Epoxy-terminated polyoxazolidones and process for the preparation thereof

A process for the preparation of an epoxy-terminated polyoxazolidone having, when cured, glass transition temperature greater than about 135.degree. C. and N-methylpyrrolidone pick-up of less than about 0.5 percent which process comprises reacting a polyepoxide compound with a polyisocyanate compound in the presence of a catalyst for the reaction of the epoxy and isocyanate groups at an elevated temperature, said process being characterized by

• (A) adding (1) from about 5 to about 30 weight percent of the polyisocyanate compound within a period of time of from about 3 to about 90 minutes to (2) a mixture comprising (a) from about 70 to about 95 weight percent of the polyepoxide compound and (b) from about 0.01 to about 2 weight percent of the catalyst, said weight percentages being based on the combined weight of the polyepoxide compound and polyisocyanate compound;
• and
• (B) heating the reaction mixture obtained in step A to a temperature of from about 110.degree. C. to about 200.degree. C., for a period of time from about 5 to about 180 minutes;
• so as to obtain an epoxy-terminated polyoxazolidone having from about 50 to about 100 percent of the original isocyanate groups converted to oxazolidone rings and from about 0 to about 50 percent of the original isocyanate groups converted to isocyanurate rings.