Preparation of rigid polyurethane foams catalyzed by delayed action catalyst derived from copper-amine complexes and carboxylic acid

Abstract

In this research, a delayed action catalyst system is used in the preparation of rigid polyurethane foams. The delayed action catalysts were synthesized from reaction between copper-amine complexes and carboxylic acids in ethylene glycol as a solvent to give the salts of copper-amine complex and carboxylic acid. Copper-amine complexes used in this study were Cu(OAc)2(en)2 and Cu(OAc)2(trien) (where en = ethylenediamine and trien = triethylenetetramine). Carboxylic acids used were salicylic acid (Sal) and acetic acid (Ac). Copper-amine complex/carboxylic acid salts, namely Cu(OAc)2(en)2/Sal, Cu(OAc)2(en)2/Ac and Cu(OAc)2(trien)/Sal were studied. UV-Visible spectroscopy and IR spectroscopy were used to characterize the structure of copper-amine complex/salicylic acid salts. The reaction times in the foam formation, physical and mechanical properties of foams are studied. When only copper-amine complex was used as a catalyst, the foam formation was fast. However, there was a problem with the fast gel time which resulted in difficulty in the foam processing. This problem could be solved by using copper-amine complexes/carboxylic acid salts as catalysts, which gave longer gel time while the tack free time was not too long. Cu(OAc)2(en)2/Sal and Cu(OAc)2(trien)/Sal at the mole ratios of 1:1 and 1:0.5, respectively were suitable catalysts, which had gel time about 60 seconds while tack free time was not too slow when compared with commercial catalyst (DMCHA). The gel time of 60 sec was long enough for pouring the mixture of foam formulation into a mold.