METHOD FOR PRODUCING FOAMED POLYPROPYLENIC RESIN PARTICLES, FOAMED PARTICLES OF POLYPROPYLENIC RESIN AND IN-MOLD EXPANSION FORMED ARTICLES OF POLYPROPYLENIC RESIN

摘要

PROBLEM TO BE SOLVED: To provide a method for producing foamed polypropylenic particles having low expansion ratio by using an inorganic foaming agent, free from non-foamed resin particles in the foamed particles, having small variation of the expansion ratio among the foamed particles and having small variation of the foam film thickness among the foamed particles.;SOLUTION: The method for producing foamed polypropylene particles includes a step of charging a pressure vessel with polypropylenic resin particles containing ≥0.005 pt.wt. and ≤1 pt.wt. of an inorganic compound containing crystal water based on 100 pts.wt. of the polypropylenic resin, together with water, an inorganic dispersing agent and a dispersion assistant, a step of stirring and dispersing the content in the presence of an inorganic foaming agent while raising the temperature to increase the pressure in the pressure vessel to ≥0.9 MPa(G) and ≤3.5 MPa(G) and a step of releasing the dispersion liquid in the pressure vessel to a space having a pressure lower than the inner pressure of the pressure vessel, to effect the expansion of the particles.;COPYRIGHT: (C)2009,JPO&INPIT