Method for manufacturing a fuel cell separator and fuel cell separator

Abstract

To provide a manufacturing method of a separator for a fuel cell, capable of reducing a material to be disposed, and provide the separator for the fuel cell.SOLUTION: A manufacturing method of a separator, comprises a base material generation step, a preparatory molded body formation step, a trimming step, a main molding step, and a pulverization step. In the base material generation step, a first resin and a second resin having a fusion point lower than that of the first resin and an amount smaller than the first resin are used to generate the base material, and a pulverized end material is used as a part of the base material. In the preparatory molded body formation step, a preparatory molded body is formed by pressing the base material while heating it to a first temperature T1 that is a temperature higher than the fusion point of the second resin and is lower than the fusion point of the first resin. In the trimming step, the preparatory molded body is trimmed. In the main molding step, a separator is formed by being pressed while heating the preparatory molded body to a second temperature T2 higher than the fusion point of the first resin. In the pulverization step, the end material removed in the trimming step, is pulverized.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a separator for a fuel cell and a separator for a fuel cell.

Background Art

[0002] Patent Document 1 describes a manufacturing method for forming a separator for a fuel cell as a molded product by compression molding using a molding material obtained by adding a filler to a powdery thermoplastic resin. In the manufacturing method described in Patent Document 1, first, the molding material is put into a primary molding die, and a sheet-like tablet is formed by melting the molding material. The primary molding die is preheated to a temperature not lower than the melting point of the thermoplastic resin in advance. Thereafter, the tablet is cooled together with the primary molding die to a temperature not higher than the melting point of the thermoplastic resin. Next, the tablet is transferred to a secondary molding die, and gas flow paths are formed on the front and back surfaces of the tablet by heating the tablet. The secondary molding die is preheated to a temperature not lower than the melting point of the thermoplastic resin in advance. Thereafter, the tablet is cooled together with the secondary molding die while being pressed by the secondary molding die, and is demolded from the secondary molding die after cooling. Thus, a separator for a fuel cell is formed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in such a manufacturing method for a separator for a fuel cell, after the molding material is put into a primary molding die to form a predetermined shape, the end material is removed. Since the end material thus removed is discarded, there is room for improvement in this regard.

Means for Solving the Problems

[0005] A method for manufacturing a fuel cell separator to solve the above problems is a method for manufacturing a fuel cell separator having an uneven gas channel through which a reaction gas flows by heating and pressing a base material comprising a thermoplastic resin and a conductive material, comprising: a base material production step in which the base material is produced using a first resin and a second resin having a lower melting point than the first resin and in a smaller quantity than the first resin; a pre-molded body formation step in which a sheet-like pre-molded body is formed by heating and pressing the base material to a first temperature which is higher than the melting point of the second resin and lower than the melting point of the first resin; a trimming step in which the pre-molded body is trimmed; a main molding step in which the separator having the gas channel is formed by heating and pressing the pre-molded body to a second temperature which is higher than the melting point of the first resin; and a crushing step in which the scraps removed in the trimming step are crushed, wherein in the base material production step, the crushed scraps are used as part of the base material.

[0006] Furthermore, a fuel cell separator for solving the above problems is formed from a base material containing a thermoplastic resin and a conductive material, and has a gas channel with an uneven shape through which a reaction gas flows, wherein the resin contains a first resin and a second resin which has a lower melting point than the first resin and is in a smaller quantity than the first resin.

[0007] According to this method and configuration, a pre-molded body is formed in the pre-molded body formation process by melting only the second resin. Since the first resin contained in the pre-molded body is not mixed with the second resin, the first resin contained in the scraps removed in the trimming process, and consequently the first resin contained in the scraps crushed in the crushing process, is not mixed with the second resin. Therefore, the first resin can be easily separated from the second resin by crushing the scraps in the crushing process. Thus, the crushed scraps can be easily used in the base material production process. Consequently, the amount of waste material can be reduced. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view of a fuel cell separator according to one embodiment. [Figure 2] Figure 2 is a flowchart showing the steps in order for the manufacturing method of the fuel cell separator shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing the pre-molded body formation process. [Figure 4] Figure 4 is a cross-sectional view of the preform. [Figure 5] Figure 5 is a cross-sectional view showing the trimming process. [Figure 6] Figure 6 is a cross-sectional view showing this molding process. [Modes for carrying out the invention]

[0009] A method for manufacturing a fuel cell separator and an embodiment of the fuel cell separator will be described below with reference to Figures 1 to 6. <Separator 10> First, we will explain the general configuration of the fuel cell separator (hereinafter referred to as separator 10).

