JP2015209539A - Polymer electrolyte and application of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer electrolyte which is excellent in processability and has excellent proton conductivity especially under low-moisture conditions and its film.SOLUTION: A polymer electrolyte has structures of formulae (1) and (2) in the principal chain. In formula (1), Ar is a benzene ring, a naphthalene ring or a benzene or naphthalene ring with a carbon atom constituting the ring substituted with a hetero atom; X is Hor a cation; 'a' and b are independently an integer of 0-4, with a total of 'a' and b of 1 or greater; c is an integer of 1 or greater; and d is an integer of 0 or greater. In formula (2), Ar is the same as that of formula (1); Y is CO, SO, C(CH)or C(CF); e and f are independently an integer of 1 or greater; g is an integer of 1-7; and Z is a direct bond, O or S.

Description

The present invention relates to a polymer electrolyte suitable for a solid polymer fuel cell, a polymer electrolyte membrane using the polymer electrolyte, a membrane / electrode assembly, and a 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 that requirement. 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 materials 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. Furthermore, 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.

Examples of the rigid structure include a benzophenone structure. However, it is generally difficult to increase the molecular weight of such a polymer having a rigid structure due to the problem of solubility in a reaction solvent. In Patent Document 1, a carbonyl group having a benzophenone structure is converted to an alkyl ether during polymerization to enhance solubility. And after performing high molecular weight, the process which returns alkyl ether to a carbonyl group by acid treatment is performed. In Patent Document 2, a polyetheretherketone containing a rigid benzophenone structure is synthesized. In order to obtain a high molecular weight polymer, a t-butyl group is introduced into some aromatic rings. Thus, it is generally difficult to increase the molecular weight of a polymer containing a benzophenone structure, and it is necessary to devise measures such as increasing the solubility. However, these are polymers containing an ether bond and have a relatively high solubility, but when used as an electrolyte membrane for a fuel cell, there is a problem that they are easily deteriorated.

As an example of a polymer that does not include an ether bond and includes a benzophenone structure, a random copolymer partially including poly (4,4′-benzophenone) as shown in Reference Synthesis Example 3 of Patent Document 3 can be given. However, only a number average molecular weight of about 12,000 has been obtained, and it can be seen that it is difficult to increase the molecular weight. Moreover, although this polymer is sulfonated, a sulfonic acid group cannot usually be introduced into the poly (4,4'-benzophenone) structure by this method.

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. In order to obtain poly (4,4'-benzophenone), the carbonyl group of the monomer is converted to an imino group, polymerized, and then hydrolyzed after the polymerization to return to the carbonyl group. 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 have found that a polymer electrolyte containing a specific polymer having a sulfonic acid group advantageous for proton conductivity and having a rigid carbonyl structure in the main chain As a result, it was found that the proton conductivity in a situation where the membrane strength is high and the moisture content is low is excellent, and the present invention has been completed.

（式中、Ａｒはベンゼン環、ナフタレン環、あるいはそれらの環を形成する炭素がヘテロ原子へと置換されたものを示し、Ｘはプロトン、あるいは陽イオンを示し、ａおよびｂはそれぞれ独立に０〜４の整数であり、ａとｂの合計は１以上である。ｃは１以上の整数を示し、ｄは０以上の整数を示す。）

（式中、Ａｒは前記と同様。ＹはＣＯ、ＳＯ_２、Ｃ（ＣＨ_３）_２、Ｃ（ＣＦ_３）_２を示す。ｅおよびｆはそれぞれ独立に１以上の整数を示し、ｇは１以上７以下の整数を示し、Ｚは直接結合、酸素、または硫黄を示す。）
で示される構造を主鎖に有する高分子電解質に関する。 That is, the present invention provides the following formulas (1) and (2):

(In the formula, Ar represents a benzene ring, a naphthalene ring, or a carbon in which those rings are substituted with a hetero atom, X represents a proton or a cation, and a and b are each independently 0. The total of a and b is 1 or more, c represents an integer of 1 or more, and d represents an integer of 0 or more.

