Solvent-free production of porous polymer structures

Abstract

A method for producing porous polymer structures, particularly membranes, comprising providing a mixture of one or more polymers and one or more salt nanoparticles and / or microparticles, molding the blend, and removing the one or more salt particles, wherein at least a portion of the one or more salt nanoparticles and / or microparticles are one or more solid acids, whereby the polymer to particle ratio is in the range of 3:1 to 1:10 by weight. Also provided are mixtures suitable for obtaining such porous polymer structures, the porous polymer structures described herein, shaped articles containing such structures, and uses of such porous polymer structures, shaped articles, and mixtures.

Description

[Technical Field]

[0001] In a first aspect, the present invention relates to a method for producing porous polymer structures, in a second aspect to mixtures suitable for producing such structures, in a third aspect to kits for producing said mixtures, in a fourth aspect to novel porous polymer structures and shaped articles comprising such structures, and in a fifth aspect to the use of such mixtures, structures and shaped articles. [Background technology]

[0002] Porous polymer membranes are used in various separation processes, such as fluid filtration. The methods for producing such porous polymer membranes must meet various objectives, including (i) fluid throughput, i.e., achieving high porosity to enable high fluid throughput; (ii) retention, i.e., providing separation of particulate matter in the filtrate while maintaining high fluid throughput; and (iii) process, i.e., producing such porous polymer membranes on a large scale and cost-effectively. With regard to the latter, environmental and sustainability considerations are becoming increasingly important.

[0003] Today, most membranes are obtained by phase separation or template-based processes. For example, U.S. Patent No. 4,247,498 discloses the preparation of a microporous polymer product with a homogeneous three-dimensional cellular structure, which comprises heating a thermoplastic polymer with a suitable compatible liquid to form a homogeneous solution, cooling the resulting solution to initiate liquid-liquid phase separation, and then continuing the cooling to solidify the polymer and remove the liquid to form a microporous material. Template-based membrane manufacturing approaches involving a polymer, a solvent, and a salt template are also known in the art, for example, from the disclosures in U.S. Patent No. 5,514,378, U.S. Patent No. 8,944,257, WO 2012 / 097967, EP 2,178,873, and EP 2,665,767.

[0004] U.S. Patent No. 3,062,760 discloses a process for preparing porous polymer structures using a monomer as the sole raw material or as a solvent for the corresponding polymer. A pore-forming agent is dispersed in the monomer or monomer-polymer mixture. Polymerization is initiated to form a moldable mass, which is further polymerized in a subsequent step after being formed into a well-defined shape. Finally, an aqueous solution is used to dissolve the pore-forming agent.

[0005] However, the aforementioned prior art is not environmentally friendly because it uses solvents, monomers, cosolvents, and / or anti-solvent systems to fabricate the membranes. Recycling the solvents can be difficult and requires detailed knowledge. Furthermore, today's polymer membrane production requires significant amounts of water, either directly related to the process (i.e., the coagulation bath of the phase inversion process) or for membrane post-treatment. Solvent-based membrane production processes contaminate the process water stream as residual organic solvents from previous process steps dissolve completely or partially in the aqueous phase, which causes additional waste.

[0006] A method for preparing porous polymer membranes without using organic solvents is known from WO 02 / 34819, in which a polymer and a particulate inorganic component are hot mixed and cast into a film form, and the film form is subsequently immersed in an acidic or alkaline solution to dissolve and thus remove the particulate inorganic component. The method is intended for preparing waterproof and gas-permeable polymer membranes layered directly on films or fibers.

[0007] EP 0477689 discloses a process for preparing porous polysulfone media suitable for use in filtration: Polysulfone is blended with a particulate solid or a particulate solid and a water-soluble second polymer, the blend is formed into a desired shape, and immersed in a solvent in which the polysulfone is insoluble, causing the soluble polymer and particulate solid to leach out of the filter, thereby leaving pores.

[0008] However, the above-mentioned process is not suitable for producing relatively thick porous polymer structures with high porosity because template dissolution becomes increasingly difficult as the film thickness increases due to diffusion limitations of the solvent used for template removal. Achieving complete dissolution is particularly difficult or time-consuming when a polymer is used as a pore-forming template. Template removal is further hindered by the fact that pores at or near the surface of such extrudates are not easily accessible to the solvent due to skin formation, i.e., a fairly closed pore structure, resulting from caulking. Caulking is typically performed by a unit downstream of the extruder to fix the extruded material to the desired product dimensions. As a result, the resulting porous polymer membranes feature reduced throughput. Summary of the Invention [Problem to be solved by the invention]

[0009] It is therefore an object of the present invention to overcome these and other drawbacks of the prior art, and in particular to provide an improved method for producing porous polymer structures that is not based on the use of any organic solvents and that is reliable, cost-effective, rapid, and compatible with existing manufacturing processes in the industry. A further object is to provide porous polymer structures, in particular membranes, that are suitable for advanced applications such as breathable textile materials or filters for liquid and / or air purification. [Means for solving the problem]

[0010] These objects are achieved by a method for producing a porous polymer structure, a mixture for producing said structure, a kit for providing said mixture, a porous polymer membrane, a shaped article and the use of the mixture or the kit in a method for producing a porous polymer structure according to the independent claims. Preferred embodiments are disclosed in this specification and in the dependent claims.

[0011] The present invention will be described in more detail below.It is understood that the various embodiments, preferences and scopes provided / disclosed herein can be arbitrarily combined.It is further understood that all references specified herein are incorporated by reference in their entirety.

[0012] According to a first aspect of the present invention, a method for producing a porous polymer structure, in particular a membrane, having pore sizes of 1 to 5000 nm, preferably 2 to 1000 nm, most preferably 5 to 400 nm, is provided, comprising: (a) 1 to 90 wt. % of one or more polymers and / or oligomeric precursors of polymers; . providing a mixture comprising 5-95 wt. % of one or more salt nanoparticles and / or microparticles, 0-70 wt. % of one or more fillers, and 0-40 wt. % of one or more additives, wherein at least a portion of the one or more salt nanoparticles and / or microparticles, preferably 1-100 wt. % of the one or more salt nanoparticles and / or microparticles, more preferably 40-85 wt. % of the one or more salt nanoparticles and / or microparticles, is one or more solid acids, and the polymer to particle ratio is in the range of 3:1 to 1:10 by weight; (b) optionally adapting the water content of the mixture; and (c) optionally homogenizing the mixture to form a blend. (d) molding the blend; (e) optionally coating a substrate with the blend; (f) optionally subjecting the resulting material to a drying and / or cooling step; (g) optionally subjecting the material thus obtained to further reshaping and / or processing; (h) optionally subjecting the material thus obtained to a polymerization or crosslinking step; (i) removing the one or more salt particles with a non-organic solvent, preferably by dissolving the salt particles in a non-organic solvent; and (j) optionally removing the resulting porous polymer structure from the substrate.

[0013] Surprisingly, it has been found that template removal can be significantly accelerated by replacing at least a portion of one or more salt nanoparticles and / or microparticles with one or more solid acids. This allows for the production of thicker porous polymer structures at a given production rate while maintaining good throughput and retention properties of the resulting membrane. Of course, it is contemplated that the entire amount of nanoparticles and / or microparticles used can be replaced with one or more solid acids according to the present invention. It was also surprising that the use of particulate salts provides an improved process that, on the one hand, provides suitable pores in the structure and, on the other hand, provides improved production speed. This is unexpected, as one skilled in the art would expect the salt nanoparticles and / or microparticles to be individually coated by the molten polymer and thus protected from template dissolution.

