JP2014154273A - Release film for fuel cell manufacture, laminate, and manufacturing method of fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film capable of prolonging the lifetime of a solid polymer fuel cell by improving surface smoothness of an electrolyte membrane and/or electrode membrane of the fuel cell and thickness uniformity even when a release layer is thin.SOLUTION: As a release film for manufacturing a membrane-electrode assembly of a solid polymer fuel cell, a release film is used which includes a base material layer and a release layer laminated on at least one side of the base material layer and formed from a cyclic olefin-based resin, and in which a centerline average roughness Ra of a surface of the release layer is 0.001 to 0.05 μm and an average thickness of the release layer is 0.2 to 5 μm. The release layer may also be formed by coating. The release film may also be a film for laminating an electrolyte membrane and/or an electrode membrane containing an ion exchange resin thereon and for releasing from the membrane-electrode assembly after the membrane-electrode assembly is manufactured.

Description

  The present invention relates to a release film used when manufacturing (forming a membrane) a membrane electrode assembly that is a constituent member of a polymer electrolyte fuel cell, a laminate (laminated film) including the release film, and the release film. The present invention relates to a method for producing the membrane electrode assembly using a mold film.

  A polymer electrolyte fuel cell has a basic configuration called a membrane electrode assembly (MEA). MEA is a laminate obtained by laminating an electrode membrane (catalyst layer or electrode catalyst membrane) mainly composed of carbon powder carrying a platinum group metal catalyst on both surfaces of a solid polymer electrolyte membrane which is an ion exchange membrane. Is further sandwiched between a fuel gas supply layer and an air supply layer which are conductive porous membranes. In this MEA, both the electrolyte membrane and the electrode membrane contain an ion exchange resin, but the electrolyte membrane and the electrode membrane are usually formed by a casting method and / or a coating method. As a method of laminating an electrolyte membrane and an electrode membrane, usually, both layers formed on a support are brought into contact with each other, and are adhered by thermocompression bonding at about 130 to 150 ° C. and a pressure of about 1 to 10 MPa. A method of peeling the body is used. For this reason, a release film is used as the support, and the release film is required to have appropriate peelability and adhesion to the electrolyte membrane and the electrode film, as well as heat resistance.

  For example, a fluorine-based film is also known as a release film, and Japanese Unexamined Patent Application Publication No. 2010-272136 (Patent Document 1) discloses a fuel cell electrode using a polytetrafluoroethylene film as a release film. A manufacturing method is disclosed.

  However, the fluorine-based film has excellent heat resistance, releasability, and non-contamination, is expensive, and is difficult to burn in waste incineration after use, and generates toxic gases. Have. Furthermore, since the elastic modulus is low, it is difficult to manufacture by a roll-to-roll method, and productivity is low. In particular, since the fluorine-based film is an extruded film, irregularities such as fish eyes are easily generated, and the surface smoothness is low. When the smoothness of the release film is low and the thickness is not uniform, the surfaces of the electrolyte membrane and the electrode film are also affected by the release film, and the smoothness is lowered. As a result, at the interface between the electrolyte membrane and the electrode membrane and between the electrode membrane and the gas diffusion layer, a portion that contacts closely and a portion that contacts sparsely occur, resulting in a difference in the degree of deterioration of the catalyst, thereby shortening the battery life. .

  Japanese Unexamined Patent Application Publication No. 2010-234570 (Patent Document 2) discloses a release film made of a cycloolefin copolymer, and a cycloolefin copolymer solution is coated on a base film such as a polyethylene terephthalate film. A release film formed in this way is also described. This document does not describe the surface smoothness of the release film. In the examples, a solution containing a copolymer of ethylene and norbornene is formed on a polyethylene terephthalate film using a casting apparatus. A release film having a thickness of 0.5 μm is formed by casting.

  However, this release film also has low surface smoothness and cannot improve battery life. In addition, since the general purpose film improves handling properties such as anti-blocking properties, storability in roll form, and roll feedability, the film surface has an appropriate roughness.

JP 2010-272136 A (Claims) JP 2010-234570 A (Claims, paragraph [0025], Example 2)

  Accordingly, an object of the present invention is to improve the surface smoothness and thickness uniformity of the electrolyte membrane and / or electrode membrane of the solid polymer fuel cell even if the release layer is thin, and the fuel cell Disclosed is a release film capable of improving life, a laminated film including the release film, and a method for producing a membrane electrode assembly (electrolyte membrane and / or electrode membrane) of a fuel cell using the release film. .

  Another object of the present invention is to provide a release film capable of stably producing an electrolyte membrane and / or an electrode membrane having a smooth surface and a uniform thickness and having a releasability suitable for producing a membrane / electrode assembly, and An object of the present invention is to provide a laminated film including the release film and a method for producing a membrane electrode assembly (electrolyte membrane and / or electrode membrane) of a fuel cell using the release film.

