JP4269553B2 - Manufacturing method of fuel cell separator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for producing a molded article comprising a mixture of graphite powder and a polymer compound, and more particularly to a method for producing a separator used in a polymer electrolyte fuel cell.
[0002]
[Prior art]
Fuel cell separators are required to have excellent gas impermeability, high electrical conductivity, and excellent corrosion resistance and strength. Conventionally, as separators for fuel cells, those manufactured using impregnated graphite obtained by impregnating a graphite sintered body with resin, graphite / resin molded products obtained by mixing and molding graphite powder and resin, etc. have been used. ing.
[0003]
[Problems to be solved by the invention]
However, the former requires high-temperature heat treatment at 2000 ° C. or higher, and further requires cutting because of shrinkage during the high-temperature heat treatment, which is expensive to manufacture. Further, the latter has a problem that since the blending ratio of the graphite powder is increased in order to obtain high conductivity, the flowability of the material is poor and the molding accuracy is poor. Further, when a thermoplastic resin is used as the polymer compound, the mold temperature is increased from the supply temperature of the mixture to a temperature equal to or higher than the melting point of the thermoplastic resin, and then the mold temperature is changed to that of the thermoplastic resin. Since the separator is taken out at a temperature lower than the melting point, there is a problem that the molding time is long.
[0004]
The present invention solves the above-mentioned problems, and provides a method for producing a separator for a fuel cell having a high molding accuracy and a short molding time in a graphite / resin compound having a high blending ratio of graphite powder and poor flowability. For the purpose.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a method for producing a fuel cell separator according to claim 1 of the present invention comprises: 70 to 90% by mass of graphite powder and 30 to 10% by mass of a polymer compound among upper and lower molds. The mixture is fed into the lower mold, the heating apparatus is heated after inserting the heating device between the upper and lower molds with the lower mold temperature fixed and the upper and lower molds opened. The mixture is formed into a predetermined shape by melting the polymer compound, removing the heating device, and then closing and solidifying the mold.
[0007]
A method of manufacturing a fuel cell separator according to claim 2 of the present invention, in the structure according to claim 1, wherein the heating apparatus is a high-frequency heating apparatus, the heating of said mixture, a high-frequency characterized Rigyo Ukoto by that irradiated inductively heating the graphite powder in the mixture.
[0008]
Further, the method of manufacturing a fuel cell separator according to claim 3 of the present invention, in the structure according to claim 1, wherein the heating device is a microwave heating apparatus, the heating of said mixture, Ma Micro the polymer compound in the mixture is irradiated with a wave, characterized in Rigyo Ukoto by the fact that dielectric heating.
[0009]
Further, the method of manufacturing a fuel cell separator according to claim 4 of the present invention, in the structure according to claim 1, wherein the heating device is an infrared heating apparatus, the heating of the mixture, the infrared characterized by Rigyo Ukoto.
[0010]
According to each of the above configurations, in the present invention, the mold is kept at a constant temperature, only the mixture is heated, the temperature is raised to a temperature equal to or higher than the melting point of the thermoplastic resin in the mixture, and compression molding is performed. The cooling time is shortened and the molding time can be shortened.
[0013]
In the method for producing a fuel cell separator according to claim 5 of the present invention, a mixture of graphite powder of 70 to 90% by mass and polymer compound of 30 to 10 % by mass of the upper and lower molds is used as the lower mold. The mixture itself is heated by an ultrasonic vibrator while the upper and lower molds are closed, and the mixture is cooled to be molded into a predetermined shape.
[0016]
In each said structure, since a mixture is heated in the state which closed the metal mold | die, a separator with a sufficient shaping | molding precision can be obtained.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0018]
(Embodiment 1)
In the first embodiment of the present invention, a mixture of graphite powder and a polymer compound is supplied to a mold, and the mixture is heated to melt and solidify the polymer compound, thereby forming a predetermined shape. Thus, the molding time can be shortened.
[0019]
In the mixture of graphite powder and polymer compound, the graphite powder can be either artificial graphite or natural graphite. The particle size of the graphite powder is not particularly defined, but in order to obtain high conductivity, those having an average particle size of 10 μm to 200 μm, preferably 30 μm to 100 μm can be used. As the polymer compound, thermoplastic resins such as PPS, PPE, and PBT can be used from the viewpoint of heat resistance and chemical resistance.
