JP2022151522A - Silica particle, and production method of the same - Google Patents

Abstract

To provide a silica particle having a narrow charge distribution when taking an electrical charge.SOLUTION: A silica particle includes a nitrogen element-containing compound, where B/A is 1.2 or larger and 5 or smaller, and B is 0.2 cm3/g or larger and 3 cm3/g or smaller when the volumes of pores having a pore diameter of 1 nm or larger and 50nm or smaller found by pore distribution curves of a nitrogen gas adsorption method before and after calcination at 350°C are respectively A and B.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to silica particles and a method for producing the same.

Silica particles are used as an additive component or as a main component in powder coatings, cosmetics, rubbers, abrasives, etc., and play roles such as improving the strength of resins, improving fluidity of powders, and suppressing packing.

For example, in Patent Document 1, "a hydrophobic silica powder having (1) a degree of hydrophobicity of 50% or more, and (2) a quaternary ammonium ion produced by a mixed solvent of methanol and an aqueous methanesulfonic acid solution, The extraction amount X of at least one compound selected from the group consisting of a monoazo complex and a mineral acid ion is 0.1% by mass or more, and (3) the X and the extraction amount Y of the compound with water are , a hydrophobic silica powder that satisfies the following formula (I) Y/X<0.15”.

In addition, Patent Document 2 describes "a silica powder containing a plurality of silica particles in which a quaternary ammonium salt is introduced into a silica structure having an "Si--O" bond as a repeating unit. ” is disclosed.

In addition, Patent Document 3 describes "carrier particles made of hydrophobic spherical silica fine particles having an average particle size of 20 to 500 nm obtained by subjecting the surface of hydrophilic spherical silica fine particles obtained by a sol-gel method to a hydrophobic treatment, and and a charge control agent coated on the surface of the carrier particles”.

Further, Patent Document 4 discloses that "spherical hydrophobic silica fine particles having an average primary particle size of 0.01 to 5 μm are prepared from a quaternary ammonium salt compound, a fluoroalkyl group-containing betaine compound, and a silicone oil. Silica fine particles treated with a compound selected from the group” are disclosed.

Further, Patent Document 5 describes "particles obtained by treating silica fine particles having a degree of hydrophobicity of 80% or more with an amphoteric surfactant and silica fine particles having a degree of hydrophobicity of 80% or more treated with a quaternary ammonium salt or a quaternary ammonium group. "Particles treated with a polymer having" are disclosed.

JP 2019-073418 A JP 2017-039618 A JP 2011-185998 A Japanese Patent Application Laid-Open No. 2001-194825 JP-A-09-166884

The object of the present invention is to obtain silica particles containing a nitrogen element-containing compound from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350 ° C. The pore volumes with a pore diameter of 1 nm or more and 50 nm or less are A and B, respectively. The object of the present invention is to provide silica particles having a narrower charge distribution when charged than when B/A is less than 1.2 or B is less than 0.2 cm ³ /g.

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

<1>
containing a nitrogen element-containing compound,
B/A is 1.2 or more and 5 or less, where A and B are the pore volumes with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after baking at 350° C., and Silica particles having a B of 0.2 cm ³ /g or more and 3 cm ³ /g or less.

<2>
The silica particles according to <1>, wherein the B/A is 1.4 or more and 3 or less.

<3>
The silica particles according to <1> or <2>, wherein the B is 0.3 cm ³ /g or more and 1.8 cm ³ /g or less.

<4>
The silica particles according to any one of <1> to <3>, which have a number average particle diameter of 10 nm or more and 200 nm or less.

<5>
The silica particles according to <4>, having a number average particle diameter of 10 nm or more and 80 nm or less.

<6>
The nitrogen element-containing compound is at least one selected from the group consisting of quaternary ammonium salts, primary amine compounds, secondary amine compounds, tertiary amine compounds, amide compounds, imine compounds, and nitrile compounds. The silica particles according to any one of <1> to <5>.

<7>
The silica particles according to any one of <1> to <6>, which have an average circularity of 0.60 or more and 0.96 or less.

<8>
The silica particles according to any one of <1> to <7>, which have an average circularity of 0.70 or more and 0.92 or less.

<9>
The silica particles according to any one of <1> to <8>, which have a volume resistivity of 1.0×10 ⁷ Ωcm or more and 1.0×10 ^11.5 Ωcm or less.

<10>
The silica particles according to any one of <1> to <9>, wherein Ra/Rb is 0.01 or more and 0.8 or less, where Ra and Rb are volume resistivities before and after firing at 350°C.

<11>
The integrated value C of the signal observed in the range of chemical shift -50 ppm or more -75 ppm or less in the ²⁹ Si solid-state nuclear magnetic resonance (NMR) spectrum by the cross polarization / magic angle spinning (CP / MAS) method, and the chemical shift -90 ppm or more The silica particle according to any one of <1> to <10>, wherein the ratio C/D of the integrated value D of the signal observed in the range of -120 ppm or less is 0.10 or more and 0.75 or less.

<12>
silica base particles;
Nitrogen element covering at least a part of the surface of the silica base particles, composed of a reaction product of a trifunctional silane coupling agent, and at least part of the pores of the reaction product of the trifunctional silane coupling agent a structure to which a contained compound is adsorbed;
The silica particles according to any one of <1> to <11>.

<13>
a first step of forming a structure composed of a reaction product of a trifunctional silane coupling agent on at least a part of the surface of the silica base particles;
a second step of adsorbing a nitrogen element-containing compound into at least part of the pores of the reaction product of the trifunctional silane coupling agent;
The method for producing silica particles according to any one of <1> to <12>.

According to the invention according to <1>, in silica particles containing a nitrogen element-containing compound, the pore volume with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350 ° C. and B, silica particles having a narrow charge distribution when charged are provided compared to B/A of less than 1.2 or B of less than 0.2 cm ³ /g.

According to the invention relating to <2>, silica particles having a narrower charge distribution when charged are provided as compared with the case where B/A is less than 1.4.

According to the invention relating to <3>, silica particles having a narrower charge distribution when charged are provided compared to the case where B is less than 0.3 cm ³ /g.

According to the invention according to <4> or <5>, in the silica particles containing a nitrogen element-containing compound, fine pores with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350 ° C. When the pore volume is A and B respectively, the number average particle diameter is 10 nm or more and 200 nm or less, or 10 nm or more and 80 nm, compared to the case where B/A is less than 1.2 or B is less than 0.2 cm ³ /g. Even below, silica particles having a narrow charge distribution when charged are provided.

According to the invention according to <6>, in the silica particles containing a nitrogen element-containing compound, the pore volume with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350 ° C. and B ^, quaternary ammonium salts, primary amine compounds, secondary amine compounds, secondary Silica particles containing at least one selected from the group consisting of a tertiary amine compound, an amide compound, an imine compound and a nitrile compound and having a narrow charge distribution when charged are provided.

According to the invention according to <7> or <8>, in the silica particles containing a nitrogen element-containing compound, fine pores having a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350 ° C. When the pore volume is A and B, respectively, the ^average circularity is 0.60 or more and 0.96 or less, or Even if it is 0.70 or more and 0.92 or less, silica particles having a narrow charge distribution when charged are provided.

According to the invention according to <9>, silica particles having a narrow charge distribution when charged are provided compared to the case where the volume resistivity exceeds 1.0×10 ^11.5 Ωcm.

According to the invention according to <10>, when the volume resistivity before and after firing at 350 ° C. is Ra and Rb, respectively, compared to the case where Ra / Rb is less than 0.01, the silica particles have a narrow charge distribution when charged. is provided.

According to the invention according to <11>, the signal observed in the chemical shift range of −50 ppm or more and −75 ppm or less in the ²⁹ Si solid-state nuclear magnetic resonance (NMR) spectrum by the cross polarization/magic angle spinning (CP/MAS) method Compared to the case where the ratio C/D of the integrated value C and the integrated value D of the signal observed in the chemical shift range of −90 ppm or more and −120 ppm or less is less than 0.10 or more than 0.75, the charge distribution when charged Provided are silica particles having a narrow diameter.

According to the invention according to <12>, in the silica particles containing a nitrogen element-containing compound, pores with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350 ° C. When the volume is A and B respectively, compared to the case where B/A is less than 1.2 or B is less than 0.2 cm ³ /g, the surface of the silica base particle and at least a part of the silica base particle and a structure composed of a reaction product of a trifunctional silane coupling agent, and having a nitrogen element-containing compound adsorbed to at least part of the pores of the reaction product of the trifunctional silane coupling agent. It provides silica particles having a narrow charge distribution when charged.

According to the invention pertaining to <13>, at least a part of the surface of the silica base particles does not have a structure composed of a reaction product of a trifunctional silane coupling agent, silica that adsorbs a nitrogen element-containing compound. Provided is a method for producing silica particles having a narrower charge distribution when charged compared to the method for producing particles.

Embodiments of the present invention are described below. These descriptions and examples are illustrative of embodiments and do not limit the scope of embodiments.

