JP4505573B2 - Aromatic sulfonic acid derivatives, sulfonated polymers, solid polymer electrolytes and proton conducting membranes - Google Patents

Description

  The present invention relates to an aromatic sulfonic acid derivative having an ether bond, a sulfonated polymer having a structural unit derived from the derivative, a solid polymer electrolyte containing the sulfonated polymer, and a proton conducting membrane.

  An important application of a solid polymer electrolyte is a fuel cell that uses this as a proton conductor. As a polymer electrolyte membrane (proton conductive membrane) used in a fuel cell, a perfluorohydrocarbon polymer having a sulfonic acid group has been conventionally used. However, since this family of materials has a softening point near 80 ° C., it cannot be used at high temperatures exceeding 100 ° C.

Therefore, as a solid polymer electrolyte that can be used even at a high temperature, a material in which a sulfonic acid group is introduced into an aromatic polymer has been studied (for example, see Patent Document 1). Although these materials have a high softening temperature, the introduction of sulfonic acid groups into the polymer skeleton has a problem in that mechanical properties are deteriorated, for example, the strength and elongation (toughness) are impaired. Further, when the concentration of the sulfonic acid group is increased in order to increase proton conductivity, there are problems such as a large dimensional change caused by water absorption especially under high temperature and high humidity conditions, and a significant decrease in strength.
US Pat. No. 5,403,675

  An object of the present invention is to provide a sulfonated polymer having excellent hot water resistance and mechanical properties, a monomer for obtaining the polymer, and a sulfonated polymer even when the amount of sulfonic acid groups introduced is increased. The object of the present invention is to provide a solid polymer electrolyte and a proton conductive membrane that are high in power generation performance.

  The present inventors have intensively studied to solve the above problems. As a result, the following problems can be solved by providing an aromatic compound having the following ether bond, a sulfonated polymer having a structural unit derived from the compound, a solid polymer electrolyte containing the polymer, and a proton conducting membrane. The headline and the present invention were completed.

  That is, the aromatic sulfonic acid derivative according to the present invention is represented by the following general formula (A).

In the formula (A), X represents a halogen atom, —OSO ₂ CH ₃ or —OSO ₂ CF ₃ , and R represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or a hydrocarbon group having 1 to 20 carbon atoms. Show.

  The sulfonated polymer according to the present invention has a constitutional unit represented by the following general formula (A ′).

  The solid polymer electrolyte and the proton conducting membrane according to the present invention are characterized by including the sulfonated polymer of the present invention.

  According to the present invention, an aromatic sulfonic acid derivative having three sulfonic acid groups in the phenyl ether skeleton, a sulfone containing a structural unit derived from the compound and having three sulfonic acid groups in the side chain phenyl ether skeleton. The polymerized polymer, the solid polymer electrolyte comprising the polymer, and the proton conducting membrane can be provided.

  That is, the sulfonated polymer obtained by using the aromatic sulfonic acid derivative of the present invention as a monomer is characterized by a structure having a high concentration of sulfonic acid groups in a highly rigid side chain. Thereby, even when sulfonic acid groups are introduced at a high concentration, a solid polymer electrolyte excellent in proton conductivity can be obtained without impairing hot water resistance and mechanical properties.

  Hereinafter, an aromatic sulfonic acid derivative according to the present invention, a sulfonated polymer having a structural unit derived from the derivative, a solid polymer electrolyte containing the polymer, and a proton conductive membrane will be described in detail.

<Aromatic sulfonic acid derivative>
The aromatic sulfonic acid derivative of the present invention is represented by the following general formula (A).

Wherein (A), X is a halogen atom (fluorine, chlorine, bromine, iodine), - indicating the OSO ₂ CH ₃ or -OSO ₂ CF _3. In these, a fluorine atom and a chlorine atom are preferable. R represents a hydrogen atom; an alkali metal atom such as lithium, sodium or potassium; an alkaline earth metal atom such as magnesium, calcium or barium; or a hydrocarbon group having 1 to 20 carbon atoms.

