JP5771161B2 - Method for producing spherical ceramic particles - Google Patents

Description

  The present invention relates to a method for producing spherical ceramic particles useful as a filler for various materials.

  The filler is added to a base material such as plastic, rubber, paint, fiber, paper, glass, metal, and improves the physical properties of the base material and contributes to the improvement of workability and the function of the final product. Among these, ceramic particles have stable physicochemical properties and have been variously studied as fillers. Since the filler is spherical and has high fluidity and excellent filling properties, it is easy to increase the filler content in the base material, and as a result, it has excellent performance for imparting the physical properties of the filler to the base material. doing.

  In addition, a technique has been proposed in which a double oxide formed from two or more oxides having light diffusibility, electrical characteristics, etc., which are superior to conventionally used silica and alumina, is used as a filler.

For example, in Patent Document 1, the total amount of Al ₂ O ₃ or MgO and SiO ₂ is 80% by weight or more, and the weight ratio of Al ₂ O ₃ or MgO to SiO ₂ [(Al ₂ O ₃ or MgO) / SiO ₂ ] is 0.1 to 15, the average particle size is 0.01 to 50 μm, and a filler manufactured by a flame melting method is disclosed.

Patent Document 2 contains MgO and Al ₂ O ₃ as main components, the MgO / Al ₂ O ₃ weight ratio is 0.05 to 5, and the average particle size is 0.5 to 500 μm. Spherical ceramic particles produced by flame melting are disclosed.

JP2007-39304A JP2008-162825

  However, in the conventional manufacturing method, the composition ratio of two or more kinds of oxides contained in the raw material particles of the double oxide may differ from the composition ratio of the oxides contained in the obtained spherical ceramic particles. In this case, in order to obtain spherical ceramic particles having a desired composition ratio, after investigating the type and amount of the oxide that decreases in the process of producing the spherical ceramic particles, the blending amount of any oxide is determined. In some cases, the composition ratio of two or more kinds of oxides in the raw material particles had to be adjusted by increasing the number.

  Further, when the amount of any oxide contained in the raw material particles is increased, the amount reduced in the process of producing the spherical ceramic particles is wasted and the yield is deteriorated.

  The present invention is intended to solve the above-mentioned problems, and in the production method for obtaining spherical ceramic particles containing a double oxide formed of two or more kinds of oxides, two or more kinds of oxidations contained in the raw material particles. An object of the present invention is to provide a method for producing spherical ceramic particles, in which spherical ceramic particles having a small difference from the composition ratio of the product can be obtained efficiently.

The present invention produces spherical ceramic particles using raw material particles having a main component of a double oxide composed of at least two selected from Al ₂ O ₃ , MgO and SiO ₂ and having an average particle diameter of 0.01 to 20 μm. This is a method for producing spherical ceramic particles having the following steps (1) to (3).
Step (1): Step of preparing the slurry of the raw material particles Step (2): Step of spraying the slurry obtained in the step (1) onto the melting zone Step (3): The above-mentioned contained in the sprayed slurry Process of melting raw material particles in the melting zone and making them spherical

  According to the present invention, in the production method for obtaining spherical ceramic particles containing a double oxide formed of two or more kinds of oxides, the difference from the composition ratio of the two or more kinds of oxides contained in the raw material particles is small. It is possible to provide a method for producing spherical ceramic particles, in which spherical ceramic particles can be obtained efficiently.

  The reason for such an effect is not clear, but is considered as follows. That is, when a double oxide formed of two or more kinds of oxides is put into the melting zone as a powder, excessive evaporation of an oxide having a relatively low melting point occurs at a high temperature, resulting in a composition ratio of raw material particles. And the composition ratio of the obtained spherical ceramic particles may be greatly different. However, as in the present invention, when a double oxide formed of two or more kinds of oxides is charged into the melting zone in a slurry state, the latent heat of vaporization of the oxides is taken away by the evaporation of the slurry solvent. It is considered that excessive evaporation can be suppressed, and as a result, spherical ceramic particles having a small difference from the composition ratio of two or more kinds of oxides contained in the raw material particles can be obtained.