  Still another object of the present invention is to provide a release film having high heat resistance and capable of producing an electrolyte membrane and / or an electrode membrane of a polymer electrolyte fuel cell in a roll-to-roll manner. An object of the present invention is to provide a laminated film including a release film and a method for producing a membrane electrode assembly (electrolyte membrane and / or electrode membrane) of a fuel cell using the release film.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have formed a cyclic olefin-based resin on the base material layer, and the surface center line average roughness Ra is 0.001 to 0.05 μm. By using a release film on which a release layer having an average thickness of 0.2 to 5 μm is laminated as a release film for producing a membrane electrode assembly of a polymer electrolyte fuel cell, release Even if the layer is thin, the surface smoothness and thickness uniformity of the electrolyte membrane and / or electrode membrane of the polymer electrolyte fuel cell can be improved, and the battery life of the fuel cell can be improved.

  That is, the release film of the present invention is a release film for producing a membrane electrode assembly of a polymer electrolyte fuel cell, and is laminated on at least one surface of the base material layer. And a release layer formed of a cyclic olefin resin, the centerline average roughness Ra of the release layer surface is 0.001 to 0.05 μm, and the average thickness of the release layer is 0 .2-5 μm. The release layer may be a layer formed by coating. The center line average roughness Ra on the surface of the base material layer may be 0.001 to 0.05 μm. The base material layer may be formed of at least one selected from the group consisting of polyolefin, polyvinyl alcohol polymer, polyester, polyamide, and cellulose derivative. The release film of the present invention may be a film for peeling an electrolyte membrane and / or electrode membrane containing an ion exchange resin from the membrane electrode assembly after the membrane and electrode membrane are laminated thereon. Good.

  The present invention provides a laminate for producing a polymer electrolyte fuel cell, the release film, and a layer laminated on the release layer of the release film and containing an ion exchange resin. A formed laminate is also included. The layer containing the ion exchange resin may be an electrolyte membrane and / or an electrode membrane.

  In the present invention, a membrane / electrode assembly of a polymer electrolyte fuel cell is manufactured through a lamination step of laminating an electrolyte membrane and / or an electrode membrane containing an ion exchange resin on the release layer of the release film. The method of doing is also included. In the laminating step, an electrolyte membrane may be laminated on the release layer of the first release film by coating, and an electrode film may be laminated on the release layer of the second release film by coating. . The method of the present invention further includes an adhesion step of preparing a membrane / electrode assembly by closely adhering the electrolyte membrane and the electrode membrane respectively laminated on the release layers of the first and second release films. Also good. The method of the present invention may further include a peeling step of peeling the release film from the electrolyte membrane and / or the electrode membrane.

  In the present invention, the separation is made of a cyclic olefin resin on the base material layer, the surface centerline average roughness Ra is 0.001 to 0.05 μm, and the average thickness is 0.2 to 5 μm. Since the release film with the mold layer laminated is used as a release film for producing a membrane electrode assembly of a polymer electrolyte fuel cell, the polymer electrolyte fuel cell can be used even if the release layer is thin. The surface smoothness and thickness uniformity of the electrolyte membrane and / or electrode membrane can be improved, and the battery life of the fuel cell can be improved. In addition, since the surface of the release layer is smooth and has an appropriate surface roughness, and the adhesion between the base material layer and the release layer is high, an electrolyte membrane having a smooth surface and a uniform thickness and / or Alternatively, it is possible to stably produce the electrode film and to realize releasability suitable for producing a membrane electrode assembly. Furthermore, since it has high heat resistance and moderate surface roughness, it is possible to manufacture an electrolyte membrane and / or an electrode membrane of a polymer electrolyte fuel cell by a roll-to-roll method.

[Release film]
The release film of the present invention is a release film for producing a membrane electrode assembly (MEA) of a polymer electrolyte fuel cell, and comprises a base material layer and at least one surface of the base material layer (usually normal) , One surface) and a release layer formed of a cyclic olefin-based resin, the centerline average roughness Ra of the release layer surface is 0.001 to 0.05 μm, and The average thickness of the release layer is 0.2 to 5 μm. In particular, the release film of the present invention may be a film for peeling an MEA after laminating an electrolyte membrane and / or an electrode membrane containing an ion exchange resin on the membrane.

(Release layer)
The center line average roughness Ra of the surface of the release layer is 0.001 to 0.05 μm. In the present invention, since the centerline average roughness Ra of the release layer surface is in this range, the surface smoothness is excellent, and the surface smoothness and thickness of the electrolyte membrane and / or electrode membrane of the solid polymer fuel cell are uniform. In addition to improving the properties, it has an appropriate roughness, so that the adhesion between the base material layer and the release layer is high, and it can be used for production in a roll-to-roll system. If Ra is too small, in addition to lowering the adhesion between the base material layer and the release layer, it becomes difficult to produce by a roll-to-roll method. On the other hand, if Ra is too large, surface smoothness is obtained. Decreases, and the surface smoothness and thickness uniformity of the electrolyte membrane and / or electrode membrane are reduced, and the life of the fuel cell is shortened. The center line average roughness Ra may be 0.001 to 0.04 μm, preferably 0.0015 to 0.03 μm, more preferably 0.002 to 0.025 μm (particularly 0.0025 to 0.022 μm). Degree.

