Method for producing plate-shaped fuel cell component, in particular bipolar plate, and fuel cell component produced according to method

Abstract

The invention relates to a method for producing a plate-shaped fuel cell component (6), in particular a bipolar plate, from an additive component thermoplastic material having good electrical and thermal conductivity, the plate-shaped fuel cell component being produced by means of an injection moulding device by means of an injection moulding technique, the injection molding device comprises at least one injection molding unit and at least one molding unit, and the molding unit is provided with a wall part surrounding a corresponding cavity. According to the invention, an efficient production of a plate-shaped fuel cell component is achieved in that a molten thermoplastic material and an additive component are injected as a molten mass under pressure by means of at least one injection-molding unit (2) into a cavity of a corresponding cavity (31) of at least one molding unit, which cavity remains unchanged corresponding to the geometry of the fuel cell component, and in that the at least one injection-molding unit (2) is pressed by means of the at least one injection-molding unit (2), and in that the at least one injection-molding unit (2) is pressed by means of the at least one injection-molding unit (2). The heat transfer by means of the wall (30) is matched to the thermal conductivity, the thermal capacity and the injection rate of the molten material in such a way that the molten material as the molding material (5) completely fills the corresponding cavity (31) before the temperature of the molten material is below the melting point thereof.

Description

[0001] The present invention relates to a method for manufacturing a plate-shaped fuel cell component, in particular a bipolar plate, from a thermoplastic material having an additive component with good electrical conductivity and thermal conductivity, wherein the plate-shaped fuel cell component is manufactured by an injection molding technique by means of an injection molding device, which includes at least one injection unit and at least one molding unit, and the molding unit has a wall portion surrounding a corresponding cavity.

[0002] Furthermore, the present invention also relates to a plate-shaped fuel cell component manufactured according to the above method, and a device for manufacturing such a plate-shaped fuel cell component.

[0003] Such a method and a plate-shaped fuel cell component, in particular a bipolar plate, manufactured from a modified thermoplastic material are known from WO 94 / 25995A1. In this known method, polyether sulfone (PES) is used as a preferred thermoplastic material. In addition, it has the advantage that the material can be processed by injection molding or extrusion molding, so that the individual components of the fuel cell can be connected to each other by plastic welding or bonding using PES. To achieve the electrical conductivity required for the fuel cell, the thermoplastic material is modified by adding conductive particles, such as conductive carbon black, graphite, etc., and the conductive particles are added to the molten polymer. No further detailed information about the injection molding process itself is provided.

[0004] Since such a plate-shaped fuel cell component, in particular a bipolar plate or an electrode plate, has a very thin wall thickness when it is relatively large in planar extension (for example, the size is that of an A4 paper), and usually the thickness is less than 1 mm, therefore, due to the rapid cooling in the molding unit during the injection molding process, its manufacturing by injection molding technology is difficult. To prevent the rapid cooling before the thin and large-area cavity of the molding unit is completely filled, usually the wall portion of the cavity is heated when injecting the molten material, and an extrusion process is carried out subsequently. In this way, rapid heat dissipation of the molten material can be avoided during the injection molding process, and complete filling of the cavity with the molten material can be achieved. It can also be considered that the molten material modified with conductive particles has a relatively high thermal conductivity for applications in fuel cells, which also leads to rapid heat dissipation. The re-extrusion requires additional processes and a correspondingly complex design of the injection molding device. Subsequently, before the molded part in the form of a plate-shaped fuel cell component is ejected, the cooling and solidification required for the molten material or the molding material additionally prolong the injection molding cycle. In addition, the heating device and the cooling device in the variable temperature design are energy-consuming.

[0005] A method for manufacturing a plate-shaped fuel cell component by means of an injection molding device is given in US2004 / 0115505A1, wherein an adjustable forming component is used to extrude the injection molding material filled into the cavity of the molding die or the injection molding material in the filling state. The share of the conductive filling material in the molding material is 60% to 95% by weight. The adjustable forming component and its operation require additional costs.