(In the formula, Ar is the same as described above. Y represents CO, SO ₂ , C (CH ₃ ) ₂ , and C (CF ₃ ) _2. E and f each independently represent an integer of 1 or more, and g represents 1 And represents an integer of 7 or less, and Z represents a direct bond, oxygen, or sulfur.)
It is related with the polymer electrolyte which has a structure shown by this in a principal chain.

In Formula (2), it is preferable that e and f are 1.

A polymer electrolyte using only a compound having a molecular weight of less than 2000 as a raw material constituting the main chain is preferable.

It is preferable that the polymer is a polymer electrolyte having only the structure represented by the formula (1) or the repeating structure as the hydrophilic portion structure in the polymer.

（式中、Ｘ、ａ、ｂは前記と同様。ｈは０〜４の整数であり、いくつかある場合は同一でなくてもよい。ｍは１以上の整数、ｎは０以上の整数。）
で示される構造であることが好ましい。 The structure represented by the formula (1) is represented by the following formula (3):

(In the formula, X, a and b are the same as described above. H is an integer of 0 to 4, and may be not the same in some cases. M is an integer of 1 or more, and n is an integer of 0 or more. )
It is preferable that it is a structure shown by these.

（式中、Ｙ、ｍは前記と同様。）
で示される構造であることが好ましい。 The structure represented by the formula (2) is represented by the following formula (4) and / or (5):

(In the formula, Y and m are the same as described above.)
It is preferable that it is a structure shown by these.

（式中、Ｙは前記と同様。Ｒ^１はハロゲン原子、またはＯＳＯ_２Ｒ^２で表される基である。Ｒ^２はアルキル基、アリール基あるいはハロゲン化アルキル基を示す。）
で示される構造を有する化合物から合成されることが好ましい。 The structures represented by the formulas (4) and (5) are represented by the following formulas (6) and (7), respectively:

(Wherein, Y is .R ² the same .R ¹ is a group represented by halogen atom or _OSO 2 ^{R 2,} represents an alkyl group, an aryl group or a halogenated alkyl group.)
It is preferably synthesized from a compound having a structure represented by

The total of the structure represented by the formula (1) is preferably included at 10% by weight or more of the whole.

A polymer electrolyte composed of a block copolymer including a hydrophilic segment having a sulfonic acid group and a hydrophobic segment having no sulfonic acid group is preferable.

It is preferable that 10% by weight or more of the hydrophilic segment having a sulfonic acid group is a polymer electrolyte having a structure represented by the formula (1).

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

The present invention also relates to a membrane / electrode assembly or a polymer electrolyte fuel cell comprising the polymer electrolyte membrane, and further to a polymer electrolyte fuel cell comprising the membrane / electrode assembly.

Since the polymer electrolyte of the present invention contains a specific polymer having a sulfonic acid group advantageous for proton conductivity and having a rigid carbonyl structure in the main chain, the polymer electrolyte membrane has high membrane strength. It can have excellent proton conductivity in a low moisture condition.

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.

（式中、Ａｒはベンゼン環、ナフタレン環、あるいはそれらの環を形成する炭素がヘテロ原子へと置換されたものを示し、Ｘはプロトン、あるいは陽イオンを示し、ａおよびｂはそれぞれ独立に０〜４の整数であり、ａとｂの合計は１以上である。ｃは１以上の整数を示し、ｄは０以上の整数を示す。）

（式中、Ａｒは前記と同様。ＹはＣＯ、ＳＯ_２、Ｃ（ＣＨ_３）_２、Ｃ（ＣＦ_３）_２を示す。ｅおよびｆはそれぞれ独立に１以上の整数を示し、ｇは１以上７以下の整数を示し、Ｚは直接結合、酸素、または硫黄を示す。）
で示される構造をポリマーの主鎖に有することを特徴とする。
前記式（１）において、ｃの上限は特に限定されないが、３以下が好ましい。ｄは０以上の整数であるが、１以上が好ましく、上限は特に限定されないが、３以下が好ましい。前記式（２）において、合成の容易さの点から、ｅおよびｆがともに１であることが好ましい。ｇは１以上７以下の整数であるが、１以上３以下の整数であることがより好ましい。７を超えると、ブロックポリマーの疎水部が大きくなり、ミクロ相分離のサイズが細かく均一な膜が得られなくなる傾向がある。
ここで、陽イオンとしては、リチウム、ナトリウム、カリウムなどの第１族の金属イオンや、マグネシウム、カルシウムなどの第２族の金属イオン、アルミニウムなどの第１３族の金属イオン、第３族〜第１２族の遷移金属の金属イオンなどが挙げられる。 <1. Polymer electrolyte>
The polymer electrolyte of the present invention has the following formulas (1) and (2):

