JP2007179945A - Separator for fuel cell, and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for a fuel cell, free from blisters, moldable in a short time, and excellent in conductivity and fluidity. <P>SOLUTION: A composition for molding the separator for the fuel cell contains (A) an epoxy resin, (B) a curing agent, (C) a hardening accelerator comprising a tertiary amine compound having a molecular weight of 120-1,000, and (D) a carbon material containing expanded graphite, and the separator for the fuel cell is manufactured by applying injection molding to the composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell separator and a method for producing the same.

  For example, as shown in a schematic perspective view in FIG. 1, the fuel cell separator 10 is formed by standing a plurality of partition walls 12 at predetermined intervals on both surfaces of a flat plate portion 11. In order to obtain a fuel cell, a large number of fuel cell separators 10 are stacked in a protruding manner of the partition wall 12 (vertical direction in the figure). And by this lamination | stacking, it has the structure which distribute | circulates reaction gas (hydrogen and oxygen) to the channel 13 formed of a pair of adjacent partition 12.

  A fuel cell separator is manufactured by molding a molding composition containing a resin material and a carbon material such as graphite into the shape described above. The resin material is thermosetting such as phenol resin or epoxy resin. In general, a molding composition used as a resin is put into a mold provided with a flow path of gas or cooling water, and is molded by hot compression molding in which this is pressed hot. In recent years, in order to improve productivity, it has been attempted to perform injection molding instead of hot compression molding (see Patent Documents 1 to 3). In this method, a compound composed of a molding composition is injected from a cylinder into a mold and molded into a desired fuel cell separator shape in the mold. At this time, the compound is transferred to the mold cavity through a narrow channel called a runner, and at this time, the mold is in a closed state so that the mold is completely filled to obtain a molded article with high dimensional accuracy. For this, the compound needs to have high fluidity.

  In a molding composition using an epoxy resin and a carbon material, an organic phosphine such as triphenylphosphine is generally used as a curing accelerator. However, when an organic phosphine is melt-kneaded in a blending system using an epoxy resin, only those having low conductivity can be obtained. In particular, when expanded graphite is used as the carbon material, the expanded graphite is crushed by melt-kneading and the conductivity is deteriorated. On the other hand, when artificial graphite or natural graphite is used as the carbon material, it is necessary to add a large amount of the carbon material, and the resulting composition has a high viscosity. In order to lower the viscosity, it is necessary to reduce the carbon material, and the conductivity deteriorates.

  In addition to crystalline epoxy resin, curing agent and expanded graphite, triphenylphosphine is blended as a curing accelerator, and it is also proposed to obtain a molding composition by dry mixing, which is a kneading method in which expanded graphite particles are not crushed. (See Patent Document 4). However, the molding composition obtained by dry mix is excellent in conductivity, but has a viscosity so high that it hardly flows, and cannot be filled in a mold by injection molding.

  It has also been proposed to use a urea compound such as diuron ((3,4-dichlorophenyl) -1,1-dimethylurea) as a curing accelerator (see Patent Document 5). When urea-based curing accelerators are used, they have excellent thermal stability, so there is a merit that thickening does not occur at the time of molding material production, but swelling occurs due to the gas generated by decomposition of the urea compound during curing molding. May occur. In particular, when expanded graphite is used as a conductive material, swelling tends to occur. In addition, when a urea compound is used, if it is cured in a short time, swelling is likely to occur due to insufficient curing. By adding a large amount of a urea compound, the composition hardens in a short time. However, since a large amount of decomposition gas is generated, a large amount of swelling may occur. When swelling occurs in the molded body, the sealing property of the reaction gas is deteriorated, and the power generation performance of the fuel cell stack is deteriorated.

JP 2003-338294 A JP 2003-297386 A JP 2003-242994 A JP 2003-257447 A JP 2002-201257 A

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a fuel cell separator that is free from blistering, can be molded in a short time, and has excellent conductivity and fluidity. .

