JP6748525B2 - Sulfonate-containing polyphenylene ether, proton conductive membrane - Google Patents

Description

The present invention relates to a sulfone group-containing polyphenylene ether and a proton conductive membrane.

In a polymer electrolyte fuel cell, electrodes are joined to both sides of a proton conducting membrane, hydrogen is supplied to the anode side of the proton conducting membrane-electrode structure and oxygen or air is supplied to the cathode side, and power is generated from the potential difference generated at both ends of the electrode. It is a thing.

At this time, the solid polymer electrolyte used for the proton conductive membrane is required to have high proton conductivity, low gas permeability, and high chemical and mechanical stability.

As the proton conductive membrane, a very expensive perfluoroalkyl sulfonic acid polymer, which is typified by Nafion (registered trademark, manufactured by DuPont, USA), has been adopted. Although the perfluorosulfonic acid type membrane shows high proton conductivity and high stability, it has problems that the proton conductivity is not sufficient in a high temperature and low humidity region and the manufacturing cost is high.

As a means for overcoming such a drawback, attention has been paid to a proton conductive membrane in which a sulfone group is introduced into a hydrocarbon-based polymer. For example, those obtained by sulfonation of polyaryl ether sulfone (for example, refer to Non-Patent Document 1), those obtained by sulfonation of polyether ether ketone (for example, refer to Patent Documents 1 and 2), and the like are exemplified.

Further examples include those obtained by sulfonation of polyphenylene ether (for example, see Non-Patent Document 2). In this example, poly(2,6-dimethyl-1,4 phenylene ether), which is a polyphenylene ether used as a general-purpose engineering plastic, is used as a base material, and such a proton conductive membrane is easy to modify and is excellent in economical efficiency. Therefore, it is one of the most promising materials.

JP-A-6-93114 JP, 2005-255850, A JP 2002-110174 A US Patent Application Publication No. 2002/0091225 (pages 1-2)

Journal of Membrance Science, Vol. 83 (1993) p. 211-220 Journal of Applied Polymer Science, Vol. 29 (1984) p. 4017-4027

However, in the case of poly(2,6-dimethyl-1,4-phenylene ether), which is expected to be applied to polymer membranes due to its excellent economic efficiency, the sulfone introduced onto the aromatic ring of the main chain skeleton by sulfonation is used. It was difficult to suppress the elimination of the base due to heat. The elimination of the sulfone group occurs because the main chain skeleton of polyphenylene ether is electron-rich.

In order to solve this problem, a method has been reported in which a Lewis acid and a sultone are used to introduce a sulfone group into the mother skeleton of polyphenylene ether via an alkyl group (see, for example, Patent Document 3). However, this method is not necessarily a practical method because it requires high temperature and long reaction conditions due to the low reactivity of sultone.

Further, as a polymer in which elimination of a sulfone group by heat is suppressed, a highly thermally stable sulfonation obtained by polymerizing using a monomer having a sulfone group introduced on an electron-withdrawing aromatic ring. A polyarylethersulfone compound has been reported (see, for example, Patent Document 4). However, in this method, the polymerization reaction time required to obtain the polymer becomes long due to the low reactivity of the monomer, and there is a problem in the economical efficiency of the polymer.

Further, although there are reports of a non-fluorine type aromatic polymer membrane that is highly designed to improve thermal stability and proton conductivity, there is a problem that the synthesis method is complicated.

Therefore, an object of the present invention is to provide a sulfone group-containing polyphenylene ether, which has good thermal stability, excellent proton conductivity, and high hot water solubility, and which is suitable as a material for a proton conductive membrane.

Under these circumstances, as a result of intensive studies to solve the problems associated with the above-mentioned conventional techniques, a divalent electron-withdrawing group and an aryl group were introduced into the main chain skeleton of polyphenylene ether, and then a sulfo group was added. It has been found that the sulfonated polyphenylene ether can be a proton conductive membrane that is thermally stable, has excellent putron conductivity, has high solubility in hot water, and is electrochemically stable after heat treatment by introducing it. Came to.
In the present invention, by introducing a divalent electron-withdrawing group into the main chain skeleton of polyphenylene ether, the electron abundance of the mother skeleton is reduced, and the skeleton around the mother skeleton is sterically crowded. Is less likely to occur. Then, sulfonation preferentially occurs in the aromatic hydrocarbon group of the side chain, which is less crowded than the area around the mother skeleton (a reaction is apt to occur spatially). Due to the above circumstances, in the present invention, desulfonation due to heat can be effectively suppressed.
Further, the present invention is economically excellent because it can be efficiently produced by a simple synthesis method and inexpensive general-purpose engineering plastics can be used.

That is, the present invention is as follows.