Examples of the hydrocarbon group having 1 to 20 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, s-butyl group, pentyl group, isopentyl group, neopentyl group, and cyclopentyl. Group, hexyl group, cyclohexyl group, heptyl group, octyl group, 2-ethylhexyl group, cyclopentylmethyl group, adamantyl group, cyclohexylmethyl group, adamantylmethyl group, tetrahydrofurfuryl group, 2-methylbutyl group, 3,3-dimethyl- Linear hydrocarbon groups such as 2,4-dioxolane methyl group, bicyclo [2.2.2] heptyl group, bicyclo [2.2.1] heptylmethyl group, branched hydrocarbon groups and alicyclic hydrocarbons Groups and the like. Of these, neopentyl, tetrahydrofurfuryl, cyclopentylmethyl, cyclohexylmethyl, adamantylmethyl, and bicyclo [2.2.1] heptyl are preferred.

  Examples of the aromatic sulfonic acid derivative represented by the general formula (A) (hereinafter also referred to as “compound (A)”) include the following compounds.

  In the above compound, other isomers having different positions of chlorine atom or fluorine atom can be exemplified. In addition, examples in which a chlorine atom or a fluorine atom is replaced with another halogen atom can be given. Furthermore, isomers having different positions of the sulfonic acid group can be exemplified. The said compound (A) may be used independently or may be used in combination of 2 or more type.

The compound (A) can be synthesized, for example, by the following reaction.
First, a corresponding compound is synthesized by a Friedel-Crafts reaction between an acid chloride represented by the following general formula (1) and diphenyl ether.

In formula (1), X has the same meaning as X in formula (A).
Examples of the compound represented by the general formula (1) include 2,4-dichlorobenzoic acid chloride, 2,5-dichlorobenzoic acid chloride, 2,6-dichlorobenzoic acid chloride, and 2,4-difluorobenzoic acid chloride. 2,5-difluorobenzoic acid chloride, 2,6-difluorobenzoic acid chloride and the like. In these compounds, those in which a halogen atom is replaced with a bromine atom or an iodine atom can also be mentioned as examples.

  The Friedel-Crafts catalyst that can be used in the above reaction is not particularly limited as long as it is a commonly used catalyst, and examples thereof include aluminum chloride, iron chloride, tin chloride, titanium chloride, and zinc chloride. Can be mentioned. In these compounds, those in which a chlorine atom is replaced by a fluorine atom, a bromine atom or an iodine atom can also be used. Of these, aluminum chloride is preferred.

  The above reaction can be carried out without solvent or can be carried out using a solvent. Examples of the solvent that can be used include halogenated hydrocarbons such as dichloromethane, chloroform, 1,2-dichloroethane, and chlorobenzene, and nitrobenzene. Moreover, the said reaction is normally performed in the range of -20 degreeC-200 degreeC.

  Next, the compound obtained by the above reaction is sulfonated using a sulfonating agent. Examples of the sulfonating agent include sulfuric acid, chlorosulfonic acid, fuming sulfuric acid, anhydrous sulfuric acid and the like, and fuming sulfuric acid is preferable. The reaction is performed so that the sulfonic acid group is introduced into the target aromatic ring by controlling the kind of sulfonating agent, reaction temperature, reaction time, and the like. The preferred reaction temperature is 50 ° C to 150 ° C.

When the sulfonated product obtained in the above step is derived into a sulfonate ester, it can be synthesized by the following reaction.
First, the sulfonated product obtained is converted to acid chloride. In this reaction, thionyl chloride, phosphoryl chloride, phosphorus pentachloride, phosphorus trichloride, or the like can be used. When chlorosulfonic acid is used as the sulfonating agent, this step can be omitted because it can be isolated in the form of acid chloride.

