Polyurethane (PU) is a particularly versatile and high-performance plastic. It is used when resistance and durability are required. It is particularly suitable for foams that insulate or cushion. In house facades, refrigerators, car seats or mattresses, for example, such foams are usually in use for many years. Unfortunately, however, they can hardly be recycled afterwards. In the EU alone, for example, around 40 million mattresses end up in landfills or incinerators every year. That has to change.
Together with our colleagues from the Comfort & Insulation business line and Process Engineering, we have developed a process that allows polyurethane to be chemically recycled. Typical PU foams for mattresses are produced by reacting isocyanate (TDI) with polyether polyol and water and adding various additives. As a by-product, CO2 is released, which foams the matrix before the polymer hardens - similar to the way a cake rises in the oven. As difficult as it is to turn a cake back into butter, eggs, flour and sugar, it is also difficult to reverse the polymerization of a foam mattress - actually. However, we succeeded in this feat: Shredded old mattresses are chemically decomposed for this purpose in a hydrolysis reactor using heat, pressure and special catalysts, and then processed into pure amine, the direct precursor of isocyanate, and polyol - the basic ingredients of polyurethane.
Completely new territory
Evonik has long been the leading manufacturer of additives and catalysts for the production of PU foams. It is only thanks to such process auxiliaries that foaming and thus the properties of the finished foam can be precisely controlled. Accordingly, Evonik's Comfort & Insulation Business Line knows the processes and the market very well. "Developing the recycling process was completely new territory for us," says Emely Schweissinger, Project Lead and Technology Manager in the Product Line Comfort. "However, our competencies in Creavis make it possible to tackle completely new innovation projects as well." To this end, as the Group's business incubator, we link new research with practical user knowledge from the business. With success, as it turns out.
First pilot plant
The first pilot plant capable of recycling large quantities of mattresses is due to go on stream shortly in Hanau. Scalability is crucial: plastics play an important role in the circular economy. An EU regulation commonly known as the "Plastics Directive" stipulates that from 2025 onwards, certain plastic products must consist of a quarter recycled material. To be sure, this still applies primarily to single-use packaging. But durable products such as mattresses and other PU applications will inevitably follow suit. It is therefore important to make solutions ready for practical use now.