JP2014032952A - Polymer electrolyte membrane consisting of aromatic polymer membrane base material and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer electrolyte membrane excellent in terms not only of endurance factors at times of long-term operations such as proton conductivity, high-temperature mechanical characteristics, oxidation resistance, etc. but also of fuel impermeability and optimal for portable appliances using methanol, hydrogen, etc. as fuels; and fuel cells for family-use cogenerators and automobiles.SOLUTION: The provided polymer electrolyte membrane is prepared by graft-polymerizing, within solvents including an amide-based solvent and an alcohol solvent, a vinyl monomer with an aromatic polymer membrane base material including a polyester structure so as to introduce a graft chain to the latter and subsequently by partially converting the graft chain and/or a portion of the aromatic polymer chain into a sulfonate group chemically; a method for manufacturing the same is also provided.

Description

  The present invention provides a polymer electrolyte fuel by graft-polymerizing a vinyl monomer onto an aromatic polymer film as a base material and then chemically converting the graft chain or / and the aromatic polymer chain into a sulfonic acid group. The present invention relates to a polymer electrolyte membrane suitable for a battery, and to a polymer electrolyte membrane having excellent proton conductivity, mechanical properties, oxidation resistance, and fuel impermeability, and a method for producing the same.

Fuel cells using polymer electrolyte membranes have a low operating temperature of 150 ° C or less and high power generation efficiency and energy density. Therefore, power supplies for portable devices and cogeneration power supplies for homes that use methanol, hydrogen, etc. as fuel. It is expected as a power source for fuel cell vehicles. In this fuel cell, there are important elemental technologies related to a polymer electrolyte membrane, an electrode catalyst, a gas diffusion electrode, a membrane electrode assembly, and the like. Among them, the development of a polymer electrolyte membrane having excellent characteristics as a fuel cell is one of the most important technologies.

In a polymer electrolyte fuel cell, the electrolyte membrane functions as a so-called “electrolyte” for conducting hydrogen ions (protons), and also functions as a “membrane” for preventing direct mixing of hydrogen, methanol, and oxygen as fuel. To do. The polymer electrolyte membrane has a large ion exchange capacity, chemical stability that can withstand long-term use, and particularly excellent resistance (oxidation resistance) to hydroxyl radicals, etc., which are the main cause of membrane deterioration. In addition, heat resistance at 80 ° C. or higher, which is the operating temperature of the battery, is required, and in order to keep electric resistance low, the water retention of the film is required to be constant and high. On the other hand, due to the role as a diaphragm, it is required that the film has excellent mechanical strength and dimensional stability, and has low hydrogen, methanol and oxygen permeability.

As an electrolyte membrane for a polymer electrolyte fuel cell, a perfluorosulfonic acid membrane “Nafion (registered trademark of DuPont)” developed by DuPont has been generally used. However, conventional fluorine-containing polymer electrolyte membranes such as Nafion are excellent in chemical durability and stability, but have a small ion exchange capacity of around 1 meq / g and insufficient water retention. As a result, the ion exchange membrane is dried, resulting in a decrease in proton conductivity, or when methanol is used as a fuel, membrane swelling or methanol crossover occurs. Furthermore, there was a drawback that the mechanical characteristics under operating conditions exceeding 100 ° C. required for the power source for automobiles were remarkably deteriorated. Furthermore, since the fluororesin-based polymer electrolyte membrane starts from the synthesis of the monomer, the number of manufacturing processes is increased, and therefore it is expensive, which is a big problem when it is put to practical use as a power source for household cogeneration systems or a power source for fuel cell vehicles. It becomes an obstacle.
Therefore, development of a low-cost polymer electrolyte membrane replacing the fluororesin polymer electrolyte membrane has been actively promoted. For example, a polymer electrolyte fuel cell is obtained by introducing a styrene monomer into a fluorine-based polymer membrane substrate such as polytetrafluoroethylene, polyvinylidene fluoride or ethylene-tetrafluoroethylene copolymer by graft polymerization and then sulfonating the polymer. Attempts have been made to produce electrolyte membranes for use (see Patent Documents 1 and 2). However, since the fluoropolymer membrane substrate has a low glass transition temperature, mechanical hitting at a high temperature of 100 ° C. or higher is remarkably reduced, and when a large current is passed through the membrane for a long time, sulfonic acid introduced into polystyrene. There was a drawback that the ion dropping ability of the group occurred and the ion exchange ability of the membrane was greatly lowered, and further crossover of hydrogen and oxygen as fuels occurred.

On the other hand, as a low-cost polymer electrolyte membrane, a structure in which an aromatic polymer membrane with excellent mechanical strength at high temperatures represented by engineering plastics and low fuel permeability such as methanol, hydrogen, oxygen, etc. is sulfonated is proposed. Has been. The sulfonated aromatic polymer electrolyte membrane is obtained by synthesizing an aromatic monomer to which a sulfonic acid group responsible for proton conduction is bonded, synthesizing an aromatic polymer by the polymerization reaction, and then forming a membrane ( (See Patent Documents 3, 4, and 5). However, when the amount of sulfonic acid groups introduced is increased in order to increase the electrical conductivity, the mechanical strength and handling properties are lowered with an increase in water solubility. Furthermore, since sulfonic acid groups are randomly present in the aromatic polymer chain, the separation of the hydrophobic portion maintaining mechanical strength and the electrolyte layer responsible for proton conduction is not clear. Long-term operation represented by proton conductivity, fuel impermeability and oxidation resistance compared to polymer electrolyte membranes that have a phase separation structure, such as molecular electrolyte membranes and commercially available fluoropolymer electrolyte membranes (Nafion, etc.) It was inferior in durability.

