Method for manufacturing a fuel cell separator and fuel cell separator

Abstract

To provide a method for manufacturing a fuel cell separator that exhibits minimal 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. [Solution] 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 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 150-300 μm, and the pulse energy per unit area is 8-50 mJ / mm². 2 A method for manufacturing a fuel cell separator, characterized by the following:

Description

[Technical Field]

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

[0002] Fuel cell separators serve to provide conductivity to each unit cell, ensure passages for fuel and air (oxygen) supplied to the unit cell, and act as separation boundary walls between them. Therefore, fuel cell separators are required to have 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 the surface of a molded body made by molding a composition containing graphite powder, epoxy resin, and phenolic resin is roughened by blasting or the like, the resin on the surface of the molded body is removed by irradiating it with an infrared laser, and then a 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 this requires a pulse energy of 5 mJ for the infrared laser and a spot diameter 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 / mm². 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. 2 Because of its high temperature, thin separators are prone to warping when irradiated, leading to problems such as increased contact resistance during lamination. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-164996 [Patent Document 2] Special Publication No. 2024-509572 [Overview of the project] [Problems that the invention aims to solve]

[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 minimal 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. [Means for solving the problem]

[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 is 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 performing a hydrophilic treatment, The beam quality (M) of the infrared laser 2 The pulse energy is 2.8 or less, the spot diameter is 150-300 μm, and the pulse energy per unit area is 8-50 mJ / mm². 2 A method for manufacturing a fuel cell separator, characterized by the above, 2. A 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. A 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 for the atmospheric pressure plasma treatment is a gas containing nitrogen gas. 6. A fuel cell separator obtained by irradiating the surface of a molded body, which is formed from 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 then performing a hydrophilic treatment, characterized in that it has a warp of less than 5 mm. 7. A fuel cell separator according to 6, wherein the arithmetic mean height Sa of the surface is 1.5 to 4.0 μm. 8. The fuel cell separator according to 6, 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. 9. The contact resistance is 7 mΩ·cm. 2 A fuel cell separator described in 6, which is less than 6, 10. A fuel cell separator according to 6, wherein the static contact angle is less than 10°. To provide. [Effects of the Invention]

[0011] According to the method for manufacturing a separator for a fuel cell of the present invention, it is possible to obtain a separator for a fuel cell having a small warp, a low contact resistance during lamination, excellent conductivity, and good hydrophilicity.

Embodiment for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in more detail. [Method for Manufacturing a Separator for a Fuel Cell] The method for manufacturing a separator for a fuel cell according to the present invention is a method for manufacturing a separator for a fuel cell in which an infrared laser is irradiated onto the surface of a molded body obtained by molding a composition containing graphite powder and an epoxy resin component containing a main agent, a curing agent, and a curing accelerator, thereby removing the resin on the surface of the molded body and further performing a hydrophilic treatment. The beam quality (M 2 ) of the infrared laser 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 / mm 2 This is characterized by being.

[0013] (1) Production of Molded Body In the manufacturing method of the present invention, first, a molded body is produced by molding a composition containing graphite powder and an epoxy resin component containing a main agent, a curing agent, and a curing accelerator.

[0014] The graphite powder used in the present invention may be appropriately selected from those conventionally used for separators for fuel cells, 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. [[ID=三十五]]

[0015] Average particle size d of the graphite powder 50 is not particularly limited, but considering that it appropriately maintains the gaps between the graphite particles, increases the contact area between the graphite particles, and particularly suppresses the generation of irregularities 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 size 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 the graphite particles inside the separator can be sufficiently maintained, so that the conductivity in the thickness direction of the separator can also be improved. Also, when the average particle size d 50 is 200 μm or less, since the gaps between the graphite particles are appropriate, even if the resin filled in the gaps between the graphite particles on the separator surface disappears due to laser irradiation, large irregularities 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 measurement method of the above average particle size d 50 is as described in the examples described later.

[0016] The main agent constituting the epoxy resin component is not particularly limited as long as it has an epoxy group. For example, orthocresol novolak type epoxy resin, phenol novolak 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, biphenyl novolak type epoxy resin, etc. can be mentioned, and these can be used alone or in combination of two or more. Among these, orthocresol novolak type epoxy resin alone, biphenyl type epoxy resin alone, and mixtures thereof are preferable. 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 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 phenyl groups are preferred. Specific examples of imidazole compounds having an aryl group at the 2-position include 2-phenylimidazole and 2-phenyl-4-methylimidazole. Furthermore, using imidazole compounds with short-chain alkyl groups, such as 2-methylimidazole, may result in a curing time that is too fast, making uniform molding impossible. On the other hand, using imidazole compounds with long-chain alkyl groups, such as 2-undecylimidazole, may result in a curing time that is too slow, leading to a longer molding time.

