Hebei Messi Biology Co., Ltd. stated that magnesium hydroxide flame retardant is one of the most widely used varieties of halogen-free flame retardants. Magnesium hydroxide is widely used in polyvinyl chloride (PVC), polypropylene (PP), Polyethylene (PE), vinyl acetate (EVA), polystyrene (PS), polyamide (PA) and other plastics, elastomers and rubber materials. The ideal magnesium hydroxide flame retardant added to the polymer requires high purity and suitable particle size distribution.
Because magnesium hydroxide needs a higher filling amount as a flame retardant, if the particles of magnesium hydroxide used are larger, the composite material obtained by adding it to the matrix will easily form cracks between the magnesium hydroxide and the matrix, thus affecting the material. overall performance. The purity of magnesium hydroxide is one of the decisive factors for the electrical performance of composite materials, so the ideal magnesium hydroxide as a flame retardant filler has high requirements for product purity, element content, and particle size range.
At present, there are two main methods for producing magnesium hydroxide: one is the direct crushing method of brucite; the other is the reaction conversion method of magnesium-containing raw materials. Due to the low purity of natural brucite, adding it as a flame retardant to polymer materials often leads to a decline in the electrical properties of composite materials. The magnesium-containing raw material conversion method can prepare different specifications of magnesium hydroxide flame retardant products by controlling different reaction conditions, so it has become the main method for producing magnesium hydroxide flame retardants at present.
The main precipitant used in the prior art utilizing magnesium-containing raw material conversion method is sodium hydroxide, ammonia water, milk of lime. Because sodium hydroxide and ammoniacal liquor are used as precipitating agents alone, the cost price of the resulting product is relatively high, so people are more and more inclined to prepare magnesium hydroxide products with milk of lime, which is easy to get as a precipitating agent.
In a prior art, a magnesium hydroxide product with a magnesium hydroxide purity greater than 98.5% and a calcium oxide content less than 0.2% is prepared using magnesium chloride and milk of lime as raw materials. This preparation method uses a single milk of lime as a precipitant. Due to the nature of calcium hydroxide itself, it is difficult to accurately control some process parameters in the reaction process in actual production, which brings certain difficulties to production operations and affects the final quality of the product. . In another prior art, saturated lime solution is used to react with refined brine to produce magnesium hydroxide product. Due to the low solubility of calcium hydroxide, there are disadvantages of low yield and high cost in actual production.
Aiming at the problems that the purity of the product obtained by the preparation method of magnesium hydroxide flame retardant in the prior art is not high enough, the preparation cost is high, etc., the present invention provides a method for preparing a magnesium hydroxide flame retardant with sufficiently high purity of the obtained product and a method with sufficiently high purity , The magnesium hydroxide flame retardant with lower preparation cost.
The invention provides a preparation method of a magnesium hydroxide flame retardant and the magnesium hydroxide flame retardant prepared by the preparation method. The preparation method of the magnesium hydroxide flame retardant includes the steps: first, adding magnesium chloride to the reactor to form a magnesium chloride solution, and correspondingly heating to the set temperature T; then, adding calcium oxide, magnesium oxide, hydroxide The composite precipitating agent formed after mixing sodium and water; then, after the composite precipitating agent is added completely, continue the constant temperature reaction at the set temperature T, and then wash and filter the chloride ions in the reactor; moreover, the magnesium hydroxide filter cake Carry out repulping treatment; finally, the magnesium hydroxide filter cake after repulping treatment is subjected to physical crushing treatment to obtain magnesium hydroxide flame retardant. The purity of the magnesium hydroxide in the magnesium hydroxide flame retardant prepared by the preparation method of the magnesium hydroxide flame retardant of the present invention is greater than or equal to 99.0%.