JP5686563B2 - Magnesium hydroxide fine particles and magnesium oxide fine particles, and methods for producing them - Google Patents

Description

  The present invention relates to high-purity magnesium hydroxide fine particles and high-purity magnesium oxide fine particles having a small particle diameter and uniform, and methods for producing them.

  Magnesium hydroxide and magnesium oxide are inorganic materials used in various fields. Examples of the former use include additives, resin fillers, high-functional materials, and catalysts, and the latter use includes Examples include refractories, additives, resin fillers, highly functional materials, electromagnetic steel materials, and catalysts. Including these applications, magnesium hydroxide and magnesium oxide are often required to have high purity, small particle size, and uniform fine particle form.

  As a method for producing uniform magnesium hydroxide having a small particle size, a method of preparing magnesium hydroxide fine particles of 10 nm to 1000 nm by adding an alkaline substance and then a surfactant has been proposed (patent) Reference 1). However, in the specific example, there was a problem that the amount of alkali added was large and impurities were eluted from the autoclave container, and impurities could be mixed.

  Further, in a method for producing magnesium hydroxide by hydrothermal reaction of magnesium chloride and an alkaline substance in an aqueous medium, an aspect of magnesium hydroxide obtained by adding boric acid, silicic acid or a water-soluble salt thereof. A method for arbitrarily controlling the ratio has also been proposed (see Patent Document 2). However, this method has a problem that it is difficult to control the particle size, and fine particles having a uniform particle size cannot be obtained.

JP 2009-62214 A JP 2005-200300 A

  An object of the present invention is to solve the above-mentioned problems and to provide uniform high-purity magnesium hydroxide fine particles and high-purity magnesium oxide fine particles having a small particle diameter and a method for producing them.

The present invention has a BET specific surface area of 5 m ² / g or more, a volume-based cumulative 50% particle diameter (D ₅₀ ) of 0.1 to 0.5 μm by laser diffraction scattering particle size distribution measurement, and laser diffraction scattering particle size distribution measurement. The ratio D ₉₀ / D ₁₀ of the volume-based cumulative 10% particle size (D ₁₀ ) to the volume-based cumulative 90% particle size (D ₉₀ ) by ₁₀ is 10 or less, and the purity is 99.5% by mass or more. It relates to magnesium fine particles.

Further, the present invention has a BET specific surface area of 5 m ² / g or more, a volume-based cumulative 50% particle diameter (D ₅₀ ) of 0.1 to 0.5 μm by laser diffraction scattering particle size distribution measurement, and a laser diffraction scattering particle size. The ratio D ₉₀ / D ₁₀ of the volume-based cumulative 10% particle diameter (D ₁₀ ) and the volume-based cumulative 90% particle diameter (D ₉₀ ) by distribution measurement is 10 or less, and the purity is 99.5% by mass or more. It relates to magnesium oxide fine particles.

Furthermore, the present invention provides
Preparing a magnesium chloride aqueous solution (A);
A step (B) of obtaining a magnesium hydroxide slurry by reacting an aqueous magnesium chloride solution with an alkaline aqueous solution of 1 to 18 N at a reaction rate of 101 to 210 mol%;
The magnesium hydroxide slurry is maintained at a temperature of 101 to 200 ° C. with stirring to obtain a hydrothermally treated magnesium hydroxide slurry (C); and the hydrothermally treated magnesium hydroxide slurry is filtered, washed and Step of drying to obtain magnesium hydroxide fine particles (D)
The manufacturing method of the magnesium hydroxide microparticles | fine-particles containing this.

  In addition, the present invention provides the production of magnesium oxide fine particles, comprising the step (E) of firing the magnesium hydroxide fine particles or the magnesium hydroxide fine particles obtained by the production method in an air atmosphere at 500 to 1500 ° C. Regarding the method.

  The magnesium hydroxide fine particles and magnesium oxide fine particles of the present invention are highly pure, have a small particle size and are uniform, and are highly useful in various fields. In addition, according to the production method of the present invention, the fine particles as described above can be easily prepared, which is highly convenient.

