The preparation method of nano-sized magnesium hydroxide
Technical field
The invention belongs to nano powder preparation technology, be specifically related to the preparation method's, particularly nano-sized magnesium hydroxide of the auxiliary synthesis of nano powder of a kind of ultrasonic wave ultrasonic wave assisted synthesizing method.
Background technology
Mg (OH)
2As important inorganic combustion inhibitor is one of the highest fire retardant of cost performance.It has that decomposition temperature is higher, thermostability is high, nontoxic, smokeless and press down characteristics such as cigarette, be a kind of environment amenable environmental type fire retardant.And most performances are better than aluminium hydroxide fire retardant, have catered to non-halogen to fire retardant, the low demand that poisons, presses down fuming of 21 century, have obtained development faster.But common Mg (OH)
2Be used for the fire-retardant of polymkeric substance, flame retarding efficiency is low, and is poor with the consistency of matrix.Make the flame retardant properties of material reach certain requirement, Mg (OH)
2Addition usually will be up to more than 50%.This mechanical property and processing characteristics influence to material is very big, makes all remarkable deterioration of the mechanical property of materials, particularly resistance to impact shock and elongation, is difficult to reach service requirements.One of best method that addresses this problem is to make Mg (OH)
2Particle develops to the nanometer direction.
Although the chemical synthesis that extensively adopts on the at present domestic and international industrial production prepares nano-sized magnesium hydroxide and has advantage simple to operate, that raw material sources are wide, but still there are some problems to some extent in this preparation technology in actual production, for example: the reaction that adds alkali generation magnesium hydroxide owing to magnesium salts is very fast, in case the reactant contact reacts is just carried out rapidly fully, the product particle is inhomogeneous, the gained particle size distribution is wide, pattern is difficult to control thereby cause; On the other hand, because the nano-sized magnesium hydroxide particle has very high surface energy, and be strong polar material, the agglomeration of nano-sized magnesium hydroxide is very serious in solution.This just makes the nano-sized magnesium hydroxide of preparation polymolecularity become very difficult.
Development in recent years several methods that prepare nano-sized magnesium hydroxide.Having reported that as Chinese patent CN1341694A with rotating packed bed be reactor, is raw material with solubility magnesium salts and ammoniacal liquor or ammonia, and the reaction disposed slurry prepares the method for nano-sized magnesium hydroxide after several hours 80 ℃ of slakings.This method equipment has high input, and the magnesium hydroxide that reaction generates easily in the filler space deposition, stops up packed bed.Chinese patent CN1542036A is a raw material with solubility magnesium salts and water soluble alkali; under the effect of macromolecule dispersant; by high-shear homogenizing emulsifying device forced emulsification precipitation preparation magnesium hydrate nano powder, only reacted digestion time just reaches 12 hours, and the reaction times is oversize.Chinese patent CN1332116A similarly adopts homogeneous fluid process of preparing nanometer magnesium hydroxide, although adopt the slurry after the thermal ageing processing reaction, but still needs 100 ℃ to wear out more than 6 hours, even also wants thermal ageing 3 hours at 300 ℃.Chinese patent CN1982410A has prepared flake nano-magnesium hydrate simultaneously with synthetic being combined in two stages of hydrothermal treatment consists of precipitation that the precipitator method prepare magnesium hydroxide, reaction and hydrothermal treatment consists temperature are respectively up to 160 ℃ with 180 ℃, this method severe reaction conditions, operational difficulty is difficult to suitability for industrialized production.
Chinese patent CN1389521A has introduced and has adopted sol-gel method to prepare the method for nano-sized magnesium hydroxide.This method is to prepare the aqueous solution of solubility magnesium salts and ammoniacal liquor earlier, and adds a little tensio-active agent in ammonia soln; Under brute force stirs, magnesium salt solution slowly is added drop-wise in the ammonia soln of preparation then, forms milky colloid; Evaporation behind the magnesium hydroxide colloid sonic oscillation 3~5h of preparation except that desolvating, at last at 300 ℃ of following roasting 2~3h, is ground and obtained white nano-sized magnesium hydroxide powder.This patent is carried out oscillation treatment with ultrasonic wave to previously prepared magnesium hydroxide colloid, have ultra-sonic dispersion and prevent the effect of reuniting, but ultrasonic time is long, particularly the evaporative removal solvent, make this patented method production cycle long, energy consumption is big, cost is high, is unfavorable for industrialization promotion.
Summary of the invention
Deficiency at above-mentioned prior art, the object of the present invention is to provide a kind of preparation method that can at room temperature synthesize good dispersity, the uniform nano-sized magnesium hydroxide of particle size distribution fast, i.e. the method for the auxiliary precipitator method synthesis of nano of ultrasonic wave magnesium hydroxide.
