JP2018055877A - Solid polymer electrolyte membrane, method for manufacturing the same, membrane-electrode assembly for solid polymer fuel cell, and solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a solid polymer electrolyte membrane which is hard to break even in such an environment that humidification and drying are repeated and which enables the enhancement in the power generation performance of a solid polymer fuel cell; a method for manufacturing the solid polymer electrolyte membrane; and a membrane-electrode assembly for a solid polymer fuel cell and a solid polymer fuel cell which are each arranged by use of the solid polymer electrolyte membrane.SOLUTION: A solid polymer electrolyte membrane comprises a polymer (I) having a particular unit with one or two sulfone imide groups, of which the film thickness is 1-20 μm. A membrane-electrode assembly 10 comprises: an anode 13 having a catalyst layer 11 and a gas diffusion layer 12; a cathode 14 having a catalyst layer 11 and a gas diffusion layer 12; and a solid polymer electrolyte membrane 15 which is disposed between the anode 13 and the cathode 14 in the state of being in contact with the catalyst layers 11 thereof. The solid polymer electrolyte membrane 15 is the above solid polymer electrolyte membrane.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polymer electrolyte membrane and a method for producing the same, a membrane electrode assembly for a polymer electrolyte fuel cell, and a polymer electrolyte fuel cell.

  In the polymer electrolyte fuel cell, for example, a cell is formed by sandwiching a membrane electrode assembly for a polymer electrolyte fuel cell between two separators, and a plurality of cells are stacked. The membrane electrode assembly for a polymer electrolyte fuel cell includes an anode and a cathode having a catalyst layer, and a solid polymer electrolyte membrane disposed between the anode and the cathode.

  As the solid polymer electrolyte membrane, for example, in Examples of Patent Documents 1 and 2, a solid polymer electrolyte having a thickness of 25 μm including a copolymer having a unit having a sulfonic acid group and a unit derived from tetrafluoroethylene is used. A membrane is disclosed.

In a polymer electrolyte fuel cell, humidification and drying are repeated depending on operating conditions. Since the solid polymer electrolyte membrane contains an ion exchange resin, it swells when humidified and shrinks when dried. For this reason, the solid polymer electrolyte membrane repeats swelling due to humidification and shrinkage due to drying, so that wrinkles are likely to occur in the solid polymer electrolyte membrane, and breakage is likely to occur due to wrinkles. In addition, during operation, fine cracks are likely to be generated in the solid polymer electrolyte membrane due to carbon fibers or the like blended in the catalyst layer, and the solid polymer electrolyte membrane may be broken even if the crack progresses due to repeated swelling and shrinkage. Prone to occur.
From the viewpoint of reducing the resistance of the solid polymer electrolyte membrane and improving the power generation performance of the solid polymer fuel cell, it is required to reduce the thickness of the solid polymer electrolyte membrane. When a thin solid polymer electrolyte membrane is made thin, breakage due to repeated swelling and shrinkage becomes remarkable.

International Publication No. 2007/013533 International Publication No. 2008/090990

  The present invention relates to a solid polymer electrolyte membrane that can hardly be broken even in an environment where humidification and drying are repeated, and can improve the power generation performance of a solid polymer fuel cell, and a method for producing the solid polymer electrolyte membrane; A membrane electrode assembly for a polymer electrolyte fuel cell having excellent performance; a polymer electrolyte fuel cell having excellent power generation performance in which breakage of the polymer electrolyte membrane is suppressed;

The present invention has the following configuration.
[1] A solid polymer electrolyte membrane comprising a polymer (I) having any one or both of a unit represented by the following formula (u1) and a unit represented by the following formula (u2): A solid polymer electrolyte membrane having a thickness of 1 μm or more and 20 μm or less.

However, in formula (u1), Q ¹¹ is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ¹² may have a single bond or an etheric oxygen atom. A perfluoroalkylene group, Y ¹ is a fluorine atom or a monovalent perfluoro organic group, s is 0 or 1, and R ^f1 is a perfluoroalkyl group optionally having an etheric oxygen atom And Z ⁺ is H ⁺ , a monovalent metal ion, or an ammonium ion in which one or more hydrogen atoms may be substituted with a hydrocarbon group.
In Formula (u2), Q ² is a single bond or a perfluoroalkylene group that may have an etheric oxygen atom, Y ² is a fluorine atom or a monovalent perfluoroorganic group, t is 0 or 1, R ^f2 is a perfluoroalkyl group which may have an etheric oxygen atom, Z ⁺ is H ⁺ , a monovalent metal ion, or one or more hydrogen atoms Is an ammonium ion which may be substituted with a hydrocarbon group.
[2] In the polymer (I), the ratio of the unit represented by the formula (u1) and the unit represented by the formula (u2) is 10 to 10 times the total of all the units of the polymer (I). The solid polymer electrolyte membrane according to [1], which is 40 mol%.
[3] The polymer (I) has both a unit represented by the formula (u1) and a unit represented by the formula (u2), and the unit represented by the formula (u1) and the formula (u2) The ratio (molar ratio) of the unit represented by the formula (u2) to the total of the units represented is 0.05 to 0.3, and the solid polymer electrolyte membrane according to [1] or [2] .
[4] The solid polymer electrolyte membrane according to any one of [1] to [3], wherein the polymer (I) further has a unit derived from tetrafluoroethylene.
[5] The solid polymer electrolyte membrane according to any one of [1] to [4], wherein the elongation at break of the polymer (I) is 400% or more.
[6] An anode having a catalyst layer, a cathode having a catalyst layer, and the solid polymer electrolyte membrane according to any one of [1] to [5] disposed between the anode and the cathode A membrane electrode assembly for a polymer electrolyte fuel cell provided.
[7] A polymer electrolyte fuel cell comprising the membrane electrode assembly for a polymer electrolyte fuel cell according to [6].
[8] A method for producing a solid polymer electrolyte membrane according to any one of [1] to [5], wherein the polymer (F) is converted to a sulfonimide group by converting a —SO ₂ F group into a sulfonimide group. A method for producing a solid polymer electrolyte membrane, comprising obtaining (I) and forming a solid polymer electrolyte membrane using the polymer (I).
Polymer (F): a polymer having one or both of a unit represented by the following formula (u′1) and a unit represented by the following formula (u′2).

However, in formula (u′1), Q ¹¹ is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ¹² has a single bond or an etheric oxygen atom. Y ¹ is a fluorine atom or a monovalent perfluoro organic group, and s is 0 or 1.
In formula (u′2), Q ² is a single bond or a perfluoroalkylene group which may have an etheric oxygen atom, and Y ² is a fluorine atom or a monovalent perfluoroorganic group. Yes, t is 0 or 1.
[9] after conversion to the sulfonamide group -SO 2 _F groups of the polymer (F), to obtain the polymer (I) by converting the sulfonamido group sulfonimide group, as described in [8] Solid A method for producing a polymer electrolyte membrane.

The solid polymer electrolyte membrane of the present invention is not easily broken even in an environment where humidification and drying are repeated, and can improve the power generation performance of the solid polymer fuel cell.
According to the method for producing a solid polymer electrolyte membrane of the present invention, it is possible to obtain a solid polymer electrolyte membrane that is not easily broken even in an environment in which humidification and drying are repeated and that can improve the power generation performance of the solid polymer fuel cell.
The membrane / electrode assembly for a polymer electrolyte fuel cell of the present invention is excellent in power generation performance because the solid polymer electrolyte membrane is hardly broken.
The polymer electrolyte fuel cell of the present invention is excellent in power generation performance because the breakage of the polymer electrolyte membrane is suppressed.

It is sectional drawing which shows an example of the membrane electrode assembly for polymer electrolyte fuel cells of this invention. It is sectional drawing which shows the other example of the membrane electrode assembly for polymer electrolyte fuel cells of this invention.

  In this specification, a unit represented by the formula (u1) is referred to as a unit (u1). A compound represented by the formula (m1) will be referred to as a compound (m1). The same applies to units and compounds represented by other formulas.

