| 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. |
