Method for manufacturing surface-coated inorganic oxide hollow particle

Abstract

To provide a method for manufacturing a surface-coated inorganic oxide hollow particle whose hollow structure is less prone to breakage and which is useful as a filler material in an electronic material field.SOLUTION: A method for manufacturing a surface-coated inorganic oxide hollow particle includes surface treatment of inorganic oxide hollow particles with a silane coupling agent by a dry treatment method using a planetary-type kneader.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing surface-coated inorganic oxide hollow particles.

Background Art

[0002] In recent years, with the spread of high-speed communication standards such as 5G and 6G, materials used in high-frequency band devices are required to have excellent dielectric properties such as low relative permittivity and dielectric loss tangent. Inorganic oxide hollow particles have excellent dielectric properties, and thus the demand for them as filler materials in the field of electronic materials is increasing.

[0003] As such a filler material, for example, hollow silica particles having an outer shell portion forming an internal space and the outer shell portion being composed of a component containing silica are known, and the surface of the hollow silica particles is surface-treated with a nitrogen-containing silane coupling agent (Patent Document 1). Also, when heated from 25°C / min to 50 to 1000°C, the number of desorbed water molecules is 0.001 to 0.010 mmol / g, and spherical silica particles having a specific surface area of 0.1 to 2.0 m 2 / g have also been proposed (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to develop inorganic oxide hollow particles applicable as a filler material in the field of electronic materials, the inventors kneaded inorganic oxide hollow particles with a resin. As a result, as the content of the inorganic oxide hollow particles in the resin composition increased, the viscosity of the resin composition increased and the kneadability decreased. In response to such a problem, Patent Document 1 states that thickening of the resin composition can be suppressed by surface-treating hollow silica particles with a nitrogen-containing silane coupling agent by a wet treatment method. However, when the inventors surface-treated inorganic oxide hollow particles different from hollow silica particles with a nitrogen-containing silane coupling agent by a wet treatment method, a problem occurred in that the hollow structure was destroyed. Therefore, an object of the present invention is to provide a method for producing surface-coated inorganic oxide hollow particles that are difficult to have their hollow structure destroyed and are useful as a filler material in the field of electronic materials.

Means for Solving the Problems

[0006] As methods for treating silane coupling agents, a wet treatment method and a dry treatment method are known. The wet treatment method is a method in which a solvent is added to inorganic oxide hollow particles to form a slurry, and then a silane coupling agent is added and stirred and mixed. Since it is difficult to apply an external force to the inorganic oxide hollow particles, it is difficult to destroy the hollow structure. On the other hand, the dry treatment method is a method in which a silane coupling agent is dropped or sprayed onto the inorganic oxide hollow particles in a tank while stirring and mixing, and a Henschel mixer, a vibration mixer, etc. are usually used for stirring and mixing. However, when using these mixers, since an external force is applied to the inorganic oxide hollow particles, destruction of the hollow structure cannot be avoided. Under such circumstances, the inventors have examined in detail the method for treating inorganic oxide hollow particles by the dry treatment method, and have found that even if it is the dry treatment method, destruction of the hollow structure can be suppressed by using a mixer of a specific type.

[0007] That is, the present invention provides the following [1] to [6]. 〔1〕 A method for producing surface-coated inorganic oxide hollow particles, wherein inorganic oxide hollow particles are surface-treated with a silane coupling agent by a dry treatment method using a planetary kneader. 〔2〕The production method according to 〔1〕 above, wherein the silane coupling agent is a nitrogen-containing silane coupling agent. 〔3〕The production method according to 〔1〕 or 〔2〕 above, wherein the amount of the silane coupling agent used is 0.01 to 10% by mass based on the inorganic oxide hollow particles. 〔4〕The production method according to any one of 〔1〕 to 〔3〕 above, wherein the porosity of the inorganic oxide hollow particles is 45% or more. 〔5〕The production method according to any one of 〔1〕 to 〔4〕 above, wherein the planetary mixer is a planetary twin-screw kneader. 〔6〕The production method according to any one of 〔1〕 to 〔5〕 above, wherein the inorganic oxide hollow particles are composed of one or more inorganic oxides containing an element selected from Group 1, Group 2, Group 4, Group 8, Group 9, Group 10, Group 11, Group 12, Group 13, and Group 15 elements of the periodic table and silicon oxide.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a method for producing surface-coated inorganic oxide hollow particles that are difficult to have their hollow structures destroyed and are useful as filler materials in the field of electronic materials. Further, the present invention is also useful as a method for surface-treating inorganic oxide hollow particles having a high porosity.

