MAGNESIUM HYDROXIDE, IN THE FORM OF FINE POWDER, MANUFACTURING PROCESS AND APPLICATION THEREOF AND PLASTIC MATERIAL CONTAINING ITS

摘要

Finely powdered magnesium hydroxide, in particular for use as a flame retardant filler for plastic compounds, in which the particles may have a thin coating of a surface active substance. The particle size of the magnesium hydroxide, as determined by laser diffraction, is less than 10 mu m and the mean particle size is greater than 0.8 mu m but not more than 3 mu m. The magnesium hydroxide has a water-soluble ionic impurities content, i.e., Ca++, Na+, K+, SO4-- and Cl-, below the following limits (in parts by mass): Ca++ 1000 ppm, Na+ 20 ppm, K+ 20 ppm, SO4-- 1500 ppm and Cl- 1000 ppm, and Mn, Ni and Cu contents below the following limits (in parts by mass): MnO 100 ppm, NiO 100 ppm and CuO 10 ppm. In the method for preparing the magnesium hydroxide, magnesium oxide obtained by spray roasting a magnesium chloride solution free of impurities is hydrated by mixing with water, the resultant magnesium hydroxide is filtered off and the filter cake material is then washed with water.