Silica particles and method for producing the same

Abstract

A silica particle having: a silica parent particle; and a structure body covering at least a part of a surface of the silica parent particle and composed of a reaction product of a 3-functional silane coupling agent, the silica particle containing a nitrogen element-containing compound, a content of the nitrogen element-containing compound with respect to the silica particle being 0.005 mass% or more and 0.50 mass% or less in terms of N atoms, a degree of hydrophobization being 10% or more and 60% or less, a volume resistivity being 1 x 10 8 Ω·cm or more and 1 x 10 12.5 Ω·cm or less.

Description

Technical Field

[0001] This invention relates to a silicon dioxide particle and a method 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 the strength of resins, improve the flowability of powders, and inhibit packing.

[0003] For example, Patent Document 1 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 aqueous solution is 0.1% by mass or more, and (3) the extraction amount X and the extraction amount Y of the compound extracted by water satisfy the following formula (I) Y / X < 0.15".

[0004] Furthermore, Patent Document 2 discloses "a silica powder comprising a plurality of silica particles, wherein the silica particles are incorporating quaternary ammonium salts in a silica structure having "Si-O" bonds as repeating units."

[0005] Furthermore, Patent Document 3 discloses "an external charge control particle, which consists of a transport particle and a charge control agent adhering to the surface of the transport particle, wherein the transport particle is composed of hydrophobic spherical silica particles with an average particle size of 20 to 500 nm obtained by hydrophobizing the surface of hydrophilic spherical silica particles obtained by sol-gel method."

[0006] Furthermore, Patent Document 4 discloses "a silica microparticle, which is prepared by treating spherical hydrophobic silica microparticles with an average particle size of 0.01 to 5 μm with a compound selected from the group consisting of quaternary ammonium salt compounds, betaine compounds containing fluoroalkyl groups and silicone oils".

[0007] Furthermore, Patent Document 5 discloses "particles formed by treating silica particles with a hydrophobicity of 80% or more with an amphoteric surfactant and particles formed by treating silica particles with a hydrophobicity of 80% or more with a quaternary ammonium salt or a polymer having a quaternary ammonium group".

[0008] Patent Document 1: Japanese Patent Application Publication No. 2019-073418

[0009] Patent Document 2: Japanese Patent Application Publication No. 2017-039618

[0010] Patent Document 3: Japanese Patent Application Publication No. 2011-185998

[0011] Patent Document 4: Japanese Patent Application Publication No. 2001-194825

[0012] Patent Document 5: Japanese Patent Application Publication No. 09-166884 Summary of the Invention

[0013] The objective of this invention is to provide silica particles in which nitrogen-containing compounds are adsorbed onto silica masterbatches that do not have a structure consisting of reaction products of trifunctional silane coupling agents, wherein the content of the nitrogen-containing compounds is less than 0.005% by mass (in N atoms), the hydrophobicity is less than 10% or more than 60%, or the volume resistivity exceeds 1 × 10⁻⁶. 12.5 Compared to the case of Ω, the charge distribution is narrower when charged.

[0014] The specific methods used to solve the above problems include the following approaches.

[0015] <1>

[0016] A type of silica particle having:

[0017] Silica masterbatch; and

[0018] A structure comprising at least a portion of the surface of the silica masterbatch and composed of the reaction product of a trifunctional silane coupling agent.

[0019] The silica particles contain nitrogen-containing compounds, and the content of these nitrogen-containing compounds relative to the silica particles, expressed in N atoms, is 0.005% by mass or more and 0.50% by mass or less.

[0020] Hydrophobicity is between 10% and 60%.

[0021] The volume resistivity is 1×10 8 Ω·cm or more and 1×10 12.5 Below Ω·cm.

[0022] <2>

[0023] According to the silicon dioxide particles described in <1>, wherein,

[0024] On the micropore distribution curve of the nitrogen adsorption method, there is a first peak in the range of micropore diameter above 0.01 nm and below 2 nm, and a second peak in the range of micropore diameter above 1.5 nm and below 50 nm.

[0025] <3>

[0026] According to the silicon dioxide particles described in <1> or <2>, wherein,

[0027] At least a portion of the micropores of the reaction product of the trifunctional silane coupling agent adsorbs the nitrogen-containing compound.

[0028] <4>

[0029] The silica particles according to any one of <1> to <3> have a hydrophobicity of 10% or more and 50% or less.

[0030] <5>

[0031] The silica particles according to any one of <1> to <4> have a volume average particle size of 10 nm or more and 200 nm or less.

[0032] <6>

[0033] The silica particles described in <5> have a volume average particle size of 10 nm or more and 80 nm or less.

[0034] <7>

[0035] The silica particles according to any one of <1> to <6> have an average sphericity of 0.60 or more and 0.96 or less.

[0036] <8>

[0037] The silica particles described in <7> have an average sphericity of 0.70 or higher and 0.92 or lower.

[0038] <9>

[0039] The silicon dioxide particles according to any one of <1> to <8>, wherein,

[0040] The nitrogen-containing compound is selected from 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.

[0041] According to <1> or <3> of the present invention, silica particles can be provided in the following cases: silica masterbatch containing nitrogen-containing compounds adsorbed on a structure not having a reaction product of a trifunctional silane coupling agent; the content of the nitrogen-containing compound is less than 0.005 by mass in N atom conversion; the hydrophobicity is less than 10% or more than 60%; or the volume resistivity exceeds 1×10⁻⁶. 12.5 Compared to the case of Ω·cm, the charge distribution is narrower when charged.

[0042] According to <2> of the present invention, silica particles can be provided that have a narrow charge distribution when charged, compared with the case where there is no second peak on the micropore distribution curve of the nitrogen adsorption method.

[0043] According to <4> of the present invention, silica particles can be provided that have a narrow charge distribution when charged compared to cases where the hydrophobicity is less than 10% or more than 60%.

[0044] According to <5> or <6> of the present invention, silica particles can be provided in the following cases: silica masterbatch containing nitrogen-containing compounds adsorbed on a structure not having a reaction product of a trifunctional silane coupling agent; the content of the nitrogen-containing compound is less than 0.005% by mass (in N atoms); the hydrophobicity is less than 10% or more than 60%; or the volume resistivity exceeds 1×10⁻⁶. 12.5 Compared to the case of Ω·cm, even if the volume average particle size is above 10nm and below 200nm or above 10nm and below 80nm, the charge distribution is narrow when charged.

[0045] According to <7> or <8> of the present invention, silica particles can be provided in the following cases: silica masterbatch containing nitrogen-containing compounds adsorbed on a structure not having a reaction product of a trifunctional silane coupling agent; the content of the nitrogen-containing compound is less than 0.005% by mass (in N atoms); the hydrophobicity is less than 10% or more than 60%; or the volume resistivity exceeds 1×10⁻⁶. 12.5 Compared to the case of Ω·cm, even if the average roundness is above 0.60 and below 0.96 or above 0.70 and below 0.92, the charge distribution is narrow when charged.

[0046] According to <9> of the present invention, silica particles can be provided in the following cases: silica masterbatch having a nitrogen-containing compound adsorbed on a structure not having a reaction product of a trifunctional silane coupling agent; the content of the nitrogen-containing compound (in N atoms) is less than 0.005% by mass; the hydrophobicity exceeds 60%; or the volume resistivity exceeds 1×10⁻⁶. 12.5 Compared to the case of Ω·cm, the compound contains at least one nitrogen-containing compound 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, and has a narrow charge distribution when charged. Detailed Implementation

[0047] The embodiments of the present invention will be described below. These descriptions and examples illustrate the embodiments but do not limit the scope of the embodiments.

[0048] In the numerical ranges described in this specification, the upper or lower limit of a numerical range can be replaced with the upper or lower limit of other numerical ranges described in different stages. Furthermore, in the numerical ranges described in this invention, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the embodiments.

