| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of producing a propylene-based block copolymer which has a high ratio of propylene-ethylene random copolymer parts and a high intrinsic viscosity of the copolymer parts, while suppressing gel formation.SOLUTION: A method of producing a propylene-based block copolymer comprises producing a crystalline propylene polymer in a first gas-phase reactor and then producing a propylene-ethylene random copolymer in a second gas-phase reactor, under operation conditions (1) to (5). Conditions: (1) the average residence time of the powder held in the first reactor<the average residence time of the powder held in the second reactor; (2) the polymerization temperature of the second reactor is 70°C or lower: (3) the difference between the polymerization temperature of the second reactor and the polymerization temperature of the first reactor is -10 to 10°C; (4) the mol ratio of hydrogen to propylene in the second reactor is 0.01 or lower; and (5) the mol ratio (alcohol/organic aluminum) of the alcohol supplied to the second reactor to the amount of the organic aluminum supplied to the first reactor is 1.0-2.0. |
