JP2008147001A - Polymer electrolyte - Google Patents

Abstract

A hydrocarbon electrolyte exhibiting excellent proton conductivity without depending on humidity or temperature is provided.
A polyphenylene polymer having a polymer unit containing an electron-withdrawing group, an electron-donating group, and a sulfonated aromatic group in the molecule, and an ion exchange capacity of 2.8 to 3.8 meq / g. A polymer electrolyte characterized by being: By introducing a certain amount of the sulfonic acid group into the side chain of the polyphenylene polymer, the ion exchange capacity is increased (proton conductivity is improved) without dissolving in water.
[Selection] Figure 1

Description

  The present invention relates to a polymer electrolyte and a fuel cell using the same.

  A polymer electrolyte fuel cell (PEFC) has attracted attention as a power source that can reduce the release of environmentally hazardous gas from the power source. In PEFC, a power generation reaction proceeds by proton conduction in the battery. The presence of water is indispensable for proton conduction in PEFC, and therefore a humidifier is required to advance the power generation reaction of PEFC. When a fuel cell is applied to a vehicle or the like, since a humidifier is desired to be small from the viewpoint of in-vehicle performance, an electrolyte that can perform proton conduction well even under low humidification is required. Fluoropolymer electrolytes represented by Nafion (registered trademark, manufactured by DuPont) and Aciplex (registered trademark, manufactured by Asahi Kasei) have excellent proton conductivity under low humidity and are widely used in PEFC. Material.

  However, since the fluororesin electrolyte is a polymer material made of fluorine, it has a problem in terms of recyclability. Considering the widespread use of fuel cell vehicles, the question of whether or not it can be recycled is important, and the environmental impact of materials that cannot be recycled cannot be ignored. Furthermore, when a fluorine resin electrolyte is applied alone as an electrolyte membrane, there is a problem in terms of high temperature durability. Therefore, the need for an alternative material for the fluororesin electrolyte is increasing.

  In recent years, hydrocarbon-based electrolytes have been developed as an alternative material. Hydrocarbon materials generally have higher temperature durability than fluororesin electrolytes and are expected to replace fluororesin electrolytes.

For example, Patent Documents 1 to 3 report sulfonated engineering plastics as hydrocarbon-based electrolytes. The proton conductivity of the sulfonated engineering plastic exhibits proton conductivity equivalent to that of the fluororesin electrolyte under high humidification conditions, but the proton conductivity under low humidification conditions is significantly reduced. Under such circumstances, Patent Documents 4 and 5 report polyphenylene-based electrolyte materials as electrolytes having excellent proton conductivity even under low humidification conditions.
JP-A-6-93114 JP-A-9-245818 Japanese Patent Laid-Open No. 11-116679 US Pat. No. 5,403,675 JP 2005-149810 A

  For example, the sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) (PPBP) reported in Patent Document 4 and the polyphenylene polymer reported in Patent Document 5 are compared to other hydrocarbon electrolytes. Although the proton conduction under low humidification is remarkably improved, the proton conduction under low humidification of the fluorine-based resin electrolyte is not enough. Accordingly, an object of the present invention is to provide a hydrocarbon electrolyte exhibiting excellent proton conductivity without depending on humidity and temperature.

  As a result of intensive studies, the present inventors have found that the above problem can be solved by using a polyphenylene polymer having a specific ion exchange capacity.

  That is, the present invention provides a polymer electrolyte having a polymer unit represented by the following chemical formula (1) and having an ion exchange capacity of 2.8 to 3.8 meq / g;

In the formula, A represents an electron-withdrawing group, B ₁ and B ₂ represent an electron-donating group, Ar ₁ and Ar ₂ represent an aromatic group, and k and m represent a number of 0 or more (provided that k and m are not 0 at the same time), and x and y are integers of 0 or more (provided that x and y are not 0 at the same time);

  When the polyphenylene polymer of the present invention is applied as an electrolyte of a fuel cell, it exhibits excellent proton conductivity without depending on humidity, and thus can be applied to vehicles and the like that require adaptability to the operating environment. In addition, the polyphenylene polymer of the present invention can reduce the environmental load as compared with conventional fluororesin electrolytes.

  Generally, in a carbon-hydrogen electrolyte, in order to improve proton conduction, if the ion exchange capacity of the electrolyte is increased, that is, if the number of sulfo groups (sulfonic acid groups) is increased, the electrolyte dissolves in water. There was a problem of doing. Moreover, it was difficult to introduce a large number of sulfo groups into PPBP because of the molecular structure. The present inventors paid attention to the water resistance in the vicinity of the main chain of the polyphenylene polymer, and introduced a certain amount of sulfonic acid group into the side chain of the polyphenylene polymer, thereby eliminating the ion exchange capacity without dissolving in water. The increase in proton conductivity (improvement of proton conductivity) was found. Further, the present inventors have found that proton conduction is remarkably improved even under low humidification by setting the amount of sulfo group of the polyphenylene polymer within a certain range.

