JP2009123491A - Manufacturing method of sheet shape molding material for fuel cell separator and manufacturing method of fuel cell separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a sheet-shape molding material for a fuel cell separator for manufacturing a fuel cell separator in high productivity endowed with high conductivity and high thickness accuracy, as well as a manufacturing method of the fuel cell separator. <P>SOLUTION: Firstly, a form 1 of a BMC (a bulk molding compound) is formed from materials containing graphite, resin, a thickener, or the like. The BMC form 1 is formed into a sheet-shape molding material 10 by being rolled between two rolls 21a, 21b in a state arranged on a film 12a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a sheet-shaped molding material for a fuel cell separator and a method for producing a fuel cell separator.

  A basic cell used in a polymer electrolyte fuel cell is a membrane / electrode assembly (MEA) formed by sandwiching an electrolyte membrane made of an ion exchange membrane between an anode (fuel electrode) and a cathode (air electrode). Assembly) and two fuel cell separators sandwiching the membrane / electrode assembly from both sides.

  Then, depending on the electrical output required for the fuel cell system, several tens to several hundreds of such basic cells are stacked in series to constitute a fuel cell.

  The fuel cell separator described above has a function as a shielding plate for separating the fuel gas and the oxidizing gas, and high conductivity and plate thickness accuracy are required.

  In this fuel cell separator formation process, when a mixture of resin and conductive filler (graphite) is molded by hot pressing, in order to obtain a separator having high conductivity, the content of the conductive filler is increased in the molding material. There is a need to. However, if the amount of the conductive filler is increased, the fluidity is deteriorated, so that there is a problem that the material is difficult to homogenize in the mold at the time of curing and the thickness accuracy is lowered.

  At present, in order to compensate for this poor fluidity, there are many methods in which a preform (sheet-like molding material) is first prepared and this is molded with a mold. In order to improve the productivity of the separator, it is necessary to improve the productivity of the sheet-shaped molding material.

  In JP 2002-198062 A, a uniform sheet is formed by extruding pellets made of carbon powder and thermoplastic resin in order to continuously produce sheets.

In Japanese Patent Publication No. 2003-523066, a mixture of conductive powder and non-conductive polymer powder is heated and pressurized with a calendar or a calendar-like device, and the non-conductive polymer powders are fused together. A sheet is obtained. In order to form a uniform paste in the form of a compound, two patterns are described in the above publication: a case where a low viscosity liquid such as water is mixed with the powder mixture, and a case where only the powder is mixed without using the liquid. ing.
JP 2002-198062 A Special table 2003-523066 gazette

  However, in order to produce a uniform sheet using an extruder as described in JP-A No. 2002-198062, it is necessary to apply a high pressure to the material to increase the density of the material. Therefore, a large force is applied to the carbon powder, and the carbon powder is destroyed. Thereby, electroconductivity falls.

  Moreover, when using a liquid as described in Japanese translations of PCT publication No. 2003-523066, it is necessary to heat and dry the paste-like mixture containing this liquid. When the liquid is not mixed, after the materials are uniformly mixed at a temperature not higher than the melting point of the polymer, the mixture is heated to a temperature higher than that of the polymer to fuse the powders. In either case, in order to fuse the powders, a time longer than a certain time for heating is required, and the productivity is limited.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet-shaped molding material for a fuel cell separator for producing a fuel cell separator having high conductivity and high thickness accuracy with high productivity. A manufacturing method and a manufacturing method of a fuel cell separator are provided.

  The method for producing a sheet-shaped molding material for a fuel cell separator according to the present invention is a method for producing a sheet-shaped molding material for a fuel cell separator for processing into a fuel cell separator by molding, and includes the following steps.

  First, a bulk molding compound (hereinafter referred to as “BMC”) is formed from a raw material containing graphite and resin. The BMC is rolled between two rolls in a state where the BMC is disposed on the film to obtain a sheet-shaped molding material.

  In the present invention, BMC is a concept including BMC foam. Here, the BMC foam is one in which a well-kneaded BMC is put into a box-like container such as a bat and formed into a rectangular parallelepiped shape. The shape may be any, but preferably the width is 50 mm to 500 mm, long The thickness is about 100 mm to 1000 mm and the thickness is about 10 mm to 60 mm. The end of the BMC foam may be a slope instead of a vertical plane.

  According to the method for producing a sheet-shaped molding material for a fuel cell separator of the present invention, since the BMC is rolled between two rolls in a state of being placed on a film, the sheet-shaped molding material is heated. There is no need, and the time for heating becomes unnecessary, and the productivity is improved. Moreover, since it rolls between two rolls, the force added to graphite can be made smaller than the case of extrusion molding. Thereby, destruction of graphite can be suppressed and conductivity can be maintained high. In addition, since a sheet-shaped molding material is produced as a preform, high thickness accuracy can be ensured even if the graphite content is increased.

  Preferably, in the method for producing a sheet-shaped molding material for a fuel cell separator, the BMC is guided between the two rolls via an inclined portion that approaches the perpendicular from the upper side with respect to the perpendicular in the opposing direction of the two rolls. It is burned.

  As a result, when the BMC is bitten between the two rolls, the BMC is pressed against the lower film by its own weight, so that it is difficult to slip with respect to the lower film. For this reason, BMC does not slip with respect to a lower film, but becomes easy to be bitten between two rolls together with the film. Thereby, it can prevent that BMC becomes difficult to enter between two rolls, and can stabilize the width | variety of the BMC sheet contained in a sheet-like molding material.

