Delamination of polyamide/polyolefin multilayer films by selective glycolysis of polyurethane adhesive

Abstract

Recycling of multilayer packaging is challenging due to the heterogeneity of plastic types that can be comingled by chemical bonding with adhesives. For this purpose, delamination of polyamide(PA)/polyolefin (PO) multilayers, glued together by polyurethane (PUR), was investigated. A previous method, using solvent targeted dissolution-precipitation (STRAP) for fractionation of the outer plastic layers (PO or PA) gave mixed fractions. In contrast, specifically targeting the PUR adhesive by glycolysis-depolymerization accomplished highly selective separation. A single processing step at mild temperatures in sustainable solvents based on ethylene glycol oligomers, detached the PA from the PO fraction, leading to split films without impurities. This study is the first of its kind to analyze the chemistry of delamination in depth and introduces a process that could be generally applicable for a multitude of other multilayers that are bonded by PUR adhesives.