Start-up procedure for an underwater granulating die

摘要

An underwater granulating method in which thermoplastic resin material is kneaded and melted by a kneading extruder while the melted resin material is extruded into cooling water from nozzles of a die with its external surface covered with the cooling water, and the resin material extruded in thin strings is cut by a cutter device driven to move along the external surface of the die. The method is characterized by the following steps: increasing the heating magnitude of the die so that the softened resin material filling the neighborhood of the external surface of the nozzles is melted; temporarily stopping the kneading extruder in the heating state where the kneading extruder is supplied with resin material; stopping the cutter device; reducing the heating quantity of the die; covering the external surface of the nozzles with the cooling water in the condition where the resin material filling the neighborhood of the external surface in the nozzles is softened to close the nozzles; and thereafter starting the drive of the cutter device and, at the same time, the drive of the kneading extruder.