[0020] Furthermore, in addition to the above-mentioned components, the composition used in the present invention may also contain any other components, such as an internal mold release agent, as appropriate. As the internal release agent, it is acceptable to select from various internal release agents conventionally used for molding separators. Specific examples include stearic acid-based waxes, amide-based waxes, montanic acid-based waxes, carnauba waxes, polyethylene waxes, 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 per 100 parts by mass of graphite powder, more preferably 27 to 35 parts by mass, and even more preferably 30 to 33 parts by mass. 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 add 0.98 to 1.08 equivalents of the hardening agent relative to the main component, 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 the main agent and the 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. As for the mold to be used, it is preferable to use a mold for producing fuel cell separators that can form grooves that serve as gas passages on one or both sides of the surface of the molded body. The press forming conditions are not particularly limited, but typically include a mold temperature of 80-200°C, a forming pressure of 1.0-50 MPa, preferably 5-40 MPa, and a forming time of 10 seconds to 1 hour, preferably 20-180 seconds, more preferably 30-90 seconds. Furthermore, after press molding, the material may be heated at 150-200°C for 1-600 minutes to accelerate heat curing.

[0024] The resulting molded body 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 resulting molded body. In this case, it is preferable to irradiate the bottom (recessed) and / or top (protruding) portions of the grooves that serve as gas channels in a molded body having grooves that serve as gas channels on one or both sides. The laser may be aimed only at these portions, or it may be irradiated onto the entire gas channel surface including these portions.

[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. In addition, 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.

[0028] The pulse energy per unit area of ​​an infrared laser is 8-50 mJ / mm². 2 However, 10-48 mJ / mm 2 Preferably, the pulse energy per unit area is 8 to 50 mJ / mm². 2 Within 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 infrared laser spots is preferably 5-30%, and more preferably 10-30%. The above-mentioned overlap rate of 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 5-30% is preferable because it allows the arithmetic mean height Sa of the gas flow channel groove bottoms (concave parts) 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 3000 to 10000 mm / sec is preferred, and 5000 to 8000 mm / sec is more preferred.

[0032] The arithmetic mean height Sa of the molded surface irradiated with an infrared laser 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. If the arithmetic mean height Sa is less than 1.15 μm, resin may remain on the surface of the bottom and top of the separator gas channel grooves, potentially increasing contact resistance and static contact angle. On the other hand, if the arithmetic mean height Sa exceeds 4.0 μm, graphite particles at the bottom and top of the separator gas channel grooves may easily fall off, potentially increasing contact resistance and static contact angle. Furthermore, the difference in arithmetic mean height Sa between the surface of the peak (convex portion) and the bottom (concave portion) of the groove that serves as the gas passage is preferably less than 20% of the arithmetic mean height Sa of the peak, more preferably 15% or less, and even more preferably 10% or less. The method for measuring the arithmetic mean height Sa is as described in the examples below.

[0033] Furthermore, blast treatment may be performed on the surface of the molded body before irradiating it with a laser, if necessary. Alternatively, blast treatment may be omitted. Blasting treatments include shot blasting, air blasting, and wet blasting, and any of these can be performed as long as the arithmetic mean height Sa of the molded surface after laser irradiation falls within the above range.

[0034] (3) Hydrophilization treatment Next, the surface of the molded body irradiated with an infrared laser, preferably the entire gas channel surface of a molded body having grooves that serve as gas channels on its surface, is subjected to a hydrophilic treatment. In this case, the hydrophilization treatment after laser irradiation only needs to be applied to the gas flow path surface that comes into contact with the water generated by the power generation, but it may also be applied to the cooling surface (the opposite side in the separator where the gas flow path surface is on one side) as needed. While there are no particular limitations on the hydrophilization treatment, corona treatment, excimer UV light treatment, and plasma treatment are preferred, with plasma treatment being the most preferred among them.

[0035] Methods for hydrophilization by plasma treatment include, for example, vacuum plasma treatment and atmospheric pressure plasma treatment. Among these, atmospheric pressure plasma treatment is preferred because the equipment is simple and productivity is good, and remote atmospheric pressure plasma treatment is more preferred.

