JP7612998B2 - Silica Composite Particles - Google Patents

Description

The present invention relates to silica composite particles .

Silica particles are used as an additive or main component in toners, cosmetics, rubber, abrasives, etc., and play roles such as improving the strength of resins, improving the fluidity of powders, and suppressing packing. The properties of silica particles are thought to depend on the shape and surface properties of the silica particles, and surface treatment of silica particles and compounding silica with metals or metal compounds have been proposed.

For example, Patent Document 1 discloses "silica powder containing a plurality of silica particles in which a quaternary ammonium salt has been introduced into a silica structure having an "Si-O" bond as a repeating unit."

Patent Document 2 also discloses an external additive for toner for developing electrostatic images, which is characterized by comprising silica fine particles obtained by treating spherical hydrophobic silica fine particles having an average primary particle diameter of 0.01 to 5 μm with a compound selected from the group consisting of quaternary ammonium salt compounds, fluoroalkyl group-containing betaine compounds, and silicone oils, and which satisfies the following requirement (i): the silica fine particles are uniformly dispersed even when mixed and shaken in a weight ratio of 5:1 in an organic compound having a dielectric constant of 1 to 40 F/m, and (ii): when the silica fine particles are dispersed in methanol, the methanol is removed by heating in an evaporator, and the dispersion is held at a temperature of 100°C for 2 hours, the ratio of the amount of primary particles remaining as primary particles to the amount of primary particles initially present is 20% or more.

JP 2017-039618 A JP 2001-194825 A

The object of the present invention is to provide a silica composite particle containing a quaternary ammonium salt and an aluminum atom,
When the ratio (F _BEFORE /F AFTER) of the maximum frequency of pores having a diameter of 2 nm or less obtained from the pore distribution curve of the silica composite particles before washing (F _BEFORE ) and the maximum frequency of pores having a diameter of 2 nm or less obtained from the pore distribution curve of the silica composite particles after _washing (F _AFTER ) is less than 0.90,
Or,
when the ratio (C AFTER /C BEFORE) of the capacitance C BEFORE of the resin particles having silica composite particles attached to their surfaces, which is separated from a mixture of resin particles having unwashed silica composite particles attached to their surfaces, and ferrite powder, which are mixed under specific conditions to prepare a mixture, and the capacitance C _AFTER of the resin particles having silica composite particles attached to their surfaces, which is separated from a mixture of resin particles having washed silica composite particles attached to their surfaces _, and ferrite powder, which are mixed under _specific conditions to _prepare a mixture, is greater than 1.5,
The object of the present invention is to provide silica composite particles in which an increase in electrostatic capacitance is suppressed.

Specific means for solving the above problems include the following aspects:

<1> Contains a quaternary ammonium salt and an aluminum atom,
Silica composite particles, in which the ratio (F _BEFORE /F AFTER) of the maximum frequency of pores with diameters of 2 nm or _less obtained from a pore distribution curve of the silica composite particles before washing, F BEFORE, obtained from a pore distribution curve of the nitrogen gas adsorption method, to the maximum frequency of pores with diameters of 2 nm or less obtained from the pore distribution curve of the silica composite particles _{after washing} , F _AFTER , is 0.90 or more and 1.10 or less.
<2> Contains a quaternary ammonium salt and an aluminum atom,
Resin particles having silica composite particles attached to their surfaces before cleaning and ferrite powder are mixed under specific conditions to prepare a mixture, and then the electrostatic capacitance C _BEFORE of the resin particles having silica composite particles attached to their surfaces separated from the mixture;
the resin particles having the washed silica composite particles attached to their surfaces and the ferrite powder are mixed under specific conditions to prepare a mixture, and then the capacitance C _AFTER of the resin particles having the silica composite particles attached to their surfaces separated from the mixture;
The silica composite particles have a ratio (C _AFTER /C _BEFORE ) of 1.5 or less.
<3> The silica composite particle according to any one of <1> and <2>, wherein the quaternary ammonium salt contains a compound represented by general formula (AM):

(In general formula (AM), R ¹ , R ² , R ³ and R ⁴ each independently represent an alkyl group, an aralkyl group or an aryl group which may have a substituent, and X ⁻ represents an anion. In general formula (AM), two or more of R ¹ , R ² , R ³ and R ⁴ may be bonded to each other to form a ring.)
<4> The silica composite particle according to <3>, wherein in the compound represented by the general formula (AM), R ¹ , R ² , R ³ and R ⁴ each independently represent an alkyl group having 1 to 16 carbon atoms or an aralkyl group having 7 to 10 carbon atoms, each of which may have a substituent.
<5> The silica composite particles according to any one of <1> to <4>, having a number average particle diameter of 5 nm or more and 300 nm or less.
<6> The silica composite particles according to <5>, having a number average particle diameter of 5 nm or more and 100 nm or less.
<7> A maximum frequency F _BEFORE of pores having a diameter of 2 nm or less obtained from a pore distribution curve of the silica composite particles before washing by a nitrogen gas adsorption method; and
The silica composite particles according to any one of <1> to <6>, wherein the ratio (F _SINTERING /F _BEFORE /) of the maximum frequency of pores with diameters of 2 nm or less, F _SINTERING , determined from a pore distribution curve of a nitrogen gas adsorption method in the silica composite particles after baking at 600° C. before washing, is 5 or more and 20 or less.
<8> The silica composite particle according to any one of <1> to <7>, wherein a ratio (Si/Al) of an amount of silicon element present, Si, detected by X-ray photoelectron spectroscopy to an amount of aluminum element present, Al, detected by X-ray photoelectron spectroscopy, is 0.01 or more and 0.30 or less.
<9> The silica composite particle according to any one of <1> to <8>, wherein a ratio of an amount N of nitrogen element derived from a quaternary ammonium salt detected by oxygen/nitrogen analysis (N/silica composite particle×100) is 0.01 or more and 1.0 or less.
<10> The silica composite particles according to any one of <1> to <9>, having an average pore diameter of 0.55 nm or more and 2.0 nm or less.
<11> The silica composite particle according to any one of <1> to <10>, which is a hydrophobically treated particle.
<12> A preparation step of preparing a suspension containing silica particles containing aluminum atoms;
a surface treatment step of surface-treating the silica particles in the suspension with a quaternary ammonium salt;
A method for producing silica composite particles, comprising the steps of:
<13> After the surface treatment step,
The method for producing silica composite particles according to <12>, further comprising a second surface treatment step of surface-treating the silica particles, which have been surface-treated with the quaternary ammonium salt in a supercritical fluid, with an organosilicon compound.

According to the invention pertaining to [1], [3], [4], [5], [6] or [11], there is provided a silica composite particle containing a quaternary ammonium salt and an aluminum atom, in which an increase in capacitance is suppressed as compared with a case in which the ratio (F _{BEFORE /F AFTER) of the maximum value of the frequency of pores having a diameter of 2 nm or less obtained from a pore distribution curve of the silica composite particles before washing, F BEFORE ,} obtained from a pore distribution curve of the silica composite particles after washing, F _AFTER , obtained from a pore distribution curve of the silica composite particles after washing, F _AFTER , is less than 0.90.

