WO2009035131A1

WO2009035131A1 - Process for producing polyelectrolyte membrane, polyelectrolyte membrane, membrane-electrode assembly, and fuel cell

Info

Publication number: WO2009035131A1
Application number: PCT/JP2008/066805
Authority: WO
Inventors: Hirohiko Hasegawa
Original assignee: Sumitomo Chemical Company, Limited
Priority date: 2007-09-11
Filing date: 2008-09-10
Publication date: 2009-03-19
Also published as: JP2010056051A

Abstract

This invention provides a process for producing a polyelectrolyte membrane, comprising a membrane forming step of forming a membrane from a polyelectrolyte solution containing a hydrocarbon block-type polyelectrolyte and a solvent to produce a solvent-containing block-type polyelectrolyte membrane and a heat treatment step of heating the solvent-containing block-type polyelectrolyte membrane to form a polyelectrolyte membrane. The process is characterized in that the temperature of the heat treatment is a temperature above the heat decomposition start temperature of the hydrocarbon block-type polyelectrolyte, and the residual amount of the solvent in the polyelectrolyte membrane after the heat treatment is brought to not less than 1% by weight.

Description

Specification

Polymer electrolyte membrane manufacturing method, polymer electrolyte membrane, membrane-electrode assembly, and fuel cell technical field

The present invention relates to a method for producing a polymer electrolyte membrane, a polymer electrolyte membrane obtained by the production method, a membrane-one-electrode assembly and a fuel cell using the polymer electrolyte membrane. More specifically, a method for producing a polymer electrolyte membrane suitable for a direct methanol fuel cell, a polymer electrolyte membrane obtained by the production method, a membrane-electrode assembly using the polymer electrolyte membrane, and It relates to fuel cells. Background art

In recent years, polymer electrolyte fuel cells have attracted attention as energy devices for housing and automobile power. Among them, direct methanol fuel cells using methanol as fuel are attracting attention as power sources for personal computers and portable devices because of their small size.

As is well known, a fuel cell is composed of basic minimum units called cells. Each unit cell is composed of an electrolyte membrane, a catalyst layer provided on both sides of the electrolyte membrane, and a gas diffusion layer provided outside the catalyst layer. Each unit cell is separated and stacked by a separator provided outside the gas diffusion layer to constitute one fuel cell.

The catalyst layer provided on both sides of the electrolyte membrane, or the catalyst layer and the gas diffusion layer constitute an electrode part of the unit cell, and fuel (hydrogen molecule, methanol aqueous solution, etc.) is supplied to one electrode part (anode) When the fuel reaches the catalyst layer through the fine pores (diffusion layer) in the anode, an acid-rich reaction occurs in the catalyst layer, and hydrogen ions and electrons are released. Hydrogen ions enter the electrolyte membrane and move in the direction of the other electrode part (force sword) in the electrolyte membrane. The electrons reach the external circuit through the anode, and reach the catalyst layer on the power sword side through the external circuit. In the catalyst layer on the force sword side, electrons that have reached through the external circuit, hydrogen ions that have moved from the anode into the electrolyte membrane, and oxygen introduced from the outside through the gas diffusion layer of the force sword Molecules (air) react to form water, and the water is discharged out of the system through the gas diffusion layer.

In addition, the electrode in the unit cell of the fuel cell as described above may indicate only the catalyst layer, or may indicate a joined body of the catalyst layer and the gas diffusion layer. An assembly in which an electrolyte membrane is sandwiched between such electrodes is called a membrane-electrode assembly (MEA = MembraneElectrodeAssembly). Accordingly, the membrane-electrode assembly means a catalyst layer or an assembly in which an electrolyte membrane is sandwiched between a catalyst layer and a gas diffusion layer. That is, the membrane-electrode assembly is an assembly in which at least a catalyst layer is formed on both surfaces of the electrolyte membrane.

Currently, as described above, a fuel cell has a principle of directly extracting electric power and heat from a fuel (hydrogen or methanol aqueous solution) and oxygen (air) by an electrochemical reaction, while an electrolyte serving as a passage for hydrogen ions (protons). It is classified into multiple types according to the type.

Among these, the polymer electrolyte fuel cell is mainly composed of a perfluoroalkane polymer electrolyte membrane represented by “Nafion J (a registered trademark of DuPont)” (fluorine resin ion exchange). Such polymer electrolyte fuel cells operate at relatively low temperatures from room temperature to almost 10 ° C, so they are promising as power sources for automobiles, homes, and portables. Is being viewed.

Among these polymer electrolyte fuel cells, a methanol aqueous solution is used as the fuel, and direct methanol fuel cells (DMFC: Dielectric Me thanol Fuel 1 Ce 1 1) are handled because the fuel is liquid. It is easy to use and requires no auxiliary equipment such as a humidifier, so it can be downsized and is attracting attention as a battery source for portable equipment such as personal computers and mobile phones.

As described above, a direct methanol fuel cell supplies an aqueous methanol solution as fuel to the anode (fuel electrode). Therefore, the anode (fuel electrode) and the power sword (empty Polymer electrolyte membrane (proton conductive membrane) between the gas electrode and the electrode ί Phenomena in which methanol passes through the polymer electrolyte membrane and moves into a force sword when the barrier property to methanol (methanol paraffinity) is low Occurs. This phenomenon is called methanol crossover (MCO), and if a phenomenon occurs, power generation performance deteriorates or methanol leaks from the power sword, causing damage to the battery itself. Such a problem may occur.

However, the perfluoroalkane polymer electrolyte membranes used in conventional solid polymer fuel cells have low methanol barrier properties and are susceptible to methanol crossover. If the fuel cell configuration is directly applied to a methanol fuel cell, sufficient power generation performance cannot be obtained.

For these reasons, the development of inexpensive, high-performance hydrocarbon polymer electrolyte membranes has been activated in place of the perfluoroalkane polymer electrolyte membranes that have been heavily used as solid polymer electrolyte membranes. (WO 2003/033566 pamphlet). However, in general, the methanol barrier property of the solid polymer electrolyte membrane and the proton conductivity related to power generation performance are in conflict with each other. At present, the solid polymer electrolyte membrane for high-performance solid polymer fuel cells There are no molecular electrolyte membranes or solid polymer electrolyte membranes suitable for direct methanol fuel cells. Disclosure of the invention

In view of conventional circumstances, the present invention provides a method for producing a polymer electrolyte membrane capable of achieving both high methanol barrier properties and proton conductivity, a polymer electrolyte membrane obtained by the production method, and the polymer electrolyte. A membrane-one electrode assembly and a fuel cell using a membrane are provided.

That is, the present invention provides the following inventions.

[1] A membrane forming step of obtaining a solvent-containing block-type polymer electrolyte membrane by forming a polymer electrolyte solution containing a hydrocarbon-based block-type polymer electrolyte and a solvent, and the solvent-containing block A heat treatment process for obtaining a polymer electrolyte membrane by heating the mouth-pack type polymer electrolyte membrane, wherein the temperature of the heat treatment is set to the hydrocarbon-based block type A method for producing a polymer electrolyte membrane, wherein the temperature is higher than the thermal decomposition start temperature of the polymer electrolyte, and the residual solvent amount of the polymer electrolyte membrane after the heat treatment is 1 wt% or more.

In the present specification, the hydrocarbon block-type polymer electrolyte used in the production method of the present invention is also simply referred to as a polymer electrolyte. Further, the polymer electrolyte membrane obtained in the production method of the present invention is a hydrocarbon block type polymer electrolyte membrane obtained from a hydrocarbon block type polymer electrolyte. It is called a membrane.

[2] The polystyrene-equivalent number average molecular weight determined by a gel permeation chromatography method of the hydrocarbon-based block polymer electrolyte after the heat treatment is higher than that before the heat treatment. [1] A method for producing a polymer electrolyte membrane.

[3] The method for producing a polymer electrolyte membrane according to [1] or [2], wherein the polymer electrolyte membrane is used for a direct methanol fuel cell.

[4] The polymer electrolyte according to any one of [1] to [3], wherein at least 10% of the cation exchange groups possessed by the hydrocarbon-based block type polymer electrolyte is a proton type A method for producing a membrane. .

