The present invention provides a run-flat tire excellent in run-flat durability. In the run-flat tire, a vulcanized rubber of a rubber composition containing a rubber component and a vulcanization accelerator that contains tetrabenzylthiuramdisulfide is used for at least one member selected from the group consisting of a side-reinforcing rubber layer and a bead filler. In the vulcanized rubber of the run-flat tire, a proportion of monosulfide bonds and disulfide bonds in all sulfide bonds is 65% or more.

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.

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.

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 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.

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 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 derived unit from a modification initiator; a repeating unit derived from a conjugated diene-based monomer; and a derived unit from a modifier, and satisfying the conditions of i) a weight average molecular weight: 1,000,000 g/mol or more, ii) a glass transition temperature: −40° C. or less, iii) the N content: 70 ppm or more based on a total weight of the polymer, iv) the Si content: 70 ppm or more based on a total weight of the polymer, and v) a coupling number: greater than 2.5 and less than 5.0.