Titanate pigments

Lead antimonate [13510-89-9] (Naples yellow), Pb2(Sb0 2> mol wt 993.07, d = 6.58g/cm, is an orange-yeUow powder that is insoluble in water and dilute acids, but very slightly soluble in hydrochloric acid. Lead antimonates are modifiers for ferroelectric lead titanates, pigments in oil-base paints, and colorants for glasses and glazes (see Colorants for ceramics). They are made by the reaction of lead nitrate and potassium antimonate solutions, followed by concentration and crystallization. 

Titanate Pigments. When a nickel salt and antimony oxide are calcined with mtile titanium dioxide at just below 1000°C, some of the added metals diffuse into the titanium dioxide crystal lattice and a yellow color results. In a similar manner, a buff may be produced with chromium and antimony a green, with cobalt and nickel and a blue, with cobalt and aluminum. These pigments are relatively weak but have extreme heat resistance and outdoor weatherabihty, eg, the yellow is used where a light cadmium could not be considered. They are compatible with most resins. 

Titanates are valuable in other paint applications. Corrosion-resistant coatings have been described for tinplate, steel, and aluminum (440—444). Incorporation of phosphoric acid or polyphosphates enhances the corrosion resistance. Because titanates promote hardening of epoxy resins, they are often used in epoxy-based paint (445). Silicones (polysiloxanes) are often cured by titanates. Pigments, eg, Ti02, Si02, Al O and Zr02, are frequently pretreated with titanates before incorporation into paints (441,446). In these applications, the Ti(OR)4 compounds are often mixed with Si(OR)4, Al(OR)3, Zr(OR)4, and other metal alkoxides (12). 

Maloney, J., Titanate Pigments Gol-ored Rutile, Priderite and Pseudo-brookite Structured Pigments, in High Performance Pigments (Ed. H. Smith), Wiley-VGH, Weinheim, 2002... 

Bismuth vanadate pigments have a much higher chroma than yellow iron oxide and nickel titanate pigments. In full shades and the palest tints, bismuth vanadate pigments show superlative fastness to weathering. 

Iron titanates are formed from combinations of iron(II) oxide and Ti02- These formulations are commonly modified by additions of iron(III) oxide, zinc(II) oxide, and aluminum(lll) oxide. Like the cobalt titanates, these are inverse spinels stmc-tures. Iron titanate pigments yield light yellow-brown to dark reddish-brown hues. In many cases these pigments exhibit greater heat stability than zinc ferrite or iron oxide browns, and are generally used in applications for this purpose. 

The only other commercially important grade of titanate pigment, besides those listed above, is barium nickel titanium yellow priderite. The name priderite, just as with spinel and rutile above, refers to the crystal structure of this compound. These... 

Titanate Pigments Colored Rutile, Priderite, and Pseudobrookite Structured Pigments... 

The family of titanate pigments are listed below in Tables 6-1 and 6-2 according to their listing in the DCMA handbook. They fall into three crystal classes rutile, priderite, and pseudobrookite. Note that the Fe(III) pseudobrookite (Fc2Ti05) pigments were incorrectly categorized in the DCMA Handbook, as well as in company product literature, as FeTi-spinels. The spinel formula, Fc2Ti04, would require them to be Fe species instead of Fe species. 

A literature search on the specified titanate pigments yielded the 22 independent patents listed in Table 6—4. The majority of the patents deal with DR pigments. They cover compositions, processing, and improved properties. The older patents were concerned with ceramic applications, while the newer patents are primarily targeted at improved stability in polymers and paints. 

Many of the properties of titanate pigments need to be controlled or monitored to give good, reprodudble performance in the various applications. The properties to be discussed are ... 

Most of the titanate pigments have neutral pH values. Treated pigments that utilize certain mineralizers, modifiers, oxidizers, or additives can have acidic or basic character and exhibit pH values in the range of 4—10. The pigment pH can be important in some applications such as acid-catalyzed paint systems. 

J. Livingston, Mixed Metal Oxide Titanate Pigments , Ti02 93 Conference, 1993. 

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