[0049] In this specification, each component may contain multiple corresponding substances.

[0050] In this specification, when referring to the amount of each component in the composition, if there are multiple substances in the composition corresponding to each component, unless otherwise specified, it refers to the total amount of the multiple substances present in the composition.

[0051] Silica Particles

[0052] The silica particles involved in this embodiment have: silica masterbatch; and a structure that covers at least a portion of the surface of the silica masterbatch and is composed of the reaction product of a trifunctional silane coupling agent.

[0053] Furthermore, the silica particles involved in this embodiment have the following characteristics (1) to (3).

[0054] (1) Contains nitrogen-containing compounds, wherein the content of nitrogen-containing compounds relative to silicon dioxide particles is more than 0.005% by mass and less than 0.50% by mass in terms of N atoms.

[0055] (2) The degree of hydrophobicity is above 10% and below 60%.

[0056] (3) The volume resistivity is 1×10 8 Ω·cm or more and 1×10 12.5 Below Ω·cm.

[0057] The silica particles involved in this embodiment have a narrow charge distribution when charged due to the above-described structure. The reason for this is speculated as follows.

[0058] Silica particles have a high negative charge and can sometimes become overcharged. As a result, the charge distribution becomes wider.

[0059] For example, in powder coating, powder coatings that are charged through contact charging, corona discharge, or other methods are sprayed onto the object to be coated, allowing them to adhere electrostatically. Then, the object is heated to form a coating film.

[0060] However, if silica particles with a wide charge distribution are used as additives in powder coatings, the charge distribution of the powder coating will be biased, and the amount of powder coating adhering to the coated object will be difficult to be uniform.

[0061] On the other hand, if nitrogen-containing compounds are incorporated into silicon dioxide particles, the excessive negative charge of the silicon dioxide particles can be suppressed. Nitrogen-containing compounds are positively charged, and silicon dioxide particles containing these compounds counteract excessive negative charge, thus suppressing it. Therefore, the charge distribution of the silicon dioxide particles becomes narrower.

[0062] However, nitrogen-containing compounds have positive charge. If they are contained on the outermost surface of silicon dioxide particles, the charge distribution will broaden towards both negative and positive charge.

[0063] Therefore, in the silica particles involved in this embodiment, a structure composed of the reaction product of a trifunctional silane coupling agent (e.g., SiO2) is provided on the silica masterbatch. 2 / 3 The CH3 layer contains nitrogen-containing compounds with a content of more than 0.005% by mass and less than 0.50% by mass, expressed in terms of N atoms.

[0064] Furthermore, by setting the degree of hydrophobicity to 10% or more and 60% or less, and reducing the volume resistivity to 1×10⁻⁶, 8 Ω·cm or more and 1×10 12.5 Below Ω·cm, excessive charging of silicon dioxide particles can be suppressed.

[0065] Therefore, the narrowing of the charge distribution based on nitrogen-containing compounds is improved.

[0066] Based on the above speculation, the silicon dioxide particles involved in this embodiment have a narrow charge distribution when charged.

[0067] Furthermore, for example, if the silica particles involved in this embodiment are used as an additive in powder coatings, the charge of the powder coating is less likely to deviate, and the amount of powder coating adhering to the coated object can be made uniform.

[0068] The silica particles involved in this embodiment will be described in detail below.

[0069] (The composition of silicon dioxide particles)

[0070] The silica particles involved in this embodiment have: a silica masterbatch; and a structure consisting of a reaction product of a trifunctional silane coupling agent covering the surface of the silica masterbatch. Moreover, for example, it is preferable that at least a portion of the pores of the reaction product of the trifunctional silane coupling agent is adsorbed with a nitrogen-containing compound.

[0071] Furthermore, in the silica particles involved in this embodiment, the surface of the structure composed of the reaction product of the trifunctional silane coupling agent may have a hydrophobic treatment structure.

[0072] -Silica masterbatch-

[0073] Silica masterbatch is silica particles that become the object of forming structures composed of reaction products of trifunctional silane coupling agents.

[0074] Examples of silica masterbatches include dry silica particles and wet silica particles.

[0075] Examples of dry silica particles include combustion silica (gas phase silica) obtained by burning silane compounds and deflagration silica obtained by exploding and burning metallic silicon powder.

[0076] Examples of wet silica particles include wet silica particles obtained by the neutralization reaction of sodium silicate with an inorganic acid (precipitated silica synthesized and condensed under alkaline conditions, and gel silica particles synthesized and condensed 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 the hydrolysis of organosilane compounds (e.g., alkoxysilanes).

[0077] Among these, from the viewpoint of narrowing the charge distribution, silica masterbatch, for example, sol-gel silica particles are preferred.

[0078] -Reaction products of 3-functionalized silane coupling agents-

[0079] 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, nitrogen-containing compounds are easily adsorbed deep into the pores, resulting in a higher adsorption amount (i.e., higher content). By attaching positively charged nitrogen-containing compounds to the negatively charged silica surface, an effect of counteracting excessive negative charge is achieved. Furthermore, since the nitrogen-containing compounds are adsorbed within the low-density structure rather than on the outermost surface of the silica particles, it prevents the positive charge from becoming too strong and broadening the charge distribution. By only counteracting excessive negative charge, the narrowing of the charge distribution is further enhanced.

[0080] The reaction products of 3-functional silane coupling agents can be exemplified by the following general formula (TA) OR 2 The reaction products with OH groups as substitutes, OR 2 The reaction products obtained by the condensation of compounds with OH groups as substitutes, OR 2 The reaction products are obtained by condensation polymerization of compounds with OH groups and SiOH groups of silica particles. Furthermore, the reaction products of trifunctional silane coupling agents include these OR... 2 The reaction products obtained by complete or partial substitution, or by complete or partial condensation polymerization.

[0081] 3-functional silane coupling agents are nitrogen-free compounds that do not contain N (nitrogen).

[0082] Specifically, trifunctional silane coupling agents can be exemplified by the trifunctional silane coupling agent represented by the following general formula (TA).

[0083] General formula (TA): R1 -Si(OR 2 )3

[0084] In the general formula (TA), R 1 R represents a saturated or unsaturated aliphatic hydrocarbon group with 1 or more but less than 20 carbon atoms, or an aromatic hydrocarbon group with 6 or more but less than 20 carbon atoms. 2 Represents a halogen atom or an alkoxy group. Multiple Rs 2 They can be the same group or different groups.

[0085] R 1 The aliphatic hydrocarbon group can be any of straight-chain, branched, and cyclic, but is preferably straight-chain or branched. The aliphatic hydrocarbon group preferably has 1 or more and 20 or less carbon atoms, more preferably 1 or more and 18 or less carbon atoms, even more preferably 1 or more and 12 or less carbon atoms, and even more preferably 1 or more and 10 or less carbon atoms. The aliphatic hydrocarbon group can be any of saturated and unsaturated, but is preferably saturated aliphatic hydrocarbon groups, more preferably alkyl groups.

[0086] 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.).

[0087] Examples of unsaturated aliphatic hydrocarbon groups include alkenyl (ethenyl, 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.).

[0088] R 1 The aromatic hydrocarbon group represented is preferably composed of 6 or more and 20 or less carbon atoms, more preferably 6 or more and 18 or less carbon atoms, even more preferably 6 or more and 12 or less carbon atoms, and even more preferably 1 or more and 10 or less carbon atoms.

[0089] Examples of aromatic hydrocarbon groups include phenylene, biphenylene, terphenylene, naphthyl, and anthracene.

[0090] As R 2 Examples of halogen atoms include fluorine, chlorine, bromine, and iodine. Chlorine, bromine, or iodine atoms are preferred as halogen atoms.

