Ion exchange membrane, method for producing ion exchange membrane, membrane electrode assembly, and hydrogen production device

Abstract

This ion exchange membrane has a short side and a long side of 80 m or more. A membrane thickness deviation rate A, ion exchange capacity deviation rate B, and ion exchange group residual ratio C, which are calculated by a predetermined method, are within a specific numerical range.

Description

Ion exchange membrane, method for manufacturing ion exchange membrane, membrane electrode assembly, and hydrogen production device

[0001] The present disclosure relates to an ion exchange membrane, a method for producing an ion exchange membrane, a membrane electrode assembly, and a hydrogen production device.

[0002] As a method for producing hydrogen, water electrolysis, which generates hydrogen gas and oxygen gas by electrolyzing water, is being studied. Hydrogen produced using the energy obtained by a method that suppresses the generation of carbon dioxide as electricity does not contain CO ２ It is called free hydrogen or green hydrogen and is expected to be the next generation of clean energy that will replace fossil fuels.

[0003] Among water electrolysis methods, AEM water electrolysis using an anion exchange membrane (AEM) has attracted attention because it does not require the use of expensive precious metals as a catalyst. Against this background, in order to expand the use of AEM water electrolysis devices, there is a demand for AEMs that are more cost-effective and have good production efficiency. For example, the use of a roll-shaped AEM facilitates the continuous production process of electrolysis devices, leading to cost reductions for electrolysis devices. Patent Document 1 discloses an AEM in the form of a roll that is obtained by impregnating a porous support with a polymerizable composition, then winding the porous support, and then heating the wound roll in an oven.

[0004] Furthermore, in order to reduce the manufacturing cost of AEM, Patent Documents 2 and 3 disclose AEM using photopolymerization as a method for shortening the polymerization time and improving production efficiency. However, both of these relate to batch-produced AEM and do not take into consideration the production of long AEM with high uniformity.

[0005] Japanese Patent Application Laid-Open No. 2006-225459 International Publication No. 2016 / 027595 Special Publication No. 2022-502522

[0006] According to at least one aspect of the present disclosure, it is possible to provide an ion exchange membrane that is efficiently produced with high uniformity, a method for producing the ion exchange membrane, a membrane electrode assembly including the ion exchange membrane, and a hydrogen production device.

[0007] The present inventors have found that the above-mentioned problems can be solved by an ion exchange membrane in which the membrane thickness deviation rate A, the ion exchange capacity deviation rate B, and the ion exchange group residual rate C, which are calculated by a predetermined method, are within specific numerical ranges, and by a membrane electrode assembly and a hydrogen production device that include this ion effect membrane.

[0008] According to the present disclosure, the following ion exchange membrane, method for producing the ion exchange membrane, membrane electrode assembly, and hydrogen production device are provided.

[0009] Specifically, the present disclosure relates to the following [1] to

[12] . [1] An ion exchange membrane, wherein the ion exchange membrane has short sides and long sides, and the length of the long sides is 80 m or more; a plurality of test pieces are collected from a predetermined region of the ion exchange membrane, and the membrane thickness is measured at a plurality of measurement points on each test piece, and the arithmetic mean value of the membrane thickness for each test piece is calculated to obtain an overall mean membrane thickness T, and the value of the arithmetic mean membrane thicknesses for each test piece that is the largest difference from T is defined as a maximum dissociation value S. When this is done, a membrane thickness deviation rate A (%) expressed by the following formula (1) is less than 5.0%; when the ion exchange capacity of each test piece is measured, and the arithmetic mean value of the ion exchange capacity measured for each test piece is defined as an overall mean ion exchange capacity W, and the value of the ion exchange capacity values ​​for each test piece that is the largest difference from W is defined as a maximum dissociation value V, a membrane thickness deviation rate B (%) expressed by the following formula (2) is less than 10.0%; and an ion exchange group residual rate C obtained by measuring the ion exchange capacity of the ion exchange membrane before and after an alkaline durability test is 70% or more; Thickness deviation rate A (%) = |(T - S) / T x 100| (1) Ion exchange capacity deviation rate B (%) = |(W - V) / W x 100| (2). [2] The ion exchange membrane according to [1], wherein W is 1.5 to 3.5 meq. / g. [3] The ion exchange membrane according to [1] or [2], comprising a porous support having pores and an ion exchange resin filled in the pores. [4] The ion exchange membrane according to [3], wherein the ion exchange resin is a hydrocarbon polymer. [5] The ion exchange membrane according to [3] or [4], wherein the ion exchange resin comprises an anion exchange resin. [6] The ion exchange membrane according to any one of [3] to [5], wherein the porous support comprises a polyolefin resin. [7] The ion exchange membrane according to any one of [3] to [6], wherein the ion exchange resin comprises a cured product of a polymerizable composition having a viscosity change rate of less than 10% as measured by liquid viscosity according to Japanese Industrial Standards (JIS) Z8803:2011. [8] The ion exchange membrane according to any one of [3] to [7], wherein the ion exchange resin comprises a cured product of a polymerizable composition comprising a curable monomer having a cationic group, a crosslinkable monomer, and an alkylene glycol.[9] A method for producing an ion exchange membrane according to any one of [3] to [8], comprising: an impregnation step of impregnating the porous support with a polymerizable composition; a coating step of covering the porous support impregnated with the polymerizable composition with an upper film and a lower film; and an irradiation step of irradiating the coated porous support with ultraviolet light.

[10] A method for producing an ion exchange membrane according to [9], wherein the impregnation step, the coating step, and the irradiation step are carried out continuously while transporting the porous support, and the transport speed in the irradiation step is 0.5 m / min or more and 5.0 m / min or less.

[11] A membrane electrode assembly comprising the ion exchange membrane according to any one of [1] to [8] and an electrode.

[12] A hydrogen production device comprising the ion exchange membrane according to any one of [1] to [8] or the membrane electrode assembly of claim 11.

[0010] The present disclosure provides an ion exchange membrane that has high uniformity in thickness and ion exchange capacity and excellent alkali durability, a membrane electrode assembly and a hydrogen production device that use the same, and a method for producing the ion exchange membrane.

[0011] 1 is a schematic diagram illustrating an example of an ion exchange membrane manufacturing apparatus, a cross-sectional view illustrating an example of a hydrogen production apparatus according to an embodiment of the present disclosure, a schematic diagram illustrating measurement points of a film thickness deviation rate of an ion exchange membrane, and a schematic diagram illustrating measurement points of a film thickness deviation rate of an ion exchange membrane.

[0012] In the present disclosure, expressions such as "XX or more and YY or less" or "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined arbitrarily. Furthermore, in the present disclosure, expressions such as "at least one selected from the group consisting of XX, YY, and ZZ" mean any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ.

[0013] An ion exchange membrane according to an embodiment of the present disclosure will be described in detail below. [Ion Exchange Membrane] The ion exchange membrane according to an embodiment of the present disclosure has excellent alkaline durability and can therefore be used in hydrogen production devices, water electrolysis devices, fuel cells, electrodialysis devices, diffusion dialysis devices, pure water production devices, ion-exchanged water production devices, etc. The ion exchange membrane can be suitably used as an anion exchange membrane for an AEM hydrogen production device, an AEM water electrolysis device, or a fuel cell.

[0014] An ion exchange membrane is a rectangular membrane having short and long sides. Typically, the short side is referred to as the "width" and the long side is referred to as the "length," and the ion exchange membrane can be wound in a roll shape in the length direction. The length L2 of the short side of the ion exchange membrane is, for example, 150 mm or more and 1200 mm or less, preferably 300 mm or more and 1200 mm or less. The length L1 of the long side of the ion exchange membrane is, for example, 80 m or more and 600 m or less, preferably 100 m or more and 600 m or less. The ratio L1 / L2 of the length L2 of the short side of the ion exchange membrane to the length L1 of the long side of the ion exchange membrane is, for example, 60 to 4000, preferably 90 to 2000. Such a shape in which the length is sufficiently long relative to the width is also called a "long" shape. Generally, a long ion exchange membrane may have variations in characteristics along its length, but the ion exchange membrane according to an embodiment of the present disclosure can suppress non-uniformity along its length.

[0015] The thickness of the ion exchange membrane is, for example, 10 μm or more and 200 μm or less. When a thick ion exchange membrane is used, the membrane resistance tends to increase. When a thin ion exchange membrane is used, the membrane resistance tends to decrease. The thickness of the ion exchange membrane is preferably 20 μm or more and 150 μm or less, and more preferably 20 μm or more and 100 μm or less. The thickness of the ion exchange membrane here refers to the overall average membrane thickness T obtained by the measurement method described below.