The following definitions of terms apply throughout this specification and the claims.
“Unit” means a unit derived from a monomer formed by polymerization of the monomer. A unit means a unit in which a part of the unit is converted into another structure by treating the polymer in addition to the unit directly formed by the polymerization reaction of the monomer.
The “perfluoro organic group” means a group containing at least one carbon atom and all hydrogen atoms covalently bonded to the carbon atom substituted with fluorine atoms.
“Perfluoroalkyl group” means a group in which all hydrogen atoms covalently bonded to carbon atoms of an alkyl group are substituted with fluorine atoms.
The “perfluoroalkylene group” means a group in which all hydrogen atoms covalently bonded to carbon atoms of the alkylene group are substituted with fluorine atoms.
The “ion exchange group” means a group in which a part of the cation contained in the group can exchange with another cation, and means a group having H ⁺ , a monovalent metal cation, an ammonium ion, or the like. To do. Examples of the ion exchange group include a sulfonic acid group, a sulfonimide group, and a sulfonemethide group.
The “sulfonic acid group” means —SO ³ —H ⁺ and —SO ³ —M ⁺ (wherein M ⁺ is a monovalent metal ion or one or more hydrogen atoms may be substituted with a hydrocarbon group) An ammonium ion).
“TQ value” is an indicator of the molecular weight and softening temperature of a polymer. It shows that molecular weight is so large that TQ value is large. This is a temperature at which the polymer extrusion rate is 100 mm ³ / sec when melt extrusion is performed under the condition of an extrusion pressure of 2.94 MPa using a nozzle having a length of 1 mm and an inner diameter of 1 mm.
“Elongation at break” is a value expressed as a percentage of the initial length before stretching, when the polymer film is pulled at a constant speed and the polymer film is broken. The larger the elongation at break, the better the elongation of the polymer film.

[Solid polymer electrolyte membrane]
The solid polymer electrolyte membrane of the present invention is a solid polymer electrolyte membrane containing polymer (I) and having a thickness of 1 μm or more and 20 μm or less.

The polymer (I) is a polymer having one or both of the unit (u1) and the unit (u2). As the polymer (I), those having the unit (u1) are preferable, and those having both the unit (u1) and the unit (u2) are more preferable from the viewpoint that the effects of the present invention are sufficiently exhibited. From the viewpoint of excellent mechanical strength and chemical durability, those further having units derived from tetrafluoroethylene (hereinafter also referred to as TFE) (hereinafter also referred to as TFE units) are preferable.
From the viewpoint of mechanical strength, the polymer (I) preferably contains units (u1) and TFE units, more preferably contains units (u1), units (u2) and TFE units, and units (u1) More preferably, the unit consists of units (u2) and TFE units. One or more units derived from a fourth monomer other than the unit (u1), the unit (u2), and the TFE unit (hereinafter also referred to as a fourth monomer unit) may be included as necessary.

  The unit (u1) is a unit represented by the following formula (u1).

However, in formula (u1), Q ¹¹ is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ¹² may have a single bond or an etheric oxygen atom. A perfluoroalkylene group, Y ¹ is a fluorine atom or a monovalent perfluoro organic group, s is 0 or 1, and R ^f1 is a perfluoroalkyl group optionally having an etheric oxygen atom And Z ⁺ is H ⁺ , a monovalent metal ion, or an ammonium ion in which one or more hydrogen atoms may be substituted with a hydrocarbon group. A single bond means that the carbon atom of CY ¹ and the sulfur atom of SO ₂ are directly bonded.

When the perfluoroalkylene group of Q ¹¹ and Q ¹² has an etheric oxygen atom, the oxygen atom may be one or two or more. The oxygen atom may be inserted between the carbon atom-carbon atom bond of the perfluoroalkylene group or may be inserted at the carbon atom bond terminal, but is not inserted at the terminal directly bonded to the sulfur atom. .
The perfluoroalkylene group may be linear or branched, and is preferably linear.
1-6 are preferable and, as for carbon number of a perfluoroalkylene group, 1-4 are more preferable. If the number of carbon atoms is 6 or less, the boiling point of the raw material monomer becomes low, and distillation purification becomes easy. Moreover, if carbon number is 6 or less, the fall of the ion exchange capacity of polymer (I) will be suppressed, and the fall of conductivity will be suppressed.

Q ¹² is preferably a C 1-6 perfluoroalkylene group which may have an etheric oxygen atom. When Q ¹² is a perfluoroalkylene group having 1 to 6 carbon atoms which may have an etheric oxygen atom, the polymer electrolyte fuel cell was operated for a long period of time as compared with the case where Q ¹² is a single bond. In particular, the stability of the power generation performance is excellent.
At least one of Q ¹¹ and Q ¹² is preferably a C 1-6 perfluoroalkylene group having an etheric oxygen atom. A monomer having a C1-C6 perfluoroalkylene group having an etheric oxygen atom can be synthesized without undergoing a fluorination reaction with a fluorine gas, so that the yield is good and the production is easy.

When the perfluoroalkyl group of R ^f1 has an etheric oxygen atom, the oxygen atom may be one or may be two or more. The oxygen atom may be inserted between the carbon atom-carbon atom bonds of the perfluoroalkyl group, but is not inserted at the carbon atom bond terminal.
The perfluoroalkyl group for R ^f1 may be linear or branched, and is preferably linear.
1-6 are preferable and, as for carbon number of a perfluoroalkyl group, 1-4 are more preferable. As the perfluoroalkyl group, a perfluoromethyl group, a perfluoroethyl group and the like are preferable.
The two R ^f1 units in the unit (u1) may be the same group or different groups.

Y ¹ is preferably a fluorine atom or a linear C 1-6 perfluoroalkyl group which may have an etheric oxygen atom, and more preferably a fluorine atom.

  As the unit (u1), units (u1-1) to (u1-3) are preferable from the viewpoint of easy production of the polymer (I) and easy industrial implementation.

  The unit (u2) is a unit represented by the following formula (u2).

However, in formula (u2), Q ² is a single bond or a perfluoroalkylene group which may have an etheric oxygen atom, Y ² is a fluorine atom or a monovalent perfluoro organic group, t is 0 or 1, R ^f2 is a perfluoroalkyl group which may have an etheric oxygen atom, Z ⁺ is H ⁺ , a monovalent metal ion, or one or more hydrogen atoms Is an ammonium ion which may be substituted with a hydrocarbon group. The single bond means that the carbon atom of CY ² and the sulfur atom of SO ₂ are directly bonded.

When the perfluoroalkylene group of Q ² has an etheric oxygen atom, the oxygen atom may be one or may be two or more. The oxygen atom may be inserted between the carbon atom-carbon atom bond of the perfluoroalkylene group or may be inserted at the carbon atom bond terminal, but is not inserted at the terminal directly bonded to the sulfur atom. .
The perfluoroalkylene group may be linear or branched.
1-6 are preferable and, as for carbon number of a perfluoroalkylene group, 1-4 are more preferable. If carbon number is 6 or less, the fall of the ion exchange capacity of polymer (I) will be suppressed, and the fall of conductivity will be suppressed.

When the perfluoroalkyl group of R ^f2 has an etheric oxygen atom, the oxygen atom may be one or may be two or more. The oxygen atom may be inserted between the carbon atom-carbon atom bonds of the perfluoroalkyl group, but is not inserted at the carbon atom bond terminal.
The perfluoroalkyl group for R ^f2 may be linear or branched, and is preferably linear.
1-6 are preferable and, as for carbon number of a perfluoroalkyl group, 1-4 are more preferable. As the perfluoroalkyl group, a perfluoromethyl group, a perfluoroethyl group and the like are preferable.
Y ² is preferably a fluorine atom or a perfluoroalkyl group, more preferably a fluorine atom or a trifluoromethyl group.

  As the unit (u2), units (u2-1) to (u2-4) are preferable from the viewpoint of easy production of the polymer (I) and easy industrial implementation.

The polymer (I) may further have a fourth monomer unit as long as the effects of the present invention are not impaired.
Examples of the fourth monomer include chlorotrifluoroethylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride, ethylene, propylene, perfluoro α-olefin (such as hexafluoropropylene), and (perfluoroalkyl) ethylene (perfluorobutyl). ) Ethylene), (perfluoroalkyl) propene (3-perfluorooctyl-1-propene, etc.), perfluorovinyl ether (hereinafter also referred to as PFVE), and the like.
Examples of PFVE include perfluoro (alkyl vinyl ether), perfluoro (etheric oxygen atom-containing alkyl vinyl ether), and the like.

  10-40 mol% is preferable with respect to the sum total of all the units of polymer (I), and, as for the ratio of the sum total of the unit (u1) and unit (u2) in polymer (I), 15-30 mol% is more preferable. If the total ratio of the unit (u1) and the unit (u2) is within the above range, it is easy to adjust the ion exchange capacity of the polymer (I) to a preferable range, and the elongation at break becomes higher, and humidification and drying. It is easy to obtain a solid polymer electrolyte membrane that is not easily broken even in an environment where is repeated.

