JP4251261B2 - Method for producing matrix layer for phosphoric acid fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a method for manufacturing a matrix layer for a phosphoric acid fuel cell.
[0002]
[Prior art]
  As is well known, a phosphoric acid type fuel cell retains phosphoric acid in an electrolyte matrix layer, and continuously supplies a fuel gas (for example, hydrogen) and an oxidant gas (for example, air) as a reaction gas to the fuel electrode and the oxidant electrode. The energy of the fuel is electrochemically converted into electrical energy. FIG. 6 shows a schematic configuration of an example of a cell stack of a conventional phosphoric acid fuel cell.
[0003]
  In FIG. 6, the cell 1 includes an electrolyte layer 11 holding phosphoric acid, a fuel electrode 12 as an diffusible electrode having an electrode catalyst layer on the matrix layer side, an oxidant electrode 13, and a reaction to each electrode. It consists of porous ribbed substrates 14 and 15 provided with gas flow paths (grooves) for supplying gas. A separator 2 as a gas shielding plate is stacked on the unit cell 1 and laminated, and a cooling plate 3 for removing reaction heat is inserted for each predetermined number of unit cells to constitute a fuel cell stack.
[0004]
  The electrolyte layer 11 is configured by holding phosphoric acid as an electrolyte in a matrix layer in which silicon carbide fine particles (SiC fine particles) are dispersed in a binder made of PTFE (polytetrafluoroethylene). The fuel electrode 12 and the oxidant electrode 13 are usually provided with an electrode catalyst layer on the surface of an electrode substrate made of carbon paper so that hydrogen as a fuel gas and oxygen as an oxidant gas can diffuse. Thus, a so-called gas diffusion electrode (hereinafter referred to as an electrode substrate) is formed. The electrode catalyst layer is formed by binding catalyst particles carrying precious metal fine particles on the surface of a catalyst carrier with PTFE particles.
[0005]
  As a method for forming the matrix layer for a phosphoric acid fuel cell, conventionally, as shown in FIG. 6, a method of forming the matrix layer in a sheet shape (thickness of 100 to 150 μm) in advance and sandwiching it between the electrode substrates is good. Are known.
[0006]
  By the way, in a phosphoric acid fuel cell, the thinner the matrix layer (for example, 80 μm or less), the lower the electric resistance (ion transfer resistance) in the electrolyte layer, and the power generation voltage is improved. As described above, in the case of a method of forming a matrix layer sheet in advance (hereinafter referred to as a sheet forming method or S method), it is difficult to manufacture a thin film having a desired thickness (for example, 50 μm). Even so, the sheet is weak and difficult to handle. In addition, many man-hours are required for forming the sheet, and there is a problem in terms of manufacturing cost.
[0007]
  In order to deal with the problems of the sheet forming method (S method) as described above,(1)By screen printing,(2)By flow coater,(3)Spray coating,(Four)Other manufacturing methods such as a method using a reverse roll coater have been proposed.
[0008]
  Said(1)According to the screen printing method, a desired thin film can be obtained depending on the production conditions, but since the paste contains PTFE as a binder, screen clogging easily occurs, and a matrix layer of the same quality is continuously produced. There is a difficult problem to do. Furthermore, in the work of pulling the screen away from the printing surface immediately after application, there are problems that bubbles are generated on the printing surface and the uneven pattern of the screen is transferred.
[0009]
  next(2)The flow coater method can obtain a thin matrix layer having a smooth coated surface when a paste having a low viscosity is used, but there is a problem that foaming tends to occur when the paste flows down. In addition, the film thickness tends to be too thin (for example, 20 μm or less), and the shielding property of the reaction gas between the fuel electrode (anode) and the oxidant electrode (cathode) is lowered, which may reduce the power generation characteristics. It was. When the viscosity of the paste is increased, there is a problem that it becomes difficult to obtain the uniformity of thickness and the smoothness of the coated surface.
[0010]
  next(3)Although it is possible to obtain a thin matrix layer by the spray coating method, due to the nature of the matrix paste containing PTFE as a binder, the spray nozzle tends to be clogged, and it is difficult to produce a large amount of the matrix layer continuously. There was a title.