  In the present specification, the center line average roughness Ra can be measured by a method based on JIS B0601.

  The average thickness of the release layer is 0.2 to 5 μm. In the present invention, even if the release layer is such a thin wall, by adjusting the average roughness Ra of the substrate surface, the influence of the uneven shape of the substrate surface is suppressed, and the average roughness of the release layer is reduced. The thickness Ra can be adjusted to the above-mentioned appropriate range. If the thickness of the release layer is too thick, the influence of the substrate is reduced, so that the effect of the present invention cannot be exhibited and the economic efficiency is also lowered. On the other hand, if the thickness of the release layer is too thin, it is difficult to maintain the uniformity of thickness, and the adhesion to the substrate is lowered. The average thickness of the release layer may be 0.22 to 4 μm, for example, 0.25 to 3 μm, preferably 0.28 to 2.5 μm, more preferably 0.3 to 2 μm (particularly 0.3 to About 1 μm).

  In the present specification, the average thickness can be calculated based on the coating amount (solid content weight per unit area) and density of the release layer.

  The cyclic olefin-based resin contains a cyclic olefin as a polymerization component. The cyclic olefin is a polymerizable cyclic olefin having an ethylenic double bond in the ring, and can be classified into a monocyclic olefin, a bicyclic olefin, a tricyclic or higher polycyclic olefin, and the like.

Examples of monocyclic olefins include cyclic C _4-12 cycloolefins such as cyclobutene, cyclopentene, cycloheptene, and cyclooctene.

Examples of the bicyclic olefin include 2-norbornene; alkyl groups such as 5-methyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, and 5-butyl-2-norbornene. Norbornenes having (C _1-4 alkyl group); norbornenes having an alkenyl group such as 5-ethylidene-2-norbornene; 5-methoxycarbonyl-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene Norbornenes having an alkoxycarbonyl group such as: norbornenes having a cyano group such as 5-cyano-2-norbornene; aryl groups such as 5-phenyl-2-norbornene and 5-phenyl-5-methyl-2-norbornene Having norbornenes; octaline; 6-ethyl-oct Examples include octaline having an alkyl group such as tahydronaphthalene.

  Examples of the polycyclic olefin include dicyclopentadiene; 2,3-dihydrodicyclopentadiene, methanooctahydrofluorene, dimethanooctahydronaphthalene, dimethanocyclopentadienonaphthalene, methanooctahydrocyclopentadienaphthalene, and the like. Derivatives having substituents such as 6-ethyl-octahydronaphthalene; adducts of cyclopentadiene and tetrahydroindene, 3-pentamers of cyclopentadiene, and the like.

  These cyclic olefins can be used alone or in combination of two or more. Of these cyclic olefins, bicyclic olefins are preferred because they have a good balance between peelability and flexibility. The ratio of bicyclic olefins (particularly norbornenes) to the whole cyclic olefins may be 10 mol% or more, for example, 30 mol% or more, preferably 50 mol% or more, more preferably 80 mol% or more ( In particular, it is 90 mol% or more), and may be a bicyclic olefin alone (100 mol%). In particular, when the ratio of the tricyclic or higher polycyclic olefin is increased, it becomes difficult to use for production in a roll-to-roll system.

As typical bicyclic olefins, for example, norbornene (2-norbornene) which may have a substituent, octaline (octahydronaphthalene) which may have a substituent, and the like can be exemplified. Examples of the substituent include an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acyl group, a cyano group, an amide group, and a halogen atom. These substituents may be used alone or in combination of two or more. Of these bicyclic olefins, norbornenes such as norbornene and norbornene having an alkyl group (C _1-4 alkyl group such as methyl group or ethyl group) are particularly preferable.

  The cyclic olefin-based resin is preferably a cyclic olefin-chain olefin copolymer further containing a chain olefin as a polymerization component because it can be used for production in a roll-to-roll system.

Examples of the chain olefin include chain C such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene. _2-10 olefins etc. are mentioned. These chain olefins can be used alone or in combination of two or more. Among these chain olefins, α-chain C _2-8 olefins are preferable, and α-chain C _2-4 olefins (particularly ethylene) are more preferable.

  The ratio (molar ratio) between the cyclic olefin and the chain olefin is, for example, cyclic olefin / chain olefin = 100/0 to 1/99, preferably 90/10 to 10/90, and more preferably 70/30 to 15 / 85 (particularly 50/50 to 20/80). If the ratio of the cyclic olefin is too small, the peelability is lowered.

  Other copolymerizable monomers include, for example, vinyl ester monomers (eg, vinyl acetate, vinyl propionate, etc.); diene monomers (eg, butadiene, isoprene, etc.); (meth) acrylic monomers Monomer [for example, (meth) acrylic acid or derivatives thereof ((meth) acrylic acid ester etc.)] etc. can be illustrated. These other copolymerizable monomers may be used alone or in combination of two or more. The content of these other copolymerizable monomers is, for example, 5 mol% or less, preferably 1 mol% or less, based on the entire cyclic olefin resin.

