JP6150616B2 - Polymer electrolyte composition and polymer electrolyte membrane - Google Patents

Description

  The present invention relates to a polymer electrolyte composition used for a polymer electrolyte fuel cell and the like, a method for producing the same, and a polymer electrolyte membrane.

  A fuel cell is one that converts the chemical energy of the fuel directly into electrical energy by electrochemically oxidizing fuel such as hydrogen and methanol in the battery, and is a clean electrical energy supply source. Attention has been paid. In particular, solid polymer electrolyte fuel cells are expected to be used as alternative power sources for automobiles, home cogeneration systems, portable generators, and the like because they operate at a lower temperature than other fuel cells.

  Such a solid polymer electrolyte fuel cell has a membrane electrode in which gas diffusion electrodes having a structure in which an electrode catalyst layer (anode catalyst layer, cathode catalyst layer) and a gas diffusion layer are laminated are bonded to both surfaces of a proton exchange membrane. At least a joined body is provided. The proton exchange membrane here is a polymer electrolyte membrane made of a composition having a strongly acidic group such as a sulfonic acid group or a carboxylic acid group in a polymer chain and a property of selectively transmitting protons. As a composition used for such a proton exchange membrane, a perfluoro resin composition typified by Nafion (registered trademark, manufactured by DuPont) having high chemical stability can be mentioned, and a proton exchange membrane using the composition is used. Are preferably used.

  During operation of the fuel cell, fuel (eg, hydrogen) is supplied to the gas diffusion electrode on the anode side, and oxidant (eg, oxygen or air) is supplied to the gas diffusion electrode on the cathode side. The operation of the fuel cell is realized by connecting both electrodes with an external circuit. Specifically, when hydrogen is used as fuel, hydrogen is oxidized on the anode catalyst in the anode catalyst layer to generate protons. After passing through the proton conductive polymer in the anode catalyst layer, the proton moves in the proton exchange membrane and reaches the cathode catalyst in the same layer through the proton conductive polymer in the cathode catalyst layer. On the other hand, electrons generated simultaneously with protons due to oxidation of hydrogen reach the gas diffusion electrode on the cathode side through an external circuit. On the cathode catalyst in the cathode catalyst layer, the protons react with oxygen in the oxidant to produce water. At this time, electric energy is extracted.

  At this time, the proton exchange membrane must also serve as a gas barrier partition by lowering the gas permeability. When the gas permeability of the proton exchange membrane is high, leakage of anode-side hydrogen to the cathode and leakage of cathode-side oxygen to the anode, that is, cross-leakage occurs. When a cross leak occurs, a so-called chemical short circuit occurs and a good voltage cannot be taken out. There is also a problem that the hydrogen on the anode side reacts with the oxygen on the cathode side to generate hydrogen peroxide, which causes chemical degradation of the proton exchange membrane.

  In order to solve such problems, a proton exchange membrane having improved chemical durability by compounding an additive such as polybenzimidazole or polyphenylene sulfide having an effect of suppressing generation of hydrogen peroxide with an ion exchange resin. It has been proposed (see Patent Documents 1 and 2).

On the other hand, from the viewpoint of reducing the internal resistance of the battery and increasing the output, it has been studied to reduce the thickness of the proton exchange membrane that is an electrolyte. However, if this proton exchange membrane is thinned, the effect as a gas barrier partition is reduced, and the problem of cross leak becomes more serious. Furthermore, since the mechanical strength of the membrane itself is reduced by reducing the thickness of the proton exchange membrane, it becomes difficult to manufacture the membrane electrode assembly and handle the membrane during cell assembly, and the water generated on the cathode side becomes difficult. There is a physical problem that the film is torn by changing the dimensions including.
Therefore, in order to solve such a problem, a proton exchange membrane in which a porous membrane is filled with an ion exchange resin has been proposed (see Patent Documents 3 to 6).

International Publication No. 2005/000949 International Publication No. 2008/102851 Japanese Patent Publication No. 5-75835 Japanese Examined Patent Publication No. 7-68377 Japanese Patent No. 4402625 International Publication No. 2012/046777

  However, the proton exchange membranes described in Patent Documents 1 to 6 have excellent performance in long-term chemical durability and mechanical strength, but there is room for improvement in terms of gas permeability. If the gas permeability can be reduced and the gas barrier property can be increased, a polymer electrolyte membrane having further durability and high power generation efficiency can be obtained.

  This invention is made | formed in view of the said problem, and it aims at providing the polymer electrolyte composition excellent in gas barrier property, its manufacturing method, and a polymer electrolyte membrane.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have made the present invention. That is, the present invention is as follows.
[1] 100 parts by mass of a fluoropolymer electrolyte (A) having an ion exchange capacity of 0.50 to 3.0 meq / g and sulfonation having an ion exchange capacity of 0.50 to 3.0 meq / g It is seen containing a modified hydrocarbon polymer electrolyte (B) 0.10 to 50 parts by weight, wherein the sulfonated modified hydrocarbon polymer electrolyte (B), a sulfonated modified polyphenylene ether resin, Polymer electrolyte composition .
[2] The polymer electrolyte composition, a compound having a thioether group further including (C), [1] Symbol placement of the polymer electrolyte composition.
[ 3 ] The polymer electrolyte composition according to [1] or [2], wherein the polymer electrolyte composition further includes a compound (D) having an azole ring.
[ 4 ] A polymer electrolyte membrane comprising a microporous membrane and the polymer electrolyte composition according to any one of [1] to [ 3 ] present in the voids of the microporous membrane.
[ 5 ] The polymer electrolyte membrane according to [ 4 ], wherein the microporous membrane contains polytetrafluoroethylene.

  ADVANTAGE OF THE INVENTION According to this invention, the polymer electrolyte composition excellent in gas-barrier property, its manufacturing illegal method, and a polymer electrolyte membrane can be provided.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiment, and can be implemented with various modifications within the scope of the gist.

  The polymer electrolyte composition of the present embodiment is a polymer electrolyte containing 100 parts by mass of a fluorine-based polymer electrolyte (A) and 0.1 to 50 parts by mass of a sulfonated modified hydrocarbon polymer electrolyte (B). It is a composition. Further, the polymer electrolyte membrane of the present embodiment includes the polymer electrolyte composition, and preferably includes a microporous membrane and the polymer electrolyte composition present in the voids of the microporous membrane. .

[Polymer electrolyte composition]
<Fluorine polymer electrolyte (A)>
The fluorine-based polymer electrolyte is a polymer electrolyte having a fluorine atom in at least one repeating unit. As a specific example, a perfluorocarbon polymer compound having a structural unit represented by the following general formula (1) ( Resin).
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF ((- O-CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( CF ₂ ) _f −X ⁴ )] _g − (1)
Here, in formula (1), X ¹ , X ² and X ³ are each independently selected from the group consisting of a halogen atom and a C 1-3 perfluoroalkyl group, and the halogen atom is a fluorine atom. , A chlorine atom, a bromine atom and an iodine atom, preferably a fluorine atom or a chlorine atom.

X ⁴ is a monovalent group represented by the general formula of —COOZ, —SO ₃ Z, —PO ₃ Z _2, or —PO ₃ HZ. In this case, Z represents a hydrogen atom, a lithium atom, an alkali metal atom such as a sodium atom or a potassium atom, or an amine (NH ₄ , NH ₃ R ¹ , NH ₂ R ¹ R ² , NHR ¹ R ² R ³ , NR ¹ R ² R ³ R ⁴ ). Alternatively, among a plurality of fluoropolymer electrolyte, X ⁴ _{is, -COOZOOC -, - SO 3 ZO} 3 S -, - Table at PO ₃ Z ₂ O ₃ P- or -PO ₃ HZHO ₃ P- formula It may be a divalent group. In this case, Z represents an alkaline earth metal atom such as a calcium atom or a magnesium atom. R ¹ , R ² , R ³ and R ⁴ are each independently selected from the group consisting of an alkyl group and an aryl group. When X ⁴ is —PO ₃ Z ₂ , the _two Zs may be the same as or different from each other.

The alkyl group is not particularly limited, but is a monovalent group represented by the general formula C _n H _{2n + 1} (n represents an integer of 1 or more and an integer of 1 to 20). And preferably an integer of 1 to 10. Specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, and a hydrogen atom is substituted. May be. The hydrogen atom of the aryl group may also be substituted.

R ¹ and R ² are each independently selected from the group consisting of a halogen atom, a C 1-10 perfluoroalkyl group and a fluorochloroalkyl group, and the halogen atom includes a fluorine atom, a chlorine atom, a bromine atom and An iodine atom is mentioned, It is preferable that they are a fluorine atom or a chlorine atom.

  a and g are numbers satisfying 0 ≦ a <1, 0 <g ≦ 1, and a + g = 1. b is an integer of 0-8. c is 0 or 1; d, e and f are each independently an integer of 0 to 6 (provided that d, e and f are not 0 at the same time).

Among these, as the fluoropolymer electrolyte, a perfluorocarbon sulfonic acid polymer compound represented by the following general formula (3) or (4) or a metal salt thereof is particularly preferable.
_{- [CF 2 CF 2] a} - [CF 2 -CF ((- O-CF 2 -CF (CF 3)) b -O- (CF 2) h -SO 3 X)] g - (3)
In formula (3), a and g are numbers satisfying 0 ≦ a <1, 0 <g ≦ 1, and a + g = 1, b is an integer of 1 to 3, and h is an integer of 1 to 8. And X is a hydrogen atom or an alkali metal atom.
_{- [CF 2 CF 2] a} - [CF 2 -CF (-O- (CF 2) h -SO 3 X)] g - (4)
In the formula (4), a and g are numbers satisfying 0 ≦ a <1, 0 <g ≦ 1, and a + g = 1, h is an integer of 1 to 8, and X is a hydrogen atom or an alkali metal Is an atom.

In the present embodiment, the fluorine-based polymer electrolyte may include a perfluorocarbon polymer compound having an ion exchange group. Examples of such a polymer compound include a precursor represented by the following general formula (5). It may be one that can be produced by polymerizing the polymer, followed by alkali hydrolysis, acid treatment, and the like.
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF ((- O-CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( ^{_{CF 2) f -X 5)]}} g - (5)
In the formula, X ¹ , X ² and X ³ are each independently selected from the group consisting of a halogen atom and a perfluoroalkyl group having 1 to 3 carbon atoms, and the halogen atom is a fluorine atom, a chlorine atom or a bromine atom. And an iodine atom, and a fluorine atom or a chlorine atom is preferable.

