| 摘要 |
A pre-expanded polypropylene resin particle can be produced in the following manner: a polypropylene resin particle produced by an under water cut method, water, a dispersing agent, and a foaming agent are charged in a pressure-resistant container, the resulting mixture is heated to a temperature equal to or higher than the softening temperature of the polypropylene resin particle to allow the polypropylene resin particle to be impregnated with the foaming agent under pressure, and the resulting product is released into the atmosphere having a pressure lower than the pressure of the inside of the pressure-resistant container. As the polypropylene resin composition, a composition is used which comprises 100 parts by weight of a polypropylene resin and 1 to 20 parts by weight of a polyethylene resin having a melt viscosity of 10 to 2000 mPa·s at 140° C., whereby it becomes possible to reduce the pressure of a heated molding vapor required for producing an in-mold expanded molding product having a fusion rate of 75% or higher.
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