Inorganic oxide hollow particles

Abstract

Provided are inorganic oxide hollow particles having a carbon content of 0.0060-0.055 mass%.

Description

Inorganic oxide hollow particles 【0001】 This invention relates to inorganic oxide hollow particles. 【0002】 Inorganic oxide hollow particles, having a cavity surrounded by an outer shell, are lighter than non-hollow particles, have low thermal conductivity, and excellent thermal stability, making them widely used as thermal insulation materials, heat shielding materials, catalyst supports, building materials, and electronic materials. In recent years, the performance and miniaturization of electronic devices have progressed rapidly, and there is a growing demand for thinner coatings, resin products, and film products used in electronic devices. As a result, the inorganic oxide hollow particles used in these products need to be extremely small. 【0003】 Conventionally, as minute inorganic oxide hollow particles, for example, a minute hollow glass sphere is known in which the average particle diameter is 5 to 50 μm and particles of 5 to 50 μm account for 80% or more of the total (Patent Document 1). In addition, an average particle diameter (by volume) of 15 μm or less, a maximum particle diameter of 45 μm or less, and a particle density of 0.5 g / cm³ are known. 3 The following and (d 10 -d 90 ) / d 50 There are also reports of micro-hollow glass spheres in which the particle size gradient calculated by is 2.0 or less, and the B2O3 content contained in the glass is 9.0 to 20.0% by mass (Patent Document 2). 【0004】 Japanese Patent Publication No. 9-20526, International Publication No. 2001 / 2314 【0005】 However, when minute inorganic oxide hollow particles are mixed with resin for use in electronic materials, if the inorganic oxide hollow particles are glassy, ​​they tend to become electrostatically charged due to collisions and friction during mixing. This raises concerns about poor handling due to particle aggregation and electrostatic discharge damage to electronic devices. The objective of the present invention is to provide inorganic oxide hollow particles that can suppress electrostatic discharge. 【0006】 The inventors have discovered that static electricity can be suppressed by incorporating a certain amount of carbon into hollow inorganic oxide particles. 【0007】The present invention provides the following [1] to

[13] : [1] Hollow inorganic oxide particles having a carbon content of 0.0060 to 0.055 mass%. [2] Hollow inorganic oxide particles according to [1], which are polyfoaming. [3] Hollow inorganic oxide particles according to [1] or [2], which are composed of an inorganic oxide containing calcium oxide, magnesium oxide, boron oxide, aluminum oxide, and silicon oxide. [4] Hollow inorganic oxide particles according to any one of [1] to [3], which are composed of an inorganic oxide containing 1 to 25 mass% calcium oxide, 0.05 to 5 mass% magnesium oxide, 10 to 40 mass% boron oxide, 5 to 35 mass% aluminum oxide, and 30 to 70 mass% silicon oxide. [5] Hollow inorganic oxide particles according to any one of [1] to [4], which have a sodium oxide content of 3 mass% or less. [6] Volume resistivity of 1 × 10 16 [1] to [5] above, wherein the inorganic oxide hollow particle has a diameter of Ω·cm or less. [7] The inorganic oxide hollow particle has an average particle diameter of 10 μm or less. [8] The inorganic oxide hollow particle has an average particle diameter of 0.1 μm or more and 10 μm or less. [9] The inorganic oxide hollow particle has a hollow ratio of 55% or more.

[10] The inorganic oxide hollow particle has a hollow ratio of 55% or more and 95% or less. 【0008】

[11] A method for producing inorganic oxide hollow particles, comprising the step of spraying a liquid to be sprayed from a spraying device installed in a spray pyrolysis apparatus, and thermally decomposing droplets of the sprayed liquid to produce inorganic oxides and carbon, wherein the liquid to be sprayed contains 0.04 to 2.5% by mass of a surfactant as a carbon source.

[12] The method for producing inorganic oxide hollow particles according to

[11] , wherein the surfactant is a nonionic surfactant.

