Patent ID: 9650486
Date: 2017-05-16
CPC Classifications: C08J

Claim:
1. A method for producing expanded polyolefin resin beads, comprising: a step of preparing preliminary resin particles containing a polyolefin resin having a particle weight of 5×10 a step of heat-treating the preliminary resin particles at a temperature that is higher by from 12 to 25° C. than a melting point of the preliminary resin particles, so as to produce resin particles having a peak temperature (T a step of dispersing the resin particles in a dispersion medium within a closed vessel (dispersing step); a step of impregnating the resin particles with an blowing agent at a temperature of the softening point of the resin particles or higher within a closed vessel (blowing agent impregnating step); a step of heating the dispersion medium having the resin particles dispersed therein to a temperature within a range of a temperature that is lower by 15° C. than a melting point (Tm) of the resin particles or more and less than a melting end temperature (Te) where the resin particles are completely melted, and retaining at the temperature for from 10 to 60 minutes (retaining step); and a step of, after the retaining step, controlling the temperature of the dispersion medium to a temperature within a range of from (Tm−5° C.) to (Te+5° C.), and at that temperature, discharging the resin particles containing the blowing agent from the vessel to a low pressure area, thereby expanding the resin particles, so as to provide expanded beads having two melting peaks in a DSC curve obtained by heating the expanded beads from 20° C. to 200° C. at a heating rate of 10° C./min (expanding step).