Fluoropolymers containing fluorosulfonyl groups and their manufacturing methods, fluoropolymers containing sulfonic acid groups and their manufacturing methods, solid polymer electrolyte membranes, membrane electrode assemblies, and solid polymer fuel cells.

Abstract

This invention provides a fluorosulfonyl-containing fluoropolymer and its manufacturing method, capable of producing a solid polymer electrolyte membrane with excellent conductivity and hot water resistance; an acid-sulfonic acid-containing fluoropolymer and its manufacturing method; a solid polymer electrolyte membrane; a membrane electrode assembly; and a solid polymer fuel cell. The manufacturing method of the fluorosulfonyl-containing fluoropolymer of this invention involves, within a reactor in the presence of a free radical polymerization initiator, polymerization of monomer m1(CF2=CFCF2O-Q) 1 A method for manufacturing TFE by copolymerizing SO2F with TFE at a temperature of 150 to 200°C, wherein a free radical polymerization initiator is continuously or batch-wise added to the reactor during copolymerization, such that the concentration of the free radical polymerization initiator in the reactor is maintained below 2.5 ppm by mass of the monomer m1 added to the reactor before copolymerization begins, and the molar ratio of the total amount of monomer m1 added to the total amount of TFE added is 1.5 to 20.

Description

Technical Field

[0001] This invention relates to fluoropolymers containing fluorosulfonyl groups and their manufacturing methods, fluoropolymers containing acidic sulfonic acid groups and their manufacturing methods, solid polymer electrolyte membranes, membrane electrode assemblies, and solid polymer fuel cells. Background Technology

[0002] Solid polymer fuel cells have structures, for example, where a membrane electrode assembly is sandwiched between two separators to form a cell, and multiple cells are stacked together. The membrane electrode assembly includes an anode and a cathode each having a catalyst layer, and a solid polymer electrolyte membrane disposed between the anode and the cathode. The solid polymer electrolyte membrane is obtained by forming a membrane from a fluoropolymer containing acidic sulfonic acid groups.

[0003] As a method for manufacturing such a polymer with acidic sulfonic acid groups, Patent Document 1 discloses the following method: after copolymerizing tetrafluoroethylene with a monomer shown as CF2=CFCF2OCF2CF2SO2F in the presence of a free radical polymerization initiator at a temperature of 100~200°C, the -SO2F group is hydrolyzed to acidify it, thereby converting it into a sulfonic acid group.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-18674 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In recent years, from the perspective of improving the power generation efficiency of solid polymer fuel cells, there has been a search for solid polymer electrolyte membranes with high conductivity. Furthermore, during power generation in solid polymer fuel cells, the solid polymer electrolyte membrane is further exposed under high temperature and humidity conditions; therefore, the fluoropolymers containing acidic sulfonic acid groups that constitute the solid polymer electrolyte membrane are required to have resistance to hot water.

[0009] The inventors evaluated a solid polymer electrolyte membrane obtained using a fluoropolymer containing acidic sulfonic acid groups, manufactured by the method described in Patent Document 1. The results showed that the conductivity and hot water resistance were insufficient and could be improved. Specifically, when a solid polymer electrolyte membrane with high ion exchange capacity was manufactured to obtain high conductivity of 0.08 S / cm or higher, the hot water resistance was significantly reduced. Therefore, the manufacturing method described in Patent Document 1 could not produce a solid polymer electrolyte membrane that simultaneously achieved high conductivity of 0.08 S / cm or higher and hot water resistance.

[0010] In view of the above-mentioned circumstances, the present invention aims to provide a fluoropolymer containing fluorosulfonyl groups and a method for manufacturing the same, a fluoropolymer containing acid sulfonic acid groups and a method for manufacturing the same, a solid polymer electrolyte membrane, a membrane electrode assembly, and a solid polymer fuel cell, which are capable of producing solid polymer electrolyte membranes with excellent conductivity and hot water resistance.

[0011] Solution for solving the problem

[0012] The inventors conducted in-depth research on the above-mentioned issues and found that: when a fluorosulfonyl-containing fluoropolymer is produced by copolymerizing the monomer shown in Formula m1 (described later) with tetrafluoroethylene in the presence of a free radical polymerization initiator (hereinafter also referred to as "initiator"), by setting the copolymerization temperature within a specified range, adding the initiator to the reactor, and maintaining the concentration of the initiator in the reactor during copolymerization at less than 2.5 ppm by mass of the monomer shown in Formula m1 added to the reactor before the start of polymerization, and setting the molar ratio of the total amount of monomer shown in Formula m1 to the total amount of tetrafluoroethylene added within a specified range, a fluorosulfonyl-containing fluoropolymer capable of producing a solid polymer electrolyte membrane with excellent conductivity and hot water resistance is obtained, thus completing the present invention.

[0013] That is, the inventors have discovered that the above-mentioned problems can be solved by the following configuration.

[0014] [1] A method for manufacturing a fluoropolymer containing fluorosulfonyl groups, characterized in that, in a reactor, in the presence of a free radical polymerization initiator, a monomer represented by formula m1 (described later) is copolymerized with tetrafluoroethylene at a temperature of 150 to 200°C to produce a fluoropolymer containing fluorosulfonyl groups, wherein, in the copolymerization, the free radical polymerization initiator is continuously or batch-wise added to the reactor such that the concentration of the free radical polymerization initiator in the reactor is maintained at less than 2.5 ppm by mass of the monomer represented by formula m1 added to the reactor before the copolymerization begins, and the molar ratio of the total amount of monomer represented by formula m1 added to the total amount of tetrafluoroethylene added is 1.5 to 20.

[0015] In the formula m1 described later, Q 1 It is a single bond or optionally a perfluoroalkylene group with an ether-bonded oxygen atom.

[0016] [2] A method for manufacturing a fluorosulfonyl fluorinated polymer, characterized in that, in a reactor, in the presence of a free radical polymerization initiator, the monomer shown in formula m1 (described later) is copolymerized with tetrafluoroethylene at a temperature of 150–200 °C, thereby manufacturing a fluorosulfonyl fluorinated polymer.

[0017] The ratio of the total amount of the free radical polymerization initiator added to the reactor to the total amount of the monomer represented by formula m1 added to the reactor is 0.01 to 4 ppm by mass per hour of copolymerization time.

[0018] The molar ratio of the total amount of monomers shown in formula m1 to the total amount of tetrafluoroethylene is 1.5 to 20.

[0019] In the formula m1 described later, Q 1 It is a single bond or optionally a perfluoroalkylene group with an ether-bonded oxygen atom.

[0020] [3] The method for manufacturing a fluoropolymer containing fluorosulfonyl groups according to [1] or [2], wherein the monomer shown in formula m1 above is the monomer shown in formula m11 described later.

[0021] In the following expression m11, x is an integer from 1 to 12.

[0022] [4] A method for manufacturing a fluoropolymer containing fluorosulfonyl groups according to any one of [1] to [3], wherein the free radical polymerization initiator is a bis(perfluoroalkyl) peroxide or a dialkyl peroxide.

[0023] [5] A fluorosulfonyl-containing fluoropolymer, characterized in that it has a unit represented by formula f1 described later and a tetrafluoroethylene-based unit, wherein the Q value of the fluorosulfonyl-containing fluoropolymer is 0.2 to 60.0 mm. 3 / second, the proportion of the unit shown in formula f1 above in the above-mentioned fluorosulfonyl fluorinated polymer to all units is 21 to 59 mol%.

[0024] The Q value mentioned above refers to the value obtained by filling the fluoropolymer containing fluorosulfonyl groups to a cross-sectional area of ​​1 cm² using a flow tester. 2 In a barrel, at 260℃ and a load of 30kg, material is extruded from a nozzle with an inner diameter of 1mm and a length of 1mm at a pressure of 2.94MPa. The extruded volume (mm³) per unit time is [value missing]. 3 / Second).

[0025] In the following equation f1, Q 1 It is a single bond or optionally a perfluoroalkylene group with an ether-bonded oxygen atom.

[0026] [6] According to [5], the fluorinated polymer containing fluorosulfonyl groups, wherein the fluorinated polymer containing acidic sulfonate groups when the fluorosulfonyl groups in the fluorinated polymer containing fluorosulfonyl groups are acidic sulfonic acid groups, has an ion exchange capacity of 1.45 to 2.50 milliequivalents / gram of dry resin.

[0027] [7] The fluoropolymer containing fluorosulfonyl groups according to [5] or [6], wherein the unit shown in formula f1 above is the unit shown in formula f11 described later.

[0028] In the following expression f11, x is an integer from 1 to 12.

[0029] [8] A method for manufacturing a fluoropolymer containing sulfonic acid groups, characterized in that the fluorosulfonyl groups of the fluoropolymer containing fluorosulfonyl groups manufactured by any one of the manufacturing methods of [1] to [4] are converted into sulfonic acid groups.

[0030] [9] A fluoropolymer containing sulfonic acid groups, characterized in that it has units represented by the formula u1 described later and tetrafluoroethylene-based units, such that the Q value of the fluoropolymer containing sulfonic acid groups when the sulfonic acid groups in the above-described fluoropolymer are fluorosulfonyl groups is 0.2 to 60.0 mm. 3 / second, the proportion of the unit shown in formula u1 above in the above-mentioned sulfonic acid-containing fluoropolymer is 21 to 59 moles relative to all units.

[0031] The Q value mentioned above refers to the value obtained by filling the fluoropolymer containing fluorosulfonyl groups to a cross-sectional area of ​​1 cm² using a flow tester. 2 In a barrel, at 260℃ and a load of 30kg, material is extruded from a nozzle with an inner diameter of 1mm and a length of 1mm at a pressure of 2.94MPa. The extruded volume (mm³) per unit time is [value missing]. 3 / Second).

[0032] In the following equation u1, Q 1 Z is a perfluoroalkylene group with a single bond or optionally an ether-bonded oxygen atom. + For H + Metal ions or ammonium ions.

[0033]

[10] According to [9], the sulfonic acid group in the fluorinated polymer is an acidic sulfonic acid group, and the ion exchange capacity of the acidic sulfonic acid group fluorinated polymer is 1.45 to 2.50 milliequivalents / gram of dry resin.

[0034]

[11] The fluoropolymer containing sulfonic acid groups according to [9] or

[10] , wherein the unit shown in the above formula u1 is the unit shown in the formula u11 described later.

[0035] In the following expression u11, x is an integer from 1 to 12, and Z + For H + Metal ions or ammonium ions.

[0036]

[12] A liquid composition comprising any one of [9] to

[11] a fluoropolymer containing a sulfonic acid group and a liquid medium.

[0037]

[13] The liquid composition according to

[12] , wherein the liquid medium comprises a mixture of an alcohol having 1 to 4 carbon atoms and water.

[0038]

[14] The liquid composition according to

[12] or

[13] further comprises one or more atoms selected from the group consisting of cerium atoms and manganese atoms.

[0039]

[15] A solid polymer electrolyte membrane, characterized in that it comprises any one of the sulfonic acid groups in [9] to

[11] ,

[0040] The sulfonic acid groups in fluoropolymers containing sulfonic acid groups are acidic sulfonic acid groups.

[0041]

[16] The solid polymer electrolyte membrane according to

[15] further comprises a reinforcing material.

[0042]

[17] The solid polymer electrolyte membrane according to

[16] , wherein the reinforcing material is formed of PTFE porous body.

[0043]

[18] The solid polymer electrolyte membrane according to any one of

[15] to

[17] has a membrane thickness of 5 to 200 μm.

[0044]

[19] The solid polymer electrolyte membrane according to any one of

[15] to

[18] further comprises one or more atoms selected from the group consisting of cerium atoms and manganese atoms.

[0045]

[20] A membrane electrode assembly, characterized in that it comprises: an anode having a catalyst layer comprising a catalyst and a polymer having ion exchange groups; a cathode having a catalyst layer comprising a catalyst and a polymer having ion exchange groups; and a solid polymer electrolyte membrane disposed between the anode and the cathode and comprising a polymer having ion exchange groups.

[0046] The polymer selected from the group consisting of a polymer containing ion exchange groups in the anode, a polymer containing ion exchange groups in the cathode, and a polymer containing ion exchange groups in the solid polymer electrolyte membrane is a fluorinated polymer containing sulfonic acid groups as described in any one of [9] to

[11] .

[0047]

[21] According to the membrane electrode assembly of

[20] , wherein the catalyst layer of at least one of the anode and cathode comprises a polymer having ion-exchange groups, which is a polymer having units comprising cyclic ether structures and having sulfonic acid functional groups.

[0048] The polymer containing ion exchange groups in the solid polymer electrolyte membrane is any one of the fluorinated polymers containing sulfonic acid groups in [9] to

[11] .

[0049]

[22] According to the membrane electrode assembly of

[21] , the unit containing the cyclic ether structure comprises the unit shown in formula u12 or the unit shown in formula u22 described later.

[0050] In the following equation u12, R 21 It is a perfluoroalkylene group having 1 to 6 carbon atoms or a perfluoroalkylene group having 2 to 6 carbon atoms with ether-bonded oxygen atoms between the carbon atoms; R 22 It is a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms with ether-bonded oxygen atoms between carbon atoms, or -R 21 (SO2X(SO2R f ) a ) - M + The group shown. M + For H + A monovalent metal cation, or an ammonium ion in which one or more hydrogen atoms are optionally substituted with a hydrocarbon group; R f X is a straight-chain or branched perfluoroalkyl group that may be selected from those containing an ether bond oxygen atom; X is an oxygen atom, a nitrogen atom, or a carbon atom. When X is an oxygen atom, a = 0; when X is a nitrogen atom, a = 1; and when X is a carbon atom, a = 2.

[0051] In the following equation u22, s is 0 or 1, R 51 and R 52 Each is independently a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a spirocyclic ring formed by their interconnection (where s is 0), R 53 and R 54 Each is independently a perfluoroalkyl group having 1 to 5 carbon atoms, R 55 It is a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms.

[0052]

[23] The membrane electrode assembly according to any one of

[20] to

[22] , wherein the sulfonic acid group of the fluoropolymer containing the sulfonic acid group is an acidic sulfonic acid group.

[0053]

[24] A solid polymer fuel cell, characterized in that it comprises a membrane electrode assembly as described in any one of

[20] to

[23] .

[0054] The effects of the invention

[0055] According to the present invention, there are fluoropolymers containing fluorosulfonyl groups and methods for manufacturing the same, fluoropolymers containing acid sulfonic acid groups and methods for manufacturing the same, solid polymer electrolyte membranes, membrane electrode assemblies, and solid polymer fuel cells that can produce solid polymer electrolyte membranes with excellent conductivity and hot water resistance. Attached Figure Description

[0056] Figure 1 This is a schematic cross-sectional view illustrating an example of the membrane electrode assembly of the present invention. Detailed Implementation

[0057] Unless otherwise specified, the definitions of the following terms are generally applicable in this specification and claims.

[0058] "Salt-type sulfonic acid group" refers to the salt-type sulfonic acid group (-SO3). - M + Among them, M + (It is a metal ion or ammonium ion).

[0059] "Acidic sulfonic acid group" refers to the acidic sulfonic acid group (-SO3). - H + ).

[0060] "Sulfonic acid group" refers to both salt-type and acid-type sulfonic acid groups. In this specification, when the salt-type or acid-type is not specified and is abbreviated as "sulfonic acid group," it refers to the aforementioned collective term -SO3. - Z + (where Z) + For H + Groups represented by metal ions or ammonium ions.

[0061] In polymers, a "unit" refers to a group of atoms derived from one molecule of a monomer, formed through polymerization. A unit can be a group of atoms formed directly through the polymerization reaction, or it can be obtained by processing the polymer obtained through polymerization, thereby transforming a portion of the unit into a different structure. It should be noted that structural units derived from individual monomers are sometimes described using the name derived from the monomer name, which is labeled "unit."

