JP2009224294A - Manufacturing method for fuel cell separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily and inexpensively manufacturing a fuel cell separator capable of satisfying various requirements such as conductivity, corrosion resistance, mechanical strength, and thinning. <P>SOLUTION: In the manufacturing method for the fuel cell separator, at least one of a recessed groove 23 for supplying gas and a recessed groove 24 for cooling which are formed on a metal base plate 21 is formed through: (1) a process of filling an electrically conductive resin ink including an electrically conductive filler onto an engraved plate shaped with a convex pattern plate and hardening it, thereby manufacturing a convex electrically conductive resin; (2) a process of applying the electrically conductive resin ink on a metal base plate 21, thereby forming an electrically conductive resin ink layer; (3) a process of setting the engraved plate having the convex electrically conductive resin on the electrically conductive resin ink layer; (4) a process of hardening the electrically conductive resin ink layer; and (5) a process of separating the engraved plate from the convex electrically conductive resin and transcribing the convex electrically conductive resin on the electrically conductive resin ink layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a separator for a fuel cell, and more particularly to a method for manufacturing a separator for a fuel cell having a metal substrate.

A fuel cell is a power generation method that converts the chemical energy of fuel into electrical energy by electrochemically reacting a fuel such as hydrogen with an oxidant such as air, and has high power generation efficiency, excellent quietness, and atmospheric pressure. It is expected as new energy because of the advantages such as NOx and SOx that cause pollution and low CO ₂ emission that causes global warming.
Examples of its application include a variety of uses and scales such as long-term power supply for portable electrical devices, stationary power generation hot water supply machines for cogeneration, and fuel cell vehicles.

  The types of fuel cells are classified into solid polymer type, phosphoric acid type, molten carbonate type, solid oxide type, alkaline type, etc., depending on the electrolyte used. Is also different. A polymer electrolyte fuel cell using a cation exchange membrane as an electrolyte can operate at a relatively low temperature, and the internal resistance can be reduced by reducing the thickness of the electrolyte membrane, so that high output and compactness are possible. .

  In a fuel cell, separators are arranged on both sides of a membrane electrode assembly (hereinafter sometimes referred to as MEA) in which an anode (fuel electrode) is provided on one surface of an electrolyte membrane and a cathode (oxidant electrode) is provided on the other surface. It has a structure in which one or more single battery cells are stacked.

FIG. 4 is a cross-sectional explanatory view of one embodiment of a membrane electrode assembly in which electrode catalyst layers are formed on both surfaces of the electrolyte membrane.
The membrane electrode assembly 12 is formed by joining and laminating the catalyst layers 2 and 3 on both surfaces of the electrolyte membrane 1 by a conventional method.

FIG. 5 is an exploded sectional view showing the configuration of an embodiment of a single cell of a polymer electrolyte fuel cell equipped with the membrane electrode assembly 12.
As shown in FIG. 4 and FIG. 5, a conventional unit cell of a polymer electrolyte fuel cell (PEFC) has a solid polymer electrolyte membrane 1 (perfluorocarbon sulfonic acid membrane) formed on a carbon black particle as a catalyst substance [mainly. [Platinum (Pt) or platinum group metal (Ru, Rh, Pd, Os, Ir)] supported between the air electrode side catalyst layer 2 and the fuel electrode side catalyst layer 3, and the air electrode side catalyst layer 2 and the fuel. There is provided a membrane electrode assembly 12 that constitutes an air electrode 6 and a fuel electrode 7 by sandwiching an electrode side catalyst layer 3 between an air electrode side gas diffusion layer 4 and a fuel electrode side gas diffusion layer 5.
Then, facing the air electrode side gas diffusion layer 4 and the fuel electrode side gas diffusion layer 5, there is provided a concave groove (gas channel) 8 for circulating the reaction gas, and a cooling water channel 9 for circulating cooling water on the opposing main surface. A single cell is configured by being sandwiched by a pair of separators 10 made of a conductive and gas-impermeable material.
An oxidant such as air is supplied to the air electrode 6, and a fuel gas containing hydrogen or an organic fuel is supplied to the fuel electrode 7 to generate electricity.

