JP2002260705A - Solid polymer electrolyte material, liquid composite, solid polymer fuel cell, fluorine-containing polymer and solid polymer electrolyte film consisting of fluorine-containing polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer fuel cell which can constantly obtain a high fuel output power by involving a solid polymer electrolyte material with excellent ionie conductivity, water repellency and gas permeability, and further, to provide a solid polymer electrolyte material with high softening temperature suitable for a high-temperature operation. SOLUTION: The solid polymer electrolyte material consists of copolymers containing a repetition unit based on a fluorine-containing polymer giving a main chain a polymer having an aliphatic ring structure and a repetition unit based on a fluorine-containing vinyl compound as expressed with CF2 = CF(R<f> )j SO2 X. [j is 0 or 1, X denotes a group expressed by F, Cl, or OM (M denotes H, Na, K or the like), and R<f> denotes a perfluoroalkylene group with 1 to 20 carbon number (which may contain oxygen atom of ether linkage property)].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid polymer electrolyte material, a liquid composition, a solid polymer fuel cell, and a fluoropolymer applicable to these.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell has high cell characteristics and is easy to reduce in size and weight, so that it can be used as a power source for a mobile vehicle such as an electric vehicle or a small cogeneration system. Practical application is expected.
The polymer electrolyte fuel cell currently under study has a low operating temperature range and it is difficult to use its exhaust heat, so operating conditions with high utilization rates of anode reactant gas such as hydrogen and cathode reactant gas such as air are high. In such a case, high power generation efficiency and performance capable of obtaining a high output density are required.

Conventionally, in a polymer electrolyte fuel cell, fine particles of a catalyst such as a metal-supported carbon black coated with the same or different ion exchange resin as the polymer electrolyte membrane have been used as a constituent material of an electrode catalyst layer. The so-called three-dimensional reaction site in the catalyst layer is intended to improve the battery output.

[0004] However, under the above-mentioned operating conditions in which the reaction rate of the battery reaction is relatively high, the amount of water moving with the protons moving through the polymer electrolyte membrane from the anode to the cathode. And the amount of water generated and condensed by the electrode reaction of the cathode increases. Therefore, the water is not quickly discharged from the cathode to the outside, and the phenomenon that the pores for supplying the reaction gas formed in the catalyst layer of the cathode are blocked by the water, that is, the phenomenon of flooding is likely to occur. Was.

[0005] When such flooding occurs, supply of the cathode reaction gas to the reaction site of the catalyst layer is hindered, and a desired battery output cannot be stably obtained. Therefore, in order to improve the battery output and obtain the output stably, it is necessary to improve the gas diffusion property and the water repellency without lowering the ion conductivity in the electrode catalyst layer.

On the other hand, if it is intended to reduce the ion exchange capacity (hereinafter referred to as A _R ) of the ion exchange resin in the catalyst layer to ensure gas diffusion and water repellency in the catalyst layer, the As a result, the water content decreases, the ionic conductivity decreases, and the battery output decreases. Further, in this case, the gas permeability of the ion exchange resin also decreases,
The supply of gas supplied to the reaction site is delayed. As a result, the concentration overvoltage increases and the battery output decreases.

On the other hand, by increasing the A _R of the ion exchange resin contained in the catalyst layer, its ionic conductivity and when intended to improve the gas permeability water content of the ion exchange resin is increased flooding occurs And it is difficult to stably obtain a high battery output.

For this reason, Japanese Patent Application Laid-Open No. 5-36418 discloses that polytetrafluoroethylene (hereinafter referred to as PTFE), tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoro ( There has been proposed a polymer electrolyte fuel cell in which a fluorine-containing polymer such as an (alkyl vinyl ether) copolymer is contained in a cathode catalyst layer. In this specification, “A / B copolymer” refers to a copolymer composed of a repeating unit based on A and a repeating unit based on B.

Japanese Unexamined Patent Publication (Kokai) No. 7-212324 proposes a polymer electrolyte fuel cell in which pitch fluoride is contained in a cathode catalyst layer together with PTFE. Further, Japanese Patent Application Laid-Open No. 7-192938 proposes a method in which the surface of a catalyst is coated with a fluorinated film and used to form a cathode catalyst layer of a polymer electrolyte fuel cell. In addition, Japanese Patent Application Laid-Open Nos. H5-251086 and H7-134993 also propose a method of giving a gradient to the water repellency in the thickness direction of the electrode.

[0010]

However, when a water repellent is contained in the catalyst layer as in the polymer electrolyte fuel cell described in Japanese Patent Application Laid-Open No. 5-36418, the insulating property of the water repellent is reduced. As a result, the cathode's polarization characteristics are rather lowered due to an increase in the electric resistance of the cathode due to the increase in the electric resistance of the cathode due to the increase in the thickness of the catalyst layer, and the battery output cannot be improved. In addition, when the content of the water repellent in the catalyst layer is reduced to increase the battery output, the water repellency in the catalyst layer is reduced, and the polarization characteristics of the electrode are reduced in a relatively short time from the start. Has a problem that flooding occurs.

In the polymer electrolyte fuel cells described in JP-A-7-212324 and JP-A-7-192338, the surface of the catalyst contained in the catalyst layer is uniformly coated with an ion exchange resin. However, there is a problem that a sufficient reaction site corresponding to the amount of the catalyst contained in the cathode catalyst layer cannot be secured, and a high battery output cannot be stably obtained. Furthermore, the polymer electrolyte fuel cells described in JP-A-5-251806 and JP-A-7-134993 have a problem that the manufacturing process is complicated.

The problem of ensuring good gas diffusibility and water repellency in the catalyst layer of the gas diffusion electrode as described above is that the gas diffusion electrode is applied to other electrochemical processes such as electrolysis of water or salt. In this case, it is important in improving the polarization characteristics to improve the efficiency of the process.

Further, the polymer electrolyte fuel cells currently under study have a problem that the operating temperature range is as low as 60 to 90 ° C. and the exhaust heat thereof is difficult to use. In automotive applications, a fuel cell that can be operated at a temperature higher than 100 ° C. is required to reduce the size of a cooling system and reduce catalyst poisoning due to carbon monoxide contained in fuel gas.

At present, in consideration of the practical use of fuel cells, CF ₂ = CF
OCF ₂ CF (CF ₃ ) O (CF ₂ ) _n SO ₃ H (where n represents 2 or 3)
A perfluoro ion exchange resin composed of a copolymer of ethylene and tetrafluoroethylene is mainly used. However, the softening temperature is lower than 100 ° C., and the strength decreases at a high temperature of 100 ° C. or higher. It is difficult to operate at high temperatures. In particular, there is a demand for a membrane material for a fuel cell that has a softening temperature of 100 ° C. or higher and has strength enough to withstand use of the fuel cell.

[0015] The polymer layers are usually also contained in the catalyst layers of the anode and the cathode, and it is preferable that the polymer electrolytes also have a softening temperature higher than the operating temperature from the viewpoint of durability in high-temperature operation. Furthermore, CF ₂ = CFOCF ₂ CF ₂ SO ₃
H and tetrafluoroethylene copolymer has a softening temperature of 1
It is known that the temperature is higher than 00 ° C (ACS Symp. Ser.
(1989), Vol. 395, pp 370-400), but the production cost is high and it is difficult to produce industrially.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a fluorine-containing polymer having excellent ion conductivity, water repellency and gas permeability, a solid polymer electrolyte material comprising the same, and a solid polymer electrolyte. A liquid polymer composition comprising a polymer electrolyte material, a membrane comprising the polymer electrolyte material, and a polymer electrolyte fuel cell capable of stably obtaining a high battery output by including the polymer electrolyte material as a constituent material. The purpose is to provide. Another object of the present invention is to provide a solid polymer electrolyte material having a softening temperature higher than that of the related art, in order to enable the operation of the polymer electrolyte fuel cell at a higher temperature than before.

[0017]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a fluorinated sulfonic acid polymer having an aliphatic ring structure in a polymer has high ionic conductivity. When this is used as the solid polymer electrolyte material of the electrode catalyst layer of the polymer electrolyte fuel cell, it is possible to improve the output of the fuel cell while ensuring sufficient ion conductivity in the catalyst layer. Heading, the present invention has been reached. Further, the present inventors have found that the fluorinated sulfonic acid polymer having an aliphatic ring structure has a high ionic conductivity, and at the same time, has a higher softening temperature than a conventional sulfonic acid polymer, and a solid polymer type The material was found to be suitable for high-temperature operation of fuel cells.

That is, the present invention relates to a repeating unit based on a fluorine-containing monomer A which gives a polymer having an aliphatic ring structure in the main chain by radical polymerization, and a repeating unit based on a fluorine-containing monomer B represented by the following formula (1). The present invention provides a solid polymer electrolyte material comprising a copolymer containing CF ₂ = CF (R ^f ) _j SO ₂ X (1) Here, in the formula (1), j represents 0 or 1, and X represents a fluorine atom, a chlorine atom or a group represented by OM. And
M in the group represented by OM represents a hydrogen atom, an alkali metal atom, or a group represented by NR ¹ R ² R ³ R ⁴ . Furthermore, NR ¹
R ¹ , R ² , R ³ and R ^{4 in the} group represented by R ² R ³ R ⁴ may be the same or different and each represents a hydrogen atom or a monovalent organic group, but is preferably a hydrogen atom or a monovalent organic group. C 1-4
Is an alkyl group. R ^f is a linear or branched polyfluoroalkylene group having 1 to 20 carbon atoms, and may contain an etheric oxygen atom.

