JP2024014316A - Inorganic oxide hollow particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide inorganic oxide hollow particles with lower relative permittivity and dielectric loss tangent than conventional ones and with excellent dielectric properties.

SOLUTION: Inorganic oxide hollow particles contain boron oxide, calcium oxide, aluminum oxide, and silicon oxide. The mass ratio of the aluminum oxide to the silicon oxide (aluminum oxide/silicon oxide) is 0.35 or greater.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to inorganic oxide hollow particles.

Inorganic oxide hollow particles have a cavity surrounded by an outer shell, so they are lighter, have lower thermal conductivity, and have superior thermal stability than non-hollow particles, and are used as heat insulating materials, heat shielding materials, and catalysts. It is widely used as carriers, building materials, electronic materials, etc.

The inorganic oxide hollow particles are, for example, siliceous hollow particles made from natural glassy rocks such as pearlite and obsidian, with internal spaces separated by partition walls, and have a weight of 0.15 to 0.35 g/ cm ³ and the thickness of the shell at the thinnest part is 0.5 to 5 μm (Patent Document 1). In addition, spherical silica particles formed by aggregating and bonding hollow silica fine particles having an average particle diameter of 5 to 300 nm and a specific surface area of 50 to 1500 m ² /g (Patent Document 2), and shells containing silica ( Silica-containing hollow particles (Patent Document 3) have also been reported, which have metal and/or metal compound nanoparticles encapsulated in the shell.

Japanese Patent Application Publication No. 2010-172863 Japanese Patent Application Publication No. 2009-114010 Japanese Patent Application Publication No. 2016-150880

In recent years, with the remarkable progress in information network technology and the expansion of services that utilize information networks, electronic devices are becoming larger in information capacity and faster in processing speed. In order to transmit large-capacity digital signals at high speed, it is important to reduce transmission loss in printed wiring boards for electronic devices. It is desired that the dielectric properties be lower and the dielectric properties be excellent.
An object of the present invention is to provide inorganic oxide hollow particles that have lower dielectric constant and dielectric loss tangent than conventional ones and have excellent dielectric properties.

The present inventors studied in view of the above problems and found that an inorganic material containing boron oxide, calcium oxide, aluminum oxide, and silicon oxide as essential components and containing aluminum oxide and silicon oxide in a specific quantitative ratio It has been found that oxide hollow particles have lower relative permittivity and dielectric loss tangent than conventional ones, and have excellent dielectric properties.

That is, the present invention provides the following [1] to [12].
[1] Contains boron oxide, calcium oxide, aluminum oxide and silicon oxide,
The mass ratio of aluminum oxide to silicon oxide (aluminum oxide/silicon oxide) is 0.35 or more,
Inorganic oxide hollow particles.
[2] The inorganic oxide hollow particles according to [1] above, wherein the boron oxide content is 5 to 50% by mass.
[3] The inorganic oxide hollow particles according to [1] or [2] above, wherein the content of calcium oxide is 3 to 40% by mass.
[4] The inorganic oxide hollow particles according to any one of [1] to [3] above, wherein the content of aluminum oxide is 5 to 40% by mass.
[5] The inorganic oxide hollow particles according to any one of [1] to [4] above, wherein the content of silicon oxide is 20 to 70% by mass.
[6] The inorganic oxide hollow particles according to any one of [1] to [5] above, which further contain magnesium oxide and have a magnesium oxide content of 7% by mass or less.
[7] The inorganic oxide hollow particles according to any one of [1] to [6] above, having a dielectric loss tangent of 0.005 or less.
[8] The inorganic oxide hollow particles according to any one of [1] to [7] above, having a relative dielectric constant of 3 or less.
[9] The inorganic oxide hollow particles according to any one of [1] to [8] above, having a voidage ratio of 60% or more.
[10] The inorganic oxide hollow particles according to any one of [1] to [9] above, having an average particle diameter of 10 μm or less.
[11] The inorganic oxide hollow particle is one of any one of [1] to [10] above, wherein the cavity covered with an outer shell has a plurality of independent spaces separated by one or more partition walls. Inorganic oxide hollow particles described in .
[12] The inorganic oxide hollow particles according to [11] above, wherein the outer shell is porous.

