Injection molding equipment maker Engel has developed a process that eliminates the pelletizing step in plastics recycling, making it possible to process plastic waste as flakes in injection molding immediately after grinding. In addition to improving the CO2 footprint, the process also significantly reduces recycling costs, said Engel. The company presented the technology during its virtual symposium held from June 22 to 24.
The two-stage technology separates plasticizing and injection molding into independent but aligned process steps, explained Engel. “In the first stage, plastic flakes originating from post-consumer collection are melted in a conventional plasticizing screw. In the second stage of the process, the melt is transferred to a second screw for injection into the cavity. The two-stage process makes it possible to integrate a melt filter and a degassing unit on the injection unit side of the molding machine, so that products with a consistently high quality are obtained, even from contaminated plastic flakes,” said Engel in a news release.
Alternatively, the plasticizing screw can be combined with a piston, added Engel. This variation on the two-stage process is suited for processing shot weights up to 160 kg at comparatively low injection pressure. It enables a more compact system design and lower unit cost than a conventional single-stage plasticizing and injection process.
Engel added that it has developed a new piston design to improve the performance of piston injection units when changing materials. The rheologically optimized piston tip supports uniform flushing, enabling rapid material and color changes.
Applications include containers, pallets, and, in some cases, large fittings. The technology accommodates shot weights starting at 20 kg.