High-performance logistic equipment from PET mixture fraction - LogiPET

Aims

This project is funded within the activity "integrated environmental protection in the packaging industry" within the environmental research programme of the Federal Ministry for Education and Research (BMBF).

PET is finding increasing use in a variety of packaging applications (e.g. drinking bottles, foils, trays). The treatment and recycling processes currently available on the market are designed for pure PET waste. In these "bottle-to-bottle" processes, pure PET bottle waste is used for the production of new bottles, which must meet strict requirements regarding their contact with food products. In order to recycle mixed PET waste collected as part of Germany's waste separation policy (DSD), a new method has been developed. This allows PET, with its excellent properties, to be used as a secondary raw material for high-quality products in the increasingly important logistics sector.

Research

Mechanical treatment of the DSD PET fraction is the first step towards creating a processable starting material. Suitable processes such as comminution, cleaning and separation of unwanted materials such as labels, PVC and metals must be selected and applied to the starting material on a semi-industrial scale.

For the processing of the treated PET grinding material, an extrusion and processing method was developed and adjusted to take account of the influencing factors. Various degassing concepts were investigated. As regards the choice of additives, emphasis was placed on hydrolysis protection methods, thermal stabilisers and impact-resistance.

Results

In the context of the project it was demonstrated that the DSD PET fraction could be mechanically processed to create a processable PET mixture fraction with a low content of unwanted materials.

The processing of the PET mixture fraction using a unit configuration with two separate vacuums allows compounding to be carried out without significant damage to the material. The relative molar mass of the regranulate after compounding is at the level of the starting product. This unit configuration enables PET to be processed without the need to dry the material or the need for postcondensation subsequent to extrusion to increase the relative molar mass. The introduction of additives to protect the material against hydrolysis means that relative molar masses above those of the starting material can be achieved. Impact strength modifiers allow the mechanical properties to be adjusted to the requirement profile.

Due to its significant material properties in terms of the abovementioned results, new application fields are opening up for the generated PET reclaim. Besides the logistics sector, possibilities include the automotive and electronics industry.

Diagram 1: Composition of mixed waste

Diagram 2: Configuration of unit for processing undried PET waste