[0014] While the prior art uses a combination of polymers, organic solvents, and / or salt nanoparticles and / or microparticles as starting materials, the present invention uses only polymers and salt nanoparticles and / or microparticles, i.e., those containing one or more solid acids, as starting materials without using any organic solvents, which is considered advantageous as the environmental burden of solvent-driven processes is increasing and their use is becoming increasingly restricted, especially for solvents that fall under the Substances of Very High Concern (SVHC) category (e.g., N,N-dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, among others).

[0015] It is also believed that the described processes may be considered advantageous with respect to the use of process water, since contamination of water by organic solvents is not a factor due to the lack of organic solvents in the manufacturing processes described herein.

[0016] The manufacturing methods described below provide porous materials of virtually unlimited size. Because manufacturing steps (a)-(j) impose no limitations on the size of the material (excluding the equipment used), large sheet materials can be obtained in terms of length, width, and thickness. For example, the present invention also provides the methods disclosed herein, in which the porous polymer structures have an area of ​​greater than 100 cm2, preferably greater than 400 cm2.

[0017] The manufacturing process is also believed to be advantageous because the individual steps are already known and used in industry. Furthermore, the process described herein can be carried out in a continuous process, which has a beneficial effect on the speed and efficiency of the overall production process and production costs.

[0018] Unless otherwise stated, the following definitions apply herein. The "porosity" of a material described herein is the volume percentage (vol %) of pores of the total material. Porosity can be determined by porosimetry, by measuring the apparent material density, by BET analysis, or from microscopic images. In case of discrepancies between values ​​obtained by different methods, the value obtained by porosimetry according to ISO 15901-2 applies. For the invention described herein, the pore structure is essentially an open pore structure.

[0019] The "permeability" of a material described herein is defined as the flux of a fluid (i.e., a liquid or gaseous medium) through the interconnected pores of the material. Permeability can be determined by measuring the volume of liquid or gas passing through a given area of ​​the porous structure in a given time at an applied pressure. A typical measure of this flux is milliliters per square centimeter, bar, and milliliters per minute (ml / cm2 * bar * min).

[0020] The term "nanoparticles and microparticles" as used herein includes crystalline, semi-crystalline, or amorphous materials. Such particles have diameters in the submicron to micron range. The primary particle size is preferably 1 to 50,000 nm. A suitable method for determining primary particle size can be found in Limbach et al. (Environmental Science & Technology, 2005. 39(23): pp. 9370-9376). Salt nanoparticles and microparticles can be obtained from a range of preparation methods, including high-temperature gas-phase processes (such as flame synthesis, laser processes, and plasma processes) and liquid-phase chemical methods (such as precipitation and sol-gel processes).

[0021] The term "solid acid" as used herein refers to a compound that is solid at the temperature used for forming the mixture containing the polymer and particles, and that causes a decrease in pH when added to distilled water. The solid acid that can be used in accordance with the present invention is essentially unreactive in the absence of water under the conditions used for forming the mixture containing one or more polymers and one or more salt nanoparticles and / or microparticles. In particular, the solid acid used has a melting point above 50°C, preferably above 110°C, and most preferably above 170°C.

[0022] The term "primary molding" (German "Urformen") as used herein refers to the production of solids from shapeless materials by creating cohesive forces (DIN 8580). Shapeless materials are any starting material without a defined shape, such as powders, fibers, chips, granules, solutions, melts, etc. Primary molding of polymers can be divided into two groups based on the product's shape and its further processing: products produced by primary molding that are further processed by molding, shearing, cutting, and joining, and products produced by primary molding that essentially have the shape and dimensions of a finished component or final product. In the latter case, the shape of such a product essentially corresponds to the product's purpose.

[0023] The "specific surface area" of a material described herein is the total air-polymer interfacial area per amount of polymer mass. This surface area can be determined by physical adsorption of gas molecules, such as nitrogen molecules, using the BET method (Janssen et al., Journal of Applied Polymer Science 52, 1913, 1994). The basic principle of the measurement is that a material with a large surface area can adsorb more molecules of nitrogen on its surface (assuming a molecular monolayer).

[0024] A "washing solvent" as used herein is a non-organic solvent (e.g., water) used to remove salt particles from a polymer matrix by dissolving them in said non-organic solvent. Washing solvents are characterized by not dissolving the polymers used in the manufacturing processes described herein. Furthermore, washing solvents are preferably used in the methods described herein, but are not necessarily used in a liquid aggregate state.

[0025] The first aspect of the invention is described in further detail below, whereby the process steps are described first and suitable materials are described afterwards.

[0026] Step (a): A mixture of salt nanoparticles and / or microparticles, polymer and / or its oligomeric precursor, and optionally additives and / or fillers is first provided. The polymer content is 1-90 wt.%, preferably 5-65 wt.%, most preferably 10-45 wt.%. The salt nanoparticle and / or microparticle content is 0. .The content of the filler is 0 to 70 wt%, preferably 0 to 40 wt%, and the content of the additive is 0 to 40 wt%. Preferably, no additives are added to the mixture. It has been found particularly advantageous to combine these starting materials in powder form. In this way, thorough mixing can be achieved by vigorously stirring the components of the mixture. At least a portion of the one or more salt nanoparticles and / or microparticles, preferably 1 to 100 wt% of the one or more salt nanoparticles and / or microparticles, more preferably 40 to 85 wt% of the one or more salt nanoparticles and / or microparticles, is one or more solid acids. The polymer:particle ratio (wt%) is in the range of 3:1 to 1:10, preferably 2:1 to 1:9. Such a relatively high amount of salt nanoparticles and / or microparticles ensures proper pore formation within the resulting porous polymer structure. Without being bound by theory, it is believed that smaller amounts do not provide interconnected necks.

[0027] Step (b): The water content of the mixture is optionally adapted to account for the different moisture absorption behavior of different polymers. As used herein, the term "adapted" means that the water content of the mixture is measured and adjusted to a target value.

[0028] Step (c): Optionally, the same mixture is further homogenized to obtain a homogenous blend. This process step can be part of the subsequent step (d). Homogenization can be carried out at elevated temperatures, i.e., above the glass transition temperature of the mixture, and / or under inert conditions to avoid polymer degradation and degradation of the blend properties, respectively. Homogenizing the mixture has the advantage that the salt particles are uniformly distributed throughout the polymer matrix, resulting in a uniform distribution of pores in the structure.

[0029] Step (d): The blend of step (c) is shaped, i.e., the blend containing the mixture of salt nanoparticles and / or microparticles, i.e., the blend containing one or more solid acids, and the polymer in a shapeless state are given an initial shape. It is understood that the homogenization step (c) and the shaping step (d) can each coincide or occur in one combined step.

[0030] Step (e): Optionally, the blend can be applied onto a substrate by a suitable coating method known in the art, such as extrusion, dip coating, or casting, among others. This results in a substrate-supported coating comprising a percolating network of salt particles, i.e., one or more solid acids, in a polymer matrix (i.e., a bicontinuous structured network of polymer and salt). Coating a substrate has the advantage that the substrate acts as a support material and can determine the preliminary or final shape of the porous polymer structure to be formed.

[0031] Step (f): The coated material may then be subjected to a drying or cooling step, thereby achieving dimensional stability of the physically solidified or thermoplastic material.

[0032] Step (g): The material obtained from step (e) may also be subjected to further reshaping and / or processing steps intended to adapt the thickness of the material and / or to join said material to further composites. Suitable methods are known in the art and include lamination, pleating, or post-calendering.

[0033] Step (h): The coated material of step (e) may be subjected to a polymerization and / or cross-linking step. This step is optional and may be applied when suitable starting materials are used, in particular oligomers and / or monomers that can be polymerized, optionally in the presence of an initiator (polymerization), or when the polymer contains groups that can be cross-linked, optionally in the presence of a cross-linking agent (cross-linking step).