Next, sulfonic acid ester is obtained by esterifying the obtained acid chloride and various alcohols. Examples of the alcohol include methanol, ethanol, propanol, isopropanol, t-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, n-butyl alcohol, n-pentyl alcohol, neopentyl alcohol, cyclopentyl alcohol, n-hexyl alcohol, cyclohexyl alcohol, Heptyl alcohol, octyl alcohol, 2-ethylhexyl alcohol, cyclopentylmethyl alcohol, adamantyl alcohol, cyclohexylmethyl alcohol, adamantylmethyl alcohol, tetrahydrofurfuryl alcohol, 2-methylbutyl alcohol, 3,3-dimethyl-2,4-dioxolane methyl alcohol , Bicyclo [2.2.1] heptyl alcohol, bicyclo [2.2.1] hept Such as methyl alcohol. Among these, neopentyl alcohol, tetrahydrofurfuryl alcohol, cyclopentylmethyl alcohol, cyclohexylmethyl alcohol, adamantylmethyl alcohol, and bicyclo [2.2.1] heptylmethyl alcohol are preferable.

In the esterification reaction, it is preferable that a basic compound such as pyridine, triethylamine, tripropylamine, or trioctylamine coexists.
<Sulfonated polymer>
The sulfonated polymer according to the present invention has a structural unit represented by the following general formula (A ′) (hereinafter also referred to as “structural unit (A ′)”). By including this polymer in the solid polymer electrolyte, a high ion exchange capacity can be obtained without impairing hot water resistance and mechanical properties, and high proton conductivity is exhibited.

  The sulfonated polymer of the present invention may be a polymer having a structure obtained by polymerizing the above compound (A) as one component of a monomer, specifically, polyphenylene, polyarylene, polyether, polyether. Examples include ketones and polyether sulfones.

  The sulfonated polymer of the present invention may be a homopolymer having only the structural unit (A ′) as a repeating unit, and a copolymer obtained by copolymerizing the compound (A) and a copolymerizable compound. It may be. Furthermore, in the case of a copolymer, a random copolymer or a block copolymer may be used. When the sulfonated polymer of the present invention is used as a solid polymer electrolyte, it is preferably a copolymer in consideration of hot water resistance and mechanical properties.

The sulfonated polymer of the present invention can be synthesized mainly by the following two methods.
The first method is a method in which the compound (A) is subjected to coupling polymerization by a method described in, for example, JP-A No. 2004-137444. At this time, the substituent X in the compound (A) is preferably a halogen atom other than fluorine, and the substituent R is preferably a hydrocarbon group having 1 to 20 carbon atoms, and has 4 carbon atoms. More preferably, it is ~ 20. In this polymerization, the substituent X of the compound (A) is eliminated and a phenylene bond is formed. That is, polyphenylene or polyarylene is obtained. Next, the R group is converted to H. That is, the sulfonated polymer of the present invention can be synthesized by deesterifying the resulting polyarylene having a sulfonate group and converting the sulfonate group to a sulfonate group.

  In this method, examples of the compound copolymerizable with the compound (A) include aromatic compounds having two or more halogen atoms other than fluorine. In addition, it is preferable that the halogen atom is activated by the adjacent electron withdrawing group. Specifically, 4,4′-dichlorobenzophenone, 2,4′-dichlorobenzophenone, 2,2′-dichlorobenzophenone, 2,5-dichlorobenzophenone, 2,4-dichlorobenzophenone, 2,6-dichlorobenzophenone, etc. Is mentioned.

  The polymerization is carried out in the presence of a catalyst, and the catalyst used in this case is a catalyst system containing a transition metal compound. As this catalyst system, (1) a compound that becomes a transition metal salt and a ligand, Alternatively, a transition metal complex coordinated with a ligand and (2) a reducing agent may be essential components, and a salt may be added to increase the polymerization rate.

  Specific examples of these catalyst components, the use ratio of each component, the polymerization conditions such as the reaction solvent, concentration, temperature, time, and the like can include the conditions described in JP-A-2001-342241.

  For example, as the transition metal salt, nickel chloride, nickel bromide and the like are preferably used, and as the ligand, triphenylphosphine, 2,2'-bipyridine and the like can be mentioned. As the reducing agent, iron, zinc, manganese and the like are preferable. As the salt, sodium bromide, sodium iodide, potassium bromide, tetraethylammonium bromide, and tetraethylammonium iodide are preferable. Examples of the solvent used for polymerization include tetrahydrofuran, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and the like.

