flow rate through the composite.

[0020] The filter layer is made of a solution-processable polymer (referred to as the "filter layer polymer"), meaning that the filter layer polymer can be dissolved in a solvent to form a polymer solution that can be used to coat the filter layer polymer onto a hollow fiber support. As an example, a polymer solution layer containing the filter layer polymer dissolved in a solvent can be coated as a coating polymer solution layer onto an outer portion of the hollow fiber support; subsequently, the coated polymer solution can be exposed to a non-solvent (meaning that the filter layer polymer dissolved therein is essentially an insoluble liquid), and the filter layer polymer will precipitate (e.g., coagulate) to form a precipitated (coagulated) filter layer polymer layer on the outer surface of the hollow fiber support.

[0021] Filter membranes can be used to filter liquids that must be used at high purity levels in commercial or industrial processes (i.e., to remove materials from them). The process can be any process that requires high-purity liquid materials as input, with non-limiting examples including processes for fabricating microelectronic or semiconductor devices, specific examples being methods for filtering liquid process materials (e.g., solvents or solvent-containing liquids) used in semiconductor photolithography, or cleaning and etching processes. Examples of contaminants present in process liquids or solvents used to fabricate microelectronic or semiconductor devices may include metal ions dissolved in the liquid, solid particles suspended in the liquid, and gel or coagulated materials present in the liquid (e.g., generated during photolithography).

[0022] In one aspect, a composite hollow fiber filter membrane comprises: a polymeric microporous hollow fiber support having an outer surface, an inner surface, a thickness extending between the outer surface and the inner surface, and micropores; and a porous polymeric filter layer comprising a condensed polymer in contact with the outer surface. In some embodiments, the porous polymeric filter layer penetrates no more than a portion of the thickness of the hollow fiber support. In other embodiments, the porous polymeric filter layer substantially penetrates the thickness of the hollow fiber support.

[0023] On the other hand, a method for preparing a composite hollow fiber filter membrane comprising a hollow fiber support and a porous polymeric filter layer is disclosed. The method includes: placing a polymer solution coating on the outer surface of the polymeric microporous hollow fiber support, the polymer solution comprising a polymer dissolved in a solvent; and contacting the polymer solution coating with a coagulation solution such that the dissolved polymer in the polymer solution coating forms a coagulated polymer layer on the outer surface, the coagulated polymer layer contacting the outer surface and not exceeding partially penetrating into the thickness of the hollow fiber support.

[0024] On the other hand, a filter comprising a composite hollow fiber filter membrane includes: a polymeric microporous hollow fiber support having an outer surface, an inner surface, a thickness extending between the outer surface and the inner surface, and micropores; and a porous polymeric filter layer comprising a condensed polymer in contact with the outer surface and not exceeding a portion of the thickness penetrating into the hollow fiber support. Attached Figure Description

[0025] Figure 1A A schematic diagram of a system for coating the filter layer of the present invention onto a hollow fiber support to produce a composite as described.

[0026] Figure 1B This shows a schematic diagram of the cross-section of the composite hollow fiber as described.

[0027] Figure 2 and 3 Examples of the filter and the filter components comprising the composite hollow fiber filter membrane described herein are shown.

[0028] The diagram is a schematic and may not be to scale. Detailed Implementation

[0029] The applicant has identified a novel composite hollow fiber filter membrane and a method for preparing the composite hollow fiber filter membrane (sometimes referred to herein as a "composite membrane," "composite filter membrane," "complex," or the like). The composite filter membrane comprises a hollow fiber support and a filter layer disposed on the hollow fiber support. The hollow fiber support performs either sieving or non-sieving filtration functions, while also mechanically supporting the composite during use and providing location for the filter layer within the hollow fiber filter cartridge or hollow fiber filter membrane. The hollow fiber support does not need to act as a filtration component of the composite, but can provide the composite with useful support and useful physical and mechanical properties and good flow characteristics to allow fluid to flow through the support and through the filter layer during use of the composite as a filter. The filter layer performs the function of filtering the fluid flow through the composite filter membrane (i.e., removing unwanted material from it). The composite can exhibit a combination of useful or advantageous flow characteristics and filtration performance.

[0030] The hollow fiber support (also simply referred to herein as the "support") is a porous polymeric hollow fiber material that effectively supports the filter layer to allow fluid to pass through it, for example, when a composite hollow fiber filter membrane is contained within a filter cartridge or filter. The hollow fiber support is polymeric, porous, and sufficiently rigid yet flexible to allow its use as a support component for composite hollow fiber membranes as described. The support has characteristics such as porosity, pore size, thickness, and composition (i.e., polymeric composition), which collectively contribute to the properties of the support. The support should be sufficiently porous and have a suitable pore size to allow liquid fluid to pass through it at a flow rate sufficient for the composite filter membrane intended for use in commercial filtration applications. In some embodiments of the composite, in addition to acting as a support, the hollow fiber support can also effectively function as a filter to remove unwanted materials from the fluid flow via sieving or non-sieving filtration mechanisms. In these example composites, physical properties (e.g., pore size, thickness) and the chemical composition of the hollow fiber support, or both, are effective for filtration via sieving, non-sieving, or both mechanisms.

[0031] Hollow fiber supports can have any porosity that makes the porous support effective as described herein, allowing suitable liquid flow rates through the support and through a filter layer positioned on the support, and allowing the hollow fiber support to perform filtration functions through sieving or non-sieving filtration mechanisms when needed. Examples of useful hollow fiber supports can have a porosity of up to 90%, for example, in the range of 60% to 90%, such as 65% to 80%. As used herein and in the field of porous bodies, the “porosity” (sometimes also referred to as “void”) of a porous body is a measure of the percentage of void (i.e., “empty”) space in the body to the total volume of the body, and is calculated as the fraction of the void volume of the body relative to the total volume of the body. A body with 0% porosity is entirely solid.