[0011]
  Last(Four)A method using a reverse roll coater is described, for example, in JP-A-60-151968 as a method for producing an electrode for a fuel cell, and a conceptual diagram for explaining this method is shown in FIG.
[0012]
  In the method shown in FIG. 7, the electrode base material 10 to which the paste is to be applied is sandwiched between the coating roll 20 in which the traveling direction and the rotational direction of the electrode base material 10 are opposite, and the backup roll 21 having the same rotational direction. In addition, a doctor roll 22 that rotates reversely to the coating roll 20 is provided, and the paste is transferred onto the electrode substrate as the coating roll 20 rotates.
[0013]
  According to the method using the reverse roll coater, the paste can be applied at a high speed, and there is an advantage that the equipment cost and maintenance cost of the manufacturing apparatus are reduced.
[0014]
[Problems to be solved by the invention]
  However, when the method using the reverse roll coater is applied to a method for producing a matrix layer, there are the following problems to be solved.
[0015]
  According to this manufacturing method, the electrode substrate receives strong friction between the backup roll and the coating roll by the coating roll. Therefore, in the case of a roll-like sheet, reliable sheet feeding is possible on the delivery side and the take-up side. However, in the case of an electrode substrate for a fuel cell, the electrode substrates are not completely fixed to the conveyance table one by one. As long as the electrode substrate slips due to the force opposite to the traveling direction received from the coating roll, the electrode substrate surface may be damaged in some cases.
[0016]
  As another problem, the paste is subjected to a strong shearing force between the coating roll and the doctor roll. As a result, PTFE as a binder is made into fibers and the paste properties gradually change, which makes it difficult to produce a continuous and homogeneous matrix layer.
[0017]
  Furthermore, there is a problem that the state of the paste changes with time due to generation of frictional heat between the coating roll and the doctor roll.
[0018]
  Furthermore, as a problem common to all methods of forming a matrix layer by applying a paste, in the heat treatment step after application, a fine crack may occur in the matrix layer. Since the gas sealability is lowered, a basic problem that causes a drop in cell voltage and a drop in bubble pressure occurs.
[0019]
  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a phosphoric acid capable of stably and continuously producing a matrix thin film layer having a thickness suitable for power generation characteristics and high quality at a high speed. An object of the present invention is to provide a method for producing a matrix layer for a fuel cell.
[0020]
[Means for Solving the Problems]
  In order to solve the above-mentioned problems, the present invention is a method for forming a matrix layer by applying a paste in which silicon carbide fine particles (SiC fine particles) and PTFE as a binder are dispersed in a liquid solvent to the electrode substrate surface. Then, using a transport roll for transporting the electrode substrate, a coating roll and a backup roll provided facing each other across the electrode substrate, and a pressing member (squeegee) biased by the coating roll, In the state where the coating roll and the backup roll are rotated in the same direction as the electrode substrate conveying direction, the electrode substrate is conveyed by the conveying roll, and the paste flow formed on at least one of the coating roll and the squeegee By supplying the paste from the groove onto the electrode substrate surface,A paste is applied to the electrode substrate surface, heat-treated to form a first matrix layer, and the paste is again applied on the surface of the first matrix layer by the same procedure as described above. In addition, heat treatment is performed to form a second matrix layer, and the particle size of the SiC fine particles in the second layer matrix paste is smaller than the particle size of the SiC fine particles in the first layer paste.(Invention of Claim 1)
The present invention is also a method for forming a matrix layer by applying a paste in which silicon carbide fine particles (SiC fine particles) and PTFE as a binder are dispersed in a liquid solvent to the electrode substrate surface, Using a conveyance roll for conveyance, a coating roll and a backup roll provided opposite to each other with an electrode substrate interposed therebetween, and a pressing member (squeegee) biased by the coating roll, the coating roll and the backup roll are The electrode substrate is conveyed by the conveying roll in a state rotated in the same direction as the electrode substrate conveying direction, and the paste is removed from the paste flow groove formed in at least one of the coating roll and the squeegee. Applying paste on the electrode substrate surface by supplying on the surface Then, this is heat-treated to form a first matrix layer, and the paste is applied on the surface of the first matrix layer again by the same procedure as described above, and heat-treated to form a second layer. A matrix layer is formed, and the thickness of the second matrix layer is made smaller than the thickness of the first matrix layer (Invention of Claim 2).