The magnesium hydroxide fine particles of the present invention have a BET specific surface area of 5 m ² / g or more, and a volume-based cumulative 50% particle diameter (D ₅₀ ) by laser diffraction scattering type particle size distribution measurement is 0.1 to 0.5 μm. Yes, the ratio D ₉₀ / D ₁₀ of the volume-based cumulative 10% particle diameter (D ₁₀ ) and the volume-based cumulative 90% particle diameter (D ₉₀ ) by laser diffraction scattering type particle size distribution measurement is 10 or less. Since such magnesium hydroxide fine particles have a small particle shape and excellent reactivity, they are suitable for additives, resin fillers, catalysts, and the like, and also have a small particle shape, little variation in particle size, and excellent dispersibility. Also, it can be suitably used for highly functional materials. The BET specific surface area of the magnesium hydroxide fine particles of the present invention is preferably 10 m ² / g or more, D ₅₀ is preferably 0.2 to 0.5 μm, and D ₉₀ / D ₁₀ is preferably 5 or less.

  The magnesium hydroxide fine particles of the present invention have a purity of 99.5% by mass or more. If it is this range, the elution of an impurity will be suppressed extremely and it can use it suitably for a highly functional material. The purity of the magnesium hydroxide fine particles of the present invention is preferably 99.9% by mass or more.

In the present specification, the purity refers to the impurity element (Ag, Al, B, Ba, Bi, Cd, Cl, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, Na in the target fine particles. , Ni, P, Pb, S, Si, Sr, Tl, V, Zn, Ti, and Zr) are measured, and the total content is subtracted from 100% by mass. In the present specification, high purity means that the purity calculated as described above is 99.5% by mass or more.
Impurity elements to be measured (Ag, Al, B, Ba, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, Na, Ni, P, Pb, S, Si , Sr, Tl, V, Zn, Ti, and Zr), using an ICP emission spectrometer, the sample was dissolved in acid, then the mass was measured, and the Cl amount was measured using a spectrophotometer. Is dissolved in an acid and the mass is measured.

  The magnesium hydroxide fine particles of the present invention preferably have a total content of Fe, Ti, Ni, Cr, Mo and Mn of 500 mass ppm or less. When the total content of these is 500 mass ppm or less, elution of metal impurities is extremely suppressed, and it can be suitably used for additives, resin fillers, and highly functional materials. The total content is more preferably 450 ppm by mass or less.

  The magnesium hydroxide fine particles of the present invention preferably have a chlorine content of 500 mass ppm or less. When the content is 500 mass ppm or less, particle growth is extremely suppressed when obtaining magnesium oxide fine particles by firing, and a fine magnesium oxide powder can be obtained. The content is more preferably 450 ppm by mass or less.

  In the magnesium hydroxide fine particles of the present invention, the ratio Dv / Dn between the volume average particle diameter (Dv) and the number average particle diameter (Dn) is preferably 1 to 10. When this Dv / Dn is 1 to 10, it is excellent in ink fixability when used for an ink fixing agent, heat resistance when added to a resin, flame retardancy, flexibility function, and catalyst function, and Improves acid resistance and moisture resistance. Dv / Dn is more preferably 1-8.

The magnesium oxide fine particles of the present invention have a BET specific surface area of 5 m ² / g or more, and a volume-based cumulative 50% particle diameter (D ₅₀ ) measured by laser diffraction scattering type particle size distribution is 0.1 to 0.5 μm. The ratio D ₉₀ / D ₁₀ between the volume-based cumulative 10% particle diameter (D ₁₀ ) and the volume-based cumulative 90% particle diameter (D ₉₀ ) measured by laser diffraction / scattering particle size distribution measurement is 10 or less. Since such magnesium oxide fine particles have a small particle shape and excellent reactivity, they are suitable for refractories, additives, resin fillers, electromagnetic steel materials, catalysts, and the like, and also have a small particle shape and little variation in particle size. Because of its excellent dispersibility, it can be suitably used for highly functional materials.
The BET specific surface area of the magnesium oxide fine particles of the present invention is preferably 20 m ² / g or more, more preferably 40 m ² / g or more, D ₅₀ is preferably 0.2 to 0.4 μm, and D ₉₀ / D ₁₀ Is preferably 5 or less.

