MANUFACTURING METHOD OF POLYSTYRENE RESIN FOAMED SHEET FOR THERMOFORMING, POLYSTYRENE RESIN FOAMED SHEET FOR THERMOFORMING, AND FORMED ARTICLE OBTAINED BY THERMOFORMING THE FOAMED SHEET

摘要

PPROBLEM TO BE SOLVED: To provide a manufacturing method of a polystyrene resin foamed sheet for thermoforming which can be thermoformed with aging in a short time and also has a long sheet life and which is free of the nonuniformity in secondary foaming properties according to regions and enables attainment of a formed article having a prescribed secondary thickness. PSOLUTION: In a method for obtaining the foamed sheet having a thickness of 0.5-3.0 mm and an apparent density of more than 150 to 420 kg/mSP3/SPby extrusion foaming of a polystyrene resin and a physical foaming agent, the physical foaming agent constituted mainly of a mixed physical foaming agent constituted of isobutane of 50-95 mol% and a carbon dioxide or/and water of 5-50 mol% is added so that the amount of addition of the isobutane per 1 kg of the polystyrene resin may satisfy the relation of formula (1): 30(mol/mSP3/SP)d65(mol/mSP3/SP). Herein is the amount of addition of the isobutane per 1 kg of the polystyrene resin and d is the apparent density (kg/mSP3/SP) of the foamed sheet. PCOPYRIGHT: (C)2005,JPO&NCIPI