Patent ID: 7858716

Claim:
A method for producing a propylene-based polymer by a gas-phase process where reaction heat is removed mainly by heat of vaporization of liquefied propylene, comprising: (I) gas-phase polymerizing propylene by contacting propylene with a solid catalyst component (A); wherein the solid catalyst component (A) is prepared by contacting the following components (A1), (A2) and (A3): a component (A1): a solid component containing titanium, magnesium and a halogen as essential components; a component (A2): a vinylsilane compound; and a component (A3): at least one of an organosilicon compound having an alkoxy group (A3a) and a compound having at least two ether bonds (A3b); wherein the gas-phase polymerizing includes a first stage where propylene is homo-polymerized or co-polymerized with one or more kinds of comonomers selected from the group consisting of ethylene and a C 4 to C 8 α-olefin; and a second stage where propylene is co-polymerized with one or more kinds of comonomers selected from the group consisting of ethylene and a C 4 to C 8 α-olefin in the higher ratio of the said comonomer than that at the first stage; (II) during at least one of the first stage and the second stage, adding, as a killing agen: a component (F): an electron donating compound.