[13] The method for producing inorganic oxide hollow particles according to

[11] or

[12] , wherein the surfactant is one or more selected from polyoxyalkylene alkyl ether, polyoxyalkylene alkylphenyl ether, alkyl glucoside, polyoxyalkylene fatty acid ester, sorbitan fatty acid ester, polyoxyalkylene sorbitan fatty acid ester, and fatty acid alkanolamide. 【0009】 According to the present invention, it is possible to provide inorganic oxide hollow particles capable of suppressing static electricity. The inorganic oxide hollow particles of the present invention are particularly useful as electronic materials because they eliminate concerns such as deterioration of handling properties due to aggregation of particles and electrostatic discharge of inorganic oxide hollow particles. 【0010】 [Inorganic Oxide Hollow Particles] The inorganic oxide hollow particles of the present invention are characterized by containing carbon, with the carbon content being controlled within a specific range. This makes it possible to suppress static electricity. 【0011】 In this specification, "hollow particle" refers to a particle having a cavity inside its outer shell. Here, "outer shell" refers to the outermost wall of the particle that is in contact with only one independent bubble inside the particle (hereinafter also referred to as "closed bubble"). 【0012】The inorganic oxide hollow particles of the present invention are preferably polyfoamed from the viewpoint of further suppressing static electricity. In this specification, "polyfoamed" means that the cavity covered by the outer shell has multiple independent cells separated by one or more partitions. Note that the independent cells are separated by partitions and are therefore not in communication with each other. Here, "partition" refers to a wall that separates two adjacent independent cells inside the particle. Therefore, polyfoamed inorganic oxide hollow particles are different from hollow spherical inorganic oxide hollow particles that have only one cavity inside the outer shell. 【0013】 The inorganic oxide hollow particles of the present invention preferably have no openings in their outer shell and are closed pores. This completely seals off the closed air bubbles, thus differentiating them from porous particles that have multiple pores extending from the particle surface into the interior. The fact that the outer shell is a closed pore can be confirmed by scanning electron microscope (SEM) images or by observing that the inorganic oxide hollow particles float on water. 【0014】 In this specification, "carbon" refers to a substance consisting solely of carbon atoms and does not include organic compounds. That is, the "carbon" according to the present invention does not include organic compounds that are detected as carbon when inorganic oxide hollow particles are calcined. 【0015】 The inorganic oxide hollow particles of the present invention have a carbon content of 0.0060 to 0.055 mass%, but from the viewpoint of suppressing static electricity, 0.0070 mass% or more is preferred, 0.0080 mass% or more is more preferred, 0.0090 mass% or more is even more preferred, 0.010 mass% or more is even more preferred, and 0.012 mass% or more is even more preferred. Furthermore, from the viewpoint of ensuring a hollow structure, 0.050 mass% or less is preferred, 0.045 mass% or less is more preferred, 0.040 mass% or less is even more preferred, and 0.035 mass% or less is even more preferred. That is, the carbon content in the inorganic oxide hollow particles is preferably 0.0070 to 0.050 mass%, more preferably 0.0080 to 0.045 mass%, even more preferably 0.0090 to 0.040 mass%, even more preferably 0.010 to 0.040 mass%, and even more preferably 0.012 to 0.035 mass%. 【0016】Carbon is present at least in the outer shell of the inorganic oxide hollow particles, and may be present on the outer surface side or the inner surface side, and the position of existence is not particularly limited. Further, when the inorganic oxide hollow particles are foamy, it is preferable that carbon is present not only in the outer shell but also in the partition walls. Thereby, more carbon can be distributed inside the hollow particles, so that the electrostatic suppression effect can be further enhanced. 【0017】 From the viewpoint of electrostatic suppression, the inorganic oxide hollow particles of the present invention preferably have a volume resistivity of 1 × 10 16 Ω·cm or less, more preferably 1 × 10 15 Ω·cm or less, still more preferably 1 × 10 14 Ω·cm or less, still more preferably 1 × 10 13 Ω·cm or less, still more preferably 1 × 10 12 Ω·cm or less, still more preferably 1 × 10 11 Ω·cm or less, and even more preferably 1 × 10 5 Ω·cm or more. The lower limit value of the volume resistivity is not particularly limited, but from the viewpoint of ensuring the hollow structure, 1 × 10 6 Ω·cm or more is preferable, 1 × 10 7 Ω·cm or more is more preferable, 1 × 10 8 Ω·cm or more is still more preferable, 1 × 10 9 Ω·cm or more is even more preferable. Here, in this specification, the "volume resistivity" refers to a value measured in accordance with JIS K 6911. 【0018】 The outer shell of the inorganic oxide hollow particles of the present invention is composed of an inorganic oxide. When the inorganic oxide hollow particles are foamy, the outer shell and the partition walls are composed of an inorganic oxide. 【0019】 The inorganic oxide is not particularly limited as long as it contains elements constituting the inorganic oxide. For example, oxides containing one or more elements selected from Group 1 elements to Group 16 elements can be mentioned. Note that a single inorganic oxide may contain one or more elements. Here, in this specification, the "Group 1 element" refers to an element belonging to Group 1 in the periodic table, and the same meaning shall be construed for elements belonging to other groups. 