JP2011171111A - Manufacturing method of separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for productively manufacturing a separator for a fuel cell hardly clogging a flow channel due to water produced at power generation, suppressing decrease in power generation efficiency and increase in contact resistance, having excellent mechanical strength and gas non-permeability, and superior in homogeneity. <P>SOLUTION: The manufacturing method of a separator 1 for a fuel cell is provided with a process for manufacturing a dense member 31 by making into a sheet-like shape and press-forming a slurry-like dense part forming material containing carbonaceous powder for dense part formation and a thermosetting resin binder for dense part formation, a process for manufacturing a preliminary molding sheet 21 for porous part formation by making a slurry-like porous part forming material containing carbonaceous powder for porous part formation, a resin binder for porous part formation and a thickener into a sheet-like shape, and a process for filling the dense member and the preliminary molding sheet for porous part formation and integrating by hot-press forming so as a molding surface and the preliminary molding sheet for porous part formation to face each other in a molding die having the molding surface corresponding to a gas flow channel shape. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a fuel cell separator.

  Fuel cells convert the chemical energy of fuel directly into electrical energy, which has high conversion efficiency to electrical energy and low noise and vibration, so it can be used in various fields such as portable devices, automobiles, railways, and cogeneration. Future development is expected as a power source.

  Among the fuel cells, the polymer electrolyte fuel cell is sandwiched between an anode electrode plate and a cathode electrode plate carrying a catalyst such as platinum on both sides of an ion conductive polymer membrane (ion exchange membrane), and both outer sides thereof. The unit cell is composed of a single cell having a plate-like separator disposed thereon, and is composed of a stack in which several tens to several hundreds of the single cell are stacked, and two current collectors provided on the outside thereof. Typically, there is a ribbed electrode system in which grooves as flow paths for fuel gas such as hydrogen and oxidant gas such as air are engraved on the separator side surface of each electrode plate, and on the surface of each separator. There is a rib-type separator system provided (see, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2000-21421)).

  The plate separator requires a high degree of gas impermeability in order to supply the fuel gas and the oxidant gas to the electrode in a completely separated state, and in order to increase power generation efficiency, the internal resistance of the battery Is required to have high conductivity. In addition, when forming a stack, it is necessary to strongly tighten the single cells so that they are in close contact with each other, so that it is required to have high material strength, and when mounted in an automobile, vibration, impact, temperature change, etc. Material properties that suppress cracks and breakage caused by expansion and contraction are required.

  Carbon-based materials have been used for separators that require such material characteristics, and carbon-resin curable molding that combines and integrates carbon powders such as graphite with thermosetting resin as a binder. The body is preferably used.

  By the way, in the fuel cell separator, since the groove that is the gas flow path is likely to be blocked by the water generated during power generation, as a means for solving this technical problem, the groove surface that is the gas flow path has been conventionally used. Methods such as providing short fibers having water repellency (see, for example, Patent Document 2) and hydrophilization have been proposed. In these methods, post-treatment is required after hydrophilization. In addition, there has been a technical problem that the battery performance deteriorates due to an increase in the contact resistance of the separator.

JP 2000-21421 A JP-A-8-130024

  In order to solve the above technical problem, the present inventors diligently studied. As a result, a fuel cell separator having a porous portion and a dense portion, in which at least a part of the wall surface of the gas channel is formed by the porous portion. If this is the case, the water generated during power generation can be diffused in the porous part, so that the gas flow path is less likely to be blocked, and by forming the dense part together with the porous part, it is reduced with the formation of the porous part. Since the strength and gas impermeability can be compensated for by the dense part, it was conceived that an excellent fuel cell separator can be obtained.

  Therefore, a method of compressing and heat-curing the dense part forming raw material and the porous part forming raw material in advance and then heat-compressing in a mold was considered. It has been found that the bonding strength is low and the contact resistance is generated at the interface between the porous portion and the dense portion because the portion and the dense portion are not sufficiently joined.

  In addition, as described in Patent Document 1, a method of manufacturing a separator material for a fuel cell is generally a method in which graphite powder and a thermosetting resin are mixed, dried, pulverized, and then molded with a mold. However, after drying and pulverizing the raw material mixture, it requires a certain amount of time and processing time, such as filling the powdered pulverized product into a mold, and in particular, a graphite powder having an average particle size of 50 μm or more. When a slurry-like raw material mixture is obtained by mixing with a thermosetting resin, it has been found that a slurry-like raw material mixture having excellent dispersibility of the graphite powder is difficult to obtain because the graphite powder easily settles. In recent years, especially in automobile applications, there is a strong demand for downsizing of the fuel cell stack and thinning of the separator. However, if the dispersibility of the graphite powder in the slurry-like raw material mixture is lowered, the soot (void) after molding is reduced. Or a variation in thickness, making it difficult to obtain a homogeneous separator.

  Under such circumstances, the present invention is less likely to block the flow path due to water generated during power generation, suppresses a decrease in power generation efficiency and an increase in contact resistance, and has excellent strength and gas impermeability. The object of the present invention is to provide a method for producing a fuel cell separator excellent in homogeneity with high productivity.

  In order to solve the above technical problem, the present inventors have further studied, and as a method for producing a fuel cell separator, a slurry containing carbonaceous powder for forming a dense part and a thermosetting resin binder for forming a dense part. Slurry comprising a step of producing a dense member by forming a dense portion forming material into a sheet and press-molding, a porous portion forming carbonaceous powder, a porous portion forming resin binder, and a thickener Forming a porous part forming material into a sheet by forming the porous part forming material into a sheet; and a forming die having a forming surface corresponding to the shape of the gas flow path. Gas channel wall surface by filling the dense member and the porous part forming sheet so as to face the mass part forming preformed sheet, and subjecting them to hot press molding and integration. At least one of Has been found to be able to solve the above technical problem by adopting a method for producing a fuel cell separator having a porous part and a dense part, wherein the present invention is completed. It came to.

That is, the present invention
(1) A method for producing a fuel cell separator having a porous part and a dense part, wherein at least a part of a wall surface of a gas flow path is formed by a porous part,
Forming a dense member by forming a slurry-like dense part forming material containing a dense part-forming carbonaceous powder and a dense part-forming thermosetting resin binder into a sheet, and press-molding; and
A process for preparing a porous part forming preform sheet by forming a slurry-like porous part forming material containing a porous part forming carbonaceous powder, a porous part forming resin binder, and a thickener. When,
The dense member and the porous part forming preform sheet so that the molding surface and the porous part forming preform sheet are opposed to each other in a molding die having a molding surface corresponding to the gas flow path shape. Filling and integrating by hot pressing
A method for producing a separator for a fuel cell, characterized by:
(2) The method for producing a fuel cell separator according to the above (1), wherein the thickener contained in the slurry-like porous portion forming material is a cellulose-based thickener,
(3) Production of fuel cell separator according to (1) or (2) above, wherein the volume average particle size of the porous part forming carbonaceous powder contained in the slurry-like porous part forming material is 50 to 500 μm. Method,
(4) The method for producing a fuel cell separator according to any one of (1) to (3), wherein the slurry-like dense part forming material or the porous part forming material is formed into a sheet by a doctor blade method,
(5) The pressurizing force at the time of producing the dense member is 20 to 100 MPa, and the pressurizing force at the time of hot pressing the dense member and the porous part forming preformed sheet is 1 MPa or more and less than 20 MPa ( A method for producing a fuel cell separator according to any one of 1) to (4),
(6) The above-mentioned (1) to (1) to which a hydrophilization treatment step is further performed as a subsequent step of the step of filling the dense member and the porous portion forming sheet into a molding die and hot pressing to integrate them. The manufacturing method of the separator for fuel cells in any one of (5) is provided.

According to the present invention, since at least a part of the wall surface of the gas flow path constituting the obtained fuel cell separator is formed by the porous portion, diffusion of water generated during power generation is facilitated, and the gas flow It is possible to suppress the blockage of the road, to suppress a decrease in power generation efficiency, and to suppress an increase in contact resistance.
In addition, according to the present invention, the obtained fuel cell separator has a dense portion together with the porous portion, whereby excellent strength and gas impermeability can be obtained.
Furthermore, according to the present invention, a slurry-like molding material is formed into a sheet to form a dense part and a porous part, so that a dried product of the dense part forming material and the porous part forming material (raw material mixture) is pulverized. Further, the filling process into the mold can be performed more easily because the process can be omitted and the sheet can be supplied as a sheet instead of a pulverized product.
In addition, according to the present invention, since the slurry-like porous part-forming material contains a thickener, the porous part-forming carbonaceous powder is well dispersed and a highly homogeneous separator is easily obtained. be able to.

