JP2006040631A - Polymer electrolyte membrane and polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte membrane enhancing mechanical strength and dimension stability and to provide a polymer electrolyte fuel cell using the polymer electrolyte membrane. <P>SOLUTION: The polymer electrolyte membrane is equipped with a reinforcement layer 2 having first ion exchange resin and a reinforcement 5 and irregularity 5b formed on at least one surface 5a and an ion exchange resin layer 3 formed on the surface 5a on which the irregularity 5b is formed so as to cover the irregularity 5b and having second ion exchange resin, the reinforcement layer 2 has a plurality of through holes 4 formed in substantially the direction perpendicular to the surface 5a, and the first ion exchange resin is filled in the through holes 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polymer electrolyte membrane used for a polymer electrolyte fuel cell.

  A fuel cell using a polymer electrolyte generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidizing gas containing oxygen such as air.

  The structure is made by first using a carbon powder carrying a metal catalyst such as platinum as a catalyst on both sides of a polymer electrolyte membrane that selectively transports hydrogen ions, and then mixing this with a hydrogen ion conductive polymer electrolyte. To form a catalytic reaction layer.

  On the other hand, a water-repellent carbon layer composed of conductive carbon having both air permeability and fuel conductivity is formed on a gas diffusion layer substrate such as carbon paper. The electrode obtained by joining the hydrogen ion conductive polymer electrolyte membrane having the catalyst reaction layer and the gas diffusion layer base material is referred to as a polymer electrolyte fuel cell electrode (MEA).

  In general, the polymer electrolyte membrane has a thickness of about 20 to 120 μm, and a cation exchange membrane made of a perfluorocarbon polymer having a chemically stable sulfonic acid is often used. However, the mechanical strength is not sufficient, and wrinkles, breakage, etc. occur during MEA fabrication. Furthermore, at the time of power generation, sufficient moisture is necessary for the ionic conductivity of the polymer electrolyte to be exhibited, and therefore, the fuel and the oxidizing gas are humidified and supplied. The polymer electrolyte contained water due to the moisture and water produced by the humidification, and the dimensions changed depending on the moisture content, and the reliability of the battery was not always sufficient. Therefore, development of a polymer electrolyte membrane having sufficient mechanical strength, chemical stability, and dimensional stability is being promoted.

  As a method for solving the above problems, a method using a reinforcing material has been reported. For example, a polymer electrolyte membrane in which a polytetrafluoroethylene porous membrane is used as a reinforcing material and impregnated with a polymer electrolyte having a sulfonic acid group has been proposed (see, for example, Patent Document 1).

  In addition, a polymer electrolyte membrane reinforced with a fibril-like, woven-like, or non-woven-like perfluorocarbon polymer has been proposed (see, for example, Patent Document 2). By using this reinforcement, an improvement in mechanical strength was observed.

  However, as described above, the dimensional stability at the time of hydration is not sufficient although it is due to the effect of suppressing the stress that the polymer electrolyte stretches by the reinforcing material.

  Although the frequency of the fuel cell varies depending on the actual power generation mode, it repeatedly starts and stops and the output fluctuates. At this time, the amount of moisture contained as humidification in the fuel and the oxidizing gas and the amount of moisture generated by power generation change. When the dimensional stability due to the water content is low, the reinforcing part is peeled off due to the sticking / shrinking of the polymer electrolyte part in the polymer electrolyte film, which leads to damage of the polymer electrolyte film. That is, the binding property between the reinforcing material and the polymer electrolyte is important.

On the other hand, the method of improving the permeability of the polymer electrolyte solution by hydrophilizing the reinforcing material (for example, see Patent Document 3), and conversely, the contact angle of the polymer electrolyte solution with respect to the reinforcing material is increased. A method for adjusting and increasing the penetrating power (for example, see Patent Document 4) has been reported.
Japanese Patent Publication No. 05-75835 Japanese Patent Publication No. 06-231799 Japanese Patent Laid-Open No. 06-271688 JP 2003-41031 A

  However, none of the above methods has been sufficient to improve the binding properties of the polymer electrolyte and the reinforcing material. For this reason, mechanical strength and dimensional stability are reduced, which is one factor for accelerating the deterioration of the polymer electrolyte membrane when the fuel cell is repeatedly started and stopped.

  In view of the above conventional problems, an object of the present invention is to provide a polymer electrolyte membrane with improved mechanical strength and dimensional stability and a polymer electrolyte fuel cell using the same.

In order to achieve the above object, the first present invention provides:
A reinforcing material layer having a first ion exchange resin and a reinforcing material, wherein at least one surface has irregularities;
It is a polymer electrolyte membrane provided with the ion exchange resin layer which has the 2nd ion exchange resin formed in the surface in which the said unevenness | corrugation was formed so that the said unevenness | corrugation might be covered.

The second aspect of the present invention is
The reinforcing material has a plurality of through holes formed in a direction substantially perpendicular to the surface, and the first ion exchange resin is filled in the through holes. It is a polymer electrolyte membrane.

The third aspect of the present invention
The first ion exchange resin and the second ion exchange resin are the polymer electrolyte membrane according to the first aspect of the present invention, which is the same ion exchange resin.