[0010] As shown in Figure 1, the separator 10, together with other separators, is a component that constitutes a single cell by sandwiching the power generation section (not shown) of the fuel cell. On the first surface 10a of the separator 10, which faces the power generation section, a gas flow path 11 with an uneven shape through which the reaction gas flows is formed. On the second surface 10b of the separator 10, which is the surface opposite to the surface on which the gas flow path 11 is formed, a plurality of groove-shaped cooling medium flow paths 12 are formed. The cooling medium flow paths 12 are formed between adjacent gas flow paths 11.

[0011] The separator 10 is formed by heating and pressing a base material containing a thermoplastic resin and a conductive material. When the total amount of the base material is 100% by weight, the base material contains, for example, 20% by weight of thermoplastic resin and 80% by mass of conductive material.

[0012] The thermoplastic resin used consists of a first resin and a second resin in a smaller amount than the first resin. When the total amount of thermoplastic resin is 100% by weight, the thermoplastic resin contains 50% by weight or less of the second resin. The second resin has a lower melting point than the first resin. The difference in melting points between the first and second resins is preferably 80 degrees or more. More specifically, the difference in melting points between the first and second resins is preferably 100 degrees or more. The second resin is preferably softer than the first resin.

[0013] As the first resin, one material can be used alone or two or more materials can be used in appropriate combinations, for example, from polyphenylene sulfide (PPS), liquid crystal polymer (LCP), and polyether ether ketone (PEEK).

[0014] As the second resin, for example, one material can be used alone or two or more materials can be used in appropriate combinations from among polystyrene (PS), polyethylene (PE), acrylonitrile styrene (AS), and polyvinylidene fluoride (PVDS).

[0015] As conductive materials, for example, one type of material such as graphite and natural graphite can be used alone, or two or more types of materials can be used in appropriate combinations. <Manufacturing equipment 100> Next, the manufacturing apparatus 100 for the separator 10 will be described.

[0016] The manufacturing apparatus 100 includes an extrusion device, a conveying device, and a cutting device (not shown). Furthermore, the manufacturing apparatus 100 includes a first mold 60 (see Figure 3) and a second mold 70 (see Figure 6).

[0017] The extruder is configured to mix a mixed material, which consists of granular first resin, granular second resin, granular conductive material, and solvent, and to extrude it in a strip shape. The conveying device is configured to convey the belt-shaped mixed material extruded in a belt shape from the extrusion device.

[0018] The cutting device is configured to form the sheet-shaped base material 20 of a predetermined length by cutting the belt-shaped mixed material conveyed on the conveying device. Note that the extrusion device, the conveying device, and the cutting device have well-known configurations.

[0019] As shown in FIG. 3, the first mold 60 is configured to form the sheet-shaped preform 25 by pressing while heating the base material 20. The first mold 60 includes a fixed mold 61 and a movable mold 62 provided so as to be able to advance and retreat with respect to the fixed mold 61. The fixed mold 61 and the movable mold 62 are each provided with molding surfaces 61a and 62a that face each other and mold the base material 20. Each of the molding surfaces 61a and 62a is planar. Further, heaters 63 and 64 for heating them are provided inside the fixed mold 61 and the movable mold 62, respectively. Further, cooling channels 65 and 66 through which a refrigerant for cooling them flows are provided inside the fixed mold 61 and the movable mold 62, respectively.

