JP2008117590A - Complex polymer electrolyte membrane and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a complex polymer electrolyte membrane with durability improved in case of use for a fuel cell, through solution of a problem of insufficient mechanical strength and improvement of durability of a hydrocarbon system polymer solid electrolyte membrane. <P>SOLUTION: The complex polymer electrolyte membrane is made by complexifying an ionic-group-containing polymer with a porous film made of an ionic-group-free polymer. The ionic-group-containing polymer and the ionic-group-free polymer are soluble to an identical organic solvent, with a softening temperature of the ionic-group-containing polymer of 140 to 250°C. The ionic-group-containing polymer is preferred to have a structural unit of a chemical formula 1. In the chemical formula 1, X denotes a -S(=O)<SB>2</SB>- group, or a -C(=O)- group, Y denotes H or a monovalent cation, Z<SP>1</SP>denotes either O or S atom, Z<SP>2</SP>denotes either O atom, S atom, -C(CH<SB>3</SB>)<SB>2</SB>- group, -C(CF<SB>3</SB>)<SB>2</SB>- group, -CH<SB>2</SB>- group, or cyclo hexyl group, and n1 denotes an integer of 1 or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrolyte membrane, and more particularly to applications such as a composite polymer electrolyte membrane, a polymer electrolyte membrane / electrode assembly, and a fuel cell having excellent durability.

  Examples of electrochemical devices that use polymer solid electrolytes as ion conductors include water electrolyzers and fuel cells. The polymer membrane used for these must have high proton conductivity as a cation exchange membrane and be sufficiently stable chemically, thermally, electrochemically and mechanically. For this reason, a perfluorocarbon sulfonic acid membrane has been used as one that can be used over a long period of time. In the polymer electrolyte fuel cell field, which is currently attracting particular attention, in addition to problems in characteristics such as the large permeation of hydrogen gas, which is a fuel, it contains fluorine, causing environmental pollution during disposal and during power generation This is pointed out as an obstacle to the practical application of fuel cells, such as the fact that hydrofluoric acid corrodes the fuel cell system. In addition, a fuel cell using an aqueous methanol solution has a problem that methanol permeability is too high, which is an obstacle to practical use.

  On the other hand, as electrolyte membranes that replace perfluorocarbon sulfonic acid membranes, so-called hydrocarbon polymer solid electrolytes in which ionic groups such as sulfonic acid groups are introduced into polymers such as polyetheretherketone, polyethersulfone, and polysulfone have recently become popular. It is being considered. However, it is pointed out that the hydrocarbon polymer solid electrolyte is hydrated and swollen more easily than perfluorocarbon sulfonic acid, and its dimensional change is large. Has been.

  As a method for improving the mechanical strength of the polymer solid electrolyte membrane and suppressing dimensional changes, a composite polymer solid electrolyte membrane in which various reinforcing materials are combined with the polymer solid electrolyte membrane has been proposed. A composite polymer solid electrolyte membrane (see, for example, Patent Document 1) obtained by impregnating a perfluorocarbon sulfonic acid polymer, which is an ion exchange resin, in the voids of the stretched porous polytetrafluoroethylene membrane is an integral part of the perfluorocarbon sulfonic acid polymer. A composite polymer solid electrolyte membrane (for example, see Patent Document 2) in which fibrillated polytetrafluoroethylene is dispersed as a reinforcing material in the membrane is described. However, it still contains fluorine as an element, and the problems of environmental pollution during disposal and hydrofluoric acid generated during power generation are still not solved.

  On the other hand, as a polymer solid electrolyte reinforced with a hydrocarbon-based reinforcing material, a polymer solid electrolyte membrane (for example, see Patent Document 3) in which a polybenzoxazole porous membrane and a polymer solid electrolyte are combined is described. Yes. However, the composite membranes produced by these methods are peeled off at the interface because the swelling properties of the porous membrane, which is a reinforcing material, and the solid polymer electrolyte in water or methanol are different when power generation is actually repeated in the fuel cell. Durability is insufficient because there is an increase in the permeation amount of hydrogen gas and methanol estimated to have occurred.

  There is also an electrolyte membrane obtained by polymerizing a polymer having ion conductivity from a monomer permeated into a porous substrate (see, for example, Patent Document 4). However, this method has a problem that it is difficult to completely fill the voids with the polymer, and defects and the like are formed, so that hydrogen gas leak and methanol permeation cannot be sufficiently suppressed, and proton conductivity is not sufficient.

  As a polymer electrolyte membrane that solves the above problems, the present inventors have proposed a polymer electrolyte membrane reinforced with a material that can be dissolved in the same solvent as the ion conductive polymer (see, for example, Patent Document 5). However, when used in a fuel cell, in addition to high durability of the polymer electrolyte membrane itself, high durability is also required for a so-called membrane / electrode assembly in which an electrode catalyst layer is bonded to the polymer electrolyte membrane. It has been.

JP-A-8-162132 JP 2001-35508 A International Publication No. WO00 / 22684 Pamphlet JP 2002-83612 A Japanese Patent Application No. 2005-223990

  The present invention was made against the background of the problems of the prior art, and solves the shortage of mechanical strength, which was a problem of hydrocarbon-based polymer solid electrolyte membranes, and improved durability as a reinforcing membrane, It is another object of the present invention to provide a composite polymer electrolyte membrane that can further improve durability when used in a fuel cell, a polymer electrolyte membrane / electrode assembly using the composite polymer electrolyte membrane, and a fuel cell. Is.

As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention is the following composite polymer electrolyte membrane and a production method thereof.
(1) A composite polymer electrolyte membrane in which an ionic group-containing polymer is combined with a porous film made of an ionic group-free polymer, and the ionic group-containing polymer and the ionic group-free polymer are the same organic solvent And a softening temperature of the ionic group-containing polymer is 140 to 250 ° C.
(2) The composite polymer electrolyte membrane according to (1), wherein the ionic group is at least one group selected from the group consisting of a sulfonic acid group, a phosphonic acid group, and a phosphoric acid group. .
(3) The composite polymer electrolyte membrane according to (1), wherein the ionic group-containing polymer has a structural unit represented by the following chemical formula 1.

［化学式１において、Ｘは−Ｓ（＝Ｏ）_２−基又は−Ｃ（＝Ｏ）−基を、ＹはＨ又は１価の陽イオンを、Ｚ^１はＯ又はＳ原子のいずれかを、Ｚ^２は、Ｏ原子、Ｓ原子、−Ｃ（ＣＨ_３）_２−基、−Ｃ（ＣＦ_３）_２−基、−ＣＨ_２−基、シクロヘキシル基のいずれかを、ｎ１は１以上の整数を表す。］
（４）イオン性基含有ポリマーが、化学式２で表される構造をさらに有する前記（３）に記載の複合高分子電解質膜。

[In Chemical Formula 1, X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, Z ¹ represents either an O or S atom, Z ² represents an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, or a cyclohexyl group, and n 1 represents an integer of 1 or more. To express. ]
(4) The composite polymer electrolyte membrane according to (3), wherein the ionic group-containing polymer further has a structure represented by Chemical Formula 2.

［化学式２において、Ａｒ^１は二価の芳香族基を、Ｚ^３はＯ又はＳ原子のいずれかを、Ｚ^４は、Ｏ原子、Ｓ原子、−Ｃ（ＣＨ_３）_２−基、−Ｃ（ＣＦ_３）_２−基、−ＣＨ_２−基、シクロヘキシル基のいずれかを、ｎ２は１以上の整数を表す。］

[In Chemical Formula 2, Ar ¹ is a divalent aromatic group, Z ³ is either an O or S atom, Z ⁴ is an O atom, an S atom, a —C (CH ₃ ) ₂ — group, —C Any one of (CF ₃ ) ₂ —, —CH ₂ — and cyclohexyl groups, n2 represents an integer of 1 or more. ]

(5) The composite polymer electrolyte membrane according to (4), wherein Ar ¹ in Chemical Formula 2 is one or more groups selected from structures represented by Chemical Formulas 3 to 6 below.