JP 2001-348439 A JP 2004-246376 A JP 2004-288497 A JP 2004-346163 A JP 2006-12791 A

The present invention solves the decrease in mechanical strength at high temperatures, which is a problem of fluororesin-based electrolytes, and crossover of fuel, as well as proton conductivity and mechanical strength, which are problems of sulfonated aromatic polymer electrolyte membranes, In order to solve the problem of compatibility of handling properties, a graft chain is introduced into an aromatic polymer membrane by graft polymerization, and then the graft chain or / and the aromatic polymer chain is sulfonated to provide excellent protons. The present invention provides a polymer electrolyte membrane having durability in long-term operation such as conductivity, fuel impermeability, and oxidation resistance.

The present invention relates to a polymer electrolyte membrane suitable for use in a fuel cell, having high proton conductivity, high mechanical properties at high temperature, high durability in long-term operation such as oxidation resistance, and low fuel permeability. And a method for manufacturing the same.

That is, the present invention is prepared by graft-polymerizing a vinyl monomer onto an aromatic polymer membrane substrate and then chemically converting a graft chain or / and part of the aromatic polymer chain to a sulfonic acid group. And a method for producing the polymer electrolyte membrane.

The aromatic polymer membrane substrate is preferably a polymer membrane substrate having a polyetheretherketone structure, a polyimide structure, a polysulfone structure, and a polyester structure.

Although the polymer electrolyte membrane produced by the present invention can be produced at a very low cost as compared with the fluororesin polymer electrolyte membrane, it exhibits high mechanical properties and low fuel permeability at high temperatures. In addition, the introduction of graft chains by graft polymerization has characteristics that combine high proton conductivity and oxidation resistance compared to conventional sulfonated aromatic polymer electrolyte membranes, so that long-term use durability is particularly desirable. It is suitable for use in fuel cells for automobiles that can withstand high temperatures of 100 ° C or higher.

The aromatic polymer membrane substrate that can be used in the present invention is not particularly limited as long as it is a polymer membrane made of an aromatic hydrocarbon. For example, an aromatic polymer membrane substrate such as polyether ketone derivative, polyimide derivative, polysulfone derivative, polyester derivative, polyamide derivative, polycarbonate, polyphenylene sulfide, or polybenzimidazole can be used. As the polyetherketone derivative, polyetheretherketone and the like are preferable because the membrane shape can be maintained in a reaction solution in graft polymerization and sulfonation, and the obtained polymer electrolyte membrane exhibits high mechanical properties. As the polyimide derivative, polyetherimide or the like is preferable because the membrane shape can be maintained in a reaction solution in graft polymerization and sulfonation, and the obtained polymer electrolyte membrane exhibits high mechanical properties. As the polysulfone derivative, polyetherimide or the like is preferable because the membrane shape can be maintained in a reaction solution in graft polymerization and sulfonation, and the obtained polymer electrolyte membrane exhibits high mechanical properties. As the polyester derivative, polyethylene naphthalate, liquid crystal polyester, and the like are preferable because the membrane shape can be maintained in a reaction solution in graft polymerization and sulfonation, and the obtained polymer electrolyte membrane exhibits high mechanical properties.

In the present invention, (1) vinyl monomer having an aromatic ring capable of retaining a sulfonic acid group, and (2) halogenation capable of being converted into a sulfonic acid group by hydrolysis. A sulfonyl group, a vinyl monomer having a sulfonic acid ester group, (3) a vinyl monomer having a halogen capable of introducing a sulfonic acid group by a sulfonation reaction, and (4) an electrophilic substitution sulfonation reaction to an aromatic polymer chain, Examples thereof include aliphatic vinyl monomers that are not sulfonated, aromatic vinyl monomers, and perfluoroalkyl vinyl monomers.

(1) As vinyl monomers having an aromatic ring capable of retaining a sulfonic acid group, alkyl styrene such as styrene, α-methylstyrene, 4-vinyltoluene, 4-tert-butylstyrene, 2-chlorostyrene, 4-chlorostyrene, Halogenated styrene such as 2-bromostyrene, 3-bromostyrene, 4-bromostyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 4-methoxystyrene, 4-methoxymethylstyrene, 2,4- Alkoxy styrene such as dimethoxy styrene, vinyl phenyl allyl ether, 4-hydroxy styrene, 4-acetoxy styrene, 4-tert-butoxy styrene, 4-tert-butyloxy carbonyloxy styrene, 4-vinyl benzyl alkyl ether which hydroxy Examples thereof include styrene derivatives.

