JP2005071888A - Manufacturing method for separator-molding resin composition for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator-molding resin composition for a fuel cell used for molding a separator for the fuel cell composing a carbon composite material using a thermosetting resin as a binder, suppressing the cleavage of a graphite particle that is the carbon composite material to maintain the high fluidity of the composition, and improving moldability to obtain the separator having excellent electric characteristics and mechanical characteristics. <P>SOLUTION: A raw material containing the graphite particles and the thermosetting resin is put into a vessel 5, and contents in the vessel 5 are stirred and mixed by rotating a stirrer 6 in the vessel 5 such that a peripheral speed of an outermost edge becomes 15 m/s or below. Next, a solvent dissolving the thermosetting resin is added into the vessel 5, and the stirrer 6 is rotated such that the peripheral speed of the outermost edge becomes 15 m/s or below to perform the stirring and mixing, and granulation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a resin composition for molding a separator used in a fuel cell.

  In general, a fuel cell is composed of a cell stack in which several tens to several hundreds of unit cells are stacked in series, thereby obtaining a predetermined voltage.

  The most basic structure of the unit cell has a configuration of “separator / fuel electrode (anode) / electrolyte / oxidant electrode (cathode) / separator”. In this unit cell, the chemical energy of the reaction is obtained by oxidizing the fuel by electrochemical reaction by supplying fuel to the fuel electrode and supplying the oxidant to the oxidant electrode of the pair of electrodes facing each other through the electrolyte. Direct conversion to electrochemical energy.

  Such fuel cells are classified into several types depending on the type of electrolyte. Recently, solid polymer fuel cells using a solid polymer electrolyte membrane as an electrolyte have attracted attention as fuel cells that can provide high output. Has been.

  FIG. 3 shows an example of a polymer electrolyte fuel cell. A solid polymer fuel cell is formed between two fuel cell separators 1 and 1 each having a plurality of convex portions (ribs) 1a formed on both left and right side surfaces. A single cell (unit cell) is formed by interposing the polymer electrolyte membrane 2 and gas diffusion electrodes (fuel electrode and oxidant electrode) 3 and 3, and several tens to several hundreds of unit cells are arranged in parallel. Thus, a battery body (cell stack) is formed. The convex portion 1a constitutes a gas supply / discharge groove 4 which is a flow path for hydrogen gas as a fuel and oxygen gas as an oxidant between adjacent convex portions 1a.

  Such a cell stack can be composed of, for example, 50 to 100 unit cells in a stationary type for home use, and can be composed of 400 to 500 unit cells for automobile loading.

In this polymer electrolyte fuel cell, hydrogen gas, which is a fluid, is supplied to a fuel electrode, and oxygen gas, which is a fluid, is supplied to an oxidizer electrode, thereby extracting current from an external circuit. In the reaction, the reaction shown in the following formula occurs.
Fuel electrode reaction: H ₂ → 2H ⁺ + 2e ⁻ (1)
Oxidant electrode reaction: 2H ⁺ + 2e ⁻ + 1 / 2O ₂ → H ₂ O (2)
Overall reaction: H ₂ + 1 / 2O ₂ → H ₂ O
That is, hydrogen (H ₂ ) becomes proton (H ⁺ ) on the fuel electrode, and this proton moves through the solid polymer electrolyte membrane to the oxidant electrode and reacts with oxygen (O ₂ ) on the oxidant electrode. To produce water (H ₂ O). Therefore, for the operation of the polymer electrolyte fuel cell, it is necessary to supply and discharge the reactive gas and take out the current.

  In addition, the polymer electrolyte fuel cell is normally assumed to operate in a humid atmosphere in the range of room temperature to 120 ° C., and therefore water is often handled in a liquid state. It is necessary to manage the replenishment of liquid water and discharge the liquid water from the oxidizer electrode.

  Among the components constituting such a fuel cell, the fuel cell separator has a plurality of gas supply / discharge grooves on one or both sides of a thin plate-like body as shown in FIGS. 3 (a) and 3 (b). 4 and has the function of separating the fuel gas, oxidant gas and cooling water flowing in the fuel cell so that they do not mix, and also transmits the electric energy generated by the fuel cell to the outside And plays an important role of radiating the heat generated in the fuel cell to the outside.

  The following demands are generally made for the fuel cell separator. (1) High conductivity, (2) Corrosion resistance (acid resistance) against corrosive electrolytes, (3) Airtightness to separate gases, (4) Tightening with bolts and nuts when assembling to a fuel cell It has strength to prevent cracks and cracks in the separator during assembly work, etc., and mechanical strength, especially when it is used as a power source for automobiles etc., it has excellent vibration resistance and impact resistance Furthermore, creep resistance, (5) formability for forming complex shapes, (6) low cost, (7) swelling resistance (those that do not swell when immersed in water or aqueous sulfuric acid), (8) It is required to simultaneously satisfy required properties such as heat resistance (withstand heat generation during reaction (90 to 120 ° C.)).

  As separators for polymer electrolyte fuel cells, carbon composite materials using various thermoplastic resins or thermosetting resins, which are advantageous in terms of productivity and cost, as binders have been proposed.

  As a method for producing such a resin composition for molding a separator, the following have been proposed as typical ones so far. For example, Patent Document 1 proposes a method of kneading with a pressure kneader, granulating while adding water using a pin type granulator, and then drying. Further, in Patent Document 2, a method for producing a molding material having a predetermined particle size distribution as a high fluidization method for improving moldability, that is, wet-mixing granulation with a granulator to further regulate the particle size and control the particle size distribution. A method has been proposed. Patent Document 3 and Patent Document 4 propose a method of compacting graphite as a raw material or a method of granulating with a Henschel mixer or the like at a temperature equal to or higher than the resin melting temperature as a method that can greatly improve the orientation of graphite in a graphite molded body. Yes. Patent Document 5 proposes a method of granulating while mixing in a non-pressurized state as a method for improving fluidity during molding, or granulating after mixing.