In order to achieve the above object, the present invention provides the following composition for molding a fuel cell separator and a method for producing the same, and a fuel cell separator and a method for producing the same.
(1) It contains (A) an epoxy resin, (B) a curing agent, (C) a curing accelerator composed of a tertiary amine compound having a molecular weight of 120 to 1000, and (D) a carbon material containing expanded graphite. A fuel cell separator molding composition.
(2) (D) The content of the carbon material is 35 to 85% by mass of the total amount of the composition, and (D) 5 to 100% by mass of the carbon material is expanded graphite. The composition for forming a separator for a fuel cell as described in the above).
(3) The content of (C) curing accelerator is 0.1 to 20 parts by weight with respect to 100 parts by weight of (B) curing agent, for fuel cell according to (1) or (2) above Separator molding composition.
(4) The composition for molding a fuel cell separator according to any one of (1) to (3) above, wherein the (C) curing accelerator is an amine compound shown below.

(5) The composition for molding a fuel cell separator according to any one of (1) to (4), wherein the (B) curing agent has two or more phenolic hydroxyl groups in the molecule. .
(6) The composition for molding a fuel cell separator according to any one of (1) to (5) above, wherein the epoxy resin (A) is a polyfunctional epoxy resin.
(7) The fuel as described in any one of (1) to (6) above, wherein each component is melt-kneaded at a temperature equal to or higher than the softening temperature of (A) the epoxy resin or (B) the curing agent. A method for producing a battery separator molding composition.
(8) A method for producing a fuel cell separator using the fuel cell separator composition according to any one of (1) to (6) above, wherein (A) an epoxy resin or (B) A method for producing a fuel cell separator, comprising melting and kneading each component at a temperature equal to or higher than a softening temperature of a curing agent, and injection-molding the obtained kneaded product.
(9) A fuel cell separator comprising the composition for molding a fuel cell separator according to any one of (1) to (6) above.

  According to the present invention, it is possible to obtain a fuel cell separator that is free from blistering, can be molded in a short time, and has excellent conductivity and fluidity.

  Hereinafter, the present invention will be described in detail.

  The fuel cell separator molding composition of the present invention (hereinafter, also simply referred to as “molding composition”) includes (A) an epoxy resin, (B) a curing agent, and (C) a tertiary amine compound having a molecular weight of 120 to 1,000. And (D) a carbon material as essential components.

  The epoxy resin is a compound having two or more epoxy groups, and conventionally known ones can be used. Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, halogenated bisphenol A type epoxy resin, and the like. Epoxy resin; phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolak type epoxy resin, tris-hydroxyphenylmethane type epoxy resin, phenol dicyclopentadiene type epoxy resin, halogenated phenol novolak type epoxy resin, naphthol novolak Type epoxy resin, resorcinol epoxide, tetraphenylol ethane type epoxy resin, etc .; alicyclic epoxy resin; Eniru type epoxy resin; naphthalene type epoxy resins; glycidyl ester type epoxy resin, including but include glycidylamine type epoxy resins are not limited thereto. Among the above-mentioned epoxy resins, since a molded product having high heat resistance and strength is obtained, a polyfunctional epoxy resin is preferably used in the present invention. The epoxy equivalent is preferably 50 to 500, more preferably 100 to 300. When the epoxy equivalent is too low, the resulting fuel cell separator becomes brittle. On the other hand, when the epoxy equivalent is too high, only a fuel cell separator having low heat resistance and strength can be obtained. Further, the amount of the epoxy resin is not particularly limited, but the molding composition has fluidity suitable for injection molding, and considering the strength and dimensional accuracy of the resulting fuel cell separator, It is preferable to set it as 15-65 mass% of the molding composition whole quantity, More preferably, it is 20-40 mass%.