The manufacturing method of the spherical ceramic particles in the present embodiment is a raw material particle having as a main component a double oxide composed of at least two kinds selected from Al ₂ O ₃ , MgO and SiO ₂ and having an average particle diameter of 0.01 to 20 μm. In the method for producing spherical ceramic particles using the method, the following steps (1) to (3) are included.
Step (1): Step of preparing the slurry of the raw material particles Step (2): Step of spraying the slurry obtained in the step (1) onto the melting zone Step (3): The above-mentioned contained in the sprayed slurry Process of melting raw material particles in the melting zone and making them spherical

[Adjustment of raw material particles]
The raw material particles contain as a main component a double oxide composed of at least two selected from Al ₂ O ₃ , MgO and SiO ₂ . In this specification, “mainly composed of a double oxide composed of at least two selected from Al ₂ O ₃ , MgO and SiO ₂ ” means Al ₂ O ₃ , MgO and SiO ₂ in the components of the entire raw material particles. The total content of the double oxides selected from the group consisting of 80 wt% or more, preferably 90 wt% or more, more preferably 95 wt% or more, and even more preferably 100 wt%. . When the content of the double oxide in the components of the entire raw material particles is 80% by weight or more, the physical properties of the obtained spherical ceramic particles are stabilized, and when the spherical ceramic particles are used as a filler, The function can be sufficiently expressed with a small filling amount.

Examples of the double oxide include mullite (chemical formula: 3Al ₂ O ₃ · 2SiO ₂ ) which is a double oxide of Al ₂ O ₃ and SiO _2, and forsterite (chemical formula: which is a double oxide of MgO and SiO ₂ ). 2MgO · _SiO 2), and spinel are mixed oxide of MgO and _Al 2 _{O 3} (chemical formula: MgO · _Al 2 _{O 3)} is preferable because the effect of modifying the resin can be fully expressed as a filler .

Further, the method for producing spherical ceramic particles in the present embodiment is particularly remarkable when the raw material particles contain SiO ₂ as a raw material component, that is, when the main component of the raw material particles is forsterite and / or mullite. Has an effect. This is considered as follows.

The melting point (1720 ° C.) and boiling point (2950 ° C.) of SiO ₂ are lower than the melting point (2830 ° C.) and boiling point (3600 ° C.) of MgO, and the melting point (2013 ° C.) and boiling point (2777 ° C.) of Al ₂ O _3. . Therefore, when raw material particles containing SiO ₂ as a raw material component are charged in a high-temperature melting zone in a powder state, the amount of SiO ₂ evaporated may be larger than the amount of other oxides evaporated. In this case, there is a tendency that the composition ratio of the two or more oxides contained in the raw material particles and the composition ratio of the two or more oxides contained in the obtained spherical ceramic particles are further greatly different. However, in the method for producing spherical ceramic particles in the present embodiment, excessive evaporation of SiO ₂ having a relatively low melting point and the like can be suppressed by spraying the raw material particles on the molten zone in a slurry state. The difference between the composition ratio of the two or more oxides contained in the particles and the composition ratio of the two or more oxides contained in the obtained spherical ceramic particles can be reduced.

The weight ratio (Al ₂ O ₃ / SiO ₂ ) between Al ₂ O ₃ and SiO ₂ contained in the mullite is 0.1 to 17, preferably 0 from the viewpoint of expressing the physicochemical properties of the mullite. 0.5 to 10, more preferably 1.0 to 5.0, still more preferably 1.5 to 3.5, and still more preferably 2.0 to 3.0.

The weight ratio (MgO / SiO ₂ ) between MgO and SiO ₂ contained in the forsterite is 0.1 to 17, preferably 0.3 to 10, from the viewpoint of expressing the physical and chemical properties of the forsterite. More preferably, it is 0.5-5.0, More preferably, it is 0.8-2.5, More preferably, it is 1.0-2.0.

The weight ratio (MgO / Al ₂ O ₃ ) between MgO and Al ₂ O ₃ contained in the spinel is 0.05 to 5.0, preferably 0 from the viewpoint of expressing the physical and chemical properties of the spinel. 0.1 to 4.0, more preferably 0.15 to 3.0, still more preferably 0.20 to 1.0, and still more preferably 0.25 to 0.50.

  The average particle diameter of the raw material particles is 0.01 μm or more from the viewpoint of further suppressing variation in the composition accompanying component evaporation in the melting zone, and from the viewpoint of improving the filling properties of the obtained spherical ceramic particles as a filler. 0.1 μm or more is preferable, 0.5 μm or more is more preferable, and 0.9 μm or more is more preferable. In addition, the average particle size is from the viewpoint of ensuring dispersibility in a solvent (described later), from the viewpoint of obtaining spherical ceramic particles having high sphericity, and from the viewpoint of expressing the function of the spherical ceramic particles as a filler with a small addition amount. 20 μm or less, preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 7 μm or less. When these viewpoints are combined, the average particle diameter of the raw material particles is 0.01 to 20 μm, preferably 0.1 to 10 μm, more preferably 0.5 to 8 μm, and further preferably 0.9 to 7 μm.

