JP2023019772A - Aluminosilicate hollow particle - Google Patents

Abstract

To provide an aluminosilicate hollow particle having a low bulk density and a high compressibility ratio.SOLUTION: In an aluminosilicate hollow particle, a bulk density is 0.015 g/cm3 or less, and a compressibility ratio is 85% or more.SELECTED DRAWING: None

Description

The present invention relates to aluminosilicate hollow particles.

Inorganic oxide hollow particles are used in the fields of heat insulating materials, heat insulating materials, soundproofing/sound absorbing materials, catalyst carriers, building materials, and electronic materials. For example, the inorganic oxide hollow particles are fine aluminosilicate hollow particles having shells defining hollow chambers, and have a structural composition with a SiO ₂ content of 70 to 90% by mass and an Al ₂ O ₃ content of 10 to 30% by mass. , the Fe ₂ O ₃ content is 1% by mass or less, the average circularity is 0.85 or more, the average particle size is 1 μm to 20 μm, the shell thickness is 500 nm or less, and the softening start temperature is 1100° C. or more. Certain fine aluminosilicate hollow particles are known (Patent Document 1).

JP 2016-121026 A

Hollow aluminosilicate particles have cavities surrounded by outer shells, so they are lighter than non-hollow particles, but a low bulk density is advantageous for further weight reduction. However, when the bulk density of the aluminosilicate hollow particles is lowered, the volume increases, which increases labor and costs during transportation. In this case, if the aluminosilicate hollow particles can be compressed without being damaged, the volume can be reduced, and the load during transportation can be reduced.
An object of the present invention is to provide hollow aluminosilicate particles having a low bulk density and a high compressibility.

The inventors of the present invention have conducted studies in view of the above problems, and have found hollow aluminosilicate particles that have a lower bulk density and a higher compressibility than conventional ones.

That is, the present invention provides the following [1] to [4].
[1] Hollow aluminosilicate particles having a bulk density of 0.015 g/cm ³ or less and a compressibility of 85% or more.
[2] The aluminosilicate hollow particles according to [1] above, which have a circularity of 0.70 or less.
[3] The aluminosilicate hollow particles according to [1] or [2] above, which have an angle of repose of 50° or more.
[4] The aluminosilicate hollow particles according to any one of [1] to [3], which have a BET specific surface area of 15 m ² /g or more.

According to the present invention, hollow aluminosilicate particles having a low bulk density and a high compressibility can be provided.

As used herein, the term "aluminosilicate" refers to a compound in which a portion of silicon in silicate is replaced with aluminum, and the total content of _SiO2 and _Al2O3 is 65% by mass or more _. say.
In addition, the term “hollow particles” as used herein refers to particles having cavities (hollow structure) inside. The cavity is enclosed by the shell and may have one or more. Hollow particles therefore differ from porous particles, which have a plurality of pores extending from the surface of the particle into the interior. The hollow particles can be clearly distinguished from the porous particles by scanning electron microscope (SEM) images.

The aluminosilicate hollow particles of the present invention have an outer shell made of aluminosilicate.
In the aluminosilicate hollow particles of the present invention, the total content of SiO ₂ and Al ₂ O ₃ is 65% by mass or more, but from the viewpoint of low bulk density and high compressibility, it is preferably 70% by mass or more, and 75% by mass. % or more, and more preferably 80 mass % or more. The upper limit of the total content of SiO ₂ and Al ₂ O ₃ may be 100% by mass.
Further, the mass ratio of SiO ₂ and Al ₂ O ₃ (Al ₂ O ₃ /SiO ₂ ) is preferably 0.2 to 0.3, more preferably 0.21 to 0.2, from the viewpoint of low bulk density and high compressibility. 0.28 is more preferred, and 0.23 to 0.26 is even more preferred.

