JP7007982B2 - Colloidal silica - Google Patents

Description

The present invention relates to a dispersion liquid (colloidal silica) of nano-sized silica particles.

Colloidal silica, which is composed of silica particles and a dispersion medium, can be mixed with a resin, resin raw material, etc. to obtain properties such as strength, hardness, heat resistance, and insulation without impairing the moldability and transparency of the resin. Since it can be improved, it is useful for applications such as adhesive materials, dental materials, optical members, coating materials (for hard coats and antiglares), and nanocomposite materials. Further, silica particles having a fine particle size are also used as an abrasive because of their hardness. Particularly in recent years, nano-sized colloidal silica has attracted attention.

For example, Patent Document 1 describes that an aqueous silica sol having an average particle diameter of 10 to 30 millimicrons can be obtained by contacting an aqueous solution of an alkali metal silicate with a hydrogen-type strong acid cation exchange resin. ..

Patent Document 2 describes a hydrolyzed solution obtained by hydrolyzing alkyl silicate at a temperature of 20 ° C. or lower in a mother liquor composed of water or alkaline water having a pH of 12 or less (for example, alkaline water to which tetramethylammonium hydroxide is added). It is described that silica particles having a primary particle diameter of 24.2 nm and a secondary particle diameter of 30.0 nm can be obtained by adding the above.

Japanese Patent No. 3225553 Japanese Unexamined Patent Publication No. 2013-82584

However, in the case of the hydrothermal synthesis method of Patent Document 1, metal impurities cannot be completely eliminated due to strong alkaline conditions, and the particle size varies widely, so that the silica particles can be used for various purposes. There was a problem when using it. Further, in Patent Document 2, silica particles are produced by the sol-gel method, but according to the study by the present inventors, the silica particles obtained in Patent Document 2 have a small true density of about 1.8 and have pores. There was a problem with strength because there were many.

Therefore, an object of the present invention is to provide colloidal silica that can be used without problems in terms of purity, strength, etc., even if it is nano-sized silica particles.

The present invention that solves the above problems is as follows.

[1] Silica particles having an arithmetic average particle diameter of 100 nm or less and a dispersion medium obtained based on a transmission electron micrograph are included, and the true density of the silica particles is 1.90 g / cm ³ or more and the pH is. Colloidal silica having an Al concentration of 500 ppm (mass basis) or less and 9.0 or more.
[2] The colloidal silica according to [1], which contains an amine.
[3] The colloidal silica according to [2], wherein the pKa of the H ⁺ adduct of the amine is 7.5 or less.
[4] The colloidal silica according to [3], wherein the amine is a compound that does not contain a hydroxyl group and an ether bond.
[5] The colloidal silica according to any one of [1] to [4], wherein the dispersion medium is water or a mixed solvent of water and an alcohol-based solvent.
[6] The colloidal silica according to any one of [1] to [5] on which the silica particles are surface-treated.
[7] The colloidal silica according to any one of [1] to [6], wherein the coefficient of variation of the particle size of the silica particles obtained based on a transmission electron micrograph is 20% or less.
[8] The colloidal silica according to any one of [1] to [7], wherein the Na concentration is 200 ppm (mass standard) or less and the Fe concentration is 50 ppm (mass standard) or less.
[9] The colloidal silica according to any one of [1] to [8], wherein the Na concentration is 5 ppm (mass standard) or less and the K concentration is 5 ppm (mass standard) or less.
[10] The colloidal silica according to any one of [1] to [9] is filtered through an ultrafiltration membrane, subsequently treated with a cation exchange resin, and then replaced with an organic solvent different from the solvent of the colloidal silica. A method for producing an organic solvent dispersion of silica particles.
[11] The production method according to [10], wherein the organic solvent is at least one selected from an ether solvent, a ketone solvent, a hydrocarbon solvent, a halogenated hydrocarbon solvent, and an ester solvent.

According to the present invention, in colloidal silica containing nano-order silica fine particles, since the true density of the silica fine particles is increased and the Al concentration is reduced, excellent performance in terms of purity, strength, etc. can be exhibited. ..

