The present invention relates to beige-brown encapsulated pigments based on zirconium silicate as the casing substance into which colored compounds are encased as discrete phases. In a further aspect, the present invention relates to a method of producing these encapsulated pigments.
Encapsulated pigments have become known from the prior art, as for example, DE-PS 23 12 535. They consist of transparent crystals of glaze-stable substances such as e.g. zirconium silicate, zirconium oxide or tin oxide into which inorganic, moisture-free, colored compounds are included or encapsulated, as a discrete phase. Thenard's blue (cobalt blue), titanium yellow and especially cadmium yellow and cadmium red are known as colored compounds. Zirconium iron rose with Fe.sub.2 O.sub.3 encased in a zirconium silicate casing is also known. The production of these encapsulated pigments takes place by means of heating the casing substances or their precursors and the colored substances to be encapsulated or their precursor in the presence of mineralizers to temperatures up to 1200.degree. C. However, it was found that not all conceivable colored compounds can be encased into the casing substances in an appreciable yield with this method.
The palette of brown colors is not very large. Brown bodies are obtained essentially from iron oxides in combination with other oxides such as e.g. manganese oxide, zinc oxide, nickel oxide or cobalt oxide. Brown encapsulated pigments were not known in the past.