In the present specification, the "solid polymer electrolyte material" includes its precursor. That is, -SO ₃ when X of the —SO ₂ X group shown in the formula (1) is OM described above.
In addition to the ionic conductivity of the fluoropolymer having an M group in the molecule, the fluoropolymer also solid high having a -SO ₂ F group or -SO ₂ Cl group is a precursor of the -SO ₃ M group in the molecule It is referred to as a molecular electrolyte material. When the solid polymer electrolyte material of the present invention is a fluoropolymer having a —SO ₂ F group or a —SO ₂ Cl group in the molecule, the solid polymer electrolyte material is subjected to a hydrolysis treatment using an aqueous base solution or the like to obtain a —SO ₃ M
It can be converted into a fluorine-containing ion-conductive polymer having a group in the molecule and used as a solid polymer electrolyte material.

Therefore, when discussing the ionic conductivity of the solid polymer electrolyte material of the present invention in the following description,
When the obtained solid polymer electrolyte material is a fluorine-containing polymer having a —SO ₂ F group or a —SO ₂ Cl group in the molecule by X shown in the formula (1), this is subjected to hydrolysis treatment, _It shows the ionic conductivity of a fluorine-containing ion conductive polymer having a 3M group in the molecule.

In the present invention, the "fluorinated monomer A which gives a polymer having an aliphatic ring structure in the main chain" is a polymer which has an aliphatic ring structure in the main chain by radical polymerization. Specifically, there are two kinds of monomers: a monomer having an aliphatic ring structure in the molecule, and a cyclopolymerizable monomer having no aliphatic ring structure in the molecule but forming an aliphatic ring structure with the progress of the polymerization reaction. There are types. Further, “having an aliphatic ring structure in the main chain” means that at least one carbon atom of the aliphatic ring structure in the repeating unit is shared by the main chain.

It is considered that the solid polymer electrolyte material of the present invention has high gas permeability because it has a repeating unit based on the above-mentioned fluorine-containing monomer A. Also,
Since it has a repeating unit based on the fluorine-containing monomer B having a —SO ₂ X group, it also has high ion conductivity. Further, the fluorine atoms bonded to the carbon chains in these repeating units contribute to water repellency. Therefore, if the solid polymer electrolyte material of the present invention is used as a constituent material of the electrode catalyst layer of the polymer electrolyte fuel cell, the gas diffusion property is maintained in the catalyst layer while maintaining high ion conductivity and water repellency. As a result, the output of the battery is improved, and the occurrence of flooding is effectively prevented, so that the high output can be obtained stably.

As described above, the reason why the polymer electrolyte fuel cell using the polymer electrolyte material of the present invention for the electrode catalyst layer exhibits a high output has not been clearly elucidated, but the polymer electrolyte material is not clearly understood. It is thought to be due to the aliphatic ring structure contained in the repeating unit based on the fluorine-containing monomer A therein. That is, it is considered that the gas permeability is improved as compared with the conventional solid polymer electrolyte material by making the solid polymer electrolyte material amorphous due to the aliphatic ring structure. In addition, a gas diffusion electrode provided with a catalyst layer containing the solid polymer electrolyte material of the present invention as a constituent material, or a polymer electrolyte membrane formed from the solid polymer electrolyte material of the present invention is a solid polymer fuel cell only. Instead, it can also be used for electrochemical processes such as salt electrolysis.

The present invention also provides a solid polymer electrolyte material as described above, wherein the terminal -SO ₂ X group of the repeating unit based on the fluorine-containing monomer B is a -SO ₃ M group. Is dissolved or dispersed in an organic solvent having a hydroxyl group in the molecule. Here, M has the same meaning as M described in Formula (1). Further, the liquid composition may contain water, and when the boiling point of the organic solvent is lower than the boiling point of water, by adding water to the liquid composition and distilling off the organic solvent, A liquid composition in which the sulfonic acid polymer is dissolved or dispersed in water substantially free of an organic solvent can also be obtained.

In the solid polymer electrolyte material of the present invention,
When the SO ₂ X group is a —SO ₃ M group, it can be dissolved or satisfactorily dispersed in an organic solvent having a hydroxyl group in the molecule. For example, when a liquid in which catalyst fine particles are dispersed in a liquid composition obtained by dissolving or dispersing a solid polymer electrolyte material having a -SO ₃ H group in the organic solvent among the solid polymer electrolyte materials of the present invention, A catalyst layer of a polymer fuel cell can be easily formed, and a catalyst layer having excellent gas permeability can be provided.

Further, the present invention relates to a polymer electrolyte fuel cell having an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode, wherein the polymer electrolyte is a fluorine-containing fuel cell. monomer B provides a polymer electrolyte fuel cell which comprises a solid polymer electrolyte material having a -SO ₃ H group as a cathode of the material.

As described above, the solid polymer electrolyte fuel cell using the solid polymer electrolyte material of the present invention as a constituent material of the catalyst layer of the cathode is capable of obtaining a stable and high battery output for a long time. This is because the diffusion of oxygen gas is improved while the ion conductivity and water repellency in the catalyst layer of the cathode are sufficiently ensured, so that the oxygen concentration overvoltage is reduced and flooding is effectively prevented. Can be

Also, the solid polymer electrolyte material of the present invention comprises:
Since it has an aliphatic ring structure in the main chain, it has a higher softening temperature than conventional sulfonic acid polymers and is suitable for high-temperature operation of fuel cells.

Further, the present invention relates to a copolymer substantially comprising a repeating unit represented by the following formula (I) and a repeating unit based on a fluorine-containing monomer D represented by the following formula (II). And a fluorine-containing polymer having a content of the repeating unit based on the fluorine-containing monomer D of 10 to 75 mol% and a number average molecular weight of 5,000 to 5,000,000.

[0030]

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In the formulas (I) and (II), R ^f16
And R ^f17 may be the same or different and each represents a fluorine atom or a trifluoromethyl group; k ′ represents 0 or 1; Y has the same ^meaning as Y in formula (2);
Has the same meaning as M in Formula (1).

The present invention also relates to a copolymer substantially consisting of a repeating unit based on perfluoro (3-butenyl vinyl ether) and a repeating unit based on the fluorine-containing monomer D represented by the formula (II). Wherein the content of the repeating unit based on the fluorine-containing monomer D is 10 to 75.
Mol%, and the number average molecular weight is 5,000 to 500.
0000 is provided.

The present invention further relates to a repeating unit based on perfluoro (2-methylene-4-methyl-1,3-dioxolane) and a repeating unit based on the fluorine-containing monomer D represented by the above formula (II). Wherein the content of the repeating unit based on the fluorine-containing monomer D is from 10 to 75 mol%, and the number-average molecular weight is from 5,000 to 5,000,000. Provide a polymer.

These fluoropolymers of the present invention are considered to have particularly high gas permeability among the solid polymer electrolyte materials of the present invention, and also have particularly high ionic conductivity. Further, the fluorine atoms bonded to the carbon chains in these repeating units contribute to water repellency. Therefore, the above-mentioned fluoropolymer of the present invention can be preferably used as a constituent material of a gas diffusion electrode or a polymer electrolyte membrane provided in the above-mentioned electrochemical process. In addition, it has a higher softening temperature than conventional sulfonic acid polymers and is suitable for high-temperature operation of fuel cells.

In a fluoropolymer substantially consisting of a repeating unit represented by the formula (I) and a repeating unit based on the fluorine-containing monomer D represented by the formula (II),
If the content of the repeating unit based on the fluorine-containing monomer D in the fluorine-containing polymer is less than 10 mol%, the proton conductivity is undesirably reduced. On the other hand, if the above content exceeds 75 mol%, the gas diffusivity becomes small, which is not preferable. And from a viewpoint similar to the above, it is more preferable that the content of the repeating unit based on the fluorine-containing monomer D in the copolymer is 15 to 60 mol%.

Further, when the number average molecular weight of the fluoropolymer is less than 5,000, the physical properties such as the degree of swelling change with time, resulting in insufficient durability. On the other hand, when the number average molecular weight exceeds 5,000,000, it becomes difficult to prepare a solution. And from a viewpoint similar to the above, it is more preferable that the number average molecular weight of the fluoropolymer is 10,000 to 3,000,000.

Further, a fluorine-containing polymer substantially consisting of a repeating unit based on perfluoro (3-butenylvinyl ether) and a repeating unit based on the fluorine-containing monomer D represented by the formula (II) is also represented by the aforementioned formula (I). Like the fluorine-containing polymer containing the repeating unit represented by I), the content of the repeating unit based on the fluorine-containing monomer D in this fluorine-containing polymer is preferably from 10 to 75 mol%, and preferably from 15 to 60 mol%. % Is more preferable. Further, the number average molecular weight of this fluoropolymer is also 5,000 to
500000, preferably 10,000 to 3
More preferably, it is 000000.

Further, perfluoro (2-methylene-4-
A fluorine-containing polymer substantially consisting of a repeating unit based on methyl-1,3-dioxolane) and a repeating unit based on the fluorine-containing monomer D represented by the formula (II) is also represented by the aforementioned formula (I). Like the fluorine-containing polymer containing a repeating unit, the content of the repeating unit based on the fluorine-containing monomer D in the fluorine-containing polymer is preferably from 10 to 75 mol%, more preferably from 15 to 60 mol%. preferable. Further, the number average molecular weight of this fluoropolymer is also preferably 5,000 to 5,000,000, and more preferably 10,000 to 3,000,000.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments when the present invention is applied to a polymer electrolyte fuel cell will be described below in detail.

