A propylene-ethylene block copolymer in the presence of a catalyst comprises as main components, a solid titanium-containing catalytic component and an organoaluminum compound having the formula AIR.sub.m.sup.1 Cl.sub.3-m (R.sup.1 represents a C.sub.1-20 hydrocarbon moiety; and m is 3.gtoreq.m>1.5) by producing a homopolymer of propylene or a propylene-ethylene copolymer by polymerizing propylene or both propylene and ethylene at a vapor phase propylene concentration of 90 mol % or higher based on the sum of propylene and ethylene in a first step and producing a propylene-ethylene block copolymer by copolymerizing propylene and ethylene at a vapor phase propylene concentration of less than 90 mol % based on the sum of propylene and ethylene in the presence of the polymer resulted in the first step and the catalyst in a second step is produced by newly adding an aluminum compound having the formula AlR.sub.n.sup.2 X.sub.3-n (R.sup.2 represents a C.sub.1-20 hydrocarbon moiety; X represents a halogen atom and n is 1.5.gtoreq.n.gtoreq.0) to the components for the copolymerization in the second step.
在催化剂的存在下,
丙烯乙烯嵌段共聚物的主要成分包括固体
钛催化组分和具有AIRm1Cl3-m公式的
有机铝化合物(其中R1表示C1-20碳氢基团;m为3≥m>1.5)。首先通过在蒸汽相
丙烯浓度为90摩尔%或更高的条件下聚合
丙烯或
丙烯和
乙烯的总和,制备
丙烯均聚物或
丙烯-
乙烯共聚物。其次,在第一步中产生的聚合物和催化剂的存在下,在蒸汽相
丙烯浓度小于90摩尔%的条件下共聚
丙烯和
乙烯,制备
丙烯乙烯嵌段共聚物。第二步通过向第二步的共聚组分中新添加具有AlRn2X3-n公式的铝化合物(其中R2表示C1-20碳氢基团;X表示卤素原子,n为1.5≥n≥0)来产生。