Innovative quaternary ammonium and metal based catalyst systems for CFC free isocyanurate foams

This paper explains and introduces novel quaternary ammonium and metal based catalyst systems in CFC free polyisocyanurate (PIR) rigid foam applications. CFC elimination in polyurethane (PUR) applications has successfully been achieved, in most cases, with the more environmentally acceptable HCFCs, hydrocarbons (HCs) and water (CO2) blown systems. The survey of next generation HFC blowing agents still is expanding. In PIR foam applications, however, inferior foam properties, as well as the decline in flame resistance, in HCFCs, HCs and CO2 blown systems, are major issues. In general, PIR foams are produced by complex reactions such as the trimerization of isocyanate, urethane and urea, which all proceed simultaneously. The catalyst plays an important role in the control of these reaction rates, foaming profiles and foam properties such as adhesive strength, dimensional stability and flammability resistance. A number of catalysts, such as alkali metals, quaternary ammonium compounds and tertiary amines, have been proposed and used in PIR rigid foam applications as trimerization catalysts. All catalysts cannot, however, always meet the present industrial requirements. For example, alkali metals exhibit high trimerization activity at high temperature but much less activity at lower temperature, which results in inadequate rise profiles and severe friability, namely inferior adhesive strength. Quaterary ammonium compounds and tertiary amine catalysts provide better rise profiles, flow properties and moldability, however, they exhibit lower trimerization activity products, less flame resistance property and strong odor. Tosoh Corporation has successfully developed several new innovations in quaternary ammonium, metal based catalysts, as well as a flowability analysis system, using a Long Range Laser Displacement (LLD) apparatus, which can be applied to HCFC-141b/CO2 as well as all CO2 blown PIR foam. This technology assists in the successful production of PIR foams with excellent physical properties, including high conversion of trimerization, as well as improved flame resistance, flowability and friability.