JP2003327826A - Composition containing acidic group-containing polybenzimidazole-based compound and acidic group- containing polymer, ion-conductive film, adhesive, composite material and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition useful as a polymer electrolyte film capable of maintaining its ion-conductive characteristics at a high temperature for a long period by incorporating only a small amount of an acidic compound to a polybenzimidazole-based polymer excellent in heat resistance. <P>SOLUTION: This ion-conductive film having a high stability at a high temperature and maintaining a good ion-conductivity for a long period is obtained by a composition characterized by containing the polybenzimidazole-based compound having sulfonic acid group and/or phosphonic acid on a specific heterocyclic ring together with an inorganic acid and/or organic acid. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition useful as a polymer electrolyte membrane comprising an acidic group-containing polybenzimidazole compound and an acid compound as constituent components.

[0002]

2. Description of the Related Art As an example of an electrochemical device using a solid polymer electrolyte as an ionic conductor instead of a liquid electrolyte, a water electrolysis cell or a fuel cell can be used. The polymer membranes used for these must be sufficiently stable chemically, thermally, electrochemically and mechanically as a cation exchange membrane together with proton conductivity. Therefore, as a material that can be used for a long period of time, a perfluorocarbon sulfonic acid membrane typified by "Nafion (registered trademark)" manufactured by DuPont, USA has been mainly used. However, if you try to operate at a temperature above 100 ° C,
The water content of the membrane drops sharply, and the membrane softens significantly, so that the fuel cell cannot exhibit sufficient performance.
It is also pointed out that the cost of the membrane is too high as an obstacle to the establishment of fuel cell technology.

In order to overcome such drawbacks, various studies have been made on polymer electrolyte membranes in which a sulfonic acid group is introduced into an aromatic ring-containing polymer. For example, sulfonated polyaryl ether sulfone (Journal of Membrane
Science, 83 , 211 (1993)), sulfonated polyetheretherketone (JP-A-6-93114), sulfonated polystyrene and the like. However, a sulfonic acid group introduced on an aromatic ring from a polymer as a raw material is apt to undergo a desulfonic acid reaction due to an acid or heat, and cannot be said to have sufficient durability for use as an electrolyte membrane for a fuel cell.

As a polymer having high heat resistance and high durability, aromatic polyazole-based polymers such as polybenzimidazole are known, and it is conceivable to introduce a sulfonic acid group into these polymers and utilize them for the above purpose. . As such a polymer structure, polybenzimidazole containing sulfonic acid is described in Uno et al., J. Polym. Sc.
i., Polym. Chem., 15 , 1309 (1977) 3,3'-
What is synthesized from diaminobenzidine and 3,5-dicarboxybenzenesulfonic acid or 2,5-dicarboxybenzenesulfonic acid is 1,2,4,5-benzenetetramine and 2,5-dicarboxybenzene in USP-531295. It has been reported to synthesize sulfonic acid as a main component. However, in these reports, although attention has been paid to the solubility and heat resistance of the sulfonic acid-containing polybenzimidazole, the electrochemical characteristics of the sulfonic acid group, such as those used for electrolyte membranes, have not been considered. In particular, these materials are inferior in terms of satisfying both heat resistance, solvent resistance, mechanical properties and ionic conduction properties, and are unsuitable for use in polymer electrolyte membranes and the like.

Further, few aromatic polymers having phosphonic acid groups, which are considered to have better heat resistance than sulfonic acid groups, have been noticed from the viewpoint of application as a solid polymer electrolyte. As a slight example, 4,4 '-(2,2,2-trifluoro-1-
In polybenzoxazole composed of (trifluoromethyl) ethylidene) bis (2-aminophenol), a polymer in which 5 to 50% of the dicarboxylic acid component is 3,5-dicarboxyphenylphosphonic acid has been reported (USP 5, 498,784), focusing on good solubility and possibility as a composite material, it was not considered as a solid polymer electrolyte for fuel cell applications. In fact, it is clear that this polymer is characterized by its alcohol solubility, making it unsuitable for use as a solid polymer electrolyte for fuel cells fueled with methanol. Further, since it also shows a low ionic conductivity, it can be said that it is not suitable for a solid polymer electrolyte for a fuel cell.

On the other hand, it has been reported that the excellent thermal stability of polybenzimidazole is further increased by impregnating it with phosphoric acid (EJ Powers et al., High Performance Polymers:
Their Origin and Development, Elsevier, New York
(1986), P.355), and an electrolyte membrane for a fuel cell at high temperature, which has an ionic conduction function extracted by phosphoric acid (Japanese Patent Publication No. 11-503262, JS Wainright et al., J.
Electrochem. Soc., 142, L121 (1995)). However, since polybenzimidazole itself does not have ionic conductivity properties, it requires a large amount of phosphoric acid to be impregnated, and the phosphoric acid, which is a low-molecular compound, gradually flows out and the ionic conductivity decreases with time. There was a problem. On the other hand, a polymer electrolyte membrane in which a polymer obtained by introducing a sulfonic acid group into polybenzimidazole contains an inorganic acid or an organic acid has been reported (JP 2001-81294A).
Since the sulfonic acid group is introduced on the aromatic ring in the benzimidazole ring or in the form of being bonded to the nitrogen element as a side chain portion, sufficient heat resistance cannot be maintained.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polybenzimidazole-based polymer having excellent heat resistance with a high level of ion conductivity even at a high temperature even if it contains a small amount of an acid compound. It is to obtain a composition useful as a molecular electrolyte membrane.

[0008]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors, an inorganic acid and / or an organic acid together with a polybenzimidazole compound having a sulfonic acid group and / or a phosphonic acid group on a specific aromatic ring have been obtained. It has been found that a composition characterized in that it contains an acid achieves the above object.

That is, the present invention is achieved by the following (1) to (9).

(1) A composition containing a polybenzimidazole compound containing a constituent represented by the following formula (1) and an inorganic acid and / or an organic acid.

