Pneumatic tire

Abstract

A pneumatic tire has a carcass layer extending from a tread portion to bead portions on both sides thereof, a belt layer on an outer side of a crown portion thereof, and an inner liner disposed on an inner side of the carcass layer. The inner liner is composed of a first layer disposed on an inner side of the tire, and a second layer disposed in contact with a rubber layer of said carcass layer. The first layer is an elastomer composition containing a thermoplastic elastomer, an ultraviolet absorber and an antioxidant, the thermoplastic elastomer containing at least one of a styrene-isobutylene-styrene block copolymer and a SIBS modified copolymer obtained by modifying a styrene block portion of a styrene-isobutylene-styrene block copolymer with one of acid chloride and acid anhydride having an unsaturated bond. The second layer contains an elastomer containing at least one of a styrene-isoprene-styrene block copolymer and a styrene-isobutylene block copolymer. The first layer and the second layer are elastomer compositions containing the ultraviolet absorber and the antioxidant by 0.5 parts by mass to 40 parts by mass relative to 100 parts by mass of an elastomer component. In the inner liner, an average thickness Gs in a buttress region Rs extending from a tire largest width position to a corresponding position Lu at a belt layer end is thinner than an average thickness Gb in a bead region Rb extending from the tire largest width position to a bead toe.

1 . A pneumatic tire having a carcass layer extending from a tread portion to bead portions on both sides thereof, a belt layer on an outer side of a crown portion thereof, and an inner liner disposed on an inner side of said carcass layer,
 said inner liner being composed of a first layer disposed on an inner side of the tire, and a second layer disposed in contact with a rubber layer of said carcass layer,   (A) said first layer being an elastomer composition containing a thermoplastic elastomer, an ultraviolet absorber and an antioxidant, the thermoplastic elastomer containing at least one of a styrene-isobutylene-styrene block copolymer and a SIBS modified copolymer obtained by modifying a styrene block portion of a styrene-isobutylene-styrene block copolymer with one of acid chloride and acid anhydride having an unsaturated bond,   (B) said second layer containing an elastomer containing at least one of a styrene-isoprene-styrene block copolymer and a styrene-isobutylene block copolymer,   said first layer and said second layer being elastomer compositions containing the ultraviolet absorber and the antioxidant by 0.5 parts by mass to 40 parts by mass relative to 100 parts by mass of an elastomer component, and   in said inner liner, an average thickness Gs in a buttress region Rs extending from a tire largest width position to a corresponding position Lu at a belt layer end being thinner than an average thickness Gb in a bead region Rb extending from the tire largest width position to a bead toe.   
     
     
         2 . The pneumatic tire according to  claim 1 , wherein a ratio (Gs/Gb) between the average thickness Gs in the buttress region and the average thickness Gb in the bead region of said inner liner is 0.5 to 0.7. 
     
     
         3 . The pneumatic tire according to  claim 1 , wherein the average thickness Gs in the buttress region of said inner liner is 0.06 mm to 0.30 mm. 
     
     
         4 . The pneumatic tire according to  claim 1 , wherein the elastomer composition of one of said first layer and said second layer has blended therein the SIBS modified copolymer by 5 percent by mass to 100 percent by mass of the elastomer component. 
     
     
         5 . The pneumatic tire according to  claim 1 , wherein the elastomer composition of one of said first layer and said second layer has blended therein one of a tackifier and polyisobutylene.