For achieving the above object, the preparation method of nano-sized magnesium hydroxide of the present invention, characteristics are that the soluble magnesium salts solution that will be added with dispersion agent joins and are positioned in the there-necked flask in the ultrasonic tank, that agitator is installed; Turn on agitator is also adjusted rotating speed, opens ultrasonic equipment and adjusts ultrasonic frequency and ultrasonic power, will slowly be added dropwise in the there-necked flask with the solubility alkali lye of above-mentioned magnesium salt solution equivalent and react under 15-35 ℃, obtains the magnesium hydroxide suspension liquid; The magnesium hydroxide suspension liquid was 15-35 ℃ of following ultrasonic aging 4~30 minutes; Magnesium hydroxide after the ageing is after filtering and washing, and drying is 2~6 hours under 80~120 ℃, obtains the nano-sized magnesium hydroxide powder, and above-mentioned dispersion agent is selected anion surfactant or polymeric surface active agent for use, and its add-on is 1~5wt% of magnesium salts; Described magnesium salt solution is magnesium chloride, sal epsom, magnesium nitrate aqueous solution or bittern water, its Mg
2+Concentration is 0.5~5.0mol/L; Described alkali lye is ammoniacal liquor, sodium hydroxide or potassium hydroxide aqueous solution, its OH
-Concentration is 1.0~10.0mol/L.
Anion surfactant of the present invention is selected stearate, sulfonate, carboxylate salt etc. usually for use; Polymeric surface active agent is then selected polyoxyethylene glycol (PEG), polyvinyl alcohol (PVA), polyvinylpyrrolidone etc. usually for use.
The present invention adjusts agitator speed according to reaction density and product particle diameter, and reaction density increases, and agitator speed strengthens; Required product particle diameter is more little, and corresponding agitator speed will strengthen.The selected agitator speed of the present invention is 50~1200rpm.
Main points of the present invention are all to apply ultrasonic wave in the synthetic and ageing stage of nano-sized magnesium hydroxide, experimental results show that to have produced good effect.
Sonochemistry is a kind of convenience that physical method and chemical process are combined, effective, safe technology, is the brand-new science that goalkeeper's ultrasonics and ultrasonic technology and chemistry are combined closely.The present invention adjusts ultrasonic frequency and power according to reactant concn, product particle diameter and in reaction and ageing different steps.Increase with reaction density, ultrasonic frequency and power strengthen; Required product particle diameter is more little, and corresponding ultrasonic frequency and power will increase; In step of reaction, it is big that frequency of ultrasonic and power are wanted, and in the ageing stage, frequency of ultrasonic and power can suitably reduce.Ultrasonic equipment of the present invention, selected ultrasonic frequency are 10~106kHz, and power is 50~800W.
The present invention is in the presence of dispersion agent, owing to apply ultrasonic wave in the reaction of solubility magnesium salts and water soluble alkali and the ageing stage of nano-sized magnesium hydroxide.In the precipitin reaction stage, ultrasonic cavitation can impel moment to generate a large amount of nucleus, and the microbubble that cavitation effect produces can be in the induce reaction micro-whirling motion of liquid of nucleating surface, play mechanical agitation, the diffusion of accelerated reaction system, make newborn nuclei growth become stable nanoparticles, thereby suppressed further growing up of secondary nucleation and nucleus; In the ageing stage, the heat effect that ultrasonic cavitation produces helps improving the degree of crystallinity of nano particle, can shorten the digestion time of nano-sized magnesium hydroxide greatly; Simultaneously, in whole process of preparation, strong shock wave and microjet that ultrasonic cavitation produces have porphyrization, can effectively stop the formation of hydrogen bond between nano-sized magnesium hydroxide, reach to prevent the purpose of reuniting.So, preparation nano-sized magnesium hydroxide method of the present invention, technology is simple, with short production cycle, working condition is gentle, cost is low, and good product dispersibility, particle size distribution are even.
Description of drawings
Fig. 1 is the X-ray diffraction style of the nano-sized magnesium hydroxide of embodiment 1 preparation, and diffraction peak positions all in the spectrogram is consistent with the magnesium hydroxide of JCPDS 84-2164, does not detect other impure impurity.
Fig. 2 amplifies 60,000 times field emission scanning electron microscope photo for the nano-sized magnesium hydroxide of embodiment 1 preparation.
Fig. 3 is the transmission electron microscope photo of the nano-sized magnesium hydroxide of embodiment 1 preparation.
From electromicroscopic photograph as can be seen, the inventive method synthetic nanometer Mg (OH)
2The about 70nm of particle size, granule-morphology is a sheet, particle size distribution is even, has dispersed preferably.
Embodiment
Embodiment 1
With 28.5g MgCl
26H
2O and 0.86g polyoxyethylene glycol are dissolved in the deionized water, stir to be made into the 100ml magnesium salt solution; In addition 11.2g NaOH also is dissolved in and is made into 100ml alkali lye in the deionized water.Earlier magnesium salt solution is added in the 250ml there-necked flask, start agitator, control rotating speed 600rpm; Open ultrasonic wave simultaneously, control ultrasonic frequency 59KHz, ultrasonic power are 100W.Slowly the dropping sodium aqueous solution obtains the magnesium hydroxide suspension liquid 25 ℃ of reactions in there-necked flask then, subsequently magnesium hydroxide suspension liquid ultrasonic aging is handled 10 minutes.Filter suspension liquid, to can't check chlorion, filter cake obtains the flake magnesium hydroxide powder of median size 70 nanometers 110 ℃ of dryings 4 hours with deionized water wash.
