METHOD FOR PRODUCING POLYBUTADIENE, POLYBUTADIENE, RUBBER COMPOSITION AND TIRE

The present invention provides a method for synthesizing a polybutadiene more efficiently and stably which is possible to obtain a rubber composition and a tire excellent in durability (fracture resistance, wear resistance and crack growth resistance). A method for producing a polybutadiene, where a butadiene monomer is polymerized with the existence of rare-earth element compounds represented by the following formula (i): M-(NQ) 1 NQ) 2 (NQ) 3 (i) (in the formula, M is at least one selected from lanthanides, scandium and yttrium; (NQ) 1 , (NQ) 2 and (NQ) 3 are amide groups which may be the same or different to each other, and have M-N bonds).