  The polymer electrolyte of the present invention has the following chemical formula (1);

It has a polymer unit represented by.

In the chemical formula (1), A represents an electron withdrawing group. Examples of the electron withdrawing group include a carbonyl group, a sulfonyl group, a sulfinyl group, a carboxylate group (—COO—), an amide group, — (CF ₂ ) ₁ — (where l is an integer of 1 to 10), —C (CF ₃ ) ₂ — and the like can be mentioned. Among these, A is preferably a carbonyl group, a sulfonyl group, a sulfinyl group, a carboxylic acid ester group (—COO—) or an amide group, and since A is highly hydrolyzable, a carbonyl group, a sulfonyl group It is more preferable that

In the chemical formula (1), B ₁ and B ₂ each independently represent an electron donating group. B ₁ and B ₂ may be the same or different, but it is preferable that B ₁ and B ₂ are the same electron donating group. Examples of the electron donating group include an alkylene group such as a methylene group, an ethylene group, and an isopropylene group, an ether group, —S—, —CH═CH—, —C—C≡C—, or the following chemical formula (3). And the like.

  Of these, an ether group having a lower chemical reactivity to radical species, -S-, is preferred, and an ether group is more preferred.

In the chemical formula (1), Ar ₁ and Ar ₂ each independently represent an aromatic group. Ar ₁ and Ar ₂ may be the same or different. The aromatic group is not particularly limited, but an aromatic hydrocarbon group having 6 to 16 carbon atoms such as a phenyl group, a naphthyl group, an anthracenyl group, a phenanthryl group, a naphthacenyl group, a pyrenyl group, or a biphenylene group; An aromatic heterocyclic group such as a benzofuranyl group, an isobenzofuranyl group, or a carbazolyl group, and the like can be given. Especially, in order to introduce | transduce a sulfo group efficiently, an aromatic hydrocarbon group is preferable and it is more preferable that it is a phenyl group.

In the chemical formula (1), k represents a number of 0 or more, preferably 1 or more and 5 or less, more preferably 1 or more and 3 or less, and most preferably 1. m represents a number of 0 or more, preferably 1 or more and 5 or less, more preferably 1 or more and 3 or less, and most preferably 1. Note that k and m are not 0 at the same time. In the case of k = 0, end is a hydrogen atom (i.e. _-B 2 H).

  In the chemical formula (1), x and y each independently represent an integer of 0 or more. Note that x and y are not 0 simultaneously. x and y define the introduction amount of the sulfo group of the polyphenylene polymer, and are designed so that the ion exchange capacity of the polymer electrolyte of the present application is 2.8 to 3.8 meq / g. Therefore, if the ion exchange capacity of the polymer electrolyte is 2.8 to 3.8 meq / g, x and y are not particularly limited, but each polymer unit represented by the following formula (1) It is preferable to determine x and y so that the average value of S values is preferably 2.5 or more and 3.8 or less, more preferably 2.9 or more and 3.5 or less.

Here, molecular weight of M _B1 : B ₁ site, molecular weight of M _B2 : B ₂ site, molecular weight of M _Ar1 : Ar ₁ site, molecular weight of M _Ar2 : Ar ₂ site, molecular weight of Mso _3H : SO ₃ H (= 81 .1), Mn: molecular weight of the site represented by the following chemical formula (4).

  It is preferable for the S value to be in the above range because the polymer electrolyte has water solubility resistance regardless of the structure other than the main chain.

  In addition, although the polymer unit which comprises the polymer electrolyte of this invention may be 1 type, or 2 or more types may be sufficient, it is preferable that it is 1 type from a viewpoint of industrial productivity.

  The polymer electrolyte of the present invention preferably has the above polymer unit preferably 250 or more, more preferably 350 or more, and still more preferably 500 or more. When the degree of polymerization is within this range, it is preferable because the production of the polymer electrolyte is easy and the introduction amount can be easily adjusted when the sulfo group is introduced into the polymer.

  The polymer electrolyte of the present invention has an ion exchange capacity of 2.8 to 3.8 meq / g, preferably 2.8 to 3.5 meq / g, more preferably 3.0 to 3.3 meq / g. It is. Conventionally used PPBP has a problem that proton conduction under low humidification is inferior to that of fluorine resin electrolyte even though proton conduction under high humidification is equivalent to that of fluorine resin electrolyte. As a result of studying this cause, the present inventors have found that the conventional PPBP has an ion exchange capacity of about 2.7 meq / g, and this low ion exchange capacity is a cause of a decrease in proton conduction under low humidification. As a result, the present invention was reached.