  The sulfonated polymer of the present invention can be obtained by deesterifying a polymer having a sulfonate group of this precursor by the method described in JP-A No. 2004-137444. Deesterification is preferably carried out in the above-mentioned solvent using a salt such as lithium bromide, lithium iodide, sodium bromide or sodium iodide.

  Examples of the second synthesis method of the sulfonated polymer of the present invention include a method of polymerizing the compound (A) and various compounds having a phenolic hydroxyl group by a nucleophilic substitution reaction. At this time, X in the compound (A) is preferably a fluorine atom or a chlorine atom, and R is preferably a hydrogen atom or an alkali metal atom. In this polymerization, the substituent X in the compound (A) and the hydrogen atom in the hydroxyl group of the compound having a phenolic hydroxyl group are eliminated, and an ether bond is formed. That is, in this method, a polymer having an ether bond such as polyarylene ether, polyether ketone, or polyether sulfone can be obtained.

  Examples of the compound having a phenolic hydroxyl group include 2,2-bis (4-hydroxyphenyl) propane and 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoro. Examples include propane, 4,4′-dihydroxybiphenyl, 9,9-bis (4-hydroxyphenyl) fluorene, resorcinol, hydroquinone, 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxybenzophenone, and the like. Moreover, you may use the compound which has a thiol group instead of a phenolic hydroxyl group. In this case, a polymer having a thioether bond is obtained. These compounds may be used alone or in combination of two or more.

  Further, as other components, a dihalide having no sulfonic acid group can be copolymerized. Examples of such a dihalide include 4,4′-dichlorobenzophenone, 2,4′-dichlorobenzophenone, 2,2′-dichlorobenzophenone, 2,5-dichlorobenzophenone, 2,4-dichlorobenzophenone, 2, 6-dichlorobenzophenone, 4,4′-dichlorodiphenyl sulfone, 2,4′-dichlorodiphenyl sulfone, 2,2′-dichlorodiphenyl sulfone, 2,5-dichlorodiphenyl sulfone, 2,4-dichlorodiphenyl sulfone, 2, Examples include 6-dichlorodiphenyl sulfone, 2,6-dichlorobenzonitrile, 2,5-dichlorobenzonitrile, and 2,4-dichlorobenzonitrile. Moreover, the compound which substituted the chlorine atom of these compounds by the fluorine atom can also be mentioned as an example.

The polymerization is preferably carried out in the presence of an alkali metal carbonate, alkali metal, alkali hydrogen metal, or alkali metal hydroxide. Specifically, potassium carbonate, lithium carbonate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, lithium carbonated water, lithium hydride,
Examples thereof include sodium hydride, potassium hydride, lithium hydroxide, sodium hydroxide, and potassium hydroxide.

  The solvent used for the polymerization is preferably a polar solvent, and examples thereof include dimethylacetamide, dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone. Moreover, you may coexist the solvent azeotropically with water, such as benzene, toluene, and xylene.

  In any of the synthesis methods, when the obtained polymer is used as a solid polymer electrolyte, it is treated with an acid to convert sulfonic acid groups from various metal salt states to free states. It is preferable.

  The ion exchange capacity of the sulfonated polyarylene produced by the method as described above is usually 0.3 to 5 meq / g, preferably 0.5 to 4 meq / g, more preferably 0.8 to 3.5 meq / g. g. If the ion exchange capacity is lower than the above range, the proton conductivity tends to be low and the power generation performance tends to be low, and if it exceeds the above range, the water resistance may be significantly reduced.

  The weight average molecular weight (Mw) of the sulfonated polyarylene of the present invention is 10,000 to 1,000,000, preferably 20,000 to 500,000, more preferably 30,000 to 30 in terms of polystyrene by gel permeation chromatography (GPC). Ten thousand.