  When the polymer (I) has both the unit (u1) and the unit (u2), the ratio (molar ratio) of the unit (u2) to the sum of the unit (u1) and the unit (u2) is 0.05 or more and 0.00. 3 or less is preferable, and 0.05 or more and less than 0.2 is more preferable. The higher the ratio of the unit (u2), the higher the elongation at break, and it is easier to obtain a solid polymer electrolyte membrane that is less likely to break even in an environment where humidification and drying are repeated. The lower the proportion of the unit (u2), the higher the ion exchange capacity of the polymer (I), and the easier it is to obtain a solid polymer electrolyte membrane with low resistance.

  20-90 mol% is preferable with respect to the sum total of all the units of polymer (I), and, as for the ratio of the TFE unit in polymer (I), 20-85 mol% is more preferable. When the proportion of TFE units is at least the lower limit of the above range, the mechanical strength and chemical durability of the polymer (I) are further improved. If the ratio of TFE units is less than or equal to the upper limit of the above range, the effects of units (u1) and units (u2) are unlikely to be impaired.

The proportion of the fourth monomer unit in the polymer (I) is preferably from 0 to 70 mol%, more preferably from 0 to 65 mol%, based on the total of all units of the polymer (I). When the ratio of the fourth monomer unit is within the above range, the effects of the unit (u1), the unit (u2), and the TFE unit are hardly impaired.
The polymer (I) may have one each of the unit (u1), the unit (u2), and the fourth monomer unit, or may have two or more of each.

  The ion exchange capacity of the polymer (I) is preferably 0.5 to 4.0 meq / g dry resin, more preferably 0.7 to 2.5 meq / g dry resin, and 0.8 to 2.0. More preferred are milliequivalents / g dry resin. If the ion exchange capacity of the polymer (I) is not less than the lower limit of the above range, the conductivity will be high, so that a membrane electrode assembly for a polymer electrolyte fuel cell with further excellent power generation performance can be obtained. When the ion exchange capacity of the polymer (I) is not more than the upper limit of the above range, the synthesis of a polymer having a high molecular weight is easy. Further, since the polymer (I) does not swell excessively with water, it is easy to maintain the mechanical strength.

  The elongation at break of the polymer (I) is preferably 400% or more, more preferably 500 to 1500%, further preferably 550 to 1000%. If the breaking elongation of the polymer (I) is not less than the lower limit of the above range, the solid polymer electrolyte membrane can easily follow the swelling due to humidification and the shrinkage due to drying, and the progress of fine cracks generated in the solid polymer electrolyte membrane In addition, the solid polymer electrolyte membrane is not easily broken due to wrinkles. If the breaking elongation of the polymer (I) is less than or equal to the upper limit of the above range, the amount of deformation in an environment where humidification and drying are repeated is reduced, and cracking of the catalyst layer in contact with the solid polymer electrolyte membrane can be suppressed. .

  The larger the WF value when the polymer (I) is a film having a thickness of 25 μm, the less the solid polymer electrolyte membrane breaks. The WF value is preferably 0.5 or more, and more preferably 0.7 or more. If the WF value is equal to or greater than the above value, fine cracks generated in the solid polymer electrolyte membrane are unlikely to progress, and the solid polymer electrolyte membrane is not easily broken.

  The conductivity of the polymer (I) is preferably 0.01 S / cm or more, more preferably 0.02 S / cm or more, and further preferably 0.03 S / cm or more under the conditions of 80 ° C. and 50% relative humidity. When the conductivity of the conductivity of the polymer (I) is at least the lower limit of the above range, a membrane electrode assembly for a polymer electrolyte fuel cell with further excellent power generation performance can be obtained. The upper limit value of the conductivity of the polymer (I) is not particularly limited, but is practically 10 S / cm.

  The water content of the polymer (I) is preferably 10 to 500%, more preferably 15 to 300%. If the water content of the polymer (I) is not less than the lower limit of the above range, the conductivity will be high, so that a membrane electrode assembly with further improved power generation performance can be obtained. If the water content of the polymer (I) is not more than the upper limit of the above range, the polymer (I) does not swell excessively with water, so that the mechanical strength can be maintained.

(Production method of polymer (I))
Polymer (I) can be prepared by converting the -SO ₂ F groups of the polymer (F) having -SO ₂ F groups to sulfonimide groups.
The polymer (F) is a polymer (I) precursor and has one or both of the unit (u′1) and the unit (u′2). The polymer (F) preferably further has a TFE unit from the viewpoint of easily obtaining the polymer (I) having excellent mechanical strength and chemical durability.

  The unit (u′1) is a unit represented by the following formula (u′1).

However, ^{Q 11, Q 12, Y 1} , s in formula (u'1) is the same as ^{Q 11, Q 12, Y 1} , s in the unit (u1), a preferred form same.
As the unit (u′1), units (u′1-1) to (u′1-3) are preferable from the viewpoint of easy production of the polymer (F) and easy industrial implementation.

  The unit (u′2) is a unit represented by the following formula (u′2).

However, ^{Q 2, Y} 2, t in formula (u'2) is the same as ^{Q 2, Y} 2, t in the unit (u2), which is the preferred form as well.
As the unit (u′2), units (u′2-1) to (u′2-4) are preferable from the viewpoint of easy production of the polymer (F) and easy industrial implementation.

  The polymer (F) may further have the fourth monomer unit mentioned in the polymer (I) within a range not impairing the effects of the present invention.

What is necessary is just to adjust suitably the ratio of each unit of a polymer (F) so that the ratio of each unit of a polymer (I) may become the preferable range mentioned above.
The polymer (F) may have one or both of the unit (u′1) and the unit (u′2). In view of sufficiently exerting the effects of the present invention, those having units (u′1) are preferred, and those having both units (u′1) and units (u′2) are more preferred. From the viewpoint of excellent mechanical strength and scientific durability, those further having TFE units are preferred.
From the viewpoint of mechanical strength, the polymer (F) preferably includes units (u′1) and TFE units, and more preferably includes units (u′1), units (u′2) and TFE units. Preferably, those composed of the unit (u′1), the unit (u′2) and the TFE unit are more preferable. If necessary, a fourth monomer unit may be included.

  The TQ value of the polymer (F) is preferably 150 ° C or higher, more preferably 170 ° C to 340 ° C, and further preferably 170 ° C to 300 ° C. When the TQ value of the polymer (F) is not less than the lower limit of the above range, the breaking elongation of the solid polymer electrolyte membrane is improved. When the TQ value of the polymer (F) is not more than the upper limit of the above range, the moldability of the polymer (F) is further improved.

  As a method for producing the polymer (F), a known method can be employed. For example, either or both of the compound (m1) and the compound (m2), and, if necessary, either TFE or the fourth monomer Or the method of superposing | polymerizing the monomer component containing both is mentioned.

  The compound (m1) is a compound represented by the following formula (m1).

However, ^{Q 11, Q 12, Y 1} , s in the formula (m1) is the same as ^{Q 11, Q 12, Y 1} , s in the unit (u1), a preferred form same.
As the compound (m1), compounds (m1-1) to (m1-3) are preferable.

  Compound (m1) can be produced by a known synthesis method.

  The compound (m2) is a compound represented by the following formula (m2).

However, ^{Q 2, Y} 2, t in the formula (m2) is the same as ^{Q 2, Y} 2, t in the unit (u2), which is the preferred form as well.
As the compound (m2), compounds (m2-1) to (m2-4) are preferable.

  Compound (m2) is, for example, D.I. J. et al. Vauham, “Du Pont Innovation”, Vol. 43, No. 3, 1973, p. 10 and the method described in the examples of US Pat. No. 4,358,412 can be used for the production by known synthetic methods.

  The polymerization method is not particularly limited, and the polymerization can be performed by a known polymerization method.

As a method of converting -SO 2 _F groups of the polymer (F) to sulfonimide groups, -SO 2 _F groups of the polymer (F) is converted to a sulfonamide group after the polymer (A), the polymer ( A method of converting the sulfonamide group of A) into a sulfonimide group is preferred. By converting once sulfonamide group -SO 2 _F groups of the polymer (F), that part of the -SO 2 _F groups of the polymer (F) is hydrolyzed to sulfonic acid groups in the sulfonated imidization can be suppressed, sulfonimide of -SO 2 _F group can be performed with high efficiency.