  In the present specification, the particle diameter of the raw material particles is measured by the method described in the examples. Moreover, in this specification, an average particle diameter means D50 (The median particle diameter of 50% of volume references | standards), and it measures by the method as described in an Example.

  D90 of the raw material particles (90% passing particle diameter in the volume average particle size distribution) is preferably 0.5 μm or more, more preferably 1.0 μm or more, from the viewpoint of improving the filling property as a filler of the obtained spherical ceramic particles. 1.5 μm or more is more preferable, and 2.0 μm or more is even more preferable. In addition, D90 is preferably 40 μm or less, more preferably 30 μm or less, further preferably 20 μm or less, and even more preferably 15 μm or less from the viewpoint of improving the fluidity of the obtained spherical ceramic particles as a filler. In addition, in this specification, D90 is measured by the method as described in an Example. Taking these viewpoints together, D90 of the raw material particles is preferably 0.5 to 40 μm, more preferably 1.0 to 30 μm, further preferably 1.5 to 20 μm, and still more preferably 2.0 to 15 μm.

  Further, from the viewpoint of narrowing the particle size distribution of the obtained spherical ceramic particles, it is preferable that the value obtained by dividing D90 by D50 (D90 / D50) is smaller. Specifically, 3 or less is preferable, and 2.5 or less is more preferable.

  The shape of the raw material particles in the present embodiment is not particularly limited and may be an indefinite shape, but the obtained spherical ceramic particles preferably have a sphericity of 0.95 or more from the viewpoint of improving fluidity as a filler. 0.96 or more, more preferably 0.98 or more. Further, from the viewpoint of ensuring residence time in the melting zone, melting in the melting zone and quickly spheroidizing, and obtaining particles having a narrow particle size distribution and high sphericity, the major axis / minor axis of the raw material particles The ratio is preferably 9 or less, more preferably 4 or less, and even more preferably 2 or less. In this specification, the sphericity and the major axis / minor axis ratio are measured by the methods described in the examples.

The raw material particles used in the present embodiment are a mixing method, precipitation method, sol-gel method, spray pyrolysis method, hydrothermal method, CVD method, etc., using an Al ₂ O ₃ source, a MgO source, a SiO ₂ source, etc., which will be described later. This method can be obtained by adjusting the weight ratio of the main component of the target raw material. Among them, a special apparatus and a mixing method that does not require a specific raw material are preferable. In addition, the mixing method is a mixing step of mixing an Al ₂ O ₃ source, an MgO source, an SiO ₂ source, etc. with a mixer, a baking step of baking the mixed one, and sizing and classifying the one obtained by baking. A sizing step.

The mixing step is preferably wet mixing with water slurry, and the slurry concentration is preferably 20 to 80% by weight, more preferably 40 to 75% by weight, and further preferably 50 to 70% by weight from the viewpoint of improving the mixing efficiency. The mixing method in the mixing step is preferably a method of mixing while pulverizing an Al ₂ O ₃ source, an MgO source, an SiO ₂ source, etc., and more specifically, wet mixing by a ball mill is more preferable.

The firing temperature in the firing step is preferably 1000 ° C. or higher, more preferably 1200 ° C. or higher, and further preferably 1400 ° C. or higher from the viewpoint of reactivity such as Al ₂ O ₃ source, MgO source, SiO ₂ source and the like. In addition, the firing temperature is preferably 1800 ° C. or less, more preferably 1700 ° C. or less, and further preferably 1600 ° C. or less from the viewpoint of productivity. When these viewpoints are put together, the firing temperature is preferably 1000 to 1800 ° C, more preferably 1200 to 1700 ° C, and further preferably 1400 to 1600 ° C.

The firing time in the firing step is preferably 1 hour or longer, more preferably 3 hours or longer, and more preferably 6 hours or longer from the viewpoint of the reactivity of the Al ₂ O ₃ source, MgO source, SiO ₂ source and the like. The firing time is preferably 16 hours or shorter, more preferably 12 hours or shorter, and even more preferably 10 hours or shorter from the viewpoint of productivity. Taking these viewpoints together, the firing time is preferably 1 to 16 hours, more preferably 3 to 12 hours, and even more preferably 6 to 10 hours.