It is a figure which shows the example of preparation of the dense member used by this invention. It is a figure which shows the example of the manufacturing method of the separator for fuel cells which concerns on this invention. It is a figure which shows the example of the manufacturing method of the separator for fuel cells which concerns on this invention. It is explanatory drawing of the single cell for fuel cells using the separator for fuel cells obtained by the method of this invention.

The method for producing a fuel cell separator of the present invention comprises:
A method for producing a fuel cell separator having a porous part and a dense part, wherein at least a part of a wall surface of a gas flow path is formed by a porous part,
Forming a dense member by forming a slurry-like dense part forming material containing a dense part-forming carbonaceous powder and a dense part-forming thermosetting resin binder into a sheet, and press-molding; and
A process for preparing a porous part forming preform sheet by forming a slurry-like porous part forming material containing a porous part forming carbonaceous powder, a porous part forming resin binder, and a thickener. When,
In a mold having a molding surface corresponding to the gas flow path shape, the dense member and the porous part forming sheet are placed so that the molding surface and the porous part forming preformed sheet are opposed to each other. Filling, hot pressing and integrating,
It is characterized by giving.

<Preparation of dense material>
In the present invention, the dense member is prepared by forming a slurry-like dense part forming material containing a dense part-forming carbonaceous powder and a dense part-forming thermosetting resin binder into a sheet and press-molding it. Is done.

  In the method of the present invention, as a specific mode for producing a dense member, a thermosetting resin binder for forming a dense part is dissolved in an organic solvent together with a phenol resin curing agent and a curing accelerator as necessary, and the binder is used. A step of producing a resin liquid (binder resin liquid production step) and a step of dispersing a dense part forming carbonaceous powder in the binder resin liquid to produce a slurry dense part forming material (slurry dense part forming material) Manufacturing step), applying the slurry onto a film, drying, and then releasing to form a green sheet as a dense part forming material (green sheet manufacturing step), and forming the obtained green sheet And a method of performing pressure forming by filling the mold.

(1) Binder resin liquid preparation process Binder resin liquid (thermosetting resin binder-containing liquid for forming dense parts) is a thermosetting resin binder for forming dense parts, and if necessary, phenol resin curing agent or curing accelerator. The mixture is stirred and mixed, and further, the minimum necessary amount of dispersant capable of dispersing the dense part-forming carbonaceous powder described later is stirred and dissolved in an appropriate organic solvent at a desired mass ratio. be able to.

  The thermosetting resin binder for forming the dense part is not particularly limited as long as it has acid resistance to an electrolyte such as sulfonic acid and heat resistance that can withstand the operating temperature of the fuel cell. For example, a resol type phenol resin, Furan resins such as phenol resin, furfuryl alcohol resin, furfuryl alcohol furfural resin, furfuryl alcohol phenol resin represented by novolac type phenol resin, polyimide resin, polycarbodiimide resin, polyacrylonitrile resin, pyrene-phenanthrene resin , Epoxy resins such as polyvinyl chloride resin, bifunctional aliphatic alcohol ether type epoxy resin and polyfunctional phenol type epoxy resin, urea resin, diallyl phthalate resin, unsaturated polyester resin, melamine resin, etc. It is, can be used in combination alone or in combination.

  As a thermosetting resin binder for forming dense parts, a bifunctional aliphatic alcohol ether type epoxy resin, a polyfunctional phenol type epoxy resin, a bifunctional aliphatic alcohol ether type epoxy resin and a polyfunctional phenol type epoxy resin are combined. The mixed resin is preferable.

  The bifunctional aliphatic alcohol ether type epoxy resin has a number average molecular weight of 1500 to 3500 and a number average molecular weight / epoxy equivalent of 2 or more and is represented by the following general formula (I). Ether type epoxy resins are preferred.

G-O- (RO) _k -G (I)
(However, when G is a glycidyl group, O is an oxygen atom, R is an alkylene group having 2 to 10 carbon atoms, k is an integer of 1 or more, and k is an integer of 2 or more, a plurality of R are the same. It may or may not be.)

  In the epoxy resin represented by the general formula (I), when the total number of carbon atoms contained in the k alkylene groups R existing between the two glycidyl groups G and G is more than 120, the flexibility of the resin becomes high. Therefore, the breaking strain of the separator material is increased, but the bending strength is reduced to, for example, less than 30 MPa. On the other hand, if the total number of carbon atoms is less than 30, the molecular chain between the two glycidyl groups G and G is too short, so that the flexibility is lowered. Moreover, k is preferably 8-30, and more preferably 15-25.

  Examples of the bifunctional aliphatic alcohol ether type epoxy resin represented by the general formula (I) include a hexanediol type epoxy resin, a polyethylene glycol type epoxy resin, a polypropylene glycol type epoxy resin, and a polyoxytetramethylene glycol type epoxy resin. Among these resins, those having a relatively low proportion of oxygen atoms are preferable, and when the proportion of oxygen atoms is relatively low, water resistance is improved, and the water absorption swelling of the resulting separator Sex can be suppressed.

  Since the bifunctional aliphatic alcohol ether type epoxy resin represented by the general formula (I) has a linear single bond structure, the molecular chain is easy to move, has flexibility, and has a structure that easily exhibits rubber elasticity. Therefore, excellent flexibility, stretchability, and strain at break can be imparted to the separator.

  On the other hand, the polyfunctional phenol type epoxy resin is not particularly limited as long as it is a compound having a phenol skeleton in the molecule and having two or more epoxy groups. For example, bisphenol type epoxy resin, novolac type epoxy resin, orthocresol novolak Type epoxy resin, biphenyl type epoxy resin, naphthalene skeleton-containing type epoxy resin, and the like.

  Examples of bisphenol type epoxy resins include bifunctional phenol type epoxy resins.

  The bifunctional phenol type epoxy resin has two epoxy groups in the molecule, and examples of the bifunctional phenol type epoxy resin include a bisphenol A type epoxy resin represented by the general formula (II). it can.

  In the bifunctional phenol type epoxy resin represented by the general formula (II), n is an integer of 1 to 10, preferably an integer of 1 to 5, and more preferably an integer of 2 to 3.

  The bisphenol A type epoxy resin represented by the general formula (II) has a planar benzene ring, so that the molecule does not move easily and has low flexibility, but its structure gives the separator high bending strength. Can do.

  Moreover, as a polyfunctional phenol type epoxy resin, the polyfunctional phenol type epoxy resin which has a 3 or more functional group can be mentioned, for example. As such a polyfunctional phenol type epoxy resin, the epoxy resin represented by general formula (III) can be mentioned, for example.

  In the polyfunctional phenol type epoxy resin represented by the general formula (III), m is an integer of 3 to 8, preferably an integer of 4 to 8, and more preferably an integer of 5 to 7.

  Among the polyfunctional phenol type epoxy resins represented by the general formula (III), for example, a pentafunctional phenol type epoxy resin (an epoxy resin in which m is 3 in the general formula (III)) has 5 in the molecule. It has an epoxy group and a benzene ring in the molecular skeleton, and when cured, it forms a three-dimensional structure and exhibits a hard and brittle nature, but its structure can impart high bending strength to the separator. .

  In the method of the present invention, when a mixed resin of a bifunctional aliphatic alcohol ether type epoxy resin and a polyfunctional phenol type epoxy resin is used as a thermosetting resin binder for forming a dense part, the resulting separator is thinned Even so, sufficient flexibility (flexibility) and bending strength can be imparted.

  And when using the mixed resin of the said bifunctional aliphatic alcohol ether type epoxy resin and a polyfunctional phenol type epoxy resin as a thermosetting resin binder for dense part formation, the separator which balanced flexibility and intensity | strength In order to obtain the ratio, the ratio of the amount of the bifunctional aliphatic alcohol ether type epoxy resin to the total amount of the mixed resin and the phenol resin curing agent described later is preferably 25 to 50% by mass, and preferably 30 to 45% by mass. It is more preferable that it is 35-40 mass%. When the ratio is less than 25% by mass, the breaking strain of the separator is reduced and the separator is easily cracked, and when it exceeds 50% by mass, the mechanical strength of the separator becomes insufficient. Moreover, it is preferable that the ratio of the amount of polyfunctional phenol type epoxy resin with respect to the total amount of the said mixed resin and the phenol resin hardening | curing agent mentioned later is 25-50 mass%, It is more preferable that it is 30-45 mass%, More preferably, it is 35-40 mass%.

