A process for the preparation of polyethylene or polypropylene

Details A process for the preparation of polyethylene or polypropylene A process for the preparation of polyethylene or polypropylene

C - Chemistry, Metallurgy

08

F

C08F 210/16 (2006.01) C08F 4/52 (2006.01) C08F 10/00 (2006.01) C08F 236/20 (2006.01) C08F 4/659 (2006.01)

Patent

CA 2281957

A process for the preparation of (i) polyethylene or (ii) polypropylene, which is essentially isotactic or a mixture of atactic and isotactic polypropylenes comprising contacting ethylene or propylene per se, or in admixture with one or more alpha-olefins, under polymerization conditions, with a catalyst system comprising: (a) a precatalyst comprising a mixture of racemic and meso stereoisomers of a metallocene catalyst containing two cycloalkadienyl ligands joined by a bridging linkage, said ligands complexed to a metal atom; and (b)(1) to obtain polyethylene made by the rac epimer only, a cocatalyst selected from the group consisting of tris(perfluorophenyl)borane and isobutyl alumoxane; (2) to obtain polyethylene made by both the rac and the meso epimers, a cocatalyst selected from the group consisting of dimethylanilinium tetrakis(perfluorophenyl)borate and triphenylmethyl tetrakis(perfluorophenyl)borate; (3) to obtain polypropylene, which is essentially isotactic, a cocatalyst selected from the group consisting of tris(perfluorophenyl)borane and isobutyl alumoxane; (4) to obtain polypropylene, which is a mixture of atactic and isotactic polypropylenes in a weight ratio of atactic to isotactic polypropylenes of about 0.01:1 to about 1:1, a cocatalyst selected from the group consisting of dimethylanilinium tetrakis(perfluorophenyl)borate and triphenylmethyl tetrakis(perfluorophenyl)borate -33- wherein, in the catalyst system, the atomic ratio of aluminum, if present, to the metal atom in the precatalyst is in the range of about 1:1 to about 1000:1 and the atomic ratio of boron, if present, to the metal atom in the precatalyst is about 1:1 to about 3:1 and when isobutyl alumoxane is used, a mixture of isobutyl alumoxane and the precatalyst is heated to a temperature of at least about 90 degrees C for at least about one hour prior to use.

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