  The magnesium oxide fine particles of the present invention have a purity of 99.5% by mass or more. If it is this range, the elution of an impurity will be suppressed extremely and it can use it suitably for a highly functional material. The purity of the magnesium oxide fine particles of the present invention is preferably 99.9% by mass or more.

  The magnesium oxide fine particles of the present invention preferably have a total content of Fe, Ti, Ni, Cr, Mo and Mn of 500 mass ppm or less. When the total content of these is 500 mass ppm or less, elution of metal impurities is extremely suppressed, and it can be suitably used for additives, resin fillers, and highly functional materials. The total content is more preferably 450 mass ppm or less.

  The magnesium oxide fine particles of the present invention preferably have a chlorine content of 500 mass ppm or less. When the content is 500 mass ppm or less, elution of chlorine is extremely suppressed, and it can be suitably used for additives, resin fillers, and highly functional materials. The content is more preferably 450 ppm by mass or less.

  In the magnesium oxide fine particles of the present invention, the ratio Dv / Dn of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is preferably 1 to 10. When this Dv / Dn is 1 to 10, ink fixability when used for an ink fixing agent, heat resistance when added to a resin, flame retardancy, flexibility function, light diffusion effect, and catalyst It is excellent in an effect, and acid resistance and moisture resistance become good, More preferably, it is 1-8.

  The magnesium oxide fine particles of the present invention preferably have a citric acid activity (final reaction rate 40%, 20.0 ° C.) of 20 to 2000 seconds. When the citric acid activity is 20 to 2000 seconds, the reactivity with iron is excellent, and it can be suitably used as an electromagnetic steel material for an insulating material for an electromagnetic steel sheet and an insulating coating material for a dust core. The citric acid activity is preferably 20 to 500 seconds.

The magnesium hydroxide fine particles of the present invention are
Preparing a magnesium chloride aqueous solution (A);
A step (B) of obtaining a magnesium hydroxide slurry by reacting an aqueous magnesium chloride solution with an alkaline aqueous solution of 1 to 18 N at a reaction rate of 101 to 210 mol%;
The magnesium hydroxide slurry is maintained at a temperature of 101 to 200 ° C. with stirring to obtain a hydrothermally treated magnesium hydroxide slurry (C); and the hydrothermally treated magnesium hydroxide slurry is filtered, washed and Step of drying to obtain magnesium hydroxide fine particles (D)
Can be obtained by a method comprising

  Step (A) is a step of preparing an aqueous magnesium chloride solution. The magnesium chloride aqueous solution preferably has a concentration of 0.1 to 10 mol / L. When the concentration is less than 0.1 mol / L, the production efficiency is deteriorated. On the other hand, when the concentration is higher than 10 mol / L, the viscosity of the magnesium hydroxide slurry increases and handling becomes worse. The concentration of the magnesium chloride aqueous solution is preferably 0.5 to 5 mol / L.

Step (A) is, for example,
Preparing a crude magnesium chloride aqueous solution (A-1);
A step of reacting a crude magnesium chloride aqueous solution with a 1-18 N alkaline aqueous solution at a reaction rate of 1 to 30 mol% to obtain a crude magnesium hydroxide slurry (A-2); and a flocculant in the crude magnesium hydroxide slurry After the addition, the magnesium hydroxide is filtered to obtain a magnesium chloride solution as a filtrate, or a flocculant is added to cause the magnesium hydroxide to coagulate and precipitate to obtain a magnesium chloride aqueous solution as a supernatant (A-3 )
Can be included.

  Step (A-1) is a step of preparing a crude magnesium chloride solution. For example, magnesium chloride (magnesium chloride hexahydrate or anhydrous magnesium chloride, seawater, brine, or bitter juice can be used as magnesium chloride) and pure water (through an ion exchange resin having an electric conductivity of 0. By adding water purified to 1 μS / cm or less, a crude magnesium chloride aqueous solution can be obtained. The concentration of the crude magnesium chloride aqueous solution can be 0.5 to 10 mol / L, preferably 1 to 5 mol / L, and more preferably 2 to 4 mol / L.

  Step (A-2) is a step of obtaining a crude magnesium hydroxide slurry by reacting a 1-18N alkaline aqueous solution with a crude magnesium chloride aqueous solution so that the reaction rate is 1-30 mol%. The reaction rate is a value calculated assuming that the amount of alkali necessary for all magnesium chloride to become magnesium hydroxide is 100 mol%.