（６）化学式２におけるＡｒ^１が化学式６で表される構造である前記（５）に記載の複合高分子電解質膜。
（７）化学式１におけるＺ^１及びＺ^２がいずれもＯ原子であり、かつ、ｎ１が３以上である前記（３）に記載の複合高分子電解質膜。
（８）化学式２におけるＺ^３及びＺ^４がいずれもＯ原子であり、かつ、ｎ２が３以上である前記（４）に記載の複合高分子電解質膜。
（９）イオン性基含有ポリマーが、下記化学式７で表される構造をさらに有する前記（３）に記載の複合高分子電解質膜。

(6) The composite polymer electrolyte membrane according to (5), wherein Ar ¹ in Chemical Formula 2 has a structure represented by Chemical Formula 6.
(7) The composite polymer electrolyte membrane according to (3), wherein Z ¹ and Z ² in Chemical Formula 1 are both O atoms, and n1 is 3 or more.
(8) The composite polymer electrolyte membrane according to (4), wherein Z ³ and Z ⁴ in Chemical Formula 2 are both O atoms, and n2 is 3 or more.
(9) The composite polymer electrolyte membrane according to (3), wherein the ionic group-containing polymer further has a structure represented by the following chemical formula 7.

［化学式７において、Ｘは−Ｓ（＝Ｏ）_２−基又は−Ｃ（＝Ｏ）−基を、ＹはＨ又は１価の陽イオンを、Ｚ^５はＯ又はＳ原子のいずれかを表す。］

[In Chemical Formula 7, X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ⁵ represents either an O or S atom. . ]

(10) The composite polymer electrolyte membrane according to (9), wherein the ionic group-containing polymer further has a structure represented by Chemical Formula 2.
(11) The composite polymer electrolyte membrane according to (10), wherein the ionic group-containing polymer further has a structure represented by the following chemical formula 8.

［化学式８において、Ａｒ^２は２価の芳香族基を、Ｚ^６はＯ又はＳ原子のいずれかを表す。］

[In Chemical Formula 8, Ar ² represents a divalent aromatic group, and Z ⁶ represents either O or S atom. ]

(12) The composite polymer electrolyte membrane according to (11), wherein Ar ² in Chemical Formula 8 is one or more groups selected from structures represented by Chemical Formulas 3 to 6.
(13) The composite polymer electrolyte membrane according to (12), wherein Ar ² in Chemical Formula 8 has a structure represented by Chemical Formula 6.
(14) The composite polymer electrolyte membrane according to (9), wherein Z ¹ and Z ² in Chemical Formula 1 are O and / or S atoms, and n1 is 1.
(15) The composite polymer electrolyte membrane according to (10), wherein Z ³ and Z ⁴ in Chemical Formula 2 are O and / or S atoms, and n2 is 1.

(16) The polymer electrolyte membrane according to (1) to (15), wherein the ion exchange capacity is in the range of 0.5 to 5.0 meq / g.
(17) The composite polymer electrolyte membrane according to any one of (1) to (16), wherein the organic solvent is an organic polar solvent.
(18) The composite polymer electrolyte membrane according to any one of (1) to (17), wherein the ionic group-free polymer is polyamideimide.

(19) A polymer electrolyte membrane / electrode assembly having the composite polymer electrolyte membrane according to any one of (1) to (18).
(20) A fuel cell using the polymer electrolyte membrane / electrode assembly according to (19).
(21) The fuel cell according to (20), wherein methanol is used as a fuel.

In the composite polymer electrolyte membrane of the present invention, since the ionic group-containing polymer is strongly combined with the porous membrane of the ionic group-free polymer and the membrane strength is reinforced, this is a drawback of the conventional reinforced membrane. Interfacial separation, which is considered to occur during repeated power generation in the fuel cell, does not occur, and there is no disadvantage that the permeation amount of hydrogen gas or methanol increases with time.
That is, since the ionic group-containing polymer and the ionic group-free polymer forming the composite film have solubility characteristics in the same organic solvent, the porous film of the ionic group-free polymer is the ionic group-containing polymer. When the pores of the porous membrane are filled with the organic solvent solution, the surface of the porous membrane and the surface of the internal pores are partially dissolved in the organic solvent, and then the solvent is removed by heat treatment or the like. The ionic group-free polymer and the ionic group-containing polymer are mixed at the boundary portion, and the ionic group-free polymer and the ionic group-containing polymer are firmly bonded. As a result, a composite polymer electrolyte membrane with improved durability can be obtained.

  Furthermore, when the softening temperature of the ionic group-containing polymer is in the range of 140 to 250 ° C., the bondability with the electrode catalyst layer is improved, and the above-mentioned excellent characteristics as a polymer electrolyte membrane are maintained while maintaining a high level. The durability of the molecular electrolyte membrane / electrode assembly and the fuel cell using the same can be improved.

  Furthermore, since the ionic group-containing polymer is a polymer having a repeating structure of a specific structure, the bondability with the electrode catalyst layer is improved, and the above-mentioned excellent characteristics as a polymer electrolyte membrane are maintained while maintaining a high level. The durability of the molecular electrolyte membrane / electrode assembly and the fuel cell using the same can be improved.

Hereinafter, the present invention will be described in detail. In the present invention, the weight means mass.
In the composite polymer electrolyte membrane of the present invention, an ionic group-containing polymer (a polymer having an ionic group in a molecule) is combined with a porous film made of an ionic group-free polymer (a polymer having no ionic group). The ionic group-containing polymer and the ionic group-free polymer are soluble in the same organic solvent, and the softening temperature of the ionic group-containing polymer is 140 to 250 ° C. It is the composite polymer electrolyte membrane characterized.
Examples of the ionic group-containing polymer include polyether ether ketone, polyether sulfone, polyphenyl sulfone, polysulfone, polyimide, polyphenylene, polyarylene, polyarylene ether, polyarylene sulfide, and copolymers such as copolymers having these structures. A polymer solid electrolyte having an ionic group such as a sulfonic acid group introduced therein and having a softening temperature in the range of 140 to 250 ° C. described later is used. When the softening temperature is less than 140 ° C., the composite polymer membrane may be broken or deteriorated when the electrode catalyst layer is joined or when power is generated at a high temperature, and the composite polymer membrane and the electrode catalyst layer may be separated. , It may be easier to get up. When the softening temperature exceeds 250 ° C., the bondability with the electrode catalyst layer is lowered, which may cause peeling.

  Further, the ionic group-free polymer used in the present invention is not particularly limited as long as it is a polymer that dissolves in an organic solvent in which the ionic group-containing polymer dissolves, but heat resistance, chemical stability, In view of the strength after the conversion, the same type of polymer as the ionic group-containing polymer and polyether ether ketone, polyether sulfone, polyphenyl sulfone, polysulfone, polyimide, polyphenylene, polyarylene, polyimide, soluble in organic solvents, Polyamideimide or the like is desirable. Of these, polyamideimide is more preferable because a porous film excellent in porosity and porosity can be easily obtained. The softening temperature of an ionic group-free polymer (a polymer having no ionic group) is not particularly limited, but when the temperature is 100 ° C. or lower, when the electrode catalyst layer is heated, deformation of the membrane increases. There is.

  It is important that the ionic group of the ionic group-containing polymer of the present invention contains one or more of a sulfonic acid group, a phosphonic acid group, and a phosphoric acid group. For the introduction of ionicity into the polymer, a known method can be used. For example, the polymer may be polymerized from a monomer having a sulfonic acid group, a phosphonic acid group, or a phosphoric acid group. The group may be introduced by a known method.

  The organic solvent that can be used in the present invention is not particularly limited as long as it can dissolve the polymer. However, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, Organic polar solvents such as N, N-dimethylformamide, tetramethylurea, dimethylimidazolidinone, dimethyl sulfoxide, and hexamethylphosphonamide are desirable.

  In addition to the organic polar solvent as described above, γ-butyrolactone, 2-acetylbutyrolactone, ε may be used as a solvent for dissolving the ionic group-containing polymer for complexation with the ionic group-free polymer. -Solvents such as lactone solvents such as caprolactone, γ-valerolactone, and δ-valerolactone can be used in combination with solvents that dissolve ionic group-containing polymers but do not dissolve ionic group-free polymers.

