Method of making microporous polymer structures

Abstract

A method of manufacturing a microporous polymer structure (1) having at least one porous region (2) and a substantially non-porous support structure (3) configured to support the at least one porous region (2), the method comprising the steps of: i) providing a substrate (4); ii) providing a first composition (5) comprising a first polymer (5a), at least one solvent (5b) for the first polymer, and one or both of nanoparticles and / or microparticles (5c) dispersed in the first composition (5); iii) providing a second composition (6) comprising a second polymer (6a); iv) applying a first composition (5) to the surface (4a) of the substrate (4) to form a first coating (7); v) effecting a phase separation in the first coating (7) to obtain a phase-separated coating (7 '); vi) applying a second composition (6) to the same surface (4a) of the substrate (4) and / or to the phase-separated first coating (7 '); vii) physically hardening or curing the second composition (6) applied in step vi) to obtain a non-porous support structure (3); viii) dissolving the nanoparticles and / or microparticles (5c) with a washing solvent to obtain a porous region (2) wherein the non-porous support structure and the porous region are arranged on the substrate such that they form a common interface, and wherein the phase separation in the first coating (7) in step v) is effected from one side of the first coating (7).

Description

[0001] The invention relates to a method for producing a microporous polymer structure, a microporous polymer structure and a filtration device according to the independent claims.

[0002] Filtration is a common method for separating solids from fluids using porous membranes. Particles smaller than the membrane pores can still pass through this mechanical barrier, while larger particles accumulate on the feed side. Based on the actual pore size, membranes can be divided into microfiltration membranes, with pore sizes as small as 100 nm, and ultrafiltration membranes, with pore sizes between 2 and 100 nm. When the pore size is reduced to nanofiltration membranes, with pore sizes between 0.5 and 2 nm, and reverse osmosis, with pore sizes below 0.5 nm, separation occurs more precisely due to the mechanical barrier of the polymer chains than to actual pores.

[0003] Microfiltration and ultrafiltration membranes are typically manufactured using phase inversion processes, such as those described in US Pat. No. 6,267,916 B1. These processes involve casting a polymer dope solution onto a substrate and subsequently quenching the dope solution. During this precipitation step, pores form in the polymer layer. This process is also known as non-solvent-induced phase separation (NIPS). In addition to using a non-solvent, separation can also be induced by lowering the temperature of the cast polymer dope solution. For example, US Pat. No. 5,444,097 A further describes this temperature-induced phase separation (TIPS) process.

[0004] In addition to membrane manufacturing processes based on any type of phase separation, manufacturing processes that use plain or coated template particles to create pores have also shown great potential and relevance for large-scale membrane manufacturing. For example, as described in EP2665767A1, this process uses nanoparticles and / or microparticles as pore templates to form a polymer-template composite. In a subsequent step, the template particles are dissolved to reveal the porous membrane structure. Since high porosity is important for achieving high permeability, this template-based process provides simple control of the desired porosity using a minimal amount of template particles.

[0005] However, no matter how the manufacturing method is adopted, the higher the porosity, the worse the mechanical properties of the porous membrane become. To some extent, the deterioration of mechanical properties can be offset by introducing a porous support, such as a woven or nonwoven fabric, to form a composite porous membrane, for example as described in EP1666129B1, but this in turn impairs permeability.

[0006] To improve the mechanical properties of the membrane while maintaining its self-supporting properties, the membrane thickness can certainly be increased, but this reduces the manufacturing speed due to the additional solvent involved. Furthermore, since flow resistance is proportional to the square of the pore diameter and the pore length, permeability is also compromised. Therefore, thick membranes with small pores tend to have particularly low permeability.

[0007] Recently, processes have been developed to produce asymmetric membranes that offer a good compromise between mechanical stability and permeability. For example, US Pat. No. 6,736,971 B2 and US Pat. No. 8,123,992 B2 describe an apparatus for producing bilayer membranes with different porosities. This allows the selective layer with smaller pores to be made thinner without sacrificing the stability of the typically thicker membrane. However, these membranes do not achieve the optimal smooth transition or gradient in pore size between the bottom side or surface and the top side or surface.

[0008] In addition to requiring highly permeable membranes, it is generally also required that the membranes be securely sealed against the filter housing that houses them. Sealing can be achieved by gluing or welding the membrane edges together or by gluing or welding them into a sealing cap. Although gluing is considered simpler, additives in the glue may leak out later, which can be a problem, especially if the membrane is intended for use in drinking water applications or pharmaceutical environments. Therefore, thermal bonding, such as ultrasonic welding or infrared welding, is the preferred method for sealing membrane edges without increasing the risk of leaking components. However, this method also has certain disadvantages, especially the fact that it applies thermal and mechanical stresses to the membrane, which can damage the porous areas and negatively affect membrane performance. This would be desirable if the membrane had a sealing area with ideally no porosity and a filtration area with high and asymmetric porosity.

[0009] The object of the present invention is to overcome these and other disadvantages of the prior art and, in particular, to provide an improved method for producing microporous polymer structures, in particular membranes, which method enables the porosity within the microporous polymer structure to be controlled, which is cost-effective, reliable, and easy to operate. Another object is to provide a microporous polymer structure, in particular a membrane, which can be safely and easily connected to a mating device, such as a filter housing, and which is characterized by a high and asymmetric porosity while maintaining good mechanical stability.

[0010] This object is achieved by a method for producing a microporous polymer structure, a microporous polymer structure, and a filtration device comprising at least one microporous polymer structure, as disclosed herein and according to the independent claims, wherein the microporous polymer structure has at least one porous region and a substantially non-porous support structure configured to support the at least one porous region. Advantageous embodiments are subject to the dependent claims.

[0011] In the context of the present invention, the term "non-porous" means that the respective area comprises essentially no interconnected pores.

[0012] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0013] A method of making a microporous polymer structure having at least one porous region and a substantially non-porous support structure configured to support the at least one porous region comprises the following steps:

[0014] In step a), a substrate is provided. The substrate can be, in particular, a porous substrate or a non-porous substrate selected from the group consisting of fabrics, nonwovens, foams, synthetic polymers, biopolymers, ceramics, metals, glass, and combinations thereof. Additionally or alternatively, the substrate can have a two-dimensional or three-dimensional shape.

[0015] In step b), a first composition is provided, comprising a first polymer, at least one solvent for the first polymer, and one or both of nanoparticles and microparticles dispersed in the first composition.

