Formaldehyde → Melamine formaldehyde

Participants

Reaction Conditions

Reaction Steps

A 30 l laboratory vessel with stirrer, reflux condenser and thermometer was charged with 6717 g (87.2 mol) of 39% strength aqueous formaldehyde and this initial charge was heated to 68° C. Then 31.5 ml of 2 N sodium hydroxide solution were added followed immediately by 3450 g (27.4 mol) of melamine. Because of the exothermic reaction of melamine and formaldehyde, the mixture rose in temperature to about 83° C. and was held at this temperature until all of the melamine had dissolved. It was then cooled to 55° C. and 16560 g (517 mol) of methanol and 30 ml of 53% strength nitric acid were added. The reaction mixture was heated to 59° C. and stirred at this temperature until a clear solution was formed. After a further 30 minutes, the reaction was terminated by adding about 140 ml of 2 N NaOH. The pH was adjusted to 10. Excess methanol was removed by distillation under reduced pressure (generated by a water jet pump) and the mass fraction of solids of the resin was adjusted to 75% (measured on a 2 g sample, dried at 120° C. for 1 h in a glass dish). The resin had the following characteristics: content (mass fraction of solids): 75%; viscosity at 23° C.: 480 mPa·s, mass fraction of free formaldehyde: 0.17%; water dilutability: unlimited.

Provenance & Evidence