However, even if these methods are used, when kneading using a kneader or the like, the graphite particles and the resin are not sufficiently mixed, and when granulating with a Henschel mixer or the like, the graphite particles are cleaved. As a result, the fluidity of the resulting composition was hindered and the moldability deteriorated, resulting in a decrease in electrical and mechanical properties.
JP 2000-173630 A JP 2001-325967 A JP 2002-114572 A JP 2002-348110 A JP 2003-86198 A

  The present invention has been made in view of the above points, and is a method for producing a resin composition used for molding a fuel cell separator made of a carbon composite material using a thermosetting resin as a binder. Resin for fuel cell separator molding that can suppress the cleavage of graphite particles, which are carbon composite materials, maintain high fluidity of the composition, and improve the moldability to obtain a separator having high electrical and mechanical properties. It aims at providing the manufacturing method of a composition.

  The method for producing a resin composition for molding a fuel cell separator according to the present invention is a method for producing a resin composition for molding a fuel cell separator containing graphite particles and a thermosetting resin as essential components. A raw material containing a curable resin is put in the container 5, and the contents in the container 5 are rotated by rotating the stirring tool 6 in the container 5 so that the peripheral speed of its outermost edge is 15 m / sec or less. Next, a solvent for dissolving the thermosetting resin is added to the container 5 and the stirring tool 6 is rotated so that the peripheral speed of its outermost edge is 15 m / sec or less. It is characterized by performing. By stirring and mixing at such a rotational speed and adding a solvent in which the thermosetting resin dissolves, the contents are sufficiently stirred and mixed, and graphite is added to the thermosetting resin. It is possible to obtain a composition in which other components such as particles are sufficiently dispersed and mixed, and the cleavage of graphite particles in the process of stirring and mixing is suppressed, and the fluidity of the prepared composition is deteriorated. It is possible to maintain high moldability during the production of the separator with this composition.

  The solvent in which the thermosetting resin is dissolved is preferably added to the container 5 by spraying. In this way, the resin component and the graphite particles can be mixed while being blended, and a fine granular composition can be obtained by preventing the formation of large lumps in the composition. A composition having excellent moldability can be obtained.

  Another method for producing a fuel cell separator molding resin composition according to the present invention is a method for producing a fuel cell separator molding resin composition containing graphite particles and a thermosetting resin as essential components. Raw materials other than the synthetic resin are put in the container 5 and the contents in the container 5 are stirred and mixed by rotating the stirring tool 6 in the container 5 so that the peripheral speed of its outermost edge is 15 m / second or less. Then, the thermosetting resin is added to the container 5 in a state of being dissolved in a solvent, and the stirring tool 6 is rotated so that the peripheral speed of its outermost edge is 15 m / sec or less. It is characterized by performing. By stirring and mixing at such a rotational speed and stirring and mixing in a state where the thermosetting resin is dissolved in a solvent, the contents are sufficiently stirred and mixed, and the graphite particles are mixed with the thermosetting resin. A composition in which other components are sufficiently dispersed and mixed can be obtained, and the cleavage of the graphite particles in the stirring and mixing process is suppressed, thereby preventing deterioration of the fluidity of the prepared composition. Thus, it is possible to maintain a high moldability during the production of a separator using this composition.

  It is preferable to add the thermosetting resin dissolved in the above solvent into the container 5 by spraying. In this way, the resin component and the graphite particles can be mixed while being blended, and a fine granular composition can be obtained by preventing the formation of large lumps in the composition. A composition having excellent moldability can be obtained.

  Moreover, it is also preferable to perform stirring and mixing while heating at a temperature higher than the melting start temperature of the thermosetting resin. In this case, stirring and mixing can be performed in a state where the thermosetting resin is melted, and a more uniformly mixed composition can be obtained.

  The amount of the graphite particles used is preferably 75 to 90% by weight of the whole raw material. Thereby, while providing the electroconductivity excellent to the separator formed, the gas permeability and moldability required for a separator can fully be maintained.

  Furthermore, it is preferable that the graphite particles are natural graphite or artificial graphite and have been purified. Since ash and ionic impurities are low, it is possible to reduce the elution of impurities from the obtained separator and to prevent deterioration of the characteristics of the fuel cell.

  In the present invention, a composition in which other components such as graphite particles are sufficiently dispersed and mixed with the thermosetting resin can be obtained, and cleavage of the graphite particles in the process of stirring and mixing is suppressed. The deterioration of the fluidity of the prepared composition can be prevented, and high moldability at the time of production of the separator by this composition can be maintained.

  Embodiments of the present invention will be described below.

The fuel cell separator molding resin composition according to the present invention contains a thermosetting resin and graphite particles as essential components, but preferably does not contain a primary amine and a secondary amine. That is, it is preferable that this composition does not contain a compound having substituents —NH and —NH ₂ . Further, it is preferable not to contain a tertiary amine. For this reason, the fuel cell separator 1 formed from this composition does not poison the platinum catalyst in the fuel cell, and suppresses a decrease in electromotive force when the fuel cell is used for a long time. it can.

  As the thermosetting resin, appropriate ones applicable to resin molding can be used, but it is preferable to include one or both of epoxy resin and phenol resin, and these have good resin viscosity. It is suitable because it has few impurities. In particular, epoxy resins are particularly excellent because they contain few ionic impurities. Thus, when including at least one among an epoxy resin and a phenol resin as a thermosetting resin, the total amount of an epoxy resin and a phenol resin is in the range of 50 to 100 weight% with respect to the thermosetting resin whole quantity. Preferably there is.