[0006] Other injection molding devices for plate-shaped formed parts, wherein the forming process also uses adjustable components of the molding die, see JP 2006-327051A and JP 2009-226641A.

[0007] The technical problem to be solved by the present invention is to provide a method for manufacturing a plate-shaped fuel cell component, especially a bipolar plate, which can efficiently manufacture high-quality plate-shaped fuel cell components and provide corresponding fuel cell components.

[0008] The above technical problem is achieved by the method having the features described in claim 1 and the plate-shaped fuel cell component having the features described in claim 5.

[0009] According to the method of the present invention, a molten thermoplastic material and an additive component are injected as a molten material into the cavity of a corresponding cavity of at least one forming unit under pressure by means of at least one injection unit. The cavity remains unchanged and corresponds to the geometry of the fuel cell component, and the heat transfer through the wall is matched with the thermal conductivity, heat capacity and injection speed of the molten material, so that the molten material is completely filled into the corresponding cavity before the temperature of the molten material is lower than its melting point as a molding material.

[0010] The plate-shaped fuel component according to the present invention refers to a component manufactured by means of the above method, especially those components having sufficient self-rigidity for application in fuel cells.

[0011] During the injection molding process, the parameters of the injection molding device and the injection molding process are mutually matched, including the state and characteristics of the injected molten material. Among them, the heat dissipation matching the injected molten material is so small that the molten material can reliably fill the cavity before solidifying into the molded material. Through the above matching, the injection molding process and the molding of the plate-shaped fuel cell component can be efficiently achieved with as little energy consumption as possible and in the shortest possible time. The wall portion around the cavity is applied with an appropriate temperature precisely matching the injection molding process, and then can be cooled below the solidification temperature within a corresponding short time until demolding. Thereby, the injection molding cycle can be significantly shortened with as low energy consumption as possible, so as to efficiently manufacture the plate-shaped fuel cell component. For example, the wall portion of the corresponding cavity can be constructed or insulated with a plastic material having a correspondingly high temperature stability and a significantly lower thermal conductivity (unit: W / (k·m)) than the molten material, so as to avoid the heat in the molten material from dissipating too quickly, that is, before the molten material fills the entire cavity volume. In addition, it is suitable that the wall portion is composed of a metal and a temperature regulating element that can be well controlled or adjusted to achieve rapid heat input and heat output. Among them, the heat-insulating coating of the wall portion for controlling the temperature around the cavity is also conducive to achieving efficient process control.

[0012] To implement the method, it is stipulated to use an injection molding device having at least one injection unit for inputting a thermoplastic raw material with a conductive additive component, especially containing graphite particles. The injection molding device also has at least one molding unit, which has a nozzle-side molding section corresponding to the injection nozzle device and a push-side molding section corresponding to the push side. The nozzle-side and push-side molding sections face each other in the separation plane by means of corresponding separation areas. At least one molding unit respectively includes a part of the corresponding molding part in the molding part accommodating part. The molding part includes a molding insert and a molding core. Among them, a cavity that can be opened in the separation plane and closed during the injection molding process is formed in the molding insert. The cavity is connected to the injection unit through an input unit with a hot runner system or a cold runner system to inject the molten raw material into its cavity as the molten material. During the molding process, until at least one molding unit is opened, the geometric shape of the cavity of the cavity together with the inner surface of the molding insert surrounding the cavity remains unchanged and is adapted to the geometric shape of the fuel part to be manufactured. There is no re-extrusion device for changing the geometric shape of the cavity during the molding process.

[0013] The structure of a plate-shaped fuel cell component or bipolar plate that is beneficial to the operating principle of a fuel cell is achieved as follows: graphite is incorporated into a thermoplastic material as a conductive additive component, and optionally carbon black is also added (up to 5 wt%, 10 wt%, or 25 wt% of the additive component, or up to 5 vol%, 10 vol%, or 25 vol%), and its mass ratio in the total mass or total volume of the raw materials added to the injection molding unit is greater than 5%, greater than 20%, or greater than 30%, preferably greater than 50%, for example, between 5% and 90% or 95%, especially between 30% and 70% or 87%. As a conductive additive component, other additives can also be considered for additional use.