That is, when a reaction gas is supplied to each of the fuel electrode 7 and the air electrode 6, an electrochemical reaction of the following formulas (1) and (2) occurs on the surface of the catalyst particles in each electrode catalyst layer to generate DC power. appear.
Fuel electrode side: 2H ₂ → 4H ⁺ + 4e ⁻ Formula (1)
Air electrode side: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O Formula (2)
The oxidation reaction of hydrogen molecules (H ₂ ) occurs on the fuel electrode side, and the reduction reaction of oxygen molecules (O ₂ ) occurs on the air electrode side, so that H ⁺ ions generated on the fuel electrode 7 side are solid polymer electrolytes. The film 1 moves toward the air electrode 6 side, and e ⁻ (electrons) move to the air electrode 6 side through an external load.
On the other hand, on the air electrode 6 side, oxygen contained in the oxidant gas reacts with H ⁺ ions and e ⁻ that have moved from the fuel electrode 7 side to generate water. Thus, the polymer electrolyte fuel cell generates a direct current from hydrogen and oxygen to generate water.

As described above, the surface of the separator 10 facing the fuel electrode 7 is provided with the concave groove 8 for allowing the fuel to flow.
In addition, a concave groove 8 for allowing the oxidant gas to flow is provided on the surface of the separator 10 facing the air electrode 6.

  As the fuel, a reformed gas (or hydrogen gas) mainly composed of hydrogen, an aqueous methanol solution, or the like is used.

However, the reduction reaction on the air electrode side (4-electron reduction of oxygen molecules (O ₂ )) is difficult, and the following electrochemical reaction (2-electron reduction of oxygen molecules (O ₂ )) occurs as a side reaction on the air electrode side. A lot of H ₂ O ₂ is generated. When Fe (II) or the like is present as an impurity, H ₂ O ₂ is decomposed by the catalytic action, and OH · (OH radical) and OH ⁻ are generated.

Air electrode side: O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O ₂
H ₂ O ₂ + Fe (II) → OH · + OH ⁻ + Fe (III)
The generated OH · (OH radical) has a large oxidizing power and oxidizes and decomposes and degrades the solid polymer electrolyte membrane 1.

  The direct methanol fuel cell is a fuel cell that directly supplies an aqueous methanol solution to the MEA, and does not require a gas reformer and can use an aqueous methanol solution with a high volume-based energy density. Development of portable electric devices (for example, portable music players, mobile phones, notebook computers, portable televisions, etc.) as portable power sources is expected.

As a power generation method of the direct methanol fuel cell, methanol and oxygen (included in the oxidant gas) are passed through the electrolyte membrane 1 and the surface of the catalyst particles contained in the fuel electrode side catalyst layer 3 and the air electrode side catalyst layer 2. The method of causing the electrochemical reaction of the following formulas (3) to (5) is used.
Fuel electrode side reaction: CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ Formula (3)
Air electrode side reaction: 6H ⁺ + (3/2) O ₂ + 6e ⁻ → 3H ₂ O Formula (4)
Total reaction: CH ₃ OH + (3/2) O ₂ → CO ₂ + 2H ₂ O Formula (5)

On the fuel electrode 7 side, the supplied methanol and its aqueous solution are dissociated into carbon dioxide, hydrogen ions, and electrons by the reaction of the formula (3) in the fuel electrode side catalyst layer 3.
At this time, a small amount of intermediate products such as formic acid are also generated.

  The generated hydrogen ions move in the electrolyte membrane 1 from the fuel electrode 7 to the air electrode side 6, and in the air electrode catalyst layer 2, react with oxygen gas and electrons supplied from the air according to the equation (4), Water is produced.