In the first and second aspects of the invention, after applying the paste to the electrode substrate surface, the paste is dried at a temperature of 30 to 90 ° C. for a predetermined time, and then heat-treated at a temperature of 250 to 300 ° C. for a predetermined time in an inert gas atmosphere. Thus, it is preferable to form a matrix layer. Moreover, it is preferable to dry naturally at room temperature for 30 minutes or more before drying at the temperature of 30 to 90 ° C. for a predetermined time.
[0021]
  Claim 1Or 2According to the method of the present invention, the electrode substrate is not slipped or damaged. Here, examples of the pressing member include a plate shape and a rod shape. By using such a pressing member (squeegee) and pressing it against the coating roll with a predetermined pressure, such as a spring or air pressure, the shearing force received by the paste is reduced between the coating roll and the doctor. Compared to the conventional method using rolls, it is greatly reduced.
[0022]
  As a result, fiber formation of PTFE in the matrix paste can be prevented. Furthermore, the problem of frictional heat that has conventionally occurred between the coating roll and the doctor roll is greatly reduced by switching to the pressing plate, and as a result, the paste properties can be stabilized.
[0023]
  Moreover, the occurrence of cracks in the matrix layer is suppressed.be able to. By the way, even if the occurrence of cracks in the matrix layer is not detected visually, the presence of the crack may be found by observation with an electron microscope. A decrease occurs.
In the coating method using the roll coater according to the manufacturing method according to claim 1 or 2, the coating roll comes into contact with the electrode at a relatively high pressure. In addition, the matrix paste is pushed into the fine cracks (cracks) on the first matrix application surface. As a result, cracks in at least the first matrix layer are negligibly small. As a result, the gas sealing property of the matrix layer is remarkably improved, and power generation characteristics and life are improved.
The surface of the matrix layer applied as the second layer has fine cracks similar to the surface of the first layer after heat treatment, but at least at the boundary between the first layer and the second layer, the first layer cracks. Is filled with the second layer paste, and there is a layer having a sufficient gas sealing property. Therefore, fine cracks on the coating surface of the second layer no longer affect the quality of the gas sealing property.
Here, by making the particle size of the SiC fine particles in the second layer matrix paste smaller than the particle size of the SiC fine particles in the first layer paste (the invention of claim 1), the above effect can be further improved. Can be increased.
Further, as described above, since the crack of the first layer is filled with the paste of the second layer, the thickness of the matrix layer of the second layer is set to the thickness of the matrix layer of the first layer as in the invention of claim 2. It can be made thinner than the thickness. The thinner one is preferable in terms of battery characteristics.
[0024]
  Moreover, in the manufacturing method according to claim 1 or 2, the paste flow groove is a plurality of grooves provided uniformly in the axial direction of the outer peripheral surface of the coating roll (invention of claim 3). Thereby, a matrix layer having a thickness suitable for power generation characteristics can be formed substantially uniformly over the entire width. As will be described later, the film thickness of the matrix layer can be finely adjusted by the contact pressure between rolls, the contact pressure between the squeegee and the coating roll, the paste viscosity, the solid content concentration, the electrode substrate transport speed, and the like.
[0025]
  As embodiments of the coating roll and its groove, the inventions of the following claims 4 to 6 are preferable. That is, in the manufacturing method according to claim 3, the plurality of uniformly provided grooves are cut grooves having a V-shaped cross section, and the cut pitch is 200 to 1000 μm (the invention of claim 4). . Moreover, in the manufacturing method of Claim 4, the cut angle of the said V-shaped cut groove shall be 50-90 degree | times (invention of Claim 5).
