Preparation of flexible polyurethane foam catalyzed by copper-amine and zinc-amine complexes

Abstract

In this research, catalysts for flexible polyurethane (FPUR) foam preparation were developed in order to reduce the use of the expensive commercial catalysts. These catalysts were metal-amine complexes, namely M(OAc)₂(Y)₂, where M = Cu and Zn; Y = ethylenediamine (en), triethylenetetramine (trien) and diethylamine (dea). M(OAc)₂(Y)₂ could be synthesized from the reaction between metal acetates and amines using ethylene glycol as a solvent. UV-visible spectroscopy and mass spectrometry were used to characterize the metal-amine complexes. FPUR foams were prepared by the reaction between methylene diphenyl diisocyanate prepolymer (MDIP) and ethylene oxide triol in the presence of metal-amine complexes as catalysts. The catalytic activity was compared with that of commercial catalyst, namely 1,4-diazabicyclo(2.2.2)octane (Dabco® EG) by investigation of the reaction time, physical and mechanical properties of FPUR foams. The experimental results showed that the solution of M(OAc)₂(Y)₂ in ethylene glycol could be easily dissolved in the raw materials of FPUR foam formulation. Cu(OAc)₂(en)2 had the highest catalytic activity, however, the foam had low density. When Dabco® EG: Cu(OAc)2(en)2, which was a mixture of Cu(OAc)₂(en)₂ and Dabco® EG at the mole ratio of 0.50 : 0.50 was used as a catalyst, higher catalytic activity than Dabco® EG or Cu(OAc)₂(en)₂ was obtained. Dabco® EG:Cu(OAc)₂(en)₂ gave the foam having good physical and mechanical properties. Therefore, Dabco® EG:Cu(OAc)₂(en)₂ was a suitable catalyst for FPUR foam.