[5] A block copolymer comprising the hydrocarbon-based block-type polyelectrolyte power, a block having a cation exchange group, and a block having substantially no ion exchange group. [1] ] The manufacturing method of the polymer electrolyte membrane as described in any one of-[4].

[6] The block having a cation exchange group has the following general formula (1)

[In the formula (1), Ar ¹¹ represents a divalent aromatic group, and the divalent aromatic group is a C 1-20 alkyl group which may have a substituent, An optionally substituted alkoxy group having 1 to 20 carbon atoms, an optionally substituted aryl group having 6 to 20 carbon atoms, and an optionally substituted carbon number 6 May have at least one selected from the group consisting of an aryloxy group of ˜20, and an acyl group of 2 to 20 carbon atoms which may have a substituent. In the divalent aromatic group, at least one cation exchange group is directly bonded to the aromatic ring, X ¹¹ is a direct bond, a group represented by 1-O, a group represented by 1S-, a carbonyl Represents a group or a sulfo group, and d is an integer of 5 or more. [5] The method for producing a polymer electrolyte membrane according to [5].

[7] The block having the cation exchange group is represented by the following general formula (2) or (3):

[In the formulas (2) and (3), each R ¹ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an aryl having 6 to 20 carbon atoms. Group, an aryloxy group having 6 to 20 carbon atoms, or an acyl group having 2 to 20 carbon atoms, and X ¹² is a direct bond, a group represented by 1O—, a group represented by 1S—, a carbo Represents a dil group or a sulfonyl group, J ¹ represents a cation exchange group, and p and q are 1 or 2 And d is an integer greater than or equal to 5. [5] The method for producing a polymer electrolyte membrane according to [5].

[8] The block having substantially no ion exchange group is represented by the following general formula (4):

[In the formula (4), Ar ²² represents a divalent aromatic group, and the divalent aromatic group is a carbon number:! -20 alkyl group, a carbon number 1-20 alkoxy group, a carbon number It may have at least one selected from the group consisting of an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, and an acyl group having 2 to 20 carbon atoms, and X ²² is directly A bond, a group represented by 1 O—, a group represented by 1 S—, a carbonyl group or a sulfole group, and e is an integer of 5 or more. ] The manufacturing method of the polymer electrolyte membrane as described in any one of [5]-[ ⁷ ] characterized by having the structural unit represented by these.

[9] The block having substantially no ion exchange group is represented by the following general formula (5):

-Ar ^z -X-Ar ³ -Y--Ar ⁴ -X '+-

[In the formula (5), Ar ² , Ar ³ , Ar ⁴ and Ar ⁵ independently represent a divalent aromatic group, and the divalent aromatic group is an alkyl group having 1 to 20 carbon atoms. And at least one selected from the group consisting of an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, or an acyl group having 2 to 20 carbon atoms. X and X ′ each independently represent a direct bond or a divalent group, and Y, Υ, and independently represent a group represented by 1Ο— or a group represented by 1 S—, The table A, b and c each independently represent 0 or 1, and n represents an integer of 5 or more. ] The manufacturing method of the polymer electrolyte membrane as described in any one of [5]-[7] characterized by having the structural unit represented by these. [10] A polymer electrolyte membrane obtained by the production method according to any one of [1] to [9].

[1 1] A membrane-one-electrode assembly comprising the polymer electrolyte membrane according to [10] and a catalyst layer provided on both surfaces of the polymer electrolyte membrane.

[12] A fuel cell comprising the membrane-electrode assembly according to [1 1]. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments. In the method for producing a polymer electrolyte membrane of the present invention, first, a polymer electrolyte solution containing a hydrocarbon block type polymer electrolyte and a solvent is formed into a membrane to obtain a solvent-containing block type polymer electrolyte membrane (membrane) Process). Next, the solvent-containing block type polymer electrolyte membrane is heated (heat treatment step) to obtain a polymer electrolyte membrane for a fuel cell.

The following is a method for forming a hydrocarbon block polymer electrolyte, a method for forming a polymer electrolyte solution containing the polymer electrolyte and a solvent, a method for heat-treating a filmed solvent-containing block-type polymer electrolyte membrane, and heat treatment The polymer electrolyte membrane obtained by the above, and the membrane-electrode assembly and fuel cell obtained using this polymer electrolyte membrane will be described.

(Hydrocarbon block type polymer electrolyte)

In the production method of the present invention, a hydrocarbon block type polymer electrolyte (simply a polymer) The term “electrolyte” refers to a block copolymer having a cation exchange group and 50% or more of the total number of atoms composed of carbon and hydrogen.

“Plock-type polymer electrolyte” refers to an electrolyte composed of a copolymer in which two or more types of Plock forces having different chemical properties are bonded directly or through a linking group. In the production method of the present invention, the copolymer constituting the polymer electrolyte is substantially free of an ion exchange group and a block having a cation exchange group as two or more types of chemically different properties. A block copolymer having a block is preferable. When the block copolymer has a block having a cation exchange group and a block having substantially no ion exchange group, the effect of the present invention is remarkably exhibited.

The polymer electrolyte preferably contains an aromatic block copolymer from the viewpoint of heat resistance and ease of recycling. The aromatic block copolymer means a block copolymer having an aromatic ring in the main chain of the polymer chain and having a cation exchange group in the side chain and Z or the main chain of the polymer chain. As such an aromatic block copolymer, a solvent-soluble one is usually used. It is preferable that it is soluble in a solvent because it can be easily formed into a film by a known solution casting method.

The cation exchange group of these aromatic block copolymers may be directly substituted on the aromatic ring constituting the main chain of the polymer, and is linked to the aromatic ring constituting the main chain. It may be linked through a group or a combination thereof. The polymer electrolyte is preferably one in which at least 10% or more of the cation exchange group is in a proton type.

The cation exchange group is preferably a sulfonic acid group, a phosphonic acid group, or a sulfonyl imide group. Among these, a sulfonic acid group in which the cation exchange group is a strong acid group is more preferable. The polymer electrolyte may have one of these, or may have two or more of these.

The polymer electrolyte is preferably one that forms a Mikuguchi phase separation structure when filmed. When a polymer electrolyte that forms such a Mikuguchi phase separation structure is used, the effects of the present invention Appears prominently. Here, “microphase separation structure” means that when polymer electrolyte is made into a membrane, different polymer segments are bonded by chemical bonds, resulting in microscopic phase separation on the order of molecular chain size. Refers to the structure formed by For example, when observed with a transmission electron microscope (TEM), a fine phase (microdomain) having a high density of a block having a cation exchange group and a density of a block having substantially no ion exchange group are present. It refers to a structure in which high fine phases (microdomains) are mixed and the domain width of each microdomain structure, that is, the identity period is several nm to several OO nm. The identity period is 5 η π! ˜100 nm is preferred.

Specific examples of the block copolymer include “a block copolymer having a sulfonated aromatic polymer block” described in JP-A-2001-250567, JP-A-2003-31232, “Polyetherketone, polyethersulfone has a main chain structure and a block having a sulfonic acid group” described in JP-A-2004-359925, JP-A-2005-232439, JP-A-2003-113136, etc. "Plock copolymer".

In the above block copolymer, the block having a cation exchange group is preferably a block including a structure in which a plurality of structural units represented by the following general formula (1) are linked, cation exchange groups is preferably at 0.5 or more on average, and more preferably an average of 1. is 0 or more Re, ₀

Ar 11. -X ¹屮 (1)

d

[In the formula (1), Ar ¹¹ represents a divalent aromatic group, and the divalent aromatic group represents a C 1-20 alkyl group which may have a substituent, or a substituent. An optionally substituted alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms that may have a substituent, and an aryloxy group having 6 to 20 carbon atoms that may have a substituent. Group, extension, setting The divalent aromatic group may have at least one selected from the group consisting of an acyl group having 2 to 20 carbon atoms which may have a substituent. A cation exchange group is directly bonded to the aromatic ring, X ¹¹ represents a direct bond, a group represented by 1 O—, a group represented by 1 S—, a carbo group or a sulfonyl group, d is An integer greater than or equal to 5. ]

Examples of the alkyl group having 1 to 20 carbon atoms that may have the substituent include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and an isoptyl group. N-pentyl group, 2,2-dimethylpropyl group, cyclopentyl group, n-hexyl group, cyclohexyl group, 2-methylpentyl group, 2-ethylhexyl group, nor group, decyl group, Alkyl groups having 1 to 20 carbon atoms such as dodecyl group, hexadecyl group, adamantyl group, and icosyl group, and these groups include fluorine atom, hydroxyl group, nitryl group, amino group, methoxy group, ethoxy group An isopropyloxy group, a phenyl group, a naphthyl group, a phenoxy group, a naphthyloxy group, and the like, and an alkyl group having 1 to 20 carbon atoms in total.