[0020]
The compounding ratio of the graphite powder and the polymer compound may be 70 to 90% by mass of graphite powder and 30 to 10% by mass of polymer compound from the viewpoint of conductivity. When the graphite powder is less than 70% by mass , the volume specific resistance of the separator increases and the battery performance deteriorates. Moreover, when there are more graphite powders than 90 wt%, the intensity | strength of a separator will become weak.
[0021]
The mold is composed of an upper mold and a lower mold, and a gas flow path pattern is formed on both or one of them. Metal, ceramics, graphite, etc. can be used as the material of the mold. In particular, it is preferable to use a metal from the viewpoint of mold strength and wear resistance.
[0022]
The molding conditions when a thermoplastic resin is used as the polymer compound will be described with reference to FIG. 1 showing changes in the mold temperature or the mixture temperature over time. In FIG. 1, 1 is a curve representing the temperature change of the mold in the conventional manufacturing method, 2 is a curve representing the temperature change of the mixture in the conventional manufacturing method, 3 is a line representing the temperature change of the mold in this embodiment, 4 is a curve representing the temperature change of the mixture in the present embodiment, and 5 is the melting point temperature of the thermoplastic resin.
[0023]
As shown in FIG. 1, in this embodiment, the mold is kept at a constant temperature, only the mixture is heated to a temperature higher than the melting point of the thermoplastic resin in the mixture, and compression molding is performed. The time for temperature and cooling is shortened, and the molding time can be shortened.
[0024]
(Embodiment 2)
In the second embodiment of the present invention, as in the first embodiment, a mixture of graphite powder and a polymer compound is supplied to a mold, and in particular, the mixture itself is heated with the mold 6 opened. The mold is closed and molded into a predetermined shape, whereby the temperature of the mixture itself can be easily raised.
[0025]
The manufacturing method of the separator for fuel cells of this embodiment is demonstrated using FIG. As shown in FIG. 2A, the mixture 7 is supplied into the mold 6 with the mold 6 opened. Thereafter, the mixture 7 is flattened with a squeegee 8 as shown in FIG. 2 (b), and then the heating device 9 enters between the upper mold and the lower mold above the mixture 7 as shown in FIG. 2 (c). Let me. After the mixture 7 is heated to a predetermined temperature, the heating device 9 is removed as shown in FIG. 2D, the mold 6 is closed, and molding is performed at a predetermined pressure. After cooling and solidifying while maintaining a predetermined pressure, the mold 6 is opened and the molded product is taken out. Thus, since the mixture 7 is heated in a state where the mold 6 is opened, the temperature of the mixture 7 can be easily raised.
[0026]
(Embodiment 3)
In the third embodiment of the present invention, as in the second embodiment, a mixture of graphite powder and a polymer compound is supplied to a mold, and the mold is opened. After the powder is induction-heated, the mold is closed and molded into a predetermined shape. This allows the mixture to be heated in a short time, thereby shortening the molding time. Further, since the graphite powder is heated, this action and effect does not depend on the type of polymer compound.
[0027]
FIG. 3 shows an apparatus for forming a mixture using a high-frequency heating device. In FIG. 3, reference numeral 10 denotes a multi-turn coil as a high-frequency heating device. Due to the high frequency from the coil 10, an eddy current flows through the graphite powder, and heat is generated by the resistance loss. For example, a frequency of 1 kHz to 300 MHz can be used as the frequency of the high frequency to be irradiated. The mixture 7 of the graphite powder and the polymer compound is supplied to the mold 6, the high frequency from the coil 10 is irradiated to the mixture 7, and the graphite powder in the mixture 7 is induction-heated to melt the polymer compound, Thereafter, the mold 6 is closed and molded. Since the high frequency induction heats the graphite powder itself in the mixture 7, the mixture 7 can be heated regardless of the type of the polymer compound.
[0028]
(Embodiment 4)
In the fourth embodiment of the present invention, as in the third embodiment, a mixture of graphite powder and a polymer compound is supplied to a mold, and the mold is opened. After the dielectric heating of the polymer compound, the mold is closed and molded into a predetermined shape, whereby the polymer compound can be efficiently and uniformly melted in a short time.