  When the amount of the thermosetting resin binder for forming the dense part is small, the strength of the separator obtained is lowered. Conversely, when the amount of the thermosetting resin binder for forming the dense part is increased, the electric resistance is increased.

  The phenol resin curing agent constituting the binder resin liquid is not particularly limited as long as it has a phenol structure in the molecule. Phenol novolak resin, cresol novolac resin, xylene type phenol resin, dicyclopentadiene type phenol resin, bisphenol Type novolac resins such as novolak resins, bisphenols such as bisphenol A, bisphenol F, bisphenol S, and tetrabromobisphenol A, the bisphenols may be polymerized with diglycidyl ether of the bisphenols, Examples thereof include bisphenol-based resins obtained by reacting the latter in excess.

  When the polyfunctional phenol type epoxy resin is used as the thermosetting resin binder for forming the dense part, the content ratio of the phenol resin curing agent is equivalent to the total phenolic hydroxyl groups in the phenol resin with respect to the total epoxy groups in the epoxy resin. The ratio (total phenolic hydroxyl groups in phenol resin / total epoxy groups in epoxy resin) is preferably 0.5 to 1.5, more preferably 0.7 to 1.5, and 0.9 It is more preferable that it is -1.1, and it is especially preferable that it is about 1.0. If the equivalent ratio is less than 0.5 or exceeds 1.5, the remaining amount of the unreacted mixed resin or phenol resin curing agent increases, and the efficiency is lowered.

  Moreover, as a hardening accelerator which comprises a binder resin liquid, 1 or more types chosen from a phosphorus compound, a tertiary amine, imidazole, an organic acid metal salt, a Lewis acid, an amine complex salt, etc. can be mentioned, When using a polyfunctional phenol type epoxy resin as a thermosetting resin binder for part formation, it can usually be added in a range of 0.05 to 3 parts by mass with respect to 100 parts by mass of the resin.

  The total amount of the dense part-forming thermosetting resin binder, phenol resin curing agent, and curing accelerator contained in the binder resin liquid is 10 parts by mass with respect to 100 parts by mass of the dense part-forming carbonaceous powder. It is preferable that it is -35 mass parts.

  The organic solvent that constitutes the binder resin liquid is not particularly limited as long as it is generally available and can dissolve the thermosetting resin binder for forming the dense part, and examples thereof include ethyl alcohol and isopropyl alcohol. Alcohols, ketones such as acetone and methyl ethyl ketone are often used, and among these organic solvents, the slurry stability and viscosity and the sheet drying speed when forming a green sheet by forming the slurry described later into a doctor blade. In view of the above, methyl ethyl ketone is most preferable.

  When the amount of the organic solvent is increased, the carbonaceous powder for forming the dense part is rapidly settled, and there may be a difference in structure between the front and back of the green sheet, which will be described later, resulting in warping. Conversely, when the amount of the organic solvent decreases, the viscosity of a slurry described later increases, and the formation of a sheet becomes difficult because the carbonaceous powder in which the blades are aggregated is dragged to form irregularities on the surface.

  Examples of the dispersant constituting the binder resin liquid include a nonionic surfactant, a cationic surfactant, and an anionic surfactant.

  Examples of the nonionic surfactant include aromatic ether type, carboxylic acid ester type, acrylic acid ester type, phosphoric acid ester type, sulfonic acid ester type, fatty acid ester type, urethane type, fluorine type, aminoamide type, The thing which consists of various polymers of an acryl amide type is mentioned.

  Examples of the cationic surfactant include those made of various polymers containing an ammonium group, a sulfonium group, and a phosphonium group.

Examples of the anionic surfactant include those made of various polymers of carboxylic acid type, phosphoric acid type, sulfonic acid type, hydroxy fatty acid type, and fatty acid amide type.
The molecular weight of each of the surfactants is a polystyrene-reduced weight average molecular weight by gel permeation chromatography in order to disperse the carbonaceous powder for forming the dense part in the organic solvent, and ranges from 2,000 to 100,000. It is desirable to be in When the weight average molecular weight is less than 2,000, the polymer component cannot form a sufficient three-dimensional repulsion layer when the dispersant is adsorbed on the surface of the dense part forming carbonaceous powder, This is not preferable because reaggregation occurs. On the other hand, if the weight average molecular weight exceeds 100,000, the production reproducibility may be reduced or the flocculant may act.

These surfactants can be used alone or in admixture of two or more.
The dispersant is preferably added in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the dense part-forming carbonaceous powder. If the amount of the dispersant added is less than 0.1 parts by mass with respect to 100 parts by mass of the dense part forming carbonaceous powder, the dense part forming carbonaceous powder will settle immediately without being dispersed. Moreover, when the addition amount is more than 5 parts by mass with respect to 100 parts by mass of the dense part forming carbonaceous powder, the resin characteristics are deteriorated, and as a result, the mechanical characteristics of the separator material are deteriorated (strength reduction). In addition, chemical resistance, in particular, deterioration of characteristics in sulfuric acid acidic solution is caused.

  In addition to the above dispersant, the binder resin liquid may contain additives such as a wetting penetrating agent, an antiseptic, an antifoaming agent, and a surface conditioner as long as it does not hinder the purpose of the present invention. It can contain suitably. By containing these additives, a stable slurry can be produced and a green sheet with a smooth surface can be obtained.

  The binder resin liquid is added to the above organic solvent with a thermosetting resin binder for forming a dense part together with a phenol resin curing agent, a curing accelerator, a dispersing agent, etc., if necessary, and stirred and mixed with a stirrer. It can produce by doing. The stirring time is preferably about 1 hour, and the rotation speed of the stirrer is preferably about 100 to 1000 rotations / minute.

(2) Slurry dense part forming material manufacturing process
The binder resin liquid obtained in the step (1) and the dense part forming carbonaceous powder are mixed to produce a slurry-like dense part forming material in which the dense part forming carbonaceous powder is dispersed.

  Examples of the carbonaceous powder for forming the dense portion include graphite powder such as artificial graphite powder, natural graphite powder, expanded graphite powder, or a mixture thereof. Among these, separators such as bending strength and breaking strain are used. Considering the mechanical properties of the material, artificial graphite powder alone or a mixed powder of artificial graphite powder and natural graphite powder is preferable, and each of the above graphite powders is appropriately pulverized and sieved to adjust the particle size. It is preferable to use it.

  The dense part-forming carbonaceous powder preferably contains 30 to 90% by mass of particles having a particle diameter of 1 to 30 μm and a maximum particle diameter of 50 to 150 μm.

  The amount of particles having a particle size of 1 to 30 μm constituting the dense part forming carbonaceous powder is 30 to 90% by mass, so that even if the amount of the solution is small, the fluidity is good and the slurry becomes stable, and the green sheet is formed. Occasionally, cracking due to drying shrinkage can be suppressed to achieve densification, and a separator with improved mechanical strength can be obtained. On the other hand, when the amount of particles having a particle diameter of 1 to 30 μm constituting the dense part forming carbonaceous powder is less than 30% by mass, the mechanical strength of the obtained separator is reduced. Resistance value will rise. Moreover, if the maximum particle size of the dense part forming carbonaceous powder is less than 50 μm, the resistance value of the separator increases, and if the maximum particle size exceeds 150 μm, the gas impermeability decreases. Furthermore, since the carbonaceous powder includes both particles having a particle diameter of 1 to 30 μm and particles having a particle diameter of 50 to 150 μm, there is also a filling effect that small particles enter into the gaps of the large particles when the green sheet is produced in the next step. A dense green sheet can be obtained.

  The carbonaceous powder having the above particle size distribution can be produced by mixing the carbonaceous powder whose particle size is adjusted by the above sieving in an appropriate quantitative ratio.

  Moreover, as the dense part forming carbonaceous powder, those having a compression repulsion rate of 120% or less are preferable, those having 100 to 115% are more preferable, and those having 100 to 110% are more preferable. The compression repulsion rate was expressed as a percentage of the volume when the carbonaceous powder was compressed under pressure at 50 MPa and the ratio of the volume after depressurization (volume after depressurization / volume when compressed and compressed). Is.

  The binder resin solution and the dense part forming carbonaceous powder are mixed and dispersed to prepare a slurry-like dense part forming material.

