JP4836438B2 - Polymer electrolyte laminate film - Google Patents

Description

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

A fuel cell obtains electric energy by electrochemical reaction from a fuel (hydrogen source) and an oxidant (oxygen) in the cell. In other words, the chemical energy of the fuel is directly converted into electrical energy. As the fuel source, pure hydrogen and other oils containing hydrogen elements, natural gas (methane, etc.), methanol, and the like can be used.
Since the fuel cell itself has no mechanical part, it generates less noise, and is characterized in that it can generate electric power semi-permanently by continuing to supply external fuel and oxidant.
Electrolytes are classified into liquid electrolytes and solid electrolytes. Among them, a polymer electrolyte fuel cell is one that uses a polymer electrolyte membrane as an electrolyte.
In particular, since the polymer electrolyte fuel cell operates at a low temperature as compared with others, it is expected as an alternative power source such as an automobile, a household cogeneration system, and a portable generator.
The polymer electrolyte fuel cell includes at least a membrane electrode assembly in which a gas diffusion electrode in which an electrode catalyst layer and a gas diffusion layer are laminated is bonded to both surfaces of a proton exchange resin membrane. The proton exchange resin membrane here is a material having a strong acidic group such as a sulfonic acid group or a carboxylic acid group in a polymer chain and a property of selectively transmitting protons. As such a proton exchange resin membrane, a perfluoro proton exchange resin membrane represented by Nafion (registered trademark, manufactured by DuPont, USA) having high chemical stability is preferably used.

During operation of the fuel cell, fuel (for example, hydrogen) is supplied to the gas diffusion electrode on the anode side, and oxidant (for example, oxygen or air) is supplied to the gas diffusion electrode on the cathode side, and both electrodes are connected by an external circuit. It works by. Specifically, when hydrogen is used as the fuel, hydrogen is oxidized on the anode catalyst to generate protons, and these protons move through the proton conductive polymer in the anode catalyst layer and then move through the proton exchange resin membrane. And reaches the cathode catalyst through the proton conducting polymer in the cathode catalyst layer. On the other hand, electrons generated simultaneously with protons due to the oxidation of hydrogen reach the cathode side gas diffusion electrode through an external circuit, and react with the protons and oxygen in the oxidant on the cathode catalyst to generate water. Sometimes electrical energy can be taken out. At this time, the proton exchange resin membrane also needs to play a role as a gas barrier. If the gas permeability of the proton exchange resin membrane is high, leakage of anode side hydrogen to the cathode side and leakage of cathode side oxygen to the anode side, That is, a cross leak occurs, so that a so-called chemical short circuit (chemical short circuit) occurs and a good voltage cannot be taken out.
Such a polymer electrolyte fuel cell is usually operated near 80 ° C. in order to obtain high output characteristics. However, when used for automobiles, the fuel cell can be operated even under high-temperature and low-humidification conditions (operating temperature around 100 ° C., humidification at 60 ° C. (equivalent to humidity 20% RH)) assuming that the vehicle is driven in summer. Is desired. However, when a fuel cell is operated for a long time under a high temperature and low humidity condition using a conventional perfluoro proton exchange resin membrane, there is a problem that a pinhole is generated in the proton exchange resin membrane and a cross leak occurs. I could not get sex.
As a method for improving the durability of the perfluoro proton exchange membrane, a method of reinforcing by adding fibrillar PTFE (see Patent Document 1 and Patent Document 2), a method of reinforcing by a stretched PTFE porous membrane (Patent Document) 3 and Patent Document 4) are known, but these methods cannot solve the above problem. Moreover, although the laminated body (refer patent documents 5-7) of the perfluorocarbon polymer film from which a moisture content differs is known, high durability was not able to be implement | achieved even with such a laminated body.

On the other hand, it has been reported that a proton exchange membrane in which polybenzimidazole (hereinafter referred to as PBI) having high heat resistance is doped with a strong acid such as phosphoric acid can be operated at a high temperature of 100 ° C. or more ( (See Patent Document 8). However, since liquid water is present when the fuel cell is operated at a temperature lower than 100 ° C., the strong acid is eluted from the membrane into the water and the output is reduced. Therefore, the fuel cell is not suitable for the fuel cell operation at a temperature lower than 100 ° C. . Therefore, the operation is frequently turned on and off, and it has been difficult to use in automobile applications that require driving the fuel cell even at temperatures below 100 ° C.
Further, as a polymer blend with PBI, a composition with a sulfonated aromatic polyether ketone (see Patent Document 9), a hydrocarbon polymer having an ion exchange group in the presence of an aprotic solvent, and a basic polymer Proton exchange membranes obtained by casting after blending (see Patent Document 10 and Patent Document 11) are known as representative examples. However, such a blend polymer of hydrocarbon-based polymer and PBI has insufficient chemical stability, and it has not been possible to solve the above-described problem of cross leak occurrence.
Further, Patent Document 12 discloses a composite solid polymer electrolyte membrane including a porous polymer substrate in which ion conductive materials are interpenetrated, and Patent Document 13 discloses a composite of a nitrogen-containing film such as PBI and an ion conductive film. ing. However, in such a case, the ion conductive material exists separately from the porous polymer substrate or the nitrogen-containing film such as PBI, and the chemical stability of the ion conductive material itself is not improved, Sufficient durability could not be obtained.

On the other hand, a blend film of PBI and Nafion is disclosed in Patent Document 14 and Comparative Example 3 of Patent Document 15. This blend membrane is manufactured by dissolving PBI and Nafion in dimethylacetamide, mixing and casting. However, in such a manufacturing method, PBI cannot be finely dispersed uniformly in Nafion, and PBI is unevenly dispersed to form a mottled film. In other words, there are parts where PBI is small and the desired effect cannot be obtained, but such parts are not sufficiently chemically stable like ordinary Nafion and cause cross leaks. . Therefore, with such a blend membrane, sufficient durability could not be obtained in fuel cell operation under high temperature and low humidification conditions.
Thus, a highly practical polymer electrolyte membrane that is excellent in chemical stability, mechanical strength and heat resistance and has high durability even when used at high temperatures has not been obtained in the prior art. Specifically, no cross-leak occurs even if the operation is performed for a long time under high temperature and low humidification conditions (60 ° C. humidification (equivalent to 20% humidity) at an operation temperature of about 100 ° C.), and the operation is turned on / off. The polymer electrolyte membrane that can be used advantageously to produce an excellent fuel cell that does not deteriorate its output characteristics even if it is frequently used is not obtained in the prior art, and the development of such a polymer electrolyte membrane has not been achieved. It is desired.

JP-A-53-149981 Japanese Examined Patent Publication No. 63-61337 Japanese Patent Publication No. 5-75835 Japanese National Patent Publication No. 11-501964 Japanese Patent Laid-Open No. 6-231781 Japanese Patent Application Laid-Open No. 6-231782 JP-A-6-231783 Japanese National Patent Publication No. 11-503262 JP 2002-529546 A Japanese translation of PCT publication No. 2002-512285 Japanese translation of PCT publication No. 2002-512291 JP-T-2001-514431 Japanese Patent No. 3425405 Korean Published Patent Publication No. 2004-36396 Korean Published Patent Publication No. 2003-32321

An object of the present invention is to provide a polymer electrolyte membrane that is excellent in chemical stability, mechanical strength, and heat resistance and has high durability even at high temperatures. Also, a highly durable fuel cell that does not generate cross-leakage even when operated for a long time under high temperature and low humidification conditions (for example, 60 ° C. humidification at an operating temperature of 100 ° C. (equivalent to a humidity of 20% RH)) is provided. With the goal.
The present inventors have intensively studied in order to solve the above-described problems of the prior art. As a result, surprisingly, it is a laminate of two or more films having a proton exchange resin, and at least one layer of the basic polymer (b) is finely dispersed uniformly in the fluorine-based polymer electrolyte (a). It has been found that the above object can be achieved by a polymer electrolyte laminate film characterized by being a reinforcing layer composed of a polymer electrolyte having the above structure. In addition, the inventors of the present invention provide a liquid medium containing a protic solvent in which the reinforcing layer includes a polymer mixture composed of (a) a fluorine-based polymer electrolyte having an ion exchange group and (b) a basic polymer. It has been found that it can be produced by providing a mixed casting solution, casting the casting solution on a support, forming a liquid coating on the support, and removing the liquid medium from the liquid coating. The polymer electrolyte laminate film in which the reinforcing layer thus obtained is laminated is excellent in chemical stability, mechanical strength and heat resistance, and has high durability even when used at high temperatures. Even when the polymer fuel cell is operated for a long time under high temperature and low humidification conditions (operating temperature near 100 ° C., 60 ° C. humidification (equivalent to humidity 20% RH)), no cross leak occurs. In addition, the solid polymer fuel cell using the above polymer electrolyte laminated membrane is similar to the fuel cell using a conventional perfluoro proton exchange membrane, and the output of the fuel cell can be obtained even if the operation is frequently turned on and off. It was confirmed that the characteristics did not deteriorate. Based on these findings, the present invention has been completed. That is, the present invention is as follows.
(1) A polymer electrolyte laminate film comprising a laminate of two or more layers of a film having a proton exchange resin, wherein at least one layer of the film is 50.00 to 99.99% by mass of a fluorine-based polymer A polymer electrolyte laminate film, which is a reinforcing layer composed of an electrolyte and 0.01 to 50.00% by mass of a basic polymer.
(2) The polymer electrolyte laminate according to (1), wherein the basic polymer is poly [(2,2 ′-(m-phenylene) -5,5′-bibenzimidazole]. film.
(3) The converted haze value (H ₅₀ ) is 25% or less, and the converted haze value (H ₅₀ ) is defined as a haze value calculated on the assumption that the film thickness of the polymer electrolyte laminated film is 50 μm. The converted haze value (H ₅₀ ) is calculated by the following formula: the polymer electrolyte laminate film according to (1) or (2).