X ⁵ is a monovalent group represented by the general formula of —COOR ³ , —COR ⁴ or —SO ₂ R ⁴ . R ³ is an alkyl group having 1 to ³ carbon atoms. R ⁴ is a halogen atom.

R ¹ and R ² are each independently selected from the group consisting of a halogen atom, a C 1-10 perfluoroalkyl group and a fluorochloroalkyl group, and the halogen atom includes a fluorine atom, a chlorine atom, a bromine atom and iodine. An atom is mentioned, It is preferable that it is a fluorine atom or a chlorine atom.

  a and g are numbers satisfying 0 ≦ a <1, 0 <g ≦ 1, and a + g = 1. b is an integer of 0-8. c is 0 or 1; d, e and f are each independently an integer of 0 to 6 (provided that d, e and f are not 0 at the same time).

  The precursor polymer represented by the general formula (5) can be produced, for example, by copolymerizing a fluorinated olefin compound and a vinyl fluoride compound.

Here, as a fluorinated olefin compound, the compound represented by the following general formula (1a) is mentioned, for example.
CF ₂ = CX ¹ X ² (1a)
In formula, X < ¹ > and X < ² > are synonymous with the thing in General formula (5).

Specific examples of the compound represented by the general formula (1a) include compounds represented by CF ₂ = CF ₂ , CF ₂ = CFCl, and CF ₂ = CCl ₂ .

Moreover, as a vinyl fluoride compound, the compound represented by the following general formula (1b) is mentioned, for example.
_{CF 2 = CF ((- O} -CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - (CF 2) f -X 5) (1b)
In the formula, X ³ , X ⁵ , R ¹ , R ² , b, c, d, e, and f have the same meaning as in general formula (5).

As the compound represented by the general formula (1b), specifically, CF ₂ = CFO (CF ₂ ) _j —SO ₂ F, CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _j − _{SO 2 F, CF 2 = CF} (OCF 2 CF (CF 3)) j - (CF 2) j-1 -SO 2 F, CF 2 = CFO (CF 2) j -CO 2 R, CF 2 = CFOCF 2 _{CF (CF 3) O (CF} 2) j -CO 2 R, CF 2 = CF (CF 2) j -CO 2 R, CF 2 = CF (OCF 2 CF (CF 3)) j - (CF 2) 2 And a compound represented by —CO ₂ R (where j represents an integer of 1 to 8, and R represents a hydrocarbon alkyl group having 1 to 3 carbon atoms).

The precursor polymer as described above can be synthesized by a known method. The synthesis method is not particularly limited, and examples include the following methods (i) to (v).
(I) A method (solution polymerization) in which a polymerization solvent such as fluorine-containing hydrocarbon is used, and polymerization is performed by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state where the polymerization solvent is filled and dissolved. Examples of the fluorine-containing hydrocarbon include a group of compounds generally referred to as “fluorocarbons” such as trichlorotrifluoroethane, 1,1,1,2,3,4,4,5,5,5-decafluoropentane, and the like. It can be preferably used.
(Ii) A method in which a vinyl fluoride compound is polymerized using a vinyl fluoride compound itself as a polymerization solvent without using a solvent such as a fluorine-containing hydrocarbon (bulk polymerization).
(Iii) A method (emulsion polymerization) in which an aqueous solution of a surfactant is used as a polymerization solvent and a vinyl fluoride compound and a fluorinated olefin gas are reacted in a state of being charged and dissolved in the polymerization solvent.
(Iv) A method in which an aqueous solution of an interfacial polymerizer and a co-emulsifier such as alcohol is used, and polymerization is performed by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state where the aqueous solution is filled and emulsified (mini-emulsion polymerization, Microemulsion polymerization).
(V) A method (suspension polymerization) in which an aqueous solution of a suspension stabilizer is used, and polymerization is performed by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state of being filled and suspended in the aqueous solution.

  In the present embodiment, a melt mass flow rate (hereinafter sometimes abbreviated as “MFR”) can be used as an index of the polymerization degree of the precursor polymer. In the present embodiment, from the viewpoint of molding processing, the MFR of the precursor polymer is preferably 0.01 or more, more preferably 0.1 or more, and still more preferably 0.3 or more. Although the upper limit of MFR is not specifically limited, From a viewpoint of a shaping | molding process, 100 or less are preferable, 50 or less are more preferable, and 10 or less are still more preferable.

The precursor polymer produced as described above is hydrolyzed in a basic reaction liquid, sufficiently washed with warm water or the like, and acid-treated. By this hydrolysis treatment and acid treatment, for example, the perfluorocarbon sulfonic acid resin precursor is protonated to become a perfluorocarbon sulfonic acid resin that is an SO ₃ H form.

  The fluorine-based polymer electrolyte in the present embodiment has an ion exchange capacity of 0.50 to 3.0 meq / g and has an ion exchange group so as to satisfy this condition. By setting the ion exchange capacity of the fluorine-based polymer electrolyte to 3.0 meq / g or less, when a polymer electrolyte composition containing this polymer electrolyte is used for the polymer electrolyte membrane, the high temperature during fuel cell operation is high. Swelling under high humidification tends to be reduced. Reduction of the swelling of the polymer electrolyte membrane causes problems such as a decrease in strength of the polymer electrolyte membrane, generation of wrinkles and separation from the electrode, and a problem of reduced gas barrier properties. Can improve. On the other hand, by setting the ion exchange capacity to 0.50 milliequivalent / g or more, the fuel cell including the polymer electrolyte membrane that satisfies such conditions can maintain its power generation capability satisfactorily. From these viewpoints, the ion exchange capacity of the fluorine-based polymer electrolyte (A) is more preferably 0.65 meq / g, more preferably 1.3 meq / g, particularly from the viewpoint of maintaining the power generation capacity. In particular, from the viewpoint of reducing swelling, it is more preferably 2.8 meq / g or less, still more preferably 2.5 meq / g or less.

In addition, the ion exchange capacity of the polymer electrolyte in this embodiment is measured as follows.
First, a membrane made of a polymer electrolyte in which the counter ion of the ion exchange group is in a proton state is immersed in a saturated NaCl aqueous solution at 25 ° C., and the aqueous solution is stirred for a sufficient time. Subsequently, the proton in the saturated NaCl aqueous solution is neutralized and titrated with a 0.01N sodium hydroxide aqueous solution. A membrane made of a polymer electrolyte in which the counter ion of the ion exchange group obtained by filtration after neutralization is in the form of sodium ions is rinsed with pure water, further vacuum-dried, and weighed. The amount of sodium hydroxide required for neutralization is M (mmol), the mass of a membrane made of a polymer electrolyte in which the counter ion of the ion exchange group is sodium ion is W (mg), and the equivalent mass EW ( g / equivalent).
EW = (W / M) −22
Furthermore, the ion exchange capacity (milli equivalent / g) is calculated by taking the inverse of the obtained EW value and multiplying it by 1000.

  Therefore, the fluoropolymer electrolyte in the present embodiment has an equivalent mass (EW) value of preferably 330 to 2000 g / equivalent, more preferably 355 to 1540 g / equivalent, and still more preferably 400 to 770 g / equivalent. It is.

  This ion exchange capacity can be adjusted to fall within the above numerical range by adjusting the number of ion exchange groups present in 1 g of the membrane made of a fluorine-based polymer electrolyte.

  In the present embodiment, the fluoropolymer electrolyte (or a mixture thereof in the case where two or more fluoropolymer electrolytes are contained) preferably has a glass transition temperature of 80 ° C. or more from the viewpoint of heat resistance during operation of the fuel cell. Yes, more preferably 100 ° C or higher, still more preferably 120 ° C or higher, particularly preferably 130 ° C or higher. Here, the glass transition temperature of the polymer electrolyte is measured according to JIS-C-6481 (1996). Specifically, the polymer electrolyte molded into a film shape is cut into a width of 5 mm, and the test piece is heated from room temperature at a rate of 2 ° C./minute using a dynamic viscoelasticity measuring device. The dynamic viscoelasticity and loss tangent of the specimen are measured. The measured peak temperature of loss tangent is defined as the glass transition temperature. The glass transition temperature can be adjusted by controlling the structural formula, molecular weight, and ion exchange capacity of the polymer electrolyte contained in the fluorine-based polymer electrolyte.

<Sulfonated modified hydrocarbon polymer electrolyte (B)>
The sulfonated modified hydrocarbon-based polymer electrolyte (B) used in the present embodiment is not particularly limited. For example, a sulfonated polyarylethersulfone resin having an aromatic polyether structure (for example, JP 2005-133146), sulfonated polyether ether ketone resin (for example, see JP-A-6-93114), and sulfonated polyphenylene ether resin. In view of its economic efficiency, a polymer electrolyte having a sulfonated aromatic polyether structure is preferably used, a sulfonated polyphenylene ether resin is more preferable, and a sulfonated modified poly (2,6-dimethyl-1, 4-phenylene ether) (hereinafter abbreviated as “SPPE”) is more preferable. Hereinafter, the polymer electrolyte (B) will be described using SPPE as an example. However, the polymer electrolyte (B) is not limited to SPPE. In the following description, other polymer electrolytes (B) are used instead of SPPE. It may be.

  Although there is no restriction | limiting in particular in the manufacturing method of SPPE which can be used for this embodiment, For example, Journal of Applied Polymer Science, Vol. 29 (1984) p. The method described in 4017-4027 can be used.

  That is, poly (2,6-dimethyl-1,4 phenylene ether) (hereinafter abbreviated as “PPE”) is dissolved in chloroform, and chlorosulfonic acid is added dropwise to the PPE solution and reacted at room temperature to cause SPPE. Can be obtained. As the sulfonation reaction proceeds, SPPE becomes insoluble in chloroform and precipitates as an amorphous solid.

  The solid treatment method is not particularly limited. For example, the solid precipitated in chloroform after the sulfonation reaction is dissolved in a solvent such as methanol, ethanol, propanol, or dimethyl sulfoxide, and then cast on a tray and dried. Then, the film-like SPPE thus obtained can be pulverized to obtain a granular or flaky SPPE.

  The means for granulating or flaking SPPE is not particularly limited. It can be implemented using known methods and devices that are generally available. Examples thereof include freeze pulverization, roll milling, and disk milling.

  The average particle size and particle size distribution of the obtained granular or flaky SPPE can be measured by a known particle size analysis method such as laser light scattering analysis. Further, the shape information such as the aspect ratio can be obtained by observation with a known microscopic measurement method (for example, a scanning electron microscope).