  In addition, BMC is not forcibly supplied to the roll, but only a necessary amount can be supplied to the roll by its own weight. For this reason, only the amount of BMC that can pass through a certain clearance of the two rolls is bitten into the roll, and a sheet-shaped molding material including a BMC sheet with small variation in weight per unit area can be obtained. .

  In addition, since the BMC is caught between the two rolls without slipping with respect to the lower film, the amount of BMC caught between the rolls is less likely to fluctuate in this respect as well, and the variation in weight per unit area is caused. A sheet-like molding material containing a small BMC sheet can be obtained.

  In the above method for producing a sheet-shaped molding material for a fuel cell separator, the inclination angle of the inclined portion with respect to the perpendicular is preferably 10 ° to 60 °.

  In order for BMC to be bitten well between the two rolls, it is necessary to affix the BMC to the lower film. When the inclination angle of the inclined portion is less than 10 °, the force with which the BMC is pressed against the lower film by its own weight is reduced, and the BMC may not stick to the lower film, and the lower film at the roll portion. The BMC will be slippery on the top. Further, when the inclination angle of the inclined portion exceeds 60 °, the apparatus becomes too large, and the vicinity of the lower side of the BMC arranged in the inclined portion is deformed by the weight of the BMC. The width of the material BMC sheet becomes unstable.

  In the above method for producing a sheet-shaped molding material for a fuel cell separator, the distance L along the perpendicular between the lower end of the inclined portion and the center of the upper roll of the two rolls is preferably 50 mm or more and 170 mm or less.

  When this distance L exceeds 170 mm, the distance between the slope of the inclined portion and the roll becomes too large, and the position where the BMC is pressed against the lower film by its own weight is greatly separated from the position where the two rolls are bitten. Thus, when the distance between the slope of the inclined portion and the roll becomes too large, BMC corresponding to the distance is placed on the lower film in front of the roll, and the film enters the roll at a constant speed. All of the BMC is forcibly rolled into a roll. For this reason, it is not possible to supply only the necessary amount to the roll due to the weight of the BMC as described above, and the variation in weight per unit area of the BMC sheet contained in the sheet-shaped molding material increases, so that the sheet-shaped molding is performed. The yield of the material becomes worse. Further, when the distance L is less than 50 mm, the distance between the inclined surface of the inclined portion and the roll is reduced, so that the thickness of the BMC placed on the inclined portion is also reduced, and the production efficiency is lowered.

  Preferably, in the method for producing a sheet-shaped molding material for a fuel cell separator, when the distance between the inclined surface of the inclined portion and a tangent line parallel to the inclined surface of the upper roll surface of the two rolls is h, The thickness of BMC is 10 mm or more and h or less.

  Considering the work efficiency, the thickness of the BMC is preferably as thick as possible. By doing so, many BMCs can be supplied at once, and the number of times of supplying BMC to the inclined portion can be reduced. Therefore, the thickness of BMC is preferably 10 mm or more. However, if the BMC is too thick, the rotational force of the roll is not transmitted to the BMC well, so the BMC does not bite well. Therefore, the thickness of the BMC is preferably equal to or less than the distance h between the surface of the upper roll and the inclined surface of the inclined portion.

  In the above method for producing a sheet-shaped molding material for a fuel cell separator, the thickness of the BMC is preferably 60 mm or less.

  In the above method for producing a sheet-shaped molding material for a fuel cell separator, there is no particular upper limit if the radius of each of the two rolls is 75 mm or more, but it is usually 200 mm or less.

  When the BMC passes through the roll, it is gradually compressed and rolled from the inlet to the outlet (the clearance is the smallest), but when the roll radius is less than 75 mm, the compression is too rapid and the resistance at the roll portion increases. The roll is bent and the clearance cannot be kept constant.

  In the method for producing a fuel cell separator according to the present invention, the fuel cell separator is formed by molding the sheet-like molding material for a fuel cell separator produced by the method for producing a sheet-like molding material for a fuel cell separator as described above. It is formed.

  According to the method for manufacturing a fuel cell separator of the present invention, a fuel cell separator having high conductivity and thickness accuracy can be manufactured with high productivity.

  As described above, according to the present invention, since the BMC is rolled between two rolls in a state where the BMC is disposed on the film, a sheet-shaped molding material is obtained. Therefore, high conductivity and high thickness accuracy are achieved. The fuel cell separator can be manufactured with high productivity.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a method for producing a sheet-shaped molding material for a fuel cell separator according to an embodiment of the present invention. Referring to FIG. 1, in the method for producing a sheet-shaped molding material for a fuel cell separator in the present embodiment, first, a BMC foam is produced from a raw material containing graphite, resin, and the like (step S1). By rolling this BMC foam using two films and two rollers, a sheet-shaped molding material including a BMC sheet is formed from the BMC foam (step S2). The sheet-shaped molding material is peeled off and molded by a mold to form a fuel cell separator (step S3).

Next, the process for forming the BMC foam (step S1: FIG. 1) will be described.
As described above, the BMC foam is manufactured from raw materials including graphite, resin, and the like.

(graphite)
Examples of graphite include artificial graphite, natural graphite, glassy carbon, carbon black, acetylene black, and ketjen black. Particles and powders can be used alone or in combination. There is no particular limitation on the shape of these particles and powder, and any of particle shape, foil shape, scale shape, plate shape, needle shape, spherical shape, and amorphous shape may be used. Also, expanded graphite obtained by chemically treating graphite can be used. Considering the conductivity, artificial graphite, natural graphite, and expanded graphite are preferable in that a separator having a high degree of conductivity can be obtained in a smaller amount.

