JP2018073651A - Method for manufacturing polymer electrolyte for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polymer electrolyte for a fuel cell, by which a polymer electrolyte of a high molecular weight can be manufactured by a simple synthetic route at low cost.SOLUTION: A method for manufacturing a polymer electrolyte for a fuel cell comprises the step of polymerizing a dihalogen compound including an ion-exchange group, a functional group capable of performing ion exchange, and a dihalogen compound including no ion-exchange group in the coexistence of a catalyst including a transition metal complex, a reductant and an activator operable to activate the reductant, whereby a block copolymer having a segment including an ion-exchange group and a segment including no ion-exchange group can be obtained. The polymer electrolyte for a fuel cell can be manufactured from the block copolymer.SELECTED DRAWING: Figure 1

Description

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

  In recent years, fuel cells have attracted attention as an effective power source for solving environmental problems and energy problems. In a fuel cell, fuel such as hydrogen is oxidized by an oxidant such as oxygen, and chemical energy generated at this time is converted into electric energy. Among the fuel cells, since the polymer main body of the polymer electrolyte fuel cell is small, the polymer electrolyte fuel cell is particularly expected as an in-vehicle power source or a home stationary power source.

  In a polymer electrolyte fuel cell, an electrode reaction proceeds by proton conduction in an electrolyte. As electrolytes for polymer electrolyte fuel cells, many perfluoro electrolytes represented by Nafion (registered trademark) manufactured by DuPont have been proposed so far. However, Nafion requires a complicated synthesis route for production, which increases the production cost of the polymer electrolyte fuel cell. In addition, the glass transition temperature of Nafion is lower than the endurance temperature required for in-vehicle use. Therefore, if a stable membrane that can withstand high temperatures (100 ° C. or higher) is required, such as direct methanol fuel cells (DMFC) and cells that increase the temperature to increase catalytic activity, Nafion is suitable. I can't say that.

  Therefore, development of hydrocarbon polymer electrolytes has been promoted for the electrolytes of the above-described polymer electrolyte fuel cells. Examples of the hydrocarbon polymer electrolyte include aromatic polymers obtained by sulfonating engineering plastics such as sulfonated polyether ether ketone (see Patent Document 1) and sulfonated polyethersulfone (see Patent Document 2), An aromatic copolymer composed of a segment containing an ion exchange group and a segment not containing an ion exchange group (see Patent Document 3) has been proposed. Since these aromatic hydrocarbon polymer electrolytes are easier to manufacture than Nafion, the manufacturing costs can be reduced. Further, the heat resistant temperature is higher than that of Nafion, and it can be used in a high temperature atmosphere.

JP-A-6-93114 JP-A-9-245818 Japanese Patent No. 5295655

  In the spread of fuel cells, an electrolyte membrane that operates under high temperature and low humidity is desired. However, in the aromatic hydrocarbon polymer electrolytes of Patent Documents 1 and 2, when the hydrophilic group in the polymer is increased in order to increase proton conductivity and ion exchange capacity, the electrolyte easily swells with moisture, Mechanical strength decreases.

In Patent Document 3, both proton conductivity and mechanical strength can be achieved. However, aromatic copolymers are synthesized using a transition metal complex catalyst and a reducing agent. However, it is necessary to activate the reducing agent separately before the synthesis, resulting in a complicated synthesis route. Cost is unlikely to be low (see FIG. 3). In addition, the activity of the reducing agent is reduced during the synthesis, and there is a possibility that a high molecular weight polymer electrolyte (aromatic copolymer) cannot be obtained.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polymer electrolyte for a fuel cell capable of producing a high molecular weight polymer electrolyte at a low cost by a simple synthesis route. It is to provide a manufacturing method.

  A method for producing a polymer electrolyte for a fuel cell according to an aspect of the present invention includes a block having an ion exchange group that is a functional group capable of performing ion exchange, and a segment not containing an ion exchange group A method for producing a polymer electrolyte for a fuel cell containing a copolymer, comprising a dihalogen compound containing an ion exchange group and a dihalogen compound containing no ion exchange group, a catalyst containing a transition metal complex, and a reducing agent The present invention includes a polymerization step of polymerizing in the presence of an activator for activating a reducing agent to obtain a block copolymer.

  According to the present invention, a high molecular weight polymer electrolyte can be produced at a low cost by a simple synthesis route.

