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 C4-C10 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 α-olefins CH2=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.
一种制备
丙烯聚合物组合物的工艺,该组合物包括在 25℃下不溶于二
甲苯的
丙烯(共)聚合物部分(按重量计)50%至 90%,以及在 25℃下可溶于二
甲苯的
乙烯共聚物部分(按重量计)10%至 50%,所述工艺包括:
(i) 第一步,在
乙烯和/或 C4-C10 α 烯烃任选存在的情况下,使
丙烯聚合,生成至少 85% (按重量计)在 25°C 时不溶于二
甲苯的
丙烯(共)聚合物;以及
(ii) 在气相中,在步骤(i)的产物存在下,进行
乙烯与一种或多种 α-烯烃
CH2=CHR 的混合物共聚的连续步骤,其中 R 是具有 1-10 个碳原子的烃基,以生产
乙烯共聚物;
该工艺在催化剂体系存在下进行,该催化剂体系包括: 与下列物质接触得到的产物
(a) 固体催化剂组分,包括卤化
镁、至少具有一个
钛-卤素键的
钛化合物和至少两个内 部电子供体化合物,其中一个电子供体化合物的含量为供体总量的 35-90%(摩尔), 且选自
琥珀酸酯,另一个选自 1,3-
二醚,内部电子供体化合物的总量低于固体催 化剂组分总重量的 14.0%(重量比);与
(b) 烃基铝化合物,以及可选的
(c) 外部电子供体化合物。