Extrusion die and extrusion method

摘要

An extrusion head for preforms has annular feed passages (3a, 3b, 3c) for three different materials. Translucent material to produce an inspection strip is injected through a side port (8) into the passages (3b, 3c) carrying material for the outer skin at a point upstream of the junction with the passage (3a) that carries material for the body. An extrusion head for preforms has annular feed passages (3a, 3b, 3c) for three different materials. Translucent material to produce an inspection strip is injected through a side port (8) into the passages (3b, 3c) carrying material for the outer skin at a point upstream of the junction with the passage (3a) that carries material for the body. The injection port (8) has a flow divider to accurately split the flow and give a defined strip. An Independent claim is also included for a process using an extrusion head with separate flow passages and injection of translucent material into the outer layers only, before all the flows join (7) for co-extrusion. The extrusion head can be designed for continuous extrusion or include a reservoir piston mechanism for intermittent extrusion.