In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of the numerical range described in other steps. good. Moreover, in the numerical ranges described in the present disclosure, the upper or lower limits of the numerical ranges may be replaced with the values shown in the examples.

In the present specification, each component may contain multiple types of corresponding substances.

When referring to the amount of each component in the composition in this specification, if there are multiple types of substances corresponding to each component in the composition, unless otherwise specified, the multiple types present in the composition means the total amount of substances in
<<Silica particles>>
The silica particles according to the present embodiment contain a nitrogen element-containing compound, and the pore volumes with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after baking at 350 ° C. are A and B, respectively. When, B/A is 1.2 or more and 5 or less, and B is 0.2 cm ³ /g or more and 3 cm ³ /g or less.

Here, hereinafter, "the pore volume A with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before 350°C firing" is also referred to as "the pore volume A before 350°C firing".

On the other hand, "the pore volume B with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method after firing at 350°C" is also referred to as "the pore volume B after firing at 350°C".

Due to the above configuration, the silica particles according to the present embodiment have a narrow charge distribution when charged. The reason is presumed as follows.

Silica particles are highly negatively charged and may be excessively charged. Therefore, the charge distribution is widened. In particular, under a low-temperature and low-humidity environment, excessive charging tends to occur, and the tendency for the charging distribution to widen increases.

For example, in powder coating, a powder coating charged by a method such as contact electrification or corona discharge is sprayed onto an object to be coated and electrostatically adhered, followed by heating to form a coating film. .

However, when silica particles with a wide charge distribution are used as an external additive for powder coatings, the charging of the powder coatings becomes uneven, making it difficult to achieve uniform adhesion of the powder coatings to the object to be coated.

On the other hand, when the nitrogen element-containing compound is adsorbed on the silica particles, excessive negative charging when the silica particles are charged can be suppressed. A nitrogen element-containing compound has a positive charging property, and the silica particles to which the nitrogen element-containing compound is adsorbed cancels excessive negative charging and suppresses excessive negative charging.

However, the nitrogen element-containing compound has a positive charging property, and when it is adsorbed on the outermost surface of the silica particles, the charging distribution spreads to negative charging and positive charging. Therefore, the nitrogen element-containing compound preferably exists in the pores and the like rather than covering the surfaces of the silica particles.

Therefore, in the silica particles according to the present embodiment, the pore volume A before sintering at 350° C. and the pore volume B after sintering at 350° C. are characteristics that satisfy the above relationship.

The pore volume B after firing at 350° C. is the pore volume after volatilization of the nitrogen-element-containing compound that has been adsorbed in the pores of the silica particles and partially blocked the pores by firing. Therefore, when B/A is 1.2 or more and 5 or less and B is 0.2 cm ³ /g or more and 3 cm ³ /g or less, the nitrogen element-containing compound is sufficient for at least some pores of the silica particles. of nitrogen element-containing compounds are adsorbed. Therefore, the narrowing of the charge distribution by the nitrogen element-containing compound is improved.

From the above, it is presumed that the silica particles according to the present embodiment have a narrow charge distribution when charged.

Then, for example, when the silica particles according to the present embodiment are used as an external additive for a powder coating, even in a low-temperature and low-humidity environment, variation in charging of the powder coating is unlikely to occur, and the amount of powder coating attached to the object to be coated is uniformity is achieved.

^In addition, the silica particles according to the present embodiment show chemical The ratio C/D between the integrated value C of the signal observed in the range of shift -50 ppm or more and -75 ppm or less and the integrated value D of the signal observed in the range of chemical shift -90 ppm or more and -120 ppm or less is 0.10 or more It is preferably 0.75 or less.

Since the silica particles according to the present embodiment have a signal integral value that satisfies the above range, the charge distribution tends to be narrow when charged. The reason is presumed as follows.

Having a signal integral value that satisfies the above range means that a sufficient amount of a nitrogen element-containing compound is adsorbed on at least a portion of the silica particle surface. It shows that a structure (eg, SiO _2/3 CH ₃ layer) is formed. The structure composed of the reaction product of the trifunctional silane coupling agent has a low density and a pore shape that facilitates adsorption of the nitrogen element-containing compound.

Furthermore, by reducing the amount of OH groups that inhibit the adsorption of the nitrogen element-containing compound, a sufficient amount of the nitrogen element-containing compound is easily adsorbed on the structure composed of the reaction product of the trifunctional silane coupling agent, Increases adsorption capacity.

Therefore, the narrowing of the charge distribution by the nitrogen element-containing compound is improved.

The silica particles according to this embodiment will be described in detail below.
(pore volume)
In the silica particles according to the present embodiment, the ratio B/A of the pore volume B after sintering at 350° C. to the pore volume A before sintering at 350° C. is 1.2 or more and 5 or less. from the viewpoint of, 1.4 or more and 3 or less are preferable, and 1.4 or more and 2.5 or less are more preferable.

The pore volume B after firing at ³⁵⁰ ° C. is 0.2 cm ³ /g or more and ³ cm ³ /g or less. It is preferably 0.6 cm ³ /g or more and 1.5 cm ³ /g or less.

350 degreeC baking is specifically implemented as follows.

In a nitrogen environment, the silica particles to be measured are heated to 350° C. at a heating rate of 10° C./min, and held at 350° C. for 3 hours. After that, it is cooled to room temperature (25° C.) at a heating rate of 10° C./min.

Pore volume is measured as follows.

First, the silica particles to be measured are cooled to liquid nitrogen temperature (-196° C.), nitrogen gas is introduced, and the adsorption amount is determined by the constant volume method or gravimetric method. An adsorption isotherm is created by gradually increasing the pressure of the introduced nitrogen gas and plotting the amount of nitrogen gas adsorbed against each equilibrium pressure. From this adsorption isotherm, a pore size distribution curve is obtained by the calculation formula of the BJH method, in which the vertical axis is the frequency and the horizontal axis is the pore diameter.

Then, from the obtained pore size distribution curve, an integrated pore volume distribution is obtained, in which the vertical axis is the volume and the horizontal axis is the pore diameter. From the obtained cumulative pore volume distribution, the pore volume with a pore diameter in the range of 1 nm or more and 50 nm or less is integrated, and this is defined as "the pore volume with a pore diameter of 1 nm or more and 50 nm or less".
(CP/MAS NMR spectrum)
The ratio of the integrated value C of the signal observed in the range of chemical shift -50 ppm or more and -75 ppm or less in the Si-CP / MAS NMR spectrum and the integrated value D of the signal observed in the range of chemical shift -90 ppm or more -120 ppm or less C/D is 0.10 or more and 0.75 or less, preferably 0.12 or more and 0.45 or less, more preferably 0.15 or more and 0.40 or less, from the viewpoint of narrowing the charge distribution.

From the viewpoint of narrowing the charge distribution, the ratio of the integrated value C of the signal observed in the chemical shift range of -50 ppm to -75 ppm when the integrated value of the signal in the Si-CP/MAS NMR spectrum is 100% ( Signal ratio) is preferably 5 (unit: %) or more, more preferably 7 (unit: %) or more. In addition, the upper limit of the ratio of the integrated value C of the signal is, for example, 60% or less.

A Si-CP/MAS NMR spectrum is obtained by performing measurement by nuclear magnetic resonance spectroscopy under the following conditions.
・ Spectrometer: AVENCE300 (manufactured by Brunker)
・Resonance frequency: 59.6MHz
・Measurement nucleus: ²⁹ Si
・Measurement method: CPMAS method (using Bruker's standard parc sequence cp.av)
・Wait time: 4 seconds ・Contact time: 8 milliseconds ・Accumulation times: 2048 times ・Measurement temperature: Room temperature (measured value 25°C)
・Observation center frequency: -3975.72Hz
・MAS rotation speed: 7.0mm-6kHz
・Reference substance: Hexymethylcyclotrisiloxane (composition of silica particles)
The silica particles according to this embodiment contain a nitrogen element-containing compound.

Specifically, in the silica particles according to the present embodiment, a silica base particle and at least a part of the surface of the silica base particle are coated with a reaction product of a trifunctional silane coupling agent, and further, the reaction product is A structure in which a nitrogen element-containing compound is adsorbed on at least a part thereof can be mentioned. By forming the structure, the pore volume characteristics and the Si-CP/MAS NMR spectral characteristics can be controlled. In addition, the degree of hydrophobicity and the amount of OH groups, which will be described later, can also be controlled.

In addition, the silica particles according to the present embodiment may have a hydrophobized structure on the surface of the structure.
-Silica mother particles-
At least part of the surface of the silica base particles is composed of a reaction product of the trifunctional silane coupling agent, and at least part of the pores of the reaction product of the trifunctional silane coupling agent contain a nitrogen element-containing compound. Silica particles from which adsorbed structures are formed.

Examples of silica base particles include dry silica particles and wet silica particles.

Dry silica particles include combustion silica (fumed silica) obtained by burning a silane compound and deflagration silica obtained by explosively burning metallic silicon powder.