  Examples of the pulverization method in the sizing step include a roll mill, a hammer mill, a roller mill, a vibration mill, and a ball mill. From the viewpoint of preventing coloration due to contamination of impurities, dry pulverization using a ball mill is preferable.

  The classification method in the granulation step is preferably dry classification from the viewpoint of processing capability. Dry classifiers include sieving machines, air classifiers such as cyclones, and rotor rotary classifiers equipped with rotating rotors. From the viewpoint of narrowing the particle size distribution of raw material particles, rotor rotary air classifiers are used. More preferred.

Examples of the Al ₂ O ₃ source include aluminum alkoxide such as aluminum oxide (alumina), aluminum hydroxide, boehmite, aluminum sulfate, aluminum nitrate, aluminum chloride, alumina sol, and aluminum isopropoxide, bauxite, and bang shale. it can. Among these, alumina is preferable from the viewpoint that a relatively high purity can be easily obtained.

Examples of the SiO ₂ source include silica, silica sand, quartz, cristobalite, amorphous silica, feldspar, pyrophyllite, fumed silica, ethyl silicate, silica gel, and the like. Among these, silica stone is preferable from the viewpoint that a relatively high purity can be easily obtained.

  Examples of the MgO source include magnesium carbonate, magnesium oxide, magnesium hydroxide, olivine, pyroxene dunstone, serpentine, and olivine minerals. Among these, magnesium hydroxide is preferable from the viewpoint that a relatively high purity can be easily obtained.

Examples of the (A1 ₂ O ₃ + SiO ₂ ) source include kaolin, van earth shale, bauxite, mica, sillimanite, andalusite, mullite, zeolite, montmorillonite, and hyrosite.

Examples of the (MgO + SiO ₂ ) source include forsterite, clinoenstatite, enstatite, olivine, pyroxene, dunstone, serpentinite, basalt, olivine mineral, and talc.

Examples of the (Al ₂ O ₃ + MgO) source include spinel.

  The above-mentioned raw materials can be used alone or in admixture of two or more.

[Step (1)]
In step (1), a slurry of the raw material particles (hereinafter referred to as raw material slurry) is prepared.

  In the said process (1), the said raw material slurry can be prepared using a well-known general method. An example of a method for adjusting the raw material slurry is a method of obtaining raw material particle slurry by mixing raw material particles having a predetermined particle diameter with a solvent. Moreover, the raw material powder can be mixed with a solvent and adjusted to a predetermined particle size by wet pulverization to obtain a slurry.

  The solvent is not particularly limited as long as it is vaporized by combustion, decomposition, or evaporation, but water is preferable in terms of handling properties and cost. Note that a dispersant may be added to the raw slurry in order to impart dispersibility and fluidity of the particles.

  The concentration of the raw material particles in the raw material slurry (hereinafter referred to as the raw material slurry concentration) is preferably 0.1% by weight or more, more preferably 1% by weight or more from the viewpoint of improving the productivity of the spherical ceramic particles. In addition, the concentration reduces the difference in composition ratio between the spherical ceramic particles and the raw material particles, and suppresses the fusion and coalescence of part of the particles during melting, thereby increasing the D50 increase rate (described later) and From the viewpoint of reducing the D90 increase rate (described later), it is preferably 70% by weight or less, more preferably 40% by weight or less, and still more preferably 20% by weight or less. From these viewpoints, the raw material slurry concentration is preferably 0.1 to 70% by weight, more preferably 1 to 40% by weight, and further preferably 1 to 20% by weight.

[Step (2)]
In the step (2), the raw material slurry is sprayed on the melting zone.

  In the step (2), spraying of the raw material slurry onto the melting zone is performed using a known sprayer such as a two-fluid nozzle sprayer, an ultrasonic sprayer, a rotary disk sprayer, etc., but from the viewpoint of mass productivity and dispersibility To two-fluid nozzle atomizers are preferred.

  When spraying the raw material slurry onto the melting zone with a two-fluid nozzle sprayer, spray gas is sprayed from the nozzle in order to spray the raw material slurry to be ejected in a mist form. When the melting zone is formed by a flame melting method (described later), since the spray gas is preferably a component that contributes to flame generation, a combustion-supporting gas such as air or oxygen is preferably used, but the productivity is improved. From the viewpoint, oxygen is more preferable.

