JP2009252723A - Electrolyte membrane for polymer electrolyte fuel cell, its manufacturing method, and membrane-electrolyte assembly for polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte membrane high in strength even when thickness is small, excelling in dimensional stability in absorbing water, and low in resistance; a manufacturing method of the electrolyte membrane; and a membrane-electrolyte assembly for a polymer electrolyte fuel cell having high power output and excelling in durability. <P>SOLUTION: This electrolyte membrane for a polymer electrolyte fuel cell is reinforced by a nonwoven fabric and contains an ion exchange resin as a main constituent. The electrolyte membrane for a polymer electrolyte fuel cell is characterized in that the nonwoven fabric is formed of a fiber of polypropylene having an average fiber diameter of 0.01-6 μm, and a basis weight of 1.0-4.0 g/m<SP>2</SP>, and has, as the outermost layer(s) of one surface or both surfaces, an unreinforced layer formed of an ion exchange resin that may be identical to or different from that of the above ion exchange resin; the total thickness of the unreinforced layer is 2-10 μm; and the thickness of the whole electrolyte membrane for a polymer electrolyte fuel cell is 10-20 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrolyte membrane for a polymer electrolyte fuel cell reinforced with a nonwoven fabric, a production method thereof, and a membrane electrode assembly for a polymer electrolyte fuel cell having the electrolyte membrane.

  In recent years, research on polymer electrolyte fuel cells using a proton-conductive polymer membrane as an electrolyte has been advanced. A polymer electrolyte fuel cell operates at a low temperature, has a high output density, and can be miniaturized, and is expected to be promising for uses such as an in-vehicle power source.

  As the electrolyte membrane for a polymer electrolyte fuel cell, a proton conductive ion exchange membrane having a thickness of 10 to 200 μm is usually used. In particular, a perfluorocarbon polymer having a sulfonic acid group (hereinafter referred to as a sulfonic acid type perfluorocarbon polymer). The cation exchange membrane consisting of) is widely studied because of its excellent basic properties. Fuel cell electrolyte membranes intended for actual in-vehicle use have been required to have particularly low membrane ohmic loss. Although the membrane ohmic loss depends on the conductivity of the electrolyte polymer used, an electrolyte membrane having a thickness of about 10 to 30 μm is being studied.

  Methods for reducing the electrical resistance of the cation exchange membrane include increasing the sulfonic acid group concentration and reducing the film thickness. However, when the concentration of the sulfonic acid group is remarkably increased, the mechanical strength of the membrane is lowered, and the membrane is likely to creep during the long-term operation of the fuel cell, resulting in a decrease in the durability of the fuel cell. On the other hand, when the film thickness is reduced, the mechanical strength of the film is lowered, and when a membrane electrode assembly is produced by joining the membrane to the gas diffusion electrode, problems such as difficulty in processing and handling are caused.

  In addition, the above electrolyte membrane tends to increase in size when it contains water, and easily causes various harmful effects. For example, when producing a membrane electrode assembly, there is a problem that handling becomes difficult due to dimensional changes. When operation is performed with the membrane electrode assembly incorporated in a fuel cell, the membrane swells due to water generated by the reaction or water vapor supplied together with the fuel gas, and the size of the membrane increases. Usually, since the membrane and the electrode are joined, the electrode follows the dimensional change of the membrane. Since the membrane electrode assembly is usually restrained by a separator or the like in which grooves are formed as gas flow paths, the increase in the dimension of the membrane becomes “wrinkles”. And the wrinkle may fill the groove of the separator and obstruct the gas flow.

  As a method for solving the above problem, a method of impregnating a porous body made of polytetrafluoroethylene (hereinafter referred to as PTFE) with a sulfonic acid type perfluorocarbon polymer has been proposed (Patent Document 1). However, since the porous body of PTFE is derived from the material and is relatively soft, it is required to perform a stretching operation with a high stretching ratio, and it is difficult to say that it is highly productive. Further, although a method of filling a porous body made of polyolefin with an ion exchange resin has been proposed (Patent Document 2), the increase in membrane resistance is large and not practically sufficient.

  Patent Document 3 proposes an electrolyte membrane for a polymer electrolyte fuel cell reinforced with polyethylene fiber, woven fabric, or non-woven fabric. Since these reinforcing bodies have low heat resistance of polyethylene, there is a concern that the structure cannot be maintained as a reinforcing body in the operating environment of the fuel cell. Moreover, the proposal regarding a nonwoven fabric has a comparatively large basis weight, and it is thought that it raises a membrane resistance in an actual driving environment.

  Further, Patent Document 4 proposes an electrolyte membrane for a polymer electrolyte fuel cell reinforced with a fluororesin nonwoven fabric. By these methods, electrolyte membranes for high performance and high durability fuel cells that have both sufficient performance and durability can be obtained, but these reinforcements have a high material viscosity and stably produce non-woven fabrics with thin fiber diameters. In addition, in order to produce a high-strength non-woven fabric, the adhesion of the interface with the ion exchange resin is weak for some fluororesins, and the resistance is sufficiently increased even after surface treatment. It may be difficult to suppress.

Japanese Patent Publication No. 5-75835 (Claims) Japanese Patent Publication No. 7-68377 (Claims) JP 2000-231928 A (Claims) JP 2007-1895 A (Claims)

  An object of the present invention is to provide an electrolyte membrane for a polymer electrolyte fuel cell that has high strength even when it is thin, has excellent dimensional stability when containing water, and has low resistance while realizing high productivity. .

  Furthermore, for polymer electrolyte fuel cells, it is possible to produce high-productivity electrolyte membranes for polymer electrolyte fuel cells with high strength, excellent dimensional stability when containing water, and low resistance even when they are thin. An electrolyte membrane manufacturing right method is provided.