[0016] In order for the method to work particularly reliably, the viscosity of the first composition, when provided in step b), can in particular be about 2000 to 30000 mPa·s, as measured with a viscometer equipped with a suitable cone for the viscosity range at a shear rate of 100 1 / s and a temperature of 30° C. Additionally or alternatively, it is preferred that the concentration of the first polymer in the first composition is 10% to 35%, based on the total weight of the first composition.

[0017] The first polymer can especially be one or more polymers selected from polysulfone, polyethersulfone, polycarbonate, polystyrene, polyacrylate, polysiloxane, polyarylate, polyurethane, polyester, polyether, polyimide, polyamide, halogenated polyolefin, cellulose acetate and liquid crystal polymer. Alternatively, the first polymer can be a polymer or copolymer as mentioned in the preceding sentence, which is functionalized by post-polymerization, sulfonation and phosphorylation, amination, or quaternization. In addition or alternatively, it is conceivable that the first polymer can be selected from oligomers that can be polymerized or polymers that can be cross-linked. Using oligomers provides lower viscosity and can contribute to the coating of substrate, especially when substrate is characterized by complex shape or when expectation covers substrate completely. Crosslinking can enhance the durability of coating and / or its durability after self-supporting microporous polymer structure is removed from substrate respectively.

[0018] In order for the method to work particularly reliably, the average molecular weight of the first polymer can in particular be about 5,000 to 500,000 g / mol, as determined by gel permeation chromatography (GPC). Those skilled in the art will appreciate that the internal standard and solvent used for molecular weight determination by GPC can vary depending on the polymer.

[0019] It will be appreciated by those skilled in the art that a suitable solvent for the first polymer can be selected according to the corresponding polymer or multiple polymers to be dissolved. Preferably, the solvent for the first polymer is characterized by a boiling point below 230°C. Within this temperature range, compared with solvents with higher boiling points, energy can be saved, and the risk of destroying the microporous polymer structure due to thermal stress or thermal oxidation stress is also reduced. Examples of suitable solvents for the first polymer include water or an organic solvent selected from alcohols, ethers, ketones, esters, halogenated alkanes, alkanes, cycloalkanes, sulfoxides, amides, pyrrolidones, lactones, and lactams.

[0020] For the method to work particularly reliably, the first composition may contain nanoparticles and / or microparticles in a particle to polymer ratio of about 49:51 to 90:10 (particle:polymer), based on the weight of the first polymer.

[0021] The first composition may include one or more additives selected from various known additives in the art and mixtures thereof. Specifically, the additives may be selected from surfactants, polymerization initiators, stabilizers, crosslinkers, wetting agents, thickeners, curing agents, leveling agents, film flow agents, film leveling agents, defoamers, anti-orange peel agents, and mixtures thereof. In a preferred embodiment, the first composition includes at least one hydrophilicity-enhancing additive, particularly those disclosed in WO 02 / 42530 A1. The one or more hydrophilicity-enhancing additives are used to reduce the adhesion of air bubbles or other hydrophobic materials to the pores, which can adversely affect flow.

[0022] In step c), a second composition is provided. The second composition comprises a second polymer or a precursor of a second polymer. Optionally, the second composition further comprises at least one solvent for the second polymer.

[0023] For particularly reliable operation of the method, the viscosity of the second composition provided in step c) can in particular be approximately 500 to 10,000 mPa·s, as measured at 30° C. using a viscometer having a cone suitable for the viscosity range. Additionally or alternatively, it is preferred that the concentration of the second polymer in the second composition is 10% to 35%, based on the total weight of the second composition.

[0024] The first polymer and / or the second polymer may be selected from polysulfones, polyethersulfones, polycarbonates, polystyrenes, polyacrylates, polysiloxanes, polyarylates, polyurethanes, polyesters, polyethers, polyimides, polyamides, halogenated polyolefins, cellulose acetate, liquid crystal polymers and precursors thereof.

[0025] In order for the method to work more reliably, the average molecular weight of the second polymer can be in particular about 5,000 to 500,000 g / mol, as determined by GPC. As with the first polymer, those skilled in the art will appreciate that the internal standard and solvent used for molecular weight determination by GPC can vary depending on the polymer.

[0026] It will be understood by those skilled in the art that a suitable solvent for the second polymer can be selected based on the corresponding polymer or polymers to be dissolved.

[0027] In step d), a first composition is applied to the surface of the substrate provided in step a) to form a first coating layer on the substrate.

[0028] In order for the method to work particularly reliably, it is preferred if the temperature of the first composition during or at the time of application in step d) is from 20° C. to 40° C.

[0029] In optional step e), the first coating formed in step d) is placed in an atmosphere that promotes evaporation of at least one solvent for the first polymer.

[0030] In order for the method to work particularly reliably, it is preferred that in step e) the first coating is heated to a temperature of 60° C. to 80° C. Additionally or alternatively, it is preferred that the evaporation in step e) is carried out for a period of 0.5 minutes to 15 minutes.

[0031] In step f), phase separation is achieved in the first coating layer to obtain a phase-separated first coating layer. Phase separation in the first coating layer in step f) is achieved from one side of the first coating layer. This is to create an asymmetric structure in the first coating layer, which will later become the porous regions of the microporous polymer structure. Phase separation in the first coating layer can be induced by exposing the first coating layer to a non-solvent atmosphere (drying process) and / or by temperature changes, as described further below. Preferably, phase separation in the first coating layer in step f) is achieved from the substrate side, which allows for particularly good control of this process step and minimizes the risk of damage to the unsupported surface facing away from the substrate.

[0032] In step g), a second composition is applied to the same surface of the substrate provided in step a) that was coated with the first composition in step d). The second composition is applied in a patterned manner, depending on the desired or required shape of the support structure used to support the porous region. Additionally or alternatively, the second composition is applied in a patterned manner to the phase-separated first coating formed in step d). It is also contemplated that the application of the first composition in step d) and the application of the second composition in step g) can be performed substantially simultaneously, as described in more detail herein below.

[0033] In order for the method to work particularly reliably, it is preferred that the temperature of the second composition during or during the application of the second composition in step g) is between 0.5 minutes and 15 minutes.

[0034] In step h), the second composition applied in step g) is physically hardened (eg by evaporation of the solvent) or cured to obtain a non-porous support structure. The non-porous support structure and the porous region are arranged on the substrate such that they form a common interface.

[0035] In step i), the nanoparticles and / or microparticles are dissolved with a washing solvent to obtain a porous region. In order to achieve faster dissolution, it is preferred to use an acidic aqueous solution to dissolve the nanoparticles and / or microparticles.

