Extruded material edge scrap recycling appts. - has secondary extruder for feeding scrap into main extruder

摘要

In an appts. for continuous direct reintroduction of borders into an extrusion circuit, having a secondary extruder (8) which is fed with the borders and which delivers into a main extruder (2) fed with fresh granules. A border and scrap combining station (A), forming a tensioned strand (12) of material, is located immediately downstream of the border and scrap cutting station. A station (B), for introducing the strand (12) into the barrel (7) of the secondary extruder (8), is located above the inlet opening (25) and next to the screw (13) of the secondary extruder (8). The secondary extruder (8) is divided into a first stuffing zone, which operates at below 80 deg. C and in which each screw turn has an interspace vol. equal to the drawn strand vol., and a second fusion zone, operating at the melting temp. of the material and having a reduced turn interspace vol. The main extruder (2) is equipped with a regulator for adjusting the feed rate of fresh material as a function of the pressure measured in its screw (4) upstream of the secondary extruder (8). USE/ADVANTAGE - For recycling of scrap material from edge trimming of extruded thermoplastic films. The appts. allows continuous scrap delivery to and uniform product output from the main extruder.