Pearlescent coatings

The majority of pearlescent coatings in the automotive industry are based on a two-stage process, in which pearlescent pigments with good opacity are included in... 

Afflair, Pearlescents, coated mica platelets, EM Industries Inc. 

Waxes are used in water-resistant coating on cars and furniture. They are also used in lipsticks and eyebrow pencils and in liquid soaps and shampoos to give a pearlescent effect (the tiny flakes of the wax glycol distearate reflect the light). 

Pearlescent pigments give rise to a white pearl effect often accompanied by a coloured iridescence. The most important pearlescent pigments consist of thin platelets of mica coated with titanium dioxide which partly reflect and partly transmit incident light. Simultaneous reflection from many layers of oriented platelets creates the sense of depth which is characteristic of pearlescent lustre and, where the particles are of an appropriate thickness, colours are produced by interference phenomena. Pearlescent pigments are used in automotive finishes, plastics and cosmetics. 

Colorants have been developed for special effects. Pearlescent or iridescent give an attractive appearance. They are often used for coating paper (e.g., cosmetic packaging). The pigment consists of thin platelets, less than 1 pm thickness, which have a high refractive index, e.g., mica coated with Ti02. 

Pearlescent pigments contain small flakes or platelets of the mineral mica that are additionally coated with a very thin layer of titanium dioxide. The simultaneous reflection of light from many layers of small platelets creates an impression of luster and sheen. By varying the thickness of the coating on the surface of the mica particles, pigment manufacturers can achieve a range of colors for the pearlescent effect. 

The presence of mica in pearlescent pigments only partly accounts for the appearance of the pigment. A very thin layer of the inorganic oxide titanium dioxide (TiC>2) or iron oxide (Fe2C>3) or both is coated on the mica platelets. The various colors and pearlescent effects are created as light is both refracted and reflected from the titanium dioxide layers. The very thin platelets are highly reflective and transparent. With their plate-like shape, the platelets are easily oriented into parallel layers as the paint medium is applied. Some of the incident light is reflected... 

Lustre/pearlescent pigments have found wide application in automotive coatings, coloured plastics, synthetic leather, printing inks, ceramic products and cosmetics, e.g. nail polish, lipstick and mascara. 

The development of the mica-based pigments started with pearlescent colors (Fig. 76 A, TiOz - mica). It was followed by brilliant, mass-tone-colored combination pigments (i.e., mica, Ti02, and another metal oxide) with one color (interference color same as mass tone) or two colors (interference and mass tone different) that depend on composition and viewing angle (Fig. 76 B). In the 1980s further development was made by coating mica particles with transparent layers of iron(III) oxide (Fig. 76 C) [5.222]. 

Merck in Japan has recently patented [16] a process for the production of water and weather-resistant pearlescent pigments produced by coating mica with hydrous zirconia. This is in many ways similar to processes operated in the titanium oxide industry and mentioned previously. The zirconium hydroxide aids dispersion and gives better compatibility with the polymer matrix that it is incorporated in. 

Thin hexagonal monocrystalline AI2O3 flakes can be produced by hydrothermal processes [5.150-5.152]. The thickness of the resulting flakes is not uniform. Therefore, the resulting coated pigments merely assume a dull pearlescence. 

Pearlescent pigments. Mica pigments coated with titanium dioxide, or iron oxide, or both are industrially important pigments. They are safe, stable, and environmentally acceptable for use in coatings. The pearlescent effect is produced by the behavior of incident light on the oxide-coated mica partial reflection from the partial transmission through the plates creates a sense of depth. 

Pearlescence comes about by multiple partial reflection of every incident ray of light on several platelet-shaped particles at different depths in the coating. 

Mearlin . [Mearl] Titanium dioxide/ mica for pearlescent, metallic, antique, and iridescent effects in powd. coating systems. 

Timiron . [Rcma] Titanium dioxide-coated mica pearlescent for lipsticks, I essed powdm, makeup. 

Everyone by now is aware of pearlescent and interference pigments. Although not a household word, they are used extensively in every imaginable application. They are incorporated in plastics, coated on substrates, used in printing inks, in cosmetics and used extensively in... 

Although pearlescent pigments encompass the natural pearl essence derived from the fish and also the various crystal forms of bismuth oxychloride, it is the coatings of titanium dioxide and iron oxide on mica that have gained the most acceptance and are the most commercially successful. It is the coatings of titanium dioxide on mica and their derivatives that are the subjects of this study. 

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