Process for preparing a red iron oxide pigment

Details Process for preparing a red iron oxide pigment Process for preparing a red iron oxide pigment

C - Chemistry, Metallurgy

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C01G 49/06 (2006.01) C09C 1/24 (2006.01)

Patent

CA 1085588

TITLE OF THE INVENTION "PROCESS FOR PREPARING A RED IRON OXIDE PIGMENT" ABSTRACT OF THE DISCLOSURE This invention describes a process for producing a red Fe2O3 pigment in spherical shape with average sphere size of 0.1-0.4 microns from ferrous salts, by simultaneous reduction of aromatic nitro compounds to aromatic amines. The invention is characterized in that (a) FeSO4, aqueous NaOH and an aromatic nitro compound, with a molar ratio between NaOH and FeSO4 ? 1:1 and with a molar ratio between NaOH and NO2 groups ? 12:1, are brought in contact in a first stage at 85-103°C and at a pH ? 7.5, such as to form a suspension of nuclei of Fe2O3 not exceeding 40 g/l; b) in a second stage, to an aqueous mixture containing FeSO4, an organic nitro compound and Fe2O3 nuclei from the first stage, aqueous NaOH is gradually fed in order to maintain in the mixture a pH between 6.0 and 7.5, up to a maximum of ca. 2 moles/mole of FeSO4, the molar ratio between NaOH and NO2 groups being ? 12:1; at 85-103°C, such as to form a suspension of Fe2O3 pigment not exceeding 110 g/l; (c) the pigment and the aromatic amine are recovered from the reaction mixture. - 1 -

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