Method for producing ion exchange membrane with catalyst layer

Abstract

A method for producing an ion exchange membrane with a catalyst layer, said method comprising: a step (A) in which a catalyst dispersion layer is disposed on at least one surface side of an ion exchange membrane, said catalyst dispersion layer being obtained by molding a catalyst dispersion containing a catalyst and an ionomer resin and having a viscosity of 1-500 Pas at 25 DEG C into a prescribed shape; and obtaining a laminate having an ion exchange membrane and a polygonal catalyst dispersion layer; and a step (B) in which the laminate heated to a temperature of 100 DEG C to 200 DEG C is pressed.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an ion exchange membrane with a catalyst layer. Background Technology

[0002] In recent years, the application of hydrogen has attracted attention from the perspective of renewable energy applications. Furthermore, solid polymer water electrolysis is one method of hydrogen production. In solid polymer water electrolysis, in recent years, catalyst-coated membranes (CCM) have been used as components of water electrolysis devices. These catalyst-coated membranes have electrode catalyst layers containing a catalyst for water electrolysis and a solid electrolyte (e.g., an ionomer resin) formed on both sides of a solid polymer membrane (PEM) that serves as an ion exchange membrane.

[0003] As a catalyst layer for water electrolysis in a CCM, the following catalyst layers are generally known: for example, using Pt / C (carbon-supported platinum) as a H (hydrogen) generation catalyst and IrO2 as an O2 (oxygen) generation catalyst, these catalysts are dispersed in an ion-polymer resin, and then dispersed in water or a lower alcohol to prepare a catalyst ink. The obtained catalyst ink is coated on a release material, dried, and then the layer formed by the catalyst ink is thermally transferred onto the ion exchange membrane to form the catalyst.

[0004] Furthermore, regarding the manufacture of catalyst ink, Japanese Patent Application Publication No. 2021-150174 discloses the following process: dispersing catalyst-loaded particles in a solvent by jet milling to generate a catalyst dispersion; and shearing a mixture containing ionomers in the catalyst dispersion to generate catalyst ink for fuel cells. Furthermore, Japanese Patent Publication No. 6310741 discloses that, with the goal of obtaining a uniform coating shape, a coating method in which a coating liquid is intermittently coated in a prescribed manner uses catalyst ink as the coating liquid. Summary of the Invention

[0005] The technical problem to be solved by the invention

[0006] In ion exchange membranes with catalyst layers suitable for solid polymer water electrolysis devices, the catalyst layer with excellent shape stability is arranged at a specified position on the ion exchange membrane, which is considered an important factor from the point of view of efficient hydrogen production.

[0007] However, in the method of forming a catalyst layer on an ion exchange membrane by thermal transfer after wet coating and drying using catalyst ink, it is not easy to obtain a catalyst layer with excellent shape stability.

[0008] Furthermore, regarding the shape of the catalyst layer, from the perspective of piping layout within a water electrolysis unit, there is a need to adopt a polygonal shape. However, when a catalyst layer is formed in a polygonal shape, edge defects can sometimes occur. Edge defects in the catalyst layer can significantly impair hydrogen production efficiency.

[0009] The present invention was made in view of the above circumstances.

[0010] One embodiment of the present invention aims to solve the problem of providing a method for manufacturing an ion exchange membrane with a catalyst layer capable of forming a catalyst layer with excellent dimensional stability.

[0011] means for solving technical problems

[0012] The present invention includes the following methods.

[0013] <1> A method for manufacturing an ion exchange membrane with a catalyst layer, comprising: Step A involves depositing a catalyst dispersion layer, comprising a catalyst and an ionomer resin, having a viscosity of 1 Pa·s to 500 Pa·s at 25°C, into a predetermined shape on at least one side of an ion exchange membrane, and obtaining a laminate having the aforementioned ion exchange membrane and the aforementioned catalyst dispersion layer; and Step B involves pressing the aforementioned laminate, which has been heated to a temperature of 100°C to 200°C.

[0014] <2> The method for manufacturing an ion exchange membrane with a catalyst layer as described in <1>, wherein, The catalyst dispersions described above contain alcohols.

[0015] <3> The method for manufacturing an ion exchange membrane with a catalyst layer as described in <2>, wherein, The alcohol mentioned above is selected from at least one of ethanol and 2-propanol.

[0016] <4> A method for manufacturing an ion exchange membrane with a catalyst layer according to any one of <1> to <3>, wherein, The catalyst described above comprises aggregates with an average secondary particle size of less than 10 μm.

[0017] <5> A method for manufacturing an ion exchange membrane with a catalyst layer according to any one of <1> to <4>, wherein, In step A above, the catalyst dispersion layer is formed on both sides of the ion exchange membrane, and the laminate is obtained.

[0018] <6> A method for manufacturing an ion exchange membrane with a catalyst layer according to any one of <1> to <5>, wherein, In step A, a catalyst dispersion layer formed into a predetermined shape is disposed on one side of the substrate X. After obtaining a transfer material X having the substrate X and the catalyst dispersion layer, at least one side of the ion exchange membrane is overlapped with the catalyst dispersion layer of the transfer material X to obtain the laminate.

[0019] <7> The method for manufacturing an ion exchange membrane with a catalyst layer as described in <6>, wherein, Process A includes the following steps: after preheating the catalyst dispersion layer of the transfer material X to a temperature of 70°C to 180°C, at least one side of the ion exchange membrane is overlapped with the catalyst dispersion layer to obtain the laminate.

[0020] Invention Effects

[0021] According to one embodiment of the present invention, a method for manufacturing an ion exchange membrane with a catalyst layer capable of forming a catalyst layer with excellent dimensional stability is provided. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating an example of implementing a series of steps including step A and step B, wherein step A includes the step of forming a catalyst dispersion layer on at least one side of an ion exchange membrane using a transfer substrate X.

[0023] Figure 2 This is a schematic diagram of an image inspection apparatus used to evaluate the dimensional stability of a catalyst layer.

[0024] Figure 3 This is a photograph of the entire decagonal catalyst layer formed in Example 1, taken from the top surface.