[0011]

[Chemical 4] (In the formula (1), m ¹ represents an integer of 1 to 4,
R ¹ represents a tetravalent aromatic bond unit capable of forming an imidazole ring, R ² represents a divalent aromatic bond unit, R ¹
Each of R ² and R ² may be a single aromatic ring, a combination of a plurality of aromatic rings, or a condensed ring, and may have a stable substituent. Z is a sulfonic acid group and /
Alternatively, it may represent a phosphonic acid group, and a part thereof may have a salt structure. )

(2) The polybenzimidazole-based compound has a bonding unit represented by the structures represented by the following formulas (2) and (3) as a constituent component at a molar ratio of n ¹ : (1-n ¹ ). The composition according to the first invention, characterized in that it comprises:

[0013]

[Chemical 5] (In the formulas (2) and (3), m ¹ is from 1 to 4
Of Ar, Ar represents a divalent aromatic bond unit, X ¹ represents —O—, —SO ₂ —, —C (CH ₃ ) ₂ —, —C.
_{(CF 3) 2 -, -} OPhO- from at least one selected from the group, Ph denote the divalent aromatic bond unit. Further, the molar ratio satisfies the formula of 0.2 ≦ n ¹ ≦ 1.0)

(3) The polybenzimidazole-based compound has a binding unit represented by the structures represented by the following formulas (4) and (5) as a constituent component at a molar ratio of n ² : (1-n ² ). The composition according to the first invention, characterized in that it comprises:

[0015]

[Chemical 6] (In the formulas (4) and (5), m ¹ is from 1 to 4
Represents an integer, Ar represents an aromatic bond unit, X ²
Is _{-O -, - SO 2 -,} - S -, - CH 2 -, - OPhO
-Is one or more selected from the group, and Ph represents a divalent aromatic bond unit. Also, the molar ratio is
0.2 ≦ n ² ≦ 1.0 is satisfied)

(4) The composition according to any one of the first to third inventions, wherein the inorganic acid and / or the organic acid is selected from phosphoric acid, sulfuric acid, organic sulfonic acid and organic phosphonic acid compounds. object.

(5) The ratio of the inorganic acid and / or the organic acid used is 0.1 with respect to 1 mol of nitrogen atoms in the polymer.
The composition according to any one of the first to fourth inventions, wherein the composition is 5 mol.

(6) An ion-conducting membrane containing the composition according to any one of the first to fifth inventions.

(7) A composite comprising the ion conductive membrane according to the sixth invention and an electrode.

(8) A fuel cell containing the composite material according to the seventh invention.

(9) An adhesive containing the composition according to any one of the first to fifth inventions.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The composition containing an inorganic acid and / or an organic acid together with the polybenzimidazole compound having a sulfonic acid group or a phosphonic acid group according to the present invention is not only durable but also processable and ionic conductive. It is a new material that exhibits excellent properties. Due to such excellent properties, the composition of the present invention can be suitably used as a material for a solid polymer electrolyte membrane for fuel cells.

The acidic group-containing polybenzimidazole compound in the present invention is characterized by containing a structure represented by the following formula (1).

[0025]

[Chemical 7] (In the formula (1), m ¹ represents an integer of 1 to 4, R ¹ represents a tetravalent aromatic bond unit capable of forming an imidazole ring, R ² represents a divalent aromatic unit, R 1 ¹
Each of R ² and R ² may be a single aromatic ring, a combination of a plurality of aromatic rings, or a condensed ring, and may have a stable substituent. Z is a sulfonic acid group and /
Alternatively, it may represent a phosphonic acid group, and a part thereof may have a salt structure. )

The route for synthesizing the acidic group-containing polybenzimidazole compound of the present invention containing the structure represented by the above formula (1) is not particularly limited, but it is usually an aromatic tetramine capable of forming an imidazole ring in the compound. One or more compounds selected from the group consisting of classes and derivatives thereof,
It can be synthesized by a reaction with one or more compounds selected from the group consisting of aromatic dicarboxylic acids and their derivatives. At that time, it is possible to introduce a sulfonic acid group or a phosphonic acid group into the obtained polyazole by using a dicarboxylic acid containing a sulfonic acid group or a phosphonic acid group or a salt thereof in the dicarboxylic acid used. it can.
The dicarboxylic acid containing a sulfonic acid group or a phosphonic acid group can be used in combination of one or more kinds, but it is also possible to use the dicarboxylic acid containing a sulfonic acid group and the dicarboxylic acid containing a phosphonic acid group at the same time.

Here, a benzimidazole bond unit which is a constituent of the polybenzimidazole compound of the present invention, an aromatic dicarboxylic acid bond unit having a sulfonic acid group and / or a phosphonic acid group, and a sulfonic acid group having a phosphon group. The aromatic dicarboxylic acid bond unit having no acid group and other bond units are preferably bonded by random polymerization and / or alternating polymerization. Further, these polymerization forms are not limited to one kind, and two or more kinds of polymerization forms may coexist in the same compound.

Among the sulfonic acid group-containing polybenzimidazole compounds containing the constituents represented by the above formula (1), the binding unit represented by the structure represented by the following formulas (2) and (3) is n. Those which are included as a constituent in a molar ratio of ¹ : (1-n ¹ ) are particularly preferable.

[0029]

[Chemical 8] (In the formulas (2) and (3), m ¹ is from 1 to 4
Of Ar, Ar represents a divalent aromatic bond unit, X ¹ represents —O—, —SO ₂ —, —C (CH ₃ ) ₂ —, —C.
_{(CF 3) 2 -, -} OPhO- from at least one selected from the group, Ph denote the divalent aromatic bond unit. Further, the molar ratio satisfies the formula of 0.2 ≦ n ¹ ≦ 1.0)

In the above formulas (2) and (3), when m ¹ is larger than 5, the water resistance of the obtained polymer tends to be poor, and when the molar ratio n ¹ is smaller than 0.2, it is sufficient. It tends to not exhibit excellent ionic conductivity.

