| 摘要 |
A process for the preparation of a heterophasic copolymer of propylene and ethylene comprising polymerising propylene and ethylene in the gas phase in the presence of a solid particulate catalyst free from an external carrier comprising:
(i) a symmetrical complex of formula (I):
wherein
M is zirconium or hafnium;
each X is a sigma ligand;
L is a divalent bridge selected from -R' 2 C-, -R' 2 C-CR' 2 -, -R' 2 Si-, -R' 2 Si-SiR' 2 -, -R' 2 Ge-, wherein each R' is independently a hydrogen atom, C1-C20-alkyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl, C7-C20-arylalkyl or C7-C20-alkylaryl;
R 2 is a C1-C20 hydrocarbyl radical;
R 5 is a C1-C20 hydrocarbyl radical;
R 6 is a tertiary C4-C20 hydrocarbyl radical;
R 7 is a hydrogen atom or a C 1-10 -hydrocarbyl radical;
n is 0 to 3;
R 1 is a C1-C20 hydrocarbyl radical and optionally two adjacent R 1 groups taken together can form a further mono or multicyclic ring condensed to Ph ring optionally substituted by one or two groups R 4 ; and
R 4 is a C1-C10 alkyl radical
and (ii) a cocatalyst, preferably comprising an organometallic compound of a Group 13 metal;
wherein the xylene soluble fraction (XS) of the heterophasic copolymer of propylene and ethylene has an intrinsic viscosity of at least 1.5 dl/g and an ethylene content of 10 to 70 wt%. |
