High Throughput Screening of Rigid Polyisocyanurate Foam Formulations: Quantitative Characterization of Isocyanurate Yield via the Adiabatic Temperature Method

Abstract

To reduce the time-to-market, a high throughput experimentation (HTE) method has been introduced at Bayer MaterialScience for the rapid development and optimization of polyurethane (PU) foam formulations and for the fast screening of new PU raw materials. The foam processor developed for this purpose allows automated PU foam production on a scale of 0.4 L, which is ten times smaller than the usual lab-scale foam volume. In order to optimize formulations for the increasing polyisocyanurate (PIR) foam market, a rapid in situ method has additionally been developed that is able to quantify isocyanurate concentration and yield. This method, the adiabatic temperature method (ATM), is based on the temperature profile measured within the foam bun in the HTE foam processor. By comparison with attenuated total reflection (ATR)-FTIR spectra of the cured foams, it is shown that the isocyanurate concentration found in the 0.4 L foams is comparable with that of larger foams typically used in the laboratory (ca. 5 L). This demonstrates that the 0.4 L foams can be used to investigate the trimerization of isocyanates to form isocyanurate. The suitability of the ATM is demonstrated and verified by ATR-FTIR spectroscopy for the influence of the index on isocyanurate yield and concentration for a pentane blown and a water co-blown PIR formulation. Isocyanurate yield is shown to be negligible at indices close to 100 but increases to an almost constant level at higher indices, the height of which depends on the type of the formulation. A level of approximately 70% has been observed for the physically blown formulations, whereas the water co-blown formulations only reach a level of around 40%. Due to the successful implementation of the ATM, Bayer MaterialScience is increasingly using high throughput experimentation to optimize PIR recipes and to examine new raw materials and additives for polyisocyanurate foams. This has led to an increase in the efficiency of our polyurethane research and opened up possibilities that were not available to us before.