[0032] In combination with porosity, thickness, and inner and outer diameter dimensions, the pore size of a hollow fiber support (i.e., the average pore size throughout the hollow fiber support) can be such that it enables the required flow of liquid fluid through the hollow fiber support, provides a porous surface that can be bonded to a polymer filter layer, and allows the hollow fiber support to perform filtration functions through sieving or non-sieving filtration mechanisms when needed.

[0033] The pore size suitable for a particular hollow fiber support (e.g., in a particular composite membrane) may depend on factors such as: the thickness of the hollow fiber support; the thickness, porosity, composition, and pore size of the filter layer; the extent to which the hollow fiber support will function as a filter to remove unwanted materials from a fluid flow; the desired flow and filtration properties of the composite; and the characteristics of the method by which the filter layer is deposited (e.g., coated) onto the hollow fiber support containing the viscoelastic properties of the polymer solution to which the coating is applied. For some currently known examples of immersion coating methods useful for placing a filter layer on a hollow fiber support (as described herein), the pore size of the hollow fiber support can range from about 30 nm, 50 nm, 0.05 μm to 10 μm, for example having sizes sometimes classified as “micropores,” “metapores,” or “nanoporous.” For the purposes of this specification, the term “micropore” is sometimes used to refer to pores within any of these size ranges, including micropore and submicropore sizes, as a way to distinguish materials with larger pore sizes, i.e., to distinguish materials considered “macropores.” Examples of the average pore size of hollow fiber supports may be at least 30 nanometers, at least 50 nanometers, or at least 0.1 or 0.5 micrometers, and at most about 4, 6, 8 or 10 micrometers.

[0034] A specific degree of penetration may be desired during the coating of the polymer solution onto the support. The degree of penetration can be any useful degree, i.e., high or low penetration. If the pore size of the support is large, the polymer solution coated onto the support (for placing the filter layer) will tend to penetrate into the pores of the support to a relatively large depth (compared to penetration into a support with a smaller pore size), potentially an unnecessary or undesirable depth. If the pore size of the support is too small, the pores may be closed, blocked, blocked, or filled by the polymer solution in a way that unacceptably inhibits or prevents liquid flow through the pores during use, resulting in a significant reduction in the ability of the liquid to flow through the hollow fiber support during use as a component of the composite filter membrane, for example, unacceptably reducing flux. At least based on differences in pore size, tubular braided hollow membranes, such as those described in U.S. Patent 5,472,607, may be unsuitable or unpreferred as hollow fiber supports for use in composite hollow fiber membranes as described.

[0035] The hollow fiber support may have effective thickness, inner diameter, and outer diameter dimensions for serving as a support assembly for a composite filter membrane as described. Examples of suitable wall thicknesses for the hollow fiber support are in the range of 25 to 250 micrometers, for example, 30 to 150 or 200 micrometers. Examples of suitable inner diameters for the hollow fiber support are in the range of 300 to 1000 micrometers, for example, 400 to 700 or 900 micrometers. Examples of suitable outer diameters for the hollow fiber support are in the range of 500 to 1500 micrometers, for example, 600 to 1200 or 1300 micrometers.

[0036] The hollow fiber support can be made of any polymer suitable for forming hollow fibers suitable for use as composite filter membranes as described herein. When used as a component of the composite filter membrane in a filtration step, the support should be chemically resistant (e.g., not chemically degraded) to the liquid that will pass through it. Suitable examples include polymers that have been used or found suitable for use as hollow fiber filter membranes for filtering fluids (e.g., solvents or process fluids) used in semiconductor and microelectronics processing, examples of which include known fluoropolymers (e.g., Teflon™), polyethylene, polypropylene, and nylon that are compatible with photolithography solvents used in semiconductor manufacturing. If the intended use of the filter membrane is in semiconductor dilution wetting etching and cleaning processes, the hollow fiber support can be a fluoropolymer or sulfone polymer hollow fiber, such as Teflon. These examples cover homopolymers and copolymers of polyolefins such as polypropylene and polyethylene, specifically ultra-high molecular weight polyethylene (UPE), nylon (e.g., polyamide), and other known polymers. Hollow fiber support polymers are preferably (but not necessarily) compatible with solvents used to treat filter coatings, examples of which include NMP, DMF, DMAc, and acetone. Fluoropolymers of Teflon, polyethylene, polypropylene, and nylon are examples of such polymers.

[0037] Certain polymers may be useful or preferred for hollow fiber supports that are effective for filtration using non-sieving methods. Examples of polymers suitable as a portion of the filter membrane for non-sieving filtration functionality include polyamides (e.g., nylon); polyimides; polyamide-polyimides; and surface-treated forms of polyamides, polyimides, or polyamide-polyimides. The desired polymer can be selected based on the type of contaminants to be removed. For example, nylon polymers are effective at removing organic gels or dissolved metallic contaminants from organic solvents. Polymers containing anionic (negatively charged) surface groups are effective at removing cationic (positively charged) contaminants dissolved or suspended in liquids.

[0038] In some instances, the hollow fiber support may be made of ultra-high molecular weight polyethylene (“UPE”), which is generally understood to mean a polyethylene polymer with a molecular weight of at least 1,000,000 Daltons. The term “polyethylene” refers to a polymer that has a linear molecular structure that partially or substantially has repeating -CH2-CH2- units. Polyethylene can be obtained by reacting a monomer composition comprising, consisting of, or substantially consisting of ethylene monomers. Therefore, a polyethylene polymer can be a polyethylene homopolymer prepared by reacting monomers consisting of or substantially consisting of ethylene monomers. Alternatively, the polyethylene polymer may be a polyethylene copolymer prepared by reacting a combination of ethylene and non-ethylene monomers comprising, consisting of, or substantially consisting of ethylene monomers with another type of monomer (e.g., another α-olefin monomer, such as butene, hexene, or octane, or combinations thereof). For the polyethylene copolymer, the amount of ethylene monomer used to produce the copolymer may be any applicable amount relative to the non-ethylene monomer, based on the total weight of all monomers (ethylene monomers and non-ethylene monomers) in the monomer composition used to prepare the ethylene copolymer, for example, at least 50%, 60%, 70%, 80%, or 90% (by weight) of the ethylene monomer.

