Historical Development of Titanium Dioxide
Titanium dioxide has grown to a 4 million ton business from its discovery in 1791 and first commercial manufacture in 1916.
Discovery
Impure titanium dioxide was first isolated in 1791, when the Reverend William Gregor from Devon, England, isolated a white metallic oxide unknown to contemporary chemists from the local magnetic black sands. Gregor's analysis of the black sand showed it contained:
Iron oxide 51.00%
'Titanium' oxide 45.25%
Silica 3.50%
Manganese oxide 0.25%
The discovery of this new white oxide caused little interest at the time but in 1795, Martin Klaproth noted that this material was similar to an oxide he had extracted from Hungarian rutile deposits. Klaproth named the oxide element "Titanium" after the mythological Titans, the first sons of the Earth in Greek legend, and this name has persisted.
Commercial development
It was many years before titanium dioxide was developed into a commercial product, with the first, very small quantities of pigment being available in 1916. The original pigments were of the anatase crystal form and were produced as a composite with calcium or barium carbonate or sulfate. Further development led to the introduction of pure anatase TiO2 in the late 1920's and eventually rutile pigments in the 1940's with even better opacity and durability.
Although these early pigments have been surpassed by the more advanced pigments available today, they represented a significant advance over previous white opacifying pigments such as white lead, zinc oxide, lithopone or zinc sulfide. Titanium dioxide pigments gave much higher opacity due to their much higher refractive index a significant reduction in toxicity, better stability and improved durability.
Product development
The development of TiO2 may be viewed as two separate but interlinked processes: development and improvement of its pigmentary properties and development of the manufacturing process.
Firstly, it was recognized that although it is relatively easy to disperse pure anatase TiO2 in water for fine paper making applications, an untreated TiO2 pigment surface can be difficult to disperse into paint resins (and later plastics polymers) and once dispersed, the system may lack the desired stability. In addition, whilst TiO2 may improve the durability of an organic binder (paint or plastic) by adsorbing ultra-violet radiation, free radicals are produced at its surface which leads to photocatalytic breakdown.
These deficiencies were addressed by the development of specific inorganic and organic surface treatments or coatings, which are applied to the core TiO2 particles as a 'finishing' step prior to drying, milling and packing. In the 1950's and 60's the trend was to produce specific pigments for different types of paint, ink, plastic, paper, vitreous enamel, synthetic fiber delustring and sundry applications but more recently multi-purpose or 'universal' products with wide ranges of application have been introduced.
Secondly, all early TiO2 pigments, whether anatase or rutile were manufactured by extracting the TiO2 value from the ore with sulfuric acid using the lengthy, liquid phase sulfate process. Separate development led to the more technically challenging, vapor phase chloride process which extracts TiO2 from the ore with chlorine. Currently, approximately 47% of TiO2 pigments are made by the sulfate manufacturing process and 53% by the chloride process.
Millennium Inorganic Chemicals produces high performance Tiona® pigments by both the sulfate and chloride manufacturing processes.
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