Anion exchange membrane

Abstract

Provided is an anion exchange membrane that has low resistance and exhibits a stable function as a diaphragm without being damaged even when pressure is applied from both surfaces.　This anion exchange membrane comprises a base material film obtained by molding a base polymer into a film. The base polymer has a graft chain having an ion exchange group bonded thereto. The thickness of the anion exchange membrane is not less than 50 µm. The conductivity of the anion exchange membrane is not less than 13 mS / cm when, in a state where the counter anion is a chlorine ion, a 0.5 N sodium chloride aqueous solution is disposed on both sides of the anion exchange membrane at 25°C, and the conductivity was measured by applying 1 kHz AC.

Description

Anion exchange membrane

[0001] This invention relates to an anion exchange membrane, and more particularly to an anion exchange membrane suitable for electrolytic devices involving electrochemical reactions, wherein an anode, a cathode, and at least one layer of anion exchange membrane are inserted between them.

[0002] In recent years, environmentally conscious technological development has attracted attention. One example of the effective utilization of natural energy is the production of methane from carbon dioxide, but hydrogen is required in this reaction. Research is being conducted on hydrogen production by water electrolysis using electrochemical cells with the aim of supplying hydrogen. For example, an anion exchange membrane type water electrolysis device (hereinafter sometimes referred to as an AEMWE cell) in which a single layer of anion exchange membrane is inserted between the anode and the cathode is attracting attention. Compared to a cation exchange membrane type water electrolysis device that has a cation exchange membrane instead of an anion exchange membrane, AEMWE has advantages such as not requiring the use of precious metals in the electrodes and simplifying the water quality management required for water electrolysis.

[0003] In AEMWE, by applying voltage from the power supply to the anode and cathode, water is decomposed on the cathode side and OH － Ions are generated. OH － Ions move through the anion exchange membrane, generating water and oxygen at the anode. Therefore, an anion exchange membrane with high anionic conductivity is required. Furthermore, since the generated hydrogen is difficult to store, it is desirable to store it under high pressure. For this reason, it is desirable that the hydrogen generated at the cathode be pressurized. In order to perform water electrolysis under these conditions, it is necessary to tighten the cell with a constant pressure to prevent leakage of the liquid flowing through it or the generated gas to the outside. Therefore, it is desirable that the anion exchange membrane has sufficient strength to withstand the pressure from both electrodes.

[0004] For example, one proposed method for increasing the strength of anion exchange membranes is to fill the interior of reinforcing materials such as porous membranes, nonwoven fabrics, and woven fabrics with anion exchange polymers.

[0005] In addition, Patent Document 1 discloses a membrane obtained by a graft polymerization method as a homogeneous membrane that does not use a reinforcing material and is easy to ensure strength, and proposes an anion exchange membrane suitable for seawater concentration applications.

[0006] Japanese Patent No. 5120541

[0007] When filling an anion exchange type polymer inside a reinforcing material such as a porous membrane, a non-woven fabric, and a woven fabric in order to increase the strength of the anion exchange membrane, the reinforcing material reduces the area of the ion conduction path in the membrane thickness direction (lowers the aperture ratio), so the specific resistance also increases. In order to reduce the resistance of the anion exchange membrane including the reinforcing material, it is necessary to fill a polymer having a higher ion exchange group density. As a result, the water content rate of the anion exchange membrane becomes high, and the strength of the anion exchange membrane itself to be filled decreases, so it is difficult to obtain a sufficient reinforcing effect.

[0008] The anion exchange membrane disclosed in Patent Document 1 is a membrane for electrodialysis. Therefore, Patent Document 1 does not disclose a membrane having a thickness of a certain level or more suitable for a case where a high pressure is applied while being sandwiched between electrodes such as an electrochemical cell and having a low resistance.

[0009] In addition, in AEMWE, when hydrogen is generated, pressure is applied to the hydrogen generation electrode, so it is desirable that there is no leakage to the counter electrode. From the above, it is desirable that the anion exchange membrane is thick, but on the other hand, if it is thick, the resistance becomes high.

[0010] An object of the present invention is to provide an anion exchange membrane that exhibits a function as a stable diaphragm without being damaged even when pressure is applied from both sides and has a low resistance.

[0011] The present invention encompasses the following embodiments: [1] An anion exchange membrane comprising a base film formed from a base polymer into a film, wherein a graft chain having an ion exchange group is bonded to the base polymer, wherein the thickness of the anion exchange membrane is 50 μm or more, and the conductivity measured when a 0.5 N sodium chloride aqueous solution is placed on both sides of the anion exchange membrane at 25°C with a 1 kHz alternating current applied, with the counter anion being a chloride ion, is 13 mS / cm or more. [2] The anion exchange membrane according to [1], wherein the base polymer is a polyolefin. [3] The anion exchange membrane according to [2], wherein the polyolefin is polyethylene. [4] The anion exchange membrane according to any one of [1] to [3], wherein the thickness of the anion exchange membrane is 75 μm or more. [5] The anion exchange membrane according to any one of [1] to [4], wherein the conductivity is 15 mS / cm or more. [6] The anion exchange membrane according to any one of [1] to [5], wherein the conductivity is 20 mS / cm or more. [7] An anion exchange membrane according to any one of [1] to [6], wherein the ion exchange capacity of the dried anion exchange membrane is 2.5 mmol / g or more. [8] An anion exchange membrane according to any one of [1] to [7], wherein the graft rate, which is the ratio of the mass of the graft chain to the mass of the substrate film before polymerization in which the graft chain is introduced, is 130% by mass or more. [9] An anion exchange membrane according to any one of [1] to [8], wherein the graft chain has a crosslinked structure made of a crosslinkable monomer, and the proportion of the crosslinkable monomer used in the polymerization step in which the graft chain is introduced is 1.5 to 20 parts by mass with respect to 100 parts by mass of the total amount of monomers used in the polymerization step.

[10] An anion exchange membrane according to any one of [1] to [9], obtained by setting the monomer concentration in the monomer solution to 30 to 100% by weight in the polymerization step in which the graft chain is introduced, and setting the polymerization temperature in the polymerization step to 30 to 60°C.

[11] The anion exchange membrane according to any one of [1] to

[10] , wherein the graft chain comprises a quaternary ammonium group derived from trimethylamine or a compound represented by any of the formulas (a1) to (a7) described later.

[12] A method for producing an anion exchange membrane in which a graft chain having an anion exchange group is bonded to the base polymer, comprising the steps of: using a base film formed from a base polymer into a film; irradiating the base film with ionizing radiation to generate radicals in the base polymer; graft polymerizing a raw material monomer containing an anion exchange group introduction monomer having a functional group capable of introducing an anion exchange group onto the base film; and introducing anion exchange groups into units derived from the anion exchange group introduction monomer to the base film obtained by the graft polymerization, wherein the anion exchange membrane has a thickness of 50 μm or more, and with the counter anion being a chloride ion, the conductivity measured by applying a 1 kHz alternating current with 0.5 N sodium chloride aqueous solution placed on both sides of the anion exchange membrane at 25°C is 13 mS / cm or more.

[13] The method for producing an anion exchange membrane according to

[12] , wherein the graft polymerization is carried out at a polymerization temperature of 30 to 60°C.

[14] A method for producing an anion exchange membrane according to

[12] or

[13] , wherein the dose of the ionizing radiation is 10 to 1000 kGy.

[15] A method for producing an anion exchange membrane according to any one of

[12] to

[14] , wherein the dose of the ionizing radiation is 40 to 300 kGy.

[16] A method for producing an anion exchange membrane according to any one of

[12] to

[15] , wherein the polymerization time for the graft polymerization is 3 hours or more and 10 hours or less.

[17] A water electrolysis apparatus having an anion exchange membrane according to any one of [1] to

[11] .

[18] A water electrolysis apparatus according to

[17] , having a cathode electrode that generates hydrogen, an anode electrode that generates oxygen, and an anion exchange membrane disposed between the two electrodes, wherein the cathode electrode is provided with a mechanism that pressurizes the internal pressure to a state higher than atmospheric pressure by controlling the release of hydrogen.

[0012] According to the above embodiment, it is possible to provide an anion exchange membrane that can function stably as a diaphragm without being damaged even when pressure is applied from both sides, and that also has low resistance.

[0013] It is a schematic configuration diagram of an anion exchange membrane type water electrolysis device. It is a schematic configuration diagram schematically showing a measuring device for membrane resistance. It is an explanatory diagram schematically showing an example of a process of irradiating ionizing radiation. It is a graph showing the relationship between the membrane thickness and conductivity of the anion exchange membrane in the examples and comparative examples. It is a schematic configuration diagram of an anion exchange membrane type water electrolysis device.

[0014] The terms in this specification and the claims are defined as follows.

[0015] [Surface roughness Ra and Rz] The surface roughness is a value obtained by measuring with a tactile surface roughness measuring machine. Specifically, the wet anion exchange membrane is placed on a glass plate without drying and adhered, and the moisture on the surface (that is, the measurement surface) is wiped off and measured within 5 minutes. If 5 minutes or more have elapsed, the sample is immersed in water for 5 minutes or more again and then measured. A stylus with a tip radius of 2 μm and a tip angle of 60° is attached to a tactile surface roughness measuring machine (for example, product name "Surftest SJ-310" manufactured by Mitutoyo Corporation) as a standard detector, and Ra and Rz of the measurement surface are measured. The roughness Rz means the "maximum height of the roughness curve" defined in JIS B0601:2013. The roughness Ra means the "arithmetic mean height of the roughness curve" defined in JIS B0601:2013. For the measurement of the surface roughness Ra and Rz, the anion exchange membrane before cutting out the sample for measuring each of the above physical properties can be used and measured before performing the evaluation.