[0039] As used herein, a composition claimed to be “substantially composed of” the specified composition, ingredient, or combination of ingredients means a composition containing the specified composition, ingredient, or combination of ingredients and other ingredients in no more than a non-physical amount, such as no more than 3, 2, 1, 0.5, or 0.1% by weight of any other material. A monomer substantially composed of ethylene monomer means a composition containing ethylene monomer and any other monomer in no more than 3, 2, 1, 0.5, or 0.1% by weight of the total weight of all monomers in the composition. A monomer substantially composed of ethylene and α-olefin monomers means a composition containing ethylene and α-olefin monomers and any other monomer in no more than 3, 2, 1, 0.5, or 0.1% by weight of the total weight of all monomers in the composition.

[0040] Hollow fiber supports can be prepared in any known or future applicable manner to produce hollow fiber supports with the properties described. Examples of known methods for preparing hollow fibers are thermally induced phase separation (TIPS) and immersion precipitation (also known as non-solvent-induced phase separation of NIPS).

[0041] The composite hollow fiber filter membrane comprises a filter layer disposed on a hollow fiber support, the position and amount of which allow the filter layer to act as a filter to remove unwanted materials from a fluid flow passing through the composite. The filter layer is porous, relatively thin relative to the thickness of the hollow fiber support, and preferably coated onto the outer porous surface of the hollow fiber support in a manner that mechanically secures the filter layer to the outer porous surface without substantially or excessively covering, blocking, or filling the pores of the outer porous surface.

[0042] The composition and physical characteristics (e.g., porosity and pore size) of the filter layer are independent of the composition and physical characteristics of the hollow fiber support. The primary function of the filter layer is to filter the liquid fluid as it flows through it (i.e., to remove unwanted materials). To perform this function, the filter layer should be positioned to allow the liquid to flow through it as it flows through the support. For example, the filter layer may be positioned on the outer porous surface of the support. The filter layer should be evenly distributed above the outer porous surface and should cover substantially the entire area of ​​the outer porous surface to effectively function as a filter. The filter layer may have any thickness, porosity, and pore size (average) suitable for effectively performing the filtration function by a sieving mechanism, a non-sieving mechanism, or both. Generally, the filter layer may have a substantially smaller thickness relative to the support (i.e., the filter layer is substantially thinner than the support). In various exemplary embodiments, the filter layer may have a smaller pore size relative to the support pore size, or may have a pore size that is approximately the same as or larger than the support pore size.

[0043] Example filter layers may have any porosity that allows the filter layer to function effectively as a filter layer. Examples of suitable filter layers may have a porosity of up to 90%, for example, in the range of 60% to 85%, or 65% to 80%.

[0044] In combination with the porosity, thickness, and composition of the filter layer, the pore size of the filter layer (i.e., the average pore size throughout the filter layer) can provide a useful or advantageous level of filtration functionality (e.g., as measured by retention rate) as the liquid passes through the composite filter membrane, while also allowing for any size of fluid flow rate through the filter layer (and composite filter membrane) that is commercially useful.

[0045] In specific embodiments of the composite as described, the filter layer may have smaller pores relative to the hollow fiber support. According to these embodiments, the resistance to fluid flow through the filter layer (based on thickness) will be greater than the resistance to fluid flow through a support with larger pores (based on thickness). Preferred examples of these composites may also comprise a thicker hollow fiber support with good flow characteristics and a relatively thinner filter layer with good filtration characteristics to produce a composite exhibiting a favorable combination of good flow characteristics through the composite and highly useful or advantageously high filtration performance provided by the relatively thin filter layer. The composite also has suitable mechanical properties including the desired levels of flexibility and stiffness, wherein the filter layer is effectively secured to the support, and neither the support nor the filter layer is excessively brittle or fragile.

[0046] The suitable pore size of the filter layer may depend on factors such as: the thickness, porosity, and composition of the filter layer; the desired flow characteristics and filtration performance characteristics (e.g., retention rate) of the composite filter membrane; and the characteristics of the method by which the filter layer is deposited (e.g., coated) onto the hollow fiber support. For some currently applicable examples of placing the filter layer on the hollow fiber support by dip coating, the example pore size of the filter layer may be at least 1 nanometer, such as at least 10, 30, or 50 nanometers, or from 0.05 micrometers to 2, 4, 6, or 8 micrometers.

[0047] The filter layer may have a thickness that will produce the effective filtration and flow properties described herein. Furthermore, the thickness of the filter layer should allow it to penetrate into and contact the inner surface of the porous hollow fiber support to mechanically secure the filter layer to the hollow fiber support. The filter layer may penetrate partially or completely into the hollow fiber support to become mechanically bonded and well-fixed to the support without causing significant clogging or filling of the pores of the hollow fiber support. Examples of suitable filter layer thicknesses are in the range of 5 to 40 micrometers, for example, 10 to 20 micrometers (excluding the distance the filter layer penetrates into the support). Examples of the distance the filter layer penetrates into the thickness of the hollow fiber support are less than 2 micrometers or less than 1 micrometer, although distances greater than these are also applicable, potentially including a filter layer that penetrates completely into the support layer.

[0048] For effective use in filtering liquids, the filter layer may be made of a polymer (“filter layer polymer”) that is resistant to solvents and other chemical materials present in the liquid to be processed using the filter layer. Filter layer polymers currently understood to be useful according to this specification include those polymers that are chemically resistant (e.g., do not degrade chemically) to liquids used in semiconductor and microelectronics processing (e.g., solvents or process fluids). Examples may generally include polymers suitable for (currently or in the future) preparing hollow fiber filter membranes for filtering fluids (e.g., solvents or process fluids) used in semiconductor and microelectronics processing, wherein specific examples include homopolymers and copolymers of polyimides, polyamides, polyamide-imides, and polysulfone family polymers, such as polyimides, polyamides, polysulfones, polyethersulfones, and polyphenylsulfones.