  It is another object of the present invention to provide a membrane electrode assembly for a polymer electrolyte fuel cell having high output and excellent durability by having such an electrolyte membrane at low cost.

The electrolyte membrane for a polymer electrolyte fuel cell of the present invention is an electrolyte membrane for a polymer electrolyte fuel cell mainly composed of an ion exchange resin reinforced with a nonwoven fabric, and the nonwoven fabric has an average fiber diameter of 0.00. Ion exchange consisting of 01 to 6 μm polypropylene fibers and having a basis weight of 1.0 to 4.0 g / m ² and may be the same as or different from the ion exchange resin as the outermost layer on one or both sides It has an unreinforced layer made of resin, the total thickness of the unreinforced layer is 2 to 10 μm, and the total thickness of the electrolyte membrane for a polymer electrolyte fuel cell is 10 to 20 μm.

  The mass fraction of the nonwoven fabric when immersed in warm water at 90 ° C. for 2 hours is preferably 5 to 10% by mass.

In the method for producing an electrolyte membrane for a polymer electrolyte fuel cell according to the present invention, the electrolyte membrane for a polymer electrolyte fuel cell is made of polypropylene fibers having an average fiber diameter of 0.01 to 6 μm and has a basis weight of 1.0. It is an electrolyte membrane for a polymer electrolyte fuel cell mainly composed of an ion exchange resin reinforced with a nonwoven fabric of ~ 4.0 g / m ² , and is the same as or different from the above ion exchange resin as an outermost layer on one or both sides. An unreinforced layer made of an ion exchange resin may be disposed, the total thickness of the unreinforced layer is 2 to 10 μm, and the total thickness of the electrolyte membrane for a polymer electrolyte fuel cell is 10 to 20 μm And a drying step of drying the electrolyte membrane for a polymer electrolyte fuel cell, wherein the drying step is performed by applying ethanol to the electrolyte membrane for a polymer electrolyte fuel cell and drying at 150 ° C. or lower. And features.

  A membrane electrode assembly for a polymer electrolyte fuel cell according to the present invention comprises a cathode and an anode having a catalyst layer containing a catalyst and an ion exchange resin, and a polymer electrolyte membrane disposed between the cathode and the anode. The membrane electrode assembly for a polymer electrolyte fuel cell comprising the polymer electrolyte membrane comprises the electrolyte membrane for a polymer electrolyte fuel cell of the present invention.

  The electrolyte membrane for a polymer electrolyte fuel cell of the present invention has little increase in resistance due to reinforcement, is excellent in dimensional stability when containing water, and has high productivity.

  According to the method for producing an electrolyte membrane for a polymer electrolyte fuel cell of the present invention, the electrolyte membrane for a polymer electrolyte fuel cell has a high strength even when it is thin, has excellent dimensional stability when containing water, and has a low resistance. Can be manufactured with high productivity.

  The membrane / electrode assembly for polymer electrolyte fuel cells of the present invention has high output and excellent durability.

  The electrolyte membrane for a polymer electrolyte fuel cell of the present invention (hereinafter also referred to as an electrolyte membrane) is reinforced by using a nonwoven fabric made of polypropylene resin fibers with a minimum basis weight, thereby increasing the resistance due to reinforcement. Therefore, it is possible to reduce the cost because it has excellent dimensional stability when containing water and has high productivity.

  In the present invention, as described in JIS L-0222, the nonwoven fabric is a fiber sheet, web, or pad, in which fibers are unidirectionally or randomly arranged, entangled, and / or fused, and / or bonded. The fibers are bonded by the above. The nonwoven fabric used for the electrolyte membrane of the present invention is preferably bonded between fibers by fusion because the increase in resistance can be suppressed.

  The nonwoven fabric used for the electrolyte membrane of the present invention is made of polypropylene resin fibers. It is preferable that the fibers of the nonwoven fabric used in the present invention have an aspect ratio of 10,000 or more. The fiber length is desirably 20 mm or more.

  Since the nonwoven fabric in the present invention is composed of fibers having a large aspect ratio, sufficient entanglement between the fibers is formed, and the number of fiber end portions that can be mechanical defects is extremely small. Moreover, since at least a part of the intersections between the fibers is fixed, the elastic modulus is high.

  The nonwoven fabric used for the electrolyte membrane of the present invention has an average fiber diameter (diameter) of 0.01 to 6 μm, more preferably 0.01 to 3 μm, and particularly preferably 0.1 to 3 μm. preferable.

  In addition, the average fiber diameter in this invention measures the fiber diameter of 200 fibers in electron microscope observation, and makes the average fiber diameter the average value except 10 data and 10 thick data among data. .

  By controlling the average fiber diameter of the fibers to 6 μm or less, proton transfer can be performed smoothly and the thickness of the nonwoven fabric can be suppressed, so that an increase in resistance due to reinforcement can be suppressed. Moreover, since the intersection between the fibers in the same film thickness can be increased when the average fiber diameter is 6 μm or less, the strength of the nonwoven fabric can be enhanced and the dimensional stability of the electrolyte membrane can be improved. On the other hand, by setting the average fiber diameter to 0.01 μm or more, the tensile strength per fiber can be increased, and it becomes easy to use practically in terms of handling.

The basis weight of the nonwoven fabric used for the electrolyte membrane of the present invention is 1.0 to 4.0 g / m ² , preferably 2.0 to 3.0 g / m ² . When the weight per unit area is 1.0 g / m ² or more, sufficient strength is obtained, and when the basis weight is 4.0 g / m ² or less, an increase in resistance of the electrolyte membrane can be suppressed.