[0016] The "~" indicating a numerical range means including the numerical values described before and after it as the lower limit value and the upper limit value.

[0017] <<Anion exchange membrane>> The anion exchange membrane of this embodiment includes a base film formed by molding a base polymer into a film shape, and a graft chain having an ion exchange group is bonded to the base polymer. The anion exchange membrane has a thickness of 50 μm or more, and when 0.5 N sodium chloride aqueous solution is placed on both sides of the anion exchange membrane at 25°C with the counter anion being chloride ion and 1 kHz alternating current is applied for measurement, the conductivity is 13 mS / cm or more.

[0018] Figure 1 shows a schematic diagram of an AEMWE cell. The AEMWE cell 1 shown in Figure 1 has an anion exchange membrane 44 as a diaphragm for water electrolysis between the anode 41 and the cathode 42. In addition, to promote the electrochemical reaction shown in Figure 1, a cathode catalyst layer and a gas diffusion layer 45 may be provided between the cathode 42 and the anion exchange membrane 44, and an anode catalyst layer and a gas diffusion layer 46 may be provided between the anode 41 and the anion exchange membrane 44 as needed. As an example, the anode 41 and cathode 42 are grooved current collector plates that supply electrolyte solution or water to the membrane surface via the cathode catalyst layer and gas diffusion layer 45 or the anode catalyst layer and gas diffusion layer 46, and discharge the electrolyte solution (or water) together with the generated gas. The anode 41 and cathode 42 also have optional through holes for supplying and discharging electrolyte solution (or water) from the outside to the cathode catalyst layer and gas diffusion layer 45 and the anode catalyst layer and gas diffusion layer 46. Reference numeral 47 indicates a gasket. In AEMWE, by applying voltage from the power supply 43 to the anode 41 and cathode 42, water is decomposed on the cathode 42 side and OH － Ions are generated. OH － Ions move through the anion exchange membrane 44, generating water and oxygen at the anode 41. In AEMWE cells, multiple through-holes are provided in the anode 41, allowing for the introduction of electrolytes such as water or potassium hydroxide solution, which may result in a flow of liquid discharged along with the generated oxygen.

[0019] The thickness of the anion exchange membrane is 50 μm or more, preferably 75 μm or more, more preferably 90 μm or more, and even more preferably 100 μm or more. When the thickness of the anion exchange membrane is 50 μm or more, the strength of the anion exchange membrane is improved. As a result, for example, when the anion exchange membrane is used in an AEMWE cell, it is possible to pressurize and store the hydrogen generated on the cathode side. Furthermore, it is possible to increase the pressure used to fasten the cell to prevent leakage of the liquid passing through the AEMWE cell or the generated gas, and the efficiency of the cell is improved in applications where cross-leakage of gas is undesirable.

[0020] The thickness of the anion exchange membrane is preferably 250 μm or less, more preferably 200 μm or less, and particularly preferably 150 μm or less. When the anion exchange membrane thickness is 250 μm or less, the resistance can be kept low when the anion exchange membrane is applied to the AEMWE cell.

[0021] The surface of the anion exchange membrane may be roughened. The roughened surface may have fine irregularities. Only one side of the anion exchange membrane may be roughened, or both sides may be roughened. On one or both sides of the anion exchange membrane, the entire surface may be roughened.

[0022] In an anion exchange membrane, the surface roughness Rz is preferably 1 to 40 μm, more preferably 5 to 30 μm, even more preferably 8 to 25 μm, and particularly preferably 10 to 20 μm. If Rz is above the lower limit of the above range, the surface area of ​​the anion exchange membrane increases, and the contact area with adjacent components such as electrodes or catalyst layers increases. If it is below the upper limit of the above range, it is possible to suppress localized reductions in membrane strength due to excessive roughness, such as external leakage from the sealing portion around the membrane when mounted on an electrolytic cell. In an anion exchange membrane, for similar reasons, the surface roughness Ra is preferably 0.1 to 10 μm, more preferably 1 to 5 μm, and even more preferably 1.5 to 3.5 μm. In an anion exchange membrane, it is preferable that at least Rz is within the above range, and it is more preferable that both Rz and Ra are within the above range.

[0023] The conductivity of the anion exchange membrane is 13 mS / cm or higher, preferably 15 mS / cm or higher, and more preferably 20 mS / cm or higher. When the conductivity of the anion exchange membrane is 13 mS / cm or higher, the anion conductivity is high even when the thickness of the anion exchange membrane is 50 μm or more, making it suitable for use as a diaphragm in an AEMWE cell. Furthermore, because the anion exchange membrane of the present invention has a large film thickness, it is effective in stabilizing an electrochemical cell in which the cathode, an electrochemical catalyst layer placed between the cathode and the anion exchange membrane as needed, the anion exchange membrane, an electrochemical catalyst layer placed between the anode and the anion exchange membrane as needed, and the anode are in contact in this order, and the entire structure is fastened under pressure to efficiently generate electrode reactions. In addition, the anion exchange membrane is suitable because its low resistance can increase the electrical efficiency of the electrochemical cell. In electrochemical cells, such as those used in water electrolysis or carbon dioxide reduction reactions, where gases are involved in the raw materials and products, and where high pressure is applied to the electrode side handling the gas to improve reaction efficiency and product storage efficiency, the anion exchange membrane of the present invention is suitable because its high strength is effective in maintaining cell stability, and because its low resistance can improve the electrical efficiency of the electrochemical cell.

[0024] Anion exchange membranes, used as dialysis membranes in electrodialysis, such as those used for seawater concentration, have a problem where if their conductivity is too high, water will permeate through the membrane, reducing dialysis efficiency. Therefore, directly repurposing anion exchange membranes used as dialysis membranes for electrochemical cell diaphragms is undesirable because their low conductivity results in a high voltage.

[0025] Examples of anion exchange membranes that can be used as diaphragms in electrochemical cells include those with aromatic main chains and those with chloromethylstyrene main chains, as described in ACS.Appl.Mater.Interfaces.,2021,13,51917. However, these are composed only of main chains with anion exchange groups that readily attract water, and in applications such as long-term heating and circulation of basic aqueous solutions, there is a concern that the mechanical properties may deteriorate due to membrane swelling, making the presence of reinforcing materials preferable. On the other hand, using reinforcing materials reduces the ion exchange capacity by the volume occupied by the reinforcing materials and increases resistance, which is not necessarily preferable for use as diaphragms in electrochemical cells. In contrast, the anion exchange membrane of the present invention has components with ion exchange groups and the base film uniformly dispersed at the molecular level within the membrane, so there are no ion-blocking areas occupied by the reinforcing materials mentioned above, enabling efficient ion conduction and ensuring the strength and swelling resistance of the base film.

[0026] Furthermore, as anion exchange membranes made of copolymers such as block copolymers, examples include styrene-ethylene / butylene-styrene block copolymers chloromethylated, as described in Japanese Patent Publication No. 2023-521327. In this case, the ethylene-butylene blocks responsible for maintaining membrane strength correspond to branched polyethylene, and their strength is not necessarily high. Also, since the ethylene-butylene blocks are formed by anionic polymerization, the degree of polymerization is not sufficient to ensure adequate strength. On the other hand, as will be described later, the anion exchange membrane of the present invention is obtained by graft polymerization. This makes it possible to obtain an anion exchange membrane with sufficient membrane strength and a sufficiently high molecular weight. Such anion exchange membrane can ensure sufficient strength and high ion exchange capacity, and is a thick and low-resistance membrane.

[0027] The ion exchange capacity of the dried anion exchange membrane is preferably 2.5 mmol / g or more, more preferably 2.7 mmol / g or more, and even more preferably 3 mmol / g or more. When the ion exchange capacity of the dried anion exchange membrane is 2.5 mmol / g or more, the anion conductivity is high even when the thickness of the anion exchange membrane is thick, such as 50 μm or more, and it can be used as a diaphragm for AEMWE cells.

[0028] The larger the size of the anion exchange membrane, the more prone it is to bending and wrinkling during mounting. Similarly, the thinner the membrane, and the poorer its slipperiness (i.e., the higher the surface smoothness and the larger the contact area when the membrane contacts the component), the more prone it is to bending and wrinkling. Anion exchange membranes are typically cut to fit the size of the frame. In this specification, the planar shape of the anion exchange membrane refers to the shape of the region enclosed by the frame. Various shapes can be applied to the planar shape of the anion exchange membrane, such as polygons, circles, and ellipses. The maximum distance between any two points on the outer perimeter of the planar shape is defined as the "maximum width of the planar shape."

[0029] In this embodiment, the greater the maximum width of the planar shape of the anion exchange membrane, the greater the effect obtained by controlling the thickness of the anion exchange membrane to have a preferred surface roughness as needed. In this regard, the maximum width of the planar shape of the anion exchange membrane is preferably 20 cm or more, particularly preferably 50 cm or more, more preferably 100 cm or more, and particularly advantageous and preferable at 150 cm or more.

[0030] <Base Film> The base film is formed from a base polymer into a film. In addition to the base polymer, the base film may contain additives as needed. The thickness of the base film is designed to be smaller than the thickness of the anion exchange membrane to be obtained, taking into account the increase in film thickness due to graft polymerization. Therefore, the preferred thickness of the base film varies depending on the conditions under which it is applied, but for example, 30 to 200 μm is preferred, 40 to 150 μm is more preferred, 50 to 120 μm is even more preferred, and 60 to 100 μm is particularly preferred.