Embodiments for Carrying Out the Invention

[0009] The method for producing surface-coated inorganic oxide hollow particles of the present invention is characterized in that surface treatment is performed with a silane coupling agent by a dry treatment method using a planetary mixer.

[0010] <Inorganic Oxide Hollow Particles> As used herein, the term "hollow particle" refers to a particle having a cavity (hollow structure) inside and having an outer shell portion that partitions the hollow portion, and is different from a porous particle having a plurality of pores extending from the surface of the particle to the inside. Note that hollow particles can be distinguished from porous particles by a transmission electron microscope (TEM) image. Further, the term "inorganic oxide hollow particle" refers to a hollow particle in which the outer shell portion that partitions the hollow portion is composed of an inorganic oxide.

[0011] The inorganic oxide is not particularly limited as long as it can constitute the outer shell portion of the hollow particle. For example, one or more inorganic oxides containing an element selected from Group 1 elements of the periodic table, Group 2 elements of the periodic table, Group 4 elements of the periodic table, Group 8 elements of the periodic table, Group 9 elements of the periodic table, Group 10 elements of the periodic table, Group 11 elements of the periodic table, Group 12 elements of the periodic table, Group 13 elements of the periodic table, and Group 15 elements of the periodic table, and silicon oxide can be mentioned.

[0012] Examples of Group 1 elements of the periodic table include lithium, sodium, potassium, and cesium. Examples of Group 2 elements of the periodic table include magnesium, calcium, strontium, and barium. Examples of Group 4 elements of the periodic table include titanium and zirconium. Examples of Group 8 elements of the periodic table include iron and ruthenium. Examples of Group 9 elements of the periodic table include cobalt, rhodium, and iridium. Examples of Group 10 elements of the periodic table include nickel, palladium, and platinum. Examples of Group 11 elements of the periodic table include copper, silver, and gold. Examples of Group 12 elements of the periodic table include zinc and cadmium. Examples of Group 13 elements of the periodic table include boron, aluminum, gallium, indium, and thallium. Examples of Group 15 elements of the periodic table include phosphorus, arsenic, antimony, and bismuth.

[0013] Specific examples of the inorganic compound include, for example, sodium oxide, potassium oxide, magnesium oxide, barium oxide, calcium oxide, zinc oxide, copper oxide, boron oxide, aluminum oxide, iron oxide, aluminosilicate, aluminoborosilicate, barium borosilicate, etc. Composite oxides formed by combining these oxides can also be included.

[0014] Among them, in terms of easily enjoying the effects of the present invention, it is preferably composed of one or more inorganic oxides containing elements selected from Group 1 elements, Group 2 elements, and Group 13 elements of the periodic table, and silicon oxide. More preferably, it is composed of one or more inorganic oxides containing elements selected from Group 2 elements and Group 13 elements of the periodic table, and silicon oxide. Even more preferably, it is composed of one or more inorganic oxides containing elements selected from magnesium, calcium, boron, and aluminum, and silicon oxide.

[0015] Preferred chemical compositions of the inorganic oxide hollow particles can include the following aspects. (i) Inorganic oxide hollow particles composed of an inorganic oxide containing preferably 10% by mass or less, more preferably 5% by mass or less of a Group 1 element oxide of the periodic table, preferably 35% by mass or less, more preferably 1 - 35% by mass of a Group 2 element oxide of the periodic table, preferably 60% by mass or less, more preferably 4 - 50% by mass of a Group 13 element oxide of the periodic table, and preferably 30% by mass or more, more preferably 35 - 60% by mass of silicon oxide. Note that the content of the Group 1 element oxide of the periodic table may be 0% by mass. (ii) Inorganic oxide hollow particles composed of an inorganic oxide containing preferably 1 - 35% by mass, more preferably 3 - 30% by mass, even more preferably 5 - 20% by mass of a Group 2 element oxide of the periodic table, preferably 2 - 60% by mass, more preferably 15 - 50% by mass, even more preferably 30 - 50% by mass of a Group 13 element oxide of the periodic table, and preferably 30 - 65% by mass, more preferably 35 - 60% by mass, even more preferably 40 - 50% by mass of silicon oxide. (iii) Preferably 1 to 25% by mass, more preferably 2 to 20% by mass, still more preferably 3 to 15% by mass of calcium oxide, preferably 10% by mass or less, more preferably 0.1 to 10% by mass, still more preferably 0.1 to 5% by mass of magnesium oxide, preferably 1 to 40% by mass, more preferably 3 to 30% by mass, still more preferably 10 to 25% by mass of boron oxide, preferably 1 to 40% by mass, more preferably 3 to 30% by mass, still more preferably 10 to 25% by mass of aluminum oxide, and preferably 30 to 65% by mass, more preferably 35 to 60% by mass, still more preferably 40 to 50% by mass of silicon oxide, and the inorganic oxide hollow particles are composed of an inorganic oxide containing the same.

