| 摘要 |
<p>PURPOSE:To certainly and easily obtain an expanded injection molded article having an extremely flat surface and good quality, by rapidly lowering specific internal gas pressure when a mold cavity, on which specific internal pressure is acted, is filled with a specific amount of an expansible resin. CONSTITUTION:The set pressure of a relief valve 18 is adjusted to 20kg/cm<2> or more. When the set pressure is 17kg/cm<2> or less, a swirl mark is generated to the surface of an expanded injection molded article while the expansion state of the inner layer part of the molded article becomes non-uniform and, when the set pressure is about 17-19kg/cm<2>, the surface thereof is offten made unclean. In the next step, when the plasticized expansible resin fills 80-90 deg.% by volume of a mold cavity 5, the pressurized gas in the mold cavity is released to the open air at a stretch to rapidly lower internal gas pressure. When the filling ratio of the expansible resin in the mold cavity 5 is about 75% or less, a swirl mark is generated to the surface of the expanded molded article and, when the filling ratio is about 95% or more, expansion is hardly performed because an expansion suppressed state succeeds to the last by pressurized gas.</p> |
