JP2003288916A - Direct methanol fuel cell membrane and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct methanol fuel cell membrane hardly permeating alcohol such as methanol in addition to characteristics of the fuel cell membrane represented by proton conductivity. <P>SOLUTION: This direct alcohol fuel cell membrane is made from an aromatic polymer compound into which proton conductive substituent groups are introduced and/or an aromatic polymer compound to which proton conductive substances are mixed, and is preferable to have a hydrolysis resistance in boiling water of 0.5 hours or more. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct alcohol fuel cell membrane which can be used in a direct alcohol fuel cell using alcohol (mainly methanol) which is a liquid fuel as a fuel.

[0002]

2. Description of the Related Art In recent years, fuel cells have been in the limelight as a clean energy source due to increasing awareness of environmental problems and energy saving. Among them, the polymer electrolyte fuel cell that uses a proton-conducting polymer membrane as the electrolyte is unique to other fuel cells (phosphoric acid type, solid oxide type, molten carbonate type), such as low temperature operation and small size and light weight. Therefore, its application to automobiles and household cogeneration has been investigated.

On the other hand, in the field of electronic devices, portable electronic devices such as mobile phones and notebook computers are rapidly becoming popular. Currently, as the power generation device for these applications, secondary batteries represented by nickel-hydrogen secondary batteries and lithium-ion secondary batteries are the mainstream, but they have not yet reached the level of guaranteeing sufficient continuous use time. Therefore, it is considered that power consumption will further increase due to higher performance in the future. Therefore, there is a demand for the development of a power generation device that has a high energy density, is small, and can be used for a long time. Along with this, theoretically, the use of polymer electrolyte fuel cells with high power generation efficiency and high energy density is being studied.

Conventionally, Nafion has been used as a proton conductive membrane used in a polymer electrolyte fuel cell.
n, a registered trademark of DuPont. The same applies to perfluorocarbon sulfonic acid membranes. Among polymer electrolyte fuel cells, direct alcohol fuel cells that use alcohols such as methanol, which is said to be suitable for reducing size and weight, as fuel (when using methanol, direct methanol fuel cells, When a perfluorocarbon sulfonic acid membrane is used for (DMFC), there is a problem that the methanol permeates (crossovers) together with water that moves with protons in the membrane, thereby lowering the efficiency of the fuel cell. Further, in order to suppress crossover, only a methanol aqueous solution having a low concentration of about several% can be used as a fuel, and the energy density per unit weight or unit volume becomes low, so that it cannot be applied to small portable device applications. There was a problem.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a direct alcohol fuel cell membrane which has excellent proton conductivity and is less permeable to alcohol fuel such as methanol.

[0006]

That is, the present invention is directed to an aromatic polymer compound having a proton-conducting substituent introduced therein and / or an aromatic polymer compound having a proton-conducting substance mixed therein. An alcohol fuel cell membrane having a hydrolysis resistance of 0.5 in boiling water.
It is preferable that the time is longer than that. Also, in the membrane 25
Methanol permeability coefficient at ℃ 9 × 10 ^-12 kmol
It is also possible to use those having a viscosity of m / (m ² · s · kPa) or less. The solubility in methanol at room temperature is 0.
It is preferably less than 01% by weight.

The aromatic polymer compound is preferably an aromatic polymer compound comprising at least one repeating unit selected from the group of the following general formulas (1) to (7).

[0008]

[Chemical 6] [Wherein Ar _{1 to} Ar ₄ are the same or different from each other in formulas (8) to (17):

[0009]

[Chemical 7] Is a divalent aromatic unit represented by. Ar _{5 to} Ar ₇ are
They are the same or different tetravalent aromatic units. X, Y, Z
Are the same or different, and are -O-, -CO-,-
CONH -, - COO -, - S -, - SO-, SO 2 -
It is a divalent organic group selected from the group R ₁ ~ R
₁₂ are the same or different, respectively, a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, an allyl group,
It is an aryl group or a phenyl group. Further, the aromatic polymer compound is more preferably at least one selected from the following group (A). Group (A): polybenzoxazole (PBO), polybenzothiazole (P
BT), polybenzimidazole (PBI), polysulfone (PSU), polyethersulfone (PES), polyetherethersulfone (PEES), polyarylethersulfone (PAS), polyphenylenesulfone (PPSU), polyphenyleneoxide (PPO),
Polyphenylene sulfoxide (PPSO), polyphenylene sulfide (PPS), polyphenylene sulfide sulfone (PPS / SO ₂ ), polyparaphenylene (PPP), polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK) ) A plasticizer may be further added to the above aromatic polymer compound.

On the other hand, the production method of the present invention comprises the following general formula (1):
To (7) are obtained by bringing an aromatic polymer compound comprising at least one repeating unit selected from the group (7) into contact with a film comprising a plasticizer optionally added and a sulfonating agent. This is a method for producing a direct alcohol fuel cell membrane comprising a sulfonated aromatic polymer compound membrane.

