Polymeric porous film and method for producing same

Abstract

One or more embodiments of the present invention relate to a polymeric porous film including a hydrophobic polymer. The hydrophobic polymer includes 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, and is such that the average pore diameter of a first surface is 3 to 160 nm and the porosity is 0.5 to 30% when the water content is less than 10% by mass. This makes it possible to provide a polymeric porous film that can be used in membrane filtration, is such that water permeability improves after water containing impurities has been treated, and reduces operating costs.

Description

Polymer porous membrane and method for producing the same

[0001] The present invention relates to a polymeric porous membrane containing a hydrophobic polymer, which can be suitably used in water treatment such as wastewater treatment and water purification, and to a method for producing the same.

[0002] Numerous water treatment methods have been developed to remove impurities contained in river water and industrial water. One of these methods, membrane filtration, is used in many fields, such as water purifier cartridges and wastewater treatment membrane units. One of the filter materials used in this membrane filtration method is a polymer-based porous membrane that can be continuously produced in large quantities with stable quality. For example, Patent Document 1 proposes a porous membrane for water treatment using a polymer that contains one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, which has excellent chemical resistance and physical strength.

[0003] International Public Gazette No. 2018 / 230330

[0004] However, the porous membrane described in Patent Document 1, when used for membrane filtration, had the problem of low permeability after treating water containing impurities, which increased operating costs.

[0005] To solve the above-mentioned problems, the present invention provides a polymer porous membrane that can be used in membrane filtration to improve the permeability after treating water containing impurities and reduce operating costs, as well as a method for producing the same.

[0006] One or more embodiments of the present invention relate to a polymeric porous membrane containing a hydrophobic polymer, wherein the hydrophobic polymer contains 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, and the average pore diameter of the first surface is 3 to 160 nm and the porosity is 0.5 to 30% when the water content is less than 10% by mass.

[0007] One or more embodiments of the present invention relate to a method for producing a polymer porous membrane, comprising the step of contacting a polymer solution containing a hydrophobic polymer, a porosity opening agent, and a good solvent with a coagulation solution containing water to coagulate, wherein the hydrophobic polymer contains 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, the porosity opening agent contains an ionic compound or a hydrophilic polymer, the ionic compound is an ionic compound that dissociates into anions and cations when dissolved in water, the hydrophilic polymer is one or more selected from the group consisting of polyethylene glycol and polyvinylpyrrolidone, the good solvent is one or more selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, dimethylformamide, and acetone, the temperature of the coagulation solution is 15 to 75°C, and the concentration of water in the coagulation bath is 50% by mass or more.

[0008] According to one or more embodiments of the present invention, it is possible to provide a polymer porous membrane that can be used in membrane filtration, improves the permeability after treating water containing impurities, and reduces operating costs. Furthermore, according to the manufacturing method of one or more embodiments of the present invention, it is possible to obtain a polymer porous membrane that can be used in membrane filtration, improves the permeability after treating water containing impurities, and reduces operating costs.

[0009] The inventors of the present invention have diligently studied how to improve the water permeability of a polymer porous membrane when used for membrane filtration, using a hydrophobic polymer containing 20% ​​by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides. As a result, they found that by setting the average pore diameter of the first surface of the polymer porous membrane to 3 to 160 nm and the porosity to 0.5 to 30% when the water content is less than 10% by mass (hereinafter also simply referred to as the dry state), and using the polymer porous membrane in membrane filtration so that the first surface is the inflow side surface of the water to be filtered, the amount of water permeable after treating water containing impurities is improved, and operating costs can be reduced. It is presumed that because the average pore diameter of the first surface in the dry state is 3 to 160 nm and the porosity to 0.5 to 30%, impurities such as organic matter and microorganisms are less likely to adhere to the first surface of the polymer porous membrane during water treatment, thus improving the amount of water permeable after treating water containing impurities such as organic matter and microorganisms.

[0010] Furthermore, the inventors of the present invention have found that when producing a polymer porous membrane using a non-solvent-induced phase separation method with a hydrophobic polymer containing constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, a polymer porous membrane can be obtained in which the average pore diameter and porosity of the first surface satisfy the above-mentioned range by using specific good solvents, coagulation solutions, and porosity opening agents, and by setting the temperature of the coagulation solution within a specific range. Specifically, in a process of solidifying a polymer solution containing a hydrophobic polymer, a porosity-opening agent, and a good solvent by contacting it with a solidification solution, one or more selected from the group consisting of dimethyl sulfoxide (DMSO), dimethylacetamide, dimethylformamide, and acetone is used as the good solvent; one or more hydrophilic polymers selected from the group consisting of polyethylene glycol and polyvinylpyrrolidone are used as the porosity-opening agent, ionic compounds that dissociate into anions and cations when dissolved in water, or polyethylene glycol and polyvinylpyrrolidone are used; a solidification solution containing 50% by mass or more of water is used; and the temperature of the solidification solution is adjusted to a range of 15 to 75°C, thereby obtaining a polymer porous membrane having an average pore diameter of 3 to 160 nm and an opening ratio of 0.5 to 30% on the first surface when the water content is less than 10% by mass.

[0011] In this specification, "hydrophobic polymer" means a polymer containing 50% by mass or more of constituent units derived from hydrophobic monomers, and having a solubility in water at 25°C of less than 1000 mg / kg. In this specification, "first surface of polymer porous membrane" means the inlet-side surface of the polymer porous membrane that is being filtered (hereinafter also referred to as the membrane inlet surface). In this specification, "wet state" means a state in which the water content of the polymer porous membrane is 10% by mass or more, and "dry state" means a state in which the water content of the polymer porous membrane is less than 10% by mass. In the following, unless otherwise specified, "dry state" is used.

[0012] In this specification, when a numerical range is indicated by "~", the numerical range includes both endpoints (upper and lower limits). For example, the numerical range "X~Y" includes both endpoints, X and Y. Furthermore, when multiple numerical ranges are described in this specification, the range shall include numerical ranges formed by appropriately combining the upper and lower limits of different numerical ranges. Furthermore, when multiple upper and lower limits of a numerical range are described separately in this specification, the range shall include numerical ranges formed by appropriately combining the upper and lower limits.

