JP5792018B2 - Polymer electrolyte membrane, membrane-electrode assembly, and polymer electrolyte fuel cell - Google Patents

Description

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

  In recent years, fuel cells have attracted attention as highly efficient power generation systems. 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), and generating electricity by supplying a fuel made of a reducing agent to the anode and an oxidant to the cathode, From the viewpoints of low temperature operability, reduction in size and weight, etc., application to automobile power supplies, portable equipment power supplies, and household cogeneration systems that simultaneously use electricity and heat are being studied.

Accordingly, various polymer electrolyte membranes suitable for solid polymer fuel cells have been proposed.
For example, the main component is a block copolymer containing a polymer block (A) composed of a structural unit derived from an aromatic vinyl compound having an ion conductive group and a flexible polymer block (B) in a predetermined ratio. 25 ° C., tensile speed 500 mm / min. There has been proposed a polymer electrolyte membrane having a 100% modulus in a tensile test under the conditions of 15 MPa or less, a breaking strength of 15 MPa or more, and a breaking elongation of 300% or more (see Patent Document 1). Such a polymer electrolyte membrane has high bondability with an electrode.

JP 2010-67526 A

The interior of the polymer electrolyte fuel cell is in a high humidity atmosphere during startup and in a low humidity atmosphere during shutdown. A polymer electrolyte membrane used for a polymer electrolyte fuel cell swells in a high humidity atmosphere and contracts in a low humidity atmosphere. In recent years, in polymer applications where the use of polymer electrolyte fuel cells is expected, the polymer electrolyte fuel cells are frequently started and stopped repeatedly. For this reason, the polymer electrolyte membrane is required to have durability against membrane breakage (hereinafter simply referred to as “durability”) as the polymer electrolyte fuel cell is repeatedly started and stopped.
On the other hand, in order to quickly start power generation at the time of startup, the polymer electrolyte membrane needs to be excellent in ion conductivity in a low humidity atmosphere. As a means for increasing ion conductivity, it is common to increase the content (ion exchange capacity) of ion conductive groups in the polymer electrolyte membrane. However, the durability tends to decrease as the ion exchange capacity in the polymer electrolyte membrane is increased. From this point of view, the polymer electrolyte membrane disclosed in Patent Document 1 still has room for improvement.

  Accordingly, an object of the present invention is to provide a polymer electrolyte membrane having both durability and high ion conductivity in a low humidity atmosphere; a membrane-electrode assembly including the polymer electrolyte membrane; and the membrane-electrode assembly. The object is to provide a polymer electrolyte fuel cell.

According to the present invention, the above object is
[1] A polymer block (A ₀ ) having no ion conductive group, an amorphous olefin polymer block (B) having no ion conductive group, and the following general formula having no ion conductive group The polymer block (A ₀ ) is composed of 7 or 8 polymer blocks composed of an aromatic vinyl compound polymer block (C) composed of repeating units of structural units derived from the aromatic vinyl compound represented by (a). ) Or the polymer block (C) as a terminal polymer block, and the polymer block (Z ₀ ) in which the polymer block bonded to both ends of the polymer block (B) is only the polymer block (C), It has a structure in which an ion conductive group is introduced into the polymer block (A ₀ ), and has a temperature of 25 ° C., a relative humidity of 50%, and a tensile speed of 500 mm / min. A polymer electrolyte membrane containing a block copolymer (Z) having an elongation at break of 300% or more;
[ 2 ] The polymer electrolyte membrane according to [1], wherein the polymer block (A ₀ ) having no ion conductive group is a polymer block composed of a structural unit derived from an aromatic vinyl compound;
[3] The ion-conducting group is, -SO ₃ M or _-PO 3 HM (wherein, M represents a hydrogen atom, an ammonium ion or an alkali metal ion) above is a group represented by [1] or [2 any of the polymer electrolyte membrane];
[ 4 ] The polymer electrolyte membrane according to any one of [1] to [ 3 ], wherein the polymer block (B) is an amorphous olefin polymer block having a softening temperature of 30 ° C. or lower;
[ 5 ] A membrane-electrode assembly comprising the polymer electrolyte membrane according to any one of [1] to [ 4 ]; and [ 6 ] a solid polymer fuel cell comprising the membrane-electrode assembly according to [ 5 ]. Achieved by providing.

（式中、Ｒ^１は水素原子又は炭素数１〜４のアルキル基を表し、Ｒ^２〜Ｒ^４はそれぞれ独立して水素原子又は炭素数３〜８のアルキル基を表し、かつＲ^２〜Ｒ^４の少なくとも１つは炭素数３〜８のアルキル基を表す）

Wherein R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ^{2 to} R ⁴ each independently represents a hydrogen atom or an alkyl group having 3 to 8 carbon atoms, and R ^{2 to} R ^At least one of ⁴ represents an alkyl group having 3 to 8 carbon atoms)

  According to the present invention, a polymer electrolyte membrane excellent in durability and ion conductivity in a low-humidity atmosphere; a membrane-electrode assembly comprising the polymer electrolyte membrane; and a solid polymer type comprising the membrane-electrode assembly A fuel cell can be provided.

[Block copolymer]
The block copolymer (Z) constituting the polymer electrolyte membrane of the present invention is a polymer block (A ₀ ) having no ion conductive group (hereinafter simply referred to as “polymer block (A ₀ )”). ), An amorphous olefin polymer block (B) having no ion conductive group (hereinafter, sometimes simply referred to as “polymer block (B)”), and having no ion conductive group It consists of 7 or 8 polymer blocks consisting of an aromatic vinyl compound polymer block (C) (hereinafter sometimes simply referred to as “polymer block (C)”), and the polymer block (A ₀ ) A polymer block of a block copolymer (Z ₀ ) in which the polymer block (C) is a terminal polymer block and the polymer block bonded to both ends of the polymer block (B) is only the polymer block (C) ( A ₀ ) It has a structure in which an on conductive group is introduced to form a polymer block (A).

Here, for convenience, the polymer block (A ₀ ), the polymer block (B), and the polymer block (C) are described above. However, the polymer block (A ₀ ) is the polymer block (B) or the polymer. The polymer block (A ₀ ) is indistinguishable from the block (C) in terms of structure, and a polymer block that becomes an polymer block (A) by introducing an ion conductive group is a polymer block (A ₀ ). That is, the block copolymer (Z ₀ ) has the polymer block (A) or the polymer block (C) as a terminal polymer block, and the polymer block bonded to both ends of the polymer block (B) is a polymer block. The block copolymer (A) of the block copolymer (Z) that is only (C) has a structure in which the ion conductive group of the block copolymer (A) is replaced with hydrogen to form a polymer block (A ₀ ).

From the viewpoint of durability of the polymer electrolyte membrane containing the block copolymer (Z), the block copolymer (Z) has a temperature of 25 ° C., a relative humidity of 50%, and a tensile speed of 500 mm / min. The elongation at break is 300% or more, preferably in the range of 350 to 1000%, and more preferably in the range of 400 to 800%.
Here, the elongation at break was determined by preparing a film having a thickness of 30 μm from the block copolymer (Z), punching out a dumbbell-shaped test piece, and adjusting the humidity under conditions of 25 ° C. and 50% relative humidity. Machine, 25 ° C., relative humidity 50%, tensile speed 500 mm / min. Measure under the following conditions. The film can be obtained by applying a solution obtained by dissolving the block copolymer (Z) in an appropriate solvent on the release film, drying and removing the solvent, and then removing the solvent from the release film.

The number average molecular weight of the block copolymer (Z ₀ ) is preferably 11,000 to 500,000, more preferably 14,000 to 450,000, and more preferably 17,000 to 350,000 as the number average molecular weight in terms of standard polystyrene. 000 is more preferable, and 20,000 to 300,000 is particularly preferable.

The block copolymer (Z ₀ ) is 15 to 45% by mass of a polymer block (A ₀ ) having no ion conductive group and 15 to 35% by mass of a polymer block (B) having no ion conductive group. % And polymer block (C) having no ion conductivity of 35 to 55% by mass.

In the block copolymer (Z ₀ ), the mass ratio (A ₀ : C) of the total amount of the polymer block (A ₀ ) and the total amount of the polymer block (C) is 80:20 to 10:90. Is more preferable, 75:25 to 15:85 is more preferable, and 65:35 to 20:80 is still more preferable. When the mass ratio of the polymer block (C) becomes too small, it becomes difficult to maintain the strength during drying and wetting. 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 block obtained from the block copolymer (Z ₀ ) The polymer electrolyte membrane containing the copolymer (Z) tends to have low ionic conductivity.

In the block copolymer (Z ₀ ), the mass ratio (B: C) of the total amount of the polymer block (B) and the total amount of the polymer block (C) is preferably 85:15 to 5:95. 75:25 to 10:90 is more preferable, and 70:30 to 12:88 is more preferable. When (B: C) is in the above range, the polymer electrolyte membrane containing the block copolymer (Z) obtained from the block copolymer (Z ₀ ) is excellent in shape retention and toughness.

The block copolymer (Z) is composed of 7 or 8 polymer blocks comprising the polymer block (A), the polymer block (B), and the polymer block (C), and the polymer block (A) or The polymer block (C) is a terminal block, and the polymer block bonded to both ends of the polymer block (B) is composed of only the polymer block (C).
The block copolymer (Z) has a structure in which an ion conductive group is introduced into the polymer block (A ₀ ) of the block copolymer (Z ₀ ), and the polymer block (A) is a polymer block (A ₀ ). It is a polymer block having a structure in which an ion conductive group is introduced.