Examples of the method for obtaining the polymer (A) by converting the —SO ₂ F group of the polymer (F) into a sulfonamide group include a method of contacting the polymer (F) with ammonia.
Examples of a method for converting the sulfonamide group of the polymer (A) into a sulfonimide group include trifluoromethanesulfonyl fluoride and pentafluoroethanesulfonyl fluoride in the presence of a basic compound such as an alkali metal fluoride or an organic amine. a compound having a -SO 2 _F group etc. the method of contacting the polymer (a). By using a compound having —SO ₂ F group in excess relative to the sulfonamide group of the polymer (A), even if some of the —SO ₂ F group is hydrolyzed, Sulfonimidization proceeds sufficiently by the reaction.

The polymer (F) and the polymer (A) used for sulfonimide formation may be in a solid state, in a state swollen with a solvent, or in a state dissolved in a solvent. The polymer (F) and the polymer (A) are preferably swollen with a solvent or dissolved in a solvent from the viewpoint of smoothly proceeding with sulfonimide formation.
Examples of the solvent include fluorine-containing solvents such as polyfluorotrialkylamine compounds (perfluorotributylamine, etc.) and fluoroalkanes (perfluorohexane, perfluorooctane, 1H-perfluorohexane, 1H-perfluorooctane, etc.). Non-fluorinated solvents such as acetonitrile, methanol, ethanol, 2-propanol, dimethyl sulfoxide, N, N-dimethylformamide, 1,4-dioxane, tetrahydrofuran, N, N, N ′, N′-tetramethylethylenediamine, etc. Can be mentioned.

  The film thickness of the solid polymer electrolyte membrane of the present invention is from 1 μm to 20 μm, preferably from 2 μm to 15 μm, and more preferably from 3 μm to 12 μm. If the thickness of the solid polymer electrolyte membrane is smaller than the lower limit of the above range, the solid polymer electrolyte membrane is likely to be wrinkled and more easily broken. If the thickness of the solid polymer electrolyte membrane is larger than the upper limit of the above range, the membrane resistance increases, and a membrane / electrode assembly inferior in power generation performance tends to be obtained.

  The solid polymer electrolyte membrane may be reinforced with a reinforcing material. Examples of the reinforcing material include porous bodies, fibers, woven fabrics, and nonwoven fabrics. Examples of the reinforcing material include polytetrafluoroethylene, TFE-hexafluoropropylene copolymer, TFE-perfluoro (alkyl vinyl ether) copolymer, polyethylene, polypropylene, and polyphenylene sulfide.

  The solid polymer electrolyte membrane may contain one or more atoms selected from the group consisting of cerium and manganese in order to further improve the durability. Cerium and manganese decompose hydrogen peroxide, which is a causative substance that causes deterioration of the solid polymer electrolyte membrane. Cerium and manganese are preferably present as ions in the solid polymer electrolyte membrane, and as long as they are present as ions, they may be present in any state in the solid polymer electrolyte membrane.

  In the solid polymer electrolyte membrane of the present invention described above, since it contains the polymer (I) having either one or both of the unit (u1) and the unit (u2) containing a sulfonimide group, Since it easily follows shrinkage, it has excellent mechanical resistance even when it is thinned, and it is difficult to break even in an environment where humidification and drying are repeated. Further, since the solid polymer electrolyte membrane of the present invention is thinned, the membrane resistance is low, and excellent power generation performance can be expressed in the polymer electrolyte fuel cell.

  The factor that makes it difficult to break by using the polymer (I) is not necessarily clear, but is considered as follows. In a solid polymer electrolyte membrane using a polymer having a sulfonic acid group, since the sulfonic acid group is easily ionized, the intermolecular interaction through water molecules in the side chain containing the sulfonic acid group is large, and the main chain of the polymer Movement is limited, the film is difficult to stretch, hard and brittle. On the other hand, the sulfonimide group of the polymer (I) has more resonance structure and higher charge dispersibility than the sulfonic acid group. Therefore, in the polymer electrolyte membrane using the polymer (I), the intermolecular interaction in the side chain is smaller and the movement of the main chain of the polymer (I) is difficult to be restricted. It is thought to improve.

[Method for producing solid polymer electrolyte membrane]
As a method for producing a solid polymer electrolyte membrane, a polymer (I) is obtained by converting a —SO ₂ F group of a polymer (F) into a sulfonimide group as described above, and then a solid is formed using the polymer (I). A method of forming a polymer electrolyte membrane is preferred.
The sulfonidation of the —SO ₂ F group of the polymer (F) is performed by converting the —SO ₂ F group of the polymer (F) to a sulfonamide group and then converting the sulfonamide group to a sulfonamide group from the viewpoint of the efficiency of sulfonimidation. A method of converting to an imide group is preferred.

  As a method for forming a solid polymer electrolyte membrane using the polymer (I), for example, a base film is formed from a liquid composition containing the polymer (I) and a liquid medium, and the polymer (I) is dispersed in the liquid medium. Alternatively, a method of coating on the catalyst layer and drying (casting method) can be mentioned.

  As a liquid medium, the thing containing hydrocarbon alcohol is preferable from the point that the dispersibility of polymer (I) is favorable, and the mixed solvent of hydrocarbon alcohol and water is more preferable. Examples of the hydrocarbon alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and the like. A hydrocarbon alcohol may be used individually by 1 type, and 2 or more types may be mixed and used for it.

The ratio of the hydrocarbon alcohol in the liquid medium is preferably 5 to 95% by mass, and more preferably 15 to 85% by mass.
The ratio of the polymer (I) in the liquid medium is preferably 1 to 50% by mass, and more preferably 3 to 30% by mass.
Examples of the method for preparing the liquid composition include a method in which shearing such as stirring is applied to the polymer (I) in the liquid medium under atmospheric pressure or a state sealed with an autoclave or the like. You may provide shearing, such as an ultrasonic wave, as needed. The temperature during the preparation of the liquid composition is preferably 50 to 180 ° C, more preferably 80 to 130 ° C. The time is preferably 1 to 48 hours, more preferably 2 to 24 hours.

  In order to stabilize the solid polymer electrolyte membrane, it is preferable to perform an annealing treatment after the liquid composition is applied on a substrate film and dried. The annealing temperature is preferably 120 to 200 ° C. When the annealing temperature is 120 ° C. or higher, the perfluoroblock polymer of the present invention does not contain excessive water. If the temperature of annealing treatment is 200 degrees C or less, the thermal decomposition of an ion exchange group will be suppressed.

  According to the method for producing a solid polymer electrolyte membrane of the present invention described above, since it is thinned using the polymer (I), it has high mechanical resistance and is difficult to break even in an environment where humidification and drying are repeated, In addition, a solid polymer electrolyte membrane that can improve the power generation performance of the polymer electrolyte fuel cell can be obtained.

[Membrane electrode assembly for polymer electrolyte fuel cells]
A membrane electrode assembly for a polymer electrolyte fuel cell of the present invention (hereinafter also simply referred to as “membrane electrode assembly”) includes an anode having a catalyst layer, a cathode having a catalyst layer, the anode, and the cathode. It is a membrane electrode assembly provided with the solid polymer electrolyte membrane of this invention arrange | positioned between.
FIG. 1 is a cross-sectional view showing an example of the membrane electrode assembly of the present invention. The membrane electrode assembly 10 is in contact with the catalyst layer 11 between the anode 13 having the catalyst layer 11 and the gas diffusion layer 12, the cathode 14 having the catalyst layer 11 and the gas diffusion layer 12, and the anode 13 and the cathode 14. And a solid polymer electrolyte membrane 15 arranged in the above state.

The catalyst layer is a layer containing a catalyst and an ion exchange resin.
Examples of the catalyst include a supported catalyst in which platinum or a platinum alloy is supported on a carbon support.
Examples of the carbon carrier include carbon black powder, bluffed carbon, carbon fiber, and carbon nanotube.
Examples of the ion exchange resin include known ion exchange resins used for the catalyst layer. From the viewpoint of forming a catalyst layer that is difficult to crack, the polymer (I) or the —SO ₂ F group of the polymer (F) is — Polymers converted to ion exchange groups other than sulfonimide groups such as SO ₃ H groups are preferred.

The gas diffusion layer has a function of uniformly diffusing gas in the catalyst layer and a function as a current collector.
Examples of the gas diffusion layer include carbon paper, carbon cloth, carbon felt and the like.
The gas diffusion layer is preferably subjected to water repellent treatment with polytetrafluoroethylene or the like.