[0016] In this specification, each content of the inorganic oxides described above is a value obtained by measuring the chemical components by fluorescent X-ray analysis and calculating the chemical components in terms of oxides. The chemical components are calculated by correcting with the following formula so that the total value of the oxides of the elements to be analyzed becomes 100%.

[0017] Chemical composition (after correction) (%) = Chemical composition (before correction) × 100 / (100 - Impurities (%)) 〔Impurities (%) is the value obtained by subtracting the total value of the chemical composition of the above-described oxides from 100.〕

[0018] The porosity of the inorganic oxide hollow particles is usually 45% or more, preferably 50% or more, more preferably 55% or more, still more preferably 60% or more, still more preferably 65% or more, even more preferably 70% or more, and particularly preferably 75% or more. The upper limit of such porosity is preferably 95% or less, more preferably 90% or less, from the viewpoint of ensuring sufficient strength. Here, in this specification, the "porosity" is a value calculated from the following formula using a dry-type automatic densitometer to measure the bulk density and true density of the particles. Since it is difficult to measure each individual particle, it is the porosity of the particle group. Here, in this specification, the "bulk density" shall be measured by the gas displacement method in accordance with JIS R 1620. The "true density" shall be measured with a dry-type automatic densitometer after heating in a box-type electric furnace at a temperature equal to or higher than the melting point for 6 hours to remove the hollow part and then cooling. As the density measuring device, for example, an Accupic (manufactured by Shimadzu Corporation) which is a dry-type automatic densitometer can be used, and as the dry-type automatic densitometer, for example, an Accupic (Shimadzu) can be used.

[0019] Porosity = (True density - Bulk density) × 100 / True density

[0020] The inorganic oxide hollow particles may be commercially available ones or those produced by known methods. The production method of the inorganic oxide hollow particles is not particularly limited, and examples thereof include the sol-gel method and the spray pyrolysis method. For the production of inorganic oxide hollow particles by the sol-gel method, for example, it is possible to refer to JP-A-2015-044987 and JP-A-2013-193950, and for the production of inorganic oxide hollow particles by the spray pyrolysis method, for example, it is possible to refer to JP-A-2003-019427 and JP-A-2013-220967.

[0021] <Silane coupling agent> Examples of the silane coupling agent include silane compounds having at least one organic functional group capable of expecting a reaction or interaction with an organic substance and at least one hydrolyzable group in one molecule. Examples of the organic functional group include hydrocarbon groups such as alkyl group, aryl group, aralkyl group, alkenyl group, and styryl group; halogenated hydrocarbon groups such as fluoroalkyl group and fluoroaryl group; oxygen-containing groups such as (meth)acryloyl group, glycidyl group, acid anhydride group, carboxy group, and carbinol group; nitrogen-containing groups such as amino group, isocyanurate group, ureido group, and isocyanate group; and sulfur-containing groups such as mercapto group. Among them, from the viewpoint of easily enjoying the effects of the present invention, it is preferable to have a nitrogen-containing group, and it is more preferable to have an amino group. Examples of the hydrolyzable group include alkoxy group, acetoxy group, and halo group. Among them, from the viewpoint of easily enjoying the effects of the present invention, an alkoxy group is preferable. From the viewpoint of treatment efficiency, methoxy group and ethoxy group are preferable as the alkoxy group. Further, the hydrolyzable group is preferably bifunctional or trifunctional, and more preferably trifunctional. Note that one or more silane coupling agents can be used, and they may be produced by a known method or commercially available.

[0022] Among them, as the silane coupling agent, from the viewpoint of easily enjoying the effects of the present invention, a nitrogen-containing silane coupling agent is preferable, a trifunctional nitrogen-containing silane coupling agent is more preferable, and a trifunctional amino group-containing silane coupling agent is further preferable. Note that the amino group-containing silane coupling agent may be in the form of a salt. Examples of such a silane coupling agent include, but are not limited to, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and hydrochloride of N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane.