The spray concentration of the raw material slurry onto the melting zone is appropriately changed according to the melting zone forming means (described later). As an example, when the melting zone is formed by a flame melting method (described later), from the viewpoint of ensuring sufficient dispersibility of the raw material particles, the flow rate per hour (kg / h) of the slurry is used for combustion. The value divided by the total amount (Nm ³ / h) of the flow rate per hour of the natural gas and the support gas and the flow rate per hour of the support gas used for spraying (Nm ³ / h) is 0.01 to 5 kg / Nm ³ more it is preferable, more preferably 0.05~1kg / Nm ^3, more preferably from ^{0.08~0.50kg / Nm 3, 0.10~0.30kg / Nm} 3 Further preferred.

[Step (3)]
In the step (3), while vaporizing the solvent of the slurry contained in the sprayed raw material slurry, the raw material particles contained in the raw material slurry are melted and spheroidized in the melting zone.

  The melting zone for melting and spheroidizing the raw material particles contained in the sprayed raw material slurry can be formed by an electric heating method, a plasma heating method, a burner combustion method of combustible gas, etc. From the viewpoint of cost, the flame combustion method (flame melting method) is preferable. When a melting zone is formed by the flame melting method, the flame is composed of flammable gas such as propane, butane, methane, natural liquefied gas, LPG, and fuel such as heavy oil, kerosene, light oil, pulverized coal, etc. It is generated by burning with sex gas. Among these, LPG and oxygen are preferable from the viewpoints of economy and productivity.

  In the step (3), the temperature of the melting zone for melting the raw material particles is preferably 1700 to 5000 ° C., from the viewpoint of melt spheroidizing the raw material particles and further suppressing the composition fluctuation due to the evaporation of the raw material, 3000 degreeC is more preferable, 1800-2500 degreeC is further more preferable, and 1900-2200 degreeC is still more preferable.

In the case of forming a molten zone by the flame melting method, the amount of the fuel supplied is appropriately determined according to the type of fuel used from the viewpoint of improving the sphericity of the spherical ceramic particles. As an example, when LPG is used as the fuel, 4 to 16 Nm ³ / h is preferable, 6 to 14 Nm ³ / h is more preferable, and 8 to 12 Nm ³ / h is more preferable.

In the case of forming a melting zone by the flame melting method, the supply amount of oxygen is appropriately determined depending on the type of fuel used from the viewpoint of improving the sphericity of the spherical ceramic particles. As an example, when LPG is used as the fuel, ^{3 to} 100 Nm ³ / h is preferable, 10 to 80 Nm ³ / h is more preferable, and 20 to 40 Nm ³ / h is more preferable.

  From the viewpoint of complete combustion, the fuel to oxygen ratio (fuel / oxygen) is preferably 0.1 to 1.3, more preferably 0.2 to 1.0, and more preferably 0.25 to 0.50 in terms of volume ratio. Is more preferable, and 0.30 to 0.40 is still more preferable.

  In the case where the melting zone is formed by the flame melting method, it is preferable that the flame generator uses an oxygen / gas burner from the viewpoint of generating a high-temperature flame. Although the structure of the burner is not particularly limited, the burners disclosed in JP-A-7-48118, JP-A-11-132421, JP-A-2000-205523, or JP-A-2000-346318 are disclosed. preferable.

  Examples and the like specifically showing the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

[Composition of raw material particles and spherical ceramic particles]
Elemental analysis is performed by the fluorescent X-ray method (JIS R2216 “Fluorescent X-ray analysis method for refractory bricks and refractory mortars”) to determine the composition of each atom of Al, Mg, and Si. From this result, the amounts of Al ₂ O ₃ , MgO and SiO ₂ are calculated, and the composition ratio (weight ratio) is calculated.

[Particle size of raw material particles and spherical ceramic particles]
The average particle diameter is measured by a laser diffraction / scattering method using Horiba LA-920. Further, the particle diameter at which the cumulative volume frequency calculated by the volume fraction is 90% calculated from the smaller particle diameter was defined as 90% diameter (D90).

[Long axis / short axis ratio of raw material particles]
Measure the longest diameter (major axis) and the diameter (minor axis) perpendicular to the midpoint of the longest diameter of any one of the raw material particle images taken with a scanning electron microscope. The midpoint of the longest diameter and the diameter perpendicular to the midpoint] is calculated. Similarly, calculation is performed for 50 particles, and the average value of the obtained values is taken as the major axis / minor axis ratio.