It is process drawing explaining the manufacturing method of the polymer electrolyte for fuel cells which concerns on one Embodiment of this invention. It is a conceptual diagram explaining the synthetic | combination mechanism in the manufacturing method of the polymer electrolyte for fuel cells which concerns on one Embodiment of this invention. It is process drawing explaining the manufacturing method of the conventional polymer electrolyte for fuel cells.

An embodiment of the present invention will be described with reference to the drawings. The method for producing a polymer electrolyte for a fuel cell according to this embodiment is a method for producing a polymer electrolyte for a fuel cell containing a block copolymer having segments containing ion exchange groups and segments not containing ion exchange groups. Then, a dihalogen compound containing an ion exchange group and a dihalogen compound not containing an ion exchange group are polymerized in the presence of a catalyst containing a transition metal complex, a reducing agent, and an activator that activates the reducing agent. And a polymerization step for obtaining the above-mentioned block copolymer.
The ion exchange group is a functional group capable of performing ion exchange and is a group that contributes to ion conduction when used as a polymer electrolyte. Specific examples include a sulfonic acid group, a phosphoric acid group, and a carboxylic acid group, and a sulfonic acid group is preferable.

  If a polymer electrolyte is produced by the method for producing a polymer electrolyte for a fuel cell according to this embodiment, a polymer electrolyte having a high molecular weight can be produced at a low cost by a simple synthesis route. More specifically, in the prior art, as shown in FIG. 3, a dihalogen compound containing an ion exchange group and a dihalogen compound not containing an ion exchange group are combined in the presence of a catalyst containing a transition metal complex and a reducing agent. Polymerize, but do not allow an activator to activate the reducing agent. In this prior art, an activator (for example, an acid such as an organic acid) is brought into contact with the reducing agent and activated before the polymerization, and the activated reducing agent is used for the polymerization. Accordingly, the synthesis process of the polymer electrolyte has two steps, and it is necessary to remove the activator from the reducing agent before use in the polymerization. Therefore, the synthesis route is complicated and the production cost is not easily lowered.

  In contrast, in the method for producing a polymer electrolyte for a fuel cell according to this embodiment, as shown in FIGS. 1 and 2, a dihalogen compound containing an ion exchange group and a dihalogen compound not containing an ion exchange group are transitioned. Polymerization is performed in the presence of a catalyst containing a metal complex, a reducing agent, and an activator that activates the reducing agent, so that the synthesis process of the polymer electrolyte is a single step, and the reducing agent is used before polymerization. There is no need to remove the activator from. Therefore, a high molecular weight polymer electrolyte can be produced at a low cost by a simple synthesis route. Furthermore, since the activator coexists in the reaction system, and the activator acts on the reducing agent in the reaction system, the activity of the reducing agent is unlikely to decrease during the synthesis of the polymer electrolyte.

Examples of the halogen of the two kinds of dihalogen compounds include fluorine, chlorine, bromine and iodine, and preferably chlorine and bromine.
The transition metal complex is one in which a ligand forms a coordinate bond with a transition metal. Examples of the transition metal complex include a nickel complex, a palladium complex, a platinum complex, a copper complex, a rhodium complex, a zirconium complex, and an iron complex. Among these, when a nickel complex or a palladium complex is used, the reaction efficiency can be increased and the reaction can be performed under mild conditions. The transition metal complex may be a commercially available product or may be synthesized separately. Examples of the method for synthesizing the transition metal complex include a method in which a halide of a transition metal or an oxide of a transition metal is reacted with a ligand and synthesized.

  As the ligand, 2,2′-bipyridyl, 1,10-phenanthroline, N, N, N ′, N′-tetramethylethylenediamine, acetylacetonate, triphenylphosphine, tolylphosphine, tributylphosphine, 1, Any of 2-bis (diphenylphosphino) ethane, 1,3-bis (diphenylphosphino) propane, 1,4-bis (diphenylphosphino) butane, and 1,1′-bis (diphenylphosphino) ferrocene It is preferable to have at least one of these. The transition metal complex may have one of these ligands alone or in combination of two or more.

Examples of the reducing agent include iron, zinc, manganese, aluminum, magnesium, sodium, calcium, and the like. Of these, zinc, magnesium and manganese are preferred.
Examples of the activator include tin, antimony, iodine and the like. In particular, it is preferable to use iodine which dissolves the metal as the reducing agent well.

