Method for producing hollow spherical alumina particles

Abstract

To provide a method for easily producing hollow spherical alumina particles by using an aqueous solution of basic aluminum lactate in two steps of granulation and firing.SOLUTION: A first step of drying and granulating an aqueous solution of basic aluminum lactate at a gas pressure of 0.01 to 1MPa in the atmosphere or an inert gas at a temperature of 210 to 280 °C to form a hollow dried granulated substance in which a volatile content of the granulated substance is controlled to 0 to 10% and a bulk density is controlled to 0.2 to 0. 7g / cm3; 1050 1200, A second step of obtaining hollow spherical alumina particles, wherein the basic aluminum lactate aqueous solution is a specific one having a low impurity content, and the obtained hollow spherical alumina particles have a D50 of from 5 to 50 μm and a D90 of at most 200 μ m, and the crystal phase is an α - phase.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing hollow spherical alumina particles. [Background technology]

[0002] Hollow alumina particles are produced by various methods. For example, Japanese Patent No. 4271045 (Patent Document 1) and Japanese Patent No. 4043805 (Patent Document 2) disclose methods for producing hollow alumina particles, which involve irradiating an aqueous solution of raw material containing aluminum nitrate or aluminum acetate and an organic acid selected from citric acid, amino acids, and malic acid with ultrasound, and then transferring fine droplets from a droplet selection section to a calcination furnace where they are calcined in air at 1200 to 1300°C. To obtain hollow alumina particles using this method, it is necessary to limit the amount of droplets introduced. Furthermore, to synthesize α-alumina from an aqueous solution, a series of processes from drying to calcination must be carried out in the furnace, which increases the size of the equipment and reduces productivity.

[0003] Patent Document 3 (Japanese Patent No. 6316153) describes a method for producing hollow alumina particles, which involves spraying an aluminum salt aqueous solution with a spray nozzle and passing it through both a drying zone at 300-600°C and a pyrolysis zone at 600-1600°C to obtain hollow particles primarily composed of γ-alumina, and then heating the resulting hollow particles primarily composed of γ-alumina to 1000-1150°C. To obtain γ-alumina by spray pyrolysis in a furnace with two zones (a drying zone at 300-600°C and a pyrolysis zone at 600-1600°C) requires a large-scale apparatus, resulting in poor productivity. Furthermore, a step is required to further heat the γ-alumina to 1000-1150°C to produce hollow alumina with the α phase. This two-step process results in poor production efficiency, and the two-step calcination process results in poor thermal efficiency.

[0004] Patent Document 4 (Japanese Patent No. 6730045) describes a method for producing α-alumina particles for friction materials that are at least one of spherical and irregularly shaped, characterized by heating at least one of boehmite aggregates and pseudo-boehmite aggregates for 1 to 20 hours at a temperature in the range of 1200 to 1500°C. In this production method, plate-like boehmite and pseudo-boehmite aggregates are granulated and fired at a temperature of 1200 to 1500°C, so even if the particles are spherical, hollow bodies cannot be produced.

[0005] Patent Document 5 (Patent No. 5568399) describes a method for producing a granular material with a specific surface area of ​​10 to 20 m 2 A method for producing spherical alumina particles is disclosed, which is characterized by spraying an alcohol slurry of fine alumina powder of 0.1g / g into a flame having a flame temperature of 1300 to 1650° C. In this production method, since an alcohol slurry of ultrafine alumina powder is sprayed into a flame, hollow particles cannot be obtained, and since ultrafine alumina powder is used as a raw material, a high sintering temperature of 1300 to 1650° C. is required to sinter the α-alumina powder particles together, which reduces productivity.

[0006] Patent Document 6 (Japanese Patent No. 7406444) describes a method for producing spherical particulate material, which includes a first pickling step in which a raw material particle material containing alumina as the main component is immersed in an acid solution to produce the raw material particle material, a melting and spheroidizing step in which the raw material particle material is melted and rapidly cooled to produce a coarse spherical particle material, and a second pickling step in which the coarse spherical particle material is immersed in an acid solution to produce a spherical particle material. In this production method, at least one of the first and second pickling steps must be performed in a high-temperature environment, and the raw material particle material must be immersed in nitric acid, sulfuric acid, hydrofluoric acid, etc., which makes the process complicated and requires the use of large amounts of acid, and may make it impossible to produce hollow alumina. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4271045 [Patent Document 2] Patent No. 4043805 [Patent Document 3] Patent No. 6316153 [Patent Document 4] Patent No. 6730045 [Patent Document 5] Patent No. 5568399 [Patent Document 6] Patent No. 7406444 Summary of the Invention [Problem to be solved by the invention]

[0008] We have discovered a method for easily producing hollow, spherical alumina particles using a basic aluminum lactate aqueous solution in two steps: granulation and calcination. [Means for solving the problem]

[0009] That is, the present invention includes the following aspects: [1] The basic aluminum lactate aqueous solution is dried and granulated at a temperature of 210 to 280°C under a gas pressure of 0.01 to 1 MPa in the atmosphere or inert gas, and the volatile content of the granulated product is reduced to 0 to 10% and the bulk density to 0.2 to 0.7 g / cm. 3 a first step of forming a controlled hollow dry granulation; a second step of calcining the dried granules obtained in the first step at a temperature within a range of 1050°C or higher and lower than 1200°C for 2 to 8 hours to obtain hollow spherical alumina particles; the basic aluminum lactate aqueous solution contains iron (Fe) in amounts of 0 to 0.01% by mass, calcium (Ca) in amounts of 0 to 0.01% by mass, magnesium (Mg) in amounts of 0 to 0.01% by mass, and silicon (Si) in amounts of 0.005 to 1.2% by mass, has a basicity of 60 to 80%, and contains aluminum in an amount of 8 to 13% by mass calculated as Al2O3; The obtained hollow spherical alumina particles have a D50 of 5 to 50 μm and a D90 of 200 μm or less in particle size distribution measurement, are hollow inside, have through holes on the outside, and have a specific surface area of ​​1 to 20 m 2 / g, and the crystalline phase is an α phase. [2] The hollow spherical alumina particles have a loss on drying of 4% or less, a loss on ignition of 6% or less, and a bulk density of 0.4 to 0.7 g / cm, as determined by aluminum oxide analysis in accordance with the Standards for Pharmaceutical and Medical Devices 2021. 3 The method for producing hollow spherical alumina particles according to [1], characterized in that: [3] The method for producing hollow spherical alumina particles according to [1] or [2], characterized in that the basic aqueous aluminum lactate solution is obtained by mixing an aluminum chloride solution with either or both of sodium aluminate and potassium aluminate, and water to form an aluminum hydroxide gel, washing the resulting gel with water, adding water to obtain an aluminum hydroxide slurry, and then adding lactic acid to cause a reaction. [4] The method for producing hollow spherical alumina particles according to [1] or [2], wherein the drying and granulation in the first step is performed by a spray drying method. [5] The method for producing hollow spherical alumina particles according to [1] or [2], wherein the firing in the second step is carried out in air, nitrogen, an inert gas, or a vacuum. [Effects of the Invention]

