Method for separating and recovering polyethylene and aluminum from a polylaminate material

The invention relates to an innovative treatment of food packaging residues (polycoupled). In particular it refers to a method for separating and recovering polyethylene and aluminum, using innovative, recyclable and low cost solvents.

Title of the patent Method for separating and recovering polyethylene and aluminum from a polylaminate material
Thematic area Chemistry and biotechnology
Ownership Alma Mater Studiorum – University of Bologna
Inventors Paola Galletti, Danilo Malferrari, Chiara Samorì, Emilio Tagliavini.
Protection Europe
Licensing status Available for licensing agreements
Keywords Recycle, polyethylene, aluminum, food packaging, Swithchable solvents
Filed on Nov 14, 2016

The polylaminates packaging systems are very versatile materials largely exploited in the food industry. With the increase in the number of applications, the volume of these laminates in municipal solid waste has grown steadily, and their recyclability is becoming an environmental and socio-economic problem.

Since LDPE and aluminum recovery would be very advantageous, different techniques have been developed, both laboratory and pilot plants scale. These different techniques into thermal mechanical and chemical processes can be grouped.

The thermal approach (for example, incineration, plasma or pyrolysis) aims to generate energy and recovery of aluminum. The quality can be affected by the formation of a high percentage of aluminum oxide and pyrolysis residue.

The mechanical technology is mainly based on the exfoliation of the multilayer material also using chemicals such as aqueous mixtures, surfactants, organic solvents or acidic solutions.

Finally, the chemistry strategy is based on solubilization of the LDPE and the precipitation of aluminum, followed by separation and recovery of the LDPE by evaporation of the solvent or after adding an anti-solvent. In the latter case, few are solvents able to effectively dissolving the LDPE (for example toluene and xylenes); among these, the use of vegetable oil is one of the most environmentally sustainable options, despite the fact that chloroform or alcohols are then required for the removal of oil residues from LDPE and aluminum. The quality and purity of the recovered materials (Al and LDPE) strongly influences their commercial value.

The invention relates to a new technology based on switchable hydrophilic solvents (SHS) for the separation and recovery of low density polyethylene (LDPE) and aluminum from food packaging (polycoupled). The new method, fully sustainable, allows the recovery of both materials in high amounts (> 99% for aluminum and> 80% for polyethylene) and good quality (≥ 86% of non-oxidized aluminum). The invention belongs to the chemical approaches for separating LDPE and aluminum from shredded polylaminate residues.

Main advantages provided by the invention:

- Separation and recycling of both polylaminate packaging components with good yield and good properties;

- Closed loop with complete recovery of the reactants;

- Little aggressive reaction, low pressures and temperatures;

- Separation and recovery of polylaminate (Al and LDPE) in good quantity and quality. Low cost reagents recycling and easy realization of the procedure;

- Recycling of raw materials for food packaging.