（式中、ｔは高分子電解質積層膜の膜厚（μｍ）を表し、Ｈ_t はＪＩＳ Ｋ ７１３６に従って測定した高分子電解質積層膜のヘイズ値を表す。）
（４） 上記補強層が、上記（ａ）成分を主体とする海構造と上記（ｂ）成分を主体とする島構造から構成される補強層であることを特徴とする（１）〜（３）のいずれかに記載の高分子電解質積層膜。
（５） （１）〜（４）のいずれかに記載の高分子電解質積層膜がアノードとカソードの間に密着保持されてなる膜／電極接合体であって、アノードはアノード触媒層からなり、プロトン伝導性を有し、カソードはカソード触媒層からなり、プロトン伝導性を有することを特徴とする膜／電極接合体。
（６） （５）に記載の膜／電極接合体であって、高分子電解質積層膜を構成する補強層がカソード触媒層に隣接しており、該補強層に於けるフッ素系高分子電解質（ａ）の含有率が７０〜９９質量％、該補強層に於ける塩基性重合体（ｂ）の含有率が１〜３０質量％、該補強層の膜厚が１〜２０μｍであることを特徴とする膜／電極接合体。
（７） （５）又は（６）の膜／電極接合体を包含し、アノードとカソードが、高分子電解質積層膜の外側に位置する電子伝導性材料を介して互いに結合されていることを特徴とする固体高分子形燃料電池。

(In the formula, t represents the film thickness (μm) of the polymer electrolyte laminate film, and H _t represents the haze value of the polymer electrolyte laminate film measured according to JIS K 7136.)
(4) The reinforcing layer is a reinforcing layer composed of a sea structure mainly composed of the component (a) and an island structure mainly composed of the component (b). The polymer electrolyte laminate film according to any one of the above.
(5) A membrane / electrode assembly in which the polymer electrolyte laminate film according to any one of (1) to (4) is held tightly between an anode and a cathode, the anode comprising an anode catalyst layer, A membrane / electrode assembly having proton conductivity, a cathode comprising a cathode catalyst layer, and having proton conductivity.
(6) The membrane / electrode assembly according to (5), wherein the reinforcing layer constituting the polymer electrolyte laminated film is adjacent to the cathode catalyst layer, and the fluorine-based polymer electrolyte ( The content of a) is 70 to 99% by mass, the content of the basic polymer (b) in the reinforcing layer is 1 to 30% by mass, and the thickness of the reinforcing layer is 1 to 20 μm. And a membrane / electrode assembly.
(7) The membrane / electrode assembly according to (5) or (6) is included, and the anode and the cathode are bonded to each other through an electron conductive material located outside the polymer electrolyte laminated film. Solid polymer fuel cell.

  The polymer electrolyte laminate film of the present invention is excellent in chemical stability, mechanical strength, and heat resistance. In addition, by using the polymer electrolyte laminate film of the present invention, even if it is operated for a long time under high temperature and low humidification conditions (for example, 60 ° C. humidification at an operating temperature of 100 ° C. (equivalent to a humidity of 20% RH)) A highly durable fuel cell that does not cause leakage can be provided.

The present invention is described in detail below.
The polymer electrolyte laminate film of the present invention is composed of a laminate of two or more films having a proton exchange resin, and at least one film of the film is 50.00 to 99.99% by mass of a fluorine-based polymer electrolyte. And a reinforcing layer composed of 0.01 to 50.00% by mass of a basic polymer.
The fluorine-based polymer electrolyte constituting the reinforcing layer is not particularly limited, but Nafion (registered trademark; manufactured by DuPont, USA), Aciplex (registered trademark; manufactured by Asahi Kasei Corporation, Japan), Flemion (registered trademark; Japan) As a representative example, a perfluorocarbon polymer having an ion exchange group represented by the following chemical formula (1) represented by the following chemical formula (1) represented by Kuniasa Asahi Glass Co., Ltd. can be given.
_{^{[CF 2 CX 1 X 2]}} a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - (CF _{2) f} -X ^4)] _g
... (1)
Wherein X ¹ , X ² and X ³ are each independently a halogen element or a perfluoroalkyl group having 1 to 3 carbon atoms, 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, 0 ≦ b ≦ 8, c is 0 or 1, d, e and f are each independently a number in the range of 0-6 (where d + e + f is not equal to 0), R ¹ and R ² are each independently a halogen element, A perfluoroalkyl group or a fluorochloroalkyl group having 1 to 10 carbon atoms, and X ⁴ is —COOZ, —SO ₃ Z, —PO ₃ Z ₂ , —PO ₃ HZ (Z is a hydrogen atom, a metal atom (Na , K, Ca, etc.) or amines (NH ₄ , NH ₃ R, NH ₂ R ² , NHR ³ , NR ⁴ (R is an alkyl group or arene group))
Among these, a perfluorocarbon polymer represented by the following formula (2) or (3) is preferable. _{[CF 2 CF 2] a -} [CF 2 -CF (-O- (CF 2 -CF (CF 3)) b -O- (CF 2) f -X 4)] g ··· (2)
(Where 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, 1 ≦ b ≦ 3, 1 ≦ f ≦ 8, and X ⁴ represents —COOH, —SO ₃ H, —PO ₃ H ₂ or — PO ₃ H.)
_{[CF 2 CF 2] a -} [CF 2 -CF (-O- (CF 2) f -X 4)] g
... (3)
(Where 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, 1 ≦ f ≦ 8, and X ⁴ is —COOH, —SO ₃ H, —PO ₃ H ₂ or —PO ₃ H. )

The perfluorocarbon polymer as described above may be a copolymer further including units derived from a perfluoroolefin such as hexafluoropropylene or chlorotrifluoroethylene, or a comonomer such as perfluoroalkyl vinyl ether.
The content of the fluorine-based polymer electrolyte (a) in the reinforcing layer is 50.00 to 99.99% by mass, preferably 60.0 to 99.9% by mass, more preferably 70 to 99% by mass. %, More preferably 80 to 98% by mass, most preferably 85 to 95% by mass. By setting the content of the fluorine-based polymer electrolyte (a) within the above range, a polymer electrolyte laminate film having high durability can be obtained while maintaining good proton conductivity.
The basic polymer (b) constituting the reinforcing layer is not particularly limited, and examples thereof include a nitrogen-containing aliphatic basic polymer and a nitrogen-containing aromatic basic polymer.
Examples of nitrogen-containing aliphatic basic polymers include polyethyleneimine. Examples of nitrogen-containing aromatic basic polymers include polyaniline and heterocyclic compounds such as polybenzimidazole, polypyridine, polypyrimidine, polyvinylpyridine, polyimidazole, polypyrrolidine, and polyvinylimidazole. Among these, polybenzimidazole is particularly preferable because of its high heat resistance.
Examples of polybenzimidazole include compounds represented by chemical formula (4) and chemical formula (5), poly 2,5-benzimidazole represented by chemical formula (6), and the like.

及びアルカン鎖、又はフルオロアルカン鎖などの二価の基である。
ここで各Ｒ¹ はそれぞれ独立に水素原子、アルキル、フェニル、又はピリジルである。
また、上記式中、ｘは、１０以上１．０×１０⁷ 以下の数である。

And a divalent group such as an alkane chain or a fluoroalkane chain.
Here, each R ¹ is independently a hydrogen atom, alkyl, phenyl, or pyridyl.
In the above formula, x is a number of 10 or more and 1.0 × 10 ⁷ or less.

（式中、ｌは、１０以上１．０×１０⁷ 以下の数、ＲとＲ¹ は、上記式（４）で定義したのと同じである）

(In the formula, l is a number of 10 or more and 1.0 × 10 ⁷ or less, and R and R ¹ are the same as defined in the above formula (4)).

（式中、ｍは、１０以上１．０×１０⁷ 以下の数であり、Ｒ¹ は、上記式（４）で定義したのと同じである）
以上のようなポリベンズイミダゾールの中でも、下記式（７）で表されるポリ[ ２、２’−（ｍ−フェニレン）−５，５’−ビベンゾイミダゾール] が特に好ましい。

(In the formula, m is a number of 10 or more and 1.0 × 10 ⁷ or less, and R ¹ is the same as defined in the above formula (4)).
Among the polybenzimidazoles as described above, poly [2,2 ′-(m-phenylene) -5,5′-bibenzimidazole] represented by the following formula (7) is particularly preferable.