  The carbonaceous powder for forming the dense part is the total amount of the resin component in a mass ratio with respect to the total amount (resin component total amount) of the thermosetting resin binder for forming the dense part, the phenol resin curing agent, and the curing accelerator. : Carbonaceous powder for forming dense part = 10: 90 to 35:65 It is preferable to mix with the binder resin liquid. If the mass proportion of the total amount of the resin components is less than 10% and the mass proportion of the carbonaceous powder is more than 90%, the amount of thermosetting resin binder is reduced, so that the fluidity at the time of molding is lowered and uniform. It becomes difficult to mix and the composition tends to be non-uniform. On the other hand, if the mass proportion of the total amount of the resin components is more than 35% and the mass proportion of the carbonaceous powder is less than 65%, the moldability is improved, but the molded article comprising the carbonaceous powder and the thermosetting resin binder. When the fuel cell is manufactured using the obtained separator, the performance of the fuel cell is deteriorated.

  The mixing and dispersing treatment of the binder resin liquid and the carbonaceous powder is preferably carried out using a dispersing machine such as a universal stirrer, ultrasonic treatment device, cutter mixer, three rolls, etc., and the carbonaceous powder in the binder resin liquid It is preferable to make a slurry by adjusting the viscosity to 100 to 2000 mPa · s, preferably 100 to 1000 mPa · s by adding an organic solvent as appropriate. When the viscosity of the slurry is less than 100 mPa · s, the raw material slurry flows out from the doctor blade when the green sheet is produced, and the sheet spreads, so that a sheet having a uniform thickness cannot be formed. On the other hand, when the viscosity of the slurry exceeds 2000 mPa · s, it becomes difficult to form a sheet because the blade is dragged by the agglomerated carbonaceous powder when the green sheet is produced, and the surface is uneven.

  In addition, when the green sheet is produced, the air entrained by the mixing and dispersing process may form irregularities on the surface of the green sheet and reduce the homogeneity. Therefore, the slurry may be obtained by a method such as centrifugation or vacuum deaeration. It is desirable to produce a green sheet after degassing the air inside.

(3) Green sheet preparation process The slurry prepared at the said (2) process is apply | coated on films, such as polyester, by the doctor blade method. At this time, after appropriately adjusting the gap between the doctor blade and the film to about 0.2 to 0.8 mm, the slurry which is well stirred with a stirrer is poured into the slurry hopper of the doctor blade, preferably on the film coated with a release agent. Apply to a uniform thickness.

  The thickness of the obtained green sheet can be adjusted by adjusting the gap distance between the doctor blade and the film and the slurry concentration, and can be controlled so that the thickness after drying is 0.1 to 0.5 mm. preferable.

  The obtained green sheet is preferably air-dried or, if desired, cut to a certain length and then blown and dried using a fan or the like, and dried until the solvent content is volatilized visually. In addition, after the solvent has evaporated and the surface is dry, a predetermined size is cut with a cutter knife, or a punching die is used for a predetermined shape and size, followed by drying or cooling for a predetermined time. It is preferable to release the film from the surface after making it easy to release from the film.

  Thus, in the doctor blade method, a slurry composed of raw material powder such as carbonaceous powder, thermosetting resin binders, dispersant, organic solvent, etc. is formed on the carrier film using a doctor blade device to a certain thickness. It is a method of obtaining a green sheet by drying and evaporating and evaporating the organic solvent after continuous coating, and a production method that continuously performs sheet forming, drying, winding, punching processing, etc. A green sheet which is a dense part forming material can be produced with high production efficiency. For this reason, the working efficiency and productivity at the time of separator manufacture can be improved compared with the conventional method which manufactures a separator, after drying a slurry-like raw material mixture and producing a molding powder.

  Since the green sheet obtained in this way is composed of a dense resin film, the gas impermeability of the separator material obtained can be improved.

  The green sheet thus obtained is suitably 0.1 to 1.0 mm thick, more suitably 0.15 to 0.8 mm, and 0.2 to 0.6 mm. It is further appropriate that

(4) Pressure forming step A dense member is produced by pressure forming after laminating a plurality of the green sheets obtained in the step (3) as appropriate according to the thickness of the separator material to be obtained. can do.

  The pressure forming of the dense part forming green sheet is performed, for example, by placing a desired number of green sheets in a mold and using a hot plate or the like to melt the dense part forming thermosetting resin binder. This can be performed by preheating the mold together with the above temperature or a temperature at which the thermosetting resin binder for forming the dense part is melted and heat-cured, and then putting it in a press machine and applying pressure. The pressure-molded product is preferably taken out before the mold temperature is lowered to room temperature.

  For example, the pressure molding is performed by using a dense body portion forming green sheet 31a and a dense portion edge portion forming green sheet 31b as shown in FIG. The green sheet 31a and the dense part edge forming green sheet 31b are placed in a mold in a state of being overlapped as shown in FIG. 1B, and the above temperature is set together with the mold using a hot plate or the like. After preheating in an atmosphere, it can be performed by putting in a press machine and pressurizing. In this way, a dense member 31 having an edge as shown in FIG. 1C can be obtained (the upper view of FIG. 1C is a perspective view of the dense member 31, FIG. (C) The lower figure is a vertical sectional view with respect to the main surface of the dense member 31). The number of layers of the dense body portion forming green sheet 31a, the dense portion edge forming green sheet 31b, and the like may be appropriately changed according to the thickness of the dense member to be obtained.

  It is preferable that the dense member is formed by laminating 2 to 6 green sheets. When the dense member takes an embodiment as shown in FIG. It is preferable that 1 to 3 green sheets 31a and 1 to 3 dense part edge forming green sheets 31b are laminated and pressure-molded.

  The dense member 31 may have a planar shape (flat plate shape) by laminating green sheets of the same size in a mold and press-molding them.

  The pressure at the time of the pressure molding (hot pressure molding) is preferably 10 to 100 MPa, more preferably 20 to 80 MPa, and still more preferably 20 to 60 MPa. Moreover, it is preferable that the temperature at the time of hot press molding is 150-250 degreeC. The pressing time at the time of hot pressing is preferably 1 second to 600 seconds, more preferably 1 second to 300 seconds, and further preferably 1 second to 30 seconds. Further, at the time of pressurization, the depressurization may be performed by releasing the pressurization state in a timely manner, instead of continuously maintaining the pressurization state. When the pressure at the time of pressurization is within the above range, desired strength and gas impermeability can be imparted to the obtained separator.

  The thickness of the dense member is suitably 0.05 to 0.5 mm, more suitably 0.075 to 0.4 mm, and 0.1 to 0.3 mm. It is more appropriate. In this specification, when the dense member takes the form as shown in FIG. 1C, the thickness indicated by t in FIG. 1C corresponds to the thickness of the dense member. .

  Since the obtained dense member is made of the green sheet having the dense structure, a separator having a high degree of gas impermeability can be produced even when the thickness is small.

<Preparation of preformed sheet for forming porous portion>
In the method of the present invention, the preform for forming a porous part forms a slurry-like porous part forming material containing a carbonaceous powder for forming a porous part, a resin binder for forming a porous part, and a thickener. It is produced by this.

  In the method of the present invention, as a specific embodiment for producing a preformed sheet for forming a porous part, a resin binder and a thickener for forming a porous part are combined with a phenol resin curing agent and a curing accelerator, if necessary. A step of preparing a binder resin solution by dissolving in a solvent (binder resin solution preparation step), and a step of preparing a slurry-like porous portion forming material by dispersing the porous carbon forming powder in the binder resin solution (slurry) And a step of producing a green sheet as a porous part forming material by releasing the slurry after applying the slurry on a film, drying, and applying the slurry (green sheet producing process) A method can be mentioned.

(1) Binder resin liquid preparation step The binder resin liquid (resin binder-containing liquid for forming the porous part) stirs the resin binder for forming the porous part and the thickener together with a phenol resin curing agent and a curing accelerator as necessary. The minimum required amount of a dispersant capable of mixing and further dispersing a carbonaceous powder for forming a porous part, which will be described later, if necessary, can be prepared by stirring and dissolving in an appropriate organic solvent at a desired mass ratio. it can.

  Examples of the resin binder for forming the porous portion include a thermosetting resin or a thermoplastic resin.

  When the porous part forming resin binder is a thermosetting resin, specific examples and blending ratios thereof are used to prepare a dense part forming binder resin liquid using the above-described dense part forming thermosetting resin binder. The specific examples and blending ratios of the phenol resin curing agent and the curing accelerator are the same as in the case of producing the dense part forming binder resin liquid.

