Polybutadiene, Modified Polybutadiene, Method for Producing Both, and Rubber-Reinforced Styrene Resin Composition Using Same

A polybutadiene characterized in that (1) content of 1,2-structure in the polybutadiene is 4 to 30%, (2) content of cis-1,4-structure in the polybutadiene is 65 to 95%, and (3) content of trans-1,4-structure in the polybutadiene is 5% or less, a ratio (Tcp/ML1+4) of a 5% toluene solution viscosity (Tcp) measured at 25° C. and a Mooney viscosity (ML1+4) at 100° C. is 2.0 or higher, a molecular weight distribution (Mw/Mn) is 2.80 or less, a gel content is 0.06 wt % or less, and an APHA color is 20 or less.

A method for producing a polybutadiene characterized, by adding a polymerization inhibitor to a polybutadiene solution in a polymerization process of the polybutadiene in which (1) content of 1,2-structure in the polybutadiene is 4 to 30%, (2) content of cis-1,4-structure in the polybutadiene is 65 to 95%, (3) content of trans-1,4-structure in the polybutadiene is 5% or less, and a ratio (Tcp/ML1+4) of a 5% toluene solution viscosity (Tcp) measured at 25 C and a Mooney viscosity (ML1+4) at 100° C. is 2.0 or higher, thereby to stop a polymerization in a stirring state where polymerization inhibitor particles each having a particle size of 135 mm or less are dispersed in the polybutadiene solution.

A modified polybutadiene produced by modifying a raw polybutadiene in which (1) content of 1,2-structure in the polybutadiene is 4 to 30%, (2) content of cis-1,4-structure in the polybutadiene is 65 to 95%, (3) content of trans-1,4-structure in the polybutadiene is 5% or less, and having a ratio (Tcp/ML1+4) of a 5% toluene solution viscosity (Tcp) measured at 25° C. and a Mooney viscosity (ML1+4) at 100° C., of 2.0 or higher, in the presence of a transition metal catalyst for modification, characterized in that a molecular weight distribution (Mw/Mn) is 2.80 or less, a gel content is 0.06 wt % or less, and an APHA color is 20 or less.

A method for producing a modified polybutadiene characterized by comprising adding a transition metal catalyst for modification to a raw polybutadiene in which (1) content of 1,2-structure in the polybutadiene is 4 to 30%, (2) content of cis-1,4-structure in the polybutadiene is 65 to 95%, (3) content of trans-1,4-structure in the polybutadiene is 5% or less, and a ratio (Tcp/ML1+4) of a 5% toluene solution viscosity (Tcp) measured at 25° C. and a Mooney viscosity (ML1+4) at 100° C. is 2.0 or higher, thereby to modify it, and adding a polymerization inhibitor to the polybutadiene solution thereby to stop a polymerization in a stirring state where polymerization inhibitor particles each having a particle size of 130 mm or less are dispersed in the polybutadiene solution.