From the viewpoint of low bulk density and high compressibility, the content of SiO ₂ in the aluminosilicate hollow particles is preferably 60% by mass or more, more preferably 61% by mass or more, still more preferably 63% by mass or more, and 65% by mass. % or more, preferably 80% by mass or less, more preferably 79% by mass or less, and even more preferably 78% by mass or less.
The content of Al ₂ O ₃ is preferably 15% by mass or more, more preferably 16% by mass or more, and still more preferably 17% by mass or more in the aluminosilicate hollow particles from the viewpoint of low bulk density and high compressibility. And it is preferably 25% by mass or less, more preferably 23% by mass or less, and even more preferably 21% by mass or less.

The aluminosilicate hollow particles of the present invention may contain metals other than silicon and aluminum to compensate for the loss of positive charge caused by replacing a portion of the silicon in the silicate with aluminum. Examples of metal oxides containing metals other than silicon and aluminum include group 1 element oxides, group 2 element oxides, boron oxides, and group 4 element oxides.

Examples of group 1 element oxides include _Li2O , _Na2O , _K2O , _Rb2O and _Cs2O .
Examples of Group 2 element oxides include MgO, CaO, SrO, BaO, and RaO.
B ₂ O ₃ is preferred as the boron oxide.
Examples of Group 4 element oxides include TiO ₂ , ZrO ₂ and HfO ₂ .

The content of metal oxides containing metals other than silicon and aluminum can be appropriately selected within a range that does not impair the effects of the present invention. For example, the following aspects are possible.
From the viewpoint of low bulk density and high compressibility, the content of the Group 2 element oxide is preferably 12% by mass or less, more preferably 10% by mass or less, and further 8% by mass or less in the aluminosilicate hollow particles. Preferably, 6% by mass or less is even more preferable. In addition, the lower limit of the content of the Group 2 element oxide is not particularly limited, and it may be 0% by mass in the aluminosilicate hollow particles. .5% by mass or more is preferable, 1% by mass or more is more preferable, and 2% by mass or more is even more preferable.
From the viewpoint of low bulk density and high compressibility, the content of boron oxide in the aluminosilicate hollow particles is preferably 20% by mass or less, preferably 19% by mass or less, more preferably 15% by mass or less, and 12% by mass. % or less is even more preferable. The lower limit of the content of boron oxide is not particularly limited, and it may be 0% by mass in the aluminosilicate hollow particles, but is preferably 0.1% by mass or more, more preferably 0.3% by mass. It can be at least 0.5% by mass, more preferably at least 0.5% by mass.

Among them, the metal oxide containing a metal other than silicon and aluminum is preferably one or more selected from Group 2 element oxides and B ₂ O ₃ from the viewpoint of low bulk density and high compressibility, MgO and B One or more selected from ₂ O ₃ is more preferable, and at least MgO is even more preferable.

The aluminosilicate hollow particles of the present invention are characterized by having a lower bulk density than conventional ones. Specifically, the bulk density of the aluminosilicate hollow particles of the present invention is preferably 0.015 g/cm ³ or less, more preferably 0.013 g/cm ³ or less, and even more preferably 0.012 g/cm ³ or less. Although the lower limit of the bulk density is not particularly limited, it is preferably 0.0001 g/cm ³ or more, more preferably 0.0005 g/cm ³ or more, and more preferably 0.001 g/cm ³ from the viewpoint of ensuring sufficient strength. The above is more preferable. In this specification, "bulk density" means "loose bulk density" and shall be measured according to JIS R 1628-1997.

The aluminosilicate hollow particles of the present invention are characterized by having a higher compressibility than conventional ones. Specifically, the compressibility of the aluminosilicate hollow particles of the present invention is preferably 85% or higher, more preferably 86% or higher, and even more preferably 87% or higher. From the viewpoint of ensuring sufficient strength, the upper limit of the degree of compression is preferably 97% or less, more preferably 95% or less, and even more preferably 93% or less. Here, the term "compressibility" as used herein refers to a value calculated by the following formula (1), and the "hard bulk density" in the following formula (1) is defined in accordance with JIS R 1628-1997. shall be measured. For the measurement of the loose bulk density and the firm bulk density, for example, a tap density meter JV200i (manufactured by COPLEY) can be used.