[0013] In one or more embodiments of the present invention, a "porous membrane" refers to a membrane having a large number of micropores inside, in which these micropores are interconnected, and through which gas or liquid can pass from one surface to the other. In one or more embodiments of the present invention, the internal structure of the porous membrane can be confirmed by observing a cross-section parallel to the thickness direction of the porous membrane with a scanning electron microscope. In the polymer porous membrane of one or more embodiments of the present invention, it is preferable that the hydrophobic polymer has a three-dimensional network structure and has at least one through-hole that penetrates from the first surface to the surface on the opposite side in the thickness direction. This improves the filtration performance during water treatment.

[0014] The polymer porous membrane contains a hydrophobic polymer. In the polymer porous membrane, the content of the hydrophobic polymer is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. The polymer porous membrane may consist of 100% by mass of the hydrophobic polymer.

[0015] The hydrophobic polymer may contain 20% by mass or more of constituent unit A derived from one or more halogen-containing monomers (hydrophobic monomers) selected from the group consisting of vinyl halides and vinylidene halides, and is not particularly limited, but from the viewpoint of chemical resistance, it is preferable to contain 25% by mass or more of constituent unit A, preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, and still more preferably 45% by mass or more.

[0016] The vinyl halogen is preferably, for example, vinyl chloride and / or vinyl bromide, and the vinylidene halogen is preferably vinylidene chloride and / or vinylidene bromide. In other words, the halogen-containing monomer is preferably a chlorine-containing monomer and / or a bromine-containing monomer. Thus, when the halogen-containing monomer is not a fluorine-containing monomer but a chlorine-containing monomer and / or a bromine-containing monomer, that is, when the hydrophobic polymer is not a fluorine-containing resin, the fouling resistance is improved compared to when a fluororesin such as vinylidene fluoride resin is used, and there is no risk of generating organofluorine compounds (PFAS) that are a concern for adverse effects on the human body, as is the case when a fluororesin such as vinylidene fluoride resin is used, which is therefore preferable.

[0017] The hydrophobic polymer may consist only of constituent unit A, but from the viewpoint of strength, it is preferable to include constituent unit B derived from acrylonitrile (hydrophobic monomer) in addition to constituent unit A. From the viewpoint of fouling resistance, the hydrophobic polymer preferably contains 15% by mass or more of constituent unit B, preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, even more preferably 40% by mass or more, and even more preferably 45% by mass or more. The hydrophobic polymer may also contain 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, or 55% by mass or less of constituent unit B.

[0018] From the viewpoint of chemical resistance and fouling resistance, the hydrophobic polymer preferably contains 20 to 85% by mass of constituent unit A and 15 to 80% by mass of constituent unit B, more preferably 25 to 80% by mass of constituent unit A and 20 to 75% by mass of constituent unit B, even more preferably 30 to 70% by mass of constituent unit A and 30 to 70% by mass of constituent unit B, even more preferably 35 to 65% by mass of constituent unit A and 35 to 65% by mass of constituent unit B, even more preferably 40 to 60% by mass of constituent unit A and 40 to 60% by mass of constituent unit B, and even more preferably 45 to 55% by mass of constituent unit A and 45 to 55% by mass of constituent unit B. The hydrophobic polymer preferably contains a total of 50% by mass or more of constituent unit A and constituent unit B, which are constituent units derived from hydrophobic monomers.

[0019] In addition to constituent units A and B, the hydrophobic polymer may also contain constituent unit C derived from a vinyl monomer (hydrophilic monomer) having an ionic substituent, from the viewpoint of fouling resistance. The hydrophobic polymer preferably contains 10% by mass or less of constituent unit C, and may contain 0.1 to 9% by mass, 0.2 to 8% by mass, 0.3 to 7% by mass, 0.4 to 6% by mass, 0.5 to 5% by mass, or 1 to 3% by mass. More specifically, the hydrophobic polymer preferably contains 20 to 85% by mass of constituent unit A, 15 to 80% by mass of constituent unit B, and 0 to 10% by mass of constituent unit C; more preferably contains 29.5 to 70% by mass of constituent unit A, 29.5 to 70% by mass of constituent unit B, and 0.5 to 5% by mass of constituent unit C; and even more preferably contains 39 to 60% by mass of constituent unit A, 39 to 60% by mass of constituent unit B, and 1 to 3% by mass of constituent unit C.

[0020] The vinyl monomer having the ionic substituent is not particularly limited, and various vinyl monomers having different ionic substituents can be used. The ionic substituent may be anionic or cationic. Furthermore, the ionic substituent can be of the strongly electrolytic type, which has a degree of ionization of 99% or more in water, or of the weakly electrolytic type, which has a degree of ionization of less than 99% in water. The strongly electrolytic type anionic substituent is not particularly limited, but examples include sulfonic acid groups. The weakly electrolytic type anionic substituent is not particularly limited, but examples include carboxylic acid groups and phosphoric acid groups. The strongly electrolytic type cationic substituent is not particularly limited, but examples include ammonium groups, phosphonium groups, and onium groups such as sulfonium groups. The weakly electrolytic type cationic substituent is not particularly limited, but examples include primary to tertiary amino groups, pyridyl groups, and imino groups.

[0021] The vinyl monomer having the ionic substituent is preferably a vinyl monomer having a strongly electrolytic anionic substituent, and more preferably a vinyl monomer containing a sulfonic acid group. The vinyl monomer containing a sulfonic acid group is not particularly limited, but examples include allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrene sulfonic acid, 2-methyl-1,3-butadiene-1-sulfonic acid, and salts thereof (sodium salts, etc.).

[0022] The vinyl monomer having the ionic substituent may be used individually or in combination of two or more.

