JP2002367627A - Sulfonated polyimide polymer electrolyte film and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer electrolyte film made of sulfonated polyimide with excellent film forming property, large ion-exchange capacity, excellent mechanical strength, and to provide a manufacturing method of the same, and to provide a solid polymer fuel cell having the above polymer electrolyte film as a solid polymer electrolyte film. SOLUTION: The sulfonated polyimide polymer film is formed by turning polyamide acid obtained by the reaction of diamine compound having 1,4,5,8- naphthalenetetracarboxylicdianhydride and at least one sulfonate group, and diamine compound without sulfonate group, into polyimide film which has an ion-exchange capacity of not less than 1.30 meq/g, a tensile shear strength of not less than 25 MPa, and a tensile elongation at break of not less than 3%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sulfonated polyimide polymer electrolyte membrane and a method for producing the same, and more particularly, to a sulfonated polyimide having excellent film forming properties, a large ion exchange group capacity, and excellent mechanical strength. The present invention relates to a polymer electrolyte membrane and a method for producing the same. The present invention also relates to a polymer electrolyte fuel cell containing a sulfonated polyimide polymer electrolyte membrane as a solid polymer electrolyte membrane.

[0002]

2. Description of the Related Art Fuel cell power generation has attracted attention because of its high power generation efficiency and supply of clean energy. A fuel cell is a device that obtains electric energy based on an operation principle based on a reverse operation of electrolysis of water. In a fuel cell, in general, hydrogen is obtained by reforming a fuel such as natural gas, methanol, or coal, and oxygen in the air is supplied to generate water and obtain DC power.

[0003] Fuel cells are classified into phosphoric acid type, molten carbonate type, solid oxide type, solid polymer type and the like, depending on the type of electrolyte used. Among them, a polymer electrolyte fuel cell using an ion exchange membrane (solid polymer electrolyte membrane) as an electrolyte is a cell consisting essentially of a solid, so that there is no problem of electrolyte dissipation and retention, 10
It has the advantages of operating at a low temperature of 0 ° C. or lower, having a very short start-up time, being capable of achieving high energy density, and being compact and lightweight.

Therefore, polymer electrolyte fuel cells are being developed as distributed power supplies for homes and buildings, automobile power supplies, spacecraft power supplies, portable power supplies, and the like. 2. Description of the Related Art In recent years, polymer electrolyte fuel cells have attracted much attention as fuel cells for vehicles, from the viewpoints of environmental problems such as global warming and measures against automobile exhaust gas.

As shown in the sectional view of FIG. 3, the polymer electrolyte fuel cell has an ion exchange membrane (solid polymer electrolyte membrane) 31.
Has an all-solid-type structure in which gas diffusion electrode layers 32 and 33 are joined to both surfaces. The cathode (oxidant electrode) 32 and anode (fuel electrode) 33 are connected by an external circuit 35 (load 34).

When oxygen or air is supplied to the cathode 32 and hydrogen is supplied to the anode 33,
Hydrogen is oxidized to produce protons and electrons. Protons move in the ion exchange membrane 31 with water molecules, and are used at the anode 32 of the counter electrode together with the electrons supplied from the external circuit 35 (load 34) to reduce oxygen and generate water.

[0007] The polymer electrolyte fuel cell is used in the form of a stack in which a number of single cells each composed of an ion exchange membrane-electrode assembly are stacked as shown in FIG. Specifically, on both sides of the ion-exchange membrane-electrode assembly, a conductive separator having a function of separating an electrode chamber and a gas supply flow path is adhered and laminated.

[0008] Although the polymer electrolyte fuel cell has the above-mentioned advantages, the material of the battery such as an ion exchange membrane is expensive, and the ion exchange membrane has good conductivity in a hydrated state. For this reason, it has disadvantages such as the need to control the water content of the ion exchange membrane.

[0009] The polymer constituting the ion exchange membrane is generally required to have high ionic conductivity and properties to form a thin film having excellent mechanical strength. The ion exchange membrane is required to retain high ionic conductivity not only in a wet state but also in a dry state, and to have excellent thermal stability, resistance to oxidation and reduction, mechanical strength, and the like.

Conventionally, a solid polymer electrolyte membrane of a polymer electrolyte fuel cell has been manufactured by DuPont's Nafion.
on; registered trademark) is used. This fluororesin-based ion-exchange membrane is difficult to reduce in cost because the manufacturing process is complicated. In addition, fluororesin-based ion-exchange membranes are made of linear polymers that do not have a cross-linking structure, so they can be made into solution when the ion-exchange group concentration is high, and they can easily swell and shrink due to the surrounding water concentration. If the thickness is reduced, there is a problem that the water content increases and the mechanical strength and creep resistance decrease.

Recently, it has been proposed to use a sulfonated polyimide membrane instead of a fluororesin-based ion exchange membrane as an ion exchange membrane for a polymer electrolyte fuel cell (Japanese Patent Publication No. 2000-510511). However, according to the results of the additional tests by the present inventors, it was found that under the polymerization conditions disclosed in the publication, it was not possible to obtain a sulfonated polyimide precursor (ie, polyamic acid) having excellent film-forming properties. .

[0012] For example, in Example 4 of the publication, a mixed solvent of phenol and para-chlorophenol contains
4'-diamino- (1,1'-biphenyl) -2,2 '
Disulfonic acid, 1,4,5,8-naphthalenetetracarboxylic dianhydride and 4,4'-oxy-benzeneamine, which is understood to be oxybis (4,4'-benzeneamine) ] At a time and add
It is described that polymerization was carried out by heating for an hour.