The fourth aspect of the present invention is
The said unevenness | corrugation is a polymer electrolyte membrane of 1st this invention which is an unevenness | corrugation formed by 1 or more types of physical surface treatments selected from a blast process, a plasma etching process, a corona discharge process, and a flame process. .

The fifth aspect of the present invention is
The arithmetic average roughness (Ra) of the surface on which the irregularities are formed is the polymer electrolyte membrane according to the first aspect of the present invention, which is 1 μm or more and 5 μm or less.

The sixth aspect of the present invention
The thickness of the reinforcing material layer is the polymer electrolyte membrane according to the first aspect of the present invention, which is 10 μm or more and 20 μm or less.

The seventh aspect of the present invention
In the polymer electrolyte membrane according to the second aspect of the present invention, the opening ratio of the through holes with respect to the surface is 30% or more and 80% or less.

Further, the eighth aspect of the present invention is
The average cross-sectional area per one of said through holes, 0.03 mm ² or more and 1 mm ² or less, a polymer electrolyte membrane of the second aspect of the present invention.

The ninth aspect of the present invention provides
The reinforcing material layer has the irregularities on both sides,
The ion exchange resin layer is formed on both sides of the reinforcing material layer,
The reinforcing material layer and the ion exchange resin layer are the polymer electrolyte membrane according to the first aspect of the present invention, wherein 3 or more and 7 or less layers are laminated.

The tenth aspect of the present invention is
The reinforcing material layer and the ion exchange resin layer are laminated in a plurality of layers,
At least the reinforcing material layer is two or more layers,
The plurality of through holes formed in each of the adjacent reinforcing material layers is the polymer electrolyte membrane according to the second aspect of the present invention formed so that the centers do not coincide with each other.

The eleventh aspect of the present invention is
Any one of the first to tenth polymer electrolyte membranes of the present invention;
A pair of gas diffusion electrodes formed on both sides of the polymer electrolyte membrane;
A polymer electrolyte fuel cell comprising a plurality of stacked unit cells having a pair of separators provided so as to sandwich the pair of gas diffusion electrodes from both sides.

  According to the present invention, it is possible to provide a polymer electrolyte membrane with improved mechanical strength and dimensional stability and a polymer electrolyte fuel cell using the same.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1A is a perspective view of the polymer electrolyte membrane according to the first embodiment. FIG. 1B is a cross-sectional view of the polymer electrolyte membrane shown in FIG.

  As shown in FIGS. 1 (a) and 1 (b), a polymer electrolyte membrane 1 in Embodiment 1 includes a reinforcing material layer 2, and a polymer electrolyte layer 3 formed so as to sandwich the reinforcing material layer 2. It has. An example of the ion exchange resin layer of the present invention corresponds to the polymer electrolyte layer 3, and an example of the second ion exchange resin of the present invention corresponds to the polymer electrolyte included in the polymer electrolyte layer 3. The polymer electrolyte layer 3 improves ionic conductivity.

  Further, the reinforcing material layer 2 is penetrated substantially perpendicularly (in parallel with the laminating direction) to the surface in contact with the polymer electrolyte layer 3, and the reinforcing material 5 having a large number of through holes 4 is formed. And a polymer electrolyte which is an example of the first ion exchange resin of the present invention filled in the holes 4. As a method for obtaining the reinforcing material 5 having a large number of through-holes 4, a punching die or the like is used to mechanically punch a non-porous sheet serving as a base material, or a laser beam is used to form holes. There is a method of forming. The type of polymer electrolyte in the polymer electrolyte layer 3 and the polymer electrolyte in the through-hole 4 may be the same or different.

  The surface 5a of the reinforcing material 5 in contact with the polymer electrolyte layer 3 is subjected to one or more types of physical surface treatments.

  Examples of the physical surface treatment method include blast treatment, plasma etching treatment, corona discharge treatment, flame treatment, and the like. Blasting is an industrially established technique that can control the roughness imparted to the surface of the object to be treated by the media used. Furthermore, in recent years, treatment with ice or dry ice in which no medium remains has been developed, and physical surface treatment may be performed using these methods.

  As shown in FIG. 1B, the unevenness 5b is given to the surface 5a of the reinforcing material 5 subjected to the physical surface treatment. FIG. 2A is an enlarged view of a boundary portion between the polymer electrolyte layer 3 and the reinforcing agent layer 2. As shown in FIG. 2A, the polymer electrolyte layer 3 formed on the surface 5a is formed so as to completely cover the unevenness 5b. For example, as shown in FIG. 2 (b), if there is a portion where the unevenness 5b is not covered, the reinforcing material 5 and the polymer electrolyte peel from each other while the start and stop and the output fluctuation are repeated, and the electrical Short circuit and gas permeability may be increased.

  A carbon carrier carrying a catalyst metal on both sides of the polymer electrolyte membrane 1 having the reinforcing material layer 2 and the polymer electrolyte layer 3 and a catalyst in which an ion conductive polymer electrolyte is mixed and attached to the carbon carrier. The layers are brought into close contact to produce a membrane electrode structure. Then, a polymer electrolyte fuel cell is manufactured using this membrane electrode structure.

