Mechanical Film Recycling

Q: What film grades can be processed in a mechanical film recycling line?
A: Modern mechanical film recycling lines can process a wide range of film grades, including post-industrial and post-consumer materials. While the same recycling line can handle different film types, the quality of the incoming material ultimately influences the quality of the recycled pellets produced. However, advanced processing technologies can significantly enhance recyclate quality. Herbold's washing, separation and drying technologies help remove contaminants and prepare a wide range of film waste streams for downstream processing. Building on this, Coperion’s twin screw extruder technology provides excellent homogenization, efficient devolatilization, and reliable melt filtration, helping to remove contaminants, improve material consistency, and produce higher-quality recycled pellets even from challenging input streams.

Q: How much contamination can film waste contain for mechanical recycling?
A: For optimal recycling performance and high-quality recycled pellets, contamination levels such as paper, sand, stones, and dirt should generally remain below 1% for the material stream that is fed into the extruder. Excessive contamination can negatively impact extrusion process efficiency and recycled resin quality. Herbold washing lines help reduce contamination through technologies such as pre-washing, hydrocyclone density separation and drying, preparing challenging film waste streams for downstream extrusion.

Q: Can printed PE films be mechanically recycled?
A: Yes. Printed PE films can generally be mechanically recycled. The recyclability depends on the type and amount of printing inks used. Herbold washing and optional hot washing technologies can help remove surface contamination and adhesive residues from printed films prior to extrusion. Thanks to intensive devolatilization and degassing during extrusion volatile sustances are removed effectively so that even heavily printed film production scrap can often be successfully recycled.

Q: Can stretch films, agricultural films, and household films be processed and recycled together?
A: Yes. Different PE film grades such as stretch films, agricultural films, and household films can be processed together. After washing and contaminant removal in the Herbold process, twin screw extruders provide excellent mixing performance, enabling these materials to be blended efficiently into a homogeneous recycled product.

Q: When is hot washing recommended?
A: Hot washing is recommended for film waste streams containing adhesives, labels, organic residues or other persistent contaminants. By combining controlled temperature, retention time and additive dosing, hot washing helps improve material cleanliness and film transparency while supporting the production of higher-quality recyclates.

Q: How can lightweight film flakes efficiently be fed into the extrusion process?
A: Lightweight films can be fed directly into the extrusion process using a combination of a weight belt feeder and the Coperion ZS-B MEGAfeed side feeder. This reduces additional process steps and investment costs while improving energy efficiency and minimizing material degradation.

In addition, gravimetric feeding technology provides further process and economic advantages. By continuously controlling and maintaining a precise feed rate, it ensures consistent processing conditions, which helps achieve stable product quality. Gravimetric feeding also enables highly accurate recipe control, minimizing the consumption of costly additives. 

Q: What melt flow rate (MFR) range can the recycling process maintain?
A: Typical film grades have an MFR between 0.3 and 3 g/10 min. With the appropriate twin screw configuration, the process can be adapted to maintain virtually any target MFR, ensuring consistent recycled resin quality.

Q: Can NIAS (Non-Intentionally Added Substances) be reduced during mechanical film recycling?
A: Yes. Advanced devolatilization and degassing technology in twin screw extruders can remove a wide range of unwanted substances from the polymer melt, including both low- and high-molecular-weight compounds. This helps reduce NIAS levels and improve the quality of the recycled resin.