The present invention relates to nano-sized colloidal silica. The size of the silica particles contained in the colloidal silica is determined by the arithmetic average particle diameter (hereinafter, referred to as "TEM diameter" and may be represented by the symbol d _TEM ) obtained based on a transmission electron micrograph. Specifically, the TEM diameter (d _TEM ) is 100 nm or less. The TEM diameter (d _TEM ) is preferably 70 nm or less, more preferably 50 nm or less, still more preferably 30 nm or less, and may be, for example, 3 nm or more, preferably 5 nm or more, and more preferably 10 nm or more.

The TEM diameter (d _TEM ) is determined by observing silica particles with a transmission electron microscope having a magnification of 200,000 times, and among the silica particles contained in the obtained transmission electron microscope image, about 50 to 100 silica particles. Each major axis can be measured and calculated as an average value (arithmetic average value) based on the number of each.

The silica particles preferably have a sharp particle size distribution. The coefficient of variation of the TEM diameter (d _TEM ) is, for example, 20% of the coefficient of variation of the particle diameter of the silica particles (value obtained by dividing the standard deviation by the arithmetic mean value × 100) obtained based on a transmission electron micrograph. Hereinafter, it is preferably 15% or less, more preferably 10% or less, and for example, 2% or more, further 4% or more is also allowed.

Further, it is preferable that the silica particles are not aggregated in the dispersion liquid, and specifically, the average measured by a dynamic light scattering method when a colloidal silica whose concentration is adjusted as necessary is used as a measurement sample. The secondary particle size (hereinafter, may be referred to as “DLS diameter” and may be represented by the symbol d _DLS ) is, for example, 80 nm or less, preferably 60 nm or less, more preferably 40 nm or less, and particularly preferably 20 nm or less. Yes, for example, 1 nm or more, preferably 2 nm or more.

In the dynamic light scattering method, the particle size is measured based on the moving speed of the silica particles in the measurement sample, and the moving speed of the silica particles in the measurement sample correlates with the volume occupied by the silica particles. The particle size (secondary particles) according to the aggregation of silica particles can be measured. Specifically, the measurement sample is irradiated with laser light (preferably wavelength 650 nm), the autocorrelation function is obtained by the photon correlation method from the temporal fluctuation fluctuation of the scattered light intensity, and the average particle size (fluid dynamics) is obtained by the cumulant method. Diameter) is calculated. Further, in the present invention, the particle size is measured in a state where the concentration of colloidal silica is kept constant (9% by mass) while using colloidal silica as a measurement sample. If the colloidal silica concentration is higher than 9% by mass, dilute it with the same dispersion medium as the colloidal silica to make the concentration 9% by mass, and use it as a measurement sample. The concentration is concentrated to 9% by mass by external filtration to obtain a measurement sample.

The silica particles are also characterized in that the true density is 1.90 g / cm ³ or more. Since the true density is high, the strength above a predetermined level can be maintained. The true density is preferably 1.95 g / cm ³ or more, and more preferably 2.00 g / cm ³ or more. The upper limit of the true density is, for example, 2.5 g / cm ³ or less, preferably 2.3 g / cm ³ or less.

Further, the silica particles may be surface-treated, if necessary. A surface treatment agent is usually used for the surface treatment, and the surface treatment agent may contain at least one of an organosilicon compound such as a silane coupling agent and a disilazan compound; an organic acid; and a titanium coupling agent. It is preferable to contain at least an organosilicon compound.

The silane coupling agent means a compound in which a hydrolyzable group (a group capable of forming a silanol group by hydrolysis) and a functional group are bonded to a central silicon atom, and for example, methyltrimethoxysilane and methyltriethoxysilane. , Dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltri Methoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, p-styryltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3- (2-aminoethylamino) propyltrimethoxysilane, 3- (2-aminoethylamino) propyltriethoxysilane , 3-Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3 -Isocyanapropyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, trifluoropropyltrimethoxysilane, phenyltrimethoxysilane, phenyl Triethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, Alkoxysilane compounds such as 3-acryloxypropyltrimethoxysilane, 3-acryloxypropylmethyldimethoxysilane; methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, methylvinyldichlorosilane, phenyltrichlorosilane, diphenyldichlorosilane. , Methyldiphenylchlorosilane, etc. Chlorosilane compounds; acyloxysilane compounds such as tetraacetoxysilane, methyltriacetoxysilane, phenyltriacetoxysilane, dimethyldiacetoxysilane, diphenyldiacetoxysilane, trimethylacetoxysilane; silazane compounds such as hexamethyldisilazane; dimethylsilanediol , Silanol compounds such as diphenylsilanediol and trimethylsilanol; and the like.