[0010] The hollow spherical alumina particles of this invention possess the heat resistance, thermal shock resistance, chemical resistance, and high-temperature strength properties inherent to alpha alumina, and their hollow and spherical properties give them excellent light weight, insulation, fluidity, etc., so they are expected to be used as high-performance compounding materials for resins and rubbers, heat-dissipating fillers for electronic materials, polishing fillers for electronic components, etc. Furthermore, by designing them in accordance with the 2021 Standards for Quasi-Drug Ingredients, they can be used as cosmetic ingredients, scrubs, etc. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a graph showing the particle size distribution of the alumina particles obtained in Example 1, measured in a dry state using a laser diffraction particle size distribution analyzer (Mastersizer 3000, manufactured by Malvern Panalytical). [Figure 2] FIG. 2 is a diagram showing the results of measurement of the alumina particles obtained in Example 1 using an X-ray diffractometer (MiniFlex manufactured by Rigaku Corporation) with a Cu target by the θ / 2θ method. [Figure 3] FIG. 10 is a diagram showing the results of measurement of the alumina particles obtained in Comparative Example 4 using an X-ray diffractometer (MiniFlex manufactured by Rigaku Corporation) with a Cu target by the θ / 2θ method. [Figure 4] 1 is a 100,000-power SEM image of the alumina particles of Example 1 measured using a field emission scanning electron microscope (FE-SEM: JSM-7001F manufactured by JEOL Ltd.). [Figure 5] 1 is a 10,000-power SEM image of the alumina particles of Example 1 measured using a field emission scanning electron microscope (FE-SEM: JSM-7001F manufactured by JEOL Ltd.). [Figure 6] 1 is a 25,000-power SEM image of the alumina particles of Example 1 measured using a field emission scanning electron microscope (FE-SEM: JSM-7001F manufactured by JEOL Ltd.). DETAILED DESCRIPTION OF THE INVENTION

[0012] (Definition of terms) In this specification, "hollow" means that there are voids inside the particle, and does not mean that there is a perfectly spherical space. Therefore, there are voids or spaces in part of the interior of the alumina particle. Furthermore, "the presence of through holes" does not mean that all particles have through holes, but rather that the voids inside the particle continue to the particle surface. In this specification, "spherical" does not mean a perfect sphere, but rather that the surface is uneven, but that the overall shape appears spherical.

[0013] In the present invention, an aqueous solution of basic aluminum lactate is dried and granulated at a temperature of 210 to 280°C under a gas pressure of 0.01 to 1 MPa in the atmosphere or an inert gas, and the volatile content of the granulated product is adjusted to 0 to 10% and the bulk density to 0.2 to 0.7 g / cm. 3 and a second step of calcining the dried granules obtained in the first step at a calcination temperature within a temperature range of 1050°C or higher and lower than 1200°C for 2 to 8 hours to obtain alumina particles, wherein the aqueous basic aluminum lactate solution contains 0 to 0.01 mass% of iron (Fe), 0 to 0.01 mass% of calcium (Ca), 0 to 0.01 mass% of magnesium (Mg), and 0 to 0.01 mass% of silicon (Si), and also contains alkali metal element ions in an amount of 0.005 to 1.2 mass%, has a basicity of 60 to 80%, and contains 8 to 13 mass% of aluminum calculated as Al2O3, and further, the obtained alumina particles have, in particle size distribution measurement, a D50 of 5 to 50 μm and a D90 of 200 μm or less, are hollow inside and have through-holes connecting the inside and the outside, and have a specific surface area of ​​1 to 20 m 2 / g, and in the aluminum oxide analysis according to the Standards for Pharmaceutical and Medical Devices 2021, the loss on drying is 4% or less, the loss on ignition is 6% or less, and the bulk density is 0.4 to 0.7 g / cm 3 The present invention is characterized in that it can provide a method for producing hollow spherical alumina particles having an α-phase crystal phase.

[0014] (raw materials) The raw materials used for synthesizing the hollow spherical alumina particles of the present invention must be selected as follows: (I) The basic aluminum lactate aqueous solution is controlled to have iron (Fe) of 0 to 0.01 mass %, calcium (Ca) of 0 to 0.01 mass %, magnesium (Mg) of 0 to 0.01 mass %, and silicon (Si) of 0 to 0.01 mass %. (II) The basic aluminum lactate aqueous solution contains alkali metal ions in an amount of 0.005 to 1.2% by mass, has a basicity of 60 to 80%, and contains Al in an amount of 8 to 13% by mass in terms of Al2O3. (III) The basic aluminum lactate aqueous solution is obtained by mixing, as necessary, an aluminum chloride solution with a sodium aluminate or potassium aluminate solution or a combination of both, and water to form an aluminum hydroxide gel, washing the gel with water, adding water to obtain an aluminum hydroxide slurry, and then adding lactic acid to cause a reaction.

[0015] In the present invention, the aqueous solution of basic aluminum lactate used as the main raw material contains 0 to 0.01% by mass of iron (Fe), 0 to 0.01% by mass of calcium (Ca), 0 to 0.01% by mass of magnesium (Mg), and 0 to 0.01% by mass of silicon (Si), and the amount of alkali metals is controlled to control the basicity and aluminum content within predetermined ranges. The solution is then spray-dried and calcined at a temperature of 1050°C or higher and lower than 1200°C for 2 to 8 hours, thereby providing hollow, spherical, and through-hole hollow spherical alumina particles that meet predetermined specifications for particle size, specific surface area, loss on drying, loss on ignition, and a predetermined bulk density.

[0016] The present invention is produced using the materials described above in (I), (II), and (III) by the following production method.

[0017] (Manufacturing method) (Step 1) A basic aluminum lactate aqueous solution that satisfies the requirements (I) and (II) above is dried and granulated at a temperature of 210 to 280°C under a gas pressure of 0.01 to 1 MPa in air or an inert gas, to reduce the volatile content of the granulated product to 0 to 10% and the bulk density to 0.2 to 0.7 g / cm. 3 and forming a controlled dry granulation. (Step 2) The dried granulated material obtained in step 1 is placed in an alumina crucible or sagger and fired in a firing furnace at a firing temperature within the range of 1050°C or higher and lower than 1200°C for 2 to 8 hours to obtain hollow spherical alumina particles exhibiting the α phase.

[0018] The raw materials and production method used to produce the hollow spherical alumina particles will be described in detail below.

[0019] (basic aluminum lactate aqueous solution) The basic aluminum lactate aqueous solution used in the present invention has the following properties (I) to (III): (I) The basic aluminum lactate aqueous solution is controlled to have iron (Fe) of 0 to 0.01 mass %, calcium (Ca) of 0 to 0.01 mass %, magnesium (Mg) of 0 to 0.01 mass %, and silicon (Si) of 0 to 0.01 mass %. (II) The basic aluminum lactate aqueous solution contains alkali metal ions in an amount of 0.005 to 1.2 mass %, has a basicity of 60 to 80%, and contains Al in an amount of 8 to 13 mass % in terms of Al2O3.