However, in this polymerization method, a polyamic acid having a sufficiently high degree of polymerization could not be synthesized, and a satisfactory film could not be obtained using the obtained polyamic acid. The reason may be that the publication does not sufficiently disclose the details of the polymerization conditions, but that is not the only reason.Poor control of the polymerization conditions such as the polymerization catalyst, the monomer charging order, the reaction temperature, and the reaction time is insufficient. Turned out to be.

Macromol. Symp. 106, 345-351 (1996) states that 1,4,5,8-naphthalenetetracarboxylic dianhydride and 2,2 'in phenol in the presence of benzoic acid and triethylamine. -Benzidine disulfonate (i.e.
4,4'-diamino- (1,1'-biphenyl) -2,
2′-disulfonic acid] at 180 ° C. to synthesize water-soluble sulfonated polynaphthyl imide (PNIS).

However, the sulfonated polymer disclosed in this document is water-soluble and thus is unsuitable as a solid polymer electrolyte membrane. The document does not describe details such as the amount of each component used and the polymerization time. Also, the document does not teach a method for producing a sulfonated polymer having a polyimide skeleton insoluble in water.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ion-exchange membrane for a polymer electrolyte fuel cell comprising a sulfonated polyimide having excellent film-forming properties, a large ion exchange group capacity and excellent mechanical strength. To provide a polymer electrolyte membrane and a method for producing the same.

Another object of the present invention is to provide a polymer electrolyte fuel cell containing a sulfonated polyimide polymer electrolyte membrane having such excellent characteristics as a polymer electrolyte membrane.

The present inventors have conducted intensive studies to achieve the above object, and have found that 1,4,5,8-naphthalenetetracarboxylic dianhydride, a diamine compound having at least one sulfonic acid group, and a sulfonic acid A polyamic acid is synthesized by reacting with a diamine compound having no group,
In a method for producing a sulfonated polyimide polymer electrolyte membrane to be imidized after forming the polyamic acid, a method for polycondensing the polyamic acid in a specific two-step process has been conceived.

The polyamic acid obtained by the production method of the present invention has excellent film-forming properties. The sulfonated polyimide membrane obtained by the production method of the present invention has a large ion exchange group capacity, exhibits an appropriate volume resistivity and water absorption, and is excellent not only under dry conditions but also under wet conditions, and has excellent tensile breaking stress, It shows moderate elongation at break. Therefore, this sulfonated polyimide membrane is suitable as a polymer electrolyte membrane for a polymer electrolyte fuel cell. The present invention has been completed based on these findings.

[0020]

According to the present invention, the following formula is provided.
(I)

[0021]

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And a structural unit (I) represented by the following formula (II):

[0023]

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In the formula, Ar ₁ and Ar ₂ are divalent organic groups which may be the same or different from each other, and Ar ₁ is further substituted by at least one sulfonic acid group. Is substituted with a sulfonated polyimide having an ion exchange group capacity of 1.30 meq / g or more and a tensile rupture stress of 2
A sulfonated polyimide polymer electrolyte membrane having 5 MPa or more and a tensile elongation at break of 3% or more is provided.

According to the present invention, 1,4,5,8-
A polyamic acid is synthesized by reacting naphthalenetetracarboxylic dianhydride with a diamine compound (A1) having at least one sulfonic acid group and a diamine compound (A2) having no sulfonic acid group, and then synthesizing the polyamic acid. In the method for producing a sulfonated polyimide polymer electrolyte membrane which is imidized after film formation, the polyamic acid is subjected to the following steps: (1) in a mixed solvent of phenol and p-chlorophenol in the presence of triethylamine and benzoic acid , 1,4,
Reacting 5,8-tetracarboxylic dianhydride with a diamine compound (A1) having at least one sulfonic acid group at a temperature of 150 ° C. or higher, and (2) lowering the temperature of the reaction mixture to 100 ° C. or lower After that, a diamine compound having no sulfonic acid group (A2) was charged, and then 100 ° C.
There is provided a method for producing a sulfonated polyimide polymer electrolyte membrane, characterized in that the synthesis is performed by a step of continuing the reaction at the following temperature.

Further, according to the present invention, there is provided a sulfonated polyimide polymer electrolyte membrane obtained by the above production method.

Further, according to the present invention, there is provided a polymer electrolyte fuel cell containing a sulfonated polyimide polymer electrolyte membrane as a solid polymer electrolyte membrane.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, 1,4,5,8-naphthalenetetracarboxylic dianhydride is used as a polycarboxylic acid (polyimide precursor) and a tetracarboxylic acid component constituting polyimide. As the diamine component,
Diamine compound having at least one sulfonic acid group (A
1) and a diamine compound having no sulfonic acid group (A2) are used in combination.

The diamine compound (A1) having at least one sulfonic acid group has a chemical formula of NH ₂ Ar ₁ (SO
_{And 3} H) a compound represented by NH ₂ .
In this chemical formula, Ar ₁ is a divalent organic group,
At least one (substituted) aromatic ring having 0 carbon atoms, an aromatic (substituted) heterocyclic ring having 5 to 10 atoms and containing hetero atoms such as S, N, O, and the like; Diamine compounds having a structure such as a ring are preferred. The diamine compound (A1) has at least one sulfonic acid group, but is preferably a diamine compound having two sulfonic acid groups.

Preferred specific examples of the diamine compound (A1) having at least one sulfonic acid group include 2,2'-
Benzidine disulfonic acid [ie, 4,4'-diamino-
(1,1'-biphenyl) -2,2'-disulfonic acid], 1,4-diaminobenzene-3-sulfonic acid,
1,3-diaminobenzene-4-sulfonic acid, 4,4 '
-Diamino-5,5'-dimethyl- (1,1'-biphenyl) -2,2'-disulfonic acid. Among these, benzidine 2,2'-disulfonate is preferred.