Examples of the alkoxy group having 1 to 20 carbon atoms which may have the substituent include, for example, a methoxy group, an ethoxy group, an n-propyloxy group, an isopropyloxy group, an n-butyloxy group, a sec group. Butyloxy group, tert-butyloxy group, isoptyloxy group, n-pentyloxy group, 2,2-dimethylpropyloxy group, cyclopentyloxy group, n-hexyloxy group, cyclohexyloxy group, 2-methylpentyloxy group, 21 Alkyloxy group, decyloxy group, adamantyloxy group, hexadecyloxy group, icosyloxy group, etc., an alkoxy group having 1 to 20 carbon atoms, fluorine atom, hydroxyl group, ditrityl group Group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenol group, naphthyl group , Phenoxy group, and Nafuchiruokishi group is substituted, the total carbon number and an alkoxy group having 1 to 2 0.

Examples of the aryl group having 6 to 20 carbon atoms which may have the above substituent include aryl groups such as phenyl group, naphthyl group, anthracenyl group, biphenyl group, and the like. These groups are substituted with fluorine atoms, hydroxyl groups, nitrile groups, amino groups, methoxy groups, ethoxy groups, isopropyloxy groups, phenol groups, naphthyl groups, phenoxy groups, naphthyloxy groups, etc. Aryl groups with 6 to 20 carbon atoms are listed.

Examples of the aryloxy group having 6 to 20 carbon atoms which may have a substituent include, for example, aryloxy groups such as phenoxy group, naphthyloxy group, anthraceroxy group, biphenyloxy group, and the like, and these groups Is substituted with fluorine atom, hydroxyl group, nitrile group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl group, naphthyl group, phenoxy group, naphthyloxy group, etc., and the total carbon number is 6 ~ 2 And 0 aryloxy group.

Examples of the acyl group having 2 to 20 carbon atoms which may have the substituent include, for example, an acetyl group, a propiol group, a butyryl group, an isoptylyl group, a benzoyl group, 1 a naphthoyl group, and a 2-naphthoyl group. Such as an acyl group having 2 to 20 carbon atoms, and a fluorine atom, a hydroxyl group, a nitrile group, an amino group, a methoxy group, an ethoxy group, an isopropyloxy group, a phenyl group, a naphthyl group, Examples include an acyl group substituted with a phenoxy group, a naphthyloxy group, or the like, and having a total carbon number of 20 or less. Here, d is an integer of 5 or more that represents the degree of polymerization of the block, 5 to: 100 is preferable, more preferably 10 to 100, and particularly preferably 20 to 5 0 0. A value of d of 5 or more is preferred because the proton conductivity is sufficient as a polymer electrolyte for fuel cells. On the other hand, if the value of d is 1 00 0 0 or less, it is preferable because the production of the block is easier.

The block having a cation exchange group is more preferably a block represented by the following general formula (2) or (3).

[In the formula, each R ¹ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or 6 to 2 carbon atoms. Represents an aryloxy group of 0, or an acyl group having 2 to 20 carbon atoms, and X ¹² is a direct bond, a group represented by ____, a group represented by S-, a carbo group or a sulfol group. J ¹ represents a cation exchange group, p and q are 1 or 2, and d is an integer of 5 or more. ]

Having a block having an ion exchange group as described above, in addition to obtaining a high level of proton conductivity and water absorption dimensional stability in the obtained polymer electrolyte membrane, further improving the membrane strength. Can do.

In addition, R ¹ represents a substituent as described above. However, it is preferable that a phenylene group or a naphthalenedyl group has substantially no substituent other than a cation exchange group, and is preferably a hydrogen atom. More preferred.

As a specific example of the block represented by the general formula (2), the cation exchange group represented by a sulfonic acid group can be represented by the following formulas (2 a-1) to (2 a-3 0). Examples thereof include a block in which d structural units selected from the group consisting of the structural units shown are connected. Here, d is the number of definitions equivalent to d in the above general formula (2), that is, an integer of 5 or more.

SO, H _t , SO3H,,

3 (2a-1) ³ (2a-2) S0 ₃ H (2a-3)

-18)

27)

S 0 ₃ H

(2a-28) 29) (2a— 30)

As specific examples of the block represented by the general formula (3), cation exchange groups represented by sulfonic acid groups are represented by the following (3b-1) to (3b-28). A block in which d structural units selected from the group consisting of structural units are connected. Here, d is the same number of definitions as d in general formula (2), that is, an integer of 5 or more.

The block represented by the general formula (2) or (3) can be manufactured based on, for example, a manufacturing method described in JP-A-2004-90002. Furthermore, as the block having the cation exchange group, a structural unit constituting the block represented by the general formula (2) or a structural unit constituting the block represented by the general formula (3), Each of the blocks may be a block formed by connecting d pieces, and it constitutes a structural unit constituting the block represented by the general formula (2) and a block represented by the general formula (3). It may be a block consisting of d structural units connected together. Next, the block having substantially no ion exchange group will be described.

Here, “substantially free of ion exchange groups” means that most of the repeating units mainly constituting this block do not have ion exchange groups. Specifically, the average number of ion-exchange groups per structural unit constituting this block is 0.1 or less, preferably 0.05 or less, and ions are contained in the structural unit. More preferably, no exchange groups are included.

The block having substantially no ion exchange group is preferably a block represented by the following general formula (4).

_Ar 22 1 X 22.

[In the formula (4), Ar ²² represents a divalent aromatic group, and the divalent aromatic group includes an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, It may have at least one selected from the group consisting of an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, and an acyl group having 2 to 20 carbon atoms, X ²² represents a direct bond, a group represented by 1 O—, a group represented by 1 S—, a carbo group or a sulfo group, and e is an integer of 5 or more. ]

Here, specific examples of the alkyl group, the alkoxy group, the aryl group, the aryl group, and the opacyl group, which are the substituents of the aromatic group Ar ²² of the general formula (4), are as described above. It is equivalent to general formula (1).

E is an integer of 5 or more representing the degree of polymerization of the block, preferably 5 to 1000, more preferably 10 to 1000, and still more preferably 20 to 500. A value of e of 5 or more is preferable because a polymer electrolyte membrane having excellent membrane strength can be obtained. On the other hand, if the value of e is 1000 or less, it is preferable because the production of the block is easier.

The block having substantially no ion-exchange group is more preferably a block represented by the following general formula (5).

-Ar ² -X- Ar ³ -Y-4-Ar ⁴ -X '-Ar ⁵ — Y -Ar ² -X -Ar ³ +

v ΙΛ ノ b

[In formula (5), Ar ² , Ar ³ , Ar ⁴ , and Ar ⁵ independently represent a divalent aromatic group, and the divalent aromatic group has 1 to 20 carbon atoms. At least one selected from the group consisting of an alkyl group, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 2 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an acyl group having 2 to 20 carbon atoms. X and X ′ each independently represent a direct bond or a divalent group, and Y and Y ′ each independently represent a group represented by 1— or 1 S—. A, b, c each independently represents 0 or 1, and n represents an integer of 5 or more. In Formula (5), n is an integer of 5 or more representing the degree of polymerization related to the block, preferably 5 to 1,000, more preferably 10 to 1000, and still more preferably 20 to 500. A value of n of 5 or more is preferable because a polymer electrolyte membrane having excellent membrane strength can be obtained. On the other hand, if the value of n is 1000 or less, it is preferable because the production of the block is easier.

Specific examples of the block represented by the general formula (5) include blocks represented by the following general formulas (5-1) to (5-22).

