Patent ID: 7531116

Claim:
A process of producing a foamed molding, comprising the steps of: (A) filling, in a mold cavity, expanded beads selected from the group consisting of: (I) expanded, substantially non-cross-linked first resin beads obtained by a method comprising the steps of: (a) dispersing substantially non-cross-linked resin particles of a first base resin including a polypropylene resin in a dispersing medium containing an organic peroxide to obtain a dispersion, (b) maintaining said dispersion at a temperature lower than the melting point of said first base resin but sufficient to decompose said organic peroxide, thereby obtaining substantially non-cross-linked, surface-modified resin particles, and (c) foaming and expanding said non-cross-linked, surface-modified resin particles using a blowing agent to obtain the expanded, substantially non-cross-linked first resin beads, (II) expanded, substantially non-cross-linked second resin beads of a second base resin, including a polypropylene resin, in a mold cavity, said expanded second resin beads having a surface region and an inside region surrounded by said surface region, wherein said surface and inside regions show, respectively, first and second high temperature endothermic peaks, in DSC curves thereof, in addition to respective first and second intrinsic endothermic peaks located, respectively, at a lower temperature side of said first and second high temperature peaks, and wherein said first and second high temperature endothermic peaks of said surface region and said inside region have heat of fusion of Hs and Hi, respectively, and wherein Hs and Hi have the following relationship: Hs < 0.86 ×Hi, (III) expanded, substantially non-cross-linked third resin beads of a third base resin, including a polypropylene resin, in a mold cavity, said expanded third resin beads exhibiting a third high temperature endothermic peak, in a DSC curve thereof, in addition to a third intrinsic endothermic peak located at a lower temperature side of said third high temperature peak, each of said expanded third resin beads having a surface region showing a melt initiation temperature not higher than the melting point of said third base resin, and (IV) expanded, substantially non-cross-linked fourth resin beads of a fourth base resin, including a polypropylene resin, in a mold cavity, said expanded fourth resin beads exhibiting a fourth high temperature endothermic peak, in a DSC curve thereof, in addition to a fourth intrinsic endothermic peak located at a lower temperature side of said fourth high temperature peak, each of said expanded fourth resin beads having a surface region with an extrapolated melt initiation temperature, as measured by micro differential thermoanalysis, not higher than (Tm +4° C.) where Tm is the melting point of the fourth base resin; (B) heating the expanded resin beads in the mold cavity to fuse-bond together, into a unitary body, the expanded resin beads in the mold cavity; and (C) cooling said unitary body.