  For the granular or flaky SPPE obtained after pulverization, the preferred average particle diameter of this embodiment is not particularly limited as long as it is equal to or less than the thickness of the finally obtained polymer electrolyte membrane, but from the viewpoint of uniform dispersibility Therefore, it is preferably 0.01 μm to 10 μm, more preferably 0.02 μm to 8 μm, and particularly preferably 0.05 μm to 6 μm.

  For the granulated or flaked SPPE obtained after pulverization, from the viewpoint of fine packing properties, the preferred aspect ratio (major axis / minor axis) of this embodiment is 1 or more on average, more preferably 2 or more. .

  In the SPPE suitably used in the present embodiment, there is no particular limitation on the PPE used as the raw material, but PPE having an intrinsic viscosity of 0.25 to 1.45 dL / g can be used. When the intrinsic viscosity of PPE is 0.25 dL / g or more, it is excellent in isolation and heat resistance from the solvent when SPPE is used, and when it is 1.45 dL / g or less, the viscosity during the sulfonation reaction increases. However, it is excellent in handling properties such as stirring and liquid feeding. More preferably, it is PPE having an intrinsic viscosity of 0.30 to 0.70 dL / g. The intrinsic viscosity is determined as follows. That is, after dissolving 0.5 g of PPE in chloroform and obtaining two or more kinds of solutions having different concentrations of 100 mL or more (concentration of 0.5 g / dL or less), they are different using an Ubbelohde viscometer at 25 ° C. The specific viscosity for each concentration is measured, and the viscosity when the concentration is 0 is derived from the relationship between the specific viscosity and the concentration, and is defined as the limiting viscosity.

  The sulfonation rate of SPPE used in this embodiment (when the number of moles of sulfonated 2,6-dimethylphenylene oxide units is (P) and the number of moles of unsubstituted 2,6-dimethylphenylene oxide units is Q (P) / (P + Q) × 100%)) is not particularly limited, but the sulfonation rate is preferably 20% or more. When the sulfonation rate is 20% or more, the power generation efficiency when using a polymer electrolyte membrane is further improved.

  The sulfonated modified hydrocarbon polymer electrolyte in the present embodiment has an ion exchange capacity of 0.50 to 3.0 meq / g, and has an ion exchange group so as to satisfy this condition. By setting the ion exchange capacity of the hydrocarbon polymer electrolyte to 3.0 meq / g or less, the polymer electrolyte membrane containing the polymer electrolyte can be swollen under high temperature and high humidity during fuel cell operation. It tends to be reduced. Reduction of the swelling of the polymer electrolyte membrane causes problems such as a decrease in strength of the polymer electrolyte membrane, generation of wrinkles and separation from the electrode, and a problem of reduced gas barrier properties. Can improve. On the other hand, by setting the ion exchange capacity to 0.50 milliequivalent / g or more, the fuel cell including the polymer electrolyte membrane that satisfies such conditions can maintain its power generation capability satisfactorily. From these viewpoints, the ion exchange capacity of the sulfonate-modified hydrocarbon-based polymer electrolyte (B) is more preferably 0.65 meq / g or more, more preferably 1 from the viewpoint of maintaining the power generation capacity. .3 meq / g or more, and more preferably 2.8 meq / g or less, more preferably 2.5 meq / g or less, particularly from the viewpoint of reducing swelling.

  This ion exchange capacity can be adjusted to fall within the above numerical range by adjusting the number of ion exchange groups present in 1 g of a membrane comprising a sulfonated modified hydrocarbon polymer electrolyte.

  In the polymer electrolyte composition of the present embodiment, the mixing ratio of the fluorine-based polymer electrolyte (A) and the sulfonate-modified hydrocarbon-based polymer electrolyte (B) is determined from the viewpoint of gas barrier properties. A) The polymer electrolyte (B) is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and further preferably 5 parts by mass or more with respect to 100 parts by mass.

  On the other hand, from the viewpoint of chemical durability, the polymer electrolyte (B) is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and further preferably 100 parts by mass of the polymer electrolyte (A). Is 40 parts by mass or less.

  In addition to the polymer electrolyte, the polymer electrolyte composition of the present embodiment contains additives such as a compound having a thioether group and / or a compound having an azole ring for the purpose of improving durability. Also good. These additives are used singly or in combination of two or more.

<Compound having a thioether group>
The compound having a thioether group that can be used in the present embodiment is represented by the general formula: — (R—S) _r — (S is a sulfur atom, R is a divalent hydrocarbon group, and r is an integer of 1 or more). A compound having a chemical structure. Specific examples of the compound having such a chemical structure include dialkyl thioethers such as dimethylthioether, diethylthioether, dipropylthioether, methylethylthioether, and methylbutylthioether; tetrahydrothiophene, tetrahydrothiapyran, and the like. Cyclic thioethers; aromatic thioethers such as methylphenyl sulfide, ethylphenyl sulfide, diphenyl sulfide, and dibenzyl sulfide. In addition, you may use what was illustrated here as a compound which has a thioether group as it is, or the polymer obtained by using what was illustrated for a monomer like polyphenylene sulfide (PPS), for example, is thioether. You may use as a compound which has group.

  By adding a compound having a thioether group, chemical deterioration of the polymer electrolyte composition can be suppressed. For example, under high-temperature and low-humidification conditions (for example, at a temperature of 100 ° C., 50 ° C. humidification (humidity 12 RH% However, it is possible to impart high durability to the polymer electrolyte composition.

  The compound having a thioether group is preferably a polymer (oligomer or polymer) having r of 10 or more from the viewpoint of durability, and more preferably a polymer having r of 1000 or more. A particularly preferred compound having a thioether group is polyphenylene sulfide (PPS).

  Here, polyphenylene sulfide will be described. Examples of polyphenylene sulfide that can be preferably used in the present embodiment include polyphenylene sulfide having a paraphenylene sulfide skeleton of preferably 70 mol% or more, more preferably 90 mol% or more.

  The method for producing the polyphenylene sulfide is not particularly limited. For example, a method in which a halogen-substituted aromatic compound (p-dichlorobenzene or the like) is polymerized in the presence of sulfur and sodium carbonate, a halogen-substituted aromatic compound in a polar solvent. Is polymerized in the presence of sodium sulfide or sodium hydrogen sulfide and sodium hydroxide, a method of polymerizing a halogen-substituted aromatic compound in the presence of hydrogen sulfide and sodium hydroxide or sodium aminoalkanoate in a polar solvent, or A method by self-condensation of p-chlorothiophenol is mentioned. Among these, a method of reacting sodium sulfide and p-dichlorobenzene in an amide solvent such as N-methylpyrrolidone or dimethylacetamide or a sulfone solvent such as sulfolane is preferably used.

  The content of -SX group (S is a sulfur atom, X is an alkali metal atom or a hydrogen atom) in polyphenylene sulfide is preferably 10 μmol / g to 10,000 μmol / g, more preferably 15 μmol / g. g to 10,000 μmol / g, more preferably 20 μmol / g to 10,000 μmol / g.

  That the content of the —SX group is in the above range means that there are many reaction active sites. -By using polyphenylene sulfide in which the content of the -SX group satisfies the above range, the dispersibility is improved as the miscibility with the polymer electrolyte according to this embodiment is improved, and under high temperature and low humidification conditions. It is considered that higher durability can be obtained.

  Moreover, as the compound having a thioether group, a compound having an acidic functional group introduced at the terminal can also be suitably used. The acidic functional group to be introduced is selected from the group consisting of sulfonic acid group, phosphoric acid group, carboxylic acid group, maleic acid group, maleic anhydride group, fumaric acid group, itaconic acid group, acrylic acid group, and methacrylic acid group. Are preferred, and sulfonic acid groups are particularly preferred.

  In addition, the introduction method of an acidic functional group is not specifically limited, A general method is used. For example, when a sulfonic acid group is introduced into a compound having a thioether group, it can be introduced under known conditions using a sulfonating agent such as sulfuric anhydride or fuming sulfuric acid. More specifically, for example, K. Hu, T. Xu, W. Yang, Y. Fu, Journal of Applied Polymer Science, Vol. 91, E. Montoneri, Journal of Polymer Science: Part A: Polymer Chemistry, It can be introduced under the conditions described in Vol. 27, 3043-3051 (1989).

  In addition, those in which the introduced acidic functional group is further substituted with a metal salt or an amine salt are also suitably used as the compound having a thioether group. The metal salt is preferably an alkali metal salt such as sodium salt or potassium salt, or an alkaline earth metal salt such as calcium salt.

  Further, when the compound having a thioether group is used in the form of powder, the average particle size of the compound having a thioether group is a viewpoint of achieving a good life-span effect by improving the dispersibility in the polymer electrolyte. Therefore, it is preferably 0.01 μm to 2.0 μm, more preferably 0.01 μm to 1.0 μm, still more preferably 0.01 μm to 0.5 μm, and particularly preferably 0.01 μm to 0.1 μm. This average particle size is a value measured by a laser diffraction / scattering particle size distribution measuring device (for example, model number: LA-950, manufactured by Horiba, Ltd.).

  Examples of a method for finely dispersing a compound having a thioether group in a polymer electrolyte include, for example, a method in which high shear is applied during melt kneading with a polymer electrolyte or the like to pulverize and finely disperse, and a polymer electrolyte solution described later was obtained. Then, the solution is filtered, the compound particle | grains which have a coarse thioether group are removed, the method of using the solution after filtration, etc. are mentioned. From the viewpoint of molding processability, the melt viscosity of polyphenylene sulfide suitably used for melt kneading is preferably 1 to 10,000 poise, more preferably 100 to 10,000 poise. The melt viscosity is a value obtained by holding for 6 minutes at 300 ° C., a load of 196 N, L / D (L: orifice length, D: orifice inner diameter) = 10/1 using a flow tester.

  In the polymer electrolyte composition of the present embodiment, the total amount of the polymer electrolyte (the polymer electrolyte contained in the polymer electrolyte composition with respect to the mass (Wd) of the compound having a thioether group. However, the modified polyazole compound described later is excluded. ) Mass (Wa) ratio (Wa / Wd) is preferably 60/40 to 99.99 / 0.01, more preferably 70/30 to 99.95 / 0.05, and 80/20. ˜99.9 / 0.1 is more preferable, and 90/10 to 99.5 / 0.5 is particularly preferable. By setting the mass ratio of the polymer electrolyte to 60 or more, better ion conductivity can be realized, and better battery characteristics can be realized. On the other hand, by setting the mass ratio of the compound containing a thioether group to 40 or less, durability in battery operation under high-temperature and low-humidification conditions can be improved.

