Hollow silica particle and method for producing the same

0001The present disclosure relates to hollow silica particles and a method for producing the same.

0002Hollow silica particles having an outer shell portion forming an internal space and having an outer shell portion composed of a component containing silica have characteristics such as low refractive index, low dielectric constant, low thermal conductivity, and low density. It is expected to be applied as an antireflection material, a low dielectric material, a heat insulating material, and a low density filler, and is attracting attention.

0003As a method for producing hollow silica particles, an outer shell composed of a component containing silica on the surface of the template particles by assembling and condensing silica precursors on the surface of the template particles (emulsifying oil droplets) which is a space inside the particles. A method (template method) for producing hollow silica particles by removing template particles after forming a portion is known (for example, Patent Documents 1 and 2).

0004Further, as another method for producing hollow silica particles, an aqueous solution of an alkali metal silicate such as sodium silicate (water glass) is spray-dried to prepare silica precursor particles, and the silica precursor particles are acid-treated. A method of removing the alkali metal in the precursor particles to produce hollow silica particles is known (for example, Patent Documents 3 and 4).

<p num="0005"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2009-203115</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2011-126761</text></patcit><patcit num="3"><text>WO2013 / 121703</text></patcit><patcit num="4"><text>JP-A-2015-155373</text></patcit></p>

<p num="0006"> The template method disclosed in Patent Documents 1 and 2 is expensive because the process is complicated and the silica concentration is low.</p><p num="0007"> The production method using spray drying of water glass disclosed in Patent Documents 3 and 4 can be lower in cost than the template method, but it is necessary to remove the alkali metal by acid treatment after spray drying. When used in electronic materials, further reduction of alkali metals is required.</p><p num="0008"> The present disclosure provides a method for producing hollow silica particles, which can easily obtain hollow silica particles having a reduced alkali metal content.</p>

<p num="0009"> The present disclosure relates to, in one aspect, a method for producing hollow silica particles, which comprises the following steps (1) and (2). (1) A step of spray-drying a silica solution prepared by dissolving silica in an organic alkaline aqueous solution to obtain a hollow silica precursor. (2) A step of calcining the hollow silica precursor to obtain hollow silica particles.</p><p num="0010"> The present disclosure is, in another aspect, hollow silica particles having an outer shell portion forming an internal space, wherein the outer shell portion is composed of a component containing silica, and the outer shell portion is a closed pore. The closed pores relate to hollow silica particles which are pin-dot-shaped when the fractured surface of the outer shell portion is observed.</p><p num="0011"> The present disclosure is, in another aspect, hollow silica particles comprising an outer shell portion forming an internal space, wherein the outer shell portion is composed of a component containing silica, and the outer shell portion has closed pores. The hollow silica particles have a BET specific surface area of 20 m.²For hollow silica particles that are less than / g.</p>

<p num="0012"> The present disclosure can exert an effect that hollow silica particles having a reduced alkali metal content can be easily obtained.</p>

0013<figref num="1">FIG. 1 is an example of an SEM image of the hollow silica particles of Example 1.</figref><figref num="2">FIG. 2 is an example of an SEM image of a resin split cross section containing hollow silica particles of Example 1.</figref><figref num="3">FIG. 3 is an example of an SEM image of the fractured surface of the outer shell portion of the hollow silica particles of Example 1.</figref><figref num="4">FIG. 4 is an example of an SEM image of the fractured surface of the outer shell portion of the hollow silica particles of Comparative Example 3.</figref>

0014The present disclosure is based on the finding that hollow silica particles having a reduced alkali metal content can be easily obtained by spray-drying a silica solution prepared by dissolving silica in an organic alkaline aqueous solution.

0015That is, the present disclosure relates to a method for producing hollow silica particles (hereinafter, also referred to as "manufacturing method according to the present disclosure"), which comprises the following steps (1) and (2) in one aspect. (1) A step of spray-drying a silica solution prepared by dissolving silica in an organic alkaline aqueous solution to obtain a hollow silica precursor. (2) A step of calcining the hollow silica precursor to obtain hollow silica particles.

0016According to the production method according to the present disclosure, it is possible to easily obtain hollow silica particles having a reduced alkali metal content.

0017The details of the mechanism by which the effects of the present disclosure are exhibited are not clear, but are presumed as follows. That is, by using an organic alkaline aqueous solution for dissolving silica, the alkali metal content in the silica solution used for spray drying can be reduced, and hollow silica particles having a reduced alkali metal content can be obtained. Further, it is considered that the organic alkali in the hollow silica precursor disappears or evaporates in the firing step, so that fine and uniform closed pores are formed in the outer shell portion, and the porosity of the hollow silica particles is improved. However, the present disclosure may not be construed as limiting to these mechanisms.

0018In the present disclosure, the "hollow silica particles" are hollow silica particles having an outer shell portion forming an internal space and the outer shell portion is composed of a component containing silica, and are formed by the outer shell portion. Silica particles in which a gas such as air exists in the internal space. In the present disclosure, the "outer shell portion composed of components containing silica" means that the main component forming the skeleton of the outer shell portion is silica, and the component of the outer shell portion is preferably 50% by mass or more. , More preferably 70% by mass or more, still more preferably 90% by mass or more, and even more preferably 95% by mass or more is silicon dioxide. In the present disclosure, the "hollow silica precursor" is a powder particle obtained by spray-drying a silica solution, and is a particle that becomes a hollow silica particle by firing in the step (2).

