1. Field of the Invention
This invention relates to novel diene polymer compositions and more particularly to a diene polymer composition containing a copolymer of conjugated diene and 2,3-dimethylbutadiene having a high content of cis-1,4-bond.
2. Description of the Prior Art
As regards polymers containing 2,3-dimethylbutadiene, it is known that the copolymers being relatively rich in trans-bond may be obtained by the use of an alkyl lithium catalyst or by radical polymerization (see, for example, U.S. Pat. No. 4,294,942 and No. 4,124,546).
However, 2,3-dimethylbutadiene copolymer having a high content of cis-1,4-bond has not yet been known.
USPTO Backgrounds
USPTO Backgrounds