Fuel cell separators

Abstract

The cumulative particle size distribution d10 is 10 to 20 μm, and the volume porosity measured by ASTM D6086 is 12 to 30 cm at a measurement pressure of 30 MPa. 3 A fuel cell separator molded from a resin composition containing graphite powder at a concentration of 100g / 100g and an epoxy resin component containing a base resin, a curing agent, and a curing accelerator has excellent hydrogen gas impermeability, electrical conductivity, and mechanical properties even when compression molded in a short period of time.

Description

[Technical Field]

[0001] The present invention relates to a separator for a fuel cell. [Background technology]

[0002] Fuel cell separators have the role of providing electrical conductivity to each unit cell, as well as ensuring passages for fuel and air (oxygen) to be supplied to the unit cells, and also functioning as a separating boundary wall between them. For this reason, the separator is required to have various properties such as high electrical conductivity, high gas impermeability, chemical stability, heat resistance, and hydrophilicity.

[0003] Regarding the improvement of these properties, for example, Patent Document 1 proposes a fuel cell separator that can suppress gas permeability while improving both mechanical strength and electrical conductivity by welding and integrating multiple composite sheets and a resin composition. Furthermore, Patent Document 2 proposes a fuel cell separator that suppresses gas permeation by comprising a plate containing granular or fibrous graphite and granular or fibrous resin as constituent materials, and a barrier layer that has better gas barrier properties than the plate.

[0004] However, although the fuel cell separator of Patent Document 1 suppresses gas permeability by welding and integrating multiple composite sheets and a resin composition, the hydrogen gas permeability coefficient at a measurement temperature of 80°C is 1.1 × 10 -13 ~6.8×10 -13 mol m / m 2 ·Pa·sec, and there is a problem in that its hydrogen gas impermeability is insufficient. On the other hand, in Patent Document 2, although gas impermeability is reduced by providing a barrier layer with excellent gas barrier properties, the separator requires a long molding time of 1 to 6 minutes, resulting in poor production efficiency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-145014 [Patent Document 2] International Publication No. 2023 / 286332 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a fuel cell separator that has excellent hydrogen gas impermeability, electrical conductivity, and mechanical properties even when compression molded in a short period of time. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above object, the present inventors have discovered that by using a composition containing graphite powder having predetermined physical properties and an epoxy resin component, it is possible to obtain a fuel cell separator that is excellent in hydrogen gas impermeability, electrical conductivity, and mechanical properties even when compression molded in a short period of time, and have completed the present invention.

[0008] That is, the present invention is 1. The cumulative particle size distribution d10 is 10 to 20 μm, and the volume porosity measured by ASTM D6086 is 12 to 30 cm at a measurement pressure of 30 MPa. 3 a separator for a fuel cell, which is obtained by molding a resin composition containing graphite powder having a particle size of 1 / 100 g and an epoxy resin component containing a base resin, a curing agent, and a curing accelerator; 2. The fuel cell separator of 1, wherein the powder resistivity of the graphite powder is less than 3.0 mΩ cm when measured at a pressure of 30 MPa. 3. The fuel cell separator of 1, wherein the spring back of the graphite powder is 13 to 50%. 4. The fuel cell separator of 1, wherein the base resin of the epoxy resin is at least one selected from a cresol novolac type epoxy resin and a biphenyl type epoxy resin. 5. The fuel cell separator according to 1, wherein the curing agent for the epoxy resin is a novolac phenolic resin. 6. The fuel cell separator according to 1, wherein the curing accelerator contains an imidazole compound having a phenyl group at the 2-position. 7. A fuel cell separator, wherein the resin composition contains 20 to 42 parts by mass of the epoxy resin component per 100 parts by mass of the graphite powder. 8. The hydrogen permeability coefficient at a measurement temperature of 80°C is 1.7 x 10 -16 mol m / m 2 Less than 1 Pa sec and a specific resistance of 23 mΩ c m un A fuel cell separator according to any one of 1 to 7, 9. A fuel cell separator according to any one of 1 to 7, having a bending strength of 44 MPa or more and a bending modulus of elasticity of less than 13 GPa. 10. The cumulative particle size distribution d10 is 10 to 20 μm, and the volume porosity measured by ASTM D6086 is 12 to 30 cm at a measurement pressure of 30 MPa. 3 A method for producing a separator for a fuel cell, comprising compression molding a resin composition containing graphite powder with a mass of 100g / 100g and an epoxy resin component containing a base resin, a curing agent, and a curing accelerator for a compression time of 40 seconds or less. to provide. [Effects of the Invention]

