Process for preparing an effect pigment

Abstract

The present invention relates to a process for preparing a coloured effect pigment, comprising the steps of (a) preparing in an aqueous coating medium at least one layer of a hydroxyl-containing metal oxide on a substrate, thereby obtaining in the aqueous coating medium a first coloured pigment material CPM1 comprising the substrate coated with the hydroxyl-containing metal oxide, wherein the substrate is made of aluminium or aluminium alloy which optionally comprises at least one passivating layer, and wherein the hydroxyl-containing metal oxide is a hydroxyl-containing iron oxide or a hydroxyl-containing titanium oxide or a mixture thereof, (b) providing the first coloured pigment material CPM1 in a liquid post-treatment medium comprising one or more high boiling organic liquids, and (c) heating the liquid post-treatment medium to a temperature of at least 90° C. so as to convert the first coloured pigment material CPM1 to a second coloured pigment material CPM2.

Dependencies are inferred from the claim text.