  As described above, the surface 5a of the reinforcing material 5 subjected to the physical surface treatment is given a surface roughness on the order of micrometers, and the surface area in contact with the ion conductive polymer electrolyte layer 3 is increased. An anchor effect is exhibited by increasing the contact area between the reinforcing material layer 2 and the polymer electrolyte layer 3, and an improvement in the binding property between the reinforcing material 5 and the polymer electrolyte is expected. This improvement in binding properties leads to an improvement in dimensional stability of the polymer electrolyte membrane 1. Thereby, the deterioration of the polymer electrolyte membrane due to the start / stop of the fuel cell and the output change is reduced, and a solid polymer electrolyte fuel cell capable of realizing a long-term stable output can be provided.

  The increase in the surface area of the reinforcing material layer 2 imparted to the reinforcing material layer 2 by the physical surface treatment is preferably 1 μm or more and 5 μm or less in terms of the arithmetic average roughness of the surface irregularities 5b. When a surface roughness greater than 5 μm is applied, as described above, it becomes a factor for deterioration of the polymer electrolyte membrane during battery operation. Furthermore, the catalyst layer may be damaged at the time of fastening. On the other hand, when the lower limit value is 1 μm or less, since the unevenness 5b is small, the anchor effect cannot be sufficiently obtained, and the mechanical strength and the dimensional stability are not sufficient.

  The thickness of the reinforcing material layer 2 is desirably 10 μm to 20 μm. If the thickness of the reinforcing material layer 2 is too thin, the polymer electrolyte membrane cannot be sufficiently reinforced, and if it is too thick, the ion conduction resistance becomes high, and there is a possibility that sufficient battery output cannot be obtained. Furthermore, if it is too thin, sufficient strength may not be obtained.

  Moreover, it is desirable that the opening ratio of the portion having the through hole 4 with respect to the surface of the reinforcing material layer 2 is 30% or more and 80% or less. If the aperture ratio is too low, the ion conductivity is hindered, and if it is too high, the resulting polymer electrolyte membrane cannot be sufficiently reinforced, resulting in insufficient mechanical strength.

Furthermore, one of the average cross-sectional area of the plurality of through holes 4 is 0.03 mm ² or more is desirably 1 mm ² or less. If the size of the through-holes 4 is too small, the number of holes per unit area becomes very large, so that the productivity of the porous sheet used as the reinforcing material 5 is reduced, and it is difficult to fill the ion-exchange resin. On the other hand, if the size of the through hole 4 is too large, the obtained polymer electrolyte membrane cannot be sufficiently reinforced and the mechanical strength becomes insufficient. The size and shape of the through-hole 4 may be uniform or non-uniform, and two or more types and sizes may be mixed.

  In the first embodiment, the configuration in which the polymer electrolyte layer 3 is formed on both surfaces of the reinforcing material layer 2 is shown. However, as shown in FIG. 3, only one surface of the reinforcing material 5 is subjected to physical surface treatment. Alternatively, a two-layer structure in which the polymer electrolyte layer 3 is formed only on the treated surface may be used.

  Further, the reinforcing material layer 2 and the polymer electrolyte layer 3 mainly including the polymer electrolyte may be laminated more than the three layers shown in FIGS. 1A and 1B of the first embodiment. good. When three or more layers are laminated, it is more desirable that the polymer electrolyte layer 3 is formed on both surfaces of the reinforcing material layer 2. In the case where eight or more layers are laminated, at least four or more layers are composed of layers including a reinforcing material, so that the production process becomes complicated and the productivity is lowered. Furthermore, in order to suppress an increase in electrical resistance due to lamination, it is necessary to make the thickness of each layer thinner, making control and handling difficult. Therefore, when the reinforcing material layer 2 and the polymer electrolyte layer 3 are laminated, 3 to 7 layers are desirable.

  In this case, the reinforcing material layer 2 and the polymer electrolyte layer 3 may overlap with each other or may overlap with each other through a layer made of only the polymer electrolyte layer 3. Moreover, when the reinforcing material layer 2 is two or more layers, it is desirable that the center of the through hole 4 does not overlap with the center of the through hole 4 of the layer existing above or below the thickness direction. This is because the case where they do not overlap leads to improvement in the mechanical strength of the obtained polymer electrolyte membrane.

  Hereinafter, the polymer electrolyte membrane of the present invention will be described more specifically in Examples.

Example 1
First, through a 15 μm thick polyphenyl sulfide film (manufactured by Toray Industries, Inc.) with a punching machine, φ400 μm through holes (average cross-sectional area of 0.126 mm ² per piece) are arranged in a staggered arrangement so that the center-to-center distance is 500 μm. Open a hole. The produced porous sheet is used as a reinforcing material. The aperture ratio of the porous sheet reinforcing material is 58%.

  A blast treatment (SFK-1 type, Fuji Seisakusho) was applied to the reinforcing material 5 as a physical surface treatment. As a blasting method, an air-blasting method capable of efficiently injecting even a fine abrasive was adopted, and silicon carbide alumina was used as the abrasive. The particle size range of silicon carbide alumina was 2.5 to 3.5 μm.

  Next, the reinforcing material 5 subjected to physical surface treatment is placed on a PET substrate having a thickness of 100 μm, and an ion conductive polymer electrolyte ethanol dispersion is applied by a die coating method so that the total thickness becomes 25 μm. Dry at 0C.