[0026]
  Furthermore, in the manufacturing method in any one of Claims 1 thru | or 5, the material of the said coating roll shall be rubber | gum, and the hardness (JIS-A) shall be 40-80 (invention of Claim 6).
[0027]
  Further, in the manufacturing method according to claim 1 or 2, the liquid solvent in the paste is any one of ethylene glycol, diethylene glycol, and dipropylene glycol, or a mixture of any one of the above and water (claim). 7 invention). Conventionally, alcohol is used as this type of liquid solvent, but the liquid solvent is less likely to evaporate than alcohol, so that changes in paste properties (viscosity, solid content concentration, etc.) during operation must be suppressed. This is preferable.
[0028]
  Furthermore, it is preferable that solid content concentration other than the liquid solvent in the said paste shall be 40 to 80 weight% like the invention of Claim 8.
[0029]
  Further, the solid content concentration in the second layer matrix paste (mainly indicating the SiC content in the paste) is made lower than the solid content concentration of the first layer paste (claims).9The above-mentioned effect of improving the gas sealing property can be further increased by lowering the viscosity of the paste and increasing the permeability to cracks.
[0030]
  And claims10As in the present invention, by making the binder content of the second layer matrix paste larger than the binder content of the first layer paste, the effect of cracks in the first layer can be further suppressed to a negligible level. It is possible to improve the gas sealing property of the matrix layer.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described below with reference to the drawings.
[0032]
  In FIG. 1, the schematic structure of the coating device in connection with the manufacturing method of the Example of this invention is shown. In FIG. 1, 30 is a coating roll (hereinafter also referred to as C roll), 31 is a backup roll (hereinafter also referred to as B roll), and 32 is a pressing plate as a pressing member (hereinafter also referred to as squeegee). , 34 is an electrode substrate, 35 is a transport roll, and 33 is a matrix paste.
[0033]
  FIG. 2 shows a schematic perspective view of the C roll, and FIG. 3 shows a partially enlarged sectional view of the C-shaped V-shaped groove of the C roll (a sectional view taken along the line AA in FIG. 2). In this embodiment, the groove pitch P is 400 μm and the cutting angle Θ is 60 degrees. A roll having a flat surface not engraved with grooves was used as the B roll. In this example, EPDM rubber rolls having a hardness of about 60 (JIS-A: strictly speaking, JISK6253 type A) were used for both the C roll and the B roll.
[0034]
  The thickness of the matrix layer is mainly adjusted by the size of the V-shaped groove of the C roll, the pressure for pressing the squeegee against the C roll, and the contact pressure between the C roll and the B roll. In this example, the squeegee was pressed against the C roll at a pressure of about 0.1 MPa. Moreover, as a standard of the contact pressure between C roll and B roll, it adjusted so that the sum total of the deflection amount at the time of contact of C roll and B roll might be set to about 1 mm. Furthermore, the coating thickness of the matrix layer can be finely adjusted by the viscosity of the paste, the solid content concentration, the substrate conveyance speed, and the like.
[0035]
  As the matrix paste, for example, silicon carbide having a particle diameter of about 1 μm was dispersed in diethylene glycol having a concentration of 100%, and PTFE dispersion having a weight of silicon carbide of 1/20 or less was mixed with this. In this example, the solid concentration in the paste was 60%.
[0036]
  When an appropriate amount of matrix paste 33 is put between the C roll 30 and the squeegee 32 and the C roll 30 is rotated, and the electrode substrate 34 is sent between the C and B rolls, the paste becomes the C roll 30 and the squeegee 32. Is passed through the gap on the electrode substrate 34 to form a paste layer with an appropriate thickness to form a matrix layer. In this embodiment, the substrate feed rate was 2 m / min.
[0037]
  By applying the paste under the conditions as described above, a matrix layer having a thickness of about 50 μm after heat treatment described later was obtained. Although it is possible to obtain a thinner matrix layer depending on the coating conditions, this thickness is preferable in order to achieve both reliable gas shielding and low electrical resistance.