[0025] Figure 4 It is a photograph used to illustrate irregular edges in the evaluation of dimensional stability. Detailed Implementation

[0026] The following describes a method for manufacturing an ion exchange membrane with a catalyst layer according to the present invention. However, the method for manufacturing an ion exchange membrane with a catalyst layer according to the present invention is not limited to any of the following embodiments, and can be appropriately modified to be implemented within the scope of the objectives of the present invention.

[0027] In this invention, the numerical range represented by "~" indicates the range encompassed by the values ​​recorded before and after "~", which are considered as lower and upper limits. In the numerical ranges described in stages in this invention, the upper limit value recorded within a certain numerical range can be replaced with the upper limit value of another numerical range described in stages, and the lower limit value recorded within a certain numerical range can be replaced with the lower limit value of another numerical range described in stages. In the numerical ranges described in stages in this invention, the upper or lower limit value recorded within a certain numerical range can be replaced with the values ​​represented in the embodiments.

[0028] In this invention, a combination of two or more preferred methods is a more preferred method.

[0029] In this specification, unless otherwise specified, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition.

[0030] In this invention, the term "process" includes not only independent processes, but also processes that achieve the desired purpose of the process, even when they cannot be clearly distinguished from other processes.

[0031] In this invention, "mass%" and "weight%" have the same meaning, and "parts of mass" and "parts of weight" have the same meaning.

[0032] In this invention, "total solids content" refers to the total mass of the components after removing the solvent from the overall composition. "Solids content" refers to components that can be solid or liquid at 25°C.

[0033] The method for manufacturing an ion exchange membrane with a catalyst layer according to the present invention comprises: step A (hereinafter also simply "step A"), which involves depositing a catalyst dispersion (hereinafter also simply "specific catalyst dispersion") comprising a catalyst and an ionomer resin and having a viscosity of 1 Pa·s to 500 Pa·s at 25°C into a predetermined shape on at least one side of the ion exchange membrane, and obtaining a laminate having an ion exchange membrane and a catalyst dispersion layer; and step B (hereinafter also simply "step B"), which involves pressing the laminate heated to a temperature of 100°C to 200°C.

[0034] In addition to steps A and B, the method for manufacturing the ion exchange membrane with a catalyst layer involved in this invention may include other steps as needed.

[0035] According to the method for manufacturing an ion exchange membrane with a catalyst layer of the present invention, an ion exchange membrane with a catalyst layer exhibiting excellent dimensional stability can be obtained. The reason for this is not yet clear, but is speculated as follows.

[0036] In the method for manufacturing an ion exchange membrane with a catalyst layer according to the present invention, in step A, a specific catalyst dispersion with a viscosity of 1 Pa·s to 500 Pa·s is used, thus enabling the acquisition of a laminate of catalyst dispersion layers with a predetermined shape and good precision at predetermined positions on the ion exchange membrane. Specifically, the high viscosity of the specific catalyst dispersion (1 Pa·s to 500 Pa·s) results in excellent edge shape stability and a desired thickness in both top-view and cross-sectional views of the obtained catalyst dispersion layer. Furthermore, the viscosity of the specific catalyst dispersion (1 Pa·s to 500 Pa·s) significantly reduces the load during drying of the catalyst dispersion layer, thereby effectively suppressing deformation during the formation of the catalyst dispersion layer on the ion exchange membrane and / or substrate X.

[0037] Furthermore, in process B, the laminate is heated to a temperature of 100°C to 200°C during pressing. By pressing the laminate in a heated state, the melting of the ionomer resin can be controlled, effectively suppressing the thermal deformation of the obtained catalyst layer.

[0038] Therefore, it is believed that an ion exchange membrane with a catalyst layer and excellent dimensional stability can be obtained.

[0039] On the other hand, neither Japanese Patent Application Publication No. 2021-150174 nor Japanese Patent No. 6310741 discloses any process A and process B equivalent to those of the catalyst-layered ion exchange membrane involved in this invention.

[0040] Furthermore, while catalysts used for water electrolysis contain precious rare metals such as platinum, the method for manufacturing an ion exchange membrane with a catalyst layer according to the present invention can use only the amount of a specific catalyst dispersion required to form the catalyst layer, thus also having the advantage of not causing the loss of rare metals.

[0041] Furthermore, the method for manufacturing the catalyst-layered ion exchange membrane according to the present invention has the advantage of eliminating the need for a drying process. Drying is a highly energy-intensive process, known to account for a large portion of the power and heat energy costs in manufacturing. In other words, drying is a process that generates significant carbon dioxide emissions. Originally, techniques for efficiently extracting hydrogen were considered for reducing carbon dioxide emissions and could also contribute to achieving carbon neutrality. Therefore, it is desirable that a method for efficiently producing hydrogen itself could suppress carbon dioxide emissions. The method for manufacturing the catalyst-layered ion exchange membrane according to the present invention also addresses this requirement.

[0042] The following describes the steps involved in the manufacturing method of the ion exchange membrane with a catalyst layer according to the present invention.

[0043] [Process A]

[0044] Step A is a process of forming a catalyst dispersion layer (specific catalyst dispersion) of a catalyst dispersion containing a catalyst and an ionomer resin and having a viscosity of 1 Pa·s to 500 Pa·s at 25°C into a specified shape on at least one side of an ion exchange membrane, and obtaining a laminate having an ion exchange membrane and a catalyst dispersion layer.

[0045] In step A, a catalyst dispersion layer, in which a specific catalyst dispersion is shaped into a predetermined shape, is disposed on at least one side of the ion exchange membrane. The predetermined shape can be set to the shape of the catalyst layer desired when assembling the ion exchange membrane with the catalyst layer into a water electrolysis device.

[0046] The shape described above can be a circle or a polygon when viewed from above, preferably a convex polygon. For example, a convex polygon can be a quadrilateral, pentagon, hexagon, heptagon, octagon, nonagon, decagon, uneconoid, or dodecagon. A portion or all of the angles of a convex polygon can have curves (in other words, "arcs").

[0047] The thickness of the catalyst dispersion layer in the above-mentioned laminate can be set to, for example, 0.5 μm to 50 μm.