  The voltage of the unit battery cell is theoretically about 1.2 V in the vicinity of room temperature, but methanol crossover or hydrogen that moves in the electrolyte membrane 1 to the air electrode side 6 without electrochemical reaction at the fuel electrode 7 or hydrogen. The resistance is substantially 0.85 to 1.0 V due to the resistance when ions pass through the electrolyte membrane 1.

  In practice, the current density is set so that the voltage is about 0.3 to 0.6 V under continuous operation conditions. Therefore, when actually used as a power source, a plurality of voltages are used so that a predetermined voltage can be obtained. It is necessary to use unit battery cells (the single cells) connected in series.

As the battery structure, for the purpose of increasing the output density and making the entire fuel cell compact, a structure in which a plurality of single battery cells in which the MEA 12 is sandwiched between the separators 10 is stacked is used.
Depending on the power required, the number of stacks varies. Generally, a portable power supply for portable electric devices has several to about 10 sheets, a stationary electric and hot water supply machine for cogeneration has about 60 to 90 sheets, and an automotive application has 250 to 400 sheets. It is said to be about a sheet.
In order to increase the output, the number of stacks must be increased, and the thickness and cost of a single cell greatly affect the size and price of the fuel cell body.

  The fuel cell separator is a holding support that forms a unit cell of the fuel cell, and serves as a supply path for supplying fuel (hydrogen, methanol, etc.) and oxygen. The separator surface facing the fuel electrode is provided with a concave groove which is a fuel gas flow path for allowing the fuel to flow. In addition, a concave groove which is an oxidant gas flow path for allowing the oxidant gas to flow is provided on the separator surface facing the air electrode.

  In addition to controlling the supply of fuel and oxygen, the fuel cell separator also has a role as a current collector. Therefore, excellent conductivity is required so that the overall volume resistance is small and the contact resistance with the MEA is low. These are also exposed to reducing hydrogen gas, oxidant gases such as air, cooling media such as cooling water, and other reaction by-products (formic acid, water vapor, etc.), and are also subject to electrochemical reactions due to energization. Corrosion resistance is also an important property. In addition, it plays a major role in removing reaction products such as water and preventing external leakage of fuel.

The base material for the fuel cell separator can be roughly classified into a non-metallic type and a metallic type. Non-metallic separators include carbon-based materials such as dense carbon graphite (Patent Document 1) and resin materials. Carbon-based materials are excellent in corrosion resistance, but are difficult to reduce in thickness due to poor mechanical resistance. In addition, it is difficult to press work, and as a result of forming the flow path and the manifold by cutting, the processing cost increases and there is a problem in mass productivity.
Therefore, by using resin materials, the problems of gas impermeability and workability are solved to some extent, but it is difficult to develop conductivity unless conductive filler is mixed, and too much conductive filler is mixed. It is difficult to ensure sufficient gas impermeability.

  Examples of the material for the metal separator include stainless steel (SUS), titanium, and aluminum (Patent Document 2). Since these materials are excellent in strength and ductility, they are easy to press for molding flow paths and manifolds, have low processing costs, and are excellent in mass productivity. Furthermore, it is possible to use a metal with a thin plate thickness, and there is an effect that the mass and volume of the fuel cell stack can be reduced.

However, the metal separator has a problem in corrosion resistance in the environment where the fuel cell is used.
When the potential of the separator substrate is in the active state region and the overpassive region, the corrosion of the metal is promoted, and the contact resistance between the separator and the MEA is increased. In addition, when the eluted metal ions from the separator are captured by the electrolyte membrane, the proton conductivity of the electrolyte membrane decreases.
Further, when the eluted metal ions are present, radical chemical species such as hydrogen peroxide are generated at the air electrode, and the electrolyte membrane is also deteriorated by the action of the radical chemical species.
When the potential of the separator substrate is in a passive region, the progress of corrosion is small, but a passive film grows. Usually, the passive film is composed of hydroxide, oxyhydroxide, oxide or the like. Since most of these compounds have poor electrical conductivity, the electrical resistance increases and the battery performance deteriorates as the passive film of the metal separator grows.

