JP2006299082A - Aromatic sulfonic acid derivative bearing nitrile group, sulfonated polymer, polymeric solid electrolyte and proton-conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aromatic sulfonic acid derivative, a sulfonated polymer that is composed of the sulfonic acid derivative and exhibits excellent hot-water resistance and mechanical properties, and a polymeric solid electrolyte. <P>SOLUTION: The aromatic sulfonic acid derivative is represented by general formula (A) (wherein X is a halogen atom, -OSO<SB>2</SB>CH<SB>3</SB>or -OSO<SB>2</SB>CF<SB>3</SB>; Y is -CO- or -SO<SB>2</SB>-; Z is -O-, -S- or a direct bond; R is a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or a 1-20C hydrocarbon group; Ar is a phenyl or naphthyl group bearing an SO<SB>3</SB>R group; k is an integer of 1-4; and m and n are each an integer of 0-4). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aromatic sulfonic acid derivative having a nitrile group, a sulfonated polymer having a structural unit derived from the compound, 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 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 are solved by providing an aromatic sulfonic acid derivative having the following nitrile group, a sulfonated polymer having a structural unit derived from the compound, a solid polymer electrolyte containing the polymer, and a proton conducting membrane. The present inventors have found that this can be done and have completed the present invention.

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

In formula (A), X represents a halogen atom, —OSO ₂ CH ₃ or —OSO ₂ CF ₃ , Y represents —CO— or —SO ₂ —, Z represents —O—, —S— or a direct bond R represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or a hydrocarbon group having 1 to 20 carbon atoms, Ar represents a phenyl group or a naphthyl group having a SO ₃ R group, k represents 1 to 4 represents an integer, and m and n each represent an integer of 0 to 4.

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

In formula (A ′), Y represents —CO— or —SO ₂ —, Z represents —O—, —S— or a direct bond, and Ar ′ represents a phenyl group or naphthyl group having an SO ₃ H group. K is 1 to
4 represents an integer, and m and n each represent an integer of 0 to 4.

  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 a nitrile group, a sulfonated polymer derived from the compound, comprising a structural unit having a sulfonic acid group in the side chain and a nitrile group in the main chain, and the polymer A solid polymer electrolyte and a proton conductive 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 sulfonic acid group in the side chain and a nitrile group in the main chain. As a result, even when sulfonic acid groups are introduced at a high concentration, a solid polymer electrolyte and a proton conductive membrane having excellent 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 compound, 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. Y represents —CO— or —SO ₂ —, and is preferably —SO ₂ —. Z represents —O—, —S— or a direct bond. Ar represents a phenyl group having a SO ₃ R group or a naphthyl group,
One or more SO ₃ R groups may be present. k represents an integer of 1 to 4, and m and n each represents an integer of 0 to 4. 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 Group and the like. Among these, a neopentyl group, a tetrahydrofurfuryl group, a cyclopentylmethyl group, a cyclohexylmethyl group, an adamantylmethyl group, and a bicyclo [2.2.1] heptyl group are preferable, and a neopentyl group is particularly preferable.

  Examples of the aromatic sulfonic acid derivative represented by the above 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 bonding positions of sulfonic acid groups can also be mentioned as examples. 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, the dihalogenated benzonitrile is sulfonated and then converted to sulfonic acid chloride.

  Examples of the dihalogenated benzonitrile include 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,5-dichlorobenzonitrile, 2,5-difluorobenzonitrile, 2,4-dichlorobenzonitrile, 2 , 4-difluorobenzonitrile and the like.

  For the sulfonation, a sulfonating agent such as concentrated sulfuric acid, chlorosulfonic acid, fuming sulfuric acid, and anhydrous sulfuric acid can be used. Among these, fuming sulfuric acid is preferable. The reaction temperature for sulfonation is preferably 50 to 200 ° C. The obtained sulfonated product can be converted to sulfonic acid chloride by treating the resulting sulfonated product with phosphoryl chloride, phosphorus pentachloride, chlorosulfonic acid, thionyl chloride or the like.

  Next, Friedel-Crafts reaction is performed between the obtained sulfonic acid chloride and a compound represented by the following general formula (1).

In formula (1), Z represents —O—, —S— or a direct bond, w represents an integer of 0 to 8, and Ar ″ represents a phenyl group or a naphthyl group.
Examples of the compound represented by the above formula (1) include benzene, naphthalene, biphenyl, diphenyl ether, diphenyl sulfide, 1,4-diphenoxybenzene, 1,3-diphenoxybenzene, p-terphenyl, m-ter. Phenyl, o-terphenyl, p-quarterphenyl and the like can be mentioned.

  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 reaction temperature is preferably in the range of 50 ° C to 200 ° 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 obtained sulfonated product is converted into sulfonic 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.

  Finally, the aromatic sulfonic acid derivative of the present invention is obtained by esterifying the obtained sulfonic acid chloride and various alcohols. Examples of the alcohol include 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] heptyl methyl alcohol, etc. are mentioned. Among these, neopentyl alcohol, tetrahydrofurfuryl alcohol, cyclopentylmethyl alcohol, cyclohexylmethyl alcohol, adamantylmethyl alcohol, and bicyclo [2.2.1] heptylmethyl alcohol are preferable, and neopentyl alcohol is particularly 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 ′)”). When the solid polymer electrolyte contains this polymer, proton conductivity is obtained.

