JP2013231127A - Polymer electrolyte and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrocarbon-based polymer electrolyte excellent in processability and having excellent proton conductivity.SOLUTION: A polymer electrolyte has, in the main chain: a structure represented by formula (1) (wherein X represents a proton or a monovalent metal ion, and p denotes an integer of 2 or more); and a structure represented by formula (2) (wherein Arrepresents a divalent aromatic group, q denotes an integer of 1 or more, and a plurality of Ars may be different from each other).

Description

The present invention relates to a polymer electrolyte suitable for a polymer electrolyte fuel cell, a polymer electrolyte membrane using the polymer electrolyte, a membrane-electrode assembly, and a polymer electrolyte fuel cell including these.

In recent years, development of highly efficient and clean energy sources has been demanded from the viewpoint of environmental problems such as global warming. Fuel cells are attracting attention as one candidate for this. A fuel cell directly supplies power by supplying a fuel such as hydrogen gas or methanol and an oxidant such as oxygen to electrodes separated by an electrolyte, while oxidizing the fuel on the one hand and reducing the oxidant on the other. is there.

Among the fuel cell materials described above, one of the most important members is an electrolyte. Various types of electrolyte membranes have been developed so far to separate the electrolyte fuel and oxidant, and in recent years, the electrolyte membrane is composed of a polymer compound containing a proton conductive functional group such as a sulfonic acid group. The development of polymer electrolytes is thriving.

In addition to the solid polymer fuel cell, such a polymer electrolyte is used as a raw material for electrochemical elements such as a humidity sensor, a gas sensor, and an electrochromic display element. Among these polymer electrolyte utilization methods, in particular, polymer electrolyte fuel cells are expected as one of the pillars of new energy technology. For example, a polymer electrolyte fuel cell using an electrolyte membrane made of a polymer compound having a proton-conducting functional group has features such as operation at a low temperature and reduction in size and weight. Application to consumer cogeneration systems and consumer small portable devices is under consideration.

As an electrolyte membrane used in a polymer electrolyte fuel cell, there is a styrene-based cation exchange membrane developed in the 1950s. However, the fuel cell has poor stability under a fuel cell operating environment and has a sufficient lifetime. Has not yet been manufactured. On the other hand, as an electrolyte membrane having practical stability, a perfluorocarbon sulfonic acid membrane represented by Nafion (registered trademark) has been widely studied. Perfluorocarbon sulfonic acid membranes are said to have high proton conductivity and excellent chemical stability such as acid resistance and oxidation resistance. However, Nafion (registered trademark) has a drawback that it is very expensive because of the high raw materials used and the complicated manufacturing process. In addition, it has been pointed out that it is deteriorated by hydrogen peroxide generated by the electrode reaction and by-product hydroxy radical. In addition, due to its structure, there is a limit to the introduction of sulfonic acid groups that are proton conducting groups.

Against this background, the development of hydrocarbon electrolyte membranes has come to be expected. The reason for this is that the hydrocarbon electrolyte membrane is easy to have a variety of chemical structures, the range of introduction of proton conducting groups such as sulfonic acid groups can be adjusted widely, compounding with other materials, introduction of crosslinking, etc. This is because there is a feature that is relatively easy.

In recent years, there are examples in which proton conductivity is improved by introducing a large number of sulfonic acid groups into the electrolyte membrane, but such membranes have a large swelling in the water-containing state, and the strength of the membrane can be improved by repeating the water-containing state and the dry state. This is a problem for use as an electrolyte membrane for fuel cells. Therefore, attempts have been made to increase the strength of the membrane by introducing a rigid structure into the electrolyte membrane.

In order to produce a membrane with excellent proton conductivity, it is said that it is effective to form a microphase separation in the membrane and create a hydrophilic phase effective for water retention as a proton conduction path. As a method of forming this microphase separation, there is a method of forming a film with a block copolymer comprising a hydrophilic part and a hydrophobic part. In this case, since the strength of the phase composed of the hydrophobic portion is greatly reflected in the strength of the entire membrane, it is necessary to introduce a rigid structure into the hydrophobic portion in order to obtain a strong membrane.

An example of a rigid structure that can be used for the hydrophobic portion is a polyimide structure. However, there are few examples of synthesizing block polymers having a polyimide structure and excellent proton conductivity. They are also often low molecular weight polymers. As described above, a polymer including a rigid structure such as a polyimide structure is difficult to obtain a high molecular weight polymer, and the characteristics of the polyimide structure cannot be sufficiently extracted.

Patent Documents 1 and 2 disclose aromatic polyether polymers containing a benzophenone structure for the purpose of improving the strength of the film.

On the other hand, as an example of a polymer that does not include an ether bond and includes a benzophenone structure, a random copolymer that partially includes poly (4,4′-benzophenone) as shown in Reference Synthesis Example 3 of Patent Document 3. Although there are coalesced ones, only those having a number average molecular weight of about 12,000 are obtained, indicating that it is difficult to increase the molecular weight. In Example 2 of this document, this polymer is sulfonated, but this method limits the poly (4,4'-benzophenone) structure into which sulfonic acid groups can be introduced.