  In the present invention, by setting the ion exchange capacity to 2.8 meq / g or more, proton conduction under low humidification is remarkably improved. Further, it is a feature of the polyphenylene electrolyte that the film size can be maintained even at a high temperature (usually 130 ° C. or higher) as compared with the fluorine resin electrolyte. The polyphenylene electrolyte having an ion exchange capacity of 2.8 to 3.8 meq / g not only maintains the membrane dimensions even at 100 ° C. or higher when water starts to evaporate, but also adsorbs more water than the conventional polyphenylene electrolyte. Has a large amount of retained water and is excellent in proton conduction at high temperatures. Moreover, it is excellent in water-resistant dissolution because the ion exchange capacity of the polymer electrolyte is 3.8 meq / g or less. An ion exchange capacity of 2.8 to 3.8 meq / g can be obtained by appropriately adjusting the amount of sulfo group introduced.

  The ion exchange capacity refers to the number of moles of sulfo groups present per 1 g of the polymer electrolyte membrane. Specifically, the value measured by the method described in the examples is adopted in the present application.

  In the polymer electrolyte of the present invention, the polymer unit represented by the chemical formula (1) is preferably 50% by mass or more, more preferably 80% by mass or more with respect to 100% by mass of the total electrolyte. More preferably, it is 100% by mass.

  The weight average molecular weight of the polymer electrolyte of the present invention is not particularly limited, but the weight average molecular weight is preferably from 100,000 to 500,000 as measured by GPC (gel permeation chromatograph) of an unsulfonated compound. More preferably, it is 200,000 to 500,000. In addition, the weight average molecular weight shall employ | adopt what was calculated on the conditions of GPC described in the following table | surfaces.

[Production method]
The method for producing the polymer electrolyte of the present invention is not particularly limited, and can be produced by appropriately referring to conventionally known knowledge. For example, the manufacturing method which superposes | polymerizes after the monomer of the following compound (2) is mentioned.

In the chemical formula (2), A, B ₁ , B ₂ , Ar ₁ , Ar ₂ , k, and m are the same as those defined in the chemical formula (1), and X ₁ and X ₂ are respectively Independently, it is either a chlorine atom, a bromine atom, or an iodine atom. X ₁ and X ₂ may be the same or different, but are preferably the same.

  Although the manufacturing method of the monomer of a compound (2) is not specifically limited, For example, when the electron withdrawing group represented by A is a carbonyl group, it can synthesize | combine as follows. First, the following compound (A) is prepared.

Here, A is synonymous with that defined in chemical formula (1), and X ₁ , X ₂ and X ₃ are each independently any one of a chlorine atom, a bromine atom and an iodine atom. A compound (A) may be used independently and may use 2 or more types together. A is a carbonyl group, a sulfonyl group, a sulfinyl group, a carboxylic ester group (—COO—), an amide group, — (CF ₂ ) ₁ — (where l is an integer of 1 to 10), —C (CF ₃ ) _2. -Is preferable, and a carbonyl group or a sulfonyl group is more preferable. From the viewpoint of reaction efficiency, the compound represented by the compound (A) is preferably 2,5-dichlorobenzoyl chloride. 2,5-dichlorobenzoyl chloride can be produced, for example, by the method described in US Pat. No. 5,403,675.

  Next, a compound (2) can be obtained by making a compound (A) and the following compound (B) react.

In the above formula, B ₁ , B ₂ , Ar ₁ , Ar ₂ , k and m are as defined in the above chemical formula (1). The reaction conditions in this case are not particularly limited, but the reaction temperature is preferably 25 to 80 ° C., more preferably 40 to 70 ° C., the reaction time is preferably 8 to 48 hours, and more preferably 16 to 32. Reaction takes place in time. The pressure during the reaction is not particularly limited, and may be any of under pressure, normal pressure (atmospheric pressure), or reduced pressure, and may be appropriately set depending on circumstances, but is preferably under normal pressure. The atmosphere in which the reaction is performed is not particularly limited, but it is preferably performed in an inert gas atmosphere such as argon gas or nitrogen gas. A compound (B) may be used independently and may use 2 or more types together. From the viewpoint of reaction efficiency and proton conduction of the resulting polymer, the compound represented by the compound (B) is preferably 1,4-diphenoxybenzene.

  The compound (B) is preferably 50 to 100 mol% and more preferably 80 to 100 mol% with respect to 100 mol% of the compound (A).

  The catalyst used at this time may be a Lewis acid catalyst, and an example of the Lewis acid catalyst is anhydrous aluminum chloride. The catalyst is preferably 100 to 200 mol%, more preferably 100 to 150 mol%, relative to 100 mol% of the compound (A).

  The monomer thus obtained can be purified by recrystallization using a solvent such as cyclohexane.

