Abstract: In a process and apparatus for the discontinuous production of preforms for producing hollow bodies from thermoplastic material, the wall of which is a laminate having at least first and second layers, by extrusion blow molding, the flow of material for forming the laminate is guided within the extrusion head which serves to produce the preforms, by suitable dimensioning of the volume of the duct system accommodating the laminate, such that regions of disturbed laminate occur in the end portions of the preform which are squeezed off the extruded preform by the blow molding mold as a waste portion.

Abstract: In a process and apparatus for the production of hollow bodies from thermoplastic material, having a wall of a laminate formed by at least first and second layers, by means of extrusion blow molding, a preform having a wall structure with a suitable number of layers is first produced in a batch-wise procedure using an extrusion head. The material required to produce the preform is guided in the extrusion head in such a way that disturbed portions of the laminate pass into the waste flash portions at the ends of the hollow body produced from the preform, so that the wall of the finished hollow body is devoid of disturbed laminate portions of that kind.

Abstract: In a process and apparatus for the production of hollow bodies from thermoplastic material, the walls of the hollow bodies are of a laminate structure having at least first and second layers, by means of extrusion blow molding, the pressure within the extrusion head and more particularly at the location at which the laminate is formed by the discharge of flows of material from a storage chamber in the head is maintained within limits such as to avoid disturbing the laminate to such an extent as to have an adverse effect on its function. The pressure at the time of a transition between filling and emptying of the storage chamber and between emptying and filling of the storage chamber is maintained substantially at a pressure level which approximately corresponds to the storage chamber emptying pressure.

Abstract: A barrel of thermoplastic material has at least one connecting portion having an emptying opening and arranged in a trough-like depression in the upper end part of the barrel. In the region of the connecting portion the barrel has at least one inclined surface which extends between the upper end part of the barrel and the side wall of the barrel. The inclined surface is of such a configuration that in a barrel emptying position the emptying opening forms the lowest part of the interior of the barrel to permit at least almost complete emptying of the barrel.

Abstract: The invention concerns a process and an apparatus for the production of hollow bodies from thermoplastic material, the wall of which is in the form of a laminate, by extrusion blow molding. Tubular preforms for making the hollow bodies are first produced in an intermittent mode of operation, the wall thereof also being in the form of a laminate which includes a suitable number of layers. Within an extrusion head having an annular storage chamber for receiving the laminate-formation preform and an annular piston for emptying the storage chamber, the flows of material for forming the layers of the laminate of the preform are passed through the annular piston into the storage chamber in which they combine to form the laminate. The width of the outlets at which the flows of material issue from the annular piston can be so selected that it is proportional to the thickness of the respective layers to be formed therefrom in the laminate produced in the storage chamber.