(2) 4-vinylbenzenesulfonic acid sodium salt, 4-vinylbenzylsulfonic acid sodium salt as vinyl monomers having a sulfonyl halide group, a sulfonic acid ester group, and a sulfonic acid group that can be converted into a sulfonic acid group by hydrolysis, 4-methoxy sulfonyl styrene, 4-ethoxy sulfonyl styrene, 4-styrene sulfonyl _{fluoride, CF 2 = CF-O- (} CF 2) n-SO 2 F ( _{wherein, n = 1~5), CF 2} = CF _{-O-CF2-CF (CF 3} ) -O- (CF 2) n-SO 2 F ( wherein, n = 1 to 5) perfluoro (fluorosulfonyl vinyl ether) derivatives such as, CF ₂ = CF-SO _And fluorosulfonyltetrafluorovinyl derivatives such as ₂ F.

(3) As the vinyl monomer having a halogen sulfonic acid group can be introduced by sulfonation reaction, 4-chloromethyl _{styrene, CH 2 = CH-O- (} CH 2) nX ( wherein, n 1-5. X is a halogen group, chlorine or fluorine), CF ₂ = CF—O— (CH ₂ ) nX (where n is 1 to 5, X is a halogen group, chlorine or fluorine), CH _{2 = CH-O- (CF 2)} nX ( wherein, n 1~5.X a halogen group, chlorine or _{fluorine), CF 2 = CF-O-} (CF 2) nX ( in wherein, n 1 to 5. X is a halogen group, which is chlorine or fluorine), CF ₂ = CF—O—CF ₂ —CF (CF ₃ ) —O— (CF ₂ ) nX (where n is 1 to 5). X is a halogen group, chlorine or fluorine).

(4) As an aliphatic vinyl monomer that is not sulfonated by an electrophilic substitution sulfonation reaction to an aromatic polymer chain, a vinyl monomer having an aromatic ring or a perfluoroalkyl vinyl monomer, acrylonitrile, acrylic acid, acrylic Acrylic acid derivatives such as methyl acid, methacrylic acid derivatives such as methacrylic acid and methyl methacrylate, alkyl-substituted styrene derivatives such as 2,4,6-trimethylstyrene, tetrafluorostyrene, 4-fluorostyrene, 4-chlorostyrene, etc. electron-deficient aromatic vinyl monomer _{derivatives, CH 2 = CH-O- (} CH 2) n-CH 3 ( wherein, n _{1~5), CF 2 = CF-} O- (CH 2) n - CH 3 (Where n is 1 to 5), alkyl vinyl ether derivatives such as CH ₂ = CH-O- (CF ₂ ) n-CF ₃ (where n is 1 to 5), CF ₂ = CF-O- ( CF ₂₎ n- CF ₃ (wherein, n _{1~5), CF 2 = CF-} O-CF2-CF (CF 3) -O- (CF 2) n- C And perfluoroalkyl vinyl ether derivatives such as F ₃ (wherein n is 1 to 5).

It is also possible to crosslink the graft chain by using a crosslinking agent such as a polyfunctional monomer in combination with the vinyl monomer. Further, after graft polymerization, graft chains, aromatic polymer chains, and graft chains and aromatic polymer chains can be cross-linked by addition of a polyfunctional monomer or irradiation with radiation. Polyfunctional monomers used as crosslinking agents include bis (vinylphenyl) ethane, divinylbenzene, 2,4,6-triallyloxy-1,3,5-triazine (triallyl cyanurate), triallyl-1,2,4 -Benzene tricarboxylate (triallyl trimellitate), diallyl ether, bis (vinylphenyl) methane, divinyl ether, 1,5-hexadiene, butadiene and the like. The crosslinking agent is preferably used in an amount of 10% or less by weight with respect to the vinyl monomer. If used over 10%, the polymer electrolyte membrane becomes brittle.

As the polymer electrolyte membrane has a higher electrical conductivity having a positive correlation with the ion exchange capacity, the performance as the polymer electrolyte membrane is better. Here, the ion exchange capacity is the amount of ion exchange groups (g / g) per gram of dry electrolyte membrane. However, when the electric conductivity of the ion exchange membrane at 25 ° C is 0.02 ([Ω · cm] ^-1 ) or less, the output performance as a fuel cell often decreases significantly. In many cases, the conductivity is designed to be 0.02 ([Ω · cm] ⁻¹ ) or more, and higher performance polymer electrolyte membranes are designed to be 0.10 ([Ω · cm] ⁻¹ ) or more.

In the present invention, a polymer electrolyte membrane is produced by graft polymerization of a vinyl monomer using a radical generated on an aromatic polymer membrane substrate by the action of radiation and then chemical conversion to a sulfonic acid group. . Therefore, by controlling the graft rate and the sulfonation rate, the ion exchange capacity and thus the electrical conductivity of the resulting membrane can be controlled.

In the present invention, the radiation is applied to the aromatic polymer membrane substrate at 1 to 1000 kGy at room temperature to 150 ° C. in an inert gas or in the presence of oxygen. More preferably, irradiation is performed at 10 to 500 kGy. If it is 10 kGy or less, it is difficult to obtain a graft ratio necessary for obtaining a conductivity of 0.02 ([Ω · cm] ⁻¹ ) or more, and if it is 500 kGy or more, the polymer membrane substrate becomes brittle. Graft polymerization is a simultaneous irradiation method in which an aromatic polymer membrane substrate and a monomer are simultaneously irradiated and graft polymerized, and an aromatic polymer membrane substrate is irradiated with radiation and then contacted with a vinyl monomer for graft polymerization. It can be performed by any of the pre-irradiation methods.

