Polyphenylene ether solution, porous membrane, method for producing porous membrane, alkali electrolysis diaphragm, pharmaceutical process filter, and water treatment membrane

Abstract

The purpose of the present invention is to provide a polyphenylene ether solution with which it is possible to form a porous film at around room temperature (20°C). The solution to that problem is a polyphenylene ether solution containing polyphenylene ether and a water-soluble organic solvent having a solubility of 50 g / 100 mL or more in water at 20°C. The polyphenylene ether is a polyphenylene ether solution containing 1-99 mol% of repeating units derived from a phenol represented by formula (1) and 1-99 mol% of repeating units derived from a phenol represented by formula (2) per a total of 100 mol% of repeating units derived from a phenol represented by formula (1) and repeating units derived from a phenol represented by formula (2).

Description

Polyphenylene ether solution, porous membrane, method for producing porous membrane, separator for alkaline electrolysis, pharmaceutical process filter, water treatment membrane

[0001] The present invention relates to a polyphenylene ether solution, a porous membrane, a method for producing a porous membrane, a separator for alkaline electrolysis, a pharmaceutical process filter, and a water treatment membrane.

[0002] As a raw material for a porous membrane used in liquid separation applications, a polysulfone-based polymer is cited as an excellent material. Polysulfone-based polymers have many water-soluble organic solvents as good solvents, and it is possible to produce various membranes such as flat membranes and hollow fiber membranes using the non-solvent induced phase separation method (see Non-Patent Document 1 and Patent Document 1 below). In addition, polysulfone-based polymers can also be melt-molded as resins, and it is also possible to produce various membranes using the melt film-forming method. That is, polysulfone-based polymers are materials with a high degree of freedom in membrane processing and can freely produce membranes having the required pore diameters.

[0003] On the other hand, polyphenylene ether-based polymers have hardly been produced and used as porous membranes for liquid treatment. One of the reasons is that the conventional general polyphenylene ether-based polymer, poly(2,6-dimethyl-1,4-phenylene oxide), has low solubility in water-soluble organic solvents used for non-solvent induced phase separation. In the method for producing a porous membrane in polyphenylene ether-based polymers reported in the past (see Patent Document 2 below), since the solubility in water-soluble organic solvents is not sufficient as described above, a heating operation exceeding the flash point of the solvent, such as 160 °C or higher, is required to prepare a uniform solution, and a heating operation to maintain 90 °C or higher is also required during film formation. Therefore, from the viewpoints of safety and handling, there is a problem that it is extremely difficult to industrially produce a porous membrane by this method.

[0004] Japanese Patent Application Laid-Open No. 5-7745, Patent No. 5420836

[0005] Membrane Technology (2nd Edition), IPC, Author: Marcel Molder, Supervised and Translated by Masakazu Yoshikawa, Tsuyoshi Matsuura, Tsutomu Nakagawa (1997), P. 16, 45 - 51, 256, 275 - 280

[0006] In conventionally disclosed technologies, polyphenylene ethers with the ability to form porous films at room temperature have not been obtained.

[0007] The object of the present invention is to provide a polyphenylene ether solution capable of forming a porous film at around room temperature (20°C). The object of the present invention is to provide a porous film containing polyphenylene ether formed at around room temperature (20°C). Furthermore, the object of the present invention is to provide a method for producing a porous film capable of forming a porous film at around room temperature (20°C). Moreover, the object of the present invention is to provide an alkaline electrolysis diaphragm, a pharmaceutical process filter, and a water treatment membrane made of such a porous film.

[0008] The inventors of the present invention diligently studied to solve the above problems and found that the above problems can be solved by a polyphenylene ether solution containing a polyphenylene ether having a specific structure and a water-soluble organic solvent, thus completing the present invention.

[0009] [1] A polyphenylene ether solution comprising a water-soluble organic solvent having a solubility in water at 20°C of 50 g / 100 mL or more, and polyphenylene ether, wherein the polyphenylene ether comprises 1 to 99 mol% of repeating units derived from phenol represented by the following formula (1) and 1 to 99 mol% of repeating units derived from phenol represented by the following formula (2), based on a total of 100 mol% of repeating units derived from phenol represented by the following formula (1) and repeating units derived from phenol represented by the following formula (2). (In formula (1), R 11 Each independently represents a saturated hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, R 12 Each of these independently represents a hydrogen atom, an optionally substituted hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom. (In formula (2), R 21is a partial structure represented by the following formula (3), where R 22 each independently represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, provided that two R 22 are not both hydrogen atoms.) (In formula (3), R 31 each independently represents a linear alkyl group having 1 to 8 carbon atoms which may be substituted, or two R 31 may be bonded to each other to form a cyclic alkyl structure having 1 to 8 carbon atoms; R 32 each independently represents an alkylene group having 1 to 8 carbon atoms which may be substituted; R 33 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may be substituted, or a phenyl group which may be substituted; b is each independently 0 or 1; * represents a bond.)

[0010] [2] In a total of 100 parts by mass of the water-soluble organic solvent and the polyphenylene ether, the content of the water-soluble organic solvent is 50 to 99 parts by mass, and the content of the polyphenylene ether is 1 to 50 parts by mass. The polyphenylene ether solution according to [1].

[0011] [3] The polyphenylene ether contains 20 to 95 mol% of repeating units derived from the phenol represented by the formula (1) and 5 to 80 mol% of repeating units derived from the phenol represented by the formula (2) with respect to a total of 100 mol% of the repeating units derived from the phenol represented by the formula (1) and the repeating units derived from the phenol represented by the formula (2). The polyphenylene ether solution according to [1] or [2].

[0012] [4] The partial structure represented by the formula (3) is a tert-butyl group. The polyphenylene ether solution according to any one of [1] to [3].

[0013] [5] The water-soluble organic solvent is miscible with water. The polyphenylene ether solution according to any one of [1] to [4].

[0014] [6] The polyphenylene ether solution according to any one of [1] to [5], wherein the water-soluble organic solvent is N-methyl-2-pyrrolidone.

[0015] [7] The polyphenylene ether solution according to any one of [1] to [5], wherein the water-soluble organic solvent is a nitrogen-containing solvent.

[0016] [8] The polyphenylene ether solution according to [7], wherein the nitrogen-containing solvent is a compound represented by the following formula (10). (In formula (10), R １ (This represents a hydrogen atom, an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom.)

[0017] [9] A method for producing a porous membrane, comprising a dissolution step of dissolving polyphenylene ether in a solvent at 80°C or below, and produced by a non-solvent-induced phase separation method.

[0018]

[10] The method for producing a porous membrane according to [9], wherein in the dissolution step, polyphenylene ether is dissolved in a solvent at 0 to 50°C.

[0019]

[11] A porous membrane comprising a polyphenylene ether, wherein the polyphenylene ether comprises 1 to 99 mol% of repeating units derived from phenol represented by the following formula (1) and 1 to 99 mol% of repeating units derived from phenol represented by the following formula (2), based on a total of 100 mol% of repeating units derived from phenol represented by the following formula (1) and repeating units derived from phenol represented by the following formula (2). (In formula (1), R 11 Each independently represents a saturated hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, R 12 Each of these independently represents a hydrogen atom, an optionally substituted hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom. (In formula (2), R21 This is a substructure represented by the following formula (3), R 22 Each independently represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms (which may be substituted), an aryl group having 6 to 12 carbon atoms (which may be substituted), or a halogen atom, provided that two R 22 (Neither of them are hydrogen atoms.) (In formula (3), R 31 Each independently represents a linear alkyl group having 1 to 8 carbon atoms, which may be substituted, or two R 31 They may be bonded to each other to form a cyclic alkyl structure with 1 to 8 carbon atoms, R 32 Each of these independently represents an alkylene group having 1 to 8 carbon atoms, which may be substituted. 33 (where represents a hydrogen atom, an optionally substituted alkyl group having 1 to 8 carbon atoms, or an optionally substituted phenyl group; where b is independently 0 or 1; and where * represents a bond.)

[0020]

[12] The porous membrane according to

[11] , wherein the polyphenylene ether comprises 20 to 95 mol% of repeating units derived from phenol represented by formula (1) and 5 to 80 mol% of repeating units derived from phenol represented by formula (2), based on a total of 100 mol% of repeating units derived from phenol represented by formula (1) and repeating units derived from phenol represented by formula (2).

[0021]

[13] A method for producing a porous membrane according to

[11] or

[12] , which is produced by a non-solvent-induced phase separation method.

[0022]

[14] A method for producing a porous membrane according to any one of

[11] to

[13] , comprising: a step of preparing a polyphenylene ether solution; a step of adjusting the temperature of the polyphenylene ether solution; a film-forming step of forming a thin film of the polyphenylene ether solution on a substrate by coating; a solidification step of immersing the substrate and the thin film in a solidification solution; and a step of removing the thin film from the solidification solution and drying it under appropriate conditions, wherein the temperature of the polyphenylene ether solution in the step of adjusting the temperature of the polyphenylene ether solution is 80°C or lower.