[0049] Polyamides are a class of well-known polymers containing nylon. Chemically, polyamides are considered polymers comprising a plurality of repeating carbon-carbon organic polymeric backbone units separated by repeating amide bonds. Polyamides can be prepared by reacting monomers or reactive components containing combinable functional groups to form a polymer backbone with repeating amide bonds. Examples of suitable combinations of monomers for preparing polyamides include diamine monomers and dicarboxylic acid monomers. Example polyamides comprise copolymers and trimers prepared by polymerizing combinations of two or three diamine and dicarboxylic acid monomers. Some currently preferred polyamides contain nylon, such as nylon 6 and nylon 6,6.

[0050] Polyimide (sometimes simply referred to as PI) is a polymer that contains imide bonds in its carbon-carbon polymer backbone. Polyimide polymers can be "pure" polyimides containing imide bonds but no ester or amide bonds, or alternatively containing other non-carbon-carbon bonds, such as ester or amide bonds. Some currently preferred polyamides include those known as P84 and Matrimid polyimides.

[0051] Polyamide-polyimide polymers (sometimes simply referred to as PAIs) contain amide and imide bonds. Some specific examples of polyamide-imide polymers include those prepared from aromatic diamines and aromatic acyl chloride anhydrides (acyl chloride pathway), while others can be prepared from aromatic diisocyanates and anhydrides (diisocyanate pathway). Examples of commercially available polyamide-imides are those sold under the trademark Torlon by Solvay Specialty Polymers.

[0052] If contained in a relatively thick membrane (or other structure), such as if the polymer is used by itself to form the entire thickness of a hollow fiber membrane, some polyimide or polyamide polymers may be mechanically brittle or inflexible. If used alone to form the entire thickness of a porous hollow fiber membrane (e.g., a thickness of at most or greater than 30 or 50 micrometers), some polyimides will tend to be mechanically brittle or fragile to the extent that they would prevent the hollow fiber membrane from being commercially useful. However, as determined by the applicant, thinner layers of these polymers as described (e.g., in the form of a thin filter layer of a composite membrane) can exhibit mechanical properties (including flexibility and reduced brittleness) that allow the polymer to be placed on a support and processed and formed into and used as a filter without mechanical unsuitability.

[0053] For processability, the preferred filter layer polymer is one that can be effectively (and preferably efficiently) applied to the outer porous surface of a support as described by a suitable coating method. The preferred filter layer polymer is a polymer solution that can be dissolved in a solvent to form a polymer solution that can be coated onto the porous outer surface of the hollow fiber support and then precipitated from the polymer solution onto the surface of the outer porous surface to form an effective filter layer as described. Currently applicable and preferred filter layer polymers can be dissolved in a solvent to form a polymer solution that can be coated onto the outer porous surface of a hollow fiber membrane using a ring die, and subsequently coagulated by an immersion precipitation method to form a suitable filter layer. The amount (e.g., thickness) and location of the filter layer are sufficient to allow the filter layer to exhibit highly efficient filtration performance (e.g., as measured by retention rate) as a filter layer of a composite hollow fiber filter membrane, while still allowing a desired high level of liquid flow through the composite hollow fiber filter membrane as described.

[0054] Suitable filter layer polymers can be provided as coatings on porous polymeric films using any suitable coating technique, such as precipitation coating, preferably from polymer solutions in which the filter layer polymer is dissolved in a solvent. Therefore, preferred filter layer polymers are solvent-handleable and soluble in solvents for coating onto supports, such as hollow fiber supports. The solvent can be any suitable solvent, examples of which include NMP (n-methylpyrrolidone), DMF (N,N-dimethylformamide), and N,N-dimethylacetamide (DMAC). The solvent is preferably water-free or contains no more than a small amount of water, for example, no more than about 2, 1, or 0.5% by weight. The polymer solution may also contain non-solvents, for example, selected from non-limiting examples including alcohols, acids, ethers, etc. Similarly, in addition to optional non-solvents, the polymer solution may contain other additives, such as pore-forming agents, such as polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), etc.

[0055] The polymer solution may contain any effective amount of solvent and dissolved filter layer polymer. Example polymer solutions may contain any effective amount of filter layer polymer, for example, in the range of 5 to 30% by weight, such as 10 to 20 (or 25)% by weight of filter layer polymer, wherein the remainder is solvent (e.g., an organic solvent as described herein, optionally in combination with a non-solvent and a pore-forming agent).

[0056] The filter layer polymer may, but does not need to, be curable or self-reactive, such as crosslinked. Therefore, the polymer solution containing the filter layer polymer dissolved in the solvent does not need to contain and may optionally exclude (e.g., contain less than 0.05, 0.01, or 0.005% by weight) any chemical components suitable for producing the curing reactants of the coated filter polymer, such as crosslinking agents, catalysts, or initiators.

[0057] Composite hollow fiber filter membranes comprise a hollow fiber support and a filter layer. Where additional layers or materials may optionally be included, the described composites do not require, and in some embodiments preferably exclude, other layers, coatings, or materials. For example, some example composite membranes of this specification do not require, and preferably exclude, an intermediate coating or layer located between the porous support and the filter layer, such as a primer or coating applied to the outer porous surface of the support for the purpose of improving the adhesion of the filter layer to the support. In these embodiments, the filter layer may be directly applied to the outer porous surface of the support.

[0058] In examples of currently preferred methods for preparing hollow fiber composites as described, the filter layer is formed on the hollow fiber support by forming a polymer solution containing the filter layer polymer and placing the filter layer polymer on the outer porous surface of the hollow fiber support by immersion precipitation or thermally induced phase inversion coating. Generally, by immersion precipitation, a polymer solution containing the polymer dissolved in a solvent is cast onto the support layer and subsequently immersed in a coagulation bath containing a “non-solvent,” which means a liquid in which the polymer is substantially insoluble. Due to solvent-non-solvent exchange, the polymer precipitates from the polymer solution onto the support layer. The polymer must be highly soluble in the solvent of the polymer solution and substantially insoluble in the “non-solvent” so that the polymer precipitates or coagulates upon contact with the non-solvent (e.g., an aqueous liquid) of the coagulation bath.