（式（１）中、Ｒ^１〜Ｒ^３は、各々独立して、水素、ハロゲン、アルキル基、フッ素化アルキル基、アリル基、アリール基、シアノ基からなる群より選ばれる少なくとも一つであり；Ｘは、二価の電子求引基であり；Ａｒ^１は、スルホン基以外の基で置換されていてよいアリール基である。）

（式（２）中、Ｒ^４〜Ｒ^６は、各々独立して、水素、ハロゲン、アルキル基、フッ素化アルキル基、アリル基、アリール基、シアノ基からなる群より選ばれる少なくとも一つであり；Ｘは、二価の電子求引基であり；Ａｒ^２は、少なくとも一つのスルホン基で置換されているアリール基である。） [1] A sulfone group-containing polyphenylene ether containing the constituent components represented by the general formula (1) and the general formula (2).

(In the formula (1), R ^{1 to} R ³ are each independently at least one selected from the group consisting of hydrogen, halogen, an alkyl group, a fluorinated alkyl group, an allyl group, an aryl group, and a cyano group. X is a divalent electron-withdrawing group; Ar ¹ is an aryl group which may be substituted with a group other than a sulfone group.)

(In formula (2), R ^{4 to} R ⁶ are each independently at least one selected from the group consisting of hydrogen, halogen, an alkyl group, a fluorinated alkyl group, an allyl group, an aryl group, and a cyano group. X is a divalent electron-withdrawing group; Ar ² is an aryl group substituted with at least one sulfone group.)

[2] The ratio of the constituent component represented by the general formula (1) to the constituent components represented by the general formula (1) and the general formula (2) is 30 to 95 mol %, ) The sulfone group-containing polyphenylene ether according to [1], wherein the proportion of the constituent component represented by the formula (5) is 5 to 70 mol %.

[3] A proton-conducting membrane comprising the sulfone group-containing polyphenylene ether according to [1] or [2].

According to the present invention, a polysulfone group-containing polyphenylene ether having good thermal stability, good thermal stability, excellent proton conductivity, high hot water solubility, and suitable as a material for a proton conductive membrane is prepared. Can be provided.

INDUSTRIAL APPLICABILITY The present invention provides a sulfonation group-containing polyphenylene ether, which is suppressed in elimination of sulfone groups and is excellent in thermal stability, by a novel sulfonation introduction method, and is excellent in ion conductivity, particularly for fuel cells. A polymer material useful as an electrolyte membrane is provided.

Hereinafter, modes for carrying out the present invention (hereinafter, also referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist.

（式（１）中、Ｒ^１〜Ｒ^３は、各々独立して、水素、ハロゲン、アルキル基、フッ素化アルキル基、アリル基、アリール基、シアノ基からなる群より選ばれる少なくとも一つであり；Ｘは、二価の電子求引基であり；Ａｒ^１は、スルホン基以外の基で置換されていてよいアリール基である。）

（式（２）中、Ｒ^４〜Ｒ^６は、各々独立して、水素、ハロゲン、アルキル基、フッ素化アルキル基、アリル基、アリール基、シアノ基からなる群より選ばれる少なくとも一つであり；Ｘは、二価の電子求引基であり；Ａｒ^２は、少なくとも一つのスルホン基で置換されているアリール基である。） (Sulfonyl group-containing polyphenylene ether)
The sulfone group-containing polyphenylene ether of the present embodiment is characterized by containing constituent components represented by the following general formula (1) and general formula (2).

(In the formula (1), R ^{1 to} R ³ are each independently at least one selected from the group consisting of hydrogen, halogen, an alkyl group, a fluorinated alkyl group, an allyl group, an aryl group, and a cyano group. X is a divalent electron-withdrawing group; Ar ¹ is an aryl group which may be substituted with a group other than a sulfone group.)

(In formula (2), R ^{4 to} R ⁶ are each independently at least one selected from the group consisting of hydrogen, halogen, an alkyl group, a fluorinated alkyl group, an allyl group, an aryl group, and a cyano group. X is a divalent electron-withdrawing group; Ar ² is an aryl group substituted with at least one sulfone group.)

In formula (1) and formula (2), the following modes are preferable.
The number of carbon atoms of the alkyl group and the fluorinated alkyl group for R ^{1 to} R ⁶ is preferably 1 to 12, and more preferably 1 to 4.
The allyl group of R ^{1 to} R ⁶ is preferably a 2-propenyl group, a 2-methyl-2-propenyl group or a 2-hexenyl group.
The aryl group of R ^{1 to} R ⁶ (that is, the main chain side) is preferably a phenyl group or a benzyl group.
Examples of the divalent electron-withdrawing group for X include -C(O)-(carbonyl group (keto group)), -S(O)-(sulfoxide), -S(O) _2- (sulfone), -P. (O) _2- (phosphonyl group) is mentioned, and -C(O)-(carbonyl group (keto group)) is preferable.
The aryl group of Ar ² (that is, the side chain side) is preferably a phenyl group, a naphthyl group, an anthracenyl group, or a benzyl group.

