Лако-красочные материалы — производство

Thermal treatment at temperatures up to 1000 °C improves the pigment properties of the ZnO and is mainly applied to oxide produced by the direct method. Controlled atmospheric calcination also improves the photoconducting properties of the high — purity oxide used in photocopying. The ZnO surface is made more organophilic by coating it with oil […]

Zinc oxide is also produced industrially from purified solutions of zinc sulfate or chloride by precipitating the basic carbonate, which is then washed, filtered, and finally calcined. This method produces a grade of zinc oxide with a high specific surface area. Products of this type are also obtained from waste hydroxides which are purified by […]

The zinc is boiled, and the resulting vapor is oxidized by combustion in air under defined conditions. The crystallographic and physical properties of the ZnO can be controlled by adjustment of the combustion conditions (e. g., flame turbulence and air excess). The chemical composition of the ZnO is solely a function of the composition of […]

The direct process is noted for its simplicity, low cost, and excellent thermal ef­ficiency. It consists of an initial high-temperature reduction (1000-1200 °C) of a zinc-containing material (as oxide), the reducing agent being coal. Reduction takes place according to Boudouard’s equations: ZnO+ C ^Zn+ CO ZnO + CO ^Zn + CO2 C + O2 ^CO2 […]

In the early days, the raw materials were mainly zinc ores or concentrates for the direct process, or metal from zinc producers for the indirect process. Nowadays, zinc oxide manufacturers mainly use residues and secondary zinc. This fact, combined with the demand for chemical purity imposed by the users, means that processes have had to […]

Zinc oxide is amphoteric; it reacts with organic and inorganic acids, and also dissolves in alkalis and ammonia solution to form zincates. It combines readily with acidic gases (e. g., CO2, SO2, and H2S). It reacts at high temperatures with other oxides to form compounds such as zinc ferrites. 2.3.3 Production The total production capacity […]

2.3.2.1 Physical Properties Zinc oxide is a fine white powder that turns yellow when heated above 300 °C. It absorbs UV light at wavelengths below 366 nm. Traces of monovalent or trivalent elements introduced into the crystal lattice impart semiconducting properties. The elementary particles of ZnO obtained by the thermal method may be granular or […]

2.3.1 Introduction Zinc oxide [1314-13-2], ZnO, Mr 81.38, was formerly used only as a white pigment, and was named zinc white (C. I. Pigment White 4), Chinese white, or flowers of zinc. The term zinc white now denotes zinc oxide produced by the combustion of zinc metal according to the indirect or French process. Historical […]

The use of zinc sulfide and barium sulfate in contact with foods is permitted by the FDA (United States) and in most European countries. Some restrictions apply in France, Italy, the United Kingdom, and Czechoslovakia. Soluble zinc is toxic in large amounts, but the human body requires small quan­tities (10-15 mg d-1) for metabolism. Zinc […]

Total world production of zinc sulfide pigments in 2003 was 260 x103 t. This was subdivided as follows (103 t): Germany 20 People’s Republic of China 200 Others 40 Only estimated figures are available for the People’s Republic of China. A decrease in output is to be expected because replacement by TiO2 is not yet […]