[0059] In some embodiments of the preparation of hollow fiber composites as described, the filter polymer may be dissolved in a solvent to form a polymer solution that can be coated onto the external porous surface of a hollow fiber support by an immersion precipitation method. A general method includes one or more steps comprising: forming or additionally providing a polymer solution comprising a filter layer polymer; applying the polymer solution to the external porous surface of the hollow fiber support; causing the filter layer polymer of the polymer solution to precipitate (e.g., coagulate) from the solution and precipitate (e.g., coagulate) onto the external porous surface of the hollow fiber support; and drying the precipitated filter layer polymer to form a composite comprising a filter layer coated on the external porous surface of the hollow fiber support.

[0060] An example of this method may involve using an annular mold to guide and support an uncoated hollow fiber support, moving through the annular mold while a polymer solution passes through the annular mold and onto the outer porous surface of the hollow fiber support. The annular mold comprises an inner cylindrical support and an outer cylindrical support, concentrically aligned to form an annular opening of substantially uniform size (width) between the outer surface of the inner cylindrical support and the inner surface of the outer cylindrical support. The inner cylindrical support also defines a circular opening sized to contain and guide the movement of the hollow fiber support. As the hollow fiber support passes through the annular mold (e.g., pulled through the mold in a vertically downward direction), the polymer solution flows through the annular opening to coat the outer surface of the hollow fiber support. The diameter of the circular opening is sufficient for the desired fit of the hollow fiber support within the circular opening, for example, to allow the hollow fiber support to pass through the circular opening at the desired speed. The size (width) of the annular opening effectively places a coating of polymer solution of the desired thickness onto the outer surface of the hollow fiber support as the support passes through the circular opening.

[0061] Any effective coating equipment, conditions, and processing parameters can be used, including, for example, the draw rate of the support, the flow rate of the polymer solution, and the relative size of the annular die to the diameter of the support. The flow rate of the polymer solution and the speed at which the hollow fiber support passes through the die determine the thickness of the coated filter layer.

[0062] According to certain examples of this type of coating technology, the coated polymer solution (placed onto the hollow fiber support via a ring die) may optionally be exposed to air after the coating step (after passing through the ring die) and before contacting the polymer with a non-solvent in the condensation bath. Exposure to air after coating and before entering the condensation bath is not necessary, but allows for partial drying of the coated polymer before contact with the condensation bath. Although not necessary or required, exposure to air before the condensation bath may be useful for obtaining greater penetration of the coated polymer layer into the hollow fiber support to achieve better mechanical interlocking between the support and the coated layer. However, if the air gap is too large, the penetration may be too great and the membrane flux may be negatively affected. Alternatively, the air gap can be used to achieve specific microstructures in the coated layer by evaporating the solvent during exposure to air, which may cause some degree of phase separation. If an air gap is present, the amount of time the coated polymer solution is exposed to air before contact with the non-solvent may be less than, for example, less than 2 seconds, less than 1 second, or less than 0.5 seconds, depending on the need.

[0063] Mention Figure 1A The image shown is part of an immersion coating system that is effective for preparing an example composite hollow fiber 70 as described. Figure 1B This shows a cross-sectional view of the composite hollow fiber 70.

[0064] System 10 includes a hollow fiber support 20, a polymer solution 30, and an annular mold 34. The source side (not shown) of the hollow fiber support 20 is positioned, for example, by a spool or bobbin wound with a continuous length of the hollow fiber support 20, to allow the hollow fiber support 20 to be supplied to system 10. One or more rollers (also not shown) may be used to guide the hollow fiber support 20 to and through different components and locations of system 10.

[0065] Polymer solution 30 is supplied to an annular mold 34, which includes an inner cylindrical support 36, an outer cylindrical support 38, a circular opening 40 (defined by the inner surface of the inner cylindrical support 36), and an annular opening 42 (between the inner cylindrical support 36 and the outer cylindrical support 38). Hollow fiber support 20 is screwed through the circular opening 40 and advanced through the circular opening 40 (in... Figure 1A The polymer solution 30 is distributed through the annular opening 42 in a downward direction. A syringe or pump (not shown) causes the polymer solution 30 to flow at a steady rate from the bottom of the annular opening 42 at the desired pressure and flow level, so as to place a continuous and substantially uniform coating (in an uncondensed form) of the polymer coating 50 on the outer surface of the support 20.

[0066] Vertically positioned below the annular mold 34 is a condensation bath 60 containing a non-solvent 62. A hollow fiber support 20 exits the annular mold 34, with an uncondensed polymer coating 50 present on the outer porous surface of the hollow fiber support 20. To allow the dissolved polymer of the polymer coating 50 to condense on the outer surface of the hollow fiber support 20 and form a filter layer (thin porous coating) 64, the hollow fiber support 20 with the uncondensed polymer coating 50 subsequently contacts the non-solvent 62 of the condensation bath 60. The non-solvent 62 contacts the polymer coating 50 and interacts with the solvent and the dissolved filter layer polymer of the polymer coating 50, causing the dissolved filter polymer to precipitate from the solution (e.g., condensate) to form a filter polymer layer on the outer surface of the support 20. The product is a composite hollow fiber 70 made from the support 20, with the filter layer 64 (undried, as illustrated) coated on its outer porous surface.

[0067] As may be and as described, the support 20 having the uncondensed polymer coating 50 passes through the air gap 52 after exiting the annular mold 34 and before contacting the non-solvent 62 of the coagulation bath 60. Upon entering the coagulation bath 60, the non-solvent 62 causes phase separation of the polymer solution 50 and forms a porous coating (filter layer) 64 of the composite hollow fiber 70. In other exemplary embodiments, no air gap exists between the annular mold 34 and the non-solvent 62, phase separation occurs in the coagulation bath, and the polymer coating 50 (on the support 20) is immediately present on the annular mold 34.