[0016] The ion exchange membrane according to an embodiment of the present disclosure has a thickness deviation rate A in the long side direction of less than 5.0%. The thickness deviation rate A of the ion exchange membrane in the long side direction is a parameter that indicates the variation in thickness of the ion exchange membrane in the long side direction, calculated using a method described below. A small thickness deviation rate A in the long side direction means that the ion exchange membrane has high thickness uniformity in the long side direction. Using an ion exchange membrane with high thickness uniformity in the long side direction makes it possible to produce a roll-shaped ion exchange membrane that is less likely to wrinkle during the winding operation of the ion exchange membrane after drying. Furthermore, the electrolysis performance of the AEM water electrolysis device is likely to be stabilized. Furthermore, the handleability of the ion exchange membrane is improved in the continuous production process of the AEM water electrolysis device, allowing for stable device production. The thickness deviation rate A is preferably 4.0% or less, and more preferably 3.5% or less. The lower limit of the thickness deviation rate A is not particularly limited, but is, for example, 1.0% or more, and in another example, 2.0% or more. That is, the film thickness deviation rate A may be, for example, 1.0% or more and less than 5.0%, 1.0% or more and 4.0% or less, 1.0% or more and 3.5% or less, 2.0% or more and less than 5.0%, 2.0% or more and 4.0% or less, or 2.0% or more and 3.5% or less.

[0017] The thickness deviation rate A can be controlled by the magnitude of change in viscosity of the polymerizable composition used as a raw material for producing the ion exchange membrane. When the viscosity change is large, the impregnation time into the support and the amount of entrainment fluctuate, resulting in a non-uniform thickness of the resulting ion exchange membrane, and the thickness deviation rate A increases. On the other hand, when the viscosity change is small, the impregnation time into the support and the amount of entrainment remain constant, resulting in a uniform thickness of the resulting ion exchange membrane, and the thickness deviation rate A decreases. Furthermore, the viscosity change of the polymerizable composition can be controlled by the solvent contained in the polymerizable composition. To minimize the viscosity change, it is preferable that the polymerizable composition contains a high-boiling point solvent such as alkylene glycol. On the other hand, when a low-boiling point solvent such as water or methanol is used, these solvents tend to volatilize easily, resulting in a large viscosity change. Furthermore, as will be described later with respect to the method for producing an ion exchange membrane, the viscosity change of the polymerizable composition can be suppressed and the thickness deviation rate A can be controlled by sequentially performing impregnation, winding, and curing in the production process, covering the support after impregnation with a film, controlling the conveying speed within a predetermined range, and the like.

[0018] The film thickness deviation rate A is obtained by measuring the film thickness at multiple measurement points on each of multiple test pieces taken from a predetermined region of the ion exchange membrane, calculating the overall average film thickness T from the arithmetic average film thickness of each test piece, determining the maximum dissociation value S as the value with the greatest difference from T among the arithmetic average film thicknesses for each test piece, and then subtracting S from T and dividing the result by T to obtain the absolute value. That is, the film thickness deviation rate A is expressed by the following formula (1): Film thickness deviation rate A (%) = |(T - S) / T × 100| ... (1)

[0019] The method for measuring the thickness deviation rate A will be described in more detail. First, an ion exchange membrane is immersed in a 0.5 mol / L NaCl aqueous solution for 10 hours or more, then washed with ion-exchange water and air-dried at room temperature (25°C) for 12 hours or more to prepare a dried chloride ion-type ion exchange membrane. A test piece for measurement is obtained from this ion exchange membrane. A method for obtaining a test piece for calculating the thickness deviation rate A of an ion exchange membrane will be described with reference to Figures 3 and 4. As shown in Figure 3, the length of the long side 301 of the ion exchange membrane 109 is defined as L1, and the length of the short side 302 is defined as L2. The long side of the ion exchange membrane is divided equally into five parts and four lines perpendicularly intersecting the long side 301 are used to divide the short side into two parts. The intersections of these four lines, which are defined as intersections 303 (circles in Figure 3), are the intersections of four lines perpendicularly intersecting the long side 301 and one line perpendicularly intersecting the short side 302. Square test pieces, each 100 mm long on a side, were collected from each of the intersections 303, with the intersections 303 serving as the geometric center, to obtain a total of four test pieces 400. As shown in FIG. 4 , 16 intersections 401 (denoted by triangles in FIG. 4 ), which are the intersections of eight lines dividing the collected test piece 400 into 20 mm squares, were used as measurement points for each test piece. For each test piece, the ion exchange membrane thickness was measured at the 16 measurement points using a film thickness meter, and the arithmetic mean value for each test piece was calculated. The arithmetic mean values ​​obtained for the four test pieces were summed and divided by four to obtain the overall average ion exchange membrane thickness T. The value with the largest difference from T among the arithmetic mean values ​​for each of the four test pieces was designated the maximum dissociation value S. From the obtained values ​​of T and S, the film thickness deviation rate A was calculated using the above formula (1).

[0020] The ion exchange capacity deviation rate B in the long side direction of the ion exchange membrane according to an embodiment of the present disclosure is less than 10.0%. The ion exchange capacity deviation rate B of the ion exchange membrane in the long side direction is a parameter that indicates the variation in ion exchange capacity in the long side direction of the ion exchange membrane, calculated by a method described below. A small value of the ion exchange capacity deviation rate B means that the ion exchange capacity in the long side direction of the ion exchange membrane is highly uniform. Use of an ion exchange membrane with high uniformity of ion exchange capacity in the long side direction can stabilize the electrolysis performance of the AEM water electrolysis apparatus. The ion exchange capacity deviation rate B is preferably less than 10.0%, more preferably 7.5% or less, and even more preferably 5.0% or less. The lower limit of the ion exchange capacity deviation rate B is not particularly limited, but is, for example, 1.0% or more, and in another example, 3.0% or more. That is, the ion exchange capacity deviation rate B may be, for example, 1.0% or more and less than 10.0%, 1.0% or more and 7.5% or less, 1.0% or more and 5.0%, 3.0% or more and less than 10.0%, 3.0% or more and 7.5% or less, or 3.0% or more and 5.0% or less.

[0021] The ion exchange capacity deviation rate B can be controlled by the magnitude of the change in viscosity of the polymerizable composition that is the raw material for producing the ion exchange membrane, in the same manner as the membrane thickness deviation rate A.

[0022] The ion exchange capacity deviation rate B is obtained by measuring the ion exchange capacity at multiple measurement points on the test piece used to measure the above-mentioned film thickness deviation rate A, taking the arithmetic average of the ion exchange capacities for each test piece as the overall average ion exchange capacity W, taking the value of the ion exchange capacity for each test piece that differs most from W as the maximum dissociation value V, and then subtracting V from W and dividing the result by W, and then calculating the absolute value of the result. That is, the ion exchange capacity deviation rate B is expressed by the following formula (2): Ion exchange capacity deviation rate (%) = |(W - V) / W × 100| (2).

[0023] The method for measuring the ion exchange capacity deviation rate B will be described in more detail. First, the test piece 400 used for measuring the film thickness deviation rate A was treated with 0.2 mol / L NaNO ３ Immerse in the aqueous solution for 30 minutes. ３The aqueous solution is replaced and the sample is further immersed for 30 minutes. ３ The replacement of the aqueous solution and the immersion were repeated two more times for a total of 2 hours. ３ The aqueous solution is used immediately after preparation. This procedure yields a test piece of an ion exchange membrane in which the counter ions have been replaced from chloride ions to nitrate ions.

[0024] For each test piece, the amount of chloride ions liberated during the substitution with nitrate ions is measured using a potentiometric titrator with a silver nitrate solution. The obtained value is the chloride ion amount D (mol) of each test piece. As the potentiometric titrator, for example, a COMTITE-900 manufactured by Hiranuma Sangyo Co., Ltd. is used.

[0025] Next, the test pieces whose counterions have been replaced with nitrate ions are immersed in a 0.5 mol / L NaCl aqueous solution for 30 minutes. The NaCl aqueous solution is then replaced, and the test pieces are immersed for another 30 minutes. The replacement of the NaCl aqueous solution and immersion are repeated two more times, for a total immersion time of 2 hours. Again, the 0.5 mol / L NaCl aqueous solution is used immediately after preparation. The test pieces are then removed from the NaCl aqueous solution and thoroughly rinsed with ion-exchanged water. After rinsing, the surface of the test pieces is wiped dry, and the test pieces are dried under reduced pressure at 50°C for 12 hours or more. The mass of the dried test pieces is measured and defined as mass E (g). The ion exchange capacity of each test piece is calculated using the following formula based on the amount of liberated chloride ions (D) and the mass (E) of the test pieces.

