Zinc oxide American process

Leaded Zinc Oxide. Oxides containing more than 5 wt % basic lead sulfate are classified as leaded and are made ia the American process from high lead materials, usually lead sulfide mineral, or by blending ziac oxide and basic lead sulfate. There is only one manufacturer ia the United States and the product contains 20—28 wt % basic lead sulfate. Leaded oxides are used only ia mbber ia the United States. 

Zinc oxide is made either by the oxidation of the metal in oxygen (the indirect, IP, or French process), by the direct decomposition of zinc ores in air (the direct or American process) or by the thermal decomposition of zinc salts (TD zinc oxide). IP zinc oxides differ from TD zinc oxides in that their surfaces do not contain absorbed water. Also, whereas TD zinc oxide reacts with plain eugenol, IP zinc oxide hardly reacts unless activated by an acetic add or zinc acetate accelerator (Table 9.2). 

An activator in rubber compounds containing organic accelerators. In polychloroprene, zinc oxide is considered to be the accelerator rather than the activator. The use of zinc oxide as a reinforcing agent and as a white colouring agent is obsolescent. Zinc oxide is manufactured by either the French (or indirect) process or by the American (or direct) process. It can be used as a filler to impart high thermal conductivity. 

Both these methods give zinc oxides of low activity. Zinc oxide from the American process can have a varying sulphur content, dependant upon the ore s source, and unless known and allowed for, this can affect the compound vulcanisation rate. 

American Also known as the Wetherill process, and the Direct process. A process for making zinc oxide, in the form of a white pigment, from a zinc oxide ore. The ore is usually franklinite, which is predominately ZnFe204. The ore is mixed with coal and heated in a furnace to approximately 1,000°C, forming zinc vapor in a reducing atmosphere. The vapors pass to a second chamber in which they are oxidized with air, forming zinc oxide and carbon dioxide. See also French. 

Flicker A process for producing zinc oxide by direct oxidation of zinc vapor. Operated by the Fricker s Metal Company at Luton and Burry Port, UK, in the 1920s and 30s, subsequently acquired by the Imperial Smelting Corporation. Also operated by the Anglo American Corporation, South Africa, after World War II. 

Direct weighing, of fibers, 11 182 Direct (American) zinc oxide process, 26 611-612... 

Direct or American Process. 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 ... 

The direct American process is basically a metallurgical operation. Zinc oxide ores are reduced using coal (qv) in a rotary kiln at temperatures of 1000—1200°C to zinc metal. At these temperatures the produced zinc metal evaporates and is oxidized with air to ZnO in the upper part of the kiln. 

In the indirect French process, metallurgically refined zinc metal is boiled and the generated vapors combust with air to form zinc oxide. Metallic zinc is the starting material of this latter process, making it more expensive than the American one. The French process is the preferred production method, however, because it yields a purer product. Volatile metals, such as lead and cadmium, are again the main impurities that can be found in zinc white. Complex purification methods, such as fractional distillation, have been devised to reduce the amount of these impurities to acceptable levels. 

The raw materials for the manufacture of zinc oxide by the American process are roasted ores, concentrates of zinc ores or more recently zinc hydroxide or zinc carbonate from the processing of scrap. These are reduced with coal and directly reoxidized to ZnO in the same reaction chamber. The purity of the zinc oxide is normally somewhat inferior to that from the French process. Grades of various purities can be produced by fractionation. 

Zinc oxide is produced either by the French or by the American process. Both processes are pyrometallurgical techniques in which the metal in a vapor state reacts with oxygen, forming zinc oxide. The difference between the methods is in the raw material used for the synthesis. In the French process, pure metal is evaporated, and the final product is as pure as the metal used for its production. In the American process, zinc vapor is obtained directly from an ore by burning it as a mixture with coal or in an electrothermic process where electric current provides the heat. More recently, a new method, somewhat similar to the French process, was introduced by Nanophase Technologies Corporation who patented a physical vapor synthesis process in which zinc metal is vaporized. The vapor is rapidly cooled in the presence of oxygen, causing nucleation and condensation of nanoparticle size zinc oxide. The particles are non-porous and free of contamination. 

Zinc Oxide. Rowers of zinc philosopher s wool zinc white C.l. Pigment White 4 C.l. 77947. OZn mol wt 81.38. Zn 80.34%, O 19.66%. ZnO. Occurs as the mineral zincite. Prepd by vaporization of metallic zinc and oxidation of the vapors with preheated air (French process) also from franklinite, (American process) or from zinc sulfide Faith, Keyes Clark s Industrial Chemicals. F. A. Lowenheim. M. K. Moran, Eds. (Wiley-In terscience. New York, 4th ed 1975) pp 882-888. Purification Depew, U.S. pat. 2,372,367 (1945 to American Zinc, Lead Smelting). The medicinal grade contains 99.5% or more ZnO technical grades contain 90-99% ZnO and a few tenths of 1% of lead. See also Colour Index vol, 4 (3rd ed., 1971) p 4687. 

White or yellowish -white, odorless powder. Hexagonal crystals d 5.67. Also reported as dj 5.607. Sublimes at normal pressure. nD 2.0041, 2.O203- American process zinc oxide pH 6.95. French process zinc oxide pH 7,37, Practically insol in water sol in dil acetic or mineral acids, ammonia, ammonium carbonate, fixed alkali hydroxide solns. 

CHEMICAL PROPERTIES noncombustible solid gradually absorbs carbon dioxide upon exposure to air reacts with hydrochloric acid to produce zinc chloride reacts with sulfuric acid to produce zinc sulfate, and it reacts with carbon monoxide or hydrogen to produce elemental zinc reacts lowly with fatty acids in oils and fats to produce lumpy masses of zinc oleate, stearate, etc. forms cement-like products when mixed with a strong solution of zinc chloride or with phosphoric acid, owing to the formation of oxy-salts hydrogen peroxide is produced when ointments containing zinc oxide and water are melted and exposed to UV light FP (NA) LFL/UFL (NA) AT (NA) HC (NA) HF (-350.5 kJ/mol crystal at 25°C) pH (6.95 American process zinc oxide, 7.37 French process zinc oxide). 

American process zinc oxide n. Zinc oxide pigment made directly from zinc ores. Sometimes called direct process. 

There are two production types of zinc oxide, namely the French process and the American process. In the French process, zinc metal is vaporized in large containers by external heating. In an adjoining off-take pipe or combustion chamber, the vapor is burned off in the air to fine zinc oxide powder. In the American process, oxidized ores of roasted sulfide concentrates are mixed with anthracite coal and smelted in a WetheriU-type flat bed furnace. The coal, plus the products of partial combustion, particularly CO, reduce the ore to metallic zinc, which issues as a vapor. In the off-take pipe, the vapor, together with the gases... 

Zinc oxide is available from three different processes (the American, French, and wet methods) as shown in Figure 10.2. 

Figure 10.2 Three processes for producing zinc oxide the American process (direct), the French process (indirect), and the wet process...

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