JP5109238B2 - Manufacturing method of electrolyte membrane - Google Patents

Description

  The present invention relates to an electrolyte membrane used in a polymer electrolyte fuel cell, a production method thereof, a membrane electrode assembly including the electrolyte membrane, and a fuel cell.

  A polymer electrolyte fuel cell (PEFC) is known as one of the fuel cells. As shown in FIG. 9, the polymer electrolyte fuel cell includes a membrane electrode assembly (MEA) 5 as a main component, which is a separator 4 provided with a fuel (hydrogen) gas flow path and an air gas flow path. 4, one fuel cell 6 called a single cell is formed. The membrane electrode assembly 5 includes an anode side electrode (catalyst layer) 2a and a diffusion layer 3a laminated on one side of an electrolyte membrane 1 that is an ion exchange membrane, and a cathode side electrode (catalyst layer) 2b on the other side. The diffusion layer 3b has a stacked structure.

  The electrolyte membrane used in the polymer electrolyte fuel cell is usually about 10 μm to 200 μm thick and does not have sufficient strength. Therefore, when the catalyst layer or the diffusion layer is laminated to form a membrane electrode assembly, be careful. Work is required. In addition, when the operating temperature is high, the elastic modulus of the film is lowered and is easily damaged, which may shorten the battery life.

  Therefore, methods for improving the strength of the electrolyte membrane are proposed in Patent Documents 1 and 2 and the like. Patent Document 1 describes that fine particles of inorganic material are dispersed with a concentration gradient in the film thickness direction so that the concentration in the central portion of the electrolyte membrane is high and the concentration in the vicinity of the membrane surface is low. This inorganic material is present in a composite form in the electrolyte membrane, which is a polymer membrane, thereby improving the membrane strength.

  Patent Document 2 discloses a solid polymer electrolyte having improved strength and heat resistance by dispersing silica particles having an average particle diameter of 5 to 500 nm in a hydrolyzate matrix of an organosilicon compound having proton conductivity. A membrane is described.

JP 2002-352818 A JP 2003-308855 A

  As described above, the conventional technique for improving the strength of the electrolyte membrane is to disperse and mix some kind of atomized reinforcing material throughout the thickness direction of the membrane, and although it is slight, it adversely affects the ionic conductivity. There is a risk of affecting.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electrolyte membrane having improved physical strength and a method for producing the same while maintaining the ionic conductivity inherent to the electrolyte membrane. To do. Moreover, it aims at providing the membrane electrode assembly and fuel cell provided with such an electrolyte membrane.

  The present inventor conducted a lot of research and experiments to solve the above problems, and when the dispersed reinforcing material was dispersed and mixed in the surface layer portion of the resin film or sheet, the resin film or sheet was obtained by a so-called anchor effect. Although it is known that the physical strength of the electrolyte membrane is improved, when this technique is applied when manufacturing the electrolyte membrane, it is possible to improve the strength while substantially maintaining the ionic conductivity inherent in the electrolyte membrane. I found out that I can do it.

  The present invention is based on the above findings, and the electrolyte membrane according to the present invention is an electrolyte membrane used in a polymer electrolyte fuel cell, in which the atomized reinforcing material is dispersed inside the surface layer portion of the electrolyte membrane. It is characterized by mixing.

  In the electrolyte membrane according to the present invention, since the atomized reinforcing material exists only in the surface layer portion of the membrane and does not substantially exist in the inner layer portion, the ionic conductivity itself of the electrolyte membrane has a great influence. Not receive. On the other hand, since the so-called anchor effect is generated by the atomized reinforcing material dispersed and mixed in the surface layer portion, the strength of the electrolyte membrane is improved.