[0026] Ion exchange capacity [meq. / g] = D x 1000 / E The ion exchange capacity measurements obtained for the four test pieces are summed and divided by 4 to obtain the overall average ion exchange capacity W of the ion exchange membrane. Of the ion exchange capacity values ​​of the four test pieces, the value with the largest dissociation from W is defined as the maximum dissociation value V. From the obtained values ​​of W and V, the ion exchange capacity deviation rate B is calculated using the above formula (2).

[0027] The overall average value W of the ion exchange capacity of the ion exchange membrane is, for example, 1.5 meq / g or more, in another example, 2.0 meq / g or more, and in yet another example, 2.5 meq / g or more. The ion exchange membrane according to an embodiment of the present disclosure can achieve a high ion exchange capacity because a polymerizable composition having a high concentration of a quaternary ammonium salt can be used. The upper limit of W is not particularly limited, but in one example, it is 3.5 meq / g or less, and in another example, it is 3.0 meq / g or less. That is, the overall average value W of the ion exchange capacity of the ion exchange membrane may be, for example, 1.5 to 3.5 meq / g, 1.5 to 3.0 meq / g, 2.0 to 3.5 meq / g, 2.0 to 3.0 meq / g, 2.5 to 3.5 meq / g, or 2.5 to 3.0 meq / g.

[0028] In an ion exchange membrane according to an embodiment of the present disclosure, the ion exchange group residual rate C, obtained by measuring the ion exchange capacity before and after an alkaline durability test, is 70% or more. A high ion exchange group residual rate means that the ion exchange membrane has high alkaline durability. The ion exchange group residual rate C is preferably 80% or more, and more preferably 90% or more. The upper limit of this ion exchange group residual rate C is not particularly limited, but in one example it is 100%, and in another example it is 95% or less. That is, examples of the ion exchange group residual rate include 70 to 100%, 80 to 100%, 90 to 100%, 70 to 95%, 80 to 95%, and 90 to 95%.

[0029] The ion exchange group residual ratio C can be controlled by the alkali durability of the curable monomer containing a cationic group contained in the polymerizable composition. When a vinyl group or an allyl group is used as the polymerizable group, the alkali durability of the curable monomer increases, and the ion exchange group residual ratio C increases. On the other hand, when an acryloyl group or a methacryloyl group is used as the polymerizable group, the alkali durability of the curable monomer decreases, and the ion exchange group residual ratio C decreases.

[0030] The ion exchange group residual rate C is measured by the following method. First, a test piece measuring 100 mm × 100 mm is taken from a location different from the location where the test piece was taken when measuring the film thickness deviation rate A. This test piece is immersed in 300 mL of a 1 mass % potassium hydroxide aqueous solution and left to stand in an oven at 90°C for one week, thereby conducting a heating test. The ion exchange capacity X of the test piece after the heating test is calculated by the same method as above. The ion exchange capacity X after the heating test is divided by the overall average value W of the ion exchange capacity described above (X / W × 100) and is defined as the ion exchange group residual rate C (%).

[0031] The membrane resistance of the ion exchange membrane is, for example, 2.0 Ω cm ２ or less, and in another example, 1.0 Ω cm ２ There is no particular lower limit for the membrane resistance, but in one example, it is 0.1 Ω cm ２ or more, and in another example, 0.2 Ω cm ２ The membrane resistance of the ion exchange membrane is, for example, 0.1 to 2.0 Ω cm ２ ,0.1~1.0Ω・cm ２ ,0.2~2.0Ω・cm ２ ,0.2~1.0Ω・cm ２ Examples include:

[0032] The water content of the ion exchange membrane is, for example, 20% or more, in another example, 30% or more, and in still another example, 40% or more. From the viewpoint of increasing the mechanical strength of the membrane, the water content of the ion exchange membrane is preferably 120% or less, and more preferably 100% or less.

[0033] The ion exchange membrane may include or may be composed of a porous support having pores and an ion exchange resin filled in the pores of the porous support.

[0034] The porous support functions as a support for the ion exchange resin. The porous support is preferably a porous membrane. Examples of porous supports that can be used include porous films, woven fabrics, nonwoven fabrics, sponges, and films. When a porous membrane is used as the porous support, the pores of the porous support are preferably filled with an ion exchange resin. By using a porous support, the strength of the ion exchange resin filled in the pores can be increased. Among these, it is particularly preferable to use a porous film in terms of strength and thickness uniformity.

[0035] The porous support is, for example, at least one selected from the group consisting of polyolefin resin, fluorine-based resin, polyacrylonitrile, polyvinyl chloride, polyester, polyamide, polysulfone, polyethersulfone, polyphenylene sulfone, polyphenylene sulfide, polyimide, polyethermide, polyamideimide, polycarbonate, polyacrylate, cellulose acetate, polyetheretherketone, and copolymers thereof. The polyolefin resin is, for example, at least one selected from the group consisting of polyethylene, polypropylene, polybutadiene, polymethylpentene, polybutene, polypentene, polyhexene, polymethylheptene, and copolymers thereof. The fluorine-based resin is, for example, at least one selected from the group consisting of polytetrafluoroethylene, poly(tetrafluoroethylene-hexafluoropropylene), polyvinylidene fluoride, polyhexafluoropropylene, polychlorotrifluoroethylene, and copolymers thereof. From the viewpoint of alkali durability, the porous support preferably contains a polyolefin resin, and more preferably contains at least one of polyethylene and polypropylene.

[0036] The thickness of the porous support is, for example, 10 μm or more and 200 μm or less, preferably 20 μm or more and 150 μm or less, more preferably 20 μm or more and 100 μm or less. Although the porous film is not limited, it is preferable that the porous film has a uniform thickness as much as possible, and it is preferable that the thickness deviation rate of the porous film when measured by the same method as the above-mentioned thickness deviation rate A is less than 5.0%.

[0037] The porosity of the porous support is, for example, 25% or more and 80% or less, preferably 30% or more and 75% or less, and more preferably 35% or more and 70% or less.

[0038] The ion exchange resin is preferably a hydrocarbon polymer. Here, a hydrocarbon polymer refers to a polymer that is substantially free of carbon-fluorine bonds and in which the majority of the bonds in the main chain and side chains that make up the polymer are carbon-carbon bonds. More specifically, a hydrocarbon polymer refers to a polymer in which the proportion of carbon and hydrogen among the elements that make up the polymer is 75 elemental % or more. In other words, small amounts of other atoms such as oxygen, nitrogen, silicon, sulfur, boron, and phosphorus may be present between the carbon-carbon bonds that make up the main chain and side chains via ether bonds, ester bonds, amide bonds, siloxane bonds, etc.

[0039] The ion exchange resin preferably comprises, and more preferably consists of, an anion exchange resin, which has positively charged groups (cationic groups) as ion exchange groups within the resin and is capable of adsorbing and exchanging anions as counter ions.

[0040] The ion exchange resin contains, as an ion exchange group, at least one selected from the group consisting of, for example, a quaternary ammonium group, a quaternary phosphonium group, a quaternary imidazolium group, a quaternary pyridinium group, a quaternary pyrrolidinium group, and a quaternary piperidinium group. The ion exchange group is not particularly limited, but a quaternary ammonium group is preferred due to its ease of production and high alkali durability. Examples of counter ions for the ion exchange resin include at least one selected from the group consisting of halide ions, triflate, bistrifluoromethanesulfonimide, hydroxide ions, carbonate ions, and bicarbonate ions. The counter ion is preferably at least one selected from the group consisting of carbonate ions, bicarbonate ions, and halide ions. Ion exchange resins containing these ions are suitable as anion exchange resins.

[0041] <Polymerizable Composition> The ion exchange resin according to an embodiment of the present disclosure can be obtained by curing a polymerizable composition. In other words, the ion exchange resin according to an embodiment of the present disclosure may include a cured product of the polymerizable composition. Specifically, for example, by performing photopolymerization by a roll-to-roll process using a polymerizable composition having a small viscosity change rate, an ion exchange membrane having a small film thickness deviation rate A and ion exchange capacity deviation rate B and a high ion exchange group residual rate C can be obtained.

[0042] The polymerizable composition for forming the ion exchange resin preferably contains a curable monomer containing a cationic group and a crosslinkable monomer. The polymerizable composition may also contain a solvent, which may contain alkylene glycol. The ion exchange resin may contain a cured product of a polymerizable composition containing a curable monomer containing a cationic group, a crosslinkable monomer, and an alkylene glycol. In a 23°C, 50% humidity environment, the viscosity change rate of the polymerizable composition is preferably less than 20%, more preferably less than 10%, and even more preferably less than 8%. A viscosity change rate of less than 10% allows for the production of an ion exchange membrane with a small membrane thickness deviation rate A and ion exchange capacity deviation rate B, even when a long-length ion exchange membrane is produced over a long period of time. The lower the viscosity change rate, the more uniform the ion exchange membrane can be produced. Such a polymerizable composition can be obtained, for example, by using a curable monomer containing a cationic group, a crosslinkable monomer, and a solvent, as described below.