[0048] The area of ​​the catalyst dispersion layer in the aforementioned laminate is not limited in size and can be determined based on the shape of the catalyst dispersion layer and its placement on the ion exchange membrane. For example, the area of ​​the catalyst dispersion layer in the aforementioned laminate can be set to 2 cm² in a top view. 2 ~100000cm 2 .

[0049] As for the ion exchange membrane, there are no particular limitations as long as it has proton conductivity and can be used in a solid polymer water electrolysis device. Examples of resins constituting the ion exchange membrane include perfluorosulfonic acid polymers and hydrocarbon polymers, with perfluorosulfonic acid polymers being preferred.

[0050] Ion exchange membranes can be single sheets or strips, but from a productivity point of view, strips are preferred.

[0051] In step A, as a way to obtain a laminate having an ion exchange membrane and a catalyst dispersion layer, the catalyst dispersion layer can be formed by directly molding a specific catalyst dispersion into a predetermined shape on at least one side of the ion exchange membrane.

[0052] In step A, from a productivity point of view, the preferred method for obtaining a laminate having an ion exchange membrane and a catalyst dispersion layer is as follows: a catalyst dispersion layer having a catalyst dispersion shaped into a predetermined shape is disposed on one side of a substrate X; after obtaining a transfer material X having a substrate X and a catalyst dispersion layer, at least one side of the ion exchange membrane is overlapped with the catalyst dispersion layer of the transfer material X to obtain a laminate.

[0053] Methods for forming a catalyst dispersion layer on an ion exchange membrane or substrate X include, for example, filling a specific catalyst dispersion into a polygonal template, printing methods such as screen printing, inkjet printing, spraying, dispensers, and die coating machines. In one method, screen printing is preferred. By using screen printing, a better shape can be formed without damaging the edge portions of the formed specific dispersion layer.

[0054] When forming a catalyst dispersion layer, it is preferable to dry the specific catalyst dispersion after it has been given a predetermined shape on an ion exchange membrane or substrate X.

[0055] As a drying method, conventional drying methods can be used, such as drying with hot air using an oven or drying with electromagnetic waves using microwaves.

[0056] The drying temperature can be set according to the components such as solvents contained in the specific catalyst dispersion. For example, the drying temperature can be set from 30°C to 300°C.

[0057] Drying times, for example, can be in the range of 1 second to 1 hour.

[0058] The following method will be described: A catalyst dispersion layer, in which a specific catalyst dispersion is shaped into a predetermined form, is disposed on one side of a substrate X. After obtaining a transfer material X having a substrate X and a catalyst dispersion layer, at least one side of an ion exchange membrane is overlapped with the catalyst dispersion layer of the transfer material X to obtain a laminate (hereinafter referred to as "Method X"). Method X is a method of obtaining the above-mentioned laminate using a so-called transfer method.

[0059] The substrate X can be a single sheet or a strip, but from a productivity point of view, a strip is preferred.

[0060] As substrate X, for example, fluoropolymers such as polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), and polypropylene (PP) film substrates can be used. Substrate X functions as a release material.

[0061] A laminate in which at least one side of an ion exchange membrane overlaps with a catalyst dispersion layer of a transfer material X can be obtained, for example, by placing and contacting at least one side of an ion exchange membrane with a catalyst dispersion layer of a transfer material X and then applying pressure.

[0062] As a means of applying pressure, roller presses, flatbed presses, etc. can be used.

[0063] The pressure during pressurization can be set to, for example, 0.1 MPa to 100 MPa.

[0064] In step A, it is preferable to form a catalyst dispersion layer on both sides of the ion exchange membrane to obtain a laminate. The catalyst dispersion layer can be formed on one side of the ion exchange membrane and then on the other side, or the catalyst dispersion layer can be formed on both sides of the ion exchange membrane simultaneously.

[0065] When configuring catalyst dispersion layers by forming catalyst dispersions on both sides of an ion exchange membrane, it is preferable to have two catalyst dispersion layers facing each other across the ion exchange membrane with the same shape, and to arrange these two catalyst dispersion layers at positions where they overlap each other without offset across the ion exchange membrane, thus forming a laminate. By performing step A, catalyst dispersion layers can be formed with good precision at desired positions on both sides of the ion exchange membrane.

[0066] (Specific catalyst dispersion)

[0067] The specific catalyst dispersion used in process A includes a catalyst and an ionomer resin, with a viscosity of 1 Pa·s to 500 Pa·s at 25°C.

[0068] <Viscosity>

[0069] The viscosity of the specific catalyst dispersion at 25°C is 1 Pa·s to 500 Pa·s, preferably 0.5 Pa·s to 700 Pa·s, and more preferably 0.3 Pa·s to 800 Pa·s. Since the viscosity of the specific catalyst dispersion is within the above range, it is easy to shape the specific catalyst dispersion into a convex polygonal shape, thereby further improving the productivity of the ion exchange membrane with the catalyst layer.

[0070] The viscosity of a specific catalyst dispersion can be adjusted by the type and amount of components contained in the specific catalyst dispersion, such as the catalyst and ionomer resin.

[0071] The viscosity of a specific catalyst dispersion can be measured using a Type B viscometer.

[0072] <Catalyst>

[0073] A specific catalyst dispersion contains a catalyst. In solid polymeric water electrolysis, there are no particular limitations on the catalyst used in the catalyst layer.

[0074] As a catalyst, preferred materials include elemental noble metals such as platinum, iridium, ruthenium, rhodium, and palladium; alloys of platinum with manganese, iron, cobalt, nickel, copper, and zinc; and ternary alloys of platinum, ruthenium, manganese, iron, cobalt, nickel, copper, and zinc. The catalyst can be an oxide containing the above-mentioned metals (e.g., iridium oxide).

[0075] Catalysts can be supported on conductive particles. Preferably, conductive particles include carbon particles such as oil furnace black, gas furnace black, acetylene black, thermal carbon black, graphite, carbon nanotubes, and graphene, as well as metal oxide particles such as tin oxide. Examples of catalysts supported on conductive particles include, for instance, platinum supported on carbon particles (hereinafter also referred to as carbon-supported platinum).