For graft polymerization of a polymer film substrate, a method of immersing the polymer film substrate in a vinyl monomer liquid is generally used. However, in the present invention, in the graft polymerization of the vinyl monomer onto the aromatic polymer membrane substrate, the graft polymerizability of the polymer substrate, in the polymerization solution of the graft polymer membrane substrate obtained by graft polymerization. Dichloroethane, chloroform, N-methylformamide, N-methylacetamide, N-methylpyrrolidone, γ-ptyrolactone, n-hexane, methanol, ethanol, 1-propanol, t-butanol, toluene, cyclohexane A method of immersing the polymer membrane substrate in a vinyl monomer solution diluted with a solvent such as cyclohexanone or dimethyl sulfoxide is used. When an amide solvent that swells the aromatic polymer membrane substrate is used as the graft polymerization solvent, the penetration of the vinyl monomer into the polymer membrane substrate is promoted, and the graft ratio is improved. Examples of the amide solvent include N-methylformamide and N-methylpyrrolidone. Furthermore, when an alcohol having a low solubility of the vinyl monomer and an aqueous solution thereof are used, the vinyl monomer is efficiently transferred into the aromatic polymer membrane substrate during the graft polymerization process, so that the graft polymerization is promoted. Examples of the alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and aqueous solutions thereof.

In the present invention, the graft ratio is 2 to 120% by weight, more preferably 4 to 80% by weight, based on the polymer membrane substrate. If it is 4% by weight or less, it is difficult to obtain a conductivity of 0.02 ([Ω · cm] ⁻¹ ) or more. If it is 80% by weight or more, the mechanical strength of the graft polymer film cannot be obtained.

In the present invention, the method for introducing a sulfonic acid group varies depending on the vinyl monomers (1) to (4) used for graft polymerization. In the graft polymer membrane obtained from the vinyl monomer (1), sulfonation to the aromatic ring in the graft chain is carried out by reacting concentrated sulfuric acid, fuming sulfuric acid, or dichloroethane solution or chloroform solution of chlorosulfonic acid. be able to. Depending on the graft ratio of the graft polymer membrane, the sulfonation rate for showing conductivity applicable to the polymer electrolyte membrane varies. Here, the sulfonation rate is 100% when one molecule of sulfonic acid is introduced per vinyl monomer unit of the graft chain. The sulfonation rate is preferably adjusted to 10 to 150% by changing the reaction time and the reaction temperature. More preferably, it is 30 to 100%. If it is 30% or less, it is difficult to obtain a conductivity of 0.02 ([Ω · cm] ⁻¹ ) or more. If it is 100% or more, the heat resistance and oxidation resistance of the graft chain are remarkably lowered.

In the graft polymer membrane obtained from the vinyl monomer (2), hydrolysis of a sulfonyl halide group, a sulfonate group, and a sulfonate group in the graft chain into a sulfonate group is carried out by using a neutral aqueous solution, an alkaline aqueous solution, Or it can process by processing with acidic aqueous solution. In graft copolymerization with vinyl monomers other than vinyl monomer (2), the sulfonation rate is preferably adjusted to 10 to 100% by changing the composition ratio. More preferably, it is 30 to 100%. If it is 30% or less, it is difficult to obtain a conductivity of 0.02 ([Ω · cm] ⁻¹ ) or more. If it is 100% or more, the heat resistance and oxidation resistance of the graft chain are remarkably lowered.

In the graft polymer membrane obtained from the vinyl monomer (3), the chemical conversion of the halogen atom in the graft chain to the sulfonate is carried out by using a sodium sulfite aqueous solution, a sodium hydrogen sulfite aqueous solution, or a mixture thereof with dimethyl sulfoxide. Can be treated with a solution. In graft copolymerization with vinyl monomers other than the vinyl monomer (3), the sulfonation rate is preferably adjusted to 10 to 100% by changing the composition ratio. More preferably, it is 30 to 100%. If it is 30% or less, it is difficult to obtain a conductivity of 0.02 ([Ω · cm] ⁻¹ ) or more. If it is 100% or more, the heat resistance and oxidation resistance of the graft chain are remarkably lowered.

The graft polymer membrane obtained from the vinyl monomer (4) includes a polymer electrolyte membrane prepared by utilizing the radiation graft polymerization reported so far, and the vinyl monomers (1) to (1) of the present invention. 3) Unlike the polymer electrolyte membrane prepared by using 3), the graft chain has mechanical strength as a hydrophilic phase in which the region derived from the polymer membrane substrate bears conductivity by sulfonated to the polymer membrane substrate. It is characterized by acting as a hydrophobic matrix phase that bears the above. Therefore, the vinyl monomer (4) to be graft polymerized is not particularly limited as long as it has mechanical properties and heat resistance. Preferably, the mechanical strength and heat resistance are further improved by using a crosslinking agent such as a polyfunctional monomer in combination with the vinyl monomer. Further, by subjecting the graft polymer membrane after graft polymerization or the polymer electrolyte membrane after sulfonation to heat treatment, mechanical strength and heat resistance are improved by introducing a further crosslinked structure on the graft chain. Sulfonation of the aromatic base membrane into the aromatic ring can be carried out by reacting concentrated sulfuric acid, fuming sulfuric acid, dichloroethane solution of chlorosulfonic acid or chloroform solution. Depending on the grafting rate of the graft polymer membrane, the sulfonation rate to show the conductivity applicable to the polymer electrolyte membrane is different, so the sulfonation rate is adjusted to 10-150% by changing the reaction time and reaction temperature It is preferable to do. More preferably, it is 20 to 100%. If it is 20% or less, it is difficult to obtain a conductivity of 0.02 ([Ω · cm] ⁻¹ ) or more, and if it is 100% or more, the heat resistance and oxidation resistance of the graft chain are remarkably lowered.