The ionic group-containing polymer in the composite polymer electrolyte membrane of the present invention preferably has a structural unit represented by Chemical Formula 1.
In Chemical Formula 1, X is preferably a —S (═O) ₂ — group because solubility in a solvent is improved. It is preferable that X is a —C (═O) — group because the softening temperature of the polymer can be lowered to further enhance the bonding property with the electrode, or the photocrosslinking property can be imparted to the electrolyte membrane. When used as a polymer electrolyte membrane, Y is preferably an H atom. However, if Y is an H atom, it is easily decomposed by heat or the like. Therefore, during processing such as manufacturing of an electrolyte membrane, Y is set as an alkali metal salt such as Na or K, and Y is converted to H atom by acid treatment after processing. A polymer electrolyte membrane can also be obtained by conversion. Z ¹ is preferably O since it has advantages such as less coloring of the polymer and easy availability of raw materials. Z ¹ is preferably S because oxidation resistance is improved. n1 is preferably in the range of 1 to 30, and when n1 is 3 or more, a plurality of units having different n1 may be included. Z ² represents an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, a cyclohexyl group, and more preferably an O atom or an S atom. This is preferable because the bondability is further improved. n1 When in the case of 3 or more is Z ² is O atom, preferably in particular for improving bondability between the electrode catalyst layer in the case of the polymer electrolyte membrane.

It is preferable that the ionic group-containing polymer having a structural unit represented by Chemical Formula 1 further contains a structural unit represented by Chemical Formula 2.
In Chemical Formula 2, it is preferable that Z ³ is O because there are advantages such as little coloring of the polymer and easy availability of raw materials. Z ³ is preferably S because oxidation resistance is improved. n2 is preferably in the range of 1 to 30, and when n2 is 3 or more, a plurality of units different in n2 may be included. Z ⁴ represents an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, a cyclohexyl group, and more preferably an O atom or an S atom. This is preferable because the bondability is further improved. n2 When the case 3 or more is Z ⁴ is O atom, preferably in particular for improving bondability between the electrode catalyst layer in the case of the polymer electrolyte membrane.

  When the ionic group-containing polymer constituting the composite polymer electrolyte membrane of the present invention is mainly composed of a structural unit represented by Chemical Formula 1 and a structural unit represented by Chemical Formula 2, each molar ratio Is preferably in the range of 7:93 to 50:50. The molar ratio of 7:93 means that the number of moles of the structural unit represented by Chemical Formula 2 is 93 when the number of moles of the structural unit represented by Chemical Formula 1 is 7. When the number of structural units represented by the chemical formula 1 is larger than the molar ratio of 50:50, the fuel permeability may be increased when the polymer electrolyte membrane is used, which is not preferable. If the number of structural units represented by Chemical Formula 1 is less than the molar ratio of 7:93, it is not preferable because proton conductivity in a polymer electrolyte membrane is lowered and resistance is increased. The range of 10:90 to 40:60 is more preferable. The ionic group-containing polymer in the present invention has an appropriate softening temperature by having the structural unit represented by Chemical Formula 1 and Chemical Formula 2, and exhibits good bonding properties with an electrode when a polymer electrolyte membrane is formed. .

Ar ¹ in Chemical Formula 2 is preferably a divalent aromatic group having an electron-withdrawing group. Examples of the electron-withdrawing group include a sulfone group, a sulfonyl group, a sulfonic acid group, a sulfonic acid ester group, a sulfonic acid amide group, a sulfonic acid imide group, a carboxyl group, a carbonyl group, a carboxylic acid ester group, a cyano group, a halogen group, Although a trifluoromethyl group, a nitro group, etc. can be mentioned, it is not limited to these, What is necessary is just a well-known arbitrary electron withdrawing group.

A preferred structure of Ar ¹ is a structure represented by Chemical Formulas 3-6. The structure of Chemical Formula 3 is preferable because it can increase the solubility of the polymer. The structure of Chemical Formula 4 is preferable because it lowers the softening temperature of the polymer to increase the bonding property with the electrode and impart photocrosslinking properties. The structure of Chemical Formula 5 or 6 is preferable because the swelling of the polymer can be reduced, and the structure of Chemical Formula 6 is more preferable. Among the chemical formulas 3 to 6, the structure of the chemical formula 6 is most preferable.

One of the more preferable embodiments of the ionic group-containing polymer constituting the composite polymer electrolyte membrane of the present invention is that the polymer electrolyte membrane is mainly composed of a structure represented by Chemical Formula 1 and a structure represented by Chemical Formula 2. And Z ¹ and Z ² in Chemical Formula 1 are both O atoms, and n1 is 3 or more. It is preferable to use such an ionic group-containing polymer because the bondability with the electrode is particularly improved.

One of the more preferable embodiments of the ionic group-containing polymer is more preferably that Z ³ and Z ⁴ in Chemical Formula 2 are both O atoms, and n2 is 3 or more. It is preferable to use such an ionic group-containing polymer because the bondability with the electrode is further improved.

One of the more preferable embodiments of the ionic group-containing polymer constituting the composite polymer electrolyte membrane of the present invention is an ionic group-containing polymer having a structural unit represented by the chemical formula 7 in addition to the chemical formulas 1 and 2. . In addition to the structural units represented by the chemical formulas 1 and 2, it is preferable to further include the structural unit represented by the chemical formula 7, because the morphological stability of the membrane when the polymer electrolyte membrane is obtained can be improved. . In Chemical Formula 7, X is preferably a —S (═O) ₂ — group because solubility in a solvent is improved. It is preferable that X is a —C (═O) — group because the softening temperature of the polymer can be lowered to further enhance the bonding property with the electrode, or the photocrosslinking property can be imparted to the electrolyte membrane. When used as a polymer electrolyte membrane, Y is preferably an H atom. However, if Y is an H atom, it is easily decomposed by heat or the like. Therefore, during processing such as manufacturing of an electrolyte membrane, Y is set as an alkali metal salt such as Na or K, and Y is converted to H atom by acid treatment after processing. A polymer electrolyte membrane can also be obtained by conversion. Z ⁵ is preferably O, because there are advantages such as little polymer coloring and easy availability of raw materials. Z ⁵ is preferably S because oxidation resistance is improved.

When the ionic group-containing polymer constituting the composite polymer electrolyte membrane of the present invention has structural units represented by chemical formulas 1, 2, and 7, Z ¹ and Z ² are O or S It is preferable that it is an atom and n1 is 1, since the bonding property with the electrode catalyst layer in the case of a polymer electrolyte membrane and the morphological stability of the membrane become better. In addition, when Z ³ and Z ⁴ are O or S atoms and n2 is 1, the bonding property with the electrode catalyst layer and the morphological stability of the membrane are further improved when the polymer electrolyte membrane is used. This is preferable.

When the ionic group-containing polymer constituting the composite polymer electrolyte membrane of the present invention further has a structural unit represented by the chemical formula 8, in addition to the structural units represented by the chemical formulas 1, 2, and 7, When a molecular electrolyte membrane is used, it is more preferable because the bondability with the electrode catalyst layer and the morphological stability of the membrane can be greatly improved. Z ⁶ in the chemical formula 8 is preferably O, because there are advantages such as little polymer coloring and easy availability of raw materials. Z ⁶ is preferably S because oxidation resistance is improved. Ar ² in Chemical Formula 8 is preferably a divalent aromatic group having an electron-withdrawing group. Examples of the electron-withdrawing group include a sulfone group, a sulfonyl group, a sulfonic acid group, a sulfonic acid ester group, a sulfonic acid amide group, a sulfonic acid imide group, a carboxyl group, a carbonyl group, a carboxylic acid ester group, a cyano group, a halogen group, Although a trifluoromethyl group, a nitro group, etc. can be mentioned, it is not limited to these, What is necessary is just a well-known arbitrary electron withdrawing group.

A preferable structure of Ar ² is a structure represented by Chemical Formulas 3-6. The structure of Chemical Formula 3 is preferable because it can increase the solubility of the ionic group-containing polymer. The structure of Chemical Formula 4 is preferable because it lowers the softening temperature of the ionic group-containing polymer to further enhance the bonding property with the electrode or impart photocrosslinkability. The structure of Chemical Formula 5 or 6 is preferable because the swelling of the ionic group-containing polymer can be reduced, and the structure of Chemical Formula 6 is more preferable. Among the chemical formulas 3 to 6, the structure of the chemical formula 6 is most preferable.

  When the ionic group-containing polymer constituting the composite polymer electrolyte membrane of the present invention has all the structural units represented by the chemical formulas 1, 2, 7, and 8, respectively, mol% of the respective structural units. It is preferable that the mol% of other structural units satisfy the following formulas 1 to 3.