[0076] The catalyst preferably comprises aggregates with an average secondary particle size of 20 μm or less, more preferably aggregates with an average secondary particle size of 10 μm or less. By making the secondary particle size of the catalyst 20 μm or less (preferably 10 μm or less), it is easy to control the viscosity of a specific catalyst dispersion within the range of 1 Pa·s to 500 Pa·s, and the shape of the catalyst tends to be more uniform, which helps to improve the performance of the ion exchange membrane with the catalyst layer. The lower limit of the average secondary particle size is preferably, for example, 0.01 μm.

[0077] The aforementioned agglomerates can be obtained, for example, by pulverizing the solid material composed of the catalyst. Examples of pulverizing methods include ball mills, jet mills, and homogenizers.

[0078] The average secondary particle size should be determined using a particle size distribution measuring device. A laser diffraction / scattering particle size distribution measuring device (product name: LA-960, manufactured by HORIBA, Ltd.) can be used as the particle size distribution analysis device. Specifically, a sample solution is prepared by diluting the catalyst dispersion to be measured in a test solvent, and the particle size distribution in the sample solution is measured using a particle size distribution measuring device, thereby determining the secondary particle size of the aggregates. The measurement is performed three times, and the obtained values ​​are arithmetically averaged and rounded to the nearest decimal place to obtain the average secondary particle size.

[0079] The content of catalyst in a specific catalyst dispersion, relative to the total amount of the specific catalyst dispersion, is preferably 1% to 90% by mass, more preferably 5% to 70% by mass, and even more preferably 7% to 50% by mass.

[0080] <Ionomer Resins>

[0081] The specific catalyst dispersion contains an ionomer resin. The ionomer resin preferably has proton conductivity.

[0082] Examples of ionomer resins include perfluorosulfonic acid polymers and hydrocarbon polymers.

[0083] A specific catalyst dispersion may contain only one type of ionomer resin or two or more types.

[0084] Commercially available ionomer resins can be used. Examples of commercially available ionomer resins include Nafion (registered trademark, manufactured by Chemours Company), Aquivion (registered trademark, manufactured by Solvay Company), Flemion (registered trademark, manufactured by ASAHI GLASS CO.,LTD.), Ashiplex (registered trademark, manufactured by Asahi Kasei Corporation), and Fumion F (registered trademark, manufactured by FuMA-Tech Company).

[0085] When an ionomer resin is included in a specific catalyst dispersion, from the viewpoint of uniformly dispersing the ionomer resin within the specific catalyst dispersion, it is preferable to use a pulverizing method to pulverize and refine the solid material of the ionomer resin. Examples of pulverizing methods include mills, ball mills, jet mills, and homogenizers. Uniform dispersion of the ionomer resin in the specific catalyst dispersion helps to improve the performance of the ion exchange membrane with the catalyst layer.

[0086] Furthermore, when obtaining and using a solution containing an ionomer resin, it is preferable to pulverize and micronize the cured product obtained by drying and curing the solution containing the ionomer resin.

[0087] The content of ionomer resin in a specific catalyst dispersion is preferably 0.5% to 50% by mass relative to the total amount of the specific catalyst dispersion, more preferably 1% to 30% by mass, and even more preferably 2% to 20% by mass.

[0088] <Solvent>

[0089] A solvent may be included as long as the viscosity of a particular catalyst dispersion at 25°C is between 1 Pa·s and 500 Pa·s. The solvent functions as a dispersion medium for the catalyst in the particular catalyst dispersion. Examples of solvents that are hydroxyl-containing solvents include, for example, solvents containing hydroxyl groups, and preferably, at least one selected from water and alcohols.

[0090] When a particular catalyst dispersion contains a solvent, the content of the solvent in the particular catalyst dispersion, relative to the total amount of the particular catalyst dispersion, is preferably 85% by mass or less, more preferably more than 0% by mass and 65% by mass or less, and even more preferably 0.1% by mass to 25% by mass.

[0091] <<alcohol>>

[0092] The specific catalyst dispersion preferably contains an alcohol. That is, in one embodiment, the specific catalyst dispersion is preferably a catalyst dispersion containing a catalyst, an ionomer resin and an alcohol as a solvent, and having a viscosity of 1 Pa·s to 500 Pa·s at 25°C.

[0093] By including alcohol in a specific catalyst dispersion, the dispersibility of the catalyst in the catalyst dispersion and the adhesion between the catalysts and / or between the catalyst and the ion exchange membrane or substrate X are improved, thereby obtaining a catalyst layer with excellent dimensional stability.

[0094] When a specific catalyst dispersion contains alcohol, the specific catalyst dispersion can contain alcohol in a viscosity range of 1 Pa·s to 500 Pa·s at 25°C.

[0095] As an alcohol, examples include monohydric alcohols, preferably at least one selected from the group consisting of methanol, ethanol, 2-propanol (also known as isopropanol), 1-propanol and butanol, and more preferably at least one selected from the group consisting of ethanol and 2-propanol from the viewpoint of the dispersibility of ionomer resins.

[0096] A particular catalyst dispersion may not contain solvent; that is, the solvent content relative to the total amount of the particular catalyst dispersion may be 0 by mass.

[0097] <Other Ingredients>

[0098] Specific catalyst dispersions may contain other components. Specifically, it is also possible to add dispersants for controlling the dispersibility of the catalyst, viscosity modifiers for adjusting the viscosity of the dispersion and / or the sedimentation of the catalyst, surfactants for controlling surface tension, antioxidants for preventing oxidation of the catalyst and / or ionomers, curing agents for controlling the thermosetting of the resin, and slip agents for controlling the transport or adhesion properties of the film, etc.

[0099] Process A can be implemented as follows, for example.

[0100] <Preparation of Specific Catalyst Dispersions>

[0101] Specific catalyst dispersions can be prepared by mixing a catalyst, an ionomer resin, a solvent as needed, and any other components.