【0020】 Examples of Group 1 element oxides include lithium oxide, sodium oxide, potassium oxide, rubidium oxide, and cesium oxide. Examples of Group 2 element oxides include magnesium oxide, calcium oxide, strontium oxide, and barium oxide. Examples of Group 3 element oxides include yttrium oxide. Examples of Group 4 element oxides include titanium oxide and zirconium oxide. Examples of Group 5 element oxides include niobium oxide and tantalum oxide. Examples of Group 6 element oxides include chromium oxide, molybdenum oxide, and tungsten oxide. Examples of Group 7 element oxides include manganese oxide. Examples of Group 8 element oxides include iron oxide and ruthenium oxide. Examples of Group 9 element oxides include cobalt oxide, rhodium oxide, and iridium oxide. Examples of Group 10 element oxides include nickel oxide, palladium oxide, and platinum oxide. Examples of Group 11 element oxides include copper oxide, silver oxide, and gold oxide. Examples of Group 12 element oxides include zinc oxide and cadmium oxide. Examples of Group 13 element oxides include boron oxide, aluminum oxide, gallium oxide, indium oxide, and thallium oxide. Examples of Group 14 element oxides include silicon oxide, germanium oxide, tin oxide, and lead oxide. Examples of Group 15 element oxides include phosphorus oxide, arsenic oxide, antimony oxide, and bismuth oxide. Examples of Group 16 element oxides include sulfur oxides and selenium oxide. Hereinafter, "Group 1 element oxide" refers to an oxide of an element belonging to Group 1 of the periodic table, and the same meaning shall apply to oxides of elements belonging to other groups. In addition, composite oxides combining these oxides can also be mentioned. Examples of composite oxides include aluminosilicate, calcium silicate, aluminoborosilicate, and bariumborosilicate. 【0021】In particular, as an inorganic compound, it is preferable that it be in any of the following forms (i) to (iii), with (ii) or (iii) being more preferable, and (iii) being even more preferable, in that it is easy to enjoy the electrostatic discharge suppression effect while ensuring a hollow structure.Optionally, one or more Group 1 element oxides, for example, selected from sodium oxide and potassium oxide, may be included, but it is preferable that it does not contain Group 1 element oxides, especially sodium oxide. (i) One or more inorganic oxides selected from Group 2 element oxides, Group 13 element oxides and Group 14 element oxides (ii) One or more inorganic oxides selected from calcium oxide, magnesium oxide, boron oxide, aluminum oxide and silicon oxide (iii) Inorganic oxides containing calcium oxide, magnesium oxide, boron oxide, aluminum oxide and silicon oxide 【0022】The inorganic oxide hollow particles of the present invention can have an appropriate chemical composition, but for example, a preferred embodiment in (i) is as follows: The content of Group 2 element oxides is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. That is, the content of Group 2 element oxides is preferably 3 to 25% by mass, more preferably 5 to 20% by mass, and even more preferably 7 to 15% by mass. The content of Group 13 element oxides is preferably 15% by mass or more, more preferably 25% by mass or more, even more preferably 35% by mass or more, and preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. That is, the content of Group 13 element oxides is preferably 15 to 60% by mass, more preferably 25 to 55% by mass, and even more preferably 35 to 50% by mass. The content of Group 14 element oxides is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, and preferably 70% by mass or less, more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, and even more preferably 55% by mass or less. That is, the content of Group 14 element oxides is preferably 30 to 70% by mass, more preferably 35 to 65% by mass, even more preferably 40 to 60% by mass, and even more preferably 40 to 55% by mass. If Group 1 element oxides are included, the content of Group 1 element oxides is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less. The lower limit of the content of Group 1 element oxides is not particularly limited and may be 0% by mass. 【0023】In other words, the preferred embodiment in (i) is more specifically as follows: (i-1) Inorganic oxides containing 3 to 25 mass% of Group II element oxides, 15 to 60 mass% of Group III element oxides, 30 to 70 mass% of Group IV element oxides, and 3 mass% or less of Group I element oxides. (i-2) Inorganic oxides containing 5 to 20 mass% of Group II element oxides, 25 to 55 mass% of Group III element oxides, 35 to 65 mass% of Group III element oxides, and 1 mass% or less of Group I element oxides. (i-3) Inorganic oxides containing 7 to 15 mass% of Group II element oxides, 35 to 50 mass% of Group III element oxides, 40 to 60 mass% of Group III element oxides, and 0.5 mass% or less of Group I element oxides. (i-4) Inorganic oxides containing 7 to 15 mass% of Group II element oxides, 35 to 50 mass% of Group III element oxides, and 40 to 55 mass% of Group III element oxides. 【0024】Furthermore, preferred embodiments in (ii) or (iii) are as follows: The calcium oxide content is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and even more preferably 12% by mass or less. That is, the calcium oxide content is preferably 1 to 25% by mass, more preferably 3 to 20% by mass, even more preferably 5 to 15% by mass, and even more preferably 5 to 12% by mass. The magnesium oxide content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.15% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.5% by mass or less. That is, the magnesium oxide content is preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass, even more preferably 0.15 to 1% by mass, and even more preferably 0.15 to 0.5% by mass. The boric acid oxide content is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 22% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 27% by mass or less. That is, the boric acid oxide content is preferably 10 to 40% by mass, more preferably 15 to 35% by mass, even more preferably 20 to 30% by mass, and even more preferably 22 to 27% by mass. The aluminum oxide content is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less. That is, the aluminum oxide content is preferably 5 to 35% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 25% by mass. The silicon oxide content is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, and 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 even more preferably 50% by mass or less.That is, the silicon dioxide content is preferably 30 to 70% by mass, more preferably 35 to 65% by mass, even more preferably 40 to 60% by mass, even more preferably 40 to 55% by mass, and even more preferably 40 to 50% by mass. When one or more selected from sodium oxide and potassium oxide are included, the total content of sodium oxide and potassium oxide is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less. The lower limit of the total content of sodium oxide and potassium oxide is not particularly limited and may be 0% by mass. Furthermore, the sodium oxide content is preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and may be 0% by mass. 