PURPOSE: To obtain a passivated metallic pigment by gas phase decomposition of a volatile phosphorous compound and a volatile nitrogen-containing silicon compound using steam and/or oxygen in the pigment particles under agitation.
CONSTITUTION: As a pigment particle employable in the method, there can be exemplified a metallic pigment obtained by coating aluminum as the base with a metal oxide (e.g. iron oxide). The pigment particle preferably has a diameter of 5-100 μm and an intrinsic surface area of 1-7 m2/g. As the phosphorous compound is preferable one having a distinct vapor pressure at a temperature of 500°C or below, e.g. tri- and di-alkyl ester of phosphorous acid. As the silicon compound is preferable one having a high vapor pressure at a temperature of 500°C or below, e.g. 3-amino-propyltriethoxysilane. The passivation method can be carried out in a fluidized bed reactor. The pigment particles are at first fluidized with an inert gas (e.g. nitrogen) and heated to a reaction temperature of 100-350°C. Then vaporized phosphorus, silicon and steam and/or oxygen are introduced.
NORUBERUTO MURONGA
HARARUTO KERAA
YUAN ANTONIO GONZARESU GOMESU