Below, the manufacturing method of the polymer electrolyte which consists of the above-mentioned block copolymer is demonstrated in detail.
When polymerizing a polymer electrolyte that is a block copolymer, two dihalogen compounds that are monomers are polymerized in the presence of a transition metal complex, a reducing agent, and an activator.
As the transition metal complex, it is more preferable to use a zero-valent transition metal complex such as a zero-valent nickel complex or a zero-valent palladium complex, and it is more preferable to use a zero-valent nickel complex.

Examples of the zerovalent nickel complex include bis (1,5-cyclooctadiene) nickel (0), (ethylene) bis (triphenylphosphine) nickel (0), tetrakis (triphenylphosphine) nickel (0), and the like. Can be mentioned. In particular, bis (1,5-cyclooctadiene) nickel (0) is suitable for use in the synthesis of polymer electrolytes because it is readily available.
As the zero-valent transition metal complex, a commercially available product may be used as described above, or a separately synthesized product may be used. As a method for synthesizing the zero-valent transition metal complex, a known method such as a method of reducing the transition metal compound to a zero valence by using a reducing agent such as zinc or magnesium can be used.

  In synthesizing a zero-valent transition metal complex, a divalent transition metal compound is usually used, but a zero-valent transition metal compound may be used. As the divalent transition metal compound, it is preferable to use a divalent nickel compound or a divalent palladium compound. Examples of the divalent nickel compound include nickel chloride, nickel bromide, nickel iodide, nickel acetate, nickel acetylacetonate, nickel chloride bis (triphenylphosphine), nickel bromide bis (triphenylphosphine), nickel iodide. And bis (triphenylphosphine). Examples of the divalent palladium compound include palladium chloride, palladium bromide, palladium iodide, palladium chloride bis (triphenylphosphine), palladium bromide bis (triphenylphosphine), and palladium iodide bis (triphenylphosphine). Can be mentioned.

  When polymerizing using a transition metal complex, it is preferable to add a compound that can be a ligand of the transition metal complex used in the reaction system. Thereby, the reactivity of a polymerization reaction is improved and the yield of a block copolymer and a polymerization degree are raised. The compound to be added may be the same as or different from the ligand of the transition metal complex used. For example, triphenylphosphine and 2,2'-bipyridyl are preferable because they are versatile and inexpensive. In particular, when 2,2'-bipyridyl is used in combination with bis (1,5-cyclooctadiene) nickel (0), it becomes possible to increase the yield and molecular weight of the block copolymer.

The addition amount of the ligand is preferably 10 mol% or more and 1,000 mol% or less, more preferably 100 mol% or more and 500 mol% or less, with respect to 100 mol% of the zero-valent transition metal complex. .
The usage-amount of a zerovalent transition metal complex is 1 mol% or more with respect to 100 mol% of dihalogen compounds containing the ion exchange group which is a monomer. It can suppress that the yield of a block copolymer and a polymerization degree fall that the usage-amount of a zerovalent transition metal complex is 1 mol% or more. Although there is no restriction | limiting in particular about the upper limit of the usage-amount of a zerovalent transition metal complex, The post-process of superposition | polymerization becomes easy as it is 500 mol% or less.

The amount of the reducing agent used is preferably 10 mol% or more and 10,000 mol% or less, more preferably 100 mol% or more and 5,000 mol% or less with respect to 100 mol% of the zero-valent transition metal complex. preferable.
The amount of the activator used is preferably 0.1 mol% or more with respect to 100 mol% of the reducing agent. When the usage-amount of an activator is 0.1 mol% or more, activation of a reducing agent is fully performed and it can suppress that the yield of a block copolymer and a polymerization degree fall. Although there is no restriction | limiting in particular about the upper limit of the usage-amount of an activator, The post-process of superposition | polymerization becomes easy as it is 100 mol% or less.

  If necessary, sodium compounds such as sodium fluoride, sodium chloride, sodium bromide, sodium iodide and sodium sulfate, and potassium such as potassium fluoride, potassium chloride, potassium bromide, potassium iodide and potassium sulfate Compounds and ammonium compounds such as tetraethylammonium fluoride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, and tetraethylammonium sulfate may be used in combination with the activator.