  As the alkaline aqueous solution, an aqueous sodium hydroxide solution can be used, and the concentration can be 1 to 18 mol / L, preferably 5 to 18 mol / L, more preferably 10 to 18 mol / L.

  In the step (A-3), after adding a flocculant to the crude magnesium hydroxide slurry, the magnesium hydroxide is filtered to obtain a magnesium chloride solution as a filtrate, or the flocculant is added and the magnesium hydroxide is added. This is a step of coagulating and precipitating to obtain an aqueous magnesium chloride solution as the supernatant.

  As the flocculant, acrylamide / sodium acrylate copolymer, acrylamide / sodium acrylamide-2-methylpropanesulfonate copolymer, polyacrylamide, alkylaminomethacrylate quaternary ammonium salt polymer, alkylaminoacrylate quaternary ammonium A flocculant mainly composed of a salt / acrylamide copolymer, polyamidine hydrochloride or the like can be appropriately selected and used, and an acrylamide / sodium acrylate copolymer is preferred. The addition amount of the flocculant can be 100-1000 mass ppm with respect to the amount of dry magnesium hydroxide in the crude magnesium hydroxide slurry.

  The concentration of the magnesium chloride aqueous solution thus obtained can be adjusted to obtain a magnesium chloride aqueous solution having a concentration of 0.1 to 10.0 mol / L.

  Step (B) is a step of obtaining a magnesium hydroxide slurry by reacting an aqueous magnesium chloride solution with an alkaline aqueous solution of 1 to 18 N at a reaction rate of 101 to 210 mol%. When the reaction rate is less than 101 mol%, crystals grow too much during the hydrothermal treatment of the magnesium hydroxide slurry, and the particle size becomes too large. Further, when the reaction rate is higher than 210 mol%, the specific elements (Fe, Ti, Ni, Cr, Mo, and Mn) are eluted from the autoclave container and impurities are easily mixed. The reaction rate is preferably 103 to 200 mol%, more preferably 105 to 180%.

  The alkaline aqueous solution is preferably a sodium hydroxide aqueous solution having a concentration of 1 to 18 mol / L. When the concentration of the sodium hydroxide aqueous solution is less than 1 mol / L, the production efficiency is deteriorated. Moreover, when a density | concentration becomes higher than 18 mol / L, the viscosity of a magnesium hydroxide slurry will become high and handling will worsen. The concentration of the sodium hydroxide aqueous solution is preferably 4 to 16 mol / L.

  Step (C) is a step of obtaining a magnesium hydroxide slurry hydrothermally treated by holding the magnesium hydroxide slurry at a temperature of 101 to 200 ° C. while stirring.

  The hydrothermal treatment can be performed by holding the magnesium hydroxide slurry at 101 ° C. to 200 ° C. with stirring, for example, using an autoclave. When the hydrothermal treatment temperature is lower than 101 ° C., crystals do not grow, and aggregated particles are generated, resulting in poor dispersion. On the other hand, when the hydrothermal treatment temperature is higher than 200 ° C., crystals grow too much and the particle size tends to be too large. The hydrothermal treatment temperature is preferably 105 ° C to 150 ° C. The hydrothermal treatment time can be 0.5 to 3 hours. When the hydrothermal treatment time is within this range, the crystal growth and the particle diameter can be controlled within appropriate ranges. The hydrothermal treatment time is preferably 1 to 2 hours.

  In order to obtain stable fine particles having a uniform particle diameter, if necessary, the concentration of the magnesium hydroxide slurry subjected to hydrothermal treatment is adjusted to 30 g / L to 150 g / L by adding pure water. Also good.

  The step (D) is a step of obtaining magnesium hydroxide fine particles by filtering, washing and drying the hydrothermal magnesium hydroxide slurry.

Step (D) is, for example,
Step (D-1) of filtering and washing the hydrothermally treated magnesium hydroxide slurry to obtain a first magnesium hydroxide cake;
Step of adding 5 to 100 times pure water to the first magnesium hydroxide cake relative to the dry magnesium hydroxide mass reference amount and stirring, followed by filtration and washing with water to obtain a second magnesium hydroxide cake ( D-2);
Instead of the first magnesium hydroxide cake, the step (D-2) is repeated 1 to 20 times for the second magnesium hydroxide cake to obtain a high purity magnesium hydroxide cake (D-3); And drying the high purity magnesium hydroxide cake to obtain magnesium hydroxide fine particles (D-4);
Can be included.