[0023] The hydrophobic polymer may contain, as appropriate, other monomer-derived monomers in addition to constituent units A, B, and C. The other monomers may be hydrophobic monomers or hydrophilic monomers, and are preferably hydrophilic monomers such as unsaturated carboxylic acids like (meth)acrylic acid and their salts; esters of unsaturated carboxylic acids like methyl (meth)acrylate and glycidyl (meth)acrylate; and vinyl esters like vinyl acetate and vinyl butyrate. In the hydrophobic polymer, the content of the other monomer-derived monomers may be 20% by mass or less, 10% by mass or less, or 5% by mass or less.

[0024] In the polymer porous membrane, the average pore diameter of the first surface in a dry state (moisture content less than 10% by mass) is 3 to 160 nm, and the porosity is 0.5 to 30%. By using the first surface of the polymer porous membrane, which has an average pore diameter of 3 to 160 nm and a porosity of 0.5 to 30%, as the inlet-side surface of the polymer porous membrane to be filtered, the permeability after treating water containing impurities can be improved, and operating costs can be reduced. Preferably, the first surface has an average pore diameter of 3 to 100 nm and a porosity of 0.5 to 20% in a dry state (moisture content less than 10% by mass), more preferably an average pore diameter of 3 to 50 nm and a porosity of 1 to 20%, and even more preferably an average pore diameter of 9 to 50 nm and a porosity of 1 to 7%. In this specification, the average pore diameter and porosity of the first surface of a polymer porous membrane in a dry state (water content less than 10% by mass) are calculated using an image of the first surface (the membrane inflow surface), and can be measured as described in the examples.

[0025] The polymer porous membrane is not particularly limited, but for example, it is preferably 0.01 to 1 mm thick, and more preferably 0.05 to 0.5 mm thick. If the thickness is 0.01 mm or more, defects such as cracks are less likely to occur and filtration performance is easily improved, and if the thickness is 1 mm or less, water permeability performance is easily improved.

[0026] In the polymer porous membrane, from the viewpoint of reducing the difference in membrane performance between the dry state and the wet state, it is preferable that the ratio Eo / Ei of the porosity Eo of the first layer, which is less than 500 nm deep from the first surface in the dry state (moisture content less than 10% by mass), and the porosity Ei of the second layer, which is adjacent to the first layer in the depth direction and is 500 to 1000 nm deep from the first surface, is 0.5 to 5. This suppresses membrane cracking in the dry state (moisture content less than 10% by mass) and makes it easier to suppress the difference in membrane performance, such as water permeability, between the polymer porous membrane in the wet state (moisture content of 10% by mass or more) and the polymer porous membrane in the dry state (moisture content less than 10% by mass). It is more preferable that Eo / Ei be 0.55 or more, even more preferable that it be 0.6 or more, even more preferable that it be 0.65 or more, and even more preferable that it be 0.7 or more. From the viewpoint of reducing the difference in membrane performance between the dry and wet states, the Eo / Ei ratio is more preferably 4.5 or less, even more preferably 4 or less, even more preferably 3.5 or less, even more preferably 3 or less, even more preferably 2.5 or less, and even more preferably 2 or less. More specifically, the Eo / Ei ratio may be 0.5 to 5, 0.55 to 4.5, 0.6 to 4, 0.6 to 3.5, 0.6 to 3, 0.65 to 2.5, or 0.7 to 2. In this specification, the porosity Eo of the first layer and the porosity Ei of the second layer in the dry state (moisture content less than 10% by mass) of the polymer porous membrane are calculated by freezing and cutting the polymer porous membrane in a direction perpendicular to the first surface (membrane inflow surface) and using the image of the obtained cross-section, and specifically can be measured as described in the examples.

[0027] In the polymer porous membrane, the porosity Eo of the first layer in a dry state (water content less than 10% by mass) is preferably 1 to 40%, more preferably 2 to 35%, even more preferably 3 to 30%, even more preferably 4 to 30%, even more preferably 5 to 30%, even more preferably 6 to 30%, even more preferably 7 to 25%, and even more preferably 8 to 20%, from the viewpoint of reducing the difference in membrane performance between the dry state and the wet state.

[0028] In the polymer porous membrane, the porosity Ei of the second layer in the dry state (water content less than 10% by mass) is preferably 2 to 80%, more preferably 3 to 70%, even more preferably 4 to 60%, even more preferably 5 to 50%, even more preferably 6 to 40%, even more preferably 7 to 30%, even more preferably 8 to 25%, and even more preferably 9 to 20%, from the viewpoint of reducing the difference in membrane performance between the dry state and the wet state.

[0029] The aforementioned porous polymer membrane has a water permeability (also referred to as initial water permeability) H in a wet state with a water content of 10% by mass or more, in order to reduce the difference in membrane performance between dry and wet states. W And, the permeability H in a dry state with a moisture content of less than 10% by mass. D Ratio H D / H W It is preferably 0.5 to 2.0, more preferably 0.6 to 1.8, even more preferably 0.7 to 1.6, even more preferably 0.8 to 1.4, and even more preferably 0.9 to 1.2. In this specification, the permeability H of a polymer porous membrane in a wet state with a water content of 10% by mass or more. W And, the water permeability H of a polymer porous membrane in a dry state with a water content of less than 10% by mass. D This can be measured and calculated as described in the examples.

[0030] The shape of the polymer porous membrane is not limited, and any shape can be selected depending on the specific application and purpose, such as hollow fiber, flat membrane, spiral, pleated, and tubular shapes. Among these, hollow fiber and flat membrane shapes are preferred from the viewpoint of being easy to manufacture, low cost, and usable at low pressure.

[0031] From the viewpoint of excellent water permeability after treating water containing impurities in membrane filtration, the water permeation amount of the polymer porous membrane when an aqueous solution of 50 ppm sodium alginate prepared by dissolving sodium alginate in a 0.5 mM aqueous sodium hydrogen carbonate solution is allowed to pass through for 30 minutes (hereinafter also referred to as the water permeation amount after fouling) is 100 L / (m 2 ・atm・h) or more, preferably 110 L / (m 2 ・atm・h) or more, more preferably 120 L / (m 2 ・atm・h) or more, still more preferably 140 L / (m 2 ・atm・h) or more, even more preferably 200 L / (m 2 ・atm・h) or more. In the present specification, the water permeation amount after fouling can be specifically measured as described in the Examples.