The polymer electrolyte fuel cell of the present invention has an anode, a cathode, and a structure disposed between the anode and the cathode. Each of the cathode and anode, which are gas diffusion electrodes, comprises a gas diffusion layer and a catalyst layer adjacent to the gas diffusion layer. As a constituent material of the gas diffusion layer, a porous body having electron conductivity (for example, carbon cloth or carbon paper) is used.

The catalyst layer of the cathode mainly contains the above-mentioned solid polymer electrolyte material (-SO ₃ H type) of the present invention and a catalyst, thereby improving the battery output and stabilizing the high battery output. It is intended to ensure good ion conductivity and water repellency in the catalyst layer, which can be obtained by the above method, and to improve gas diffusibility.

The solid polymer electrolyte material of the present invention contained in the catalyst layer of the cathode comprises a copolymer containing a repeating unit based on the fluorinated monomer A and a repeating unit based on the fluorinated monomer B. Fluorine monomer A,
It is preferable that both the fluorinated monomers B are perfluoro monomers. In particular, the fluorine-containing monomer B is preferably a compound represented by the following formula (2), and particularly preferably a compound represented by the formula (6).

[0043]

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Here, in the equations (2) and (6), k is 0
An integer of 1 to 2, m is an integer of 1 to 12, k ′ represents 0 or 1, Y represents a fluorine atom or a trifluoromethyl group, and X has the same meaning as X in the above formula (1). is there.
Thus, the fluorine-containing monomer A and the fluorine-containing monomer B
When both are perfluoromonomers, the water repellency and durability of the resulting solid polymer electrolyte material are improved. Further, when the fluorine-containing monomer B is a compound represented by the formula (2), the obtained solid polymer electrolyte material shows good ion conductivity.

As described above, the fluorine-containing monomer A in the present invention specifically includes two types of a monomer having an aliphatic ring structure in the molecule and a cyclopolymerizable monomer. However, the repeating unit based on the fluorine-containing monomer A is preferably represented by any of the following formulas (3) to (5).

[0046]

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[0047]

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Here, in the formula (3), p, q and r each independently represent 0 or 1, R ^f1 and R ^f2 may be the same or different, and each represents a fluorine atom and a carbon number of 1-5.
Represents a perfluoroalkyl group or a perfluoroalkoxy group having 1 to 5 carbon atoms, and R ^f3 represents 1 to 3 carbon atoms.
Wherein the substituent is a perfluoroalkyl group having 1 to 5 carbon atoms or a perfluoroalkyl group having 1 to 5 carbon atoms.
May have a perfluoroalkoxy group.

In the formula (4), s represents 0 or 1,
R^f4, R^f5, R^f6And R^f7May be the same or different
Each of which is a fluorine atom or a perfluoro group having 1 to 5 carbon atoms.
R represents any one of^f8Is a fluorine atom, carbon
1 to 5 perfluoroalkyl group or 1 to 5 carbon atoms
Shows a perfluoroalkoxy group. However, the above R ^f4
And R^f5And are linked when s = 0 to form a spiro ring
You may.

Further, in the formula (5), R ^f9 , R ^f10 , R ^f11 and R ^f12 may be the same or different and each represents a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms. .

The structure of the repeating unit represented by the above formula (3) can be formed from a cyclopolymerizable monomer,
A perfluoroalkyl group having 1 to 5 carbon atoms or a perfluoroalkoxy group having 1 to 5 carbon atoms may be bonded as a substituent to the perfluoroalkylene group represented by R ^f3 . When cyclopolymerization is carried out, in the formula (3), q
When r = 0, r = 1, and when q = 1, r = 0.
Specific examples of the repeating unit include those represented by the following formulas (7) to (22).

[0052]

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[0053]

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[0054]

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The structure of the repeating unit represented by the above formula (4) can be formed from a monomer having an aliphatic ring structure in the molecule. As the repeating unit, specifically, for example, the following formulas (23) to (32)
The following are mentioned. Further, in the structure of the repeating unit represented by the formula (4), when s = 0, when the spiro ring formed by R ^f4 and R ^f5 is a 4- to 6-membered ring, ether is used as an element constituting this ring. And a perfluoroalkyl group may be bonded as a substituent to this ring. Examples of the structure of the repeating unit based on a monomer having an aliphatic ring structure in the molecule include those represented by the following formula (33).

[0056]

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[0057]

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Further, the structure of the repeating unit represented by the above formula (5) can also be formed from a monomer having an aliphatic ring structure in the molecule. As the repeating unit, specifically, for example, the following formulas (34) to (36)
The following are mentioned.

[0059]

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Among the repeating units based on the fluorine-containing monomer A, in particular, from the group consisting of the repeating units represented by the formulas (7), (23), (24), (29) and (34), respectively. One or more selected is preferred. The monomers (fluorinated monomers A) used as raw materials for introducing these repeating units into the copolymer constituting the solid polymer electrolyte material are as follows. Formula (7): Perfluoro (3-butenyl vinyl ether), Formula (23): Perfluoro (2,2-dimethyl-1,3-dioxole), Formula (24): Perfluoro (1,3-dioxole) , Formula (29): 2,2,4-
Trifluoro-5-trifluoromethoxy-1,3-dioxole, formula (34): perfluoro (2-methylene-4-methyl-1,3-dioxolane).

These repeating units and the above formula (6)
A solid polymer electrolyte material comprising a copolymer containing a repeating unit based on a monomer represented by the following formula (1) is particularly preferable because it has high ion conductivity, excellent water repellency, and excellent oxygen permeability. In particular, the inclusion of those with -SO ₃ H groups of the copolymer in the catalyst layer of the cathode of a polymer electrolyte fuel cell, the output of the solid polymer electrolyte fuel cell obtained be made higher than the conventional it can.

Among the solid polymer electrolyte materials of the present invention,
A repeating unit represented by the above formula (I);
And a repeating unit based on the fluorine-containing monomer D represented by the formula: wherein the content of the repeating unit based on the fluorine-containing monomer D is 10 to 75 mol%, and the number average molecular weight is Is 5000 to 5,000,000
Is preferred. In addition, a copolymer substantially consisting of a repeating unit based on perfluoro (3-butenyl vinyl ether) and a repeating unit based on the fluorine-containing monomer D represented by the above formula (II) is also available. Further, a fluorine-containing polymer having a repeating unit content of 10 to 75 mol% based on the fluorine-containing monomer D and a number average molecular weight of 5,000 to 5,000,000 is also preferable.

Further, a repeating unit based on perfluoro (2-methylene-4-methyl-1,3-dioxolane) and a repeating unit based on the fluorine-containing monomer D represented by the above formula (II) And a fluorine-containing polymer having a repeating unit content of 10 to 75 mol% based on the fluorine-containing monomer D and a number average molecular weight of 5,000 to 5,000,000 is also preferable.

Further, as in the present embodiment, the present invention
Solid polymer electrolyte material for polymer electrolyte fuel cell electrolyte
When used as a material, based on fluorine-containing monomer A
A repeating unit based on a repeating unit and a fluorine-containing monomer B
-SO of the copolymer containing _TwoX group is -SO_ThreeOther than H group
In the case of_ThreeConvert to H group
Before using. The precursor, -SO_TwoOf the F group
The hydrolysis treatment is carried out, for example, with a base such as NaOH or KOH.
Aqueous solution or a mixed solution of the base, water and a water-soluble organic solvent
Use -SO_ThreeNa group, -SO_ThreeConvert to a K group or the like. This
These acid-forming treatments are performed, for example, with water such as hydrochloric acid, nitric acid and sulfuric acid.
Using the solution, -SO_ThreeConvert to H group.

The softening temperature of the copolymer which is the solid polymer electrolyte material of the present invention is preferably 100 ° C. or higher. Here, the softening temperature of the solid polymer electrolyte material in the present invention is, in the evaluation test of the dynamic viscoelasticity of the solid polymer electrolyte material, while gradually increasing the temperature of the solid polymer electrolyte material from around room temperature. It shows the temperature at which the elastic modulus of the solid polymer electrolyte material starts to drop sharply when the elastic modulus is measured. Therefore, the softening temperature in the present invention is different from the glass transition temperature usually obtained from the value of tan δ, and generally indicates a temperature observed in a temperature range lower than the glass transition temperature.

The softening temperature can be specifically measured by a thermal mechanical analyzer (TMA) by a penetration method using a quartz probe having a diameter of 1 mm. That is, the solid polymer electrolyte material to be measured is cast from a solution into a film, and a quartz probe is brought into contact with the film from the normal direction of the surface of the film, and
The temperature is increased at a rate of 10 ° C./min, and the temperature at which the thickness of the film begins to rapidly decrease due to the probe being immersed in the film is measured as the softening temperature.

It should be noted that the value of the softening temperature obtained by this method coincides with the above-mentioned temperature value at which a sudden decrease in the elastic modulus which appears in the profile of the temperature dependence of the elastic modulus of the polymer starts to be observed. Confirmed in advance. When the load of the probe applied to the film is too small, thermal expansion of the film is observed. However, by optimizing the load, it is possible to measure the degree of indentation of the probe at the softening temperature of the film without any trouble.