[0011]

[Chemical 8] [Wherein Ar _{1 to} Ar ₄ are the same or different from each other in formulas (8) to (17):

[0012]

[Chemical 9] Is a divalent aromatic unit represented by. Ar _{5 to} Ar ₇ are
They are the same or different tetravalent aromatic units. X, Y, Z
Are the same or different, and are -O-, -CO-,-
CONH -, - COO -, - S -, - SO-, SO 2 -
It is a divalent organic group selected from the group R ₁ ~ R
₁₂ are the same or different, respectively, a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, an allyl group,
It is an aryl group or a phenyl group. Further, a direct alcohol-type fuel cell membrane can be produced by irradiating at least one kind of radiation selected from the group consisting of γ-ray, electron beam and ion beam.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The direct alcohol fuel cell membrane of the present invention comprises an aromatic polymer compound having a proton-conducting substituent introduced therein and / or an aromatic polymer compound having a proton-conducting substance mixed therein. It is the obtained direct alcohol fuel cell membrane.

Among them, those having a hydrolysis resistance of the membrane in boiling water of 0.5 hours or more are preferable. The term "hydrolysis resistance" as used herein means that the membrane does not decompose or dissolve when the proton conductive polymer membrane is immersed in boiling water of at least 95 ° C or higher.

The durability of the fuel cell membrane is 5 for automobile applications.
Over 000 hours, 4 for home cogeneration
0000 to 100,000 hours, tens of thousands of hours are required for small portable device applications in place of secondary batteries. That is, the direct alcohol fuel cell membrane of the present invention is intended for a small-sized portable device as a secondary battery substitute as a main application, and therefore requires substantially tens of thousands of hours for hydrolysis resistance. Whether or not the fuel cell membrane has durability that can withstand practical use is
Although it is necessary to confirm it by the operating conditions under actual use conditions, it is difficult to clearly distinguish the factors of load fluctuation and factors such as deterioration and matching of other materials such as catalysts and electrodes. Therefore, in the present invention, hydrolysis resistance of 0.5 hour or longer is set as an index of the durability of the direct alcohol fuel cell membrane. Although the correlation with the actual durability is not always clear, a film having a hydrolysis resistance of 0.5 hours or more in boiling water can be used even in a longer-term test (for example, 95 ° C. 10,000 hours or more). No deterioration of the film was observed, and in the evaluation near room temperature (about 25 ° C), which is the assumed operating temperature for small portable devices, the film deteriorated in several thousand hours, and the hydrolysis resistance in boiling water was 0.5.
It has been experimentally shown to be less than time.

The methanol permeation coefficient of the direct alcohol fuel cell membrane of the present invention at 25 ° C. is 9 × 10 ^-12 k
It is preferably not more than mol · m / (m ² · s · kPa). There is no standardized method for measuring the methanol permeation coefficient, and any method may be selected.
Permeation through the membrane by adding a device that vaporizes methanol or installing a cell that can hold methanol according to the “gas permeability test method for plastic films and sheets” specified in IS K 7126. It is preferable to quantify the amount of methanol formed by gas chromatography.
When the methanol permeation coefficient is larger than the above range, the performance as a fuel cell tends to be poor. When the methanol permeation coefficient is in the above range, deterioration of power generation characteristics due to methanol crossover is suppressed. When a conventional perfluorocarbon sulfonic acid membrane is used,
The concentration of the aqueous methanol solution, which was about 5%, can be set to a high concentration, and the energy density per unit weight or unit volume during actual use can be increased, which is preferable. The direct alcohol fuel cell membrane of the present invention preferably has a solubility in methanol at room temperature of less than 0.01% by weight. If the solubility is higher than this range, when used in direct alcohol fuel cells such as direct methanol fuel cells that use methanol as a fuel, the membrane gradually dissolves in the methanol that is the fuel, resulting in deterioration of characteristics and There is a risk of destruction.

The aromatic polymer compound in the present invention is preferably an aromatic polymer compound comprising at least one repeating unit selected from the group of the following general formulas (1) to (7).

[0018]

[Chemical 10] [Wherein Ar _{1 to} Ar ₄ are the same or different from each other in formulas (8) to (17):

[0019]

[Chemical 11] Is a divalent aromatic unit represented by. Ar _{5 to} Ar ₇ are
They are the same or different tetravalent aromatic units. X, Y, Z
Are the same or different, and are -O-, -CO-,-
CONH -, - COO -, - S -, - SO-, SO 2 -
It is a divalent organic group selected from the group R ₁ ~ R
₁₂ are the same or different, respectively, a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, an allyl group,
It is an aryl group or a phenyl group. ] More preferably, it is composed of a proton conductive substituent and at least one aromatic polymer compound selected from the following group (A). Group (A): polybenzoxazole (PBO), polybenzothiazole (PBT), polybenzimidazole (PBI), polysulfone (PSU), polyethersulfone (PES), polyetherethersulfone (P)
EES), polyaryl ether sulfone (PAS),
Polyphenylene sulfone (PPSU), polyphenylene oxide (PPO), polyphenylene sulfoxide (P
PSO), polyphenylene sulfide (PPS), polyphenylene sulfide sulfone (PPS / SO ₂ ),
Polyparaphenylene (PPP), polyetherketone (PEK), polyetheretherketone (PEE)
K), polyetherketoneketone (PEKK) These aromatic polymer compounds may be used alone or in combination of two or more kinds, or as a mixture of two or more kinds, if necessary. . As a result, the direct alcohol fuel cell membrane of the present invention has excellent proton conductivity, chemical stability represented by hydrolysis resistance / oxidation resistance, fuel barrier property of alcohols such as methanol, oxygen / air It is preferable because it has an excellent oxidant blocking property.