  The step (D-1) is a step of obtaining a first magnesium hydroxide cake by filtering and washing the hydrothermally treated magnesium hydroxide slurry. The washing with water can be performed by adding 5 to 100 times, preferably 20 to 50 times, pure water after filtration with respect to dry magnesium hydroxide.

  In the step (D-2), 5 to 100 times pure water is added to the first magnesium hydroxide cake with respect to the dry magnesium hydroxide mass reference amount, stirred, filtered, washed with water, This is a step of obtaining a magnesium hydroxide cake, and a step of repulp washing. In this step, for example, 5 to 100 times pure water is added on a mass basis with respect to the dried magnesium hydroxide of the first magnesium hydroxide cake to obtain a second magnesium hydroxide slurry. The magnesium hydroxide slurry can be stirred and then filtered and washed with water to obtain a second magnesium hydroxide cake. Stirring can be performed, for example, at 10 to 50 ° C. and at a rotation speed of 100 to 800 rpm for 0.5 to 5 hours. Filtration can be performed after completion | finish of stirring using a filter paper etc., and water washing can be performed by throwing in 5-100 times pure water on a mass basis with respect to dry magnesium hydroxide.

  In the step (D-3), instead of the first magnesium hydroxide cake, the repulp washing in the step (D-2) is performed once for the second magnesium hydroxide cake, and this is performed 1 to 20 times. This process is repeated to obtain a high purity magnesium hydroxide cake.

  Step (D-4) is a step of drying the high purity magnesium hydroxide cake to obtain magnesium hydroxide fine particles.

  In this way, the magnesium hydroxide particles of the present invention can be obtained.

  The magnesium oxide fine particles of the present invention can be obtained by subjecting the magnesium hydroxide fine particles of the present invention to a step (E) of firing at 500 to 1200 ° C. in an air atmosphere.

  In this step, for example, magnesium hydroxide fine particles are heated in the air at a rate of temperature increase of 1 to 20 ° C./min (preferably 3 to 10 ° C./min, more preferably 6 ° C./min) to 500 ° C. to 1200 ° C. The magnesium oxide fine particles of the present invention can be obtained by heating up to 600 to 800 ° C. and firing the mixture at 500 to 1200 ° C., preferably 600 to 800 ° C. for 0.1 to 5 hours. it can. Moreover, after drying the high purity magnesium hydroxide cake obtained at the process (D-3) and loosening lightly, you may attach | subject to said baking processing.

  In this way, it is possible to easily prepare magnesium hydroxide fine particles and magnesium oxide fine particles that are highly pure, have a small particle size, and are uniform.

  The magnesium hydroxide fine particles and the magnesium oxide fine particles of the present invention are highly useful in various fields. For example, as the use of magnesium hydroxide fine particles, as an additive, an ink fixing agent for ink jet paper, etc., as a resin filler, a raw material for a separator heat-resistant layer for a secondary battery, a flame retardant, a film sheet modifier ( High performance materials such as heat resistance and flexibility), such as fuel cell ceramic raw material, phosphor raw material, superconducting thin film base material, tunnel magnetoresistive element (TMR element) tunnel barrier raw material, etc. Examples of the catalyst include wastewater treatment and exhaust gas treatment. Moreover, as a use of magnesium oxide microparticles | fine-particles, a highly functional material, a catalyst, etc. are mentioned. Magnesium oxide microparticles make use of their high activity, such as ceramic sintering aids as refractories, ink fixing agents for inkjet paper as additives, and resin fillers for secondary batteries. As a high-functional material such as a separator heat-resistant layer raw material, a film sheet modifier (heat resistance and flexibility improvement), an LED sealing resin refractive index adjuster, a light diffusing agent, a fuel cell ceramic raw material, Phosphor raw material, raw material for superconducting thin film, tunnel barrier material for tunnel magnetoresistive element (TMR element), etc., as electromagnetic steel material, raw material for insulating material for electromagnetic steel sheet, insulating coating material for dust core, etc. The catalyst is suitable for wastewater treatment, exhaust gas treatment, and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

  The particle diameter, specific surface area, purity and activity of the obtained magnesium hydroxide fine particles and magnesium oxide fine particles were measured by the following methods.

