Polypropylene copolymers and method of preparing polyproylene 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.
Claims15
A method of preparing non-filled controlled rheology heterophasic polypropylene copolymers for molded articles 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, 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 without said increase in half life while achieving substantially the same degree of vis-breaking.
A method of preparing non-filled controlled rheology heterophasic polypropylene copolymers for molded articles 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 same copolymer degraded with the peroxide at temperatures higher than 215° C. while achieving substantially the same degree of vis-breaking.
A method of preparing non-filled controlled rheology heterophasic polypropylene copolymers for molded articles comprising introducing a heterophasic polypropylene copolymer having an ethylene content of from 5 to 20% by weight of polymer and a melt flow index of from about 0.05 to about 5 g/10 min 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, and allowing the peroxide to degrade the polypropylene copolymer to obtain a copolymer having an increase of from 50% or greater in notched Izod impact strength without said increase in half life while achieving substantially the same degree of vis-breaking.
Dependencies are inferred from the claim text.