[0062] The unit represented by equation u1 is denoted as unit u1. Units represented by other equations are also denoted in the same way.

[0063] The monomer shown in formula m1 is denoted as monomer m1. The monomers shown in other formulas are also denoted in the same way.

[0064] The range of values ​​represented by “~” refers to the range of values ​​recorded before and after “~” as the lower and upper limits.

[0065] "Total A addition" refers to the total amount of A added to the reactor for polymer polymerization. For example, when A is added to the reactor before and during polymerization, it refers to the total amount of A added before polymerization and the total amount of A added during polymerization. It should be noted that "A" is the component used in the polymerization, which may include, for example, TFE, monomer m1, or initiator, as described later.

[0066] "Productivity index (Rp)" means the amount of polymer (g) generated per hour of polymerization time relative to the total amount of SO2F-based monomers (100g) input before and during copolymerization.

[0067] "Time of gathering" refers to the period from the start of the gathering to the end of the gathering.

[0068] The "moment of initiation of copolymerization" can be categorized as follows: the moment when the monomer and initiator coexist in the reactor at a specified pressure after the reactor temperature has been raised above a specified level; and the moment when the reactor temperature is raised above a specified level after the monomer and initiator have coexisted in the reactor. It should be noted that the specified temperature refers to a temperature above 80°C and above [(the 10-hour half-life temperature of the initiator) - 30]°C. The specified pressure refers to a pressure where the partial pressure of tetrafluoroethylene, as the monomer, is 0.02 MPa or higher.

[0069] Examples of "times to stop copolymerization" include: the moment when the reactor temperature is lowered to a specified level, the moment when tetrafluoroethylene (TEF) is purged as a monomer, and the moment when a polymerization inhibitor is added to the reactor. It should be noted that purging TEF refers to reducing the partial pressure of TEF to below 0.01 MPa.

[0070] It should be noted that when copolymerization is restarted through reversible operations (such as heating the reactor back to a specified temperature or adding tetrafluoroethylene again) after copolymerization has stopped, this time is included in the polymerization time.

[0071] [Method for manufacturing the fluoropolymer containing fluorosulfonyl groups according to the first embodiment]

[0072] The method for manufacturing a fluoropolymer containing fluorosulfonyl groups according to the first embodiment of the present invention is to copolymerize monomer m1 with tetrafluoroethylene (hereinafter also referred to as "TFE") at a temperature of 150 to 200°C in the presence of an initiator in a reactor, thereby manufacturing a fluoropolymer containing fluorosulfonyl groups.

[0073] Furthermore, in the above copolymerization, the initiator is added continuously or in batches to the reactor such that the concentration of the initiator in the reactor is maintained at less than 2.5 ppm by mass of the monomer m1 added to the reactor before the start of the copolymerization.

[0074] Furthermore, the molar ratio of the total addition amount of the aforementioned monomer m1 to the total addition amount of the aforementioned TFE is 1.5 to 20.

[0075] In this specification, the fluoropolymer containing fluorosulfonyl groups obtained by the manufacturing method in the first embodiment will also be referred to as "polymer Fx".

[0076] According to this manufacturing method, it is possible to manufacture fluoropolymers containing fluorosulfonyl groups, which can be used to manufacture solid polymer electrolyte membranes with excellent conductivity and hot water resistance.

[0077] In the embodiments of Patent Document 1, the initiator was used at a high concentration. However, the inventors have discovered that by setting the amount of initiator to a low concentration, a polymer with high conductivity and good hot water resistance can be obtained.

[0078] In other words, it can be assumed that in the copolymerization of monomer m1 and TFE, by maintaining the initiator concentration below a specified value, the stopping reaction in the copolymerization of TFE and monomer m1 is less likely to occur. It can be inferred that, as a result, the molecular weight of polymer Fx increases, and therefore, the hot water resistance of the solid polymer electrolyte membrane made from the fluoropolymer containing acidic sulfonic acid groups obtained by making the fluorosulfonyl group of polymer Fx acidic (hereinafter also referred to as "polymer HAx") is improved.

[0079] Furthermore, while reducing the amount of initiator typically leads to a decrease in polymerization rate and a significant reduction in productivity, surprisingly, according to the method of the present invention, copolymerization can be carried out at an industrially feasible level.

[0080] That is, even when the initiator concentration is low as described above, by setting the copolymerization temperature of monomer m1 and TFE to a high temperature of 150 to 200°C, it is possible to suppress the decrease in reaction rate during the manufacture of polymer Fx.

[0081] Furthermore, by setting the molar ratio of the total amount of monomer m1 to the total amount of TFE to 1.5–20, the content of monomer m1-based units in polymer Fx is increased, thus increasing the ion exchange capacity of polymer HAx. As a result, the conductivity of the solid polymer electrolyte membrane made from polymer HAx is considered to be improved.

[0082] Furthermore, it was surprisingly discovered that the polymer also exhibited superior chemical durability.

[0083] <Single m1>

[0084] The monomer m1 is the monomer shown in the following formula m1.

[0085] CF2=CFCF2O-Q 1 -SO2F(m1)

[0086] In formula m1, Q 1 It is a single bond or optionally a perfluoroalkylene group with an ether-bonded oxygen atom.

[0087] Perfluoroalkylene compounds can be linear or branched.

[0088] From the viewpoint of being able to suppress the decrease in ion exchange capacity of polymer HAx and obtain a solid polymer electrolyte membrane with better conductivity, the number of carbon atoms in the perfluoroalkyl group is preferably 1 to 12, more preferably 1 to 6, and particularly preferably 1 to 4.

[0089] When a perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms can be one or more, preferably two or fewer.

[0090] From the viewpoint of easy manufacturing of polymer Fx and easy industrial implementation, monomer m1 is preferably monomer m11, and particularly preferably monomer m11-1.

[0091] CF2=CFCF2O(CF2) x SO2F (m11)

[0092] CF2=CFCF2OCF2CF2SO2F (m11-1)

[0093] In formula m11, x is an integer from 1 to 12, preferably an integer from 1 to 6, and particularly preferably an integer from 1 to 4.

[0094] <Other monomers>

[0095] In this manufacturing method, monomers other than TFE and monomer m1 (hereinafter also referred to as "other monomers") can be used.

[0096] From the viewpoint of improving the chemical durability of the polymer, perfluorinated monomers are preferred as other monomers. From the viewpoint of increasing the amount introduced into the polymer, perfluoroallyl ethers or perfluorovinyl ethers are more preferred. From the viewpoint of easily improving the physical properties of the polymer, perfluoroallyl ethers are even more preferred. It should be noted that perfluorovinyl ethers sometimes function as chain transfer agents based on their own chain transfer at 150–200°C, and therefore can be used for the purpose of not only improving physical properties but also adjusting molecular weight.

[0097] Specific examples of other monomers are shown below.

[0098] CF2=CFCF2O(CF2) n1 F,

[0099] CF2 = CF(CF2) n2 F,

[0100] CF2 = CFCF2[OCF2CF(CF3)] n3 OCF2CF2CF3、

[0101] CF2 = CFO(CF2) n4 CF3

[0102] CF2 = CFOCF2CF(CF3)O(CF2) n5 CF3

[0103] CF2 = CF[OCF2CF(CF3)] n6 O(CF2)3F,

[0104]

[0105] In the above formula, n1 is an integer from 1 to 4, n2 is an integer from 1 to 11, n3 is 1 or 2, n4 is an integer from 1 to 9, n5 is an integer from 1 to 9, n6 is 2 or 3, and n7 is an integer from 1 to 6.

[0106] <Initiator>

[0107] Examples of initiators include bis(fluoroacyl)peroxides, bis(perfluoroalkyl)peroxides (e.g., (CF3)3COOC(CF3)3), bis(chlorofluoroacyl)peroxides, dialkyl peroxides (e.g., (CH3)3COOC(CH3)3), peroxide esters, azo compounds, and persulfates. From the viewpoint of improving the chemical durability of solid polymer electrolyte membranes, bis(perfluoroalkyl)peroxides and dialkyl peroxides are preferred. From the viewpoints of excellent initiator availability and low cost, higher decomposition start temperature, and ability to polymerize at high temperatures, dialkyl peroxides are particularly preferred. Among dialkyl peroxides, (CH3)3COOC(CH3)3 is most preferred from the viewpoint of lower chain transferability.

[0108] Initiators can be used alone or in combination of two or more.

[0109] <Gathering>

[0110] Specific examples of copolymerization methods include bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. From the viewpoint of avoiding the reduction in the molecular weight of polymer Fx caused by the chain transfer property of the polymerization solvent, bulk polymerization, which substantially does not use a polymerization solvent, is preferred.

[0111] When using solution polymerization, a polymerization solvent with a low chain transfer constant is preferred. Examples of such polymerization solvents include compounds that do not possess atoms other than carbon, fluorine, oxygen, and nitrogen atoms. Specifically, examples include perfluorotributylamine, perfluorotripropylamine, perfluorohexane, perfluorooctane, perfluorodecane, perfluorododecane, perfluoro(2,7-dimethyloctane), perfluorodecahydronaphthalene, perfluorocyclohexane, perfluoro(1,3-dimethylcyclohexane), perfluoro(1,3,5-trimethylcyclohexane), perfluorodimethylcyclobutane (regardless of structural isomers), perfluoro(2-butyltetrahydrofuran), perfluorobenzene, liquefied carbon dioxide, and supercritical carbon dioxide.

[0112] In addition, hydrofluorocarbons, hydrochlorofluorocarbons, and hydrofluoroethers with a small number of hydrogen atoms can be used as polymerization solvents.

[0113] Specific examples of hydrofluorocarbons with a small number of hydrogen atoms include 1H-perfluorohexane, 1H-perfluorooctane, 1H,4H-perfluorobutane, 2H,3H-perfluoropentane, 3H,4H-perfluoro(2-methylpentane), 1,1,1,3,3-pentafluorobutane, and 1,1,2,2,3,3,4-heptafluorocyclopentane.

[0114] 1,3-Dichloro-1,1,2,2,3-pentafluoropropane is a specific example of hydrochlorofluorocarbons with a small number of hydrogen atoms.

[0115] Specific examples of hydrofluoroethers with a small number of hydrogen atoms include HCF2CF2OCH2CF3, n-C3F7OCH3, n-C3F7OCHFCF3, n-C3F7OCH2CF3, n-C4F9OCH3, iso-C4F9OCH3, n-C4F9OCH2CH3, n-C4F9OCH2CF3, CF3OCF(CF3)CF2OCH3, and n-C3F7OCF(CF3)CF2OCHFCF3.

[0116] In addition, chlorofluorocarbons (CFCs) that do not have hydrogen atoms can be used.

[0117] The copolymerization temperature of monomer m1 and TFE is 150-200°C. From the viewpoint of further increasing the reaction rate of monomer, it is preferably 155°C or higher, and particularly preferably 160°C or higher. From the viewpoint of easily suppressing the decomposition rate of initiator and easily controlling copolymerization, it is preferably 190°C or lower, and particularly preferably 180°C or lower.

[0118] The polymerization pressure is appropriately set based on the copolymerization temperature and the ion exchange capacity of the polymer HAx. From the viewpoint of improving the yield of polymer Fx and the ion exchange capacity of polymer HAx, the partial pressure of TFE is preferably 0.02 to 1.2 MPa. The polymerization pressure is preferably 0.1 to 1.9 MPaG.

[0119] In this manufacturing method, monomer m1 is pre-introduced into the reactor, and then copolymerization begins.

[0120] The initiator can be added to the reactor along with monomer m1 before copolymerization begins, or it can be added to the reactor in which monomer m1 has been introduced.

[0121] TFE and other monomers used as needed can be added to the reactor along with monomer m1 before copolymerization begins, or they can be added to the reactor with monomer m1 already in it, or they can be added to the reactor after the copolymerization of monomer m1 has begun.

[0122] Monomers (TFE, monomer m1, and other monomers used as needed) and initiators can be added to the reactor continuously or in batches.

[0123] In this invention, "batch addition" refers to a method of dividing and intermittently adding the additives (e.g., monomers, initiators) used in polymerization, which means alternating between periods when the additives are added and periods when they are not added, and having more than two addition periods.

[0124] Furthermore, in this invention, "continuous addition" refers to a method of adding the additives (e.g., monomers, initiators) used in polymerization without interruption within a specified period, meaning a method of adding the additives without adding them outside the specified period.

[0125] The molar ratio of the total amount of monomer m1 to the total amount of TFE is 1.5 to 20. From the viewpoint of further improving the ion exchange capacity of polymer HAx, it is preferably 1.7 or more, more preferably 2.0 or more, and particularly preferably 2.2 or more. From the viewpoint of improving the mechanical durability of the solid polymer electrolyte membrane or improving the yield of polymer Fx, it is preferably 15 or less, more preferably 10 or less, and particularly preferably 8 or less.

[0126] When adding other monomers to the reactor, from the viewpoint of further maximizing the effects of the present invention, the molar ratio of the total amount of other monomers added to the total amount of TFE or the total amount of monomer m1 is preferably 0.01 to 0.5, and particularly preferably 0.05 to 0.2.

[0127] In this invention, during the copolymerization of monomer m1 and TFE, an initiator is continuously or batch-wise added to the reactor, such that the concentration of the initiator in the reactor is maintained below 2.5 ppm by mass of monomer m1 added to the reactor before the copolymerization begins.

[0128] If the initiator concentration in the copolymerization is below 2.5 ppm by mass, the solid polymer electrolyte membrane exhibits excellent hot water resistance. Furthermore, as an unexpected effect, the solid polymer electrolyte membrane also demonstrates excellent chemical durability. The reason for this excellent chemical durability is not yet clear, but it can be speculated that the lower initiator concentration in the reactor reduces the proportion of initiator-derived chemical structural sites incorporated into the polymer via chain transfer, thus reducing the number of easily degraded sites in the polymer's HAx (hydrogen peroxide).

[0129] From the viewpoint of further improving the hot water resistance and chemical durability of the solid polymer electrolyte membrane, the concentration of the initiator in the copolymerization is preferably 2.5 ppm by mass or less of the mass of monomer m1 added to the reactor before starting the above copolymerization, more preferably 2 ppm by mass or less, and particularly preferably 1.5 ppm by mass or less.

[0130] From the viewpoint of further increasing the polymerization rate of monomers and from the viewpoint of conducting polymerization well, the concentration of the initiator in copolymerization is preferably 0.01 ppm or more by mass of the monomer m1 added to the reactor before starting the above copolymerization, more preferably 0.05 ppm or more by mass, and particularly preferably 0.1 ppm or more by mass.

[0131] When adding initiators in batches or continuously, from the viewpoint of controlling the amount added and ensuring the safety of copolymerization, it is preferable to dilute the initiator with monomers (monomer m1 and other monomers used as needed) or polymerization solvent before adding it. From the viewpoint of avoiding a decrease in the molecular weight of polymer Fx due to chain transfer in the polymerization solvent, and from the viewpoint of mitigating the decrease in polymerization rate associated with a decrease in the concentration of monomer m1 due to the copolymerization reaction, it is preferable to dilute with monomer m1. From the viewpoint of improving the controllability of the amount added and ensuring the safety of copolymerization, the concentration of the initiator in the initiator solution used in batch or continuous addition is preferably 10 to 10,000 ppm by mass, more preferably 50 to 3,000 ppm by mass, and particularly preferably 100 to 1,000 ppm by mass.

[0132] Here, according to the theory of free radical polymerization, the thermal decomposition of the initiator can be approximated as a single reaction. Therefore, the concentration of the initiator in the reactor after a unit time elapsed since the start of copolymerization, relative to the mass of monomer m1 added to the reactor before the start of copolymerization [I], is calculated by Equation 1 below.