  When the resin binder for forming the porous portion is a thermoplastic resin, the thermoplastic resin includes polyolefin resin, polyester resin, polycarbonate resin, polystyrene resin, acrylic resin, polyamide resin, polyphenylene ether resin, polyphenylene sulfide. Resin, polysulfone resin and the like. Of these thermoplastic resins, polyphenylene sulfide resins are preferred from the viewpoint of chemical resistance, durability, and mechanical strength, and polyolefin resins and polyphenylene ether resins can also be suitably used.

  When the porous part forming resin binder contained in the binder resin liquid is a thermoplastic resin, the blending amount thereof is 10 to 35 parts by mass with respect to 100 parts by mass of the porous part forming carbonaceous powder. Is preferred.

  Specific examples of the dispersant used as necessary for the preparation of the binder resin liquid (resin binder-containing liquid for forming the porous part) are the same as those for producing the dense part forming binder resin liquid.

  Examples of the thickener include organic polymer resins such as a cellulose-based thickener, and examples of the cellulose-based thickener include cellulose acetate (cellulose acetate), ethylcellulose, cellulose nitrate, cellulose sulfate, methylcellulose, hydroxy Examples include ethyl cellulose and carboxymethyl cellulose.

  As the thickener, an organic polymer resin soluble in an organic solvent is particularly preferable, and specific examples thereof include cellulose acetate (cellulose acetate), ethyl cellulose, cellulose nitrate, cellulose sulfate, and amylose acetate.

  In addition, examples of the thickener include water-soluble organic polymer resins, and specific examples include methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and the like. When a water-soluble organic polymer resin is used as the thickener, a water-soluble one such as a water-soluble phenol resin is also used as the porous portion forming resin binder.

The blending ratio of the thickener is preferably 0.1 to 10 parts by mass and more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the porous part forming carbonaceous powder described later. Preferably, it is 1 to 10 parts by mass.
When the blending ratio of the thickener is 0.1 to 10 parts by mass with respect to 100 parts by mass of the carbonaceous powder for forming a porous part to be described later, the viscosity of the slurry for forming the porous part is controlled within a desired range. Moreover, since the sedimentation of the carbonaceous powder for porous part formation can be suppressed, a separator having excellent homogeneity can be obtained.

  Further, the total amount of the porous part forming resin binder and the thickener contained in the binder resin liquid (when the resin binder is a thermosetting resin, a phenol resin curing agent and a curing accelerator were further added. The total amount) is preferably 10 to 45 parts by mass with respect to 100 parts by mass of the porous part forming carbonaceous powder.

  In the present invention, the porous part forming material contains a thickener, so that even if a carbonaceous powder having an average particle size of 50 μm or more is used as the porous part forming carbonaceous powder, the graphite powder is precipitated. Can be made into a homogeneous slurry, and a highly homogeneous separator can be easily obtained.

  The organic solvent constituting the binder resin liquid is not particularly limited as long as it is generally available and can dissolve the thermosetting resin binder for forming the porous portion and the thickener. For example, acetone, methyl ethyl ketone Of these organic solvents, methyl ethyl ketone is considered in view of the stability and viscosity of the slurry when the slurry described later is formed into a green sheet by forming a slurry, and the drying speed of the sheet. Is most preferred.

  When the amount of the organic solvent is increased, the carbonaceous powder for forming the porous part is quickly settled, and there may be a difference in structure between the front and back of the green sheet, which will be described later, causing warping. Conversely, when the amount of the organic solvent decreases, the viscosity of a slurry described later increases, and the formation of a sheet becomes difficult because the carbonaceous powder in which the blades are aggregated is dragged to form irregularities on the surface.

  In addition to the above dispersant, the binder resin liquid may contain additives such as a wetting penetrating agent, an antiseptic, an antifoaming agent, and a surface conditioner as long as it does not hinder the purpose of the present invention. It can contain suitably. By containing these additives, a stable slurry can be produced and a green sheet with a smooth surface can be obtained.

  The method for preparing the binder resin liquid for forming the porous part is the same as the method for preparing the binder resin liquid for forming the dense part.

(2) Slurry porous part forming material production process
The binder resin liquid obtained in the step (1) and the carbonaceous powder for forming the porous part are mixed to produce a slurry-like porous part forming material in which the carbonaceous powder for forming the porous part is dispersed.

Examples of the carbonaceous powder for forming a porous part include graphite powder such as artificial graphite powder, natural graphite powder, expanded graphite powder, or a mixture thereof, and among these, after being integrated with a dense member In view of the contact resistance, a high hardness is preferable. Further, the porous part forming carbonaceous powder preferably has an aspect ratio of 1.0 to 2.0, more preferably 1.0 to 1.7, and 1.0 to 1.5. Some are more preferred. When the porous part forming carbonaceous powder has an aspect ratio of about 1.0 to 2.0, when the porous part forming preform sheet is integrated with the dense member by hot pressing, both Since the carbonaceous powder for forming the porous part is difficult to orient at the interface of the porous part and is integrated with a part of the porous part biting into the dense part, the contact resistance at the interface between the dense part and the porous part Can be lowered (adhesion between the dense portion and the porous portion can be improved).
In this application document, the aspect ratio of the carbonaceous powder for forming the porous portion is:
It means the average value of the ratio of the length in the vertical direction and the length in the horizontal direction when 10 carbonaceous powders are measured by a scanning electron microscope image.

  The porous part-forming carbonaceous powder preferably has a volume average particle size of 50 to 500 μm, more preferably 50 to 400 μm, and still more preferably 50 to 300 μm. When the average particle size of the carbonaceous powder for forming the porous portion is 50 to 500 μm, good drainage can be imparted to the obtained separator.

  In addition, in this application document, the said volume average particle diameter means the value measured by the laser diffraction type particle size distribution measuring apparatus.

  The mixing ratio of the binder resin liquid and the carbonaceous powder for forming the porous part, and the method for producing the slurry-like porous part forming material by mixing and dispersing are the same as the method for producing the slurry-like dense part forming material. It is.

  The slurry-like porous part forming material obtained in this step preferably has a viscosity at 25 ° C. of 500 to 5000 mPa · s, more preferably 750 to 4000 mPa · s, and 1000 to 3000 mPa · s. Is more preferable. The viscosity of the slurry-like porous part forming material can be adjusted by adjusting the type and blending amount of the thickener.

  Since the viscosity of the slurry-like porous portion forming material is adjusted to the above range, the carbonaceous powder in the slurry can be prevented from settling, and thus a separator having excellent homogeneity can be obtained.

(3) Green sheet production process A green sheet is produced by the doctor blade method using the slurry-like porous part forming material prepared in the process (2).
The method for producing the green sheet from the slurry-like porous part liquid material is the same as the method for producing the green sheet from the slurry-like dense part forming material described above, and the thickness of the obtained green sheet is also the same.

<Filling process and hot pressing process>
In the present invention, the dense member and the porous portion are formed so that the forming surface and the preformed sheet for forming the porous portion are opposed to each other in a forming die having a forming surface corresponding to the gas flow path shape. It is filled with a pre-formed sheet for use, and is formed by hot pressing.

  As a shaping | molding die, what consists of a pair of upper mold | type and lower mold | type can be mentioned, What has a shaping | molding surface shape according to the separator shape to obtain can be mentioned. For example, when the separator to be obtained has a cross-sectional shape as shown in FIG. 2 (c), a molding die in which an uneven molding surface corresponding to the gas flow path shape is formed on the molding surface of the upper mold. In the case where the separator to be obtained has a cross-sectional shape as shown in FIG. 3C, the shape where the upper mold surface can be processed into a corrugated shape of the entire gas flow path portion. A molding die formed in the above can be mentioned. A mold release agent may be appropriately applied to the molding surface of the mold.

  In the filling step, for example, after the dense member 31 having a cross-sectional shape as shown in FIG. 2 (a) is filled on the lower mold, as shown in FIG. 2 (b), on the dense member 31, A porous part forming preformed sheet 21 in which a predetermined number of porous part forming green sheets are stacked so as to form a porous part with a desired thickness is filled, and the porous part forming preformed sheet 21 is filled. And an upper mold in which irregularities corresponding to the shape of the gas flow path are formed on the molding surface.

