| http://www.w3.org/ns/prov#value | - The extrusion system according to claim 1 wherein the die is a coaxial tube coextrusion die, whereby the extrudate, due to repetitive variations of the relative speeds of the gear pumps, is formed with inner and outer distinct coaxial layers of the first and second kinds of materials respectively, the layers varying in thickness repetitively along the length of the extrudate.
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