Silica particles

Abstract

To provide a silica particle having a narrow charge distribution, and excellent in maintaining property of a narrow charge distribution when taking an electrical charge.SOLUTION: A silica particle includes a nitrogen element-containing compound including a molybdenum element, where the ratio (Mo / Si) of a Net strength of a molybdenum element to a Net strength of a silicon element measured by fluorescent X-ray analysis is 0.035 or larger and 0.35 or smaller.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to silica particles. [Background technology]

[0002] Silica particles are used as an additive or main component in powder coatings, cosmetics, rubber, abrasives, etc., and play roles such as improving the strength of resins, improving the fluidity of powders, and suppressing packing.

[0003] For example, Patent Document 1 discloses "a hydrophobic silica powder, (1) having a hydrophobicity of 50% or more, (2) an extractable amount X of at least one compound selected from the group consisting of quaternary ammonium ions, monoazo complexes, and mineral acid ions in a mixed solvent of methanol and an aqueous methanesulfonic acid solution is 0.1 mass% or more, and (3) the X and the extractable amount Y of the compound in water satisfy the following formula (I): Y / X<0.15."

[0004] Furthermore, Patent Document 2 discloses "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."

[0005] Furthermore, Patent Document 3 discloses "external charge control particles comprising carrier particles made of hydrophobic spherical silica microparticles with an average particle size of 20 to 500 nm obtained by subjecting the surface of hydrophilic spherical silica microparticles obtained by a sol-gel method to a hydrophobic treatment, and a charge control agent adhered to the surface of the carrier particles."

[0006] Furthermore, Patent Document 4 discloses "silica microparticles obtained by treating spherical hydrophobic silica microparticles having an average primary particle size 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."

[0007] Furthermore, Patent Document 5 discloses "particles in which silica microparticles having a hydrophobicity of 80% or more are treated with an amphoteric surfactant, and particles in which silica microparticles having a hydrophobicity of 80% or more are treated with a quaternary ammonium salt or a polymer having a quaternary ammonium group." [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-073418 [Patent Document 2] Japanese Patent Application Publication No. 2017-039618 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-185998 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-194825 [Patent Document 5] Japanese Patent Application Publication No. 09-166884 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to provide silica particles containing a nitrogen-containing compound containing molybdenum, which have a narrow charge distribution when charged, compared to silica particles in which the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), as measured by X-ray fluorescence analysis, is less than 0.035 or exceeds 0.35, and which are excellent in maintaining the narrow charge distribution in high-temperature, high-humidity environments and low-temperature, low-humidity environments. [Means for solving the problem]

[0010] Specific means for solving the above problems include the following aspects. <1> A nitrogen-containing compound containing molybdenum, and the ratio of the net intensity of molybdenum element to the net intensity of silicon element (Mo / Si), as measured by X-ray fluorescence analysis, is 0.035 or more and 0.35 or less. <2> The nitrogen-containing compound is at least one selected from the group consisting of a quaternary ammonium salt containing molybdenum and a mixture of a quaternary ammonium salt and a metal oxide containing molybdenum. <1> The silica particles according to claim 1. <3> The number average particle size is 10 nm or more and 200 nm or less. <1> or <2> The silica particles according to claim 1. <4> The composition comprises silica base particles and at least one reaction product selected from the group consisting of a monofunctional silane coupling agent, a bifunctional silane coupling agent, and a trifunctional silane coupling agent, the reaction product coating at least a portion of the surface of the silica base particles, and a structure in which a nitrogen-containing compound is adsorbed in at least a part of the pores of the reaction product. <1> ~ <3> The silica particles according to any one of the preceding claims. <5> The degree of hydrophobicity is 10% or more and 60% or less. <1> ~ <4> The silica particles according to any one of the preceding claims. <6> When the pore volumes of pores with diameters of 1 nm to 50 nm obtained from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350°C are A and B, respectively, B / A is 1.2 to 5, and B is 0.2 cm 3 / g or more 3cm 3 / g or less <1> ~ <5> The silica particles according to any one of the preceding claims. <7> Cross polarization / magic angle spinning (CP / MAS) 29 The ratio C / D of the integral value C of the signal observed in the chemical shift range of -50 ppm to -75 ppm in the Si solid-state nuclear magnetic resonance (NMR) spectrum to the integral value D of the signal observed in the chemical shift range of -90 ppm to -120 ppm is 0.10 or more and 0.75 or less. <1> ~ <6> The silica particles according to any one of the preceding claims. <8> the amount X of the nitrogen-containing compound extracted by the ammonia / methanol mixed solution is 0.1 mass% or more; The amount X of the nitrogen-containing compound extracted and the amount Y of the nitrogen-containing compound extracted by water satisfy the formula: Y / X<0.3. <1> ~ <7> The silica particles according to any one of the preceding claims. <9> The average circularity is 0.60 or more and 0.96 or less. <1> ~ <8> The silica particles according to any one of the preceding claims. <10> 10. The silica particles according to claim 1, wherein the number particle size distribution index is 1.1 or more and 2.0 or less. [Effects of the Invention]

[0011] <1> , or <2> According to the present invention, silica particles containing a nitrogen-containing compound containing molybdenum element have a narrow charge distribution when charged, compared to silica particles containing a molybdenum element-containing nitrogen-containing compound having a ratio (Mo / Si) of the net intensity of molybdenum element to the net intensity of silicon element, as measured by X-ray fluorescence analysis, of less than 0.035 or more than 0.35, and the silica particles are excellent in maintaining the narrow charge distribution under high-temperature, high-humidity environments and low-temperature, low-humidity environments.

[0012] <3> According to the invention, in silica particles containing a nitrogen-containing compound containing molybdenum, the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), as measured by fluorescent X-ray analysis, is less than 0.035 or more than 0.35, and even when the number-average particle diameter is 10 nm or more and 200 nm or less, the silica particles have a narrow charge distribution when charged and are excellent in maintaining the narrow charge distribution in high-temperature, high-humidity environments and low-temperature, low-humidity environments.

[0013] <4> According to the invention, silica particles containing a nitrogen-containing compound including molybdenum have a ratio (Mo / Si) of the net intensity of molybdenum to the net intensity of silicon, as measured by fluorescent X-ray analysis, of less than 0.035 or more than 0.35, compared to silica particles containing a nitrogen-containing compound including molybdenum. The invention provides silica particles having a structure comprising silica base particles and a structure that coats at least a portion of the surface of the silica base particles and is composed of at least one reaction product selected from the group consisting of monofunctional silane coupling agents, difunctional silane coupling agents, and trifunctional silane coupling agents, and in which a nitrogen-containing compound is adsorbed in at least a portion of the pores of the reaction product, and that have a narrow charge distribution when charged and are excellent in maintaining the narrow charge distribution in high-temperature, high-humidity environments and low-temperature, low-humidity environments.

[0014] <5> According to the present invention, silica particles are provided which have a narrow charge distribution when charged, and which are excellent in maintaining the narrow charge distribution under high-temperature, high-humidity environments and low-temperature, low-humidity environments, compared to silica particles having a hydrophobicity of less than 10% or more than 60%.

[0015] <6> According to the invention, in silica particles in which nitrogen-containing compounds are detected when heated in a temperature range of 300°C or higher and 600°C or lower, when the pore volumes of pores having diameters of 1 nm or higher and 50 nm or lower obtained from a pore distribution curve obtained by a nitrogen gas adsorption method before and after firing at 350°C are A and B, respectively, B / A is less than 1.2 or B is 0.2 cm 3 / g, the silica particles have a narrow charge distribution when charged and are excellent in maintaining the narrow charge distribution under high-temperature, high-humidity environments and low-temperature, low-humidity environments.

[0016] <7> According to the present invention, when a nitrogen-containing compound is detected in silica particles that are heated in a temperature range of 300°C or more and 600°C or less, the nitrogen-containing compound is detected by a cross polarization / magic angle spinning (CP / MAS) method. 29The silica particles provided have a narrow charge distribution when charged, and are excellent in maintaining the narrow charge distribution in high-temperature, high-humidity environments and low-temperature, low-humidity environments, compared to silica particles having a ratio C / D of the integral value C of the signal observed in the chemical shift range of -50 ppm to -75 ppm in a Si solid-state nuclear magnetic resonance (NMR) spectrum to the integral value D of the signal observed in the chemical shift range of -90 ppm to -120 ppm in a Si solid-state nuclear magnetic resonance (NMR) spectrum that is less than 0.10 or more than 0.75.

[0017] <8> According to the invention, silica particles are provided which have a narrower charge distribution when charged and are excellent in maintaining the narrow charge distribution under high-temperature, high-humidity environments and low-temperature, low-humidity environments, compared to when the amount X of the nitrogen-containing compound extracted with an ammonia / methanol mixed solution is less than 0.1 mass %, or when the amount X of the nitrogen-containing compound extracted with water and the amount Y of the nitrogen-containing compound extracted with water do not satisfy the formula: Y / X<0.3.