[0091] As R 2 The alkoxy group referred to can be alkoxy groups having 1 or more and 10 or fewer carbon atoms (for example, preferably 1 or more and 8 or fewer, more preferably 1 or more and 4 or fewer). Examples of alkoxy groups include methoxy, ethoxy, isopropoxy, tert-butoxy, n-butoxy, n-hexoxy, 2-ethylhexoxy, and 3,5,5-trimethylhexoxy. Alkoxy groups also include substituted alkoxy groups. Examples of substituents that can be substituted into an alkoxy group include halogen atoms, hydroxyl groups, amino groups, alkoxy groups, amide groups, and carbonyl groups.

[0092] The trifunctional silane coupling agent represented by the general formula (TA), such as R, is preferred. 1 It is a saturated aliphatic hydrocarbon group with 1 or more carbon atoms and less than 20 carbon atoms, R 2 It is a trifunctional silane coupling agent with halogen or alkoxy atoms.

[0093] Examples of trifunctional silane coupling agents include the following:

[0094] 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 or aromatic hydrocarbon groups;

[0095] 3-Glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane (the above are R...) 1 Compounds containing substituted aliphatic or aromatic hydrocarbon groups, etc.

[0096] 3-functional silane coupling agents can be used alone or in combination with two or more.

[0097] Among these, from the viewpoint of narrowing the charge distribution, alkyl trifunctional silane coupling agents are preferred, and R in general formula (TA) is more preferred. 1 The alkyl group, R, represents an alkyl group having 1 or more and 20 or fewer carbon atoms (e.g., preferably having 1 or more and 15 or fewer carbon atoms).2 Alkyl trifunctional silane coupling agents representing alkyl groups with 1 or more but less than 2 carbon atoms.

[0098] From the viewpoint of narrowing the charge distribution, the amount of the structure formed by the reaction product of the trifunctional silane coupling agent is preferably 0.005% by mass or more and 0.5% by mass or less, more preferably 0.005% by mass or more and 0.2% by mass or less, relative to the silica masterbatch.

[0099] -Nitrogen-containing compounds-

[0100] 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.

[0101] Nitrogen-containing compounds are preferably adsorbed into at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

[0102] 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.

[0103] Examples of primary amine compounds include phenylethylamine, toluidine, catecholamines, and 2,4,6-trimethylaniline.

[0104] Examples of secondary amine compounds include dibenzylamine, 2-nitrodiphenylamine, and 4-(2-octylamino)diphenylamine.

[0105] Examples of tertiary amine compounds include 1,8-bis(dimethylamino)naphthalene, N,N-dibenzyl-2-aminoethanol, and N-benzyl-N-methylethanolamine.

[0106] 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.

[0107] 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).

[0108] Examples of nitrile compounds include 3-indoleacetonitrile, 4-[(4-chloro-2-pyrimidinyl)amino]benzyl nitrile, and 4-bromo-2,2-diphenylbutyronitrile.

[0109] Among these, from the viewpoint of narrowing the charge distribution, quaternary ammonium salts are preferred as nitrogen-containing compounds.

[0110] Quaternary ammonium salts can be used alone or in combination with two or more.

[0111] There are no particular restrictions on quaternary ammonium salts; any known quaternary ammonium salts can be used.

[0112] From the viewpoint 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.

[0113] [Chemical Formula 1]

[0114]

[0115] 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 that may have substituents, X - Represents anion. Wherein, R 1 R 2 R 3 and R 4 At least one of them indicates that it may be an alkyl, aralkyl, or aryl group having a substituent. Furthermore, R 1 R 2 R 3 and R 4 Two or more of them can connect to form an aliphatic ring, an aromatic ring, or a heterocyclic ring.

[0116] As R 1 ~R 4 Examples of alkyl groups include straight-chain alkyl groups with 1 or more and 20 or fewer carbon atoms, and branched alkyl groups with 3 or more and 20 or fewer carbon atoms.

[0117] Examples of linear alkyl groups with 1 or more but less than 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.

[0118] Examples of branched alkyl groups with 3 or more but less than 20 carbon atoms include isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, sec-hexyl, tert-hexyl, isoheptyl, sec-heptyl, tert-heptyl, isooctyl, sec-octyl, tert-octyl, isononyl, sec-nonyl, tert-nonyl, isodel, sec-decyl, tert-decyl, etc.

[0119] In the above, as R 1 ~R4 The alkyl group represented is preferably an alkyl group with 1 or more carbon atoms and less than 15, such as methyl, ethyl, butyl, tetradecyl, etc.

[0120] As R 1 ~R 4 The aralkyl group to be referred to can be an aralkyl group with 7 or more but less than 30 carbon atoms.

[0121] Examples of aryl alkyl groups with 7 or more but less than 30 carbon atoms include benzyl, phenylethyl, phenylpropyl, 4-phenylbutyl, phenylpentyl, phenylhexyl, phenylheptyl, phenyloctyl, phenylnonyl, naphthylmethyl, naphthylethyl, anthraceneylmethyl, and phenyl-cyclopentylmethyl.

[0122] In the above, as R 1 ~R 4 The aralkyl group represented is preferably an aralkyl group with 7 or more carbon atoms and 15 or fewer, such as benzyl, phenylethyl, phenylpropyl, or 4-phenylbutyl.

[0123] As R 1 ~R 4 Examples of aryl groups that can be represented include those with 6 or more but less than 20 carbon atoms.

[0124] Examples of aryl groups with 6 to 20 carbon atoms include phenyl, pyridyl, and naphthyl.

[0125] In the above, as R 1 ~R 4 The aryl group represented is preferably an aryl group with 6 or more but less than 10 carbon atoms, such as phenyl.

[0126] As X - The anions represented can be organic anions or inorganic anions.

[0127] 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).

[0128] 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.

[0129] In the general formula (AM), R 1 R 2 R 3 and R 4 Two or more elements can be connected to form a loop. As R... 1 R 2 R 3 and R 4 Examples of rings formed by the interconnection of two or more carbon atoms include alicyclic rings with 2 or more but less than 20 carbon atoms, and heterocyclic amines with 2 or more but less than 20 carbon atoms.

[0130] In compounds represented by the general formula (AM), R 1 R 2 R 3 and R 4 Each can have substituents independently. Examples of substituents include nitrile, carbonyl, ether, amide, siloxane, silyl, and silanealkoxy groups.

[0131] R 1 R 2 R 3 and R 4 For example, it is preferable that each of the following is independently represented: alkyl group with 1 or more carbon atoms and 16 or less, aralkyl group with 7 or more carbon atoms and 10 or less, or aryl group with 6 or more carbon atoms and 20 or less.

[0132] Among these, from the viewpoint of narrowing the charge distribution, compounds represented by the general formula (AM) are preferably those with a total number of carbon atoms of 18 or more and 35 or less, more preferably 20 or more and 32 or less.

[0133] The following shows X in compounds represented by the general formula (AM). - Examples of structures other than those described herein are provided, but this embodiment is not limited to them.

[0134] [Chemical Formula 2]

[0135]

[0136] From the viewpoint of narrowing the charge distribution and maintaining the charge distribution, nitrogen-containing compounds are preferably nitrogen-containing compounds containing molybdenum, and more preferably at least one selected from the group consisting of quaternary ammonium salts containing molybdenum (especially quaternary ammonium salts containing molybdenum) and mixtures of quaternary ammonium salts and metal oxides containing molybdenum.

[0137] If the nitrogen-containing compound contains molybdenum, it enhances the reactivity of nitrogen. Even if the nitrogen-containing compound exists inside the pores rather than on the surface of the silica particles, it can still exhibit a moderate positive charge of nitrogen. Therefore, the charge distribution is narrow when charged, and the maintenance of the charge distribution is also easier.

[0138] In particular, the molybdenum-containing salts of quaternary ammonium exhibit improved charge distribution maintenance due to the strong bonding between the molybdenum-containing anion (as anion) and the quaternary ammonium cation (as a cation).

[0139] 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.

[0140] 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).