In an aspect of the invention, Ar ¹ may be substituted with groups other than sulfone groups. At least one of the substituents on the aromatic ring skeleton of Ar ² is a sulfone group. Here, the bonding position of the sulfone group in the aromatic ring skeleton is not particularly limited. Further, the number of bonding positions of the sulfone group is not limited to one, and may be two or three.

In the aspect of the present invention, elimination of the sulfone group can be suppressed by selectively introducing the sulfone group onto the aromatic ring other than the main chain of the polyphenylene ether. As a result, a thermally stable sulfone group-containing polyphenylene ether can be provided.

In the sulfone group-containing polyphenylene ether of the present embodiment, the ratio of the constituent component represented by the general formula (1) to the constituent components represented by the general formula (1) and the general formula (2) is 30 for the following reason. To 95 mol %, the proportion of the constituent component represented by the general formula (2) is preferably 5 to 70 mol %, and the proportion of the constituent component represented by the general formula (1) is 60 to 95 mol %. It is more preferable that the ratio of the constituent component represented by the general formula (2) is 5 to 40 mol %. The ratio of the constituent component represented by the general formula (2) to the constituent component represented by the general formulas (1) and (2) is also referred to as a sulfonation rate.
When the sulfonation rate is within the above range, high proton conductivity can be obtained and high membrane strength can be maintained when the sulfone group-containing polyphenylene ether is used as a solid polymer electrolyte membrane.
The sulfonation rate is preferably 5 mol% or more, more preferably 15 mol% or more, and further preferably 25 mol% from the viewpoint of enhancing the power generation efficiency of a fuel cell including a resin as a solid polymer electrolyte membrane. % Is particularly preferable, and from the viewpoint of reducing the swelling of the solid polymer electrolyte membrane, it is preferably 70 mol% or less, more preferably 60 mol% or less, and 50 mol% or less. It is more preferable that the content is 40 mol% or less, and particularly preferably 35 mol% or less.
In addition, the sulfonation rate of the resin refers to a value after the resin is dried at room temperature (for example, 30° C.) for 24 hours, unless otherwise specified.

The ion exchange capacity of the sulfone group-containing polyphenylene ether of the present embodiment is not particularly limited as long as desired proton conductivity can be expressed, but for the same reason as the reason of the sulfonation rate, 0.5 to 3.5 meq/g. (Milliequivalent/g) is preferable, 0.5 to 2.5 meq/g (milliequivalent/g) is more preferable, and 1.5 to 2.5 meq/g is further preferable. Particularly preferably, it is 1.2 to 2.5 meq/g.
The ion exchange capacity can be determined by a conventional method.

If the amount of sulfonation of the resin is too large, the water resistance of the resin may be lowered and dissolution/decomposition in water may occur, which is not preferable as a proton conductive membrane.

The ion exchange capacity can be adjusted by the amount of the sulfonating agent, the concentration in the reaction solution, the reaction time of the reaction with the sulfonating agent, and the reaction temperature. It may be increased and the reaction time with the sulfonating agent may be lengthened.

Structure of the sulfonic group-containing polyphenylene ether in the present embodiment, for example, by an infrared absorption ^{spectrum, 677cm -1, 1,140cm -1,} in the presence or absence of the absorption peak of the sulfonic groups of 3,400 cm ^-1, it can be confirmed ..
The above structure can also be confirmed by, for example, ¹ H-NMR.

(Method for producing sulfone group-containing polyphenylene ether)
The method for producing the sulfone group-containing polyphenylene ether of the present embodiment is not particularly limited, for example, by introducing a divalent electron withdrawing group and an aryl group to the base polyphenylene ether, to synthesize a modified polyphenylene ether, and then And a method of synthesizing a sulfone group-containing polyphenylene ether by introducing a sulfone group into the modified polyphenylene ether.

The method for synthesizing the modified polyphenylene ether is not particularly limited, but for example, an acyl group having an acyl group, particularly an aromatic hydrocarbon group, in the aromatic ring skeleton of the polyphenylene ether using a Friedel-Crafts acylation reaction; sulfone Group, in particular, a sulfone group having an aromatic hydrocarbon group; a sulfinyl group, in particular, a sulfinyl group having an aromatic hydrocarbon group; a phosphonyl group, in particular, a phosphonyl group having an aromatic hydrocarbon group; Is mentioned.
In the Friedel-Crafts acylation reaction, more specifically, polyphenylene ether is reacted with an acid halide or the like in the presence of a Lewis acid (metal halide) such as aluminum chloride or tin chloride.