[0133] [I] = [I0] × exp(-K) d ·t) Equation 1

[0134] [I]: The concentration of the initiator in the reactor after a unit time elapsed since the start of copolymerization, relative to the mass of monomer m1 added to the reactor before copolymerization begins [mass ppm].

[0135] [I0]: The concentration of the initiator in the reactor at the beginning of a unit time, relative to the mass of monomer m1 added to the reactor before copolymerization begins [mass ppm].

[0136] K d Decomposition rate coefficient

[0137] t: unit time

[0138] It should be noted that exp refers to the exponential function.

[0139] Here, the starting point of a unit of time can be listed as, for example, the moment when copolymerization begins, or the moment immediately after the initiator is added in batches.

[0140] In Equation 1 above, K d The decomposition rate coefficient is calculated using Equation 2 below.

[0141] K d =A×exp(-E a / RT) Equation 2

[0142] R: 8.314 [J·K] -1 ·mol -1 ]

[0143] T: Temperature [K]

[0144] E a Activation energy [kJ / mol]

[0145] A: Frequency factor [h] -1 ]

[0146] K d This is a coefficient defined based on the type of initiator and the copolymerization temperature. It is known to be used to calculate K. d A and E in Equation 2 aThe concentration of the solvent and initiator varies depending on the environment of the reaction field, but in this specification, the value obtained by measuring the thermal decomposition rate is used. The thermal decomposition rate is measured using an initiator solution obtained by dissolving the initiator in benzene as a solvent (initiator concentration: 0.10 [mol / L]).

[0147] For example, when (CH3)3COOC(CH3)3 (hereinafter also referred to as "tBPO") is used as the initiator, Ea is 155.8 [kJ / mol] and A is 2.23 × 10⁻⁶. 19 [h -1 The 10-hour half-life temperature is 123.7℃. Therefore, when monomer m1 is copolymerized using tBPO at a copolymerization temperature of 160℃ (T = 160 + 273.15 = 433.15 [K]), if the values ​​of Ea, A, and T are substituted into Equation 2, then K... d 3.62[h -1 ].

[0148] If other examples of initiators are listed, then when (CH3)3COOC(CH3)2-C6H4-C(CH3)2OOC(CH3)3 is used, E a The value is 166.3 [kJ / mol], and A is 9.93 × 10⁻⁶. 20 [h -1 The 10-hour half-life temperature is 119.2℃. When using C6H5-C(CH3)2OOC(CH3)2-C6H5, E... a The value is 158.0 [kJ / mol], and A is 1.06 × 10⁻⁶. 20 [h -1 The 10-hour half-life temperature is 116.4℃. When using CH3CH2CH2C(CH3)2OOC(CH3)2CH2CH2CH3, E... a The value is 154.5 [kJ / mol], and A is 3.71 × 10⁻⁶. 19 [h -1 The 10-hour half-life temperature is 116.4℃. When using (CH3)3COOC(CH3)2CH2CH2C(CH3)2OOC(CH3)3, E a The value is 152.0 [kJ / mol], and A is 1.39 × 10⁻⁶. 19 [h -1 The 10-hour half-life temperature is 117.9℃. When using (CH3)3COOC(CH3)2C6H5, E... a The value is 173.1 [kJ / mol], and A is 7.59 × 10⁻⁶. 21 [h -1The 10-hour half-life temperature is 119.5℃. When using (CH3)3COOC(CH3)2C≡CC(CH3)2OOC(CH3)3, E a The value is 151.3 [kJ / mol], and A is 3.36 × 10⁻⁶. 18 [h -1 The 10-hour half-life temperature is 128.4℃. When using (CF3)3COOC(CF3)3(PFtBPO), E a The value is 148.8 [kJ / mol], and A is 5.68 × 10⁻⁶. 19 [h -1 The half-life temperature after 10 hours is 98.5℃.

[0149] Next, taking the case of adding the initiator in batches during copolymerization as an example, an example of a method for setting the amount of initiator to be added in batches is shown.

[0150] Using tBPO as an initiator, with the mass of monomer m1 added to the reactor before copolymerization starting set to 1000 g, and the concentration of the initiator in the reactor at the start of copolymerization set to 2.0 ppm (i.e., equivalent to [I0] in Equation 1) relative to the mass of monomer m1 added to the reactor before copolymerization starting, the mass of tBPO in the reactor at the start of copolymerization is 2 mg. Under these conditions, after copolymerization starts at 160 °C, the concentration of tBPO (i.e., equivalent to [I] in Equation 1) after 0.5 hours (i.e., equivalent to t in Equation 1) is 0.327 ppm (i.e., equivalent to [I] in Equation 1) relative to the mass of monomer m1 added to the reactor before copolymerization starting.

[0151] Therefore, if we want to set the concentration of tBPO immediately after each addition to the same concentration as the concentration of tBPO in the reactor at the start of copolymerization (2.0 ppm by mass) relative to the mass of monomer m1 added to the reactor before copolymerization begins, only 1.67 mg of tBPO needs to be added. In other words, the concentration of tBPO recovers to 2.0 ppm by mass every 0.5 hours.

[0152] Next, taking the case of continuous addition of the initiator as an example, an example of a method for setting the initiator addition rate [mg / h], that is, the amount of initiator added per hour, is shown.

[0153] The reduction rate of the initiator can be determined by differentiating Equation 1.

[0154] Initiator reduction rate = -[Io] × K d [mass ppm / h]

[0155] For example, using tBPO as an initiator, with the mass of monomer m1 added to the reactor before copolymerization starting set to 1000 g, and the initiator concentration in the reactor at the start of copolymerization relative to the mass of monomer m1 added to the reactor before copolymerization starting set to 2.0 ppm by mass (i.e., equivalent to [I0] in Equation 1), under these conditions, when copolymerization is carried out at 160 °C, the initiator reduction rate is -7.24 [ppm by mass / h], which, when converted to mass, is 7.24 [mg / h]. In other words, if tBPO is continuously added at a rate of 7.24 [mg / h], the initiator concentration in the copolymerization relative to the mass of monomer m1 added to the reactor before copolymerization starting can be maintained at 2.0 ppm by mass.

[0156] It should be noted that when the initiator is added in batches or continuously according to the aforementioned method for setting the amount of initiator, the concentration of the initiator gradually decreases as copolymerization progresses, relative to the total amount of all monomers, solvents, and polymers generated in the reactor, due to the increase in the amount of polymer generated as copolymerization proceeds and the increase in the amount of monomers or solvents added to the reactor as the initiator is diluted (described later). In this case, as defined in this invention, if the initiator is added continuously or in batches to the reactor such that the concentration of the initiator in the reactor is maintained at less than 2.5 ppm by mass of the monomer m1 added to the reactor before the start of the aforementioned copolymerization, the effects of the invention can be achieved.

[0157] Regarding the ratio of the total amount of initiator added to the reactor to the total amount of monomer m1 added to the reactor, from the viewpoint of further maximizing the effects of the present invention, it is preferably 0.01 to 4 ppm by mass, more preferably 0.1 to 3 ppm by mass, and particularly preferably 0.5 to 2.5 ppm by mass, based on the average copolymerization time per hour.

[0158] From the viewpoint of improving productivity, the productivity index (Rp) in the manufacturing method of the present invention is preferably 0.5 or more, more preferably 0.6 or more, and particularly preferably 0.7 or more. Furthermore, from the viewpoint of suppressing inhomogeneity in copolymerization, the Rp value is preferably 5.0 or less, more preferably 4.0 or less, and particularly preferably 3.0 or less.

[0159] After manufacturing polymer Fx, it can be contacted with fluorine gas to fluorinate the unstable terminal groups of polymer Fx. This further suppresses the decomposition of polymer HAx obtained using polymer Fx, thus further improving the chemical durability of the solid polymer electrolyte membrane.

[0160] Here, unstable terminal groups are groups formed through chain transfer reactions, groups derived from initiators, etc. Specifically, -COOH, -CF=CF2, -COF, and -CF2H can be listed.

[0161] Fluorine gas is preferably diluted with inactive gases (nitrogen, helium, carbon dioxide, etc.).

[0162] The temperature at which polymer Fx comes into contact with fluorine gas is preferably 150–200°C, and more preferably 170–190°C. The contact time between polymer Fx and fluorine gas is preferably 1 minute to 1 week, and more preferably 1 to 50 hours.

[0163] [Method for manufacturing the fluoropolymer containing fluorosulfonyl groups according to the second embodiment]

[0164] The method for manufacturing the fluoropolymer containing fluorosulfonyl groups according to the second embodiment of the present invention is to copolymerize monomer m1 with TFE at a temperature of 150 to 200°C in the presence of an initiator in a reactor, thereby manufacturing the fluoropolymer containing fluorosulfonyl groups.

[0165] Furthermore, the ratio of the total amount of the aforementioned initiator added to the reactor to the total amount of the aforementioned monomer m1 added to the reactor is 0.01 to 4 ppm by mass per hour of copolymerization time.

[0166] Furthermore, the molar ratio of the total addition amount of the aforementioned monomer m1 to the total addition amount of the aforementioned TFE is 1.5 to 20.

[0167] In the specification, the fluorosulfonyl fluorinated polymer obtained by the manufacturing method in the second embodiment is also referred to as "polymer Fy".

[0168] According to this manufacturing method, a fluoropolymer containing fluorosulfonyl groups can be manufactured to produce a solid polymer electrolyte membrane with excellent conductivity and hot water resistance.

[0169] In the embodiments of Patent Document 1, the initiator was used at a high concentration. However, the inventors have discovered that by setting the amount of initiator to a low concentration, a polymer with high conductivity and good hot water resistance can be obtained.

[0170] That is, it can be considered that by setting the ratio of the total amount of the aforementioned initiator added to the reactor to the total amount of monomer m1 added to the reactor within a specified range, the stopping reaction in the copolymerization of TFE and monomer m1 is less likely to occur. It can be inferred that, as a result, the molecular weight of polymer Fy increases, and therefore, the hot water resistance of the solid polymer electrolyte membrane made from the fluoropolymer containing acidic sulfonic acid groups obtained by making the fluorosulfonyl group of polymer Fy acidic (hereinafter also referred to as "polymer HAy") is improved.

[0171] Furthermore, while reducing the amount of initiator typically leads to a decrease in polymerization rate and a significant reduction in productivity, surprisingly, according to the method of the present invention, copolymerization can be carried out at an industrially feasible level.

[0172] That is, even when the initiator concentration is low as described above, by setting the copolymerization temperature of monomer m1 and TFE to a high temperature of 150 to 200°C, it is possible to suppress the decrease in reaction rate during the manufacture of polymer Fy.

[0173] Furthermore, by setting the molar ratio of the total amount of monomer m1 to the total amount of TFE to 1.5–20, the content of monomer m1-based units in polymer Fy is increased, thus increasing the ion exchange capacity of polymer HAy. As a result, the conductivity of the solid polymer electrolyte membrane made from polymer HAy is considered to be improved.

[0174] Furthermore, it was surprisingly discovered that the polymer also exhibited superior chemical durability.

[0175] In the manufacturing method of the second embodiment, instead of "in the above copolymerization, the initiator is continuously or batch-wise added to the reactor so that the concentration of the initiator in the reactor is maintained at less than 2.5 ppm by mass of the monomer m1 added to the reactor before the start of the copolymerization", the requirement is that "the ratio of the total amount of the initiator added to the reactor to the total amount of the monomer m1 added to the reactor is 0.01 to 4 ppm by mass on average for every hour of copolymerization time". Otherwise, it is the same as the manufacturing method of the first embodiment.

[0176] Furthermore, the components used in the manufacturing method of the second embodiment and their suitable methods are the same as those used in the manufacturing method of the first embodiment.

[0177] The ratio of the total amount of initiator added to the reactor to the total amount of monomer m1 added to the reactor is 0.01 to 4 ppm by mass per hour of copolymerization time. From the viewpoint of further maximizing the effects of the present invention, it is preferably 0.1 to 3 ppm by mass, and particularly preferably 0.5 to 2.5 ppm by mass.

[0178] In the manufacturing method of the second embodiment, from the viewpoint of further maximizing the effects of the present invention, similar to the manufacturing method of the first embodiment, the initiator is continuously or batch-wise added to the reactor during the copolymerization, such that the concentration of the initiator in the reactor is maintained at less than 2.5 ppm by mass of the monomer m1 added to the reactor before the copolymerization begins.

[0179] [Fluoropolymers containing fluorosulfonyl groups]

[0180] Polymers Fx and Fy are preferably fluoropolymers containing fluorosulfonyl groups having the characteristics shown below (hereinafter also referred to as "polymer F1"). It should be noted that polymers Fx and Fy are sometimes collectively referred to as "polymer F" below.

[0181] That is, polymer F1 is a polymer having unit f1 and TFE unit, characterized in that the Q value of polymer F1 is 0.2 to 60.0 mm. 3 / second, the proportion of unit f1 in polymer F1 to all units is 21-59 mol%.

[0182] If a fluoropolymer containing acidic sulfonic acid groups (hereinafter also referred to as "polymer HA1") is used to obtain polymer F1 by making the fluorosulfonyl group an acidic sulfonic acid group, it is possible to manufacture a solid polymer electrolyte membrane with excellent conductivity and hot water resistance.

[0183]

[0184] Q in equation f1 1 The definition of Q in the above equation m1 is the same as that in the above equation. 1 They have the same meaning.

[0185] From the viewpoint of easy manufacturing of polymer F1 and easy industrial implementation, unit f1 is preferably unit f11, and particularly preferably unit f11-1.

[0186]

[0187] The x in equation f11 has the same meaning as the x in equation m11 above.

[0188] Polymer F1 may have units based on the other monomers mentioned above (other monomer units).

[0189] The content of TFE units relative to all units in polymer F1 is preferably 41–79 mol%, more preferably 63–78 mol%, and particularly preferably 66–76 mol%. If the content is above the lower limit, the water content of the solid polymer electrolyte membrane decreases, and the mechanical durability is further improved. If the content is below the upper limit, the conductivity of the solid polymer electrolyte membrane is superior.

[0190] The content of unit f1 relative to all units in polymer F1 is 21–59 mol%, preferably 22–37 mol%, and particularly preferably 24–34 mol%. If it is above the lower limit, the conductivity of the solid polymer electrolyte membrane is better; if it is below the upper limit, the water content of the solid polymer electrolyte membrane is reduced, and the mechanical durability is further improved.

[0191] When polymer F1 contains other monomer units, from the viewpoint of further maximizing the effects of the present invention, the content of the other monomer units relative to all units in polymer F1 is preferably 0.01 to 10 mol%, more preferably 0.1 to 8 mol%, and particularly preferably 0.5 to 5 mol%.

[0192] The Q value of polymer F1 refers to the value obtained by filling polymer F1 to a cross-sectional area of ​​1 cm² using a flow tester. 2 In a barrel, at 260℃ and a load of 30kg, material is extruded from a nozzle with an inner diameter of 1mm and a length of 1mm at a pressure of 2.94MPa. The extruded volume (mm³) per unit time under these conditions is [data missing]. 3 / Second).

[0193] The Q value is an indicator similar to MFR (melt flow rate) and is related to molecular weight. The lower the Q value of polymer F1, the larger the molecular weight of polymer F1; the higher the Q value of polymer F1, the smaller the molecular weight of polymer F1.

[0194] The Q value of polymer F1 is preferably 0.2 to 60.0 mm. 3 / second, more preferably 0.5 to 55 mm 3 / second, further preferably 0.8~50mm 3 / second, preferably 3.0–45 mm 3 / second. If the Q value of polymer F1 is within the above range, then the molecular weight of polymer F1 is sufficiently high, and therefore, the solid polymer electrolyte membrane has superior hot water resistance.