[0020] As described in (I) above, the basic aluminum lactate aqueous solution used in the present invention has iron (Fe) of 0 to 0.01% by mass, calcium (Ca) of 0 to 0.01% by mass, magnesium (Mg) of 0 to 0.01% by mass, and silicon (Si) of 0 to 0.01% by mass. If the Fe, Ca, Mg, or Si content of the basic aluminum lactate aqueous solution exceeds 0.01% by mass, this can cause the formation of a crystal phase other than alumina during firing and can lead to defects such as coloration. The Fe, Ca, Mg, and Si contents are each preferably 0.007% by mass or less, and more preferably 0.006% by mass or less.

[0021] As described in (II) above, the basic aluminum lactate aqueous solution used in the present invention must contain 0.005 to 1.2 mass% of alkali metal ions. It is more preferable that the alkali metal ions be 0.01 to 0.5 mass%. If the alkali metal ion content is less than 0.005 mass%, the amount of alkali metal ions is too small, increasing the temperature at which the phase transition to α-alumina occurs, and α-alumina is not produced below 1200°C. On the other hand, if the alkali metal ion content exceeds 1.2 mass%, the amount of alkali metal ions is too high, resulting in the production of β-alumina and other substances other than α-alumina, making it impossible to obtain the desired α-alumina.

[0022] The alkali metal ion species contained in the basic aluminum lactate aqueous solution used in the present invention must be at least one selected from sodium and potassium.

[0023] The basic aluminum lactate aqueous solution used in the present invention must have a basicity of 60 to 80% and must contain 8 to 13 mass% Al in terms of Al2O3. If the basicity is less than 60%, the lactic acid content is too high, resulting in poor solubility in water. On the other hand, if the basicity is more than 80%, insoluble aluminum hydroxide precipitates, the solution becomes cloudy, and hollow dried granules cannot be obtained when spray-dried. Furthermore, if the Al content is less than 8 mass% in terms of Al2O3, hollow dried granules cannot be obtained when spray-dried. On the other hand, if the Al content is more than 13 mass%, the amount of Al is too high, resulting in poor storage stability and the formation of precipitates in the basic aluminum lactate aqueous solution, making it unsuitable for spray-drying. The basicity of the basic aluminum lactate aqueous solution is preferably 62 to 78%, more preferably 64 to 76%. "Basicity" is a value indicating what percentage of valences that can be substituted by bases are filled. Since aluminum is trivalent, if 2 / 3 (divalent of the trivalent) is used, this means that the basicity is 66.66% (i.e., approximately 67%). It is measured in accordance with JIS K1475, a method for measuring the basicity of liquid polyaluminum chloride for water supply. The mass of aluminum (Al) in the basic aluminum lactate aqueous solution, converted into Al2O3, is preferably 8.5 to 12.5% ​​by mass, more preferably 9 to 12% by mass. The mass of Al in terms of Al2O3 is the mass normally used when using aluminum salts, and the amount of aluminum is determined by converting it into the mass of Al2O3.

[0024] The basic aluminum lactate aqueous solution used in the present invention is preferably obtained by the method described in (III) above. Specifically, the basic aluminum lactate aqueous solution is obtained by mixing an aluminum chloride solution with a sodium aluminate or potassium aluminate solution or a combination of both, and water to form an aluminum hydroxide gel, washing the gel with water, adding water to obtain an aluminum hydroxide slurry, and then adding lactic acid to cause a reaction. Of course, the basic aluminum lactate aqueous solution may be obtained by any method as long as it satisfies the above (I) and (II), but the basic aluminum lactate aqueous solution obtained by the above (III) is more preferred.

[0025] (Method for producing hollow spherical alumina particles) The hollow spherical alumina particles of the present invention are produced by the following steps 1 and 2: (Step 1) The aqueous solutions of basic aluminum lactate (I) and (II) (and optionally (III)) are dried and granulated at a temperature of 210 to 280°C in air or an inert gas at a gas pressure of 0.01 to 1 MPa to reduce the volatile content of the granulated product to 0 to 10% and the bulk density to 0.2 to 0.7 g / cm. 3 and forming a controlled dry granulation. (Step 2) The dried granulated material obtained in step 1 is placed in an alumina crucible or sagger and fired in a firing furnace at a firing temperature within the range of 1050°C or higher and lower than 1200°C for 2 to 8 hours to obtain hollow spherical alumina particles exhibiting the α phase.

[0026] In step 1, the basic aluminum lactate aqueous solution is dry-granulated at a temperature of 210 to 280°C under a gas pressure of 0.01 to 1 MPa in the atmosphere or an inert gas, and the volatile content of the granulated product is reduced to 0 to 10% and the bulk density to 0.20 to 0.7 g / cm. 3Dry granulation is performed in the atmosphere or in an inert gas, and the inert gas may be a rare gas (e.g., helium, neon, or argon) or nitrogen gas. Drying is usually performed in the atmosphere. The drying temperature is 210 to 280°C, preferably 230 to 270°C. Dry granulation at a temperature below 210°C has the drawback that the high moisture content of the dried product tends to cause agglomerations in the dried state, and independent hollow spherical alumina particles do not form after firing. Dry granulation at a temperature above 280°C has the drawback that a portion of the organic component of the basic aluminum lactate oxidizes, causing the dried product to turn brown, deteriorating its physical properties, and losing its spherical shape during firing. If the gas pressure is less than 0.01 MPa, the pressure is insufficient to obtain a spherical dried product, which results in the problem that hollow spherical alumina cannot be obtained even after firing, while if the gas pressure is more than 1 MPa, the pressure is too high, which results in the through-holes becoming too large, which prevents the dried product from maintaining its spherical shape, and therefore results in the problem that hollow spherical alumina cannot be obtained even after firing. The gas pressure is preferably 0.1 to 0.8 MPa, more preferably 0.2 to 0.7 MPa.

[0027] The drying and granulation in step 1 is generally performed by spray drying, but it is not limited to spray drying. Usable drying and granulation methods include spray drying, fluidized bed drying, and spray freeze drying.

[0028] The dried granules obtained in step 1 have a volatile content of 0 to 10% and a bulk density of 0.2 to 0.7 g / cm 3 If the volatile content exceeds 10%, the drying will be insufficient and the moisture content of the dried product will be high, which will tend to cause agglomerates in the dried state and result in the failure to form independent hollow spherical alumina particles after firing. The volatile content is preferably 0. The dried granules should have a bulk density of 0.20 to 0.7 g / cm. 3 , preferably 0.25 to 0.65 g / cm 3 , more preferably 0.3 to 0.6 g / cm 3 The bulk density is 0.2 g / cm 3 If it is smaller than this, the hollowness increases and the thickness of the outer shell becomes thin, which has the drawback of reducing the strength of the hollow spherical alumina particles. 3If the particle size is larger, the hollowness during granulation decreases and the thickness of the outer shell increases, which makes the granules more susceptible to deformation and makes it difficult to form a spherical shape. The volatile content is measured using an A&D MX50 heat and dry moisture meter at 105°C for 30 minutes. The bulk density is the value obtained by dividing the mass by the volume. In the examples of the present invention, powder passed through a 1 mm sieve is weighed to an accuracy of 0.1 mass%, and approximately 40 g of sample (M) is placed in a 100 ml measuring cylinder (minimum scale unit 1 ml), the surface is lightly smoothed, the loose bulk volume (V0) is read, and the bulk density: M / V0 (g / cm 3 The volatile content can be adjusted by the temperature and liquid feed rate during granulation, and the bulk density can be controlled by the air pressure during spray granulation.