  In the electrolyte membrane according to the present invention, the “surface layer portion of the electrolyte membrane” means the surface layer of the electrolyte membrane in a range in which a physical phenomenon of strength improvement by the anchor effect occurs due to the presence of the dispersed atomized reinforcing material. This is a partial region, which varies depending on the material of the electrolyte membrane and the particle diameter of the reinforcing material, but is in the range of several microns from the electrolyte membrane surface, more preferably in the range of 1 μm to 10 μm. Further, the dispersion amount is preferably an amount that occupies about 30% or less of the electrolyte membrane in the state of being dispersed and mixed on the surface layer on average, and when the dispersion amount exceeds 30%, the ionic conduction of the electrolyte membrane There is a risk of reducing the sex. Preferably, it is in the range of 20% to 25%, and when it is less than 5%, a sufficient anchor effect cannot be obtained.

In the electrolyte membrane according to the present invention, as the electrolyte material constituting the electrolyte membrane, all electrolyte materials constituting the electrolyte membrane used in the conventional membrane electrode assembly for a polymer electrolyte fuel cell can be used. However, as will be described later, when an electrolyte membrane is made from a so-called solvent-type electrolyte material (H-type electrolyte material) in which an electrolyte polymer is dispersed in a solvent, and an electrolyte material (F-type electrolyte) made of a precursor polymer of the electrolyte polymer The manufacturing method is different from the case where an electrolyte membrane is made depending on the material. However, in any case, any reinforcing material can be used as long as it is a nonmetallic material. Preferably, alumina (e.g., boehmite (AlO (OH)), silica (SiO ₂₎ based, acrylic resin-based, silicone resin, and the like.

  The size of the atomized reinforcing material varies depending on the thickness of the electrolyte membrane to be manufactured, but preferably the average particle size is 0.01 μm or more and 10 μm or less. When the particle size is less than 0.01 μm, a sufficient anchor effect cannot be exhibited, and a desired strength improvement effect does not appear. When the thickness exceeds 10 μm, the reinforcing material cannot be dispersed and mixed only in the surface layer portion of the electrolyte membrane, and the reinforcing material tends to exist even in the inner layer portion, and the sufficient anchor effect may not be exhibited. Occur. It also has a negative effect on ion exchange properties.

  The electrolyte membrane according to the present invention may have a form in which the atomized reinforcing material is dispersed and mixed on both the front and back surfaces of the electrolyte membrane, and further, electrolyte membranes having different physical properties are further laminated on the front and back surfaces. It may be a form. In this case, the different physical properties include, for example, an EW value (equivalent weight of ion exchange group). The electrolyte membrane may be composed of a single membrane of an electrolyte material, or may be in a form in which a porous reinforcing membrane such as a PTFE porous membrane is impregnated with an electrolyte material.

  The present invention also discloses a method for producing the above electrolyte membrane. One of them is a method for producing an electrolyte membrane used in a polymer electrolyte fuel cell, and a surface layer portion of a semi-electrolyte material is injected by injecting atomized reinforcing material onto the surface of the electrolyte material in a molten state. It includes at least a step of dispersing and mixing the atomized reinforcing material therein. In this method, for example, when the atomized reinforcing material is injected using a bubble jet type injection nozzle or the like, the reinforcing material is made of the semi-electrolyte material by giving a required kinetic energy to the atomized reinforcing material. It enters in a dispersed state inside the surface layer. The electrolyte membrane according to the present invention is manufactured by fixing and cooling the electrolyte material in a molten state in the same manner as in the case of a normal electrolyte membrane.

  Another aspect of the method for producing an electrolyte membrane according to the present invention is a method for producing an electrolyte membrane used in a polymer electrolyte fuel cell, the step of dispersing the atomized reinforcing material on the surface of the electrolyte membrane, And a step of heating and pressing the surface to disperse and mix the reinforcing material inside the surface layer portion of the electrolyte membrane. In this method, an electrolyte membrane manufactured by a conventional method is used. For example, a blast nozzle or the like is used to disperse the atomized reinforcing material on the surface, and the dispersed surface is heated and pressurized by a hot press or the like. Thereby, the surface layer portion of the electrolyte membrane is melted, and the dispersed reinforcing material enters the inside of the surface layer portion of the electrolyte membrane and is in a dispersed and mixed state.

