**1. Introduction**

Titanium dioxide (TiO<sup>2</sup> ) is used in a variety of applications, all of which have different sets of performance requirements. As a result, the pigments designed for the various applications

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are different. Variations in crystal structure (anatase/rutile), inorganic coating and organic treatments provide a wide range of titanium dioxide grades, each with different properties.

• After-treatment with Zr, Ti, Al and Si compounds.

zirconium and aluminum: cca. 90% TiO<sup>2</sup>

For coloring of plastics, usually smaller TiO<sup>2</sup>

80–85%.

inorganic coating (TiO<sup>2</sup>

the pigment [3].

**1.1. About TiO2**

TiO<sup>2</sup>

gloss.

*1.1.2. Uses of TiO2*

Titanium dioxide pigment (TiO<sup>2</sup>

cations such as the following:

• paints and coatings

• printing inks

• plastics • paper

*1.1.1. Pigment properties*

pigment properties of TiO<sup>2</sup>

• After-treatment with merely 1–3% of alumina [15–18].

typically >95%).

**2.** Pigments with porous coating for use in emulsion paints obtained by simple treat-

**3.** Lightfast pigments with dense surface coatings for the paper laminate industry that have a highly stabilized lattice and a surface coating based on silicates or phosphates of titanium,

Before micronizing the pigment in a jet-mill and sometimes also before drying, the pigment surface is further modified by adding organic substances to improve dispersibility and facilitate further processing. The nature of the compounds used depends on the intended use of

Scattering power, hiding power (tinting strength), brightness, mass tone (or color), gloss formation, gloss haze, dispersibility, lightfastness and weather resistance are the most important

's theoretical optimum particle size is between 0.2 and 0.3 μm, but the pigment obtained is considerably larger mainly because of the formation of agglomerates while handling during the manufacturing process. The presence of agglomerates affects hiding power, tinting strength and other end-use properties of the coating. The graph in **Figure 1** illustrates the effect of TiO<sup>2</sup>

dispersion states vs. particle size distribution on pigment properties. A well-dispersed system helps to develop coatings with improved optical properties, hiding power, tinting strength and

its opacity, high chemical stability, excellent whiteness and brightness. It is required in appli-

stabilization, primary particle size, particle size distribution and the coating.

pigments; these properties are a function of chemical purity, lattice

) is an important material used in many applications due to

content of

423

's

particles are used with typically less than 3% of

TiO2 Applications as a Function of Controlled Surface Treatment

http://dx.doi.org/10.5772/intechopen.72945

ment with Ti, Al and Si compounds, giving a silica content of 10% and a TiO<sup>2</sup>

.

Generally, the properties of a pigment are determined by the particle size distribution of the base pigment, the chemical composition and the morphology of the surface treatment. The morphology of the treatment layers can, in turn, have an effect on the final properties of the pigment.

TiO<sup>2</sup> pigments are generally coated to improve their performance in many end-use applications. Thus, the pH, temperature, reagents, order of addition and other factors can affect product characteristics. Optimum treatment conditions need to be determined after the surface treatment chemicals have been selected [1].

There are differences between grades, partially based on the fact that TiO<sup>2</sup> particle surfaces may be modified differently with inorganic and organic post treatments. With regard to colloidal chemistry, a TiO<sup>2</sup> with an Al<sup>2</sup> O3 surface treatment behaves completely different from one having a SiO<sup>2</sup> surface treatment [2]. Both of these, again, are different from a pure, untreated TiO<sup>2</sup> , which has its IEP at pH values between 4.5 and 6.5.

Surface treatment of TiO<sup>2</sup> particles by colorless inorganic compounds of low solubility affects dispersibility of the pigments in the matrix and weather resistance and lightfastness of the pigmented organic matrix [3].

These treatments are most commonly precipitated in layers. However, some of the components can be co-precipitated to alter the pigment characteristics [1]. There are many works regarding this subject in literature [4–14].

Inorganic surface treatment influences optical performance of the pigment approximately in proportion to the decrease in the TiO<sup>2</sup> content. Surface coatings prevent direct contact between the binder matrix and the reactive surface of the TiO<sup>2</sup> . The treatment process also affects dispersibility of the pigment, and therefore a compromise often has to be made. High weather resistance and good dispersibility of the pigment in the binder or matrix are usually desired. These effects are controlled by using different coating densities and porosities. In addition, organic substances can be added during the final milling of the dried pigment [3].

Several types of treatment are known:


Typical groups of inorganic coatings are as follows:

	- Homogeneous precipitation of SiO<sup>2</sup> with precise control of temperature, pH and precipitation rate.

For coloring of plastics, usually smaller TiO<sup>2</sup> particles are used with typically less than 3% of inorganic coating (TiO<sup>2</sup> typically >95%).

Before micronizing the pigment in a jet-mill and sometimes also before drying, the pigment surface is further modified by adding organic substances to improve dispersibility and facilitate further processing. The nature of the compounds used depends on the intended use of the pigment [3].