[0029] In step 2 of the method for producing hollow spherical alumina particles of the present invention, the dried granulated material obtained in step 1 is placed in an alumina crucible, sagger, or the like, and fired in a firing furnace at a firing temperature within a range of 1050°C or higher but lower than 1200°C for 2 to 8 hours to obtain hollow spherical alumina particles exhibiting the α phase. The dried granulated material obtained in step 1 is fired at a temperature of 1050°C or higher but lower than 1200°C for 2 to 8 hours. If the firing temperature is lower than 1050°C, firing will be insufficient, and crystalline phases other than α-alumina will remain. On the other hand, if the firing temperature exceeds 1200°C, a firing furnace with heat resistance measures will be required, which will result in a decrease in productivity. Regarding firing times, if the firing time is shorter than 2 hours, firing will be insufficient, and crystalline phases other than α-alumina will remain. On the other hand, if the firing time exceeds 8 hours, productivity will be reduced.

[0030] In the firing of step 2, the firing furnace in which the material is placed in a crucible or sagger is preferably a batch furnace, lift furnace, pusher furnace, or conveyor furnace. If firing is performed in a rotary kiln or rapid drop-type firing furnace, collisions during firing can cause the shape to collapse or agglomerates to form, making it impossible to obtain hollow spherical alumina particles.

[0031] The atmosphere for firing in step 2 may be any of air, nitrogen, vacuum, inert gas, etc., as long as the organic components disappear and the desired alumina crystal system is properly formed when firing is performed at a predetermined firing temperature and time. If the atmosphere is inappropriate, the organic components may not be sufficiently vaporized during firing, remaining in the particles as residual carbon, causing defects, or the desired crystal phase may not be formed, resulting in defects.

[0032] (hollow spherical alumina particles) The hollow spherical alumina particles of the present invention are produced by the above-mentioned steps 1 and 2. The hollow spherical alumina particles obtained by this method have, in particle size distribution measurement, a D50 of 5 to 50 μm and a D90 of 200 μm or less, are hollow inside and have through-holes connecting to the outside, and have a specific surface area of ​​1 to 20 m 2 / g, and the crystal system (also called the crystalline phase) exhibits the α phase.

[0033] The particle size distribution was measured using a laser diffraction particle size analyzer (Malvern Panalytical Mastersizer 3000) under dry conditions. Figure 1 shows the particle size distribution of the alumina particles of Example 1. In the particle size distribution, D50 refers to the diameter below which half of the population lies, and D90 refers to the diameter below which 90% of the population lies. As shown in Figure 1, the particle size distribution of the alumina particles of Example 1 was confirmed to have a D50 of 6 μm and a D90 of less than 100 μm. If the D50 is less than 5 μm, the powder fluidity becomes poor and handling becomes difficult, and if the D50 is 50 μm or greater, the range of applications becomes narrow. Furthermore, if the D90 exceeds 200 μm, the range of applications becomes narrow. In terms of particle size distribution, the alumina particles of the present invention preferably have a D50 of 5.5 to 45 μm, more preferably 6 to 35 μm. D90 is preferably 60 to 120 μm, more preferably 70 to 90 μm.

[0034] The alumina particles obtained by the production method of the present invention are often hollow inside and have through-holes connecting them to the outside. As described in the definition of the term, "hollow" and "through-hole" do not mean perfectly spherical hollows. For example, as shown in electron microscope photographs of the alumina particles of Example 1 in Figures 5 and 6, some have fairly spherical cavities, but other cases include cases where one or more voids of various shapes are present. Through-holes are not necessarily present, and cases where the internal voids and the outside are simply connected by some kind of cavity are also included. As described in the definition of the term, the alumina particles of the present invention are not perfectly spherical, but merely appear to be spherical.

[0035] The hollow spherical alumina particles obtained by the production method of the present invention have a specific surface area of ​​1 to 20 m 2 / g, and the crystal system is the α phase. The specific surface area is the surface area per unit mass or per unit volume of a certain object, and in the present invention, the specific surface area is measured with an automatic specific surface area measuring device (Shimadzu Corporation, Gemini7 2390) using N2, and the data analyzed by the BET method are used. The specific surface area of ​​the alumina particles of the present invention is 1 m 2 If the specific surface area is less than 20m / g, the specific surface area is too small, and there are few adsorption sites when performing surface treatment using a dispersant, etc., which makes surface treatment difficult. 2 If it is larger than 1 / g, the amount of N2 adsorbed on the alumina surface is too large, which causes a drawback in that crystal growth of α-alumina is insufficient. The specific surface area of ​​the hollow spherical alumina particles of the present invention is preferably 3 to 15 m 2 / g, more preferably 5 to 13 m 2 / g. The crystal system of the hollow spherical alumina particles of the present invention is α-type. The present invention does not assume that other crystal systems such as γ-type alumina particles are mixed in. The crystal system is mainly measured by the θ / 2θ method using an X-ray diffractometer (specifically, MiniFlex manufactured by Rigaku Corporation) with a Cu target.

[0036] The hollow spherical alumina particles of the present invention preferably have a loss on drying of 4% or less, a loss on ignition of 6% or less, and a bulk density of 0.4 to 0.7 g / cm, as determined by aluminum oxide analysis in accordance with the Standards for Pharmaceutical and Medical Devices 2021. 3 is.

[0037] Loss on drying in the Pharmaceutical and Medical Devices Raw Materials Standards 2021 is determined by weighing approximately 1 g of raw material on a precision balance into a glass dish (A), drying it for 2 hours in a hot air circulation dryer set to 105°C, allowing it to cool naturally to room temperature in a desiccator, and then measuring the weight again on the precision balance (B). The loss on drying is calculated using the following formula (i), and is considered acceptable if it is 4.0% or less. (B - A) / A × 100 (i) The hollow spherical alumina particles of the present invention preferably have a loss on drying of 3.0% or less, more preferably 2.0% or less.

[0038] The ignition loss in the Pharmaceutical and Medical Devices Standards 2021 is determined by weighing approximately 1 g of raw material into an alumina crucible using a precision balance (C), placing it in an electric furnace set to 850°C, heating for 30 minutes, allowing it to cool naturally to room temperature, and then weighing it again using the precision balance (D). The weight is calculated using the following formula (ii). If it is 6.0% or less, it is considered to have passed the test. (C - D) / C × 100 (ii) The hollow spherical alumina particles of the present invention preferably have a loss on drying of 4.0% or less, more preferably 3.0% or less.

