WO2011122498A1

WO2011122498A1 - Polyelectrolyte, polyelectrolyte membrane, membrane-electrode assembly, and solid polymer fuel cell

Info

Publication number: WO2011122498A1
Application number: PCT/JP2011/057461
Authority: WO
Inventors: 小野　友裕; 竹友山下; 謙太俊成; 和哉清水; 久保　敬次; 須郷　望
Original assignee: 株式会社クラレ
Priority date: 2010-03-29
Filing date: 2011-03-25
Publication date: 2011-10-06
Also published as: JPWO2011122498A1; JP5629761B2; TW201203681A

Abstract

Disclosed is a solid polymer fuel cell that achieves both desired output characteristics and mechanical strength when wet. Further disclosed are: a polyelectrolyte favorable in said solid polymer fuel cell; a polyelectrolyte membrane that uses same and that is concomitantly provided with both mechanical strength and favorable bondability with an electrode; and a membrane-electrode assembly provided with said polyelectrolyte membrane. The polyelectrolyte is characterized by: comprising a copolymer having as constituents two polymer blocks (A) having an ion-conducting group, one polymer block (B) that does not have ion conductivity, and four polymer blocks (C) that do not have ion conductivity; the aforementioned polymer block B having a softening temperature that is at least 20°C lower than that of the aforementioned polymer blocks C; and both ends of the aforementioned polymer blocks A and the aforementioned polymer block B being bonded to the aforementioned polymer blocks C.

Description

Polymer electrolyte, polymer electrolyte membrane, membrane-electrode assembly, and solid polymer fuel cell

The present invention relates to a polymer electrolyte useful for a polymer electrolyte fuel cell, a polymer electrolyte membrane, a membrane-electrode assembly, and a polymer electrolyte fuel cell.

In recent years, fuel cells have attracted attention as a clean power generation system that is friendly to the global environment. Fuel cells are classified into molten carbonate type, solid oxide type, phosphoric acid type, solid polymer type, etc., depending on the type of electrolyte. Among these, a polymer electrolyte membrane having a structure in which a polymer electrolyte membrane is sandwiched between electrodes (anode and cathode), a solid polymer fuel cell that generates electricity by supplying a fuel made of a reducing agent to the anode and an oxidant to the cathode, From the viewpoint of low-temperature operability and reduction in size and weight, application to automobile power supplies, portable equipment power supplies, and household cogeneration systems that simultaneously use electricity and heat are being considered.

Solid polymer fuel cells are required to have both high output under low humidity and high durability when wet. This requirement is particularly strong in a polymer electrolyte fuel cell using hydrogen fuel.

In order to increase the output under low humidity, a means to increase proton conductivity is usually taken by increasing the ion exchange capacity of the polymer electrolyte used in the polymer electrolyte membrane. The swelling of the membrane increases and the mechanical strength also decreases, and the polymer electrolyte membrane tends to creep during the long-term operation of the polymer electrolyte fuel cell, causing problems such as the durability of the polymer electrolyte fuel cell being reduced. . In addition, a method of reducing the membrane resistance of the polymer electrolyte membrane by reducing the thickness of the polymer electrolyte membrane and increasing the output has been proposed, but the mechanical strength of the polymer electrolyte membrane is reduced. When the polymer electrolyte membrane is bonded to the gas diffusion electrode to produce a membrane-electrode assembly, another problem such as poor workability occurs.
Thus, as a measure for improving the mechanical strength, it has also been proposed to use an electrolyte composite membrane made of a reinforcing material such as a polymer electrolyte and a polytetrafluoroethylene porous film as the polymer electrolyte membrane (see Patent Document 1). Since the proton conductivity of the reinforcing material is low, the membrane resistance of the electrolyte composite membrane tends to increase, and the power generation characteristics tend to deteriorate.

On the other hand, in order to increase the mechanical strength of the polymer electrolyte membrane when wet, a block polymer has been proposed in which a block polymer having a segment that is not easily sulfonated at the end and a segment that is easily sulfonated in between is sulfonated. (See Patent Document 2). However, the recent demand for high performance cannot be fully met, and there is still room for improvement.

Thus, in the polymer electrolyte used in the solid polymer fuel cell, a polymer electrolyte membrane that has both high proton conductivity and high mechanical strength when wet is desired.

Japanese Patent Publication No. 5-75835 Special table 2009-503137

An object of the present invention is to provide a polymer electrolyte fuel cell that has both output characteristics and mechanical strength when wet. Further, in order to achieve this object, a polymer electrolyte suitable for the solid polymer fuel cell, a polymer electrolyte membrane using the polymer electrolyte having both mechanical strength and good bonding property with an electrode, and An object of the present invention is to provide a membrane-electrode assembly provided with the polymer electrolyte membrane.

As a result of intensive studies to solve the above-mentioned problems, the present inventors specify the type and order of bonding of polymer blocks in a polymer electrolyte composed of a copolymer containing a polymer block as a constituent component. The inventors have found that the above-described problems can be solved, and have completed the present invention.

That is, the present invention
[1] Two polymer blocks (A) having an ion conductive group, one polymer block (B) having no ion conductivity, and four polymer blocks (C) having no ion conductivity A polymer electrolyte comprising a copolymer as a constituent component, wherein the polymer block (B) has a softening temperature lower by 20 ° C. or more than the polymer block (C), and the polymer block (A) and the polymer block (B) A polymer electrolyte characterized in that both ends of the polymer block (B) are bonded to the polymer block (C);
[2] The polymer electrolyte according to [1], wherein the polymer block (A) is composed of a repeating unit of an aromatic vinyl compound unit;
[3] The polymer block (C) is represented by the following general formula (a):

Wherein R ¹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ² to R ⁴ each independently represents a hydrogen atom or an alkyl group having 3 to 8 carbon atoms, but at least one of them is carbon The polyelectrolyte according to the above [1] or [2], wherein the polymer electrolyte is a repeating unit of an aromatic vinyl compound unit represented by formula (3).
[4] The polymer block (B) is composed of at least one repeating unit selected from alkene units having 2 to 8 carbon atoms and conjugated diene units having 4 to 8 carbon atoms. 1] to [3]
[5] The above [1] to [4], wherein the ion conductive group is a group represented by —SO ₃ M or —PO ₃ HM (wherein M represents a hydrogen atom, an ammonium ion or an alkali metal ion). ] The polymer electrolyte according to any one of
[6] A polymer electrolyte membrane comprising the polymer electrolyte according to any one of [1] to [5] above;
[7] A polymer electrolyte fuel cell comprising a membrane-electrode assembly comprising the polymer electrolyte membrane according to [6] above; and [8] a polymer electrolyte fuel cell comprising the membrane-electrode assembly according to [7] above.

The copolymer comprising the polymer block (A), polymer block (B) and polymer block (C) constituting the polymer electrolyte of the present invention as a constituent component causes an ion conductive group by causing microphase separation. The polymer blocks (A) having the above are gathered to form an ion channel, which becomes a passage for ions such as protons. Moreover, a polymer block (B) is a polymer block whose softening temperature is 20 degreeC or more lower than a polymer block (C). By setting the temperature between the softening temperatures of the polymer block (B) and the polymer block (C) as the use temperature range, the polymer electrolyte of the present invention can obtain desired performance.
That is, the polymer electrolyte of the present invention is elastic and flexible when used at a temperature higher than the softening temperature of the polymer block (B). Further, by using the polymer block (C) at a temperature lower than the softening temperature, the form stability at the use temperature, durability, heat resistance, mechanical strength under wet conditions, and the like are improved. In addition, since the softening temperature of the polymer block (B) is low, the moldability (assembling property, bonding property, tightening property, etc.) in producing the membrane-electrode assembly and the polymer electrolyte fuel cell is improved. .

In the polymer electrolyte of the present invention, since both ends of the polymer block (A) are bonded to the polymer block (C), the polymer block (A) having an ion conductive group is formed when wet. Even when the ion channel contains water, it is possible to improve the form stability, durability, heat resistance, mechanical strength when wet, and the like when the polymer electrolyte membrane is formed. In addition, the presence of two polymer blocks (A) having an ion conductive group makes it easier to form a pseudo-crosslinked structure due to the interaction between the ion conductive groups, thereby improving the durability when containing water. Moreover, when both ends of the polymer block (B) are bonded to the polymer block (C), the toughness can be further increased in the operating temperature range when the polymer electrolyte membrane is formed.

In addition, since the polymer block (B) has both ends bonded to the polymer block (C), the polymer electrolyte of the present invention exhibits good rubber elasticity in the operating temperature range, and the polymer electrolyte Mechanical strength such as tear strength of the film is increased.

Here, “microphase separation” means phase separation in a microscopic sense, and more specifically, means phase separation in which the formed domain size is less than or equal to the wavelength of visible light (3800 to 7800 mm). Shall.

Hereinafter, the present invention will be described in detail.
The polymer electrolyte of the present invention comprises two polymer blocks (A) having an ion conductive group, one polymer block (B) having no ion conductivity, and four polymers having no ion conductivity. It consists of a copolymer having the block (C) as a constituent component.
The copolymer constituting the polymer electrolyte of the present invention need not be a single copolymer, and may be a mixture of a plurality of types. In addition, other polymers, low molecular weight organic compounds, inorganic compounds, and the like may be included as long as the object of the present invention is not impaired. Further, the structure of the two polymer blocks (A) and four polymer blocks (C) constituting the copolymer constituting the polymer electrolyte of the present invention (constituent repeating unit, degree of polymerization, ratio of ion conductive group, etc.) ) Need not be the same, and may be a polymer block having an ion conductive group or a polymer block having no ion conductivity.

<Polymer block (A)>
The copolymer constituting the polymer electrolyte of the present invention comprises two polymer blocks (A) having ion conductive groups as constituent components.
As the polymer block (A), a polymer block having an aromatic vinyl compound unit as a repeating unit, a polyether ketone block, a polysulfide block, a polyphosphazene block, a polyphenylene block, a polybenzimidazole block, a polyether sulfone block, Polyphenylene oxide block, polycarbonate block, polyamide block, polyimide block, polyurea block, polysulfone block, polysulfonate block, polybenzoxazole block, polybenzothiazole block, polyphenylquinoxaline block, polyquinoline block, polytriazine block, polyacrylate block , Polymerization in which ion conductive groups are introduced into each polymer block such as polymethacrylate block Among them, a polymer block having an aromatic vinyl compound unit as a repeating unit, a polyether ketone block, a polysulfide block, a polyphosphazene block, a polyphenylene block, a polybenzimidazole block, a polyethersulfone block, and a polyphenylene oxide block are selected. A polymer block in which an ion conductive group is introduced into the polymer block is preferable, and a polymer in which an ion conductive group is introduced into a polymer block having an aromatic vinyl compound unit as a repeating unit from the viewpoint of easy synthesis. Blocks are more preferred.