[0043] The viscosity is measured in accordance with Japanese Industrial Standards (JIS) Z8803:2011. The viscosity of the polymerizable composition 1 minute after preparation is defined as Y, and the viscosity of the polymerizable composition after standing for 1 hour at a temperature of 23°C and humidity of 50% is defined as Z. The viscosity change rate is the absolute value of the value (Z-Y) obtained by subtracting the viscosity Y after preparation from the viscosity Z after standing, divided by the viscosity Y 1 minute after preparation. That is, the viscosity change rate is expressed by the following formula: Viscosity change rate (%) = |(Z-Y) / Y x 100|

[0044] The viscometer used is a tuning fork vibration viscometer SV-1A manufactured by A&D Co., Ltd.

[0045] <Curable Monomer Containing a Cationic Group> Examples of curable monomers containing a cationic group include curable monomers containing at least one cationic group selected from the group consisting of a quaternary ammonium group, a quaternary phosphonium group, a quaternary imidazolium group, a quaternary pyridinium group, a quaternary pyrrolidinium group, and a quaternary piperidinium group. Furthermore, the curable monomer containing a cationic group contains a radically polymerizable group. As the radically polymerizable group, highly reactive functional groups such as acryloyl groups and methacryloyl groups are preferred in the curing reaction. On the other hand, in terms of alkali durability, vinyl groups and allyl groups are preferred. Therefore, the curable monomer containing a cationic group preferably has at least one group selected from the group consisting of an acryloyl group, a methacryloyl group, an acrylamide group, a vinyl group, and an allyl group. In particular, the curable monomer preferably has a vinyl group or an allyl group, and is particularly preferably a quaternary ammonium represented by the following formula (I): The curable monomer containing a quaternary ammonium group represented by formula (I) is easily available and has high alkaline durability, and is therefore suitable as a monomer for water electrolysis.

[0046]

[0047] In the above formula (I), R １ is an alkenyl group having 2 to 5 carbon atoms. １ is preferably a vinyl group or an allyl group, more preferably a vinyl group.

[0048] R ２ is an alkylene group having 1 to 10 carbon atoms. ２ is preferably an alkylene group having 1 to 5 carbon atoms, more preferably a methylene group or an ethylene group, and even more preferably a methylene group.

[0049] R ３ , R ４ , and R ５ are each independently a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched alkoxy group having 1 to 4 carbon atoms. ３ , R４ , and R ５ are each independently preferably a linear alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group.

[0050] X － X may be a monovalent anion or a divalent anion. － is, for example, a halide ion, tetrafluoroborate, bicarbonate ion, hydroxide ion, triflate, or bistrifluoromethanesulfonimide. The halide ion is, for example, a fluoride ion, a chloride ion, or a bromide ion. X － is preferably a chloride ion, a triflate, or a bistrifluoromethanesulfonimide. － When X is a chloride ion, an ion exchange resin having a large amount of ion exchange groups per unit mass can be obtained. － However, when the quaternary ammonium salt is a triflate or bistrifluoromethanesulfonimide, the solubility of the composition is increased, and the concentration of the quaternary ammonium salt in the polymerizable composition tends to be increased. By using such a polymerizable composition, an ion exchange resin having a high molar amount of ion exchange groups per unit mass can be obtained.

[0051] The polymerizable composition may contain only one type of curable monomer, but preferably contains two or more types. The polymerizable composition more preferably contains, as the monomer represented by formula (I), two or more quaternary ammoniums selected from the group consisting of para-quaternary ammonium, meta-quaternary ammonium, and ortho-quaternary ammonium, which are structural isomers. A composition containing quaternary ammoniums that are structural isomers tends to be less likely to crystallize and more soluble in solvents than a composition that does not contain quaternary ammoniums that are structural isomers.

[0052] Specific examples of curable monomers containing a cationic group include (vinylbenzyl)trimethylammonium chloride, (vinylbenzyl)trimethylammonium triflate, (vinylbenzyl)trimethylammonium bistrifluoromethanesulfonimide, (vinylbenzyl)dimethylethylammonium chloride, (vinylbenzyl)dimethylethylammonium triflate, (vinylbenzyl)dimethylethylammonium bistrifluoromethanesulfonimide, (vinylbenzyl)trimethylammonium tetrafluoroborate, (vinylbenzyl)trimethylammonium bicarbonate, and (vinylbenzyl)trimethylammonium hydroxide.

[0053] Specific examples of other curable monomers containing a cationic group include 4-ethenyl-N,N-dimethylbenzeneethanaminium chloride, 4-ethenyl-N,N-dimethylbenzeneethanaminium triflate, 4-ethenyl-N,N-dimethylbenzeneethanaminium bistrifluoromethansulfonium, 4-ethenyl-N,N-dimethylbenzeneethanaminium hydroxide, 4-ethenyl-N,N-dimethylbenzenepropanaminium chloride, 4-ethenyl-N,N-dimethylbenzenepropanaminium triflate, 4-ethenyl-N,N-dimethylbenzenepropanaminium bistrifluoromethansulfonium, 4-ethenyl-N,N-dimethylbenzenepropanaminium hydroxide, and the like.

[0054] As the curable monomer containing a cationic group, it is preferable to use a (vinylbenzyl)trimethylammonium salt, and it is more preferable to use at least one salt selected from the group consisting of (vinylbenzyl)trimethylammonium chloride, (vinylbenzyl)trimethylammonium triflate, and (vinylbenzyl)trimethylammonium bistrifluoromethanesulfonylimide. (Vinylbenzyl)trimethylammonium salts have high solubility and therefore tend to easily increase the concentration of the curable monomer containing a cationic group in the polymerizable composition.

[0055] The proportion of the curable monomer containing a cationic group in the polymerizable composition is, for example, 5% by mass or more and 95% by mass or less. This proportion is preferably 50% by mass or more, more preferably 60% by mass or more, and more preferably 65% ​​by mass or more. A higher proportion results in an ion exchange resin with a higher amount of ion exchange groups per unit mass. This proportion may be 92% by mass or less, 85% by mass or less, or even 80% by mass or less. The proportion of the curable monomer containing a cationic group in the polymerizable composition may be within the following ranges: 5 to 95% by mass, 50 to 95% by mass, 50 to 92% by mass, 50 to 85% by mass, 50 to 80% by mass, 60 to 95% by mass, 60 to 92% by mass, 60 to 85% by mass, 60 to 80% by mass, 65 to 95% by mass, 65 to 92% by mass, 65 to 85% by mass, or 65 to 80% by mass.

[0056] The proportion of the curable monomer containing a cationic group in the polymerizable composition can be measured, for example, by subtracting the mass of the curable monomer containing a cationic group that remains unreacted after the polymerization reaction from the total mass of the curable monomer containing a cationic group used as a raw material. １ H-NMR and １３ This can be measured by analyzing using a known analytical method such as C-NMR, etc. The same applies to the components other than the curable monomer containing a cationic group hereinafter.

[0057] In the polymerizable composition, the preferred range of the proportion of the curable monomer containing a cationic group varies depending on the type of the monomer. The concentration of vinylbenzyltrimethylammonium chloride is, for example, 60% by mass or more and 70% by mass or less. The concentration of vinylbenzyltrimethylammonium triflate is, for example, 75% by mass or more and 85% by mass or less. The concentration of vinylbenzyltrimethylammonium bistrifluoromethanesulfonimide is, for example, 85% by mass or more and 95% by mass or less.

[0058] <Crosslinking Monomer> The crosslinking monomer may be a comonomer that polymerizes with the curable monomer containing a cationic group. The crosslinking monomer can crosslink the curable monomers containing a cationic group to each other, thereby increasing the durability of the cured product.

[0059] The crosslinkable monomer may have one radical polymerizable group per molecule, or may have two or more radical polymerizable groups per molecule. The radical polymerizable group may be at least one selected from the group consisting of a vinyl group, an allyl group, an acryloyl group, and a methacryloyl group. Among these, a vinyl group is preferred because of its high alkali resistance and high reactivity.

[0060] Examples of the crosslinkable monomer include at least one selected from the group consisting of vinyl compounds having one vinyl group, divinyl compounds having two vinyl groups, allyl compounds having one allyl group, diallyl compounds having two allyl groups, and dienes. The crosslinkable monomer preferably has two polymerizable groups, and is more preferably a divinyl compound.

