Process for preparing propylene copolymers comprising C4-C12-alpha olefin comonomer units

The present invention relates to a process for producing a copolymer of propylene, optionally ethylene, and at least one comonomer selected from alpha olefins having from 4 to 12 carbon atoms by usinga specific class of metallocene complexes in combination with a cocatalyst system comprising a boron containing cocatalyst and an aluminoxane cocatalyst, preferably in a multistage polymerization process including a gas phase polymerization step. 本发明涉及一种用于生产丙烯、任选的乙烯和至少一种选自具有4至12个碳原子的α-烯烃的共聚单体的共聚物的方法，该方法将特定种类的茂金属络合物与包括含硼助催化剂和铝氧烷助催化剂的助催化剂体系结合使用，优选地在包括气相聚合步骤的多阶段聚合方法中。