[0195] The ion exchange capacity of polymer HA1 is preferably 1.45 to 2.50 mEq / g, more preferably 1.50 to 2.00 mEq / g, and particularly preferably 1.55 to 1.90 mEq / g. If the value is above the lower limit, the conductivity of polymer HA1 becomes higher, thus enabling sufficient battery output when fabricating a solid polymer electrolyte membrane for a solid polymer fuel cell. If the value is below the upper limit, the solid polymer electrolyte membrane exhibits excellent mechanical strength.

[0196] The ion exchange capacity of polymer HA1 was determined by the method described in the Example section below.

[0197] [Manufacturing method of fluoropolymers containing sulfonic acid groups]

[0198] The method for manufacturing the fluoropolymer containing sulfonic acid groups of the present invention includes a method for converting the fluorosulfonyl group of the above polymer F into a sulfonic acid group.

[0199] As an example of a method for converting the fluorosulfonyl group of polymer F into a sulfonic acid group, the following methods can be listed: hydrolyzing the fluorosulfonyl group of polymer F to prepare a salt-type sulfonic acid group; or hydrolyzing the fluorosulfonyl group of polymer F manufactured by the above-mentioned polymer F manufacturing method to prepare a salt-type sulfonic acid group, and making the salt-type sulfonic acid group acidic to prepare an acidic sulfonic acid group.

[0200] In this specification, the fluorinated polymer containing sulfonic acid groups obtained by this manufacturing method will also be referred to as "polymer H".

[0201] According to the former method, a fluoropolymer containing salt-type sulfonic acid groups in polymer H can be obtained (hereinafter also referred to as "polymer HB"). According to the latter method, a fluoropolymer containing acid-type sulfonic acid groups in polymer H can be obtained (i.e., polymer HAx or polymer HAy. Hereinafter, polymer HAx and polymer Hay are sometimes collectively referred to as polymer HA).

[0202] Polymer H is a polymer obtained using polymer F described above. Therefore, based on polymer H, it is possible to manufacture a solid polymer electrolyte membrane with excellent electrical conductivity, hot water resistance, and chemical durability.

[0203] Hydrolysis is carried out, for example, by contacting polymer F with a basic compound in a solvent. Specific examples of basic compounds include sodium hydroxide, potassium hydroxide, and triethylamine. Specific examples of solvents include water and mixtures of water and polar solvents. Specific examples of polar solvents include alcohols (methanol, ethanol, etc.) and dimethyl sulfoxide.

[0204] Acidification is carried out, for example, by contacting a polymer having salt-type sulfonic acid groups with an aqueous solution of hydrochloric acid, sulfuric acid, nitric acid, etc.

[0205] The preferred processing temperature for hydrolysis and acidification is 0–120°C. Preferably, the polymer is washed with water after hydrolysis or acidification.

[0206] To remove organic matter that may be present in polymer H as impurities, the organic matter can be decomposed by immersing the polymer in hydrogen peroxide water or other treatments, either in the hydrolyzed salt state or after acidification.

[0207] The concentration of hydrogen peroxide in the hydrogen peroxide solution is preferably 0.1% to 30% by mass, particularly preferably 1% by mass or more but less than 10% by mass. If the concentration of hydrogen peroxide in the hydrogen peroxide solution is above the lower limit of the above range, the decomposition effect on organic matter is sufficient. If the concentration of hydrogen peroxide in the hydrogen peroxide solution is below the upper limit of the above range, polymer H is not easily decomposed.

[0208] The preferred temperature for hydrogen peroxide solution is 15–90°C, particularly preferably 40°C or higher but less than 80°C. If the temperature of the hydrogen peroxide solution is above the lower limit of the above range, the decomposition of organic matter is sufficient. If the temperature of the hydrogen peroxide solution is below the upper limit of the above range, hydrogen peroxide is not easily decomposed.

[0209] The immersion time of polymer H in hydrogen peroxide water varies depending on the thickness of polymer H and the amount of organic matter it contains. For example, when polymer H is a 50 μm thick film, 0.5 to 100 hours is preferred. If the immersion time is more than 0.5 hours, decomposition is easily carried out until the organic matter inside the film is removed. If the immersion time is less than 100 hours, it is preferred from a productivity point of view.

[0210] The polymer H is preferably washed with water after being immersed in hydrogen peroxide water. Ultrapure water is preferred as the water used for washing. In addition, an acidification treatment can be performed before washing.

[0211] The final polymer H after the above treatment can be in the form of powder, granules, or film.

[0212] [Fluoropolymers containing sulfonic acid groups]

[0213] Polymer H is preferably a fluorinated polymer containing sulfonic acid groups (hereinafter also referred to as "polymer H1") having the characteristics shown below.

[0214] That is, polymer H1 is a polymer having unit u1 and TFE unit. Furthermore, the Q value of the fluorosulfonyl-containing polymer (i.e., polymer F1) with sulfonate groups in polymer H1 being fluorosulfonyl groups is 0.2–60.0 mm. 3 / second. Furthermore, the proportion of unit u1 in polymer H1 relative to all units is 21–59 mol%.

[0215] Polymer H1 can be a fluoropolymer containing acidic sulfonic acid groups (i.e., polymer HA1) where the sulfonic acid groups in polymer H1 are acidic sulfonic acid groups, or a fluoropolymer containing salt sulfonic acid groups (hereinafter also referred to as "polymer HB1") where the sulfonic acid groups in polymer H1 are salt-type sulfonic acid groups.

[0216] Based on polymer H1, it is possible to manufacture solid polymer electrolyte membranes with excellent conductivity, hot water resistance, and chemical durability.

[0217]

[0218] Q in equation u1 1 Q in the above formula m1 1 The same meaning, Z + For H +Metal ions or ammonium ions. Preferably, alkali metals are used as the metal ions.

[0219] From the viewpoint that polymer H1 is easy to manufacture, easy to implement in industry, and capable of manufacturing solid polymer electrolyte membranes with superior conductivity and hot water resistance, unit u1 is preferably unit u11, and particularly preferably unit u11-1.

[0220]

[0221] The x in equation u11 has the same meaning as the x in equation m11 above. Furthermore, Z in equations u11 and u11-1... + With Z in the above formula u1 + They have the same meaning.

[0222] Polymer H1 may have units based on the other monomers mentioned above (other monomer units).

[0223] The content of each unit in polymer H1 is preferably the same as the content of each unit in polymer F1.

[0224] The definition and suitability of the Q value in polymer H1 are the same as those in polymer F1. More specifically, the Q value of the fluorosulfonyl-containing polymer in polymer H1, where the sulfonic acid group is a fluorosulfonyl group, is the same as that of polymer F1.

[0225] The method and suitable procedure for determining the ion exchange capacity of polymer H1 are the same as those for polymer HA1. It should be noted that polymer HA1 is a fluorinated polymer containing acidic sulfonic acid groups, where the salt-type sulfonic acid group of polymer HB1 is converted to an acidic sulfonic acid group.

[0226] [Solid polymer electrolyte membrane]

[0227] The solid polymer electrolyte membrane of the present invention comprises the above-mentioned polymer HA1.

[0228] The solid polymer electrolyte membrane of the present invention contains polymer HA1, and therefore has excellent conductivity and hot water resistance, as well as excellent chemical durability.

[0229] The thickness of the solid polymer electrolyte membrane is preferably 5–200 μm, and particularly preferably 10–130 μm. If the thickness is above the lower limit of the above range, sufficient hydrogen barrier properties can be ensured. If the thickness is below the upper limit of the above range, the membrane resistance can be sufficiently reduced.

[0230] The conductivity of the solid polymer electrolyte membrane is preferably 0.08 S / cm or higher, more preferably 0.09 S / cm or higher, and particularly preferably 0.1 S / cm or higher. If the conductivity is above these values, it becomes a solid polymer electrolyte membrane with sufficiently low membrane resistance, enabling the fabrication of fuel cells with excellent power generation performance. There is no particular upper limit, but it is typically 0.5 S / cm.

[0231] The mass reduction rate, which is an indicator of the hot water resistance of the solid polymer electrolyte membrane, is preferably 10% or less, more preferably 7% or less, and particularly preferably 6% or less. If the mass reduction rate is below the above values, the amount of dissolution of the membrane in the high-temperature water generated during the operation of the fuel cell can be sufficiently suppressed, and a long-life fuel cell with performance that is not easily degraded can be manufactured.

[0232] Solid polymer electrolyte membranes may further include reinforcing materials. Specific examples of reinforcing materials include porous materials, fibers, woven fabrics, and nonwoven fabrics.

[0233] The reinforcing material is preferably composed of a material selected from the group consisting of polytetrafluoroethylene (hereinafter also referred to as "PTFE"), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter also referred to as "PFA"), polyether ether ketone (hereinafter also referred to as "PEEK") and polyphenylene sulfide (hereinafter also referred to as "PPS"), and more preferably a porous PTFE.

[0234] To further improve durability, the solid polymer electrolyte membrane may contain one or more metals, metal compounds, or metal ions selected from the group consisting of cerium and manganese atoms. It can be assumed that cerium and manganese atoms will decompose the substances that cause degradation of the solid polymer electrolyte membrane, namely hydrogen peroxide or hydroxyl radicals and hydrogen peroxide free radicals.

[0235] In solid polymer electrolyte membranes, silica or heteropoly acids (e.g., zirconium phosphate, phosphomolybdic acid, phosphotungstic acid) may be included as water-retaining agents to prevent drying. Methods for including water-retaining agents in solid polymer electrolyte membranes include: contacting a solution containing a water-retaining agent with the solid polymer electrolyte membrane; and including a water-retaining agent in a liquid composition described later.

[0236] When obtaining a solid polymer electrolyte membrane from the liquid composition described later via the casting method, it is preferable to perform heat treatment after manufacturing the solid polymer electrolyte membrane to stabilize it. The heat treatment temperature varies depending on the type of polymer HA1, but is preferably 130–200°C. If the heat treatment temperature is above 130°C, the water content of the polymer HA1 becomes suitable. If the heat treatment temperature is below 200°C, the thermal decomposition of the sulfonic acid groups is suppressed, and the excellent conductivity of the solid polymer electrolyte membrane can be maintained.

[0237] The solid polymer electrolyte membrane can be treated with hydrogen peroxide water as needed. The treatment method can be the same as that used for the aforementioned polymer H1.

[0238] As an example of a method for manufacturing a solid polymer electrolyte membrane, one can be described as a method of coating a liquid composition containing polymer HA1 onto the surface of a substrate film or catalyst layer and then drying it (casting method).

[0239] As an example of a manufacturing method for a solid polymer electrolyte membrane containing a reinforcing material, one method is to impregnate the reinforcing material with a liquid composition containing polymer HA1 and then dry it.

[0240] [Liquid Composition]

[0241] The liquid composition preferably comprises polymer HA1 and a liquid medium. The polymer HA1 in the liquid composition may be dispersed in the liquid medium or dissolved in the liquid medium.

[0242] Specific examples of liquid media include water and organic solvents. The liquid medium may use only water, only organic solvents, or a mixture of water and organic solvents, with a mixture of water and organic solvents being preferred.

[0243] When water is included as the liquid medium, the dispersibility or solubility of polymer HA1 relative to the liquid medium is easily improved. When organic solvents are included as the liquid medium, electrolyte membranes that are not easily broken are readily obtained.

[0244] From the viewpoint of easily obtaining an electrolyte membrane that is not easily broken, alcohols are preferred as organic solvents, and from the viewpoint of easily evaporating organic solvents, alcohols with 1 to 4 carbon atoms are more preferred.

[0245] Examples of alcohols having 1 to 4 carbon atoms include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoro-1-propanol, 2,2,3,3-tetrafluoro-1-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, and 3,3,3-trifluoro-1-propanol.

[0246] Organic solvents can be used alone or in combination of two or more.

[0247] When the liquid medium is a mixture of water and an organic solvent, the water content relative to the total mass of the liquid medium is preferably 10 to 99% by mass, and particularly preferably 20 to 99% by mass.

[0248] When the liquid medium is a mixture of water and an organic solvent, the content of the organic solvent is preferably 1 to 90% by mass, and particularly preferably 1 to 80% by mass.

[0249] If the contents of water and organic solvents are within the above range, it is easy to obtain a solid polymer electrolyte membrane with excellent dispersibility or solubility of polymer HA1 relative to the liquid medium and which is not easily broken.

[0250] The content of polymer HA1 relative to the total mass of the liquid composition is preferably 1 to 50% by mass, particularly preferably 3 to 30% by mass. If it is above the lower limit of the above range, a film with a stable thickness can be obtained during film formation. If it is below the upper limit of the above range, the viscosity of the liquid composition becomes suitable.

[0251] The liquid composition is obtained by mixing polymer H1 with a liquid medium.

[0252] Examples of mixing methods include, for instance, applying shearing, such as stirring, to the polymer H1 in a liquid medium under atmospheric pressure or in a closed environment such as an autoclave.

[0253] The preferred temperature for stirring is 0–250°C, more preferably 20–150°C. Shearing, such as ultrasonic waves, can be applied as needed.

[0254] To further improve the durability of solid polymer electrolyte membranes made from liquid compositions, the liquid composition may contain one or more metals, metal compounds or metal ions selected from the group consisting of cerium atoms and manganese atoms.

[0255] [Membrane electrode assembly]

[0256] The membrane electrode assembly of the present invention comprises: an anode having a catalyst layer comprising a catalyst and a polymer having ion exchange groups; a cathode having a catalyst layer comprising a catalyst and a polymer having ion exchange groups; and a solid polymer electrolyte membrane disposed between the anode and the cathode and comprising a polymer having ion exchange groups.

[0257] Hereinafter, an example of the membrane electrode assembly of the present invention will be described with reference to the accompanying drawings.

[0258] Figure 1 This is a cross-sectional view illustrating an example of the membrane electrode assembly of the present invention. The membrane electrode assembly 10 includes: 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 disposed between the anode 13 and the cathode 14 in contact with the catalyst layer 11.

[0259] Specific examples of catalysts included in catalyst layer 11 include: supported catalysts obtained by supporting platinum, platinum alloys, or catalysts containing platinum with a core-shell structure on a carbon support or a support containing metal oxides; iridium oxide catalysts; and catalysts containing iridium oxide alloys or having a core-shell structure. Carbon black powder can be used as a carbon support. Elemental or composite oxides of metals such as aluminum, tin, zinc, nickel, cobalt, iron, titanium, cerium, zirconium, palladium, lanthanum, niobium, tantalum, and antimony can be used as supports. Furthermore, non-metallic catalysts with electrode catalytic activity, such as carbon alloy catalysts, can also be used.

[0260] As a polymer containing ion-exchange groups included in the catalyst layer 11, examples include fluorinated polymers containing ion-exchange groups, and polymer HA1 is preferred.

[0261] When using the polymer HA1 described above as the polymer containing ion-exchange groups in the catalyst layer 11, it is sufficient that at least one of the polymer containing ion-exchange groups in the catalyst layer of the anode and the polymer containing ion-exchange groups in the catalyst layer of the cathode is polymer HA1.

[0262] The preferred range for the ion exchange capacity of polymer HA1 is the same as the aforementioned values. If it is above the lower limit, the conductivity of polymer HA1 becomes higher, thus enabling sufficient battery output when used as a catalyst layer. If it is below the upper limit, flooding during power generation can be suppressed when used as a catalyst layer.

[0263] Furthermore, the preferred range of the Q value of the precursor of polymer HA1, namely polymer F1, is the same as the aforementioned values. If the Q value of polymer F1 is within the above range, the molecular weight of polymer F1 is sufficiently high, and therefore, the hot water resistance of the catalyst layer is superior, which can suppress the dissolution of the polymer outside the system caused by dissolution in the high-temperature water generated by power generation, and the associated reduction in power generation performance over time.

