The wide range of performance properties of polyurethane foams makes them essential in many consumer goods. Thus, there is much effort going into creating a more environmentally friendly production process for polyurethane’s main building blocks, polyols and isocyanates. While much progress has been made across the industry to develop bio-based routes to different polyols, developing new technologies for isocyanates has proven more elusive, due in part to the presence of highly toxic phosgene and hydrochloric acid in conventional petroleum-derived isocyanates production. Now, a novel flow-chemistry approach is being demonstrated to enable a biological production pathway for isocyanates, while avoiding risks associated with phosgene.
Algenesis Materials’ (San Diego, Calif.; www.algenesislabs.com) patented technology, originally developed in the laboratory of chemistry professor Michael Burkart at the University of California San Diego (www.ucsd.edu), converts algae-based fatty acids into isocyanates via acyl azides in a continuous-flow process. “Using flow chemistry, we never accumulate large amounts of any of the hazardous intermediates. We go right from the precursor, which is a hydrazine, to the diisocyanate in flow,” explains Stephen Mayfield, chief executive officer of Algenesis. The group has used this method to make some 25 different types of isocyanates, including some that are very similar in structure and properties to toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI), which are widely used in polyurethane foams.
Isocyanates can now be derived from algae
A benefit of the bio-based isocyanates pathway is that it can provide “different physical properties to the ultimate polyurethane — lower carbon footprint, novel properties and biodegradability — than conventional fossil-based isocyanates, says Mayfield. “What’s unique about our foams is high biological content, while meeting performance specifications like rebound and tensile strength. And we are moving toward cost parity for certain consumer applications — the benefit of algae is they grow quickly and relatively cheaply,” he adds. In combination with the company’s already-established bio-based polyols production process, Algenesis’ renewable and biodegradable polyurethane materials have been utilized in footwear, phone cases and more.
Currently, Algenesis produces several kilograms per week of renewable isocyanates, and work is ongoing to scale up to 2 ton/yr in 2025. The company has also received a grant from the U.S. Department of Defense to evaluate plans for a 10-ton/yr facility.