Urethane reaction kinetics of butanediols catalyzed by Zr(acac)₄

Abstract

The urethane reaction of isocyanate was carried out with zirconium acetyl acetonate (Zr(acac)4) as catalyst. 1,2‐Butanediol and 1,4‐butanediol were used as model compounds to investigate the reaction kinetics. It was shown that hydroxyl groups in 1,2‐butanediol appeared to have different reaction rate when reacting with phenyl isocyanate, which was labeled as kfast and kslow. It was very surprising that the reaction rate of 1,4‐butanediol (kcon) was very similar to the value of kslow at the same temperature although there is only primary hydroxyl group in its molecule. Furthermore, activation energy (Ea), activation enthalpy (ΔH), and activation entropy (ΔS) for the reaction were calculated out, from which some catalytic properties of Zr(acac)4 were revealed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Green Catalysts for Reprocessing Thermoset Polyurethanes

“…Here, we investigate zirconium acetylacetonate [Zr­(acac) 4 ] and zirconium tetrakis­(2,2,6,6-tetramethyl-3,5-heptanedionate) [Zr­(tmhd) 4 ] to reprocess PU thermosets (Figure ). Lewis acidic Zr catalysts have been used to facilitate carbamate exchange and gelation of bulk PU networks and are thought to be more sustainable and less toxic to humans and the environment than organotin compounds. − Here, both synthesized and commercial thermoset PUs were infiltrated with these catalysts, at first introduced from solution at high loading, which gave rise to reprocessable networks upon extrusion at elevated temperatures. Zr­(acac) 4 and Zr­(tmhd) 4 are both capable of rapid carbamate exchange and multicycle reprocessing.…”