Perfluoropolymer, liquid composition, polymer electrolyte membrane, membrane electrode assembly and polymer electrolyte fuel cell
To provide a perfluoropolymer capable of producing an electrolyte membrane excellent in electrical conductivity and mechanical strength under high temperature environment, as well as a liquid composition, a polymer electrolyte membrane, a membrane electrode assembly and a polymer electrolyte fuel cell, obtainable by using the perfluoropolymer. The perfluoropolymer of the present invention contains perfluoromonomer units, does not substantially contain units having a halogen atom other than a fluorine atom, does not substantially contain units having a ring structure, and has acid-type sulfonic acid groups, wherein the perfluoromonomer units contain at least one type of units A selected from the group consisting of perfluoro vinyl ether units and perfluoro allyl ether units; the ion exchange capacity is from 1.4 to 2.5 milliequivalent/gram dry resin; and the storage modulus at 120° C. is at least 60 MPa.
1 . A perfluoropolymer:
containing perfluoromonomer units,
not substantially containing units having a halogen atom other than a fluorine atom,
not substantially containing units having a ring structure, and
having acid-type sulfonic acid groups,
wherein:
the perfluoromonomer units contain at least one type of units A selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units,
the perfluoroallyl ether units are units represented by formula A-1:
where R F1 and R F2 are each independently a C 1-3 perfluoroalkylene group,
the perfluorovinyl ether units are units represented by formula (A-3)
where R F1 and R F2 are each independently a C 1-3 perfluoroalkylene group,
an ion exchange capacity of the perfluoropolymer is from 1.49 to 2.5 milliequivalents/gram dry resin, and
a storage modulus of the perfluoropolymer at 120° C. is at least 60 MPa.
2 . The perfluoropolymer according to claim 1 , wherein the ion exchange capacity is from 1.91 to 2.50 milliequivalent/gram dry resin.
3 . The perfluoropolymer according to claim 1 , wherein a hydrogen gas permeation coefficient of the perfluoropolymer under conditions of a temperature of 80° C. and a relative humidity of 10%, is at most 2.5×10 −9 cm 3 ·cm/(s·cm 2 ·cmHg).
4 . The perfluoropolymer according to claim 1 , which is a perfluoropolymer obtained by converting precursor groups of a precursor polymer in which the acid-type sulfonic acid groups are in the form of the precursor groups, into the acid-type sulfonic acid groups, wherein a TQ value of the precursor polymer is at least 220° C.
5 . The perfluoropolymer according to claim 1 , wherein a content of units A is from 7 to 45 mol % to all units in the perfluoropolymer.
6 . The perfluoropolymer according to claim 1 , wherein the perfluoromonomer units further contain tetrafluoroethylene units.
7 . A liquid composition comprising the perfluoropolymer as defined in claim 1 and a liquid medium.
8 . A polymer electrolyte membrane comprising the perfluoropolymer as defined in claim 1 .
9 . The polymer electrolyte membrane according to claim 8 , which further contains a reinforcing material.
10 . A membrane electrode assembly comprising an anode having a catalyst layer containing a catalyst and a polymer having ion exchange groups, a cathode having a catalyst layer containing a catalyst and a polymer having ion exchange groups, and the polymer electrolyte membrane as defined in claim 8 , disposed between the anode and the cathode.
11 . The membrane electrode assembly according to claim 10 , wherein at least one of the polymer having ion exchange groups contained in the anode and the polymer having ion exchange groups contained in the cathode, is a perfluoropolymer:
containing perfluoromonomer units,
not substantially containing units having a halogen atom other than a fluorine atom,
not substantially containing units having a ring structure, and
having acid-type sulfonic acid groups,
wherein:
the perfluoromonomer units contain at least one type of units A selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units,
an ion exchange capacity of the perfluoropolymer is from 1.4 to 2.5 milliequivalents/gram dry resin, and
a storage modulus of the perfluoropolymer at 120° C. is at least 60 MPa.
12 . A polymer electrolyte fuel cell comprising the membrane electrode assembly as defined in claim 10 .
13 . The perfluoropolymer according to claim 1 , wherein the ion exchange capacity is from 1.60 to 2.5 milliequivalent/gram dry resin.