  In addition to these resins, one or more resins selected from polyimide resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins and the like can be used in combination. There is a risk of hydrolysis. Among these resins, it is particularly suitable to use a polyimide resin because it contributes to improvement of heat resistance and acid resistance. As such a polyimide resin, it is particularly preferable to use a bismaleimide resin, for example, 4,4-diaminodiphenyl bismaleimide. By using this together, the heat resistance of the molded product can be further increased.

  Further, in these thermosetting resins, it is preferable that the content of chlorine ions, which are ionic impurities, and the content of sodium ions are both 5 ppm or less by weight with respect to the total amount of the thermosetting resin. In this case, the elution of impurities from the separator which is a molded product can be further reduced.

  When an epoxy resin is used as the thermosetting resin, it is preferable to use a solid resin, and it is particularly preferable to use a resin having a melting point in the range of 70 to 90 ° C. Thereby, there is little change of material and the handleability at the time of shaping | molding improves. If the melting point is less than 70 ° C., the produced molding material tends to aggregate and the handleability may be reduced.

  Such an epoxy resin is preferably contained in a proportion of 50 to 100% by weight with respect to the total amount of the thermosetting resin.

  In particular, when an epoxy resin is used, by selecting a low-viscosity resin, the moldability can be maintained and the graphite particles can be highly filled.

  Moreover, when using a phenol resin as a thermosetting resin, it is preferable to use the phenol resin which a polymerization reaction advances especially by ring-opening polymerization. Examples of such phenol resins include benzoxazine resins. In this case, no gas is generated due to dehydration in the molding process, so no voids are generated in the molded product, and a decrease in gas permeability can be suppressed. When the phenol resin in which the polymerization reaction proceeds by such ring-opening polymerization is contained, the content is preferably in the range of 5 to 50% by weight with respect to the total amount of the thermosetting resin.

  In particular, when a phenol resin is used, it is also preferable to use a resol type phenol resin. At this time, for example, in 13C-NMR analysis, ortho-ortho 25-35%, ortho-para 60-70%, para-para 5 It is preferable to use a resol type phenol resin having a structure of 10%. The resol resin is usually in a liquid state, but the above-mentioned resol type phenol resin can easily adjust the softening point and can easily obtain a resin having a melting point of 70 to 90 ° C. Thereby, there is little change of material and the handleability at the time of shaping | molding improves. If the melting point is less than 70 ° C., the produced molding material tends to aggregate and the handleability may be reduced. When such a resol type phenol resin is contained, the content thereof is preferably in the range of 10 to 70% by weight based on the total amount of the thermosetting resin.

  Further, the graphite particles are contained in order to reduce the electrical specific resistance of the molded separator 1 and improve the conductivity of the separator 1. The content of graphite particles is preferably in the range of 75 to 90% by weight with respect to the total amount of the composition. If the ratio of the graphite particles is less than 75% by weight, the conductivity required for the separator 1 may not be sufficiently obtained, and if it exceeds 90% by weight, the gas permeability and molding required for the separator 1 may be obtained. There is a risk that sufficient properties cannot be obtained.

  The graphite particles can be used without limitation as long as they exhibit high conductivity, such as graphitized carbonaceous materials such as mesocarbon microbeads, graphitized coal-based coke and petroleum-based coke. Any suitable powder such as a graphite electrode, a processed powder of a special carbon material, natural graphite, quiche graphite, expanded graphite, or the like can be used. Such graphite particles can be used alone or in combination of two or more.

  The graphite particles may be either artificial graphite powder or natural graphite powder, but natural graphite powder has the advantage of high conductivity, and artificial graphite powder is slightly inferior in conductivity to natural graphite powder. There is an advantage that there is little directivity.

  Moreover, it is preferable that the graphite particles are purified from natural graphite or artificial graphite. In this case, since the ash content and ionic impurities are low, the graphite particles are separated from the molded article separator. The elution of impurities can be suppressed.

  Here, the ash content in the graphite particles is preferably 0.05% by weight or less, and the ionic impurities in the extracted water have a sodium content of 5 ppm or less and a chlorine content of 5 ppm or less in a weight ratio with respect to the total amount of the graphite particles. It is preferable to make it. Here, the extracted water is obtained by dispersing the target component in ion-exchanged water at a rate of 100 ml of ion-exchanged water with respect to 10 g of the target component (here, graphite particles) and treating at 90 ° C. for 50 hours. Ionic impurities in the extracted water are evaluated by ion chromatography. Based on the derived amount of ionic impurities in the extracted water, the total amount of ionic impurities in the target component in the composition is converted into a weight ratio to the total amount of the target component in the composition and is derived. It is. The content of ionic impurities can be measured by the same method as above except for graphite.

  If the above ash content exceeds 0.05% by weight, there is a risk that the characteristics of the fuel cell will deteriorate. Further, when the ionic impurities in the extracted water exceed the sodium content of 5 ppm or the chlorine content exceeds 5 ppm, the characteristics of the fuel cell may deteriorate due to the elution of the impurities when the separator is molded.

  Further, graphite particles having an average particle diameter of 1 to 150 μm are preferably used, and those having an aspect ratio of 10 or less are preferable. If the average particle size is less than 1 μm, the moldability is lowered, and if it exceeds 150 μm, the surface smoothness of the molded product may be impaired. On the other hand, if the aspect ratio exceeds 10, anisotropy may occur in the molded separator 1 and warping may occur.