[0034] Step (i): The continuous salt phase in such a composite, i.e., the salt phase containing one or more solid acids, dissolves, resulting in a porous polymer structure on the substrate. Aqueous solvents, such as water or aqueous acid solutions, are particularly suitable. The choice of washing solvent depends, inter alia, on the type of salt used. The washing solvent in step (i) is selected to ensure dissolution of the salt nanoparticles and / or microparticles without dissolving the polymer.

[0035] Step (j): The substrate may optionally be removed from the porous material, for example by peeling, to obtain a free-standing porous polymer structure, or may be transferred to another substrate. This removal step may occur after washing step (i) or before washing step (i) (as further outlined below). Step (j) may be carried out using processes known per se. The purpose of removal step (j) is to remove the substrate to obtain an unsupported porous material, or to transfer the porous material to another support material to obtain a coated article.

[0036] In an alternative embodiment, the present invention provides a method as described herein, wherein step (j) is performed before any of steps (f) to (i), as shown on the right side in Figure 1.

[0037] For example, the present invention also relates to a method for producing a porous polymer structure, comprising the steps of: (a) providing a mixture of one or more solids, i.e., a mixture comprising one or more solid acids, as described herein; (b) optionally adapting the moisture content of said mixture; (c) optionally homogenizing said mixture to form a blend; (d) molding said blend; (e) optionally coating a substrate with said blend; (f) optionally subjecting the material thus obtained to a drying and / or cooling step; (g) optionally subjecting the material thus obtained to further reshaping and / or processing; (h) optionally subjecting the material thus obtained to a polymerization or crosslinking step; (j) removing the material thus obtained from said substrate; and (i) removing said one or more salt nanoparticles and / or microparticles by a dissolution step, thereby obtaining a porous polymer structure.

[0038] The preparation of suitable salt nanoparticles and / or microparticles is known in the art.In a broad sense, any salt nanoparticles and / or microparticles can be used in the mixture of the present invention.Suitable salt nanoparticles and / or microparticles can be selected from a wide range of known salts, particularly metal salts, and their combinations.

[0039] Preferably, the salt nanoparticles and / or microparticles are selected from the group consisting of oxides, carbonates (including bicarbonates), sulfates, halides, nitrates, and phosphates, preferably carbonates or oxides. Examples include CaCO3, BaCO3, SrCO3, Na2CO3, K2CO3, NaCl, ZnO, CaO.

[0040] Preferably, the one or more solid acids are selected from the group consisting of carboxylic acids, sulfonic acids, phosphonic acids, pyrophosphoric acids, amino acids, Lewis acids, and derivatives thereof.

[0041] Examples of solid acids that belong to the class of carboxylic acids or derivatives of carboxylic acids and that can be particularly preferably used in the invention described herein are oxalic acid, tartaric acid, citric acid, mandelic acid, ascorbic acid, and / or ethylenediaminetetraacetic acid.

[0042] Examples of solid acids that belong to the class of sulfonic acids or derivatives of sulfonic acids and that can be used particularly preferably in the invention described herein are sulfamic acid and / or 2-aminoethanesulfonic acid.

[0043] Examples of solid acids that belong to the class of amino acids and that can be particularly preferably used in the invention described herein are cysteine ​​and / or methionine.

[0044] Examples of solid acids that belong to the class of Lewis acids and that can be particularly preferably used in the invention described herein are boric acid, AlCl3, and / or FeCl3.

[0045] Further examples of solid acids that can be particularly preferably used in the invention described herein are acid-coated nanoparticles and / or microparticles.

[0046] Preferably, 1 to 100% by weight of the one or more salt nanoparticles and / or microparticles is replaced with one or more solid acids, particularly preferably 40 to 85% by weight of the one or more salt nanoparticles and / or microparticles is replaced with one or more solid acids.

[0047] Preferably, the salt nanoparticles and / or microparticles have a particle size of 1 to 50,000 nm, preferably 5 to 20,000 nm, most preferably 10 to 10,000 nm.

[0048] By suitable selection of salt nanoparticles and / or microparticles (size and amount) and by selection of process parameters (coating thickness, drying time, etc.), the porosity and pore size distribution can be varied over a wide range.

[0049] Preferably, the salt is prepared in a separate process prior to step (a). Thus, the present invention also relates to methods described herein, wherein the salt nanoparticles and / or microparticles are not prepared in situ.

[0050] While the use of pre-fabricated salt nanoparticles and / or microparticles is advantageous, in situ formation of salt nanoparticles and / or microparticles has been found to be less preferred.

[0051] Preferably, the salt nanoparticles and / or microparticles are selected from the group consisting of carbonates (including bicarbonates) and oxides, and the manufacturing method is carried out continuously. Surprisingly, it has been found that when using such salts as starting materials, a continuous manufacturing process for porous polymer structures can be realized. This can be attributed to the particularly rapid dissolution and complete removal of the salts in aqueous solutions, especially acidic solutions.

[0052] In a further embodiment, the washing step (i) is repeated. In this way, complete removal of salt nanoparticles and / or microparticles can be achieved, if necessary. Therefore, step (i) can also include multiple washing and drying steps. When using a multi-step protocol, either the same or different washing solvents can be used, for example, first a diluted aqueous acid solution, followed by water.

[0053] Suitable polymers include those that are not soluble in the above-mentioned wash solvents and may be selected from a wide range of known polymers, such as amorphous polymers, semi-crystalline polymers, crosslinkable polymers, polymerizable oligomers, and combinations thereof.

[0054] Thus, suitable polymers include polysulfone, polyethersulfone, polycarbonate, polystyrene, polyacrylate, polysiloxane, polyarylate, polyurethane, halogenated polyolefins such as polyvinylidene fluoride (PVDF), polyethylene, polyimide, polyamide, liquid crystal polymer, cellulose acetate, and polyetherketones such as polyetheretherketone (PEEK). The present invention also includes the use of copolymers, mixtures of polymers ("polymer blends"), and chemically modified polymers thereof, such as polymers modified by sulfonation, amination, and hydroxylation.

[0055] Preferably, the polymer used in the methods described herein is selected from the group consisting of polysulfone, polyethersulfone, polycarbonate, polystyrene, polyacrylate, polysiloxane, polyarylate, polyurethane, polyester, polyether, polyimide, polyamide, halogenated polyolefin, cellulose acetate, and liquid crystal polymer.

[0056] Optionally, said polymer is selected from the group consisting of oligomers that can be polymerized or polymers that can be crosslinked.

[0057] The use of oligomers can provide lower viscosity and facilitate coating of substrates, especially when the substrate features complex geometries or when complete coverage of the substrate is desired. Crosslinking can increase the durability of the coating and / or free-standing porous polymer structure, respectively, after removal from the substrate.

[0058] Suitable additives may be selected from a wide range of known additives and mixtures thereof, as known in the art. In particular, the additives may be selected from the group consisting of surfactants, polymerization initiators, stabilizers, crosslinkers, wetting agents.

[0059] Suitable fillers can be selected from a wide range of known additives and their mixtures, and are known in the art. In particular, fillers can be selected from the group consisting of glass, fiber, or minerals to affect tensile strength, toughness, heat resistance, color, transparency, and other properties. In contrast to salt nanoparticles and / or microparticles, fillers are not removed by the dissolution step (i) and remain within the porous polymer structure.

[0060] The addition of fillers to polymer resins can improve certain properties (e.g., mechanical properties) and reduce costs. Such improvements can consist of, but are not limited to, increased tensile strength, toughness, electrical conductivity, or heat resistance.

[0061] Suitable substrates can be selected from a wide range of known substrates. The substrate can be any support that is compatible with the manufacturing process. It is further advantageous if the coating can be adhered to the substrate during manufacturing and removed after manufacturing.

[0062] Preferably, the support material is selected from the group consisting of polymers (preferably semi-crystalline or crystalline), rubber, metal, ceramic, and glass. Alternatively, the support material is selected from the group consisting of films, woven fabrics, or non-woven textiles. In either case, the support material can have a two-dimensional or three-dimensional shape and can be coated or uncoated.