（式中、ｎは、１０以上１．０×１０⁷ 以下の数である）

(In the formula, n is a number of 10 or more and 1.0 × 10 ⁷ or less)

The content of the basic polymer (b) in the reinforcing layer is 0.01 to 50.00% by mass, preferably 0.1 to 40.0% by mass, more preferably 1 to 30% by mass. More preferably, the content is 2 to 20% by mass, and most preferably 5 to 15% by mass (note that the sum of the contents of the component (a) and the component (b) is 100% by mass).
By setting the content of the basic polymer (b) within the above range, a polymer electrolyte laminate film having high durability can be obtained while maintaining good proton conductivity.
The reinforcing layer preferably exhibits a sea / island structure when a 15 μm × 15 μm region of the cross section in the film thickness direction is observed with a transmission electron microscope (hereinafter referred to as “TEM”). The sea / island structure here refers to a state in which black island particles are dispersed in a gray or white sea (continuous phase) in an electron microscopic image obtained by observation with an electron microscope without performing a staining treatment. The shape of the island particles is not particularly limited, such as a circle, an ellipse, a polygon, and an indeterminate shape. The diameter (or major axis or maximum diameter) of the island particles is in the range of 0.01 to 10 μm. In the sea / island structure, the contrast of the black island particles is mainly caused by the basic polymer (b), and the white sea (continuous phase) part is mainly caused by the fluorine-based polymer electrolyte (a).

In the sea / island structure, the total area of the island particles of the sea / island structure is preferably 0.1 to 70%, more preferably 1 to 70% of the 15 μm × 15 μm region of the membrane cross section. More preferably, it is 5 to 50%. Moreover, it is preferable that the density of island particles having a sea / island structure is 0.1 to 100 per 1 μm ^{2 in the} 15 μm × 15 μm region of the film cross section. The total area of island particles and the density of island particles in the sea / island structure referred to here are obtained as follows. A description will be given taking the TEM image shown in FIG. 1 as an example. First, the TEM image shown in FIG. 1 is read by a scanner and digitized, and then the degree of blackening of each part (grayscale 256 gradations) using an image analyzer IP1000 (manufactured by Asahi Kasei Corporation, Japan). The horizontal axis is grayscale, and the vertical axis is the number of histograms. When the TEM image shows a sea / island structure or a structure somewhat similar to this (that is, only the black part mainly composed of the basic polymer (b), and mainly the fluorine-based polymer electrolyte (a ), The histogram has a two-peak distribution. The binarization was carried out by setting the gray scale value between the valleys of the two mountain distributions as a threshold value, determining that the gray scale value portion larger than that was black, and determining the gray scale value portion below that as white. (That is, the gray portion in the TEM photograph of FIG. 1 was determined to be black and white on the basis of the above criteria, and the gray portion determined to be black was processed to be black.) Thus, the image of FIG. 2 was obtained. In the binarized image in this way, a predetermined region (a portion corresponding to a 15 μm × 15 μm region of the membrane cross section) is mainly used as a basic polymer by using an image analysis apparatus IP1000 (manufactured by Asahi Kasei Corporation, Japan). The black island particle portion of the sea / island structure corresponding to (b) and the sea portion mainly corresponding to the fluorine-based polymer electrolyte (a) were separated by image processing. Then, the number of island particles present in the 15 μm × 15 μm region and the total area of the island particles were measured. The percentage of the total area of the island particles in the 15 μm × 15 μm region was determined. Further, the number of island particles per 1 μm ^{2 in the} 15 μm × 15 μm region was determined and used as the density of the island particles.

Having such a sea / island structure indicates that the portion mainly composed of the basic polymer (b) is uniformly finely dispersed in the portion mainly composed of the fluoropolymer electrolyte (a). And higher durability can be obtained. A typical example of such a sea / island structure is shown in FIG. The reinforcing layer having such a sea / island structure is obtained by mixing a cast liquid obtained by mixing a polymer mixture composed of a fluorine-based polymer electrolyte (a) and a basic polymer (b) with a liquid medium containing a protic solvent. It can be obtained by the method disclosed in the present application in which a film is formed using the film. On the other hand, the method shown in Patent Documents 14 and 15, that is, a cast in which a polymer mixture comprising a fluorine-based polymer electrolyte (a) and a basic polymer (b) is mixed with a liquid medium containing only an aprotic solvent. When the film is formed using the liquid, as shown in FIG. 4, the portion mainly composed of the basic polymer (b) does not have the sea / island structure, and the portion mainly composed of the fluorine-based polymer electrolyte (a). The structure is not uniformly finely dispersed. As a result, the polymer electrolyte multilayer film composed of the reinforcing layer having no sea / island structure cannot obtain high durability.
The proton exchange capacity of the reinforcing layer is not particularly limited, but is preferably 0.4 to 3.0 milliequivalent per gram, more preferably 0.6 to 2.0 milliequivalent, and most preferably 0.7 to 1. 4 milliequivalents. The use of a polymer electrolyte laminate film having a larger proton exchange capacity exhibits higher proton conductivity under high temperature and low humidification conditions, and when used in a fuel cell, a higher output can be obtained during operation.
The proton exchange capacity can be measured by the following method. First, the polymer electrolyte laminated film cut out to about 10 cm ^{2 is} vacuum-dried at 110 ° C. to obtain a dry weight W (g). This membrane is immersed in 50 ml of a 25 ° C. saturated NaCl aqueous solution to release H ⁺ , neutralized with 0.01 N sodium hydroxide aqueous solution using phenolphthalein as an indicator, and the equivalent amount of NaOH required for neutralization. Obtain M (millimeter equivalent). The value obtained by dividing M thus determined by W is the proton exchange capacity (milli equivalent / g). The value obtained by dividing W by M and multiplying by 1000 is the equivalent mass EW, which is the dry mass in grams per equivalent of proton exchange groups.
The thickness of the reinforcing layer is not limited, but is preferably 0.1 to 400 μm, more preferably 0.2 to 100 μm, still more preferably 0.5 to 50 μm, and most preferably 1 to 20 μm. The thicker the film thickness, the better the durability and the worse the initial characteristics. Therefore, it is preferable to set the film thickness within the above range.

The state of the fluorine-based polymer electrolyte (a) and the basic polymer (b) in the reinforcing layer may be, for example, a state where the component (a) and the component (b) are simply physically mixed, A state in which at least a part of (a) and at least a part of component (b) react with each other (for example, a state in which an ionic bond is formed to form an acid-base ion complex, or a state in which a covalent bond is formed) )
Whether or not the fluorine-based polymer electrolyte (a) and the basic polymer (b) are chemically bonded as described above is determined by, for example, a Fourier-Transform Infrared Spectrometer (hereinafter referred to as “FT-”). (Referred to as “IR”). That is, when the FT-IR measurement of the polymer electrolyte laminated film having the reinforcing layer composed of the fluorine-based polymer electrolyte (a) and the basic polymer (b) is performed, the fluorine-based polymer electrolyte (a) and the basic property are obtained. If an absorption peak derived from any other than the polymer (b) is observed, it can be determined that chemical bonding has occurred. For example, the perfluorocarbon polymer represented by the above formula (3) and the poly [(2,2 ′-(m-phenylene) -5,5′-bibenzimidazole] represented by the above formula (7) (hereinafter, , in the case of the polymer electrolyte laminated membrane of the present invention having a reinforcing layer consisting of a called) and PBI, Doing FT-IR measurement, 1460cm ^-1, 1565cm ^-1, absorption peaks observed around 1635 cm ^-1 It can be seen that chemical bonds exist.

  The polymer electrolyte laminate film of the present invention comprises at least each of a laminate formed by laminating two or more of the above reinforcing layers, an unreinforced layer made of a proton exchange resin not containing the basic polymer, and the above reinforcing layers. Any of the laminated bodies formed by laminating one layer corresponds to this. For example, when the laminate has two layers, the reinforcing layer / reinforcing layer, the reinforcing layer / non-reinforcing layer, and in the case of three layers, the reinforcing layer / reinforcing layer / reinforcing layer, the reinforcing layer / non-reinforcing layer / reinforcing layer, reinforcing In the case of 4 layers, reinforcing layer / reinforcing layer / reinforcing layer / reinforcing layer, reinforcing layer / reinforcing layer / reinforcing layer / unreinforcing layer Reinforced layer / reinforced layer / unreinforced layer / reinforced layer, reinforced layer / unreinforced layer / reinforced layer / unreinforced layer, unreinforced layer / reinforced layer / reinforced layer / unreinforced layer / Reinforcing layer / Reinforcing layer / Reinforcing layer / Reinforcing layer, Non-reinforcing layer / Reinforcing layer / Reinforcing layer / Reinforcing layer / Reinforcing layer, Reinforcing layer / Non-reinforcing layer / Reinforcing layer / Reinforcing layer / Reinforcing layer, Reinforcing layer / Reinforcing layer / Unreinforced layer / reinforced layer / reinforced layer, reinforced layer / unreinforced layer / reinforced layer / unreinforced layer / reinforced layer, reinforced layer / unreinforced layer / reinforced layer / reinforced layer / unreinforced layer, reinforced layer / reinforced layer / Unreinforced layer / Reinforcement / Unreinforced layer, unreinforced layer / reinforcing layer / reinforcing layer / reinforcing layer / unreinforced layer, structure such as unreinforced layer / reinforcing layer / unreinforced layer / reinforcing layer / unreinforced layer. Moreover, when using a some reinforcement layer or a non-reinforcement layer, each may have a different composition and physical property. For example, in the case of two layers, reinforcing layer 1 / reinforcing layer 2 and in the case of three layers, reinforcing layer 1 / reinforcing layer 2 / reinforcing layer 3 and in the case of four layers, reinforcing layer 1 / reinforcing layer 2 / reinforcing layer 3 / Reinforcing layer 4, unreinforced layer 1 / reinforced layer 1 / unreinforced layer 2 / reinforced layer 2 and the like can be formed.

