| 摘要 |
PROBLEM TO BE SOLVED: To provide a process for producing expanded polypropylene-based resin beads which are free from cell unevenness and cell size reduction unlike conventional expanded beads and in which cell diameter and expansion ratio can be independently controlled with ease, and when subjected to in-mold foam molding, the expanded beads show satisfactory fusibility and give a product of foam molding which has excellent surface properties. SOLUTION: The process for producing the expanded polypropylene-based resin beads having 0.1-7 wt.% volatile component rate, 8-25 time expansion ratio, 130-500μm average cell diameter and <0.4 dispersion of the cell diameters comprises dispersing the following polypropylene-based resin particles in an aqueous dispersion medium in a closed vessel, heating the dispersion to a temperature not lower than the softening temperature of the polypropylene-based resin particles, and then discharging the dispersion into a zone having a lower pressure than the internal pressure of the closed vessel to cause the expansion. The polypropylene-based resin particles comprise 100 pts.wt. polypropylene-based resin having 2-9 g/10 min melt index, 0.01-5 pts.wt. water-absorbing substances not having the function of forming cell nuclei, and 0.005-1 pt.wt. nucleating agent for expansion. COPYRIGHT: (C)2009,JPO&INPIT |