The aromatic ring of the aromatic vinyl compound unit is preferably a carbocyclic aromatic ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a pyrene ring.

Specific examples of monomers that can form these aromatic vinyl compound units include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 2,4-dimethylstyrene, 2,5- Aromatic vinyl compounds such as dimethylstyrene, 3,5-dimethylstyrene, 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, vinylbiphenyl, vinylterphenyl, vinylnaphthalene, vinylanthracene, 4-phenoxystyrene It is done.
The polymer block (A) is a portion corresponding to the polymer block (A) of the copolymer obtained by polymerization including the step of polymerizing these aromatic vinyl compounds (ion conductivity of the polymer block (A)). It is a precursor block having a structure in which a group is substituted with hydrogen, and can be produced by selectively introducing an ion conductive group into a polymer block (hereinafter sometimes referred to as “polymer block (A ₀ )”). In that case, it is desirable that there are no functional groups on the aromatic ring of these monomers that inhibit the reaction for introducing the ion conductive group. For example, if hydrogen on the aromatic ring of styrene (particularly hydrogen at the 4-position) is substituted with an alkyl group (particularly an alkyl group having 3 or more carbon atoms), it may be difficult to introduce an ion conductive group. The aromatic ring is preferably not substituted with another functional group, or an aryl group or the like is preferably substituted with a substituent capable of introducing an ion conductive group, and the ion conductive group can be easily introduced. From the viewpoint of increasing the density of the ion conductive group, styrene and vinyl biphenyl are more preferable.

Of the hydrogen atoms on the vinyl group of the aromatic vinyl compound, the hydrogen atom bonded to the α-position carbon (α-carbon) of the aromatic ring is substituted with another substituent, and the α-carbon is 4 It may have a structure that is a secondary carbon. Examples of the substituent in which the hydrogen atom bonded to the α-carbon atom may be substituted include an alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group). Group, sec-butyl group, or tert-butyl group), a halogenated alkyl group having 1 to 4 carbon atoms (chloromethyl group, 2-chloroethyl group, 3-chloroethyl group, etc.) or phenyl group. Examples of the aromatic vinyl compound having the substituent include α-methylstyrene, α-methyl-4-methylstyrene, α-methyl-2-methylstyrene, α-methyl-4-ethylstyrene, 1,1-diphenylethylene. Is preferred.

These aromatic vinyl compounds can be used as a monomer in forming the polymer block (A) by combining one or more kinds. When two or more types are used in combination as a monomer, two types are selected from styrene, α-methylstyrene, 4-methylstyrene, 4-ethylstyrene, α-methyl-4-methylstyrene, and α-methyl-2-methylstyrene. It is preferable to select the above. The copolymerization method in the case of forming a polymer block (A ₀ ) having a structure in which two or more of these are copolymerized to replace the ion conductive group of the polymer block (A) with hydrogen is random copolymerization. Is preferred.

The polymer block (A) may contain one or more other monomer units as long as the effects of the present invention are not impaired. Examples of monomers that can constitute such other monomer units include conjugated dienes having 4 to 8 carbon atoms (1,3-butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4 -Hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene, etc.), alkenes having 2 to 8 carbon atoms (ethylene, propylene, 1-butene, 2 -Butene, isobutene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 1-heptene, 2-heptene, 1-octene, 2-octene, etc.), (meth) acrylic acid esters ((meth) acrylic) Methyl ester, ethyl (meth) acrylate, butyl (meth) acrylate, etc.), vinyl esters (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.), Vinyl ether (methyl vinyl ether, isobutyl vinyl ether, etc.), and the like. Random copolymerization is desirable as a copolymerization method with the other monomer.

When the polymer block (A) has an aromatic vinyl compound unit as a repeating unit, it is advantageous in causing microphase separation from the polymer block (B), and as a result, ion conductivity can be increased.

The molecular weight of the polymer block (A ₀ ) is usually preferably selected from the range of 1,000 to 100,000 as the number average molecular weight in terms of standard polystyrene, and selected from the range of 2,000 to 70,000. More preferably, it is more preferably selected from the range of 3,000 to 50,000, and particularly preferably selected from the range of 4,000 to 30,000.

The molecular weight of the polymer block (A ₀ ) is appropriately selected depending on the properties of the polymer electrolyte membrane, required performance, other polymer components, and the like. When the molecular weight is large, the mechanical strength of the polymer electrolyte membrane tends to be high, but when it is greater than 100,000, it may be difficult to form and form the polymer electrolyte. Further, when the molecular weight is less than 1,000, it is difficult to form a microphase separation structure and thus an ion channel, so that the ionic conductivity tends to be lost and the mechanical strength tends to be lowered.

The polymer block (A) may be crosslinked by a known method within a range not impairing the effects of the present invention. By introducing the crosslinking, the ion channel phase formed by the polymer block (A) is less likely to swell, the structure in the electrolyte membrane is easily maintained, and the performance tends to be stable.

The polymer block (A) in the polymer electrolyte of the present invention needs to have an ion conductive group. Examples of ions in the present invention when referring to ionic conductivity include protons. The ion conductive group is not particularly limited as long as the polymer electrolyte membrane and membrane-electrode assembly produced using the polymer electrolyte can express sufficient ionic conductivity. A sulfonic acid group, phosphonic acid group, carboxyl group or a salt thereof represented by ₃ M or —PO ₃ HM, —CO ₂ M (wherein M represents a hydrogen atom, an ammonium ion or an alkali metal ion) is used. From the viewpoint of exhibiting particularly high ion conductivity, a sulfonic acid group represented by —SO ₃ M or —PO ₃ HM (wherein M represents a hydrogen atom, an ammonium ion or an alkali metal ion), phosphone Acid groups or their salts are preferably used.

All the repeating units in the polymer block (A) do not need to have an ion conductive group, and the amount of the ion conductive group can be appropriately adjusted according to the performance. Although there is no restriction | limiting in particular about the position of the ion conductive group in a polymer block (A), Usually, it introduce | transduces into a polymer block (A) at random. When there is a compound having an aromatic ring as a repeating unit, it is preferably introduced onto the aromatic ring from the viewpoint of facilitating ion channel formation. Further, when the aromatic vinyl compound unit is a repeating unit, it is particularly effective for improving the radical resistance of the polymer electrolyte by introducing an ion conductive group onto the aromatic ring of the aromatic vinyl compound unit. .

The amount of ion-conducting group introduced is appropriately selected depending on the required performance of the obtained polymer electrolyte membrane, etc., but exhibits sufficient ion conductivity for use as a polymer electrolyte membrane for a polymer electrolyte fuel cell. In general, the amount is preferably such that the ion exchange capacity of the polymer electrolyte is 0.80 meq / g or more, more preferably 1.30 meq / g or more. It is more preferably 1.40 meq / g or more, and particularly preferably 1.80 meq / g or more. The upper limit of the ion exchange capacity of the polymer electrolyte is preferably 4.00 meq / g or less, because if the ion exchange capacity becomes too large, the hydrophilicity tends to increase and the water resistance becomes insufficient. It is more preferably 80 meq / g or less, and still more preferably 3.60 meq / g or less.

<Polymer block (B)>
The copolymer constituting the polymer electrolyte of the present invention comprises one polymer block (B) having no ionic conductivity as a constituent component.
The polymer electrolyte membrane of the present invention is elastic and flexible in the operating temperature range due to the polymer block (B), and has moldability in the production of membrane-electrode assemblies and solid polymer fuel cells. (Assemblyability, bondability, tightenability, etc.)

Here, the polymer block (B) does not have ionic conductivity, and the softening temperature (that is, the softening temperature when the polymer block independently becomes a polymer) is the polymer block (C ) (That is, the polymer softening temperature when the polymer block independently becomes a polymer) is 20 ° C. or more lower than the softening temperature.
Here, when the softening temperature of each polymer block (C) constituting the copolymer is different, the softening temperature of the polymer block (B) is 20 than that of the polymer block (C) showing the lowest softening temperature. More than ℃. The softening temperature of the polymer block (B) is preferably 40 ° C. or more lower than that of the polymer block (C), since it has high elasticity in a wide use temperature range and easily exhibits flexibility. More preferably, it is lower.
The repeating unit constituting the polymer block (B) includes alkene units having 2 to 8 carbon atoms, cycloalkene units having 5 to 8 carbon atoms, vinylcycloalkane units having 7 to 10 carbon atoms, and 7 to 10 carbon atoms. Vinylcycloalkene unit, conjugated diene unit having 4 to 8 carbon atoms, conjugated cycloalkadiene unit having 5 to 8 carbon atoms, acrylate ester unit having a side chain having 1 to 12 carbon atoms, and 1 to 12 carbon atoms Examples include methacrylic acid ester units having side chains. You may use the repeating unit chosen from these groups individually or in combination of 2 or more types.

The softening temperature of the polymer block (B) is preferably 50 ° C. or less, more preferably 40 ° C. or less, and further preferably 30 ° C. or less in view of a suitable use temperature range and molding temperature. preferable.

Among the monomers constituting such a repeating unit, the alkene having 2 to 8 carbon atoms includes ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 1-hexene, Cycloalkene having 5 to 8 carbon atoms such as 2-hexene, 1-heptene, 2-heptene, 1-octene, 2-octene and the like, and cycloalkene having 5 to 8 carbon atoms such as cyclopentene, cyclohexene, cycloheptene and cyclooctene, etc. As vinylcyclopentane, vinylcyclohexane, vinylcycloheptane, vinylcyclooctane and the like. As the vinylcycloalkene having 7 to 10 carbon atoms, vinylcyclopentene, vinylcyclohexene, vinylcycloheptene, vinylcyclooctene, etc. As the conjugated diene of , 3-butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3 -Heptadiene, etc., conjugated cycloalkadiene having 5 to 8 carbon atoms such as cyclopentadiene, 1,3-cyclohexadiene, etc., and acrylic acid esters having a side chain having 1 to 12 carbon atoms, such as methyl acrylate, acrylic acid Examples of the methacrylic acid ester having a side chain having 1 to 12 carbon atoms such as ethyl, butyl acrylate and octyl acrylate include methyl methacrylate, ethyl methacrylate, butyl methacrylate and octyl methacrylate. These monomers may be used alone or in combination of two or more. When copolymerizing two or more monomers to form the polymer block (B), the copolymerization method is preferably random copolymerization. Further, when the monomer to be copolymerized has a plurality of carbon-carbon double bonds, any of them may be used for polymerization, and in the case of a conjugated diene, It may be a 4-bond.