  The nonwoven fabric in the present invention is preferably subjected to at least one surface treatment selected from the group consisting of irradiation with radiation, plasma irradiation and chemical treatment with metallic sodium. By performing these surface treatments, polar groups such as -COOH groups, -OH groups, and -COF groups are introduced on the fiber surface, and the adhesion at the interface between the ion-exchange resin as the matrix and the nonwoven fabric as the reinforcing material is improved. As a result, the reinforcing effect can be enhanced.

  In the present invention, the ion exchange resin that is the main component of the electrolyte membrane may be a cation exchange resin, such as a cation exchange resin made of a hydrocarbon polymer or a partially fluorinated hydrocarbon polymer. it can. When used in a fuel cell, a cation exchange resin comprising a sulfonic acid type perfluorocarbon polymer having excellent durability is preferred. The ion exchange resin in the electrolyte membrane may consist of a single ion exchange resin or a mixture of two or more ion exchange resins.

As the sulfonic acid type perfluorocarbon polymer, known polymers are widely used. For example, a sulfonic acid type perfluorocarbon polymer can be obtained by hydrolyzing and acidifying a precursor made of a resin having a SO ₂ F group. In the present specification, the perfluorocarbon polymer may contain an etheric oxygen atom or the like.

As the precursor comprising the resin having SO ₂ F gas, a fluorosulfonyl group-containing perfluoro compound represented by the following formula (1) used for producing a general-purpose sulfonic acid group-containing perfluorocarbon polymer: Or a monomer unit based on a perfluoro compound having one or two fluorosulfonyl groups represented by the following formulas (2) to (6), a perfluoroolefin such as tetrafluoroethylene or hexafluoropropylene, chlorotri Copolymers containing monomer units based on fluoroethylene or perfluoro (alkyl vinyl ether) are preferred. Particularly preferred are copolymers comprising monomer units based on the following fluorosulfonyl group-containing perfluoro compounds and monomer units based on tetrafluoroethylene.

Further, as the precursor comprising a resin having a SO 2 _F group, the monomer units based on fluorosulfonyl group-containing perfluoro compound of the following may be contained two or more.

In the formula, Y represents a fluorine atom or a trifluoromethyl group, n represents an integer of 1 to 12, m represents an integer of 0 to 3, and p represents 0 or 1 (where m + p> 0). k shows the integer of 2-6. R ^f1 and R ^f2 each independently represent a C 1-6 linear perfluoroalkylene group which may have a single bond or an etheric oxygen atom. q represents 0 or 1; R ^f3 represents a C 1-6 perfluoroalkylene group. R ^f4 and R ^f5 each independently represent a C 1-8 perfluoroalkylene group. R ^f6 represents a C 1-6 perfluoroalkylene group.

The weight average molecular weight of the sulfonic acid type perfluorocarbon polymer is preferably 1 × 10 ⁴ to 1 × 10 ⁷ , and particularly preferably 5 × 10 ^{4 to} 5 × 10 ⁶ . When the weight average molecular weight is 1 × 10 ⁴ or more, the physical properties such as the degree of swelling hardly change with time, and the durability of the electrolyte membrane is sufficient. If the weight average molecular weight is 1 × 10 ⁷ or less, solutionization and molding become easy.

Moreover, as a cation exchange resin of polymers other than a perfluorocarbon polymer, the polymer containing the monomer unit represented, for example by following formula (1), and the monomer unit represented by following formula (2) is mentioned. . Here, P ¹ is a phenyltolyl group, a biphenyltolyl group, a naphthalene reel group, a phenanthrene reel group, and an anthracylene group, P ² is a phenylene group, a biphenylene group, a naphthylene group, a phenanthrylene group, and an anthracylene group, and A ¹ is a —SO ₃ M ² group (M ² is a hydrogen atom or an alkali metal atom, the same shall apply hereinafter), a —COOM ² group or a group that is converted to these groups by hydrolysis, and B ¹ and B ² are each independently An oxygen atom, a sulfur atom, a sulfonyl group or an isopropylidene group; Structural isomers of P ¹ and P ² is not particularly limited, one or more fluorine atoms of the hydrogen atom of the P ¹ and P ^2, a chlorine atom, be substituted by a bromine atom or an alkyl group having 1 to 3 carbon atoms Good.

  The ion exchange capacity of the ion exchange resin in the present invention is 0.5 to 2.0 meq / g dry resin, particularly 0.7 to 1.6 meq when used as a polymer electrolyte membrane for a fuel cell. / G dry resin is preferred. If the ion exchange capacity is too low, the resistance increases. On the other hand, if the ion exchange capacity is too high, the affinity for water is too strong, and thus the electrolyte membrane may be dissolved during power generation.

  The electrolyte membrane of the present invention has an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin reinforced with a nonwoven fabric as the outermost layer on one or both sides. Thereby, when using the electrolyte membrane of this invention as a polymer electrolyte membrane for a polymer electrolyte fuel cell, the resistance in the junction part of an electrolyte membrane and an electrode can be reduced. In this invention, it is preferable to have a layer which is not reinforced as an outermost layer of both surfaces.

  In the present invention, the thickness of the non-reinforced layer made of an ion exchange resin is 2 to 10 μm, and more preferably 4 to 8 μm. When the thickness is 2 μm or more, the fuel gas barrier property of the fuel cell is excellent, and when the thickness is 10 μm or less, an increase in membrane resistance and a dimensional change can be suppressed.

  In addition, the thickness of the layer which is not reinforced in this specification can be measured by cross-sectional observations such as an optical microscope, a laser microscope, and an SEM. The thickness of the unreinforced layer means the shortest distance between the electrolyte membrane surface and the nonwoven fabric fibers.