The diamine compound (A2) having no sulfonic acid group includes a compound represented by the chemical formula NH ₂ Ar ₂ NH ₂ . In this chemical formula, Ar ₂ is
A divalent organic group having at least one (substituted) aromatic ring having 6 to 10 carbon atoms, having 5 to 10 atoms, and aromatic atoms including hetero atoms such as S, N, and O; Diamine compounds having a structure such as a (substituted) heterocycle and a mixed ring thereof are preferred. The substituted aromatic ring and the substituted heterocyclic ring have no sulfonic acid group as a substituent.

Examples of the diamine compound (A2) having no sulfonic acid group include 2,2'-di (p-aminophenyl) -6,6'-bibenzoxazole and 2,2 '
-Di (p-aminophenyl) -5,5'-bibenzoxazole, m-phenylenediamine, 1-isopropyl-2,4-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3, 3 '
-Diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-
Diaminodiphenylmethane, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfone, 3,
3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 1,4-bis (4-aminophenoxy) benzene, benzidine, 4,4 "-diamino-p-terphenyl, 3,3 ″ -diamino-p-terphenyl, bis (p-aminocyclohexyl) methene, bis (p-β-
Amino-t-butylphenyl) ether, bis (p-β
-Methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, , 6-Diaminonaphthalene, 2,4-bis (β-amino-t-butyl) toluene, 2,4-diaminotoluene, m-xylene-
2,5-diamine, p-xylene-2,5-diamine,
m-xylylenediamine, p-xylylenediamine,
Aromatic diamines such as 4,4 '-[2,2,2-trifluoro- (1-trifluoromethyl) -ethylidene] -benzenamine; 2,6-diaminopyridine, 2,5
-Diaminopyridine, 2,5-diamino-1,3,4-
Heterocyclic diamines such as oxadiazole can be mentioned. Among these, 4,4'-diaminodiphenyl ether is preferable.

The tetracarboxylic acid components 1, 4, 5,
8-Naphthalenetetracarboxylic dianhydride and the diamine component are generally used in approximately equimolar proportions. When both ends of the polymer are amines, they may be used in a molar ratio in which the diamine component is slightly excessive. On the other hand, when both ends of the polymer are carboxylic anhydride groups,
The 4,5,8-naphthalenetetracarboxylic dianhydride may be used in a molar ratio that slightly increases. Further, a polymer terminal may be formed by using a small amount of phthalic anhydride, naphthalene-1,8-dicarboxylic anhydride, or the like as a chain limiter.

In the diamine component, the diamine compound (A1) having at least one sulfonic acid group and the diamine compound (A2) having no sulfonic acid group have a molar ratio (A1: A2),
It is preferable to use it at a ratio of 5:95 to 95: 5.
The molar ratio (A1: A2) is more preferably from 15:85 to 8
5:15, more preferably 20:80 to 80:20,
Particularly preferably, the ratio is from 25:75 to 75:25.

If the molar ratio of the diamine compound (A1) having at least one sulfonic acid group is too small, it becomes difficult to obtain a polymer electrolyte membrane having a sufficiently high ion exchange group capacity. If the molar ratio of the diamine compound (A1) having at least one sulfonic acid group is too large, the mechanical strength of the polymer electrolyte membrane will decrease, and particularly, the tensile rupture stress in a wet state will decrease. In many cases, the molar ratio (A1: A2) is 30:
Good results can be obtained by setting the ratio in the range of 70 to 70:30.

In the present invention, a polyamic acid is synthesized by the following steps (1) and (2). (1) Diamine compound having at least one sulfonic acid group with 1,4,5,8-tetracarboxylic dianhydride in the presence of triethylamine and benzoic acid in a mixed solvent of phenol and p-chlorophenol (A1 A) at a temperature of 150 ° C. or higher.

(2) After lowering the temperature of the reaction mixture obtained in the first step to 100 ° C. or less, a diamine compound (A2) having no sulfonic acid group is added, and then the mixture is heated at a temperature of 100 ° C. or less. Second step of continuing the reaction.

The weight ratio of phenol to p-chlorophenol in the mixed solvent is preferably from 10:90 to 90: 1.
0, more preferably 20:80 to 80:20, particularly preferably 30:70 to 70:30. In most cases, 40-70% by weight of phenol and 30 of p-chlorophenol
Good results can be obtained by using at a ratio of ６０60% by weight. By using this mixed solvent,
In combination with other conditions, the polycondensation reaction can be smoothly performed.

In the present invention, in the first step, triethylamine is present in the reaction system. Specifically, triethylamine is added to the mixed solvent. Triethylamine is understood to act as a solubilizer for the diamine compound (A1) having at least one sulfonic acid group.
Triethylamine is used in a proportion of preferably 0.5 to 3 mol, more preferably 1 to 2.5 mol, per 1 mol of the diamine compound (A1) having at least one sulfonic acid group. By using triethylamine, the polycondensation reaction can be smoothly performed in combination with other conditions.

In the present invention, in the first step, benzoic acid is present in the reaction system. Specifically, benzoic acid is added to the mixed solvent. Benzoic acid acts as a polymerization catalyst. Benzoic acid is preferably used in an amount of 0.1 mol per mol of the diamine compound (A1) having at least one sulfonic acid group.
It is used in a proportion of 1 to 1.5 mol, more preferably 0.3 to 1 mol. By using benzoic acid as a polymerization catalyst, a polyamic acid having a high molecular weight and excellent film-forming properties can be obtained.