[0264] As the polymer containing ion-exchange groups included in the catalyst layer 11, it is also preferable to use a polymer having cyclic ether structural units and sulfonic acid functional groups.

[0265] From the viewpoint of obtaining a catalyst layer with better oxygen permeability, the cyclic ether structural unit preferably includes at least one unit selected from the group consisting of unit u11, unit u12, unit u13, unit u22 and unit u24, more preferably unit u12 and unit u22, and particularly preferably unit u22.

[0266]

[0267] R11 and R 14 Each is independently a monovalent perfluorinated organic group, fluorine atom, or -R group, optionally possessing an ether-bonded oxygen atom. 17 SO2X(SO2R f ) a - M + The group shown.

[0268] As a monovalent perfluorinated organic group, a perfluoroalkyl group is preferred. When the perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms can be one or more. Furthermore, the oxygen atom can be located between the carbon atoms of the perfluoroalkyl group or at the end of the carbon bond. The perfluoroalkyl group can be linear or branched, preferably linear.

[0269] R 17 The organofluorine group is a divalent perfluorinated organic group, optionally containing an ether-bonded oxygen atom. The organic group has one or more carbon atoms. As a divalent perfluorinated organic group, a perfluoroalkylene group is preferred. When the perfluoroalkylene group contains an ether-bonded oxygen atom, the number of oxygen atoms can be one or more. Furthermore, the oxygen atom can be located between the carbon atoms of the perfluoroalkylene group or at the end of the carbon bond. The perfluoroalkylene group can be linear or branched, preferably linear.

[0270] M + For H + A monovalent metal cation (e.g., potassium ion, sodium ion) or an ammonium ion in which one or more hydrogen atoms are optionally substituted with a hydrocarbon group (e.g., methyl, ethyl), preferably H from the viewpoint of high conductivity. + .

[0271] R f It is a straight-chain or branched perfluoroalkyl group, optionally containing an ether-bonded oxygen atom. The perfluoroalkyl group preferably has 1 to 8 carbon atoms, particularly preferably 1 to 6. It has two or more R atoms. f At that time, more than 2 R f They can choose to be the same or different from each other.

[0272] X can be an oxygen atom, a nitrogen atom, or a carbon atom. When X is an oxygen atom, a = 0; when X is a nitrogen atom, a = 1; and when X is a carbon atom, a = 2.

[0273] As -(SO2X(SO2R) f ) a ) - M + Specific examples of radicals include sulfonic acid groups (-SO3). - M + ), sulfonylimide group (-SO2N(SO2R) f )- M + (-SO2C(SO2R)) or sulfonylmethyl group f )2) - M + base).

[0274] R 12 R 13 R 15 and R 16 Each of the components is independently a monovalent perfluorinated organic group or a fluorine atom, optionally possessing an ether-bonded oxygen atom. As a monovalent perfluorinated organic group, a perfluoroalkyl group is preferred. From the viewpoint of high polymerization reactivity, R is preferred. 15 and R 16 At least one of them is a fluorine atom, and both are particularly preferred to be fluorine atoms.

[0275] Formula u11 contains 2 Rs 17 At that time, 2 R 17 They can choose to be the same or different from each other.

[0276] Unit u11 is preferably unit u11-1 or unit u11-2.

[0277]

[0278]

[0279] In equation u12, R 21 It is a perfluoroalkylene group having 1 to 6 carbon atoms, or a perfluoroalkylene group having 2 to 6 carbon atoms with ether-bonded oxygen atoms between the carbon atoms. When the perfluoroalkylene group has ether-bonded oxygen atoms, the number of oxygen atoms can be one or more. The perfluoroalkylene group can be linear or branched, preferably linear.

[0280] R 22 It is a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms with ether-bonded oxygen atoms between carbon atoms, or -R 21 (SO2X(SO2R f ) a ) - M + The group shown. When the perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms can be one or more. The perfluoroalkyl group can be linear or branched, preferably linear. Formula u12 contains two R groups. 21 At that time, 2 R 21 They can choose to be the same or different from each other.

[0281] M + R fX and a are respectively related to M in equation u11 + R f X and a have the same meaning.

[0282] As specific examples of unit u12, units u12-1 and u12-2 can be listed. In the formula, M... + M of formula u11 + They have the same meaning.

[0283]

[0284]

[0285] In equation u13, R 31 It is a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms with ether-bonded oxygen atoms between carbon atoms, or -R 37 SO2X(SO2R f ) a - M + The group shown.

[0286] When a perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms can be one or more. The perfluoroalkyl group can be linear or branched, preferably linear.

[0287] R 37 It is a perfluoroalkylene group having 1 to 6 carbon atoms, or a perfluoroalkylene group having 2 to 6 carbon atoms with ether-bonded oxygen atoms between the carbon atoms. When the perfluoroalkylene group has ether-bonded oxygen atoms, the number of oxygen atoms can be one or more. The perfluoroalkylene group can be linear or branched, preferably linear.

[0288] R 32 ~R 35 Each component is independently a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or a perfluoroalkyl group having 2 to 6 carbon atoms with ether-bonded oxygen atoms between the carbon atoms. When the perfluoroalkyl group has ether-bonded oxygen atoms, the number of oxygen atoms can be one or more. The perfluoroalkyl group can be linear or branched, preferably linear.

[0289] R 36 It is a perfluoroalkylene group with a single bond and 1 to 6 carbon atoms, or a perfluoroalkylene group with 2 to 6 carbon atoms having an ether-bonded oxygen atom between the carbon atoms. When the perfluoroalkylene group has an ether-bonded oxygen atom, the number of oxygen atoms can be one or more. The perfluoroalkylene group can be linear or branched, preferably linear.

[0290] M + Rf X and a are respectively related to M in equation u11 + R f X and a have the same meaning.

[0291]

[0292] In formula u22, s is 0 or 1, preferably 0.

[0293] R 51 and R 52 Each is an independent fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a spirocyclic ring formed by their interconnection (where s is 0).

[0294] R 53 and R 54 Each is independently a perfluoroalkyl group having 1 to 5 fluorine atoms or carbon atoms.

[0295] R 55 It is a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. From the viewpoint of high polymerization reactivity, R 55 The preferred atom is fluorine.

[0296] Perfluoroalkyl and perfluoroalkoxy compounds can be linear or branched, with linear being preferred.

[0297] Unit u22 is preferably unit u22-1.

[0298]

[0299] In equation u24, R 71 ~R 76 Each of the components is independently a monovalent perfluorinated organic group or a fluorine atom, optionally possessing an ether-bonded oxygen atom. As a monovalent perfluorinated organic group, a perfluoroalkyl group is preferred. When the perfluoroalkyl group possesses an ether-bonded oxygen atom, the number of oxygen atoms can be one or more. Furthermore, the oxygen atom can be inserted between the carbon atoms of the perfluoroalkyl group or at the end of a carbon bond. The perfluoroalkyl group can be linear or branched, preferably linear.

[0300] From the perspective of high polymerization reactivity, R 71 ~R 74 The preferred atom is fluorine.

[0301] From the viewpoint of achieving better power generation efficiency in fuel cells, the content of cyclic ether structural units is preferably 30 mol% or more, more preferably 40 mol% or more, further preferably 50 mol% or more, and particularly preferably 70 mol% or more, relative to all units contained in a polymer having cyclic ether structural units and sulfonic acid functional groups.

[0302] The upper limit of the content of cyclic ether structural units is preferably 100 mol% relative to all units contained in a polymer having cyclic ether structural units and sulfonic acid functional groups, and particularly preferably 80 mol%.

[0303] Polymers having cyclic ether structural units and sulfonic acid functional groups may contain only one type of unit containing a cyclic ether structure, or they may contain two or more types. When two or more types are contained, the above-mentioned content refers to their total amount.

[0304] The gas diffusion layer 12 has the functions of uniformly diffusing gas in the catalyst layer and acting as a current collector. Specific examples of gas diffusion layers include carbon paper, carbon cloth, carbon felt, and porous bodies made of titanium (specifically, sintered bodies of titanium particles or fibers, etc.).

[0305] To prevent the adhesion of the generated gas, the gas diffusion layer can be treated with PTFE or other materials to make it hydrophobic or hydrophilic, or it can be made hydrophilic using polymers with ion exchange groups.

[0306] Figure 1 The membrane electrode assembly includes a gas diffusion layer 12, but the gas diffusion layer is an optional component and may not be included in the membrane electrode assembly.

[0307] The polymer containing ion-exchange groups in the solid polymer electrolyte membrane 15 is preferably the polymer HA1 described above. That is, the solid polymer electrolyte membrane 15 is preferably the solid polymer electrolyte membrane of the present invention described above.

[0308] The anode 13 and cathode 14 may have other components besides those described above.

[0309] As a specific example of other components, a carbon layer (not shown) disposed between the catalyst layer 11 and the gas diffusion layer 12 can be cited. If a carbon layer is disposed, the gas diffuseability of the surface of the catalyst layer 11 is improved, which can further improve the power generation performance of the fuel cell.

[0310] The carbon layer may comprise, for example, carbon and a nonionic fluoropolymer. A specific example of carbon is preferably carbon nanofibers with a diameter of 1–1000 nm and a length of 1000 μm or less. A specific example of a nonionic fluoropolymer is PTFE.

[0311] Examples of methods for manufacturing membrane electrode assemblies include forming a catalyst layer on a solid polymer electrolyte membrane and further clamping the resulting assembly with a gas diffusion layer; and forming an electrode (anode, cathode) by forming a catalyst layer on a gas diffusion layer and clamping the solid polymer electrolyte membrane with the electrode.

[0312] It should be noted that the method for manufacturing the catalyst layer can include applying a catalyst layer forming coating liquid to a specified location and drying it as needed. The catalyst layer forming coating liquid is a liquid obtained by dispersing a polymer having ion exchange groups and a catalyst in a dispersion medium. The catalyst layer forming coating liquid can be prepared, for example, by mixing a liquid composition containing a polymer having ion exchange groups with a dispersion of the catalyst. To further improve the durability of the catalyst layer 11, the catalyst layer forming coating liquid may contain one or more metals, metal compounds, or metal ions selected from the group consisting of cerium and manganese.

[0313] [Solid polymer fuel cell]

[0314] The solid polymer fuel cell of the present invention includes the above-described membrane electrode assembly.

[0315] The solid polymer fuel cell of the present invention includes the above-mentioned membrane electrode assembly, and therefore has excellent power generation performance and durability.

[0316] The solid polymer fuel cell of the present invention may have separators with grooves forming gas flow paths on both sides of the membrane electrode assembly.

[0317] Specific examples of separators include: metal separators, carbon separators, separators made of materials mixed with graphite and resin, and separators made of various conductive materials.

[0318] In solid polymer fuel cells, oxygen-containing gas is supplied to the cathode and hydrogen-containing gas is supplied to the anode to generate electricity.

[0319] It should be noted that the above-mentioned membrane electrode assembly can also be used in methanol fuel cells that supply methanol to the anode for power generation.

[0320] Example

[0321] The present invention will be described in detail below with examples. Examples 1-1 to 1-6, 2-1 to 2-6, 3-1 to 3-6, 4-1 to 4-6, 5-1, 6-1 to 6-3, and 8-2 to 8-10 are examples, and Examples 1-7 to 1-11, 2-7 to 2-11, 3-7 to 3-11, 4-7 to 4-11, 5-2, 6-4, 8-1, and 8-11 are comparative examples. The fluorinated polymer containing sulfonic acid groups described in the examples is referred to as "Polymer H", and the fluorinated polymer containing sulfonic acid groups described in the comparative examples is referred to as "Polymer H'". Furthermore, the fluorinated polymer containing fluorosulfonyl groups described in the examples is referred to as "Polymer F", and the fluorinated polymer containing fluorosulfonyl groups described in the comparative examples is referred to as "Polymer F'". However, the present invention is not limited to these examples. It should be noted that unless otherwise specified, the mixing amounts of each component in the following tables represent the mass standard.

[0322] [Ion exchange capacity]

[0323] A fluoropolymer containing acidic sulfonic acid groups was vacuum-dried at 120°C for 12 hours, then impregnated in a 0.85 mol / g sodium hydroxide solution (solvent: water / methanol = 10 / 90 (mass ratio)) to neutralize the ion exchange groups. The neutralized sodium hydroxide solution was then back-titrated with 0.1 mol / L hydrochloric acid to determine the ion exchange capacity of the fluoropolymer containing acidic sulfonic acid groups.

[0324] [Proportions of each structural unit]

[0325] Regarding the proportions of various structural units such as TFE units and PSAE units in fluoropolymers containing fluorosulfonyl groups, for each polymer, [the following information is provided]. 19 The result is obtained from the F-NMR measurement.

[0326] 19 F-NMR was measured at 282.7 MHz, with hexafluorobenzene as the solvent and CFCl3 as the chemical shift standard.

[0327] It should be noted that the proportions of each structural unit in fluorinated polymers containing sulfonic acid groups are the same as those in fluorinated polymers containing fluorosulfonyl groups.

[0328] [Q value, TQ value]

[0329] Using a flow tester with a nozzle having an inner diameter of 1 mm and a length of 1 mm (Shimadzu CFT-500D, a thin-tube rheometer flow tester), fill the material to a cross-sectional area of ​​1 cm². 2 Polymer F or polymer F' in the barrel is extruded from the nozzle at a pressure of 2.94 MPa under a load of 30 kg and a temperature of 260 °C. The volumetric flow rate (mm) of the extruded polymer when the extrusion speed is stabilized is then recorded.3 The Q value is set as (per second). A lower Q value means a larger molecular weight of the polymer, and a higher Q value means a smaller molecular weight of the polymer.

[0330] Furthermore, the Q value will reach 100mm 3 The temperature per second is set as the TQ value.

[0331] [Conductivity]

[0332] A solid polymer electrolyte membrane (5 mm wide, 25 μm thick) was tightly bonded to a substrate with four-terminal electrodes spaced 5 mm apart. The resistance of the membrane was measured using a known four-terminal method under constant temperature and humidity conditions of 80°C and 50% relative humidity, with AC current at 10 kHz and voltage at 1 V. The conductivity was then calculated. It should be noted that the reference dimensions and thickness of the membrane used in the calculations were measured under conditions of 23°C and 50% RH.

[0333] [Moisture content]

[0334] A solid polymer electrolyte membrane (25 μm thick) was immersed in warm water at 80°C for 16 hours, and then cooled until the water temperature reached below 25°C. The membrane was removed, and the water adhering to its surface was wiped off with filter paper. The membrane mass W1 was measured. The water-containing membrane was then placed in a glove box filled with dry nitrogen gas (dew point below -70°C) and dried at room temperature (approximately 15–25°C) for at least 40 hours. The membrane mass W2 was then measured inside the glove box. The water content was calculated using the following formula.

[0335] Moisture content = {(W1-W2) / W2} × 100

[0336] [Hot Water Resistance]

[0337] A solid polymer electrolyte membrane (25 μm thick) was placed in a glove box filled with dry nitrogen (dew point below -70°C) and dried at room temperature (approximately 15–25°C) for at least 40 hours. The mass (W1) was then measured inside the glove box. A 120 mL pressure-resistant container was filled with an amount of ultrapure water sufficient to fully impregnate the membrane, and the container was placed in an oven at 120°C. After 24 hours, heating was stopped and the membrane was water-cooled. The membrane was then removed from the pressure-resistant container, and surface moisture was wiped away with filter paper (Advantech, No. 2). The membrane containing water was then placed in a glove box filled with dry nitrogen (dew point below -70°C) and dried at room temperature (approximately 15–25°C) for at least 40 hours. The mass (W2) was then measured inside the glove box. The mass reduction rate (mass%) was calculated using the following formula.