The disilazane compound means a compound having a Si—N—Si bond in the molecule, for example, 1,1,1,3,3,3-hexamethyldisilazan, 1,1,3,3-tetra. Methyl disilazane, 1,3-bis (3,3,3-trifluoropropyl) -1,1,3,3-tetramethyldisilazane, 1,3-bis (chloromethyl) tetramethyldisilazane, 1, 3-Diphenyltetramethyldisilazan, 1,3-divinyl-1,1,3,3-tetramethyldisilazan, 2,2,4,4,6,6-hexamethylcyclotrisilazane, 2,4,6 -Trimethyl-2,4,6-trivinylcyclotrisilazane, heptamethyldisilazan, octamethylcyclotetrasilazane, hexamethyldisilazan lithium, hexamethyldisilazan sodium, hexamethyldisilazan potassium and the like can be mentioned.

The organic acid is preferably a compound having a carboxy group (hereinafter, may be referred to as a "carboxylic acid compound"), and the carboxylic acid compound is a cation (for example, a metal cation such as an alkali metal cation or an alkaline earth metal cation). It may form a salt with a molecular cation such as an ammonium ion).

The carboxylic acid compound includes (meth) acrylic acids; one or more substituents selected from the group consisting of an ester group, an ether group, an amide group, a thioester group, a thioether group, a carbonate group, a urethane group and a urea group (hereinafter, Carboxylic acid having a "specific substituent"); linear carboxylic acid (linear aliphatic carboxylic acid, preferably linear saturated aliphatic carboxylic acid, etc.), branched chain carboxylic acid (such as linear saturated aliphatic carboxylic acid). Branched chain aliphatic carboxylic acid, preferably branched chain saturated aliphatic carboxylic acid, etc.), cyclic carboxylic acid (lipid ring carboxylic acid, preferably alicyclic carboxylic acid having no unsaturated double bond, etc.) and A compound having 4 to 20 carbon atoms having a carboxy group, which is one or more (preferably one) selected from aromatic carboxylic acids and the like; is preferably adopted.

Specific examples of the carboxylic acid compound include (meth) acrylic acids (eg, acrylic acid and methacrylic acid), (meth) acryloxy C _1-6 alkylcarboxylic acids and the like (eg, 3-acryloxypropionic acid and the like). Half esters of C _3-9 aliphatic dicarboxylic acid (meth) acryloxy C _1-6 alkyl alcohol (for example, 2-acryloxyethyl succinic acid, 2-methacryloxyethyl succinic acid, etc.), C _5-10 alicyclic Half esters of (meth) acryloxy C _1-6 alkyl alcohol of formula dicarboxylic acid (eg 2-acryloxyethyl hexahydrophthalic acid, 2-methacryloxyethyl hexahydrophthalic acid, 2-acryloxyethyl phthalic acid, 2 -Hatyloxyethylphthalic acid, etc.), C _8-14 Fragrant dicarboxylic acid (meth) acryloxi C _1-6 Half esters of alkyl alcohols (eg, 2-acryloxyethyl phthalic acid, 2-methacryloxyethyl phthalic acid) Etc.); carboxylic acids having ester groups such as butyric acid, valeric acid, hexanoic acid, hepanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, stearic acid and other linear carboxylic acids; pivalic acid, 2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,2-dimethylvaleric acid, 2,2-diethylbutyric acid, 3,3-diethylbutyric acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, 3- Examples thereof include branched chain carboxylic acids such as methylhexanoic acid, 3-ethylhexanoic acid, 2-methylheptanic acid, 4-methyloctanoic acid and neodecanoic acid; and cyclic carboxylic acids such as naphthenic acid and cyclohexanedicarboxylic acid.

Examples of the titanium coupling agent include isopropyltriisostearoyl titanate, isopropyldimethacrylisostearoyl titanate, isopropyltri (dodecyl) benzenesulfonyl titanate, neopentyl (diallyl) oxy-tri (dioctyl) phosphate titanate, and neopentyl (diallyl). Oxy-trineododecanoyl titanate and the like can be mentioned.

