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Recent
Developments of Organotransition-metal Catalysts for Polymerization
2. d-Block Transition Metal catalysts for Diene Elastomers
Shojiro KAITA
Yasuo WAKATSUKI
OM Chem-Tech. Co., Ltd./RIKEN, Cooperation Center, Saitama, Japan
Nippon Gomu Kyokaishi,(2004),77(11),393-396 General Review in Japanese
Abstract
Diene elastomers, in particular,
high cis polybutadiene (BR) and high cis polyisoprene
(IR), are widely used as synthetic rubber. Industrially, Ziegler-Natta
catalyst systems using Ni, Co, and Nd metals have been employed for
the production of BRs which have high 1,4-cis contents (94-98%),
but the molecular weight and molecular weight distribution of the
resulting polymers in these systems can not be well controlled (MWD
3-4). Since homogeneous catalysts can better control molecular weight,
d-block transition metal metallocene/MAO catalyst systems, e.g. ,
have been developed recently. In such "single-site" catalyst
systems, cis-specific living polymerization (sharp MWD) of
1,3-butadiene have been realized. This article is a brief introduction
of recent topics, including modification of the
system. Mechanistic studies of the 1,4-polymerization of butadiene
affected by organometallic catalysts are also described.
Keywords:
d-Block Transition Metal, Organometallic Catalyst, Metallocene
Catalyst, Single-Site Catalyst, Diene Polymerization, Polymerization
Mechanism
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