Ibrahim S. Bechara

Some Aspects of I nnovative Catalysis of the Isocyanate Trimerization Reaction — Polyisocyanurate Foam Formation and Properties

Isocyanurate-based polymers posses superior thermal and hydrolytic properties when compared with polyurethanes. Flammability properties have been shown to be superior to polyurethanes. Wide utilization of isocyanurate-modified foams has been forecast for 1980 (1). Past projections of growth showed that 27 million pounds will be sold this year in the construction area alone (2). Their incorporation into flexible foam (3) is expected to further increase their volume. In recent years much has been written about isocyanurates (4-15). Dr. Frisch and co-workers have compared their properties with urethane foams (16). Their processing has also been described (17). The trimerization reaction itself is an old one (18, 19) and recently has been investigated by various groups (20-25); however, little attention has been given to the effect of trimer catalysts on the competing reactions involved in the preparation of a commercial isocyanurate foam and on the properties of the resulting products. In this paper we intend to report on studies we have carried out on the catalysis of the reactions involved in making modified isocyanurate foams. Some emphasis will be placed on the effect of trimer catalysts on the competing reactions involved in the preparation of a commercial isocyanurate foam and on the properties of the resulting products. In this paper we intend to report on studies we have carried out on the catalysis of the reactions involved in making modified isocyanurate foams. Some emphasis will be placed on the effect of cata !ysts on the various physical properties of the foams and foam processing characteristics.

Unusual Catalysts For Flexible Urethane Foams

ascertained. It is generally assumed that the hydroxyl group reacts with isocyanate and thus gets tied up in the polymer backbone. This loss in mobility was assumed to be the reason for the relatively low activity of such catalysts (5). Our own experience with the catalysis of the urethane reactions by DMEA type of compound convinced us that catalysts with primary hydroxyl group are more effective than those with secondary hydroxyl and those in turn are more effective than the analogous catalysts with tertiary hydroxyls as shown in Figures 1 and 2. The hydroxyl group, apparently, has an important influence on the activity of the catalysts. Observations such as those were intriguing enough that we decided to conduct further research on the catalysis by this type of compound.

Novel Organometallic Compounds for Urethane Catalysis

The significance and importance of catalysis in the polymerization of urethanes has been long recognized and is well documented in the literature (1-13). The role of tertiary amines and organometallic compounds individually and in combination has been studied extensively (14). Amines are generally considered to contribute to the blowing reactions resulting from the reaction of water and isocyanate. Organometallics, and in particular the organotin compounds, catalyze reactions of polyols and isocyanates. The rates derived from using a combination of organometallic and amines surpass the rates of reaction of these catalysts separately (7). This synergism has been shown to occur with combinations of many amines and organotins. The most notable contribution occurs with