<Compound having azole ring>
Examples of the compound having an azole ring that can be used in the present embodiment include a polymer of a compound having a hetero five-membered ring containing at least one nitrogen atom in the ring as a constituent element. More specifically, examples include polyimidazole compounds, polybenzimidazole compounds, polybenzobisimidazole compounds, polybenzoxazole compounds, polyoxazole compounds, polythiazole compounds, and polybenzothiazole compounds. In addition, the said hetero 5-membered ring may contain an oxygen atom, a sulfur atom, etc. other than a nitrogen atom.

  By adding a compound having an azole ring, not only can chemical degradation due to hydrogen peroxide etc. be suppressed, but by adding a relatively rigid additive such as polyazole, the mechanical strength of the polymer electrolyte composition Therefore, the physical durability of the polymer electrolyte composition tends to be further improved.

  Moreover, it is preferable in the molecular weight of the compound which has an azole ring that it is 300-500,000 (polystyrene conversion) as a weight average molecular weight at the time of performing GPC measurement.

  Examples of the compound having the five-membered ring as a constituent element include p-phenylene group, m-phenylene group, naphthalene group, diphenylene ether group, diphenylene sulfone group, biphenylene group, terphenyl group, and 2,2-bis. From the viewpoint of obtaining heat resistance, it is preferable to use a compound in which a divalent aromatic group represented by (4-carboxyphenylene) hexafluoropropane group is bonded to a hetero five-membered ring. Specifically, polybenzimidazole is preferably used as the compound having an azole ring.

  The compound having an azole ring may be a compound into which an ion exchange group has been introduced (modified polyazole compound) using the following general modification method. As such a modified polyazole compound, for example, one or more groups selected from the group consisting of an amino group, a quaternary ammonium group, a carboxyl group, a sulfonic acid group, and a phosphonic acid group are introduced into a compound having an azole ring. Things. In addition, by introducing an anionic ion exchange group into the compound having an azole ring, the ion exchange capacity of the entire polymer electrolyte composition of the present embodiment can be increased, resulting in a fuel cell operation. Since a high output can be obtained, it is useful. The ion exchange capacity of the modified polyazole compound is preferably 0.10 to 3.5 meq / g.

  The method for modifying the compound having an azole ring is not particularly limited. For example, fuming sulfuric acid, concentrated sulfuric acid, sulfuric anhydride and its complex, sultone such as propane sultone, α-bromotoluenesulfonic acid, chloroalkylsulfonic acid, etc. And a method of introducing an ion exchange group into a compound having an azole ring, a method of polymerizing by adding an ion exchange group at the time of monomer synthesis of a compound having an azole ring, and the like.

  The compound having an azole ring is preferably dispersed in an island shape in the polymer electrolyte phase. Here, “dispersed in the form of islands” means that a phase containing a compound having an azole ring in the phase of the polymer electrolyte is dispersed in the form of particles when TEM observation is performed without performing a dyeing treatment. Means the state. Dispersion in such a state indicates that the portion containing the compound having an azole ring is uniformly finely dispersed in the portion mainly composed of the polymer electrolyte, which is preferable from the viewpoint of durability.

  Further, the polymer electrolyte and the compound having an azole ring may form, for example, a state in which an ionic bond forms an acid-base ion complex, or a state in which they are covalently bonded. Good. That is, for example, when the polymer electrolyte has a sulfonic acid group and the compound having an azole ring has a reactive group such as an imidazole group, an oxazole group, or a thiazole group, the sulfonic acid group and the azole ring in the polymer electrolyte are The nitrogen atom which each reactive group in the compound has may bind to each other by ionic bond or covalent bond.

Whether or not the ionic bond or the covalent bond exists can be confirmed using a Fourier-Transform Infrared Spectrometer (hereinafter referred to as FT-IR). For example, perfluorocarbon sulfonic acid resin was used as the polymer electrolyte, and poly [2,2 ′ (m-phenylene) -5,5′-benzimidazole] (hereinafter referred to as “PBI”) was used as the compound having an azole ring. In this case, when measured by FT-IR, the shifted absorption peaks derived from the chemical bond between the sulfonic acid group in the polymer electrolyte and the imidazole group in PBI are 1458 cm ⁻¹ , 1567 cm ⁻¹ , 1634 cm. ^-1 is recognized near.

  In addition, when a polymer electrolyte membrane to which PBI was added as a compound having an azole ring was prepared and a dynamic viscoelasticity test was performed on the membrane, a loss tangent (tan δ) peak obtained during a temperature rising process from room temperature to 200 ° C. The temperature (Tg) is higher than that of the polymer electrolyte membrane to which PBI is not added. Such an increase in Tg is preferable because the heat resistance and mechanical strength of the polymer electrolyte membrane can be improved.

  In the polymer electrolyte composition of the present embodiment, the ratio (Wc / Wd) of the mass (Wc) of the compound having an azole ring to the mass (Wd) of the compound having a thioether group is chemical stability and durability. From the viewpoint of balance with (dispersibility), it is preferably 1/99 to 99/1. Further, from the same viewpoint, Wc / Wd is more preferably 5/95 to 95/5, further preferably 10/90 to 90/10, and particularly preferably 20/80 to 80/20.

  Furthermore, the proportion of the total mass of the compound having an azole ring and the compound having a thioether group in the polymer electrolyte composition is preferably 0.01% by mass to 50% by mass. From the viewpoint of balance between ion conductivity and durability (dispersibility), the total mass is more preferably 0.05% by mass to 45% by mass, and further preferably 0.1% by mass to 40% by mass. 0.2 mass% to 35 mass% is even more preferred, and 0.3 mass% to 30 mass% is particularly preferred.

[Microporous membrane]
The raw material of the microporous membrane according to the present embodiment is not limited, and for example, a simple substance such as polytetrafluoroethylene, polyamide, polyimide, polyolefin, polycarbonate, or a mixture thereof may be used, but polytetrafluoroethylene (hereinafter, “ It may be abbreviated as “PTFE”.) From the viewpoint of chemical durability of the polymer electrolyte, and more preferably made of PTFE.

  The production method of the PTFE microporous membrane preferably used in the present embodiment is not particularly limited, but is preferably an expanded PTFE microporous membrane from the viewpoint of suppressing the dimensional change of the polymer electrolyte membrane. The stretched PTFE microporous membrane is produced by a known method as disclosed in, for example, JP-A-51-30277, JP-A-1-01876, JP-A-10-30031, and the like. be able to. Specifically, first, a liquid lubricant such as solvent naphtha or white oil is added to the fine powder obtained by coagulating the PTFE emulsion polymerization aqueous dispersion, and paste extrusion is performed in a rod shape. Then, this rod-like paste extrudate (cake) is rolled to obtain a PTFE green body film. The film of the green body at this time is stretched at an arbitrary magnification in the longitudinal direction (MD direction) and / or the width direction (TD direction). The stretched PTFE microporous membrane can be obtained by removing the liquid lubricant filled at the time of stretching or after stretching by heating or extraction.

  In the present embodiment, the microporous membrane may be added with known additions such as non-fibrosis products (for example, low molecular weight PTFE), ultraviolet absorbers, light stabilizers, antistatic agents, antifogging agents, and coloring pigments as necessary. You may contain an agent in the range which does not impair the achievement and effect of the subject of this invention.

  The microporous membrane in the present embodiment is preferably such that the distribution center (peak) of the pore distribution is in the range of the pore diameter of 0.3 μm to 5.0 μm. Here, the pore distribution in the microporous membrane is JIS-K. It means a value measured by the bubble point half dry method using the bubble point method described in -3832 (1990).

  Here, if the distribution center of the pore diameter is 0.3 μm or more, it can be easily filled with an additive or an electrolyte solution having a hydrogen peroxide suppressing effect and the like, and generation of voids in the polymer electrolyte membrane can be suppressed, and the polymer Since a sufficient filling speed of the electrolyte composition can be secured, the processability tends to be excellent. If the distribution center of the pore diameter is 5.0 μm or less, the dimensional change of the polymer electrolyte membrane can be suppressed, and a sufficient membrane reinforcing effect tends to be obtained.

  From the viewpoint of initial power generation characteristics, the distribution center of the pore distribution of the microporous membrane is preferably 0.4 μm or more, more preferably 0.5 μm or more, and 0.6 μm or more. More preferably, it is particularly preferably 0.7 μm or more. From the viewpoint of the reinforcing effect of the membrane, the distribution center of the pore distribution of the microporous membrane is preferably 4.5 μm or less, more preferably 4.0 μm or less, and 3.5 μm or less. More preferably, it is particularly preferably 3.0 μm or less.

  In addition, in the pore distribution of the microporous membrane in the present embodiment, the abundance of pores having a pore diameter of 0.3 μm to 5.0 μm of the microporous membrane is preferably 0.5 or more (quantity ratio). Here, the “abundance of pores” of the microporous membrane means a pore diameter measurement range of 0.065 μm to 10% by a bubble point half dry method using a bubble point method described in JIS-K-3832 (1990). The ratio of the number of pores existing in the range of pore diameters of 0.3 μm to 5.0 μm to the total number of pores of the microporous membrane measured at 0.0 μm.

  If the amount of pores having a pore diameter of 0.3 μm to 5.0 μm is adjusted to be 0.5 or more (quantity ratio), the pore diameter of the microporous membrane becomes relatively uniform. It becomes easy to uniformly fill the voids in the porous membrane with the electrolyte. As a result, when the polymer electrolyte composition contains an additive, the additive can be uniformly dispersed in the membrane, so that voids are hardly generated in the membrane, and the polymer electrolyte membrane exhibits high chemical durability. Tend to. Further, when the additive does not have proton conductivity, the pores of the microporous membrane are not blocked by the additive by making the pore size of the microporous membrane equal to or larger than the median diameter of the additive. Can be adjusted as follows. This indicates that, as a result, proton conduction in the membrane tends to be performed smoothly without being inhibited, and it is possible to exhibit excellent effects such as improvement of the initial characteristics of the polymer electrolyte membrane It becomes.

