Extrusion die for tubular films

摘要

Extrusion die for tubular films comprising an outer casing and a mandrel which is arranged centrally within the outer casing, forming a melt gap of the same cross-sectional shape around the circumference, and which is formed in the region adjoining the melt inlet as a spiral distributor provided with a multiple-flighted spiral formed from flat grooves, the flow profile of the melt flowing through the gap having a number of flow maxima and minima corresponding to the number of flights forming the spiral when viewed on the gap circumference and in a normal section, the flow cross-section narrowing at the locations of the gap circumference with flow maxima and widening at the locations with flow minima in at least one normal section taken through the spiral distributor.