- 07/07/2026
- Article
- Sustainability
Packaging Films: Deinking as the Key to High-Quality Recyclate
Printing inks are one of the factors that determine whether high-quality recyclates can be produced from used packaging films. The LoopCycling research project is investigating how deinking, adapted formulations and recyclable film design can help make the PCR requirements of the EU Packaging and Packaging Waste Regulation achievable for contact-sensitive packaging.
Written by Alexander Stark
The EU Packaging and Packaging Waste Regulation (PPWR) sets minimum quotas for post-consumer recyclates (PCR) in plastic packaging. For contact-sensitive packaging, such as cosmetics and food packaging, 10% PCR will be required from 2030 and 25% from 2040. These requirements present industrial recycling technologies with new challenges, as high-quality recyclates are currently available only in small quantities and usually come from separate material streams. “To achieve the PCR quotas, it is essential to be able to produce high-quality recyclate grades by recycling waste from household collection systems (yellow bag). At present, this is not possible with mechanical recycling methods for flexible packaging made of polyolefins,” emphasises Steven Zimmer, M. Sc., research associate for sustainable materials from recycling processes at the Institute for Plastics Processing (IKV) in Industry and Craft at RWTH Aachen University.
Concentrated Recycling Expertise
In the collaborative research project “LoopCycling”, a consortium of 21 companies and the Institute for Plastics Processing (IKV) at RWTH Aachen University is exploring the potential of mechanical recycling with the aim of achieving maximum decontamination. In this way, the use of recyclates from household packaging waste in contact-sensitive packaging is to be made possible. The consortium includes manufacturers of sorting systems, experts in washing technologies, manufacturers of recycling systems, suppliers of raw materials and additives, specialists in decontamination technologies, as well as processors, recyclers and well-known brand owners. “From sorting through to blown film production, the best industrially established technologies are used in every process step,” explains Steven Zimmer. Deinking, in other words the process-based removal of printing inks, is a particular focus of the project.
Which Deinking Formulation Works?
Printing inks are used especially in the field of flexible packaging to convey the required customer information and present the packaged product as attractively as possible. “In addition to the pigments they contain, it is above all the binders in printing inks that cause considerable contamination of the recyclates,” explains Zimmer. The binders currently used mostly contain nitrocellulose (NC), which degrades at temperatures above 160 °C. “This produces volatile compounds, some of which have an unpleasant odour and may even be harmful to health,” says Prof. Dr.-Ing. Achim Grefenstein, Scientific Director Circular Economy at the Institute for Plastics Processing at RWTH Aachen University and Senior Vice President Group R&D at Constantia Flexibles Holding. In addition, residues remain in the final step of degradation, darkening the recyclate and appearing as specks in recyclate films.
“Since the recycling of packaging waste inevitably takes place at elevated temperatures, upstream deinking is essential for the production of high-quality recyclates,” says Grefenstein.
Deinking is an additional processing step in mechanical recycling that takes place after cold washing. After coarse contaminants such as food residues or labels have been removed, the flakes are washed at elevated temperatures using an alkaline surfactant solution and high friction. For deinking, lye is first used, which penetrates the binder and causes the printing ink layer to swell. Supported by the surfactant, the swollen printing ink is removed from the film surface under friction and stabilised in so-called micelles. The stabilisation of the printing inks in the washing solution prevents the flakes from being re-stained.
“Current laboratory-scale investigations of polyethylene film waste have shown that an increased temperature and a longer washing time can significantly improve the deinking result,” explains Dr.-Ing. Lukas Seifert, Head of the Department for Extrusion and Rubber Technology at the Institute for Plastics Processing at RWTH Aachen University.
The choice of surfactant combination and the correct adjustment of the lye concentration are further important factors for the successful removal of printing inks. The key here is to select the suitable surfactant for the degree of contamination of the films and the suitable lye concentration for the amount of printing ink to be removed. “The friction introduced by an industrial deinking system also enables the complete removal of surface printing, even at lower temperatures and with shorter washing times,” says Zimmer.
Film Laminates as a Particular Challenge
“Since deinking requires direct contact between the printing ink and the washing solution, film laminates with reverse printing are, according to the current state of the art, hardly deinkable,” points out Prof. Dr.-Ing. Achim Grefenstein. Various approaches are currently being investigated in order to achieve complete deinking of these film systems. For example, primer layers are being used that dissolve at elevated pH levels. “In deinking, these layers cause delamination and expose the printing ink. Similarly, the printing ink formulation can also be adapted so that it can be detached even more effectively during deinking,” says Prof. Grefenstein. However, since these approaches still require the washing solution to diffuse via the cut edges of the flakes, previous trials on the deinking of these films have only been successful at very high lye concentrations.
Further research priorities are therefore currently focusing on reducing this diffusion path by process engineering means, so that film laminates can also be deinked within industrially feasible washing times and lye concentrations. At the same time, developments in the field of “design for recycling” are creating recycling-friendly alternatives for reverse-printed film laminates. Surface-printed film systems are achieving ever higher barrier effects while complying with the guidelines on the “monomaterial approach” stipulated in the PPWR,” says Prof. Grefenstein. Participation in the collaborative LoopCycling project remains possible.
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