JP2022148992A - Composition, cured product, method for producing cured product, solid electrolyte membrane, fuel cell, water electrolysis device, redox flow battery, and actuator - Google Patents

Abstract

To provide a composition that yields a cured product having excellent ionic (proton) conductivity when cured.SOLUTION: Provided is a composition that contains a polymer compound having a repeating unit represented by the following formula (1) and a radical polymerization initiator. (In the formula, Ar11 represents an arylene group or a heteroarylene group, L11 represents a single bond or a divalent group, m represents an integer from 2 to 40, the plurality of Ar11 and L11 may be the same or different, and for each of the repeating units, at least one of the hydrogen atoms of the group represented by Ar11 is substituted with a group having a sulfonic acid group or a salt thereof).SELECTED DRAWING: Figure 7

Description

TECHNICAL FIELD The present invention relates to a composition, a cured product, a method for producing a cured product, a solid electrolyte membrane, a fuel cell, a water electrolysis device, a redox flow battery, and an actuator.

Hydrocarbon-based proton-conducting solid electrolytes are known. Patent Document 1 describes "a proton-conducting polymer electrolyte composed of a sulfonated polyphenyl compound having a plurality of repeating units, in which an average of two or more sulfone groups are introduced into each repeating unit. polyelectrolyte.” is described.

WO2017/029967

The proton-conducting polymer electrolyte described in Patent Document 1 has room for improvement in ionic conductivity.
Accordingly, an object of the present invention is to provide a composition which, when cured, yields a cured product having excellent ionic (proton) conductivity. Another object of the present invention is to provide a cured product, a method for producing the cured product, a solid electrolyte membrane, a fuel cell, a water electrolysis device, a redox flow battery, and an actuator.

As a result of intensive studies aimed at achieving the above object, the inventors of the present invention have found that the above object can be achieved with the following configuration.

[1] A composition comprising a polymer compound having a repeating unit represented by formula 1 below and a radical polymerization initiator.
[2] The composition according to [1], wherein the mass-based ratio of the content of the radical polymerization initiator to the content of the polymer compound is 0.05 to 0.30.
[3] The composition according to [1] or [2], wherein the repeating unit represented by Formula 1 described later is a repeating unit represented by Formula 2 described later.
[4] The composition according to [3], wherein the repeating unit represented by formula 2 is a repeating unit represented by formula 3 described below.
[5] The composition according to [4], wherein the repeating unit represented by formula 3 above is a repeating unit represented by formula 4 described below.
[6] The composition according to any one of [1] to [5], wherein the radical polymerization initiator is an azo compound.
[7] Any one of [1] to [3], wherein the total number of groups having a sulfonic acid group or a salt thereof in the polymer compound is 2 to 6 per repeating unit. composition.
[8] A cured product obtained by curing the composition according to any one of [1] to [7].
[9] The cured product of [8], wherein the polymer compound is crosslinked via -S(=O) ₂ -.
[10] The cured product according to [8] or [9], which does not contain the radical polymerization initiator.
[11] A method for producing a cured product, comprising heating the composition according to any one of [1] to [7] to obtain a cured product.
[12] The method for producing a cured product according to [11], comprising immersing the cured product in an acidic solution.
[13] A solid electrolyte membrane comprising the cured product according to any one of [8] to [10].
[14] A fuel cell comprising the solid electrolyte membrane of [13].
[15] A water electrolysis device including the solid electrolyte membrane according to [13].
[16] A redox flow battery comprising the solid electrolyte membrane of [13].
[17] An actuator including the solid electrolyte membrane according to [13].

ADVANTAGE OF THE INVENTION According to this invention, the composition from which hardened|cured material which has the outstanding ion conductivity is obtained when hardened can be provided. The present invention can also provide a cured product, a method for producing a cured product, a solid electrolyte membrane, a fuel cell, a water electrolysis device, a redox flow battery, and an actuator.

1 is an exploded perspective view of an example of an embodiment of a fuel cell of the present invention; FIG. FIG. 2 is a cross-sectional view of a laminate included in the fuel cell of FIG. 1; It is an example of embodiment of the water electrolysis apparatus of this invention. 1 is an example of an embodiment of a redox flow battery of the present invention. It is a cross-sectional schematic diagram of an example of embodiment of the actuator of this invention. It is the result of having evaluated the presence or absence of the radical polymerization initiator in hardened|cured material using FTIR(Fourier Transform Infrared Spectroscopy). It is the measurement result of the mechanical properties of the cured product.

The present invention will be described in detail below.
Although the description of the constituent elements described below may be made based on representative embodiments of the present invention, the present invention is not limited to such embodiments.
In this specification, a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.

[Composition]
A composition according to an embodiment of the present invention (hereinafter also referred to as "this composition") contains a polymer compound represented by formula 1 described below and a radical polymerization initiator. Although the mechanism by which the present composition solves the problem is not necessarily clear, the present inventors speculate as follows.

The hydrocarbon-based polymer electrolyte described in Patent Document 1 undergoes dehydration condensation of some of the sulfonic acid groups responsible for proton conduction and intermolecular cross-linking via -S(=O) ₂ -, resulting in water resistance and It is compatible with proton conductivity. This cured product tended to have a dense and strong crosslinked structure.

The composition contains a radical polymerization initiator. Therefore, when heated, the radical species generated by the radical polymerization initiator first promotes the bonding between the ends of the polymer compound, thereby causing a reaction such as elongation of the molecular chain of the polymer compound. It is assumed that

After that, when it is further heated, -S(=O) ₂ -crosslinks are formed by dehydration condensation. It is presumed that changes such as an increase in the molecular weight between cross-linking points occurred, and a cross-linking structure different from that of conventional hydrocarbon-based polymer electrolytes was obtained. It is speculated that this change in the crosslinked structure surprisingly led to an improvement in ionic conductivity. Each component of the present composition is described in detail below.