Since the operating temperature of a polymer electrolyte fuel cell is generally 80 ° C. or lower, if the softening temperature of the solid polymer electrolyte material contained in the catalyst layer is 100 ° C. or higher, the catalyst layer during the operation of the cell may be used. It is possible to suppress a temporal change in physical properties such as the degree of swelling of the solid polymer electrolyte material therein. Therefore, the durability of the solid polymer electrolyte material in the catalyst layer during operation of the battery is improved. In addition, the softening temperature is 1
If a solid polymer electrolyte material at a temperature of 00 ° C. or higher is used as a material for the anode catalyst layer and the polymer electrolyte membrane in addition to the cathode catalyst layer, the electrolyte material in the anode catalyst layer during the operation of the battery as described above. Alternatively, the durability of the polymer electrolyte membrane is improved, and thus the battery life can be improved.

Further, in this case, the operating temperature of the conventional solid polymer fuel cell is made higher than 80 ° C. by using a solid polymer electrolyte material having a softening temperature of 100 ° C. or more also for the polymer electrolyte membrane. be able to. As a result, the exhaust heat of the battery can be more effectively used, and the heat of the battery can be easily removed, so that the temperature control of the battery during operation becomes easier.

In this case, catalyst poisoning due to carbon monoxide or the like contained in the anode reaction gas can be reduced, and in this respect, the battery life can be improved. Furthermore, even when the solid polymer electrolyte material of the present invention is used as a solid acid catalyst, if the softening temperature can be increased, the reaction temperature can be increased, so that the desired reaction can be performed in a higher temperature range. Becomes possible.

In order to have a high softening temperature and obtain practical strength as a film, the repeating unit represented by the above formula (I) and the fluorine-containing monomer D represented by the formula (II)
And a copolymer substantially consisting of a repeating unit based on tetrafluoroethylene,
The repeating unit represented by the above formula (I) contains 5 to 70 mol%, preferably 10 to 60 mol%, more preferably 20 mol%.
６０60 mol%, and the repeating unit based on tetrafluoroethylene is 10８５85 mol%, preferably 15７7 mol%.
0 mol%, more preferably 20 to 60 mol%, and the content of the repeating unit based on the fluorine-containing monomer D represented by the formula (II) is 5 to 40 mol%, preferably 10 to 3 mol%.
0 mol% and a number average molecular weight of 5,000 to 50
A fluorinated polymer of 00000 is particularly preferred.

Further, the solid polymer electrolyte material of the present invention comprises:
A _R is 0.5 to 2.5 meq / g dry resin (hereinafter, m
eq. / G). A _R is 0.5meq the polymer electrolyte material. / G is less than
Since the water content of the polymer electrolyte material is reduced and its ionic conductivity is reduced, sufficient battery output is obtained when the polymer electrolyte material is used as a constituent material of the catalyst layer of the electrode of the polymer electrolyte fuel cell. It becomes difficult.

[0073] On the other hand, A _R of the solid polymer electrolyte material 2.
5meq. / G, the density of ion exchange groups in the solid polymer electrolyte material increases, and the strength of the solid polymer electrolyte material tends to decrease. Further, when used as a constituent material of the catalyst layer of the electrode of the polymer electrolyte fuel cell, the water content becomes too high, so that the gas diffusion property or drainage property in the catalyst layer is reduced, and flooding is likely to occur. In addition,
A _R is 0.7~2.0meq the polymer electrolyte material of the present invention from the same viewpoint as described above. / G, more preferably 0.9 to 1.5 meq. / G is more preferable.

Further, the number average molecular weight of the solid polymer electrolyte material of the present invention is not particularly limited, and may be appropriately set by changing the degree of polymerization of the copolymer according to the intended use. When used as a constituent material of a catalyst layer of a cathode of a polymer electrolyte fuel cell,
000000, preferably 10,000 to 30
More preferably, it is 00000. When the number average molecular weight of the solid polymer electrolyte material is less than 5,000, the physical properties such as the degree of swelling change with time, resulting in insufficient durability. On the other hand, when the number average molecular weight exceeds 5,000,000,
Preparation of the solution becomes difficult.

The ratio (substance ratio) of the repeating unit based on the fluorinated monomer A to the repeating unit based on the fluorinated monomer B in the solid polymer electrolyte material of the present invention is not particularly limited. it may be appropriately set, when used as a constituent material of the cathode catalyst layer of a polymer electrolyte fuel cell as in the present embodiment is preferably chosen to match the range of the a _R .

Further, the solid polymer electrolyte material of the present invention includes a repeating unit other than the repeating unit based on the fluorinated monomer A and the repeating unit based on the fluorinated monomer B as a repeating unit constituting the solid polymer electrolyte material. The unit may be contained as required for adjusting the strength. The monomer providing such another repeating unit is not particularly limited, for example, tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, hexafluoropropylene, trifluoroethylene, vinyl fluoride, ethylene, Equation (37)-
A fluorine-containing vinyl compound represented by (40) is exemplified.

In order to improve the strength of the obtained copolymer, among these monomers, tetrafluorotetrafluoroethylene is preferred from the viewpoints of high activity for polymerization reaction, durability (perfluoro structure) and easy availability. Preferably, ethylene is used. CH ₂ ＣＨCHR ^f13 (37) CH ₂ ＣＨCHCH ₂ R ^f13 (38)

[0078]

Embedded image

CF ₂ = CFOR ^f14 Z (40)

Here, in equations (37) and (38), R
^f13 represents a perfluoroalkyl group having 1 to 12 carbon atoms. In the formula (39), a represents an integer of 0 to 3;
Represents a fluorine atom or a trifluoromethyl group, R ^f15
Represents a C1-C12 perfluoroalkyl group having a linear or branched structure. Further, in the formula (40), R ^f14 is a perfluoroalkylene group having 1 to 12 carbon atoms having a linear or branched structure, which may contain an oxygen atom having an ether bond, and Z represents —CN , -COOR ^{f1 6} (R
^f16 represents an alkyl group having 1 to 6 carbon atoms. ) Or -CO
Any one selected from the group consisting of F.

When the solid polymer electrolyte material of the present invention contains other repeating units other than the repeating unit based on the fluorinated monomer A and the repeating unit based on the fluorinated monomer B, the content of the other repeating unit May be appropriately set according to the use of the solid polymer electrolyte material.When used as a constituent material of the catalyst layer of the cathode of the polymer electrolyte fuel cell as in the present embodiment, the solid polymer electrolyte material It is preferable that the content of the other repeating unit in the copolymer constituting is less than 35% by mass. When this value exceeds 35% by mass, the effect of increasing the output of the fuel cell is reduced.

Further, among the fluorine-containing vinyl ether compounds represented by the formula (39), the following formulas (41) to (43)
It is preferable to use a fluorine-containing vinyl ether compound represented by the following formula: However, in the following formulas (41) to (43), b
Represents an integer of 1 to 8, d represents an integer of 1 to 8, and e represents 2 or 3.

[0083]

Embedded image

The catalyst contained in the catalyst layer of the cathode in the present invention is not particularly limited. For example, a catalyst in which a platinum group metal such as platinum or an alloy thereof is supported on carbon is preferable.

Further, in the catalyst layer of the cathode, the range of the mass ratio of the catalyst to the solid polymer electrolyte material is as follows: mass of the catalyst (total mass of the metal and the carbon support): mass of the solid polymer electrolyte material = 20 : 80 to 95: 5, more preferably 30:70 to 90:10.

Here, if the content of the catalyst with respect to the solid polymer electrolyte material is too low, the amount of the catalyst becomes small, so that there is a tendency that reaction sites become insufficient. Further, the thickness of the coating layer of the solid polymer electrolyte material covering the catalyst tends to increase, and the diffusion rate of the reaction gas in the solid polymer electrolyte material tends to decrease. Furthermore, the pores required for the diffusion of the reaction gas may be blocked by the resin, which may cause a flooding phenomenon.

On the other hand, if the content of the catalyst with respect to the solid polymer electrolyte material is too high, the amount of the solid polymer electrolyte material coating the catalyst with respect to the catalyst becomes insufficient, so that the number of reaction sites decreases and the battery output decreases. Tend. Further, the solid polymer electrolyte material also functions as a binder for the catalyst layer and an adhesive between the catalyst layer and the polymer electrolyte membrane, but the function is insufficient and the tendency of the catalyst layer structure to be unable to be stably maintained increases. .

The configuration of the anode catalyst layer of this fuel cell is not particularly limited, and can be the same as that of the conventional solid polymer electrolyte fuel cell anode catalyst layer. It may contain, or may contain another resin.

The thickness of the cathode and anode catalyst layers in the present invention is preferably 1 to 500 μm, more preferably 5 to 100 μm. Further, if necessary, PTFE may be added to the catalyst layer in the present invention.
And the like. However, since the water repellent is an insulator, it is desirable that the amount thereof is small, and the addition amount is preferably 30% by mass or less.

As the polymer electrolyte membrane used in the polymer electrolyte fuel cell of the present invention, an ion exchange membrane showing good proton conductivity in a wet state is used. Is preferred. As the solid polymer material constituting the polymer electrolyte membrane, for example, the solid polymer electrolyte material of the present invention may be used, and an ion exchange resin or the like used in a conventional solid polymer fuel cell may be used. Is also good.