(resin)
As the resin, for example, a thermosetting resin is used. Examples of the thermosetting resin include an epoxy resin, a phenol resin, an unsaturated polyester resin, and a vinyl ester resin, and among them, a vinyl ester resin is preferable.

  The unsaturated polyester resin may be a conventionally known one, and an unsaturated polyester obtained by reacting a polybasic acid and a polyhydric alcohol is converted into an ethylenically unsaturated monomer such as styrene which is polymerized therewith. The conventionally well-known resin which melt | dissolved is mentioned.

  The vinyl ester resin may be a conventionally known one. For example, an epoxy acrylate obtained by reacting an epoxy resin with an unsaturated monobasic acid such as (meth) acrylic acid is polymerized with styrene such as styrene. A resin dissolved in an ethylenically unsaturated monomer for crosslinking may be mentioned.

  Examples of the epoxy resin include bisphenol A type, bisphenol F type, naphthalene type, flame retardant type, and tertiary butyl catechol type epoxy resin. Examples of the phenol resin include water-soluble, water-dispersible, organic solvent-soluble types such as a resol type and a novolac type resin.

  These thermosetting resins are used by blending a curing agent and, if necessary, a curing accelerator. For example, as an example of a curing catalyst when an unsaturated polyester resin or vinyl ester resin is used, a curing agent composed of an organic peroxide or a curing accelerator blended with such a curing agent as necessary, Curing agents that decompose at low temperatures of about 40-130 ° C. are used. Here, as the organic peroxide, t-butyl peroxybenzoate, benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, t-butyl peroxy-2-ethylhexanoate, 1,1-di-t -Butylperoxycyclohexane, t-butylperoxyisopropyl carbonate, etc. are used. As the curing accelerator, cobalt naphthenate or dimethylaniline is mainly used. It is preferable that such a hardening | curing agent is mix | blended in the range of 0.5-5 mass parts generally with respect to 100 mass parts of said thermosetting resins.

  Examples of the curing catalyst in the case of using an epoxy resin are not particularly limited as long as they are generally known curing agents, but are amine-based curing agents such as chain or cyclic aliphatic amines, aromatic amines, Examples include polyaminoamide curing agents such as polyaminoamide, acid anhydride curing agents such as aliphatic, alicyclic or aromatic, basic active hydrogen compounds such as dicyandiamide, imidazoles, Lewis acids and Bronsted acid salts. It is done.

  Further, examples of the curing catalyst in the case of using a phenol resin are not particularly limited as long as they are generally known curing agents as described above. However, amine-based catalysts such as hexamethylenetetramine are used in novolac systems, and p-types are used in resole systems. -Organic acids such as toluenesulfonic acid and inorganic acids such as phosphoric acid.

(Thickener)
In addition to graphite and resin, a thickener may be included as a raw material for BMC. As this thickener, a conventionally known organic compound or inorganic compound that exerts a thickening effect on the thermosetting resin can be used, and such a compound can be appropriately selected and used depending on the application. .

  As said organic compound which can be used as a thickener, a polyisocyanate compound, a polycarbodiimide compound, a metal alkoxy compound etc. are mentioned, for example. Examples of the inorganic compound include metal oxides such as finely divided silica and magnesium oxide.

  Examples of thickener organic compounds include polyisocyanate compounds, polycarbodiimide compounds, metal alkoxy compounds, and the like. Among these, a polyisocyanate compound is preferred when it reacts with the hydroxyl group in the thermosetting resin and thickens even under mild conditions from room temperature to around 50 ° C.

  Examples of the polyisocyanate compound include 1,6-hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, 1,4-cyclohexane diisocyanate, 4, Examples include 4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, and norbornene diisocyanate. Moreover, the isocyanurate compound obtained by making various isocyanate compounds isocyanurate is also mentioned. These may be used alone or in combination of two or more.

  In addition, as an example of the organic compound of the thickener, acrylic resin-based fine particles are preferable because they are easily thickened by heating. Examples of such commercially available acrylic resin-based fine particles include polymethyl methacrylate resin-based product name “F303” (manufactured by Nippon Zeon).

  Furthermore, examples of the inorganic compound of the thickener include fine powdered silica and metal oxides such as magnesium oxide. When the viscosity is increased using magnesium oxide, the thermosetting resin composition preferably contains a compound having an acid group. For example, a copolymer of styrene and (meth) acrylic acid is desirable from the viewpoint of water resistance.

(Other additives)
In addition, the raw material of BMC further includes a low shrinkage agent, a polymerization inhibitor, an internal mold release agent, a compatibilizing agent, other additives, a colorant, etc., if necessary, the above-mentioned thermosetting resin, conductive material and thickening agent. It can be mixed with the agent to increase the viscosity. Other additives include silane and titanate coupling agents, flame retardants, UV stabilizers, antioxidants, antistatic agents, hydrophilicity-imparting agents, antibacterial agents, water repellents, defoamers, and air blocking agents. Etc. can also be used.

(Method for forming BMC foam)
In manufacturing the BMC of the present embodiment, for example, graphite, a thermosetting resin, and a thickener are charged together or dividedly charged and kneaded in a mixing apparatus.

  Under the present circumstances, the ratio (mass ratio) of graphite and a thermosetting resin is graphite / thermosetting resin = 60 / 40-99 / 1 normally, Preferably it is 60 / 40-95 / 5, More preferably, it is 70 / 30-90 / 10. If the proportion of graphite is too small, the conductivity is lowered. On the other hand, if the proportion of graphite is too large, the in-mold fluidity is insufficient and the moldability is lowered.

