| 摘要 |
<p>A molten resin mixed with a foaming agent by means of an extruder is extruded to form a cylindrical foamed parison, and the parison is placed in a mold and blow-molded to obtain a hollow blow-molded foam. In this case, where a polypropylene resin is used as a base resin, there could not be obtained a molded foam having a high expansion ratio and a large wall thickness. In the present invention, for the production of a blow-molded foam, there is used a base resin which is mainly composed of a polypropylene resin and has, at 230 DEG C, a melt tension (MT) of 10 gf or over and a melt flow rate (MFR) of 0.5 g/10 minutes or over. A foaming agent is added to the base resin, followed by melt kneading by means of an extruder under high temperature and high pressure conditions to provide a foamable melt. This melt is subjected to extrusion from a circular die 5 and expanded to form a cylindrical foamed parison 4. Thereafter, molds 6,6 are clamped, and the parison 4 in a softened condition is placed in the molds 6, 6, and a pressurized gas is blown into the parison 4 from a gas blowing port 7 for blow molding in the form of a hollow shape conforming to the mold profile to produce a blow-molded foam.</p> |