[0018] <9> According to the invention, in silica particles containing a nitrogen-containing compound containing molybdenum, the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), as measured by fluorescent X-ray analysis, is less than 0.035 or exceeds 0.35, and even if the average circularity is 0.60 or more and 0.96 or less, the silica particles have a narrow charge distribution when charged and are excellent in maintaining the narrow charge distribution in high-temperature, high-humidity environments and low-temperature, low-humidity environments.

[0019] <10> According to the invention, in silica particles containing a nitrogen-containing compound containing molybdenum, the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), as measured by fluorescent X-ray analysis, is less than 0.035 or exceeds 0.35, and even if the number particle size distribution index is 1.1 or more and 2.0 or less, the silica particles have a narrow charge distribution when charged and are excellent in maintaining the narrow charge distribution in a high-temperature, high-humidity environment and a low-temperature, low-humidity environment. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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.

[0021] In the present specification, the upper or lower limit of one numerical range may be replaced by the upper or lower limit of another numerical range. In addition, in the numerical ranges described in this disclosure, the upper or lower limit of the numerical range may be replaced by the values ​​shown in the examples.

[0022] In this specification, each component may contain multiple types of corresponding substances. In this specification, when referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

[0023] <Silica particles> The silica particles according to this embodiment contain a nitrogen-containing compound containing molybdenum (hereinafter also referred to simply as "nitrogen-containing compound"), and the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), measured by X-ray fluorescence analysis, is 0.035 or more and 0.35 or less.

[0024] The silica particles according to the present embodiment, due to the above-described configuration, have a narrow charge distribution when charged and are excellent in maintaining the narrow charge distribution under high-temperature, high-humidity environments and low-temperature, low-humidity environments. The reason for this is presumed to be as follows.

[0025] Silica particles have a high negative chargeability and can be excessively charged, resulting in a wide charge distribution. In particular, in a high-temperature, high-humidity environment and a low-temperature, low-humidity environment, excessive charging is likely to occur, increasing the tendency for the charge distribution to become wide. For example, in powder coating, powder paint is charged by a method such as contact charging or corona discharge, sprayed onto the object to be coated, and electrostatically adheres to it, and then heated to form a coating film. However, when silica particles, which have a wide charge distribution, are used as an external additive to powder paint, the charge of the powder paint varies, making it difficult to achieve a uniform amount of powder paint adhered to the object to be coated.

[0026] On the other hand, when a nitrogen-containing compound is adsorbed onto silica particles, excessive negative charging can be suppressed when the silica particles are charged. The nitrogen-containing compound has positive charging properties, and the silica particles having the nitrogen-containing compound adsorbed thereon cancel out the excessive negative charging and suppress the excessive negative charging.

[0027] However, simply adsorbing a nitrogen-containing compound onto silica particles results in a charge distribution that is broadened to include negative and positive charges. As described above, excessive charging is likely to occur, particularly in a high-temperature, high-humidity environment (e.g., 30°C, 90% RH) and a low-temperature, low-humidity environment (e.g., 10°C, 10% RH), and the charge distribution tends to become broader, and the maintainability of the charge distribution also decreases.

[0028] Therefore, a nitrogen-containing compound containing molybdenum is used as the nitrogen-containing compound, and the ratio (Mo / Si) of the net intensity of molybdenum to the net intensity of silicon of the silica particles measured by fluorescent X-ray analysis is set to 0.035 or more and 0.35 or less. When a nitrogen-containing compound containing molybdenum is used as the nitrogen-containing compound, the activity of the nitrogen element is enhanced. Even if the nitrogen-containing compound is present inside the pores of the silica particles rather than on the outermost surface, the positive charging property of the nitrogen element makes it easier to suppress excessive charging, particularly under high-temperature, high-humidity environments and low-temperature, low-humidity environments. Furthermore, the interaction with the cationic moiety containing the nitrogen element is enhanced, making it less likely for the cationic moiety to detach, thereby improving retention. Furthermore, the chargeability of the silica particles can be adjusted from positive to negative chargeability as required by changing the ratio of molybdenum present. Furthermore, by incorporating a nitrogen-containing compound containing molybdenum, which has such properties, into silica particles with a ratio (Mo / Si) of the net strength of molybdenum to the net strength of silicon within the above range, the charge distribution becomes narrow and its maintenance is improved even in high-temperature, high-humidity environments and low-temperature, low-humidity environments.

[0029] From the above, it is presumed that the silica particles according to this embodiment have a narrow charge distribution when charged and are excellent in maintaining the narrow charge distribution in a high-temperature, high-humidity environment and a low-temperature, low-humidity environment.

[0030] For example, when the silica particles according to this embodiment are used as an external additive to powder paint, the powder paint is less likely to have variations in charge, even in low-temperature, low-humidity environments, and this charge is highly maintainable, resulting in a uniform amount of powder paint adhering to the object to be coated.

[0031] The silica particles according to this embodiment preferably satisfy either the following aspect (A) or the following aspect (B).

[0032] Aspect (A): When the pore volumes of pores with diameters of 1 nm to 50 nm obtained from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350°C are A and B, respectively, B / A is 1.2 to 5, and B is 0.2 cm 3 / g or more 3cm 3 / g or less. Hereinafter, "pore volume A of pores with diameters of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before firing at 350°C" will also be referred to as "pore volume A before firing at 350°C". On the other hand, "pore volume B of pores with diameters 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 "pore volume B after firing at 350°C."

[0033] Aspect (B): Cross polarization / magic angle spinning (CP / MAS) 29In a Si solid-state nuclear magnetic resonance (NMR) spectrum (hereinafter also referred to as "Si-CP / MAS NMR spectrum"), the ratio C / D of the integral value C of signals observed in the chemical shift range of -50 ppm to -75 ppm to the integral value D of signals observed in the chemical shift range of -90 ppm to -120 ppm is 0.10 or more and 0.75 or less.

[0034] The silica particles according to the embodiment (A) or (B) have a narrow charge distribution when charged due to the above-mentioned constitution. The reason for this is presumed to be as follows.

[0035] As described above, when a nitrogen-containing compound is adsorbed onto silica particles, excessive negative charging can be suppressed when the silica particles are charged. The nitrogen-containing compound has positive charging properties, and the silica particles having the nitrogen-containing compound adsorbed thereon cancel out the excessive negative charging and suppress the excessive negative charging.

[0036] However, since the nitrogen-containing compound has a positive charge property, if it is adsorbed on the outermost surface of the silica particles, the charge distribution will be spread to negative and positive charges. Therefore, it is preferable that the nitrogen-containing compound is present in the pores of the silica particles rather than coating the surface of the silica particles.

[0037] Therefore, in the silica particles according to the embodiment (A), the pore volume A before firing at 350° C. and the pore volume B after firing at 350° C. are set to have the above-mentioned relationship. The pore volume B after firing at 350°C is the pore volume after firing and evaporation of the nitrogen-containing compound that was adsorbed in the pores of the silica particles and partially blocked the pores. Therefore, B / A is 1.2 or more and 5 or less, and B is 0.2 cm 3 / g or more 3cm 3 / g or less indicates that a sufficient amount of the nitrogen-containing compound is adsorbed in at least some of the pores of the silica particles, thereby improving the narrowing of the charge distribution by the nitrogen-containing compound.

[0038] On the other hand, in the silica particles according to aspect (B), the ratio C / D of the integral value C of the signal observed in the chemical shift range of -50 ppm or more and -75 ppm or less in the Si-CP / MAS NMR spectrum to the integral value D of the signal observed in the chemical shift range of -90 ppm or more and -120 ppm or less is set to the above range. The signal integral value satisfying the above range indicates that a sufficient amount of nitrogen-containing compound is adsorbed on the surface of at least a part of the silica particles, and the silica particles have a low density and a structure (e.g., SiO 2 / 3 This shows that a CH3 layer is formed. Structures made from the reaction products of silane coupling agents (especially trifunctional silane coupling agents) have low density and pore shapes that allow nitrogen-containing compounds to easily adsorb. Therefore, the charge distribution can be narrowed more effectively by the nitrogen-containing compound.

[0039] From the above, it is presumed that the silica particles according to the embodiment (A) or (B) have a narrow charge distribution when charged.

[0040] Hereinafter, the silica particles according to this embodiment will be described in detail.

[0041] (Ratio to net strength (Mo / Si)) In the silica particles according to this embodiment, the ratio of the net intensity of molybdenum element to the net intensity of silicon element (Mo / Si), measured by X-ray fluorescence analysis, is 0.035 or more and 0.35 or less, but from the viewpoint of narrowing the charge distribution and maintaining the charge distribution, it is preferably 0.07 or more and 0.32 or less, and more preferably 0.10 or more and 0.30 or less.

[0042] From the viewpoint of narrowing the charge distribution and maintaining the charge distribution, the net strength of the molybdenum element is preferably 5 kcps or more and 75 kcps or less, 7 kcps or more and 50 kcps or less, 8 kcps or more and 55 kcps or less, or 10 kcps or more and 40 kcps or less.