  The amount of ion-conductive group introduced is usually the ion exchange capacity of the block copolymer (Z) in order to exhibit sufficient ion conductivity for use as a polymer electrolyte membrane for a polymer electrolyte fuel cell. 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, and particularly preferably 1.80 meq / g or more. preferable. On the other hand, from the viewpoint of water resistance of the polymer electrolyte membrane, the ion exchange capacity of the block copolymer (Z) is preferably 4.00 meq / g or less, more preferably 3.60 meq / g or less. The amount that is 3.20 meq / g or less is more preferable.

  The ion exchange capacity of the block copolymer (Z) can be calculated using an acid-base titration method.

  In the block copolymer (Z), the polymer block (B) functions as a phase responsible for the elasticity and flexibility of the polymer electrolyte membrane containing the block copolymer (Z). In the block copolymer (Z), both ends of the polymer block (B) are bonded to the polymer block (C) functioning as a constraining phase. That is, the block copolymer (Z) has a block bond of (C)-(B)-(C). As a result, a decrease in mechanical strength when wet is suppressed, and the elongation at break is improved. It is estimated that the heat resistance is further improved.

On the other hand, in general, an α-β-γ type block copolymer in which a polymer block (α) and a polymer block (γ) sandwich a polymer block (β) is formed between a polymer block (α) and a polymer block. Each (γ) forms a domain with another polymer and forms a bridge structure sandwiching the polymer block (β) to express mechanical strength (in this case, the form of the chain taken by the polymer block (β) Called the bridge chain). On the other hand, when the block copolymer forms a loop structure and the polymer block (α) and the polymer block (γ) form the same domain, and the loop structure is formed, the ratio of the bridge structure decreases, so the mechanical strength Decreases. That is, the mechanical strength can be increased by reducing the loop structure and increasing the bridge structure.
Since the block copolymer (Z) has a block bond of (A)-(C)-(B)-, only the bridge structure is formed, and the polymer block (C) forms a bridge chain. From this, it is presumed that the mechanical strength of the polymer electrolyte membrane containing the block copolymer (Z) is improved.

  When the block copolymer (Z) is composed of seven polymer blocks, the bonding mode of the polymer block includes A-C-A-C-B-C-A, A-C-B-C -B-C-A, C-A-C-B-C-A-C, C-A-C-A-C-B-C, C-B-C-A-C-B-C, C -B-C-B-C-A-C and the like are mentioned, but from the viewpoint of suppressing membrane breakage when the polymer electrolyte membrane swells, both ends of the polymer block (A) function as a constraining phase. C-A-C-B-C-A-C, C-A-C-A-C-B-C, and C-B-C-A-C- having structures linked to the polymer block (C) B-C and C-B-C-B-C-A-C are preferable, and C-A-C-B-C-A-C and C-A-C-A-C-B-C are more preferable. From the viewpoint of film forming properties, C-A-C-B-C-A-C Preferred in La.

  When the block copolymer (Z) is composed of eight polymer blocks, at least one of the terminal polymer blocks is the polymer block (A), thereby improving the ionic conductivity of the polymer electrolyte membrane. It is advantageous from the viewpoint. Further, when preparing a coating liquid containing the block copolymer (Z) of the present invention and a solvent or a dispersion medium, which will be described later, the coating liquid is an emulsion liquid containing water as a dispersion medium. It is thought that the emulsification stability of the is increased. Specific examples of the bonding mode of the polymer block include A-C-B-C-A-C-A-C, A-C-A-C-A-C-B-C, and A-C-A- C-B-C-A-C, A-C-B-C-B-C-A-C, A-C-B-C-A-C-B-C, A-C-A-C- B-C-B-C, A-C-B-C-B-C-B-C, etc. are mentioned, but from the viewpoint of ionic conductivity, mechanical strength when wet, film forming property, etc., A-C -A-C-B-C-A-C is preferred.

  A block copolymer (Z) may be used individually by 1 type, or may use multiple types together.

(Polymer block (A))
The polymer block (A) constituting the block copolymer (Z) is different in polarity and structure from the polymer block (B) and is different in polarity from the polymer block (C), so microphase separation is likely to occur. . The polymer block (A) is a polymer electrolyte membrane containing a block copolymer (Z) in order to form an ion channel in a state of microphase separation with the polymer block (B) and the polymer block (C). It is presumed that it is advantageous in increasing the ionic conductivity.

The polymer block (A) has a structure in which an ion conductive group is introduced into a polymer block (A ₀ ) having no ion conductive group in the block copolymer (Z ₀ ). As described later, the block copolymer (Z) is prepared by, for example, producing a specific block copolymer (Z ₀ ) having no ion-conductive group, and then producing a heavy polymer in the block copolymer (Z ₀ ). It can be prepared by selectively introducing ion-conducting groups on polymer block in the position to be converted into polymer block _(a) (a 0).
As the polymer block (A ₀ ), a polymer block comprising a structural unit derived from an aromatic vinyl compound, a polyetherketone block, a polysulfide block, a polyphosphazene block, a polyphenylene block, a polybenzimidazole block, a polyethersulfone 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 And polymer blocks such as polymethacrylate blocks. Among them, polymers selected from polymer blocks composed of structural units derived from aromatic vinyl compounds, polyether ketone blocks, polysulfide blocks, polyphosphazene blocks, polyphenylene blocks, polybenzimidazole blocks, polyethersulfone blocks, and polyphenylene oxide blocks. From the viewpoint that the block is preferable and easy to produce, a polymer block composed of a structural unit derived from an aromatic vinyl compound is more preferable.

  The aromatic ring contained in the structural unit derived from the aromatic vinyl compound 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 the aromatic vinyl compound include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 2,4-dimethylstyrene, and 2,5-dimethylstyrene. 3,5-dimethylstyrene, 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, vinylbiphenyl, vinylterphenyl, vinylnaphthalene, vinylanthracene, 4-phenoxystyrene, and the like. These aromatic vinyl compounds may be used individually by 1 type, or may use multiple types together.

When only one kind of the aromatic vinyl compound is used alone, it is preferable to use any one of styrene, α-methylstyrene, vinylbiphenyl, and 1,1-diphenylethylene. It is preferable to select a plurality of types from the group consisting of -methylstyrene, 4-methylstyrene, 4-ethylstyrene, α-methyl-4-methylstyrene, α-methyl-2-methylstyrene. In the case where these plural kinds of aromatic vinyl compounds are used in combination, the polymer block (A ₀ ) is preferably formed by random copolymerization.

  It is desirable that the aromatic ring of such an aromatic vinyl compound has no substituent that inhibits the reaction for introducing an ion conductive group. For example, when the aromatic ring is a benzene ring, if the hydrogen (particularly hydrogen at the 4-position) on the benzene ring is substituted with an alkyl group (particularly an alkyl group having 3 or more carbon atoms) or the like, an ion conductive group Therefore, it is preferable that the aromatic ring does not have other substituents, or has a substituent capable of introducing an ion conductive group, such as an aryl group. . Also, from the viewpoint of easy introduction of ion conductive groups, high density of ion conductive groups, etc., among the above aromatic vinyl compounds, those having 8 to 15 carbon atoms such as styrene, α-methylstyrene, vinyl biphenyl and the like. Aromatic vinyl compounds are more preferred.

  In the aromatic vinyl compound, among the hydrogen atoms on the vinyl group, the hydrogen atom bonded to the α-position carbon atom (α-carbon atom) of the aromatic ring is substituted with another substituent, and α -The structure in which a carbon atom is a quaternary carbon atom may be used. Examples of the substituent in which the hydrogen atom bonded to the α-carbon atom may be substituted include, for example, an alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group). , An isobutyl group, a sec-butyl group, or a tert-butyl group), a halogenated alkyl group having 1 to 4 carbon atoms (chloromethyl group, 2-chloroethyl group, 3-chloroethyl group, etc.), a phenyl group, and the like. As specific examples, α-methylstyrene, α-methyl-4-methylstyrene, α-methyl-4-ethylstyrene, α-methyl-2-methylstyrene, and 1,1-diphenylethylene are preferable.

When the polymer block (A ₀ ) is a polymer block composed of a structural unit derived from an aromatic vinyl compound, the polymer block (A ₀ ) contains a structural unit derived from another monomer as long as the effects of the present invention are not impaired. May be. Examples of such other monomers include conjugated dienes having 4 to 8 carbon atoms (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.), C2-C8 alkene (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) acrylate (methyl (meth) acrylate, ethyl (meth) acrylate, (meth) ) Butyl acrylate, etc.), vinyl esters (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.), vinyl ether (methyl vinyl ether) Le, isobutyl vinyl ether, etc.), and the like. It is preferable that the monomer and the aromatic vinyl compound form a polymer block (A ₀ ) by random copolymerization. It is preferable that the content rate of the structural unit derived from the said other monomer is 5 mol% or less of the structural unit which comprises a polymer block ( _A0 ).

The molecular weight per polymer block (A ₀ ) is usually preferably in the range of 1,000 to 100,000 as the number average molecular weight in terms of standard polystyrene, and in the range of 2,000 to 70,000. More preferably, it is more preferably in the range of 3,000 to 50,000, and particularly preferably in the range of 4,000 to 30,000.
If the molecular weight is 1,000 or more, microphase separation is likely to occur, and ion channels are easily formed. Therefore, ion conductivity tends to be high, and mechanical properties tend to be excellent. For example, the moldability and film formability of the polymer electrolyte membrane are improved.

