Hebei Messi Biology Co., Ltd. stated that magnesium hydroxide is not a strong base. Strong bases include sodium hydroxide, barium hydroxide, potassium hydroxide, and calcium hydroxide. The basis for judging strong and weak bases is that weak bases are electrolytes that are insoluble or poorly soluble in water, and strong bases are those that can be completely dissolved. However, magnesium hydroxide is a medium-strong base because although it is difficult to dissolve in water, it is a strong electrolyte because of its strong degree of ionization, so it is classified as a medium-strong base.
Magnesium hydroxide products are divided into flame-retardant grade, high-purity grade, pharmaceutical grade, food grade, etc. in terms of application; in terms of structure, they are divided into flake, ultra-fine, whisker, nano-grade, etc. Among them, the ones with better development potential are ultrafine magnesium hydroxide and magnesium hydroxide whiskers.
1. Flake magnesium hydroxide
Flake magnesium hydroxide can be used as an additive flame retardant. The carbonization method uses magnesite or dolomite as raw materials and undergoes calcination, digestion, impurity removal, carbonization, and precipitation to obtain the product. Using dolomite as raw material, ammonia water as precipitant and adding surface modifier cetyltrimethylammonium bromide, rhombohedral lamellar magnesium hydroxide is hydrothermally prepared. This method has a higher degree of separation of magnesium and calcium. The extraction rate is 90.02%, and the product yield is 88.21%; the precipitation method uses magnesite or dolomite as raw materials, and the product is obtained by calcination, leaching, impurity removal, and precipitation. Using dolomite as raw material, it is leached with hydrochloric acid and sulfuric acid successively, and the product can be obtained by adding self-made complex precipitating agent and surface modifier polyethylene glycol, with a yield of 85.20%. The acid hydrolysis method uses a variety of magnesium-containing minerals as raw materials, and produces products through acid hydrolysis, impurity removal, and precipitation. Using dolomite as raw material, it is acidified with hydrochloric acid and impurities are removed, and dolomite milk is used as a precipitant. The purity of the product is 98%. The dolomite milk is prepared by calcining and digesting dolomite.
2. Ultrafine magnesium hydroxide
Ultrafine magnesium hydroxide can be used as a flame retardant component of composite materials. Adding different surface modifiers can change the particle size of the product. Using magnesium chloride solution as the raw material, ammonia water as the precipitant, the product particle size is <400nm; adding a self-made surface modifier, the particle size is 150nm; switching to polyethylene glycol, the particle size is 89.5nm; switching to magnesium sulfate solution as the raw material, Add a self-made surface modifier and the particle size is 380nm. These magnesium salt solutions can be prepared by acid leaching after acid hydrolysis or calcination of magnesium-containing minerals, in which the magnesium chloride solution can be replaced by brine.
3. Magnesium hydroxide whiskers
Magnesium hydroxide whiskers are short fiber functional materials, mainly added to polymer materials as flame retardants and reinforcing materials. Precipitation method, improving the precipitation process can change the aspect ratio. Using magnesium chloride solution as raw material, adding alkali and surface modifier, the product is hydrothermally synthesized. Using sodium hydroxide as the precipitant and glycerin as the surface modifier, using microwave hydrothermal treatment, the diameter is 0.1 to 0.3 μm and the length is 80 to 110 μm; instead, ammonia and sodium hydroxide are used as the precipitant, and acrylic acid is used as the surface modifier. Sex agent, diameter is 8~15nm, length is 50~150nm; medium and low concentration ammonia water and low concentration magnesium chloride solution, the product has good dispersion; basic magnesium sulfate whisker is used as the precursor, and sodium hydroxide is used as the precipitate Agent, potassium oleate is used as a surface modifier, and a product with a diameter of 1 to 2 μm and a length of 100 to 200 μm is produced by hydrothermal treatment; adding a surface modifier cannot reduce the particle size, but will prevent the basic magnesium sulfate whiskers from moving to Magnesium hydroxide whisker transformation.