Embodiment 2
With 28.5g MgCl
26H
2O and 0.57g polyvinyl alcohol are dissolved in the deionized water, stir to be made into the 100ml magnesium salt solution; In addition 15.7g KOH also is dissolved in and is made into 100ml alkali lye in the deionized water.Earlier magnesium salt solution is added in the 250ml there-necked flask, start agitator, control rotating speed 500rpm; Open ultrasonic wave simultaneously, control ultrasonic frequency 33KHz, ultrasonic power are 100W.Slowly the dropping sodium aqueous solution obtains the magnesium hydroxide suspension liquid 25 ℃ of reactions in there-necked flask then, subsequently magnesium hydroxide suspension liquid ultrasonic aging is handled 15 minutes.Filter suspension liquid, to can't check chlorion, filter cake obtains the flake magnesium hydroxide powder of median size 90 nanometers 120 ℃ of dryings 3 hours with deionized water wash.
Embodiment 3
With 28.5g MgCl
26H
2O and 1.14g Zinic stearas are dissolved in the deionized water, stir to be made into the 100ml magnesium salt solution; In addition 44.0ml ammoniacal liquor also is dissolved in and is made into 100ml alkali lye in the deionized water.Earlier magnesium salt solution is added in the 250ml there-necked flask, start agitator, control rotating speed 700rpm; Open ultrasonic wave simultaneously, control ultrasonic frequency 80KHz, ultrasonic power are 100W.Slowly the dropping sodium aqueous solution obtains the magnesium hydroxide suspension liquid 25 ℃ of reactions in there-necked flask then, subsequently magnesium hydroxide suspension liquid ultrasonic aging is handled 8 minutes.Filter suspension liquid, to can't check chlorion, filter cake obtains the flake magnesium hydroxide powder of median size 50 nanometers 100 ℃ of dryings 6 hours with deionized water wash.
Embodiment 4
With 57g MgCl
26H
2O and 1.43g sodium laurylsulfonate are dissolved in the deionized water, stir to be made into the 100ml magnesium salt solution; In addition 22.4g NaOH also is dissolved in and is made into 100ml alkali lye in the deionized water.Earlier magnesium salt solution is added in the 250ml there-necked flask, start agitator, control rotating speed 900rpm; Open ultrasonic wave simultaneously, control ultrasonic frequency 59KHz, ultrasonic power are 300W.Slowly the dropping sodium aqueous solution obtains the magnesium hydroxide suspension liquid 20 ℃ of reactions in there-necked flask then, subsequently magnesium hydroxide suspension liquid ultrasonic aging is handled 20 minutes.Filter suspension liquid, to can't check chlorion, filter cake obtains the flake magnesium hydroxide powder of median size 50 nanometers 95 ℃ of dryings 6 hours with deionized water wash.
Embodiment 5
With 35.9g Mg (NO
3)
26H
2O and 0.36g polyvinylpyrrolidone are dissolved in the deionized water, stir to be made into the 100ml magnesium salt solution; In addition 11.2g NaOH also is dissolved in and is made into 100ml alkali lye in the deionized water.Earlier magnesium salt solution is added in the 250ml there-necked flask, start agitator, control rotating speed 600rpm; Open ultrasonic wave simultaneously, control ultrasonic frequency 59KHz, ultrasonic power are 100W.Slowly the dropping sodium aqueous solution obtains the magnesium hydroxide suspension liquid 27 ℃ of reactions in there-necked flask then, subsequently magnesium hydroxide suspension liquid ultrasonic aging is handled 25 minutes.Filter suspension liquid, to can't check chlorion, filter cake obtains the flake magnesium hydroxide powder of median size 60 nanometers 100 ℃ of dryings 5 hours with deionized water wash.
Embodiment 6
With 34.5g MgSO
47H
2O and 1.38g sodium polyacrylate are dissolved in the deionized water, stir to be made into the 100ml magnesium salt solution; In addition 11.2g NaOH also is dissolved in and is made into 100ml alkali lye in the deionized water.Earlier magnesium salt solution is added in the 250ml there-necked flask, start agitator, control rotating speed 600rpm; Open ultrasonic wave simultaneously, control ultrasonic frequency 59KHz, ultrasonic power are 100W.Slowly the dropping sodium aqueous solution obtains the magnesium hydroxide suspension liquid 30 ℃ of reactions in there-necked flask then, subsequently magnesium hydroxide suspension liquid ultrasonic aging is handled 10 minutes.Filter suspension liquid, to can't check chlorion, filter cake obtains the flake magnesium hydroxide powder of median size 75 nanometers 100 ℃ of dryings 6 hours with deionized water wash.