[0061] Specific examples of crosslinkable monomers include divinylbenzene, divinylbenzene derivatives, divinyl sulfone, butadiene, chloroprene, divinylphenyl, trivinylbenzenes, divinylnaphthalene, allylamine, diallylamine, divinylpyridine, methylstyrene, vinylbiphenyl, diallyl isocyanurate, 1,2-bis(4-vinylphenyl)ethane, trivinylbenzene, and 1,6-bis(4-vinylbenzyloxy)hexane.

[0062] As the crosslinkable monomer, it is preferable to use at least one styrene derivative selected from the group consisting of divinylbenzene, 1,2-bis(4-vinylphenyl)ethane, trivinylbenzene, and 1,6-bis(4-vinylbenzyloxy)hexane.

[0063] The proportion of the crosslinkable monomer in the polymerizable composition is, for example, 0.1% by mass to 50% by mass, preferably 1% by mass to 20% by mass, and more preferably 2% by mass to 10% by mass. If this proportion is high, the durability of the cured product tends to be enhanced. If this proportion is too high, the performance of the ion exchange resin may be reduced.

[0064] In the polymerizable composition, the ratio M1 / M2 of the mass M1 of the curable monomer containing a cationic group to the mass M2 of the crosslinkable monomer is, for example, 1 or more and 100 or less, preferably 3 or more and 50 or less, and more preferably 5 or more and 25 or less. When this ratio is large, the performance of the ion exchange resin tends to be improved. When this ratio is small, the durability of the cured product tends to be improved.

[0065] <Solvent> The polymerizable composition may contain a solvent. To obtain an ion exchange membrane according to an embodiment of the present disclosure, it is preferable to use a polymerizable composition that not only sufficiently dissolves the curable monomer containing a cationic group but also exhibits little change in viscosity over the relatively long production time required to produce a long ion exchange membrane. The magnitude of change in viscosity of the polymerizable composition can significantly affect the uniformity of the ion exchange membrane produced. If the viscosity change is large, the impregnation time and amount of the polymerizable composition may fluctuate when the polymerizable composition is impregnated into the porous support, resulting in an uneven thickness of the resulting ion exchange membrane. Furthermore, since the viscosity change is caused by solvent volatilization, a large change in viscosity can change the concentration of the curable monomer containing a cationic group in the polymerizable composition. As a result, the ion exchange capacity of the ion exchange membrane may be uneven. Conventionally, water is known as a solvent that highly dissolves curable monomers containing quaternary ammonium groups, but water is not preferred due to its large change in solution viscosity. However, unavoidable water may be present, and the proportion of water in the polymerizable composition is preferably less than 1% by mass. In order to reduce the viscosity change rate of the polymerizable composition, it is preferable that the polymerizable composition contains a high-boiling point solvent as a solvent, and it is preferable that the polymerizable composition contains at least one solvent selected from the group consisting of alkylene glycol, dimethyl sulfoxide, and dimethylformamide. Among these, from the viewpoint of the solubility of the curable monomer containing a cationic group, it is most preferable that the polymerizable composition contains alkylene glycol. When alkylene glycol is used, it is preferable to use two or more monomers represented by the above formula (I) that are structural isomers as the curable monomer containing a cationic group. Since alkylene glycol has a lower polarity than water, it has traditionally been difficult to increase the solubility of cationic monomers. However, as described above, solubility can be increased by using a quaternary ammonium salt consisting of a structural isomer.

[0066] The number of carbon atoms in the alkylene glycol is preferably 1 to 3, and more preferably 2. The boiling point of the alkylene glycol is preferably 110° C. or higher, and more preferably 120° C. or higher. There is no particular upper limit to this boiling point, but in one example, it is 300° C. or lower.

[0067] The flash point of the alkylene glycol is preferably 90° C. or higher, and more preferably 110° C. or higher. There is no particular lower limit to this flash point, but one example is 200° C. or higher.

[0068] Specific examples of the alkylene glycol include at least one selected from the group consisting of methylene glycol, ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butylene glycol, and tetramethylene glycol. As the alkylene glycol, ethylene glycol is preferably used.

[0069] The proportion of alkylene glycol in the polymerizable composition is, for example, 1% by mass or more and 50% by mass or less, preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 35% by mass or less. When this proportion is high, the compatibility of the polymerizable composition tends to be enhanced. When this proportion is excessively high, the performance of the ion exchange resin may be reduced. This proportion can also be measured, for example, by analyzing the alkylene glycol remaining in the cured product after curing and before washing using a known method. When a solvent other than alkylene glycol is used, the total mass of the solvent in the polymerizable composition is also within the above range.

[0070] In the polymerizable composition, the ratio M1 / M3 of the mass M1 of the curable monomer containing a cationic group to the mass M3 of the alkylene glycol is, for example, 0.01 or more and 95 or less, preferably 1 or more and 50 or less, and more preferably 1.5 or more and 10 or less. When this ratio is large, the performance of the ion exchange resin tends to be improved. When this ratio is small, the compatibility of the polymerizable composition tends to be improved.

[0071] In the polymerizable composition, the ratio M2 / M3 of the mass M2 of the crosslinkable monomer to the mass M3 of the alkylene glycol is, for example, 0.02 or more and 1 or less, preferably 0.05 or more and 0.5 or less, and more preferably 0.10 or more and 0.25 or less. When this ratio value is large, the durability of the cured body tends to be increased. When this ratio value is small, the compatibility of the polymerizable composition tends to be increased.

[0072] The polymerizable composition according to the embodiment may contain a sub-solvent, a polymerization initiator, other additives, and the like in addition to the above.

[0073] The co-solvent may be at least one selected from the group consisting of 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, N,N'-dimethylpropyleneurea (DMPU), 1-methyl-2-pyrrolidone, N-methyl-2-piperidone, 1,3-dimethyl-2-imidazolidinone, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, and tetramethylurea. The co-solvent may function as a stabilizer that suppresses separation of the polymerizable composition. The co-solvent is preferably an alcohol having 6 to 10 carbon atoms, and specifically, at least one long-chain alcohol compound selected from the group consisting of 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol is preferred. These may also function as surfactants. In other words, polymerizable compositions containing these co-solvents may have excellent wettability. Therefore, for example, the polymerizable composition can be quickly impregnated into a porous support, thereby increasing the production efficiency of ion exchange membranes.

[0074] The proportion of the auxiliary solvent in the polymerizable composition is, for example, 1% by mass to 15% by mass, preferably 1% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass. When this proportion is high, the compatibility of the polymerizable composition tends to be improved. When this proportion is excessively high, the performance of the ion exchange resin may be reduced.

[0075] In a preferred embodiment, when the total mass ratio of the curable monomer and the crosslinkable monomer is M4, the mass of the solvent is M3, and the mass of the co-solvent is M5, the ratio of the sum of M3 and M5 to M4 (M4 / (M3+M5)) is preferably 1.3 to 2.5, more preferably 1.5 to 2.0. The ratio of M5 to M3 (M5 / M3) is preferably 0.05 to 0.4, more preferably 0.1 to 0.3.

[0076] The polymerization initiator may be a photopolymerization initiator or a thermal polymerization initiator. Alternatively, both a photopolymerization initiator and a thermal polymerization initiator may be used. Two or more types of photopolymerization initiators and two or more types of thermal polymerization initiators may be used. Examples of the photopolymerization initiator include at least one selected from the group consisting of 1-phenyl-2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-benzyl-2-(N,N-dimethylamino)-1-(4-morpholinophenyl)butan-1-one, and 2-methyl-1-[4-(methylthio)phenyl]-2-2morpholinopropan-1-one. The thermal polymerization initiator may be at least one selected from the group consisting of benzoyl peroxide, p-chlorobenzoyl peroxide, decanoyl peroxide, lauroyl peroxide, acetyl peroxide, tert-butyl (2-ethylhexanoyl) peroxide hexanoate, and tert-butyl peroxyoctoate.

[0077] The proportion of the polymerization initiator in the polymerizable composition is, for example, 0.1% by mass or more and 10% by mass or less, and preferably 1% by mass or more and 5% by mass or less.

[0078] Other additives that can be used include known additives such as antioxidants, polymerization inhibitors, plasticizers, and surfactants.

[0079] As the polymerization inhibitor, for example, at least one selected from the group consisting of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-OH-TEMPO), 4-tert-butylcatechol (TBC), cupferron, and benzoquinone can be used.

[0080] The proportion of the polymerization inhibitor in the polymerizable composition is, for example, 0.0001% by mass or more and 2% by mass or less, preferably 0.001% by mass or more and 1.0% by mass or less, and more preferably 0.005% by mass or more and 0.1% by mass or less. This proportion can be measured, for example, by gas chromatography.