  Moreover, after filling the dense member 31 having corrugated irregularities formed as shown in FIG. 3A on the lower mold having the irregular surface corresponding to the corrugated shape, FIG. ), A porous part forming preformed sheet 21 in which a predetermined number of porous part forming green sheets are superposed on the dense member 31 so that a porous part having a desired thickness is formed. It may be filled and opposed to an upper mold having an uneven molding surface corresponding to the corrugated shape (in this case, the unevenness on the lower surface of the dense member 31 meshes with the unevenness on the lower mold forming surface, and the upper surface of the dense member 31 has an upper surface. The dense member 31 is arranged so that the irregularities mesh with the irregularities of the upper mold forming surface).

  As the porous part forming preformed sheet 21, a preform formed by hot press molding a predetermined number of porous part forming green sheets to form a porous part having a desired thickness may be used. Well, it is preferable that the hot press molding conditions at the time of preforming are the same as the hot press molding conditions described in detail below.

  Further, if necessary, it is preferable to apply hot pressing to a bonding surface of the dense member and the porous portion forming preformed sheet by applying a binder resin solution by a spray coating method or the like. Examples of the binder resin liquid include those similar to those used in the production of the dense member, and are applied so that the thickness after drying becomes 1 to 15 μm on the joint surface. It is preferable. By applying the binder resin liquid to the joining surface between the dense member and the preformed sheet for forming the porous portion, the adhesive strength between the two can be further improved.

  The temperature at the time of hot-press molding of the dense member and the preformed sheet for forming the porous part is suitably about 150 to 250 ° C.

  The molding pressure at the time of hot-pressure molding is suitably 1 MPa or more and less than 20 MPa, more suitably 1 MPa to 15 MPa, and even more suitably 1 MPa to 10 MPa. If the molding pressure is less than 1 MPa, the strength sufficient to maintain the shape of the porous portion may not be obtained. If the molding pressure is 20 MPa or more, the pores are buried, and the porous portion can take a porous structure. There may not be.

  Further, the obtained hot-pressed product may be further machined as necessary, and may be after-cured at a temperature of about 150 to 250 ° C. as necessary.

  The obtained hot-pressed product is preferably subjected to a hydrophilic treatment as appropriate. The hydrophilic treatment can be performed, for example, by treatment with ozone gas. The hydrophilization treatment by ozone gas treatment is preferably performed by exposure to ozone gas having a concentration of 1000 to 50000 ppm (mg / L) in a temperature atmosphere of 0 to 100 ° C. for 0.5 to 10 hours.

  By the above-described hot pressing, the dense part forming thermosetting resin binder and the porous part forming thermosetting resin binder are cured, and the dense part forming carbonaceous powder and the porous part forming carbonaceous powder are respectively obtained. It is possible to manufacture a separator in which the dense part and the porous part are firmly joined and integrated to reduce the contact resistance generated at the interface between the two while binding and integrating.

  As illustrated in FIG. 2C and FIG. 3C, the separator 1 obtained by the method of the present invention is formed by forming at least part of the wall surface constituting the gas flow path 4 with the porous portion 2. The structure has a porous portion 2 and a dense portion 3.

  The porous part constituting the separator preferably has a thickness of 0.1 to 2.0 mm, more preferably 0.2 to 1.5 mm, and further preferably 0.3 to 1.0 mm. preferable. When the separator adopts the structure shown in FIG. 2C (flat structure) or the structure shown in FIG. 3C (corrugated structure), the thickness indicated by h in FIGS. 2C and 3C is shown. It corresponds to the thickness of the porous part. The porous part preferably has a pore diameter of 5 to 60 μm, more preferably 10 to 55 μm, and still more preferably 15 to 50 μm. The porous part preferably has a porosity of 5 to 50%, more preferably 12.5 to 50%, and still more preferably 20 to 50%. In the present application documents, the pore diameter and porosity mean values measured by a mercury intrusion method defined in JIS R 1655.

  In the present invention, the powder material forming the dense part and the powder material forming the porous part are put in the same mold and hot-pressed at once, or each of the porous parts formed by hot-pressing in advance. Rather than putting the dense part in the same mold and heat compression molding, first, the dense part forming material is pressurized to obtain a dense member, and then the dense part and the porous part forming spare A separator is produced by hot-pressing the molded sheet. In the present invention, since the dense part forming material is preliminarily pressed at a desired pressure to produce a dense member, the dense part can be finally given a desired gas impermeability, A porous part having a desired porosity can be formed by controlling the conditions of hot-pressure forming in a state where the dense member and the porous part forming preform sheet are stacked and filled.

  In addition, according to the present invention, a slurry-like molding material is formed into a sheet to form a dense part and a porous part, so that a dry product of the dense part forming material and the porous part forming material (raw material mixture) is pulverized. The process can be omitted, and since it can be supplied into the mold as a sheet instead of a pulverized product, the filling operation to the mold can be performed more easily, thereby improving productivity. Can do. In addition, according to the present invention, since the slurry-like porous part-forming material contains a thickener, the graphite powder can be well dispersed and a suitable porous part-forming preform sheet can be produced. For this reason, a separator with high homogeneity can be easily manufactured.

The dense part constituting the separator preferably has a thickness of 0.15 to 0.5 mm, more preferably 0.15 to 0.4 mm, and preferably 0.15 to 0.3 mm. Further preferred. In addition, when a separator takes the aspect shown in FIG.2 (c) and FIG.3 (c), the thickness shown by T in these figures is equivalent to the thickness of a dense part. Also, the dense portion is appropriate that the gas permeability coefficient is ^{1 × 10 -12 ~1 × 10 -10} mol · m · m -2 · sec -1 · MPa -1, 1 × 10 - ^{12 to} 5 × 10 ⁻¹¹ mol · m · m ⁻² · sec ⁻¹ · MPa ⁻¹ is more appropriate, and 1 × 10 ⁻¹² to 1 × 10 ⁻¹¹ mol · m · m ⁻² · It is more suitable that it is sec < ^-1 > * MPa- ¹ .

  In the present application document, the gas permeability coefficient can be obtained by measuring the gas permeation amount per unit time and unit cross-sectional area when a differential pressure of 0.2 MPa is applied with nitrogen gas.

  According to the present invention, the obtained fuel cell separator has a dense portion together with a porous portion, whereby excellent gas impermeability can be obtained.

Further, the contact resistance of the dense portion and a porous portion constituting the separator is suitably be at 1 M.OMEGA · cm ² or less, it is more appropriate is 0.5mΩ · cm ² or less.
In the present application document, the contact resistance means a value when measured at an energization amount of 1 A while applying a pressure of 1 MPa to a test piece obtained by appropriately cutting a separator.

  According to the present invention, since at least a part of the wall surface of the gas flow path constituting the obtained fuel cell separator is formed by the porous portion, diffusion of water generated during power generation is facilitated, and the gas flow It is possible to suppress the blockage of the road, to suppress a decrease in power generation efficiency, and to suppress an increase in contact resistance.

  The separator obtained by the method of the present invention can be suitably used as a separator for a polymer electrolyte fuel cell.

  The single cell of the fuel cell using the separator obtained by the method of the present invention is, for example, as shown in FIGS. 4 (a) and 4 (b), a polymer membrane having ion conductivity (ion exchange membrane). 5 is sandwiched between an anode electrode plate 6 and a cathode electrode plate 7 supporting a catalyst such as platinum, and a plate-like separator having a porous portion 2 and a dense portion 4 is arranged on both outer sides thereof. Can do.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited at all by the following examples.

Example 1
1. Production of dense member (1) Production process of binder resin liquid Epoxy resin (polyfunctional phenol type epoxy resin, manufactured by DIC Corporation, EPICLON N-680, softening point 85) ℃) and a novolak type phenolic resin (Miwa Kasei Co., Ltd., H-1, softening point 85 ° C.) which is a curing agent, DIC Corporation EPICLON N-680 and Meiwa Kasei Co., Ltd. H- 1 so that the weight ratio is 2: 1) and mixed so as to be 20 parts by mass with respect to 100 parts by mass of graphite powder as a dense part-forming carbonaceous powder described later. In addition to this mixed resin, 2-ethyl-4-methylimidazole, which is a curing accelerator, is further equivalent to the total phenolic hydroxyl group in the phenolic resin relative to the total epoxy group in the epoxy resin. While adding so that (total phenolic hydroxyl group in phenol resin / total epoxy group in epoxy resin) becomes 1, 110 parts by mass of methyl ethyl ketone (MEK) as a solvent with respect to 100 parts by mass of graphite powder to be described later In addition, an anionic surfactant (polycarboxylic acid type polymer, Homogenol L-18 manufactured by Kao Co., Ltd.), which is a dispersant, is further added at a ratio of 1 part by mass with respect to 100 parts by mass of graphite powder described later. It added so that binder resin liquid might be produced.
The curing temperature of the dense part forming thermosetting resin binder constituting the obtained binder resin liquid can be regarded as 120 ° C.

