Лако-красочные материалы — производство

The use of pearls and nacreous shells for decorative purposes goes back to ancient times (e. g., in Chinese wood intarsia). The history of pearl pigments dates back to 1656, when the French rosary maker Jaquin isolated a silky lustrous suspension from fish scales (pearl essence) and applied this to small beads to create artificial pearls. It took more than 250 years to isolate the pearl essence material (guanine platelets) and understand the pearl effect. Attempts were made to create synthetic pearl colors as organic or inorganic, transparent, highly refractive coatings, and pearl pigments as crystalline platelets. From 1920 onward, hydroxides, halides, phosphates, carbonates, and arsenates of zinc, calcium, barium, mercury, bis­muth, lead, and other cations were produced for this purpose. Only the traditional natural pearl essence, basic lead carbonate, and bismuth oxychloride, is still of importance.

The strong demand for pearl effects came from the growing coatings and plas­tics industries, which wanted to improve the acceptance and popularity of their products. Furthermore, pearlescent pigments also allowed artists and designers to create new visual effects similar to those found in nature. The breakthrough for pearlescent pigments came with the invention of mica coated with metal oxides. Mica-based pearlescent pigments now account for > 90% of the world market.

Pearlescent pigments are used to obtain pearl, iridescent (rainbow), or metallic effects, and in transparent color formulations to obtain brilliance or two-tone color, luster flops and color travel effects (changing with viewing angle). The most important applications are plastics, industrial coatings, printing inks, cosmetics, and automotive paints.

Table 7.1 shows an overview of pigments with luster effects. Effect pigments can be classified as metal platelets, oxide-coated metal platelets, oxide-coated mica platelets, oxide-coated silica and alumina flakes, platelet-like monocrystals, com­minuted PVD films (PVD = physical vapor deposition), and liquid crystal polymer platelets (LCP-pigments) [1, 2]. Aims of new developments are new effects and colors, improvement of hiding power, more intense interference colors, increased light and weather stability, and improved dispersibility. Of special interest are pig­ments which are toxicologically safe and which can be produced by ecologically acceptable processes.

7.2.1