0.9 ≤ (n3 + n4 + n5 + n6) / (n3 + n4 + n5 + n6 + n7) ≤ 1.0 Formula 1
0.05 ≤ (n3 + n4) / (n3 + n4 + n5 + n6) ≤ 0.7 Formula 2
0.01 ≤ (n4 + n6) / (n3 + n4 + n5 + n6) ≤ 0.95 Equation 3
(In the above formula, n3 represents mol% of the structural unit represented by Chemical Formula 7, n4 represents mol% of the structural unit represented by Chemical Formula 1, and n5 represents mol% of the structural unit represented by Chemical Formula 8, n6 represents mol% of the structural unit represented by Chemical Formula 2, and n7 represents mol% of the other structural unit.)

  When (n3 + n4 + n5 + n6) / (n3 + n4 + n5 + n6 + n7) is smaller than 0.9, good characteristics cannot be obtained when a polymer electrolyte membrane is obtained, which is not preferable. More preferred is a range of 0.95 to 1.0.

  When (n3 + n4) / (n3 + n4 + n5 + n6) is smaller than 0.05, it is not preferable because sufficient proton conductivity cannot be obtained when a polymer electrolyte membrane is obtained. On the other hand, if it is larger than 0.9, the swellability of the polymer electrolyte membrane is remarkably increased, which is not preferable. A more preferred range is from 0.1 to 0.7.

  Further, (n3 + n4) / (n3 + n4 + n5 + n6) is preferably in the range of 0.07 to 0.5, and more preferably in the range of 0.1 to 0.4. If it is larger than 0.5, the fuel permeability may be increased, and if it is smaller than 0.07, the proton conductivity may decrease and the resistance may increase.

  When (n4 + n6) / (n3 + n4 + n5 + n6) is less than 0.01, it is not preferable because the bonding property with the electrode catalyst layer is lowered when a polymer electrolyte membrane is formed. If it is greater than 0.95, the swellability of the polymer electrolyte membrane may become too large, which is not preferable. 0.05 to 0.8 is a more preferable range. More preferably, it is in the range of 0.4 to 0.8.

  In the ionic group-containing polymer of the present invention, the bonding mode of each structural unit represented by each chemical formula is not particularly limited, and any of random bonds, alternating bonds, bonds in a continuous block structure, etc. But you can.

  Preferred examples of the ionic group-containing polymer structure that can be used for the composite polymer electrolyte membrane of the present invention are shown below, but are not limited to these, and any suitable one that satisfies the requirements of the present invention is preferable. It is possible to use. In the following specific examples of the ionic group-containing polymer skeleton, n, n ′, n ″, m, m ′, m ″, o, o ′, o ″, p, p ′, p ″, f are independent of each other. Represents an integer of 1 or more.

  Among the ionic group-containing polymers constituting the composite polymer electrolyte membrane of the present invention, examples of the ionic group-containing polymer having a sulfonic acid group on the aromatic ring include polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, It can be obtained by reacting a suitable sulfonating agent with an aromatic polymer copolymerized with at least one polyether ketone. Examples of such a sulfonating agent include those using concentrated sulfuric acid or fuming sulfuric acid, which have been reported as an example of introducing a sulfonic acid group into an aromatic ring-containing polymer (for example, Solid State Ionics, 106, P.A. 219 (1998)), those using chlorosulfuric acid (for example, J. Polym. Sci., Polym. Chem., 22, P. 295 (1984)), those using anhydrous sulfuric acid complex (for example, J. Polym Sci., Polym.Chem., 22, P.721 (1984), J. Polym.Sci., Polym.Chem., 23, P.1231 (1985)) and the like are effective. In order to obtain such an ionic group-containing polymer in which at least one of polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyether ketone is copolymerized, these reagents are used according to each polymer. It can be carried out by selecting the reaction conditions. Moreover, it is also possible to use the sulfonating agent described in Japanese Patent No. 2884189. However, for the composite polymer membrane of the present invention, it is necessary to use a polymer having a softening temperature of 140 to 250 ° C. among the above ionic group-containing polymers.

  Among the ionic group-containing polymers, for example, an ionic group-containing polymer obtained by copolymerizing at least one of polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyether ketone is at least one of the monomers used for polymerization. It can also be synthesized using a monomer containing an acidic group as one kind. For example, in a polyimide synthesized from an aromatic diamine and an aromatic tetracarboxylic dianhydride, an ionic group-containing polyimide can be obtained by using a sulfonic acid group-containing diamine as at least one of the aromatic diamines. In the case of polybenzoxazole synthesized from aromatic diamine diol and aromatic dicarboxylic acid, and polybenzthiazole synthesized from aromatic diamine dithiol and aromatic dicarboxylic acid, at least one kind of aromatic dicarboxylic acid contains sulfonic acid group By using a dicarboxylic acid or a phosphonic acid group-containing dicarboxylic acid, an ionic group-containing polybenzoxazole or polybenzthiazole can be obtained. Polysulfone, polyethersulfone, polyetherketone, etc. synthesized from aromatic dihalide and aromatic diol are synthesized by using sulfonic acid group-containing aromatic dihalide or sulfonic acid group-containing aromatic diol as at least one monomer. be able to. At this time, it can be said that it is preferable to use a sulfonic acid group-containing dihalide rather than using a sulfonic acid group-containing diol because the degree of polymerization tends to increase and the thermal stability of the resulting ionic group-containing polymer increases.

  In the ionic group-containing polymer constituting the composite polymer electrolyte membrane of the present invention, the repeating structural unit represented by the chemical formulas 1 and 2 increases the flexibility of the polymer, suppresses breakage against deformation, and has a glass transition temperature. By lowering, the effect of improving the bonding property with the electrode is brought about. Further, the repeating structural units represented by the chemical formulas 7 and 8 have the effect of reducing the swelling property of the whole polymer and reducing the methanol permeability.

  The composite polymer electrolyte membrane of the present invention may contain other materials in addition to the reinforcing material. For example, other materials may be included in the matrix of the ionic group-containing polymer. Examples of other materials include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamides such as nylon 6, nylon 66, nylon 610, and nylon 12, polymethyl methacrylate, polymethacrylates, and polymethyl. Acrylate resins such as acrylates and polyacrylates, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, various polyolefins including polystyrene and diene polymers, polyurethane resins, cellulose acetate, cellulose such as ethyl cellulose Resin, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyethersulfone, Aromatic polymers such as polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, polybenzthiazole, thermosetting resins such as epoxy resin, phenol resin, novolac resin, benzoxazine resin, etc. There is no particular limitation. A resin composition with a basic polymer such as polybenzimidazole or polyvinylpyridine can be said to be a preferable combination for improving the polymer dimensionality, and when a sulfonic acid group is further introduced into these basic polymers, The processability of the composition becomes more preferable. Other materials include antioxidants, heat stabilizers, lubricants, tackifiers, plasticizers, crosslinking agents, viscosity modifiers, antistatic agents, antibacterial agents, antifoaming agents, dispersants, polymerization inhibitors, etc. These various additives may be included.

  As a method for synthesizing the ionic group-containing polymer in the present invention, a known method can be adopted and is not particularly limited. As a preferred example of a raw material monomer used for synthesis, a monomer having a structure represented by the following chemical formulas 13 to 15 is used. Can be mentioned. Furthermore, it is preferable to further use a monomer having a structure represented by the chemical formula 16 because physical properties such as film form stability are improved.

In Chemical Formulas 13 to 16, X is a —S (═O) ₂ — group or —C (═O) — group, Y is H or a monovalent cation, and Z ⁷ and Z ¹⁰ are each independently Any one of Cl atom, F atom, I atom, Br atom and nitro group, Z ⁸ and Z ¹¹ are each independently OH group, SH group, —O—NH—C (═O) —R group, -S-NH-C (= O) -R group is represented by [R represents an aromatic or aliphatic hydrocarbon group. Z ⁹ represents any one of an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, and a cyclohexyl group, and Ar ⁴ represents a molecule in the molecule. And an aromatic group having an electron-withdrawing group such as a perfluoroalkyl group such as a sulfone group, a carbonyl group, a sulfonyl group, a phosphine group, a cyano group or a trifluoromethyl group, a nitro group or a halogen group.