In formula (A ′), Y, Z, k, m and n have the same meanings as Y, Z, k, m and n in formula (A), and Ar ′ is a phenyl group having a SO ₃ H group. Or a naphthyl group is shown.
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. 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, sodium hydride, potassium hydride, lithium hydroxide, sodium hydroxide, potassium hydroxide Can be mentioned.

  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 polymer 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. It is. 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 polymer of the present invention is 10,000 to 1,000,000, preferably 20,000 to 500,000, more preferably 30,000 to 300,000 in terms of polystyrene by gel permeation chromatography (GPC). It is.

<Solid polymer electrolyte>
The solid polymer electrolyte of the present invention comprises the above sulfonated polymer and contains an antioxidant such as a phenolic hydroxyl group-containing compound, an amine compound, an organic phosphorus compound, and an organic sulfur compound as long as the proton conductivity is not impaired. But you can.

  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 for an electrochemical device such as a fuel cell or a water electrolysis apparatus, the shape is preferably a membrane (proton conductive membrane).

<Proton conducting membrane>
The proton conducting membrane of the present invention is prepared using a solid polymer electrolyte containing the sulfonated polymer. 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, for example, a casting method in which the sulfonated polymer 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 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 polymer. 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.

[Synthesis Example] Synthesis of 3,5-dichloro-4-cyanobenzenesulfonic acid chloride After weighing 10 g (58 mmol) of 2,6-dichlorobenzonitrile into a 100 mL three-necked flask equipped with a stirrer and cooling to 0 ° C. 10 mL of concentrated sulfuric acid was added and stirred for 30 minutes. Next, 10 mL of 60% fuming sulfuric acid was added, and the mixture was stirred at 110 ° C. for 6 hours. The reaction solution was poured into 200 mL of ice water, and salt was added to salt out the reaction product. It was again dissolved in 200 mL of water, neutralized with a 10% aqueous sodium hydroxide solution, salted out with sodium chloride, and dried to obtain a sulfonated product.

  Next, 10.0 g (36 mmol) of the obtained sulfonated product and 20 mL of chlorosulfonic acid were weighed into a 100 mL three-necked flask equipped with a stirrer and reacted at 145 ° C. for 5 hours. The reaction solution was poured into 300 mL of ice water, and the precipitate was collected, washed and dried to obtain 3,5-dichloro-4-cyanobenzenesulfonic acid chloride.

[Example 1] Synthesis of sulfonated product (1)
In a 200 mL three-necked flask equipped with a condenser and a stirrer, 4.0 g (26 mmol) of biphenyl, 2.9 g (22 mmol) of aluminum chloride, 5.4 g (20 mmol) of 3,5-dichloro-4-cyanobenzenesulfonic acid chloride and 100 mL of 1,2-dichloroethane was weighed. After heating to reflux and stirring for 12 hours, the reaction solution was poured into excess ice water containing hydrochloric acid, and the organic layer was concentrated and dried to obtain the desired product.

  Next, 5.0 g (13 mmol) of the product was taken in a 100 mL three-necked flask equipped with a stirrer, and cooled in an ice bath. To this was added 5 mL of concentrated sulfuric acid and dissolved, and then 60% fuming sulfuric acid was added and reacted at 90 ° C. for 6 hours. The reaction solution was poured into 100 g of ice and then neutralized with 10% sodium hydroxide. The precipitate was filtered and dried to obtain a sulfonated product represented by the following formula.

[Example 2] Synthesis of sulfonated product (2)
The reaction was conducted in the same manner as in Example 1 except that 4.4 g of diphenyl ether was used instead of 4.0 g of biphenyl, to obtain a sulfonated product represented by the following formula.

[Example 3] Synthesis of sulfonate ester 7.1 g of the sulfonated product obtained in Example 2 and 30 g of sulfolane were weighed into a 200 mL three-necked flask equipped with a stirrer, a thermometer, a condenser tube and a nitrogen inlet tube, and iced. Cooled in bath. After 15.3 g of phosphoryl chloride was added dropwise thereto, the temperature was raised to 80 ° C. and stirred for 3 hours. The reaction solution was poured into ice water, extracted with ethyl acetate, and then washed with an aqueous sodium bicarbonate solution. After the solvent was distilled off, recrystallization from ethyl acetate / n-hexane gave 6.0 g of sulfonic acid chloride.

  In a 200 mL three-necked flask equipped with a stirrer and a nitrogen inlet tube, 6.0 g of sulfonic acid chloride and 10 g of pyridine were weighed, and 2.5 g of neopentyl alcohol was added. The mixture was stirred at room temperature for 8 hours, diluted with toluene, and washed with an aqueous hydrochloric acid solution. The solvent was distilled off, and recrystallization from ethyl acetate / n-hexane gave 5.1 g of a sulfonic acid ester represented by the following formula.