[0036] Examples of gases used to generate plasma include oxygen gas containing oxygen atoms, ozone gas, water, nitrogen gas containing nitrogen atoms, ammonia gas, sulfur dioxide gas containing sulfur atoms, and sulfur trioxide gas. Air can also be used. By performing plasma treatment using these gases, hydrophilic functional groups such as carbonyl groups, hydroxyl groups, amino groups, and sulfo groups can be introduced to the surface of the molded body, thereby imparting hydrophilicity to the surface. Among these, a gas containing 80% or more by volume of nitrogen gas is preferred, and a gas composed of 80% or more by volume of nitrogen gas with the remainder being oxygen gas is more preferred.

[0037] [Fuel cell separator] As described above, the fuel cell separator of the present invention is obtained by irradiating the surface of a molded body, which is formed from 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 then performing a hydrophilic treatment, and is characterized by having a warp of less than 5 mm.

[0038] The fuel cell separator of the present invention has a warp of less than 5 mm, preferably 4.5 mm or less, resulting in low contact resistance during lamination and excellent conductivity. The arithmetic mean height Sa of the surface of the fuel cell separator of the present invention 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 of the gas flow path groove bottom (recess) and peak (convex) of the fuel cell separator of the present invention is removed, it 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.

[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 Less than 7 mΩ·cm is preferable. 2 Less than is preferable. Furthermore, the static contact angle, particularly the static contact angle at the bottom (recess) of the gas flow channel groove, is preferably less than 11.5°, and more preferably less than 10°. [Examples]

[0040] The present invention will be described more specifically 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] The particle size distribution was measured using a particle size analyzer (manufactured by Nikkiso Co., Ltd.). [Measurement of various parameters related to laser irradiation] (1) Beam quality (M 2 ) measurement M 2 The 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 using the following formula, after measuring the average laser power output and spot diameter. The repetition frequency is determined by the laser oscillator setting. (i) Measurement of average laser power The power was measured using a power meter (NOVAII, manufactured by Ophir Optronics Solutions). (ii) Measurement of laser spot area The spot diameter was measured using a laser beam profile measurement camera (NOVAII, manufactured by Ophir Optronics Solutions), and the spot area was calculated. Pulse energy (mJ) = Laser average power (W) ÷ Repetition frequency (kHz) Pulse energy per unit area (mJ / mm 2 ) = Pulse energy (mJ) ÷ Spot area (mm²) 2 ) (3) Overlap rate The overlap rate was calculated using the following formula based on 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. The difference between these values ​​was defined as the warp. (2) Measurement of the arithmetic mean height Sa of the surface of the summit (convex portion) and the bottom (concave portion) of the separator gas flow path. The arithmetic mean height Sa, as defined in ISO 25178-2:2012, was measured on the surface of the gas channel peaks (convex portions) and channel groove bottoms (concave portions) of the separator using a laser microscope (Olympus Corporation, LEXT OLS5000). (3) The difference in arithmetic mean height Sa between the peak (convex part) and the bottom (concave part) of the gas flow path of the separator. The difference (%) between the arithmetic mean height Sa of the gas channel peak (convex portion) and the gas channel groove bottom (concave portion) of the separator was calculated. (4) Measurement of contact resistance of separator (i) Carbon paper + separator sample Two of the fabricated separator samples were stacked on top of each other, carbon paper (TGP-H060, manufactured by Toray Industries, Inc.) was placed above and below them, and 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 the electrodes was measured using the four-terminal method. (ii) Carbon paper Copper electrodes were placed above and below a sheet of carbon paper, a surface pressure of 1 MPa was applied in the vertical direction, and the voltage between the electrodes was measured using the four-terminal method. (iii) Contact resistance calculation method 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 5 μL of deionized water was dropped into the bottom (recess) of the fuel cell separator gas flow path in atmospheric air, 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 1-19] 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) in a Henschel mixer 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 on one side that serves as a gas passage. The bottom (recessed) or peak (convex) of the gas channel grooves 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 separator for fuel cells. [Atmospheric pressure plasma treatment conditions] (i) Frequency 30kHz, pulse width 9μs, plasma electrode 550mm, voltage 420V, current 4.5A (ii) Plasma gas: Nitrogen-oxygen mixed gas, nitrogen concentration 99.5% by volume (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] [Table 1]

[0044] [Table 2]

[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 performing a hydrophilic treatment, 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 spots of the infrared laser 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 for the atmospheric pressure plasma treatment is a gas containing nitrogen gas.

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