[0039] The hollow spherical alumina particles in the present application have a bulk density of 0.4 to 0.7 g / cm 3 More preferably, it is 0.5 to 0.65 g / cm 3 If the bulk density is less than 0.4, the outer shell becomes too thin and the hollow spherical alumina particles cannot be maintained in their shape. On the other hand, if the bulk density is 0.7 g / cm 3If the thickness exceeds this value, the outer shell becomes too thick and the hollow spherical alumina particles will no longer function. Bulk density is calculated by dividing the mass by the volume. Specifically, powder passed through a 1 mm sieve is weighed to an accuracy of 0.1 mass%, and approximately 40 g of sample (M) is placed in a 100 ml measuring cylinder (minimum unit: 1 ml), the surface is lightly smoothed, and the loose bulk volume (V0) is read and the bulk density is calculated as M / V0 (g / cm 3 ) is calculated.

[0040] (Example) The present invention will be described in more detail with reference to examples. The present invention should not be construed as being limited to these examples. In the examples, % and parts are based on mass unless otherwise specified.

[0041] Example 1 Using a 10 L jacketed GL stirring kettle (with a glass-lined inner wall), cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred, while 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as calculated as Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as calculated as Al2O3, 18.0 wt% Na as calculated as Na2O) were simultaneously added, yielding 5000 g of an aluminum hydroxide gel solution.

[0042] The resulting aluminum hydroxide gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 2190 g. Next, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 157.1 g of tap water, and the mixture was stirred for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. Then, the mixture was slowly cooled to produce 300 g of basic aluminum lactate aqueous solution (8.8% Al by mass in terms of Al2O3, 70.2% basicity, 0.01% sodium ion, 0.005% Si by mass, 0.0048% Ca by mass, 0.0007% Mg by mass, and 0.0015% Fe by mass).

[0043] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (the volatile content of the granules was 4.3% and the bulk density was 0.35 g / cm 3 ) was placed in an alumina crucible and fired at a peak firing condition of 1100°C for 5 hours to obtain alumina particles.

[0044] The particle size distribution of the obtained alumina particles was measured, and the D50 and D90 were determined and listed in Table 1. The particle size distribution was measured in a dry state using a laser diffraction particle size analyzer (Malvern Panalytical Mastersizer 3000). Figure 1 shows the particle size distribution results for Example 1. D50 means the diameter below which half of the population lies, and D90 means that 90% of the population lies below this value. As shown in Figure 1, the particle size distribution of the alumina particles in Example 1 was confirmed to have a D50 of 6 μm and a D90 of less than 100 μm.

[0045] Table 1 shows the volatile content and bulk density of the dried granules of the aqueous solution of basic aluminum lactate. The volatile content was measured using an MX50 heat and dry moisture meter manufactured by A&D at 105°C for 30 minutes. The bulk density was measured using the same method as that used to measure the bulk density of alumina particles described below. Table 1 also shows the specific surface area (m 2 / g), bulk density (g / cm 3 The data also includes the crystal system, loss on drying (mass%), loss on ignition (mass%), and the content of the impurities sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), silicon (Si), and iron (Fe). Specific surface area was measured using an automatic specific surface area measuring device (Shimadzu Corporation, Gemini7 2390) with N2, and the data was analyzed using the BET method. Bulk density is calculated by dividing mass by volume. Specifically, powder was sieved through a 1 mm mesh and weighed to an accuracy of 0.1 mass%, and approximately 40 g of sample (M) was placed in a 100 ml measuring cylinder (minimum unit: 1 ml). The surface was lightly smoothed, and the loose bulk volume (V0) was read. The bulk density was calculated as M / V0 (g / cm).3 ) was calculated. The crystal system (crystalline phase) was measured using an X-ray diffractometer (MiniFlex, manufactured by Rigaku Corporation) with a Cu target by the θ / 2θ method, and the results are shown in Table 1. Figure 2 shows the measurement results of the crystal system of the alumina particles obtained in Example 1. The loss on drying and loss on ignition were measured in accordance with the measurement method for aluminum oxide in the Standards for Pharmaceutical and Medical Devices 2021, and the results are shown in Table 1. The contents of Na, K, Ca, Si, Mg, and Fe were measured using energy dispersive X-ray fluorescence analysis (EDX) with a tabletop scanning electron microscope (SEM: JCM-7000, manufactured by JEOL Ltd.).

[0046] From the X-ray diffraction results of the alumina particles of Example 1 shown in FIG. 2, it was confirmed that the alumina particles of Example 1 were made of α-alumina.

[0047] Figures 4, 5, and 6 are SEM images of the alumina particles of Example 1 measured using a field emission scanning electron microscope (FE-SEM: JEOL Ltd. JSM-7001F). Figure 4 is an SEM image at 100,000x magnification, and it can be seen that α-alumina crystallites aggregate to form an outer shell of hollow spherical alumina. Figure 5, an SEM image at 10,000x magnification of the alumina particles of Example 1, confirms that the hollow spherical alumina particles have through holes. Figure 6, an SEM photograph at 25,000x magnification of the alumina particles of Example 1, confirms that the hollow spherical alumina is hollow. Therefore, it was confirmed that the alumina particles obtained in Example 1 were hollow spherical alumina particles.

[0048] Example 2 Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred, while 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as converted to Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as converted to Al2O3, 18.0 wt% Na as converted to Na2O) were simultaneously added, yielding 5000 g of an aluminum hydroxide gel solution.

[0049] The resulting aluminum hydroxide gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 2190 g. Next, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 157.1 g of tap water, and the mixture was stirred for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. Then, the mixture was slowly cooled to produce 300 g of basic aluminum lactate solution (8.8% Al by mass in terms of Al2O3, 70.2% basicity, 0.01% sodium ion by mass, 0.005% Si by mass, 0.0048% Ca by mass, 0.0007% Mg by mass, and 0.0015% Fe by mass).

[0050] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 5.2% and bulk density 0.39 g / cm 3 ) was placed in an alumina crucible and fired at a peak firing condition of 1150°C for 5 hours to obtain alumina particles.

[0051] The volatile content and bulk density of the dried granules of the basic aluminum lactate aqueous solution were measured in the same manner as in Example 1, and the results are shown in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying and loss on ignition, and the contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were measured in the same manner as in Example 1, and the results are shown in Table 1. Although FE-SEM images and X-ray diffraction images are not shown, it was confirmed that the alumina particles had an α crystal system and were hollow spherical.

[0052] Example 3 Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred. 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as calculated as Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as calculated as Al2O3, 18.0 wt% Na as calculated as Na2O) were simultaneously added, yielding 5000 g of aluminum hydroxide gel solution.

[0053] The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 2190 g. Next, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 157.1 g of tap water, and the mixture was stirred for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. Then, the mixture was slowly cooled to produce 300 g of basic aluminum lactate solution (8.8% Al by mass in terms of Al2O3, 70.2% basicity, 0.01% sodium ion, 0.005% Si by mass, 0.0048% Ca by mass, 0.0007% Mg by mass, and 0.0015% Fe by mass).

[0054] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 220°C, an outlet temperature of 95°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 6.0% and bulk density 0.45 g / cm 3 ) was placed in an alumina crucible and fired at a peak firing condition of 1100°C for 5 hours to obtain alumina particles.

[0055] The volatile content and bulk density of the dried granules of the basic aluminum lactate aqueous solution were measured in the same manner as in Example 1, and the results are shown in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying and loss on ignition, and the contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were measured in the same manner as in Example 1, and the results are shown in Table 1. Although FE-SEM images and X-ray diffraction images are not shown, it was confirmed that the alumina particles had an α crystal system and were hollow spherical.