[0063] In a preferred embodiment, the primary shaping in step (d) is carried out by extruding the mixture through a die to form a continuous structure, preferably with a constant cross section, such as a flat membrane, a sheet, a single tube, a multi-hole tube, or a honeycomb structure, among others.

[0064] The term "sheet material" or "porous foil" indicates that the material has a length and width that are at least one order of magnitude greater (preferably two orders of magnitude greater) than the thickness of the material. Such films and sheets consist solely of the porous polymer material according to the present invention.

[0065] In an alternative embodiment, the initial shaping in step (d) is carried out by casting the mixture, preferably to form a part having a shape other than a film or sheet. In particular, such a part may comprise multiple materials with different properties and / or non-uniform cross-sections. Suitable casting methods are known in the art, such as injection molding.

[0066] The term "non-uniform cross-section" indicates that the cross-sectional profile of a portion varies across said cross-section and / or that the cross-sectional thickness of the porous polymer structure itself varies across said cross-section.

[0067] Preferably, one or more of steps (a) to (j), preferably all steps (a) to (j), are carried out consecutively.

[0068] As used herein, the term "continuously carried out" refers to a flow production method used to manufacture, produce, or process materials without interruption, i.e., the material being processed is in continuous motion, undergoes chemical reactions, or is subjected to mechanical or thermal treatments. Continuous processing is contrasted with batch production.

[0069] Preferably, the coating step (e) is selected from the group consisting of spraying, roll-to-roll processes.

[0070] By adapting at least some steps of the methods disclosed herein to a continuous process, the production of porous polymer structures can be designed to be rapid and cost-effective.

[0071] It has been found that the surface of the primary molding mixture is characterized by a substantially closed structure, i.e. the size of the pores connecting the interior of the porous polymer structure to its exterior is significantly smaller compared to the pore size found in the bulk material. This closed pore structure of the surface is due to the calibration of the mixture during primary molding and / or due to the contact of the mixture with objects such as rollers used to transport the primary molding material and which form an interface between the porous polymer structure and said calibration or transport unit.

[0072] Preferably, the methods disclosed herein include an additional step (k) of exposing the interior bulk material of the primary molding mixture. In this embodiment, step (k) is performed after step (d) and before any of steps (e)-(i). Alternatively, step (k) is performed after any of steps (d)-(h) and before step (i).

[0073] This internal porous structure can be exposed by, for example, splitting the extruded sheet into two equal halves by attaching them to two cooling rollers moving relative to each other. As will be explained in more detail later, the still-warm, and therefore moldable, material inside the sheet is eventually torn open. The resulting porous polymer structure is characterized by an asymmetric longitudinal cross-section, with one side having a more open structure than the other, i.e., the membrane has a fairly closed pore structure on one side and a particularly open pore structure on the opposite side.

[0074] In a second aspect, the present invention relates to intermediates, i.e., mixtures, useful for producing porous polymer structures according to the methods disclosed herein. This aspect of the invention will be described in more detail below.

[0075] Suitable mixtures can be prepared from the above starting materials using known techniques. In a preferred embodiment, the mixture for producing porous polymer structures, in particular the mixture for use in the methods described herein, comprises 1 to 90 wt. %, preferably 5 to 65 wt. %, and most preferably 10 to 45 wt. % polymer; 0.5 to 95 wt. %, preferably 20 to 90 wt. %, and most preferably 40 to 85 wt. % salt nanoparticles and / or microparticles having a primary particle size of 1 to 50,000 nm, preferably 5 to 20,000 nm, and most preferably 10 to 10,000 nm; 0 to 70 wt. %, preferably 0 to 40 wt. % filler; and 0 to 40 wt. % additive as defined herein, wherein at least a portion of the one or more salt nanoparticles and / or microparticles, preferably 1 to 100 wt. % of the one or more salt nanoparticles and / or microparticles, more preferably 40 to 85 wt. % of the one or more salt nanoparticles and / or microparticles, is one or more solid acids, whereby the polymer to nanoparticle ratio is in the range of 3:1 to 1:10 (wt. %), preferably 2:1 to 1:9 (wt. %).

[0076] Preferably, the polymer is selected from the group consisting of polysulfone, polyethersulfone, polycarbonate, polystyrene, polyacrylate, polysiloxane, polyarylate, polyurethane, polyester, polyether, polyimide, polyamide, halogenated polyolefin, cellulose acetate, and liquid crystal polymer.

[0077] Preferably, the mixture is additive-free. According to a third aspect of the invention, the invention relates to a kit for preparing the mixtures described herein. This aspect of the invention will be explained in more detail below.

[0078] In certain embodiments, it has been found that the polymer can react with other parts of the mixture. Nevertheless, such mixtures are suitable for the methods of the present invention. Accordingly, the present invention relates to both the mixtures and kits of parts described herein, wherein the kits of parts comprise at least two parts, a first part comprising one or more types of salt nanoparticles and / or microparticles, wherein at least a portion of the one or more salt nanoparticles and / or microparticles, preferably 1 to 100% by weight of the one or more salt nanoparticles and / or microparticles, more preferably 40 to 85% by weight of the one or more salt nanoparticles and / or microparticles, is one or more solid acids, and a second part comprising one or more polymers.

[0079] Preferably, a kit of parts according to the present invention disclosed herein comprises a first part comprising salt nanoparticles and / or microparticles, wherein at least a portion of the one or more salt nanoparticles and / or microparticles, preferably 1-100% by weight of the one or more salt nanoparticles and / or microparticles, more preferably 40-85% by weight of the one or more salt nanoparticles and / or microparticles, is one or more solid acids, additives, and fillers as described herein, and a second part comprising a polymer, additive, and filler as described herein.

[0080] In a fourth aspect, the present invention relates to novel porous polymer structures, in particular membranes, and shaped articles comprising such porous polymer structures. This aspect of the invention will be described in more detail below.

[0081] In one embodiment, the present invention relates to porous polymer structures, particularly membranes, obtainable by the methods disclosed herein.

[0082] In a preferred embodiment, the porous polymer structure according to the invention is characterized by a maximum wall thickness of 1000 μm, preferably 50 nm to 400 μm, for structures with a constant cross section, or 4000 μm, preferably 800 μm to 3100 μm, for sections with a non-uniform cross section, and / or a porosity of 10 vol. % to 95 vol. %, preferably 20 vol. % to 90 vol. %, and / or a pore size of 1 nm to 5 μm, preferably 2 nm to 1 μm, most preferably 5 nm to 400 nm.

[0083] In a preferred embodiment, the porous polymer structure of the present invention has a porosity of 10 to 95%, preferably greater than 20 to 90%, and a pore size of 1 nm to 5 μm, preferably 2 nm to 1 μm, most preferably 5 nm to 400 nm.

[0084] In further embodiments, the present invention relates to porous polymer structures as described herein that are impermeable to biological materials, including bacteria, viruses, cells, and / or are impermeable to inorganic materials, including salt nanoparticles and / or microparticles.

[0085] In a further embodiment, the present invention relates to porous polymer structures described herein that are permeable to liquids (including water), gases (including air), and dissolved materials (including metal ions and proteins). Typically, the cutoff of the porous polymer structures of the present invention is in the range of 5 to 400 nm. Typically, the flow of the porous polymer structures of the present invention is in the range of 0.01 to 200 ml / min / cm2 at 1 bar, preferably 0.1 to 10 ml / min / cm2 at 1 bar.