[0023]

[15] A diaphragm for alkaline water electrolysis, comprising the porous membrane described in

[11] or

[12] .

[0024]

[16] A pharmaceutical process filter comprising the porous membrane described in

[11] or

[12] .

[0025]

[17] A water treatment membrane comprising the porous membrane described in

[11] or

[12] .

[0026] According to the present invention, a polyphenylene ether solution capable of forming a porous film at around room temperature (20°C) can be provided. According to the present invention, a porous film containing polyphenylene ether formed at around room temperature (20°C) can be provided. Furthermore, according to the present invention, a method for producing a porous film capable of forming a porous film at around room temperature (20°C) can be provided. Moreover, according to the present invention, a diaphragm for alkaline electrolysis, a process filter for pharmaceuticals, and a water treatment membrane made of such a porous film can be provided.

[0027] The present invention will be described in detail below based on its embodiments.

[0028] <Explanation of Terms> In this specification, "hydrocarbon group" includes "aliphatic hydrocarbon group" and "aromatic hydrocarbon group". "Aliphatic hydrocarbon group" includes "chain hydrocarbon group" and "alicyclic hydrocarbon group". From another perspective, "aliphatic hydrocarbon group" includes "saturated hydrocarbon group" and "unsaturated hydrocarbon group". In this specification, "saturated hydrocarbon group" includes, for example, chain hydrocarbon groups such as methyl group, ethyl group, propyl group, n-butyl group, isopropyl group, isobutyl group, 1-methylpentyl group, 1-ethylpentyl group, sec-butyl group, and tert-butyl group as monovalent saturated hydrocarbon groups; and alicyclic hydrocarbon groups such as cyclopropyl group and cyclobutyl group. In this specification, "unsaturated hydrocarbon group" refers to a linear or branched hydrocarbon group having 2 to 6 carbon atoms and containing at least one carbon-carbon double or triple bond. Specifically, examples include vinyl group, allyl group, methyl vinyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, ethynyl group, 2-propynyl group, etc. In this specification, "aryl group" refers to a monovalent aromatic hydrocarbon group, which may be monocyclic or polycyclic, and has 6 to 20 carbon atoms. Examples include phenyl group, 1-naphthyl group, 2-naphthyl group, anthryl group, phenanthryl group, pyrenyl group, indenyl group, or indanyl group. In this specification, "alkyl group" may be a linear, branched, or cyclic alkyl group, and examples include a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, tert-pentyl group, neopentyl group, 1,2-dimethylpropyl group, n-hexyl group, isohexyl group, (n-)heptyl group, (n-)octyl group, (n-)nonyl group, (n-)decyl group, (n-)undecyl group, (n-)dodecyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, or cyclononyl group. In this specification, "alkylene group" may be a divalent group obtained by removing one arbitrary hydrogen atom from the "alkyl group". Examples of "halogen atoms" include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0029] <Polyphenylene ether solution> The polyphenylene ether solution of this embodiment comprises a water-soluble organic solvent having a solubility in water of 50 g / 100 mL or more at 20°C, and polyphenylene ether, wherein the polyphenylene ether contains 1 to 99 mol% of repeating units derived from phenol represented by the following formula (1) and 1 to 99 mol% of repeating units derived from phenol represented by the following formula (2), with respect to a total of 100 mol% of repeating units derived from phenol represented by the following formula (1) and repeating units derived from phenol represented by the following formula (2). (In formula (1), R 11 Each independently represents a saturated hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, R 12 Each of these independently represents a hydrogen atom, an optionally substituted hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom. (In formula (2), R 21 This is a substructure represented by the following formula (3), R 22 Each independently represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms (which may be substituted), an aryl group having 6 to 12 carbon atoms (which may be substituted), or a halogen atom, provided that two R 22 (Neither of them are hydrogen atoms.) (In formula (3), R 31 Each independently represents a linear alkyl group having 1 to 8 carbon atoms, which may be substituted, or two R 31 They may be bonded to each other to form a cyclic alkyl structure with 1 to 8 carbon atoms, R 32 Each of these independently represents an alkylene group having 1 to 8 carbon atoms, which may be substituted. 33(wherein b represents a hydrogen atom, an optionally substituted alkyl group having 1 to 8 carbon atoms, or an optionally substituted phenyl group, b is independently 0 or 1, and * represents a bond.) With the above polyphenylene ether solution, a porous film can be formed at room temperature (around 20°C).

[0030] In the polyphenylene ether solution of this embodiment, it is preferable that, of a total of 100 parts by mass of the water-soluble organic solvent and the polyphenylene ether, the content of the water-soluble organic solvent is 50 to 99 parts by mass and the content of the polyphenylene ether is 1 to 50 parts by mass. When the ratio of the water-soluble organic solvent to the polyphenylene ether is within the above range, a suitable viscosity and a suitable porosity of the porous film are obtained during film formation. Furthermore, it is more preferable that, of a total of 100 parts by mass of the water-soluble organic solvent and the polyphenylene ether, the content of the water-soluble organic solvent is 65 to 90 parts by mass and the content of the polyphenylene ether is 10 to 35 parts by mass, and even more preferable that the content of the water-soluble organic solvent is 75 to 85 parts by mass and the content of the polyphenylene ether is 15 to 25 parts by mass.

[0031] (Water-soluble organic solvent) The water-soluble organic solvent in this embodiment is used to dissolve the polyphenylene ether in this embodiment, and is preferably a good solvent for water. The water-soluble organic solvent may be a single type or two or more types may be used in combination.

[0032] The aforementioned water-soluble organic solvent has a solubility in water at 20°C of 50 g / 100 mL or more, more preferably 80 g / 100 mL or more, and even more preferably 100 g / 100 mL or more, and is further preferably miscible with water (optionally miscible). In other words, it is preferable that the water-soluble organic solvent is water-miscible.

[0033] The solubility parameter (SP value) of the water-soluble organic solvent is preferably 10 or higher, preferably 15 or higher, and more preferably 20 or higher.

[0034] Furthermore, from the viewpoint of environmental impact, a non-halogenated water-soluble organic solvent is preferred as the water-soluble organic solvent. Specific examples of water-soluble organic solvents include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, and γ-butyrolactone. Two or more of these can also be used in combination. Among these, N-methyl-2-pyrrolidone is preferred from the viewpoint of solubility of the polyphenylene ether used in the present invention and its high boiling point and ease of handling.

[0035] Furthermore, the water-soluble organic solvent is more preferably a nitrogen-containing solvent. A nitrogen-containing solvent is a compound having at least one nitrogen atom. Specific examples of the above nitrogen-containing solvents include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone, N-butyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide.

[0036] The above nitrogen-containing solvent is preferably a compound represented by the following formula (10) from the viewpoint of high solubility of polyphenylene ether, and more preferably N-methyl-2-pyrrolidone. (In formula (10), R １ (This represents a hydrogen atom, an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom.)

[0037] The water-soluble organic solvent may be a mixture of a nitrogen-containing solvent and any other solvent, as long as it does not impair the solubility of polyphenylene ether and its miscibility with water. While there are no particular limitations on the solvent, a water-soluble organic solvent such as dimethyl sulfoxide is preferred from the viewpoint of miscibility with the nitrogen-containing solvent.

[0038] The content of the nitrogen-containing solvent relative to 100% by mass of the total water-soluble organic solvent is preferably 10 to 99% by mass. If the nitrogen-containing solvent content is 10% by mass or more, film formation by non-solvent-induced phase separation using this solution becomes easy, and if it is 99% by mass or less, the strength of the porous film produced becomes sufficient. From a similar viewpoint, the nitrogen-containing solvent content is more preferably 30 to 95% by mass, particularly preferably 50 to 90% by mass, and most preferably 60 to 85% by mass.

[0039] In one preferred embodiment, the polyphenylene ether solution comprises a water-soluble solvent containing a nitrogen-containing solvent and polyphenylene ether, wherein the concentration of polyphenylene ether is 1% by mass or more. A more preferred concentration of polyphenylene ether will be described later.

[0040] The boiling point of the water-soluble organic solvent in this embodiment is preferably 30°C to 300°C. From the viewpoint of ease of handling during film formation, the lower limit of the boiling point is preferably 60°C or higher, preferably 80°C or higher, and more preferably 100°C or higher. Furthermore, from the viewpoint of ease of removal from the film during drying, the upper limit of the boiling point is more preferably 220°C or lower.

