Polypropylene resin expanded particles and polypropylene resin in-mold foaming molded body

A method for producing polypropylene resin expanded particles, comprising the steps of:

• dispersing polypropylene resin particles together with a dispersant in water in a presence of a foaming agent in a vessel, the polypropylene resin particles containing a polypropylene resin as a base material resin, the polypropylene resin having at least three melting peaks on a DSC curve obtained by measurements of melting points with use of a differential scanning calorimeter, the at least three melting peaks including (i) a lowest-temperature melting peak of 100° C. or more but 130° C. or less and (ii) a highest-temperature melting peak of 140° C. or more but 160° C. or less;
• heating the polypropylene resin particles to a foaming temperature under pressure, and impregnating the foaming agent to the polypropylene resin particles;
• and thereafter
• releasing and foaming a dispersion substance including the polypropylene resin particles in the vessel to a low pressure area while keeping a temperature and pressure in the vessel constant, so that the polypropylene resin expanded particles are obtained, wherein
• the polypropylene resin expanded particles, comprising:
• a polypropylene resin as a base material resin which has at least three melting peaks on a DSC curve obtained by measurements of melting points with use of a differential scanning calorimeter, the DSC curve being obtained in a second temperature rise in raising a temperature of the polypropylene resin from 20° C. to 220° C. at a heating rate of 10° C./min, lowering the temperature from 220° C. to 20° C. at a cooling rate of 10° C./min, and raising the temperature again from 20° C. to 220° C. at a heating rate of 10° C./min, the at least three melting peaks including (i) a lowest-temperature melting peak of 100° C. or more but 130° C. or less and (ii) a highest- temperature melting peak of 140° C. or more but 160° C. or less.

A method for producing polypropylene resin expanded particles, comprising the steps of:

• dispersing polypropylene resin particles together with a dispersant in water in a presence of a foaming agent in a vessel, the polypropylene resin particles containing a polypropylene resin as a base material resin, the polypropylene resin being obtained by means of multi-stage polymerization and having at least three melting peaks on a DSC curve obtained by measurements of melting points with use of a differential scanning calorimeter, the at least two melting peaks including (i) a lowest-temperature melting peak of 100° C. or more but 130° C. or less and (ii) a highest-temperature melting peak of 140° C. or more but 160° C. or less;
• heating the polypropylene resin particles to a foaming temperature under pressure, and impregnating the foaming agent to the polypropylene resin particles;
• and thereafter
• releasing and foaming a dispersion substance including the polypropylene resin particles in the vessel to a low pressure area while keeping a temperature and pressure in the vessel constantly, so that the polypropylene resin expanded particles are obtained, wherein
• the polypropylene resin expanded particles, comprising:
• a polypropylene resin as a base material resin which has at least three melting peaks on a DSC curve obtained by measurements of melting points with use of a differential scanning calorimeter, the DSC curve being obtained in a second temperature rise in raising a temperature of the polypropylene resin from 20° C. to 220° C. at a heating rate of 10° C./min, lowering the temperature from 220° C. to 20° C. at a cooling rate of 10° C./min, and raising the temperature again from 20° C. to 220° C. at a heating rate of 10° C./min, the at least three melting peaks including (i) a lowest-temperature melting peak of 100° C. or more but 130° C. or less and (ii) a highest-temperature melting peak of 140° C. or more but 160° C. or less.