Industrial availability, properties of the resulting membrane,
In consideration of the above, the aromatic polymer compound used in the present invention is at least one selected from the group consisting of polyphenylene sulfoxide (PPSO), polyphenylene sulfide (PPS), and polyphenylene sulfide sulfone (PPS / SO ₂ ). Preferably there is.

The direct alcohol fuel cell of the present invention is
This is a system in which alcohols typified by methanol are directly used as a fuel to generate protons on the catalyst of the catalyst-supporting gas diffusion electrode bonded to the membrane and generate power according to the formula shown below. Fuel electrode: CH ₃ OH + H ₂ O → CO ₂ + 6
H ⁺ + 6e ⁻ Oxidizer electrode: 3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3
H ₂ O battery reaction: CH ₃ OH + 3 / 2O ₂ → CO ₂ +
H ₂ O The fuel type that can be used depends strongly on the performance of the catalyst, and currently methanol is commonly used. Fuels other than alcohols can be used as long as they can generate protons depending on the selection and performance of the catalyst. Therefore, the direct alcohol fuel cell of the present invention means a direct liquid fuel cell in a broad sense, and a direct methanol fuel cell in a narrow sense.

Examples of the proton conductive substituents of the direct alcohol fuel cell membrane of the present invention include sulfonic acid group, phosphoric acid group, carboxylic acid group and phenolic hydroxyl group, which are effective as direct methanol fuel cell membrane. A sulfonic acid group is preferable from the viewpoint of exhibiting excellent proton conductivity.

On the other hand, examples of the proton-conducting substance of the present invention include sulfuric acid, phosphoric acid, tungstophosphoric acid, etc., or monomers or polymers containing the above-mentioned proton-conducting substituents, and direct alcohol fuel cell membranes. From the viewpoint of exhibiting effective proton conductivity, it is preferably at least one selected from the group consisting of sulfuric acid, phosphoric acid and tungstophosphoric acid. Further, in the direct alcohol fuel cell membrane of the present invention, the aromatic polymer compound is polyphenylene sulfide (PP).
S), which has a repeating structural unit of sulfonated polyphenylene sulfide represented by the following general formula (18), in which the proton conductive substituent is a sulfonic acid group.

[0024]

[Chemical 12] [In the formula, n is an integer of 1 to 4] As a result, in the properties which are indispensable as a direct alcohol fuel cell membrane, proton conductivity, alcohol barrier property represented by methanol, water resistance and hydrolysis resistance are obtained. It is possible to obtain a film having excellent mechanical properties such as chemical stability and handleability.

The direct alcohol fuel cell membrane of the present invention comprises:
Further, it is preferably composed of the aromatic polymer compound containing a plasticizer. As a result, the aromatic polymer compound is plasticized and becomes flexible, and the handling property of the obtained direct alcohol fuel cell membrane tends to be significantly improved. Along with this, physical film breakage is less likely to occur during the manufacturing process and power generation, which is preferable.

The plasticizer usable in the present invention varies depending on the kind of aromatic polymer compound used and the mixing method. For example, when the aromatic polymer compound and the plasticizer are melt-mixed, it is preferable to select a plasticizer having a boiling point higher than the melting temperature of the aromatic polymer compound. When the boiling point of the plasticizer is significantly lower than the boiling point of the aromatic polymer compound, the mixture of the aromatic polymer compound and the plasticizer tends not to have a desired mixing ratio.

Examples of the plasticizer usable in the present invention include phosphoric acid ester compounds such as tributyl phosphate, triphenyl phosphate, tricresyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate and phthalate. Di-n-octyl acid,
Di-2-ethylhexyl phthalate, diisononyl phthalate, octyldecyl phthalate, diisodecyl phthalate,
Phthalates such as butylbenzyl phthalate, butyl oleate, aliphatic monobasic ester such as glycerin monooleate, di-n-butyl adipate, di-n-hexyl adipate, adipic acid Di-2-ethylhexyl, alkyl adipate 61
0, di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate and the like, dibasic acid ester compounds, diethylene glycol benzoate, triethylene glycol di-2-ethyl butyrate and other dihydric alcohols Ester compounds, methyl acetylricinoleate, butyl acetylricinoleate,
Butylphthalyl butyl glycolate, oxyacid ester compounds such as tributyl acetylcitrate, chlorinated paraffin, chlorinated biphenyl-2-nitrobiphenyl, dinonylnaphthalene, o-toluenesulfonethylamide, p-toluenesulfonethylamide, Methyl abietic acid, etc. can be illustrated. Among the plasticizers exemplified above, from the viewpoint of imparting compatibility with a polymer compound and flame retardancy, it is preferable to use a phosphate compound, particularly triphenyl phosphate or tricresyl phosphate. Is preferred.