<Polymer compound>
(Unit 1)
The polymer compound includes a repeating unit represented by the following formula 1 (hereinafter also referred to as "unit 1"), and at a predetermined position of each repeating unit, at least one sulfonic acid group or a salt thereof; has a group with

In Formula 1, Ar ¹¹ represents an arylene group or a heteroarylene group. Ar ¹¹ preferably has 6 to 20 carbon atoms, more preferably 6 to 15 carbon atoms, and even more preferably 6 to 12 carbon atoms. Ar ¹¹ may be a group represented by AR1 below.
Ar ¹¹ is preferably a p-phenylene group in terms of obtaining a composition having more excellent effects of the present invention.

In Formula 1, L ¹¹ represents a single bond or a divalent group. Examples of divalent groups include -C(=O)-, -C(=O)O-, -OC(=O)-, -O-, -S- and -S(=O) ₂ - , -NR ^A - (R ^A represents a hydrogen atom or a monovalent organic group), a hydrocarbon group (preferably having 1 to 10 carbon atoms) in which the hydrogen atom may be substituted with a halogen atom, and these and the like.

Among them, from the viewpoint of obtaining a composition having more excellent effects of the present invention, the divalent group of L ¹¹ includes —O—, —S—, —CH ₂ —, and —C(CH ₃ ) ₂ At least one group selected from the group consisting of -, -C(CF ₃ ) ₂ -, -C(=O)- and -S(=O) ₂ - is preferred.

In Formula 1, m represents an integer of 2 to 40, preferably an integer of 2 to 20, more preferably an integer of 2 to 10.

Unit 1 includes a plurality of groups represented by Ar ¹¹ and a plurality of groups represented by L ¹¹ . The multiple Ar ¹¹ and L ¹¹ may be the same or different. That is, the unit 1 may contain multiple types of Ar ¹¹ and/or L ¹¹ .
From the viewpoint of obtaining a composition having more excellent effects of the present invention, it is preferable that the unit 1 contains a plurality of types of Ar ¹¹ and a plurality of types of L ¹¹ .

- Group containing sulfonic acid group, etc. The polymer compound is a group having one or more sulfonic acid groups or salts thereof (hereinafter also referred to as "sulfonic acid group, etc.") per unit 1 (hereinafter referred to as "sulfonic acid group (also referred to as "iso-containing group"). This group containing a sulfonic acid group or the like is bonded by substituting any one hydrogen atom of the groups represented by Ar ¹¹ contained in the unit 1 . The hydrogen atom to be substituted is preferably a hydrogen atom directly bonded to a carbon atom constituting the ring of Ar ¹¹ .

Here, among the sulfonic acid group-containing groups, the structure of the group having a sulfonic acid group is not particularly limited, but a group represented by S1 below is preferable.

In the above formula S1, L ^S1 is a single bond or an m + n + monovalent group, m and n are each independently an integer of 0 or more, and when L ^S1 is a single bond, m is 0 and n is 1, and when L ^S1 is an m+n+1-valent group, n represents an integer of 1 or more, m represents an integer of 0 or more, and * represents a bonding position.
In Formula S1, R ¹ represents a hydrogen atom or a monovalent substituent, preferably a hydrogen atom.
Moreover, it is preferable that m is 0 and n is 1 in order to obtain a more excellent effect of the present invention.

The m+n+1-valent group of L ^S1 is not particularly limited, but examples of the divalent group include the same divalent groups as the group represented by L ¹¹ in Formula 1.

The group having a valence of 3 or more for L ^{1 S1} is not particularly limited, and examples thereof include groups represented by the following formulas (1a) to (1d).

In formula (1a), L3 represents a _trivalent group. T3 represents a single bond or a divalent group, and _{three T3s} may be the same or different.
L ₃ is a nitrogen atom, a trivalent hydrocarbon group (preferably having 1 to 10 carbon atoms; the hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group), or Examples thereof include trivalent heterocyclic groups (preferably 5- to 7-membered heterocyclic groups), and the hydrocarbon groups may contain a heteroatom (eg, —O—). Specific examples of L3 include a nitrogen atom _, a glycerin residue, a trimethylolpropane residue, a phloroglucinol residue, a cyclohexanetriol residue, and the like.

In formula (1b), L4 represents a _tetravalent group. T4 represents a single bond or a divalent group, and _{four T4s} may be the same or different.
A preferred form of L ₄ is a tetravalent hydrocarbon group (preferably having 1 to 10 carbon atoms. The hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group.), A tetravalent heterocyclic group (preferably a 5- to 7-membered heterocyclic group) may be mentioned, and the hydrocarbon group may contain a heteroatom (eg, —O—). Specific examples of _L4 include a pentaerythritol residue and a ditrimethylolpropane residue.

In formula (1c), L5 represents a _pentavalent group. T5 represents a single bond or a divalent group, and _{five T5s} may be the same or different.
A preferred form of L ₅ is a pentavalent hydrocarbon group (preferably having 2 to 10 carbon atoms. The hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group.), Alternatively, a pentavalent heterocyclic group (preferably a 5- to 7-membered heterocyclic group) may be mentioned, and the hydrocarbon group may contain a heteroatom (eg, —O—). Specific examples of _L5 include an arabinitol residue, a phloroglucidol residue, a cyclohexanepentaol residue, and the like.

In formula (1d), L6 represents a _hexavalent group. T6 represents a single bond or a divalent group, and _{six T6s} may be the same or different.
A preferred form of L ₆ is a hexavalent hydrocarbon group (preferably having 2 to 10 carbon atoms. The hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group.), Alternatively, a hexavalent heterocyclic group (preferably a 6- to 7-membered heterocyclic group) may be mentioned, and the hydrocarbon group may contain a heteroatom (eg, —O—). Specific examples of L6 include mannitol residue, sorbitol residue, dipentaerythritol residue, _{hexahydroxybenzene} , and hexahydroxycyclohexane residue.