  As conditions for the polymerization reaction, the reaction temperature is preferably 0 ° C. or higher and 200 ° C. or lower, and more preferably 50 ° C. or higher and 100 ° C. or lower. The reaction time is preferably 0.5 hours or more and 100 hours or less, more preferably 1 hour or more and 40 hours or less. The polymerization reaction is preferably performed in an inert gas atmosphere such as nitrogen or argon. According to such conditions, the yield and degree of polymerization of the block copolymer due to the polymerization reaction are increased.

  As a polymerization solvent for polymerization, for example, aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, sulfolane, toluene, xylene, mesitylene, Aromatic hydrocarbon solvents such as benzene and butylbenzene, ether solvents such as tetrahydrofuran, 1,4-dioxane, dibutyl ether and tert-butyl methyl ether, and ester systems such as ethyl acetate, butyl acetate and methyl benzoate Examples thereof include solvents and alkyl halide solvents such as chloroform and dichloroethane. These polymerization solvents are preferably used after sufficiently dehydrated.

  In order to increase the yield and degree of polymerization of the block copolymer by the polymerization reaction, it is desirable that the block copolymer is sufficiently dissolved in the polymerization solvent. Therefore, tetrahydrofuran, 1,4-dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, toluene, etc., which are good solvents for the block copolymer Is preferably used. In particular, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, and a mixture of two or more of these solvents are preferably used.

  The concentration of the total amount of the dihalogen compound containing an ion exchange group in the polymerization solvent is preferably 1% by mass or more and 90% by mass or less. Moreover, it is preferable that the density | concentration of the total amount of the dihalogen compound which does not contain the ion exchange group in a polymerization solvent is 5 mass% or more and 40 mass% or less. When the lower limit of the monomer concentration is such a value, the produced block copolymer can be easily recovered. In addition, when the upper limit of the monomer concentration is such a value, stirring of the reaction mixture during the reaction becomes easy.

  A block copolymer is synthesized by such a method. When taking out the produced block copolymer from a reaction mixture, a conventional method can be applied. For example, the block copolymer can be precipitated by adding a poor solvent to the reaction mixture, and the target product can be obtained by filtration or the like. Moreover, the obtained block copolymer can be refine | purified by refine | purifying with a normal refinement | purification method as needed. Examples of the purification method include washing with water, reprecipitation using a good solvent and a poor solvent, and the like.

  Further, when the block copolymer is used as an electrolyte membrane for a fuel cell, if the sulfonic acid group in the produced block copolymer is in the form of a salt such as sodium salt, the sulfonic acid group is liberated from the salt. Conversion to the acid form is preferred. Conversion to the free acid is usually performed by washing with an acidic solvent. Examples of the acid used include hydrochloric acid, sulfuric acid, nitric acid and the like, and hydrochloric acid is particularly preferable.

  The amount of ion exchange groups introduced into the polymer electrolyte is preferably 0.5 meq / g or more and 4.0 meq / g or less, expressed as ion exchange capacity, and 1.0 meq / g or more and 3 or less. More preferably, it is 0.0 meq / g or less. When the ion exchange capacity is 0.5 meq / g or more, when used as an electrolyte membrane of a polymer electrolyte fuel cell, proton conductivity is improved, so that the power generation performance of the fuel cell is enhanced. Further, when the ion exchange capacity is 4.0 meq / g or less, water resistance and mechanical strength as an electrolyte membrane of the polymer electrolyte fuel cell are enhanced.

  In addition, the polymer electrolyte has a molecular weight, expressed as a polystyrene-reduced weight average molecular weight, of preferably 10,000 or more and 1,000,000 or less, and more preferably 20,000 or more and 500,000 or less. When the molecular weight is 5000 or more, when used as an electrolyte membrane of a polymer electrolyte fuel cell, the film formability and mechanical strength of the membrane are improved. Moreover, manufacture becomes simpler because molecular weight is 1,000,000 or less.

  Preferable examples of the dihalogen compound containing an ion exchange group used in the method for producing a polymer electrolyte for a fuel cell according to this embodiment include compounds represented by the following formula (1).