[0041] (Polyphenylene ether) The polyphenylene ether of this embodiment contains 1 to 99 mol% of repeating units derived from phenol represented by the following formula (1) and 1 to 99 mol% of repeating units derived from phenol represented by the following formula (2), based on a total of 100 mol% of repeating units derived from phenol represented by the following formula (1) and repeating units derived from phenol represented by the following formula (2). (In formula (1), R 11 Each independently represents a saturated hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, R 12 Each of these independently represents a hydrogen atom, an optionally substituted hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom. (In formula (2), R21 This is a substructure represented by the following formula (3), R 22 Each independently represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms (which may be substituted), an aryl group having 6 to 12 carbon atoms (which may be substituted), or a halogen atom, provided that two R 22 (Neither of them are hydrogen atoms.) (In formula (3), R 31 Each independently represents a linear alkyl group having 1 to 8 carbon atoms, which may be substituted, or two R 31 They may be bonded to each other to form a cyclic alkyl structure with 1 to 8 carbon atoms, R 32 Each of these independently represents an alkylene group having 1 to 8 carbon atoms, which may be substituted. 33 (wherein b represents a hydrogen atom, an optionally substituted alkyl group having 1 to 8 carbon atoms, or an optionally substituted phenyl group, b is independently 0 or 1, and * represents a bond.) The polyphenylene ether of this embodiment contains repeating units derived from phenol represented by formula (1) and repeating units derived from phenol represented by formula (2) in the above proportions, thereby increasing its solubility in water-soluble organic solvents, and enabling the formation of porous films at around room temperature (20°C).

[0042] The polyphenylene ether of this embodiment preferably contains 5 to 80 mol% of the repeating units derived from the phenol represented by formula (2), more preferably 5 to 50 mol%, even more preferably 5 to 40 mol%, even more preferably 5 to 30 mol%, particularly preferably 5 to 20 mol%, and most preferably 5 to 15 mol%. If the proportion of the repeating units derived from the phenol represented by formula (2) is 5 mol% or more, the solubility in water-soluble organic solvents tends to improve. Furthermore, if the proportion of the repeating units derived from the phenol represented by formula (2) is 80 mol% or less, the handling properties of the film tend to improve, if it is 60 mol% or less, the film has flexibility, and if it is 30 mol% or less, the film has sufficient strength.

[0043] The polyphenylene ether of this embodiment preferably contains 20 to 95 mol% of the repeating units derived from the phenol represented by formula (1), more preferably 50 to 95 mol%, even more preferably 60 to 95 mol%, even more preferably 70 to 95 mol%, particularly preferably 80 to 95 mol%, and most preferably 85 to 95 mol%. If the proportion of the repeating units derived from the phenol represented by formula (1) is 20 mol% or more, the handling properties of the membrane tend to improve; if the proportion of the repeating units derived from the phenol represented by formula (2) is 40 mol% or more, the membrane has flexibility; and if it is 70 mol% or less, the membrane has sufficient strength.

[0044] Preferably, the polyphenylene ether contains 20 to 95 mol% of repeating units derived from the phenol represented by formula (1) and 5 to 80 mol% of repeating units derived from the phenol represented by formula (2), based on a total of 100 mol% of repeating units derived from the phenol represented by formula (1) and repeating units derived from the phenol represented by formula (2). More preferably, it contains 60 to 95 mol% of repeating units derived from the phenol represented by formula (1) and 5 to 40 mol% of repeating units derived from the phenol represented by formula (2).

[0045] In the above formula (1), R 11 Each of these independently represents a saturated hydrocarbon group having 1 to 6 carbon atoms, which may be substituted, an aryl group having 6 to 12 carbon atoms, or a halogen atom. 11 Each of these groups independently preferably represents a saturated hydrocarbon group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably a methyl group or a phenyl group, and even more preferably a methyl group.

[0046] In the above formula (1), R 12 Each of these independently represents a hydrogen atom, an optionally substituted hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom. Also, R 12 Each of these preferably independently represents a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

[0047] In the above formula (2), R 21The above formula (3) represents a substructure. The substructure represented by formula (3) is preferably a group containing secondary and / or tertiary carbons, such as an isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, tert-amyl group, 2,2-dimethylpropyl group, cyclohexyl group, or a structure having a phenyl group at its terminal. More preferably, it is an isopropyl group, tert-butyl group, or cyclohexyl group, even more preferably a tert-butyl group or cyclohexyl group, and particularly preferably a tert-butyl group.

[0048] In the above formula (2), R 22 Each of these independently represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms (which may be substituted), an aryl group having 6 to 12 carbon atoms (which may be substituted), or a halogen atom. 22 Each of these preferably independently represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms, or an aryl group having 6 to 12 carbon atoms which may be substituted with an alkyl group having 1 to 6 carbon atoms; more preferably, each of these represents a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms which may be substituted with an alkyl group having 1 to 6 carbon atoms; and even more preferably, each of these represents a hydrogen atom or a methyl group. In formula (2), the two R 22 It is preferable that they are different, and more preferably that one represents a hydrogen atom and the other represents a hydrocarbon group having 1 to 6 carbon atoms (preferably a methyl group).

[0049] In the above formula (3), R 31 Each independently represents a linear alkyl group having 1 to 8 carbon atoms, which may be substituted, or two R 31 These may bond to each other to form a cyclic alkyl structure having 1 to 8 carbon atoms. 31 Each of these groups preferably independently represents a linear alkyl group having 1 to 8 carbon atoms, and most preferably a methyl group.

[0050] In this embodiment, the structure of polyphenylene ether can be identified by analyzing it using techniques such as NMR and mass spectrometry. Specific methods for identifying the structure of polyphenylene ether include field desorption mass spectrometry (FD-MS), which is known to be less prone to fragmentation, and estimating the repeating units based on the spacing of detected ions. Furthermore, a method for estimating the structure of polyphenylene ether can be proposed that combine electron ionization (EI) peak analysis of fragment ions with structural analysis by NMR.

[0051] Since the phenol represented by formula (1) does not have an unsubstituted ortho position (i.e., hydrogen atoms are not bonded to the two ortho carbon atoms of the carbon atom to which the hydroxyl group is bonded), it can react with other phenolic monomers only at the phenolic hydroxyl group and the para carbon atom. Therefore, the repeating units derived from formula (1) include repeating units having the structure represented by the following formula (5). (In formula (5), R 11 and R 12 This is the same as equation (1).

[0052] The phenol represented by formula (2) has a phenolic hydroxyl group in addition to the R of phenol. 21 It can react with another phenolic monomer at either the ortho or para position where it is not bonded. Therefore, the repeating unit derived from the phenol represented by formula (2) may have a structure represented by the following formula (6) or formula (7), or a combination thereof. (R in equations (6) and (7)) 21 , R 22 This is the same as equation (2).

[0053] The polyphenylene ether of this embodiment may contain repeating units derived from phenol represented by the following formula (4). (In equation (4), X represents any linking group with an a-valence, a is an integer from 2 to 6, and R 4Each of these is independently either a linear alkyl group having 1 to 8 carbon atoms, or a substructure represented by formula (3), and the R 4 (The -O- bonded atom is attached to at least one of the carbon atoms at positions 2 or 6, with the carbon atom of the benzene ring to which it is attached being position 1, and k is an integer from 1 to 4, independently of the others.)

[0054] In the above formula (4), R 4 Each of these is independently one of a linear alkyl group having 1 to 8 carbon atoms, such as a methyl group, an ethyl group, or an n-propyl group, and one of the substructures represented by formula (3) above, and it is preferable that each is a methyl group or one of the substructures represented by formula (3) above. Each of the a substructures may have the same structure or may be different. In particular, from the viewpoint of having even better solubility in water-soluble organic solvents, it is preferable that each of the a substructures has the same structure.

[0055] In the above formula (4), k is an integer from 1 to 4, and preferably an integer from 2 to 4.

[0056] In the above formula (4), R 4 The R bonded to the benzene ring is positioned at position 2 and at least one of the carbon atoms at positions 2 and 6, with the carbon atom to which the -O- bond is attached being at position 1. 4 When is a linear alkyl group having 1 to 8 carbon atoms, it is preferable that it is bonded to both the 2nd and 6th positions, and R bonded to the 2nd and / or 6th positions 4 When the substructure is represented by formula (3), it is preferable that it is bonded to only one of either the 2nd or 6th position.

[0057] The polyphenylene ether of this embodiment may also include repeating units derived from the phenol represented by formula (4), repeating units derived from the phenol represented by formula (1), and repeating units derived from the phenol represented by formula (2). In this case, R of formula (2) 21 and R in the above equation (4) 4If both are substructures (functional groups) represented by formula (3) (i.e., both the phenol compound represented by formula (2) and the phenol compound represented by formula (4) are substituted with the substructures (functional groups) represented by formula (3)), the structures of each substructure (functional group) represented by formula (3) may be the same or different.

[0058] When the polyphenylene ether contains repeating units derived from the phenol represented by formula (4), repeating units derived from the phenol represented by formula (1), and repeating units derived from the phenol represented by formula (2), the proportion of these repeating units is preferably such that, based on 100 mol% of the total of the repeating units derived from the phenol represented by formula (1), the repeating units derived from the phenol represented by formula (2), and the repeating units derived from the phenol represented by formula (4), the repeating units consist of 50 to 100 mol% of the repeating units derived from the phenol represented by formula (1), 0 to 30 mol% of the repeating units derived from the phenol represented by formula (2), and 0 to 40 mol% of the repeating units derived from the phenol represented by formula (4).

