Process for producing propylene-ethylene block copolymers

Details Process for producing propylene-ethylene block copolymers Process for producing propylene-ethylene block copolymers

1979-04-16

1981-03-03

Michl, Paul R.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C08F29708

Patent

active

042542375

ABSTRACT:
A process for producing propylene-ethylene block copolymers by a three-step polymerization technique using a stereoregular catalyst, characterized in that the first-step polymerization is carried out by supplying propylene alone or a propylene/ethylene mixture so that the ethylene/propylene reaction ratio is 6/94 or less, thereby polymerizing 60 to 95% by weight of the total polymerization amount, the second-step polymerization is carried out by supplying a propylene/ethylene mixture so that the ethylene/propylene reaction ratio is 15/85 to 79/21, thereby polymerizing 1 to 20% by weight of the total polymerization amount, and the third-step polymerization is carried out by supplying a propylene/ethylene mixture so that the ethylene/propylene reaction ratio is 50/50 to 89/11, thereby polymerizing 4 to 35% by weight of the total polymerization amount, with the ethylene/propylene reaction ratio in the third step made larger than that in the second step. Said process can give propylene-ethylene block copolymers markedly well balanced in impact strength, stiffness, transparency and impact blushing.

REFERENCES:
patent: 3268624 (1966-08-01), Jezl
patent: 3296338 (1967-01-01), Jezl
patent: 3442978 (1969-05-01), Khelghatian
patent: 3911052 (1975-10-01), Castagna
patent: 3974237 (1976-08-01), Brumbaugh
patent: 4066718 (1978-01-01), Saito

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