(In the formula, Ar represents a benzene ring, a naphthalene ring, or a carbon in which those rings are substituted with a hetero atom, X represents a proton or a cation, and a and b are each independently 0. The total of a and b is 1 or more, c represents an integer of 1 or more, and d represents an integer of 0 or more.

(In the formula, Ar is the same as described above. Y represents CO, SO ₂ , C (CH ₃ ) ₂ , and C (CF ₃ ) _2. E and f each independently represent an integer of 1 or more, and g represents 1 And represents an integer of 7 or less, and Z represents a direct bond, oxygen, or sulfur.)
It has the structure shown by this in the principal chain of a polymer.
In the formula (1), the upper limit of c is not particularly limited, but is preferably 3 or less. d is an integer of 0 or more, preferably 1 or more, and the upper limit is not particularly limited, but is preferably 3 or less. In the formula (2), it is preferable that e and f are both 1 from the viewpoint of ease of synthesis. g is an integer of 1 to 7, more preferably an integer of 1 to 3. If it exceeds 7, the hydrophobic part of the block polymer becomes large, and there is a tendency that a micro-phase-separated size is fine and a uniform film cannot be obtained.
Here, as the cation, a Group 1 metal ion such as lithium, sodium, or potassium; a Group 2 metal ion such as magnesium or calcium; a Group 13 metal ion such as aluminum; Examples include metal ions of group 12 transition metals.

In the polymer electrolyte of the present invention, the total content of the structure represented by the formula (1) is preferably 10% by weight or more, and more preferably 15% by weight or more. Moreover, it is preferable that it is 70 weight% or less, and it is more preferable that it is 50 weight% or less. If it is less than 10% by weight, it may not have sufficient proton conductivity. Moreover, when it exceeds 70 weight%, the solubility resistance to water may worsen.

A polymer electrolyte having only the structure represented by the formula (1) or a repeating structure thereof is preferable because the radical durability is enhanced as the hydrophilic portion structure in the polymer.

（式中、Ｘ、ａ、ｂは前記と同様。ｈは０〜４の整数であり、いくつかある場合は同一でなくてもよい。ｍは１以上の整数、ｎは０以上の整数。）
で示される構造であることが好ましい。高分子電解質が式（３）で示される構造を有する場合、前記式（３）で示される構造の合計が全体の１０重量％以上であることが好ましく、２０重量％以上であることがより好ましい。上限については特に限定されない。１０重量％未満では、充分なプロトン伝導性を有さなくなる可能性がある。 The structure represented by the above formula (1) has the following formula (3) in which Ar is benzene from the viewpoint of easy availability of raw materials:

(In the formula, X, a and b are the same as described above. H is an integer of 0 to 4, and may be not the same in some cases. M is an integer of 1 or more, and n is an integer of 0 or more. )
It is preferable that it is a structure shown by these. When the polymer electrolyte has a structure represented by the formula (3), the total structure represented by the formula (3) is preferably 10% by weight or more, more preferably 20% by weight or more. . The upper limit is not particularly limited. If it is less than 10% by weight, it may not have sufficient proton conductivity.

（式中、Ｙ、ｍは前記と同様。）
で示される構造であることが好ましい。 The structure represented by the above formula (2) has the following formulas (4) and / or (5) because of ease of synthesis and workability:

(In the formula, Y and m are the same as described above.)
It is preferable that it is a structure shown by these.

（式中、Ｙは前記と同様。Ｒ^１はハロゲン原子、またはＯＳＯ_２Ｒ^２で表される基である。Ｒ^２はアルキル基、アリール基あるいはハロゲン化アルキル基を示す。）
で示される構造を有する化合物から合成されることが好ましい。 The structures represented by the above formulas (4) and (5) are represented by the following formulas (6) and (7), respectively, in terms of ease of synthesis and availability of raw materials.