  Specific examples of the compound represented by Chemical Formula 13 include 3,3′-disulfo-4,4′-dichlorodiphenylsulfone, 3,3′-disulfo-4,4′-difluorodiphenylsulfone, 3,3′- Disulfo-4,4′-dichlorodiphenyl ketone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, 3,3′-disulfobutyl-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfobutyl- 4,4′-difluorodiphenyl sulfone, 3,3′-disulfobutyl-4,4′-dichlorodiphenyl ketone, 3,3′-disulfobutyl-4,4′-difluorodiphenyl sulfone, and their sulfonic acid groups are monovalent Examples include salts with cation species. The monovalent cation species may be sodium, potassium, other metal species, various amines, or the like, but is not limited thereto. Examples of the compound represented by Chemical Formula 13 in which the sulfonic acid group is a salt include sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone, 3,3′-disulfonic acid. Sodium-4,4′-difluorodiphenylsulfone, sodium 3,3′-disulfonate-4,4′-dichlorodiphenylketone, sodium 3,3′-disulfonate-4,4′-difluorodiphenylsulfone, 3,3 'Sodium disulfonate-4,4'-difluorodiphenyl ketone, potassium 3,3'-disulfonate-4,4'-dichlorodiphenylsulfone, potassium 3,3'-disulfonate-4,4'-difluorodiphenylsulfone 3,3′-Disulfonic acid potassium-4,4′-dichlorodiphenyl ketone, 3,3′-di Sulfonic acid potassium-4,4'-difluoro diphenyl sulfone, etc. 3,3'-disulfonic acid potassium-4,4'-difluoro diphenyl ketone and the like.

  Specific examples of the compound represented by Chemical Formula 14 include 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 4,4′-thiobisbenzenethiol, 4,4′-oxybisbenzenethiol, bis (4-hydroxyphenyl) sulfide, 4,4′-dihydroxydiphenyl ether, 1,1-bis (4-hydroxyphenyl) cyclohexane, etc. 4,4′-thiobisbenzenethiol, bis (4-hydroxyphenyl) sulfide, 1,1-bis (4-hydroxyphenyl) cyclohexane, terminal hydroxyl group-containing phenylene ether oligomer (in the following chemical formula 17) Are preferred).

  The monomer having the structure represented by Chemical Formula 14 increases the flexibility of the ionic group-containing polymer, suppresses breakage against deformation, reduces the glass transition temperature, and improves the bondability with the electrode catalyst layer. Can bring about the effect.

  Examples of the compound represented by Chemical Formula 15 include compounds having a leaving group in a nucleophilic substitution reaction such as halogen and nitro group on the same aromatic ring and an electron-withdrawing group for activating it. Specific examples include 2,6-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-difluorobenzonitrile, 4,4′-dichlorodiphenylsulfone, 4,4 ′. -Difluorodiphenyl sulfone, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, decafluorobiphenyl, and the like, but not limited thereto, other aromatics active in aromatic nucleophilic substitution reaction A group dihalogen compound, an aromatic dinitro compound, an aromatic dicyano compound, and the like can also be used.

  Examples of the compound represented by Chemical Formula 16 include 4,4'-biphenol, 4,4'-dimercaptobiphenol, and 4,4'-biphenol is preferred.

  In the above aromatic nucleophilic substitution reaction, other various activated dihalogen aromatic compounds, dinitroaromatic compounds, bisphenol compounds, and bisthiophenol compounds can be used in combination with the compounds represented by chemical formulas 13 to 16. .

  Examples of other bisphenol compounds or bisthiophenol compounds include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, and bis (4-hydroxyphenyl). ) Sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, 2,2-bis (4- Hydroxy-3,5-dimethylphenyl) propane, bis (4-hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane , Hydroquinone, resorcin, bis (4-hydroxyphenyl) ketone, 1,4-benze Examples include dithiol, 1,3-benzenedithiol, phenolphthalein, 10- (2,5-dihydroxyphenyl) -9,10-dihydro-9-oxa-10-phosphenanthrene-10-oxide. In addition, various aromatic diols or various aromatic dithiols that can be used for polymerization of polyarylene ether compounds by aromatic nucleophilic substitution reaction can also be used, and are not limited to the above compounds. .

  When the ionic group-containing polymer constituting the composite polymer electrolyte membrane of the present invention is polymerized by an aromatic nucleophilic substitution reaction, a compound having a structure represented by Chemical Formulas 13 to 16 and, if necessary, other activated dihalogens A polymer can be obtained by adding an aromatic compound, a dinitroaromatic compound, an aromatic diol, or an aromatic dithiol and reacting in the presence of a basic compound. By adjusting the molar ratio of the reactive halogen group or nitro group and the reactive hydroxy group and thiol group in the monomer to an arbitrary molar ratio, the degree of polymerization of the resulting ionic group-containing polymer can be adjusted. However, it is preferably 0.8 to 1.2, more preferably 0.9 to 1.1, and preferably 0.95 to 1.05. It is most preferable because an ionic group-containing polymer having a high degree of polymerization can be obtained.

  The polymerization can be carried out in the temperature range of 0 to 350 ° C, but preferably in the range of 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not tend to proceed sufficiently. When the temperature is higher than 350 ° C., decomposition of the ionic group-containing polymer also tends to start to occur. The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more.

  Examples of basic compounds include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc., but aromatic diols and aromatic dimercapto compounds can be made into an active phenoxide structure. If it is a thing, it is not limited to these but can be used. The basic compound can be polymerized satisfactorily when used in an amount of 100 mol% or more with respect to the total of the bisphenol compound and the bisthiophenol compound, and preferably 105 to 105% with respect to the total of the bisphenol compound or the bisthiophenol compound. The range is 125 mol%. An excessive amount of bisphenol compound or bisthiophenol compound is not preferable because it causes side reactions such as decomposition.

  Further, in the above polymerization reaction, a bisphenol compound or bisthiophenol compound reacted with an isocyanate compound to form a carbamoylate without using a basic compound, and an activated dihalogen aromatic compound or dinitro aromatic compound are directly combined. It can also be reacted.

  In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water absorbing material such as molecular sieve can also be used. When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is in the range of 5 to 50% by mass. When the amount is less than 5% by mass, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by mass, the viscosity of the reaction system becomes too high, and post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired ionic group-containing polymer. In addition, the ionic group-containing polymer can be precipitated as a solid by adding the reaction solution into a solvent having low polymer solubility, and the ionic group-containing polymer can be obtained by filtering the precipitate. Further, by-product salts can be removed by filtration to obtain an ionic group-containing polymer solution.

The ionic group-containing polymer in the present invention preferably has one or more of the above structural units per molecule. The number of structural units per molecule is preferably in the range of 10 to 10,000, and more preferably in the range of 100 to 1,000. The number of structural units can be determined by measuring the molecular weight by any known method such as size exclusion chromatography, light scattering, or solution viscosity.
In addition, the molecular weight of the ionic group-containing polymer in the present invention can be expressed by measuring a polymer logarithmic viscosity measured by a method described later, and the logarithmic viscosity is preferably 0.1 dL / g or more. When the logarithmic viscosity is less than 0.1 dL / g, the membrane tends to become brittle when molded as a polymer electrolyte membrane. The logarithmic viscosity is more preferably 0.3 dL / g or more. On the other hand, when the logarithmic viscosity exceeds 5 dL / g, problems in processability such as difficulty in dissolving the polymer occur, which is not preferable. As a solvent for measuring the logarithmic viscosity, polar organic solvents such as N-methylpyrrolidone and N, N-dimethylacetamide can be generally used. When the solubility in these is low, concentrated sulfuric acid is used. It can also be measured.

A desirable method for producing the composite polymer electrolyte membrane of the present invention is as follows. First, a solution of an ionic group-free polymer cast at a predetermined thickness by a casting method or the like is immersed in a poor solvent for the ionic group-free polymer to prepare a porous film by phase separation.
The porosity and thickness of the porous membrane are not particularly limited, but from the balance of proton conductivity and reinforcing effect, the porosity is preferably 40 to 90% and the thickness is preferably 10 to 100 μm. If the porosity is less than 40%, the filling rate of the ionic group-containing polymer may be insufficient and the proton conductivity may decrease, and if it exceeds 90%, the reinforcing effect of the ionic group-free polymer is exhibited. This is because it becomes difficult. If the thickness is less than 10 μm, handling becomes difficult, and if it exceeds 100 μm, the resistance of the film may be too high.
The obtained porous film is sufficiently washed with water to remove the solvent and then dried. Next, the target composite polymer electrolyte membrane is obtained by filling the porous membrane with a solution in which the ionic group-containing polymer is dissolved and sufficiently drying the solvent.