  An epoxy resin produces | generates an epoxy hardened | cured material by reacting with a hardening | curing agent. Various known compounds can also be used as the curing agent. For example, aliphatic, cycloaliphatic, aromatic polyamines or carbonates thereof such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, mensendiamine, isophoronediamine, N-aminoethylpiperazine, m-xylenediamine, diaminodiphenylmethane; Phthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl nadic anhydride, dodecyl succinic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, trimellitic anhydride, polyazeline acid anhydride, etc. Acid anhydrides; polyphenols such as phenol novolac and cresol novolac; polymer captans, but not limited thereto. A plurality of curing agents can be used in combination. Among the above, curing agents such as polyamines, carbonates thereof, acid anhydrides, polyphenols, and polymercaptans are called polyaddition type curing agents because they themselves form an epoxy cured product by a polyaddition reaction with an epoxy compound. Since excess and deficiency of the polyaddition type curing agent leads to residual unreacted functional groups, there is an appropriate range for the amount added. In general, it is preferred to use 0.7 to 1.2 equivalents, particularly 0.8 to 1.1 equivalents of a polyaddition type curing agent per epoxy group of the epoxy resin precursor. The curing rate of the thermosetting resin can be arbitrarily changed by variously selecting the type and amount of the curing agent, the type of the thermosetting resin, the type and the amount of the curing accelerator. Those skilled in the art will be able to easily determine the type and amount of thermosetting resin, curing agent and curing accelerator according to the desired curing conditions.

  In the present invention, the curing agent is preferably a compound having two or more phenolic hydroxyl groups. Examples of such compounds include phenol novolak, cresol novolak, bisphenol A novolak, aralkyl type phenol novolak, triphenylmethane type phenol resin, terpene phenol resin, naphthol novolak, and phenol dicyclopentadiene resin as described above. Is mentioned. A curing agent having two or more phenolic hydroxyl groups can provide a fuel cell separator with high heat resistance.

  In the present invention, a tertiary amine compound having a molecular weight of 120 to 1000 is used as a curing accelerator. The tertiary amine compound is not particularly limited, and examples thereof include trisdimethylaminomethylphenol (molecular weight 265), N, N-dimethylcyclohexylamine (molecular weight 127), tri-n-butylamine (molecular weight 185), bis ( p-aminohexyl) methane (molecular weight 210), tetramethyl-1,3-diaminopropane (molecular weight 130), N, N-dimethylcyclohexylamine (molecular weight 127), N-ethyl (cyclohexyl) amine (molecular weight 127), 3 -Dimethylaminophenol (molecular weight 137), triphenylamine (molecular weight 245), tridecylamine (molecular weight 522), bis [(2-dimethylamino) ethyl] ether (molecular weight 160), benzyldimethylamine (molecular weight 137), N , N-dimethylbenzylamine (molecular weight 135) and the like, but are not limited thereto. In addition, an amine compound adducted (prepolymerized) such as an epoxyamine adduct prepolymerized using an addition reaction between an amine compound such as dialkylamine and an epoxy resin can also be used.

  The amine compound has an unshared electron pair on the nitrogen atom, which accelerates the reaction between the epoxy resin and the curing agent. Here, the larger the number of hydrocarbons or hydrocarbon derivatives bonded to the nitrogen atom, the higher the electron density of the nitrogen atom, and thus the stronger the action as a curing accelerator. The number of hydrocarbons bonded to the nitrogen atom is the amine series. Therefore, the action of a tertiary amine as a curing accelerator is the strongest among all amine compounds.

  When a tertiary amine compound having a large molecular weight is used, a fuel cell separator with high thermal stability can be obtained. However, if the molecular weight is extremely high, the curing reaction becomes slow or the curing reaction needs to be performed at a high temperature. There are problems such as a reduction in the molding cycle and thermal decomposition of the epoxy resin and curing agent during the curing reaction. On the other hand, if the molecular weight is too low, there may be a problem such as a problem in thermal stability or a problem of volatilization and disappearance. Thus, in the present invention, there is a preferred range for the molecular weight of the tertiary amine compound used. In the present invention, the molecular weight of the tertiary amine compound used is 120 to 1000, preferably 200 to 500, and more preferably 250 to 400.

  Among the tertiary amine compounds, those containing an aromatic ring in the molecule are particularly preferred because of their high thermal stability and a high reaction rate at a specific temperature or higher. As a tertiary amine compound satisfying this condition, trisdimethylaminomethylphenol shown below is easily available, and a fuel cell separator having high thermal stability can be obtained, so that it is particularly preferable in the present invention.