0019Hereinafter, the details of the above steps (1) and (2) and each component used therein will be described.

0020[Process (1): Spray drying] The step (1) in the production method according to the present disclosure is a spray drying step of spray-drying a silica solution prepared by dissolving silica in an organic alkaline aqueous solution to obtain a hollow silica precursor. When the silica solution is spray-dried, the surface of the droplets of the silica solution dries to form a dense film, and the inside of the droplets dries to become hollow, and precursor particles having a hollow structure (hollow silica precursor) are obtained. Be done. The silica solution can be prepared, for example, by mixing silica with an organic alkaline aqueous solution. Therefore, the step (1) in the production method according to the present disclosure can include, for example, a dissolution step of mixing silica with an organic alkali aqueous solution and dissolving silica in the organic alkali aqueous solution to prepare a silica solution.

0021&lt;Silica&gt; Examples of silica used for preparing the silica solution include crystalline silica, amorphous silica, fumed silica, wet silica, colloidal silica, etc., from the viewpoint of ease of production, purity, and cost of the silica solution. Amorphous silica is preferred.

0022The state of silica before being mixed with the organic alkaline aqueous solution is not particularly limited, and examples thereof include powder, sol, and gel. From the viewpoint of use in electronic materials, high-purity silica is preferable, and ultra-high-purity silica is more preferable.

0023&lt;Organic alkaline aqueous solution&gt; The organic alkaline aqueous solution used for preparing the silica solution may be any one that can dissolve silica, and examples thereof include an organic alkaline aqueous solution having a pH of 11 or higher.

0024The organic alkali contained in the organic alkali aqueous solution may be any as long as it can dissolve silica, and the particle structure of the hollow silica particles is made uniform, the thickness of the outer shell is made uniform, the outer shell is formed stably, and the productivity is increased. From the viewpoint of improvement, for example, a secondary amine, a tertiary amine, a quaternary ammonium salt and the like can be mentioned, and from the viewpoint of ease of producing a silica solution, a quaternary ammonium salt is preferable.

0025As the quaternary ammonium salt, for example, from the viewpoint of homogenizing the particle structure of the hollow silica particles, homogenizing the thickness of the outer shell, forming the stable outer shell, and improving productivity, for example, the following formula (I) is used. Examples thereof include a salt composed of a quaternary ammonium cation and a hydroxide represented.<chemistry num="1"><img id="000003" he="32" wi="139" file="JP2017193462A_D0001.tif" img-format="tif" img-content="drawing" /></chemistry>

0026In the above equation (I), R₁, R₂, R₃And R₄Is at least one selected independently from an alkyl group having 1 or more and 22 or less carbon atoms, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group. The number of carbon atoms of the alkyl group is preferably 1 or more and 12 or less from the viewpoints of uniform particle structure of hollow silica particles, uniform thickness of outer shell, stable formation of outer shell, and improvement of productivity. More preferably 1 or more and 3 or less. Examples of the alkyl group include a linear alkyl group and a branched alkyl group, but a linear alkyl group is preferable from the viewpoint of making the thickness of the outer shell portion uniform.

0027Specific examples of the quaternary ammonium salt include tetramethylammonium hydroxide (hereinafter, also referred to as TMAH), tetraethylammonium hydroxide (hereinafter, also referred to as TEAH), dimethylbis (2-hydroxyethyl) ammonium hydroxide, and trimethyl. At least one selected from ethylammonium hydroxide can be mentioned, and TMAH or TMAH or from the viewpoint of homogenizing the particle structure of hollow silica particles, homogenizing the thickness of the outer shell, forming a stable outer shell, and improving productivity. TEAH is preferred.

0028Examples of the secondary amine include dimethylamine, diethylamine, dipropylamine, diethanolamine, diisopropanolamine, hexamethylenediamine and the like. Examples of the tertiary amine include trimethylamine, triethylamine triethanolamine, tetramethylhexanediamine, dimethylaminohexanol, butyldiethanolamine, tetramethylethylenediamine and the like.

0029&lt;Silica solution&gt; The silica solution can be obtained, for example, by mixing silica and an aqueous solution of an organic alkali to dissolve silica. The dissolution method is not particularly limited as long as silica can be dissolved, and a known dissolution method can be used. Examples of the melting method include heating treatment, pressure treatment, mechanical pulverization treatment, and the like, and these may be used in combination. The heating condition can be set to, for example, 60 to 200 ° C. The pressurizing condition can be set to, for example, 0 to 3 MPa. Mechanical pulverization can be performed using, for example, a ball mill or the like. Further, ultrasonic vibration may be applied when the silica is dissolved in the organic alkaline aqueous solution.

0030The silica concentration in the silica solution is preferably 2% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, and from the viewpoint of suppressing the formation of irregularly shaped particles and improving productivity. 30% by mass or less is preferable, 25% by mass or less is more preferable, and 20% by mass or less is further preferable. The content of silica in the silica solution can be measured using a thermogravimetric measuring device.

