| 摘要 |
Iron oxide pigments are produced by treating an iron oxide - "black" suspension prepared by nitrobenzene reduction and having a seed content of 140-600 g/ referred to Fe, and an FeCl2 content of ca. 20-70 g/l referred to Fe, at 20 degrees C under oxidising conditions with such an amt. of Ca(OH)2 that the initial pH of 3-5 rise in ca. 5-360 mins. to a final pH of ca. 5.5-7, the growth rate of the ppted. iron oxide on the added seed being 0.02 to 6% by t. per minute, and the black pigment obtained is converted, after separatn. from the reaction medium by washing and drying, into the corresponding iron oxide red pigment by calcination at 600 degrees-1000 degrees C. More specifically concn. of Ca(OH)2 is 100-300 g/l and pref. Ca(OH)2 is prepared in situ by addn. of CaO. |
