Spiral fed multi-layer tubular die

An extrusion die apparatus for extruding a multiple layer tubular product including a plurality of annular die elements mounted co-axially one behind the other on a mandrel forming annular thickness control passages between the die elements and the mandrel. The die elements have inner and outer conical surfaces inclined rearwardly with respect to the longitudinal axis of the mandrel. The die elements are nested together with the outer conical surfaces of one die element facing the inner conical surfaces of an adjacent die element. The inner and outer conical surfaces form conical passages which communicate with the annular thickness control passages and a plurality of helical grooves are provided on the outer conical surface of each die element. A binary divider system is provided for distributing a molten thermoplastic material from an inlet to a plurality of outlets communicating with said grooves on each die element.