[0056] Example 4 Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1531.6 g of tap water was added to the kettle and stirred, while 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as converted to Al2O3, basicity 2.4%) and 1559.0 g of a sodium aluminate aqueous solution (20.0 wt% Al as converted to Al2O3, 18.9 wt% Na as converted to Na2O) were simultaneously added, yielding 5000 g of an aluminum hydroxide gel solution.

[0057] The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 1920 g. Next, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 157.1 g of tap water, and stirred for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. Then, the mixture was slowly cooled to produce 300 g of basic aluminum lactate solution (8.9% Al by mass in terms of Al2O3, 71.5% basicity, 0.05% sodium ion, 0.0052% Si by mass, 0.0040% Ca by mass, 0.0006% Mg by mass, and 0.0012% Fe by mass).

[0058] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 4.9% and bulk density 0.42 g / cm3 ) was placed in an alumina crucible and fired at a peak firing condition of 1100°C for 5 hours to obtain alumina particles.

[0059] The volatile content and bulk density of the dried granules of the basic aluminum lactate aqueous solution were measured in the same manner as in Example 1, and the results are shown in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying and loss on ignition, and the contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were measured in the same manner as in Example 1, and the results are shown in Table 1. Although FE-SEM images and X-ray diffraction images are not shown, it was confirmed that the alumina particles had an α crystal system and were hollow spherical.

[0060] Example 5 Using a 1 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 153.1 g of tap water was added to the kettle and stirred, while 190.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as converted to Al2O3, basicity 2.4%) and 155.9 g of a sodium aluminate aqueous solution (20.0 wt% Al as converted to Al2O3, 18.9 wt% Na as converted to Na2O) were simultaneously added, yielding 500 g of an aluminum hydroxide gel solution.

[0061] The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated five times. The resulting washed gel weighed 195 g. Next, 103.7 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 156.6 g of tap water, and stirred for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 1.5 hours. Then, the mixture was slowly cooled to produce 300 g of basic aluminum lactate solution (8.6% Al by mass in terms of Al2O3, 72.4% basicity, 0.02% sodium ion, 0.0041% Si by mass, 0.0043% Ca by mass, 0.0008% Mg by mass, and 0.0017% Fe by mass).

[0062] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 5.7% and bulk density 0.37 g / cm 3 ) was placed in an alumina crucible and fired at 1100°C for 5 hours under peak firing conditions to obtain alumina particles exhibiting the α phase.

[0063] The volatile content and bulk density of the dried granules of the aqueous basic aluminum lactate solution were measured in the same manner as in Example 1, and are shown in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying and loss on ignition, and contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were measured in the same manner as in Example 1, and the results are shown in Table 2. Although FE-SEM images and X-ray diffraction images are not shown, it was confirmed that the alumina particles had an α crystal system and were hollow spherical.

[0064] Example 6 Using a 1 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 153.1 g of tap water was added to the kettle and stirred. 190.4 g of aluminum chloride aqueous solution (10.0 wt% Al as calculated on Al2O3, 2.4% basicity), 153.9 g of sodium aluminate aqueous solution (20.0 wt% Al as calculated on Al2O3, 18.9 wt% Na as calculated on Na2O), and 2 g of potassium aluminate powder were simultaneously added, yielding 500 g of aluminum hydroxide gel solution. The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated five times. The resulting washed gel weighed 195 g.

[0065] Next, 103.7 g of the resulting washed gel was added to a 1-L glass separable flask placed on a mantle heater, followed by 156.6 g of tap water, and the mixture was stirred for 30 minutes to yield 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 5 hours. After gradual cooling, 300 g of basic aluminum lactate solution (Al2O3 equivalent: 8.8% by mass Al, basicity: 72.4%, sodium ion: 0.02% by mass, potassium ion: 0.01% by mass, Si: 0.0047% by mass, Ca: 0.0050% by mass, Mg: 0.0006% by mass, Fe: 0.0011% by mass) was produced.

[0066] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 5.8% and bulk density 0.44 g / cm 3 ) was placed in an alumina crucible and fired at a peak firing condition of 1100°C for 5 hours to obtain alumina particles.

[0067] The volatile content and bulk density of the dried granules of the aqueous basic aluminum lactate solution were measured in the same manner as in Example 1, and are shown in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying and loss on ignition, and contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were measured in the same manner as in Example 1, and the results are shown in Table 2. Although FE-SEM images and X-ray diffraction images are not shown, it was confirmed that the alumina particles had an α crystal system and were hollow spherical.

[0068] Example 7 Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred. 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as calculated as Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as calculated as Al2O3, 18.0 wt% Na as calculated as Na2O) were simultaneously added, yielding 5000 g of aluminum hydroxide gel solution.

[0069] The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 2190 g. Next, using a 1 L glass separable flask placed on a mantle heater, 103.2 g of the resulting washed gel was added, followed by 157.1 g of tap water, and the mixture was stirred for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. Then, the mixture was slowly cooled to produce 300 g of a basic aluminum lactate solution of the present invention (8.8% Al by mass in terms of Al2O3, 70.2% basicity, 0.01% sodium ion by weight, 0.0050% Si by mass, 0.0048% Ca by mass, 0.0007% Mg by mass, and 0.0015% Fe by mass).

[0070] The obtained aqueous solution of basic aluminum lactate was spray dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and an atomizer at 18,000 rpm. The collected dried granules (volatile content 7.4% and bulk density 0.51 g / cm 3 ) was placed in an alumina crucible and fired at a peak firing condition of 1100°C for 5 hours to obtain hollow spherical alumina particles.

[0071] The volatile content and bulk density of the dried granules of the aqueous basic aluminum lactate solution were measured in the same manner as in Example 1, and are shown in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying and loss on ignition, and contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were measured in the same manner as in Example 1, and the results are shown in Table 2. Although FE-SEM images and X-ray diffraction images are not shown, it was confirmed that the alumina particles had an α crystal system and were hollow spherical.

[0072] (Comparative Example 1) Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred, while 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as converted to Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as converted to Al2O3, 18.0 wt% Na as converted to Na2O) were simultaneously added, yielding 5000 g of an aluminum hydroxide gel solution.

[0073] The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 2190 g. Next, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 157.1 g of tap water. The mixture was stirred for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. The mixture was then slowly cooled to produce 300 g of basic aluminum lactate solution (8.8% Al by mass in terms of Al2O3, 70.2% basicity, 0.01% sodium ion, 0.0050% Si by mass, 0.0048% Ca by mass, 0.0007% Mg by mass, and 0.0015% Fe by mass).

[0074] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 150°C, an outlet temperature of 65°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 12.5% ​​and bulk density 0.90 g / cm3 ) was placed in an alumina crucible and fired at a peak firing condition of 1100°C for 5 hours to obtain alumina particles.