Wet-process silica particles include wet-process silica particles obtained by a neutralization reaction between sodium silicate and mineral acid (precipitation silica particles synthesized and aggregated under alkaline conditions, gel-process silica particles synthesized and aggregated under acidic conditions), and acidic silicic acid. Examples include colloidal silica particles (silica sol particles) obtained by alkalinizing and polymerizing, and sol-gel method silica particles obtained by hydrolyzing an organic silane compound (eg, alkoxysilane).

Among these, sol-gel method silica particles are preferable as the silica base particles from the viewpoint of narrowing the charge distribution.
-Reaction product of trifunctional silane coupling agent-
Since the adsorption structure composed of the reaction product of the trifunctional silane coupling agent has a low density and a high affinity with the nitrogen element-containing compound, the nitrogen element-containing compound is easily adsorbed deep into the pores, The adsorption amount (that is, the content) of the nitrogen element-containing compound increases. Adherence of the positively charged nitrogen element-containing compound to the negatively charged silica surface produces an effect of canceling excessive negative charging. In addition, since the nitrogen element-containing compound is adsorbed not on the outermost surface of the silica particles but inside the low-density structure, it prevents the positive charging property from becoming too strong and the charging distribution from spreading, and only cancels excessive negative charging. , the narrowing of the charge distribution is further improved.

The reaction product of the trifunctional silane coupling agent is, for example, a reaction product in which OR ² is substituted with an OH group in the following general formula (TA), and a reaction in which OR ² is substituted with an OH group by polycondensation. A product, OR ² substituted with OH group, and a reaction product obtained by polycondensation with SiOH group of silica particles can be mentioned. Further, the reaction products of trifunctional silane coupling agents include reaction products in which OR ² is wholly or partially substituted, and reaction products in which all or some of them are polycondensed.

A trifunctional silane coupling agent is a non-nitrogen element-containing compound that does not contain N (nitrogen).

Specifically, the trifunctional silane coupling agent includes a trifunctional silane coupling agent represented by the following general formula (TA).

General formula (TA): R ¹ —Si(OR ² ) ₃
In general formula (TA), R ¹ represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 20 carbon atoms or an aromatic hydrocarbon group having 6 to 20 carbon atoms, and R ² represents a halogen atom or represents an alkoxy group. A plurality of R ² may be the same group or different groups.

The aliphatic hydrocarbon group represented by R ¹ may be linear, branched or cyclic, but linear or branched is preferred. The number of carbon atoms in the aliphatic hydrocarbon group is preferably from 1 to 20 carbon atoms, more preferably from 1 to 18 carbon atoms, still more preferably from 1 to 12 carbon atoms, and even more preferably from 1 to 10 carbon atoms. The aliphatic hydrocarbon group may be either saturated or unsaturated, preferably a saturated aliphatic hydrocarbon group, more preferably an alkyl group.

Examples of saturated aliphatic hydrocarbon groups include linear alkyl groups (methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, hexadecyl group , icosyl group, etc.), branched alkyl groups (isopropyl group, isobutyl group, isopentyl group, neopentyl group, 2-ethylhexyl group, tertiary butyl group, tertiary pentyl group, isopentadecyl group, etc.), cyclic alkyl groups ( cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, tricyclodecyl group, norbornyl group, adamantyl group, etc.).

Examples of unsaturated aliphatic hydrocarbon groups include alkenyl groups (vinyl group (ethenyl group), 1-propenyl group, 2-propenyl group, 2-butenyl group, 1-butenyl group, 1-hexenyl group, 2-dodecenyl group, pentenyl group, etc.), alkynyl groups (ethynyl group, 1-propynyl group, 2-propynyl group, 1-butynyl group, 3-hexynyl group, 2-dodecynyl group, etc.).

The aromatic hydrocarbon group represented by R ¹ preferably has 6 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, still more preferably 6 to 12 carbon atoms, still more preferably 6 to 10 carbon atoms. It is below.

The aromatic hydrocarbon group includes phenylene group, biphenylene group, terphenylene group, naphthalene group, anthracene group and the like.

Halogen atoms represented by R ² include fluorine, chlorine, bromine and iodine atoms. A chlorine atom, a bromine atom, or an iodine atom is preferable as the halogen atom.

The alkoxy group represented by R ² includes an alkoxy group having 1 to 10 carbon atoms (preferably 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms). Examples of alkoxy groups include methoxy, ethoxy, isopropoxy, t-butoxy, n-butoxy, n-hexyloxy, 2-ethylhexyloxy, and 3,5,5-trimethylhexyloxy groups. be done. Alkoxy groups also include substituted alkoxy groups. A halogen atom, a hydroxyl group, an amino group, an alkoxy group, an amide group, a carbonyl group, etc., can be mentioned as the substituent that can be substituted on the alkoxy group.

The trifunctional silane coupling agent represented by the general formula (TA) is a trifunctional silane coupling agent in which R ¹ is a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms and R ² is a halogen atom or an alkoxy group. A ring agent is preferred.

Examples of trifunctional silane coupling agents include
vinyltrimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, n-octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, vinyltriethoxysilane Silane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, hexyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltriethoxysilane methoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, decyltrichlorosilane, phenyltrichlorosilane (compounds in which R ¹ is an unsubstituted aliphatic hydrocarbon group or an unsubstituted aromatic hydrocarbon group);
3-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-glycidyloxypropylmethyldimethoxysilane (where R ¹ is compounds that are substituted aliphatic hydrocarbon groups or substituted aromatic hydrocarbon groups);
etc.

The trifunctional silane coupling agents may be used singly or in combination of two or more.

Among these, ^{alkyltrialkoxysilane} is preferable as the trifunctional silane coupling agent from the viewpoint of narrowing the charge distribution. and 15 or less), and R ² is more preferably an alkyl group having 1 or more and 2 or less carbon atoms.

From the viewpoint of narrowing the charge distribution, the adhesion amount of the structure composed of the reaction product of the trifunctional silane coupling agent is preferably 5.5% by mass or more and 30% by mass or less with respect to the silica particles, and 7% by mass. More preferably, the content is 22% by mass or less.
-Nitrogen element-containing compound-
The nitrogen element-containing compound is a nitrogen element-containing compound excluding ammonia and a compound in a gaseous state at a temperature of -200°C or higher and 25°C or lower.

The nitrogen element-containing compound is preferably adsorbed in at least part of the pores of the reaction product of the trifunctional silane coupling agent.

The nitrogen element-containing compound is at least one selected from the group consisting of quaternary ammonium salts, primary amine compounds, secondary amine compounds, tertiary amine compounds, amide compounds, imine compounds, and nitrile compounds. exemplified.

Here, the primary amine compounds include phenethylamine, toluidine, catecholamine, and 2,4,6-trimethylaniline.

Secondary amine compounds include dibenzylamine, 2-nitrodiphenylamine, 4-(2-octylamino)diphenylamine.

Tertiary amine compounds include 1,8-bis(dimethylamino)naphthalene, N,N-dibenzyl-2-aminoethanol, N-benzyl-N-methylethanolamine.

Amide compounds include N-cyclohexyl-p-toluenesulfonamide, 4-acetamido-1-benzylpiperidine, N-hydroxy-3-[1-(phenylthio)methyl-1H-1,2,3-triazole-4- yl]benzamides.

Examples of imine compounds include diphenylmethanimine, 2,3-bis(2,6-diisopropylphenylimino)butane, and N,N'-(ethane-1,2-diylidene)bis(2,4,6-trimethylaniline). mentioned.

Nitrile compounds include 3-indoleacetonitrile, 4-[(4-chloro-2-pyrimidinyl)amino]benzonitrile, 4-bromo-2,2-diphenylbutyronitrile.

Among these, the quaternary ammonium salt is preferable as the nitrogen element-containing compound from the viewpoint of narrowing the charge distribution.

A quaternary ammonium salt may be used individually by 1 type, or may use 2 or more types together.

The quaternary ammonium salt is not particularly limited, and known quaternary ammonium salts can be applied.

From the viewpoint of narrowing the charge distribution, the quaternary ammonium salt preferably contains a compound represented by the general formula (AM). The compounds represented by general formula (AM) may be used singly or in combination of two or more.

In general formula (AM), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an optionally substituted alkyl group, aralkyl group or aryl group ^; represents an anion. However, at least one of R ¹ , R ² , R ³ and R ⁴ represents an optionally substituted alkyl group, aralkyl group or aryl group. Two or more of R ¹ , R ² , R ³ and R ⁴ may be linked to form an aliphatic ring, an aromatic ring, or a hetero ring.

Examples of alkyl groups represented by R ¹ to R ⁴ include linear alkyl groups having 1 to 20 carbon atoms and branched alkyl groups having 3 to 20 carbon atoms.

Linear alkyl groups having 1 to 20 carbon atoms include, for example, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n -octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group and the like.

Examples of branched alkyl groups having 3 to 20 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group and sec-hexyl. group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec -decyl group, tert-decyl group and the like.