【0025】 In other words, preferred embodiments in (iii) are more specifically as follows: (iii-1) Inorganic oxides containing 1 to 25% by mass of calcium oxide, 0.05 to 5% by mass of magnesium oxide, 10 to 40% by mass of boric acid oxide, 5 to 35% by mass of aluminum oxide, 30 to 70% by mass of silicon oxide, and 3% by mass or less of sodium oxide. (iii-2) Inorganic oxides containing 3 to 20% by mass of calcium oxide, 0.1 to 3% by mass of magnesium oxide, 15 to 35% by mass of boric acid oxide, 5 to 35% by mass of aluminum oxide, 35 to 65% by mass of silicon oxide, and 1% by mass or less of sodium oxide. (iii-3) Inorganic oxides containing 5 to 15% by mass of calcium oxide, 0.15 to 1% by mass of magnesium oxide, 20 to 30% by mass of boric acid oxide, 10 to 30% by mass of aluminum oxide, 40 to 60% by mass of silicon oxide, and 0.5% by mass or less of sodium oxide. (iii-4) Inorganic oxides containing 5-15% by mass of calcium oxide, 0.15-1% by mass of magnesium oxide, 20-30% by mass of boric acid oxide, 10-30% by mass of aluminum oxide, and 40-55% by mass of silicon oxide. (iii-5) Inorganic oxides containing 5-12% by mass of calcium oxide, 0.15-0.5% by mass of magnesium oxide, 22-27% by mass of boric acid oxide, 15-25% by mass of aluminum oxide, and 40-50% by mass of silicon oxide. 【0026】In this specification, the content of each inorganic oxide described above shall be measured in oxide equivalent for Group 1 to Group 16 elements by X-ray fluorescence analysis, and each inorganic oxide shall be calculated by correcting the amount of oxides of elements other than carbon that are detected at a concentration of 0.1% by mass or more using the following formula. That is, oxides of elements other than carbon that are detected at a concentration of less than 0.1% by mass are considered to be oxides derived from unavoidable impurities contained in the raw material compound and are excluded. 【0027】 Chemical composition (corrected) (%) = Chemical composition (uncorrected) × 100 / [100 - impurities (%)] 【0028】 The hollow inorganic oxide particles of the present invention preferably have a hollowness ratio of 55% or more, more preferably 60% or more, even more preferably 65% ​​or more, and even more preferably 70% or more. The upper limit of the hollowness ratio is preferably 95% or less, more preferably 90% or less, even more preferably 85% or less, and even more preferably 80% or less, from the viewpoint of ensuring sufficient strength. That is, the hollowness ratio is preferably 55 to 95%, more preferably 60 to 90%, even more preferably 65 to 85%, even more preferably 70 to 85%, and even more preferably 70 to 80%. Here, in this specification, "hollowness ratio" shall be calculated by the following formula. The apparent density of the particles is measured by the gas displacement method using a dry automatic densimeter. The prepared particles are melted at a temperature above the melting temperature and vitrified. The glass is crushed until it passes through a 1 mm sieve completely, and the density of the powder is measured by the gas displacement method to obtain the true density. Note that since it is difficult to measure for individual particles, this is the cavity ratio of the particle group as a whole. As a dry-type automatic densimeter, for example, the Accupic (manufactured by Shimadzu Corporation) can be used. 【0029】 Hollowness ratio (%) = [1 - (Apparent density) / (True density)] × 100 【0030】The inorganic oxide hollow particles of the present invention are assumed to be applied to electronic device components that require miniaturization and thinning, and are preferably minute. More specifically, the average particle diameter of the inorganic oxide hollow particles is preferably 10 μm or less, more preferably 8 μm or less, still more preferably 5 μm or less, and even more preferably 3 μm or less. In addition, from the viewpoint of ensuring the hollow structure, the lower limit value of the average particle diameter is preferably 0.1 μm or more, more preferably 0.3 μm or more, still more preferably 0.5 μm or more, and even more preferably 0.8 μm or more. That is, the average particle diameter is preferably 0.1 to 10 μm, more preferably 0.3 to 8 μm, still more preferably 0.5 to 5 μm, and even more preferably 0.8 to 3 μm. Here, in this specification, the "average particle diameter" means the particle diameter (d 50 ) corresponding to 50% of the cumulative distribution curve when the particle size distribution of the sample is created on a volume basis in accordance with JIS R 1629. For the measurement of the particle size distribution, for example, a laser diffraction / scattering type particle size distribution measuring device can be used. 【0031】 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. However, since static electricity is suppressed, they are useful for electronic materials, particularly wiring circuit boards, semiconductor encapsulating materials, etc. 【0032】 〔Method for producing inorganic oxide hollow particles〕 The inorganic oxide hollow particles of the present invention can be produced, for example, by a spray pyrolysis method. More specifically, for example, it includes a step of spraying a sprayed liquid from a spraying device installed in a spray pyrolysis device and thermally decomposing the droplets of the sprayed liquid to generate an inorganic oxide and carbon. Thereby, the inorganic oxide generated by thermal decomposition can form an outer shell and partition walls, and carbon can be included therein. 【0033】 The spray pyrolysis device preferably has a heat decomposition furnace with a shape of a rigid cylinder, and the size of the heat decomposition furnace can be appropriately selected according to the production scale. 【0034】The liquid to be sprayed contains a raw material compound having an element constituting an inorganic oxide, a solvent, and an organic compound as a carbon source. Note that the liquid to be sprayed may be prepared by mixing the raw material compound, the solvent, and the carbon source, and the mixing order of each component is not particularly limited. 【0035】 As the raw material compound, one or more compounds containing an element selected from Group 1 elements to Group 16 elements may be appropriately selected. The raw material compound is preferably soluble in water, and for example, it is preferably in the form of a salt or an alkoxide. The salt may be an inorganic salt or an organic salt. Examples of the inorganic salt include nitrates, sulfates, carbonates, hydroxides, and halides. Examples of the organic salt include formates, acetates, propionates, oxalates, and citrates. 