In the present embodiment, the abundance (quantity ratio) of pores having a pore diameter of 0.3 μm to 5.0 μm in the microporous membrane is more preferably 0.7 or more, and further preferably 0.8 or more. 0.9 or more is more preferable, and 1 is particularly preferable.
Further, from the same viewpoint, the abundance (quantity ratio) of pores having a pore diameter of 0.5 μm to 5.0 μm of the microporous membrane is preferably 0.5 or more, more preferably 0.7 or more, still more preferably. Is 0.8 or more, more preferably 0.9 or more, and particularly preferably 1.
From the same viewpoint, the abundance (quantity ratio) of pores having a pore diameter of 0.7 μm to 5.0 μm of the microporous membrane is preferably 0.5 or more, more preferably 0.7 or more, and still more preferably. Is 0.8 or more, more preferably 0.9 or more, and particularly preferably 1.

  The microporous membrane in the present embodiment preferably has at least two distribution centers in the pore distribution. When the pore distribution of the microporous membrane has two distribution centers, (i) the pore having a pore diameter near the larger distribution center plays a role in promoting discharge of reaction product water and easy filling of additives. (Ii) Since the pores having a pore size near the smaller distribution center play a role of suppressing the volume swelling of the electrolyte by the mechanical strength of the microporous membrane, A polymer electrolyte membrane using this microporous membrane tends to be compatible with both chemical durability and physical durability.

  The pore size of the microporous membrane depends on the type of lubricant, the dispersibility of the lubricant, the stretching ratio of the microporous membrane, the lubricant extraction solvent, the heat treatment temperature, the heat treatment time, the extraction time, and the extraction temperature. It can adjust to the said range.

  In addition, the microporous membrane in the present embodiment may be a single layer or may be composed of multiple layers as necessary. From the viewpoint that defects do not propagate even if defects such as voids and pinholes occur in each single layer, multiple layers are preferable. On the other hand, a single layer is preferable from the viewpoint of the filling properties of the electrolyte and the additive. Examples of a method for forming a microporous film as a multilayer include a method in which two or more single layers are bonded by thermal lamination, and a method in which a plurality of cakes are stacked and rolled.

  The microporous membrane according to the present embodiment preferably has an elastic modulus of at least one of a machine flow direction (MD) and a direction perpendicular to the microfluidic direction (MD) at the time of production of 1000 MPa or less, and 500 MPa or less. Is more preferable, and 250 MPa or less is more preferable. By setting the elastic modulus of the microporous membrane to 1000 MPa or less, the dimensional stability of the polymer electrolyte membrane is improved. Here, the elastic modulus of the microporous membrane refers to a value measured according to JIS-K7113 (1995).

  Proton conduction in the polymer electrolyte is made possible by the polymer electrolyte absorbing water and hydrating the ion exchange groups. Accordingly, the higher the ion exchange group density and the larger the ion exchange capacity, the higher the conductivity at the same humidity. Also, the higher the humidity, the higher the conductivity.

When the sulfone group density is high, the polymer electrolyte in the present embodiment exhibits high conductivity even under low humidity, but becomes extremely hydrated under high humidity. For example, in the operation of a household fuel cell, starting and stopping are usually performed once or more once a day, and the polymer electrolyte membrane repeatedly swells and contracts due to a change in humidity at that time. It is not preferable in terms of both performance and durability that the polymer electrolyte membrane repeats such wet and dry dimensional changes. When the ion exchange capacity of the polymer electrolyte in the present embodiment is high, the polymer electrolyte is easy to contain water, and when the membrane is formed as it is, the change in wet and dry dimensions is large. However, by using a microporous film having an elastic modulus of 1000 MPa or less, it is possible to relieve the stress due to the volume change of the film with the microporous film and suppress the dimensional change. On the other hand, if the elastic modulus of the microporous membrane is too small, the strength of the membrane tends to decrease.
Therefore, the elastic modulus of the microporous membrane is preferably 1 to 1000 MPa, more preferably 10 to 800 MPa, and still more preferably 100 to 500 MPa.

  The microporous membrane according to this embodiment preferably has a porosity of 50% to 90%, more preferably 60% to 90%, still more preferably 60% to 85%, and 50% to 90%. 85% is particularly preferable. When the porosity is in the range of 50% to 90%, the ionic conductivity of the polymer electrolyte membrane, the strength of the polymer electrolyte membrane, and the suppression of dimensional change tend to be compatible. Here, the porosity of the microporous membrane refers to a value measured by a mercury porosimeter (for example, manufactured by Shimadzu Corporation, trade name: Autopore IV 9520, initial pressure of about 20 kPa) by a mercury intrusion method.

  The numerical value of the porosity of the microporous membrane can be adjusted to the above range depending on the number of pores in the microporous membrane, the pore diameter, the pore shape, the draw ratio, the amount of liquid lubricant added, and the type of liquid lubricant. As a means for increasing the porosity of the microporous film, for example, a method of adjusting the addition amount of the liquid lubricant to 5 to 50% by mass can be mentioned. By adjusting the addition amount of the liquid lubricant within this range, the moldability of the resin constituting the microporous membrane is maintained and the plasticizing effect is sufficient. It can be highly fibrillated in the axial direction and can efficiently increase the draw ratio. On the other hand, examples of means for lowering the porosity include reducing the amount of liquid lubricant and decreasing the draw ratio.

  The microporous membrane in this embodiment preferably has a thickness of 0.1 μm to 50 μm, more preferably 0.5 μm to 30 μm, still more preferably 1.0 μm to 20 μm, and 2.0 μm to 20 μm. Is particularly preferred. When the film thickness is in the range of 0.1 μm to 50 μm, the polymer electrolyte can be satisfactorily filled in the microporous film and the dimensional change of the polymer electrolyte tends to be suppressed. Here, the film thickness of the microporous membrane is determined by sufficiently allowing the membrane to stand in a constant temperature and humidity room of 50% RH, and then using a known film thickness meter (for example, trade name “B-1 manufactured by Toyo Seiki Seisakusho”). ")" Means the value measured using.

  The value of the film thickness of the microporous film can be adjusted to the above range by the solid content of the cast solution, the amount of the extruded resin, the extrusion speed, and the stretching ratio of the microporous film.

Furthermore, the microporous membrane according to this embodiment has a high absolute strength in consideration of the elastic modulus and film thickness of the microporous membrane in order to suppress changes in the wet and dry dimensions of the polymer electrolyte membrane and maintain the strength of the membrane. preferable.
The absolute strength here is determined by the following formula.
Absolute strength (N / cm) = elastic modulus (MPa) × thickness (μm) × 10 −2
The absolute strength is preferably 0.1 to 120 N / cm, preferably 1 to 100 N / cm, and more preferably 10 to 80 N / cm.

  It is preferable that the microporous membrane in the present embodiment is further subjected to a heat setting treatment to reduce shrinkage. By performing this heat setting treatment, shrinkage of the microporous membrane in a high temperature atmosphere can be reduced, and the dimensional change of the polymer electrolyte membrane can be reduced. The heat setting is performed on the microporous film by, for example, relaxing the stress in the TD (width direction) direction in a temperature range below the melting point of the microporous film raw material with a TD (width direction) tenter. In the case of PTFE preferably used in the present embodiment, a preferable stress relaxation temperature range is 200 ° C to 420 ° C.

  In addition, the microporous membrane in the present embodiment may be subjected to surface treatment such as application of a surfactant or chemical modification, as necessary, within a range that does not impair the problems and effects of the present invention. By performing the surface treatment, the surface of the microporous membrane can be hydrophilized, and in addition to the effect of high filling of the polymer electrolyte solution, the water content of the polymer electrolyte membrane can be adjusted.

[Polymer electrolyte membrane]
The polymer electrolyte membrane of the present embodiment is a membrane containing the polymer electrolyte composition. From the viewpoint of more effectively and reliably achieving the effects of the present invention, the polymer electrolyte membrane includes the microporous membrane and the polymer electrolyte composition present in the voids (fine pores) of the microporous membrane. It is preferable that it contains. Such a polymer electrolyte membrane can be obtained by filling the voids of the microporous membrane with the polymer electrolyte composition.

  In the present embodiment, the thickness of the polymer electrolyte membrane is preferably 1 μm to 500 μm, more preferably 2 μm to 100 μm, still more preferably 5 μm to 50 μm, and particularly preferably 5 μm to 35 μm. Adjusting the film thickness to the above range can reduce inconveniences such as direct reaction between hydrogen and oxygen, resulting in differential pressure and distortion during handling during fuel cell production and during fuel cell operation. However, it is preferable in that the film is hardly damaged. Furthermore, from the viewpoint of maintaining the ion permeability of the polymer electrolyte membrane and maintaining the performance as a solid polymer electrolyte membrane, it is preferable to adjust the film thickness to the above range.

In the present embodiment, the dimensional change in the planar direction of the polymer electrolyte membrane in water at 80 ° C. is preferably 15% or less, more preferably 13% or less, and even more preferably 11% or less.
Here, the dimensional change in the planar direction in 80 ° C. water of the present embodiment is measured as follows.

  A membrane sample is cut into a 4 cm × 3 cm rectangular membrane, left in a constant temperature and humidity room (23 ° C., 50% RH) for 1 hour or longer, and each dimension in the planar direction of the dried rectangular membrane sample is measured. Next, the rectangular membrane sample whose dimensions were measured was boiled in hot water at 80 ° C. for 1 hour, so that the mass change due to moisture in the electrolyte membrane was 5% or less (volume swelling due to moisture absorption was saturated). Fully absorb water). At this time, the film is taken out from the hot water, and the mass change amount is confirmed to be 5% or less with an electronic balance in a state where water on the surface is sufficiently removed. The wet membrane sample that has absorbed water and expanded is taken out of the hot water, and each dimension in the plane direction (longitudinal (MD) direction, width (TD) direction) is measured. Taking each dimension in the planar direction in the dry state as a reference, taking the average of the increment of each dimension (MD direction and TD direction) in the planar direction in the wet state from each dimension in the dry state, %).

  The dimensional change in the planar direction can be adjusted to the above range by adjusting the structure of the microporous membrane, the elastic modulus and film thickness, the EW of the polymer electrolyte, the heat treatment temperature of the polymer electrolyte membrane, and the like.

  The polymer electrolyte membrane according to this embodiment preferably has a water content at 80 ° C. of 5% by mass to 150% by mass, more preferably 10% by mass to 100% by mass, and still more preferably 20% by mass to 80% by mass. It is mass%, Most preferably, it is 30 mass%-70 mass%. When the water content of the polymer electrolyte is adjusted to the above range, there is an effect that long-term dimensional stability and high battery performance are exhibited even under high temperature and low humidification conditions. When the water content at 80 ° C. is 5% by mass or more, there is sufficient water for proton transfer, so that excellent battery performance is exhibited when used in a fuel cell. On the other hand, when the water content at 80 ° C. is 150% by mass or less, the polymer electrolyte is less likely to be gelled and can be formed as a membrane.

