| 摘要 |
PURPOSE:To simply and efficiently obtain the subject particles useful for heat insulating material or packaging cushioning material, etc., having small variability of expansion by impregnating thermoplastic resin particles in a cylindrical state, etc., with a given amount of an inorganic gas in a vapor phase, introducing steam to the particles under a specific condition. CONSTITUTION:Thermoplastic resin particles such as polystyrenic resin particles of cylindrical shape or irregular shape are impregnated with an inorganic gas (e.g. carbon dioxide gas) as a blowing agent in a vapor phase at a mild temperature and under mild pressure not to stick the particles to give fomable resin particles having >=0.05mol/kg inorganic gas content. Then, before the inorganic gas content of the particles is reduced to <0.05mol/g, steam is introduced into the particles at a temperature 10-40 deg.C higher than Vicat softening temperature of the resin particles for an enough time to deform the shape of the particles into an approximately spherical shape to give the objective approximately spherical particles. |
