Abstract: The present invention provides a catalyst system that exhibits unprecedented catalyst efficiencies and control of desired properties in the polymer product. The catalyst system includes a Toho-type, new generation titanium catalyst in combination with an electron donor described by the formula: ##STR1## wherein R.sub.1 is a bulky, basic alkyl or cycloalkyl group containing at least one secondary or tertiary carbon atom; R.sub.2 and R.sub.3 are alkyl or aryl groups; and R.sub.4 is an alkyl group with a primary carbon atom attached to the silicon atom. The system has a catalyst efficiency of at least about 30 kg/g-cat.2h as the Al/Si mole ratio varies from 20-200 in the system. The system easily achieves efficiencies over 60 kg/g-cat.2h. The system also exhibits good control over the xylene solubles, melt flow and molecular weight distribution of the polymer product.

Abstract: The invention provides a metallocene catalyst for use in preparing syndiotactic polyolefins. The catalyst comprises a bridged metallocene in which one of the cyclopentadienyl rings is substituted in a substantially different manner from the other ring. It was discovered that this type of catalyst is highly syndiospecific, and it also produces a polymer with a novel microstructure. The invention further includes the use of one or more of the catalysts in a polymerization process. The catalyst is generally described by the formulaR"(CpR.sub.n)(CpR'.sub.m)MeQ.sub.kwherein each Cp is a cyclopentadienyl or substituted cyclopentadienyl ring; each R.sub.n and R'.sub.m is the same or different and is a hydrocarbyl radicals having 1-20 carbon atoms; R" is a structural bridge between the two Cp rings imparting stereoigidity to the catalyst; Me is a group 4b, 5b, or 6b metal from the Periodic Table of Elements; each Q is a hydrocarbyl radical having 1-20 carbon atoms or is a halogen; 0.ltoreq.k.ltoreq.3; 0.ltoreq.n.

Abstract: The present invention provides a catalyst system for the polymerization and copolymerization of olefins with the system comprising a chiral, stereorigid hafnium metallocene catalyst in combination with an aluminum compound. The aluminum compound is preferably an alumoxane and may be a mixture of alumoxane and trimethyl aluminum. It was discovered that this mixture causes a transformation of the catalyst over time. The catalyst system may also include a solvent to increase the solubility of the metallocene catalyst. It was discovered that these catalyst systems produce useful polymer products with molecular weights greater than 10,000.

Abstract: A process for pretreating a Ziegler-type catalyst for use in olefin polymerization reactions. An olefin monomer is aded to a fluid carrier stream containing a Ziegler-type catalyst. The carrier stream containing the monomer and the catalyst is passed through an elongated tubular reactor at a flow rate sufficient to provide a residence time in the tubular reactor of less than 1 minute and under temperature conditions to prepolymerize the catalyst within the tubular reactor without plugging of the reactor. In a specific embodiment the residence time within the reactor is no more than 10 seconds, and more particularly, no more than 2 seconds.

Abstract: Polyolefins having a broad molecular weight distribution are obtained by polymerizing ethylene or higher alpha-olefins in the presence of a catalyst system comprising two or more metallocenes each having different propagation and termination rate constants and alumoxane.

Abstract: Isotactic-stereoblock polypropylene comprising recurring polypropylene units, said isotactic-stereoblock polypropylene characterized by comprising alternating blocks of monomers having an average block length greater than 2 having methine carbons with the same relative configuration and wherein the methine carbon atoms in adjacent blocks are of opposite configuration.