[0043] The net intensity of molybdenum element and silicon element is measured as follows.

[0044] Approximately 0.5 g of silica particles is compressed under a load of 6 t for 60 seconds using a compression molding machine to produce a disk with a diameter of 50 mm and a thickness of 2 mm. This disk is used as a sample and qualitative and quantitative elemental analysis is performed using a scanning X-ray fluorescence analyzer (XRF-1500, manufactured by Shimadzu Corporation) under the following conditions to determine the net intensities (unit: kilocounts per second, kcps) of the molybdenum and silicon elements. Tube voltage: 40kV ·Tube current: 90mA ·Measurement area (analysis diameter): Diameter 10mmφ Measurement time: 30 minutes Anticathode: Rhodium

[0045] (pore volume) In the silica particles according to this embodiment, the ratio B / A of the pore volume B after firing at 350°C to the pore volume A before firing at 350°C is 1.2 or more and 5 or less, but from the viewpoint of narrowing the charge distribution, it is preferably 1.4 or more and 3 or less, and more preferably 1.4 or more and 2.5 or less.

[0046] The pore volume B after firing at 350°C is 0.2 cm 3 / g or more 3cm 3 / g or less, but from the viewpoint of narrowing the charge distribution, 3 / g or more 1.8cm 3 / g or less is preferable, and 0.6cm 3 / g or more 1.5cm 3 / g or less is more preferable.

[0047] Specifically, the 350°C firing is carried out as follows. In a nitrogen environment, the silica particles to be measured are heated to 350°C at a rate of 10°C / min and held at 350°C for 3 hours. After that, they are cooled to room temperature (25°C) at a rate of 10°C / min.

[0048] 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 amount of adsorption is determined by constant volume or gravimetric methods. The pressure of the introduced nitrogen gas is gradually increased, and an adsorption isotherm is created by plotting the amount of nitrogen gas adsorbed for each equilibrium pressure. From this adsorption isotherm, a pore size distribution curve, with the vertical axis representing frequency and the horizontal axis representing pore diameter, is calculated using the BJH method formula. Then, from the obtained pore size distribution curve, the cumulative pore volume distribution, where the vertical axis is volume and the horizontal axis is pore diameter, is calculated. From the obtained cumulative pore volume distribution, the pore volume in the pore diameter range of 1 nm to 50 nm is integrated, and this is defined as the "pore volume of pore diameters of 1 nm to 50 nm."

[0049] (CP / MAS NMR spectrum) The ratio C / D of the integral value C of the signal observed in the chemical shift range of -50 ppm to -75 ppm in the Si-CP / MAS NMR spectrum to the integral value D of the signal observed in the chemical shift range of -90 ppm to -120 ppm is 0.10 to 0.75, but from the viewpoint of narrowing the charge distribution, it is preferably 0.12 to 0.45, and more preferably 0.15 to 0.40. From the viewpoint of narrowing the charge distribution, when the integral value of all signals in the Si-CP / MAS NMR spectrum is taken as 100%, the ratio (signal ratio) of the integral value C of signals observed in the chemical shift range of -50 ppm to -75 ppm is preferably 5 (unit: %) or more, more preferably 7 (unit: %) or more. The upper limit of the ratio of the integral value C of the signals is, for example, 60% or less.

[0050] The Si-CP / MAS NMR spectrum can be obtained by carrying out measurements by nuclear magnetic resonance spectroscopy under the following conditions. Spectrometer: AVENCE300 (Brunker) ·Resonance frequency: 59.6MHz Measurement nuclei: 29 Si Measurement method: CPMAS method (using Bruker's standard Palk Sequence cp.av) Wait time: 4 seconds Contact time: 8 milliseconds Accumulation count: 2048 times Measurement temperature: Room temperature (actual measurement value 25°C) Observation center frequency: -3975.72Hz MAS rotation speed: 7.0mm-6kHz Reference substance: hexymethylcyclotrisiloxane

[0051] (Composition of Silica Particles) The silica particles according to this embodiment contain a nitrogen-containing compound. Specifically, the silica particles according to this embodiment have a structure in which at least a portion of the surface of a silica base particle is coated with at least one reaction product selected from the group consisting of a monofunctional silane coupling agent, a difunctional silane coupling agent, and a trifunctional silane coupling agent (hereinafter also referred to as a "silane coupling agent reaction product"), and a nitrogen-containing compound is adsorbed to at least a portion of the reaction product. By forming this structure, the pore volume characteristics and the Si-CP / MAS NMR spectrum characteristics can be controlled. Furthermore, the degree of hydrophobicity and the amount of OH groups, which will be described later, can also be controlled. Furthermore, in the silica particles according to this embodiment, the surface of the structure may have a hydrophobic treated structure.

[0052] -Silica mother particles- The silica base particles are silica particles on at least a portion of the surface of which a structure is formed in which a nitrogen-containing compound is adsorbed in at least a portion of the pores of the reaction product of the silane coupling agent. Examples of the silica base particles include dry silica particles and wet silica particles. Examples of dry silica particles include combustion silica (fumed silica) obtained by burning a silane compound, and deflagration silica obtained by explosively burning metallic silicon powder. Examples of wet silica particles include wet silica particles obtained by the neutralization reaction of sodium silicate and mineral acid (precipitation silica synthesized and agglomerated under alkaline conditions, and gel-process silica particles synthesized and agglomerated under acidic conditions), colloidal silica particles (silica sol particles) obtained by polymerizing acidic silicic acid in an alkaline state, and sol-gel silica particles obtained by hydrolysis of organic silane compounds (e.g., alkoxysilanes). Among these, sol-gel silica particles are preferred as the silica base particles from the viewpoint of narrowing the charge distribution.

[0053] -Reaction products of silane coupling agents- The adsorption structure composed of the reaction product of a silane coupling agent (especially a trifunctional silane coupling agent) has a low density and a high affinity for nitrogen-containing compounds, which allows the nitrogen-containing compounds to be easily adsorbed deep into the pores, resulting in a high adsorption amount (i.e., content) of the nitrogen-containing compounds. The adhesion of the positively charged nitrogen-containing compounds to the negatively charged silica surface effectively counteracts excess negative charge. Furthermore, because the nitrogen-containing compounds are adsorbed within the low-density structure rather than on the outermost surface of the silica particles, they prevent the charge distribution from becoming too strong and widening, and only counteract excess negative charge, further narrowing the charge distribution.

[0054] The reaction product of the silane coupling agent is, for example, a compound represented by the following general formula (TA): OR 2 The reaction product, OR, is substituted with an OH group. 2 The reaction product of polycondensation between the OH-substituted OR 2 The reaction products of silane coupling agents include those in which the OH group is substituted with the OH group and those in which the OH group is polycondensed with the SiOH group of silica particles. 2 This includes fully or partially substituted reaction products and fully or partially polycondensed reaction products.

[0055] The silane coupling agent is a non-nitrogen element-containing compound that does not contain N (nitrogen element). Specifically, the silane coupling agent may be a silane coupling agent represented by the following general formula (TA). General formula (TA):R 1 n -Si(OR 2 ) 4-n

[0056] In the 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 an alkoxy group. 2 may be the same group or different groups, and n represents an integer of 1 or more and 3 or less.

[0057] R 1 The aliphatic hydrocarbon group represented by the formula (I) may be linear, branched, or cyclic, but is preferably linear or branched. The number of carbon atoms in the aliphatic hydrocarbon group is preferably 1 to 20, more preferably 1 to 18, even more preferably 1 to 12, and still more preferably 1 to 10. The aliphatic hydrocarbon group may be saturated or unsaturated, but is preferably a saturated aliphatic hydrocarbon group, and more preferably an alkyl group.

[0058] Examples of saturated aliphatic hydrocarbon groups include linear alkyl groups (methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, hexadecyl, and icosyl groups), branched alkyl groups (isopropyl, isobutyl, isopentyl, neopentyl, 2-ethylhexyl, tertiary butyl, tertiary pentyl, and isopentadecyl groups), and cyclic alkyl groups (cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, tricyclodecyl, norbornyl, and adamantyl groups).

[0059] Examples of unsaturated aliphatic hydrocarbon groups include alkenyl groups (vinyl groups (ethenyl groups), 1-propenyl groups, 2-propenyl groups, 2-butenyl groups, 1-butenyl groups, 1-hexenyl groups, 2-dodecenyl groups, pentenyl groups, etc.), and alkynyl groups (ethynyl groups, 1-propynyl groups, 2-propynyl groups, 1-butynyl groups, 3-hexynyl groups, 2-dodecenyl groups, etc.).

[0060] R 1 The aromatic hydrocarbon group represented by the formula (I) preferably has 6 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, even more preferably 6 to 12 carbon atoms, and still more preferably 6 to 10 carbon atoms.