[0014] Other advantageous measures include: for an efficient injection molding process, the thermoplastic material for the matrix should be a matrix material with a free π electron system, especially PEEK material, and only graphite is used as the conductive additive component. The present invention is based on the following consideration in this design, that is, graphite is conductively connected through the π electron system in the matrix polymer of the molding material, without adding conductive carbon black particles required for traditional conductive connections. Avoiding the use of conductive carbon black enables the filling degree of the additive component to be reduced and contributes to an efficient injection molding process. Since re-extrusion is avoided, the orientation formed by graphite particles during the injection molding process can be advantageously used as a preferred direction to make the manufactured plate-shaped fuel cell component have good electrical conductivity.

[0015] Another advantageous design feature of the plate-shaped fuel component or bipolar plate is that the thickness (d) perpendicular to its surface in a top view of the plate-shaped fuel cell component is manufactured to be, for example, at most 5 mm, especially at most 2 mm, at most 1 mm, or at most 0.5 mm or 0.2 mm, wherein the plate-shaped fuel cell component has sufficient self-rigidity for use in a fuel cell.

[0016] For the manufacturing process and function of the plate-shaped fuel cell component, other advantageous measures lie in that the average particle size D of the graphite particles 50 is in the range of 5 μm to 50 μm or 100 μm, and / or the aspect ratio (the ratio of the thickness to the minimum extension dimension perpendicular to the thickness direction) is less than 5, especially less than 1 or less than 0.5.

[0017] In addition, the advantageous manufacturing of the plate-shaped fuel cell component or bipolar plate is achieved as follows: during the injection molding process, at least one connecting element, fixing element, circuit element, and / or sealing element is provided for the fuel cell component or bipolar plate by forming (Einformen) and / or injection (Anspritzen). These measures can significantly contribute to the manufacturing of fuel cells as a whole and also significantly contribute to the manufacturing of fuel cell stacks, wherein different application conditions can be flexibly adapted to.

[0018] In order to achieve an injection molding process that can be well controlled for the efficient manufacture of plate-shaped fuel cell components, such as bipolar plates, other advantageous designs of the injection molding device lie in that temperature regulating devices are arranged between the molding insert and the molding core in the nozzle side and / or ejection side molding sections, and in particular in that the temperature regulating devices include heating devices and / or cooling devices. For example, the heating device can be heated inductively by the current heat achieved through the electrical circuit device or by means of a heat transfer fluid guided through a channel, and / or the cooling device can operate by means of a cooling fluid guided through a channel or be equipped with an electrically operated cooling device, and / or at least the molding insert is made of a material with good thermal conductivity, especially metal or ceramic, and the molding components including at least the molding insert and the molding core are surrounded by heat-insulating separating components.

[0019] The present invention will be described in more detail below with reference to the accompanying drawings according to embodiments; in the drawings:

[0020] Figure 1 An injection molding device for manufacturing plate-shaped fuel cell components, such as bipolar plates, is shown in a schematic cross-sectional view.

[0021] Figure 2 An embodiment of the plate-shaped fuel cell component is shown in a schematic perspective view, and

[0022] Figure 3 The molding die of the injection molding device is shown in cross-section in sub-views a) and b).

[0023] Figure 1 An embodiment of the injection molding device 1 is shown in a schematic longitudinal sectional view, which injection molding device includes an injection unit 2 and a molding unit 3 connected thereto.

[0024] The injection unit 2 includes a housing 20 having a funnel-shaped feed member 21, and a conveying unit 22 having a conveying screw and a drive unit 23.

[0025] The molding unit 3 includes a molding component having a cavity 31 configured corresponding to the plate-shaped component to be manufactured, and the cavity 31 is surrounded by a wall portion 30. In order to remove the component obtained through the injection molding process, here namely the plate-shaped fuel cell component 6 (see Figure 2 ), that is, the bipolar plate, the molding unit 3 is equipped with an opening device (not shown in detail) and a take-out - or ejection device.