When the monomer for forming the polymer block (B) has a plurality of carbon-carbon double bonds such as vinylcycloalkene, conjugated diene and conjugated cycloalkadiene, it is usually after polymerization. The carbon-carbon double bond remains in the polymer block. When the polymer block has a carbon-carbon double bond as described above, 30% by mole or more of the carbon-carbon double bond is hydrogenated from the viewpoint of improving heat deterioration resistance. More preferably, 50 mol% or more is hydrogenated, and 80 mol% or more is more preferably hydrogenated.
The hydrogenation rate of the carbon-carbon double bond can be calculated by a commonly used method, for example, iodine value measurement method, ¹ H-NMR measurement or the like. As described above, the polymer block (B) does not have a carbon-carbon double bond or has a reduced structure, so that deterioration of the polymer electrolyte membrane can be suppressed.

When the polymer block (B) is made into a polymer electrolyte membrane, it becomes elastic and flexible in the operating temperature range, and the moldability (assembly) is assured in the production of membrane-electrode assemblies and solid polymer fuel cells. From the viewpoint of easy improvement in the properties, bonding properties, fastening properties, etc.), alkene units having 2 to 8 carbon atoms, cycloalkene units having 5 to 8 carbon atoms, vinylcycloalkene units having 7 to 10 carbon atoms, and 4 carbon atoms. It is preferably a polymer block comprising at least one repeating unit selected from the group consisting of a conjugated diene unit having 8 to 8 and a conjugated cycloalkadiene unit having 5 to 8 carbon atoms, an alkene unit having 3 to 8 carbon atoms, More preferably, it is a polymer block composed of at least one repeating unit selected from conjugated diene units having 4 to 8 carbon atoms, an alkene unit having 4 to 6 carbon atoms, and 4 to 6 carbon atoms. It is more preferably a polymer block comprising at least one repeating unit selected from conjugated diene units. In the above, the most preferable alkene unit is a structural unit (1-butene unit, 2-butene unit) in which a double bond of an isobutene unit or 1,3-butadiene unit is saturated, or a double bond of an isoprene unit is saturated. Structural units (2-methyl-1-butene unit, 3-methyl-1-butene unit, 2-methyl-2-butene unit). A structural unit saturated with a bond (1-butene unit, 2-butene unit) or a structural unit saturated with a double bond of an isoprene unit (2-methyl-1-butene unit, 3-methyl-1-butene unit, 2-methyl-2-butene units) are most preferred. Most preferred conjugated diene units are 1,3-butadiene units and isoprene units.
In the production of the polymer electrolyte of the present invention, when a polymer block (A) is formed by introducing an ion conductive group after polymerizing a copolymer having no ion conductive group, the polymer block ( If B) is a saturated hydrocarbon structure, it is preferable because an ion conductive group is hardly introduced into the polymer block (B).

Moreover, as a monomer for forming the polymer block (B), the purpose of the polymer block (B) that gives elasticity to the polymer electrolyte in the operating temperature region is not impaired in addition to the above-mentioned monomers. In range, other monomers such as aromatic vinyl compounds such as styrene and vinyl naphthalene; halogen-containing vinyl compounds such as vinyl chloride, vinyl esters (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.), Vinyl ether (methyl vinyl ether, isobutyl vinyl ether, etc.) may be used. In this case, the copolymerization method of the monomer with another monomer is preferably random copolymerization. The amount of these other monomers used is preferably 5 mol% or less.

The molecular weight of the polymer block (B) is usually selected from the range of 5,000 to 250,000, preferably from the range of 7,000 to 150,000, as the number average molecular weight in terms of standard polystyrene. More preferably, it is selected from the range of 8,000 to 100,000, more preferably from the range of 10,000 to 70,000.

<Polymer block (C)>
The block copolymer constituting the polymer electrolyte of the present invention comprises four polymer blocks (C) having no ionic conductivity as constituent components.
The polymer block (C) functions as a constraining phase. Since the restraint function is easily exhibited in a wide use temperature range, the softening temperature of the polymer block (C) (that is, the softening temperature of the polymer when the polymer block independently becomes a polymer) is 80 ° C. It is preferably above, more preferably 90 ° C. or higher, and further preferably 100 ° C. or higher.

The polymer block (C) includes a polymer block mainly composed of an aromatic vinyl compound unit, a polyether ketone block, a polysulfide block, a polyphosphazene block, a polyphenylene block, a polybenzimidazole block, a polyether sulfone block, and a polyphenylene. Oxide block, polycarbonate block, polyamide block, polyimide block, polyurea block, polysulfone block, polysulfonate block, polybenzoxazole block, polybenzothiazole block, polyphenylquinoxaline block, polyquinoline block, polytriazine block, polyacrylate block, Polymethacrylate block, etc. Polymer block repeating units are preferred. In particular, the polymer block (C) has the following general formula (a):

Wherein R ¹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ² to R ⁴ each independently represents a hydrogen atom or an alkyl group having 3 to 8 carbon atoms, but at least one of them is carbon (Representing an alkyl group of several 3 to 8) is preferable from the viewpoint of easy synthesis and easy obtaining of a restraining function.
That is, when a polymer block (A) is formed by introducing an ion conductive group after polymerization of a copolymer having no ion conductive group, ions to the polymer block (C) are formed by R ² to R ⁴ . Since introduction of a conductive group is hindered, it is preferable. Moreover, since the softening temperature becomes relatively high, the operating temperature range can be widened.

Examples of the monomer capable of forming the repeating unit of the aromatic vinyl compound unit represented by the general formula (a) include 4-isopropylstyrene, 4-n-propylstyrene, 4-isopropylstyrene, 4-n-butyl. Aromatic vinyl compounds such as styrene, 4-isobutyl styrene, 4-tert-butyl styrene, 4-n-octyl styrene, α-methyl-4-tert-butyl styrene, α-methyl-4-isopropyl styrene .

These can be used alone or in combination of two or more, among which 4-tert-butylstyrene, 4-isopropylstyrene, α-methyl-4-tert-butylstyrene, and α-methyl-4-isopropylstyrene are preferable. Random copolymerization is preferred as the copolymerization method in the case of copolymerizing two or more of these.

The polymer block (C) may contain one or more other monomer units within a range not impairing the effects of the present invention. Examples of such other monomers include conjugated dienes having 4 to 8 carbon atoms (1,3-butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4-hexadiene, 2,3- Dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene, etc.), alkenes having 2 to 8 carbon atoms (ethylene, propylene, 1-butene, 2-butene, isobutene, 1-butene, etc.) Pentene, 2-pentene, 1-hexene, 2-hexene, 1-heptene, 2-heptene, 1-octene, 2-octene, etc.), (meth) acrylic acid esters (methyl (meth) acrylate, (meth) acrylic) Ethyl acetate, butyl (meth) acrylate, etc.), vinyl esters (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.), vinyl ether (methyl) Vinyl ether, isobutyl vinyl ether, etc.), and the like. The copolymerization method with the other monomer is preferably random copolymerization. The amount of these monomers used is preferably 5 mol% or less.

The molecular weight of the polymer block (C) is appropriately selected depending on the properties of the polymer electrolyte, required performance, other polymer components, and the like. The molecular weight is preferably selected from the range of 1,000 to 50,000, more preferably from the range of 1,500 to 30,000, as the number average molecular weight in terms of standard polystyrene. More preferably, it is selected from the range of 2,000 to 20,000. When the molecular weight of the polymer block (C) is large, the mechanical strength of the polymer electrolyte tends to be high, but when it is larger than 50,000, it becomes difficult to mold and form the polymer electrolyte. When the molecular weight of the polymer block (C) is smaller than 1,500, the mechanical strength tends to be low, and it is important to appropriately select the molecular weight according to the required performance.

[Polymer electrolyte]
The polymer electrolyte of the present invention comprises two polymer blocks (A) having an ionic group, one polymer block (B) having no ionic group, and four polymer blocks having no ionic group (C ) And a constituent component. Furthermore, by defining the structure, it is possible to achieve both high proton conductivity and high mechanical strength when wet.

Specifically, both ends of the polymer block (A) are bonded to the polymer block (C) functioning as a constraining phase. Since the polymer block (A) has an ion conductive group, the ion channel formed by the polymer block (A) at the time of wetting tends to contain water and swell so that the ion conductivity tends to increase. Tend to decrease the mechanical strength. When both ends of the polymer block (A) are bonded to the polymer block (C) that functions as a constraining phase even when wet, there is a tendency that a decrease in strength can be suppressed.

In addition, the polymer block (B) functions as a phase responsible for elasticity and flexibility in a use temperature range when formed into a polymer electrolyte membrane. In order to increase toughness, in the polymer electrolyte of the present invention, both ends of the polymer block (B) are bonded to the polymer block (C) functioning as a constraining phase. The polymer block (A) also has a function as a constrained phase at the time of drying. However, when the polymer block (A) is wet, the ion channel formed by the polymer block (A) contains water and swells, so that the ability as a constrained phase is reduced. Therefore, by bonding both ends of the polymer block (B) with the polymer block (C) that functions as a constraining phase even when wet, there is a tendency that a decrease in strength can be suppressed even when wet.

In addition, the polymer electrolyte membrane using the copolymer has high mechanical strength. This is presumably because the polymer block in the copolymer contains a block structure of-(A)-(C)-(B)-.
Generally, an XYZ type block copolymer with a polymer block (Y) sandwiched between the polymer block (X) and the polymer block (Z) forms a domain with another polymer. By forming a bridge structure sandwiching (Y), mechanical strength is expressed (in this case, the form of the chain taken by the polymer block (Y) is called a bridge chain). On the other hand, when the block copolymer forms a loop structure and the polymer block (X) and the polymer block (Z) constitute the same domain, the ratio of the bridge structure is lowered, so that the mechanical strength is lowered. That is, the mechanical strength can be increased by reducing the loop structure and increasing the bridge structure.
The copolymer constituting the polymer electrolyte of the present invention has only a bridge structure when the polymer block takes a block structure of-(A)-(C)-(B)-, and the polymer block (C) has a bridge structure. By forming a chain, the mechanical strength of the polymer electrolyte membrane tends to increase.