[0023] <Dry treatment> The dry process is a method in which a silane coupling agent or a silane coupling agent diluted with an appropriate solvent is dropped or spray-sprayed onto inorganic oxide hollow particles being stirred in a tank to coat the surface of the inorganic oxide hollow particles with the silane coupling agent. Examples of the solvent used for diluting the silane coupling agent include alcohol, ether, ketone, and hydrocarbon. The solvents can be used alone or in combination of two or more. The concentration of the silane coupling agent in the diluent can be set as appropriate, but is usually 10 to 50% by mass.

[0024] From the viewpoints of preventing the destruction of the hollow structure and economy, the amount of the silane coupling agent used is preferably 0.01 to 10% by mass, more preferably 0.03 to 7% by mass, and still more preferably 0.07 to 5% by mass with respect to the inorganic oxide hollow particles. Here, the amount used refers to the effective amount of the silane coupling agent.

[0025] In the present invention, a planetary mixer is used for the dry process. A planetary mixer is a kneader in which a multi-axis blade rotates and revolves (planetary motion) throughout the tank. The blades are usually 2 to 4 axes, preferably 2 axes. Examples of the shape of the blade include a hook type and a frame type, and the frame type is preferred. As the planetary mixer, an industrially available one may be used. For example, a planetary mixer (planetary twin-screw kneader) (5DMV-01-rr type, manufactured by Dalton Co., Ltd.) can be mentioned.

[0026] The kneading conditions can be set as appropriate. For example, the rotation speed is preferably 100 ± 20 (min -1 ), and the revolution speed is preferably 50 ± 10 (min -1 ). The rotation direction can be selected as appropriate. The kneading time is usually 10 ± 5 minutes, and the kneading temperature is usually normal temperature (20 ± 15°C).

[0027] Incidentally, as kneading apparatuses, there are known a fluidized kneading apparatus (for example, Henschel mixer, micro speed mixer) that rotates blades attached to the bottom of a tank at high speed and disperses and mixes a sample like a fluid by the strong shearing and impact actions of the blades, a vibratory kneading apparatus (for example, low-frequency resonance acoustic mixer) that generates resonance energy by applying vibration of a specific frequency to the sample and mixes with this resonance energy, a rocking mixer (for example, rocking type OM mixer) that uses no stirring blades and mixes while rocking a sample on a rocking plate with a flexible rubber ball in random directions, etc. However, these apparatuses have different principles from a planetary kneader, and since a strong external force is applied to the inorganic oxide hollow particles, the inventors confirmed that the hollow structure is easily destroyed.

[0028] In this way, by dry-treating the inorganic oxide hollow particles with a silane coupling agent, surface-coated inorganic oxide hollow particles with the particle surface coated with the silane coupling agent can be obtained.

[0029] <Drying> The surface-coated inorganic oxide hollow particles may be dried if necessary. Examples of the drying method include a box dryer, a band dryer, and a spray dryer. The drying temperature and drying time can be appropriately set according to the type of solvent used, etc.

[0030] The surface-coated inorganic oxide hollow particles produced by the method of the present invention can have the following characteristics. (i) The average particle diameter is preferably 5 μm or less, more preferably 4.5 μm or less, and still more preferably 4 μm or less. Incidentally, the lower limit value of such an average particle diameter is preferably 0.3 μm or more, more preferably 0.4 μm or more, and still more preferably 0.5 μm or more from the viewpoint of ensuring a sufficient cavity. Here, in this specification, the "average particle diameter" means the particle diameter (D 50) is meant. For the measurement of the particle size distribution, for example, a laser diffraction / scattering type particle size distribution measuring device can be used. (ii) The dielectric loss tangent is preferably 0.0022 or less, more preferably 0.0021 or less, and still more preferably 0.0020 or less. The lower limit of the dielectric loss tangent is not particularly limited and may be 0. Here, in this specification, the "dielectric loss tangent" refers to the dielectric loss tangent at 1 GHz, and it is measured at 1 GHz in an environment of a temperature of 25°C and a humidity of 60%. The dielectric loss tangent can be measured, for example, using a perturbation type cavity resonator (manufactured by KEYCOM). (iii) The amount of adhering moisture is preferably 2% by mass or less, more preferably 1.5% by mass or less, and still more preferably 1% by mass or less. The lower limit of the amount of adhering moisture is not particularly limited and may be 0% by mass. Here, in this specification, the "moisture adhesion rate" is calculated from the weight loss amount after curing for 100 hours in an environment of a temperature of 50°C and a humidity of 95% RH and then heating to 300°C by thermogravimetric measurement. As the thermogravimetric measuring device, for example, a high-sensitivity differential type differential thermal balance (STA 2500 Regulus, manufactured by Bruker AXS) can be used.