  Further, as the graphite particles, it is particularly preferable to use those having two or more kinds of particle size distributions, that is, those obtained by mixing two or more kinds of particle groups having different average particle diameters. In this case, it is particularly preferable that the average particle size is in the range of 1 to 50 μm and the average particle size is in the range of 50 to 100 μm. When graphite particles having such a particle size distribution are used, particles having a large particle size have a small surface area, so that it is expected that kneading is possible even with a small amount of resin. It is expected that the strength of the molded product will be increased while improving the contact property of the separator, thereby improving the performance such as improvement of the bulk density of the separator 1, improvement of conductivity, improvement of gas impermeability, improvement of strength, etc. Can be achieved. At this time, the mixing ratio of the particles having an average particle diameter of 1 to 50 μm and the particles having an average particle diameter of 50 to 100 μm is appropriately adjusted. In particular, the mixing ratio of the former to the latter is 40:60 by weight. It is preferable that it is -90: 10, especially 65: 35-85: 15.

  The composition may contain additives such as a curing initiator, a curing catalyst, a wax (release agent), and a coupling agent as necessary. Since it is preferable not to contain a primary amine and a secondary amine in a composition at this time, it is preferable not to use such an amine compound also as these additives.

  That is, it is preferable to use a non-amine compound as a curing initiator (curing agent) used when an epoxy resin is used. In the case of using an amine-based material, it is difficult to maintain the electric conductivity of the obtained separator 1 in a high state, and there is a risk of poisoning the fuel cell catalyst. Further, it is preferable not to use an acid anhydride compound as a curing initiator. An acid anhydride compound may be hydrolyzed in an acid-resistant environment such as a sulfuric acid acid environment, resulting in a decrease in electrical conductivity or an increase in impurity elution.

  As the curing initiator, it is particularly preferable to use a phenol compound, and in this case, a cured product having excellent characteristics can be obtained.

  The content of such a curing initiator is appropriately set, but it is preferable that the stoichiometric equivalent ratio of the epoxy resin to the curing initiator is 1 to 0.85.

  Moreover, as a curing catalyst (curing accelerator) used when using an epoxy resin, although an appropriate thing can be contained, in order not to contain a primary amine and a secondary amine in a composition. It is preferable to use a non-amine compound. For example, amine-based diaminodiphenylmethane is not preferable because the residue may poison the fuel cell catalyst. In addition, imidazoles are not preferred because they easily release chlorine ions after curing, which may cause impurity elution.

  As a curing catalyst for the epoxy resin, a phosphorus compound is preferably used. An example thereof is triphenylphosphine. When such a phosphorus compound is contained, elution of chlorine ions from the separator which is a molded product can be suppressed.

  Also in the curing initiator and the curing catalyst as described above, it is preferable that the content of chlorine ions, which are ionic impurities, and the content of sodium ions are both 5 ppm or less in weight ratio. In this case, elution of ionic impurities from the separator, which is a molded product, can be further suppressed. If each content exceeds 5 ppm, the amount of impurities elution increases, resulting in deterioration of characteristics as a fuel cell. There is a fear.

  The content of such a curing catalyst is appropriately adjusted, but is preferably in the range of 0.5 to 3 parts by weight with respect to the epoxy resin.

  Moreover, a coupling agent can be contained in the composition. As this coupling agent, an appropriate one is used, but it is preferable not to use aminosilane since the primary amine and secondary amine are not contained in the composition. When aminosilane is used, there is a risk of poisoning the fuel cell catalyst, which is not preferable. Further, it is preferable not to use mercaptosilane as a coupling agent. The use of this mercaptosilane is also not preferable because it may similarly poison the fuel cell catalyst.

  As an example of the coupling agent used, a silicon-based silane compound, titanate-based, or aluminum-based one can be used. For example, epoxy silane is suitable as a silicon-based coupling agent.

  The coupling agent is preferably attached to the surface of the graphite particles by spraying or the like in advance. The amount of addition is appropriately set, and it is necessary to consider the coating area per unit weight of the coupling agent to be used as compared with the specific surface area of the graphite particles. The total amount is in the range of 0.5 to 2 times the total surface area of the graphite particles. When this value increases, it is not preferable because it bleeds on the surface of the molded product and contaminates the mold surface.

  In addition, when a wax (release agent) is contained in the composition, an appropriate one is used, and natural carnauba wax is particularly preferably used. Further, the content of the wax is appropriately set, but is preferably in the range of 0.1 to 2.5% by weight with respect to the total amount of the composition, and if this content is less than 1% by weight, it is sufficient at the time of molding the mold. If the mold release property is not obtained, and if it exceeds 2.5% by weight, sufficient wettability with water required for the separator 1 may not be obtained.

  Also in such a wax, it is preferable that the content of chlorine ions, which are ionic impurities, and the content of sodium ions are both 5 ppm or less in terms of weight. If the content of each ionic impurity exceeds 5 ppm, when the molded product is used as a fuel cell, the impurities may elute and the characteristics may deteriorate.

  In the present invention, it is preferable that the ratio of the contact resistance between the flow direction of the resin during molding and the direction orthogonal to the flow direction in the molded separator is 2 or less. When this value exceeds 2, the resistance value becomes anisotropic, and the characteristics as the fuel cell separator 1 are deteriorated.

  Moreover, it is preferable that the composition prepared in the present invention has a TOC (total organic carbon) of a molded article formed from the composition of 100 ppm or less.

Here, TOC is a numerical value measured using an aqueous solution after processing a molded article having a specific surface area of 20 cm ² / g at 90 ° C. for 50 hours. Such a TOC can be measured by, for example, Shimadzu total organic carbon analyzer “TOC-50” in accordance with JIS K0102. In the measurement method, the concentration of carbon in the sample is quantified by measuring the CO ₂ concentration generated by burning the sample by a non-dispersive infrared gas analysis method. By measuring the carbon concentration, the concentration of organic substances contained indirectly can be measured, the inorganic carbon (IC) and total carbon (TC) in the sample are measured, and the difference between the total carbon and inorganic carbon (TC− IC) to measure total organic carbon (TOC).