  A hardening accelerator is 0.1-20 weight part with respect to 100 weight part of hardening | curing agents, Preferably 1-10 weight part is mix | blended. If the curing accelerator is less than 0.1 part by weight, the effect of promoting the curing reaction is not sufficient, and if it exceeds 20 parts by weight, the fluidity of the molding composition is lowered, resulting in problems such as crushing of expanded graphite. The fuel cell separator also has low conductivity and low strength.

  The carbon material in the present invention is a conductive material whose main component is a carbon atom, specifically, expanded graphite, scaly artificial graphite, spherical artificial graphite, natural scaly graphite, carbon black, carbon fiber. , Carbon nanofiber, carbon nanotube, diamond-like carbon, fullerene, carbon nanohorn, and the like, but not limited thereto.

  Normal scale-like graphite is a laminate of thin plate crystals. In contrast, expanded graphite is obtained by treating scaly graphite with concentrated sulfuric acid, nitric acid, hydrogen peroxide, etc., intercalating these chemicals into the gaps between the thin plate crystals, and further intercalating by heating. Refers to graphite obtained by widening the gaps between the thin plate crystals when the chemical solution is vaporized. Expanded graphite has a lower bulk density, a larger surface area, and a thinner thin plate than scale-like graphite and spherical graphite. For this reason, a conductive path can be easily formed when mixed with a resin, and a highly conductive fuel cell separator can be obtained. In addition, since expanded graphite has a thin plate shape, it is more flexible than artificial graphite and natural graphite, and a fuel cell separator using the expanded graphite is also flexible.

  Expanded graphite is an essential component as a carbon material. All of the carbon material may be expanded graphite, some may be expanded graphite, and the others may be other carbon materials described above. At this time, the ratio of the expanded graphite to the total carbon material is preferably 10 to 100% by mass, more preferably 20 to 80% by mass, still more preferably 30 to 70% by mass, and particularly preferably 40 to 60% by mass. When the ratio of expanded graphite is low, the contact resistance is high. In addition, since expanded graphite has a low bulk density, when the ratio of expanded graphite is high, material handling properties during kneading for compound production are poor, and there is a concern that the working environment may be contaminated.

  Further, the carbon material needs to be 35 to 85% by mass of the total amount of the molding composition. When the ratio of the carbon material is too low, the conductivity is lowered. On the other hand, if the ratio of carbon material is too high, the strength will be low, and the fluidity of the compound will be low, so that it will be molded in the mold after being injected into the mold during hot compression molding or injection molding. This is a problem because the pressure distribution of the material becomes large and the dimensional accuracy of the fuel cell separator to be molded deteriorates.

  You may mix | blend another additive with the said molding composition as needed. For example, a lubricant such as carnauba wax can be added to prevent sticking to a mold or a kneader during molding. As the lubricant, stearic acid, montanic acid wax, and metal salts thereof can be used. In addition, an inorganic filler such as glass fiber, silica, talc, clay, calcium carbonate, an organic filler such as wood powder, and a plasticizer can be added as long as the conductivity is not lowered.

  The molding composition of the present invention is obtained by melt mixing. Of the molding composition, the epoxy resin and the curing agent soften at a certain temperature or higher. This softening temperature is called the softening point. In the present invention, each component may be mixed (melt kneaded) with an apparatus adjusted so that either the epoxy resin or the curing agent is equal to or higher than the softening temperature. When either the epoxy resin or the curing agent is liquid at room temperature, it may be mixed at room temperature. As a device used for mixing, various conventional devices can be used, for example, a pressureless kneader, a pressure kneader, a twin screw extruder, a single screw extruder, a Banbury mixer, an intermix, a two roll mill, A three-roll mill or the like can be mentioned, but the invention is not limited to these. Moreover, you may melt-mix the material which performed the preliminary mixing by the dry mix.

  The fuel cell separator of the present invention is obtained by molding the molding composition thus obtained by a conventionally known molding method for thermosetting resin molding materials. As a molding method, compression molding is also possible, but since the moldable composition of the present invention is excellent in fluidity, it is preferable to perform injection molding excellent in productivity. Moreover, you may implement secondary bridge | crosslinking as needed. If necessary, it is also possible to perform cutting after forming.