The surface treatment agent is preferably a surface treatment agent having a (meth) acryloyl group, and the surface treatment agent having a (meth) acryloyl group is a silane coupling agent having a (meth) acryloyl group or a (meth). Organic acids having an acryloyl group are preferred.

As the silane coupling agent having a (meth) acryloyl group (hereinafter, may be referred to as “(meth) acryloyl group-containing silane coupling agent”), those in which the hydrolyzable group is an alkoxy group are preferable, for example. Bifunctional (meth) acryloyl group-containing silane cups such as 3-acryloxypropyldimethoxymethylsilane, 3-acryloylpropyldiethoxymethylsilane, 3-methacryloxypropyldimethoxymethylsilane, 3-methacryloxypropyldiethoxymethylsilane Ring agent; Trifunctional (meth) acryloyl group-containing silane such as 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane. Coupling agent; etc.

Examples of the organic acid having a (meth) acryloyl group include 2-acryloxyethyl succinic acid, 2-methacryloxyethyl succinic acid, 2-acryloxyethyl hexahydrophthalic acid, 2-methacryloxyethyl hexahydrophthalic acid, 2-. Examples thereof include acryloyloxyethyl phthalic acid and 2-methacryloxyethyl phthalic acid.

The concentration of the silica particles as described above in colloidal silica is, for example, 3% by mass or more, preferably 5% by mass or more, and may be 8% by mass or more. The concentration may be, for example, 40% by mass or less, but is, for example, 30% by mass or less, preferably 20% by mass or less.

The colloidal silica of the present invention containing the silica particles has a pH of 9.0 or higher. By increasing the pH, the acidic hydroxyl group on the surface of silica can be basicized, and the aggregation of silica can be prevented. The pH of colloidal silica is preferably 9.1 or more, more preferably 9.3 or more, and for example, 11.0 or less, preferably 10.0 or less, more preferably 9.8 or less. By not raising the pH too high, it is possible to prevent the residual of excess base. Since the pH is affected by the dispersion medium, in the present invention, it is defined as the pH when water or water / methanol is used as the dispersion medium, and when the pH in water or water / methanol is different, the pH is in water. The pH of is the correct value. Therefore, when colloidal silica uses a dispersion medium other than water and water / methanol, it is replaced with water or water / methanol while removing the dispersion medium (volatilization, etc.) under the condition that the basic component is not removed, and the silica particle concentration is adjusted. A water or water / methanol dispersion kept at the same level as the original colloidal silica is prepared, and the pH of this water or water / methanol dispersion is defined as the pH of the colloidal silica.

Amine is preferable as the base contained for the pH control. The presence of amines more effectively prevents the aggregation of silica particles. The amine may be any of a primary, secondary or tertiary amine, and the primary, secondary or tertiary amine has an improved pH as compared to the quaternary ammonium salt. It is effective for.
Primary, secondary, or tertiary amines are classified into amines with a ring structure and amines without a ring structure (ie, chain structure only), and amines with a ring structure are further ringed. It is classified into amines whose structure is a hydrocarbon ring (aromatic hydrocarbon ring or aliphatic hydrocarbon ring) and amines whose ring structure has a nitrogen-containing heterocycle. Examples of the amine having a ring structure of a hydrocarbon ring include aniline (pKa = 4.87), and examples of the amine having a nitrogen-containing heterocyclic ring structure include pyridine (pKa = 5.2) and quinoline (pKa =). It has an aromatic ring such as 4.92), 2,2'-bipyridyl (pKa = 4.42), imidazole (pKa = 6.9), 1-methylimidazole (pKa = 7.2) and the fragrance. Amine whose group ring is a nitrogen-containing heterocycle; has a nitrogen-containing non-aromatic heterocycle such as 1,2,3,4-tetrahydroquinoline (pKa = 5.0) and indolin (pKa = 5.0). Amine having an aromatic ring condensed in the heterocycle; an amine having a bridging heterocycle such as hexamethylenetetramine (pKa = 5.13); a nitrogen-containing non-fragrance such as thiazolidine (pKa = 6.31). Examples include amines containing only group heterocycles. Examples of amines having only a chain structure include monoamines such as dimethylaminoacetonitrile (pKa = 4.2) and hydrazine-type amines such as acetohydrazide (pKa = 3.24). In the above example, pKa in parentheses indicates the pKa of the compound in which H ⁺ is added to the exemplified amine. From the viewpoint of ensuring good dispersibility, amines having an aromatic ring are preferable, and among them, amines having an aromatic ring and not containing an aromatic heterocycle (for example, aniline); having an aromatic ring and the same. Amines in which the aromatic ring is a nitrogen-containing heterocycle (eg, pyridine, quinoline, 2,2'-bipyridyl, imidazole, 1-methylimidazole); or have a nitrogen-containing non-aromatic heterocycle and the heterocycle is aromatic. Amines having a fused ring (eg, tetrahydroquinoline, indolin) are more preferred. In particular, an amine having an aromatic ring and the aromatic ring being a nitrogen-containing heterocycle or an amine having a nitrogen-containing non-aromatic heterocycle and having an aromatic ring condensed in the heterocycle. Amines having 9 or more carbon atoms (eg, tetrahydroquinolin) are preferred.