As a reaction solvent, dichloromethane, chloroform, methylene chloride or the like is used.
The reaction conditions include Li, Q. Liu, L.; Liang, S.; Li, Q.; Jin, B.; Bai, R.; Polym. Chem. , 2014, 5, 2425-2432. The conditions described in can be adopted.

The base polyphenylene ether is not particularly limited, but poly(2,6-dimethyl-1,4-phenylene ether), poly(2,6-dimethyl-1,4-phenylene ether) and poly(2,2 A block copolymer with 3,6-trimethyl-1,4-phenylene ether), a mixture thereof, and a random copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol are preferable.

（式（３）中、Ｙは、フッ素以外のハロゲンであり；Ｒ^７〜Ｒ^１１は、各々独立して、水素、ハロゲン、アルキル基、フッ素化アルキル基、アリル基、アリール基、シアノ基であり、ここで、Ｒ^７〜Ｒ^１１の少なくとも一つは、水素である。） The acid halide is not particularly limited, but examples thereof include compounds represented by the following general formula (3).

(In the formula (3), Y is a halogen other than fluorine; R ^{7 to} R ¹¹ are each independently hydrogen, halogen, an alkyl group, a fluorinated alkyl group, an allyl group, an aryl group, or a cyano group. Where, at least one of R ^{7 to} R ¹¹ is hydrogen.)

Further, as the acid halide, in the general formula (3), a side chain aromatic hydrocarbon group bonded to a carbonyl group is replaced with a phenyl group, and a polycyclic aromatic group such as a naphthyl group or anthracenyl group is used. A compound having a hydrocarbon group is also included.
Further, in the above general formula (3), the group bonded to the carbonyl group is replaced with a phenyl group, and the two are linked in such a manner that an alkyl group is sandwiched between the carbonyl group and the side chain aromatic hydrocarbon group. A compound having an aryl group (for example, a benzyl group or the like) that enables the above is also included.

Further, as the acid halide, a compound (also referred to as a sulfonyl halide) in which, in the general formula (3), a [-S(O) _2- ] moiety is used instead of the [-C(O)-] moiety; In the general formula (3), a compound (also referred to as a halogenated sulfinyl) having a [-S(O)-] moiety in place of the [-C(O)-] moiety; A compound (also referred to as halogenated phosphonyl) having a [-P(O)-] moiety in place of the C(O)-] moiety;

The acylation by the Friedel-Crafts acylation reaction is particularly preferably 100 mol %, more preferably 90 to 100 mol %, further preferably 85 to 100 mol %.
The acylation can be confirmed by ¹ H-NMR.

The intrinsic viscosity of the polyphenylene ether is preferably 0.25 dL/g or more, and more preferably 0.30 dL/g or more, from the viewpoint of enhancing the isolation from the solvent when the sulfone group is introduced and the heat resistance. It is more preferably 1.45 dL/g or less, and 0.70 dL or less from the viewpoint of preventing the solution viscosity at the time of introducing the sulfone group from becoming too high and enhancing the handling property such as stirring and liquid feeding. /G or less is more preferable.
The intrinsic viscosity is calculated as follows. That is, 0.5 g of modified polyphenylene ether is dissolved in chloroform to obtain two or more kinds of solutions having different concentrations of 100 mL or more (concentration of 0.5 g/dL or less). Then, at 30° C., using a Ubbelohde viscometer, the specific viscosities of the solutions having different concentrations were measured, the viscosity at the concentration of 0 was derived from the relationship between the specific viscosities and the concentrations, and this viscosity was calculated. It has an intrinsic viscosity.

As a method of introducing a sulfone group into the modified polyphenylene ether wholly or partially, a modified polyphenylene ether is reacted with a sulfonating agent such as fuming sulfuric acid, sulfuric acid, and chlorosulfonic acid in the absence of a solvent or in the presence of a solvent. There is a method of doing.

In addition to the method of introducing a sulfone group by the sulfonating agent, a sulfonate metal salt, a sulfoester group, a sulfonyl chloride group, etc. are introduced, and then ion exchange, deesterification, hydrolysis, etc. are performed to obtain a sulfone group. May be adopted.

As the solvent, halogenated hydrocarbons such as dichloroethane, tetrachloroethane, chloroform and methylene chloride may be used.
The reaction temperature is not particularly limited, but is usually −20 to 180° C., preferably 0 to 100° C.
The reaction time is generally 0.5 to 48 hours, preferably 1 to 10 hours.

Further, as a method of introducing a sulfone group, for example, the method described in Non-Patent Document 2 can be used. That is, poly(2,6-dimethyl-1,4-phenylene ether) is dissolved in chloroform, chlorosulfonic acid is added dropwise to this solution, and the mixture is reacted at room temperature to obtain a sulfone group-containing polyphenylene ether. it can. The sulfo group-containing polyphenylene ether becomes insoluble in chloroform as the sulfonation reaction progresses, precipitates as an amorphous solid, and can be recovered by filtration.