Non-Patent Document 1 synthesizes poly (2,5-benzophenone) having the same composition as poly (4,4'-benzophenone) and compares their properties. Poly (4,4′-benzophenone) has higher crystallinity and lower solubility than poly (2,5-benzophenone) because the bonding sites are different even for polymers of the same composition. It is difficult and cannot be synthesized by the same method. Therefore, in order to obtain poly (4,4′-benzophenone), the carbonyl group of the monomer is converted into an imino group, polymerized, and then converted into a carbonyl group by hydrolysis after polymerization. . Thus, poly (4,4'-benzophenone) was difficult to synthesize directly.

JP 2007-59374 A JP 2009-200030 A JP 2001-192531 A

Macromolecules 1994, 27, 2354-2356.

An object of the present invention is to provide a hydrocarbon polymer electrolyte having excellent processability and proton conductivity, particularly excellent proton conductivity in a low water content, and a membrane thereof.

As a result of intensive studies to solve the above problems, the present inventors use a specific polymer electrolyte having a sulfonic acid group advantageous for proton conductivity and having a rigid carbonyl structure in the main chain. As a result, the present inventors have found that the proton conductivity in a situation where the membrane strength is increased and the moisture content is low, and the present invention has been completed.

That is, the present invention provides the following formula (1):

(In the formula, A represents CO, SO ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ or a direct bond, X represents a proton or a monovalent metal ion, and p represents an integer of 2 or more. .)
And the following formula (2):

(In the formula, Ar ¹ represents a divalent aromatic group. Q represents an integer of 1 or more. A plurality of Ar ¹ may be different from each other.)
It is related with the polymer electrolyte which has a structure shown by this in a principal chain.

In the above formula (1), A is preferably CO.

Following formula (4):

(In the formula, X, Ar ¹ , p and q are the same as described above. Ar ² represents a divalent aromatic group. R represents an integer of 1 or more. Ar ¹ and Ar ² are the same. A plurality of Ar ¹ may be different from each other.)
It is preferable to have a structure represented by

The present invention also relates to a polymer electrolyte membrane containing the polymer electrolyte.

The present invention also relates to a membrane-electrode assembly or a polymer electrolyte fuel cell comprising the polymer electrolyte membrane.

The present invention also relates to a polymer electrolyte fuel cell comprising the membrane-electrode assembly.

The polymer electrolyte of the present invention can provide a polymer electrolyte membrane having a high membrane strength and an excellent proton conductivity in a situation where moisture is low.

1 is a structural diagram of a cross section of a main part of a polymer electrolyte fuel cell using a polymer electrolyte of the present invention.

An embodiment of the present invention will be described as follows. The present invention is not limited to the following description.

<1. Polymer electrolyte>
The polymer electrolyte of the present invention has the following formula (1) as a hydrophilic segment:

(In the formula, A represents CO, SO ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ or a direct bond, X represents a proton or a monovalent metal ion, and p represents an integer of 2 or more. )). Here, examples of the monovalent metal ion include lithium, sodium, and potassium.

X is preferably proton, sodium or potassium among protons and monovalent metal ions from the viewpoint of the solvent solubility of the polymer electrolyte. In order to increase the viscosity of the solution and the strength of the membrane, X is divalent or polyvalent. A valent metal ion may be added.

Further, as a hydrophobic segment, the following formula (2):

(In the formula, Ar ¹ represents a divalent aromatic group. Q represents an integer of 1 or more. A plurality of Ar ¹ may be different from each other.)
It has the structure shown by.

Examples of Ar ¹ include the following.

(In the formula, R is an optionally substituted fluorinated alkyl or alkoxy group having 1 to 10 carbon atoms, or an optionally fluorinated phenyl group, phenoxy group, naphthyl group or naphthyloxy group having 6 to 10 carbon atoms. B represents O, S, CH ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ , CO, SO ₂ , fluorenylidene or a direct bond, and when there are a plurality of them, they may be different. A represents an integer of 0 to 4.)

Among these, the following are preferable from the viewpoint of the solvent solubility of the polymer electrolyte.

Ar ¹ preferably has no sulfonic acid group.

The structure represented by the above formula (1) has the following formula (3) in which A is CO in terms of easy availability of raw materials:

(In the formula, X and p are the same as in the above formula (1).)
It is preferable that it is a structure shown by these.

Further, the hydrophobic segment has the following formula (5):

(In the formula, Ar ¹ and q are the same as described above. Ar ² represents a divalent aromatic group. R represents an integer of 1 or more. Ar ¹ and Ar ² may be the same. Ar ¹ may be different from each other.)
It is more preferable that it is a structure shown by these.

Examples of Ar ² include the following.

(In the formula, R, B and a are the same as described above.)

Among these, the following are preferable from the viewpoint of ease of synthesis.

Ar ² preferably has no sulfonic acid group.

Furthermore, from the ease of synthesis, the polymer electrolyte of the present invention has the following formula (4):

(In the formula, X, Ar ¹ , Ar ² , p, q and r are the same as described above.)
It is preferable to have a structure represented by

The polymer electrolyte of the present invention may be a random copolymer, a graft copolymer or a block copolymer as long as it has the above structure in the main chain. Under low humidification conditions, the water inside the polymer electrolyte membrane is reduced, but in order to increase proton conduction, it is necessary to effectively use the water that serves as the proton conduction medium. More preferably, it is a block copolymer capable of producing a water-rich phase.

The block copolymer that forms microphase separation has a sulfonic acid group because more water can be collected in the hydrophilic phase by separating the hydrophilic phase and the hydrophobic phase. A block copolymer comprising a hydrophilic segment and a hydrophobic segment having no sulfonic acid group is preferred.

