Formaldehyde → Benzoxazines

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. The reaction mixture is heated to atmospheric reflux and refluxed for 3 hours. The reaction mixture is 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 The upper water layer is withdrawn and discarded.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 application of vacuum until a temperature of 70° C. at about 5.0 kPa pressure is reached. The very viscous product is removed from the reactor and allowed to cool. The light yellow semi-solid product has 67% closed dihydrobenzoxazine ring. Upon standing, the clear amorphous product slowly crystallizes to an opaque, grainy solid.

Provenance & Evidence