[0026] The injection molding device 1 can also include a plurality of injection units 2 and / or molding units 3. At least one molding unit is designed for injection molding by direct pouring or by means of a distribution system (cold runner and / or hot runner system).

[0027] The injection molding device 1 advantageously has a mechanical or vacuum venting device (not shown) of the molding unit. In addition, the injection molding device can also be designed as a two-component or multi-component tool for injection-molding a sealing system surrounded by a suitable polymer material.

[0028] For the injection molding process, the pre-prepared raw material 4 composed of a thermoplastic material and an additive component is placed in the hopper 21 and fed into the conveying unit 22 by a conveying screw. The additive component is especially graphite here, and optionally also includes carbon black. The raw material 4 is heated by the heating device arranged in the conveying unit 22 to a temperature above the melting point by thermal energy and to the temperature required to form a molten material. The molten material is injected into the cavity 31 of the molding unit 3 through a correspondingly designed gate section on the outlet side of the conveying unit 22 at a preset injection pressure until the cavity 31 is completely filled with the molding material 5 contained therein. The molding material 5 corresponds to the plate-shaped fuel cell component 6 to be manufactured, i.e., the plate-shaped fuel cell component here.

[0029] The additive component introduced into the raw material 4 for modifying the thermoplastic material, especially in the form of graphite and optionally in the form of carbon black, is used to achieve the electrical conductivity required for the operation of a fuel cell or a fuel cell stack, and to achieve good thermal conductivity to dissipate the heat generated in the fuel cell. Depending on specific requirements, the mass fraction or volume fraction of the additive component relative to the raw material for manufacturing the plate-shaped fuel cell component 6 is higher than 5%, higher than 20%, higher than 30% or higher than 40%, and its range is between 5% and 95%, between 20% and 90%, between 30% and 80% or between 40% and 80%. Among them, the mass fraction or volume fraction can be appropriately varied or adapted according to the thermoplastic material, the electrical conductivity required for fuel cell operation, and the geometric structure of the plate-shaped fuel cell component 6.

[0030] Figure 3Also as an example, two parts of the molding unit 3 of the injection molding device 1 are shown in the sub-views a) and b), namely, a nozzle-side molding section 3' and an ejection-side molding section 3'' designed to be connected to the injection molding unit 2, which together form a cavity 31 required for molding a plate-shaped fuel cell component by forming a wall 30. Here, the wall 30 of the cavity 31 is formed by means of a molding insert 32, which is composed of a first part located in the nozzle-side molding section 3' and a second part located in the ejection-side molding section 3''. The first part and the second part of the molding insert 32 are arranged on corresponding molding cores 33, and the molding insert 32 and the molding core 33 are surrounded as a unit by corresponding insulating parts 34 on their outer sides facing away from the cavity 31, so as to prevent heat from being dissipated from the unit composed of the molding insert 32 and the molding core 33 as much as possible, and to carry out targeted temperature regulation of the cavity and the injected molten material or molding material, so that the molten material maintains the temperature required to completely fill the cavity 31 during the injection molding process, and the best possible temperature regulation between the cavity 31 and the injected molten material is achieved.

[0031] The unit consisting of two parts, namely the molding insert 32 and the molding core 33, constitutes the molding part of the molding unit 3, which is arranged in the molding part accommodating part 35, which itself consists of two parts, one of which is arranged in the nozzle side molding section 3' and the other part is arranged in the ejection side molding section 3''. The molding part accommodating part 35 is also insulated on its outer side by means of insulating parts 34 or 34' to avoid heat loss as much as possible. The molding part accommodating part 35 has positioning parts 36 on its outer side parallel to the planar extension direction of the cavity 31 to achieve precise positioning.

[0032] In the illustrated embodiment of the molding unit 3 , an inlet unit 24 with a hot runner system is located in the nozzle-side molding section 3 ′ connected to the injection molding unit 2 , and serves to inject molten material into the molding cavity 31 .