[0032] From the viewpoint of excellent initial water permeability, the polymer porous membrane preferably has an initial water permeation amount of 1000 L / (m 2 ・atm・h) or more, more preferably 1100 L / (m 2 ・atm・h) or more, still more preferably 1200 L / (m 2 ・atm・h) or more, even more preferably 1500 L / (m 2 ・atm・h) or more, particularly preferably 1800 L / (m 2 ・atm・h) or more. In the present specification, the initial water permeation amount can be specifically measured as described in the Examples.

[0033] In one or more embodiments of the present invention, the polymer porous membrane can be produced by a non-solvent induced phase separation method. Specifically, the method comprises a membrane forming step of bringing a polymer solution containing a hydrophobic polymer, a pore-forming agent, and a good solvent into contact with a coagulation liquid containing water to coagulate the polymer solution. As the hydrophobic polymer, the hydrophobic polymer described above can be used.

[0034] The pore-forming agent comprises an ionic compound or a hydrophilic polymer. Thereby, a porous polymer membrane that contains a hydrophobic polymer containing 20% by mass or more of structural units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halide and vinylidene halide, and satisfies the above-mentioned ranges in terms of the average pore diameter and porosity of the first surface can be obtained. From the viewpoint of easily obtaining a porous polymer membrane whose Eo / Ei satisfies the above-mentioned range, the pore-forming agent is preferably an ionic compound.

[0035] The ionic compound is an ionic compound that ionizes when dissolved in water and dissociates into anions and cations. From the viewpoint of pore control, the anion in the ionic compound is preferably a monovalent anion, and may be a monovalent inorganic anion or a monovalent organic anion. Examples of the monovalent inorganic anion include halide ions, nitrate ions, and the like. Examples of the monovalent organic anion include acetate ions and the like. From the viewpoint of pore control, the anion is more preferably one or more selected from the group consisting of halide ions, acetate ions, and nitrate ions, and is further preferably one or more inorganic anions selected from the group consisting of halide ions and nitrate ions. Examples of the halide ion include fluoride ions, chloride ions, bromide ions, iodide ions, and the like.

[0036] From the viewpoint of pore control, the cation in the ionic compound is preferably an alkali metal ion, an alkaline earth metal ion, an ammonium ion, or the like. Examples of the alkali metal ion include lithium ions, sodium ions, potassium ions, and the like. Examples of the alkaline earth metal ion include calcium ions, magnesium ions, strontium ions, and the like. From the viewpoint of pore control, the cation is more preferably one or more selected from the group consisting of sodium ions, calcium ions, ammonium ions, and the like.

[0037] The ionic compound can be used as an aqueous solution. The concentration of the aqueous solution of the ionic compound is not particularly limited, but may be, for example, 4 to 30% by mass, or 5 to 25% by mass. From the viewpoint of use as an aqueous solution, the ionic compound is preferably one or more selected from the group consisting of sodium chloride, lithium chloride, calcium chloride, and calcium nitrate.

[0038] The aqueous solution of the ionic compound may be prepared using a buffer such as a phosphate buffer. The pH of the phosphate buffer is not particularly limited, but may be, for example, pH 2 to 12 or pH 5 to 9.

[0039] The hydrophilic polymer is one or more selected from the group consisting of polyethylene glycol and polyvinylpyrrolidone, and preferably contains polyethylene glycol. The degree of polymerization of polyethylene glycol is not particularly limited, but for example, a degree of polymerization of about 100 to 5000 can be suitably used.

[0040] The good solvent is one or more selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, dimethylformamide, and acetone. This makes it possible to obtain a polymer porous film containing a hydrophobic polymer that contains 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, and which satisfies the above-mentioned range for the average pore diameter and porosity of the first surface, and preferably satisfies the above-mentioned range for Eo / Ei. The good solvent is preferably one or more selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide, and more preferably dimethyl sulfoxide.

[0041] The polymer solution can be prepared, for example, by mixing the hydrophobic polymer, an aqueous solution of the ionic compound or an aqueous solution of the hydrophilic polymer, and the good solvent. In the polymer solution, the concentration of the hydrophobic polymer can be appropriately selected according to the pore size and water permeability of the target polymer porous membrane, and is not limited, but is preferably 5 to 30% by mass, more preferably 8 to 20% by mass. When the concentration of the hydrophobic polymer is within the above range, the processability during film formation and the strength of the resulting polymer porous membrane are improved.

[0042] From the viewpoint of easily obtaining a polymer porous film in which the average pore diameter and porosity of the first surface satisfy the above-mentioned range, the polymer solution preferably contains 3 to 30 parts by mass of the ionic compound, more preferably 4 to 25 parts by mass, and even more preferably 5 to 15 parts by mass of the ionic compound per 100 parts by mass of the hydrophobic polymer.

[0043] The polymer solution also preferably contains 150 to 420 parts by mass, more preferably 180 to 410 parts by mass, even more preferably 200 to 400 parts by mass, and even more preferably 280 to 400 parts by mass of the hydrophilic polymer per 100 parts by mass of the hydrophobic polymer, from the viewpoint of easily obtaining a polymer porous film in which the average pore diameter and porosity of the first surface satisfy the above-mentioned range.

[0044] Furthermore, when preparing polymer solutions, various film-forming aids such as lubricants and stabilizers may be used in combination as needed, within a range that does not hinder the effects of the present invention. The amount of these film-forming aids added can be arbitrarily adjusted to suit the desired physical properties, as long as it does not hinder the effects of the present invention and allows for film formation.