Examples of the proton exchange resin constituting the unreinforced layer include polyether sulfone resin, polyether ether ketone resin, phenol-formaldehyde resin, polystyrene resin, polytrifluorostyrene resin, trifluorostyrene resin, poly (2,3-diphenyl- 1,4-phenylene oxide) resin, poly (allyl ether ketone) resin, poly (allyl ether sulfone) resin, poly (phenylquinosan phosphorus) resin, poly (benzylsilane) resin, polystyrene-graft-ethylenetetrafluoroethylene resin, Polystyrene-graft-polyvinylidene fluoride resin, polystyrene-graft-tetrafluoroethylene resin, polyimide resin, polybenzimidazole resin, etc. While those introduced this is true, most preferred are fluorine-based polymer electrolytes shown above.
The proton exchange capacity of the polymer electrolyte laminate film of the present invention is not particularly limited, but is preferably 0.5 to 4.0 milliequivalents per gram, more preferably 0.8 to 3.0 milliequivalents, most preferably 1 0.0 to 1.5 milliequivalents. The use of a polymer electrolyte laminate film having a larger proton exchange capacity exhibits higher proton conductivity under high temperature and low humidification conditions, and when used in a fuel cell, a higher output can be obtained during operation.
The thickness of the polymer electrolyte laminate film of the present invention is not limited, but is preferably 1 to 500 μm, more preferably 2 to 150 μm, still more preferably 5 to 75 μm, and most preferably 5 to 50 μm. The thicker the film thickness, the better the durability and the worse the initial characteristics. Therefore, it is preferable to set the film thickness within the above range.
When the polymer electrolyte laminate film of the present invention has a film thickness of 50 μm, the haze value measured according to JIS K 7136 is preferably 25% or less, more preferably 20% or less, and most preferably 15% or less. . The haze value is influenced by the degree of internal scattering of light and is a value depending on the film thickness. When the film thickness of the polymer electrolyte laminate film of the present invention is not 50 μm, the converted haze value (H ₅₀ ) is preferably 25% or less, and the converted haze value (H ₅₀ ) is the polymer electrolyte laminate film. Is defined as a haze value calculated on the assumption that the film thickness is 50 μm,
The converted haze value (H ₅₀ ) is calculated by the following formula.

（式中、ｔは高分子電解質積層膜の膜厚（μｍ）を表し、Ｈ_t はＪＩＳ Ｋ ７１３６に従って測定した高分子電解質積層膜のヘイズ値を表す。）

(In the formula, t represents the film thickness (μm) of the polymer electrolyte laminate film, and H _t represents the haze value of the polymer electrolyte laminate film measured according to JIS K 7136.)

When the haze value is in the above range (that is, when the film thickness is 50 μm, the haze value measured according to JIS K 7136 is 25% or less, or when the film thickness is not 50 μm, the converted haze value ( H ₅₀ ) is 25% or less) means that the island structure part mainly composed of the basic polymer (b) is finely dispersed uniformly in the sea structure part mainly composed of the fluoropolymer electrolyte (a). This means that higher durability can be obtained.
Further, the polymer electrolyte laminate film of the present invention may be reinforced by other known techniques. Examples of known reinforcing methods include reinforcement by addition of fibrillar PTFE (Japanese Patent Laid-Open No. 53-149981 (corresponding to US Pat. No. 4,218,542) and Japanese Patent Publication No. 63-61337). No. (corresponding to EP 94679))), reinforcement with a stretched PTFE porous membrane (Japanese Patent Publication No. 5-75835 and Japanese Patent Publication No. 11-501964 (US Pat. No. 5,599, 614 and U.S. Pat. No. 5,547,551)) and inorganic particles (Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO _2, etc.) are added for reinforcement (Japanese Unexamined Patent Publication No. 6) No.-1111827, Japanese Patent Laid-Open No. 9-219206 and US Pat. No. 5,523,181), reinforcement by crosslinking (see Japanese Patent Laid-Open No. 2000-188013) Reinforcement by incorporating silica into the membrane using sol-gel reaction ((KA Mauritz, RF Storey and CK Jones, in Multiphase Polymer Materials: Blends and Ionomers, LA Utracki and RA Weiss, Editors, ACS Symposium Series No. 395, p. 401, American Chemical Society, Washington, DC (1989)).

(Production example of the polymer electrolyte laminate film of the present invention)
As a method for producing the polymer electrolyte laminate film of the present invention, a reinforcing layer and, if necessary, a non-reinforcing layer are prepared, and these are laminated in a known press such as a hot press, a roll press, or a vacuum press. Examples of the bonding method include using a technique or a lamination technique. Under the present circumstances, you may join in the state which formed the reinforcement layer and the non-reinforcement layer as needed on base materials, such as a general polymer film, metal foil, an alumina, and Si. Moreover, you may peel the used base material after joining. The reinforcing layer is manufactured as follows, for example.
(A) The fluorine-based polymer electrolyte having an ion exchange group is 50.00 to 99.99% by mass based on the total mass of the component (a) and the component (b), and (b) the basic polymer is the component (a And a polymer mixture composed of 0.01 to 50.00% by mass with respect to the total mass of the component (b) is provided with a casting liquid mixed with a liquid medium containing a protic solvent,
A production method comprising casting the casting liquid onto a support, forming a liquid coating film on the support, and removing the liquid medium from the liquid coating film to form a reinforcing layer.
The cast liquid is, for example, an emulsion (in which a liquid particle is dispersed as a colloidal particle or a coarser particle in the liquid to form a milky state), a suspension (a solid particle in the liquid is colloidal particles or a microscope). Such as particles dispersed as visible particles), colloidal liquid (macromolecules dispersed), or micellar liquid (a lyophilic colloidal dispersion system formed by the intermolecular force of many small molecules). These composite systems may also be used.

By the above production method using a casting liquid containing a liquid medium containing a protic solvent, a reinforcing layer in which the basic polymer (b) is finely dispersed uniformly in the fluorine-based polymer electrolyte (a) can be formed. The protic solvent mentioned here is a solvent having a functional group capable of emitting protons, and examples thereof include water, alcohols (methanol, ethanol, propanol, isopropanol, etc.), and phenols. Of these protic solvents, the most preferred is water. The amount of the protic solvent is not particularly limited, but is preferably 0.5 to 99.5% by mass, more preferably 1 to 90% by mass, and most preferably based on the mass of the liquid medium of the casting liquid. Is 10-60 mass%.
Moreover, you may use these protic solvents 1 type or in mixture of 2 or more types. In particular, a mixed solvent of water and alcohol is preferably used, and a mixed solvent of water / ethanol = 3/1 to 1/3 (volume ratio) and water / isopropanol = 3/1 to 1/3 (volume ratio) is used. It is more preferable.
It is preferable that the liquid medium of the casting liquid further includes an aprotic solvent. Here, the aprotic solvent is a solvent other than the protic solvent, and examples thereof include N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, acetone, and methyl ethyl ketone. Can be mentioned. These aprotic solvents may be used alone or in combination of two or more. It is particularly preferable to use N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide. The amount of the aprotic solvent is not particularly limited, but is preferably 99.5 to 0.5% by mass, more preferably 99 to 10% by mass, and most preferably based on the mass of the liquid medium of the casting liquid. It is 90-40 mass%.

Although the density | concentration of the liquid medium in a casting liquid is not limited, 20.000-99.989 mass% is preferable with respect to the mass of a casting liquid, 40.000-99.895 mass% is more preferable, 75.000- 98.990 mass% is most preferable.
Although the density | concentration of the fluorine-type polymer electrolyte (a) in a casting liquid is not limited, 0.010-50.000 mass% is preferable with respect to the mass of a casting liquid, More preferably, it is 0.100-40.000 mass. %, Most preferably 1.000 to 20.000 mass%.
Moreover, the density | concentration of the basic polymer (b) in a cast liquid is although it is not limited, 0.001-30.000 mass% is preferable with respect to the mass of a cast liquid, More preferably, 0.005-20.000. % By mass, most preferably from 0.010 to 5.000% by mass.
The mass ratio of the fluorine-based polymer electrolyte (a) and the basic polymer (b) in the casting solution (
The fluorine-based polymer electrolyte (a): basic polymer (b)) is not particularly limited, but is preferably in the range of 99.99: 0.01 to 50.00: 50.00, more preferably 99.9: 0.1-60.0: 40.0, even more preferably 98: 2-80: 20, most preferably 95: 5-85: 15.
By using such a casting solution, it is easy to remove the liquid medium, and the island structure portion mainly composed of the basic polymer (b) is the sea structure portion mainly composed of the fluoropolymer electrolyte (a). A reinforcing layer that is uniformly finely dispersed therein can be produced, and a polymer electrolyte laminate film having high durability can be obtained while maintaining good proton conductivity.
The casting liquid includes, for example, a polymer solution obtained by dissolving the basic polymer (b) in an aprotic solvent such as dimethylacetamide (hereinafter referred to as “pre-stage solution A”), and a fluorine-based polymer electrolyte (a). Is added to and stirred with a polymer solution (hereinafter referred to as “pre-stage solution B”) dissolved in an aprotic solvent such as dimethylacetamide, and the fluorine-based polymer electrolyte (a) is further added to the protic solvent. A polymer solution dissolved in (hereinafter referred to as “preliminary solution C”) is added and stirred.