(Wherein, Y is .R ² the same .R ¹ is a group represented by halogen atom or _OSO 2 ^{R 2,} represents an alkyl group, an aryl group or a halogenated alkyl group.)
It is preferably synthesized from a compound having 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.

Furthermore, in the block copolymer that forms microphase separation, it is possible to collect more water in the hydrophilic phase by separating the hydrophilic phase and the hydrophobic phase. The block copolymer is preferably composed of a hydrophilic segment having a hydrophobic segment and a hydrophobic segment having no sulfonic acid group.

The molecular weights of the hydrophilic segment and the hydrophobic segment are each preferably less than 2000, and more preferably less than 1000. When the molecular weight is 2000 or more, the hydrophobic portion of the block polymer becomes large, and there is a tendency that a microphase-separated size is fine and a uniform film cannot be obtained.

The hydrophilic segment having a sulfonic acid group preferably has a structure represented by the formula (1). In terms of resistance to dissolution in water, the hydrophilic segment preferably has a structure represented by the formula (1) at 10% by weight or more, and more preferably 20% by weight or more. The upper limit is not particularly limited. If it is less than 10% by weight, the solubility in water tends to decrease.

When the polymer electrolyte of the present invention is a block copolymer comprising a hydrophilic segment having a sulfonic acid group and a segment not having a sulfonic acid group, the hydrophilic segment having a sulfonic acid group is represented by the above formula ( The structure shown in 1) may be contained in the main chain, but d is preferably c or more from the viewpoint of ease of synthesis.

The ion exchange capacity of the polymer electrolyte of the present invention is preferably 0.5 to 5.0 meq / g from the viewpoint that both proton conductivity and the strength of the polymer electrolyte membrane are excellent, 0.8 It is more preferably ˜4.0 meq / g, and further preferably 1.1 to 3.5 meq / g.

<Synthesis of the polymer electrolyte of the present invention>
For the synthesis of the polymer electrolyte of the present invention, a general polymerization reaction ("Experimental Chemistry Course 4th edition: Organic Synthesis VII Synthesis with organometallic reagents" p.353-366 (1991) Maruzen Co., Ltd.) should be applied. Can do.

As a material used for polymerization, a compound having a leaving group at two or more positions can be used, and a compound having a leaving group such as a halogen group or a sulfonate group can be used. From the point of material availability and reactivity, leaving groups such as halogen groups such as chlorine, bromine and iodine, or leaving groups such as sulfonic acid esters such as methanesulfonyl group, trifluoromethanesulfonyl group, benzenesulfonyl group and toluenesulfonyl group can be used. It is preferable that it is a compound which has in two places.

The molecular weight of the raw material constituting the main chain of the polymer is preferably less than 2000, more preferably 50 or more and less than 2000. In particular, the molecular weight of the raw material having a sulfonic acid group is preferably 70 or more and less than 2000, and has no sulfonic acid group. The molecular weight of the raw material is preferably 70 or more and less than 2000. When the molecular weight is 2000 or more, the hydrophobic portion of the block polymer becomes large, and there is a tendency that a microphase-separated size is fine and a uniform film cannot be obtained.

The weight average molecular weight of the polymer electrolyte of the present invention synthesized from these raw materials is preferably 10,000 to 5,000,000, and more preferably 20,000 to 3,000,000. Processability for producing the polymer electrolyte membrane and the polymer electrolyte membrane Both are preferable because of their excellent strength.

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 referred to as NMP), N, N-dimethylimidazolidinone (hereinafter referred to as DMI), N, N-dimethylacetamide (hereinafter referred to as DMAc), N, N-dimethylformamide (hereinafter referred to as DMF), cyclic ethers (dioxane, tetrahydrofuran, etc.) ), Chain ethers (diethyl ether, ethylene glycol dialkyl ether, etc.), nitrile compounds (acetonitrile, glutarodinitrile, methoxyacetonitrile, etc.), aprotic polar substances (dimethyl sulfoxide (hereinafter DMSO), sulfolane, etc.), nonpolar Medium to enumerate (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 this range, the reaction rate is slow, and if the temperature is higher, there is a concern that the polymer may be greatly affected by a small amount of impurities and 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, diluting, or adding a polymerization inhibitor. You may take out the polymer | macromolecule produced | generated after the polymerization reaction process. Further purification steps may be 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 sulfonic acid ester. A compound having a leaving group on the aromatic ring is preferable, and a dichlorobenzene derivative and a dichlorobenzophenone derivative are more preferable because of easy availability of materials.