[0075] The volatile content and bulk density of the dried granules of the basic aluminum lactate aqueous solution were measured in the same manner as in Example 1 and are listed in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying and loss on ignition, and the contents of Na, K, Ca, Si, Mg, and Fe of the resulting alumina particles were measured in the same manner as in Example 1, and the results are listed in Table 3. Although an X-ray diffraction image is not shown, it was confirmed that the alumina particles have an α-crystal system. However, in Comparative Example 1, drying during spray drying was insufficient, resulting in the formation of agglomerates during firing, and the D50 of the particle size distribution showed a large value of 530 μm.

[0076] (Comparative Example 2) Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred. 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as calculated as Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as calculated as Al2O3, 18.0 wt% Na as calculated as Na2O) were simultaneously added, yielding 5000 g of aluminum hydroxide gel solution.

[0077] The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 2190 g. Next, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 157.1 g of tap water, and stirred for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. Then, the mixture was slowly cooled to produce 300 g of basic aluminum lactate solution (8.8% Al by mass in terms of Al2O3, 70.2% basicity, 0.01% sodium ion, 0.0050% Si by mass, 0.0048% Ca by mass, 0.0007% Mg by mass, and 0.0015% Fe by mass).

[0078] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 4.4% and bulk density 0.45 g / cm 3 ) was placed in an alumina crucible and fired at a peak firing condition of 800°C for 5 hours to obtain alumina particles.

[0079] The volatile content and bulk density of the dried granules of the aqueous basic aluminum lactate solution were measured in the same manner as in Example 1, and are shown in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying and loss on ignition, and contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were measured in the same manner as in Example 1, and the results are shown in Table 3. In Comparative Example 2, the final firing conditions were 800°C for 5 hours, and the crystal system was γ-alumina, not single-phase α-alumina.

[0080] (Comparative Example 3) Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred, while 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as converted to Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as converted to Al2O3, 18.0 wt% Na as converted to Na2O) were simultaneously added, yielding 5000 g of an aluminum hydroxide gel solution.

[0081] The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 2190 g. Next, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 157.1 g of tap water, and stirred for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. Then, the mixture was slowly cooled to produce 300 g of basic aluminum lactate solution (8.8% Al by mass in terms of Al2O3, 70.2% basicity, 0.01% sodium ion, 0.0050% Si by mass, 0.0048% Ca by mass, 0.0007% Mg by mass, and 0.0015% Fe by mass).

[0082] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 4.3% and bulk density 0.47 g / cm 3 ) was placed in an alumina crucible and fired at 1050°C for 1 hour under peak firing conditions.

[0083] The volatile content and bulk density of the dried granules of the aqueous basic aluminum lactate solution were measured in the same manner as in Example 1 and are shown in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying, loss on ignition, and contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were measured in the same manner as in Example 1, and the results are shown in Table 3. In Comparative Example 3, the final firing conditions were 1,050°C for 1 hour, which was an insufficient firing time, and although an X-ray diffraction image is not shown, the product was a mixed alumina of α-alumina and γ-alumina, not a single phase of α-alumina.

[0084] Comparative Example 4 Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred. 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as calculated as Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as calculated as Al2O3, 18.0 wt% Na as calculated as Na2O) were simultaneously added, yielding 5000 g of aluminum hydroxide gel solution.

[0085] The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 2190 g. Next, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 152.1 g of tap water, and the mixture was stirred for 30 minutes to obtain 255.3 g of slurry. Next, 34.7 g of lactic acid (90% lactic acid) and 10.0 g of calcium chloride were added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. The mixture was then slowly cooled to produce 300 g of basic aluminum lactate solution (8.2% Al by mass in terms of Al2O3, 70.5% basicity, 0.01% sodium ion, 0.0050% Si by mass, 1.2% Ca by mass, 0.0007% Mg by mass, and 0.0015% Fe by mass).

[0086] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 4.6% and bulk density 0.50 g / cm 3 ) was placed in an alumina crucible and fired at 1100°C for 5 hours under peak firing conditions.

[0087] The volatile content and bulk density of the dried granules of the basic aluminum lactate aqueous solution were measured in the same manner as in Example 1, and the results are shown in Table 1. The particle size distribution D50 and D90, specific surface area, bulk density, crystalline system, loss on drying and loss on ignition, and contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were also measured in the same manner as in Example 1, and the results are shown in Table 3. Figure 3 shows the X-ray diffraction results of Comparative Example 4. The peak pattern is different from that in Figure 1, confirming the formation of a composite oxide of aluminum and calcium. Furthermore, the energy dispersive X-ray fluorescence evaluation results in Table 3 also show a high Ca value.

[0088] (Comparative Example 5) Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred. 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as calculated as Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as calculated as Al2O3, 18.0 wt% Na as calculated as Na2O) were simultaneously added, yielding 5000 g of aluminum hydroxide gel solution.

[0089] Next, the resulting gel solution was dehydrated using a centrifugal dehydrator, and the resulting washed gel weighed 2,430 g. Water was added to the washed gel, and without further washing, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 157.1 g of tap water. Stirring was performed for 30 minutes to obtain 260.3 g of slurry. Next, 39.7 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. Then, the mixture was slowly cooled to produce 300 g of basic aluminum lactate solution (Al2O3 equivalent Al content 8.8 mass%, basicity 70.2%, sodium ion 1.7 wt%, Si: 0.0050 mass%, Ca: 0.0048 mass%, Mg: 0.0007 mass%, Fe: 0.0015 mass%).

[0090] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) at an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules (volatile content 7.5% and bulk density 0.54 g / cm 3 ) was placed in an alumina crucible and fired under peak firing conditions of 1100°C for 5 hours.

[0091] The volatile content and bulk density of the dried granules of the aqueous basic aluminum lactate solution were measured in the same manner as in Example 1, and are shown in Table 1. The D50 and D90 of the particle size distribution, specific surface area, bulk density, crystal system, loss on drying and loss on ignition, and contents of Na, K, Ca, Si, Mg, and Fe of the obtained alumina particles were measured in the same manner as in Example 1, and the results are shown in Table 4. In Comparative Example 5, it was confirmed that the amount of Na in the basic aluminum lactate solution was too high, and therefore the alumina particles were not composed solely of α-alumina.

[0092] (Comparative Example 6) Using a 10 L jacketed GL stirring kettle, cooling water at 5°C was first circulated through the jacket. Next, 1429.8 g of tap water was added to the kettle and stirred. 1909.4 g of an aluminum chloride aqueous solution (10.0 wt% Al as calculated as Al2O3, basicity 2.4%) and 1660.8 g of a sodium aluminate aqueous solution (23.0 wt% Al as calculated as Al2O3, 18.0 wt% Na as calculated as Na2O) were simultaneously added, yielding 5000 g of aluminum hydroxide gel solution.

[0093] The resulting gel solution was then dehydrated using a centrifugal dehydrator, and the process of adding water and stirring was repeated seven times. The resulting washed gel weighed 2190 g. Next, 103.2 g of the resulting washed gel was added to a 1 L glass separable flask placed on a mantle heater, followed by 157.1 g of tap water, and the mixture was stirred for 30 minutes to obtain 260.3 g of slurry. Next, 70 g of lactic acid (90% lactic acid) was added to the resulting slurry, and the mixture was heated and stirred at 100°C for 3 hours. The mixture was then slowly cooled to produce 300 g of basic aluminum lactate solution (8.8% Al by mass in terms of Al2O3, 45% basicity, 0.01% sodium ion, 0.0050% Si by mass, 0.0048% Ca by mass, 0.0007% Mg by mass, and 0.0015% Fe by mass).