The polymer block (A) in the block copolymer (Z) has an ion conductive group. In addition, a proton etc. are mentioned as an ion in the case of mentioning ion conductivity by this invention.
As the ion conductive group, any polymer electrolyte membrane and membrane-electrode assembly containing the block copolymer (Z) may be a group capable of exhibiting sufficient ionic conductivity. For example, a cation such as proton is conducted. as ion-conducting _{group, -SO 3 M, -PO 3 HM} , -CO ( wherein, M represents a hydrogen atom, an ammonium ion or an alkali metal ion) 2 M sulfonic acid group represented by, a phosphonic acid group, a carboxyl A sulfonic acid group represented by —SO ₃ M or —PO ₃ HM (wherein M is as defined above), from the viewpoint of exhibiting a particularly high cation conductivity. Phosphonic acid groups or their salts are preferred.

It is not necessary for all the structural units constituting the polymer block (A) to have an ion conductive group, and the introduction amount of the ion conductive group can be appropriately controlled according to the required 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 at random into the structural unit which comprises a polymer block ( _A0 ). In the case of a structural unit having an aromatic ring, the ion conductive group is preferably on the aromatic ring from the viewpoint of facilitating ion channel formation. In the case of a structural unit derived from an aromatic vinyl compound, if there is an ion conductive group on the aromatic ring, the radical resistance of the block copolymer (Z) is improved.

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

(Polymer block (B))
The polymer block (B) constituting the block copolymer (Z) is an amorphous olefin polymer block having no ion conductive group. Here, the amorphous olefin polymer block is a polymer block composed of structural units derived from olefins and refers to an amorphous one. Amorphous property can be confirmed by the measurement of dynamic viscoelasticity by the absence of a change in storage elastic modulus derived from the crystalline olefin polymer. In the polymer electrolyte membrane of the present invention using the block copolymer (Z), the polymer block (B) is likely to undergo microphase separation with the polymer block (A) and the polymer block (C), and the operating temperature range. In the production of a membrane-electrode assembly and a polymer electrolyte fuel cell, it is excellent in moldability (assembling property, bonding property, tightening property, etc.).

The softening temperature of the polymer block (B) is preferably 50 ° C. or lower, more preferably 40 ° C. or lower, and further preferably 30 ° C. or lower.
Examples of the structural unit derived from the olefin constituting the polymer block (B) include 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 carbon. Examples thereof include vinylcycloalkene units having 7 to 10 carbon atoms, conjugated diene units having 4 to 8 carbon atoms, and conjugated cycloalkadiene units having 5 to 8 carbon atoms. One of these may be present alone, or a plurality of these may be present.

Examples of the olefin include ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 1-heptene, 2-heptene, 1-octene and 2-octene. C2-C8 alkene such as cyclopentene, cyclohexene, cycloheptene and cyclooctene, etc. C5-C8 cycloalkene such as vinylcyclopentane, vinylcyclohexane, vinylcycloheptane and vinylcyclooctane Vinylcycloalkane; vinylcycloalkene having 7 to 10 carbon atoms such as vinylcyclopentene, vinylcyclohexene, vinylcycloheptene, vinylcyclooctene; butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4- Hexadiene, 2, -Conjugated dienes having 4 to 8 carbon atoms such as dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene; 5-carbon atoms such as cyclopentadiene and 1,3-cyclohexadiene 8 conjugated cycloalkadienes. These monomers may be used individually by 1 type, or may use multiple types together.
When a plurality of types of monomers are used in combination, these monomers are preferably randomly copolymerized to form the polymer block (B).

When the monomer for forming the polymer block (B) has a plurality of carbon-carbon double bonds, any of them may be used for polymerization, for example, 1,2-bond in the case of a conjugated diene. It may be any unit of units or 1,4-bond units. A polymer block formed by polymerizing a conjugated diene usually retains a carbon-carbon double bond, but from the viewpoint of improving heat deterioration resistance, a hydrogenation reaction after polymerization (hereinafter referred to as “hydrogenation reaction”). The carbon-carbon double bond is preferably hydrogenated (hereinafter referred to as “hydrogenation”). The hydrogenation rate of such a carbon-carbon double bond (hereinafter referred to as “hydrogenation rate”) is preferably 30 mol% or more, more preferably 50 mol% or more, and further preferably 95 mol% or more. Thus, the deterioration of a polymer electrolyte membrane can be suppressed by reducing the carbon-carbon double bond in a polymer block (B).
The hydrogenation rate of the carbon-carbon double bond can be calculated by ¹ H-NMR measurement.

  When the block copolymer (Z) is used as a polymer electrolyte membrane, the polymer block (B) is elastic and flexible in the operating temperature range, and is a membrane-electrode assembly or solid polymer type. From the viewpoint of excellent formability (assembleability, bondability, tightenability, etc.) in the production of a fuel cell, an alkene unit having 2 to 8 carbon atoms, a cycloalkene unit having 5 to 8 carbon atoms, and a vinyl having 7 to 10 carbon atoms. The polymer block is preferably a polymer block comprising at least one structural unit selected from the group consisting of a cycloalkene unit, a conjugated diene unit having 4 to 8 carbon atoms, and a conjugated cycloalkadiene unit having 5 to 8 carbon atoms. It is more preferably a polymer block composed of at least one structural unit selected from 3 to 8 alkene units and conjugated diene units having 4 to 8 carbon atoms, and alkene units having 4 to 6 carbon atoms and More preferably a polymer block comprising at least one structural unit selected from the conjugated diene units of prime 4-6.

Of the above, more preferable as the alkene unit is an isobutene unit, two structural units based on a butadiene unit (1-butene unit, 2-butene unit), and three structural units based on an isoprene unit (2-methyl). -1-butene unit, 3-methyl-1-butene unit, 2-methyl-2-butene unit), and from the viewpoint of high flexibility, two structural units (1-butene unit, 2 -Butene unit) or three structural units based on isoprene units (2-methyl-1-butene unit, 3-methyl-1-butene unit, 2-methyl-2-butene unit) are most preferred. Most preferred as conjugated diene units are butadiene units and isoprene units.
Further, when a block copolymer (Z ₀ ) having no ion conductive group is polymerized and then introduced into the block copolymer (Z) by introducing an ion conductive group, the polymer block (B) is saturated. A hydrocarbon structure is preferable because an ion conductive group is hardly introduced into the polymer block (B). Therefore, when the hydrogenation reaction of the carbon-carbon double bond remaining in the polymer block (B) after polymerizing the block copolymer (Z ₀ ) having no ion conductive group is performed, the ion conductive group It is desirable to do it before introducing.

  In addition to the structural unit, the polymer block (B) may have other single amounts within a range that does not impair the purpose of the polymer block (B) to impart elasticity to the block copolymer (Z) in the operating temperature range. For example, 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 ethers (methyl vinyl ether, isobutyl vinyl ether, etc.) ) Etc. may contain other structural units. In this case, it is preferable that the above-mentioned olefin and these other monomers are randomly copolymerized to form the polymer block (B). The content of structural units derived from these other monomers is preferably 5 mol% or less of the structural units constituting the polymer block (B).

  The molecular weight per polymer block (B) is usually preferably in the range of 5,000 to 250,000, and in the range of 7,000 to 150,000, as the number average molecular weight in terms of standard polystyrene. Is more preferable, and the range of 8,000 to 100,000 is more preferable, and the range of 10,000 to 70,000 is particularly preferable.

(Polymer block (C))
The polymer block (C) constituting the block copolymer (Z) is a polymer block composed of a structural unit derived from an aromatic vinyl compound having no ion conductive group. The polymer block (C) has a polarity different from that of the polymer block (A) and a structure different from that of the polymer block (B), so that microphase separation is likely to occur. The polymer block (C) is in a microphase-separated state from the polymer block (A) and the polymer block (B), and the softening temperature (that is, the polymer block (C) becomes a polymer independently) It is presumed that it functions as a constraining phase when used at a temperature lower than that, which is advantageous in enhancing the durability of the polymer electrolyte membrane containing the block copolymer (Z).

The softening temperature of the polymer block (C) may be 20 ° C. or more higher than the softening temperature of the polymer block (B) (softening temperature when the polymer block (B) independently becomes a polymer). Preferably, from the viewpoint of functioning as a constraining phase in a wide use temperature range, it is more preferably 40 ° C. or higher, and more preferably 70 ° C. or higher, compared to the softening temperature of the polymer block (B).
From the same viewpoint, the softening temperature of the polymer block (C) is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, and further preferably 100 ° C. or higher.