[0068] In some examples of the coating method, the polymer solution (as polymer coating 50) penetrates at least partially into the pores of the outer porous surface of the hollow fiber support 20. During the condensation of the filter polymer of the polymer coating 50, a mechanical interlock occurs between the coated (condensed) filter layer 64 and the outer porous surface of the hollow fiber support 20. In some embodiments, the extent (depth) to which the polymer solution 30 penetrates into the hollow fiber support 20 at the outer porous surface is sufficiently small such that the fluid transport resistance through the composite 70 remains sufficiently low to allow the composite 70 to function as a suitable filter membrane.

[0069] As one or more optional subsequent steps, a washing tank, heating step, drying step, annealing step, godet rolls, or winding section may be used for further processing or treatment of the composite 70. For example, after the phase separation (coagulation) step, the composite hollow fibers 70 may be guided through a washing tank to extract residual solvent. Subsequently, the washed (still wet) composite may optionally be collected on the rolls before or after the post-treatment annealing or drying step.

[0070] The composite filter membrane described herein is applicable to removing one or more contaminants from a liquid by passing the liquid through the filter membrane, producing a filtered (or “purified”) liquid (sometimes referred to as “permeate”). The filtered liquid will contain a reduced amount of contaminants compared to the amount of contaminants present in the liquid before the liquid passes through the composite filter membrane. If necessary, to maintain the position of the filter layer on the outer surface of the support, the liquid can flow in the direction of flow from the outer surface to the hollow opening inside the composite; that is, the liquid can first pass through the filter layer at the outer surface of the hollow composite from the outside, then through the hollow fiber support, and subsequently enter and flow along the hollow interior of the composite.

[0071] The compound described herein may provide a suitable, desired, or advantageous combination of physical properties, including performance (such as filtration performance as measured by “retention rate”), pore size or bubble point (related to pore size), flow rate, and mechanical properties (flexibility and durability or reduced brittleness).

[0072] One way to measure the effectiveness of a composite filter membrane in removing unwanted materials (i.e., "contaminants") from a liquid is as a "retention rate". Regarding the effectiveness of a filter membrane (such as a composite filter membrane as described), the retention rate generally refers to the total amount of impurities removed from a liquid containing impurities (actually or during performance testing) relative to the total amount of impurities in the liquid as it passes through the filter membrane. The "retention rate" value of a filter membrane is therefore a percentage, where a filter with a higher retention rate value (higher percentage) is relatively more effective at removing particles from a liquid, and a filter with a lower retention rate value (lower percentage) is relatively less effective at removing particles from a liquid.

[0073] Particle retention can be measured by measuring the number of test particles removed from a fluid stream by a membrane placed in the fluid stream. One method for particle retention is to measure it by passing a sufficient amount of a 0.1% Triton X-100 feed aqueous solution containing 8 ppm of polystyrene particles (Duke Scientific G25B, nominal diameter 0.03 μm) through a membrane at a constant flow rate of 7 mL / min to achieve 1% monolayer coverage, and collecting the permeate. The concentration of polystyrene particles in the permeate can be calculated from the absorbance of the permeate. The particle retention is then calculated using the following equation:

[0074] .

[0075] As used herein, “nominal diameter” refers to the particle diameter as determined by photon correlation spectroscopy (PCS), laser diffraction, or optical microscopy. Typically, the calculated or nominal diameter is expressed as the diameter of a sphere having the same projected area as the image projected onto the particle. PCS, laser diffraction, and optical microscopy techniques are well-known in their respective fields. See, for example, Jillavenkatesa, A. et al.; “Particle Size Characterization”; NIST Recommended Practice Guide; National Institute of Standards and Technology Special Publication 960-1; January 2001.

[0076] In preferred embodiments of the composite membranes as described, the composite membranes exhibit retention rates exceeding 90% for monolayer coverage of 0.5%, 1.0%, 1.5%, and 2.0%, and exceeding 95% for monolayer coverage of 0.5% and 1.0%. With these levels of retention, these examples of the composite membranes of the present invention exhibit higher retention rates compared to many currently available commercial filter membranes (e.g., similar sheet and hollow fiber filter membranes made from UPE). These examples of composite membranes also allow for useful, good, or excellent flow rates (low flow times) and exhibit mechanical properties that allow for the fabrication of composite membranes and their assembly into filter cartridges or filtration products.

[0077] The bubble point is a known characteristic of porous materials, including the characteristics of composite filter membranes as described. The bubble point can correspond to pore size, which in turn corresponds to filtration performance. Smaller pore sizes may be associated with higher bubble points and potentially with higher filtration performance (higher retention). However, generally, higher bubble points are also associated with relatively higher flow resistance and lower flux through porous materials. According to certain preferred embodiments, composite filter membranes can exhibit a combination of relatively high bubble points and good filtration performance, while still exhibiting good or favorable flow (relatively high flow rates or relatively high flux), for example, the flux associated with much lower bubble points in other hollow fiber membrane designs or compositions.

[0078] According to a method for determining the bubble point of a porous material, a sample of the porous material is immersed in and wetted with a liquid having a known surface tension, and a gas pressure is applied to one side of the sample. The gas pressure is gradually increased. The minimum pressure at which gas flows through the sample is called the bubble point. Examples of suitable bubble points for porous filter membranes as described, measured at temperatures of 20 to 30 (typically 25) degrees Celsius using ethoxy-nonafluorobutane (HFE 7200) from Novec, IPA or water, compressed air or compressed N2 gas, are in the range of 2 to 500 psi, for example 50 to 500 psi, 2 to 400 psi or 135 to 185 psi.

[0079] Combined with desired bubble point and filtration performance (e.g., measured by retention rate), the composite membranes described can exhibit a usefully or advantageously low resistance to liquid flow through the composite membrane. The resistance to liquid flow can be measured with respect to flux. The composite membranes described can preferably have a relatively high flux, preferably combined with a relatively high and good filtration performance bubble point. An example of a useful or preferred flux may be at least 10 LMH / bar (liters / m² / hour), for example at least 20 LMH / bar, or at least 30 LMH / bar, or in the range of 20 to 8000 LMH / bar.