[0086] As outlined above, a wide variety of polymers can be used in the porous polymer structure of the present invention. This is considered advantageous because currently known porous polymer structures are limited in terms of suitable materials and / or pore characteristics. Suitable polymers can be selected from the group of polymers soluble in organic solvents, including polyesters; polyethers such as polyetheretherketone (PEEK); polysulfones (PSU); polyethersulfones (PES); polyphenylene sulfones (PPSU); polycarbonates (PC); polyacrylates such as polymethacrylates (PMMA); polystyrenes (PS); polysiloxanes such as polydimethylsiloxanes (PDMS); polyimides (PI); polyamides (PA); polyethylenes (PE); halogenated polyolefins such as polyvinylidene fluoride (PVDF); cellulose acetates (CA), and liquid crystal polymers.

[0087] As outlined above, the materials of the present invention are porous and characterized by the size, type, and amount of pores, which can be influenced by the starting materials, the ratio of salt nanoparticles and / or microparticles to polymer, and the manufacturing process.

[0088] The pore size of the porous polymer structure of the present invention (defined by the diameter of the salt nanoparticles and / or microparticles) is typically in the nanoscale or microscale range, typically 1 to 5,000 nm, preferably 2 to 1,000 nm, and more preferably 5 to 400 nm. Pore size can be determined by microscopy. Furthermore, the pore size distribution can be precisely adjusted based on the starting materials used.

[0089] The pore size of particles with a particle size between 0.01 µm and 5 µm is determined by the fluorescence readout from fluorescently labeled polystyrene or silica microspheres according to the following measurement protocol, which shows test particles with a size of 0.5 µm as an example.

[0090] (i) Preparation of challenge solution: Fluorescent particles available from ThermoFisher (FluoSpheres™, 0.5 μm, red fluorescence (580 / 605), F8812) or Micromod Partikeltechnologie GmbH (product code: 42-00-502sicastar®-greenF) are diluted with 0.01% volume of polyoxyethylene (20) sorbitan monooleate (Tween® 80) in deionized water to give a final particle concentration of 1:1000.

[0091] (ii) Bead retention test The sample of porous polymer structure to be analyzed is mounted in a filter housing (effective filter area 6-20 cm2) equipped with a woven or nonwoven support structure (e.g., Novatexx 2413, Freudenberg) to support the sample in the filter housing. The support must be such that mechanical stress on the membrane is minimized and the membrane does not stretch under pressure. A defined volume of challenge solution is poured into the resulting test cell. The challenge solution is passed through the sample at an air pressure of 1-6 bar until the membrane's inherent bubble point is overcome and the entire volume of the challenge solution has passed through the sample. The permeate is discarded and step (ii) is repeated. This time, the permeate is collected in a clean plastic weighing dish for analysis.

[0092] (iii) Analysis Pipette deionized water, challenge solution, and permeate solution (250 µL each) into a well plate (e.g., a 96-well plate). Perform fluorescence readout using a plate reader (e.g., Tecan) using the following protocol: ●Followed by 10 seconds of orbital shaking, Top readout of red fluorescent particles without lid, Ex. / Em. 540(25) / 620(20) nm, "full" signal, 25 flashes, 20 μs integration time, gain calculated from a well with a filled 3x3 square readout with a 1000 μm boundary. Top readout of green fluorescent particles without lid, Ex. / Em. 465(20) / 510(20) nm, "full" signal, 25 flashes, 20 μs integration time, gain calculated from a well with a filled 3x3 square readout with a 1000 μm boundary.

[0093] The water reading represents the blank signal, the challenge solution reading represents the full signal, and the permeate reading represents the sample signal.

[0094] The retention rate R is then calculated from the wells as follows:

[0095]

number

[0096] If R is greater than 90%, the challenge particle is filtered out and the porous polymer structure is said to have a pore size smaller than the challenge particle size (in this example, it is 0.5 μm).

[0097] (iv) Dilution Adaptation If the blank fluorescence reading is more than 10% of the full fluorescence reading, the dilution shall be reduced until the blank is less than 10% of full.

[0098] The pore size of particles with a particle size between 1 nm and 100 nm is determined by a dextran rejection test performed to determine the molecular weight cutoff (for details, see G. Tkacik, S. Michaels, Nature Biotechnology. 9:941-946, 1991): membranes capable of rejecting at least 90% of macromolecules of 1000 kDa can be classified as having a MWCO of 1000 kDa. A 0.1 wt% mixture of different dextran standards (5 kDa, 25 kDa, 80 kDa, 150 kDa, 270 kDa, 410 kDa, 670 kDa, and 1400 kDa) (Fluka, CH) was prepared in 0.1 M sodium nitrate (denoted as NaNO) buffer solution. Equal amounts of the individual standards were mixed. The mixture was filtered (forward flow) through the membrane using a high-vacuum pump (Edwards Vacuum Ltd). The permeate and the mixture were compared using gel permeation chromatography.

[0099] Thus, for example, the MWCO of a membrane that exhibits a minimum rejection of 95% for a 1400 kDa dextran standard molecule can be classified as 1400 kDa.

[0100] If the two methods described herein for determining pore size yield different results, the results obtained by fluorescence readout are definitive.

[0101] The porosity, i.e., the volume of pores relative to the volume of the entire structure, can vary within a wide range. The materials of the present invention exhibit a porosity in the range of 10 to 95% by volume, preferably 20 to 90% by volume. The porosity can be determined by porosimetry.

[0102] The pores of a material can be arranged so that the material is permeable, partially permeable, or impermeable. If essentially all of the pores of a material have dead ends, the material is impermeable. Conversely, if essentially all of the pores of a material have open ends, the material is considered permeable. Consequently, if some of the pores have dead ends, the material is considered partially permeable.

[0103] In an advantageous embodiment, the present invention provides a porous polymer structure in which at least 90% of said pores are interconnected.

[0104] A wide variety of articles may be equipped with the porous polymeric structures of the present invention or may be produced directly using the porous polymeric structures of the present invention.

[0105] In one embodiment, the present invention relates to a molded article comprising the porous polymeric structure described herein.

[0106] In a further embodiment, the shaped article comprises a substrate and a coating, preferably a top coating, said coating consisting of a porous material as defined herein.

[0107] In a further embodiment, the present invention relates to an article obtainable or obtained by the methods described herein.

[0108] Preferably, the shaped article is selected from the group consisting of pleated or non-pleated filters, woven or non-woven fabrics (wherein the porous polymer structure is laminated onto the fabric), or molded parts that can again form filter units.

[0109] In particular, direct molding into the final element is considered inventive because the process allows for the reduction of additional process steps (e.g., no attachment or bonding of the porous polymer structure to the molded article). This is also beneficial to the overall efficiency of the process. Furthermore, avoiding a post-attachment or bonding step also reduces the risk of poorly bonded parts. Therefore, the present invention may increase the reliability of the parts.

[0110] The present invention further provides a method for producing a porous polymer structure as described herein, comprising subjecting a shaped article (containing a substrate and a coating) to a dissolution step (i) and, optionally, a step (step j) of removing said support from the shaped article thus obtained. Dissolution step (i) aims to remove all or essentially all salt particles from said article, as outlined above. Removal step (j) aims to remove the substrate to obtain an unsupported porous material or to transfer the porous material to another support material to obtain a coated article, as outlined above.

[0111] In a fifth aspect, the present invention relates to uses or methods of using the intermediates, porous polymer structures, and shaped articles described herein.

[0112] In one embodiment, the present invention relates to the use of a mixture as described herein or a kit of parts as described herein in a method for producing a porous polymeric structure of the present invention.

[0113] In an alternative embodiment, the present invention relates to the use of the porous polymer structures described herein in filter (e.g., pleated or non-pleated) devices or as part of a woven or nonwoven fabric. The porous polymer structures of the present invention have been found to be useful in many applications, including filter materials and textile materials.

[0114] The porous polymer structures of the present invention are self-supporting ("free-standing"). Therefore, they are distinct from known porous polymer structures of similar thickness and porosity on a support. However, the materials of the present invention are suitable for coating any suitable support. The possibility of producing such porous polymer structures independently of a specific support makes them highly versatile.