【0036】 For example, in the above-described aspect (i), one or more raw material compounds selected from a Group 2 element-containing compound, a Group 13 element-containing compound, and a Group 14 element-containing compound, preferably a raw material compound containing a Group 2 element-containing compound, a Group 13 element-containing compound, and a Group 14 element-containing compound, may be appropriately selected to prepare the liquid to be sprayed. The raw material compound may optionally contain a Group 1 element-containing compound, but it is preferably free of sodium compounds in particular. Note that the raw material compound is preferably contained in the liquid to be sprayed at a concentration of 0.01 mol / L to the saturation concentration. Further, the content of each compound in the raw material compound is an amount that satisfies the stoichiometric composition of the inorganic compound hollow particles formed from the compound, preferably an amount that satisfies the stoichiometric composition of the inorganic oxide hollow particles composed of the inorganic oxide in any of the above-described aspects (i-1) to (i-4). 【0037】Examples of Group 2 element-containing compounds include magnesium compounds such as magnesium salts and calcium compounds such as calcium salts. Examples of magnesium salts include magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium phosphate, and magnesium hydroxide. Examples of calcium salts include calcium nitrate, calcium chloride, calcium hydroxide, calcium formate, calcium acetate, and calcium propionate. Examples of Group 13 element-containing compounds include boron compounds such as boric acid and borates, and aluminum compounds such as aluminum salts and aluminum alkoxides. Examples of borates include metaborates such as sodium borate and potassium borate, tetraborates such as sodium tetraborate and potassium tetraborate, and pentaborates such as sodium pentaborate and potassium pentaborate. Examples of aluminum salts include aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum phosphate, aluminum hydroxide, aluminum acetate, and aluminum oxalate. Examples of aluminum alkoxides include aluminum methoxide, aluminum ethoxide, and aluminum isopropoxide. Examples of Group 14 element-containing compounds include silicon compounds such as silicates and silicate alkoxides. Examples of silicates include sodium silicate, potassium silicate, and tetramethylammonium silicate, while examples of silicate alkoxides include tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS), and tetrabutoxysilane. It is also possible to use composite compounds containing structures in which two or more elements are chemically bonded, such as aluminosilicates. Examples of aluminosilicates include sodium aluminosilicate, potassium aluminosilicate, and calcium aluminosilicate. 【0038】Furthermore, in the embodiment of (ii) described above, the spray liquid may be prepared using a raw material compound containing one or more selected from calcium compounds, magnesium compounds, boron compounds, aluminum compounds, and silicon compounds, preferably one or more boron compounds selected from calcium salts, magnesium salts, boric acid, and borates, aluminum compounds selected from aluminum salts and aluminum alkoxides, and silicon compounds selected from silicates and silicate alkoxides. Furthermore, in the embodiment of (iii) described above, the spray liquid may be prepared using a raw material compound containing calcium compounds, magnesium compounds, boron compounds, aluminum compounds, and silicon compounds, preferably a calcium salt, a magnesium salt, one or more boron compounds selected from boric acid and borates, aluminum compounds selected from aluminum salts and aluminum alkoxides, and silicon compounds selected from silicates and silicate alkoxides. It is preferable that the raw material compound be contained in the spray liquid at a concentration from 0.01 mol / L to saturation. Furthermore, the content of each compound in the raw material compound is such that the amount of inorganic compound hollow particles formed from the compound satisfies the stoichiometric composition described above, preferably an amount that satisfies the stoichiometric composition of inorganic oxide hollow particles composed of an inorganic oxide in any of the embodiments described in (iii-1) to (iii-5) above. 【0039】 The carbon source is not particularly limited as long as it carbonizes through thermal decomposition, but examples include surfactants and organic solvents. One or more carbon sources can be used. 【0040】 The surfactant may be ionic or nonionic, and is not particularly limited. Furthermore, one or more surfactants can be used in combination. 【0041】Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. Anionic surfactants include, for example, carboxylic acid type, sulfonic acid type, sulfate ester type, and phosphate ester type, and any of these is acceptable. Examples of carboxylic acid type anionic surfactants include sodium laurate, sodium stearate, sodium polyoxyethylene (4,5) lauryl ether acetate, sodium lauroyl sarcosinate, sodium octanoate, sodium decanoate, sodium myristic acid, sodium palmitate, and coconut oil fatty acid (C) 8-18 Examples of sulfonic acid type anionic surfactants include sodium lauryl sulfoacetate, sodium 1-hexanesulfonate, sodium 1-octanesulfonate, sodium 1-decanesulfonate, sodium 1-dodecanesulfonate, sodium toluenesulfonate, sodium cumenesulfonate, sodium naphthalenesulfonate, disodium naphthalenedisulfonate, trisodium naphthalenetrisulfonate, and sodium alphaolefin sulfonate. Examples of sulfate ester type anionic surfactants include sodium lauryl sulfate, sodium myristyl sulfate, sodium polyoxyethylene (3) lauryl ether sulfate, sodium cetyl sulfate, sodium cocoglyceryl sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate, and triethanolamine laureth sulfate. Examples of phosphate ester type anionic surfactants include sodium lauryl phosphate, sodium polyoxyethylene cetyl ether phosphate, lauryl phosphate, and potassium lauryl phosphate. 【0042】Cationic surfactants include, for example, aliphatic amine salts and aliphatic ammonium salts. Examples of aliphatic ammonium salts include tetramethylammonium chloride, tetrabutylammonium chloride, dodecyldimethylbenzylammonium chloride, alkyltrimethylammonium chloride, octyltrimethylammonium chloride, dodecyltrimethylammonium chloride, benzalkonium chloride, benzethonium chloride, as well as monomethylamine hydrochloride and dimethylamine hydrochloride. Examples of amphoteric surfactants include glycine type, betaine type, and amine oxide type, and any of these is acceptable. Examples of glycine type amphoteric surfactants include sodium cocoamphoacetate, sodium lauroamphoacetate, and disodium cocoamphodiacetate. Examples of betaine type amphoteric surfactants include lauryldimethylaminoacetate betaine, laurylhydroxysulfobetaine, stearyldimethylaminoacetate betaine, dodecylaminomethyldimethylsulfopropylbetaine, and coconut oil fatty acid (C) 8-18 Examples of amidopropyl betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, and lauric acid amidopropyl betaine are also mentioned. Examples of amine oxide type amphoteric surfactants include lauryldimethylamine oxide and alkyl (C 8-18 ) Dimethylamine oxide (N,N-dimethylalkyl (C 8-18 Examples of amine oxides include coconut alkyldimethylamine oxide, decyldimethylamine oxide, myristyldimethylamine oxide, dihydroxyethyl laurylamine oxide, and oleyldimethylamine oxide. 