[Example 4] Synthesis of sulfonated polymer (1)
In a 500 mL three-necked flask equipped with a stirrer, thermometer, Dean-stark tube, nitrogen introducing tube and condenser tube, 26.0 g (44.0 mmol) of the sulfonated product synthesized in Example 1 and 2,6-dichlorobenzonitrile 3 0.2 g (18.8 mmol), 4,4′-dihydroxybiphenyl 11.7 g (62.8 mmol) and potassium carbonate 11.3 g (81.6 mmol) were weighed. After substituting with dry nitrogen, 100 mL of sulfolane and 50 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. Thereafter, the reaction temperature was raised to 195 ° C. and stirring was continued for 12 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 69 g of the target polymer. This polymer had a weight average molecular weight of 113,000 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 5] Synthesis of sulfonated polymer (2)
The amount of the sulfonic acid derivative synthesized in Example 1 was changed to 33.5 g (56.5 mmol), the amount of 2,6-dichlorobenzonitrile was changed to 1.1 g (6.3 mmol), The reaction was conducted in the same manner as in Example 4 except that 92.0 '(62.8 mmol) of 9,9'-bis (4-hydroxyphenyl) fluorene was used instead of 4'-dihydroxybiphenyl, and 96 g of sulfonated polymer was obtained. Got. The weight average molecular weight of the obtained polymer was 127,000, and the ion exchange capacity was 1.9 meq / g. The obtained polymer is presumed to be a sulfonated polymer represented by the following formula.

[Example 6] Synthesis of sulfonated polymer (3)
Instead of the sulfonated product synthesized in Example 1, 28.5 g (40.2 mmol) of the sulfonated product synthesized in Example 2 was used, and 2,2-bis (4-hydroxyphenyl) was substituted for 4,4′-dihydroxybiphenyl. ) -1,1,1,3,3,3-hexafluoropropane (21.1 g, 62.8 mmol) was used, and the amount of 2,6-dichlorobenzonitrile charged was changed to 3.9 g (22.6 mmol). Except for this, the reaction was carried out in the same manner as in Example 4 to obtain 91 g of a sulfonated polymer. The weight average molecular weight of the obtained polymer was 116,000, and the ion exchange capacity was 1.8 meq / g. The obtained polymer is presumed to be a sulfonated polymer represented by the following formula.

[Example 7] Synthesis of sulfonated polymer (4)
The amount of sulfonated product synthesized in Example 2 was changed to 22.3 g (31.4 mmol), the amount of 2,6-dichlorobenzonitrile was changed to 5.4 g (31.4 mmol), and 2,2 Reaction similar to Example 6 except that 6.9 g (62.8 mmol) of resorcinol was used instead of bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane To obtain 50 g of a sulfonated polymer. The weight average molecular weight of the obtained polymer was 107,000, and the ion exchange capacity was 1.9 meq / g. The obtained polymer is presumed to be a sulfonated polymer represented by the following formula.

[Example 8] Synthesis of sulfonated polymer (5)
In a 200 mL three-necked flask equipped with a stirrer, a nitrogen inlet tube and a thermometer, 7.7 g (9 mmol) of the sulfonate ester obtained in Example 3, 10.3 g (41 mmol) of 2,5-dichlorobenzophenone, bis ( Weigh 0.98 g (2.0 mmol) of triphenylphosphine) nickel dichloride, 0.23 g (2.0 mmol) of sodium iodide, 5.2 g (20 mmol) of triphenylphosphine and 7.8 g (120 mmol) of zinc, and dry nitrogen. Replaced. 45 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., diluted with 40 mL of DMAc, and insoluble matter was filtered off.

  The obtained filtrate was put into a 300 mL three-necked flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, heated and stirred at 115 ° C., and 2.6 g (33 mmol) of lithium bromide was added. After stirring for 7 hours, the product was precipitated by pouring into 500 mL of acetone. Next, 1N hydrochloric acid and pure water were washed in this order and dried to obtain 13.5 g of the desired sulfonated polymer. The weight average molecular weight of the obtained polymer was 108,000, and the ion exchange capacity was 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 4 to 8 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 4 to 8) can reduce the water content in hot water even when the ion exchange capacity is increased, and has high proton conductivity. Express degree.

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 ;
Y represents —CO— or —SO ₂ —, Z represents —O—, —S— or a direct bond,
R represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or a hydrocarbon group having 1 to 20 carbon atoms;
Ar represents a phenyl group having a SO ₃ R group or a naphthyl group,
k represents an integer of 1 to 4, and m and n each represents an integer of 0 to 4. ] A sulfonated polymer having a structural unit represented by the following general formula (A ′).

[In the formula (A ′), Y represents —CO— or —SO ₂ —;
Z represents —O—, —S— or a direct bond;
Ar ′ represents a phenyl group or naphthyl group having a SO ₃ H group,
k represents an integer of 1 to 4, and m and n each represents an integer of 0 to 4. ]   A solid polymer electrolyte comprising the sulfonated polymer according to claim 2.   A proton conducting membrane comprising the sulfonated polymer according to claim 2.