  As the polymer block (C), the following general formula (a)

（式中、Ｒ^１は水素原子又は炭素数１〜４のアルキル基を表し、Ｒ^２〜Ｒ^４はそれぞれ独立して水素原子又は炭素数３〜８のアルキル基を表し、かつＲ^２〜Ｒ^４の少なくとも１つは炭素数３〜８のアルキル基を表す）
で示される芳香族ビニル化合物に由来する構造単位からなる重合体ブロックが、合成が容易であり、かつ拘束相として機能するという観点から好ましい。また、イオン伝導性基を有さないブロック共重合体（Ｚ_０）を重合した後に重合体ブロック（Ａ_０）にイオン伝導性基を導入する場合に、Ｒ^２〜Ｒ^４が存在することで、重合体ブロック（Ｃ）へのイオン伝導性基の導入が妨げられる。さらに、該重合体ブロックの軟化温度が高くなるので、使用温度域を広くすることができる。

Wherein R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ^{2 to} R ⁴ each independently represents a hydrogen atom or an alkyl group having 3 to 8 carbon atoms, and R ^{2 to} R ^At least one of ⁴ represents an alkyl group having 3 to 8 carbon atoms)
A polymer block composed of a structural unit derived from an aromatic vinyl compound represented by the formula (1) is preferred from the viewpoint of easy synthesis and functioning as a constraining phase. In addition, when an ion conductive group is introduced into the polymer block (A ₀ ) after polymerizing the block copolymer (Z ₀ ) having no ion conductive group, R ^{2 to} R ⁴ are present. , Introduction of an ion conductive group into the polymer block (C) is hindered. Furthermore, since the softening temperature of the polymer block is increased, the operating temperature range can be widened.

  Examples of the aromatic vinyl compound for forming the structural unit represented by the general formula (a) include 4-propylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-isobutylstyrene, and 4-tert-butylstyrene. , 4-octyl styrene, α-methyl-4-tert-butyl styrene, α-methyl-4-isopropyl styrene, and the like. 4-tert-butyl styrene, 4-isopropyl styrene, α-methyl-4-tert- Butyl styrene and α-methyl-isopropyl styrene are more preferred. These may be used individually by 1 type, or may use multiple types together. When two or more of the above aromatic vinyl compounds are used in combination, it is preferable that these are randomly copolymerized to form a polymer block (C).

  The polymer block (C) is a monomer that does not impair the effects of the present invention, such as conjugated dienes having 4 to 8 carbon atoms (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 ester ( Methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, etc.), vinyl esters (vinyl acetate, vinyl propionate, vinyl butyrate, pivalic acid) Sulfonyl, etc.), vinyl ethers (methyl vinyl ether, may contain a structural unit derived from isobutyl vinyl ether) and the like. It is preferable that the aromatic vinyl compound and the other monomer are randomly copolymerized to form a polymer block (C). The content of structural units derived from these other monomers is preferably 5 mol% or less of the structural units constituting the polymer block (C).

  The molecular weight per polymer block (C) is usually preferably in the range of 1,000 to 50,000 as the number average molecular weight in terms of standard polystyrene, and is in the range of 1,500 to 30,000. Is more preferable, and the range of 2,000 to 20,000 is even more preferable. If the molecular weight is 1,500 or more, the mechanical properties of the polymer electrolyte membrane tend to be excellent, and if it is 50,000 or less, the moldability and film-forming property of the polymer electrolyte are good.

(Method for producing block copolymer (Z))
Process for producing the block copolymer (Z) is not particularly limited, but may be a known method, after production of the block copolymer (Z _0), a method of introducing an ion-conducting group is preferred.

The production method of the block copolymer (Z ₀ ) includes the polymer block (A ₀ ), the polymer block (B), the type of monomer units constituting the polymer block (C), and the Depending on the molecular weight and the like, a radical polymerization method, an anionic polymerization method, a cationic polymerization method, a coordination polymerization method and the like can be appropriately selected, but industrially preferred are a radical polymerization method, an anionic polymerization method and a cationic polymerization method. In particular, the living polymerization method is preferable from the viewpoint of molecular weight control, molecular weight distribution control, and polymer structure control, and specifically, a living radical polymerization method, a living anion polymerization method, and a living cation polymerization method are preferable.

A specific example will be described below.
Polymer block (C) composed of a structural unit represented by the general formula (a) such as 4-tert-butylstyrene, polymer block composed of a structural unit derived from an aromatic vinyl compound such as styrene ( When producing a block copolymer (Z ₀ ) having no ion-conducting group consisting of a polymer block (B) composed of a structural unit derived from A ₀ ) and a conjugated diene, a living anion polymerization method is preferred. . Specifically, a block copolymer obtained by sequentially polymerizing monomers in a solvent such as cyclohexane in the presence of an anionic polymerization initiator such as an organic lithium compound at 10 to 100 ° C. is blocked. It can be a copolymer (Z ₀ ).

Further, the block copolymer obtained by hydrogenating the carbon-carbon double bond of the polymer block composed of the structural unit derived from the conjugated diene of the block copolymer thus obtained is used as a block copolymer. It may be a polymer (Z ₀ ). In this case, the amorphous olefin polymer block after the hydrogenation reaction becomes the polymer block (B). As a method for the hydrogenation reaction, a solution of a block copolymer obtained by living anionic polymerization is charged into a pressure vessel, a Ziegler catalyst such as Ni / Al is added, and the hydrogenation reaction is performed in a hydrogen atmosphere. The method of performing can be illustrated.

Next, an ion conductive group is introduced into the polymer block (A ₀ ) of the block copolymer (Z ₀ ) to obtain the block copolymer (Z).
A method (sulfonation) for introducing a sulfonic acid group into the polymer block (A ₀ ) of the block copolymer (Z ₀ ) will be described. For the sulfonation, a known sulfonation method can be applied. For example, a block copolymer (Z ₀ ) and an organic solvent are mixed to prepare a solution or suspension, and a sulfonating agent is added. Examples thereof include a method of adding a gaseous sulfonating agent to the copolymer (Z ₀ ).

  Examples of sulfonating agents 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, 2, 4 And aromatic organic sulfonic acids such as 6-trimethylbenzenesulfonic acid. Examples of the organic solvent include halogenated hydrocarbons such as methylene chloride, and aliphatic hydrocarbons such as hexane and cyclohexane. These may be used individually by 1 type, or may be used in mixture of multiple types.

Next, a method (phosphonation) for introducing a phosphonic acid group into the polymer block (A ₀ ) of the block copolymer (Z ₀ ) will be described. For phosphonation, a known method can be applied. For example, a block copolymer (Z ₀ ) and an organic solvent are mixed to prepare a solution or a suspension, and anhydrous aluminum chloride and chloromethyl ether are added to add a fragrance. A method in which a halomethyl group is introduced into a ring, followed by addition of phosphorus trichloride and anhydrous aluminum chloride, followed by a hydrolysis reaction; a block copolymer (Z ₀ ) and an organic solvent are mixed to prepare a solution or suspension Then, after adding phosphorus trichloride and anhydrous aluminum chloride and introducing a phosphinic acid group into the aromatic ring, nitric acid is added to oxidize the phosphinic acid group to form a phosphonic acid group.

  The ion conductive group such as a sulfonic acid group or a phosphonic acid group may be a salt neutralized with a counter ion such as an alkali metal ion or an ammonium ion.

  The reaction solution containing the block copolymer (Z) after carrying out the reaction for introducing an ion conductive group by the above method is prepared by pouring the reaction solution into water to deposit the block copolymer (Z) and then organically depositing the block copolymer (Z). It can be isolated by a method of distilling off the solvent and water, a method of gradually adding water as a terminator to the reaction solution to precipitate the block copolymer (Z), and then distilling off the solvent and water. Among these, from the viewpoint of finely dispersing the block copolymer (Z) and increasing the washing efficiency with water in the isolation step, water is gradually added to the reaction solution to precipitate the block copolymer (Z). Is preferred.

[Polymer electrolyte membrane]
The polymer electrolyte membrane of the present invention contains a block copolymer (Z). The polymer electrolyte membrane is a composition containing such a block copolymer (Z) or block copolymer (Z) (hereinafter referred to as “a composition containing a block copolymer (Z) or a block copolymer (Z)”). "Is simply referred to as a" composition containing a block copolymer (Z) "), but it is liquid-permeable to a polymer electrolyte layer comprising a composition containing the block copolymer (Z). A high reinforcing material layer may be laminated. The content of the block copolymer (Z) in the composition containing the block copolymer (Z) is preferably 90 to 100% by mass, and 93% by mass or more from the viewpoint of ion conductivity. It is more preferable that it is 95 mass% or more.
The reinforcing material layer is required to have high liquid permeability, and is preferably a porous material having a plurality of through holes penetrating the main surface of the reinforcing material layer, and more preferably a woven fabric and a non-woven fabric. Among these, non-woven fabrics are more preferable from the viewpoints of workability (easiness of compounding with electrolyte, ease of thinning of reinforcing material, etc.), and availability of materials, and from the viewpoint of low water absorption, acid resistance, and chemical resistance. Therefore, a nonwoven fabric made of liquid crystal polyester fiber mainly composed of aromatic units is particularly preferable. Polymer electrolyte membranes having these nonwoven fabrics as reinforcing material layers have good durability and output characteristics when used in solid polymer fuel cells.
When the reinforcing material layer is a porous material, the composition containing the block copolymer (Z) may be impregnated in part or all of the inside of the porous material.

  In the polymer electrolyte membrane of the present invention, the film thickness is preferably in the range of 5 to 500 μm, more preferably in the range of 7 to 200 μm, and in the range of 8 to 80 μm from the viewpoint of membrane strength, handling properties, and the like. More preferably.

  When the polymer electrolyte membrane of the present invention is composed only of the composition containing the block copolymer (Z), the film thickness is preferably in the range of 5 to 200 μm from the viewpoint of gas barrier properties and membrane resistance. More preferably, it is in the range of 7 to 100 μm, and more preferably in the range of 8 to 70 μm. If the film thickness is 5 μm or more, the mechanical properties and gas barrier properties of the film tend to be sufficient. On the other hand, if the film thickness is 200 μm or less, the film resistance becomes small and sufficient ion conductivity is exhibited, so that power generation characteristics tend to be good.