[0338] Mass reduction rate = {(W1-W2) / W1}×100

[0339] [Chemical durability]

[0340] A membrane electrode assembly containing a solid polymer electrolyte membrane was fabricated, and the membrane electrode assembly was assembled into a power generation battery cell. As an accelerated test, the following open circuit test (OCV test) was carried out.

[0341] The current density is equivalent to 0.2 A / cm². 2 Hydrogen (utilization rate 50%) and air (utilization rate 50%) were supplied to the anode and cathode at atmospheric pressure, respectively. The cell temperature was set to 90°C, the gas dew point at the anode was set to 61°C, and the gas dew point at the cathode was set to 61°C. The cell operated in an open-circuit state without generating electricity. During this time, the discharged gas was bubbled into a 0.1 mol / L potassium hydroxide aqueous solution for 24 hours to capture the discharged fluoride ions. Furthermore, the fluoride ion concentration was quantified using ion chromatography, and the cumulative amount of fluoride ions discharged was calculated.

[0342] Durability is evaluated according to the following criteria, based on the value obtained by dividing the cumulative amount of fluoride ions emitted 200 hours after the start of the open-circuit test by the electrode area.

[0343] ○: The cumulative emission of fluoride ions is 150 μg / cm³. 2 the following.

[0344] △: The cumulative emission of fluoride ions exceeds 150 μg / cm³. 2 And it is 300 μg / cm 2 the following.

[0345] ×: Cumulative emissions of fluoride ions exceed 300 μg / cm³ 2 .

[0346] [Power Generation Characteristics]

[0347] The membrane electrode assembly (MEA) was assembled into the power generation cell. The MEA was maintained at 95°C. Hydrogen (70% utilization) was pressurized to 151 kPa (absolute pressure) and supplied to the anode, while air (50% utilization) was pressurized to 151 kPa (absolute pressure) and supplied to the cathode. The relative humidity of both the hydrogen and air was set to 20% RH, and the recorded current density was 2 A / cm². 2 The voltage of the battery cell at that time. The higher the battery cell voltage, the better the power generation characteristics of the solid polymer fuel cell.

[0348] [Wet-dry cycle durability (dry-wet cycle durability)]

[0349] The wet-dry cycle test was conducted according to the method described in Yeh-Hung Lai, Cortney K. Mittelsteadt, Craig S. Gittleman, David A. Dillard, “VISCOELASTIC STRESS MODEL AND MECHANICAL CHARACTERIZATION OF PERFLUOROSULFONIC ACID (PFSA) POLYMER ELECTROLYTE MEMBRANES”, Proceedings of Fuel Cell 2005, Third International Conference on Fuel Cell Science, Engineering and Technology, Fuel Cell 2005, (2005), 74120.

[0350] The membrane electrode assembly obtained in each example is assembled into a power generation battery cell (electrode area 25 cm²). 2 In this study, nitrogen was supplied to the anode and cathode at a rate of 1 L / min at a cell temperature of 80°C. One cycle consisted of supplying nitrogen at 150% RH for 2 minutes followed by 2 minutes of nitrogen at 0% RH, and this process was repeated. Every 1000 cycles, the nitrogen supply was stopped, and hydrogen was supplied to the anode and pressurized to create a pressure difference between the anode and cathode. The leakage of hydrogen from the anode to the cathode via the membrane electrode assembly was measured. The number of cycles until hydrogen leakage occurred and the crossover rate, expressed as the leakage rate per unit area per unit time, reached five times the initial value was measured. A higher number of cycles at this point indicates better wet-dry cycle durability of the solid polymer fuel cell.

[0351] [Abbreviation]

[0352] The following abbreviations are used for monomers, initiators, and solvents.

[0353] TFE: Tetrafluoroethylene

[0354] PSAE: CF2=CFCF2OCF2CF2SO2F

[0355] tBPO:(CH3)3COOC(CH3)3

[0356] PFtBPO:(CF3)3COOC(CF3)3

[0357] HFE-347pc-f:CF3CH2OCF2CF2H

[0358] HFC-52-13p: CF3(CF2)5H

[0359] [Manufacturing of polymer F and polymer F']

[0360] The following procedures are followed to manufacture polymers F-1 to F-4 and polymers F'-1 to F'-5.

[0361] <Example 1-1>

[0362] 525.0 g of PSAE (monomer) was added to an autoclave equipped with an air-cooled condenser (hereinafter referred to as A / C, internal volume 500 mL, made of Hastelloy alloy), and cooled and degassed with liquid nitrogen. Nitrogen gas was introduced into the gas phase, and the autoclave was heated in an oil bath until the internal temperature reached 160°C. The pressure at this point was 0.445 MPa (gauge pressure). Next, 10.67 g of TFE was introduced into the autoclave. The pressure at this point was 0.89 MPa (gauge pressure), and the partial pressure of TFE at the polymerization temperature reached 0.445 MPa.

[0363] Copolymerization was initiated by adding 0.79 g of an initiator solution (tBPO dissolved in PSAE at a concentration of 667 ppm by mass) to begin copolymerization. At this point, the amount of tBPO added was 0.53 mg, and the concentration of tBPO in the autoclave was 1.0 ppm by mass of the PSAE added to the autoclave before copolymerization began. TFE was continuously added while maintaining the pressure at 0.89 MPa (gauge pressure), and polymerization continued for 10 hours. During this period, 0.66 g of the aforementioned initiator solution (0.44 mg by mass of tBPO) was added every 30 minutes, for a total of 19 additions, introducing a total of 8.34 mg of tBPO into the autoclave. In other words, tBPO was added such that the tBPO concentration immediately after addition reached 1.0 ppm by mass relative to the mass of PSAE added to the autoclave before copolymerization began. Through the above operations, the total amount of PSAE added to the autoclave reached 537.5 g, and the total amount of tBPO added to the autoclave reached 8.87 mg. Therefore, the ratio of the total tBPO addition to the total PSAE addition was 1.6 ppm by mass per hour of polymerization time (recorded in the table as "time-average initiator ratio"). In addition, the additional TFE addition reached 20.5 g. It should be noted that stirring during copolymerization was performed using anchor blades at a speed of 250 rpm.

[0364] After cooling to below 30°C internally, the gas inside the autoclave was purged. 550g of HFE-347pc-f, equal in mass to PSAE, was added to the reaction solution, causing the polymer to aggregate and filter. Subsequently, the process of stirring the polymer in an equal volume of HFE-347pc-f and washing with HFE-347pc-f was repeated twice. Vacuum drying at 120°C yielded 42.7g of the copolymer of TFE and PSAE monomers, namely polymer F-1. The Q value was 15.5mm. 3 / second, TQ value above 300℃. The results are shown in Table 1-1.

[0365] <Example 1-2>

[0366] By changing the conditions in Example 1-1 as shown in Table 1-1, and otherwise operating in the same manner as in Example 1-1, polymer F-2 was obtained. The results are shown in Table 1-1.

[0367] <Example 1-3>

[0368] The autoclave (2500 mL, stainless steel) was depressurized, and 2625.0 g of PSAE (monomer) was evacuated and added to the autoclave. The pressure was repeatedly increased to 0.3 MPa (gauge pressure) with nitrogen and then released to 0.05 MPa five times to remove dissolved oxygen. Nitrogen was then introduced into the gas phase, and the autoclave was heated in an oil bath until the internal temperature reached 160°C. The pressure at this point was 1.02 MPa (gauge pressure). Next, 46.9 g of TFE was introduced into the autoclave. The pressure at this point was 1.36 MPa (gauge pressure), and the partial pressure of TFE at the polymerization temperature reached 0.34 MPa.

[0369] Copolymerization was initiated by adding 4.38 g of an initiator solution (tBPO dissolved in PSAE at a concentration of 300 ppm by mass) to begin copolymerization. At this point, the amount of tBPO added was 1.31 mg, and the concentration of tBPO in the autoclave reached 0.5 ppm by mass relative to the mass of PSAE added to the autoclave before copolymerization began. TFE was continuously added while maintaining the pressure at 1.36 MPa (gauge pressure), and polymerization continued for 8 hours. During this period, to maintain the tBPO concentration at 0.5 ppm by mass relative to the mass of PSAE added to the autoclave before copolymerization began, the aforementioned initiator solution was continuously added at a rate of 15.8 g / h (4.75 mg / h based on the mass of tBPO), and this was stopped after 7 hours. Through the above operations, the total amount of PSAE introduced into the autoclave reached 2735.9 g, and the total amount of tBPO introduced into the autoclave reached 34.6 mg. Therefore, the ratio of the total tBPO addition to the total PSAE addition was 1.6 ppm by mass per hour of polymerization time. Furthermore, the additional TFE addition reached 63.1 g. It should be noted that stirring during copolymerization was performed using a double-helix bladed mixer at a speed of 150 rpm.

[0370] After cooling to below 30°C internally, the gas inside the autoclave was purged. 5288 g of HFE-347pc-f (1.9 times the mass of PSAE) was added to the reaction mixture, causing the polymer to aggregate and filter. Subsequently, the process of stirring the polymer in an equal volume of HFE-347pc-f and washing with HFE-347pc-f was repeated twice. Vacuum drying at 120°C yielded 171.0 g of the copolymer of TFE and PSAE monomers, namely polymer F-3. The Q value was 15.8 mm. 3 / second, TQ value above 300℃. The results are shown in Table 1-1.

[0371] <Examples 1-4~1-6>

[0372] As shown in Table 1-1, the conditions of Examples 1-3 were changed, except that the same procedures were followed as in Examples 1-3 to obtain polymer F-4 in Example 1-4, polymer F-5 in Example 1-5, and polymer F-6 in Example 1-6. In Example 1-5, PFtBPO was used as the polymerization initiator. The results are shown in Table 1-1.

[0373] <Example 1-7>

[0374] Polymer F'-1 was manufactured using the method described in Example 1 of Japanese Patent No. 5217708.

[0375] Specifically, 87.96 g of PSAE (monomer) and 1.8 mg of tBPO as an initiator were added to a 125 mL stainless steel autoclave, and the mixture was thoroughly degassed under liquid nitrogen cooling. The concentration of tBPO in the autoclave reached 20 ppm by mass of the PSAE added to the autoclave before copolymerization. The autoclave was then heated to 100 °C, and TFE was introduced, maintaining the pressure at 0.39 MPaG. Nitrogen was added to produce a pressure of 0.72 MPaG. The pressure was then increased to 145 °C to produce a pressure of 0.95 MPaG. A 5.2% by mass initiator solution, obtained by dissolving tBPO in compound s-1, was added in batches every 30 minutes. The amount added in batches was set at 0.67 mg of solid tBPO per batch, for a total of 12 additions. (It should be noted that 0.67 mg corresponds to a tBPO concentration of 7.6 ppm by mass relative to the mass of PSAE added to the autoclave before copolymerization. After 30 minutes at 145°C, the residual tBPO was approximately 68%, therefore, the tBPO concentration immediately after addition was above 7.6 ppm by mass). After the 12th addition, the gas in the autoclave was purged after 30 minutes, and the autoclave was cooled to complete the reaction. Stirring was carried out at 145°C for 6.5 hours. The total amount of tBPO added was 9.84 mg.

[0376] The product was diluted with compound s-1, and then compound s-2 was added to aggregate polymer F'-1, followed by filtration. Subsequently, polymer F'-1 was stirred in compound s-1, re-aggregated with compound s-2, and dried under reduced pressure at 80°C overnight. The yield was 10.8 g. The Q value was 423 mm. 3 / second, TQ value is 217℃. The results are shown in Table 1-2.

[0377] CClF₂CF₂CHClF(s⁻¹)

[0378] CH3CCl2F(s-2)

[0379] <Example 1-8>

[0380] Polymer F'-2 was manufactured using the method described in Example 4 of Japanese Patent No. 5217708.

[0381] 87.96 g of PSAE (monomer) and 0.9 mg of tBPO as an initiator were added to a 125 mL stainless steel autoclave, and the mixture was thoroughly degassed under liquid nitrogen cooling. The concentration of tBPO in the autoclave reached 10 ppm by mass of the PSAE added to the autoclave before copolymerization. The autoclave was then heated to 100 °C, and TFE was introduced, maintaining the pressure at 0.35 MPaG. Nitrogen was added to produce a pressure of 0.65 MPaG. The pressure was then increased to 170 °C to produce a pressure of 1.59 MPaG. A 5.2% by mass initiator solution, obtained by dissolving tBPO in compound s-1, was added in batches every 30 minutes. The amount added in each batch was set at 0.33 mg of solid tBPO, for a total of 12 additions. (It should be noted that 0.33 mg corresponds to a tBPO concentration of 3.8 ppm by mass relative to the mass of PSAE added to the autoclave before copolymerization. After 30 minutes at 170°C, the residual tBPO concentration is approximately 1%, therefore, the initial tBPO concentration is above 3.8 ppm by mass.) After the 12th addition, the autoclave was purged after 30 minutes, and the autoclave was cooled to complete the reaction. Stirring at 170°C was carried out for 6.5 hours. The total amount of tBPO added was 4.86 mg.

[0382] The product was diluted with compound s-1, and then compound s-2 was added to aggregate polymer F'-2, followed by filtration. Subsequently, polymer F'-2 was stirred in compound s-1 and re-aggregated with compound s-2, then dried under reduced pressure at 80°C overnight. The yield was 3.5 g. The Q value was 232 mm. 3 / second, TQ value 240℃. The results are shown in Table 1-2.

[0383] <Example 1-9>

[0384] Polymer F'-3 was manufactured using the method described in Example 1 of Japanese Patent No. 5862372.

[0385] After depressurizing a 2575 mL stainless steel autoclave, it was repeatedly purged with nitrogen three times under pressure, then depressurized again and 1959 g of PSAE (monomer) was added. Subsequently, the temperature was raised to 120 °C, and nitrogen was introduced into the autoclave to produce 0.38 MPaG. TFE at 0.46 MPa was then added, setting the total pressure to 0.84 MPaG.

[0386] Add 3.91 g of an initiator solution (5% by mass of PFtBPO dissolved in PSAE) to begin copolymerization. The initial amount of PFtBPO added is 195.50 mg, and the concentration of PFtBPO in the autoclave is 100.0 ppm by mass of the PSAE added to the autoclave before copolymerization. While maintaining the pressure at 0.84 MPG, add 2.41 g of the initiator solution every hour, in four batches, and continue the reaction for 5 hours (each batch addition is for a solid PFtBPO content of 120.5 mg. This amount corresponds to a PFtBPO concentration of 61.5 ppm by mass relative to the mass of PSAE added to the autoclave before copolymerization. After 1 hour at 120°C, the residual PFtBPO is approximately 38%, therefore, the concentration of PFtBPO immediately after addition is above 61.5 ppm by mass). After the fourth addition, the autoclave was cooled and the gas inside was purged after 1 hour to complete the reaction. The total amount of PFtBPO added was 677.50 mg.

[0387] The product was diluted with HFC-52-13p, and HFE-347pc-f was added to aggregate polymer F'-3, followed by filtration. Subsequently, the polymer F'-3 in HFC-52-13p was stirred and re-aggregated with HFE-347pc-f, then dried under reduced pressure at 80°C overnight. The yield was 323 g. The Q value was 55.6 mm. 3 / second, TQ value 295℃. The results are shown in Table 1-2.

[0388] <Example 1-10 and Example 1-11>

[0389] As shown in Table 1-2, the conditions in Example 1-1 were changed, and the copolymerization was stirred at 250 rpm using a double helix with blades. Otherwise, the same procedure as in Example 1-1 was followed to obtain polymer F'-4 in Example 1-10 and polymer F'-5 in Example 1-11. The results are shown in Table 1-2.