[0033] The nozzle-side molding section here has guide pins which protrude from the surface of the nozzle-side molding section 3' which is located in the dividing plane of the molding unit 3 and cooperate precisely with guide receptacles (not shown) which are arranged correspondingly in the position in the facing plane of the ejection-side molding section 3'' in order to guide the molding component 3 to close and, after the molding process, to guide it to open and to eject the molded plate-shaped fuel cell component.

[0034] In order to perform targeted temperature regulation on the cavity 31 during the molding process, temperature regulating devices 7 are arranged between the corresponding molding inserts 32 and the molding core members 33 in both the nozzle-side molding section 3' and the ejection-side molding section 3''. The temperature regulating device 7 includes a heating device 70 and may also include a cooling device 71 for rapidly and specifically cooling the molding material. Here, the heating device 70 can be electrically designed, for example, as an energized electrical heating circuit or as an inductively loaded heating element, or as a heating channel through which a heat carrier fluid (liquid or gas medium) flows. The cooling device 71 is designed as a cooling channel or an embedded pipeline through which a cooling fluid flows, or as an electrically operated cooling device. The components of the molding insert 32 are advantageously made of a metal with good thermal conductivity, such as tool steel, or of other materials with good thermal conductivity, such as ceramics. The molding core member 33 can also be made of metal, or alternatively of a temperature-resistant plastic material, or of ceramics, for example. By means of isolation achieved by surrounding the unit formed by the molding insert 32 and the molding core member 33 with an isolation member 34, a temperature regulation that can be well controlled and has a rapid response and is matched to the injection molding process is realized.

[0035] In the present invention, as an advantageous measure, it is also stipulated that a thermoplastic material is used as the molten material or the molding material, and graphite is preferably used as the only additive component and mixed in the thermoplastic material as well-conductive particles. Here, the thermoplastic polymer material is used as the base material of the plate-shaped fuel cell component to be manufactured, and preferably as a base material having a free π electron system, such as a PEEK material containing a benzene ring. Here, the graphite particles form a conductive connection through the π electron system of the base material without having to use conductive carbon black. This enables the manufacturing process by injection molding to be favorably affected, and a relatively low filling rate of the conductive additive component can be selected compared to the additive component containing conductive carbon black. Thereby, manufacturing parameters such as the injection pressure, injection time, and holding pressure can be favorably selected during the injection molding process while achieving good fluidity in the cavity 31. In addition, two preferred directions of the graphite layer are formed in the molding material through the injection molding process. In the region near the wall, the graphite particles are preferably oriented along the flow direction, while in the core region, the orientation of the particles is mainly perpendicular to the flow direction. Thereby, a favorable effect on the conductivity is produced for the functions of plate-shaped fuel cell components, such as bipolar plates.

[0036] Furthermore, it is advantageous to select the particle size of the additive component or the D describing the particle size in the range of 5 μm to 50 μm or 100 μm, for example, in the range of 10 μm to 30 μm. 50Value, wherein it can also be adjusted according to the thickness of the selected plate-shaped fuel cell component. Additionally, it is advantageous to select graphite particles with a smaller aspect ratio (the ratio of thickness to the smallest extension dimension perpendicular to the thickness), that is, to select graphite particles that extend as flatly as possible and are flaky, wherein an aspect ratio of less than 5, especially less than 1 or 0.5, is suitable. With reference to the raw material, the filling rate of the graphite particles can be in the range of 5 vol% to 95 vol%, for example, 20 vol% to 80 vol%, or, if necessary, in the range of 5 wt% to 95 wt%, or 20 wt% to 87 wt% or 80 wt%.

Claims

1. A method for manufacturing a plate-shaped fuel cell component (6), in particular a bipolar plate, from a thermoplastic material with an additive component having good electrical and thermal conductivity, wherein, The plate-shaped fuel cell component is manufactured by an injection molding technique with an injection molding device (1), which includes at least one injection unit (2) and at least one molding unit (3), and the molding unit has a wall portion surrounding a corresponding cavity. It is characterized in that the molten thermoplastic material and an additive component are injected as a molten material into the cavity of a corresponding cavity (31) of at least one molding unit (3) under pressure by means of at least one injection unit (2), and this cavity remains unchanged corresponding to the geometry of the fuel cell component, and the heat transfer through the wall portion (30) is matched with the thermal conductivity, heat capacity and injection speed of the molten material, so that the molten material is completely filled into the corresponding cavity (31) as a molding material (5) before the temperature of the molten material is lower than its melting point.