Specific examples of the aromatic tetramine which gives the sulfonic acid group-containing polybenzimidazole compound containing the component represented by the above formula (1) are not particularly limited, but for example, 1,2 , 4,5-Tetraaminobenzene, 3,3′-diaminobenzidine, 3,
3 ', 4,4'-tetraaminodiphenyl ether,
3,3 ', 4,4'-tetraaminodiphenyl thioether, 3,3', 4,4'-tetraaminodiphenyl sulfone, 2,2-bis (3,4-diaminophenyl) propane, bis (3,4) -Diaminophenyl) methane,
2,2-bis (3,4-diaminophenyl) hexafluoropropane, 1,4-bis (3,4-diaminophenoxy) benzene, and the like, and derivatives thereof. Among these, 3,3 ′, 4,4′-tetraaminodiphenyl ether, 3,3 ′, 4,4′-tetraaminodiphenyl sulfone, which can form a binding unit represented by the formula (2), 2,2-bis (3,4-diaminophenyl) propane, 2,2-bis (3,4-diaminophenyl) hexafluoropropane, 1,4-bis (3,4-diaminophenoxy) benzene and derivatives thereof Is particularly preferable.

Specific examples of the derivatives of these aromatic tetramines include salts with acids such as hydrochloric acid, sulfuric acid and phosphoric acid. Further, these compounds may be used alone or in combination of two or more at the same time.
In addition, these compounds may optionally contain tin chloride (I
A known antioxidant such as I) or a phosphorous acid compound may be contained.

The sulfonic acid group-containing dicarboxylic acid giving the structure of the above formula (1) can be selected from those containing 1 to 4 sulfonic acid groups in the aromatic dicarboxylic acid. Examples include, for example, 2,5-dicarboxybenzenesulfonic acid, 3,5-dicarboxybenzenesulfonic acid, 2,5-dicarboxy-1,4-benzenedisulfonic acid, 4,6-dicarboxy-1, 3-benzenedisulfonic acid, 2,2'-disulfo-4,4'-
Biphenyldicarboxylic acid, 3,3′-disulfo-4,
Examples thereof include sulfonic acid-containing dicarboxylic acids such as 4′-biphenyldicarboxylic acid and derivatives thereof.
Examples of the derivative include alkali metal salts such as sodium and potassium, ammonium salts, alkylammonium salts and the like. The structure of the sulfonic acid group-containing dicarboxylic acid is not particularly limited to these. M ¹ in Formula (1) described above is selected from integers of 1 to 4. When m ¹ is 5 or more, the water resistance of the polymer tends to decrease, which is not preferable.

The sulfonic acid group-containing dicarboxylic acids can be introduced not only by themselves but also in the form of copolymerization with dicarboxylic acids containing no sulfonic acid group and phosphonic acid group. Examples of dicarboxylic acids that can be used with the sulfonic acid group-containing dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, biphenyl dicarboxylic acid, terphenyl dicarboxylic acid, 2,
A general dicarboxylic acid reported as a polyester raw material such as 2-bis (4-carboxyphenyl) hexafluoropropane can be used, and is not limited to those exemplified here.

The purity of the dicarboxylic acid containing a sulfonic acid group is not particularly limited, but is preferably 98% or more, more preferably 99% or more. Polyimidazole polymerized from a dicarboxylic acid containing a sulfonic acid group as a raw material, as compared with the case of using a dicarboxylic acid not containing a sulfonic acid group, the degree of polymerization tends to be lower, it contains a sulfonic acid group The dicarboxylic acid to be used is preferably as pure as possible. When a dicarboxylic acid containing no sulfonic acid group is used together with the sulfonic acid group-containing dicarboxylic acid, the effect of the sulfonic acid can be clarified by setting the sulfonic acid group-containing dicarboxylic acid to 20 mol% or more of all dicarboxylic acids. it can. In order to bring out the remarkable effect of the sulfonic acid, it is more preferably 50 mol% or more. When the content of the aromatic dicarboxylic acid having a sulfonic acid group is less than 20 mol%, the conductivity of the polybenzimidazole compound of the present invention tends to be low and the polybenzimidazole compound of the present invention tends to be unsuitable as a material for a solid polymer electrolyte. There is.

As the phosphonic acid group-containing polybenzimidazole compound containing the constituents represented by the above formula (1), a binding unit represented by the structures represented by the following formulas (4) and (5) is used. Those containing as a constituent in a molar ratio of n ² : (1-n ² ) are particularly preferable.

[0037]

[Chemical 9] (In the formulas (4) and (5), m ¹ is from 1 to 4
Represents an integer, Ar represents an aromatic bond unit, X ²
Is _{-O -, - SO 2 -,} - S -, - CH 2 -, - OPhO
-Is one or more selected from the group, and Ph represents a divalent aromatic bond unit. Also, the molar ratio is
0.2 ≦ n ² ≦ 1.0 is satisfied)

In the above formulas (4) and (5), when m ² is larger than 5, the water resistance of the obtained polymer tends to be poor, and when the molar ratio n ² is smaller than 0.2, it is sufficient. It tends to not exhibit excellent ionic conductivity.

Specific examples of the aromatic tetramine which gives the phosphonic acid group-containing polyimidazole represented by the above formula (1) are not particularly limited, but for example,
1,2,4,5-tetraaminobenzene, 3,3'-diaminobenzidine, 3,3 ', 4,4'-tetraaminodiphenyl ether, 3,3', 4,4'-tetraaminodiphenylthioether, 3 , 3 ', 4,4'-Tetraaminodiphenyl sulfone, 2,2-bis (3,4-
Diaminophenyl) propane, bis (3,4-diaminophenyl) methane, 2,2-bis (3,4-diaminophenyl) hexafluoropropane, 1,4-bis (3,3
4-diaminophenoxy) benzene and the like and derivatives thereof. Of these, the above equation (4)
Can form a binding unit represented by
3 ', 4,4'-tetraaminodiphenyl ether,
3,3 ', 4,4'-tetraaminodiphenyl sulfone, 3,3', 4,4'-tetraaminodiphenyl thioether, bis (3,4-diaminophenyl) methane,
1,4-bis (3,4-diaminophenoxy) benzene and derivatives thereof are especially preferred.