In the present invention, in order to increase the electric conductivity of the polymer electrolyte membrane, it is also conceivable to make the polymer electrolyte membrane thin. However, at present, an excessively thin polymer electrolyte membrane is easily damaged, and it is difficult to manufacture the membrane itself. Therefore, in the present invention, a polymer electrolyte membrane of 30 to 200 μm is preferable. More preferred is a polymer electrolyte membrane in the range of 20 to 100 μm.

In the present invention, the energy imparted by radiation acts on the aromatic polymer chain to generate an active species such as a radical that initiates graft polymerization of the vinyl monomer on the polymer chain. Therefore, radiation is not particularly limited as long as it is an energy source that causes a reaction that generates active species such as radicals on the polymer chain. Specific examples include γ rays, electron beams, ion rays, and X-rays.

Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to this. In addition, each measured value was calculated | required by the following measurements.

(1) Graft rate (%)
When the polymer membrane substrate is the main chain part and the graft polymerized part with the vinyl monomer is the graft chain part, the weight ratio of the graft chain part to the main chain part is the graft ratio (X _dg [wt%]) Represented as:

(2) Ion exchange capacity (meq / g)
The ion exchange capacity (IEC) of the polymer electrolyte membrane is expressed by the following equation.

[n (acidic group) _obs ] is measured by immersing the polymer electrolyte membrane in a 1M sulfuric acid solution at 50 ° C for 4 hours to form a complete proton type (H type), and then in a 3M NaCl aqueous solution at 50 ° C. Re-SO ₃ Na type by immersion for 4 hours. After removing the polymer electrolyte membrane, the remaining NaCl aqueous solution was neutralized and titrated with 0.2 M NaOH to obtain the acidic group concentration of the polymer electrolyte membrane as a substituted proton (H ⁺ ).

(3) Moisture content (%)
Remove the H-type polymer electrolyte membrane stored in water at room temperature, gently wipe off the water on the surface (after about 1 minute), and then measure the weight (W (g)). This membrane is vacuum-dried at 60 ° C. for 16 hours and then weighed to obtain the dry weight W _d (g) of the polymer electrolyte membrane, and the moisture content is calculated from W _s and W _d by the following formula.

(4) Electrical conductivity (Ω ^-1 cm ^-1 )
In accordance with the measurement by the AC method (New Experimental Chemistry Course 19, Polymer Chemistry (II), p998, Maruzen), using a normal membrane resistance measurement cell and Hewlett Packard LCR meter, E-4925A, polymer The membrane resistance (Rm) of the electrolyte membrane was measured. The cell was filled with a 1M aqueous sulfuric acid solution, the resistance between two platinum electrodes (distance 5 mm) was measured, and the electrical conductivity of the polymer electrolyte membrane was calculated using the following equation.

(5) Oxidation resistance (weight residual rate%)
The weight of the polymer electrolyte membrane after vacuum impression at 60 ° C. for 16 hours is defined as W _3, and the dry weight of the electrolyte membrane after 24 hours in a 3% hydrogen peroxide solution at 80 ° C. is defined as W ₄ .

(Reference Example 1)
A 2 cm x 3 cm polyetheretherketone (hereinafter abbreviated as PEEK) film (film thickness: 25 μm) was placed in a separable container made of glass with a cock and deaerated, and the inside of the glass container was replaced with argon gas. In this state, the PEEK film was irradiated with γ rays from a ⁶⁰ Co source at 30 kGy at room temperature. Subsequently, 20 g of a 1 wt-propanol solution of 50 wt% styrene degassed by bubbling argon gas was added to the glass container so that the irradiated PEEK film was immersed therein. After replacing with argon gas, the glass container was sealed and allowed to stand at 80 ° C. for 48 hours. The obtained graft polymer membrane was washed with cumene and dried. After standing in a 1,2-dichloroethane solution of 0.05 M chlorosulfonic acid at 0 ° C. for 8 hours, a polymer electrolyte membrane was obtained by performing a hydrolysis treatment by washing with water. Table 1 shows the graft ratio, ion exchange capacity, and electrical conductivity of the polymer electrolyte membrane obtained in this example.