[0031] The base film may have a roughened surface on one or both sides. As will be described later, by roughening the surface of the base film, the surface state of the base film is reflected in the surface state of the anion exchange membrane, and a roughened surface is obtained in the anion exchange membrane. The roughened surface of the base film has fine irregularities. It is preferable that both sides of the base film are roughened. It is preferable that the entire surface of one or both sides of the base film is roughened.

[0032] In a substrate film having a roughened surface, the state of surface roughening is not particularly limited and may change during the subsequent process of forming an anion exchange membrane. For example, in a substrate film, the surface roughness Rz is preferably 3 to 30 μm, more preferably 5 to 25 μm, and even more preferably 7 to 20 μm. In a substrate film, the surface roughness Ra is preferably 0.3 to 10 μm, more preferably 0.5 to 7 μm, and even more preferably 1 to 3 μm. In a substrate film, it is preferable that at least Rz is within the above range, and it is more preferable that both Rz and Ra are within the above range.

[0033] <Base Polymer> The base polymer constituting the substrate film is preferably a fluororesin or a polyolefin. Examples of fluororesins include copolymers containing ethylene (hereinafter referred to as E) units and tetrafluoroethylene (hereinafter referred to as TFE) units (hereinafter referred to as ETFE), copolymers containing E units and chlorotrifluoroethylene (hereinafter referred to as CTFE) units, copolymers containing 50 mol% or more of trifluoroethylene units, vinylidene fluoride units, or vinyl fluoride units, or homopolymers thereof. One type of fluororesin may be used alone, or two or more types may be used in combination.

[0034] In ETFE, the molar ratio (TFE / E) of the unit based on TFE and the unit based on E is preferably from 40 / 60 to 80 / 20, more preferably from 50 / 50 to 70 / 30. If the molar ratio of the unit based on TFE is too small, the heat resistance, weather resistance, chemical resistance, gas barrier property, fuel barrier property, etc. of the base film will be low. If the molar ratio of the unit based on TFE is too large, the melt formability of ETFE will not be sufficient, and the mechanical strength, etc. of the base film will tend to be low. When within the above range, ETFE has excellent melt formability, and the base film is excellent in heat resistance, weather resistance, chemical resistance, gas barrier property, fuel barrier property, mechanical strength, etc., and can be expected to have a wide range of applications to chemical solutions and applicability to high operating temperatures in the applications of the present invention.

[0035] In addition to the units based on TFE and E, ETFE may contain units based on other monomers (a) copolymerizable with TFE and E. Examples of the other monomer (a) include vinylidene fluoride, CTFE, hexafluoropropylene (hereinafter referred to as HFP), CF ２ =CFR １ (where R １ represents a perfluoroalkyl group having 2 to 6 carbon atoms. The same applies hereinafter.), CH ２ =CHR ２ (where R ２ represents a polyfluoroalkyl group having 1 to 8 carbon atoms. The same applies hereinafter.), CF ２ =CHR ３ (where R ３ represents a perfluoroalkyl group having 1 to 6 carbon atoms. The same applies hereinafter.), CH ２ =CFR ２ and other fluoroolefins (excluding TFE), CF ２ =CFOR ４ (where R ４ represents a perfluoroalkyl group having 1 to 10 carbon atoms which may contain an oxygen atom.), and other fluorovinyl ethers such as CF ２ =CFOR ５ COX １ (where R ５ represents a divalent perfluoroalkylene group having 1 to 10 carbon atoms which may contain an oxygen atom, and X １ represents a hydroxyl group, an alkoxy group having 3 or less carbon atoms or a halogen atom.), CF２ = CFOR ６ SO ２ X ２ (R ６ X is a divalent perfluoroalkylene group which may contain oxygen atoms having 1 to 10 carbon atoms. ２ ) represents a halogen atom or hydroxyl group. Fluorovinyl ethers containing functional groups such as CF ２ = CF (CF ２ ) ｎ OCF = CF ２ Examples include (where n represents 1 or 2), perfluoro(2-methylene-4-methyl-1,3-dioxolane), hydrocarbon olefins such as propylene and butene (except for E), aliphatic vinyl carboxylates such as vinyl acetate and vinyl butanoate, polymerizable unsaturated compounds having an acid anhydride structure such as maleic anhydride, itaconic anhydride, and citraconic anhydride, and vinyl ethers such as hydroxybutyl vinyl ether and glycidyl vinyl ether. Other monomers (a) copolymerizable with TFE and E may be used alone or in combination of two or more. Other monomers (a) copolymerizable with TFE and E include CH ２ =CHR ２ HFP, CF ２ = CFOR ４ A polymerizable unsaturated compound having an acid anhydride structure is preferred. The inclusion of units based on a polymerizable unsaturated compound having an acid anhydride structure is preferable because it improves the hydrophilicity when used in an anion exchange membrane. Furthermore, the above CH ２ =CHR ２ When units based on are included, the base film exhibits excellent mechanical properties. ２As such, perfluoroalkyl groups having 1 to 6 carbon atoms are more preferred, and perfluoroalkyl groups having 2 to 4 carbon atoms are most preferred. The content of units based on monomer (a) is preferably 7 mol% or less, preferably 6 mol% or less, more preferably 6 mol% or less, and particularly preferably 4 mol% or less, relative to the total amount of TFE units and E units. Furthermore, if the base polymer contains units based on monomer (a), the content of units based on monomer (a) is preferably 1 mol% or more, more preferably 1.4 mol% or more, more preferably 1.5 mol% or more, and particularly preferably 2 mol% or more, relative to the total amount of TFE units and E units. If the content of units based on monomer (a) is above the lower limit, the crystallinity of the polymer is low and the film is suitable for graft polymerization, and if it is below the upper limit, the melting point of the polymer is high and the potable temperature when it is made into an ion exchange membrane can be high. The upper and lower limits of the content of units based on monomer (a) can be arbitrarily combined.

[0036] A copolymer containing E units and CTFE units is preferably obtained by replacing TFE with CTFE in the ETFE.

[0037] Examples of polyolefins include polyethylene, polypropylene, poly(4-methyl-1-pentene), or polynorbornene. Polyolefins may be used individually or in combination of two or more. Polyethylene is preferred as the polyolefin, and among these, linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and ultra-high molecular weight polyethylene (UHMWPE), copolymerized with ethylene and α-olefins, are preferred from the viewpoint of strength. High-density polyethylene and ultra-high molecular weight polyethylene are particularly preferred.

[0038] <Anion Exchange Groups> Examples of anion exchange groups include quaternary ammonium groups, tertiary amino groups, secondary amino groups, primary amino groups, and imidazole groups as shown in formula (1) below (wherein R is the second amino group). １１ ~R １５ At least one selected from is a bonding hand, and the rest are each independently a C1-C8 alkyl group which may contain a hydrogen atom, an etheric oxygen atom between the carbon-carbon bonds, or -N- between the carbon-carbon bonds, or R １１~R １５ This represents an alkylene group in which any two of the following are bonded. Examples include ( ), but in order to exhibit the high conductivity of the present invention, a quaternary ammonium is preferred. The bond of the imidazole group represented by formula (1) (hereinafter sometimes referred to as "imidazole group (1)") is bonded to the graft chain. Multiple imidazole groups (1) contained in the anion exchange membrane may have different numbers of bond sites. １１ ~R １５ There are no particular restrictions on the number of bonds among them, but the average number per mole of imidazole groups (1) contained in the anion exchange membrane is preferably 3 or less, more preferably 2 or less, and particularly preferably 1.5 or less.

[0039]

[0040] <Graft Chains> The graft chains of an anion exchange membrane are polymer chains formed by graft polymerization of raw material monomers onto a base polymer, and they possess anion exchange groups. The anion exchange groups of the graft chains are groups derived from the raw material monomers, groups introduced after graft polymerization, or both.

[0041] When the raw material monomer contains one or more monomers having anion exchange groups, a graft chain having anion exchange groups derived from the raw material monomers is formed. The monomers having anion exchange groups are preferably compounds having one or more polymerizable carbon-carbon double bonds.

[0042] Examples of monomers having anion exchange groups include 4-vinylbenzyltrimethylammonium chloride represented by formula (3) below; quaternary ammonium salt-containing acrylic acid esters such as 2-(acryloyloxy)-N,N,N-trimethylethaneaminium chloride represented by formula (4) below and (3-acrylamidopropyl)trimethylammonium chloride represented by formula (5) below; acrylamides; allylamines such as allylamine, diallylamine, and diallylmethylamine and their salts with acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and acetic acid; diallyldialkyl quaternary ammonium salts such as diallyldimethylammonium chloride; and the like.

[0043]

[0044] When the raw material monomers include one or more monomers for introducing anion exchange groups that do not have anion exchange groups, a graft chain having units derived from the monomers for introducing anion exchange groups is formed. After graft polymerization, a graft chain having anion exchange groups is obtained by introducing anion exchange groups into the units derived from the monomers for introducing anion exchange groups.