Further, it is preferable that the pKa of the H ⁺ adduct of the amine is 7.5 or less. When silica particles are prepared by the sol-gel method, if an amine having a pKa of 7.5 or less is allowed to coexist with a basic catalyst, silica particles having excellent properties such as particle size, distribution, and true density can be obtained. By leaving such amines in colloidal silica in trace amounts, the stability of colloidal silica can be enhanced. The pKa is preferably 7.3 or less, for example 3.0 or more, preferably 3.5 or more, and more preferably 4.0 or more.

Further, the amine may be an amine having a hydroxyl group such as an alkanolamine; an amine having an ether bond such as morpholine, but an amine having no hydroxyl group or an ether bond is preferable.

The amine may be used alone or in combination of two or more.

The amount of amine in colloidal silica may be in the range where the predetermined pH can be achieved, for example, 0.05 to 5% by mass, preferably 0.1 to 2% by mass.

The colloidal silica of the present invention is also characterized in that the Al concentration is low. The Al concentration is 500 ppm (mass standard) or less, preferably 100 ppm (mass standard) or less, more preferably 10 ppm (mass standard) or less, particularly preferably 5 ppm (mass standard) or less, and most preferably 1 ppm (mass standard). It is as follows. The lower limit of the Al concentration is not particularly limited, but may be more than 0 ppm (mass basis).

Further, colloidal silica preferably has low metal impurities (Na, K, Fe, etc.) other than Al. The Na concentration is, for example, 200 ppm (mass standard) or less, preferably 50 ppm (mass standard) or less, more preferably 10 ppm (mass standard) or less, and particularly preferably 5 ppm (mass standard) or less. The lower limit of the Na concentration is not particularly limited, but may be more than 0 ppm (mass basis). The K concentration is, for example, 50 ppm (mass standard) or less, preferably 10 ppm (mass standard) or less, and more preferably 5 ppm (mass standard) or less. The lower limit of the K concentration is not particularly limited, but may be more than 0 ppm (mass basis). The Fe concentration is, for example, 50 ppm (mass standard) or less, preferably 10 ppm (mass standard) or less, and more preferably 5 ppm (mass standard) or less. The lower limit of the Fe concentration is not particularly limited, but may be more than 0 ppm (mass basis). In particular, it is a preferable aspect to achieve both a Na concentration of 200 ppm (mass standard) or less and an Fe concentration of 50 ppm (mass standard) or less, and a Na concentration of 5 ppm (mass standard) or less and a K concentration of 5 ppm (mass standard) or less. It is also a preferable aspect. It is most preferable that Na, K, and Fe are all 1 ppm (mass basis) or less.

Further, the colloidal silica preferably has a low amount of Ca, Mg, Zn, Ni, Co, Cr, U and the like, and these amounts are, for example, 10 ppm (mass standard) or less, preferably 5 ppm (mass standard) or less, respectively. Particularly preferably, it is 1 ppm (mass basis) or less.

The content of impurity metals such as Al, Na, K, Fe, Ca, Mg, Zn, Ni, Co, Cr and U was measured using a high frequency plasma emission spectrophotometer (Agient 8800; manufactured by Agilent Technologies, etc.). can do. Specifically, colloidal silica is added and mixed with a mixed solution of hydrofluoric acid and nitric acid, and nitric acid and hydrogen peroxide solution are sequentially added to this mixed solution to make a total volume of 50 mL, which is measured as a measurement sample solution. can do.