[0036] As used herein, a "wash solvent" is a non-organic solvent (e.g., water) used to remove the salt particles from their polymer matrix, i.e., the phase-separated first coating, by dissolving them in the non-organic solvent. The wash solvent is characterized in that it does not dissolve the polymer(s) contained in the first and second compositions used in the manufacturing process described herein. Furthermore, the wash solvent used in the methods described herein is preferably, but not necessarily, in a liquid aggregate. It is also contemplated that step i) comprises multiple washes, optionally with drying between washes. When a multi-step approach comprising multiple washes is employed, the same or different wash solvents may be used, for example, using a dilute acidic aqueous solution followed by water.

[0037] In optional step j), the microporous polymer structure obtained after step i) is dried. Drying can be performed until a predetermined weight loss or constant weight is achieved. For particularly reliable operation of the method, it is preferred that in step j), the microporous polymer structure obtained after step i) is heated to a temperature of 60°C to 180°C. Additionally or alternatively, it is preferred that the drying in step j) be performed for a period of 0.5 to 15 minutes.

[0038] The microporous polymer structures disclosed herein may be, inter alia, membranes, and the methods herein may be, inter alia, methods of making membranes.

[0039] The methods disclosed herein for making microporous polymer structures are cost-effective, reliable and easy to operate. The methods disclosed herein produce microporous polymer structures, especially membranes, which are structurally different from membranes formed by lamination or extrusion processes of two or more polymer membranes because the microporous polymer structures herein are characterized by a true asymmetric pore size distribution, which is further achieved by phase separation. In addition, the methods disclosed herein make it possible to achieve "open areas", i.e., porous areas, of almost any size, which is not possible when using traditional woven or non-woven materials, but is possible by using "flowing" polymers, i.e., the first composition. When designing the manufacturing process, the mutual diffusion of the first composition and the second composition can be taken into account, which will be obvious to those skilled in the art, so that using the methods disclosed herein, larger, individually adjustable "open areas" can still be obtained.

[0040] The asymmetric microporous polymer structure provided by the present invention generally includes a relatively thin, for example, 10 nm to 50 nm thin dense separation layer and a relatively thick porous layer, the latter providing mechanical stability and effective filtrate transport. Therefore, the asymmetric porous polymer structure disclosed herein has both the high permeate flow provided by the separation layer or selective layer and the reasonable mechanical stability obtained by the relatively thick porous layer. The substantially non-porous support structure disclosed herein further significantly enhances mechanical stability. In addition, the microporous polymer structure disclosed herein exhibits a pore size gradient, which further distinguishes it from a membrane formed by lamination of two or more polymer membranes.

[0041] The microporous polymer structures disclosed herein are self-supporting ("free-standing"). Therefore, they differ from known porous polymer structures of similar thickness and porosity that are attached to supports. However, the microporous polymer structures disclosed herein are also suitable for coating suitable supports. The ability to fabricate such microporous polymer structures is independent of a specific support, making their applications highly versatile.

[0042] The microporous polymer structures disclosed herein are useful for applications in fields such as ultrafiltration (UF) and microfiltration (MF). Ultrafiltration is used to separate particles between 2 and 100 nm, such as viruses, proteins, and colloids. Microfiltration is used to separate particles between 100 and 1000 nm, such as bacteria.

[0043] The method disclosed herein may further comprise a step k) of removing the microporous polymer structure from the substrate. In this embodiment, step k) is performed after any of steps g) to j). In this way, a self-supporting microporous polymer structure, in particular a self-supporting membrane, is obtained.

[0044] In a preferred embodiment of the process disclosed herein, steps d) and g) are carried out simultaneously, followed by step f). This results in a particularly fast and efficient production process.

[0045] In preferred embodiments of the methods disclosed herein, the application of the first composition in step d) and / or the application of the second composition in step g) is performed by solvent casting, extrusion, or printing. The first and / or second compositions can be processed or applied very effectively in the aforementioned manner. Printing is particularly preferred because it allows for the production of particularly fine or delicate structures, which is particularly advantageous when processing the second composition, as the resulting support structure can be designed particularly efficiently.

[0046] In a preferred embodiment of the method disclosed herein, the phase separation in step f) is achieved by applying heat above 40° C. on one side of the first coating layer, preferably from the substrate side. Heating from the substrate side, i.e., from the side facing away from the accessible surface of the first coating layer and through the substrate, reduces the risk of damaging the surface during heating, for example due to convection, and thus enables a higher surface quality to be achieved.

[0047] In a preferred embodiment of the method disclosed herein, the second composition comprises a precursor of the second polymer, wherein the precursor is selected from one or more of a radiation-curable monomer and a radiation-curable oligomer. In this embodiment, curing of the second composition in step h) is performed by radiation curing using ultraviolet (UV) light or high-energy electrons from an electron beam (EB) source.

[0048] The advantage of using UV light to cure the second composition compared to thermal curing is that curing times are significantly reduced, typically in the range of seconds. This, in turn, is advantageous for high-throughput or continuous processes because it eliminates the need for long drying sections, which are space-intensive and costly. In addition to improving run times, UV curing of the second composition also enables the production of finer, more defined structures in the second composition because the rapid curing with UV light reduces the second composition's tendency to flow or mix with the first composition.

[0049] The UV light used to cure the second composition preferably has a wavelength of 280 to 400 nm. UV light in this wavelength range allows for deep penetration and curing, resulting in a durable coating with a significantly reduced number of unreacted reactive groups that might otherwise cause the corresponding monomers or oligomers to leach out of the cured composition. This is particularly important in medical applications, where harmful or even toxic compounds should not escape from the porous polymeric material.

[0050] A wide variety of polymers can be used in the microporous polymer structures of the present invention. This is believed to be advantageous because the porous polymer structures known in the art are limited with regard to suitable materials and / or the characteristics of their pores.

[0051] In a preferred embodiment of the methods disclosed herein, the first polymer and the second polymer are identical, i.e., the at least one first polymer contained in the first composition and the at least one second polymer contained in the second composition are the same polymer. This can reduce the complexity of the overall method and can reduce costs. However, it is also conceivable that the first polymer and the second polymer are not identical, i.e., the at least one first polymer contained in the first composition and the at least one second polymer contained in the second composition are different polymers. In the latter case, one skilled in the art will select the polymers based on their solubility in the same solvent, their coprecipitation behavior, and / or their shrinkage behavior.