As a measure for improving the metal separator, a method of coating a noble metal having high conductivity and corrosion resistance by plating, sputtering or the like (Patent Documents 3 and 4) has been reported.
However, since a considerable amount of metal is required to coat the entire separator surface with a film thickness that does not cause pinholes, there is a concern about cost problems.
Japanese Patent Laid-Open No. 2001-6703 JP 2002-190305 A JP 2001-297777 A JP 2003-338296 A

  The object of the present invention is to consider the problems in the background art described above, and by using a metal as a separator substrate and forming a resin layer mixed with a conductive filler on the surface, conductivity, corrosion resistance, mechanical strength, thinness It is an object of the present invention to provide a method for easily and inexpensively manufacturing a fuel cell separator that satisfies various required characteristics such as conversion.

According to the first aspect of the present invention, a concave groove for gas supply for supplying a reaction gas to the electrode is formed on one surface on the metal substrate, and a cooling refrigerant is supplied on the other surface. In the manufacturing method of the separator for a fuel cell formed by forming a concave groove for cooling,
At least one of the concave groove for gas supply and the concave groove for cooling is formed by using the following steps (1) to (5).
(1) A step of filling a conductive resin ink containing a conductive filler into an intaglio stamped from a convex mold and curing it to produce a convex conductive resin. (2) Conductivity on the metal substrate. Step of applying resin ink to form a conductive resin ink layer (3) Step of placing an intaglio plate having the convex conductive resin on the conductive resin ink layer (4) Curing the conductive resin ink layer (5) A step of peeling the intaglio from the convex conductive resin and transferring the convex conductive resin onto the conductive resin ink layer. The invention according to claim 2, wherein the intaglio It consists of silicone resin, The manufacturing method of the separator for fuel cells of Claim 1 characterized by the above-mentioned.
The invention according to claim 3 is the method for producing a separator for a fuel cell according to claim 1 or 2, wherein the conductive filler is carbon fiber, conductive powder or a mixture thereof.
According to a fourth aspect of the present invention, in the fuel cell according to any one of the first to third aspects, the depths of the concave groove for gas supply and the concave groove for cooling are 50 μm or more and 700 μm or less. It is a manufacturing method of a separator.
The invention according to claim 5 is that the metal substrate is formed using at least one material selected from the group consisting of pure iron, iron alloy, pure copper, copper alloy, aluminum, and aluminum alloy. It is a manufacturing method of the separator for fuel cells in any one of Claims 1-4 characterized by the above-mentioned.

  According to the present invention, a fuel cell satisfying various required characteristics such as conductivity, corrosion resistance, mechanical strength, and thinning is formed by using a metal as a separator substrate and forming a resin layer with a conductive filler on the surface. It is possible to provide a method for easily and inexpensively manufacturing the separator for use.

  Further, in the present invention, it is possible to provide a fuel cell separator that has a high mechanical strength due to the use of a metal substrate and is thin and lightweight while maintaining its robustness, and a conductive resin. Since it has a portion, it can have conductivity while ensuring high corrosion resistance without causing a decrease in conductivity due to oxide film growth, which is a concern for metal substrates. In addition, since a wet process can be used as a method for forming a conductive corrosion-resistant film, it is possible to manufacture a separator continuously and inexpensively without requiring expensive equipment as in the case of applying a dry process. Become.

  Furthermore, in the present invention, when the convex conductive resin formed by the intaglio is transferred, the convex conductive is passed through the conductive resin ink layer made of the conductive resin ink previously applied on the metal substrate. It is characterized by adhering resin. Thereby, the transfer of the convex conductive resin is facilitated, and the separator can be more easily manufactured. Further, since the convex conductive resin can be completely cured before the transfer, it is possible to prevent a dimensional change of the shape at the time of transfer and to reproduce a desired shape more accurately. In addition, the corrosion resistance of the metal substrate can be further improved, and the adhesion between the metal substrate and the conductive resin can be improved.