The structure of the copolymer constituting the polymer electrolyte of the present invention comprises two polymer blocks (A) having an ion conductive group, one polymer block (B) having no ion conductivity, and ion conductivity. C—A—C—B—C—A—C—Heptablock copolymer, C—A—C—A—C—B—C—Hepta block Examples include copolymers

The mass ratio of the total amount of the two polymer blocks (A ₀ ) and the total amount of the four polymer blocks (C) is preferably 80:20 to 10:90, and is preferably 75:25 to 15:85. More preferably, it is more preferably 65:35 to 20:80. When the mass ratio of the polymer block (C) becomes too small, it becomes difficult to maintain strength during drying and wetness. Further, if the mass ratio of the polymer block (A ₀ ) becomes too small, the amount of ion conductive groups introduced into the polymer block decreases, and the ion conductivity when the polymer electrolyte membrane is formed is sufficient. It becomes difficult to ensure.

The mass ratio of the polymer block (B) and the total amount of the four polymer blocks (C) is preferably 85:15 to 5:95, more preferably 75:25 to 10:90, 70 : 30 to 12:88 is more preferable. When the mass ratio of one polymer block (C) becomes too small, it is difficult to maintain the strength as an electrolyte membrane. Moreover, when the mass ratio of one said polymer block (B) becomes small too much, it will become difficult to hold | maintain toughness and it exists in the tendency which becomes weak.

Further, the number average molecular weight of the copolymer constituting the polymer electrolyte of the present invention is not particularly limited, but is usually 11,000 to as the number average molecular weight in terms of standard polystyrene in a state where no ion conductive group is introduced. It is preferably selected from the range of 500,000, more preferably selected from the range of 14,000 to 350,000, still more preferably selected from the range of 17,000 to 250,000, 20 It is particularly preferred that it is selected from the range of 2,000 to 200,000.

The method for producing the copolymer constituting the polymer electrolyte of the present invention is not particularly limited, and a known method can be used. However, after producing a copolymer having no ion conductive group, A method of introducing a group is preferred.

In the production of the polymer electrolyte of the present invention, an ion comprising a plurality of types of monomers as a constituent component and a polymer block (A ₀ ), a polymer block (B), and a polymer block (C) as constituent components. When a copolymer having no conductive group is obtained and then produced by introducing an ion conductive group into the polymer block (A ₀ ), copolymerization of the copolymer having no ion conductive group is performed. According to the method, the polymer block (A ₀ ), the polymer block (B), the type of monomer unit constituting the polymer block (C), the molecular weight, etc., radical polymerization method, anionic polymerization method, cationic polymerization method, Although it is appropriately selected from coordination polymerization method and the like, radical polymerization method, anionic polymerization method and cationic polymerization method are preferably selected from the viewpoint of industrial ease. In particular, the so-called living polymerization method is preferable from the viewpoint of molecular weight control, molecular weight distribution control, polymer structure control, ease of bonding between the polymer block (A ₀ ) and the polymer block (B) and the polymer block (C), etc. Specifically, a living radical polymerization method, a living anion polymerization method, and a living cation polymerization method are preferable.

An example of a method for producing a copolymer constituting the polymer electrolyte of the present invention will be described below. Here, a method of introducing an ion conductive group after producing a copolymer having no ion conductive group is shown.

First, a polymer block (C) containing an aromatic vinyl compound such as 4-tert-butylstyrene as a main repeating unit, a polymer block (A ₀ ) containing an aromatic vinyl compound such as styrene as a main repeating unit, and A method for producing a block copolymer having no ion conductivity and comprising a polymer block (B) made of conjugated diene or the like as a constituent component will be described. In this case, the living anionic polymerization method is preferred from the viewpoint of industrial ease, molecular weight, molecular weight distribution, ease of bonding of the polymer block (C), the polymer block (B) and the polymer block (A ₀ ).
Specifically, an aromatic vinyl compound such as 4-tert-butylstyrene is polymerized at a temperature of 10 to 100 ° C. using an anionic polymerization initiator in a cyclohexane solvent, and then styrene, 4-tert - method of obtaining butyl styrene, conjugated dienes, 4-tert-butylstyrene, styrene, 4-tert butyl styrene were sequentially polymerized _{C-a 0 -C-B-} C-a 0 -C type block copolymer, Etc. can be employed / applied.

The copolymer produced in this way may be subjected to a hydrogenation reaction of double bonds of conjugated diene units having 4 to 8 carbon atoms constituting the polymer block (B). As a method for the hydrogenation reaction, a solution of a copolymer obtained by anionic polymerization or the like is charged into a pressure vessel, and a hydrogenation reaction is performed in a hydrogen atmosphere using a Ziegler-type hydrogenation catalyst such as a Ni / Al type. The method of performing can be illustrated.

Next, a method for obtaining a copolymer constituting the polymer electrolyte of the present invention by introducing an ion conductive group into the copolymer having no ion conductive group will be described.
First, a method for introducing a sulfonic acid group into a copolymer will be described. Sulfonation can be performed by a known sulfonation method. Examples of such a method include a method of preparing an organic solvent solution or suspension of a copolymer, adding a sulfonating agent and mixing, a method of adding a gaseous sulfonating agent directly to the copolymer, and the like. Is done.

Sulfonating agents used include sulfuric acid, a mixture of sulfuric acid and aliphatic acid anhydride, chlorosulfonic acid, a mixture of chlorosulfonic acid and trimethylsilyl chloride, sulfur trioxide, a mixture of sulfur trioxide and triethyl phosphate. Examples thereof include aromatic organic sulfonic acids represented by 2,4,6-trimethylbenzenesulfonic acid. Examples of the organic solvent to be used include halogenated hydrocarbons such as methylene chloride, linear aliphatic hydrocarbons such as hexane, cyclic aliphatic hydrocarbons such as cyclohexane, and the like. You may use it, selecting suitably from several combinations.

As a method for taking out the sulfonated product as a solid from the obtained reaction solution containing the desired copolymer (sulfonated product), the reaction solution is poured into water to precipitate the sulfonated product, and then the solvent is distilled off at atmospheric pressure. In addition, there is a method in which water as a terminator is gradually added and suspended in the reaction solution, and the sulfonated product is precipitated, and then the solvent is distilled off at atmospheric pressure. From the viewpoint of increasing the washing efficiency with water, a method in which water as a terminator is gradually added and suspended in the reaction solution to precipitate a sulfonated product is preferably used.

Next, a method for introducing phosphonic acid groups into the copolymer will be described. Phosphonation can be performed by a known phosphonation method. Specifically, an organic solvent solution or suspension of the copolymer is prepared, the copolymer is reacted with chloromethyl ether or the like in the presence of anhydrous aluminum chloride, and a halomethyl group is introduced into the aromatic ring. For example, phosphorus trichloride and anhydrous aluminum chloride may be added and reacted, followed by hydrolysis to introduce a phosphonic acid group. Alternatively, a method may be exemplified in which phosphorus trichloride and anhydrous aluminum chloride are added to the copolymer and reacted to introduce a phosphinic acid group into the aromatic ring, and then the phosphinic acid group is oxidized with nitric acid to form a phosphonic acid group.

As the degree of sulfonation or phosphonation, the ion exchange capacity of the copolymer is preferably 0.80 meq / g or more, more preferably 1.30 meq / g or more, still more preferably 1.40 meq / g or more, particularly preferably. It is sulfonated or phosphonated until it is 1.80 meq / g or more, but preferably 4.00 meq / g or less, more preferably 3.80 meq / g or less, and even more preferably 3.60 meq / g or less. It is desirable. Thereby, practical ion conduction performance is obtained. The ion exchange capacity of a sulfonated or phosphonated copolymer, or the sulfonation rate or phosphonation rate in an aromatic vinyl compound in the copolymer is determined by acid value titration method, infrared spectroscopic measurement, nuclear magnetic resonance. It can be calculated using analytical means such as spectrum ( ¹ H-NMR spectrum) measurement.

The ion conductive group may be introduced in the form of a salt neutralized with a suitable metal ion (for example, alkali metal ion) or counter ion (for example, ammonium ion). For example, a block copolymer having a sulfonic acid group in a salt form can be obtained by ion exchange by an appropriate method.

The polymer electrolyte of the present invention can be added to various additives such as a softening agent, a stabilizer, a light stabilizer, an antistatic agent, a release agent, a flame retardant, a foaming agent, a pigment, and a dye as long as the effects of the present invention are not impaired. Further, each of them may contain a brightener or the like alone or in combination of two or more.

Examples of the softener include petroleum softeners such as paraffinic, naphthenic or aromatic process oils, paraffin, vegetable oil softeners, plasticizers, and the like.

Stabilizers include phenol-based stabilizers, sulfur-based stabilizers, phosphorus-based stabilizers, and the like. Specific examples include 2,6-di-tert-butyl-p-cresol, pentaerystyryl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) Benzene, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-to Azine, 2,2, -thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-tert- Butyl-4-hydroxy-hydrodinamide), 3,5-di-tert-butyl-4-hydroxy-benzylphosphonate-diethyl ester, tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate 3,9-bis {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxa Phenolic stabilizers such as spiro [5.5] undecane; pentaerythrityltetrakis (3-laurylthiopropionate), dis Sulfur stabilizers such as allyl 3,3′-thiodipropionate, dilauryl 3,3′-thiodipropionate, dimyristyl 3,3′-thiodipropionate; trisnonylphenyl phosphite, tris (2,4 Phosphorus stabilizers such as -di-tert-butylphenyl) phosphite, diasteryl pentaerythritol diphosphite, bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, etc. It is done.

From the viewpoint of ion conductivity, the content of the copolymer constituting the polymer electrolyte of the present invention is preferably 90% by mass or more, more preferably 93% by mass or more, and 95% by mass. % Or more is more preferable.

