Patent ID: 7799866

Claim:
A method for producing a propylene-ethylene block copolymer, comprising: a first polymerization process which is performed using two or more polymerization tanks connected in series and in which a solid catalyst or a prepolymerized catalyst containing a solid catalyst, and propylene are continuously supplied to a first polymerization tank to produce polypropylene particles containing the solid catalyst, and propylene and polypropylene particles continuously extracted from a former polymerization tank are continuously supplied to a second or following polymerization tank, so that each of the polypropylene particles is grown; and a second polymerization process in which propylene, ethylene, and polypropylene particles continuously extracted from the last polymerization tank of the first polymerization process are supplied to a polymerization tank to produce a copolymer of propylene and ethylene within the polypropylene particles, wherein an average retention time of the polypropylene particles in each polymerization tank of the first polymerization process is 0.1 to 1.5 h and the sum total of average retention times of the polypropylene particles in the polymerization tanks of the first polymerization process is 1.5 to 3.0 h, wherein a silicon compound represented by Formula [1] is supplied to the polymerization tank of the second polymerization process: Si(OL) 4 [1] wherein L is independently in each occurrence a monovalent hydrocarbon group having 1 to 20 carbon atoms, wherein the weight of the propylene-ethylene block copolymer obtained through the first and second polymerization processes is 20,000 to 40,000 parts by weight, where the amount of the solid catalyst supplied per unit time to the first polymerization tank is let be 1 part by weight.