In the present invention, instead of reacting all the monomer components at once, first, in a mixed solvent of phenol and p-chlorophenol, in the presence of triethylamine and benzoic acid, first, 1,4,5,8-tetraethyl Diamine compounds having carboxylic dianhydride and at least one sulfonic acid group
(A1) is reacted at a temperature of 150 ° C. or higher. The reaction temperature in the first step is preferably from 150 to 190C, more preferably from 160 to 185C. The reaction time is preferably 1 to 24 hours, more preferably 2 to 12 hours, particularly preferably 3 to 10 hours.

Next, in the second step, after lowering the temperature of the reaction mixture obtained in the first step to 100 ° C. or less,
Diamine compound having no sulfonic acid group (A2) is charged,
Next, the reaction is continued at a temperature of 100 ° C. or lower. The reaction temperature is preferably 55-100 ° C, more preferably 60 ° C.
９０90 ° C. The reaction time is preferably 5 to 72 hours, more preferably 8 to 30 hours, particularly preferably 10 to 72 hours.
~ 25 hours. In the second step, the reaction may be continued by lowering the reaction temperature stepwise within the above range.

By such a specific two-stage polymerization method, a polyamic acid having excellent film-forming properties can be obtained, and when imidized after film formation, various properties as a polymer electrolyte membrane are good. A highly sulfonated polyimide membrane can be obtained.

After completion of the reaction, the reaction mixture is poured into a non-solvent (for example, methanol, ethanol or the like) of the produced polyamic acid to precipitate the produced polyamic acid. If necessary, perform methanol washing. The precipitate is filtered and dried to recover the polyamic acid.

Polyamic acid can be formed into a film by dissolving in a solvent (for example, m-cresol), casting the resulting solution on a support such as a glass plate, and drying. The resulting film is usually polyimideated by heating to dehydrate and ring-close the polyamic acid. If desired, a chemical ring closure method may be employed. The sulfonated polyimide membrane thus obtained is, if necessary,
Treat with hydrochloric acid solution and wash thoroughly with deionized water.

The sulfonated polyimide polymer electrolyte membrane of the present invention has the following formula (I)

[0047]

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And a structural unit (I) represented by the following formula (II):

[0049]

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Wherein Ar ₁ and Ar ₂ are divalent organic groups which may be the same or different from each other, and Ar ₁ is further substituted by at least one sulfonic acid group. Substituted).) Is a membrane formed from a sulfonated polyimide having the formula: This sulfonated polyimide can be represented by the following formula (III).

[0051]

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In the formula, Ar ₁ and Ar ₂ are divalent organic groups which may be the same or different from each other, and Ar ₁ is
It is further substituted by at least one sulfonic acid group. m is an integer of 1 or more, preferably 1 to 5,
000, more preferably 4 to 300. n is an integer of 1 or more, preferably 1 to 5,000, and more preferably 4 to 300. As the structural unit (I), the following formula (Ia)

[0053]

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The structural unit represented by the following is preferred. As the structural unit (II), the following formula (IIa)

[0055]

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The structural unit represented by the following is preferred. Therefore, as a sulfonated polyimide, the following formula (IIIa)

[0057]

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A sulfonated polyimide having a chemical structure represented by the following formula is preferred.

The sulfonated polyimide polymer electrolyte membrane of the present invention has an ion exchange group capacity of usually 1.30 meq / g or more, preferably 1.50 meq / g or more, more preferably 1.80 meq / g or more. The sulfonated polyimide polymer electrolyte membrane of the present invention has an ion exchange group capacity of 2.00 m if necessary by adjusting the polymerization conditions.
It can be increased to eq / g or more, more preferably to 2.30 meq / g or more, and further to 2.50 meq / g or more. The upper limit of the ion exchange group capacity is 3.3 me
It is about q / g.

The sulfonated polyimide polymer electrolyte membrane of the present invention has a tensile rupture stress in a dry state of usually 25 MPa or more, preferably 25 to 150 MPa, more preferably 3 MPa.
0 to 100 MPa, and excellent in mechanical strength. The sulfonated polyimide polymer electrolyte membrane of the present invention has a tensile rupture stress upon absorption of water of usually 5 to 100 MPa, preferably 6 to 100 MPa.
６０60 MPa, more preferably 10５０50 MPa, and the mechanical strength in a wet state is good.

The sulfonated polyimide polymer electrolyte membrane of the present invention has a tensile elongation at break of 3% or more, preferably 3 to 25%, more preferably 5 to 20% when dried, and has good flexibility. is there. The sulfonated polyimide polymer electrolyte membrane of the present invention has almost the same tensile elongation at break when absorbing water as the elongation at break when dry, and has good wet state flexibility.

The sulfonated polyimide polymer electrolyte membrane of the present invention has a platinum electrode having a length of 10 mm, a distance between the electrodes of 10 mm,
The volume resistivity measured at an alternating current of 1.0 V to 10 kHz is usually 2 to 35 Ωcm, preferably 3 to 30 Ωcm, more preferably 5 to 25 Ωcm. The sulfonated polyimide polymer electrolyte membrane of the present invention has a water absorption of usually 5 to 100%,
Preferably 10-80%, more preferably 15-70%
It is.

Further, the sulfonated polyimide polymer electrolyte membrane of the present invention is insoluble in water, maintains high ion conductivity in a wet state, and is a fluorine resin ion exchange membrane having a general sulfonic acid group. It has better thermal stability, resistance to oxidation and reduction, mechanical strength and the like than (perfluoropolymer electrolyte membrane). Therefore, the sulfonated polyimide polymer electrolyte membrane of the present invention is suitable as an ion exchange membrane for a polymer electrolyte fuel cell.

[0064]

The present invention will be described more specifically below with reference to examples and comparative examples.

