Poly-2-oxazolidones

An alternative route involves the reaction of 1,2-epoxides with isocyanates to yield poly-2-oxazolidones (Figure 27.12). 

By using isocyanates as hardeners, more complicated cured resins are obtained. It is well known that poly-2-oxazolidone is obtained by the reaction of a diepoxide and a diisocyanate compound 49 50). 

Epoxides. Epoxides are used as raw materials to make poly-2-oxazolidone foams. In foam preparation fast reaction is essential, and therefore aromatic epoxides are favored. Aromatic polyepoxides include bisphenol-A-based epoxides and novolac-based epoxides, as shown below. 

Poly-2-oxazolidone by the Reaction of Isocyanates with Epoxides. 136... 

Preparation of the Poly-2-oxazolidone from the Reaction of 2,4-Toluene Diisocyanate... 

POLY-2-OXAZOLIDONE BY THE REACTION OF ISOCYANATES WITH EPOXIDES... 

Sandler, Berg, and Kitazawa [9] reported that 2,4-toluene diisocyanate reacts with diglycidyl ethers to give poly-2-oxazolidones. A similar reaction was also reported for monoisocyanates reacting with monoepoxides [9,10]. The reaction takes place in DMF as a solvent and is catalyzed by tetramethyl-ammonium iodide at 160°C for 6 hr. A recent review of this reaction is worth consulting for additional background material [10a]. 

Preparation of the Poly-2-oxazolidone from the Reaction of 2,4-Toluene Diisocyanate and the Diglycidyl Ether of 2,2-Bis(4-hydroxyphenyl)-propane [9]... 

Sandler [11] also reported that poly-2-oxazolidones can be prepared by the reaction of trimerized isocyanates, i.e., isocyanurates on reaction with diepoxides. A variety of poly-2-oxazolidones have been reported (see Table IX). The reactions can be used to cure diisocyanate prepolymers as an alternate cure method to the diamines. Some typical preparations are reported in Table IX. 

Sandler [12] and later Ashida and Frisch [13] reported that poly-2-oxazolidones can be converted to polyisocyanurates. 

When an NC0 epoxy ratio of 2 1 was used, an NCO-terminated, oxazolidone-containing prepolymer was formed that was then trimerized by employing a trimerization catalyst to yield poly(oxazolidone-isocyanurates) as shown below ... 

Poly(oxazolidone-urethane-isocyanurates) were prepared from an excess of isocyanate-terminated oxazolidone prepolymers and poly(oxypropylene) glycols of different chain lengths via the formation of NCO-terrainated poly(oxazolidone-urethanes) followed by trimerization of the terminal isocyanate groups as shown in the following reaction scheme ... 

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