  The die coating method is a coating method in which an object to be coated is fixed on a horizontal table and a liquid coating material is applied by a die head.

  The obtained film was peeled from the PET base material, the front and back sides were reversed, and placed on a separately prepared PET base material. Similarly, the dispersion was applied by a die coating method to a total thickness of 35 μm and dried at 80 ° C. The polymer electrolyte membrane 1 has a 10 μm-thick polymer electrolyte layer 3 made of only a polymer electrolyte on both sides of a reinforcing material 5 subjected to the above surface physical treatment and a 15 μm-thick reinforcing material layer 2 made of a polymer electrolyte. Has a laminated structure.

  Next, production of MEA and assembly of a fuel cell (unit cell) were performed as follows.

  Ketjen Black (registered trademark) EC (AKZO Chemie, Netherlands) carrying 50% by weight of platinum particles having an average particle diameter of about 30 mm was used as catalyst-carrying particles on the air electrode side. On the other hand, 25 wt% platinum particles and ruthenium particles having an average particle size of about 30 mm were supported on Ketjen Black EC as catalyst-supported particles on the fuel electrode side.

  Water was first added to the catalyst-carrying particles, and then an ethanol dispersion of hydrogen ion conductive polymer electrolyte (Flemion manufactured by Asahi Glass Co., Ltd.) was mixed and stirred to coat the surface of the catalyst-carrying particles with the electrolyte. Here, as the hydrogen ion conductive polymer, an ethanol dispersion of 9% by weight perfluorocarbon sulfonic acid was used. Further, the introduction amount of the hydrogen ion conductive polymer electrolyte was added so that both the cathode and the anode ink were 80% by weight with respect to the weight of the carbon carrying the catalyst. Then, the catalyst ink was directly applied to the polymer electrolyte membrane 1 by a spraying process of spraying the catalyst ink into the air.

  Next, a water repellent treatment was applied to the carbon nonwoven fabric that will be the gas diffusion layer of the electrode. After impregnating a carbon nonwoven fabric (TGP-H-90, manufactured by Toray Industries, Inc., conductive carbon particles) having an outer size of 16 cm × 20 cm and a thickness of 270 μm into an aqueous dispersion containing fluororesin (manufactured by Daikin Industries, NEOFLON ND1), It was dried and heated at 350 ° C. for 30 minutes to give water repellency.

Furthermore, a water-repellent carbon layer was formed on one surface of the carbon nonwoven fabric by applying an ink obtained by mixing a conductive carbon powder and an aqueous solution in which PTFE fine powder was dispersed using a screen printing method. This carbon nonwoven fabric was joined by hot pressing so that the surface coated with the water repellent layer was in contact with the catalyst layer side, and this was used as MEA. The hot pressing was performed at a pressure of 10 kgfcm ⁻² and a temperature of 120 ° C. for 1 minute.

  Further, the MEA was sandwiched between two separators composed of a resin-impregnated graphite plate, and this was used as a unit cell.

  The fuel cell is maintained at 70 ° C., and heated and humidified hydrogen gas and air are supplied to the anode and cathode so that the dew points are 64 ° C. and 70 ° C., respectively. The rate was set at 40%.

(Example 2)
The same reinforcing material 5 as in Example 1 was subjected to oxygen plasma treatment as a physical surface treatment of the reinforcing material. A plasma etching apparatus (SAMCO, BP-1) was used, and the process was performed for 1 minute at an oxygen pressure of 20 Pa and an output of 150 W. Other conditions for producing the polymer electrolyte membrane are the same as in Example 1.

(Comparative Example 1)
In contrast to Example 1, the porous sheet as the reinforcing material 5 was used without being subjected to physical surface treatment. Other conditions for producing the polymer electrolyte membrane are the same as in Example 1.

  Table 1 shows the surface roughness of the reinforcing material 5. The unevenness of the surface of the reinforcing material after the surface treatment was measured with a surface roughness meter (Mitutoyo, Surf Test SV-9634), and the arithmetic average roughness (Ra) was calculated and compared. (Table 1) shows that the surface roughness of the reinforcing material 5 of Comparative Example 1 that is not subjected to physical treatment is 0.9 μm, whereas the reinforcing material of Example 1 that has been sandblasted is 2.3 μm, oxygen plasma treatment. In the reinforcing material 5 of Example 2 subjected to the above, the thickness was 2.5 μm. In any physical surface treatment, the surface roughness of the reinforcing material 5 increased and the contact area with the polymer electrolyte layer 3 increased.

又、（表２）に引張弾性率および寸法変化率を併せて示す。まず、高分子電解質膜１を幅、長さともに１００ｍｍに切り出し、標線間距離２５ｍｍ、チェック間距離５０ｍｍとなるようにし、試験速度５０ｍｍ／分にて引張試験を行い、得られた変位と荷重のチャートから初期１０％の歪の傾きを求め、その傾きより引張弾性率を求めた。引張弾性率の増加は高分子電解質膜の機械的強度の増加を意味する。

Table 2 also shows the tensile modulus and dimensional change rate. First, the polymer electrolyte membrane 1 is cut out to 100 mm in both width and length, the distance between marked lines is 25 mm, the distance between checks is 50 mm, a tensile test is performed at a test speed of 50 mm / min, and the obtained displacement and load are obtained. The initial 10% strain slope was determined from the chart, and the tensile modulus was determined from the slope. An increase in tensile modulus means an increase in the mechanical strength of the polymer electrolyte membrane.

