| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for polymerizing a propylene yielding a high melt index and well-balanced rigidity and toughness.SOLUTION: Following (1) a step of obtaining, by prepolymerizing propylene or by prepolymerizing an olefin mixture including propylene and another α-olefin in the vapor or liquid phase in the presence of a Ziegler-Natta catalyst under conditions of -10 to 50°C and 0.1-10.0 MPa, a prepolymer whose degree of propylene polymerization with respect to 1 g of the catalyst is confined to a range of 2-3000 g and then (2) a step of homopolymerizing propylene or copolymerizing propylene and another α-olefin in the vapor phase in the presence of a Ziegler-Natta catalyst under conditions of a relatively high temperature, namely 91 to 105°C, and 1-6 MPa by using the prepolymer of propylene obtained at the step (1), the homopolymerization or copolymerization of the propylene is further executed continuously. |