[0102] Specific catalyst dispersions can be prepared, for example, by mixing a catalyst, a dispersion of an ionomer resin, and a solvent (preferably an alcohol) using any stirring method.

[0103] As a mixing method, a homogenizer (e.g., a rotary homogenizer) can be used.

[0104] The stirring speed can be set to, for example, 100 rpm to 10,000 rpm (revolutions per minute). The prepared specific catalyst dispersion can be filled into any container for use.

[0105] The concentration of the solid component of a specific catalyst dispersion is preferably set to 5% to 30% by mass.

[0106] In step A, after preheating (i.e., preheating) the catalyst dispersion layer of the transfer material X to a temperature of 70°C to 180°C, at least one side of the ion exchange membrane can be overlapped with the catalyst dispersion layer to obtain a laminate.

[0107] The preheating described above can also be used to heat the laminate in process B.

[0108] Before step B, in step A, the catalyst dispersion layer of the transfer material X is preheated, thereby melting the ionomer resin contained in the catalyst dispersion layer. When pressing is performed in step B, the adhesion between the ion exchange membrane and the catalyst layer is further improved, which is therefore preferred.

[0109] Examples of heating methods used for the aforementioned preheating include heaters and microwaves.

[0110] [Process B]

[0111] In step B, the laminate heated to a temperature of 100°C to 200°C is pressed. By pressing, the ion exchange membrane and the catalyst dispersion layer are thermally fused together, thereby forming a catalyst layer on at least one side of the ion exchange membrane, thus obtaining an ion exchange membrane with a catalyst layer.

[0112] In step B, the laminate must be heated to a temperature of 100°C to 200°C at the start of pressing. In one embodiment, the temperature of the laminate is preferably 120°C to 130°C. The heating temperature in step B is preferably set to the melting point of the ionomer resin or a temperature near the melting point. The temperature near the melting point is, for example, the melting point ±20°C.

[0113] In process B, the temperature of the laminate refers to the surface temperature of the catalyst dispersion layer within the laminate. A thermocouple can be used to measure the temperature.

[0114] The laminate can be adjusted to a temperature of 100°C to 200°C by means of (1) or (2) below.

[0115] Method (1): The laminate obtained in process A is heated to 100℃~200℃.

[0116] The laminate can be a laminate in which a specific catalyst dispersion is formed into a predetermined shape directly on at least one side of an ion exchange membrane to form a catalyst dispersion layer.

[0117] The laminate can be a laminate in the following manner: a catalyst dispersion layer formed into a specified shape is disposed on one side of a substrate X, and after obtaining a transfer material X having a substrate X and a catalyst dispersion layer, at least one side of an ion exchange membrane is overlapped with the catalyst dispersion layer of the transfer material X.

[0118] Method (2): In step A, a laminate is obtained by preheating the catalyst dispersion layer of the transfer material X to a temperature of 70°C to 180°C and then overlapping at least one side of the ion exchange membrane with the catalyst dispersion layer.

[0119] In this method, the laminate can be heated to 100°C to 200°C and then pressed without the temperature of the laminate reaching 100°C.

[0120] In this method, pressing can be directly performed when the temperature of the laminate exceeds 100°C.

[0121] Furthermore, if the temperature of the laminate, which has been heated to 100°C to 200°C, drops to less than 100°C, it can be reheated to 100°C to 200°C.

[0122] In step B, the pressure applied when pressing the laminate can be appropriately set. From the viewpoint of the tightness of the ion exchange membrane and the catalyst layer, the pressure is preferably 1 MPa to 20 MPa, and more preferably 1 MPa to 10 MPa.

[0123] As a means of applying pressure, roller presses, flatbed presses, etc. can be used.

[0124] The pressurization time is preferably 0.1 to 20 minutes, and more preferably 0.5 to 10 minutes.

[0125] When using a roller press, the feed speed can be set to approximately 0.5 m / min to 5 m / min.

[0126] In the method for manufacturing an ion exchange membrane with a catalyst layer according to the present invention, when using transfer material X, step B preferably includes a step of further peeling off the substrate X after the above pressing.

[0127] In the process of peeling off substrate X, substrate X is peeled off from the pressed laminate.

[0128] As a peeling method, peeling rods, adsorption rollers, vacuum chucks, etc. can be used.

[0129] Figure 1 This is a schematic diagram illustrating an example of performing a series of processes including process A and process B using transfer substrate X.

[0130] like Figure 1 As shown, in this example, firstly, a specific catalyst dispersion layer is formed using screen printing to create transfer material X1 and transfer material X2.

[0131] Specifically, a screen printing plate 16 is superimposed on a substrate Xa or substrate Xb placed on a support 10. In this example, the support 10, substrate Xa, and substrate Xb are disposed on a heating tray 14. The heating tray 14 is a heating means for preheating.

[0132] Next, in the preparation of transfer material X1, a specific catalyst dispersion 20A filled in dispenser 18A is applied to the template of screen printing plate 16. In this example, the specific catalyst dispersion 20A is a slurry containing iridium (O2 catalyst), ionomer resin, and alcohol as catalysts. Furthermore, in the preparation of transfer material X2, a specific catalyst dispersion 20B filled in dispenser 18B is applied to the frame of screen printing plate 16. In this example, the specific catalyst dispersion 20B is a slurry containing platinum (H2 catalyst), ionomer resin, and alcohol as catalysts.

[0133] The specific catalyst dispersion 20A or 20B applied to the template of the screen printing plate 16 is preferably smoothed using a smoothing means such as a scraper 22.

[0134] Next, after removing the screen printing plate 16, the specific catalyst dispersion 20A disposed on one side of the substrate Xa and the specific catalyst dispersion 20B disposed on one side of the substrate Xb are dried in the drying oven 24 to obtain transfer material X1 having substrate Xa and specific catalyst dispersion layer 26A and transfer material X2 having substrate Xb and specific catalyst dispersion layer 26B.