Next, the method for producing the direct alcohol fuel cell membrane of the present invention will be briefly described. The direct alcohol fuel cell membrane made of an aromatic polymer compound having a proton conductive substituent introduced therein can be produced by the following methods (1) to (3).

(1) An aromatic polymer compound having a proton-conducting substituent is polymerized using a monomer component containing a proton-conducting substituent, and the polymer compound is dissolved in an arbitrary solvent to support it. A method of directly casting on the body to remove the solvent and directly obtaining an alcohol fuel cell membrane.

(2) Protons are reacted by reacting any aromatic polymer compound with a proton-conducting substituent-introducing agent (in the case of a sulfonic acid group, a sulfonating agent such as chlorosulfonic acid, concentrated sulfuric acid, fuming sulfuric acid). An aromatic polymer compound having a conductive substituent is synthesized, and the polymer compound is dissolved in an arbitrary solvent and cast on a support to remove the solvent to directly obtain an alcohol fuel cell membrane. Method.

(3) After a film made of any aromatic polymer compound is produced, this film and a proton conductive substituent introducing agent (in the case of a sulfonic acid group, chlorosulfonic acid, concentrated sulfuric acid, fuming sulfuric acid, etc. A sulfonating agent) to directly obtain an alcohol fuel cell membrane.

A direct alcohol fuel cell membrane comprising a mixture of an aromatic polymer compound and a proton conductive material typified by sulfuric acid, phosphoric acid, tungstophosphoric acid, etc.
It can be manufactured by the method (5).

(4) A film made of an aromatic polymer compound is produced by an arbitrary method, and the film is brought into contact with a liquid proton-conducting substance to hold the proton-conducting substance in the film, thereby directly producing an alcohol fuel cell membrane. .

(5) A homogeneous mixed solution of an arbitrary aromatic polymer compound and a proton conductive substance is prepared and cast on a support to remove an unnecessary solvent to form a direct alcohol fuel cell membrane. How to get. In the present invention, a proton conductive substituent and a proton conductive substance may be used in combination.

The direct alcohol fuel cell membrane of the present invention comprises:
An aromatic polymer compound composed of at least one repeating unit selected from the group of the following general formulas (1) to (7), a film composed of a plasticizer optionally added, and a sulfonating agent: It is preferably obtained by contacting.

[0036]

[Chemical 13] [Wherein Ar _{1 to} Ar ₄ are the same or different from each other in formulas (8) to (17):

[0037]

[Chemical 14] Is a divalent aromatic unit represented by. Ar _{5 to} Ar ₇ are
They are the same or different tetravalent aromatic units. X, Y, Z
Are the same or different, and are -O-, -CO-,-
CONH -, - COO -, - S -, - SO-, SO 2 -
It is a divalent organic group selected from the group R ₁ ~ R
₁₂ are the same or different, respectively, a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, an allyl group,
It is an aryl group or a phenyl group. ] Further, it is preferable to contact the sulfonating agent in the presence of a solvent.

By such a production method, an aromatic polymer compound having a proton-conducting substituent such as a sulfonic acid group is obtained, and then various kinds of recovery, washing and The drying process can be simplified and it is industrially useful.

As the sulfonating agent usable in the present invention, known sulfonating agents for aromatic hydrocarbon compounds can be used. Considering the ease of introduction of a sulfonic acid group, in particular, it is at least one selected from the group consisting of chlorosulfonic acid, sulfur trioxide-triethyl phosphate, concentrated sulfuric acid, fuming sulfuric acid, and trimethylsilyl chlorosulfate. Is preferred. Particularly in the present invention, it is preferable to use chlorosulfonic acid because it is easy to introduce a sulfonic acid group.

In the present invention, the sulfonic acid group is uniformly introduced into the film of the aromatic polymer compound, and the film characteristics are brought about by direct contact with the sulfonating agent or excessive introduction of the sulfonic acid group. In order to prevent the deterioration of (1) (reduction of mechanical strength, etc.), the sulfonating agent is preferably contacted in the presence of a solvent. As the solvent that can be used in the present invention, any solvent that does not practically react with the sulfonating agent and does not deteriorate the film made of the aromatic polymer compound can be used. In particular, considering that the sulfonic acid group is uniformly introduced into the inside of the film, it is preferable to use a solvent alone or a mixed system of a sulfonating agent and a solvent, which easily swells the polymer film. Examples of such a solvent include hydrocarbon solvents such as n-hexane, ether solvents such as tetrahydrofuran and dioxane, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, N-diethyl. Formamide solvents such as formamide, acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, 1,1 , 2,2-tetrachloroethane, 1,1,1,2-tetrachloroethane, 1,
1,1-trichloroethane, 1,2-dichloroethane,
Examples include trichloroethylene, tetrachloroethylene, dichloromethane, chloroform and the like. In the present invention, especially 1,1,2,2-tetrachloroethane, 1,
At least one selected from 1,1,2-tetrachloroethane, 1,1,1-trichloroethane, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, dichloromethane and chloroform is preferable.