  Further, the non-reinforced layer made of ion exchange resin may contain a component that does not cause an increase in resistance other than the reinforcing material.

  When the electrolyte membrane of the present invention is used as a polymer electrolyte membrane for a polymer electrolyte fuel cell, proton movement is shielded by non-woven fibers. If the thickness of the layer that is not reinforced is too thin, the distance for the current to bypass the fiber and bypass it becomes large, which may cause an unnecessary increase in resistance. In particular, when the thickness of the layer that is not reinforced is equal to or less than half the average fiber diameter of the nonwoven fabric fibers, the resistance tends to increase. When the thickness of the layer that is not reinforced is equal to the average fiber diameter of the nonwoven fabric fibers, it is preferable to reduce the current bypass distance and avoid unnecessary increase in resistance as a result.

  In the electrolyte membrane of the present invention, the thickness of the entire electrolyte membrane is 10 to 20 μm, preferably 12 to 18 μm.

  By making the thickness of the entire electrolyte membrane 20 μm or less, the resistance can be reduced, and when it is used as a polymer electrolyte membrane of a fuel cell, the thinner one causes reverse diffusion of the generated water generated on the cathode side. Can be made easier. By setting the thickness of the entire electrolyte membrane to 10 μm or more, the mechanical strength can be sufficiently increased, and the occurrence of gas leakage and the like can be suppressed.

  Moreover, from the viewpoint of the thickness of the electrolyte membrane, the thickness of the nonwoven fabric is preferably 0.5 to 16 μm or less, and particularly preferably 8 to 16 μm.

  Examples of a method for producing an electrolyte membrane mainly composed of an ion exchange resin reinforced with a non-woven fabric include (1) coating or impregnating a non-woven fabric with a solution or dispersion of an ion exchange resin, followed by drying and manufacturing. Examples thereof include a casting method for forming a film, and (2) a method in which an ion-exchange resin film-form formed in advance is laminated on a non-woven fabric by heat lamination. You may reinforce the composite film of this nonwoven fabric and ion exchange resin by an extending | stretching process etc.

  As described above, when the composite membrane of the nonwoven fabric and the ion exchange resin is formed, an unreinforced layer made of the ion exchange resin may be formed as the outermost layer. In addition, after the formation of the composite membrane, the surface of the composite membrane is not reinforced with an ion exchange resin by coating with a solution or dispersion of the ion exchange resin or by laminating a single membrane of the ion exchange resin. A layer can be formed.

  In the electrolyte membrane of the present invention, the mass fraction of the nonwoven fabric when immersed in warm water at 90 ° C. for 2 hours is preferably from 5 to 10 mass%, particularly preferably from 5 to 8 mass%. A dimensional change is suppressed by setting it as 5 mass% or more, and an electrolyte membrane with a low film | membrane resistance rise can be obtained by setting it as 10 mass% or less. The mass fraction of the nonwoven fabric when immersed in warm water at 90 ° C. for 2 hours is the ratio of the mass of the nonwoven fabric to the mass of the electrolyte membrane immersed in warm water at 90 ° C. for 2 hours.

  The method for producing an electrolyte membrane of the present invention includes a drying step for drying the electrolyte membrane for a polymer electrolyte fuel cell. In the drying step, 150 is applied by applying ethanol to the electrolyte membrane for a polymer electrolyte fuel cell. Dry at a temperature below ℃. By performing the drying, the dimensional stability of the electrolyte membrane can be improved. Further, by applying ethanol and drying it, the electrolyte membrane can be sufficiently dried even if the drying temperature of the electrolyte membrane is 150 ° C. or lower, so that thermal deterioration of the polypropylene nonwoven fabric can be avoided. The drying temperature range is preferably 110 to 150 ° C, particularly preferably 130 to 150 ° C.

  The electrolyte membrane of the present invention is used as a polymer electrolyte membrane of a membrane electrode assembly for a polymer electrolyte fuel cell. A membrane electrode assembly for a polymer electrolyte fuel cell includes a cathode and an anode having a catalyst layer containing a catalyst and an ion exchange resin, and a polymer electrolyte membrane disposed between the cathode and the anode. .

  The membrane / electrode assembly for a polymer electrolyte fuel cell can be obtained in the following manner, for example, according to a usual method. First, obtain a uniform dispersion composed of a liquid composition containing a conductive carbon black powder carrying platinum catalyst or platinum alloy catalyst fine particles and an electrolyte material, and form a gas diffusion electrode by one of the following methods: Thus, a membrane electrode assembly is obtained.

  The first method is a method in which the dispersion liquid is applied to both surfaces of the electrolyte membrane, dried, and then both surfaces are adhered to each other with two carbon cloths or carbon paper. The second method is a method in which the dispersion liquid is applied and dried on two sheets of carbon cloth or carbon paper and then sandwiched from both surfaces of the electrolyte membrane so that the surface to which the dispersion solution is applied is in close contact with the electrolyte membrane. . The third method is to apply the above dispersion on a separately prepared substrate film and dry it to form a catalyst layer, then transfer the electrode layer to both sides of the electrolyte membrane, and then add two sheets of carbon cloth or carbon paper This is a method of sticking both sides together. Here, the carbon cloth or the carbon paper has a function as a gas diffusion layer and a function as a current collector for diffusing the gas uniformly by the layer containing the catalyst.

  The obtained membrane electrode assembly is formed with a groove serving as a passage for fuel gas or oxidant gas, and is sandwiched between separators. Hydrogen gas is supplied to the anode side of the membrane electrode assembly, and oxygen is supplied to the cathode side. Or air is supplied and a polymer electrolyte fuel cell is obtained.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 3 are examples, and examples 4 to 15 are comparative examples.

