Embodiments of the present disclosure are directed to functionalized copolymers produced by copolymerization of at least one conjugated diolefin monomer and at least one vinyl monomer, the functionalized copolymer comprising at least one functional group having silica reactive moieties, wherein the functionalized copolymer has a degree of hydrogenation of 75% to 98 mol % as measured using proton nuclear magnetic resonance spectroscopy (.sup.1H NMR).

To provide a rubber composition in which wet performance, wear resistance, low rolling resistance, and breaking resistance are highly balanced. A rubber composition comprising a rubber component comprising at least three polymers and a filler, wherein the rubber component is separated into at least two polymer phases: a polymer phase (1) with the highest tan δ peak temperature; and a polymer phase (2) with the lowest peak temperature; the polymer phases (1) and (2) are incompatible with each other; the polymer phase (1) at least comprises the modified conjugated diene-based polymers (A1) and (A2), and the filler; the modified conjugated diene-based polymer (A1) has a particular weight-average molecular weight and a particular contracting factor (g′); and when a filler concentration and an average aggregate area of the filler in the polymer phase (1) are defined as X and Y, respectively, an formula (1): Y<4.8X+1200 is satisfied.

To provide a rubber composition in which wet performance, wear resistance, low rolling resistance, and breaking resistance are highly balanced. A rubber composition comprising a rubber component comprising at least three polymers and a filler, wherein the rubber component is separated into at least two polymer phases: a polymer phase (1) with the highest tan δ peak temperature; and a polymer phase (2) with the lowest peak temperature; the polymer phases (1) and (2) are incompatible with each other; the polymer phase (1) at least comprises the modified conjugated diene-based polymers (A1) and (A2), and the filler; the modified conjugated diene-based polymer (A1) has a particular weight-average molecular weight and a particular contracting factor (g′); and when a filler concentration and an average aggregate area of the filler in the polymer phase (1) are defined as X and Y, respectively, an formula (1): Y<4.8X+1200 is satisfied.

A conjugated diene-based polymer of the present invention has an absolute molecular weight measured by viscosity detector-equipped GPC-light scattering measurement, of 40×10.sup.4 or more and 5000×10.sup.4 or less, has a branching number (Bn) measured by the viscosity detector-equipped GPC-light scattering measurement, of 8 or more, and has a modification ratio of 60% by mass or more.

A conjugated diene-based polymer of the present invention has an absolute molecular weight measured by viscosity detector-equipped GPC-light scattering measurement, of 40×10.sup.4 or more and 5000×10.sup.4 or less, has a branching number (Bn) measured by the viscosity detector-equipped GPC-light scattering measurement, of 8 or more, and has a modification ratio of 60% by mass or more.

The purpose is to provide rubber compositions and pneumatic tires which have reduced changes in hardness over time. The present invention relates to a rubber composition containing a copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound, the rubber composition having a heat aging resistance index defined by equation (1) of 10 or less.

The purpose is to provide rubber compositions and pneumatic tires which have reduced changes in hardness over time. The present invention relates to a rubber composition containing a copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound, the rubber composition having a heat aging resistance index defined by equation (1) of 10 or less.

To provide a rubber composition in which wet performance, wear resistance, low rolling resistance, and breaking resistance are highly balanced. A rubber composition comprising a rubber component comprising at least three polymers and a filler, wherein the rubber component is separated into at least two polymer phases: a polymer phase (1) with the highest tan δ peak temperature; and a polymer phase (2) with the lowest peak temperature; the polymer phases (1) and (2) are incompatible with each other; the polymer phase (1) at least comprises the modified conjugated diene-based polymers (A1) and (A2), and the filler; the modified conjugated diene-based polymer (A1) has a particular weight-average molecular weight and a particular contracting factor (g′); and when a filler concentration and an average aggregate area of the filler in the polymer phase (1) are defined as X and Y, respectively, an formula (1): Y<4.8X+1200 is satisfied.

To provide a rubber composition in which wet performance, wear resistance, low rolling resistance, and breaking resistance are highly balanced. A rubber composition comprising a rubber component comprising at least three polymers and a filler, wherein the rubber component is separated into at least two polymer phases: a polymer phase (1) with the highest tan δ peak temperature; and a polymer phase (2) with the lowest peak temperature; the polymer phases (1) and (2) are incompatible with each other; the polymer phase (1) at least comprises the modified conjugated diene-based polymers (A1) and (A2), and the filler; the modified conjugated diene-based polymer (A1) has a particular weight-average molecular weight and a particular contracting factor (g′); and when a filler concentration and an average aggregate area of the filler in the polymer phase (1) are defined as X and Y, respectively, an formula (1): Y<4.8X+1200 is satisfied.

Described herein is a coating composition including one or more (meth)acrylic polymers including moieties of formula (I)

*—C(═O)—O—CH.sub.2—Si(R.sup.a).sub.3−x(R.sup.b).sub.x  (I)

where R.sup.a=methoxy; R.sup.b=an alkyl group containing 1 to 4 carbon atoms or an alkoxy group containing 1 to 4 carbon atoms; x is 0 or 1; and the asterisk * denotes the position at which the moiety of formula (I) is attached to the polymeric backbone of the (meth)acrylic polymer; further containing one or more catalysts of formula (II)

H.sub.3C—C(R.sup.c)(R.sup.d)—C(═O)—O.sup.−M.sup.+  (II)

where R.sup.c and R.sup.d=alkyl groups containing 1 to 6 carbon atoms, with the proviso that the sum of the number of carbon atoms in residues R.sup.c and R.sup.d ranges from 2 to 7, and M=for Li, K or Na, and further containing one or more aprotic organic solvents.