Patent ID: 8232358

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: contacting the following components (A1), (A2) and (A3) to form a bare catalyst: (A1): a solid component containing titanium, magnesium and a halogen as essential components; (A2): a vinylsilane compound; and (A3): an organosilicon compound having an alkoxy group (A3a), and/or, a compound having at least two ether bonds (A3b); then contacting, for pre-polymerization, the bare catalyst with propylene to form a solid catalyst component (A); and contacting the solid catalyst component (A) with gas-phase propylene to polymerize the propylene and form polypropylene, wherein a reaction heat formed as the propylene polymerizes is removed by the heat of vaporization of liquefied propylene.