In the polymer electrolyte of the present invention, the content of the structure represented by the formula (1) is preferably 5 to 70% by weight, and more preferably 9 to 50% by weight. If it exceeds 70% by weight, the mechanical strength of the membrane tends to decrease, and if it is less than 5% by weight, proton conductivity tends to be too low. Here, the total weight of the polymer electrolyte is the dry weight of the polymer electrolyte after the polymer electrolyte is treated with an acid and the sulfonic acid group in the polymer is in the SO ₃ H state. Regarding the weight ratio contained in the polymer electrolyte, the weight ratio between the component having a sulfonic acid group and the component having no sulfonic acid group can be determined from the ion exchange capacity of the polymer electrolyte. When there are some components having a sulfonic acid group, the component ratio can be determined from an analytical method such as a ¹ H-NMR spectrum.

Moreover, 30 to 95 weight% is preferable and, as for content of the structure shown by Formula (2) or Formula (5), 50 to 91 weight% is more preferable. If it exceeds 95% by weight, the proton conductivity of the membrane tends to be too low, and if it is less than 30% by weight, the mechanical strength of the membrane tends to decrease.

<Synthesis of the polymer electrolyte of the present invention>
The polymer electrolyte of the present invention is synthesized by applying a general polymerization reaction ("Experimental Chemistry Course 4th Edition Organic Synthesis VII Synthesis Using Organometallic Reagents" p.353-366 (1991) Maruzen Co., Ltd.). Can do.

As a material used for polymerization, a compound having two or more leaving groups can be used, and a compound having a leaving group such as a halogen group or a sulfonate group can be used. From the viewpoint of availability of materials and reactivity, a compound having halogen groups such as chlorine, bromine and iodine as two leaving groups is preferable.

The molecular weight of the material is preferably 50 to 1,000,000 in terms of polystyrene-equivalent number average molecular weight (hereinafter, simply abbreviated as molecular weight unless otherwise specified), and the molecular weight of the material forming the hydrophilic segment having a sulfonic acid group is particularly 100. The molecular weight of the material forming the hydrophobic segment having no sulfonic acid group is preferably 1000 to 100,000.

When the material forming the hydrophobic segment is a polymer, the molecular weight is preferably 1000 to 100,000.

The molecular weight of the polymer electrolyte of the present invention synthesized by these materials is preferably 10,000 to 5,000,000, and more preferably 20,000 to 1,000,000, the processability for producing the polymer electrolyte membrane and the strength of the polymer electrolyte membrane. Are preferable because both are excellent.

The polymerization reaction can be performed in an inert gas atmosphere such as a nitrogen gas atmosphere or an argon atmosphere, but is preferably performed in a nitrogen atmosphere.

The solvent in the polymerization reaction step is not particularly limited as long as polymerization is not prohibited, and carbonate compounds (ethylene carbonate, propylene carbonate, etc.), heterocyclic compounds (3-methyl-2-oxazolidinone, 1-methyl-2- Pyrrolidone (hereinafter NMP), N, N-dimethylimidazolidinone (hereinafter DMI), cyclic ethers (dioxane, tetrahydrofuran, etc.), chain ethers (diethyl ether, ethylene glycol dialkyl ether, etc.), nitrile compounds (acetonitrile) , Glutaronitrile, methoxyacetonitrile, etc.), aprotic polar substances (N, N-dimethylacetamide (hereinafter DMAc), N, N-dimethylformamide (hereinafter DMF), dimethyl sulfoxide (hereinafter DMSO), sulfolane, etc.), nonpolar The solvent can be enumerated (toluene, xylene), etc., among them DMAc or DMF from solubility, NMP, DMI, DMSO and the like is preferable because of high solubility in the polymer. Of these, DMAc and DMSO are preferred because of their high polymer solubility. These may be used alone or in combination of two or more. In addition, in order to remove a small amount of water in the solvent, it is effective to remove water by azeotropy by adding an azeotropic solvent such as benzene, toluene, xylene and cyclohexane.

What is necessary is just to set the reaction temperature of a polymerization reaction process suitably according to a polymerization reaction. Specifically, it may be set to 0 ° C to 200 ° C, more preferably 20 ° C to 170 ° C, and further preferably 40 ° C to 140 ° C. If the temperature is lower than 0 ° C., the reaction rate is slow. If the temperature is higher than 200 ° C., the reaction is greatly affected by a small amount of impurities, and there is concern that coloring of the polymer or unwanted side reactions may occur.

In the polymerization reaction step, it is preferable to perform a stopping operation, which can be performed by cooling, dilution, addition of a polymerization inhibitor or the like. The polymer produced after the polymerization reaction step may be taken out, and a purification step may be further added.

When synthesizing the polymer electrolyte of the present invention as a block copolymer, a compound having two or more leaving groups can be used as a material for forming a hydrophilic segment having a sulfonic acid group. Examples of the leaving group include a halogen group and a sulfonate group. A compound having a leaving group on the aromatic ring is preferable, and a dichlorobenzophenone derivative and a dichlorodiphenylsulfone derivative are more preferable in view of availability of materials.

Moreover, a monomer or an oligomer can be used as a material for forming a hydrophobic segment having no sulfonic acid group. The monomer can be synthesized from naphthalene-1,4,5,8-tetracarboxylic dianhydride and an aromatic amine compound having a leaving group. The oligomer is an aromatic amine compound further having a leaving group on an oligomer having an acid anhydride terminal obtained by polymerization of naphthalene-1,4,5,8-tetracarboxylic dianhydride and an aromatic diamine compound. It can be synthesized by reacting.

