摘要:
A process for the gas-phase polymerization of α-olefms carried out in two interconnected polymerization zones, wherein the growing polymer particles flow through the first of said polymerization zones (riser) under fast fluidization conditions, leave said riser and enter the second of said polymerization zones (downcomer) through which they flow downward in a densified form, the process being characterized in that: (a) the gas mixture present in the riser is totally or partially prevented from entering the downcomer by introducing into the upper part of said downcomer a liquid stream LB having a composition different from the gaseous mixture present in the riser; (b) the ratio R between the flow rate Fp of polymer circulated between said downcomer and said riser and the flow rate LB of said liquid being adjusted in a range from 10 to 50.
摘要:
A polyolefin composition, particularly fit for the production of extrusion blow molded articles, comprising (a) a propylene-ethylene copolymer having a content of units deriving from ethylene of 4.0 % by weight or higher, and (b) a nucleating agent and having a crystallization temperature (Tc) higher than 117°C can be obtained by copolymerizing propylene and ethylene in the presence of a catalyst system obtained by contacting a solid catalyst component comprising a magnesium halide, a titanium compound having at least a Ti-halogen bond and at least two electron donor compounds one of which being present in an amount from 40 to 90% by mol with respect to the total amount of donors and selected from succinates and the other selected from 1,3 diethers, an aluminum hydrocarbyl compound, and optionally an external electron donor compound.
摘要:
A process for the preparation of propylene polymer compositions comprising from 50 to 90 % by weight of a propylene (co)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 comprising: (i) a first step of polymerizing propylene in the optional presence of ethylene and/or C 4 -C 10 alpha olefins, to produce a propylene (co)polymer being for at least 85% by weight insoluble in xylene at 25°C; and (ii) a successive step, carried out in gas-phase, in the presence of the product coming from step (i), of copolymerizing a mixture of ethylene with one or more ±-olefins CH 2 =CHR in which R is a hydrocarbon radical having 1-10 carbon atoms, to produce an ethylene copolymer; the process being carried out in the presence of a catalyst system comprising: the product obtained by contacting: (a) a solid catalyst component comprising a magnesium halide, a titanium compound having at least a Ti-halogen bond and at least two internal electron donor compounds one of which being present in an amount from 35 to 90% by mol with respect to the total amount of donors and being selected from succinates and the other being selected from 1,3-diethers, the total amount of internal electron donor compounds being lower than 14.0% by weight with respect to the total weight of the solid catalyst component; with (b) an aluminum hydrocarbyl compound, and optionally with (c) an external electron donor compound.
摘要:
Process for the preparation of a porous propylene carried out in the presence of a catalyst system comprising (a) a Ziegler-Natta catalyst containing at least two electron donor compounds one of which being present in an amount from 50 to 90% by mol with respect to the total amount of donors and selected from succinates and the other being selected from 1,3 diethers, (b) an aluminum alkyl and comprising the following steps: i) contacting the catalyst components (a) and (b) for a period of time ranging from 1 to 60 minutes, at a temperature ranging from 35 to 55°C; optionally, ii) pre-polymerizing with one or more olefins of formula CH2=CHR, where R is H or a C1-C10 hydrocarbon group, up to forming amounts of polymer from about 0.1 up to about 1000 g per gram of solid catalyst component (a); and iii) polymerizing propylene in the optional presence of minor amounts of ethylene and/or C4-C10 alpha olefins producing said porous propylene (co)polymer.
摘要:
A process for the preparation of random copolymer of propylene containing up to 6.0 % by weight of ethylene units, suitable for the manufacture of pipes, by copolymerizing propylene and ethylene in the presence of a catalyst system comprising the product obtained by contacting the following components: (a) a solid catalyst component comprising a magnesium halide, a titanium compound having at least a Ti-halogen bond and at least two electron donor compounds one of which being present in an amount from 40 to 90% by mol with respect to the total amount of donors and selected from succinates and the other being selected from 1,3 diethers, (b) n aluminum hydrocarbyl compound, and (c) optionally an external electron donor compound.