In the sulfone group-containing polyphenylene ether of the present embodiment, the side-chain aromatic ring skeleton bonded to the aromatic ring skeleton through the electron-withdrawing group is more preferable than the aromatic ring skeleton of the main chain of the electron-rich polyphenylene ether. A sulfone group is introduced. Therefore, even under high temperature conditions (for example, 170° C.), it is possible to obtain the effect that it is difficult for the sulfonic group to be removed by heat. And, by the above effect, the ion exchange capacity of the sulfone group-containing polyphenylene ether of the present embodiment after being placed under high temperature conditions is compared with the ion exchange capacity of the conventional sulfone group-containing polyphenylene ether after being placed under high temperature conditions. ,growing.

The sulfone group-containing polyphenylene ether of the present embodiment may contain other constituent components in addition to the constituent components represented by the general formula (1) and the general formula (2). The ratio of the other constituent component relative to the constituent component shown in (1) and 100 mol% of the other constituent component is particularly preferably 0 mol%, more preferably 0 to 10 mol%, and more preferably 0 to 20 mol%. It is preferable if it is mol %.

Examples of the constituent components other than the constituent components represented by the general formulas (1) and (2) include a unit derived from a cross-linking agent added for adjusting the film strength and the molecular weight. Examples of the cross-linking agent include terephthalic acid dichloride and oxalyl chloride, which are capable of promoting the Friedel-Crafts reaction at two places.

(Proton conductive membrane)
The proton conductive membrane of the present embodiment is characterized by containing the sulfone group-containing polyphenylene ether of the present embodiment.
The content of the sulfone group-containing polyphenylene ether of this embodiment in the proton conductive membrane of this embodiment is 100% by mass (that is, the proton conductive membrane of this embodiment is made of the sulfone group-containing polyphenylene ether of this embodiment). Is particularly preferable, but is more preferably 95 to 100% by mass, and is preferably 90 to 100% by mass.

The proton conductive membrane of the present embodiment can be suitably used as a solid polymer electrolyte membrane alone in a polymer electrolyte fuel cell, a redox flow battery, or the like.

The proton conductive membrane of the present embodiment is obtained by completely dissolving the sulfone group-containing polyphenylene ether in a solvent (organic solvent) such as methanol, ethanol, propanol or dimethyl sulfoxide, and then casting this solution on the substrate. Thus, it can be manufactured by forming a film by a casting method or the like for forming a film and drying the obtained film.
Specific examples of the casting method include a spray method, a spin coating method, a doctor spray method and the like.

Examples of the substrate used in the casting method include a glass plate and a plastic film. The plastic film is preferably a polyethylene terephthalate film, a polytetrafluoroethylene film or a polyimide film.

Examples of the solvent for dissolving the sulfone group-containing polyphenylene ether include alcohols such as methanol, ethanol, propanol, iso-propyl alcohol, sec-butyl alcohol, tert-butyl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether. , Alkylene glycol monoalkyl ethers such as propylene glycol monoethyl ether; ethers such as tetrahydrofuran and 1,3-dioxane; N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2- Aprotic polar solvents such as pyrrolidone and acetonitrile; and the like. These may be used alone or in combination of two or more.

The solid concentration of the sulfone group-containing polyphenylene ether in the solution used for casting is 5 to 40% by mass, preferably 7 to 30% by mass, depending on the molecular weight of the polymer.
If the polymer concentration is lower than the lower limit of the above range, it is difficult to form a thick film, and if it exceeds the upper limit of the above range, the solution viscosity is too high to form a film, and a uniform coating film may not be obtained.

The drying after the film formation by the casting may be performed under the condition of maintaining the temperature at 50 to 170° C. for 0.1 to 12 hours.

Hereinafter, the embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Unless otherwise specified, as a raw material for the sulfone group-containing polyphenylene ethers of Examples and Comparative Examples, poly(2,6-dimethyl-1,4-phenylene ether) (S201A, manufactured by Asahi Kasei Chemicals Corporation) (intrinsic viscosity: 0 0.47 dL/g) was used.

The methods for measuring and evaluating various physical properties in Examples and Comparative Examples are shown below.

(1) Sulfonation rate Using a ¹ H-NMR apparatus (ECA-500, manufactured by JEOL Co., Ltd.), the sulfone group-containing polyphenylene ethers of Examples and Comparative Examples were subjected to frequency: 500 MHz, relaxation time: 5 sec, number of integration: The NMR measurement was performed 512 times at room temperature. The specific method for obtaining the sulfonation rate (%) of the synthesized phenyl group-containing polyphenylene ether was as described in the following examples. The results are shown in Table 1.

