Iron oxide pigment for preparing colorant that comes into contact with foods, preparing heterogeneous catalyst, preparing red iron oxide, or coloring building materials, plastics, or paper, contains calcium

摘要

Iron oxide pigment has L* of 58-62, a* or 7-13, and b* of 43-50 as measured in full shade in CIELAB units. The pigment also has calcium (10-6500 mg/kg of iron oxide pigment), and water soluble content (0.01-2.1 wt.% based on iron oxide pigment). The pigment has particle length to width ratio of 3:1-30:1, and isoelectric point of 6-9. An independent claim is included for preparing iron oxide pigments comprising introducing as initial charge an aqueous solution of iron (II) component, simultaneously or subsequently adding an alpha -iron oxyhydroxide yellow nucleus, carrying out oxidation, and adding calcium carbonate when oxidation begins. The calcium carbon is added as aqueous suspension, powder, or granules as precipitant.