Silica particles and method for manufacturing the same

Abstract

This invention provides silica particles and a method for manufacturing the same. The silica particles contain nitrogen-containing compounds, and the silica particles are obtained by the cross-polarized magic angle rotation (CP / MAS) method. 29 In the Si solid-state nuclear magnetic resonance (NMR) spectrum, the ratio C / D of the integral value C of the signal observed in the range of chemical shift -50 ppm to -75 ppm to the integral value D of the signal observed in the range of chemical shift -90 ppm to -120 ppm is 0.10 to 0.75, the amount X of the nitrogen-containing compound extracted from silica particles using an ammonia / methanol mixed solution is 0.1% by mass or more, and the extraction amount X of the nitrogen-containing compound and the extraction amount Y of the nitrogen-containing compound extracted using water satisfy the formula: Y / X < 0.3.

Description

Technical Field

[0001] This invention relates to silica particles and methods for manufacturing the same. Background Technology

[0002] Silica particles are used as additives or main components in powder coatings, cosmetics, rubber, abrasives, etc., for example, to improve resin strength, improve powder flowability, and inhibit accumulation.

[0003] For example, Japanese Patent Application Publication No. 2019-073418 discloses "a hydrophobic silica powder, wherein (1) the degree of hydrophobicity is 50% or more; (2) the extraction amount X of at least one compound selected from the group consisting of quaternary ammonium ions, monoazo complexes and inorganic acid radicals extracted by a mixed solvent of methanol and methanesulfonic acid is 0.1% by mass or more; (3) the above-mentioned X and the extraction amount Y of the above-mentioned compound extracted by water satisfy formula (I) Y / X < 0.15".

[0004] In addition, Japanese Patent Application Publication No. 2017-039618 discloses "a silica powder comprising a plurality of silica particles, wherein the silica particles have a quaternary ammonium salt incorporated into a silica structure having "Si-O" bonds as repeating units".

[0005] In addition, Japanese Patent Application Publication No. 2011-185998 discloses "an external charge control particle, which consists of a transport particle and a charge control agent adhered to the surface of the transport particle, wherein the transport particle is formed from hydrophobic spherical silica particles with an average particle size of 20 to 500 nm obtained by hydrophobicating the surface of hydrophilic spherical silica particles obtained by sol-gel method".

[0006] In addition, Japanese Patent Application Publication No. 2001-194825 discloses "a silica microparticle, which is made by treating spherical hydrophobic silica microparticles with an average particle size of 0.01 to 5 μm using a compound selected from the group consisting of quaternary ammonium salt compounds, betaine compounds containing fluorinated alkyl groups and silicone oil".

[0007] In addition, Japanese Patent Application Publication No. 09-166884 discloses "particles made by treating silica particles with a hydrophobicity of 80% or more with an amphoteric surfactant and particles made by treating silica particles with a hydrophobicity of 80% or more with a quaternary ammonium salt or a polymer having a quaternary ammonium group". Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a silica particle and a method for manufacturing the same, which has a narrow charge distribution during charging compared to the following situation: silica particles containing nitrogen-containing compounds, in a cross-polarized magic angle rotation (CP / MAS) method. 29 In Si solid-state nuclear magnetic resonance (NMR) spectra, the ratio C / D of the integral value C of the signal observed in the range of chemical shift from -50 ppm to -75 ppm to the integral value D of the signal observed in the range of chemical shift from -90 ppm to -120 ppm is less than 0.10 or greater than 0.75; the extraction amount X of nitrogen-containing compounds extracted using ammonia / methanol mixed solution is less than 0.1% by mass or the extraction amount X of nitrogen-containing compounds extracted using water does not satisfy the formula: Y / X < 0.3.

[0009] According to a first aspect of the present invention, a silica particle is provided, comprising a nitrogen-containing compound, wherein the silica particle is determined by the cross-polarization magic angle rotation (CP / MAS) method. 29 In the Si solid-state nuclear magnetic resonance (NMR) spectrum, the ratio C / D of the integral value C of the signal observed in the range of chemical shift -50 ppm to 75 ppm to the integral value D of the signal observed in the range of chemical shift -90 ppm to 120 ppm is 0.10 to 0.75, the amount X of the above-mentioned nitrogen-containing compound extracted from silica particles using an ammonia / methanol mixed solution is 0.1% by mass or more, and the extraction amount X of the above-mentioned nitrogen-containing compound and the extraction amount Y of the above-mentioned nitrogen-containing compound extracted using water satisfy the formula: Y / X < 0.3.

[0010] According to the second aspect of the present invention, the average particle size of the aforementioned silica particles is 10 nm or more and 200 nm or less.

[0011] According to the third aspect of the present invention, the average particle size of the aforementioned silica particles is 10 nm or more and 80 nm or less.

[0012] According to the fourth aspect of the present invention, the average roundness of the aforementioned silica particles is 0.60 or more and 0.96 or less.

[0013] According to the fifth aspect of the present invention, the average roundness of the aforementioned silica particles is 0.70 or more and 0.92 or less.

[0014] According to the sixth aspect of the present invention, the volume resistivity of the aforementioned silicon dioxide particles is 1.0 × 10⁻⁶. 7 Ωcm or more 1.0×10 11.5 Below Ωcm.

[0015] According to the seventh aspect of the present invention, when the volume resistivity before and after firing at 350°C is set as Ra and Rb respectively, Ra / Rb is 0.01 or more and 0.8 or less in the above-mentioned silica particles.

[0016] According to the eighth aspect of the present invention, in the above-mentioned silica particles, when the pore volumes with pore diameters of 1 nm to 50 nm, obtained from the pore distribution curves of silica particles obtained by nitrogen adsorption method before and after firing at 350°C, are respectively set as A and B, B / A is 1.2 to 5, and B is 0.2 cm. 3 / g or more 3cm 3 / g or less.

[0017] According to the ninth aspect of the present invention, in the aforementioned silica particles, the nitrogen-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.

[0018] According to a 10th aspect of the present invention, the silica particles comprise: silica master particles; and a structure covering at least a portion of the surface of the silica master particles, the structure being composed of a reaction product of a trifunctional silane coupling agent, and the structure having a nitrogen-containing compound adsorbed in at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

[0019] According to the eleventh aspect of the present invention, a method for manufacturing the above-mentioned silica particles is provided, comprising the following steps:

[0020] The first step involves forming a structure composed of the reaction product of a trifunctional silane coupling agent on at least a portion of the surface of the silica master particle; and

[0021] The second step involves adsorbing a nitrogen-containing compound into at least a portion of the pores of the reaction product of the aforementioned trifunctional silane coupling agent.

[0022] The effects of the invention

[0023] According to the first embodiment described above, a silica particle is provided, and in the silica particle containing a nitrogen-containing compound, a cross-polarized magic angle rotation (CP / MAS) method is used. 29In Si solid-state nuclear magnetic resonance (NMR) spectra, the ratio C / D of the integral value C of the signal observed in the range of chemical shift from -50 ppm to -75 ppm to the integral value D of the signal observed in the range of chemical shift from -90 ppm to -120 ppm is less than 0.10 or greater than 0.75; compared with the case where the amount of nitrogen-containing compound extracted using ammonia / methanol mixed solution is less than 0.1% by mass or the amount of nitrogen-containing compound extracted using water is less than Y / X < 0.3, the charge distribution during charging is narrow.

[0024] According to the second or third embodiment described above, a silica particle is provided, wherein the silica particle contains a nitrogen-containing compound, and the cross-polarized magic angle rotation (CP / MAS) method is used. 29 In Si solid-state nuclear magnetic resonance (NMR) spectra, the ratio C / D of the integral value C of the signal observed in the range of chemical shift from -50 ppm to -75 ppm to the integral value D of the signal observed in the range of chemical shift from -90 ppm to -120 ppm is less than 0.10 or greater than 0.75; compared with the case where the extraction amount X of nitrogen-containing compounds extracted using ammonia / methanol mixed solution is less than 0.1% by mass or the extraction amount X of nitrogen-containing compounds extracted using water does not satisfy the formula: Y / X < 0.3, even if the number average particle size is 10 nm to 200 nm and the particle size distribution is 1.1 to 2.0 or 10 nm to 80 nm, the charge distribution during charging is narrow.

[0025] According to the fourth or fifth embodiment described above, a silica particle is provided, wherein the silica particle contains a nitrogen-containing compound, and the cross-polarized magic angle rotation (CP / MAS) method is used. 29 In Si solid-state nuclear magnetic resonance (NMR) spectra, the ratio C / D of the integral value C of the signal observed in the range of chemical shift from -50 ppm to -75 ppm to the integral value D of the signal observed in the range of chemical shift from -90 ppm to -120 ppm is less than 0.10 or greater than 0.75; compared with the case where the extraction amount X of nitrogen-containing compounds extracted using ammonia / methanol mixed solution is less than 0.1% by mass or the extraction amount X of nitrogen-containing compounds extracted using water does not satisfy the formula Y / X < 0.3, even if the average roundness is 0.60 to 0.96 or 0.70 to 0.92, the charge distribution during charging is narrow.

[0026] According to the sixth scheme mentioned above, a silicon dioxide particle is provided with a volume resistivity higher than 1.0 × 10⁻⁶. 11.5 Compared to the case of Ωcm, the charge distribution during charging is narrower.

[0027] According to the seventh scheme above, a silica particle is provided that has a narrow charge distribution during charging compared to the case where Ra / Rb is less than 0.01 when the volume resistivity before and after firing at 350°C is set as Ra and Rb, respectively.