Specific examples of the derivatives of these aromatic tetramines include salts with acids such as hydrochloric acid, sulfuric acid and phosphoric acid. Further, these compounds may be used alone or in combination of two or more at the same time.
In addition, these compounds may optionally contain tin chloride (I
A known antioxidant such as I) or a phosphorous acid compound may be contained.

The aromatic dicarboxylic acid having a phosphonic acid group and its derivative used for synthesizing the polybenzimidazole compound having a phosphonic acid group represented by the above formula (1) are not particularly limited. A compound having 1 to 4 phosphonic acid groups in the aromatic dicarboxylic acid skeleton can be preferably used. As a specific example, 2,5-dicarboxyphenylphosphonic acid,
Mention may be made of aromatic dicarboxylic acids having phosphonic acid groups such as 3,5-dicarboxyphenylphosphonic acid and 2,5-bisphosphonoterephthalic acid, and derivatives thereof. Having 5 or more phosphonic acid groups in the aromatic dicarboxylic acid skeleton is not preferable because it tends to reduce the water resistance of the polymer.

Here, examples of the phosphonic acid derivative of the aromatic dicarboxylic acid having these phosphonic acid groups include alkali metal salts such as sodium and potassium, ammonium salts, and alkylammonium salts. Further, these compounds may be used alone,
It is possible to use more than one at the same time. Furthermore, these compounds may optionally contain known antioxidants such as tin (II) chloride and phosphorous acid compounds.

The structure of the aromatic dicarboxylic acid having a phosphonic acid group is not limited thereto, but the aromatic dicarboxylic acid having a phenylphosphonic acid group-type phosphonic acid group as shown here is preferable. .

The purity of the aromatic dicarboxylic acid having a phosphonic acid group used in the synthesis of the polybenzimidazole compound of the present invention is not particularly limited, but is preferably 97% or more, more preferably 98% or more. The polybenzimidazole-based compound polymerized from an aromatic dicarboxylic acid having a phosphonic acid group as a raw material has a polymerization degree higher than that when an aromatic dicarboxylic acid having no sulfonic acid group and a phosphonic acid group is used as a raw material. Since it tends to be low, it is preferable to use the aromatic dicarboxylic acid having a phosphonic acid group as high in purity as possible. That is, when the purity of the aromatic dicarboxylic acid is less than 97%, the degree of polymerization of the obtained polybenzimidazole compound tends to be low, and the polybenzimidazole compound tends to be unsuitable as a material for a solid polymer electrolyte.

Although the above-mentioned aromatic dicarboxylic acids having a phosphonic acid group may be used alone, they can be used in the present invention by copolymerization reaction with an aromatic dicarboxylic acid having no sulfonic acid group and phosphonic acid group. It may be used for the synthesis of a polybenzimidazole compound having a phosphonic acid group. The sulfonic acid group and aromatic dicarboxylic acid having no phosphonic acid group that can be used together with the aromatic dicarboxylic acid having a phosphonic acid group are not particularly limited, and examples thereof include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. , Diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, biphenyl dicarboxylic acid, terphenyl dicarboxylic acid, 2,
A general aromatic dicarboxylic acid reported as a polyester raw material such as 2-bis (4-carboxyphenyl) hexafluoropropane can be used.

Further, these compounds may be used alone, or a plurality of them may be used at the same time. Furthermore, these compounds may optionally contain known antioxidants such as tin (II) chloride and phosphorous acid compounds.

In the synthesis of the polybenzimidazole compound of the present invention, when an aromatic dicarboxylic acid having a phosphonic acid group and an aromatic dicarboxylic acid having no phosphonic acid group are used, a wholly aromatic dicarboxylic acid is used. By blending so that the content of the aromatic dicarboxylic acid having a phosphonic acid group therein is 20 mol% or more, the excellent effect of the polybenzimidazole compound of the present invention having a phosphonic acid group is clarified. can do. Further, in order to bring out the remarkable effect of the polybenzimidazole compound of the present invention having a phosphonic acid group, the content of the aromatic dicarboxylic acid having a phosphonic acid group is blended so as to be 50 mol% or more. Is more preferable. When the content of the aromatic dicarboxylic acid having a phosphonic acid group is less than 20 mol%,
The electrical conductivity of the polybenzimidazole compound of the present invention tends to be low, making it unsuitable as a material for a solid polymer electrolyte.

Here, the above-mentioned aromatic dicarboxylic acid having a sulfonic acid group and aromatic dicarboxylic acid having a phosphonic acid group may be used alone, but they are not It may be used for the synthesis of the polybenzimidazole compound having a sulfonic acid group and / or a phosphonic acid group of the invention.

At this time, the above-mentioned aromatic dicarboxylic acid having a sulfonic acid group and aromatic dicarboxylic acid having a phosphonic acid group may be used alone, but a sulfonic acid group and a phosphonic acid group may be used. The polybenzimidazole compound having a sulfonic acid group and / or a phosphonic acid group of the present invention may be synthesized by a copolymerization reaction with an aromatic dicarboxylic acid that does not contain it.

