Abstract: Thermoplastic mixtures suitable for foaming in the extrusion or injection molding process consisting of polymerizate mixtures of (A) from 50 to 95% by weight of a vinyl chloride polymerizate prepared by free-radical polymerization selected from the group consisting of (1) bulk polymerization and (2) emulsion and suspension polymerization with continuous agitation, of vinyl chloride containing up to 20% by weight of ethylenically-unsaturated monomers copolymerizable with vinyl chloride and (B) from 5 to 50% by weight of a vinyl chloride polymerizate prepared by polymerization of a stable, aqueous monomeric dispersion of vinyl chloride containing up to 20% by weight of ethylenically-unsaturated monomers copolymerizable with vinyl chloride prehomogenized in the presence of emulsifiers and oil-soluble catalysts, and a foaming agent.

Abstract: An apparatus for the production of extruded profiles of foamed thermoplasts consisting of an extruder having an extrusion screw and a form-giving extruder head having a flow channel therethrough characterized in that at least part of the length of said flow channel is divided by separating walls having a thickness of 0.2 to 3 mm arranged in the axial direction into individual channels of such a length and cross-section area whereby each individual channel has a nozzle coefficient k of from 0.1 to 2 mm.sup.3 ; as well as the process of extrusion.