Patent ID: 6379449
Filing Date: 2002-04-30
Classification: C01B,C01P

Abstract:
A process for producing a red to yellow pigment based on a nitride or oxidenitride with at least one metal of a valence state in the range from +3 to +5, comprising nitriding a pulverulent metal compound or a mixture of metal compounds from the series of oxides, oxide hydrates, mixed oxides, carbonates, nitrates, oxidenitrides having a lower degree of nitriding than an oxidenitride to be produced, halides, oxidehalides and nitridehalides excluding SiO2, GeO2, SnO2, TiO2, ZrO2 and HfO2, wherein the oxygen of an oxidenitride to be produced originates from the metal compound(s) used, with ammonia flowing over the metal compound(s) at 700 to 1250Â° C., and wherein the nitriding step is performed in a rotary tube or fluidised bed reactor in the presence of at least one pulverulent oxide uniformly dispersed in the metal compound(s) to be nitrided and selected from the series SiO2, GeO2, SnO2, TiO2, ZrO2 and HfO2, and wherein the selected nitriding temperature substantially excludes nitriding of the pulverulent oxides of the tetravalent metals from said series SiO2, GeO2, SnO2, TiO2, ZrO2 and HfO2.