[Example 1]
[Production of unreinforced layer (single layer) made of ion exchange resin]
CF ₂ = CF ₂ and _{CF 2 = CF-OCF 2 CF} (CF 3) -OCF 2 CF 2 SO 2 and F were copolymerized to obtain a precursor of a sulfonic acid type perfluorocarbon polymer. This precursor is hydrolyzed and acidified to convert it to an ion exchange resin having an ion exchange capacity of 1.1 meq / g dry resin, and then a mixture of the ion exchange resin in water and ethanol is used. A solution (solid concentration 15% by mass) as a solvent was prepared. Subsequently, a solution of cerium nitrate dissolved in distilled water is added to this solution, and a solution of a resin in which 15% of the sulfonic acid groups in the ion exchange resin are ion exchanged with Ce ³⁺ (hereinafter referred to as ion exchange resin (A)). Got. This solution is cast on a fluororesin (trade name: Film Aflex) product number 100N (thickness: 100 μm) manufactured by Asahi Glass Co., Ltd. by die coating, dried at 80 ° C. for 15 minutes, and reinforced with the above ion exchange resin (A). No monolayer was obtained.

[Production of non-woven fabric continuum]
Using polypropylene as the material, using a melt blown manufacturing apparatus manufactured by Kasei Nozzle Co., Ltd., adjusting the temperature, hot air for drawing, and flow rate as appropriate, the average fiber diameter is 2.0 μm, and the basis weight is 3.0 g / m ² . A nonwoven fabric continuous body RA1 of polypropylene was produced.

[Thickness adjustment (thickening)]
Next, using a simple laminating apparatus shown in FIG. 1 (VAII-700 manufactured by TAISEI LAMINATOR), a polypropylene nonwoven fabric continuous body RA1 (41) is placed on a commercially available continuous polyethylene terephthalate support 42 having a thickness of 100 μm. Densification was performed to obtain a continuous PET support / thickened non-woven fabric continuum RAP1 (43).

  When the thickness of the thickened nonwoven fabric RAP1 was measured with a contact-type micrometer (manufactured by Keyence Corporation: AT-005V 5 mmΦ circular Tip), the average was 9.3 μm. Note that the temperature of the metal roll 44 and the temperature of the rubber roll 45 at the time of densification are 120 ° C., and the force of the roll pressurization is 0.026 MPa / m with respect to a roll surface length of 600 mm. The speed was 0.15 m / min. The obtained temporary pressure-bonded product of continuous PET support / thickened nonwoven fabric RAP1 (43) was excellent in handling properties.

[Electrolyte film formation]
Further, the continuous PET support / thickened non-woven fabric continuous body RAP1 and the single layer are thermocompression bonded using the simple laminating apparatus of FIG. 1 (VAII-700 manufactured by TAISEI LAMINATOR), and the continuous PET support / intermediate laminated body P1 was obtained. Note that the temperature of the metal roll 44 and the temperature of the rubber roll 45 at the time of densification are 120 ° C., and the pressure of the roll pressurization is 0.026 MPa / m with respect to a roll surface length of 600 mm. The insertion speed of the laminate P1 was 0.15 m / min.

  Next, using the continuous coating system shown in FIG. 2, using the intermediate laminate P1 (51) obtained by peeling the continuous PET support from the continuous PET support / intermediate laminate P1, an ion exchange resin ( Using a solution of a mixture of A) water and ethanol solution (solid content concentration 15% by mass), coating was performed by the die coater 52 and dried in a drying furnace 53 at 80 ° C. for 20 minutes.

Thereafter, ethanol was applied to the obtained electrolyte membrane by 25 g / m ² die coat 52, and a residual solvent was dried under conditions of 140 ° C. for 30 minutes to obtain a reinforced electrolyte membrane R1. From the cross-sectional observation of the electron microscope, the total thickness of the non-reinforced layer on the surface was about 8.3 μm, and the total thickness of the reinforcing film was 15.6 μm.

[Measurement of mass fraction of nonwoven fabric and dimensional change rate when water is contained]
The mass of the electrolyte membrane R1 per unit area after the electrolyte membrane R1 was immersed in 90 ° C. ion exchange water for 2 hours was measured. From the measured mass per unit area and the basis weight of the nonwoven fabric, the mass fraction of the nonwoven fabric when immersed in ion-exchanged water at 90 ° C. for 2 hours was determined.

Further, the electrolyte membrane R1 is cut into two strips (2 cm × 10 cm) each in the vertical direction and the horizontal direction, and lines with an interval of 6 cm are drawn parallel to the short side direction. It is exposed to an atmosphere of temperature 25 ° C. and humidity 50% for 2 hours, and the length between lines is measured. Next, after immersing in ion exchange water at 90 ° C for 2 hours with one of 20 mN tension applied to one sample and 60 mN applied to the other, the length between the lines was measured in water. To do. In order to remove the influence of the tension from the sample elongation measured here, the elongation of the sample at which the tension becomes zero is calculated by the equation (1), and the average value of the elongation in the vertical direction and the elongation in the horizontal direction is obtained. Dimensional change rate.
(Elongation of tension 0N) = (elongation of tension 20 mN) − ((elongation of tension 60 mN) − (elongation of tension 20 mN)) ÷ 2 (1).