[0028] According to the eighth scheme mentioned above, a silica particle is provided, wherein when the pore volume (within 1 nm to 50 nm, determined by nitrogen adsorption method before and after firing at 350 °C) is set as A and B respectively, B / A is less than 1.2 or B is less than 0.2 cm. 3 Compared to the case of / g, the charge distribution during charging is narrower.

[0029] According to the ninth embodiment described above, a silica particle is provided, wherein the silica particle contains a nitrogen-containing compound, and the cross-polarized magic angle rotation (CP / MAS) method is used. 29 In Si solid-state nuclear magnetic resonance (NMR) spectra, the ratio C / D of the integral value C of the signal observed in the range of chemical shift from -50 ppm to -75 ppm to the integral value D of the signal observed in the range of chemical shift from -90 ppm to -120 ppm is less than 0.10 or greater than 0.75; compared with the case where the amount of nitrogen-containing compound X extracted using an ammonia / methanol mixed solution is less than 0.1% by mass or the amount of nitrogen-containing compound X extracted using water extract does not satisfy the formula: Y / X < 0.3, and when the nitrogen-containing compound contains at least one of the group consisting of quaternary ammonium salts, primary amine compounds, secondary amine compounds, tertiary amine compounds, amide compounds, imine compounds, and nitrile compounds, the charge distribution during charging is narrow.

[0030] According to the aforementioned tenth embodiment, a silica particle is provided, wherein the silica particle contains a nitrogen-containing compound, and the cross-polarized magic angle rotation (CP / MAS) method is used. 29In Si solid-state nuclear magnetic resonance (NMR) spectra, the ratio C / D of the integral value C of the signal observed in the range of chemical shift -50 ppm to 75 ppm to the integral value D of the signal observed in the range of chemical shift -90 ppm to 120 ppm is less than 0.10 or greater than 0.75; compared to cases where the extraction amount X of nitrogen-containing compounds extracted using an ammonia / methanol mixed solution is less than 0.1% by mass or the extraction amount X of nitrogen-containing compounds extracted using water does not satisfy the formula: Y / X < 0.3, the silica particles in this scheme have a structure consisting of silica master particles and at least a portion of the surface of the silica master particles coated with silica master particles, the structure being composed of the reaction product of a trifunctional silane coupling agent, and where at least a portion of the pores of the reaction product of the trifunctional silane coupling agent adsorbs nitrogen-containing compounds, the silica particles exhibit a narrow charge distribution during charging.

[0031] According to the 11th embodiment above, a method for manufacturing silica particles is provided, which, compared with the method for manufacturing silica particles by adsorbing nitrogen-containing compounds onto silica master particles whose surface does not have a structure composed of reaction products of trifunctional silane coupling agents, has a narrow charge distribution during charging. Detailed Implementation

[0032] The embodiments of the present invention will now be described. These descriptions and examples are for illustrative purposes only and do not limit the scope of the embodiments.

[0033] In this specification, the upper or lower limit of a numerical range described in stages can be replaced with the upper or lower limit of other numerical ranges described in other stages. Furthermore, the upper or lower limit of the numerical range described in this invention can be replaced with the values ​​shown in the embodiments.

[0034] Each component in this instruction manual may contain two or more corresponding substances.

[0035] In this specification, when referring to the amount of each component in the composition, if there are two or more substances corresponding to each component in the composition, it refers to the total amount of the two or more substances present in the composition unless otherwise stated.

[0036] Silica particles

[0037] The silica particles of this embodiment contain nitrogen-containing compounds and satisfy the following characteristics (1) and (2).

[0038] Feature (1): Based on the cross-polarization magic angle rotation (CP / MAS) method 29In Si solid-state nuclear magnetic resonance (NMR) spectra (hereinafter also referred to as "Si-CP / MAS NMR spectra"), the ratio C / D of the integral value C of the signal observed in the chemical shift range of -50 ppm to -75 ppm 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.

[0039] Feature (2): The amount of nitrogen-containing compounds X extracted using ammonia / methanol mixed solution is more than 0.1% by mass, and the amount of nitrogen-containing compounds X extracted using water and the amount of nitrogen-containing compounds Y extracted using water satisfy the formula: Y / X<0.3.

[0040] The silica particles in this embodiment, due to the above-described configuration, exhibit a narrow charge distribution during charging. The reason for this is presumably as follows.

[0041] Silica particles have a high negative charge, which may lead to overcharging. Therefore, the charge distribution becomes wider. This tendency to overcharge and widen the charge distribution is especially pronounced in low-temperature, low-humidity environments.

[0042] For example, in powder coating, powder coating that has been charged by methods such as contact charging or corona discharge is sprayed out and electrostatically adhered to the object to be coated, and then a coating film is formed by heating.

[0043] However, when silica particles that are charged with a wide charge distribution are used as additives in powder coatings, the charge distribution of the powder coating will be biased, making it difficult to achieve uniform adhesion of the powder coating on the substrate.

[0044] On the other hand, when silica particles adsorb nitrogen-containing compounds, excessive negative charging of the silica particles during charging can be suppressed. Nitrogen-containing compounds have positive charges, and the silica particles adsorbed with nitrogen-containing compounds counteract excessive negative charging, thus suppressing excessive negative charging.

[0045] However, nitrogen-containing compounds are positively charged, and when they are adsorbed onto the outermost surface of silica particles, the charge distribution of both negative and positive charges widens. Therefore, it is preferable that the nitrogen-containing compounds exist not on the surface of the silica particles, but rather in the pores or the like.

[0046] Therefore, in the silica particles of this embodiment, the ratio C / D of the integral value C of the signal observed in the Si-CP / MAS NMR spectrum in the range of chemical shift -50ppm to 75ppm to the integral value D of the signal observed in the range of chemical shift -90ppm to 120ppm is within the above range.

[0047] An integral value of a signal satisfying the above range indicates that such a structure (e.g., SiO2) has formed on the surface of at least a portion of the silica particles. 2 / 3 CH3 layer: This structure can adsorb sufficient amounts of nitrogen-containing compounds, has a low density, and is composed of the reaction products of a trifunctional silane coupling agent. The structure composed of the reaction products of the trifunctional silane coupling agent has a low density and forms a fine porous shape that easily adsorbs nitrogen-containing compounds.

[0048] Furthermore, by reducing the amount of OH groups that hinder the adsorption of nitrogen-containing compounds, it is easier for the structure composed of the reaction products of the trifunctional silane coupling agent to adsorb a sufficient amount of nitrogen-containing compounds, thus increasing the adsorption amount.

[0049] Furthermore, in the silica particles of this embodiment, the extraction amount X of the nitrogen-containing compound extracted using an ammonia / methanol mixed solution is 0.1% by mass or more, and the extraction amount X of the nitrogen-containing compound and the extraction amount Y of the nitrogen-containing compound extracted using water satisfy the formula: Y / X<0.3.

[0050] That is, as nitrogen-containing compounds, nitrogen-containing compounds that are difficult to dissolve in water, i.e., that do not easily adsorb moisture from the air, are used.

[0051] In silica particles containing nitrogen-containing compounds, if the nitrogen-containing compounds adsorb moisture, the charge distribution becomes wider, and the nitrogen-containing compounds easily detach from the silica particles.

[0052] However, for silica particles containing nitrogen-containing compounds that do not easily adsorb moisture from the air, even in the presence of a large amount of moisture in the air (even under high temperature and high humidity conditions), the charge distribution does not easily broaden, and the nitrogen-containing compounds do not easily detach, thus maintaining a narrow charge distribution.

[0053] Therefore, it can improve the narrowing of the charge distribution brought about by nitrogen-containing compounds.

[0054] Based on the above, it can be inferred that the charge distribution of the silica particles in this embodiment becomes narrower when they are charged.

[0055] Furthermore, for example, when the silica particles of this embodiment are used as an additive for powder coatings, the charge deviation of the powder coating is not easily caused even in low temperature and low humidity environments, and the amount of powder coating adhering to the coated object can be made uniform.

[0056] Furthermore, in the silica particles of this embodiment, when the pore volumes with pore diameters of 1 nm to 50 nm, determined by the nitrogen adsorption method before and after firing at 350°C, are respectively set as A and B, it is preferable that B / A is 1.2 to 5 and B is 0.2 cm.3 / g or more 3cm 3 / g or less.

[0057] Here, in the following text, "the pore volume A with a pore diameter of more than 1 nm and less than 50 nm, obtained from the pore distribution curve by nitrogen adsorption method before firing at 350℃" is also referred to as "pore volume A before firing at 350℃".

[0058] On the other hand, "the pore volume B with a pore diameter of more than 1 nm and less than 50 nm, obtained from the pore distribution curve by nitrogen adsorption method after firing at 350℃" is also called "pore volume B after firing at 350℃".

[0059] The micropore volume B after firing at 350℃ refers to the micropore volume after the nitrogen-containing compounds that were adsorbed onto the silica particles and partially blocked the micropores have volatilized. Therefore, B / A is between 1.2 and 5, and B is 0.2 cm⁻¹. 3 / g or more 3cm 3 When the concentration is below a certain value (e.g.), it indicates that a sufficient amount of nitrogen-containing compound is adsorbed into at least a portion of the fine pores of the silica particles. This can thus improve the narrowing of the charge distribution caused by the nitrogen-containing compound.

[0060] The silica particles of this embodiment will now be described in detail.

[0061] (CP / MAS NMR spectrum)

[0062] In Si-CP / MAS NMR spectra, the ratio C / D of the integral value C of the signal observed in the range of chemical shift -50ppm to 75ppm to the integral value D of the signal observed in the range of chemical shift -90ppm to 120ppm is 0.10 to 0.75 or less. From the perspective of narrowing the charge distribution, it is preferably 0.12 to 0.45 or less, and more preferably 0.15 to 0.40 or less.