[0045] As monomers for introducing anion exchange groups that can introduce anion exchange groups, monomers that are conventionally known and used in the manufacture of anion exchange resins and anion exchange membranes can be used without particular limitation. Specifically, compounds represented by the following formula (6) (wherein R １８ Examples include an alkylene group having 1 to 8 carbon atoms, which may contain an etheric oxygen atom between the carbon-carbon bonds, and where X is a halogen atom. 4-vinylpyridine, styrene, vinyltoluene, vinylxylene, α-methylstyrene, acenaphthylene, vinylnaphthalene, α-halogenated styrene, α,β,β'-trihalogenated styrene, chlorostyrene, 2-vinylpyridine, methylvinylpyridine, ethylvinylpyridine, vinylpyrrolidone, vinylcarbazole, vinylimidazole, aminostyrene, alkylaminostyrene, trialkylaminostyrene, acrylamide, acrylamide, oxium, glycidyl methacrylate, vinylimidazole and its derivatives. Of these, specifically, m-chloromethylstyrene, p-chloromethylstyrene, 3-chloropropylstyrene, 4-chlorobutylstyrene, 4-bromobutylstyrene, and 4-vinylpyridine are preferred from the viewpoint of easily obtaining films with low resistance, and m-chloromethylstyrene and p-chloromethylstyrene are more preferred from the viewpoint of being able to increase the ratio of anion exchange groups per unit weight of graft chains.

[0046]

[0047] Methods for introducing anion exchange groups into monomer-derived units for introducing anion exchange groups into graft chains can be based on known methods. Examples of compounds for introducing anion exchange groups include ammonia, methylamine, dimethylamine, etc., which can introduce weakly basic ion exchange groups to haloalkyl groups such as chloromethylstyrene and epoxy groups such as glycidyl methacrylate; trimethylamine, dimethylamine ethanol, triethanolamine, cyclic tertiary amines (e.g., compounds represented by formulas (a1) to (a7) below), or imidazoles (e.g., compounds represented by formula (7) below), which can introduce strongly basic ion exchange groups. Among these compounds, trimethylamine is preferred because it can lower the resistance of the resulting film. The above compounds may be used individually or as a mixture of two or more compounds. Furthermore, pyridines such as 4-vinylpyridine and imidazoles such as vinylimidazole can be reacted with alkyl sulfates, alkyl carbonates, or haloalkanes to produce quaternary ammonium groups, which are anion exchange groups. The alkyl sulfate esters and other compounds mentioned above may be used individually or as a mixture of two or more compounds. Furthermore, for monomers having an aromatic ring that do not have a group to which an anion exchange group can be introduced (e.g., styrene), a method can be employed in which a haloalkyl group is introduced to the terminal by a Friedel-Crafts alkylation reaction with a compound having 1 to 8 carbon atoms and multiple halogen groups in the molecule, or by a chloromethylation reaction using chloromethyl methyl ether, and then an anion exchange group is introduced using the method described above. Additionally, for monomers with halogen atoms bonded to the aromatic ring, a method can be employed in which a haloalkyl group is introduced to the terminal by Grignard coupling with a compound having 1 to 8 carbon atoms and multiple halogen groups in the molecule, and then an anion exchange group is introduced using the method described above.

[0048]

[0049] In equations (a1) to (a7), R ２１ ~R ２６Each of these independently represents a hydrocarbon group, a fluorinated hydrocarbon group, or a fluorinated carbide group. The term "hydrocarbon group" refers to a group that contains a C-H bond but does not contain a C-F bond. The term "fluorinated hydrocarbon group" refers to a hydrocarbon group in which some of the hydrogen atoms bonded to the carbon atoms are replaced by fluorine atoms. The term "fluorinated carbide group" refers to a hydrocarbon group in which all of the hydrogen atoms bonded to the carbon atoms are replaced by fluorine, that is, a group that contains only C-F bonds in its molecule. ２１ ~R ２６ Each of these may independently contain an ether bond, a sulfonyl bond, and / or a hydroxyl group. Also, R ２１ ~R ２６ If a hydroxyl group is present, a tertiary alcohol is preferred to prevent oxidation. ２１ ~R ２６ The structure is not particularly limited and may be a linear or cyclic structure. Furthermore, R ２１ ~R ２６ Aromatic groups may be included. In particular, from the viewpoint of ionic conductivity, a structure with as few carbon atoms as possible or a cyclic structure is preferred, especially trimethylamine and the structures of formula a1 to 7 above, and considering the viewpoints of availability, conductivity and film strength, trimethylamine or any of the structures a1, 2, 4, 5, and 7 and R ２１ ~R ２５ A methyl group is even more preferable.

[0050]

[0051] In equation (7), R ３１ ~R ３４ Each of these is independently selected from a hydrogen atom and an alkyl group having 1 to 8 carbon atoms, R ３１ and R ３２ They may be bonded to each other to form a ring. ３３ It is preferable that it is not hydrogen.

[0052] The graft chain may also preferably have a crosslinked structure due to a crosslinkable monomer. When the raw material monomer contains a crosslinkable monomer, a graft chain having a crosslinked structure is formed by graft polymerization. As a result, the strength of the anion exchange membrane is improved. The crosslinkable monomer is preferably a compound having two or more polymerizable carbon-carbon double bonds. Examples of crosslinkable monomers include divinylbenzene (DVB), trivinylbenzene, divinyltoluene, divinylnaphthalene, styrene derivatives represented by the following formulas (8) and (9), ethylene glycol dimethacrylate, etc., with DVB being preferred. In formula (9), R ４１ This represents an alkylene group having 1 to 8 carbon atoms, which may contain an etheric oxygen atom between the carbon-carbon bonds.

[0053]

[0054] When the raw material monomers include crosslinkable monomers, there are no particular restrictions on the proportion of crosslinkable monomers used relative to the total mass of the raw material monomers. Since it also depends on the difference in polymerization properties between monomers having anion exchange groups and monomers for introducing anion exchange groups, it should be adjusted to achieve a membrane resistance suitable for the application. For a total of 100 parts by mass of monomers having anion exchange groups, monomers for introducing anion exchange groups, and any monomers described later, the amount of crosslinkable monomers is 0 to 20 parts by mass, preferably 1.5 to 10 parts by mass, and particularly preferably 2 to 5 parts by mass. If the amount of crosslinkable monomers is 20 parts by mass or less, the membrane strength can be improved while maintaining a low resistance value.

[0055] The graft chain may contain any monomer other than monomers having anion exchange groups, monomers for introducing anion exchange groups, and crosslinkable monomers. There are no particular restrictions on the arbitrary monomers, but examples include vinyl esters such as acrylonitrile, vinyl acetate, and vinyl pivalate; vinyl silanes such as vinyltrimethylsilane, vinyltrimethoxysilane, and vinyldimethoxymethylsilane; acrylamides such as acrylamide, N-methylacrylamide, and N,N-dimethylacrylamide. There are no particular restrictions on the amount of arbitrary monomers used, but it is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and particularly preferably 50 parts by mass or less, relative to 100 parts by mass of the total of monomers having ion exchange groups and monomers that can introduce anion exchange groups. If the amount of arbitrary monomers is too large, the ratio of monomers having anion exchange groups and monomers that can introduce anion exchange groups will be low, which is undesirable because it will result in insufficient ionic conductivity (membrane resistance) of the resulting anion exchange membrane. Furthermore, among the groups to which anion exchange groups can be introduced as described above, those that do not react in the ion exchange group introduction reaction after polymerization may also be used. For example, when chloromethylstyrene is used as a monomer to which anion exchange groups can be introduced and anion exchange groups are introduced using an amine compound, monomers that do not react with the amine compound, such as styrene or pyridine, fall under the category of the aforementioned arbitrary monomers.

[0056] <Manufacturing Method> The anion exchange membrane of this embodiment can be manufactured, for example, by the following manufacturing methods (1) to (2). Manufacturing method (1): A method in which a base film is a film formed from a base polymer is used, radicals are generated in the base polymer by irradiating the base film with ionizing radiation, and raw material monomers containing monomers having anion exchange groups are graft polymerized. Manufacturing method (2): A method in which a base film is a film formed from a base polymer is used, radicals are generated in the base polymer by irradiating the base film with ionizing radiation, raw material monomers containing monomers for introducing anion exchange groups that have functional groups capable of introducing anion exchange groups are graft polymerized, and then anion exchange groups are introduced into units derived from the monomers for introducing anion exchange groups.

[0057] In manufacturing methods (1) and (2), the base film may be a film with a smooth surface or a base film with a roughened surface, or a base film without a roughened surface may be used, and the surface may be roughened after graft polymerization of the raw material monomers.

[0058] As a method for roughening the surface of a film (including a base film), a transfer method can be applied in which a mold or roll with an uneven surface is brought into contact with the surface of the film, either under pressure or without pressure, while heated as needed, to transfer the surface. Specifically, for example, the uneven surface can be transferred to the film by creating an uneven surface on the surface of at least one of a pair of rolls and passing the film between the rolls. Alternatively, a method can be applied in which a releaseable film with an uneven surface is used instead of a mold or roll with an uneven surface. Other methods besides the transfer method include roughening the surface of the film by spraying fine particles onto it (also called the blasting method), and etching using a chemical solution that oxidizes and dissolves the surface of the film. The transfer method using a mold or roll with an uneven surface is preferred in terms of its ability to eliminate the influence on the surface properties of the film, the influence of residual treatment agents, and the simplicity of the process.

[0059] In manufacturing methods (1) to (2), known methods can be applied to the graft polymerization step. For example, a method in which a substrate film irradiated with ionizing radiation is immersed in a polymerization solution to carry out the polymerization reaction is preferred. The polymerization solution contains raw material monomers that form graft chains. It may also contain a solvent. The solvent is not particularly limited, but examples include hydrocarbons such as benzene, xylene, toluene, n-hexane, cyclohexane, n-decane, and decalin; alcohols such as methanol, ethanol, isopropyl alcohol, n-butanol, 2-butanol, isobutyl alcohol, t-butanol, cyclohexanol, and 2-ethylhexyl alcohol; ketones such as acetone, methyl isopropyl ketone, and cyclohexanone; ethers such as dioxane and tetrahydrofuran; esters such as ethyl acetate and butyl acetate; nitrogen-containing compounds such as N-methylformamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidinenon; and so on. One solvent may be used, or two or more may be used in combination.

