Patent ID: 6184317
Filing Date: 2001-02-06
Classification: C08F,Y10S

Abstract:
In a method of producing copolymers of ethylene monomer with at least one alpha olefin monomer by reaction of said comonomers in the presence of a catalyst system comprising a metallocene component with a cocatalyst, the improvement which comprises:a) controlling the stereochemistry of monomer insertion in the polymer chain by carrying out said reaction in the presence of said catalyst system wherein said metallocene is a bridged, asymmetric cyclopentadienyl-fluorenyl complex of the general formula: ##STR7##in which:i) M is a Group 3, 4 or 5 Transition metal, a Lanthanide or an Actinide;ii) X and X' are the same or different uninegative ligands;iii) L is at least a mono-substituted cyclopentadienyl (Cp) ring of the formula: ##STR8##wherein R.sub.1 is a substituted or unsubstituted alkyl, alkylsilyl or aryl substitutent of 1 to about 30 carbon atoms and not part of a ring with any one of R.sub.2 -R.sub.4, R.sub.2 -R.sub.4 are the same or different hydrogen or substituted or unsubstituted alkyl, alkylsilyl or aryl substituents from 1 to about 30 carbon atoms; and any adjacent pair of R.sub.2 -R.sub.4 may be connected in a ring;iv) Flu is a substituted or unsubstituted fluorenyl ligand;v) Y is a bridging group; andvi) said catalyst assymetry, in the presence of said comonomers, exhibits a first coordination site A in state M, and a second coordination site B in State M', wherein the kinetic selectivity of each site for the insertion of the comonomers is different; andb) said reaction is carried out for a time sufficient to produce copolymers having alternating ethylene/alpha olefin structure in which the copolymers are characterized by an r.sub.1 r.sub.2 of less than about 0.1.