(1) a laser diffraction scattering particle size distribution measurement laser diffraction scattering particle size distribution measuring apparatus (trade name: MT3300, manufactured by Nikkiso Co., Ltd.) was used, a cumulative 10% particle diameter on a volume basis (D _10), the cumulative volume-based The 50% particle size (D ₅₀ ) and the volume-based cumulative 90% particle size (D ₉₀ ) were measured. The volume average particle diameter (Dv) and the number average particle diameter (Dn) were also measured with the above apparatus.

(2) BET specific surface area measuring method Using a specific surface area measuring device (trade name: Macsorb 1210, manufactured by Mountec Co., Ltd.), the specific surface area was measured by the BET method of gas adsorption.

(3) Magnesium hydroxide and magnesium oxide impurity element mass measurement method Impurity elements to be measured (Ag, Al, B, Ba, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, Na, Ni, P, Pb, S, Si, Sr, Tl, V, Zn, Ti and Zr) are obtained using an ICP emission spectrometer (trade name: SPS-5100, manufactured by Seiko Instruments Inc.). After dissolving the sample in acid, the mass was measured.
The amount of Cl was measured using a spectrophotometer (trade name: UV-2550, manufactured by Shimadzu Corporation) after dissolving the sample in acid.

(4) Purity measurement method The purity of magnesium hydroxide and magnesium oxide fine particles is calculated as a value obtained by subtracting the total mass of impurity elements measured by the above-mentioned “magnesium hydroxide and magnesium oxide impurity amount measurement method” from 100% by mass. did.

(5) Method of measuring citric acid activity (40%) 2.02 g of magnesium oxide fine particles were weighed so that 100 ml of 0.4N citric acid aqueous solution corresponded to 40% of the neutralized amount of magnesium oxide, and 30.0 The magnesium oxide fine particles were added to the citric acid aqueous solution while stirring the citric acid aqueous solution at a temperature, and the time until all of the citric acid reacted with magnesium oxide, that is, the time until pH 7 was exceeded was measured.

[Example 1]
A crude magnesium chloride aqueous solution having a purity of 90% by mass or more and a concentration of 3.5 mol / L was prepared. The concentration was adjusted by adding pure water (water purified by passing through an ion exchange resin to have an electric conductivity of 0.1 μS / cm or less) to this magnesium chloride aqueous solution, and a crude magnesium chloride aqueous solution having a concentration of 2.0 mol / L. It was.

  Next, a sodium hydroxide aqueous solution with a concentration of 17.84 mol / L was added to the crude magnesium chloride aqueous solution with a concentration of 2.0 mol / L so as to achieve a reaction rate of 20 mol%. An acrylamide / sodium acrylate copolymer was added in an amount of 500 ppm by mass to the produced magnesium hydroxide, the magnesium hydroxide was coagulated and precipitated, and the supernatant was taken out to obtain an aqueous magnesium chloride solution.

  The concentration of the obtained magnesium chloride aqueous solution was adjusted to obtain a magnesium chloride aqueous solution having a concentration of 2.0 mol / L. This magnesium chloride aqueous solution was reacted with a sodium hydroxide aqueous solution having a concentration of 17.84 mol / L so that the reaction rate was 200 mol% to prepare a magnesium hydroxide slurry having a concentration of 100 g / L.

  The obtained magnesium hydroxide slurry was held with stirring at 150 ° C. for 1 hour using an autoclave, and subjected to hydrothermal treatment (heated stirring treatment). The first magnesium hydroxide slurry subjected to hydrothermal treatment was filtered and washed with water to obtain a first magnesium hydroxide cake. Washing with water was performed by adding 40 times the pure water after mass filtration to the dried magnesium hydroxide.

