| Magnesium hydroxide flame-retardant has been a hot focus forresearchers at home and abroad for its characteristics of highdecomposition temperature, heat stability, harmless, no smoke, and etc. InChina, there are abundant magnesium resources such as huge reserves ofmagnesium chloride in salt lakes and magnesite. However, the behindhandtechnology and process blocked the production of high quality magnesiumhydroxide. So more and more colleges and institutes began to grope for thepreparation of high quality magnesium hydroxide flame retardant with theabove two raw materials. But there are no any reports about the preparationof high quality magnesium hydroxide flame retardant using the byproductof magnesium chloride in chemical plant as raw materials.In this paper, we studied the preparation techniques of high qualitymagnesium hydroxide flame retardant using byproduct magnesium chloridein chemical plant as raw materials, which was very economical andenvironmental-friendly. Weighing the advantage and disadvantage of technical processes, the two-step process was chosen which was applied inthe preparation technology, the first step was to obtain common magnesiumhydroxide by titration of magnesium hydroxide (AR) into ammonia, thesecond step was to modify magnesium hydroxide by hydrothermal methodat 200℃in special autoclave.The better reaction conditions were concluded as follow by plentifulexperiments.Titration order: magnesium chloride adding into ammoniaConcentration of magnesium chloride: 1.5～2.5mol/LVelocity of titration: 2.5mL/minCMgCl2/CNH3.H2O: 1/1pH at ending of reaction: 10.0Temperature of precipitation: 40℃Temperature of post-precipitation: 40℃Time of post-precipitation: 60minHydrothermal time: 4 hHydrothermal temperature: 200℃The samples were characterized by XRD, SEM and BET, the resultsshowed that the samples with above 99％purity and below 10m2/g BETwere regular hexa-plate, and the quality of samples could satisfy thedemand of flame retardants. After analyzing the crystallizationcharacteristics of nanometer magnesium hydroxide and its crystallization mechanism, we confirmed that it was necessary to control nucleation andgrowth velocity in order to achieve the high dispersive products. Thefunction of surface modifiers was also discussed, which proved thatcomposite surface modifier-sodium oleate and sodium dodecyl sulfate wasbetter than single one.In contrast to magnesium hydroxide provided by chemical plants, thetwo products which were prepared respectively by the magnesiumchloride(AR) and the byproducts of magnesium chloride produced bychemical plants had been turned out to be similar resultsin the morphology,size and BET, which indicated that the conditions and rules of preparationobtained from our research could be useful in the coming industrialproduction.
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