S08990 / 800 df / X3d

I £ lSC0 / 600i O

Specifically, in the present invention, examples of suitable block copolymers include the copolymers (6-1) to (6-18) having the combination constitution shown in the following (Table 1). In the following (Table 1), (2a-1), (2a-4), (2a-19) and (2a-25) described in the column of the block having a cation exchange group are (5), (5-2), (5-9), ((5)) indicates the structural unit that constitutes the block having a cation exchange group, and is described in the column of the block having substantially no ion exchange group. 5-10), (5-21), and (5-22) represent structural units constituting a block substantially free of the ion exchange group.

[table 1]

(table 1)

The block copolymers are preferably those represented by the following general formulas (7-1) and (7-2).

As the block copolymer, the ion exchange capacity of the block copolymer is 0.5 by adjusting the abundance ratio of the block having a cationic group and the block having substantially no ion group. It is preferable to be in the range of ˜4. Ome qZg, more preferably in the range of 0.8 to 3.5 me qZg. The ion exchange capacity can be determined by a titration method.

The above-mentioned block type polyelectrolyte can obtain the optimum molecular weight range as appropriate depending on its structure, etc., but generally expressed in terms of polystyrene-reduced number average molecular weight by GPC (gel permeation chromatography) method, 1000-1000000 is preferred. The lower limit of the number average molecular weight is more preferably 5000, further preferably 10000, while the upper limit is more preferably 500000, further preferably 300000.

When the average molecular weight is 1000 or more, the film strength tends to be further improved. When the average molecular weight is 1000000 or less, the solubility of the polymer electrolyte in a solvent is improved, and the solution viscosity of the resulting solution is lowered. Therefore, film formation by the solution casting method becomes easy.

It is preferable that at least a part of the cation exchange group of the block type polymer electrolyte is a proton type. In this case, the thermal decomposition initiation temperature of the block-type molecular electrolyte Accordingly, the heat treatment temperature in the heat treatment described later can be lowered. In the cation exchange group, the proportion of the proton type cation exchange group is preferably 10% or more. More preferably, it is 50% or more, and further preferably 80% or more.

(Solvent-containing block-type polymer electrolyte membrane and method for forming the membrane)

Solvent-containing block-type polymer electrolyte membranes can be obtained by membrane-forming a polymer electrolyte solution obtained by dissolving the polymer electrolyte in a suitable solvent (hereinafter also simply referred to as a solution). Process).

The method for forming the polymer electrolyte solution into a film is not particularly limited, and a known method such as a spin coating method or a solution casting method can be used, but a solution casting method is preferable. The solution casting method for producing a solvent-containing block type polymer electrolyte membrane on the support material by applying the solution on a support substrate and reducing the amount of solvent is easy to operate.

As another membrane formation method, a solution obtained by dissolving the above polymer electrolyte in an appropriate solvent is applied to a porous membrane support, and the polymer electrolyte is retained on the porous membrane support. Then, by reducing the amount of the solvent in the solution, a membrane forming method is also possible in which a composite membrane comprising the porous membrane-like support and the polymer electrolyte held on the membrane-like support is obtained. . A polymer electrolyte membrane may be produced by using this composite membrane as a solvent-containing block type polymer electrolyte membrane. Examples of the porous membrane support used in this membrane formation method include polyimide, polysulfone, polyamide, polytetrafluoroethylene (PTFE), and ethylene-tetrafluoroethylene copolymer (ETFE). A porous membrane can be used.

Polyethylene terephthalate (PET) film, polytetrafluoroethylene (PTFE) film, etc. are preferably used.

The solvent is not particularly limited as long as it can dissolve the polyelectrolyte and can be removed thereafter. For example, N, N-dimethylformamide (hereinafter, “DM F ”), N, N-dimethylacetamide (hereinafter referred to as“ DMA c ”), N-methyl-2-pyrrolidone (hereinafter referred to as“ NMP ”), dimethyl sulfoxide (hereinafter referred to as“ DM SO ”) Aprotic polar solvents such as dichloromethane, chlorohonolem, chlorinated solvents such as 1,2-dichloroethane, black benzene and dichlorobenzene, alcohols such as methanol, ethanol and propanol, ethylene glycol Examples thereof include alkylene glycol monoalkyl ethers such as monomethylenoatenole, ethylene glycolenomonoethylenoleate, propyleneglycolenomonomethyle / leinetenole, and propyleneglycolonemonoethylether. Among them, N, N-dimethylformamide (hereinafter referred to as “DMF”), N, N-dimethylacetamide (hereinafter referred to as “DMA c”), N-methyl-2-pyrrolidone (hereinafter referred to as “DMC”). Aprotic polar solvents such as “NMP” and dimethyl sulfoxide (hereinafter referred to as “DMSO”) are preferred.

These can be used alone, but can be used by mixing two or more solvents as necessary. Among them, DMF, DMAc, NMP, DMSO, etc. are preferable because the solubility of the block type polymer electrolyte is high.

The support substrate used in the solution casting method is not particularly limited as long as the solvent-containing block type polymer electrolyte membrane obtained after strong film formation can be peeled off without swelling or dissolving by the solution. However, for example, glass, stainless steel, stainless steel belt, polyethylene terephthalate (PET) film, polytetrafluoroethylene (PTFE) film, etc. are preferably used. The surface of the base material may be subjected to a mold release process, a mirror surface process, an embossing process, or an erasing process as necessary. The concentration of the block type polyelectrolyte in the solution used in the solution casting method is usually 5 to 40% by weight, preferably 5 to 30% by weight, although it depends on the molecular weight of the block type polyelectrolyte itself used. . When the concentration of the block-type polymer electrolyte is 5% by weight or more, a polymer electrolyte membrane having a practical film thickness is easy to process, and when the concentration is 40% by weight or less, the solution viscosity of the resulting solution is lowered. Therefore, it becomes easy to obtain a film having a smooth surface. Further, in this solution casting method (film formation step), heating may be performed in order to reduce the amount of solvent and cure the coating film. In this case, the temperature range of the heating is the heat of the block type polymer electrolyte. It is preferable that the temperature is not higher than the decomposition start temperature. (Heat treatment process for solvent-containing block type polymer electrolyte membrane)

The solvent-containing block type polymer electrolyte membrane is heat-treated to obtain a desired polymer electrolyte membrane. In this heat treatment step, the solvent-containing block-type polymer electrolyte membrane is heated at a temperature higher than the thermal decomposition start temperature of the block-type polymer electrolyte constituting the solvent-containing block-type polymer electrolyte membrane. Heat treatment is preferably performed at a temperature 10 to 100 ° C higher than the thermal decomposition start temperature, and heat treatment is performed at a temperature 20 ° C to 80 ° C higher than the thermal decomposition start temperature. Is more preferable. In this case, the thermal decomposition starting temperature of the block-type polymer electrolyte can be measured by TGNODTA. When heat at a predetermined temperature higher than the thermal decomposition start temperature of the block-type polymer electrolyte is applied to the solvent-containing block-type polymer electrolyte membrane, the block-type polymer electrolyte in a state where the solvent remains at that temperature The degree of thermal decomposition of can be reduced. That is, even if the polymer electrolyte is heated at a temperature at which thermal decomposition starts, if the solvent remains, it may be possible to increase the molecular weight of the polymer electrolyte before the polymer electrolyte decomposes. is there. Preferably, in the range in which the polymer electrolyte is soluble in the solvent, the molecular weight of the block type polymer electrolyte constituting the polymer electrolyte membrane after the heat treatment is increased as compared with that before the heat treatment. The degree of increase in the molecular weight of the polymer electrolyte is preferably such that the number average molecular weight after the heat treatment is 1.05 times or more, and 1.10 times or more as compared to the number average molecular weight before the heat treatment. More preferably.

Further, the heating time in this heat treatment largely depends on the kind of the solvent-containing block type polymer electrolyte membrane and the heat treatment temperature, but constitutes the solvent-containing block type polymer electrolyte membrane. In order to suppress the degree of thermal decomposition of the block type polymer electrolyte and obtain a high treatment effect and productivity, it is preferably from 1 minute to 5 hours, more preferably from 5 minutes to 3 hours. In order to increase the molecular weight of the block-type polymer electrolyte within the range soluble in the solvent, the control of the heating temperature and the heating time within the above range and the amount of residual solvent in the polymer electrolyte membrane after the heat treatment are set. It is important to maintain the amount of residual solvent in the polymer electrolyte membrane after the heat treatment to be 1% by weight or more.

