Mica-based effect pigments

Mica platelets can be coated with a variety of other compounds to produce further pigments. Solid-state reactions and CVD processes extend the possibilities for the synthesis of mica pigments. In addition, the calcination of the materials in the presence of inert (e.g., N2, Ar) or reactive gases (e.g., NH3, H2, hydrocarbons) allows the formation of phases, which carmot be produced by working in air. Table 5.17 contains a summary of mica-based effect pigments with special coloristic properties. 

Tab. 5.17 Examples of mica-based effect pigments with special coloristic properties.

Silicates NajAIeSie O24S (ultramarine) Mica based effect pigments +... 

Nacreous and interference pigments are used as colorants or part of color formulations for all applications where traditional pigments are used, but where additional color depth, brilliance, iridescence, color shift (flop), and other spectacular effects are desired [5.253]. Mica-based pigments dominate their combination of pearl and interference effects, brilliance, stability, and weather resistance is unsurpassed. Furthermore, they are non-toxic [5.221],... 

For ceramic and glaze applications, the effect pigments based on substtates like mica are coated with an additional Sn02 layer to give stabilization against the aggressiveness of the frits at high temperatures [5.165]. 

Mica-Tek has an interesting approach to exploiting the variety of forms and colors of mica. A range of mica-based products have been developed which differ in the color and the shape of particle as well as in their glittering and sparkling effects. These decorative pigments are used in housewares, bathwares, toys, interior decorating, etc. 

Special effect pigments based on mica are regarded as toxicologically harmless. Their economic importance has arisen steadily production amounted to ca. 15 000 t in 1996. 

Metal effect pigments are mainly based on small metallic flakes of aluminium or bronze. In another class are mica-metal oxide multilayer interference pigments for perlescent effects. 

On the other hand, new pigments based on transparent silica flakes show extremely strong optical effects, which are different to mica pigments [5.244]. Angle dependent colors and other effects, achieved by the combination of these Si02-flakes with... 

These are pigments based on thin platelets of transparent mica, coated with titanium dioxide or iron oxide, producing interference patterns. Titanium dioxide (Ti()2)-coated mica pigments have a 2-10 pm particle size, for incrca.sed lustre, whiteness, and coverage there are also silver sparkle effects. A two-tone effect can be obtained with absorption colours deposited directly on interference pigments of TiOj-coated mica (such as Mearlin Dynacolor). 

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