| 摘要 |
Processes and apparatus for extruding a tubular film of polymer material. The apparatus comprises a circular coextrusion die having an inlet (10) for the or each component and having an exit channel (18) ending in a circular exit orifice (21) which is located radially outwardly from the die axis compared to the inlet (10). The die comprises several planar or conical die parts (5, 6, 7, 28, 29) clamped together, with surfaces supplied with grooves (14) shaped to form channels (11, 12, 13) for the flow polymer material. The shape of the channels is adapted to equalize the flow over the circumference of the exit orifice (21), and the flow of material is divided between the inlet (10) and the exit (21) into a number of part flows (13) of generally helical form with space (15) provided for overflow of material between said part flows, whereby the part are adapted so that they join to one common, circular flow. |