Hereinafter, an example of a method for producing a fluoropolymer used for a solid polymer electrolyte material in the present invention will be described. First, as the fluorine-containing monomer B, -SO
_{One having a 2} F group or a —SO ₂ Cl group is used. The polymerization reaction between the fluorinated monomer A and the fluorinated monomer B is not particularly limited as long as the polymerization reaction is carried out under conditions in which radicals are generated. For example, the polymerization may be performed by bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, polymerization in liquid or supercritical carbon dioxide, and the like.

The method for generating radicals is not particularly limited. For example, a method of irradiating radiation such as ultraviolet rays, γ rays, and an electron beam may be used, and a method of using a radical initiator used in ordinary radical polymerization may be used. May be used. The reaction temperature of the polymerization reaction is not particularly limited.
About 150 ° C. When a radical initiator is used, examples of the radical initiator include bis (fluoroacyl) peroxides, bis (chlorofluoroacyl) peroxides, dialkylperoxydicarbonates, diacyl peroxides, peroxyesters, Examples include azo compounds and persulfates.

When performing the solution polymerization, the solvent to be used usually preferably has a boiling point of 20 to 350 ° C., and preferably has a boiling point of 40 to 150 ° C. from the viewpoint of handleability. Is more preferred. Then, a predetermined amount of a fluorinated monomer and a fluorinated vinyl compound are charged into a solvent, and a radical initiator or the like is added to generate a radical to perform polymerization.

Here, usable solvents include, for example,
If (i) perfluorotributylamine, perfluoro
Polyfluorotrialkylamines such as rotripropylamine
Min compound, (ii) perfluorohexane, perflu
Orooctane, perfluorodecane, perfluorodode
Can, perfluoro (2,7-dimethyloctane), 2
H, 3H-perfluoropentane, 1H-perfluoro
Hexane, 1H-perfluorooctane, 1H-perf
Luorodecane, 1H, 4H-perfluorobutane, 1
H, 1H, 1H, 2H, 2H-perfluorohexane,
1H, 1H, 1H, 2H, 2H-perfluoroocta
1H, 1H, 1H, 2H, 2H-perfluorodeca
3H, 4H-perfluoro (2-methylpentane
), 2H, 3H-perfluoro (2-methylpentane)
(Iii) 3,3-dichloro
B-1,1,1,2,2-pentafluoropropane,
1,3-dichloro-1,1,2,2,3-pentafluoro
Lopropane, 1,1-dichloro-1-fluoroethane, etc.
Chlorofluoroalkane, (iv) hexafluorop
Dimer of lopene, trimer of hexafluoropropene, etc.
A fluoroolefin having no double bond at the molecular chain end,
(V) perfluorodecalin, perfluorocyclohexene
San, perfluoro (1,2-dimethylcyclohexa
), Perfluoro (1,3-dimethylcyclohexa)
), Perfluoro (1,3,5-trimethylcyclohexane)
Xan), perfluorodimethylcyclobutane (structural differences)
Polyfluorocycloalkanes of any nature), (v
i) Perfluoro (2-butyltetrahydrofuran) etc.
(Vii) n-C
_ThreeF₇OCH_Three, N-C_ThreeF₇OCH_TwoCF_Three, N-C_ThreeF₇O
CHFCF_Three, N-C_ThreeF₇OC_TwoH_Five, N-C_FourF₉OC
H_Three, Iso-C_FourF₉OCH_Three, N-C_FourF₉OC_TwoH_Five, I
so-C_FourF₉OC_TwoH_Five, N-C_FourF₉OCH_TwoCF_Three, N-
C_FiveF₁₁OCH_Three, N-C₆F₁₃OCH_Three, N-C_FiveF₁₁O
C_TwoH_Five, CF_ThreeOCF (CF_Three) CF_TwoOCH_Three, CF_ThreeO
CHFCH _TwoOCH_Three, CF_ThreeOCHFCH_TwoOC_TwoH_Five, N
-C_ThreeF₇OCF_TwoCF (CF_Three) OCHFCF_ThreeHide
Lofluoroethers, (viii) fluorine-containing low molecular
Polyether, (ix) tert-butanol and the like.
It is. Incidentally, these solvents may be used alone,
You may mix and use 2 or more types.

Other examples of the solvent used for carrying out the solution polymerization include 1,1,2-trichloro-1,1
2,2-trifluoroethane, 1,1,1-trichloro-2,2,2-trifluoroethane, 1,1,1,3-
Tetrachloro-2,2,3,3-tetrafluoropropane, 1,1,3,4-tetrachloro-1,2,2,3
Chlorofluorocarbons such as 4,4-hexafluorobutane can be mentioned. However, although these chlorofluorocarbons can be used technically, their use is not preferred in view of the impact on the global environment.

The copolymer obtained by the polymerization is -SO ₂ F
Since it has a group or a —SO ₂ Cl group, it is subjected to hydrolysis and, if necessary, acidification treatment to be converted to a —SO ₃ M group.

Next, an example of a method for producing the polymer electrolyte fuel cell of the present invention will be described, and a preferred embodiment in which the liquid composition of the present invention is applied to a polymer electrolyte fuel cell will be described. I do. The method for producing the gas diffusion electrode having the cathode and anode catalyst layers of the polymer electrolyte fuel cell of the present invention is not particularly limited, and can be produced by a known method.

For example, the catalyst layer of the cathode is composed of -SO ₃ H
The solid polymer electrolyte material of the present invention having a group is formed using a coating solution for forming a catalyst layer prepared by mixing a catalyst with a liquid composition obtained by dissolving or dispersing in a solvent having a hydroxyl group in a molecule. Can be.

The solid polymer electrolyte material of the present invention comprises -SO
_When it has a 3M group, it can be well dissolved or dispersed in an organic solvent having a hydroxyl group. The organic solvent having a hydroxyl group is not particularly limited, but an organic solvent having an alcoholic hydroxyl group is preferable.

Examples of the organic solvent having an alcoholic hydroxyl group include, for example, methanol, ethanol, 1-propanol, 2-propanol, 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoro -1
-Propanol, 2,2,3,3-tetrafluoro-1
-Propanol, 4,4,5,5,5-pentafluoro-1-pentanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 3,3,3-trifluoro-1 -Propanol, 3,3,4,4,5,5,6
6,6-nonafluoro-1-hexanol, 3,3
4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol and the like. Also,
As an organic solvent other than alcohol, an organic solvent having a carboxyl group such as acetic acid can be used.

As the organic solvent having a hydroxyl group, the above-mentioned solvents may be used alone, or two or more kinds may be used as a mixture, and may be used as a mixture with water or another fluorine-containing solvent. You may. Examples of other fluorinated solvents include the fluorinated solvents exemplified as preferred fluorinated solvents in the solution polymerization reaction in the production of the solid polymer electrolyte material described above.

When an organic solvent having a hydroxyl group is used as a mixed solvent with water or another fluorinated solvent, the content of the organic solvent having a hydroxyl group is 10% based on the total mass of the solvent.
% Or more, and more preferably 20% or more. In this case, the solid polymer electrolyte material may be dissolved or dispersed in the mixed solvent from the beginning,
Further, after the solid polymer electrolyte material is first dissolved or dispersed in an organic solvent having a hydroxyl group, water or another fluorinated solvent may be mixed. Further, the dissolution or dispersion of the solid polymer electrolyte material in such a solvent may be carried out at a pressure of 0 to 25 at atmospheric pressure or under a condition in which the material is closed and pressurized in an autoclave or the like.
It is preferably carried out in a temperature range of 0 ° C.
It is more preferable to carry out in the range of ° C.

The content of the solid polymer electrolyte material in the liquid composition of the present invention is 1 to 5 with respect to the total mass of the liquid composition.
It is preferably 0%, more preferably 3 to 30%. When the content of the solid polymer electrolyte material is less than 1%, a coating solution is prepared by mixing a catalyst with the solution, and a catalyst having a desired thickness is prepared when the coating solution is prepared using the coating solution. Efficient manufacturing operations such as increasing the number of coatings to form a layer, and such coating liquids involve a large amount of an organic solvent and are costly and require a long time to remove them. Hateful. On the other hand, when the content of the solid polymer electrolyte material exceeds 50%, the viscosity of the liquid composition becomes too high, which makes it difficult to handle.

Further, the liquid composition may contain, in addition to the solid polymer electrolyte material of the present invention, a resin which is another solid polymer electrolyte material. In this case, the liquid composition is used as a raw material. From the viewpoint of ensuring sufficient gas diffusivity and water repellency of the obtained catalyst layer, the content of the solid polymer electrolyte material of the present invention in the liquid composition is determined by the sum of all the solid polymer electrolyte materials in the liquid composition. It is preferably at least 20%, more preferably at least 50%, based on the mass.

The catalyst layer of the cathode is formed by using a coating liquid for forming a catalyst layer prepared by mixing a catalyst composed of fine particles such as carbon black carrying platinum with the liquid composition of the present invention. It can be formed on a molecular electrolyte membrane, a gas diffusion layer, or a support plate so as to have a uniform thickness, and after drying and removing the solvent, performing hot pressing as necessary. The coating liquid may be prepared by mixing the liquid composition of the present invention and the catalyst, if desired, and then distilling off the solvent to take out a solid content and redispersing it in another solvent. The redispersion solution is usually selected from the above-mentioned alcoholic solvents and may contain water. In this way, a cathode catalyst layer having excellent gas diffusion properties and water repellency can be obtained.