[0135] Next, in this example, after a laminate 30 is formed by overlapping one side of the ion exchange membrane 28 with a specific catalyst dispersion layer 26B of the transfer material X2, the specific catalyst dispersion layer 26B of the transfer material X2 and the specific catalyst dispersion layer 26A of the transfer material X1 are aligned in such a way that their outer peripheries overlap without shifting, separated by the ion exchange membrane 28. Figure 1 The text describes an example of aligning a specific catalyst dispersion layer 26A with a specific catalyst dispersion layer 26B by flipping the formed transfer material X1, but the alignment method is not limited to the above.

[0136] Next, the laminate 30 and the transfer material X1 are heated to a temperature of 100°C to 200°C and pressed in the direction of arrow A (i.e., hot pressing).

[0137] After pressing, by peeling off substrate Xa and substrate Xb, an ion exchange membrane 34 with catalyst layers can be obtained, which has an iridium catalyst layer 32A and a platinum catalyst layer 32B on both sides of the ion exchange membrane 28.

[0138] In this example, both transfer material X1 and transfer material X2 are used during pressing, but it is also possible to hot press one of transfer material X1 and transfer material X2 first, and then hot press the other.

[0139] In the method for manufacturing an ion exchange membrane with a catalyst layer according to the present invention, steps A and B can be repeated after performing steps A and B. By repeating steps A and B, the thickness of the catalyst layer can be adjusted to any thickness. Specifically, in step A, a polygonal catalyst dispersion layer is formed by arranging a catalyst dispersion in a polygonal shape on a catalyst layer already formed on at least one side of the ion exchange membrane, and then step B is performed.

[0140] [Other processes]

[0141] In addition to steps A and B, the method for manufacturing the ion exchange membrane with a catalyst layer involved in this invention may include other steps.

[0142] Example

[0143] The following examples illustrate the method for manufacturing the catalyst-coated ion exchange membrane according to the present invention in more detail. However, the method for manufacturing the catalyst-coated ion exchange membrane according to the present invention is not limited to the following examples as long as it does not depart from its spirit. Furthermore, unless otherwise specified, "%" refers to mass.

[0144] <Example 1>

[0145] [Process A]

[0146] =Fabrication of Platinum Catalyst Sheets=

[0147] (Preparation of platinum catalyst dispersion 1)

[0148] Prepare 7.2g of carbon-supported platinum, 21.4g of 20% Nafion dispersion (ionomer resin dispersion, DE2020CS type manufactured by FUJIFILM WakoPure Chemical Corporation), and 47.6g of 2-propanol (manufactured by FUJIFILM Wako Pure Chemical Corporation for the electronics industry) as a dispersion solvent. Weigh these ingredients in a glove box and add them to a vial to form turbidity.

[0149] A platinum-containing catalyst liquid 1 was obtained by stirring the turbid material taken from the glove box at 2000 rpm using a rotary homogenizer. The prepared platinum-containing catalyst liquid 1 had a solid content concentration of 15% and a viscosity of 1500 CP (1.5 Pa·s) at 25 °C.

[0150] Regarding the obtained platinum-containing catalyst liquid 1, the average secondary particle size of the catalyst (aggregate) was determined using a particle size analyzer manufactured by HORIBA, Ltd.: Partica LA-9600V2.

[0151] The average secondary particle size is 3 μm.

[0152] The solvent was evaporated from the prepared platinum-containing catalyst liquid 1 using an evaporator, increasing the solid component concentration to 90% and the viscosity at 25°C to 10000 CP (10 Pa·s), thereby obtaining platinum catalyst dispersion 1 (specific catalyst dispersion).

[0153] (Fabrication of platinum catalyst sheets)

[0154] As substrate X, PET sheets (50μm thick, 150mm square) were prepared.

[0155] A screen printing machine was used in the formation of a specific catalyst dispersion layer.

[0156] A PTFE sheet is placed on a screen printing machine, and platinum catalyst dispersion 1 is applied to the template of the screen printing plate to form a decagon with a thickness of 20 μm (area: approximately 100 cm²). 2 A specific catalyst dispersion layer was formed to obtain a platinum catalyst sheet 1 (transfer material X) with a platinum catalyst dispersion layer.

[0157] Platinum catalyst sheets were placed on a hot press (160°C, manufactured by Toyo Seiki Seisaku-sho, Ltd., product name: mini test press-10), and left to stand for 1 minute. Then, they were brought into contact with an ion exchange membrane (manufactured by Chemours, Nafion N115) with a thickness of 125 μm and a square diameter of 150 mm. This resulted in a laminate formed by overlapping the ion exchange membrane with a specific catalyst dispersion layer containing platinum catalyst sheets.

[0158] [Process B]

[0159] Next, a 500 μm thick elastic sheet was further laminated onto the above-mentioned laminate, and then pressed at 1.5 MPa for 5 minutes using a hot press. The initial temperature of the laminate was 140°C. This resulted in the formation of a platinum catalyst layer on one side of the ion exchange membrane.

[0160] After compression and release, cooling was performed to peel off the elastic sheet and PTFE sheet.

[0161] Through the above, the catalyst-layered ion exchange membrane of Example 1, which has a platinum catalyst layer on one side of the ion exchange membrane, was obtained.

[0162] <Example 2>

[0163] In Example 1, platinum catalyst sheet 2 was fabricated by using platinum catalyst dispersion 2 prepared below instead of platinum catalyst dispersion 1. Otherwise, an ion exchange membrane with a catalyst layer of Example 2 having a platinum catalyst layer on one side of the ion exchange membrane was obtained in the same manner as in Example 1.

[0164] (Preparation of platinum catalyst dispersion 2)

[0165] Prepare 7.2g of carbon-supported platinum, 21.4g of 20% Nafion dispersion (manufactured by FUJIFILM Wako Chemical Corporation, DE2020CS type), and 47.6g of 2-propanol (manufactured by FUJIFILM Wako PureChemical Corporation, for electronics industry use) as the dispersion solvent. Weigh these ingredients in a glove box and add them to a vial.

[0166] Liquid 2 containing platinum catalyst was obtained by stirring the turbidity removed from the glove box at 2000 rpm using a rotary homogenizer. The solid content concentration of liquid 2 containing platinum catalyst was adjusted to 15%.