[0115] In yet another alternative embodiment, the porous polymer structures of the present invention are used in known microfiltration, ultrafiltration, and / or nanofiltration processes. Microfiltration is used to separate particles of 100-1000 nm, such as bacteria. Ultrafiltration is used to separate particles of 10-100 nm, such as viruses, proteins, and colloids. Nanofiltration is used to separate particles of 1-10 nm, such as salts, pesticides, and sugars.

[0116] Generally, the shaped articles of the present invention retain the beneficial properties of the porous polymeric structures defined herein and are therefore suitable for all uses applicable to such porous polymeric structures, including in particular the uses disclosed herein such as microfiltration, ultrafiltration, nanofiltration (e.g., sterile or viral filtration, or concentration of biological molecules such as proteins).

[0117] In a further embodiment, the present invention relates to the use of an article as defined herein in a filter and / or textile material.

[0118] The following further embodiments of the invention are contemplated: I. A method for producing porous polymer structures, in particular membranes, having pore sizes of 1 to 5000 nm, preferably 2 to 1000 nm, most preferably 5 to 400 nm, comprising: a) providing a mixture, 1 to 90% by weight, preferably 5 to 65% by weight, most preferably 10 to 45% by weight of one or more polymers and / or oligomeric precursors of said polymers, having a primary particle size of 1 to 50,000 nm, preferably 5 to 20,000 nm, and most preferably 10 to 10,000 nm . 5 to 95% by weight, preferably 20 to 90% by weight, most preferably 40 to 85% by weight of one or more salt nanoparticles and / or microparticles, 0 to 70% by weight, preferably 0 to 40% by weight, of one or more fillers, containing 0 to 40% by weight of one or more additives, preferably no additives, a polymer:particle ratio in the range of 3:1 to 1:10 by weight, preferably 2:1 to 1:9; b) optionally adapting the water content of said mixture; c) optionally homogenizing the mixture; d) molding the mixture; e) optionally coating a substrate with said mixture; f) optionally subjecting the obtained material to a drying and / or cooling step; g) optionally subjecting the material thus obtained to further reshaping and / or further processing; h) optionally subjecting the material thus obtained to a polymerization or crosslinking step; i) removing said one or more salt particles with a non-organic solvent, preferably by dissolving said salt particles in a non-organic solvent; j) optionally removing the resulting porous polymer structure from said substrate.

[0119] II. The method of embodiment I, wherein step (j) is performed before any of steps (f)-(i).

[0120] III. The method of embodiment I or II, wherein the forming in step (d) is carried out by extruding the mixture through a die to form a porous polymeric structure, preferably having a constant cross-section.

[0121] IV. The method of embodiment I or II, wherein the forming in step (d) is carried out by casting the mixture to form a part, preferably having a non-uniform cross-section.

[0122] V. The method of any preceding embodiment I-IV, wherein one or more of steps (a)-(j) are performed sequentially.

[0123] VI. The method of any of the preceding embodiments I-V, wherein said coating step (e) is selected from the group consisting of spraying, roll-to-roll processes.

[0124] VII.a) the nanoparticles and / or microparticles are selected from the group consisting of oxides, carbonates, sulfates, halides, nitrates, and phosphates, preferably carbonates and oxides, most preferably CaCO3, BaCO3, SrCO3, Na2CO3, K2CO3, NaCl, ZnO, and CaO; and / or b) The method of any of the preceding embodiments I-VI, wherein the nanoparticles and / or microparticles have a particle size of 1-50000 nm, preferably 5-20000 nm, and most preferably 10-10000 nm.

[0125] VIII. The polymer i) polysulfones, polyethersulfones, polycarbonates, polystyrenes, polyacrylates, polysiloxanes, polyarylates, polyurethanes, polyesters, polyethers, polyimides, polyamides, halogenated polyolefins, cellulose acetate, and liquid crystal polymers; and / or ii) a polymer that can be crosslinked.

[0126] IX.a) the support material is made from or essentially comprises polymers, rubbers, metals, ceramics, and glasses; and / or b) the support material is a film, woven fabric, or nonwoven fabric; and / or c) The method of any of the preceding embodiments I-VIII, wherein the support material has a two-dimensional or three-dimensional shape.

[0127] X. A mixture for producing a porous polymer structure, in particular for carrying out the method according to any one of embodiments I to IX, 1 to 90% by weight, preferably 5 to 65% by weight, most preferably 10 to 45% by weight of one or more polymers, having a primary particle size of 1 to 50,000 nm, preferably 5 to 20,000 nm, and most preferably 10 to 10,000 nm . 5 to 95% by weight, preferably 20 to 90% by weight, most preferably 40 to 85% by weight of salt nanoparticles and / or microparticles; 0 to 70% by weight, preferably 0 to 40% by weight, of a filler; A mixture comprising 0-40% by weight of additives, preferably no additives, whereby the polymer:nanoparticle ratio is in the range of 3:1 to 1:10 by weight, preferably 2:1 to 1:9.

[0128] XI. A kit of parts for producing the mixture of embodiment X, wherein a first part comprises one or more types of salt nanoparticles and / or microparticles, and a second part comprises one or more polymers, preferably wherein the first part comprises salt nanoparticles and / or microparticles, additives, fillers, and the second part comprises polymers, additives, fillers.

[0129] XII. Porous polymer structures, in particular membranes, obtainable by the method according to any one of embodiments I to IX.

[0130] XIII. The porous polymer structure of embodiment XII, which comprises: a maximum wall thickness of 1000 μm, preferably 50 nm to 400 μm, for porous polymer structures with a constant cross section, or a maximum wall thickness of 4000 μm, preferably 800 μm to 3100 μm, for porous polymer structures with a non-uniform cross section; and / or a porosity of 10% to 95% by volume, preferably 20% to 90% by volume, and / or A porous polymer structure characterized by a pore size of 1 nm to 5 μm, preferably 2 nm to 1 μm, most preferably 5 nm to 400 nm.

[0131] XIV. A molded article comprising a porous polymer structure according to embodiment XII or XIII, in particular a molded article comprising a porous polymer structure according to embodiment XII or XIII, a) pleated or non-pleated filters, or b) woven or nonwoven fabrics, or c) Molded articles selected from the group consisting of molded parts.

[0132] XV. Use of the mixture according to embodiment X or the kit of parts according to embodiment XI in a method for producing a porous polymer structure, in particular in a method for producing a porous polymer structure according to any of embodiments I to IX.

[0133] The present invention will now be further described in more detail by the figures, in which, unless otherwise stated, like reference numerals will be used to refer to the same or similar elements. [Brief explanation of the drawings]

[0134] [Figure 1] 1 is a schematic diagram of a method for producing a porous polymer structure according to the present invention. [Figure 2] FIG. 1 is a schematic illustration of the variability of porous polymer structures obtained by using different dies. [Figure 3] 1 is an SEM image of a poly(propylene) membrane not according to the present invention. [Figure 4] 1 is an SEM image of a poly(ethylene) membrane according to the present invention. [Figure 5a] FIG. 1 is a schematic illustration of a method disclosed herein including exposing the interior bulk material of the primary molding mixture. [Figure 5b] FIG. 5a is an SEM image of a poly(propylene) film obtained by the method described above. DETAILED DESCRIPTION OF THE INVENTION

[0135] One embodiment of a method for producing a porous polymer membrane 1 of the present invention is shown in the left column of Figure 1. In the first step (a), a mixture 2 containing salt nanoparticles and / or microparticles is provided, where at least a portion of one or more salt nanoparticles and / or microparticles is one or more solid acids and a polymer. In the next step (b), the water content of the mixture 2 is optionally adjusted, and the components are thoroughly mixed in step (c) to obtain a homogeneous blend used to coat the substrate 3 in steps (d) and (e). The bicontinuous structured network of polymer and salt 4 thus obtained is optionally subjected to a drying and / or cooling step (f) and can be further reshaped and / or processed in step (g). Optionally, the coating 4 can be subjected to a polymerization or crosslinking step (h). Finally, in step (i), the nanoparticles and / or microparticles are removed from the coating 4 with a washing solvent to obtain a substrate-supported porous material 5. Then, in step (j), the porous polymer film 5 is removed from the support material 3 to obtain the membrane 1.