[0045] The coagulation solution used during film formation contains 50% by mass or more of water. This allows for the production of a polymer porous film containing a hydrophobic polymer that includes 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, and which satisfies the above-mentioned range for the average pore diameter and porosity of the first surface, preferably with Eo / Ei satisfying the above-mentioned range. From the viewpoint of easily obtaining a polymer porous film that satisfies the above-mentioned range for the average pore diameter and porosity of the first surface, the coagulation solution used during film formation preferably contains 70% by mass or more of water, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably more than 95% by mass or more, and particularly preferably 99% by mass or more. The coagulation solution used during film formation may also contain 30% by mass or less of the above-mentioned good solvent in addition to water, or it may be a water bath consisting of 100% by mass of water.

[0046] The temperature of the coagulation solution is 15 to 75°C. This makes it possible to obtain a polymer porous membrane containing a hydrophobic polymer that contains 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, and whose average pore diameter and porosity of the first surface satisfy the above range. The temperature of the coagulation solution is preferably 20 to 70°C, more preferably 25 to 65°C, and even more preferably 25 to 60°C.

[0047] The above manufacturing method may include a water washing step after the film formation step. The water washing step can remove good solvents from the polymer porous film. In the water washing step, for example, water at 5°C or higher can be used, and the water temperature may be 10 to 80°C or 20 to 70°C.

[0048] The above manufacturing method may include a drying step after the washing step, if necessary. Drying may be done, for example, by heating air. The temperature of the heated air may be 30 to 80°C or 40 to 60°C. The drying time may be, for example, 1 to 5 hours or 2 to 3 hours.

[0049] More specifically, the polymer porous membrane can be obtained, for example, by applying the copolymer solution prepared as described above to a support using an applicator, then coagulating and washing it with water as described above. If necessary, drying may be performed after washing with water. As the support, a filter paper made of cellulose fibers can be used. In such a polymer porous membrane, the side opposite the support such as the filter paper becomes the inflow side of the material to be filtered, and the surface opposite the support such as the filter paper becomes the first surface of the polymer porous membrane.

[0050] The aforementioned porous polymer membrane can be suitably used to remove impurities contained in various treated waters, such as river water and industrial water. For example, it can be used as a filter material in water purifier cartridges or membrane units for wastewater treatment.

[0051] The present invention will be described in detail below based on examples. However, the present invention is not limited to these examples.

[0052] (Example 1) Copolymer 1, comprising 48.0% by mass of constituent units derived from vinyl chloride, 50.5% by mass of constituent units derived from acrylonitrile, and 1.5% by mass of constituent units derived from sodium styrene sulfonate, was synthesized by emulsion polymerization. 55 g of copolymer 1, 209 g of polyethylene glycol (degree of polymerization 200, manufactured by Fujifilm Wako Pure Chemical Industries), and 236 g of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries) were mixed to obtain a copolymer solution. The obtained copolymer solution was applied to filter paper (Advantec Toyo No. 2 qualitative filter paper) using an applicator with a gap of 200 μm, solidified in a 25°C water bath (coagulation solution), and then washed with 20°C water to obtain a polymer porous membrane.

[0053] (Example 2) 50 g of copolymer 1, 25 g of an aqueous solution of sodium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (sodium chloride concentration 10% by mass), and 425 g of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed to obtain a copolymer solution. The obtained copolymer solution was applied to filter paper (Advantec Toyo No. 2 qualitative filter paper) using an applicator with a gap of 200 μm, solidified in a 60°C water bath (coagulation solution), and then washed with 20°C water to obtain a polymer porous membrane.

[0054] (Example 3) 75 g of copolymer 1, 25 g of an aqueous solution of sodium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (sodium chloride concentration 10% by mass), and 400 g of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed to obtain a copolymer solution. The obtained copolymer solution was applied to filter paper (Advantec Toyo No. 2 qualitative filter paper) using an applicator with a gap of 200 μm, solidified in a 60°C water bath (coagulation solution), and then washed with 20°C water to obtain a polymer porous membrane.

[0055] (Example 4) 60 g of copolymer 1, 25 g of an aqueous solution of calcium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (calcium chloride concentration 10% by mass), and 415 g of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed to obtain a copolymer solution. The obtained copolymer solution was applied to filter paper (Advantec Toyo No. 2 qualitative filter paper) using an applicator with a gap of 200 μm, solidified in a 25°C water bath (coagulation solution), and then washed with 20°C water to obtain a polymer porous membrane.

[0056] (Example 5) 60 g of copolymer 1, 25 g of sodium chloride phosphate buffer solution (sodium chloride concentration 10% by mass, pH 8), and 415 g of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries) were mixed. The resulting copolymer solution was applied to filter paper (Advantec Toyo No. 2 qualitative filter paper) using an applicator with a gap of 200 μm, solidified in a 60°C water bath (coagulation solution), and then washed with 20°C water to obtain a polymer porous membrane. The sodium chloride phosphate buffer solution used was prepared as follows: 0.4 mL of phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries) and 0.64 g of sodium dihydrogen phosphate dihydrate (manufactured by Fujifilm Wako Pure Chemical Industries) were mixed and made up to 100 mL to prepare a 0.1 M phosphate buffer solution with a pH of 2. 17.3 g of disodium hydrogen phosphate dodecahydrate and 0.35 g of anhydrous sodium phosphate were mixed and diluted to 50 mL to prepare a 1 M phosphate buffer solution with pH 11. Then, 10 mL of the 1 M phosphate buffer solution with pH 11 was taken and diluted to 100 mL to prepare a 0.1 M phosphate buffer solution with pH 11. The 0.1 M phosphate buffer solution with pH 2 and the 0.1 M phosphate buffer solution with pH 11 were mixed to adjust the pH to 8. Then, 5 g of sodium chloride (manufactured by Fujifilm Wako Pure Chemical Industries) and 45 g of the 0.1 M phosphate buffer solution with pH 8 were mixed to prepare a 10% by weight sodium chloride phosphate buffer solution (pH 8).