According to the invention pertaining to [2], [3], [4], [5], [6] or [11], there is provided a silica composite particle containing a quaternary ammonium salt and an aluminum atom, in which an increase in capacitance is further suppressed, as compared to a case in which a ratio (C AFTER /C BEFORE) of a capacitance C _BEFORE of a resin particle having silica composite particles attached to its surface, which is separated from a mixture of resin particles having the unwashed silica composite particles attached to its surface, and a capacitance C _AFTER of a resin particle having silica composite particles attached to its surface, which is separated from a mixture of resin particles having washed silica composite particles attached to its surface _, which is mixed with ferrite powder under specific conditions, exceeds _1.5 .

According to the invention related to [7], there is provided silica composite particles in which an increase in capacitance is further suppressed, as compared with a case in which the ratio (F SINTERING /F BEFORE) of the maximum value F _BEFORE of the frequency of pores with diameters of 2 nm or less obtained from a pore distribution curve of silica composite particles before washing, as determined from a nitrogen gas adsorption method, to the maximum value F _SINTERING of the frequency of pores with diameters of 2 nm or _less obtained from a pore distribution curve of silica composite particles after baking the silica composite particles before washing at ₆₀₀ °C is less than 5.

The invention according to [8] provides silica composite particles in which the increase in capacitance is more suppressed than when the ratio (Si/Al) of the amount of silicon element present, Si, detected by X-ray photoelectron spectroscopy to the amount of aluminum element present, Al, detected by X-ray photoelectron spectroscopy is less than 0.01 or exceeds 0.30.

The invention according to [9] provides silica composite particles in which the increase in capacitance is more suppressed than when the ratio of the amount of nitrogen element N derived from the quaternary ammonium salt detected by an oxygen/nitrogen analyzer (N/silica composite particle x 100) is less than 0.01% or exceeds 1.0%.

According to the invention related to [10],
The silica composite particles provided have a more suppressed increase in capacitance than silica composite particles having an average pore diameter of less than 0.55 nm or more than 2.00 nm.

The invention according to [12] or [13] provides a method for producing silica composite particles in which the increase in capacitance is suppressed compared to a production method that does not include the surface treatment step.

The following describes embodiments of the present invention. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

In the numerical ranges described in this specification in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Also, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

In this specification, each component may contain multiple corresponding substances.
In this specification, when referring to the amount of each component in a composition, if multiple substances corresponding to each component are present in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

<Silica composite particles>
The silica composite particles according to the first embodiment contain a quaternary ammonium salt and an aluminum atom, and the ratio (F BEFORE /F AFTER) of the maximum value F _BEFORE of the frequency of pores with a diameter of 2 nm or less obtained from a pore distribution curve of the silica composite particles before washing, as determined from a nitrogen gas adsorption method, to the maximum value F _AFTER of the frequency of pores with a diameter of 2 nm or less obtained from the pore distribution curve of the silica composite particles after washing, as determined from a nitrogen gas _adsorption method, is 0.90 or _more and 1.10 or less.

The silica composite particles according to the second embodiment contain a quaternary ammonium salt and aluminum atoms, and the ratio (C AFTER /C BEFORE) of the capacitance C BEFORE of the resin particles having silica composite particles attached to their surfaces, which is separated from a mixture of resin particles having unwashed silica composite particles attached to their surfaces and ferrite powder under specific conditions to the capacitance C _AFTER of the resin particles _having silica composite particles attached to their surfaces, which is separated from a mixture of resin particles having washed silica composite particles attached to their surfaces and ferrite powder under specific _conditions , is 1.5 or less _.

Hereinafter, the silica composite particles according to the first embodiment and the silica composite particles according to the second embodiment will be collectively referred to as the silica composite particles according to this embodiment.

Silica composite particles are used in a variety of applications, including as fillers and external additives. However, conventional silica particles tend to have a high electrostatic capacitance on the particle surface. This tends to increase the electrical resistance of the contact material that comes into contact with the silica particles or the mixture in which the silica particles and the contact material are mixed, meaning that static electricity tends to accumulate.

On the other hand, the silica composite particles according to this embodiment have the above-mentioned configuration, and thus the increase in capacitance is suppressed. The reason for this is not entirely clear, but is presumed to be as follows.

The silica composite particles according to the present embodiment contain a quaternary ammonium salt. The quaternary ammonium salt has a positive charge, and the silica composite particles containing this quaternary ammonium salt tend to be less likely to be triboelectrically charged than the silica composite particles not containing the quaternary ammonium salt because the silica composite particles have a charge of the opposite polarity on the particle surface.
In addition, the silica composite particles according to the present embodiment contain aluminum atoms. The aluminum atoms form composite particles together with the silica particles. The aluminum atoms present as composite particles tend to interact with the quaternary ammonium salt, and thus the quaternary ammonium salt tends to be fixed to the silica composite particles.

Furthermore, the silica composite particle according to the first embodiment has a ratio (F _BEFORE /F _AFTER ) of the maximum frequency of pores with diameters of 2 nm or less, which is calculated from the pore distribution curve of the nitrogen gas adsorption method in the silica composite particle before and after washing, of 0.90 or more and 1.10 or less. In other words, because silica contains aluminum, the quaternary ammonium salt contained in the silica composite particle before and after washing tends to be difficult to be released from the surface. As a result, it is considered that the increase in the capacitance on the particle surface of the silica composite particle is suppressed.

On the other hand, the silica composite particles according to the second embodiment have a capacitance ratio (C AFTER /C _BEFORE ) of 1.5 or less for the resin particles with silica composite particles attached to the surface after mixing and separating the resin particles with silica composite particles attached to the surface and the ferrite powder under the _above conditions. In other words, even after the resin particles with silica composite particles attached to the surface are brought into contact with the ferrite powder, the chargeability of the ferrite powder is difficult to increase, that is, static electricity tends to be difficult to accumulate. As a result, it is considered that the increase in capacitance on the particle surface of the silica composite particles is suppressed.

[Properties of Silica Composite Particles]
Maximum Frequency Value Obtained from the Pore Distribution Curve by Nitrogen Gas Adsorption Method In the silica composite particles according to the first embodiment, the ratio (F BEFORE /F AFTER) of the maximum frequency value F _BEFORE of the pores having a pore diameter of 2 nm or less obtained from the pore distribution curve by nitrogen gas adsorption method in the silica composite particles before washing to the maximum frequency value F _AFTER of the pores having a pore diameter of 2 nm or less obtained from the pore distribution curve by nitrogen gas adsorption method in the silica composite particles _after washing is 0.90 or more and 1.10 or less, and from the viewpoint of further suppressing an increase in capacitance, _it is preferably 0.97 or more and 1.15 or less, and more preferably 0.95 or more and 1.1 or less.

In the silica composite particles according to the second embodiment, the ratio (F _{BEFORE /F AFTER) of the maximum value F BEFORE} of the frequency of pores with a diameter of 2 nm or less obtained from the pore distribution curve of the silica composite particles before washing, as determined from the nitrogen gas adsorption method, to the maximum value F _AFTER of the frequency of pores with a diameter of 2 nm or _less obtained from the pore distribution curve of the silica composite particles after washing, as determined from the nitrogen gas adsorption method, is _preferably 0.90 or more and 1.10 or less, more preferably 0.97 or more and 1.15 or less, and even more preferably 0.95 or more and 1.1 or less, from the viewpoint of further suppressing an increase in capacitance.