  The cyclic olefin-based resin may be a resin obtained by addition polymerization or a resin obtained by ring-opening polymerization (ring-opening metathesis polymerization or the like). The polymer obtained by ring-opening metathesis polymerization may be a hydrogenated hydrogenated resin. The polymerization method of the cyclic olefin resin is a conventional method, for example, ring-opening metathesis polymerization using a metathesis polymerization catalyst, addition polymerization using a Ziegler type catalyst, addition polymerization using a metallocene catalyst (usually a metathesis polymerization catalyst). The ring-opening metathesis polymerization used) can be used.

  Although the glass transition temperature (Tg) of cyclic olefin resin can be selected from the range of about 10-220 degreeC, from a heat resistant point, for example, 30-215 degreeC, Preferably it is 50-215 degreeC, More preferably, it is 100-215. It is about ℃. If the glass transition temperature is too low, the heat resistance is lowered, and if it is too high, production in a roll-to-roll system becomes difficult. In the present specification, the glass transition temperature can be measured using a differential scanning calorimeter (DSC).

  The number average molecular weight of the cyclic olefin-based resin is, for example, 1000 to 150,000, preferably 5000 to 120,000, more preferably 10,000 to 100,000 (particularly 20000 to 90000) in terms of polystyrene in gel permeation chromatography (GPC). .

  The release layer may further contain a conventional additive. Examples of conventional additives include fillers, lubricants (waxes, fatty acid esters, fatty acid amides, etc.), antistatic agents, stabilizers (antioxidants, heat stabilizers, light stabilizers, etc.), flame retardants, viscosity adjustments Agents, thickeners, antifoaming agents and the like may be included. In addition, organic or inorganic particles (particularly, anti-blocking agents such as zeolite) may be included as long as the surface smoothness is not impaired.

  In particular, in the present invention, it is preferable that the releasability can be improved without containing a low molecular weight release agent such as a silicone compound that easily contaminates the electrolyte membrane or the electrode membrane, and it is preferable that the silicone compound is not substantially contained. .

(Base material layer)
The base material layer can improve the dimensional stability of the release film in the manufacturing process of the fuel cell. In particular, even when tension is applied in the roll-to-roll method, it can suppress the elongation, and further, the drying process and thermocompression bonding A base material having high heat resistance and high dimensional stability is preferable from the viewpoint of maintaining high dimensional stability even when exposed to a high temperature by treatment, etc., and suppressing peeling from the electrolyte membrane or electrode film, and an elastic modulus at 150 ° C. May be formed of a synthetic resin of 100 to 1000 MPa. The elastic modulus may be, for example, about 120 to 1000 MPa, preferably about 150 to 1000 MPa, and more preferably about 200 to 1000 MPa. When the elastic modulus is too small, the dimensional stability is lowered, and peeling from the electrolyte membrane and the electrode membrane occurs in the production by the roll-to-roll method, and the productivity of the fuel cell is lowered.

As such a synthetic resin, for example, various thermoplastic resins and thermosetting resins can be used, but a thermoplastic resin is preferable from the viewpoint of flexibility that can be manufactured by a roll-to-roll method. Examples of the thermoplastic resin include polyolefin (polypropylene resin, cyclic polyolefin, etc.), polyvinyl alcohol polymer, polyester, polyamide, polyimide, polycarbonate, polyphenylene ether, polyphenylene sulfide, and cellulose derivatives. These thermoplastic resins can be used alone or in combination of two or more. Of these thermoplastic resins, at least one selected from the group consisting of polyolefins, polyvinyl alcohol polymers, polyesters, polyamides, and cellulose derivatives is preferred, and polyesters are preferred because of their excellent balance between heat resistance and flexibility. Particularly preferred. Furthermore, as the polyester, poly C _2-4 alkylene arylate resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) can be preferably used.

  Since the release layer is thin and the uneven shape on the surface of the base material layer is easily followed by the release layer, the surface of the base material layer preferably has an appropriate surface smoothness. The center line average roughness Ra on the surface of the base material layer may be 0.001 to 0.05 μm, for example, 0.001 to 0.04 μm, preferably 0.0015 to 0.03 μm, More preferably, it is about 0.002 to 0.025 μm (particularly 0.0025 to 0.022 μm). If Ra is too small, the adhesiveness between the base material layer and the release layer is lowered, and it is difficult to use for production in a roll-to-roll method. On the other hand, if Ra is too large, the release layer Surface smoothness decreases.