Hereinafter, the manufacturing method of the separator for fuel cells of this invention is demonstrated using drawing.
FIG. 1 is an explanatory view schematically showing a cross section of a main part of a fuel cell separator of the present invention.
As shown in FIG. 1, in the separator for a fuel cell of the present invention, a concave groove A23 for supplying a reaction gas on one surface of a metal substrate 21 supplies a coolant for cooling on the other surface. The concave groove B24 is formed by the conductive resin 22 configured to contain, for example, carbon powder as the conductive filler. Since the concave grooves 23 and 24 are respectively formed on both sides of the smooth metal substrate 21, the concave groove B 24 is formed without depending on the shape of the concave groove A23 as compared with the flow path formed by pressing. And an optimal design can be applied to each flow path. In addition, for example, by using a silicone resin for the intaglio, filling the intaglio with conductive resin ink, taking a mold, and transferring to a metal substrate (hereinafter also referred to as a silicone mold-making method), it is not possible with a normal printing method. It is possible to form a convex shape having a height of about several hundred μm.

  2A to 2C show a method for producing an intaglio in the present invention. The solution 26 made of silicone resin is poured onto the convex mold 25 having the same shape as the concave groove A and the concave groove B, and is peeled from the convex mold 25 after being cured. An intaglio 27 is formed.

  The material of the convex mold 25 is preferably a material such as metal or glass that is hard and not easily deformed, and is not affected by the solvent of the solution 26 made of, for example, a silicone resin. In addition, the convex shape may be a method of forming a resin on the surface of the substrate by a photolithography method or a method of forming a groove by processing the substrate itself. That's not the case.

  As a method of pouring the solution 26 made of silicone resin onto the convex mold 25, a necessary amount of silicone resin is arranged at the end of the convex mold 25, and pushed into the groove portion with a rod-shaped squeegee, while the convex mold 25 A method of processing the opposite surface of the surface smoothly or a method of filling by screen printing can be considered. Since the smoothness of the uneven surface of the intaglio 27 affects the dimensional accuracy during the transfer of the conductive resin onto the metal substrate 25, the method of forming the intaglio 27 needs to be a method that can form the back of the uneven surface of the intaglio 27 smoothly. There is.

  Since the intaglio 27 is formed of a silicone resin, it can have a certain degree of flexibility and can be easily peeled off when peeled from the convex mold 25. Further, the strength is required so that the uneven shape is not deformed during transfer of the conductive resin. As a method for curing the silicone resin filled in the intaglio plate 27, thermal curing, UV curing, or the like is conceivable. However, since it varies depending on the composition of the silicone resin, a sufficient curing condition may be appropriately selected. Upon curing, the silicone resin mold may not be able to reproduce the convex matrix shape due to dimensional changes such as curing shrinkage. Therefore, it is preferable to select a resin with as little dimensional change as possible.

FIG. 3 shows the concave groove transfer process of the present invention.
As shown in FIG. 3, the intaglio plates 27 and 28 are filled with the ink of the conductive resin 22, and the metal substrate 21 and the intaglio plates 27 and 28 are placed so that the concave and convex sides face each other. The conductive resin 22 is transferred onto the metal substrate 21 by a roll laminator having a mechanism for feeding out the base material while being sandwiched. On the metal substrate 21, a conductive resin ink is applied in advance to form a conductive resin ink layer 29, which is cured and integrated when a convex conductive resin is installed. The thickness of the conductive resin 22 formed on the metal substrate 21 varies depending on the distance (gap) between the rollers installed in the roll laminating apparatus and the pressing pressure, the thickness of the metal substrate 21, and the thickness of the intaglio plates 27 and 28. Moreover, you may arrange | position conductive resin only to a convex part by the said conditions.

  When transferring the convex conductive resin 22 filled in the intaglio plates 27 and 28, it is preferable that the convex conductive resin 22 is cured before transfer. When conductive resin ink containing solvent is cured at the same time as transfer, it takes time to cure because it is not possible to secure a discharge path for the solvent during transfer, and in the worst case, it becomes uncured or has a large dimensional change after drying / curing. It is expected to change.