[0141] The content of nitrogen-containing compounds relative to silicon dioxide particles is 0.005% by mass or more and 0.50% by mass or less. From the viewpoint of narrowing the charge distribution, it is preferable, for example, to be 0.015% by mass or more and 0.20% by mass or less, and more preferably 0.018% by mass or more and 0.10% by mass or less.

[0142] The content of nitrogen-containing compounds, calculated using N atoms, was determined as follows.

[0143] The presence of nitrogen was determined using an oxygen-nitrogen analysis apparatus (e.g., EMGA-920 manufactured by HORIBA, Ltd.) with a cumulative time of 45 seconds, as a ratio of N to Si. Furthermore, 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 24 hours.

[0144] Here, when a nitrogen-containing compound containing molybdenum is used as the nitrogen-containing compound, from the viewpoint 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, more preferably 0.07 or more and 0.32 or less, and even more preferably 0.10 or more and 0.30 or less.

[0145] From the viewpoint of narrowing the charge distribution, the net intensity of molybdenum is preferably, for example, 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.

[0146] The net strength of molybdenum and silicon was measured as follows.

[0147] Approximately 0.5g of silica particles were compressed using a compression molding machine under a load of 6t for 60 seconds to create a disc with a diameter of 50mm and a thickness of 2mm. This disc was used as a sample for qualitative and quantitative elemental analysis using a scanning fluorescence X-ray analysis device (XRF-1500, manufactured by SHIMADZU CORPORATION) under the following conditions to determine the Net intensities (unit: kilo counts per second, kcps) of molybdenum and silicon.

[0148] • Tube voltage: 40kV

[0149] Tube current: 90mA

[0150] • Measurement area (analytical diameter): Diameter

[0151] • Measurement time: 30 minutes

[0152] • For cathode: rhodium

[0153] -Extraction rate of nitrogen-containing compounds-

[0154] The extraction amount X of nitrogen-containing compounds extracted using an ammonia / methanol mixed solution is, for example, 0.1% by mass or more, and the extraction amount X of nitrogen-containing compounds and the extraction amount Y of nitrogen-containing compounds extracted using water preferably satisfy the formula: Y / X < 0.3.

[0155] In other words, nitrogen-containing compounds are difficult to dissolve in water, meaning they are unlikely to absorb moisture from the air.

[0156] 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.

[0157] However, even if moisture is present in the air (even under high humidity), silica particles containing nitrogen-containing compounds that are difficult to adsorb moisture from the air do not easily broaden their charge distribution, and the nitrogen-containing compounds are not easily detached, thus maintaining a narrow charge distribution.

[0158] The extraction amount X of nitrogen-containing compounds is preferably 50% by mass, for example. However, due to surface tension, the solution has difficulty penetrating into the pores, and some of the nitrogen-containing compounds will not dissolve and remain. Therefore, the upper limit of the extraction amount X of nitrogen-containing compounds is, for example, 95% by mass or less.

[0159] The ratio of the amount of nitrogen-containing compound extracted, X, to the amount of nitrogen-containing compound extracted, "Y / X", is preferably less than 0.3, for example. However, the lower limit of "Y / X" is ideally 0, but since there is a measurement error range of about ±1% for X and Y, it is, for example, 0.01 or more.

[0160] Here, the extraction amounts X and Y of nitrogen-containing compounds were determined as follows.

[0161] First, the silica particles to be measured are analyzed using a thermogravimetric-mass spectrometry (TG-MS) instrument (e.g., a gas chromatograph-mass spectrometer manufactured by NETZSCH Japan K.K.) at a constant temperature of 400°C. The cumulative mass fraction of compounds in which hydrocarbons with at least one carbon atom are covalently bonded to nitrogen atoms relative to the silica particles is measured and set as W1.

[0162] On the other hand, 1 part by mass of the silica particles of the target substance 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, the silica powder and 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 with at least one carbon atom covalently bonded to a nitrogen atom relative to the silica particles was determined using a thermogravimetric-mass spectrometry (TGA) system at a constant temperature of 400°C. This fraction was designated as W2.

[0163] Then, the amount of nitrogen-containing compound extracted, X, is calculated using the following formula.

[0164] Equation: X = W1 - W2

[0165] Furthermore, 1 part by mass of silica particles of the target substance was added to 30 parts by mass of water at a liquid temperature of 25°C, and after ultrasonic treatment for 30 minutes, the silica particles and 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 with at least 1 carbon atom covalently bonded to nitrogen atoms relative to silica particles was determined using a thermogravimetric-mass spectrometry (TGA) system at a constant temperature of 400°C. This fraction was designated as W3.

[0166] Then, the extraction amount Y of nitrogen-containing compounds is calculated using the following formula.

[0167] Equation: Y = W1 - W3

[0168] (Hydrophobic treatment structure)

[0169] The hydrophobicated structure is a structure that has reacted with a hydrophobic treatment agent.

[0170] Organosilicon compounds can be used as hydrophobic treatment agents, for example.

[0171] Examples of organosilicon compounds include:

[0172] Alkoxysilane compounds or halosilane compounds having lower alkyl groups, such as methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, and trimethylmethoxysilane; vinyltrimethoxysilane compounds having vinyl groups, such as vinyltriethoxysilane;

[0173] Alkoxysilane compounds with epoxy groups, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0174] Alkoxysilane compounds containing a styrene group, such as p-styrenetrimethoxysilane and p-styrenetriethoxysilane;

[0175] 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;

[0176] Alkoxysilane compounds containing isocyanate alkyl groups, such as 3-isocyanate propyltrimethoxysilane and 3-isocyanate propyltriethoxysilane;

[0177] Hexamethyldisilazane, tetramethyldisilazane, and other silazane compounds.

[0178] (Properties of silica particles)

[0179] -Hydrophobicity-

[0180] The degree of hydrophobicity of the silica particles involved in this embodiment is 10% or more and 60% or less, but from the viewpoint of narrowing the charge distribution, it is more preferably 20% or more and 55% or less, and even more preferably 28% or more and 53% or less.

[0181] If the hydrophobicity of silica particles is below 10%, the coating of the structure generated by the reaction with a trifunctional silane coupling agent is low, and the content of nitrogen-containing compounds is reduced. Therefore, the charge distribution is more likely to broaden.

[0182] On the other hand, if the hydrophobicity of silica particles exceeds 60%, the density of the structure increases due to the reaction of the trifunctional silane coupling agent, resulting in fewer pores and a decrease in the content of nitrogen-containing compounds. Therefore, the charge distribution tends to broaden.

[0183] The degree of hydrophobicity of silica particles was determined as follows.

[0184] 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 from a burette. Calculate the mass fraction of methanol in the methanol-water mixture at the endpoint of total sample precipitation as the degree of hydrophobicity.

[0185] -OH basic content-

[0186] In the silica particles involved in this embodiment, the amount of OH radicals, as measured by the Sears method, is preferably 0.05 per nm. 2More than 5 per nm 2 From the viewpoint of narrowing the charge distribution, 0.1 charges / nm is preferred. 2 More than 4 per nm 2 Below, 0.2 per nm is further preferred. 2 More than 3 per nm 2 the following.

[0187] The amount of OH groups determined using the Sears method can be adjusted within the above range by fully forming the structure composed of the reaction product of the trifunctional silane coupling agent in the silica masterbatch.

[0188] By reducing the amount of OH groups that hinder the adsorption of nitrogen-containing compounds to the aforementioned range, the nitrogen-containing compounds can easily penetrate deep into the pores of the silica particle structure. Then, hydrophobic interactions act on the nitrogen-containing compounds, thereby strengthening their adhesion to the silica particles. Therefore, the adsorption capacity of the nitrogen-containing compounds increases. Furthermore, the nitrogen-containing compounds become less prone to detachment. Thus, the narrowing of the charge distribution based on the nitrogen-containing compounds is improved, and the maintenance of this narrow charge distribution is also enhanced.

