Rubber composition and pneumatic tire using the same

1. A rubber composition comprising:

(A) 100 parts by mass of a diene rubber, not less than 10 parts by mass out of 100 parts by mass of the diene rubber (A) having a hetero atom-containing functional group in a main chain and/or a terminal thereof:

(B) from 5 to 200 parts by mass of silica;

(C) from 1 to 20 mass % of a silane coupling agent relative to the silica;

(D) from 1 to 20 mass % of a glycerin mono-fatty acid ester relative to a mass of the silica (B), the glycerin mono-fatty acid ester being derived from a fatty acid having from 8 to 24 carbons; and

at least one type of copolymers (1) to (3) and a hydrogenated product (4), wherein:

the copolymer (1) is an α-pinene-aromatic vinyl copolymer;

the copolymer (2) is a β-pinene-aromatic vinyl copolymer;

the copolymer (3) is a copolymer of an aromatic vinyl and at least two types selected from the group consisting of α-pinene, β-pinene, and dipentene; and

the hydrogenated product (4) is a hydrogenated product of the copolymers (1) to (3).

2. The rubber composition according to claim 1 , wherein the diene rubber having the hetero atom-containing functional group in the main chain and/or the terminal thereof is a conjugated diene rubber (A′) obtained by reacting a polyorganosiloxane represented by General Formula (I′) with a conjugated diene polymer chain having an active terminal obtained by forming a polymer block (C) on a polymer block (B) in succession with the polymer block (B), wherein:

the polymer block (B) is a polymer block with a weight average molecular weight of from 500 to 15,000 having an active terminal containing from 80 to 95 mass % of an isoprene monomer unit and from 5 to 20 mass % of an aromatic vinyl monomer unit; and

the polymer block (C) is a polymer block having an active terminal containing 1,3-butadiene and/or an aromatic vinyl monomer unit,

where, R 101 to R 108 are the same or different alkyl groups having from 1 to 6 carbons or aryl groups having from 6 to 12 carbons, X 101 and X 104 are the same or different groups selected from the group consisting of alkyl groups having from 1 to 6 carbons, aryl groups having from 6 to 12 carbons, alkoxy groups having from 1 to 5 carbons, and epoxy group-containing groups having from 4 to 12 carbons, X 102 is an alkoxy group having from 1 to 5 carbons or an epoxy group-containing group having from 4 to 12 carbons, and a plurality of X 102 moieties may be the same as or different from one another, X 103 is a group containing from 2 to 20 repeating alkylene glycol units, and when there are a plurality of X 103 moieties, they may be the same as or different from one another, m′ is an integer of from 3 to 200,

n′ is an integer of from 0 to 200, and

k′ is an integer of from 0 to 200.

3. The rubber composition according to claim 1 , wherein from 1 to 10 mass % of a compound represented by General Formula (1) is further compounded with the silica:

where, R 100 is an alkyl group having from 1 to 20 carbons, and Et is an ethyl group.

4. The rubber composition according to claim 1 , wherein the glycerin mono-fatty acid ester (D) contains an unsaturated bond.

5. A pneumatic tire comprising a tread including the rubber composition according to claim 1 .

6. The rubber composition according to claim 2 , wherein from 1 to 10 mass % of a compound represented by General Formula (1) is further compounded with the silica:

where, R 100 is an alkyl group having from 1 to 20 carbons, and Et is an ethyl group.

7. The rubber composition according to claim 6 , wherein the glycerin mono-fatty acid ester (D) contains an unsaturated bond.

8. A pneumatic tire comprising a tread including the rubber composition according to claim 7 .