Patent ID: 8445572

Claim:
A rubber composition for a pneumatic tire, prepared in a plurality of mixing steps, comprising: (I) a first mixing step of preparing a mixture by mixing: (A) natural rubber, butadiene rubber, styrene-butadiene copolymer rubber, or a mixture thereof; (B) 50 to 120 parts by weight, per 100 parts by weight of the component (A), of silica; (C) 0.2 to 20 parts by weight, per 100 parts by weight of the component (A), of an amine salt represented by the following general formula (I): wherein R 1 represents a saturated or unsaturated organic group of 1 to 12 carbons not having a hydroxyl group, or a saturated or unsaturated organic group of 1 to 12 carbons having 1 or more hydroxyl groups; R 2 , R 3 , and R 4 each independently represent a hydrogen atom, a saturated or unsaturated chain hydrocarbon group of 1 to 12 carbons, a saturated or unsaturated alicyclic hydrocarbon group of 3 to 12 carbons, an aromatic hydrocarbon group of 6 to 18 carbons, or a heterocyclic group of 5 to 18 ring atoms and 2 or more carbons or at least two of R 2 , R 3 , and R 4 join together with the nitrogen atoms to which they are bonded to form a heterocyclic group of 5 to 18 ring atoms and 2 or more carbons, k, l, and n are each integers of 1 or more, and m is an integer of 2 or more, with a proviso that k, l, m, and n satisfy a relational expression k×l=m×n=2 or more; and (D) 1 to 20% by weight, based on the component (B), of (D) a silane coupling agent and additives other than sulfur and vulcanization acceleration agents; and (II) a second mixing step of mixing sulfur and a vulcanization acceleration agent with the mixture obtained in the first mixing step; wherein a strain shear elastic modulus difference ΔG′ between strain shear elastic modulus G′ strains of 0.28% and 100%, ΔG′=G′ 0.28% −G′ 100% , at a temperature of 110° C. is 90 or less.