Abstract:
A process for the preparation of high purity propylene polymers carried out in the presence of a catalyst comprising the product obtained by contacting: (a) a solid catalyst component comprising Mg, Ti and at least a first internal electron donor compound (HD) selected among the succinates and a second internal electron donor compound (2ID) selected among the 1,3-diethers, wherein the molar ratio of first internal donor over second internal donor 1ID:2ID is comprised between 4:6 and 9:1, with (b) an organo-aluminium compound, and optionally with (c) an external electron donor compound, said process being carried out at a temperature equal or higher than 78° C. and by employing a molar ratio of organo-aluminum compound over solid catalyst component (b):(a) of lower than 5.
Abstract:
A process for the preparation of propylene polymer compositions comprising from 50 to 90% by weight of a propylene polymer fraction insoluble in xylene at 25°C, and from 10 to 50% by weight of an ethylene copolymer fraction soluble in xylene at 25°C, said process being carried out in the presence of a specific catalyst system, is also characterized by the following step: (i) contacting the catalyst components (a), (b) and optionally (c) for a period of time ranging from 0.1 to 120 minutes, at a temperature ranging from 0 to 90°C; (ii) polymerizing propylene in the optional presence of ethylene and/or C 4 -C 10 alpha olefins producing a propylene (co)polymer being for at least 85% by weight of insoluble in xylene at 25°C and (iii) in a successive step, carried out in gas-phase, in the presence of the product coming from (ii), polymerizing mixtures of ethylene with α-olefins CH 2 =CHR in which R is a hydrocarbon radical having 1-10 carbon atoms, to produce an ethylene copolymer. An increased reactivity in the last step is observed.
Abstract:
Articles, particularly pressure pipes, having high strength as well as high stiffness and very good impact resistance even at low temperatures can be obtained by using a heterophasic polyolefϊn composition comprising (percent by weight) 70-90% of a random copolymer of propylene with 0.5-6% of 1-hexene, and 10-30% of a polymer of ethylene with a C 3 -C 10 α- olefϊn and optionally a diene, wherein the polymer of ethylene has an ethylene content higher than 45% and an intrinsic viscosity [η] value from 3 to 5 dl/g. A particular advantage of the present invention is that articles comprising the above heterophasic polyolefϊn composition show a low ductile to brittle transition temperature (DBTT).