[0136] The right column in Figure 1 shows an alternative embodiment of the inventive method for producing a porous polymer membrane 1, in which step (j), i.e., separation of the salt / polymer composite film 4 from the substrate 3, is carried out before steps (f)-(i). Thus, an unsupported, "free-standing," bicontinuous structured network of polymer and salt 5 is first obtained, followed by dissolution of the salt particles in step (i) to obtain the porous membrane 1.

[0137] Figure 2 illustrates the variability of the shaping step (d) of a mixture 2 containing a polymer, salt nanoparticles and / or microparticles, and at least one solid acid when using different shaping techniques. Die processes (d1) and (d2) can be used to produce continuous structures with a constant cross-section, such as flat films or tubes, respectively. It may be desirable for a portion to include an impermeable region 6, be composed of two or more materials, and / or feature a non-uniform cross-section. This situation is taken into account by the fact that the edges 6 of the exemplary hollow rectangular prism shown in Figure 2(d3) are depicted differently from the sides of the prism. Such structures can be obtained, for example, by two-piece injection molding. Figure 2 further illustrates that the porous structure 1 is formed in process step (i) by melting an extruded or molded part to obtain the porous membrane 1 of the present invention in the form of a flat film, tube, or part containing multiple materials with different properties.

[0138] The following examples are provided to further illustrate the present invention, but are not intended to limit the scope of the invention.

[0139] I. Preparation of Starting Materials The preparation of salt nanoparticles is described in WO 2005 / 087660. The synthesis of calcium carbonate (denoted as CaCO), barium carbonate (denoted as BaCO), strontium carbonate (denoted as SrCO), potassium carbonate (denoted as KCO), and sodium carbonate (denoted as NaCO) nanoparticles is briefly described below, using FSP equipment as described in WO 2005 / 087660.

[0140] a) Preparation of CaCO3 nanoparticles: Ca-2-ethylhexanoate (Molekula) in 2-ethylhexanoic acid was diluted with tetrahydrofuran (THF) to a final calcium content of 3.9 wt%. This precursor was fed to a spray nozzle (9 ml / min, HNP Mikrosysteme, micro-annular gear pump mzr-2900), dispersed with oxygen (9 L / min, PanGas Tech.), and ignited with a premixed methane-oxygen flame (CH4, 1.2 L / min, O2, 2.2 L / min). The off-gas was filtered through a glass fiber filter (Whatman Ltd., USA) by a vacuum pump (Busch SA, Switzerland). The resulting powder was collected on the glass fiber filter and removed with a spatula.

[0141] b) Preparation of BaCO3 nanoparticles: Ba-2-ethylhexanoate (Alfa Aesar) in 2-ethylhexanoic acid was diluted with tetrahydrofuran (THF) to a final barium content of 4.6 wt%. The precursor was fed to a spray nozzle (5 ml / min, HNP Mikrosysteme, micro-annular gear pump mzr-2900), dispersed with oxygen (5 L / min, PanGas Tech.), and ignited with a premixed methane-oxygen flame (CH4, 1.2 L / min, O2, 2.2 L / min). The off-gas was filtered through a glass fiber filter (Whatman Ltd., USA) by a vacuum pump (Busch SA, Switzerland). The resulting powder was collected on the glass fiber filter and removed with a spatula.

[0142] c) Preparation of SrCO3 nanoparticles: Sr-2-ethylhexanoate in 2-ethylhexanoic acid (Strem Chemicals) was diluted with tetrahydrofuran (THF) to a final strontium content of 4.7 wt%. The precursor was fed into a spray nozzle (5 ml / min, HNP Mikrosysteme, micro-annular gear pump mzr-2900), dispersed with oxygen (5 l / min, PanGas Tech.), and ignited with a premixed methane-oxygen flame (CH4, 1.2 l / min, O2, 2.2 l / min). The off-gas was filtered through a glass fiber filter (Whatman Ltd., USA) by a vacuum pump (Busch SA, Switzerland). The resulting powder was collected on the glass fiber filter and removed with a spatula.

[0143] d) Preparation of K2CO3 nanoparticles: 20 wt% K-2-ethylhexanoate (Alfa Aesar) was dissolved in 2-ethylhexanoic acid and further diluted with tetrahydrofuran (THF) to a final potassium content of 3.5 wt%. The precursor was fed into a spray nozzle (5 ml / min, HNP Mikrosysteme, Micro Annular Gear Pump mzr-2900), dispersed with oxygen (5 L / min, PanGas Tech.), and ignited with a premixed methane-oxygen flame (CH4, 1.2 L / min, O2, 2.2 L / min). The off-gas was filtered through a glass fiber filter (Whatman Ltd., USA) by a vacuum pump (Busch SA, Switzerland). The resulting powder was collected on the glass fiber filter and removed with a spatula.

[0144] e) Preparation of Na2CO3 nanoparticles: 20 wt% Na-2-ethylhexanoate (Aldrich Fine Chemicals) was dissolved in 2-ethylhexanoic acid and further diluted with tetrahydrofuran (THF) to a final sodium content of 2.4 wt%. The precursor was fed to a spray nozzle (5 ml / min, HNP Mikrosysteme, micro-annular gear pump mzr-2900), dispersed with oxygen (5 L / min, PanGas Tech.), and ignited with a premixed methane-oxygen flame (CH4, 1.2 L / min, O2, 2.2 L / min). The off-gas was filtered through a glass fiber filter (Whatman Ltd., USA) by a vacuum pump (Busch SA, Switzerland). The resulting powder was collected on the glass fiber filter and removed with a spatula.

[0145] II. Preparation of polymer membranes a) Preparation of poly(propylene) membranes (not according to the invention): 30 wt% poly(propylene) resin (Aldrich Chemestry, USA) was heated in a ceramic beaker until the polymer was completely melted. 70 wt% ZnO particles (Hongwu, China) were added with stirring until a paste-like molasses was formed. The molasses was cast onto a hot metal plate using a metal roller to obtain a thin film. The film was allowed to cool for 5 minutes. Finally, salt particles were dissolved in 1 M hydrochloric acid (denoted as HCl) for 10 minutes to reveal the porous structure.

[0146] The formation of a porous structure was confirmed by scanning electron microscopy (Nanosem450, FEI). As seen in Figure 3, dissolving ZnO particles in hydrochloric acid resulted in visible porosity on both the upper side of the membrane (Figure 3, top left) and the lower side facing the substrate (Figure 3, top right). The apparent pore size is due to the size of the ZnO particles used (50 nm to 100 nm); incompletely dispersed particles, i.e., agglomerates, resulted in the formation of larger pores in the porous material. The membrane cross-section shown in the bottom row in Figure 3 shows the residual ZnO particles in the poly(propylene) matrix (left side) and the interconnected pores (right side) after repeated dissolution steps.

[0147] b) Preparation of poly(ethylene) membranes according to the present invention: 33 wt% polyethylene resin (CleanHDPE, Polytechs) was cycled at 180 °C and 60 rpm in an extruder (HAAKE MiniLab). While operating in closed-loop mode in the extruder, 33 wt% CaCO3 particles (Solvay, USA) were gradually added to the polymer. While operating in closed-loop mode in the extruder, 33 wt% sulfamic acid was gradually added to the composite. The final composite was extruded and pressed to form a flat film. This film was allowed to cool for 5 minutes. Finally, the salt particles were dissolved in 1 M hydrochloric acid (denoted HCl) for 10 minutes to reveal the porous structure.