[0059] In formula (4) above, X is any a-valent linking group and is not particularly limited, but examples include hydrocarbon groups such as chain hydrocarbon groups and cyclic hydrocarbon groups; hydrocarbon groups containing one or more atoms selected from nitrogen, phosphorus, silicon, and oxygen; atoms such as nitrogen, phosphorus, and silicon; or groups combining these. X may be a linking group excluding single bonds. X may be a linking group that links a substructures together.

[0060] As for X above, R is connected via a single bond or an ester bond, etc. 4 R 4 R 4 Examples include α-valent heterocyclic skeletons bonded to a benzene ring.

[0061] Here, the alkyl skeleton is not particularly limited, but examples include a linear hydrocarbon (e.g., a linear saturated hydrocarbon) with at least a number of carbon atoms (2 to 6) whose branched ends are directly bonded to a benzene ring of the substructure (it is sufficient that a benzene ring is bonded to a branched end, and there may be branched ends that are not bonded to a benzene ring). Also, the aryl skeleton is not particularly limited, but examples include a benzene ring, a mesitylene group, or a 2-hydroxy-5-methyl-1,3-phenylene group bonded via a single bond or an alkyl chain, R 4 Examples include skeletons that bond to a benzene ring to which R is attached. Furthermore, there are no particular limitations on the heterocyclic skeleton, but for example, a triazine ring is bonded via a single bond or alkyl chain, 4 Examples include skeletons that bond to the benzene ring to which the compound is attached.

[0062] In the above formula (4), a is an integer between 2 and 6, preferably between 2 and 4.

[0063] If the phenol represented by formula (4) does not have an unsubstituted ortho position, the structural unit derived from the phenol represented by formula (4) has the structure represented by formula (8) below. On the other hand, if the phenol represented by formula (4) has an unsubstituted ortho position, the structural unit derived from the phenol of formula (4) has the structure represented by formula (8) below, or the structure represented by formula (9) below, or a combination thereof. (R in equations (8) and (9)) 4 This is the same as equation (4).

[0064] The number-average molecular weight (Mn) of the polyphenylene ether in this embodiment is preferably, for example, 3,000 or more and 400,000 or less. If the number-average molecular weight is within this upper limit, it is soluble in water-soluble organic solvents used in film formation, and at the same time, the film strength as a porous film tends to be high. The preferred lower limit of the number-average molecular weight (Mn) is 5,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, even more preferably 8,000 or more, and most preferably 10,000 or more. If the number-average molecular weight (Mn) is 5,000 or more, the resulting porous film has excellent handling properties, and if it is 10,000 or more, the film strength is sufficient. More preferably, the upper limit of the number-average molecular weight (Mn) is 200,000 or less. If the number-average molecular weight (Mn) is 200,000 or less, it has excellent solubility in water-soluble organic solvents and excellent handling properties of the solution during film formation.

[0065] The weight-average molecular weight (Mw) of the polyphenylene ether in this embodiment is preferably, for example, 5,000 or more and 1,000,000 or less. If the weight-average molecular weight (Mw) is below this upper limit, it is soluble in water-soluble organic solvents used in film formation, and at the same time, the film strength as a porous film tends to be high. The preferred lower limit of the weight-average molecular weight is 10,000 or more, more preferably 15,000 or more, even more preferably 20,000 or more, particularly preferably 25,000 or more, and most preferably 30,000 or more. If the weight-average molecular weight (Mw) is 10,000 or more, the resulting porous film has excellent handling properties, and if it is 30,000 or more, the film strength is sufficient. The upper limit of the weight-average molecular weight (Mw) is more preferably 500,000 or less. If the weight-average molecular weight (Mw) is 500,000 or less, it has excellent solubility in water-soluble organic solvents and excellent handling properties of the solution during film formation.

[0066] The weight-average molecular weight / number-average molecular weight of the polyphenylene ether in this embodiment is, for example, 2.0 or more and 30.0 or less. When the weight-average molecular weight / number-average molecular weight is 2.0 or more, the solution viscosity during film formation is favorable. A weight-average molecular weight / number-average molecular weight of 3.0 or more is more preferable, and an even more preferable of 4.0 or more. Furthermore, when the weight-average molecular weight / number-average molecular weight is 30.0 or less, the porosity of the porous film tends to be high when a porous film is formed using the polyphenylene ether solution, resulting in excellent water permeability of the film. The upper limit of the weight-average molecular weight / number-average molecular weight is more preferably 10 or less, and even more preferably 5.0 or less. Note that the number-average molecular weight and weight-average molecular weight of the polyphenylene ether are values ​​measured by gel permeation chromatography. The number-average molecular weight and weight-average molecular weight of the polyphenylene ether can be controlled by changing the aeration time during polymerization. For example, the number-average molecular weight and weight-average molecular weight can be increased by increasing the aeration time during polymerization.

[0067] In this embodiment, the reduced viscosity of the polyphenylene ether is preferably, for example, 0.2 or more and 0.5 or less. When the lower limit of the reduced viscosity of the polyphenylene ether is 0.2 or more, the solution viscosity during film formation is suitable. A lower limit of the reduced viscosity of the polyphenylene ether is more preferably 0.3 or more. When the upper limit of the reduced viscosity of the polyphenylene ether is 0.5 or less, the porosity of the porous film tends to be high, resulting in excellent water permeability of the film. A more preferable upper limit of the reduced viscosity of the polyphenylene ether is 0.4 or less. In this embodiment, the reduced viscosity of the polyphenylene ether is the value measured in a 0.5 g / dL chloroform solution at 30°C using an Ubbelohde-type viscosity tube.

[0068] When the entire polyphenylene ether solution of this embodiment is considered to be 100% by mass, the concentration of polyphenylene ether is, at a lower limit, 1% by mass or more, preferably 5% by mass or more, more preferably 8% by mass or more, and particularly preferably 10% by mass or more. If the lower limit of the polyphenylene ether concentration is 5% by mass or more, it has a viscosity that is excellent for coating film processability during film formation, and if it is 10% by mass or more, the resulting film tends to have high strength. The upper limit of the polyphenylene ether concentration is 60% by mass or less, preferably 50% by mass or less, more preferably 45% by mass or less, and most preferably 40% by mass or less. If the upper limit of the polyphenylene ether concentration is 60% by mass or less, a uniformly dissolved solution is obtained, and if it is 40% by mass or less, the porosity of the porous film is sufficient.

[0069] A hydrophilic agent may be added to the polyphenylene ether solution of the present invention to control the pore size. The amount of hydrophilic agent added is 0 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, even more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more, per 100 parts by mass of the total of polyphenylene ether and water-soluble organic solvent. Alternatively, it may be 30 parts by mass or less, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

[0070] As hydrophilizing agents, water-soluble polymers such as polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyethylene oxide, polyethylene glycol-polypropylene glycol block copolymer, polyacrylamide, polyvinylpyrrolidone, polyhydroxyacrylate, polyhydroxymethacrylate, polyacrylic acid, polymethacrylic acid, polyitaconic acid, polyfumaric acid, polycitraconic acid, poly-p-styrenesulfonic acid, sodium poly-p-styrenesulfonate, N,N-dimethylacrylamide, carboxymethylcellulose, starch, corn starch, polychitosan, polychitin, and polystyrene-polyethylene glycol copolymer can be used. Among these, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and polystyrene-polyethylene glycol copolymer are preferred, and polyvinylpyrrolidone is preferred.

[0071] The polyphenylene ether solution of this embodiment may contain the above-mentioned water-soluble organic solvent, polyphenylene ether, and other components such as optionally added hydrophilic agents. The content of these other components can be appropriately set within a range that does not hinder the effects of the present invention.

[0072] (Method for producing polyphenylene ether solution) The polyphenylene ether solution of this embodiment can be produced, for example, by mixing the above-mentioned water-soluble organic solvent, polyphenylene ether, optionally a hydrophilizing agent, and optionally other components.

[0073] The present invention also relates to a method for producing a polyphenylene ether solution. A preferred method for producing a polyphenylene ether solution includes the steps of: determining a specific polyphenylene ether; identifying a solvent having a saturation concentration of 1% by mass or more of the polyphenylene ether; determining one or more solvents from among the solvents; and dissolving the polyphenylene ether resin in the solvent at 0 to 100°C, wherein the solvent contains at least one nitrogen-containing solvent and the concentration of the polyphenylene ether is 1% by mass or more. Conventionally, poly(2,6-dimethyl-1,4-phenylene oxide), which has been widely used as a polyphenylene ether, has low solubility in water-soluble organic solvents such as nitrogen-containing solvents, and in order to obtain a solution of a predetermined concentration or higher, it was necessary to produce the polyphenylene ether solution at a high temperature of 110°C or higher. In contrast, the above-described method for producing a polyphenylene ether solution makes it possible to produce a high-concentration polyphenylene ether solution without going through a high-temperature process. The polyphenylene ether in this production method is not particularly limited as long as it can be used to produce a solution by the above production method. The polyphenylene ether is preferably a polyphenylene ether containing repeating units derived from the phenol represented by formula (1) and repeating units derived from the phenol represented by formula (2). Furthermore, since halogenated polyphenylene ethers are susceptible to deterioration and crosslinking in the presence of alkaline aqueous solutions, it is preferable that the polyphenylene ether is not a halogenated polyphenylene ether. More specifically, it is preferable that the polyphenylene ether is not a polyphenylene ether in which at least one substituent of the benzene ring is a halogen atom or a halogenated alkyl group. The nitrogen-containing solvent is as described above, and the above explanation applies.