  The polymerization of the monomer is not particularly limited, but it is preferable to react in the presence of a specific catalyst. The catalyst used in this case is a catalyst system containing a transition metal compound. The catalyst system includes a ligand component, a transition metal complex coordinated with a ligand (including a copper salt), and a reducing agent. May be added as an essential component, and a salt may be added to increase the polymerization rate.

  Examples of the ligand component include triphenylphosphine, 2,2′-bipyridine, 1,5-cyclooctadiene, 1,3-bis (diphenylphosphino) propane, and the like. Of these, triphenylphosphine and 2,2'-bipyridine are preferred. The compound which is the said ligand component may be used individually by 1 type, and may use 2 or more types together. The ligand component is preferably 1 to 100 mol% and more preferably 1 to 20 mol% with respect to 100 mol% of the monomer.

  Examples of transition metal complexes in which a ligand is coordinated include nickel chloride bis (triphenylphosphine), nickel bromide bis (triphenylphosphine), nickel iodide bis (triphenylphosphine), and nickel nitrate bis (tri Phenylphosphine), nickel chloride (2,2′-bipyridine), nickel bromide (2,2′-bipyridine), nickel iodide (2,2′-bipyridine), nickel nitrate (2,2′-bipyridine), Bis (1,5-cyclooctadiene) nickel, tetrakis (triphenylphosphine) nickel, tetrakis (triphenylphosphite) nickel, tetrakis (triphenylphosphine) palladium, or the like can be given. Of these, nickel chloride bis (triphenylphosphine) and nickel chloride (2,2'-bipyridine) are preferred. The transition metal complex is preferably 1 to 100 mol% and more preferably 1 to 20 mol% with respect to 100 mol% of the monomer.

  Examples of the reducing agent that can be used in the catalyst system include iron, zinc, manganese, aluminum, magnesium, sodium, and calcium. Of these, zinc, magnesium and manganese are preferred. These reducing agents can be used after being more activated by bringing them into contact with an acid such as an organic acid. The reducing agent is preferably 1 to 100 mol% and more preferably 10 to 30 mol% with respect to 100 mol% of the monomer.

  Examples of salts that can be used in the above catalyst system include sodium compounds such as sodium fluoride, sodium chloride, sodium bromide, sodium iodide, sodium sulfate; potassium fluoride, potassium chloride, potassium bromide, iodide. Examples include potassium compounds such as potassium and potassium sulfate; ammonium compounds such as tetraethylammonium fluoride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, and tetraethylammonium sulfate. Of these, sodium bromide, sodium iodide, potassium bromide, tetraethylammonium bromide, and tetraethylammonium iodide are preferred. The salt is preferably 1 to 100 mol% and more preferably 10 to 30 mol% with respect to 100 mol% of the monomer.

  Examples of the solvent used in the polymerization include tetrahydrofuran, cyclohexanone, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, N , N′-dimethylimidazolidinone and the like. Of these, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and N, N'-dimethylimidazolidinone are preferred. These polymerization solvents are preferably used after sufficiently dried.

  The polymerization temperature and polymerization time during the polymerization are not particularly limited, and may be appropriately set depending on the molecular weight, the polymerization concentration, and the like. For example, when it is intended to obtain a polymer having a weight average molecular weight of 100 to 500,000, the polymerization temperature is preferably 25 to 80 ° C., more preferably 40 to 70 ° C., and the polymerization time is preferable from the viewpoint of reaction efficiency. Is carried out in 8 to 40 hours, more preferably 16 to 32 hours. The polymerization pressure during the polymerization is not particularly limited, and may be any of under pressure, normal pressure (atmospheric pressure), or reduced pressure, and may be appropriately set depending on the case, but is preferably under normal pressure.

  As a method of sulfonation, a method using a known sulfonating agent such as sulfuric acid, sulfuric anhydride, fuming sulfuric acid, chlorosulfonic acid, or sodium sulfite, or a method of oxidizing the polymer through a thiol compound is used. Thus, sulfonation can be performed.

  If the ion exchange capacity of the finally obtained polymer is 2.8 to 3.8 meq / g, the conditions for sulfonation are not particularly limited, but the temperature is usually 25 to 80 ° C., preferably 25 to 40. The sulfonation is carried out at a temperature of 5 ° C. for 5 to 100 hours, preferably 24 to 60 hours. Moreover, it is preferable to carry out in inert gas atmosphere, such as argon gas and nitrogen gas. Moreover, when performing sulfonation, you may carry out using a solvent or under absence of solvent. Furthermore, the amount of the sulfonating agent used can be appropriately adjusted according to the reactivity of the sulfonating agent. For example, when sulfuric acid is used, it is preferably used in a range of 10 to 100 moles relative to the monomer equivalent to which a sulfo group is to be introduced. The amount of the sulfonating agent at this time is adjusted according to the ion exchange capacity of the electrolyte resin described later.