  Next, the dimensional change rate was calculated as follows. The polymer electrolyte membrane 1 was immersed for 12 hours in warm water at 70 ° C., which is equal to the temperature of the stack portion during actual operation of the fuel cell. The dimensions before and after immersion in hot water were measured, and the dimensional change rate was measured. A small dimensional change rate is rich in dimensional stability during actual operation of the fuel cell and is expected to improve durability.

（表２）より実施例１および２ともに、比較例１に対して、引張弾性率は大きく、寸法変化率は小さく算出された。これより、補強材表面処理によるアンカー効果により、高分子電解質との結着性が向上していることが分かる。また、表面処理の方法によらず、アンカー効果による結着性の向上は確認された。

From Table 2, in both Examples 1 and 2, the tensile modulus was large and the dimensional change rate was small compared to Comparative Example 1. From this, it can be seen that the binding effect with the polymer electrolyte is improved by the anchor effect by the reinforcing material surface treatment. Further, it was confirmed that the binding property was improved by the anchor effect regardless of the surface treatment method.

  FIG. 4 shows the effect of surface treatment on actual fuel cell operation. When used as a household fuel cell, the startup time is estimated to be about 12 hours per day. Therefore, in this experiment, the start time and the stop time were set to 30 minutes, respectively, and this was repeated, and the change in the battery voltage at the start and the hydrogen gas permeation amount at the stop were measured.

  As for the hydrogen gas permeation amount, the amount of hydrogen gas contained in the cathode exhaust gas when the battery operation was stopped was detected by gas chromatography. In Example 1 using the porous sheet, which is the reinforcing material 5 subjected to physical treatment, even if the start and stop are repeated, the decrease in the battery voltage and the increase in the gas permeation amount are small, and the polymer electrolyte membrane 1 is not deteriorated. It was suggested that it was not progressing.

  As described above, the physical surface treatment for the reinforcing material 5 increases the contact area between the reinforcing material 5 and the polymer electrolyte, and the ion-exchange resin is impregnated into the irregularities on the surface of the reinforcing material 5, whereby the ion conductive polymer electrolyte is obtained. It was suggested that the mechanical strength and dimensional stability required for the polymer electrolyte membrane were improved by increasing the binding property with the polymer electrolyte membrane. Moreover, it was confirmed that this improvement in dimensional stability leads to improvement in durability even in actual operation of the polymer electrolyte membrane fuel cell.

(Example 3)
The physical treatment was applied to Example 1 so that the surface roughness of the surface 5a of the reinforcing material 5 was different. Air-blast treatment was selected as the surface treatment method. In order to change the surface roughness, the particle size distribution of the particle size distribution of silicon carbide alumina as an abrasive is 2.5 to 3.5 μm, 4.7 to 5.9 μm, 5.9 to 7.1 μm, 7.1 Four types of ˜8.9 μm were selected and used.

  Other methods for producing the polymer electrolyte membrane are the same as in Example 1.

  FIG. 5 is a graph in which Ra of the reinforcing material 5 produced in Example 3 is taken on the horizontal axis, and the gas permeation amount at 1000 hours when the same start / stop test as in Example 1 is conducted is taken on the vertical axis. is there. In addition, since the gas permeation amount was measured and plotted for four types of different reinforcing materials of Ra produced by the abrasives having the respective particle size distribution widths, FIG. 5 shows data with a total of 16 types of different Ra values. It is shown.

  From the result of FIG. 5, when the surface unevenness 5b imparted by the surface treatment is larger than 5 μm in Ra, the gas permeation amount suddenly increases from 100 ppm to 200 ppm, and the unevenness 5b exceeding 5 μm starts and stops. It can be seen that the deterioration of the polymer electrolyte membrane 1 is advancing while repeating the above.

  Further, the surface roughness of the reinforcing material itself (when physical surface treatment is not performed) is 0.1 μm or more and less than 1 μm in the material of the third embodiment. Here, the white circles in FIG. 5 indicate the hydrogen leak amount at 1000 hours in Comparative Example 1 (Ra is 0.9 μm) (see FIG. 4). FIG. 5 shows that when Ra is less than 1 μm, the polymer electrolyte membrane is deteriorated and the anchor effect does not occur.

  From the above, it is desirable that the surface unevenness 5b imparted to the reinforcing material 5 by physical treatment is 1 μm or more and 5 μm or less in terms of Ra.

Example 4
A porous sheet having a diameter and a mean cross-sectional area of the through-hole 4 subjected to physical surface treatment as compared with Example 1 was used as the reinforcing material 5. The diameter and average cross-sectional area of the through-hole 4 were changed in eight ways as shown in (Table 3). In any porous sheet, the distance between the centers of the pores was adjusted so that the aperture ratio was 58%, which was the same as in Example 1. The physical surface treatment and the method for producing the polymer electrolyte membrane are the same as in Example 1.