  On the other hand, the amount of the thickener used varies depending on the combination of the thermosetting resin used and the compound used as the thickener. The ratio between the thermosetting resin and the thickener may be adjusted as appropriate so that the viscosity of the thickened material is within an appropriate range.

  For kneading, a mixing device such as a kneader, a stirrer, or a mixer can be used. Such kneading may be performed under normal pressure or under reduced pressure. Moreover, it is preferable that the temperature at the time of kneading | mixing is room temperature-60 degreeC.

  After this kneading, the kneaded product is taken out into a box-like container such as a vat and stored in a heated atmosphere at room temperature to 80 ° C., thereby promoting aging and thickening. Thereby, for example, a BMC foam 1 as shown in FIG. 2 is formed.

Next, the formation process (step S2: FIG. 1) of a sheet-like molding material is demonstrated.
FIG. 3 is a schematic view showing a method for producing a sheet-shaped molding material in one embodiment of the present invention. Referring to FIG. 3, the BMC foam 1 formed as described above is rolled by being caught between two rolls 21a and 21b. In this rolling, the films 12a and 12b are disposed above and below the BMC foam 1, and the BMC foam 1 is rolled by the two rolls 21a and 21b together with the films 12a and 12b. Thereby, the sheet-like molding material 10 containing a BMC sheet is formed.

  The BMC form 1 is guided between the two rolls 21 a and 21 b via the inclined portion 22. The inclined surface 22a of the inclined portion 22 is inclined so that the height decreases as it approaches the rolls 21a and 21b. Specifically, as the inclined surface 22a of the inclined portion 22 approaches the rolls 21a and 21b, the facing direction of the two rolls 21a and 21b (the virtual line A connecting the centers O1 and O2 of the two rolls 21a and 21b) It is inclined so as to approach the vertical line BB from the upper side in the figure with respect to the vertical line BB in the direction along -A).

  The inclination angle θ1 of the inclined surface 22a of the inclined portion 22 with respect to the perpendicular line BB is preferably 10 ° or more and 60 ° or less. Moreover, it is preferable that the distance L along the perpendicular line BB between the lower end 22b of the inclined surface 22a and the center O1 of the upper roll 21a among the two rolls 21a and 21b is 50 mm or more and 170 mm or less.

  Further, when the distance between the inclined surface 22a of the inclined portion 22 and the tangent line CC parallel to the inclined surface 22a of the upper roll 21a of the two rolls 21a and 21b is h, the thickness T of the BMC foam 1 Is preferably 10 mm or more and h or less. The thickness T of the BMC foam 1 is more preferably 60 mm or less.

  There is no particular upper limit as long as the radius r of each of the two rolls 21a and 21b is 75 mm or more, but it is usually preferably 200 mm or less. The radius r of each of the two rolls 21a and 21b may be the same radius or different radii as long as the dimensions are within the above range. Moreover, it is preferable that the space | interval D of the two rolls 21a and 21b is 0.5 mm or more and 8 mm or less. Since BMC is a soft material, the BMC sheet 11 may be deformed when the films 12a and 12b are peeled from the sheet-shaped molding material 10 unless the thickness of the sheet-shaped molding material 10 is 0.5 mm or more. Moreover, since the maximum value of the thickness of a separator does not usually exceed 8 mm, the thickness of the sheet-like molding material 10 shall be 8 mm or less.

  FIG. 4 is a perspective view schematically showing the structure of a sheet-shaped molding material formed by rolling using the above roll. Referring to FIG. 4, a sheet-shaped molding material 10 formed by rolling using the above roll includes a BMC sheet 11 and two films 12 a and 12 b coated on both sides of the BMC sheet 11. have. The BMC sheet 11 is made of the above-described material, and each of the films 12a and 12b is made of, for example, PET (polyethylene terephthalate). Moreover, the thickness of film 12a, 12b is 10-100 micrometers, for example.

  Next, the process of forming a fuel cell separator using the above sheet-shaped molding material (step S3: FIG. 1) will be described.

  The above-mentioned sheet-shaped molding material 10 is peeled off from the films 12a and 12b so as to be in the state of a BMC sheet 11, and is put into a compression molding die and is pressed in this die. At this time, the mold is heated, and the BMC sheet 11 is heated through the mold. When a thermosetting resin is used as the resin binder by this heating and pressing, the thermosetting resin is solidified to form a fuel cell separator molded body. Thereafter, the molded fuel cell separator is taken out from the mold. Further, when a resin binder in which a small amount of a thermoplastic resin is mixed with a thermosetting resin is used, the thermoplastic resin is melted by the heating and pressing described above.

  When a resin binder obtained by mixing a small amount of a thermoplastic resin with a thermosetting resin is used, the mold is subsequently cooled. Also during this cooling, the BMC sheet 11 is pressurized in the mold. By this cooling and pressurization, the thermoplastic resin in a molten state is solidified to form a fuel cell separator molded body. Thereafter, the molded fuel cell separator is taken out from the mold.

  When the resin binder is made of a thermosetting resin as described above, the BMC sheet 11 is heated and pressed with a compression mold to obtain a fuel cell separator molded body. However, the resin binder is a thermoplastic resin and a thermosetting resin. In the case of the resin, the BMC sheet 11 is heated and pressurized and cooled and pressurized with a compression molding die to obtain a fuel cell separator molded body.

