Лако-красочные материалы — производство

Chromium(III) oxide crystallizes in the rhombohedral structure of the corundum type; space group D3d6 -R3c, p = 5.2 g cm-3. Because of its high hardness (ca. 9 on the Mohs scale) the abrasive properties of the pigment must be taken into account in certain applications [3.54]. It melts at 2435 °C but starts to evaporate […]

Chromium oxide pigments, also called chromium oxide green pigments, consist of chromium(III) oxide [1308-38-9], Cr2O3, Mr 151.99. Chromium oxide green is one of the few single-component pigments with green coloration. Chrome green is a blend ofchrome yellow and iron blue pigments; phthalochrome green is a blend ofchrome yellow and blue phthalocyanine pigments. Natural, profitable deposits […]

Accurate production figures for natural and synthetic iron oxide pigments are difficult to obtain, because statistics often also include nonpigmentary oxides (e. g., red mud from bauxite treatment, intermediate products used in ferrite production). World production of synthetic iron oxides in 2002 was estimated to be 700,000 t with a value of about 970 millions […]

All synthetic iron oxides possess good tinting strength and excellent hiding power. They are also lightfast and resistant to alkalis. These properties are responsible for their versatility. The principle areas of use are shown in Table 3.3 [3.49, 3.50]. The main usage is in the construction industry followed by coatings but this differs by geographical […]

The red and black iron oxide pigments produced by the methods described have a Fe2O3 content of 92-96 wt.%. For special applications (e. g., ferrites) analytically pure pigments with Fe2O3 contents of99.5-99.8 wt.% are produced. The Fe2O3 con­tent of yellow and orange pigments lies between 85 and 87 wt.% corresponding to FeOOH contents of 96-97 […]

The Berufsgenossenschaft der Chemischen Industrie (Germany’s workers health authority for the chemical industry) has recommended that all iron oxide pigments should be classified as inert fine dusts with an MAK value of 3 mg m-3 [3.46]. Iron oxide pigments produced from pure starting materials may be used as col­orants for food and pharmaceutical products [3.47]. […]

The three processes already described are the only ones that are used on a large scale. The following processes are used on a small scale for special applications: 1. Thermal decomposition of Fe(CO)5 to form transparent iron oxides (see Sec­tion 5.4.1) [3.44] 2 3.1.1.3

The Bechamp reaction (i. e., the reduction of aromatic nitro compounds with anti­mony or iron), which has been known since 1854, normally yields a black-gray iron oxide mud that cannot be transformed into an inorganic pigment. By adding iron(II) chloride or aluminum chloride solutions, sulfuric acid, and phosphoric acid, Laux modified the process to yield […]

In principle, all iron oxide hydroxide phases can be prepared from aqueous solutions of iron salts (Table 3.2). However, precipitation with alkali produces neutral salts (e. g., Na2SO4, NaCl) as byproducts, which enter the wastewater. Precipitation is especially suitable for producing soft pigments with a pure, bright hue. The manufacture of a-FeOOH yellow is described […]

Black iron oxides obtained from the Laux process (see below) or other processes may be calcined in rotary kilns with an oxidizing atmosphere under countercurrent flow to produce a wide range of different red colors, depending on the starting material (Eq. (3.2)). The pigments are ground to the desired particle size in pendular mills, pin […]