Specific examples and preferred forms of the divalent groups represented by T ₃ to T ₆ in formulas (1a) to (1d) may be the same as the divalent groups of L ^{1 S1} already described.

Among them, the group represented by the formula S2 is preferable as the group having a sulfonic acid group.

In formula S2, L ^S2 represents a single bond or a divalent group, and the divalent group of L ^S2 includes the forms shown as the divalent group of L ^S1 , and preferred forms are also the same as above. be.

The group having a sulfonic acid salt is preferably a salt of the above sulfonic acid group, and the counter ion is preferably a metal cation, such as Li, Na, K, Mg, Ca, Sr, Ti, Al, Fe, Rh, Pt, Ru, Ir, Pd, etc., can be mentioned, and Li, Na, or K is preferred.

The content of the unit 1 in the polymer compound is not particularly limited, but from the viewpoint of obtaining a composition having a more excellent effect of the present invention, when the total repeating units of the polymer compound are 100 mol%, 90 mol % or more is preferable, and 95 mol % or more is more preferable. The polymer compound preferably consists of 1 unit.

(Unit 2)
Unit 1 is preferably a repeating unit represented by the following formula 2 (hereinafter also referred to as "unit 2") in that a composition having more excellent effects of the present invention can be obtained.

In Formula 2, Ar ²¹ , Ar ²² and Ar ²³ each independently represent an arylene group or a heteroarylene group, and include the same groups as those represented by Ar ¹¹ in Formula 1, preferably The morphology is the same.

In Formula 2, L ²¹ and L ²² are each independently a single bond, or —O—, —S—, —CH ₂ —, —C(CH ₃ ) ₂ —, —C(CF ₃ ) ₂ represents a divalent group selected from the group consisting of -, -C(=O)-, and -S(=O) ₂ -;

In Formula 2, p represents an integer of 1 to 5, preferably 1 or 2, q represents an integer of 0 to 30, preferably 1 to 20, more preferably 2 to 10.

Unit 2 includes a plurality of each of a group represented by Ar ²¹ , a group represented by Ar ²² , a group represented by Ar ²³ , a group represented by L ²¹ , and a group represented by L ²² . may be These plural groups may be the same or different.

One or more sulfonic acid group-containing groups are included per unit 2. A group containing a sulfonic acid group or the like is bonded by replacing a hydrogen atom possessed by at least one group selected from the group consisting of groups represented by Ar ²¹ , Ar ²² and Ar ²³ contained in a plurality of units 2. ing. This substituted hydrogen atom is preferably a hydrogen atom directly bonded to a carbon atom constituting a ring of the groups represented by Ar ²¹ , Ar ²² and Ar ²³ .

The content of unit 2 in the polymer compound is not particularly limited, but is the same as the content of unit 1 already described, and the preferred form is also the same.

(Unit 3)
Unit 2 is preferably a repeating unit represented by the following formula 3 (hereinafter also referred to as "unit 3") in order to obtain a composition having more excellent effects of the present invention.

In Formula 3, L ³¹ and L ³² each independently represent a single bond, an oxygen atom, a sulfur atom, or —SO ₂ —, preferably an oxygen atom.
Moreover, X ³¹ , X ³² and X ³³ each independently represent a hydrogen atom, a lithium atom, a sodium atom or a potassium atom, preferably a hydrogen atom or a sodium atom. Further, m represents an integer of 1 to 5, preferably 1 or 2, r represents an integer of 1 to 3, preferably 2, and n represents an integer of 0 to 10, preferably 1.

Also, y ₁ , y ₂ and y ₃ each independently represent an integer of 0 to 4, at least one of which is 1 or more. That is, the sum of y ₁ to y ₃ is 1 or more, preferably 2 or more, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.
In particular, y ₁ and y ₂ are preferably 0 to 2, and y ₃ is preferably 0 to 2, in order to obtain a composition having more excellent effects of the present invention.

Although the content of unit 3 in the polymer compound is not particularly limited, it is the same as the content of unit 1 already described, and the preferred form is also the same.

(Unit 4)
Unit 3 is preferably a repeating unit represented by the following formula 4 (hereinafter also referred to as "unit 4") in order to obtain a composition having more excellent effects of the present invention.

In Formula 4, X ⁴¹ , X ⁴² , X ⁴³ and X ⁴⁴ are each independently a hydrogen atom, a lithium atom, a sodium atom or a potassium atom, preferably a hydrogen atom or a sodium atom.
z ₁ , z ₂ , z ₃ and z ₄ each independently represents an integer of 0 to 4, and at least one selected from the group consisting of z ₁ , z ₂ , z ₃ and z ₄ is 1 or more is. That is, the sum of z ₁ to z ₄ is 1 or more, preferably 2 or more, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.
Among them, z ₁ and z ₂ are preferably 0 to 2, and z ₃ and z ₄ are preferably 0 to 2, in order to obtain a composition having more excellent effects of the present invention.

Although the content of unit 4 in the polymer compound is not particularly limited, it is the same as the content of unit 1 already described, and the preferred form is also the same.

The polymer compound may have repeating units other than Unit 1, Unit 2, and Unit 3. The content of other repeating units is preferably 10 mol % or less when the total repeating units of the polymer compound are taken as 100 mol %.

Although the molecular weight of the polymer compound is not particularly limited, it is generally preferably from 20,000 to 1,000,000, more preferably from 50,000 to 500,000.

The method for producing the polymer compound is not particularly limited, and known methods can be used. A method for producing a polymer compound is described, for example, in paragraphs 0007 to 0029 of WO 2016/072350, which is incorporated herein.
More specifically, the polymer compound is desalted and polycondensed using an aromatic dihalogen compound and an aromatic dihydroxy compound in an aprotic polar solvent in the presence of potassium carbonate. is shown in Scheme 1 below.