  The fuel cell separator manufactured using the sheet-shaped molding material has, for example, the shape shown in FIG. Referring to FIG. 5, examples of the fuel cell separator 31 include a rib shape that serves as a gas or liquid supply path on both sides, and a rib shape provided on one side. Any shape can be adopted for the fuel cell separator 31. The shape of the fuel cell separator 31 can be arbitrarily designed by appropriately selecting the shape of the shaping portion of the compression molding die.

  A fuel cell can be manufactured using the fuel cell separator 31 of the present embodiment obtained as described above. FIG. 6 is a perspective view showing an example of a cell structure of a fuel cell using the fuel cell separator according to one embodiment of the present invention. Referring to FIG. 6, the fuel cell 30 has a fuel cell separator 31 and an electrolyte membrane / membrane assembly 35. The electrolyte membrane / membrane assembly 35 includes, for example, a fuel electrode 32, an oxidant electrode 33, and a solid polymer electrolyte membrane. A pair of fuel cell separators 31, 31 are arranged so as to sandwich the electrolyte membrane / membrane assembly 35, thereby forming a polymer electrolyte fuel cell 30. The fuel cell of the present embodiment can be used even if it is composed of a single fuel cell 30, but usually a fuel in which a plurality of fuel cells 30 are arranged in series for the purpose of improving power generation performance. It is considered as a battery stack.

  The fuel cell separator 31 obtained in the present embodiment is suitable for various fuel cells such as a hydrazine type, a direct methanol type, an alkaline type, and a phosphoric acid type in addition to the solid polymer type fuel cell. Can be applied.

  According to the present embodiment, as shown in FIG. 3, the BMC foam 1 is rolled between the two rolls 21 a and 21 b in a state where the BMC foam 1 is disposed on the lower film 12 a, thereby forming the sheet-shaped molding material 10. Therefore, it is not necessary to heat at the time of rolling, and time for heating becomes unnecessary. In addition, since the BMC foam 1 is rolled only by the two rolls 21a and 21b, the production speed of the sheet-shaped molding material 10 can be controlled only by the rotation speed of the rolls 21a and 21b. For this reason, productivity becomes favorable by controlling appropriately the rotation speed of the rolls 21a and 21b.

  Moreover, since it rolls between the two rolls 21a and 21b, the force added to the graphite in the BMC foam 1 can be made smaller than in the case of extrusion molding. Thereby, destruction of the graphite in the BMC foam 1 can be suppressed, and the conductivity of the fuel cell separator 31 can be maintained high.

  Further, since a sheet-like molding material 10 having a BMC sheet with small variation in weight per unit area can be manufactured as a preform, even if the content of graphite in the BMC foam 1 is increased, the BMC foam 1 is directly molded to form a fuel. Compared with the case where the battery separator 31 is manufactured, high thickness accuracy can be ensured. This will be described below.

  The BMC foam 1 for a fuel cell separator contains a large amount of graphite in order to obtain high conductivity, and therefore has poor fluidity. For this reason, when the BMC foam 1 is directly molded into the fuel cell separator 31, the thickness of the separator 31 varies. On the other hand, when the pressure in the mold is increased, the variation in the thickness of the separator 31 is improved, but the graphite in the BMC foam 1 is destroyed by the high pressure, and the conductivity of the fuel cell separator 31 is lowered.

  Moreover, it is difficult to produce the BMC foam 1 with a thin thickness like the BMC sheet 11. This is because, in order to form the BMC foam 1 with a small thickness, it is necessary to scrape the excess thickness on the upper side of the kneaded material with a squeegee after the kneaded material is taken out into the bat so that the thickness is slightly thicker than desired. However, at this time, since the thickness of the kneaded material in the bat is thin, the kneaded material of a necessary thickness portion is also scraped off by scraping the squeegee, making it difficult to control the thickness.

  On the other hand, in this Embodiment, since the sheet-like molding material 10 which has the thin BMC sheet 11 as a preforming body by roll rolling can be manufactured with high thickness accuracy, this BMC sheet 11 is shape | molded. Thus, the fuel cell separator 31 having high conductivity and high thickness accuracy can be manufactured.

  Further, since the BMC foam 1 is guided between the two rolls 21a and 21b via the inclined portion 22, only the necessary amount of the BMC foam 1 is naturally caught between the two rolls 21a and 21b by its own weight. I can do it. As a result, only the amount of BMC foam 1 that can pass through a certain clearance between the rolls 21a and 21b is caught in the rolls 21a and 21b. For this reason, the BMC foam 1 that is insufficient for the biting portions of the rolls 21a and 21b can be supplied between the two rolls 21a and 21b so that the weight per unit area is constant. Therefore, the sheet-shaped molding material 10 having the BMC sheet 11 with small variation in weight per unit area can be obtained.

  Further, when the BMC foam is bitten between the two rolls 21a and 21b, the BMC foam 1 is pressed against the lower film 12a by its own weight, so that it is difficult to slip with respect to the lower film 12a. For this reason, the BMC foam 1 is likely to be bitten between the two rolls 21a and 21b together with the lower film 12a. Thereby, the width | variety of the sheet-like molding material 10 can be stabilized by preventing that the BMC foam 1 becomes difficult to enter between the two rolls 21a and 21b.

  In addition, since the BMC foam 1 is easily caught between the two rolls 21a and 21b together with the lower film 12a, the amount of the BMC foam 1 caught between the two rolls 21a and 21b is not easily changed. A sheet-shaped molding material 10 having a BMC sheet with a small variation in weight per unit area can be obtained.