[0031] The surface-coated inorganic oxide hollow particles produced by the method of the present invention can be applied to heat insulating materials, heat shielding materials, catalyst carriers, building materials, electronic materials, etc. However, because of their small particle size and low dielectric loss tangent, they are useful for electronic materials, particularly wiring circuit boards, semiconductor encapsulants, etc.

[0032] For example, the surface-coated inorganic oxide hollow particles can be mixed and used with a medium. The medium is not particularly limited, and examples thereof include resins, paints, rubbers, and solvents. The mixing method and mixing conditions can be appropriately selected according to the use. When using a resin as the medium, it can be made into a resin composition for forming electronic materials such as wiring circuit boards and semiconductor encapsulants. Note that the resin is not particularly limited as long as it is commonly used in the fields of wiring circuits and semiconductor encapsulants. The content of the surface-coated inorganic oxide hollow particles in the resin composition can be appropriately selected according to its use, but is usually 1 to 97% by mass, preferably 5 to 60% by mass, and more preferably 15 to 40% by mass.

Examples

[0033] Hereinafter, the embodiments of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[0034] 1. Analysis of chemical composition The inorganic oxide hollow particles were molded with a press to produce briquettes, and the briquettes were measured by a fluorescence X-ray analyzer (ZSX primus II, manufactured by Rigaku Corporation) in terms of oxide conversion. The chemical components were calculated by correcting according to the following formula so that the total value of the oxides (SiO2, Al2O3, CaO, MgO, B2O3) of the elements to be analyzed was 100%.

[0035] Chemical composition (after correction) (%) = Chemical composition (before correction) × 100 / (100 - Impurity (%)) 〔In the formula, Impurity (%) is the value obtained by subtracting the total value of the chemical composition of the above-mentioned oxides from 100.〕

[0036] 2. Measurement of average particle size Using a laser diffraction particle size distribution measuring device (MT3000II, manufactured by Microtrac Bell Co., Ltd.), a volume-based particle size distribution was created in accordance with JIS R 1629, and the particle size (D 50 ) corresponding to 50% of the cumulative distribution curve was obtained.

[0037] 3. Measurement of porosity and cracking rate Using a dry-type automatic densitometer (Accupic, manufactured by Shimadzu Corporation), the bulk density and true density of the inorganic oxide hollow particles were measured, the porosity was calculated according to the following formula (1), and the cracking rate of the inorganic oxide hollow particles was calculated according to the following formula (2). The "bulk density" was measured by the gas displacement method in accordance with JIS R 1620. The true density was measured with a dry-type automatic densitometer before and after treatment with a silane coupling agent to remove the hollow part.

[0038] Porosity = (True density - Bulk density) × 100 / True density (1)

[0039] Cracking rate (%) = 100 - (Bulk density before treatment / Bulk density after treatment) × 100 (2)

[0040] 4. Measurement of the amount of adsorbed moisture After curing for 100 hours in an environment of temperature 50°C and humidity 95%RH, using a high-sensitivity differential scanning calorimeter (STA 2500 Regulus, manufactured by Bruker AXS), heating was carried out up to 300°C to measure the weight, and the amount of adsorbed moisture was measured from the weight loss amount.

[0041] 5. Measurement of dielectric loss tangent Using a perturbation-type cavity resonator (manufactured by KEYCOM), measurement was carried out at a frequency of 1 GHz in an environment of temperature 25°C and humidity 60%.

[0042] Production Example 1 Raw material compounds (colloidal silica, tetraethyl orthosilicate, aluminum nitrate nonahydrate, magnesium nitrate hexahydrate, boric acid) were dissolved in 250 kg of ion-exchanged water to achieve the molar concentrations shown in Table 1, and the raw material mixed aqueous solution was charged into a solution tank. The charged aqueous solution was sent to a two-fluid nozzle by a liquid feed pump. The spraying conditions of the two-fluid nozzle were set as nozzle air volume 500 L / min and liquid feed rate 470 mL / min. The raw material mixed aqueous solution was sprayed from the two-fluid nozzle into a spray pyrolysis furnace and heated at 1100°C. It was rapidly cooled by a cooling mechanism installed at the reaction zone outlet, and then the inorganic oxide hollow particles were recovered using a bag filter. The chemical composition of the obtained inorganic oxide hollow particles is shown in Table 2.