[0052] In preferred embodiments of the methods disclosed herein, the nanoparticles and / or microparticles are selected from oxides, carbonates, sulfates, halides, nitrates, and phosphates. Preferably, the nanoparticles and / or microparticles are selected from oxides and carbonates, most preferably calcium carbonate (CaCO3), barium carbonate (BaCO3), strontium carbonate (SrCO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), sodium chloride (NaCl), zinc oxide (ZnO), and calcium oxide (CaO). These salts and oxides are generally readily available, reasonably priced, and readily soluble, particularly under acidic aqueous conditions.

[0053] Additionally or alternatively, the nanoparticles and / or microparticles have a particle size of 1 to 5000 nm, preferably 5 to 600 nm. The above particle sizes represent a preferred compromise between pore size, porosity, interpore connectivity and particle exudability.

[0054] The particle size of nanoparticles and / or microparticles present in polymer dispersions is determined by laser diffraction spectroscopy combined with polarized intensity differential scattering (PIDS). To calculate the particle size distribution, the refractive index ratio is selected according to the solvent used.

[0055] The pore size of particles with a particle size between 0.01 μm and 5 μm is determined by fluorescence reading of fluorescently labeled polystyrene or silica microspheres according to the following measurement protocol, where test particles with a size of 0.5 μm are given as an example:

[0056] (i) Preparation of the excitation solution:

[0057] Fluospheres were purchased from ThermoFisher ( TM, 0.5 μm, red fluorescence (580 / 605), F8812) or Micromod Partikeltechnologie GmbH (product number: 42-00-502 sicastar ® -greenF) fluorescent particles were diluted with 0.01% by volume of polyoxyethylene (20) sorbitan monooleate (Tween® 80) in deionized water to obtain a final particle concentration of 1:1000.

[0058] (ii) Bead retention test

[0059] The sample of the porous polymer structure to be analyzed is mounted on a filter housing (effective filtration area 6-20 cm 2 ), wherein the filter housing includes a woven or nonwoven support structure (e.g., Novatexx 2413, Freudenberg) for supporting the sample in the filter housing. The support must minimize mechanical stress on the membrane so that the membrane does not stretch under pressure. A defined volume of a challenge solution is poured into the test cell thus obtained. The challenge solution is forced through the sample using an air pressure of 1-6 bar, such that the inherent bubble point of the membrane is overcome, until the entire challenge solution volume has passed through the sample. The permeate is discarded and step (ii) is repeated. At this point, the permeate is collected in a clean plastic weighing dish for analysis.

[0060] (iii) Analysis

[0061] Pipette deionized water, excitation solution, and permeate (250 μL each) into a well plate (e.g., 96-well plate). Read the fluorescence using a microplate reader (e.g., Tecan) using the following protocol:

[0062] • 10 s orbital shaking, followed by

[0063] • Readout of red fluorescent particles from the top without cover; Ex. / Em. 540(25) / 620(20) nm; Gain calculated from the aperture using "full" signal, 25 flashes, 20 μs integration time, 3x3 square filling with 1000 μm sides,

[0064] • Readout of green fluorescent particles from the top without cover; Ex. / Em. 465(20) / 510(20) nm; gain calculated from the hole using “full” signal, 25 flashes, 20 μs integration time, 3x3 square filling with 1000 μm sides.

[0065] The readings for water represent the blank signal, the readings for the challenge solution represent the full signal, and the readings for the permeate represent the sample signal.

[0066] The retention rate R is then calculated from the wells as follows:

[0067]

[0068] If R is greater than 90%, the excitation particles are filtered and the porous polymer structure is said to have a pore size smaller than the excitation particle size (which would be 0.5 μm in this example).

[0069] (iv) Dilution adjustment

[0070] If the blank fluorescence reading is equal to or greater than 10% of the full fluorescence reading, the dilution should be reduced until the blank is less than 10% of the full fluorescence reading.

[0071] The pore size of particles with a diameter between 1 nm and 100 nm was determined using a dextran retention test, which has been performed to determine the molecular weight cutoff (MWCO; see G. Tkacik, S. Michaels, Nature Biotechnology, 9:941-946, 1991). Membranes that retain at least 90% of macromolecules larger than 1000 kDa are classified as having a MWCO of 1000 kDa. A mixture of 0.1 wt% of various dextran standards (5 kDa, 25 kDa, 80 kDa, 150 kDa, 270 kDa, 410 kDa, 670 kDa, and 1400 kDa) (Fluka, CH) was prepared in a 0.1 M sodium nitrate (NaNO3) buffer solution. Equal amounts of the individual standards were mixed. The mixture was filtered (direct flow) through the membrane using a high vacuum pump (Edwards Vacuum Ltd). The permeate and the mixture were compared using gel permeation chromatography.

[0072] Thus, for example, a membrane that exhibits a minimum retention of 95% for a 1400 kDa dextran standard molecule would be classified as having a MWCO of 1400 kDa.

[0073] In cases where the two methods described herein for determining pore size led to different results, the result obtained by fluorescence reading prevailed.

[0074] The pores of a material can be arranged in such a way that the material is permeable, partially permeable, or impermeable. If substantially all of the pores of a material have dead ends, the material is impermeable. Conversely, if substantially all of the pores of a material have open ends, i.e., the pores are interconnected, the material is considered permeable. Thus, if a portion of the pores have dead ends, the material is considered partially permeable.

[0075] In advantageous embodiments, the present invention provides a microporous polymer structure wherein at least 90% of the pores in the porous region are interconnected.

[0076] The porosity, i.e. the ratio of the volume of pores to the total volume of the structure, can vary over a wide range. The materials of the present invention exhibit a porosity in the range of 10-95% by volume, preferably 20-90% by volume. The porosity can be determined by porosimetry.

