Polypropylene copolymers and method of preparing polypropylene copolymers
AssigneeFina Technology, Inc.
InventorsLisa K. Albe, William R. Wheat, Jeff Nairn, Scott Cooper, Philippe VanDeurzen, Michel Daumerie
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Abstract
Polypropylene heterophasic copolymers are produced having increased impact strength through the use of controlled rheology techniques by the addition of a peroxide at conditions which increase the deactivation or half life of the peroxide. The increased half life slows down the vis-breaking process and allows better dispersion of rubber particles within the polymer. In this way, copolymers having a high melt flow can be prepared while obtaining high impact strength and lower stiffness values, without the need for additional elastomeric modifiers.
Claims23
A method of preparing controlled rheology heterophasic polypropylene copolymers to increase impact strength of such copolymers comprising introducing a heterophasic polypropylene copolymer into an extruder along with a peroxide under conditions wherein the half life of the peroxide is increased by a factor of at least 2 compared to a half life of the peroxide under a normal extruder condition, and allowing the peroxide to degrade the polypropylene copolymer so that the copolymer obtained has a notched Izod impact strength that is increased by at least 50% compared to the same copolymer extruded with the peroxide under the normal extruder condition.
A heterophasic polypropylene copolymer prepared by introducing a heterophasic polypropylene copolymer into an extruder along with a peroxide under conditions wherein the temperature within the extruder is from about 150° C. to about 215° C. and wherein the half life of the peroxide is increased by a factor of at least 2 compared to a half life of the peroxide under a normal extruder condition in which the extruder temperature is greater than 215° C., and allowing the peroxide to degrade the polypropylene copolymer so that the copolymer obtained has a notched Izod impact strength that is increased by at least 50% compared to the same copolymer extruded with the peroxide under the normal extruder condition, the degraded polypropylene copolymer having a melt flow index of greater than about 5 g/10 min.
A method of preparing controlled rheology heterophasic polypropylene copolymers to increase impact strength of such copolymers comprising introducing a heterophasic polypropylene copolymer into an extruder along with a peroxide under conditions where the temperature within the extruder is from about 150° C. to about 215° to obtain a copolymer having an increase of from 50% or greater in notched Izod impact strength compared to the copolymer degraded with the peroxide at temperatures higher than 215° C.
Dependencies are inferred from the claim text.