Non-silking yellow iron oxide pigments with high variegation

摘要

Iron oxide pigment of the alpha -FeOOH modification has a specified Silking index for use in coloring lacquers, paints and plastics. Iron oxide pigment of the alpha -FeOOH modification has a Silking index (SI) of less than 5 whose coloristic values in the CIELAB color space at pigment volume concentrations of 10% in the test lacquer for a asterisk 8-14, for b asterisk 48.5-52 and for L asterisk 54-62. An Independent claim is also included for the preparation of the pigment comprising: (a) forming alpha -FeOOH-seeds by precipitating from a Fe(II)-containing solution with an alkali precipitating agent in the presence of soluble aluminum salts in an amount of 3-9 wt.% Al2O3 and subsequently oxidizing to alpha -FeOOH; (b) forming the pigment structure by precipitating out further iron with simultaneous oxidation, where the seed-time-yield is less than 0.3 hour-1 and the pH over the total time period for the structure formation; and (c) stopping the pigment structure formation at a duplication factor of 3-20.