However, _{R 1} and _{R 2} in the formula (1) are each _{independently, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH The group consisting of — (CH ₂ ) _a —, — (CF ₂ ) _a —, —O— (CF ₂ ) _a —, —S— (CF ₂ ) _a —, and —NH— (CF ₂ ) _a —. And a is an integer of 2 or more. X ₁ and X ₂ each independently represent a halogen atom, and Y ₁ and Y ₂ are each independently a Group 1 element, Group 2 element, or a hydrocarbon group having 5 to 20 carbon atoms. , Z is a linking group selected from the group consisting of —CO—, —O—, —S—, and —SO ₂ —.

Specific examples of Y ₁ and Y ₂ in the above formula (1) include group ions such as hydrogen ions, lithium ions, sodium ions, potassium ions, rubidium ions, magnesium ions, calcium ions, strontium ions, barium ions. Group II element ions such as n-hexyl group, cyclohexyl group, 2-ethylhexyl group, n-pentyl group, iso-pentyl group, tert-pentyl group, n-heptyl group, tert-heptyl group, n- Examples thereof include hydrocarbon groups such as octyl group, sec-octyl group, cyclopentylmethyl group, cyclopentylethyl group, cyclohexylmethyl group, and tetrahydrofurfuryl group. Y ₁ and Y ₂ may be different, but the same one facilitates the synthesis of a dihalogen compound containing an ion exchange group. In order to facilitate the production of the block copolymer, Y ₁ and Y ₂ are preferably Group 1 element ions and hydrocarbon groups.

X ₁ and X ₂ in the above formula (1) are groups composed of halogen atoms such as fluorine, chlorine, bromine and iodine. X ₁ and X ₂ may be different atoms, but synthesis of the dihalogen compound of the above formula (1) becomes easier when they are the same atom. In order to facilitate the production of the block copolymer, X ₁ and X ₂ are preferably chlorine or bromine. Whether X ₁ and X ₂ are chlorine or bromine is selected according to the polymerization method.

The dihalogen compound of the above formula (1) includes R ₁ and R ₂ that are linking groups between the —SO ₃ Y ₁ group and the —SO ₃ Y ₂ group and the benzene ring. R ₁ and R ₂ are linking groups as described above, but in order to facilitate the synthesis of the dihalogen compound of the above formula (1), R ₁ and R ₂ are —O— (CH ₂ ) _a —. And a is preferably 3 or 4. R ₁ and R ₂ may be different linking groups, but synthesis of the dihalogen compound of the above formula (1) becomes easier when they are the same linking group.

  Generally, a polyarylene type polymer electrolyte whose main chain is composed of an aromatic ring has an ion exchange group directly bonded to the aromatic ring. In such a structure, since the main chain itself has hydrophilicity and the stack of polymer main chains is inhibited, the presence of water molecules around the main chain is stabilized, resulting in swelling of the polymer electrolyte. The term “stack” means that polymer main chains are physically connected by weak interaction such as van der Waals force.

On the other hand, in the dihalogen compound of the above formula (1), the ion exchange group and the benzene ring are kept away by providing the linking groups R ₁ and R ₂ . Therefore, in the polymer electrolyte using the dihalogen compound of the above formula (1) as a monomer, a decrease in water resistance is suppressed, and swelling hardly occurs.
Preferable examples of the dihalogen compound containing no ion exchange group used in the method for producing a polymer electrolyte for a fuel cell according to this embodiment include compounds represented by the following formula (2).

However, Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ in formula (2) are each independently a divalent aromatic group, and B ₁ and B ₂ are each independently a single bond or 2 C ₁ and C ₂ each independently represent an oxygen atom or a sulfur atom. X ₃ and X ₄ each independently represent a halogen atom, b, c, d and e are each independently 0 or 1, and n is an integer of 5 or more.

Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ in the above formula (2) are substituted with a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a nitrile group, or the like. It may be a divalent aromatic group. In addition, these alkyl groups and alkoxy groups may have a substituent.

When B ₁ or B ₂ in the above formula (2) is a divalent linking group, B ₁ and B ₂ are a carbonyl group, a sulfonyl group, a 2,2-isopropylidene group, a 2,2-hexafluoroisopropylate. A linking group based on a redene group or a 9,9-2 substituted fluorene is preferred.
N in the above formula (2) is an integer of 5 or more, preferably 5 or more and 200 or less, and more preferably 10 or more. When n is 5 or more, when the polymer electrolyte is used as an electrolyte membrane of a polymer electrolyte fuel cell, sufficient film formability, mechanical strength, and durability can be obtained.

