Fuel cell separator manufacturing method and fuel cell separator

Abstract

This fuel cell separator manufacturing method comprises: irradiating, with infrared lasers, the surface of a molded body formed by molding a composition containing a graphite powder and an epoxy resin component containing a main agent, a curing agent, and a curing accelerator to remove the resin on the surface of the molded body; and further performing hydrophilic treatment. The infrared lasers have: a beam quality (M2) of 2.8 or less; a spot diameter of 150-300 μm; and a pulse energy per unit area of 8-50 mJ / mm2. The fuel cell separator manufacturing method is for manufacturing a fuel cell separator having: small warpage after irradiation even when the thin fuel cell separator is irradiated with lasers; low contact resistance and excellent electrical conductivity when laminated; and good hydrophilicity.

Description

Method for manufacturing a fuel cell separator and fuel cell separator

[0001] This invention relates to a method for manufacturing a separator for fuel cells and to a separator for fuel cells.

[0002] Fuel cell separators play a role in providing conductivity to each unit cell, ensuring passages for fuel and air (oxygen) supplied to the unit cells, and acting as separation boundary walls between them. Therefore, fuel cell separators require various properties such as high conductivity, high gas impermeability, high thickness accuracy, chemical stability, heat resistance, and hydrophilicity. Among these properties, irradiation with an infrared laser is known as a method to enhance hydrophilicity.

[0003] For example, Patent Document 1 proposes a fuel cell separator in which a molded body made from a composition containing graphite powder, epoxy resin, and phenolic resin is subjected to surface roughening treatment such as blasting, then the resin on the surface of the molded body is removed by irradiation with an infrared laser, and further hydrophilization treatment such as atmospheric pressure plasma treatment is performed.

[0004] However, the pulse energy of the infrared laser used in Patent Document 1 is 5 to 30 mJ, and the spot diameter is 50 to 800 μm. To efficiently remove the resin from the surface of the molded body, the pulse energy per unit area should be 50 mJ / mm². 2 The following is preferable, but to achieve this, the pulse energy of the infrared laser must be 5 mJ and the spot diameter must be larger than 350 μm. When the spot diameter is larger than 350 μm, the energy within the spot becomes non-uniform, requiring a high overlap rate, which resulted in poor production efficiency.

[0005] Patent Document 2 describes a method for forming a hydrophilic surface on a graphite-containing material, which involves at least 0.5 MW / mm 2 A method has been proposed in which a pulsed laser with a power density of [value] is irradiated.

[0006] However, the pulse energy per unit area of ​​the infrared laser used in Patent Document 2 is 0.1 J / mm². 2Because of its high temperature, thin separators are prone to warping when irradiated, leading to problems such as increased contact resistance during lamination.

[0007] Japanese Patent Publication No. 2014-164996, Japanese Patent Publication No. 2024-509572

[0008] This invention has been made in view of these circumstances, and aims to provide a method for manufacturing a fuel cell separator that exhibits small warping after laser irradiation, low contact resistance during lamination, excellent conductivity, and good hydrophilicity, even when a thin-walled fuel cell separator is irradiated with a laser, and a fuel cell separator obtained by this method.

[0009] As a result of diligent research to achieve the above objective, the inventors have discovered that by using an infrared laser having a predetermined beam quality, a predetermined spot diameter, and a pulse energy per unit area within a predetermined range, even when irradiating a thin-walled fuel cell separator with the laser, it is possible to reduce warping after irradiation, and to obtain a fuel cell separator with low contact resistance during lamination, excellent conductivity, and good hydrophilicity, thus completing the present invention.