There are no particular limitations on the specific method for setting the ratio (F _BEFORE /F _AFTER ) before and after washing within the above range. For example, in the production of silica composite particles, a method may be mentioned in which aluminum atoms are composited with silica particles as an aluminum compound to form silica composite particles, and the surfaces of the composite particles are then surface-treated with a quaternary ammonium salt.

In the silica composite particles according to this embodiment, the ratio (F SINTERING /F BEFORE) of the maximum value F _BEFORE of the frequency of pores with a diameter of 2 nm or less obtained from a pore distribution curve of the silica composite particles before washing, as determined from a nitrogen gas adsorption method, to the maximum value F _SINTERING of the frequency of pores with a diameter of 2 nm or less obtained from a pore distribution curve of the silica composite particles after baking the silica composite particles before washing at ₆₀₀ ° C., is preferably 5 or more and 20 _or less, more preferably 5 or more and 15 or less, and even more preferably 7 or more and 12 or less, from the viewpoint of further suppressing an increase in capacitance.

There are no particular limitations on the specific method for setting the ratio (F _SINTERING /F _BEFORE ) before and after firing within the above range. For example, in the production of silica composite particles, silica composite particles are prepared in which aluminum atoms are composited with silica particles as an aluminum compound, and the surfaces of the composite particles are then surface-treated with a quaternary ammonium salt.

The pore size distribution curve for the nitrogen gas adsorption method is derived from various calculation formulas based on the adsorption isotherm obtained by measuring the amount of adsorbed nitrogen gas. First, the silica composite particles, which are the adsorbent, are cooled to liquid nitrogen temperature (-196°C), nitrogen gas is introduced, and the amount of adsorption is determined by a constant volume method or a gravimetric method. The pressure of the introduced nitrogen gas is gradually increased, and an adsorption isotherm is created by plotting the amount of adsorbed nitrogen gas for each equilibrium pressure. From this adsorption isotherm, a pore size distribution curve is calculated using calculation formulas such as the MP method, HK method, SF method, and CY method, where the vertical axis represents frequency and the horizontal axis represents pore diameter. From the resulting pore size distribution curve, the maximum frequency when the pore diameter is 2 nm or less is determined.

Capacitance In the silica composite particles according to the first embodiment, a capacitance C BEFORE of a resin particle having silica composite particles attached to its surface and a ferrite powder is mixed under specific conditions to prepare a mixture, and then the resin particle having silica composite particles attached to its surface is separated from the mixture. A capacitance C _AFTER of a silica composite particle is mixed under specific conditions to prepare a mixture, and then the resin particle having washed silica composite particles attached to its surface and a ferrite powder is mixed under specific conditions to prepare a mixture, and then the silica composite particle is separated from the mixture. In view of further suppressing an increase in capacitance, the ratio (C _AFTER /C _BEFORE ) is preferably _1.5 or less, more preferably 1.3 or less, and even more preferably 1.1 or less.

In the silica composite particles according to the second embodiment, the ratio (C AFTER /C BEFORE) of the capacitance C _BEFORE of the resin particles having silica composite particles attached to their surfaces, which is separated from a mixture of resin particles having unwashed silica composite particles attached to their surfaces and ferrite powder under specific conditions to prepare a mixture, to the capacitance C _AFTER of the resin particles having silica composite particles attached to their surfaces, which is separated from a mixture of washed silica composite particles and ferrite powder under specific conditions to prepare a mixture, is 1.5 or _less , and from the viewpoint of further suppressing an increase in capacitance, the ratio is preferably 2.0 _or less, and more preferably 2.5 or less.

There are no particular limitations on the specific method for setting the ratio (C _AFTER /C _BEFORE ) before and after washing within the above range. For example, in the production of silica composite particles, a method may be mentioned in which aluminum atoms are composited with silica particles as an aluminum compound to form silica composite particles, and the surfaces of the composite particles are then surface-treated with a quaternary ammonium salt.

The resin particles are not particularly limited, but an acrylic resin (for example, MA1010 manufactured by Nippon Shokubai Co., Ltd.) was used.
The ferrite powder used is soft ferrite (for example, KNI106GSM manufactured by JFE Chemical Corporation).
The specific conditions refer to the following conditions:
Mass ratio: silica composite particles/resin particles = 2/100, silica-adhered resin particles/ferrite powder = 1/10
・Mixing temperature: room temperature (10℃)
Mixing device: Turbula shaker/mixer (e.g., T2F manufactured by Shinmaru Enterprises Co., Ltd.)
・Mixing time: 5 minutes ・Mixing speed: 49 rpm

The capacitance is measured as follows.
2 g of the sample after stirring with the Turbula shaker mixer is placed in a metal container lined with a 20 μm mesh stainless steel wire screen, and the capacitance is measured with a capacitance measuring device (product name TB-200, manufactured by Toshiba Chemical Corporation).

Method for Washing Silica Composite Particles The silica composite particles are washed as follows.
1 g of silica composite particles, 2.5 g of ethanol, and 2.5 g of ion-exchanged water are placed in a 20 ml lab screw tube and mixed in an ultrasonic cleaner (e.g., a tabletop ultrasonic cleaner W-113 manufactured by Honda Electronics Co., Ltd., vibration frequency 45 Hz) to obtain a mixture. The mixture is then centrifuged at 10,000 rpm in a centrifuge (e.g., FB-4000 manufactured by KURABO Corporation) for 30 minutes, the supernatant is discarded, and the precipitated silica composite particles are removed. This process is repeated twice, and the silica composite particles are dried. This is called the washed silica composite particles.

Method for Calcining Silica Composite Particles Calcination of silica composite particles is carried out as follows.
1 g of silica composite particles is placed in a 20 ml crucible for firing, and the silica composite particles are fired using a firing machine (e.g., KM-100 manufactured by Advantec Toyo Co., Ltd.) under conditions of a nitrogen atmosphere, 600°C, and 1 hour. The resulting fired product is used as fired silica composite particles.

Proportion of Each Element Detected by X-ray Photoelectron Spectroscopy In the silica composite particles according to this embodiment, the ratio (Si/Al) of the amount of silicon element present, Si, detected by X-ray photoelectron spectroscopy, to the amount of aluminum element present, Al, detected by X-ray photoelectron spectroscopy, is preferably 0.01 or more and 0.30 or less, more preferably 0.03 or more and 0.2 or less, and even more preferably 0.05 or more and 0.1 or less, from the viewpoint of further suppressing an increase in capacitance.

The specific method for bringing the ratio (Si/Al) into the above range is not particularly limited, but an example of this is a method for adjusting the ratio and time for mixing a suspension containing untreated silica particles with an aluminum compound in the production of silica composite particles.

In the silica composite particles according to this embodiment, the ratio of the amount of nitrogen element N derived from the quaternary ammonium salt detected by oxygen/nitrogen analysis (N/silica composite particle x 100) is preferably 0.01% or more and 1.0% or less, more preferably 0.02% or more and 1.0% or less, and even more preferably 0.03% or more and 0.80% or less, from the viewpoint of further suppressing the increase in capacitance.

The specific method for bringing the ratio (N/total particles x 100) into the above range is not particularly limited, but an example of this is a method for adjusting the ratio and time for mixing a suspension containing aluminum-atom-containing silica particles with a quaternary ammonium salt in the production of silica composite particles.

