| abstract |
Provided is a butadiene-based polymer having a high cis-1,4 bond content, a low vinyl bond content, and a molecular weight distribution in a specific range. A butadiene-based polymer containing a 1,3-butadiene monomer unit has a cis-1,4 bond content measured by Fourier transform infrared spectroscopy in the 1,3-butadiene monomer unit. The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 1.6 to 3.5 when the content is 98.0% or more and the vinyl bond content is 0.3% or less. It is a characteristic butadiene-based polymer. The butadiene polymer can be produced by polymerizing a monomer containing 1,3-butadiene at a temperature of 25 ° C. or lower in the presence of a catalyst system containing a specific rare earth element-containing compound. [Selection figure] None |