[0010] In other words, the present invention relates to a method for manufacturing a fuel cell separator, comprising: 1. Removing the resin from the surface of a molded body, which is formed by molding a composition containing graphite powder and an epoxy resin component comprising a main agent, a curing agent and a curing accelerator, by irradiating the surface of the molded body with an infrared laser, and further performing a hydrophilic treatment, wherein the beam quality (M) of the infrared laser 2 The pulse energy is 2.8 or less, the spot diameter is 150 to 300 μm, and the pulse energy per unit area is 8 to 50 mJ / mm². 21. A method for manufacturing a fuel cell separator, characterized in that the infrared laser spot overlap rate is 5 to 30%. 2. A method for manufacturing a fuel cell separator according to claim 1, wherein the hydrophilization treatment is atmospheric pressure plasma treatment. 4. A method for manufacturing a fuel cell separator according to claim 3, wherein the atmospheric pressure plasma treatment is remote atmospheric pressure plasma treatment. 5. A method for manufacturing a fuel cell separator according to claim 3, wherein the treatment gas for the atmospheric pressure plasma treatment is a gas containing nitrogen gas. 6. A fuel cell separator obtained by the manufacturing method according to any one of claims 1 to 5. 7. A fuel cell separator obtained by irradiating the surface of a molded body, which is made by molding a composition containing graphite powder and epoxy resin components including a main agent, a curing agent and a curing accelerator, with an infrared laser to remove the resin from the surface of the molded body, and further performing a hydrophilization treatment, characterized in that the warpage is less than 5 mm. 8. A fuel cell separator according to claim 7, wherein the arithmetic mean height Sa of the surface is 1.5 to 4.0 μm. 9. The fuel cell separator according to claim 7, wherein the fuel cell separator has grooves on one or both sides that serve as gas passages, and the difference in arithmetic mean height Sa between the bottom and top of the grooves is less than 20% of the arithmetic mean height Sa of the top of the grooves, 10. Contact resistance is 7 mΩ·cm 2 The fuel cell separator described in 7 is less than 10°, and the fuel cell separator described in 7 is provided, having a static contact angle of less than 10°.

[0011] According to the present invention's method for manufacturing a fuel cell separator, it is possible to obtain a fuel cell separator that has low warping, low contact resistance when stacked, excellent conductivity, and good hydrophilicity.

[0012] The present invention will be described in more detail below. [Method for manufacturing a fuel cell separator] The method for manufacturing a fuel cell separator according to the present invention is a method for manufacturing a fuel cell separator which involves removing the resin from the surface of a molded body obtained by molding a composition containing graphite powder and epoxy resin components including a main agent, a curing agent and a curing accelerator, by irradiating the surface of the molded body with an infrared laser, and further performing a hydrophilization treatment, wherein the beam quality (M) of the infrared laser 2)(1) is 2.8 or less, the spot diameter is 150 to 300 μm, and the pulse energy per unit area is 8 to 50 mJ / mm² 2 is characterized by the above.

[0013] (1) Production of the molded body In the production method of the present invention, first, a composition containing graphite powder and an epoxy resin component containing a main agent, a curing agent, and a curing accelerator is molded to produce a molded body.

[0014] The graphite powder used in the present invention may be appropriately selected from those conventionally used for fuel cell separators, and either natural graphite or artificial graphite may be used. Examples of artificial graphite include artificial graphite obtained by firing needle coke, artificial graphite obtained by firing lump coke, spheroidized artificial graphite, and artificial graphite whose surface is treated with pitch coating or the like. On the other hand, examples of natural graphite include flaky natural graphite, soil graphite, spheroidized natural graphite, and natural graphite whose surface is treated with pitch coating or the like. These can be used alone or in combination of two or more.

[0015] The average particle diameter d of the graphite powder 50 is not particularly limited, but considering maintaining appropriate voids between graphite particles, increasing the contact area between graphite particles, and particularly suppressing the generation of unevenness after laser treatment to enhance conductivity (reduce contact resistance), 10 to 200 μm is preferable, and 10 to 100 μm is more preferable. That is, when the average particle diameter d of the graphite powder 50 is 10 μm or more, when the molded body is irradiated with an infrared laser, the resin on the surface layer of the molded body can be removed to improve the conductivity of the separator surface, and the contact area between graphite particles inside the separator can be sufficiently maintained, so that the conductivity in the thickness direction of the separator can also be improved. Further, when the average particle diameter d 50 is 200 μm or less, since the voids between graphite particles are appropriate, even if the resin filled in the voids between graphite particles on the separator surface disappears due to laser irradiation, large unevenness will not be formed on the separator surface. As a result, the contact resistance of the separator is low, and the conductivity of the separator itself does not deteriorate. Incidentally, the above average particle diameter d 50The measurement method is as described in the examples below.

