DE102008025928A1 - Laminating press for hot-pressing layer material stack to e.g. polymer electrolyte membrane, for producing membrane electrode assembly for fuel cell, has pressing block with surface formed as ferromagnetic insert heated by coil arrangement - Google Patents

Abstract

The press (10) has pressing blocks (20, 30) with respective pressing surfaces arranged opposite to one another, where outer surfaces of a layer material stack (40) rests against the pressing surfaces. The blocks are subjected to an action of force and slidable perpendicular to the pressing surfaces relative to one another. The blocks are electrically heatable in a region of the pressing surfaces. The surface of the block (20) is formed as a ferromagnetic insert (23) inductively heated by an electrical coil arrangement (24) in a corresponding opening of the block (20).

Description

Field of the invention

• – einen ersten Pressenblock mit einer ersten Pressfläche, an der bei bestimmungsgemäßem Betrieb eine erste Außenfläche des Schichtmaterialstapels anliegt, sowie
• – einen zweiten Pressenblock mit einer zweiten Pressfläche, an der bei bestimmungsgemäßem Betrieb eine zweite Außenfläche des Schichtmaterialstapels anliegt, umfasst,

wobei die Pressflächen einander gegenüberliegend angeordnet sind und die Pressblöcke senkrecht zu den Pressflächen relativ zueinander verschiebbar und kraftbeaufschlagbar sind und wobei wenigstens einer der Pressenblöcke wenigstens im Bereich seiner Pressfläche elektrisch heizbar ist.The invention relates to a laminating press for hot pressing a stack of layer material into a multilayer laminate, the

• A first press block having a first pressing surface against which a first outer surface of the layer material stack bears during normal operation; and
• A second press block having a second pressing surface, against which a second outer surface of the layer material stack bears during normal operation,

wherein the pressing surfaces are arranged opposite to each other and the pressing blocks are displaceable and kraftbeaufschlagbar perpendicular to the pressing surfaces relative to each other and wherein at least one of the press blocks is electrically heated at least in the region of its pressing surface.

State of the art

such Laminating presses are well known. They are preferred the production of so-called membrane-electrode assemblies, short MEAs, which is used for the production of fuel cells be used. An MEA typically comprises a laminate, consisting of a polymer electrolyte membrane, short PEM, and on both sides with this connected electrodes and gas diffusion layers. The electrodes exist from a thin porous layer of a catalyst material which is finely dispersed on a carbon black. The gas diffusion layers are constructed of a fibrous material, such as a Carbon fleece. In the sense of an optimal MEA performance, d. H. the highest possible current density during conversion of the fuel gas in the fuel cell, the individual layers should be so with each other be connected, that optimal contact, but at the same time a good gas permeability of the porous layers is guaranteed. Furthermore, the layers should be as thin as possible be. The total thickness of an MEA is typically between 400 and 1000 microns.

At the typical manufacturing process of an MEA done the production the PEM and the gas diffusion electrodes, consisting of electrode and gas diffusion layer, usually separated. The PEM will be in this Case so positioned between two gas diffusion electrodes their surface is contacted by the electrodes. However, there are also known manufacturing processes in which the PEM on both sides with a catalyst material, eg. B. in the form of a Catalyst Ink z. B. in the context of an inkjet process, coated becomes. After drying to evaporate the solvent the catalyst ink is a catalyst-coated membrane, short CCM (catalyst coated membrane) before, on the two-sided flat Fiber material is laminated to form gas diffusion layers.

The Connection or lamination to an operational MEA then follows by hot pressing. For this purpose, the layer material stack positioned on the pressing surface of the first press block. Of the second press block is then force applied to the first press block moved so that the second pressing surface on the second Surface of the layer material stack is applied. Further Kraftbeaufschlagung sets the material stack a desired Pressing off. Then one of the pressing blocks, the inside of it with an electrical resistance heating is provided to a desired, relatively high Pressing temperature heated up. After reaching the pressing temperature, the Heating typically for a given period of time regulated to a constant temperature. Subsequently, will the entire pressing device cooled back to normal temperature. This is typically done in one or mostly two press blocks arranged, coolant-flowed cooling coils. After cooling, the produced laminate, i. H. the principle Ready-to-use MEA are removed and fed to their further use.

to Achieving an optimal bond of the MEA laminate should be and pressure guidance as precise as possible Meaning of a temporally defined temperature and pressure program be controllable. During the heating process of the press the polymer of the PEM ideally passes through the glass transition and softens, so that an optimal bond to the porous Electrode layer can be formed. It should be the pressurization be chosen so that the softening polymer reproducible and only to a well-defined degree in the porous electrode layer can penetrate. Before removing the MEA from the hot-pressing device the MEA laminate should be cooled down enough so that the polymer is again in the glassy state, and the produced Composite is stabilized.