As an aromatic amine compound having a leaving group,

(In the formula, R, B, and a are the same as described above. Y represents chlorine, bromine, iodine, methanesulfonic acid ester, trifluoromethanesulfonic acid ester, benzenesulfonic acid ester, or toluenesulfonic acid ester.)
Is mentioned. As an aromatic diamine compound

(In the formula, R is an optionally substituted fluorinated alkyl or alkoxy group having 1 to 10 carbon atoms, or an optionally fluorinated phenyl group, phenoxy group, naphthyl group or naphthyloxy group having 6 to 10 carbon atoms. B represents O, S, CH ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ , CO, SO ₂ , fluorenylidene or a direct bond, and when there are a plurality of them, they may be different. A represents an integer of 0 to 4.)
Is mentioned.

When synthesizing the polyelectrolyte of the present invention, by protecting part or all of the carbonyl group contained in the hydrophilic segment and the hydrophobic segment material, the rigidity is lowered and a polymer having a higher molecular weight is obtained. You can also.

The protection of a carbonyl group is a method generally performed in organic synthesis, and when a carbonyl group works adversely in the course of synthesis, it is temporarily converted to a functional group having different properties. Usually, a protected carbonyl group can be converted to a carbonyl group by deprotection.

For protecting the carbonyl group, for example, a general method (“Protective Groups in Organic Synthesis Edition”, p. 293-368 (1999) John Wiley & Sons, Inc., written by Theodora W. Greene) can be applied. . Protection can be carried out at the monomer stage, the oligomer stage, or the polymer stage.

A specific example of the protection of the carbonyl group is a method of converting the carbonyl group into an acetal or ketal by reacting the carbonyl group with an alcohol. For example, the method of patent document 1 etc. are mentioned. Another example is a method in which a carbonyl group is reacted with an amine to convert it to an imine or ketimine. For example, the method of nonpatent literature 1 etc. are mentioned. In any case, as a deprotection method, the method described in the cited literature can be used. Acetals, ketals, imines and ketimines mentioned here are hydrolyzable and can be deprotected in a solvent containing water. In general, it is carried out under acidic conditions to accelerate deprotection.

Specifically, there is a method in which the carbonyl group of the above formula (1) is protected and converted to CR ¹ R ² or C═NR ³ . R ¹ and R ² represent an alkoxy group or an aryloxy group, and CR ¹ R ² may have a cyclic structure. R ³ represents an alkyl group or an aryl group.

When the carbonyl group is deprotected, it can be easily deprotected by contacting it with water or an acidic aqueous solution. Deprotection is preferably performed in the form of a film from the viewpoint of ease of processing.

The carbonyl group may be protected at any stage of monomer, oligomer, or polymer, but deprotection is preferably performed at the polymer stage.

The polymer electrolyte of the present invention can be used in various industries, and its use (use) is not particularly limited, but is suitable for a polymer electrolyte membrane, a membrane-electrode assembly, and a fuel cell. It is.

<2. Polymer electrolyte membrane of the present invention>
The polymer electrolyte membrane according to the present invention is obtained by molding the polymer electrolyte into a membrane by an arbitrary method. As such a film forming method, a known method can be appropriately used. Examples of the known methods include film forming methods from solutions such as hot extrusion methods, inflation methods, melt extrusion molding such as T-die methods, casting methods, and emulsion methods. For example, a casting method is exemplified as a method for forming a film from a solution. This is a method in which a polymer electrolyte solution with adjusted viscosity is applied onto a flat plate such as a glass plate using a bar coater, a blade coater or the like, and the solvent is evaporated to obtain a film. Industrially, it is also common to apply a solution continuously from a coating die onto a belt and vaporize the solvent to obtain a long product.

Furthermore, in order to control the molecular orientation of the polymer electrolyte membrane, the obtained polymer electrolyte membrane is subjected to a treatment such as biaxial stretching or a heat treatment for controlling the crystallinity. Also good. In addition, it is also within the scope of the present invention to add various fillers in order to improve the mechanical strength of the polymer electrolyte membrane or to combine a reinforcing agent such as a glass nonwoven fabric with the polymer electrolyte membrane by pressing. is there.

As the thickness of the polymer electrolyte membrane, any thickness can be selected according to the application. For example, when considering reducing the internal resistance of the obtained polymer electrolyte membrane, the thinner the polymer electrolyte membrane, the better. On the other hand, in consideration of gas barrier properties and handling properties of the obtained polymer electrolyte membrane, it may not be preferable if the thickness of the polymer electrolyte membrane is too thin. Considering these, the thickness of the polymer electrolyte membrane is preferably 1.2 μm or more and 350 μm or less. When the thickness of the polymer electrolyte membrane is within the range of the above numerical values, handling is improved such that handling is easy and damage is unlikely to occur. In addition, the proton conductivity of the obtained polymer electrolyte membrane can be expressed within a desired range.

In order to further improve the characteristics of the polymer electrolyte membrane of the present invention, it is possible to irradiate radiation such as electron beam, γ-ray, ion beam and the like. As a result, a crosslinked structure or the like can be introduced into the polymer electrolyte membrane, and the performance may be further improved. In addition, various surface treatments such as plasma treatment and corona treatment can improve properties such as improving adhesion to the catalyst layer on the surface of the polymer electrolyte membrane.