The direct alcohol fuel cell membrane of the present invention comprises:
It is preferable to irradiate at least one kind of radiation selected from the group consisting of γ-rays, electron beams and ion beams. By irradiating with radiation to modify the membrane, the proton conductivity of the fuel cell membrane is improved. In particular, an electron beam is preferable from the viewpoints of radiation dose, material permeability, irradiation time (industrial continuous irradiation), and the like.

The radiation irradiation atmosphere can be selected from air, an oxygen-free atmosphere, and a vacuum atmosphere. An atmosphere in which the film material is not deteriorated by irradiation with radiation may be appropriately selected. Further, in order to efficiently carry out the film modification by irradiation of radiation, the irradiation atmosphere or the film may be heated. Also in this case, the condition that the film material is not deteriorated may be appropriately set.

The acceleration voltage of radiation is 0.01 to 5.0M.
It is preferably eV. When the accelerating voltage is low, the permeability of radiation to the material is low, and it is difficult to obtain a uniform film inside the material. In addition, long-term irradiation is required to secure the necessary irradiation dose, which may significantly reduce productivity. If it is larger than this range, the device may be unnecessarily large-scaled or material deterioration may be accelerated.

The irradiation dose of radiation is 10 to 1000 kGy.
Is preferred. If the irradiation dose is less than this range, the sufficient irradiation effect may not be exhibited.

The direct alcohol fuel cell membrane of the present invention comprises:
It is preferable that the proton conductivity at room temperature is 1.0 × 10 ⁻² S / cm or more. When it is smaller than this range, the membrane resistance against the movement of protons increases, and it tends to be difficult to exhibit sufficient power generation characteristics.

The direct alcohol fuel cell membrane of the present invention comprises:
The thinner the better, as long as it has practical mechanical strength and fuel / oxidant barrier properties. If the ion exchange capacity and the proton conductivity are the same, the thinner the thickness, the lower the membrane resistance. Therefore, the membrane resistance is generally 5 to 200 μm, and further 20 to 150 μm.
The thickness is preferably

The direct alcohol fuel cell membrane of the present invention comprises:
Since it has proton conductivity, chemical / thermal stability, and mechanical properties, it is preferably used as a proton conductive polymer membrane for a direct alcohol fuel cell represented by a direct methanol fuel cell. In fact, when using
Alcohol-type fuel cell unit is directly connected from the catalyst and electrode on the membrane by a known method applied to perfluorocarbon sulfonic acid membrane typified by Nafion Can be configured. Further, in order to obtain a required output, a plurality of cells may be arranged to form a stack and be used.

The direct alcohol fuel cell will be described below with reference to the drawings as an example.

FIG. 1 is a sectional view of a main part of a direct alcohol fuel cell using the direct alcohol fuel cell membrane of the present invention. This is a direct alcohol fuel cell membrane (1) of the present invention, and a catalyst-supporting electrode (2) is joined to both sides of the membrane of (1) to form a membrane-electrode assembly. A required number of the membrane-electrode assemblies are arranged in a plane on both sides of a fuel (alcohol) tank (3) having a fuel (alcohol) filling section (4) and a supply section (4). Further outside,
The support (5) having the oxidant flow channel (6) formed therein is arranged and sandwiched between them to form a cell or stack of a direct alcohol fuel cell.

In addition to the above example, the direct alcohol fuel cell membrane of the present invention is disclosed in JP-A-2001-313046, JP-A-2001-313047, and JP-A-2001.
-93551, JP 2001-93558 A, JP 2001-93561 A, JP 2001-A1
No. 102069, JP 2001-102070 A, JP 2001-283888 A, JP 2000
-268835, JP-A-2000-268836, JP-A-2001-283892, etc., and can be used as a membrane material for a direct alcohol fuel cell represented by a direct methanol fuel cell. is there.

[0051]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples, and various modifications can be made without departing from the scope of the invention.

(Method for measuring ion exchange capacity) The test sample is immersed in a saturated aqueous solution of sodium chloride and reacted in a water bath at 60 ° C. for 3 hours. After cooling to room temperature, the sample was thoroughly washed with ion-exchanged water, and titrated with a 0.01 N sodium hydroxide aqueous solution using a phenolphthalein solution as an indicator to calculate the ion-exchange capacity.

(Proton conductivity) A test body (10 mm × 40 mm) stored in ion-exchanged water is taken out, and water on the surface of the test body is wiped off with a filter paper. A test piece was attached between platinum electrodes with a distance between electrodes of 30 mm, and the test piece was placed in a Teflon (registered trademark) cell of a two-pole non-sealed system, and then a voltage of 0.2 V was applied at room temperature.
AC impedance method (frequency: 42Hz ~
The membrane resistance of the test body was measured at 5 MHz) to calculate the proton conductivity.