<Solid polymer electrolyte>
The solid polymer electrolyte of the present invention contains the above sulfonated polyarylene and contains antioxidants such as phenolic hydroxyl group-containing compounds, amine compounds, organic phosphorus compounds, organic sulfur compounds, etc., as long as proton conductivity is not impaired. May be included.

  The solid polymer electrolyte can be used in various shapes such as a granular shape, a fibrous shape, and a membrane shape depending on the intended use. For example, when it is used in an electrochemical device such as a fuel cell or a water electrolysis apparatus, it is desirable that the shape is a film.

<Proton conducting membrane>
The proton conducting membrane of the present invention is prepared using a solid polymer electrolyte containing the sulfonated polyarylene. In preparing the proton conducting membrane, in addition to the solid polymer electrolyte, an inorganic acid such as sulfuric acid or phosphoric acid, an organic acid such as carboxylic acid, an appropriate amount of water, or the like may be used in combination.

The proton conducting membrane of the present invention can be produced by a casting method or the like in which the sulfonated polyarylene is dissolved in a solvent and then cast on a substrate to form a film.
Examples of the solvent for dissolving the sulfonated polymer include N-methyl-2-pyrrolidone, N, N-dimethylformamide, γ-butyrolactone, N, N-dimethylacetamide, dimethyl sulfoxide, dimethylurea, and dimethylimidazolidinone. Among these, N-methyl-2-pyrrolidone (hereinafter also referred to as “NMP”) is preferable from the viewpoints of solubility and solution viscosity. The aprotic polar solvent may be used alone or in combination of two or more.

  In addition, as the solvent, a mixture of the aprotic polar solvent and alcohol can also be used. Examples of the alcohol include methanol, ethanol, propyl alcohol, iso-propyl alcohol, sec-butyl alcohol, tert-butyl alcohol and the like.

When a mixture of an aprotic polar solvent and an alcohol is used as the solvent, the aprotic polar solvent is 95 to 25% by weight, preferably 90 to 25% by weight, and the alcohol is 5 to 75% by weight, preferably It is used at a ratio of 10 to 75% by weight (however, the total is 100% by weight).

  The polymer concentration of the solution in which the sulfonated polymer of the present invention is dissolved is usually 5 to 40% by weight, preferably 7 to 25% by weight, although it depends on the molecular weight of the polymer. If the polymer concentration is lower than the above range, it is difficult to increase the film thickness, and pinholes tend to be easily generated. On the other hand, when the above range is exceeded, the solution viscosity is too high to be formed into a film, and the surface smoothness may be lacking.

  The solution viscosity is usually 2,000 to 100,000 mPa · s, preferably 3,000 to 50,000 mPa · s, although it depends on the molecular weight and polymer concentration of the sulfonated polyarylene. If the solution viscosity is lower than the above range, the retention of the solution during film formation is poor and may flow from the substrate. If it exceeds the above range, the viscosity is too high to be extruded from the die, and It tends to be difficult to form a film by the rolling method.

  After film formation as described above, the organic solvent in the undried film can be replaced with water by immersing the obtained undried film in water, and the amount of residual solvent in the resulting proton conducting membrane Can be reduced.

  In addition, after film formation, before immersing an undried film in water, you may predry an undried film. The preliminary drying is performed by holding the undried film at a temperature of usually 50 to 150 ° C. for 0.1 to 10 hours.

  When the undried film is immersed in water, a batch method or a continuous method may be used. The temperature of water when the undried film is immersed in water is preferably in the range of 5 to 80 ° C. Usually, a temperature range of 10 to 60 ° C. is convenient because of the replacement speed and ease of handling. The immersion time is usually in the range of 10 minutes to 240 hours, preferably 30 minutes to 100 hours, although depending on the initial residual solvent amount, contact ratio, and treatment temperature.

  When the undried film is immersed in water and dried as described above, a proton conductive membrane with a reduced amount of residual solvent is obtained. The amount of residual solvent in the proton conductive membrane thus obtained is usually 5 wt. % Or less.