According to the present invention, it is possible to provide inorganic oxide hollow particles having a lower dielectric constant dielectric loss tangent and excellent dielectric properties than conventional ones.

1 is a diagram showing a scanning electron microscope (SEM) image of inorganic oxide hollow particles obtained in Example 1. FIG.

As used herein, the term "hollow particle" refers to a particle that has a hollow structure inside and has an outer shell that defines the hollow part. Therefore, it differs from a porous particle, which has a plurality of pores extending from the surface of the particle into the interior. Note that hollow particles can be distinguished from porous particles by a transmission electron microscope (TEM) image. Furthermore, the term "inorganic oxide hollow particles" refers to hollow particles whose outer shells that define a hollow part are made of an inorganic oxide.

The inorganic oxide hollow particles of the present invention have an outer shell composed of an inorganic oxide containing boron oxide, calcium oxide, aluminum oxide, and silicon oxide, and have a mass ratio of aluminum oxide to silicon oxide (aluminum oxide to silicon oxide). oxide/silicon oxide) is higher than that of conventionally known inorganic oxide hollow particles. As a result, inorganic oxide hollow particles having a lower dielectric constant and a lower dielectric loss tangent than conventional ones and excellent dielectric properties can be obtained.

As the boron oxide, B ₂ O ₃ is preferable from the viewpoint of reducing the dielectric constant and dielectric loss tangent.
As the calcium oxide, CaO is preferable from the viewpoint of reducing the dielectric constant and dielectric loss tangent.
As the aluminum oxide, Al ₂ O ₃ is preferable from the viewpoint of reducing the dielectric constant and dielectric loss tangent.
As the silicon oxide, SiO ₂ is preferable from the viewpoint of reducing the dielectric constant and the dielectric loss tangent.

The inorganic oxide hollow particles of the present invention have a mass ratio of aluminum oxide to silicon oxide (aluminum oxide/silicon oxide) of 0.35 or more, but from the viewpoint of reducing the relative permittivity and dielectric loss tangent. , preferably 0.37 or more, more preferably 0.39 or more, and even more preferably 0.41 or more. The upper limit of the mass ratio of aluminum oxide and silicon oxide (aluminum oxide/silicon oxide) is not particularly limited, but from the viewpoint of reducing the relative permittivity and dielectric loss tangent, it is preferably 0.70 or less, and 0.70 or less. It is more preferably 65 or less, even more preferably 0.60 or less, and even more preferably 0.58 or less.

The content of boron oxide in the inorganic oxide hollow particles of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, and 13% by mass or more from the viewpoint of reducing the relative permittivity and dielectric loss tangent. More preferably 17% by mass or more, even more preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, even more preferably 35% by mass or less, still more preferably 30% by mass or less. Preferably, 25% or less is even more preferable.

The content of calcium oxide in the inorganic oxide hollow particles of the present invention is preferably 3% by mass or more, more preferably 5% by mass or more, and 7% by mass or more from the viewpoint of reducing the relative permittivity and dielectric loss tangent. More preferably, 9% by mass or more, even more preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, even more preferably 25% by mass or less, still more preferably 20% by mass or less. It is preferably 15% by mass or less, more preferably 12% by mass or less, even more preferably 12% by mass or less.

The content of aluminum oxide in the inorganic oxide hollow particles of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, and 14% by mass or more from the viewpoint of reducing the relative permittivity and dielectric loss tangent. It is more preferably 18% by mass or more, even more preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, even more preferably 25% or less.

The content of silicon oxide in the inorganic oxide hollow particles of the present invention is preferably 20% by mass or more, more preferably 30% by mass or more, and 35% by mass or more from the viewpoint of reducing the relative permittivity and dielectric loss tangent. More preferably 40% by mass or more, even more preferably 70% by mass or less, more preferably 65% by mass or less, even more preferably 60% by mass or less, even more preferably 55% by mass or less, and less than 50% by mass. Especially preferred.