The nitrogen-containing aromatic basic polymer that is an example of the basic polymer (b) is generally soluble in an aprotic solvent, but is insoluble in a protic solvent. However, surprisingly, even if the pre-stage solution A and the pre-stage solution B are mixed as described above and then the pre-stage solution C containing a protic solvent is added and mixed therewith, surprisingly, the nitrogen-containing aromatic basicity The polymer can be kept dissolved or uniformly finely dispersed in the casting solution without precipitating. The mechanism of this has not been fully elucidated, but it is presumed that the nitrogen-containing aromatic basic polymer (b) is stabilized by some interaction with the fluorine-based polymer electrolyte (a). .
The basic polymer (b) can be produced by a polymerization method described in known literature (for example, see Experimental Chemistry Course 28, Polymer Synthesis 4th Edition, edited by the Chemical Society of Japan, Nippon Kunimaru Maruzen Co., Ltd.). ). Although the weight average molecular weight of a basic polymer (b) is not limited, Preferably it is 10,000-1 million, More preferably, it is 20000-100,000, Most preferably, it is 50000-100,000. The weight average molecular weight can be measured by gel permeation chromatography (GPC).
Moreover, you may use an intrinsic viscosity (dl / g) as a parameter | index instead of such a weight average molecular weight. Intrinsic viscosity includes viscosity ηP (mPa · s) of polymer solution obtained by dissolving basic polymer (b) in dimethylacetamide, viscosity ηS (mPa · s) of dimethylacetamide, and concentration Cp ( g / dL) and can be determined using the following formula. The viscosity here is a value measured using, for example, a conical plate type rotary viscometer (E-type viscometer) at 25 ° C.
Intrinsic viscosity = ln (ηP / ηS) / Cp
(In the formula, ln represents a natural logarithm.)

The intrinsic viscosity of the basic polymer (b) is preferably 0.1 to 10.0 dL / g, more preferably 0.3 to 5.0 dL / g, most preferably 0.5 to 1.0 dL / g. It is.
The pre-stage solution A can be obtained by a method in which the basic polymer (b) and the aprotic solvent are put in an autoclave and subjected to heat treatment at 40 to 300 ° C. for 10 minutes to 100 hours. The content of the basic polymer (b) in the pre-stage solution A is preferably 0.01 to 50% by mass, more preferably 0.1 to 30% by mass, most preferably based on the mass of the pre-stage solution A. Preferably it is 1-10 mass%.
A perfluorocarbon polymer having a proton exchange group, which is a representative example of the fluorine-based polymer electrolyte (a) contained in the pre-stage solution B and the pre-stage solution C, represents a precursor polymer represented by the following formula (8) as follows: After polymerization by the method, it can be produced by hydrolysis and acid treatment.
_{^{[CF 2 CX 1 X 2]}} a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -Oc- (CFR 1) d - (CFR 2) e - (CF 2 ) _F −X ⁵ )] _g
... (8)
(Wherein X ¹ , X ² and X ³ are each independently a halogen element or a C 1-3 perfluoroalkyl group, 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, b is 0 to 8, c is 0 or 1, d, e and f are each independently a number from 0 to 6 (where d + e + f is not equal to 0), R ¹ and R ² are each independently a halogen element , A C 1-10 perfluoroalkyl group or fluorochloroalkyl group, X ⁵ is —COOR ³ , —COR ⁴ or —SO ₂ R ⁴ (R ³ is a C 1-3 alkyl group (fluorinated not even one), the precursor polymer R ⁴ is represented by a halogen element)) the equation (8) is prepared by copolymerizing a fluorinated olefin with vinyl fluoride compound. Specific examples of the fluorinated olefin include CF ₂ = CF ₂ , CF ₂ = CFCl, CF ₂ = CCl _{2 and the} like. Specific fluorinated vinyl _{compounds, CF 2 = CFO (CF 2} ) z -SO 2 F, CF 2 = CFOCF 2 CF (CF 3) O (CF 2) z -SO 2 F, CF 2 = CF ( _{CF 2) z -SO 2 F,} CF 2 = CF (OCF 2 CF (CF 3)) z - (CF 2) z-1 -SO 2 F, CF 2 = CFO (CF 2) z -CO 2 R, _{CF 2 = CFOCF 2 CF (CF} 3) O (CF 2) z -CO 2 R, CF 2 = CF (CF 2) z -CO 2 R, CF 2 = CF (OCF 2 CF (CF 3)) z - (CF ₂ ) ₂ —CO ₂ R (Z represents an integer of 1 to 8, R represents an alkyl group having 1 to 3 carbon atoms (not substituted with fluorine)) and the like.

As a method for polymerizing such a precursor polymer, a solution polymerization method in which a vinyl fluoride compound is dissolved in a solvent such as chlorofluorocarbon and then reacted with a tetrafluoroethylene gas to perform polymerization. Polymerization is performed without using a solvent such as chlorofluorocarbon. Examples thereof include a bulk polymerization method, and an emulsion polymerization method in which a vinyl fluoride compound is charged with water in a surfactant and emulsified, and then reacted with tetrafluoroethylene gas for polymerization. In any of the above polymerization methods, the reaction temperature is preferably 30 to 90 ° C., and the reaction pressure is preferably 280 to 1100 kPa.
The melt index MI (g / 10 minutes) measured at 270 ° C., load 2.16 kgf, orifice inner diameter 2.09 mm based on JIS K-7210 of the precursor polymer thus produced is not limited. It is preferably 0.001 or more and 1000 or less, more preferably 0.01 or more and 100 or less, and most preferably 0.1 or more and 10 or less.
Next, the precursor polymer is immersed in a basic reaction liquid and subjected to a hydrolysis treatment at 10 to 90 ° C. for 10 seconds to 100 hours. The basic reaction liquid is not limited, but an aqueous solution of an alkali metal or alkaline earth metal hydroxide such as potassium hydroxide or sodium hydroxide is preferred. The content of the alkali metal or alkaline earth metal hydroxide in the basic reaction liquid is not limited, but is preferably 10 to 30% by mass with respect to the mass of the basic reaction liquid. The basic reaction liquid preferably contains a swellable organic compound such as dimethyl sulfoxide or methyl alcohol. As a content rate of the swellable organic compound in a basic reaction liquid, it is preferable that it is 1-30 mass% with respect to the mass of a basic reaction liquid.
After the hydrolysis treatment as described above, the perfluorocarbon polymer having a proton exchange group is produced by further acid treatment with hydrochloric acid or the like. The proton exchange capacity of the perfluorocarbon polymer having a proton exchange group is not limited, but is preferably 0.6 to 4.1 per gram, more preferably 1.0 to 3.5, and most preferably 1.2 to 2. 0.

Next, a perfluorocarbon having a proton exchange group in the protic solvent is obtained by a method in which a perfluorocarbon polymer having a proton exchange group and a protic solvent are placed in an autoclave and heat-treated at 40 to 300 ° C. for 10 minutes to 100 hours. A pre-stage solution C in which the polymer is dissolved can be obtained. The solution here includes a state in which the perfluorocarbon polymer is dispersed in a micelle form. The content of the perfluorocarbon polymer in the pre-stage solution C is preferably 0.1 to 50 mass%, more preferably 0.1 to 30 mass%, most preferably 1 with respect to the mass of the pre-stage solution C. -10 mass%.
For the pre-stage solution B, a perfluorocarbon polymer having a proton exchange group and an aprotic solvent are placed in an autoclave and subjected to heat treatment at 40 to 300 ° C. for 10 minutes to 100 hours, or solvent substitution of the pre-stage solution C (The aprotic solvent is volatilized and then an aprotic solvent is added). The content of the perfluorocarbon polymer in the pre-stage solution B is preferably 0.01 to 50 mass%, more preferably 0.1 to 30 mass%, most preferably 1 with respect to the mass of the pre-stage solution B. -10 mass%.
The pre-stage solution A and the pre-stage solution B produced as described above are mixed by a known stirring method, and the pre-stage solution C is further added and stirred to mix. Further, if necessary, concentration is performed. In this way, a casting liquid is obtained.