[0029]
FIG. 4 shows an apparatus for forming a mixture using the microwave heating apparatus 20. The microwave irradiated from the microwave oscillator 14 is irradiated to the mixture 7 through the waveguide 11. A power monitor 12 that measures the reflected power and an isolator 13 that absorbs the reflected power are attached in the middle of the waveguide 11, and high-efficiency microwaves can be stably and highly efficiently irradiated. Since the polymer compound is dielectrically heated by the microwave irradiation, the polymer compound can be uniformly melted in a short time, and the molding time can be shortened.
[0030]
As the microwave, for example, a microwave having a frequency of 300 MHz to 30 GHz can be used. A mixture 7 of graphite powder and a polymer compound is supplied into the mold 6, microwaves are irradiated to the mixture 7, the polymer compound is dielectrically heated, and after the polymer compound is melted, the mold 6 is closed. Mold. Since the polymer compound itself is dielectrically heated by the microwave, the polymer compound can be uniformly melted in a shorter time than the induction heating method using the high frequency. However, some polymer compounds are difficult to be heated by microwaves, and in that case, the induction heating method using high frequency in the third embodiment is effective.
[0031]
(Embodiment 5)
In the fifth embodiment of the present invention, as in the third and fourth embodiments, a mixture of graphite powder and a polymer compound is supplied to a mold and the mold is opened. After heating itself, the mold is closed and molded into a predetermined shape, whereby the mixture can be heated uniformly and a separator with good molding accuracy can be obtained.
[0032]
FIG. 5 shows an apparatus for forming a mixture using an infrared heating device. In FIG. 5, 15 is an infrared irradiation device as an infrared heating device, which can simultaneously heat the graphite powder and the polymer compound in the mixture 7. A far infrared heater, an infrared lamp, etc. can be used for infrared irradiation. A mixture 7 of graphite powder and a polymer compound is supplied into a mold 6 and irradiated with infrared rays to melt the polymer compound, and then the mold 6 is closed and molded. By using infrared rays, the heating time is longer as compared with the heating method by the high frequency or microwave in the third and fourth embodiments, but the graphite powder and the polymer compound can be heated at the same time. Even samples with poor fluidity can be molded with higher accuracy.
[0033]
(Embodiment 6)
In the sixth embodiment of the present invention, as in the first to fifth embodiments, a mixture of graphite powder and a polymer compound is supplied to a mold, and the mixture itself is kept in a state where the mold is closed. By heating and forming into a predetermined shape, a separator with good forming accuracy can be obtained. The manufacturing method of the separator for fuel cells of this embodiment is demonstrated using FIG.
[0034]
As shown in FIG. 6A, the mixture 7 is supplied to the mold with the mold 6 opened. Then, after flattening the mixture 7 with the squeegee 8 as shown in FIG. 6B, the mold 6 is closed as shown in FIG. 6C, and the mixture 7 is kept at a predetermined temperature while applying a predetermined pressure. Heat to. As shown in FIG. 6 (d), after cooling and solidifying while maintaining a predetermined pressure, the mold 6 is opened and the molded product is taken out. Thus, since the mixture is heated in a state where the mold 6 is closed, a separator with good molding accuracy can be obtained.
[0035]
(Embodiment 7)
In the seventh embodiment of the present invention, as in the sixth embodiment, the mixture 7 of graphite powder and polymer compound is supplied to the mold and then the mold is closed. In the present embodiment, the mixture 7 The mixture 7 itself is heated by being energized to be molded into a predetermined shape. FIG. 7 shows an apparatus for forming a mixture by electric heating. A terminal 17 for energizing the mold 6 is provided, and the mixture 7 is energized from the energizing device 16.
[0036]
The mold 6 uses an insulating material such as ceramics or forms an insulating material on the mold surface. When the mixture 7 is energized, the amount of power to be energized is determined by the size of the separator to be produced, the energization time, the molding temperature, and the resistivity of the mixture 7. The mold 6 is provided with a groove-shaped gas flow path pattern (not shown) corresponding to the gas flow path shape of the separator on both sides. When the mixture 7 is energized from the upper surface to the lower surface, the gas flow path pattern is uniform. In addition, current does not flow through the mixture 7 and heating unevenness is likely to occur.