[0081] [Method for Producing Ion Exchange Membrane] A method for producing an ion exchange membrane according to an embodiment of the present disclosure may include impregnating a porous support with a polymerizable composition to obtain a first structure, and irradiating the first structure with ultraviolet light to obtain a second structure. Preferably, the method for producing an ion exchange membrane according to an embodiment of the present disclosure includes an impregnation step of impregnating a porous support with a polymerizable composition, a coating step of covering the porous support impregnated with the polymerizable composition with an upper film and a lower film, and an irradiation step of irradiating the coated porous support with ultraviolet light. The method for producing an ion exchange membrane may also include a step of impregnating a porous support with a polymerizable composition, a step of coating the impregnated porous film by conveying the upper film, the impregnated porous film, and the lower film between nip rolls, and a step of irradiating the impregnated porous film coated with the upper film and the lower film with ultraviolet light. Preferred aspects of the porous support and the polymerizable composition are as described above.

[0082] In the method for producing an ion exchange membrane according to an embodiment of the present disclosure, it is preferable to use a curable monomer containing a cationic group (ion exchange group) in the polymerizable composition. This eliminates the need for a step of introducing ion exchange groups into the polymerized resin, compared to using a polymerizable composition consisting solely of a compound lacking ion exchange groups. Furthermore, because a portion or all of the polymerizable composition is polymerized by UV irradiation, the ion exchange membrane can be produced in a shorter time than by thermal polymerization. This allows for so-called roll-to-roll polymerization, which offers advantages in terms of production cost. Because thermal polymerization requires a long polymerization time, obtaining a long ion exchange membrane roll requires impregnating a porous support with the polymerizable composition, winding it up, and then heating the wound roll in an oven. During this process, tension differences occur between the inside and outside of the roll, which can lead to uneven amounts of polymerizable composition supported on the porous support, resulting in large variations in the thickness of the resulting ion exchange membrane. By performing the polymerization by roll-to-roll irradiation with ultraviolet light, the polymerizable composition can be cured while the amount of the polymerizable composition supported remains constant, and therefore an ion exchange membrane with uniform properties such as thickness can be obtained.

[0083] Hereinafter, a manufacturing method according to an embodiment of the present disclosure will be described in detail with reference to Fig. 1. However, the following method is an example and is not limited to this. Fig. 1 is a schematic diagram illustrating an example of an ion exchange membrane manufacturing apparatus.

[0084] The method for impregnating the porous support with the polymerizable composition is not particularly limited. The polymerizable composition may be applied to the porous support by spraying or dripping. Alternatively, the porous support may be immersed in the polymerizable composition. The impregnation process is preferably performed by immersing the porous support 101 in a liquid tank 103 containing the polymerizable composition 102, as shown in FIG. 1, because this method has simple equipment specifications and is inexpensive. In particular, in order to suppress changes in the viscosity of the polymerizable composition due to humidity, it is preferable that the liquid tank 103 be a tank that is closed except for the inlet through which the porous support 101 is introduced and the outlet through which the impregnated porous support is removed. Furthermore, the porous support is not limited to a single layer, and may be a laminated film of two or three layers.

[0085] In the coating step, the porous support 104 impregnated with the polymerizable composition is preferably coated with a film 106 using nip rolls 105. By coating both surfaces of the porous support 104 with the film 106 while applying a constant pressure with the nip rolls, the surface smoothness of the ion exchange membrane is increased, resulting in an ion exchange membrane with a more uniform thickness. Furthermore, by covering both surfaces with a film, contact with air can be prevented, thereby suppressing viscosity changes in the polymerizable composition and preventing polymerization termination due to oxygen. The film covering the upper surface of the porous support 104 is also referred to as the upper film, and the film covering the lower surface is also referred to as the lower film. The film 106 is preferably a resin film, and examples of the resin film material include at least one selected from the group consisting of polyethylene terephthalate, polyester, perfluoroethylene propene copolymer, and tetrafluoroethylene-hexaethylene propylene copolymer.

[0086] In the irradiation step, the porous support 107 covered with the film 106 is irradiated with ultraviolet light by an ultraviolet irradiator 108, thereby obtaining an ion exchange membrane 109 in which the polymerizable composition is polymerized and cured. The irradiation wavelength of the ultraviolet light is, for example, preferably 300 nm or more and 400 nm or less, more preferably 330 nm or more and 380 nm or less. The ultraviolet light intensity is, for example, 1 mW / cm. ２More than 10000mW / cm ２ Preferably, it is equal to or less than 50 mW / cm ２ More than 8000mW / cm ２ The irradiation time is not particularly limited as long as it is a time that allows curing to occur to the extent that the thickness of the polymerizable composition does not change, and is, for example, from 0.5 seconds to 30 minutes, preferably from 1 second to 3 minutes, and more preferably from 40 seconds to 3 minutes. Examples of the irradiation source that can be used include ultraviolet light-emitting diodes (LEDs), halogen lamps, xenon lamps, tungsten lamps, and mercury lamps. From the viewpoints of ease of control of the irradiation wavelength and low heat generation, it is preferable to use LEDs.

[0087] It is preferable to continuously carry out the impregnation step, the coating step, and the irradiation step while transporting the porous support. This eliminates the need for a step of winding up the porous support after impregnation, resulting in superior production efficiency. The transport speed of the porous support in the impregnation step and the irradiation step is not particularly limited as long as sufficient irradiation time can be ensured. For example, the transport speed is 0.5 m / min to 5 m / min, preferably 0.5 m / min to 2.5 m / min, and more preferably 0.5 m / min to 1.5 m / min. A transport speed of 5 m / min or less shortens the production time and reduces viscosity changes in the polymerizable composition, resulting in a high-quality ion exchange membrane with minimal variation in membrane thickness and ion exchange capacity. On the other hand, a transport speed of 0.5 m / min or more ensures sufficient reaction time for the photopolymerization reaction, resulting in sufficient curing of the polymerizable composition. In the method for producing an ion exchange membrane according to one embodiment of the present disclosure, the impregnation step to the irradiation step can be carried out under atmospheric pressure because humidity-induced changes in the viscosity of the polymerizable composition can be suppressed. However, from the viewpoint of avoiding contact with moisture in the air as much as possible, a sealed container may be used during the impregnation, or the impregnation may be carried out in a nitrogen atmosphere.

[0088] After obtaining an ion exchange membrane in which the polymerizable composition is polymerized, the ion exchange membrane may be heat-treated. After partially polymerizing the polymerizable composition by ultraviolet irradiation, the polymerizable composition may be completely polymerized by thermal polymerization. During the heat treatment, the heating temperature is, for example, 50°C or higher and 150°C or lower, preferably 80°C or higher and 130°C or lower. The heating time is, for example, 1 minute or higher and 12 hours or lower, preferably 3 minutes or higher and 6 hours or lower. The heating method may be a hot plate, oven, infrared heater, heating furnace, or the like.

[0089] The ion exchange membrane obtained after light irradiation, heating, or both light irradiation and heating may be washed with water, an organic solvent (ethanol, acetone, chloroform, dichloromethane, etc.), or a mixed solvent thereof to wash away the solvent such as ethylene glycol, 1-hexanol, 1-heptanol, etc. contained in the polymerizable composition. When water is used, a counterion substitution treatment described below may also be carried out.

[0090] The ion exchange membrane obtained by the above method may be subjected to a drying treatment. During the drying treatment, the drying temperature may be, for example, from 20 to 90° C., and the drying time may be, for example, from 1 minute to 1 hour.

[0091] The ion exchange membrane obtained by the above method may be subjected to a counterion substitution treatment. This allows the counter ions of the ion exchange resin to be substituted with other types of counter ions. For example, when the counter ions are triflate or bistrifluoromethanesulfonimide, the anions can be substituted with halide ions by immersing the ion exchange membrane in a halogen-containing aqueous solution such as hydrogen chloride solution or hydrogen bromide solution for a certain period of time. When the counter ions are halide ions, the counter ions can be substituted with hydroxide ions by immersing the ion exchange membrane in an alkali metal hydroxide solution such as sodium hydroxide solution for a certain period of time. When the counter ions are hydroxide ions, the counter ions can be substituted with carbonate ions or bicarbonate ions by immersing the ion exchange membrane in a carbonate solution such as potassium carbonate solution or sodium bicarbonate solution for a certain period of time. Alternatively, when an ion exchange membrane has hydroxide ions as counter ions, the anions can be substituted with carbonate ions or bicarbonate ions by exposing the ion exchange membrane to the atmosphere for a certain period of time.