(2) Thermal Stability The sulfone group-containing polyphenylene ethers of Examples and Comparative Examples were measured using TGA under nitrogen at a temperature rising rate of 10° C./min. In the measurement, mass loss due to water evaporation was first observed up to 140°C, mass loss due to elimination of sulfone group was observed at 140 to 270°C, and mass loss due to aromatic ring decomposition was observed at 270°C or higher. It was From the TGA profile, the temperature at which the removal of the sulfone group of each polymer started (sulfone group desorption initiation temperature) (°C) was examined. The results are shown in Table 1.

(3) Ion exchange capacity 0.02 g of the membrane prepared using the sulfone group-containing polyphenylene ethers of Examples and Comparative Examples was immersed in 30 mL of saturated NaCl aqueous solution at 25° C. and left for 30 minutes while stirring. Next, the proton in the saturated NaCl aqueous solution was neutralized and titrated with 0.01N sodium hydroxide aqueous solution using phenolphthalein as an indicator. After neutralization, a sulfone group-containing polyphenylene ether in which the counter ion of the ion exchange group was a sodium ion was obtained by filtration. The obtained polymer was rinsed with pure water, dried at 160° C. under vacuum, and then weighed for absolute dry weight.
Assuming that the amount of sodium hydroxide required for neutralization is M (mmol) and the mass of the sulfone group-containing polyphenylene ether whose counter ion of the ion exchange group is sodium ion is W (mg), the formula: EW=(W /M)-22, the equivalent mass EW (g/equivalent) was determined. Further, the reciprocal of the obtained EW value was taken and multiplied by 1000 to calculate the ion exchange capacity meq/g (milliequivalent/g).

(4) Evaluation of hot water resistance 10 mg of the polyphenylene ether containing a sulfone group of the examples and comparative examples was immersed in 4 mL of hot water at 90° C. and left for 60 minutes. The solubility of the polymer in hot water was visually evaluated according to the criteria described below; “X” when the polymer was dissolved, and “◯” when it was not dissolved.

Hereinafter, each example and each comparative example will be described in detail.

<Example 1>
Poly(2,6-dimethyl-1,4-phenylene ether) (90 g) and dichloromethane (2250 mL) were added to a 5 L four-necked flask that had been purged with argon, and the mixture was stirred. To the polyphenylene ether solution prepared above, a dichloromethane solution (750 mL) of aluminum chloride (109 g) and benzoyl chloride (104 g) was added dropwise at room temperature over 45 minutes. After completion of dropping, the reaction solution was heated using a mantle heater and reacted at 40° C. for 6 hours, and then the reaction solution was allowed to cool to room temperature. After sampling a small amount of the reaction solution, it was added to methanol (18 L) to precipitate a polymer, and a crude product was collected by filtration. Further, the recovered crude product was dissolved in chloroform (1.4 L), and the solution was added into methanol (10 L) to carry out precipitation purification. The precipitate was filtered under reduced pressure to recover the modified polyphenylene ether (acylated polyphenylene ether) as a product.

The structure of the modified polyphenylene ether was identified by ¹ H-NMR.
¹ H-NMR (THF-d ₈ ) δ 7.84 (s, 2.0H), 7.48 (m, 3.0H), 6.24 (s, 1.0H), 1.86 (m, 6.4H)
The signal of the raw material (2,6-dimethyl-1,4-phenylene ether) was not observed.
From this result, it was found that a polymer composed of the constituent components represented by the following general formula (4) was produced.

Fuming sulfuric acid (1.3 kg) was added to a 3 L four-necked flask in which argon was replaced, and the mixture was stirred with a stirring blade using a mechanical stirrer. The above acylated polyphenylene ether (130 g) was slowly added into the reaction vessel. After stirring at room temperature for 10 hours, the reaction solution was slowly poured into ice water (8 L) to stop the reaction. The precipitated solid was collected by vacuum filtration and washed in ion-exchanged water (5 L). The same washing operation was repeated 9 times until the pH of the water separated by washing in this washing operation became 5 or more. The washed solid was dried under reduced pressure at 50° C. for 60 hours.

（式（５）中、ｎは、整数である。） The structure of the obtained polymer was identified by ¹ H-NMR.
¹ H-NMR (THF-d ₈ ) δ 8.17-7.45 (m, 3.5H), 6.24 (s, 1.0H), 1.86 (s, 5.7H).
From this result, it was found that a polymer composed of the constituent components represented by the following general formulas (4) and (5) was produced.

(In the formula (5), n is an integer.)

^In the result of ¹ H-NMR, sulfonation of the area of the signal derived from the aromatic ring of the unreacted acylated polyphenylene ether unit with reference to the signal derived from the main chain aromatic ring of the acylated polyphenylene ether (δ 6.24 ppm) The sulfonation rate (%) was obtained by calculating the decrease before and after the change as the amount of the position of the aromatic ring of the sulfonated acylated polyphenylene ether unit.
The sulfonation ratio of the sulfone group-containing polyphenylene ether of Example 1 was 31.5%.
The sulfone group elimination initiation temperature of the sulfone group-containing polyphenylene ether of Example 1 was 185°C.