[Polymer electrolyte membrane]
The polymer electrolyte membrane of the present invention preferably has a thickness of 5 to 200 μm from the viewpoint of performance, membrane strength, handling properties, etc. required as a polymer electrolyte membrane for a polymer electrolyte fuel cell, More preferably, it is about 100 μm. When the film thickness is less than 5 μm, the mechanical strength of the film and the gas barrier property tend to be insufficient. On the other hand, when the film thickness is greater than 200 μm, the membrane resistance increases and sufficient proton conductivity does not appear, so the power generation characteristics of the battery tend to be low. The film thickness is more preferably 8 to 70 μm.

As a method for producing the polymer electrolyte membrane of the present invention, any method can be adopted as long as it is a normal method for such production. For example, the copolymer constituting the polymer electrolyte of the present invention and the above-described method The additive is mixed with an appropriate solvent to prepare a homogeneous solution or emulsion of 5% by mass or more of the copolymer, and then applied to a release-treated PET film using a coater or applicator. The film can be formed by using a known method such as a method of obtaining a polymer electrolyte membrane having a desired thickness by removing the solvent under appropriate conditions.

When the polymer electrolyte membrane of the present invention is produced using a uniform solution, the solvent used in the homogeneous solution is a solution having a viscosity that allows solution coating without destroying the structure of the polymer electrolyte. As long as it can be prepared, it is not particularly limited. Specifically, halogenated hydrocarbons such as methylene chloride, aromatic hydrocarbons such as toluene, xylene, and benzene, linear aliphatic hydrocarbons such as hexane and heptane, and cyclic aliphatic carbonization such as cyclohexane. Examples thereof include ethers such as hydrogen and tetrahydrofuran, alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol and isobutyl alcohol, or mixed solvents thereof.
Depending on the composition of the polymer block of the copolymer constituting the polymer electrolyte, the molecular weight, the ion exchange capacity, etc., one or more combinations of the above exemplified solvents may be appropriately selected and used. However, from the viewpoint of easy production of a tough polymer electrolyte membrane, a mixed solvent of toluene and isobutyl alcohol, a mixed solvent of toluene and isopropyl alcohol, a mixed solvent of cyclohexane and isopropyl alcohol, a mixed solvent of cyclohexane and isobutyl alcohol , Tetrahydrofuran solvent, a mixed solvent of tetrahydrofuran and methanol are preferable, and a mixed solvent of toluene and isobutyl alcohol and a mixed solvent of toluene and isopropyl alcohol are particularly preferable.

The case where a polymer electrolyte membrane is produced using the polymer electrolyte emulsion of the present invention will be described. The polymer electrolyte of the present invention has a protective colloid forming ability because the polymer block (A) having an ion conductive group is hydrophilic, and the polymer block (B) and the polymer block (C) are hydrophobic. An emulsion can be obtained without using a surfactant. In addition, by using a polar solvent such as water as a dispersion medium, particles having an ion conductive group having a high polarity in the outer shell can be easily produced.

Although a known method can be used as a method for preparing the emulsion, the phase inversion emulsification method is preferably applied in that an emulsion having a narrow particle size distribution can be obtained. That is, a polar solvent such as water is added while stirring a solution obtained by dissolving the polymer electrolyte in an appropriate organic solvent with an emulsifier. Initially, a polar solvent such as water is dispersed in the organic solvent system as particles, but when the polar solvent exceeds a certain amount, it becomes a co-continuous state, and the viscosity rapidly increases. Further, when a polar solvent is added, the polar solvent becomes a continuous phase and the organic solvent becomes fine particles, and the viscosity rapidly decreases. By using this method, an emulsion having a uniform particle size can be obtained.

However, if the emulsion has a large particle diameter exceeding 1 μm, the polymer electrolyte has a phase-separated structure within the particle, and not all ion-conducting groups have come out in the outer shell. Cannot be used effectively. Therefore, although it depends on the molecular weight of the copolymer constituting the polymer electrolyte and the ratio of each polymer block of the copolymer, it is desirable to make the particles finer until the average particle size becomes 1 μm or less. In many cases, since the average particle diameter in the pre-emulsification is 1 μm or more, further fine dispersion is required.
As a fine dispersion method, a known method can be used, but a method that does not use a medium such as a ball for grinding in a ball mill is preferable from the viewpoint of preventing impurities from being mixed. Specific examples include a high-pressure collision method.

In addition, after applying using a coater, applicator, etc., the solvent is removed under appropriate conditions to obtain a polymer electrolyte membrane having a desired thickness. Any conditions can be selected as long as the solvent can be completely removed at a temperature equal to or lower than the temperature at which the ion-conducting group is removed. In order to express desired physical properties, a plurality of temperatures may be arbitrarily combined, or a combination of ventilation and vacuum may be arbitrarily combined. Specifically, a method of removing the solvent by hot air drying at about 60 to 100 ° C. over 4 minutes, a method of removing the solvent in 2 to 4 minutes by hot air drying at about 100 to 140 ° C., After preliminarily drying at about 25 ° C. for about 1 to 3 hours and then drying with hot air drying at about 100 ° C. for several minutes, or after preliminary drying at about 25 ° C. for about 1 to 3 hours, 25 Examples include a method of drying for about 1 to 12 hours by vacuum drying under an atmosphere of about 40 ° C.
From the viewpoint of easily producing a polymer electrolyte membrane having good toughness, a method of removing the solvent by hot air drying at about 60 to 100 ° C. over 4 minutes, or preliminary drying at about 25 ° C. for about 1 to 3 hours And then drying by hot air drying at about 100 ° C. for several minutes, or by pre-drying at about 25 ° C. for about 1 to 3 hours, and then by vacuum drying in an atmosphere at about 25 to 40 ° C. A method of drying for about 12 hours is preferably used.

[Membrane-electrode assembly]
Next, a membrane-electrode assembly using the polymer electrolyte membrane of the present invention will be described. The production of the membrane-electrode assembly is not particularly limited, and a known method can be applied. For example, an ion conductive binder, a conductive catalyst carrier, and a catalyst paste containing a dispersion medium can be printed or sprayed. By applying and drying on the gas diffusion layer, a bonded body of the catalyst layer and the gas diffusion layer is formed, and then a pair of bonded bodies with the catalyst layer inside, hot pressing on both sides of the polymer electrolyte membrane, etc. The above catalyst paste is applied to both sides of the polymer electrolyte membrane by the printing method or spray method and dried to form a catalyst layer, and a gas diffusion layer is pressure-bonded to each catalyst layer by hot press etc. There is a way to make it.
As yet another production method, a solution or suspension containing an ion conductive binder is applied to both surfaces of the polymer electrolyte membrane and / or the catalyst layer surface of a pair of gas diffusion electrodes, and the polymer electrolyte membrane and the catalyst layer surface There is a method of bonding them together by thermocompression bonding. In this case, the solution or suspension may be applied to either the electrolyte membrane or the catalyst layer surface, or may be applied to both.
As another manufacturing method, first, the catalyst paste is applied to a base film made of polytetrafluoroethylene (PTFE) and dried to form a catalyst layer, and then a pair of base films on the base film is formed. The catalyst layer is transferred to both sides of the polymer electrolyte membrane by thermocompression bonding, and the base film is peeled off to obtain a joined body of the polymer electrolyte membrane and the catalyst layer. A gas diffusion layer is formed on each catalyst layer by hot pressing. There is a method of crimping.
In these methods, the ion conductive group may be converted into a salt with a metal such as sodium, and a treatment for returning to a proton type by an acid treatment after bonding may be performed.

Examples of the ion-conductive binder constituting the membrane-electrode assembly include existing perfluorosulfones such as “Nafion” (registered trademark, manufactured by DuPont) and “Gore-select” (registered trademark, manufactured by Gore). An ion conductive binder made of an acid polymer, an ion conductive binder made of sulfonated polyethersulfone or sulfonated polyetherketone, an ion conductive binder made of polybenzimidazole impregnated with phosphoric acid or sulfuric acid can be used. . Moreover, you may use the polymer electrolyte which comprises the polymer electrolyte membrane of this invention as an ion conductive binder.
In order to further improve the adhesion between the polymer electrolyte and the gas diffusion electrode, the same structure as the polymer electrolyte membrane located on the surface in close contact with the gas diffusion electrode (polymer repeating unit, copolymerization ratio, molecular weight) It is preferable to use an ion conductive binder having a common or similar ion conductive group, ion exchange capacity, etc., in particular, a polymer repeating unit or a common or similar ion conductive group). .

Regarding the constituent material of the catalyst layer of the membrane-electrode assembly, the conductive catalyst carrier is not particularly limited, and examples thereof include a carbon material. Examples of the carbon material include carbon black such as furnace black, channel black, and acetylene black, activated carbon, graphite, and the like. These may be used alone or in combination of two or more. The catalyst metal may be any metal that promotes the oxidation reaction of fuel such as hydrogen or methanol and the reduction reaction of oxygen, such as platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, Cobalt, nickel, chromium, tungsten, manganese, palladium, etc., or alloys thereof, for example, platinum-ruthenium alloy can be mentioned. Of these, platinum and platinum alloys are often used. The particle size of the catalytic metal is usually 10 to 300 angstroms. The amount of the catalyst metal supported on a conductive catalyst carrier such as carbon is small and advantageous in terms of cost. The catalyst layer may contain a water repellent as necessary. Examples of the water repellent include various thermoplastic resins such as polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene copolymer, and polyether ether ketone.

The gas diffusion layer of the membrane-electrode assembly is made of a material having conductivity and gas permeability, and examples of such a material include porous materials made of carbon fibers such as carbon paper and carbon cloth. Moreover, in order to improve water repellency, this material may be subjected to water repellency treatment.

[Polymer fuel cell]
By inserting the membrane-electrode assembly obtained by the method as described above between the conductive separator material that also serves as a gas supply flow path to the electrode separation and the electrode, a solid polymer fuel A battery is obtained. The membrane-electrode assembly of the present invention uses a pure hydrogen type using hydrogen as a fuel gas, a methanol reforming type using hydrogen obtained by reforming methanol, and hydrogen obtained by reforming natural gas. Natural gas reforming type, gasoline reforming type using hydrogen obtained by reforming gasoline, direct methanol type using methanol directly, etc. is there.

Hereinafter, the present invention will be more specifically described with reference to reference examples, examples and comparative examples, but the present invention is not limited to these examples.

