Abstract: The production of approximately spherical polyolefin foam particles having a coarse cell structure and a narrow cell size distribution by dispersion foaming is achieved by a process in which the reactor contents, which essentially comprise polyolefin particles, a liquid dispersion medium and, if desired, a volatile blowing agent, are first treated at a first temperature above the crystallite melting point T.sub.m of the polyolefin, and subsequently passed through a cooling device, in which the dispersion is brought to a second, lower temperature, and the polymer particles are then foamed at this temperature. The foamed particles can be converted into moldings by known methods.

Abstract: A continuous process for manufacturing foam beads using a simple apparatus, wherein the expansion agent can be easily recycled. Polymer particles and a dispersing medium are fed continuously to an unstirred mass transfer column having a high length to diameter ratio which is operated under pressure. The polymer particles and dispersing medium are subjected to thermal processing under pressure in the mass transfer column, and the resulting dispersion is sprayed into a low pressure space causing the polymer particles to expand. Accordingly, foam beads of constant quality and a uniform cell diameter and a uniform degree of expansion are manufactured without costly process means.

Abstract: Foamed polyolefin particles are prepared by dispersion foaming of components consisting essentially of polyolefin particles, a liquid dispersing agent and optionally a volatile blowing agent in a reaction system consisting essentially of a reactor equipped with a stirrer containing said components and a discharge jet, comprising the step of:gassing the components of the reactor by injecting an inert gas into the dispersion below the surface of the liquid in the reactor;and simultaneouslydischarging a three phase mixture of liquid dispersing agent, polymer particles and gas through said jet.