Oxygen and nitrogen analysis is performed using a combustion method elemental analyzer (e.g., EMGA-920 manufactured by Horiba, Ltd.) with a measurement time of 30 minutes and a furnace temperature of 830°C. The ratio of the amount of nitrogen element present, N (N/total particles x 100), is obtained and used as the amount of nitrogen element present derived from the quaternary ammonium salt.

From the viewpoint of further suppressing an increase in capacitance, the average pore diameter of the silica composite particles according to this embodiment is preferably 0.55 nm or more and 2.0 nm or less, more preferably 0.55 nm or more and 1.5 nm or less, and even more preferably 0.55 nm or more and 1.0 nm or less.

The average pore size of the silica composite particles is derived from various calculation formulas based on the adsorption isotherm obtained by measuring the amount of adsorption of nitrogen gas. First, the silica composite particles, which are the adsorbent, are cooled to liquid nitrogen temperature (-196°C), nitrogen gas is introduced, and the amount of adsorption is determined by a constant volume method or a gravimetric method. The pressure of the introduced nitrogen gas is gradually increased, and the amount of adsorption of nitrogen gas for each equilibrium pressure is plotted to create an adsorption isotherm. From this adsorption isotherm, the average pore size is determined by calculation formulas such as the MP method, the HK method, the SF method, and the CY method.
The nitrogen gas adsorption amount is measured using a high-precision gas adsorption amount measuring device (for example, BELSORP MAXII by MicrotrackBell).

The specific method for setting the average pore size in the silica composite particles within the above range is not particularly limited, but examples include 1) a method of adjusting the dropping speed during particle granulation; 2) a method of adjusting the drying temperature, etc.

From the viewpoint of further suppressing an increase in capacitance, the number average particle diameter of the silica composite particles according to this embodiment is preferably 5 nm or more and 300 nm or less, more preferably 5 nm or more and 200 nm or less, and even more preferably 5 nm or more and 100 nm or less.

The number average particle size of the silica composite particles is determined as follows.
The silica composite particles are photographed with a scanning electron microscope (SEM), and the equivalent circle diameter (nm) of each of 100 randomly selected primary particles is determined by image analysis. The equivalent circle diameter of the cumulative 50% (50th particle) from the small diameter side in the distribution of the equivalent circle diameters is taken as the number average particle diameter.

From the viewpoint of further suppressing an increase in capacitance, it is preferable that the silica composite particles according to this embodiment are particles that have been subjected to a hydrophobic treatment.

[Material of Silica Composite Particles]
(aluminum atom)
The silica composite particles according to this embodiment contain aluminum atoms.
The aluminum atom may be combined with the silica particle as an aluminum compound, such as a compound in which an aluminum atom is bonded to an organic group via an oxygen atom.

As the organic group (containing the oxygen atom) that is bonded to the aluminum atom via an oxygen atom in the aluminum compound, at least one group selected from the group consisting of an alkoxy group, an acyloxy group, an alkylacetoacetate group (anion of an alkylacetoacetate compound), and an acetylacetonate group (anion of an acetylacetone compound) is preferred, and at least one group selected from the group consisting of an alkoxy group and an alkylacetoacetate group (anion of an alkylacetoacetate compound) is more preferred.

Specific examples of aluminum compounds in which an organic group is bonded to an aluminum atom via an oxygen atom include aluminum alkoxides such as aluminum methoxide, aluminum ethoxide, aluminum n-propoxide, aluminum i-propoxide, aluminum n-butoxide, aluminum i-butoxide, aluminum sec-butoxide, and aluminum tert-butoxide; chelates such as aluminum ethylacetoacetate diisopropylate, aluminum trisethylacetoacetate, aluminum bisethylacetoacetate monoacetylacetonate, and aluminum trisacetylacetonate; aluminum oxide acylates such as aluminum oxide 2-ethylhexanoate and aluminum oxide laurate; complexes of aluminum with β-diketones such as acetylacetonate; complexes of aluminum with β-ketoesters such as ethylacetoacetate; complexes of aluminum with carboxylic acids such as acetic acid, butyric acid, lactic acid, and citric acid; and the like.

From the viewpoints of the controllability of the reaction rate and the shape, particle size, particle size distribution, etc. of the resulting silica composite particles, it is preferable that the aluminum compound is an aluminum compound having one or more alkoxy groups (more preferably two or more). In other words, it is preferable that the aluminum compound is an aluminum compound having one or more alkoxy groups (an alkyl group bonded to an aluminum atom via an oxygen atom) bonded to an aluminum atom. The number of carbon atoms in the alkoxy group is preferably 8 or less, more preferably 2 to 4, from the viewpoints of the controllability of the reaction rate and the shape, particle size, particle size distribution, etc. of the resulting silica composite particles.

Among them, from the viewpoint of hardness uniformity, it is particularly preferable that the aluminum compound is at least one compound selected from the group consisting of aluminum ethylacetoacetate diisopropylate, aluminum tris-ethylacetoacetate, aluminum bis-ethylacetoacetate monoacetylacetonate, and aluminum tris-acetylacetonate.

(Quaternary ammonium salts)
The silica composite particles according to this embodiment contain a quaternary ammonium salt.
The quaternary ammonium salts may be used alone or in combination of two or more kinds.
The quaternary ammonium salt is not particularly limited, and any known quaternary ammonium salt can be used.

From the viewpoint of further suppressing an increase in capacitance, the quaternary ammonium salt preferably contains a compound represented by general formula (AM). The compound represented by general formula (AM) may be used alone or in combination of two or more kinds.

In formula (AM), R ¹ , R ² , R ³ and R ⁴ each independently represent an alkyl group, an aralkyl group or an aryl group which may have a substituent, and X ⁻ represents an anion.

Examples of the alkyl group represented by R ¹ to R ⁴ include a linear alkyl group having 1 to 20 carbon atoms, and a branched alkyl group having 3 to 20 carbon atoms.
Examples of the linear alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, and an n-hexadecyl group.
Examples of branched alkyl groups having 3 to 20 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group.
Among the above, the alkyl group represented by R ¹ to R ⁴ is preferably an alkyl group having 1 to 15 carbon atoms, such as a methyl group, an ethyl group, a butyl group, or a tetradecyl group.

The aralkyl group represented by R ¹ to R ⁴ includes an aralkyl group having 7 to 30 carbon atoms.
Examples of the aralkyl group having 7 to 30 carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, a 4-phenylbutyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, a phenylnonyl group, a naphthylmethyl group, a naphthylethyl group, an anthrathylmethyl group, and a phenyl-cyclopentylmethyl group.
Among the above, the aralkyl groups represented by R ¹ to R ⁴ are preferably aralkyl groups having 7 to 15 carbon atoms, such as a benzyl group, a phenylethyl group, a phenylpropyl group, and a 4-phenylbutyl group.

Examples of the aryl group represented by R ¹ to R ⁴ include aryl groups having 6 to 20 carbon atoms.
Examples of the aryl group having 6 to 20 carbon atoms include a phenyl group, a pyridyl group, a naphthyl group, and the like.
Among the above, the aryl group represented by R ¹ to R ⁴ is preferably an aryl group having 6 to 10 carbon atoms, such as a phenyl group.