  The water content of the polymer electrolyte membrane at 80 ° C. is the molecular weight, MFR, crystallinity and ion exchange capacity of the polymer electrolyte, the hydrophilic treatment area of the microporous membrane surface, the heat treatment temperature and time of the polymer electrolyte membrane, etc. It can be controlled by adjusting. Examples of means for increasing the water content at 80 ° C. include increasing the ion exchange group density of the polymer electrolyte, increasing the MFR of the polymer electrolyte precursor polymer, and decreasing the heat treatment temperature and heat treatment time to increase the polymer content. Examples include suppressing crystallization of the electrolyte or modifying the surface of the microporous membrane with a hydrophilic group.

  On the other hand, as means for lowering the water content at 80 ° C., for example, the ion exchange group density of the polymer electrolyte is lowered, the MFR of the polymer electrolyte precursor polymer is lowered, or the polymer electrolyte membrane is removed by an electron beam or the like. And crosslinking.

The water content at 80 ° C. of the polymer electrolyte membrane is measured as follows. First, a sample is cut into a 30 mm × 40 mm square from the polymer electrolyte membrane, and the film thickness is measured. Next, the membrane sample is immersed in ion-exchanged water heated to 80 ° C, and after 1 hour, the membrane is taken out from the ion-exchanged water at 80 ° C. After wiping off the water, the mass is measured with an electronic balance, and the mass is defined as W1 (g). Next, the membrane sample is dried in a constant temperature and humidity chamber (23 ° C., 50% RH). After drying for 1 hour or longer, the membrane sample is placed in a halogen moisture meter (model number: HB43, manufactured by METTLER TOLEDO), dried at 160 ° C. for 1 minute, and then the mass of the membrane sample is measured. The mass (absolute dry mass) of this membrane sample is defined as W2 (g). The water content of the polymer electrolyte membrane at 80 ° C. is calculated from the above W1 and W2 by the following formula.
Moisture content = (W1-W2) / W2 × 100

[Production Method of Polymer Electrolyte Composition]
The method for producing a polymer electrolyte composition of the present embodiment is a method for producing the polymer electrolyte composition, wherein the ion exchange capacity is 0.50 to 3.0 meq / g, a sulfonated modified hydrocarbon system. A solution obtained by dissolving 0.10 to 50 parts by mass of a polymer electrolyte (B) and 100 parts by mass of a fluorine-based polymer electrolyte (A) having an ion exchange capacity of 0.50 to 3.0 meq / g in a solvent. And a step of removing the solvent from the solution. In the step of obtaining the solution, from the viewpoint of uniform dispersibility, the polymer electrolyte (B) is preferably granulated or flaked having an average particle diameter of 0.01 to 10 μm. In addition, the solvent used in the step of obtaining the solution may be any one exemplified in the following description of the polymer electrolyte solution, and the “solution” includes a dispersion. Furthermore, the method of removing the solvent in the step of removing the solvent is not particularly limited, and the solvent may be removed by heating (heat treatment) or reduced pressure, and may be filtered if the solution is a dispersion. The temperature at the time of the heat treatment may be, for example, the temperature of the heat treatment shown in the following description of the method for producing a polymer electrolyte membrane.

[Production method of polymer electrolyte membrane]
Next, the manufacturing method of the polymer electrolyte membrane of this embodiment is demonstrated. The polymer electrolyte membrane of this embodiment can be obtained by filling the polymer electrolyte composition into the fine pores of the microporous membrane.

  The method of filling the pores of the microporous membrane with the polymer electrolyte composition is not particularly limited. For example, a method of applying a polymer electrolyte solution described later to the microporous membrane, or a microporous membrane in the polymer electrolyte solution. The method of drying after impregnating a film | membrane is mentioned. For example, a coating film of a polyelectrolyte solution is formed on an elongated casting substrate (sheet) that is moving or standing, and an elongated microporous membrane is brought into contact with the coating film of the solution. A composite structure is produced. The incomplete composite structure is dried in a hot air circulation tank. Next, a method of forming a polymer electrolyte membrane by further forming a coating film of a polymer electrolyte solution on the dried incomplete composite structure can be mentioned. The contact between the polymer electrolyte solution and the microporous membrane may be performed in a dry state, in an undried state or in a wet state. Moreover, when making it contact, you may carry out pressure-bonding with a rubber roller, or controlling the tension | tensile_strength of a microporous film. Further, a sheet containing a polymer electrolyte may be preliminarily formed by extrusion molding, cast molding, or the like, and this sheet may be filled by being hot-pressed over the microporous film.

  Further, for the purpose of improving the conductivity and mechanical strength of the polymer electrolyte membrane, one or more layers containing the polymer electrolyte are laminated on at least one main surface of the polymer electrolyte membrane thus produced. May be. Moreover, in the polymer electrolyte membrane of this embodiment, you may bridge | crosslink the compounds contained there using a crosslinking agent, an ultraviolet-ray, an electron beam, a radiation.

  The polymer electrolyte membrane of the present embodiment is preferably further subjected to heat treatment after being produced as described above. By this heat treatment, the crystal part in the polymer electrolyte membrane and the polymer solid electrolyte part are firmly bonded, and as a result, the mechanical strength can be further stabilized. The temperature of this heat treatment is preferably 100 ° C to 230 ° C, more preferably 110 ° C to 230 ° C, and still more preferably 120 ° C to 200 ° C. By adjusting the temperature of the heat treatment to the above range, the adhesion between the crystal part and the electrolyte composition part tends to be improved. Moreover, the said temperature range is suitable also from a viewpoint of maintaining the high moisture content and mechanical strength of a polymer electrolyte membrane. Although depending on the temperature of the heat treatment, the heat treatment time is preferably 5 minutes to 3 hours, more preferably 10 minutes to 2 hours from the viewpoint of obtaining a highly durable polymer electrolyte membrane.

<Polymer electrolyte solution>
The polymer electrolyte solution that can be used when producing the polymer electrolyte membrane according to the present embodiment contains the polymer electrolyte composition, a solvent, and other additives as required. This polymer electrolyte solution is used as it is or after passing through processes such as filtration and concentration, as a filling liquid for the microporous membrane. Alternatively, this solution can be used alone or mixed with another electrolyte solution.

  A method for producing the polymer electrolyte solution will be described. The method for producing the polymer electrolyte solution is not particularly limited. For example, after obtaining a solution in which the polymer electrolyte is dissolved or dispersed in a solvent, the additive is dispersed in the solution as necessary. Alternatively, first, the polymer electrolyte and the additive are mixed through steps such as melt extrusion and stretching, and the mixture is dissolved or dispersed in a solvent. In this way, a polymer electrolyte solution is obtained.

  More specifically, first, a molded product made of a polymer electrolyte precursor polymer is immersed in a basic reaction liquid and hydrolyzed. By this hydrolysis treatment, the precursor polymer of the polymer electrolyte is converted into a polymer electrolyte. Next, the hydrolyzed molded product is sufficiently washed with warm water or the like, and then the molded product is subjected to an acid treatment. The acid used for the acid treatment is not particularly limited, but mineral acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as oxalic acid, acetic acid, formic acid and trifluoroacetic acid are preferred. By this acid treatment, the precursor polymer of the polymer electrolyte is protonated, and a polymer electrolyte such as a perfluorocarbon sulfonic acid resin is obtained.

  The above-mentioned molded product (molded product containing a polymer electrolyte) treated with an acid as described above is dissolved or suspended in a solvent (solvent having good affinity with the resin) that can dissolve or suspend the polymer electrolyte. It is. Examples of such solvents include protic organic solvents such as water, ethanol, methanol, n-propanol, isopropyl alcohol, butanol, and glycerin, N, N-dimethylformamide, N, N-dimethylacetamide, and N-methyl. Examples include aprotic organic solvents such as pyrrolidone. These are used singly or in combination of two or more. In particular, when one kind of solvent is used, the solvent is preferably water. Moreover, when using combining 2 or more types, the mixed solvent of water and a protic organic solvent is preferable.

  The method for dissolving or suspending the polymer electrolyte in the solvent is not particularly limited. For example, the polymer electrolyte may be dissolved or dispersed as it is in the above solvent, but the polymer electrolyte may be dissolved in a temperature range of 0 to 250 ° C. under atmospheric pressure or under conditions of airtight pressure in an autoclave or the like. It is preferable to dissolve or disperse in. In particular, when water and a protic organic solvent are used as the solvent, the mixing ratio of water and the protic organic solvent depends on the dissolution method, dissolution conditions, type of polymer electrolyte, total solid content concentration, dissolution temperature, stirring speed, etc. The ratio of the mass of the protic organic solvent with respect to water is preferably 0.1 to 10 with respect to water 1, and more preferably with respect to water 1. 0.1-5.

  The polyelectrolyte solution is an emulsion (a liquid particle in which liquid particles are dispersed as colloidal particles or coarser particles to form a milky state), a suspension (solid particles in a liquid are colloidal particles or 1) a colloidal liquid (a state in which macromolecules are dispersed), a micellar liquid (a lyophilic colloidal dispersion system formed by associating many small molecules with intermolecular forces) Species or two or more embodiments are included.

  In addition, the polymer electrolyte solution can be concentrated or filtered according to the molding method and application of the polymer electrolyte membrane. The concentration method is not particularly limited. For example, there are a method of heating a polymer electrolyte solution and evaporating the solvent, and a method of concentrating under reduced pressure. When the polymer electrolyte solution is used as a coating solution, if the solid content of the polymer electrolyte solution is too high, the viscosity tends to increase and it becomes difficult to handle, whereas if it is too low, the productivity tends to decrease. Therefore, it is preferably 0.5% by mass to 50% by mass. The method for filtering the polymer electrolyte solution is not particularly limited, but a typical example is a method of pressure filtration using a filter. It is preferable to use a filter medium having a 90% collection particle size of 10 to 100 times the average particle size of solid particles contained in the polymer electrolyte solution. Examples of the material of the filter medium include paper and metal. In particular, when the filter medium is paper, the 90% collection particle diameter is preferably 10 to 50 times the average particle diameter of the solid particles. When using a metal filter, it is preferable that the 90% collection particle diameter is 50 to 100 times the average particle diameter of the solid particles. Setting the 90% collection particle size to 10 times or more of the average particle size suppresses that the pressure required for liquid feeding becomes too high or that the filter is blocked in a short period of time. Can be suppressed. On the other hand, setting the 90% collection particle size to 100 times or less of the average particle size is preferable from the viewpoint of satisfactorily removing particle agglomerates and resin undissolved materials that cause foreign matters on the film.

