A method of producing a polymer composition is provided, including: kneading (A) a conjugated diene-based polymer that is a polymer of a conjugated diene compound or a copolymer of a conjugated diene compound and an aromatic vinyl compound, and is a reaction product between an active polymerization end and a compound represented by any one of the general formulae (1) to (3), and (B) a basic compound having an acid dissociation constant of 8.0 or more; and kneading a kneaded product from (A) and a crosslinking agent.

It could be helpful to provide a rubber composition that can achieve both reinforcement property and low loss property at a high level. In order to solve the aforementioned problems, the disclosure is a rubber composition comprising a rubber component, carbon black, and silica, wherein the silica has a CTAB adsorption specific surface area of 250 m.sup.2/g or more; the silica has a diameter in the form of aggregates (D.sub.CPS) and a primary particle diameter (D.sub.I), as measured by disk centrifugal particle size analysis, that satisfy: 700≥D.sub.CPS.sup.3/D.sub.I.sup.3≥300 (1); the rubber component contains at least one selected from natural rubber and polyisoprene rubber, and at least one selected from modified butadiene rubber and modified styrene butadiene rubber; and the carbon black is contained by a mass ratio of 70% or more with respect to the total mass content of the carbon black and the silica.

Provided is a pneumatic tire having both improved run-flat durability and excellent wet grip properties; the pneumatic tire including a rubber composition used in a tread part, and a rubber support layer having a gauge thickness in a specified range; the rubber composition including specified compounded amounts of natural rubber, a terminal-modified styrene-butadiene rubber, silica, and a thermoplastic resin, wherein the rubber composition is largely strain-dependent for the storage elastic modulus.

Provided is an all-season tire tread rubber composition in which braking performance and wear performance are secured at the same time. A rubber composition for tire tread according to the present disclosure comprises: 100 parts by weight of raw rubber comprising solution polymerized styrene-butadiene rubber which has a styrene content of 20 to 30 wt % and a vinyl content within butadiene of 20 to 30 wt %, and is manufactured by a continuous method; 90 to 110 parts by weight of silica; and 20 to 40 parts by weight of modified liquid butadiene rubber.

A modified conjugated diene-based polymer and a rubber composition including the same are disclosed herein. In some embodiments, the modified conjugated diene-based polymer includes a functional group derived from a modification monomer represented by Formula 1 and a functional group derived from a modifier, and the polymer has a unimodal molecular weight distribution, and a polydispersity index of 1.0 to less than 1.7. The polymer has excellent processability, tensile properties and viscoelasticity properties.

A modified conjugated diene-based polymer and a rubber composition including the same are disclosed herein. In some embodiments, the modified conjugated diene-based polymer includes a functional group derived from a modification monomer represented by Formula 1 and a functional group derived from a modifier, and the polymer has a unimodal molecular weight distribution, and a polydispersity index of 1.0 to less than 1.7. The polymer has excellent processability, tensile properties and viscoelasticity properties.

The present invention relates to a modified conjugated diene-based polymer and a rubber composition including the same, and provides a modified conjugated diene-based polymer satisfying the following: a) a molecular weight distribution curve by gel permeation chromatography (GPC) has a unimodal shape; b) molecular weight distribution (PDI: MWD) is 1.00 or more and less than 1.70; c) cold flow is 1.00 or less; and d) the Si content is 100 ppm or more based on a total weight of the modified conjugated diene-based polymer.

The present disclosure relates to a modified conjugated diene-based polymer and a rubber composition including the same, and provides a modified conjugated diene-based polymer including a first polymer chain and a second polymer chain, including a repeating unit derived from a conjugated diene-based monomer and a derived unit from a nitrogen-containing modification initiator, in each, wherein the first polymer chain includes a derived unit from an aminoalkoxysilane-based modifier in at least one terminal, the second polymer chain includes a derived unit from an aminoepoxy-based modifier in at least one terminal, and the aminoalkoxysilane-based modifier includes 6 or more alkoxy groups in a molecule.

A process for preparing a functionalized polybutadiene is provided. The process comprises the following steps: a) homopolymerising butadiene with a catalytic system based on at least one preforming conjugated diene, a salt of one or more rare earth metals of an organic phosphoric acid, an aluminium-containing alkylating agent, an alkylaluminium halide; b) adding a polyfunctional compound to the pseudo-living elastomer formed in step (a); and c) adding a functionalizing agent to the mixture formed in step (b). The total molar amount of aluminium in the polymerization medium is such that the (aluminium/rare earth salt) molar ratio has a value between 1 and 5 and the polymerization is carried out at a temperature between 40° C. and 90° C. A functionalized polybutadiene that can be obtained by the process, and a rubber composition containing the functionalized polybutadiene is also provided.

A process for preparing a functionalized polybutadiene is provided. The process comprises the following steps: a) homopolymerising butadiene with a catalytic system based on at least one preforming conjugated diene, a salt of one or more rare earth metals of an organic phosphoric acid, an aluminium-containing alkylating agent, an alkylaluminium halide; b) adding a polyfunctional compound to the pseudo-living elastomer formed in step (a); and c) adding a functionalizing agent to the mixture formed in step (b). The total molar amount of aluminium in the polymerization medium is such that the (aluminium/rare earth salt) molar ratio has a value between 1 and 5 and the polymerization is carried out at a temperature between 40° C. and 90° C. A functionalized polybutadiene that can be obtained by the process, and a rubber composition containing the functionalized polybutadiene is also provided.