[0074] The use of the polyphenylene ether solution of this embodiment is not particularly limited, but it is preferably used in the manufacture of porous membranes.

[0075] <Porous membrane> The porous membrane of this embodiment contains a polyphenylene ether, wherein the polyphenylene ether contains 1 to 99 mol% of the repeating units derived from the phenol represented by the following formula (1) and 1 to 99 mol% of the repeating units derived from the phenol represented by the following formula (2), based on a total of 100 mol% of the repeating units derived from the phenol represented by the following formula (1) and the repeating units derived from the phenol represented by the following formula (2). (In formula (1), R 11 Each independently represents a saturated hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, R 12 Each of these independently represents a hydrogen atom, an optionally substituted hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom. (In formula (2), R 21 This is a substructure represented by the following formula (3), R 22 Each independently represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms (which may be substituted), an aryl group having 6 to 12 carbon atoms (which may be substituted), or a halogen atom, provided that two R 22 (Neither of them are hydrogen atoms.) (In formula (3), R 31 Each independently represents a linear alkyl group having 1 to 8 carbon atoms, which may be substituted, or two R 31 They may be bonded to each other to form a cyclic alkyl structure with 1 to 8 carbon atoms, R 32 Each of these independently represents an alkylene group having 1 to 8 carbon atoms, which may be substituted. 33 (wherein b represents a hydrogen atom, an optionally substituted alkyl group having 1 to 8 carbon atoms, or an optionally substituted phenyl group, b is independently 0 or 1, and * represents a bond.) In the porous membrane of this embodiment, the explanations for formulas (1), (2), and (3) above are referred to in the section on <Polyphenylene ether solution>.

[0076] Furthermore, the explanation regarding polyphenylene ether contained in the porous membrane is the same as that given in the section on (polyphenylene ether).

[0077] The form of the porous membrane in this invention is not particularly limited, but typical examples include flat membranes and hollow fiber membranes.

[0078] The porosity of the porous membrane in this embodiment is preferably 30% or more, and more preferably 50% to 90%. From the viewpoint of membrane water permeability, the lower limit of the porosity of the porous membrane is more preferably 60% or more, even more preferably 62% or more, particularly preferably 65% ​​or more, and especially preferably 72% or more. From the viewpoint of membrane strength, the upper limit of the porosity of the porous membrane is even more preferably 85% or less, and particularly preferably 80% or less.

[0079] The porous membrane of this embodiment can be used for any liquid separation application targeting size separation. Particularly suitable applications include filters used in medical, pharmaceutical, and food and beverage applications, as well as related applications, water electrolysis applications, and water treatment applications. Specifically, these include various filters used in medical applications such as plasma filtration, virus removal, and various blood purification applications including hemodialysis; various process filters used in pharmaceutical applications such as the purification process of synthetic pharmaceuticals such as anticancer agents and antibiotics, the purification process of highly purified amino acids for pharmaceutical use, and the purification process of antibody drugs such as polyclonal antibodies and monoclonal antibodies; and various process filters used in food applications such as filters used in the production of various beverages such as sake, beer, wine, sparkling wine, tea, oolong tea, vegetable juice, and fruit juice. In particular, it can also be used as a process filter for the purpose of removing aggregates of immunoglobulins, which are antibody drugs. Furthermore, blood treatment applications in this invention refer to blood treatment applications such as blood purification, and include plasma filtration filters, virus removal filters, and hollow fiber filters for hemodialysis, which are included in the medical applications mentioned above. A specific example of a water electrolysis application is a diaphragm used to prevent the mixing of gases generated in the water electrolyte. Specific examples of its use in water treatment include water purification, process water production, sewage treatment, industrial wastewater treatment, and seawater desalination.

[0080] The porous membrane of this embodiment is particularly preferably used for alkaline water electrolysis, pharmaceutical process filters, or water treatment.

[0081] In this invention, a porous membrane is a membrane used for separating solids, liquids, and gases from a mixed liquid that is liquid at the temperature at which the separation process is performed. However, membranes in which the separation principle is based on dissolution / diffusion of the target substance into the membrane rather than size are not included in the category of porous membranes in this invention.

[0082] (Method for Manufacturing Porous Membrane) The porous membrane of this embodiment can be manufactured by a non-solvent-induced phase separation method. This is a typical method for manufacturing porous membranes, in which a porous membrane is produced by immersing a homogeneous polymer solution in a non-solvent. The non-solvent-induced phase separation method in this invention may include, for example, the steps of preparing a polyphenylene ether solution, adjusting the temperature of the polyphenylene ether solution, forming a film on a substrate by coating, solidification, immersing the substrate and the film in a solidification solution, and removing the film from the solidification solution and drying it under appropriate conditions. An example of the non-solvent-induced phase separation method in this invention is the method described in Polymers 2023, 15(21), 4307, Andrey Basko, "Mechanism of PVDF Membrane Formation by NIPS Revisited: Effect of Precipitation Bath Nature and Polymer-Solvent Affinity".

[0083] The method for manufacturing a porous membrane according to this embodiment is described in more detail below. The method for manufacturing a porous membrane according to this embodiment includes the steps of: preparing a polyphenylene ether solution; adjusting the temperature of the polyphenylene ether solution; forming a film on a substrate by coating; immersing the substrate and the thin film in a solidification solution; and removing the thin film from the solidification solution and drying it under appropriate conditions, characterized in that the temperature of the polyphenylene ether solution in the step of adjusting the temperature of the polyphenylene ether solution is 80°C or lower. According to the above method for manufacturing a porous membrane, a porous membrane can be manufactured at room temperature (around 20°C) using polyphenylene ether.

[0084] [Process for preparing polyphenylene ether solution] In the process for preparing a polyphenylene ether solution, the polyphenylene ether solution can be prepared by mixing polyphenylene ether, a water-soluble organic solvent, and any other components.

[0085] The polyphenylene ether and water-soluble organic solvent are the same as those in the polyphenylene ether solution described above, and the explanation in the section on <Polyphenylene ether solution> is applied. Optional components include hydrophilizing agents, etc.

[0086] [Step to adjust the temperature of the polyphenylene ether solution] In the step to adjust the temperature of the polyphenylene ether solution, the temperature of the polyphenylene ether solution is 80°C or lower. In the method for producing a porous membrane according to the present invention, the solution temperature in the step to adjust the temperature of the polyphenylene ether solution is 10°C or higher as a lower limit and below the flash point of the water-soluble organic solvent in the polyphenylene ether solution as an upper limit. By maintaining these temperature conditions, the handling and safety of the solution during membrane production are improved. The upper limit of the solution temperature in the step to adjust the temperature of the polyphenylene ether solution is preferably 50°C or lower. By maintaining these temperature conditions, a viscosity suitable for processing into a membrane, which is desirable as a film stock solution of polyphenylene ether, can be obtained.

[0087] There are no particular limitations on the method for adjusting the temperature of a polyphenylene ether solution, but examples include heating a non-metallic container using an oven, hot water bath, oil bath, aluminum block constant temperature bath, etc., or directly heating the solution by placing an immersion heater in it to adjust the temperature.

[0088] [Film-forming process for forming a thin film of polyphenylene ether solution on a substrate by coating] In the film-forming process for forming a thin film of polyphenylene ether solution on a substrate by coating (hereinafter sometimes simply referred to as the "film-forming process"), the polyphenylene ether solution prepared in the process for preparing the polyphenylene ether solution is coated onto the substrate to form a thin film.

[0089] The coating method is not particularly limited and can be carried out using known methods. Examples of coating methods include coating using a bar coater or coating by dipping.

[0090] Examples of substrates include glass plates, stainless steel plates, aluminum plates, and polyimide films.

[0091] [Solidification step of immersing the substrate and the thin film in a solidification solution] In the solidification step of immersing the substrate and the thin film in a solidification solution (hereinafter also simply referred to as the "solidification step"), the substrate and the thin film formed on the substrate in the film formation step are immersed in a solidification solution to solidify the thin film.

[0092] The coagulation solution used in the coagulation process refers to a substance that, upon contact with the film stock solution, induces non-solvent-induced phase separation and forms a film from the contact surface. Specifically, pure water, monoalcohol-based solvents, polyol-based solvents represented by the following formula (14), or mixtures of two or more of these are preferably used. In formula (14), R ９ This is an organic functional group containing 1 to 20 carbon atoms, or a structure containing 1 or more oxygen atoms and 1 to 20 carbon atoms, R ９It may contain one or more hydroxyl groups, ether bonds, ester groups, ketone groups, carboxylic acids, etc. Examples of polyol solvents represented by formula (14) include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, glycerin, propylene glycol, 1,2-butanediol, and 1,4-butanediol.

