JP2019077586A - Method for producing hollow silica particles - Google Patents

Abstract

To provide a method for producing hollow silica particles by spray drying a silica dissolving solution which can change the porosity of hollow silica particles.SOLUTION: There is provided a method for producing hollow silica particles which comprises the following steps (1) and (2): (1) a step of spray drying a silica dissolved solution obtained by dissolving silica and a water-soluble polymer in an organic alkaline aqueous solution to obtain a hollow silica precursor; and (2) a step of firing the hollow silica precursor to obtain hollow silica particles.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to methods of making hollow silica particles.

  A hollow silica particle having an outer shell forming an inner space and the outer shell comprising a component containing silica has characteristics such as low refractive index, low dielectric constant, low thermal conductivity, and low density, It is expected to be applied as an antireflective material, low dielectric material, heat insulating material, and low density filler, and has attracted attention.

  As a method for producing hollow silica particles, an outer shell composed of a component containing silica on the surface of a template particle is prepared by aggregating and condensing a precursor of silica on the surface of a template particle (emulsified oil droplet) which is a space inside the particle. There is known a method (template method) in which hollow silica particles are produced by removing template particles after forming a part (for example, Patent Documents 1 and 2).

  Furthermore, 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 produce silica precursor particles, and the silica precursor particles are acid-treated Methods of removing alkali metal in precursor particles to produce hollow silica particles are known (for example, Patent Documents 3 and 4).

JP, 2009-203115, A JP, 2011-126761, A WO 2013/121703 JP, 2015-155373, A

  The template method disclosed in Patent Documents 1 and 2 is expensive because it is a complicated process and synthesis is performed at a low concentration of silica.

  The manufacturing method using spray drying of water glass disclosed in Patent Documents 3 and 4 can be lower cost than the template method, but it is necessary to remove the alkali metal by acid treatment after spray drying. And when using for the use of an electronic material, the further reduction of an alkali metal is calculated | required.

  With respect to these problems, the applicant has found that a hollow silica particle having a reduced alkali metal can be obtained by spray-drying a silica solution in which silica is dissolved in an organic alkali aqueous solution, and a patent application ( Japanese Patent Application No. 2016-084437 was carried out.

  The present disclosure provides a method of manufacturing hollow silica particles using the above-described spray drying of a silica solution, in which the porosity of the hollow silica particles can be changed.

The present disclosure relates, in one aspect, to a method for producing hollow silica particles, which comprises the following steps (1) and (2).
(1) A step of spray-drying a silica solution in which silica and a water-soluble polymer are dissolved in an organic alkali aqueous solution to obtain a hollow silica precursor.
(2) A step of firing the hollow silica precursor to obtain hollow silica particles.

  The present disclosure can easily obtain hollow silica particles with a reduced alkali metal content, and can exhibit the effect of being able to change the porosity of the hollow silica particles.

FIG. 1 is an example of a SEM image of the hollow silica particles of Example 1. FIG. 2 is an example of a SEM image of a fractured surface of the outer shell of the hollow silica particle of Example 1.

  In the present disclosure, hollow silica particles having a reduced alkali metal content can be easily obtained by spray-drying a silica solution in which silica and a water-soluble polymer are dissolved in an organic alkali aqueous solution, and water solubility is further achieved. The present invention is based on the finding that the porosity of hollow silica particles can be changed as compared to the case of spray-drying a silica solution to which no polymer is added.

That is, the present disclosure relates, in one aspect, to a method for producing hollow silica particles (hereinafter, also referred to as “production method according to the present disclosure”) including the following steps (1) and (2).
(1) A step of spray-drying a silica solution in which silica and a water-soluble polymer are dissolved in an organic alkali aqueous solution to obtain a hollow silica precursor.
(2) A step of firing the hollow silica precursor to obtain hollow silica particles.

  According to the manufacturing method according to the present disclosure, hollow silica particles having a reduced alkali metal content can be easily obtained, and further, the effect that the porosity of the hollow silica particles can be changed can be exhibited. . In particular, it is preferable to improve the porosity of the hollow silica particles in that hollow silica particles having a low dielectric constant can be obtained.

The details of the mechanism by which the effects of the present disclosure appear are not clear, but are presumed as follows.
That is, in the production method of the present disclosure, by using an organic alkali aqueous solution for dissolving silica, it is possible to reduce the alkali metal content in the silica solution to be used for spray drying, and hollow silica having a reduced alkali metal content. Particles can be obtained.
In addition, when a silica solution in which silica is dissolved in an organic alkali aqueous solution is spray-dried, the sprayed droplets become highly concentrated by drying and finally become hollow silica particles. In order to obtain particles with high porosity, it is considered important to quickly form a film on the surface of the spray droplet to suppress the shrinkage of the droplet. In the present disclosure, when the concentration of the spray droplets is increased by further adding a water-soluble polymer, particularly a water-soluble polymer having spinnability to the silica solution used for spray drying, it is preferable to It is considered that the porosity is improved as compared with the case where the water-soluble polymer is not added to the silica solution used for the spray drying because the film is formed faster by the threadability. However, it is considered that the porosity decreases as the molecular weight of the water-soluble polymer increases.
Furthermore, when the organic alkali and the water-soluble polymer in the hollow silica precursor disappear or evaporate in the firing step, fine and uniform closed pores are formed in the outer shell portion, and the porosity of the hollow silica particles is improved. Conceivable.
However, the present disclosure may not be interpreted as being limited to these mechanisms.

  In the present disclosure, the “hollow silica particles” are hollow silica particles comprising an outer shell forming an inner space, wherein the outer shell is composed of a component containing silica, and is formed by the outer shell It refers to silica particles in which a gas such as air is present in the internal space. In the present disclosure, “the outer shell composed of a component containing silica” means that the main component that forms the skeleton of the outer shell is silica, and preferably 50% by mass or more of the components of the outer shell It is more preferably 70% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, and 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 step (2).

