| 摘要 |
<p>TITLE OF THE INVENTION "PROCESS FOR THE PREPARATION OF YELLOW IRON HYDROXIDE PIGMENT" This invention describes a process for producing iron hydroxide pigment FeO(OH), of a yellow colour, in acicular shape with average dimensions of the needles of the order of 0.12 x 0.7 microns, by the simultaneous reduction, by these ferrous salts of aromatic nitro compounds to aromatic amines. The invention is characterized in that (a) ferrous sulphate, aqueous ammonia and an aromatic nitro compound, with a molar ratio between NH4OH and FeSO4 of less than 1:1 and with a molar ratio between NH4OH and NO2-groups equivalent to or less than 6:1 are brought in contact in a first at 20-70.degree.C, such as to form a suspension of nuclei of FeO(OH) not exceeding 80 g/l; (b) in a second stage, an aqueous solution of FeSO4, an aromatic nitro compound and the pigment nuclei of the first stage, at 20-70.degree.C, are mixed with a maximum of 2.0-2.5 moles of aqueous ammonia per mole of FeSO4, the molar ratio between NH4OH and NO2-groups being equal or less than 12:1, such as to form a suspension of FeO(OH) pigment not exceeding 120 g/l; (c) the pigment and the aromatic amine are recovered from the reaction product.</p> |