As used herein, “the amount of residual solvent in the polymer electrolyte membrane is 1% by weight or more” means that the amount of residual solvent is 1% by weight or more with respect to the weight of the entire polymer electrolyte membrane. The The “residual solvent amount” means the amount of the solvent remaining in the polymer electrolyte membrane after the heat treatment. Here, “solvent” refers to the solvent used in the casting film formation. Note that “after heat treatment” means a time range within 6 hours from the end of the heat treatment step. That is, in the method for producing a polymer electrolyte membrane of the present invention, the amount of residual solvent in the polymer electrolyte membrane is 1 in a certain time within a time range of 6 hours or less immediately after the end of the heat treatment step. weight. More than / o. This residual solvent amount can be determined by a gas chromatography method.

That is, in the method for producing a polymer electrolyte membrane of the present invention, a solvent-containing block type polymer electrolyte membrane obtained by forming the solution into a membrane is used as a block type high polymer electrolyte membrane constituting the solvent-containing block type polymer electrolyte membrane. Treating at a temperature higher than the thermal decomposition start temperature of the molecular electrolyte, and maintaining the amount of solvent in the solvent-containing polymer electrolyte membrane so that the amount of residual solvent after the heat treatment is 1% by weight or more As a result, it is possible to reduce the thermal decomposition degree of the block-type polymer electrolyte in a state where the solvent remains. That is, even if the polymer electrolyte is heated at a temperature at which thermal decomposition begins, if the solvent remains, the molecular weight of the polymer electrolyte can be increased before the polymer electrolyte decomposes. It may become. Preferably, the molecular weight of the block-type polymer electrolyte constituting the polymer electrolyte membrane after the heat treatment is increased in the range in which the polymer electrolyte is soluble in the solvent as compared with that before the heat treatment. As a result, the obtained polymer electrolyte membrane has been increased in molecular weight (densified) while maintaining flexibility. Due to such a reaction mechanism, the polymer electrolyte membrane obtained by the production method of the present invention has a solid polymer fuel cell that has high proton conductivity and hardly permeates methanol, and has excellent handling properties. Especially direct methanol This is considered to be suitable for a fuel cell. When the amount of the residual solvent is less than 1% by weight, the flexibility and handling properties of the polymer electrolyte membrane are insufficient. The reason why such an effect is manifested is not necessarily clear, but the present inventor estimates as follows. That is, in the block-type hydrocarbon polymer electrolyte, the block having a cation exchange group has a relatively dense collection of cation exchange groups, and the accumulated cation exchange groups react with each other. It is estimated that good methanol pariasis is developed.

In the above heat treatment process, if the heat treatment is performed in an atmosphere in which a large amount of oxygen exists, an undesirable side reaction such as oxidation of the polymer electrolyte membrane due to oxygen occurs. Therefore, in a vacuum or an inert gas It is preferable to do so.

Further, it is preferable that the film-forming step (solution casting method) is performed in a temperature region below the thermal decomposition start temperature of the polymer electrolyte, and then the above-described heat treatment is continuously performed. By performing the film-forming step in a temperature range below the thermal decomposition start temperature in advance, it is possible to prevent the appearance failure of the polymer electrolyte membrane due to rapid volatilization of the solvent, and the like. Maintenance of the residual solvent amount is also facilitated. Further, even if the heat treatment for increasing the molecular weight of the subsequent film is performed at a high temperature exceeding the thermal decomposition start temperature of the block type polymer electrolyte by the solvent component remaining by such control, the heat treatment is not performed. The obtained polymer electrolyte membrane is highly flexible, hardly cracks, and has excellent handling properties.

It is preferable to convert the cation exchange group of the polymer electrolyte in the polymer electrolyte membrane into a proton type by acid treatment of the polymer electrolyte membrane after the heat treatment with sulfuric acid or hydrochloric acid. Furthermore, in order to remove the residual solvent, it is preferable to perform a water washing treatment on the polymer electrolyte membrane after the heat treatment. A polymer electrolyte membrane can be produced by the method for producing a polymer electrolyte membrane of the present invention.

The thickness of the polymer electrolyte membrane of the present invention is not particularly limited, but is 5 to 200 m. preferable. When it is 5 μπι or more, a membrane strength that can be practically used can be obtained, and when it is 200 μm or less, membrane resistance can be reduced, that is, power generation performance can be improved. More preferably, it is 8 to 100 μππι, and even more preferably 15 to 80.

The polymer electrolyte membrane of the present invention can be suitably applied to a fuel cell. Among these, the direct methanol fuel cell can be preferably applied.

(Membrane-electrode assembly and fuel cell)

Next, the membrane-electrode assembly (MEA) of the present invention and the fuel cell of the present invention will be described. The membrane-electrode assembly of the present invention can be produced by forming at least a catalyst layer on both surfaces of the obtained polymer electrolyte membrane.

The catalyst layer contains a catalyst material. The catalyst substance is not particularly limited as long as it can activate an acid reduction reaction between methanol and oxygen, and a known substance can be used. Examples of the catalyst substance include noble metals such as platinum and platinum-ruthenium alloys, and complex electrode catalysts (for example, “Fuel Cell and Polymer” edited by the Society of Polymer Science, Fuel Cell Materials Research Group, 1 2 pages, Kyoritsu Shuppan, 2 2005 1 January 10th issue)). Among these, it is preferable to use fine particles of platinum or a platinum-ruthenium alloy. Usually, platinum or platinum-ruthenium alloy (fine particles) is used as the catalyst for the catalyst layer (first catalyst layer) on the fuel electrode (anode) side, and the catalyst layer (second catalyst layer) on the air electrode (force sword) side. ) Platinum (fine particles) is used as the catalyst. In addition, it is preferable to use a conductive material carrying the catalyst substance on the surface as the catalyst substance because hydrogen ions and electrons can be easily transported in the catalyst layer. Examples of the conductive material include known materials such as conductive carbon materials such as car pump racks and carbon nanotubes, and ceramic materials such as titanium oxide.

The catalyst layer preferably contains a polymer electrolyte. The polymer electrolyte has ion conductivity and a binder that binds the catalyst substance. As long as it works, there is no particular limitation, and examples include conventionally known Nafion (trade name), aliphatic polymer electrolyte, and aromatic polymer electrolyte made by DuPont. In addition to the catalyst substance and the polymer electrolyte, the catalyst layer may contain a water repellent material such as PTFE for the purpose of enhancing the water repellency of the catalyst layer, and calcium carbonate for the purpose of enhancing the gas diffusibility of the catalyst layer. In addition, a stabilizer such as a metal oxide may be contained for the purpose of enhancing the durability of the obtained membrane-one-electrode assembly. The membrane-one electrode assembly preferably has a gas diffusion layer outside the catalyst layer in order to diffuse the fuel efficiently and uniformly. The gas diffusion layer is not particularly limited as long as it has conductivity, but is preferably a porous carbon nonwoven fabric or carbon paper because it is inexpensive and easy to handle. As a method for forming the catalyst layer on both surfaces of the polymer electrolyte membrane, a method in which the catalyst layer is directly formed on the polymer electrolyte membrane and a catalyst layer is formed in advance on a substrate other than the polymer electrolyte membrane. There is a method of joining the catalyst layer and the polymer electrolyte membrane later. There is no particular limitation on the method for forming the catalyst layer on the polymer electrolyte membrane or on a substrate other than the polymer electrolyte membrane (hereinafter also referred to as other substrates). Die coater, screen printing A known method such as a spray method or an ink jet method can be used.

The other base material is not particularly limited as long as it does not swell or dissolve when the catalyst layer is formed. For example, the gas diffusion layer, glass, stainless steel material, stainless steel belt, polyethylene terephthalate (PET ) Film etc. are preferably used. Other substrate surfaces may be subjected to a mold release treatment, a mirror finish treatment, an embossing treatment, a matting treatment, or the like as necessary.

In the case of a method in which a catalyst layer is formed on another substrate in advance and the catalyst layer is bonded to the polymer electrolyte membrane, it is preferable to perform a hot press method in which heating and pressurization are performed during the bonding. The heating temperature is not particularly limited as long as the resulting polymer electrolyte membrane is not denatured, but is preferably 30 ° C. or higher and 30 ° C. or lower. Such temperature range As a result, the bondability between the catalyst layer and the polymer electrolyte membrane is improved, and the resulting polymer electrolyte membrane is not altered. 50 ° C or more and 250 ° C or less is more preferable.

