Patent ID: 6077878
Filing Date: 2000-06-20
Classification: C08F,C08J,C08L

Abstract:
A foamed extrudate comprising a modified polypropylene resin which is a grafted copolymer of a polypropylene resin and an aromatic vinyl monomer, wherein the aromatic vinyl monomer added is in an amount from 0.1 to 40 parts by weight for 100 parts by weight of the raw polypropylene resin, the average number of grafted aromatic vinyl chains in one molecule of said graft copolymer is at least 1, the weight average molecular weight of said aromatic vinyl chains is not less than 200, and the elongational viscosity .eta.e (poise), which is defined below, varies with measuring time t (second) in the manner described below: ##EQU5## wherein .sigma. is a stress per cross-sectional area (dynes/cm.sup.2), and .gamma. is a strain rate (/sec) represented by the following equation: ##EQU6## wherein L is a length of a sample (cm), and when a graph is plotted wherein the abscissa represents a logarithm of t and the ordinate represents a logarithm of .eta.e, in the resulting curve, a gradient ratio of a straight line drawn from a slowly increasing portion at an initial stage to a straight line drawn from a drastically increasing portion with a lapse of time is not less than 2.