TWI529133B - Method for producing magnesium hydroxide microparticle and magnesium oxide microparticle - Google Patents

Description

Method for producing magnesium hydroxide microparticles and magnesium oxide microparticles

The present invention relates to high-purity magnesium hydroxide fine particles and high-purity magnesium oxide fine particles having a small particle size and uniformity, and a method for producing the fine particles.

Magnesium hydroxide and magnesium oxide are inorganic materials used in various fields, and the use of the former may be an additive, a resin filler, a highly functional material, a catalyst, etc., and the latter may be used. Refractories, additives, resin fillers, highly functional materials, electromagnetic steel sheet materials, and catalysts. Including such applications, requirements for magnesium hydroxide and magnesium oxide are high purity, small particle size, and uniform microparticle morphology.

In the method of producing magnesium hydroxide having a small particle size and uniformity, it is proposed to add an alkali substance in an aqueous solution containing magnesium hydroxide, followed by addition of a surfactant, thereby preparing magnesium hydroxide fine particles of 10 nm to 1000 nm. Method (refer to Patent Document 1). However, in a specific example, the amount of alkali added is large, and the impurities are eluted from the autoclave container, and there is a problem that impurities are mixed.

Further, it is also proposed to add boric acid, citric acid or such water-soluble salts to a method for producing magnesium hydroxide by hydrothermal reaction of magnesium chloride and an alkali substance in an aqueous medium, and arbitrarily control the obtained A method of an aspect ratio of magnesium hydroxide (see Patent Document 2). However, in this method, there is a problem that it is difficult to control the particle diameter, and it is impossible to obtain fine particles having a uniform particle diameter.

(previous technical literature) (Patent Literature)

(Patent Document 1) Japanese Patent Laid-Open Publication No. 2009-62214

(Patent Document 2) Japanese Patent Laid-Open Publication No. 2005-200300

An object of the present invention is to provide a high-purity magnesium hydroxide fine particle and a high-purity magnesium oxide fine particle having a small particle size and uniformity, and a method for producing the fine particle.

The present invention relates to a magnesium hydroxide microparticle having a BET specific surface area of 5 m ² /g or more, and a cumulative 50% particle diameter (D ₅₀ ) obtained by a volumetric reference obtained by a laser diffraction scattering particle size distribution measurement of 0.1 to 0.5. [mu] m, a laser diffraction scattering particle size distribution measurement based on volume of the resulting cumulative 10% particle size (D ₁₀₎ and the volume-based cumulative 90% particle size (D ₉₀₎ of the ratio of D ₉₀ / D ₁₀ of 10 or less, The purity is 99.5 mass% or more.

Further, the present invention relates to a magnesium oxide fine particle having a BET specific surface area of 5 m ² /g or more, and a cumulative 50% particle diameter (D ₅₀ ) of a volume basis obtained by a laser diffraction scattering particle size distribution measuring method of 0.1 to 0.5. [mu] m, a laser diffraction scattering particle size distribution measurement based on volume of the resulting cumulative 10% particle size (D ₁₀₎ and the volume-based cumulative 90% particle size (D ₉₀₎ of the ratio of D ₉₀ / D ₁₀ of 10 or less, The purity is 99.5 mass% or more.

Furthermore, the present invention relates to a process for producing magnesium hydroxide fine particles comprising the following steps: a step (A) of preparing an aqueous magnesium chloride solution; and 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%. And obtaining the step (B) of the magnesium hydroxide slurry; maintaining the temperature of the magnesium hydroxide slurry at a temperature of 101 to 200 ° C while stirring, obtaining the step (C) of the hydrothermally treated magnesium hydroxide slurry; and passing the water The heat-treated magnesium hydroxide slurry is filtered, washed with water and dried to obtain a step (D) of magnesium hydroxide fine particles.

In addition, the present invention relates to a method for producing magnesium oxide fine particles comprising the steps described above, wherein the magnesium hydroxide fine particles or the magnesium hydroxide fine particles obtained by the above production method are calcined at 500 to 1500 ° C in an atmospheric environment. Step (E).