[0061] Examples of the aromatic hydrocarbon group include a phenylene group, a biphenylene group, a terphenylene group, a naphthalene group, and an anthracene group.

[0062] R 2 Examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. The halogen atom is preferably a chlorine atom, a bromine atom, or an iodine atom.

[0063] R 2 Examples of the alkoxy group represented by the formula (I) include alkoxy groups having 1 to 10 carbon atoms (preferably 1 to 8, more preferably 1 to 4). Examples of the alkoxy group include a methoxy group, an ethoxy group, an isopropoxy group, a t-butoxy group, an n-butoxy group, an n-hexyloxy group, a 2-ethylhexyloxy group, and a 3,5,5-trimethylhexyloxy group. The alkoxy group also includes a substituted alkoxy group. Examples of the substituent that can be substituted on the alkoxy group include a halogen atom, a hydroxyl group, an amino group, an alkoxy group, an amide group, and a carbonyl group.

[0064] n is preferably an integer of 1 or 2, and more preferably 1.

[0065] The silane coupling agent represented by the general formula (TA) is R 1is a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, and R 2 A trifunctional silane coupling agent in which is a halogen atom or an alkoxy group and n is 1 is preferred.

[0066] Examples of trifunctional silane coupling agents include: Vinyltrimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, n-octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, hexyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, decyltrichlorosilane, phenyltrichlorosilane (all of the above, R 1 is an unsubstituted aliphatic hydrocarbon group or an unsubstituted aromatic hydrocarbon group); 3-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-glycidyloxypropylmethyldimethoxysilane (R 1 is a substituted aliphatic hydrocarbon group or a substituted aromatic hydrocarbon group); Examples include: The trifunctional silane coupling agents may be used alone or in combination of two or more.

[0067] Among these, from the viewpoint of narrowing the charge distribution, alkyltrialkoxysilane is preferred as the trifunctional silane coupling agent, and in the general formula (TA), R 1 represents an alkyl group having 1 to 20 carbon atoms (preferably 1 to 15 carbon atoms), and R 2More preferred is an alkyltrialkoxysilane in which R represents an alkyl group having 1 to 2 carbon atoms.

[0068] The amount of the structure composed of the reaction product of the silane coupling agent attached is preferably 5.5% by mass or more and 30% by mass or less, and more preferably 7% by mass or more and 22% by mass or less, relative to the silica particles, from the viewpoint of narrowing the charge distribution and maintaining the charge distribution.

[0069] -Nitrogen-containing compounds- The nitrogen-containing compound is a nitrogen-containing compound containing molybdenum, excluding ammonia and compounds that are in a gaseous state at temperatures of -200°C or higher and 25°C or lower. Specifically, from the viewpoint of narrowing the charge distribution and maintaining the charge distribution, the nitrogen-containing compound is preferably at least one selected from the group consisting of quaternary ammonium salts containing molybdenum (particularly, quaternary ammonium salts containing molybdenum) and mixtures of quaternary ammonium salts and metal oxides containing molybdenum. In particular, in the case of a quaternary ammonium salt containing molybdenum, the anion containing molybdenum, which is an anion, is strongly bonded to the quaternary ammonium cation, which is a cation, and therefore the charge distribution is highly maintainable. The nitrogen-containing compound is preferably adsorbed to at least a portion of the pores of the reaction product of the silane coupling agent. The molybdenum-containing nitrogen-containing compound may be used alone or in combination of two or more. The molybdenum-containing nitrogen-containing compound may also be used in combination with a molybdenum-free nitrogen-containing compound (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, preferably a quaternary ammonium salt).

[0070] The quaternary ammonium salt (quaternary ammonium salt not containing molybdenum element) is not particularly limited, and any known quaternary ammonium salt can be used.

[0071] Quaternary ammonium salts (quaternary ammonium salts that do not contain molybdenum) have a narrow charge distribution. The compounds represented by general formula (AM) may be used singly or in combination of two or more.

[0072] [ka] In the general formula (AM), R 1 , R 2 , R 3 and R 4 each independently represents a hydrogen atom, or an alkyl group, an aralkyl group, or an aryl group which may have a substituent; X - represents an anion, where R 1 , R 2 , R 3 and R 4 At least one of R represents an alkyl group, an aralkyl group, or an aryl group which may have a substituent. 1 , R 2 , R 3 and R 4 Two or more of these may be linked to form an aliphatic ring, an aromatic ring, or a heterocycle.

[0073] R 1 ~R 4 Examples of the alkyl group represented by the formula 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, R 1 ~R 4 The alkyl group represented by the formula (I) 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.

[0074] R 1 ~R 4 Examples of the aralkyl group represented by the formula (I) include aralkyl groups having 7 to 30 carbon atoms. Examples of aralkyl groups having 7 to 30 carbon atoms include benzyl, phenylethyl, phenylpropyl, 4-phenylbutyl, phenylpentyl, phenylhexyl, phenylheptyl, phenyloctyl, phenylnonyl, naphthylmethyl, naphthylethyl, anthrathymethyl, and phenylcyclopentylmethyl. Among the above, R 1 ~R 4 The aralkyl group represented by the formula (I) is preferably an aralkyl group having 7 to 15 carbon atoms, such as a benzyl group, a phenylethyl group, a phenylpropyl group, or a 4-phenylbutyl group.

[0075] R 1 ~R 4 Examples of the aryl group represented by the formula include an aryl group having 6 to 20 carbon atoms. Examples of the aryl group having 6 to 20 carbon atoms include a phenyl group, a pyridyl group, and a naphthyl group. Among the above, R 1 ~R 4The aryl group represented by the formula (I) is preferably an aryl group having 6 to 10 carbon atoms, such as a phenyl group.

[0076] X - Examples of the anion represented by the formula (I) include organic anions and inorganic anions. Examples of organic anions include polyfluoroalkylsulfonate ions, polyfluoroalkylcarboxylate ions, tetraphenylborate ions, aromatic carboxylate ions, and aromatic sulfonate ions (such as 1-naphthol-4-sulfonate ions). Inorganic anions include OH - , F - , Fe(CN)6 3- , Cl - , Br - , NO2 - , NO3 - , CO3 2- , PO4 3- , SO4 2- etc.

[0077] In the general formula (AM), R 1 , R 2 , R 3 and R 4 Two or more of R may be linked to each other to form a ring. 1 , R 2 , R 3 and R 4 Examples of the ring formed by linking two or more of the above include an alicyclic ring having 2 to 20 carbon atoms, and a heterocyclic amine having 2 to 20 carbon atoms.

[0078] In the compound represented by general formula (AM), R 1 , R 2 , R 3 and R 4 may each independently have a substituent, such as a nitrile group, a carbonyl group, an ether group, an amide group, a siloxane group, a silyl group, or a silane alkoxy group. R 1 , R 2 , R 3 and R 4each independently preferably 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.

[0079] Among these, from the viewpoint of narrowing the charge distribution, the compound represented by general formula (AM) preferably has a total of 18 to 35 carbon atoms, more preferably 20 to 32 carbon atoms.

[0080] X in the compound represented by general formula (AM) - Examples of structures other than those are shown below, but the present embodiment is not limited to these.

[0081] [ka]

[0082] From the viewpoint of narrowing the charge distribution, the quaternary ammonium salt containing molybdenum is a compound represented by the general formula (AM), - As an anion, molybdate ion (MoO4 2- , Mo2O7 2- , Mo3O 10 2- , Mo4O 13 2- , Mo7O 24 2- , Mo8O 26 4- Specifically, the quaternary ammonium salt containing molybdenum is preferably a compound represented by [N + (CH)3(C 14 C 29 )2]4, Mo8O 28 4- , [N + (C4H9)2(C6H6)2]2Mo2O7 2- , [N + (CH3)2(CH2C6H6)(CH2) 17 CH3]2MoO4 2- , [N + (CH3)2(CH2C6H6)(CH2) 15 CH3]2MoO42- etc. Metal oxides containing molybdenum include molybdenum oxides (molybdenum trioxide, molybdenum dioxide, Mo9O 26 ), alkali metal molybdates (lithium molybdate, sodium molybdate, potassium molybdate, etc.), alkaline earth metal molybdates (magnesium molybdate, calcium molybdate, etc.), other composite oxides (Bi2O3·2MoO3, γ-Ce2Mo3O 13 etc.)

