Formaldehyde → Dihydrobenzoxazine

Participants

Reaction Conditions

Reaction Steps

To a suitably equipped glass resin reactor equipped with stirrer is charged 450 parts phenol, 450 parts methylene chloride and 144 parts of ethylene diamine. The temperature of the reaction mixture is adjusted to 25° C. and 595 parts of 50% formalin is added while maintaining the temperature below 30° C. The reaction mixture is stirred for 2 hours at 30° C. after formaldehyde addition is complete. It is then heated to atmospheric reflux, refluxed for 3 hours and allowed to cool and separate into two layers. The upper water layer is withdrawn and discarded. The lower organic layer is reheated to atmospheric reflux and distilled to remove solvent. Heating is continued with the gradual reduction of pressure until a temperature of 70° C. at about 5.0 kPa pressure is reached. Cellosolve (450 parts) is added to the resin slowly, keeping the temperature near 70° C. A uniform yellow solution forms which is cooled and filtered. The product has 66% closed dihydroxybenzoxazine ring and a calculated equivalent wt. of 224. The solution has a solids content of 60.2%.

Provenance & Evidence