  If the above TOC exceeds 100 ppm, there is a risk that the characteristics of the fuel cell will deteriorate, and if it is 100 ppm or less, such characteristics deterioration can be suppressed.

  Here, in the present invention, the TOC value can be reduced and adjusted by selecting a high-purity raw material, adjusting the equivalent ratio of the resin, or performing post-curing treatment.

  Moreover, it is preferable that content of the chlorine ion and sodium ion which are water-soluble ion in the whole composition is 5 ppm or less by weight ratio with respect to the composition whole quantity, respectively. If this value exceeds 5 ppm, the elution of impurities from the molded separator may cause a decrease in characteristics as a fuel cell such as a decrease in starting voltage. By making this value 5 ppm or less, Such characteristic deterioration can be prevented from occurring.

Based on the weight of the composition, the content of the above-mentioned chlorine ions and sodium ions is obtained by extracting water-soluble ions from a molded product obtained by molding the composition and evaluating and measuring the ions by ion chromatography. It can be derived by conversion. Extraction of water-soluble ions at this time can be performed by treating a molded article having a specific surface area of 20 cm ² / g in 90 mL of ion-exchanged water at 90 ° C. for 50 hours.

  When preparing the resin composition for a fuel cell separator, the above components are mixed by an appropriate method, and kneading and granulation are performed as necessary. Below, the preparation method of the resin composition for separator formation for fuel cells is demonstrated.

  The mixing stirrer for preparing the composition used in the present invention is provided with a stirring tool 6 that rotates uniaxially inside the container 5. The agitator 6 may have an appropriate configuration, and a plurality of types of agitators 6 may be provided. The direction of the rotating shaft 12 of the agitator 6 can also be set as appropriate. However, the stirrer 6 can be formed so as to rotate around the substantially horizontal rotating shaft 12 or rotate around the approximately vertical rotating shaft 12. It can be formed as follows.

  FIG. 1 shows an example of a mixing stirrer for preparing a composition. This is provided in the container 5 with a stirring tool 6 that rotates around the rotation axis 12 in the substantially vertical direction.

  In the illustrated example, a lower blade 6 a and an upper blade 6 b that rotate about the same rotating shaft 12 are provided as a stirring tool 6 at the bottom of the container 5. The lower blade 6a is formed of two rotating arms 19 that extend radially from the rotating shaft 12 in opposite directions. The upper blade 6b supports a ring-shaped rotating wheel 17 at the tips of a plurality of support arms 16 projecting radially outward from the rotating shaft, and radially disengages the two arm portions 18 from the outer edge of the rotating wheel 17. It has a shape that protrudes in the direction.

  Moreover, it is preferable to form so that the contents of the container 5 can be heated. For example, the contents of the container 5 can be formed so as to be heatable by forming a hollow partition wall 5 and circulating a heating medium in the partition wall.

  Moreover, it is preferable to provide a decompression mechanism for decompressing the inside of the container 5. For example, the container 5 can be formed so as to be hermetically sealed, and a suction port is provided in the container 5, and the inside of the container 5 can be formed so as to be depressurized by suction from the suction port.

  FIG. 2 shows yet another example of a mixing stirrer for preparing the composition. As shown in FIG. 1, a stirrer 6 that rotates around a rotating shaft 12 in the container 5 is provided in the container 5. In the illustrated example, the stirrer 6 has a substantially horizontal rotating shaft. 12 is formed so as to be rotationally driven around the center.

  The agitator 6 may have an appropriate configuration, and a plurality of types of agitators 6 may be provided. In the illustrated one, a mixing arm 6 c and a chopper 6 d are provided as the stirring tool 6. The mixing arm 6c and the chopper 6d are connected to different substantially horizontal rotating shafts 12 at positions along inner walls facing each other of the container.

  The mixing arm 6c is provided with a plurality of arms 13 projecting radially outward from the base end connected to the rotating shaft 12 (12a). It is bent in a substantially horizontal direction toward the side.

  Moreover, it is preferable to provide a decompression mechanism for decompressing the inside of the container 5. For example, the container 5 can be formed so as to be hermetically sealed, and a suction port is provided in the container 5, and the inside of the container 5 can be formed so as to be depressurized by suction from the suction port.

  Two choppers 6d are provided in the illustrated example. The chopper 6d is formed so as to extend in a substantially horizontal direction from the base end connected to the rotary shaft 12 (12b) toward the opposing inner wall, and the chopper 6d It is arranged at a position surrounded by a plurality of arms 13. On the outer peripheral surface of the chopper 6d, a plurality of stirring rods 14 project radially outwardly.

  Reference numeral 15 in the figure denotes a spray nozzle that sprays liquid into the container 5 in a spray form.

  In preparing the composition using such a mixing stirrer shown in FIGS. 1 and 2, the peripheral speed of the outermost edge portion of the stirring tool 6 is kept in a state where the raw material of the composition is put in the container 5. Rotate to 15 m / sec or less. When a plurality of stirring tools 6 and a plurality of types of stirring tools 6 are provided, all the stirring tools 6 are rotated under such conditions. That is, in the example shown in FIG. 1, the outermost edge part (tip of the arm part 18) of the upper blade 6a and the outermost edge part (tip of the rotating arm 19) of the lower blade 6b both have a peripheral speed of 15 m / second or less. In the example shown in FIG. 2, the outermost edge of the mixing arm 6c (the outermost edge of the arm 13) and the outermost edge of the chopper 6d (the tip of the stirring bar 14) are Both are rotated so that the peripheral speed is 15 m / sec or less.