[0063] From the perspective of narrowing the charge distribution, assuming the integral value of all signals in the Si-CP / MAS NMR spectrum is 100%, the proportion (signal ratio) of the integral value C of the signal observed in the range of chemical shift from -50 ppm to 75 ppm is preferably 5% or more, more preferably 7% or more. It should be noted that the upper limit of the proportion of the integral value C of the signal is, for example, 60% or less.

[0064] The Si-CP / MAS NMR spectra were obtained by nuclear magnetic resonance spectrophotometry under the following conditions.

[0065] • Spectrometer: AVENCE300 (manufactured by Brunker)

[0066] • Resonant frequency: 59.6MHz

[0067] • Measurement nucleus: 29 Si

[0068] • Measurement method: CPMAS (using Bruker's solid-state crosspolarized magic angle spinning NMR cp.av)

[0069] Waiting time: 4 seconds

[0070] • Contact time: 8 milliseconds

[0071] Points earned: 2048

[0072] • Measurement temperature: room temperature (actual value 25℃)

[0073] • Observation center frequency: -3975.72Hz

[0074] MAS speed: 7.0mm-6kHz

[0075] • Reference material: hexamethylcyclotrisiloxane

[0076] (Extraction amount of nitrogen-containing compounds)

[0077] The extraction amount X of nitrogen-containing compounds extracted using an ammonia / methanol mixed solution is greater than 0.1% by mass, and the extraction amount X of nitrogen-containing compounds and the extraction amount Y of nitrogen-containing compounds extracted using water satisfy the equation: Y / X < 0.3.

[0078] The extraction amount X of nitrogen-containing compounds is preferably 50% by mass or more. Regarding the upper limit of the extraction amount X of nitrogen-containing compounds, considering that the solution does not easily penetrate into the pores due to surface tension and that some of the nitrogen-containing compounds remain undissolved, this upper limit is, for example, 95% by mass or less.

[0079] The ratio of the amount of nitrogen-containing compound extracted, X, to the amount of nitrogen-containing compound extracted, Y, "Y / X", is preferably less than 0.3, and more preferably less than 0.15. Ideally, the lower limit of the ratio "Y / X" is 0, but since the measurement error range of X and Y is observed to be within ±1%, this lower limit is, for example, 0.01 or more.

[0080] Here, the extraction amounts X and Y of nitrogen-containing compounds were determined as follows.

[0081] First, the target material—silica particles—is analyzed using a thermogravimetric-mass spectrometer (e.g., a gas chromatograph-mass spectrometer manufactured by Netch Japan Co., Ltd.) at 400°C under certain conditions. The mass fraction of compounds formed by the covalent bonding of hydrocarbons with at least one carbon atom and nitrogen atoms relative to the silica particles is determined and is taken as W1.

[0082] On the other hand, 1 part by mass of the analyte—silica particles—was added to 30 parts by mass of an ammonia / methanol solution (manufactured by Sigma-Aldrich, ammonia / methanol mass ratio = 1 / 5.2) at a liquid temperature of 25°C. After ultrasonic treatment for 30 minutes, silica powder and extract were separated. The separated silica particles were dried in a vacuum dryer at 100°C for 24 hours. The mass fraction of compounds composed of hydrocarbons with at least one carbon atom covalently bonded to nitrogen atoms relative to silica particles was determined by thermogravimetric-mass spectrometry at 400°C under certain conditions, and this fraction was taken as W2.

[0083] The extraction amount X of nitrogen-containing compounds was then calculated using the following formula.

[0084] Equation: X = W1 - W2

[0085] In addition, 1 part by mass of the analyte—silica particles—was added to 30 parts by mass of water at a liquid temperature of 25°C. After ultrasonic treatment for 30 minutes, the silica particles and extract were separated. The separated silica particles were dried at 100°C for 24 hours using a vacuum dryer. The mass fraction of compounds composed of hydrocarbons with at least one carbon atom covalently bonded to nitrogen atoms relative to the silica particles was determined using thermogravimetric-mass spectrometry at 400°C under certain conditions. This fraction was taken as W3.

[0086] The extraction amount Y of nitrogen-containing compounds was then calculated using the following formula.

[0087] Equation: Y = W1 - W3

[0088] (Volume of fine pores)

[0089] In the silica particles of this embodiment, the ratio of the pore volume B after firing at 350°C to the pore volume A before firing at 350°C, B / A, is 1.2 or more and 5 or less. From the perspective 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.

[0090] The pore volume B after firing at 350℃ is 0.2 cm³. 3 / g or more 3cm 3 For a charge distribution of 0.3 cm or less, from the perspective of narrowing the charge distribution, 0.3 cm is preferred. 3 / g or more 1.8cm 3 / g or less, more preferably 0.6cm 3 / g or more 1.5cm 3 / g or less.

[0091] The firing process at 350℃ is specifically implemented as follows.

[0092] The silica particles of the test subject were heated to 350°C at a heating rate of 10°C / min under nitrogen atmosphere and held at 350°C for 3 hours. They were then cooled to room temperature (25°C) at a cooling rate of 10°C / min.

[0093] The pore volume was measured as follows.

[0094] First, the target material—silica particles—is cooled to liquid nitrogen temperature (-196°C), and nitrogen gas is introduced. The adsorption capacity is determined by constant volume method or gravimetric method. The pressure of the introduced nitrogen gas is slowly increased, and the adsorption capacity of nitrogen is plotted against various equilibrium pressures to create an adsorption isotherm. From this adsorption isotherm, the pore size distribution curve, with the vertical axis representing frequency and the horizontal axis representing pore diameter, is calculated using the BJH method.

[0095] Next, the cumulative pore volume distribution, with the vertical axis representing volume and the horizontal axis representing pore diameter, is obtained from the pore diameter distribution curve. From the obtained cumulative pore volume distribution, the pore volume in the range of pore diameter from 1 nm to 50 nm is accumulated and taken as the "pore volume with pore diameter from 1 nm to 50 nm".

[0096] (Composition of silica particles)

[0097] The silica particles in this embodiment contain nitrogen-containing compounds.

[0098] Specifically, the silica particles of this embodiment can be exemplified by silica master particles and structures in which at least a portion of the surface of the silica master particle is coated with a reaction product of a trifunctional silane coupling agent, and further, at least a portion of the reaction product is adsorbed with a nitrogen-containing compound. By forming the above structure, the micropore volume characteristics and the Si-CP / MASNMR spectral characteristics can be controlled. Furthermore, the degree of hydrophobicity and the amount of OH groups, described later, can also be controlled.

[0099] In addition, the silica particles of this embodiment may also have a hydrophobic structure on the surface of the above-described structure.

[0100] -Silica masterbatch-

[0101] Silica master particles are silica particles whose surface at least a portion is the object of forming the following structure, which is composed of the reaction product of a trifunctional silane coupling agent, and in which at least a portion of the pores of the reaction product of the trifunctional silane coupling agent is adsorbed with nitrogen-containing compounds.

[0102] Examples of silica master particles include dry silica particles and wet silica particles.

[0103] Examples of dry silica particles include: combustion silica (gas-phase silica) obtained by burning silane compounds, and detonation silica obtained by explosively burning metallic silicon powder.

[0104] Examples of wet silica particles include: wet silica particles obtained by neutralization reaction of sodium silicate with inorganic acid (precipitated silica synthesized / aggregated under alkaline conditions, and gel silica particles synthesized / aggregated under acidic conditions); colloidal silica particles (silica sol particles) obtained by making acidic silicic acid alkaline and polymerizing it; and sol-gel silica particles obtained by hydrolysis of organosilane compounds (e.g., alkoxysilanes).

[0105] Among these, sol-gel silica particles are preferred as silica master particles from the perspective of narrowing the charge distribution.

[0106] -Reaction products of 3-functionalized silane coupling agents-

[0107] The adsorption structure formed by the reaction products of the trifunctional silane coupling agent is low-density and has a high affinity for nitrogen-containing compounds. Therefore, it easily adsorbs nitrogen-containing compounds deep into the pores, increasing the adsorption amount (i.e., content) of these compounds. By attaching positively charged nitrogen-containing compounds to the negatively charged silica surface, an effect of counteracting excessive negative charge can be achieved. Furthermore, since the nitrogen-containing compounds are adsorbed into the low-density structure rather than on the outermost surface of the silica particles, excessive positive charge and a broadened charge distribution are prevented. By only counteracting excessive negative charge, the narrowing of the charge distribution can be further improved.

[0108] Examples of reaction products of 3-functional silane coupling agents include: OR in the following general formula (TA). 2 The reaction product after being replaced with an OH group; OR 2 The reaction products formed by the condensation of compounds after being replaced with OH groups; OR 2 The reaction products are formed by the condensation of the compound, after being replaced with OH groups, and the SiOH groups of silica particles. Additionally, the reaction products of trifunctional silane coupling agents include those containing OR groups.2 Reactions formed by complete or partial substitution, or by complete or partial condensation polymerization.

[0109] 3-functional silane coupling agents are non-nitrogen-containing compounds that do not contain N (nitrogen).

[0110] Specifically, as a trifunctional silane coupling agent, the trifunctional silane coupling agent represented by the following general formula (TA) can be cited.

[0111] General formula (TA): R 1 -Si(OR 2 )3

[0112] In the general formula (TA), R 1 R represents a saturated or unsaturated aliphatic hydrocarbon group with 1 to 20 carbon atoms, or an aromatic hydrocarbon group with 6 to 20 carbon atoms. 2 Represents a halogen atom or an alkoxy group. Two or more R groups 2 They can be the same group or different groups.