[0189] Furthermore, by reducing the amount of OH radicals to the above range, the environmental dependence of the charge properties is reduced, and it is easy to achieve a narrowing of the charge distribution based on nitrogen-containing compounds under any environment.

[0190] The OH radical content was determined using the Sears method. Details are as follows.

[0191] 1.5 g of silica particles were added to a mixture of 50 g of pure water and 50 g of ethanol, and the mixture was 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 with 0.01 mol / L sodium hydroxide aqueous solution was performed to prepare the differential curve of the titration. The titration amount at the inflection point where the differential value of the titration curve becomes the largest at 1.8 or higher was defined as E.

[0192] The surface silanol group density ρ (numbers / nm) of silica particles was calculated using the following formula. 2 ).

[0193] Formula: ρ=((0.01×E-0.1)×NA / 1000) / (M×S BET ×10 18 )

[0194] E: The titration amount of 0.01 mol / L sodium hydroxide aqueous solution becomes the largest at the inflection point where the differential value of the titration curve becomes 1.8 or higher.

[0195] NA: Avogadro's constant

[0196] M: Quantity of silica particles (1.5g)

[0197] S BET Specific surface area of ​​silica particles (m²) 2 / g)

[0198] The specific surface area of ​​silica particles was determined using the BET-type nitrogen adsorption three-point method. The equilibrium relative pressure was set to 0.3.

[0199] -Volume resistivity-

[0200] The volume resistivity of the silica particles involved in this embodiment is 1×10⁻⁶. 8 Ω·cm or more and 1×10 12.5 Below Ω·cm, but from the viewpoint of narrowing the charge distribution, for example, 1.0 × 10⁻⁶ is preferred. 8 Ω·cm or more and 1.0×10 11.5 Below Ω·cm, more preferably 1.0×10 9 Ω·cm or more and 1.0×10 11.0 Below Ω·cm.

[0201] By reducing the volume resistivity to the range described above, excessive charging of silica particles can be suppressed. Therefore, the narrowing of the charge distribution is improved.

[0202] In addition, the volume resistivity can be adjusted according to the content of nitrogen-containing compounds.

[0203] Volume resistivity was measured as follows. The measurement environment was set at 20°C and 50% RH.

[0204] With a 20cm configuration 2 The surface of the circular clamp of the electrode plate is covered with silica particles, the object of measurement, to form a silica particle layer with a thickness of approximately 1 mm to 3 mm. A 20 cm layer of the same material is then placed on top of this layer. 2 Electrode plates were used to add a layer of silica particles. To eliminate voids between the silica particles, a pressure of 0.4 MPa was applied to the electrode plates placed on the silica particle layer, and the thickness (cm) of the silica particle layer was measured. Two electrodes above and below the silica particle layer were connected to an impedance analyzer (manufactured by Solartron Analytical). The impedance was measured at 10... -3 Hz and above and 106 Measurements were taken at frequencies below Hz, resulting in the Nyquist plot. Assuming the existence of three resistive components—volume resistance, particle interface resistance, and electrode contact resistance—and plotting them in an equivalent circuit, the volume resistance R was calculated.

[0205] The formula for calculating the volume resistivity (Ω·cm) of silica particles is shown below.

[0206] Formula: ρ=R / L

[0207] In the formula, ρ is the volume resistivity of the silicon dioxide particles (Ω·cm), R is the bulk resistance (Ω), and L is the thickness of the silicon dioxide particle layer (cm).

[0208] -Pore volume-

[0209] In the silica particles involved in this embodiment, for example, it is preferable to have a first peak in the range of pore diameter of 0.01 nm or more and 2 nm or less, a second peak in the range of pore diameter of 1.5 nm or more and 50 nm or less, more preferably a second peak in the range of 2 nm or more and 50 nm or less, even more preferably a second peak in the range of 2 nm or more and 40 nm or less, and even more preferably a second peak in the range of 2 nm or more and 30 nm or less.

[0210] On the micropore distribution curve of the nitrogen adsorption method, the presence of a first peak and a second peak within the aforementioned range of micropore diameter indicates that nitrogen-containing compounds can easily enter and be absorbed deep into the micropores of the structure. This further enhances the narrowing of the charge distribution.

[0211] The micropore distribution curve of nitrogen adsorption method is derived from the adsorption isotherm obtained by measuring the amount of nitrogen adsorbed, and is derived from various calculation formulas.

[0212] First, the silica particles to be measured are cooled to liquid nitrogen temperature (-196°C), and nitrogen gas is introduced. The adsorption amount is determined using the constant volume method or gravimetric method. The pressure of the introduced nitrogen gas is slowly increased, and adsorption isotherms are constructed by plotting the amount of nitrogen adsorbed relative to each equilibrium pressure. Based on the adsorption isotherms, a pore diameter distribution curve is calculated using the BJH method, with frequency as the vertical axis and pore diameter as the horizontal axis.

[0213] Then, based on the obtained micropore distribution curve, the cumulative micropore volume distribution with the vertical axis representing volume and the horizontal axis representing micropore diameter is calculated, and the position of the peak of micropore diameter is confirmed.

[0214] -A method for detecting structures having nitrogen-containing compounds adsorbed in at least a portion of the pores of the reaction product of a trifunctional silane coupling agent-

[0215] When at least a portion of the pores of the reaction product of a trifunctional silane coupling agent adsorbs nitrogen-containing compounds, these compounds are detected after heating in a temperature range above 300°C and below 600°C. The increase in pore volume, calculated from the pore distribution curves obtained by nitrogen adsorption before and after calcination at 350°C, indicates a pore diameter greater than 1 nm and less than 50 nm. This is then used for detection. Details are as follows.

[0216] In the detection of nitrogen-containing compounds, a fall-type pyrolysis gas chromatography-mass spectrometry (GC-MS) system using He as the carrier gas is employed, for example. Nitrogen-containing compounds can be detected under inert gas conditions with a thermal decomposition temperature above 300°C and below 600°C. Specifically, by introducing 0.1 mg to 10 mg of silica particles into the GC-MS system, the presence or absence of nitrogen-containing compounds can be confirmed based on the MS spectrum of the detected peaks.

[0217] As a component generated from silicon dioxide particles containing nitrogen-containing compounds through thermal decomposition, examples include amines or aromatic nitrogen compounds of order 1 or higher and order 3 or lower, represented by the following general formula (N).

[0218] In the following general formula (N), R N1 ~R N3 Each independently represents a hydrogen atom or an alkyl, aralkyl, or aryl group that may have substituents, R N1 ~R N3 The meaning of R in the general formula (AM) 1 R 2 and R 3 same.

[0219] For example, when the nitrogen-containing compound is a quaternary ammonium salt, a portion of the side chain is released through thermal decomposition at 600°C, and it is detected as a tertiary amine.

[0220] [Chemical Formula 3]

[0221]

[0222] The following determines the increase in pore volume for pores with a diameter greater than 1 nm and less than 50 nm, determined by the pore distribution curves obtained from the nitrogen adsorption method before and after calcination at 350℃.

[0223] First, the increase ratio of pore volume, for example, the ratio of pore volume B after calcination at 350℃ to pore volume A before calcination at 350℃, B / A is set to be above 1.2 and below 5.

[0224] Specifically, the calcination at 350℃ is carried out as follows.

[0225] In a nitrogen environment, the silica particles of the test subject were heated to 350°C at a heating rate of 10°C / min and held at 350°C for 3 hours. Then, they were cooled to room temperature (25°C) at a cooling rate of 10°C / min.

[0226] The volume of pores with a diameter of 1 nm or more and less than 50 nm is determined by the following method.