(2) Slurry preparation step The desired amount of the scale-like natural graphite powder containing 50% by mass of particles having a particle size of 1 to 30 μm and adjusted to a maximum particle size of 150 μm in the desired amount of the binder resin liquid obtained in the step (1). It is obtained in the step (1) by adding the appropriate amount of methyl ethyl ketone (MEK), kneading sufficiently with a stirrer to adjust the viscosity to 200 mPa · s, and degassing the air entrained by the centrifugal method. The resin component total amount: dense with respect to the total amount (resin component total amount) of the thermosetting resin binder for forming the dense portion, the phenol resin curing agent, and the curing accelerator constituting the binder resin liquid. The raw material slurry mixed so that the carbon powder for part formation = 17: 83 was obtained.

(3) Green sheet production process (2) By injecting the raw material slurry obtained in the process into a green sheet molding apparatus having a doctor blade, producing a sheet-like material by the doctor blade method, and sufficiently drying, A green sheet having a thickness of about 0.3 mm was formed.

(4) Pressure forming step (3) The green sheet obtained in step (3) is punched into a predetermined shape with a punching die, and after the green sheet is peeled off from the film, the dense main body has the form shown in FIG. A green having a form as shown in FIG. 1B, which is adjusted to have a predetermined thickness by laminating two green sheets 31a for part formation and two green sheets 31b for dense part edge formation. A sheet laminate was obtained.
Next, the green sheet laminate was inserted into a mold having an outer shape of 270 × 270 mm composed of a pair of an upper mold and a lower mold having a molding surface coated with a fluorine-based mold release agent. And in the state which inserted the said green sheet laminated body, the dense member 31 was produced by pressurizing for 60 second under the temperature conditions of 180 degreeC with the pressure of 40 Mpa.
The dense member 31 obtained has a thickness of the thinnest part of 0.20 mm.

2. Production of porous part forming powder (1) Production process of binder resin liquid Epoxy resin (polyfunctional phenol type epoxy resin, DIC Corporation, EPICLON N-680, which is a thermosetting resin binder for porous part formation) Softening point 85 ° C.) and novolak type phenolic resin (Miwa Kasei Co., Ltd., H-1, softening point 85 ° C.) as a curing agent, DIC Corporation EPICLON N-680 and Meiwa Chemical Mixing H-1 made so that the weight ratio is 2: 1 to obtain a mixed resin of 10 parts by mass with respect to 100 parts by mass of graphite powder as a porous part forming carbonaceous powder described later, To this mixed resin, 2-ethyl-4-methylimidazole, which is a curing accelerator, is further added, with an equivalent ratio of phenolic hydroxyl groups in the phenol resin to all epoxy groups in the epoxy resin (phenol). The total phenolic hydroxyl group in the resin / total epoxy group in the epoxy resin) is added to 1 and the solvent acetone is 110 parts by mass with respect to 100 parts by mass of graphite powder described later. In addition, an anionic surfactant (polycarboxylic acid type polymer, Homogenol L-18 manufactured by Kao Co., Ltd.), which is a dispersant, is added so as to have a ratio of 1 part by mass with respect to 100 parts by mass of graphite powder described later. At the same time, cellulose acetate as a thickener was added so as to have a ratio of 5 parts by mass with respect to 100 parts by mass of graphite powder described later, and stirred well with a stirrer to prepare a binder resin liquid.
The curing temperature of the porous part forming thermosetting resin binder constituting the obtained binder resin liquid can be regarded as 120 ° C.

(2) Slurry preparation step (1) Into the desired amount of the binder resin liquid obtained in the step, 100 parts by mass of artificial graphite powder (aspect ratio 1.0 to 2.0) whose particle size was adjusted to an average particle size of 160 μm was charged. While appropriately adding acetone, the mixture was sufficiently kneaded with a stirrer, and the air entrained by the centrifugal method was degassed to obtain a porous part forming raw material slurry. It was 2000 cp when the viscosity at 25 degreeC of the obtained raw material slurry for shaping | molding a porous part was measured with the B-type viscosity meter according to prescription | regulation of JISK7117-1. The results are shown in Table 1.
In addition, the said raw material slurry for porous part shaping | molding is the sum total of the thermosetting resin binder for dense part formation which comprises the binder resin liquid obtained at the (1) process, a phenol resin hardening | curing agent, a hardening accelerator, and a thickener. The resin component is mixed in such a manner that the resin component total amount: porous part forming carbonaceous powder = 13: 87 in terms of mass ratio with respect to the amount (resin component total amount).

(3) Green sheet production process (2) By injecting the raw material slurry obtained in the process into a green sheet molding apparatus having a doctor blade, producing a sheet-like material by the doctor blade method, and sufficiently drying, A green sheet having an average thickness of about 0.5 mm was formed.
Using the obtained green sheet, the thickness of a measurement sample having a length of 200 mm and a width of 200 mm was measured using a micrometer, and the difference between the thickest part and the thinnest part was divided by the average thickness (0.5 mm) to obtain a porous The accuracy of the thickness of the green part forming green sheet was determined to be 3%. The results are shown in Table 1.

3. Filling and hot-pressure molding As the mold, it consists of a pair of upper and lower molds. On the upper mold surface, a groove shape with a width of 1 mm and a depth of 0.6 mm is engraved on the surface, within a range of 200 x 200 mm. A molding die having an outer shape of 270 × 270 mm coated with a fluorine-based mold release agent was used.
After placing the dense member 31 having the cross-sectional shape shown in FIG. 2 (a) on the lower mold of the molding die, as shown in FIG. The sheet was filled to form a porous part forming preformed sheet 21, and in this state, hot pressing was performed at a temperature of 180 ° C. and a pressure of 5 MPa for 60 seconds to obtain a hot pressing product.

  The obtained hot-pressed product is subjected to a hydrophilization treatment (oxidation treatment) by exposing it to ozone gas having a concentration of 30000 ppm (mg / L) in a temperature atmosphere of 25 ° C. for 5 hours. A fuel cell separator having a cross-sectional shape as shown in FIG.

  The obtained fuel cell separator had a length of 270 mm, a width of 270 mm, a dense portion thickness T of 0.30 mm, and a porous portion thickness h of 0.30 mm.

In the obtained fuel cell separator, the porosity and pore diameter of the porous part, the specific resistance of the separator, the contact resistance at the interface between the porous part and the dense part, the gas permeability coefficient of the separator, The drainage was measured by the following method. The results are shown in Table 2 .

<Porosity of porous part (μm) and porosity (%)>
It measured by the mercury intrusion method prescribed | regulated to JISR1655.

<Specific resistivity of separator (mΩ · cm)>
Measured according to JIS C 2525.

<Contact resistance (mΩ · cm ² ) at the interface between the porous portion and the dense portion>
The test piece obtained by cutting the obtained separator into a desired size was measured under the condition of an energization amount of 1 A while applying a pressure of 1 MPa.

<Gas Permeation Coefficient (10 ⁻¹² mol · m · m ⁻² · sec ⁻¹ · MPa ⁻¹ )>
It was determined by measuring the gas permeation amount per unit time and unit cross-sectional area when a differential pressure of 0.2 MPa was applied with nitrogen gas.

<Drainage>
The state of water generated during power generation was visually observed and judged by the presence or absence of flooding.

  A cell is formed by sandwiching a Dufon Nafion membrane between an anode electrode plate and a cathode electrode plate carrying platinum and arranging the fuel cell separator obtained in Example 1 on the anode side and the cathode side, respectively. After generating power for 1 hour, the cell was disassembled, and the water accumulation in the groove of the separator was visually observed, and judged by the presence or absence of flooding.

(Example 2)
Example 1-3. In Example 1, a battery separator was prepared in the same manner as in Example 1 except that the hot pressing of the dense member and the porous part forming preformed sheet was performed by pressurizing at 1 MPa in a temperature atmosphere of 180 ° C. Obtained.
The precision of the viscosity of the porous part forming raw material slurry used for the forming and the thickness of the porous part forming green sheet were measured in the same manner as in Example 1. The results are shown in Table 1.
In the obtained fuel cell separator, the porosity and pore diameter of the porous part, the specific resistance of the separator, the contact resistance at the interface between the porous part and the dense part, the gas permeability coefficient of the separator, The drainage was measured by the same method as in Example 1. The results are shown in Table 2.