  By stirring and mixing under such conditions, the contents of the container 5 are sufficiently stirred and mixed to obtain a composition in which other components such as graphite particles are sufficiently dispersed and mixed with the thermosetting resin. In addition, the cleavage of the graphite particles in the process of stirring and mixing is suppressed, so that the fluidity of the prepared composition is prevented from being deteriorated. It can be maintained. Here, the lower limit of the peripheral speed of the outermost edge portion of the agitator 6 is not particularly limited, but it is preferable to set the peripheral speed to 5 m / second or more in order to mix uniformly.

  Moreover, it is preferable to heat the content containing the thermosetting resin in the container 5 at a temperature equal to or higher than the melting start temperature of the thermosetting resin at the time of stirring and mixing by rotating the stirring tool 6. In this case, stirring and mixing are performed in a state where the thermosetting resin is melted, and further uniform stirring and mixing can be performed.

  A more specific example of the method for preparing the composition using the mixing stirrer as shown in FIGS.

  For example, first, a mixture of components constituting the composition is put into the container 5, and the agitator 6 is rotationally driven and mixed under predetermined conditions. At this time, it is preferable to heat the contents of the container 5 to a temperature equal to or higher than the melting start temperature of the thermosetting resin in the composition by heating the container 5. Although the heating temperature of this container 5 is suitably set according to the kind of thermosetting resin which comprises a composition, Preferably the upper limit of this heating temperature shall be 120 degreeC. Moreover, it is preferable that the stirring time at this time shall be 5 to 30 minutes. Thus, by mixing the thermosetting resin in a molten state, the thermosetting resin and other components such as graphite particles can be mixed uniformly.

  Next, a solvent in which the thermosetting resin is dissolved is added into the container 5, and the stirring tool 6 is further rotated under predetermined conditions to continue mixing. The stirring time at this time is preferably 5 to 30 minutes. Thereby, the thermosetting resin and other components such as graphite particles can be further uniformly mixed. At the same time, by heating the container 5 in the same manner as described above, if the contents are heated to a temperature equal to or higher than the melting start temperature of the thermosetting resin in the composition, further uniform mixing is possible. Can do.

  Although said solvent is suitably selected according to the kind etc. of thermosetting resin, isopropyl alcohol can be mentioned, for example. The amount of the solvent used is adjusted to an appropriate amount so that all the thermosetting resin can be dissolved. Preferably, the amount of the solvent used is 50% by weight based on the total solid content of the composition raw material. %, And if the amount of the solvent used exceeds this range, the time required for the solvent to evaporate becomes longer and the productivity decreases. The amount used is more preferably 25% by weight or less.

An appropriate method can be adopted when adding the solvent, but it is preferable to drop or spray the solvent into the container 5. Especially when added by spraying, the resin component and graphite particles can be mixed while blending, and it becomes possible to obtain a fine granular composition by preventing the formation of large lumps in the composition. A composition having excellent moldability can be obtained. The solvent injection conditions are preferably a spray pressure of 0.05 to 0.3 MPa, an amount of spray air of 5 to 50 ml / min, and a fluid pressure of 0.05 to 0.5 MPa. Next, the composition is granulated by further rotating the stirring tool 6 under predetermined conditions and volatilizing the solvent. The stirring time at this time is preferably 5 to 30 minutes.
Volatilization of the solvent can be performed by heating the inside of the container 5 or reducing the pressure inside the container 5. For example, the solvent can be volatilized by heating the inside of the container 5 and reducing the pressure. At this time, for example, the inside of the container 5 is heated to a temperature higher than the temperature at which the thermosetting resin dissolves, and the inside of the container 5 is set to 0. The pressure can be reduced to a pressure range of 1 MPa to 0.01 MPa. When stirring and mixing are continued in such a state, the solvent is volatilized, the viscosity of the contents is increased, granulation is performed, and a granular composition is prepared. If the solvent remains, voids may be generated in the molded product and gas permeability may be reduced.

  Moreover, the obtained composition can be further pulverized with a granulator or the like to be formed into a smaller particle size, for example, a particle size of 500 μm or less.

  Another example of the method for preparing the composition using the above mixing stirrer will be described.

  In this example, out of the components constituting the composition, the one excluding the thermosetting resin is first put into the container 5, and the stirrer 6 is rotationally driven to be mixed. The stirring time at this time is preferably 5 to 30 minutes.

  Next, the thermosetting resin is added to the container 5 in a state dissolved in a solvent, and stirring and mixing are continued. The solvent is appropriately selected according to the type of thermosetting resin, and examples thereof include isopropyl alcohol. The amount of the solvent used is adjusted to an appropriate amount so that all the thermosetting resin can be dissolved. Preferably, the amount of the solvent used is 50% by weight based on the total solid content of the composition raw material. %, And if the amount of the solvent used exceeds this range, the time required for the solvent to evaporate becomes longer and the productivity decreases. The amount used is more preferably 25% by weight or less.

  An appropriate method can be adopted when adding the thermosetting resin dissolved in the solvent, but it is preferable to drop or spray this into the container 5. In particular, when added by spraying, the resin component and graphite particles can be mixed while being blended, and it becomes possible to obtain a fine granular composition by preventing the formation of large lumps in the composition. A composition having excellent moldability can be obtained. The spray conditions of the thermosetting resin dissolved in the solvent are preferably a spray pressure of 0.05 to 0.3 MPa, a spray air amount of 5 to 50 ml / min, and a fluid pressure of 0.05 to 0.5 MPa. The above effects are sufficiently exhibited.

  The stirring time at this time is preferably 5 to 30 minutes. Thus, by performing stirring and mixing in a state where the thermosetting resin is dissolved in the solvent, the thermosetting resin and other components such as graphite particles are further uniformly mixed.