Among the above, alkyl groups represented by R ¹ to R ⁴ are preferably alkyl groups having 1 to 15 carbon atoms such as methyl group, ethyl group, butyl group and tetradecyl group.

Aralkyl groups represented by R ¹ to R ⁴ include aralkyl groups having 7 to 30 carbon atoms.

Aralkyl groups having 7 to 30 carbon atoms include, for example, benzyl group, phenylethyl group, phenylpropyl group, 4-phenylbutyl group, phenylpentyl group, phenylhexyl group, phenylheptyl group, phenyloctyl group and phenylnonyl group. , naphthylmethyl group, naphthylethyl group, anthratylmethyl group, phenyl-cyclopentylmethyl group and the like.

Among the above, the aralkyl group represented by R ¹ to R ⁴ is preferably an aralkyl group having 7 to 15 carbon atoms, such as a benzyl group, phenylethyl group, phenylpropyl group, 4-phenylbutyl group, and the like. .

Examples of the aryl group represented by R ¹ to R ⁴ include aryl groups having 6 or more and 20 or less carbon atoms.

Examples of the aryl group having 6 to 20 carbon atoms include phenyl group, pyridyl group, 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 or more and 10 or less carbon atoms such as a phenyl group.

Anions represented by X ⁻ include organic anions and inorganic anions.

Examples of organic anions include polyfluoroalkylsulfonate ions, polyfluoroalkylcarboxylate ions, tetraphenylborate ions, aromatic carboxylate ions, aromatic sulfonate ions (1-naphthol-4-sulfonate ions, etc.), and the like. is mentioned.

Examples of inorganic anions include molybdate ions (MoO ₄ ^2- , Mo ₂ O ₇ ^2- , Mo ₃ O ₁₀ ^2- , Mo ₄ O ₁₃ ^2- , Mo ₇ O ₂₄ ^2- , Mo ₈ O ₂₆ ^4- etc. ), OH ⁻ , F ⁻ , Fe(CN) ₆ ³⁻ , Cl ⁻ , Br ⁻ , NO ₂ ⁻ , NO ₃ ⁻ , CO ₃ ²⁻ , PO ₄ ³⁻ , SO ₄ ²⁻ and the like.

In general formula (AM), two or more of R ¹ , R ² , R ³ and R ⁴ may be linked together to form a ring. Examples of the ring formed by combining two or more of R ¹ , R ² , R ³ and R ⁴ include alicyclic rings having 2 to 20 carbon atoms, heterocyclic amines having 2 to 20 carbon atoms, and the like. mentioned.

In the compound represented by general formula (AM), each of R ¹ , R ² , R ³ and R ⁴ may independently have a substituent. Examples of substituents include nitrile groups, carbonyl groups, ether groups, amide groups, siloxane groups, silyl groups, silanealkoxy groups, and the like.

R ¹ , R ² , R ³ and R ⁴ each independently represents an alkyl group having 1 to 16 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. is preferred.

Among these, from the viewpoint of narrowing the charge distribution, the compound represented by the general formula (AM) preferably has a total carbon number of 18 or more and 35 or less, more preferably 20 or more and 32 or less.

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

The nitrogen element-containing compound is preferably a nitrogen element-containing compound containing a molybdenum element from the viewpoint of narrowing the charge distribution and maintaining the charge distribution. ), and a mixture of a quaternary ammonium salt and a metal oxide containing a molybdenum element.

When the nitrogen element compound contains the molybdenum element, the activity of the nitrogen element is enhanced, and even if the nitrogen element-containing compound is present not on the outermost surface of the silica particles but inside the pores, the positive charging property of the nitrogen element is appropriately expressed. be able to. Therefore, when charged, the charge distribution is narrow, and the charge distribution maintainability tends to be high.

In particular, in the quaternary ammonium molybdenum element-containing salt, the molybdenum element-containing anion, which is an anion, strongly bonds with the cation, quaternary ammonium cation, so that the charge distribution maintenance property is enhanced.

Quaternary ammonium salts containing molybdenum include [N ⁺ (CH) ₃ (C ₁₄ C ₂₉ ) ₂ ] ₄ Mo ₈ O ₂₈ ^4- , [N ⁺ (C ₄ H ₉ ) ₂ (C ₆ H ₆ ) ₂ ] ₂ Mo ₂ O ₇ ²⁻ , [N ⁺ (CH ₃ ) ₂ (CH ₂ C ₆ H ₆ )(CH ₂ ) ₁₇ CH ₃ ] ₂ MoO ₄ ²⁻ , [N ⁺ (CH ₃ ) ₂ (CH ₂ C ₆ H ₆ )(CH ₂ ) ₁₅ CH ₃ ] ₂ MoO ₄ ^2- and the like.

Examples of metal oxides containing molybdenum include molybdenum oxides (molybdenum trioxide, molybdenum dioxide, Mo ₉ O ₂₆ ), alkali metal molybdate salts (lithium molybdate, sodium molybdate, potassium molybdate, etc.), molybdenum alkaline earth. metal salts (magnesium molybdate, calcium molybdate, etc.) and other complex oxides (Bi ₂ O ₃ .2MoO ₃ , γ-Ce ₂ Mo ₃ O ₁₃ , etc.).
- Detection and content of nitrogen element-containing compounds -
When the silica particles according to the present embodiment are heated in a temperature range of 300° C. or higher and 600° C. or lower, a nitrogen element-containing compound is detected. Specifically, for example, it is as follows.

For the detection of nitrogen element-containing compounds, for example, a heating furnace type dropping pyrolysis gas chromatograph mass spectrometer using He as a carrier gas is used. A nitrogen element-containing compound can be detected under thermal decomposition temperature conditions of 300° C. or higher and 600° C. or lower under an inert gas. Specifically, 0.1 mg or more and 10 mg or less of silica particles can be introduced into a pyrolysis gas chromatograph mass spectrometer, and the presence or absence of a nitrogen element-containing compound can be confirmed from the MS spectrum of the detected peak. Examples of components generated by thermal decomposition of silica particles containing a nitrogen element-containing compound include primary to tertiary amines and aromatic nitrogen compounds represented by the following general formula (N).

In the following general formula (N), R ^N1 to R ^N3 each independently represent a hydrogen atom, or an optionally substituted alkyl group, aralkyl group or aryl group, and R ^N1 to ^RN3 has the same definition as R ¹ , R ² and R ³ in general formula (AM).

For example, when the nitrogen element-containing compound is a quaternary ammonium salt, thermal decomposition at 600° C. causes part of the side chain to be eliminated and detected as a tertiary amine.

From the viewpoint of narrowing the charge distribution, the content of the nitrogen element-containing compound is preferably 0.008% by mass or more and 0.45% by mass or less, and 0.015% by mass or more and 0.45% by mass or less in terms of N atoms with respect to the silica particles. 20% by mass or less is more preferable, and 0.018% by mass or more and 0.10% by mass or less is even more preferable.

The content of the nitrogen element-containing compound in terms of N atoms is measured as follows.

Using an oxygen/nitrogen analyzer (for example, EMGA-920 manufactured by Horiba Ltd.), the amount of nitrogen element present is measured at an integration time of 45 seconds to obtain the ratio of N (N/Si). As a sample pretreatment, the silica particles are dried at 100° C. for 24 hours or more to remove impurities such as ammonia from the silica particles.

Here, when a nitrogen element-containing compound containing molybdenum element is used as the nitrogen element-containing compound, from the viewpoint of narrowing the charge distribution, the net intensity of molybdenum element and the net intensity of silicon element measured by fluorescent X-ray analysis (Mo/Si) is preferably 0.035 or more and 0.35 or less, preferably 0.07 or more and 0.32 or less, and more preferably 0.10 or more and 0.30 or less.

From the viewpoint of narrowing the charge distribution, the Net intensity of the molybdenum element is preferably 5 kcps to 75 kcps, 7 kcps to 50 kcps, 8 kcps to 55 kcps, or 10 kcps to 40 kcps.

The net intensity of molybdenum element and silicon element is measured as follows.

About 0.5 g of silica particles are compressed using a compression molding machine with a load of 6 t and a pressure of 60 seconds to produce a disk with a diameter of 50 mm and a thickness of 2 mm. Using this disk as a sample, using a scanning fluorescent X-ray analyzer (XRF-1500, manufactured by Shimadzu Corporation), qualitative and quantitative elemental analysis was performed under the following conditions, and the Net intensity of each of the molybdenum element and the silicon element (Unit: kilo counts per second, kcps).
・Tube voltage: 40 kV
・Tube current: 90mA
・Measurement area (analysis diameter): diameter 10mmφ
・Measurement time: 30 minutes ・Anticathode: rhodium - extraction amount of nitrogen element-containing compound -
The amount X of the nitrogen element-containing compound extracted by the ammonia/methanol mixed solution is 0.1% by mass or more, and the extraction amount X of the nitrogen element-containing compound and the extraction amount Y of the nitrogen element-containing compound by water are represented by the formula: It is preferable to satisfy Y/X<0.3.