Note that in this specification, each content of the inorganic oxide constituting the outer shell is a value obtained by measuring the chemical components in terms of oxides by fluorescent X-ray analysis.

The inorganic oxide hollow particles of the present invention may further contain an inorganic oxide other than the above as an inorganic oxide constituting the outer shell. For example, magnesium oxide can be contained from the viewpoint of reducing the dielectric constant and dielectric loss tangent.
As the magnesium oxide, MgO is preferable from the viewpoint of reducing the dielectric constant and dielectric loss tangent.
The content of magnesium oxide in the inorganic oxide hollow particles of the present invention is preferably 7% by mass or less, more preferably 5% by mass or less, and 3% by mass or less from the viewpoint of reducing the dielectric constant and dielectric loss tangent. More preferred. The lower limit of the content of magnesium oxide is not particularly limited and may be 0% by mass, but preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and 0.1% by mass. The above is more preferable.

Further, the inorganic oxide hollow particles of the present invention may further contain a Group 1 element oxide as an inorganic oxide constituting the outer shell.
Examples of Group 1 element oxides include lithium oxide, sodium oxide, potassium oxide, rubidium oxide, and cesium oxide. Among these, sodium oxide and potassium oxide are preferred. As the sodium oxide, Na ₂ O is preferred, and as the potassium oxide, K ₂ O is preferred. Note that one type or two or more types of Group 1 element oxides can be contained.

The content of the Group 1 element oxide in the inorganic oxide hollow particles of the present invention is preferably as small as possible from the viewpoint of reducing the relative permittivity and dielectric loss tangent. The content of the Group 1 element oxide in the inorganic oxide hollow particles of the present invention is, for example, preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and 0. .2% by mass or less is even more preferable. Note that the lower limit of the content of the Group 1 element oxide in the inorganic oxide hollow particles of the present invention is not particularly limited, and may be 0% by mass, but the softening point of the glass component may be appropriately controlled. From the viewpoint of this, the content is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, and even more preferably 0.01% by mass or more. Note that the content of Group 1 element oxides is the total amount of Group 1 element oxides, and the above content is applied even when only one type of Group 1 element oxide is contained.

Furthermore, the inorganic oxide hollow particles of the present invention contain, for example, a group 2 element oxide or a group 4 element oxide other than calcium oxide and magnesium oxide as the inorganic oxide constituting the outer shell. It's okay.
Examples of Group 2 element oxides other than calcium oxide and magnesium oxide include SrO, BaO, and RaO. Furthermore, examples of the Group 4 element oxide include TiO ₂ , ZrO ₂ , and HfO ₂ .
Note that the content of these inorganic oxides can be appropriately selected within a range that does not impede the effects of the present invention.

As shown in FIG. 1, the inorganic oxide hollow particles of the present invention may have a plurality of independent spaces in which a cavity covered with an outer shell is separated by one or more partition walls. Since the independent spaces are formed by cells that are separated by partition walls and do not communicate with each other (hereinafter also referred to as "independent cells"), the relative permittivity and dielectric loss tangent can be lowered. The "outer shell" here refers to the wall located on the surface side of the particle, which is in contact with only one closed cell inside the particle, and the "partition wall" refers to the wall between two adjacent cells inside the particle. A wall that separates closed cells from each other. Note that when the inorganic oxide hollow particles of the present invention have closed cells, the outer shell and partition walls are formed of the inorganic oxide described above.

Further, the inorganic oxide hollow particles of the present invention are preferably non-porous with no openings in the outer shell from the viewpoint of reducing the relative permittivity and dielectric loss tangent. In particular, by forming inorganic oxide hollow particles with closed cells and no pores, the closed cells are completely sealed, which not only further reduces the relative dielectric constant and dielectric loss tangent, but also provides excellent heat insulation. The particle strength can be increased by the multiple partition walls of closed cells. Note that the fact that the outer shell is porous can be confirmed by a scanning electron microscope (SEM) image or by floating on water.