0031The molar ratio of silica (silica / organic alkali) to the organic alkali in the silica solution is preferably 0.5 or more, more preferably 1.0 or more, further preferably 1.5 or more, and 3.5 or less from the viewpoint of improving the porosity. Preferably, 3.0 or less is more preferable, and 2.5 or less is further preferable.

0032In the present disclosure, the silica solution may contain an aqueous solvent. Examples of the aqueous solvent include distilled water, ion-exchanged water, ultrapure water and the like.

0033&lt;Spray drying method&gt; Examples of the spray drying method include known methods such as a rotating disk method, a pressure nozzle, a two-fluid nozzle method, and a four-fluid nozzle method. For spray drying, for example, a commercially available spray drying device can be used.

0034The inlet temperature of the hot air in the spray drying is 80 ° C to 250 ° C. from the viewpoint of uniform particle structure of hollow silica particles, uniform thickness of outer shell, stable formation of outer shell, and improvement of productivity. ° C is preferable, 100 ° C to 220 ° C is more preferable, and 120 ° C to 200 ° C is even more preferable. From the same viewpoint, the outlet temperature of hot air in spray drying is preferably 50 ° C to 120 ° C, more preferably 60 ° C to 110 ° C, and even more preferably 70 ° C to 100 ° C. The outlet temperature can be adjusted by controlling the inlet temperature.

0035The spray pressure, spray amount, air volume, etc. at the time of spray drying may be appropriately set according to the spray drying device or the like to be used.

0036In the step (1), the silica solution used for spray drying (hereinafter, also referred to as "spray solution") may be diluted at the time of use. When a diluted silica solution is used as a spray solution, an aqueous solvent such as distilled water, ion-exchanged water, or ultrapure water can be used for dilution. From the viewpoint of improving productivity, the silica concentration in the spray liquid is preferably 2% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, and preferably 30% by mass or less, preferably 25% by mass. The following is more preferable, and 20% by mass or less is further preferable. The content of silica in the spray liquid can be calculated by the same method as the above silica solution.

0037In the present disclosure, the silica solution and the spray solution may contain other components as long as the effects of the present disclosure are not impaired. Examples of other components include organic binders and activators.

0038In the present disclosure, it is preferable that the silica solution and the spray solution do not substantially contain alkali metals such as Na and K from the viewpoint of application of hollow silica particles to electronic material applications. That is, the total amount of alkali metals in the silica solution or spray solution is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and further preferably 0.005% by mass or less. The alkali metal content in the silica solution or spray solution can be measured by the same method as for hollow silica particles described later.

0039The hollow silica precursor obtained in step (1) can be recovered by, for example, air classification. Therefore, in the production method according to the present disclosure, an air classification step of air-classifying the hollow silica precursor obtained by spray drying and selectively recovering it is performed between the step (1) and the step (2) described later. Can include. By air classification, the particle size can be made uniform, and particles with a particle size suitable for the intended use can be obtained. The air classification can be performed by a known method using, for example, an airflow type classifier, a bag filter, or the like.

0040[Process (2): Baking] The step (2) in the manufacturing method according to the present disclosure is a firing step of firing the hollow silica precursor obtained in the step (1). By this step (2), the organic alkali contained in the outer shell of the hollow silica precursor disappears or evaporates, so that a plurality of fine closed pores due to the organic alkali are formed as shown in FIG. Hollow silica particles having a shell portion can be obtained.

0041The firing temperature is preferably 700 ° C. or higher, more preferably 800 ° C. or higher, further preferably 900 ° C. or higher, and from the viewpoint of appropriately firing the pores, improving the porosity and improving the particle strength, and 1500 ° C or less is preferable, 1300 ° C or less is more preferable, and 1200 ° C or less is further preferable.

0042Firing can be performed using, for example, an electric furnace or the like. The firing time varies depending on the firing temperature and the like, but can usually be set to 0.5 to 100 hours, and 0.5 to 48 hours is preferable from the viewpoint of productivity.

0043[Hollow silica particles] The hollow silica particles obtained by the production method of the present disclosure are spherical particles as shown in FIG. 1 in one or more embodiments. Then, in one or more embodiments, the hollow silica particles obtained by the production method of the present disclosure have a hollow structure as shown in FIG. 2 when the SEM image of the resin split cross section containing the hollow silica particles is observed. It is a particle. In the SEM image of FIG. 2, the circular black part is the space inside the particle. That is, the present disclosure relates to hollow silica particles having an outer shell portion forming an internal space and the outer shell portion being composed of a component containing silica (hereinafter, also referred to as "hollow silica particles according to the present disclosure"). .. Then, the hollow silica particles according to the present disclosure are the step (1) of obtaining a hollow silica precursor by spray-drying a silica solution prepared by dissolving silica in an organic alkaline aqueous solution in one or more embodiments, and the hollow silica. It is obtained through the steps (2) of firing the precursor in order.