That is, the nitrogen element-containing compound has a property of being difficult to dissolve in water, that is, it is difficult to adsorb moisture in the air.

In silica particles containing a nitrogen element-containing compound, when the nitrogen element-containing compound adsorbs moisture, the charge distribution is widened and the nitrogen element-containing compound is easily released from the silica particles.

However, silica particles containing a nitrogen element-containing compound that hardly adsorbs moisture in the air are difficult to widen the charge distribution even if there is a lot of moisture in the air (even under high humidity), and the nitrogen element is contained. Compounds are less likely to leave and a narrow charge distribution is easily maintained.

The extraction amount X of the nitrogen element-containing compound is preferably 50% by mass or more. However, the upper limit of the extraction amount X of the nitrogen element-containing compound is, for example, 95 mass because it is difficult for the solution to penetrate into the inside of the pores due to surface tension, and a part of the nitrogen element-containing compound remains without being dissolved. % or less.

The ratio “Y/X” of the extraction amount X of the nitrogen element-containing compound to the extraction amount Y of the nitrogen element-containing compound is preferably less than 0.3, more preferably 0.15 or less. However, although the lower limit of the ratio "Y/X" is ideally 0, it is, for example, 0.01 or more because the measurement error range of X and Y is about ±1%.

Here, the extraction amounts X and Y of the nitrogen element-containing compound are measured as follows.

First, the silica particles to be measured are analyzed with a thermogravimetric/mass spectrometer (for example, a gas chromatograph mass spectrometer manufactured by Netsch Japan Co., Ltd.) at a constant temperature of 400 ° C., and hydrocarbons having at least 1 or more carbon atoms are nitrogen atoms. Measure the integrated mass fraction of the compound covalently bonded to the silica particles and set it as W1.

On the other hand, 1 part by mass of silica particles to be measured is added to 30 parts by mass of an ammonia/methanol solution (manufactured by Sigma-Aldrich, mass ratio of ammonia/methanol = 1/5.2) at a liquid temperature of 25°C, and the mixture is stirred for 30 minutes. After ultrasonication, the silica powder and the extract are separated. The separated silica particles are dried in a vacuum dryer at 100°C for 24 hours, and are analyzed by a thermogravimetric/mass spectrometer under constant conditions of 400°C to obtain silica particles of a compound in which a hydrocarbon having at least 1 or more carbon atoms is covalently bonded to a nitrogen atom. is measured and designated as W2.

Then, the extraction amount X of the nitrogen element-containing compound is calculated by the following formula.
・Formula: X=W1-W2
In addition, 1 part by mass of silica particles to be measured is added to 30 parts by mass of water at a liquid temperature of 25° C., ultrasonically treated for 30 minutes, and then the silica particles and the extract are separated. The separated silica particles are dried in a vacuum dryer at 100°C for 24 hours, and are analyzed by a thermogravimetric/mass spectrometer under constant conditions of 400°C to obtain silica particles of a compound in which a hydrocarbon having at least 1 or more carbon atoms is covalently bonded to a nitrogen atom. The mass fraction for is measured and defined as W3.

Then, the extraction amount Y of the nitrogen element-containing compound is calculated by the following formula.
・Formula: Y=W1-W3
(Hydrophobic treatment structure)
The hydrophobized structure is a structure reacted with a hydrophobizing agent.

As the hydrophobizing agent, for example, an organosilicon compound is applied.

Examples of organosilicon compounds include
alkoxysilane compounds or halosilane compounds having a lower alkyl group such as methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, trimethylmethoxysilane;
Alkoxysilane compounds having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane;
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycid Alkoxysilane compounds having an epoxy group such as xypropyltriethoxysilane;
Alkoxysilane compounds having a styryl group such as p-styryltrimethoxysilane and p-styryltriethoxysilane;
N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, Alkoxysilane compounds having aminoalkyl groups such as 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine and N-phenyl-3-aminopropyltrimethoxysilane;
Alkoxysilane compounds having an isocyanate alkyl group such as 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane;
silazane compounds such as hexamethyldisilazane and tetramethyldisilazane;
etc.
(Characteristics of silica particles)
-Hydrophobicity-
From the viewpoint of narrowing the charge distribution, the hydrophobicity of the silica particles according to the present embodiment is preferably 10% or more and 60% or less, more preferably 20% or more and 55% or less, and even more preferably 28% or more and 53% or less.

When the degree of hydrophobicity of the silica particles is 10% or less, the coverage of the structure is low due to reaction generation of the trifunctional silane coupling agent, and the content of the nitrogen element-containing compound is reduced. Become.

On the other hand, when the degree of hydrophobization of silica particles exceeds 60%, the density of the structure increases due to the reaction production of the trifunctional silane coupling agent, the number of pores decreases, and the content of the nitrogen element-containing compound decreases. Therefore, the electrification distribution tends to spread.

The degree of hydrophobicity of silica particles is measured as follows.

0.2% by mass of silica particles as a sample is added to 50 ml of ion-exchanged water, and methanol is added dropwise from a burette while stirring with a magnetic stirrer. is obtained as the degree of hydrophobicity.
-Number average particle size and number particle size distribution index-
The number average particle diameter of the silica particles according to the present embodiment is preferably 10 nm or more and 200 nm or less, more preferably 10 nm or more and 80 nm or less, and even more preferably 10 nm or more and 60 nm or less.

When the number average particle diameter of the silica particles is within the above range, the specific surface area is large and excessive charging tends to occur. is realized.

The number particle size distribution index of the silica particles according to the present embodiment is preferably 1.1 or more and 2.0 or less, more preferably 1.15 or more and 1.6 or less.

When the number particle size distribution index of the silica particles according to the present embodiment is within the above range, there are few coarse powders that tend to have a large charge amount and fine powders that tend to have a small charge amount, and the narrowing of the charge distribution is realized. becomes easier.

Here, the number average particle diameter and number particle size distribution index of silica particles are measured as follows.

Observe the silica particles at a magnification of 40,000 using a scanning electron microscope (SEM), analyze the image of the observed silica particles with image processing analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.), and determine the circles of at least 200 particles. Find the equivalent diameter. Then, the cumulative distribution of the number of individual particles is drawn from the small diameter side, and the particle diameter and the number average particle diameter at which the cumulative 50% is obtained from the small diameter side.

In addition, the square root of the value obtained by dividing the particle size D84 at which the cumulative 84% is obtained by the particle size D16 at which the cumulative 16% is obtained from the small diameter side is defined as the "number particle size distribution index" (GSD). That is, number particle size distribution index (GSD) = (D84/D16) ^0.5 .
-Circularity-
The average circularity of the silica particles according to the present embodiment is preferably 0.60 or more and 0.96 or less, more preferably 0.70 or more and 0.92 or less, and even more preferably 0.75 or more and 0.90 or less.

When the average circularity of the silica particles is within the above range, the specific surface area is large and excessive charging tends to occur. be done.

Here, the circularity of silica particles is measured as follows.

The silica particles were observed at a magnification of 40,000 using a scanning electron microscope (SEM), and the images of the observed silica particles were analyzed using image processing analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.). The circularity of the particles is determined and arithmetically averaged to calculate the average circularity.

In addition, circularity is calculated by the following formulas.

Circularity = equivalent circle diameter perimeter/perimeter = [2 x (Aπ) ^1/2 ]/PM
In the above formula, A represents the projected area and PM represents the perimeter.
－Volume resistivity－
The volume resistivity of the silica particles according to the present embodiment (that is, the volume resistivity before firing at 350° C.) is preferably 1.0×10 ⁷ Ωcm or more and 1.0×10 ^11.5 Ωcm or less, and 1.0× 10 ⁸ Ωcm or more and 1.0×10 ¹¹ Ωcm or less is more preferable.

When the volume resistivity of the silica particles according to the present embodiment is within the above range, the content of the nitrogen element-containing compound is large, excessive charging is difficult to occur, and narrowing of the charging distribution is easily realized.

In the silica particles according to the present embodiment, Ra/Rb is preferably 0.01 or more and 0.8 or less when the volume resistivity of the silica particles before and after firing at 350° C. is Ra and Rb, respectively. 015 or more and 0.6 or less is more preferable.

When Ra/Rb is within the above range, the content of the nitrogen element-containing compound is large, excessive charging is difficult to occur, and narrowing of the charging distribution is easily achieved.

350° C. firing is carried out as described above.

On the other hand, the volume resistivity is measured as follows. The measurement environment is assumed to have a temperature of 20° C. and a humidity of 50% RH.