Further, the inorganic oxide hollow particles of the present invention are preferably non-agglomerated primary particles from the viewpoint of reducing the dielectric constant and dielectric loss tangent. Moreover, it is possible to clearly distinguish them from porous particles and secondary particles by scanning electron microscopy (SEM) images.

In the inorganic oxide hollow particles of the present invention, the voidage ratio is preferably 60% or more, more preferably 65% or more, and still more preferably 70% or more, from the viewpoint of reducing the dielectric constant and dielectric loss tangent. In addition, from the viewpoint of ensuring sufficient strength, the upper limit value of the voidage ratio is preferably 95% or less, and more preferably 90% or less. Here, in this specification, the "void ratio" is a value calculated by the following formula from the measured bulk density and true density of particles using a dry automatic densitometer. Note that since it is difficult to measure individual particles, the void ratio is shown as a group of particles. In addition, the "true density" shall be measured by heating the product at a temperature above the melting point in a box-type electric furnace for 6 hours in order to remove hollow portions, cooling it, and using a dry automatic density meter. As a dry automatic density meter, for example, Accupic (Shimadzu Corporation) can be used.

Cavity ratio = (true density - bulk density) x 100/true density

Since the inorganic oxide hollow particles of the present invention are minute particles, they can be easily applied to electronic device parts that need to be made smaller and thinner. More specifically, the average particle diameter of the inorganic oxide hollow particles of the present invention is usually 10 μm or less, preferably 8 μm or less, more preferably 7 μm or less, still more preferably 6 μm or less, and more More preferably, it is 5 μm or less. Note that the lower limit of the average particle diameter is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more, from the viewpoint of ensuring sufficient cavities. Here, in this specification, the "average particle diameter" refers to the particle diameter (D _{50 )} corresponding to 50% of the integrated distribution curve when the particle size distribution of the sample is created on a volume basis in accordance with JIS R 1629. means. Note that, for example, a laser diffraction/scattering type particle size distribution measuring device can be used for measuring the particle size distribution.

The shape of the inorganic oxide hollow particles of the present invention is preferably non-spherical. By making it non-spherical, when added to resin etc., the contact area between the particles is small, and further reduction in thermal conductivity can be expected. When the average circularity of the inorganic oxide hollow particles is usually 0.85 or more, preferably 0.90 or more, it is determined that the inorganic oxide hollow particles are approximately spherical. In this specification, the circularity of 100 particles is measured, and the average value is defined as the average circularity. Note that the circularity can be calculated using the following procedure. First, the projected area (A) and perimeter length (PM) of the particles are measured from a scanning electron micrograph. If the area of a perfect circle relative to the perimeter (PM) is (B), the circularity of the particle is expressed as A/B. Here, the perimeter and area of a perfect circle with the same perimeter as the particle perimeter (PM) are expressed as PM = 2πr and B = πr ^2, respectively, so B = π x (PM/2π) It becomes ² . Therefore, the circularity of the particles can be calculated by circularity=A/B=A×4π/(PM) ² .

The inorganic oxide hollow particles of the present invention have a particle density of usually 0.1 to 1.5 g/cm ³ , preferably 0.2 to 1.0 g/cm ³ , more preferably 0.3 g/cm 3 . ~0.8 g/ ^cm3 . Note that the particle density can be measured by a gas displacement method in accordance with JIS R 1620. As the particle density measuring device, for example, a dry automatic density meter "Accupic" (manufactured by Shimadzu Corporation) can be used.