[0113] R 1 The aliphatic hydrocarbon group can be any of straight-chain, branched, and cyclic, preferably straight-chain or branched. The aliphatic hydrocarbon group preferably has 1 to 20 carbon atoms, more preferably 1 to 18 carbon atoms, even more preferably 1 to 12 carbon atoms, and even more preferably 1 to 10 carbon atoms. The aliphatic hydrocarbon group can be any of saturated and unsaturated groups, preferably saturated aliphatic hydrocarbon groups, and more preferably alkyl groups.

[0114] Examples of saturated aliphatic hydrocarbon groups include straight-chain alkyl groups (methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, hexadecyl, eicosyl, etc.), branched-chain alkyl groups (isopropyl, isobutyl, isopentyl, neopentyl, 2-ethylhexyl, tert-butyl, tert-pentyl, isopentadecanyl, etc.), and cyclic alkyl groups (cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, tricyclodecyl, norbornyl, adamantyl, etc.).

[0115] Examples of unsaturated aliphatic hydrocarbon groups include alkenyl (ethenyl group, 1-propenyl, 2-propenyl, 2-butenyl, 1-butenyl, 1-hexenyl, 2-dodecenyl, pentenyl, etc.) and alkynyl (ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 3-hexynyl, 2-dodecynyl, etc.).

[0116] R 1The aromatic hydrocarbon group represented preferably has 6 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, even more preferably 6 to 12 carbon atoms, and even more preferably 6 to 10 carbon atoms.

[0117] Examples of aromatic hydrocarbon groups include phenylene, biphenylene, triphenylene, naphthyl, and anthracene.

[0118] As R 2 Examples of halogen atoms include fluorine, chlorine, bromine, and iodine. Chlorine, bromine, or iodine atoms are preferred as halogen atoms.

[0119] As R 2 The alkoxy group referred to can be alkoxy groups with 1 to 10 carbon atoms (preferably 1 to 8, more preferably 1 to 4). Examples of alkoxy groups include methoxy, ethoxy, isopropoxy, tert-butoxy, n-butoxy, n-hexyloxy, 2-ethylhexyloxy, and 3,5,5-trimethylhexyloxy. Alkoxy groups also include substituted alkoxy groups. Examples of substituents that can be substituted on the alkoxy group include halogen atoms, hydroxyl groups, amino groups, alkoxy groups, amide groups, and carbonyl groups.

[0120] The preferred trifunctional silane coupling agent represented by the general formula (TA) is R. 1 It is a saturated aliphatic hydrocarbon group with 1 to 20 carbon atoms, R 2 It is a trifunctional silane coupling agent with halogen or alkoxy atoms.

[0121] Examples of trifunctional silane coupling agents include:

[0122] 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 (the above are R...) 1 (Compounds consisting of unsubstituted aliphatic hydrocarbon groups or unsubstituted aromatic hydrocarbon groups);

[0123] 3-Epoxypropoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-epoxypropoxypropylmethyldimethoxysilane (the above are R...) 1Compounds containing substituted aliphatic or aromatic hydrocarbon groups; etc.

[0124] 3-functional silane coupling agents can be used alone or in combination of two or more.

[0125] Among these, from the perspective of narrowing the charge distribution, alkyltrialkoxysilanes are preferred as trifunctional silane coupling agents, and R in the general formula (TA) is more preferred. 1 alkyl groups, R, representing 1 to 20 carbon atoms (preferably 1 to 15 carbon atoms) 2 Alkyltrialkoxysilanes are alkyl groups with 1 to 2 carbon atoms.

[0126] Regarding the amount of the structure formed by the reaction product of the trifunctional silane coupling agent, from the perspective of narrowing the charge distribution, it is preferably 5.5% to 30% by mass and more preferably 7% to 22% by mass relative to the silica particles.

[0127] -Nitrogen-containing compounds-

[0128] Nitrogen-containing compounds are those other than ammonia and compounds that are in a gaseous state at temperatures above -200°C and below 25°C.

[0129] Nitrogen-containing compounds are preferably adsorbed into at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

[0130] Examples of nitrogen-containing compounds include 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.

[0131] Examples of primary amine compounds include phenethylamine, toluidine, catecholamine, and 2,4,6-trimethylaniline.

[0132] Examples of secondary amine compounds include dibenzylamine, 2-nitrodiphenylamine, and 4-(2-octylamino)diphenylamine.

[0133] Examples of tertiary amine compounds include 1,8-bis(dimethylamino)naphthalene, N,N-dibenzyl-2-aminoethanol, and N-benzyl-N-methylethanolamine.

[0134] Examples of amide compounds include N-cyclohexyl-p-toluenesulfonamide, 4-acetamide-1-benzylpiperidine, and N-hydroxy-3-[1-(phenylthio)methyl-1H-1,2,3-triazol-4-yl]benzamide.

[0135] Examples of imine compounds include diphenylmethane imine, 2,3-bis(2,6-diisopropylphenylimino)butane, and N,N'-(ethane-1,2-diimide)bis(2,4,6-trimethylaniline).

[0136] Examples of nitrile compounds include 3-indoleacetonitrile, 4-[(4-chloro-2-pyrimidinyl)amino]benzonitrile, and 4-bromo-2,2-diphenylbutyronitrile.

[0137] Among these, from the perspective of narrowing the charge distribution, quaternary ammonium salts are preferred as nitrogen-containing compounds.

[0138] Quaternary ammonium salts can be used alone or in combination with two or more.

[0139] There are no particular restrictions on quaternary ammonium salts; any known quaternary ammonium salt can be used.

[0140] From the perspective of narrowing the charge distribution, quaternary ammonium salts preferably include compounds represented by the general formula (AM). A single compound represented by the general formula (AM) may be used, or two or more may be used in combination.

[0141]

[0142] General formula (AM)

[0143] In the general formula (AM), R 1 R 2 R 3 and R 4 Each independently represents a hydrogen atom or an alkyl, aralkyl, or aryl group with or without substituents, X - This represents an anion. Wherein, R... 1 R 2 R 3 and R 4 At least one of them represents an alkyl, aralkyl, or aryl group, with or without substituents. Additionally, R 1 R 2 R 3 and R 4 Two or more of them can be linked to form aliphatic rings, aromatic rings or heterocycles.

[0144] As R 1 ~R 4 Examples of alkyl groups include straight-chain alkyl groups with 1 to 20 carbon atoms and branched alkyl groups with 3 to 20 carbon atoms.

[0145] Examples of linear alkyl groups with 1 to 20 carbon atoms include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecanyl, and n-hexadecyl.

[0146] Examples of branched alkyl groups with 3 to 20 carbon atoms include isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, sec-hexyl, tert-hexyl, isohexyl, sec-heptyl, tert-heptyl, isooctyl, sec-octyl, tert-octyl, isononyl, sec-nonyl, tert-nonyl, isodel, sec-decyl, tert-decyl, etc.

[0147] Of the above, as R 1 ~R 4 The alkyl group represented is preferably an alkyl group with 1 to 15 carbon atoms, such as methyl, ethyl, butyl, or tetradecyl.

[0148] As R 1 ~R 4 The aralkyl group to be represented can be an aralkyl group with 7 to 30 carbon atoms.

[0149] Examples of aralkyl groups with 7 to 30 carbon atoms include benzyl, phenylethyl, phenylpropyl, 4-phenylbutyl, phenylpentyl, phenylhexyl, phenylheptyl, phenyloctyl, phenylnonyl, naphthylmethyl, naphthylethyl, anthraceneylmethyl, and phenyl-cyclopentylmethyl.

[0150] Of the above, as R 1 ~R 4 The aralkyl group represented is preferably an aralkyl group with 7 to 15 carbon atoms, such as benzyl, phenylethyl, phenylpropyl, or 4-phenylbutyl.

[0151] As R 1 ~R 4 Examples of aryl groups that can be represented include those with 6 to 20 carbon atoms.

[0152] Examples of aryl groups with 6 to 20 carbon atoms include phenyl, pyridyl, and naphthyl.

[0153] Of the above, as R 1 ~R 4 The aryl group represented is preferably an aryl group with 6 to 10 carbon atoms, such as a phenyl group.

[0154] As X - The anions represented can be organic anions or inorganic anions.

[0155] Examples of organic anions include polyfluoroalkyl sulfonate ions, polyfluoroalkyl carboxylate ions, tetraphenylborate ions, aromatic carboxylate ions, and aromatic sulfonate ions (such as 1-naphthol-4-sulfonate ions).

[0156] As an inorganic anion, molybdate ion (MoO4) can be cited as an example. 2- Mo2O7 2- Mo3O 10 2- Mo4O 13 2- Mo7O 24 2- Mo8O 26 4- etc.), OH - F - Fe(CN)6 3- Cl - ,Br - NO2 - NO3 - CO3 2- PO4 3- SO4 2- wait.

[0157] In the general formula (AM), R 1 R 2 R 3 and R 4 Two or more elements can be interconnected to form a loop. As R 1 R 2 R 3 and R 4 A ring formed by the interconnection of two or more carbon atoms can be exemplified by alicyclic rings with 2 to 20 carbon atoms and heterocyclic amines with 2 to 20 carbon atoms.

[0158] In compounds represented by the general formula (AM), R 1 R 2 R 3 and R 4 Each can have a substituent independently. Examples of substituents include nitrile, carbonyl, ether, amide, siloxane, silyl, and silanealkoxy groups.

