Abstract: The present invention belongs to the field of polyolefin alloy preparation, and particularly relates to a polyolefin composite material in good form with adjustable composition and performances, produced by controlling a composite catalyst composed of Zieglar-Natta catalyst and metallocene catalyst to be catalytic by stage in the olefin polymerization reaction. This material is composed of propylene polymer and ethylene copolymer which is obtained by copolymerizing ethylene with alpha olefin or diolefin, wherein: the molar content of alpha olefin or diolefin in the ethylene copolymer is 0%˜60%, and the ethylene copolymer is 3˜80% by weight of the polyolefin composite material; the polyolefin composite material is in particle form, and the ethylene copolymer has a molecular weight distribution of 1˜6 and a glass transition temperature of ?80˜0° C.; and the ethylene copolymer produced in the reaction is dispersed homogeneously in the propylene polymer particles to form the polyolefin composite material.

Abstract: A process for preparing polypropylene compositions having high impact strength at low temperatures is disclosed in which the reaction is catalyzed by Ziegler-Natta/metallocene hybrid catalysts by the in-situ polymerization of one or more olefins of the formula CH2?CHR, in which R is hydrogen or an alkyl, cycloalkyl or aryl group having from 1 to 10 carbon atoms, and more specifically comprises preparing an olefin polymer by Ziegler-Natta catalyst components of the titanium or vanadium/metallocene hybrid catalysts while the metallocene components are inactivated beforehand by catalyst inactivators; and polymerizing one or more olefins in the presence of the above olefin polymer, followed by a reactivation of the metallocene components.