The magnesium hydroxide fine particles and the magnesium oxide fine particles of the present invention are high in purity, small in particle diameter, and uniform, and have high usefulness in various fields. Further, according to the production method of the present invention, the fine particles as described above can be easily prepared, and the convenience is high.

The magnesium hydroxide fine particles of the present invention have a BET specific surface area of 5 m ² /g or more, and a cumulative 50% particle diameter (D ₅₀ ) of a volume-based measurement by a laser diffraction scattering particle size distribution of 0.1 to 0.5 μm, laser diffraction scattering particle size distribution measurement of the volume-based cumulative 10% particle size (D ₁₀₎ and the volume-based cumulative 90% particle size (D ₉₀₎ of the ratio of D ₉₀ / D ₁₀ of 10 or less. Such magnesium hydroxide fine particles have a small particle shape and are excellent in reaction, so they are suitable for additives, resin fillers, catalysts, etc., and have small particle shapes, small variations in particle size, and excellent dispersibility. Highly functional materials and the like are also suitable for use. The magnesium hydroxide fine particles of the present invention preferably have a BET specific surface area of 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 purity of the magnesium hydroxide fine particles of the present invention is 99.5% by mass or more. When it is in this range, the elution of impurities can be suppressed extremely, and it can be suitably used 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 is an impurity element (Ag, Al, B, Ba, Bi, Cd, Cl, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, which is a particle to be measured). The content of Na, Ni, P, Pb, S, Si, Sr, Tl, V, Zn, Ti and Zr), and the total content of these is deducted from 100% by mass. In the present specification, the high purity means that the purity calculated as described above is 99.5% by mass or more.

As the impurity element (Ag, Al, B, Ba, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, Na, Ni, P, Pb, S, which is the object of measurement) Si, Sr, Tl, V, Zn, Ti, and Zr) are obtained by dissolving a sample in an acid using an ICP emission spectrometer, and measuring the mass. The amount of Cl is measured by dissolving the sample in an acid using a spectrophotometer. .

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

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

The magnesium hydroxide fine particles of the present invention preferably have a ratio Dv/Dn of a volume-based average particle diameter (Dv) to a number-based average particle diameter (Dn) of from 1 to 10. When the Dv/Dn is from 1 to 10, it has excellent ink fixing property when used for an ink fixing agent, and is excellent in heat resistance, flame retardancy, flexibility, and catalytic function when added to a resin or the like. It is also resistant to acid and has good moisture resistance. Dv/Dn is preferably from 1 to 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 cumulative 50% particle diameter (D ₅₀ ) of a volume basis obtained by laser diffraction scattering particle size distribution measurement is 0.1 to 0.5 μm, and laser diffraction The ratio of the cumulative 10% particle diameter (D ₁₀ ) of the volume basis obtained by the scattering particle size distribution measurement to the cumulative 90% particle diameter (D ₉₀ ) of the volume basis is D ₉₀ /D ₁₀ of 10 or less. Since such a magnesium oxide fine particle has a small particle shape and excellent reactivity, it is suitable as a refractory, an additive, a resin filler, an electromagnetic steel sheet material, a catalyst, etc., and also has a small particle size and a variation in particle size. It has few dispersibility and is suitable for use in highly functional materials.

The Mn 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 the following.

The purity of the magnesium oxide fine particles of the present invention is 99.5% by mass or more. Within this range, the dissolution of impurities is extremely suppressed, and it is suitable for use in highly functional materials. 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 ppm by mass or less. When the total content of these is 500 ppm by mass or less, the elution of the metal impurities is extremely suppressed, and it can be suitably used for an additive, a resin filler, or a highly functional material. The total content is preferably 450 ppm by mass or less.