0044The outer shell portion of the hollow silica particles according to the present disclosure has closed pores. Then, in one or more embodiments, the closed pores have a pin-dot shape as shown in FIG. 3 when the fractured surface of the outer shell portion is observed by SEM. In the SEM image of FIG. 3, the portion that can be visually recognized as a black dot is a pin dot-shaped closed air hole. In the present disclosure, "closed pores" means pores caused by organic alkali as shown in FIG. 3 as described above in one or more embodiments. The "pores caused by organic alkali" are formed by the disappearance or evaporation of the organic alkali in the hollow silica precursor during the firing of the above-mentioned step (2) in one or more embodiments. Is. In one or more embodiments, the size of the closed pores when the fractured surface of the outer shell is observed by SEM is 5 nm or more and 100 nm or less. In the present disclosure, it is preferable that a plurality of closed pores are formed in the outer shell portion from the viewpoint of improving the porosity and the particle strength. In the present disclosure, from the viewpoint of improving the porosity and the particle strength, the fracture surface of the outer shell portion is 1 μm.²The average number of closed pores per unit is preferably 30 or more, more preferably 50 or more, further preferably 80 or more, preferably 300 or less, more preferably 250 or less, still more preferably 200 or less. The average number of closed pores can be measured by the method described in Examples.

0045According to the hollow silica particles according to the present disclosure, hollow silica particles having closed pores in the outer shell portion can be obtained. For example, since the hollow silica particles of the present disclosure have closed pores in the outer shell portion, the average particle size and the thickness of the outer shell portion are the same, as compared with the hollow silica particles having no closed pores in the outer shell portion. It is considered that the porosity can be improved, and further, when the hollow silica particles of the present disclosure have a large number of closed pores in the outer shell portion, the porosity can be further improved. Further, in the hollow silica particles of the present disclosure, for example, when the size of the closed pores formed in the outer shell portion is small (for example, about 5 to 30 nm), or when a plurality of closed pores are uniformly formed in the outer shell portion. When dispersed, it is considered that the propagation of cracks caused by an external impact or the like can be suppressed or the direction can be changed, and the decrease in particle strength can be suppressed.

0046The average particle size of the hollow silica particles according to the present disclosure can be appropriately adjusted in consideration of the application, etc., but from the viewpoint of dispersibility in the resin when the hollow silica particles are used as a resin-added filler or the like, 0.1 μm or more. Is preferable, 0.5 μm or more is more preferable, 1.0 μm or more is even more preferable, and 50 μm or less is preferable. The average particle size can be measured using a laser diffraction / scattering particle size distribution measuring device ("LA-750" manufactured by Horiba Seisakusho) or a Coulter counter ("Multisizer 3" manufactured by Beckman Coulter).

0047The BET specific surface area of the hollow silica particles according to the present disclosure is 20 m from the viewpoint of ensuring the denseness of the outer shell portion surface of the hollow silica particles.²/ G or less is preferable, 15m²/ G or less is more preferable, 10m²It is more preferably / g or less. The "BET specific surface area" can be measured by the method described in Examples described later.

0048In the present disclosure, the average particle size of the hollow silica particles can be appropriately adjusted depending on the concentration of each component in the silica solution, spraying conditions, firing conditions, and the like.

0049The bulk density of the hollow silica particles according to the present disclosure is 0.44 g / cm from the viewpoint of reducing the dielectric constant of the hollow silica particles and improving the particle strength.³The above is preferable, 0.66 g / cm³The above is more preferable, 0.88 g / cm³The above is more preferable, and 1.98 g / cm³The following is preferred, 1.76 g / cm³The following are more preferred, 1.54 g / cm³The following are more preferred and preferred. In the present disclosure, "bulk density" can be measured by a gas pycnometer. Specifically, it can be measured by the method described in Examples.

0050The porosity of the hollow silica particles according to the present disclosure is preferably 10% or more, more preferably 20% or more, further preferably 30% or more, and further preferably 30% or more, from the viewpoint of reducing the dielectric constant of the hollow silica particles and the strength. , 80% or less is preferable, 70% or less is more preferable, and 60% or less is further preferable. The porosity can be calculated by the following formula using a true density measuring device. Specifically, it can be measured by the method described in Examples. Porosity (%) = [1- (True density of hollow silica particles / True density of silica particles)] x 100

0051From the viewpoint of improving the quality of the electronic material, the hollow silica particles according to the present disclosure preferably do not substantially contain alkali metals such as Na and K. That is, the total content of the alkali metals in the hollow silica particles is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and further preferably 0.005% by mass or less. The alkali metal content in the hollow silica particles can be measured by the method described in Examples.

0052The hollow silica particles according to the present disclosure can be used in various fields in which the hollow silica particles can be used, and are used, for example, in a catalyst carrier; an enzyme carrier; an adsorption material; a separation material; an optical material; and a multilayer wiring structure of an electronic circuit. Insulation material; Semiconductor encapsulation material; Electronic material; Low dielectric constant material used for low-dielectric film and coating agent for low-dielectric film; Insulation material; Shielding material; Building material; Skin care cosmetics, Makeup cosmetics , Body care cosmetics, fragrance cosmetics and other cosmetic materials;

0053The present disclosure further discloses the following production methods, hollow silica particles, or uses. &lt;1&gt; A method for producing hollow silica particles, which comprises the following steps (1) and (2). (1) A step of spray-drying a silica solution prepared by dissolving silica in an organic alkaline aqueous solution to obtain a hollow silica precursor. (2) A step of calcining the hollow silica precursor to obtain hollow silica particles.