[0159] R 1 R 2 R 3 and R 4 Preferably, each of the following is independently represented: alkyl group with 1 to 16 carbon atoms, aralkyl group with 7 to 10 carbon atoms, or aryl group with 6 to 20 carbon atoms.

[0160] Among these, from the perspective of narrowing the charge distribution, the total number of carbon atoms in the compound represented by the general formula (AM) is preferably 18 to 35, more preferably 20 to 32.

[0161] The following shows compounds represented by the general formula (AM) excluding X. - Examples of structures other than those described herein are provided, but this implementation is not limited to them.

[0162]

[0163] From the perspective of narrowing the charge distribution and maintaining the charge distribution, the nitrogen-containing compound is preferably a nitrogen-containing compound containing molybdenum, preferably selected from at least one of the group consisting of a quaternary ammonium salt containing molybdenum (especially a quaternary ammonium salt containing molybdenum); and a mixture of both quaternary ammonium salt and a metal oxide containing molybdenum.

[0164] The difference between "quaternary ammonium salt containing molybdenum" and "quaternary ammonium salt containing molybdenum" is that the former refers to a quaternary ammonium salt in which molybdenum has entered a certain part of the structure, while the latter refers to a quaternary ammonium salt in which the counter ion contains molybdenum.

[0165] When nitrogen compounds contain molybdenum, the activity of nitrogen is enhanced. Even if the nitrogen-containing compound exists within the pores of silica particles rather than on the outermost surface, it can still exhibit a moderate positive charge characteristic of nitrogen. Consequently, the charge distribution during charging becomes narrower, and the maintenance of the charge distribution is also more easily improved.

[0166] In particular, in quaternary ammonium salts containing molybdenum, the binding between the molybdenum anion (as anion) and the quaternary ammonium cation (as cation) is strong, thus improving the maintenance of charge distribution.

[0167] Examples of quaternary ammonium salts containing molybdenum include [N + (CH)3(C 14 C 29 )2]4Mo8O 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]2MoO4 2- wait.

[0168] Examples of 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.), and other complex oxides (Bi₂O₃·2MoO₃, γ-Ce₂Mo₃O₃). 13 wait).

[0169] -Detection and content of nitrogen-containing compounds-

[0170] When the silica particles of this embodiment are heated in a temperature range of 300°C to 600°C, nitrogen-containing compounds are detected. Specifically, for example, as described below.

[0171] In the detection of nitrogen-containing compounds, a furnace-type falling-descent pyrolysis gas chromatography-mass spectrometry (GC-MS) instrument is used, employing He as the carrier gas. Nitrogen-containing compounds can be detected under an inert gas atmosphere at a thermal decomposition temperature between 300°C and 600°C. Specifically, 0.1 mg to 10 mg of silica particles can be introduced into the pyrolysis GC-MS instrument, and the presence of nitrogen-containing compounds can be confirmed by the MS mass spectrum of the detected peaks. Examples of components generated by the thermal decomposition of silica particles containing nitrogen-containing compounds include amines or aromatic nitrogen compounds represented by the following general formula (N), ranging from primary to tertiary amines.

[0172] In the following general formula (N), R N1 ~R N3 Each independently represents a hydrogen atom or an alkyl, aralkyl, or aryl group with or without substituents, R N1 ~R N3 R of general formula (AM) 1 R 2 and R 3 They have the same meaning.

[0173] For example, in the case of nitrogen-containing compounds that are quaternary ammonium salts, a portion of the side chain is released through thermal decomposition at 600°C, and tertiary amines are detected.

[0174]

[0175] General formula (N)

[0176] From the perspective of narrowing the charge distribution, the content of nitrogen-containing compound relative to silicon dioxide particles, in terms of N atoms, is preferably 0.008% to 0.45% by mass, more preferably 0.015% to 0.20% by mass, and even more preferably 0.018% to 0.10% by mass.

[0177] The content of nitrogen-containing compounds, converted from N atoms, was determined as follows.

[0178] The presence of nitrogen, i.e., the N / Si ratio, was determined using an oxygen and nitrogen analysis device (such as the EMGA-920 manufactured by Horiba Seisakusho) with a cumulative time of 45 seconds. It should be noted that, as a sample pretreatment, impurities such as ammonia were removed from the silica particles by drying them in a vacuum dryer at 100°C for more than 24 hours.

[0179] Here, when using a nitrogen-containing compound that contains molybdenum as the nitrogen-containing compound, from the perspective of narrowing the charge distribution, the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si) as determined by fluorescence X-ray analysis 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.

[0180] From the perspective of narrowing the charge distribution, the preferred net intensity of molybdenum is 5 kcps to 75 kcps, 7 kcps to 50 kcps, 8 kcps to 55 kcps, or 10 kcps to 40 kcps.

[0181] The net strength of molybdenum and silicon was measured as follows.

[0182] Approximately 0.5 g of silica particles were compressed using a compression molding machine under a load of 6 t for 60 seconds to produce an ingot with a diameter of 50 mm and a thickness of 2 mm. This ingot was then used as a sample for qualitative and quantitative elemental analysis using a scanning fluorescence X-ray analyzer (XRF-1500, manufactured by Shimadzu Corporation) under the following conditions to determine the Net intensities (unit: kilo counts per second, kcps) for molybdenum and silicon.

[0183] • Tube voltage: 40kV

[0184] Tube current: 90mA

[0185] • Measurement area (analytical diameter): Diameter

[0186] • Measurement time: 30 minutes

[0187] • For cathode: rhodium

[0188] (Hydrophobic treatment structure)

[0189] Hydrophobicated structures are structures formed after the hydrophobic treatment agent has reacted.

[0190] As a hydrophobic treatment agent, organosilicon compounds are used, for example.

[0191] Examples of organosilicon compounds include:

[0192] Alkoxysilane compounds or halosilane compounds containing lower alkyl groups, such as methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, and trimethylmethoxysilane;

[0193] Vinyltrimethoxysilane, vinyltriethoxysilane, and other alkoxysilane compounds containing vinyl groups;

[0194] Alkoxysilane compounds with epoxy groups, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, and 3-epoxypropoxypropyltriethoxysilane.

[0195] Alkoxysilane compounds containing a styrene group, such as p-styrenetrimethoxysilane and p-styrenetriethoxysilane;

[0196] N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane and other alkoxysilane compounds containing aminoalkyl groups;

[0197] Alkoxysilane compounds containing isocyanate alkyl groups, such as 3-isocyanate propyltrimethoxysilane and 3-isocyanate propyltriethoxysilane;

[0198] Silazane compounds such as hexamethyldisilazane and tetramethyldisilazane; etc.

[0199] (Properties of silica particles)

[0200] -Hydrophobicity-

[0201] From the perspective of narrowing the charge distribution, the degree of hydrophobicity of the silica particles in this 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.

[0202] If the hydrophobicity of silica particles is less than 10%, the coating of the structure generated by the reaction based on the trifunctional silane coupling agent will be low, the content of nitrogen-containing compounds will be reduced, and the charge distribution will be more likely to become wider.

[0203] On the other hand, if the hydrophobicity of silica particles exceeds 60%, the density of the structure generated by the reaction based on the trifunctional silane coupling agent increases, the pores decrease, and the content of nitrogen-containing compounds decreases. Therefore, the charge distribution tends to broaden.

[0204] The hydrophobicity of the silica particles was determined as follows.

[0205] Add 0.2% by mass of silica particles (as the sample) to 50 ml of ion-exchanged water. While stirring with a magnetic stirrer, add methanol dropwise through a burette. Calculate the mass fraction of methanol in the methanol-water mixture at the endpoint when all the sample has settled, and use this fraction as the degree of hydrophobicity.

[0206] -Number mean particle size and number-size distribution index-

[0207] In this embodiment, the average particle size of the silica particles 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.

[0208] When the average particle size of silica particles is within the above range, the specific surface area is large and overcharging is easy to occur. However, in the silica particles of this embodiment, even if the average particle size is within the above range, the charge distribution can be narrowed.

[0209] In this embodiment, the number-size distribution index of silica particles is preferably 1.1 or more and 2.0 or less, more preferably 1.15 or more and 1.6 or less.

[0210] When the number and particle size distribution index of silica particles in this embodiment is within the above range, there are fewer coarse powders that tend to increase charge and fewer micro powders that tend to decrease charge, making it easier to achieve a narrower charge distribution.

[0211] Here, the number average particle size and number particle size distribution index of silica particles are determined as follows.

[0212] Silica particles were observed using a scanning electron microscope (SEM) at 40,000x magnification. The images of the observed silica particles were analyzed using WinRoof image processing software (manufactured by Mitani Corporation), and the equivalent circle diameter of at least 200 particles was determined. Subsequently, the cumulative distribution of the number of each particle was plotted from the small diameter side, and the particle diameter and number-average particle diameter at the cumulative 50% point from the small diameter side were determined.

[0213] Furthermore, the square root of the quotient obtained by dividing the cumulative particle size D84 (84% of the points from the small diameter side) by the cumulative particle size D16 (16% of the points) is defined as the "Number Particle Size Distribution Index" (GSD). That is, Number Particle Size Distribution Index (GSD) = (D84 / D16) 0.5 .

[0214] -Roundness-

[0215] In this embodiment, the average roundness of the silica particles 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.

[0216] If the average sphericity of the silica particles is within the above range, the specific surface area increases, making overcharging more likely. However, even if the average sphericity of the silica particles in this embodiment is within the above range, the charge distribution can be narrowed.

[0217] Here, the roundness of the silica particles is measured as follows.

[0218] Silica particles were observed at 40,000x magnification using a scanning electron microscope (SEM). The images of the observed silica particles were analyzed using WinRoof (manufactured by Mitani Corporation) image processing and analysis software. The roundness of at least 200 particles was determined, and the arithmetic mean was calculated to obtain the average roundness.

