PROCESS FOR THE PREPARATION OF POLYPROPYLENE WITH LOW ASH CONTENT

摘要

Process for the preparation of a polypropylene in a sequential polymerization process comprising at least three reactors connected in series wherein the polymerization takes place in the presence of a Ziegler Natta catalyst said Ziegler Natta catalyst comprises ? a pro catalyst comprising a compound of a transition metal (TM) a compound of a metal which metal is selected from one of the groups 1 to 3 of the periodic table (IUPAC) and an internal electron donor ? a co catalyst (Co) and ? an external donor (ED) wherein further the mol ratio of co catalyst (Co) to external donor (ED) [Co/ED] is in the range of above 12 to below 25 and the mol ratio of co catalyst (Co) to transition metal (TM) [Co/TM] is in the range of above 100 to below 200.