  As described above, the polymer electrolyte membrane of the present embodiment described above is excellent in gas barrier properties, and is suitably used as an electrolyte material for a solid polymer electrolyte fuel cell. Moreover, the polymer electrolyte membrane of this embodiment has both high durability and power generation efficiency.

As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the said this embodiment. The present invention can be variously modified without departing from the gist thereof.
Unless otherwise specified, the various parameters described above are measured according to the measurement methods in the following examples.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited only to these examples. Measurement methods and evaluation methods for various physical properties in Examples and the like are as follows.

(1) Pore distribution of microporous membrane The pore distribution of the microporous membrane was measured as follows. First, a microporous membrane sample was cut into a size of φ25 mm, and measurement was performed using a through pore distribution / gas fluid permeability analyzer (manufactured by Xonics Corporation, apparatus name: Porometer 3G). The measurement by this apparatus was based on the bubble point method described in JIS-K-3832 (1990). First, the pore volume of the microporous membrane was completely filled with a test solution (porofil (registered trademark)). After that, the pressure applied to the microporous membrane is gradually increased to obtain the pore distribution from the surface tension of the test liquid, the pressure of the applied gas, and the supply flow rate (bubble point half dry method).
The pore distribution of the microporous membrane was measured by setting the pore measurement range to 0.065 μm to 10.0 μm and using compressed air as the flow gas.
Moreover, the abundance of the pores was calculated by the following formula.
(Abundance of pores) = (Number of pores existing in a pore diameter range of 0.3 μm to 5.0 μm) / (Total number of pores of a microporous membrane existing in a pore diameter of 0.065 μm to 10.0 μm)

(2) Ion-exchange capacity A membrane is formed from a polymer electrolyte in which the counter-ion of the ion-exchange group is in the proton state (with one main surface area of approximately ² to 20 cm ² ), and saturated at 25 ° C. It was immersed in 30 mL of NaCl aqueous solution and left for 30 minutes with stirring. Subsequently, the proton in the saturated NaCl aqueous solution was neutralized and titrated as a 0.01N sodium hydroxide aqueous solution using phenolphthalein as an indicator. The polymer electrolyte membrane in which the counter ion of the ion exchange group obtained by filtration after neutralization was in the state of sodium ion was rinsed with pure water, further vacuum dried and weighed. The amount of sodium hydroxide required for neutralization is M (mmol), the mass of a membrane made of a polymer electrolyte whose ion-exchange group counter ion is sodium ion is W (mg), and the equivalent mass EW (g / Equivalent).
EW = (W / M) −22
Furthermore, the ion exchange capacity (milli equivalent / g) was calculated by taking the inverse of the obtained EW value and multiplying it by 1000.

(3) Film thickness After the film sample was allowed to stand in a constant temperature and humidity room at 23 ° C. and 50% RH for 1 hour or longer, the film was measured using a film thickness meter (trade name “B-1” manufactured by Toyo Seiki Seisakusho). The thickness was measured.

(4) Particle size measurement The particle size of the granulated and flaked SPPE filler was measured in a flow-type measurement cell using a laser scattering particle size analyzer SALD-3100 (model number) manufactured by Shimadzu Corporation. Hexane was used as the dispersion medium.

(5) Sulfonation rate The sulfonation rate of SPPE is ECA-500 (model number) which is 1H-NMR manufactured by JEOL Co., Ltd., DMSO-d6 is used as a solvent, 1H frequency is 500 MHz, relaxation time is 5 sec, and the number of integrations. Was measured at room temperature, the peak near 6.0 ppm was sulfonated 2,6-dimethylphenylene oxide unit (P), the peak near 6.4 ppm The dimethylphenylene oxide unit (Q) was identified, and the sulfonation rate = the area of the peak (P) / (the area of the peak (P) + the area of the peak (Q)) × 100 (%) was determined from the peak area ratio. .

(6) Gas permeability The gas permeability of hydrogen and oxygen of the membrane sample was measured using a flow type gas permeability measuring device GTR-30XFAFC (model number) manufactured by GT Tech Co., Ltd. The supply gas flow rates were TEST gas (hydrogen or oxygen) 30 cc / min and FLOW gas (He) 20 cc / min. Two conditions of 40 ° C., 50% RH, 80 ° C., and 90% RH were adopted as the heating and humidifying conditions for the gas.

  Hydrogen or oxygen gas that had permeated the membrane sample from the TEST gas side to the FLOW side was introduced into a gas chromatograph G2700TF (model number) manufactured by Yanaco Analytical Co., Ltd., and the gas permeation amount was quantified.

The gas permeation amount is X (cc), the correction factor 2 is B (= 1.0), the film thickness of the membrane sample is T (cm), the hydrogen or oxygen partial pressure is P (Pa), and the gas permeation area of the membrane sample is Gas permeation L (cc / (cm · sec · Pa)) when A (cm ² ) and measurement time was D (sec) was calculated from the following formula.
L = (X × B × T / (P × A × D))
The test was terminated when the gas permeation amount became stable after 24 hours from the start of measurement.

[Example 1]
<Preparation of polymer electrolyte solution>
A precursor of perfluorosulfonic acid resin obtained from a compound represented by tetrafluoroethylene and CF ₂ ═CFO (CF ₂ ) ₂ —SO ₂ F, which is a polymer polymer precursor polymer (hydrolysis and acid treatment) Later ion exchange capacity: 1.4 meq / g) pellets were prepared. Next, the precursor pellet was contacted with an aqueous solution in which potassium hydroxide (15% by mass) and methanol (50% by mass) were dissolved at 80 ° C. for 20 hours to perform a hydrolysis treatment. Then, the pellet was immersed in 60 degreeC water for 5 hours. Next, the treatment of immersing the pellets immersed in water in a 2N aqueous hydrochloric acid solution at 60 ° C. for 1 hour was repeated 5 times, each time replacing the aqueous hydrochloric acid solution with a new one. And the pellet after having been repeatedly immersed in hydrochloric acid aqueous solution was washed with ion-exchange water and dried. As a result, a perfluorocarbon sulfonic acid resin (hereinafter abbreviated as “PFSA”) pellet as a polymer electrolyte was obtained.

  Next, S201A (Intrinsic viscosity: 0.51 dL / g, product name) manufactured by Asahi Kasei Chemicals Corporation was used as the raw material PPE. 30.0 g of raw material PPE was dissolved in 450 mL of chloroform, and 14.1 g of chlorosulfonic acid was added dropwise thereto over 20 minutes, and the mixture was reacted at room temperature for 30 minutes. The supernatant was removed from the SPPE precipitated with the progress of the reaction, and washed with 300 mL of chloroform three times. The obtained SPPE was dissolved in 300 mL of methanol. A polytetrafluoroethylene sheet was laid on a stainless steel tray, a methanol solution of SPPE was applied onto the polytetrafluoroethylene sheet by a cast method, and air-dried at room temperature for 12 hours to obtain a film-like SPPE having a thickness of about 4 μm. The film-like SPPE was cut into about 5 mm squares with scissors, transferred to a 3 L plastic tank, and washed with 600 mL of distilled water. The same washing operation was repeated 5 times until the pH of the washing separated water in this washing operation became 5 or more. The washed SPPE was air-dried at room temperature for 24 hours to obtain dry SPPE. The sulfonation rate of the obtained SPPE was 72% as measured by 1H-NMR.

  The dried SPPE was coarsely pulverized while being cooled using a turbo disk mill (TD-150) manufactured by Freund Turbo Corporation to obtain coarsely pulverized SPPE. By observation with a microscope, it was confirmed that the particles were pulverized to an apparent size of about 40 μm.

  Subsequently, this coarsely pulverized SPPE was dispersed in hexane to obtain a 5% by mass slurry. The slurry was finely pulverized while being cooled using Ultra Apex Mill UAM-1 (trade name, YTZ balls are used as beads) manufactured by Kotobuki Industries Co., Ltd. The average particle diameter of SPPE after fine powder reprocessing was 6 μm.

The obtained slurry was filtered and vacuum-dried at room temperature to obtain an SPPE filler.
Observation of the SPPE filler with a scanning electron microscope revealed a thickness of 3 μm and an average aspect ratio of 2.7.

  Next, PFSA pellets and SPPE filler were mixed at a ratio of 20 parts by mass of SPPE filler to 100 parts by mass of PFSA pellets.

  The obtained mixture was placed in a 5 L autoclave together with an aqueous ethanol solution (water: ethanol = 50.0 / 50.0 (mass ratio)), sealed, heated to 160 ° C. with stirring with a blade, and held for 5 hours. . Thereafter, the autoclave was naturally cooled to obtain a uniform polymer electrolyte solution having a solid content concentration of 5% by mass. This was concentrated under reduced pressure at 80 ° C., then diluted with water and ethanol to prepare a solution of ethanol: water = 60: 40 (mass ratio) having a viscosity of 500 cP and a solid content of 15.0% by mass, Solution 1 was obtained.

<Production of polymer electrolyte membrane>
The above solution 1 is applied onto a base film (trade name “Kapton 200H” manufactured by Toray DuPont Co., Ltd., the same applies hereinafter) using a bar coater (manufactured by Matsuo Sangyo Co., Ltd., bar No. 200, WET film thickness 200 μm). (Applying area: width of about 200 mm × length of about 500 mm), the membrane was dried in an oven at 90 ° C. for 20 minutes. Further, this membrane was heat treated in an oven at 170 ° C. for 1 hour to obtain a polymer electrolyte membrane having a thickness of about 25 μm on the base film. The polymer electrolyte membrane was peeled off from the base film as necessary, and various evaluations were performed. The evaluation results are shown in Table 1.

[Example 2]
<Preparation of polymer electrolyte solution>
A solution 2 was obtained in the same manner as in Example 1 except that the mixing ratio of the PFSA pellet and the SPPE filler was changed to 5 parts by mass of the SPPE filler with respect to 100 parts by mass of the PFSA pellets.

<Production of polymer electrolyte membrane>
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the solution 1 was changed to the solution 2. The evaluation results are shown in Table 1.