Silica particles to be measured are placed on the surface of a circular jig on which an electrode plate of 20 cm ² is arranged so as to have a thickness of about 1 mm or more and 3 mm or less to form a silica particle layer. A 20 cm ² electrode plate similar to the above is placed on this, and the silica particle layer is sandwiched therebetween. In order to eliminate voids between silica particles, a pressure of 0.4 MPa is applied to the electrode plate placed on the silica particle layer, and then the thickness (cm) of the silica particle layer is measured. Both electrodes above and below the silica particle layer are connected to an impedance analyzer (manufactured by Solartron Analytical I) to measure frequencies of 10 ⁻³ Hz to 10 ⁶ Hz and obtain Nyquist plots. Assuming that there are three kinds of resistance components, ie, the electrode contact resistance and the electrode contact resistance, an equivalent circuit is fitted to obtain the bulk resistance R.
The formula for calculating the volume resistivity (Ω·cm) of silica particles is as shown below.
・ Formula: ρ = R / L
In the formula, ρ represents the volume resistivity (Ω·cm) of the silica particles, R represents the bulk resistance (Ω), and L represents the thickness (cm) of the silica particle layer.
(OH group amount)
In the silica particles according to the present embodiment, the amount of OH groups measured by the Sears method is preferably 0.2/nm ² or more and 5.5/nm ² or less, and from the viewpoint of narrowing the charge distribution, 0.2 2 or more/nm ² or more and 4/nm ² or less are more preferable, and 0.2 or more/nm ² or more and 3/nm ² or less are more preferable.

The amount of OH groups measured by the Sears method can be adjusted to the above range by sufficiently forming a structure composed of a reaction product of a trifunctional silane coupling agent in the silica base particles.

By reducing the amount of OH groups that inhibit the adsorption of the nitrogen element-containing compound to the above range, the nitrogen element-containing compound can easily enter deep into the pores of the silica particles (for example, the pores of the adsorption layer described later). Then, the hydrophobic interaction with the nitrogen element-containing compound acts to strengthen the adhesion to the silica particles. Therefore, the adsorption amount of the nitrogen element-containing compound is increased. In addition, the nitrogen element-containing compound becomes difficult to detach. Therefore, the narrowing of the charge distribution due to the nitrogen element-containing compound is improved, and the maintainability of the narrow charge distribution is also improved.

In addition, by reducing the amount of OH groups to the above range, the environmental dependence of charging characteristics is reduced, and under any environment (especially under a low temperature and low humidity environment where excessive negative charging tends to occur), It becomes easy to realize narrowing of the electrification distribution.

The amount of OH groups is measured by the Sears method. Specifically, it is as follows.

1.5 g of silica particles are added to a mixture of 50 g of pure water and 50 g of ethanol, and stirred for 2 minutes with an ultrasonic homogenizer to prepare a dispersion. 1.0 g of a 0.1 mol/L hydrochloric acid aqueous solution is added dropwise while stirring in an environment of 25° C. to obtain a test liquid. The obtained test liquid is placed in an automatic titrator, and potentiometric titration is performed with a 0.01 mol/L sodium hydroxide aqueous solution to create a differential curve of the titration curve. Let E be the titration amount at which the titration amount of the 0.01 mol/L sodium hydroxide aqueous solution is the largest among the inflection points at which the differential value of the titration curve is 1.8 or more.

The surface silanol group density ρ (number/nm ² ) of silica particles is calculated using the following formula.

Formula: ρ = ((0.01 × E-0.1) × NA/1000) / (M × S _BET × 10 ¹⁸ )
In the formula, the details of the symbols are as follows.

E: Among the inflection points where the derivative value of the titration curve is 1.8 or more, the titration amount at which the titration amount of 0.01 mol / L sodium hydroxide aqueous solution is the largest NA: Avogadro's number M: Silica particle amount (1. 5g)
S _BET : Specific Surface Area of Silica Particles (m ² /g) The specific surface area of silica particles is measured by a BET-type nitrogen adsorption three-point method. The equilibrium relative pressure is assumed to be 0.3.
<<Method for producing silica particles>>
An example of the method for producing silica particles according to the present embodiment is
a first step of forming a structure composed of a reaction product of a trifunctional silane coupling agent on at least a part of the surface of the silica base particles;
a second step of adsorbing a nitrogen element-containing compound into at least part of the pores of the reaction product of the trifunctional silane coupling agent;
have

In the method for producing silica particles according to the present embodiment, after or during the second step, the surface of at least a part of the silica base particles is coated, and is composed of a reaction product of a trifunctional silane coupling agent, and a third step of subjecting the silica base particles having a structure in which a nitrogen element-containing compound is adsorbed to at least part of the pores of the reaction product of the trifunctional silane coupling agent to hydrophobization treatment. good.

Hereinafter, the steps of the method for producing silica particles according to the present embodiment will be described in detail.
[Preparation process]
First, the step of preparing silica base particles will be described.

As a preparation process, for example,
(i) a step of mixing a solvent containing alcohol and silica base particles to prepare a silica base particle suspension; (ii) a step of granulating silica base particles by a sol-gel method to obtain a silica base particle suspension; is mentioned.

Silica base particles used in (i) include sol-gel silica particles (silica particles obtained by a sol-gel method), aqueous colloidal silica particles, alcoholic silica particles, fused silica particles obtained by a gas phase method, and fused silica particles. etc.

The alcohol-containing solvent used in (i) above may be a solvent of alcohol alone, or a mixed solvent of alcohol and other solvents. Examples of alcohols 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; In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, more preferably 85% by mass or more.

The step (1-a) is preferably a step of granulating silica base particles by a sol-gel method to obtain a silica base particle suspension.

More specifically, step (1-a) includes, for example,
an alkali catalyst solution preparation step of preparing an alkali catalyst solution containing an alkali catalyst in a solvent containing alcohol;
A step of generating silica base particles by supplying a tetraalkoxysilane and an alkali catalyst in an alkali catalyst solution to generate silica base particles;
It is preferably a sol-gel method containing.

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

The alcohol-containing solvent may be a solvent of alcohol alone, or a mixed solvent of alcohol and other solvents. Examples of alcohols 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; In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, more preferably 85% by mass or more.

The alkali catalyst is a catalyst for promoting the reaction (hydrolysis reaction and condensation reaction) of tetraalkoxysilane, and examples thereof include basic catalysts such as ammonia, urea and monoamine, with ammonia being particularly preferred.

The concentration of the alkali catalyst in the alkali catalyst solution is preferably 0.5 mol/L or more and 1.5 mol/L or less, more preferably 0.6 mol/L or more and 1.2 mol/L or less, and 0.65 mol/L or more and 1.1 mol. /L or less is more preferable.

In the step of generating silica base particles, tetraalkoxysilane and an alkali catalyst are respectively supplied into an alkali catalyst solution, and the tetraalkoxysilane is reacted (hydrolysis reaction and condensation reaction) in the alkali catalyst solution to generate silica base particles. It is a process to do.

In the silica base particle generation step, after the core particles are generated by the reaction of the tetraalkoxysilane at the beginning of the supply of the tetraalkoxysilane (nuclear particle generation stage), through the growth of the core particles (nuclear particle growth stage), the silica base particles are formed. is generated.

Tetraalkoxysilanes include, for example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and the like. Tetramethoxysilane or tetraethoxysilane is preferred from the viewpoint of the controllability of the reaction rate or the uniformity of the shape of silica mother particles to be produced.

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

The supply 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 step of generating silica base particles, the temperature of the alkali catalyst solution (temperature during supply) is preferably 5°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower.
[First step]
The first step forms a structure composed of the reaction product of a trifunctional silane coupling agent.

Specifically, in the first step, for example, a trifunctional silane coupling agent is added to a suspension of silica mother particles, the surface of the silica mother particles is reacted with the trifunctional silane coupling agent, and a trifunctional silane coupling agent is added. A structure composed of the reaction product of the ring agent is formed. The trifunctional silane coupling agent is produced by reaction between the functional groups of the trifunctional silane coupling agent and between the functional groups of the trifunctional silane coupling agent and the OH groups on the surface of the silica particles. Form a structure composed of objects.

The reaction of the trifunctional silane coupling agent is carried out by adding the trifunctional silane coupling agent to the silica base particle suspension and then heating the suspension while stirring.

Specifically, for example, the suspension is heated to 40° C. to 70° C., a trifunctional silane coupling agent is added, and then stirred. The duration of stirring is preferably 10 minutes or more and 24 hours or less, more preferably 60 minutes or more and 420 minutes or less, and even more preferably 80 minutes or more and 300 minutes or less.
[Second step]
In the second step, a nitrogen element-containing compound is adsorbed on at least part of the pores of the reaction product of the trifunctional silane coupling agent.

Specifically, in the second step, first, for example, a nitrogen element-containing compound is added to a suspension of silica base particles, and the mixture is stirred in a temperature range of, for example, 20°C or higher and 50°C or lower. Thereby, the nitrogen element-containing compound is adsorbed to at least part of the pores of the reaction product of the trifunctional silane coupling agent.

In the second step, for example, an alcohol solution containing a nitrogen element-containing compound may be added to the silica particle suspension.

The alcohol may be of the same type as the alcohol contained in the silica base particle suspension, or may be of a different type, but is more preferably of the same type.