[0092] [Method for manufacturing a membrane electrode assembly] A membrane electrode assembly according to an embodiment of the present disclosure includes an ion exchange membrane according to an embodiment and an electrode. In the membrane electrode assembly (MEA), the ion exchange membrane and the electrode are integrated. The electrodes may include a first electrode that is a cathode and a second electrode that is an anode. The membrane electrode assembly may have an ion exchange membrane interposed between the first electrode and the second electrode.

[0093] The membrane electrode assembly can be used for hydrogen production devices, water electrolysis devices, fuel cells, and the like.

[0094] The electrode may contain a metal catalyst and, optionally, an ion conductive agent, a conductive agent, and a binder, and the proportions of the metal catalyst, the ion conductive agent, the conductive agent, and the binder in the electrode are, for example, 50% by mass or more and 99% by mass or less, 0.1% by mass or more and 30% by mass or less, 0.1% by mass or more and 30% by mass or less, and 0.1% by mass or more and 30% by mass or less, respectively.

[0095] The metal catalyst promotes the oxidation or reduction reaction. The metal catalyst is typically in the form of particles. Examples of the metal catalyst include platinum, gold, silver, palladium, iridium, rhodium, ruthenium, tin, iron, cobalt, nickel, manganese, molybdenum, tungsten, vanadium, chromium, tantalum, zirconium, aluminum, zinc, oxides or hydroxides thereof, or alloys thereof. The metal catalyst for the anode preferably contains nickel. The metal catalyst for the cathode preferably contains platinum, gold, silver, palladium, iridium, rhodium, ruthenium, tin, iron, cobalt, nickel, manganese, or alloys thereof.

[0096] The ion conductive agent increases the ionic conductivity of the electrode. Examples of the ion conductive agent include perfluorocarbon polymers, aromatic polyether ether ketones, polysulfones, polyfluorenes, and polystyrenes, each having a basic functional group. An ion exchange resin may be used as the ion conductive agent. The ion exchange resin may be an ion exchange resin according to an embodiment of the present disclosure, or another ion exchange resin may be used. As the other ion exchange resin, for example, an ion exchange resin having an imidazole group is used.

[0097] The conductive agent enhances the electronic conductivity of the electrode. The conductive agent may be used as a support for the metal catalyst. Examples of the conductive agent include carbon black, activated carbon, graphite, fullerene, carbon nanotubes, and mixtures thereof.

[0098] The binder increases the rigidity of the electrode, and examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing rubber, polyacrylic acid compounds, imide compounds, and mixtures thereof.

[0099] The membrane electrode assembly is produced, for example, by the following method.

[0100] First, an ion exchange membrane according to an embodiment of the present disclosure is prepared by the method described above. The ion exchange membrane may be in a wet state, but is preferably in a dry state.

[0101] Next, a metal catalyst is mixed with, optionally, an ion conductive agent, a conductive agent, a binder, and an organic solvent to prepare a composition for forming a first electrode. This composition for forming a first electrode is applied, for example, to a release paper to obtain a first coating film. This first coating film is dried. The dried first coating film is peeled off from the release paper and laminated on one main surface of the ion exchange membrane. An ion conductive agent may be applied to one main surface of the ion exchange membrane. The composition for forming a first electrode may be applied directly to one main surface of the ion exchange membrane to form the first coating film.

[0102] Next, a metal catalyst is mixed with, optionally, an ion conductive agent, a conductive agent, a binder, and an organic solvent to prepare a composition for forming a second electrode. This composition for forming a second electrode is applied, for example, to a release paper to obtain a second coating film. This second coating film is dried. The dried second coating film is peeled off from the release paper and laminated on the other main surface of the ion exchange membrane. An ion conductive agent may be applied to the other main surface of the ion exchange membrane. The first electrode composition may be applied directly to the other main surface of the ion exchange membrane to form a second coating film. Alternatively, the first coating film may be formed after the second coating film is formed.

[0103] The resulting laminate is then subjected to heating, pressure, or both to integrate the first and second coating films with the ion exchange membrane. In this manner, a membrane / electrode assembly is obtained in which the first electrode, the ion exchange membrane, and the second electrode are stacked in this order. Note that the first electrode or the second electrode may be omitted.

[0104] [Structure of Hydrogen Production Apparatus] The hydrogen production apparatus according to an embodiment of the present disclosure includes an ion exchange membrane according to an embodiment of the present disclosure. The hydrogen production apparatus may include a membrane electrode assembly according to an embodiment of the present disclosure.

[0105] The hydrogen production device includes an ion exchange membrane according to an embodiment of the present disclosure, and therefore has excellent uniformity in the ion exchange membrane, enabling efficient water decomposition.

[0106] Hereinafter, a hydrogen production device including a membrane electrode assembly according to an embodiment of the present disclosure will be described in detail with reference to FIG.

[0107] 2 is a cross-sectional view schematically illustrating an example of a hydrogen production device according to an embodiment of the present disclosure. The hydrogen production device 1 shown in FIG. 1 includes a membrane electrode assembly 4, and a first electrode chamber 2 and a second electrode chamber 3 separated by the membrane electrode assembly 4.

[0108] The membrane electrode assembly 4 includes an anion exchange membrane 5, a first electrode 6 supported on one main surface of the anion exchange membrane 5, and a second electrode 7 supported on the other main surface of the anion exchange membrane. The first electrode 6 and the second electrode 7 are connected to a power source via conductors (not shown). Gas diffusion layers may be provided on the surfaces of the first electrode and the second electrode. Examples of gas diffusion layers that can be used include carbon paper, carbon cloth, nickel foam, titanium foam, and porous graphite.

[0109] The first electrode chamber 2 is provided with a first electrode 6 and is connected to a hydrogen discharge pipe 8. The hydrogen discharge pipe 8 is connected to a hydrogen tank (not shown). The first electrode chamber 2 may be provided with a first partition wall (not shown). The first partition wall is provided with a plurality of grooves connecting to the first electrode chamber 2 and a hydrogen discharge channel connected to these grooves and the hydrogen discharge pipe 8. The first partition wall is preferably made of an electron-conductive material. For example, a metal plate is used as the first partition wall. The first partition wall may be in contact with the gas diffusion layer described above.

[0110] The second electrode chamber 3 is equipped with a second electrode 7, and is connected to an oxygen exhaust pipe 9 and a water supply pipe 10. The oxygen exhaust pipe 9 is connected to an oxygen tank (not shown). The water supply pipe 10 is connected to a water supply device (not shown). The second electrode chamber 3 may be provided with a second partition wall (not shown). The second partition wall is provided with a plurality of grooves connecting to the second electrode chamber 3, and oxygen exhaust channels connected to these grooves, the oxygen exhaust pipe 9, and the water supply pipe 10. The second partition wall is preferably made of an electron-conductive material. For example, a metal plate is used for the second partition wall. The second partition wall may be in contact with the above-mentioned gas diffusion layer.

[0111] Next, a hydrogen production method using the hydrogen production device will be described in detail with reference to FIG.

[0112] First, the liquid to be treated is supplied to the second electrode chamber 3 via the water supply pipe 10. The liquid to be treated may be water or an alkaline aqueous solution. The alkaline aqueous solution is, for example, an aqueous solution of an alkali metal hydroxide, carbonate, or bicarbonate. The pH of the alkaline aqueous solution is, for example, 10 or more and 14 or less. The concentration of the alkaline aqueous solution is, for example, 0.1 mass % or more and 30 mass % or less.

[0113] The liquid to be treated that has come into contact with the membrane electrode assembly 4 is held by the anion exchange membrane 5. The liquid to be treated is supplied to the first electrode chamber 2 via the anion exchange membrane 5.

[0114] Next, power is supplied from a power source (not shown) to the first electrode 6 and the second electrode 7. As a result, water (H ２ O) is decomposed to hydrogen (H ２ ) and hydroxide ions (OH － The hydroxide ions thus produced are supplied to the second electrode 7 via the anion exchange membrane 5. At the second electrode 7, the supplied hydroxide ions are converted into oxygen (O ２ ) and water (H ２ O).

[0115] 2H ２ O + 2e － → H ２ +2OH － (A) 2OH － → 1 / 2O ２ +H ２ O + 2e － (B) The hydrogen gas produced in the first electrode chamber 2 is supplied to the hydrogen tank via the hydrogen discharge pipe 8. The oxygen gas produced in the second electrode chamber 3 is supplied to the oxygen tank via the oxygen discharge pipe 9.

[0116] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0117] The properties of the porous membranes used in the examples and comparative examples of the present disclosure, and the properties of the ion exchange membranes using those porous membranes, were evaluated by the following methods. Unless otherwise specified, measurements were performed at room temperature (25°C). Furthermore, for the evaluation of the ion exchange membrane, unless otherwise specified, a chloride ion-type dried membrane was used, which was obtained by immersing the ion exchange membrane in a 0.5 mol / L NaCl aqueous solution for 10 hours or more, washing with ion-exchange water, and air-drying at room temperature (25°C) for 12 hours or more.

