3 ноября, 2015 
Pokraskin Mixed metal oxide pigments are manufactured by a solid state chemical reaction at very high temperatures of approximately 800 to 1300 °C. Raw materials include metal oxides and salts, that can be converted into oxide upon heating. During the high temperature calcination process, the mixture of metal oxides is converted into a new chemical compound, which already possesses some color properties. Color and other physical properties are optimized for the end-use by finishing the crude pigment. This finishing involves micronizing and — in most cases — washing and drying the pigment. A manufacturing scheme is illustrated in Figure 3.7.
Detailed know-how and process control of each of the manufacturing steps is critical in achieving optimized pigment performance. Since, manufacturing involves solid-state chemistry and a high temperature process, much effort must be given to optimizing the process in order to obtain easily dispersible pigments with favorable color properties.
For rutile yellows, different colors can be obtained by variation of the calcination temperature. A higher calcination temperature gives darker grades with a higher chroma. However, the tinting strength drops in the same direction. With regard to
opacity, optimum performance is found for medium shades, which can be explained by achieving a compromise between particle size (scattering) and lightness value (absorption) [3.94]. High strength versions have been introduced which both optimize particle size distribution and the amount of coloring ions that are included as dopants in the titanium oxide rutile structure.
For hematites and (inverse) spinels, color is also influenced by the calcination temperature. However, the main driving factor is the actual chemical composition, including the use of mineralizing agents. This opens numerous possibilities to obtain colored pigments with different shades.
3.1.3.2
Опубликовано в рубрике 