  The important point of the present invention is to use expanded graphite and a tertiary amine compound having a specific molecular weight in combination and melt-mix them. Even when a tertiary amine compound having a specific molecular weight is used, when general graphite such as natural graphite or artificial graphite is used, a molding composition having excellent thermal stability that does not cure during melt kneading or in a screw can be obtained. However, in order to obtain the same conductivity as when expanded graphite is used, it is necessary to add a large amount of graphite. That is, the amount of resin that improves the fluidity of the molding composition decreases, and the amount of carbon material that decreases the fluidity increases. For this reason, fluidity | liquidity falls and the moldability falls significantly for the composition for shaping | molding. Even when expanded graphite is used, when triphenylphosphine or the like, which is a general curing accelerator, is used, the curing reaction proceeds during the melt mixing of the molding composition or in an injection molding screw. For this reason, the viscosity rapidly increases as the curing reaction proceeds, and the expanded graphite is crushed during melt mixing or in an injection-molded screw. As a result, the strength of the resulting fuel cell separator is also reduced, and the conductivity is also greatly reduced. In addition, when curing at a low temperature, it is necessary to add a large amount of curing accelerator, but when a large amount of curing accelerator is added, the strength and conductivity are further deteriorated due to expanded graphite crushing as described above, Also, the moldability deteriorates due to the decrease in fluidity. On the other hand, when both the tertiary amine compound having a specific molecular weight and the expanded graphite are used in combination, these problems can be solved.

  A tertiary amine compound having a specific molecular weight hardly suppresses the shearing force applied by kneading because the molding reaction is difficult to proceed at a low temperature of 100 ° C. or less as expected when the molding composition is kneaded or in an injection molding cylinder. It becomes possible. As a result of the suppression of the shearing force, the pulverization of the expanded graphite in the molding composition is minimized. Expanded graphite, which has a lower bulk density, larger surface area, and thinner particles compared to flaky graphite and spherical graphite, forms a conductive path easily when mixed with resin, and sufficiently It becomes an appropriate pulverized state in which the molding material flows. That is, when a conventional organic phosphine is used as a curing accelerator, expanded graphite is pulverized and a conductive path is hardly formed, but by using a tertiary amine compound, expanded graphite is not pulverized and a conductive path is easily formed. By using the expanded graphite and the tertiary amine compound in combination, the pulverization of the expanded graphite having high conductivity can be suppressed, so that the conductivity of the molding composition can be secured even when the amount of the resin is increased. The fluidity of the material is increased, and the dimensional accuracy of the obtained fuel cell separator is greatly improved. Tertiary amine compounds exhibit activity by heating and promote the curing reaction, but the softening temperature and viscosity are proportional to the molecular weight of the amine compound, and the activity appears at low temperatures when the molecular weight is low, and at high temperatures when the molecular weight is large. Activity is expressed. The above-described tertiary amine compound having a molecular weight in the preferred range is difficult to disperse during the kneading step, and rapidly disperses when heated to the mold temperature during curing and exhibits activity as a curing accelerator. During the kneading or in the cylinder of the injection molding machine, it is difficult for the viscosity to increase due to the progress of the curing reaction. Therefore, the viscosity of the molding composition can be kept low, and the mold can be filled at a low pressure. In addition, there is an advantage that the mold is hardly deformed during filling, and the dimensional accuracy is excellent.

  Hereinafter, the present invention will be further described with reference to examples and comparative examples, but the present invention is not limited thereto.

<Examples 1-6, Comparative Examples 1-5>
(Preparation of molding composition)
In accordance with the formulation shown in Table 1, 500 g of the total material was premixed with a 10 L Henschel mixer, and then melt kneaded for 5 minutes at a chamber temperature of 100 ° C. using a 1 L pressure kneader. After the kneaded product was naturally cooled, it was pulverized into pellets having a particle diameter of about 2 mm by a pulverizer and pelletized. In addition, the unit of the mixing | blending of Table 1 is the mass%.