The polymer electrolyte membrane of the present invention preferably has an ion exchange capacity of 0.4 to 6.5 meq / g, more preferably 0.5 to 4.0 meq / g, and 0.6 to 3. More preferably, it is 0 meq / g. When it is less than 0.4 meq / g, proton conductivity tends to be too low, and when it exceeds 6.5 meq / g, mechanical strength tends to be remarkably lowered due to swelling with water.

<3. Membrane-electrode assembly and polymer electrolyte fuel cell according to the present invention>
The membrane-electrode assembly (hereinafter referred to as “MEA”) according to the present invention uses the polymer electrolyte or polymer electrolyte membrane of the present invention. Such an MEA can be used, for example, in a fuel cell, in particular, a polymer electrolyte fuel cell.

The methods for producing MEA are conventionally studied polymer electrolyte membranes made of perfluorocarbon sulfonic acid and other hydrocarbon polymer electrolyte membranes (for example, sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfone). A known method performed with oxidized polysulfone, sulfonated polyimide, sulfonated polyphenylene sulfide, or the like is applicable.

In addition to the examples described above, the polymer electrolyte according to the present invention can be used as an electrolyte of a polymer electrolyte fuel cell known in, for example, Japanese Patent Application Laid-Open No. 2006-179298. Based on these known patent documents, those skilled in the art can easily construct a solid polymer fuel cell using the polymer electrolyte of the present invention.

Hereinafter, examples will be shown, and the embodiment of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention.

Measurement methods for the molecular weight of the polymer, the ion exchange capacity of the polymer electrolyte, the proton conductivity, the dimensional change rate in the in-plane direction of the membrane due to water swelling and the gas permeability are as follows.

[Measurement method of molecular weight]
The molecular weight was measured by GPC method. The conditions are as follows.
GPC measuring device: HLC-8220 (manufactured by Tosoh Corporation)
Column: Super AW 4000 and Super AW 2500 (Showa Denko Co., Ltd.) connected in series Column temperature: 40 ° C
Mobile phase solvent: NMP (LiBr added to 10 mmol / dm ³ )
Solvent flow rate: 0.3 mL / min
Standard material: TSK standard polystyrene (manufactured by Tosoh Corporation)
Hereinafter, the number average molecular weight converted with standard polystyrene is expressed as Mn, and the weight average molecular weight converted with standard polystyrene is expressed as Mw.

[Measurement method of ion exchange capacity (hereinafter abbreviated as IEC)]
The target polymer electrolyte (about 100 mg, sufficiently dried) was immersed in 20 mL of a saturated aqueous sodium chloride solution at 25 ° C., and subjected to an ion exchange reaction in a water bath at 60 ° C. for 3 hours. After cooling to 25 ° C., the membrane was thoroughly washed with ion exchanged water, and all of the saturated aqueous sodium chloride solution and the washing water were collected. To this collected solution, a phenolphthalein solution was added as an indicator, and neutralization titration was performed with a 0.01N sodium hydroxide aqueous solution to calculate IEC.

[Measurement method of proton conductivity]
Proton conductivity measurement is performed using a constant temperature and humidity chamber (manufactured by Espec Co., Ltd., SH-221), keeping the temperature and humidity constant (about 3 hours), and using an impedance analyzer (manufactured by Hioki Electric Co., Ltd., 3532-50). Then, the resistance of the electrolyte was measured. Specifically, the frequency response from 50 kHz to 5 MHz was measured with an impedance analyzer, and the proton conductivity was calculated from the following equation.
Proton conductivity (S / cm) = D / (W × T × R)
Here, D is a distance between electrodes (cm), W is a film width (cm), T is a film thickness (cm), and R is a measured resistance value (Ω). In this measurement, D = 1 cm and W = 1 cm, and the film thickness was a value measured using a micrometer for each sample. The temperature and humidity were 80 ° C. and 30% RH, respectively.

[Method of measuring the rate of dimensional change in the in-plane direction of the film due to water swelling]
A circular sample having a diameter of 2 cm was prepared from the dried membrane, and the diameter was measured. Next, the same sample was immersed in water at 25 ° C. for 24 hours, and then the sample was taken out and quickly sandwiched between transparent films, and the diameter was measured. The dimensional change rate was obtained from the following equation.
Dimensional change rate = (dimension after immersion−dimension after drying) / dimension after drying

[Measurement method of gas permeability]
The gas permeation measurement was performed using a gas permeation measuring apparatus (20XAFK, manufactured by GTR-Tech Inc.). Hydrogen gas and oxygen gas were used as test gases, and argon and helium were used as flow gases, respectively. The measurement was performed by the isobaric method. The measurement conditions are as follows.
The concentration of the test gas in the flow gas when the gas is allowed to flow for a certain period of time is measured by gas chromatography. From this, the gas permeability coefficient [(cm ³ (STP) · cm / Cm ² · sec · cmHg)].
In this embodiment, the value of the gas permeation coefficient is converted to a standard value.
Test gas flow rate: 20 ml / min
Flow gas flow rate: 15 ml / min
Test membrane area: 7.065 (cm ² )
Measurement temperature: 80 ° C
Relative humidity: 95% RH

[Synthesis Example 1]
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, 6.70 g of naphthalene-1,4,5,8-tetracarboxylic dianhydride, 8.65 g of bis [4- (3-aminophenoxy) phenyl] sulfone, 40 ml of NMP And 15 ml of toluene were mixed in a nitrogen atmosphere and heated to 180 degrees. After removing water generated by refluxing toluene, an additional 2.0 g of 4-chloroaniline was added after 72 hours, cooled to room temperature after 18 hours, the reaction solution was added to acetone, and the precipitated solid was filtered and dried. Then, the solid was dissolved in m-cresol, the obtained polymer solution was added to ethanol, the precipitated solid was filtered, rinsed with ethanol, and the solid obtained as a residue was dried at 170 ° C. for 12 hours to obtain a polymer ( (Hereinafter referred to as P1). The molecular weight of the obtained P1 was Mn = 6300 and Mw = 18800.