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

The magnesium oxide fine particles of the present invention preferably have a ratio Dv/Dn of a volume-based average particle diameter (Dv) to a number-based average particle diameter (Dn) of from 1 to 10. When the Dv/Dn is from 1 to 10, the fixing property of the ink used in the fixing agent application of the ink is excellent, and when it is added to a resin or the like, it has excellent heat resistance, flame retardancy, flexibility, light diffusion effect, and It has good catalytic effect and good acid resistance and moisture resistance, and more preferably 1 to 8.

The magnesium oxide fine particles of the present invention preferably have a citric acid activity (final reaction rate of 40%, 20.0 ° C) of from 20 to 2000 seconds. When the citric acid activity is 20 to 2000 seconds, the reactivity with iron is excellent. When it is made of an electromagnetic steel sheet material, it can be suitably used for an insulating material for an electromagnetic steel sheet and an insulating coating material for a dust core. The citric acid activity is preferably from 20 to 500 seconds. The magnesium hydroxide fine particles of the present invention are obtained by the steps of: preparing a step (A) of preparing an aqueous magnesium chloride solution; and reacting an aqueous magnesium chloride solution with an aqueous alkaline solution of 1 to 18 N at a reaction rate of 101 to 210 mol%; And obtaining the step (B) of the magnesium hydroxide slurry; maintaining the magnesium hydroxide slurry at a temperature of 101 to 200 ° C under stirring to obtain the step (C) of the hydrothermally treated magnesium hydroxide slurry; and passing the water The heat-treated magnesium hydroxide slurry is filtered, washed with water and dried to obtain a step (D) of magnesium hydroxide fine particles.

Step (A) is a step of preparing an aqueous solution of magnesium chloride. The aqueous magnesium chloride solution is preferably present in a concentration of from 0.1 to 10 mol/L. When the concentration is less than 0.1 mol/L, the production efficiency is not good. Further, when the concentration is higher than 10 mol/L, the viscosity of the magnesium hydroxide slurry becomes high, and workability is not good. The concentration of the aqueous magnesium chloride solution is preferably from 0.5 to 5 mol/L.

The step (A) is, for example, a step comprising the steps of: preparing a crude magnesium chloride aqueous solution (A-1); and reacting the crude magnesium chloride aqueous solution with an aqueous solution of 1 to 18 N at a reaction rate of 1 to 30 mol% to obtain a crude Magnesium hydroxide slurry step (A-2); and after adding a flocculating agent to the coarse magnesium hydroxide slurry, filtering magnesium hydroxide to obtain a magnesium chloride solution as a filtrate, or adding a coagulant to agglomerate and precipitate magnesium hydroxide, and The step (A-3) of obtaining an aqueous solution of magnesium chloride from the clear liquid.

Step (A-1) is a step of preparing a crude magnesium chloride solution. For example, in magnesium chloride (in the case of magnesium chloride, magnesium chloride 6 water or anhydrous magnesium chloride, or sea water, alkaline water, or bitter juice) may be added with pure water (purified by ion exchange resin to have an electrical conductivity of 0.1 μS/cm or less). The water) can thereby be used to prepare a crude aqueous solution of magnesium chloride. The crude magnesium chloride aqueous solution can be used in a concentration of 0.5 to 10 mol/L, preferably 1 to 5 mol/L, more preferably 2 to 4 mol/L.

The step (A-2) is a step of obtaining a crude magnesium hydroxide slurry by reacting a crude magnesium chloride aqueous solution to a reaction rate of 1 to 30 mol% in an aqueous solution of 1 to 18 N. The reaction rate is a value calculated by making the amount of alkali required for all magnesium chloride to be magnesium hydroxide to be 100 mol%. For example, 200 mol% means 2 times the equivalent amount of alkali.

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

Step (A-3) is: after adding a flocculating agent to the coarse magnesium hydroxide slurry, filtering the magnesium hydroxide to obtain a magnesium chloride solution as a filtrate, or adding a flocculating agent to cause the magnesium hydroxide to aggregate and precipitate, and as a supernatant liquid And a step of obtaining an aqueous solution of magnesium chloride.

