Rubber composition for use in tire treads

A rubber composition for use in tire treads comprising:

• from 60 to 130 parts by weight of silica per 100 parts by weight of diene rubber containing not less than 50% by weight of hydroxyl group-containing modified styrene butadiene rubber,
• wherein:
• a weight ratio of oil with respect to filler containing the silica is not greater than 0.25,
• a silane coupling agent having a mercapto group and an Si—O bond is compounded in an amount from 4 to 15% by weight of the silica content,
• diethylene glycol is compounded in an amount from 1 to 6% by weight of the silica content;
• the silane coupling agent having a mercapto group and an Si—O bond is a mercaptosilane compound represented by general formula (2) below, or a copolymer having the structures of general formulas (3) and (4) below, or a polysiloxane having an average composition formula represented by general formula (5) below:
• (wherein R3, R4, and R5 are mutually independently selected from hydrogen, alkyl groups having from 1 to 8 carbons, alkoxy groups having from 1 to 8 carbons, linear polyether groups having a chain length of from 4 to 30, and aryl groups having from 6 to 30 carbons, and, at least one is the alkoxy group and at least one is the linear polyether group, and R6 is an alkylene group having from 1 to 30 carbons);
• (wherein R7 and R8 may form a ring structure, and R7 is selected from hydrogen, halogen, or alkyl groups or alkylene groups having from 1 to 30 carbons, alkenyl groups or alkenylene groups having from 2 to 30 carbons, alkynyl groups or alkynylene groups having from 2 to 30 carbons, and groups in which a terminal of the above alkyl group or alkenyl group is substituted with a hydroxyl group or carboxyl group;
• R8 is an alkylene group having from 1 to 30 carbons, an alkenylene group having from 2 to 30 carbons, or an alkynylene group having from 2 to 30 carbons;
• x is an integer of 1 or greater);
• (wherein R9 and R10 may form a ring structure, and R9 is selected from a hydrogen, halogen, or alkyl groups or alkylene groups having from 1 to 30 carbons, alkenyl groups or alkenylene groups having from 2 to 30 carbons, alkynyl groups or alkynylene groups having from 2 to 30 carbons, and groups in which a terminal of the above alkyl group or alkenyl group is substituted with a hydroxyl group or carboxyl group;
• R10 is an alkylene group having from 1 to 30 carbons, an alkenylene group having from 2 to 30 carbons, or an alkynylene group having from 2 to 30 carbons;
• y is an integer of 1 or greater);
• (A)a(B)b(C)c(D)d(R11)eSiO(4-2a-b-c-d-e)/2 (5)
• (wherein A is a bivalent organic group containing a sulfide group;
• B is a monovalent hydrocarbon group having from 5 to 10 carbons;
• C is a hydrolyzable group;
• D is an organic group containing a mercapto group;
• R11 is a monovalent hydrocarbon group having from 1 to 4 carbons;
• and a to e satisfy relationships 0≦a <1, 0≦b<a, 0<c<3, 0<d<1, 0≦e<2, and 0<2a+b+c+d+e<4;
• however, at least one of a and b is not 0).