Лако-красочные материалы — производство

Mixed metal oxide (MMO) pigments are inorganic high performance pigments with outstanding fastness properties, which are used in paints, plastics, building materi­als, glass coatings and ceramics. For ceramics, numerous other complex inorganic colored mixed oxides (“stains”) exist, which can be consulted in the literature. The following description concentrates on mixed metal oxides for paints, plastics […]

Toxicological or carcinogenic effects have not been detected in rats receiving up to 5% chromium(III) oxide in their feed [3.81] nor in medical studies performed in chemical plants producing chromium(III) oxide and chromium(III) sulfate [3.82]. The oral LD50 for chromium(III) oxide in the rat is >10,000 mg kgg ; it does not irritate the skin […]

Important producers are Elementis (USA and UK), Lanxess (Germany), NovoChrom (Novotroisk, Russia), ACCP (Aktubinsk, Kazakhstan) and Nihon Denko (Japan). Sta­tistical data on the consumption of chromium oxide have not been published recently. However, it can be assumed that the world capacity in 2002 was about 100,000 t a-1; the consumption as pigments in 2002 was […]

The use of chromium(III) oxide as a pigment for toys, cosmetics, and in plastics and paints that come into contact with food is permitted in national and international regulations [3.72-3.79]. Maximum limits for heavy metals or their soluble fractions are usually a prerequisite. Because pure starting materials are used, these limits are satisfied by most […]

Chromium(III) oxide pigments are thermally stable and insoluble in water. They are not classified as hazardous materials and are not subject to international transport regulations. As long as they are kept dry their utility as a pigment is practically unlimited.

International, technical specifications for chromium oxide pigments are defined in ISO 4621 (1986), they must have a minimum Cr2O3 content of 96 wt.%. Various grades are defined according to their particle fineness as measured by the residue on a 45 pm sieve: grade 1, 0.01% residue (max.); grade 2, 0.1% (max.); and grade 3, 0.5% […]

Since alkali dichromates or chromic acid anhydride are used as starting materials for the production of chromium(III) oxides, occupational health requirements for the handling of hexavalent chromium compounds must be observed [3.69]. The sulfur dioxide formed on reduction with excess sulfur must be removed from the flue gases according to national regulations, e. g., by […]

Other production processes are suggested in the patent literature, but have not so far gained industrial importance. For instance, sodium dichromate can be mixed with heating oil and reacted at 300 °C. The soda formed must be washed out prior to calcining at 800 °C to avoid reoxidation in the alkaline melt [3.66]. In alkaline […]

Chromium(III) oxide can be obtained by thermal decomposition of ammonium dichromate. Above ca. 200 °C, a highly voluminous product is formed with elimi­nation of nitrogen [3.58]. The pigment is obtained after addition of alkali salts (e. g., sodium sulfate) and subsequent calcination [3.59]. In the industrial process, a mixture of ammonium sulfate or chloride and […]

Alkali dichromates are used as starting materials for the production of chromium(III) oxide pigments. They are available as bulk industrial products in the required purity. High impurity levels have an unfavorable effect on the hue. Reduction of Alkali Dichromates In industrial processes, solid alkali dichromates are reacted with reducing agents such as sulfur or carbon […]