Isocyanurate-oxazolidone resins

Numata and Kinjo (52) have shown rubber-modified isocyanurate-oxazolidone resins may be effectively modified with carboxyl-reactive nitrile liquids. The viscoelastic behavior of models using a polyglycidyl ether of phenol-formaldehyde novolac resin and di-phenylmethane-4,4 -diisocyanate is discussed. Such resins have suggested utility in thin films as electrical varnishes. 

The calculated isocyanurate/oxazolidone ratio, as described above, is not enough to evaluate the properties of the resin, and so, their softening points and glass transition temperatures were determined and related to the reaction conditions used to prepare the films. The reaction parameters were studied systematically to establish the influence of the following variables on the relaxation temperatures of the resultant resins ... 

By changing the ratio epoxy/isocyanate, the cured resins are composed of oxazolidone and isocyanurate rings in a varying ratio. 

Oxazolidone-isocyanurate polymers were prepared by reacting five glycidyl ethers with 4, 4 -diisocyanato-diphenylmethane in the presence of 2-ethyl-4-methylimidazole. The degree of cure of the resins was followed by IR spectroscopy by measuring the fraction of the isocyanurate to oxazolidone linkages (377). 

Kinjo coined the term ISOX to identify resins combining isocyanurate and oxazolidone structures, in which the isocyanurate structure preponderates through using a threefold excess of isocyanate over that required for oxazolidone formation. In consequence of their high degree of isocyanurate cross-linking, such resins may have high T s (ca. 300 C). Pyridines and ter-... 

Table 11 compares the peak heights for oxazolidone and isocyanurate absorptions, with these frequencies normalised to the absorption at 1510 cm From these results, we concluded hat HEXA had the greatest efficiency as an oxazolidone forming catalyst under the conditions of the film casting procedure. In contrast, the DABCO catalysed resin had the strongest isocyanurate... 

Second, for the preparation of ISOX resins, the preliminary finding is that EMI, being an effective catalyst for the formation of both oxazolidone and isocyanurate, is the preferred catalyst. This conclusion is based on finding that DABCO is a strong catalyst for isocyanurate formation and HEXA a good catalyst for oxazolidone formation. This latter conclusion is to be regarded as preliminary. 

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