The pressure is preferably 5 kgf / cm ² or more and 300 kgf Zcm ² or less. In such a pressure region, the obtained polymer electrolyte membrane is not deformed. 3 O kgf Zcni ² or more and 2 OO kgf Zcm ² or less are more preferable. In this way, a membrane-electrode assembly comprising the polymer electrolyte membrane of the present invention and the catalyst layers provided on both surfaces of the polymer electrolyte membrane is obtained. When this membrane-electrode assembly is used in a direct methanol fuel cell (DMFC), the resulting DMFC is excellent in power generation performance and markedly suppresses battery damage due to methanol crossover.

In the above description, the force described by taking the case where the membrane-electrode assembly of the present invention is applied to a direct methanol fuel cell (D MFC) as an example. In addition, it can be suitably used for a fuel cell using hydrogen as a raw material. Hereinafter, examples of the present invention will be described. However, the examples shown below are suitable examples for explaining the present invention, and do not limit the present invention at all. Before specifically describing the examples of the present invention, the polymer electrolytes obtained in each production example, each example and each comparative example, and the molecular weight of the polymer electrolyte membrane, the residual solvent amount, and the proton conductivity Each measurement method for measuring various characteristic values of methanol permeability coefficient and ion exchange capacity (IEC) is described below.

[Molecular weight measurement]

The number average molecular weight in terms of polystyrene was determined by gel permeation chromatography (GPC) under the following conditions. G PC measuring device HLC-8220 manufactured by TOSOH

Column TOSOH TSK-GEL GMHHR— カラム Column temperature 40 ° C

Mobile phase solvent DMA c (L i Br added to 1 Ommo 1 Z dm ³ ) Solvent flow rate 0.5 m L / min

[Residual solvent amount]

After the heat treatment process, the heat-treated polymer electrolyte membrane was placed at room temperature and atmospheric pressure, dissolved in a sample solution (dimethylformamide) within 6 hours, and measured by gas chromatography using a GC device. . The obtained measured values were analyzed based on the following analysis method, and the amount of residual solvent remaining in the polymer electrolyte membrane was calculated.

GC apparatus: “6890” (trade name, manufactured by Hewlett-Packard Company) Analysis method: A calibration curve was prepared with the horizontal axis representing the set concentration of the standard solution and the vertical axis representing the peak area value. The residual solvent amount in the polymer electrolyte membrane was calculated using the following calculation formula. Residual solvent amount (p pm) = {(PA-Y _ao ) / G _ao } X {SS / PEM} where PA: peak area

Y _ac : y-intercept of calibration curve

G _ac : The slope of the calibration curve

S S: Sample solution volume (mL)

. PEM: polymer electrolyte membrane weighing value (g)

[Measurement of proton conductivity (σ)]

New Experimental Chemistry Lecture 19 Polymer Chemistry (II) 992 ρ (Edited by The Chemical Society of Japan, Maruzen) The membrane resistance of the polymer electrolyte membrane obtained in each example was measured by the method described in the following. However, the cell used was made of carbon, and the platinum black-plated platinum electrode was not used, and the impedance measurement device terminal was connected directly to the cell. First, set the polymer electrolyte membrane in the cell 8066805

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Then, the resistance value was measured, then, the polymer electrolyte membrane was removed, the resistance value was measured again, and the membrane resistance was calculated from the difference between the two. As a solution to be brought into contact with both sides of the polymer electrolyte membrane, lmo 1 / L dilute sulfuric acid was used. The proton conductivity was calculated from the film thickness and resistance value when immersed in dilute sulfuric acid.

[Measurement of methanol permeability coefficient (D)]

The polymer electrolyte membrane sample obtained in each example was immersed in a 10 wt ° / o methanol water solution for 2 hours, and then this sample polymer electrolyte membrane was formed into an H-shaped diaphragm consisting of cell A and cell B. Hold in the center of the cell, put 10 wt% methanol aqueous solution into cell A and pure water into cell B, and leave at 23 ° C for the initial state and for a certain time t (sec) from the initial state. The methanol concentration in cell B was analyzed, and the methanol permeability coefficient D (cm ² / sec) was determined by the following equation.

D = {(VX L) / (AX t)} X 1 n {one C _ra ) / (C ₂ -C _n )} where

V: Volume of liquid in cell B (cm ³ )

L: Sample polymer electrolyte membrane thickness (cm)

A: Cross section of sample polymer electrolyte membrane (cm ² )

t: Time (s e c)

C,: Methanol concentration in cell B in the initial state (mol l Zcm ³ )

C ₂ : —Methanol concentration in cell B after standing for a fixed time t (mo 1 / cm ³ )

C _m : Methanol concentration in cell A in the initial state (mo 1 / cm ³ )

C _n : Methanol concentration in cell A after standing for a certain time t (mo 1 / cm ³ ) Note that the methanol permeation rate is sufficiently small, so V is a constant value of the initial pure water capacity, and C _m = determined by C _n as the initial concentration (10 wt%).

[Calculation of characteristic parameter (DZa)]

Polymer electrolyte membrane suitable for direct methanol fuel cell is proton conductivity (σ) PT / JP2008 / 066805

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Is a membrane with a high methanol permeability coefficient (D). As the index, the value of was calculated as a characteristic parameter from the value obtained in the above. If this value is small, the conductivity (σ) is the same, and the methanol permeability is low, indicating that it is excellent as a polymer electrolyte membrane for direct methanol fuel cells (DMFC).

[Ion exchange capacity of polymer electrolyte membrane (I EC)]

The obtained polymer electrolyte membrane was dried at 110 ° C. with a halogen moisture content meter (Mettler Toledo Co., Ltd., trade name “Η R73”) to determine the absolute dry weight. This polymer electrolyte membrane was immersed in 5 mL of a 0.1 mo 1ZL aqueous solution of sodium hydroxide and then 50 mL of ion exchanged water was added and left for 2 hours. Thereafter, the solution in which the polymer electrolyte membrane was immersed was titrated by gradually adding 0.1 mol 1 ZL of hydrochloric acid to determine the neutralization point. The ion exchange capacity was determined from the absolute dry weight and the amount of 0.1 lmo 1 / L hydrochloric acid required for the neutralization point. In addition, the salt exchange rate Y (%) was determined by the following formula (B).

Y = (1 -Η / Τ) X I 00 (Β)

Τ: Total ion exchange groups per gram of polymer electrolyte membrane before salt substitution treatment Η: Ion exchange group amounts of proton exchanged counter ion per gram of polymer electrolyte membrane after salt substitution treatment [thermal decomposition start temperature ]

The thermal decomposition starting temperature was measured using TG / DTA (Seiko Instruments Inc., SSC-5 200). Increase the temperature from 30 ° C to 110 ° C at 50 ° C _/ min, hold at 110 ° C for 30 minutes, then increase the temperature from 110 ° C to 300 ° C in 5 ° 0 minutes, reducing weight The temperature at which is started was defined as the thermal decomposition start temperature.

(Production example 1: Production example of polymer electrolyte)

In a flask with a distillation tube under an argon atmosphere, 3, 3, 2008/066805

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4 '— Dihydroxybiphenol: 1 5. 3 2 g (45. 28 mm o 1), 4, 4, – Diphnololeophyleninores norephone: 1 0.6 6 2 g (4 1. 7 7 mmo l), potassium carbonate: 6.57 g (47.54 mmo 1), dimethyl sulfoxide (DMS O): 1 1 4 ml, and toluene: 1 8 ml 1 were added and stirred. Next, the pass temperature was raised to 150 ° C, and toluene was distilled off by heating to azeotropically dehydrate water in the system. After the toluene was distilled off, the reaction was carried out at the same temperature for 2 hours. This is the reaction mass [A].