During the process of hot compression, additional sub-processes can take place, which can increase the requirements for process control and process reliability. So describes DE 10301810 A1 a method for producing an MEA for high-temperature polymer electrolyte fuel cells, wherein during the process of hot pressing additionally a redistribution of a dopant from the electrodes into the electrolyte membrane of the MEA with complex diffusion and transport steps and subsequent material changes takes place.

First obtained after completion of the Heißverpressungss step the electrolyte membrane has its desired properties, in particular Their proton conductivity, the basic requirement for an efficient electrode reaction.

Of the described process is due to the long associated with it Heating and cooling times unfavorably lengthy. To increase the efficiency of the production of MEAs are therefore typically several each to a laminate to be pressed part-layer material stack one above the other arranged to a total layer material stack in the press. In this way, multiple MEAS can be produced simultaneously become. To prevent the MEAS from sticking together, you can if necessary separating layers between the individual partial layer material stacks to be ordered.

These Increase efficiency by producing multiple MEAs simultaneously However, it comes at a price. The more part-layer material stack at the same time hot-pressed, the bigger must be the pressure applied by the pressing blocks. This not only requires more sophisticated pressure generating devices, such as for example mechanical, hydraulic or pneumatic devices, but also requires a stronger training of the press blocks themselves. These are therefore typically large-sized Stainless steel blocks. This results in addition to the higher Device costs also a not insignificant extension the heating and cooling times, combined with a corresponding higher energy consumption. It also turns out often a temperature gradient over the total layer material stack so that some MEAs are generated at a different press temperature than others. This can disadvantageously contribute to dispersions of lead the operation in a fuel cell relevant properties. This gradient formation can only with a limitation of the height of the Total layer material stack and a heating of both press blocks be countered. This increases the efficiency through simultaneous Manufacturing several MEAs limited and the constructive and energetic Expenses for the apparatus increased adversely. moreover is the required precision in terms of temperature and pressure control due to the massive design of the Press blocks only partially realizable.

task

It The object of the present invention is a laminating press to provide more efficient production allowed by MEAs.

Presentation of the invention

These Task is combined with the features of the preamble of Claim 1 solved by the fact that the first pressing surface at least in some areas as one by means of an electric coil arrangement inductively heatable ferromagnetic insert in a corresponding Recess of the first press block is formed.

preferred Embodiments of the invention are the subject of the dependent Claims.

The Invention turns away from the above-described, general Trend to increase efficiency by simultaneous compression of a Variety of stacked part-layer material stacks. Rather, the invention returns to the idea of Single lamination and aims at a shortening of the Heating and cooling times by minimizing the temperature to be tempered Volume. Due to the formation of the first pressing surface as ferromagnetic insert in one otherwise preferably not ferromagnetic material, such as plastic, a made of non-ferromagnetic metal or a corresponding metal alloy Press block can by the invention, inductive heating the volume to be heated substantially to the limited first pressing surface. Corresponding Heating can be done quickly. Also the cooling takes place accordingly quickly. When using a plastic as Material of the press block can additionally a thermal Isolation of the first pressing surface can be achieved. Of course it is also possible, the invention Idea to apply to both press blocks, d. H. both the first and the second pressing surface at least partially to design as a ferromagnetic, inductively heatable insert.

to Heating of the ferromagnetic insert is the electrical Coil assembly is charged with an alternating electrical current, the generates an alternating magnetic field in the area of the insert which induces circulating currents in the insert which are the desired ones Cause heating. The coil arrangement can be outside be arranged of the first press block. This allows a special simple construction of the first press block. In other embodiments For example, the electric coil assembly may also be in the first press block be integrated. This has the advantage that the coil for energy transfer positioned more favorably to the ferromagnetic insert can be. Is the first press block essentially one made electrically insulating plastic, the coil assembly can embedded in a simple manner in the press block during its manufacture, z. B. be poured.

