Patent ID: 6077875
Filing Date: 2000-06-20
Classification: C08J

Abstract:
Foamed and expanded beads of a polypropylene resin for molding, which comprise an uncrosslinked propylene-ethylene random copolymer having a melting point of at least 140.degree. C. as a base resin, wherein the time required to attenuate an air pressure within the foamed and expanded beads applied by a pressurizing treatment with air from 1.2 kgf/cm.sup.2 (G) to 0.8 kgf/cm.sup.2 (G) under atmospheric pressure at 23.degree. C. is at least 80 minutes, and the CNI value of the foamed and expanded beads, which is defined by the following equation (1):CNI=log.sub.10 (Pw.times.Er.div.(2.24.times.D.sup.3 .times.B)(1)wherein Pw is an average weight (mg) per foamed and expanded bead, Er is a bulk expansion ratio (time) of the foamed and expanded beads, D is a cell diameter (mm) of the foamed and expanded beads, and B is a density of the base resin, is 2.00-3.6, and the foamed and expanded beads have an average weight of at least 0.2 mg but at most 1.1 mg per foamed and expanded bead and a bulk expansion ratio of 22 to 80 times, andwherein on a DSC curve obtained by the differential scanning calorimetry of the foamed and expanded beads, a high-temperature peak appears on the temperature side higher than a temperature at which an inherent peak corresponding to the heat of fusion of the base resin of the foamed and expanded beads appears, and the quantity of heat at the high-temperature peak is not lower than 10 J/g but lower than 17 J/g.