  A method for producing a polymer electrolyte membrane using the polymer electrolyte thus obtained is not particularly limited. For example, the polyphenylene electrolyte of the present invention is dissolved in a solvent to form a solution, and then cast. The casting method etc. which cast on a base | substrate and shape | mold into a film form are mentioned.

  In film formation, the viscosity is preferably 10 to 10000 mPa · s, more preferably 10 to 1000 mPa · s. Within the above range, the residual amount of solvent is small, and there is a low risk of generating a large amount of bubbles when the solution is dried, and the unevenness in thickness can be reduced due to the leveling effect, ensuring stable proton conductivity. Is done.

  The electrolyte concentration at this time is usually 2.5 to 50% by mass, preferably 7 to 25% by mass, although it depends on the molecular weight. If it is in the said range, it is excellent in film forming property.

  Examples of the solvent used in this case include N-methyl-2-pyrrolidone, N, N-dimethylformamide, γ-butyrolactone, N, N-dimethylacetamide, dimethyl sulfoxide, dimethylurea, dimethylimidazolidinone and the like. Aprotic polar solvents, alcohol solvents such as methanol, ethanol, propyl alcohol, iso-propyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone. These solvents may be used alone or in combination of two or more. Moreover, you may use what added water to these solvents. Among these mixtures, a mixture of methanol and an aprotic polar solvent is preferable because it has an effect of reducing the solution viscosity in a wide composition range.

  The polymer solution whose viscosity is adjusted is cast onto a substrate. Examples of the substrate to be cast include metal materials such as aluminum, steel, and nickel, glass, ceramics, and plastics. The shape of the substrate is not particularly limited, and a desired shape such as a plate shape, a disk shape, a film shape, a metal foil shape, a pool shape, a corrugated plate shape, a tubular shape, or the like can be used. Further, the base material may be left standing or may be moved in a straight line, translation, rotation, amplitude, or the like at a constant speed or acceleration.

  In the temperature distribution on the surface of the substrate on which the polymer solution is cast, the difference between the maximum temperature and the minimum temperature in the vertical component in the resin traveling direction is preferably within 30 ° C, more preferably within 20 ° C. If the temperature distribution on the surface of the substrate is too large, the drying speed of the polymer solution is different, so that the polymer may aggregate at a portion where the drying speed is high. For this reason, there exists a possibility that a film thickness may become non-continuously nonuniform.

  The film formed on the substrate is preferably heated and dried at 25 to 140 ° C. for 0.1 to 24 hours to obtain a polymer electrolyte membrane.

  The polymer electrolyte and polymer electrolyte membrane of the present invention can be used for fuel cells. In this case, a significant reduction in electrical energy loss can be achieved.

  In particular, the polymer electrolyte of the present invention can be used as an electrolyte contained in a catalyst layer including a catalyst component and a conductive carrier that supports the catalyst component. In this case, the polymer electrolyte of the present invention is contained in the catalyst layer in an amount of preferably 25 to 100% by mass, more preferably 35 to 85% by mass with respect to 100% by mass of the catalyst component. Further, it can be used in combination with the polymer electrolyte of the present invention. A conventionally well-known thing can be used for the electroconductive support | carrier which carry | supports the said catalyst component and catalyst component.

  As for other members constituting the fuel cell, a conventionally known configuration in the field of the fuel cell can be employed as it is or after being appropriately modified. An example of the application is PEFC. In the current-voltage output process when the polymer electrolyte and / or polymer electrolyte membrane of the present invention is used as a constituent material constituting the PEFC, an effect showing a higher output density than that of a conventional fluororesin electrolyte is obtained. The PEFC has a configuration in which a separator, a gas diffusion layer, a cathode catalyst layer, an electrolyte membrane, an anode catalyst layer, a gas diffusion layer, and a separator are arranged in this order. However, the basic configuration of the PEFC is not limited to the above, and the present invention can also be applied to PEFCs having other configurations.

  The method for producing the fuel cell of the present invention is not particularly limited, and can be produced by appropriately referring to conventionally known knowledge in the field of fuel cells.

  The type of fuel for the fuel cell is not particularly limited. For example, hydrogen, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, secondary butanol, tertiary butanol, dimethyl ether, diethyl ether, ethylene glycol, Diethylene glycol or the like can be used. Of these, hydrogen and methanol are preferred because they can increase the output.

  Furthermore, a stack in which a plurality of membrane electrode assemblies are stacked via a separator and connected in series may be formed so that the fuel cell can obtain a desired voltage or the like. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  The application application of the fuel cell is not particularly limited, but it is preferably applied to a vehicle. Since the polymer electrolyte of the present invention is excellent in proton conductivity under low humidification, it is possible to reduce the size of the humidifier, which is particularly advantageous when the fuel cell is applied to a vehicle from the viewpoint of in-vehicle use. is there.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to the following Example.