  When the inclination angle θ1 of the inclined portion 22 is 10 ° or more, the force with which the BMC foam 1 presses the lower film 12a with its own weight increases. Thereby, it becomes difficult for the BMC foam 1 to slide on the lower film 12a, and when the inclination angle θ1 of the inclined portion 22 is 60 ° or less, an increase in the size of the apparatus can be suppressed, and the inclined portion Since the vicinity of the lower side of the arranged BMC foam can be prevented from being deformed by the weight of the BMC foam, the width of the BMC sheet 11 included in the sheet-shaped molding material 10 formed into a sheet by the roll is stabilized.

  When the distance L is 50 mm or more, the distance h between the inclined surface 22a of the inclined portion 22 and the roll 21a can be increased to some extent. For this reason, the thickness T of the BMC foam 1 placed on the inclined portion 22 can be increased to some extent, and a reduction in production efficiency can be suppressed. When the distance L is 170 mm or less, the position where the BMC foam 1 is pressed against the lower film 12a by its own weight is not greatly separated from the position where it is bitten by the two rolls 21a and 21b. For this reason, it becomes easy to supply the BMC foam 1 between the two rolls 21a and 21b so that the weight per unit area is constant, and the BMC foam 1 per unit area of the BMC sheet 11 included in the sheet-shaped molding material 10 Variation in the weight of the sheet is reduced, and the yield of the sheet-shaped molding material 10 is increased.

  When the thickness T of the BMC foam 1 is 10 mm or more, a large amount of the BMC foam 1 can be supplied to the inclined portion 22 at a time, and the number of times of supplying the BMC foam 1 to the inclined portion 22 can be reduced. Further, when the thickness T of the BMC foam 1 is equal to or less than the distance h between the inclined surface 22a of the inclined portion 22 and the upper roll 21a, the rotational force of the rolls 21a and 21b is well transmitted to the BMC foam 1 and the distance between the rolls 21a and 21b. Bite well.

  In addition, when the radius r of each of the two rolls 21a and 21b is 75 mm or more, the compression of the BMC foam 1 by the rolls 21a and 21b proceeds slowly, so that the resistance at the roll portion is reduced and the roll is bent. Can be suppressed. Further, when the radius r of each of the two rolls 21a and 21b is 200 mm or less, the rolls 21a and 21b can be prevented from being enlarged.

Next, examples of the present invention will be described.
Example 1
Weight per unit area of a sheet-like molding material produced by rolling a BMC foam by a roll, a BMC sheet produced by manually expanding and a BMC sheet produced by extruding with an extruder. And the average particle size of graphite were measured. Production methods, measurement methods, and measurement results of those sheet-shaped molding materials and BMC sheets are described below.

(1) Preparation of vinyl ester resin Into a 2 L four-necked flask equipped with nitrogen and air introduction pipes were charged 910 g of bisphenol A epoxy resin (epoxy equivalent 190), 398 g of methacrylic acid, and 0.4 g of hydroquinone. The temperature was raised to 90 ° C. under a gas flow in which the mixture was mixed 1: 1. 2-methylimidazole 2.0g was put here, and it heated up at 105 degreeC, and made it react for 10 hours. In this way, a vinyl ester resin was obtained.

  Next, this vinyl ester resin was dissolved in 503 g of styrene, 210 g of divinylbenzene (purity 80%), and 0.2 g of toluhydroquinone to obtain a vinyl ester resin liquid having a solid content of 65% by weight. This is designated as thermosetting resin V-1.

(2) Adjustment of thermosetting conductive BMC 1235 g of carbon powder (SGS250, manufactured by ESC Corporation) having an average particle size of 250 microns, 315 g of thermosetting resin V-1 and BIC as a curing agent in a kneader having a stirring capacity of 2 L -75 (organic peroxide, manufactured by Kayaku Akzo) 3.2g, UF-80 (polyethylene powder, manufactured by Sumitomo Seika) as a low shrinkage agent, 4.8g as a thickener, F303 (acrylic fine powder, Nippon Zeon) (Made) 43.2 g was charged and stirred and mixed at room temperature.

  Next, after taking out to the stainless steel bat (width 150mm, length 300mm) of thickness 40mm, it covered with the sheet | seat made from PET in order to prevent volatilization. Further, the bat was inserted into a styrene-impermeable multilayer film bag and sealed. The vat was allowed to stand for 24 hours in a 45 ° C. storage, then taken out and allowed to cool at room temperature. By taking out the BMC from this vat, BMC foam F-1 having a thickness of 40 mm, a width of 150 mm and a length of 300 mm was obtained.

  Using this BMC foam F-1, sheet-like molding materials of Invention Examples 1 to 4 described below were produced, and BMC sheets were produced in Comparative Examples 1 and 2.

[Invention Example 1]
In the sheet forming apparatus shown in FIG. 3 (the diameter of the rolls 21a and 21b is 300 mm), a perpendicular line B-B between the lower end 22b of the inclined portion 22 and the center O1 of the upper roll 21a of the two rolls 21a and 21b. The distance L along was set to 100 mm, and the angle θ1 of the inclined portion 22 was set to 45 °. Thereafter, BMC foam F-1 was formed into a sheet using this sheet forming apparatus, and a continuous sheet-shaped molding material having a thickness of 2.5 mm was produced. This was cut into 200 mm × 200 mm to obtain a sheet-shaped molding material.

[Invention Example 2]
In the sheet forming apparatus, except that the distance L was set to 90 mm, the BMC foam F-1 was formed into a sheet under the same conditions as in the present invention example 1 to obtain a sheet-like molding material having the same shape as the present invention example 1.