The obtained sulfone group-containing polyphenylene ether is dissolved in methanol, a polytetrafluoroethylene sheet is spread on a stainless steel tray, the solution is applied on the polytetrafluoroethylene sheet by the casting method, and the applied product is air dried at room temperature for 24 hours. did. Thus, a film-shaped proton conductive membrane having a thickness of about 4 μm was obtained.
The ion exchange amount of the proton conductive membrane of Example 1 was 1.26 meq/g.

The obtained sulfone group-containing polyphenylene ether did not appear to dissolve in hot water.

<Examples 2, 3, 4, 5>
A sulfo group-containing polyphenylene ether was prepared in the same manner as in Example 1 except that the reaction time of fuming sulfuric acid with the above-mentioned acylated polyphenylene ether was changed as shown in Table 1.
The evaluation results of the obtained polymer are shown in Table 1.

<Example 6>
After obtaining a sulfone group-containing acylated polyphenylene ether (sulfonation rate: 31.5%) by the same method as in Example 1, this was heat-treated in an oven at 170° C. for 30 minutes in a nitrogen atmosphere.
The evaluation results of the polymer after heat treatment are shown in Table 1.

<Example 7>
A sulfone group-containing polyphenylene ether was prepared in the same manner as in Example 1 except that phenylacetyl chloride was used instead of benzoyl chloride.

（式（７）中、ｎは、整数である。） The structure of the obtained polymer was identified by ¹ H-NMR.
¹ H-NMR (THF-d ₈ ) δ 7.15-7.45 (m, 3.4H), 6.24 (s, 1.0H), 3.93 (s, 2.0H), 1. 86 (s, 5.9H)
From this result, it was found that a polymer composed of the constituent components represented by the following general formulas (6) and (7) was produced.

(In the formula (7), n is an integer.)

^{In the 1} H-NMR result, a signal derived from the side chain phenyl group of the unreacted acylated polyphenylene ether unit (δ 7 based on the signal derived from the main chain aromatic ring of the acylated polyphenylene ether (δ 6.24 ppm)). The sulfonation rate (%) was calculated by calculating the decrease in the area of 0.15 to 7.45 ppm) before and after the sulfonation as the sulfonated acylated polyphenylene ether unit.
Also, the sulfone group desorption start temperature and the amount of ion exchange were determined in the same manner as in Example 1.
The evaluation results of the obtained polymer are shown in Table 1.

<Example 8>
A sulfone group-containing polyphenylene ether was prepared in the same manner as in Example 1 except that benzenesulfonyl chloride was used instead of benzoyl chloride.

（式（９）中、ｎは、整数である。） The structure of the obtained polymer was identified by ¹ H-NMR.
¹ H-NMR (THF-d ₈ ) δ 7.45-8.20 (m, 3.4H), 6.26 (s, 1.0H), 1.86 (s, 5.9H).
From this result, it was found that a polymer composed of the constituent components represented by the following general formulas (8) and (9) was produced.

(In the formula (9), n is an integer.)

^{In the 1} H-NMR result, a signal derived from the side chain phenyl group of the unreacted sulfonylated polyphenylene ether unit (δ 7 based on the signal derived from the main chain aromatic ring of the sulfonylated polyphenylene ether (δ 6.26 ppm)). The sulfonation rate (%) was calculated by calculating the decrease in the area of (.45-8.20 ppm) before and after the sulfonation as the sulfonated acylated polyphenylene ether unit.
Also, the sulfone group desorption start temperature and the amount of ion exchange were determined in the same manner as in Example 1.
The evaluation results of the obtained polymer are shown in Table 1.

<Comparative Example 1>
Sulfonation of poly(2,6-dimethyl-1,4-phenylene ether) was carried out with reference to Non-Patent Document 2 (particularly p.4023).
Chloroform (450 g) was placed in a 500 mL three-necked flask whose atmosphere was replaced with argon, and the mixture was stirred with a mechanical stirrer. Chlorosulfonic acid (9.0 g) was added dropwise at room temperature over 30 minutes, 30 g of poly(2,6-dimethyl-1,4-phenylene ether) was added, and the mixture was stirred at room temperature for 30 minutes. 14 g of chlorosulfonic acid was placed in a dropping funnel, added dropwise over 20 minutes, and then stirred at room temperature for 30 minutes. The supernatant was removed from the precipitated solid. Chloroform was added to the residual solid to wash it, and the supernatant was removed. The obtained residue was collected by vacuum filtration and washed in ion-exchanged water (5 L). The same washing operation was repeated 5 times until the pH of the separated water for washing in this washing operation became 5 or more. The washed solid was dried under reduced pressure at room temperature for 24 hours.

