Rubber composition and pneumatic tire using same
The present technology provides a rubber composition containing: (A) a diene rubber, (B) from 5 to 200 parts by mass of silica per 100 parts by mass of the diene rubber, (C) from 1 to 20 mass % of a sulfur-containing silane coupling agent relative to the amount of the silica, (D) for example, from 1 to 20 mass % of n-octyltriethoxysilane relative to the amount of the silica; and (E) from 1 to 20 mass % of a glycerol monofatty acid ester derived from a fatty acid having from 8 to 24 carbons relative to the mass of the silica (B).
1. A rubber composition, comprising:
(A) a diene rubber,
(B) from 5 to 200 parts by mass of silica per 100 parts by mass of the diene rubber, a nitrogen adsorption specific surface area (N 2 SA) of the silica being from 150 to 300 m 2 /g,
(C) from 1 to 20 mass % of a sulfur-containing silane coupling agent relative to the amount of the silica,
(D) from 1 to 20 parts by mass of a fatty acid metal salt per 100 parts by mass of the diene rubber,
(E) from 1 to 20 mass % of a glycerol fatty acid ester component relative to the mass of the silica (B);
wherein the glycerol fatty acid ester component consists of a glycerol monofatty acid ester derived from a fatty acid having from 8 to 24 carbons and wherein the glycerol fatty acid ester component consisting of the glycerol monofatty acid ester is the only glycerol fatty acid ester component in the rubber composition; and
(F) one or more types selected from the group consisting of copolymers (1) to (3) below and hydrogenated products (4) below:
(1) α-pinene-aromatic vinyl copolymers;
(2) β-pinene-aromatic vinyl copolymers;
(3) copolymers of an aromatic vinyl and two or more types selected from the group consisting of α-pinene, β-pinene, and dipentene; and
(4) hydrogenated products of the copolymers of (1) to (3) above.
2. The rubber composition according to claim 1 , further comprising from 1 to 20 mass % of an alkyltriethoxysilane represented by formula (1) below relative to the amount of the silica, wherein the compounded amount of the glycerol monofatty acid ester (E) is from 10 to 1000 mass % relative to the amount of the alkyltriethoxysilane (D) represented by formula (1):
wherein, R1 represents an alkyl group having from 1 to 20 carbons, and Et represents an ethyl group.
3. The rubber composition according to claim 2 , wherein the glycerol monofatty acid ester (E) contains an unsaturated bond.
4. The rubber composition according to claim 2 , comprising from 6 to 20 mass % of the alkyltriethoxysilane represented by formula (1) relative to the amount of the silica.
5. The rubber composition according to claim 2 , comprising from 12 to 40 parts by mass of the alkyltriethoxysilane per 100 parts by mass of diene rubber.
6. The rubber composition according to claim 1 , wherein the glycerol monofatty acid ester (E) contains an unsaturated bond.
7. A pneumatic tire using the rubber composition described in claim 1 in a tread.
8. The rubber composition according to claim 1 , comprising the (3) copolymers of the aromatic vinyl and two or more types selected from the group consisting of α-pinene, β-pinene, and dipentene.
9. The rubber composition according to claim 1 , comprising the hydrogenated products of the copolymers of each of (1), (2) and (3).
10. The rubber composition according to claim 1 , comprising from 4 to 20 mass % of the sulfur-containing silane coupling agent relative to the amount of the silica.
11. The rubber composition according to claim 1 , comprising (D) from 16 to 20 parts by mass of the fatty acid metal salt per 100 parts by mass of the diene rubber.