[0020] As shown in FIG. 6, the second mold 70 is configured to form the separator 10 by pressing while heating the preform 25. The second mold 70 includes a fixed mold 71 and a movable mold 72 provided so as to be able to advance and retreat with respect to the fixed mold 71. The fixed mold 71 and the movable mold 72 are each provided with molding surfaces 71a and 72a that face each other and mold the preform 25. A plurality of grooves 71b and 72b for transferring the gas flow path 11 and the cooling medium flow path 12 to the preform 25 are provided on each of the molding surfaces 71a and 72a, respectively. The portion between adjacent grooves 72b is provided at a position overlapping the groove 71b in the advancing and retreating direction of the movable mold 72. Further, heaters 73 and 74 for heating them are provided inside the fixed mold 71 and the movable mold 72, respectively. Further, cooling channels 75 and 76 through which a refrigerant for cooling them flows are provided inside the fixed mold 71 and the movable mold 72, respectively.

[0021] Next, we will explain how to manufacture the separator 10. As shown in Figure 2, the method for manufacturing the separator 10 comprises a base material generation step, a pre-molded body formation step, a trimming step, and a main molding step.

[0022] Furthermore, the method for manufacturing the separator 10 includes a crushing step for crushing the scrap material removed in the trimming step. In the base material production process, the crushed scraps mentioned above are used as part of the base material 20.

[0023] Next, we will explain each step in detail. <Base material production process> First, a sheet-like base material 20 is formed from the mixed material using an extrusion device, a conveying device, and a cutting device.

[0024] The above-mentioned scrap material is supplied in such a manner that it accounts for 10% or less by weight when the total amount of base material 20 is considered to be 100% by weight. <Pre-molded body formation process> Next, the base material 20 is placed on the molding surface 61a of the fixed mold 61. At this time, the fixed mold 61 and the movable mold 62 are preheated by heaters 63 and 64 to a first temperature T1, which is higher than the melting point of the second resin and lower than the melting point of the first resin.

[0025] As shown in Figure 3, a pre-molded body 25 is formed by pressing the base material 20 to a first temperature T1 using the first mold 60. The pre-molded body 25 is formed to a predetermined thickness by being pressed.

[0026] After this, the pre-molded body 25 is cooled together with the first mold 60. The pre-molded body 25 is cooled while being clamped by the first mold 60. In the pre-molded body 25 thus formed, as shown in Figure 4, only the second resin 22 among the resins constituting the pre-molded body 25 melts and integrates, while the first resin 21 remains in a solid state without mixing with the second resin 22. Note that "23" indicates a conductive material.

[0027] <Trimming process> Next, as shown in Figure 5, the pre-molded body 25 is trimmed. Specifically, the outer periphery of the pre-molded body 25 is trimmed so that it takes on a predetermined shape. In this embodiment, the predetermined shape is the shape of the outer periphery of the separator 10. The portion removed by trimming becomes the scrap material 26.

[0028] <Main molding process> Next, the trimmed pre-molded body 25 is placed on the molding surface 71a of the fixed mold 71. At this time, the fixed mold 71 and the movable mold 72 are preheated by heaters 73 and 74 to a second temperature T2 that is higher than the melting point of the first resin.

[0029] As shown in Figure 6, the separator 10 is formed by pressing the pre-molded body 25 with the second mold 70 while heating it to a second temperature T2. In the separator 10 thus formed, the first resin and the second resin are mixed together.

[0030] <Grinding process> In the crushing process, the scrap material 26 removed in the trimming process is crushed using a crusher (not shown). The scrap material 26 is crushed, for example, until it becomes granular.

[0031] Next, the operation of this embodiment will be described. In the pre-molded body formation process, the pre-molded body 25 is formed by melting only the second resin 22. Therefore, the first resin 21 contained in the pre-molded body 25 is not mixed with the second resin 22 (see Figure 4). Consequently, the first resin 21 contained in the scrap material 26 removed in the trimming process, and furthermore, the first resin 21 contained in the scrap material 26 crushed in the crushing process, is not mixed with the second resin 22. As a result, the first resin 21 can be easily separated from the second resin 22 when the scrap material 26 is crushed in the crushing process. Therefore, the crushed scrap material 26 can be easily used in the base material production process.