(Hydrolysis resistance test) Ion-exchanged water is boiled in a 100 mL beaker to immerse the test body.
The membrane state after 0.5 hours was visually observed, the ion exchange capacity and the proton conductivity were measured, and the hydrolysis resistance was evaluated.

(Methanol Permeability Measurement) JIS K 7
By the method according to 126, GTR-Tech Co., Ltd. GTR-
Using the VOC, the methanol permeation amount (25
℃) was measured and the methanol permeation coefficient was calculated.

(Solubility in methanol) Room temperature (about 2
Under an atmosphere of 5 ° C.), a predetermined sample was weighed in a screw tube, methanol was added so that the sample concentration was 0.01% by weight, and the mixture was stirred with a stirrer. The solubility was judged by visual observation.

(Measurement of Tensile Strength and Elongation at Break) JIS
The tensile strength and the elongation at break of a predetermined sample were measured by the method according to K 7127.

Example 1 According to the following method, the formula (1
A direct alcohol fuel cell membrane comprising a sulfonated polyphenylene sulfide membrane having the constituents represented by 8) was prepared.

[0059]

[Chemical 15] [In the formula, n is an integer of 1 to 4] A polyphenylene sulfide film (trade name: Torelina, manufactured by Toray Industries, Inc., film thickness: 50 μm) was used.

In a 900 mL mayonnaise bottle, 966 g of dichloromethane and 4.83 g of chlorosulfonic acid were weighed,
A chlorosulfonic acid solution was prepared. A polyphenylene sulfide film (2.24 g) was weighed, contacted by immersion, and allowed to stand at room temperature for 20 hours (the amount of chlorosulfonic acid was 2 equivalents based on the aromatic unit of polyphenylene sulfide). After leaving at room temperature for 20 hours, collect the film,
It was washed with ion-exchanged water until it became neutral.

This film was dried by leaving it for 30 minutes in a thermo-hygrostat whose temperature was adjusted to 23 ° C. under relative humidity of 98%, 80%, 60% and 50%, respectively, to obtain sulfonated polyphenylene. A direct alcohol fuel cell membrane consisting of a sulfide membrane was obtained. The evaluation results of the characteristics are shown in Tables 1-5.

Example 2 According to the following method, the formula (1
A direct alcohol fuel cell membrane comprising a sulfonated polyphenylene sulfide membrane having the constituents represented by 8) was prepared.

[0063]

[Chemical 16] [In the formula, n is an integer of 1 to 4] Instead of the polyphenylene sulfide film of Example 1, a film made of an aromatic polymer compound containing polyphenylene sulfide as a main component obtained by the following method was used, Same as Example 1. The evaluation results of the characteristics are shown in Tables 1-5.

Polyphenylene sulfide (trade name: FZ-2200-A5, manufactured by Dainippon Ink and Chemicals, Inc., hereinafter referred to as PPS) composed of an aromatic polymer compound was used. Also, as a plasticizer, tricresyl phosphate (trade name: TCP, manufactured by Daihachi Chemical Industry Co., Ltd., TC
(Denoted as P) was used.

2 parts by weight of TCP was added to 100 parts by weight of PPS and melt-mixed by a twin-screw extruder having a screw temperature of 290 ° C. to prepare pellets of a mixture of PPS and TCP. Further, the pellets are heated to a screw temperature of 290
A film having a thickness of 50 μm and containing PPS as a main component was obtained by melt extrusion under the conditions of ℃ and T-die temperature of 320 ° C.

Example 3 An accelerating voltage of 4.6 M was applied to the sulfonated polyphenylene sulfide film obtained in Example 1.
Example 1 was performed in the same manner as in Example 1 except that an alcohol fuel cell membrane was directly prepared by irradiating an electron beam with eV and an irradiation dose of 500 kGy. The evaluation results of the characteristics are shown in Tables 1 and 5.

Example 4 An accelerating voltage of 4.6 M was applied to the sulfonated polyphenylene sulfide film obtained in Example 2.
Example 1 was performed in the same manner as in Example 1 except that an alcohol fuel cell membrane was directly prepared by irradiating an electron beam with eV and an irradiation dose of 500 kGy. The evaluation results of the characteristics are shown in Tables 1 and 5.

(Comparative Example 1) As a direct alcohol fuel cell membrane, Nafion 115 (manufactured by DuPont) consisting of the constituent components represented by the formula (19) was used.

[0069]

[Chemical 17] [Wherein m> = 1, n = 2, x = 5-13.5, y = 1
[000] The evaluation results of characteristics are shown in Tables 1, 2, and 4.

Comparative Example 2 According to the following method, the formula (2
A direct alcohol fuel cell membrane comprising a sulfonated polyimide membrane having the constituents represented by 0) was prepared.