In the case of an aggregating agent, the main component is acrylamide, sodium acrylate copolymer, acrylamide, acrylamide-methyl 2-methylpropane sulfonate copolymer, polypropylene decylamine, alkylaminomethyl A fourth-stage ammonium salt polymer of acrylic acid, an alkylamino acrylate fourth-grade ammonium salt, an acrylamide copolymer, a polyamidine hydrochloride or the like, preferably a acrylamide/sodium acrylate copolymer. Things. The amount of the aggregating agent added may be set to 100 to 1000 ppm by mass based on the amount of dry magnesium hydroxide in the coarse magnesium hydroxide slurry.

The concentration of the aqueous magnesium chloride solution obtained in this manner is adjusted to prepare an aqueous magnesium chloride solution having a concentration of 0.1 to 10.0 mol/L.

The 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%, the crystal growth is excessive in the hydrothermal treatment of the magnesium hydroxide slurry, and the particle diameter becomes excessive. In addition, when the reaction rate is higher than 210 mol%, specific elements (Fe, Ti, Ni, Cr, Mo, and Mn) are eluted from the autoclave container, and impurities are likely to be mixed. The reaction rate is preferably from 103 to 200 mol%, more preferably from 105 to 180 mol%.

The alkaline aqueous solution is preferably an aqueous sodium hydroxide solution having a concentration of 1 to 18 mol/L. When the concentration of the aqueous sodium hydroxide solution is less than 1 mol/L, the production efficiency is not good. Further, when the concentration is higher than 18 mol/L, the viscosity of the magnesium hydroxide slurry becomes high, and workability is not good. The concentration of the aqueous sodium hydroxide solution is preferably 4 to 16 mol/L.

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

The hydrothermal treatment is carried out by holding a magnesium hydroxide slurry, for example, using an autoclave at 101 ° C to 200 ° C while stirring. When the hydrothermal treatment temperature is lower than 101 ° C, the crystal does not grow, and aggregated particles are formed and the dispersion is not good. When the hydrothermal treatment temperature is higher than 200 ° C, the crystal growth excessively increases, and the particle diameter tends to become excessively large. The hydrothermal treatment temperature is preferably from 105 to 150 °C. The hydrothermal treatment time can be set at 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 an appropriate range. The hydrothermal treatment time is preferably from 1 to 2 hours.

In order to obtain stable fine particles having a uniform particle diameter, pure water may be added if necessary, and the concentration of the magnesium hydroxide slurry to be hydrothermally treated may be adjusted to 30 g/L to 150 g/L.

The step (D) is a step of filtering the hydrothermally treated magnesium hydroxide slurry, washing with water, and drying to obtain magnesium hydroxide fine particles.

The step (D) is a step (D-1) which may contain, for example, filtering and water-washing the hydrothermally treated magnesium hydroxide slurry to obtain a first magnesium hydroxide cake; the first magnesium hydroxide a mud cake, which is added to the pure magnesium hydroxide mass reference amount of 5 to 100 times, stirred, filtered, washed with water to obtain a second magnesium hydroxide cake (D-2); instead of the first hydrogen a magnesium oxide mud cake, and the second magnesium magnesium mud cake, step (D-2) is repeated 1 to 20 times to obtain a high-purity magnesium hydroxide mud cake step (D-3); and high-purity hydrogen The step (D-4) of drying the magnesium oxide cake to obtain magnesium hydroxide fine particles.

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 water washing is carried out by filtering the dried magnesium hydroxide into 5 to 100 times, preferably 20 to 50 times, the pure water based on the mass basis.