[0083] -Detection and content of nitrogen-containing compounds- When the silica particles according to this embodiment are heated in a temperature range of 300° C. to 600° C., nitrogen-containing compounds are detected. Specific examples of the detection are as follows. Nitrogen-containing compounds can be detected, for example, using a heating furnace-type drop-type pyrolysis gas chromatograph mass spectrometer using He as a carrier gas. Nitrogen-containing compounds can be detected under pyrolysis temperature conditions of 300°C to 600°C under inert gas. Specifically, 0.1 mg to 10 mg of silica particles are introduced into the pyrolysis gas chromatograph mass spectrometer, and the presence or absence of nitrogen-containing compounds can be confirmed from the MS spectrum of the detected peak. Examples of components generated by pyrolysis from silica particles containing nitrogen-containing compounds include primary to tertiary amines or aromatic nitrogen compounds represented by the following general formula (N): In the following general formula (N), R N1 ~R N3 each independently represents a hydrogen atom, or an alkyl group, an aralkyl group, or an aryl group which may have a substituent; R N1 ~R N3 is R in general formula (AM) 1 , R 2 , and R 3 is synonymous with. For example, if the nitrogen-containing compound is a quaternary ammonium salt, part of the side chain is eliminated by thermal decomposition at 600°C, and detected as a tertiary amine. [ka]

[0084] From the viewpoint of narrowing the charge distribution, the content of the nitrogen-containing compound is preferably 0.008% by mass or more and 0.45% by mass or less, more preferably 0.015% by mass or more and 0.20% by mass or less, and even more preferably 0.018% by mass or more and 0.10% by mass or less, in terms of N atoms, relative to the silica particles.

[0085] The content of nitrogen-containing compounds calculated as N element is measured as follows. Using an oxygen / nitrogen analyzer (e.g., HORIBA EMGA-920) for 45 seconds, the amount of nitrogen present is measured as the ratio of N (N / Si). As a sample pretreatment, impurities such as ammonia are removed from the silica particles by drying them in a vacuum dryer at 100°C for at least 24 hours.

[0086] -Extraction amount of nitrogen-containing compounds- The amount X of the nitrogen-containing compound extracted by the ammonia / methanol mixed solution is 0.1 mass % or more, and the amount X of the nitrogen-containing compound extracted by the water and the amount Y of the nitrogen-containing compound extracted by the water preferably satisfy the formula: Y / X<0.3.

[0087] That is, the nitrogen-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 becomes broader and the nitrogen-element-containing compound becomes more likely to separate from the silica particles. However, silica particles containing a nitrogen-containing compound that does not easily adsorb moisture in the air are less likely to have a widening charge distribution even when there is a large amount of moisture in the air (even under high humidity conditions), and the nitrogen-containing compound is less likely to detach, making it easier to maintain a narrow charge distribution.

[0088] The extracted amount X of the nitrogen-containing compound is preferably 50% by mass, but the upper limit of the extracted amount X of the nitrogen-containing compound is, for example, 95% by mass or less, because the solution is difficult to penetrate into the pores due to surface tension, and a portion of the nitrogen-containing compound remains undissolved. The ratio "Y / X" of the amount of nitrogen-containing compound extracted X to the amount of nitrogen-containing compound extracted Y is preferably less than 0.3. However, the lower limit of the ratio "Y / X" is ideally 0, but since the measurement error range of X and Y is about ±1%, the lower limit is, for example, 0.01 or more.

[0089] Here, the extracted amounts X and Y of the nitrogen-containing compound are measured as follows. First, the silica particles to be measured are analyzed at a constant temperature of 400°C using a thermogravimetric / mass spectrometer (e.g., a gas chromatograph mass spectrometer manufactured by Netsch Japan Co., Ltd.), and the integrated mass fraction of compounds in which hydrocarbons with at least one carbon atom are covalently bonded to a nitrogen element relative to the silica particles is measured and designated as W1.

[0090] Separately, 1 part by mass of the silica particles to be measured was added to 30 parts by mass of an ammonia / methanol solution (Sigma-Aldrich, ammonia / methanol mass ratio = 1 / 5.2) at 25°C, and after 30 minutes of ultrasonic treatment, the silica powder and the extract were separated. The separated silica particles were dried in a vacuum dryer at 100°C for 24 hours, and the mass fraction of compounds in which hydrocarbons with at least one carbon atom are covalently bonded to nitrogen atoms was measured with a thermogravimetric-mass spectrometer at a constant temperature of 400°C, and this was designated W2. Then, the extracted amount X of the nitrogen element-containing compound is calculated using the following formula. ·Formula:X=W1-W2

[0091] In addition, 1 part by mass of silica particles to be measured is added to 30 parts by mass of water at 25°C, and after 30 minutes of ultrasonic treatment, the silica particles are separated from the extract. The separated silica particles are dried in a vacuum dryer at 100°C for 24 hours, and the mass fraction of compounds in which hydrocarbons with at least one carbon atom are covalently bonded to nitrogen atoms is measured relative to the silica particles using a thermogravimetric / mass spectrometer at a constant temperature of 400°C, and this is designated as W3. Then, the extracted amount Y of the nitrogen element-containing compound is calculated using the following formula. ·Formula: Y=W1-W3

[0092] (Hydrophobic treated structure) The hydrophobic treated structure is a structure that has been reacted with a hydrophobic treatment agent. As the hydrophobic treatment 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, and trimethylmethoxysilane; Alkoxysilane compounds having a vinyl group, such as vinyltrimethoxysilane and vinyltriethoxysilane; alkoxysilane compounds having an epoxy group, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; alkoxysilane compounds having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane; alkoxysilane 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; Alkoxysilane compounds having an isocyanate alkyl group, such as 3-isocyanatepropyltrimethoxysilane and 3-isocyanatepropyltriethoxysilane; silazane compounds such as hexamethyldisilazane and tetramethyldisilazane; Examples include:

[0093] (Characteristics of silica particles) - Hydrophobicity - The hydrophobicity of the silica particles according to this embodiment is preferably 10% to 60%, more preferably 20% to 55%, and even more preferably 28% to 53%, from the viewpoint of narrowing the charge distribution. If the hydrophobicity of the silica particles is 10% or less, the amount of coating on the structure due to the reaction product of the silane coupling agent is low, and the content of the nitrogen element-containing compound is reduced, which makes the charge distribution more likely to spread. On the other hand, if the hydrophobicity of the silica particles exceeds 60%, the density of the structure increases due to the reaction of the silane coupling agent, the number of pores decreases, and the content of the nitrogen-containing compound decreases, which makes the charge distribution more likely to spread.

[0094] The hydrophobicity of silica particles is measured as follows. 0.2% by mass of sample silica particles is placed in 50 ml of ion-exchanged water, and methanol is added dropwise from a burette while stirring with a magnetic stirrer. The mass fraction of methanol in the methanol-water mixed solution at the end point when the entire sample has sunk is determined as the degree of hydrophobicity.

[0095] -Number average particle size and number particle size distribution index- The number average particle size of the silica particles according to this 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 is likely to occur. However, the silica particles according to the present embodiment achieve a narrow charge distribution even when the number-average particle diameter is within the above range.

[0096] The number particle size distribution index of the silica particles according to this embodiment is preferably 1.1 or more and 2.0 or less, and more preferably 1.15 or more and 1.6 or less. When the number particle size distribution index of the silica particles according to this embodiment is within the above range, there is little coarse powder, which tends to have a large charge amount, and little fine powder, which tends to have a small charge amount, and therefore it is easy to achieve a narrow charge distribution.

[0097] Here, the number average particle size and number particle size distribution index of the silica particles are measured as follows. Silica particles are observed at 40,000x magnification using a scanning electron microscope (SEM), and the images of the observed silica particles are analyzed using image processing and analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.) to determine the circular equivalent diameters of at least 200 particles. A cumulative distribution of the number of individual particles is then drawn, starting from the smallest diameter side, and the particle size at 50% of the cumulative diameter from the smallest diameter side, the number-average particle size, is determined. The square root of the particle diameter D84 at 84% cumulative size from the smallest diameter side divided by the particle diameter D16 at 16% cumulative size is defined as the "number particle size distribution index" (GSD). That is, the number particle size distribution index (GSD) = (D84 / D16) 0.5 is.

[0098] -Circularity- The average circularity of the silica particles according to this 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 silica particles is within the above range, the specific surface area is large and excessive charging is likely to occur. However, the silica particles according to this embodiment achieve a narrow charge distribution even when the average circularity is within the above range.

[0099] Here, the circularity of the silica particles is measured as follows. Silica particles are observed at 40,000x magnification using a scanning electron microscope (SEM), and the images of the observed silica particles are analyzed using image processing analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.). The circularity of at least 200 particles is determined, and the arithmetic mean is calculated to determine the average circularity. The circularity is calculated by the following formula. Circularity = Equivalent circle diameter / Perimeter = [2 × (Aπ) 1 / 2 ] / PM In the above formula, A represents the projected area and PM represents the perimeter.

[0100] -Volume resistivity- The volume resistivity of the silica particles according to this embodiment (i.e., the volume resistivity before firing at 350°C) is 1.0 × 10 7 Ωcm or more 1.0×10 11.5 Ωcm or less is preferable, and 1.0×10 8 Ωcm or more 1.0×10 11 Ωcm or less is more preferable. When the volume resistivity of the silica particles according to this embodiment is within the above range, the content of the nitrogen element-containing compound is large, excessive charging is unlikely to occur, and narrowing of the charge distribution is easily achieved.