  Hereinafter, the details of the steps (1) and (2) and the components used therein will be described.

[Step (1): spray drying]
The step (1) in the production method according to the present disclosure comprises silica (hereinafter, also referred to as “component a”) and a water-soluble polymer (hereinafter, also referred to as “component b”) an organic alkaline aqueous solution (hereinafter, “component c”) And a spray-drying step of obtaining a hollow silica precursor by spray-drying a silica solution (hereinafter also referred to as “the silica solution of the present disclosure”) dissolved in the solution. When the silica solution of the present disclosure is spray-dried, the droplet surface of the silica solution is dried to form a dense film, and the inside of the droplet is dried to form a cavity, which is a hollow precursor particle (hereinafter referred to as “hollow”. (Also referred to as “silica precursor”). The silica solution of the present disclosure can be prepared, in one or more embodiments, by mixing at least component a, component b and component c simultaneously or in any order. Therefore, in step (1) of the production method according to the present disclosure, in one or more embodiments, at least component a, component b and component c are mixed, component a and component b are dissolved in component c, and silica is dissolved A dissolution step can be included to prepare the solution. Component b, in one or more embodiments, may be pre-dissolved in water prior to mixing with component c.

<Silica (Component a)>
As silica (component a) used for preparation of the silica solution of this indication, crystalline silica, amorphous silica, fumed silica, wet silica, colloidal silica etc. are mentioned, for example, and manufacture of a silica solution is easy Amorphous silica is preferred from the viewpoint of properties, purity and cost. Component a can be used alone or in combination of two or more.

  The state of the component a before being mixed with the organic alkali aqueous solution may not be particularly limited, and examples thereof include powder, sol and gel. From the viewpoint of use for the application of the electronic material, the component a is preferably high purity silica, more preferably ultra high purity silica.

<Water-soluble polymer (component b)>
As the water-soluble polymer (component b) used for preparing the silica solution of the present disclosure, a water-soluble polymer having spinnability is preferable from the viewpoint of changing the porosity. Component b may be used alone or in combination of two or more.

  In the present disclosure, “water-soluble” of component b means having a solubility of 0.5 g / 100 mL or more in water (20 ° C.), and preferably, having a solubility of 2 g / 100 mL or more.

  In the present disclosure, “stringiness” is a so-called “threading” property in which the stretching property of an object appears, and “natto threading” and the like are mentioned as an example thereof. In one or more embodiments, spinnability exhibits a continuous thread-like structure without breaking to form droplets when the liquid composition is dropped at a low speed or stretched while holding one end thereof. It is a property and, for example, "stringing of mucus in animals and plants" and the like can be mentioned as an example. Spinnability is one of the elastic relaxation phenomena of liquid compositions, and it is generally known that physical properties are completely independent of surface tension and viscosity.

  In the present disclosure, the presence or absence of the spinnability of the water-soluble polymer can be determined by the following method. For example, using a polymer aqueous solution obtained by dissolving a water-soluble polymer in purified water so as to obtain a predetermined concentration (for example, 10% by mass), it is determined by a method according to the following [spinning property determination method] When having spinnability, it can be judged as a water-soluble polymer having spinnability.

[Method for determining spinnability]
When the dropping operation is gently performed from a Pasteur pipette (glass, for example, ASAHITECHNO GLASS, IK-PAS-5P) having an inner diameter of 1 mm at the tip, the aqueous solution obtained by twisting a thread is an aqueous solution exhibiting spinnability in the present disclosure it can.

  As the water-soluble polymer having spinnability of component b, from the viewpoint of changing the porosity, polymers having at least one group selected from vinyl group, pyrrolidone group, oxyalkylene group, and hydroxy group are mentioned. Be Examples of the oxyalkylene group include an oxyethylene group and an oxypropylene group. Specific examples include, for example, polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), polyvinyl alcohol (PVA), and hydroxymethyl cellulose (HMC). Among these, polyvinyl pyrrolidone (PVP) is preferable from the viewpoint of changing the porosity. In addition, polyethylene glycol (PEG) is preferable from the viewpoint of increasing the porosity.

  When component b is PVP, the weight average molecular weight of component b is preferably 1,000 or more, more preferably 5,000 or more, and still more preferably 10,000 or more, from the viewpoint of changing the porosity. 3,000,000 or less is preferable, 2,000,000 or less is more preferable, 1,200,000 or less is still more preferable. From the same viewpoint, the weight average molecular weight of the component b is preferably 1,000 or more and 3,000,000 or less, more preferably 5,000 or more and 2,000,000 or less, and 10,000 or more and 1,200,000 or less Is more preferred.

  When component b is PEG, the weight average molecular weight of component b is preferably 500 or more, more preferably 1,000 or more, still more preferably 2,000 or more, from the viewpoint of changing the porosity. 000,000 or less is preferable, 1,000,000 or less is more preferable, 500,000 or less is more preferable. From the same viewpoint, the weight average molecular weight of the component b is preferably 500 or more and 2,000,000 or less, more preferably 1,000 or more and 1,000,000 or less, and still more preferably 2,000 or more and 500,000 or less.

  In the present disclosure, the weight average molecular weight of the component b can be measured by gel permeation chromatography (GPC) using liquid chromatography (L-6000 high performance liquid chromatography manufactured by Hitachi Ltd.).

<Organic alkaline aqueous solution (component c)>
The organic alkaline aqueous solution (component c) used for preparation of the silica solution of the present disclosure may be any one as long as it can dissolve the component a and the component b, and examples thereof include an organic alkaline aqueous solution having a pH of 11 or more.