  In the case of this manufacturing method, it is necessary that the electrolyte material is thermally strong. Preferably, an electrolyte membrane made of an electrolyte material (F-type electrolyte material) made of a precursor polymer of an electrolyte polymer is used. After the reinforcing material is dispersed and mixed as described above, the electrolyte membrane according to the present invention is manufactured by performing hydrolysis for proton conduction by a conventional method.

  Another aspect of the method for producing an electrolyte membrane according to the present invention is a method for producing an electrolyte membrane for use in a polymer electrolyte fuel cell by casting a solvent-type electrolyte material a plurality of times and then performing a drying treatment. As a solvent-type electrolyte material constituting the casting film, an electrolyte material in which atomized reinforcing materials are dispersed is used. Even in this method, it is not necessary to explain that the electrolyte membrane according to the present invention in which the reinforcing material is dispersed and mixed only in the surface layer portion.

  According to the present invention, an electrolyte membrane with improved physical strength can be obtained while maintaining the ionic conductivity inherent to the electrolyte membrane. Moreover, since the strength of the electrolyte membrane is improved, the fuel cell using the membrane electrode assembly provided with the electrolyte membrane according to the present invention can maintain stable power generation performance over a long period of time.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings. FIG. 1 to FIG. 7 are diagrams for explaining electrolyte membranes of different forms according to the present invention together with the manufacturing method thereof, and FIG. 8 shows an electrolyte membrane with a reinforcing means according to the present invention and an electrolyte membrane without a reinforcing means. It is a graph which shows an example of the comparison of tensile strength.

  In the form shown in FIG. 1, a conventionally known electrolyte material 10 in a molten state is accommodated in an extrusion die 20 and is extruded into a film shape by a conventional method. As shown in FIG. 1a, in the vicinity of the exit of the extrusion die 20, an injection device 30 for injecting the atomized reinforcing material P with a required kinetic energy is located at a distance of 10 mm or less, and the molten melt extruded. The atomized reinforcing material P is sprayed on the front and back surfaces of the electrolyte membrane 11 in a state. The injected atomized reinforcing material P enters the surface layer portion of the electrolyte membrane 11 by its own kinetic energy.

  In this example, the atomized reinforcing material P is a resin-reinforced powder having an average particle size of 10 μm or less having chemical resistance and heat resistance (300 ° C. or higher), more specifically, boehmite which is an alumina-based powder. (AlO (OH)) is used, and as the injection device 30, a bubble jet type injection nozzle is used. The atomized reinforcing material P diffused in the alcohol and water is sprayed toward the electrolyte membrane 11 in a molten state by alcohol and water being heated and foamed at the heating portion at the tip of the nozzle, and dispersed and mixed in the surface layer portion. It becomes a state.

  The electrolyte membrane 11 in which the reinforcing material P is dispersed and mixed in the surface layer portions on the front and back surfaces thereafter passes through the fixing / cooling roll 31 as in the conventional case, as shown in FIG. 1b. As a result, the reinforcing material P is fixed to the surface layer portion of the electrolyte membrane 11 and becomes an electrolyte membrane 50 as shown in FIG. 1c. The atomized reinforcing material P dispersed and mixed within a range s of several microns from the front and back surfaces exhibits an anchor effect in the region s and reinforces a range of several microns from the front and back surfaces of the electrolyte membrane 50. Thereby, the strength of the electrolyte membrane 50 is improved and the reinforcing material P is not present in the inner layer portion, so that the ion exchange performance of the electrolyte membrane 50 itself is maintained as it is.