[0057] (Example 6) 55 g of copolymer 1, 25 g of sodium chloride phosphate buffer solution (sodium chloride concentration 10% by mass, pH 8), and 420 g of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries) were mixed to obtain a copolymer solution. The obtained copolymer solution was applied to filter paper (Advantec Toyo No. 2 qualitative filter paper) using an applicator with a gap of 200 μm, solidified in a 60°C water bath (coagulation solution), and then washed with 20°C water to obtain a polymer porous membrane. The sodium chloride phosphate buffer solution was prepared in the same manner as in Example 5.

[0058] (Comparative Example 1) 75 g of copolymer 1, 199.5 g of polyethylene glycol (degree of polymerization 200, manufactured by Fujifilm Wako Pure Chemical Industries), and 225.5 g of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries) were mixed to obtain a copolymer solution. The obtained copolymer solution was applied to filter paper (Advantec Toyo No. 2 qualitative filter paper) using an applicator with a gap of 200 μm, solidified in a 10°C water bath (coagulation solution), and then washed with 20°C water to obtain a polymer porous membrane.

[0059] (Comparative Example 2) 60 g of copolymer 1, 25 g of an aqueous solution of calcium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (calcium chloride concentration 10% by mass), and 415 g of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed to obtain a copolymer solution. The obtained copolymer solution was applied to filter paper (Advantec Toyo No. 2 qualitative filter paper) using an applicator with a gap of 200 μm, solidified in an 80°C water bath (coagulation solution), and then washed with 20°C water to obtain a polymer porous membrane.

[0060] (Comparative Example 3) 75 g of copolymer 1, 200 g of polyethylene glycol (degree of polymerization 200, manufactured by Fujifilm Wako Pure Chemical Industries), and 225 g of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries) were mixed to obtain a copolymer solution. The obtained copolymer solution was applied to filter paper (Advantec Toyo No. 2 qualitative filter paper) using an applicator with a gap of 200 μm, solidified in a 60% DMSO aqueous solution (coagulation solution) at 25°C, and then washed with water at 20°C to obtain a polymer porous membrane.

[0061] The average pore diameter, porosity, void ratio, initial moisture content (moisture content in wet state), moisture content after drying (moisture content in dry state), initial water permeability (water permeability in wet state), water permeability after drying (water permeability in dry state), water permeability after fouling, and the number and size of film cracks after drying (dry state) were measured and calculated as follows for the polymer porous membranes obtained in the examples and comparative examples on the surface opposite to the filter paper side (first surface). The results are shown in Tables 1 and 2 below. Table 1 below also shows the concentration of copolymer 1 in the polymer solution (polymer solution), the type and amount of porosity-opening agent, as well as the temperature of the coagulation solution and the concentration of water. Note that in Table 1 below, the amount of porosity-opening agent is per 100 parts by mass of copolymer 1.

[0062] (Average pore size and porosity) After drying the polymer porous membrane in a 40°C constant temperature oven for 3 hours, the pores on the membrane surface (first surface) of the polymer porous membrane were observed using a scanning electron microscope (Hitachi High-Tech S-4800). Images of the membrane surface (first surface) were acquired at 5,000x and 50,000x magnification. If the estimated pore size was less than 50 nm, the 50,000x image was used to calculate the average pore size and porosity. If the pore size was 50 nm or more, the 5,000x image was used. WinROOF2018 (Mitani Corporation) was used for image analysis. After setting the image resolution and length per pixel in WinROOF, the analysis range was specified. The analysis range was 10 μm square for the 5,000x image and 1 μm square for the 50,000x image, selecting areas without defects or other abnormalities and with an average pore state. After checking the luminance histogram within the specified analysis range, the image brightness was adjusted so that the average luminance value for the entire analysis range was between 95 and 105. To enhance the color of the image, the color density distribution within the analysis range was transformed and adjusted so that 99.95% of the range extended throughout the entire image. The adjusted image was converted to a monochrome image, the brightness was set to +20 and the contrast to +50, and then black and white binarization was performed in the range of 0 to 60. After five morphological processes—(1) degeneracy (1 time), (2) isolated point removal (bright points), (3) exclusive expansion (1 time), (4) closing, and (5) hole filling—the area of ​​each measurement site (black parts corresponding to voids) was calculated. After calculating the area, measurement sites overlapping on the boundary line of the analysis range were deleted, and the equivalent circle diameter was calculated based on the area of ​​the remaining individual measurement sites. <Method for calculating average hole diameter> The average of the equivalent circle diameters of each measurement site within the entire analysis range was used as the average hole diameter. <Method for Calculating Open Area Ratio> [Formula 1] Open area ratio (%) = {Sum of the areas of individual measurement points / Area of ​​the analysis range} × 100%

[0063] (Porosity) After drying a polymer porous membrane in a 40°C forced-air constant-temperature oven for 3 hours, it was cut into 5 cm x 1 cm sections to create samples. The samples were immersed in liquid nitrogen and, while frozen, folded to create fracture surfaces. Scanning electron microscope (Hitachi High-Tech, S-4800) was used to acquire 50,000x magnified images of the film fracture surfaces at 1280 x 960 pixels. Two fracture surfaces were created for each sample, and images were acquired and analyzed for each fracture surface. WinROOF2018 (Mitani Corporation) was used for image analysis. After setting the image resolution and length per pixel in WinROOF2018, the analysis range was specified. For the first layer, where the depth from the film surface (first surface of the film) is less than 500 nm, and for the second layer, where the depth is from 500 to 1000 nm, the analysis range was specified as a 300 nm square area for each layer. After checking the luminance histogram within the specified analysis range, the image brightness was adjusted so that the average luminance value for the entire analysis range was between 95 and 105. To enhance the color of the image, the color density distribution within the analysis range was transformed and adjusted so that 99.95% of the range extended across the entire image. The adjusted image was converted to a monochrome image, the brightness was set to +20 and the contrast to +50, and then black and white binarization was performed in the range of 0 to 60. After five morphological processes—(1) degeneracy (1 time), (2) isolated point removal (bright points), (3) exclusive expansion (1 time), (4) closing, and (5) hole filling—the area of ​​the measured part (the total area of ​​all black parts corresponding to voids) was calculated, and the porosity Eo of the first layer and the porosity Ei of the second layer were determined using the following formula. Porosity of the first layer Eo (%) = (Area of ​​measurement site / Area of ​​analysis range) × 100 Porosity of the second layer Ei (%) = (Area of ​​measurement site / Area of ​​analysis range) × 100