In particular, the softening temperature of the polymer itself is 100 ° C.
When a coating solution is prepared from the liquid composition containing the solid polymer electrolyte material described above to form a catalyst layer, gas diffusivity in the layer is significantly improved. When the softening temperature of the solid polymer electrolyte material is 100 ° C. or higher, the solid polymer electrolyte material is unlikely to shrink when the solvent gradually evaporates from the coating solution, so that the inside of the solid polymer electrolyte material or the solid polymer This is presumably because pores of an appropriate size are formed between the aggregates of the catalyst particles coated with the electrolyte material.

Further, the anode catalyst layer can be formed in the same manner as the above-mentioned cathode catalyst layer. However,
The coating liquid for forming the catalyst layer of the anode may use the liquid composition of the present invention, or may be prepared using a liquid in which a conventional solid polymer electrolyte material is dissolved or dispersed in a predetermined solvent.

By disposing the prepared cathode catalyst layer and anode catalyst layer between the polymer electrolyte membrane and the gas diffusion layer, a polymer electrolyte fuel cell can be manufactured. Here, when the catalyst layer is formed on the polymer electrolyte membrane, for example, a separately prepared gas diffusion layer is arranged or joined adjacent to the catalyst layer. When the catalyst layer is formed on the gas diffusion layer and the gas diffusion electrode is formed in advance, for example, a separately prepared polymer electrolyte membrane is arranged or joined adjacent to the catalyst layer. Further, when the catalyst layer is formed on the support plate, for example, it is transferred to a separately prepared polymer electrolyte membrane, and then the support plate is peeled off and a separately prepared gas diffusion layer is arranged adjacent to the catalyst layer. Or join.

The bonding between the polymer electrolyte membrane and the catalyst layer, or between the catalyst layer and the gas diffusion layer, may be performed by, for example, hot pressing or roll pressing. At this time, the two may be joined by non-heating using a perfluorosulfonic acid polymer solution or the like as an adhesive.

As described above, a polymer electrolyte membrane constituting a battery may be manufactured using the solid polymer electrolyte material of the present invention.

The preferred embodiments of the present invention have been described in detail, but the present invention is not limited to the above embodiments. For example, in the above embodiment, the polymer electrolyte fuel cell in the case where a gas containing hydrogen as a main component is used as the anode reaction gas has been described. A configuration in which methanol gas is directly introduced into the anode as a gas may be used.

Further, in the above embodiment, the case where the liquid composition containing the solid polymer electrolyte material of the present invention is used for the catalyst layer of the electrode of the polymer electrolyte fuel cell has been described. Can be used. For example, when a membrane is formed using the solid polymer electrolyte material of the present invention, 1) a cation selective permeable membrane used for salt electrolysis and the like, 2) a membrane for water electrolysis, 3) hydrogen peroxide production, ozone production It can be used in various electrochemical processes as a cation exchange membrane for electrodialysis and the like, which is used for proton permeation membrane used for recovery of waste acid, etc., and 4) desalination or salt production.

Further, in addition to the electrochemical process, a film is formed by using the solid polymer electrolyte material of the present invention.
Membrane for diffusion dialysis used for separation and purification of acids, bases, and salts, charged porous membrane for protein separation (charged reverse osmosis membrane, charged ultrafiltration membrane, charged microfiltration membrane, etc.), dehumidification membrane It can also be used as a humidifying film. Further, the solid polymer electrolyte material of the present invention includes, for example, a polymer electrolyte for a lithium ion battery, a solid acid catalyst, a cation exchange resin, a sensor using a modified electrode, and an ion exchange filter for removing trace ions in the air. And actuators.

[0114]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following description of Examples and Comparative Examples, the following compounds are described using the following abbreviations. PSVE: CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ C
_{F 2 SO 2 F, PSVE-} H: CF 2 = CFOCF 2 CF (CF 3) OC
_{F 2 CF 2 SO 3 H,} BVE: perfluoro (3-butenyl vinyl ether), PDD: perfluoro (2,2-dimethyl-1,3-dioxole), MMD: perfluoro (2-methylene-4-methyl −
1,3-dioxolane) TFE: tetrafluoroethylene IPP: (CH ₃ ) ₂ CHOC (＝ O) OOC (＝ O) O
CH (CH ₃ ) ₂ , HCFC141b: CH ₃ CCl ₂ F, HCFC225cb: CCLF ₂ CF ₂ CHClF.

[Synthesis Example 1] (PDD / PSVE-H copolymer 1) PDD was placed in a 0.2 L stainless steel autoclave.
26.0 g, PSVE 127.8 g, IPP 0.46 g
, And the gas in the autoclave was purged with nitrogen, and then nitrogen was introduced so that the total pressure became 0.3 MPa (gauge pressure). Next, the temperature in the autoclave was set to 40 ° C.
The polymerization was started while stirring the contents. Ten hours after the start of the polymerization, the autoclave was cooled, the gas in the system was purged to stop the polymerization, the polymerization was stopped, diluted with HCFC225cb, and then poured into hexane to precipitate the polymer, which was washed twice with hexane and once with HCFC141b. did.

After filtration, vacuum drying at 80 ° C. for 16 hours
Thereby, 41.6 g of a white polymer was obtained. Elemental content
The sulfur content is determined by precipitation and is based on the PDD in the polymer.
Moles of repeating units and repeating units based on PSVE
Ratio (PDD / PSVE) and A _RAnd asked, PD
D / PSVE = 56.5 / 43.5, A_R= 1.
31 meq. / G. In addition, polymer by GPC
The number average molecular weight of the
The number average molecular weight in terms of chill was 33,000. Weight average
The molecular weight was 56,000.

Next, the obtained polymer was immersed in a water / ethanol mixed solution of KOH to carry out a hydrolysis treatment.
It was immersed in a dilute sulfuric acid aqueous solution to perform an acid-form treatment. Next, the polymer was washed with ion-exchanged water and dried, and then dissolved in ethanol to obtain a clear ethanol solution of 10% by mass of the polymer (PDD / PSVE-H copolymer 1).

A cast film was prepared using the above-mentioned ethanol solution of the polymer, and the softening temperature of the polymer was measured by the penetration method using the 1 mmφ quartz probe described above. First, a mixed solution of 10 parts by mass of an ethanol solution of a polymer and 2 parts by mass of butanol was prepared, and a cast film was formed at room temperature using this solution.
After drying for a minute, a cast film having a thickness of about 200 μm was obtained. Next, the obtained cast film was set on TMA (manufactured by Mac Science).

Then, while increasing the temperature of the cast film at a rate of 5 ° C./min, a vibration load (load vibration range: load vibration range: 0.2 Hz) was applied to the contact portion between the cast film and the 1 mmφ quartz probe. 1 to 6 g, average load:
3.5 g), and the change in thickness of the cast film was measured. Then, the temperature at which the thickness of the film began to rapidly decrease due to the indentation of the probe into the cast film was measured as the softening point. As a result, the softening temperature of this polymer is 15
It was 0 ° C.

[Synthesis Example 2] (PDD / PSVE-H copolymer 2) PDD was placed in a stainless steel autoclave having a volume of 0.2 L.
36.4 g, PSVE 123.1 g, IPP 0.48 g
And polymerization was started in the same manner as in Synthesis Example 1. After 3.2 hours from the start of the polymerization, the autoclave was cooled, the polymerization was stopped by purging the gas in the system, and the mixture was diluted with HCFC225cb and then poured into hexane to precipitate.
Twice, and once with HCFC141b.

After filtration, the resultant was vacuum-dried at 80 ° C. for 16 hours to obtain 25.3 g of a white polymer. The obtained polymer was subjected to hydrolysis and acidification treatment in the same manner as in Synthesis Example 1 to obtain PDD / PSVE-H copolymer 2, and was subjected to the same characterization as in Synthesis Example 1. As a result, PDD / PSVE = 69.8 / 30.
2, A _R = 0.99meq. / G, number average molecular weight in terms of polymethyl methacrylate: 58,000, weight average molecular weight:
950,000, softening temperature: 180 ° C.

[Synthesis Example 3] (BVE / PSVE-H copolymer 1) In a nitrogen atmosphere, a 300 mL flask was placed in a flask.
BVE 120.0 g, PSVE 128.5 g, IPP
0.76 g was added, and the temperature in the flask was set to 40 ° C.
The polymerization was started while stirring the contents. 1 from the start of polymerization
After 6.7 hours, the polymerization was stopped by cooling the inside of the flask, and the polymer was precipitated by pouring into hexane, followed by washing with hexane three times.

After filtration, the resultant was vacuum-dried at 80 ° C. for 16 hours to obtain 47.8 g of a white polymer. The obtained polymer was subjected to hydrolysis and acidification treatment in the same manner as in Synthesis Example 1 to obtain BVE / PSVE-H copolymer 1, and was subjected to the same characterization as in Synthesis Example 1. As a result, BVE / PSVE = 67.0 / 33.
0, A _R = 0.99 meq. / G, number average molecular weight in terms of polymethyl methacrylate: 29,000, weight average molecular weight 42,000, and softening temperature: 110 ° C.

[Synthesis Example 4] (BVE / PSVE-H copolymer 2) Under a nitrogen atmosphere, a 300 mL flask was placed in a flask.
BVE 150.0 g, PSVE 103.0 g, IPP
0.77 g was added, and polymerization was started in the same manner as in Synthesis Example 3. After 10.7 hours from the start of the polymerization, the inside of the flask was cooled to stop the polymerization, and the polymer was precipitated by pouring the mixture into hexane. The polymer was precipitated three times with hexane and further with HCFC141b.
Washed twice.

