Patent ID: 6174930
Filing Date: 2001-01-16
Classification: C08F,C08J

Abstract:
A method of forming a foamed isotactic polypropylene polymer comprising:(a) homopolymerizing propylene in the presence of a metallocene and a first concentration of chain transfer agent sufficient to produce a first propylene homopolymer having a melt flow rate in the range from 0.15 dg/min to 4.0 dg/min and a molecular weight distribution in the range of 1.8 to 2.5;(b) homopolymerizing propylene in the presence of the first propylene homopolymer and the metallocene in the presence of a second concentration of chain transfer agent sufficient to produce a second propylene homopolymer having a molecular weight distribution in the range of 1.8 to 2.5 and a melt flow rate in the range from 5 dg/min to 1000 dg wherein an isotactic polypropylene polymer is formed and wherein the isotactic polypropylene polymer is a blend of the first and second homopolymer having a molecular weight distribution in the range of from 2.5 to 20 and wherein the first homopolymer comprises from 40 percent to 80 percent of the isotactic polypropylene and the second homopolymer comprises from 20 percent to 60 percent of the isotactic polypropylene polymer;(c) contacting the isotactic polypropylene polymer formed by steps (a) and (b) with a foaming agent such that the foamed isotactic polypropylene polymer is formed.