[0060] Graft polymerization of raw material monomers onto the base polymer of a substrate film may be carried out by a so-called pre-irradiation method, in which the substrate film is irradiated with ionizing radiation and then polymerized with the raw material monomers, or by a so-called simultaneous irradiation method, in which the substrate film and raw material monomers are irradiated simultaneously to carry out the polymerization reaction. The pre-irradiation method is preferred because it produces less homopolymer that does not graft onto the substrate film. The pre-irradiation method may be carried out by irradiating the substrate film in an inert gas or by irradiating the substrate film in an atmosphere in which oxygen is present.

[0061] Specific examples of ionizing radiation include alpha rays, beta rays, gamma rays, electron beams, and ultraviolet rays. Electron beams are preferred because they can uniformly activate the substrate film. A preferred method involves using electron beams as the ionizing radiation and continuously irradiating the substrate film with the electron beam while transporting it. This method offers excellent industrial productivity because it can uniformly activate the substrate film even when irradiating a large quantity of substrate film with ionizing radiation.

[0062] Figure 3 is a schematic diagram illustrating an example of the process of irradiating with ionizing radiation. The procedure of "continuously irradiating with an electron beam" described above will be explained in detail using Figure 3. First, the base film 10 wound on the roll 12 is unwound in the transport direction A and transported to the electron beam irradiation position where the electron beam irradiation device 20 is installed. Next, the electron beam 22 is irradiated onto the base film 10 at the electron beam irradiation position, and then the base film 10 is transported in the transport direction A and wound up on the roll 14 after irradiation with the electron beam 22. In this way, the electron beam 22 is continuously irradiated onto the base film 10.

[0063] The dose of ionizing radiation to the substrate film is preferably 10 to 1000 kGy, more preferably 30 to 500 kGy, even more preferably 40 to 300 kGy, and particularly preferably 40 to 200 kGy, from the viewpoint of activating the substrate film. The ionizing radiation may be irradiated in a single dose to achieve the desired dose (continuous irradiation), or it may be irradiated in multiple doses to achieve the desired total dose (intermittent irradiation). In particular, when a dose of 80 kGy or more is required, continuous irradiation with an electron beam may cause the substrate film to heat up, and the radicals generated by the irradiation may undergo side reactions such as deactivation or crosslinking, making it difficult to obtain the target graft polymerization chain. In addition, continuous irradiation of the substrate film with an electron beam may cause the film to deform due to heat (e.g., elongation of the film). To address these problems, intermittent irradiation allows the substrate film to cool during periods of non-irradiation, thereby suppressing thermal deterioration of the substrate film. In particular, when the material constituting the substrate film is polyethylene, intermittent irradiation is preferable because the change in mechanical strength due to heat is large. During intermittent irradiation, it is preferable to cool the substrate film until the temperature falls below the softening point of the material constituting the substrate film.

[0064] A specific example of the intermittent irradiation method will be explained using Figure 3. First, the electron beam 22 is irradiated onto a specific location of the base film 10 that has been transported from the roll 12 in the transport direction A (first irradiation), and then the portion of the base film 10 including the specific location is wound onto the roll 14. The specific location of the base film 10 wound onto the roll 14 may be heated by the irradiation. In that case, after cooling it sufficiently as necessary, the base film 10 is unwound in the opposite direction to the transport direction A, and the base film 10 is transported again to the electron beam irradiation position, the electron beam 22 is irradiated onto the specific location of the base film 10 (second irradiation), and then the portion of the base film 10 including the specific location is wound onto the roll 12. Alternatively, the base film 10 wound onto the roll 14 may be placed back into the position of the roll 12, unwound again in the direction of the transport direction A, and the base film 10 is transported again to the electron beam irradiation position, the electron beam 22 is irradiated onto the specific location of the base film 10 (second irradiation), and then the portion of the base film 10 including the specific location is wound onto the roll 14. In this way, the substrate film 10 can be irradiated with an electron beam twice. If more than two irradiations are required, the above operation should be performed to irradiate the desired number of times. When more than two irradiations are performed, the irradiation may be performed from the same side of the film, or from both the front and back sides for any number of times. When more than two irradiations are performed, it may be preferable to irradiate the front and back sides for an equal number of times (if the number of irradiations is odd, one side should be irradiated one more time). When it is desired to irradiate the entire substrate film 10, it is preferable to use PET film or the like as lead film attached to both ends of the substrate film 10 in the longitudinal direction with adhesive tape, as this improves the utilization efficiency of the substrate film 10.

[0065] The temperature of the substrate film 10 during irradiation is preferably -10 to 50°C, preferably below room temperature. If there is a large spatial or temporal difference between ionizing radiation irradiation and graft polymerization, for example, when the above-mentioned continuous or intermittent irradiation is performed, the alteration or disappearance of radicals before graft polymerization can be suppressed by storing the irradiated film roll in a dry ice-filled box or a freezer (preferably below -30°C). Next, the irradiated substrate film is removed in the atmosphere, transferred to a glass container, and then the polymerization solution is filled into the container. The polymerization solution used is one from which oxygen gas has been removed in advance by bubbling with an inert gas that does not contain oxygen or by freeze-degassing. Alternatively, a polymerization apparatus such as a continuous polymerization apparatus (for example, Japanese Patent Publication No. 2004-137385, Japanese Patent Publication No. 2005-60555, International Publication No. 2018 / 030498) may be used. Graft polymerization, which introduces graft chains into an irradiated substrate film, is usually carried out at room temperature to 80°C, preferably 40 to 70°C.

[0066] The graft rate (the ratio of the mass of graft chains to the mass of the substrate film before polymerization (unit: mass%)) is preferably 130% by mass or more, more preferably 150% by mass, particularly preferably 160% or more, and even more preferably 170% by mass or more. A graft rate of this value or higher allows for an increase in the proportion of anion exchange groups, and the resistance can be kept low even if the thickness of the anion exchange membrane is 50 μm or more. Furthermore, a graft rate of 300% by mass or less is preferable, more preferably 250% by mass or less, and particularly preferably 220% by mass or less. A graft rate of this value or lower is preferable because it ensures the film strength. The upper and lower limits of the graft rate can be arbitrarily combined. The graft rate can be adjusted by irradiation dose, polymerization temperature, polymerization time, etc. The polymerization time is preferably 2 hours to 12 hours, more preferably 3 hours to 10 hours, and even more preferably 4 hours to 9 hours. If the polymerization time is too short, contact with the monomer solution tends to become uneven, especially when the surface area of ​​the film to be polymerized is large, which may result in a heterogeneous film. On the other hand, if the polymerization time is too long, there is a risk that the radicals formed in the film will be deactivated, making it difficult to obtain the desired grafting rate, and this is also undesirable from the viewpoint of production efficiency.

[0067] The step of introducing an anion exchange group after graft polymerization can be performed using known methods. For example, the following is a specific example of introducing an amino group as an anion exchange group. The above-mentioned amine compounds (for example, compounds represented by formulas (a1) to (a7) and (7) above) are used as the compounds to introduce the anion exchange group. When chloromethylstyrene is graft polymerized as a monomer to which anion exchange groups can be introduced, the resulting polymerized film is immersed or contacted with a solution of the amine compound prepared to a concentration of 0.2 to 3.2 mol / L (preferably 0.5 to 1.5 mol / L) at room temperature to 100°C for 1 to 96 hours, thereby quaternizing the chloromethyl groups of chloromethylstyrene and generating an anion exchange group. After the reaction is complete, the film is thoroughly washed to obtain an anion exchange film. There are no particular restrictions on the solvent used to prepare the solution of the amine compound in this reaction, and multiple solvents may be mixed and used, but it is preferable that the solvent be able to dissolve the amine compound in question. Furthermore, since it is particularly preferable to use water for washing after the reaction, particularly preferred solvents include (a) water, and (b) water-soluble solvents such as methanol, ethanol, 1-propanol, 2-propanol, acetone, methyl ethyl ketone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and ethylene glycol dimethyl ether. Two or more of these solvents may be used in mixture form. When using a solvent selected from (a) or (b), it is preferable that the amine compound used is homogeneously dissolved. The preferred reaction temperature varies depending on the solvent used, the boiling point of the compound, and its reactivity, but when using compounds with low boiling points such as trimethylamine, methanol, and acetone, the reaction temperature is preferably 60°C or lower, and more preferably 50°C or lower. The monomer concentration in the monomer solution in graft polymerization is preferably 20 to 100% by weight, more preferably 30 to 70% by weight, and even more preferably 40 to 60% by weight. If the monomer concentration is excessively high, the utilization efficiency of the monomer used will not be sufficient, and it will not necessarily be effective. On the other hand, if the monomer concentration is excessively low, problems may arise such as difficulty in obtaining the desired polymerization rate and a slow polymerization rate.In graft polymerization, the polymerization temperature is preferably in the range of 20 to 80°C, more preferably 30 to 70°C, even more preferably 30 to 60°C, and particularly preferably 30 to 50°C. If the polymerization temperature is too high, the presence of low-boiling point components in the monomer solution may increase the pressure within the system, or losses may occur due to volatilization. In addition, radicals formed in the film during polymerization may be deactivated, which may result in problems such as not being able to obtain a high polymerization rate. On the other hand, if the temperature is too low, the polymerization rate will decrease, making it difficult to obtain a high polymerization rate, and the reaction time will be long, which may result in inefficiency.