As a material for forming a hydrophobic segment having no sulfonic acid group, a compound having two or more leaving groups can be used. Examples of the leaving group include a halogen group and a sulfonic acid ester. A compound having a leaving group on an aromatic ring is preferable, and a compound having a structure represented by the above formula (6) or (7), or at least synthesized using these compounds as a raw material, has two or more leaving groups. Compounds are more preferred.

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 of 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.

<3. Membrane / electrode assembly and 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.

Methods for producing MEA are conventionally studied polymer electrolyte membranes made of perfluorocarbon sulfonic acid and other hydrocarbon polymer electrolyte membranes (for example, sulfonic acid polyether ether ketone, sulfonic acid polyether sulfone, sulfone). A known method performed with acid polysulfone, sulfonic acid polyimide, sulfonic acid 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.

The measurement methods of the molecular weight of the polymer, the ion exchange capacity of the polymer electrolyte, and the proton conductivity 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: Showa Denko Co., Ltd. Super AW 4000 and Super AW 2500 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 with a 0.01N sodium hydroxide aqueous solution was performed to calculate IEC (meq / g).

[Measurement method of proton conductivity]
Proton conductivity measurement is performed using a constant temperature and humidity chamber (manufactured by ESPEC, SH-221), keeping the temperature and humidity constant (about 3 hours), and using an impedance analyzer (manufactured by Hioki Electric Co., Ltd., 3532-50). 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 of the measurement conditions with low humidification were 80 ° C. and 30% RH, respectively.

[Synthesis Example 1]
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, 10 g of 4,4′-difluorodiphenylsulfone, 12 g of 4-chlorophenol, 7 g of potassium carbonate, 30 ml of DMAc and 10 ml of toluene were mixed in a nitrogen atmosphere and heated to 170 ° C. Water produced by refluxing toluene was removed, and after 6 hours, the reaction solution was added to water after cooling to room temperature. The precipitated solid was filtered, and the residue was washed with methanol. The obtained solid was dried under reduced pressure at 60 ° C. for 12 hours to obtain a white solid (hereinafter referred to as M1). Molecular formula of the resulting M1 is _{C 24 H 16 Cl 2 O 4} S, a molecular weight of 471.35.

[Synthesis Example 2]
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, 5 g of 4,4′-difluorodiphenylsulfone, 6 g of 3-chlorophenol, 4 g of potassium carbonate, 40 ml of DMAc and 10 ml of toluene were mixed in a nitrogen atmosphere and heated to 175 ° C. The water produced by refluxing toluene was removed, and after 12 hours, the reaction solution was added to water after cooling to room temperature. The precipitated solid was filtered, and the residue was washed with methanol. The obtained solid was dried under reduced pressure at 60 ° C. for 12 hours to obtain a white solid (hereinafter referred to as M2). Molecular formula of the resulting M2 is _{C 24 H 16 Cl 2 O 4} S, a molecular weight of 471.35.

[Synthesis Example 3]
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, 5 g of 4,4′-dichlorobenzophenone, 6 g of 3-chlorophenol, 4 g of potassium carbonate, 40 ml of DMAc and 10 ml of toluene were mixed in a nitrogen atmosphere and heated to 175 ° C. Water produced by refluxing toluene was removed, and after 12 hours, the reaction solution was added to water after cooling to room temperature. The precipitated solid was filtered, and the residue was washed with methanol. The obtained solid was dried under reduced pressure at 60 ° C. for 12 hours to obtain a white solid (hereinafter referred to as M3). Molecular formula of the resulting M3 is _{C 25 H 16 Cl 2 O 3} , molecular weight is 435.30.

[Synthesis Example 4]
A 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube was charged with 5.86 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. After 6 hours, the reaction solution was added to water after cooling to room temperature, and the precipitated solid was mixed with a mixer. After finely pulverizing and filtering, 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 P1). The molecular weight of the obtained P1 was Mn = 7400 and Mw / Mn = 2.52.

