Titanium Dioxide (TiO2) is best known as a white pigment used in paints, plastics and paper, where it is the pigment of choice to give opacity and whiteness to a large variety of everyday materials. What is lesser known is that TiO2 can also be used as an ingredient to manufacture coloured pigments and more specifically complex inorganic coloured pigments (CiCPs) also called Mixed Metal Oxide (MMO) pigments.
Complex Inorganic Coloured Pigments provide improved performance in areas such as exterior durability and chemical stability. They are very stable pigments, and for all practical purposes are chemically inert. They can withstand the most chemically aggressive environments and still retain their colour. They will not fade in the presence of ozone, acid rain, SOx, NOx or other air pollutants common in industrialized areas. These CICPs were initially used safely in decorative ceramics and pottery, but nowadays are also used in industrial and coil coatings and plastics.
CICPs are made at very high temperatures in a process called calcination. Metal oxides or oxide precursors are blended together and then strongly heated. At the calcining temperature, the solids themselves become reactive. Metal and oxygen ions in the solids rearrange to a new, more stable structure, forming the CICPs. The pigments themselves are completely stable, and do not discolour upon exposure.
There is a wide colour variation depending on the combination of the different metal oxides.
Rutile Titanates enjoy a colour range which can go from bright green-shade yellow to dark browns. “Titanate pigments” often refer to the coloured doped-rutile pigments such as Nickel Antimony Titanium Yellow Rutile. CICPs with this structure contain a large fraction of TiO2 as a host metal oxide accommodating a variety of metal ion dopants. Colours range from the bright yellow of Nickel Antimony Titanium Yellow Rutile to the orange-to-brown Chromium Antimony Titanium Buff Rutile, to the dark browns of Manganese Antimony Titanium Buff Rutile.
Tin zinc Titanates show a colour range from orange to yellow bright orange and yellow pigments based on materials containing titanium, tin and zinc have been commercialized as CI Pigment Yellow 216 and Orange 82.
Pseudobrookites Iron titanate pigments, known variously as Iron Titanium Black Spinel, Fe2TiO4, or Pseudobrookite, Fe2TiO5 range from light to dark brown and are similar in colour to ferrite spinels.
Tronox anatase TiO2 pigments, such as TiONA® AT-1 are being widely used in this application. A higher purity grade, TiONA® ATP-01 was introduced recently and has been well accepted by the coloured pigments industry major players.
Beyond its reputation for being the brightest, whitest pigment available, titanium dioxide helps to create a world of color.
Tronox is continuously developing new CristalACTiV™ materials to meet existing and future environmental regulations and respond to the needs of innovative applications.