  The base material layer may be formed of a stretched film from the viewpoint of improving the film strength. The stretching may be uniaxial stretching, but biaxial stretching is preferred from the viewpoint that the film strength can be improved. Further, the biaxial stretching may be sequential biaxial stretching, but simultaneous biaxial stretching is preferred from the viewpoint of excellent surface smoothness. In sequential biaxial stretching, scratches are easily caused by contact with the roll during longitudinal stretching, and when scratches are present, the average roughness Ra increases, the peelability of the release layer decreases, and the electrolyte membrane and electrode membrane Surface smoothness is lowered, and battery characteristics (such as a reduction in battery life due to a decrease in adhesive strength) are likely to occur. The draw ratio may be, for example, 1.5 times or more (for example, 1.5 to 6), preferably 2 to 5 times, more preferably about 3 to 4 times in the longitudinal and transverse directions, respectively. is there. If the draw ratio is too low, the film strength tends to be insufficient.

  The average thickness of a base material layer is 1-300 micrometers, for example, Preferably it is 5-200 micrometers, More preferably, it is about 10-100 micrometers (especially 20-80 micrometers). If the thickness of the base material layer is too large, production by the roll-to-roll method becomes difficult, and if it is too thin, the dimensional stability is lowered.

  The surface of the base material layer may be subjected to a surface treatment in order to improve the adhesion with the release layer. Examples of the surface treatment include conventional surface treatments such as corona discharge treatment, flame treatment, plasma treatment, ozone and ultraviolet irradiation treatment. Of these, corona discharge treatment is preferred.

(Manufacturing method of release film)
The release film can be produced by a method of coating (or casting) a solution containing a cyclic olefin resin on the base material layer and then drying.

  As the coating method, conventional methods such as roll coater, air knife coater, blade coater, rod coater, reverse coater, bar coater, comma coater, die coater, gravure coater, screen coater method, spray method, spinner method and the like can be mentioned. It is done. Of these methods, the bar coater method is widely used.

  As the solvent, a nonpolar solvent can be used, for example, aliphatic hydrocarbons such as hexane, alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as toluene and xylene, and aromatics such as solvent naphtha. Oil can be used. These solvents may be used alone or in combination of two or more. Of these, aromatic hydrocarbons such as toluene and aromatic oils such as solvent naphtha are preferred.

  The solid content concentration in the solution is, for example, about 1 to 50% by weight, preferably 3 to 30% by weight, more preferably 5 to 25% by weight (particularly 10 to 20% by weight).

  Drying may be natural drying, or the solvent may be evaporated by heating and drying. 50 degreeC or more may be sufficient as drying temperature, for example, 50-200 degreeC, Preferably it is 60-150 degreeC, More preferably, it is about 80-120 degreeC.

[Laminate]
The laminate of the present invention is a laminate for producing a polymer electrolyte fuel cell. The laminate is laminated on a release film and a release layer of the release film and contains an ion exchange resin ( Electrolyte membrane, electrode membrane, membrane electrode assembly).

As the ion exchange resin, conventional ion exchange resins used in fuel cells can be used. Among them, cation exchange resins such as strong acid cation exchange resins and weak acid cation exchange resins are preferable, and sulfonic acid An ion exchange resin having a group (for example, a fluororesin having a sulfonic acid group, a sulfonated product of crosslinked polystyrene) is particularly preferable. In particular, in a polymer electrolyte fuel cell, a fluororesin having a sulfonic acid group (or —CF ₂ CF ₂ SO ₃ H group) in the side chain, for example, [2- (2-sulfotetrafluoroethoxy) hexafluoropropoxy] A block copolymer of trifluoroethylene and tetrafluoroethylene is preferably used.

  The ion exchange capacity of the ion exchange resin may be 0.1 meq / g or more, for example, 0.1 to 2.0 meq / g, preferably 0.2 to 1.8 meq / g, more preferably 0.3. It may be about ~ 1.5 meq / g (particularly 0.5 to 1.5 meq / g).

  Examples of such ion exchange resins include “Registered trademark: Nafion” manufactured by DuPont, “Registered trademark: Flemion” manufactured by Asahi Glass Co., Ltd., and “Registered trademark: Aciplex manufactured by Asahi Kasei Corporation. ) "," Registered trademark: GORE-SELECT "manufactured by Japan Gore-Tex Co., Ltd. can be used. In addition, as an ion exchange resin, you may use the ion exchange resin etc. which are described in Unexamined-Japanese-Patent No. 2010-234570.

  The layer containing the ion exchange resin may be an electrolyte membrane formed of the ion exchange resin, an electrode membrane containing the ion exchange resin and catalyst particles.

  In an electrode film (catalyst layer or electrode catalyst film), the catalyst particles contain a metal component having a catalytic action (particularly, a noble metal element such as platinum or an alloy containing a noble metal). In addition, the electrode film for an anode electrode contains a platinum-ruthenium alloy. Furthermore, the catalyst particles are usually used as composite particles in which the metal component is supported on a conductive material (carbon material such as carbon black). In the electrode film, the ratio of the ion exchange resin is, for example, about 5 to 100 parts by weight, preferably about 10 to 80 parts by weight, and more preferably about 20 to 50 parts by weight with respect to 100 parts by weight of the catalyst particles.

  The average thickness of the electrolyte membrane is, for example, about 1 to 500 μm, preferably 5 to 300 μm, and more preferably about 10 to 200 μm.