[0071]

[Chemical 18] [Wherein, x and y are integers of 0 to 4 and n is an integer of 1 or more] The evaluation results of the characteristics are shown in Tables 1 and 2. 15.02 g (0.075 mol) of 4,4′-diaminodiphenyl ether and N-methyl-2 were placed in a 0.5 L separable flask.
-148.28 g of pyrrolidone was taken and stirred under a nitrogen stream at room temperature for 0.5 hours. Next, 22.05 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride
(0.075 mol) was added all at once, and the mixture was stirred at room temperature for 1 hour under a nitrogen stream, and then at 80 ° C. for another hour. 300 on the float glass
It is applied to a thickness of μm, and under reduced pressure, 50 ° C, 100 ° C, 1
The solvent was removed at a temperature of 50 ° C. and 200 ° C. for 0.5 hours to obtain a 40 μm polyimide film.

In a 900 mL mayonnaise bottle, weigh 720 g of dichloromethane and 3.60 g of chlorosulfonic acid,
A chlorosulfonic acid solution was prepared. 1.77 g of the above-mentioned polyimide film was weighed, contacted by immersion, and left at room temperature for 20 hours (the amount of chlorosulfonic acid was 4 equivalents based on the aromatic unit derived from the diamine component of the polyimide film).

After standing at room temperature for 20 hours, the film was recovered and washed with ion-exchanged water until it became neutral.

This film was dried by leaving it in a thermo-hygrostat whose temperature was adjusted to 23 ° C. under relative humidity conditions of 98%, 80%, 60% and 50% for 30 minutes, respectively, and dried. A film was obtained.

Comparative Example 3 According to the following method, the formula (2
A direct alcohol fuel cell membrane comprising a sulfonated polystyrene membrane having the constituents represented by 1) was prepared.

[0076]

[Chemical 19] The evaluation results of the characteristics are shown in Tables 1, 2, and 5. A 900 mL mayonnaise bottle was weighed with 792 g of dichloromethane and 3.93 g of chlorosulfonic acid to prepare a chlorosulfonic acid solution. Syndiotactic polystyrene film (trade name: Zarek, thickness: 5) manufactured by Idemitsu Petrochemical Co., Ltd.
0 μm) 3.51 g is weighed, immersed in contact, and allowed to stand for 2
It was left for 0 hours (the amount of chlorosulfonic acid was 1 equivalent to the aromatic unit of syndiotactic polystyrene).

After standing at room temperature for 20 hours, the film was recovered and washed with ion-exchanged water until it became neutral.

This film was dried by leaving it in the thermo-hygrostat controlled at 23 ° C. for 30 minutes under controlled humidity of 98%, 80%, 60% and 50% relative humidity respectively. A direct alcohol fuel cell membrane consisting of a membrane was obtained.

[0079]

[Table 1]

[0080]

[Table 2]

[0081]

[Table 3]

[0082]

[Table 4]

[0083]

[Table 5] From the comparison between Examples 1 to 4 and Comparative Example 1 in Table 1, the direct alcohol fuel cell membrane of the present invention shows a proton conductivity of 10 ^-2 S / cm or more and is useful as a membrane for fuel cells. The same proton conductivity as that of Nafion 115 of Comparative Example 1 was obtained. From comparison between Examples 1 to 4 and Comparative Example 2, the direct alcohol fuel cell membrane of the present invention showed excellent proton conductivity. Further, from the comparison between Examples 1 to 4 and Comparative Example 3, it is clear that the direct alcohol fuel cell membrane of the present invention is a uniform and normal membrane, whereas the membrane of Comparative Example is non-uniform. became. Therefore, the direct alcohol fuel cell membrane of the present invention was shown to be useful.

From the comparison between Examples 1 and 2 and Examples 3 and 4 in Table 1, it was clarified that the electron conductivity was improved, and the effectiveness of the present invention was shown.

From the comparison between Examples 1 and 2 and Comparative Examples 2 and 3 in Table 2, the direct alcohol fuel cell membrane of the present invention was not ion-exchanged even after the hydrolysis resistance test. No decrease in capacity or proton conductivity was observed. Therefore,
The direct alcohol fuel cell membranes of the present invention have been shown to be useful.

From the comparison between Examples 1 and 2 in Table 3, it became clear that the elongation at break was improved by adding the plasticizer, and the effectiveness of the present invention was shown.

From the comparison between Examples 1 and 2 and Comparative Example 1 in Table 4, the direct alcohol fuel cell membrane of the present invention showed a methanol permeation coefficient lower by about one order than the conventional fuel cell membrane. . Therefore, it was revealed that the direct alcohol fuel cell membrane of the present invention has an excellent methanol barrier property, and it was shown to be useful as a direct alcohol fuel cell membrane.

From the comparison of Examples 1 to 4 and Comparative Example 3 in Table 5, the methanol solubility of the membrane for direct alcohol fuel cell of the present invention at room temperature is less than 0.01 weight, and it is substantially insoluble. It became clear that the effectiveness of the present invention was demonstrated.