Regarding the separator material, since the entire surface of the separator for a fuel cell of the present invention is covered with the above resin layer, it is not necessary to consider corrosion resistance. Therefore, in addition to workability, robustness, ease of handling for thinning, etc., it has physical strength, and it is versatile and easily available, and the material cost is low. Any material can be used in the present invention and is not particularly limited.
Examples of the metal substrate used in the present invention include a material selected from the group consisting of pure iron, iron alloy, pure copper, copper alloy, aluminum, and aluminum alloy. In order to reduce the weight of the fuel cell stack, an aluminum-based metal that is a metal material having a small specific gravity is preferable.

  The conductive corrosion-resistant film made of the conductive resin used in the present invention has sufficient resistance to a fuel cell fuel (hydrogen, reformed gas, methanol, etc.), an oxidant (oxygen or a mixed gas thereof), or a strong acidic atmosphere. The material must have sufficient conductivity. In the present invention, a conductive resin containing a conductive filler that is relatively simple and enables film formation in a short time is employed.

  The resin component constituting the conductive resin used in the present invention is a resin having sufficient corrosion resistance in a power generation environment, and is not particularly limited as long as wet coating is possible. Specifically, for example, a phenol resin, A mixture of one or more selected from epoxy resins, silicone resins, fluororesins, aromatic polyimide resins, polyamides, polyamideimides, polyethylene terephthalates, polyether ether ketones, and the like can be used. From the viewpoint of higher corrosion resistance, a fluororesin is preferable. For example, PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), ETFE (tetrafluoroethylene / ethylene copolymer) , PVDF (polyvinylidene fluoride), PCTFE (polychlorotrifluoroethylene), and ECTFE (chlorotrifluoroethylene-ethylene copolymer). The molecular weight represented by the weight average molecular weight of these resins is preferably larger considering mechanical strength as long as workability such as wet coating is not hindered, and is preferably 10,000 to 10,000,000, more preferably 20,000 to 5 million.

  As the conductive filler used in the present invention, a fibrous conductive filler or a powdered conductive filler is desirable in consideration of corrosion resistance, conductivity, price, and the like. Specific examples of the fibrous conductive filler include one or more fibrous carbons selected from carbon nanofibers, carbon nanotubes, and the like. The carbon fiber preferably has a powder resistance of 0.015 Ω · cm or less and a single fiber specific resistance of 1 mΩ · cm or less in order to ensure high conductivity.

  In the present invention, when the fibrous conductive filler and the powdered conductive filler are used in combination, the conductivity of the conductive resin film itself can be further reduced. The powdery conductive filler is not particularly limited as long as it has sufficient conductivity and has sufficient corrosion resistance in a power generation environment, and specifically, for example, acetylene black, vulcan, ketjen black One or more selected from carbon powders such as WC, TiC, metal carbides, TiN, TaN, etc., metal silicides such as TiSi, ZrMoSi, and corrosion-resistant metals such as Ag, Au, etc. Can be mentioned. The powdery conductive filler preferably has a powder resistance of 0.015 Ω · cm or less and a single specific resistance of 1 mΩ · cm or less in order to ensure high conductivity.

  A method of forming a through hole as a reactive gas path in a metal substrate is a chemical processing such as a wet etching method, a machining method such as a press method or a cutting method, or a processing method capable of partially removing the metal substrate such as electric discharge machining. If so, it is possible to apply. Considering productivity, it is preferable to use a press method or a wet etching method because a large area can be processed in one step.

  The size of the through hole and the concave groove varies depending on the type of fuel cell used, but a sufficient amount of fuel gas and oxidant gas for generating the necessary power is uniformly and stably supplied to the MEA. It is necessary. Therefore, in order to supply fuel gas and oxidant gas exhaustively to the power generation site, it is preferable to form a concave groove serving as a reaction gas flow path at least in a part of the separator, and to be uniform in the plane. In consideration of supply, it is more preferable to use a combination of a plurality of through-holes and a plurality of through-holes in a pattern flow path such as a meandering shape, a straight line shape, a grid shape, and a cylindrical shape, or a surface in contact with a power generation site.