(Preparation of test specimen)
Using the above pellets, a molded body having a square thin plate shape with a side of 100 mm and a thickness of 2 mm was formed by injection molding, and cut to obtain a test body. The injection molding machine uses a thermosetting resin molding machine (manufactured by Ryoya Seiko) with a clamping force of 80 t, the cylinder temperature is 50 ° C. under the hopper, the nozzle is 90 ° C., the mold temperature is 170 ° C., and the injection speed is 20 mm / sec, the curing time was 60 to 180 seconds. The molding pressure was appropriately set in the range of 30 to 70 MPa. In the case where the molded body was swollen, a part other than the swollen was sampled to obtain a test body.

(Evaluation of conductivity)
The resistance in the penetration direction was measured by the method shown in FIG. 2 and the conductivity was evaluated. The test body 21 is set on the electrode 23 via the carbon paper 22, and the electric resistance is calculated from the current (measured with the ammeter 24) passed between the electrodes and the voltage between the carbon paper (measured with the voltmeter 25). Further, this was multiplied by the sample area to obtain the resistivity in the penetration direction. The results are shown in Table 1.

(Measurement of hot bending strength)
It was determined in accordance with JIS K7171 Plastics-Test method for bending properties. The test was performed at 100 ° C. in a test atmosphere using an Instron universal testing machine with a thermostatic bath. The results are shown in Table 1.

(Confirmation of occurrence of swelling)
The number of formed bodies that swelled during the above molding was counted to determine the number of swelled parts (number of swelled compacts / total number of compacts). The results are shown in Table 1.

(Evaluation of liquidity)
The above-mentioned pellets were determined in accordance with JIS-K-6911 general thermosetting plastic test method “extruded flow, good phenol resin flow” and used as an index of fluidity. The results are shown in Table 1.

(Measurement of curing reaction progress)
Using a moving die rheometer, the torque change accompanying the progress of the curing reaction at 100 ° C. or 170 ° C. of the pellets was measured. The measurement time was 15 minutes. An increase in torque indicates that curing has proceeded. The torque change at 100 ° C. is shown in FIGS. 3 to 6 and the torque change at 170 ° C. is shown in graphs in FIGS.

  As shown in Table 1, all of the examples and comparative examples use bisphenol A novolac type epoxy resin and phenol novolac as a curing agent. In each of the examples, a tertiary amine compound having a specific molecular weight is added as a curing accelerator, and expanded graphite and artificial graphite are used as the carbon material. In Examples 1 and 2, trisdimethylaminomethylphenol (molecular weight 265) was added, in Examples 3 and 4, triphenylamine (molecular weight 245) was added, and in Examples 5 and 6, tri-n-butylamine (molecular weight 185) was added. ing. Trisdimethylaminomethylphenol and triphenylamine contain an aromatic ring in the molecule, but tri-n-butylamine does not contain an aromatic ring. In contrast, in Comparative Example 1, 3- (3,4-dichlorophenyl) -1,1-dimethylurea was used as a curing accelerator, and in Comparative Example 2, triethylenediamine (molecular weight 112), which is a tertiary amine having a molecular weight of less than 120, was used. In Comparative Example 3, triphenylphosphine is used, and in Comparative Example 4, 2-methylimidazole is used. In Comparative Example 5, trisdimethylaminomethylphenol which is a tertiary amine compound having a molecular weight of 120 or more is used as a curing accelerator, but only artificial graphite is used as a carbon material without using expanded graphite.

  Due to such a difference in blending, as a result of the test, in each example, no swelling was observed in the molded body, and no problem in appearance occurred. It has good fluidity and is easy to injection mold. In each example, the torque rises after a certain induction period at 170 ° C., which is the molding temperature, so that the mold can be filled with high fluidity until the start of the curing reaction. Further, since the rate of increase after the torque starts increasing is high, the curing reaction can be completed quickly, and the molding cycle can be shortened. Further, since the torque change at 100 ° C. hardly occurs within at least 5 minutes, the progress of the curing reaction at 100 ° C. is very slow and the thermal stability is excellent. In addition, in each Example, curing at 100 ° C. is hardly confirmed even after 15 minutes, and the thermal stability is very excellent.

