Process for the production of boron nitride

Claim 1

A PROCESS FOR THE PRODUCTION OF TURBOSTRATIC BORON NITRIDE, SAID PROCESS COMPRISING ADMIXING 1 MOLE OF ORTHOBORIC ACID AND FROM 0.5 TO 4 MOLES OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF UREA, THIOUREA, BIURET, TRIURET, CYANURIC ACID, AMMELIDE, MELAMINE, GUANIDINE, AMINOGUANIDINE, CYANAMIDE, DICYANDIAMIDE, SEMICARBAZIDE, THIOSEMICARBAZIDE, SALTS OF THE FOREGOING WITH VOLATILE ACIDS, AND MIXTURES OF THE FOREGOING; HEATING SAID MIXTURE TO A TEMPERATURE OF 150*C. UNDER SUBATMOSPHERIC PRESSURE; FURTHER HEATING SAID MIXTURE TO ABOUT 400*C. AND WITHDRAWING GASES EVOLVED THEREFROM FROM THE REACTION ZONE WITH A STREAM OF INERT GAS, UNTIL SAID MIXTURE IS CONVERTED TO A SELF-SUPPORTING SOLID INTERMEDIATE; AND HEATING SAID SOLID INTERMEDIATE TO A TEMPERATURE BELOW 1000* C. IN CONTACT WITH ADDED AMMONIA, UNTIL SAID SOLID INTERMEDIATE IS CONVERTED TO SUBSTANTIALLY PURE TURBOSTRATIC BORON NITRIDE.