X ₃ and X ₄ in the above formula (2) are groups composed of halogen atoms such as fluorine, chlorine, bromine and iodine. X ₃ and X ₄ may be different halogen atoms, but synthesis of the dihalogen compound of the above formula (2) becomes easier when they are the same halogen atom. In order to facilitate the production of the block copolymer, X ₁ , X ₂ , X ₃ and X ₄ are preferably the same halogen atom, and preferably chlorine or bromine. Whether X ₁ , X ₂ , X ₃ , or X ₄ is chlorine or bromine is selected according to the polymerization method.
Specific examples of the dihalogen compound not containing an ion exchange group represented by the above formula (2) are listed below by chemical formula.

  The method for producing a polymer electrolyte for a fuel cell according to the present invention will be further described below with reference to specific examples. The obtained polymer electrolyte (block copolymer) was evaluated by molecular weight measurement and ion exchange capacity measurement.

<Molecular weight measurement>
The molecular weight of the polymer electrolyte was measured by gel permeation chromatography (GPC). The measurement conditions are as follows.
GPC device: GPC device HLC-8120 manufactured by Tosoh Corporation
Column: TSKgel SuperAWM-H (6.0 mm ID × 15 cm) connected in series. Detector: Differential refractometer (RI detector), Polarity = (+)
・ Eluent: N, N-dimethylformamide + LiBr + phosphoric acid ・ Flow rate: 0.6 mL / min
-Column temperature: 40 ° C
Sample concentration: 1 mg / mL
Sample injection volume: 20 μL

<Ion exchange capacity measurement>
After drying the polymer electrolyte in which the sulfonic acid group, which is an ion exchange group, is in a free acid state, a predetermined amount was weighed, stirred in a 2M aqueous sodium chloride solution overnight, and filtered. The filtrate was titrated with a standard solution of NaOH using phenolphthalein as an indicator, and the ion exchange capacity was determined from the neutralization point.

<Synthesis of dihalogen compounds containing ion exchange groups>
50 g (157 mmol) of bis (5-chloro-2-hydroxyphenyl) sulfone was placed in an eggplant flask, and 660 g of absolute ethanol was added and dissolved. To this solution, 26.69 g (667 mmol) of sodium hydroxide was added and stirred at 80 ° C. for 30 minutes. Next, 72.49 g (593 mmol) of 1,3-propane sultone was added to the stirred solution, and the mixture was heated to reflux for 10 hours. The precipitated white solid was collected by filtration. The collected solid was washed with a water / ethanol solution and then filtered again, and the filtrate was collected and dried under reduced pressure to obtain 67.53 g (white solid, yield: 65%) of the target compound, M1, represented by the following formula. )Obtained.

<Synthesis of dihalogen compound containing no ion exchange group>
In a three-necked flask, 7.40 g (25.7 mmol) of 4,4′-dichlorodiphenylsulfone, 7.83 g (23.3 mmol) of 2,2′-bis (4-hydroxyphenyl) hexafluoropropane, 4.20 g of potassium carbonate ( 30.3 mmol) was added, and the atmosphere was replaced with nitrogen. 150 mL of N, N-dimethylacetamide (DMAc) and 20 mL of toluene were added, and the mixture was refluxed with heating, and reacted while removing water in the system.

  After completion of the above reaction, 1.00 g (3.48 mmol) of 4,4′-dichlorodiphenylsulfone was added and the reaction was further carried out at 180 ° C. for 3 hours. The solution after completion of the reaction was poured into methanol for reprecipitation. The precipitate was collected by filtration, washed with water, and dried under reduced pressure at 105 ° C. for 2 hours. The collected solid was dissolved again in chloroform and poured into methanol for reprecipitation. The precipitate was collected by filtration and then dried under reduced pressure at 105 ° C. for 3 hours to obtain the desired product, which is compound M2 represented by the following formula. The obtained solid had a molecular weight (Mw) of 20,000.

<Polymer electrolyte synthesis (polymerization)>
[Example 1]
A polymerization reaction between a dihalogen compound (M1) containing an ion exchange group and a dihalogen compound (M2) containing no ion exchange group was carried out. Under nitrogen, 38.8 g of dehydrated dimethyl sulfoxide, 3.85 g (6.1 mmol) of a dihalogen compound containing an ion exchange group (6.1 mmol), a dihalogen compound containing no ion exchange group (M2), 1. 48 g, NiCl ₂ (bpy) 0.174 g (0.61 mmol), 2,2′-bipyridyl 0.114 g (0.73 mmol), zinc powder 1.60 g (24.4 mmol), iodine 0.037 g (0.15 mmol) ) Was added and dissolved at 40 ° C.