[0077] The surfaces of the nanoparticles and / or microparticles described above may be functionalized. Surface functionalization of the nanoparticles and / or microparticles can be achieved using surface functionalization agents and techniques known to those skilled in the art. Suitable coating materials for the particles can be selected from anhydrides, such as polymaleic anhydride acid (PMAH), its homopolymers, copolymers containing PMAH, and mixtures of PMAH, or carboxylic acids, such as C6-34 carboxylic acids and mixtures of carboxylic acids. In the context of the present invention, PMAH can be linear or branched. Furthermore, copolymers containing PMAH may also contain other functional groups, such as alkanes or olefins. In the context of the present invention, carboxylic acids can be linear or branched. Furthermore, carbocyclic acids may contain one or more double bonds. The term "carboxylic acid" also includes monocarboxylic acids and dicarboxylic acids. Suitable carboxylic acids are selected from naturally occurring fatty acids, such as stearic acid, and naturally occurring dicarboxylic acids, such as pimelic acid or sebacic acid. They can also be selected from alkyl-aryl-alkoxysilanes, aryl-alkoxysilanes, alkyl-alkoxysilanes, and mixtures of such silanes. In the context of the present invention, these silanes can be selected from trialkoxysilane derivatives, dialkoxysilane derivatives and monoalkoxysilane derivatives. In addition, these silane derivatives can be cyclic or linear, thus including the corresponding oligomers. Suitable silanes are selected from ((C 2-16 )alkyl)Si(OMe)3, ((C2-C 16 )alkyl)Si(OEt)3, ((C2-C 16 )alkyl)2·Si(OMe)2、(C2-C 16 )alkyl)2·Si(OEt)2 and corresponding, optionally substituted phenyl-containing derivatives, such as ((C2-C 16 )alkyl)-Ph·Si(OMe) 2. For arylsilanes, one or more of the above alkyl groups are substituted with at least one phenyl or substituted phenyl group.

[0078] In a preferred embodiment of the method disclosed herein, at least one of the first and second compositions further comprises plain or functionalized fibers. Such fibers serve to improve the mechanical properties of the final microporous polymer structure and to adjust the rheological properties of the composition, for example, to slow deliquescence or flow after application or to enhance shape retention of the applied composition.

[0079] In a preferred embodiment of the method disclosed herein, the second composition consists of the at least one second polymer and optionally one or more additives. The additives may be selected from surfactants, polymerization initiators, stabilizers, crosslinkers, wetting agents, thickeners, curing agents, leveling agents, film flow agents, film leveling agents, defoaming agents, anti-orange peel agents, and combinations thereof.

[0080] In a preferred embodiment of the methods disclosed herein, the first composition comprises, preferably consists of:

[0081] - 1-25% of at least one first polymer;

[0082] - 50% to 99% of at least one solvent for the first polymer;

[0083] - 0.5-40% of one or more nanoparticles and / or microparticles;

[0084] - 0-5% additives;

[0085] Each is based on the total weight of the first composition.

[0086] Additionally or alternatively, the second composition may comprise, preferably consist of:

[0087] - 1-35% of at least one second polymer;

[0088] - 50% to 99% of at least one solvent for the second polymer;

[0089] - 0-40% of one or more nanoparticles and / or microparticles;

[0090] - 0-5% additives;

[0091] Each is based on the total weight of the second composition.

[0092] The objects are also achieved by a microporous polymer structure obtained by the method disclosed herein. The microporous polymer structure comprises a top surface and a bottom surface, with a thickness between the top surface and the bottom surface. The microporous polymer structure further comprises at least one porous region formed from a first composition and a substantially non-porous support structure formed from a second composition, the substantially non-porous support structure extending along at least a portion of the thickness between the top surface and the bottom surface. The porous region comprises an anisotropic distribution of pore diameters from the top surface to the bottom surface along the thickness between the top surface and the bottom surface.

[0093] Such microporous polymer structures are characterized by both high filtration performance and high mechanical strength. The microporous polymer structure can be, in particular, a membrane. Compared to the microporous polymer structures known in the prior art, the method for obtaining the microporous polymer structure disclosed herein is reflected in the different properties of the microporous polymer structure disclosed herein, namely flow rate and test particle retention. The flow rate can be assessed by measuring the volume of water passing through a defined membrane area under a given time frame and a given inlet pressure. Particle retention can be assessed by filtering an excitation solution containing fluorescent polymer beads of known size, followed by fluorescence analysis as described above.

[0094] In a preferred embodiment of the microporous polymer structure disclosed herein, the pore diameter at the top surface is in the relatively small pore diameter range of 5 nm to 5000 nm, while the pore diameter at the bottom surface is in the relatively large pore diameter range of 500 nm to 50000 nm. Thus, the pore diameter within the thickness between the top and bottom surfaces is in the pore diameter range of 5 nm to 5000 nm.

[0095] In preferred embodiments of the microporous polymer structures disclosed herein, the porosity of the porous region is between 10% and 90% by volume, based on the total volume of the porous region.

[0096] In preferred embodiments of the microporous polymer structures disclosed herein, the porous region occupies at least 40% of the total volume of the microporous polymer structure and the non-porous support structure occupies at most 60% of the total volume of the microporous polymer structure. Additionally or alternatively, the porous region extends to at least 40% of the total coated substrate area and the non-porous support structure extends to at most 60% of the total coated substrate area.

[0097] In preferred embodiments of the microporous polymer structures disclosed herein, the substantially non-porous support structure is an integral part of the microporous polymer structure. In the context of the present invention, "integral part" is understood to mean that at least a portion of the support structure is surrounded by porous areas on all accessible sides.

[0098] Such microporous polymer structures are particularly stable and, in particular, may be self-supporting.

[0099] In a preferred embodiment of the microporous polymer structure disclosed herein, the substantially non-porous support structure comprises a plurality of networks. A first set of networks are arranged substantially parallel to one another. By maintaining one or more mechanisms for applying the second composition in a fixed relationship to one another and applying the second composition to a movable substrate, such structures can be manufactured in a continuous process particularly efficiently and at high throughput. For example, a manifold can be used with the moving substrate, the number of outlets of the manifold corresponding to the number of parallel networks forming the substantially non-porous support structure.

[0100] Optionally, the second network is arranged substantially perpendicular to the network of the first network. Thus, in a later alternative, the network of non-porous support structures is arranged in a checkerboard or diamond pattern. Such support structures can be manufactured particularly easily using two reciprocating mechanisms for applying the second composition laterally to a moving substrate, for example, using two movable outlets or nozzles. Such structures can be manufactured particularly efficiently and at high throughput in a continuous process.

[0101] Embodiments of microporous polymer structures comprising networks can include at least two networks forming a boundary network that forms a boundary of the microporous polymer structure on at least two opposing sides. The boundary network extends along the entire thickness of the porous region. Preferably, the boundary network encloses the edges of the microporous polymer structure. In the case of a substantially planar microporous polymer structure, such as a substantially flat membrane, this means that the boundary network completely surrounds the membrane within the plane. In the same embodiment, at least some of the networks disposed between the boundary networks extend along a portion of the thickness (d) of the porous region. Furthermore, substantially all of the networks are interconnected.

