| 摘要 |
<p>1436090 Acicular iron oxide BAYER AG 16 Sept 1974 [21 Sept 1973] 40173/74 Heading C1A An acicular, magnetic iron oxide pigment containing 0À1-4% by weight of zinc ions and 0À1-2% by weight of phosphate ions (calculated as PO 4 <SP>3-</SP>) is claimed per se, the zinc and phosphate ions being present in the reaction system which produces the pigment before seed formation. Cobalt, nickel and/or manganese may each be present in the pigment to an extent of 1- 10% by weight. The pigment may be produced by (a) reacting part of the iron in an iron (II) salt solution with a basically reacting pre- cipitant so as to form a precipitate of iron hydroxide, iron carbonate or a basic iron salt, the iron salt solution and/or the basically reacting precipitant containing 0À1-4% by weight of zinc ions and 0À1-2% by weight of phosphate ions (based on theα-FeOOH to be precipitated), (b) oxidizing the precipitate at a pH of 2-8 to give seed crystals ofα-FeOOH, (c) growing theα-FeOOH seeds according to the Penniman process, or according to the precipitation process by oxidizing the precipitate at a pH of 2-8, and (d) dehydrating, reducing and optionally reoxidizing the acicular FeOOH thus formed.</p> |