In Scheme 1 above, sulfonation and recrystallization of bis(4-fluorophenyl)sulfone can be carried out, for example, by the following methods. First, a mixture of bis(4-fluorophenyl)sulfone and 30% by weight fuming sulfuric acid is heated (for example, at 120° C. for 12 hours), and the heated mixture is poured into brine to precipitate the product. The precipitate is filtered, then redissolved in water and neutralized with aqueous NaOH. Salt may then be added to obtain a precipitate of the crude product and the crude product may be recrystallized with a water-ethanol mixture. Thus, sulfonediphenylsulfone (denoted as "SFPS" in the above scheme) is obtained.

Next, the SFPS and 4,4′-biphenol (described as “BP” in the above scheme) are subjected to desalting polycondensation to give 2S-PPSU (two sulfonic acid groups per repeating unit). (Scheme 1 above, which forms a salt with the counterion Na ⁺ ) is introduced into the "2-sulfonated polyphenylsulfone") is obtained. In the formula, n represents an integer of 2 or more.

As a method of desalting polycondensation, for example, SFPS, BP, K ₂ CO ₃ , DMSO (dimethyl sulfoxide), and toluene are mixed, and a method of heating this mixture under a nitrogen gas atmosphere (for example, 24 at 140 ° C. time) can be used. After polymerization, the polymer is precipitated in sulfuric acid, filtered to obtain a crude product, and then the obtained crude product is redissolved in water, dialyzed, dehydrated and dried. good. Further, the resulting polymer may be washed with sulfuric acid to activate the sulfonic acid groups (--SO ₃ Na to --SO ₃ H).

As a method for producing a polymer compound, for example, the method described in Scheme 2 below can also be used.

2S-PPSU and concentrated sulfuric acid are mixed, the mixture is heated at 60° C. for 2 days, the heated mixture is poured into ice water, dialyzed, dehydrated and dried in a vacuum oven at 80° C. for 2 days. As a result, 4S-PPSU (“4-sulfonated polyphenylsulfone” in which four sulfonic acid groups are introduced per repeating unit) is obtained as described in the above scheme. In Scheme 2, n1 and n2 represent integers of 2 or more.

Similarly, PPSU (polyphenylsulfone) and 30 wt% fuming sulfuric acid are mixed, and this mixture is heated at about 50 ° C. for 3 days or more to sulfonate, resulting in D6S-PPSU (one repeating unit , a "6-sulfonated polyphenylsulfone" into which six sulfonic acid groups are introduced is obtained. This reaction is shown in Scheme 3. In Scheme 3, n1 and n2 represent integers of 2 or more.

Although the details will be described later, a polymer compound has a group containing a sulfonic acid group or the like, and can form a crosslinked structure by causing a dehydration reaction with an active hydrogen atom bonded to a carbon atom with a high electron density. . A carbon atom with a high electron density includes, for example, hydrogen bonded to an aromatic ring.
An example of such a polymer compound cross-linking reaction is shown in Scheme 4 below. In Scheme 4, n represents an integer of 2 or more. As shown in the scheme below, the polymer compound is crosslinked via —SO ₂ —.

The cross-linking reaction can typically proceed by heating the specific polymer in the presence of a dehydrating agent as needed.
When a dehydrating agent is used, a known dehydrating agent can be used, and is not particularly limited. Phosphorus pentoxide, polyphosphoric acid, and the like can be used, and these can be dissolved in a solvent and used as a liquid dehydrating agent. Examples of solvents include alkylsulfonic acids such as methanesulfonic acid and trifluoromethanesulfonic acid; aromatic sulfonic acids such as chlorobenzenesulfonic acid; and the like.

<Radical polymerization initiator>
The radical polymerization initiator may be a photo-radical polymerization initiator that initiates radical polymerization by light, or a thermal radical polymerization initiator that initiates radical polymerization by heat, or these may be used in combination. good too. The present composition preferably produces a cured product by sequentially causing radical generation and dehydration condensation, and from the viewpoint that both of the above reactions proceed by heating, the radical polymerization initiator is a thermal radical polymerization initiator. is preferred.

A known radical polymerization initiator can be used, and for example, those described in International Publication No. 2018/016614 can be used.

Thermal radical polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(methyl isobutyrate), 2,2'-azobis-2,4-dimethylvaleronitrile, and 1 , 1′-azobis (1-acetoxy-1-phenylethane) and other azo compounds; benzoyl peroxide, di-t-butylbenzoyl peroxide, t-butyl peroxypivalate, and di(4-t- butyl cyclohexyl) peroxydicarbonate; and persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate. Among them, an azo compound or a peroxide is preferred, and an azo compound is more preferred, in that a composition exhibiting more excellent effects of the present invention can be obtained.
When the composition contains an azo compound, the resulting cured product has superior flexibility.

Examples of photoradical polymerization initiators include acetophenone-based compounds, benzyl-based compounds, benzophenone-based compounds, thioxanthone-based compounds, bisimidazole-based compounds, acridine-based compounds, acylphosphine-based compounds, and oxime ester compounds.

The content of the radical polymerization initiator in the composition is not particularly limited. The ratio of the content of the agent on a mass basis (content of the radical polymerization initiator/content of the polymer compound) is preferably 0.01 or more, more preferably 0.03 or more, and more preferably 0.05. It is preferably 0.05 or more, preferably 0.30 or less, more preferably 0.20 or less, still more preferably 0.15 or less, and particularly preferably less than 0.15.

When the above ratio exceeds 0.05, the resulting cured product has better ionic conductivity in a high-temperature, low-humidity environment. In this case, the above ratio is preferably 0.30 or less, more preferably 0.20 or less, and even more preferably 0.15 or less.

Further, when the above ratio is more than 0.05 and less than 0.15, the obtained cured product has excellent ionic conductivity at low temperature (low/high humidity) and at high temperature and high humidity.