The electrolyte membrane 50A shown in FIG. 2 is integrated by disposing electrolyte membranes 51 and 51 having different EW values on the front and back surfaces of the electrolyte membrane 50 manufactured as described above (FIG. 2a) and heat-pressing them. (FIG. 2b), an electrolyte membrane 50A having a composite membrane structure is formed. In this case, the ion exchange performance of the electrolyte membrane 50 and the electrolyte membrane 51 may be deteriorated by heating. Therefore, when such heat treatment is performed later, it is preferable to use an electrolyte material (F-type electrolyte material) made of a precursor polymer of a thermally strong electrolyte polymer as the electrolyte material. After the complexation, hydrolysis treatment for proton conduction (for example, treatment such as conversion from SO ₂ F to SO ₃ H at the terminal of the sulfonyl fluoride) is performed to obtain an electrolyte membrane.

  In the embodiment shown in FIG. 3, the atomized reinforcing material P accommodated in the blast nozzle 32 is applied to one surface of the electrolyte membrane 52 made of the F-type electrolyte material as described above from the nozzle using air. It is dispersed and sprayed (FIG. 3a). The electrolyte membrane 52 on which the atomized reinforcing material P scattered on the surface is placed is placed on the lower die 33 of the hot press and is slowly pressed by the upper die 34 heated to about 130 ° C. to 280 ° C. (FIG. 3b). The membrane surface layer portion is gradually melted by heating, and the reinforcing material P on the surface penetrates into the surface layer portion of the electrolyte membrane 52 and is fixed (FIG. 3c). By cooling and taking out from the press, an electrolyte membrane 50B in which the reinforcing material P is dispersed and impregnated in one surface layer portion is obtained (FIG. 3d). When the reinforcing material P is dispersed and impregnated in the surface layer portion on the back side, the electrolyte membrane 50B is inverted and the same processing is repeated.

  In the form shown in FIG. 4, a reinforcing material Pa dispersed in alcohol and water is coated on one surface of the electrolyte membrane 52 made using the F-type electrolyte material (FIG. 4 a), and dried to allow the alcohol and By blowing water, the reinforcing material P is attached to the membrane surface (FIG. 4b). A similar electrolyte membrane 50B can be obtained by performing the subsequent steps shown in FIG. 3b on the electrolyte membrane shown in FIG. 4b.

  The electrolyte membrane 50C shown in FIG. 5 is obtained by melt-bonding two electrolyte membranes 50B in which the reinforcing material P is dispersed and impregnated only on one side of the form shown in FIG. The electrolyte membrane is dispersed and impregnated.

  The electrolyte membrane 50D shown in FIG. 6 is formed by laminating the electrolyte membrane 50B described above on the front and back surfaces of the porous reinforcing membrane 40, and heating it from both sides using a hot press as shown in FIG. Is made into a molten state, which is impregnated in the porous reinforcing membrane 40 to form an electrolyte membrane 50D. In this embodiment, the strength of the inner layer portion is also improved by the porous reinforcing film 40 in addition to the strength improvement of the surface layer portion brought about by the anchor effect by the atomized reinforcing material P. For the porous reinforcing film 40, a material such as a PTFE porous film conventionally used for an electrolyte film can be used as appropriate.

  In the form shown in FIG. 7, an example in the case of manufacturing an electrolyte membrane using the solvent-type electrolyte material 10A is shown. In this case, the heat treatment step is not included in the manufacturing process. As shown in FIG. 7a, after the process of drying the cast electrolyte solution 10A is repeated a plurality of times in the container 36, the reinforcing material P is dispersed in the electrolyte solution containing the solvent on the electrolyte membrane 52. The electrolyte solution 53 was cast (FIG. 7b), dried, and the solvent was blown off (FIG. 7c). By taking it out from the casting container, an electrolyte membrane 50E (FIG. 7d) in which the atomized reinforcing material P is dispersed and impregnated inside one surface layer portion is obtained. When obtaining an electrolyte membrane in which the reinforcing material P is dispersed and impregnated on the surface layer portions on both sides, the electrolyte membrane 50E in the form shown in FIG. 7d may be inverted and the same steps may be repeated.