【0043】 Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, alkyl glucosides, polyoxyalkylene fatty acid esters, sorbitan fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, and fatty acid alkanolamides. 【0044】Examples of polyoxyalkylene alkyl ethers include polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and other polyoxyethylene C 12-18 Examples of alkyl ethers include polyoxyalkylene alkylphenyl ethers such as polyoxyethylene styrene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene distylenide phenyl ether, and polyoxyethylene tripenzylphenyl ether. Examples of alkyl glucosides include decyl glucoside and lauryl glucoside. Examples of polyoxyalkylene fatty acid esters include polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, polyethylene glycol distearate, polyethylene glycol diolate, and polypropylene glycol diolate. 【0045】 Examples of sorbitan fatty acid esters include sorbitan monocaprylate, sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, and sorbitan monosesquioleate. Examples of polyoxyalkylene sorbitan fatty acid esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan triisostearate. Examples of fatty acid alkanolamides include coconut oil fatty acid diethanolamide, beef tallow fatty acid diethanolamide, lauric acid diethanolamide, and oleic acid diethanolamide. 【0046】 Furthermore, in addition to polyoxyalkylene alkyl ethers such as polyoxyethylene polyoxypropylene glycol and polyoxyethylene fatty acid esters, other nonionic surfactants such as polyoxyalkyl glycol, polyoxyethylene hydrogenated castor oil ether, sorbitan fatty acid ester alkyl ether, alkyl polyglucoside, sorbitan monooleate, and sucrose fatty acid ester can also be used. 【0047】 The organic solvent is not particularly limited as long as it carbonizes upon thermal decomposition, but a high boiling point is preferred, and a solvent with a boiling point of 300°C or higher is preferred. One or more organic solvents can be used in combination. Examples of high boiling point solvents include liquid paraffin, hydrocarbons such as alkyl-substituted benzenes, alkyl benzoates, alkyl phthalates, and alkyl trimellitates. 【0048】 In particular, as a carbon source, surfactants are preferred, nonionic surfactants are more preferred, and one or more selected from polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, alkyl glucosides, polyoxyalkylene fatty acid esters, sorbitan fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, and fatty acid alkanolamides are even more preferred, polyoxyalkylene alkyl ethers are even more preferred, and polyoxyethylene C 12-18 Alkyl ethers are even more preferred. 【0049】 The carbon source may be added, for example, together with the raw material compound when preparing the spray liquid, or after preparing the raw material compound-containing solution, and the order in which the raw material compound and surfactant are mixed is not particularly limited. 【0050】 Water is preferred as the solvent for the sprayed liquid, considering its environmental impact and manufacturing costs. 【0051】The amount of raw material compound and solvent (excluding the carbon source) used is such that the total concentration of the raw material compound in the sprayed liquid is typically 0.01 to 1.0 mol / L, preferably 0.1 to 0.9 mol / L. The individual contents of the raw material compound in the sprayed liquid should be such that they satisfy the predetermined stoichiometric composition of the inorganic oxide hollow particles. 【0052】 The amount of carbon source used is not particularly limited as long as the carbon content in the hollow particles after thermal decomposition falls within the above-mentioned range, and the amount used can be appropriately determined depending on the type of carbon source so as not to satisfy a predetermined stoichiometric amount. For example, from the viewpoint of suppressing static electricity, the carbon source content in the sprayed liquid is preferably 0.04% by mass or more, more preferably 0.055% by mass or more, even more preferably 0.070% by mass or more, and even more preferably 0.085% by mass or more. From the viewpoint of ensuring a hollow structure, it is preferably 2.5% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.5% by mass or less. That is, the carbon source content in the sprayed liquid is preferably 0.04 to 2.5% by mass, more preferably 0.055 to 2.0% by mass, even more preferably 0.070 to 2.0% by mass, and even more preferably 0.085 to 1.5% by mass. 【0053】 Examples of spraying devices include fluid nozzles such as two-fluid nozzles, three-fluid nozzles, and four-fluid nozzles. There are two types of fluid nozzles: an internal mixing method where the gas and raw material solution are mixed inside the nozzle, and an external mixing method where the gas and raw material solution are mixed outside the nozzle; both can be used. The gas supplied to the nozzle can be, for example, air, nitrogen, argon, or other inert gases. Of these, air is preferred from an economic standpoint. The spraying device can be installed as one or more units. 【0054】 The flow rate of the sprayed liquid is typically 1 to 100 L / h, preferably 3 to 80 L / h, and more preferably 5 to 60 L / h. The droplet ejection velocity is typically 1 to 50 m / s, preferably 5 to 35 m / s, and more preferably 10 to 20 m / s. 【0055】Examples of heating devices include combustion burners, hot air heaters, and electric heaters. One or more heating devices can be installed. Generally available combustion burners, hot air heaters, and electric heaters can all be used. The temperature of the heating device is typically 400 to 1800°C, but from the viewpoint of incorporating carbon into the outer shell and partitions, 600 to 1500°C is preferred, 700 to 1400°C is more preferred, and 800 to 1300°C is even more preferred. 