[0038]
  The heat treatment after coating the matrix layer was dried in an electric furnace at 50 ° C. for 15 hours in this example. Thereby, a part of the water | moisture content and organic-solvent component contained in PTFE dispersion were removed.
[0039]
  Subsequently, a heat treatment step was performed at 270 ° C. for 20 minutes in a nitrogen atmosphere. As a result, the organic solvent component and the surfactant component in the PTFE dispersion were completely removed, and PTFE was partially dissolved to develop the properties as a binder. It was confirmed that any of the organic solvents described in the invention of claim 7 had a boiling point of about 250 ° C. or less and could be completely removed by the heat treatment step. Furthermore, even after going through a series of steps described in the present invention, it was confirmed that these organic solvents had no adverse effect on the power generation characteristics of the electrode.
[0040]
  In FIG. 1, an example of a flat plate having a flat surface as a contact surface of the squeegee 32 with respect to the C roll 30 is shown, but one having an arcuate surface (for example, a cross-sectional shape is a circle or a semicircle). It may be a rod-like squeegee or the like, and the overall shape can be variously modified.
[0041]
  next2Examples in the case of forming a matrix of layers and experimental results of the fuel cell will be described below. First, an example of a two-layer matrix manufacturing method will be described.
[0042]
  The paste is applied by the same method as that applied to the first layer on the first matrix layer that has been completed up to the heat treatment step described above, and heat treatment is performed in the same manner as the first layer. Even if the second layer of the matrix paste has exactly the same composition and properties as the first layer, a certain effect can be obtained. The coating thickness of the second layer may be about 1/2 to 1/3 of the first layer. For example, if the thickness of the first matrix layer is 50 μm, the second layer may be about 20 μm.
[0043]
  In order to enhance the effect, it is preferable that the SiC particle diameter in the paste used for the second layer be smaller than that of the first layer. As a result, as described above, the second-layer paste easily enters the cracks generated by the first-layer heat treatment. For example, when SiC having a particle diameter of about 1 μm is used for the first layer, the SiC particles in the second layer paste may be about 0.1 μm.
[0044]
  It is also effective to lower the solid content concentration in the second layer matrix paste (mainly indicating the SiC content in the paste) compared to the first layer. As a result, the viscosity of the paste is lowered, so that the second layer paste is likely to enter the crack generated by the heat treatment of the first layer. For example, when the solid content concentration of the first layer paste is 60%, it is effective to set the second layer content to about 45 to 50%.
[0045]
  A method of increasing the PTFE content used as a binder in the second layer matrix paste is also effective. This is because cracks due to heat treatment are less likely to occur as the amount of binder in the paste increases. However, if the binder content is too high, the water repellency due to PTFE increases and the electrolyte solution retention of the matrix layer decreases, so care must be taken. For example, when the PTFE content of the first layer is 1/10 of the SiC weight, the PTFE content of the second layer is 1/5 of the SiC weight, and the thickness is 1/3 to 1 of the first layer. When it is set to about / 4, it has been confirmed that both the phosphoric acid retention and the gas sealability in the entire matrix layer can be achieved.
[0046]
  In addition, in a general conventional coating method, a method of applying a matrix layer to both electrodes to avoid imperfect gas sealing due to pinholes or accidental coating unevenness is also employed. The matrix layer may be applied only to either the fuel electrode or the air electrode.
[0047]
  Next, the results of comparison experiments with the sheet forming method (S method) regarding the cell life test, open circuit voltage, and the like for the examples of the present invention including the one and two matrix layers will be described below.
[0048]
  FIG. 4 shows a comparison experiment result of the open circuit voltage. In FIG. 4, A and B show a battery using the matrix according to the present invention (the method of the present invention), and S shows the result of the sheet forming method (S method). Said B corresponds to the case where the occurrence of cracks in the matrix layer is not detected by visual observation, but its existence can be seen by observation with an electron microscope, and the open circuit voltage is lower by 30 to 60 mV compared to A and S. showed that. In the case of the two matrix layers according to the invention of claim 9, an open circuit voltage such as B is not shown, and in the case of the single layer according to the invention of claim 2, an open circuit voltage such as B is shown. There are rare occurrences of
[0049]
  FIG. 5 shows the cell life test results, the vertical axis shows the cell voltage (V), and the horizontal axis shows the operation time. In FIG. 5, A and B show the results of the method of the present invention, and S shows the results of the sheet forming method (S method). B shows the result of a deterioration case that rarely occurs in the case of one layer according to the invention of claim 2. In the case of the method of the present invention, since the thickness of the matrix layer is thin compared to the sheet forming method, the internal resistance is small, and the cell voltage is high compared to the sheet forming method.