As shown in FIG. 2, the membrane electrode assembly 10 may have a carbon layer 16 between the catalyst layer 11 and the gas diffusion layer 12.
By disposing the carbon layer, the gas diffusibility on the surface of the catalyst layer is improved, and the power generation performance of the polymer electrolyte fuel cell is greatly improved.
The carbon layer is a layer containing carbon and a nonionic fluorine-containing polymer.
Examples of carbon include carbon particles and carbon fibers, and carbon nanofibers having a fiber diameter of 1 to 1000 nm and a fiber length of 1000 μm or less are preferable.
Examples of the nonionic fluorine-containing polymer include polytetrafluoroethylene.

  The solid polymer electrolyte membrane is the solid polymer electrolyte membrane of the present invention.

When the membrane / electrode assembly does not have a carbon layer, the membrane / electrode assembly is produced, for example, by the following method.
A method in which a catalyst layer is formed on a solid polymer electrolyte membrane to form a membrane catalyst layer assembly, and the membrane catalyst layer assembly is sandwiched between gas diffusion layers.
A method in which a catalyst layer is formed on a gas diffusion layer to form electrodes (anode, cathode), and a solid polymer electrolyte membrane is sandwiched between the electrodes.

When the membrane / electrode assembly has a carbon layer, the membrane / electrode assembly is produced, for example, by the following method.
-A dispersion containing carbon and a nonionic fluorine-containing polymer is coated on a base film, dried to form a carbon layer, a catalyst layer is formed on the carbon layer, and the catalyst layer and solid polymer electrolyte A method in which a membrane is bonded, a base film is peeled off to form a membrane catalyst layer assembly having a carbon layer, and the membrane catalyst layer assembly is sandwiched between gas diffusion layers.
A membrane-catalyst layer assembly in which a dispersion containing carbon and a nonionic fluoropolymer is applied on the gas diffusion layer and dried to form a carbon layer, and a catalyst layer is formed on the solid polymer electrolyte membrane Is sandwiched between gas diffusion layers having a carbon layer.

Examples of the method for forming the catalyst layer include the following methods.
A method in which a coating liquid for forming a catalyst layer is applied onto a solid polymer electrolyte membrane, a gas diffusion layer, or a carbon layer and dried.
A method in which a catalyst layer forming coating solution is applied onto a substrate film, dried to form a catalyst layer, and the catalyst layer is transferred onto a solid polymer electrolyte membrane.

  The coating liquid for forming a catalyst layer is a liquid in which an ion exchange resin and a catalyst are dispersed in a liquid medium. The coating liquid for forming a catalyst layer can be prepared, for example, by mixing the liquid composition of the present invention and a catalyst dispersion.

  Since the membrane / electrode assembly for a polymer electrolyte fuel cell of the present invention described above includes the polymer electrolyte membrane of the present invention, the polymer electrolyte membrane is hardly broken and has excellent power generation performance.

[Polymer fuel cell]
The solid polymer fuel cell of the present invention comprises the membrane electrode assembly of the present invention. A polymer electrolyte fuel cell can be obtained by disposing separators in which grooves serving as gas flow paths are formed on both surfaces of the membrane electrode assembly.
Examples of the separator include a separator made of various conductive materials such as a metal separator, a carbon separator, and a separator made of a material in which graphite and a resin are mixed.

  In a polymer electrolyte fuel cell, power generation is performed by supplying a gas containing oxygen to the cathode and a gas containing hydrogen to the anode. The membrane electrode assembly can also be applied to a methanol fuel cell that generates power by supplying methanol to the anode.

  Since the polymer electrolyte fuel cell of the present invention described above includes the membrane electrode assembly of the present invention, breakage of the solid polymer electrolyte membrane is suppressed, and the power generation performance is excellent.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited by the following description.
Examples 1 to 6 are experimental examples, Example 7 is an example, and Examples 8 to 10 are comparative examples.

(Percentage of each unit)
About the ratio of each unit in a polymer (F), it calculated | required from the measurement result of ¹⁹ F-NMR.

(TQ value)
Using a flow tester CFT-500A (manufactured by Shimadzu Corporation) equipped with a nozzle having a length of 1 mm and an inner diameter of 1 mm, the temperature is changed under the condition of an extrusion pressure of 2.94 MPa, and the polymer extrusion rate becomes 100 mm ³ / second ( TQ value) was obtained. The higher the TQ, the higher the molecular weight of the polymer.

(Tensile test)
The polymer film having a thickness of 25 μm obtained in each example was punched into the shape of a No. 7 type dumbbell defined in JIS K 6251, and the test piece was pulled at a tensile rate of 60 mm / min in an environment of temperature 80 ° C. and humidity 3% RH. Tensile and elongation at break were measured. The elongation at break was normalized as a percentage of the length at break relative to the initial length. As the tensile tester, RTE-1210 (product name: universal tester (Tensilon), manufactured by Orientec Corp.) was used.

(WF value)
The polymer film with a thickness of 25 μm obtained in each example was punched into the shape of a No. 7 dumbbell specified by JIS K 6251, and the length in the direction perpendicular to the tensile direction at both ends in the center of the tensile direction of the test piece. 0.5 mm straight cracks (notches) were formed. The test piece was pulled at a tensile speed of 100 mm / min in an environment of a temperature of 80 ° C. and a humidity of 3% RH, and the force corresponding to the tensile distance until the cracks were united and the test piece broke was measured. Plot the graph with the tensile distance (unit: mm) on the X axis and the force (unit: N) corresponding to the tensile distance on the Y axis, and calculate the area of the part surrounded by the plotted graph and the X axis The WF value was used. As the tensile tester, RTE-1210 (product name: universal tester (Tensilon), manufactured by Orientec Corp.) was used. The WF value is a value corresponding to the work (energy) required until the test piece breaks, and is a value reflecting the resistance to crack growth of the film. The higher the WF value, the harder the cracks to progress.

(Ion exchange capacity)
The polymer film having a thickness of 25 μm obtained in each example was vacuum-dried at 120 ° C. for 12 hours. The polymer membrane was immersed in a 0.85 mol / g sodium hydroxide solution (solvent: water / methanol = 10/90 (mass ratio)) to neutralize the ion exchange groups. The sodium hydroxide solution after neutralizing the ion exchange groups was back titrated with 0.1 mol / L hydrochloric acid to determine the ion exchange capacity (milli equivalent / g dry resin) of the polymer membrane.

(Power generation performance)
The membrane electrode assembly obtained in each example was incorporated into a power generation cell, the temperature of the membrane electrode assembly was maintained at 95 ° C., hydrogen (utilization rate 70%) at the anode, and oxygen (utilization rate 50%) at the cathode, respectively. The pressure was supplied to 151 kPa (absolute pressure). The humidity of the gas was 20% RH for both hydrogen and oxygen, and the current density when the cell voltage was 0.6 V was recorded as the power generation performance. A higher current density is preferable because an output density in the fuel cell can be increased.

(Abbreviation)
TFE: tetrafluoroethylene (CF ₂ = CF ₂ ),
P2SVE: Compound (m1-2),
PSVE: Compound (m2-1),
HFC-52-13p: CF ₃ (CF ₂ ) ₅ H,
HCFC-141b: CCl ₂ FCH ₃ ,
HCFC-225cb: CClF ₂ CF ₂ CHClF,
DMAc: N, N-dimethylacetamide.

(Production Example 1: Production of polymer (F-1))
In an autoclave (internal volume: 1 L, made of stainless steel), 800.0 g of P2SVE was put, and the inside of the autoclave was deaerated to the vapor pressure under ice cooling. The internal temperature was raised to 57 ° C., TFE was introduced into the autoclave, and the pressure was set to 0.9 MPaG (gauge pressure). Polymerization was started by adding a solution prepared by dissolving 0.323 g of dimethyl 2,2′-azobis (2-methylpropionate) in 8.0 g of HFC-52-13p, and maintaining the temperature and pressure. Polymerization was carried out by continuously adding TFE. After 6 hours, when the amount of TFE added reached 45.8 g, the autoclave was cooled to stop the polymerization, and the gas in the system was purged.
As a post-treatment after the polymerization, the reaction solution was diluted with HFC-52-13p, a mixed solution of HCFC-141b and normal hexane was added, and the polymer was aggregated and filtered. Thereafter, the operation of stirring the polymer in HFC-52-13p and reaggregating with a mixed solution of HCFC-141b and normal hexane was repeated twice. It dried under reduced pressure at 120 degreeC overnight, and 109.7g of the polymer (F-1) which consists of a TFE / P2SVE copolymer was obtained.
The composition of the polymer (F-1) was TFE units / P2SVE units = 82.7 / 17.3 (molar ratio). The TQ value of the polymer (F-1) was 264 ° C.