0054&lt;2&gt; The production method according to &lt;1&gt;, wherein the step (1) includes a dissolution step of mixing silica with an organic alkali aqueous solution and dissolving silica in an organic alkali aqueous solution to prepare a silica solution. &lt;3&gt; The production method according to &lt;1&gt; or &lt;2&gt;, wherein the organic alkali is a quaternary ammonium salt. &lt;4&gt; The production method according to &lt;3&gt;, wherein the quaternary ammonium salt is a salt composed of a quaternary ammonium cation and a hydroxide represented by the following formula (I).<chemistry num="2"><img id="000004" he="32" wi="139" file="JP2017193462A_D0001.tif" img-format="tif" img-content="drawing" /></chemistry>&lt;5&gt; In equation (I), R₁, R₂, R₃And R₄The production method according to &lt;4&gt;, wherein each is independently selected from an alkyl group having 1 or more and 22 or less carbon atoms, a hydroxymethyl group, a hydroxyethyl group and a hydroxypropyl group. &lt;6&gt; The production method according to &lt;5&gt;, wherein the alkyl group preferably has 1 or more and 12 or less carbon atoms, and more preferably 1 or more and 3 or less carbon atoms in the formula (I). &lt;7&gt; The production method according to &lt;5&gt; or &lt;6&gt;, wherein the alkyl group is a linear alkyl group or a branched alkyl group, preferably a linear alkyl group in the formula (I). &lt;8&gt; The quaternary ammonium salt is at least one selected from tetramethylammonium hydroxide, tetraethylammonium hydroxide, dimethylbis (2-hydroxyethyl) ammonium hydroxide, and trimethylethylammonium hydroxide, and is tetramethyl. The production method according to &lt;4&gt;, wherein ammonium hydroxide is preferable. &lt;9&gt; The production method according to any one of &lt;1&gt; to &lt;8&gt;, wherein the silica concentration in the silica solution is preferably 2% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more. .. &lt;10&gt; The production method according to any one of &lt;1&gt; to &lt;9&gt;, wherein the silica concentration in the silica solution is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less. &lt;11&gt; The production method according to any one of &lt;1&gt; to &lt;10&gt;, wherein the silica concentration in the silica solution is 2% by mass or more and 30% by mass or less. &lt;12&gt; The molar ratio of silica (silica / organic alkali) to the organic alkali in the silica solution is preferably 0.5 or more, more preferably 1.0 or more, still more preferably 1.5 or more, any of &lt;1&gt; to &lt;11&gt;. The manufacturing method described in. &lt;13&gt; The molar ratio of silica (silica / organic alkali) to the organic alkali in the silica solution is preferably 3.5 or less, more preferably 3.0 or less, still more preferably 2.5 or less, any of &lt;1&gt; to &lt;12&gt;. The manufacturing method described in. &lt;14&gt; The total amount of alkali metals in the silica solution is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, still more preferably 0.005% by mass or less, according to any one of &lt;1&gt; to &lt;13&gt;. Production method. &lt;15&gt; The inlet temperature of the hot air in the spray drying of the step (1) is preferably 80 ° C to 250 ° C, more preferably 100 ° C to 220 ° C, further preferably 120 ° C to 200 ° C, from &lt;1&gt;. The manufacturing method according to any one of &lt;14&gt;. &lt;16&gt; The outlet temperature of hot air in the spray drying of step (1) is preferably 50 ° C to 120 ° C, more preferably 60 ° C to 110 ° C, and even more preferably 70 ° C to 100 ° C. The manufacturing method according to any one of 1&gt; to &lt;15&gt;. &lt;17&gt; An air classification step of air-classifying and selectively recovering the hollow silica precursor obtained by spray drying is further included between the steps (1) and (2), from &lt;1&gt; to &lt;16&gt;. The manufacturing method described in any of&gt;. &lt;18&gt; The production method according to any one of &lt;1&gt; to &lt;17&gt;, wherein the firing temperature in the step (2) is preferably 700 ° C. or higher, more preferably 800 ° C. or higher, and even more preferably 900 ° C. or higher. .. &lt;19&gt; The production method according to any one of &lt;1&gt; to &lt;18&gt;, wherein the firing temperature in the step (2) is preferably 1500 ° C or lower, more preferably 1300 ° C or lower, and even more preferably 1200 ° C or lower. .. &lt;20&gt; Hollow silica particles having an outer shell portion forming an internal space, the outer shell portion being composed of a component containing silica, the outer shell portion having closed pores, and the closed pores being the outer outer shell. Hollow silica particles that are pin-dot-shaped when the fractured surface of the shell is observed. &lt;21&gt; Hollow silica particles having an outer shell portion forming an internal space and the outer shell