Compression rate c (%) = (ρ _p - ρ _A )/ρ _p ×100 (1)
[In the formula, ρ _A indicates a loose bulk density and ρ _p indicates a firm bulk density. ]

The shape of the aluminosilicate hollow particles of the present invention is preferably non-spherical. By making it non-spherical, it is possible to suppress an increase in volume even if the bulk density is low, so that it is possible to reduce labor and cost when transporting.

It can be judged from the degree of circularity that the aluminosilicate hollow particles of the present invention have a non-spherical particle shape. The circularity of the aluminosilicate hollow particles of the present invention is preferably 0.70 or less, more preferably 0.67 or less, and even more preferably 0.65 or less. It should be noted that when the degree of circularity is 0.85 or more, it is usually judged to be substantially spherical. As used herein, the term "circularity" refers to a value calculated by the following method. That is, the projected area (A) and perimeter (PM) of a particle are measured from a scanning electron micrograph, and if the area of a perfect circle with respect to the perimeter (PM) is (B), the degree of circularity of the particle is A/ Denoted as B. Here, since the perimeter and area of a perfect circle having the same perimeter as the perimeter (PM) of the sample particle are respectively PM=2πr and B=πr ² , B=π×(PM/2π) ² Thus, the circularity of this particle is calculated as circularity=A/B=A×4π/(PM) ² . Then, the circularity of 100 particles is measured, and the average value is taken as the "circularity" of the aluminosilicate hollow particles.
Further, the inorganic oxide hollow particles of the present invention preferably have a non-spherical particle shape, that is, the proportion of particles with a low degree of circularity is a specific proportion. A certain percentage of particles with low circularity improves compressibility. Specifically, when the circularity of the above 100 particles is measured, the number ratio of particles having a circularity of 0.5 or less is preferably 10% or more in all particles, and 20 % or more is more preferable. In addition, such a ratio may be 100% in all particles.

The aluminosilicate hollow particles of the present invention preferably have an angle of repose of 50° or more, more preferably 52° or more, and even more preferably 54° or more. Although the upper limit of the angle of repose is not particularly limited, it is preferably 70° or less, more preferably 65° or less, and even more preferably 60° or less from the viewpoint of improving handling properties. As used herein, the “angle of repose” shall be measured according to ISO 902. For measuring the angle of repose, for example, a powder tester PT-D type (manufactured by Hosokawa Powder Laboratory Co., Ltd.) can be used.

The aluminosilicate hollow particles of the present invention are characterized by having a large BET specific surface area. Specifically, the BET specific surface area of the aluminosilicate hollow particles of the present invention is preferably 15 m ² /g or more, more preferably 20 m ² /g or more, and even more preferably 25 m ² /g or more. Although the upper limit of the BET specific surface area is not particularly limited, it is preferably 45 m ² /g or less, more preferably 40 m ² /g or less, more preferably 35 m ² /g, from the viewpoint of increasing the surface pore volume and decreasing the particle strength. More preferred are: As used herein, the term "BET specific surface area" means a surface area measured by the BET method (method for measuring surface area using adsorption of gas molecules). FlowSorb III 2305 (manufactured by Shimadzu Corporation) can be used for measurement.

The hollowness of the aluminosilicate hollow particles of the present invention is preferably 29% or more, more preferably 30% or more, and even more preferably 31% or more. From the viewpoint of ensuring sufficient strength, the upper limit of the hollowness is preferably 95% or less, more preferably 90% or less. Here, the "hollowness" as used herein is a value calculated by the following formula from the values obtained by measuring the particle density and the true density of particles using a dry automatic densitometer. In addition, since it is difficult to measure individual particles, it is the void ratio as a particle group. Also, the "true density" shall be measured by a dry automatic densimeter after heating for 6 hours above the melting point in a box-shaped electric furnace in order to remove the hollow portion, and then cooling. As a dry automatic density meter, for example, Accupic (Shimadzu Corporation) can be used.

