Coperion unveils FDA-compliant recycling tech for energy-efficient rPET bottle production

13 Jul 2021 --- Coperion is unveiling its ZSK twin-screw extruders for PET bottle-to-bottle recycling. The system condenses shredded PET in a Solid State Polycondensation (SSP) reactor and feeds it directly into a twin-screw extruder, eradicating the more energy-intensive industry norm of pre-drying the material into pellets.

The US Food and Drug Administration (FDA) has approved the process for food contact applications.

The bottle-to-bottle recycling process achieves throughput rates between 2-8 tons per hour through a highly-efficient plastification within the ZSK extruder.

Coperion says its ZSK twin-screw extruders enable recyclers to profit from high product quality, reduced operating and logistic expenses, and up to 30 percent cost savings compared to conventional PET recycling methods.

Demand for recycled PET is growing. Notably, the EU’s Single-Use Plastics Directive targets include incorporating 25 percent recycled plastic in PET beverage bottles from 2025, extending to 30 percent in all plastic beverage bottles from 2030.Coperion ZSK twin screw extruders provide enhanced devolatilization with short residence times in the process section, as well as high dispersion, contributing to high end product quality.

The legislation also requires a 77 percent separate collection target for plastic bottles by 2025, increasing to 90 percent by 2029.

Plastics Recyclers Europe recently told PackagingInsights the new measures give the plastic recycling industry the confidence to continue investing in higher quality recycling.

Efficient bottle-to-bottle recycling
Coperion highlights that PET is a high-value and highly recyclable plastic and plays an increasingly important role in recycling, especially as its use in single and reusable bottles continues to grow. PET bottles are also recovered via deposit return schemes in numerous countries.

Before PET can be reprocessed, it must first be shredded to flakes and then cleaned. Standard technologies require pre-drying, crystallization or agglomeration of the PET flakes after washing.

However, Coperion’s specialized technology allows the shredded PET to be fed directly into the ZSK twin screw extruder and compounded.The high-accuracy Coperion K-Tron SWB feeder precisely feeds PET flakes into the extruder.

The shredded flakes are fed into the ZSK extruder using high-accuracy Smart Weigh Belt (SWB) feeders or gravimetric feeders from Coperion K-Tron.

Additionally, other regrind materials, new materials, or mixtures can be added. Melting, intensive devolatilization, and complete homogenization occur in the ZSK process section before the melt is transferred via a gear pump and filter with an automatic screen pack changer to a strand or underwater pelletizer for pellet production. Pellets are then condensed in an SSP reactor for virgin-quality, food-grade material.

Flexible color changes
The ZSK extruders’ high torque enables processing at low temperatures and with almost no viscosity loss, while self-cleaning enables rapid recipe and color changes.

Due to the ZSK twin screw extruder’s enhanced devolatilization options, volatile components such as monomers, oligomers, and water are reliably removed and channeled away from the exhaust flow in suitable separators before discharging the process section.Typical set-up of a recycling system for economically processing PET flakes into PET pellets for manufacturing bottles.

Alongside the high product quality, direct processing of PET flakes offers further advantages, including reduced operating costs and energy consumption and lower logistic expense.

“With FDA certification, we have officially confirmed the high product quality of the PET recyclates,” reiterates Jochen Schofer, business segment manager for recycling and direct extrusion at Coperion.

“With the Coperion solution, we make a technology available to recyclers that is economical and at the same time allows them to make a decisive contribution to the plastic industry’s path toward a circular economy.”

Last year, Coperion developed a closed-loop concept for flexible multi-layer film production in which up to 100 percent of waste can be reprocessed and fed back into production.

By Joshua Poole