[0016] The main component constituting the epoxy resin is not particularly limited as long as it has an epoxy group. Examples include orthocresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, biphenyl aralkyl type epoxy resin, trisphenol type epoxy resin, brominated epoxy resin, dicyclopentadiene type epoxy resin, and biphenyl novolac type epoxy resin. These can be used individually or in combination of two or more. Among these, orthocresol novolac type epoxy resin alone, biphenyl type epoxy resin alone, or mixtures thereof are preferred. The epoxy equivalent of the epoxy resin used in the present invention is not particularly limited, but in the case of orthocresol novolac type epoxy resin, 194 to 215 g / eq is preferred, and in the case of biphenyl type epoxy resin, 180 to 200 g / eq is preferred.

[0017] The hydrolyzable chlorine content of the epoxy resin main component is preferably 450 ppm or less. When the hydrolyzable chlorine content is 450 ppm or less, the crosslinking density of the cured product increases, resulting in improved heat resistance of the resulting separator. On the other hand, there is no particular lower limit, but since epoxy resins with a hydrolyzable chlorine content of less than 370 ppm are very expensive, a lower limit of 370 ppm is preferable from a cost perspective.

[0018] Phenolic resins are preferred as curing agents for the epoxy resin components. Specific examples include novolac-type phenolic resins, cresol-novolac-type phenolic resins, resol-type phenolic resins, aralkyl-modified phenolic resins, biphenyl-novolac-type phenolic resins, and trisphenolmethane-type phenolic resins, which may be used individually or in combination of two or more. Among these, novolac-type phenolic resins are preferred. The hydroxyl group equivalent of the phenolic resin used in this invention is not particularly limited, but 100 to 106 g / eq is preferred.

[0019] The curing accelerator that constitutes the epoxy resin component is not particularly limited as long as it promotes the reaction between the epoxy group and the curing agent, and examples 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 aryl groups include phenyl groups, tolyl groups, and naphthyl groups, but the phenyl group is preferred. Specific examples of imidazole compounds having an aryl group at the 2-position include 2-phenylimidazole and 2-phenyl-4-methylimidazole. Note that if an imidazole compound having a short-chain alkyl group such as 2-methylimidazole is used, the curing time may be too fast and uniform molding may not be possible, while if an imidazole compound having a long-chain alkyl group such as 2-undecylimidazole is used, the curing time may be too slow and the molding time may be long.

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

[0021] The amounts of graphite powder and epoxy resin components (main agent, curing agent, and curing accelerator) used are not particularly limited, but preferably 22 to 40 parts by mass of epoxy resin component, more preferably 27 to 35 parts by mass, and even more preferably 30 to 33 parts by mass per 100 parts by mass of graphite powder. By using epoxy resin components within this range, the fluidity of the molding material becomes appropriate, resulting in good moldability, and it is possible to prevent a significant decrease in the gas impermeability and conductivity of the resulting fuel cell separator. In this case, it is preferable to blend the curing agent in an amount of 0.98 to 1.08 equivalents relative to the main agent, and more preferably 0.99 to 1.05 equivalents. Furthermore, the amount of curing accelerator used is not particularly limited, but preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the mixture of main agent and curing agent.

[0022] The composition can be prepared, for example, by mixing graphite powder, main component, curing agent, and curing accelerator in any order and in predetermined proportions. For this mixing, a planetary mixer, ribbon blender, Reidige mixer, Henschel mixer, rocking mixer, Nauter mixer, etc., can be used. If any optional components, such as an internal release agent, are used, their mixing order is also arbitrary.