[0009] The fuel cell separator of the present invention uses a composition containing graphite powder that is easy to compress and pack and has a low volume porosity, and therefore has excellent hydrogen gas impermeability, electrical conductivity, and mechanical properties even when compression molded for a short period of time, such as 40 seconds or less. Furthermore, by using graphite powder with low powder resistivity, the electrical conductivity of the resulting fuel cell separator can be further improved. Furthermore, by using graphite powder with a predetermined spring back (elastic recovery), the mechanical properties of the resulting fuel cell separator can be further improved. In particular, fuel cell separators made from graphite powder that combines the three properties of specified springback, volumetric porosity, and powder resistance have excellent hydrogen gas impermeability, electrical conductivity, and mechanical properties, even when compression molded in a short time of 30 seconds or less. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic side view of a die used in measuring springback of graphite powder. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in more detail below. The fuel cell separator according to the present invention has a cumulative particle size distribution d10 of 10 to 20 μm and a volume void ratio measured by ASTM D6086 of 12 to 30 cm at a measurement pressure of 30 MPa. 3 The resin composition is characterized by being formed by molding a resin composition containing graphite powder in an amount of 100g / 100g, and an epoxy resin component containing a base resin, a curing agent, and a curing accelerator.

[0012] In the present invention, the cumulative particle size distribution d10 of the graphite powder is 10 to 20 μm, preferably 12 to 16 μm, and more preferably 13 to 15 μm. If the average particle size d10 is less than 10 μm, the epoxy resin tends to cover the surface of the graphite powder, reducing the contact area between the particles and deteriorating the conductivity of the separator itself. On the other hand, if the average particle size d10 exceeds 20 μm, the contact area between the graphite particles and the epoxy resin becomes small, which may result in a deterioration in the gas impermeability of the separator. The average particle size d10 in the present invention is a value measured by a wet method using a particle size distribution measuring device (MT3000 manufactured by Microtrac-Bell Corporation).

[0013] The volumetric porosity of graphite powder measured by ASTM D6086 is 30 cm when the measurement pressure is 30 MPa. 3A volume void ratio of 30 cm3 / 100g or less is preferable because sufficient gas impermeability can be obtained. 3 If the amount exceeds 100g / 100g, a large amount of resin is required to fill the gaps between the graphite powder particles, which may result in poor conductivity of the separator. In addition, the volume void ratio is 12m 3 If the weight is less than 100g / 100g, the graphite powder will be packed too densely, which may result in a loss of flexibility of the separator. The void volume ratio in the present invention is a value measured at a pressure of 30 MPa using a DVV400 manufactured by Micromeritics Instruments Corporation.

[0014] To further enhance electrical conductivity, the powder resistivity of the graphite powder is preferably less than 3.0 mΩ·cm when measured at a pressure of 30 MPa. If the powder resistivity is 3.0 mΩ·cm or higher, the amount of resin added must be reduced to ensure electrical conductivity in the fuel cell separator, which may result in poor gas impermeability of the separator. While a lower powder resistivity is preferable, the lower limit is usually around 1.0 mΩ·cm.

[0015] The spring back of the graphite powder is preferably 13 to 50% from the viewpoint of further improving gas impermeability, flexibility, and productivity. If the spring back exceeds 50%, the gaps between the graphite powder particles are difficult to collapse during molding of the separator, which may result in a decrease in the gas impermeability of the separator. Furthermore, if the springback value is less than 13%, the flexibility and strength of the separator may be impaired, whereas if the springback value of the graphite powder exceeds 50%, it may take a long time to close the gaps between the graphite powder particles, which may reduce the productivity of fuel cell separators. In the present invention, the spring back refers to the spring back of the powder itself, and specifically, as will be described in detail in the Examples below, it is a value calculated from the height X of the powder when the powder is placed in a predetermined mold and compressed under a predetermined pressure, and the height Y of the powder when the pressure is released, as follows: (YX) / X×100(%).