2. The method according to claim 1, wherein Graphite is incorporated into the thermoplastic material as a modified conductive additive component with or without mixing a small amount of carbon black, and the mass fraction of the additive component in the total mass of the raw materials input into the injection unit (2) is greater than 5%, greater than 20% or greater than 30%, preferably greater than 50%, for example, between 5% and 95%, especially between 30% and 70% or 87%.

3. The method according to claim 1 or 2, characterized in that A polymer material with a free π electron system, especially a PEEK material, is used as the thermoplastic material of the matrix material constituting the plate-shaped fuel cell component, and only graphite particles, especially graphite particles with an aspect ratio, that is, the ratio of thickness to the minimum extension dimension, less than 5, especially less than 1 or 0.5, are used as the conductive additive component.

4. The method according to claim 1 or 2, characterized in that, The thickness (d) of the plate-shaped fuel cell component (6) perpendicular to the plane extension direction of the plate-shaped fuel cell component in a top view is at most 2 mm, at most 1 mm, at most 0.5 mm or at most 0.2 mm.

5. The method according to any one of the preceding claims, characterized in that, The size D of the particles of the electrically conductive additive component 50 is in the range from 5 μm to 50 μm or 100 μm.

6. The method according to any one of the preceding claims, characterized in that During the injection molding process, at least one connecting element, fixing element, circuit element and / or sealing element is provided for the fuel cell component (6) by molding and / or injection.

7. A plate-shaped fuel cell component (6), in particular a bipolar plate, characterized in that, The plate-shaped fuel cell component is manufactured by using the method described in any one of the preceding claims.

8. An injection molding device for performing the method according to any one of claims 1 to 6, the injection molding device having at least one injection unit (2) for inputting raw material (4), the raw material comprising a thermoplastic material and a conductive additive component, in particular comprising graphite particles, the injection molding device further having at least one molding unit, the molding unit having at least one nozzle-side molding section (3') corresponding to the injection nozzle device and a push-side molding section (3'') corresponding to the push side, which are arranged in a molding part receiving portion (35) and face each other in a separating plane, and each include a part of a corresponding molding part having a molding insert (32) and a molding core (33), wherein, In the molding insert (32), corresponding cavities (31) are constructed which can be opened in a separating plane and closed during the injection molding process, and the cavities (31) are connected to the injection unit (2) through an input unit (24) with a hot runner system or a cold runner system to inject the molten raw material (4) as a molten material into the cavity of the cavity (31). It is characterized in that during the molding process, until at least one molding unit (3) is opened, the geometry of the cavity of the cavity (31) together with the inner surface of the molding insert (32) surrounding the cavity remains unchanged and is adapted to the geometry of the fuel component to be manufactured.

9. The injection molding device according to claim 8, characterized in that, Temperature regulating devices (7) are arranged between the molding insert (32) and the molding core (33) in the nozzle side and / or ejection side molding sections (3', 3'').

10. The injection molding device according to claim 9, characterized in that, The temperature regulating device (7) includes a heating device (70) and / or a cooling device (71).

11. The injection molding device according to claim 10, wherein, The heating device (70) can be heated inductively by means of electrothermal heat realized through an electrical circuit device or by means of a heat transfer fluid guided through a pipe, and / or The cooling device (71) can be cooled by means of a cooling fluid guided through a channel or is equipped with an electrically operated cooling device.

12. The injection molding device according to any one of claims 8 to 11, characterized in that, At least the forming insert (32) is made of a material with good heat conductivity, in particular metal or ceramic, and the forming components, which at least include the forming insert (32) and the forming core (33), are surrounded by a heat-insulating separating part (34).

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