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 to selectively depolymerize 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 selected process. Moreover, CHRONICLE targets to formulate these recycled depolymerization products in combination with CO₂ to produce non-isocyanate olyurethanes 

(NIPUs), a green alternative for polyurethanes, and to evaluate the recyclability of the new materials. 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 to 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 (NCPs), primarily dominated by 

PU, are a very important 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. It is therefore of utmost importance to have efficient recycling solutions available for these types of materials, which would enable to realize the target set by the Flanders Industry Innovation Moonshot to achieve the recycling of 60% of 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 treat efficiently flexible PU, still important challenges remain. These include (1) high (energy) cost to isolate the glycol from the reaction mixture, (2) difficulty to treat rigid or mixtures of PU, and (3) limitations to valorize 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 amino-lysis). This approach has important conceptual advantages for the treatment of these types of materials. These include (1) the production 

of less complex reaction mixtures, (2) maximize the valorization of recyclates through the conversion of the nitrogen-containing fraction into valuable compounds (diamines, urea, or urea-diamine depending on the approach), (3) allowing tailored solvent selection, allowing to improve solvent diffusion into rigid umaterials and reducing separation costs. Moreover, the use of amines as nucleophiles is expected to allow milder process reaction conditions, possibly even catalyst-free. On the path to circularity, the second target of CHRONICLE is to chemically modify and reformulate ALL the recycled depolymerized mixtures in combination with CO₂ into NIPUs for applications focusing on self-blowing foams (mimicking the conventional PU foaming) and adhesives. By capitalizing on the intrinsic features of NIPUs (dynamic and exchangeable bonds) enabling their reprocessing, even for thermoset materials, the recyclability of the new materials will be evaluated via mechanical recycling. As second recycling scenario, these NIPU materials will re-enter the CHRONICLE chemical depolymerization loop. To secure the sustainability of the new technological route, a process model will be developed and validated, which will be used to guide the separation and purification of the building blocks, and to enable a first techno-economic assessment & life cycle assessment.