Next, a cast liquid is cast on a support, a liquid coating film is formed on the support, and a liquid medium is removed from the liquid coating film, whereby a reinforcing layer can be obtained. As a casting method, a known coating method such as a gravure roll coater, a natural roll coater, a reverse roll coater, a knife coater, or a dip coater can be used. Although the support body used for casting is not limited, a general polymer film, a metal foil, a substrate made of alumina, Si, or the like can be suitably used. Such a support is optionally removed from the reinforcing layer when a membrane / electrode assembly (described later) is formed. Further, the porous medium obtained by stretching the PTFE film described in Japanese Patent Publication No. 5-75835 was impregnated with the casting liquid, and then the liquid medium was removed, thereby including a reinforcing body (the porous film). A reinforcing layer can also be produced. Further, by adding a fibrillated fiber made of PTFE or the like to the casting solution and casting it, and removing the liquid medium, it is shown in Japanese Patent Publication No. 53-149981 and Japanese Patent Publication No. 63-61337. It is also possible to produce a reinforcing layer reinforced with fibrillated fibers. The reinforcing layer thus obtained may be subjected to heat treatment (annealing) at 40 to 300 ° C., preferably 80 to 200 ° C., if desired.
A plurality of reinforcing layers manufactured by the above method, or a non-reinforcing layer composed of a reinforcing layer and a proton exchange resin is prepared, and these are laminated in a known press technology such as hot press, roll press, vacuum press, etc. The polymer electrolyte laminate film of the present invention can be produced by bonding using a lamination technique. At this time, if necessary, the reinforcing layer or the non-reinforcing layer may be bonded on a general polymer film, metal foil, alumina, Si, or other substrate, and may be bonded as necessary. You may peel the used base material. A polymer electrolyte membrane obtained by laminating a plurality of reinforcing layers having the same composition and using the same basic polymer is regarded as a uniform membrane and does not correspond to the polymer electrolyte laminated membrane of the present invention.

As temperature conditions at the time of the said joining, it is preferable that it is 10-300 degreeC, More preferably, it is 40-250 degreeC, Most preferably, it is 80-200 degreeC. Moreover, as a press pressure condition at the time of the said joining, it is preferable that it is 0.01-100 Mpa, More preferably, it is 0.1-10 Mpa, Most preferably, it is 1-5 Mpa. The pressing time is preferably 0.01 to 100 minutes, more preferably 0.1 to 50 minutes, and most preferably 1 to 20 minutes, depending on the pressing pressure. Furthermore, the atmospheric pressure at the time of joining is preferably 0.01 to 200 kPa, more preferably 0.1 to 100 kPa, and most preferably 1 to 50 kPa.
The polymer electrolyte laminate film thus obtained may be subjected to heat treatment (annealing) at 40 to 300 ° C., preferably 80 to 200 ° C., if desired. Further, acid treatment with hydrochloric acid, nitric acid or the like may be carried out if desired in order to fully exhibit the original proton exchange capacity. In addition, stretch orientation can be imparted by using a horizontal uniaxial tenter or a simultaneous biaxial tenter.
(Membrane / electrode assembly)

When the polymer electrolyte laminate film of the present invention is used in a polymer electrolyte fuel cell, a membrane / electrode assembly in which the polymer electrolyte laminate film of the present invention is held tightly between an anode and a cathode (Hereinafter often referred to as "MEA"). Here, the anode is composed of an anode catalyst layer and has proton conductivity, and the cathode is composed of a cathode catalyst layer and has proton conductivity. Further, a gas diffusion layer (described later) joined to the outer surface of each of the anode catalyst layer and the cathode catalyst layer is also referred to as MEA.
The anode catalyst layer includes a catalyst that easily oxidizes fuel (for example, hydrogen) to easily generate protons, and the cathode catalyst layer reacts protons and electrons with an oxidizing agent (for example, oxygen or air) to generate water. Includes catalyst. For both the anode and the cathode, platinum or a catalyst in which platinum and ruthenium are alloyed is preferably used as the catalyst, and the catalyst particles are preferably 10 to 1000 angstroms or less. Such catalyst particles are preferably supported on conductive particles having a size of about 0.01 to 10 μm such as furnace black, channel black, acetylene black, carbon black, activated carbon, and graphite. The amount of catalyst particles supported relative to the projected area of the catalyst layer is preferably 0.001 mg / cm ^{2 to} 10 mg / cm ² or less.
Further, the anode catalyst layer and the cathode catalyst layer preferably contain a perfluorocarbon sulfonic acid polymer represented by the above formula (2) or the above formula (3). The supported amount with respect to the projected area of the catalyst layer is preferably 0.001 mg / cm ^{2 to} 10 mg / cm ² or less.

In the MEA, it is preferable that the reinforcing layer constituting the polymer electrolyte laminated film is adjacent to the cathode catalyst layer. Furthermore, the content of the fluorine-based polymer electrolyte (a) in the reinforcing layer is 70 to 99% by mass, the content of the basic polymer (b) in the reinforcing layer is 1 to 30% by mass, The thickness is preferably 1 to 20 μm. Since MEA has such a structure, more excellent durability can be obtained.
As a method for manufacturing the MEA, for example, the following method can be given. First, a commercially available platinum-supporting carbon (for example, TEC10E40E manufactured by Kuninaka Tanaka Kikai Co., Ltd.) is used as a catalyst in a perfluorocarbon sulfonic acid polymer dissolved in a mixed solution of alcohol and water to form a paste. A certain amount of this is applied to one side of each of the two PTFE sheets and dried to form a catalyst layer. Next, the coated surfaces of the PTFE sheets face each other, the polymer electrolyte laminate film of the present invention is sandwiched therebetween, and is transferred and bonded by hot pressing at 100 to 200 ° C., and then the PTFE sheet is removed to remove the MEA. Can be obtained. A person skilled in the art knows how to make MEAs. The method for producing MEA is described in, for example, JOURNAL OF APPLIED ELECTROCHEMISTRY, 22 (1992) p. 1-7.
As the gas diffusion layer, commercially available carbon cloth or carbon paper can be used. Representative examples of the former include carbon cloth E-tek, B-1 manufactured by DE NORA NORTH AMERICA, USA. Representative examples of the latter include CARBEL (registered trademark, Japan Gore-Tex, Japan), Japan. Examples include TGP-H manufactured by Kunito Toray Industries, Inc., and carbon paper 2050 manufactured by SPECTRACORP USA. A structure in which the electrode catalyst layer and the gas diffusion layer are integrated is called a “gas diffusion electrode”. MEA can also be obtained by bonding the gas diffusion electrode to the polymer electrolyte laminate film of the present invention. A typical example of a commercially available gas diffusion electrode is a gas diffusion electrode ELAT (registered trademark) manufactured by DE NORA NORTH AMERICA (using carbon cloth as a gas diffusion layer).
(Solid polymer fuel cell)

Basically, when the MEA anode and cathode are bonded to each other via an electron conductive material located outside the polymer electrolyte laminate film, an operable solid polymer fuel cell can be obtained. A person skilled in the art knows how to make a polymer electrolyte fuel cell. The polymer electrolyte fuel cell is prepared by, for example, FUEL CELL HANDBOOK (VAN NOSTRAND REINHOLD, AJ APPLEBY et.al, ISBN 0-442-31926-6), Chemical One Point, Fuel Cell (Second Edition). ), Masao Taniguchi, Manabu Senoo, Kyoritsu Shuppan (1992).
As the electron conductive material, a current collector such as a composite material of graphite or resin having a groove for flowing a gas such as fuel or oxidant on its surface, or a metal plate is used. When the MEA does not have a gas diffusion layer, the MEA is incorporated into a single cell casing (for example, PEFC single cell manufactured by Electrochem Inc., USA) with the gas diffusion layer positioned on the outer surface of each anode and cathode of the MEA. Thus, a polymer electrolyte fuel cell can be obtained.

In order to extract a high voltage, the fuel cell is operated as a stack cell in which a plurality of single cells as described above are stacked. In order to produce such a fuel cell as a stack cell, a plurality of MEAs are produced and assembled into a stack cell casing (for example, PEFC stack cell manufactured by US Electrochem Corp.). In such a fuel cell as a stack cell, a current collector called a bipolar plate is used which serves to separate the fuel and oxidant of adjacent cells and to serve as an electrical connector between the adjacent cells.
The fuel cell is operated by supplying hydrogen to one electrode and oxygen or air to the other electrode. The higher the operating temperature of the fuel cell, the higher the catalyst activity. Usually, it is often operated at 50 to 80 ° C., where moisture management is easy, but it can also be operated at 80 to 150 ° C.
The polymer electrolyte laminate film of the present invention can also be used for chloralkali electrolysis, water electrolysis, hydrohalic acid electrolysis, salt electrolysis, oxygen concentrator, humidity sensor, gas sensor and the like. For a method of using the polymer electrolyte membrane for the oxygen concentrator, see, for example, Chemical Engineering, 56 (3), p. 178-180 (1992) and U.S. Pat. No. 4,879,016. For a method of using a polymer electrolyte membrane for a humidity sensor, see, for example, Journal of the Japan Ion Exchange Society, 8 (3), p. 154-165 (1997) and J. Fang et al., Macromolecules, 35, 6070 (2002). For a method of using a polymer electrolyte membrane for a gas sensor, see, for example, Analytical Chemistry, 50 (9), p. 585-594 (2001), X. Yang,
See S. Johnson, J. Shi, T. Holesinger, B. Swanson: Sens. Actuators B, 45, 887 (1997).

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not restrict | limited to these Examples. Evaluation methods and measurement methods used in Examples and Comparative Examples are as follows.
(Haze value measurement)
Based on JIS K 7136, the haze value of the polymer electrolyte membrane was measured using a haze guard II manufactured by Toyo Seiki Seisakusho, Japan. When the film thickness was other than 50 μm, the converted haze value H ₅₀ was calculated by the following formula.

