Application fields and quality requirements

Production of magnesium hydroxide flame retardant Flame retardant refers to an additive that can make the polymer not easy to catch fire and slow down its combustion after it catches fire. Inorganic flame retardants, such as aluminum hydroxide and magnesium hydroxide, play a flame retardant role by absorbing heat and releasing water through chemical decomposition. They have the characteristics of non-toxicity, smoke suppression and stable chemical properties of decomposition products (aluminum oxide and magnesium oxide), so they do not cause secondary harm. The flame retardant filler prepared from brucite has the dual functions of filling and flame retardant, and has the following characteristics: 1) it does not contain halogen and belongs to non-halogen flame retardant; 2) The processing temperature is high (the initial decomposition temperature is much higher than that of aluminum hydroxide, up to 320℃, and that of aluminum hydroxide is 220℃), so it is suitable for resins with higher processing temperature; 3) It is non-toxic and tasteless, does not produce toxic gas when burning, does not corrode the mold, does not produce secondary pollution, and has excellent flame retardant and smoke elimination performance. However, the use of magnesium hydroxide as flame retardant has the following disadvantages: First, the flame retardant efficiency is relatively low, which requires a higher addition amount; Second, its surface is naturally hydrophilic and oleophobic, and it is difficult to disperse uniformly in organic polymers. High-grade magnesium hydroxide flame retardant can be prepared from brucite after superfine grinding and proper surface modification. China has not specified relevant quality standards for flame retardants prepared from brucite. Table 1 shows the main technical parameters of Zerogen series products prepared and synthesized from brucite by Huber Company of the United States. Production of magnesium oxide and magnesium metal The main component of brucite is magnesium hydroxide. After crushing and calcining it, it is decomposed into magnesium oxide (divided into light burned magnesium and heavy burned magnesium). Producing magnesium oxide with brucite has the advantages of saving energy, reducing pollution and low cost. The product can be used in refractory materials, building materials and other fields. At present, the production of light burned magnesium and heavy burned magnesium is the main use of brucite in China. Using brucite to produce magnesium metal is also one of its application fields. It has the advantages of environmental protection, low energy consumption and low cost, just as brucite is used to produce magnesium oxide. Reinforcing and reinforcing fiber Because fibrous brucite is hard, it is easy to disperse in slurry. Needle-shaped fiber bundles are easy to loosen after being soaked with water, and not easy to clump. Compared with other fibers, fibrous brucite is an excellent reinforcing and reinforcing material. At present, fibrous brucite is mainly used to produce microporous calcium silicate, calcium silicate board and other intermediate insulation materials. It is characterized by high whiteness, small bulk density and low cost, and can replace asbestos fiber to manufacture asbestos-free thermal insulation materials. fireproofing By calcining brucite at high temperature, light burned magnesia and heavy burned magnesia (brucite bitter soil) can be prepared. If lithium hydride or lithium fluoride is further mixed, pressed into pellets with a diameter of 40-60 ㎜, then put into smelting, and magnesium agent and rare earth catalyst are added in the smelting process, high-purity magnesia can be obtained. The brucite and dolomite are calcined at high temperature into oxides of magnesium and calcium, then ground into fine powder, then mixed with organic binder, pressed into mold, and then calcined twice to produce refractory bricks. This refractory brick can be used in metallurgical industry instead of magnesia refractory brick. Other fields Brucite can also be used as a protective layer for nuclear reactors in nuclear power plants; Magnesium flux and electrode coating; Heat insulating material; Fuel corrosion inhibitors and handicrafts, etc. In recent years, some researchers have used brucite powder as a neutralizer for acidic wastewater. Because magnesium hydroxide is less alkaline than calcium hydroxide, it will not harm human body, and it has a certain ability of adsorbing heavy metals, so it is safer and more efficient than lime, but its price is more expensive than lime, and its application is limited to some extent. Some researchers use brucite to make magnesium hydroxide slurry for flue gas desulfurization.