[0089]

INDUSTRIAL APPLICABILITY According to the present invention, a direct alcohol fuel obtained from an aromatic polymer compound into which a proton-conducting substituent is introduced and / or an aromatic polymer compound into which a proton-conducting substance is mixed. The cell membrane has excellent hydrolysis resistance and methanol barrier properties in addition to the properties required for a fuel cell membrane represented by proton conductivity, and is useful as a direct alcohol fuel cell membrane.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a direct alcohol fuel cell.

[Explanation of symbols]

1: Direct alcohol fuel cell membrane 2: Electrode 3: Fuel (alcohol tank) 4: Fuel (alcohol) filling section 5: Oxidant channel forming support 6: Oxidizer channel

Claims (14)

[Claims] 1. A direct alcohol fuel cell membrane obtained from an aromatic polymer compound having a proton-conducting substituent introduced therein and / or an aromatic polymer compound having a proton-conducting substance mixed therein. 2. The direct alcohol fuel cell membrane according to claim 1, wherein the membrane has a hydrolysis resistance in boiling water of 0.5 hours or more. 3. The direct alcohol fuel cell membrane according to claim 1, wherein the methanol permeation coefficient at 25 ° C. of the membrane is 9 × 10 ⁻¹² kmol · m / (m ² · s · kPa) or less. 4. The solubility at room temperature in methanol is 0.
The direct alcohol fuel cell membrane according to claim 1, which is less than 01% by weight. 5. The aromatic polymer compound has the following general formula (1):
5. An aromatic polymer compound comprising at least one repeating unit selected from the group of (7) to (7).
8. A direct alcohol fuel cell membrane according to any one of 1. [Chemical 1] [Wherein Ar _{1 to} Ar ₄ are the same or different from each other in the formulas (8) to (17): Is a divalent aromatic unit represented by. Ar _{5 to} Ar ₇ are
They are the same or different tetravalent aromatic units. X, Y, Z
Are the same or different, and are -O-, -CO-,-
CONH -, - COO -, - S -, - SO-, SO 2 -
It is a divalent organic group selected from the group R ₁ ~ R
₁₂ are the same or different, respectively, a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, an allyl group,
It is an aryl group or a phenyl group. ] 6. The direct alcohol fuel cell membrane according to claim 1, wherein the aromatic polymer compound comprises at least one selected from the group (A) below. (A) group:
Polybenzoxazole (PBO), polybenzothiazole (PBT), polybenzimidazole (PBI),
Polysulfone (PSU), Polyethersulfone (PE
S), polyether ether sulfone (PEES), polyaryl ether sulfone (PAS), polyphenylene sulfone (PPSU), polyphenylene oxide (P
PO), polyphenylene sulfoxide (PPSO), polyphenylene sulfide (PPS), polyphenylene sulfide sulfone (PPS / SO ₂ ), polyparaphenylene (PPP), polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketone Ketone (PEKK) 7. The aromatic polymer compound is polyphenylene sulfoxide (PPSO), polyphenylene sulfide (PPS), polyphenylene sulfide sulfone (PP).
At least one direct alcohol fuel cell membrane according to any one of claims 1 to 4 selected from the group consisting of S / SO _2). 8. The direct alcohol fuel cell membrane according to claim 1, wherein the proton conductive substituent is a sulfonic acid group. 9. The proton conductive substance is at least one selected from the group consisting of phosphoric acid, sulfuric acid and tungstophosphoric acid.
The direct alcohol fuel cell membrane according to claim 1, which is a seed. 10. A repeating structural unit of sulfonated polyphenylene sulfide represented by the following general formula (18), wherein the aromatic polymer compound is polyphenylene sulfide (PPS) and the proton-conducting substituent is a sulfonic acid group. The direct alcohol fuel cell membrane according to any one of claims 1 to 4. [Chemical 3] [In the formula, n is an integer of 1 to 4] 11. The direct alcohol fuel cell membrane according to claim 1, further comprising a plasticizer. 12. An aromatic polymer compound comprising at least one repeating unit selected from the group consisting of the following general formulas (1) to (7), and a film comprising a plasticizer added if necessary: A method for producing a direct alcohol fuel cell membrane comprising a sulfonated aromatic polymer compound membrane obtained by contacting with a sulfonating agent. [Chemical 4] [Wherein Ar _{1 to} Ar ₄ are the same or different from each other in the formulas (8) to (17): Is a divalent aromatic unit represented by. Ar _{5 to} Ar ₇ are
They are the same or different tetravalent aromatic units. X, Y, Z
Are the same or different, and are -O-, -CO-,-
CONH -, - COO -, - S -, - SO-, SO 2 -
It is a divalent organic group selected from the group R ₁ ~ R
₁₂ are the same or different, respectively, a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, an allyl group,
It is an aryl group or a phenyl group. ] 13. The method for producing a direct alcohol fuel cell membrane according to claim 12, which comprises contacting a sulfonating agent in the presence of a solvent. 14. The method for producing a direct alcohol fuel cell membrane according to claim 12, which comprises irradiating at least one kind of radiation selected from the group consisting of γ rays, electron beams and ion beams. .