[Example 1] 1. Reactor In a reactor consisting of a glass flask with a volume of 300 ml,
A stirrer, a nitrogen gas inlet, a temperature probe, and a cooling tube were attached. The heating of the reactor was performed using an oil bath having a temperature control function.

2. Preparation of Reaction Medium 70 g of phenol and 50 g of p-chlorophenol were charged into a reactor as a solvent, and the reactor was heated in an oil bath with stirring to raise the temperature of the solvent to 60 ° C. Next, in the reactor, triethylamine as a dissolution aid was added.
226 g (0.022 mol) and 0.671 g (0.0055 mol) of benzoic acid as a polymerization catalyst were charged,
Stir for 30 minutes.

3. First polymerization step 3.788 g of benzidine 2,2'-disulfonic acid [that is, 4,4'-diamino- (1,1'-biphenyl) -2,2'-disulfonic acid] was placed in the above reactor. .0
11 mol) and stirred for 30 minutes. Thereafter, 4.290 g (0.016 mol) of 1,4,5,8-naphthalenetetracarboxylic dianhydride was charged into the reactor,
Heating the mixture in the reactor to 180 ° C. while stirring;
And it stirred at 180 degreeC for 4 hours.

4. Second polymerization step The temperature of the mixture in the reactor was reduced to 80 ° C.
At that time, 1.001 g (0.005 mol) of 4,4'-diaminodiphenyl ether [i.e. oxybis (4,4'-benzeneamine)] was charged into the reactor, and at 80 [deg.] C. Stir for 5 hours. afterwards,
The temperature of the mixture in the reactor was reduced to 60 ° C. and
Stirred at 0 ° C. for 18 hours.

5. Post-treatment step The polymerization reaction was terminated by pouring the reaction mixture in the reactor into a 3 liter beaker containing 1 liter of methanol while stirring the methanol. After stirring for 30 minutes, the precipitated fibrous solid (polymer) was isolated by suction filtration. Further, the fibrous solid was put into a 3 liter beaker into which 500 ml of methanol was poured while stirring methanol, and stirred for 30 minutes. Thereafter, a fibrous solid purified by suction filtration was isolated.
This purification treatment using methanol was repeated once. The isolated fibrous solid was vacuum dried at 120 ° C. for 6 hours. Thus, the polyamic acid (that is, the polyimide precursor) was recovered.

6. Film-forming step The polyamic acid obtained above was crushed in a mortar. On the other hand, 92.5 g of m-cresol was placed in the same reactor as above.
It was charged and heated to 60 ° C. with stirring. Into this reactor, 7.5 g of polyamic acid crushed in a mortar was charged in three portions at intervals of 30 minutes and dissolved. The obtained polymer solution (concentration: 7.5% by weight) was placed in a doctor knife 500.
It was cast on a glass plate with a thickness of μm. The coating formed on the glass plate was heated in a thermostat at a rate of 10 ° C./min.
The polyamide acid was imidized (dehydration ring closure) by curing under heating conditions at 10 ° C. for 10 minutes.

After the completion of the heat curing, a transparent brown-colored film (polyimide film) was formed on the glass plate. This coating was peeled from the glass plate. Removed polyimide film,
The mixture was poured into a 1-liter beaker into which 100 ml of 1N hydrochloric acid had been poured, and the beaker was capped and heated in a water bath at 60 ° C. for 18 hours. Thereafter, the polyimide film was taken out from the hydrochloric acid solution and sufficiently washed with ion-exchanged water. Thus, a sulfonated polyimide polymer electrolyte membrane (about 20 μm in thickness) was obtained.

7. Characteristics of Polymer Electrolyte Membrane The sulfonated polyimide polymer electrolyte membrane obtained above has an ion exchange group capacity of 2.89 meq / g, a volume resistivity (a platinum electrode having a length of 10 mm, a distance between the electrodes of 10 mm, and an AC of 1.0 V). (Measured at -10 kHz) was 6.1 Ωcm, and the water absorption was 62%. The sulfonated polyimide polymer electrolyte membrane has a tensile strength of 39 MPa.
The tensile elongation at break was 8%, the tensile elongation at break when absorbing water was 15 MPa, and the elongation at break was 7%.

FIG. 1 shows the dynamic viscoelasticity (mechanical elastic modulus) of the sulfonated polyimide polymer electrolyte membrane (11) obtained above and a commercially available perfluoro-based polymer electrolyte membrane (12).
The relationship between temperature and temperature is shown. From this measurement result, it is understood that the sulfonated polyimide polymer electrolyte membrane of the present invention has better mechanical hardness at a high temperature than a commercially available perfluoro-based polymer electrolyte membrane.

FIG. 2 shows the relationship between the proton conductivity and the temperature of the sulfonated polyimide polymer electrolyte membrane (21) obtained above and a commercially available perfluoro-based polymer electrolyte membrane (22). From these measurement results, it is understood that the sulfonated polyimide polymer electrolyte membrane of the present invention has better proton conductivity at a higher temperature than a commercially available perfluoro-based polymer electrolyte membrane. The measurement conditions are as follows.

Atmosphere: 100% relative humidity at each temperature Electrodes: 10 mm long, 2 platinum electrodes and 10 m distance between electrodes
m, power source: AC 10 kHz-1 V The proton conductivity was calculated from the volume resistivity (R) obtained under the above measurement conditions by the following formula. Proton conductivity (S / cm) = 1 / R (Ωcm)

Example 2 A sulfonated polyimide polymer electrolyte membrane was prepared in the same manner as in Example 1 except that the amounts of the dissolution aid, the polymerization catalyst, and each monomer were changed as follows. did.

