Basell Poliolefine Italia, S.p.a.

Contitech Techno-chemie Gmbh

Ulrich Dahn

Roland Hingmann

Wolfgang Bidell

Günther Schweier

Joachim Rösch

Hans-Jürgen Zimmermann

Jürgen Oelze

Justin Richards

Daniel Schauberger

The invention relates to highly flowable propylene block copolymers that comprise 50 to 80 wt.-% of a propylene homopolymer and 10 to 70 wt.-% of a propylene copolymer having 5 to 50 wt.-% of a C&#x2013;Calk-1-ene polymerized into it that is different from propylene, and that are obtainable from the gaseous phase by a two-step polymerization by means of a Ziegler-Natta catalyst system. In a first polymerization step, the propylene is polymerized at a pressure of 10 to 50 bar, a temperature of 50 to 100&#xb0; C. and an average dwelling time of the reaction mixture of 0.3 to 5 hours in the presence of at least 2.0% by volume, based on the total volume, of hydrogen. The propylene homopolymer obtained in said first polymerization step is transferred together with the Ziegler-Natta catalyst system into an intermediate container, expanded for 0.01 to 5 minutes to less than 5 bar and maintained at a temperature of 10 to 80&#xb0; C. The pressure in the intermediate container is then increased by 5 to 60 bar by introducing under pressure a gaseous mixture, and the propylene homopolymer is then transferred to a second polymerization step together with the Ziegler-Natta catalyst system. In said second polymerization step, a mixture from propylene and a C&#x2013;Calk-1-ene is polymerized into the propylene homopolymer at a pressure of 10 to 50 bar, a temperature of 50 to 100&#xb0; C. and an average dwelling time of 0.5 to 5 hours. The weight ratio between the monomers reacted in the first and those reacted in the second polymerization step are adjusted to be in the range of from 4:1 to 1:1.

Highly flowable propylene block copolymers

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Mannheim, Germany

Ulrich Dahn