Pneumatic tire and method for producing pneumatic tire
Provided is a pneumatic tire having well-improved fuel economy, rubber tensile strength, and abrasion resistance while maintaining adequate productivity. The present invention relates to a pneumatic tire formed from a rubber composition, the rubber composition containing a hydrogenated copolymer and a sulfur donor, the hydrogenated copolymer containing a structural unit derived from an aromatic vinyl compound and a structural unit derived from a conjugated diene compound and having a degree of hydrogenation of the conjugated diene portion of 75 mol % or more, the hydrogenated copolymer being present in an amount of 75% by mass or more based on 100% by mass of a rubber component in the rubber composition, the sulfur donor being present in an amount of 0.2 to 8 parts by mass per 100 parts by mass of the rubber component.
1. A pneumatic tire, formed from a rubber composition, the rubber composition comprising a hydrogenated copolymer and a sulfur donor which is at least one of a dithiophosphate compound represented by following formula (I):
wherein x represents an integer of 1 or more, and R 11 to R 14 are the same as or different from one another and each represents a branched or unbranched C1-C18 alkyl group or a C5-C12 cycloalkyl group, or
a thiuram vulcanization accelerator represented by following formula (II):
wherein y represents an integer of 1 or more, and R 21 to R 24 are the same as or different from one another and each represent a C1-C30 hydrocarbyl group, and R 21 and R 22 , or R 23 and R 24 , may be joined together to form a ring,
the hydrogenated copolymer containing a structural unit derived from an aromatic vinyl compound and a structural unit derived from a conjugated diene compound and having a degree of hydrogenation of the conjugated diene portion of 75 mol % or more,
the hydrogenated copolymer being present in an amount of 75% by mass or more based on 100% by mass of a rubber component in the rubber composition,
the sulfur donor being present in an amount of 0.2 to 8 parts by mass per 100 parts by mass of the rubber component.
2. The pneumatic tire according to claim 1 , wherein the hydrogenated copolymer has a weight average molecular weight of 200,000 to 2,000,000.
3. The pneumatic tire according to claim 1 , wherein the hydrogenated copolymer has a degree of hydrogenation of 90 mol % or more.
4. The pneumatic tire according to claim 1 , wherein the hydrogenated copolymer is a hydrogenated styrene-butadiene copolymer.
5. The pneumatic tire according to claim 4 , wherein the hydrogenated styrene-butadiene copolymer is a hydrogenated modified styrene-butadiene copolymer.
6. The pneumatic tire according to claim 4 , wherein the hydrogenated styrene-butadiene copolymer has a styrene content of 5% to 40% by mass.
7. The pneumatic tire according to claim 4 , wherein the hydrogenated styrene-butadiene copolymer is present in an amount of 90% to 100% by mass based on 100% by mass of the rubber component.
8. The pneumatic tire according to claim 1 , wherein the rubber composition further comprises, per 100 parts by mass of the rubber component, 1 to 200 parts by mass of silica and 1 part by mass or more of carbon black.
9. A method for producing the rubber composition used to form the pneumatic tire according to claim 1 , the method comprising:
a base kneading step of kneading the rubber component including the hydrogenated copolymer to form a first kneadate, and
a final kneading step of adding the sulfur donor to the first kneadate obtained in the base kneading step and kneading the sulfur donor and the first kneadate to produce the rubber composition.
10. The pneumatic tire according to claim 2 , wherein the hydrogenated copolymer has a degree of hydrogenation of 90 mol % or more.
11. The pneumatic tire according to claim 6 , wherein the hydrogenated styrene-butadiene copolymer is present in an amount of 90% to 100% by mass based on 100% by mass of the rubber component.
12. The pneumatic tire according to claim 11 , wherein the hydrogenated copolymer has a weight average molecular weight of 200,000 to 2,000,000.
13. The pneumatic tire according to claim 12 , wherein the hydrogenated copolymer has a degree of hydrogenation of 90 mol % or more.