(Example 1) Synthesis and film formation of sulfonated poly (4- (4-phenoxy) -phenoxybenzoyl-1,4-phenylene) (1) Synthesis of 2,5-dichlorobenzoyl chloride: By adding 87.3 g of 5-dichlorobenzoic acid, 271.8 g of thionyl chloride and 3 ml of dimethylformamide and stirring with heating at 45 ° C. for 4 hours, 2,5-dichlorobenzoyl chloride was obtained.

  (2) Synthesis of 2,5-dichloro-4- (4-phenoxy) -phenoxybenzophenone: 7.54 g of 2,5-dichlorobenzoyl chloride obtained in (1), 13.4 g of 1,4-diphenoxybenzene 1,2-dichloroethane (100 ml) and aluminum chloride (5.9 g) were added, and the mixture was stirred for 1 hour in a nitrogen atmosphere. The organic component of the reaction solution was recovered by extraction and recrystallized using cyclohexane. After drying, 2,5-dichloro-4- (4-phenoxy) -phenoxybenzophenone was obtained.

(3) Synthesis of poly (4- (4-phenoxy) -phenoxybenzoyl-1,4-phenylene): 16 g of 2,5-dichloro-4′-phenoxybenzophenone obtained in (2) and triphenylphosphine 4. 7 g, 0.98 g of bis (triphenylphosphine) nickel (II) dichloride, 0.90 g of sodium iodide, 5.85 g of zinc and 55 ml of N-methyl-2-pyrrolidone were added, and the mixture was stirred at 50 to 80 ° C. for 24 hours. It was. This reaction solution was mixed and dissolved in 1,2-dichloroethane, and the catalyst was removed in a hydrochloric acid solution. Thereafter, dissolution in dichloroethane, filtration and drying were repeated. As a result, poly (4- (4-phenoxy) -phenoxybenzoyl-1,4-phenylene) having a weight average molecular weight of 262,000 and a number average molecular weight of 78,000 was obtained. (Degree of polymerization n = 509)
(4) 100 ml of sulfuric acid was added to 10 g of poly (4- (4-phenoxy) -phenoxybenzoyl-1,4-phenylene) obtained in (3), and the mixture was stirred at room temperature for 72 hours under a nitrogen atmosphere. After completion of the stirring, the solution was added to purified water and acid removal was repeated until the pH reached 7. Unsulfonated product was removed by repeatedly dissolving the obtained compound in N-methyl-2-pyrrolidone, filtering, and drying. As a result, sulfonated poly (4- (4-phenoxy) -phenoxybenzoyl-1,4-phenylene) was obtained. The ion exchange capacity by the following measurement method was 3.3 meq / g.

  (5) 5 g of the resulting sulfonated poly (4- (4-phenoxy) phenoxybenzoyl-1,4-phenylene) was dissolved in 50 ml of dimethyl sulfoxide. After casting the polymer solution onto a cast plate (glass substrate) for a predetermined area, the solvent is gradually removed while heating and drying at 80 ° C. for 480 minutes, and the polymer electrolyte membrane having a thickness of 42 μm is formed by peeling off the cast plate. Obtained. The polymer electrolyte membrane thus obtained was further subjected to acid washing, acid removal and drying.

(Example 2)
The same procedure as in Example 1 was performed except that 100 ml of sulfuric acid was added to 10 g of poly (4- (4-phenoxy) -phenoxybenzoyl-1,4-phenylene) and the mixture was stirred at room temperature in a nitrogen atmosphere for 48 hours. The ion exchange capacity by the following measurement method was 2.9 meq / g.

(Example 3)
5 g of sulfonated poly (4- (4-phenoxy) phenoxybenzoyl-1,4-phenylene) obtained in Example 1 (4) was dissolved in 250 ml of ethanol, and 5 g of platinum-supported carbon (platinum support ratio 50%) Mixed. 1 g of the mixed solution was applied to the polymer electrolyte membrane (10 cm × 10 cm) obtained in Example 4, and heated and dried at 120 ° C. for 240 minutes to prepare a membrane electrode assembly.

(Comparative Example 1) Synthesis and film formation of sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) (1) Synthesis of 2,5-dichlorobenzoyl chloride: -Dichlorobenzoyl chloride was obtained.

  (2) Synthesis of 2,5-dichloro-4′-phenoxybenzophenone: 86.1 g of 2,5-dichlorobenzoyl chloride obtained in (1), 104.9 g of phenyl ether, 270 ml of 1,2-dichloroethane, and chloride 71.2 g of aluminum was added and stirred for 1 hour in a nitrogen atmosphere. The organic component of the reaction solution was recovered by extraction and recrystallized using cyclohexane. After drying, 2,5-dichloro-4'-phenoxybenzophenone was obtained.

