CHRONICLE

The project CHRONICLE aims to develop and optimize a novel chemical recycling approach for polyurethane materials (PU) based on chemolysis with ammonia/amines. The process will allow selective depolymerization of these materials into valuable diols, while simultaneously converting the nitrogen-containing fraction into functional building blocks, being urea, diamines, and/or urea-diamine compounds depending on the process. To secure the sustainability of the new technological route developed, CHRONICLE also targets to develop and validate a process model that will allow to guide the separation and purification of the building blocks and enable a first techno-economic assessment & life cycle assessment. 

The extensive use of polymers causes the production of several million tons of waste plastics (29.1 Mt/y in 2020 in the EU) of which only 34.6% are recycled. Most of the recycling techniques are still based on mechanical methods that necessitate high feedstock purity and produce lower-performance materials. An alternative recycling method, that is especially promising to treat heteropolymer-based materials, concerns selective depolymerization. This type of chemical recycling process is unique because it allows the production of functional compounds that can be reused within the polymer cycle or employed as building blocks to design new materials. Nitrogen-containing polymers, primarily dominated by PU, are a prominent class of heteropolymers. They constitute around 10% of the total plastics demand in 2020, mainly due to their versatile use in sectors such as automotive, textile, building, and construction. Therefore, having efficient recycling solutions available for these types of materials is crucial, enabling the realization of the target set by Moonshot Flanders to achieve the recycling of 60% of the post-consumer volume of heteropolymers by 2030.

The chemical recycling of PU-based materials currently mostly focuses on depolymerization based on glycolysis. Although this process can efficiently treat flexible PU, important challenges still remain. These include (i) high (energy) cost to isolate the glycol from the reaction mixture, (ii) difficulty to treat rigid PU or mixtures thereof, and (iii) limited valorization of the full material, i.e., more specifically the product fraction linked to the isocyanates especially important in isocyanate-rich materials such as polyisocyanurate (PIR).

To provide answers to these challenges, CHRONICLE aims to develop a unique and innovative solution for the treatment of PU-based materials, including rigid PU and PIR, based on depolymerization via chemolysis with ammonia or diamines (ammono- and aminolysis, resp.). This approach has important conceptual advantages for the treatment of these types of materials. These include (i) the production of less complex reaction mixtures, (ii) maximizing the valorization of recyclates through the conversion of the nitrogen-containing fraction into valuable compounds (diamines, urea, or urea-diamine depending on the approach), (iii) allowing tailored solvent selection, allowing to improve solvent diffusion into rigid PU materials and reducing separation costs. Moreover, the use of amines as nucleophiles is expected to allow milder process reaction conditions, possibly even catalyst-free.