(Example 3)
Example 1-2. In Example 1, the artificial graphite powder whose particle size was adjusted to have a volume average particle size of 240 μm was used as the carbonaceous powder for forming the porous portion. The separator for a fuel cell in the same manner as in Example 1 except that the hot pressing of the dense member and the preformed sheet for forming the porous portion was performed at a pressure of 10 MPa in a temperature atmosphere of 180 ° C. Got.
The viscosity of the porous part forming raw material slurry used for the forming and the accuracy of the porous part forming green sheet thickness were measured in the same manner as in Example 1. The results are shown in Table 1.
In the obtained fuel cell separator, the porosity and pore diameter of the porous part, the specific resistance of the separator, the contact resistance at the interface between the porous part and the dense part, the gas permeability coefficient of the separator, The drainage was measured by the same method as in Example 1. The results are shown in Table 2.

Example 4
Example 1-2. In the above, as the carbonaceous powder for forming the porous part, an artificial graphite powder whose particle size is adjusted so that the volume average particle diameter is 500 μm is used, and the addition amount of the thickener is 100 parts by mass of the carbonaceous powder for forming the porous part. In addition to the ratio of 7 parts by mass relative to the In the same manner as in Example 1, except that the hot pressing of the dense member and the preformed sheet for forming the porous portion was performed by pressurizing at 15 MPa in a temperature atmosphere of 180 ° C. Got.
The precision of the viscosity of the porous part forming raw material slurry used for the forming and the thickness of the porous part forming green sheet were measured in the same manner as in Example 1. The results are shown in Table 1.
In the obtained fuel cell separator, the porosity and pore diameter of the porous part, the specific resistance of the separator, the contact resistance at the interface between the porous part and the dense part, the gas permeability coefficient of the separator, The drainage was measured by the same method as in Example 1. The results are shown in Table 2.

(Example 5)
Example 1-2. In the above, as the carbonaceous powder for forming the porous part, artificial graphite powder whose particle size is adjusted so as to have a volume average particle diameter of 50 μm is used, and the amount of the thickener added is 100 parts by mass of the carbonaceous powder for forming the porous part. And 3 parts by mass in Example 1. In the same manner as in Example 1, except that the hot pressing of the dense member and the preformed sheet for forming the porous portion was performed by pressurizing at 1 MPa in a temperature atmosphere of 180 ° C. Got.
The precision of the viscosity of the porous part forming raw material slurry used for the forming and the thickness of the porous part forming green sheet were measured in the same manner as in Example 1. The results are shown in Table 1.
In the obtained fuel cell separator, the porosity and pore diameter of the porous part, the specific resistance of the separator, the contact resistance at the interface between the porous part and the dense part, the gas permeability coefficient of the separator, The drainage was measured by the same method as in Example 1. The results are shown in Table 2.

(Example 6)
Example 1 In Example 1, a fuel cell separator was obtained in the same manner as in Example 1 except that the molding pressure at the time of forming the dense member was 80 MPa.
The precision of the viscosity of the porous part forming raw material slurry used for the forming and the thickness of the porous part forming green sheet were measured in the same manner as in Example 1. The results are shown in Table 1.
In the obtained fuel cell separator, the porosity and pore diameter of the porous part, the specific resistance of the separator, the contact resistance at the interface between the porous part and the dense part, the gas permeability coefficient of the separator, The drainage was measured by the same method as in Example 1. The results are shown in Table 2.

(Comparative Example 1)
Example 1 A separator for a fuel cell was obtained in the same manner as in Example 1 except that a porous member-forming preformed sheet was laminated on the dense member obtained in Step 1 to form a separator without hot pressing. .
In the obtained fuel cell separator, the specific resistance of the separator, the gas permeability coefficient of the separator, and the drainage during power generation were measured in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 2)
Example 1-2. A porous part forming raw material slurry was prepared in the same manner as in Example 1 except that a porous part forming raw material slurry was prepared without adding a thickener in step 1. Since the slurry flowed out and the sheet spread, a uniform thickness sheet could not be formed.
The viscosity of the porous part molding raw material slurry used for the molding was measured in the same manner as in Example 1. The results are shown in Table 1.

  From the results of Table 1, in Examples 1 to 6, since the porous part forming material contains a thickener, the carbon part powder for forming the porous part is well dispersed, and high thickness accuracy is obtained. A porous part forming green sheet can be obtained, and for this reason, a separator with high homogeneity can be easily produced, whereas in Comparative Example 2, the porous part forming material contains a thickener. Since it is not, it turns out that the green sheet for porous part shaping | molding which has uniform thickness cannot be produced.

Further, from the results of Table 2, the fuel cell separators obtained in Examples 1 to 6 were prepared by press-molding a dense member forming the dense part in advance. Is molded together with the preformed sheet for forming the porous portion, the dense portion and the porous portion are produced by applying different pressures when the separator is produced. For this reason, the fuel cell separators obtained in Examples 1 to 6 are excellent in that the dense part imparts high gas impermeability and the porous part has high porosity and pore diameter. It can be seen that the drainage can be imparted.
On the other hand, in Comparative Example 1, since the separator does not have a porous portion, it can be seen that drainage is low.

  Moreover, since the aspect ratio of the graphite powder used for the preformed sheet for forming the porous portion is in the range of 1.0 to 2.0, the porous member is porous when being compacted and integrated with the dense member. It can be seen that the contact resistance at the interface is reduced (the adhesiveness between the dense part and the porous part is high) because the part is integrated in a state where a part of the part has penetrated into the dense part.

  Furthermore, according to Examples 1 to 6, since the slurry-like forming material is formed into a sheet to form the dense part and the porous part, the dense part forming material and the porous part forming material (raw material mixture) The step of pulverizing the dried product can be omitted, and since it can be supplied into the mold as a sheet instead of the pulverized product, the filling operation into the mold can be performed more easily. Productivity can be improved.

  According to the present invention, the flow path is not easily clogged by water generated during power generation, and it is possible to suppress a decrease in power generation efficiency and an increase in contact resistance, and has excellent strength and gas impermeability, and homogeneity. It is possible to provide a method for producing a fuel cell separator excellent in productivity with high productivity.

DESCRIPTION OF SYMBOLS 1 Fuel cell separator 2 Porous part 3 Dense part 4 Gas flow path 21 Porous part forming preform sheet 31 Dense member 31a Dense body part forming green sheet 31b Dense part edge forming green sheet

Claims (6)

A method for producing a fuel cell separator having a porous part and a dense part, wherein at least a part of a wall surface of a gas flow path is formed by a porous part,
Forming a dense member by forming a slurry-like dense part forming material containing a dense part-forming carbonaceous powder and a dense part-forming thermosetting resin binder into a sheet, and press-molding; and
A process for preparing a porous part forming preform sheet by forming a slurry-like porous part forming material containing a porous part forming carbonaceous powder, a porous part forming resin binder, and a thickener. When,
The dense member and the porous part forming preform sheet so that the molding surface and the porous part forming preform sheet are opposed to each other in a molding die having a molding surface corresponding to the gas flow path shape. Filling and integrating by hot pressing
The manufacturing method of the separator for fuel cells characterized by performing these.   The method for producing a fuel cell separator according to claim 1, wherein the thickener contained in the slurry-like porous portion forming material is a cellulose-based thickener.   3. The method for producing a fuel cell separator according to claim 1, wherein the volume-average particle size of the carbonaceous powder for forming a porous part contained in the slurry-like porous part forming material is 50 to 500 μm.   The method for producing a fuel cell separator according to any one of claims 1 to 3, wherein the slurry-like dense portion forming material or the porous portion forming material is formed into a sheet by a doctor blade method.   The pressing force at the time of creating the dense member is 20 to 100 MPa, and the pressing force at the time of hot pressing the dense member and the preformed sheet for forming the porous portion is 1 MPa or more and less than 20 MPa. Item 5. A method for producing a fuel cell separator according to Item 4.   6. The hydrophilization treatment step is further performed as a subsequent step of the step of filling the dense member and the porous portion forming sheet into a mold and integrating them by hot pressing. The manufacturing method of the separator for fuel cells in any one.