[0219] It should be noted that roundness is calculated using the following formula.

[0220] Roundness = circumference of equivalent circle / circumference = [2 × (Aπ)] 1 / 2 ] / PM

[0221] In the above formula, A represents the projected area, and PM represents the perimeter.

[0222] -Volume resistivity-

[0223] The volume resistivity of the silica particles in this embodiment (i.e., the volume resistivity before firing at 350°C) is preferably 1.0 × 10⁻⁶. 7 Ωcm or more 1.0×10 11.5 Ωcm or less, more preferably 1.0×10 8 Ωcm or more 1.0×10 11 Below Ωcm.

[0224] When the volume resistivity of the silica particles in this embodiment is within the above-mentioned range, the content of nitrogen-containing compounds is high, making it less prone to overcharging and easier to achieve a narrower charge distribution.

[0225] In the silica particles of this embodiment, when the volume resistivity of the silica particles before and after firing at 350°C is set as 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.

[0226] When Ra / Rb is within the above range, the content of nitrogen-containing compounds is high, overcharging is less likely to occur, and it is easier to achieve narrowing of the charge distribution.

[0227] Firing at 350℃ is carried out as described above.

[0228] On the other hand, the volume resistivity was measured as follows. It should be noted that the measurement environment was 20°C and 50% RH.

[0229] The test object—silica particles—was placed on a substrate with a thickness of approximately 1 mm to 3 mm in a 20 cm thick container. 2 A layer of silica particles is formed on the surface of the circular clamp of the electrode plate. A 20cm electrode plate, similar to the one described above, is then placed on top of it. 2 An electrode plate was used to sandwich a layer of silica particles. To eliminate the voids between the silica particles, a pressure of 0.4 MPa was applied to the electrode plate placed on the silica particle layer, and then the thickness (cm) of the silica particle layer was measured. The two electrodes above and below the silica particle layer were connected to an impedance analyzer (manufactured by Solartron Analytical) at a frequency of 10... -3 10 Hz and above 6 Measurements were taken below Hz to obtain the Nyquist curve. Assuming the existence of three resistive components—volume resistance, particle interface resistance, and electrode contact resistance—an equivalent circuit was fitted to calculate the volume resistance R.

[0230] The formula for calculating the volume resistivity (Ω·cm) of silica particles is shown below.

[0231] Formula: ρ=R / L

[0232] In the formula, ρ represents the volume resistivity of the silica particles (Ω·cm), R represents the bulk resistance (Ω), and L represents the thickness of the silica particle layer (cm).

[0233] (OH base amount)

[0234] In this embodiment, the silica particles preferably contain 0.2 OH radicals per nm, as determined by the Sears method. 2 The above 5.5 units / nm 2 From the perspective of narrowing the charge distribution, a more preferred value is 0.2 units / nm. 2 The above 4 / nm 2The following, and more preferably 0.2 per nm 2 The above 3 / nm 2 the following.

[0235] By fully forming a structure consisting of the reaction product of a trifunctional silane coupling agent on silica master particles, the amount of OH groups determined by the Sears method can be adjusted to the above range.

[0236] By reducing the amount of OH groups that hinder the adsorption of nitrogen-containing compounds to the aforementioned range, nitrogen-containing compounds can easily penetrate deep into the pores of silica particles (e.g., the pores of the adsorption layer described later). Consequently, the hydrophobic interactions with the nitrogen-containing compounds take effect, enhancing the adhesion to the silica particles. Therefore, the amount of nitrogen-containing compounds adsorbed increases. Furthermore, the nitrogen-containing compounds are less prone to detachment. Therefore, the narrowing of the charge distribution caused by the nitrogen-containing compounds can be improved, and the maintenance of this narrow charge distribution can also be enhanced.

[0237] In addition, by reducing the amount of OH radicals to the above range, the environmental dependence of the charge properties is reduced, and the narrowing of the charge distribution brought about by nitrogen-containing compounds can be easily achieved in any environment (especially in low-temperature and low-humidity environments where excessive negative charge is easily generated).

[0238] The OH radical content was determined using the Sears method. Specifically, as described below.

[0239] 1.5 g of silica particles were added to a mixture of 50 g of pure water and 50 g of ethanol, and stirred for 2 minutes using an ultrasonic homogenizer to prepare a dispersion. While stirring at 25°C, 1.0 g of 0.1 mol / L hydrochloric acid aqueous solution was added dropwise to obtain the test solution. The obtained test solution was placed in an automatic titration apparatus, and potentiometric titration was performed using 0.01 mol / L sodium hydroxide aqueous solution to generate a differential titration curve. The titration with the highest titer of 0.01 mol / L sodium hydroxide aqueous solution among the inflection points of the titration curve with a differential value above 1.8 was taken as E.

[0240] The surface silanol group density ρ (numbers / nm) of silica particles was calculated using the following formula. 2 ).

[0241] Formula: ρ=((0.01×E-0.1)×NA / 1000) / (M×S BET ×10 18 )

[0242] The details of the symbols in the formula are as follows.

[0243] E: Among the inflection points of the titration curve with a differential value above 1.8, the titer with the highest titer for a 0.01 mol / L sodium hydroxide aqueous solution is...

[0244] NA: Avogadro's constant

[0245] M: Quantity of silica particles (1.5g)

[0246] S BET Specific surface area of ​​silica particles (m²) 2 The specific surface area of ​​the silica particles (g) was determined by the nitrogen adsorption BET three-point method. It should be noted that the equilibrium relative pressure was 0.3.

[0247] Methods for manufacturing silica particles

[0248] An example of the method for manufacturing silica particles according to this embodiment includes the following steps:

[0249] The first step involves forming a structure composed of the reaction product of a trifunctional silane coupling agent on at least a portion of the surface of the silica master particle; and

[0250] The second step involves adsorbing nitrogen-containing compounds into at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

[0251] The method for manufacturing silica particles according to this embodiment may further include a third step of hydrophobizing silica master particles having a structure in which at least a portion of the surface of the silica master particles is coated after or during the second step, the structure is composed of a reaction product of a trifunctional silane coupling agent, and a nitrogen-containing compound is adsorbed into at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

[0252] The steps of the method for manufacturing silica particles according to this embodiment will be described in detail below.

[0253] [Preparation Steps]

[0254] First, the steps for preparing silica masterbatch will be explained.

[0255] As a preparatory step, for example, the following can be cited:

[0256] (i) The step of mixing a solvent containing alcohol with silica master particles to prepare a silica master particle suspension;

[0257] (ii) The step of granulating silica master particles by sol-gel method to obtain silica master particle suspension; etc.

[0258] Examples of silica master particles used in (i) above 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 the gas phase method, and fused silica particles.

[0259] The solvent containing the alcohol used in (i) above can be a solvent containing only the alcohol or a mixture of the alcohol and other solvents. Examples of alcohols 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; cellosols such as methyl cellosol, ethyl cellosol, butyl cellosol, and acetic acid cellosol; ethers such as dioxane and tetrahydrofuran; and so on. 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.

[0260] The preferred preparation step is to obtain a silica master particle suspension by granulation of silica master particles using the sol-gel method.

[0261] More specifically, the preparation steps are preferably a sol-gel method, for example, including the following steps:

[0262] The steps for preparing an alkaline catalyst solution include preparing an alkaline catalyst solution containing the alkaline catalyst in a solvent containing an alcohol; and

[0263] In the step of generating silica master particles, tetraalkoxysilane and an alkaline catalyst are supplied to an alkaline catalyst solution to generate silica master particles.

[0264] The preferred step in preparing the alkaline catalyst solution is to prepare a solvent containing an alcohol and mix the solvent with the alkaline catalyst to obtain the alkaline catalyst solution.

[0265] The solvent containing the alcohol can be a solvent containing only the alcohol or a mixture of the alcohol and other solvents. Examples of alcohols 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; cellosols such as methyl cellosol, ethyl cellosol, butyl cellosol, and acetic acid cellosol; ethers such as dioxane and tetrahydrofuran; and so on. 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.

[0266] Alkaline catalysts are catalysts used to promote the reactions (hydrolysis and condensation reactions) of tetraalkoxysilanes. Examples of alkaline catalysts include ammonia, urea, and monoamines, with ammonia being particularly preferred.

[0267] The concentration of the alkaline catalyst in the alkaline catalyst solution is preferably 0.5 mol / L to 1.5 mol / L, more preferably 0.6 mol / L to 1.2 mol / L, and even more preferably 0.65 mol / L to 1.1 mol / L.

[0268] The steps for generating silica master particles are as follows: Tetraalkoxysilane and an alkaline catalyst are supplied to an alkaline catalyst solution, and the tetraalkoxysilane is reacted (hydrolysis and condensation) in the alkaline catalyst solution to generate silica master particles.

[0269] In the silica master particle generation step, in the initial stage of tetraalkoxysilane supply, core particles are generated through the reaction of tetraalkoxysilane (core particle generation stage), and then the core particles grow (core particle growth stage) to generate silica master particles.

[0270] Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. From the perspective of controllability of the reaction rate or uniformity of the shape of the generated silica masterbatch, tetramethoxysilane or tetraethoxysilane is preferred.

[0271] Examples of alkaline catalysts supplied to the alkaline catalyst solution include ammonia, urea, monoamines, and quaternary ammonium salts, with ammonia being particularly preferred. The alkaline catalyst supplied together with the tetraalkoxysilane may be the same type as or a different type from the alkaline catalyst pre-contained in the alkaline catalyst solution, but the same type is preferred.