（表３）に機械的強度の指標である引張弾性率および実運転時の内部電気抵抗を示す。内部電気抵抗は、主に高分子電解質膜のイオン伝導性に依存する。イオン伝導性が低いほど、抵抗値は大きくなり、電池電圧の低下につながる。平均断面積が０．０３ｍｍ^２より小さい場合は電気抵抗が上昇し、１ｍｍ^２より大きい場合は引張弾性率が減少していることが分かる。また、０．０３ｍｍ^２より小さい、平均断面積が０．０２５４ｍｍ^２（貫通孔直径１８０μｍ）の場合の貫通孔数は、実施例１の０．１２６ｍｍ^２の孔数の５倍必要であり、生産時間も５倍長くなる。

Table 3 shows the tensile modulus as an index of mechanical strength and the internal electrical resistance during actual operation. The internal electrical resistance mainly depends on the ionic conductivity of the polymer electrolyte membrane. The lower the ionic conductivity, the higher the resistance value, leading to a decrease in battery voltage. The average cross-sectional area 0.03 mm ² electrical resistance increases if less, it can be seen that 1 mm ² greater than the tensile modulus of elasticity is decreased. Further, the number of through holes in the case where the average cross-sectional area is smaller than 0.03 mm ² and the average cross-sectional area is 0.0254 mm ² (through hole diameter 180 μm) is required to be five times the number of holes of 0.126 mm ² in Example 1, and production Time is also 5 times longer.

From the above, the average cross-sectional area 0.03 mm ² or more is desirably 1 mm ² or less.

In the present embodiment, the determination is rejected for those having a tensile elastic modulus of 50 kgfmm ⁻² or less and an internal resistance of 100 mΩcm ⁻² or more. This is because the polymer electrolyte membrane swells and contracts during start-stop operation durability when the tensile modulus is less than or equal to the judgment value, and the battery voltage decreases when the internal electrical resistance value is greater than or equal to the judgment value. This is because. Note that this determination value may be appropriately changed depending on the fuel cell to be manufactured.

(Example 5)
A porous sheet having a different thickness and subjected to a physical surface treatment as compared with Example 1 was used as the reinforcing material 5. The thickness of the reinforcing material 5 was changed in seven ways as shown in (Table 4). The physical surface treatment method and the method for producing the polymer electrolyte membrane are the same as in Example 1.

（表４）に引張弾性率および実運転時の内部電気抵抗値を示す。厚さが１０μｍより薄くなると引張強度が減少し、２０μｍより厚くなると内部電気抵抗が上昇していることが分かる。

Table 4 shows the tensile modulus and the internal electrical resistance value during actual operation. It can be seen that the tensile strength decreases when the thickness is less than 10 μm, and the internal electrical resistance increases when the thickness is greater than 20 μm.

  From the above, it is desirable that the thickness of the porous sheet used as the reinforcing material 5 is 10 μm or more and 20 μm or less.

(Example 6)
For Example 1, a porous sheet having been subjected to a physical surface treatment and having a different opening ratio with respect to the surface was used as the reinforcing material 5. The aperture ratio was changed in seven ways as shown in Table 5. The physical surface treatment and the method for producing the polymer electrolyte membrane are the same as in Example 1.

（表５）に引張弾性率および実運転時の内部電気抵抗値を示す。開口率が８０％以上になると、引張弾性率が減少し、開口率が３０％以下になると内部電気抵抗が上昇していることがわかる。

Table 5 shows the tensile modulus and the internal electrical resistance value during actual operation. It can be seen that when the aperture ratio is 80% or more, the tensile elastic modulus is decreased, and when the aperture ratio is 30% or less, the internal electrical resistance is increased.

  From the above, it is desirable that the aperture ratio of the porous sheet used as the reinforcing material 5 is 30% or more and 80% or less.

(Example 7)
When the average cross-sectional area of the through holes of the reinforcing material is 0.03 mm ² , the thickness is 10 μm, and the aperture ratio is 30% (the lower limit value of each item in Examples 4 to 6), the arithmetic average roughness (Ra ) Was changed as shown in (Table 6), and the tensile modulus at that time and the gas permeation amount at 1000 hours were shown.

又、補強材の貫通孔の平均断面積を１ｍｍ^２、厚さを２０μｍ、開口率を８０％（上記実施例４〜６における各項目の上限値）としたときに、算術平均粗さ（Ｒａ）を（表７）に示す様に変化させ、そのときの引張弾性率および、１０００時間目のガス透過量を示した。

Further, when the average cross-sectional area of the through holes of the reinforcing material is 1 mm ² , the thickness is 20 μm, and the aperture ratio is 80% (the upper limit value of each item in Examples 4 to 6), the arithmetic average roughness (Ra ) Was changed as shown in Table 7, and the tensile modulus at that time and the gas permeation amount at 1000 hours were shown.

上記（表６）及び（表７）の結果からも、（実施例３）と同様に補強材５に物理的処理により賦与される表面の凹凸５ｂは、Ｒａにして１μｍ以上、５μｍ以下であることが望ましいことが分かる。

From the results of the above (Table 6) and (Table 7), as in (Example 3), the surface irregularities 5b imparted to the reinforcing material 5 by physical treatment are 1 μm or more and 5 μm or less in terms of Ra. It turns out that is desirable.