(Measurement method of ion exchange capacity of block copolymer)
Weigh the block copolymer (weighing value a (g)) in a glass container that can seal the sample, add an excess amount of a saturated aqueous sodium chloride solution ((300 to 500) × a (ml)), and stir for 12 hours. did. Using phenolphthalein as an indicator, hydrogen chloride generated in water was titrated (a titration b (ml)) with a 0.01 N NaOH standard aqueous solution (titer f).
The ion exchange capacity was determined by the following formula.
Ion exchange capacity (meq / g) = (0.01 × b × f) / a

(Method for measuring the number average molecular weight of the block copolymer)
The number average molecular weight was measured by the gel permeation chromatography (GPC) method under the following conditions.
Device: manufactured by Tosoh Corporation, trade name: HLC-8220GPC
Eluent: THF
Column: manufactured by Tosoh Corporation, trade name: 1 TSK-GEL (TSKgel G3000HxL (inner diameter 7.6 mm, effective length 30 cm)), TSKgel Super Multipore HZ-M (inner diameter 4.6 mm, effective length 15 cm) 3 in total)
Column temperature: 40 ° C
Detector: RI
Liquid feed amount: 0.35 ml / min Number average molecular weight calculation: Standard polystyrene conversion

(Storage modulus and softening temperature)
Using a wide-range dynamic viscoelasticity measuring device (“DVE-V4FT Rheospectr” manufactured by Rheology Co., Ltd.), the polymer electrolyte membrane is heated in a tensile mode (frequency 11 Hz) from −80 ° C. to 250 ° C. The storage elastic modulus E ′, loss elastic modulus E ″ and loss tangent tan δ were measured at 3 ° C. per minute, and the peak temperature Tα (° C.) of the loss tangent was defined as the softening temperature. In addition, since the peak temperature of the loss tangent of a polymer block (C) and a polymer block (A) is near, it divided | segmented into each peak by the peak division | segmentation process, and specified the said peak temperature T (alpha) (degreeC).

[Reference Example 1: Production of block copolymer comprising polystyrene, hydrogenated polyisoprene and poly (4-tert-butylstyrene)]
In the same manner as described in WO2007 / 94185, 450 ml of dehydrated cyclohexane and 1.50 ml of sec-butyllithium (1.05 M-cyclohexane solution) were charged into a 1000 ml autoclave, and then 4-tert-butylstyrene 5 .20 ml, 14.3 ml of styrene, 5.20 ml of 4-tert-butylstyrene, 40.7 ml of isoprene, 5.20 ml of 4-tert-butylstyrene, 14.3 ml of styrene, and 5.20 ml of 4-tert-butylstyrene Added, polymerized at 60 ° C., poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-polyisoprene-b-poly (4-tert-butylstyrene) ) -B-polystyrene-b-poly (4-t rt- butylstyrene) (hereinafter, abbreviated as TSTITST) was synthesized.
The number average molecular weight of TSTITST obtained was 73,230, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) measurement was 94.0%, and the content of styrene units was 36. The content of 0% by mass and 4-tert-butylstyrene unit was 24.0% by mass.

A cyclohexane solution of synthesized TSTISTST was prepared and charged into a pressure-resistant vessel that had been sufficiently purged with nitrogen, and then a Ni / Al Ziegler-based hydrogenation catalyst was used under a hydrogen pressure of 0.5 to 1.0 MPa under a hydrogen pressure of 0.5 to 1.0 MPa. A hydrogenation reaction was carried out at a temperature of 18 ° C. for 18 hours, and poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-hydrogenated polyisoprene-b-poly (4-tert -Butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as TSSETST).
An attempt was made to calculate the amount of residual double bonds of the obtained TSETST by ¹ H-NMR (400 MHz) spectrum measurement, which was below the detection limit.

[Production Example 1: Synthesis of sulfonated TSSETST]
A sulfonating reagent was prepared by reacting 61.2 ml of acetic anhydride and 27.4 ml of sulfuric acid at 0 ° C. in 122 ml of methylene chloride by the same method as described in WO2007 / 94185. On the other hand, 30 g of the block copolymer TSETST obtained in Reference Example 1 was put in a glass reaction vessel equipped with a 3 L stirrer, vacuum-nitrogen introduction was repeated three times, and 400 ml of methylene chloride was added while nitrogen was introduced. The mixture was dissolved by stirring at room temperature for 4 hours. After dissolution, 176 ml of sulfonation reagent was added dropwise over 5 minutes. After stirring at room temperature for 48 hours, 22 ml of distilled water was added to stop the reaction. Thereafter, 500 ml of distilled water was gradually added dropwise with stirring to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.0 L of distilled water was added, and after washing with stirring, the solid content was collected by filtration. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the finally recovered polymer was vacuum-dried to obtain a sulfonated TSSETST, which is a copolymer constituting the polymer electrolyte of the present invention.
The sulfonation rate of the benzene ring of the styrene unit in the obtained sulfonated TSSETST was 100 mol% from ¹ H-NMR (400 MHz) analysis, and the result of titration was an ion exchange capacity of 2.71 meq / g.

[Reference Example 2: Production of block copolymer comprising polystyrene, hydrogenated polyisoprene and poly (4-tert-butylstyrene)]
In the same manner as in Reference Example 1, 675 ml of dehydrated cyclohexane and 2.30 ml of sec-butyllithium (1.05 M-cyclohexane solution) were charged into a 1400 mL autoclave, and then 13.0 ml of 4-tert-butylstyrene and 21.styrene of styrene. 9 ml, 4-tert-butylstyrene 13.0 ml, isoprene 37.1 ml, 4-tert-butylstyrene 13.0 ml, styrene 21.9 ml, and 4-tert-butylstyrene 13.0 ml were sequentially added at 60 ° C. Polymerized poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-polyisoprene-b poly (4-tert-butylstyrene) -b-polystyrene-b -Poly (4-tert-butylstyrene) (hereinafter TS Abbreviated as ITST) was synthesized.
The number average molecular weight of TSTITST obtained was 61,900, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) measurement was 94.0%, and the styrene unit content was 34. The content of 9% by mass and 4-tert-butylstyrene unit was 40.4% by mass.

[Production Example 2: Synthesis of sulfonated TSSETST]
In the same manner as in Production Example 1, a sulfonating reagent was prepared by reacting 61.5 ml of acetic anhydride and 27.5 ml of sulfuric acid at 123C in 123 ml of methylene chloride. On the other hand, 30 g of the block copolymer TSETST obtained in Reference Example 2 was put in a glass reaction vessel equipped with a 3 L stirrer, vacuum-nitrogen introduction was repeated three times, and 400 ml of methylene chloride was added with nitrogen introduced. The mixture was dissolved by stirring at room temperature for 4 hours. After dissolution, 177 ml of the sulfonation reagent was added dropwise over 5 minutes. After stirring at room temperature for 48 hours, 22 ml of distilled water was added to stop the reaction. Thereafter, 500 ml of distilled water was gradually added dropwise with stirring to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.0 L of distilled water was added, and after washing with stirring, the solid content was collected by filtration. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the finally recovered polymer was vacuum dried to obtain a sulfonated TSSETST, which is a copolymer constituting the polymer electrolyte of the present invention.
The sulfonation rate of the benzene ring of the styrene unit in the obtained sulfonated TSSETST was 100 mol% from ¹ H-NMR (400 MHz) analysis, and the ion exchange capacity was 2.61 meq / g as a result of titration.

[Reference Example 3: Production of block copolymer comprising polystyrene, hydrogenated polyisoprene and poly (4-tert-butylstyrene)]
In the same manner as in Reference Example 1, 519 ml of dehydrated cyclohexane and 2.36 ml of sec-butyllithium (1.0 M-cyclohexane solution) were charged into a 1400 mL autoclave, and then 21.6 ml of 4-tert-butylstyrene and 30.styrene of 30. 1 ml, 86.9 ml of isoprene, 30.1 ml of styrene and 21.6 ml of 4-tert-butylstyrene were added successively and polymerized at 60 ° C. to obtain poly (4-tert-butylstyrene) -b-polystyrene-b-polyisoprene. -B-Polystyrene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as TSIST) was synthesized.
The number average molecular weight of the obtained TSIST was 79,100, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) measurement was 94.0%, and the content of styrene units was 35. The content of 0% by mass and 4-tert-butylstyrene unit was 24.0% by mass.

A cyclohexane solution of the synthesized TSIST was prepared and charged in a pressure-resistant vessel that had been sufficiently purged with nitrogen. Then, using a Ni / Al Ziegler hydrogenation catalyst under a hydrogen pressure of 0.5 to 1.0 MPa, A hydrogenation reaction was carried out at 70 ° C. for 18 hours, and poly (4-tert-butylstyrene) -b-polystyrene-b-hydrogenated polyisoprene-b-polystyrene-b-poly (4-tert-butylstyrene) (hereinafter referred to as “poly (4-tert-butylstyrene)”) (Abbreviated as TSEST).
An attempt was made to calculate the amount of residual double bonds of the obtained TSEST by ¹ H-NMR (400 MHz) spectrum measurement, but it was below the detection limit.

[Production Example 3: Synthesis of sulfonated TSEST]
In the same manner as in Production Example 1, 59.5 ml of acetic anhydride and 26.6 ml of sulfuric acid were reacted in 119 ml of methylene chloride at 0 ° C. to prepare a sulfonation reagent. On the other hand, 30 g of the block copolymer TSEST obtained in Reference Example 3 was put in a glass reaction vessel equipped with a 3 L stirrer, vacuum-nitrogen introduction was repeated three times, and 400 ml of methylene chloride was added with nitrogen introduced. The mixture was dissolved by stirring at room temperature for 4 hours. After dissolution, 171 ml of the sulfonation reagent was added dropwise over 5 minutes. After stirring at room temperature for 48 hours, 22 ml of distilled water was added to stop the reaction. Thereafter, 500 ml of distilled water was gradually added dropwise with stirring to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.0 L of distilled water was added, and after washing with stirring, the solid content was collected by filtration. This washing and filtration operation is repeated until there is no change in the pH of the washing water, and the finally recovered polymer is vacuum-dried to obtain a sulfonated TSEST that is a copolymer that does not belong to the present invention. It was.
The sulfonation rate of the benzene ring of the styrene unit in the obtained sulfonated TSEST was 100 mol% from ¹ H-NMR (400 MHz) analysis, and the ion exchange capacity was 2.65 meq / g as a result of titration.