The inorganic oxide hollow particles of the present invention preferably have a relative dielectric constant of 3 or less at 1 GHz, more preferably 2.8 or less, and 2.5 or less from the viewpoint of lowering the dielectric constant and lowering the dielectric loss tangent. It is more preferably 2.2 or less, even more preferably 2 or less, and even more preferably 2 or less.
Further, from the viewpoint of lowering the dielectric constant and lowering the dielectric loss tangent, the inorganic oxide hollow particles of the present invention preferably have a dielectric loss tangent of 0.005 or less at 1 GHz, more preferably 0.004 or less, and 0.005 or less at 1 GHz. 003 or less is more preferable.
Here, in this specification, "relative permittivity" and "dielectric loss tangent" are measured at 1 GHz in an environment of a temperature of 25° C. and a humidity of 60%. Note that the dielectric constant and the dielectric loss tangent can be measured using, for example, a perturbation type cavity resonator (manufactured by KEYCOM).

The inorganic oxide hollow particles of the present invention can be applied to heat insulating materials, heat shielding materials, catalyst carriers, building materials, electronic materials, etc., and are microparticles with low relative dielectric constant and dielectric loss tangent, and high strength. Therefore, it is useful for electronic materials, especially printed circuit boards, semiconductor sealing materials, etc.

The method for producing inorganic oxide hollow particles of the present invention is not particularly limited as long as inorganic oxide hollow particles having the above structure can be obtained, but for example, a liquid to be sprayed containing a raw material compound is installed in a spray pyrolysis apparatus A method of spraying from a spray device and thermally decomposing the sprayed droplets (mist) can be mentioned.

Examples of the raw material compound include compounds containing boron, calcium, aluminum, or silicon as elements constituting the inorganic oxide. Such a compound is not particularly limited as long as it is a compound that dissolves in water, but examples thereof include inorganic salts, organic salts, and alkoxides, and one or more of them may be contained. Examples of inorganic salts include nitrates, sulfates, carbonates, hydroxides, and halides. Examples of organic salts include formates, acetates, propionates, oxalates, and citrates.

Examples of the boron-containing compound include borate and boric acid. Examples of borates include metaborate salts such as sodium borate and potassium borate, tetraborate salts such as sodium tetraborate and potassium tetraborate, and pentaborate salts such as sodium pentaborate and potassium pentaborate. Mention may be made of acid salts.

Examples of the calcium-containing compound include calcium salts such as calcium nitrate, calcium chloride, calcium hydroxide, calcium formate, calcium acetate, and calcium propionate.

Examples of aluminum-containing compounds include inorganic salts such as aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum phosphate, aluminum hydroxide, aluminum acetate, and aluminum oxalate, and aluminum such as aluminum methoxide, aluminum ethoxide, and aluminum isopropoxide. Mention may be made of alkoxides. Further, an aluminosilicate, a solution of aluminum oxide dispersed in a solvent, and a sol solution of aluminum oxide can also be used as the raw material compound solution. Examples of the aluminosilicate include sodium aluminosilicate, potassium aluminosilicate, and calcium aluminosilicate.

Examples of silicon-containing compounds include silicate alkoxides. Examples of the silicate alkoxide include tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS), and tetrabutoxysilane. Further, a solution of silicon oxide dispersed in a solvent or a sol solution of silicon oxide can also be used as the raw material compound solution.

In the present invention, a compound containing an element other than boron, calcium, aluminum, and silicon may be further included as a raw material compound.
Such a compound is not particularly limited as long as it is a metal compound that dissolves in water, and examples thereof include magnesium-containing compounds and Group 1 element-containing compounds. Examples of these compounds include inorganic salts, organic salts, and alkoxides, and specific examples thereof are as explained above.

Examples of the magnesium-containing compound include magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium phosphate, and magnesium hydroxide.

The Group 1 element-containing compound is not particularly limited as long as it is a compound containing a Group 1 element, and examples include lithium-containing compounds, sodium-containing compounds, potassium-containing compounds, rubidium-containing compounds, and cesium-containing oxides. Examples of sodium-containing compounds include sodium chloride, sodium hydroxide, and sodium sulfate. Note that the same inorganic salts as for the sodium-containing compound can be used in the lithium-containing compound, the potassium-containing compound, the rubidium-containing compound, and the cesium-containing oxide.