1.619 g of triethylamine (0.01
6mol), 0.488 g of benzoic acid (0.0040 mo)
l), 2.755 g of benzidine 2,2'-disulfonate
(0.008 mol), 4.290 g of 1,4,5,8-naphthalenetetracarboxylic dianhydride (0.016 mol
l), 4,4'-diaminodiphenyl ether 1.60
2 g (0.008 mol).

The sulfonated polyimide polymer electrolyte membrane thus obtained had an ion exchange group capacity of 2.48 m.
eq / g, volume resistivity (measured at 10 mm length platinum electrode, distance between electrodes 10 mm, AC 1.0 V-10 kHz)
1.0 Ωcm and the water absorption was 38%. The tensile properties of the sulfonated polyimide polymer electrolyte membrane are as follows: tensile stress at break is 61 MPa, tensile elongation at break is 7%,
The tensile rupture stress during water absorption was 25 MPa, and the tensile rupture elongation was 8%.

Example 3 A sulfonated polyimide polymer electrolyte membrane was prepared in the same manner as in Example 1 except that the amounts of the dissolution aid, the polymerization catalyst, and each monomer were changed as follows. did.

1.012 g of triethylamine (0.01
0 mol), 0.305 g of benzoic acid (0.0025 mol)
l), 1.783 g of benzidine 2,2'-disulfonate
(0.005 mol), 4.290 g of 1,4,5,8-naphthalenetetracarboxylic dianhydride (0.016 mol
l), 4,4'-diaminodiphenyl ether 2.13
6 g (0.011 mol).

The sulfonated polyimide polymer electrolyte membrane thus obtained has an ion exchange group capacity of 1.58 m.
eq / g, volume resistivity (measured at 10 mm length platinum electrode, distance between electrodes 10 mm, AC 1.0 V-10 kHz)
It was 4.0 Ωcm and the water absorption was 21%. The tensile properties of this sulfonated polyimide polymer electrolyte membrane were such that the tensile rupture stress was 70 MPa, the tensile rupture elongation was 16%, the tensile rupture stress upon water absorption was 48 MPa, and the tensile rupture elongation was 11%. .

[0082]

[Table 1]

[Comparative Example 1] Reactor Into a reactor consisting of a 500 ml glass flask,
A stirrer, a nitrogen gas inlet, a temperature probe, and a cooling tube were attached. The heating of the reactor was performed using an oil bath having a temperature control function.

2. Preparation of reaction medium In a reactor, 210 g of phenol and 140 g of p-chlorophenol were charged as solvents.

3. Polymerization Step In a reactor, benzidine 2,2'-disulfonic acid [ie, 4,4'-diamino- (1,1'-biphenyl)-
2,2'-disulfonic acid] 5 g (0.015 mol),
12.97 g (0.048 mol) of 1,4,5,8-naphthalenetetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether [that is, oxybis (4,4 '
6.7 g (0.034 mol) were added all at once. The mixture in the reactor was heated to 150 ° C. with stirring in an oil bath and stirred at 150 ° C. for 5 hours. Thereafter, the reaction mixture was cooled to 60 ° C.

[0086] 4. Post-treatment step The reaction mixture in the reactor was poured into 2 liters of methanol while stirring the methanol. After stirring for 30 minutes, the precipitated solid (polymer) was isolated by filtration.
The isolated solid was again poured into 2 liters of methanol while stirring, and after stirring for 30 minutes, the precipitated solid was isolated by filtration. 120 ° C.
For 6 hours under vacuum. Thus, the polyamic acid (that is, the polyimide precursor) was recovered.

5. Film-forming process In the same four reactors as above, m-cresol 5 was added.
5.5 g, N-methyl-2-pyrrolidone (NMP) 5
5.5 g, dimethyl sulfoxide (DMSO) 55.5
g, and N, N-dimethylacetamide (DMAc) 5
5.5 g was charged and heated to 60 ° C. For each reactor,
4.5 g of polyamic acid was added at 30 minute intervals in three portions and stirred. At this stage, the polyamic acid is DMSO
Insoluble in Nc and DMAc, partially dissolved in NMP, and completely dissolved in m-cresol.

The above-prepared NMP solution (polyamide acid dissolving portion) and m-cresol solution were each cast on a glass plate with a doctor knife thickness of 500 μm. The film formed on the glass plate is heated at a rate of 10 ° C.
/ Min, and 1 hour at 120 ° C., 1 hour at 200 ° C.
The polyamide acid was imidized by curing under heating conditions of 0 minutes and 250 ° C. for 10 minutes. However, all of the cured products were in a red-brown powder state, and a satisfactory film could not be obtained.

[Comparative Example 2] Reactor Into a reactor consisting of a 500 ml glass flask,
A stirrer, a nitrogen gas inlet, a temperature probe, and a cooling tube were attached. The heating of the reactor was performed using an oil bath having a temperature control function.

2. Preparation of reaction medium In a reactor, 128 g of phenol was charged as a solvent,
The reactor was heated in an oil bath with stirring to raise the temperature of the solvent to 60 ° C. In this reactor, 1.619 g (0.016 mol) of triethylamine was used as a dissolution aid.
And 1.953 g (0.016 g) of benzoic acid as a polymerization catalyst
0 mol) and stirred for 30 minutes.

3. Polymerization Step In the above reactor, 5.510 g (0.016 mol) of benzidine 2,2′-disulfonate, 1,4,5,8-
12.872 g of naphthalenetetracarboxylic dianhydride
(0.048 mol) and 6.408 g (0.032 mol) of 4,4'-diaminodiphenyl ether were added at one time. While stirring the mixture in the reactor, 180
The temperature was raised to about ℃. However, at around 110 ° C., the mixture was solidified so that the stirring bar could not be turned.