Step (D-2) is the first magnesium hydroxide mud cake, adding 5 to 100 times of pure water for the dry magnesium hydroxide mass basis amount, stirring, filtering, and washing with water to obtain a second magnesium hydroxide. The step of the mud cake is the step of repulping the washing. In this step, for example, the first magnesium hydroxide cake is put into pure water of 5 to 100 times based on the mass of the dry magnesium hydroxide to obtain a second magnesium hydroxide slurry, and the second hydrogen peroxide is obtained. The magnesium slurry was stirred, filtered, and washed with water to obtain a second magnesium hydroxide cake. The stirring is, for example, carried out at 10 to 50 ° C for 0.5 to 5 hours at a rotational speed of 100 to 800 rpm. After the completion of the stirring, the filtration can be carried out using a filter paper or the like, and the water washing can be carried out by adding pure water of 5 to 100 times the mass of the dried magnesium hydroxide.

Step (D-3) is to replace the first magnesium hydroxide cake, and for the second magnesium hydroxide cake, the pulp of step (D-2) is washed once, and this is repeated 1 to 20 steps to obtain a high-purity magnesium hydroxide cake.

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

Thus, the magnesium hydroxide particles of the present invention can be obtained.

The magnesium oxide fine particles of the present invention are obtained by calcining the magnesium hydroxide particles of the present invention in an air atmosphere at 500 to 1200 ° C in the step (E).

In this step, for example, the magnesium hydroxide fine particles are heated to 500 ° C in an atmosphere at a temperature increase rate of 1 to 20 ° C / min (preferably 3 to 10 ° C / min, more preferably 6 ° C / min). The magnesium oxide fine particles of the present invention can be obtained at 1120 ° C, preferably at 600 ° C to 800 ° C, after heating, at 500 ° C to 1200 ° C, preferably at 600 to 800 ° C for 0.1 to 5 hours. Further, the high-purity magnesium hydroxide mud cake obtained in the step (D-3) is dried, gently loosened, and then subjected to the above calcination treatment.

Thus, it is easy to prepare magnesium hydroxide fine particles and magnesium oxide fine particles having high purity and small particle diameter and uniformity.

The magnesium hydroxide particles and magnesium oxide fine particles of the present invention have high usefulness in various fields. For example, as the use of the magnesium hydroxide fine particles, an ink fixing agent which can be used as an additive for inkjet paper can be used as a resin filler, and it can be used as a raw material for separating a heat-resistant layer for a secondary battery. As a highly functional material, it can be used as a material for ceramics for fuel cells, a raw material for phosphors, and a material for superconducting film substrates. The tunnel barrier material used for the TMR (tunnel magnetoresistance) component can be used as a catalyst for drainage treatment and exhaust treatment. Moreover, as for the use of the magnesium oxide fine particles, a highly functional material, a catalyst, etc. are mentioned. Further, the magnesium oxide fine particles can be used as a refractory in the case of utilizing their high activity, and can be used as a ceramic sintering aid or the like as an additive, and can be used as an ink filling agent for inkjet paper as a resin filler. The raw material for separating the heat-resistant layer for the secondary battery, the modifier (heat resistance, and improved flexibility) of the film sheet, etc., as a highly functional village material, can be used as a refractive index adjuster and a light diffusing agent for the LED sealing resin. , raw materials for ceramics for fuel cells, raw materials for phosphors, raw materials for superconducting thin film substrates, tunnel barrier materials for tunneling magnetoresistive elements (TMR elements), etc., as electromagnetic steel sheet materials, can be used for insulation of electromagnetic steel sheets. The raw material of the material, the insulating coating material for the powdered iron core, etc., can be used as a catalyst for drainage treatment and exhaust treatment.

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples. However, the invention is not limited by 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) Laser diffraction scattering particle size distribution measurement

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

(2) BET specific surface area measurement method

The specific surface area was measured by a BET method by a gas adsorption method using a specific surface area measuring device (trade name: Macsorb 1210, manufactured by Mounteck Co., Ltd.).

(3) Determination of the impurities of magnesium hydroxide and magnesium oxide impurities

Determination of impurity elements (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) were measured by dissolving the sample in an acid using an ICP emission spectrometer (trade name: SPS-5100, manufactured by Seiko Instruments Co., Ltd.).

The amount of Cl was measured by dissolving a sample in an acid using a spectrophotometer (trade name: UV-2550, manufactured by Shimadzu Corporation).