The composition may contain one type of radical polymerization initiator alone, or may contain two or more types. When the composition contains two or more radical polymerization initiators, the total content is preferably within the above numerical range.

<Other ingredients>
The composition may contain other components in addition to the above components. Other components include, for example, solvents. The solvent is not particularly limited, but from the viewpoint that the cured product obtained by curing the composition tends to have more excellent ionic conductivity, both the polymer compound and the radical polymerization initiator are dissolved (or used alone). Solvents capable of molecular dissolution and diffusion are preferred. From the above viewpoint, the solvent is preferably an aprotic polar solvent such as dichloromethane, tetrahydrofuran, acetone, dimethylformamide, acetonitrile, and dimethylsulfoxide.

Although the content of the solvent in the composition is not particularly limited, it is preferably 10 to 100 mL, more preferably 20 to 80 mL, relative to 1 g of the total of the polymer compound and the radical polymerization initiator.

<Method for producing composition>
The method for producing the composition is not particularly limited, and the above components may be mixed. The order of mixing is not particularly limited, but for example, a polymer compound is dissolved in a solvent to prepare a polymer compound solution, a radical polymerization initiator is dissolved in a solvent to prepare a radical polymerization initiator solution, and the above two It can be produced by mixing solutions.

[Use of composition]
According to the above composition, a cured product having excellent ion conductivity can be formed. Moreover, the obtained cured product has excellent proton conductivity. Therefore, the cured product can be used as a solid electrolyte membrane in a polymer electrolyte fuel cell (PEFC). The above composition can be used for producing a solid polymer electrolyte (membrane).

The cured product can also be used as an ion (cation) exchange membrane, and the ion exchange membrane containing the cured product is, for example, a water-permeable support and a layered cured product placed on the support. It can be used as a cation exchange membrane having The cation exchange membrane can be used, for example, in combination with an anion exchange membrane for electrochemical measuring devices, water electrolysis devices, wastewater treatment devices, and the like.

[Cured product]
A cured product according to an embodiment of the present invention is a cured product obtained by curing the already-described composition.
As already explained, since the present composition contains a radical polymerization initiator, radical species generated from the radical polymerization initiator act on the terminal portion of the polymer compound, causing elongation of the molecular chain and dehydration condensation. It is speculated that the reaction causes intermolecular cross-linking. The order in which these two reactions occur may be either first or in parallel. , preferably a dehydration condensation reaction occurs.

From the above point of view, as a method for producing a cured product, when the radical polymerization initiator is a thermal radical polymerization initiator, it is held at a temperature of 30 to 120 ° C. for 6 to 72 hours, and then at a temperature of 160 to 200 ° C. Holding for 6 to 72 hours is preferred.
By doing so, the generation of radical species by the thermal radical polymerization initiator tends to precede the initiation of the dehydration condensation reaction.

In the dehydration condensation reaction, water molecules are generated, so a dehydrating agent may be used. In this case, a known dehydrating agent can be used, and examples include, but are not particularly limited to, phosphorus pentoxide and polyphosphoric acid.

The resulting cured product may be washed. By washing the cured product, the radical polymerization initiator and the like can be removed from the cured product. The cleaning method is not particularly limited, but includes a method of immersing the cured product in a cleaning liquid and eluting the removal target into the cleaning liquid.
Among them, it is preferable to wash using an alkaline cleaning solution and an acid cleaning solution in that order, in order to obtain a cured product having a more excellent effect of the present invention. Finally, when it is immersed in an acidic solution (sulfuric acid, etc.) to dissociate the salt of the sulfonic acid group and convert it to a sulfonic acid group (activation treatment), the resulting cured product tends to exhibit better ionic conductivity. .

The alkaline cleaning liquid is not particularly limited, but examples thereof include sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, lithium hydroxide aqueous solution, and alkali metal hydroxide aqueous solution such as calcium hydroxide aqueous solution.

The acid washing liquid is not particularly limited, but sulfuric acid and the like can be mentioned. By washing with sulfuric acid, the sulfonic acid groups in the form of salts can be dissociated, so that a cured product having better proton conductivity can be easily obtained. Hereinafter, the cleaning process including acid cleaning may be referred to as activation treatment.

In addition to the acid cleaning liquid and the alkaline cleaning liquid, it is also preferable to wash the cured product with water. For example, it is preferable to wash by sequentially changing the washing liquid in the order of alkali washing, water washing, acid washing, and water washing.

Although the temperature of the cleaning liquid during cleaning is not particularly limited, it is generally preferably 10 to 150°C, more preferably 30 to 100°C.

The cured product preferably does not contain a radical polymerization initiator. The washing step removes unreacted radical polymerization initiator from the cured product. The term "the cured product does not contain a radical polymerization initiator" means that the free radical polymerization initiator contained in the composition has been removed from the cured product.
A structure derived from a radical polymerization initiator that is incorporated into the molecular structure of a polymer compound (for example, bonded by a covalent bond or the like) is not included in the term "radical polymerization initiator" as used herein. That is, even a cured product containing no radical polymerization initiator may have a structure derived from the radical polymerization initiator in the molecule of the polymer compound.

(Drying process)
The drying step is a step of drying the washed cured product to obtain a dried cured product. The drying method is not particularly limited, but includes a method of holding the cured product with or without heating. When heating, the temperature is not particularly limited, but generally 30 to 80°C is preferable.

[Use]
The cured product has excellent proton conductivity even at high temperature and low humidity. Furthermore, when the cured product is a crosslinked product, it also has better mechanical properties due to the crosslinked structure.
Since the cured product has the properties as described above, it can be used as a solid electrolyte in a polymer electrolyte fuel cell (PEFC) or the like.

[Fuel cell]
FIG. 1 is an exploded perspective view of an embodiment of the fuel cell of the present invention. The fuel cell includes an electrolyte layer including a solid electrolyte membrane containing the cured product, a pair of catalyst layers sandwiching the electrolyte layer from both sides, and a gas layer disposed on the surface of the catalyst layer opposite to the cured product. A polymer electrolyte fuel cell having a laminate having a diffusion layer.