[0050]
  The reason why the cell voltage drop phenomenon occurs as shown in FIG. 5B will be described below. Even in the case where the cell voltage is not affected in the initial stage of operation, in the fuel cell using the liquid electrolyte, such as the phosphoric acid fuel cell, the gas sealing property of the matrix layer does not influence the amount of the electrolyte in the cell. It is known to receive. In the case of the coating method matrix according to the present invention, since the original gas sealability is lower than that of the sheet forming method, in order to obtain sufficient gas sealability compared to the matrix by the sheet forming method, a larger amount of electrolyte solution is required. It was necessary. In particular, after long-term operation, even if there is a sufficient amount of electrolyte remaining in the cell if the sheet formation method matrix is present, the phenomenon that power generation characteristics deteriorate in cells using the coating method matrix is generally Was seen. That is, since the gas sealing property of the matrix layer is low, in the case of the coating method, the life is generally shortened even if the electrolytic mass is the same.
[0051]
  FIG. 5 is a test result comparing the lifetimes when the electrolytic mass charged into the cell during assembly is intentionally reduced and the matrix formed by the sheet formation method and the matrix of the coating method of the present invention are used. In the case of B, which occurs rarely, as shown by a broken line in FIG. 5, the time that can be operated with a constant electrolytic mass is shortened by about 20% or more compared to the matrix S by the sheet forming method. I understand.
[0052]
  However, in the case of A, the lifetime is equivalent to that of S, the cell voltage is generally high, and the battery characteristics are excellent.
[0053]
【The invention's effect】
  As described above, according to the present invention, a paste in which silicon carbide fine particles (SiC fine particles) and PTFE as a binder are dispersed in a liquid solvent is applied to the electrode substrate surface to form a matrix layer. The coating roll using a transport roll for transporting the electrode substrate, a coating roll and a backup roll provided opposite to each other with the electrode substrate interposed therebetween, and a pressing member (squeegee) biased by the coating roll In the state where the backup roll is rotated in the same direction as the electrode substrate conveyance direction, the electrode substrate is conveyed by the conveyance roll, and the paste roll is formed in at least one of the coating roll and the squeegee. Supply paste on electrode substrate surfaceBy applying a paste to the electrode substrate surface, heat-treating it to form a first matrix layer, on the surface of the first matrix layer again, by the same procedure as the procedure, A paste is applied and heat treatment is performed to form a second matrix layer. The particle size of the SiC fine particles in the second matrix paste is determined by the particle size of the SiC fine particles in the first layer paste. (Invention of claim 1),
Alternatively, the first matrix layer and the second layer are processed in the same procedure as in the first aspect of the invention. And the thickness of the second matrix layer is made thinner than the thickness of the first matrix layer (Invention of Claim 2).By
  A matrix thin film layer having a thickness suitable for power generation characteristics and high quality can be continuously produced stably at high speed.
[0054]
  Also, MaIt is possible to suppress the problem that fine cracks are generated in the trick layer.
[0055]
  further, MaIt is possible to solve the problem that a fine crack of a level detected by microscopic observation in the trick layer can be solved, and a fuel cell having excellent power generation characteristics and a long life can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a coating apparatus related to a manufacturing method according to an embodiment of the present invention.
FIG. 2 is a perspective view of a coating roll in FIG.
3 is a partially enlarged sectional view of a groove provided in the coating roll in FIG.
FIG. 4 is a comparison experiment result of the present invention and the sheet forming method regarding open circuit voltage.
