CICP Pigments

Of the CICP brown pigments, the titanate Yellow 164 does not rely on iron oxide to provide the absorption mechanisms to provide a tan or brown color. Historically, this has led it to be used extensively in RPVC where iron oxide can react with the resin causing premature degradation. It is one of the most durable CICP pigments to produce a brown shade, and provides excellent IR reflection as shown in Figure 24.5. 

CICP pigments contain transition metals, and the absorptions that provide color are due to ligand field theory [9], In these pigments optical absorptions tend to be broad with the maximum in the middle of the band. This shape is due to vibrational interactions and crystal field irregularities. 

Phthalocyanine blues and ultramarine blues do not have this absorption, but do not have the high-performance durability of CICP pigments. When possible, color formulations wiU try to formulate without blue additions to maintain a high IR reflectance. 

To improve solar reflection and provide a wider range of green shades, CICP pigments have been developed that are soUd solutions of chrome and alumina, and often additional modifiers. An example of this modified Green 17 pigment is shown in Figure 24.11. The increase in IR reflection compared to the traditional... 

Rutile titanates represent by far the largest commercial class of CICPs. Chromium antimony titanate yellows (C.I. Pigment Brown 24) are the most widely used, followed by nickel antimony titanate yellows (C.I. Pigment Yellow 53). Manganese antimony titanate browns (C.I. Pigment Yellow 164) occupy a much smaller market share, and the other rutile grades a significantly smaller fraction still. 

Rutile CICPs contain a significant amount of titania as a base oxide. Typically they range from 70 to 90 % Ti02 by pigment weight. Transition metal cations Ni(II), Cr(III), and Mn(III) are responsible for producing the color, while the colorless ions... 

CICPs that contain aluminum oxide, AI2O3, or alumina as a colorless base oxide are called aluminates. These almost always employ cobalt(II) oxide, CoO, as one of the coloring oxides. All of these pigments adopt the spinel crystal structure, and all have color hues in the blue to teal range. 

Cobalt aluminate blues are the most durable blue pigments commercially available. They have excellent chemical and heat stability, and can be used in chemically aggressive environments and exterior durable applications vithout color fade. One drawback is that these blues are poor UV absorbers when compared to other CICPs. 

A large number of CICPs contain transition metal oxides without a significant amount of a colorless base oxide. These pigments, listed in Table 5-3, employ either green chromium(III) oxide, red iron(III) oxide, or a combination of the two as a base. They are thus referred to as chromites or ferrites, for the chromium and iron bases, respectively. Most adopt the spinel configuration, with the other important structures being those of corundum and hematite. 

Figure 5-5 Reflectance spectra of two I R-reflective CICPs compared with a non-reflective Pigment Black 28. Dips in reflection centered at 1700 and 2300 nm are due to the polymer matrix.

The great feature of these pigments is their good IR reflectivity. They generally have higher IR reflectivity than other dark IR-reflective CICPs, as demonstrated in Figure 5-5. These browns and blacks are primarily used to prepare dark exterior durable colors with low heat build-up. 

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