The anion represented by X ⁻ includes organic anions and inorganic anions.
Examples of the organic anion include a polyfluoroalkylsulfonate ion, a polyfluoroalkylcarboxylate ion, a tetraphenylborate ion, an aromatic carboxylate ion, and an aromatic sulfonate ion (eg, 1-naphthol-4-sulfonate ion).
Examples of inorganic anions include MoO ₄ ²⁻ , OH ⁻ , F ⁻ , Fe(CN) ₆ ³⁻ , Cl ⁻ , Br ⁻ , NO ₂ ⁻ , NO ₃ ⁻ , CO ₃ ²⁻ , PO ₄ ³⁻ , and SO ₄ ²⁻ .

In general formula (AM), two or more of R ¹ , R ² , R ³ and R ⁴ may be bonded to each other to form a ring. Examples of the ring formed by bonding two or more of R ¹ , R ² , R ³ and R ⁴ to each other include an alicyclic ring having from 2 to 20 carbon atoms and a heterocyclic amine having from 2 to 20 carbon atoms.

In the silica composite particles according to this embodiment, from the viewpoint of further suppressing an increase in capacitance, in the compound represented by general formula (AM), it is preferable that R ¹ , R ² , R ³ and R ⁴ each independently represent an alkyl group having 1 to 16 carbon atoms or an aralkyl group having 7 to 10 carbon atoms, which may have a substituent.

Examples of structures other than X 1 ^- in the compound represented by formula (AM) are shown below, but the present embodiment is not limited thereto.

[Application]
The silica composite particles according to this embodiment can be used in various fields such as fillers, abrasives, toners, and cosmetics.
In particular, by adding the silica composite particles according to this embodiment to tire rubber, the accumulation of static electricity in the tire can be suppressed, and the adverse effects of electromagnetic noise on electronic devices can be prevented.

<Method for producing silica composite particles>
The method for producing silica composite particles according to this embodiment includes, in this order, a preparation step of preparing a suspension containing silica particles containing aluminum atoms, and a first surface treatment step of surface-treating the silica particles in the suspension with a quaternary ammonium salt.
The method for producing silica composite particles according to this embodiment includes the first surface treatment step, and thus can produce silica composite particles in which an increase in capacitance is suppressed.

The steps of the manufacturing method according to this embodiment are described in detail below.

[Preparation process]
The method for producing silica composite particles according to this embodiment includes a preparation step.
In the preparation step, a suspension containing silica particles containing aluminum atoms is prepared.
The method for preparing the suspension containing silica particles containing aluminum atoms is not particularly limited. For example, the suspension containing silica particles containing aluminum atoms may be prepared by surface treatment with an aluminum compound.

Hereinafter, silica particles surface-treated with an aluminum compound are also referred to as aluminum-bonded silica particles, and a suspension containing silica particles surface-treated with an aluminum compound (i.e., silica particles containing aluminum atoms) is also referred to as an aluminum-bonded silica particle suspension.

The aluminum-bonded silica particle suspension contains, for example, a solvent containing alcohol and aluminum-bonded silica particles. The alcohol-containing solvent may be a solvent containing alcohol alone or a mixed solvent containing alcohol and other solvents. Examples of the alcohol include lower alcohols such as methanol, ethanol, n-propanol, isopropanol, and butanol. Other solvents include water; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and cellosolve acetate; ethers such as dioxane and tetrahydrofuran; and the like. In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, and more preferably 90% by mass or more.

The preparation process may, for example, be
A step (1-a) of preparing a silica particle suspension containing silica particles;
a step (1-b) of mixing the silica particle suspension with an aluminum compound to subject the silica particles to an aluminum composite treatment with the aluminum compound;
may also include

Step (1-a) may be carried out, for example, as follows:
(i) a step of mixing an alcohol-containing solvent with silica particles to prepare a silica particle suspension; and (ii) a step of granulating the silica particles by a sol-gel method to obtain a silica particle suspension.
Examples of the silica particles used in (i) include sol-gel silica particles (silica particles obtained by a sol-gel method), aqueous colloidal silica particles, alcoholic silica particles, fumed silica particles obtained by a gas phase method, fused silica particles, and the like.
The alcohol-containing solvent used in (i) may be a solvent of alcohol alone or a mixed solvent of alcohol and other solvents. Examples of the alcohol include lower alcohols such as methanol, ethanol, n-propanol, isopropanol, and butanol. Examples of other solvents include water; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and cellosolve acetate; and ethers such as dioxane and tetrahydrofuran. In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, more preferably 90% by mass or more.

The step (1-a) is preferably a step of granulating silica particles by a sol-gel method to obtain a silica particle suspension.
More specifically, step (1-a) may include, for example,
An alkaline catalyst solution preparation step of preparing an alkaline catalyst solution containing an alkaline catalyst in a solvent containing alcohol;
a silica particle producing step of producing silica particles by supplying tetraalkoxysilane and an alkali catalyst into an alkali catalyst solution;
It is preferable that the method is a sol-gel method comprising the steps of:

The alkaline catalyst solution preparation step is preferably a step of preparing a solvent containing alcohol and mixing this solvent with an alkaline catalyst to obtain an alkaline catalyst solution.

The solvent containing alcohol may be a solvent of alcohol alone or a mixed solvent of alcohol and other solvents. Examples of alcohol include lower alcohols such as methanol, ethanol, n-propanol, isopropanol, and butanol. Other solvents include water; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and cellosolve acetate; and ethers such as dioxane and tetrahydrofuran. In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, and more preferably 90% by mass or more.

The alkaline catalyst is a catalyst for promoting the reaction (hydrolysis reaction and condensation reaction) of tetraalkoxysilane. Examples of the alkaline catalyst include ammonia, urea, monoamines, etc., and ammonia is particularly preferred.

From the viewpoint of increasing the uniformity of the particle size and circularity of the generated silica particles, the concentration of the alkaline catalyst in the alkaline catalyst solution is preferably 0.5 mol/L or more and 1.0 mol/L or less, more preferably 0.6 mol/L or more and 0.8 mol/L or less, and even more preferably 0.65 mol/L or more and 0.75 mol/L or less.

The silica particle production process is a process in which tetraalkoxysilane and an alkaline catalyst are separately supplied to an alkaline catalyst solution, and the tetraalkoxysilane is reacted (hydrolysis reaction and condensation reaction) in the alkaline catalyst solution to produce silica particles.

In the silica particle production process, nucleus particles are produced by the reaction of tetraalkoxysilane at the beginning of the supply of tetraalkoxysilane (nucleus particle production stage), and then these nucleus particles grow (nucleus particle growth stage) to produce silica particles.

Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. From the viewpoint of controllability of the reaction rate or uniformity of the shape of the silica particles produced, tetramethoxysilane or tetraethoxysilane is preferred.

Examples of the alkaline catalyst supplied to the alkaline catalyst solution include basic catalysts such as ammonia, urea, monoamines, and quaternary ammonium salts, with ammonia being particularly preferred. The alkaline catalyst supplied together with the tetraalkoxysilane may be of the same type as the alkaline catalyst already contained in the alkaline catalyst solution, or may be of a different type, but it is preferable that it is of the same type.

The method for supplying the tetraalkoxysilane and the alkali catalyst into the alkali catalyst solution may be a continuous supply method or an intermittent supply method.