[0068] <Applications> The anion exchange membrane of the present invention can be used in applications known in the field of anion exchange membranes. It is particularly suitable for cells involving electrochemical reactions in which a cathode, an anode, and a single layer of anion exchange membrane are inserted between them. For example, it can be suitably used as a diaphragm in electrolysis devices such as a water electrolysis device that generates hydrogen by electrolyzing water as shown in Figure 1, a carbon dioxide electrolysis device that introduces carbon dioxide into electrodes and converts it into useful compounds such as carbon monoxide and ethylene by a reduction reaction, and an electrolysis device for the electrolysis of organic compounds (for example, a method of replacing benzene, toluene, etc. with hexane and methylhexane by electrolytic hydrogenation).

[0069] In the applications of the present invention, trace amounts of decomposition products may be present in the liquid and / or gas discharged from cells involving electrochemical reactions. In such cases, it is preferable to place adsorbents such as cation exchange resins, anion exchange resins, and activated carbon in the relevant discharge system. For example, in the case of water electrolysis, adsorbents may be placed in the oxygen and / or hydrogen gas discharge line after gas-liquid separation. In the case of electrochemical cells that electrolytically reduce carbon dioxide or electrolytically hydrogenate benzene or toluene, adsorbents may be placed in the line that discharges the products. In these examples, for example, if the discharged liquid and / or gas contains amine-based decomposition products, cation exchange resins, preferably acidic cation exchange resins, and particularly preferably strongly acidic cation exchange resins such as styrene sulfonic acid or perfluorosulfonic acid, or activated carbon may be placed as adsorbents. If organic acids derived from oxides such as anion exchange membranes or catalyst-supported carbon are present in the discharged liquid and / or gas, basic anion exchange resins, activated carbon, and alkalinity-based metal oxides may be placed as adsorbents. By placing adsorbents in this way, the purity of the products can be increased.

[0070] Depending on the application, the counter anions of the anion exchange membrane obtained in this invention can be used after being pre-substituted with any desired ions such as chloride ions, hydroxide ions, or carbonate ions. For example, carbonate ions can be obtained by repeatedly immersing the anion exchange membrane in an aqueous potassium carbonate solution as needed, sulfate ions can be obtained by using an aqueous sulfuric acid solution or an aqueous sodium sulfate solution, and hydroxide ions can be obtained by using an aqueous potassium hydroxide solution or an aqueous sodium hydroxide solution. For water electrolysis using the anion exchange membrane, known methods such as those described in Japanese Patent Publication No. 2024-515943 can be applied.

[0071] In electrolytic devices, to prevent raw materials and / or generated gases from leaking to the opposite electrode through the anion exchange membrane, or from leaking gases to the outside of the cell, it is necessary to sandwich the anion exchange membrane between electrodes, insert a gasket or the like around the anion exchange membrane, and fasten it under high pressure. In this case, the electrode surface comes into contact with the anion exchange membrane surface and pressure is applied, so the anion exchange membrane needs to be thick to prevent membrane damage. The anion exchange membrane of the present invention has low resistance and a thickness of 50 μm or more, so it can function as a stable diaphragm without being damaged even when pressure is applied from both sides.

[0072] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0073] <Measurement Method> [Membrane Resistance and Conductivity] For each example of anion exchange membrane, the membrane resistance was measured and the conductivity was calculated using the following method.

[0074] The conductivity of the anion exchange membrane was measured by the following method. The sample to be measured was an anion exchange membrane immersed in a 0.5 mol / L sodium chloride aqueous solution to convert the counteranions of the anion exchange groups in the membrane to Cl ions, and then conditioned overnight in a constant temperature bath at 25°C. In this example, two 4 cm × 8 cm samples were cut from the center of the obtained membrane, and measurements were taken at the longitudinal center. The arithmetic mean of the two points was taken as the membrane resistance, and the conductivity was determined from this membrane resistance data and the thickness measured above.

[0075] Figure 2 is a schematic diagram showing a membrane resistance measuring device. Reference numeral 30 denotes a cylindrical half-cell with a circular opening 32 with a diameter of 15 mm. Reference numeral 31 denotes the liquid inlet. Reference numeral 33 denotes a platinum-black platinum wire. Reference numeral 34 denotes the membrane to be measured for resistance. The anion exchange membrane 34 to be measured was sandwiched from both sides by the half-cell 30 and fixed with a constant pressure using a spring coil or the like. Next, the inside of the cell 30 was filled with 0.5 mol / L NaCl. The platinum wire 33 was connected to an AC resistance meter and the AC resistance (unit: Ω) at 1 kHz was measured. After that, the anion exchange membrane 34 was quickly removed so as not to leak the liquid inside, and the resistance (unit: Ω) was measured again without the membrane. Using these measured values, the membrane resistance (unit: Ω・cm) was calculated using the following formula (r1). ２ The following was calculated: Resistance of the anion exchange membrane = {(Resistance between platinum wires with the anion exchange membrane installed) - (Resistance between platinum wires with the anion exchange membrane removed)} × 1.77 …(r1)

[0076] The membrane resistance was measured in a constant temperature booth at 25°C, and the resistance at 25°C was used as the resistance value of the anion exchange membrane. The arithmetic mean of the two samples was used as the resistance value of the anion exchange membrane. The conductivity of the present invention was calculated using the following formula (r2) from the membrane resistance obtained by formula (r1) and the membrane thickness (in μm): Conductivity (mS / cm) = {Membrane thickness (μm)} ÷ Membrane resistance (Ω・cm) ２ ) ÷ 10 ... (r²)

[0077] [Membrane Thickness] The membrane thickness was measured using a micrometer (Mitutoyo product name "MDC-25SX"). Specifically, measurements were taken at five points (10 points in total) at equal intervals including both ends in the longitudinal direction of each of the two 4cm x 8cm samples cut out from the center of the obtained membrane to measure membrane resistance and ion exchange capacity, and the arithmetic mean was taken as the thickness of the anion exchange membrane. The membrane was measured within 5 minutes after wiping off moisture from both sides without drying. If more than 5 minutes had passed, the sample was immersed in water again for 5 minutes or more before measurement. For the base film, as described in Example 1, two 4cm x 8cm pieces were cut out from the center of the 10cm square sample cut out for thickness measurement, and measurements were taken at five points (10 points in total) at equal intervals including both ends in the longitudinal direction of each sample, and the arithmetic mean was taken as the thickness of the base film.

[0078] [Ion Exchange Capacity] The ion exchange capacity of the anion exchange membrane was measured by the following method. In each example, two 4 cm × 8 cm samples, the same as those used for the membrane resistance measurement, were used. Each obtained sample was immersed in a 0.1 N hydrochloric acid aqueous solution for 2 hours, and then thoroughly washed with deionized water. Washing was repeated by immersing in deionized water for 30 minutes or more until the conductivity of the rinse water was 20 μS / cm or less. After that, the membrane was immersed in 100 mL of 0.2 mol / L sodium nitrate aqueous solution for 1 hour twice, and the Cl ions eluted from the resulting solution were quantified using the Mohr method with potassium chromate aqueous solution as an indicator and 0.1 N silver nitrate aqueous solution. For quantification, 100 mL of 0.2 mol / L sodium nitrate aqueous solution was also titrated as a blank, and the amount obtained at that time was subtracted for quantification. The treated membrane was again immersed in a 0.1 N hydrochloric acid aqueous solution for 2 hours, and then thoroughly washed with deionized water. Subsequently, the samples were dried in a 50°C oven for 7 hours, quickly removed, and allowed to return to room temperature in a drying desiccator. The dry weight was then measured immediately. The ion exchange capacity is the arithmetic mean of the measurements for each sample, obtained using the following formula: Ion exchange capacity (mol / g dry film) = (Cl ions quantified by Cl titration / mol) ÷ (film dry weight)

[0079] <Raw Materials> The abbreviations in the table are as follows: CMS: Chloromethylstyrene, isomer mixture (p-isomer / m-isomer approximately 1:1), or 100% p-isomer (including those with 94% or more p-isomer and substantially 100%), used after being pretreated with activated alumina. Here, p-isomer refers to p-chloromethylstyrene, and m-isomer refers to m-chloromethylstyrene. BBS: 4-bromobutylstyrene, used after being pretreated with activated alumina. DVB: Divinylbenzene (55% purity), used after being pretreated with activated alumina. TMA: Trimethylamine BDMA: n-butyldimethylamine C6A: R in formula (a1) above ２１ Compounds in which the group is a methyl group

[0080] [Preparation Example 1: Preparation of Polymerization Solution (1)] 2 L of a solution (polymerization solution (1)) was prepared by mixing 30 parts by mass of CMS (isomer mixture), 1 part by mass of DVB, and 40 parts by mass of n-butyl acetate (solvent 1).

[0081] [Preparation Example 2: Preparation of Polymerization Solution (2)] 2 L of a solution (polymerization solution (2)) was prepared by mixing 40 parts by mass of CMS (isomer mixture) and 60 parts by mass of n-butyl acetate (solvent 1).

[0082] [Preparation Example 3: Preparation of Polymerization Solution (3)] 2 L of a solution (polymerization solution (3)) was prepared by mixing 40 parts by mass of CMS (isomer mixture), 1.33 parts by mass of DVB, and 60 parts by mass of n-butyl acetate (solvent 1).

[0083] [Preparation Example 4: Preparation of Polymerization Solution (4)] 2 L of a solution (polymerization solution (4)) was prepared by mixing 40 parts by mass of CMS (isomer mixture), 40 parts by mass of n-butyl acetate (solvent 1), and 20 parts by mass of 2-butanol (solvent 2).