In the alcohol liquid containing the nitrogen element-containing compound, the concentration of the nitrogen element-containing compound is preferably 0.05% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 6% by mass or less.
[Third step]
In the third step, after or during the second step, silica mother particles having a structure in which a nitrogen element-containing compound is adsorbed in at least part of the pores of the reaction product of the trifunctional silane coupling agent. , perform hydrophobic treatment.

Specifically, in the third step, for example, a nitrogen element-containing compound is added to the suspension of silica base particles on which the structures are formed, and then a hydrophobizing agent is added.

In the hydrophobizing agent, the functional groups of the hydrophobizing agent react with each other, and the functional groups of the hydrophobizing agent react with the OH groups of the silica mother particles to form a hydrophobizing layer.

The reaction of the hydrophobizing agent is carried out by adding the trifunctional silane coupling agent to the silica base particle suspension and then heating the suspension while stirring.

Specifically, for example, the suspension is heated to 40° C. or higher and 70° C., added with a hydrophobizing treatment agent, and then stirred. The duration of stirring is preferably 10 minutes or more and 24 hours or less, more preferably 20 minutes or more and 120 minutes or less, and even more preferably 20 minutes or more and 90 minutes or less.
[Drying process]
In the method for producing silica particles according to the present embodiment, it is preferable to carry out a drying step for removing the solvent from the suspension after carrying out the second step or the third step. In addition, you may implement a drying process in a 2nd process or a 3rd process.

Drying includes, for example, thermal drying, spray drying, and supercritical drying.

Spray-drying can be carried out by a conventionally known method using a commercially available spray dryer (such as a disc rotating type and a nozzle type). For example, it is carried out by spraying the spray solution into a stream of hot air at a rate of 0.2 liter/hour or more and 1 liter/hour or less. At this time, the temperature of the hot air is preferably in the range of 70° C. or higher and 400° C. or lower as the inlet temperature, and in the range of 40° C. or higher and 120° C. or lower as the outlet temperature. Here, if the inlet temperature is less than 70° C., drying of the solid content contained in the dispersion becomes insufficient. On the other hand, if it exceeds 400°C, the shape of the particles will be distorted during spray drying. On the other hand, if the outlet temperature is less than 40° C., the solid content is poorly dried and adheres to the interior of the device. A more preferable inlet temperature is in the range of 100°C or higher and 300°C or lower.

The silica particle concentration of the silica particle suspension at the time of spray drying is preferably in the range of 10% by mass or more and 30% by mass or less in terms of solid content.

In supercritical drying, by removing the solvent with a supercritical fluid, the surface tension between particles is less likely to work, and the primary particles contained in the suspension are dried in a state in which aggregation is suppressed. Therefore, it becomes easy to obtain silica particles having a highly uniform particle diameter.

Substances used as supercritical fluids include carbon dioxide, water, methanol, ethanol, and acetone. The solvent removal step is preferably a step using supercritical carbon dioxide from the viewpoint of treatment efficiency and the viewpoint of suppressing the generation of coarse particles.

Specifically, supercritical drying is performed, for example, by the following operations.

After the suspension is placed in the closed reactor and then liquefied carbon dioxide is introduced, the closed reactor is heated and the pressure inside the closed reactor is increased by a high-pressure pump to bring the carbon dioxide in the closed reactor into a supercritical state. do. Then, liquefied carbon dioxide flows into the closed reactor and supercritical carbon dioxide flows out from the closed reactor, thereby allowing the supercritical carbon dioxide to flow through the suspension in the closed reactor. While the supercritical carbon dioxide is flowing through the suspension, the solvent dissolves in the supercritical carbon dioxide and is removed along with the supercritical carbon dioxide flowing out of the closed reactor.

The temperature and pressure in the above-mentioned closed reactor are the temperature and pressure at which carbon dioxide is brought to a supercritical state. Where the critical point of carbon dioxide is 31.1° C./7.38 MPa, the temperature and pressure are, for example, temperature of 40° C. or higher and 200° C. or lower/pressure of 10 MPa or higher and 30 MPa or lower.

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

The obtained silica particles are preferably pulverized or sieved as necessary to remove coarse particles and aggregates. The pulverization is performed using a dry pulverization device such as a jet mill, vibration mill, ball mill, pin mill, or the like. The sieving is performed by, for example, a vibrating sieve, a wind sieving machine, or the like.

The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following description, all "%" are based on mass unless otherwise specified.
≪Production of silica particles≫
[Examples 1, 3 to 36, 39 to 44]
A suspension containing silica particles in each example was prepared as described below.
-Preparation of alkaline catalyst solution-
Methanol, ion-exchanged water, and aqueous ammonia (NH ₄ OH) in the amounts and concentrations shown in Table 1 are placed in a glass reaction vessel equipped with a metal stirring rod, a dropping nozzle, and a thermometer, and stirred and mixed to form an alkali. A catalyst solution was obtained.
- Granulation of silica base particles by sol-gel method -
The temperature of the alkaline catalyst solution was adjusted to 40° C., and the alkaline catalyst solution was purged with nitrogen. Then, while stirring the alkaline catalyst solution, the amount of tetramethoxysilane (TMOS) shown in Table 1 and 124 parts by mass of ammonia water (NH ₄ OH) with a catalyst (NH ₃ ) concentration of 7.9% were added dropwise at the same time. to obtain a silica base particle suspension.
- Addition of trifunctional silane coupling agent -
The type and amount of trifunctional silane coupling agent shown in Table 1 were added to the silica base particle suspension while heating and stirring at 40°C. After that, stirring was continued for 120 minutes to react the trifunctional silane coupling agent. Thereby, an adsorption structure was formed.
- Addition of nitrogen element-containing compound -
An alcohol solution was prepared by diluting the nitrogen element-containing compounds of the types shown in Table 1 with butanol.

Next, an alcohol solution obtained by diluting a nitrogen element-containing compound with butanol was added to the suspension. At this time, the alcohol solution was added so that the number of parts of the nitrogen element-containing compound was the amount shown in Table 1 with respect to 100 parts by mass of the solid content of the silica base particle suspension. Then, the mixture was stirred at 30° C. for 100 minutes to obtain a suspension containing a nitrogen element-containing compound.
-Drying-
Subsequently, 300 parts by mass of the suspension was placed in a reaction vessel, CO ₂ was added while stirring, and the temperature and pressure in the reaction vessel were raised to the temperature and pressure shown in Table 1. CO ₂ was allowed to flow in and out at a flow rate of 5 L/min while stirring while maintaining the temperature and pressure. After that, the solvent was removed over 120 minutes to obtain silica particles of each example.
[Example 2]
Using a mini spray dryer B-290 (manufactured by Nippon Buchi Co., Ltd.), the inside of the cylinder is set to the temperature and pressure shown in Table 1, and the silica particle suspension is fed at a liquid feed rate of 0.2 L / hour. Silica particles were obtained in the same manner as in Example 1, except that spray drying was performed.
[Example 37]
After adding the nitrogen element-containing compound, hexamethyldisilazane (HMDS) was added in an amount of 100% by mass based on the solid content of the silica base particles, and the mixture was stirred at 65° C. for 3 hours, except that the surfaces of the silica base particles were hydrophobized. , in the same manner as in Example 1 to obtain silica particles.

[Example 38]
Silica particles were obtained in the same manner as in Example 1, except that 30 g of dry-process silica AEROSIL 130 (manufactured by Nippon Aerosil) was dispersed in 300 g of methanol to obtain a silica base particle suspension.
[Comparative Examples 1, 2, 3]
Silica particles were obtained in the same manner as in Example 1, except that the types and addition amounts of the trifunctional silane coupling agent and the nitrogen element-containing compound were as shown in Table 1.
[evaluation]
(Various characteristics)
The following properties of the obtained silica particles were measured according to the methods described above.

・Number average particle size (indicated as “particle size” in the table)
・Average circularity (indicated as “circularity” in the table)
- Pore volume A with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before 350°C firing (referred to as "pore volume A before 350°C firing" in the table).

・Pore volume B with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method after 350 ° C. firing (referred to as “pore volume B after 350 ° C. firing” in the table)
・Volume resistivity Ra before firing at 350°C (indicated as “volume resistivity before firing Ra” in the table)
・Volume resistivity Rb after firing at 350°C (referred to as “volume resistivity after firing Rb” in the table)
・ OH group amount measured by Sears method (indicated as "OH group amount" in the table)
・ Percentage of the integrated value C of the signal observed in the chemical shift range of -50 ppm to -75 ppm when the integrated value of all signals in the Si-CP / MAS NMR spectrum is 100% (in the table, "(Si -CP/MAS area ratio C”)
・Integral value C of the signal observed in the range of chemical shift -50 ppm or more -75 ppm or less in the Si-CP / MAS NMR spectrum, and integral value D of the signal observed in the range of chemical shift -90 ppm or more -120 ppm or less Ratio C/D (denoted as "(Si-CP/MAS ratio C/D" in the table)
(Low Humidity Charge Amount and High Humidity Charge Amount/Charging Dependence of Capacitance)
The low-humidity charge amount and the high-humidity charge amount of the silica particles of each example were measured as follows, and the environmental dependence of the capacitance was evaluated. Of the criteria, A to B are acceptable.

