Abstract: A die, associated with an extruder and provided with an inwrought flow channel with displacement cores for shaping a plasticized synthetic resin bulk stream into a profile cross-section with hollow chambers, has a die housing that is composed of several die members with vertical and/or horizontal mold joints. The displacement cores in the flow channel are connected to the die housing by core-holding webs that separate the flow channel by distances corresponding to the thicknesses of the webs, thus subdividing the bulk stream into separate partial streams, the cross-section of the combined partial streams being equal to the cross-section of the bulk stream, and the displacement cores being enlarged by the thickness of the core-holding webs so that the partial streams, with the flow cross-sections remaining the same, are conducted along the core-holding webs.

Abstract: A process for reducing the shrinkage of profiled elements of thermoplastic synthetic resins, which normally occurs due to undesired stresses frozen in during extrusion in an extruder die and calibration in a calibrating device, involves the step of maintaining the extrusion speed of the profiled element upon exiting from the extruder die at least the same or almost the same as the calibrating speed and/or take-off speed of the profiled element during its subsequent passage through the calibrating device. Also, it is advantageous to cool selected and defined portions of the periphery of the extrudate during the initial stage of calibration within the calibrating device so that a reinforced frame or corset is formed within the extrudate.

Abstract: A process for forming a foamed thermoplastic material in which a carrier member made, for example, of a vegetable material such as lignocellulose-containing fibers or cork particles, and having bonded thereto, by either capillary bonding or molecular bonding, a gas bubble forming medium, such as water or aqueous dispersions, is added to the plastic material, whereby, when the temperature of the plastic is raised above the temperature at which the medium forms bubbles, gas bubbles, are formed and form cavities in the plastic. The carrier can also act as a reinforcing agent for the plastic.