  Next, repulp washing was performed on the obtained first magnesium hydroxide cake. In the repulp washing, first, 40 times pure water was added on a mass basis with respect to the dried magnesium hydroxide of the first magnesium hydroxide cake to obtain a second magnesium hydroxide slurry. Next, the second magnesium hydroxide slurry is stirred at room temperature using a stirrer at a rotation speed of 500 rpm for 1 hour, and the second magnesium hydroxide slurry after the stirring is further filtered using filter paper. Then, with respect to the dried magnesium hydroxide, 20 times as much pure water was added after filtration and washed with water to obtain a second magnesium hydroxide cake. The above-described repulp washing was performed once, and the repulp washing was further repeated 10 times to obtain a high purity magnesium hydroxide cake. The high purity magnesium hydroxide cake was dried to obtain high purity magnesium hydroxide fine particles.

[Example 2]
The reaction was performed in the same manner as in Example 1 except that the reaction rate in the reaction between the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution was 120 mol% and the hydrothermal treatment time was 0.5 hour.

Example 3
The same procedure as in Example 1 was performed except that the reaction rate in the reaction between the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution was 105 mol% and the hydrothermal treatment time was 3 hours.

Example 4
The same procedure as in Example 1 was carried out except that the hydrothermal treatment temperature was 130 ° C. and the aqueous sodium hydroxide solution was diluted to 8.92 mol / L with pure water.

Example 5
The hydrothermal treatment temperature was set to 105 ° C., and the same procedure as in Example 1 was performed except that the magnesium hydroxide slurry subjected to the hydrothermal treatment was changed to 130 g / L.

Example 6
The same operation as in Example 1 was carried out except that the aqueous sodium hydroxide solution was diluted to 4.96 mol / L with pure water.

Example 7
The same operation as in Example 1 was conducted except that the magnesium hydroxide slurry subjected to hydrothermal treatment was diluted with pure water to 50 g / L.

[Comparative Example 1]
The same procedure as in Example 1 was conducted except that the reaction rate in the reaction between the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution was 250 mol%.

[Comparative Example 2]
The same procedure as in Example 1 was performed except that the reaction rate in the reaction between the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution was 90 mol%.

[Comparative Example 3]
The reaction was performed in the same manner as in Example 1 except that the reaction rate in the reaction between the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution was 105 mol%, and hydrothermal treatment was not performed.

[Comparative Example 4]
It carried out similarly to Example 1 except having changed the sodium hydroxide aqueous solution into 21 mol / L with pure water.

Example 8
The magnesium hydroxide fine particles prepared in Example 1 were baked at 1000 ° C. for 1 hour in an air atmosphere to obtain magnesium oxide fine particles.

Example 9
The magnesium hydroxide fine particles prepared in Example 3 were baked at 600 ° C. for 1 hour in an air atmosphere to obtain magnesium oxide fine particles.

[Comparative Example 5]
The magnesium hydroxide fine particles prepared in Example 1 were fired at 1400 ° C. for 1 hour in the air atmosphere to obtain magnesium oxide fine particles.

  Table 1 shows the measurement results regarding the magnesium hydroxide fine particles obtained by the above Examples and Comparative Examples, and Table 2 shows the measurement results regarding the magnesium oxide fine particles.

  The magnesium hydroxide fine particles and the magnesium oxide fine particles in the examples both had a purity of 99.9% by mass or more, had a small particle size, and were uniform.

The magnesium hydroxide fine particles and the magnesium oxide fine particles of the present invention are highly useful in various fields because of their high purity, small particle size, uniformness, and good dispersibility (because the particle size distribution is sharp). . In addition, according to the production method of the present invention, the fine particles as described above can be easily prepared, which is highly convenient. For example, the use of magnesium hydroxide fine particles includes additives, resin fillers, highly functional materials, and catalysts.
Specifically, as additives, ink fixing agents for inkjet paper, etc .; as resin fillers, raw materials for separator heat-resistant layers for secondary batteries, flame retardants, film sheet modifiers (improved heat resistance and flexibility) High-functional materials include fuel cell ceramic raw materials, phosphor raw materials, raw materials for superconducting thin films, tunnel magnetoresistive elements (TMR elements) tunnel barrier raw materials, etc .; And can be used for applications such as exhaust gas treatment.
Examples of the use of the magnesium oxide fine particles include refractories, additives, resin fillers, highly functional materials, electromagnetic steel materials, and catalysts.
Specifically, as refractories, ceramic sintering aids, etc .; as additives, ink fixing agents for inkjet paper, etc .; as resin fillers, raw materials for separator heat-resistant layers for secondary batteries, film sheet modifications Quality materials (improving heat resistance and flexibility), etc .; as high-functional materials, refractive index adjusting agent for LED sealing resin, light diffusing agent, raw material for ceramic for fuel cell, phosphor raw material, superconducting thin film base Raw materials, tunnel barrier raw materials for tunnel magnetoresistive elements (TMR elements), etc .; as electromagnetic steel materials, raw materials for insulating materials for magnetic steel sheets, insulating coating materials for dust cores, etc .; as catalysts, wastewater treatment and exhaust gas treatment It can be used for such applications.

