FIELD: chemistry.
SUBSTANCE: polymerisation method involves contacting propylene and optionally at least one other olefin with a catalyst composition in a first polymerisation reactor under gas-phase polymerisation conditions, the catalyst composition containing a procatalyst, a cocatalyst and a mixed external electron donor (M-EED) containing a first selectivity control agent (SCA1), a second selectivity control agent (SCA2), and an activity limiting agent (ALA); forming, in a first polymerisation reactor, an active propylene-based polymer having a melt flow rate greater than about 100 g/10 min as measured in accordance with ASTM D1238-01 (230°C, 2.16 kg); contacting the active propylene-based polymer with at least one olefin in a second reactor under polymerisation conditions; and obtaining an impact-resistant propylene copolymer having a melt flow rate greater than about 60 g/10 min. A version of the method and the polymer is disclosed.
EFFECT: obtaining an impact-resistant polymer with a high melt flow rate and low content of volatile substances.
10 cl, 4 tbl, 8 ex
