Fluoro-rubber composition and bladder for tire fabrication

1. A fluoro rubber composition comprising a rubber component comprising:

a fluoro rubber;

carbon black; and

a vulcanization system compounding agent containing a co-crosslinking agent,

wherein the fluoro rubber is at least one member selected among (A) a copolymer of tetrafluoroethylene/perfluoroalkyl vinyl ether, (B) a copolymer of tetrafluoroethylene/propylene, and (C) a copolymer made of (i) at least one monomer selected among tetrafluoroethylene, hexafluoropropylene, pentafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride, perfluoroalkyl vinyl ether and propylene, and (ii) vinylidene fluoride;

in a kneading step of compounding the carbon black in the rubber component, an average shear rate of a rotor tip point of a kneading machine is 100 (1/sec) or more, and a kneading maximum temperature T m is 120° C. or higher and not higher than 200° C.; and

in a dynamic viscoelasticity test of an unvulcanized rubber by a rubber process analyzer (RPA) (measurement temperature: 100° C., measurement frequency: 1 Hz), a difference δG A ′ (G′(1%)−G′(100%)) between a shear modulus G′(1%) at the time of a dynamic strain of 1% and a shear modulus G′(100%) at the time of a dynamic strain of 100% is 120 kPa or more and not more than 3,000 kPa,

wherein the elongation at break at 25° C. of the fluoro rubber composition after vulcanization is 400% or more and not more than 800%, and

wherein a compounding amount of the co-crosslinking agent is 0.5 to 2.5 parts by mass based on 100 parts by mass of the rubber component.

2. The fluoro rubber composition according to claim 1 , wherein

in a dynamic viscoelasticity test of a vulcanized rubber by a rubber process analyzer (RPA) (measurement temperature: 60° C., measurement frequency: 1 Hz), a difference βG B ′ (G′(1%)−G′(10%)) between a shear modulus G′(1%) at the time of a dynamic strain of 1% and a shear modulus G′(10%) at the time of a dynamic strain of 10% is 200 kPa or more and not more than 10,000 kPa.

3. The fluoro rubber composition according to claim 1 , wherein after vulcanization, a tensile strength at 25° C. is 10 MPa or more and not more than 50 MPa, and a tensile strength at 160° C. is 1 MPa or more and not more than 20 MPa, and an elongation at break at 160° C. is 150% or more and not more than 500%.

4. The fluoro rubber composition according to claim 1 , wherein after vulcanization, a tear strength at 25° C. is 20 N/mm or more and not more than 60 N/mm, and a tear strength at 160° C. is 3 N/mm or more and not more than 30 N/mm.

5. The fluoro rubber composition according to claim 1 , wherein a compounding amount of the carbon black is 10 parts by mass or more and not more than 50 parts by mass based on 100 parts by mass of the rubber component.

6. The fluoro rubber composition as set forth in claim 2 , wherein the vulcanization system compounding agent contains an organic peroxide, and the organic peroxide is a dialkyl peroxide.

7. The fluoro rubber composition according to claim 2 , wherein the co-crosslinking agent is triallyl isocyanurate.

8. A bladder for tire fabrication, which is manufactured using the fluoro rubber composition according to claim 1 .