Claims (4)

Step of preparing a magnesium chloride aqueous solution (A)
A step (B) of obtaining a magnesium hydroxide slurry by reacting an aqueous magnesium chloride solution with an alkaline aqueous solution of 1 to 18 N at a reaction rate of 101 to 210 mol%;
The magnesium hydroxide slurry is maintained at a temperature of 101 to 200 ° C. with stirring to obtain a hydrothermally treated magnesium hydroxide slurry (C); and the hydrothermally treated magnesium hydroxide slurry is filtered, washed and Step of drying to obtain magnesium hydroxide fine particles (D)
Only including,
Step (D)
Step (D-1) of filtering and washing the hydrothermally treated magnesium hydroxide slurry to obtain a first magnesium hydroxide cake;
Step of adding 5 to 100 times pure water to the first magnesium hydroxide cake relative to the dry magnesium hydroxide mass reference amount and stirring, followed by filtration and washing with water to obtain a second magnesium hydroxide cake ( D-2);
Instead of the first magnesium hydroxide cake, the step (D-2) is repeated 1 to 20 times for the second magnesium hydroxide cake to obtain a high purity magnesium hydroxide cake (D-3); as well as
Drying the high purity magnesium hydroxide cake to obtain magnesium hydroxide fine particles (D-4);
The manufacturing method of magnesium hydroxide microparticles | fine-particles containing . Step (A) is
Preparing a crude magnesium chloride aqueous solution (A-1);
A step of reacting crude magnesium chloride with a 1-18 N alkaline aqueous solution at a reaction rate of 1-30 mol% to obtain a crude magnesium hydroxide slurry (A-2); and a flocculant in the crude magnesium hydroxide slurry After the addition, the magnesium hydroxide is filtered to obtain a magnesium chloride solution as a filtrate, or a flocculant is added to cause the magnesium hydroxide to coagulate and precipitate to obtain a magnesium chloride aqueous solution as a supernatant (A-3 )
The containing process according to claim 1, wherein the magnesium hydroxide particles. Step of preparing a magnesium chloride aqueous solution (A)
A step (B) of obtaining a magnesium hydroxide slurry by reacting an aqueous magnesium chloride solution with an alkaline aqueous solution of 1 to 18 N at a reaction rate of 101 to 210 mol%;
Step (C) of obtaining a magnesium hydroxide slurry hydrothermally treated by holding the magnesium hydroxide slurry at a temperature of 101 to 200 ° C. while stirring; and
Step (D) of obtaining magnesium hydroxide fine particles by filtering, washing and drying the hydrothermally treated magnesium hydroxide slurry
Including
Step (A) is
Preparing a crude magnesium chloride aqueous solution (A-1);
A step of reacting crude magnesium chloride with a 1-18N aqueous alkali solution at a reaction rate of 1-30 mol% to obtain a crude magnesium hydroxide slurry (A-2); and
After adding the flocculant to the crude magnesium hydroxide slurry, the magnesium hydroxide is filtered to obtain a magnesium chloride solution as the filtrate, or the flocculant is added to coagulate and precipitate the magnesium hydroxide, and as the supernatant Step of obtaining an aqueous magnesium chloride solution (A-3)
The manufacturing method of magnesium hydroxide microparticles | fine-particles containing. The 請 Motomeko 1 - magnesium hydroxide fine particles obtained in 3 any one of claims way, in an air atmosphere, comprising the step (E) is fired at 500 to 1500 ° C., the manufacturing method of the magnesium oxide particles.