“Green” Isocyanate: Renewable and Phosgene-Free
Title: POLYISOCYANATES FROM FUSED BICYCLIC POLYOLS AND POLYURETHANES THEREFROM
Applicant/Assignee: IOWA STATE UNIVERSITY
Publication date: 24-04-2014
“Gist”: Isocyanates from acyl azides derived from isosorbide
Why it is interesting: Fused bicyclic polyols are reacted with anhydrides to form polyacids which are converted to acyl halides which in turn are converted to acyl azides. The acyl azides rearrange to isocyanates (Curtius Rearragment). For example isosorbide is reacted with succinic anhydride, then with thionylchloride (SOCl2) to form the di-acylchloride and then with sodium azide (NaN3) to form the di-acylazide which rearranges into the di-isocyanate under liberation of nitrogen. The isocyanate can be reacted with more isosorbide to form a polyurethane. Clever chemistry but hard to judge if it is industrially viable.
Completely renewable polyurethane according to the invention . Click to enlarge.