The evaluation method is as follows.

5 g of MA1010 manufactured by Nippon Shokubai Co., Ltd. in which 2% by mass of the silica particles thus produced was added to the surface, and 50 g of KNI106GSM manufactured by JFE Chemical Co., Ltd. were mixed. The mixed sample on the left was stirred for 5 minutes in a 10°C 10% RH chamber using a Turbula shaker, and the charge was measured using a Toshiba TB200. was used to stir for 5 minutes, and the charge was measured with TB200 manufactured by Toshiba.

A (◎): FA/FC is 0.8 or more and less than 1.1 B (○): FA/FC is 0.65 or more and less than 0.8 C (△): FA/FC is 0.5 or more and 0.65 Less than D (x): FA/FC is less than 0.5 (charging distribution under low temperature and low humidity environment)
As follows, the charge distribution of the silica particles of each example was evaluated under a low-temperature and low-humidity environment (under an environment of 10° C. and 10% RH).

5 g of MA1010 manufactured by Nippon Shokubai Co., Ltd. in which 2% by mass of the silica particles thus produced was added to the surface, and 50 g of KNI106GSM manufactured by JFE Chemical Co., Ltd. were mixed. The mixed sample on the left was stirred for 5 minutes in a 10° C. 10% RH% chamber using a Turbula shaker and evaluated by CSG (charge spectrograph method) image analysis. The charge distribution is a value obtained by dividing the difference between the 20% charge amount Q (20) and the 80% charge amount Q (80) of the cumulative integration of the charge distribution by the 50% charge amount Q (50), that is, [Q (80) −Q(20)]/Q(50). Evaluation criteria are as follows.

A (◎): [Q (80) - Q (20)] / Q (50) value is less than 0.7 B (○): [Q (80) - Q (20)] / Q (50) value is Less than 0.8 0.7 or more C (△): [Q (80) - Q (20)] / Q (50) value is less than 1.0 0.8 or more D (×): [Q (80) - Q(20)]/Q(50) value is 1.0 or more
(Maintainability of narrow charge distribution under normal temperature and humidity environment)
As follows, the silica particles of each example were evaluated for maintenance of a narrow charge distribution under a normal temperature and normal humidity environment (under an environment of 20° C. and 50% RH).

5 g of MA1010 manufactured by Nippon Shokubai Co., Ltd. in which 2% by mass of the silica particles thus produced was added to the surface, and 50 g of KNI106GSM manufactured by JFE Chemical Co., Ltd. were mixed. The mixed sample on the left was stirred for 100 minutes using a Turbula shaker in a chamber at 20° C. and 50% RH, and evaluated by CSG (charge spectrograph method) image analysis. The charge distribution is a value obtained by dividing the difference between the 20% charge amount Q (20) and the 80% charge amount Q (80) of the cumulative integration of the charge distribution by the 50% charge amount Q (50), that is, [Q (80) −Q(20)]/Q(50). Evaluation criteria are as follows.

A (◎): [Q (80) - Q (20)] / Q (50) value is less than 0.75 B (○): [Q (80) - Q (20)] / Q (50) value is Less than 0.85 0.75 or more C (△): [Q (80) - Q (20)] / Q (50) value is less than 1.0 0.85 or more D (x): [Q (80) - Q(20)]/Q(50) value of 1.0 or more Table 1 shows the evaluation results.

The details of the abbreviations in Table 1 are as follows.
・MTMS: methyltrimethoxysilane ・DTMS: n-dodecyltrimethoxysilane ・TP-415: [N ⁺ (CH) ₃ (C ₁₄ C ₂₉ ) ₂ ] ₄ Mo ₈ O ₂₈ ^4- (manufactured by Hodogaya Chemical Industry Co., Ltd. , N,N-Dimethyl-N-tetradecyl-1-tetradecanaminium, hexa-μ-oxotetra-μ3-oxodi-μ5-oxotetradecaoxooctamolybdate (4-) (4:1) (extraction amount with ammonia / methanol mixed solution X = 61 ~ 89% by mass, the ratio X/Y between the extraction amount X and the extraction amount Y with water = 0.03 to 0.26)
- Dimethylstearylammonium chloride (extraction amount X with ammonia/methanol mixed solution = 75% by mass, ratio X/Y of extraction amount X to water extraction amount Y = 0.28)
・Tributylamine (extraction amount X with ammonia/methanol mixed solution = 65% by mass, ratio X/Y of extraction amount X to water extraction amount Y = 0.29)
・Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (extraction amount X with ammonia/methanol mixed solution = 76% by mass, ratio X/Y between extraction amount X and water extraction amount Y = 0.25)
・ Quaternium-80 (extraction amount X = 80% by mass with ammonia / methanol mixed solution, ratio X / Y of extraction amount X and water extraction amount Y = 0.09)
- Ditetrakis(dibutyldibenzylammonium) molybdic acid (extraction amount X with ammonia/methanol mixed solution = 65% by mass, ratio X/Y of extraction amount X to water extraction amount Y = 0.15)
- Phenethylamine (extraction amount X with ammonia/methanol mixed solution = 55% by mass, ratio X/Y of extraction amount X to water extraction amount Y = 0.28)
4-(2-octylamino)diphenylamine (extraction amount X with ammonia/methanol mixed solution = 78% by mass, ratio X/Y of extraction amount X to water extraction amount Y = 0.14)
- N-benzyl-N-methylethanolamine (extraction amount X with ammonia/methanol mixed solution = 58% by mass, ratio of extraction amount X to water extraction amount Y = 0.27)
2,3-bis(2,6-diisopropylphenylimino)butane (extraction amount X with ammonia/methanol mixed solution = 81% by mass, ratio X/Y of extraction amount X to water extraction amount Y = 0.11 )
- 3-indole acetonitrile (extraction amount X with ammonia / methanol mixed solution = 80% by mass, ratio of extraction amount X to water extraction amount Y = 0.12)
・n-Hexadecyltrimethylammonium bromide (extraction amount X with ammonia/methanol mixed solution = 18% by mass, ratio X/Y of extraction amount X to water extraction amount Y = 5.28)

From the above results, it can be seen that the silica particles of Examples have a narrower charge distribution when charged than the silica particles of Comparative Examples.

Claims (13)

containing a nitrogen element-containing compound,
B/A is 1.2 or more and 5 or less, where A and B are the pore volumes with a pore diameter of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after baking at 350° C., and Silica particles having a B of 0.2 cm ³ /g or more and 3 cm ³ /g or less. 2. The silica particles according to claim 1, wherein the B/A is 1.4 or more and 3 or less. The silica particles according to claim 1 or 2, wherein said B is 0.3 cm ³ /g or more and 1.8 cm ³ /g or less. The silica particles according to any one of claims 1 to 3, having a number average particle diameter of 10 nm or more and 200 nm or less. 5. The silica particles according to claim 4, having a number average particle diameter of 10 nm or more and 80 nm or less. The nitrogen element-containing compound is at least one selected from the group consisting of quaternary ammonium salts, primary amine compounds, secondary amine compounds, tertiary amine compounds, amide compounds, imine compounds, and nitrile compounds. The silica particles according to any one of claims 1 to 5. The silica particles according to any one of claims 1 to 6, having an average circularity of 0.60 or more and 0.96 or less. The silica particles according to any one of claims 1 to 7, having an average circularity of 0.70 or more and 0.92 or less. The silica particles according to any one of claims 1 to 8, which have a volume resistivity of 1.0 × 10 ⁷ Ωcm or more and 1.0 × 10 ^11.5 Ωcm or less. The silica particles according to any one of claims 1 to 9, wherein Ra/Rb is 0.01 or more and 0.8 or less, where Ra and Rb are volume resistivities before and after firing at 350°C. The integrated value C of the signal observed in the range of chemical shift -50 ppm or more -75 ppm or less in the ²⁹ Si solid-state nuclear magnetic resonance (NMR) spectrum by the cross polarization / magic angle spinning (CP / MAS) method, and the chemical shift -90 ppm or more The silica particles according to any one of claims 1 to 10, wherein the ratio C/D of the integrated value D of signals observed in the range of -120 ppm or less is 0.10 or more and 0.75 or less. silica base particles;
Nitrogen element covering at least a part of the surface of the silica base particles, composed of a reaction product of a trifunctional silane coupling agent, and at least part of the pores of the reaction product of the trifunctional silane coupling agent a structure to which a contained compound is adsorbed;
The silica particles according to any one of claims 1 to 11. a first step of forming a structure composed of a reaction product of a trifunctional silane coupling agent on at least a part of the surface of the silica base particles;
a second step of adsorbing a nitrogen element-containing compound into at least part of the pores of the reaction product of the trifunctional silane coupling agent;
A method for producing silica particles according to any one of claims 1 to 12.