The structure of the obtained polymer was identified by ¹ H-NMR.
¹ H-NMR (DMSO-d ₆ : CDCl ₃ = 1:2 (v/v)) δ 6.45 (s, 2.0H), 6.16 (0.21H), 2.51 (s, 0). .88H), 2.06 (s, 6.0H), 1.99 (s, 0.88H)
From this result, it was found that a polymer composed of the constituent components represented by the following general formulas (10) and (11) was produced.

^In the result of ¹ H-NMR, the peak around δ 6.2 ppm was replaced with the proton (P) at the 3- or 5-position of the sulfonated 2,6-dimethylphenylene oxide unit, and the peak around δ 6.5 ppm was not substituted. Identified as protons (Q) at the 3- and 5-positions of the 2,6-dimethylphenylene oxide unit of No. 2, and the sulfonation rate=peak area (P)/(peak (P ) Area + area of peak (Q)/2) x 100 (%).
The sulfonation rate of the sulfone group-containing polyphenylene ether of Comparative Example 1 was 17.4%.

When the ion exchange amount of the sulfonic group-containing polyphenylene ether of Comparative Example 1 was measured in the same manner as in Example 1, it was 1.2 meq/g.

<Comparative example 2>
In the same manner as in Comparative Example 1, after obtaining a sulfone group-containing polyphenylene ether (sulfonation ratio: 17.4%), this was heat-treated in an oven at 170° C. for 30 minutes in a nitrogen atmosphere.
The evaluation results of the polymer after heat treatment are shown in Table 1.

<Comparative example 3>
Chloroform (450 g) was placed in a 500 mL three-necked flask whose atmosphere was replaced with argon, and the mixture was stirred with a mechanical stirrer. Chlorosulfonic acid (9.0 g) was added dropwise at room temperature over 30 minutes, 30 g of poly(2,6-dimethyl-1,4-phenylene ether) was added, and the mixture was stirred at room temperature for 30 minutes. 20 g of chlorosulfonic acid was placed in a dropping funnel, added dropwise over 20 minutes, and then stirred at room temperature for 120 minutes. The supernatant was removed from the precipitated solid. Chloroform was added to the residual solid to wash it, and the supernatant was removed. The obtained residue was collected by vacuum filtration and washed in ion-exchanged water (5 L). The same washing operation was repeated 5 times until the pH of the separated water for washing in this washing operation became 5 or more. The washed solid was dried under reduced pressure at room temperature for 24 hours.

The sulfonation rate of the sulfone group-containing polyphenylene ether of Comparative Example 3 was 38%.

Similarly to the case of Example 1, the ion exchange amount of the sulfone group-containing polyphenylene ether of Comparative Example 3 was measured and found to be 2.4 meq/g.

In particular, the sulfone group-containing polyphenylene ether of Comparative Example 3 was found to dissolve in hot water.

As shown in Table 1, in Examples 1 to 8, the sulfone group desorption initiation temperature of the sulfone group-containing polyphenylene ether having polyphenylene ether, which is an inexpensive general-purpose engineering plastic in the mother skeleton, is sufficient to withstand film forming conditions. I was able to raise it. Further, in Examples 1 to 8, the solubility in hot water could be reduced while increasing the sulfonation rate.

INDUSTRIAL APPLICABILITY The sulfone group-containing polyphenylene ether of the present invention has industrial applicability as a solid polymer electrolyte membrane and a proton conductive membrane that can be suitably used in solid polymer fuel cells, redox flow batteries and the like.

Claims (3)

A sulfone group-containing polyphenylene ether comprising the constituent components represented by the general formulas (1) and (2).

(In the formula (1), R ^{1 to} R ³ are each independently at least one selected from the group consisting of hydrogen, halogen, an alkyl group, a fluorinated alkyl group, an allyl group, an aryl group, and a cyano group. X is a divalent electron-withdrawing group; Ar ¹ is an aryl group which may be substituted with a group other than a sulfone group.)

(In formula (2), R ^{4 to} R ⁶ are each independently at least one selected from the group consisting of hydrogen, halogen, an alkyl group, a fluorinated alkyl group, an allyl group, an aryl group, and a cyano group. X is a divalent electron-withdrawing group; Ar ² is an aryl group substituted with at least one sulfone group.) The ratio of the constituent component represented by the general formula (1) to the constituent components represented by the general formula (1) and the general formula (2) is 30 to 95 mol %, and the proportion represented by the general formula (2) is represented. The sulfo group-containing polyphenylene ether according to claim 1, wherein the ratio of the constituent components is 5 to 70 mol %. A proton conducting membrane comprising the sulfonic group-containing polyphenylene ether according to claim 1 or 2.