[0037]
Therefore, for energization of the mixture 7, the electrode portion 17 is installed on the mold 6 so that a current flows in the surface direction of the mixture 7. According to this energization heating method, since the mixture 7 can be heated and melted while the mold 6 is closed and pressure is applied, the molding accuracy is higher than the method of heating and melting the mixture 7 with the mold 6 opened. A good separator can be obtained. Furthermore, the molding time can be shortened as compared with a method in which the mixture is heated by heat conduction from a conventional mold.
[0038]
(Embodiment 8)
As in the sixth and seventh embodiments, the eighth embodiment of the present invention supplies a mixture of graphite powder and a polymer compound to a mold in a solid state, then closes the mold, Ultrasonic vibration is applied to the mixture through a mold, and the mixture itself is heated to be molded into a predetermined shape. FIG. 8 shows a molding apparatus using ultrasonic vibration. Ultrasonic waves are irradiated from the ultrasonic vibrator 18, the direction is changed by the LL converter 19, and vibration energy is given to the mixture 7. When ultrasonic vibration is used, the vibration frequency is preferably 1 kHz to 100 kHz, and the larger the amplitude, the more easily the effect is exhibited. However, the vibration frequency is set according to the ability of the ultrasonic vibrator 18 and the fatigue level of the mold 6. To do. The ultrasonic vibration causes the formation position of the cavity of the mold 6 to coincide with the resonance abdomen. Further, by causing the resonance node to coincide with the mold holding part, vibrations in the mold holding part can be reduced.
[0039]
It is necessary that ultrasonic vibration is applied to the entire mold 6 for a time from when the mold 6 is closed to when it is opened by supplying at least the mixture 7 of the graphite powder and the polymer compound to the mold. At that time, it is desirable to control the temperature of the mold 6 itself according to the polymer compound. By applying ultrasonic waves, the mixture 7 itself vibrates and fluidity is improved, so that the molding accuracy is improved and the temperature of the mixture 7 is raised by the frictional heat of the mixture 7, so that the time required for heating and cooling is short. Thus, the molding time can be shortened.
[0040]
【Example】
Examples of the present invention will be described below.
[0041]
Example 1
Artificial graphite powder with an average particle size of 50 μm (SCG grade manufactured by ESC) and PPS resin powder (Torellina powder made by Toray) were mixed at a ratio of 80% by mass of artificial graphite powder and 20% by mass of PPS resin powder. As shown, the mixture 7 was fed into the mold 6 in powder form. The temperature of the mold 6 is kept constant at 150 ° C. Next, the mixture 7 is flattened with a squeegee 8 as shown in FIG. 9 (b), and the high-frequency oscillator 21 (Fuji Electric Works) comprising the coil 10 is opened with the mold opened as shown in FIG. 9 (c). Machine), and a high frequency of 40 MHz was irradiated from the top of the mixture 7. When the temperature of the mixture 7 reached 350 ° C., the high-frequency oscillation device 21 was removed as shown in FIG. 9D, the mold 6 was closed, and the pressure was increased to 400 kgf / cm ² . After 30 seconds, the mold 6 was opened and the molded product was taken out. The battery characteristics when the obtained molded body was used showed the same characteristics as those of the conventional separator.
[0042]
(Example 2)
Artificial graphite powder with an average particle size of 50 μm (SCG grade manufactured by ESC) and PPS resin powder (Torelina powder manufactured by Toray) were mixed at a ratio of 80% by mass of artificial graphite powder and 20% by mass of PPS resin powder, and the result is shown in FIG. As shown, the mixture 7 was fed into the mold 6 in powder form. The temperature of the mold 6 is kept constant at 150 ° C. Next, the mixture 7 was flattened with a squeegee 8 as shown in FIG. 10 (b), and a microwave transmitter 14 (magnetron) was provided with the mold 6 opened as shown in FIG. 10 (c). A microwave heating device 20 was inserted, and microwaves with a frequency of 2450 MHz were irradiated from the top of the mixture 7. When the temperature of the mixture 7 reached 350 ° C., the microwave heating device 20 was removed as shown in FIG. 10 (d), and the mold 6 was closed and pressurized with a pressure of 400 kg / cm ² . After 30 seconds, the mold 6 was opened and the molded product was taken out. The battery characteristics when the obtained molded body was used showed the same characteristics as those of the conventional separator.