As shown in FIG. 1, the fuel cell 10 has a laminate 11, gas diffusion layers 12 and 13 sandwiching the laminate 11 from both sides, and the fuel cell 10 is arranged on the opposite side of each gas diffusion layer. Separators 14 and 15 are provided.
FIG. 2 is a cross-sectional view of the laminate 11. As shown in FIG. The laminate 11 has an electrolyte layer 21 having a cured product, and catalyst layers 22 and 23 sandwiching the electrolyte layer from both sides.

Here, the separators 14 and 15 are each made of a material having electrical conductivity and low gas permeability. Examples of such materials include, but are not particularly limited to, corrosion-resistant metal plates and carbon-based materials such as calcined carbon.

The separator 14 is arranged to face the gas diffusion layer 12 and has a channel 16 having a comb-like structure on the side facing the gas diffusion layer 12 so that the reaction gas can flow. A similar channel 17 is also provided in the separator 15 .
A cooling water flow path 18 is formed on the surface of the separator 14 opposite to the flow path 16 , and a cooling water flow path 19 is formed on the opposite side of the separator 15 to the flow path 17 .

The fuel gas first passes through the channel 16 of the separator 14 and the oxidant gas first passes through the channel 17 of the separator 15 .
A fuel gas (for example, hydrogen, methane, etc.) is supplied to the laminate 11 through the gas diffusion layer 12 while passing through the channels 16 of the separator 14 . On the other hand, the oxidant gas (oxygen, air, etc.) is supplied to the laminate 11 via the gas diffusion layer 13 while passing through the flow paths 17 of the separator 15 .
Both the gas diffusion layers 12 and 13 are made of a material with high electrical conductivity and high gas diffusivity. Although this material is not particularly limited, a porous material is preferable.
The thickness of the gas diffusion layers 12 and 13 is not particularly limited, but is generally preferably 50 to 1000 μm.

The laminate 11 has an electrolyte layer 21, a catalyst layer 22 arranged on one surface of the electrolyte layer 21, and a catalyst layer 23 arranged on the other surface.

The laminate 11 has an electrolyte layer 21 formed in layers. The form of the cured product of the electrolyte layer 21 is as already explained, and the preferred form is also the same, so the explanation is omitted.
Although the thickness of the electrolyte layer 21 is not particularly limited, it is generally preferably 1 to 500 μm. A thickness of 1 μm or more is preferable in terms of ease of production and handling. On the other hand, when the thickness is 500 μm or less, the film resistance is preferably smaller.

Catalyst layers 22 and 23 each include catalyst particles and an electrolyte. Although the shape when viewed from the plane is not particularly limited, a substantially rectangular shape is easy to form.

Although the catalyst particles are not particularly limited, platinum group elements such as platinum, palladium, ruthenium, iridium, rhodium, and osmium can be used. Metals such as iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, as well as alloys, oxides, and multiple oxides thereof can also be used.
The electrolyte used for the catalyst layers 22 and 23 may have ionic conductivity.
According to the above fuel cell, the cured product has excellent proton conductivity, and as a result, it is possible to generate electric current more efficiently.

[Ion exchange membrane]
The ion-exchange membrane that is an embodiment of the present invention is an ion-exchange membrane having a cured product as already described.
Since the cured product can be used as a cation exchange membrane, the ion exchange membrane may be formed only from the cured product. It is preferably a laminate having a layer (cured material layer) containing the formed cured material.

Although the substrate is not particularly limited, a substrate having water permeability is preferable. The water-permeable substrate typically includes a porous member, and the porous member includes, for example, a continuous inorganic oxide porous membrane containing a chemically stable inorganic oxide. be done. Examples of inorganic oxides include, but are not limited to, titanium oxide, silicon oxide, aluminum oxide, niobium oxide, tantalum oxide, and nickel oxide. Moreover, as the porous member, a porous polymer having a halogenated polymer or the like can be used.

Moreover, the ion-exchange membrane, which is a laminate, may further have an anion-exchange membrane on the surface of the substrate opposite to the surface on which the cured product layer is arranged. The anion exchange membrane is not particularly limited, and known anion exchange membranes can be used.
Since the cured product has excellent ion conductivity, the ion exchange membrane has excellent ion conductivity.

[Water electrolysis device]
FIG. 3 is an example of an embodiment of the water electrolysis device of the present invention.
The water electrolysis device 30 has a pair of electrodes (electrode 31 and electrode 32 ), and these electrodes are separated from each other by an ion exchange membrane 33 . Also, the electrodes 31 and 32 and the ion exchange membrane 33 are arranged in the container 34 so as to be in contact with the electrolytic solution 35 . The electrodes 31 and 32 are electrically connected to a potential/current control device (not shown), respectively, so that the current and potential can be controlled and measured.

When raw water is supplied to the water electrolysis device 30, an electric current is passed between the pair of electrodes to electrolyze the raw water to produce hydrogen and oxygen.
For the water electrolysis method, a known method can be applied as electrolysis conditions (raw material water, current density, etc.). Known methods are described, for example, in JP-A-57-131376.

[Redox flow battery]
FIG. 4 is an example of an embodiment of the redox flow battery of the present invention.
The redox flow battery 40 is divided into a positive electrode cell 42 and a negative electrode cell 43 by a separation membrane 41 made of the solid electrolyte membrane. Positive cell 42 and negative cell 43 contain a positive electrode and a negative electrode, respectively. The cathode cell 42 is connected to a cathode tank 46 for supplying and discharging a cathode electrolyte 44 through a pipe. The anode cell 43 is also connected to the anode tank 47 for supplying and discharging the anode electrolyte 45 through a pipe. The electrolyte is circulated through pumps 48 and 49, and an oxidation/reduction reaction (that is, a redox reaction) in which ionic oxidized water is changed occurs, thereby charging and discharging the positive electrode and the negative electrode.