(Production Example 2: Production of polymer (F-2))
In an autoclave (inner volume 2.5 L, made of stainless steel), 123.8 g of PSVE, 1550.6 g of P2SVE, 108.6 g of HCFC-225cb, and dimethyl 2,2′-azobis (2-methylpropionate) 0.179 g was added, and the inside of the autoclave was deaerated to the vapor pressure under ice cooling. The internal temperature was raised to 66 ° C., TFE was introduced into the autoclave, and the pressure was adjusted to 1.14 MPaG. While maintaining the temperature and pressure, TFE was continuously added for polymerization. After 6.4 hours, when the amount of TFE added reached 124.7 g, the autoclave was cooled to stop the polymerization, and the gas in the system was purged.
The post-process similar to manufacture example 1 was performed, and 276g of the polymer (F-2) which consists of a TFE / PSVE / P2SVE copolymer was obtained.
The composition of the polymer (F-2) was TFE unit / PSVE unit / P2SVE unit = 83.0 / 1.7 / 15.3 (molar ratio). The TQ value of the polymer (F-2) was 230 ° C.

(Production Example 3: Production of polymer (F-3))
In an autoclave (internal volume 230 mL, manufactured by Hastelloy), 170.0 g of PSVE, 3.3 g of HCFC-225cb as a solvent, 52.00 mg of 2,2′-azobis (isobutyronitrile) as an initiator, It was degassed by cooling with liquid nitrogen. Thereafter, the temperature was raised to 65 ° C., TFE was introduced into the system, and the pressure was maintained at 1.07 MPaG. Polymerization was performed by continuously adding TFE so that the pressure was constant at 1.07 MPaG. After the elapse of 8.0 hours, when the amount of TFE added was 9.1 g, the autoclave was cooled and the gas in the system was purged to stop the polymerization.
The obtained polymer solution was diluted with HCFC-225cb, and then HCFC-141b was added to cause aggregation. After washing with HCFC-225cb and HCFC-141b, it was dried to obtain 17.8 g of a polymer (F-3) comprising a TFE / PSVE copolymer. The composition of the polymer (F-3) was TFE unit / PSVE unit = 78.1 / 21.9 (molar ratio). The TQ value of the polymer (F-3) was 234 ° C.

(Production Example 4: Production of polymer (F-4))
An autoclave (internal volume: 230 mL, manufactured by Hastelloy) was charged with 123.8 g of PSVE, 35.2 g of HCFC-225cb as a solvent, and 63.62 mg of 2,2′-azobis (isobutyronitrile) as an initiator, It was degassed by cooling with liquid nitrogen. Thereafter, the temperature was raised to 70 ° C., TFE was introduced into the system, and the pressure was maintained at 1.14 MPaG. Polymerization was performed by continuously adding TFE so that the pressure was constant at 1.14 MPaG. After 7.9 hours, when the amount of TFE added was 12.4 g, the autoclave was cooled and the gas in the system was purged to stop the polymerization.
The post-process similar to manufacture example 3 was performed, and 25.1g of the polymer (F-4) which consists of a TFE / PSVE copolymer was obtained. The composition of the polymer (F-4) was TFE unit / PSVE unit = 82.3 / 17.7 (molar ratio). The TQ value of the polymer (F-4) was 225 ° C.

(Production Example 5: Production of polymer (F-5))
In an autoclave (internal volume: 1 L, made of stainless steel), 495.0 g of P2SVE, 76.0 g of HCFC-225cb, and 0.343 g of 2,2′-azobis (isobutyronitrile) were placed, and the autoclave was cooled with ice. The inside was deaerated to the vapor pressure. The internal temperature was raised to 65 ° C., TFE was introduced into the autoclave, and the pressure was adjusted to 1.15 MPaG. While maintaining the temperature and pressure, TFE was continuously added for polymerization. After 11.5 hours, when the amount of TFE added reached 39.8 g, the autoclave was cooled to stop the polymerization, and the gas in the system was purged.
The post-process similar to manufacture example 1 was performed, and 98.5g of the polymer (F-5) which consists of a TFE / P2SVE copolymer was obtained.
The composition of the polymer (F-5) was TFE unit / P2SVE unit = 85.6 / 14.4 (molar ratio). The TQ value of the polymer (F-5) was 245 ° C.

(Production Example 6: Production of polymer (F-6))
In an autoclave (internal volume 230 mL, manufactured by Hastelloy), 49.4 g of PSVE, 84.2 g of P2SVE, 9.9 g of HCFC-225cb, and 0.029 g of dimethyl 2,2′-azobis (isobutyronitrile) were added. The autoclave was deaerated to the vapor pressure under ice cooling. The internal temperature was raised to 65 ° C., TFE was introduced into the autoclave, and the pressure was adjusted to 1.14 MPaG. While maintaining the temperature and pressure, TFE was continuously added for polymerization. After 7.0 hours, when the amount of TFE added reached 7.5 g, the autoclave was cooled to stop the polymerization, and the gas in the system was purged.
The post-process similar to manufacture example 1 was performed, and 16.0g of the polymer (F-6) which consists of a TFE / PSVE / P2SVE copolymer was obtained.
The composition of the polymer (F-6) was TFE unit / PSVE unit / P2SVE unit = 82.8 / 7.7 / 9.5 (molar ratio). The TQ value of the polymer (F-6) was 242 ° C.

(Example 1)
40 g of the polymer (F-1) obtained in Production Example 1 was put in a 2.5 L autoclave equipped with a thermometer and a stirrer together with 3000 g of HFC-52-13p, and heated to 125 ° C. to prepare a solution. did. After the solution was cooled, the autoclave was opened and dissolution of the polymer (F-1) was confirmed. The solution was a whitish clear liquid. The autoclave was closed again and the gas phase portion was replaced with nitrogen, and then the autoclave was immersed in a dry ice / ethanol bath and cooled with stirring at a speed of 200 rpm. After the internal temperature decreased to −20 ° C., 35.6 g of ammonia gas was introduced from the gas phase. Ammonia gas was introduced while adjusting the speed so that the internal temperature did not exceed -15 ° C. During this time, the internal temperature was controlled to be -21 ° C to -17 ° C. The internal pressure at this time was 0.1 MPa. After the introduction, cooling of the autoclave was finished. When the temperature rose to −12 ° C., nitrogen was introduced into the gas phase and the internal pressure was increased to 0.5 MPa. The temperature was gradually raised to room temperature over 6 hours, and then the reaction was continued at room temperature for 48 hours. Ammonia gas was purged and the internal pressure of the container was returned to normal pressure. When the pressure vessel was opened after the purge was completed, it was confirmed that a white to light yellow polymer was precipitated in the solution. The precipitated polymer was separated from the solvent by suction filtration, and the polymer was washed with HFC-52-13p. The polymer was washed 6 times with 3N hydrochloric acid, further washed 5 times with ultrapure water and then dried to obtain 40.5 g of a white solid.
When the obtained white solid was analyzed by infrared spectroscopy, the peak derived from the —SO ₂ F group in the vicinity of 1468 cm ^{−1 of} the polymer (F-1) completely disappeared, and instead of the vicinity of 1386 cm ⁻¹ . A peak derived from a sulfonamide group (—SO ₂ NH ₂ group) appears, that is, a sulfonamide type polymer (A-1) in which —SO ₂ F group is converted to —SO ₂ NH ₂ group is formed. Confirmed that.

