| 摘要 |
PURPOSE:To manufacture foamed product provided with the uniform thickness of skin layer by setting the pressure of gas, supplied to a cavity, stepwise in accordance with injection speeds. CONSTITUTION:The gas, such as CO2 or the like, is sealed into a mold 15 from a supplying source 4 thereof through the path 5a of a pressure-reducing valve 10 by opening a switching valve 6. When the inside of the mold 15 has come to the high pressure of a set gas pressure P1, molten resin, including foaming agent, is poured through another pouring port into the mold 15 to form the skin layer 21 having a high density on the resin outer skin uniformly by reducing the injection speed V1 of the resin. Subsequently, the gas in the mold is extracted by the switching valve 7 and the pressure-reducing valve 11 to reduce the pressure P2 to the set gas pressure while the injecting speed of the resin is increased to a value V2 and foaming is started. Further, a core layer 22 is formed by the switching valve 8 and the pressure-reducing valve 12 as well as the switching valve 9 and the pressure-reducing valve 13 under set gas pressures P3, P4 and set injecting speeds V3, V4. The thickness of the skin layer may be uniformed and the foaming condition of the core layer may be controlled in such manner. |