(Reference Example 2)
A 2 cm x 3 cm PEEK film (film thickness: 25 μm) was put in a glass separable container with a cock and deaerated, and the inside of the glass container was replaced with argon gas. In this state, the PEEK film was irradiated with 100 gGy of γ rays from a ⁶⁰ Co radiation source at room temperature. Subsequently, 20 g of an N-methylpyrrolidone solution of 50 wt% ethyl p-styrenesulfonate degassed by bubbling with argon gas was added to the glass container so that the irradiated PEEK membrane was immersed therein. After replacing with argon gas, the glass container was sealed and left at 80 ° C. for 12 hours. The obtained graft polymer membrane was washed with N-methylpyrrolidone and dried. The sulfonate ester on the graft chain is hydrolyzed by immersing it in a 0.5M aqueous hydrochloric acid solution at 80 ° C for 12 hours, and then washed with water to obtain a polymer electrolyte membrane having a sulfonate group in the graft chain. It was. Table 1 shows the graft ratio, ion exchange capacity, and electrical conductivity of the polymer electrolyte membrane obtained in this example.
(Reference Example 3)
A 2 cm x 3 cm PEEK membrane (25 μm) was placed in a glass separable container with a cock and deaerated, and the inside of the glass container was replaced with argon gas. In this state, the PEEK film was irradiated with γ rays from a ⁶⁰ Co source at 30 kGy at room temperature. Subsequently, 20 g of a 1 wt-propanol solution of 50 wt% acrylonitrile degassed by bubbling with argon gas was added to the glass container so that the PEEK film was immersed therein. After replacing with argon gas, the glass container was sealed and left at 80 ° C. for 24 hours. The obtained graft polymer membrane was washed with cumene and dried. The graft polymer membrane was allowed to stand at 200 ° C. for 3 hours under a nitrogen atmosphere to crosslink and cyclize the polyacrylonitrile graft chain. This cross-linked graft membrane was treated in a 1,2-dichloroethane solution of 0.05 M chlorosulfonic acid at 0 ° C. for 8 hours, and then hydrolyzed by washing with water to obtain a polymer having a sulfonic acid group in the aromatic polymer chain. A molecular electrolyte membrane was obtained. Table 1 shows the graft ratio, ion exchange capacity, and electrical conductivity of the polymer electrolyte membrane obtained in this example.
(Reference Example 4)
A 2 cm × 3 cm polyetherimide (hereinafter abbreviated as PEI) membrane (50 μm) was placed in a separable container made of glass with a cock and deaerated, and the inside of the glass container was replaced with argon gas. In this state, the PEI film was irradiated with 100 kGy of γ rays from a ⁶⁰ Co ray source at room temperature. Subsequently, 20 g of a 1-propanol solution of 70 wt% styrene degassed by bubbling with argon gas was added to the glass container so that the PEI film was immersed therein. After replacing with argon gas, the glass container was sealed and left at 60 ° C. for 24 hours. The obtained graft polymer membrane was washed with cumene and dried. A polymer electrolyte membrane was obtained by leaving it to stand in a 1,2-dichloroethane solution of 0.02M chlorosulfonic acid at 0 ° C. for 1 hour and then performing a hydrolysis treatment by washing with water. Table 1 shows the graft ratio, ion exchange capacity, and electrical conductivity of the polymer electrolyte membrane obtained in this example.
(Reference Example 5)
A 2 cm × 3 cm PEI membrane (50 μm) was placed in a glass separable container with a cock, and after deaeration, the inside of the glass container was replaced with argon gas. In this state, the PEI film was irradiated with γ rays from a ⁶⁰ Co ray source at room temperature for 30 kGy. Subsequently, 20 g of a 1 wt-propanol solution of 70 wt% acrylonitrile degassed by bubbling with argon gas was added to the glass container so that the PEI film was immersed therein. After replacing with argon gas, the glass container was sealed and left at 60 ° C. for 24 hours. The obtained graft polymer membrane was washed with cumene and dried. The graft polymer membrane was allowed to stand at 200 ° C. for 3 hours in a nitrogen atmosphere to crosslink and cyclize the polyacrylonitrile graft chain. This cross-linked graft membrane was treated for 1 hour at 0 ° C. in a 1,2-dichloroethane solution of 0.02M chlorosulfonic acid, and then hydrolyzed by washing with water to obtain a polymer having a sulfonic acid group in the aromatic polymer chain. A molecular electrolyte membrane was obtained. Table 1 shows the graft ratio, ion exchange capacity, and electrical conductivity of the polymer electrolyte membrane obtained in this example.
(Reference Example 6)
A 2 cm × 3 cm polysulfone (hereinafter abbreviated as PSU) membrane (50 μm) was placed in a separable container made of glass with a cock, and after deaeration, the inside of the glass container was replaced with argon gas. In this state, the PSU film was irradiated with γ rays from a ⁶⁰ Co ray source at room temperature for 30 kGy. Subsequently, 20 g of a 1 wt-propanol solution of 50 wt% styrene degassed by bubbling with argon gas was added to the glass container so that the PSU film was immersed therein. After replacing with argon gas, the glass container was sealed and left at 40 ° C. for 48 hours. The obtained graft polymer membrane was washed with cumene and dried. A polymer electrolyte membrane was obtained by leaving it to stand at 0 ° C. for 3 hours in a 1,2-dichloroethane solution of 0.02M chlorosulfonic acid, followed by a hydrolysis treatment by washing with water. Table 1 shows the graft ratio, ion exchange capacity, and electrical conductivity of the polymer electrolyte membrane obtained in this example.
(Reference Example 7)
A 2 cm × 3 cm PSU membrane (50 μm) was placed in a glass separable container with a cock and deaerated, and the inside of the glass container was replaced with argon gas. In this state, the PSU film was irradiated with γ rays from a ⁶⁰ Co source at a room temperature of 30 kGy. Subsequently, 20 g of a 1 wt-propanol solution of 50 wt% acrylonitrile degassed by bubbling with argon gas was added to the glass container so that the PSU film was immersed therein. After replacing with argon gas, the glass container was sealed and left at 60 ° C. for 24 hours. The obtained graft polymer membrane was washed with cumene and dried. The graft polymer membrane was allowed to stand at 200 ° C. for 3 hours in a nitrogen atmosphere to crosslink and cyclize the polyacrylonitrile graft chain. This crosslinked graft membrane is treated with 0.02M chlorosulfonic acid in 1,2-dichloroethane for 3 hours at 0 ° C., and then hydrolyzed by washing with water, so that the aromatic polymer main chain has a sulfonic acid group. A polymer electrolyte membrane was obtained. Table 1 shows the graft ratio, ion exchange capacity, electrical conductivity, and electrical conductivity of the polymer electrolyte membrane obtained in this example.