[0102] Said object is also achieved by a filtration device comprising at least one microporous polymer structure as disclosed herein.At least one microporous polymer structure is connected to the filtration device via a non-porous support structure of said microporous polymer structure.

[0103] The filter device can be a filter housing or a textile.

[0104] Membrane preparation

[0105] The general procedure for the preparation of microporous polymer structures as disclosed herein is as follows:

[0106] Polysulfone and polyvinylpyrrolidone (1:1) were mixed with N,N-dimethylacetamide and calcium carbonate (particle-to-polymer ratio 2:1) to a concentration of 32.6 wt%. The mixture was then ground in a ball mill (WAB Dyno®-Mill Multi Lab, pumping rate 10 rpm, grinding speed 3800 rpm, using 2 mm ZrO2 grinding beads) to obtain a first composition. A second composition was obtained by mixing polysulfone and polyvinylpyrrolidone (1:1) with N,N-dimethylacetamide to a concentration of 13.9 wt%. The two mixtures were cast simultaneously on a continuous pilot coater (Coatema GmbH, SC19) using a doctor blade arrangement. The basket containing the casting solution was divided into three sections: a wide central section for the first composition and two smaller sections containing the second composition adjacent to each side of the wide section. The film was cast onto a PET support layer at a line speed of 0.1 m / min. The layer was then heated from below at 80°C for a period of 4 minutes and subsequently dried at 110°C to 150°C for 10 minutes. The resulting composite material was then placed in diluted aminosulfonic acid for 5 minutes to remove the template. The resulting membrane 1 was then rinsed in deionized water and air-dried for 2 hours. The resulting interface between the porous region 2 and the non-porous support structure 3, formed from the first and second compositions, respectively, was confirmed by scanning electron microscopy (Nanosem 450, FEI), as shown in FIG. Figure 6a and Figure 6b Visible in.

[0107] The present invention will be better understood with reference to the following description of preferred embodiments and the accompanying drawings, in which like reference numerals are used to denote like or equivalent features in the various embodiments and examples.

[0108] Figure 1 a flow chart illustrating a sequence of embodiments of a method of making a porous polymer structure as disclosed herein;

[0109] Figure 2a Schematic representation of steps b) to h) of the method disclosed herein;

[0110] Figure 2b A further schematic diagram of steps b) to h) of the method disclosed herein;

[0111] Figure 3a a top view of a microporous polymer structure precursor on a substrate;

[0112] Figure 3b along Figure 3a Line AA passes through Figure 3a a cross section of the precursor shown;

[0113] Figure 3c along Figure 3b The line BB passes through Figure 3b a cross section of the precursor shown;

[0114] Figure 4 a cross-section of a self-supporting embodiment of a microporous polymeric structure disclosed herein;

[0115] Figure 5 Cross-sections of additional embodiments of microporous polymer structures disclosed herein;

[0116] Figure 6a SEM images of cross sections of microporous polymer structures obtained by the methods as disclosed herein;

[0117] Figure 6b SEM image of a cross-section of a microporous polymer structure obtained by the method as disclosed herein.

[0118] Figure 1A flow chart illustrating an embodiment of a method for producing a porous polymer structure 1 according to the present invention, which may particularly be a membrane. In this example, the method comprises step a) of providing a substrate 4. Substrate 4 may particularly be a porous or non-porous substrate as disclosed herein and may be substantially planar, i.e., have a two-dimensional shape, or non-planar, i.e., have a three-dimensional shape. In step b) a first composition 5 is provided, wherein the first composition comprises a first polymer, at least one solvent for the first polymer, and one or both of nanoparticles and / or microparticles dispersed therein. Subsequently, in step d) the first composition 5 is applied to surface 4a of substrate 4 to form a first coating 7. The first composition 5 can be applied to the respective substrate surface 4a by any method known to those skilled in the art, depending on its properties, particularly its rheological properties. For example, the first composition 5 can be applied to a predetermined thickness using a doctor blade. Optionally, the first coating 7 can be exposed to an atmosphere that promotes evaporation of the at least one solvent for the first polymer, such as a discharge flow or reduced pressure, as indicated by dashed arrow e. It should be noted that optional step e) is not identical to the subsequent step f), in which phase separation in the first coating 7 is achieved from one side of the first coating 7 to obtain a phase-separated first coating 7'. Phase separation can be initiated, in particular, from the substrate side, as will be explained in greater detail further below. Before or after this step f), a second composition 6 comprising a second polymer and, optionally, at least one solvent for the second polymer is provided in step c). In step g), the second composition 6 is applied in a patterned manner to the same substrate surface 4a to which the first composition 5 was previously applied. It is also conceivable that the first and second compositions 5, 6, are applied to the substrate surface 4a substantially simultaneously, i.e., steps d) and g) are performed in parallel. Additionally or alternatively, in step g), the second composition 6 can also be applied to the phase-separated first coating 7' obtained in step f), i.e., at least partially on top of it. The second composition 6, which later becomes the non-porous support structure, and the first composition 5, which later becomes the porous region, are arranged on the substrate 4 such that they form a common interface, meaning that the first composition 5 and the second composition 6 are applied so that they are in contact with each other. In step h), the second composition 6 is physically hardened or cured to obtain the non-porous support structure 3 of the microporous polymer structure 1. Subsequently, in step i), the nanoparticles and / or microparticles contained in the phase-separated first coating are dissolved using an aqueous solution to obtain the porous regions 2 of the microporous polymer structure 1. The microporous polymer structure thus obtained thus comprises at least one porous region 2 and a substantially non-porous support structure 3 configured to support the at least one porous region 2, as will be described in further detail below.In an optional step j) indicated by dotted arrows, the microporous polymer structure 1 comprising the porous regions 2 and the substantially non-porous regions 3 serving as a support structure for the porous regions 2 may be dried. Figure 1 In the illustrated embodiment, the method further comprises a step k) of removing the microporous polymer structure 1 from the substrate 4 to obtain a self-supporting microporous polymer structure 1'. Figure 1 It is obvious that step k) is performed after any one of steps g) to j).