In the silica particle production process, the temperature of the alkaline catalyst solution (temperature at the time of supply) is preferably 5°C or higher and 50°C or lower, and more preferably 15°C or higher and 40°C or lower.

The step (1-b) is a step of mixing a silica particle suspension with an aluminum compound to subject the silica particles to an aluminum composite treatment with the aluminum compound.
By going through the step (1-b), the functional groups of the aluminum compound (for example, organic groups such as alkoxy groups) react with the silanol groups on the surface of the silica particles to produce aluminum-bonded silica particles.

Step (1-b) is carried out, for example, by adding an aluminum compound to a silica particle suspension and reacting the mixture under stirring at a temperature ranging from 20°C to 80°C.

Preferably, the aluminum compound is a compound having an organic group bonded to an aluminum atom via an oxygen atom. Examples of such compounds include aluminum alkoxides such as aluminum methoxide, aluminum ethoxide, aluminum n-propoxide, aluminum i-propoxide, aluminum n-butoxide, aluminum i-butoxide, aluminum sec-butoxide, and aluminum tert-butoxide; chelates such as aluminum ethyl acetoacetate diisopropylate, aluminum trisethyl acetoacetate, aluminum bisethyl acetoacetate monoacetylacetonate, and aluminum trisacetylacetonate; aluminum oxide acylates such as aluminum oxide 2-ethylhexanoate and aluminum oxide laurate; complexes of aluminum with β-diketones such as acetylacetonate; complexes of aluminum with β-ketoesters such as ethyl acetoacetate; complexes of aluminum with amines such as triethanolamine; complexes of aluminum with carboxylic acids such as acetic acid, butyric acid, lactic acid, and citric acid; and the like.

From the viewpoint of controllability of the reaction rate or the shape, particle size, particle size distribution, etc. of the aluminum-bonded silica particles produced, the aluminum compound is preferably an aluminum compound having one or more (preferably two or more) alkoxy groups. In other words, the aluminum compound is preferably an aluminum compound having one or more (preferably two or more) alkoxy groups (alkyl groups bonded to the aluminum atom via one oxygen atom) bonded to the aluminum atom. From the viewpoint of controllability of the reaction rate or the shape, particle size, particle size distribution, etc. of the aluminum-bonded silica particles produced, the number of carbon atoms in the alkoxy group is preferably 8 or less, and more preferably 2 to 4.

Specific preferred examples of aluminum compounds include chelates such as aluminum ethylacetoacetate diisopropylate, aluminum trisethylacetoacetate, aluminum bisethylacetoacetate monoacetylacetonate, and aluminum trisacetylacetonate.

The step (1-b) is preferably carried out by mixing the silica particle suspension with an alcohol liquid containing an aluminum compound in alcohol. Therefore, the manufacturing method according to this embodiment further includes a step of preparing an alcohol liquid containing an aluminum compound in alcohol, and it is preferable to carry out this step in advance.

Examples of alcohols include lower alcohols such as methanol, ethanol, n-propanol, isopropanol, and butanol.

When the aluminum compound is a compound having an alkoxy group, from the viewpoint of controllability of the reaction rate or the shape, particle size, particle size distribution, etc. of the aluminum-bonded silica particles produced, it is preferable that the alcohol has a smaller carbon number than the carbon number of the alkoxy group of the aluminum compound (specifically, for example, the difference in carbon number is 2 or more and 4 or less).

The alcohol may be the same type as the alcohol contained in the silica particle suspension or a different type, but it is more preferable that it be the same type.

In an alcohol solution containing an aluminum compound in alcohol, the aluminum compound concentration is preferably 0.05% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 5% by mass or less.

From the viewpoint of controllability of the reaction rate or the shape, particle size, particle size distribution, etc. of the aluminum-bonded silica particles produced, the total amount of the aluminum compounds is preferably at least 0.001% by mass, more preferably at least 0.01% by mass, and even more preferably at least 0.1% by mass, with the upper limit being preferably at most 10% by mass, more preferably at most 5% by mass, and even more preferably at most 3% by mass, based on the solid content of the silica particle suspension.

There are no particular limitations on the conditions for surface treatment of silica particles with an aluminum compound, and the treatment can be carried out, for example, by reacting the aluminum compound under stirring at a temperature range of 5°C or higher and 50°C or lower.

[First surface treatment step]
The method for producing silica composite particles according to this embodiment includes a first surface treatment step.
In the first surface treatment step, the silica particles in the suspension are surface-treated with a quaternary ammonium salt.

Preferred examples of quaternary ammonium salts include those exemplified as quaternary ammonium salts in the silica composite particles according to this embodiment.

The total amount of quaternary ammonium salts is preferably 0.5% by mass or more, more preferably 1.5% by mass or more and 10% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less, based on the solid content of the silica particle suspension.

There are no particular limitations on the conditions for surface treatment of silica particles with a quaternary ammonium salt, and the treatment can be carried out, for example, by reacting the quaternary ammonium salt under stirring at a temperature range of 20°C or higher and 50°C or lower.

The first surface treatment step is preferably carried out, for example, by mixing a silica particle suspension with an alcohol liquid containing a quaternary ammonium salt in alcohol. Therefore, the manufacturing method according to this embodiment further includes a step of preparing an alcohol liquid containing a quaternary ammonium salt in alcohol, and it is preferable to carry out this step in advance.

The alcohol may be the same type as the alcohol contained in the silica particle suspension or a different type, but it is more preferable that it be the same type.

In an alcohol solution containing a quaternary ammonium salt in alcohol, the concentration of the quaternary ammonium salt is preferably 0.05% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 6% by mass or less.

[Second surface treatment step]
The method for producing silica composite particles according to this embodiment may further include a second surface treatment step after the first surface treatment step.
In the second surface treatment step, the silica particles that have been surface-treated with the quaternary ammonium salt in a supercritical fluid are further surface-treated with an organosilicon compound.
By passing through the second surface treatment step, the functional groups of the organosilicon compound react with the OH groups on the surface of the aluminum-bonded silica particles, and there is a tendency for silica composite particles to be produced that contain, for example, an atomic group of -Si-O-Al-O-Si-R (R is an organic group) on the surface. It is also believed that by carrying out a wet treatment in which the surface is treated in an alcohol liquid or a surface treatment in a supercritical fluid, the surface treatment is carried out between the organosilicon compound and the surface of the aluminum-bonded silica particles.

Specifically, the second surface treatment step using wet processing is carried out, for example, by the following procedure. The silica particle suspension after the first surface treatment step is heated to 60°C while being mixed with a stirrer, and an organosilicon compound is added to perform the surface treatment. The stirring time is preferably from 10 minutes to 24 hours, more preferably from 20 minutes to 120 minutes, and even more preferably from 20 minutes to 90 minutes.

