| 摘要 |
1,206,525. Multi-layer extrusion; extrusion dies. AMERICAN CAN CO. 6 Nov., 1968 [27 Feb., 1968], No. 52682/68. Headings B5A and B5B. In a method of extruding a multilayer thermoplastic film using a die having a separate flow passage for each of the layers which converge in a common passage within the die, the flow passages can be individually restricted to adjust the amount of material flowing in the passage(s) and the relative amounts of the different thermoplastic materials entering the common passage. In a preferred embodiment for extruding a three-layer film of two resins comprising an intermediate layer of polyethylene and outer layers of polypropylene, three separate screw extrusion units 21, 22, 23 are arranged to feed into a single elongated extrusion die. Each unit has a central inlet port 24 and an elongate manifold 25 connected to a source of molten resin and a narrow flow passage 26 which follows a serpentine path leading from the manifold and intersecting with the passages from the other two manifolds in common outlet passage 28. A manually adjustable restrictor bar 27 is set into and forms a part of one wall of the flow passage between manifold 25 and outlet passage 28 and controls the flow from the manifold. The position of bar 27 can be adjusted by rotating the nuts 32 carried on the ends of a row of threaded studs 31 which extend through the die section. A die lip assembly 33 mounted on the bottom of the die body comprises a pair of die lips 34, 35, and defines a continuation 28a of outlet passage 28. Left-hand lip 34 is constructed for flexure so that the die slot may be adjusted by a row of screws 36. The multi-layer extrusion die is thus capable of two separate adjustments, (i) an overall adjustment for gauge control of the composite film by means of die lip assembly 33 and (ii) individual adjustment of each flow passage 26 by means of restrictor bars 27. The extrudate may be delivered to a chill roll, as shown, or directly on to a web substrate. |