  The organic alkali contained in the component c may be any one as long as it can dissolve the component a and the component b, uniformizing the particle structure of the hollow silica particles, uniformizing the thickness of the outer shell, forming a stable outer shell, And from a viewpoint of productivity improvement, a secondary amine, a tertiary amine, quaternary ammonium salt etc. are mentioned, for example, and a viewpoint of manufacture easiness of a silica solution, a quaternary ammonium salt is preferred. The component c may be used alone or in combination of two or more.

From the viewpoint of homogenization of the particle structure of hollow silica particles, uniformity of the thickness of the outer shell, formation of a stable outer shell, and improvement of productivity as the quaternary ammonium salt, for example, the following formula (I) And salts of quaternary ammonium cation and hydroxide.

In the above formula (I), R ₁ , R ₂ , R ₃ and R ₄ are each independently at least at least one selected from an alkyl group having 1 to 22 carbon atoms, a hydroxymethyl group, a hydroxyethyl group and a hydroxypropyl group. It is one kind. The number of carbon atoms of the alkyl group is preferably 1 or more and 12 or less from the viewpoints of the uniformity of the particle structure of the hollow silica particles, the uniformity of the thickness of the outer shell, the formation of a stable outer shell, and the improvement of productivity. 1 or more and 3 or less are more preferable. Although a linear alkyl group or a branched alkyl group is mentioned as said alkyl group, A linear alkyl group is preferable from a viewpoint of making thickness of an outer shell part uniform.

  Specific examples of the quaternary ammonium salt include tetramethyl ammonium hydroxide (hereinafter also referred to as TMAH), tetraethyl ammonium hydroxide (hereinafter also referred to as TEAH), dimethyl bis (2-hydroxyethyl) ammonium hydroxide, and At least one selected from trimethylethylammonium hydroxide is mentioned, and from the viewpoint of homogenization of the particle structure of the hollow silica particles, uniformity of the thickness of the shell, formation of a stable shell, and improvement of productivity, TMAH Or TEAH is preferred.

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

Silica solution
In the silica solution of the present disclosure, as described above, in one or more embodiments, at least component a, component b and component c are mixed simultaneously or in any order to dissolve component a and component b in component c Can be obtained by The dissolution method is not particularly limited as long as the component a and the component b can be dissolved in the component c, and a known dissolution method can be used. As the dissolution method, for example, heating treatment, pressure treatment, mechanical crushing treatment and the like can be mentioned, and these may be used in combination. As heating conditions, it can set as 60-200 degreeC, for example. As pressurizing conditions, it can be set, for example, as 0 to 3 MPa. Mechanical grinding can be performed using, for example, a ball mill or the like. Furthermore, when dissolving the component a and / or the component b in the component c, ultrasonic vibration may be applied.

  The concentration of silica (component a) in the silica solution of the present disclosure is preferably 2% by mass or more, more preferably 5% by mass or more, and 10% by mass from the viewpoint of suppression of generation of irregularly shaped particles and improvement of productivity. The above is more preferable, and 30% by mass or less is preferable, 25% by mass or less is more preferable, and 20% by mass or less is more preferable. From the same viewpoint, the concentration of silica (component a) in the silica solution of the present disclosure is preferably 2% by mass to 30% by mass, more preferably 5% by mass to 25% by mass, and 10% by mass to 20% by mass. % Or less is more preferable. The content of component a in the silica solution can be measured using a thermogravimetric measurement apparatus. When component a is a combination of two or more types of silica, the content of component a refers to their total content.

  The molar ratio of silica (component a) to organic alkali in the silica solution of the present disclosure (silica / organic alkali) is preferably 0.5 or more, more preferably 1.0 or more, from the viewpoint of improving the porosity. 1.5 or more is further preferable, and 3.5 or less is preferable, 3.0 or less is more preferable, and 2.5 or less is still more preferable. From the same viewpoint, the molar ratio of silica (component a) to organic alkali (silica / organic alkali) is preferably 0.5 or more and 3.5 or less, more preferably 1.0 or more and 3.0 or less, and 1.5 More preferably, it is 2.5 or less.

  The content of the water-soluble polymer (component b) in the silica solution of the present disclosure may be an amount that can change the porosity. For example, from the viewpoint of changing the porosity, the content of component b in the silica solution of the present disclosure is preferably 0.1% by mass or more, and 0.3% by mass or more, with respect to silica (component a). Is more preferably 0.5% by mass or more, and from the same viewpoint, 5% by mass or less is preferable, 3% by mass or less is more preferable, and 2% by mass or less is more preferable. From the same viewpoint, the content of component b in the silica solution of the present disclosure is preferably 0.1% by mass or more and 5% by mass or less, and 0.3% by mass or more and 3% by mass with respect to silica (component a). % Or less is more preferable, and 0.5% by mass or more and 2% by mass or less is more preferable. When the component b is a combination of two or more water-soluble polymers, the content of the component b refers to the total content of them.

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

<Spray drying method>
Examples of the spray drying method include known methods such as a rotary 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 apparatus can be used.

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

  The spray pressure, the spray amount, the air flow rate, and the like at the time of the spray drying may be appropriately set according to the spray drying apparatus and the like to be used.

  In the step (1), the silica solution (hereinafter, also referred to as “spray solution”) used for spray drying may be diluted before use. In the case where a diluted solution of the silica solution is used as a spray solution, an aqueous solvent such as distilled water, ion exchange water, ultrapure water or the like can be used for dilution.

  The concentration of silica (component a) in the spray liquid is preferably 2% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and preferably 30% by mass or less from the viewpoint of productivity improvement. 25 mass% or less is more preferable, and 20 mass% or less is still more preferable. From the same viewpoint, the concentration of silica (component a) in the spray liquid of the present disclosure is preferably 2% by mass to 30% by mass, more preferably 5% by mass to 25% by mass, and 10% by mass to 20% by mass. The following is more preferable. The content of silica in the spray liquid can be calculated by the same method as the above-mentioned silica solution.