  After immersing the undried film in water as described above, the film is dried at 30-100 ° C, preferably 50-80 ° C, for 10-180 minutes, preferably 15-60 minutes, and then 50-150 ° C. Thus, preferably, a proton conductive membrane can be obtained by vacuum drying under reduced pressure of 500 mmHg to 0.1 mmHg for 0.5 to 24 hours.

The proton conductive membrane of the present invention obtained by the above method has a dry film thickness of usually 10 to 100 μm, preferably 20 to 80 μm.
The proton conductive membrane of the present invention is, for example, a proton used in an electrolyte for primary batteries, an electrolyte for secondary batteries, a polymer solid electrolyte for fuel cells, a display element, various sensors, a signal transmission medium, a solid capacitor, an ion exchange membrane, and the like. It can be suitably used as a conductive solid polymer electrolyte membrane.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. The various measurement items in the examples were determined as follows.

(Molecular weight)
The weight average molecular weight (Mw) of the polymer was determined by GPC using polystyrene as a molecular weight using N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added as an eluent.

(Ion exchange capacity)
The obtained sulfonated polymer is washed with water until the pH becomes 4 to 6, the free remaining acid is removed and washed thoroughly with water, and after drying, a predetermined amount is weighed, and THF / water After dissolving in a mixed solvent, phenolphthalein was used as an indicator and titrated with a standard solution of NaOH, and the ion exchange capacity was determined from the neutralization point.

(Proton conductivity)
First, five platinum wires (φ = 0.5 mm) were pressed at 5 mm intervals on the surface of a strip-shaped sample film (40 mm × 5 mm), and in a constant temperature and humidity apparatus (“JW241” manufactured by Yamato Scientific Co., Ltd.) A sample was held on the substrate, and AC resistance was obtained by measuring AC impedance between platinum wires. The measurement is performed using a chemical impedance measurement system manufactured by NF Circuit Design Block Co., Ltd. as a resistance measurement device, and the line-to-line distance is changed to 5 to 20 mm under the condition of AC 10 kHz in an environment of 85 ° C. and relative humidity 90%. I went. Next, the specific resistance R of the membrane was calculated according to the following formula from the distance between the lines and the resistance gradient, and the proton conductivity was calculated from the reciprocal of the specific resistance R.

Specific resistance R (Ω · cm) = 0.5 (cm) × film thickness (cm) × resistance-to-resistance gradient (Ω / cm)
(Moisture content)
A proton conductive membrane having a thickness of 50 μm was immersed in hot water at 120 ° C. for 24 hours in a pressure cooker, and the ratio of the weight immediately after removal (water content) to the weight of the film before immersion was determined.

[Example 1] Synthesis of trisulfonated product (1)
In a 100 ml three-necked flask equipped with a nitrogen introduction tube and a stirrer, 2.1 g of aluminum chloride and 6 ml of 1,2-dichloroethane were weighed and cooled in an ice bath. 3,5-Dichlorobenzoic acid chloride was added thereto, and then a solution obtained by dissolving 2.55 g of diphenyl ether in 2 ml of 1,2-dichloroethane was added dropwise. After dropping, the reaction solution was poured into ice water, and the separated organic layer was concentrated to dryness. This was dissolved in 30 ml of acetone and the salt was filtered. The filtrate was concentrated to dryness to obtain 4.6 g of 3,5-dichloro-4′-phenoxybenzophenone.

31.7 g of 3,5-dichloro-4′-phenoxybenzophenone obtained as described above was weighed into a 100 ml three-necked flask equipped with a nitrogen introducing tube and a stirrer, and cooled in an ice bath. To this was added 30 ml of concentrated sulfuric acid, and then 32 ml of 60% fuming sulfuric acid was added and stirred for 1 hour. Next, it heated to 70 degreeC and stirring was continued for 15 hours. After cooling the reaction solution, it was poured into 400 ml of ice water, and the pH was adjusted to 6-7 with an aqueous sodium hydroxide solution and filtered. The filtrate was concentrated and extracted with 400 ml dimethyl sulfoxide. The insoluble material was filtered off, the filtrate was concentrated, and the residue was dissolved in 60 ml of water and heated to 60 ° C. Water was added thereto until no more precipitate was formed, and the product was filtered to obtain 46.3 g of a trisulfonated product. The ¹ H-NMR spectrum of this compound is shown in FIG. It was confirmed that the structure of the obtained trisulfonated product was represented by the following formula.