[Reference Example 4: Production of block copolymer comprising polystyrene, hydrogenated polyisoprene and poly (4-tert-butylstyrene)]
In the same manner as in Reference Example 3, a 1400 mL autoclave was charged with 600 ml of dehydrated cyclohexane and 5.57 ml of sec-butyllithium (1.0 M-cyclohexane solution), and then 35.6 ml of 4-tert-butylstyrene and 29.29 of styrene. 1 ml, 54.3 ml of isoprene, 29.1 ml of styrene and 35.6 ml of 4-tert-butylstyrene are added successively, polymerized at 60 ° C., and poly (4-tert-butylstyrene) -b-polystyrene-b-polyisoprene. -B-Polystyrene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as TSIST) was synthesized.
The number average molecular weight of the obtained TSIST was 26,000, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) measurement was 94.0%, and the styrene unit content was 33. The content of 4% by mass and 4-tert-butylstyrene unit was 42.2% by mass.

[Production Example 4: Synthesis of sulfonated TSEST]
In the same manner as in Production Example 1, 70.9 ml of acetic anhydride and 31.7 ml of sulfuric acid were reacted in 142 ml of methylene chloride at 0 ° C. to prepare a sulfonation reagent. On the other hand, 30 g of the block copolymer TSEST obtained in Reference Example 4 was put into a glass reaction vessel equipped with a 3 L stirrer, vacuum-nitrogen introduction was repeated three times, and 400 ml of methylene chloride was added while nitrogen was introduced. The mixture was dissolved by stirring at room temperature for 4 hours. After dissolution, 204 ml of sulfonation reagent was added dropwise over 5 minutes. After stirring at room temperature for 48 hours, 22 ml of distilled water was added to stop the reaction. Thereafter, 500 ml of distilled water was gradually added dropwise with stirring to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.0 L of distilled water was added, and after washing with stirring, the solid content was collected by filtration. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the finally recovered polymer was vacuum-dried to obtain a sulfonated TSEST, which is a copolymer that does not belong to the present invention. .
The sulfonation rate of the benzene ring of the styrene unit in the obtained sulfonated TSEST was 100 mol% from ¹ H-NMR (400 MHz) analysis, and the ion exchange capacity was 2.56 meq / g as a result of titration.

[Reference Example 5: Production of block copolymer composed of polystyrene, hydrogenated polyisoprene and poly (4-tert-butylstyrene)]
In the same manner as in Reference Example 1, 593 ml of dehydrated cyclohexane and 2.92 ml of sec-butyllithium (1.00 M-cyclohexane solution) were charged in a 1400 mL autoclave, then 11.9 ml of 4-tert-butylstyrene and 32.styrene. 6 ml, 4-tert-butylstyrene 11.90 ml, isoprene 59.0 ml, 4-tert-butylstyrene 11.9 ml, styrene 32.6 ml, and 4-tert-butylstyrene 11.9 ml were sequentially added at 60 ° C. Polymerized poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-polyisoprene-b-poly (4-tert-butylstyrene) -b-polystyrene- b-poly (4-tert-butylstyrene) Abbreviated as STITST) was synthesized.
The number average molecular weight of the obtained TSTITST was 64,100, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) measurement was 94.0%, and the content of styrene units was 41.100. The content of 0% by mass and 4-tert-butylstyrene unit was 29.0% by mass.

A cyclohexane solution of synthesized TSTISTST was prepared and charged into a pressure-resistant vessel that had been sufficiently purged with nitrogen, and then a Ni / Al Ziegler-based hydrogenation catalyst was used under a hydrogen pressure of 0.5 to 1.0 MPa under a hydrogen pressure of 0.5 to 1.0 MPa. A hydrogenation reaction was carried out for 18 hours at a temperature of poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-hydrogenated polyisoprene-b-poly (4-tert -Butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as TSSETST).
An attempt was made to calculate the amount of residual double bonds of the obtained TSETST by ¹ H-NMR (400 MHz) spectrum measurement, which was below the detection limit.

[Production Example 5: Synthesis of sulfonated TSSETST]
In the same manner as in Production Example 1, 63.7 ml of acetic anhydride and 28.5 ml of sulfuric acid were reacted in 127 ml of methylene chloride at 0 ° C. to prepare a sulfonation reagent. On the other hand, 30 g of the block copolymer TSETST obtained in Reference Example 5 was placed in a glass reaction vessel equipped with a 3 L stirrer, vacuum-nitrogen introduction was repeated three times, and 400 ml of methylene chloride was added while nitrogen was introduced. The mixture was dissolved by stirring at room temperature for 4 hours. After dissolution, 200 ml of the sulfonation reagent was added dropwise over 5 minutes. After stirring at room temperature for 48 hours, 22 ml of distilled water was added to stop the reaction. Thereafter, 500 ml of distilled water was gradually added dropwise with stirring to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.0 L of distilled water was added, and after washing with stirring, the solid content was collected by filtration. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the finally recovered polymer was vacuum dried to obtain a sulfonated TSSETST, which is a copolymer constituting the polymer electrolyte of the present invention.
The sulfonation rate of the benzene ring of the styrene unit in the obtained sulfonated TSSETST was 100 mol% from ¹ H-NMR (400 MHz) analysis, and the ion exchange capacity was 3.00 meq / g as a result of titration.

[Reference Example 6: Production of block copolymer comprising polystyrene, hydrogenated polyisoprene and poly (4-tert-butylstyrene)]
In the same manner as in Reference Example 1, after charging 514 ml of dehydrated cyclohexane and 1.95 ml of sec-butyllithium (1.00 M-cyclohexane solution) into a 1000 mL autoclave, 5.8 ml of 4-tert-butylstyrene, 16. 1 ml, 4-tert-butylstyrene 5.8 ml, styrene 16.1 ml, 4-tert-butylstyrene 5.8 ml, isoprene 42.6 ml, and 4-tert-butylstyrene 5.8 ml were sequentially added at 60 ° C. Polymerized, poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-polyisoprene- b-poly (4-tert-butylstyrene) (hereinafter TSTST) Abbreviated as T) was synthesized.
The number average molecular weight of TSTSTIT obtained was 38,700, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) measurement was 94.0%, and the content of styrene units was 36. The content of 0% by mass and 4-tert-butylstyrene unit was 25.0% by mass.

A cyclohexane solution of synthesized TSTSTIT was prepared and charged into a pressure-resistant vessel that had been sufficiently purged with nitrogen, and then a Ni / Al Ziegler hydrogenation catalyst was used under a hydrogen pressure of 0.5 to 1.0 MPa under a hydrogen pressure of 0.5 to 1.0 MPa. Hydrogenation reaction was carried out at 18 ° C. for 18 hours, and poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) ) -B-hydrogenated polyisoprene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as TSTSTET) was obtained. An attempt was made to calculate the residual double bond amount of the obtained TSTSTET by ¹ H-NMR (400 MHz) spectrum measurement, which was below the detection limit.

[Production Example 6: Synthesis of sulfonated TSTSTET]
In the same manner as in Production Example 1, 18.3 ml of acetic anhydride and 8.2 ml of sulfuric acid were reacted in 36.5 ml of methylene chloride at 0 ° C. to prepare a sulfonation reagent. On the other hand, 10 g of the block copolymer TSTSTET obtained in Reference Example 6 was put into a glass reaction vessel equipped with a 2 L stirrer, vacuum-nitrogen introduction was repeated three times, and 125 ml of methylene chloride was added with nitrogen introduced. The mixture was dissolved by stirring at room temperature for 4 hours. After dissolution, 57.2 ml of the sulfonation reagent was added dropwise over 5 minutes. After stirring at room temperature for 48 hours, 22 ml of distilled water was added to stop the reaction. Thereafter, 400 ml of distilled water was gradually added dropwise with stirring to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.0 L of distilled water was added, and after washing with stirring, the solid content was collected by filtration. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the finally recovered polymer was vacuum dried to obtain a sulfonated TSTSTET which is a copolymer constituting the polymer electrolyte of the present invention.
The sulfonation rate of the benzene ring of the styrene unit of the obtained sulfonated TSTSTET was 92 mol% from ¹ H-NMR (400 MHz) analysis, and the ion exchange capacity was 2.50 meq / g as a result of titration.

[Reference Example 7: Production of block copolymer comprising polystyrene, hydrogenated polyisoprene and poly (4-tert-butylstyrene)]
In the same manner as in Reference Example 1, 500 ml of dehydrated cyclohexane and 3.2 ml of sec-butyllithium (1.10 M-cyclohexane solution) were charged into a 1000 ml autoclave, and then 6.0 ml of 4-tert-butylstyrene and 26.styrene of 26. 5 ml, 4-tert-butylstyrene 6.0 ml, isoprene 24.3 ml, 4-tert-butylstyrene 6.0 ml were sequentially added, polymerized at 60 ° C., and poly (4-tert-butylstyrene) -b-polystyrene. -B-poly (4-tert-butylstyrene) -b-polyisoprene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as TSTIT) was synthesized.
The number average molecular weight of TSTIT obtained was 49,000, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) measurement was 94.0%, and the content of styrene units was 44. The content of 0% by mass and 4-tert-butylstyrene unit was 20.6% by mass.

A synthesized cyclohexane solution of TSTIT was prepared and charged into a pressure-resistant vessel that had been sufficiently purged with nitrogen, and then a Ni / Al Ziegler hydrogenation catalyst was added to poly (4-tert-butylstyrene) -b-polystyrene-b. -Poly (4-tert-butylstyrene) -b-hydrogenated polyisoprene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as TSETET) was obtained.
An attempt was made to calculate the amount of residual double bonds in the obtained TSETET by ¹ H-NMR (400 MHz) spectrum measurement, which was below the detection limit.

[Production Example 7: Synthesis of sulfonated TSSET]
In the same manner as in Production Example 1, a sulfonation reagent was prepared by reacting 22.9 ml of acetic anhydride and 10.2 ml of sulfuric acid at 125C in 125 ml of methylene chloride. On the other hand, 10 g of the block copolymer TSETET obtained in Reference Example 7 was put in a glass reaction vessel equipped with a 2 L stirrer, vacuum-nitrogen introduction was repeated three times, and 400 ml of methylene chloride was added with nitrogen introduced. The mixture was dissolved by stirring at room temperature for 4 hours. After dissolution, 71.7 ml of the sulfonation reagent was added dropwise over 5 minutes. After stirring at room temperature for 48 hours, 22 ml of distilled water was added to stop the reaction. Thereafter, 500 ml of distilled water was gradually added dropwise with stirring to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.0 L of distilled water was added, and after washing with stirring, the solid content was collected by filtration. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the finally recovered polymer was vacuum dried to obtain a sulfonated TSSET which is a copolymer that does not belong to the present invention. .
The sulfonation rate of the benzene ring of the styrene unit of the obtained sulfonated TSETET was 95 mol% from ¹ H-NMR (400 MHz) analysis, and the ion exchange capacity was 3.00 meq / g as a result of titration.

