Abstract: The present invention provides a conjugated diene polymer, wherein a molecular weight between entangled portions is 2,400 g/mol or more and 3,000 g/mol or less, a Mooney viscosity measured at 100° C. is 40 or more, and Mooney stress relaxation (MSR) is 0.8 or more, and a vinyl aromatic monomer unit content is 1% by mass or more and 18% by mass or less.

Abstract: Provided are a conjugated diene-based polymer, a conjugated diene-based polymer composition, and a crosslinked product of a conjugated diene-based polymer, etc. that have no problems in practical use with processability and heat resistance and are excellent in compression set and cold resistance. The present invention provides a conjugated diene-based polymer satisfying the following mathematical expression (A): mathematical expression (A): 35 (%)?100*(b+d)/(a+b+c+d)?99 (%) wherein constituent molar ratios of respective structure units represented by the following structural formulas (1) to (4) are defined as a, b, c, and d, respectively, having a Mooney viscosity at 100° C. of 25 or more and 125 or less, having a glass transition temperature of ?50° C. or less measured by differential scanning calorimetry (DSC), and having a crystallization peak-derived heat of crystallization of 2.5 J/g or more and 50 J/g or less.

Abstract: To provide a method for producing a retreaded tire, including retreading a base tire with a sidewall section including a rubber composition including a rubbery polymer having a specified structure, to thereby effectively inhibit the sidewall section from being degraded due to heating in adhesion by co-vulcanization and to increase the number of times of utilization of a retreaded tire. A method for producing a retreaded tire, including retreading a base tire including a sidewall section containing 20 parts by mass or more of a rubbery polymer having a conjugated diene compound-based constituent unit and an ethylene-based constituent unit per 100 parts by mass of a rubber component.

Abstract: Provided is a crosslinking rubber composition containing: a rubber-like polymer (A) having an iodine value of 10 to 250 (g/100 g), comprising 3% by mass or more of an ethylene structure and less than 10% by mass of a vinyl aromatic monomer block, containing a nitrogen atom, and having a modification ratio measured by column adsorption GPC of 40% by mass or more; and a crosslinking agent (B).

Abstract: A method for producing a modified conjugated diene polymer comprising a polymerization step of obtaining a conjugated diene polymer containing a nitrogen atom in a polymer chain and an active end by copolymerizing a conjugated diene compound and a nitrogen atom-containing vinyl compound, or a conjugated diene compound, an aromatic vinyl compound and a nitrogen atom-containing vinyl compound by use of an alkali metal compound and/or an alkaline earth metal compound as a polymerization initiator, and a modification step of reacting a modifier.

Abstract: A method for producing a modified conjugated diene polymer comprising a polymerization step of obtaining a conjugated diene polymer containing a nitrogen atom in a polymer chain and an active end by copolymerizing a conjugated diene compound and a nitrogen atom-containing vinyl compound, or a conjugated diene compound, an aromatic vinyl compound and a nitrogen atom-containing vinyl compound by use of an alkali metal compound and/or an alkaline earth metal compound as a polymerization initiator, and a modification step of reacting a modifier.