Disclosed is a copolymer including a first part including an aromatic vinyl-based monomer and a conjugated diene-based monomer; and a second part including an aromatic vinyl-based monomer and a conjugated diene-based monomer, wherein the content of the aromatic vinyl-based monomer is 35 to 45% by weight based on a total weight of the copolymer, and the copolymer satisfies Equation 1 below:
V.sub.1>V.sub.2  <Equation 1> wherein V.sub.1 is a vinyl content in the first part, and V.sub.2 is a vinyl content in the second part.

Provided are copolymers which provide improved overall performance in terms of fuel economy and wet grip performance, as well as rubber compositions and tires containing the copolymers. Included is a copolymer obtained by copolymerizing an aromatic vinyl compound, a conjugated diene compound, and a compound represented by the formula (1) below or by copolymerizing a conjugated diene compound and a compound represented by the formula (1) below, the copolymer having a weight average molecular weight of 1.0×10.sup.3 to 2.5×10.sup.6, ##STR00001##
wherein R.sup.1 and R.sup.2 may be the same or different and each represents a functional group containing at least two selected from the group consisting of carbon, hydrogen, and silicon, and R.sup.1 and R.sup.2 may be joined together to form a ring structure.

Provided are copolymers which provide improved overall performance in terms of fuel economy and wet grip performance, as well as rubber compositions and tires containing the copolymers. Included is a copolymer obtained by copolymerizing an aromatic vinyl compound, a conjugated diene compound, and a compound represented by the formula (1) below or by copolymerizing a conjugated diene compound and a compound represented by the formula (1) below, the copolymer having a weight average molecular weight of 1.0×10.sup.3 to 2.5×10.sup.6, ##STR00001##
wherein R.sup.1 and R.sup.2 may be the same or different and each represents a functional group containing at least two selected from the group consisting of carbon, hydrogen, and silicon, and R.sup.1 and R.sup.2 may be joined together to form a ring structure.

The present invention provides the rubber composition for a golf ball comprising (a) a base rubber, (b) a co-crosslinking agent which is an α,β-unsaturated carboxylic acid or a metal salt thereof or both, (c) a crosslinking initiator, and (d) an alcohol, wherein the amount of component (d) is from 0.1 to 10 parts by weight per 100 parts by weight of the base rubber (a) and the compounding ratio between component (b) and component (c) is set to at least 60 of E value that is represented by “E=the molar amount of component (b)/the molar amount of the active oxygen of component (c), and a golf ball using the rubber composition, in order to achieve the object that good durability of the golf ball to impact is maintained.

The present invention provides the rubber composition for a golf ball comprising (a) a base rubber, (b) a co-crosslinking agent which is an α,β-unsaturated carboxylic acid or a metal salt thereof or both, (c) a crosslinking initiator, and (d) an alcohol, wherein the amount of component (d) is from 0.1 to 10 parts by weight per 100 parts by weight of the base rubber (a) and the compounding ratio between component (b) and component (c) is set to at least 60 of E value that is represented by “E=the molar amount of component (b)/the molar amount of the active oxygen of component (c), and a golf ball using the rubber composition, in order to achieve the object that good durability of the golf ball to impact is maintained.

The present invention provides a rubber composition obtained by kneading a rubber component, a vulcanization accelerator, silica, and a compound represented by the following formula (I): ##STR00001##
wherein the groups are as defined in the DESCRIPTION.

The present invention provides a rubber composition obtained by kneading a rubber component, a vulcanization accelerator, silica, and a compound represented by the following formula (I): ##STR00001##
wherein the groups are as defined in the DESCRIPTION.

A composition for seeded polymerization includes: a seed copolymer which has a compound having dithioate, a mercaptan compound, a first aromatic vinyl monomer, and a first conjugated diene monomer, and has an average particle diameter of 10-30 nm; a second aromatic vinyl monomer; and a second conjugated diene monomer.

Provided herein is a protective rubber track shoe for an excavator, which includes a first-stage rubber mix and a second-stage rubber mix. The first-stage rubber mix consists of a natural rubber, a chloroprene rubber, a butadiene rubber, a styrene-butadiene rubber, a tire reclaim rubber, a 120-mesh rubber powder, zinc oxide, stearic acid, an anti-aging agent 3100, an anti-aging agent CTU, paraffin wax, an intermediate super abrasion furnace carbon black and an aromatic oil. The second-stage rubber mix consists of the first-stage rubber mix, sulfur, an accelerator CZ and an auxiliary agent.

Provided herein is a protective rubber track shoe for an excavator, which includes a first-stage rubber mix and a second-stage rubber mix. The first-stage rubber mix consists of a natural rubber, a chloroprene rubber, a butadiene rubber, a styrene-butadiene rubber, a tire reclaim rubber, a 120-mesh rubber powder, zinc oxide, stearic acid, an anti-aging agent 3100, an anti-aging agent CTU, paraffin wax, an intermediate super abrasion furnace carbon black and an aromatic oil. The second-stage rubber mix consists of the first-stage rubber mix, sulfur, an accelerator CZ and an auxiliary agent.