[Synthesis Example 2]
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, 6.03 g of naphthalene-1,4,5,8-tetracarboxylic dianhydride, 8.65 g of bis [4- (3-aminophenoxy) phenyl] sulfone, 40 ml of NMP And 15 ml of toluene were mixed in a nitrogen atmosphere and heated to 180 degrees. The water produced by refluxing toluene was removed, and after 72 hours, 1.0 g of 4-chloroaniline was further added. After 18 hours, the mixture was cooled to room temperature, the reaction solution was added to acetone, and the precipitated solid was filtered and dried. Then, the solid was dissolved in m-cresol, the obtained polymer solution was added to ethanol, the precipitated solid was filtered, rinsed with ethanol, and the solid obtained as a residue was dried at 170 ° C. for 12 hours to obtain a polymer ( (Hereinafter referred to as P2). The molecular weight of the obtained P2 was Mn = 11700 and Mw = 34400.

[Synthesis Example 3]
A 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube was charged with 5.70 g of naphthalene-1,4,5,8-tetracarboxylic dianhydride, 8.65 g of bis [4- (3-aminophenoxy) phenyl] sulfone, and 40 ml of NMP. And 15 ml of toluene were mixed in a nitrogen atmosphere and heated to 180 degrees. The water produced by refluxing toluene was removed, and after 72 hours, 1.0 g of 4-chloroaniline was further added. After 18 hours, the mixture was cooled to room temperature, the reaction solution was added to acetone, and the precipitated solid was filtered and dried. Then, the solid was dissolved in m-cresol, the obtained polymer solution was added to ethanol, the precipitated solid was filtered, rinsed with ethanol, and the solid obtained as a residue was dried at 170 ° C. for 12 hours to obtain a polymer ( (Hereinafter referred to as P3). The molecular weight of the obtained P3 was Mn = 17900 and Mw = 54400.

[Synthesis Example 4]
A 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube was charged with 5.59 g of 4,4′-dichlorodiphenylsulfone, 4.64 g of 4,4′-dihydroxydiphenylsulfone, 3.33 g of potassium carbonate, 20 ml of DMAc and 5 ml of toluene under a nitrogen atmosphere. Mix and heat to 180 ° C. The water produced by refluxing toluene was removed, and after 40 hours, 1.0 g of 4,4′-dichlorodiphenylsulfone was further added, and after 6 hours, the reaction solution was added to water after cooling to room temperature. After being finely pulverized and filtered, it was dried at 80 ° C. for 12 hours. Further, the solid was dissolved in dichloromethane, added to methanol, and the precipitated solid was filtered and dried at 80 ° C. for 12 hours to obtain a polymer (hereinafter referred to as P4). The molecular weight of the obtained P4 was Mn = 7400 and Mw = 18600.

[Synthesis Example 5]
27 g of 4,4′-dichlorobenzophenone and 134 g of 30% fuming sulfuric acid were mixed in a nitrogen atmosphere and heated to 130 degrees with stirring. After 20 hours, the reaction solution was cooled to room temperature and then added to ice-cooled water. After neutralizing with an aqueous NaOH solution, the precipitated white solid was collected by filtration. The residue was dried under reduced pressure at 100 degrees to obtain a white solid (hereinafter referred to as S1).

[Synthesis Example 6]
120 g of 4,4′-dichlorodiphenylsulfone and 505 g of 30% fuming sulfuric acid were mixed in a nitrogen atmosphere and heated to 120 degrees with stirring. After 4 hours, the reaction solution was cooled to room temperature and then added to ice-cooled water. After neutralizing with an aqueous NaOH solution, the precipitated white solid was collected by filtration. The residue was dried under reduced pressure at 100 degrees to obtain a white solid (hereinafter referred to as S2).

[Example 1]
P1 (2.0 g), S1 (3.0 g), DMSO 40 ml, and toluene 15 ml were mixed in a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube in a nitrogen atmosphere and heated to 180 degrees. Toluene was refluxed to remove moisture in the flask, and then toluene was removed to cool the flask. At 70 ° C., 3.0 g of 2,2′-bipyridine and 5.0 g of bis (1,5-cyclooctadiene) nickel were added and stirred with a mechanical stirrer. After 5 minutes, the temperature was raised to 80 ° C., and after 2 hours, the mixture was cooled to room temperature. The reaction solution was diluted with 10 ml of DMSO, added to a 6N hydrochloric acid aqueous solution, and the precipitated solid was collected by filtration. The solid was dried at 80 ° C. under reduced pressure, and the solid was finely pulverized and then stirred in a 6N aqueous hydrochloric acid solution for 6 hours. Filtration was performed while washing with water, followed by drying at 100 ° C. under reduced pressure to obtain a polymer electrolyte. The molecular weight was Mn = 25000 and Mw = 147500.