[0064] (Initial moisture content) First, a polymer porous membrane was cut into a 5 cm x 3 cm section, and the surface water was wiped off with a Kimwipe. The mass of the sample (W0) was then measured. Next, the sample was dried in a 120°C forced-air constant-temperature incubator for 1 hour. The mass of the dried sample (W1) was then measured, and the moisture content was calculated using the following formula, which was defined as the initial moisture content: Moisture content (mass%) = 100 × [(W0 - W1) / W1]

[0065] (Moisture content after drying) After drying the polymer porous membrane in a 40°C forced-air constant-temperature incubator for 3 hours, a 5 cm x 3 cm sample was cut out and used as the sample. Except for this, the moisture content was measured and calculated in the same manner as for the initial moisture content, and this was recorded as the moisture content after drying.

[0066] (Initial water permeability) A porous polymer membrane (water content of 10% by mass or more) was cut into a 3 cm x 3 cm section to be used as a sample. The first surface was designated as the inlet side surface to be filtered, with an effective membrane area of ​​9 cm². 2 Using a cross-flow module for flat membranes (3 cm x 3 cm), ultrapure water was passed through under conditions of a flow rate of 34 mL / min and a pressure of 0.01 MPa (0.1 atm), and the permeability was calculated using the following formula, and the initial permeability (H W ) was assumed. In the following equation 2, V represents the volume (L) of ultrapure water that permeates through the membrane, and A represents the effective area (m²) of the membrane. 2 ) is shown, where P is the water pressure (atm) and Δt is the measurement time (h). [Equation 2] Permeability (L / m 2 ・atm・h)=V / (A×P×Δt)

[0067] (Water permeability after drying) A polymer porous membrane (water content of 10% by mass or more) was dried in a 40°C forced-air constant-temperature oven for 3 hours, then cut into 3 cm x 3 cm sections to obtain a sample (water content of less than 10% by mass), with an effective membrane area of ​​9 cm². 2 Using a (3cm x 3cm) flat membrane cross-flow module, with the first surface as the inlet surface to be filtered, pure water was passed through for 30 minutes under conditions of a flow rate of 34 mL / min and a pressure of 0.01 MPa (0.1 atm). Then, the permeability was measured in the same manner as for the initial permeability and the permeability was calculated, and the permeability after drying (H D )

[0068] (Water permeability after fouling) The water permeability after fouling was measured using a dead-end module and the following procedure was followed: A polymer porous membrane (water content of 10% by mass or more) was cut into a 3 cm x 3 cm section, the surface water was wiped off with Kimwipes, and the sample was prepared with an effective membrane area of ​​9 cm². 2A flat membrane module measuring 3 cm x 3 cm was set with the first surface facing the inlet side of the filtration target. A 50 ppm sodium alginate aqueous solution (test solution), prepared by dissolving sodium alginate in a 0.5 mM sodium bicarbonate aqueous solution, was passed through the membrane at a flow rate of 5 mL / min using a dead-end method for 40 minutes. The pressure P on the membrane was measured over time, and the permeability after 30 minutes was calculated using the above-mentioned formula 2, which was then used as the permeability after fouling.

[0069] (Confirmation of the number and size of film cracks after drying) A polymer porous membrane (water content of 10% by mass or more) was dried in a 40°C forced-air constant-temperature oven for 3 hours. Then, a 3 cm x 3 cm section was cut out as a sample (water content of less than 10% by mass). The sample was folded at a 90° angle with the first surface facing inward, and the folded part was flattened again. An image (25x magnification) was acquired using a 3D shape measuring machine (KEYENCE VR-5000). Next, areas where the film surface was peeled up within a 5 mm x 2 mm area were identified as film cracks, and the number of film cracks and the size of each crack were measured. For the measurement, the image was printed on A4 size paper, the number and size of the cracks were measured, the size of the scale bar was measured, and the size of the crack was calculated from the ratio of these values.

[0070]

[0071]

[0072] As can be seen from the data in Table 1 above, the polymer porous membranes obtained in Examples 1 to 6, where the temperature of the coagulation solution was in the range of 15 to 75°C and the water concentration of the coagulation solution was 50% by mass or more, had an average pore diameter of 3 to 160 nm on the first surface in the dry state and an opening ratio of 0.5 to 30%, resulting in high water permeability after fouling, and thus reducing operating costs. Furthermore, as can be seen from the comparison between Example 1 and Examples 2 to 6, the polymer porous membranes obtained in Examples 2 to 6, where an ionic compound was used as the porosity agent, had an Eo / Ei of 0.5 or more and did not exhibit film cracking after drying.

[0073] On the other hand, the polymer porous membrane obtained in Comparative Example 1, where the temperature of the coagulation solution was less than 15°C, had a porosity of less than 0.5% on the first surface and low water permeability after fouling. Similarly, the polymer porous membrane obtained in Comparative Example 2, where the temperature of the coagulation solution was more than 75°C, had an average pore diameter of more than 160 nm on the first surface and low water permeability after fouling. Furthermore, the polymer porous membrane obtained in Comparative Example 3, where the water concentration of the coagulation solution was less than 50% by mass, had a porosity of less than 0.5% on the first surface and low water permeability after fouling. In addition, in Comparative Examples 1 and 3, where Eo / Ei was less than 0.5, film cracking occurred after drying.