  The average thickness of the electrode film is, for example, about 1 to 100 μm, preferably 5 to 80 μm, and more preferably about 10 to 50 μm.

[Production method of membrane electrode assembly]
In this invention, a membrane electrode assembly (MEA) can be manufactured using the said laminated body. That is, the method for producing a membrane electrode assembly of the present invention comprises a layer containing an ion exchange resin (an electrolyte membrane containing an ion exchange resin and / or an electrode membrane containing an ion exchange resin) on the release layer of the release film. The laminated body is manufactured through a stacking step of stacking a), and a membrane electrode assembly of a polymer electrolyte fuel cell can be manufactured using the stacked body.

  Specifically, in the laminating step (laminated body manufacturing method), an electrolyte membrane is laminated on the release layer of the first release film by coating, and the electrolyte membrane is laminated on the release layer of the release film. The laminated body is manufactured, and the electrode film is laminated on the release layer of the second release film by coating, and the laminate in which the electrode film is laminated on the release layer of the release film is produced. May be.

  In order to form the electrolyte membrane and the electrode membrane by coating (or casting), the electrolyte membrane and the electrode membrane are coated in a state in which an ion exchange resin (and catalyst particles) is dissolved in a solvent.

Examples of the solvent include water, alcohols (C _1-4 alkanols such as methanol, ethanol, isopropanol, and 1-butanol), ketones (acetone, methyl ethyl ketone, etc.), ethers (dioxane, tetrahydrofuran, etc.), and sulfoxides. (Such as dimethyl sulfoxide). These solvents can be used alone or in combination of two or more. Among these solvents, water or a mixed solvent of water and C _1-4 alkanol is generally used from the viewpoint of handleability. The concentration of the solute (ion exchange resin, catalyst particles) in the solution is, for example, about 1 to 80% by weight, preferably about 5 to 60% by weight, and more preferably about 10 to 40% by weight.

  As a coating method, the conventional method illustrated by the manufacturing method of the said release film is mentioned. Of these methods, the blade coater method, the bar coater method and the like are widely used.

  After coating the solution containing the ion exchange resin (and catalyst particles), the solvent may be evaporated by heating and drying. The drying temperature may be 50 ° C. or more, for example, about 80 to 200 ° C. (especially 100 to 150 ° C.) for the electrolyte membrane, and 50 to 150 ° C. (particularly 60 to 120 ° C.) for the electrode membrane. )

  In this invention, since the said release film is excellent in a softness | flexibility, such a lamination process can be performed by a roll-to-roll system, and productivity can be improved. Furthermore, since the combination of the release layer and the base material layer is excellent in dimensional stability, the release film can be prevented from being stretched by tension even in the roll-to-roll method. Therefore, the layer containing the ion exchange resin can be wound up in a roll shape without peeling off, and productivity can be improved.

  The laminate obtained in the laminating step is subjected to an adhesion step. In the adhesion step, the membrane electrode assembly is prepared by closely adhering the electrolyte membrane and the electrode film respectively laminated on the release layers of the first and second release films.

  The adhesion between the electrolyte membrane and the electrode membrane is usually brought about by thermocompression bonding. The heating temperature is, for example, about 80 to 200 ° C, preferably about 100 to 180 ° C, and more preferably about 110 to 150 ° C. The pressure is, for example, about 0.1 to 20 MPa, preferably about 0.5 to 15 MPa, and more preferably about 1 to 10 MPa.

  The composite (the electrolyte layer and the electrode film are in close contact with each other) in the adhesion process is subjected to a peeling process in which the release film is peeled from the layer containing the ion exchange resin (electrolyte film and / or electrode film). The In the present invention, even a laminate that has undergone the drying process or thermocompression treatment described above has an appropriate peel strength, so that the release film and the layer containing the ion exchange resin do not peel in the lamination process or the adhesion process. In the peeling step, the release film can be easily peeled off and workability can be improved.

  The peel strength between the release layer of the release film and the layer containing the ion exchange resin (particularly, the peel strength of the laminate in the peeling step) is, for example, 0.1 to 20 mN / mm, preferably 0.5 to 15 mN. / Mm, more preferably about 1 to 13 mN / mm (particularly 2 to 10 mN / mm). If the peel strength is too high, the peeling work becomes difficult, and if it is too low, workability in the laminating step and the adhesion step is lowered.

  In this specification, the peel strength can be measured by a method in which the film is allowed to stand at 23 ° C. and 50% RH for 1 hour or longer and then peeled by 180 ° under the condition of 300 mm / min.

  Further, with respect to the electrolyte membrane from which the first release film has been peeled off, an electrode film (second release film) is further formed on the release layer of the third release film, similarly to the adhesion step and the release step. When the electrode film for the anode electrode is used, the electrode film of the cathode electrode film) is adhered and peeled off, and the fuel gas supply layer and the air supply are provided on each electrode film by a conventional method. A membrane electrode assembly (MEA) is obtained by laminating the layers.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The peelability of the release films obtained in Examples and Comparative Examples was evaluated by the following method.