[0227] First, the silica particles to be measured are cooled to liquid nitrogen temperature (-196°C), and nitrogen gas is introduced. The adsorption amount is determined using the constant volume method or gravimetric method. The pressure of the introduced nitrogen gas is slowly increased, and adsorption isotherms are constructed by plotting the amount of nitrogen adsorbed relative to each equilibrium pressure. Based on the adsorption isotherms, a pore diameter distribution curve is calculated using the BJH method, with frequency as the vertical axis and pore diameter as the horizontal axis.

[0228] Then, based on the obtained pore diameter distribution curve, the cumulative pore volume distribution with volume on the vertical axis and pore diameter on the horizontal axis is calculated. Based on the obtained cumulative pore volume distribution, the pore volume in the range of pore diameter above 1 nm and below 50 nm is accumulated and taken as "pore volume with pore diameter above 1 nm and below 50 nm".

[0229] -Number average particle size and number-particle size distribution index-

[0230] The average particle size of the silica particles involved in 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.

[0231] If the average particle size of the silica particles is within the above range, the specific surface area is large, and over-charging is likely to occur. However, even if the average particle size of the silica particles involved in this embodiment is within the above range, the charge distribution can be narrowed.

[0232] The number and particle size distribution index of silica particles involved in 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.

[0233] If the number and particle size distribution of silica particles involved in this embodiment are within the above range, then there will be fewer coarse powders with a tendency to increase charge and fewer micro powders with a tendency to decrease charge, making it easier to achieve a narrower charge distribution.

[0234] Here, the number average particle size and number particle size distribution of silica particles are determined as follows.

[0235] 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 and analysis software (manufactured by MITANI CORPORATION) to determine the equivalent circle diameter of at least 200 particles. Then, the cumulative distribution of the number of each particle was plotted from the small diameter side to determine the number-average particle size, which represents the 50% cumulative particle size from the small diameter side.

[0236] Furthermore, the square root of the value obtained by dividing the cumulative particle size D84 (84% from the smallest diameter side) by the cumulative particle size D16 (16% from the smallest diameter side) is defined as the "Number Size Distribution Index" (GSD). That is, Number Size Distribution Index (GSD) = (D84 / D16) 0.5 .

[0237] -Roundness-

[0238] The average roundness of the silica particles involved in this embodiment is preferably 0.60 or more and 0.96 or less, more preferably 0.70 or more and 0.94 or less, and even more preferably 0.70 or more and 0.92 or less.

[0239] If the average sphericity of the silica particles is within the above range, the specific surface area is large, and over-charging is likely to occur. However, even if the average sphericity of the silica particles involved in this embodiment is within the above range, the charge distribution can be narrowed.

[0240] Here, the sphericity of the silica particles is measured as follows.

[0241] 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 image processing and analysis software (manufactured by MITANI CORPORATION). The roundness of at least 200 particles was determined, and the arithmetic mean was calculated to determine the average roundness.

[0242] In addition, roundness can be calculated using the following formula.

[0243] Roundness = Equivalent circle diameter / circumference = [2 × (Aπ)] 1 / 2 ] / PM

[0244] In the above formula, A represents the projected area, and PM represents the perimeter.

[0245] Methods for manufacturing silica particles

[0246] An example of the method for manufacturing silica particles according to this embodiment includes the following steps:

[0247] The first step involves forming a structure on the surface of the silica masterbatch composed of the reaction product of a trifunctional silane coupling agent; and

[0248] The second step involves adsorbing nitrogen-containing compounds onto at least a portion of the structure.

[0249] The method for manufacturing silica particles according to this embodiment may include a third step after or during the second step, in which a silica masterbatch having the following structure is hydrophobically treated, wherein the structure covers at least a portion of the surface of the silica masterbatch, 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 adsorbs a nitrogen-containing compound.

[0250] The following is a detailed description of the steps involved in the method for manufacturing silica particles according to this embodiment.

[0251] [Preparation Process]

[0252] First, the process for preparing silica masterbatch will be explained.

[0253] As a preparatory step, examples include:

[0254] (i) The process of mixing a solvent containing alcohol and silica masterbatch to prepare a silica masterbatch suspension;

[0255] (ii) A process for obtaining a silica masterbatch suspension by granulation of silica masterbatch using the sol-gel method, etc.

[0256] Examples of silica masterbatches 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 the gas phase method, and molten silica particles.

[0257] The solvent containing the alcohol used in (i) 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; and ethers such as dioxane and tetrahydrofuran. In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0258] Step (1-a) is preferably a step of granulating silica masterbatch by sol-gel method to obtain silica masterbatch suspension.

[0259] More specifically, step (1-a) is preferably a sol-gel method including the following steps: an alkaline catalyst solution preparation step, preparing an alkaline catalyst solution containing an alkaline catalyst in a solvent containing an alcohol; and a silica masterbatch generation step, supplying a tetraalkoxysilane and an alkaline catalyst to the alkaline catalyst solution to generate silica masterbatch.

[0260] The alkaline catalyst solution preparation process is preferably, for example, the process of preparing a solvent containing an alcohol and mixing the solvent with an alkaline catalyst to obtain an alkaline catalyst solution.

[0261] 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; and ethers such as dioxane and tetrahydrofuran. In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0262] 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.

[0263] The concentration of the alkaline catalyst in the alkaline 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.

[0264] The process of generating silica masterbatch involves supplying tetraalkoxysilane and an alkaline catalyst to an alkaline catalyst solution to allow the tetraalkoxysilane to react (hydrolysis and condensation) in the alkaline catalyst solution to generate silica masterbatch.

[0265] In the silica masterbatch production process, after the initial supply of tetraalkoxysilane, the nuclei are generated through the reaction of tetraalkoxysilane (nuclei generation stage), and then the nuclei grow (nuclei growth stage) to produce silica masterbatch.

[0266] Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. From the viewpoint of controllability of the reaction rate or uniformity of the shape of the generated silica masterbatch, tetramethoxysilane or tetraethoxysilane is preferred.

[0267] 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 can be of the same type as the alkaline catalyst pre-contained in the alkaline catalyst solution, or it can be of a different type, but the same type is preferred.

[0268] The supply of tetraalkoxysilane and alkaline catalyst to the alkaline catalyst solution can be either continuous or intermittent.

[0269] In the silica masterbatch production process, the temperature of the alkaline catalyst solution (the temperature at which it is supplied) is preferably 5°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower.

[0270] [First Process]

[0271] In the first step, a structure composed of the reaction product of a trifunctional silane coupling agent is formed.

[0272] Specifically, in the first step, for example, a trifunctional silane coupling agent is added to the silica masterbatch suspension, causing the trifunctional silane coupling agent to react with the surface of the silica masterbatch to form a structure composed of the reaction products of the trifunctional silane coupling agent. The trifunctional silane coupling agent forms the structure composed of the reaction products of the trifunctional silane coupling agent through the reaction of its functional groups with each other and with the OH groups on the surface of the silica particles.

[0273] The reaction of the trifunctional silane coupling agent is carried out by adding the trifunctional silane coupling agent to the silica masterbatch suspension and then heating the suspension while stirring it.

[0274] Specifically, for example, the suspension is heated to above 40°C and below 70°C, a trifunctional silane coupling agent is added, and then the mixture is stirred. The stirring time is preferably above 10 minutes and below 24 hours, more preferably above 60 minutes and below 420 minutes, and even more preferably above 80 minutes and below 300 minutes.

[0275] [Second Process]

[0276] 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.

[0277] Specifically, in the second step, firstly, a nitrogen-containing compound is added to, for example, a silica masterbatch suspension, and stirring is performed, 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.

[0278] In the second step, for example, an alcoholic solution containing a nitrogen-containing compound can be added to the silica particle suspension.

[0279] The alcohol may be of the same type as the alcohol contained in the silica masterbatch suspension, or it may be of a different type, but more preferably the same type.

[0280] 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.