[0167] Regarding the obtained platinum-containing catalyst liquid 2, the average secondary particle size of the catalyst (aggregate) was determined using a particle size analyzer manufactured by HORIBA, Ltd.: Partica LA-9600V2.

[0168] The average secondary particle size is 3 μm.

[0169] The solvent was evaporated from the prepared platinum-containing catalyst liquid 2 using an evaporator, and then a 5:5 solution of ethanol and water was added to increase the solid component concentration to 90% and the viscosity to 10000 CP (10 Pa·s), thus obtaining platinum catalyst dispersion 2 (specific catalyst dispersion).

[0170] <Example 3>

[0171] =Fabrication of Platinum Catalyst Sheets=

[0172] Platinum catalyst sheet 1 was prepared in the same manner as in Example 1.

[0173] =Fabrication of Iridium Catalyst Sheet 1=

[0174] In Example 1, the platinum catalyst dispersion 1 was replaced with the iridium catalyst dispersion 1 shown below. Otherwise, an iridium catalyst sheet 1 (transfer material X) having a decagonal iridium catalyst dispersion layer was prepared in the same manner as in Example 1.

[0175] (Preparation of Iridium Catalyst Dispersion 1)

[0176] Prepare 3.8g of iridium oxide, 4.8g of 20% Nafion dispersion (manufactured by FUJIFILM Wako Chemical Corporation, DE2020CS type), and 4.6g of 2-propanol (manufactured by FUJIFILM Wako Pure Chemical Corporation, for electronic industry use) as the dispersion solvent. Weigh these ingredients in a glove box and add them to a vial.

[0177] The turbid material removed from the glove box was stirred at 2000 rpm using a planetary mixer to obtain liquid 1 containing iridium catalyst. The solid content concentration of the adjusted liquid 1 containing iridium catalyst was 36.4%.

[0178] Regarding the obtained iridium-containing catalyst liquid 1, the average secondary particle size of the catalyst (aggregate) was determined using a particle size analyzer: Partica LA-9600V2 manufactured by HORIBA, Ltd. The average secondary particle size was 3 μm.

[0179] After evaporating the solvent from the prepared iridium-containing catalyst liquid 1 using an evaporator, ethanol was added to obtain an iridium catalyst dispersion 1 with a 90% solids concentration and a viscosity of 10,000 CP (10 Pa·s).

[0180] Following the same procedure as in Example 1, after pressing the ion exchange membrane and platinum catalyst sheet 1 using a hot press, the iridium catalyst dispersion layer and platinum catalyst layer of the iridium catalyst sheet 1 are positioned opposite each other across the ion exchange membrane on the side of the ion exchange membrane where the platinum catalyst sheet 1 is not located. After standing for 1 minute, an elastic sheet is placed on the iridium catalyst sheet 1, and the iridium catalyst dispersion layer is transferred onto the ion exchange membrane using the same pressure as in Example 1.

[0181] Next, cooling was performed to separate the elastic sheet and the PTFE sheet.

[0182] Through the above, an ion exchange membrane with a catalyst layer, as described in Example 3, was obtained, which has a platinum catalyst layer on one side and an iridium catalyst layer on the other side.

[0183] <Example 4>

[0184] The platinum catalyst dispersion 1 prepared in Example 1 was directly applied to one side of the ion exchange membrane to form a decagon with a thickness of 20 μm (area: 100 cm²). 2 Thus, a stacked body was obtained.

[0185] The obtained laminate was pressed under the same hot pressing apparatus and pressure conditions as in Example 1.

[0186] Through the above, an ion exchange membrane with a catalyst layer, as described in Example 4, was obtained, which has a platinum catalyst layer on one side of the ion exchange membrane.

[0187] <Example 5>

[0188] On one side of the ion exchange membrane, the platinum catalyst dispersion 1 used in Example 3 was applied to form a decagon with a thickness of 20 μm (area: 100 cm²). 2 In this manner, the first specific catalyst dispersion layer is directly applied to form the first specific catalyst dispersion layer. On the other side, iridium catalyst dispersion 1 is applied at the position overlapping the first specific catalyst dispersion layer to form a decagon with a thickness of 20 μm (area: 100 cm²). 2 In a manner that directly imparts and forms a second specific catalyst dispersion layer, a laminate is obtained.

[0189] The obtained laminate was pressed under the same hot pressing apparatus and pressure conditions as in Example 3.

[0190] Through the above, an ion exchange membrane with a catalyst layer, as described in Example 5, was obtained, which has a platinum catalyst layer on one side and an iridium catalyst layer on the other side.

[0191] <Comparative Example 1>

[0192] In Example 1, a liquid 1 containing a platinum catalyst was used instead of a platinum catalyst dispersion 1. Otherwise, an ion exchange membrane with a catalyst layer of Comparative Example 1, having a platinum catalyst layer on one side of the ion exchange membrane, was obtained in the same manner as in Example 1.

[0193] <Comparative Example 2>

[0194] In Example 4, a liquid 1 containing a platinum catalyst was used instead of a platinum catalyst dispersion 1. Otherwise, an ion exchange membrane with a catalyst layer of Comparative Example 2, which has a platinum catalyst layer on one side of the ion exchange membrane, was obtained in the same manner as in Example 4.

[0195] 〔evaluate〕

[0196] The ion exchange membranes with catalyst layers obtained through the above examples were subjected to the following evaluations: Evaluation 1 (catalyst layer dimensional stability) and Evaluation 2 (coiling amount). The evaluation results are shown in Table 1.

[0197] <Evaluation 1 (Dimensional Stability of Catalyst Layer)>

[0198] The dimensional stability of the catalyst layer was evaluated by the shapeability of the edges of the catalyst layer obtained in each example.

[0199] [Evaluation Method]

[0200] Homemade as Figure 2 The image inspection apparatus 70 shown is equipped with a CCD camera 72 and an illumination 74. Using this image inspection apparatus, the ion exchange membranes with catalyst layers obtained in each example were observed, and the formability of the edges of the catalyst layer was evaluated.

