SEALANT RUBBER COMPOSITION AND PNEUMATIC TIRE

Provided are sealant rubber compositions which have excellent fracture properties and good sealing performance after aging, as well as pneumatic tires (self-sealing tires) including the rubber compositions. Included are sealant rubber compositions containing 100 parts by mass of at least one butyl-based rubber, 0.5 to 3 parts by mass of at least one thiourea crosslinking agent of formula (I), 1 to 10 parts by mass of at least one thiazole vulcanization accelerator and/or thiuram vulcanization accelerator, and 100 to 300 parts by mass of at least one liquid polymer.