  In the present disclosure, the silica solution and the spray solution can contain other components as long as the effects of the present disclosure are not impaired. Examples of the other components include organic binders other than the component b and surfactants other than the component b.

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

  The hollow silica precursor obtained in the step (1) can be recovered by, for example, air classification. Therefore, in the manufacturing method according to the present disclosure, an air classification step of air classification and selectively recovering the hollow silica precursor obtained by spray drying is carried out between the step (1) and the step (2) described later. Can be included. By air classification, the particle size can be made uniform, and particles of a particle size suitable for the purpose of use can be obtained. The air classification can be performed by, for example, a known method using an air flow classifier, a bag filter, or the like.

[Step (2): Baking]
The step (2) in the production method according to the present disclosure is a firing step of firing the hollow silica precursor obtained in the step (1). In 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 resulting from the organic alkali are formed as shown in FIG. Hollow silica particles having a shell are obtained.

  The firing temperature is preferably 700 ° C. or more, more preferably 800 ° C. or more, still more preferably 900 ° C. or more, and 1500 ° C. or less from the viewpoint of appropriately baking the pores, and the viewpoint of porosity improvement and particle strength improvement. Is preferred, 1300 ° C. or less is more preferred, and 1200 ° C. or less is even more preferred. From the same viewpoint, the firing temperature is preferably 700 ° C. or more and 1500 ° C. or less, more preferably 800 ° C. or more and 1300 ° C. or less, and still more preferably 900 ° C. or more and 1200 ° C. or less.

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

[Hollow silica particles]
The hollow silica particles obtained by the production method according to the present disclosure are spherical particles as shown in FIG. 1 in one or more embodiments. In one or more embodiments, the hollow silica particles obtained by the production method of the present disclosure are particles having a hollow structure when the SEM image of the resin fractured surface containing the hollow silica particles is observed. That is, the present disclosure relates to a hollow silica particle (hereinafter, also referred to as “hollow silica particle according to the present disclosure”) having an outer shell portion forming an inner space, and the outer shell portion is composed of a component containing silica. . And the hollow silica particle which concerns on this indication spray-dried the silica solution which melt | dissolved the silica (component a) and water-soluble polymer (component b) in the organic alkali aqueous solution (component c) in one or several embodiment. And a step (1) of obtaining a hollow silica precursor and a step (2) of calcining the hollow silica precursor.

The shell of the hollow silica particle according to the present disclosure has a closed pore. And, in one or more embodiments, the closed pores are in the form of pin dots as shown in FIG. 2 when the fractured surface of the outer shell part is observed by SEM. In the SEM image of FIG. 2, the portion visible as a black dot is a pin dot-like closed pore. In the present disclosure, “closed pores” refers to pores resulting from an organic alkali and a water-soluble polymer as shown in FIG. 2 as described above in one or more embodiments. The “pores resulting from the organic alkali and the water-soluble polymer” means, in one or more embodiments, the organic alkali and the water-soluble polymer in the hollow silica precursor at the time of firing of the above-mentioned step (2). It is formed by disappearing or evaporation. In one or more embodiments, the size of the closed pores when the fractured surface of the outer shell part 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 be formed in the outer shell from the viewpoint of porosity improvement and particle strength improvement. In the present disclosure, from the viewpoint of improving porosity and improving particle strength, the average number of closed pores per 1 μm ² of the fractured surface of the outer shell portion is preferably 30 or more, more preferably 50 or more, and further 80 or more. Preferably, 300 or less is preferable, 250 or less is more preferable, and 200 or less is more preferable. The average number of closed pores can be measured, for example, by the following method.

<SEM observation of fractured surface of outer shell and measurement of average number of closed pores>
After the hollow particles are kneaded with epoxy resin and cured, the sample is cut. Then, the fractured section of the outer shell portion of the hollow particle is magnified (for example, 50,000 times) and observed using a field emission scanning electron microscope (SEM) ("S-4000" manufactured by Hitachi, Ltd.). The average number of closed pores can be determined from the number of closed pores per 1 μm ² of each of the plurality of (for example, 3 to 10) hollow particles.

  According 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, the average particle diameter and the thickness of the outer shell are the same, compared to hollow silica particles having no closed pores in the outer shell; It is considered that the porosity can be improved, and furthermore, the porosity can be further improved when the hollow silica particle of the present disclosure has a large amount of closed pores in the outer shell. Furthermore, in the hollow silica particle of the present disclosure, for example, when the size of the closed pores formed in the outer shell is small (for example, about 5 to 30 nm), or plural closed pores are uniformly distributed in the outer shell. In the case of dispersion, it is considered that the propagation of a crack due to an external impact or the like can be suppressed or diverted, and a decrease in particle strength can be suppressed.

  The average particle diameter of the hollow silica particles according to the present disclosure may be appropriately adjusted in consideration of the application etc., but from the viewpoint of dispersibility in the resin when using the hollow silica particles as a resin-added filler etc. The above is preferable, 0.5 micrometers or more are more preferable, 1.0 micrometers or more are still more preferable, and 50 micrometers or less are preferable. From the same viewpoint, 0.1 μm or more and 50 μm or less is preferable, 0.5 μm or more and 50 μm or less is more preferable, and 1.0 μm or more and 50 μm or less is still more preferable. The average particle size can be measured using a laser diffraction / scattering particle size distribution measuring apparatus (“LA-750” manufactured by Horiba, Ltd.) or a Coulter counter (“Multisizer 3” manufactured by Beckman Coulter, Inc.).