  When the polymer electrolyte membrane of the present invention is formed by laminating a polymer electrolyte layer made of a composition containing the block copolymer (Z) and a reinforcing material layer, the thickness of the polymer electrolyte layer is the gas From the viewpoint of blocking properties and membrane resistance, the range is preferably 5 to 200 μm, more preferably 7 to 100 μm, and still more preferably 8 to 70 μm. The ratio of the thickness of the polymer electrolyte layer and the reinforcing material layer is preferably in the range of 5:95 to 80:20, more preferably in the range of 10:90 to 70:30, and 20: More preferably, it is in the range of 80-60: 40. The thickness of the reinforcing material layer is preferably 100 μm or less, more preferably in the range of 3 to 70 μm, and still more preferably in the range of 5 to 30 μm.

  The polymer electrolyte membrane 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 pigment, a dye, and a whitening agent unless the effects of the present invention are impaired. An agent or the like may be contained. Each of these additives may contain only one kind or plural kinds. These additives are usually mixed with the block copolymer (Z) to form a composition, which then becomes a polymer electrolyte membrane.

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

  Examples of the stabilizer include a phenol stabilizer, a sulfur stabilizer, and a phosphorus stabilizer. Examples of the phenol-based stabilizer include 2,6-di-t-butyl-p-cresol, pentaerystyryl-tetrakis [3- (3,5-di-t-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-hydroxy) Phenyl) propionate, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 2,4-bis (n-octylthio) -6- (4-hydroxy-3) , 5-Di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) Propionate], N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrodinamide), 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester, tris (3 , 5-Di-t-butyl-4-hydroxybenzyl) isocyanurate, 3,9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1, 1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5.5] undecane, etc .; sulfur stabilizers such as pentaerythrityltetrakis (3-laurylthiopropionate), distearyl 3,3′-thiodipropionate, dilauryl 3,3′-thiodipropionate, dimyristyl 3,3′-thiodipropionate Phosphorus stabilizers such as tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, diasterylpentaerythritol diphosphite, bis (2,6-di) -T-butyl-4-methylphenyl) pentaerythritol diphosphite, phosphorus alone and the like.

Examples of the light stabilizer include compounds having a 2,2,6,6-tetraalkylpiperidine skeleton and hindered amines.
Examples of hindered amines include dimethyl succinate / 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly ((6- (1,1,3 , 3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2,2,6,6-tetramethyl-4-pipedyl) imino) hexamethylene ((2,2, 6,6-tetramethyl-4-pipedyl) imino)), 2- (2,3-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2, 6,6-pentamethyl-4-piperidyl), 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl) -4-piperidyl), N, N′-bis (3-a Minopropyl) ethylenediamine / 2,4-bis (N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino) -6-chloro-1,3,5-triazine condensate Bis (2,2,6,6-tetramethyl-4-pipedyl) sebacate and bis (2,2,6,6-tetramethyl-4-piperidyl) succinate are mentioned.
These light stabilizers may be used alone or in combination.

  Examples of the antistatic agent include stearoamidopropyldimethyl-β-hydroxyethylammonium nitrate.

  Examples of the mold release agent include higher alcohol and / or glycerin monoester. Examples of the higher alcohol include cetyl alcohol and stearyl alcohol. Examples of the glycerin monoester include higher fatty acid glycerides such as stearic acid monoglyceride and stearic acid diglyceride.

  Examples of the flame retardant include organic halogen flame retardants such as tetrabromobisphenol A, decabromodiphenyl oxide, and brominated polycarbonate; non-halogen flame retardants such as antimony oxide, aluminum hydroxide, zinc borate, and tricresyl phosphate. Is mentioned.

  Examples of pigments, dyes, and brighteners include terphenyl, fluorescent pigments, fluorescent dyes, fluorescent white dyes, fluorescent brighteners, and fluorescent bleaching agents.

As a method for producing the polymer electrolyte membrane of the present invention, for example, the block copolymer (Z) and, if necessary, the above-mentioned additives are mixed with an appropriate solvent, and the block copolymer (Z) is mixed with 5 A coating solution containing at least mass% is prepared, applied to a release-treated PET film using a coater or applicator, etc., and the solvent is removed under appropriate conditions, thereby forming a polymer electrolyte membrane having a desired thickness. The method of obtaining etc. are mentioned.
As a production method in the case where the polymer electrolyte membrane has a reinforcing material layer, the coating liquid prepared by the above-described method is applied to a release-treated PET film or the like using a coater or an applicator, and then an appropriate method. By removing the solvent under conditions, a polymer electrolyte membrane having a desired thickness was obtained, and then a reinforcing material was laminated on the obtained polymer electrolyte membrane, and then separately prepared on the reinforcing material by the method described above. The method of apply | coating a coating liquid using a coater, an applicator, etc. and removing a solvent on suitable conditions is mentioned.

The coating liquid may be a solution, a dispersion, or an emulsion as long as the uniformity and stability of the block copolymer (Z) are high. Examples of the solvent or dispersion medium used for the coating liquid include halogenated hydrocarbons such as methylene chloride; aromatic hydrocarbons such as toluene, xylene, and benzene; aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; ethers such as tetrahydrofuran. Alcohols such as methanol, ethanol, propanol, 2-propanol, butanol, isobutyl alcohol; water.
Among these, from the viewpoint of solubility of the block copolymer (Z), a mixed solvent of toluene and isobutyl alcohol, a mixed solvent of toluene and 2-propanol, a mixed solvent of cyclohexane and 2-propanol, a mixed solvent of cyclohexane and isobutyl alcohol, A mixed solvent of tetrahydrofuran, tetrahydrofuran and methanol is preferable, and a mixed solvent of toluene and isobutyl alcohol and a mixed solvent of toluene and 2-propanol are particularly preferable. In addition, the mixing ratio (mass ratio) of the mixed solvent can be appropriately selected.

  After applying the coating solution prepared by the above method to a reinforcing material such as a nonwoven fabric or a base film such as a PET film after mold release treatment using a coater or applicator, the solvent is removed under appropriate conditions. To form a polymer electrolyte layer having a desired thickness. When the polymer electrolyte layer is formed on the reinforcing material, the polymer electrolyte membrane is composed of the polymer electrolyte layer and the reinforcing material layer. When the polymer electrolyte layer is formed on the base film, the polymer electrolyte membrane can be obtained by peeling off the base film.

  The conditions for removing the solvent from the applied coating solution may be within a temperature range in which ion conductive groups such as sulfonic acid groups possessed by the block copolymer (Z) do not fall off. A plurality of temperatures may be combined, or drying under ventilation and drying under reduced pressure may be combined. For example, a method of removing the solvent in a short time by hot air drying in the range of 60 to 100 ° C., a method of removing the solvent in a short time by hot air drying at about 100 to 140 ° C., or 1 to 3 hours at 25 ° C. A method of drying to a certain degree, followed by drying with hot air at 100 ° C. for a short time, a method of drying at about 25 ° C. for about 1 to 3 hours, and then drying at about 25 to 40 ° C. under reduced pressure for about 1 to 12 hours. Can be mentioned. From the viewpoint of easy production of a polymer electrolyte membrane having good mechanical properties, a method of removing the solvent over 4 minutes or more by hot air drying at about 60 to 100 ° C., or preliminary drying at about 25 ° C. for about 1 to 3 hours And then drying with hot air drying at about 100 ° C. over several minutes, or pre-drying at about 25 ° C. for about 1 to 3 hours, and then about 1 to 12 under reduced pressure at about 25 to 40 ° C. A method of drying for about an hour or the like is preferably used.

[Membrane-electrode assembly]
The membrane-electrode assembly of the present invention includes the above-described polymer electrolyte membrane of the present invention. There is no particular limitation on the method for producing the membrane-electrode assembly, and a known method can be applied. For example, a catalyst paste containing an ion conductive binder, a conductive catalyst carrier and a dispersion medium can be printed or sprayed. By applying onto the gas diffusion layer and drying, a joined body of the catalyst layer and the gas diffusion layer is formed, and each of the catalyst layers is in contact with the polymer electrolyte membrane with the two joined bodies thus formed. The catalyst paste is applied to both surfaces of the polymer electrolyte membrane by printing or spraying and dried to form catalyst layers, and gas is applied to each catalyst layer by hot pressing or the like. Method of pressure bonding a diffusion layer; a solution or suspension containing an ion conductive binder is applied to both surfaces of a polymer electrolyte membrane and / or a catalyst layer surface of a pair of gas diffusion electrodes, and polymer electrolysis A method in which the membrane and the catalyst layer surface are bonded together and bonded by thermocompression bonding or the like; 2 in which the catalyst paste is applied to a base film made of polytetrafluoroethylene (PTFE) and dried to form a catalyst layer Prepare a sheet, sandwich each catalyst layer in contact with the polymer electrolyte membrane, transfer the catalyst layer to both sides of the polymer electrolyte membrane by thermocompression bonding, and then peel off the base film to remove the polymer electrolyte membrane and the catalyst. And a method in which a gas diffusion layer is pressure-bonded to each catalyst layer by hot pressing. In these methods, the above-mentioned operation is performed in a state where the ion conductive group of the polymer electrolyte membrane containing the block copolymer (Z) is made into a salt with a metal such as sodium, and the acid treatment after joining is performed. You may return to the proton type.