[Example 2] Synthesis of trisulfonated product (2)
In Example 1, it synthesize | combined like Example 1 except having used 2, 5- dichloro benzoic acid chloride instead of 3, 5- dichloro benzoic acid chloride. Further, the obtained 2,5-dichloro-4′-phenoxybenzophenone was sulfonated in the same manner as in Example 1 to obtain a trisulfonated product represented by the following formula.

[Example 3] Synthesis of trisulfonated product (3)
The synthesis was performed in the same manner as in Example 1 except that 2,6-difluorobenzoic acid chloride was used instead of 3,5-dichlorobenzoic acid chloride. Further, the obtained 2,6-difluoro-4′-phenoxybenzophenone was sulfonated in the same manner as in Example 1 to obtain a trisulfonated product represented by the following formula.

[Example 4] Synthesis of sulfonic acid derivative (1)
90.9 g of the trisulfonated product obtained in Example 1 and 540 g of sulfolane were weighed into a 2 L three-necked flask equipped with a stirrer, a thermometer, a nitrogen introducing tube, a cooling tube and a dropping funnel, and cooled in an ice bath. To this, 351 g of phosphoryl chloride was slowly added dropwise, followed by stirring at 80 ° C. for 2 hours. The reaction mixture was poured into ice water and extracted with ethyl acetate. Subsequently, the solvent was distilled off, and recrystallization was performed with ethyl acetate / n-hexane to obtain 45.4 g of sulfonic acid chloride.

  In a 500 ml three-necked flask equipped with a nitrogen inlet tube and a stirrer, 31.9 g of sulfonic acid chloride, 13.2 g of neopentyl alcohol and 70 g of pyridine were taken and stirred at room temperature for 12 hours. The reaction solution was diluted with toluene and washed twice with an aqueous hydrochloric acid solution. Further, the organic layer was washed with 5% aqueous sodium hydrogen carbonate solution and dried over magnesium sulfate. Recrystallization from methanol gave 51.6 g of neopentyl ester represented by the following formula.

[Example 5] Synthesis of sulfonic acid derivative (2)
In Example 4, except that the trisulfonated product obtained in Example 1 was replaced with the trisulfonated product obtained in Example 2, the same reaction operation as in Example 4 was performed, and it was represented by the following formula. Tetrahydrofurfuryl ester was obtained.

[Example 6] Synthesis of sulfonated polymer (1)
To a 2 L three-necked flask equipped with a stirrer, a nitrogen inlet tube and a thermometer, 79.4 g (100 mmol) of the sulfonic acid derivative obtained in Example 4, 100.4 g (400 mmol) of 2,5-dichlorobenzophenone, bis ( Triphenylphosphine) nickel dichloride 9.81 g (20 mmol), sodium iodide 2.25 g (20 mmol), triphenylphosphine 52.5 g (200 mmol) and zinc 78.4 g (1200 mmol) were weighed and purged with dry nitrogen. 400 mL of N, N-dimethylacetamide (DMAc) was added thereto, and the mixture was stirred for 3 hours while maintaining the reaction temperature at 80 ° C. Then, 350 mL of DMAc was added for dilution, and insoluble matter was filtered off.

  The obtained filtrate was put into a 3 L three-necked flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, heated and stirred at 115 ° C., and 28.7 g (330 mmol) of lithium bromide was added. After stirring for 7 hours, the reaction solution was poured into 5 L of acetone to precipitate the product. Next, after washing with 1N hydrochloric acid and pure water in this order, it was dried to obtain 135 g of the desired sulfonated polymer. The weight average molecular weight of the obtained polymer was 147,000, and the ion exchange capacity was 2.1 meq / g. The obtained polymer is presumed to be a sulfonated polymer represented by the following formula.