(Example 8)
When the arithmetic mean roughness (Ra) of the reinforcing material is 1 μm, the thickness is 10 μm, and the aperture ratio is 30% (the lower limit value of each item in Examples 3, 5 and 6 above), the average cross-sectional area of the through holes Were changed as shown in (Table 8), and the tensile modulus at that time and the internal electrical resistance value during actual operation were shown.

又、補強材の算術平均粗さ（Ｒａ）を５μｍ、厚さを２０μｍ、開口率を８０％（上記実施例３、５、６における各項目の上限値）としたときに、貫通孔の平均断面積を（表９）に示す様に変化させ、そのときの引張弾性率及び、実運転時の内部電気抵抗値を示した。

Further, when the arithmetic average roughness (Ra) of the reinforcing material is 5 μm, the thickness is 20 μm, and the aperture ratio is 80% (upper limit value of each item in Examples 3, 5, and 6), the average of the through holes The cross-sectional area was changed as shown in (Table 9), and the tensile modulus at that time and the internal electrical resistance value during actual operation were shown.

上記（表８）および（表９）の結果からも（実施例４）と同様に、補強材の貫通孔の平均断面積は０．０３ｍｍ^２以上、１ｍｍ^２以下が望ましいことが分かる。

The Like the (Table 8) and from (Table 9) results (Example 4), the average cross-sectional area of the through holes of the reinforcing member is 0.03 mm ² or more, it can be seen 1 mm ² or less.

Example 9
When the arithmetic mean roughness (Ra) of the reinforcing material 5 is 1 μm, the average cross-sectional area of the through-hole is 0.03 mm ² , and the aperture ratio is 30% (the lower limit value of each item in Examples 3, 4, and 6). The thickness was changed as shown in (Table 10), and the tensile modulus at that time and the internal electrical resistance value during actual operation were shown.

又、補強材５の算術平均粗さ（Ｒａ）を５μｍ、貫通孔の平均断面積を１ｍｍ^２、開口率を８０％（上記実施例３、４、６における各項目の上限値）としたときに、厚みを（表１１）に示す様に変化させ、そのときの引張弾性率及び、実運転時の内部電気抵抗値を示した。

Further, when the arithmetic average roughness (Ra) of the reinforcing material 5 is 5 μm, the average cross-sectional area of the through-hole is 1 mm ² , and the opening ratio is 80% (upper limit values of the respective items in Examples 3, 4, and 6). The thickness was changed as shown in (Table 11), and the tensile modulus at that time and the internal electrical resistance value during actual operation were shown.

上記（表１０）および（表１１）の結果からも（実施例５）と同様に、補強材５の厚みは、１０μｍ以上、２０μｍ以下が望ましいことが分かる。

From the results of the above (Table 10) and (Table 11), it can be seen that the thickness of the reinforcing member 5 is desirably 10 μm or more and 20 μm or less, as in (Example 5).

(Example 10)
When the arithmetic mean roughness (Ra) of the reinforcing material is 1 μm, the average cross-sectional area of the through holes is 0.03 mm ² , and the thickness is 10 μm (the lower limit value of each item in Examples 3, 4, and 5). The aperture ratio was changed as shown in (Table 12), and the tensile modulus at that time and the internal electrical resistance value during actual operation were shown.

又、補強材の算術平均粗さ（Ｒａ）を５μｍ、貫通孔の平均断面積を１ｍｍ^２、厚さを２０μｍ（上記実施例３、４、５における各項目の上限値）としたときに、開口率（表１３）に示す様に変化させ、そのときの引張弾性率及び、実運転時の内部電気抵抗値を示した。

Further, when the arithmetic mean roughness (Ra) of the reinforcing material is 5 μm, the average cross-sectional area of the through holes is 1 mm ² , and the thickness is 20 μm (upper limit value of each item in Examples 3, 4, and 5), It changed as shown to an opening rate (Table 13), and showed the tensile elasticity modulus at that time, and the internal electrical resistance value at the time of an actual operation.

上記（表１２）および（表１３）の結果からも（実施例６）と同様に、補強材５の貫通孔の開口率は、３０％以上、８０％以下が望ましいことが分かる。

From the results of (Table 12) and (Table 13), it can be seen that the aperture ratio of the through holes of the reinforcing member 5 is desirably 30% or more and 80% or less, as in (Example 6).

(Example 11)
Two porous sheets subjected to the same physical surface treatment as in Example 1 were produced as reinforcing materials 5. A reinforcing material subjected to a physical surface treatment was placed on a PET substrate, and an ion conductive polymer electrolyte ethanol dispersion was applied by a die coating method to a total thickness of 21 μm and dried at 80 ° C. The obtained film was peeled from the base material, the front and back sides were reversed, and placed on a separately prepared PET base material. Similarly, the dispersion was applied by a die coating method to a total thickness of 25 μm and dried at 80 ° C. A porous sheet subjected to the physical surface treatment was disposed thereon. At this time, the first and second through holes were arranged so that the centers of the through holes overlap. Further, the dispersion was applied by a die coating method to 46 μm and dried at 80 ° C. This polymer electrolyte membrane has a laminated structure as shown in FIG.