[0119] Figure 2a is a schematic diagram of steps b) to h) of an embodiment of the method disclosed herein. Figure 2a In the upper left part of FIG, a first composition 5 is provided in step b), wherein the first composition 5 is prepared by adding a first polymer 5a, a solvent 5b for the first polymer 5a and a mixture 5c of nanoparticles and microparticles to a suitable container, such as a beaker or a stirred tank. Figure 2a In the upper right part of , in step c) a second composition 6 is provided, wherein the second composition 6 is prepared by adding a second polymer 6a and a solvent 6b for said second polymer 6a. Similar to step b), any suitable container can be selected to dissolve the second polymer 6a in the solvent 6b. However, it is not explicitly required to provide the second polymer 6a dissolved in the solvent. For example, it is conceivable that the second polymer 6a and any additives contained therein or added thereto essentially constitute the second composition 6, and that the second composition 6 is applied in a molten state. The first and second compositions are applied to the same surface side 4a of the substrate 4 (steps d) and g) respectively), phase separation in the first composition is achieved to obtain a phase-separated first coating 7' (step f), and the second composition 6 is physically hardened or cured to obtain a non-porous support structure 3 (step h), and these subsequent steps are in Figure 2a In the case where the second composition 6 is applied as a melt, for example by an extruder, the support structure 3 begins to form as the second composition 6 solidifies during cooling. Figure 2a In the example shown at the bottom, the precursor of the microporous polymer structure still contains salt particles 5c of the first composition 5, which can be washed off in step i) to produce the microporous polymer structure. Figure 2a In the embodiment shown at the bottom, the precursor and also the microporous polymer structure obtained after washing away the salt particles are supported by a substrate 4 .

[0120] Figure 2b is a further schematic diagram of steps b) to h) of an embodiment of the method disclosed herein. Figure 2b The process steps b) to h) shown are Figure 2aThe process steps already described in correspond to those in , except that the second composition 6 is not only applied in a patterned manner to the same surface 4a of the substrate 4 on which the first composition 5 was applied, but in addition it is also applied to the phase-separated first coating 7'.

[0121] Figure 3a is a schematic top view of the top surface 1a of an embodiment of a microporous polymer structure 1 on a substrate 4. Both a first composition and a second composition (not shown) are applied to one side of the substrate 4, namely the surface 4a. Figure 3a The illustrated microporous polymer structure 1 includes a substantially non-porous support structure formed from a second composition, the support structure comprising a plurality of networks 3a-3c. A first set of networks 3a are arranged substantially parallel to one another. The most widely spaced networks belonging to the first set of networks 3a are boundary networks 3c, which form boundaries of the microporous polymer structure 1 on two opposing sides and extend along the entire thickness (d) of the porous region 2, as shown in FIG. Figure 3b and 3c Furthermore, the networks 3b of the second group are arranged substantially perpendicular to the networks belonging to the first group 3a. The porous area 2 is at least partially separated by the networks 3a and 3b.

[0122] Figure 3b Shown along Figure 3a Line AA passes through Figure 3a A cross-section of a microporous polymer structure 1 is shown. As can be seen from this view, the porous polymer structure 1 has a thickness d between a top surface 1a and a bottom surface 1b, wherein the bottom surface 1b is in contact with the surface 4a of the substrate 4. The thickness d represents the extent of the porous region 2. The porous region 2 includes an anisotropic distribution of pore diameters from the top surface 1a to the bottom surface 1b along the thickness d between the top surface 1a and the bottom surface 1b (the anisotropic distribution of pore diameters is not shown in the figure due to the schematic nature of the illustration). Figure 3b As can be seen from the cross-section shown, the boundary network 3c extends along the entire thickness d of the porous area 2, while the network 3a belonging to the first group of networks and arranged between the boundary networks 3c extends along a portion of the thickness d between the top surface 1a and the bottom surface 1b, that is, along a portion of the thickness d of the porous area 2.

[0123] Figure 3c Shown along Figure 3a The line BB passes through Figure 3a The cross section of the microporous polymer structure 1 is shown. The cross section passes through a network 3b of the second group of networks, which is arranged substantially perpendicular to the networks belonging to the first group of networks 3a. Figure 3c Combine Figure 3aAs will be understood from the illustrated illustration, all networks 3a-3c are interconnected and thus together form a substantially non-porous support structure 3 configured to support the porous region 2. In addition to the supporting function of the support structure 3, another advantage of the microporous polymer structure 1 disclosed herein is that the support structure 3, in particular the boundary network 3c, serves as a sealing region suitable for securing and securely sealing the microporous polymer structure 1 in the filter housing. Such securing to the support structure 3 can be performed, for example, by welding, the thermal elasticity of the support structure 3 being much higher than that of the porous region 2, without any negative impact on the porous region 2. The non-porous support structure 3 and the porous region 2 are arranged on the substrate 4 such that the non-porous support structure 3 and the porous region 2 form a common interface, meaning that they are in contact with each other. Optionally, the microporous polymer structure 1 can be removed from the substrate 4 to obtain a self-supporting microporous polymer structure.

[0124] Figure 4 A cross-section of a self-supporting embodiment of the microporous polymer structure 1 disclosed herein is shown. In this particular embodiment, the substantially non-porous support structure 3 is an integral part of the microporous polymer structure 1, since at least part of the support structure 3, i.e. the network 3a, is surrounded on all accessible sides by the porous region 2. In other words, at least part of the support structure is embedded in the porous region 2. As described above, such a construction can be obtained by first applying a first coating of a first composition to the substrate and then applying a second composition to the first coating. Before achieving phase separation in the first coating, an additional coating of the first composition is applied. The remaining steps of the method described herein can also be performed similarly for this embodiment. The network 3a serves as a reinforcing skeleton for the entire microporous polymer structure 1 and enhances its mechanical stability. As can be seen from Figure 4 As can also be seen in FIG, the microporous polymer structure 1 is connectable to a surface, such as a filter housing of a filtration device 10, via its boundary network 3c.

[0125] Figure 5 A cross-section of another embodiment of the microporous polymer structure 1 disclosed herein is shown. In this particular example, the microporous polymer structure 1 is connected to a textile substrate 9 via connection points 8 between the textile substrate 9 and at least some of the networks 3a of the substantially non-porous support structure 3. In the manufacturing methods disclosed herein, the connection of the microporous polymer structure 1 to the textile 9 can be performed before or after removal of the support 4 (not shown) used. Similarly, the thickness d between the top and bottom surfaces of the microporous polymer structure 1 corresponds to the thickness of its porous region 2.