portion being composed of a component containing silica, the outer shell portion having closed pores, and the hollow silica particles. BET specific surface area is 20m²Hollow silica particles that are less than / g. &lt;22&gt; Hollow silica particles having an outer shell portion forming an internal space and the outer shell portion being composed of a component containing silica, and the hollow silica particles are silica-dissolved in which silica is dissolved in an organic alkaline aqueous solution. It is obtained through a step of spray-drying the liquid to obtain a hollow silica precursor and a step of firing the hollow silica precursor in order, and the outer shell portion is a hollow silica particle having closed pores. &lt;23&gt; From &lt;20&gt;, preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more of the components of the outer shell portion are silicon dioxide. The hollow silica particles according to any one of &lt;22&gt;. &lt;24&gt; The hollow silica particles according to any one of &lt;20&gt; to &lt;23&gt;, wherein the closed pores are pores caused by an organic alkali. &lt;25&gt; The BET specific surface area of hollow silica particles is 20 m.²/ G or less is preferable, 15m²/ G or less is more preferable, 10m²The hollow silica particles according to any one of &lt;20&gt; to &lt;24&gt;, more preferably less than / g. &lt;26&gt; Fracture cross section of outer shell 1 μm²The hollow silica particles according to any one of &lt;20&gt; to &lt;25&gt;, wherein the average number of closed pores per particle is preferably 30 or more, more preferably 50 or more, and even more preferably 80 or more. &lt;27&gt; Fracture cross section of outer shell 1 μm²The hollow silica particles according to any one of &lt;20&gt; to &lt;26&gt;, wherein the average number of closed pores per particle is preferably 300 or less, more preferably 250 or less, and even more preferably 200 or less. &lt;28&gt; Fracture cross section of outer shell 1 μm²The hollow silica particles according to any one of &lt;20&gt; to &lt;27&gt;, wherein the average number of closed pores per particle is 30 or more and 300 or less. &lt;29&gt; The hollow silica particles according to any one of &lt;20&gt; to &lt;28&gt;, wherein the size of the closed pores when observing the fractured surface of the outer shell portion is 5 nm or more and 100 nm or less. &lt;30&gt; The hollow silica particles according to any one of &lt;20&gt; to &lt;29&gt;, wherein the porosity of the hollow silica particles is preferably 10% or more, more preferably 20% or more, still more preferably 30% or more. &lt;31&gt; The hollow silica particles according to any one of &lt;20&gt; to &lt;30&gt;, wherein the porosity of the hollow silica particles is preferably 80% or less, more preferably 70% or less, still more preferably 60% or less. &lt;32&gt; The hollow silica particles according to any one of &lt;20&gt; to &lt;31&gt;, wherein the porosity of the hollow silica particles is 10% or more and 80% or less. &lt;33&gt; The hollow silica particles according to any one of &lt;20&gt; to &lt;32&gt;, wherein the average particle size of the hollow silica particles is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1.0 μm or more. &lt;34&gt; The hollow silica particles according to any one of &lt;20&gt; to &lt;33&gt;, wherein the hollow silica particles have an average particle size of 50 μm or less. &lt;35&gt; The hollow silica particles according to any one of &lt;20&gt; to &lt;34&gt;, wherein the average particle size of the hollow silica particles is 0.5 μm or more and 50 μm or less. &lt;36&gt; The bulk density of hollow silica particles is 0.44 g / cm.³The above is preferable, 0.66 g / cm³The above is more preferable, 0.88 g / cm³The hollow silica particles according to any one of &lt;20&gt; to &lt;35&gt;, wherein the above is more preferable. &lt;37&gt; The bulk density of hollow silica particles is 1.98 g / cm.³The following is preferred, 1.76 g / cm³The following are more preferred, 1.54 g / cm³The hollow silica particles according to any one of &lt;20&gt; to &lt;36&gt;, wherein the following are more preferred and preferred. &lt;38&gt; The total content of alkali metals in the hollow silica particles is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, still more preferably 0.005% by mass, according to any one of &lt;20&gt; to &lt;37&gt;. Hollow silica particles. &lt;39&gt; The hollow silica particles according to any one of &lt;20&gt; to &lt;38&gt;, such as a catalyst carrier, an enzyme carrier, an adsorption material, a separation material, an optical material, an insulating material, a semiconductor encapsulation material, an electronic material, and a low dielectric constant. Use in at least one material selected from materials, insulating materials, shielding materials, building materials and cosmetic materials.