[Production and evaluation of fuel cells]
The fuel cell is assembled as follows. First, the ion exchange resin (A) is charged into a mixed solvent of ethanol and water (mass ratio of 1: 1), dissolved in a flask having a reflux function by stirring at 60 ° C. for 16 hours, and a polymer having a solid content of 9%. Obtain a solution. Next, a platinum-supported carbon is sequentially added in the order of water and ethanol to obtain a catalyst dispersion (solid content 9% by mass) dispersed in a mixed dispersion medium (1: 1 by mass) of ethanol and water. Thereafter, the polymer solution and the catalyst dispersion are mixed at a mass ratio of 4: 5 to prepare a coating solution. Next, this coating solution is applied onto an ETFE substrate by a die coating method and dried to form a catalyst layer having a thickness of 10 μm and a platinum loading of 0.2 mg / cm ² . Next, this catalyst layer is adhered to the electrolyte membrane R1 by hot pressing (temperature 130 ° C., pressure 2.6 MPa), and a carbon cloth is disposed on both outer sides as a gas diffusion layer, whereby a membrane electrode assembly is obtained. . A solid polymer fuel having an effective membrane area of 25 cm ² by disposing a carbon plate separator having zigzag cuts on the gas channel narrow grooves on both outer sides of the membrane electrode assembly, and a heater on the outer side. The battery is assembled.

The temperature of the fuel cell is maintained at 80 ° C., air is supplied to the cathode and hydrogen is supplied to the anode at 0.2 MPa, respectively, and electricity is generated at a current density of 1.0 A / cm ² for 16 hours. Next, nitrogen is supplied to the cathode and hydrogen is supplied to the anode at 0.2 MPa, respectively, and an AC applied voltage of 1 mV is swept up to a frequency of 20 kHz to 5 Hz, and impedance is measured. At this time, the cell resistance of the frequency at which the phase angle of the impedance is 0 degree is measured, and the contact resistance or the like is subtracted from this resistance value to obtain the specific resistance value of the single membrane. The results are as shown in Table 1. Note that the contact resistance or the like, the thickness is measured cell resistance _{RE 1,} RE 2, RE ₃ unreinforced membrane 15,20,25Myuemu, was calculated from equation (2).
(Contact resistance or the like) = (35RE ₁ + 5RE ₂ −25RE ₃ ) ÷ 15 (2).

[Example 2]
CF ₂ = CF ₂ and _{CF 2 = CF-OCF 2 CF} (CF 3) -OCF 2 CF 2 SO 2 F and _{CF 2 = CF-OCF 2 CF} (OCF 2 CF 2 SO 2 F) -OCF 2 CF 2 SO ₂ F was copolymerized to obtain a sulfonic acid-type perfluorocarbon polymer precursor in which the ratio of each monomer unit was 82.6 mol%, 7.8 mol%, and 9.6 mol%. This precursor is hydrolyzed and acidified to convert it into an ion exchange resin having an ion exchange capacity of 1.52 meq / g dry resin, and then a mixture of the ion exchange resin in water and ethanol is used. A solution (solid content concentration 10% by mass) as a solvent was prepared. Subsequently, a solution of cerium nitrate dissolved in distilled water is added to this solution, and a solution of a resin in which 10% of the sulfonic acid groups in the ion exchange resin are ion exchanged with Ce ³⁺ (hereinafter referred to as ion exchange resin (B)). Got.

  An electrolyte membrane R2 was produced in the same manner as in Example 1 except that instead of the ion exchange resin (A) solution, a solution of the above ion exchange resin (B) in water and ethanol was used as a solvent. . The thickness of the unreinforced layer of the electrolyte R2 was about 6.5 μm, and the total thickness of the electrolyte membrane R2 was 16.3 μm. The electrolyte membrane R2 was evaluated in the same manner as in Example 1, and the results obtained are shown in Table 1.

[Example 3]
Polypropylene is used as a material, and the melt blown manufacturing apparatus described in Example 1 is used. The temperature and flow rate of hot air for drawing are adjusted, and an average fiber diameter of 0.9 μm and a basis weight of 2.6 g / m ² A nonwoven fabric continuous body RA3 was produced.

  Instead of the polypropylene nonwoven fabric RA1, a polypropylene nonwoven fabric RA3 was used to adjust the thickness (thickening) so that the thickness of the nonwoven fabric continuum RA3 was 11.5 μm. An electrolyte membrane R3 was produced in the same manner as in Example 2 except that surface treatment was performed by corona discharge using Tantec Corp. Generator Generator HV 05-2). The thickness of the unreinforced layer of the electrolyte R3 was about 5.8 μm, and the total thickness of the electrolyte membrane R3 was 12.8 μm. The electrolyte membrane R3 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

[Example 4]
Preparation of electrolyte membrane R4 by the same method as in Example 1 except that a polyethylene porous body manufactured by Teijin DSM Soltec Co. was used instead of the polypropylene nonwoven fabric RA1, and thickness adjustment (thickening) was not performed. However, the electrolyte porous membrane R4 could not be produced because thermal deformation occurred in the polyethylene porous body during drying (temperature: 140 ° C.) during film formation.

[Example 5]
As shown in FIG. 3, a special die 32 having a flow rate adjusting structure and a heated air introduction structure is attached to a single-screw extruder 31 (L / D = 24: manufactured by Tanabe Plastic Co.) having a diameter of 30 mm, and effective at the tip thereof. Ten circular discharge ports with an inner diameter of 300 μm are linearly arranged in a width of 10 cm, and the drawing hot air 36 can be ejected from a 500 μm slit so as to apply a drawing stress to the discharging resin in parallel with the arrangement direction. A special nozzle 33 for the production of melt blown nonwoven fabric manufactured by Chemical Fiber Nozzle Co., Ltd. having a stretched air outlet 331, a perfluoro resin (trade name: Aflon PFA (MFR 40 g / 10 min)) manufactured by Asahi Glass Co., Ltd., and a die temperature of 360 ° C. The hot air for drawing 36 is ejected at a temperature of 330 ° C. at a flow rate of ³ Nm ³ / hr, and has a suction pump 381 on the drive stage 37. The stainless steel mesh (20 mesh) installed in the gas suction port on the 20 mesh stainless steel mesh 35 installed in the air suction device 38 is continuously driven in one direction at a speed of 6 m / min. A nonwoven fabric A1 (34) having an average fiber diameter of 3.5 μm and a basis weight of 1.6 g / m ² was formed. However, the formed nonwoven fabric had variations in fiber diameter, and the yield for obtaining a nonwoven fabric having a desired fiber diameter was 50%. This is lower than the yield of 80% for obtaining a polypropylene nonwoven fabric having the same fiber diameter of 2.6 μm. Nonwoven fabric A1 could be wound around a paper tube having an inner diameter of 3 inches and a thickness of 7 mm to obtain a nonwoven fabric continuous body RA5 having a length of 3 m.