[Invention Example 3]
In the sheet forming apparatus, except that the angle θ1 was set to 60 °, the BMC foam F-1 was formed into a sheet under the same conditions as Example 1 of the present invention, and a sheet-shaped molding material having the same shape as Example 1 of the present invention was obtained.

[Invention Example 4]
In the sheet forming apparatus, except that the distance L is 90 mm and the angle θ1 is 60 °, the BMC foam F-1 is formed into a sheet under the same conditions as in the present invention example 1 to obtain a sheet-like molding material having the same shape as the present invention example 1. It was.

[Comparative Example 1]
A small amount of the BMC foam F-1 was cut and expanded little by little by hand to adjust the thickness to 2.5 mm, and then cut into a size of 200 mm × 200 mm to prepare a BMC sheet.

[Comparative Example 2]
The BMC foam F-1 was introduced into a twin screw extruder having a T die having a thickness of 2.5 mm and a width of 200 mm attached to the tip, and the continuously extruded sheet was cut into a length of 200 mm to obtain a thickness of 2. A BMC sheet of 5 mm and 200 mm × 200 mm was produced.

(3) Measuring method of weight variation per unit area of BMC sheet Four 80 mm x 80 mm mini-sheets were cut out from each of these BMC sheets, and the respective weights were measured. At this time, the difference between the maximum value and the minimum value was defined as the weight variation per unit area of the BMC sheet. The results are shown in Table 1 below.

(4) Measuring method of average particle diameter of graphite in BMC sheet in sheet-shaped molding material The average particle diameter of graphite was measured by a laser beam diffraction method. This laser light diffraction method utilizes the fact that the intensity distribution of the diffracted light of a particle is a function of the particle diameter. Specifically, a suspension in which particles are dispersed is caused to flow in the laser light path, one after another. In this method, the diffracted light of the particles passing through is converted into a plane wave by a lens and the intensity distribution in the radial direction is projected onto a photo director by a rotating slit and detected. The results are also shown in Table 1 below.

  From the results in Table 1, in the sheet-like molding material (Invention Examples 1 to 4) produced by the sheet forming apparatus shown in FIG. 3, the weight variation per unit area of the BMC sheet contained in the sheet-like molding material as a whole is I found it small. In addition, in the sheet-like molding material (Examples 1 to 4 of the present invention) produced by the sheet forming apparatus shown in FIG. 3, the average particle diameter of graphite is the same size as when no roll is used (Comparative Example 1). I understood. From this, it was found that graphite was not broken in the sheet-shaped molding material rolled with a roll.

  In addition, it was found that the weight variation per unit area of the BMC sheet was significantly increased in the BMC sheet (Comparative Example 1) produced by hand-spreading as compared with Examples 1 to 4 of the present invention.

  Moreover, it turned out that an average particle diameter becomes small in the BMC sheet | seat (comparative example 2) produced with the extruder compared with invention example 1-4. This is presumably because the graphite was destroyed by a large shearing force acting on the graphite at the screw portion of the extruder. Moreover, in the BMC sheet (comparative example 2) produced with the extruder, although the weight variation per unit area of a BMC sheet was better than the comparative example 1, it turned out that it does not improve to the invention examples 1-4.

(Example 2)
Next, using the sheet-like molding material of Invention Example 1 and the BMC sheets of Comparative Example 1 and Comparative Example 2, the following Invention Examples 5, 5 and 4, and the respective fuel cell separators A and the invention. The fuel cell separator B of each of Example 6 and Comparative Examples 5 and 6 was manufactured, and the thickness variation, voltage drop, and average particle size of each separator were measured. The contents are described below.

  Two types of separators A and B were prepared as separators. The separators A and B are different from each other in flow channel shape and plate thickness, and the contact area of the separator B is larger than that of the separator A (in this embodiment, the area where the electrode portion of the separator and the gold plating electrode are in contact). It has a wide and thin structure. The mold A in the following is a mold for manufacturing the separator A, and the mold B is a mold for manufacturing the separator B.

[Invention Example 5]
One sheet-shaped molding material produced using the sheet forming apparatus in Example 1 of the present invention is peeled off and put into the mold A, and hydraulic output is output by a compression molding machine: surface pressure 40 MPa, upper mold temperature: 140 ° C., lower Molding was performed under the conditions of a mold temperature of 150 ° C. and a molding time of 5 minutes to obtain a fuel cell separator A.

[Comparative Example 3]
A BMC sheet produced by manually expanding in Comparative Example 1 was molded in the same manner as in Inventive Example 5 to obtain separator A.

[Comparative Example 4]
The BMC sheet produced by the extruder in Comparative Example 2 was molded in the same manner as in Invention Example 5 to obtain separator A.

[Invention Example 6]
One sheet-shaped molding material produced by using the sheet forming apparatus in Example 1 of the present invention is peeled off and put into a mold B, and hydraulic output by a compression molding machine: surface pressure 40 MPa, upper mold temperature: 140 ° C., lower Molding was performed under the conditions of a mold temperature of 150 ° C. and a molding time of 5 minutes to obtain a fuel cell separator B.

[Comparative Example 5]
A BMC sheet produced by manually expanding in Comparative Example 1 was molded in the same manner as in Invention Example 6 to obtain separator B.

[Comparative Example 6]
The BMC sheet produced by the extruder in Comparative Example 2 was molded by the same method as in Invention Example 6 to obtain separator B.

