Abstract: Post-treatment method of polyolefin resin pre-expanded particles comprising: introducing the polyolefin resin pre-expanded particles foamed by using an inflammable blowing agent into an extraction vessel filled with steam previously; feeding an additional steam into the extraction vessel; extracting the inflammable blowing agent gas from the polyolefin resin pre-expanded particles; discharging the resulting steam which contains the extracted inflammable blowing agent gas from the extraction vessel continuously or intermittently; and liquefying the steam to separate and recover the inflammable blowing agent gas. According to the post-treatment method of polyolefin resin pre-expanded particles, the inflammable blowing agent can be extracted from the pre-expanded particles in a short period of time and the extracted inflammable blowing agent can be re-used.

Abstract: A method of manufacturing a molded resin foam by charging pre-expanded resin pellets into a cavity of a mold and subjecting them to expansion molding. In order to minimize differences in weight of the foam from product to product, the method is characterized in that prior to charging, the apparent density of the pre-expanded resin pellets is measured and, upon charging, the cracking width of the mold is regulated, on the basis of the measurement result, to a definite value determined depending upon the apparent density, whereby the weight of the pellets charged in the mold cavity is made constant.

Abstract: A process and apparatus for preparing pre-expanded particles of a thermoplastic resin which comprises; heating under an elevated pressure an aqueous dispersion comprising thermoplastic resin particles containing a volatile foaming agent and an aqueous medium in a pressure vessel; releasing the dispersion from the pressure vessel into a space within a sealed low-pressure vessel wherein the pressure is lower than that in the pressure vessel, whereby expanding the thermoplastic resin particles to give pre-expanded particles; and simultaneously recovering the foaming agent volatilized from the thermoplastic resin particles by discharging the foaming agent out of the space in the low-pressure vessel with controlling the pressure in the low-pressure vessel to substantially a given pressure. According to the process, the release of the volatile foaming agent into the air is prevented.

Abstract: A process for preparing pre-expanded particles of a thermoplastic resin which comprises; heating under an elevated pressure an aqueous dispersion comprising thermoplastic resin particles containing a volatile foaming agent and an aqueous medium in a pressure vessel; releasing the dispersion from the pressure vessel into a space within a sealed low-pressure vessel wherein the pressure is lower than that in the pressure vessel, whereby expanding the thermoplastic resin particles to give pre-expanded particles; and simultaneously recovering the foaming agent volatilized from the thermoplastic resin particles by discharging the foaming agent out of the space in the low-pressure vessel with controlling the pressure in the low-pressure vessel to substantially a given pressure. According to the process, the release of the volatile foaming agent into the air is prevented.