Pigments titanium dioxide

The starting materials for Ti02 production are ilmenite and titanium slag in the case of the sulfate process (see Section 5.9.2.2.3) and leucoxene, rutile, synthetic rutile, titanium slag and in the future possibly also anatase for the chloride process (see Section 5.9.2.2.3). 

Ilmenite (Fe,Mg,Mn)Ti03 occurs naturally in primary and secondary deposits. The Ti02-content is 43 to 61 % and the iron oxide content 34 to 39%. The impurities are mainly Mn, Mg, Al, Si, Cr, V, Nb and Sb. Primary deposits of ilmenite are found in Norway, Russia, Finland, Canada and the USA. However, secondary deposits are more important raw materials due to their easier processing (sands). They are found in South Africa, Australia, India, Brazil, Malaysia and Egypt. 

Rutile is extracted from river, coastal and dune sands yielding concentrates with 90 to 98% Ti02, which may be contaminated with Fe, Zr, V, Cr, Al, Si, Mg etc. Australia is the leading producing country supplying 216 10 t in 1994. 

Production of titanium slags by reduction of ilmenite at 1200 to 1600°C and separation of the liquid iron 

Anatase deposits with a Ti02 content of 30 to 40% have been discovered in Brazil. They contain 220 10 t Ti02, being more titanium dioxide than in all the currently known rutile deposits. It can possibly be used as a starting material for TiCl4 in the production of Ti02 pigments or in the production of metallic titanium. 

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Titanium dioxide pigment coated with pentaerythritol, trimethylolpropane, or trim ethyl ol eth an e exhibits improved dispersion characteristics when used in paint or plastics formulations. The polyol is generally added at levels of 0.1—0.5% (96). 

U.S. production of titanium dioxide in 1993 was 1.16 x 10 t, an increase of about 2.2% over 1992 (15). The annual production increased on an average of 5.4% in the 1980s (16). There are approximately 50 world producers of titanium dioxide pigments. The world s leading suppHers are Du Pont (- 24% worldwide share), Tioxide (the U.K. Co. owned by ICI), and SCM Corp. Other producers include Kerr McGee, Tiwest, Kemira Oy, Kronos, and Bayer AG (see Titanium compounds, inorganic). 

Production. Titanium is the seventh most common metallic element in the earth s cmst. Titanium minerals are plentiful in nature (19). The most common mineral /raw materials used for the production of titanium dioxide pigments are shown in Table 1. 

To produce the mtile titanium dioxide pigment, hydrolysis of the mother Hquor has to be carried out in the presence of a specially prepared hydrosol as a seeding agent. This hydrosol is made by the neutralization of a portion of the mother Hquor in the presence of hydrochloric or some other monohydric acid. Because of the large amount of the hydrosol that must be added to the mixture (about 6% concentration), the hydrolysis reaction takes only about 1 hr. 

Paints. Paints account for perhaps 3% of sulfur consumption (see Paint). The main sulfur use is for the production of titanium dioxide pigment by the sulfate process. Sulfuric acid reacts with ilmenite or titanium slag and the sulfur remains as a ferrous sulfate waste product. Difficulties with this process have led to the development of the chloride process (see Pigments, inorganic Titanium compounds). 

G. E. Haddeland and S. Monkawa, Titanium Dioxide Pigment, Process Economics Program Report No. 117, Stanford Research Institute International, Menlo Park, Calif., 1978. 

A high purity titanium dioxide of poorly defined crystal form (ca 80% anatase, 20% mtile) is made commercially by flame hydrolysis of titanium tetrachloride. This product is used extensively for academic photocatalytic studies (70). The gas-phase oxidation of titanium tetrachloride, the basis of the chloride process for the production of titanium dioxide pigments, can be used for the production of high purity titanium dioxide, but, as with flame hydrolysis, the product is of poorly defined crystalline form unless special dopants are added to the principal reactants (71). 

Fig. 1. Flow diagram for the manufacture of titanium dioxide pigments.

Table 10. Annual World Capacity for Titanium Dioxide Pigment Production, t x 10 ...

Table 13. Distribution of U.S. Titanium Dioxide Pigment Shipments and Production ...

Iron Titanates. Ferrous metatitanate [12168-52-4] FeTiO, mp ca 1470°C, density 472(0), an opaque black soHd having a metallic luster, occurs in nature as the mineral ilmenite. This ore is used extensively as a feedstock for the manufacture of titanium dioxide pigments. Artificial ilmenite may be made by heating a mixture of ferrous oxide and titanium oxide for several hours at 1200°C or by reducing a titanium dioxide/ferric oxide mixture at 450°C. 

The analytical chemistry of titanium has been reviewed (179—181). Titanium ores can be dissolved by fusion with potassium pyrosulfate, followed by dissolution of the cooled melt in dilute sulfuric acid. For some ores, even if all of the titanium is dissolved, a small amount of residue may still remain. If a hiU analysis is required, the residue may be treated by moistening with sulfuric and hydrofluoric acids and evaporating, to remove siUca, and then fused in a sodium carbonate—borate mixture. Alternatively, fusion in sodium carbonate—borate mixture can be used for ores and a boiling mixture of concentrated sulfuric acid and ammonium sulfate for titanium dioxide pigments. For trace-element deterrninations, the preferred method is dissolution in a mixture of hydrofluoric and hydrochloric acids. 

Wavelength dispersive x-ray fluorescence spectrometric (xrf) methods using the titanium line at 0.2570 nm may be employed for the determination of significant levels of titanium only by carefiil matrix-matching. However, xrf methods can also be used for semiquantitative determination of titanium in a variety of products, eg, plastics. Xrf is also widely used for the determination of minor components, such as those present in the surface coating, in titanium dioxide pigments. 

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