【0056】 The hollow inorganic oxide particles produced by the pyrolysis reaction are usually polyfoamy and are recovered from the downstream side of the pyrolysis furnace. High-performance cyclone powder recovery machines or powder recovery systems using bag filters can be used to recover the hollow inorganic oxide particles. 【0057】 The embodiments of the present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following embodiments. 【0058】 1. Analysis of Chemical Composition Briquettes were prepared by molding hollow inorganic oxide particles with a press machine. These briquettes were measured using an X-ray fluorescence analyzer (ZSX primus II, Rigaku Corporation) for elements from Group 1 to Group 16, in terms of oxide equivalent. The amount of each inorganic oxide was calculated by correcting the following formula so that the total value of oxides of elements other than carbon that were detected at 0.1% by mass or more equals 100%. Specifically, in the following formula, oxides of elements other than carbon that were detected at less than 0.1% by mass were considered to be oxides derived from unavoidable impurities contained in the raw material compound, and these were excluded as impurities. 【0059】 Chemical composition (corrected) (%) = Chemical composition (uncorrected) × 100 / [100 - impurities (%)] 【0060】 2. Analysis of Carbon Content Using a carbon-sulfur analyzer (EMIA-220V2), the inorganic oxide hollow particles, which were the sample, were placed in an oxygen stream and heated to a high temperature to burn. The contained carbon was extracted as an oxide, and the amount of infrared absorption measured was converted from a pre-determined calibration curve to calculate the carbon content in the inorganic oxide hollow particles. 【0061】3. Confirmation of Static Electricity Suppression Effect 2 kg of sample powder was placed in a 90 L polyethylene bag (manufactured by Sekisui Material Solutions Co., Ltd., product number: J5902T). The bag was tied 5 cm from the top edge, and the bag was agitated 10 times by shaking it up and down manually. Then, the bottom ends of the polyethylene bag were pinched, and the bag was turned upside down in one motion while simultaneously being spread taut. The bag was then held upside down for 5 seconds to allow the sample powder to fall by its own weight. The weight of the bag with the powder attached was then measured, and the difference between this weight and the previously measured weight of the bag was taken to determine the weight of the sample powder that remained attached to the bag without falling by its own weight. It was determined that the lower the weight of the sample powder attached to the bag, the higher the static electricity suppression effect. 【0062】 4. Analysis of Hollow Factor The hollow factor was calculated using the following formula. Specifically, the apparent density of the particles was measured using a dry automatic densimeter by the gas displacement method. The prepared particles were melted at a temperature above the melting point to vitrify them, and the resulting glass was pulverized until it could pass through a 1 mm sieve completely. The density of the resulting powder was then measured using a dry automatic densimeter by the gas displacement method and was determined to be the true density. An Accupic (manufactured by Shimadzu Corporation) was used as the dry automatic densimeter. 【0063】 Hollowness ratio (%) = [1 - (Apparent density) / (True density)] × 100 【0064】 5. Using a particle size distribution analyzer (MT3000II, manufactured by Microtrac Bell), a volume-based particle size distribution was created in accordance with JIS R 1629, and the particle size (d) corresponding to 50% of the cumulative distribution curve was calculated. 50 ) was sought. 【0065】Example 1 An aqueous solution containing the raw material compound was added to a reaction vessel and stirred for 3 hours. The aqueous solution containing the raw material compound was prepared by dissolving calcium nitrate (Wako Pure Chemical Industries, Ltd.) at 0.025 mol / L, magnesium nitrate (Wako Pure Chemical Industries, Ltd.) at 0.019 mol / L, aluminum nitrate (Wako Pure Chemical Industries, Ltd.) at 0.048 mol / L, tetraethyl orthosilicate (Kanto Chemical Co., Ltd.) at 0.138 mol / L, and boric acid (Wako Pure Chemical Industries, Ltd.) at 0.150 mol / L in tap water. Then, polyoxyethylene tridecyl ether (Daiichi Kogyo Seiyaku Co., Ltd.) was added to the aqueous solution containing the raw material compound at a concentration of 0.05% by mass as a carbon source and dissolved. Subsequently, this aqueous solution containing the raw material compound was supplied to a three-fluid nozzle and sprayed from the nozzle into a spray pyrolysis furnace, where it was calcined at 1200°C to produce polyfoaming inorganic oxide hollow particles. The recovered polyfoaming inorganic oxide hollow particles were then analyzed. Furthermore, the polyfoamy nature of the inorganic oxide hollow particles was confirmed by scanning electron microscopy (SEM) imaging. 【0066】 Examples 2-5 and Comparative Example 2: Foamy inorganic oxide hollow particles were produced using the same procedure as in Example 1, except that the amount of polyoxyethylene tridecyl ether added was changed, as shown in Table 1. The recovered foamy inorganic oxide hollow particles were then analyzed. The foamy nature of the inorganic oxide hollow particles was confirmed by scanning electron microscopy (SEM) imaging. 【0067】 Comparative Example 1: Foamy inorganic oxide hollow particles were produced using the same procedure as in Example 1, except that polyoxyethylene tridecyl ether was not added to the aqueous solution containing the raw material compound. The recovered foamy inorganic oxide hollow particles were then analyzed. The foamy nature of the inorganic oxide hollow particles was confirmed by scanning electron microscopy (SEM) imaging. 【0068】 【0069】The results of Comparative Example 1 show that inorganic oxide hollow particles with a carbon content of less than 0.0060 mass% are highly electrostatically charged due to their high adhesion to the bag, resulting in insufficient static charge suppression. Furthermore, the results of Comparative Example 2 show that while inorganic oxide hollow particles with a carbon content exceeding 0.055 mass% exhibit suppressed static electricity, their reduced hollowness limits their applications as electronic materials. In contrast, the results of Examples 1 to 5 demonstrate that controlling the carbon content to 0.0060 to 0.055 mass% suppresses static electricity without compromising hollowness, thus eliminating concerns such as poor handling due to particle aggregation and electrostatic discharge damage to electronic devices.