  Moreover, in the case of this stirring and mixing, it is preferable to heat the container 5 to a temperature equal to or higher than the melting start temperature of the thermosetting resin in the composition. Although the heating temperature of this container 5 is suitably set according to the kind of thermosetting resin which comprises a composition, it is preferable that the upper limit of heating temperature shall be 130 degreeC. Thereby, thermosetting resin and other components, such as a graphite particle, are mixed further more uniformly.

Next, the composition is granulated by further rotating the stirrer 6 under predetermined conditions and volatilizing the solvent. The stirring time at this time is preferably 5 to 30 minutes.
Volatilization of the solvent can be performed by heating the inside of the container 5 or reducing the pressure inside the container 5. For example, the solvent can be volatilized by heating the inside of the container 5 and reducing the pressure. At this time, for example, the inside of the container 5 is heated to a temperature higher than the temperature at which the thermosetting resin dissolves, and the inside of the container 5 is set to 0. The pressure can be reduced to a pressure range of 1 MPa to 0.01 MPa. When stirring and mixing are continued in such a state, the solvent is volatilized, the viscosity of the contents is increased, granulation is performed, and a granular composition is prepared. If the solvent remains, voids may be generated in the molded product and gas permeability may be reduced.

  Moreover, the obtained composition can be further pulverized with a granulator or the like to be formed into a smaller particle size, for example, a particle size of 500 μm or less.

  The resin composition for molding a fuel cell separator obtained as described above is used for molding the fuel cell separator 1. As a molding method at this time, an appropriate method such as injection molding or compression molding can be employed. As described above, the separator 1 can be formed in a shape as shown in FIG.

  In such a molding process, when the above-described preparation method is employed as a method for preparing the composition, the composition is less likely to cleave the graphite particles as described above during the molding process. The composition has good fluidity and excellent moldability. For this reason, also when forming in a complicated shape like the case where a plurality of fine convex parts (ribs) 1a are formed in the separator 1, the occurrence of unfilling at the time of molding is suppressed and molding defects are prevented. Can do. Moreover, when the particle size of the composition is 500 μm or less as described above, unfilling at the time of molding can be further suppressed.

  Further, when the separator 1 is formed from a composition not containing a primary amine and a secondary amine as described above, a fuel cell is produced using the separator 1, and when this is operated, poisoning of the platinum catalyst This can suppress the decrease in the output of the fuel cell.

  Hereinafter, the present invention will be described in detail based on examples.

(Examples 1-3, 5-8, comparative examples)
As the stirring mixer, the one having the structure shown in FIG. 2 ("Spartan Luzer RMO-2H" manufactured by Dalton Co., Ltd.) was used, and the raw materials were put into the container 5 so as to have the composition shown in Table 1, and the container In a state where 5 is heated to 90 ° C. with warm water, the stirrer 6 is planetarily rotated at the revolution number and rotation number described in the column of “Stirrer Rotation Speed” in Table 1 and stirred for 5 minutes. 25 parts by weight of (isopropanol) was added. In adding the solvent, spraying was performed under the conditions of a spraying pressure of 0.2 MPa, a spraying air amount of 25 ml / min, and a liquid pressure of 0.3 MPa. Stirring was continued for another 10 minutes after the addition of the solvent. Next, the solvent isopropanol was completely removed by drying under reduced pressure at 90 ° C. using a vacuum pump. The obtained kneaded material was pulverized to a particle size of 500 μm or less with a granulator.

The obtained pulverized product was molded for 20 minutes under conditions of a temperature of 175 ° C. and a pressure of 34.3 MPa (350 kg / cm ² ), and demolded to obtain a separator 1 having a shape as shown in FIG.

Example 4
As the stirring mixer, the one shown in FIG. 1 (“Mitsui Henschel Mixer FM20” manufactured by Mitsui Mining Co., Ltd.) is used, and the raw materials are prepared in the container 5 so that the composition shown in Table 1 is obtained except for the epoxy resin. In the state where the container 5 was heated to 90 ° C. with warm water, the stirring tool 6 was planetarily rotated at the revolution number and the rotation speed described in the column of “Stirring tool rotational speed” in Table 1 and stirred for 5 minutes. Thereafter, an epoxy resin dissolved in 25 parts by weight of a solvent (isopropanol) was added. When the epoxy resin dissolved in the solvent was added, spraying was performed under the conditions of a spraying pressure of 0.2 MPa, a spraying air amount of 25 ml / min, and a liquid pressure of 0.3 MPa. Stirring was continued for an additional 10 minutes after the addition of this solvent and epoxy resin. Next, the solvent isopropanol was completely removed by drying under reduced pressure at 90 ° C. using a vacuum pump. The obtained kneaded material was pulverized to a particle size of 500 μm or less with a granulator.

The obtained pulverized product was molded for 20 minutes under conditions of a temperature of 175 ° C. and a pressure of 34.3 MPa (350 kg / cm ² ), and demolded to obtain a separator 1 having a shape as shown in FIG.

(Evaluation)
-TOC measurement: According to JIS K0551-4.3, the molded article was first washed with methanol for 1 minute and then washed with ion-exchanged water for 1 minute. Next, the molded product and ion-exchanged water were placed in a glass bottle so that the amount of ion-exchanged water was 100 ml with respect to 10 g of the molded product, and treated at 90 ° C for 50 hours. After adjusting the pH to 2 or less by adding phosphoric acid to the ion-exchanged water after the treatment, the amount of organic carbonic acid is measured by a wet oxidation-infrared TOC measurement method (using “Toray Stro TOC Automatic Analyzer MODEL1800” manufactured by Toray Engineering Co., Ltd.). Was measured.