  Examples of the ion conductive binder used in the production of the membrane-electrode assembly include perfluorosulfonic acid such as “Nafion” (registered trademark, manufactured by DuPont) and “Gore-select” (registered trademark, manufactured by Gore). Polymers, sulfonated polyethersulfone, sulfonated polyetherketone, polybenzimidazole impregnated with phosphoric acid or sulfuric acid, and the like can be used. Moreover, you may use the block copolymer (Z) 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 membrane and the gas diffusion electrode, the same structure as the polymer electrolyte membrane (polymer repeating unit, copolymerization ratio, molecular weight, ion conductive group, ion exchange capacity) Etc. are common or similar; in particular, it is preferable to use an ion conductive binder having a polymer structural unit and an ion conductive group common or similar).

  Examples of the conductive catalyst carrier constituting the catalyst layer formed in the membrane-electrode assembly include carbon blacks such as furnace black, channel black and acetylene black, and carbon materials such as activated carbon and graphite. These may be used individually by 1 type, or may use multiple types together. The catalyst metal only needs to have an action of promoting the oxidation reaction of fuel such as hydrogen or methanol and the reduction reaction of oxygen. For example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt Nickel, chromium, tungsten, manganese, or alloys thereof. Of these, platinum and platinum-ruthenium alloys are usually used. The particle size of the catalytic metal is usually 10 to 300 angstroms. It is advantageous in terms of cost to use these on the conductive catalyst carrier described above. Further, the catalyst layer may contain a water repellent such as polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene copolymer, polyetheretherketone, if necessary.

  The gas diffusion layer of the membrane-electrode assembly is composed 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 the water repellency of the gas diffusion layer, a water repellency treatment may be performed.

[Polymer fuel cell]
In the polymer electrolyte fuel cell of the present invention, the membrane-electrode assembly of the present invention described above is inserted between a conductive separator material that also serves as a chamber for separation of the polar chamber and a gas supply flow path to the electrode. Is obtained.
The polymer electrolyte fuel cell of the present invention includes a pure hydrogen type using hydrogen, a methanol reforming type using hydrogen obtained by reforming methanol, and a hydrogen obtained by reforming natural gas, depending on the fuel used. Can be classified into a natural gas reforming type using hydrogen, a gasoline reforming type using hydrogen obtained by reforming gasoline, a direct methanol type using methanol directly.

  Hereinafter, although a reference example, an example, and a comparative example are given and the present invention is explained concretely, the present invention is not limited to these.

(Measurement method of ion exchange capacity of block copolymer (Z))
The block copolymers (1) to (4) (block copolymer (Z)) obtained in each Example and Comparative Example were weighed (weighed value a (g)), and an excess amount of a saturated sodium chloride aqueous solution (( 300-500) × a (ml)) was added and stirred in a closed system for 12 hours. Using phenolphthalein as an indicator, hydrogen chloride generated in water was titrated (a titration amount b (ml)) with a 0.01 N standard aqueous sodium hydroxide solution (titer f).
From the above results, the ion exchange capacity of the block copolymer (Z) was determined by the following equation.
Ion exchange capacity (meq / g) = (0.01 × b × f) / a

(Measurement method of number average molecular weight of block copolymer (Z ₀ ))
The number average molecular weight of the block copolymer (Z ₀ ) was measured by the gel permeation chromatography (GPC) method under the following conditions.
Device: manufactured by Tosoh Corporation, trade name: HLC-8220GPC
Eluent: Tetrahydrofuran Column: manufactured by Tosoh Corporation, trade name: 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) ) 2 in total 3 connected in series)
Column temperature: 40 ° C
Detector: RI
Liquid feed amount: 0.35 ml / min Number average molecular weight calculation: Standard polystyrene conversion

(Manufacture of test membrane)
In order to measure the physical properties of the following 1) to 3) for the block copolymers (1) to (4) obtained in Examples and Comparative Examples described later, test membranes were produced.

(Manufacture of test membrane (1))
A 13% by weight toluene / isobutyl alcohol (mass ratio: 75/25) solution of the block copolymer (1) was prepared, and about a release-treated PET film [manufactured by Mitsubishi Resin Co., Ltd., MRV (trade name)] Coated with a thickness of 450 μm, dried in a hot air dryer at 100 ° C. for 4 minutes, and then peeled off from the release-treated PET film at 25 ° C. to form a 30 μm thick polymer electrolyte membrane (test membrane (1) and Obtained).

(Production of test membrane (2))
A 14% by mass toluene / isobutyl alcohol (mass ratio 825/175) solution of the block copolymer (2) was prepared, and was released onto a release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)]. Coated with a thickness of 350 μm, dried in a hot air dryer at 100 ° C. for 4 minutes, and then peeled off from the release-treated PET film at 25 ° C. to form a 29 μm thick polymer electrolyte membrane (test membrane (2) and Obtained).

(Production of test membrane (3))
A 12% by weight toluene / isobutyl alcohol (mass ratio: 8/2) solution of the block copolymer (3) was prepared, and about a release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)] Coat with a thickness of 100 μm, dry with a hot air dryer at 100 ° C. for 4 minutes, then coat with a thickness of about 300 μm, dry with a hot air dryer at 100 ° C. for 4 minutes, and release at 25 ° C. The polymer electrolyte membrane (referred to as test membrane (3)) having a thickness of 30 μm was obtained by peeling from the finished PET film.

(Manufacture of test membrane (4))
A 19% by weight toluene / isopropyl alcohol (mass ratio 5/5) solution of the block copolymer (4) was prepared, and about a mold-treated PET film [manufactured by Mitsubishi Resin Co., Ltd., MRV (trade name)] Coated with a thickness of 350 μm, dried in a hot air dryer at 100 ° C. for 4 minutes, and then peeled off from the release-treated PET film at 25 ° C. to form a 30 μm thick polymer electrolyte membrane (test membrane (4) and Obtained).

1) Measurement of storage elastic modulus and softening temperature A test piece was cut out from the test membranes (1) to (4), and a wide-range dynamic viscoelasticity measuring device (“DVE-V4FT Rheospectr” manufactured by Rheology) was used. In the tensile mode (frequency: 11 Hz), the temperature increase rate is 3 ° C./min, the temperature is increased from −80 ° C. to 250 ° C., and the storage elastic modulus (E ′), loss elastic modulus (E ″) and loss tangent ( tan δ) was measured. Based on the fact that there was no change in storage modulus at 80 to 100 ° C. derived from the crystallized olefin polymer, the amorphous nature of the polymer block (B) was judged. As a result, the polymer block (B) was amorphous with respect to all the block copolymers obtained in the following Examples and Comparative Examples. Moreover, the softening temperature of the polymer block (B) and the polymer block (C) was measured from the peak temperature of the loss tangent. 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 softening temperature of the polymer block (C).

2) Measurement of proton conductivity A test piece of 1 cm × 4 cm was cut out from the test membranes (1) to (4), sandwiched between a pair of gold electrodes, and attached to an open cell. The measurement cell was installed in an atmosphere at a temperature of 90 ° C. and a relative humidity of 30%, and the proton conductivity was measured by the AC impedance method.

3) Elongation at break 3-1) Measurement of elongation at break at 25 ° C. and 50% relative humidity A dumbbell-shaped test piece was cut out from the test membranes (1) to (4) and conditioned under conditions of 25 ° C. and 50% relative humidity. After that, it was set in a tensile testing machine (5566 type manufactured by Instron Japan), 25 ° C., 50% relative humidity, and a tensile speed of 500 mm / min. Under these conditions, the elongation at break was measured.
3-2) Measurement of elongation at break when wet at 25 ° C. After dumbbell-shaped test pieces were cut out from the test membranes (1) to (4) and immersed in distilled water at 25 ° C. for 12 hours, 3-1) Similarly, the elongation at break was measured.

Reference Examples 1 to 4 are production examples of a block copolymer (block copolymer (Z ₀ )) composed of polystyrene, hydrogenated polyisoprene and poly (4-tert-butylstyrene).
[Reference Example 1]
After drying, 664 ml of dehydrated cyclohexane and 1.65 ml of dehydrated cyclohexane and 1.65 ml of sec-butyllithium (1.0 mol / L cyclohexane solution) were added to an autoclave with an internal volume of 1400 ml purged with nitrogen, and then stirred at 60 ° C. .4 ml, 4-tert-butylstyrene 13.8 ml, styrene 27.4 ml, 4-tert-butylstyrene 13.8 ml, isoprene 111 ml, 4-tert-butylstyrene 13.8 ml, styrene 27.4 ml, and 4-tert -13.8 ml of butyl styrene was added sequentially to polymerize, and polystyrene-b-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 abbreviated as STSTITST-1) was produced.
The number average molecular weight of the obtained STSTITST-1 was 196,000, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) was 93.8%, and the content of styrene units was 35. The content of 4 mass% and 4-tert-butylstyrene unit was 24.4 mass%.

A cyclohexane solution of STSTITST-1 obtained above was prepared, put into a pressure vessel that was purged with nitrogen, and a Ni / Al Ziegler catalyst was used. A time-hydrogenation reaction is performed, and a polymer block (C) composed of polystyrene (A ₀ ), a polymer block (B) composed of hydrogenated polyisoprene, and a polymer block (C) composed of poly (4-tert-butylstyrene) (C ), A block copolymer consisting of polystyrene-b-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 referred to as STSTETST-1) To obtain the serial to).
An attempt was made to calculate the amount of carbon-carbon double bonds derived from the resulting STSTETST-1 polyisoprene by ¹ H-NMR spectrum (400 MHz), which was below the detection limit.