[0093] The temperature of the coagulation solution used in the coagulation process can be changed to control the structure, such as the size of the pores. The temperature of the coagulation solution varies depending on the composition and concentration of the film stock solution, but from the viewpoint of the strength of the porous membrane produced, it is preferably 10°C or higher, preferably 20°C or higher, preferably 40°C or higher, preferably 60°C or higher, and preferably 80°C or higher. From the viewpoint of ease of handling during manufacturing, the temperature of the coagulation solution is below the boiling point of the coagulation solution used, preferably 5°C or more below the boiling point, and particularly preferably 10°C or more below the boiling point.

[0094] When obtaining the porous membrane of the present invention, it is possible to include water-soluble organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, and γ-butyrolactone in the coagulation solution in order to control the size of the pores and impart hydrophilicity to the membrane. The composition of the solvent will vary depending on the composition of the membrane stock solution and the contact temperature between the membrane stock solution and the coagulation solution, but generally, when the total coagulation solution is considered to be 100% by mass, it is preferable that the mass percentage of the good solvent be between 0% by mass and 90% by mass. Within this range, sufficient non-solvent-induced phase separation necessary for membrane formation can be adequately achieved.

[0095] [Process of removing the thin film from the solidification solution and drying it under appropriate conditions] In the process of removing the thin film from the solidification solution and drying it under appropriate conditions, the thin film that was immersed in the solidification solution during the solidification process is removed from the solidification solution and dried.

[0096] In the step of removing the thin film from the solidification solution and drying it under appropriate conditions, drying is carried out at a temperature that does not cause film rupture during drying, for example, within a temperature range of 20°C or higher and below the melting temperature of polyphenylene ether. Preferred drying temperatures are 50°C to 150°C, more preferably 60°C to 140°C, and particularly preferably 70°C to 130°C. The drying time is determined in relation to the drying temperature, but is generally selected from 0.01 hours to 48 hours.

[0097] It is desirable to remove dissolved gases from the film stock solution, coagulation solution, and especially the coagulation solution passed through the inside of the fiber during hollow fiber film production (hereinafter referred to as the "internal coagulation solution") used to obtain the porous film of the present invention after uniform dissolution. By removing dissolved gases, defects in the film caused by foaming of dissolved gases can be significantly improved. Furthermore, by removing oxygen in particular from the dissolved gases, oxidation reactions of the material due to film processing at high temperatures are reduced.

[0098] When manufacturing hollow fiber membranes as porous membranes, in order to further promote the coagulation of the membrane stock solution exiting from the double spindle and the internal coagulation solution, a tank (hereinafter referred to as the "coagulation tank") can be provided directly below the spindle, allowing it to come into contact with the coagulation solution (hereinafter referred to as the "external coagulation solution") that fills the coagulation tank.

[0099] When manufacturing hollow fiber membranes as porous membranes, the distance from the spindle to the external solidification liquid surface (hereinafter referred to as "free travel distance") and the temperature and humidity of the space from the spindle to the external solidification liquid surface can be adjusted to freely control the cross-sectional structure of the hollow fiber membrane, not only to a uniform structure but also to various non-uniform structures.

[0100] The lower limit of the free travel distance is 0.01 m or more, preferably 0.05 m or more, and particularly preferably 0.1 m or more. The upper limit is 2.0 m or less, preferably 1.5 m or less, and particularly preferably 1.2 m or less. The temperature in the space from the spinneret to the external solidification surface is 20°C or more, preferably 50°C or more, and particularly preferably 80°C or more. Humidity varies in conjunction with temperature, but the lower limit is 0% or more, preferably 25% or more, particularly preferably 50% or more, and the upper limit is 100% or less.

[0101] When manufacturing hollow fiber membranes as porous membranes, the winding speed can vary depending on various factors in the manufacturing conditions, such as the shape of the spinneret, the composition of the spinning solution, the composition of the internal and external coagulation solutions, and the temperature of the solution and each coagulation solution. However, a speed of approximately 600 m / hour to 9000 m / hour is generally selected.

[0102] In the porous membrane manufacturing method of this embodiment, after the coagulation step with the coagulation solution, the membrane can be immersed in a desolvation tank to enhance its strength and promote desolvation. The desolvation solution can be any solvent that can remove the remaining solvent after non-solvent-induced phase separation by the coagulation solution and does not dissolve the membrane. Generally, water, ethanol, etc., are often used as the desolvation solution.

[0103] Other preferred methods for producing porous membranes are as follows: Another preferred method for producing porous membranes includes a dissolution step of dissolving polyphenylene ether in a solvent at 80°C or below, and is produced by a non-solvent-induced phase separation method. The temperature in the above dissolution step is preferably 0 to 50°C. The above polyphenylene ether and solvent are not particularly limited. The polyphenylene ether is preferably a polyphenylene ether containing repeating units derived from phenol represented by formula (1) and repeating units derived from phenol represented by formula (2). Furthermore, since halogenated polyphenylene ethers are susceptible to deterioration and crosslinking in the presence of alkaline aqueous solutions, it is preferable that the polyphenylene ether is not a halogenated polyphenylene ether. More specifically, it is preferable that the polyphenylene ether is not a polyphenylene ether in which at least one substituent of the benzene ring is a halogen atom or a halogenated alkyl group. The solvent is preferably the above-mentioned water-soluble organic solvent.

[0104] Furthermore, other preferred methods for manufacturing porous films are as follows. Another preferred method for manufacturing porous films includes a dissolution step of dissolving polyphenylene ether in a solvent at 0 to 50°C, and a solidification step of immersing the polyphenylene ether solution in a solidification solution, characterized in that the concentration of polyphenylene ether in the solvent in the dissolution step is 1% by mass or more. The method for manufacturing porous films of this embodiment may optionally further include one or more of the following steps: adjusting the temperature of the polyphenylene ether solution, forming a film of the polyphenylene ether solution on a substrate by coating, and removing the film from the solidification solution and drying it under appropriate conditions. These steps are as described above, and the above explanation will be incorporated therein. According to the above method for manufacturing porous films, a porous film can be manufactured using polyphenylene ether without going through high-temperature processes.

[0105] [Dissolution process for dissolving polyphenylene ether in a solvent] In the process of dissolving polyphenylene ether in a solvent, the polyphenylene ether solution can be prepared by mixing polyphenylene ether, a solvent, and any other components. This process is carried out at 0 to 50°C. By controlling the temperature range to 0 to 50°C, accidents such as ignition of the solvent can be prevented. The concentration of the polyphenylene ether solution is 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and most preferably 15% by mass or more, from the viewpoint that the viscosity of the solution is sufficient for film formation and the strength of the porous film produced is sufficient. Furthermore, from the viewpoint of processability when forming a film, the viscosity of the solution is preferably 50% by mass or less, more preferably 40% by mass or less, and most preferably 25% by mass or less. The polyphenylene ether and solvent are not particularly limited. The polyphenylene ether is preferably a polyphenylene ether containing repeating units derived from phenol represented by formula (1) and repeating units derived from phenol represented by formula (2). Furthermore, since halogenated polyphenylene ethers are susceptible to deterioration and crosslinking in the presence of alkaline aqueous solutions, it is preferable that the polyphenylene ether is not a halogenated polyphenylene ether. More specifically, it is preferable that the polyphenylene ether is not a polyphenylene ether in which at least one substituent of the benzene ring is a halogen atom or a halogenated alkyl group. The solvent is preferably the water-soluble organic solvent described above.

[0106] [Coagulation step of immersing polyphenylene ether solution in coagulation solution] The coagulation solution used in the coagulation step, the temperature of the coagulation solution, and the compounds that may be contained in the coagulation solution are the same as those described in the section [Coagulation step of immersing the substrate and the thin film in coagulation solution], and the explanation in that section shall be used with reference.

[0107] <Diaphragm for Alkaline Water Electrolysis> The diaphragm for alkaline water electrolysis in this embodiment consists of the porous membrane of this embodiment.

[0108] <Pharmaceutical Process Filter> The pharmaceutical process filter of this embodiment consists of the porous membrane of this embodiment.

[0109] <Water Treatment Membrane> The water treatment membrane in this embodiment consists of the porous membrane of this embodiment.

[0110] The embodiment will be described in more detail below based on the following examples, but this embodiment is not limited to the following examples.

[0111] <Ingredients Used> (Polyphenylene Ether) The following polyphenylene ethers were used. The composition and physical properties of each polyphenylene ether are shown in Table 1. ・Polyphenylene ether-1 (PPE-1): Synthesized according to Synthesis Example 1 below ・Polyphenylene ether-2 (PPE-2): Synthesized according to Synthesis Example 2 below ・Polyphenylene ether-3 (PPE-3): Synthesized according to Synthesis Example 3 below ・Polyphenylene ether-4 (PPE-4): Synthesized according to Synthesis Example 4 below ・Polyphenylene ether-5 (PPE-5): Synthesized according to Synthesis Example 5 below ・Polyphenylene ether-6 (PPE-6): Synthesized according to Synthesis Example 6 below ・Polyphenylene ether-7 (PPE-7): Xyron S202A, manufactured by Asahi Kasei Corporation

[0112] (Hydrophilic agent) Polyvinylpyrrolidone K30 (hereinafter PVP): Manufactured by Tokyo Chemical Industry Co., Ltd.