  Using the PFA nonwoven fabric continuum RA5 instead of the polypropylene nonwoven fabric continuity RA1 and adjusting the thickness (thickening) to 11.5 μm, using the corona discharge treatment machine described in Example 3 An electrolyte membrane R6 was produced in the same manner as in Example 2 except that the surface treatment was performed by corona discharge. The thickness of the unreinforced layer of the electrolyte R6 was about 6.2 μm, and the total thickness of the electrolyte membrane R6 was 16.9 μm. The electrolyte membrane R3 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

[Example 6]
Using a single-screw extruder described in Example 5, a special die, and a special nozzle for manufacturing a melt blown nonwoven fabric, ETFE fluororesin (trade name: Aflon COP (MFR 40 g / 10 min)) manufactured by Asahi Glass Co., Ltd., and die temperature 360 The average fiber diameter is 5 μm and the weight per unit area is 1.5 g on a stainless mesh (20 mesh) which is jetted at a flow rate of ³ Nm ³ / hr at a temperature of 330 ° C. at a temperature of 330 ° C. Although an attempt was made to produce a nonwoven fabric continuum RA6 of / m ² , the fibers could not be produced because the fibers were easily cut and the fibers could not be stably formed.

[Example 7]
Polypropylene having a mean fiber diameter of less than 0.01 μm and a basis weight of 4.0 g / m ² by using polypropylene as a material and adjusting the temperature and flow rate of hot air for drawing using the melt blown manufacturing apparatus described in Example 1. An attempt was made to produce a nonwoven fabric continuum RA7. However, even if the fibers were formed, the efficiency of accumulation on the collector was low, and many scattered in the surrounding space. Part of the material collected on the collector was collected as a cloth-like continuous body. However, the bond between the fibers was weak, and the cloth-like continuous body could not be recovered, and the nonwoven fabric continuous body RA7 could not be produced.

[Example 8]
Polypropylene is used as a material, and the melt blown manufacturing apparatus described in Example 1 is used. The temperature and flow rate of hot air for drawing are adjusted, and the average fiber diameter is 6.5 μm and the weight per unit area is 4.0 g / m ² . Although an attempt was made to produce the nonwoven fabric continuous body RA8, the number of fibers was small, and the adhesion between the fibers was weak, so that the nonwoven fabric continuous body RA8 could not be produced.

[Example 9]
Polypropylene is used as a material, and the melt blown manufacturing apparatus described in Example 1 is used. The temperature and flow rate of hot air for drawing are adjusted, and an average fiber diameter of 0.9 μm and a basis weight of 0.9 g / m ² Although an attempt was made to produce the nonwoven fabric continuous body RA9, the number of fibers was small and the adhesion between the fibers was weak, and the nonwoven fabric continuous body RA9 could not be wound up as a cloth-like continuous body between 3 inch papers. could not.

[Example 10]
Polypropylene is used as a material, and the melt blown production apparatus described in Example 1 is used. The temperature and flow rate of hot air for stretching are adjusted, and a nonwoven fabric continuous with an average fiber diameter of 2 μm and a basis weight of 5.11 g / m ^2. A body RA10 was produced.

  An electrolyte membrane R10 was produced in the same manner as in Example 1 except that a polypropylene nonwoven fabric continuum RA10 was used in place of the polypropylene nonwoven fabric continuum RA1 and the thickness was adjusted (thickened) to 13 μm. did. The thickness of the unreinforced layer of the electrolyte R10 was about 7.8 μm, and the total thickness of the electrolyte membrane R10 was 18.8 μm. The electrolyte membrane R10 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

[Example 11]
Polypropylene non-woven fabric continuum RA11 having an average fiber diameter of 2 μm and a basis weight of 4 g / m ² using polypropylene as a material and adjusting the temperature and flow rate of hot air for drawing using the melt blown manufacturing apparatus described in Example 1. Was made.

  An electrolyte membrane R11 was produced in the same manner as in Example 1 except that the polypropylene nonwoven fabric continuum RA11 was used instead of the polypropylene nonwoven fabric continuum RA1 and the thickness was adjusted (thickened) to 13 μm. did. The thickness of the unreinforced layer of the electrolyte R11 was about 14.0 μm, and the total thickness of the electrolyte membrane R11 was 21.0 μm. The electrolyte membrane R11 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

[Example 12]
An electrolyte membrane R12 was produced in the same manner as in Example 2, except that the corona discharge treatment machine described in Example 3 was subjected to surface treatment by corona discharge after thickness adjustment (thickening). The thickness of the unreinforced layer of the electrolyte R12 was about 10.4 μm, and the total thickness of the electrolyte membrane R12 was 15.7 μm. The electrolyte membrane R12 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

[Example 13]
Polypropylene is used as the material, and the melt blown manufacturing apparatus described in Example 1 is used. The temperature and flow rate of hot air for drawing are adjusted, and the nonwoven fabric continuous with an average fiber diameter of 2 μm and a basis weight of 2.6 g / m ² is used. Body RA13 was produced.