[0390] [Table 1-1]

[0391]

[0392] [Table 1-2]

[0393]

[0394] The maximum initiator concentration [mass ppm] relative to the mass of PSAE added before copolymerization begins is shown in Table 2.

[0395] [Table 2]

[0396]

[0397] [Manufacturing of polymer H and polymer H']

[0398] The following procedures are performed to manufacture polymers H-1 to H-6 and polymers H'-1 to H'-5.

[0399] <Example 2-1>

[0400] Using the polymer F-1 obtained as described above, a polymer F-1 membrane was formed by pressing at a temperature lower than 10°C above the TQ value or 260°C and at 4 MPa (gauge pressure). The polymer F-1 membrane was then immersed in an alkaline aqueous solution (aqueous solution A: potassium hydroxide / water = 20 / 80 (mass ratio)) at 80°C for 16 hours to hydrolyze the -SO2F of the polymer F-1, converting it to -SO3K. Next, the polymer membrane was immersed in a 3 mol / L hydrochloric acid aqueous solution at 50°C for 30 minutes, then in ultrapure water at 80°C for 30 minutes, and finally in a 10% (w / w) hydrogen peroxide aqueous solution at 80°C for 16 hours. This cycle of immersion in hydrochloric acid and ultrapure water was repeated a total of 5 times to convert the -SO3K of the polymer to -SO3H. The membrane was repeatedly washed with ultrapure water until the pH of the water containing the polymer membrane reached 7. The polymer membrane was sandwiched between filter paper and air-dried to obtain a membrane of polymer H-1. The results are shown in Table 3.

[0401] <Example 2-2~Example 2-11>

[0402] By changing polymer F-1 to polymers F-2 to F-6 and F'-1 to F'-5, and altering the type of alkaline aqueous solution as shown in Table 3, the same procedure as in Example 2-1 was followed to obtain polymers H-2 to H-6 in Examples 2-2 to 2-6 and polymers H'-1 to H'-5 in Examples 2-7 to 2-11. The results are shown in Table 3.

[0403] It should be noted that in Table 3, the potassium hydroxide / water ratio of aqueous solution A is 20 / 80 (mass ratio), the potassium hydroxide / dimethyl sulfoxide / water ratio of aqueous solution B is 15 / 30 / 55 (mass ratio), and the potassium hydroxide / methanol / water ratio of aqueous solution C is 15 / 20 / 65 (mass ratio).

[0404] [Table 3]

[0405]

[0406] [Preparation of liquid composition S and liquid composition S']

[0407] For liquid compositions S-1 to S-6 and liquid compositions S'-1 to S'-5, the following operations are performed to manufacture them.

[0408] <Example 3-1>

[0409] 37 g of finely chopped polymer H-1 membrane and 147.9 g of a 50 / 50 (mass ratio) ethanol / water mixture were added to an autoclave (200 mL, glass). The autoclave was heated while stirring. After stirring at 110°C for 4 hours, the mixture was allowed to cool naturally and then filtered using a pressure filter (filter paper: Advantech PF040). This yielded 164.0 g of a liquid composition S-1 containing polymer H-1 dispersed in the mixed solvent. The solids concentration was 20.0%. The results are shown in Table 4.

[0410] <Example 3-2>

[0411] 37.5 g of finely cut polymer H-2 membrane and 120.0 g of a 50 / 50 (mass ratio) ethanol / water mixture were added to an autoclave (200 mL, glass). The autoclave was heated while stirring. After stirring at 110°C for 3 hours, 15.0 g of dilution water was added, and the mixture was heated for 2 hours. After natural cooling, the mixture was filtered using a pressure filter (filter paper: Advantech PF040). This yielded 161.3 g of a liquid composition S-2 containing polymer H-2 dispersed in the mixed solvent. The solids concentration was 22.1%. The viscosity was 285.2 mPas. The results are shown in Table 4.

[0412] <Example 3-3>

[0413] 126.9 g of finely cut polymer H-3 membrane and 394.0 g of a 50 / 50 (mass ratio) ethanol / water mixture were added to an autoclave (1 L, glass). The autoclave was heated while stirring. After stirring at 105°C for 6.5 hours, 5.0 g of ethanol and 106.0 g of water for dilution were added. After heating for 0.5 hours, the mixture was allowed to cool naturally and filtered using a pressure filter (filter paper: Advantech PF040). This yielded 602.7 g of a liquid composition S-3 containing polymer H-3 dispersed in the mixed solvent. The solids concentration was 19.8%. The viscosity was 210.6 mPas. The results are shown in Table 4.

[0414] <Example 3-4>

[0415] The polymer H-4 was set to 24.7 g, the ethanol / water mixture (50 / 50 mass ratio) to 80.1 g, and the diluent water to 22.5 g. Otherwise, the procedure was the same as in Example 3-2, yielding 122.9 g of liquid composition S-4. The solids concentration was 19.2%. The results are shown in Table 4.

[0416] <Example 3-5>

[0417] The polymer H-5 was set to 20.1 g, the ethanol / water mixture (40 / 60 (mass ratio)) to 57.2 g, the diluted ethanol to 12.0 g, and the diluted water to 16.9 g. Otherwise, the procedure was the same as in Example 3-3, yielding 112.2 g of liquid composition S-5. The solids concentration was 17.9%. The results are shown in Table 4.

[0418] <Example 3-6>

[0419] The polymer H-6 was set to 23.0 g, the ethanol / water mixture (50 / 50 mass ratio) to 77.0 g, the diluted ethanol to 17.6 g, and the diluted water to 17.6 g. Otherwise, the procedure was the same as in Example 3-3, yielding 135.2 g of liquid composition S-6. The solids concentration was 17.0%. The results are shown in Table 4.

[0420] <Example 3-7~Example 3-11>

[0421] Using polymers H'-1 to H'-5 instead of polymer H-1, and otherwise following the same procedure as in Example 3-1, liquid compositions S'-1 to S'-5 were obtained. The results are shown in Table 4.

[0422] [Table 4]

[0423]

[0424] [Manufacturing of solid polymer electrolyte membranes]

[0425] For solid polymer electrolyte membranes E-1 to E-6 and solid polymer electrolyte membranes E-1' to E-5', the following operations are performed to manufacture them.

[0426] <Example 4-1>

[0427] Liquid composition S-1 was coated onto a 100 μm thick ethylene-tetrafluoroethylene copolymer (ETFE) sheet using a die coater to form a film. The film was dried at 80 °C for 15 minutes and then heat-treated at 160 °C for 30 minutes to obtain a solid polymer electrolyte membrane E-1 formed from a polymer H-1 film (25 μm thick). The results are shown in Table 5.

[0428] <Example 4-2~Example 4-11>

[0429] Liquid composition S-1 was replaced by liquid compositions S-2 to S-6 or liquid compositions S'-1 to S'-5, otherwise the procedure was the same as in Example 4-1, to obtain solid polymer electrolyte membranes E-2 to E-6 and solid polymer electrolyte membranes E'-1 to E'-5. The results are shown in Table 5.

[0430] Using the method described in Example 4 of Japanese Patent Application Publication No. 2018-55877, a liquid composition (solid content concentration = 26.0% by mass, ethanol / water = 60 / 40 (mass ratio)) dispersing an acidic sulfonic acid-containing fluoropolymer with an ion exchange capacity of 1.1 mEq / g was obtained. 117g of water was added to 20.0g of a supported catalyst (manufactured by Tanaka Precious Metals Industry Co., Ltd., trade name: TEC10E50E) with 46% by mass platinum supported on carbon powder, and ultrasonication was applied for 10 minutes to uniformly disperse it. 30.8g of the above liquid composition was added, followed by 112g of ethanol, to obtain a catalyst layer forming coating solution with a solid content of 10% by mass. This catalyst layer forming coating solution was coated onto an ETFE sheet, dried at 80°C, and then heat-treated at 160°C for 30 minutes to produce a platinum content of 0.4 mg / cm³. 2 The catalyst layer (C-1).

[0431] Two catalyst layers were clamped between the two sides of the previously obtained solid polymer electrolyte membrane and heated and pressurized at 130°C for 5 minutes and 1.5 MPa to bond the catalyst layers to both sides of the solid polymer electrolyte membrane. The ETFE sheet was then peeled off to obtain an electrode with an area of ​​25 cm². 2 The membrane catalyst layer bonding assembly.

[0432] The membrane catalyst layer conjugate was sandwiched between two gas diffusion substrates (manufactured by NOK Corporation, trade name: X0086 IX92CX320) to obtain a membrane electrode conjugate. The gas diffusion substrate has a carbon layer formed of carbon and PTFE on one side of its surface, which is configured to contact the catalyst layer of the membrane catalyst layer conjugate. The fabricated membrane electrode conjugate was assembled into a power generation battery cell and evaluated using the open-circuit test described above. The results are shown in Table 5. It should be noted that "unmeasurable" means that during the evaluation, the membrane was excessively swollen, dissolved, or damaged, making it impossible to calculate a value.

[0433] [Table 5]

[0434]

[0435] As shown in Table 2, the maximum initiator concentration relative to the mass of PSAE added before copolymerization was 2.5 ppm by mass or less in Examples 1-1 to 1-6, while it was 3.0 ppm by mass or more in Examples 1-7 to 1-11, which were comparative examples. As shown in Table 5, it was confirmed that a solid polymer electrolyte membrane with excellent conductivity and hot water resistance can be manufactured compared to the case using polymer F obtained by the above manufacturing method and the case using polymer F'. Furthermore, it was confirmed that a solid polymer electrolyte membrane with excellent chemical durability can be manufactured.

[0436] Furthermore, it was confirmed that if the Q value of polymer F is between 0.2 and 60.0 mm... 3 Within the range of / second, and with the proportion of PSAE units in polymer F to all units being 21–59 mol%, the solid polymer electrolyte membrane containing polymer H obtained by converting the fluorosulfonyl groups of polymer F into acidic sulfonic acid groups exhibits excellent electrical conductivity and hot water resistance. Furthermore, the solid polymer electrolyte membrane was confirmed to have excellent chemical durability.

[0437] [Performance evaluation of polymers used as catalyst layers]

[0438] Catalyst layers C-2 and C-3, which contain polymers H and H' as catalyst layers, are manufactured as follows, and the power generation characteristics of the catalyst layers are evaluated.

[0439] <Example 5-1>

[0440] 3.00 g of a supported catalyst (manufactured by Tanaka Precious Metals Industry Co., Ltd., trade name: TEC10E50E) with 46% platinum supported on carbon powder was mixed with 19.2 g of water and ultrasonically dispersed for 10 minutes. 6.14 g of liquid composition S-5 was then added, followed by 12.8 g of ethanol, to obtain a catalyst layer forming coating solution with a solid content of 10% by mass. This catalyst layer forming coating solution was coated onto an ETFE sheet, dried at 80°C, and then heat-treated at 160°C for 30 minutes to produce a platinum content of 0.4 mg / cm³. 2 The catalyst layer C-2.

[0441] <Example 5-2>

[0442] In the dispersion of the platinum-supported catalyst, 20.0 g of water, 5.56 g of liquid composition S'-4 and 12.6 g of ethanol were added. Otherwise, the procedure was the same as in Example 5-1, yielding a coating solution for catalyst layer formation with a platinum concentration of 0.4 mg / cm³. 2 The catalyst layer C-3.

[0443] Instead of liquid composition S-1, a liquid composition containing an acidic sulfonic acid group-containing fluoropolymer with an ion exchange capacity of 1.1 mEq / g, obtained by the method described in Example 4 of Japanese Patent Application Publication No. 2018-55877, was used. Otherwise, the procedure was the same as in Example 4-1 to obtain a solid polymer electrolyte membrane with a thickness of 25 μm. Two catalyst layers (catalyst layer C-2 or catalyst layer C-3) were clamped from both sides of the solid polymer electrolyte membrane, and the membrane was heated and pressurized under conditions of 130°C, 5 minutes, and 1.5 MPa to bond the catalyst layers to both sides. The ETFE sheet was then peeled off to obtain an electrode with an electrode area of ​​25 cm². 2 The membrane catalyst layer bonding assembly.

[0444] The membrane catalyst layer conjugate was sandwiched between two gas diffusion substrates (manufactured by NOK Corporation, trade name: X0086 IX92CX320) to obtain a membrane electrode conjugate. Each gas diffusion substrate has a carbon layer formed of carbon and PTFE on one side of its surface, which is configured to contact the catalyst layer of the membrane catalyst layer conjugate. The fabricated membrane electrode conjugate was assembled into a power generation battery cell, and the aforementioned power generation characteristic evaluation tests were conducted.

[0445] The membrane electrode assembly containing catalyst layer C-2 maintained stable power generation even after 100 hours. On the other hand, in the membrane electrode assembly containing catalyst layer C-3, dissolution of the polymer used in the catalyst layer into warm water occurred due to power generation, resulting in a time-dependent decrease in the generated voltage. Furthermore, flooding occurred due to excessive swelling of the polymer used in the catalyst layer, with a voltage greater than 1.0 A / cm² compared to the membrane electrode assembly containing catalyst layer C-2. 2 Within a certain current density range, the generation voltage is relatively lower.

[0446] [Best Implementation of the Invention]

[0447] <Example 6-1>

[0448] Cerium carbonate hydrate (Ce2(CO3)3·8H2O) was added to liquid composition S-1 in such a way that the ratio of the total molar number of cerium atoms to the total molar number of sulfonic acid groups in polymer H-1 reached 0.0067, and the mixture was stirred at 50°C for 24 hours to obtain liquid composition L-1.

[0449] Liquid composition L-1 was coated onto a 100 μm ETFE sheet using a die coater to form a film. The film was dried at 80 °C for 15 minutes and then heat-treated at 185 °C for 30 minutes to obtain a solid polymer electrolyte membrane E-10 with a thickness of 25 μm.

[0450] <Example 6-2>

[0451] Cerium oxide was added to liquid composition S-1 in such a ratio that the total molar number of cerium atoms was 0.033 relative to the total molar number of sulfonic acid groups in polymer H-1. After adding zirconia beads with a diameter of 5 mm, the mixture was mixed and dispersed for 30 minutes using a planetary bead mill at a speed of 300 rpm. The mixture was then filtered through a 53 μm stainless steel sieve to obtain liquid composition L-2.

[0452] By changing the liquid composition, but otherwise operating in the same manner as in Example 6-1, a solid polymer electrolyte membrane E-11 with a thickness of 25 μm was obtained.

[0453] <Example 6-3>

[0454] Liquid composition L-1 was coated onto an ETFE substrate using a die-coating method. Immediately afterwards, a stretched porous PTFE film (10 μm thick, 80% porosity) was overlapped onto the coating layer, thereby allowing the liquid to permeate into the stretched porous PTFE film. After drying in an oven at 80°C for 15 minutes, it was further heat-treated in an oven at 185°C for 30 minutes to obtain a solid polymer electrolyte membrane E-12 with a thickness of 15 μm.

[0455] Similarly, a solid polymer electrolyte membrane E-13 with a thickness of 15 μm was obtained from the liquid composition L-2.

[0456] <Example 6-4>

[0457] Using liquid composition S'-1 instead of liquid composition S-1, the same procedure as in Example 6-1 was followed to obtain liquid composition L'-1. Furthermore, by changing the liquid composition to L'-1, the same procedure as in Example 6-3 was followed to obtain a solid polymer electrolyte membrane E'-10 with a thickness of 15 μm.

[0458] <Example 7-1>

[0459] Using the method described in Example 4 of Japanese Patent Application Publication No. 2018-55877, a liquid composition of a fluoropolymer containing an acidic sulfonic acid group with an ion exchange capacity of 1.1 milliequivalents / gram was obtained (solid component concentration = 26.0% by mass, ethanol / water = 60 / 40 (mass ratio)).

