Recycling of Rigid Polyurethane Articles and Reformulation into a Variety of Polyurethane Applications

Abstract

Recycling of thermoset polymeric materials offers a unique challenge. It is often assumed that thermoset materials in general, and polyurethanes specifically, are not recyclable or only recyclable in limited applications as regrind. Herein, we report the recyclability of polyurethane materials by glycolysis and recovery of a polyol. The glycolysis technology utilized is unique in that the residual free amine content is very low, and the entire reaction mixture is useful as a urethane polyol. This is in contrast to other glycolysis technologies that involve separation steps and ultimately in the production of other more hazardous waste streams. The reaction proceeds at ambient pressure and moderate temperature obviating the need for highly sophisticated control mechanisms. The recyclate properties are relatively insensitive to the waste stream utilized, thus permitting the mixed waste streams as raw materials in the process.

In this investigation, high density non-cellular rigid urethanes have been successfully glycolyzed and formulated into a variety of polyurethane systems. These include applications in energy management technology, as well as other rigid and semi-rigid applications. Inclusion of the recyclate shows little detriment to the physical properties of the resulting polyurethane in a variety of applications.

An example of a closed loop recycling strategy is demonstrated in rigid insulating foam. A cyclopentane blown rigid polyurethane can be glycolyzed and the resulting polyol incorporated into the original system at up to 20% of the polyol component with excellent dimensional stability and thermal conductivity results. Up to 100% replacement shows little sacrifice in physical properties.

Preliminary laboratory results also show excellent potential for both rigid insulation foam and high density, rigid, non-cellular polyurethanes to be amenable to the glycolysis process.

This paper describes aspects of our efforts to meet the challenge posed by an increasing number of our customers to render polyurethanes readily recyclable.