[0281] [Third Process]

[0282] In the third step, after or during the second step, a silica masterbatch having the following structure is subjected to hydrophobic treatment, the structure being composed of the reaction product of the silica masterbatch trifunctional silane coupling agent and having nitrogen-containing compounds adsorbed in at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

[0283] Specifically, in the third step, for example, after adding a nitrogen-containing compound to a silica masterbatch suspension in which the structure is formed, a hydrophobic treatment agent is added.

[0284] The hydrophobic treatment agent forms a hydrophobic layer by reacting the functional groups of the hydrophobic treatment agent with each other and with the OH groups of the silica masterbatch.

[0285] The reaction of the hydrophobic treatment agent is carried out by adding a trifunctional silane coupling agent to a silica masterbatch suspension and then heating the suspension while stirring it.

[0286] Specifically, for example, the suspension is heated to above 40°C and below 70°C, a hydrophobic treatment agent is added, and then the mixture is stirred. The stirring time is preferably 10 minutes or more and 24 hours or less, more preferably 20 minutes or more and 120 minutes or less, and even more preferably 20 minutes or more and 90 minutes or less.

[0287] [Drying Process]

[0288] In the method for manufacturing silica particles according to this embodiment, it is preferable to perform a drying step to remove the solvent from the suspension after performing the second or third step. Alternatively, the drying step may also be performed in the second or third step.

[0289] Drying methods include, for example, thermal drying, spray drying, and supercritical drying.

[0290] Spray drying can be performed using conventionally known methods employing commercially available spray dryers (such as rotary disc dryers or nozzle dryers). For example, it is performed by spraying a liquid onto a hot air stream at a rate of 0.2 liters / hour or more and 1 liter / hour or less. In this case, the temperature of the hot air is preferably, for example, within the range of an inlet temperature of 70°C or more and 400°C or less, and an outlet temperature of 40°C or more and 120°C or less. If the inlet temperature is below 70°C, the drying of the solid components contained in the dispersion becomes insufficient. Furthermore, if the temperature exceeds 400°C, the particle shape will deform during spray drying. And, if the outlet temperature is below 40°C, the solid components are poorly dried and will adhere to the inside of the apparatus. A more preferred inlet temperature is, for example, within the range of 100°C or more and 300°C or less.

[0291] The concentration of silica particles 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, based on the solid content.

[0292] In supercritical drying, the surface tension between particles is largely neutralized by utilizing supercritical fluids to remove the solvent, and the primary particles contained in the suspension are dried in a state of suppressed aggregation. Therefore, silica particles with high particle size uniformity are readily obtained.

[0293] Examples of substances that can be used as supercritical fluids include carbon dioxide, water, methanol, ethanol, and acetone. From the viewpoint of processing efficiency and suppressing the generation of coarse particles, the solvent removal process is preferably a process that uses supercritical carbon dioxide, for example.

[0294] Specifically, supercritical drying is carried out, for example, through the following operations.

[0295] A suspension is contained in a closed reactor. Liquefied carbon dioxide is then introduced, the reactor is heated, and a high-pressure pump is used to pressurize the reactor, causing the carbon dioxide to become supercritical. Liquefied carbon dioxide is then introduced into the closed reactor, while supercritical carbon dioxide flows out, thus allowing supercritical carbon dioxide to flow into the suspension within the closed reactor. During this flow, the solvent dissolves in the supercritical carbon dioxide, and is removed along with the supercritical carbon dioxide flowing out of the closed reactor.

[0296] The temperature and pressure inside the aforementioned closed reactor are set to the temperature and pressure required for carbon dioxide to reach a supercritical state. The critical point of carbon dioxide is 31.1℃ / 7.38MPa, for example, set at a temperature above 40℃ and below 200℃ / a pressure above 10MPa and below 30MPa.

[0297] The flow rate of the supercritical fluid in supercritical drying is preferably 80 mL / s or more and 240 mL / s or less.

[0298] The obtained silica particles are preferably decomposed, pulverized, or screened as needed to remove coarse particles or agglomerates. Decomposition and pulverization are carried out, for example, using dry pulverizing devices such as jet mills, vibratory mills, ball mills, and needle mills. Screening is carried out, for example, using vibrating screens and air-powered screens.

[0299] Example

[0300] The embodiments of the present invention will be described in detail below using examples, but the embodiments of the present invention are not limited to these examples. In the following description, unless otherwise specified, "%" refers to a mass reference.

[0301] Manufacturing of Silica Particles

[0302] [Examples 1, 3-25, 27-32, Comparative Examples 1-4]

[0303] The suspensions containing silica particles in each example were prepared as shown below.

[0304] -Preparation of alkaline catalyst solution-

[0305] A base catalyst solution was obtained by adding the amounts of methanol, ion-exchanged water and 10% ammonia (NH4OH) shown in Table 1 to a glass reaction vessel equipped with a metal stirring rod, a drip nozzle and a thermometer and stirring the mixture.

[0306] Granulation of silica masterbatch via sol-gel method-

[0307] The temperature of the alkaline catalyst solution was adjusted to 40°C, and nitrogen replacement was performed on the alkaline catalyst solution. Then, while stirring the alkaline catalyst solution, 124 parts by mass of tetramethoxysilane (TMOS) and ammonia water (NH4OH) with a catalyst concentration of 7.9% were added dropwise to obtain a silica masterbatch suspension.

[0308] -Addition of 3-functional silane coupling agents-

[0309] The silica masterbatch suspension was heated to 40°C, and while stirring, the types and amounts of trifunctional silane coupling agents shown in Table 1 were added to the suspension. Then, stirring was continued for 120 minutes to allow the trifunctional silane coupling agents to react. This resulted in the formation of an adsorption structure.

[0310] -Addition of nitrogen-containing compounds-

[0311] An alcoholic solution was prepared by diluting the nitrogen-containing compounds shown in Table 1 with butanol.

[0312] Next, an alcohol solution prepared by diluting the nitrogen-containing compound with butanol was added to the suspension. At this point, the alcohol solution was added in such a manner that the amount of the nitrogen-containing compound relative to 100 parts by mass of the solid content of the silica masterbatch suspension was as shown in Table 1. Then, the mixture was stirred at 30°C for 100 minutes to obtain a suspension containing the nitrogen-containing compound.

[0313] -dry-

[0314] Next, 300 parts by mass of the suspension were placed in a reaction vessel, and CO2 was introduced while stirring. The temperature and pressure in the reaction vessel were then increased to the levels shown in Table 1. While maintaining the temperature and pressure, CO2 was introduced and discharged at a flow rate of 5 L / min. Then, the solvent was removed over a period of 120 minutes, yielding silica particles for each example.

[0315] [Example 2]

[0316] Using a small spray dryer B-290 (manufactured by Nihon BUCHI.KK), the cylinder was set to the temperature and pressure shown in Table 1, and spray drying was carried out under the condition of feeding silica particle suspension at a feed rate of 0.2 L / h. Otherwise, silica particles were obtained in the same manner as in Example 1.

[0317] [Example 26]

[0318] After adding a nitrogen-containing compound, hexamethyldisilazane (HMDS) at a mass of 50% relative to the solid content of the silica masterbatch was added, and the surface of the silica masterbatch was hydrophobically treated by stirring at 65°C for 3 hours. The amount of nitrogen-containing compound was set to 50 parts. Otherwise, silica particles were obtained in the same manner as in Example 1.

[0319] [evaluate]

[0320] (Various characteristics)

[0321] The following properties of the obtained silica particles were determined according to the methods described above.

[0322] • Number-average particle size (labeled as "particle size" in the table)

[0323] • Average roundness (marked as "roundness" in the table)

[0324] Hydrophobicity

[0325] • OH radical content determined using the Sears method (labeled as "OH radical content" in the table)

[0326] Volume resistivity

[0327] • Peak positions on the pore distribution curve of nitrogen adsorption method (marked in the table as "first peak position of pore distribution curve" and "second peak position of pore distribution curve").

