| 摘要 |
PURPOSE:To produce a hollow expandable product free from a sink mark in the thick-wall part by introducing molten synthetic resin incorporating a foaming agent into a cavity and thereafter pressurizing and introducing gas having pressure higher than the foaming pressure of the foaming agent and then holding the inside of this molten synthetic resin at the gas pressure lower than this pressure and foaming the foaming agent and also forming a hollow part. CONSTITUTION:Molten synthetic resin 41 incorporating a foaming agent is introduced into a cavity 92 and thereafter the piston 32 of a pressurizer 3 is actuated to introduce pressurized gas into this molten synthetic resin 41. A cavity part 421 due to pressurized gas is formed in the resin 41 and a skin layer 45 is formed by pushing the resin 41 to the wall face of the cavity 92. Then the relief valves 11, 12 are actuated by a controller 10 and some quantities of gas are discharged from the cavity part 421. When the gas pressure is made lower than the foaming pressure of the foaming agent, the foaming agent in the resin 41 starts to be foamed. Expansion of the foaming layer is stopped at a point of time when both the gas pressure in the cavity part 421 and the foaming pressure of the foaming agent have been balanced. When the whole body is cooled, a hollow expandable product is obtained which has a hollow part to the inner part of the foaming layer 43 and has a skin layer 45 to the outer part thereof. |
