# Experimental Tests on Solvent Solutions for the Recycling of Coated Polypropylene in Food Packaging
###### Abstract  
The aim of this research is to analyze and develop technical methods that allow the recycling of food packaging coated in polypropylene films using solvents for the removal of the lacquer and/or aluminum layer without modifying their mechanical properties. Thus, this would allow the degranulation and re-extraction of the treated material for the creation of new polypropylene films. Water solutions of KOH 1M and methanol 99.9% were tested as solvents using the selective dissolution method. In order to rule out a significant effect of the mechanical stirring action on the removal of the surface layer, a deionized water solution was used as a control sample. By means of UV-VIS-NIR (ultraviolet, visible, near-infrared), LWIR (long-wave infrared), and ATR-IR spectrophotometers, spectrophotometric analyses were carried out on the samples before and after treatment. In order to investigate the efficiency of the solvents in removing the coating of polypropylene films, samples taken from the industry Jindal Films Europe Brindisi s.r.l., named BF (basic film, pp film not lacquered or metallized), AC (aluminum-coated pp film), and ACRC (acrylic-lacquer-coated pp film), were compared with samples treated with solvent solutions. The comparison was made by comparing the spectra obtained from the analyses carried out with the two different spectrophotometers. The absorbance values at the level of characteristic polypropylene spectrum peaks, detected with an ATR-IR, were also compared using the Pearson correlation coefficient. The results suggest that the optimal solvent for removing the aluminum and acrylic lacquer from pp films is the solution of KOH 1M. Future analyses will aim to investigate the maintenance of the mechanical characteristics of polypropylene treated with a selective dissolution using KOH. It is also planned to test the methodology of this study on an industrial scale. metallized polypropylene film; lacquered polypropylene film; selective dissolution; KOH solvent solution; methanol solvent solution; plastic films; food packaging; plastics recycle 2023314 June 2023  
they offer the best shelf-life performance because contamination would be difficult, they are the cheapest option, they increase the aesthetic value of the products, and foods packaged with plastic are easier to handle, transport, and store [1]. The packaging sector in the food market plays a very important role. The main functions of packaging are the protection and preservation of food from deterioration and external contamination, such as heat, light, oxygen, enzymes, odors, microorganisms, insects, dust, etc. This prolongs the life of food and maintains the high quality of the packaged food. In addition, some secondary packaging functions that aim to make food more appealing and attractive to consumers are becoming increasingly important [2]. In contrast to these advantages regarding the efficiency of plastic as a packaging material, there are several negative aspects, mainly due to difficulties in the recycling of these materials and the various forms of environmental pollution they cause. Over the past 50 years, the production of various types and shapes of plastic has grown worldwide. Plastic has caused the generation of considerable amounts of waste. Different types of plastics are widely used in all fields, mainly in food packaging industries [3; 4]. According to Plastics Europe [5], global plastic production in 2021 reached 390.7 Mt, 44% of which belonged to packaging use. The amount of plastic production in Europe in 2021 was 57.2 Mt, including fossil-based plastics (50.1 Mt), post-consumer recycled plastics (5.8 Mt), and bio-based plastics (1.3 Mt) [5]. In 2021, polypropylene was the first polymer type for the European converter demand, with 10.0 Mt, and the European packaging industry was the first converter demand (39.6%) of global plastic production. The number of polypropylene films for food packaging produced in Europe in one year is about 5 million tons/year.