  The solid content concentration in the conductive resin solution containing the conductive filler needs to be appropriately selected in consideration of corrosion resistance, mechanical low strength, electrical resistance, thinning, and the like. If the thickness of the convex portion formed by the conductive resin (= depth of the concave groove) is too thick, the conductivity may decrease too much, and if it is too thin, the flow resistance increases and the flow path of the reaction gas or cooling medium In view of corrosion resistance, low mechanical strength, electrical resistance, and thinning, the thickness is preferably 50 to 700 μm. In addition, when the conductive resin ink layer is formed on the bottom of the concave groove, if it is too thin, pinholes, mechanical strength and corrosion resistance may be reduced, so corrosion resistance, low mechanical strength, electrical resistance and thinning may be reduced. Considering the thickness, the thickness is preferably 10 μm or more.

  The ratio of the resin component and the conductive filler in the conductive resin varies depending on the material used. For example, when carbon nanofiber that is carbon fiber is mixed with acetylene black that is carbon powder in the conductive filler, When formed, the volume ratio of the conductive filler in the resin component is preferably 25 vol% or more. If the ratio of the conductive filler is less than 25 vol%, it is difficult to obtain sufficient conductivity.

Examples of the present invention will be described below.
<Production of convex mold>
First, a stainless steel plate (SUS304) having a thickness of 1 mm was used as a metal substrate, and a flow path shape having a desired intaglio groove on the surface was formed by cutting. A is a linear groove having a groove width of 1 mm, a depth of 0.5 mm, and a groove pitch of 2 mm, and B is a linear groove having a groove width of 2 mm, a depth of 0.5 mm, and a groove pitch of 3 mm. Convex molds A and B could be formed respectively.

<Production of silicone intaglio>
Liquid silicone rubber TSE3402 (made by Momentive Performance Material Japan GK) is mixed with liquid A and liquid B and sufficiently stirred. Next, TSE3402 is filled with an applicator on the surfaces of the convex molds A and B, and allowed to stand at room temperature for 48 hours to be cured. Silicone rubber intaglios A and B were obtained by peeling from the master mold with TSE3402 completely cured. The obtained silicone rubber intaglios A and B have a good uneven surface shape, and the back surface can be formed smoothly and uniformly, and the height from the bottom of the recess to the top of the convex is 0.5 mm, the top of the convex The thickness from the back surface to the back surface was 1 mm.

<Separator production>
As the conductive resin, Doutite A-3 (including 10 to 20 wt% carbon black) and Doutite C-3 (including 20 to 30 wt% carbon black) (two-component curable epoxy conductive resin manufactured by Fujikura Kasei Co., Ltd.) : Using Doteite A-3 / C-3 mixed at a ratio of 1: 1 and filling the silicone rubber intaglios A and B with an applicator, heat-treated in an oven at 150 ° C. for 30 minutes to give a conductive resin Cured. In addition, an aluminum plate (JIS 1050, thickness 1 mm) having a through hole formed by press punching at a desired position is prepared, and immersed for 40 seconds at room temperature using a surface treatment solution (Adeka C-74011 wt% solution). Then, after washing | cleaning with a pure water and drying a water | moisture content, it apply | coated Dotite A-3 / C-3 by thickness 10 micrometers with the applicator. In this, silicone rubber intaglios A and B filled with Doutite A-3 / C-3 were placed in a state where the silicone filling surface was in contact with the aluminum plate in a predetermined position, and a roll laminator (normal temperature, The silicone rubber intaglios A and B were fixed on the aluminum plate by a press pressure of 0.3 MPa. At that time, the gap between the upper and lower rolls of the roll laminator was 3 mm. Finally, the sample is heated in an oven at 150 ° C. for 30 minutes to cure the conductive resin applied on the aluminum plate, and then the silicone rubber intaglios A and B are peeled off to obtain a desired separator shape. I was able to.