[0023] Next, it is preferable to place the obtained composition into a predetermined mold and produce a molded body by press molding or the like. Preferably, the mold used is one for producing fuel cell separators, which can form grooves that serve as gas passages on one or both sides of the surface of the molded body. The press molding conditions are not particularly limited, but are generally a mold temperature of 80 to 200°C, a molding pressure of 1.0 to 50 MPa, preferably 5 to 40 MPa, a molding time of 10 seconds to 1 hour, preferably 20 to 180 seconds, more preferably 30 to 90 seconds. After press molding, the mold may be further heated at 150 to 200°C for 1 to 600 minutes to accelerate heat curing.

[0024] The resulting molded article preferably has grooves on one or both sides that serve as gas passages. The thickness of the molded article is not particularly limited, but is preferably 0.5 to 2 mm, and more preferably 0.5 to 1 mm.

[0025] (2) Laser irradiation Next, an infrared laser is irradiated onto the surface of the obtained molded body. In this case, it is preferable to irradiate the bottom (recessed) and / or top (protruding) of the grooves that serve as gas channels in the molded body, which has grooves that serve as gas channels on one or both sides, with the infrared laser. The laser may be irradiated only to these parts, or it may be irradiated onto the entire gas channel surface including these parts.

[0026] The infrared laser used for laser irradiation is not particularly limited as long as it satisfies the conditions of beam quality, spot diameter, and pulse energy per unit area. Examples include YAG lasers, carbon dioxide lasers, dye lasers, semiconductor lasers, and fiber lasers. Fiber lasers are preferred in terms of depth of focus, focusing ability, and transmitter lifespan. The wavelength of the infrared laser is not particularly limited, but is preferably 780 to 10600 nm, more preferably 808 to 1095 nm, and even more preferably 920 to 1070 nm.

[0027] Infrared laser beam quality (M 2 The beam quality is 2.8 or less, preferably 2.5 or less, more preferably 2 or less, and even more preferably 1.8 or less. A beam quality of 2.8 or less is preferable because it improves the focusing ability of the laser, thus eliminating the need for high energy to remove the resin from the surface layer of the molded body. Furthermore, because high energy is not required to irradiate the molded body, there is less thermal damage, and even when a thin-walled molded body is irradiated with a laser, the warping after irradiation is reduced, thus lowering the contact resistance in the fuel cell stack. Moreover, a laser beam quality of 2.8 or less increases the depth of focus, allowing the resin at the bottom of the gas flow channel groove to be removed without irradiating with high energy, thus lowering the static contact angle after atmospheric pressure plasma treatment. The lower limit of the beam quality is not particularly limited, but for example, it is around 1.5.

[0028] The pulse energy per unit area of ​​an infrared laser is 8–50 mJ / mm². 2 However, 10–48 mJ / mm 2 This is preferable. A pulse energy of 8 to 50 mJ / mm² per unit area is preferred. 2Within this range, the resin on the surface of the molded body can be completely removed, making it possible to obtain a good fuel cell separator with low contact resistance and static contact angle.

[0029] The spot diameter of an infrared laser is 150 to 300 μm. If the spot diameter is less than 150 μm, it takes a long time to roughen the surface of the molded product, resulting in poor production efficiency. On the other hand, if the spot diameter exceeds 300 μm, the energy within the spot becomes non-uniform, requiring a high overlap rate, which also results in poor production efficiency.

[0030] The overlap rate of the infrared laser spots is preferably 5 to 30%, and more preferably 10 to 30%. The above-mentioned overlap rate of the infrared lasers refers to the degree of overlap between adjacent laser spots and is calculated from the laser spot diameter and scan pitch. An overlap rate of 5 to 30% is preferable because it allows the arithmetic mean height Sa of the gas flow channel groove bottoms (recesses) and peaks (convex parts) on the surface of the molded body to be adjusted to a predetermined range.

[0031] The scanning speed when irradiating with a laser is not particularly limited, but 3,000 to 10,000 mm / sec is preferred, and 5,000 to 8,000 mm / sec is more preferred.

