Extrusion die for multi-layer blown film

摘要

An extrusion die (1) for prodn. of multilayer blown film includes a melt feed section (12) with concentric ring elements (2, 13) the lower ends (2a, 12a, 13a) of which fit closely together upstream from the start of each melt flow channel (5) which separate the individual rings (2, 13) and combine to film a single outlet nozzle (6). Circumferentially spaced recesses in the ring (2, 13) surfaces hold centering elements (11) which rest on the bases of the recesses and are made from material with a greater coefficient of expansion than the melt feed section (12) and ring elements (2, 13).