[Example 7] Synthesis of sulfonated polymer (2)
In Example 6, the reaction was performed in the same manner as in Example 6 except that the sulfonic acid derivative obtained in Example 4 was replaced with the sulfonic acid derivative obtained in Example 5, to obtain 139 g of a sulfonated polymer. . The obtained polymer had a weight average molecular weight of 131,000 and an ion exchange capacity of 2.1 meq / g. The obtained polymer is presumed to be a sulfonated polymer represented by the following formula.

[Example 8] Synthesis of sulfonated polymer (3)
In a 500 mL three-necked flask equipped with a stirrer, thermometer, Dean-stark tube, nitrogen inlet tube and condenser tube, 23.2 g (37.7 mmol) of the sulfonic acid derivative synthesized in Example 3 and 4,4′-difluorobenzophenone 5.5 g (25.1 mmol), 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane 21.1 g (62.8 mmol) and potassium carbonate 11.3 g (81.6 mmol) was weighed. After substitution with dry nitrogen, 130 mL of sulfolane and 65 mL of toluene were added, and the mixture was heated and stirred at 130 ° C. Water produced by the reaction was trapped in a Dean-stark tube. After 3 hours, when almost no water was observed, toluene was removed from the Dean-stark tube out of the system. Next, the reaction temperature was raised to 175 ° C. and stirring was continued for 3 hours. The reaction solution was allowed to cool, and diluted with 100 mL of toluene. Insoluble salts were filtered, and the filtrate was poured into 2 L of methanol to precipitate the product. The precipitated product was washed with 1N hydrochloric acid and pure water in this order and then dried to obtain 87 g of the desired polymer. This polymer had a weight average molecular weight of 126,000 and an ion exchange capacity of 1.9 meq / g. The obtained polymer is presumed to be a sulfonated polymer represented by the following formula.

[Example 9] Synthesis of sulfonated polymer (4)
Regarding the amount charged in Example 8, 19.4 g (31.4 mmol) of the sulfonic acid derivative synthesized in Example 3, 6.9 g (31.4 mmol) of 4,4′-difluorobenzophenone, 4,4′-dihydroxy The reaction was conducted in the same manner as in Example 8 except that biphenyl was changed to 11.7 g (62.8 mmol) to obtain 69 g of a sulfonated polymer. The obtained polymer had a weight average molecular weight of 125,000 and an ion exchange capacity of 1.9 meq / g. The obtained polymer is presumed to be a sulfonated polymer represented by the following formula.

[Comparative Example 1] Polyetheretherketone sulfonated product.
25 g of polyetheretherketone was added to 250 ml of concentrated sulfuric acid and stirred at 60 ° C. for 24 hours. The reaction solution was poured into water, and the precipitated sulfonated product was washed with pure water until neutral, and then dried to obtain 28 g of a sulfonated polymer. The ion exchange capacity of this polymer was 1.8 meq / g.

[Production of proton conducting membrane]
Each sulfonated polymer of Examples 6 to 9 and Comparative Example 1 was dissolved in NMP, and a proton conductive membrane having a thickness of 50 μm was produced by a casting method. The proton conductivity and water content of each proton conducting membrane were measured. The results are shown in Table 1.

  As shown in Table 1, the proton conducting membrane made of the sulfonated polymer of the present invention (Examples 6 to 9) can reduce the water content in hot water even when the ion exchange capacity is increased, and has high proton conductivity. Express degree.

2 is an NMR spectrum of a trisulfonated product obtained in Example 1.

Claims (4)

An aromatic sulfonic acid derivative represented by the following general formula (A).

[In the formula (A), X represents a halogen atom, —OSO ₂ CH ₃ or —OSO ₂ CF ₃ , and R represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or a hydrocarbon group having 1 to 20 carbon atoms. Indicates. ] A sulfonated polymer having a structural unit represented by the following general formula (A ′).

  A solid polymer electrolyte comprising the sulfonated polymer according to claim 2.   A proton conducting membrane comprising the sulfonated polymer according to claim 2.

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