(3) Synthesis of poly (4-phenoxybenzoyl-1,4-phenylene) To 15 g of 2,5-dichloro-4′-phenoxybenzophenone obtained in (2), 4.5 g of triphenylphosphine and bis (triphenylphosphine) ) 0.94 g of nickel (II) dichloride, 0.88 g of sodium iodide, 5.77 g of zinc and 55 ml of N-methylpyrrolidone were added, and the mixture was stirred at 50 to 80 ° C. for 24 hours. This reaction solution was mixed and dissolved in 1,2-dichloroethane, and the catalyst was removed in a hydrochloric acid solution. Thereafter, dissolution in dichloroethane, filtration and drying were repeated. As a result, poly (4-phenoxybenzoyl-1,4-phenylene) (PPBP) having a weight average molecular weight of 310,000 and a number average molecular weight of 88,000 was obtained.

  (4) 150 ml of sulfuric acid was added to 10.2 g of the poly (4-phenoxybenzoyl-1,4-phenylene) obtained in (3), and the mixture was stirred at room temperature in a nitrogen atmosphere for 48 hours. After completion of the stirring, the solution was added to purified water and acid removal was repeated until the pH reached 7. Unsulphonated product was removed by repeatedly dissolving the obtained compound in N-methylpyrrolidone, filtering, and drying. As a result, sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) was obtained. The ion exchange capacity by the following measurement method was 2.6 meq / g.

(5) The resulting sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) 5
g was dissolved in 50 ml of dimethyl sulfoxide. The polymer solution was cast onto a cast plate in a predetermined area, and then the solvent was gradually removed while drying by heating at 80 ° C. for 480 minutes, and the cast film having a thickness of 42 μm was obtained by peeling off from the cast plate. The cast film thus obtained was further washed with acid, removed from acid, and dried.

(Comparative Example 2)
The same procedure as in Example 1 was carried out except that 100 ml of sulfuric acid was added to 10 g of poly (4- (4-phenoxy) -phenoxybenzoyl-1,4-phenylene) and stirred for 24 hours at room temperature in a nitrogen atmosphere. The ion exchange capacity by the following measurement method was 2.6 meq / g.

(Comparative Example 3)
As Comparative Example 3, Nafion (registered trademark) NRE212 (manufactured by DuPont) was used. The ion exchange capacity by the following measurement method was 0.94 meq / g.

(Comparative Example 4)
The same procedure as in Example 1 was carried out except that 100 ml of sulfuric acid was added to 10 g of poly (4- (4-phenoxy) -phenoxybenzoyl-1,4-phenylene) and stirred for 168 hours at room temperature in a nitrogen atmosphere. The ion exchange capacity by the following measuring method was 3.9 meq / g.

(Comparative Example 5)
5 g of the sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) obtained in Comparative Example 1 (4) was dissolved in 250 ml of ethanol and mixed with 5 g of platinum-supported carbon (platinum support ratio 50%). 1 g of the mixed solution was applied to the polymer electrolyte membrane (10 cm × 10 cm) obtained in Comparative Example 2 and dried by heating at 130 ° C. for 20 minutes to produce a membrane electrode assembly.

(Measurement method of ion exchange capacity)
The ion exchange capacity of the polymer electrolyte obtained in each example and comparative example was measured by the following method. Each polymer electrolyte membrane (5 cm × 5 cm) is stirred in 1M hydrochloric acid aqueous solution for 48 hours. Thereafter, the membrane is taken out and washed with water. This is followed by stirring in purified water for 48 hours. At this time, the water is changed every 12 hours. The membrane is then removed and dried at 80 ° C. for 48 hours. The dry weight (dry weight Ag) is measured. Then, it stirred for 100 hours in the mixed solution of 25 mL of 1M sodium chloride aqueous solution, and 20 mL of 0.01M sodium hydroxide aqueous solution. 10 mL of this solution was accurately weighed with a whole pipette, and titrated with a 0.01 M hydrochloric acid aqueous solution, with PH = 7 as the end point (drop amount BmL). Similarly, 10 mL of a mixed solution of 25 mL of 1 M sodium chloride aqueous solution and 20 mL of 0.01 M sodium hydroxide aqueous solution as a blank was titrated using a 0.01 M hydrochloric acid aqueous solution, with PH = 7 as the end point (drop amount CmL). The ion exchange capacity was calculated from the following equation.

(Evaluation Example 1: Evaluation of hot water resistance)
Each polymer electrolyte membrane (5 cm × 5 cm) was immersed in water at 80 ° C. and heated and stirred overnight. The membrane weight before and after heating and stirring was measured. The results are shown in Table 2.
(Evaluation Example 2: Conductivity measurement under each relative humidity)
Each polymer electrolyte membrane (3 cm × 3 cm) was allowed to stand at 80 ° C. and each relative humidity, and the conductivity of each membrane was measured. The results are shown in Table 2 and FIG.

