Plastics Recycling

PET Recycling

First-Class Technology for the Bottle-to-Bottle, Bottle-to-Fiber and Bottle-to-Film Process

Polyethylene terephthalate (PET) is a high-value material that is on course to take over a key function in the plastics industry’s path toward a circular economy. PET plays an ever more important role in recycling, due to the large volume of packaging materials in use today. PET posses extremely good properties for reprocessing. Its continuously expanding use in single- and reusable bottles, as well as its recovery via deposit systems, add to its value. Correspondingly, it can be lucrative for companies to focus on PET recycling.

Before PET can be reprocessed, it must first be shredded to flakes and then cleaned. Ordinary technologies require pre-drying and crystallization of the PET flakes following washing. However, using the specialized technology from Coperion, the shredded PET can be fed directly into the ZSK twin screw extruder and compounded.

Thanks to the highly efficient plastification within the ZSK extruder, Coperion systems for PET recycling achieve throughput rates up to 8 tons per hour, therefore recycling companies profit from very high product quality, operating and energy cost savings, and reduced logistic expense in comparison to conventional PET recycling methods.

Advantages of PET recycling with twin screw extruders in comparison to single screw extruders

  • Highest thoughput rates
  • Energy and time savings as pre-drying and crystallization are omitted
  • Very high quality of the end product because only a minimum iV degradation occurs during processing and the crystal clear material does not become yellowish
  • High flexibility because recipes and colors can be changed very quickly due to the good self-cleaning behavior of the ZSK twin screw extruder
  • Much simpler logistics because pelletized new product and different regenerates (ground product, agglomerates, flakes) can be processed together even if they have different iV value

PET Recycling – The Process

The shredded flakes are reliably fed into the ZSK extruder using highly accurate SWB (Smart Weigh Belt) feeders or gravimetric feeders from Coperion K-Tron. In addition, other regrind materials, new materials, or mixtures can be added. Melting, intensive devolatilization, and complete homogenization take place in the ZSK process section before the melt is transferred to the next process step for production of films, fibers, or bottles.

With direct processing of PET, recyclers profit particularly from the very high end product quality. Product handling is very gentle. The residence time in the ZSK extruder is very short and dispersion is very good. The ZSK extruders’ high torque enables processing at low temperatures and with almost no viscosity loss. ZSK extruders’ self-cleaning enables rapid recipe and color changes. Thanks to the ZSK twin screw extruder’s very good 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.

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

Coperion Bottle-to-Bottle Recycling Process
Typical set-up of a recycling system for economically processing PET flakes into PET pellets that can be used in turn to manufacture bottles

New Bottles From Old Bottles: Economical and FDA-Compliant Bottle-to-Bottle Recycling

Marina Matta, Process Engineer, Coperion

“With FDA certification, we have officially confirmed the high product quality of the PET recyclate.”

Marina Matta, Process Engineer, Coperion Stuttgart

Using Coperion’s innovative technology PET flakes can be processed into bottles once again. Melting, intensive devolatilization, and complete homogenization take place 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.

Next the pellets are condensed in the SSP (Solid State Polycondensation) reactor, and can be reprocessed back into bottles again with the quality of virgin material.

PET recyclate manufactured using this innovative process has received approval from the United States Food and Drug Administration (FDA) for food-contact uses. The pellets’ quality meets the requirements of virgin material. They have received FDA Letter of Non Objection which certifies that they meet the standards for food-safe plastics and thus, can be processed into bottles once again.

COMPREHENSIVE PRODUCT RANGE

Twin screw extruders

Coperion's ZSK twin scew extruders are particularly suitable for the PET recycling processes due to the excellent homogenization and devolatilization properties. The ZSK twin screw extruder can process the PET while being essentially non-dried, and devolatilize the melt with a low energy expenditure.

ZSK Mc¹⁸ Twin Screw Extruders
B_SWB_detail

Feeding Equipment

Coperion K-Tron offers a variety of feeding solutions for plastics processing. Each technology has its own advantages – what is decisive is the process know-how that brings operational requirements and processes together. Smart Weigh Belt Feeders can reliably feed large volumes of bulk material and materials with varying flow properties, since they weigh the bulk material prior to discharge and actively adapt belt speed. Vibratory Feeders are an ideal solution where smaller recyclates or flakes are being fed, or if glass fiber is added into compounding processes. Twin Screw Feeders are ideal for the precise feeding of finer bulk materials, and are therefore often used for additives.

Material Handling

Coperion and Coperion K-Tron offer an extensive line of pneumatic conveying systems and components for the transfer of a wide range of bulk materials, such as additive powders, resin pellets, recyclates, stabilizers and colors. Our experienced global team can support you in designing, replacing, or modernizing the material handling system for your process line, taking the guesswork out of the process.

Service

We provide standardized and highly customized service packages for our machines and equipment. Our comprehensive range of services secures maximum plant reliability and lifetime.

Service

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