[0094] The obtained aqueous solution of basic aluminum lactate was granulated and dried using a spray dryer (TR-160 manufactured by PRIS Co., Ltd.) with an inlet temperature of 250°C, an outlet temperature of 110°C, and a gas pressure of 0.45 MPa using a nozzle. The collected dried granules were placed in an alumina crucible and fired under peak firing conditions of 1100°C for 5 hours.

[0095] In Comparative Example 6, the basicity of the basic aluminum lactate was lower than the lower limit of 60% to 80%, and therefore it was confirmed that the storage stability was poor, crystal precipitation occurred in the liquid during spray drying, causing clogging of the nozzle and making it impossible to perform spray drying properly. This is shown in Table 4. In Tables 1 to 4, "nd" means that it was not possible to measure.

[0096] [Table 1]

[0097] [Table 2]

[0098] [Table 3]

[0099] [Table 4]

[0100] As shown in Tables 1 and 2, the hollow spherical alumina particles shown in Examples 1 to 7 all exhibited α-alumina, and particle size distribution measurements confirmed that D50 was 5 to 50 μm and D90 was 200 μm or less. Furthermore, the loss on drying was 4% by mass or less, the loss on ignition was 6% by mass or less, and the bulk density was 0.4 to 0.7 g / cm. 3 Furthermore, when these hollow spherical alumina particles were subjected to elemental analysis using energy dispersive X-ray fluorescence, it was confirmed that they contained alkali metal element ions (Na and K) in the range of 0.005 to 1.2 mass%, and that the concentrations of Ca, Mg, Si, and Fe were not detected.

[0101] As shown in Table 3, in Comparative Example 1, drying during spray drying was insufficient (high volatile content), resulting in the formation of aggregates during firing, and a large particle size distribution D50 of 530 μm was confirmed. In Comparative Examples 2 and 3, firing conditions were inappropriate, resulting in the crystal systems being γ-alumina and α-alumina + γ-alumina, respectively, and it was confirmed that the α-alumina single phase was not formed. In Comparative Example 4, the Ca content was too high, resulting in the formation of a composite oxide of aluminum and calcium, and it was confirmed that the α-alumina single phase was not formed. As shown in Table 4, in Comparative Example 5, the Na content was too high, resulting in the formation of β-alumina together with α-alumina during firing, and it was confirmed that the α-alumina single phase was not formed.

[0102] The present invention also proposes the following aspects. [1] The basic aluminum lactate aqueous solution is dried and granulated at a temperature of 210 to 280°C under a gas pressure of 0.01 to 1 MPa in the atmosphere or inert gas, and the volatile content of the granulated product is reduced to 0 to 10% and the bulk density to 0.2 to 0.7 g / cm. 3 a first step of forming a controlled hollow dry granulation; a second step of calcining the dried granules obtained in the first step at a temperature within a range of 1050°C or higher and lower than 1200°C for 2 to 8 hours to obtain hollow spherical alumina particles; the basic aluminum lactate aqueous solution contains iron (Fe) in amounts of 0 to 0.01% by mass, calcium (Ca) in amounts of 0 to 0.01% by mass, magnesium (Mg) in amounts of 0 to 0.01% by mass, and silicon (Si) in amounts of 0.005 to 1.2% by mass, has a basicity of 60 to 80%, and contains aluminum in an amount of 8 to 13% by mass calculated as Al2O3; The obtained hollow spherical alumina particles have a D50 of 5 to 50 μm and a D90 of 200 μm or less in particle size distribution measurement, are hollow inside, have through holes on the outside, and have a specific surface area of ​​1 to 20 m 2 / g, and the crystalline phase is an α phase. [2] The hollow spherical alumina particles have a loss on drying of 4% or less, a loss on ignition of 6% or less, and a bulk density of 0.4 to 0.7 g / cm, as determined by aluminum oxide analysis in accordance with the Standards for Pharmaceutical and Medical Devices 2021. 3 The method for producing hollow spherical alumina particles according to [1], characterized in that: [3] The method for producing hollow spherical alumina particles according to [1] or [2], characterized in that the basic aqueous aluminum lactate solution is obtained by mixing an aluminum chloride solution with either or both of sodium aluminate and potassium aluminate, and water to form an aluminum hydroxide gel, washing the resulting gel with water, adding water to obtain an aluminum hydroxide slurry, and then adding lactic acid to cause a reaction. [4] The method for producing hollow spherical alumina particles according to any one of [1] to [3], wherein the drying and granulation in the first step is a spray drying method. [5] The method for producing hollow spherical alumina particles according to any one of [1] to [4], wherein the firing in the second step is carried out in air, nitrogen or an inert gas, or in vacuum.

Claims

1. The aqueous solution of basic aluminum lactate is dried and granulated at a temperature of 210 to 280°C under a gas pressure of 0.01 to 1 MPa in the atmosphere or an inert gas, and the volatile content of the granulated product is reduced to 0 to 10% and the bulk density to 0.2 to 0.7 g / cm. ３ a first step of forming a controlled hollow dry granulation; a second step of calcining the dried granules obtained in the first step at a calcination temperature within a range of 1050°C or higher and lower than 1200°C for 2 to 8 hours to obtain hollow spherical alumina particles; The basic aluminum lactate aqueous solution contains iron (Fe) in an amount of 0 to 0.01 mass %, calcium (Ca) in an amount of 0 to 0.01 mass %, magnesium (Mg) in an amount of 0 to 0.01 mass %, and silicon (Si) in an amount of 0.005 to 1.2 mass %, and has a basicity of 60 to 80%, and aluminum is Al ２ O ３ It contains 8 to 13 mass% in terms of The obtained hollow spherical alumina particles have a particle size distribution measurement of D50 of 5 to 50 μm and D90 of 200 μm or less, are hollow inside and have through holes connecting to the outside, and have a specific surface area of ​​1 to 20 m ２ / g, and the crystalline phase is an α phase.

2. The hollow spherical alumina particles have a loss on drying of 4% or less, a loss on ignition of 6% or less, and a bulk density of 0.4 to 0.7 g / cm3, as determined by aluminum oxide analysis in accordance with the Standards for Pharmaceutical and Medical Devices 2021. ３ 2. The method for producing hollow spherical alumina particles according to claim 1, wherein the alumina particles are

3. 3. The method for producing hollow spherical alumina particles according to claim 1, wherein the basic aqueous aluminum lactate solution is obtained by mixing an aluminum chloride solution with either or both of sodium aluminate and potassium aluminate, and water to form a gel of aluminum hydroxide, washing the gel with water, adding water to obtain an aluminum hydroxide slurry, and then adding lactic acid to cause a reaction.

4. 3. The method for producing hollow spherical alumina particles according to claim 1, wherein the drying and granulation in the first step is performed by a spray drying method.

5. 3. The method for producing hollow spherical alumina particles according to claim 1, wherein the firing in the second step is carried out in air, nitrogen, an inert gas, or a vacuum.

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