Method for producing polypropylene-based resin expanded beads

A method for producing polypropylene-based resin expanded beads, the method comprising:

• a mixing step of melt-mixing a polypropylene-based resin having a melt flow rate of 1 g/10 min or more and 15 g/10 min or less at 230° C. under a load of 2.16 kg and a polypropylene-based resin recovered materials comprising recovered materials of a post-consumer recycled material of a polypropylene-based resin foamed molded article with an extruder to obtain a mixture;
• an extrusion step of extruding the mixture obtained in the mixing step from the extruder and cutting the mixture to obtain polypropylene-based resin beads;
• and
• a foaming step of impregnating the polypropylene-based resin beads obtained in the extrusion step with a blowing agent and foaming the polypropylene-based resin beads impregnated with the blowing agent to obtain polypropylene-based resin expanded beads,
• wherein in the mixture, a blending ratio of the polypropylene-based resin is 30 wt % or more and 90 wt % or less, and a blending ratio of the polypropylene-based resin recovered materials is 10 wt % or more and 70 wt % or less (herein, a total of the polypropylene-based resin and the polypropylene-based resin recovered materials is 100 wt %),
• the polypropylene-based resin recovered materials contains carbon black, and a content ratio of the carbon black in the polypropylene-based resin recovered materials is 0.5 wt % or more and 5 wt % or less,
• a melting point of the polypropylene-based resin recovered materials is 135° C. or higher and 160° C. or lower,
• a melt flow rate of the polypropylene-based resin recovered materials at 230° C. under a load of 2.16 kg is higher than a melt flow rate of the polypropylene-based resin at 230° C. under a load of 2.16 kg, and
• a difference between the melt flow rate of the polypropylene-based resin recovered materials and the melt flow rate of the polypropylene-based resin ((melt flow rate of polypropylene-based resin recovered materials)−(melt flow rate of polypropylene-based resin)) is 0.1 g/10 min or more and 12 g/10 min or less.