According to the process for preparing a vulcanized rubber composition of the invention comprising (a) a step of preparing a master batch comprising a butadiene rubber and silica, (b) a step of preparing a master batch comprising an isoprene rubber and silica, (c) a step of kneading the master batch obtained in (a) and the master batch obtained in (b), and (d) a step of vulcanizing a kneaded product obtained in (c), wherein the obtained vulcanized rubber composition has a BR phase and a IR phase which are incompatible with each other and comprises a predetermined amount of a terpene resin, a predetermined abundance ratio α of silica in the BR phase satisfies 0.3≦α≦0.7 (Relation 1), and a proportion β of the butadiene rubber satisfies 0.4≦β≦0.8 (Relation 2) it is possible to improve performance on ice, wet performance and abrasion resistance in good balance and to provide a vulcanized rubber composition having excellent performance on ice, wet performance and abrasion resistance, and a studless tire with a tread made using the same.

According to the process for preparing a vulcanized rubber composition of the invention comprising (a) a step of preparing a master batch comprising a butadiene rubber and silica, (b) a step of preparing a master batch comprising an isoprene rubber and silica, (c) a step of kneading the master batch obtained in (a) and the master batch obtained in (b), and (d) a step of vulcanizing a kneaded product obtained in (c), wherein the obtained vulcanized rubber composition has a BR phase and a IR phase which are incompatible with each other and comprises a predetermined amount of a terpene resin, a predetermined abundance ratio α of silica in the BR phase satisfies 0.3≦α≦0.7 (Relation 1), and a proportion β of the butadiene rubber satisfies 0.4≦β≦0.8 (Relation 2) it is possible to improve performance on ice, wet performance and abrasion resistance in good balance and to provide a vulcanized rubber composition having excellent performance on ice, wet performance and abrasion resistance, and a studless tire with a tread made using the same.

The present invention concerns a polymer comprising:—at least one repetitive unit (V) having the following formula (T):(T)—and preferably at least one, preferably at least two, repetitive unit(s) (U) having the following formula (D):(D).

##STR00001##

The present invention concerns a polymer comprising:—at least one repetitive unit (V) having the following formula (T):(T)—and preferably at least one, preferably at least two, repetitive unit(s) (U) having the following formula (D):(D).

##STR00001##

A rubber composition for use in tires comprises: WT part(s) by weight of an aromatic modified terpene resin having a softening point of 100° C. or higher per 100 parts by weight of a diene rubber, the diene rubber containing a total of 50% by weight or greater but less than 90% by weight of a butadiene rubber and an emulsion-polymerized styrene butadiene rubber, wherein the butadiene rubber is contained in an amount of 35% by weight or greater but less than 65% by weight and the emulsion-polymerized styrene butadiene rubber is contained in an amount so that an amount of bonded styrene is 35% by weight or greater. In the rubber composition, the ratio of the compounded amount of the butadiene rubber (WB part(s) by weight) to the compounded amount of the aromatic modified terpene resin (WB/WT) is from 2.5 to 5.0.

A rubber composition for use in tires comprises: WT part(s) by weight of an aromatic modified terpene resin having a softening point of 100° C. or higher per 100 parts by weight of a diene rubber, the diene rubber containing a total of 50% by weight or greater but less than 90% by weight of a butadiene rubber and an emulsion-polymerized styrene butadiene rubber, wherein the butadiene rubber is contained in an amount of 35% by weight or greater but less than 65% by weight and the emulsion-polymerized styrene butadiene rubber is contained in an amount so that an amount of bonded styrene is 35% by weight or greater. In the rubber composition, the ratio of the compounded amount of the butadiene rubber (WB part(s) by weight) to the compounded amount of the aromatic modified terpene resin (WB/WT) is from 2.5 to 5.0.

A modified conjugated diene-based polymer, and more particularly, a modified conjugated diene-based polymer having a unimodal molecular weight distribution curve measured by gel permeation chromatography (GPC), molecular weight distribution (PDI; MWD) of less than 1.7, and a Si content of 100 ppm or more based on weight, and including a repeating unit derived from an aromatic vinyl monomer in an amount of greater than 0 wt % and less than 15 wt %, and a rubber composition including the same.

A modified conjugated diene-based polymer, and more particularly, a modified conjugated diene-based polymer having a unimodal molecular weight distribution curve measured by gel permeation chromatography (GPC), molecular weight distribution (PDI; MWD) of less than 1.7, and a Si content of 100 ppm or more based on weight, and including a repeating unit derived from an aromatic vinyl monomer in an amount of greater than 0 wt % and less than 15 wt %, and a rubber composition including the same.

Provided are a tread rubber composition that can achieve a balanced improvement in fuel economy, wet-grip performance, and abrasion resistance, and a pneumatic tire including the composition. The tread rubber composition includes: a rubber component; silica; and a silane-coupling agent containing a mercapto group, the rubber component including per 100% by mass thereof 5% by mass or more of a conjugated diene polymer (A), the polymer (A) including a monomer unit derived from a conjugated diene, a monomer unit derived from a compound of formula (1), and a monomer unit derived from a compound of formula (2), at least one end of the copolymer (A) being modified by the following compound (G) or an alkoxysilane compound, the composition including 5-150 parts by mass of the silica per 100 parts by mass of the rubber component, Compound (G): at least one compound selected from the group consisting of compounds containing an optionally-substituted amino group and a carbonyl group and compounds containing an optionally-substituted amino group and a thiocarbonyl group,
V.sup.1-S.sup.1  (1)
V.sup.2-A.sup.2  (2)
wherein V.sup.1 and V.sup.2 each represent a hydrocarbyl group containing a polymerizable carbon-carbon double bond; S.sup.1 represents a substituted silyl group, and A.sup.2 represents a substituted amino group or a nitrogen-containing heterocyclic group.

Provided are a tread rubber composition that can achieve a balanced improvement in fuel economy, wet-grip performance, and abrasion resistance, and a pneumatic tire including the composition. The tread rubber composition includes: a rubber component; silica; and a silane-coupling agent containing a mercapto group, the rubber component including per 100% by mass thereof 5% by mass or more of a conjugated diene polymer (A), the polymer (A) including a monomer unit derived from a conjugated diene, a monomer unit derived from a compound of formula (1), and a monomer unit derived from a compound of formula (2), at least one end of the copolymer (A) being modified by the following compound (G) or an alkoxysilane compound, the composition including 5-150 parts by mass of the silica per 100 parts by mass of the rubber component, Compound (G): at least one compound selected from the group consisting of compounds containing an optionally-substituted amino group and a carbonyl group and compounds containing an optionally-substituted amino group and a thiocarbonyl group,
V.sup.1-S.sup.1  (1)
V.sup.2-A.sup.2  (2)
wherein V.sup.1 and V.sup.2 each represent a hydrocarbyl group containing a polymerizable carbon-carbon double bond; S.sup.1 represents a substituted silyl group, and A.sup.2 represents a substituted amino group or a nitrogen-containing heterocyclic group.