<p num="0055"> Hereinafter, the present disclosure will be described in more detail by way of examples, but these are exemplary and the present disclosure is not limited to these examples.</p><p num="0056">1. How to measure each parameter Various measurements of particles in Examples and Comparative Examples, which will be described later, were carried out by the following methods.</p><p num="0057"> [Measurement of bulk density] Using a gas pycnometer ("Ultrapyc1200e" manufactured by Kantachrome Instruments Japan GK), the bulk density was measured after 1 minute of degassing. The measurement was performed 10 times, and the average value was the bulk density (g / cm) of the hollow silica particles.³).</p><p num="0058"> [Measurement of porosity] The porosity was calculated by the following formula from the density measured using a gas pycnometer ("Ultrapyc1200e" manufactured by Kantachrome Instruments Japan GK). The true density of silica particles is 2.2 g / cm³Is. Porosity (%) = [1- (True density of hollow silica particles / True density of silica particles)] x 100</p><p num="0059"> [Measurement of BET specific surface area] The BET specific surface area of the hollow silica particles was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, trade name "Flowsorb III2305"). The sample was pretreated by heating at 200 ° C for 15 minutes.</p><p num="0060"> [Average particle size] The average particle size of the hollow silica particles is measured using a laser diffraction / scattering type particle size distribution measuring device (measured by setting the relative refractive index of "LA-920" manufactured by HORIBA, Ltd. to 1.4), and the volume-based median diameter (D50). Measured as. Furthermore, the average particle size of the hollow silica particles was measured using a Coulter counter (manufactured by Coulter Corporation, using a 50 μm aperture tube).</p><p num="0061"> [Particle strength] Particle strength is 10g of particles with zirconia balls (10mmφZrO)₂): A pulverization treatment (95 rpm, 1 hour) was performed using 200 g, and the evaluation was made from the amount of increase in the specific gravity of the particles before and after pulverization. The evaluation criteria are shown below. The amount of increase in specific gravity is 0.03 g / cm³In the following cases, it is judged that the particle strength is excellent, and the amount of increase in specific gravity is 0.03 g / cm.³If it exceeds, it is judged that the particle strength is inferior.</p><p num="0062"> [Alkali metal content] The alkali metal content in the hollow silica particles was measured using ICP-MS ("7700S" manufactured by Agilent) in accordance with JIS-K0133. An aqueous solution in which hollow silica particles were completely dissolved with hydrofluoric acid was used as a sample. Here, the content of Na contained in the hollow silica particles was defined as the content of alkali metal in the silica solution.</p><p num="0063"> [SEM observation of fractured surface of hollow silica particles and measurement of average thickness of outer shell] The hollow particles were kneaded with an epoxy resin, cured, and then the sample was cut. Then, the fractured surface was observed by using a field emission scanning electron microscope (SEM) ("S-4000" manufactured by Hitachi, Ltd.) at a magnification of 3,000 times. Then, the thickness of the outer shell of 50 to 100 hollow particles was measured on a photograph to obtain the average thickness of the outer shell.</p><p num="0064"> [SEM observation of the fracture surface of the outer shell and measurement of the average number of closed pores] The hollow particles were kneaded with an epoxy resin, cured, and then the sample was cut. Then, the fractured surface of the outer shell of the hollow particles was observed at a magnification of 50,000 times using a field emission scanning electron microscope (SEM) ("S-4000" manufactured by Hitachi, Ltd.). Then, the fracture surface of each of the 3 to 10 hollow particles is 1 μm.²The average number of closed pores was calculated from the number of closed pores per hit.</p><p num="0065">2. Production of hollow silica particles (Examples 1 to 34 and Comparative Examples 1 to 4) (Example 1) Hollow silica particles are produced through two steps, a spray drying step (1) and a firing step (2). First, a silica solution used in the spray drying step (1) was prepared. That is, in a reaction vessel equipped with a stirrer (pressure resistant glass industry, TEM-D1500M), silica (Admatex, Admafine SOE2): 200 g, tetramethylammonium hydroxide 25% aqueous solution (Seikem Asia, pH 14). ): 640 g and ion-exchanged water: 160 g are added and the temperature is raised to 180 ° C in 1 hour and 30 minutes, and then the silica solution (silica concentration) is stirred at 180 ° C for 1 hour. : 20% by mass, molar ratio (silica / organic alkali): 1.9) was obtained. The pressure in the reaction vessel during stirring at 180 ° C was 0.85 MPa.</p><p num="0066"> Next, the prepared silica solution was used as a spray solution as it was, and spray-dried using a spray dryer (SD-1000 manufactured by Tokyo Rika Kikai Co., Ltd.) to obtain a dry powder (hollow silica precursor) (spray drying step (spray drying step (spray drying step)). 1)). A two-fluid nozzle (sample discharge hole diameter: 0.4 mm) was used as the spray nozzle of the spray dryer. The spraying conditions are inlet temperature: 130 ° C, outlet temperature: 98 ° C, spray pressure: 250kPa, air volume: 0.7m.³/ Min, spray volume: 10 mL / min.</p><p num="0067"> Next, the dry powder (hollow silica precursor) obtained by spray drying was heated in an electric furnace (manufactured by Motoyama, SK-2535E-OP) to 1100 ° C at 100 ° C / hour, and then 1100 ° C. Hollow silica particles of Example 1 were obtained by holding in C for 1 hour and firing (calcination step (2)).</p><p num="0068"> The results of measuring the physical properties of the hollow silica particles of Example 1 are shown in Table 1 below. Then, the SEM image of the hollow silica particles of Example 1 is shown in FIG. From FIG. 1, it was found that the shape of the hollow silica particles of Example 1 was spherical. Further, FIG. 3 shows an SEM image of the fractured surface of the outer shell portion of the hollow silica particles of Example 1. In FIG. 3, black spots indicating closed pores could be visually confirmed. That is, from FIG. 3, it was confirmed that closed pores were formed in the outer shell portion of the hollow silica particles of Example 1.