[0032] The arithmetic mean height Sa of the surface on at least one side of the molded body irradiated with an infrared laser, particularly, the arithmetic mean height Sa of the peaks (convex portions) and bottoms (concave portions) of the grooves serving as gas flow paths is preferably 1.15 to 4.0 μm, more preferably 1.4 to 4.0 μm, and still more preferably 1.5 to 4.0 μm. If the arithmetic mean height Sa is less than 1.15 μm, resin may remain on the surfaces of the bottoms and peaks of the separator gas flow path grooves, and there is a risk that the contact resistance and the static contact angle will increase. On the other hand, if the arithmetic mean height Sa exceeds 4.0 μm, the graphite particles at the bottoms and peaks of the separator gas flow path grooves are likely to fall off, and there is a risk that the contact resistance and the static contact angle will increase. Also, the difference in the arithmetic mean height Sa of the surfaces of the peaks (convex portions) and bottoms (concave portions) of the grooves serving as gas flow paths is preferably less than 20% of the arithmetic mean height Sa of the peaks, more preferably 15% or less, and still more preferably 10% or less. The lower limit value is not particularly limited, but is, for example, about 1%. The method for measuring the arithmetic mean height Sa is as described in the examples below.

[0033] Note that before irradiating the surface of the molded body with a laser, blast treatment may be performed as necessary. Also, blast treatment may not be performed. Examples of blast treatment include shot blast treatment, air blast treatment, wet blast treatment, etc., and any of them can be performed as long as the arithmetic mean height Sa of the surface of the molded body after laser irradiation is within the above range.

[0034] (3) Hydrophilic treatment Next, the surface of the molded body irradiated with an infrared laser, preferably the entire gas flow surface of the molded body having grooves serving as gas flow paths on the surface, is subjected to hydrophilic treatment. In this case, the hydrophilic treatment after laser irradiation may be applied to at least the gas flow surface that contacts the water generated by power generation, but may also be applied to the cooling surface (the surface on the opposite side in the case of a separator with the gas flow surface on one side) as necessary. The hydrophilic treatment is not particularly limited, but corona treatment, excimer UV light treatment, plasma treatment, etc. are preferable, and plasma treatment is more preferable among them.

[0035] As a method of hydrophilizing by plasma treatment, for example, vacuum plasma treatment, atmospheric pressure plasma treatment, etc. can be mentioned. Among these, atmospheric pressure plasma treatment, which is simple in equipment and has good productivity, is preferable, and particularly, remote type atmospheric pressure plasma treatment is more preferable.

[0036] As the gas used for generating plasma, oxygen gas containing oxygen atoms, ozone gas, water, nitrogen gas containing nitrogen atoms, ammonia gas, sulfur dioxide gas containing sulfur atoms, sulfur trioxide gas, etc. can be mentioned. Also, air can be used. By performing plasma treatment using these gases, hydrophilic functional groups such as carbonyl groups, hydroxyl groups, amino groups, sulfonic groups, etc. can be introduced onto the surface of the molded body to impart hydrophilicity to the surface. Among them, a gas containing 80% by volume or more of nitrogen gas is preferable, and a gas composed of 80% by volume or more of nitrogen gas and the balance being oxygen gas is more preferable.

[0037] [Separator for fuel cell] As described above, the separator for fuel cell of the present invention is obtained by irradiating the surface of a molded body formed by molding a composition containing graphite powder and an epoxy resin component containing a main agent, a curing agent, and a curing accelerator with an infrared laser to remove the resin on the surface of the molded body, and further performing a hydrophilization treatment, and is characterized in that the warp is less than 5 mm.

