Post consumed Amosorb recycling work update • CME has acquired the facilities to run full in-house recycling protocols mimicking Petcore conditions (not washing) – – Twin screw extruder SSP unit • Standard Amosorb 4020 at 2% LDR would pass the Petcore protocol at 10% additive flake level • CME has consulted Professor Norman Allen for advice on ways of reducing discoloration of polyester resins • A number of different antioxidant chemistries were proposed to CME and are being investigated • Amosorb 100 at 2% ( version with a primary phenolic antioxidant) passes Petcore protocol at their required 12. 5% level • We expect to further succeed in reducing PET discoloration with other antioxidants
Petcore Protocol
Thermal PET histories during recycling Polymers exposed to high temperatures are prone to discoloration due to thermooxidative reactions in the presence of oxygen leading to discoloration • Thermal histories of PET during recycling: 1. PET dried for approximately 4 -6 hours at 160 °C to remove moisture 2. First melt injection moulding into preforms at 280 -300 ° C 3. PET flakes are dried at 160 ° C for 4 -6 hours prior to extrusion 4. PET melt extrusion into pellets at 280 ° C 5. Solid state polycondensation of PET pellets under nitrogen at 250 -280 ° C to increase molecular weight 6. Second melt injection moulding at 280 ° C into plaques
Polymer autoxidation Cycle
Inhibited Autoxidation Cycle
Mechanism of activity: Phenolic antioxidant as radical scavengers
Phenolic antioxidants: Stabilisation via free radicals scavenging
Termination of Phenolic antioxidants
Mechanism of activity: Phosphites as hydroperoxide decomposer
Decomposition of hydroperoxides Co (ll)
Oxidation of Phosphites to phosphates
Mechanism of activity: Hindered Amines (free radical scavengers)
Hindered amines: Stabilisation via free radical scavenging mechanism
Other yellowing quenchers • • UV stabiliser Vitamins B, E, C Lactones Arylamines as primary antioxidants
Recyclability of Amosorb 100 versus Amosorb 4020 according to Petcore protocol • Amosorb 100 contains a primary phenolic antioxidant • • Amosorb 100 would just pass the Petcore protocol colour specifications at a loading of 12. 5% The standard Amosorb 4020 grade will pass at 10 % loading
Further work to improve Amosorb recyclability • Evaluate other Phenolic primary antioxidants (Cycle 1) • Investigate beneficial effect of hydroperoxide scavengers such as Phosphites-HALS (Cycle 2) • Try synergistic mixtures of the above suggested by Norman Allen • Try other materials with known benefit on colour: – Vitamin B, E – UV absorbers – Others
Autoxidation of Polymers: Main sites for hydrogen abstractions
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