[0201] In the image inspection apparatus 70, an ion exchange membrane 64 with a catalyst layer 62 formed thereon (an ion exchange membrane 60 with a catalyst layer) is placed on a measuring stage 76. By using a CCD camera 72 and an illumination 74 located on the upper part of the catalyst layer 62, the entire surface of the catalyst layer 62 (i.e., the entire upper surface) can be photographed. The CCD camera 72 and the illumination 74 can be moved via a connected guide 78.

[0202] The decagonal catalyst layers obtained in the above examples (area: approximately 100 mm²) were photographed. 2 The entire upper surface of ). Figure 3 The image shows a photograph of the decagonal catalyst layer obtained in Example 1.

[0203] Regarding Example 3, the platinum catalyst layer and the iridium catalyst layer were photographed respectively.

[0204] Furthermore, the obtained camera images were divided into 100 images within a 10mm square field of view, and the parts with disordered edges were extracted through image analysis. For example... Figure 4 The image shows a portion with disordered edges.

[0205] Based on the image analysis results, the formability of the catalyst layer's edge is evaluated using the following criteria, and the results are used as the evaluation of the catalyst layer's dimensional stability. A, B, C, and D represent practically acceptable grades, with A being the highest grade.

[0206] -standard-

[0207] A: The proportion of camera images with edge overflow, etc., observed is less than 1%.

[0208] B: The proportion of camera images with edge overflow, etc., is more than 1% but less than 3%.

[0209] C: The proportion of camera images with edge overflow, etc., is more than 3% but less than 5%.

[0210] D: The proportion of camera images with edge overflow, etc., is more than 5% but less than 10%.

[0211] E: The proportion of camera images with edge overflow, etc., is more than 10%.

[0212] <Evaluation 2 (Curl Quantity)>

[0213] The amount of curling (the amount of warping from the measuring plate) of ion exchange membranes with catalyst layers was evaluated.

[0214] This evaluation covers ion exchange membranes with catalyst layers obtained in the above examples, except for Example 3.

[0215] [Evaluation Method]

[0216] The catalyst-coated ion exchange membrane (150 mm square) used for evaluation was placed on a measuring plate with the catalyst layer side facing upwards. A rigid ruler was placed against each of the four corners of the membrane on the measuring plate, and the amount of curling (the amount of warping from the measuring plate) was measured. A greater amount of warping indicates stronger curling of the catalyst-coated ion exchange membrane.

[0217] The obtained measurements (curling amount) were arithmetically averaged and rounded to the first decimal place as the curl amount, and evaluated according to the following criteria. A, B, C, and D are practically acceptable grades, with A being the highest grade.

[0218] -standard-

[0219] A: The uplift is less than 1mm.

[0220] B: The uplift is more than 1mm but less than 3mm.

[0221] C: The uplift is more than 3mm but less than 5mm.

[0222] D: The uplift is more than 5mm but less than 10mm.

[0223] E: The uplift exceeds 10mm.

[0224] [Table 1]

[0225] As shown in Table 1, the catalyst layers of the ion exchange membranes with catalyst layers obtained in the examples all exhibit excellent dimensional stability.

[0226] Furthermore, the ion exchange membrane with catalyst layer obtained in the examples also has a small amount of curling.

[0227] Symbol Explanation

[0228] 10-Support, Xa, Xb-Substrate, 16-Screen printing plate, 14-Heating tray, 18A, 18B-Dispensers, 20A, 20B-Specific catalyst dispersions, 22-Scraper, 24-Drying oven, 26A, 26B-Specific catalyst dispersion layers, 28-Ion exchange membrane, 30-Laminate structure, 32B-Catalyst layer (platinum catalyst layer), 32A-Catalyst layer (iridium catalyst layer), 34-Ion exchange membrane with catalyst layer, X1, X2-Transfer material, A-Pressure direction, 70-Image inspection device, 72-CCD camera, 74-Illumination, 78-Guide, 60-Ion exchange membrane with catalyst layer, 62-Catalyst layer, 64-Ion exchange membrane.

[0229] The entire contents of Japanese Patent Application No. 2023-193025, filed on November 13, 2023, are incorporated herein by reference.

[0230] All documents, patent applications and technical standards described in this specification are incorporated herein by reference, as are the individual documents, patent applications and technical standards specifically described and incorporated by reference.

Claims

1. A method for manufacturing an ion exchange membrane with a catalyst layer, comprising: Step A involves depositing a catalyst dispersion layer, formed into a predetermined shape, on at least one side of an ion exchange membrane. The catalyst dispersion comprises a catalyst and an ionomer resin and has a viscosity of 1 Pa·s to 500 Pa·s at 25°C, thereby obtaining a laminate having the ion exchange membrane and the catalyst dispersion layer. Step B involves pressing the laminated body, which has been heated to a temperature of 100°C to 200°C.

2. The method for manufacturing an ion exchange membrane with a catalyst layer according to claim 1, wherein, The catalyst dispersion contains an alcohol.

3. The method for manufacturing an ion exchange membrane with a catalyst layer according to claim 2, wherein, The alcohol is selected from at least one of ethanol and 2-propanol.

4. The method for manufacturing an ion exchange membrane with a catalyst layer according to claim 1 or 2, wherein, The catalyst comprises aggregates with an average secondary particle size of less than 10 μm.

5. The method for manufacturing an ion exchange membrane with a catalyst layer according to claim 1 or 2, wherein, In step A, the catalyst dispersion layer is formed on both sides of the ion exchange membrane to obtain the laminate.

6. The method for manufacturing an ion exchange membrane with a catalyst layer according to claim 1 or 2, wherein, In step A, a catalyst dispersion layer formed into a predetermined shape is disposed on one side of the substrate X. After obtaining a transfer material X having the substrate X and the catalyst dispersion layer, at least one side of the ion exchange membrane is overlapped with the catalyst dispersion layer of the transfer material X to obtain the laminate.

7. The method for manufacturing an ion exchange membrane with a catalyst layer according to claim 6, wherein, The process A includes the following steps: after preheating the catalyst dispersion layer of the transfer material X to a temperature of 70°C to 180°C, at least one side of the ion exchange membrane is overlapped with the catalyst dispersion layer to obtain the laminate.

Images