  At that time, the ionic group-free polymer solution, the ionic group-containing polymer solution, the composition of the poor solvent, the temperature, etc. are not limited, and are appropriately determined according to the specifications of the processability and the composite polymer electrolyte membrane to be produced. do it. For example, by adding a small amount of a poor solvent to the ionic group-containing polymer solution, the degree of dissolution of the ionic group-free polymer porous membrane can be controlled. In addition, when forming a porous film from an ionic group-free polymer solution, in order to promote porosity, a component that dissolves in a poor solvent of the ionic group-free polymer is added to the ionic group-free polymer solution. It may be left. Also, for filling the porous film of the ionic group-containing polymer solution, it is desirable to use vacuum impregnation, pressure filling, or the like because no bubbles remain.

  The filling rate of the ionic group-free polymer in the composite polymer electrolyte membrane of the present invention is preferably 40 to 90%, more preferably 65 to 85%. When the filling rate is less than 40%, proton conductivity may be insufficient, and when it exceeds 90%, the reinforcing effect may not be exhibited.

  In the method for producing a composite polymer electrolyte membrane in which these ionic group-free polymer porous membrane and ionic group-containing polymer are combined, casting, phase separation, water washing, drying and ionization of the ionic group-free polymer solution The filling and drying of the functional group-containing polymer solution can be performed continuously or intermittently.

The membrane / electrode assembly of the present invention can be obtained by bonding the polymer electrolyte membrane of the present invention to an electrode catalyst layer.
The electrode in the present invention comprises an electrode material and a layer (electrode catalyst layer) containing a catalyst formed on the surface thereof, and a known material can be used as the electrode material. For example, a conductive porous material such as carbon paper or carbon cloth can be used, but is not limited thereto. As the conductive porous material such as carbon paper or carbon cloth, a material subjected to surface treatment such as water repellent treatment or hydrophilic treatment can be used. A known material can be used for the catalyst. For example, platinum, an alloy of platinum and ruthenium, and the like can be given, but the invention is not limited to them.
The catalyst can be used in any known form, and for example, carbon particles carrying catalyst fine particles can be used, but are not limited thereto.
An adhesive can be used for the catalyst and the electrode catalyst layer including the particles carrying the catalyst, and as the adhesive, a resin having proton conductivity can be used.

  As a method for producing a membrane / electrode assembly, a conventionally known method can be used. For example, a method of applying an adhesive to the electrode surface and bonding the polymer electrolyte membrane and the electrode catalyst layer or a polymer There is a method of heating and pressurizing the electrolyte membrane and the electrode catalyst layer. As the adhesive, a known material such as a Nafion (trade name) solution may be used, or an adhesive mainly containing an ionic group-containing polymer constituting the composite polymer electrolyte membrane of the present invention may be used. Those having other hydrocarbon proton conductive polymers as a main component may also be used. The method for producing the joined body is preferably a method in which a composition containing an adhesive and a catalyst is applied to the electrode surface and adhered. In the composite polymer electrolyte membrane of the present invention, since the ionic group-containing polymer has an appropriate softening temperature, a method of joining the polymer electrolyte membrane and the electrode by pressure heating is particularly suitable.

  The fuel cell of the present invention can be produced using the polymer electrolyte membrane or the polymer electrolyte membrane / electrode assembly of the present invention. The fuel cell of the present invention includes, for example, an oxygen electrode, a fuel electrode, a polymer electrolyte membrane sandwiched between the electrodes, an oxidant flow path provided on the oxygen electrode side, and a fuel electrode side. The fuel flow path is provided. A fuel cell stack can be obtained by connecting such unit cells with a conductive separator.

EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. Various measurements were performed as follows.
<Polymer electrolyte membrane evaluation method>
The evaluation method of a polymer electrolyte membrane is shown below. In the evaluation, unless otherwise specified, the evaluation was performed in a measurement chamber in which the room temperature was controlled to 20 ° C. and the relative humidity was controlled to 30 ± 5 RH% for the purpose of accurately measuring the thickness and mass. In the measurement, a sample that was allowed to stand in a measurement chamber for 24 hours or more was used.

<Filling ratio of ionic group-containing polymer in composite polymer electrolyte membrane>
The filling rate of the ionic group-containing polymer in the composite polymer electrolyte membrane was measured by the following method. The composite polymer electrolyte membrane weight per unit area Dc [g / m ² ] and the porous membrane produced under the same conditions as those used for the production of the composite polymer electrolyte membrane were dried without compounding the ionic group-containing polymer. From the measured basis weight Ds [g / m ² ] of the dried porous film, the filling rate of the ionic group-containing polymer was determined by the following calculation.
Filling ratio of ionic group-containing polymer [% by mass] = (Dc−Ds) / Dc × 100

<Thickness of polymer electrolyte membrane>
The thickness of the polymer electrolyte membrane was determined by measurement using a micrometer (Mitutoyo standard micrometer 0-25 mm 0.01 mm). Measurement was performed at 10 locations, and the average value was taken as the thickness.

<Ion conductivity>
Ionic conductivity σ was measured as follows. A platinum wire (diameter: 0.2 mm) is pressed against the surface of a strip-shaped membrane sample with a width of 10 mm on a self-made measurement probe (made of polytetrafluoroethylene), and the sample is held in water at 25 ° C. The AC impedance was measured by SOLARTRON 1250 FREQUENCY RESPONSE ANALYSER. The contact distance between the membrane and the platinum wire is measured by the following formula from the slope Dr [Ω / cm] of the straight line in which the distance between the electrodes is changed from 15 mm to 45 mm at 15 mm intervals and the distance between the electrodes and the measured resistance value are plotted. Canceled and calculated.
σ [S / cm ² ] = 1 / (film width [cm] × Dr)

<Softening temperature of ionic group-containing polymer>
10 Hz while heating an acid-type film having a thickness of 50 μm and a width of 5 mm prepared from the following ionic group-containing polymer solutions A to D for complexing at a chuck width of 10 mm from 50 ° C. to 250 ° C. at 2 ° C./min. The dynamic viscoelasticity was measured using Rheogel E-4000 (manufactured by Toki Sangyo Co., Ltd.). The temperature at the inflection point at which E ′ greatly decreased was defined as the softening temperature.

<Hydrogen gas permeability>
The hydrogen gas permeability of the polymer electrolyte membrane was measured by the following method. The polymer electrolyte membrane was set in a self-made gas permeability measuring cell (effective diameter 20 mm = effective area about 3.14 cm ² ), the atmosphere was adjusted to 70 ° C., and hydrogen gas (70 C., relative humidity 90%, flow rate 40 cc / min), and nitrogen gas (70 ° C., relative humidity 90%, flow rate 40 cc / min) was allowed to flow on the opposite side of the membrane. The pressures of both hydrogen gas and nitrogen gas were adjusted to the same pressure as 1 atm (= 76 cmHg). In this state, the amount of hydrogen gas permeating through the polymer electrolyte membrane and diffusing into the nitrogen gas was measured over time using a gas chromatograph, and calculated from the value when it became constant.

<Methanol permeation rate>
The liquid fuel permeation rate of the polymer electrolyte membrane was measured as the methanol permeability by the following method. A polymer electrolyte membrane immersed in a 5 mol / L (liter) aqueous methanol solution adjusted to 25 ° C. for 24 hours is sandwiched between H-type cells, and 100 mL of 5 mol / L (liter) methanol is placed on one side of the cell. The amount of methanol that diffuses into the ultrapure water through the polymer electrolyte membrane while injecting 100 mL of ultrapure water (18 MΩ · cm) into the other cell and stirring the cells on both sides at 25 ° C. Was calculated using a gas chromatograph (the area of the polymer electrolyte membrane was 2.0 cm ² ).

<Swelling / Shrinkage Repeat Test Method and Durability Evaluation Method>
The swelling / contraction repeated test and durability of the polymer electrolyte membrane were measured by the following methods. The polymer electrolyte membrane is set in a self-made swelling / contraction repeated test cell (effective diameter 40 mmφ = effective area about 12.6 cm ² ), and left in a constant temperature and humidity chamber at 75 ° C. and 30% relative humidity. Thereafter, the relative humidity in the constant temperature and humidity chamber is repeatedly changed between 30% and 95% (cycle time is 45 minutes), and changes in hydrogen gas permeability and methanol permeability over time of the polymer electrolyte membrane are changed to 50%. Each cycle was measured up to 300 cycles. At the same time, the surface of the polymer electrolyte membrane was observed for the presence of cracks, tears, pinholes, and the like.