[0016] The graphite powder used in the present invention is not particularly limited in type, and either natural graphite or artificial graphite may be used, as long as it satisfies the volume porosity measured according to ASTM D6086. Examples of artificial graphite include artificial graphite obtained by burning needle coke, artificial graphite obtained by burning lump coke, spheroidized artificial graphite, and artificial graphite whose surface is treated with a non-graphite layer by pitch coating. On the other hand, examples of natural graphite include flake natural graphite, soil graphite, spheroidized natural graphite, and natural graphite whose surface has been treated with a non-graphite layer such as pitch coating. In either case, the volume porosity of the graphite powder is measured and one falling within the range specified in the present invention is appropriately selected. These graphite powders may be used alone or in combination of two or more.

[0017] The base resin constituting the epoxy resin component is not particularly limited as long as it has an epoxy group, and examples thereof include o-cresol novolac epoxy resin, phenol novolac epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, biphenyl epoxy resin, biphenyl aralkyl epoxy resin, trisphenol epoxy resin, brominated epoxy resin, dicyclopentadiene epoxy resin, biphenyl novolac epoxy resin, etc. These can be used alone or in combination of two or more. Among these, o-cresol novolac epoxy resin alone, biphenyl epoxy resin alone, and mixtures thereof are preferred.

[0018] The curing agent constituting the epoxy resin component is not particularly limited as long as it is a phenolic resin, and specific examples thereof include novolac phenolic resins, cresol novolac phenolic resins, resol phenolic resins, aralkyl-modified phenolic resins, biphenyl novolac phenolic resins, trisphenolmethane phenolic resins, etc. These may be used alone or in combination of two or more. Among these, novolac phenolic resins are preferred.

[0019] The curing accelerator constituting the epoxy resin component is not particularly limited as long as it accelerates the reaction between the epoxy group and the curing agent, and examples thereof include phosphine compounds, amine compounds, and imidazole compounds. Among these, in the present invention, it is preferable to use an imidazole compound having an aryl group at the 2-position. Specific examples of the aryl group include a phenyl group, a tolyl group, and a naphthyl group, with a phenyl group being preferred. Specific examples of the imidazole compound having an aryl group at the 2-position include 2-phenylimidazole and 2-phenyl-4-methylimidazole. When an imidazole compound having a short-chain alkyl group such as 2-methylimidazole is used as a curing accelerator, the curing time may be too fast to achieve uniform molding, while when an imidazole compound having a long-chain alkyl group such as 2-undecylimidazole is used, the curing time may be too slow, resulting in a long molding time.

[0020] In addition to the above components, the composition used in the present invention may also contain optional components such as an internal mold release agent. The internal mold release agent may be appropriately selected from various internal mold release agents that have conventionally been used in molding separators. Specific examples include stearic acid wax, amide wax, montanic acid wax, carnauba wax, and polyethylene wax. These may be used alone or in combination of two or more.

[0021] In the composition used in the present invention, the blending amount of the epoxy resin components (main agent, curing agent, and curing accelerator) is not particularly limited, and the amount is preferably 20 to 42 parts by mass, more preferably 27 to 35 parts by mass, and even more preferably 30 to 33 parts by mass of the epoxy resin components per 100 parts by mass of graphite powder. In this case, the curing agent is preferably blended in an amount of 0.98 to 1.08 equivalents relative to the base resin, and more preferably 0.99 to 1.05 equivalents. The amount of the curing accelerator used is not particularly limited, but is preferably 0.1 to 5.0 parts by mass, more preferably 0.5 to 2.0 parts by mass, per 100 parts by mass of the mixture of the base agent and the curing agent. By using an epoxy resin component in this range, the fluidity of the molding material becomes appropriate, resulting in good moldability, and the gas impermeability and electrical conductivity of the resulting fuel cell separator also become even better. When an internal mold release agent is used, the amount used is not particularly limited, but is preferably 0.01 to 3.0 parts by mass, more preferably 0.05 to 1.5 parts by mass, per 100 parts by mass of graphite powder.