(Example 8)
A 2 cm × 3 cm liquid crystal polyester (hereinafter abbreviated as LCP) film (film thickness: 25 μm) was placed in a separable container made of glass with a cock, and after deaeration, the inside of the glass container was replaced with argon gas. In this state, the LCP film was irradiated with 60 kGy of γ rays from a ⁶⁰ Co ray source at room temperature. Subsequently, 20 g of a 1 wt-propanol solution of 50 wt% styrene degassed by bubbling argon gas was added to the glass container so that the irradiated LCP film was immersed therein. After replacing with argon gas, the glass container was sealed and allowed to stand at 80 ° C. for 48 hours. The obtained graft polymer membrane was washed with cumene and dried. After standing in a 1,2-dichloroethane solution of 0.05 M chlorosulfonic acid at 0 ° C. for 8 hours, a polymer electrolyte membrane was obtained by performing a hydrolysis treatment by washing with water. Table 1 shows the graft ratio, ion exchange capacity, and electrical conductivity of the polymer electrolyte membrane obtained in this example.

Example 9
A 2 cm × 3 cm LCP membrane (25 μm) was put into a glass separable container with a cock and deaerated, and then the inside of the glass container was replaced with argon gas. In this state, the LCP film was irradiated with γ rays from a ⁶⁰ Co ray source at room temperature for 30 kGy. Subsequently, 20 g of a 1 wt-propanol solution of 50 wt% acrylonitrile degassed by bubbling argon gas was added to the glass container so that the LCP film was immersed therein. After replacing with argon gas, the glass container was sealed and left at 80 ° C. for 24 hours. The obtained graft polymer membrane was washed with cumene and dried. The graft polymer membrane was allowed to stand at 200 ° C. for 3 hours under a nitrogen atmosphere to crosslink and cyclize the polyacrylonitrile graft chain. This cross-linked graft membrane was treated in a 1,2-dichloroethane solution of 0.05 M chlorosulfonic acid at 0 ° C. for 8 hours, and then hydrolyzed by washing with water to obtain a polymer having a sulfonic acid group in the aromatic polymer chain. A molecular electrolyte membrane was obtained. Table 1 shows the graft ratio, ion exchange capacity, electrical conductivity, and electrical conductivity of the polymer electrolyte membrane obtained in this example.

(Comparative Example 1)
When a 2 cm × 3 cm PEEK membrane (25 μm) was treated under the same sulfonation conditions as in Example 1, it completely dissolved in the reaction solution, and no polymer electrolyte membrane was obtained.
(Comparative Example 2)
A 2 cm x 3 cm PEEK membrane (25 μm) was treated with 0.05M chlorosulfonic acid in 1,2-dichloroethane for 2 hours at 0 ° C, followed by hydrolysis with water to obtain a polymer electrolyte membrane. It was. The ion exchange capacity and electrical conductivity of the polymer electrolyte membrane obtained in this example are shown in Comparative Example 2 in Table 1.
(Comparative Example 3)
When a 2 cm × 3 cm PEI membrane (25 μm) was treated under the same sulfonation conditions as in Example 4, it was completely dissolved in the reaction solution, and no polymer electrolyte membrane was obtained.
(Comparative Example 4)
A 2 cm x 3 cm PEI membrane (50 μm) was treated in 0.01M chlorosulfonic acid 1,2-dichloroethane solution at 0 ° C for 3 hours, and then hydrolyzed by water washing to form a polymer electrolyte membrane. Obtained. The ion exchange capacity and electrical conductivity of the polymer electrolyte membrane obtained in this example are shown in Comparative Example 4 in Table 1.
(Comparative Example 5)
When a 2 cm × 3 cm PSU membrane (50 μm) was treated under the same sulfonation conditions as in Example 6, it was completely dissolved in the reaction solution, and no polymer electrolyte membrane was obtained.
(Comparative Example 6)
A 2 cm x 3 cm PSU membrane (50 μm) was treated in 0.01 M chlorosulfonic acid 1,2-dichloroethane solution at 0 ° C for 3 hours, and then hydrolyzed by water washing to form a polymer electrolyte membrane. Obtained. The ion exchange capacity and electrical conductivity of the polymer electrolyte membrane obtained in this example are shown in Comparative Example 6 in Table 1.
(Comparative Example 7)
The results of ion exchange capacity, electrical conductivity, and oxygen permeability measured for Nafion 112 (manufactured by DuPont) shown in Table 1 below are shown in Comparative Example 7 in Table 1.