（式中、ｔは高分子電解質膜の膜厚（μｍ）を表し、Ｈ_t はＪＩＳ Ｋ ７１３６に従って測定した高分子電解質膜のヘイズ値を表す。）

(In the formula, t represents the film thickness (μm) of the polymer electrolyte membrane, and H _t represents the haze value of the polymer electrolyte membrane measured according to JIS K 7136.)

(Proton conductivity measurement)
A membrane sample is cut out in a wet state and the thickness T is measured. And it attached to the conductivity measuring cell of 2 terminal type which measures the conductivity of the film length direction of width 1cm and length 5cm. This cell was placed in ion exchange water at 80 ° C., and the resistance value R of the real component at a frequency of 10 kHz was measured by an alternating current impedance method, and proton conductivity σ was derived from the following equation.
σ = L / (R × T × W)
σ: proton conductivity (S / cm)
T: Thickness (cm)
R: Resistance value (Ω)
L (= 5): film length (cm)
W (= 1): film width (cm)
(OCV acceleration test)
In order to accelerate evaluation of the durability of the polymer electrolyte membrane under high temperature and low humidification conditions, the following OCV accelerated test was conducted. Here, “OCV” means an open circuit voltage.

First, the anode-side gas diffusion electrode and the cathode-side gas diffusion electrode were faced to each other, and a polymer electrolyte membrane was sandwiched between them and incorporated in an evaluation cell. As the gas diffusion electrode, a gas diffusion electrode ELAT (registered trademark) manufactured by DE NORA NORTH AMERICA (Pt loading amount of 0.4 mg / cm ² , the same shall apply hereinafter) to a 5% by mass perfluorosulfonic acid polymer solution SS-910 (Asahi Kasei Co., Ltd., equivalent mass (EW): 910, solvent composition (mass ratio): ethanol / water = 50/50) applied, dried and fixed at 140 ° C. in an air atmosphere did. The amount of polymer supported was 0.8 mg / cm ² .
After this evaluation cell was set in an evaluation apparatus (manufactured by Chino Co., Ltd., Japan) and heated, hydrogen gas was supplied to the anode side and air gas was supplied to the cathode side at 200 cc / min to maintain the OCV state. A water bubbling method was used for gas humidification, and both hydrogen gas and air gas were humidified and supplied to the cell. The test conditions were a cell temperature of 100 ° C., a gas humidification temperature of 50 ° C., and no pressure (atmospheric pressure) on both the anode side and the cathode side.
In order to investigate whether or not pinholes were generated in the polymer electrolyte membrane every 10 hours from the start of the above test, hydrogen gas permeation was performed using a flow type gas permeability measuring device GTR-100FA manufactured by GTR Tech, Japan. The rate was measured. With the anode side of the evaluation cell held at 0.15 MPa with hydrogen gas, argon gas was flowed at 10 cc / min as the carrier gas to the cathode side, and hydrogen that had permeated from the anode side to the cathode side due to cross leak in the evaluation cell. It introduce | transduces into gas chromatograph G2800 with gas, and quantifies the permeation | transmission amount of hydrogen gas. Hydrogen gas permeation amount X (cc), correction coefficient B (= 1.100), polymer electrolyte membrane thickness T (cm), hydrogen partial pressure P (Pa), hydrogen permeation area of polymer electrolyte membrane A (cm ² ) and D (sec) as the measurement time, the hydrogen gas permeability L (cc × cm / cm ² / sec / Pa) is calculated from the following equation.
L = (X × B × T) / (P × A × D)
When the hydrogen gas permeability reached 10 times the value before the OCV test, it was determined as a cross leak and the test was terminated.

[Example 1]
As a fluorine-based polymer electrolyte, a perfluorosulfonic acid polymer represented by [CF ₂ CF ₂ ] _0.812- [CF ₂ -CF (—O— (CF ₂ ) ₂ —SO ₃ H)] _0.188 (hereinafter referred to as “ PFS ”) and poly [2,2 ′-(m-phenylene) -5,5′-bibenzimidazole] (hereinafter referred to as PBI) as the basic polymer, PFS / PBI = 99 / 1 (mass ratio) film 1 (film thickness 30 μm) and PFS / PBI = 90/10 (mass ratio) film 2 (film thickness 20 μm) laminated polymer electrolyte laminate film (film thickness 50 μm) Was manufactured as follows.
PBI having a weight average molecular weight of 27000 (manufactured by Sigma Aldrich Japan Co., Ltd., Japan) was sealed together with dimethylacetamide (DMAC) in an autoclave, heated to 200 ° C. and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a PBI solution having a composition of PBI / DMAC = 10/90 (mass ratio). The intrinsic viscosity of this PBI solution was 0.8 (dl / g). Further, this PBI solution was diluted 10-fold with dimethylacetamide to prepare a pre-stage solution A having a composition of PBI / DMAC = 1/99 (mass ratio).
On the other hand, PFS was prepared as follows. First, as a PFS precursor polymer, a perfluorocarbon polymer (MI: 3.0) of tetrafluoroethylene and CF ₂ ═CFO (CF ₂ ) ₂ —SO ₂ F was produced. The precursor polymer was subjected to a hydrolysis treatment by bringing it into contact with an aqueous solution in which potassium hydroxide (15% by mass) and dimethyl sulfoxide (30% by mass) were dissolved at 60 ° C. for 4 hours. Then, it was immersed in 60 degreeC water for 4 hours. Next, it was immersed in a 2N aqueous hydrochloric acid solution at 60 ° C. for 3 hours, washed with ion-exchanged water and dried to obtain PFS having a proton exchange capacity of 1.41 meq / g.

This PFS was placed in an autoclave together with an aqueous ethanol solution (water: ethanol = 50.0: 50.0 (mass ratio)), sealed, heated to 180 ° C. and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a polymer solution having a composition of PFS: water: ethanol = 5.0: 47.5: 47.5 (mass%). The polymer solution was concentrated under reduced pressure using an evaporator, and then water was added to prepare a PFS: water = 8.5 / 91.5 (mass ratio) solution as the pre-stage solution C.
DMAC was added to the same pre-stage solution C and refluxed at 120 ° C. for 1 hour, followed by concentration under reduced pressure using an evaporator, and the PFS / DMAC = 1.5 / 98.5 (mass ratio) solution was added to the pre-stage solution. Manufactured as B.
Next, after adding 6.5 g of the pre-stage solution A to 40.0 g of the pre-stage solution B and mixing, 68.9 g of the pre-stage solution C is added and stirred, and further concentrated under reduced pressure at 80 ° C. and cast. Liquid 1 was obtained. The concentrations of PFS and PBI in this casting liquid 1 were 5.600 mass% and 0.057 mass%, respectively.
19 g of the cast solution 1 was poured into a petri dish having a diameter of 15.4 cm, and heat treatment was performed on a hot plate at 60 ° C. for 1 hour, 80 ° C. for 1 hour, and 160 ° C. for 1 hour to remove the solvent. Thereafter, ion-exchanged water was poured into the cooled petri dish, and the peeled film was dried with a filter paper to obtain a film 1 having a PFS / PBI = 99/1 (mass ratio) film thickness of 30 μm.

On the other hand, after adding 3.4 g of the pre-stage solution A to 19.0 g of the pre-stage solution B and mixing, 0.3 g of the pre-stage solution C is added and stirred, and further concentrated under reduced pressure at 80 ° C. and cast. Liquid 2 was obtained. The concentrations of PFS and PBI in the casting liquid 2 were 5.60% by mass and 0.62% by mass, respectively.
13 g of the cast solution 2 was poured into a petri dish having a diameter of 15.4 cm, and heat treatment was performed on a hot plate at 60 ° C. for 1 hour, 90 ° C. for 1 hour, and 160 ° C. for 1 hour to remove the solvent. Thereafter, ion-exchanged water was poured into the cooled petri dish, and the peeled film was dried with filter paper to obtain a film 2 having a PFS / PBI = 90/10 (mass ratio) film thickness of 20 μm.
Next, the film 1 and the film 2 obtained as described above were laminated and joined as follows. First, after laminating film 1 and film 2, both sides thereof were sandwiched between Kapton films (300H, film thickness 75 μm). This was set in a compression molding machine (VSF-10, manufactured by Kamito Kogyo Co., Ltd.), vacuum deaeration was performed until the atmosphere became 1.6 kPa, the temperature was raised to 190 ° C., and then 1.6 kPa Pressed for 10 minutes. After the press, the pressure was released and the temperature was lowered to 50 ° C., then the atmosphere was returned to atmospheric pressure, and a sample was taken out.
Furthermore, the sample was immersed in ion-exchanged water, the laminated film was peeled off from the Kapton film, dried, and then heat treated at 200 ° C. to obtain the polymer electrolyte laminated film of the present invention.
The multilayer film is uniformly but slightly yellow has bought high transparency, the haze value was 3.0% (H ₅₀ also 3.0%). Moreover, the proton conductivity of this laminated film was 0.31 S / cm.
The laminated film was assembled in a cell so that the film 1 side was facing the anode and the film 2 side was facing the cathode, and the OCV accelerated test was conducted for 200 hours, but no cross leak occurred. As described above, good results excellent in both durability and high proton conductivity were obtained.