(4) Purity determination method

The purity of the magnesium hydroxide and the magnesium oxide fine particles is calculated by subtracting the total mass of the impurity element measured by the above-described "measurement method of magnesium hydroxide and magnesium oxide impurities" by 100% by mass.

(5) Method for determining citric acid activity (40%)

2.02 g of magnesium oxide fine particles were weighed in such a manner that 100 ml of 0.4 N aqueous citric acid solution corresponded to 40% of the neutralization amount of magnesium oxide, and the citric acid aqueous solution was stirred at 30 ° C, and the magnesium oxide fine particles were added to measure all citric acid and The time during which the magnesium oxide reacts, i.e., the time required to exceed pH 7.

(Example 1)

As a crude magnesium chloride aqueous solution, an aqueous solution having a purity of 90% by mass or more and a concentration of 3.5 mol/L was prepared. Pure water (purified by ion exchange resin to obtain water having an electric conductivity of 0.1 μS/cm or less) was added to the aqueous magnesium chloride solution to adjust the concentration to obtain a crude magnesium chloride aqueous solution having a concentration of 2.0 mol/L.

Next, a solution of a crude magnesium chloride solution having a concentration of 2.0 mol/L was added to a sodium hydroxide aqueous solution having a concentration of 17.84 mol/L to cause a reaction rate of 20 mol%, and further, as a coagulant, a propylene amide amine/sodium acrylate copolymer was used. 500 ppm by mass of magnesium hydroxide was formed, and magnesium hydroxide was agglomerated and precipitated, and the supernatant liquid was taken out, thereby obtaining an aqueous magnesium chloride solution.

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

The obtained magnesium hydroxide slurry was stirred at 150 ° C for 1 hour using an autoclave, and subjected to hydrothermal treatment (heating and stirring treatment). The hydrothermally treated first magnesium hydroxide slurry was filtered and washed with water to obtain a first magnesium hydroxide cake. The water washing was carried out by adding pure water which was 40 times by mass based on the mass of the dry magnesium hydroxide after the filtration.

Next, the first magnesium hydroxide cake obtained was subjected to pulp washing. In the pulp washing, first, 40 parts of pure water based on the mass of the dry magnesium hydroxide relative to the first magnesium hydroxide cake was charged to obtain a second magnesium hydroxide slurry. Next, the second magnesium hydroxide slurry was stirred at a rotation speed of 500 rpm for 1 hour at a normal temperature using a stirring device, and the second magnesium hydroxide slurry after the completion of the stirring was filtered using a filter paper to be dried. Magnesium hydroxide was purified by 20 times of pure water on a mass basis, and after filtration, it was put into water and washed to obtain a second magnesium hydroxide cake. The above-mentioned pulp was washed once, and the pulp was washed 10 times to thereby obtain a high-purity magnesium hydroxide cake. The high-purity magnesium hydroxide mud cake is dried to obtain high-purity magnesium hydroxide microparticles.

(Example 2)

The reaction rate in the reaction between the aqueous magnesium chloride solution and the aqueous sodium hydroxide solution was changed to 120 mol%, and the hydrothermal treatment time was changed to 0.5 hour, and the same procedure as in Example 1 was carried out.

(Example 3)

The reaction rate in the reaction between the aqueous magnesium chloride solution and the aqueous sodium hydroxide solution was changed to 105 mol%, and the hydrothermal treatment time was changed to 3 hours, and the same procedure as in Example 1 was carried out.

(Example 4)

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

(Example 5)

The hydrothermal treatment temperature was changed to 105 ° C, and the magnesium hydroxide slurry to be hydrothermally treated was changed to 130 g/L, and the same procedure as in Example 1 was carried out.

(Example 6)

The same procedure 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 magnesium hydroxide slurry to be hydrothermally treated was diluted with pure water to obtain 50 g/L, and was carried out in the same manner as in Example 1.

