PIR recycling by alkaline cleavage

Applicant: RECTICEL
Inventor(s): Dirk De Vos; Thomas Vanbergen 
Patent number: WO2024133871A1    
Publication date: 2024-06-27

The innovation pertains to an enhanced technique for the reprocessing of polyisocyanurate (PIR) materials derived from a minimum of one polyol compound and a minimum of one methylene diphenyl diisocyanate based compound.

Rigid polyurethane (PUR) and polyisocyanurate (PIR) foams are commonly used as thermal insulation boards in building and construction applications, including walls, roofs, and floors. These materials are lightweight and have low thermal conductivity. 

They are produced through an exothermic reaction of polyol with isocyanate in the presence of a blowing agent. Scrap generated during manufacturing or application can be recycled by grinding it into powder and using it as a filler in new foam production. 

An alternative method for recycling PUR foam scrap materials is outlined in DE 10019662 A1. In this process, the industrial residues or scrap from the production of PUR are crushed, ground, and mixed with water and an isocyanate under high pressure and temperature to create panels. These panels can then be used as heat or sound insulation sheets in construction. The majority of rigid PUR and PIR scrap materials come from end-of-life (EoL) PUR foam and PIR foam. The primary waste processing methods for EoL PUR and PIR foam involve incineration and landfill. However, these disposal techniques not only contribute to environmental pollution but also result in economic losses due to the permanent loss of valuable materials. Therefore, the focus is on recovering and reusing these materials. While most recycling methods for rigid PUR or PIR materials aim to recover the polyol for reuse in new materials, there is still a need for a chemical recycling method for PIR materials that can successfully recover both the polyol and the amine derived from the polyisocyanate used in the original PIR materials.

This approach aims to create a sustainable circular process that minimizes waste production.

The method proposed involves recovering MDA from PIR materials and reusing it.

The process includes the following steps: (i) reacting PIR material with at least one hydroxide base in a dissolution agent at a temperature between 150 and 250 °C, resulting in a first mixture (M1) containing the MDA compound; (ii) extracting the MDA compound from the first mixture (M1) through a liquid extraction process; (iii) in the reaction mixture (M0) of Step A, the amount of at least one hydroxide base present is determined by a weight ratio of the at least one hydroxide base to the total dry weight of the PIR material, ranging from 0.01:1.00 to 0.20:1.00. 

The technique provides quick dissolution of PIR materials, enhanced reaction rates, and efficient recovery of amine compounds. This results in a sustainable closed-loop system, minimizing waste generation and allowing for the reuse of recovered compounds.