  The polymer electrolyte membrane of the present invention has a graft chain formed on an aromatic polymer membrane substrate excellent in mechanical properties and fuel impermeability at high temperatures by graft polymerization capable of controlling the structure and sulfonation rate of the sulfonic acid group. Since it can be introduced, it exhibits higher proton conductivity, durability, and fuel impermeability than conventional sulfonated aromatic polymer electrolyte membranes. As a result, this polymer is excellent in proton conductivity, durability, and fuel impermeability, ideal for portable devices powered by methanol, hydrogen, etc., fuel cells expected as power sources for household cogeneration and automobiles. An electrolyte membrane can be provided.

Embodiments of the present invention are shown below.
(1) A polymer electrolyte membrane produced by graft-polymerizing a vinyl monomer on an aromatic polymer membrane substrate and then chemically converting a part of the graft chain to a sulfonic acid group.
(2) A polymer electrolyte membrane produced by graft-polymerizing a vinyl monomer on an aromatic polymer membrane substrate and then chemically converting a part of the aromatic polymer chain to a sulfonic acid group.
(3) A polymer electrolyte produced by graft-polymerizing a vinyl monomer onto an aromatic polymer membrane substrate and then chemically converting a part of the graft chain and the aromatic polymer chain to a sulfonic acid group film.
(4) The polymer electrolyte membrane according to any one of (1) to (3), wherein the aromatic polymer membrane substrate has a polyetheretherketone structure.
(5) The polymer electrolyte membrane according to any one of (1) to (3), wherein the aromatic polymer membrane substrate has a polyimide structure.
(6) The polymer electrolyte membrane according to any one of (1) to (3), wherein the aromatic polymer membrane substrate has a polysulfone structure.
(7) The polymer electrolyte membrane according to any one of (1) to (3), wherein the aromatic polymer membrane substrate has a polyester structure.
(8) After graft polymerization of a vinyl monomer on an aromatic polymer film substrate made of polyetherketone derivative, polyimide derivative, polysulfone derivative, polyester derivative, polyamide derivative, polycarbonate, polyphenylene sulfide, or polybenzimidazole, graft chain and A method for producing a polymer electrolyte membrane, wherein a part of an aromatic polymer chain is chemically converted into a sulfonic acid group.
(9) A vinyl monomer having an aromatic ring capable of retaining a sulfonic acid group is 1) a vinyl monomer having an aromatic ring capable of retaining a sulfonic acid group, 2) a sulfonyl halide or sulfone which can be converted into a sulfonic acid group by hydrolysis. A vinyl monomer having an acid ester group, 3) a vinyl monomer having a halogen capable of introducing a sulfonic acid group by a sulfonation reaction, or 4) being sulfonated by an electrophilic substitution sulfonation reaction to an aromatic polymer chain. (8) The method according to (8), which is not an aliphatic vinyl monomer, an aromatic ring vinyl monomer or a perfluoroalkyl vinyl monomer.

Claims (5)

  Prepared by immersing an aromatic polymer membrane base material having a polyester structure in a vinyl monomer liquid containing an amide solvent and alcohol as a solvent, graft polymerization, and then chemically converting a part of the graft chain to a sulfonic acid group. A polymer electrolyte membrane characterized by comprising:   The polymer substrate with an aromatic polymer membrane having a polyester structure is immersed in a vinyl monomer liquid containing an amide solvent and alcohols as a solvent for graft polymerization, and then a part of the aromatic polymer chain is chemically converted to a sulfonic acid group. A polymer electrolyte membrane characterized by being manufactured as follows.   Aromatic polymer membrane substrate amide solvent having a polyester structure, and after graft polymerization by immersing in a vinyl monomer liquid containing alcohol as a solvent, the graft chain and a part of the aromatic polymer chain are converted to sulfonic acid groups. A polymer electrolyte membrane produced by chemical conversion.   An aromatic polymer membrane substrate having a polyester structure is immersed in a vinyl monomer liquid containing an amide solvent and an alcohol as a solvent for graft polymerization, and then a graft chain and / or a part of the aromatic polymer chain is formed. A method for producing a polymer electrolyte membrane, which is chemically converted to a sulfonic acid group.   The vinyl monomer having an aromatic ring capable of retaining a sulfonic acid group is (1) a vinyl monomer having an aromatic ring capable of retaining a sulfonic acid group, or (2) a halogenated sulfonyl group or sulfonic acid that can be converted into a sulfonic acid group by hydrolysis. A vinyl monomer having an ester group, (3) a vinyl monomer having a halogen capable of introducing a sulfonic acid group by a sulfonation reaction, or (4) being sulfonated by an electrophilic substitution sulfonation reaction to an aromatic polymer chain. 5. A process according to claim 4, characterized in that it is a free aliphatic vinyl monomer, aromatic ring vinyl monomer or perfluoroalkyl vinyl monomer.