(Comparative Example 1)

The reaction rate in the reaction between the aqueous magnesium chloride solution and the aqueous sodium hydroxide solution was changed to 250 mol%, and the same procedure as in Example 1 was carried out.

(Comparative Example 2)

The reaction rate in the reaction between the aqueous magnesium chloride solution and the aqueous sodium hydroxide solution was changed to 90 mol%, and the same procedure as in Example 1 was carried out.

(Comparative Example 3)

The reaction rate in the reaction between the aqueous magnesium chloride solution and the aqueous sodium hydroxide solution was changed to 105 mol%, and the same procedure as in Example 1 was carried out except that the hydrothermal treatment was not carried out.

(Comparative Example 4)

The same procedure as in Example 1 was carried out except that the aqueous sodium hydroxide solution was 21 mol/L in pure water.

(Example 8)

The magnesium hydroxide fine particles prepared in Example 1 were calcined 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 calcined 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 calcined at 1400 ° C for 1 hour in an air atmosphere to obtain magnesium oxide fine particles.

The measurement results of the magnesium hydroxide fine particles obtained by the above examples and comparative examples are shown in the first table, and the measurement of the magnesium oxide fine particles was completed, and it is shown in the second table.

The magnesium hydroxide fine particles and the magnesium oxide fine particles of the examples all had a purity of 99.9% by mass or more, and the particle diameter was small and uniform.

(industrial use possibility)

The magnesium hydroxide fine particles and the magnesium oxide fine particles of the present invention have high purity, are small in particle size, are uniform, and have good dispersibility (sharp shape distribution), and thus have high usefulness in various fields. Further, according to the production method of the present invention, the fine particles as described above can be easily prepared, and the convenience is high. For example, examples of the use of the magnesium hydroxide fine particles include additives, resin fillers, highly functional materials, and catalysts.

Specifically, it can be used as an additive, an ink fixing agent for inkjet paper, etc.; as a resin filler, there is a material for separating a heat-resistant layer for a secondary battery, a flame retardant, and a film sheet. For the high-performance materials, there are raw materials for ceramics for fuel cells, raw materials for fluorescent materials, raw materials for superconducting thin film substrates, and devices for tunneling magnetoresistive elements (TMR elements). The use of the tunnel barrier material, etc., as a catalyst, drainage treatment, and exhaust treatment.

Further, examples of the use of the magnesium oxide fine particles include refractories, additives, resin fillers, highly functional materials, electromagnetic steel sheet materials, and catalysts.

Specifically, it can be used as a refractory, a ceramic sintering aid, etc., as an additive, an ink fixing agent for inkjet paper, etc.; as a resin filler, a heat-resistant layer for a secondary battery Raw material, film sheet modifier (heat resistance, improved flexibility), etc.; as a highly functional material, there are LED sealing resin refractive index modifier, light diffusing agent, fuel cell ceramic raw material, phosphor Raw material, raw material for superconducting film substrate, tunnel barrier material for tunneling magnetoresistive element (TMR element), etc.; as material for electromagnetic steel sheet, raw material for insulating material for electromagnetic steel sheet, insulating coating for powdered iron core, etc. As a catalyst, it has applications such as drainage treatment and exhaust treatment.

Claims (13)