[0272] The supply of tetraalkoxysilane and alkaline catalyst to the alkaline catalyst solution can be either continuous or intermittent.

[0273] In the silica masterbatch generation step, the temperature of the alkaline catalyst solution (the temperature at which it is supplied) is preferably 5°C to 50°C, more preferably 15°C to 45°C.

[0274] [First Step]

[0275] In the first step, a structure is formed consisting of the reaction products of a trifunctional silane coupling agent.

[0276] Specifically, in the first step, for example, a trifunctional silane coupling agent is added to the silica master particle suspension, causing the trifunctional silane coupling agent to react on the surface of the silica master particles to form a structure composed of the reaction products of the trifunctional silane coupling agent. Regarding the trifunctional silane coupling agent, the functional groups of the trifunctional silane coupling agent react with each other, and with the OH groups on the surface of the silica particles, to form a structure composed of the reaction products of the trifunctional silane coupling agent.

[0277] A trifunctional silane coupling agent was added to a suspension of silica master particles, and then the suspension was heated with stirring to carry out the reaction of the trifunctional silane coupling agent.

[0278] Specifically, for example, the suspension is heated to 40°C or higher but below 70°C, a trifunctional silane coupling agent is added, and then the mixture is stirred. The stirring duration is preferably 10 minutes or more but less than 24 hours, more preferably 60 minutes or more but less than 420 minutes, and even more preferably 80 minutes or more but less than 300 minutes.

[0279] [Second Step]

[0280] In the second step, a nitrogen-containing compound is adsorbed into at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

[0281] Specifically, in the second step, firstly, a nitrogen-containing compound is added to, for example, a suspension of silica master particles, and the mixture is stirred, for example, at a temperature range of 20°C to 50°C. As a result, the nitrogen-containing compound is adsorbed onto at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

[0282] In the second step, for example, an alcoholic solution containing a nitrogen-containing compound can be added to the silica particle suspension.

[0283] The alcohol can be of the same type as the alcohol contained in the silica masterbatch suspension, or it can be of a different type, but more preferably it is of the same type.

[0284] In an alcoholic liquid containing a nitrogen-containing compound, the concentration of the nitrogen-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.

[0285] [Step 3]

[0286] In the third step, the silica master particles are hydrophobically treated, having at least a portion of the pores of the reaction product of the 3-functional silane coupling agent adsorbed with nitrogen-containing compounds after or during the second step.

[0287] Specifically, in the third step, for example, a nitrogen-containing compound is added to the silica master particle suspension that has formed the above structure, followed by the addition of a hydrophobic treatment agent.

[0288] Regarding the hydrophobic treatment agent, the functional groups of the hydrophobic treatment agent react with each other and with the OH groups of the silica master particles to form a hydrophobic treatment layer.

[0289] A hydrophobicating agent is added to a suspension of silica master particles, and then the suspension is heated under stirring to carry out the reaction of the hydrophobicating agent.

[0290] Specifically, for example, the suspension is heated to 40°C or higher but below 70°C, a hydrophobic treatment agent is added, and then the mixture is stirred. The stirring duration is preferably 10 minutes or more but less than 24 hours, more preferably 20 minutes or more but less than 120 minutes, and even more preferably 20 minutes or more but less than 90 minutes.

[0291] [Drying Steps]

[0292] In the method for manufacturing silica particles according to this embodiment, a drying step to remove the solvent from the suspension can be performed after performing the second or third step. It should be noted that the drying step can also be performed in either the second or third step.

[0293] Drying methods include, for example, thermal drying, spray drying, and supercritical drying.

[0294] Spray drying can be performed using existing known methods employing commercially available spray dryers (such as rotary disc type and nozzle type). For example, it can be performed by spraying a liquid onto a hot air stream at a rate of 0.2 liters / hour to 1 liter / hour. In this case, regarding the hot air temperature, an inlet temperature of 70°C to 400°C and an outlet temperature of 40°C to 120°C are preferred. If the inlet temperature is less than 70°C, the solid components in the dispersion will not dry sufficiently. Furthermore, if the temperature is higher than 400°C, the particle shape will deform during spray drying. Additionally, if the outlet temperature is less than 40°C, the solid components will dry poorly and adhere to the inside of the apparatus. A more preferred inlet temperature is a range of 100°C to 300°C.

[0295] The concentration of silica particles in the silica particle suspension during spray drying is preferably in the range of 10% by mass to 30% by mass based on solid content.

[0296] In supercritical drying, the solvent is removed using a supercritical fluid, and the surface tension between particles is less effective. The primary particles in the suspension are dried while their aggregation is suppressed. Therefore, silica particles with high particle size uniformity are easily obtained.

[0297] Examples of substances that can be used as supercritical fluids include carbon dioxide, water, methanol, ethanol, and acetone. From the perspective of processing efficiency and suppressing the generation of coarse particles, the solvent removal step is preferably a step using supercritical carbon dioxide.

[0298] Supercritical drying is specifically carried out, for example, by the following operations.

[0299] The suspension is collected in a closed reactor, then liquefied carbon dioxide is introduced. The closed reactor is then heated and pressurized using a high-pressure pump, causing the carbon dioxide inside to become supercritical. The liquefied carbon dioxide is then allowed to flow into the closed reactor, while the supercritical carbon dioxide flows out, thus allowing the supercritical carbon dioxide to circulate within the suspension. During this circulation, the solvent dissolves in the supercritical carbon dioxide, and is removed by being carried away by the supercritical carbon dioxide flowing out of the closed reactor.

[0300] The temperature and pressure inside the aforementioned closed reactor are those required to bring carbon dioxide to a supercritical state. The critical point of carbon dioxide is 31.1℃ / 7.38MPa. This can be achieved, for example, by setting the temperature and pressure to between 40℃ and 200℃ and between 10MPa and 30MPa.

[0301] The flow rate of the supercritical fluid in supercritical drying is preferably above 80 mL / s and below 240 mL / s.

[0302] The obtained silica particles are preferably crushed or screened as needed to remove coarse particles or agglomerates. Crushing can be carried out, for example, by dry crushing devices such as jet mills, vibratory mills, ball mills, and pin mills. Screening can be carried out, for example, by vibrating screens or air-powered screens.

[0303] Example

[0304] The following examples illustrate the implementation of the invention in detail, but the implementation of the invention is not limited to these examples. In the following description, unless otherwise stated, "%" refers to mass.

[0305] Manufacturing of Silica Particles

[0306] [Examples 1, 3-36, 39-44]

[0307] As shown below, prepare the suspension containing silica particles for each example.

[0308] Preparation of alkaline catalyst solution-

[0309] Methanol, ion-exchanged water, and ammonia (NH4OH) in the amounts and concentrations shown in Table 1 were added to a glass reaction vessel equipped with a metal stirring rod, a dropper, and a thermometer, and the mixture was stirred to obtain an alkaline catalyst solution.

[0310] Granulation of silica masterbatch based on sol-gel method-

[0311] 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, 124 parts by mass of tetramethoxysilane (TMOS) and ammonia water (NH4OH) with a catalyst (NH3) concentration of 7.9% were added dropwise to obtain a silica masterbatch suspension.

[0312] -Addition of 3-functional silane coupling agents-

[0313] The silica masterbatch suspension was heated to 40°C, and trifunctional silane coupling agents of the types and amounts shown in Table 1 were added to the suspension while stirring. Stirring continued for 120 minutes to allow the trifunctional silane coupling agents to react, thereby forming an adsorption structure.

[0314] -Addition of nitrogen-containing compounds-

[0315] The nitrogen-containing compounds shown in Table 1 were diluted with butanol to prepare alcohol solutions.

[0316] Next, an alcohol solution obtained by diluting the nitrogen-containing compound with butanol was added to the suspension. The alcohol solution was added in the manner shown in Table 1, relative to 100 parts by mass of the solid content of the silica masterbatch suspension. The mixture was then stirred at 30°C for 100 minutes to obtain a suspension containing the nitrogen-containing compound.

[0317] -dry-

[0318] Next, 300 parts by mass of the suspension were placed in the reaction vessel, and CO2 was introduced while stirring to raise the temperature and pressure of the reaction vessel to the levels shown in Table 1. While maintaining the temperature and pressure, stirring was carried out, and CO2 was introduced and discharged at a flow rate of 5 L / min. The solvent was then removed over a period of 120 minutes to obtain silica particles for each example.

[0319] [Example 2]

[0320] Using a small spray dryer B-290 (manufactured by BUCHI Corporation, Japan), the temperature and pressure inside the barrel were set as shown in Table 1. The silica particle suspension was fed at a feed rate of 0.2 L / h, and spray drying was performed under these conditions. Otherwise, silica particles were obtained in the same manner as in Example 1.

[0321] [Example 37]

[0322] After adding a nitrogen-containing compound, hexamethyldisilazane (HMDS) at 100% by mass relative to the solid content of the silica master particles was added, and the surface of the silica master particles was hydrophobically treated by stirring at 65°C for 3 hours. Otherwise, silica particles were obtained in the same manner as in Example 1.

[0323] [Example 38]

[0324] As silica master particles, 30g of dry silica AEROSIL 130 (made by NIPPON AEROSIL) was dispersed in 300g of methanol to obtain a silica master particle suspension. Otherwise, silica particles were obtained in the same manner as in Example 1.

[0325] [Compare Examples 1, 2, and 3]

[0326] The addition of the trifunctional silane coupling agent and the amount of nitrogen-containing compound are as shown in Table 1, otherwise silica particles are obtained in the same manner as in Example 1.