A sulfonic acid group is prepared by using one or more compounds selected from the group consisting of the aromatic tetramines and their derivatives and one or more compounds selected from the group consisting of aromatic dicarboxylic acids and their derivatives. The method for synthesizing the polybenzimidazole compound having a phosphonic acid group and / or a phosphonic acid group is not particularly limited, but for example, JFWolfe, Encyclopedia of Polymer
Science and Engineering, 2nd Ed., Vol.11, P.601 (1
988) dehydration using a polyphosphoric acid as a solvent,
It can be synthesized by cyclopolymerization. It is also possible to apply polymerization by a similar mechanism using a methanesulfonic acid / phosphorus pentoxide mixed solvent system instead of polyphosphoric acid. In addition, in order to synthesize a polybenzimidazole compound having high thermal stability, polymerization using polyphosphoric acid, which is commonly used, is preferable.

Further, in order to obtain the polybenzimidazole compound of the present invention, for example, a precursor polymer having a polyamide structure or the like is synthesized by a reaction in an appropriate organic solvent or in the form of a mixed raw material monomer melt. Alternatively, a method of converting into a desired polybenzimidazole structure by a subsequent cyclization reaction such as appropriate heat treatment can also be used.

The reaction time for synthesizing the polybenzimidazole compound of the present invention cannot be unconditionally defined because there is an optimum reaction time depending on the combination of individual raw material monomers. In a reaction containing a raw material monomer such as an aromatic dicarboxylic acid having a sulfonic acid group and / or a phosphonic acid group in a reaction that takes a long time, the thermal stability of the obtained polybenzimidazole compound decreases. Therefore, in this case, it is preferable to shorten the reaction time within the range in which the effect of the present invention can be obtained. By shortening the reaction time in this way,
A polybenzimidazole compound having a sulfonic acid group and / or a phosphonic acid group can also be obtained in a highly heat stable state.

The reaction temperature at the time of synthesizing the polybenzimidazole compound of the present invention cannot be unconditionally specified because there is an optimum reaction temperature depending on the combination of individual raw material monomers, but it has been reported so far. In the reaction at high temperature, in a system containing a raw material monomer such as an aromatic dicarboxylic acid having a sulfonic acid group and / or a phosphonic acid group, introduction of the sulfonic acid group and / or phosphonic acid group into the obtained polybenzimidazole compound In some cases, it becomes impossible to control the amount. In this case, it is preferable to lower the reaction temperature within the range where the effect of the present invention can be obtained.
By lowering the reaction temperature in this way, it is possible to control the introduction amount of the sulfonic acid group and / or the phosphonic acid group even in the synthesis of the polybenzimidazole compound having a large amount of acidic groups.

Further, when the raw material monomers which constitute the repeating unit after the synthesis of the polybenzimidazole compound of the present invention are composed of a plurality of kinds, the repeating units are randomly polymerized and / or alternated. By being bonded by polymerization, it has a characteristic of exhibiting stable performance as a material for the polymer electrolyte membrane. Here, in order to synthesize the polybenzimidazole-based compound of the present invention by a polymerization mode of random polymerization and / or alternating polymerization, all monomer raw materials are charged from the initial stage of polymerization at a mixing ratio in which equivalence is adjusted. It is preferable to make.

The polybenzimidazole-based compound can be synthesized by block polymerization instead of random polymerization or alternating polymerization. In that case, it is possible to prepare a polybenzimidazole-based compound by changing the equivalence to the monomer raw materials in the mixing ratio. It is preferable to synthesize an oligomer of the component, further add a monomer raw material, adjust the compounding ratio including the second component so that the equivalence is satisfied, and then perform the polymerization.

The molecular weight of the polybenzimidazole compound having a sulfonic acid group and / or a phosphonic acid group of the present invention is not particularly limited, but it is preferably 1,000 or more, more preferably 3,000 or more. It is more preferable if there is. The molecular weight is preferably 1,000,000 or less, more preferably 200,000 or less. If this molecular weight is less than 1,000,
The decrease in viscosity makes it difficult to obtain a molded product having good properties from the polybenzimidazole compound. If the molecular weight exceeds 1,000,000, it becomes difficult to mold the polybenzimidazole compound due to the increase in viscosity. The molecular weight of the polybenzimidazole compound having a sulfonic acid group and / or a phosphonic acid group of the present invention can be evaluated substantially by the logarithmic viscosity when measured in concentrated sulfuric acid. And, this logarithmic viscosity is preferably 0.25 or more, and particularly, 0.
It is more preferably 40 or more. The logarithmic viscosity is preferably 10 or less, more preferably 8 or less. If this logarithmic viscosity is less than 0.25,
The decrease in viscosity makes it difficult to obtain a molded product having good properties from the polybenzimidazole compound. Further, when the molecular weight exceeds 10, it becomes difficult to mold the polybenzimidazole compound due to the increase in viscosity.

As the inorganic acid used together with the polybenzimidazole compound in the present invention, phosphoric acid, polyphosphoric acid, sulfuric acid, nitric acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid and derivatives thereof are used. As the organic acid used together with the polybenzimidazole compound in the present invention, organic sulfonic acid and organic phosphonic acid are used. Specific examples of the organic sulfonic acid include methanesulfonic acid, ethanesulfonic acid, hexanesulfonic acid, octylsulfonic acid, dodecylsulfonic acid, cetylsulfonic acid, sulfosuccinic acid, sulfoglutaric acid, sulfoadipic acid, sulfopimelic acid, sulfosuberine. Perfluoroalkyl sulfonic acid such as acid, sulfoazelaic acid, alkyl sulfonic acid including sulfo sebacic acid, trifluoromethane sulfonic acid, pentafluoroethane sulfonic acid, heptafluoropropyl sulfonic acid, benzene sulfonic acid, 1,3- Benzenedisulfonic acid, toluenesulfonic acid, octylbenzenesulfonic acid, 2-methyl-5-isopropylbenzenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, naphthalenesulfonic acid, Aromatic sulfonic acids such as benzenebenzenesulfonic acid, phenolsulfonic acid, trichlorobenzenesulfonic acid, nitrotoluenesulfonic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, and derivatives thereof can be mentioned, but are not limited thereto. Instead, organic sulfonic acids having various structures can be used. Specific examples of the organic phosphonic acid include aromatic phosphonic acids such as phenylphosphonic acid and 1,3-dicarboxyphenylphosphonic acid, 1-hydroxyethane-1,1.
Examples thereof include aliphatic phosphonic acids such as diphosphonic acid, and derivatives thereof, but are not limited thereto, and organic phosphonic acids having various structures can be used.