[0032] Next, the effects of this embodiment will be described. (1) The method for manufacturing the separator 10 comprises a base material generation step, a pre-molded body formation step, a trimming step, a main molding step, and a grinding step. In the base material generation step, a base material 20 is generated using a first resin 21 and a second resin 22 which has a lower melting point than the first resin 21 and is in a smaller quantity than the first resin 21. In the pre-molded body formation step, a sheet-like pre-molded body 25 is formed by heating the base material 20 to a first temperature T1 which is higher than the melting point of the second resin 22 and lower than the melting point of the first resin 21, while pressing it. In the trimming step, the pre-molded body 25 is trimmed. In the main molding step, a separator 10 having a gas channel 11 is formed by heating the pre-molded body 25 to a second temperature T2 which is higher than the melting point of the first resin 21, while pressing it. In the grinding step, the scrap material 26 removed in the trimming step is ground. In the base material generation step, the ground scrap material 26 is used as part of the base material 20.

[0033] By using this method, the above-mentioned effects can be achieved, thus reducing the amount of waste material. (2) The difference in melting points between the first resin 21 and the second resin 22 is 80 degrees or more.

[0034] The smaller the difference in melting points between the first resin 21 and the second resin 22, the more difficult it is to melt only the second resin 22 in the pre-molded body formation process. In this regard, according to the above method, since the difference in melting points between the first resin 21 and the second resin 22 is 80 degrees or more, the melting of the first resin 21 can be effectively suppressed when the second resin 22 is melted in the pre-molded body formation process.

[0035] (3) The second resin 22 is softer than the first resin 21. With this configuration, since the thermoplastic resin includes a first resin 21 and a second resin 22 that is softer than the first resin 21, the separator 10 becomes more easily deformable compared to when the resin is composed of only the first resin 21. As a result, the separator 10 becomes more easily able to deform to follow the shape of other separators adjacent to it in the stacking direction of a single cell.

[0036] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0037] The second resin 22 may be a resin with the same hardness as the first resin 21, or it may be a resin that is harder than the first resin 21. In this embodiment, the difference in melting points between the first resin 21 and the second resin 22 is set to 80 degrees or more, but this is not limited to this. If the second resin 22 melts while the first resin 21 does not melt during the premolding process, the difference in melting points between the first resin 21 and the second resin 22 can be appropriately changed.

[0038] In this embodiment, a sheet-like base material 20 is formed using an extrusion device, a conveying device, and a cutting device, but the process for producing the base material 20 is not limited to this. For example, the base material 20 may be formed by pressing a mixed material using a mold (not shown). [Explanation of symbols]

[0039] 10... Separator 10a…Side 1 10b…Second side 11…Gas flow path 12…Cooling medium flow path 20…Base material 21…First resin 22...Second resin 23…Conductive materials 25…Pre-molded body 26…Scrap wood 60…First mold 61…Fixed type 62…Movable type 61a,62a…molding surface 63, 64... Heater 65, 66… Cooling channels 70…Second mold 71…Fixed type 72…Movable type 71a, 72a…molding surface 71b,72b…Groove 73, 74… Heater 75, 76… Cooling channels 100...Manufacturing equipment

Claims

1. A method for manufacturing a fuel cell separator having a gas channel with an uneven shape through which a reaction gas flows, by heating and pressing a base material containing a thermoplastic resin and a conductive material, A base material production step in which the base material is produced using a first resin and a second resin having a lower melting point than the first resin and in a smaller quantity than the first resin, A pre-molded body forming step involves forming a sheet-like pre-molded body by heating the base material to a first temperature that is higher than the melting point of the second resin and lower than the melting point of the first resin, and pressing it; A trimming step for trimming the pre-molded body, This molding process involves forming the separator having the gas channel by heating the pre-molded body to a second temperature higher than the melting point of the first resin and pressing it, The process includes a crushing step for crushing the scrap material removed in the trimming step, In the base material production step, the crushed scrap material is used as part of the base material. A method for manufacturing a separator for fuel cells.

2. The difference in melting points between the first resin and the second resin is 80 degrees or more. A method for manufacturing a fuel cell separator according to claim 1.

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