Titanium dioxide grades

In addition to the photochemical activity of titanium dioxide, grades have been developed for many other reasons discussed below. Millennium developed its Tiona RCL-188 grade for high performance extrusion. A surface treatment based on phosphate and an undisclosed organic material lowers the energy required for the process, improves the dispersion of pigment even at very high concentrations and without the addition of process aids. When stearates are used in formulation... 

Figure 19.6. The thickness of a layer of adsorbed chlorinated polyethylene on a surface of titanium dioxide vs. the acid/base parameter of the titanium dioxide grade. [Adapted, by permission, from Hedgus C R, Kamel I L, J. Coatings Technol., 65, No.821, June 1993, 49-61.]...

The average particle size of coating-grade titanium dioxide is ca 0.3 p.m. Because this size is optimum for maximum hiding power and because of its... 

Research-grade material may be prepared by reaction of pelleted mixtures of titanium dioxide and boron at 1700°C in a vacuum furnace. Under these conditions, the oxygen is eliminated as a volatile boron oxide (17). Technical grade (purity > 98%) material may be made by the carbothermal reduction of titanium dioxide in the presence of boron or boron carbide. The endothermic reaction is carried out by heating briquettes made from a mixture of the reactants in electric furnaces at 2000°C (11,18,19). 

A patent (122) for the production of pigment-grade titanium dioxide describes preparation of titanium tetrafluoride by the reaction of SiF and ilmenite. 

Calcium carbonate is also used in industrial finishes and powder coatings. These paints typically include finer products the primary purpose is rheological and gloss control. Calcium carbonate is also used in paints to extend and enhance the use of titanium dioxide. This is accompHshed by using the finest of natural ground products or precipitated grades. 

It is also possible to deflect uv radiation by physically blocking the radiation using an opaque makeup product. A low particle size titanium dioxide can reflect uv light without the undesirable whitening effect on the skin that often results from products containing, for example, zinc oxide or regular grades of titanium dioxide. 

Rutile pigments, 19 404, 25 39 finishing, 25 37-39 Rutile Ti02 grades, 25 26 Rutile titanium dioxide crystals,... 

The refractive index of these pigments is about 1.5, which means that they give a transparent blue when used in paints and clear plastics. Opacity can be increased by adding small amounts of titanium dioxide. The principal failing of ultramarine is its lack of resistance to acid, which can even decompose the pigment if there is sufficient available. Coated grades are made with substantially improved acid resistance. 

Recently, Loden et al. [83] investigated the use of titanium dioxide as an opaci-fier in topical formulations of ketoprofen. The results demonstrated qualitative differences in the level of photostabilisation based on the grade of titanium dioxide utilised. Surface-coated particles were shown to induce greater photostabilisation than pharmaceutical grades of the excipient. The authors showed clear superiority of the opacified topical formulation containing 4% titanium dioxide versus the standard clear gel. 

Titanium dioxide is mined from natural deposits. It also is produced from other titanium minerals or prepared in the laboratory. Pigment-grade dioxide is produced from tbe minerals, rutile and dmenite. Rutile is converted to pigment grade rutile by chlorination to give titanium tetrachloride, TiCU. Anhydrous tetrachloride is converted back to purified rutile form by vapor phase oxidation. 

Based on results from a field demonstration to enhance titanium dioxide recovery in the production of high-grade titanium dioxide pigment, treatment costs (including electrical power, aluminum pellets, and labor) to achieve an 85 to 90% recovery of titanium dioxide from an infiuent stream of 1100 mg/liter of titanium dioxide was estimated to be 0.10 to 0.15 per 1000 liter of overflow (D121573, p. 788). 

Once the proper pH is reached, the slurry can be filtered continuously via a rotary vacuum filtration. A clear KF filtrate can be fed directly to the AQUATECH cell stack. The collected cake is a valuable byproduct. For this case the precipitate is a titanium dioxide which is easily upgraded via washing, drying, grinding and purification to the high value pigment grade Ti0-- Even in the raw form, this byproduct will draw credits of up to 30 /T. 

Materials. Titanium dioxide was pigment-grade material (du Pont Ti-Pure R-900 brand) with spherical particles in the range of 0.2-0.5 microns. In most experiments, the material was used without further treatment. In one experiment (specified in the text), the material was dried for 18 hours at 145°C. 

Alumina is used to produce aluminum by the electrolytic process, and the purity of the aluminum is determined mainly by the purity of the alumina used. Thus, commercial grades of alumina are 99 to 99.5% pure with traces of water, silica (Si02), ferric oxide (Fe203), titanium dioxide (Ti02), and (ZnO), and very minute quantities of other metal oxides. 

Two additional rather similar routes are known. Both depend upon the reaction between ethylene oxide, rather than ethylene glycol, and terephthalic acid to form the bis-HET monomer already mentioned. The difference between the two methods lies in the point where purification is done in one case, it is the crude terephthalic acid in the other, it is the bis-HET monomer. In both cases this monomer is polymerized by known procedures to form a fiber-grade polyester. The titanium dioxide delustrant is added, as might be expected, early in the polymerizing process. 

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