Specifically, the second surface treatment step using supercritical treatment is carried out, for example, by the following operation. Substances used as supercritical fluids include carbon dioxide, water, methanol, ethanol, acetone, etc. From the viewpoint of treatment efficiency and suppression of generation of coarse particles, the second surface treatment step is preferably a step using supercritical carbon dioxide.
Silica particles surface-treated with an aluminum compound and an organosilicon compound are placed in a closed reactor equipped with an agitator, and then liquefied carbon dioxide is introduced into the closed reactor, which is then heated and the pressure in the closed reactor is increased by a high-pressure pump to bring the carbon dioxide in the closed reactor into a supercritical state.The agitator is then operated to stir the reaction system.
The temperature and pressure in the closed reactor are set to those that can put carbon dioxide into a supercritical state. The critical point of carbon dioxide is 31.1° C./7.38 MPa, and the temperature and pressure are set to, for example, 40° C. to 200° C./10 MPa to 30 MPa. The stirring time is preferably 10 minutes to 24 hours, more preferably 20 minutes to 120 minutes, and even more preferably 20 minutes to 90 minutes.

Examples of the organosilicon compound include:
Silane compounds having a lower alkyl group, such as methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, and trimethylmethoxysilane;
Silane compounds having a vinyl group, such as vinyltrimethoxysilane and vinyltriethoxysilane;
Silane compounds having an epoxy group, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane;
Silane compounds having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane;
Silane compounds having an aminoalkyl group, such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane;
Silane compounds having an isocyanate alkyl group, such as 3-isocyanatepropyltrimethoxysilane and 3-isocyanatepropyltriethoxysilane;
Silazane compounds such as hexamethyldisilazane and tetramethyldisilazane; and the like.

The obtained silica composite particles may be crushed or sieved to remove coarse particles and agglomerates. Crushing is performed, for example, using a dry grinding device such as a jet mill, a vibration mill, a ball mill, or a pin mill. Sieving is performed, for example, using a vibration sieve or a wind sieving machine.

[Solvent removal step]
The method for producing silica composite particles according to this embodiment may further include a solvent removal step, if necessary.
In the solvent removal step, a supercritical fluid is used to remove the solvent from the suspension containing the silica particles surface-treated with the quaternary ammonium salt to obtain a powder. For example, heat drying, spray drying, and supercritical drying can be used. In heat drying and spray drying, the surface tension between the particles becomes more likely to act at the end of drying, so that coarse particles are likely to be generated due to particle aggregation. However, by performing surface treatment with an organosilicon compound, it is possible to suppress the generation of coarse particles.
In supercritical drying, the solvent is removed by a supercritical fluid, so that the surface tension between particles is less likely to act, and the primary particles contained in the suspension are dried in a state in which aggregation is suppressed, making it easier to obtain silica particles with a highly uniform particle size and surface-treated with an aluminum compound.

Substances that can be used as supercritical fluids include carbon dioxide, water, methanol, ethanol, and acetone. From the standpoint of processing efficiency and suppressing the generation of coarse particles, it is preferable that the solvent removal process be a process that uses supercritical carbon dioxide.

Specifically, the solvent removal step is carried out, for example, by the following procedure.
The suspension is placed in a sealed reactor, liquefied carbon dioxide is then introduced into the sealed reactor, the sealed reactor is heated, and the pressure inside the sealed reactor is increased by a high-pressure pump, so that the carbon dioxide in the sealed reactor is brought into a supercritical state. The liquefied carbon dioxide is then flowed into the sealed reactor, and the supercritical carbon dioxide is flowed out of the sealed reactor, so that the supercritical carbon dioxide is circulated through the suspension in the sealed reactor. While the supercritical carbon dioxide is flowing through the suspension, the solvent is dissolved in the supercritical carbon dioxide, and the solvent is removed along with the supercritical carbon dioxide flowing out of the sealed reactor.
The temperature and pressure in the closed reactor are set to those that can put carbon dioxide into a supercritical state. The critical point of carbon dioxide is 31.1° C./7.38 MPa, and the temperature and pressure are set to, for example, 40° C. to 200° C./10 MPa to 30 MPa.

The flow rate of the supercritical fluid in the solvent removal process is preferably 80 mL/sec or more and 240 mL/sec or less.

The method for producing silica composite particles according to this embodiment may be, for example, a production method including a preparation step, a first surface treatment step, a second surface treatment step, and a solvent removal step, in this order.

The following examples are provided to explain the invention in detail, but the invention is not limited to these examples. In the following explanation, all percentages are by weight unless otherwise specified.

<Production of Silica Composite Particles>
[Examples 1 to 8]
First, a suspension containing silica particles containing aluminum atoms in each example was prepared as described below.

Methanol, ion-exchanged water, and 10% aqueous ammonia (NH ₄ OH) in the amounts shown in Table 1 were placed in a glass reaction vessel equipped with a metallic stirring rod, a dropping nozzle, and a thermometer, and mixed with stirring to obtain an alkaline catalyst solution.

The temperature of the alkaline catalyst solution was adjusted to 25° C., and the alkaline catalyst solution was purged with nitrogen. Next, while stirring the alkaline catalyst solution, tetramethoxysilane (TMOS) in the amount shown in Table 1 and 176 parts by mass of ammonia water (NH ₄ OH) with a catalyst (NH ₃ ) concentration of 4.4% were simultaneously dropped to obtain a silica particle suspension.

An alcohol solution was prepared by diluting an aluminum compound (aluminum ethyl acetoacetate diisopropylate, manufactured by Wako Pure Chemical Industries, Ltd.) with butanol to a concentration of 50%.

An alcohol solution was prepared by diluting quaternary ammonium salts of the types and concentrations shown in Table 1 with methanol.

The temperature of the silica particle suspension was adjusted to 25°C, and the alcohol liquid adjusted to 25°C was added. The alcohol liquid was added so that the aluminum compound was 1 part by mass per 100 parts by mass of the solid content of the silica particle suspension. The mixture was then stirred for 30 minutes to react the aluminum compound with the surfaces of the silica particles for surface treatment, thereby obtaining a suspension of silica particles containing aluminum atoms.

The temperature of the suspension of silica particles containing aluminum atoms was adjusted to 25°C, and the alcohol liquid adjusted to 25°C was added. The alcohol liquid was added so that the concentration of the quaternary ammonium salt per 100 parts by mass of the solid content of the aluminum-bonded silica particle suspension was the amount shown in Table 1. The mixture was then stirred at 30°C for 30 minutes to react the quaternary ammonium salt with the surfaces of the aluminum-bonded silica particles for surface treatment, thereby obtaining a suspension containing silica particles containing quaternary ammonium salt and aluminum atoms.

30 parts by mass of 1,1,1,3,3,3-hexamethyldisilazane (HMDS) was added to the suspension containing the quaternary ammonium salt and silica particles containing aluminum atoms. While stirring the materials, the reaction vessel was filled with _CO2 , and the temperature and pressure in the reaction vessel were raised to 150°C/15 MPa. While maintaining the temperature and pressure, _CO2 was introduced and discharged at a flow rate of 5 L/min/ ^m3 while stirring for 30 minutes, and the solvent was removed over 120 minutes to obtain powdered silica composite particles of each example.

[Example 9]
Silica composite particles were produced in the same manner as in Example 1, except that the second surface treatment step was not carried out.

[Comparative Example 1]
Silica composite particles were produced in the same manner as in Example 1, except that the first surface treatment step was not performed.