[0080] Filter membranes as described herein, or filters or filter assemblies containing composite hollow fiber filter membranes as described herein, are suitable for filtering liquid chemicals to purify the liquid chemicals or remove unwanted materials from said liquid chemicals, particularly to produce high-purity liquid chemicals suitable for industrial processes requiring inputs of chemical materials with very high purity levels. Generally, said liquid chemicals may be any of a variety of applicable commercial materials and may be liquid chemicals useful for any industrial or commercial purpose or used in any application. Specific examples of filters as described can be used to purify liquid chemicals used in or suitable for semiconductor or microelectronics manufacturing applications, such as for filtering liquid solvents or other process liquids used in semiconductor lithography methods. Some specific non-limiting examples of solvents that can be filtered using the filter membrane 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 of these, such as a mixture of PGME and PGMEA.

[0081] Composite membranes can be incorporated within larger filter structures, such as filters or filter cartridges in filtration systems. The filtration system places the composite membrane, for example as part of a filter or filter cartridge, in the flow path of the liquid chemicals so that at least a portion of the liquid chemical flow passes through the filter layer of the composite membrane, allowing the filter layer to remove a certain amount of impurities or contaminants from the liquid chemicals. The structure of the filter or filter cartridge can include one or more additional materials and structures supporting the composite membrane within the filter, allowing fluid to flow from the filter inlet through the composite membrane (including the filter layer) and through the filter outlet, thus passing through the composite membrane as it passes through the filter.

[0082] Examples of useful filters and methods for assembling filters are described in International Patent Application Publication No. WO2017 / 007683, the entire contents of which are incorporated herein by reference. Figure 2 and 3 This displays instances of these filters.

[0083] Figure 2 and 3 An example of a fluid separation device or filter incorporating the composite filter membrane described in this specification is shown. Figure 2 It is the external view of the filter and Figure 3 A composite membrane (multiple composite membranes) and the liquid flow to be separated upon entry and exit of the fluid separation device are shown. The fluid separation device (filter) includes a housing 110 comprising multiple composite membranes 112. Each membrane 112 is sealed at each of two opposing end regions to form a fluid-impermeable seal between the end regions and an open intermediate region 107. The open intermediate region 107 is not sealed and must remain open to allow permeate 106 to move through each membrane 112, as discussed below. The sealed end regions do not allow liquid to pass through and are therefore "leak-proof".

[0084] In use, the liquid feed enters the housing at connector 101 and is introduced into membrane 112 inside the housing. Membrane 112 divides the space inside the housing into a first volume 103 and a second volume 103b. When the liquid feed is exposed to membrane 112, permeate (the material that passes through membrane 112) enters the second volume 103b, and retentate (the material that does not pass through membrane 102) enters the first volume. The retentate can then be collected and further filtered when extracted from the housing via connector 105. The permeate exits through different connectors 106, where it can be concentrated, treated, or recycled back into the system.

[0085] exist Figure 2 and 3In one filter embodiment, a portion of the feed liquid passes through one of the composite membranes 112 to form permeate, and another portion of the feed liquid passes through the filter without passing through the composite membrane 112. According to other filter embodiments, the entire amount of feed liquid flows through the composite membrane 112 to form permeate, and no feed fluid portion bypasses the composite membrane 112 to form retentate. See, for example, Figure 6 of U.S. Patent 5,695,702, the entire contents of which are incorporated herein by reference.

[0086] Example

[0087] Example 1. Manufacturing composite polyimide (P84) / nylon hollow fiber.

[0088] 0.2-micron nylon hollow fibers were used as the hollow fiber support. A polymer solution consisting of P84 polyimide / NMP / propionic acid (17 / 75 / 8 wt%) was pumped at a flow rate of 1 mL / min through the annular portion of a ring mold with the following dimensions: ID = 1 mm, annular gap = 0.3 mm. The extrudate passed through a 1 cm air gap before entering a condensation bath composed of water. The hollow fiber support was drawn through the mold at a rate of 2 ft / min.

[0089] Example 2. Fabrication of composite polyamide-imide (Torlon) / nylon hollow fibers. 0.2-micron nylon hollow fibers were used as hollow fiber supports. A polymer solution consisting of cured Torlon@275°C / NMP / triethylene glycol (12 / 70 / 18 wt%) was pumped at a flow rate of 1 mL / min through the annular portion of an annular die with the following dimensions: ID = 1 mm, annular gap = 0.3 mm. The extrudate passed through a 1 cm air gap before entering a condensation bath composed of water. The hollow fiber draw rate through the die was 2 ft / min.

[0090] In one aspect, the composite hollow fiber filter membrane includes: a polymeric microporous hollow fiber support having an outer surface, an inner surface, a thickness extending between the outer surface and the inner surface, and micropores; and a porous polymeric filter layer having a condensed polymer in contact with the outer surface.

[0091] According to a second aspect of the first aspect, the filter layer comprises pores with an average pore size smaller than the average pore size of the micropores in the hollow fiber support.

[0092] According to a third aspect of the first or second aspect, the average pore size of the hollow fiber support is less than 10 micrometers.

[0093] According to the fourth aspect of the third aspect, the average pore size of the filter layer is in the range of 1 nanometer to 8 micrometers.

[0094] According to the fifth aspect of any of the foregoing aspects, the thickness of the hollow fiber support (in the absence of the filter layer) is in the range of 20 to 200 micrometers.

[0095] According to the sixth aspect of any of the foregoing aspects, the hollow fiber support comprises one or a combination of polyolefins and nylon, is composed of or substantially composed of them.

[0096] According to the seventh aspect of any of the foregoing aspects, the filter layer penetrates the thickness of the hollow fiber support to a depth of not more than 2 micrometers.