[0327] [evaluate]

[0328] (Various characteristics)

[0329] The following properties of the obtained silica particles were determined according to the method described above.

[0330] • Number-average particle size (referred to as "particle size" in the table)

[0331] • Average roundness (referred to as "roundness" in the table)

[0332] • The pore volume A with a pore diameter of 1 nm to 50 nm, obtained from the pore distribution curve by nitrogen adsorption method before firing at 350℃ (referred to as “pore volume A before firing at 350℃” in the table).

[0333] • The pore volume B after firing at 350℃, determined by the pore distribution curve using nitrogen adsorption, is the pore volume B of pores with diameters between 1 nm and 50 nm (referred to in the table as "pore volume B after firing at 350℃").

[0334] • Volume resistivity Ra before firing at 350℃ (referred to as “volume resistivity Ra before firing” in the table)

[0335] • Volume resistivity Rb after firing at 350℃ (referred to as “volume resistivity Rb after firing” in the table)

[0336] • OH radical content determined by the Sears method (“OH radical content” in the table)

[0337] • The proportion of the integrated signal C observed in the range of chemical shift above -50 ppm to below 75 ppm when the integral value of all signals in the Si-CP / MAS NMR spectrum is set to 100% (denoted as "Si-CP / MAS area ratio C" in the table).

[0338] • The ratio of the integral value C of the signal observed in the Si-CP / MAS NMR spectrum in the range of chemical shift from -50 ppm to -75 ppm to the integral value D of the signal observed in the range of chemical shift from -90 ppm to -120 ppm (denoted as "Si-CP / MAS ratio C / D" in the table).

[0339] (Charging dependence of low humidity charging amount and high humidity charging amount / capacitance)

[0340] As described below, the low-humidity and high-humidity charge of the silica particles in each example were measured to evaluate the environmental dependence of capacitance. It should be noted that the permissible standards are A to B.

[0341] The evaluation method is as follows.

[0342] 5g of silica particles (2% by mass) were added to the surface of MA1010 manufactured by Nippon Shokubai Co., Ltd., and 50g of the resulting mixture was mixed with 50g of KNI106GSM manufactured by JFE Chemical Co., Ltd. The mixture was then tested in a chamber at 10°C and 10% RH. The mixture was stirred for 5 minutes using a vibrator, and the charge was measured using a TOSHIBA TB200 instrument. The result is denoted as FC. The mixture was used in a chamber at 30°C and 90% RH. The mixture was stirred for 5 minutes using a vibrator, and the charge was measured using a TB200 manufactured by TOSHIBA Corporation. The result was denoted as FA, and the ratio FA / FC was used for evaluation.

[0343] A(◎): FA / FC is 0.8 or higher and less than 1.1.

[0344] B(〇): FA / FC is greater than 0.65 and less than 0.8.

[0345] C(△): FA / FC is greater than 0.5 and less than 0.65

[0346] D(×): FA / FC is less than 0.5

[0347] (Charge distribution under low temperature and low humidity environment)

[0348] The charge distribution of silica particles in each example under low temperature and low humidity conditions (10°C, 10% RH) is evaluated as described below.

[0349] 5g of silica particles (2% by mass) were added to the surface of MA1010 manufactured by Nippon Shokubai Co., Ltd., and 50g of the resulting mixture was mixed with 50g of KNI106GSM manufactured by JFE Chemical Co., Ltd. The mixture was then tested in a chamber at 10°C and 10% RH. The mixture was stirred for 5 minutes and evaluated using CSG (charge spectrograph method) image analysis. The charge distribution was defined as the quotient [Q(80) - Q(20)] / Q(50), obtained by dividing the difference between the cumulative integral of the charge distribution of 20% charge Q(20) and 80% charge Q(80) by the 50% charge Q(50). The evaluation criteria are as follows.

[0350] A(◎): The value of [Q(80)-Q(20)] / Q(50) is less than 0.7

[0351] B(○): The value of [Q(80)-Q(20)] / Q(50) is less than 0.8 and greater than 0.7.

[0352] C(△): [Q(80)-Q(20)] / Q(50) is less than 1.0 and greater than 0.8.

[0353] D(×): [Q(80)-Q(20)] / Q(50) has a value of 1.0 or higher.

[0354] (Maintenance of narrow band distribution under normal temperature and humidity conditions)

[0355] As described below, the maintenance of the narrow bandgap distribution of the silica particles in each example under normal temperature and humidity conditions (20°C, 50% RH) was evaluated.

[0356] 5g of silica particles (2% by mass) were added to the surface of MA1010 manufactured by Nippon Shokubai Co., Ltd., and 50g of the resulting mixture was mixed with 50g of KNI106GSM manufactured by JFE Chemical Co., Ltd. The mixture was then tested in a chamber at 20°C and 50% RH. The mixture was stirred in a vibrator for 100 minutes and evaluated using CSG (charge spectrum) image analysis. The charge distribution was defined as the difference between the cumulative integral of the charge distribution and the 20% charge Q(20) and 80% charge Q(80), divided by the 50% charge Q(50), i.e., [Q(80)-Q(20)] / Q(50). The evaluation criteria are as follows.

[0357] A(◎): The value of [Q(80)-Q(20)] / Q(50) is less than 0.75

[0358] B(○): The value of [Q(80)-Q(20)] / Q(50) is less than 0.85 and greater than 0.75.

[0359] C(△): [Q(80)-Q(20)] / Q(50) is less than 1.0 and greater than 0.85.

[0360] D(×): [Q(80)-Q(20)] / Q(50) has a value of 1.0 or higher.

[0361] The evaluation results are shown in Table 1.

[0362] It should be noted that the details of the abbreviations in Table 1 are as follows.

[0363] MTMS: Methyltrimethoxysilane

[0364] DTMS: n-Dodecyltrimethoxysilane

[0365] ·TP-415: [N + (CH)3(C 14 C 29 )2]4Mo8O 28 4- (Manufactured by Hodogaya Chemical Industry Co., Ltd., N,N-Dimethyl-N-tetradecyl-1-tetradecaneammonium, hexa-μ-oxotetra-μ3-oxodi-μ5-oxotetradecaoxooctamolybdate (4-)(4:1)(N,N-Dimethyl-N-tetradecyl-1-tetradecanaminium, hexa-μ-oxotetra-μ3-oxodi-μ5-oxotetradecaoxooctamolybdate (4-)(4:1)))

[0366] [Table 1-1]

[0367]

[0368] [Table 1-2]

[0369]

[0370] [Table 1-3]

[0371]

[0372] As can be seen from the above results, compared with the silica particles of the comparative example, the silica particles of the embodiment have a narrower charge distribution during charging.

Claims

1. A type of silica particle, comprising: Silica masterbatch; and The structure is coated with at least a portion of the surface of the aforementioned silica master particles. The structure is composed of the reaction product of a trifunctional silane coupling agent, and at least a portion of the pores of the reaction product of the trifunctional silane coupling agent are adsorbed with nitrogen-containing compounds. The nitrogen-containing compound is a positively charged nitrogen-containing compound. The ratio C / D is between 0.10 and 0.

75. The ratio C / D is the ratio of the silica particles determined by the cross-polarization magic angle rotation (CP / MAS) method. 29 In Si solid-state nuclear magnetic resonance (NMR) spectra, the ratio of the integral value C of the signal observed in the range of chemical shift from -50 ppm to -75 ppm to the integral value D of the signal observed in the range of chemical shift from -90 ppm to -120 ppm is given. The amount X of the nitrogen-containing compound extracted from silica particles using an ammonia / methanol mixed solution is 0.1% by mass or more, and the extraction amount X of the nitrogen-containing compound and the extraction amount Y of the nitrogen-containing compound extracted using water satisfy the formula: Y / X<0.

3.

2. The silica particles as described in claim 1, wherein, The average particle size is between 10 nm and 200 nm.

3. The silica particles as described in claim 2, wherein, The average particle size is between 10 nm and 80 nm.

4. The silica particles according to any one of claims 1 to 3, wherein, The average roundness is between 0.60 and 0.

96.

5. The silica particles as described in claim 4, wherein, The average roundness is between 0.70 and 0.

92.

6. The silica particles according to any one of claims 1 to 3, wherein, The volume resistivity is 1.0 × 10⁻⁶. 7 Ωcm or more 1.0×10 11.5 Below Ωcm.

7. The silica particles according to any one of claims 1 to 3, wherein, When the volume resistivity before and after firing at 350℃ is set as Ra and Rb respectively, Ra / Rb is above 0.01 and below 0.

8.

8. The silica particles according to any one of claims 1 to 3, wherein, When the volumes of pores with diameters between 1 nm and 50 nm before and after firing at 350℃ are designated as A and B respectively, the ratio of B / A is between 1.2 and 5, and B is 0.2 cm. 3 / g or more 3cm 3 / g or less The pore volume with a diameter of 1 nm to 50 nm before and after firing at 350°C was determined by the pore distribution curve of silica particles obtained by nitrogen adsorption.

9. The silica particles according to any one of claims 1 to 3, wherein, The aforementioned nitrogen-containing compounds are selected from at least one group consisting of quaternary ammonium salts, primary amine compounds, secondary amine compounds, tertiary amine compounds, amide compounds, imine compounds, and nitrile compounds.

10. A method for manufacturing silica particles, which is a method for manufacturing silica particles according to any one of claims 1 to 9, comprising the following steps: The first step involves forming a structure composed of the reaction product of a trifunctional silane coupling agent on at least a portion of the surface of the silica master particle; and The second step involves adsorbing a nitrogen-containing compound into at least a portion of the pores of the reaction product of the aforementioned trifunctional silane coupling agent.

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