[0092] 4. Post-treatment step Then, the reaction mixture in the above-mentioned step was introduced into 2 liters of methanol while stirring the methanol. After stirring for 30 minutes, the precipitated powdery solid (polymer) was isolated by filtration. The filtered solid was further poured into 2 liters of methanol with stirring, and stirred for 30 minutes after the entire amount was charged. Thereafter, the solid was isolated by filtration. The isolated solid was vacuum dried at 120 ° C. for 6 hours. Thus, the polyamic acid (that is, the polyimide precursor) was recovered.

[0093] 5. Film forming step Into the same reactor as above, 55.5 g of m-cresol was charged and heated to 60 ° C. 3. Polyamic acid in the reactor
5 g was divided into three portions and charged at intervals of 30 minutes, followed by stirring. The polyamic acid was dissolved in m-cresol. The resulting solution was cast on a glass plate with a doctor knife thickness of 500 μm. The coating on the glass plate is heated in a thermostat at a heating rate of 10 ° C./min, and heated at 120 ° C. for 1 hour, 200 ° C. for 10 minutes, and 250 ° C. for 10 minutes to obtain polyamide acid. Was imidized. As a result, although a part of the cured product had a brownish brown film portion, the majority was a reddish brown powder. Therefore, a satisfactory film could not be obtained.

[Comparative Example 3] Reactor Into a reactor consisting of a 500 ml glass flask,
A stirrer, a nitrogen gas inlet, a temperature probe, and a cooling tube were attached. The heating of the reactor was performed using an oil bath having a temperature control function.

2. Preparation of reaction medium In a reactor, 128 g of phenol was charged as a solvent,
The reactor was heated in an oil bath with stirring to raise the temperature of the solvent to 60 ° C. In this reactor, 1.619 g (0.016 mol) of triethylamine was used as a dissolution aid.
And 1.953 g (0.016 g) of benzoic acid as a polymerization catalyst
0 mol) and stirred for 30 minutes.

3. First polymerization step 5.510 g (0.016 mol) of 2,2'-disulfonic acid benzidine was charged into the above reactor, and the mixture was stirred for 30 minutes. Thereafter, 12.872 g (0.02 g) of 1,4,5,8-naphthalenetetracarboxylic dianhydride was placed in the reactor.
(48 mol), and the mixture in the reactor was heated to 180 ° C. while stirring, and stirred at 180 ° C. for 4 hours.

4. Second polymerization step The temperature of the mixture in the reactor was reduced to 80 ° C.
When the temperature reached ° C, 6.408 g (0.032 mol) of 4,4'-diaminodiphenyl ether was charged into the reactor and stirred at 80 ° C for 2.5 hours. Thereafter, the temperature of the mixture in the reactor is reduced to 60 ° C. and
Stirred at C for 18 hours.

5. Post-treatment step The reaction mixture in the reactor was poured into 2 liters of methanol while stirring the methanol. After stirring for 30 minutes, the precipitated powdery solid (polymer) was isolated by filtration. The isolated solid was again poured into 2 liters of methanol while stirring, and after stirring for 30 minutes, the precipitated solid was isolated by filtration. The isolated solid was vacuum dried at 120 ° C. for 6 hours. Thus, the polyamic acid (that is, the polyimide precursor) was recovered.

6. Film-forming step Into the same reactor as above, 55.5 g of m-cresol was charged and heated to 60 ° C. 3. Polyamic acid in the reactor
5 g was divided into three portions and charged at intervals of 30 minutes, followed by stirring. The polyamic acid was dissolved in m-cresol. The resulting solution was cast on a glass plate with a doctor knife thickness of 500 μm. The coating on the glass plate is heated in a thermostat at a heating rate of 10 ° C./min, and heated at 120 ° C. for 1 hour, 200 ° C. for 10 minutes, and 250 ° C. for 10 minutes to obtain polyamide acid. Was imidized. As a result, 80% of the cured product
The degree was a translucent brownish film, but the remaining 20% was powdery. Therefore, a satisfactory film could not be obtained.

[Comparative Example 4] Reactor Into a reactor consisting of a 500 ml glass flask,
A stirrer, a nitrogen gas inlet, a temperature probe, and a cooling tube were attached. The heating of the reactor was performed using an oil bath having a temperature control function.

2. Preparation of reaction medium In a reactor, 128 g of phenol was charged as a solvent,
The reactor was heated in an oil bath with stirring to raise the temperature of the solvent to 60 ° C. In this reactor, 1.619 g (0.016 mol) of triethylamine was used as a dissolution aid.
And 0.976 g (0.008 g) of benzoic acid as a polymerization catalyst
0 mol) and stirred for 30 minutes.

3. First polymerization step 5.510 g (0.016 mol) of 2,2'-disulfonic acid benzidine was charged into the above reactor, and the mixture was stirred for 30 minutes. Thereafter, 12.872 g (0.02 g) of 1,4,5,8-naphthalenetetracarboxylic dianhydride was placed in the reactor.
(48 mol), and the mixture in the reactor was heated to 180 ° C. while stirring, and stirred at 180 ° C. for 4 hours.

4. Second polymerization step The temperature of the mixture in the reactor was reduced to 80 ° C.
When the temperature reached ° C, 6.408 g (0.032 mol) of 4,4'-diaminodiphenyl ether was charged into the reactor, and the mixture was stirred at 80 ° C for 2.5 hours. Thereafter, the temperature of the mixture in the reactor is reduced to 60 ° C. and
Stirred at C for 18 hours.

