Lithopones production

Figure 20 is a flow diagram of lithopone production. The solutions of zinc salts contain impurities (e.g., salts of iron, nickel, chromium, manganese, silver, cadmi-... 

Figure 2.7 is a flow diagram of lithopone production. The solutions of zinc salts contain impurities (e.g., salts of iron, nickel, chromium, manganese, silver, cadmium) that depend on their origins. The main sources of zinc sulfate solutions are zinc electrolyses and the reprocessing of zinc scrap and zinc oxide. The first stage of purification consists of chlorination. Iron and manganese are precipitated as oxide-hydroxides. 

Lithopone - Lithopone production starts with the same process used for blanc fixe, except that zinc sulfate is used in place of sodiiun sulfate. The intimate mixture of barium sulfate and zinc sulfide that precipitates is filtered, washed, dried, calcined, water quenched, wet ground, and dried. The result is a white mixture of barium sulfate, zinc sulfide, and zinc oxide. Lithopone was one of the first fine white pigments for industry but is now rarely used. 

Zinc is also used extensively to galvanize other metals such as iron to prevent corrosion. Zinc oxide is a unique and very useful material for modern civilization. It is widely used in the manufacture of paints, rubber products, cosmetics, pharmaceuticals, floor coverings, plastics, printing inks, soap, storage batteries, textiles, electrical equipment, and other products. Lithopone, a mixture of zinc sulfide and barium sulfate, is an important pigment. 

Lithopone [8006-32-4] an important white pigment, is produced mainly in the former Soviet Union, the C2ech RepubHc, and the People s RepubHc of China. In China, the nation s output for Hthopone peaked in 1990 at about 233,000 t. In 1992 it was only 168,000 t. About one-third of the Hthopone produced in China was exported. Annual worldwide production can be estimated to be under 250,000 t as of this writing (ca 1995) (18) (see Barium... 

Production. Commercial production of Hthopone started in the first half of the nineteenth century, and continued to grow until the middle of the twentieth century when titanium dioxide started to dominate the white, inorganic pigment market. Lithopone is prepared by combining barium sulfide and 2inc sulfate solutions at 50—60°C ... 

C04-0121. Lithopone, a brilliant white pigment used in paints, paper, and white rubber products, is a mixture of two insoluble Ionic solids, ZnS and BaSOq. Suggest how 1.0 kg of lithopone could be prepared by a precipitation reaction. 

Sachtolith. Production is similar to that of lithopone. For process engineering reasons, a sodium sulfide solution is used as the sulfide component, and is formed according to Equation (4) ... 

Environmental Protection. 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 poly glycol. The absorbed sulfur dioxide can be recovered as a liquid product or as a raw material for sulfuric acid. Any soluble barium in the residue from the dissolution of the fused BaS is removed by treatment with... 

Commercial lithopone grades contain 30% ZnS (red seal) and 60% ZnS (silver seal). The ZnS content of Sachtolith is > 97 %. Various chemical (e.g., polyalcohols, siloxanes, silanes) and mechanical treatments (e.g., jet milling) are used to obtain other products for special applications. The technical data for commercial red seal lithopone and Sachtolith are given in Table 20. 

Total world production of lithopone in 1990 was 220 x 103 t. This was subdivided as follows (103 t) ... 

Production. Zinc sulfide production started in the United States and in Europe in the 1920s. Starting in the eady 1950s, zinc sulfide, like most white pigments, was slowly replaced by the more superior titanium white. Zinc sulfide can be prepared by a process similar to the one used to manufacture lithopone. In the first step, barium sulfide reacts with sodium sulfate to produce sodium sulfide solution ... 

Hot lithopone leaving the calciner has to be cooled quickly to prevent the oxidation of ZnS to ZnO. Rapid cooling is accomplished by its suspension in water that might contain a small amount of sulfuric acid to remove any traces of undesirable zinc oxide. The suspension is then wet milled, filtered off, and dried to the commercial product. 

Zinc oxide (ZnO), which is produced by burning zinc vapor in atmospheric oxygen, is by far the most important compound of zinc. Under the name of zinc white, the oxide is used as a paint pigment. It is also used as a base in the manufacture of enamels and glass, and as a ruler in the fabrication of automobile tires and other kinds of rubber goods. Zinc sulfide (ZnS) is also an important white paint pigment which is used either as such or in the form of lithopone, which is a mixture of zinc sulfide and barium sulfate. This widely used pigment is prepared by the metathetical reaction between zinc sulfate and barium sulfide, a reaction in which both of the products are insoluble ... 

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. 15-20 min at 250-300 °C. In contrast to the wurtzite structure of the calcined product. 

Barium sulfide is the most important intermediate in the manufacture of barium compounds (see Section 3.1.2.6.2). It is also used in the manufacture of lithopone (joint precipitation of ZnS + BaS04). The importance of Lithopone has declined with the expansion in the use of Ti02 pigments. USA production of barium sulfide, 112 10 t/a in 1965, had declined to 44 10 t/a by 1979, since when no further figures have been published. 

The use of water in place of organic solvents as a paint thinner has obvious attractions. The first important commercial product of this type was the oil-bound water paint, the vehicle being an emulsion of oil or varnish in an aqueous solution of gelatine. The preferred white pigment was lithopone (zinc sulphide/ barium sulphate), and a high ratio of pigment to binder was used. This product was eventually replaced by the emulsion paint (known as latex paint in USA and dispersion paint on the continent of Europe). It used a synthetic vinyl polymer as a binder, mainly a co-polymer of vinyl acetate with either vinyl versatate or butyl acrylate, with titanium dioxide as the white pigment. Attempts to use an alkyd emulsion based on oil as the vehicle were commercially unsuccessful. The droplet size of the dispersion at emulsion is normally about 0.2-1 //m. 

---