[0084] [Preparation Example 5: Preparation of Polymerization Solution (5)] 2 L of a solution (polymerization solution (5)) was prepared by mixing 40 parts by mass of CMS (100% p-isomer), 0.66 parts by mass of DVB, and 60 parts by mass of n-butyl acetate (solvent 1).

[0085] [Preparation Example 6: Preparation of Polymerization Solution (6)] 2 L of a solution (polymerization solution (6)) was prepared by mixing 30 parts by mass of CMS (isomer mixture), 2 parts by mass of DVB, and 96 parts by mass of cyclohexane (solvent 1). [Preparation Example 7: Preparation of Polymerization Solution (7)] 2 L of a solution (polymerization solution (7)) was prepared by mixing 40 parts by mass of CMS (100% p-isomer) and 60 parts by mass of n-butyl acetate (solvent 1). [Preparation Example 8: Preparation of Polymerization Solution (8)] 2 L of a solution (polymerization solution (8)) was prepared by mixing 40 parts by mass of BBS and 60 parts by mass of n-butyl acetate (solvent 1).

[0086] <Base Film> Ultra-high molecular weight polyethylene films (product name "Ultrapolymer" by Yodogawa Hutech Co., Ltd., thickness 27, 40, 50, or 60 μm) manufactured by the skiving method were prepared.

[0087] A high-density polyethylene film (Tamapoly Co., Ltd. product name "HD", thickness 50 μm) produced by the inflation method was prepared.

[0088] <Manufacturing of Anion Exchange Membranes> Examples 1-8, 11, 12, 12-3, 13, and 14 are examples, and Examples 9-10, 12-2, 15, 15-2, and 16-22 are comparative examples.

[0089] [Example 1] (Graft polymerization process: Production of graft polymerized film) One 30 cm square and one 10 cm square film were cut from the base film so that one side was adjacent to the other. The 10 cm square film was used to measure the thickness of the base film. A 50 μm, 60 cm wide PET film was passed through a device capable of continuously irradiating with an electron beam using a roll-to-roll method. One 30 cm square film was attached to the PET film and activated by irradiating one side with an electron beam through the device. The electron beam irradiation conditions were an acceleration voltage of 200 kV and a dose of 100 kGy. An 11 cm square film was cut from the base film after electron beam irradiation, and the weight of the film (mass A (unit: kg)) was measured.

[0090] An 11 cm square electron beam-irradiated substrate film was placed in a 2.3 L sealed cylindrical glass container (reaction vessel (I)) with a depth sufficient to fully immerse the 11 cm square film. After degassing the inside to 10 torr (approximately 1333 Pa) at room temperature, nitrogen gas was supplied to return it to atmospheric pressure, and this process was repeated twice to replace the inside with nitrogen. Then, 2 L of polymerization solution (1) was added, which had been pre-treated in a separate container by bubbling it with high-purity nitrogen gas at room temperature to remove dissolved oxygen. After adding the solution, the container was sealed and the film was immersed. The liquid temperature was adjusted to 43 ± 1 °C, and immersion was continued for 4.5 hours to carry out graft polymerization.

[0091] 4.5 hours later, the liquid in reaction vessel (I) was drained, and acetone was immediately added to reaction vessel (I) as a washing solvent to stop the polymerization. After that, the washing operation with acetone was repeated three times, and then the film was removed from reaction vessel (I), dried with hot air, and a graft polymerized film was obtained. The mass of the graft polymerized film (mass B (unit: kg)) was measured. The graft rate (polymerization rate of the graft polymerized film, unit: %) was calculated using the following formula. The results are shown in the table (the same applies below). Graft rate = (B - A) / A × 100 Note that (B - A) is also the weight of the graft polymerized chains (graft chains), and the graft rate can also be said to be the ratio of the mass of the graft chains to the mass of the substrate film before polymerization (unit: mass %).

[0092] (Amination process: Introduction of anion exchange groups) The obtained graft polymerized membrane was put back into reaction vessel (I), and the inside of reaction vessel (I) was degassed to 10 torr (approximately 1333 Pa). Then, nitrogen gas was supplied to return it to atmospheric pressure, and this process was repeated twice to purge the inside of reaction vessel (I) with nitrogen.

[0093] Next, 2 L of TMA solution (1 mol / L methanol solution) was added to reaction vessel (I), and while maintaining the liquid temperature at 40-45°C, the graft polymerized membrane was immersed in trimethylamine solution to introduce anion exchange groups (trimethylbenzylammonium chloride groups) into the graft polymerized membrane. The immersion time (circulation time) was 24 hours. After 24 hours, the liquid was drained, and the membrane was repeatedly washed with water until the methanol concentration of the washing water was 0.1% or less to obtain an ion exchange membrane (anion exchange membrane). The thickness and membrane resistance of the obtained ion exchange membrane were measured, and the results are shown in Table 1.

[0094] [Examples 2-20] (Graft polymerization process: Production of graft polymerized film) Graft polymerized films were obtained in the same manner as in Example 1, except that the production conditions were changed as shown in Table 1, including the substrate film, irradiation conditions, polymerization solutions (1) to (8), the liquid temperature of the reaction vessel (I) during polymerization, and the polymerization time. For Examples 2, 6-9, 12, and 15-18, the film was irradiated with half the dose listed in the table, then the film was turned over and irradiated again with half the dose to activate the film. In Example 16, the obtained polymerized film was irradiated again with a 240 kGy electron beam and heat-treated at 140°C for 1 hour.

[0095] (Amination process: Introduction of anion exchange groups) For Examples 1 to 15, the obtained graft polymerized membranes were subjected to the amination process in the same manner as in Example 1 to obtain ion exchange membranes (anion exchange membranes). For Examples 12 and 15, as Examples 12-2 and 15-2 respectively, the amination process was carried out in the same manner as in Example 1, except that a 30 wt% ethanol solution of BDMA was used instead of the TMA solution (1 mol / L methanol solution) used in Example 1, to obtain ion exchange membranes (anion exchange membranes). For Example 12, as Example 12-3, the amination process was carried out in the same manner as in Example 1, except that a 30 wt% ethanol solution of C6A was used, to obtain ion exchange membranes (anion exchange membranes). For Examples 16 to 20, the amination process was carried out in the same manner as in Example 1, except that a 30 wt% ethanol solution of BDMA was used instead of the TMA solution (1 mol / L methanol solution) used in Example 1, to obtain ion exchange membranes (anion exchange membranes).

[0096] Table 1 shows the conditions for manufacturing the anion exchange membranes of Examples 1 to 20, along with the graft rate, membrane resistance, film thickness, conductivity, ion exchange rate, and the number of pressurized test failures of the electrolytic cell described later. Figure 4 is a graph showing the relationship between the film thickness and conductivity of the anion exchange membranes of Examples 1 to 20.

[0097]

[0098] As shown in Table 1, in Examples 1-8, 11, 12, 12-3, 13, and 14, the conductivity was high, at 13 mS / cm or higher, even with a film thickness of 50 μm or more. On the other hand, in Example 9, the film thickness was thin, and in Example 10, the film thickness was thick, but the conductivity was low, at 7.5 mS / cm. Also, in cases where the polymerization temperature was high, such as in Examples 15, 16, and 18-20, it was difficult to obtain films with a high polymerization rate. Furthermore, compared to linear amines with many carbon atoms, as in Examples 12-2, 15-2, and 16-20, using amines with one carbon atom, such as trimethylamine, or cyclic amines resulted in films with high conductivity.

[0099] [Intensity and electrolytic evaluation of Examples 1-10] JARI standard cell (electrode area 25 cm²) developed by the Japan Automobile Research Institute (JARI) ２ An anion exchange membrane type water electrolysis apparatus shown in Figure 5 was fabricated using a diatom (with external dimensions of 110 mm square). The anion exchange membrane type water electrolysis apparatus 2 includes an anode 41, a cathode 42, an anion exchange membrane 44, a cathode catalyst layer and gas diffusion layer 45, an anode catalyst layer and gas diffusion layer 46, a gasket 47, a separator 48, and a current collector plate 49. The clamping plate 50 contacts the anode 41 or cathode 42 via an insulating sheet (not shown) and clamps and fixes the entire apparatus. The separator 48 is a grooved separator. The separator 48 has a pair of opposing liquid passage holes (not shown) at its side corners, and liquid passes from the inlet side liquid passage hole to the outlet side liquid passage hole in the direction of the arrow. The liquid passage directions intersect between the separator 48 on the anode side and the separator 48 on the cathode side.

[0100] [Intensity and electrolytic evaluation of Examples 1-22]

[0101] <Anion Exchange Membrane> As an anion exchange membrane, the center of one of the anion exchange membranes prepared in Examples 1 to 20 listed in Table 1 was cut into an 80 mm square shape to form an anion exchange membrane 44. For the test, evaluation anion exchange membranes were prepared by repeatedly synthesizing the required number of anion exchange membranes from each example.

[0102] <Gas Diffusion Layer> As the cathode gas diffusion layer, carbon paper (Toray Industries, Ltd., product name: TGP-H-120) with a square shape and sides of 50 mm was used.

[0103] <Gasket> A PTFE gasket was cut into a square shape with an outer circumference of 80 mm and an opening of 50 mm, and gasket 47 was prepared.

[0104] <Anode Catalyst Layer> Iridium oxide (manufactured by Alfa Aesar) was used as the anode catalyst. PTFE dispersion and TritonX as a surfactant were added, and the mixture was kneaded using a disperser and ultrasonic homogenizer to obtain a catalyst dispersion. This dispersion was then spray-coated onto the gas diffusion layer, and the anode catalyst layer was formed by vacuum drying.