[0101] In the silica particles according to this embodiment, when the volume resistivities of the silica particles before and after firing at 350°C are Ra and Rb, respectively, Ra / Rb is preferably 0.01 or more and 0.8 or less, more preferably 0.015 or more and 0.6 or less. When Ra / Rb is within the above range, the content of the nitrogen element-containing compound is large, excessive charging is unlikely to occur, and a narrow charge distribution can be easily achieved.

[0102] The 350°C firing is carried out as described above. On the other hand, the volume resistivity is measured as follows: The measurement environment is a temperature of 20°C and a humidity of 50% RH. 20cm 2 The silica particles to be measured are placed on the surface of a circular jig on which the electrode plate is arranged, to a thickness of about 1 mm to 3 mm, forming a silica particle layer. 2The silica particle layer is sandwiched between two electrode plates. To eliminate gaps between the silica particles, a pressure of 0.4 MPa is applied to the electrode plate placed on the silica particle layer, and the thickness (cm) of the silica particle layer is then measured. Both the top and bottom electrodes of the silica particle layer are connected to an impedance analyzer (Solartron Analytical). -3 Hz over 10 6 Hz or less are measured to obtain a Nyquist plot. This is fitted to an equivalent circuit, assuming the existence of three resistance components: bulk resistance, particle interface resistance, and electrode contact resistance, to determine the bulk resistance R. The formula for calculating the volume resistivity (Ω·cm) of silica particles is shown below. ·Formula:ρ=R / L In the formula, ρ is the volume resistivity of the silica particles (Ω·cm), R is the bulk resistance (Ω), and L is the thickness of the silica particle layer (cm).

[0103] (OH group amount) In the silica particles according to this embodiment, the amount of OH groups measured by the Sears method is 0.2 / nm 2 More than 5.5 pieces / nm 2 From the viewpoint of narrowing the charge distribution, 0.2 particles / nm or less is preferable. 2 More than 4 pieces / nm 2 Less than 0.2 particles / nm is more preferable. 2 More than 3 pieces / nm 2 The following is even more preferred: The amount of OH groups measured by the Sears method can be adjusted to fall within the above range by sufficiently forming a structure composed of a reaction product of the silane coupling agent on the silica base particles.

[0104] By reducing the amount of OH groups that inhibit the adsorption of the nitrogen-containing compound to the above range, the nitrogen-containing compound can easily penetrate deep into the pores of the silica particles (for example, the pores of the adsorption layer described below). Then, hydrophobic interactions with the nitrogen-containing compound occur, strengthening its adhesive force to the silica particles. This increases the amount of the nitrogen-containing compound adsorbed. In addition, the nitrogen-containing compound becomes less likely to detach. This improves the narrowing of the charge distribution by the nitrogen-containing compound, and also improves the maintenance of the narrow charge distribution.

[0105] Furthermore, by reducing the amount of OH groups to the above range, the environmental dependency of the charging characteristics becomes low, and it becomes easier to narrow the charge distribution using the nitrogen-containing compound in any environment (particularly in a low-temperature, low-humidity environment where excessive negative charging is likely to occur).

[0106] The amount of OH groups is measured by the Sears method, specifically as follows. 1.5g of silica particles are added to a mixture of 50g of pure water and 50g of ethanol and stirred for 2 minutes with an ultrasonic homogenizer to create a dispersion. While stirring at 25°C, 1.0g of 0.1mol / L hydrochloric acid solution is added dropwise to obtain the test solution. The resulting test solution is placed in an automatic titrator and subjected to potentiometric titration with 0.01mol / L sodium hydroxide solution, and a derivative curve of the titration curve is created. Among the inflection points where the derivative value of the titration curve is 1.8 or greater, the titer E is the one where the titer of 0.01mol / L sodium hydroxide solution is the largest. Using the following formula, the surface silanol group density ρ (particles / nm 2 ) is calculated. Formula: ρ=((0.01×E-0.1)×NA / 1000) / (M×S BET x10 18 ) In the formula, the details of the symbols are as follows: E: Among the inflection points where the derivative of the titration curve is 1.8 or more, the titer of 0.01 mol / L sodium hydroxide 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 the BET nitrogen adsorption three-point method, with the equilibrium relative pressure set to 0.3.

[0107] <Method for producing silica particles> An example of a method for producing silica particles according to this embodiment is a first step of forming a structure composed of a reaction product of a silane coupling agent on at least a portion of the surface of a silica base particle; a second step of adsorbing a nitrogen-containing compound into at least a portion of the pores of the reaction product of the silane coupling agent; It has. The method for producing silica particles according to this embodiment may further include a third step of hydrophobizing the silica base particles, which have at least a portion of the surface coated thereon after or during the second step, and which have a structure composed of a reaction product of a silane coupling agent and in which a nitrogen-containing compound is adsorbed in at least a portion of the pores of the reaction product of the silane coupling agent.

[0108] The steps of the method for producing silica particles according to this embodiment will be described in detail below.

[0109] [Preparation process] First, the step of preparing silica base particles will be described.

[0110] The preparation process includes, for example, (i) A step of preparing a silica base particle suspension by mixing an alcohol-containing solvent with silica base particles. (ii) A step of granulating silica base particles by a sol-gel method to obtain a silica base particle suspension etc. Examples of the silica base particles used in (i) include sol-gel silica particles (silica particles obtained by the sol-gel method), aqueous colloidal silica particles, alcoholic silica particles, fumed silica particles obtained by a gas phase method, and fused silica particles. The alcohol-containing solvent used in (i) above may be a solvent containing alcohol alone, or a mixed solvent containing alcohol and other solvents. Examples of 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 85% by mass or more.

[0111] 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) may be carried out, for example, by an alkaline catalyst solution preparation step of preparing an alkaline catalyst solution containing an alkaline catalyst in a solvent containing alcohol; a silica base particle producing step of producing silica base particles by supplying tetraalkoxysilane and an alkali catalyst into an alkali catalyst solution; Preferably, the method is a sol-gel method comprising:

[0112] The alkaline catalyst solution preparation step is preferably a step of preparing a solvent containing alcohol and mixing the solvent with an alkaline catalyst to obtain an alkaline catalyst solution.

[0113] The alcohol-containing solvent may be a solvent containing only alcohol, or a mixed solvent containing alcohol and other solvents. Examples of 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 85% by mass or more.

[0114] The alkaline 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.

[0115] 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 even more preferably 0.65 mol / L or more and 1.1 mol / L or less.

[0116] The silica base particle production step is a step in which tetraalkoxysilane and an alkali catalyst are supplied to an alkali catalyst solution, and the tetraalkoxysilane is reacted (hydrolysis reaction and condensation reaction) in the alkali catalyst solution to produce silica base particles.

[0117] In the silica base particle generation process, core particles are generated by the reaction of tetraalkoxysilane at the initial stage of supplying tetraalkoxysilane (core particle generation stage), and then these core particles grow (core particle growth stage) to generate silica base particles.

[0118] Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, etc. From the viewpoint of controllability of the reaction rate and uniformity of the shape of the produced silica base particles, tetramethoxysilane or tetraethoxysilane is preferred.

[0119] Examples of the alkali catalyst supplied to 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 already contained in the alkali catalyst solution, or may be of a different type, but is preferably of the same type.

[0120] 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.

[0121] In the silica base particle production step, the temperature of the alkaline catalyst solution (temperature at the time of supply) is preferably 5°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower.

[0122] [First step] In the first step, a structure composed of a reaction product of a silane coupling agent is formed. Specifically, in the first step, for example, a silane coupling agent is added to a silica base particle suspension, and the silane coupling agent is reacted with the surfaces of the silica base particles to form a structure composed of a reaction product of the silane coupling agent. The functional groups of the silane coupling agent react with each other and with OH groups on the surfaces of the silica particles to form a structure composed of the reaction product of the silane coupling agent.

[0123] The reaction of the silane coupling agent is carried out by adding the silane coupling agent to a suspension of silica base particles, and then heating the suspension while stirring. Specifically, for example, the suspension is heated to 40°C to 70°C, the silane coupling agent is added, and then the suspension is stirred. The stirring time is preferably 10 minutes to 24 hours, more preferably 60 minutes to 420 minutes, and even more preferably 80 minutes to 300 minutes.

[0124] [Second process] In the second step, a nitrogen-containing compound is adsorbed into at least some of the pores of the reaction product of the silane coupling agent. Specifically, in the second step, first, for example, a nitrogen-containing compound is added to a silica base particle suspension, and the mixture is stirred at a temperature ranging from 20° C. to 50° C. As a result, the nitrogen-containing compound is adsorbed into at least some of the pores of the reaction product of the silane coupling agent.

[0125] In the second step, for example, an alcohol liquid containing a nitrogen-containing compound may be added to the silica particle suspension. The alcohol may be the same type as the alcohol contained in the silica base particle suspension or may be a different type, but it is more preferable that the alcohol be the same type.

