PROCESS FOR PRODUCING POLYPROPYLENE-BASED RESIN EXPANDED PARTICLE

To provide a process for producing polypropylene-based resin expanded particle that reduces the load on wastewater treatment by reducing the used amount of water-absorptive substance added to obtain a high expansion ratio in a single expansion step using inorganic gas as the expanding agent as well as that hardly makes the cell size finely divided.SOLUTION: Provided is a process for producing polypropylene-based resin expanded particle in which polypropylene-based resin particles containing 3 pts.wt. to 15 pts.wt. of spherical hollow glass composition for 100 pts.wt. of polypropylene-based resin are dispersed in an aqueous dispersion medium in a closed vessel, impregnated with an inorganic gas as an expanding agent by pressurization, and heated to a temperature equal to or higher than the softening temperature of the polypropylene-based resin particles, and thus obtained polypropylene-based resin particles are released into a region having a pressure lower than the inner pressure of the closed vessel, to produce polypropylene-based resin expanded particles.SELECTED DRAWING: Figure 1 【課題】 発泡剤として無機ガスを用いて１回の発泡工程で高い倍率を得るために添加していた吸水性物質の使用量を削減して排水処理への負荷を低減しつつ、セル径が微細化しにくいポリプロピレン系樹脂発泡粒子の製造方法を提供する。【解決手段】 ポリプロピレン系樹脂１００重量部に対し、球状中空ガラス組成物を３重量部以上１５重量部以下含むポリプロピレン系樹脂粒子を、密閉容器内にて水系分散媒に分散させ、発泡剤として無機ガスを圧力をかけて含浸させ、ポリプロピレン系樹脂粒子の軟化温度以上の温度まで加熱したポリプロピレン系樹脂粒子を、密閉容器の内圧よりも低い圧力域に放出することによりポリプロピレン系樹脂発泡粒子を得る製造方法。【選択図】 図１