</p><p num="0069">(Examples 2-33) Hollow silica particles of Examples 2 to 33 were obtained by the same method as in Example 1 above, except that the concentration of each raw material in the silica solution and the spray drying conditions were changed as shown in Table 1. .. Table 1 shows the results of each physical property measurement.</p><p num="0070">(Example 34) First, a silica solution used in the spray drying step (1) was prepared. That is, in a reaction vessel equipped with a stirrer (pressure resistant glass industry, TEM-D1500M), silica (Admatex, Admafine SOE2): 200 g, tetraethylammonium hydroxide 20% aqueous solution (TEAH) (Wako Pure Chemical Industries, Ltd.) (Manufactured by Kogyo Co., Ltd.): 1287 g was added and the temperature was raised to 170 ° C in 1 hour and 30 minutes, and then the mixture was stirred at 170 ° C for 1 hour to dissolve the silica solution (silica) of Example 34. A concentration: 13% by mass and a molar ratio (silica / organic alkali): 1.9) were obtained. The pressure in the reaction vessel during stirring at 170 ° C was 1.20 MPa. Then, the hollow silica particles of Example 34 were used in the same manner as in Example 1 above, except that the silica solution of Example 34 was used as the spray liquid and the spray conditions were changed as shown in Table 1. Got Table 1 shows the results of measuring the physical properties of the hollow silica particles of Example 34.</p><p num="0071">(Comparative example 1) In a reaction vessel equipped with a stirrer, methanol (manufactured by Wako Pure Chemical Industries, Ltd.): 23.9 parts by weight, 30% aqueous solution of dodecyltrimethylammonium chloride (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 1.0 parts by weight, hexane (manufactured by Wako Pure Chemical Industries, Ltd.): 1.0 part by weight, 25% tetramethylammonium hydroxide (manufactured by Sechem Asia Co., Ltd.): 0.5 part by weight was added and stirred to prepare Solution A. Further, 71.6 parts by weight of ion-exchanged water was placed in a reaction vessel equipped with another stirrer and stirred to prepare solution B. Then, the solution B was added in 45 seconds while stirring the solution A, and then the mixture was stirred at 25 ° C. for 10 minutes to obtain an O / W type emulsion. Next, tetramethoxysilane (TMOS, manufactured by Tama Chemical Co., Ltd.): 2.0 parts by weight (solution C) was added to the O / W emulsion in 30 seconds, and then the mixture was stirred at 25 ° C for 10 minutes to obtain a cloudy liquid. It was. Then, the obtained cloudy liquid was filtered off using a filter paper of 5C, washed with water, and dried at 100 ° C. to obtain a white dry powder. The obtained dry powder was calcined at 1100 ° C. for 1 hour to obtain hollow silica particles of Comparative Example 1. Table 1 shows the results of measuring the physical properties of the hollow silica particles of Comparative Example 1.</p><p num="0072">(Comparative example 2) Comparative Example by the same method as in Example 1 above, except that colloidal silica (manufactured by Nissan Chemical Industries, Ltd., "Snowtex N", silica concentration 20% by mass) was used as silica and silica was not dissolved. 2 hollow silica particles were obtained. The obtained hollow silica particles of Comparative Example 2 had a hollow structure, but had a low porosity. Table 1 shows the results of measuring the physical properties of the hollow silica particles of Comparative Example 2.</p><p num="0073">(Comparative example 3) Water glass No. 3 (manufactured by Osaka Silica Soda Co., Ltd.) was used as silica, and spray drying was carried out in the same manner as in Example 1 above. The obtained dry powder was calcined at 500 ° C. for 1 hour to obtain the hollow silica powder of Comparative Example 4. When water glass is used as a raw material, silica dissolves when fired at a temperature of 500 ° C or higher due to the influence of sodium. The obtained silica particles of Comparative Example 3 had a hollow structure. Table 1 shows the results of measuring the physical properties of the hollow silica particles of Comparative Example 3. Then, FIG. 4 shows an SEM image of the fractured surface of the outer shell portion of the hollow silica particles of Comparative Example 3. In FIG. 4, black spots indicating closed pores could not be confirmed. That is, from FIG. 4, it was found that no closed pores were formed in the outer shell portion of the hollow silica particles of Comparative Example 3.</p><p num="0074">(Comparative example 4) Hollow silica particles of Comparative Example 4 were obtained in the same manner as in Comparative Example 1 except that the firing temperature was changed to 700 ° C. The hollow silica particles of Comparative Example 4 were mesoporous silica. The hollow silica particles of Comparative Example 4 have a bulk density of 2.20 g / cm.³, Porosity is 0%, BET specific surface area is 718m³It was / g.</p><p num="0075"><tables num="1"><img id="000005" he="222" wi="170" file="JP2017193462A_D0001.tif" img-format="tif" img-content="drawing" /></tables></p><p num="0076"> As shown in Table 1 above, in Examples 1 to 34, hollow silica particles containing no alkali metal content could be easily produced.</p><p num="0077"> Further, the average thickness and the average number of closed pores of the outer shell of the hollow silica particles of Examples 1 to 2, 11, 28 to 29, and 33, and the average closed pores of the outer shell of the hollow silica particles of Comparative Examples 1 to 3. The numbers are shown in Table 2. Furthermore, Table 2 also shows a partial excerpt of the physical characteristics of the hollow silica particles from Table 1.</p><p num="0078"><tables num="2"><img id="000006" he="83" wi="170" file="JP2017193462A_D0001.tif" img-format="tif" img-content="drawing" /></tables></p><p num="0079"> As shown in Table 2 above, the hollow silica particles of Examples 1 to 2, 11, 28 to 29, and 33 were hollow silica particles in which a plurality of closed pores were formed in the outer shell portion. On the other hand, the hollow silica particles of Comparative Examples 1 to 3 were hollow silica particles having no closed pores formed in the outer shell portion.</p>

0080According to the present disclosure, it is useful in the field of dealing with, for example, a catalyst carrier, an adsorbent, a substance separating agent, an immobilized carrier of an enzyme or a functional organic compound, an electronic material, etc., in which hollow silica particles can be used.