Inorganic oxides obtained from these raw material compounds include, for example, boron oxide, calcium oxide, alumina, silica, as well as Group 1 element oxides such as sodium oxide and lithium oxide, and magnesium oxide. A combination of composite oxides can also be mentioned.

The liquid to be sprayed may be prepared by mixing a raw material compound with water or an organic solvent such as ethanol. The blending ratio of the raw material compounds may be adjusted as appropriate depending on the type of the raw material compounds so that the inorganic oxide hollow particles have the composition described above.

The concentration of the raw material compound in the liquid to be sprayed is preferably 0.01 mol/L to 2.0 mol/L, more preferably 0.1 mol/L to 1.0 mol/L, in terms of the total amount of each element.

In the spray pyrolysis apparatus, the pyrolysis furnace preferably has a rigid cylindrical shape, and the size of the pyrolysis furnace can be appropriately selected depending on the production scale.

Examples of the spray device include fluid nozzles such as a two-fluid nozzle, a three-fluid nozzle, and a four-fluid nozzle. Here, the fluid nozzle method includes an internal mixing method in which the gas and the raw material solution are mixed inside the nozzle, and an external mixing method in which the gas and the raw material solution are mixed outside the nozzle, and either of these methods can be adopted. As the gas supplied to the nozzle, for example, air, an inert gas such as nitrogen, argon, etc. can be used. Among them, air is preferred from the viewpoint of economy. Note that one or more spray devices may be installed.

The flow rate of the liquid to be sprayed is usually 1 to 100 L/h, preferably 3 to 80 L/h, and more preferably 5 to 60 L/h.

The droplets sprayed from the spray device are heated by a heating device in the pyrolysis furnace to form a film containing an inorganic compound, and from this film, inorganic oxide hollow particles are formed.
The jetting speed of droplets is usually 1 to 50 m/s, preferably 5 to 35 m/s, and more preferably 10 to 20 m/s.

Examples of the heating device include a combustion burner, a hot air heater, and an electric heater. One or more heating devices can be installed. Note that any commonly available combustion burner, hot air heater, and electric heater can be used.
The temperature of the heating device is preferably 400 to 1800°C, more preferably 600 to 1500°C, even more preferably 700 to 1400°C, even more preferably 800 to 1200°C. At such a temperature, thermal decomposition will be sufficient, and particles will be less likely to aggregate with each other when they are discharged outside the pyrolysis furnace.

The inorganic oxide hollow particles produced by the pyrolysis reaction are recovered from the downstream side of the pyrolysis furnace. The inorganic oxide hollow particles can be recovered using a high-performance cyclone powder recovery machine or a powder recovery device using a bag filter.

In addition, in the present invention, the recovered inorganic oxide hollow particles are stirred and mixed with ethanol, the particles are once immersed in ethanol, and only the particles floating on the liquid surface are collected, thereby producing an inorganic material having closed cells. Oxide hollow particles can be obtained with high purity. The amount of ethanol used is usually 5 to 20 times the mass of the inorganic oxide hollow particles, preferably 10 to 15 times the mass of the inorganic oxide hollow particles.

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

1. Analysis of chemical composition Inorganic oxide hollow particles were molded using a press to make briquettes, and the briquettes were measured in terms of oxide using a fluorescent X-ray analyzer (ZSX primus II, manufactured by Rigaku Corporation) to determine the chemical composition. Calculated.

2. Analysis of particle density Particle density was measured by a constant volume expansion method using a dry automatic densitometer (Accupic 1340, manufactured by Shimadzu Corporation). That is, after putting a sample into a cell, the cell was filled with an inert gas, the volume of the sample was measured, and the particle density was determined from this volume and the mass of the sample measured in advance.

3. Analysis of void ratio Using Accupic (manufactured by Shimadzu Corporation) as a dry automatic density meter, the bulk density and true density of the particles were measured and calculated using the following formula. In addition, "bulk density" was measured by the gas displacement method based on JIS R 1620. In addition, the true density was measured using a dry automatic densitometer after heating the sample for 6 hours above the melting point in a box-type electric furnace to remove the hollow portion, and then cooling the sample.