[Sphericality of spherical ceramic particles]
The sphericity is obtained by obtaining the area of the particle projection cross section of the image obtained by a scanning electron microscope and the perimeter of the cross section, and then [circumference of a perfect circle having the same area as the area of the particle projection cross section] / [particle Perimeter of projected cross section] is calculated, and the average value of the values obtained for any 50 particles is defined as sphericity.

[Production example of raw material particles 1 and 2]
Alumina (purity: 99.9%) and silica powder (purity: 99.9%) were mixed so that the Al ₂ O ₃ / SiO ₂ weight ratio was 2.6 to prepare an aqueous slurry having a slurry concentration of 60%. The resulting water slurry was mixed with a ball mill for 4 hours, filtered and dried. The obtained powder was calcined at 1500 ° C. for 8 hours, then dry pulverized with a ball mill for 6 hours, and classified with a rotor rotary air classifier. The coarse powder side obtained by classification was designated as raw material particle 1, and the fine powder side was designated as raw material particle 2. Table 1 shows the physical properties of the raw material particles 1 and the raw material particles 2.

[Production Example of Raw Material Particles 3 and 4]
Magnesium hydroxide (purity 99.2%) and silica powder (purity 99.9%) were mixed so that the MgO / SiO ₂ weight ratio was 1.3 to prepare an aqueous slurry having a slurry concentration of 60%. The resulting water slurry was mixed with a ball mill for 4 hours, filtered and dried. The obtained powder was calcined at 1500 ° C. for 8 hours, then dry pulverized with a ball mill for 6 hours, and classified with a rotor rotary air classifier. The coarse powder side obtained by classification was designated as raw material particles 3, and the fine powder side was designated as raw material particles 4. Table 1 shows the physical properties of the raw material particles 3 and the raw material particles 4.

[Production Example of Raw Material Particles 5 and 6]
Magnesium hydroxide (purity 99.2%) and alumina (purity 99.9%) were mixed so that the MgO / Al ₂ O ₃ weight ratio was 0.39 to prepare an aqueous slurry having a slurry concentration of 60%. The resulting water slurry was mixed with a ball mill for 4 hours, filtered and dried. The obtained powder was calcined at 1500 ° C. for 8 hours, then dry pulverized with a ball mill for 6 hours, and classified with a rotor rotary air classifier. The coarse powder side obtained by classification was designated as raw material particles 5, and the fine powder side was designated as raw material particles 6.

Example 1
Water was added to the raw material particles 1 obtained in the above production example to prepare a raw material slurry having a concentration of 15%. Next, using a LPG (propane gas) -oxygen mixed gas burner, the raw material slurry was flowed at a flow rate of 5 kg / h in a flame (2000 ° C.) burned at a flow rate of LPG 10 Nm ³ / h and oxygen 25 Nm ³ / h. It was supplied from a two-fluid nozzle. The raw material slurry was sprayed from the center of the two-fluid nozzle, and the raw material slurry was sprayed by ejecting oxygen in an amount of 5 Nm ³ / h from the periphery. Since the total gas flow rate was 40 Nm ³ / h with respect to the supply amount of the raw material slurry of 5 kg / h, the spray amount (supply amount) of the raw material slurry was 0.125 kg / Nm ³ . The raw material particles 1 were spheroidized under the production conditions as described above to obtain spherical ceramic particles of Example 1. Table 2 shows the composition ratio of the obtained spherical ceramic particles, and Table 3 shows D50, D90, D50 increase rate, D90 increase rate, and sphericity.

  In addition, D50 increase rate shows the ratio which D50 of the spherical ceramic particle | grains obtained by the manufacturing method of this embodiment increased from D50 of raw material particle | grains. The D50 increase rate is preferably smaller, specifically 20% or less is preferable, 10% or less is more preferable, and 5% or less is more preferable.

  Moreover, D90 increase rate shows the ratio which D90 of the spherical ceramic particle | grains obtained by the manufacturing method of this embodiment increased from D90 of raw material particle | grains. The D90 increase rate is preferably as small as possible, specifically 20% or less, more preferably 10% or less, and even more preferably 5% or less.

