METHOD OF PRODUCING MELAMINE AND METHOD OF REMOVING DISSOLVED GASES FROM AQUEOUS SOLUTION OF CRUDE MELAMINE Russian patent published in 2011 - IPC C07D251/60 C07D251/62 

FIELD: chemistry.

SUBSTANCE: invention describes a method of producing melamine by converting carbamide into melamine using a non-catalytic method at temperature 365-400°C and pressure 7-10 MPa to form a gas-liquid reaction mixture, and a method of removing dissolved gases from aqueous solution of crude melamine and can be used in industrial production of melamine. In order to extract melamine, the gas-liquid reaction mixture is cooled while lowering pressure and bringing into contact with aqueous medium to form aqueous solution of crude melamine and removing a portion of dissolved gases. The obtained melamine solution is then held in order to decompose some of the impurities. Pressure and temperature are further lowered and dissolved gases are removed from the aqueous solution of crude melamine by blowing that solution with water vapour while simultaneously adding ammonia. An alkali metal hydroxide solution is then added to the obtained melamine solution and melamine is extracted from the solution through crystallisation. The technical result of the invention is higher purity of melamine and ensuring its independence from fluctuation of process parametres. Melamine-formaldehyde resins prepared using the melamine obtained using the described method have high transparency.

EFFECT: improved method.

4 cl, 6 ex, 1 tbl