Method for producing semifinished plasticized PVC products

A method for extruding a polymer composition to form an extruded homogeneous polymer comprised of (A) 30 to 80 wt % of polyvinyl chloride, (B) 0.5 to 5 wt % of a stabilizing additive, (C) 0 to 40 wt % of a solid constituent, and (D) 5 to 40 wt % of a plasticizer, liquid at room temperature, for the polyvinyl chloride, where the figures in wt % are based in each case on a total weight of the polymer composition, where the method comprises

• (I) feeding polyvinyl chloride in an uncompounded form and the stabilizing additive into an extrusion apparatus through a first inlet, wherein the extrusion apparatus has a drive unit, has at least one rotor, and has at least three kneading and/or mixing zones, wherein the first inlet is disposed in a vicinity of the drive unit and adjacent to a first conveying segment section of the at least one rotor;
• (II) feeding the plasticizer to the polyvinyl chloride mixed with the stabilizing additive through at least two inlets at a distance from one another, the plasticizer being added in at least two portions each of about 20-80 wt %, based on a total weight of the plasticizer, to the polyvinyl chloride, there being at least one of the kneading and/or mixing zones disposed between the addition of the individual portions,
• (III) working the plasticizer/polyvinyl chloride mixture at a temperature of or above the glass transition temperature of the polyvinyl chloride, the temperature of the mixture not exceeding 150° C., until the plasticizer has been incorporated substantially completely into the polyvinyl chloride,
• (IV) optionally feeding the solid constituent to the polyvinyl chloride mixed with the plasticizer in a section at which at least 80 wt % of a total amount of the plasticizer has been incorporated into the polyvinyl chloride,
• (V) optionally devolatilizing the mixture, and
• (VI) extruding the mixture through an extrusion die of the extrusion apparatus, wherein the extruded homogeneous polymer has a degree of gelation of 5% to 80%, an elongation at break of 0 to 270%, and a tensile strength of at least 1 N/mm2, and
• wherein quantity of energy introduced into the polymer composition by the extrusion apparatus during the method, as indicated by the specific energy input (SEI), is 0.03 to 0.09 kWh/kg.