Study On Preparation Of Flame Retardant Magnesium Hydroxide And Silicon Steel Magnesium Oxide From Magnesite As Raw Material

Magnesium hydroxide is an inorganic additive flame retardant,with good thermal stability,high smoking suppression performance,non-toxic,and promotes the role of carbon into the substrate,and good market prospects etc.Magnesium hydroxide as additive-type flame retardants,the crystal morphology and surface properties will directly affect the flame retardant rand mechanical property of the added products.Silicon steel grade magnesium oxide was made in silicon steel sheet as important material.But the traditional preparation of silicon steel grade magnesium oxide process is complex,energy’s consumption,and cost is very high.In this paper,CCM through the grinding,high temperature was calcined into light burning powder（mainly MgO）as raw material.Ammonia as a precipitant,steaming ammonia reaction,magnesium precipitation reaction was prepared to magnesium hydroxide.The morphology of magnesium hydroxide was analyzed by molecular simulation method.The silicon steel grade magnesium oxide was prepared by calcining the prepared magnesium hydroxide precursors at high temperature.The products were characterized by X-ray diffraction,laser particle size distribution,scanning electron microscopy and other instruments.The experimental results showed that the optimum conditions were molar ratio of NH₄⁺to MgO was 2:1.And the reaction temperature was 90℃.The reaction time was 120 minutes.The stirring rate was 300 r/min.Different kinds raw materials had different extraction rate of Mg^2+.The NH4NO3 extraction rate of Mg²⁺is about 64%.The NH4Cl extraction rate of Mg²⁺is about 77%.The（NH4）2SO4 extraction rate of Mg²⁺is about 84%.The Ammonium formate and ammonium acetateextraction rate of Mg²⁺is about 95%.Magnesium hydroxide was prepared by different ammonium salt solution at 75℃,which showed different morphologies.The effection of temperature,pressure,impurity ions and system magnification on the morphology of magnesium hydroxide were investigated in details.Experiments showed that with the temperature and pressure rising,the crystal morphology changed.It refected more and more rules.The Cl^-,NO₃^-,Ca²⁺ions had a minimal influence on the growth of magnesium hydroxide crystals at 120℃.The CHOO^-,CH₃COO^-,SO₄^2-,Fe³⁺ions had a great influence on the growth of magnesium hydroxide crystals at120℃.0.5-4L system amplification experiments showed that the magnification experiment has no effect on the morphology,dispersibility,purity,particle size and so on of magnesium hydroxide,and is suitable for industrialized mass production.The growth habits of magnesium hydroxide crystals was analyzed by using Materials Studio7.0 software,and the reasons of different morphologies was described.The prepared high purity magnesium hydroxide was calcined to prepare silicon steel grade magnesia.The optimum calcination conditions were calcined4h at 980℃.From the pectures of SEM,the precursor magnesium hydroxide had no effect on preparion of silicon steel grade magnesia.