[Example 2]
Using the same pre-stage solution as in Example 1, as a fluorine-based polymer electrolyte, PFS / PBI = 97/3 (mass ratio) film 3 (film thickness 15 μm) and PFS / PBI = 90/10 (mass ratio) ) Film 4 (film thickness of 10 μm) was manufactured as follows.
First, 3.4 g of the pre-stage solution A was added to 19.0 g of the pre-stage solution B and mixed, and then 9.6 g of the pre-stage solution C was added and stirred. Liquid 3 was obtained. The concentrations of PFS and PBI in the cast liquid 3 were 5.60% by mass and 0.17% by mass, respectively.
9.5 g of the cast solution 3 was poured into a petri dish having a diameter of 15.4 cm, and heat treatment was performed on a hot plate at 60 ° C. for 1 hour, 80 ° C. for 1 hour, and 160 ° C. for 1 hour to remove the solvent. Thereafter, ion-exchanged water was poured into the cooled petri dish, and the peeled film was dried with filter paper to obtain a film 3 having a PFS / PBI = 97/3 (mass ratio) with a film thickness of 15 μm.
On the other hand, 2,6.5 g of the cast solution used in Example 1 was poured into a petri dish having a diameter of 15.4 cm, and heat treatment was performed on a hot plate at 60 ° C. for 1 hour, 90 ° C. for 1 hour, and 160 ° C. for 1 hour. Was removed. Thereafter, ion-exchanged water was poured into the cooled petri dish, and the peeled film was dried with a filter paper to obtain a film 4 having a PFS / PBI = 90/10 (mass ratio) film thickness of 10 μm.
The films 3 and 4 obtained as described above were laminated and bonded in the same manner as in Example 1 to produce a polymer electrolyte laminated film of the present invention. The multilayer film is uniformly but slightly yellow has bought high transparency, the haze value was 5.2% (H ₅₀ 10.1%). Moreover, the proton conductivity of this laminated film was 0.30 S / cm.
The laminated film was assembled in a cell with the film 3 side facing the anode and the film 4 side facing the cathode, and an OCV accelerated test was conducted for 200 hr, but no cross leak occurred. As described above, good results excellent in both durability and high proton conductivity were obtained.

[Example 3]
Using the same pre-stage solution as in Example 1, PFS / PBI = 99 / on both sides of film 4 (film thickness: 10 μm) having the same PFS / PBI = 90/10 (mass ratio) as that prepared in Example 2 A polymer electrolyte laminate film (film thickness 50 μm) in which two 1 (mass ratio) films 5 (film thickness 20 μm) were laminated was produced as follows.
Pour 12.7 g of cast liquid 1 used in Example 1 into a petri dish with a diameter of 15.4 cm, and perform heat treatment on a hot plate at 60 ° C. for 1 hour, 80 ° C. for 1 hour, and 160 ° C. for 1 hour to remove the solvent. did. Thereafter, ion-exchanged water was poured into the cooled petri dish, and the peeled film was dried with filter paper to produce two films 5 having a PFS / PBI = 99/1 (mass ratio) film thickness of 20 μm.
Same as Example 1 except that two films 5 are laminated on both sides of film 4 (film thickness 10 μm) having the same PFS / PBI = 90/10 (mass ratio) as produced in Example 2. The polymer electrolyte laminate film of the present invention was manufactured by laminating and joining by the method. The multilayer film is uniformly but slightly yellow has bought high transparency, the haze value was 3.8% (H ₅₀ also 3.8%). Moreover, the proton conductivity of this laminated film was 0.32 S / cm.
This laminated film was incorporated into a cell and an OCV accelerated test was conducted for 200 hours, but no cross leak occurred. As described above, good results excellent in both durability and high proton conductivity were obtained.

[Comparative example]
A polymer electrolyte membrane having a proton exchange capacity of 1.41 meq / g and a film thickness of 50 μm was produced as follows using the pre-stage solution C produced in Example 1.
32 g of the pre-stage solution C was poured into a petri dish having a diameter of 15.4 cm, and heat treatment was performed on a hot plate at 60 ° C. for 1 hour and 80 ° C. for 1 hour to remove the solvent. Thereafter, the petri dish was placed in an oven and heat treated at 200 ° C. for 1 hour. Then, it took out from oven, poured ion-exchange water into the cooled petri dish, the peeled film was dried with the filter paper, and the polymer electrolyte membrane was obtained. This film was transparent and had a haze value of 0.6% (H ₅₀ was 0.6%). The proton conductivity of this membrane was 0.35 S / cm.
When an OCV accelerated test was performed on this film, the hydrogen gas permeability rapidly increased after 40 hours, and the test was terminated. As described above, although proton conductivity is good, sufficient durability was not obtained.

  The polymer electrolyte laminate film of the present invention is excellent in chemical stability, mechanical strength and heat resistance, and has high durability even when used at high temperatures. The polymer electrolyte fuel cell using the polymer electrolyte laminated membrane of the present invention is operated for a long time under high temperature and low humidification conditions (operating temperature near 100 ° C., humidification at 60 ° C. (equivalent to humidity 20% RH)). However, no film breakage (pinholes, etc.) occurs, so there is no cross leak (mixing of fuel and oxidant due to film breakage), and it can be used stably for a long time even under severe conditions. be able to.

TEM photograph of cross section of reinforcing layer in film thickness direction Image obtained by binarizing the TEM photograph of FIG. TEM photograph of the cross section in the film thickness direction of a reinforcing layer having a sea / island structure TEM photograph of the cross section in the film thickness direction of the reinforcing layer that does not have a sea / island structure

Claims (9)

A polymer electrolyte laminate film comprising a laminate of two or more films having a proton exchange resin, wherein at least one layer of the film comprises 85 to 99.99% by mass of the fluorine-based polymer electrolyte (a) and A sea structure mainly composed of the component (a) is composed of 0.01 to 15 % by mass of a basic polymer (b), and a 15 μm × 15 μm region of the cross section in the film thickness direction is observed with a transmission electron microscope. And a reinforcing layer exhibiting a sea / island structure composed of an island structure mainly composed of the component (b) .   The polymer electrolyte multilayer film according to claim 1, wherein the basic polymer is poly [(2,2 '-(m-phenylene) -5,5'-bibenzimidazole]. The converted haze value (H ₅₀ ) is 25% or less, and the converted haze value (H ₅₀ ) is defined as a haze value calculated on the assumption that the film thickness of the polymer electrolyte laminate film is 50 μm, The polymer electrolyte laminate film according to claim 1 or 2, wherein the converted haze value (H ₅₀ ) is calculated by the following formula.

(In the formula, t represents the film thickness (μm) of the polymer electrolyte laminate film, and H _t represents the haze value of the polymer electrolyte laminate film measured according to JIS K 7136.) The polymer electrolyte laminate film according to any one of claims 1 to 3, wherein the reinforcing layer is provided by a process including the following steps (1) to (3).
(1) A pre-stage solution A which is a polymer solution in which a basic polymer (b) is dissolved in an aprotic solution, and a pre-stage which is a polymer solution in which the fluoropolymer electrolyte (a) is dissolved in an aprotic solvent. A step of mixing and stirring the solution B to obtain a mixture of the pre-stage solution A and the pre-stage solution B;
(2) A step of obtaining a pre-stage solution C which is a polymer solution obtained by dissolving the fluoropolymer electrolyte (a) in a protic solvent;
(3) A step of adding the pre-stage solution C to the mixture of the pre-stage solution A and the pre-stage solution B and mixing and stirring the mixture, The polymer electrolyte membrane according to any one of claims 1 to 4, wherein the fluorine-based polymer electrolyte (a) is represented by the following formula (2).

[CF ₂ CF ₂ ] _a -[CF ₂ -CF (-O- (CF ₂ -CF (CF _Three )) _b -O- (CF ₂ ) _f -X ^Four ]] _g ... (2)
(Where 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, 1 ≦ b ≦ 3, 1 ≦ f ≦ 8, and X ^Four Is -COOH, -SO _Three H, -PO _Three H ₂ Or -PO _Three H. ) The polymer electrolyte membrane according to any one of claims 1 to 4, wherein the fluorine-based polymer electrolyte (a) is represented by the following formula (3).

[CF ₂ CF ₂ ] _a -[CF ₂ -CF (-O- (CF ₂ ) _f -X ^Four ]] _g
... (3)
(Where 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, 1 ≦ f ≦ 8, and X ^Four Is -COOH, -SO _Three H, -PO _Three H ₂ Or -PO _Three H. ) A membrane / electrode assembly in which the polymer electrolyte laminate film according to any one of claims 1 to 6 is held tightly between an anode and a cathode, wherein the anode is composed of an anode catalyst layer and has proton conductivity. The membrane / electrode assembly is characterized in that the cathode comprises a cathode catalyst layer and has proton conductivity. 8. The membrane / electrode assembly according to claim 7 , wherein the reinforcing layer constituting the polymer electrolyte laminate film is adjacent to the cathode catalyst layer, and the fluorine-based polymer electrolyte (a) in the reinforcing layer is formed. A membrane having a content of 70 to 99% by mass, a content of the basic polymer (b) in the reinforcing layer of 1 to 30% by mass, and a thickness of the reinforcing layer of 1 to 20 μm / Electrode assembly. A solid polymer comprising the membrane / electrode assembly according to claim 7 or 8 , wherein the anode and the cathode are bonded to each other via an electron conductive material located outside the polymer electrolyte laminate film. Fuel cell.

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