  From the above results, it was found that the polymer electrolyte of the present invention hardly dissolves in water and exhibits hot water resistance. Moreover, it was shown that the polymer electrolyte of the present invention has a proton conductivity comparable to that of a fluororesin electrolyte not only under high humidification but also under low humidification.

(Evaluation Example 3: Power Generation Characteristic Evaluation 1)
The polymer electrolyte membranes (10 cm × 10 cm) obtained in each Example and Comparative Example were sandwiched between platinum-supported carbon gas diffusion layers (manufactured by Johnson Matthey PLC: platinum-supported amount 0.40 mg / cm ² ) and pressure-bonded with a hot press. As a result, a membrane electrode assembly was produced. Using this membrane / electrode assembly, a power generation test was conducted at a cell temperature of 80 ° C. and a relative humidity of 95% and 30%. In the power generation test, humidified hydrogen was allowed to flow on the anode side of the cell and humidified oxygen was allowed to flow on the cathode side, and current and voltage were measured when power was generated. The results are shown in FIG. 2 (relative humidity 95%) and FIG. 3 (relative humidity 30%).

  2 and 3 show that when the polymer electrolyte membrane of the present invention is applied to a fuel cell, it has excellent battery performance both under low humidification and under high humidification. When comparing the voltages under the same current density, Examples 1 and 2 have the same voltage as Comparative Example 1 or higher than Comparative Example 1 under high humidification, and the same or Comparative Example as Comparative Example 3 under low humidification. The voltage is higher than 1. When the voltage is high, the resistance loss is reduced, so that there is an advantageous effect that the output density is increased. Also in this respect, it was shown that the polymer electrolyte membrane of the present invention has an excellent effect.

(Evaluation Example 4: Power Generation Characteristic Evaluation 2)
Using the electrode assemblies of Example 3 and Comparative Example 5, a power generation test was performed at a cell temperature of 90 ° C. and a relative humidity of 50%. The power generation test was performed in the same manner as the power generation performance evaluation 1 described above. The results are shown in FIG.

  Also in this case, it was shown that the polymer electrolyte membrane of the present invention has excellent power generation performance.

It is a figure which shows the electrical conductivity under each relative humidity of an Example and a comparative example. It is a figure which shows the electric power generation performance (relative humidity 95%, temperature 80 degreeC) of an Example and a comparative example. It is a figure which shows the electric power generation performance (relative humidity 30%, temperature 80 degreeC) of an Example and a comparative example. It is a figure which shows the electric power generation performance (relative humidity 50%, temperature 90 degreeC) of an Example and a comparative example.

Claims (8)

A polymer electrolyte having a polymer unit represented by the following chemical formula (1) and having an ion exchange capacity of 2.8 to 3.8 meq / g;
In the formula, A represents an electron-withdrawing group, B ₁ and B ₂ represent an electron-donating group, Ar ₁ and Ar ₂ represent an aromatic group, and k and m represent a number of 0 or more (provided that k and m are not 0 at the same time), and x and y are numbers greater than or equal to 0 (however, x and y are not 0 at the same time).   The polymer electrolyte according to claim 1, wherein in the chemical formula (1), the A is a carbonyl group. The polymer electrolyte according to claim 1 or 2, wherein in the chemical formula (1), the B ₁ and B ₂ are ether groups.   The polymer according to any one of claims 1 to 3, wherein the polymer unit represented by the chemical formula (1) is sulfonated (4- (4-phenoxy) phenoxybenzoyl-1,4-phenylene). Electrolytes.   A polymer electrolyte membrane according to any one of claims 1 to 4, wherein the polymer electrolyte membrane is used.   A fuel cell using one or both of the polymer electrolyte according to any one of claims 1 to 4 and the polymer electrolyte membrane according to claim 5.   A vehicle equipped with the fuel cell according to claim 6. The following compound (A);
In the formula, A represents an electron-withdrawing group, and X ₁ , X _2, and X ₃ each independently represent any one of a chlorine atom, a bromine atom, and an iodine atom;
And the following compound (B);
In the formula, B ₁ and B ₂ represent an electron donating group, Ar ₁ and Ar ₂ represent an aromatic group, k and m represent a number of 0 or more (provided that k and m are simultaneously 0) Absent);
In the presence of a catalyst at 25 to 80 ° C., a process for producing the following compound (2):
In the formula, A, B ₁ , B ₂ , Ar ₁ , Ar ₂ , m, X ₁ , and X ₂ have the same definitions as those defined for the compound (A) and the compound (B).