  On the other hand, Comparative Example 1 using a dimethylurea compound as a curing accelerator obtained a molded article having excellent thermal stability, high strength and low electrical resistance, but the molded article sometimes shows swelling. there were. Each of Comparative Examples 2, 3, and 4 has a problem in thermal stability, and both strength and electrical resistance are inferior to those of the examples. In Comparative Examples 2, 3, and 4, at 170 ° C., the induction period from the start of heating to the increase in torque is short, and curing occurs in the middle of filling the mold, resulting in a short shot. There is concern about dimensional accuracy degradation. Comparative Example 5 has a problem in that the electrical resistance is very high.

  As described above, each example is a molded body having high strength and low electrical resistance. This is presumably because the heat stability is high, the thickening accompanying the progress of the curing reaction does not easily occur at the kneading temperature and the cylinder temperature, and crushing in the kneading process and the molding process of the expanded graphite as the conductive filler is prevented. Moreover, when Examples are compared, Example 2 using a tertiary amine having an aromatic ring in the molecule is equivalent to Example 6 using a tertiary amine not having an aromatic ring at 170 ° C. However, at 100 ° C., Example 2 shows almost no increase in torque, whereas Example 6 starts increasing torque in about 10 minutes, and Example 2 has better thermal stability. Yes. Therefore, it can be said that it is preferable to use a tertiary amine having an aromatic ring because of excellent balance between thermal stability and curing rate.

  From the above, it is apparent that the present invention provides a fuel cell separator that is free from blistering and has excellent conductivity, dimensional accuracy, and strength.

It is a perspective view which shows an example of the separator for fuel cells. It is a schematic diagram which shows the structure of the apparatus used for the measurement of penetration direction conductivity. It is a graph which shows the result of having measured the torque change in 100 degreeC of the pellet of Examples 1-3. It is a graph which shows the result of having measured the torque change in 100 degreeC of the pellet of Examples 4-6. It is a graph which shows the result of having measured the torque change in 100 degreeC of the pellet of Comparative Examples 1-3. It is a graph which shows the result of having measured the torque change in 100 degreeC of the pellet of Comparative Examples 4-5. It is a graph which shows the result of having measured the torque change in 170 degreeC of the pellet of Examples 1-3. It is a graph which shows the result of having measured the torque change in 170 degreeC of the pellet of Examples 4-6. It is a graph which shows the result of having measured the torque change in 170 degreeC of the pellet of Comparative Examples 1-3. It is a graph which shows the result of having measured the torque change in 170 degreeC of the pellet of Comparative Examples 4-5.

Explanation of symbols

10 Fuel Cell Separator 11 Flat Plate 12 Bulkhead 13 Channel

Claims (9)

  (A) An epoxy resin, (B) a curing agent, (C) a curing accelerator composed of a tertiary amine compound having a molecular weight of 120 to 1000, and (D) a carbon material containing expanded graphite. Separator molding composition.   2. The fuel according to claim 1, wherein the content ratio of (D) the carbon material is 35 to 85 mass% of the total amount of the composition, and (D) 5 to 100 mass% of the carbon material is expanded graphite. Composition for battery separator molding.   3. The composition for molding a separator for a fuel cell according to claim 1, wherein the content of (C) the curing accelerator is 0.1 to 20 parts by weight with respect to 100 parts by weight of (B) the curing agent. (C) The composition for molding a fuel cell separator according to any one of claims 1 to 3, wherein the curing accelerator is an amine compound shown below.

  (B) The composition for molding a fuel cell separator according to any one of claims 1 to 4, wherein the curing agent has two or more phenolic hydroxyl groups in the molecule.   (A) Epoxy resin is polyfunctional epoxy resin, The composition for fuel cell separator shaping | molding of any one of Claims 1-5 characterized by the above-mentioned.   7. The fuel cell separator molding according to claim 1, wherein each component is melt-kneaded at a temperature equal to or higher than the softening temperature of (A) the epoxy resin or (B) the curing agent. A method for producing the composition.   A method for producing a fuel cell separator using the fuel cell separator composition according to any one of claims 1 to 6, wherein (A) an epoxy resin or (B) a curing agent has a softening temperature or higher. A method for producing a fuel cell separator, comprising melting and kneading each component at a temperature of, and injection molding the obtained kneaded product.   A fuel cell separator comprising the composition for molding a fuel cell separator according to any one of claims 1 to 6.

Images