BET specific surface area of the hollow silica particles according to the present disclosure, in order to ensure the compactness of the outer shell surface of the hollow silica particles is preferably not more than 20 m ² / g, more preferably not more than 15m ² / g, 10m ² / g or less is more preferable. The "BET specific surface area" can be measured by the method described in the examples below.

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

The bulk density of the hollow silica particles according to the present disclosure is preferably 0.44 g / cm ³ or more, more preferably 0.66 g / cm ³ or more from the viewpoint of reducing the dielectric constant of the hollow silica particles and improving the particle strength. , 0.88 g / cm ³ or more, and then, preferably 1.98 g / cm ³ or less, more preferably 1.76 g / cm ³ or less, more preferably 1.54 g / cm ³ or less. From the same viewpoint, the bulk density of the hollow silica particles is preferably from 0.44 g / cm ³ or more 1.98 g / cm ³ or less, more preferably 0.66 g / cm ³ or more 1.76 g / cm ³ or less, 0. 88 g / cm ³ or more and 1.54 g / cm ³ or less are more preferable. In the present disclosure, “bulk density” can be measured by a gas pycnometer. Specifically, it can be measured by the method described in the examples.

The porosity of the hollow silica particles according to the present disclosure is preferably 10% or more, more preferably 20% or more, and still more 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 more preferable. From the same viewpoint, the porosity of the hollow silica particles is preferably 10% to 80%, more preferably 20% to 70%, and still more preferably 30% to 60%. The porosity can be calculated by the following equation using a true density measuring device. Specifically, it can be measured by the method described in the examples.
Porosity (%) = [1− (true density of hollow silica particles / true density of silica particles)] × 100

  It is preferable that the hollow silica particle which concerns on this indication does not contain alkali metals, such as Na and K, substantially from a viewpoint of quality improvement of an electronic material. That is, 0.1 mass% or less is preferable, as for total content of the alkali metal in hollow silica particle, 0.01 mass% or less is more preferable, and 0.005 mass% or less is still more preferable. The alkali metal content in the hollow silica particles can be measured by the method described in the examples.

  The hollow silica particles according to the present disclosure can be used in various fields where hollow silica particles can be used, for example, catalyst carriers; enzyme carriers; adsorption materials; separation materials; optical materials; Insulating materials; semiconductor sealing materials; electronic materials; low dielectric constant materials used for coating of low dielectric films and low dielectric films etc. materials for heat insulating materials; shielding materials; building materials; skin care cosmetics, makeup cosmetics And cosmetic materials such as body care cosmetics and fragrance cosmetics.

The present disclosure further discloses the following production methods, hollow silica particles, or applications.
The manufacturing method of the hollow silica particle containing the <1> following process (1) and (2).
(1) A step of spray-drying a silica solution in which silica and a water-soluble polymer are dissolved in an organic alkali aqueous solution to obtain a hollow silica precursor.
(2) A step of firing the hollow silica precursor to obtain hollow silica particles.