Hollowness ratio (%) = 1 - (particle density / true density) x 100

The aluminosilicate hollow particles of the present invention are fine particles. More specifically, the particle size distribution can have the following characteristics. As used herein, the term "particle size distribution" refers to a volume-based particle size distribution measured according to JIS R 1629 "Method for measuring particle size distribution of fine ceramic raw materials by laser diffraction/scattering method". The particle size distribution is represented by a distribution curve in which the horizontal axis is the particle diameter (μm) and the vertical axis is the volume-based frequency (%). For example, Microtrac (manufactured by Nikkiso Co., Ltd.) can be used as a particle size distribution measuring device using a laser diffraction/scattering method.

For example, the cumulative 10% particle diameter (D10) in the volume-based particle size distribution is preferably 0.05 µm or more, more preferably 0.1 µm or more, still more preferably 0.3 µm or more, and preferably 3.0 µm or less. 0.5 μm or less is more preferable, and 2.0 μm or less is even more preferable.
The cumulative 50% particle diameter (D50) in the volume-based particle size distribution is preferably 1.0 μm or more, more preferably 1.5 μm or more, still more preferably 2.0 μm or more, and preferably 7.0 μm or less, and 6.0 μm The following is more preferable, and 5.0 μm or less is even more preferable.
Cumulative 90% particle diameter (D90) in volume-based particle size distribution is preferably 5.0 μm or more, more preferably 7.0 μm or more, still more preferably 9.0 μm or more, and preferably 20.0 μm or less, 15.0 μm The following are more preferable, and 10.0 μm or less is even more preferable.

The aluminosilicate hollow particles of the present invention are preferably amorphous. The fact that the material is amorphous can be confirmed by analyzing the X-ray diffraction pattern obtained by an X-ray diffractometer. As an X-ray diffraction device, for example, Bruker D8 advance (manufactured by Bruker AXS Co., Ltd.) can be used.

Since the aluminosilicate hollow particles of the present invention have the properties described above, they can be applied to various uses. For example, it can be applied to fields such as heat insulating materials, heat insulating materials, soundproofing/sound absorbing materials, catalyst carriers, building materials, and electronic materials. , heat insulating materials, soundproofing/sound absorbing materials, building materials, electronic materials, and other fillers.

The method for producing hollow aluminosilicate particles of the present invention is not particularly limited as long as the hollow aluminosilicate particles having the above configuration can be obtained. A method of spraying from a spray device and thermally decomposing the sprayed droplets (mist) can be mentioned.

Examples of raw material compounds include compounds containing silicon and aluminum as elements constituting oxides. Such a compound is not particularly limited as long as it is a compound that dissolves in water. Examples thereof include inorganic salts, organic salts, and alkoxides, and may contain one or more. Inorganic salts include, for example, nitrates, sulfates, carbonates, hydroxides, and halides. Organic salts include, for example, formates, acetates, propionates, oxalates, and citrates.

Silicon-containing compounds include, for example, silicic acid alkoxides. Examples of silicate alkoxides include tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS), and tetrabutoxysilane. A solution of silicon oxide dispersed in a solvent and a sol solution of silicon oxide can also be used as the raw material compound solution.
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, aluminum such as aluminum methoxide, aluminum ethoxide and aluminum isopropoxide. Alkoxides may be mentioned. 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 aluminosilicates include sodium aluminosilicate, potassium aluminosilicate, and calcium aluminosilicate.