[0043]

Table 1

[0044]

Table 2

[0045] Example 1 1 g (1.0 wt%) of a silane coupling agent (3-aminopropyltrimethoxysilane, KBE-903: manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of the inorganic oxide hollow particles obtained in Production Example 1, and using a planetary mixer (planetary twin-screw kneader) (5DMV-01-rr type, manufactured by Dalton), at 25°C, rotation speed 100 ± 20 min -1 , revolution speed 50 ± 10 min -1 and stirred for 10 minutes, then dried at 120°C for 3 hours. For the inorganic oxide hollow particles obtained after drying, the average particle diameter, dielectric loss tangent, and porosity were measured. Also, in order to confirm the degree of surface coating of the inorganic oxide hollow particles with the silane coupling agent, the amount of adsorbed moisture was measured. The results are shown together in Table 3.

[0046] Examples 2 to 6 The inorganic chloride hollow particles were treated and analyzed in the same procedure as in Example 1, except that the amount of the silane coupling agent used was changed to the amount shown in Table 3. The results are shown in Table 3.

[0047] Comparative Example 1 The inorganic chloride hollow particles obtained in Production Example 1 were analyzed in the same procedure as in Example 1. The results are shown in Table 3.

[0048] Comparative Example 2 To 100 g of the inorganic oxide hollow particles obtained in Production Example 1, 100 g of ion-exchanged water, 400 g of ethanol, and 1 g (1.0 wt%) of a silane coupling agent (3-aminopropyltrimethoxysilane, KBE-903: manufactured by Shin-Etsu Chemical Co., Ltd.) were added, and using a planetary mixer (planetary twin-screw kneader) (5DMV-01-rr type, manufactured by Dalton Co., Ltd.), at 25 °C, rotation speed 100 ± 20 min -1 , revolution speed 50 ± 10 min -1 The inorganic hydrochloric oxide hollow particles were analyzed in the same procedure as in Example 1, except that wet treatment was performed by stirring for 10 minutes. The results are shown in Table 3.

[0049] Comparative Example 3 The dry treatment of the inorganic oxide hollow particles was changed to a Lodige mixer (three-dimensional flow kneader) (M20 type, manufactured by Matsubo), and the inorganic hydrochloric oxide hollow particles were treated and analyzed in the same procedure as in Example 1, except that stirring was performed at 25 °C and a rotation speed of 100 ± 20 rpm for 10 minutes. The results are shown in Table 3.

[0050] Comparative Example 4 The dry treatment of the inorganic oxide hollow particles was changed to an OM mixer (oscillating kneader) (OM-10E type, manufactured by Chiyoda Machinery), and the inorganic hydrochloric oxide hollow particles were treated and analyzed in the same procedure as in Example 1, except that stirring was performed at 25 °C and a rotation speed of 100 ± 20 rpm for 10 minutes. The results are shown in Table 3.

[0051]

Table 3

[0052] From Table 3, it can be seen that by surface-treating with a silane coupling agent by a dry treatment method using a planetary kneader, even though the porosity of the inorganic oxide hollow particles exceeds 70%, surface-coated inorganic oxide hollow particles can be obtained with almost no destruction of the hollow structure.

Claims

1. A method for producing surface-coated inorganic oxide hollow particles, wherein inorganic oxide hollow particles are surface-treated with a silane coupling agent by a dry treatment method using a planetary mixer.

2. The production method according to Claim 1, wherein the silane coupling agent is a nitrogen-containing silane coupling agent.

3. The production method according to Claim 1, wherein the amount of the silane coupling agent used is 0.01 to 10% by mass based on the inorganic oxide hollow particles.

4. The production method according to Claim 1, wherein the porosity of the inorganic oxide hollow particles is 45% or more.

5. The production method according to Claim 1, wherein the planetary mixer is a planetary twin-screw kneader.

6. The production method according to any one of Claims 1 to 5, wherein the inorganic oxide hollow particles are composed of an inorganic oxide containing one or more elements selected from the elements of Group 1, Group 2, Group 4, Group 8, Group 9, Group 10, Group 11, Group 12, Group 13, and Group 15 of the periodic table, and silicon oxide.

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