  After confirming that all were dissolved, the temperature was raised to 65 ° C. and stirred for 24 hours. The solution after the reaction was added dropwise to methanol to precipitate a polymer, which was collected by filtration. The recovered polymer was washed with methanol again and protonated by stirring in 3N hydrochloric acid. The polymer was collected again by filtration, washed with water, and then dried under reduced pressure at 80 ° C. for 2 hours to obtain a polymer electrolyte P1 represented by the following formula.

[Example 2]
A polymer electrolyte P1 was synthesized in the same manner as in Example 1 except that iron powder was used instead of zinc powder.
[Example 3]
A polymer electrolyte P1 was synthesized in the same manner as in Example 1 except that manganese powder was used instead of zinc powder.

[Example 4]
A polymer electrolyte P1 was synthesized in the same manner as in Example 1 except that magnesium powder was used instead of zinc powder.
[Comparative example]
A polymer electrolyte P1 was synthesized in the same manner as in Example 1 except that iodine as an activator was not used and zinc powder activated separately was used. The zinc powder was activated by adding zinc powder to an aqueous hydrochloric acid solution, filtering, and washing with ethanol and diethyl ether.

[Evaluation results]
About the polymer electrolyte P1 obtained in Examples 1-4 and the comparative example, the molecular weight and the ion exchange capacity were measured. The results are shown in Table 1. The polymer electrolyte P1 obtained in Examples 1 to 4 had a higher molecular weight than the polymer electrolyte P1 obtained in the comparative example. Moreover, it had an ion exchange capacity as high as that of the comparative example.

  With the method for producing a polymer electrolyte for a fuel cell according to the present invention, a polymer electrolyte exhibiting a high molecular weight and an acid value can be produced by a simple synthesis route and at a low cost.

Claims (6)

A method for producing a polymer electrolyte for a fuel cell, comprising a block copolymer having a segment containing an ion exchange group, which is a functional group capable of performing ion exchange, and a segment not containing the ion exchange group. And
Polymerizing the dihalogen compound containing the ion exchange group and the dihalogen compound not containing the ion exchange group in the presence of a catalyst containing a transition metal complex, a reducing agent, and an activator for activating the reducing agent. A method for producing a polymer electrolyte for a fuel cell, comprising a polymerization step of obtaining the block copolymer.   The method for producing a polymer electrolyte for a fuel cell according to claim 1, wherein the activator is iodine.   The method for producing a polymer electrolyte for a fuel cell according to claim 1 or 2, wherein the catalyst is a zero-valent nickel complex.   The method for producing a polymer electrolyte for a fuel cell according to any one of claims 1 to 3, wherein the reducing agent is at least one of iron, zinc, manganese, and magnesium. The method for producing a polymer electrolyte for a fuel cell according to any one of claims 1 to 4, wherein the dihalogen compound containing the ion exchange group is a compound represented by the following formula (1).

However, _{R 1} and _{R 2} in the formula (1) are each _{independently, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH- _{(CH 2) a -, -} (CF 2) a -, - O- (CF 2) a -, - S- (CF 2) a -, and, -NH- _{(CF 2) a} - from the group consisting of The linking group to be selected is shown, and a is an integer of 2 or more. X ₁ and X ₂ each independently represent a halogen atom, and Y ₁ and Y ₂ are each independently a Group 1 element, Group 2 element, or a hydrocarbon group having 5 to 20 carbon atoms. , Z is a linking group selected from the group consisting of —CO—, —O—, —S—, and —SO ₂ —. The method for producing a polymer electrolyte for a fuel cell according to any one of claims 1 to 5, wherein the dihalogen compound containing no ion exchange group is a compound represented by the following formula (2).

However, Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ in formula (2) are each independently a divalent aromatic group, and B ₁ and B ₂ are each independently a single bond or 2 A valent connecting group, C ₁ and C ₂ are each independently an oxygen atom or a sulfur atom, X ₃ and X ₄ are each independently a halogen atom, b, c, d, and e are , Each independently 0 or 1, and n is an integer of 5 or more.

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