[Reference Example 2]
After drying, 851 ml of dehydrated cyclohexane and 2.79 ml of sec-butyllithium (1.15 mol / L cyclohexane solution) were added to an autoclave with an internal volume of 2000 ml purged with nitrogen, and then stirred at 60 ° C. 6.2 ml of tert-butylstyrene, 17.5 ml of styrene, 6.0 ml of 4-tert-butylstyrene, 51.0 ml of isoprene, 5.9 ml of 4-tert-butylstyrene, 17.0 ml of styrene, and 4-tert-butylstyrene 5.8 ml was sequentially added and polymerized to obtain poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-polyisoprene-b-poly (4-tert- Butylstyrene) -b-polystyrene-b-poly (4-tert-butyl) Styrene) (hereinafter, abbreviated as TSTITST) was prepared.
The number average molecular weight of TSTITST obtained was 52,000, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) was 93.8%, and the content of styrene units was 34.8. The content of mass%, 4-tert-butylstyrene unit was 24.2 mass%.

The cyclohexane solution of TSTISTST obtained above is prepared, put into a pressure vessel which is purged with nitrogen, and water is used at a hydrogen pressure of 0.5 to 1.0 MPa and 70 ° C. for 18 hours using a Ni / Al Ziegler catalyst. From the polymer block (C) consisting of a polymer block (A ₀ ) made of polystyrene, a polymer block (B) made of hydrogenated polyisoprene, and a poly (4-tert-butylstyrene). Poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-hydrogenated polyisoprene-b-poly (4-tert-butyl) Styrene) -b-polystyrene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as TSSETST) was obtained.
An attempt was made to calculate the amount of carbon-carbon double bonds derived from the polysoprene of TSSETST obtained using a ¹ H-NMR spectrum (400 MHz), which was below the detection limit.

[Reference Example 3]
After drying, 904 ml of dehydrated cyclohexane and 2.00 ml of sec-butyllithium (0.83 mol / L cyclohexane solution) were added to an autoclave having an internal volume of 2000 ml purged with nitrogen, and then stirred at 60 ° C. .8 ml, 4-tert-butylstyrene 20.8 ml, styrene 28.8 ml, 4-tert-butylstyrene 20.8 ml, isoprene 91.5 ml, 4-tert-butylstyrene 20.8 ml, styrene 28.8 ml, and 4 -20.8 ml of tert-butylstyrene was added in succession to polymerize, and polystyrene-b-poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-polyisoprene -B-poly (4-tert-butylstyrene)- - polystyrene -b- poly (4-tert-butylstyrene) (hereinafter, abbreviated as STSTITST-2) was produced.
The number average molecular weight of STSTITST-2 obtained was 126,000, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) was 93.7%, and the content of styrene units was 35. The content of .4 mass% and 4-tert-butylstyrene unit was 34.4 mass%.

After preparing a cyclohexane solution of STSTITST-2 obtained above and adding it to a pressure vessel with nitrogen substitution, using a Ni / Al Ziegler catalyst, the hydrogen pressure is reduced to 0.5 to 1.0 MPa. In this, hydrogenation reaction is performed at 70 ° C. for 18 hours, and the polymer block (A ₀ ) made of polystyrene, the polymer block (B) made of hydrogenated polyisoprene, and poly (4-tert-butylstyrene) are made. Polystyrene-b-poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-hydrogenated, which is a block copolymer comprising the polymer block (C) Polyisoprene-b-poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) Abbreviated as STSTETST-2) was obtained.
An attempt was made to calculate the amount of carbon-carbon double bonds derived from the obtained polyisoprene of STSTETST-2 by ¹ H-NMR spectrum (400 MHz), which was below the detection limit.

[Reference Example 4]
After drying, 865 ml of dehydrated cyclohexane and 1.27 ml of sec-butyllithium (1.2 mol / L cyclohexane solution) were added to an autoclave with an internal volume of 1400 ml purged with nitrogen, and then stirred at 60 ° C. tert-Butylstyrene 36.1 ml, Styrene 51.0 ml, Isoprene 148.8 ml, Styrene 49.4 ml and 4-tert-Butylstyrene 33.7 ml were sequentially added and polymerized to obtain poly (4-tert-butylstyrene)- b-polystyrene-b-polyisoprene-b-polystyrene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as TSIST) was produced.
The number average molecular weight of the obtained TSIST was 86,000, the 1,4-bond content of the polyisoprene moiety determined from ¹ H-NMR (400 MHz) was 93.8%, and the content of styrene units was 35.2. The content of mass%, 4-tert-butylstyrene unit was 25.1 mass%.

The cyclohexane solution of TSIST obtained above was prepared and added to a pressure vessel that was purged with nitrogen, and then a Ni / Al Ziegler catalyst was used at a hydrogen pressure of 0.5 to 1.0 MPa at 70 ° C. for 18 hours. A time-hydrogenation reaction is performed, and a polymer block (C) composed of polystyrene (A ₀ ), a polymer block (B) composed of hydrogenated polyisoprene, and a polymer block (C) composed of poly (4-tert-butylstyrene) (C ) Poly (4-tert-butylstyrene) -b-polystyrene-b-hydrogenated polyisoprene-b-polystyrene-b-poly (4-tert-butylstyrene) (hereinafter TSTS) Abbreviated).
An attempt was made to calculate the amount of carbon-carbon double bonds derived from the obtained TSEST polyisoprene by ¹ H-NMR spectrum (400 MHz), which was below the detection limit.

<Example 1>
(Production of block copolymer (1))
After drying, 72.7 ml of methylene chloride and 36.4 ml of acetic anhydride were added to a three-necked flask with an internal volume of 200 ml purged with nitrogen, and 16.3 ml of concentrated sulfuric acid was added dropwise with stirring at 0 ° C. A sulfonating agent was prepared by stirring for 60 minutes.
On the other hand, 20 g of the block copolymer STSTETST-1 obtained in Reference Example 1 was placed in a 3 L glass reaction vessel equipped with a stirrer, and the system was purged with nitrogen. And stirred for 4 hours to dissolve. To this solution, 114 ml of the previously prepared sulfonating agent was added dropwise over 5 minutes. After stirring at 25 ° C. for 48 hours, 25.2 ml of distilled water was added to stop the reaction, and further 225 ml of distilled water was gradually added dropwise with stirring to precipitate a block polymer. After distilling off methylene chloride from this mixed solution, the mixture was filtered to obtain a block copolymer. The obtained block copolymer was put into a beaker, 1.0 L of distilled water was added, washed with stirring, and then the block copolymer was recovered by filtration. This washing and filtration operation is repeated until there is no change in the pH of the washing water, and the resulting block copolymer is dried under reduced pressure to obtain sulfonated STSTETST-1 (hereinafter referred to as block copolymer (1)). )
The sulfonation rate of the benzene ring of the styrene unit of the obtained block copolymer (1) was 100 mol% from ¹ H-NMR (400 MHz), and the ion exchange capacity was 2.65 meq / g from the titration results.

(Manufacture of polymer electrolyte membrane)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in the production of the test membrane (1) described above.

<Example 2>
(Production of block copolymer (2))
After drying, 581 ml of methylene chloride and 290 ml of acetic anhydride were added to a three-necked flask with an internal volume of 2000 ml purged with nitrogen. An agent was prepared.
On the other hand, 130 g of the block copolymer TSETST obtained in Reference Example 2 was placed in a 5 L glass reactor equipped with a stirrer, and the system was purged with nitrogen. Stir for hours to dissolve. To this solution, 909 ml of the previously prepared sulfonating agent was added dropwise over 5 minutes. After stirring at 25 ° C. for 48 hours, 160 ml of distilled water was added to stop the reaction, and further 1465 ml of distilled water was gradually added dropwise with stirring to precipitate a block copolymer. After distilling off methylene chloride from this mixed solution, the mixture was filtered to obtain a block copolymer. The obtained block copolymer was put into a beaker, 1.0 L of distilled water was added, washed with stirring, and then the block copolymer was recovered by filtration. This washing and filtration operation is repeated until there is no change in the pH of the washing water, and the obtained block copolymer is dried under reduced pressure to obtain a sulfonated TSSETST (hereinafter referred to as block copolymer (2)). It was.
The sulfonation rate of the benzene ring of the styrene unit of the obtained block copolymer (2) was 100 mol% from ¹ H-NMR (400 MHz), and the ion exchange capacity was 2.61 meq / g from the result of titration.

(Manufacture of polymer electrolyte membrane)
A polymer electrolyte membrane having a thickness of 29 μm was obtained in the same manner as in the production of the test membrane (2) described above.

<Example 3>
(Production of polymer electrolyte membrane)
A 9% by weight toluene / isobutyl alcohol (mass ratio 75/25) solution of the block copolymer (1) was prepared, and the release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)] After coating with a thickness of 100 μm and drying with a hot air dryer at 100 ° C. for 4 minutes, a wholly aromatic liquid crystal polyester nonwoven fabric (thickness 13 μm, porosity 67%) was fixed on the electrolyte membrane, Coat with a thickness of about 100 μm, dry with a hot air dryer at 100 ° C. for 4 minutes, further coat with a thickness of about 150 μm, and dry with a hot air dryer at 100 ° C. for 4 minutes to a thickness of 23 μm The polymer electrolyte membrane was obtained.