After 17 g of polymer (A-1) and 904.6 g of DMAc dehydrated using molecular sieves 4A were placed in a 1.5 L autoclave equipped with a thermometer and a stirrer, the gas phase was replaced with nitrogen. The sulfonamide type polymer was dissolved by heating to 120 ° C. The polymer solution after dissolution was a transparent liquid having a light yellow color. After cooling the autoclave under ice cooling, 14.9 g of N, N, N ′, N′-tetramethylethylenediamine was charged all at once, and then 17.0 g of CF ₃ SO ₂ F gas was gradually added from the gas phase portion. To feed. Although the reaction system exothermed with the feed, the feed rate was adjusted so that the temperature of the reaction solution was maintained at 5-15 ° C. Thereafter, the autoclave was heated and reacted for 20 hours while maintaining the temperature of the reaction solution at 58 to 62 ° C. As the reaction progressed, the viscosity of the reaction solution gradually increased. After completion of the reaction, the reaction solution is cast on a glass petri dish, dried on a hot plate set at 80 ° C. for 4 hours, and then dried under reduced pressure for 2 hours in a vacuum dryer at 80 ° C. to form a film having a thickness of about 150 μm. Obtained.
The membrane was immersed in an aqueous alkaline solution (potassium hydroxide: 15% by mass, dimethyl sulfoxide: 30% by mass, water: 55% by mass) at 80 ° C. for 60 hours, and then washed with water until the pH of the washing water reached 7. Subsequently, it was immersed in a 10% by mass hydrogen peroxide solution and treated at 80 ° C. for 20 hours. By this operation, the color of the film which was light brown became colorless and transparent. Further, it was immersed in an aqueous 3N hydrochloric acid solution at 80 ° C. for 30 minutes, and then immersed in ultrapure water at 80 ° C. for 15 minutes. A total of five cycles of immersion in an aqueous hydrochloric acid solution and immersion in ultrapure water were performed, and then the ultrapure water cleaning was repeated until the pH of the ultrapure water in which the membrane was immersed was 7.
When the film was analyzed by infrared spectroscopy, the peaks derived from the —SO ₂ NH ₂ group around 1386 cm ^{−1 of} the polymer (A-1) disappeared, and 1065 cm ⁻¹ , 1320 cm ⁻¹ and 1340 cm ^−1. It was confirmed that a peak derived from a nearby —SO ₂ N ⁺ (H ⁺ ) SO ₂ CF ₃ group appeared. That is, it was confirmed that a sulfonimide polymer (I-1) in which —SO ₂ NH ₂ groups were converted to —CF ₂ —SO ₂ N ⁺ (H ⁺ ) SO ₂ CF ₃ groups was produced. Assuming that all —SO ₂ F groups of the polymer (F-1) are converted to sulfonimide groups, the ion exchange capacity of the polymer (I-1) is 1.51 meq / g dry resin.

  To an autoclave (internal volume 200 mL, glass), 10.5 g of finely cut polymer (I-1) and 60.0 g of 1-propanol / water mixed solvent (25/75 (mass ratio)) were added and stirred. The autoclave was heated while. After stirring at 115 ° C. for 20 hours, 30.5 g of water was added. After stirring for 1 hour, the mixture was allowed to cool and filtered using a pressure filter (filter paper: PF040, manufactured by Advantech Toyo Co., Ltd.), whereby the polymer (I-1) was dispersed in 9.9% by mass in the mixed solvent. 98.3 g of a liquid composition was obtained.

  The liquid composition was coated on a base film using a die coater and dried in a drying furnace at 110 ° C. for 30 minutes. Thereafter, heat treatment was performed in a drying furnace at 130 ° C. for 30 minutes to obtain a polymer film made of polymer (I-1) having a thickness of 25 μm.

(Example 2)
A polymer (A-2) was obtained in the same manner as in Example 1 except that the polymer (F-1) was changed to the polymer (F-2).
17 g of polymer (A-1) to 20 g of polymer (A-2), and amounts of reagents used were 380.0 g of DMAc, 16.2 g of N, N, N ′, N′-tetramethylethylenediamine, A polymer (I-2) was obtained in the same manner as in Example 1 except that the gas was changed to 21.2 g of CF ₃ SO ₂ F gas. Assuming that all SO ₂ F groups of the polymer (F-2) are converted into sulfonimide groups, the ion exchange capacity of the polymer (I-2) is 1.42 meq / g dry resin.

To an autoclave (internal volume: 1 L, glass), 28.0 g of finely cut polymer (I-2) and 158.6 g of 1-propanol / water mixed solvent (25/75 (mass ratio)) were added and stirred. The autoclave was heated while. Next, 207.0 g of a liquid composition in which the polymer (I-2) was dispersed in the mixed solvent at 13.5% by mass was obtained in the same manner as in Example 1 except that the amount of water added was 20.8 g.
A polymer film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the liquid composition in which the polymer (I-2) was dispersed was used.

(Example 3)
A polymer (A-3) was obtained in the same manner as in Example 1 except that the polymer (F-1) was changed to the polymer (F-3).
17 g of polymer (A-1) was added to 20 g of polymer (A-3), and the amount of reagents used was 380.0 g of DMAc, 11.6 g of N, N, N ′, N′-tetramethylethylenediamine, A polymer (I-3) was obtained in the same manner as in Example 1 except that the CF ₃ SO ₂ F gas was changed to 15.2 g. Assuming that all SO ₂ F groups of the polymer (F-3) are converted to sulfonimide groups, the ion exchange capacity of the polymer (I-3) is 1.05 meq / g dry resin.

To an autoclave (internal volume 200 mL, glass), 18.9 g of finely cut polymer (I-3) and 86.3 g of ethanol / water mixed solvent (60/40 (mass ratio)) were added and stirred. The autoclave was heated. Next, 102.7 g of a liquid composition in which the polymer (I-3) was dispersed in a mixed solvent at 16.3% by mass was obtained in the same manner as in Example 1 except that the amount of water added was changed to 17.4 g.
A polymer film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the liquid composition in which the polymer (I-3) was dispersed was used.

(Example 4)
The polymer (F-4) was press-molded (240 ° C., 4 MPa) to obtain a 200 μm thick film. The polymer (F−) film was immersed in an aqueous alkali solution (potassium hydroxide: 15% by mass, dimethyl sulfoxide: 30% by mass, water: 55% by mass) at 80 ° C. for 16 hours. 4) The —SO ₂ F group in 4) was hydrolyzed and converted to the —SO ₃ K group. Further, the membrane was immersed in an aqueous 3 mol / L hydrochloric acid solution at 80 ° C. for 30 minutes, and then immersed in ultrapure water at 80 ° C. for 15 minutes. A total of five cycles of immersion in an aqueous hydrochloric acid solution and immersion in ultrapure water were performed to convert —SO ₃ K groups into sulfonic acid groups (—SO ₃ H). Thereafter, washing with ultrapure water was repeated until the pH of the water in which the membrane was immersed was 7, and then the membrane was air-dried to obtain a polymer (S-1) membrane.

To an autoclave (internal volume 200 mL, made of glass), 20 g of a finely cut polymer (S-1) membrane and 56.9 g of a mixed solvent of ethanol / water (60/40 (mass ratio)) were added and stirred. The autoclave was heated. After stirring at 115 ° C. for 16 hours, the mixture is allowed to cool, and filtered using a pressure filter (filter paper: PF040, manufactured by Advantech Toyo Co., Ltd.), so that the polymer (S-1) is 26.0% by mass in the mixed solvent. 76.5 g of the dispersed liquid composition was obtained.
A polymer film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the liquid composition in which the polymer (S-1) was dispersed was used.

(Example 5)
A film of polymer (S-2) was obtained in the same manner as in Example 4 except that polymer (F-5) was used instead of polymer (F-4).
In an autoclave (internal volume 200 mL, glass), 8.4 g of finely cut polymer (S-2), 68.0 g of 1-butanol / ethanol / water mixed solvent (35/15/50 (mass ratio)) And the autoclave was heated with stirring. After stirring at 110 ° C. for 60 hours, 13.8 g of ethanol and 77.8 g of water were added. After stirring for 24 hours, the mixture was allowed to cool and filtered using a pressure filter (filter paper: Advantech Toyo Co., Ltd., PF040), whereby the polymer (S-2) was dispersed in a mixed solvent at 4.7% by mass. 152.2 g of a liquid composition was obtained.
A polymer film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the liquid composition in which the polymer (S-2) was dispersed was heat-treated in a drying furnace at 185 ° C. for 30 minutes.

(Example 6)
A film of polymer (S-3) was obtained in the same manner as in Example 4 except that polymer (F-6) was used instead of polymer (F-3).
14.2 g of finely cut polymer (S-3) and 81.2 g of a mixed solvent of ethanol / water (60/40 (mass ratio)) were added, and the autoclave was heated with stirring. Next, 107.0 g of a liquid composition in which polymer (S-3) was dispersed in a mixed solvent at 13.2% by mass was obtained in the same manner as in Example 3 except that the amount of water added was changed to 12.4 g.
A polymer film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the liquid composition in which the polymer (S-3) was dispersed was heat-treated in a drying furnace at 185 ° C. for 30 minutes.

  Table 1 shows the evaluation results of the polymer physical properties and the evaluation results of the solid polymer electrolyte membrane in each example.

