Nonwoven fabric and electrolyte membrane
View Patent ↗To obtain a nonwoven fabric which is excellent in the heat resistance and the chemical resistance, of which the fiber diameter is small, and which is excellent in the mechanical strength at a temperature at which it is used; and an electrolyte membrane which is excellent in the dimensional stability when it is swollen by water, and of which an increase in the resistance by a reinforcing material is suppressed. A nonwoven fabric 28 containing fibers 26 of an ethylene/tetrafluoroethylene copolymer having a storage elastic modulus E′ at 25° C. of at least 8×10 8 Pa and a melt viscosity measured at 300° C. of higher than 60 Pa·s and at most 300 Pa·s, wherein the average fiber diameter of the fibers is from 0.01 to 3 μm; and an electrolyte membrane reinforced by the nonwoven fabric 28.
1. A nonwoven fabric, comprising:
fibers of an ethylene/tetrafluoroethylene copolymer;
wherein
the ethylene/tetrafluoroethylene copolymer comprises repeating units based on a monomer represented by CH 2 =CX(CF 2 ) n Y wherein each of X and Y is a hydrogen atom or a fluorine atom, and n is an integer of from 2 to 8,
and a content of the repeating units based on the monomer is from 0.1 to 7 mol % based on the total repeating units of the ethylene/tetrafluoroethylene copolymer;
a storage elastic modulus E′ at 25° C. of the ethylene/tetrafluoroethylene copolymer of the fiber is at least 8×108 Pa;
a melt viscosity of the ethylene/tetrafluoroethylene copolymer of the fiber, measured at 300° C., is higher than 60 Pas and at most 300 Pas; and
an average fiber diameter of the ethylene/tetrafluoroethylene copolymer fibers is from 0.01 to 3 μm.
2. The nonwoven fabric according to claim 1 , wherein a unit weight is from 1 to 300 g/m 2 .
3. The nonwoven fabric according to claim 1 , which is produced by meltblow process.
4. The nonwoven fabric according to claim 1 , wherein at least part of intersections among the fibers are fixed by fusion.
5. The nonwoven fabric according to claim 4 , wherein the fusion is carried out by hot pressing.
6. The nonwoven fabric according to claim 1 , wherein a maximum strength in the machine direction per 100 g/m 2 of unit weight is at least 60 N/10 cm.
7. The nonwoven fabric according to claim 1 , wherein a maximum hardness in the machine direction per 100 g/m 2 of unit weight is at least 400 N/10 cm.
8. An electrolyte membrane reinforced by the nonwoven fabric as defined in claim 1 .
9. The nonwoven fabric according to claim 1 , wherein an average fiber diameter of the fibers of the nonwoven fabric is from 0.01 to 3 μm.
10. The nonwoven fabric according to claim 1 , wherein the melt viscosity of the ethylene/tetrafluoroethylene copolymer of the fiber, measured at 300° C. is from 65 Pas to 200 Pas.