(1) Evaluation method of plate thickness variation In each manufactured separator, the plate thickness of 5 electrode parts (upper right, lower right, upper left, lower left, center) was measured using a micrometer, and the difference between the maximum thickness and the minimum thickness The plate thickness variation. The results are shown in Table 2 below.

(2) Voltage drop measurement method Prepare two gold-plated electrodes with the same dimensions (14.5 cm square) as the electrode part of the molded product and carbon paper (thickness 0.4 mm) of the same size. The electrode part is sandwiched between the carbon paper and the electrode, a pressure of 6 kgf / cm ² is applied from both sides of the gold-plated electrode with a hydraulic press, an AC of 10 mA is applied under the pressure, and the voltage drop between the electrodes is measured. did.

  The results are also shown in Table 2 below.

  From the results in Table 2, separators A and B of Invention Examples 5 and 6 (Separator A produced using the sheet-like molding material of Invention Example 1 (sheet-like molding material produced by rolling with a roll)) In (B), since the variation in the weight per unit area of the BMC sheet contained in the sheet-like molding material of Invention Example 1 is small, the variation in the thickness of the separator A manufactured using the BMC sheet may be small. all right. Moreover, since the average particle diameter of the graphite of the BMC sheet contained in the sheet-like molding material of Invention Example 1 was large, it was found that the voltage drop of the separator A of Invention Example 5 was also small.

  On the other hand, in Comparative Examples 3 and 5 (separators A and B manufactured using the BMC sheet of Comparative Example 1 (the BMC sheet produced by hand spreading)), the voltage drop is small, but the BMC of Comparative Example 1 is used. Since the weight variation per unit area of the sheet is large, it has been found that the variation in the thickness of the separators A and B manufactured using the sheet is large.

  In Comparative Examples 4 and 6 (Separators A and B manufactured using the BMC sheet of Comparative Example 2 (BMC sheet produced by an extruder)), the average particle size of graphite in the BMC sheet of Comparative Example 2 is small. Therefore, it was found that the voltage drop of the separators A and B manufactured using this increased.

  The separator B (Invention Example 6, Comparative Examples 5 and 6) shows higher conductivity than the separator A (Invention Example 5, Comparative Examples 3 and 4). This is because the contact area is larger than that of the separator A and the plate thickness is thin.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is used for a fuel cell such as a phosphoric acid fuel cell, a direct methanol fuel cell, and a polymer electrolyte fuel cell, which is applied to a power source for an electric vehicle, a portable power source, an emergency power source, etc. The present invention can be applied particularly advantageously to a method for producing a possible sheet-shaped molding material for a fuel cell separator and a method for producing a fuel cell separator.

It is a block diagram which shows the manufacturing method of the sheet-like molding material for fuel cell separators in one embodiment of this invention. It is a perspective view which shows roughly the shape of the BMC foam used for the manufacturing method of the sheet-like molding material for fuel cell separators in one embodiment of this invention. It is the schematic which shows the manufacturing method of the sheet-like molding material for fuel cell separators in one embodiment of this invention. It is a perspective view which shows roughly the structure of the sheet-like molding material in one embodiment of this invention. It is a schematic perspective view which shows the structure of the fuel cell manufactured by the manufacturing method of the fuel cell separator in one embodiment of this invention. It is a perspective view which shows the example of the cell structure of the fuel cell using the fuel cell separator in one embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 BMC foam, 10 sheet-like molding material, 11 BMC sheet | seat, 12a, 12b film, 21a, 21b roll, 22 inclined part, 22a inclined surface, 22b lower end, 30 fuel cell, 31 fuel cell separator, 32 fuel electrode, 33 Oxidant electrode, 34 solid polymer electrolyte membrane, 35 membrane assembly.

Claims (8)

A method for producing a sheet-shaped molding material for a fuel cell separator for processing into a fuel cell separator by molding,
Forming a bulk molding compound from a raw material containing graphite and resin;
A method for producing a sheet-shaped molding material for a fuel cell separator, comprising a step of forming a sheet-shaped molding material by rolling between two rolls in a state where the bulk molding compound is disposed on a film.   2. The fuel cell separator according to claim 1, wherein the bulk molding compound is guided between the two rolls via an inclined portion that approaches the vertical line from above with respect to a perpendicular line in the opposing direction of the two rolls. For producing a sheet-shaped molding material.   The manufacturing method of the sheet-shaped molding material for fuel cell separators of Claim 2 whose inclination-angle of the said inclination part with respect to the said perpendicular is 10 to 60 degree.   The sheet-shaped molding for a fuel cell separator according to claim 2 or 3, wherein a distance along the perpendicular between the lower end of the inclined portion and the center of the upper roll of the two rolls is 50 mm or more and 170 mm or less. Material manufacturing method.   When the distance between the inclined surface of the inclined part and the tangent line parallel to the inclined surface of the upper roll surface of the two rolls is h, the thickness of the bulk molding compound is 10 mm or more and h or less. The manufacturing method of the sheet-like molding material for fuel cell separators in any one of Claims 2-4.   The manufacturing method of the sheet-like molding material for fuel cell separators of Claim 5 whose thickness of the said bulk molding compound is 60 mm or less.   The manufacturing method of the sheet-like molding material for fuel cell separators in any one of Claims 1-6 whose radius of each of the said 2 roll is 75 mm or more and 200 mm or less.   The manufacturing method of a fuel cell separator which forms a fuel cell separator by shape | molding the said sheet-like molding material for fuel cell separators manufactured by the method in any one of Claims 1-7.

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