In a flask equipped with a distillation tube under an argon atmosphere, potassium hydroquinone sulfonate: 4,000 g (17.5 2mmo 1), 4, 4, — difluorobenzophenone 3, 3, _disnolehon Dipotassium acid: 9.56 g (2 1. 0 3 mm o 1), carbonated potassium: 2.54 g (18.4 Ommo 1), DMS O: 60 ml, and toluene: 9 ml And stirred. Next, the path temperature was raised to 1300C, and the water in the system was azeotropically dehydrated by heating and distilling off the toluene. After toluene was distilled off, the reaction was carried out at the same temperature for 20 hours and 30 minutes. This is the reaction mass [B].

The reaction mass [A] and the reaction mass [B] were mixed while diluted with DMSO: 68 ml, and this mixture was reacted at 145 ° C for 33 hours 30 minutes. After allowing to cool, the reaction mixture was dropped into a large amount of 2 m o 1 Z L hydrochloric acid aqueous solution, and the resulting precipitate was collected by filtration, and washed and filtered repeatedly with water until the washing solution became neutral. Next, the filtrate was treated twice with a large excess of hot water for 1 hour, then dried under reduced pressure, and the target polymer electrolyte represented by the following general formula (8) (block copolymer A) 33. 3 3 g

The number average molecular weight of this block copolymer A is 79000, and the thermal decomposition onset temperature is 210 ° C.

(Production Example 2)

In a flask equipped with a distillation tube in an argon atmosphere, 3, 3'-diphenyl-4, 4, dihydroxybiphenyl: 12. 68 g (37. 48 mmo 1), 4, 4, monodiphnoreo benzophenone: 4 58 g (20. 98 mmo 1), 4, 4 'Diph / Leo mouth benzofenone 1, 3, 3' — Dipotassium disulphonate: 7. 50 g (1 6.5 Ommo 1), Carbonate: 5. 44 g (39. 36 mm o 1), N-methylpyrrolidone (NMP): 96 ml, and toluene: 44 ml were added and stirred. Next, the path temperature was raised to 190 ° C, and toluene was distilled off by heating to azeotropically dehydrate water in the system. After toluene was distilled off, the reaction was carried out at the same temperature for 9 hours and 30 minutes. After allowing to cool, the reaction mixture was dropped into a large amount of 2mo 1ZL hydrochloric acid aqueous solution, and the resulting precipitate was collected by filtration, and washed and filtered repeatedly with water until the washing solution became neutral. Next, the filtrate was treated twice with a large excess of hot water for 1 hour, then dried under reduced pressure, and the desired polymer electrolyte represented by the following general formula (9) (random copolymer A) 1 8. 99 g was obtained.

The random copolymer A had a number average molecular weight of 43,000 and a thermal decomposition starting temperature of 215 ° C. (Production Example 3)

In a flask equipped with an azeotropic distillation apparatus under an argon atmosphere, DMSO: 60 Om 1, Tonoleen: 200 mL, 2,5-dichlorosodium benzenesolephonate: 26. 8066805

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5 g (106. 3mmo 1), the following general formula (10)

Polyethersulfone represented by (Sumitomo Chemical Co., Ltd., trade name “Sumikacel PES 5200PJ”): 10.0 g, 2, 2, 1 bibilidyl: 43.8 g (2 80. 2 mmo 1) was added and stirred. Thereafter, the pass temperature was raised to 150 ° C, and the water in the system was azeotropically dehydrated by distilling off the toluene, followed by cooling to 60 ° C. 5—Cyclooctadiene) Eckel: Add 73.4 g (2 66. 9 mmol), raise the temperature to 80 ° C, and stir for 5 hours at the same temperature. The polymer was precipitated by pouring into ZL hydrochloric acid and separated by filtration.

Then, after washing and filtering with 6 mo 1 ZL hydrochloric acid were repeated several times, the filtrate was washed with water until the filtrate became neutral and dried under reduced pressure to achieve the target polymer represented by the following general formula (11) Electrolyte (Block copolymer B): 16.3 g was obtained.

The block copolymer B had a number average molecular weight of 115,000 and a thermal decomposition initiation temperature of 200 ° C.

(Example 1)

The block copolymer A (thermal decomposition start temperature 210 ° C) obtained in Production Example 1 was dissolved in NMP so as to be 20% by weight to obtain a solution, and then the solution was applied onto a glass substrate. Dried at normal pressure at ° C (filming process).

Next, it was heated in a 230 ° C. nitrogen oven for 1 hour (heat treatment step). The amount of residual solvent in the obtained polymer electrolyte membrane was 4% by weight

(Example 2)

A polymer electrolyte membrane was obtained by the same method as in Example 1 except that the temperature of nitrogen open was 2400 ° C. The amount of residual solvent in the obtained polymer electrolyte membrane was 4% by weight. (Example 3)

The block copolymer B obtained in Production Example 3 (pyrolysis start temperature 20 ° C.) was dissolved in NMP to 20% by weight to obtain a solution, and then the solution was applied onto a glass substrate. Then, it was dried at 80 ° C. under normal pressure (film forming process).

Next, the substrate was heated for 30 minutes in a nitrogen open at 210 ° C. (heat treatment step). The amount of residual solvent in the obtained polymer electrolyte membrane was 9% by weight. (Comparative Example 1)

The temperature of the nitrogen oven is 200. A polymer electrolyte membrane was obtained by the same method as in Example 1 except that C was used. The amount of residual solvent in the obtained polymer electrolyte membrane was 10% by weight. (Comparative Example 2)

The block copolymer A obtained in Production Example 1 was dissolved in NMP so as to be 20% by weight to obtain a solution, and the solution was applied on a glass substrate and dried at 80 ° C. under normal pressure. (Membrane process). It was then heated for 30 minutes in a nitrogen oven at 2700C. The amount of residual solvent in the obtained polymer electrolyte membrane was 0% by weight.

(Comparative Example 3)

The block copolymer A obtained in Production Example 1 is dissolved in NMP so as to be 20% by weight. After the solution was obtained, the solution was applied onto a glass substrate and dried at 80 ° C. under normal pressure (film formation step). The obtained polymer electrolyte membrane was washed with running water for 2 hours to remove substantially all of the remaining solvent and dried at room temperature.

Subsequently, it heated for 15 minutes in nitrogen opening of 2400 degreeC. The obtained polymer electrolyte membrane was fragile, and it was impossible to measure the methanol permeability coefficient and proton conductivity.

(Comparative Example 4)

Random copolymer A obtained in Production Example 2 (pyrolysis start temperature 2 15 ° C) was dissolved in NMP so as to be 25% by weight, and a solution was obtained. Then, the solution was applied onto a glass substrate. Then, it was dried at 80 ° C. under normal pressure (film forming process).

Subsequently, it was heated in a nitrogen oven at 240 ° C. for 1 hour (heat treatment step). The amount of residual solvent in the obtained polymer electrolyte membrane was 4% by weight. (Comparative Example 5)

Random copolymer A obtained in Production Example 2 (pyrolysis start temperature 2 15 ° C) was dissolved in NMP so as to be 25% by weight, and a solution was obtained. Then, the solution was applied onto a glass substrate. Then, it was dried at 80 ° C. under normal pressure (film forming process). Next, heating was performed for 1 hour in nitrogen open at 200 ° C. (heat treatment step). The amount of residual solvent in the obtained polymer electrolyte membrane was 11% by weight.

(Comparative Example 6)

A polymer electrolyte membrane was obtained in the same manner as in Example 3 except that the temperature of the nitrogen oven was 200 ° C. The amount of residual solvent in the obtained polymer electrolyte membrane was 16% by weight. In Comparative Example 3, the obtained film was fragile and could not be used for post-treatment. For Examples 1, 2, and 3 and Comparative Examples 1, 2, 4, 5, and 6, each polymer electrolyte membrane was immersed in hydrochloric acid of lnio 1ZL for 3 hours, and the cation exchange group was substantially added. It was converted to a Proton type and washed with running water for 3 hours. The number average molecular weight, proton conductivity (σ), and methanol permeability coefficient (D) of the obtained polymer electrolyte membrane were measured based on each of the measurement methods described above.

The measurement results of Examples 1 to 3 and Comparative Examples 1 to 6 are shown below (Table 2).

IN3 DO

O cn o

(Table 2)

The examples and comparative examples are examples examined by considering the case where a polymer electrolyte membrane is mainly used for a direct methanol fuel cell. Preferred characteristics of polymer electrolytes for direct methanol fuel cells include high proton conductivity (σ) and low methanol permeability coefficient (D), that is, low characteristic coefficient (D / σ). It is.