[Actuator]
FIG. 5 is a schematic cross-sectional view of one example of an embodiment of the actuator of the present invention. The actuator element 50 has a pair of flexible electrodes 51 and 52, and an electrolyte layer 53 disposed between the flexible electrodes. The electrolyte layer 53 is made of a solid electrolyte film containing the cured product. . In addition to excellent proton conductivity, the cured product has excellent flexibility, so that it does not interfere with the driving of the actuator.

In addition to the actuators described above, the cured product can also be applied to the actuators described in paragraphs 0054 to 0075 of JP-A-2018-189452 and paragraphs 0006 to 0024 of JP-A-2019-511259.

The present invention will be described in further detail based on examples below. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the examples shown below.

[Synthesis of polymer compound (SPPSU)]
First, PPSU (polyphenylsulfone) beads and sulfuric acid were mixed and kept at 60° C. for 2 days for sulfonation. Thereafter, the sulfonated PPSU was cooled to precipitate, washed with a dialysis membrane to pH 7, and water was removed to obtain SPPSU. When the content of sulfonic acid groups in the obtained SPPSU was determined by a titration method, the number of sulfonic acid groups per repeating unit was 2.3.
The synthesized SPPSU (IEC=3.68 meq/g) was dissolved in DMSO (dimethylsulfoxide) to obtain an SPPSU solution.

[Preparation of composition 1 (SPPSU/BPO)]
A DMSO solution of SPPSU (SPPSU/DMSO) and a DMSO solution of BPO (benzoyl peroxide) (BPO/DMSO) were prepared, and BPO/DMSO was added to SPPSU/DMSO and stirred for about 1 hour. The obtained mixed solution was placed in a petri dish and heat treated at 80° C., 120° C., 160° C. and 180° C. for 24 hours to obtain a cured product.

The resulting cured product was treated with 0.5 M NaOH at 80° C. overnight, then with boiling water for 2 hours, with 1 M H ₂ SO ₄ at 80° C. for 2 hours, then with boiling water for 2 hours. dried. Table 1 is the formulation of each composition prepared.

[Preparation of composition 2 (SPPSU/AIBN)]
A composition was prepared and a cured product was obtained in the same manner as in "Preparation of composition 1" except that AIBN (azobisisobutyronitrile) was used instead of BPO. Table 2 is the formulation of each composition prepared.

[Example 9: Preparation of cured product]
A composition (hereinafter referred to as "CSPPSU") was prepared in the same manner as in "Preparation of Composition 1" except that BPO was not used, and a cured product was obtained.

Using the obtained cured products of Examples 1 to 8 and the cured product of Example 9, mechanical properties, FTIR properties, ion exchange capacity and proton conductivity were measured by the following methods.

(FTIR characteristics)
The presence or absence of a radical polymerization initiator in the cured product was evaluated using FTIR (Thermoscitific, Nicolet 6700). FIG. 6 shows the result.

In FIG. 6, (a) represents the spectrum of AIBN, (b) represents the spectrum of SPPSU, and (c) represents the cured product obtained using the composition of Example 7. (d) represents the spectrum of the cured film obtained using the composition of Example 7 after washing (activation treatment). From this result, the cured product after washing (activation treatment) has 2998 cm ⁻¹ , 2948 cm ⁻¹ (ν _as CH ₃ ) derived from CH ₃ vibration of AIBN in (a), and 2870 cm ⁻¹ , ( The absence of ν _s CH ₃ ) revealed that AIBN was not involved.

(mechanical properties)
As mechanical properties of the cured product, tensile strength (MPa) and elongation at break (%) were measured using a tensile tester (Shimadzu, EZ-S). A sample was prepared using a super dumbbell cutter (model: SDMP-1000 special, conforming to JIS K6251-7 standard). The test was performed at room temperature and the strain rate was 1 mm/min. FIG. 7 shows the result.

(A) in FIG. 7 indicates the result of Nafion (registered trademark)-212 film (thickness=0.050 mm), which had a breaking stress of 16.9 MPa and a breaking elongation of 150% or more.

(B) is the result of the cured product (CSPPSU) (thickness=0.061 mm) of Example 9, which had a breaking stress of 55.6 MPa and a breaking elongation of 69.6%.
(C) is the result of a cured product (after activation treatment) (thickness = 0.052 mm) obtained using the composition of Example 3 (10% BPO), breaking stress 51.3 MPa, The elongation at break was 59.2%.
(D) is the result of a cured product (after activation treatment) (thickness = 0.057 mm) obtained using the composition of Example 7 (10% AIBN), breaking stress 41.2 MPa, The elongation at break was 134.7%.

From the above results, the cured product obtained using the composition of Example 7 containing an azo compound as a radical polymerization initiator has a larger elongation at break than the cured product of the composition of Example 3. I found out that

(ion exchange capacity)
The ion exchange capacity (IEC: Ion exchange capacity) of the cured product was evaluated by the titration method. After drying at 80° C., the cured product was immersed in 2M NaCl and titrated with 0.01M NaOH.
IEC (meq./g) = _{M1V1 /} W _dry
(M ₁ is the molar concentration of NaOH, V ₁ is the amount (ml) adjusted to pH 7, and W _dry is the weight of the dry cured product.)

(proton conductivity)
The proton conductivity of the cured product was measured by a four-probe method using a membrane resistance measurement system MTS740 (Scribner Associates) equipped with a PSM1735 analyzer (Newtons 4th). The measurements were carried out at temperatures of 40 and 80° C. and humidity of 0 to 90% RH. Also, the impedance measurement was performed at an applied voltage of 10 mV (peak to peak) and a frequency of 1 Hz to 1 MHz.
Table 3 shows the measurement results of ion exchange capacity and proton conductivity.