Cavity ratio = (true density - bulk true density) x 100/true density

4. Analysis of average particle size Using a particle size distribution measuring device (MT3000II, manufactured by Microtrack Bell Co., Ltd.), a volume-based particle size distribution was created in accordance with JIS R 1629, and the particle size corresponding to 50% of the integrated distribution curve ( _D50 ) was calculated.

5. Analysis of relative permittivity and dielectric loss tangent Measurements were made at 1 GHz using a perturbation type cavity resonator (manufactured by KEYCOM) in an environment of a temperature of 25° C. and a humidity of 60%.

The raw materials used in this example are shown in the table below.

Examples 1 to 11 and Comparative Examples 1 to 7
A Si source, an Al source, an a source, a Mg source, a B source, a Na source, and a K source in the proportions shown in Table 2 and water were placed in a reaction vessel, and the raw material inorganic compound-containing aqueous solution was heated for 3 hours. Stirred. Next, this raw material inorganic compound-containing aqueous solution is sent to a two-fluid nozzle, and the raw material inorganic compound-containing aqueous solution is sprayed from the nozzle into a spray pyrolysis furnace, and fired at the temperature shown in Table 2 to form inorganic oxide hollow particles. Recovered. Note that the operating conditions of the two-fluid nozzle were such that the nozzle air amount was set to 500 L/min, and the liquid feeding amount was set to 500 mL/min. Further, in Examples 8 and 9, the amount of air supplied to the nozzle was set to 3,000 L/min to form a fine mist.
Next, 20 g of the recovered inorganic oxide hollow particles were stirred and mixed with 300 g of ethanol, and after the particles were once immersed in ethanol, only the particles floating on the liquid surface were collected. Then, the collected inorganic oxide hollow particles were analyzed. The results are shown in Table 2. Further, a SEM image of the inorganic oxide hollow particles collected in Example 1 is shown in FIG.

From Table 2, inorganic oxide hollow particles with a mass ratio of aluminum oxide to silicon oxide (aluminum oxide/silicon oxide) of 0.35 or more have a low relative dielectric constant and dielectric loss tangent, and have a low dielectric constant and dielectric loss tangent. It can be seen that it has excellent characteristics. The particles obtained in Examples 1 to 11 were all inorganic oxide hollow particles having closed cells.

Claims (12)

Contains boron oxide, calcium oxide, aluminum oxide and silicon oxide,
The mass ratio of aluminum oxide to silicon oxide (aluminum oxide/silicon oxide) is 0.35 or more,
Inorganic oxide hollow particles. The inorganic oxide hollow particles according to claim 1, wherein the content of boron oxide is 5 to 50% by mass. The inorganic oxide hollow particles according to claim 1, wherein the content of calcium oxide is 3 to 40% by mass. The inorganic oxide hollow particles according to claim 1, wherein the content of aluminum oxide is 5 to 40% by mass. The inorganic oxide hollow particles according to claim 1, wherein the content of silicon oxide is 20 to 70% by mass. The inorganic oxide hollow particles according to claim 1, further comprising magnesium oxide and having a content of magnesium oxide of 7% by mass or less. The inorganic oxide hollow particles according to claim 1, having a dielectric loss tangent of 0.005 or less. The inorganic oxide hollow particles according to claim 1, having a dielectric constant of 3 or less. The inorganic oxide hollow particles according to claim 1, having a voidage ratio of 60% or more. The inorganic oxide hollow particles according to claim 1, having an average particle diameter of 10 μm or less. The inorganic oxide hollow particle according to any one of claims 1 to 10, wherein the inorganic oxide hollow particle has a plurality of independent spaces in which a cavity covered with an outer shell is separated by one or more partition walls. material hollow particles. The inorganic oxide hollow particles according to claim 11, wherein the outer shell is porous.