A modified conjugated diene-based polymer having high Mooney viscosity and good shape stability and exhibiting excellent processability and low heat build-up is obtained in as few steps as possible. The modified conjugated diene-based polymer is produced by a method of reacting a conjugated diene-based polymer having an active chain end, obtained by polymerizing a monomer containing a conjugated diene compound in the presence of an initiator that contains at least either of an alkali metal compound and an alkaline earth metal compound, with a compound [M] having at least two groups selected from the group consisting of a group “—C(R
1
)N-A
1
” and a group “—N═C(R
1
)-A
1
”, where R
1
is a hydrogen atom or a hydrocarbyl group and A
1
is a monovalent group having an alkoxysilyl group.
通过尽可能少的步骤获得具有高莫尼粘度和良好形状稳定性、表现出优异加工性和低热积聚的改性共轭二烯基聚合物。这种改性共轭二烯基聚合物是通过一种方法制备的,该方法涉及将在至少含有碱
金属化合物和碱土
金属化合物中的至少一种的
引发剂存在下聚合含有共轭二烯化合物的单体而获得具有活性链端的共轭二烯基聚合物与具有至少两个从群组“—C(R1)N-A1”和群组“—N═C(R1)-A1”中选择的基团的化合物[M]反应,其中R1是氢原子或烃基团,A1是具有烷氧基团的一价基团。