[0022] The composition used in the present invention may be prepared by mixing, for example, graphite powder, a base agent, a curing agent, and a curing accelerator in any order in predetermined proportions, using a mixer such as a planetary mixer, ribbon blender, Loedige mixer, Henschel mixer, rocking mixer, or Nauta mixer. When an internal mold release agent is used, the order of addition is also arbitrary.

[0023] The fuel cell separator of the present invention is preferably produced by placing the composition in a predetermined mold and compression molding it. The mold to be used may be a metal mold for producing fuel cell separators, which can form grooves to serve as gas flow paths on one or both surfaces of the molded body. The conditions for compression molding are not particularly limited, but the mold temperature is 150 to 190° C., and the molding pressure is 30 to 60 MPa, preferably 30 to 50 MPa. The compression molding time is not particularly limited and can be set appropriately from about 3 seconds to 1 hour, but a short time is preferable from the viewpoint of production efficiency, and specifically, 40 seconds or less is preferable, and 30 seconds or less is more preferable. In particular, in the present invention, by using the above-mentioned spring-bag graphite powder, a fuel cell separator having good properties can be obtained even when molded in a short time of 30 seconds or less. After compression molding, the mixture may be further heated at 150 to 200° C. for 1 to 600 minutes to promote thermal curing.

[0024] In the present invention, the fuel cell separator (molded body) obtained by the compression molding may be subjected to a surface roughening treatment for the purposes of removing the skin layer and adjusting the surface roughness. The roughening treatment method is not particularly limited and may be appropriately selected from various conventionally known roughening methods such as blasting and polishing. Air blasting, wet blasting, barrel polishing, and brush polishing are preferred, blasting using abrasive grains is more preferred, and wet blasting is even more preferred.

[0025] In this case, the average particle size (d=50) of the abrasive grains used in the blasting treatment is preferably 3 to 30 μm, more preferably 4 to 25 μm, and even more preferably 5 to 20 μm. The material of the abrasive grains used in the blasting process is not particularly limited, and examples thereof include alumina, silicon carbide, zirconia, glass, nylon, and stainless steel, which may be used alone or in combination of two or more. The discharge pressure during wet blasting cannot be generally defined because it varies depending on the particle size of the abrasive grains, but is preferably 0.1 to 1.0 MPa, more preferably 0.15 to 0.5 MPa.

[0026] In the fuel cell separator of the present invention, in order to maintain hydrogen impermeability while reducing the thickness of the fuel cell separator, the hydrogen permeability coefficient at a measurement temperature of 80°C is set to 1.7 × 10 -16 mol m / m2 ·Pa·sec or less is preferable, and 1.5×10 -16 mol m / m 2 The smaller the hydrogen permeability coefficient, the better. However, the lower limit is usually 0.1×10 -16 mol m / m 2 It is about ·Pa·sec. Furthermore, in order to achieve better power generation performance of the fuel cell, the specific resistance is preferably less than 23 mΩ·cm, and more preferably 20 mΩ·cm or less. Although the lower the specific resistance, the better, the lower limit is usually about 5.0 mΩ·cm. Furthermore, the bending strength is preferably 44 MPa or more, and the bending modulus is preferably less than 13 GPa. The upper limit of the bending strength is not particularly limited, but is preferably 100 MPa or less, and the lower limit of the bending modulus is not particularly limited, but is preferably 5.0 GPa or more.

[0027] A fuel cell equipped with the fuel cell separator of the present invention having these properties can maintain stable power generation efficiency for a long period of time. Generally, a solid polymer fuel cell is made up of a large number of unit cells arranged side by side, each of which is composed of a pair of electrodes sandwiching a solid polymer membrane and a pair of separators sandwiching these electrodes to form a gas supply / exhaust flow path. The fuel cell separator of the present invention can be used as some or all of these multiple separators. [Example]

[0028] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Physical properties in the examples were measured by the following methods.

