| 摘要 |
<p>1514592 Extruding scrap plastics DEERFIELD PLASTICS CO Inc 2 Feb 1976 04073/76 Heading B5A A thermoplastics mixture, comprising ground scrap and virgin pellets, is extruded from a single or multiple screw extruder by feeding the scrap and virgin pellets to the extruder barrel separately, at respective upstream and downstream inlets 26, 25, which are spaced apart by at least one turn of the screw flight to enable compression and reduction in volume of the scrap, so that a void is formed in the volume of scrap in the screw channel, for the admission of the virgin pellets from the inlet 25. The process enables uninterrupted extrusion upon blockage of the feed of the scrap, by the screw channel then being filled by the virgin thermoplastics from inlet 25. The scrap and virgin material may comprise the same or different thermoplastics, e.g. medium or low density polyethylene, or polypropylene, and the scrap may be fed to its inlet 26 admixed with virgin polymer in a weight ratio of 1 to 6:1, to yield at least 20% by weight of scrap in the extruded mixture. In the embodiment, blown tubular film is extruded and scrap film from rolls 11 is ground in grinder B and, optionally including virgin pellets of the same or different thermoplastics admixed at 16, is delivered to a cyclone hopper 19 feeding the inlet 26, by a blower 17 which enhances gravitational feed of the scrap. The virgin plelets are gravitationally fed to inlet 25, from a hopper 23. The scrap, or its admixture, is fed in amount to fill 40 to 70% of the screw flights after its compression. The inlets may be spaced apart by up to 3 turns of the screw flight and the inlets 26, 25 may be of an area ratio of 2 to 4, or 6 to 1, and may respectively be rectangular and circular. The extruder may comprise a single, or a multiple screw.</p> |
