Mitsui Chemicals, Inc.

Kenichiro Okamura

Kazutaka Tsuru

Atsushi Sakuma

The purpose of the present invention is to provide a propylene-based block copolymer, the deposition thereof on the inner wall of the polymerization vessel having been sufficiently inhibited. The propylene-based block copolymer of the present invention has a flowability evaluation value of 40% or less, the value being calculated with the following equation wherein X (sec) is the number of seconds over which 100 g of the copolymer having ordinary temperature falls from a stainless-steel funnel having an inner diameter of 11.9 mm and Y (sec) is the number of seconds over which 100 g of the copolymer which has been held at 80&#xb0; C. for 24 hours under a load of 10 kg falls from the funnel having an inner diameter of 11.9 mm.Flowability evaluation value (%)={()&#x2212;1}&#xd7;100.

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Hiroshima, Japan

Kenichiro Okamura