FIG. 5 shows the results of a comparative experiment between the present invention and the sheet forming method regarding the cell life.
FIG. 6 is an exploded perspective view of a schematic configuration of a phosphoric acid fuel cell.
FIG. 7 is a conceptual diagram of a method using a reverse roll coater related to a conventional manufacturing method.
[Explanation of symbols]
  30: coating roll, 30a: groove, 31: backup roll, 32: pressing member (squeegee), 33: matrix paste, 34: electrode substrate, 35: transport roll.

Claims (10)

A method of forming a matrix layer by applying a paste in which silicon carbide fine particles (SiC fine particles) and PTFE as a binder are dispersed in a liquid solvent to an electrode substrate surface,
Using a transport roll for transporting the electrode substrate, a coating roll and a backup roll provided facing each other across the electrode substrate, and a pressing member (squeegee) biased by the coating roll,
In the state where the coating roll and the backup roll are rotated in the same direction as the electrode substrate conveying direction, the electrode substrate is conveyed by the conveying roll, and the paste flow formed on at least one of the coating roll and the squeegee By supplying the paste from the groove onto the electrode substrate surface, the paste is applied to the electrode substrate surface, and this is heat-treated to form a first matrix layer, on the surface of the first matrix layer In the same procedure as above, the paste is applied and heat-treated to form a second matrix layer, and the particle size of the SiC fine particles in the second matrix paste is set to 1 production of phosphoric acid fuel cell matrix layer, characterized in that a smaller than the particle diameter of the SiC particles in the layers th paste Law. A method of forming a matrix layer by applying a paste in which silicon carbide fine particles (SiC fine particles) and PTFE as a binder are dispersed in a liquid solvent to an electrode substrate surface,
Using a transport roll for transporting the electrode substrate, a coating roll and a backup roll provided facing each other across the electrode substrate, and a pressing member (squeegee) biased by the coating roll,
In the state where the coating roll and the backup roll are rotated in the same direction as the electrode substrate conveying direction, the electrode substrate is conveyed by the conveying roll, and the paste flow formed on at least one of the coating roll and the squeegee By supplying the paste from the groove onto the electrode substrate surface, the paste is applied to the electrode substrate surface, and this is heat-treated to form a first matrix layer, on the surface of the first matrix layer In the same procedure as above, the paste is applied and heat-treated to form a second matrix layer, and the thickness of the second matrix layer is set to the thickness of the first matrix layer. A method for producing a matrix layer for a phosphoric acid fuel cell, characterized in that the matrix layer is made thinner than the thickness .   3. The manufacturing method according to claim 1, wherein the paste flow groove is a plurality of grooves provided uniformly in the axial direction of the outer peripheral surface of the coating roll. A method for manufacturing a matrix layer.   4. The phosphoric acid fuel cell according to claim 3, wherein the plurality of uniformly provided grooves are cut grooves having a V-shaped cross section, and the cut pitch is 200 to 1000 [mu] m. Method for manufacturing a matrix layer.   5. The method of manufacturing a matrix layer for a phosphoric acid fuel cell according to claim 4, wherein a cutting angle of the V-shaped cutting groove is 50 to 90 degrees.   6. The phosphoric acid fuel cell matrix according to claim 1, wherein the coating roll is made of rubber and has a hardness (JIS-A) of 40-80. Layer manufacturing method.   3. The manufacturing method according to claim 1, wherein the liquid solvent in the paste is any one of ethylene glycol, diethylene glycol, and dipropylene glycol, or a mixture of any of the above and water. A method for producing a matrix layer for an acid fuel cell.   8. The method for producing a matrix layer for a phosphoric acid fuel cell according to claim 7, wherein the solid content concentration other than the liquid solvent in the paste is 40 to 80% by weight. 3. The manufacturing method according to claim 1, wherein the solid content concentration of the second layer matrix paste is lower than the solid content concentration of the first layer paste. Production method. 3. The manufacturing method according to claim 1, wherein the binder content of the matrix paste of the second layer is larger than the binder content of the paste of the first layer. Production method.

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