[Coating amount]
A release film was cut into 10 cm × 25 cm to prepare a sample. After measuring the weight of the sample, the release layer was eluted from the substrate layer by using tetrahydrofuran and peeled off, and then wiped off to completely remove the release layer from the substrate layer. The weight of the base material layer from which the release layer was peeled was measured, and the coating amount was calculated based on the weight reduction amount.

[Average thickness]
The average thickness of the release layer was calculated based on the coating amount and density of the release layer.

[Average roughness Ra]
In accordance with JIS B0601 (2001), the roughness of the release layer surface of the film was measured using a non-contact surface shape measurement system (“VertScan 2.0” manufactured by Ryoka System Co., Ltd.), and the number of measurements N = 5 The average value of was used.

[Adhesion of release layer]
On the surface of the release layer of the release film under conditions of a temperature of 23 ± 5 ° C. and a relative humidity of 50 ± 10%, a tape having a length exceeding 50 mm (“Cello Tape (registered trademark) CT405AP-24” manufactured by Nichiban Co., Ltd.) ) And rubbed the tape firmly with the fingertips to make contact with the release layer. After confirming that the entire tape is uniformly attached to the release layer, within 5 minutes, grasp the end of the tape at an angle as close to 60 ° as possible with respect to the surface of the release layer, and take 0.5 to 1 second. Pulled apart. The part to which the tape was attached was observed, and the adhesion was evaluated according to the following criteria.

○… No peeling at all △… Partial peeling ×… The whole surface is peeled off.

[Peelability]
The electrolyte membranes obtained in the examples and comparative examples were cut into a size of 150 mm × 15 mm, and a double-sided tape (“Nystack NW-15” manufactured by Nichiban Co., Ltd.) was bonded onto the ion exchange membrane, and 23 ° C., 50 RH. After leaving at 1% for 1 hour or longer, 180 ° peeling was performed under the condition of 300 mm / min.

[Fuel cell characteristics]
Hydrogen and oxygen were used as the supply gas to each cell. All the supply gases were humidified by bubbling to a supply pressure of 2.5 atm, and operated with the temperature applied to the single cell maintained at 70 ° C. The cell voltage was measured up to 1000 hours at a current density of 1 A / cm ² .

[Production Example 1 of Release Film]
Cyclic olefin resin (“TOPAS 6013S” manufactured by Polyplastics Co., Ltd.) was stirred and dissolved in toluene to prepare a coating solution having a solid concentration of 15% by weight.

  A biaxially stretched polyethylene terephthalate film (“Lumirror 50T60” manufactured by Toray Industries, Inc., thickness 50 μm, centerline average roughness Ra0.010 to 0.015 μm) is used as the base layer of the release film. Corona discharge treatment was performed. The surface subjected to the corona discharge treatment is coated with the coating solution by the Mayer bar coating method, and dried at a temperature of 100 ° C. for 1 minute to form a release layer. The dry thickness of the release layer is 0.3 μm, A release film A having an average surface roughness R of 0.010 μm was obtained.

[Production Example 2 of Release Film]
A release film B having an average surface roughness Ra of 0.009 μm was obtained in the same manner as in Production Example 1 except that the dry thickness of the release layer was changed to 0.1 μm.

[Production Example 3 of Release Film]
As a base material layer, a biaxially stretched polyethylene terephthalate film (“Teonex Q65WFA, surface-treated product” manufactured by Teijin DuPont Films Ltd., thickness 125 μm, centerline average roughness Ra 0.001 to 0.003 μm) is used as a release layer. A release film C having an average surface roughness Ra of 0.003 μm was obtained in the same manner as in Production Example 1 except that the dry thickness was changed to 0.5 μm.

[Production Example 4 of Release Film]
A biaxially stretched polyethylene terephthalate film ("Embret S50" manufactured by Unitika Ltd., thickness 50 µm, centerline average roughness Ra 0.025 to 0.030 µm) is used as the base material layer, and the dry thickness of the release layer is 2 A release film D having an average surface roughness Ra of 0.022 μm was obtained in the same manner as in Production Example 1 except that the thickness was changed to 0.5 μm.

  Table 1 shows the results of measuring the center line average roughness of the release films A to C and the adhesiveness of the release layer.

  As is clear from the results in Table 1, since the release film B has a thin release layer, the release layer has low adhesion.

Example 1
(Manufacture of electrolyte membrane)
On the release layer of the release film A, an ion exchange resin solution (“Nafion (registered trademark) DE2020CS” manufactured by DuPont, water-alcohol dispersion of ion exchange resin, solid content concentration 20 as an ion exchange resin solution) The ion exchange resin solution is cast on the release layer using a doctor blade, the coating film is dried in an oven at 130 ° C., and the ion exchange resin layer as an electrolyte membrane is prepared. (Thickness 20 μm) was formed.