<Jointness between polymer electrolyte membrane and electrode; fuel cell using hydrogen as fuel (PEFC)>
After adding commercially available 40% Pt catalyst-supported carbon (Tanaka Kikinzoku Kogyo Co., Ltd. Fuel Cell Catalyst TEC10V40E) and a small amount of ultrapure water and isopropanol to DuPont 20% Nafion (registered trademark) solution, until uniform Stir to prepare a catalyst paste. The catalyst paste was uniformly applied and dried on carbon paper (TGPH-060 manufactured by Toray Industries, Inc.) so that the amount of platinum deposited was 0.5 mg / cm ² to prepare a gas diffusion layer with an electrode catalyst layer. By sandwiching the polymer electrolyte membrane between the gas diffusion layers with the electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane, pressurizing and heating at 130 ° C. and 3 MPa for 4 minutes by a hot press method, A membrane-electrode assembly was obtained. The joined body was assembled in an evaluation fuel cell FC25-02SP manufactured by Electrochem, and hydrogen and air humidified at 75 ° C. were supplied to the anode and the cathode at a cell temperature of 80 ° C., and the power generation characteristics were evaluated. The output voltage at a current density of 0.5 A / cm ² immediately after the start was taken as the initial characteristics. Moreover, as durability evaluation, continuous operation was performed on said conditions, measuring an open circuit voltage at the rate of once per hour. After power generation for a predetermined time, the polymer electrolyte / membrane electrode assembly was taken out, and the presence or absence of peeling between the polymer electrolyte membrane and the electrode catalyst layer was visually determined. The case where there was no peeling between the polymer electrolyte membrane and the electrode catalyst layer was indicated by ◯, the case where a part was peeled, and the case where more than half of the electrode area was peeled.

<Jointness between polymer electrolyte membrane and electrode; direct methanol fuel cell (DMFC)>
After adding and dampening a small amount of ultrapure water and isopropyl alcohol to Pt / Ru catalyst-supporting carbon (Tanaka Kikinzoku Kogyo TEC61E54), a DuPont 20% Nafion (registered trademark) solution (product number: SE-20192) is used. The Pt / Ru catalyst-supported carbon and Nafion were added so that the mass ratio was 2.5: 1. Next, stirring was performed to prepare an anode catalyst paste. This catalyst paste is applied to a carbon paper (TGPH-060 manufactured by Toray Industries, Inc.) serving as a gas diffusion layer by screen printing so that the amount of platinum deposited is 2 mg / cm ^2, and carbon paper with an electrode catalyst layer for anode Was made. Moreover, after adding and dampening a small amount of ultrapure water and isopropyl alcohol to Pt catalyst-supporting carbon (Tanaka Kikinzoku Kogyo TEC10V40E), a DuPont 20% Nafion (registered trademark) solution (product number: SE-20192), A cathode catalyst paste was prepared by adding the Pt catalyst-carrying carbon and Nafion at a mass ratio of 2.5: 1 and stirring. This catalyst paste was applied and dried on carbon paper (TGPH-060 manufactured by Toray Industries, Inc.) that had been subjected to water repellent treatment so that the amount of platinum deposited was 1 mg / cm ^2. Produced. By sandwiching the membrane sample between the two types of carbon paper with the electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane sample, and pressurizing and heating at 160 ° C. and 6 MPa for 3 minutes by a hot press method, A membrane-electrode assembly was obtained. This joined body was incorporated into an evaluation fuel cell FC25-02SP manufactured by Electrochem, and a power generation test was performed using a fuel cell power generation tester (manufactured by Toyo Technica). Power generation is performed while supplying a high-purity air gas (80 mL / min) adjusted to 40 ° C. and an aqueous methanol solution (1.5 mL / min) having a concentration of 5 mol / L to the anode and the cathode at a cell temperature of 40 ° C. went. After power generation for a predetermined time, the polymer electrolyte / membrane electrode assembly was taken out, and the presence or absence of peeling between the polymer electrolyte membrane and the electrode catalyst layer was visually determined. The case where there was no peeling between the polymer electrolyte membrane and the electrode catalyst layer was indicated by ◯, the case where a part was peeled, and the case where more than half of the electrode area was peeled.

<Preparation of ionic group-containing polymer solution A for conjugation>
Sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (abbreviation S-DCDPS) 100.00 g, 2,6-dichlorobenzonitrile (abbreviation: DCBN) 44.56 g, bis (4-hydroxyphenyl) Sulfide (abbreviation: BPS) 10.10 g, 4,4′-biphenol (abbreviation: BP) 77.53 g, potassium carbonate 70.34 g, N-methyl-2-pyrrolidone (abbreviation: NMP) 630 mL, toluene 120 mL were introduced into nitrogen It put into the 1000 mL branch flask equipped with the pipe | tube, the stirring blade, the Dean-Stark trap, and the thermometer, and heated under nitrogen stream, stirring in an oil bath. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Thereafter, the temperature was raised to 200 ° C. and heated for 12 hours. Thereafter, the solution cooled to room temperature was poured into 2 L of pure water to reprecipitate the polymer. The filtered polymer was washed 3 times with boiling water and 5 times with pure water at room temperature, and then dried at 120 ° C. A solution obtained by stirring 100 g of the obtained polymer and 400 g of N-methyl-2-pyrrolidone at 80 ° C. for 5 hours in a nitrogen atmosphere was cooled to room temperature, and suction filtered through a glass filter (25G1). An ionic group-containing polymer solution A for complexation was obtained.

<Preparation of ionic group-containing polymer solution B for conjugation>
S-DCDPS 40.00 g, DCBN 56.02 g, BPS 71.09 g, BP 15.16 g, potassium carbonate 61.90 g, and NMP 500 mL were used, as in the preparation of the ionic group-containing polymer solution A for conjugation. In this way, an ionic group-containing polymer solution B for conjugation was prepared.

<Preparation of ionic group-containing polymer solution C for conjugation>
S-DCDPS 35.00 g, DCBN 26.04 g, terminal hydroxyl group-containing phenylene ether oligomer (a mixture containing n of components 1 to 8 in chemical formula 17 and having an average n value of 5) (abbreviation: BPE) An ionic group-containing polymer solution C for complexation was prepared in the same manner as the preparation of the ionic group-containing polymer solution A for complexing except that 122.42 g, 33.85 g of potassium carbonate, and 550 mL of NMP were used.

<Preparation of ionic group-containing polymer solution D for conjugation>
Sodium 4,4′-dichloro-3,3′-disulfonate-benzophenone (abbreviation: S-DCBP) 75.00 g, 39.14 g of DCBN, 1,1-bis (4-hydroxyphenyl) cyclohexane (abbreviation: BHC) Except for using 10.53 g, 65.74 g of BP, 59.64 g of potassium carbonate, and 550 mL of NMP, the ionic group-containing polymer solution D for conjugation was prepared in the same manner as the preparation of the ionic group-containing polymer solution A for conjugation. Prepared.

<Preparation of ionic group-containing polymer solution E for conjugation>
A solution obtained by stirring 100 g of an ionic group-containing polymer obtained in the same manner as the preparation of the ionic group-containing polymer solution A for complexing and 400 g of γ-butyrolactone in a nitrogen atmosphere at 80 ° C. for 5 hours. The solution was cooled to room temperature and suction filtered through a glass filter (25G1) to obtain a ionic group-containing polymer solution for conjugation.

<Preparation of ionic group-containing polymer solution F for conjugation>
Except for using S-DCDPS 80.00 g, DCBN 37.13 g, BP 70.52 g, potassium carbonate 57.58 g, and NMP 510 mL, the same as for the preparation of the ionic group-containing polymer solution A for conjugation An ionic group-containing polymer solution E was prepared.

<Example 1>
Polyamideimide resin solution (Toyobo Co., Ltd., trade name: Viromax, product number: HR11NN, organic solvent: N-methyl-2-pyrrolidone) 100 parts by mass of a solution obtained by blending 18 parts by mass of polyethylene glycol # 400 at room temperature Cast on a 188 μm polyester film in an atmosphere, soak in water / N-methyl-2-pyrrolidone in a 70/30 coagulation bath (room temperature) for 3 minutes, wash with water, fix with a metal frame, and The porous membrane was produced by drying for a minute. Further, this porous membrane was vacuum impregnated with the ionic group-containing polymer solution A for 12 minutes and then treated at 80 ° C. for 30 minutes, 110 ° C. for 30 minutes, and 130 ° C. for 30 minutes. Thereafter, the obtained film-like film was peeled off, immersed in pure water at room temperature overnight, and then immersed in 2 mol sulfuric acid at room temperature twice for 1 hour in order to replace the metal salt of the ionic group with proton. Washed with water until no free sulfuric acid was detected. Thereafter, the obtained membrane is sandwiched between filter papers, both sides are further sandwiched between glass plates, and dried while standing for 2 days in a room at 20 ° C. and a relative humidity of 30% RH while applying a load to obtain a composite polymer electrolyte membrane. It was. The obtained composite polymer electrolyte membrane had a thickness of 51 μm and an ionic group-containing polymer filling rate of 72%.

