| abstract |
A molten resin mixed with a foaming agent by meansnof an extruder is extruded to form a cylindrical foamednparison, and the parison is placed in a mold and blow-moldednto obtain a hollow blow-molded foam. n In this case, where a polypropylene resin is usednas a base resin, there could not be obtained a moldednfoam having a high expansion ratio and a large wallnthickness. n In the present invention, for the production of anblow-molded foam, there is used a base resin which isnmainly composed of a polypropylene resin and has, at 230°C,na melt tension (MT) of 10 gf or over and a melt flow raten(MFR) of 0.5 g/10 minutes or over. A foaming agent isnadded to the base resin, followed by melt kneading bynmeans of an extruder under high temperature and highnpressure conditions to provide a foamable melt. This meltnis subjected to extrusion from a circular die 5 andnexpanded to form a cylindrical foamed parison 4.nThereafter, molds 6,6 are clamped, and the parison 4 in ansoftened condition is placed in the molds 6, 6, and anpressurized gas is blown into the parison 4 from a gasnblowing port 7 for blow molding in the form of a hollownshape conforming to the mold profile to produce a blow-moldednfoam. |