After dissolving 0.7 g of the obtained polymer electrolyte in 20 ml of DMSO, the solution was cast on a glass substrate, vacuum dried at 80 ° C. for 15 hours, and further vacuum dried at 100 ° C. for 18 hours. A supporting polymer electrolyte membrane (film thickness 38 μm) was obtained.

The polymer electrolyte membrane was immersed in a 6N hydrochloric acid aqueous solution for 12 hours, then immersed twice in pure water for 1 hour, and then dried at 100 ° C. under reduced pressure. The obtained membrane had an ion exchange capacity of 1.16 meq / g. When proton conductivity was measured under low humidification conditions, it was 3.7 × 10 ⁻³ S / cm. The dimensional change rate in the in-plane direction of the film due to water swelling was 5.4%.

[Example 2]
P2 (2.0 g), S1 (3.0 g), DMSO 40 ml, and toluene 15 ml were mixed in a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube in a nitrogen atmosphere and heated to 180 degrees. Toluene was refluxed to remove moisture in the flask, and then toluene was removed to cool the flask. At 70 ° C., 3.0 g of 2,2′-bipyridine and 5.00 g of bis (1,5-cyclooctadiene) nickel were added and stirred with a mechanical stirrer. After 5 minutes, the temperature was raised to 80 ° C., and after 2 hours, the mixture was cooled to room temperature. The reaction solution was diluted with 10 ml of DMSO, added to a 6N hydrochloric acid aqueous solution, and the precipitated solid was collected by filtration. The solid was dried at 80 ° C. under reduced pressure, and the solid was finely pulverized and then stirred in a 6N aqueous hydrochloric acid solution for 6 hours. Filtration was performed while washing with water, followed by drying at 100 ° C. under reduced pressure to obtain a polymer electrolyte. The molecular weight was Mn = 35000 and Mw = 87500.

After dissolving 0.7 g of the obtained polymer electrolyte in 20 ml of DMSO, the solution was cast on a glass substrate, vacuum dried at 80 ° C. for 15 hours, and further vacuum dried at 100 ° C. for 18 hours. A supporting polymer electrolyte membrane (film thickness 35 μm) was obtained.

The polymer electrolyte membrane was immersed in a 6N hydrochloric acid aqueous solution for 12 hours, then immersed twice in pure water for 1 hour, and then dried at 100 ° C. under reduced pressure. The obtained membrane had an ion exchange capacity of 1.57 meq / g. When proton conductivity was measured under low humidification conditions, it was 5.7 × 10 ⁻³ S / cm. Moreover, the dimensional change rate in the in-plane direction of the film due to water swelling was 6.2%.
As a result of gas permeation measurement, hydrogen gas was 3.75 × 10 ⁻¹⁰ cm ³ (STP) · cm / cm ² · sec · cmHg, and oxygen gas was 1.01 × 10 ⁻¹⁰ cm ³ (STP) · cm. / Cm ² · sec · cmHg.

Example 3
P3 (2.0 g), S1 (3.0 g), DMSO 40 ml, and toluene 15 ml were mixed in a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube in a nitrogen atmosphere and heated to 180 degrees. Toluene was refluxed to remove moisture in the flask, and then toluene was removed to cool the flask. At 70 ° C., 3.0 g of 2,2′-bipyridine and 5.00 g of bis (1,5-cyclooctadiene) nickel were added and stirred with a mechanical stirrer. After 5 minutes, the temperature was raised to 80 ° C., and after 2 hours, the mixture was cooled to room temperature. The reaction solution was diluted with 10 ml of DMSO, added to a 6N hydrochloric acid aqueous solution, and the precipitated solid was collected by filtration. The solid was dried at 80 ° C. under reduced pressure, and the solid was finely pulverized and then stirred in a 6N aqueous hydrochloric acid solution for 6 hours. Filtration was performed while washing with water, followed by drying at 100 ° C. under reduced pressure to obtain a polymer electrolyte. The molecular weight was Mn = 42000 and Mw = 180600.

After dissolving 0.7 g of the obtained polymer electrolyte in 20 ml of DMSO, the solution was cast on a glass substrate, vacuum dried at 80 ° C. for 15 hours, and further vacuum dried at 100 ° C. for 18 hours. A supporting polymer electrolyte membrane (film thickness 32 μm) was obtained.

The polymer electrolyte membrane was immersed in a 6N hydrochloric acid aqueous solution for 12 hours, then immersed twice in pure water for 1 hour, and then dried at 100 ° C. under reduced pressure. The obtained membrane had an ion exchange capacity of 1.01 meq / g. When the proton conductivity was measured under low humidification conditions, it was 3.5 × 10 ⁻³ S / cm. The dimensional change rate in the in-plane direction of the film due to water swelling was 4.9%.
As a result of gas permeation measurement, hydrogen gas was 6.46 × 10 ⁻¹⁰ cm ³ (STP) · cm / cm ² · sec · cmHg, and oxygen gas was 1.96 × 10 ⁻¹⁰ cm ³ (STP) · cm. / Cm ² · sec · cmHg.