Claims

1. Hollow inorganic oxide particles having a carbon content of 0.0060 to 0.055% by mass.

2. The inorganic oxide hollow particles according to claim 1, which are polyfoaming.

3. Hollow inorganic oxide particles according to claim 1 or 2, comprising an inorganic oxide containing calcium oxide, magnesium oxide, boron oxide, aluminum oxide, and silicon oxide.

4. The inorganic oxide hollow particle according to claim 1 or 2, comprising an inorganic oxide containing 1 to 25% by mass of calcium oxide, 0.05 to 5% by mass of magnesium oxide, 10 to 40% by mass of boron oxide, 5 to 35% by mass of aluminum oxide, and 30 to 70% by mass of silicon oxide.

5. The inorganic oxide hollow particles according to claim 1 or 2, wherein the sodium oxide content is 3% by mass or less.

6. The inorganic oxide hollow particle according to claim 1 or 2, wherein the hollowness ratio is 55% or more and 95% or less.

7. The inorganic oxide hollow particle according to claim 1 or 2, wherein the average particle diameter is 0.1 μm or more and 10 μm or less.

8. A method for producing hollow inorganic oxide particles, comprising the steps of spraying a liquid to be sprayed from a spraying device installed in a spray pyrolysis apparatus, and thermally decomposing the sprayed droplets of the liquid to be sprayed to produce inorganic oxides and carbon, wherein the liquid to be sprayed contains 0.04 to 2.5% by mass of a surfactant as a carbon source.

9. The method for producing inorganic oxide hollow particles according to claim 8, wherein the surfactant is a nonionic surfactant.

10. A method for producing inorganic oxide hollow particles according to claim 8 or 9, wherein the surfactant is one or more selected from polyoxyalkylene alkyl ether, polyoxyalkylene alkylphenyl ether, alkyl glucoside, polyoxyalkylene fatty acid ester, sorbitan fatty acid ester, polyoxyalkylene sorbitan fatty acid ester, and fatty acid alkanolamide.

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