[0029] [1] Cumulative particle size distribution d10 The particle size distribution was measured by wet method using a particle size distribution measuring device (MT3000 manufactured by Microtrac Bell Co., Ltd.). [2] Void volume ratio The void volume ratio was measured at a pressure of 30 MPa using a DVV400 manufactured by Micromeritics Instruments Corporation. [3] Spring back 2 g of graphite powder, the measurement sample, was placed in a mold with an inner diameter of 15 mm as shown in Figure 1(A), and after flattening the top surface of the sample, it was compressed with a press so that a load of 5.4 t was applied to the upper mold in 5 seconds (see Figure 1(B)). The compressed state was maintained for 30 seconds, and then the load was released all at once. The height of the upper surface of the upper mold in each state was measured with a height gauge, and the springback was calculated using the following formula. L0: Height of upper mold without measurement sample (mm) L1: Height of upper die under load (mm) L2: Height of upper die when the load is released (mm) Springback (%) = (L2-L1) / (L1-L0) x 100 [4] Powder resistance The powder resistance was measured at a pressure of 30 MPa using a powder resistance measurement system (MCP-PD51 manufactured by Mitsubishi Chemical Analytech Co., Ltd.). [5] Hydrogen permeability coefficient The hydrogen permeability coefficient was measured at a measurement temperature of 80°C by differential pressure gas chromatography in accordance with JIS K 7126-1 (differential pressure method). [6] Resistivity Measurement was carried out based on JIS H0602 (method for measuring resistivity of silicon single crystals and silicon wafers using four probes). [7] Strength test (flexural strength, flexural modulus) Using a 100 x 20 x 2 mm test piece cut out from the separator, a three-point bending test was performed with a support distance of 40 mm in accordance with JIS K 6911 "General test methods for thermosetting plastics" to measure the bending strength and bending modulus.

[0030] [Example 1] An epoxy resin component consisting of 100 parts by mass of graphite powder 1 having the following physical properties, 20.4 parts by mass of epoxy resin 1 (o-cresol novolac type, epoxy equivalent 198 g / eq), 10.8 parts by mass of phenolic resin (novolac type, hydroxyl group equivalent 104 g / eq), and 0.25 parts by mass of 2-phenylimidazole was placed in a Henschel mixer and mixed at 800 rpm for 3 minutes to prepare a resin composition for a fuel cell separator. The obtained composition was placed in a mold for producing a fuel cell separator and compression molded under conditions of a mold temperature of 185°C, a molding pressure of 36.6 MPa, and a molding time of 15 seconds to obtain a dense molded body having gas flow channel grooves and measuring 240 mm x 240 mm x 2 mm. Next, the entire surface of the obtained dense molded body was roughened by wet blasting using an alumina abrasive (average particle size: d50 = 6 μm) at a discharge pressure of 0.25 MPa and a conveying speed of 1.5 m / min to obtain a fuel cell separator.

[0031] Graphite powder 1: artificial graphite, acicular Cumulative particle size distribution d10: 13.0 μm Volume porosity: 17.8cm 3 / 100g Springback: 30.1% Powder resistance: 2.32mΩ·cm

[0032] [Example 2] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 2 having the following physical properties, to obtain a fuel cell separator.

[0033] Graphite powder 2: Artificial graphite, lump Cumulative particle size distribution d10: 14.9 μm Volume porosity: 13.7cm 3 / 100g Springback: 36.8% Powder resistance: 2.42mΩ·cm

[0034] [Example 3] A composition was prepared in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 3 having the physical properties described below. Further, a fuel cell separator was obtained by compression molding in the same manner as in Example 1, except that the molding time was changed from 15 seconds to 30 seconds.

[0035] Graphite powder 3: Artificial graphite, lump Cumulative particle size distribution d10: 19.5 μm Volume porosity: 29.6cm 3 / 100g Springback: 45.8% Powder resistance: 2.97mΩ·cm

[0036] [Example 4] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 4 having the following physical properties, to obtain a fuel cell separator.

[0037] Graphite powder 4: Artificial graphite, needle-shaped, with a non-graphite layer coated on the surface Cumulative particle size distribution d10: 11.1 μm Volume porosity: 12.5cm 3 / 100g Springback: 29.9% Powder resistance: 1.80mΩ·cm

[0038] [Example 5] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 5 having the following physical properties, to obtain a fuel cell separator.