[Comparative Example 2]
In the preparation step, silica particles were granulated by a sol-gel method according to the following specifications: Further, silica composite particles were produced in the same manner as in Example 1, except that the first surface treatment step was not performed.
The temperature of the alkaline catalyst solution was adjusted to 25° C., and the alkaline catalyst solution was purged with nitrogen. Next, while stirring the alkaline catalyst solution, tetramethoxysilane (TMOS) in an amount shown in Table 1, an alcohol liquid containing a quaternary ammonium salt in an amount shown in Table 1, and 176 parts by mass of ammonia water (NH ₄ OH) with a catalyst (NH ₃ ) concentration of 4.4% were simultaneously dropped to obtain a silica particle suspension.

Table 2 summarizes the results of measurements of the silica composite particles of each example, including the ratio of the maximum frequency of pore diameters of 2 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after cleaning (F _BEFORE /F _AFTER ), the ratio of the maximum frequency of pore diameters of 2 nm or less obtained from the pore _distribution curve of the nitrogen gas adsorption method before and after baking (F _SINTERING /F _BEFORE ), the capacitance ratio of the silica composite particle-attached resin particles separated from the mixture after mixing the silica composite particles and ferrite powder under the above-mentioned conditions before and after cleaning (C _AFTER /C _BEFORE ), the number average particle diameter, the average pore diameter, the ratio of the amount of silicon element Si detected by X-ray photoelectron spectroscopy (Si/Al), and the ratio of the amount of nitrogen element N detected by oxygen/nitrogen analysis (N/silica particle x 100). Note that each measurement method was as described above.
In each table, "-" means that the corresponding material is not present.

Evaluation
The silica composite particles of each example were evaluated for the increase in capacitance based on the following method and criteria, where G1 to G2 are acceptable.
The evaluation method is as follows.
The silica particles containing the prepared quaternary ammonium salt were added to MA1010 manufactured by Nippon Shokubai at 2 wt % and 2 g of MA1010 manufactured by Nippon Shokubai was mixed with 20 g of KNI106GSM manufactured by JFE Chemical Co., Ltd. The mixed sample was stirred for 5 minutes using a turbula shaker in a chamber with a humidity of 80% where charge is difficult to accumulate, and the charge was measured. The result was CA1, the data of the charge measurement after stirring for 5 minutes using a turbula shaker in a chamber with a humidity of 5% where charge is easy to accumulate was CB1, and the data of the charge measurement after stirring for 60 minutes was CB2, and the ratios of these, CB1/CA1 and CB2/CB1, were used for evaluation.

G1: CB1/CA2 is 1.0 or more and less than 1.15, and the increase in capacitance is strongly suppressed.
G2: CB1/CA2 is 1.15 or more and less than 1.3, and the increase in capacitance is suppressed.
G3: CB1/CA2 is 1.3 or more and less than 1.4, and the capacitance is slightly increased.
G4: CB1/CA2 is 1.4 or more, and the capacitance is increased.

G1: CB2/CB1 is 0.9 or more and less than 1.1, and the increase in capacitance is strongly suppressed.
G2: CB2/CB1 is 1.1 or more and less than 1.2, and the increase in capacitance is suppressed.
G3: CB2/CB1 is 1.2 or more and less than 1.3, and the capacitance is slightly increased.
G4: CB2/CB1 is 1.3 or more, and the capacitance is increased.

The abbreviations in each table refer to the following compounds.
ALCH: Aluminum ethyl acetoacetate diisopropylate TMBAC: Benzyl tributyl ammonium chloride TP-415: N,N-Dimethyl-N-tetradecyl-1-tetradecanaminium, hexa-μ-oxotetra-μ3-oxodi-μ5-oxotetradecaoxooctamolybdate(4-) (4:1)
P-51: Benzyltrimethylammonium chloride

As shown in Tables 1 and 2, it was found that the silica composite particles of the examples suppressed the increase in capacitance compared to the silica composite particles of the comparative examples.

Claims (11)

Contains a quaternary ammonium salt and an aluminum atom,
Silica composite particles, in which the ratio (F _BEFORE /F AFTER) of the maximum frequency of pores with diameters of 2 nm or _less obtained from a pore distribution curve of the silica composite particles before washing, F BEFORE, obtained from a pore distribution curve of the nitrogen gas adsorption method, to the maximum frequency of pores with diameters of 2 nm or less obtained from the pore distribution curve of the silica composite particles _{after washing} , F _AFTER , is 0.90 or more and 1.10 or less. Contains a quaternary ammonium salt and an aluminum atom,
Resin particles having silica composite particles attached to their surfaces before cleaning and ferrite powder are mixed under the specific conditions shown below to prepare a mixture, and then the capacitance C _BEFORE of the resin particles having silica composite particles attached to their surfaces separated from the mixture is measured.
Silica composite particles, in which the resin particles having the washed silica composite particles adhered to the surface thereof and ferrite powder are mixed under the specific conditions described below to prepare a mixture, and then the ratio (C _AFTER /C _BEFORE ) of the capacitance C _AFTER of the resin particles having the washed silica composite particles adhered to the surface thereof and the silica composite particles separated from the mixture is 1.5 or less.
-Specific conditions-
Mass ratio: silica composite particles/resin particles = 2/100, silica-adhered resin particles/ferrite powder = 1/10
・Mixing temperature: room temperature (10℃)
Mixing equipment: Turbula shaker mixer Mixing time: 5 minutes Mixing speed: 49 rpm The silica composite particle according to claim 1 or 2, wherein the quaternary ammonium salt comprises a compound represented by general formula (AM):

(In general formula (AM), R ¹ , R ² , R ³ and R ⁴ each independently represent an alkyl group, an aralkyl group or an aryl group which may have a substituent, and X ⁻ represents an anion. In general formula (AM), two or more of R ¹ , R ² , R ³ and R ⁴ may be bonded to each other to form a ring.) The silica composite particle according to claim 3, wherein in the compound represented by the general formula (AM), R ¹ , R ² , R ³ and R ⁴ each independently represent an alkyl group having 1 to 16 carbon atoms or an aralkyl group having 7 to 10 carbon atoms, each of which may have a substituent. Silica composite particles according to any one of claims 1 to 4, having a number average particle size of 5 nm or more and 300 nm or less. The silica composite particles according to claim 5, having a number average particle size of 5 nm or more and 100 nm or less. F _BEFORE is a maximum frequency of pores having a diameter of 2 nm or less obtained from a pore distribution curve of the silica composite particles before washing by a nitrogen gas adsorption method;
7. The silica composite particles according to claim 1, wherein the ratio (F _SINTERING /F _BEFORE /) of the maximum frequency of pores having a diameter of 2 nm or less, F _SINTERING , determined from a pore distribution curve of the silica composite particles before washing and after baking at 600° C., to F SINTERING, is 5 or more and 20 or less. The silica composite particles according to any one of claims 1 to 7, wherein the ratio (Si/Al) of the amount of silicon element present, Si, detected by X-ray photoelectron spectroscopy to the amount of aluminum element present, Al, detected by X-ray photoelectron spectroscopy, is 0.01 or more and 0.30 or less. The silica composite particles according to any one of claims 1 to 8, in which the ratio of the amount of nitrogen element N derived from the quaternary ammonium salt detected by oxygen/nitrogen analysis (N/silica composite particle x 100) is 0.01 or more and 1.0 or less. Silica composite particles according to any one of claims 1 to 9, having an average pore diameter of 0.55 nm or more and 2.0 nm or less. The silica composite particle according to any one of claims 1 to 10, which is a hydrophobically treated particle .