In Table 3, "-" indicates no data. Also, ""nafion" 212" described as a sample name means a Nafion (registered trademark)-212 membrane.

From the results in Table 3, the cured products obtained using the compositions of Examples 2 to 4 and Examples 6 to 8 were obtained using the composition of Example 9 containing no radical polymerization initiator. Compared to the cured film, it had better proton conductivity at both low temperature (40°C) and high temperature (80°C). In particular, it had better proton conductivity even at high temperature and low humidity (40% RH).

Further, from the results in Table 3, the cured product obtained by using the composition of Example 6 containing an azo compound as a radical polymerization initiator exhibited superior proton conductivity compared to the composition of Example 2. It became clear that it has a sexuality.

Further, from the results in Table 3, the content of the radical polymerization initiator with respect to the content of SPPSU (polymer compound) in the composition is more than 0.05 and less than 0.15. compared to the cured product obtained using the composition of Example 6 and the cured product obtained using the composition of Example 8, at low temperature and at high temperature (80° C.) was found to have better ionic conductivity at high humidity (90% RH).

Further, from the results in Table 3, the cured product obtained using the composition of Example 7 in which the content of the radical polymerization initiator exceeds 0.05 with respect to the content of SPPSU (polymer compound) in the composition has superior proton conductivity at high temperature (80° C.) and low humidity (40% RH) compared to the cured product obtained using the composition of Example 6. .

10: fuel cell 11: laminates 12, 13: gas diffusion layers 14, 15: separators 16, 17: flow paths 18, 19: cooling water flow paths 21: electrolyte layers 22, 23: catalyst layer 30: water electrolysis device 31, 32 : Electrode 33 : Ion exchange membrane 34 : Container 35 : Electrolyte 40 : Redox flow battery 41 : Separation membrane 42 : Positive electrode cell 43 : Negative electrode cell 44 : Positive electrode electrolyte 45 : Negative electrode electrolyte 46 : Positive electrode tank 47 : Negative electrode tank 48, 49: pump 50: actuator element 51: flexible electrode 53: electrolyte layer

Claims (17)

A composition comprising a polymer compound having a repeating unit represented by the following formula 1 and a radical polymerization initiator.

(In Formula 1, Ar ¹¹ represents an arylene group or a heteroarylene group, L ¹¹ represents a single bond or a divalent group, m represents an integer of 2 to 40, and a plurality of Ar ¹¹ , and , L ¹¹ may be the same or different, and at least one hydrogen atom of the group represented by Ar ¹¹ is substituted with a group having a sulfonic acid group or a salt thereof per one repeating unit. is done) 2. The composition according to claim 1, wherein a mass-based ratio of the content of the radical polymerization initiator to the content of the polymer compound is 0.05 to 0.30. 3. The composition according to claim 1, wherein the repeating unit represented by Formula 1 is a repeating unit represented by Formula 2 below.

(In Formula 2, Ar ²¹ , Ar ²² and Ar ²³ each independently represent an arylene group or a heteroarylene group, L ²¹ and L ²² each independently represent a single bond or -O the group consisting of -, -S-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -C(=O)- and -S(=O) ₂ - Represents a divalent group selected from more, multiple Ar ²¹ , Ar ²² , Ar ²³ , L ²¹ and L ²² may be the same or different, p represents an integer of 1 to 5, q is 0 represents an integer of to 30, and at least one selected from the group consisting of the group represented by Ar ²¹ , the group represented by Ar ²² , and the group represented by Ar ²³ per one of the repeating units at least one of the hydrogen atoms of the group is substituted with a group having a sulfonic acid group or a salt thereof) 4. The composition according to claim 3, wherein the repeating unit represented by Formula 2 is a repeating unit represented by Formula 3 below.

(In Formula 3, L ³¹ and L ³² each independently represent a single bond, an oxygen atom, a sulfur atom, or —SO ₂ —, and multiple L ³¹ and L ³² may be the same or different. X ³¹ , X ³² and X ³³ each independently represent a hydrogen atom, a lithium atom, a sodium atom or a potassium atom, m represents an integer of 1 to 5, and r represents an integer of 1 to 3 represents, n represents an integer of 0 to 10, y ₁ , y ₂ and y ₃ each independently represents an integer of 0 to 4, and is selected from the group consisting of y ₁ , y ₂ and y ₃ is 1 or more) 5. The composition according to claim 4, wherein the repeating unit represented by Formula 3 is a repeating unit represented by Formula 4 below.

(In Formula 4, X ⁴¹ , X ⁴² , X ⁴³ and X ⁴⁴ are each independently a hydrogen atom, a lithium atom, a sodium atom or a potassium atom, and z ₁ , z ₂ , z ₃ and z ₄ each independently represent an integer of 0 to 4, and at least one selected from the group consisting of z ₁ , z ₂ , z ₃ and z ₄ is 1 or more) The composition according to any one of claims 1 to 5, wherein the radical polymerization initiator is an azo compound. The composition according to any one of claims 1 to 3, wherein the total number of groups having a sulfonic acid group or a salt thereof in the polymer compound is 2 to 6 per repeating unit. thing. A cured product obtained by curing the composition according to any one of claims 1 to 7. 9. The cured product according to claim 8, wherein the polymer compound is crosslinked via -S(=O) ₂ -. The cured product according to claim 8 or 9, which does not contain the radical polymerization initiator. A method for producing a cured product, comprising heating the composition according to any one of claims 1 to 7 to obtain a cured product. The method for producing a cured product according to claim 11, comprising immersing the cured product in an acidic solution. A solid electrolyte membrane comprising the cured product according to any one of claims 8 to 10. A fuel cell comprising the solid electrolyte membrane according to claim 13 . A water electrolysis device comprising the solid electrolyte membrane according to claim 13 . A redox flow battery comprising the solid electrolyte membrane according to claim 13 . An actuator comprising the solid electrolyte membrane according to claim 13 .

Images