(Manufacture of electrode film for anode electrode)
10 parts by weight of Pt-Ru-supported carbon (“TEC66E50” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., Pt / Ru molar ratio 1/1) and 40 parts by weight of the ion-exchange resin solution were mixed by a ball mill to form an electrode film for an anode electrode It was set as the coating liquid. On the release layer of the release film A, the anode electrode catalyst coating solution was applied using a doctor blade and then dried at 80 ° C. for 10 minutes to form an anode electrode electrode film having a thickness of 30 μm. .

(Manufacture of electrode film for cathode electrode)
7 parts by weight of Pt-supported carbon (“TEC10E50E” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and 35 parts by weight of the ion exchange resin solution were mixed by a ball mill to obtain a coating solution for a cathode electrode catalyst. On the release layer of release film A, a cathode electrode catalyst coating solution was applied using a doctor blade and then dried at 80 ° C. for 10 minutes to form a cathode electrode film having a thickness of 30 μm. .

(Manufacture of fuel cells)
Between the electrode film for the anode electrode and the electrode film for the cathode electrode, the electrolyte film is laminated in the order of anode electrode / electrolyte film / cathode electrode, and bonded by hot press at 120 ° C. to form a membrane electrode assembly (MEA) It was. The release film was peeled off, and carbon paper was disposed as gas diffusion electrodes on both ends of the obtained MEA and incorporated into a single cell to obtain a cell for evaluation.

Example 2
An MEA was produced in the same manner as in Example 1 except that the release film C was used, and an evaluation cell was obtained.

Example 3
An MEA was produced in the same manner as in Example 1 except that the release film D was used, and an evaluation cell was obtained.

Comparative Example 1
An MEA was prepared in the same manner as in Example 1 except that a commercially available fluorine-based film (“Nitoflon 900UL” manufactured by Nitto Denko Corporation, polytetrafluoroethylene (PTFE) film) was used as the release film, and for evaluation. Cell.

Comparative Example 2
An MEA was prepared in the same manner as in Example 1 except that a commercially available polyolefin film (“Opylan X88B” manufactured by Mitsui Chemicals, Inc., poly-4-methyl-pentene-1) was used as the release film. I got a cell.

  Table 2 shows the results of evaluating the peelability and fuel cell characteristics of the MEAs obtained in the examples and comparative examples.

  As is clear from the results in Table 2, the MEAs of the examples have moderate peelability, excellent workability, and excellent battery characteristics. On the other hand, the MEA of Comparative Example 1 has high peelability, low workability, and low battery characteristics. Moreover, the MEA of Comparative Example 2 has a slightly high peelability and low battery characteristics.

  The release film of the present invention is used for producing a membrane electrode assembly of a polymer electrolyte fuel cell.

[Production Example 3 of Release Film]
As a base material layer, a biaxially stretched polyethylene naphthalate film (“Teonex Q65WFA, surface-treated product” manufactured by Teijin DuPont Films Ltd., thickness 125 μm, centerline average roughness Ra 0.001 to 0.003 μm) is used as a release layer. A release film C having an average surface roughness Ra of 0.003 μm was obtained in the same manner as in Production Example 1 except that the dry thickness was changed to 0.5 μm.

Claims (11)

  A release film for producing a membrane / electrode assembly of a polymer electrolyte fuel cell, comprising a base material layer, laminated on at least one surface of the base material layer, and formed of a cyclic olefin resin A release film comprising a release layer, wherein the centerline average roughness Ra of the release layer surface is 0.001 to 0.05 μm, and the average thickness of the release layer is 0.2 to 5 μm.   The release film according to claim 1, wherein the release layer is a layer formed by coating.   The release film according to claim 1 or 2, wherein the center line average roughness Ra of the surface of the base material layer is 0.001 to 0.05 µm.   The release film according to any one of claims 1 to 3, wherein the base material layer is formed of at least one selected from the group consisting of polyolefins, polyvinyl alcohol polymers, polyesters, polyamides, and cellulose derivatives.   The electrolyte membrane and / or electrode membrane containing an ion exchange resin is laminated thereon to produce a membrane / electrode assembly, which is then a film for peeling from the membrane / electrode assembly. Release film.   A laminate for producing a polymer electrolyte fuel cell, wherein the release film according to any one of claims 1 to 5 is laminated on a release layer of the release film, and an ion exchange resin A laminate formed of a layer containing   The laminate according to claim 6, wherein the layer containing an ion exchange resin is an electrolyte membrane and / or an electrode membrane.   A membrane of a polymer electrolyte fuel cell through a laminating step of laminating an electrolyte membrane and / or an electrode membrane containing an ion exchange resin on the release layer of the release film according to any one of claims 1 to 5. A method for producing an electrode assembly.   9. The laminating step includes laminating an electrolyte membrane on the release layer of the first release film by coating, and laminating an electrode film on the release layer of the second release film by coating. the method of.   The method according to claim 9, further comprising an adhesion step of preparing a membrane electrode assembly by closely adhering the electrolyte membrane and the electrode membrane respectively laminated on the release layers of the first and second release films.   The method according to any one of claims 8 to 10, further comprising a peeling step of peeling the release film from the electrolyte membrane and / or the electrode membrane.