Continuous filtering process to remove lead stabilizer from End-of Life PVC

In the focus of REMADYL Project, AIMPLAS is currently studying the removal of lead stabilizers from End-of-Life PVC, using LDH scavenger complexes, synthesized by UVEG. The removal of this lead stabilizer will be done via a continuous melt filtration process in an extruder.

Currently, several rigid PVC formulations are being tested (a virgin PVC compounded with lead, and micronized End-Of-Life PVC, both supplied by DECEUNINCK), together with different filter meshes and configuration, and extrusion parameters, in order to verify the most suitable methodology. The filter selection was done also taking into account the size of inorganic particles inherent in PVC formulations, such as Calcium Carbonate and Titanium Dioxide.

In the first filtering trial, using a single-screw extruder it was possible to filter large-size mineral fillers from PVC, including preblended LDH (without the scavenger complex). However fast saturation occurred.

Figure 1: Single-screw extruder used for first filtering trials

Results from these trials indicate that is possible to filter large-size fillers, without filter breakage, although optimization will be carried out to increase throughput. Upcoming trials include a scale-up in counter-rotating twin-screw extruder, using a screen changer to avoid saturation.

Figure 2: Filter assembly in extruder (left), filter after processing virgin PVC (center), and filter after processing virgin PVC+LDH (right)

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