[0043]
(Example 3)
Artificial graphite powder having an average particle size of 50 μm (SCG grade manufactured by ESC) and PPS resin powder (Torellina powder manufactured by Toray) were mixed at a ratio of 80% by mass of artificial graphite powder and 20% by mass of PPS resin powder. As shown, the mixture 7 was fed into the mold 6 in powder form. The mold temperature is kept constant at 150 ° C. Next, the mixture 7 is flattened with a squeegee 8 as shown in FIG. 11B, and the infrared irradiation device 15 equipped with a far-infrared lamp is opened with the mold 6 opened as shown in FIG. 11C. It was allowed to enter and heated from the top of the mixture 7. When the temperature of the mixture 7 reached 350 ° C., the infrared irradiation device 15 was removed as shown in FIG. 11 (d), the mold 6 was closed, and the pressure was increased at a pressure of 400 kg / cm ² . After 30 seconds, the mold 6 was opened and the molded product was taken out. The battery characteristics when the obtained molded body was used showed the same characteristics as those of the conventional separator.
[0044]
(Example 4)
Artificial graphite powder having an average particle size of 50 μm (SG grade manufactured by ESC) and PPS resin powder (Toray Rena powder made by Toray) were mixed at a ratio of 80% by mass of artificial graphite powder and 20% by mass of PPS resin powder. As shown, the mixture 7 was fed into the mold 6 in powder form. The mold temperature is kept constant at 150 ° C. Next, the mixture 7 is flattened with a squeegee 8 as shown in FIG. 12B, and the mold 6 is closed and pressurized with a pressure of 400 kg / cm ² as shown in FIG. After the mixture 7 was energized by the energizing device 16 through the electrode 17 provided in Fig. 12, the energization was stopped and held at the same pressure for 60 seconds as shown in Fig. 12 (d). The battery characteristics when the obtained molded body was used showed the same characteristics as those of the conventional separator.
[0045]
(Example 5)
Artificial graphite powder with an average particle size of 50 μm (SG grade manufactured by ESC) and PPS resin powder (Toray Rena powder made by Toray) were mixed in a proportion of 80% by mass of artificial graphite powder and 20% by mass of PPS resin powder. As shown, the mixture 7 was fed into the mold 6 in powder form. Next, as shown in FIG.13 (b), the mixture 7 was planarized with the squeegee 8, and the mold temperature at that time was 200 degreeC. As shown in FIG. 13 (c), the mold 6 is closed and pressurized at a pressure of 400 kg / cm ² , while the mold 6 is heated to 280 ° C. 19 kHz ultrasonic wave was applied through the LL converter 19 for 50 seconds. Thereafter, the mold 6 was cooled to 200 ° C. while the ultrasonic wave was stopped and held at the same pressure for 60 seconds. The battery characteristics when the obtained molded body was used showed the same characteristics as those of the conventional separator.
[0046]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the separator for fuel cells with a short shaping | molding time and a good shaping | molding precision can be provided using the graphite / resin compound with the high compounding ratio of graphite powder and bad flowability.
