| 摘要 |
PROBLEM TO BE SOLVED: To provide a lightweight and low-cost expanded injection moldings which show the sophisticatedly transferred surface state of a mold wall face, with high dimensional precision and have a thin skin layer and a highly expanded foam layer. SOLUTION: A molten resin 4 in which a carbon dioxide is dissolved, is packed by injection into a mold cavity 3 previously pressurized by a gas above a pressure level allowing no expansion at the flow front of the molten resin 4. Next, the molten resin 4 is pressed to the mold wall face to form the skin layer 5 while the molten resin 4 is pressurized, then the volume of the mold cavity 3 is expanded by moving the movable half 2 of a mold backward. Consequently, the molten resin 4 wrapped by the skin layer 5 is expanded to form the foam layer 6 and thus the expanded injection moldings are obtained which comprise the skin layer 5 whose thickness is equal to 20% or lower of the maximum wall thickness of the moldings and the highly expanded foam layer 6 whose expansion ratio is as high as 1.1-4.0. |