In the first press block can also be a cooling device, for example, as a coolant formed by cooling coil is formed, be embedded. Alternatively, a Peltier element or another type of cooling can be used. In a preferred embodiment, however, the cooling device is at least embedded in the second press block. If the second press block is not equipped with its own ferromagnetic insert as a second pressing surface - which is basically possible - the cooling device embedded in the second press block can be arranged in close proximity to the second pressing surface, resulting in rapid and efficient cooling. This can be further assisted in that the second press block is formed of a metal or a metal alloy having good heat conduction properties.

conveniently, becomes a metal or a metal alloy with little or no ferromagnetic properties chosen to be an inductive heater to avoid the second press block and the heater actually on the first pressing surface acting ferromagnetic Use restrict. Alternatively or in addition can also be used a plastic, preferably at the same time has thermally insulating properties.

Although it is basically irrelevant to which particular Make the relative movement and force of the press blocks takes place, this is preferably a Kraftbeaufschlagungskolben provided, which faces away from the second pressing surface Side of the second press block attacks. Because of the preferred Training the second press block of metal is a good at this Power transmission guaranteed. Moreover, this is Do not place an external coil assembly in the way or an internal coil assembly at risk of being damaged, as is the case with the first press block would be the case. The power piston is, as already mentioned, preferably mechanically, hydraulically or pneumatically driven. Of course it is also possible, both press blocks with one each own Kraftbeaufschlagungskolben to provide, with the application of force Both blocks can be the same or different.

Around To achieve a special flexibility, can at a Be further development of the invention provided that the area Extension of the ferromagnetic Einsates is smaller than the surface Extension of the first recess and a resulting gap means a corresponding frame of a non-ferromagnetic Material filled around the ferromagnetic insert around is. In other words, this development relates to the invention the idea of interchangeable ferromagnetic inserts of different Size selected depending on the current production target can be. The first press block always remains the same. Be used inserts that the first recess not completely fill in the first press block, the remaining gap becomes with a suitable frame of non-ferromagnetic Material, preferably of the same plastic material as the filled up first press block. This way results always the same and reproducible positioning of the heatable first pressing surface, but in any case only the absolutely necessary minimum volume must be heated. Calls different sizes are z. B. conceivable for the production of MEAs of different sizes or the simultaneous production of different numbers of MEAs, positioned next to each other on the first pressing surface become.

Further Features and advantages of the invention will become apparent from the following, special description and the drawings.

Brief description of the drawings

In show the drawings:

1 : A schematic sectional view of a laminating press according to the invention

2 : A schematic sectional view of a second embodiment of a first press block of a laminating press according to the invention

3 FIG. 1 is an exploded schematic sectional view of a third embodiment of a first press block of a laminating press according to the invention.

Description of preferred embodiments

1 shows a laminating press according to the invention 10 , This includes a first press block 20 and a second press block 30 between which a stack of laminates to be compressed into an MEA 40 is arranged. The first press block 20 is essentially a plastic body 21 built up. Preferably, a pressure-stable and temperature-resistant plastic is used here. In its upper end surface, the plastic body 21 a recess 22 on. In this recess is an insert 23 inserted flush from a ferromagnetic material. Below the first press block 20 is an electrical coil arrangement 24 arranged, which can be charged in an unillustrated manner with an alternating electrical current. The resulting alternating magnetic field induces in the ferromagnetic insert 22 electrical currents that heat it in the desired manner. To specifically approach and hold desired pressing temperatures, is a temperature control 50 between the ferro magnetic insert 22 and the coil assembly 24 intended.

The second press block is essentially a stable metal plate 31 formed, on which a pneumatic stamp 60 for linear movement and application of force relative to the first press block 20 attaches. In the illustrated embodiment, both in the first press block 20 as well as in the second press block 30 each a cooling device 25 respectively. 35 embedded in the form of a coolant-flowed cooling coil. In many cases, the embedding of only one cooling device in only one press block is sufficient. In this case, the second press block is preferred for this purpose 30 used. This protects due to its stable metal material, the cooling coil 35 Efficient against mechanical damage due to the pneumatic punch 60 , In addition, typically ensures better thermal conductivity of the metal material over the plastic material of the first press ram 30 a very efficient heat dissipation. The MEA 40 itself can be regarded as a negligible obstacle in the heat flow. With appropriate execution of the opposite pressing surface corresponding removable frame can also be used for precise positioning of the MEA.