[0105] <Cathode Catalyst Layer> As the cathode catalyst, platinum-supported carbon powder (manufactured by Tanaka Kikinzoku Co., Ltd., product number: TEC10E50E) was used. PTFE dispersion and TritonX as a surfactant were added, and a catalyst dispersion was obtained using a disperser and an ultrasonic homogenizer. This dispersion was then applied to the gas diffusion phase by spray coating, and the cathode catalyst layer was formed by vacuum drying.

[0106] The anode catalyst layer and cathode catalyst layer were formed to be 5 to 10 μm thicker than the PTFE gasket.

[0107] <Current collector plate, separator and clamping plate> As shown in Figure 5, an anode catalyst layer, a gas diffusion layer 46, and an anode gasket 47 are arranged on one side of the anion exchange membrane 44, and a cathode catalyst layer, a gas diffusion layer 45, and a cathode gasket 47 are arranged on the other side of the anion exchange membrane 44. At this time, the anode catalyst layer and the cathode catalyst layer are arranged in contact with the anion exchange membrane. A grooved separator 48 and a current collector plate 49 for supplying liquid and gas are placed in contact with the anode gasket 47 of this laminate as the anode 41 in Figure 1, and a grooved separator 48 and a current collector plate 49 for supplying and discharging gas are placed in contact with the cathode gasket 47 of the laminate as the cathode 42 in Figure 1. An anion exchange membrane type electrolytic device 2 was fabricated and used as a test cell by stacking insulating sheets (not shown) between the current collector plates 49 and clamping plates 50 of the anode 41 and cathode 42 as shown in Figure 5 and then clamping them together. The current collector plate 49 is connected to a power source and conducts electricity through the separator 48 to the anion exchange membrane 44, cathode catalyst layer and gas diffusion layer 45, and anode catalyst layer and gas diffusion layer 46. The insulating sheets were installed to insulate the current collector plate 49 from the clamping plate 50. The separator 48 sends gas and solution to the anode catalyst layer and gas diffusion layer 46, cathode catalyst layer and gas diffusion layer 45, and anion exchange membrane 44, conducting electricity while circulating the gas and solution. Also in Figure 5, the through holes described in Figure 1 for the anode 41 and cathode 42 are positioned so that the outlets are on the side of the separator 48 (not shown).

[0108] <Pressure Resistance Test> In addition to Examples 1 to 20 described in Table 1, a test cell as shown in Figure 5 was prepared for the anion exchange membranes described in Examples 21 and 22 described later. A 0.01 N potassium hydroxide aqueous solution was set to 70°C and passed through only the anode catalyst layer side of the anion exchange membrane type water electrolysis apparatus. The cathode side was sealed at the outlet, and a pressure of 3 MPaG was applied with nitrogen from the cathode inlet side. This test was performed 10 times for 3 days. Each test was performed for the anion exchange membranes of Examples 1 to 22, and the number of times the anion exchange membrane broke and a clear nitrogen gas leak was observed on the anode side was recorded as the "Number of Pressure Test Breakdowns" in Table 2. As a result, in Example 9, where the anion exchange membrane thickness was less than 50 μm, breakage was confirmed 9 out of 10 times. On the other hand, in Examples 1 to 8 and 10, where the anion exchange membrane thickness was 50 μm or more, the number of breakdowns was suppressed as the film thickness increased, and in particular, no breakage was confirmed for membranes of 75 μm or more. Furthermore, even when the thickness was 50 μm or more, membranes aminated with amines having a linear alkyl group such as DMBA tended to have a higher number of failures, while membranes using cyclic amines had fewer failures. [Example 21] An anion exchange membrane was prepared according to Example 3 described in WO2011 / 125717 and the pressure resistance test was performed in the same manner, but the number of failures was high at 8. [Example 22] Three types of anion exchange membranes were prepared according to Examples 1 to 3 described in JP 2022-550498 and the pressure resistance test was performed in the same manner, but the number of failures was high at 7.

[0109]

[0110] <Electrolytic Performance Test> For the anion exchange membranes described in Examples 1 to 20 in Table 1, a test cell as shown in Figure 5 was prepared as described above. A 0.1 N potassium hydroxide aqueous solution was passed through the anode-side liquid inlet at 50°C, and the current collector plates 49 of the anode 41 and cathode 42 shown in Figure 5 were connected to a power supply, resulting in an electrolytic performance of 1 A / cm². ２A current was passed through the film. The generated hydrogen was released from the cathode outlet. The experiment was performed five times for each of the films shown in Examples 1 to 10 in Table 1. For Examples 1 to 9, the lower the film resistance value listed in Table 1, the lower the voltage. For Examples 10, 12-2, and 15 to 20, the voltage was very high, making it difficult to maintain the temperature at 50°C due to heat generation. In addition, for the film in Example 9, film damage was observed in two out of five tests. The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-162640, filed on September 19, 2024, are incorporated herein by reference as disclosure of the present invention.

[0111] 1 Anion exchange membrane type water electrolysis apparatus 2 Anion exchange membrane type water electrolysis apparatus 10 Substrate film 12, 14 Rolls 20 Electron beam irradiation apparatus 22 Electron beam 41 Anode 42 Cathode 43 Power supply 44 Anion exchange membrane 45 Cathode catalyst layer and gas diffusion layer 46 Anode catalyst layer and gas diffusion layer 47 Gasket 48 Separator 49 Current collector plate 50 Clamping plate

Claims

1. An anion exchange membrane comprising a base film formed from a base polymer, wherein a graft chain having an ion exchange group is bonded to the base polymer, the anion exchange membrane having a thickness of 50 μm or more, and the conductivity measured when a 0.5 N sodium chloride aqueous solution is placed on both sides of the anion exchange membrane at 25°C and a 1 kHz alternating current is applied, with the counter anion being a chloride ion, is 13 mS / cm or more.

2. The anion exchange membrane according to claim 1, wherein the base polymer is a polyolefin.

3. The anion exchange membrane according to claim 2, wherein the polyolefin is polyethylene.

4. The anion exchange membrane according to any one of claims 1 to 3, wherein the thickness of the anion exchange membrane is 75 μm or more.

5. The anion exchange membrane according to any one of claims 1 to 3, wherein the conductivity is 15 mS / cm or more.

6. The anion exchange membrane according to any one of claims 1 to 3, wherein the conductivity is 20 mS / cm or more.

7. The anion exchange membrane according to any one of claims 1 to 3, wherein the ion exchange capacity of the dried anion exchange membrane is 2.5 mmol / g.

8. The anion exchange membrane according to any one of claims 1 to 3, wherein the graft rate, which is the ratio of the mass of the graft chains to the mass of the substrate film before polymerization in which the graft chains are introduced, is 130% by mass or more.

9. The anion exchange membrane according to any one of claims 1 to 3, wherein the graft chain has a crosslinked structure made of a crosslinkable monomer, and the proportion of the crosslinkable monomer used in the polymerization step in which the graft chain is introduced is 1.5 to 20 parts by mass with respect to 100 parts by mass of the total amount of monomers used in the polymerization step.

10. An anion exchange membrane according to any one of claims 1 to 3, obtained by, in a polymerization step for introducing the graft chain, having a monomer concentration of 30 to 100% by weight in the monomer solution and a polymerization temperature of 30 to 60°C in the polymerization step.

11. The anion exchange membrane according to any one of claims 1 to 3, wherein the graft chain comprises a quaternary ammonium group derived from trimethylamine or a compound represented by any of the following formulas (a1) to (a7). (In equations (a1) to (a7), R ２１ ~R ２６ Each of these independently represents a hydrocarbon group, a fluorinated hydrocarbon group, or a fluorinated carbide group.

12. A method for producing an anion exchange membrane in which a graft chain having an anion exchange group is bonded to a base polymer, comprising the steps of: using a base film formed from a base polymer into a film; irradiating the base film with ionizing radiation to generate radicals in the base polymer; graft polymerizing a raw material monomer containing an anion exchange group introduction monomer having a functional group capable of introducing an anion exchange group onto the base film; and introducing anion exchange groups into units derived from the anion exchange group introduction monomer on the base film obtained by the graft polymerization, wherein the anion exchange membrane has a thickness of 50 μm or more, and with the counter anion being a chloride ion, the conductivity measured by applying a 1 kHz alternating current with 0.5 N sodium chloride aqueous solution placed on both sides of the anion exchange membrane at 25°C is 13 mS / cm or more.

13. The method for producing an anion exchange membrane according to claim 12, wherein the graft polymerization is carried out at a polymerization temperature of 30 to 60°C.

14. The method for producing an anion exchange membrane according to claim 12 or 13, wherein the dose of the ionizing radiation is 10 to 1000 kGy.

15. The method for producing an anion exchange membrane according to claim 12 or 13, wherein the dose of the ionizing radiation is 40 to 300 kGy.

16. The method for producing an anion exchange membrane according to claim 12 or 13, wherein the polymerization time for the graft polymerization is 3 hours or more and 10 hours or less.

17. A water electrolysis apparatus having an anion exchange membrane according to any one of claims 1 to 3.

18. The water electrolysis apparatus according to claim 17, comprising a cathode electrode that generates hydrogen, an anode electrode that generates oxygen, and an anion exchange membrane disposed between the two electrodes, wherein the cathode electrode is provided with a mechanism that pressurizes the internal pressure to a state higher than atmospheric pressure by controlling the release of hydrogen.

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