[0039] Graphite powder 5: Natural graphite, flakes Cumulative particle size distribution d10: 11.0 μm Volume porosity: 13.0cm 3 / 100g Springback: 15.3% Powder resistance: 2.98mΩ·cm

[0040] [Example 6] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was replaced with a combination of graphite powder 2 (80 parts by mass) and graphite powder 4 (20 parts by mass), to obtain a fuel cell separator.

[0041] [Example 7] A composition was prepared and compression-molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was replaced with a combination of graphite powder 2 (60 parts by mass) and graphite powder 4 (40 parts by mass), to obtain a fuel cell separator.

[0042] [Example 8] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was changed to a combination of graphite powder 3 (80 parts by mass) and graphite powder 5 (20 parts by mass), to obtain a fuel cell separator.

[0043] [Example 9] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was changed to a combination of graphite powder 3 (60 parts by mass) and graphite powder 5 (40 parts by mass), to obtain a fuel cell separator.

[0044] [Example 10] A composition was prepared and compression-molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was replaced with a combination of graphite powder 2 (80 parts by mass) and graphite powder 9 (20 parts by mass) having the following physical properties, to obtain a fuel cell separator.

[0045] Graphite powder 9: artificial graphite, acicular Cumulative particle size distribution d10: 18.5 μm Volume porosity: 10.2cm 3 / 100g Springback: 14.1% Powder resistance: 1.53mΩ·cm

[0046] [Example 11] A composition was prepared and compression-molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was replaced with a combination of graphite powder 2 (60 parts by mass) and graphite powder 9 (40 parts by mass), to obtain a fuel cell separator.

[0047] [Example 12] A composition was prepared and compression-molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was replaced with a combination of graphite powder 2 (80 parts by mass) and graphite powder 10 (20 parts by mass) having the following physical properties, to obtain a fuel cell separator.

[0048] Graphite powder 10: Natural graphite, spherical, with a non-graphite layer coated on the surface Cumulative particle size distribution d10: 10.2 μm Volume porosity: 32.6cm 3 / 100g Springback: 20.0% Powder resistance: 1.64mΩ·cm

[0049] [Example 13] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was changed to a combination of graphite powder 2 (60 parts by mass) and graphite powder 10 (40 parts by mass), to obtain a fuel cell separator.

[0050] [Example 14] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was changed to a combination of graphite powder 4 (40 parts by mass) and graphite powder 10 (60 parts by mass), to obtain a fuel cell separator.

[0051] [Example 15] A composition was prepared in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 11 having the physical properties described below, and a fuel cell separator was obtained by compression molding in the same manner as in Example 1, except that the molding time was changed from 15 seconds to 31 seconds. Note that a fuel cell separator could not be obtained when the compression molding time was 30 seconds or less.

[0052] Graphite powder 11: Artificial graphite, lumps Cumulative particle size distribution d10: 12.4 μm Volume porosity: 29.9cm 3 / 100g Springback: 50.2% Powder resistance: 2.56mΩ·cm

[0053] [Example 16] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 12 having the following physical properties, to obtain a fuel cell separator.

[0054] Graphite powder 12: Natural graphite, flakes Cumulative particle size distribution d10: 10.4 μm Volume porosity: 12.1cm 3 / 100g Springback: 13.9% Powder resistance: 3.03mΩ·cm

[0055] [Comparative Example 1] A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 6 having the following physical properties, to obtain a fuel cell separator.

[0056] Graphite powder 6: artificial graphite, acicular Cumulative particle size distribution d10: 5.80 μm Volume porosity: 12.7cm 3 / 100g Springback: 25.1% Powder resistance: 5.22mΩ·cm

[0057] Comparative Example 2 A composition was prepared in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 7 having the following physical properties, and compression molding was performed in the same manner as in Example 1, except that the molding time was changed from 15 seconds to 70 seconds, to obtain a fuel cell separator. Note that a fuel cell separator could not be obtained when the compression molding time was 40 seconds or less.

