In the rubber and plastic industry, magnesium hydroxide flame retardant has the advantages of good thermal stability, non-volatility, non-precipitation, no corrosive and toxic gas generation, and has multiple functions such as flame retardancy, smoke elimination, drip prevention and filling, and has received widespread attention.
The brucite method is environmentally friendly to produce magnesium hydroxide, and the obtained magnesium hydroxide has high fluidity. The main component of brucite is magnesium hydroxide, and the theoretical composition includes 69.12% magnesium oxide and 30.88% water. Brucite belongs to the trigonal crystal system, and is commonly seen in flake aggregates, sometimes in fibrous aggregates; its cleavage surface is pearly luster, the hardness is 2.5, and the specific gravity is 2.3~2.6g/cm3.
At present, the main methods of processing brucite into high specific surface area magnesium hydroxide are rolling mill, air flow mill, stirred mill, ring roller mill and wet stirred mill. However, the production mechanism of the above processes is usually high-speed shearing, collision or crushing. The particle size distribution of magnesium hydroxide products is wide, the breakpoint is large, and the flaky structure is easily destroyed. In addition, the specific surface area of magnesium hydroxide powder produced by brucite currently on the market is 6-12m2/g, and the flame retardant and smoke suppression effect is still poor.
The present invention provides a preparation method of high specific surface area magnesium hydroxide, comprising the following steps: mixing brucite ore particles and an aqueous solution of a dispersing and grinding aid, and performing wet ball milling to obtain a ball mill material; the dispersing and grinding aid in the aqueous solution of the dispersing and grinding aid comprises sodium polyacrylate, sodium dodecyl sulfate and sodium hexametaphosphate; the ball mill material is dried and air-selected and classified in sequence to obtain the high specific surface area magnesium hydroxide; the specific surface area of the high specific surface area magnesium hydroxide is ≥20m2/g. The embodiments show that the high specific surface area magnesium hydroxide provided by the present invention has a specific surface area of 20.833-22.416m2/g, and has a high specific surface area; the oxygen index is 28.5-28.9%, the maximum smoke density is 86.24-88.98kg/m3, and the flame retardant and smoke suppression effects are good.