[0118] In the examples and comparative examples, the thickness of the ion exchange membrane (overall average membrane thickness T), membrane thickness deviation rate A, ion exchange capacity of the ion exchange membrane (overall average ion exchange capacity W), ion exchange capacity deviation rate B, and ion exchange group residual rate C were measured by the methods described above in this specification.

[0119] Example 1 Preparation of Polymerizable Composition 100 g of a curable monomer salt containing a cationic group (vinylbenzyltrimethylammonium chloride), 9.2 g of divinylbenzene, a solvent (ethylene glycol) in an amount sufficient to give a vinylbenzyltrimethylammonium chloride concentration of 10 mol / L, 5.5 g of 1-heptanol, 1.55 g of a photopolymerization initiator, 0.82 g of a thermal polymerization initiator, and 0.049 g of a polymerization inhibitor were mixed in a nitrogen atmosphere at room temperature and atmospheric pressure to obtain a polymerizable composition. 1-phenyl-2-hydroxy-2-methylpropan-1-one was used as the photopolymerization initiator. tert-Butyl peroxyoctoate was used as the thermal polymerization initiator. 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl was used as the polymerization inhibitor. The properties of the obtained polymerizable composition are shown in Table 1.

[0120] <Production of ion exchange membrane> First, a porous support was prepared. As shown in Table 1, a polyethylene porous film having a thickness of 25 μm and a porosity of 42% or a thickness of 20 μm and a porosity of 70% was used as the porous support.

[0121] This porous support was immersed in the polymerizable composition and then pulled out from the polymerizable composition. In this way, a first structure in which the polymerizable composition was supported on the porous support was obtained. Both main surfaces of this first structure were covered with PET films. One main surface of the first structure was irradiated with ultraviolet light using an LED to obtain a second structure. The irradiation wavelength was 365 nm, and the irradiation intensity was 400 mW / cm. ２ The irradiation time was as shown in Table 2. In the impregnation step, coating step, and irradiation step, these steps were carried out continuously while the porous support, the first structure, and the second structure were conveyed at a conveying speed of 1 m / min.

[0122] Next, the second structure was placed in a thermal dryer and subjected to a heat treatment. The heating temperature was set to 120°C so that the surface temperature of the membrane would be approximately 110°C, and the heating time was set to 15 minutes. After heating, the PET film was peeled off from the second structure to obtain an ion exchange membrane. The obtained ion exchange membrane was washed with a 58% by mass aqueous ethanol solution and then dried at 40°C for 10 minutes. In this way, an ion exchange membrane having a length of 100 m was obtained.

[0123] The properties of the obtained ion exchange membrane are shown in Table 2.

[0124] (Examples 2 to 7, Reference Example 8, Comparative Examples 1 to 3) Ion exchange membranes were obtained in the same manner as in Example 1, except that the curable monomer and solvent containing a cationic group used in obtaining the polymerizable composition, the concentration of the curable monomer having a cationic group in the polymerizable composition, the photopolymerization time, the conveying speed, the winding length, and the porosity of the porous support were changed as shown in Table 1.

[0125] Comparative Example 4: 100 g of chloromethylstyrene, 5.5 g of divinylbenzene, and 5 g of tert-butyl peroxyoctoate were mixed at room temperature and normal pressure to obtain a polymerizable composition. A porous support was immersed in the polymerizable composition and then removed from the polymerizable composition. In this manner, a first structure in which the polymerizable composition was supported on a porous support was obtained. Both main surfaces of this first structure were covered with a PET film. The impregnation and coating processes were carried out at a conveying speed of 5 m / min. Subsequently, thermal polymerization was carried out at 80°C for 5 hours under a nitrogen pressure of 0.3 MPa to obtain a second structure. The PET film was peeled off from this second structure, and the structure was immersed in a 30% aqueous trimethylamine solution for 16 hours to obtain an ion exchange membrane. The obtained ion exchange membrane was dried at 40°C for 10 minutes to obtain a 100 m long ion exchange membrane.

[0126] (Evaluation of Reference Example 8) In Reference Example 8, in the evaluation of the overall average value W of the ion exchange capacity, the ion exchange capacity deviation rate B, the membrane thickness deviation rate A, and the ion exchange group residual rate C, the evaluation was performed on a single test piece taken from one end in the long side direction instead of four test pieces. That is, in each test, the arithmetic mean values ​​at 16 measurement points on the single test piece were treated as the overall average values ​​T and W, and S and V were calculated from the measured values ​​at each measurement point instead of the arithmetic mean values ​​for each test piece, and each evaluation was performed. A comparison of the evaluation results of Example 1 and Reference Example 8 shows that the ion exchange membrane according to this example is a more uniform membrane when viewed in membrane units shorter than the entire length of the roll after cutting than when viewed as a whole roll.

[0127]

[0128]

[0129] 101: Porous support, 102: Polymerizable composition, 103: Liquid tank, 104: Porous support impregnated with polymerizable composition, 105: Nip roll, 106: Film, 107: Porous support coated with film, 108: Ultraviolet irradiator, 109: Ion exchange membrane 1: Hydrogen production device, 2: First electrode chamber, 3: Second electrode chamber, 4: Membrane electrode assembly, 5: Anion exchange membrane 5, 6: First electrode, 7: Second electrode, 8: Hydrogen discharge pipe, 9: Oxygen discharge pipe, 10: Water supply pipe 301: Long side, 302: Short side, 303: Intersection, 400: Test piece, 401: Intersection

Claims

1. An ion exchange membrane, wherein the ion exchange membrane has short sides and long sides, and the length of the long sides is 80 m or more; a plurality of test pieces are collected from a predetermined region of the ion exchange membrane, and the membrane thickness is measured at a plurality of measurement points on each test piece, and the arithmetic mean value of the membrane thickness for each test piece is calculated to obtain an overall average membrane thickness T, and the value of the arithmetic mean membrane thicknesses for each test piece that differs most from T is defined as a maximum dissociation value S. When this is done, the membrane thickness deviation rate A (%) expressed by the following formula (1) is less than 5.0%; when the ion exchange capacity of each test piece is measured, and the arithmetic mean value of the ion exchange capacity measured for each test piece is defined as an overall average ion exchange capacity W, and the value of the ion exchange capacity values ​​for each test piece that differs most from W is defined as a maximum dissociation value V, the ion exchange capacity deviation rate B (%) expressed by the following formula (2) is less than 10.0%; and the ion exchange group residual rate C obtained by measuring the ion exchange capacity of the ion exchange membrane before and after an alkaline durability test is 70% or more; Film thickness deviation rate A (%)=|(T−S) / T×100| (1) Ion exchange capacity deviation rate B (%)=|(W−V) / W×100| (2).

2. The ion exchange membrane according to claim 1, wherein W is 1.5 to 3.5 meq. / g.

3. The ion exchange membrane according to claim 1 or 2, comprising a porous support having pores and an ion exchange resin filled in the pores.

4. The ion exchange membrane according to claim 3, wherein the ion exchange resin is a hydrocarbon polymer.

5. The ion exchange membrane according to claim 3 or 4, wherein the ion exchange resin comprises an anion exchange resin.

6. The ion exchange membrane according to any one of claims 3 to 5, wherein the porous support comprises a polyolefin resin.

7. The ion exchange membrane according to any one of claims 3 to 6, wherein the ion exchange resin comprises a cured product of a polymerizable composition that exhibits a viscosity change rate of less than 10% when measured by liquid viscosity according to Japanese Industrial Standards (JIS) Z8803:2011.

8. The ion exchange membrane according to any one of claims 3 to 7, wherein the ion exchange resin comprises a cured product of a polymerizable composition comprising a curable monomer containing a cationic group, a crosslinkable monomer, and an alkylene glycol.

9. A method for producing an ion exchange membrane according to any one of claims 3 to 8, comprising: an impregnation step of impregnating the porous support with a polymerizable composition; a coating step of covering the porous support impregnated with the polymerizable composition with an upper film and a lower film; and an irradiation step of irradiating the coated porous support with ultraviolet light.

10. A method for producing an ion exchange membrane as described in claim 9, wherein the impregnation step, the coating step, and the irradiation step are carried out continuously while the porous support is being transported, and the transport speed in the irradiation step is 0.5 m / min or more and 5.0 m / min or less.

11. A membrane electrode assembly comprising the ion exchange membrane according to any one of claims 1 to 8 and an electrode.

12. A hydrogen production device comprising the ion exchange membrane according to any one of claims 1 to 8 or the membrane electrode assembly according to claim 11.

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