The inorganic acid and / or organic acid of the present invention is
It is used as a mixture with the polybenzimidazole compound of the present invention, and the ratio is such that the inorganic acid and / or the organic acid is 0.1 to 5 mol with respect to 1 mol of the nitrogen atom in the polybenzimidazole compound. In the case of, the property of maintaining particularly excellent ionic conduction property over a long period of time is exhibited. When the usage ratio is less than 0.1 mol, the tendency that the ionic conductivity does not show a sufficiently high value begins to appear, and when the usage ratio is more than 5 mol, the ionic conductivity decreases with long-term use. The tendency to increase is starting to appear.

In order to obtain a composition containing the polybenzimidazole compound of the present invention and an inorganic acid and / or an organic acid, when various molded articles are prepared from the polybenzimidazole compound of the present invention, There is a method of mixing an inorganic acid and / or an organic acid. For example, the sulfonic acid group- and / or phosphonic acid group-containing polyazole compound of the present invention can be extruded from a polymerization solution, an isolated polymer, a re-dissolved polymer solution, or the like, and can be spun, rolled, cast, or subjected to fiber formation by any method. It can be formed into a film. At this time, the composition of the present invention can be obtained as a molded product by mixing the solution or polymer with the inorganic acid and / or organic acid of the present invention. Among these molding processes, it is preferable to mold from a solution dissolved in a suitable solvent. Solvents that can be dissolved include N, N
Suitable from aprotic polar solvents such as dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, N-methyl-2-pyrrolidone and hexamethylphosphonamide, and strong acids such as polyphosphoric acid, methanesulfonic acid, sulfuric acid and trifluoroacetic acid. The items can be selected, but are not limited to these. Of these, it is particularly preferable to mold from an organic solvent system. A plurality of these solvents may be mixed and used within a possible range. Further, as a means for improving the solubility, a solvent obtained by adding a Lewis acid such as lithium bromide, lithium chloride or aluminum chloride to an organic solvent may be used. The polymer concentration in the solution is preferably in the range of 0.1 to 50% by weight. If it is too low, moldability deteriorates, and if it is too high, workability deteriorates.

As a method for obtaining a molded product from a solution, a known method can be used. For example, the solvent can be removed by heating, drying under reduced pressure, immersion in a polymer non-solvent that is miscible with a solvent that dissolves the polymer, and a molded product of a polyazole containing a sulfonic acid group and / or a phosphonic acid group can be obtained. When the solvent is an organic solvent, it is preferable to distill off the solvent by heating or drying under reduced pressure. When the solvent is a strong acid, it is preferably immersed in water, methanol, acetone or the like. At this time, if necessary, it may be formed into a fiber or film in a form of being combined with another polymer.

Examples of the polymer which can be complexed with the polybenzimidazole compound of the present invention include polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, nylon 6, nylon 6,6, nylon 6,10 and nylon 12.
Acrylate resins such as polyamides, polymethylmethacrylate, polymethacrylic acid esters, polymethylacrylate, polyacrylic acid esters, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, polystyrene and diene resins Various polyolefins including polymers, polyurethane resins,
Cellulose resin such as cellulose acetate, ethyl cellulose, polyarylate, aramid, polycarbonate,
Polyphenylene sulfide, polyphenylene oxide,
Aromatic polymers such as polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzoxazole, polybenzthiazole, epoxy resin, phenol resin, novolac resin, benzoxazine resin, etc. There is no particular limitation on the resin. It is also preferable that these polymers contain an ionic group such as a sulfonic acid group or a phosphonic acid group in order to improve the ionic conductivity. When used as a resin composition with these polymers, the polybenzimidazole compound of the present invention is preferably contained in an amount of 50% by weight or more and less than 100% by weight of the entire resin composition. More preferably 7
It is 0% by weight or more and less than 100% by weight. When the content of the alkoxy sulfonic acid group-containing polyarylene ether-based compound of the present invention is less than 50% by weight of the entire resin composition, the ion conductive membrane containing this resin composition cannot obtain good ion conductivity. There is also a tendency that the unit containing an acidic group becomes a discontinuous phase and the mobility of the ion to be conducted tends to decrease. The composition of the present invention, if necessary, for example, an antioxidant, a heat stabilizer, a lubricant, a tackifier, a plasticizer, a crosslinking agent, a viscosity modifier, an antistatic agent, an antibacterial agent, an antifoaming agent, It may contain various additives such as a dispersant and a polymerization inhibitor.

A preferred method for forming a film containing the acidic group-containing polybenzimidazole compound of the present invention as a main component is
Cast from solution. The solvent can be removed from the cast solution as described above to obtain a film of polybenzimidazole containing sulfonic acid groups and / or phosphonic acid groups, in which case the inorganic acid and / or organic acid of the present invention is mixed. You can leave it. It is preferable to remove the solvent by drying in terms of uniformity of the film. Further, in order to prevent decomposition and deterioration of the polymer and solvent, it is preferable to dry under reduced pressure at the lowest temperature possible. A glass plate, a polytetrafluoroethylene plate, or the like can be used as the substrate to be cast. When the viscosity of the solution is high, heating the substrate or the solution and casting at a high temperature lowers the viscosity of the solution, so that the solution can be easily cast. The thickness of the solution when cast is not particularly limited, but is 10 to 1000
It is preferably μm. If it is too thin, the form of the film cannot be maintained, and if it is too thick, a non-uniform film is likely to be formed. More preferably, it is 100 to 500 μm. A known method can be used for controlling the cast thickness of the solution. For example, an applicator, a doctor blade, or the like may be used to make the thickness constant, or a glass petri dish or the like may be used to make the casting area constant to control the thickness by the amount or concentration of the solution. A more uniform film can be obtained from the cast solution by adjusting the removal rate of the solvent. For example, when heating, the evaporation rate can be lowered by lowering the temperature in the first step. When immersed in a non-solvent such as water, the coagulation rate of the polymer can be adjusted by leaving the solution in air or an inert gas for an appropriate time. The film of the present invention can have any film thickness depending on the purpose, but it is preferably as thin as possible from the viewpoint of ion conductivity. Specifically 2
The thickness is preferably 00 μm or less, more preferably 50 μm or less, and most preferably 20 μm or less.