[0126] In the alcohol liquid containing the nitrogen-containing compound, the concentration of the nitrogen-containing compound 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.

[0127] [Third step] In the third step, after or during the second step, a hydrophobic treatment is performed on silica base particles having a structure in which a nitrogen-containing compound is adsorbed in at least some of the pores of the reaction product of the silane coupling agent. Specifically, in the third step, for example, a nitrogen-containing compound is added to the silica base particle suspension in which the structures have been formed, and then a hydrophobic treatment agent is added. The hydrophobic treatment agent forms a hydrophobic treatment layer by reacting with its functional groups and with the OH groups of the silica base particles.

[0128] The reaction of the hydrophobic treatment agent is carried out by adding the silane coupling agent to a suspension of silica base particles, and then heating the suspension while stirring. Specifically, for example, the suspension is heated to 40°C to 70°C, the hydrophobic treatment agent is added, and then the suspension is stirred. 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.

[0129] [Drying process] In the method for producing silica particles according to the present embodiment, a drying step for removing the solvent from the suspension may be carried out after the second step or the third step. The drying step may be carried out during the second step or the third step.

[0130] The drying method may be, for example, heat drying, spray drying, or supercritical drying. Spray drying can be performed by a conventional method using a commercially available spray dryer (including disk rotation type and nozzle type). For example, spraying the spray liquid into a hot air stream at a rate of 0.2 L / h to 1 L / h is performed. In this case, the hot air temperature is preferably in the range of 70°C to 400°C at the inlet and 40°C to 120°C at the outlet. If the inlet temperature is below 70°C, the solids contained in the dispersion are not sufficiently dried. If the temperature exceeds 400°C, the particle shape is distorted during spray drying. If the outlet temperature is below 40°C, the solids are not sufficiently dried and adhere to the inside of the device. A more preferable inlet temperature is in the range of 100°C to 300°C. The silica particle concentration in the silica particle suspension during spray drying is preferably in the range of 10% by mass or more and 30% by mass or less in terms of solid content.

[0131] In supercritical drying, the solvent is removed using a supercritical fluid, which makes it difficult for surface tension to act between particles, and the primary particles contained in the suspension are dried in a state where aggregation is suppressed, making it easier to obtain silica particles with a highly uniform particle size.

[0132] Examples of substances that can be used as supercritical fluids include carbon dioxide, water, methanol, ethanol, acetone, etc. From the viewpoints of treatment efficiency and suppressing the generation of coarse particles, the solvent removal step is preferably a step that uses supercritical carbon dioxide.

[0133] Specifically, supercritical drying is carried out, for example, by the following procedure. The suspension is placed in a sealed reactor, and then liquefied carbon dioxide is introduced into the reactor. The sealed reactor is then heated and the pressure inside the sealed reactor is increased by a high-pressure pump, thereby bringing the carbon dioxide inside the sealed reactor 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, thereby causing the supercritical carbon dioxide to flow through the suspension inside the sealed reactor. While the supercritical carbon dioxide flows through the suspension, the solvent dissolves 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 sealed reactor are those that put carbon dioxide into a supercritical state, i.e., the critical point of carbon dioxide is 31.1°C / 7.38 MPa, and the temperature and pressure are, for example, 40°C to 200°C and 10 MPa to 30 MPa.

[0134] The flow rate of the supercritical fluid in the supercritical drying is preferably 80 mL / sec or more and 240 mL / sec or less.

[0135] The obtained silica particles are preferably crushed or sieved as necessary to remove coarse particles and aggregates. Crushing is performed using, for example, a dry grinding device such as a jet mill, a vibration mill, a ball mill, or a pin mill. Sieving is performed using, for example, a vibration sieve or an air sieving machine. [Example]

[0136] Hereinafter, embodiments of the present invention will be described in detail with reference to examples, but the embodiments of the present invention are not limited to these examples. In the following description, unless otherwise specified, all "%" is by mass.

[0137] <Production of Silica Particles> [Examples 1, 3 to 33, 35, Reference Examples 1 to 9] A suspension containing silica particles in each example was prepared as follows.

[0138] -Preparation of alkaline catalyst solution- Methanol, ion-exchanged water, and ammonia water (NH4OH) in the amounts and concentrations shown in Table 1 were placed in a glass reaction vessel equipped with a metal stirring rod, a dropping nozzle, and a thermometer, and the mixture was stirred to obtain an alkaline catalyst solution.

[0139] - Granulation of silica base particles using the sol-gel method - The temperature of the alkaline catalyst solution was adjusted to 40°C, and the alkaline catalyst solution was purged with nitrogen. Next, while stirring the alkaline catalyst solution, tetramethoxysilane (TMOS) in the amounts shown in Table 1 and 124 parts by mass of ammonia water (NH4OH) with a catalyst (NH3) concentration of 7.9% were simultaneously added dropwise to obtain a silica base particle suspension.

[0140] -Addition of silane coupling agent- The silica base particle suspension was heated to 40°C and stirred, while the type and amount of silane coupling agent shown in Table 1 was added to the suspension. Stirring was then continued for 120 minutes to allow the silane coupling agent to react, thereby forming an adsorption structure.

[0141] - Addition of nitrogen-containing compounds - The nitrogen-containing compounds shown in Table 1 were diluted with butanol to prepare alcohol solutions. Next, an alcohol solution prepared by diluting a nitrogen-containing compound with butanol was added to the suspension. The alcohol solution was added so that the number of parts of the nitrogen-containing compound per 100 parts by mass of the solid content of the silica base particle suspension was the amount shown in Table 1. The mixture was then stirred at 30°C for 100 minutes to obtain a suspension containing the nitrogen-containing compound.

[0142] -Drying- Next, 300 parts by mass of the suspension was placed in a reaction vessel, and CO2 was added while stirring, and the temperature and pressure inside the reaction vessel were raised to the temperature and pressure shown in Table 1. While stirring while maintaining the temperature and pressure, CO2 was introduced and discharged at a flow rate of 5 L / min. Thereafter, the solvent was removed over 120 minutes to obtain silica particles of each example.

[0143] [Example 2] Silica particles were obtained in the same manner as in Example 1, except that spray drying was performed using a Mini Spray Dryer B-290 (manufactured by Nippon Buchi Co., Ltd.) under conditions where the temperature and pressure inside the cylinder were set as shown in Table 1 and the silica particle suspension was fed at a feed rate of 0.2 L / hour.

[0144] [Example 33] After adding the nitrogen-containing compound, hexamethyldisilazane (HMDS) was added in an amount of 30 mass% based on the solid content of the silica base particles, and the mixture was stirred at 65°C for 3 hours to hydrophobize the surface of the silica base particles. Except for this, silica particles were obtained in the same manner as in Example 1.

[0145] [Example 34] Silica particles were obtained in the same manner as in Example 1, except that 30 g of dry process silica AEROSIL130 (manufactured by Nippon Aerosil) was dispersed in 300 g of methanol to obtain a silica base particle suspension.

[0146] [Comparative Examples 1, 2, and 3] Silica particles were obtained in the same manner as in Example 1, except that the amounts of the silane coupling agent and the nitrogen-containing compound added were as shown in Table 1.

[0147] [evaluation] (Various characteristics) The following properties of the obtained silica particles were measured according to the methods described above. Net strength of molybdenum element (indicated as "Mo" in the table) The ratio of the net strength of molybdenum element to the net strength of silicon element (indicated as "Mo / Si" in the table) Number average particle size (referred to as "particle size" in the table) Number particle size distribution index (referred to as "GSD" in the table) Average circularity (referred to as "circularity" in the table) Pore ​​volume A of pores with diameters of 1 nm to 50 nm obtained from the pore distribution curve of the nitrogen gas adsorption method before calcination at 350°C (referred to as "Pore volume A before calcination at 350°C" in the table). Pore ​​volume B of pores with diameters of 1 nm to 50 nm obtained from the pore distribution curve of the nitrogen gas adsorption method after firing at 350°C (referred to as "Pore volume B after firing at 350°C" in the table) Volume resistivity Ra before firing at 350°C (referred to as "volume resistivity Ra before firing" in the table) Volume resistivity Rb after firing at 350°C (referred to as "volume resistivity Rb after firing" in the table) - Amount of OH groups measured by the Sears method (referred to as "Amount of OH groups" in the table) The ratio of the integral value C of signals observed in the chemical shift range of -50 ppm to -75 ppm when the integral value of all signals in the Si-CP / MAS NMR spectrum is taken as 100% (referred to as "(Si-CP / MAS area ratio C" in the table). The ratio C / D of the integral value C of the signal observed in the chemical shift range of -50 ppm to -75 ppm in the Si-CP / MAS NMR spectrum to the integral value D of the signal observed in the chemical shift range of -90 ppm to -120 ppm in the Si-CP / MAS NMR spectrum (referred to as "(Si-CP / MAS ratio C / D)" in the table). Hydrophobicity

