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Abstract

A process for producing foamed particles of a polyolefin resin which comprises dispersing polyolefin resin particles in water in a closed vessel, feeding a volatile blowing agent into the closed vessel, heating the dispersion to a temperature above the softening point of the polyolefin resin particles but below their melting point, opening a discharge port provided within the closed vessel below the water surface and releasing the aqueous dispersion containing the polyolefin resin particles impregnated with the blowing agent into an atmosphere kept at a lower pressure than the pressure within the closed vessel; wherein (i) when the last portion of the aqueous dispersion containing the polyolefin resin particles impregnated with the blowing agent is released from the closed vessel, the pressure within the closed vessel is at least 5 kg/cm.sup.2.G, and (ii) in order to maintain the pressure within the closed vessel at the time of releasing the last portion of the aqueous dispersion from the closed vessel at at least 5 kg/cm.sup.2.G, a pressurized inorganic gas is introduced into the closed vessel before the heating of the aqueous dispersion is started, provided that the inorganic gas is not freshly supplied to the closed vessel after starting the releasing of the aqueous dispersion.

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First Claim