[0460] 44 g of a supported catalyst (manufactured by Tanaka Precious Metals Industry Co., Ltd., TEC10E50E) containing 46% platinum supported on carbon powder was mixed with 217.8 g of water and 178.2 g of ethanol, and the mixture was pulverized using an ultrasonic homogenizer to obtain a catalyst dispersion. 117.4 g of a mixture obtained by pre-mixing / kneading 80.16 g of the above liquid composition, 44.4 g of ethanol, and 25.32 g of ZEORORA-H (manufactured by ZEON Corporation, Japan) was added to the catalyst dispersion. Further addition of 163.42 g of water and 139.12 g of ethanol was performed, and the mixture was pulverized using an ultrasonic homogenizer. The solids concentration was set to 7% by mass to obtain a coating solution for catalyst layer formation.

[0461] The catalyst layer was coated onto an ETFE sheet using a coating solution, dried at 80°C, and then heat-treated at 160°C for 30 minutes to produce a platinum content of 0.1 mg / cm³. 2 The catalyst layer C-4.

[0462] <Example 7-2>

[0463] 133.16 g of compound m32-1, 32.67 g of compound m22-1, and 14.1 g of solvent (AGC, ASAHIKLIN AC-2000) were added to a 230 mL stainless steel autoclave. The autoclave was thoroughly degassed under liquid nitrogen cooling. 3.94 g of TFE (tetrafluoroethylene) was added, and the temperature was raised to 24 °C. 40.17 mg of a free radical polymerization initiator ((C3F7COO)2) dissolved in compound s-1 at a concentration of 2.8% by mass was added. The feed line was cleaned with 1.1 g of AC-2000, and the reaction was initiated. After stirring for 8 hours, the autoclave was cooled to stop the reaction.

[0464] The product was diluted with AC-2000 and then mixed with a mixture of AC-2000 and methanol at a mass ratio of 8:2. The polymer was aggregated and filtered. The polymer was washed in a mixture of AC-2000 and methanol at a mass ratio of 7:3, separated by filtration, and the solid components were dried under reduced pressure at 80°C overnight to obtain polymer p-1.

[0465] The -SO2F groups in polymer p-1 were hydrolyzed and converted to -SO3K groups by immersing the obtained polymer p-1 in an aqueous solution containing 20% ​​by mass methanol and 15% by mass potassium hydroxide at 50°C for 40 hours. Next, the polymer was immersed in a 3 mol / L hydrochloric acid aqueous solution at room temperature for 2 hours. The same treatment was repeated four times with the hydrochloric acid solution replaced, resulting in polymer p-1 in which the -SO3K groups were converted to sulfonic acid groups. 19The results of F-NMR analysis of the structural units constituting polymer P-1 show that, relative to all units contained in polymer P-1, the content of units based on monomer m22-1 is 67 mol%, the content of units based on monomer m32-1 is 18 mol%, and the content of units based on TFE is 15 mol%. Furthermore, the TQ value of polymer P-1 is 275 °C. The ion exchange capacity of polymer P-1 is calculated to be 1.23 mEq / g dry resin.

[0466] Using a high-pressure autoclave made of Hastelloy alloy, a dispersion of polymer P-1 with a concentration of 18% by mass was prepared by stirring a mixed solvent of polymer P-1, water and 1-propanol (water / 1-propanol = 50 / 50 mass ratio) at 115°C and 150 rpm for 8 hours.

[0467] To 10g of a catalyst (manufactured by Tanaka Precious Metals Industry Co., Ltd., TEC10E50E) containing 46% by mass platinum supported on carbon powder, 49.5g of ultrapure water and 40.5g of ethanol were added, and the mixture was irradiated with ultrasound for 10 minutes to prepare a catalyst dispersion. 20.4g of the aforementioned polymer P-1 dispersion was then added, and the mass ratio of polymer P-1 to catalyst carbon (mass of polymer P-1 / mass of catalyst carbon) was set to 0.8. Further addition of 20.8g of ultrapure water and 29.8g of ethanol, setting the solids concentration to 8% by mass, yielded a coating solution for forming a cathode catalyst layer.

[0468] The catalyst layer was coated onto an ETFE sheet using a coating solution, dried at 80°C, and then heat-treated at 160°C for 30 minutes to produce a platinum content of 0.1 mg / cm³. 2 The catalyst layer C-5.

[0469]

[0470] <Example 7-3>

[0471] 16.33 g of compound m22-1, 72.84 g of compound m32-1, 2.0 g of TFE (tetrafluoroethylene), and 54.0 mg of free radical polymerization initiator ((C3F7COO)2) were added to a 125 mL stainless steel autoclave. The autoclave was then thoroughly degassed under liquid nitrogen cooling. Subsequently, the temperature was raised to 24 °C and maintained for 24 hours. The autoclave was then cooled to stop the reaction.

[0472] The procedure was the same as in Example 7-2, yielding 26.0 g of polymer p-2. Hydrolysis and subsequent processes were also performed in the same manner as in Example 7-2 to produce polymer P-2 and a product containing polymer P-2 with a platinum content of 0.1 mg / cm³. 2 The catalyst layer C-6.

[0473] <Performance Evaluation of Membrane Electrode Connectors (Examples 8-1 to 8-11)>

[0474] Solid polymer electrolyte membranes E-1, E-10 to E-13, E'-1 and E'-10, and catalyst layers C-4 to C-6 were assembled respectively. Two catalyst layers were clamped from both sides of the solid polymer electrolyte membrane. The membrane was heated and pressurized at 130°C for 5 minutes and 1.5 MPa to bond the catalyst layers to both sides of the solid polymer electrolyte membrane. The ETFE sheet was then peeled off to obtain an electrode with an area of ​​25 cm². 2 The membrane catalyst layer bonding assembly.

[0475] The membrane catalyst layer conjugate was sandwiched between two gas diffusion substrates (manufactured by NOK Corporation, trade name: X0086 IX92CX320) to obtain a membrane electrode conjugate. The gas diffusion substrate has a carbon layer formed of carbon and PTFE on one side of its surface, which is arranged in contact with the catalyst layer of the membrane catalyst layer conjugate. The fabricated membrane electrode conjugate was assembled into a power generation battery cell, and the aforementioned power generation characteristics, chemical durability, and wet-dry cycle durability were evaluated. A summary of the evaluated membrane electrode conjugates is shown in Table 6.

[0476] [Table 6]

[0477]

[0478] In Examples 8-1 to 8-11, the order of evaluation of power generation characteristics is as follows.

[0479] Example 8-1<(Example 8-2~8-4)<Example 8-11<(Example 8-5, Example 8-6)<(Example 8-7, Example 8-8)<(Example 8-9, Example 8-10)

[0480] In Examples 8-1 to 8-11, the order of chemical durability evaluation is as follows.

[0481] Example 8-1<Example 8-2<Example 8-11<(Examples 8-3~8-10)

[0482] In Examples 8-1 to 8-11, the order of evaluation for wet-dry cycle durability is as follows.

[0483] Example 8-1<(Example 8-2~8-4)<Example 8-11<(Example 8-5~8-10)

[0484] It should be noted that the examples recorded in parentheses above represent equivalent effects.

[0485] In summary, the membrane electrode assembly incorporating the solid polymer electrolyte membrane of the present invention achieves further performance improvements through the addition of cerium atoms, the reinforcement and thinning of the solid polymer electrolyte membrane achieved by combining it with reinforcing materials, and the combination with a catalyst layer containing a polymer with high oxygen permeability. On the other hand, the proton conductivity of solid polymer electrolyte membranes based on the prior art is poor. While the design of reducing membrane resistance by reinforcing and thinning the solid polymer electrolyte membrane achieved by combining it with reinforcing materials can improve the initial characteristics of power generation, the electrolyte material itself has poor resistance to hot water. Therefore, polymer leaching cannot be avoided during long-term operation, resulting in a faster rate of decline in power generation characteristics compared to the membrane electrode assembly incorporating the solid polymer electrolyte membrane of the present invention. Furthermore, for the same reason, the wet-dry cycle durability of the membrane electrode assembly incorporating this solid polymer electrolyte membrane is relatively poor.

[0486] It should be noted that the entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2019-192095, filed on October 21, 2019, are incorporated herein as disclosure of this invention.

[0487] Explanation of reference numerals in the attached figures

[0488] 10. Membrane electrode assembly

[0489] 11 Catalyst Layer

[0490] 12 Gas diffusion layer

[0491] 13 Anode

[0492] 14 Cathode

[0493] 15 Solid polymer electrolyte membrane

Claims

1. A method for manufacturing a fluoropolymer containing fluorosulfonyl groups, characterized in that, In a reactor, in the presence of a free radical polymerization initiator, the monomer shown in formula m1 is copolymerized with tetrafluoroethylene at a temperature of 155–200°C to produce a fluoropolymer containing fluorosulfonyl groups. In the copolymerization, the free radical polymerization initiator is added continuously or in batches to the reactor, such that the concentration of the free radical polymerization initiator in the reactor is maintained at a level of 0.01 ppm by mass and less than 1.5 ppm by mass of the monomer represented by formula m1 that was added to the reactor before the copolymerization began. The molar ratio of the total amount of monomers represented by formula m1 to the total amount of tetrafluoroethylene is 1.5 to 20. CF2=CFCF2O-Q 1 -SO2F(m1) In formula m1, Q 1 It is a single bond or optionally a perfluoroalkylene group with an ether-bonded oxygen atom.

2. A method for manufacturing a fluoropolymer containing fluorosulfonyl groups, characterized in that, In a reactor, in the presence of a free radical polymerization initiator, the monomer shown in formula m1 is copolymerized with tetrafluoroethylene at a temperature of 155–200°C to produce a fluoropolymer containing fluorosulfonyl groups. The ratio of the total amount of the free radical polymerization initiator added to the reactor to the total amount of the monomer represented by formula m1 added to the reactor is 0.01 to 4 ppm by mass per hour of copolymerization time. The molar ratio of the total amount of monomers represented by formula m1 to the total amount of tetrafluoroethylene is 1.5 to 20. CF2=CFCF2O-Q 1 -SO2F(m1) In formula m1, Q 1 It is a single bond or optionally a perfluoroalkylene group with an ether-bonded oxygen atom.

3. The method for manufacturing the fluoropolymer containing fluorosulfonyl groups according to claim 1 or 2, wherein, The monomer represented by formula m1 is the same monomer represented by formula m11 below. CF2=CFCF2O(CF2) x SO2F(m11) In formula m11, x is an integer from 1 to 12.

4. The method for manufacturing the fluoropolymer containing fluorosulfonyl groups according to claim 1 or 2, wherein, The free radical polymerization initiator is a bis(perfluoroalkyl) peroxide or a dialkyl peroxide.

5. A fluoropolymer containing a fluorosulfonyl group, characterized in that, It has the unit shown in formula f1 and the tetrafluoroethylene-based unit. The Q value of the fluorosulfonyl group-containing fluoropolymer is 3.0–45 mm. 3 / Second, The proportion of the unit represented by formula f1 in the fluorosulfonyl fluoride polymer is 21–59 mol% relative to all units. The Q value refers to the value obtained by filling the fluorosulfonyl-containing fluoropolymer with a cross-sectional area of ​​1 cm² using a flow meter. 2 In a barrel, at 260°C and a load of 30 kg, material is extruded from a nozzle with an inner diameter of 1 mm and a length of 1 mm at a pressure of 2.94 MPa. The extruded volume per unit time is the volume in mm³. 3 / Second, In equation f1, Q 1 It is a single bond or optionally a perfluoroalkylene group with an ether-bonded oxygen atom.

6. The fluoropolymer containing fluorosulfonyl groups according to claim 5, wherein, When the fluorosulfonyl group in the fluoropolymer containing the fluorosulfonyl group is an acidic sulfonic acid group, the ion exchange capacity of the fluoropolymer containing the acidic sulfonic acid group is 1.45 to 2.50 milliequivalents / gram of dry resin.

7. The fluoropolymer containing fluorosulfonyl groups according to claim 5 or 6, wherein, The unit shown in equation f1 is the same as the unit shown in equation f11 below. In equation f11, x is an integer from 1 to 12.

8. A method for manufacturing a fluoropolymer containing sulfonic acid groups, characterized in that, The fluorosulfonyl group of the fluoropolymer containing fluorosulfonyl groups manufactured by the manufacturing method according to any one of claims 1 to 4 is converted into a sulfonic acid group.

9. A fluoropolymer containing sulfonic acid groups, characterized in that, It has units shown in formula u1 and units based on tetrafluoroethylene. When the sulfonic acid group in the fluoropolymer containing the sulfonic acid group is a fluorosulfonyl group, the Q value of the fluoropolymer containing the fluorosulfonyl group is 3.0 to 45 mm. 3 / Second, The proportion of the unit represented by formula u1 in the sulfonic acid-containing fluoropolymer is 21–59 mol% relative to all units. The Q value refers to the value obtained by filling the fluorosulfonyl-containing fluoropolymer with a cross-sectional area of ​​1 cm² using a flow meter. 2 In a barrel, at 260°C and a load of 30 kg, material is extruded from a nozzle with an inner diameter of 1 mm and a length of 1 mm at a pressure of 2.94 MPa. The extruded volume per unit time is the volume in mm³. 3 / Second, In equation u1, Q 1 Z is a perfluoroalkylene group with a single bond or optionally an ether-bonded oxygen atom. + For H + Metal ions or ammonium ions.

10. The fluoropolymer containing sulfonic acid groups according to claim 9, wherein, The sulfonic acid group in the fluoropolymer containing sulfonic acid group is an acidic sulfonic acid group, and the ion exchange capacity of the fluoropolymer containing acidic sulfonic acid group is 1.45 to 2.50 milliequivalents / gram of dry resin.

11. The fluoropolymer containing sulfonic acid groups according to claim 9 or 10, wherein, The unit shown in equation u1 is the same as the unit shown in equation u11 below. In formula u11, x is an integer from 1 to 12, Z + For H + Metal ions or ammonium ions.

12. A liquid composition comprising the fluoropolymer containing a sulfonic acid group according to any one of claims 9 to 11 and a liquid medium.

13. The liquid composition according to claim 12, further comprising one or more atoms selected from the group consisting of cerium atoms and manganese atoms.

14. A solid polymer electrolyte membrane, characterized in that, It comprises the fluoropolymer containing sulfonic acid groups as described in any one of claims 9 to 11. The sulfonic acid group in the fluoropolymer containing the sulfonic acid group is an acidic sulfonic acid group.

15. The solid polymer electrolyte membrane according to claim 14, further comprising a reinforcing material.

16. The solid polymer electrolyte membrane according to claim 14 or 15, wherein the membrane thickness is 5 to 200 μm.

17. The solid polymer electrolyte membrane according to claim 14 or 15, further comprising one or more atoms selected from the group consisting of cerium atoms and manganese atoms.

18. A membrane electrode assembly, characterized in that, It includes: The anode has a catalyst layer comprising a catalyst and a polymer having ion-exchange groups; A cathode having a catalyst layer comprising a catalyst and a polymer having ion-exchange groups; and A solid polymer electrolyte membrane disposed between the anode and the cathode and comprising a polymer having ion-exchange groups. At least one polymer selected from the group consisting of the polymer containing ion-exchange groups in the anode, the polymer containing ion-exchange groups in the cathode, and the polymer containing ion-exchange groups in the solid polymer electrolyte membrane is a fluorinated polymer containing sulfonic acid groups as described in any one of claims 9 to 11.

19. A solid polymer fuel cell, characterized in that, It comprises the membrane electrode assembly as described in claim 18.

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