Patent ID: 7589138
Filing Date: 2009-09-15
Classification: B29C,B29K,C08K

Abstract:
1. A method for the preparation of a molded article formed of an isotactic ethylene propylene copolymer comprising: (a) providing an isotactic ethylene propylene copolymer having an ethylene content of no more than 5 weight percent produced by the copolymerization of ethylene and propylene in the presence of an isospecific metallocene catalyst; (b) heating said ethylene propylene copolymer to a molten state; (c) extruding said molten copolymer into a mold cavity to form a molded article conforming to the configuration of said mold cavity; (d) cooling said ethylene propylene copolymer within the confines of said mold cavity to a temperature effective to solidify said copolymer within said mold cavity to form a solidified molded article; (e) retrieving said solidified molded article from said mold cavity; and (f) prior to extruding said copolymer in paragraph (c) incorporating into said copolymer a nucleating agent selected from the group consisting of an oranophosphate salt and a norbornane carboxylic-acid salt in an amount effective to provide a uniform shrinkage of said molded article at 48 hours after molding of at least 85% as determined by the differential in transverse and longitudinal shrinkages at 48 hours after molding.