[0148] The formation of a porous structure was confirmed by scanning electron microscopy (Nanosem450, FEI). As can be seen in Figure 4, dissolving CaCO3 particles in hydrochloric acid resulted in visible porosity on both the upper side of the membrane (Figure 4, top left) and the lower side facing the substrate (Figure 4, top right). The apparent pore diameter correlates well with the size of the CaCO3 particles used (500-1000 nm). The membrane cross-section shown in the bottom row in Figure 4 demonstrates a network of interconnected pores obtained without repeated washing.

[0149] Figure 5a shows a schematic diagram of the method disclosed herein, including step (k) of exposing the internal bulk material of the primary molding mixture. In this embodiment, primary molding (d) of the mixture containing polymer and particles by extrusion 7 and calcination 8 results in a sandwich-like sheet 9 with solid upper and lower surfaces characterized by relatively closed pores and at least partially molten polymer in its center. Such a membrane can also be considered symmetrical with respect to its longitudinal cross section. Two chilled rollers 10 with opposite rotation directions, as indicated by arrows 11, are installed downstream of the extruder 7 to divide the extruded sheet 9 into two portions 12, and the temperature of the chilled rollers 10 is set to a maximum of half the temperature of the last zone at the extruder exit. The chilled rollers 10 allow the material to adhere to their surfaces, opening up the still-warm "liquid" center of the extruded sheet 9. After cooling and removal of salt particles with 1 M hydrochloric acid, the two membranes 12 thus obtained each have an asymmetric longitudinal cross-section with a pore structure that is rather closed on the respective roller side B and rather open on the opposite side A, as confirmed by the scanning electron microscope images of each side shown in Figure 5b. The asymmetry of the longitudinal cross-section of the membranes 12 greatly facilitates and accelerates the complete removal of salt particles in that aqueous solvents can easily penetrate the material, especially from the open-pore A side, and produce a porous polymer structure.

Claims

1. 1. A method for producing a porous polymer structure, in particular a membrane, having a pore size of 1 to 5000 nm, comprising: a) providing a mixture, 1 to 90% by weight of one or more polymers and / or oligomeric precursors of said polymers, 0.5 to 95% by weight of one or more salt particles having a primary particle size of 1 to 50,000 nm; 0 to 70% by weight of one or more fillers; - containing 0 to 40% by weight of one or more additives; The mixture is provided without any organic solvent; at least a portion of the one or more salt particles are one or more solid acids, and the polymer:particle ratio is in the range of 3:1 to 1:10 by weight; d) forming the mixture, which is carried out by extruding the mixture through a die or by casting the mixture; i) removing said one or more salt particles with a non-organic solvent.

2. The method of claim 1 further comprising the step of: b) adapting the moisture content of the mixture.

3. 3. The method of claim 1 or 2, further comprising the step of: c) homogenizing the mixture.

4. The method of any one of claims 1 to 3, further comprising the step of: e) coating a substrate with said mixture.

5. 5. The method of claim 4, wherein the coating step (e) is selected from the group consisting of spraying, roll-to-roll processes.

6. 6. The method according to any one of claims 1 to 5, further comprising the step of: f) subjecting the obtained material to a drying and / or cooling step.

7. The method according to any one of claims 1 to 6, further comprising the step of g) subjecting the material thus obtained to further reshaping and / or further processing.

8. The method according to any one of claims 1 to 7, further comprising the step of: h) subjecting the material thus obtained to a polymerization or crosslinking step.

9. 9. The method of claim 1, wherein step (i) is removing the one or more salt particles by dissolving the salt particles in a non-organic solvent.

10. The method of any one of claims 1 to 9, further comprising the step of j) removing the resulting porous polymer structure from the substrate.

11. The method of claim 10, wherein step (j) is performed before any of steps (f) to (i).

12. The method of any one of claims 1 to 11, wherein one or more of steps (a) to (j) are carried out sequentially.

13. a) the salt particles are selected from the group consisting of oxides, carbonates, sulfates, halides, nitrates, and phosphates; and / or 13. The method according to any one of claims 1 to 12, wherein b) the salt particles have a particle size of 1 to 50,000 nm.

14. 14. The method of claim 13, wherein the salt particles are selected from the group consisting of carbonates and oxides.

15. The salt particles are CaCO ３ , BaCO ３ , SrCO ３ , Na ２ CO ３ , K. ２ CO ３ 15. The method of claim 14, wherein the cations are selected from the group consisting of NaCl, ZnO and CaO.

16. The solid acid is i) carboxylic acids, in particular at least one carboxylic acid selected from the group consisting of oxalic acid, tartaric acid, citric acid, mandelic acid, ascorbic acid, and ethylenediaminetetraacetic acid, and / or ii) at least one carboxylic acid selected from the group consisting of sulfonic acids, in particular sulfamic acid and 2-aminoethanesulfonic acid, and / or iii) phosphonic acid, and / or iv) pyrophosphate, and / or v) at least one amino acid selected from the group consisting of amino acids, in particular cysteine ​​and methionine, and / or vi) Lewis acids, especially AlCl ３ and FeCl ３ at least one Lewis acid selected from the group consisting of and derivatives of said Lewis acids.

17. The polymer i) polysulfones, polyethersulfones, polycarbonates, polystyrenes, polyacrylates, polysiloxanes, polyarylates, polyurethanes, polyesters, polyethers, polyimides, polyamides, halogenated polyolefins, cellulose acetate, and liquid crystal polymers; and / or ii) a polymer that can be crosslinked.

18. a) the support material is made from or essentially comprises polymers, rubbers, metals, ceramics, and glasses; and / or b) the support material is a film, woven fabric, or nonwoven fabric; and / or c) The method according to any one of claims 1 to 17, wherein the support material has a two-dimensional or three-dimensional shape.

19. Additional steps k) exposing the inner bulk material of the primary molding mixture; Step (k) is performed after step (d) and before any of steps (e) to (i); or The method of any one of claims 1 to 18, wherein step (k) is carried out after any of steps (d) to (h) and before step (i).

20. A mixture for producing porous polymer structures, in particular for carrying out the method according to any one of claims 1 to 19, comprising 1 to 90% by weight of one or more polymers; 0.5 to 95% by weight of salt particles having a primary particle size of 1 to 50,000 nm; 0 to 70% by weight of a filler; - Contains 0 to 40% by weight of additives, the mixture does not contain any organic solvent; the mixture is in powder form; 40 to 85 wt. % of the one or more salt particles are one or more solid acids; A mixture whereby the polymer:particle ratio is in the range of 3:1 to 1:10 by weight.

21. 21. A kit of parts for making the mixture of claim 20, wherein a first part comprises one or more types of salt particles, at least a portion of the one or more salt particles being one or more solid acids, and a second part comprises one or more polymers.

22. 22. The kit of parts of claim 21, wherein the first part comprises salt particles, additives, and fillers, and the second part comprises polymers, additives, and fillers.

23. A porous polymer structure obtainable by the method according to any one of claims 1 to 19.

24. 24. The porous polymer structure of claim 23, which comprises: For porous polymer structures with a constant cross section, a maximum wall thickness of 1000 μm, or a maximum wall thickness of 4000 μm for porous polymer structures with non-uniform cross-sections; and / or a porosity of 10% to 95% by volume, and / or A porous polymer structure characterized by pore diameters between 1 nm and 5 μm.

25. 25. A molded article comprising the porous polymer structure of claim 23 or 24, a) pleated or non-pleated filters, or b) a woven or nonwoven fabric, or c) molded parts.

26. 22. Use of the mixture according to claim 20 or the kit of parts according to claim 21 in a method for producing a porous polymer structure.

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