<Comparative Example 1>
(Production of block copolymer (3))
After drying, 262 ml of methylene chloride and 131 ml of acetic anhydride were added to a 1 l three-neck flask purged with nitrogen, and 58.7 ml of concentrated sulfuric acid was added dropwise with stirring at 0 ° C., followed by stirring at 0 ° C. for 60 minutes. A sulfonating agent was prepared.
On the other hand, 72 g of the block copolymer STSTETST-2 obtained in Reference Example 3 was placed in a glass reaction vessel having an internal volume of 5 L equipped with a stirrer, purged with nitrogen, 900 ml of methylene chloride was added, and the mixture was added at 25 ° C. for 4 hours. Stir to dissolve. To this solution, 411 ml of the previously prepared sulfonating agent was added dropwise over 5 minutes. After stirring at 25 ° C. for 48 hours, 91.0 ml of distilled water was added to stop the reaction, and 1000 ml of distilled water was gradually added dropwise while stirring to precipitate a block polymer. After distilling off methylene chloride from the mixed solution, a block copolymer was obtained by filtration. The obtained block copolymer was put into a beaker, 1.0 L of distilled water was added, and washing was performed while stirring, and then the block copolymer was recovered 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 block copolymer is dried under reduced pressure to be sulfonated STSTETST-2 (hereinafter referred to as block copolymer (3)). Got.
The sulfonation rate of the benzene ring of the styrene unit of the obtained block copolymer (3) was 100 mol% from ¹ H-NMR (400 MHz), and the ion exchange capacity was 2.65 meq / g from the titration results.

(Manufacture of polymer electrolyte membrane)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in the production of the test membrane (3) described above.

<Comparative Example 2>
(Manufacture of polymer electrolyte membrane)
A 9% by weight toluene / isobutyl alcohol (mass ratio: 8/2) solution of the block copolymer (3) was prepared, and was released on a release-treated PET film [Mitsubishi Resin Co., Ltd., MRV (trade name)]. After coating with a thickness of 100 μm and drying with a hot air dryer at 100 ° C. for 4 minutes, a wholly aromatic liquid crystal polyester nonwoven fabric (thickness 13 μm, porosity 67%) was fixed on the electrolyte membrane, Coat with a thickness of about 100 μm, dry with a hot air dryer at 100 ° C. for 4 minutes, further coat with a thickness of about 150 μm, and dry with a hot air dryer at 100 ° C. for 4 minutes to a thickness of 23 μm The polymer electrolyte membrane was obtained.

<Comparative Example 3>
(Production of block copolymer (4))
After drying, 492.8 ml of methylene chloride and 246.4 ml of acetic anhydride were added to a three-necked flask with an internal volume of 2 liters purged with nitrogen, and 110.2 ml of concentrated sulfuric acid was added dropwise with stirring at 0 ° C. A sulfonating agent was prepared by stirring for 60 minutes.
On the other hand, 100 g of the block copolymer TSEST obtained in Reference Example 4 was placed in a 5 L glass reaction vessel equipped with a stirrer, purged with nitrogen, added with 1337 ml of methylene chloride, and stirred at 25 ° C. for 4 hours. And dissolved. To this solution, 566.3 ml of the previously prepared sulfonating agent was added dropwise over 5 minutes. After stirring at 25 ° C. for 48 hours, 130 ml of distilled water was added to stop the reaction, and further 1200 ml of distilled water was gradually added dropwise with stirring to precipitate a block copolymer. After distilling off methylene chloride from the mixed solution, a block copolymer was obtained by filtration. The obtained block copolymer was transferred to a beaker, 1.0 L of distilled water was added, the mixture was washed with stirring, and then the block copolymer was recovered by filtration. Washing and filtration operations were repeated until there was no change in the pH of the washing water, and the resulting block copolymer was dried under reduced pressure to obtain a sulfonated TSEST (hereinafter referred to as block copolymer (4)).
The sulfonation rate of the benzene ring of the styrene unit of the obtained block copolymer (4) was 100 mol% from ¹ H-NMR (400 MHz), and the ion exchange capacity was 2.64 meq / g from the titration results.

(Manufacture of polymer electrolyte membrane)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in the production of the test membrane (4) described above.

(Production of single cell for polymer electrolyte fuel cell)
In the following tests, in order to evaluate the durability of the polymer electrolyte membranes obtained in Examples and Comparative Examples, a single cell for a polymer electrolyte fuel cell was produced by the following procedure. A 10 mass% aqueous dispersion of Nafion is added to and mixed with the Pt 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 alcohol. The mixture was added and mixed until the ratio was 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 was prepared by drying at 130 ° C. for 30 minutes. Thereafter, the polymer electrolyte membranes produced in Examples and Comparative Examples were sandwiched with the above electrodes so that the membrane and the catalyst surface face each other, and the outside was sandwiched in sequence with two heat resistant films and two stainless steel plates. A membrane-electrode assembly was produced by hot pressing (115 ° C., 2 MPa, 8 min). Next, the produced membrane-electrode assembly is sandwiched between two conductive separators that also serve as gas supply passages, and the outside is sandwiched between two current collector plates and two clamping plates to form a solid. A single cell for a polymer fuel cell (electrode area: 25 cm ² ) was produced.

(Durability test)
After the temperature of the unit cell for the polymer electrolyte fuel cell obtained above was set to 80 ° C., 100% R.P. H. The polymer electrolyte membrane was brought into an environment similar to the wet state while the polymer electrolyte fuel cell was activated by supplying nitrogen gas humidified to 1000 ml / min for 3 minutes. Next, dry nitrogen gas was supplied at 1000 ml / min for 7 minutes to make the environment similar to the dry state while the polymer electrolyte fuel cell was stopped. The above is one cycle of the start / stop model of the polymer electrolyte fuel cell.
The operation of the start / stop model of such a polymer electrolyte fuel cell is repeated, the test is interrupted every 250 cycles, hydrogen is supplied to the anode, nitrogen is supplied to the cathode, linear sweep voltammetry is performed, and hydrogen is supplied from the anode to the cathode. The current value caused by the leakage was measured. When the current value at 0.4 V was 10 times or more compared with the value before the test, it was judged that the film was broken, and the number of cycles was recorded and used as an index of durability. In practical use, it was judged that there was no problem as long as it was 2000 cycles or more, and those in which the film did not break at 5000 cycles were particularly excellent.

  Ion exchange capacity of the block copolymers (1) to (4) used in Examples 1 and 2 and Comparative Examples 1 and 3; Proton conduction at 90 ° C. and 30% relative humidity of the test membranes (1) to (4) And the elongation at break at 25 ° C. (relative humidity 50%, when wet); and the number of cycles in which the membrane break occurred in the durability test of the polymer electrolyte membrane prepared from the block copolymers (1) to (4) Table 1 shows.

  Ion exchange capacity of the block copolymers (1) and (3) used in Example 3 and Comparative Example 2; proton conductivity and 90 ° C. of the test membranes (1) and (3) at 90 ° C. and a relative humidity of 30% Table 2 shows the number of cycles of the start / stop durability test of the polymer electrolyte membrane prepared using the block copolymers (1) and (3).

  From Table 1, the polymer electrolyte membrane of the present invention is excellent in ionic conductivity under low humidity, and excellent in durability as compared with the polymer electrolyte membrane of the comparative example. From Table 2, the polymer electrolyte membrane of the present invention is excellent in durability even when it includes a reinforcing material layer. From the above results, the membrane-electrode assembly and the polymer electrolyte fuel cell using the polymer electrolyte membrane of the present invention can achieve both durability and ionic conductivity under low humidity.

  The polymer electrolyte membrane of the present invention is excellent in durability and ion conductivity under low humidity, and is useful as a polymer electrolyte membrane of a solid polymer fuel cell.

Claims (6)

Polymer block (A ₀ ) having no ion conductive group, amorphous olefin polymer block (B) having no ion conductive group, and the following general formula (a) having no ion conductive group in made 7 or eight polymer block of an aromatic vinyl compound composed of repeating units of the structural unit derived from an aromatic vinyl compound polymer block (C) represented, the polymer block (a ₀₎ or heavy The block copolymer (Z ₀ ) having a structure in which the polymer block (C) is a terminal polymer block and the polymer block bonded to both ends of the polymer block (B) is only the polymer block (C), It has a structure in which an ion conductive group is introduced into the polymer block (A ₀ ), and has a temperature of 25 ° C., a relative humidity of 50%, and a tensile speed of 500 mm / min. A polymer electrolyte membrane comprising a block copolymer (Z) having an elongation at break of 300% or more.

Wherein R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ^{2 to} R ⁴ each independently represents a hydrogen atom or an alkyl group having 3 to 8 carbon atoms, and R ^{2 to} R ^At least one of ⁴ represents an alkyl group having 3 to 8 carbon atoms) The polymer electrolyte membrane according to claim 1, wherein the polymer block (A ₀ ) having no ion conductive group is a polymer block composed of a structural unit derived from an aromatic vinyl compound. The ion-conducting group is, _(wherein, M represents a hydrogen atom, an ammonium ion or an alkali metal ion) -SO 3 _M or -PO 3 HM is a group represented by the high according to claim 1 or 2 Molecular electrolyte membrane. The polymer electrolyte membrane according to any one of claims 1 to 3 , wherein the polymer block (B) is an amorphous olefin polymer block having a softening temperature of 30 ° C or lower. A membrane-electrode assembly comprising the polymer electrolyte membrane according to any one of claims 1 to 4 . A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 5 .