[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 ° C. 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 at 100 ° C. under reduced pressure to obtain a white solid (hereinafter referred to as S1). Molecular formula of the resulting S1 is a _{C 13 H 6 Cl 2 Na 2} O 7 S 2, the molecular weight is 455.20.

[Synthesis Example 6]
120 g of 2,5-dichlorobenzenesulfonic acid was mixed with an aqueous NaOH solution for neutralization. Water was removed by heating under reduced pressure, and the resulting solid was added to methanol and stirred, followed by filtration. The residue was dried under reduced pressure at 60 ° C. for 12 hours to obtain a white solid (hereinafter referred to as S2). It was. Molecular formula of the resulting S2 are a _{C 6 H 3 Cl 2 NaO 3} S, a molecular weight of 249.05.

[Synthesis Example 7]
120 g of 4,4′-dichlorodiphenylsulfone and 505 g of 30% fuming sulfuric acid were mixed in a nitrogen atmosphere and heated to 120 ° C. 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 at 100 ° C. under reduced pressure to obtain a white solid (hereinafter referred to as S3). Molecular formula of the resulting S3, a _{C 12 H 6 Cl 2 Na 2} O 8 S 3, a molecular weight of 491.25.

[Example 1]
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, M1 (1.4 g), S1 (2.1 g) and 2,2′-bipyridine (3.0 g) were mixed with 40 ml of DMSO and heated to 80 ° C. After completely dissolving, 15 ml of toluene was added and heated to 170 ° C., the toluene was refluxed to remove moisture in the flask, and then the toluene was removed and the mixture was cooled to 80 ° C. Bis (1,5-cyclooctadiene) nickel (5.0 g) was added under a nitrogen atmosphere, and the mixture was stirred with a mechanical stirrer. After the reaction for 4 hours, the reaction solution was cooled to room temperature, the reaction solution was slowly added to a 6N aqueous hydrochloric acid solution, and the precipitated solid was collected by filtration. Thereafter, the operation of adding the collected solid to a 6N aqueous hydrochloric acid solution, washing and filtering was repeated twice. Thereafter, it was washed with water, filtered, and dried under reduced pressure at 100 ° C. to obtain a polymer electrolyte. The molecular weight was Mn 98000, and Mw / Mn was 1.94.

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 20 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 2.79 meq / g. When the proton conductivity was measured under low humidification conditions, it was 1.5 × 10 ⁻² S / cm.

[Example 2]
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, M2 (1.6 g), S1 (2.4 g) and 2,2′-bipyridine (3.0 g) were mixed with 60 ml of DMSO and heated to 80 ° C. After completely dissolving, 10 ml of toluene was added and heated to 170 ° C., the toluene was refluxed to remove the water in the flask, and after removing the toluene, the mixture was cooled to 80 ° C. Bis (1,5-cyclooctadiene) nickel (5.0 g) was added under a nitrogen atmosphere, and the mixture was stirred with a mechanical stirrer. After the reaction for 3 hours, the reaction solution was cooled to room temperature, the reaction solution was slowly added to a 6N aqueous hydrochloric acid solution, and the precipitated solid was collected by filtration. Thereafter, the operation of adding the collected solid to a 6N aqueous hydrochloric acid solution, washing and filtering was repeated twice. Thereafter, it was washed with water, filtered, and dried under reduced pressure at 100 ° C. to obtain a polymer electrolyte. The molecular weight was Mn 19000 and Mw / Mn was 19.2.

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. A supporting polymer electrolyte membrane (film thickness 20 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 2.50 meq / g. The proton conductivity measured under low humidification conditions was 1.2 × 10 ⁻² S / cm.

Example 3
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, M3 (1.6 g), S1 (2.4 g) and 2,2′-bipyridine (3.0 g) were mixed with 60 ml of DMSO and heated to 80 ° C. After completely dissolving, 10 ml of toluene was added and heated to 170 ° C., the toluene was refluxed to remove the water in the flask, and after removing the toluene, the mixture was cooled to 80 ° C. Bis (1,5-cyclooctadiene) nickel (5.0 g) was added under a nitrogen atmosphere, and the mixture was stirred with a mechanical stirrer. After the reaction for 3 hours, the reaction solution was cooled to room temperature, the reaction solution was slowly added to a 6N aqueous hydrochloric acid solution, and the precipitated solid was collected by filtration. Thereafter, the operation of adding the collected solid to a 6N aqueous hydrochloric acid solution, washing and filtering was repeated twice. Thereafter, it was washed with water, filtered, and dried under reduced pressure at 100 ° C. to obtain a polymer electrolyte. The molecular weight was Mn62000, and Mw / Mn was 2.69.