Example 4
P3 (2.0 g), S2 (3.0 g), DMSO 40 ml, and toluene 15 ml were mixed in a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube in a nitrogen atmosphere and heated to 180 degrees. Toluene was refluxed to remove moisture in the flask, and then toluene was removed to cool the flask. At 70 ° C., 3.0 g of 2,2′-bipyridine and 5.00 g of bis (1,5-cyclooctadiene) nickel were added and stirred with a mechanical stirrer. After 5 minutes, the temperature was raised to 80 ° C., and after 2 hours, the mixture was cooled to room temperature. The reaction solution was diluted with 10 ml of DMSO, added to a 6N hydrochloric acid aqueous solution, and the precipitated solid was collected by filtration. The solid was dried at 80 ° C. under reduced pressure, and the solid was finely pulverized and then stirred in a 6N aqueous hydrochloric acid solution for 6 hours. Filtration was performed while washing with water, followed by drying at 100 ° C. under reduced pressure to obtain a polymer electrolyte. The molecular weight was Mn = 51000 and Mw = 224400.

After dissolving 0.7 g of the obtained polymer electrolyte in 20 ml of DMSO, the solution was cast on a glass substrate, vacuum dried at 80 ° C. for 15 hours, and further vacuum dried at 100 ° C. for 18 hours. A supporting polymer electrolyte membrane (thickness: 37 μm) was obtained.

The polymer electrolyte membrane was immersed in a 6N hydrochloric acid aqueous solution for 12 hours, then immersed twice in pure water for 1 hour, and then dried at 100 ° C. under reduced pressure. The obtained membrane had an ion exchange capacity of 0.92 meq / g. The proton conductivity measured under low humidification conditions was 3.2 × 10 ⁻⁴ S / cm. Moreover, the dimensional change rate in the in-plane direction of the film due to water swelling was 6.6%.

[Comparative Example 1]
In Example 1, P4 (1.5 g) was used instead of P1, S2 (1.5 g) was used instead of S1, DMSO 50 ml, toluene 16 ml, 2,2′-bipyridine 1.5 g and bis (1,5 -Cyclooctadiene) The synthesis was performed in the same manner except that 2.4 g of nickel was used. However, the polymer was dissolved when stirring was performed in a 6N hydrochloric acid aqueous solution in the polymer washing step. The polymer is recovered by neutralizing with an aqueous NaOH solution and concentrating, drying under reduced pressure at 80 ° C., washing the dried solid with water, further drying under reduced pressure at 80 ° C. for 3 hours, and further drying under reduced pressure at 100 ° C. for 10 hours. A polymer electrolyte was obtained. The molecular weight was Mn = 73000 and Mw = 124100.

After dissolving 0.7 g of the obtained polymer electrolyte in 20 ml of DMAc, the solution was cast on a glass substrate, vacuum dried at 80 ° C. for 15 hours, and further vacuum dried at 100 ° C. for 18 hours. An electrolyte membrane was obtained.

When the polymer electrolyte membrane was immersed in a 6N aqueous hydrochloric acid solution for 12 hours, the membrane was dissolved.

[Comparative Example 2]
Pellets of polyphenylene sulfide (DIC-PPS LD10p11, manufactured by DIC Corporation) were melt-extruded by a twin-screw extruder in which a T-die was set in a twin-screw kneading extruder under a screw temperature of 290 ° C and a T-die temperature of 290 ° C. Molded to obtain a polymer film. In a glass container, 634 g of 1-chlorobutane and 9 g of chlorosulfonic acid were weighed to prepare a chlorosulfonic acid solution. 1.5 g of the polymer film was weighed and immersed in the chlorosulfonic acid solution at 25 ° C. for 20 hours to obtain a polymer electrolyte membrane. (The amount of chlorosulfonic acid added is 6 times the weight of the polymer film). Thereafter, the polymer electrolyte membrane was recovered, washed with ion exchange water until neutral, and vacuum dried at 100 ° C. for 18 hours to obtain a self-supporting polymer electrolyte membrane.

The obtained membrane had an ion exchange capacity of 1.33 meq / g. The proton conductivity measured under low humidification conditions was 5.8 × 10 ⁻⁵ S / cm.

From comparison between Examples 1 to 4 and Comparative Examples 1 and 2, it can be seen that the polymer electrolyte of the present invention has excellent proton conductivity and good water resistance.

It is clear that the polymer electrolyte of the present invention is useful as a material for a solid polymer fuel cell, and particularly useful as a polymer electrolyte membrane.

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 2 Catalyst layer 3 Diffusion layer 4 Separator 5 Channel 10 Solid polymer fuel cell

Claims (7)

Following formula (1):

(In the formula, A represents CO, SO ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ or a direct bond, X represents a proton or a monovalent metal ion, and p represents an integer of 2 or more. .)
And the following formula (2):

(In the formula, Ar ¹ represents a divalent aromatic group. Q represents an integer of 1 or more. A plurality of Ar ¹ may be different from each other.)
A polymer electrolyte having a structure represented by In the said Formula (1), A is CO, The polymer electrolyte of Claim 1 characterized by the above-mentioned. Following formula (4):

(In the formula, X, Ar ¹ , p and q are the same as described above. Ar ² represents a divalent aromatic group. R represents an integer of 1 or more. Ar ¹ and Ar ² are the same. A plurality of Ar ¹ may be different from each other.)
The polymer electrolyte according to claim 1, wherein the main chain has a structure represented by: The polymer electrolyte membrane containing the polymer electrolyte as described in any one of Claims 1-3. A membrane-electrode assembly comprising the polymer electrolyte membrane according to claim 4. A solid polymer fuel cell comprising the polymer electrolyte membrane according to claim 4. A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 5.

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