In order to obtain a composition containing the polybenzimidazole compound of the present invention and an inorganic acid and / or an organic acid, the molding method introduced above is first performed without adding the inorganic acid and / or the organic acid. I made things,
A method of impregnating an inorganic acid and / or an organic acid into the molded article can also be adopted. In general, these can be impregnated by dissolving an inorganic acid and / or an organic acid in a suitable solvent such as water or alcohol, and immersing the molded product in the solvent for a suitable time. A composition containing the polybenzimidazole compound of the present invention and an inorganic acid and / or an organic acid can be obtained by removing the solvent by distilling it off.

The composition containing a polybenzimidazole-based polymer containing a sulfonic acid group and / or a phosphonic acid group of the present invention and an inorganic acid and / or an organic acid has excellent ion conductivity at high temperature, It is suitable for use as an ion exchange membrane for fuel cells and the like, and maintains good ionic conductivity for a long period of time.
Further, by using the polymer structure of the present invention as a main component, it can be used as a coating material for a binder resin or the like when producing a bonded body of the ion exchange membrane of the present invention and an electrode.

[0065]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Various measurements were performed as follows. Solution viscosity: Polymer powder was dissolved in concentrated sulfuric acid at a concentration of 0.5 g / dl, and viscosity was measured using an Ostwald viscometer in a constant temperature bath at 30 ° C. to obtain logarithmic viscosity [ln (ta / tb)].
/ C was evaluated (ta is the number of seconds of dropping the sample solution, tb is the number of seconds of dropping only the solvent, and c is the polymer concentration). Ion conductivity measurement: A platinum wire (diameter: 0.2 mm) was pressed onto the surface of a strip-shaped membrane sample on a self-made measurement probe (made of polytetrafluoroethylene), and a constant temperature and constant humidity oven at 80 ° C and 95% RH ( Nagano Scientific Machinery Works, LH
-20-01), hold the sample in place, and measure the impedance between the platinum wires by SOLARTRON 1250FREQUEN.
It was measured by CY RESPONSE ANALYSER. Measurement is performed by changing the distance between the electrodes, and the distance between the electrodes and CC
From the slope obtained by plotting the measured resistance value estimated from the plot, the conductivity in which the contact resistance between the film and the platinum wire was canceled was calculated by the following formula. Conductivity [S / cm] = 1 / membrane width [cm] x film thickness [cm] x resistance gap between electrodes [Ω / cm] Polymer logarithmic viscosity: Ostwald viscometer for a sulfuric acid solution with a polymer concentration of 0.5 g / dl It was measured at 30 ° C.

Example 1 3,3 ', 4,4'-Tetraaminodiphenylsulfone (abbreviation: TAS) 1.500 g (5.389x10 ^-3 mole), monosodium 2,5-dicarboxybenzenesulfonate (abbreviation: TAS)
STA, purity 99%) 1.445g (5.389x10-3mole), polyphosphoric acid (phosphorus pentoxide content 75%) 20.48g, phosphorus pentoxide 16.4
Weigh 1 g into a polymerization vessel. Pour nitrogen and raise the temperature to 100 ° C while stirring slowly on an oil bath. 100 ° C
Hold for 1 hour, then raise the temperature to 150 ° C for 1 hour, 2
The temperature was raised to 00 ° C and polymerization was carried out for 4 hours. After completion of the polymerization, the mixture was allowed to cool, water was added to take out the polymer, and washing with water was repeated using a household mixer until the pH test paper became neutral. The obtained polymer was dried under reduced pressure at 80 ° C. overnight. The inherent viscosity of the polymer was 1.55. 400 mg of the obtained polymer
And 170 ml on an oil bath while stirring and 4 ml of NMP.
It was heated to dissolve. To this solution, 280 mg of phenylphosphonic acid was mixed, cast on a glass plate to a thickness of about 200 μm on a hot plate, and NMP was evaporated. The film was peeled from the glass plate and dried under reduced pressure at 80 ° C. overnight to prepare a film for measuring ion conductivity. The ionic conductivity at 80 ° C. and 95% RH was 0.003 S / cm. After leaving this film in an oven at 200 ° C. for 1 week, the ionic conductivity was measured again and found to be 0.0029 S / cm.
And the same value as the initial measurement result was shown.

Example 2 In Example 1, the amount of phenylphosphonic acid added was changed to prepare a film for measuring ion conductivity, and evaluation was performed. The results are shown in Table 1.

Comparative Example 1 In Example 1, evaluation was carried out without adding phenylphosphonic acid. The results are shown in Table 1.

[0069]

[Table 1]

Example 3 The film prepared in Comparative Example 1 was immersed in an 85% aqueous phosphoric acid solution for 5 hours, washed with methanol, and dried under reduced pressure at 80 ° C. to obtain 1.4 films per nitrogen atom in the polymer. A film impregnated with phosphoric acid could be obtained. The ionic conductivity of this film at 80 ° C. and 95% RH is 0.
It was 0051 S / cm. The film was allowed to stand in an oven at 200 ° C. for 1 week, and the ionic conductivity was measured again. As a result, it was 0.0047 S / cm, which was the same value as the initial measurement result.