[0038] The fuel cell separator of the present invention has a curvature of less than 5 mm, preferably 4.5 mm or less, resulting in low contact resistance during lamination and excellent conductivity. The fuel cell separator of the present invention preferably has grooves that serve as gas passages on one or both sides, and the arithmetic mean height Sa of the surface on at least one side, particularly the arithmetic mean height Sa of the peaks (convex portions) and bottoms (concave portions) of the grooves that serve as gas passages, is preferably 1.15 to 4.0 μm, more preferably 1.4 to 4.0 μm, and even more preferably 1.5 to 4.0 μm. Because the resin on the surface layer of the bottoms (concave portions) and peaks (convex portions) of the gas passage grooves of the present invention is removed, the fuel cell separator of the present invention has low contact resistance and static contact angle, and excellent conductivity and hydrophilicity. In this case, the difference in arithmetic mean height Sa between the bottom (recess) and the top (convex) surfaces of the gas flow channel groove is preferably less than 20% of the arithmetic mean height Sa of the top surface, more preferably 15% or less, and even more preferably 10% or less. The lower limit is not particularly limited, but for example, it is about 1%.

[0039] The contact resistance of the fuel cell separator of the present invention, particularly the contact resistance at the peak (protrusion) of the gas flow path, is 7.5 mΩ·cm. 2 Preferably less than 7 mΩ·cm 2 Less than is more preferable. Furthermore, the static contact angle of the surface on at least one side of the fuel cell separator of the present invention, particularly the static contact angle of the bottom of the gas flow channel groove (recess), is preferably less than 11.5°, and more preferably less than 10°.

[0040] 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. The physical properties in the following examples were measured by the following methods. [Average particle size] Measured using a particle size distribution analyzer (manufactured by Nikkiso Co., Ltd.). [Measurement of parameters related to laser irradiation] (1) Beam quality (M 2 ) Measurement M 2The measurements were taken using a beam analyzer (BeamSquared, manufactured by Ophir Optronics Solutions). (2) Measurement of pulse energy per unit area The pulse energy per unit area was calculated by measuring the average laser power output and spot diameter using the following formula. The repetition frequency is the setting of the laser oscillator. (i) Measurement of average laser power output Measured using a power meter (NOVA II, manufactured by Ophir Optronics Solutions). (ii) Measurement of laser spot area The spot diameter was measured using a laser beam profile measurement camera (NOVA II, manufactured by Ophir Optronics Solutions), and the spot area was calculated. Pulse energy (mJ) = Average laser power output (W) ÷ Repetition frequency (kHz) Pulse energy per unit area (mJ / mm 2 ) = pulse energy (mJ) ÷ spot area (mm) 2) (3) Overlap rate The overlap rate was calculated from the following formula using the laser spot diameter (irradiation diameter of the laser spot) and scan pitch. Overlap rate (%) = (Laser spot diameter - scan pitch) / Laser spot diameter [Evaluation of fuel cell separators] (1) Measurement of separator warpage A separator irradiated with a laser was placed on a surface plate, and the maximum and minimum values ​​were measured using a height gauge, and the difference between these was defined as the warpage. (2) Measurement of the arithmetic mean height Sa of the surface of the gas flow path peaks (convex parts) and flow path groove bottoms (concave parts) of the separator The arithmetic mean height Sa specified in ISO 25178-2:2012 was measured on the surface of the gas flow path peaks (convex parts) and flow path groove bottoms (concave parts) of the separator using a laser microscope (Olympus Corporation, LEXT OLS5000). (3) Difference in arithmetic mean height Sa of gas channel peaks (convex parts) and channel groove bottoms (concave parts) of separator The difference (%) between the arithmetic mean height Sa of the gas channel peaks (convex parts) and the gas channel groove bottoms (concave parts) of the separator was calculated. (4) Measurement of contact resistance of separator (i) Carbon paper + separator sample Two of each prepared separator sample was stacked on top of each other, carbon paper (TGP-H060, manufactured by Toray Industries, Inc.) was placed above and below it, and copper electrodes were placed above and below that as well. A surface pressure of 1 MPa was applied in the vertical direction, and the voltage between electrodes was measured using the four-terminal method. (ii) Carbon paper Copper electrodes were placed above and below the carbon paper, a surface pressure of 1 MPa was applied in the vertical direction, and the voltage between electrodes was measured using the four-terminal method. (iii) Method for Calculating Contact Resistance The voltage drop between the separator sample and the carbon paper was determined from the voltage values ​​obtained in (i) and (ii) above, and the contact resistance was calculated using the following formula: Contact Resistance (mΩ・cm) 2 ) = (voltage drop × contact area) / current (5) Measurement of static contact angle of separator A 5 μL of deionized water was dropped into the bottom (recess) of the gas flow path of the fuel cell separator, and the contact angle was measured using a contact angle meter (CA-DT-A type manufactured by Kyowa Interface Chemical Co., Ltd.).