  The fuel cell separator of the present invention has a concave groove A for supplying a reaction gas to an electrode on one surface on a metal substrate, and a concave shape for supplying a coolant for cooling on the other surface. In the fuel cell separator formed with the groove B, at least one of the concave grooves A and B is formed of a conductive resin containing a conductive filler, and the concave groove A and Easy by forming at least one of B by transferring the convex shape onto the metal substrate after filling the intaglio stamped from the convex mold with the conductive resin ink containing the conductive filler In addition, a channel shape with a thick film pattern of about 50 μm to about 500 μm can be formed on both sides of the separator. In addition, the use of powdered conductive fillers can improve the conductivity of the conductive corrosion-resistant coating itself, and since it uses a metal substrate, it has high mechanical strength and can be reduced in thickness and weight while maintaining robustness. On the other hand, it is possible to maintain high conductivity while ensuring high corrosion resistance without incurring a decrease in conductivity due to oxide film growth, which is a concern when using a metal substrate because it is via a conductive resin. The effect was able to be acquired. Moreover, the separator could be more easily produced by previously applying a conductive resin ink between the separator metal substrate and the convex conductive resin, and curing and integrating the conductive resin ink layer.

It is explanatory drawing which shows typically the principal part cross section of the separator for fuel cells of this invention. It is sectional drawing for demonstrating the manufacturing method of the intaglio in this invention. It is sectional drawing for demonstrating the transfer process of the concave groove in this invention. It is sectional explanatory drawing of one embodiment of the membrane electrode assembly which formed the electrode catalyst layer on both surfaces of the electrolyte membrane. FIG. 5 is an exploded cross-sectional view showing the configuration of a single cell of a fuel cell equipped with the membrane electrode assembly shown in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte membrane 2 Air electrode side electrode catalyst layer 3 Fuel electrode side electrode catalyst layer 4 Air electrode side gas diffusion layer 5 Fuel electrode side gas diffusion layer 6 Air electrode 7 Fuel electrode 8 Concave groove (gas flow path)
9 Cooling water channel 21 Metal substrate 22 Conductive resin 23 Concave groove A (reactive gas channel)
24 Concave groove B (cooling solvent flow path)
25 Convex mold 26 Solution made of silicone resin 27 Intaglio A (reaction gas flow path side)
28 Intaglio B (cooling solvent flow path side)
29 Conductive resin ink layer

Claims (5)

A concave groove for gas supply for supplying the reaction gas to the electrode is formed on one surface on the metal substrate, and a concave groove for cooling for supplying the cooling refrigerant is formed on the other surface. In the manufacturing method of the separator for a fuel cell,
At least one of the concave groove for gas supply and the concave groove for cooling is formed by using the following steps (1) to (5).
(1) A step of filling a conductive resin ink containing a conductive filler into an intaglio stamped from a convex mold and curing it to produce a convex conductive resin. (2) Conductivity on the metal substrate. Step of applying resin ink to form a conductive resin ink layer (3) Step of placing an intaglio plate having the convex conductive resin on the conductive resin ink layer (4) Curing the conductive resin ink layer (5) Step of peeling the intaglio from the convex conductive resin and transferring the convex conductive resin onto the conductive resin ink layer   The method for producing a fuel cell separator according to claim 1, wherein the intaglio is made of a silicone resin.   The method for producing a fuel cell separator according to claim 1 or 2, wherein the conductive filler is carbon fiber, conductive powder, or a mixture thereof.   The method for producing a fuel cell separator according to any one of claims 1 to 3, wherein the depth of the gas supply concave groove and the cooling concave groove is 50 µm or more and 700 µm or less.   The metal substrate is formed using at least one material selected from the group consisting of pure iron, iron alloy, pure copper, copper alloy, aluminum, and aluminum alloy. The manufacturing method of the separator for fuel cells in any one.

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