Influence of trialkylaluminum reagents on the propylene polymerization behavior of bridged and unbridged 2-arylindene metallocene polymerization catalysts
Jlm. Petoff et al., Influence of trialkylaluminum reagents on the propylene polymerization behavior of bridged and unbridged 2-arylindene metallocene polymerization catalysts, MACROMOLEC, 32(24), 1999, pp. 7984-7989
Trialkylaluminum reagents such as triisobutylaluminum (TIBA) and trimethyla
luminum (TMA) influence the propylene polymerization behavior of methylalum
inoxane (MAO)-activated dimethylsilyl[bis(2-phenylindenyl)]zirconium dichlo
ride (1). TIBA selectively decreases the productivity of the meso diastereo
mer of 1 (1-meso). This is manifested in an increase in the isotacticity of
polypropylene blends prepared from mixtures of 1-rac and 1-meso compared t
o polymer blends prepared in the absence of TIBA. In contrast, added trimet
hylaluminum decreases the productivity of both 1-rac and l-meso. Similar tr
ends in reactivity with AlR3 are observed for unbridged bis(2-phenylindenyl
)zirconium dichloride (2) compared to a mixture of the bridged catalysts co
ntaining 57% 1-rac. Mechanical testing indicates that polypropylene from 2
has superior elastomeric properties to reactor blends prepared from mixture
s of 1-rac and 1-meso in the presence and absence of trialkylaluminum reage
nts. Reactor blends prepared without AlR3 exhibit poorer recovery at 100% a
nd 300% strain than that of the elastomeric polypropylene from 2. The react
or blends prepared in the presence of TIBA exhibit pronounced yielding and
necking during testing, characteristic of a softened plastic.