<2> The step (1) includes a dissolving step of mixing silica and a water-soluble polymer in an organic alkali aqueous solution, dissolving the silica and the water-soluble polymer in an organic alkali aqueous solution to prepare a silica solution. The manufacturing method as described in>.
<3> The method according to <1> or <2>, wherein the water-soluble polymer is a water-soluble polymer having spinnability.
<4> The method according to any one of <1> to <3>, wherein the water-soluble polymer has at least one group selected from a vinyl group, a pyrrolidone group, an oxyalkylene group, and a hydroxy group.
<5> The method according to any one of <1> to <4>, wherein the water-soluble polymer is at least one selected from polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, and hydroxymethyl cellulose.
<6> When the water soluble polymer is PVP, the weight average molecular weight of the water soluble polymer is preferably 1,000 or more, more preferably 5,000 or more, and still more preferably 10,000 or more. The manufacturing method in any one of <><5>.
<7> When the water soluble polymer is PVP, the weight average molecular weight of the water soluble polymer is preferably 3,000,000 or less, more preferably 2,000,000 or less, and 1,200,000 or less The production method according to any one of <1> to <6>, further preferably.
When the water-soluble polymer is PVP, the weight-average molecular weight of the water-soluble polymer is preferably 1,000 or more and 3,000,000 or less, more preferably 5,000 or more and 2,000,000 or less. The production method according to any one of <1> to <7>, preferably 10,000 to 1,200,000.
<9> When the water-soluble polymer is PEG, the weight-average molecular weight of the water-soluble polymer is preferably 500 or more, more preferably 1,000 or more, and still more preferably 2,000 or more, from <1> The manufacturing method in any one of <8>.
<10> When the water soluble polymer is PEG, the weight average molecular weight of the water soluble polymer is preferably 2,000,000 or less, more preferably 1,000,000 or less, and further preferably 500,000 or less. The production method according to any one of <1> to <9>, which is preferable.
<11> When the water soluble polymer is PEG, the weight average molecular weight of the water soluble polymer is preferably 500 or more and 2,000,000 or less, and more preferably 1,000 or more and 1,000,000 or less. The production method according to any one of <1> to <10>, more preferably 2,000 or more and 500,000 or less.
<12> The content of the water-soluble polymer in the silica solution is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and further preferably 0.5% by mass or more based on silica. The production method according to any one of <1> to <11>, which is preferable.
<13> The content of the aqueous solution polymer in the silica solution is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 2% by mass or less based on silica. The manufacturing method as described in any one of 12>.
<14> The content of the aqueous solution polymer in the silica solution is preferably 0.1% by mass to 5% by mass, more preferably 0.3% by mass to 3% by mass, with respect to the silica. The production method according to any one of <1> to <13>, wherein 5% by mass or more and 2% by mass or less is more preferable.
The manufacturing method as described in <14> from <1> whose <15> organic alkali is a quaternary ammonium salt.
The manufacturing method as described in <15> which is a salt which a <16> quaternary ammonium salt is represented with following formula (I), and consists of a quaternary ammonium cation and a hydroxide.
<17> In Formula (I), R ₁ , R ₂ , R ₃ and R ₄ are each 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 The manufacturing method as described in <16> which is at least 1 sort (s).
<18> In the formula (I), the carbon number of the alkyl group is preferably 1 or more and 12 or less, and more preferably 1 or more and 3 or less.
The manufacturing method as described in <17> or <18> in which the said alkyl group is a linear alkyl group or a branched alkyl group in <19> Formula (I), and a linear alkyl group is preferable.
<20> The quaternary ammonium salt is at least one selected from tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, dimethyl bis (2-hydroxyethyl) ammonium hydroxide, and trimethyl ethyl ammonium hydroxide, and is tetramethyl The manufacturing method as described in <15> or <16> which ammonium hydroxide is preferable.
2 mass% or more is preferable, 5 mass% or more is more preferable, 10 mass% or more is still more preferable, The manufacturing method in any one of <1> to <20> in <21> silica solution .
30 mass% or less is preferable, 25 mass% or less is more preferable, 20 mass% or less is still more preferable, the manufacturing method in any one of <1> to <21> in <22> silica solution .
<23> The silica concentration in the silica solution is preferably 2% by mass to 30% by mass, more preferably 5% by mass to 25% by mass, and still more preferably 10% by mass to 20% by mass, <1> The manufacturing method in any one of <22>.
<24> The molar ratio of silica to organic alkali in the silica solution (silica / organic alkali) is preferably 0.5 or more, more preferably 1.0 or more, and still more preferably 1.5 or more, from <1> The manufacturing method in any one of <23>.
<25> The molar ratio of silica to organic alkali in the silica solution (silica / organic alkali) is preferably 3.5 or less, more preferably 3.0 or less, still more preferably 2.5 or less, from <1> The manufacturing method in any one of <24>.
<26> The molar ratio of silica to organic alkali in the silica solution (silica / organic alkali) is preferably 0.5 or more and 3.5 or less, more preferably 1.0 or more and 3.0 or less, and 1.5 or more The production method according to any one of <1> to <25>, further preferably 2.5 or less.
0.1 mass% or less is preferable, as for the total amount of the alkali metal of a <27> silica solution, 0.01 mass% or less is more preferable, 0.005 mass% or less is still more preferable, <1> to <26> The manufacturing method according to any one of the above.
The inlet temperature of the hot air in the spray drying of <28> step (1) is preferably 80 ° C. to 250 ° C., more preferably 100 ° C. to 220 ° C., further preferably 120 ° C. to 200 ° C., <1> to <27> The manufacturing method according to any one of the above.
50 degreeC-120 degreeC is preferable, as for the exit temperature of the hot air in spray drying of <29> process (1), 60 degreeC-110 degreeC is more preferable, 70 degreeC-100 degreeC is still more preferable, <1><28> The manufacturing method according to any one of the above.
<30><1> to <29, further including an air classification step of air classification and selectively recovering the hollow silica precursor obtained by spray drying, between the step (1) and the step (2). The manufacturing method as described in any one of>.
700 degreeC or more is preferable, 800 degreeC or more is more preferable, and the calcination temperature in a <31> process (2) is a manufacturing method in any one of <1> to <30> still more preferable 900 degreeC or more.
1500 degrees C or less is preferable, 1300 degrees C or less is more preferable, and the calcination temperature in a <32> process (2) is a manufacturing method in any one of <1> to <31> still more preferable 1200 degrees C or less.
<33> The hollow silica particle is a hollow silica particle comprising an outer shell portion forming an inner space, wherein the outer shell portion is composed of a component containing silica, and the outer shell portion has a closed pore. The method according to any one of <1> to <32>, wherein the closed pores have a pin dot shape when observing the fractured surface of the outer shell.
In <33>, 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 of the components of the <34> outer shell part Manufacturing method described.
The manufacturing method as described in <33> or <34> whose <35> closed pore is a pore resulting from an organic alkali and a water-soluble polymer.
30 or more are preferable, 50 or more are more preferable, 80 or more are still more preferable, and the average number of closed pores per 1 μm ² of a cut surface of a <36> outer shell portion is preferably any one of <33> to <35> Manufacturing method described.
The average number of closed pores per 1 μm ² of the split surface of the <37> outer shell part is preferably 300 or less, more preferably 250 or less, still more preferably 200 or less, any of <33> to <36> Manufacturing method described.
<38> The manufacturing method according to any one of <33> to <37>, wherein an average number of closed pores per 1 μm ² of a fractured surface of the outer shell portion is 30 or more and 300 or less.
The manufacturing method in any one of <33> to <38> whose magnitude | sizes of the closed pore when the fractured surface of a <39> outer shell part is observed are 5 nm or more and 100 nm or less.
<40> BET specific surface area of the hollow silica particles is preferably not more than 20 m ² / g, more preferably not more than ^{15m 2 / g, 10m 2 /} g or less is more preferred, according to any one of <39> to <1> Manufacturing method.
The production method according to any one of <1> to <40>, wherein the porosity of the hollow silica particles is preferably 10% or more, more preferably 20% or more, and still more preferably 30% or more.
The production method according to any one of <1> to <41>, wherein the porosity of the hollow silica particles is preferably 80% or less, more preferably 70% or less, and still more preferably 60% or less.
The porosity of the <43> hollow silica particles is preferably 10% to 80%, more preferably 20% to 70%, still more preferably 30% to 60%, any of <1> to <42> Production method described in.
The average particle diameter of the <44> hollow silica particles is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 1.0 μm or more, <1> to <43> .
The manufacturing method in any one of <1> to <44> whose average particle diameter of <45> hollow silica particle is 50 micrometers or less.
The average particle diameter of the <46> hollow silica particles is preferably 0.1 μm to 50 μm, more preferably 0.5 μm to 50 μm, still more preferably 1.0 μm to 50 μm, any of <1> to <45> Production method described in.
The bulk density of the <47> hollow silica particles is preferably 0.44 g / cm ³ or more, more preferably 0.66 g / cm ³ or more, still more preferably 0.88 g / cm ³ or more, <1> to <46> The manufacturing method according to any one of the above.
<48> The bulk density of the hollow silica particles is preferably from 1.98 g / cm ³ or less, more preferably 1.76 g / cm ³ or less, more preferably 1.54 g / cm ³ or less, from the <1><47> The manufacturing method according to any one of the above.
The bulk density of <49> hollow silica particles is preferably from 0.44 g / cm ³ or more 1.98 g / cm ³ or less, 0.66 g / cm ³ or more, more preferably 1.76 g / cm ³ or less, 0.88 g The production method according to any one of <1> to <48>, more preferably ³ cm ³ or more and 1.54 g / cm ³ or less.
0.1 mass% or less is preferable, as for total content of the alkali metal in <50> hollow silica particle, 0.01 mass% or less is more preferable, 0.005 mass% is still more preferable, <1> to <49 The manufacturing method as described in any one of>.
Hollow silica particle obtained by the manufacturing method in any one of <51><1> to <50>.
<52> A catalyst carrier, an enzyme carrier, an adsorption material, a separation material, an optical material, an insulating material, a semiconductor sealing material, an electron, of the hollow silica particle obtained by the manufacturing method according to any one of <1> to <50> Use for at least one material selected from materials, low dielectric constant materials, materials for heat insulating materials, shielding materials, building materials and materials for cosmetics.