In the present invention, the raw material compound may further contain a compound containing an element other than silicon and aluminum.
Such a compound is not particularly limited as long as it is a metal compound that dissolves in water. For example, one or more elements selected from Group 1 elements, Group 2 elements, boron and Group 4 elements can be mentioned. Among them, compounds containing one or more elements selected from Group 2 elements and boron are preferred, compounds containing one or more elements selected from magnesium and boron are more preferred, and compounds containing at least magnesium are further preferred. preferable. Examples of salts of these metals include inorganic salts, organic salts and alkoxides. Specific examples of inorganic salts and organic salts are as described above. Examples of boron-containing compounds include metaborates such as sodium borate and potassium borate, sodium tetraborate and potassium tetraborate. tetraborate such as sodium pentaborate, pentaborate such as potassium pentaborate, and boric acid. Examples of magnesium-containing compounds include magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium phosphate, and magnesium hydroxide.

Examples of oxides obtained from these raw material compounds include silicon oxide, alumina, boron oxide, and magnesium oxide, and composite oxides obtained by combining these oxides.

The liquid to be sprayed can be prepared by mixing the raw material compound with water or an organic solvent such as ethanol. The mixing ratio of the raw material compounds may be appropriately adjusted according to the type of the raw material compounds so that the aluminosilicate hollow particles having the composition described above are obtained.

The raw material compound concentration 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, as 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 spray devices include fluid nozzles such as two-fluid nozzles, three-fluid nozzles, and four-fluid nozzles. Here, the fluid nozzle system includes an internal mixing system in which the gas and the raw material solution are mixed inside the nozzle and an external mixing system in which the gas and the raw material solution are mixed outside the nozzle, and both can be employed. As the gas supplied to the nozzle, for example, air, inert gas such as nitrogen or argon, or the like can be used. Among them, air is preferable from the viewpoint of economy. One or two or more spray devices can be installed.

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

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

Examples of the heating device include combustion burners, hot air heaters, electric heaters, and the like. One or more heating devices can be installed. Any commercially 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, and even more preferably 800 to 1200°C. At such a temperature, thermal decomposition is sufficient, and the particles are less likely to agglomerate when discharged from the thermal decomposition furnace.

Hollow aluminosilicate particles produced by the pyrolysis reaction are recovered from the downstream side of the pyrolysis furnace. A high-performance cyclone powder recovery machine or a powder recovery device using a bag filter can be used to recover the aluminosilicate hollow particles.

EXAMPLES The embodiments of the present invention will now be described more specifically with reference to Examples. However, the present invention is not limited to the following examples.

1. Analysis of chemical composition Hollow aluminosilicate particles were molded with a press to prepare briquettes, and the briquettes were measured in terms of oxides using a fluorescent X-ray spectrometer (ZSX primus II, manufactured by Rigaku) to calculate the chemical components. . Each chemical component was calculated by correcting with the following formula so that the total value of the oxides (SiO ₂ , Al ₂ O ₃ MgO, B ₂ O) of the elements to be analyzed would be 100%.

Chemical composition (after correction) (%) = chemical composition (before correction) x 100/(100-impurities (%))
[In the formula, the impurity (%) is obtained by subtracting the total value of the chemical composition of the oxides described above from 100. ]

2. Measurement of Bulk Density Measured according to JIS R 1628-1997 using a tap density meter JV200i (manufactured by COPLEY).

3. Measurement of compression rate The compression rate was calculated by the following formula (1).

Compression ratio c (%) = (ρp-ρA)/ρp × 100 (1)
[In the formula, ρA indicates a loose bulk density, and ρp indicates a firm bulk density. ]

4. Measurement of Particle Density, True Density, and Hollow Ratio An Accupic (manufactured by Shimadzu Corporation) was used as a dry automatic densitometer to measure the particle density and true density of the particles, and the values were calculated according to the following equations. The true density was measured with a dry automatic densitometer after heating at the melting point or higher for 6 hours in a box-type electric furnace to remove hollow portions, followed by cooling.