2 shows an alternative embodiment of the first press block 20 , In this embodiment, the coil assembly 24 in the plastic body of the first press block 20 integrated. The relative position of ferromagnetic insert 23 and coil assembly 24 is in this arrangement more favorable in terms of the induction of the heating currents in the ferromagnetic insert 23 ,

3 shows a third embodiment of a first press block 20 , For the sake of clarity 3 designed as an exploded view. Unlike the embodiments of 1 and 2 is the areal extent of the ferromagnetic insert 23 here smaller than the areal extent of the recess 22 , In the assembled state thus gapes between the interchangeable use 23 and the edge of the recess 22 a gap that is of an interchangeable frame 26 is closed. Typically, the size of the recess is adapted to a maximum size insert 23 , When using smaller inserts 23 becomes an appropriate frame 26 for reproducible positioning of the insert 23 used. Thus, when minimizing the volume to be heated, it is always possible to react flexibly to the size or number of (simultaneously) produced MEAs.

Naturally Make the ones shown in the figures and in the special description discussed embodiments only illustrative embodiments of the The expert is in the light of the local Revelation a wide range of possible variations given by. In particular, the choice of suitable materials and the process parameters, such as pressing temperature, pressing pressure, pressing time, etc. to the person skilled in the design according to the requirements be left to the individual case. Of course is the possible field of application of the invention Laminating press not limited to MEAs for fuel cells, but also includes the hot pressing of other types of Layered materials to laminates.

10

laminating

20

first press block of 10

21

Plastic body of 20

22

Recess in 21

23

ferromagnetic commitment

24

electrical coil assembly

25

cooling coil

26

positioning frame

30

second press block of 10

31

Metal body of 30

35

cooling coil

40

MEA

50

temperature control

60

pneumatic rams

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10301810 A1 [0006]

Claims (11)

Laminating press for hot pressing a stack ( 40 ) of layered material into a multilayer laminate which comprises a first press block ( 20 ) with a first pressing surface on which, when used as intended, a first outer surface of the layer material stack ( 40 ), and - a second press block ( 30 ) with a second pressing surface on which, when used as intended, a second outer surface of the layer material stack ( 40 ), wherein the pressing surfaces are arranged opposite each other and the pressing blocks ( 20 . 30 ) are perpendicular to the pressing surfaces relative to each other displaced and kraftbeaufschlagbar and wherein at least one of the press blocks ( 20 . 30 ) is electrically heated at least in the region of its pressing surface, characterized in that the first pressing surface at least partially as a means of an electric coil assembly ( 24 ) inductively heatable ferromagnetic insert ( 23 ) is formed in a corresponding recess of the first press block. Laminating press according to claim 1, characterized in that the first press block ( 20 ) is made of a non-ferromagnetic material, in particular of a plastic. Laminating press according to one of the preceding claims, characterized in that a cooling device ( 25 ) is embedded in the first press block. Laminating press according to one of the preceding claims, characterized in that the second press block ( 30 ) is made of a metal or a metal alloy with little or no ferromagnetic properties. Laminating press according to one of the preceding claims, characterized in that a cooling device ( 35 ) in the second press block ( 30 ) is embedded. Laminating press according to one of the preceding claims, characterized in that for the relative application of force to the press blocks ( 20 . 30 ) a Kraftbeaufschlagungskolben is provided, which on the side facing away from the second pressing surface side of the second press block ( 30 ) attacks. Laminating press according to claim 6, characterized that the Kraftbeaufschlagungskolben mechanically, hydraulically or is pneumatically driven. Laminating press according to one of the preceding claims, characterized in that the electrical coil arrangement ( 24 ) to the recess ( 22 ) of the first press block ( 20 ) is embedded adjacent to the first press block. Laminating press according to one of the preceding claims, characterized in that the planar extent of the ferromagnetic insert is smaller than the areal extent of the first recess ( 22 ) and a resulting gap by means of a corresponding frame ( 26 ) of a non-ferromagnetic material around the ferromagnetic insert ( 23 ) is filled in. Laminating press according to one of the preceding claims, characterized in that a control unit is provided, by means of their pressure and temperature parameters in the range between the first and the second pressing surface according to a in Control unit stored control program are controllable. Use of a laminating press according to one of the preceding Claims for producing a membrane electrode assembly, short MEA, for a fuel cell.