  Hereinafter, the present disclosure will be described in more detail by way of examples, but these are illustrative and the present disclosure is not limited to these examples.

1. Measurement Method of Each Parameter Various measurements of particles of Examples and Comparative Examples described later were performed by the following methods.

[Measurement of bulk density]
The bulk density was measured after degassing for 1 minute using a gas pycnometer ("Ultrapyc 1200e" manufactured by Cantachrome Instruments Japan Ltd.). The measurement was performed 10 times, and the average value was defined as the bulk density (g / cm ³ ) of the hollow silica particles.

[Measurement of porosity]
The porosity was calculated according to the following equation from the density measured using a gas pycnometer ("Ultrapyc 1200e" manufactured by Cantachrome Instruments Japan GK). The true density of the silica particles is 2.2 g / cm ³ .
Porosity (%) = [1− (true density of hollow silica particles / true density of silica particles)] × 100

[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 III 2305"). The sample was pretreated by heating at 200 ° C. for 15 minutes.

[Average particle size]
The average particle diameter of the hollow silica particles is measured using a laser diffraction / scattering particle size distribution measuring device (measured by setting the relative refractive index to 1.4 by Horiba, "LA-920"), and the median diameter (based on volume) It measured as D50). 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).

Particle strength
The particle strength was evaluated by grinding 10 g of particles using 200 g of zirconia balls (10 mmφ ZrO ₂ ) (95 rpm, 1 hour), and measuring the increase in specific gravity of particles before and after grinding. Evaluation criteria are shown below. When the specific gravity increment was 0.03 g / cm ³ or less, it was judged that the particle strength was excellent, and when the specific gravity increment exceeded 0.03 g / cm ³ , it was judged that the particle strength was poor.

[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 by hydrofluoric acid was used as a sample. Here, the content of Na contained in the hollow silica particles is taken as the alkali metal content in the silica solution.

[SEM observation of fractured surface of outer shell]
After the hollow particles were kneaded with epoxy resin and cured, the sample was cut. And the fractured surface of the shell part of hollow particles was expanded and observed using field emission scanning electron microscope (SEM) ("S-4000" by Hitachi, Ltd. make).

2. Production of Hollow Silica Particles (Examples 1 to 11, Reference Example 1 and Comparative Example 1)
Example 1
The hollow silica particles are produced through the following two steps: spray drying step (1) and firing step (2).
<Preparation of Silica Solution (Spray) Used in Spray Drying Step (1)>
In a reaction vessel equipped with a stirrer (TEM-D1500M, manufactured by pressure resistant glass industry), 200 g of silica (manufactured by Admatex, Admafine SOE2), 25% aqueous solution of tetramethylammonium hydroxide (manufactured by Seichem Asia, pH 14): The temperature was raised to 180 ° C. in 1 hour and 30 minutes while adding 640 g and ion exchange water: 160 g and stirring. Thereafter, the mixture was stirred at 180 ° C. for 1 hour to obtain a silica solution [silica concentration: 20% by mass, molar ratio (silica / organic alkali): 1.9]. The pressure in the reaction vessel during stirring at 180 ° C. was 0.85 MPa.
Subsequently, 500 g of the prepared silica solution was placed in a 1000 ml separable flask, and 1 g of a water-soluble polymer (polyvinyl pyrrolidone, PVP K25, weight average molecular weight 35,000, manufactured by Wako Pure Chemical Industries, Ltd.) was added. Here, the addition amount of the water-soluble polymer was 1% by mass with respect to the content of silica in the silica solution. Thereafter, the mixture was stirred for 30 minutes to dissolve the water-soluble polymer in the silica solution to obtain a spray solution.
<Spray-drying process (1)>
The prepared spray liquid was spray-dried using a spray drier (manufactured by Tokyo Rika Kikai, SD-1000) to obtain a dry powder (hollow silica precursor). A two-fluid nozzle (sample discharge hole diameter: 0.4 mm) was used as the spray nozzle of the spray dryer. Spray conditions were: inlet temperature: 120 ° C., outlet temperature: 90 ° C., spray pressure: 150 kPa, air volume: 0.7 m ³ / min, spray amount: 10 mL / min.
<Firing step (2)>
The dry powder (hollow silica precursor) obtained in the spray drying step (1) is heated to 1100 ° C. at 100 ° C./hour in an electric furnace (SK-2535 E-OP, manufactured by Motoyama Co., Ltd.), and then 1100 ° C. The hollow silica particles of Example 1 were obtained by holding and firing for 1 hour.