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: 24 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 2.84 meq / g. When proton conductivity was measured under low humidification conditions, it was 1.4 × 10 ⁻² S / cm.

Example 4
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, M1 (1.6 g), S1 (2.4 g) and 2,2′-bipyridine (3.0 g) were mixed with 60 ml of DMSO and heated to 80 ° C. After completely dissolving, 10 ml of toluene was added and heated to 170 ° C., the toluene was refluxed to remove the water in the flask, and after removing the toluene, the mixture was cooled to 80 ° C. Bis (1,5-cyclooctadiene) nickel (5.0 g) was added under a nitrogen atmosphere, and the mixture was stirred with a mechanical stirrer. After the reaction for 3 hours, the reaction solution was cooled to room temperature, the reaction solution was slowly added to a 6N aqueous hydrochloric acid solution, and the precipitated solid was collected by filtration. Thereafter, the operation of adding the collected solid to a 6N aqueous hydrochloric acid solution, washing and filtering was repeated twice. Thereafter, it was washed with water, filtered, and dried under reduced pressure at 100 ° C. to obtain a polymer electrolyte. The molecular weight was Mn 48000, and Mw / Mn was 12.7.

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. A supporting polymer electrolyte membrane (film thickness 22 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 2.32 meq / g. When proton conductivity was measured under low humidification conditions, it was 1.1 × 10 ⁻² S / cm.

Example 5
In a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube, M3 (2.0 g), S1 (1.0 g) and 2,2′-bipyridine (3.0 g) were mixed with 60 ml of DMSO and heated to 80 ° C. After completely dissolving, 10 ml of toluene was added and heated to 170 ° C., the toluene was refluxed to remove the water in the flask, and after removing the toluene, the mixture was cooled to 80 ° C. Bis (1,5-cyclooctadiene) nickel (5.0 g) was added under a nitrogen atmosphere, and the mixture was stirred with a mechanical stirrer. After the reaction for 4 hours, the reaction solution was cooled to room temperature, the reaction solution was slowly added to a 6N aqueous hydrochloric acid solution, and the precipitated solid was collected by filtration. Thereafter, the operation of adding the collected solid to a 6N aqueous hydrochloric acid solution, washing and filtering was repeated twice. Thereafter, it was washed with water, filtered, and dried under reduced pressure at 100 ° C. to obtain a polymer electrolyte. The molecular weight was Mn 68000, and Mw / Mn was 2.64.

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 27 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 1.59 meq / g. When the proton conductivity was measured under low humidification conditions, it was 5.8 × 10 ⁻⁴ S / cm.

Example 6
M1 (1.6 g), S1 (1.6 g), S2 (0.8 g) and 2,2′-bipyridine (3.0 g) were mixed with DMSO 60 ml in a 100 ml eggplant flask equipped with a reflux tube and a DeanStark tube. Then, the mixture was heated to 80 ° C. to be completely dissolved, and then 10 ml of toluene was added and heated to 170 ° C., the toluene was refluxed to remove moisture in the flask, and then the toluene was removed, followed by cooling to 80 ° C. Bis (1,5-cyclooctadiene) nickel (5.0 g) was added under a nitrogen atmosphere, and the mixture was stirred with a mechanical stirrer. After the reaction for 4 hours, the reaction solution was cooled to room temperature, the reaction solution was slowly added to a 6N aqueous hydrochloric acid solution, and the precipitated solid was collected by filtration. Thereafter, the operation of adding the collected solid to a 6N aqueous hydrochloric acid solution, washing and filtering was repeated twice. Thereafter, it was washed with water, filtered, and dried under reduced pressure at 100 ° C. to obtain a polymer electrolyte. The molecular weight was Mn 96000, and Mw / Mn was 1.98.