Example 4 Abbreviation: TAS 1.830 g (6.575 × 10 ⁻³ mol)
, 3,5-dicarboxyphenylphosphonic acid (abbreviation: DCP, purity 98%) 1.068 g (4.34)
Equivalent to 0 × 10 ^-3 mol), 0.371 g of terephthalic acid
(Corresponding to 2.236 × 10 ⁻³ mol), (polyphosphoric acid (phosphorus pentoxide content 75 mass%) 20.48 g, phosphorus pentoxide 16.41 g were weighed into a polymerization vessel. And heated to 110 ° C. while slowly stirring on an oil bath, then held at 110 ° C. for 1 hour and then heated to 150 ° C. for 1 hour and 200 ° C. for 5 hours for polymerization. After completion of the polymerization, the mixture was allowed to cool, water was added to take out the polymer, and the polymer was obtained by repeatedly washing with a household mixer until the pH test paper became neutral.
The obtained polymer was dried under reduced pressure at 80 ° C. overnight. The inherent viscosity of the polymer was 1.55. When the produced film was impregnated with phosphoric acid in the same manner as in Example 3, a film impregnated with 1.9 phosphoric acid per nitrogen atom in the polymer could be obtained. 80 ℃ of this film 95
The ionic conductivity at% RH was 0.0016 S / cm. The film was allowed to stand in a 200 ° C. oven for 1 week, and the ionic conductivity was measured again.
The value was 14 S / cm, which was the same as the initial measurement result.

0.4 g of the sulfonated polybenzimidazole compound, which is the polymer obtained in Example 1, was dissolved in 5 ml of NMP together with 0.14 g of phenylphosphonic acid. Carbon black (particle size: 20 to 30 nm) having a platinum loading of 20% (w / w) in this solution was used.
A paste was prepared by mixing and dispersing 72 g so as to be uniform. Then, the obtained paste was applied by screen printing to one surface of the solid polymer electrolyte membrane prepared in Example 1 and dried under reduced pressure. Then, the paste was similarly applied to the other surface of the solid polymer electrolyte membrane and dried under reduced pressure. The amount of platinum supported on the obtained solid polymer electrolyte membrane / electrode catalyst layer composite was 0.5 mg / cm ² . The conductivity of the solid polymer electrolyte membrane / electrode catalyst layer composite was measured and found to be 1.3 × 10 ⁻⁵ S / cm.
Met.

[0073]

INDUSTRIAL APPLICABILITY The composition of the present invention is excellent in ionic conductivity at high temperature and is suitable for use as an ion exchange membrane for fuel cells and the like in the form of a film or a membrane.
It has high stability at high temperature and maintains good ionic conductivity for a long time. Further, by using the polymer structure of the present invention as a main component, it can be used as a coating material for a binder resin or the like when producing a bonded body of the ion exchange membrane of the present invention and an electrode.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09J 11/00 C09J 11/00 179/04 179/04 A H01B 1/06 H01B 1/06 A H01M 8 / 02 H01M 8/02 P // H01M 8/10 8/10 F term (reference) 4J002 CN021 DG046 DH026 EV236 EW126 GQ00 4J040 EH021 GA25 HA256 HA286 HD13 HD23 LA07 LA08 LA09 NA19 5G301 CA30 CD01 5H026 AA06 CX05 EE18 HH05

Claims (9)

[Claims] 1. A composition comprising a polybenzimidazole compound containing a constituent represented by the following formula (1) and an inorganic acid and / or an organic acid. [Chemical 1] (In the formula (1), m ¹ represents an integer of 1 to 4,
R ¹ represents a tetravalent aromatic bond unit capable of forming an imidazole ring, R ² represents a divalent aromatic bond unit, R ¹
Each of R ² and R ² may be a single aromatic ring, a combination of a plurality of aromatic rings, or a condensed ring, and may have a stable substituent. Z is a sulfonic acid group and /
Alternatively, it may represent a phosphonic acid group, and a part thereof may have a salt structure. ) 2. A polybenzimidazole-based compound contains a binding unit represented by the structures represented by the following formulas (2) and (3) at a molar ratio of n ¹ : (1-n ¹ ) as a constituent component. The composition according to claim 1, characterized in that [Chemical 2] (In the formulas (2) and (3), m ¹ is from 1 to 4
Of Ar, Ar represents a divalent aromatic bond unit, X ¹ represents —O—, —SO ₂ —, —C (CH ₃ ) ₂ —, —C.
_{(CF 3) 2 -, -} OPhO- from at least one selected from the group, Ph denote the divalent aromatic bond unit. Further, the molar ratio satisfies the formula of 0.2 ≦ n ¹ ≦ 1.0) 3. A polybenzimidazole-based compound contains a binding unit represented by the structures represented by the following formulas (4) and (5) at a molar ratio of n ² : (1-n ² ) as a constituent component. The composition according to claim 1, characterized in that [Chemical 3] (In the formulas (4) and (5), m ¹ is from 1 to 4
Represents an integer, Ar represents an aromatic bond unit, X ²
Is _{-O -, - SO 2 -,} - S -, - CH 2 -, - OPhO
-Is one or more selected from the group, and Ph represents a divalent aromatic bond unit. Also, the molar ratio is
0.2 ≦ n ² ≦ 1.0 is satisfied) 4. The inorganic acid and / or the organic acid is phosphoric acid,
The composition according to any one of claims 1 to 3, which is selected from sulfuric acid, an organic sulfonic acid, and an organic phosphonic acid compound. 5. The ratio of the inorganic acid and / or the organic acid used is 0.1 to 5 relative to 1 mol of nitrogen atoms in the polymer.
The composition according to any one of claims 1 to 4, wherein the composition is molar. 6. An ion conductive membrane comprising the composition according to any one of claims 1 to 5. 7. A composite containing the ion conductive membrane according to claim 6 and an electrode. 8. A fuel cell containing the composite according to claim 7. 9. An adhesive comprising the composition according to any one of claims 1 to 5.