[0148] (Charge Dependence of Charge Amount at Low Humidity and Charge Amount at High Humidity / Capacitance) The low humidity charge amount and high humidity charge amount of the silica particles of each example were measured and the environmental dependency of the capacitance was evaluated as follows: Among the criteria, A to B are acceptable. The evaluation method is as follows. 5g of the prepared silica particles added at 2% by mass to the surface of MA1010 manufactured by Nippon Shokubai was mixed with 50g of KNI106GSM manufactured by JFE Chemical Corp. The mixed sample was stirred for 5 minutes using a turbula shaker in a chamber at 10°C and 10% RH, and the charge was measured using a Toshiba TB200. The result was taken as FC, and the result was stirred for 5 minutes using a turbula shaker in a chamber at 30°C and 90% RH, and the charge was measured using a Toshiba TB200. The ratio of these values, FA / FC, was used for evaluation. A(◎): FA / FC is 0.8 or more and less than 1.1 B(〇): FA / FC is 0.65 or more and less than 0.8 C(△): FA / FC is 0.5 or more and less than 0.65 D(×): FA / FC is less than 0.5

[0149] (Charge distribution in a low-temperature, low-humidity environment) The charge distribution of the silica particles of each example was evaluated in a low-temperature, low-humidity environment (10°C, 10 RH environment) as follows. Five grams of the prepared silica particles were added to the surface of Nippon Shokubai MA1010 at 2% by mass, and mixed with 50 grams of JFE Chemical KNI106GSM. The mixed sample was stirred for 5 minutes using a Turbula shaker in a chamber at 10°C and 10% RH, and evaluated using CSG (charge spectrograph) image analysis. The charge distribution is defined as the difference between the 20% charge Q(20) and the 80% charge Q(80) of the cumulative charge distribution divided by the 50% charge Q(50), i.e., [Q(80) - Q(20)] / Q(50). The 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 and 0.7 or more C(△): [Q(80)-Q(20)] / Q(50) value is less than 1.0 and 0.8 or more D(×): [Q(80)-Q(20)] / Q(50) value is 1.0 or more

[0150] (Ability to maintain narrow charge distribution in high temperature and humidity environments) The silica particles of each example were evaluated for their ability to maintain a narrow charge distribution in a high-temperature, high-humidity environment (30°C, 90% RH environment) as follows. Five grams of the prepared silica particles were added to the surface of Nippon Shokubai MA1010 at 2% by mass, and mixed with 50 grams of JFE Chemical KNI106GSM. The mixed sample was stirred for 100 minutes using a Turbula shaker in a 30°C, 90% RH chamber and evaluated using CSG (charge spectrograph) image analysis. The charge distribution is defined as the difference between the 20% charge Q(20) and the 80% charge Q(80) of the cumulative charge distribution divided by the 50% charge Q(50), i.e., [Q(80) - Q(20)] / Q(50). The 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 and 0.75 or more C(△): [Q(80)-Q(20)] / Q(50) value is less than 1.0 and 0.85 or more D(×): [Q(80)-Q(20)] / Q(50) value is 1.0 or more

[0151] (Maintaining a narrow charge distribution in low temperature and low humidity environments) The ability of the silica particles of each example to maintain a narrow charge distribution in a low-temperature, low-humidity environment (10°C, 10% RH environment) was evaluated in the same manner as the ability to maintain a narrow charge distribution in a high-temperature, high-humidity environment (30°C, 90% RH environment), except that the evaluation was performed in a low-temperature, low-humidity environment (10°C, 10% RH environment).

[0152] The evaluation results are shown in Table 1. Details of the abbreviations in Table 1 are as follows: MTMS: Methyltrimethoxysilane DTMS: n-dodecyltrimethoxysilane

[0153] ·TP-415:[N + (CH)3(C 14 C 29 )2]4Mo8O 28 4- (Hodogaya N,N-Dimethyl-N-tetradecyl-1-tetradecanaminium, hexa-μ-oxotetra-μ3-oxodi-μ5-oxotetradecaoxooctamolybdate(4-) (4:1) manufactured by Chemical Industry Co., Ltd. (amount extracted with ammonia / methanol mixed solution X = 61 to 89 mass%, ratio of extracted amount X to amount extracted with water Y) Y / X =0.03~0.26) Dimethylstearylammonium chloride (extraction with ammonia / methanol mixed solution) Extraction amount X = 75% by mass, ratio of extracted amount X to extracted amount Y by water Y / X =0.28) Tributylamine (amount extracted with ammonia / methanol mixed solution X = 65 mass%, ratio of extracted amount X to extracted amount Y with water Y / X =0.29) Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (amount extracted with ammonia / methanol mixed solution X = 76 mass%, ratio of extracted amount X to amount extracted with water Y) Y / X =0.25) Quaternium-80 (amount extracted with ammonia / methanol mixed solution X = 80 mass%, ratio of extracted amount X to extracted amount Y with water) Y / X =0.09) Ditetrakis(dibutyldibenzylammonium)molybdic acid (amount extracted with ammonia / methanol mixed solution X = 65 mass%, ratio of extracted amount X to amount extracted with water Y) Y / X =0.15) Phenethylamine (amount extracted with ammonia / methanol mixed solution X = 55% by mass, ratio of extracted amount X to amount extracted with water Y) Y / X =0.28) 4-(2-octylamino)diphenylamine (amount extracted with ammonia / methanol mixed solution X = 78 mass%, ratio of extracted amount X to amount extracted with water Y) Y / X =0.14) N-benzyl-N-methylethanolamine (amount extracted with ammonia / methanol mixed solution X = 58 mass%, ratio of extracted amount X to extracted amount Y with water) Y / X =0.27) 2,3-bis(2,6-diisopropylphenylimino)butane (amount extracted with ammonia / methanol mixed solution X = 81 mass%, ratio of extracted amount X to amount extracted with water Y) Y / X =0.11) 3-indoleacetonitrile (amount extracted with ammonia / methanol mixed solution X = 80 mass%, ratio of extracted amount X to extracted amount Y with water Y / X =0.12) n-Hexadecyltrimethylammonium bromide (ammonia / methanol mixed solution) The amount of extraction by X = 18 mass%, and the ratio of the amount of extraction by X to the amount of extraction by water Y Y / X =5.28)

[0154] [Table 1-1]

[0155] [Table 1-2]

[0156] [Table 1-3]

[0157] The above results show that the silica particles of the Examples have a narrow charge distribution when charged, and are excellent in maintaining the narrow charge distribution, compared to the silica particles of the Comparative Examples.

Claims

1. A nitrogen-containing compound containing molybdenum, and the ratio (Mo / Si) of the net intensity of molybdenum element to the net intensity of silicon element measured by fluorescent X-ray analysis is 0.035 or more and 0.35 or less, the silica base particles are composed of a reaction product of at least one selected from the group consisting of a monofunctional silane coupling agent, a bifunctional silane coupling agent, and a trifunctional silane coupling agent, the reaction product coating at least a portion of the surface of the silica base particles; The nitrogen-containing compound is at least one selected from the group consisting of a quaternary ammonium salt containing molybdenum and a mixture of a quaternary ammonium salt and a metal oxide containing molybdenum.

2. 2. The silica particles according to claim 1, wherein the nitrogen-containing compound is a quaternary ammonium salt containing molybdenum.

3. 3. The silica particles according to claim 1, wherein the number-average particle diameter is 10 nm or more and 200 nm or less.

4. Silica particles described in any one of claims 1 to 3, having a structure in which the nitrogen element-containing compound is adsorbed in at least some of the pores of the reaction product.

5. 5. The silica particles according to claim 1, wherein the degree of hydrophobicity is 10% or more and 60% or less.

6. When the pore volumes of pores with diameters of 1 nm to 50 nm obtained from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350°C are A and B, respectively, B / A is 1.2 to 5, and B is 0.2 cm ３ / g or more 3cm ３ The silica particles according to any one of claims 1 to 5, wherein the surface area of ​​the silica particles is 1 / g or less.

7. Cross polarization / magic angle spinning (CP / MAS) method ２９ 7. The silica particles according to claim 1, wherein the ratio C / D of the integral value C of the signal observed in the chemical shift range of -50 ppm to -75 ppm in a Si solid-state nuclear magnetic resonance (NMR) spectrum to the integral value D of the signal observed in the chemical shift range of -90 ppm to -120 ppm is 0.10 or more and 0.75 or less.

8. the amount X of the nitrogen-containing compound extracted by the ammonia / methanol mixed solution is 0.1 mass% or more; The amount X of the nitrogen-containing compound extracted and the amount Y of the nitrogen-containing compound extracted by water satisfy the formula: Y / X<0.

3. The silica particles according to any one of claims 1 to 7.

9. 9. The silica particles according to claim 1, wherein the average circularity is 0.60 or more and 0.96 or less.

10. The silica particles according to any one of claims 1 to 9, wherein the number particle size distribution index is 1.1 or more and 2.0 or less.

Images