A method for producing magnesium hydroxide fine particles, comprising the steps of: preparing a magnesium chloride aqueous solution (A); and 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% to obtain magnesium hydroxide. a slurry step (B); a step (C) of obtaining a hydrothermally treated magnesium hydroxide slurry by maintaining a magnesium hydroxide slurry while maintaining a temperature of 101 to 200 ° C; and filtering the hydrothermally treated magnesium hydroxide slurry And washing and drying to obtain magnesium hydroxide fine particles in the step (D), wherein the step (A) comprises the steps of: preparing the crude magnesium chloride aqueous solution (A-1); and making the crude magnesium chloride aqueous solution and 1 to 18N The alkaline aqueous solution is reacted at a reaction rate of 1 to 30 mol% to obtain a step (A-2) of the crude magnesium hydroxide slurry; and after the addition of the aggregating agent to the coarse magnesium hydroxide slurry, the magnesium hydroxide is filtered to serve as a filtrate. Obtaining a magnesium chloride solution, or adding a coagulant to agglomerate the magnesium hydroxide, and obtaining a magnesium chloride aqueous solution as a supernatant liquid (A-3), wherein the step (D) comprises the following steps: hydrothermally treating the hydroxide The magnesium mud slurry is filtered and washed to obtain the first magnesium hydroxide mud cake step (D-1); in the first magnesium hydroxide mud cake, added with respect to the dry hydrogen oxide a magnesium-based mass reference amount of 5 to 100 times pure water, after stirring, filtering, washing with water to obtain a second magnesium hydroxide cake (D-2); instead of the first magnesium hydroxide cake, a second magnesium hydroxide cake, the step (D-2) is repeated 1 to 20 times to obtain a high-purity magnesium hydroxide cake (D-3); and the high-purity magnesium hydroxide cake is dried, and The step (D-4) of obtaining magnesium hydroxide fine particles. The manufacturing method according to the first aspect of the patent application is to obtain a cumulative 50% particle diameter (D ₅₀ ) of a volume basis obtained by a laser diffraction scattering particle size distribution measurement method having a BET specific surface area of 5 m ² /g or more. The ratio of the cumulative 10% particle size (D ₁₀ ) of the volume basis obtained by the laser diffraction scattering particle size distribution measurement to the cumulative 90% particle size (D ₉₀ ) of the volume basis at 0.1 to 0.5 μm D ₉₀ /D ₁₀ It is 10 or less, and the magnesium hydroxide fine particles having a purity of 99.5% by mass or more. The production method according to claim 2, wherein the magnesium hydroxide fine particles have a purity of 99.9% by mass or more. The production method according to the second or third aspect of the invention, wherein the total content of Fe, Ti, Ni, Cr, Mo, and Mn of the magnesium hydroxide fine particles is 500 ppm by mass or less. The production method according to the second or third aspect of the invention, wherein the magnesium hydroxide fine particles have a chlorine content of 500 ppm by mass or less. The manufacturing method according to the second or third aspect of the invention, wherein a ratio Dv/Dn of a volume-based average particle diameter (Dv) of the magnesium hydroxide fine particles to a number-based average particle diameter (Dn) is 1 to 10. A method for producing magnesium oxide fine particles, which comprises the step (E) of calcining magnesium hydroxide fine particles obtained by the production method according to the first aspect of the invention, which is calcined at 500 to 1500 ° C in an air atmosphere. The manufacturing method according to item 7 of the patent application is to obtain a cumulative 50% particle diameter (D ₅₀ ) of a volume basis obtained by a laser diffraction scattering particle size distribution measuring method with a BET specific surface area of 5 m ² /g or more. The ratio of the cumulative 10% particle size (D ₁₀ ) of the volume basis obtained by the laser diffraction scattering particle size distribution measurement to the cumulative 90% particle diameter (D ₉₀ ) of the volume basis of 0.1 to 0.5 μm D ₉₀ /D ₁₀ Magnesium oxide fine particles having a purity of 99.5 mass% or more at 10 or less. The production method according to Item 8, wherein the magnesium oxide fine particles have a purity of 99.9% by mass or more. The production method according to the above-mentioned item, wherein the total content of Fe, Ti, Ni, Cr, Mo, and Mn of the magnesium oxide fine particles is 500 ppm by mass or less. The production method according to Item 8 or 9, wherein the magnesium oxide fine particles have a chlorine content of 500 ppm by mass or less. The manufacturing method according to claim 8 or 9, wherein the magnesium oxide fine particles have a citric acid activity (40%) of 20 to 2000 seconds. The manufacturing method according to claim 8 or 9, wherein the ratio Dv/Dn of the volume-based average particle diameter (Dv) of the magnesium oxide fine particles to the number-based average particle diameter (Dn) is 1 To 10.