PREFOAMING METHOD OF EXPANDABLE THERMOPLASTIC RESIN PARTICLE

PROBLEM TO BE SOLVED: To provide a method for obtaining prefoaming particles having properties with high expansion ratio equal to or more than that of very ordinary prefoaming particles and with less blocking neither giving large changes on facilities such as a prefoaming tank nor the remarkable extension of prefoaming time even under the condition that raw material particles having a small organic volatile component to be used and small environmental influence and a method for shortening the aging and curing time of the prefoaming particles between their prefoaming and their submission to molding. SOLUTION: In the prefoaming method of expandable thermoplastic resin particles, the expandable thermoplastic resin particles are charged in the prefoaming tank and then the prefoaming particles are taken out of the prefoaming tank after the once or more execution of the second prefoaming process for foaming under heat after the pneumatic pressurization in the same foaming tank of the particles obtained in the first prefoaming process in succession to the thermally foaming first prefoaming process. COPYRIGHT: (C)2004,JPO