[0074] The present invention is not particularly limited, but preferably includes the following embodiments: [1] A polymer porous membrane containing a hydrophobic polymer, wherein the hydrophobic polymer contains 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, and the average pore diameter of the first surface when the polymer porous membrane has a water content of less than 10% by mass is 3 to 160 nm and the porosity is 0.5 to 30%. [2] The polymer porous membrane according to [1], wherein the hydrophobic polymer contains 35 to 65% by mass of constituent units derived from vinyl halides and 35 to 65% by mass of constituent units derived from acrylonitrile. [3] The polymer porous membrane, when the water content is 10% by mass or more, has a permeability of 100 L / (m³) when a 50 ppm aqueous solution of sodium alginate, obtained by dissolving sodium alginate in a 0.5 mM aqueous solution of sodium bicarbonate, is passed through it for 30 minutes. 2 A polymer porous membrane according to [1] or [2], wherein the moisture content is 10% by mass or more. [4] The initial water permeability of the polymer porous membrane when the moisture content is 10% by mass or more is 1000 L / (m 2[1] to [3] a polymer porous membrane having a moisture content of 10% by mass or more. [5] A polymer porous membrane according to any one of [1] to [4], wherein, when the moisture content of the polymer porous membrane is less than 10% by mass, the ratio Eo / Ei of the porosity Eo of the first layer having a depth of less than 500 nm from the first surface to the porosity Ei of the second layer adjacent to the first layer in the depth direction and having a depth of 500 to 1000 nm from the first surface is 0.5 or more and 5 or less. [6] A polymer porous membrane according to any one of [1] to [5], wherein when the moisture content of the polymer porous membrane is less than 10% by mass, the porosity Eo of the first layer is 1 to 40%. [7] A polymer porous membrane according to any one of [1] to [6], wherein when the moisture content of the polymer porous membrane is less than 10% by mass, the porosity Ei of the second layer is 2 to 80%. [8] A method for producing a polymer porous membrane, comprising the step of contacting a polymer solution containing a hydrophobic polymer, a porosity opening agent, and a good solvent with a coagulation solution containing water to coagulate, wherein the hydrophobic polymer contains 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, the porosity opening agent contains an ionic compound or a hydrophilic polymer, the ionic compound is an ionic compound that dissociates into anions and cations when dissolved in water, the hydrophilic polymer is one or more selected from the group consisting of polyethylene glycol and polyvinylpyrrolidone, the good solvent is one or more selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, dimethylformamide, and acetone, the temperature of the coagulation solution is 15 to 75°C, and the concentration of the water in the coagulation bath is 50% by mass or more, the method for producing a polymer porous membrane. [9] The method for producing a polymer porous membrane according to [8], wherein the polymer solution contains 3 to 30 parts by mass of the ionic compound per 100 parts by mass of the hydrophobic polymer.

[10] The polymer solution comprises 150 to 420 parts by mass of the hydrophilic polymer with respect to 100 parts by mass of the hydrophobic polymer, as described in [8] or [9], a method for producing a polymer porous membrane.

[11] The method for producing a polymer porous membrane according to any one of [8] to

[10] , wherein the anion is one or more selected from the group consisting of halide ions, acetate ions, and nitrate ions.

Claims

1. A polymer porous membrane containing a hydrophobic polymer, wherein the hydrophobic polymer contains 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, and the average pore diameter of the first surface when the water content of the polymer porous membrane is less than 10% by mass is 3 to 160 nm, and the porosity is 0.5 to 30%.

2. The polymer porous membrane according to claim 1, wherein the hydrophobic polymer contains 35 to 65% by mass of constituent units derived from vinyl halide and 35 to 65% by mass of constituent units derived from acrylonitrile.

3. When the polymer porous membrane has a water content of 10% by mass or more, the permeability when a 50 ppm aqueous solution of sodium alginate, obtained by dissolving sodium alginate in a 0.5 mM aqueous solution of sodium bicarbonate, is passed through it for 30 minutes is 100 L / (m³). 2 A polymer porous membrane according to claim 1, wherein the temperature is ≥ 0.atm·h.

4. The initial water permeability of the polymer porous membrane when its water content is 10% by mass or more is 1000 L / (m³). 2 A polymer porous membrane according to claim 1, wherein the temperature is ≥ 0.atm·h.

5. The polymer porous membrane according to claim 1, wherein, when the water content of the polymer porous membrane is less than 10% by mass, the ratio Eo / Ei of the porosity Eo of a first layer having a depth of less than 500 nm from the first surface to the porosity Ei of a second layer adjacent to the first layer in the depth direction and having a depth of 500 to 1000 nm from the first surface is 0.5 or more and 5 or less.

6. The polymer porous membrane according to claim 1, wherein the porosity Eo of the first layer is 1 to 40% when the water content of the polymer porous membrane is less than 10% by mass.

7. The polymer porous membrane according to claim 1, wherein, when the water content of the polymer porous membrane is less than 10% by mass, the porosity Ei of the second layer is 2 to 80%.

8. A method for producing a polymer porous membrane, comprising the step of contacting a polymer solution containing a hydrophobic polymer, a porosity opening agent, and a good solvent with a coagulation solution containing water to coagulate, wherein the hydrophobic polymer contains 20% by mass or more of constituent units derived from one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides, the porosity opening agent contains an ionic compound or a hydrophilic polymer, the ionic compound is an ionic compound that dissociates into anions and cations when dissolved in water, the hydrophilic polymer is one or more selected from the group consisting of polyethylene glycol and polyvinylpyrrolidone, the good solvent is one or more selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, dimethylformamide, and acetone, the temperature of the coagulation solution is 15 to 75°C, and the concentration of water in the coagulation bath is 50% by mass or more.

9. The method for producing a polymer porous membrane according to claim 8, wherein the polymer solution contains 3 to 30 parts by mass of the ionic compound with respect to 100 parts by mass of the hydrophobic polymer.

10. The method for producing a polymer porous membrane according to claim 8, wherein the polymer solution contains 150 to 420 parts by mass of the hydrophilic polymer with respect to 100 parts by mass of the hydrophobic polymer.

11. The method for producing a polymer porous membrane according to claim 8, wherein the anion is one or more selected from the group consisting of halide ions, acetate ions, and nitrate ions.

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