**1.1. About TiO2**

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. 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.

 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

may be modified differently with inorganic and organic post treatments. With regard to colloi-

dispersibility of the pigments in the matrix and weather resistance and lightfastness of the

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

Inorganic surface treatment influences optical performance of the pigment approximately in

persibility 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].

pigment grinding, which results in partial coating of the pigment surface.

• Precipitation of the coating from aqueous solution onto the suspended TiO<sup>2</sup>

silicates and/or phosphates of titanium, zirconium, silicon and aluminum.

**1.** Pigments with dense surface coatings for paints or plastic made by

• Deposition from the gas phase by hydrolysis or decomposition of volatile substances.

• Addition of oxides, hydroxides or substances that can be absorbed onto the surface during

batch processes in stirred tanks starting from various compounds, which are deposited one after another under specific conditions. The most common are oxides, oxide hydrates,

surface treatment [2]. Both of these, again, are different from a pure, untreated

surface treatment behaves completely different from one

content. Surface coatings prevent direct contact between

. The treatment process also affects dis-

with precise control of temperature, pH and

particles by colorless inorganic compounds of low solubility affects

particle surfaces

particles by

There are differences between grades, partially based on the fact that TiO<sup>2</sup>

O3

, which has its IEP at pH values between 4.5 and 6.5.

TiO<sup>2</sup>

dal chemistry, a TiO<sup>2</sup>

Surface treatment of TiO<sup>2</sup>

pigmented organic matrix [3].

regarding this subject in literature [4–14].

proportion to the decrease in the TiO<sup>2</sup>

Several types of treatment are known:

having a SiO<sup>2</sup>

TiO<sup>2</sup>

treatment chemicals have been selected [1].

422 Titanium Dioxide - Material for a Sustainable Environment

with an Al<sup>2</sup>

the binder matrix and the reactive surface of the TiO<sup>2</sup>

Typical groups of inorganic coatings are as follows:

• Homogeneous precipitation of SiO<sup>2</sup>

precipitation rate.