  FIG. 8 shows a powder-reinforced electrolyte membrane manufactured by the method of the present invention (boehmite (AlO (OH)) is used as a reinforcing material), and the same electrolytic material is used to disperse and impregnate the atomized reinforcing material inside the surface layer portion. The result when carrying out the comparative test of the tensile strength on the same conditions is shown with respect to the electrolyte membrane manufactured by the same manufacturing method (unreinforced electrolyte membrane) except not performing a process. The test is performed at room temperature. As shown in the graph of FIG. 8, the tensile strength (N) with respect to the same displacement (mm) indicates that the powder-reinforced electrolyte membrane produced by the method of the present invention is large and the membrane strength is improved. It is.

The figure explaining one form of the electrolyte membrane by this invention, and its manufacturing method. The figure explaining the other form of the electrolyte membrane by this invention, and its manufacturing method. The figure explaining further another form of the electrolyte membrane by this invention, and its manufacturing method. The figure explaining further another form of the electrolyte membrane by this invention, and its manufacturing method. The figure explaining further another form of the electrolyte membrane by this invention, and its manufacturing method. The figure explaining further another form of the electrolyte membrane by this invention, and its manufacturing method. The figure explaining further another form of the electrolyte membrane by this invention, and its manufacturing method. The graph which shows the result of the tensile strength test in the electrolyte membrane manufactured with the same manufacturing method except not performing the process of carrying out the dispersion | distribution impregnation of the powder reinforced electrolyte membrane manufactured by the method of this invention, and the reinforcing material atomized inside the surface layer part. The figure for demonstrating a polymer electrolyte fuel cell.

Explanation of symbols

P: Atomized reinforcing material, s: Surface layer region of electrolyte membrane, 10 ... Electrolyte material, 11 ... Molten electrolyte membrane, 20 ... Extrusion die, 30 ... Injection device (bubble jet type injection nozzle), 31 ... Fixing -Cooling roll, 32 ... Blast nozzle, 33 ... Lower die of hot press, 34 ... Upper die of hot press, 40 ... Porous reinforcing membrane, 50, 50A, 50B, 50C, 50D ... Electrolyte membrane, 51 ... EW Electrolyte membranes with different values

Claims (4)

A process for producing an electrolyte membrane used in polymer electrolyte fuel cells, by injecting reinforcement is alumina-based material is atomized on the surface of the electrolyte material in a molten state, the surface layer portion of the electrolyte material A method for producing an electrolyte membrane comprising at least a step of dispersing and mixing the reinforcing material, which is the alumina-based material, in a range of 1 μm to 10 μm from the surface . A process for producing an electrolyte membrane used in polymer electrolyte fuel cell, a step of dispersing the electrolyte membrane reinforcing member is alumina-based material is atomized on the surface of, the alumina-based dispersion surface by heating and pressing And a step of dispersing and mixing a reinforcing material as a material in a range of 1 μm to 10 μm from the surface of the surface layer portion of the electrolyte membrane. A method for producing an electrolyte membrane for use in a polymer electrolyte fuel cell by casting a solvent-type electrolyte material a plurality of times and then subjecting it to a drying treatment, and comprising a fine particle as a solvent-type electrolyte material constituting a casting film of a surface layer portion using of the electrolytic material dispersed a reinforcing material is an alumina-based material, and wherein Rukoto dispersing a reinforcing material is the alumina-based material in the range of 1μm~10μm from the surface of the surface layer portion of the electrolyte membrane An electrolyte membrane manufacturing method. The method for producing an electrolyte membrane according to any one of claims 1 to 3 , wherein a reinforcing material having an average particle diameter of 0.01 µm or more and 10 µm or less is used as the reinforcing material which is an atomized alumina-based material .

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