Continuous production method of propylene-based block copolymer

A process for continuously producing a propylene-based block copolymer, comprising:

• polymerizing an α-olefin comprising liquid propylene as a main component in the presence of hydrogen and a stereoregular polymerization catalyst in two polymerization reactors to obtain a polymer slurry;
• feeding said polymer slurry to a copolymerization reactor;
• and
• copolymerizing propylene and an cc-olefin other than propylene substantially in a gaseous phase in the presence of said stereoregular polymerization catalyst, a deactivating compound and said polymer slurry in said copolymerization reactor to obtain a propylene block copolymer powder;
• wherein said polymer slurry discharged from a first polymerization reactor of said two polymerization reactors is classified using a classification system to obtain a) a classified polymer slurry containing a large amount of particles having a large particle diameter and b) a classified polymer slurry containing a large amount of particles having a small particle diameter;
• wherein said classified polymer slurry containing the large amount of particles having a large particle diameter is fed to a second polymerization reactor of said two polymerization reactors, while a main part of said classified polymer slurry containing said large amount of particles having a small particle diameter is recycled to said first polymerization reactor;
• wherein a part of the classified polymer slurry and containing a large amount of particles having a small particle diameter is fed to a low pressure gas post treatment system;
• and
• wherein said polymer slurry discharged from the second polymerization reactor of said two polymerization reactors is transferred to said copolymerization reactor.

A process for continuously producing a propylene-based block copolymer, comprising:

• polymerizing an α-olefin comprising liquid propylene as a main component in the presence of hydrogen and a stereoregular polymerization catalyst in two polymerization reactors to obtain a polymer slurry;
• feeding said polymer slurry to a copolymerization reactor;
• copolymerizing propylene and an α-olefin other than propylene substantially in a gaseous phase in the presence of said stereoregular polymerization catalyst, a deactivating compound and said polymer slurry in said copolymerization reactor to obtain a propylene-block copolymer powder;
• wherein a polymer slurry discharged from a first polymerization reactor of said two polymerization reactors is transferred to a second polymerization reactor of said two polymerization reactors;
• wherein a polymer slurry discharged from a second polymerization reactor of said two polymerization reactors is classified using a classification system including a classifier to obtain a) a classified polymer slurry containing a large amount of particles having a large particle diameter and b) a classified polymer slurry containing a large amount of particles having a small particle diameter;
• wherein said classified polymer slurry containing said large amount of particles having a large particle diameter is fed to the copolymerization reactor, while most part of the classified polymer slurry containing a large amount of particles having a small particle diameter is recycled to said second polymerization reactor;
• and
• wherein a part of the classified polymer slurry containing a large amount of particles having a small particle diameter is fed to a low pressure gas post treatment system.