  The physical property measurement results of the hollow silica particles of Example 1 are shown in Table 1 below. And the SEM image of the hollow silica particle of Example 1 is shown in FIG. It was found from FIG. 1 that the shape of the hollow silica particles of Example 1 was spherical. Furthermore, the SEM image of the fractured surface of the shell part of the hollow silica particle of Example 1 is shown in FIG. In FIG. 2, black spots indicating closed pores were visually confirmed. That is, it was confirmed from FIG. 2 that closed pores were formed in the outer shell of the hollow silica particles of Example 1.

(Examples 2 to 11)
Hollow silica particles of Examples 2 to 11 were obtained by the same method as in Example 1 except that the type and the addition amount of the water-soluble polymer added to the silica solution were changed as described in Table 1. . The physical property measurement results of each are shown in Table 1. When the SEM image of the fractured surface of the outer shell part of the hollow silica particle of Examples 2-11 was observed, it could be confirmed that closed pores were formed in the outer shell part.
The following water-soluble polymers were used to produce the hollow silica particles of Examples 2-11.
Examples 2 to 5: polyvinyl pyrrolidone (PVP K25, weight average molecular weight 35,000, manufactured by Wako Pure Chemical Industries, Ltd.)
Example 6: Polyvinyl pyrrolidone (PVP K30, weight average molecular weight 40,000, manufactured by Wako Pure Chemical Industries, Ltd.)
Example 7: Polyvinyl pyrrolidone (PVP K15, weight average molecular weight 10,000, manufactured by Sigma Aldrich Japan)
Example 8 polyvinyl pyrrolidone (PVP K90, weight average molecular weight 360,000, manufactured by Wako Pure Chemical Industries, Ltd.)
Example 9: Polyethylene glycol (PEG 4000, weight average molecular weight 3000 ± 300, manufactured by Wako Pure Chemical Industries, Ltd.)
Example 10: Polyethylene glycol (PEG 20000, weight average molecular weight 20,000 ± 5000, manufactured by Wako Pure Chemical Industries, Ltd.)
Example 11 polyethylene glycol (PEG 500000, weight average molecular weight 400,000 ± 100,000, manufactured by Wako Pure Chemical Industries, Ltd.)

(Reference Example 1)
Hollow silica particles of Reference Example 1 were obtained in the same manner as in Example 1, except that the water-soluble polymer was not added to the silica solution. The physical property measurement results of the hollow silica particles of Reference Example 1 are shown in Table 1. When the SEM image of the fractured surface of the outer shell of the hollow silica particle of Reference Example 1 was observed, it was confirmed that closed pores were formed in the outer shell.

(Comparative example 1)
Spray drying was performed in the same manner as in Example 1 using No. 3 water glass (manufactured by Osaka Silicate Soda Co., Ltd.) as the silica. The obtained dry powder was calcined at 500 ° C. for 1 hour to obtain a hollow silica powder of Comparative Example 1. When water glass is used as the raw material, silica is dissolved when it is fired at a temperature of 500 ° C. or more due to the influence of sodium. The silica particles of Comparative Example 1 obtained had a hollow structure. The physical property measurement results of the hollow silica particles of Comparative Example 1 are shown in Table 1. When the SEM image of the fractured surface of the outer shell of the hollow silica particle of Comparative Example 1 was observed, no closed pores were formed in the outer shell.

  As shown in the said Table 1, in Examples 1-11, compared with the comparative example 1 which used spray-drying of water glass, the hollow silica particle in which alkali metal content was reduced was able to be manufactured simply. Furthermore, in Examples 1 to 11, by using a silica solution to which a water-soluble polymer is added for spray drying, as compared to Reference Example 1 using a silica solution to which a water-soluble polymer is not added, It was possible to change the porosity.

  According to the present disclosure, for example, the present invention is useful in the field dealing with catalyst carriers, adsorbents, substance separating agents, carriers for immobilizing enzymes and functional organic compounds, electronic materials and the like which can utilize hollow silica particles.

Claims (6)

The manufacturing method of the hollow silica particle containing following process (1) and (2).
(1) A step of spray-drying a silica solution in which silica and a water-soluble polymer are dissolved in an organic alkali aqueous solution to obtain a hollow silica precursor.
(2) A step of firing the hollow silica precursor to obtain hollow silica particles.   The method for producing hollow silica particles according to claim 1, wherein the water-soluble polymer is a water-soluble polymer having spinnability.   The method for producing hollow silica particles according to claim 1 or 2, wherein the water-soluble polymer has at least one group selected from a vinyl group, a pyrrolidone group, an oxyalkylene group, and a hydroxy group.   The method for producing hollow silica particles according to any one of claims 1 to 3, wherein the water-soluble polymer is at least one selected from polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, and hydroxymethyl cellulose.   The method for producing hollow silica particles according to any one of claims 1 to 4, wherein the content of the water-soluble polymer in the silica solution is 0.5% by mass or more and 5% by mass or less with respect to the silica. .   The method for producing hollow silica particles according to any one of claims 1 to 5, wherein the organic alkali is a quaternary ammonium salt.