(Example 7)
To 44 g of a supported catalyst (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) in which 46% by mass of platinum is supported on carbon powder, 221.76 g of water and 174.24 g of ethanol are added and mixed and pulverized using an ultrasonic homogenizer. Got. A liquid mixture prepared by mixing and kneading 80.16 g of the liquid composition obtained in the same manner as in Example 4, 44.4 g of ethanol and 25.32 g of ZEOLORA-H (manufactured by Nippon Zeon Co., Ltd.) in advance in the catalyst dispersion. 102.06 g of water was further added, 26.77 g of water and 12 g of ethanol were added and mixed using an ultrasonic homogenizer to obtain a coating solution for forming a catalyst layer with a solid content concentration of 10% by mass. The catalyst layer forming coating solution is coated on an ETFE sheet with a die coater, dried at 80 ° C., and further subjected to heat treatment at 160 ° C. for 30 minutes, so that the platinum amount is 0.4 mg / cm ² . A catalyst layer was formed.

Add 77.3 g of ethanol and 151.5 g of distilled water to 50 g of vapor-grown carbon fiber (manufactured by Showa Denko KK, trade name: VGCF-H, fiber diameter: about 150 nm, fiber length: 10 to 20 μm), and stir well. did. To this, 96.2 g of the liquid composition obtained by the same method as in Example 4 was added and stirred well, and further mixed and pulverized using an ultrasonic homogenizer to prepare a coating solution for forming an intermediate layer. After coating the intermediate layer-forming coating solution on the surface of a gas diffusion substrate (manufactured by NOK, trade name: X0086 T10X13) using a die coater so that the solid content is 3 mg / cm ² , 80 A gas diffusion base material with an intermediate layer in which an intermediate layer was formed on the surface of the carbon nonwoven fabric was dried at 0 ° C.

In the same manner as in Example 1, a 10 μm-thick solid polymer electrolyte membrane formed of polymer (I-2) was obtained. The thickness of the solid polymer electrolyte membrane was controlled by adjusting the thickness of the coating film of the liquid composition.
The solid polymer electrolyte membrane is sandwiched from both sides by a catalyst layer, heated and pressed under the conditions of a press temperature of 160 ° C., a press time of 2 minutes, and a pressure of 3 MPa, and the catalyst layer is bonded to both sides of the solid polymer electrolyte membrane, The ETFE film was peeled from the layer to obtain a membrane / catalyst layer assembly having an electrode area of 25 cm ² .
A gas diffusion substrate with a carbon layer (manufactured by NOK, trade name: X0086 IX92 CX320) is arranged on the catalyst layer side on the anode side of the membrane-catalyst layer assembly so that the carbon layer is in contact with the catalyst layer. The gas diffusion base material with an intermediate layer was placed on the catalyst layer so that the intermediate layer was in contact with the catalyst layer, and then pressed under conditions of 160 ° C. and 3 MPa for 2 minutes to obtain a membrane electrode assembly.

(Example 8)
A membrane / electrode assembly was obtained in the same manner as in Example 7 except that the polymer membrane of Example 2 was used instead of the solid polymer electrolyte membrane.

(Example 9)
In the same manner as in Example 4, a polymer film having a thickness of 10 μm formed of the polymer (S-1) was obtained. The thickness of the polymer film was controlled by adjusting the thickness of the coating film of the liquid composition. A membrane / electrode assembly was obtained in the same manner as in Example 7 except that a polymer membrane having a thickness of 10 μm was used instead of the solid polymer electrolyte membrane.

(Example 10)
A membrane / electrode assembly was obtained in the same manner as in Example 7 except that the polymer membrane of Example 4 was used instead of the solid polymer electrolyte membrane.

  Table 2 shows the evaluation results of the power generation performance of the power generation cell incorporating the membrane electrode assembly of each example.

As shown in Table 1, the polymer membranes of the polymers (I-1) to (I-3) having sulfonimide groups of Examples 1 to 3 are the polymers (S-1) having sulfonic acid groups of Examples 4 to 6. Compared with the polymer film of (S-3), the elongation at break was high and the WF value was large. From this, even when the film is thinned, the films of the polymers (I-1) to (I-3) have a higher elongation at break than the polymers (S-1) to (S-3), and have a WF value. Is considered to be difficult to break. Moreover, the membranes of Examples 1 to 3 had a sufficient ion exchange capacity.
As shown in Table 2, in the membrane / electrode assembly of Example 7 provided with a polymer electrolyte membrane having a film thickness of 10 μm using the polymer (I-2), Example 8 provided with a polymer electrolyte membrane having a film thickness of 25 μm Compared to the membrane electrode assembly, the current density was high and the power generation performance was excellent.
In Examples 9 and 10 using the polymer (S-1), there was a tendency that the power generation performance was improved by reducing the film thickness. However, the polymer (S-1) has a lower elongation at break, WF. Since the value is small, breakage tends to occur.
The solid polymer electrolyte membrane of the present invention has polymer properties capable of suppressing breakage of the solid polymer electrolyte membrane under operating conditions in which humidification and drying of the polymer electrolyte fuel cell are repeated. Even when the molecular electrolyte membrane was a thin film of 10 μm to form a polymer electrolyte fuel cell, excellent power generation performance was provided.

  DESCRIPTION OF SYMBOLS 10 Membrane electrode assembly, 11 Catalyst layer, 12 Gas diffusion layer, 13 Anode, 14 Cathode, 15 Solid polymer electrolyte membrane, 16 Carbon layer

Claims (9)

A solid polymer electrolyte membrane comprising a polymer (I) having one or both of a unit represented by the following formula (u1) and a unit represented by the following formula (u2):
A solid polymer electrolyte membrane having a thickness of 1 μm to 20 μm.

However, in formula (u1), Q ¹¹ is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ¹² may have a single bond or an etheric oxygen atom. A perfluoroalkylene group, Y ¹ is a fluorine atom or a monovalent perfluoro organic group, s is 0 or 1, and R ^f1 is a perfluoroalkyl group optionally having an etheric oxygen atom And Z ⁺ is H ⁺ , a monovalent metal ion, or an ammonium ion in which one or more hydrogen atoms may be substituted with a hydrocarbon group.
In Formula (u2), Q ² is a single bond or a perfluoroalkylene group that may have an etheric oxygen atom, Y ² is a fluorine atom or a monovalent perfluoroorganic group, t is 0 or 1, R ^f2 is a perfluoroalkyl group which may have an etheric oxygen atom, Z ⁺ is H ⁺ , a monovalent metal ion, or one or more hydrogen atoms Is an ammonium ion which may be substituted with a hydrocarbon group.   In the polymer (I), the proportion of the unit represented by the formula (u1) and the unit represented by the formula (u2) is 10 to 40 mol% with respect to the total of all the units of the polymer (I). The solid polymer electrolyte membrane according to claim 1, wherein   The polymer (I) has both a unit represented by the formula (u1) and a unit represented by the formula (u2), and is represented by the unit represented by the formula (u1) and the formula (u2). The solid polymer electrolyte membrane according to claim 1 or 2, wherein a ratio (molar ratio) of the unit represented by the formula (u2) to the total of the units is 0.05 or more and 0.3 or less.   The solid polymer electrolyte membrane according to any one of claims 1 to 3, wherein the polymer (I) further has a unit derived from tetrafluoroethylene.   The solid polymer electrolyte membrane according to any one of claims 1 to 4, wherein the breaking elongation of the polymer (I) is 400% or more. An anode having a catalyst layer;
A cathode having a catalyst layer;
A membrane electrode assembly for a polymer electrolyte fuel cell, comprising: the polymer electrolyte membrane according to any one of claims 1 to 5 disposed between the anode and the cathode.   A polymer electrolyte fuel cell comprising the membrane electrode assembly for a polymer electrolyte fuel cell according to claim 6. A method for producing the solid polymer electrolyte membrane according to any one of claims 1 to 5,
-SO 2 _F groups of the following polymer (F) to obtain the polymer is converted to sulfonimide groups (I), to form a solid polymer electrolyte membrane using the polymer (I), the solid polymer electrolyte membrane Manufacturing method.
Polymer (F): a polymer having one or both of a unit represented by the following formula (u′1) and a unit represented by the following formula (u′2).

However, in formula (u′1), Q ¹¹ is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ¹² has a single bond or an etheric oxygen atom. Y ¹ is a fluorine atom or a monovalent perfluoro organic group, and s is 0 or 1.
In formula (u′2), Q ² is a single bond or a perfluoroalkylene group which may have an etheric oxygen atom, and Y ² is a fluorine atom or a monovalent perfluoroorganic group. Yes, t is 0 or 1. The solid polymer electrolyte according to claim 8, wherein the polymer (I) is obtained by converting the —SO ₂ F group of the polymer (F) into a sulfonamide group and then converting the sulfonamide group into a sulfonimide group. A method for producing a membrane.

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