5. Post-treatment step Into the same reactor as above, 55.5 g of m-cresol was charged and heated to 60 ° C. 3. Polyamic acid in the reactor
5 g was divided into three portions and charged at intervals of 30 minutes, followed by stirring. The polyamic acid was dissolved in m-cresol. The resulting solution was cast on a glass plate with a doctor knife thickness of 500 μm. The coating on the glass plate is heated in a thermostat at a heating rate of 10 ° C./min, and heated at 120 ° C. for 1 hour, 200 ° C. for 10 minutes, and 250 ° C. for 10 minutes to obtain polyamic acid. Was imidized. As a result, most of the cured product became a translucent brown-colored film, but it was very brittle and was broken into pieces when the film was peeled off from the glass plate.

[0105]

According to the present invention, a sulfonated polyimide having excellent film-forming properties, large ion exchange group capacity and excellent mechanical strength is suitable for use as an ion exchange membrane for a polymer electrolyte fuel cell. A molecular electrolyte membrane and a method for manufacturing the same are provided. Further, according to the present invention, there is provided a polymer electrolyte fuel cell containing a sulfonated polyimide polymer electrolyte membrane having such excellent properties as a solid polymer electrolyte membrane.

[Brief description of the drawings]

FIG. 1 shows a relationship between dynamic viscoelasticity (mechanical elastic modulus) and temperature of a sulfonated polyimide polymer electrolyte membrane (11) obtained in Example 1 and a commercially available perfluoropolymer electrolyte membrane (12). FIG.

FIG. 2 is a graph showing the relationship between the proton conductivity and temperature of the sulfonated polyimide polymer electrolyte membrane (21) obtained in Example 1 and a commercially available perfluoro-based polymer electrolyte membrane (22).

FIG. 3 is a sectional view showing a basic structure of a polymer electrolyte fuel cell.

[Explanation of symbols]

11: Sulfonated polyimide polymer electrolyte membrane obtained in Example 1 12: Commercially available perfluoropolymer electrolyte membrane 21: Sulfonated polyimide polymer electrolyte membrane obtained in Example 1 22: Commercially available perfluoropolymer electrolyte membrane Polymer electrolyte membrane 31: Ion exchange membrane (solid polymer electrolyte membrane) 32: Gas diffusion electrode layer (cathode) 33: Gas diffusion electrode (anode) 34: Load 35: External circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C08L 79:08 C08L 79:08 Z F term (Reference) 4F071 AA60X AF10 AF12 AF14 AF36 AH12 AH15 FA05 FA09 FB03 FB07 FC01 FD02 4J043 PA04 PA08 PC185 PC186 QB15 QB26 QB31 QB61 RA34 RA39 SA05 SA06 SA36 SA54 SA82 SB02 TA14 TA22 TB01 UA121 UA261 UA262 UA361 UA531 UB121 UB281 UB301 VA011 XA13 XA17 YA05 Z13B01 ZA13B01 ZA13B01 ZA13B01 ZA13B12 ZA11B12 HH00 HH05 HH08

Claims (8)

[Claims] 1. A compound represented by the following formula (I): And a structural unit (I) represented by the following formula (II): Wherein Ar ₁ and Ar ₂ are divalent organic groups which may be the same or different from each other, and Ar ₁ is further substituted with at least one sulfonic acid group. Having a capacity of 1.30 meq / g or more and a tensile rupture stress of 2
A sulfonated polyimide polymer electrolyte membrane having 5 MPa or more and a tensile elongation at break of 3% or more. 2. A reaction between 1,4,5,8-naphthalenetetracarboxylic dianhydride, a diamine compound (A1) having at least one sulfonic acid group and a diamine compound (A2) having no sulfonic acid group. To synthesize a polyamic acid, then, after forming the polyamic acid, in a method for producing a sulfonated polyimide polymer electrolyte membrane to be imidized,
The polyamic acid was subjected to the following steps: (1) 1,4,4 in a mixed solvent of phenol and p-chlorophenol in the presence of triethylamine and benzoic acid.
Reacting 5,8-tetracarboxylic dianhydride with a diamine compound (A1) having at least one sulfonic acid group at a temperature of 150 ° C. or higher, and (2) lowering the temperature of the reaction mixture to 100 ° C. or lower After that, a diamine compound having no sulfonic acid group (A2) was charged, and then 100 ° C.
A method for producing a sulfonated polyimide polymer electrolyte membrane, which is synthesized by a step of continuing a reaction at the following temperature. 3. In the step (1), triethylamine and benzoic acid are each added in an amount of 0.5 to 0.5 mol per 1 mol of the diamine compound (A1) having at least one sulfonic acid group.
3. The method according to claim 2, wherein 3 mol and 0.1 to 1.5 mol are present. 4. The method according to claim 1, wherein in the step (1), 1,4,5,8-
The tetracarboxylic dianhydride and the diamine compound (A1) having at least one sulfonic acid group are reacted at 150 to 190 ° C., and in the step (2), 55 to 100
3. The production method according to claim 2, wherein the reaction is continued at a temperature of ° C. 5. The method according to claim 1, wherein the diamine compound having at least one sulfonic acid group (A1) and the diamine compound having no sulfonic acid group (A2) are used in a molar ratio of 15:85 to 85:15. Item 3. The production method according to Item 2. 6. A sulfonated polyimide polymer electrolyte membrane obtained by the production method according to claim 2. Description: 7. A polymer electrolyte fuel cell comprising the sulfonated polyimide polymer electrolyte membrane according to claim 1 as a solid polymer electrolyte membrane. 8. A polymer electrolyte fuel cell comprising the sulfonated polyimide polymer electrolyte membrane according to claim 6 as a solid polymer electrolyte membrane.