[0097] According to the eighth aspect of any of the foregoing aspects, the condensed polymer is formed by immersing and depositing the filter layer polymer onto the hollow fiber support.

[0098] According to a ninth aspect of any of the foregoing aspects, the filter layer comprises a polymer soluble in a solvent selected from the group consisting of: n-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), and combinations thereof.

[0099] According to the tenth aspect of any of the foregoing aspects, the filter layer is resistant to solvents selected from the group consisting of propylene glycol methyl ether (PGME), propylene glycol methyl ether acetate (PGMEA), and cyclohexanone.

[0100] According to the eleventh aspect of any of the foregoing aspects, said coagulating polymer comprises polymers selected from the group consisting of polyimides, polyamide-imides, and polyamides.

[0101] According to the twelfth aspect of any of the foregoing aspects, the composite membrane has a flux in the range of 20 to 8000 LMH / bar and a bubble point in the range of 50 to 500 psi, measured using ethoxy-nonafluorobutane (HFE 7200) at a temperature of 25 degrees Celsius.

[0102] According to the thirteenth aspect of any of the foregoing aspects, the porous polymeric filter layer does not penetrate more than partially into the thickness of the hollow fiber support.

[0103] According to the fourteenth aspect of any one of the first to twelfth aspects, the porous polymeric filter layer substantially penetrates into the thickness of the hollow fiber support.

[0104] According to the fifteenth aspect of any of the foregoing aspects, the filter layer comprises pores with an average pore size greater than the average pore size of the micropores of the hollow fiber support.

[0105] In the sixteenth aspect, the filter comprises a composite hollow fiber filter membrane of any one of the first to fifteenth aspects.

[0106] In the seventeenth aspect, a method of filtering a fluid includes passing the fluid through a filter according to the sixteenth aspect by first passing the fluid through the filter layer in the direction of flow and then through the hollow fiber support.

[0107] According to the eighteenth aspect of the seventeenth aspect, the fluid is a semiconductor photolithography solvent.

[0108] According to the nineteenth aspect of the eighteenth aspect, the solvent is selected from the group consisting of: propylene glycol methyl ether (PGME), propylene glycol methyl ether acetate (PGMEA), cyclohexanone and n-butyl acetate.

[0109] According to the twentieth aspect of the seventeenth aspect, the solvent is selected from diluted or concentrated hydrofluoric acid, sulfuric acid, and peroxide solutions.

[0110] In a twenty-first aspect, a method is included for preparing a composite hollow fiber filter membrane comprising a polymeric microporous hollow fiber support and a porous polymeric filter layer, the method comprising: placing a polymer solution coating on an outer surface of the polymeric microporous hollow fiber support, the polymer solution comprising a polymer dissolved in a solvent; and contacting the polymer solution coating with a coagulation solution such that the dissolved polymer of the polymer solution coating forms a coagulated polymer layer on the outer surface, the coagulated polymer layer contacting the outer surface and not exceeding partially penetrating into the thickness of the polymeric microporous hollow fiber support.

[0111] According to the 22nd aspect of the 21st aspect, during placement, it further includes: passing the polymeric microporous hollow fiber support through the central opening of the annular mold; and passing the polymer solution through the annular opening of the annular mold to place the polymer solution coating on the outer surface.

[0112] According to the twenty-first or twenty-second aspect, or the twenty-third aspect, it further includes allowing a certain amount of evaporation of the polymer solution coating before contacting the polymer solution coating with the condensation solution.

[0113] According to the 24th aspect of any one of aspects 21 to 23, said coagulating polymer comprises polymers selected from the group consisting of polyimides, polyamide-imides, and polyamides.

[0114] According to the twenty-fifth aspect of any one of the twenty-first to twenty-fourth aspects, the hollow fiber support comprises, is composed of or is substantially composed of polyolefin or nylon.

Claims

1. A composite hollow fiber filter membrane, comprising: Polymerized microporous hollow fiber support, comprising: outer surface, Inner surface, The thickness extending between the outer surface and the inner surface, and Micropores; and A porous polymeric filter layer comprising a condensed polymer in contact with the outer surface. The porous polymer filter layer penetrates into the hollow fiber support, and the penetration depth is no more than 2 micrometers.

2. The composite membrane according to claim 1, wherein the filter layer comprises pores with an average pore size smaller than the average pore size of the micropores in the hollow fiber support.

3. The composite membrane according to claim 1, wherein the composition and physical characteristics of the porous polymeric filter layer are independent of the composition and physical characteristics of the polymeric microporous hollow fiber support.

4. The composite membrane according to claim 1, wherein the condensing polymer comprises a polymer selected from the group consisting of polyimide, polyamide-imide and polyamide.

5. The composite membrane according to claim 1, wherein the composite membrane has a flux in the range of 20 to 8000 LMH / bar and a bubble point in the range of 50 to 500 psi, measured using ethoxy-nonafluorobutane (HFE7200) at a temperature of 25 degrees Celsius.

6. A filter comprising a composite hollow fiber filter membrane according to any one of claims 1 to 5.

7. A method of filtering a fluid, the method comprising passing the fluid through the filter according to claim 6 by first passing the fluid through the filter layer in a flow direction and then through the hollow fiber support.

8. A method for preparing a composite hollow fiber filter membrane comprising a polymerized microporous hollow fiber support and a porous polymerized filter layer, the method comprising: A polymer solution coating is placed on the outer surface of the polymeric microporous hollow fiber support, wherein the polymer solution comprises a polymer dissolved in a solvent, and After the polymer solution coating is exposed to air, it comes into contact with a coagulation solution, causing the dissolved polymer of the polymer solution coating to form a coagulated polymer layer on the outer surface. The coagulated polymer layer contacts the outer surface and penetrates into the hollow fiber support to a depth not greater than 2 micrometers.

9. The method of claim 8, further comprising, during placement: The polymerized microporous hollow fiber support is passed through the central opening of the annular mold, and The polymer solution is passed through the annular opening of the annular mold to place the polymer solution coating on the outer surface.

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