The D50 increase rate and the D90 increase rate were determined by the following equations.
D50 increase rate (%) = (D50 of spherical ceramic particles−D50 of raw material particles) / D50 × 100 of raw material particles
D90 increase rate (%) = (D90 of spherical ceramic particles−D90 of raw material particles) / D90 × 100 of raw material particles

(Example 2)
Manufacture was performed in the same manner as in Example 1 except that the raw material particles 3 were used, and spherical ceramic particles having physical properties shown in Tables 2 and 3 were obtained.

(Example 3)
Manufacture was carried out in the same manner as in Example 1 except that raw material particles 5 were used, and spherical ceramic particles having physical properties shown in Tables 2 and 3 were obtained.

Example 4
Manufacture was performed in the same manner as in Example 1 except that the raw material particles 2 were used and the raw material slurry concentration was changed to 5%, and spherical ceramic particles having physical properties shown in Tables 2 and 3 were obtained.

(Example 5)
Manufacture was performed in the same manner as in Example 1 except that the raw material particles 4 were used and the raw material slurry concentration was changed to 5% to obtain spherical ceramic particles having the physical properties shown in Tables 2 and 3.

(Example 6)
Manufacture was performed in the same manner as in Example 1 except that the raw material particles 6 were used and the raw material slurry concentration was changed to 5%, and spherical ceramic particles having physical properties shown in Tables 2 and 3 were obtained.

(Example 7)
Manufacture was performed in the same manner as in Example 1 except that the raw material slurry concentration was 5%, and spherical ceramic particles having physical properties shown in Tables 2 and 3 were obtained.

(Example 8)
Manufacture was carried out in the same manner as in Example 7 except that the feed rate of the raw material slurry was 10 kg / h, and spherical ceramic particles having physical properties shown in Tables 2 and 3 were obtained.

(Comparative Example 1)
The raw material particles 1 obtained in the above production example are used as powders, using 5 Nm ³ / h oxygen as a carrier gas at a supply rate of 5 kg / h with an LPG (propane gas) -oxygen mixed gas burner and LPG 10 Nm ³ / h, oxygen was supplied into a flame (2000 ° C.) burned at a flow rate of 25 Nm ³ / h. Since the total gas amount was 40 Nm ³ / h at a supply rate of 5 kg / h, the raw material supply amount was 0.125 kg / Nm ³ . The raw material particles 1 were spheroidized under the production conditions as described above to obtain spherical ceramic particles of Comparative Example 1. Table 2 shows the composition ratio of the obtained spherical ceramic particles, and Table 3 shows D50, D90, D50 increase rate, D90 increase rate, and sphericity.

(Comparative Examples 2-6)
Except having replaced the raw material particle 1 with the raw material particle shown in Table 2, 3, it manufactured by the method similar to the comparative example 1, and obtained the spherical ceramic particle which has the physical property shown in Table 2, Table 3.

  As is clear from Table 2, the composition ratios of the spherical ceramic particles of Examples 1 to 8 are less varied from the composition ratio of the raw material particles than those of Comparative Examples 1 to 6.

  Moreover, as shown in Table 3, since Examples 1-8 have a D50 increase rate and a D90 increase rate smaller than those of Comparative Examples 1-6, coarse particles due to fusion and coalescence of raw material particles. It is thought that the generation of was suppressed. In Examples 4, 5, and 6, the D90 increase rate is negative (smaller than the raw material) because the irregularly shaped particles having different major axis diameters and minor axis diameters are united with other particles. This is because when the particles are made spherical, the particle size becomes small.

Claims (4)

In this method, spherical ceramic particles are produced using raw material particles mainly composed of a double oxide selected from Al ₂ O ₃ , MgO and SiO ₂ and having an average particle diameter of 0.01 to 20 μm. And the manufacturing method of the spherical ceramic particle which has the following process (1)-(3).
Step (1): Step of preparing the slurry of the raw material particles Step (2): Step of spraying the slurry obtained in the step (1) onto the melting zone Step (3): The raw material particles contained in the sprayed slurry Step of spheroidizing by melting in the melting zone   The manufacturing method of the spherical ceramic particle of Claim 1 whose density | concentration of the raw material particle in the slurry obtained at the said process (1) is 0.01 weight%-60 weight%. The method for producing spherical ceramic particles according to claim 1 or 2, wherein the total content of Al ₂ O ₃ , MgO and SiO _{2 in} the raw material particles is 80% by weight or more.   The manufacturing method of the spherical ceramic particle of any one of Claims 1-3 whose said fusion zone is a flame.