GREY-BLACK MIXED-PHASE PIGMENTS AND PROCESS FOR MANUFACTURING THEM

摘要

The grey-black inclusion pigments contain carbon black particles having specific surface areas of 10 to 1000 m<2>/g (BET) enclosed in colourless zirconium silicate crystals. The pigments are prepared by heating mixtures of zirconium oxide having a particle size distribution (D50 values) of between 7 and 10  mu m and a specific surface area of between 2 and 4 m<2>/g, silica, carbon blacks and mineralisers under reducing conditions to 900 to 1400 DEG C, followed by igniting for 0.5 to 8 hours and additional ignition under oxidising conditions in order to remove the not enclosed carbon black. The inclusion pigments according to the invention are suitable for colouring glazes.