| 摘要 |
PURPOSE:To obtain the title pre-expanded particles low in molding shrinkage, by dispersing thermoplastic resin particles containing a volatile blowing agent in water in a pressure vessel, applying a high temperature and a high pressure to the dispersion and expanding the particles by releasing the dispersion into a low-pressure atmosphere at a specified temperature. CONSTITUTION:Thermoplastic resin particles (e.g., ethylene/propylene ramdom copolymer particles) are impregnated with a volatile blowing agent (e.g., dichlorodifluoromethane) and dispersed in water in a pressure vessel. After establishing a state of high temperature and high pressure in this vessel, the dispersion is released into a low-pressure atmosphere having a pressure lower than that in the vessel and a temperature >=40 deg.C and expanded to obtain the purpose thermoplastic preexpanded particles. The obtained particles have an average cell diameter <=about 200mum, and when used in in-mold expansion molding, they can give a smooth-surfaced molding of a small molding shrinkage without imparting expandability thereto or aging them by application of pressure before molding. |