[Example 3]
<Preparation of polymer electrolyte solution>
A solution 3 was obtained in the same manner as in Example 1 except that the mixing ratio of the PFSA pellet and the SPPE filler was changed to 40 parts by mass of the SPPE filler with respect to 100 parts by mass of the PFSA pellet.

<Production of polymer electrolyte membrane>
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the solution 1 was changed to the solution 3. The evaluation results are shown in Table 1.

[Example 4]
<Preparation of polymer electrolyte solution>
A precursor of perfluorosulfonic acid resin obtained from a compound represented by tetrafluoroethylene and CF ₂ ═CFO (CF ₂ ) ₂ —SO ₂ F, which is a polymer polymer precursor polymer (hydrolysis and acid treatment) Later ion exchange capacity: 1.4 meq / g) pellets were prepared. Next, the precursor pellets were mixed with polyphenylene sulfide (manufactured by Sigma Aldrich Japan, melt viscosity at 310 ° C .: 275 poise) and a mass ratio of 90/10, twin screw extruder (manufactured by WERNER & PELEIDER, model number: ZSK-40, kneading). The mixture was melt kneaded using a temperature of 280 to 310 ° C. and a screw rotational speed of 200 rpm. The melt-kneaded resin was cut through a strand die to obtain cylindrical pellets having a diameter of about 2 mm and a length of about 2 mm. The cylindrical pellet was contacted with an aqueous solution in which potassium hydroxide (15% by mass) and methanol (50% by mass) were dissolved at 80 ° C. for 20 hours to perform a hydrolysis treatment. Then, the pellet was immersed in 60 degreeC water for 5 hours. Next, the treatment of immersing the pellets immersed in water in a 2N aqueous hydrochloric acid solution at 60 ° C. for 1 hour was repeated 5 times, each time replacing the aqueous hydrochloric acid solution with a new one. And the pellet after having been repeatedly immersed in hydrochloric acid aqueous solution was washed with ion-exchange water and dried. As a result, a PFSA pellet as a polymer electrolyte was obtained.

  Next, the PFSA pellet and the SPPE filler described in Example 1 were mixed at a ratio of 20 parts by mass of the SPPE filler to 100 parts by mass of the PFSA pellet.

  This mixture was placed in a 5 L autoclave together with an aqueous ethanol solution (water: ethanol = 50.0: 50.0 (mass ratio)), sealed, heated to 160 ° C. with stirring with a blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a uniform polymer electrolyte solution having a solid content concentration of 5% by mass. The particle size of polyphenylene sulfide in this polymer electrolyte solution is measured by a laser diffraction / scattering particle size distribution measuring device (manufactured by Horiba, model number: LA-950, the measurement sample is diluted with water and used, refractive index: 1.33) ), The median diameter of the dispersed polyphenylene sulfide particles was 0.23 μm, and the average particle diameter was 0.98 μm. This was concentrated under reduced pressure at 80 ° C. and then diluted with water and ethanol to prepare a solution of ethanol: water = 60: 40 (mass ratio) having a viscosity of 500 cP and having a solid content of 15.1% by mass, Solution 4 was obtained.

<Production of polymer electrolyte membrane>
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the solution 1 was changed to the solution 4. The evaluation results are shown in Table 1.

[Example 5]
<Preparation of polymer electrolyte solution>
A precursor of perfluorosulfonic acid resin obtained from a compound represented by tetrafluoroethylene and CF ₂ ═CFO (CF ₂ ) ₂ —SO ₂ F, which is a polymer polymer precursor polymer (hydrolysis and acid treatment) Later ion exchange capacity: 1.4 meq / g) pellets were prepared. Next, the precursor pellets were mixed with polyphenylene sulfide (manufactured by Sigma Aldrich Japan, melt viscosity at 310 ° C .: 275 poise) and a mass ratio of 90/10, twin screw extruder (manufactured by WERNER & PELEIDER, model number: ZSK-40, kneading). The mixture was melt kneaded using a temperature of 280 to 310 ° C. and a screw rotational speed of 200 rpm. The melt-kneaded resin was cut through a strand die to obtain cylindrical pellets having a diameter of about 2 mm and a length of about 2 mm. This cylindrical pellet was subjected to hydrolysis and acid treatment in the same manner as in Example 1, and then dissolved in a 5 L autoclave to obtain a solution A having a solid content concentration of 5%. Using a laser diffraction / scattering particle size distribution measuring device (manufactured by Horiba, model number: LA-950, diluting the measurement sample with water, refractive index: 1.33) As a result, the median diameter of the dispersed polyphenylene sulfide particles was 0.23 μm.

  Next, a 5% by mass perfluorocarbon acid resin solution (Aciplex-SS (registered trademark), manufactured by Asahi Kasei E-materials, ion exchange capacity: 1.4 meq / g, solvent composition (mass ratio): ethanol / water = 50/50) (hereinafter referred to as “Solution B-1”) was added dimethylacetamide (hereinafter abbreviated as “DMAC”), refluxed at 120 ° C. for 1 hour, and then concentrated under reduced pressure with an evaporator. Thus, a solution having a mass ratio of perfluorocarbon sulfonic acid resin and DMAC of 1.5 / 98.5 (hereinafter referred to as “solution B-2”) was prepared.

  Furthermore, poly [2,2 ′-(m-phenylene) -5,5′-bibenzimidazole] (hereinafter abbreviated as “PBI”; Sigma-Aldrich Japan, weight average molecular weight 27,000) together with DMAC is autoclaved. The inside was sealed, heated up to 200 ° C. and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a PBI solution having a mass ratio of PBI to DMAC of 10/90. Further, this PBI solution was diluted 10 times with DMAC to prepare a 1% by mass uniform PBI solution.

  The above solutions are mixed at Solution A / Solution B-1 / Solution B-2 / Solution C = 30.6 / 14.9 / 46.9 / 7.6 (mass ratio) until the solution becomes uniform. The mixture was stirred to obtain a mixed solution of perfluorocarbon sulfonic acid resin / polyphenylene sulfide / PBI = 92.5 / 5 / 2.5 (mass ratio).

  Next, the SPPE filler described in Example 1 was mixed at a ratio of 20 parts by mass with respect to 100 parts by mass of the solid content of the mixed solution, and stirred until the solution became uniform.

<Production of polymer electrolyte membrane>
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the solution 1 was changed to the solution 5. The evaluation results are shown in Table 1.

[Example 6]
<Preparation of polymer electrolyte solution>
Solution 1 was produced in the same manner as in Example 1.

<Preparation of microporous membrane>
To 1 kg of PTFE fine powder having a number average molecular weight of 6.5 million, 463 mL of hydrocarbon oil as an extruded liquid lubricating oil (extrusion aid) was added at 20 ° C. and mixed.

Next, a round bar-like molded body obtained by paste extrusion of this mixture was molded into a film shape by a calender roll heated to 70 ° C., and a PTFE film was obtained. This film was passed through a hot air drying oven at 250 ° C. to evaporate and remove the extrusion aid, thereby obtaining an unfired film having an average thickness of 300 μm and an average width of 150 mm.
Next, this unfired film was stretched in the longitudinal direction (MD direction) at a stretching ratio of 6.6 times and wound up.

  Both ends of the obtained MD direction stretched PTFE film were sandwiched between clips, stretched in the width direction (TD direction) at a stretch ratio of 8 times, heat-set, and a 10 μm thick stretched PTFE microporous membrane was obtained. The stretching temperature at this time was 290 ° C., and the heat setting temperature was 360 ° C. The produced expanded PTFE microporous membrane was designated as microporous membrane 1. The distribution center of the pore distribution of the microporous membrane 1 was 1.29 μm.

<Production of polymer electrolyte membrane>
The above solution 1 was applied onto a base film using a bar coater (manufactured by Matsuo Sangyo Co., Ltd., bar No. 200, WET film thickness 200 μm) (application area: width of about 200 mm × length of about 500 mm). In a state where the coating film is not completely dried, the microporous film 1 (film thickness: 10 μm, porosity: 82%, sample size: width 200 mm × length 500 mm) is laminated on the coating film of solution 1 The solution 1 and the microporous membrane were pressure-bonded from above the porous membrane using a rubber roller. At this time, after visually confirming that a part of the microporous membrane was impregnated with the solution, this membrane was dried in an oven at 90 ° C. for 20 minutes.

  Next, the solution 1 is laminated again in the same manner from above the microporous membrane of the obtained membrane to sufficiently fill the void of the microporous membrane with the solution 1, and this membrane is further dried in an oven at 90 ° C. for 20 minutes. I let you. The PTFE microporous membrane sufficiently impregnated with the solution 1 was heat-treated in an oven at 170 ° C. for 1 hour to obtain a polymer electrolyte membrane having a thickness of about 25 μm. Table 1 shows the evaluation results of the polymer electrolyte membrane.

[Comparative Example 1]
<Preparation of polymer electrolyte solution>
A solution 6 was obtained in the same manner as in Example 1 except that the mixing ratio of the PFSA pellet and the SPPE filler was changed to 0 part by mass of the SPPE filler with respect to 100 parts by mass of the PFSA pellet.

<Production of polymer electrolyte membrane>
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the solution 1 was changed to the solution 6. The evaluation results are shown in Table 1.

  The present invention provides a polymer electrolyte composition having excellent gas barrier properties. Since the polymer electrolyte membrane having the polymer electrolyte composition of the present invention has both high durability and power generation efficiency, it can be suitably used for solid polymer fuel cells and the like.

Claims (5)

100 parts by mass of a fluorine-based polymer electrolyte (A) having an ion exchange capacity of 0.50 to 3.0 meq / g and sulfonated carbonization having an ion exchange capacity of 0.50 to 3.0 meq / g a hydrogen-based polymer electrolyte (B) 0.10 to 50 parts by weight, only including,
A polymer electrolyte composition, wherein the sulfonated hydrocarbon polymer electrolyte (B) is a sulfonated polyphenylene ether resin . The polymer electrolyte composition, a compound having a thioether group further including (C), according to claim 1 Symbol placement of the polymer electrolyte composition. The polymer electrolyte composition according to claim 1 or 2 , wherein the polymer electrolyte composition further comprises a compound (D) having an azole ring. A polymer electrolyte membrane comprising a microporous membrane and the polymer electrolyte composition according to any one of claims 1 to 3 present in the voids of the microporous membrane. The polymer electrolyte membrane according to claim 4 , wherein the microporous membrane contains polytetrafluoroethylene.