[0058] Graphite powder 7: Artificial graphite, lumps Cumulative particle size distribution d10: 25.4 μm Volume porosity: 35.2cm 3 / 100g Springback: 55.8% Powder resistivity: 1.99mΩ·cm

[0059] Comparative Example 3 A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 8 having the following physical properties, to obtain a fuel cell separator.

[0060] Graphite powder 8: artificial graphite, acicular Cumulative particle size distribution d10: 30.6 μm Volume porosity: 40.2cm 3 / 100g Springback: 31.2% Powder resistance: 2.01mΩ·cm

[0061] Comparative Example 4 A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 9 having the following physical properties, to obtain a fuel cell separator.

[0062] Graphite powder 9: artificial graphite, acicular Cumulative particle size distribution d10: 18.5 μm Volume porosity: 10.2cm 3 / 100g Springback: 14.1% Powder resistance: 1.53mΩ·cm

[0063] Comparative Example 5 A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 was changed to graphite powder 10 having the following physical properties, to obtain a fuel cell separator.

[0064] Graphite powder 10: Natural graphite, spherical, with a non-graphite layer coated on the surface Cumulative particle size distribution d10: 10.2 μm Volume porosity: 32.6cm 3 / 100g Springback: 20.0% Powder resistance: 1.64mΩ·cm

[0065] Comparative Example 6 A composition was prepared and compression molded in the same manner as in Example 1, except that graphite powder 1 (100 parts by mass) was replaced with a combination of graphite powder 4 (40 parts by mass) and graphite powder 6 (60 parts by mass), to obtain a fuel cell separator.

[0066] [Example 17] In Example 1, except that the amount of epoxy resin 1 was changed from 20.4 parts by mass to 14.4 parts by mass, the amount of phenol resin was changed from 10.8 parts by mass to 7.7 parts by mass, and the amount of 2-phenylimidazole was changed from 0.25 parts by mass to 0.20 parts by mass, a composition was prepared and compression molded in the same manner as in Example 1, and a fuel cell separator was obtained.

[0067] [Example 18] In Example 1, except that the amount of epoxy resin 1 was changed from 20.4 parts by mass to 26.0 parts by mass, the amount of phenol resin was changed from 10.8 parts by mass to 13.9 parts by mass, and the amount of 2-phenylimidazole was changed from 0.25 parts by mass to 0.36 parts by mass, a composition was prepared and compression molded in the same manner as in Example 1, and a fuel cell separator was obtained.

[0068] [Example 19] A composition was prepared and compression molded in the same manner as in Example 1, except that in Example 1, 20.4 parts by mass of epoxy resin 1 was changed to 21.0 parts by mass of epoxy resin 2, the amount of phenol resin was changed from 10.8 parts by mass to 13.4 parts by mass, and the amount of 2-phenylimidazole was changed from 0.25 parts by mass to 0.31 parts by mass. To obtain a separator for a fuel cell, the composition was prepared and compression molded in the same manner as in Example 1.

[0069] Epoxy resin 2: Biphenyl type epoxy resin Epoxy equivalent: 165g / eq

[0070] [Example 20] A composition was prepared and compression molded in the same manner as in Example 1, to obtain a fuel cell separator, except that in Example 1, 20.4 parts by mass of Epoxy resin 1 was replaced by a combination of 11.0 parts by mass of Epoxy resin 1 and 10.0 parts by mass of Epoxy resin 2, the amount of phenol resin was changed from 10.8 parts by mass to 12.3 parts by mass, and the amount of 2-phenylimidazole was changed from 0.25 parts by mass to 0.30 parts by mass.

[0071] [Example 21] In Example 1, except that the amount of epoxy resin 1 was changed from 20.4 parts by mass to 13.1 parts by mass, the amount of phenol resin was changed from 10.8 parts by mass to 7.0 parts by mass, and the amount of 2-phenylimidazole was changed from 0.25 parts by mass to 0.19 parts by mass, a composition was prepared and compression molded in the same manner as in Example 1, and a fuel cell separator was obtained.