[0113] (Organic solvents) The following organic solvents were used: • N-methyl-2-pyrrolidone (hereinafter NMP): Manufactured by Hayashi Pure Chemical Industries, Ltd. (Water solubility > 100 g / 100 mL (miscible), boiling point 206 °C) • Toluene: Manufactured by Tokyo Chemical Industries, Ltd. (Water solubility = 0.05 g / mL, boiling point 111 °C)

[0114] (Manufacturing Example 1) Polyphenylene ether-1 (PPE-1) synthesis: A 40-liter jacketed polymerization tank equipped with a sparger, stirring turbine blades and baffles for introducing oxygen-containing gas at the bottom of the polymerization tank, and a reflux condenser in the vent gas line at the top of the polymerization tank, was subjected to nitrogen gas injection at a flow rate of 30.9 L / min while adding 2.4 g of cupric oxide, 18.1 g of 47% by mass aqueous solution of hydrogen bromide, 5.8 g of di-t-butylethylenediamine, 28.1 g of di-n-butylamine, 85.6 g of butyldimethylamine, 15.9 kg of toluene, and 2.0 g of trioctylmethylammonium chloride (R=C). ８ -C １０ ) was added to make a homogeneous solution. Next, using a pump, 1617 g of 2,6-dimethylphenol, 383 g of 2-tert-butyl-5-methylphenol, and 2.0 kg of toluene dropwise solution were added to the polymerization tank over 35 minutes. Simultaneously, dry air was introduced into the polymerization solution from the bottom of the polymerization tank at a rate of 21.0 L / min via a sparger, and polymerization was started. Dry air was passed through for 240 minutes to obtain the polymerization mixture. During polymerization, the internal temperature was controlled to 40°C. At the end of polymerization, the polymerization mixture (polymerization solution) was in a homogeneous solution state. Subsequently, the flow of dry air was stopped, and 25.9 g of tetrasodium ethylenediaminetetraacetate (reagent manufactured by Dojin Chemical Research Institute) was added to the polymerization mixture as an aqueous solution in 2 kg of water. The polymerization mixture was stirred at 70°C for 150 minutes, then allowed to stand for 20 minutes, and the organic phase and aqueous phase were separated by liquid-liquid separation. The above organic phase was concentrated using a rotary evaporator until the polymer concentration reached 30% by mass. Methanol was added to the solution so that the mass ratio of methanol to the solution was 4, and the polymer was precipitated. Wet polyphenylene ether was obtained by vacuum filtration using a glass filter. The wet polyphenylene ether was then washed with methanol in an amount such that the mass ratio of methanol to the wet polyphenylene ether was 4. The above washing operation was repeated three times. After that, the wet polyphenylene ether was maintained at 140°C and 1 mmHg for 120 minutes to obtain dry polyphenylene ether-1 (PPE-1).

[0115] (Production Example 2) The same procedure as in Production Example 1 was followed, except that the phenol raw materials for the synthesis of polyphenylene ether-2 (PPE-2) were 1740 g of 2,6-dimethylphenol and 260 g of 2-tert-butyl-5-methylphenol, to obtain dry polyphenylene ether-2 (PPE-2).

[0116] (Production Example 3) The procedure was carried out in the same manner as in Production Example 1, except that the time for passing dry air during the synthesis polymerization of polyphenylene ether-3 (PPE-3) was set to 210 minutes, to obtain dry polyphenylene ether-3 (PPE-3).

[0117] (Production Example 4) The procedure was carried out in the same manner as in Production Example 1, except that the time for passing dry air during the synthesis polymerization of polyphenylene ether-4 (PPE-4) was set to 270 minutes, to obtain dry polyphenylene ether-4 (PPE-4).

[0118] (Production Example 5) The procedure was carried out in the same manner as in Production Example 1, except that the phenol raw materials for the synthesis of polyphenylene ether-5 (PPE-5) were 1269 g of 2,6-dimethylphenol and 731 g of 2-tert-butyl-5-methylphenol, and dry polyphenylene ether-5 (PPE-5) was obtained.

[0119] (Manufacturing Example 6) Synthesis of polyphenylene ether-6 (PPE-6) Cardanol (product name LB-7250, manufactured by Tohoku Kako Co., Ltd., 50.0 g), p-toluenesulfonic acid monohydrate (0.851 g), and toluene (50 mL) were sequentially added to a 300 mL four-necked flask connected to a Dewar condenser at -10°C, and the mixture was stirred with a stirring blade. Then, the mixture was heated in an aluminum block heating device with the ambient temperature set to 65°C. Isobutene (21.6 g) was introduced over 2 hours and 30 minutes. After the introduction of isobutene, the mixture was stirred at an ambient temperature of 60°C for 2 hours. After raising the ambient temperature to 110°C, 27% sodium hydroxide aqueous solution (0.73 g) was added dropwise to the reaction solution. Then, ion-exchanged water (50 mL) was added, the mixture was stirred for 15 minutes, and then allowed to stand. Since the organic layer was suspended, ethyl acetate (300 mL) was added and dissolved completely. The organic layer was recovered using a separatory funnel, washed with saturated brine (200 mL), dried over magnesium sulfate, and concentrated using a rotary evaporator to obtain a brownish oily crude product (60.1 g). The obtained crude product was purified by silica gel column chromatography (column diameter: 100 mm, column height: 16 cm, silica gel: 600 g, developing solvent: heptane / ethyl acetate = 15 / 1). The obtained fraction was concentrated using a rotary evaporator to obtain a simple yellowish oily modified cardanol (46.7 g). Structural identification of the obtained compound was performed as follows: １ The analysis was performed using 1H-NMR. The results showed that the main component was modified cardanol, in which a tert-butyl group was introduced at the 2-position of the cardanol starting material before the reaction.

[0120] Cardanol raw materials: １ H-NMR (CDCl ３ ) δ 7.15-7.10 (m, 1H), 6.78-6.73 (m, 1H), 6.68-6.62 (m, 2H), 5.88-5.77 (m, 0.37H), 5.50-5.29 (m, 3.44H), 5.10-4.95 (m, 0.80H), 4.81-4.64 ( m, 1H), 2.88-2.75 (m, 2.14H), 2.55 (t, 2.13H), 2.08-1.98 (m, 3.31H), 1.69-1.53 ​​(m, 3.15H), 1.51-1.12 (m, 14.10H), 0.94-0.85 (m, 1.95H)

[0121] Modified cardanol (product): １ H-NMR (CDCl ３ ) δ 7.16 (d, 1H), 6.69 (dd, 1H), 6.49 (d, 1H), 5.88 - 5.77 (m, 0.39H), 5.50 - 5.29 (m, 3.56H), 5.10 - 4.95 (m, 0.80H), 4.64 (s, 1H), 2.87 - 2.75 (m, 2.12H), 2.56 - 2.46 (m, 2.22H), 2.12 - 1.95 (m, 3.60), 1.65 - 1.53 (m, 2.62H), 1.43 - 1.24 (m, 23.42H), 0.96 - 0.80 (m, 2.20H)

[0122] A 1.0-liter jacketed reactor, equipped with a sparger for introducing oxygen-containing gas at the bottom, stirring turbine blades and baffles, and a reflux condenser in the vent gas line at the top of the reactor, was filled with a pre-prepared mixture of 0.12 g of cuprous oxide and 0.91 g of 47% hydrogen bromide, along with 0.29 g of N,N'-di-t-butylethylenediamine, 4.31 g of dimethyl-n-butylamine, 1.42 g of di-n-butylamine, phenol raw materials (76.4 g of 2,6-dimethylphenol, 3.6 g of modified cardanol produced in Production Example 1), and 713 g of toluene. Then, while vigorously stirring, air was introduced into the reactor through the sparger at a rate of 0.84 L / min, and oxygen was introduced at the same time. The polymerization temperature was adjusted by passing a heat transfer medium through the jacket to maintain a temperature of 40°C. 120 minutes after introducing air, the air supply was stopped, and the reactor was replaced with nitrogen gas. Then, 1.30 g of tetrasodium ethylenediaminetetraacetate tetrahydrate (reagent manufactured by Dojin Chemical Research Institute) was added as an aqueous solution in 200 g of water. The mixture was heated to 70°C, and copper extraction was carried out at 70°C for 4 hours. Subsequently, the solution was separated into a polyphenylene ether solution (organic phase) and an aqueous phase to which the catalyst metal had been transferred by static separation. The above solution was mixed with methanol in a ratio of methanol to polymer solution of 10 to precipitate the polymer. Wet polyphenylene ether was obtained by vacuum filtration using a glass filter. The wet polyphenylene ether was further washed with methanol in an amount such that the mass ratio of methanol to wet polyphenylene ether was 2.5. The above washing operation was repeated three times. Then, the wet polyphenylene ether was held at 100°C and 1 mmHg for 4 hours to obtain dry polyphenylene ether-6 (PPE-6).

