| 摘要 |
PURPOSE:To produce good expandable particle efficiently relaxed from residual stress by melt-kneading a thermoplastic resin with a blowing agent and slowly cooling the resulting mixture at a specified relatively low temperature. CONSTITUTION:A thermoplastic resin is fed from a hopper 2 to a first extruder 1a, and a blowing agent is injected through an injector 2 into a (semi)molten thermoplastic resin. The resulting mixture is melt-kneaded in a second extruder 1b. The melt-kneaded mixture is extruded through the orifices of a diehead 4 into a cutter chamber 7 filled with pressurized water heated to Tg+5 deg.C or above by means of a heating medium from a heating medium unit 5 and immediately cut into particles. The particles leaving the cutter chamber 7 together with the heated pressurized water are fed to the top of a pressure vessel 12 for stress relaxation, relaxed from residual stress while they are falling at the above temperature under agitation under pressure, then sent to a pressure vessel 13 for cooling, rapidly cooled by mixing with cooling water pressurized with a pressurizing pump 16, withdrawn through a valve 17, separated from water in a centrifuge 18, and dried. |