[0041] [Examples 1-16, Comparative Examples 1-18] Graphite powder (artificial graphite, average particle size d 50A resin composition was prepared by adding an epoxy resin component consisting of 20.4 parts by mass of epoxy resin (o-cresol novolac type epoxy resin, epoxy equivalent 198 g / eq), 10.7 parts by mass of phenol resin (novolac type phenol resin, hydroxyl group equivalent 103 g / eq), and 0.25 parts by mass of 2-phenylimidazole to 100 parts by mass of (23 μm) epoxy resin component and mixing at 800 rpm for 3 minutes. The obtained composition was placed in a mold for manufacturing a fuel cell separator and compression molded under the conditions of a mold temperature of 185°C, a molding pressure of 36.6 MPa, and a molding time of 30 seconds to obtain a molded body measuring 440 mm × 120 mm × 0.7 mm with a groove for a gas channel on one side. The bottom (recess) or top (convex) of the gas channel groove on the gas channel surface of the obtained molded body was irradiated with an infrared laser under the conditions shown in Table 1 and at a scan speed of 7500 mm / sec. Subsequently, the entire surface of the gas flow path was subjected to hydrophilization treatment by atmospheric pressure plasma treatment under the following conditions using a remote atmospheric pressure glow discharge plasma generator (AP-T03, manufactured by Sekisui Chemical Co., Ltd.) to obtain a fuel cell separator. [Atmospheric pressure plasma treatment conditions] (i) Frequency 30 kHz, pulse width 9 μs, plasma electrode 550 mm, voltage 420 V, current 4.5 A (ii) Plasma gas: nitrogen-oxygen mixed gas, nitrogen concentration 99.5 vol% (nitrogen gas flow rate 330 L / min, oxygen gas flow rate 1.5 L / min)

[0042] Tables 1 and 2 summarize the above examples and comparative examples.

[0043]

[0044]

[0045] Fuel cell separators irradiated with lasers under the conditions of Examples 1 to 16 exhibit less warping due to minimal thermal damage from laser irradiation. Furthermore, since the arithmetic mean height Sa of the gas flow channel grooves and recessed surfaces is within a predetermined range, the contact resistance and contact angle are low.

Claims

1. A method for manufacturing a fuel cell separator, comprising irradiating the surface of a molded body, which is formed by molding a composition containing graphite powder and epoxy resin components including a main agent, a curing agent, and a curing accelerator, with an infrared laser to remove the resin from the surface of the molded body and further perform a hydrophilic treatment, wherein the beam quality (M) of the infrared laser 2 The pulse energy is 2.8 or less, the spot diameter is 150 to 300 μm, and the pulse energy per unit area is 8 to 50 mJ / mm². 2 A method for manufacturing a fuel cell separator, characterized by the following:

2. The method for manufacturing a fuel cell separator according to claim 1, wherein the overlap rate of the infrared laser spots is 5 to 30%.

3. The method for manufacturing a fuel cell separator according to claim 1, wherein the hydrophilization treatment is atmospheric pressure plasma treatment.

4. The method for manufacturing a fuel cell separator according to claim 3, wherein the atmospheric pressure plasma treatment is a remote atmospheric pressure plasma treatment.

5. The method for manufacturing a fuel cell separator according to claim 3, wherein the processing gas used in the atmospheric pressure plasma treatment is a gas containing nitrogen gas.

6. A fuel cell separator obtained by the manufacturing method described in any one of claims 1 to 5.

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