VERFAHREN UND VORRICHTUNG ZUR DISKONTINUIERLICHEN HERSTELLUNG MEHRSCHICHTIGER, COEXTRUDIERTER, SCHLAUCHARTIGER VORFORMLINGE AUS THERMOPLASTISCHEM KUNSTSTOFF

摘要

The invention relates to a method for discontinuously manufacturing multilayered coextruded tubular preforms made of thermoplastics for forming large-volume, multilayered hollow articles in a split blow mould, in which at least two different, annular material melts are brought together centrally within the annular ram one after the other and in the direction of extrusion to form a multilayered material melt and in which this multilayered material melt flows outwardly in the shape of a funnel into an annular accumulating space and is subsequently discharged by an axially movable annular ram, which acts as a coextrusion head and is forced upwards by the multilayered material melt, via an annular die gap, so that the individual material melts are deflected out of their extrusion direction and flow radially into the corresponding flow channels before their entry into the coextrusion head. …In order to improve the known method in such a way that cross-sectional changes no longer occur in the transitional area between the respective extruder and the annular ram, so that weak points are avoided or are reduced to such an extent that they no longer have an adverse affect on the finished hollow article, it is proposed that the individual material melts are deflected out of their extrusion direction and flow radially into the corresponding flow channels of the annular ram before their entry into the coextrusion head. ……