<Example 2>
A composite polymer electrolyte membrane was produced in the same manner as in Example 1 except that the ionic group-containing polymer solution B was used instead of the ionic group-containing polymer solution A. The resulting composite polymer electrolyte membrane had a thickness of 52 μm and an ionic group-containing polymer filling rate of 71%.

<Example 3>
A composite polymer electrolyte membrane was produced in the same manner as in Example 1 except that the ionic group-containing polymer solution C was used instead of the ionic group-containing polymer solution A. The obtained composite polymer electrolyte membrane had a thickness of 49 μm and an ionic group-containing polymer filling rate of 73%.

<Example 4>
A composite polymer electrolyte membrane was produced in the same manner as in Example 1 except that the ionic group-containing polymer solution D was used instead of the ionic group-containing polymer solution A. The obtained composite polymer electrolyte membrane had a thickness of 50 μm and an ionic group-containing polymer filling rate of 72%.

<Example 5>
A composite polymer electrolyte membrane was produced in the same manner as in Example 1 except that the ionic group-containing polymer solution D was used instead of the ionic group-containing polymer solution A. The obtained composite polymer electrolyte membrane had a thickness of 52 μm and an ionic group-containing polymer filling rate of 73%.

<Comparative Example 1>
Polybenzoxazole fiber (manufactured by Toyobo Co., Ltd., trade name: Zylon, product number: AS) was dissolved in methanesulfonic acid to prepare a 1.5% by mass polymer solution. The resulting polybenzoxazole resin solution was cast on a glass plate heated to 70 ° C., placed in a constant temperature and humidity chamber at 25 ° C. and 80% relative humidity, solidified for 1 hour, washed with water, and porous film Was made. A composite polymer electrolyte membrane was produced in the same manner as in Example 1 except that the obtained porous membrane was used. The obtained composite polymer electrolyte membrane had a thickness of 51 μm and an ionic group-containing polymer filling rate of 71%.

<Comparative example 2>
A composite polymer electrolyte membrane was produced in the same manner as in Example 1 except that the ionic group-containing polymer solution E was used instead of the ionic group-containing polymer solution A. The resulting composite polymer electrolyte membrane had a thickness of 50 μm and an ionic group-containing polymer filling rate of 71%.

<Comparative Examples 3-6>
Each of the ionic group-containing polymer solutions A to D was cast to a thickness of 500 μm on a 188 μm polyester film under an atmosphere at room temperature, and treated at 80 ° C. for 30 minutes, 100 ° C. for 30 minutes, and 130 ° C. for 30 minutes. Thereafter, the obtained film-like film was peeled off and immersed in pure water at room temperature overnight, and then immersed in 2 molar sulfuric acid at room temperature twice for 1 hour in order to replace the metal salt of the ionic group with protons. Wash with water until no free sulfuric acid was detected. After that, the obtained film is sandwiched between filter papers, both sides are sandwiched between glass plates, and dried with leaving a load in a room at 20 ° C. and a relative humidity of 30% RH for 2 days. A polymer electrolyte membrane was obtained.
The evaluation result of the polymer electrolyte membrane obtained by the Example and the comparative example is shown to Tables 1-5.

  From Tables 1 to 5, the composite polymer electrolyte membrane of the present invention shows almost no change in hydrogen gas permeability and methanol permeability over time in the swelling / shrinkage repetition test of the polymer electrolyte membrane, In the surface observation of the polymer electrolyte membrane, no cracks, tears, pinholes, etc. were observed. Further, no peeling between the polymer electrolyte membrane and the electrode catalyst layer was observed even after power generation for a predetermined time using the fuel cell. Therefore, it can be seen that the composite polymer electrolyte membrane of the present invention is significantly improved in durability as compared with the comparative example.

  The composite polymer electrolyte membrane of the present invention does not cause separation between the polymer electrolyte membrane and the electrode catalyst layer even when power is used for a long time in a fuel cell. An excellent fuel cell can be provided. The composite polymer electrolyte membrane of the present invention can be expected to greatly improve the practicality of a fuel cell using hydrogen or a methanol aqueous solution as a fuel, which greatly contributes to the development of industry.

Claims (21)

  This is a composite polymer electrolyte membrane in which an ionic group-containing polymer is combined with a porous membrane made of an ionic group-free polymer. The ionic group-containing polymer and the ionic group-free polymer are soluble in the same organic solvent. And the softening temperature of the ionic group-containing polymer is 140 to 250 ° C.   The composite polymer electrolyte membrane according to claim 1, wherein the ionic group is at least one group selected from the group consisting of a sulfonic acid group, a phosphonic acid group, and a phosphoric acid group. A composite polymer electrolyte membrane in which the ionic group-containing polymer has a structural unit represented by the following chemical formula 1.

[In Chemical Formula 1, X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, Z ¹ represents either an O or S atom, Z ² represents an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, or a cyclohexyl group, and n 1 represents an integer of 1 or more. To express. ] The composite polymer electrolyte membrane according to claim 3, wherein the ionic group-containing polymer further has a structural unit represented by Chemical Formula 2.

[In Chemical Formula 2, Ar ¹ is a divalent aromatic group, Z ³ is either an O or S atom, Z ⁴ is an O atom, an S atom, a —C (CH ₃ ) ₂ — group, —C Any one of (CF ₃ ) ₂ —, —CH ₂ — and cyclohexyl groups, n2 represents an integer of 1 or more. ] The composite polymer electrolyte membrane according to claim 4, wherein Ar ¹ in Chemical Formula 2 is one or more groups selected from structures represented by Chemical Formulas 3 to 6 below.

The composite polymer electrolyte membrane according to claim 5, wherein Ar ¹ in Chemical Formula 2 has a structure represented by Chemical Formula 6. The composite polymer electrolyte membrane according to claim 3, wherein Z ¹ and Z ² in Chemical Formula 1 are both O atoms, and n1 is 3 or more. 5. The composite polymer electrolyte membrane according to claim 4, wherein Z ³ and Z ⁴ in Chemical Formula 2 are both O atoms, and n2 is 3 or more. The composite polymer electrolyte membrane according to claim 3, wherein the ionic group-containing polymer further has a structure represented by the following chemical formula 7.

[In Chemical Formula 7, X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ⁵ represents either an O or S atom. . ]   The composite polymer electrolyte membrane according to claim 9, wherein the ionic group-containing polymer further has a structure represented by Chemical Formula 2. The composite polymer electrolyte membrane according to claim 10, wherein the ionic group-containing polymer further has a structure represented by the following chemical formula 8.

[In Chemical Formula 8, Ar ² represents a divalent aromatic group, and Z ⁶ represents either O or S atom. ] The composite polymer electrolyte membrane according to claim 11, wherein Ar ² in Chemical Formula 8 is one or more groups selected from structures represented by Chemical Formulas 3 to 6. The composite polymer electrolyte membrane according to claim 12, wherein Ar ² in Chemical Formula 8 has a structure represented by Chemical Formula 6. The composite polymer electrolyte membrane according to claim 9, wherein Z ¹ and Z ² in Chemical Formula 1 are O and / or S atoms, and n1 is 1. The composite polymer electrolyte membrane according to claim 10, wherein Z ³ and Z ⁴ in Chemical Formula 2 are O and / or S atoms, and n2 is 1.   The composite polymer electrolyte membrane according to claim 1, wherein the ion exchange capacity is in the range of 0.5 to 5.0 meq / g.   The composite polymer electrolyte membrane according to claim 1, wherein the organic solvent is an organic polar solvent.   The composite polymer electrolyte membrane according to claim 1, wherein the ionic group-free polymer is polyamideimide.   A polymer electrolyte membrane / electrode assembly comprising the composite polymer electrolyte membrane according to claim 1.   A fuel cell using the polymer electrolyte membrane / electrode assembly according to claim 19.   The fuel cell according to claim 20, wherein methanol is used as a fuel.