As can be seen from Table 2 above, Examples 1 and 2 and Comparative Example 1 both use block copolymer ブロック as the electrolyte material. Then, with respect to the thermal decomposition starting temperature 2 10 ° C, in Comparative Example 1, heat treatment (film formation) was performed at 200 ° C which is lower than the thermal decomposition starting temperature. In Examples 1 and 2, the thermal decomposition was performed. Heat treatment (film formation) at 230 ° C and 240, which are higher than the starting temperature. As a result, characteristic coefficient, in Comparative Example ^{1 8. 5 X 1 0- 6,} 7. 1 X 1 0- 6 In Example 1, Example 2, 6. 2 X 1 0 one ^6, and the electrolyte material The characteristic coefficient is smaller when heat treatment is performed at a temperature higher than the thermal decomposition start temperature.

On the other hand, in Comparative Examples 4 and 5, both use random copolymers as the electrolyte material. In contrast to the thermal decomposition start temperature of 215 ° C, in Comparative Example 4, heat treatment (film formation) was performed at 240 ° C, which is higher than the thermal decomposition start temperature. Heat treatment (film formation) at 200 ° C. As a result, characteristic coefficient, in Comparative Example 4 2. 6 X l Cr ^5, Comparative Example 5 1. 2 X 10 one becomes ^5, Kore than the thermal decomposition temperature of the electrolyte material, is better to heat treatment at a temperature The characteristic coefficient is getting larger.

In Comparative Example 2 and Comparative Example 3, the same electrolyte material (Plock Copolymer A) as in Examples 1 and 2 and Comparative Example 1 was used. Unlike 1, the amount of residual solvent after heat treatment is less than 0.1% by weight. Results remaining Solvent amount became 0.1 less than 1 wt%, has become Comparative Example 2, characteristic coefficient Ε) Ζσ poor ^{(2. 5 X 1 0- 5)} , film in Comparative Example 3 becomes brittle, Handling is poor. Examples 3 and 6 both use the block copolymer B as the electrolyte material. Then, with respect to the thermal decomposition start temperature 2 10 ° C, in Comparative Example 6, heat treatment (film formation) was performed at 20 0 ° C, which is the same as the above-mentioned thermal decomposition start temperature. Heat treatment (film formation) is performed at 210 ° C, which is higher than the thermal decomposition start temperature. As a result, characteristic coefficient, in Comparative Example ^{6 1. 2 X 1 0- 5} , Example 3, 9. 7 X 1 0, and the characteristic coefficient better to heat treatment than at higher temperatures thermal decomposition temperature of the electrolyte material Is smaller. As described above, according to the present invention, a method for producing a polymer electrolyte membrane for a fuel cell that is inexpensive and can achieve both methanol barrier properties and proton conductivity at a high level, and a high yield obtained by the method. A molecular electrolyte membrane, a membrane-one electrode assembly using the polymer electrolyte membrane, and a fuel cell can be provided. The direct methanol fuel cell using the polymer electrolyte membrane of the present invention has high power generation characteristics and low methanol crossover, and the reduction in fuel consumption is reduced based on such characteristics. It can use suitably for the use of. Industrial applicability

According to the production method of the present invention, it is possible to obtain a polymer electrolyte membrane that is inexpensive and has both high methanol pariasis and proton conductivity. The direct methanol fuel cell using the polymer electrolyte membrane of the present invention has high power generation characteristics and low methanol crossover, and the reduction in fuel consumption is reduced based on such characteristics. Can be suitably used.

Claims

The scope of the claims

1. a membrane forming step of obtaining a solvent-containing block-type polymer electrolyte membrane by forming a polymer electrolyte solution containing a hydrocarbon block-type polymer electrolyte and a solvent, and the solvent-containing block-type polymer electrolyte membrane; And a heat treatment step of obtaining a polymer electrolyte membrane by heating the polymer electrolyte membrane, wherein the temperature of the heat treatment is set to a thermal decomposition of the hydrocarbon block polymer electrolyte. A method for producing a polymer electrolyte membrane, characterized in that the temperature is higher than the start temperature, and the amount of residual solvent in the polymer electrolyte membrane after heat treatment is 1% by weight or more.

2. The polystyrene-equivalent number average molecular weight obtained by gel permeation chromatography of the hydrocarbon-based block-type polymer electrolyte after the heat treatment is higher than that before the heat treatment. A method for producing a molecular electrolyte membrane.

3. The method for producing a polymer electrolyte membrane according to claim 1, wherein the polymer electrolyte membrane is used for a direct methanol fuel cell.

4. The method for producing a polymer electrolyte membrane according to claim 1, wherein at least 10% of the cation exchange groups of the hydrocarbon-based block polymer electrolyte is a proton type.

5. The hydrocarbon block-type polyelectrolyte is a block copolymer comprising a block having a cation exchange group and a block having substantially no ion exchange group. The manufacturing method of the polymer electrolyte membrane of description.

6. The block having the cation exchange group is represented by the following general formula (1):

[In the formula (1), Ar ¹¹ represents a divalent aromatic group, and the divalent aromatic group is a C 1-20 alkyl group which may have a substituent, An optionally substituted alkoxy group having 1 to 20 carbon atoms, an optionally substituted aryl group having 6 to 20 carbon atoms, and an optionally substituted carbon number 6 May have at least one aryloxy group having ˜20 and a substituent, and may have at least one selected from the group consisting of an acyl group having 2 to 20 carbon atoms, In the divalent aromatic group, at least one cation exchange group is directly bonded to the aromatic ring, X ¹¹ is a direct bond, a group represented by 1 o-, a group represented by 1 S-, a carboel group Or a sulfonyl group, and d is an integer of 5 or more. 6. The method for producing a polymer electrolyte membrane according to claim 5, wherein the polymer electrolyte membrane has a structural unit represented by:

7. The block having the cation exchange group is represented by the following general formula (2) or (3):

[In the formulas (2) and (3), each R ¹ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an aryl having 6 to 20 carbon atoms. Group, an aryloxy group having 6 to 20 carbon atoms, or an acyl group having 2 to 20 carbon atoms, and X ¹² is a direct bond, a group represented by ¹ O—, a group represented by 1 S—, a carbo Represents a dil group or a sulfoel group, J ¹ represents a cation exchange group, and p and q are 1 or 2 45

And d is an integer greater than or equal to 5. 6. The method for producing a polymer electrolyte membrane according to claim 5, wherein the polymer electrolyte membrane has a structure represented by the following formula.

8. The block having substantially no ion exchange group is represented by the following general formula (4)

[In the formula (4), Ar ²² represents a divalent aromatic group, and the divalent aromatic group includes an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and 6 carbon atoms. May have at least one selected from the group consisting of an aryl group having ˜20, an aryloxy group having 6 to 20 carbon atoms, and an acyl group having 2 to 20 carbon atoms, and X ²² is a direct bond, 1 represents a group represented by O—, 1 represents a group represented by S—, a carbonyl group or a sulfonyl group, and e is an integer of 5 or more. 6. The method for producing a polymer electrolyte membrane according to claim 5, comprising a structural unit represented by the following formula:

9. The block having substantially no ion exchange group is represented by the following general formula (5)

[In the formula (5), Ar ² , Ar ³ , Ar ⁴ and Ar ⁵ each independently represent a divalent aromatic group, and the divalent aromatic group is an alkyl group having 1 to 20 carbon atoms. Or at least one selected from the group consisting of an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an acyl group having 2 to 20 carbon atoms. X and X ′ each independently represent a direct bond or a divalent group, and Y and Y ′ each independently represent a group represented by a single symbol, or a group represented by a single S—. , And a, b and c each independently represent 0 or 1, and n represents an integer of 5 or more. ] 6. The production of the polymer electrolyte membrane according to claim 5, wherein the polymer electrolyte membrane has a structural unit

10. A polymer electrolyte membrane obtained by the production method according to claim 1.

11. A membrane-one-electrode assembly comprising the polymer electrolyte membrane according to claim 10 and a catalyst layer provided on both surfaces of the polymer electrolyte membrane.

1. A fuel cell comprising the membrane-electrode assembly according to claim 1.