After filtration, vacuum drying was performed at 80 ° C. for 16 hours to obtain 38.0 g of a white polymer. The obtained polymer was hydrolyzed and acidified to obtain a BVE / PSVE-H copolymer 2 in the same manner as in Synthesis Example 1, and was subjected to the same characterization as in Synthesis Example 1. As a result, BVE / PSVE = 76.1 / 23.
9, A _R = 0.75 meq. / G, number average molecular weight in terms of polymethyl methacrylate: 38,000, weight average molecular weight:
53,000, softening temperature: 110 ° C.

[Synthesis Example 5] (TFE / PSVE-H copolymer) TFE conventionally used as a material for a catalyst layer of an electrode of a polymer electrolyte fuel cell or a material for a polymer electrolyte membrane.
/ PSVE copolymer was produced by a known method. The obtained polymer was subjected to hydrolysis and acidification treatment in the same manner as in Synthesis Example 1 to obtain a TFE / PSVE-H copolymer, and was subjected to characterization in the same manner as in Synthesis Example 1. TFE / PSVE = 82.2 / 17.
8, A _R = 1.1 meq. / G, softening temperature: 80 ° C.

[Synthesis Example 6] (MMD / PSVE-H copolymer 1) In a 0.2 L autoclave, IPP: 0.68 g, PSV
E: 207.1 g and MMD: 20.0 g were charged, and after degassing under reduced pressure, pressurizing purge was performed three times with nitrogen and pressurized with nitrogen so that the total pressure became 0.12 MPa (gauge pressure). 4
The temperature was raised to 0 ° C., and the reaction was performed for 2.5 hours. The polymerization solution was poured into hexane to coagulate the polymer, and then washed three times with hexane. Vacuum dry at room temperature overnight, and further at 80 ° C.
And vacuum dried overnight. Yield: 16.9 g (yield: 7.
4%).

[0128] determine the content of sulfur in the elemental analysis, was determined and A _R molar ratio (MMD / PSVE) and repeating units based on the repeating units and PSVE based on MMD in the polymer, MMD / PSVE = 76 0.0 / 24.0
A _R = 0.82 meq. / G. Also,
When the number average molecular weight of the polymer was measured by GPC, the number average molecular weight in terms of polymethyl methacrylate was 4.5.
10,000 and the weight average molecular weight was 70,000.

KOH / H ₂ O / DMSO = 1
It was immersed in a 1/59/30 (mass ratio) solution and kept at 90 ° C. for 7 days. It was returned to room temperature, washed with water, and further immersed in water at 90 ° C. This washing was repeated three times. 1m more
The resultant was immersed in ol / L hydrochloric acid at 90 ° C. for 1 day, returned to room temperature, washed with water, and further immersed in water at 90 ° C. 3 times
Repeated times. Dried in an oven at 80 ° C. for 16 hours,
Furthermore, it was vacuum-dried at 80 ° C to obtain an acidified polymer.

In the same manner as in Synthesis Example 1, 10
A mass% ethanol solution was prepared to prepare a cast film. The softening temperature of the cast film was 135 ° C.

[Synthesis Example 7] (MMD / PSVE-H copolymer 2) The charged PSVE was 207.1 g, the MMD was 13.3 g, and nitrogen was introduced to bring the total pressure to 0.11 MPa (gauge pressure).
19.6 g of a polymer was obtained in the same manner as in Synthesis Example 6 except that the reaction time was changed to 6 hours (yield: 8.9%).

The molar ratio (MMD / PSVE) and A _{R of the} repeating unit based on MMD and the repeating unit based on PSVE in the polymer were determined in the same manner as in Synthesis Example 6.
MMD / PSVE = 66.7 / 33.3 and A _R =
1.07 meq. / G. Further, the number average molecular weight in terms of polymethyl methacrylate was 24,000, and the weight average molecular weight was 39,000.

The above polymer was converted to an acid form in the same manner as in Synthesis Example 6 to obtain an MMD / PSVE-H copolymer. Synthesis Example 1
A 9.6% by mass ethanol solution of this polymer was prepared in the same manner as described above to prepare a cast film. The softening temperature of the cast film was 125 ° C.

[Synthesis Example 8] (TFE / PDD / PSVE)
-H copolymer) In a 0.2 L autoclave, 14.3 g of PDD, PSV
52.6 g of E, 76.9 g of HCFC-225cb, I
0.36 g of PP was added and the mixture was frozen and degassed. 5.9 TFE
After introducing g, the temperature was raised to 40 ° C. to initiate polymerization. At this time, the pressure was 0.26 MPa (gauge pressure). The reaction is performed at 40 ° C for 10 hours, and the pressure is 0.07 MPa (gauge pressure).
When it became, the reaction was stopped. The polymerization solution was poured into hexane to coagulate the polymer, and washed three times with hexane. Vacuum drying was performed at 80 ° C. overnight. Yield: 25.0 g
(Yield: 34.4%).

[0135] In ¹⁹ F-NMR was determined the polymer composition, a TFE / PDD / PSVE = 42/ 35/22 ( molar ratio), A _R is 0.98 meq. / G. The number average molecular weight in terms of polymethyl methacrylate by GPC was 53,000, and the weight average molecular weight was 83,000.

The polymer was pressed at 160 ° C. to a thickness of 10
A 0 μm film was produced. This film is KOH /
It was immersed in a solution of H ₂ O / DMSO = 11/59/30 (mass ratio) and kept at 90 ° C. for 17 hours for hydrolysis. After returning to room temperature, washing was performed three times. Further, it was immersed in 1 mol / L sulfuric acid at room temperature for 2 hours and washed with water. This sulfuric acid immersion and water washing were repeated three times, and finally, water washing was further performed three times. 80
The resultant was dried in an oven at a temperature of 16 ° C. for 16 hours, and further dried in a vacuum at a temperature of 80 ° C. to obtain an acid-type dried film. The softening temperature measured by the method of Synthesis Example 1 was 120 ° C. The maximum stress in the tensile test was 6.1 MPa, and the elongation at break was 3.
It was 0%. It was confirmed that the film had sufficient strength.

From the above polymer, a 14.5% by mass ethanol solution of the acid-form polymer was prepared in the same manner as in Synthesis Example 1.

The tensile test of the film was performed using a test piece type 2 specified in JIS K-7127.
(Length: 150 mm, width: 10 mm, distance between marked lines: 50 mm), and initial distance between chucks: 10
The test was performed under the conditions of 0 mm, a tensile speed of 50 mm / min, 25 ° C., and a relative humidity of 50%.

Example 1 The unit cell of Example 1 was manufactured according to the procedure described below. First, Pt-supported carbon (Pt-supported amount: 54% by mass) was added to PDD / PSVE-
A dispersion (mass of Pt-supported carbon: mass of the above-described copolymer = 6: 4) was prepared by dispersing in a 10% by mass ethanol solution of H copolymer 1. Next, after sufficiently stirring the dispersion, the solid obtained by further evaporating to dryness was pulverized. Next, this powder was mixed with 2,2,3,3,3-pentafluoro-
It was redispersed in 1-propanol to prepare a coating liquid for forming a cathode catalyst layer having a solid content of 5% by mass.

Next, Pt-supported carbon (Pt-supported amount: 4
0 mass%), TFE / PSVE-H copolymer (A _R =
1.1 meq. / G) of a 9% by mass ethanol solution and ethanol, and the mixture is dispersed, and water is further added thereto to form a coating solution for forming an anode catalyst layer having a solid concentration of 8% by mass (mass of ethanol: mass of water = 1: 1, mass of Pt-supported carbon: mass of the above copolymer = 7: 3) was prepared.

Further, one surface of a water-repellent carbon cloth (fiber woven fabric) was plugged with a water-repellent carbon powder layer (a mixture of carbon black and PTFE) as a gas diffusion layer for the anode and the cathode, and further hot-pressed. Thickness of the carbon powder layer forming the catalyst layer by flattening
A thing of 0 μm was prepared. Further, as the polymer electrolyte membrane, a polymer electrolyte membrane (trade name: Flemion HR, manufactured by Asahi Glass Co., A _R = 1.1 meq./g, dry film thickness 50 μm) made of a sulfonic acid-type perfluorocarbon polymer was prepared. .

Next, a coating solution for forming a cathode catalyst layer was applied once on the surface of the gas diffusion layer on the side of the water-repellent carbon powder layer so that the Pt amount was 0.8 mg / cm ² and dried. Thus, a catalyst layer was formed, and a cathode was produced. On the other hand, the coating liquid for forming the catalyst layer of the anode was applied once on the surface of the gas diffusion layer sheet on the side of the water-repellent carbon powder layer in the same procedure as the cathode so that the Pt amount was 0.5 mg / cm ^2. After drying, a catalyst layer was formed to obtain an anode.

Next, the obtained cathode and anode were cut out so as to have an effective electrode area of 25 cm ² . Then, both the cathode and the anode are opposed to each other with the catalyst layer side facing inward, and the cathode and anode catalyst layers and the polymer electrolyte membrane are joined by hot pressing with the polymer electrolyte membrane sandwiched therebetween, A membrane-electrode assembly was produced.