(Example 12)
In the same manner as in Example 11, two reinforcing materials 5 subjected to physical surface treatment were produced. However, with respect to Example 11, the first and second through holes were arranged so that the centers of the through holes did not overlap. The other production methods of the polymer electrolyte membrane were the same as in Example 11. This polymer electrolyte membrane has a laminated structure as shown in FIG.

  Table 14 shows the tensile elastic modulus and the gas permeation amount at 1000 hours after the start / stop test.

ガス透過量には変化はないものの、引張弾性率では、貫通孔の中心をずらして積層した方が高い値を示した。中心位置、つまり孔が重なり、垂直方向に、補強材が存在せず高分子電解質のみからなる場合、起動停止にともなうクリープ等に対する機械的強度の低下が進行していると考えられる。

Although there was no change in the gas permeation amount, the tensile modulus showed a higher value when the center of the through hole was shifted and laminated. In the case where the center position, that is, the holes are overlapped and the reinforcing material is not present in the vertical direction and only the polymer electrolyte is present, it is considered that the decrease in mechanical strength against creep or the like accompanying the start / stop is progressing.

  As described above, when the reinforcing material layer subjected to physical surface treatment and the polymer electrolyte layer are laminated, it is more preferable that the positions of the through holes are not continuous in the thickness direction because the mechanical strength increases.

  The polymer electrolyte membrane according to the present invention and the polymer electrolyte fuel cell using the same have an effect of further improving mechanical strength and dimensional stability, and can be used as a fuel cell for a household fuel cell cogeneration system. Useful.

(A) Perspective view of the polymer electrolyte membrane according to the first embodiment of the present invention (b) Cross-sectional view of the polymer electrolyte membrane according to the first embodiment of the present invention (A) Enlarged sectional view of the boundary portion between the polymer electrolyte layer and the reinforcing agent layer of the polymer electrolyte membrane according to the first embodiment of the present invention (b) The polymer electrolyte membrane in which the irregularities are not covered with the polymer electrolyte layer Enlarged sectional view of the boundary between the polymer electrolyte layer and the reinforcing agent layer Sectional schematic diagram of the modification of the polymer electrolyte membrane in Embodiment 1 concerning this invention The figure which shows the graph of the performance curve of the cell using the polymer electrolyte membrane in Example 1 and Comparative Example 1 concerning this invention The figure which showed the graph of the amount of hydrogen leaks of the 1000-hour start-stop repetition operation with respect to the arithmetic mean roughness of the cell using the polymer electrolyte membrane in Example 3 concerning this invention Sectional schematic diagram of the polymer electrolyte membrane in Example 11 according to the present invention Sectional schematic diagram of the polymer electrolyte membrane in Example 12 according to the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 2 Reinforcement material layer 3 Polymer electrolyte layer 4 Through-hole 5 Reinforcement material 5a Surface 5b Concavity and convexity

Claims (11)

A reinforcing material layer having a first ion exchange resin and a reinforcing material, wherein at least one surface has irregularities formed thereon;
A polymer electrolyte membrane comprising an ion exchange resin layer having a second ion exchange resin, which is formed so as to cover the irregularities on a surface where the irregularities are formed.   The high reinforcing material according to claim 1, wherein the reinforcing material has a plurality of through holes formed in a direction substantially perpendicular to the surface, and the first ion exchange resin is filled in the through holes. Molecular electrolyte membrane.   The polymer electrolyte membrane according to claim 1, wherein the first ion exchange resin and the second ion exchange resin are the same ion exchange resin.   The polymer electrolyte membrane according to claim 1, wherein the irregularities are irregularities formed by one or more physical surface treatments selected from blasting, plasma etching, corona discharge treatment, and flame treatment.   2. The polymer electrolyte membrane according to claim 1, wherein an arithmetic average roughness (Ra) of the surface on which the unevenness is formed is 1 μm or more and 5 μm or less.   The polymer electrolyte membrane according to claim 1, wherein the reinforcing material layer has a thickness of 10 μm or more and 20 μm or less.   3. The polymer electrolyte membrane according to claim 2, wherein an opening ratio of the through holes with respect to the surface is 30% or more and 80% or less. The average cross-sectional area per through-hole, 0.03 mm ² or more and 1 mm ² or less, according to claim 2 polymer electrolyte membrane according. The reinforcing material layer has the irregularities on both sides,
The ion exchange resin layer is formed on both sides of the reinforcing material layer,
The polymer electrolyte membrane according to claim 1, wherein the reinforcing material layer and the ion exchange resin layer are laminated in a range of 3 to 7 layers. The reinforcing material layer and the ion exchange resin layer are laminated in a plurality of layers,
At least the reinforcing material layer is two or more layers,
The polymer electrolyte membrane according to claim 2, wherein the plurality of through holes formed in each of the adjacent reinforcing material layers are formed so that the centers do not coincide with each other. A polymer electrolyte membrane according to any one of claims 1 to 10,
A pair of gas diffusion electrodes formed on both sides of the polymer electrolyte membrane;
A polymer electrolyte fuel cell comprising a plurality of stacked unit cells having a pair of separators provided so as to sandwich the pair of gas diffusion electrodes from both sides.

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