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 31 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 2.53 meq / g. When proton conductivity was measured under low humidification conditions, it was 9.4 × 10 ⁻³ S / cm.

[Comparative Example 1]
In Example 1, S2 (1.5 g) was used instead of S1, P1 (1.5 g), DMSO 50 ml, toluene 16 ml, 2,2′-bipyridine 3.0 g and bis (1,5-cyclooctadiene) nickel The synthesis was performed in the same manner except that 5.0 g 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 = 72000 and Mw / Mn = 1.67.

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 (film thickness 30 μm) 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 (Dainippon Ink Industries, Ltd., DIC-PPS LD10p11) with a screw temperature of 290 ° C. and a T die temperature of 290 ° C. The polymer film was obtained by melt extrusion molding. In a glass container, 634 g of 1-chlorobutane and 15 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 10 times the weight of the polymer film). Thereafter, the polymer electrolyte membrane was recovered, washed with ion-exchanged water until neutral, and vacuum dried at 100 ° C. for 18 hours to obtain a self-supporting polymer electrolyte membrane (film thickness 65 μm).

The obtained membrane had an ion exchange capacity of 2.20 meq / g. When the proton conductivity was measured under low humidification conditions, it was 7.5 × 10 ⁻⁴ S / cm.

From comparison between Examples 1 to 6 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 Flow path 10 Polymer electrolyte fuel cell

Claims (14)

The following formulas (1) and (2):

(In the formula, Ar represents a benzene ring, a naphthalene ring, or a carbon in which those rings are substituted with a hetero atom, X represents a proton or a cation, and a and b are each independently 0. The total of a and b is 1 or more, c represents an integer of 1 or more, and d represents an integer of 0 or more.

(In the formula, Ar is the same as described above. Y represents CO, SO ₂ , C (CH ₃ ) ₂ , and C (CF ₃ ) _2. E and f each independently represent an integer of 1 or more, and g represents 1 And represents an integer of 7 or less, and Z represents a direct bond, oxygen, or sulfur.)
A polymer electrolyte having a structure represented by The polymer electrolyte according to claim 1, wherein e and f are 1 in the formula (2). The polymer electrolyte according to claim 1 or 2, wherein only a compound having a molecular weight of less than 2000 is used as a raw material constituting the main chain. The polymer electrolyte according to any one of claims 1 to 3, wherein the hydrophilic part structure in the polymer has only the structure represented by the formula (1) or a repeating structure thereof. The structure represented by the formula (1) is represented by the following formula (3):

(In the formula, X, a and b are the same as described above. H is an integer of 0 to 4, and may be not the same in some cases. M is an integer of 1 or more, and n is an integer of 0 or more. )
The polymer electrolyte according to any one of claims 1 to 4, which has a structure represented by: The structure represented by the formula (2) is represented by the following formula (4) and / or (5):

(In the formula, Y and m are the same as described above.)
The polymer electrolyte according to any one of claims 1 to 5, which has a structure represented by: The structures represented by the formulas (4) and (5) are represented by the following formulas (6) and (7), respectively:

(Wherein, Y is .R ² the same .R ¹ is a group represented by halogen atom or _OSO 2 ^{R 2,} represents an alkyl group, an aryl group or a halogenated alkyl group.)
The polymer electrolyte according to claim 6, which is synthesized from a compound having a structure represented by: 8. The polymer electrolyte according to claim 1, wherein the total structure represented by the formula (1) is contained in an amount of 10% by weight or more of the whole. The polymer electrolyte according to any one of claims 1 to 8, comprising a block copolymer comprising a hydrophilic segment having a sulfonic acid group and a hydrophobic segment having no sulfonic acid group. The polymer electrolyte according to claim 9, wherein 10% by weight or more of the hydrophilic segment having a sulfonic acid group has a structure represented by the formula (1). The polymer electrolyte membrane containing the polymer electrolyte as described in any one of Claims 1-10. A membrane / electrode assembly comprising the polymer electrolyte membrane according to claim 11. A solid polymer fuel cell comprising the polymer electrolyte membrane according to claim 11. A polymer electrolyte fuel cell comprising the membrane / electrode assembly according to claim 12.

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