[0328] (Charge capacity in low humidity and charge capacity in high humidity)

[0329] The low-humidity charge and high-humidity charge of the silica particles in each example were measured as follows.

[0330] 5g of silica particles prepared with 2% by mass added to the surface of MBX-12 manufactured by Sekisui Chemical Co., Ltd., and 50g of SPL-100 manufactured by Unitika Ltd. were weighed and mixed. The mixed sample shown on the left was stirred in a 10°C, 10%RH chamber using a TURBLER shaker for 2 minutes, and the result obtained by measuring the charge using a TB200 manufactured by TOSHIBA CORPORATION was designated as FC. The result obtained by stirring in a 30°C, 90%RH chamber using a TURBLER shaker for 2 minutes and measuring the charge using a TB200 manufactured by TOSHIBA CORPORATION was designated as FA. Their ratio FA / FC (high wet charge / low wet charge ratio) was used for evaluation.

[0331] G1(◎): FA / FC (high humidity charge / low humidity charge ratio) is 0.8 or higher and less than 1.1.

[0332] G2(〇): FA / FC (high humidity charge / low humidity charge ratio) is 0.65 or higher and less than 0.8.

[0333] G3(△): FA / FC (high humidity charge / low humidity charge ratio) is 0.5 or higher and less than 0.65.

[0334] G4(×): FA / FC (high humidity charge / low humidity charge ratio) is less than 0.5

[0335] (Charge distribution under high temperature and high humidity environment)

[0336] The charge distribution of the silica particles in each example was evaluated as follows.

[0337] 5g of silica particles prepared with 2% by mass were added to the surface of MBX-12 manufactured by Sekisui Chemical Co., Ltd., and 50g of SPL-100 manufactured by Unitika Ltd. were weighed and mixed. The mixed sample described on the left was stirred for 2 minutes in a 30°C, 90% RH chamber using a TURBLER shaker and evaluated by CSG (charge spectrograph method) image analysis. The charge distribution was defined as [Q(80)-Q(20)] / Q(50), which is the difference between the cumulative charge Q(20) and the charge Q(80) calculated from the charge distribution and divided by the charge Q(50). The evaluation criteria are as follows.

[0338] G1(◎): The value of [Q(80)-Q(20)] / Q(50) is less than 0.7

[0339] G2(○): The value of [Q(80)-Q(20)] / Q(50) is less than 0.8 and greater than 0.7.

[0340] G3(△): [Q(80)-Q(20)] / Q(50) value is less than 1.0 and greater than 0.8

[0341] G4(×): [Q(80)-Q(20)] / Q(50) has a value of 1.0 or higher.

[0342] The evaluation results are shown in Table 1.

[0343] In addition, the details of the abbreviations in Table 1 are as follows.

[0344] MTMS: Methyltrimethoxysilane

[0345] DTMS: n-Dodecyltrimethoxysilane

[0346] ·TP-415: [N + (CH)3(C 14 C 29 )2]4Mo8O 28 4-(Manufactured by Hodogaya Chemical Co., Ltd., N,N-Dimethyl-N-tetradecyl-1-tetradecanaminium, hexa-μ-oxotetra-μ3-oxodi-μ5-oxotetradecaoxooctamolybdate(4-)(4:1))(Extraction yield X using ammonia / methanol mixed solution = 61-89% by mass, and the ratio of extraction yield X to extraction yield Y using water X / Y = 0.03-0.26)

[0347] • P51: “Vontron P51” manufactured by ORIENT CHEMICAL INDUSTRIES CO.,LTD., containing 4-hydroxynaphthalene-1-sulfonic acid benzyltributylammonium as shown in the following formula (extraction amount X = 0.78% by mass when extracted with ammonia / methanol mixed solution, and the ratio of extraction amount X to extraction amount Y when extracted with water X / Y = 0.19).

[0348] [Chemical Formula 4]

[0349]

[0350] • Trideamine (extraction yield X = 66% by mass using ammonia / methanol mixed solution, ratio of X to Y using water extraction X / Y = 0.19)

[0351] ·[3-(trimethoxysilyl)propyl]dimethyloctadecylammonium chloride

[0352] • Aminopropyltrimethoxysilane (extraction yield X = 78% by mass using ammonia / methanol mixed solution, ratio of extraction yield X to extraction yield Y using water X / Y = 0.16)

[0353] Quotanium-80 (Extraction yield X = 80% by mass using ammonia / methanol mixed solution, ratio of extraction yield X to extraction yield Y using water X / Y = 0.09)

[0354] • Bis(dibutyldibenzylammonium)molybdic acid (extraction yield X = 65% by mass using ammonia / methanol mixed solution, ratio of extraction yield X to extraction yield Y using water X / Y = 0.15)

[0355] • Phenylacetamine (extraction yield X = 55% by mass using ammonia / methanol mixed solution, ratio of extraction yield X to extraction yield Y using water X / Y = 0.28)

[0356] ·4-(2-Octylamino)diphenylamine (extraction yield X = 78% by mass using ammonia / methanol mixed solution, ratio of extraction yield X to extraction yield Y using water X / Y = 0.14)

[0357] • N-Benzyl-N-methylethanolamine (Extraction yield X = 58% by mass using ammonia / methanol mixed solution, ratio of extraction yield X to extraction yield Y using water X / Y = 0.27)

[0358] • 2,3-Bis(2,6-diisopropylphenylimino)butane (extraction yield X = 81% by mass using ammonia / methanol mixed solution, ratio of extraction yield X to extraction yield Y using water X / Y = 0.11)

[0359] ·3-Indoleacetonitrile (extraction yield X = 80% by mass using ammonia / methanol mixed solution, ratio of extraction yield X to extraction yield Y using water X / Y = 0.12)

[0360] [Table 1-1]

[0361]

[0362] [Table 1-2]

[0363]

[0364] Based on the above results, it can be seen that, compared with the silica particles of the comparative example, the silica particles of the embodiment have a narrower charge distribution when charged.

[0365] The embodiments of the present invention described above are provided for illustrative purposes. Furthermore, these embodiments do not encompass the entirety of the invention, nor do they limit the invention to the disclosed methods. It will be apparent to those skilled in the art that various modifications and variations will be readily understood. These embodiments were chosen and described to most readily explain the principles and applications of the invention. Thus, those skilled in the art can understand the invention through various modifications that are assumed to be optimized for specific uses of various embodiments. The scope of the invention is defined by the foregoing claims and their equivalents.

Claims

1. A silica particle having: Silica masterbatch; and A structure comprising at least a portion of the surface of the silica masterbatch and composed of the reaction product of a trifunctional silane coupling agent. The silica particles contain nitrogen-containing compounds, and the content of these nitrogen-containing compounds relative to the silica particles, expressed in N atoms, is 0.005% by mass or more and 0.50% by mass or less. Hydrophobicity is above 10% and below 60%. The volume resistivity is 1×10 8 Ω·cm or more and 1×10 12.5 Below Ω·cm, in, At least a portion of the micropores of the reaction product of the trifunctional silane coupling agent adsorbs the nitrogen-containing compound. The nitrogen-containing compound is selected from 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.

2. The silica particles according to claim 1, wherein, On the micropore distribution curve of the nitrogen adsorption method, there is a first peak in the range of micropore diameter above 0.01 nm and below 2 nm, and a second peak in the range of micropore diameter above 1.5 nm and below 50 nm.

3. The silica particles according to claim 1 or 2, wherein the degree of hydrophobicity is 10% or more and 50% or less.

4. The silica particles according to claim 1 or 2, wherein the volume average particle size is 10 nm or more and 200 nm or less.

5. The silica particles according to claim 4, wherein the volume average particle size is 10 nm or more and 80 nm or less.

6. The silica particles according to claim 1 or 2, wherein the average sphericity is 0.60 or more and 0.96 or less.

7. The silica particles according to claim 6, wherein the average sphericity is 0.70 or higher and 0.92 or lower.

Images