Claims

1. A method for producing a microporous polymer structure (1), in particular a membrane, said microporous polymer structure (1) having at least one porous region (2) and a substantially non-porous support structure (3) configured to support said at least one porous region (2), said method comprising the following steps: a) providing a substrate (4); b) providing a first composition (5), the first composition (5) comprising a first polymer (5a), at least one solvent (5b) for the first polymer, and one or both of nanoparticles and / or microparticles (5c) dispersed in the first composition (5); c) providing a second composition (6), said second composition (6) comprising a second polymer (6a) or a precursor of a second polymer (6a); d) applying a first composition (5) to the surface (4a) of the substrate (4) to form a first coating (7); f) achieving phase separation in the first coating (7) to obtain a phase-separated coating (7'); g) applying a second composition (6) in a patterned manner to the same surface (4a) of the substrate (4) and / or to the phase-separated first coating (7'); h) physically hardening or curing the second composition (6) applied in step g) to obtain a non-porous support structure (3); and i) dissolving the nanoparticles and / or microparticles (5c) with a washing solvent to obtain a porous region (2); wherein the non-porous support structure and the porous region are arranged on the substrate such that they form a common interface, and wherein the phase separation in the first coating (7) in step f) is achieved from one side of the first coating (7).

2. The method according to claim 1, wherein The second composition (6) provided in step c) further comprises at least one solvent (6b) for the second polymer (6a).

3. The method according to claim 1 or 2, further comprising the steps of: e) placing the first coating (7) in an atmosphere that promotes evaporation of at least one of said solvents (5b) for said first polymer (5a); Wherein, step e) is performed after step d) and before step f).

4. The method according to any one of the preceding claims, wherein the wash solvent is an acidic aqueous solution.

5. The method according to any one of the preceding claims, further comprising the steps of: j) drying the microporous polymer structure (1) obtained after step i).

6. The method according to any of the preceding claims, wherein the separation in the first coating (7) in step f) is effected from the substrate (4) side.

7. The method according to any one of the preceding claims, further comprising the steps of: k) removing the microporous polymer structure (1) from the substrate (4) to obtain a self-supporting microporous polymer structure (1'); Wherein, step k) is performed after any one of steps g) to j).

8. The method according to any one of the preceding claims, wherein steps d) and g) are performed simultaneously, followed by step f).

9. The method according to any of the preceding claims, wherein the phase separation in step f) is achieved by applying heat above 40°C to one side of the first coating (7), preferably from the substrate (4) side.

10. The method according to any one of the preceding claims, wherein the precursor of the second polymer (6a) is at least one of a radiation-curable monomer and a radiation-curable oligomer, and wherein the curing of the second composition (6) in step h) is carried out by radiation curing using ultraviolet (UV) light, preferably ultraviolet (UV) light having a wavelength of 280 to 400 nm or high-energy electrons from an electron beam (EB) source.

11. The method according to any one of the preceding claims, wherein the nanoparticles and / or microparticles (5c) are selected from oxides, carbonates, sulfates, halides, nitrates and phosphates, preferably oxides and carbonates, most preferably calcium carbonate (CaCO3), barium carbonate (BaCO3), strontium carbonate (SrCO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), sodium chloride (NaCl), zinc oxide (ZnO) and calcium oxide (CaO); and / or wherein the nanoparticles and / or microparticles (5c) have a particle size of 1 to 5000 nm, preferably 5 to 600 nm, as determined by laser diffraction spectroscopy combined with polarization intensity differential scattering (PIDS) technology.

12. The method according to claim 11, wherein the surface of the nanoparticles and / or microparticles (5c) is functionalized.

13. The method according to any one of claims 1 to 12, wherein the second composition (6) consists of the at least one second polymer (6a) and optionally one or more additives (6c), the one or more additives (6c) being selected in particular from surfactants, polymerization initiators, stabilizers, crosslinkers, wetting agents, thickeners, curing agents, leveling agents, film flow agents, film leveling agents, defoamers and anti-orange peel agents.

14. A microporous polymer structure (1), in particular a membrane, obtained by the process according to any one of claims 1 to 13, comprising: - top surface (1a) and bottom surface (1b); - a thickness (d) between the top surface (1a) and the bottom surface (1b); - at least one porous region (2) formed from a first composition (5); and - a substantially non-porous support structure (3) formed from the second composition (6); wherein the porous region (2) comprises an anisotropic distribution of pore diameters along a thickness (d) between the top surface (1a) and the bottom surface (1b) from the top surface (1a) to the bottom surface (1b), and wherein the substantially non-porous support structure (3) extends along at least a portion of the thickness (d) between the top surface (1a) and the bottom surface (1b).

15. The microporous polymer structure (1) according to claim 14, wherein the pore diameter at the top surface (1a) is in the relatively smaller pore diameter range of 5 nm to 5000 nm, wherein the pore diameter at the bottom surface (1b) is in the relatively larger pore diameter range of 500 nm to 50000 nm, and wherein the pore diameter within the thickness (d) between the top surface (1a) and the bottom surface (1b) is in the pore diameter range of 5 nm to 5000 nm, wherein the pore diameter is determined by fluorescence reading of fluorescently labeled polystyrene or silica microspheres or by a dextran retention assay.

16. The microporous polymer structure (1) according to claim 14 or 15, wherein the porous region (2) accounts for at least 40% and the non-porous support structure (3) accounts for at most 60%, each based on the total volume of the microporous polymer structure; and / or wherein the porous region (2) extends to at least 40% and the non-porous support structure (3) extends to at most 60%, each based on the total coated substrate area.

17. The microporous polymer structure (1) according to any one of claims 14 to 16, wherein the substantially non-porous support structure (3) is an integral part of the microporous polymer structure (1).

18. The microporous polymer structure (1) according to any one of claims 14 to 17, wherein the substantially non-porous support structure (3) comprises a plurality of networks, wherein a first group of networks (3a) are arranged substantially parallel to each other, and wherein optionally a second group of networks (3b) is arranged substantially perpendicular to the networks belonging to the first group of networks (3a).

19. The microporous polymer structure (1) according to claim 18, wherein at least two of the networks are boundary networks (3c), the boundary networks (3c) forming the boundaries of the microporous polymer structure (1) on at least two opposite sides and extending along the entire thickness (d) of the porous area (2), preferably, the boundary networks (3c) close the edges of the microporous polymer structure, wherein at least some of the networks arranged between the boundary networks (3c) extend along part of the thickness (d) of the porous area (2), and wherein substantially all of the networks are interconnected.

20. A filter device (10), in particular a filter housing or a textile, comprising at least one microporous polymer structure (1) according to any one of claims 14 to 17, wherein the at least one microporous polymer structure (1) is connected to the filter device (10) via a non-porous support structure (3) of the microporous polymer structure (1).

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