[0123] <Analysis of Polyphenylene Ethers> (1) Gel permeation chromatography (LC-2030C Plus, manufactured by Shimadzu Corporation) was used as the number-average molecular weight and weight-average molecular weight measurement device for polyphenylene ethers. A calibration curve was created using standard polystyrene and ethylbenzene, and the number-average molecular weight (Mw) and weight-average molecular weight (Mw) of the obtained modified polyphenylene ethers were measured using this calibration curve. Standard polystyrenes with molecular weights of 3,650,000, 2,170,000, 1,090,000, 681,000, 204,000, 52,000, 30,200, 13,800, 3,360, 1,300, and 550 were used. Two K-805L columns manufactured by Showa Denko K.K. were connected in series. Chloroform was used as the solvent, with a solvent flow rate of 1.0 mL / min and a column temperature of 40°C for measurement. A 1 g / L chloroform solution of polyphenylene ether was prepared and used as the sample for measurement. The UV wavelength of the detection unit was set to 254 nm for standard polystyrene and 283 nm for polyphenylene ether. Based on the above measurement data, the number-average molecular weight and weight-average molecular weight were calculated from the percentage of peak areas based on the molecular weight distribution curve obtained by GPC. The measurement results for each polyphenylene ether are shown in Table 1.

[0124] (2) Reduced viscosity of polyphenylene ether (ηsp / c) A 0.5 g / dL chloroform solution of polyphenylene ether was prepared, and the reduced viscosity (ηsp / c) (dL / g) at 30°C was determined using an Ubbelohde viscous tube. The measurement results are shown in Table 1.

[0125]

[0126] <Preparation of Polyphenylene Ether Solution> A polyphenylene ether solution was prepared by mixing polyphenylene ether with a water-soluble organic solvent in the proportions shown in Table 2 below.

[0127] <Evaluation Method for Polyphenylene Ether Solution> - Film Formation at Room Temperature A polyphenylene ether solution, which has been left standing at room temperature (20°C), was gently dropped onto a glass plate that had been left standing at room temperature (20°C). It was spread evenly using an applicator (wet thickness setting: 150 μm) and quickly immersed in a solidification solution (pure water) kept warm at 80°C. At this stage, the film-forming processability was evaluated according to the following criteria. The evaluation results are shown in Table 2. Good: A uniform and transparent solution was obtained, the uniformity of the polymer film was maintained even after coating, and it was easy to form a uniform film. Poor: The polymer liquid at room temperature was non-uniform, making it difficult to form a uniform film.

[0128] - As a method to confirm the porosity of the fabricated film, the porosity was measured. The following formula was used to measure the porosity: Porosity (%) = (1 - weight / (resin density × film volume)) × 100 The weight was measured using an analytical balance with a built-in calibration weight (GR-202) from A&D Co., Ltd. Film volume was determined by the product of film thickness and film area. Film thickness was measured using a micrometer (OMV-25MX) manufactured by Mitutoyo Corporation. Film area was measured using a film punched out in a 10 mm × 10 mm square, resulting in an area of ​​100 mm². ２ The calculation was performed using the following formula: The resin density is 1.06 (g / cm³), which is the bulk density of polyphenylene ether. ３ The following was used: ) The evaluation results are shown in Table 2.

[0129]

[0130] Examples 1 to 10 demonstrated excellent film-forming properties at room temperature, and porosity was confirmed. In other words, it was confirmed that porous films could be formed at room temperature (20°C). On the other hand, film formation at room temperature was difficult for Comparative Example 1. Furthermore, while film formation was possible at room temperature for Comparative Example 2, porosity was not observed, and porous film formation at room temperature was not possible.

Claims

1. A polyphenylene ether solution comprising a water-soluble organic solvent having a solubility in water at 20 °C of 50 g / 100 mL or more and a polyphenylene ether, wherein the polyphenylene ether contains 1 to 99 mol% of repeating units derived from a phenol represented by the following formula (1) and 1 to 99 mol% of repeating units derived from a phenol represented by the following formula (2) with respect to a total of 100 mol% of repeating units derived from a phenol represented by the following formula (1) and repeating units derived from a phenol represented by the following formula (2). (In formula (1), 11 each independently represents a saturated hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, and 12 each independently represents a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom.) (In formula (2), 21 is a partial structure represented by the following formula (3), and 22 each independently represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, provided that both of the two 22 are not hydrogen atoms.) (In formula (3), 31 each independently represents a linear alkyl group having 1 to 8 carbon atoms which may be substituted, and two 31 may be bonded to each other to form a cyclic alkyl structure having 1 to 8 carbon atoms, 32 each independently represents an alkylene group having 1 to 8 carbon atoms which may be substituted, 33 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may be substituted, or a phenyl group which may be substituted, b is each independently 0 or 1, and * represents a bond.) 2. The polyphenylene ether solution according to claim 1, wherein of a total of 100 parts by mass of the water-soluble organic solvent and the polyphenylene ether, the content of the water-soluble organic solvent is 50 to 99 parts by mass, and the content of the polyphenylene ether is 1 to 50 parts by mass.

3. The polyphenylene ether solution according to claim 1, wherein the polyphenylene ether comprises 20 to 95 mol% of repeating units derived from phenol represented by formula (1) and 5 to 80 mol% of repeating units derived from phenol represented by formula (2), based on a total of 100 mol% of repeating units derived from phenol represented by formula (1) and repeating units derived from phenol represented by formula (2).

4. The polyphenylene ether solution according to claim 1, characterized in that the substructure represented by formula (3) is a tert-butyl group.

5. The polyphenylene ether solution according to claim 1, wherein the water-soluble organic solvent is water-miscible.

6. The polyphenylene ether solution according to claim 1, wherein the water-soluble organic solvent is N-methyl-2-pyrrolidone.

7. The polyphenylene ether solution according to claim 1, wherein the water-soluble organic solvent is a nitrogen-containing solvent.

8. The polyphenylene ether solution according to claim 7, wherein the nitrogen-containing solvent is a compound represented by the following formula (10). (In formula (10), R １ (This represents a hydrogen atom, an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom.) 9. A method for producing a porous membrane, comprising a dissolution step of dissolving polyphenylene ether in a solvent at a temperature of 80°C or below, and manufactured by a non-solvent-induced phase separation method.

10. The method for producing a porous film according to claim 9, wherein in the dissolution step, polyphenylene ether is dissolved in a solvent at 0 to 50°C.

11. A porous membrane comprising a polyphenylene ether, wherein the polyphenylene ether comprises 1 to 99 mol% of repeating units derived from phenol represented by the following formula (1) and 1 to 99 mol% of repeating units derived from phenol represented by the following formula (2), based on a total of 100 mol% of repeating units derived from phenol represented by the following formula (1) and repeating units derived from phenol represented by the following formula (2). (In formula (1), R 11 Each independently represents a saturated hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, R 12 Each of these independently represents a hydrogen atom, an optionally substituted hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom. (In formula (2), R 21 This is a substructure represented by the following formula (3), R 22 Each independently represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms (which may be substituted), an aryl group having 6 to 12 carbon atoms (which may be substituted), or a halogen atom, provided that two R 22 (Neither of them are hydrogen atoms.) (In formula (3), R 31 Each independently represents a linear alkyl group having 1 to 8 carbon atoms, which may be substituted, or two R 31 They may be bonded to each other to form a cyclic alkyl structure with 1 to 8 carbon atoms, R 32 Each of these independently represents an alkylene group having 1 to 8 carbon atoms, which may be substituted. 33 (where b represents a hydrogen atom, an optionally substituted alkyl group having 1 to 8 carbon atoms, or an optionally substituted phenyl group; b is independently 0 or 1; and * represents a bond.) 12. The porous membrane according to claim 11, wherein the polyphenylene ether comprises 20 to 95 mol% of repeating units derived from phenol represented by formula (1) and 5 to 80 mol% of repeating units derived from phenol represented by formula (2), based on a total of 100 mol% of repeating units derived from phenol represented by formula (1) and repeating units derived from phenol represented by formula (2).

13. A method for producing a porous membrane according to claim 11, which is produced by a non-solvent-induced phase separation method.

14. A method for producing a porous membrane according to claim 11, comprising the steps of: preparing a polyphenylene ether solution; adjusting the temperature of the polyphenylene ether solution; forming a film of the polyphenylene ether solution on a substrate by coating; immersing the substrate and the film in a solidification solution; and removing the film from the solidification solution and drying it under appropriate conditions, wherein the temperature of the polyphenylene ether solution in the step of adjusting the temperature of the polyphenylene ether solution is 80°C or lower.

15. A diaphragm for alkaline water electrolysis, comprising the porous membrane described in claim 11.

16. A pharmaceutical process filter comprising the porous membrane described in claim 11.

17. A water treatment membrane comprising the porous membrane described in claim 11.

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