Лако-красочные материалы — производство

This is mainly used in plastics (Table 2.12). Functional properties such as lightening and hiding power are criteria for the use of Sachtolith. It has proved to be very useful for coloring many thermoplasts. During the dispersion process it does not cause abrasion of metallic production machinery or adversely effect the polymer, even at high […]

This is mainly used in coating materials with relatively high pigment concentrations (Table 2.12). Examples are primers, plastic masses, putties and fillers, artists’ colors, and emulsion paints. An important property of lithopone is its low binder require­ment, giving paint products with good flow and application properties. It is suitable for almost all binder media, and […]

Commercial lithopone grades contain 30% ZnS (red seal) and 60% ZnS (silver seal). The ZnS content of Sachtolith is >97%. Various chemical surface modification swith hydrophilic or hydrophobic organic or inorganic substances are made to obtain prod­ucts for special applications. The technical data for commercial red seal lithopone and Sachtolith are given in Table 2.11. […]

During the reduction of barite and the calcination of Sachtolith and lithopone, sulfur dioxide is liberated. This is removed from the waste gas in a purification stage, which is based on the reversible, temperature-dependent solubility of sulfur dioxide in polyglycol. The absorbed sulfur dioxide can be recovered as a liquid product or as a raw […]

Crystal growth of ZnS can be achieved by using a hydrothermal process instead of by calcination. The raw lithopone is precipitated with a slight excess of sulfide at pH 8.5. The pH is then adjusted to 12-13 with sodium hydroxide solution, and 0.5% sodium carbonate is added. The suspension is then autoclaved for ca. 15­20 […]

Production is similar to that oflithopone. A Na2S solution is mixed with a zinc salt solution under precisely controlled con­ditions. The resulting zinc sulfide precipitate is calcined and processed to give the finished product. Na2S + ZnSO4 ^ZnS + Na2SO4 2.2.2.4

The reaction of equimolar quantities of ZnSO4 and BaS produces a white, water — insoluble coprecipitate with the theoretical composition 29.4 wt.% ZnS and 70.6 wt.% BaSO4: ZnSO4 + BaS ^ZnS + BaSO4 By using a different molar ratio, this composition can be changed; for example, precipitation according to the following equation gives a product […]

2.2.2.1 Raw Materials The source ofzinc can be zinc oxide from a smelter, zinc dross or sweepings, ammo­nium chloride slag from hot dip galvanizing, or liquid waste such as pickle liquors from galvanizing plants. Variations in the price of zinc have a large effect on the economics of zinc sulfide pigments. The starting material for […]

Some physical and chemical properties of ZnS and BaSO4 are given in Table 2.10. Tab. 2.10: Properties of the components of zinc sulfide pigments. Property Zinc sulfide Barium sulfate* Physical properties Refractive index n 2.37 1.64 Density, g cm-3 4.08 4.48 Mohs hardness 3 3.5 Solubility in water (18 °C), wt.% 6.5 x10-5 2.5 x10-4 […]

White pigments based on zinc sulfide were first developed and patented in 1850 in France. Although they are still of economic importance, they have continually lost marketvolume since the early 1950s when titanium dioxide was introduced. Only one modern production installation for zinc sulfide pigments still exists in the western hemisphere (Sachtleben Chemie, Germany). All […]