Polyolefinic particle foams containing additives may be produced by a process, which comprises (a) initially charging a pressure-resistant reactor with a dispersion consisting essentially of polyolefin particles and a liquid dispersion medium, and also a mixture of a volatile organic blowing agent and the additive to be introduced; (b) carrying out a heat treatment in which the polyolefin particles are impregnated with the mixture; and subsequently (c) discharging the dispersion through an orifice into a low-pressure space, thus foaming the polymer particles. The process achieves efficient incorporation of the additives into the polyolefin particles. The particle foams thus-obtained are useful for the production of moldings.

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