[0072] [Example 22] In Example 1, except that the amount of epoxy resin 1 was changed from 20.4 parts by mass to 27.0 parts by mass, the amount of phenol resin was changed from 10.8 parts by mass to 14.4 parts by mass, and the amount of 2-phenylimidazole was changed from 0.25 parts by mass to 0.37 parts by mass, a composition was prepared and compression molded in the same manner as in Example 1, and a fuel cell separator was obtained.

[0073] The hydrogen permeability coefficient, resistivity, flexural strength, and flexural modulus were measured for the fuel cell separators produced in Examples 1 to 22 and Comparative Examples 1 to 6. The results are shown in Tables 1 and 2. Table 1 also shows the physical properties of the graphite powder used, and Table 2 also shows the blending amount of the epoxy resin component.

[0074] [Table 1]

[0075] [Table 2]

[0076] As shown in Tables 1 and 2, the fuel cell separators of Examples 1 to 22 obtained from the fuel cell separator resin compositions within the range specified in the present invention had a hydrogen permeability of 1.7 × 10 at a measurement temperature of 80°C even when the molding time was as short as 40 seconds or less, specifically 15 to 31 seconds. -16 mol m / m 2 ·Pa·sec, specific resistance less than 23mΩ·cm, flexural strength 44MPa or more, and flexural modulus less than 13GPa, all of which are suitable values for a fuel cell separator.

Claims

1. The cumulative particle size distribution d10 is 10 to 20 μm, and the volume porosity measured by ASTM D6086 is 12 to 30 cm when the measurement pressure is 30 MPa. 3 A fuel cell separator obtained by molding a resin composition containing graphite powder having a particle size of 1 / 100 g and an epoxy resin component containing a base resin, a curing agent, and a curing accelerator, A fuel cell separator having a hydrogen permeability coefficient of less than 1.7×10 −16 mol·m / m 2 ·Pa·sec at a measurement temperature of 80° C. and a specific resistance of less than 23 mΩ·cm.

2. 2. The fuel cell separator according to claim 1, wherein the graphite powder has a powder resistivity of less than 3.0 mΩ·cm when measured at a pressure of 30 MPa.

3. 2. The fuel cell separator according to claim 1, wherein the spring back of the graphite powder is 13 to 50%.

4. 2. The fuel cell separator according to claim 1, wherein the base resin of said epoxy resin is at least one selected from the group consisting of cresol novolac type epoxy resins and biphenyl type epoxy resins.

5. 2. The fuel cell separator according to claim 1, wherein the curing agent for the epoxy resin is a novolac type phenolic resin.

6. 2. The fuel cell separator according to claim 1, wherein the curing accelerator comprises an imidazole compound having a phenyl group at the 2-position.

7. 2. The fuel cell separator according to claim 1, wherein the resin composition contains 20 to 42 parts by mass of the epoxy resin component per 100 parts by mass of the graphite powder.

8. 8. The fuel cell separator according to claim 1, which has a flexural strength of 44 MPa or more and a flexural modulus of elasticity of less than 13 GPa.

9. A separator for a fuel cell obtained by molding a resin composition containing graphite powder having a cumulative particle size distribution d10 of 10 to 20 μm, a volume void ratio measured by ASTM D6086 of 12 to 30 cm 3 / 100 g at a measurement pressure of 30 MPa, a powder resistivity of less than 3.0 mΩ·cm at a measurement pressure of 30 MPa, and a springback of 13 to 50%, and an epoxy resin component including a base agent, a curing agent, and a curing accelerator.

10. The cumulative particle size distribution d10 is 10 to 20 μm, and the volume porosity measured by ASTM D6086 is 12 to 30 cm when the measurement pressure is 30 MPa. 3 1. A method for producing a separator for a fuel cell, comprising compression molding a resin composition containing graphite powder having a density of 100 g / 100 g, and an epoxy resin component containing a base resin, a curing agent, and a curing accelerator, for a compression time of 40 seconds or less, The method for producing a fuel cell separator, wherein the fuel cell separator has a hydrogen permeability coefficient of less than 1.7×10 −16 mol·m / m 2 ·Pa·sec at a measurement temperature of 80° C. and a specific resistance of less than 23 mΩ·cm.

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