  Instead of the polypropylene nonwoven fabric RA1, the polypropylene nonwoven fabric RA13 was used to adjust the thickness (thickening) so that the nonwoven fabric had a thickness of 8.5 μm, and then the corona discharge treatment machine described in Example 3 was used. An electrolyte membrane R13 was produced in the same manner as in Example 1 except that the surface treatment was performed by corona discharge and the thickness of the single membrane was adjusted. The thickness of the unreinforced layer of the electrolyte R13 was less than 1.0 μm, and the total thickness of the electrolyte membrane R13 was 8.6 μm. Regarding the electrolyte membrane R13, a fuel cell was produced and evaluated in the same manner as in Example 1. However, since the hydrogen cross leak was large and power generation could not be performed, the evaluation could not be performed.

[Example 14]
A solution (solid content concentration 15%) of a mixture of water and ethanol of ion exchange resin (A) as a solvent is applied onto Aflex (trade name) manufactured by Asahi Glass Co., Ltd. by die coating, dried at 80 ° C. for 20 minutes, A single membrane made of an ion exchange resin (A) having a thickness of 25 μm was obtained. Ethanol was applied to the single membrane at 25 g / m ^{2 and} dried at 140 ° C. for 30 minutes to obtain an electrolyte membrane 14. The electrolyte membrane R14 was evaluated in the same manner as in Example 1, and the results obtained are shown in Table 1.

[Example 15]
A solution (solid content concentration: 10%) of a mixture of water and ethanol of ion exchange resin (B) as a solvent is applied onto Aflex (trade name) manufactured by Asahi Glass Co., Ltd., and dried at 80 ° C. for 20 minutes. A single membrane made of ion exchange resin (B) having a thickness of 25 μm was obtained. Ethanol was applied to the single membrane at 25 g / m ^{2 and} dried at 140 ° C. for 30 minutes to obtain an electrolyte membrane R15. The electrolyte membrane R15 was evaluated in the same manner as in Example 1, and the results obtained are shown in Table 1.

  According to the present invention, an electrolyte membrane having excellent dimensional stability when containing water and having low resistance can be obtained with high productivity using an inexpensive material, so that the cost is low. The membrane electrode assembly obtained using this electrolyte membrane has a high output, excellent stability and low cost, and a solid polymer fuel cell having high power generation performance and durability can be obtained.

It is the continuous processing apparatus schematic of nonwoven fabric thickening and PET temporary pressure bonding. 1 is a schematic diagram of a continuous coating system for manufacturing a reinforced electrolyte membrane. FIG. It is an extrusion system schematic diagram used with a melt blown nonwoven fabric manufacturing device.

Explanation of symbols

31: Single screw extruder 32: Special die 33: Melt blown nonwoven fabric manufacturing method special nozzle 34: Nonwoven fabric A1
35: Stainless steel mesh 36: Hot air for stretching 37: Drive stage 38: Air suction device 39: Excess resin outlet 41: Non-woven fabric continuum RA1
42: Continuous PET support 43: Continuous PET support / thickened non-woven fabric RAP1
44, 54: Metal roll 45, 55: Rubber roll 51: Intermediate laminate P1
52: Die coater 53: Drying furnace

Claims (4)

An electrolyte membrane for a polymer electrolyte fuel cell mainly composed of an ion exchange resin reinforced with a nonwoven fabric,
The nonwoven fabric is made of polypropylene fibers having an average fiber diameter of 0.01 to 6 μm, and the basis weight is 1.0 to 4.0 g / m ² .
As an outermost layer on one or both sides, it has an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin,
The electrolyte membrane for a polymer electrolyte fuel cell, wherein the total thickness of the unreinforced layers is 2 to 10 μm, and the thickness of the entire electrolyte membrane for a polymer electrolyte fuel cell is 10 to 20 μm.   2. The electrolyte membrane for a polymer electrolyte fuel cell according to claim 1, wherein the nonwoven fabric has a mass fraction of 5 to 10 mass% when immersed in warm water of 90 ° C. for 2 hours. A method for producing an electrolyte membrane for a polymer electrolyte fuel cell, comprising:
The electrolyte membrane for a polymer electrolyte fuel cell is made of polypropylene fibers having an average fiber diameter of 0.01 to 6 μm and reinforced with a nonwoven fabric having a basis weight of 1.0 to 4.0 g / m ^2. Is an electrolyte membrane for a polymer electrolyte fuel cell mainly composed of a non-reinforcing layer made of an ion exchange resin that may be the same as or different from the ion exchange resin as an outermost layer on one or both sides, The total thickness of the unreinforced layer is 2 to 10 μm, and the total thickness of the electrolyte membrane for a polymer electrolyte fuel cell is 10 to 20 μm,
A drying step of drying the electrolyte membrane for a polymer electrolyte fuel cell, wherein the drying step is performed by applying ethanol to the electrolyte membrane for a polymer electrolyte fuel cell and drying at 150 ° C. or lower. A method for producing an electrolyte membrane for a polymer electrolyte fuel cell.   In a membrane electrode assembly for a polymer electrolyte fuel cell, comprising: a cathode and an anode having a catalyst layer containing a catalyst and an ion exchange resin; and a polymer electrolyte membrane disposed between the cathode and the anode. 3. The membrane electrode assembly for a polymer electrolyte fuel cell, wherein the polymer electrolyte membrane comprises the electrolyte membrane for a polymer electrolyte fuel cell according to claim 1 or 2.

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