  Water-soluble ion analysis (ion chromatography measurement): The molded product was washed with methanol for 1 minute and then washed with ion-exchanged water for 1 minute. Next, the molded product and ion-exchanged water were placed in a polyethylene bottle so that the amount of ion-exchanged water was 100 ml with respect to 10 g of the molded product, and treated at 90 ° C. for 50 hours. The ion-exchanged water (extracted water) after the treatment was measured by ion chromatography (“CDD-6A” manufactured by Shimadzu Corporation).

  Electrical conductivity evaluation: The molded product was washed with methanol for 1 minute and then washed with ion-exchanged water for 1 minute. Next, the molded product and ion-exchanged water were placed in a polyethylene bottle so that the amount of ion-exchanged water was 100 ml with respect to 10 g of the molded product, and treated at 90 ° C. for 50 hours. The ion-exchanged water (extracted water) after the treatment was measured with a conductivity meter.

  -Formability evaluation: For each example and comparative example, 10 samples were molded under the same conditions, the appearance was observed to check for unfilled, and the unfilled occurred as "bad" The number of occurrences was evaluated.

  -Contact resistance (area resistance) measurement method: Carbon paper was placed above and below a 3 mm thick sample (separator), copper plates were further placed above and below it, and a surface pressure of 0.5 MPa was applied in the vertical direction. . The voltage between the two carbon papers was read with a voltmeter, and at the same time, the current between the two copper plates was read with an ammeter, and the resistance (average value) was calculated. The carbon paper used is TGP-H-M series (090M: thickness 0.28 mm, 120M: thickness 0.38 mm) manufactured by Toray.

  ・ Evaluation of change rate of electromotive force value of fuel cell: For each of the examples and comparative examples, between the obtained separators 1 and 1, a solid polymer electrolyte membrane 2 and a gas diffusion electrode (fuel electrode and oxidant electrode) A fuel cell having the structure shown in FIG. Then, these fuel cells 1 were continuously operated for 1000 hours in a state where an external circuit was connected, and the state of fluctuation of the voltage value (V) of the electromotive force with time was investigated. The rate of change relative to the initial value is displayed.

The details of each component in the table are as follows: Epoxy resin A: Cresol novolak type epoxy resin (“EOCN-1020-75” manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 199, melting point 75 ° C.)
Curing initiator: phenol novolac resin (Gunei Chemical Co., Ltd. “PSM6200”, OH equivalent 105)
Phenol resin A: resol type phenol resin (“Sample A” manufactured by Gunei Chemical Co., Ltd., melting point 75 ° C., ortho-ortho 25-35% by 13C-NMR analysis, ortho-para 60-70%, para-para 5 10%)
・ Curing catalyst: Triphenylphosphine (“TPP” manufactured by Hokuko Chemical Co., Ltd.)
Graphite particles A: artificial graphite (“SGS30A” manufactured by Chuetsu Graphite Industries Co., Ltd., average particle size 30 μm, ash content 0.05%, sodium ion 3 ppm, chloride ion 1 ppm)
Graphite particles B: natural graphite (“WR50A” manufactured by Chuetsu Graphite Industries Co., Ltd., average particle size 50 μm, ash content 0.05%, sodium ion 4 ppm, chloride ion 2 ppm)
Coupling agent: Epoxy silane (“A187” manufactured by Nihon Unicar)
Wax A: natural carnauba wax (“H1-100” manufactured by Dainichi Chemical Co., Ltd., melting point: 83 ° C.)
Wax B: Montanic acid bisamide (“J-900” manufactured by Dainichi Chemical Co., Ltd., melting point: 123 ° C.)

It is sectional drawing which shows an example of embodiment of this invention. (A) (b) is sectional drawing which shows the other example of embodiment of this invention. (A) And (b) is a perspective view which shows an example of a structure of a fuel cell.

Explanation of symbols

5 Container 6 Stirrer

Claims (7)

  In a method for producing a resin composition for molding a fuel cell separator containing graphite particles and a thermosetting resin as essential components, a raw material containing graphite particles and a thermosetting resin is placed in a container, and a stirring tool is placed in the container. , The contents in the container are stirred and mixed so that the peripheral speed of the outermost edge is 15 m / second or less, and then the solvent in which the thermosetting resin is dissolved is added to the container and the stirring tool is added. , And stirring and mixing and granulation are performed so that the peripheral speed of the outermost edge is 15 m / sec or less.   2. The method for producing a fuel cell separator molding resin composition according to claim 1, wherein a solvent in which the thermosetting resin is dissolved is added into the container by spraying.   In the method for producing a fuel cell separator molding resin composition containing graphite particles and a thermosetting resin as essential components, raw materials other than the thermosetting resin are placed in a container, and a stirrer is placed in the container. The contents in the container are stirred and mixed by rotating so that the peripheral speed of the outer edge is 15 m / sec or less, and then the thermosetting resin is added to the container in a state of being dissolved in a solvent and a stirring tool is added. A method for producing a resin composition for molding a fuel cell separator, comprising stirring and mixing and granulating by rotating the outermost peripheral portion so that the peripheral speed is 15 m / sec or less.   The method for producing a resin composition for molding a fuel cell separator according to claim 3, wherein the thermosetting resin dissolved in the solvent is added into the container by spraying.   The method for producing a resin composition for molding a fuel cell separator according to any one of claims 1 to 4, wherein stirring and mixing are performed while heating at a temperature equal to or higher than a melting start temperature of the thermosetting resin.   The method for producing a resin composition for molding a fuel cell separator according to any one of claims 1 to 5, wherein the amount of the graphite particles used is 75 to 90% by weight of the whole raw material. The method for producing a fuel cell separator molding resin composition according to any one of claims 1 to 6, wherein the graphite particles are natural graphite or artificial graphite and have been purified.

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