Comparative Example 1 A membrane / electrode was prepared in the same manner as in Example 1 except that both the anode and the cathode were prepared using the coating liquid for forming a catalyst layer of the anode prepared in Example 1. A joined body was produced.

[Battery Characteristics Test] A carbon separator having a gas flow path was attached to each of the membrane / electrode assemblies of Example 1 and Comparative Example 1 to form a measurement cell, and an electronic load (Takasago Seisakusho Co., Ltd.) And a DC power supply (EX750L, manufactured by Takasago Seisakusho Co., Ltd.) and a current-voltage characteristic test of the measurement cell was performed. Measurement conditions were: hydrogen inlet pressure; 0.15
MPa, air inlet pressure: 0.15 MPa, operating temperature of the measuring cell: 80 ° C., and after 10 hours from the operation, when the output current densities were 0.3 A / cm ² and 1.0 A / cm ² , respectively. The cell voltage (iR free) was measured. Further, under these operating conditions, the flow rates of hydrogen gas and air were adjusted so that the hydrogen utilization rate was 70% and the air utilization rate was 40%.
Table 1 shows the results.

[0146]

[Table 1]

[0147]

According to the present invention, since a repeating unit having an aliphatic ring structure is introduced into a copolymer serving as a solid polymer electrolyte material, it has good ion conductivity and water repellency, In addition, it is possible to provide a solid polymer electrolyte material having excellent gas permeability, a liquid composition containing the same, and a solid polymer fuel cell capable of stably obtaining a high battery output. In addition, the solid polymer electrolyte material of the present invention has a softening temperature higher than that of the conventional one, so it can be used not only for solid polymer fuel cells, but also for ion selective permeable membranes, reverse osmosis membranes, filtration membranes, diaphragms in other electrochemical processes. When applying as etc.,
It has the feature that it can be used at high temperatures.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 8/02 H01M 8/02 P (72) Inventor Toshihiro Tanuma 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Incorporated (72) Inventor Yasuhiro Kunisaka 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. DA01 DA56 JA45 5H026 AA06 EE19 HH00 HH08

Claims (15)

[Claims] 1. A repeating unit based on a fluorine-containing monomer A that gives a polymer having an aliphatic ring structure in a main chain by radical polymerization, and a repeating unit based on a fluorine-containing monomer B represented by the following formula (1): A solid polymer electrolyte material comprising a copolymer. CF ₂ = CF (R ^f ) _j SO ₂ X (1) [In the formula (1), j represents 0 or 1, X is a fluorine atom, a chlorine atom or OM ｛M is a hydrogen atom,
An alkali metal atom or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³
And R ⁴ may be the same or different and each represents a hydrogen atom or a monovalent organic group), and represents a group represented by｝, and R ^f has a linear or branched structure It is a polyfluoroalkylene group having 1 to 20 carbon atoms, and may contain an etheric oxygen atom. ] 2. The solid polymer electrolyte material according to claim 1, wherein the fluorinated monomer A is a perfluoromonomer, and the fluorinated monomer B is represented by the following formula (2). Embedded image [In the formula (2), k represents an integer of 0 to 2, m represents an integer of 1 to 12, Y represents a fluorine atom or a trifluoromethyl group, and X has the same meaning as X in the formula (1). is there. ] 3. The solid polymer electrolyte material according to claim 1, wherein the repeating unit based on the fluorine-containing monomer A is represented by any of the following formulas (3) to (5). Embedded image [In the formula (3), p, q and r are each independently 0 or 1
Are shown, R ^f1 and R ^f2 may be the same or different, each a fluorine atom, one of the perfluoroalkoxy groups perfluoroalkyl group or 1-5 C1-5 atoms, R ^f3 Is a perfluoroalkylene group having 1 to 3 carbon atoms, and may contain a perfluoroalkyl group having 1 to 5 carbon atoms or a perfluoroalkoxy group having 1 to 5 carbon atoms as a substituent. ] [In the formula (4), s represents 0 or 1, and R ^f4 , R ^f5 , R ^f6 and R ^f7 may be the same or different and each represents a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms. ^Rf4 and ^Rf5 may be linked to each other when s = 0 to form a spiro ring, and ^Rf8 is a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms. Or a perfluoroalkoxy group having 1 to 5 carbon atoms. ] [In the formula (5), R ^f9 , R ^f10 , R ^f11 and R ^f12 may be the same or different and each represents a fluorine atom or a C 1-5 perfluoroalkyl group. ] 4. The fluorine-containing monomer A comprises perfluoro (3-butenyl vinyl ether), perfluoro (2,2-dimethyl-1,3-dioxole), perfluoro (1,3-dioxole), 2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, perfluoro (2-methylene-4-methyl-1,
The solid polymer according to any one of claims 3 to 5, wherein the fluorine-containing monomer B is at least one selected from the group consisting of (3-dioxolane), and the fluorine-containing monomer B is represented by the following formula (6). Electrolyte material. Embedded image [In the formula (6), k ′ represents 0 or 1, X has the same meaning as X in the formula (1), and Y has the same meaning as Y in the formula (2). ] 5. The fluorine-containing monomer A is perfluoro (2,2-dimethyl-1,3-dioxole), and in addition to the fluorine-containing monomer A and the fluorine-containing monomer B, a tetrafluoroethylene The solid polymer electrolyte material according to claim 4, comprising a repeating unit based on the polymer electrolyte. 6. The solid polymer electrolyte material according to claim 1, wherein the ion exchange capacity is 0.5 to 2.5 meq / g dry resin. 7. A solid polymer electrolyte material in which a terminal —SO ₂ X group of a repeating unit based on the fluorine-containing monomer B is a —SO ₃ H group, and a constituent material of a solid polymer fuel cell Claim 1 characterized by being used
7. The solid polymer electrolyte material according to any one of 6. 8. The solid polymer electrolyte material according to claim 1, wherein the softening temperature of the copolymer is 100 ° C. or higher. 9. The solid polymer electrolyte material according to claim 1, wherein the terminal —SO ₂ X group of the repeating unit based on the fluorine-containing monomer B is —SO ₃ M
｛M is a hydrogen atom, an alkali metal atom or NR ¹ R ² R ³
R ⁴ (R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents a hydrogen atom or a monovalent organic group). A liquid composition, wherein the material is dissolved or dispersed in an organic solvent having a hydroxyl group in a molecule. 10. A solid polymer electrolyte fuel cell comprising an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode, wherein the polymer electrolyte fuel cell according to claim 7. A polymer electrolyte fuel cell, comprising a material as a constituent material of the cathode. 11. A copolymer substantially consisting of a repeating unit represented by the following formula (I) and a repeating unit based on a fluorine-containing monomer D represented by the following formula (II): A fluorine-containing polymer, wherein the content of the repeating unit based on the fluorine monomer D is from 10 to 75 mol%, and the number average molecular weight is from 5,000 to 5,000,000. Embedded image [In formulas (I) and (II), R ^f16 and R ^f17 may be the same or different and each represent a fluorine atom or a trifluoromethyl group, k ′ represents 0 or 1, Y represents a fluorine atom or M represents a hydrogen atom, an alkali metal atom or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² ,
R ³ and R ⁴ may be the same or different and each represents a hydrogen atom or a monovalent organic group). ] 12. A copolymer substantially consisting of a repeating unit based on perfluoro (3-butenyl vinyl ether) and a repeating unit based on a fluorine-containing monomer D represented by the following formula (II): A fluorine-containing polymer, wherein the content of the repeating unit based on the fluorine-containing monomer D is 10 to 75 mol%, and the number average molecular weight is 5,000 to 5,000,000. Embedded image [In the formula (II), k ′ represents 0 or 1, Y represents a fluorine atom or a trifluoromethyl group, M represents a hydrogen atom,
An alkali metal atom or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³
And R ⁴ may be the same or different and each represents a hydrogen atom or a monovalent organic group). ] 13. Substantially a repeating unit based on perfluoro (2-methylene-4-methyl-1,3-dioxolane) and a repeating unit based on a fluorine-containing monomer D represented by the following formula (II) A fluorine-containing polymer having a repeating unit content based on the fluorine-containing monomer D of 10 to 75 mol% and a number average molecular weight of 5,000 to 5,000,000. Embedded image [In the formula (II), k ′ represents 0 or 1, Y represents a fluorine atom or a trifluoromethyl group, M represents a hydrogen atom,
An alkali metal atom or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³
And R ⁴ may be the same or different and each represents a hydrogen atom or a monovalent organic group). ] 14. A copolymer consisting essentially of a repeating unit represented by the following formula (I), a repeating unit based on a fluorine-containing monomer D represented by the following formula (II), and a repeating unit based on tetrafluoroethylene: And the content of the repeating unit represented by the following formula (I) is 5 to 7:
0 mol%, the content of the repeating unit based on tetrafluoroethylene is 10 to 85 mol%, the content of the repeating unit based on the fluorine-containing monomer D is 5 to 40 mol%, and the number average molecular weight is 5,000 to 5,000. A fluoropolymer having a molecular weight of 5,000,000. Embedded image [In formulas (I) and (II), R ^f16 and R ^f17 may be the same or different and each represent a fluorine atom or a trifluoromethyl group, k ′ represents 0 or 1, Y represents a fluorine atom or M represents a hydrogen atom, an alkali metal atom or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² ,
R ³ and R ⁴ may be the same or different and each represent a hydrogen atom or a monovalent organic group). ] 15. A solid polymer electrolyte membrane comprising the fluoropolymer according to claim 14.