Лако-красочные материалы — производство

Metal effect pigments consisting of flakes or lamellae of aluminum (aluminum bronzes), copper and copper-zinc alloys (“gold bronzes”), zinc, and other metals have been well known for a long time [31]. Some of these metal flakes, especially aluminum platelets, can be coated with iron oxide in a CVD process [1, 11, 19]. These are commercially […]

Special effect pigments with neutral body color, high luster, and improved spark­ling properties can be achieved from borosilicate flake substrates (glass flakes) [45, 46]. These pigments consist mostly of calcium-aluminium borosilicate plate­lets coated with metal-oxide layers such as SiO2, TiO2 or Fe2O3. The synthetically manufactured flakes can be absolutely planar and show a smooth surface. […]

Thin hexagonal monocrystalline Al2O3 flakes can be produced by hydrothermal processes [28-30]. The thickness of the resulting flakes is not uniform. Therefore, the resulting coated pigments merely assume a dull pearlescence. Al2O3 flakes of a higher quality are produced by the following steps (Figure 7.14). An aqueous solution of an aluminum salt is mixed with […]

Instead of mica, SiO2 flakes can be used as a substrate for pearlescent pigments. The SiO2 flakes are produced by a web-coating process. Synthetic SiO2 flakes offer three advantages over the use of natural mica: (1) the thickness of the SiO2 sub­strate can be controlled in the preparation so that at the end a pigment […]

Simple blending of transparent absorption pigments with pearlescent pigments is only one way to attain new coloristic effects. It is possible to produce pearlescent pigments coated with a layer of transparent absorption colorant to realize more pronounced brilliant colors with a sharper color flop. An additional advantage of such pigments is the elimination of dispersion […]

Like titanium dioxide, iron(III) oxide is suitable for coating mica platelets. It com­bines a high refractive index (metallic luster) with good hiding power and excel­lent weather resistance. Commercial Fe2O3-mica pigments are produced by pre­cipitation of iron(II) or iron(III) ions in aqueous mica suspensions and calcination of the resulting coated particles at 700-900 °C: 2 FeCl3 […]

7.2.3.1 Metal Oxide-Mica Pigments The dominant class of pearlescent pigments is based on platelets of natural mica coated with thin films of transparent metal oxides [2-8, 16]. The mica substrate acts as a template for the synthesis and as a mechanical support for the deposited thin optical layers of the pearlescent pigments. Mica minerals are […]

Titanium dioxide flakes are produced by breaking down a continuous film of TiO2 [8, 12]. The most efficient process is therefore a web-coating process involving a thermal hydrolysis of TiOCl2 on the web. Alternative procedures are the applica­tion of titanium alkoxide on a smooth flat surface and cracking the resulting film into flakes by steam […]

Micaceous iron oxide consists of pure or doped hematite (a-Fe2O3). Its density is 4.6-4.8 g/cm3. Micaceous iron oxide can also be obtained by hydrothermal synthe­sis in alkaline media. However, the dull dark color is as unappealing as that of the natural product. If substantial amounts of dopants are incorporated, the aspect ratio can be increased […]

Bismuth oxychloride is produced by the hydrolysis of very acidic (pH < 1.0) bis­muth solutions in the presence of chloride. The crystal quality can be varied by careful adjustment of bismuth concentration, temperature, pH, pressure, reactor geometry, and addition of surfactants. The usually tetragonal bipyramidal struc­ture can be flattened to platelets with a high aspect […]