Interference pigment with a high covering power
AssigneeMerck Patent GmbH
InventorsHelge Kniess, Gerhard Pfaff, Klaus Bernhardt
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Abstract
The invention relates to an interference pigment with a high covering power, comprising at least one FeTiO3-containing layer, which is applied to a lamellar inorganic substrate and whose thickness and absorbing power can be precisely set. The invention also relates to a method for producing this interference pigment and to the use thereof.
Claims10
A process for producing an interference pigment, comprising a flake-form inorganic substrate and at least one FeTiO3-containing layer thereon, where the FeTiO3 is present in a proportion of 8-100% by weight, based on the total weight of the layer, and is homogeneously distributed in the layer, and at least one further layer of metal oxides, metal oxide hydrates, MgF2 or BiOCl, said process comprising the following steps:
- a flake-form inorganic substrate is suspended in water,
- a water-soluble inorganic metal compound is added, and a pH at which a corresponding metal oxide hydrate, MgF2 or BiOCl is deposited on the substrate surface is set and kept constant,
- a water-soluble inorganic titanium compound and a water-soluble inorganic iron compound in a molar ratio of 1:0.05 to 1:1, based on the oxides TiO2 and Fe2O3, are added simultaneously to the suspension at a temperature of 50 to 100° C. and a pH kept constant in the range from 1.4 to 4.0, during which the corresponding oxide hydrates of TiO2 and Fe2O3 are deposited on the substrate surface as a mixture,
- the resultant coated substrate is separated off, optionally washed and dried, and
- thermally treated at temperatures in the range from 500° C. to 1200° C. under reducing conditions.
Dependencies are inferred from the claim text.