Hollowness ratio (%) = (1-particle density/true density) x 100

5. Measurement of angle of repose Measured according to ISO 902 using a powder tester PT-D type (manufactured by Hosokawa Powder Laboratory Co., Ltd.).

6. Measurement of Circularity The projected area (A) and perimeter (PM) of a particle are measured from a scanning electron micrograph. Expressed as A/B. Here, since the perimeter and area of a perfect circle having the same perimeter as the perimeter (PM) of the sample particle are respectively PM=2πr and B=πr ² , B=π×(PM/2π) ² Thus, the circularity of this particle is calculated as circularity=A/B=A×4π/(PM) ² . Then, the circularity of 100 particles was measured, and the average value was taken as the "circularity" of the aluminosilicate hollow particles. At that time, the number ratio of particles having a circularity of 0.5 or less was determined. As a scanning electron microscope, JSM-7001F (manufactured by JEOL Ltd.) was used.

7. Analysis of crystal structure Measurement was performed using a powder X-ray diffractometer (Bruker D8 advance, manufactured by Bruker AXS Co., Ltd.), and the crystal structure was analyzed from the obtained X-ray diffraction pattern.

8. Particle size measurement Using a particle size distribution measuring device (MT3000II, manufactured by Microtrack Bell), a volume-based particle size distribution is created in accordance with JIS R 1629, and the cumulative 10% particle size (D10) in the volume-based particle size distribution. Then, the cumulative 50% particle size (D50) in the volume-based particle size distribution and the cumulative 90% particle size (D90) in the volume-based particle size distribution were determined.

9. Measurement of BET specific surface area The BET specific surface area was measured using an automatic flow-type specific surface area measuring device (FlowSorb III 2305, manufactured by Shimadzu Corporation). A nitrogen-helium mixed gas containing 30% nitrogen was used for the measurement.

Examples 1 to 3 and Comparative Example 1
Raw material compounds (colloidal silica, tetraethyl orthosilicate, aluminum nitrate nonahydrate, magnesium nitrate hexahydrate, boric acid) were dissolved in 30 liters of distilled water so as to have a molar concentration shown in Table 1, and an aqueous raw material compound solution was prepared. was put into the solution tank. The introduced aqueous solution was sent to a two-fluid nozzle by a liquid-sending pump, sprayed in a mist form from the two-fluid nozzle, and heated in a furnace (1000° C.). The operating conditions of the two-fluid nozzle were set such that the nozzle air amount was 100 L/min and the liquid feeding amount was 67 mL/min. Then, it was quenched by a cooling mechanism installed at the outlet of the reaction zone of the furnace, and then the aluminosilicate hollow particles were collected using a bag filter. The physical properties of the recovered aluminosilicate hollow particles were analyzed. Table 2 shows the results.

It can be seen that the aluminosilicate hollow particles of Examples 1 to 3 have a lower bulk density and a higher compressibility than the aluminosilicate hollow particles of Comparative Example 1. In addition, the hollow aluminosilicate particles of Examples 1 to 3 differ in shape from the hollow aluminosilicate particles of Comparative Example 1 in that they are non-spherical, and compared to the hollow aluminosilicate particles of Comparative Example 1, the angle of repose is also BET ratio. It can be seen that the surface area is also large.

Claims (5)

Hollow aluminosilicate particles having a bulk density of 0.015 g/cm ³ or less and a compressibility of 85% or more. 2. The aluminosilicate hollow particles according to claim 1, having a circularity of 0.70 or less. 3. The aluminosilicate hollow particles according to claim 1, having an angle of repose of 50° or more. The aluminosilicate hollow particles according to any one of claims 1 to 3, having a BET specific surface area of 15 m ² /g or more. 5. The inorganic oxide hollow particles according to any one of claims 1 to 4, wherein the number ratio of particles having a circularity of 0.5 or less is 10% or more in all particles.