Table 1 shows the composition, structure and properties of the copolymers obtained in Production Examples 1 to 7.

<Example 1>
(Production of polymer electrolyte membrane)
The polymer electrolyte membrane of the present invention was prepared using the copolymer obtained in Production Example 1 as the polymer electrolyte of the present invention. An 18% by mass toluene / isobutyl alcohol (mass ratio 7/3) solution of the sulfonated TSSETST (ion exchange capacity 2.71 meq / g) obtained in Production Example 1 was prepared, and a release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)] was coated with a thickness of about 300 μm, and dried with a hot air dryer at 100 ° C. for 4 minutes to obtain a film with a thickness of 30 μm.

<Example 2>
(Production of polymer electrolyte membrane)
The polymer electrolyte membrane of the present invention was prepared using the copolymer obtained in Production Example 2 as the polymer electrolyte of the present invention. A 12% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of the sulfonated TSSETST (ion exchange capacity 2.61 meq / g) obtained in Production Example 2 was prepared, and a release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)] with a thickness of about 125 μm, dried with a hot air dryer at 100 ° C. for 4 minutes, and then again with the solution with a thickness of about 350 μm. The film was coated and dried in a hot air dryer at 100 ° C. for 4 minutes to obtain a film having a thickness of 30 μm.

<Example 3>
(Production of polymer electrolyte membrane)
The polymer electrolyte membrane of the present invention was prepared using the copolymer obtained in Production Example 5 as the polymer electrolyte of the present invention. A 18% by weight toluene / isobutyl alcohol (mass ratio 75/25) solution of the sulfonated TSSETST (ion exchange capacity 3.00 meq / g) obtained in Production Example 5 was prepared, and a release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)] was coated with a thickness of about 300 μm, and dried with a hot air dryer at 100 ° C. for 4 minutes to obtain a film with a thickness of 30 μm.

<Example 4>
(Production of polymer electrolyte membrane)
The polymer electrolyte membrane of the present invention was prepared using the copolymer obtained in Production Example 6 as the polymer electrolyte of the present invention. A 10.2% by mass toluene / isobutyl alcohol (mass ratio 9/1) solution of the sulfonated TSTSTET (ion exchange capacity 2.50 meq / g) obtained in Production Example 6 was prepared, and a release-treated PET film [ MRV (trade name) manufactured by Mitsubishi Resin Co., Ltd.] was coated with a thickness of about 275 μm, dried with a hot air dryer at 100 ° C. for 4 minutes, and then the solution was further coated thereon with about 150 μm. A film having a thickness of 30 μm was obtained by coating with a thickness and drying with a hot air dryer at 100 ° C. for 4 minutes.

<Comparative Example 1>
(Production of polymer electrolyte membrane)
A 17% by weight toluene / isobutyl alcohol (mass ratio 7/3) solution of the sulfonated TSEST (ion exchange capacity 2.65 meq / g) obtained in Production Example 3 was prepared, and a release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)] was coated with a thickness of about 350 μm, and dried with a hot air dryer at 100 ° C. for 4 minutes to obtain a film with a thickness of 30 μm.

<Comparative Example 2>
(Production of polymer electrolyte membrane)
A 13% by mass toluene / isobutyl alcohol (mass ratio 85/15) solution of the sulfonated TSEST (ion exchange capacity 2.56 meq / g) obtained in Production Example 4 was prepared, and a release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)] with a thickness of about 200 μm, dried in a hot air dryer at 100 ° C. for 4 minutes, and then again with the solution at a thickness of about 250 μm. The film was coated and dried in a hot air dryer at 100 ° C. for 4 minutes to obtain a film having a thickness of 30 μm.

<Comparative Example 3>
(Production of polymer electrolyte membrane)
A 15% by weight toluene / isobutyl alcohol (mass ratio 75/25) solution of the sulfonated TSSET (ion exchange capacity 3.00 meq / g) obtained in Production Example 7 was prepared, and a release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)] was coated with a thickness of about 350 μm and dried with a hot air dryer at 100 ° C. for 4 minutes, but a uniform film with many thickness variations could not be obtained. It was.

(Examples 1 to 4 and Comparative Examples 1 to 3: Performance Test of Polymer Electrolyte Membrane and Results thereof)
In the following tests 1) to 3), the polymer electrolyte membranes obtained in each Example and Comparative Example were evaluated.

1) Measurement of proton conductivity A 1 cm × 4 cm test piece was cut out from the obtained polymer electrolyte membrane, sandwiched between a pair of gold electrodes, and attached to an open cell. The measurement cell was placed in an atmosphere at a temperature of 80 ° C. and a relative humidity of 30%, and the proton conductivity was measured by the AC impedance method.

2) Power generation test of single cell for polymer electrolyte fuel cell using hydrogen The output performance of the single cell for polymer electrolyte fuel cell produced using the obtained polymer electrolyte membrane was evaluated. In addition, the single cell for polymer electrolyte fuel cells was produced in the following procedures.
A 10% by mass aqueous dispersion of Nafion is added to and mixed with Pt—Ru alloy catalyst-supporting carbon so that the mass ratio of carbon to Nafion is 1: 1, and then n-propyl alcohol is added to water / n-propyl. The mixture was added and mixed until the alcohol mass ratio became 1/1 to prepare a uniformly dispersed paste. This paste was uniformly applied to one side of the carbon paper by a spray method. The electrode for anode was produced by drying at 130 ° C. for 30 minutes.
Further, a 10% by mass solution of Nafion was added to and mixed with Pt catalyst-supporting carbon so that the mass ratio of carbon to Nafion was 1: 0.75, and then n-propyl alcohol was added to water / n-propyl alcohol. Was added and mixed until the mass ratio became 1/1, to prepare a uniformly dispersed paste, and a cathode electrode was produced in the same manner as the anode side.
Thereafter, the polymer electrolyte membranes produced in Examples and Comparative Examples were sandwiched between the two kinds of electrodes so that the membrane and the catalyst surface face each other, and the outside was sandwiched between two heat resistant films and two stainless steel plates. The membrane-electrode assembly was produced by sandwiching in order and hot pressing (115 ° C., 20 kg / cm ² , 8 min).
Next, the membrane-electrode assembly produced is sandwiched between two conductive separators that also serve as gas supply channels, and the outside is sandwiched between two current collector plates and two clamping plates to form a solid. An evaluation cell (electrode area is 25 cm ² ) for a polymer fuel cell was produced.

In the power generation test, hydrogen was used as the fuel and air was used as the oxidant. The supply conditions of hydrogen were stoichiometric 1.5 and humidification 30% R.V. H. It was. The air supply conditions were stoichiometric 2.0 and humidification 30% R.V. H. It was.
The cell temperature was set to 80 ° C., and the evaluation cell was set. 100% R.D. H. A pre-treatment was performed using hydrogen and oxygen that were humidified, and a power generation test was conducted to evaluate the cell voltage at 1 A / cm ² .

3) Measurement of film strength (tear strength) After making a 5 cm incision into a 2.5 cm × 7.5 cm dumbbell-shaped test piece in the long axis direction and immersing the test piece in 25 ° C. water for 12 hours, It was set in a 5566 type tensile tester manufactured by Instron Japan, and the stress was measured under the conditions of 25 ° C., relative humidity 50%, and tensile speed 250 mm / min.

Table 2 shows the performance test results of 1) to 3) regarding the polymer electrolyte membranes prepared in Examples 1 to 4 and Comparative Examples 1 and 2.

The polymer electrolyte membranes of the present invention shown in Examples 1 to 4 have equivalent ionic conductivity and power generation characteristics as compared with the polymer electrolyte membranes of Comparative Examples 1 and 2, and have a tear strength when wet. It was confirmed to be excellent.
Moreover, when it had a block structure like the comparative example 3, film forming property was bad and it was difficult to form into a film, and it was confirmed that the structure of the polymer electrolyte of this invention is important.
As described above, the membrane-electrode assembly and the polymer electrolyte fuel cell using the polymer electrolyte membrane of the present invention are excellent from the viewpoint of durability.

Industrial applicability

According to the present invention, a polymer electrolyte suitable for a solid polymer fuel cell, a polymer electrolyte membrane using the polymer electrolyte, and a polymer electrolyte membrane having good bondability with an electrode, and a membrane comprising the polymer electrolyte membrane An electrode assembly and a polymer electrolyte fuel cell using the membrane-electrode assembly and having both output characteristics and mechanical strength when wet can be provided.

Claims

Two polymer blocks (A) having an ion conductive group, one polymer block (B) having no ion conductivity, and four polymer blocks (C) having no ion conductivity as constituent components The polymer block (B) has a softening temperature lower by 20 ° C. or more than the polymer block (C), and the polymer block (A) and the polymer block A polymer electrolyte, wherein both ends of (B) are bonded to the polymer block (C).
The polymer electrolyte according to claim 1, wherein the polymer block (A) is composed of a repeating unit of an aromatic vinyl compound unit.
The polymer block (C) is represented by the following general formula (a):

Wherein R 1 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R 2 to R 4 each independently represents a hydrogen atom or an alkyl group having 3 to 8 carbon atoms, but at least one of them is carbon 3. The polymer electrolyte according to claim 1, wherein the polymer electrolyte is a repeating unit of an aromatic vinyl compound unit represented by formula (3).
The polymer block (B) is composed of at least one repeating unit selected from alkene units having 2 to 8 carbon atoms and conjugated diene units having 4 to 8 carbon atoms. The polymer electrolyte according to any one of the above.
The ion-conductive group is a group represented by -SO 3 M or -PO 3 HM (wherein M represents a hydrogen atom, an ammonium ion, or an alkali metal ion). The polymer electrolyte described in 1.
A polymer electrolyte membrane comprising the polymer electrolyte according to any one of claims 1 to 5.
A membrane-electrode assembly comprising the polymer electrolyte membrane according to claim 6.
A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 7.