[Brief description of the drawings]
FIG. 1 is a diagram showing temperature changes of a mold and a mixture in a first embodiment of the present invention. FIG. 2 (a) is a diagram showing a mixture supply state into a mold in a second embodiment of the present invention. (B) The figure which shows the state which planarized the mixture in the metal mold | die shown to this figure (a) (c) The figure which shows the state which made the heating apparatus approach (d) The figure which shows the state which closes and molds a metal mold | die FIG. 3 is a schematic diagram of a molding apparatus using a high-frequency heating device according to a third embodiment of the present invention. FIG. 4 is a schematic diagram of a molding apparatus using a microwave heating device according to a fourth embodiment of the present invention. FIG. 5 is a schematic view of a molding apparatus using an infrared heating device according to a fifth embodiment of the present invention. FIG. 6 (a) is a diagram showing a supply state of a mixture into a mold according to a sixth embodiment of the present invention. (B) The figure which shows the state which planarized the mixture in the metal mold | die shown to this figure (a) (c) A metal mold | die is closed FIG. 7 (d) is a diagram showing a state in which the mold is closed and pressure is maintained. FIG. 7 is a schematic diagram of a molding apparatus by energization heating in the seventh embodiment of the present invention. FIG. 9 is a schematic view of a molding apparatus using ultrasonic vibration in the embodiment of the present invention. FIG. 9A is a diagram showing a state of supplying the mixture into the mold in Example 1 of the present invention. FIG. (C) A diagram showing a state in which the mixture in the mold is flattened (c) A diagram showing a state in which a high-frequency transmitter is entered to irradiate the mixture with a high frequency (d) A diagram showing a state in which the mold is closed and pressurized and molded. FIG. 10A is a diagram showing a mixture supply state into a mold in Example 2 of the present invention. FIG. 10B is a diagram showing a state in which the mixture in the mold shown in FIG. Figure (d) shows a state in which a microwave heating device is entered to irradiate the mixture with microwaves. FIGS. 11A and 11B are views showing a state of molding. FIG. 11A is a diagram showing a state of supplying the mixture into the mold in Example 3 of the present invention. FIG. 11B is a plan view of the mixture in the mold shown in FIG. (C) A diagram showing a state in which the mixture is heated by injecting an infrared irradiation device (d) A diagram showing a state in which the mold is closed and pressurizing and molding is performed. The figure which shows the mixture supply state in the metal mold | die in Example 4 (b) The figure which shows the state which planarized the mixture in the metal mold | die shown to this figure (a) (c) The state which supplies with electricity to the mixture in a metal mold | die Fig. 13 (d) is a diagram showing a state in which the mold is closed and pressure is maintained. Fig. 13 (a) is a diagram showing a state of supplying the mixture into the mold in Example 5 of the present invention. A diagram showing a state in which the mixture in the mold shown in a) is flattened. (c) A diagram showing a state in which the mold is closed and ultrasonic vibration is applied. Explanation of]
1 Curve representing temperature change of mold in conventional molding 2 Curve representing temperature change of mixture in conventional molding 3 Line representing temperature change of mold in Embodiment 1 of the present invention Mixture in Embodiment 1 of the present invention Curve 5 representing temperature change of thermoplastic resin Melting point of thermoplastic resin 6 Mold 7 Mixture 9 Heating device 10 Coil (high frequency heating device)
DESCRIPTION OF SYMBOLS 15 Infrared irradiation apparatus 16 Current supply apparatus 18 Ultrasonic vibrator 20 Microwave heating apparatus 21 High frequency transmission apparatus

Claims (5)

Among the upper and lower molds, a mixture of 70 to 90% by mass of graphite powder and 30 to 10% by mass of the polymer compound was supplied into the lower mold, the lower mold temperature was kept constant, and the upper and lower molds were opened. After inserting a heating device between the upper and lower molds in a state, the heating device is heated to melt the polymer compound, and after removing the heating device, the mold is closed and solidified, A method for producing a fuel cell separator, comprising molding the mixture into a predetermined shape.   2. The fuel cell separator according to claim 1, wherein the heating device is a high-frequency heating device, and the heating of the mixture is performed by inductively heating graphite powder in the mixture by irradiating a high-frequency wave. 3. Manufacturing method.   The said heating apparatus is a microwave heating apparatus, Comprising: The heating of the said mixture is performed by irradiating a microwave and making the high molecular compound in the said mixture into a dielectric heating. Manufacturing method of separator for fuel cell.   The method for producing a fuel cell separator according to claim 1, wherein the heating device is an infrared heating device, and the mixture is heated by infrared rays. Of the upper and lower molds, a mixture of 70 to 90% by mass of graphite powder and 30 to 10% by mass of the polymer compound is supplied into the lower mold, and the mixture itself is ultrasonicated with the upper and lower molds closed. A method for producing a separator for a fuel cell, characterized in that the mixture is heated by a vibrator, the mixture is cooled and formed into a predetermined shape.

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