As the dispersion medium of colloidal silica, for example, water, an alcohol-based solvent, or a mixed solvent of water and an alcohol-based solvent is preferable. Water and alcohol-based solvents are used as synthetic solvents for silica particles, and when these are used as dispersion media, solvent substitution is not required, so that colloidal silica can be easily produced. Examples of the alcohol-based solvent include methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol, isobutyl alcohol, pentanol, methylbutanol, neopentyl alcohol, isopentyl alcohol, hexanol, 2-hexanol, and heptanol. Monool-based solvents such as 2-heptanol, octanol, 2-octanol, cyclohexanol, and methylcyclohexanol; diol-based solvents such as ethanediol, propanediol, propylene glycol, butanediol, pentanediol, methylpentanediol, and ethylpentanediol. Triol solvents such as glycerin and hexanetriol; methoxyethanol, ethoxyethanol, methoxymethoxyethanol, propylene glycol monomethyl ether, isopropoxyethanol, butoxyethanol, isopentyloxyethanol, hexyloxyethanol, phenoxyethanol, benzyloxyethanol, diethylene glycol, Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, tetraethylene glycol, polyethylene glycol, methoxypropanol (propylene glycol monomethyl ether), ethoxypropanol, dipropylene glycol, dipropylene glycol monomethyl Ether alcohol solvents such as ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, polypropylene glycol; halogenated alcohol solvents such as chloroethanol, chloropropanediol, trifluoroethanol; hydroxypropionitrile; aminoethanol, dimethyl Amino alcohol-based solvents such as aminoethanol, diethylaminoethanol, diethanolamine, N-butyldiethanolamine, and triethanolamine; and the like can be mentioned. Preferred alcohol solvents are monool solvents such as methanol, diol solvents such as propylene glycol, ether alcohol solvents such as propylene glycol monomethyl ether and the like.

The alcohol-based solvent is not used as a synthetic solvent, but may be a solvent substituted after synthesizing silica particles.

The colloidal silica of the present invention can be prepared by hydrolyzing and condensing alkoxysilane in the presence of water, a basic catalyst, and a specific amine. Since the hydrolysis condensation of alkoxysilane is used, metallic impurities such as Al can be reduced to the utmost limit. By the way, alkoxysilane is hydrolyzed and condensed in the presence of a basic catalyst, and at this time, the silicon atom contained in the alkoxysilane is OH ^- derived from the basic catalyst and OSi derived from the hydrolysis condensate of other alkoxysilanes. ^-It is said that the reaction proceeds by a mechanism similar to the S _N 2 reaction after receiving a nucleophilic attack (GJ Brinker, 1 person outside, "SOL-GEL SCIENCE", 1990, ACADEMIC PRESS LIMITED, p116- 139). As this hydrolysis condensation progresses, more hydroxy groups, SiO ^- groups, etc. with high electron nucleophilicity are bonded to the central silicon atom of alkoxysilane, and the central silicon atom becomes more susceptible to nucleophilic attack, resulting in water addition. Usually, the decomposition condensation is more likely to proceed. However, when a specific amine coexists, it interacts with the hydrogen atom of the hydroxy group, which reduces the reactivity of the central silicon atom and slows down the hydrolysis condensation, so that the particle size can be easily made nano-sized. The density of condensed particles can be increased. Further, by using amine to the extent that there is no shortage, the pH of colloidal silica can be made higher than a predetermined value.

The alkoxysilane is a compound having an alkoxy group (particularly an alkyloxy group) as a substituent of a silicon atom, and as a substituent of a silicon atom, in addition to an alkoxy group, an alkyl group having 2 to 6 carbon atoms or carbon. It may have an aromatic hydrocarbon group of several 6 to 10. Further, the hydrogen atom of the alkyl group may be substituted with a halogen atom, a vinyl group, a glycidyl group, a mercapto group, an amino group or the like.

Examples of the tetrafunctional alkoxysilane having only an alkoxy group (particularly an alkyloxy group) as a substituent of a silicon atom include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, and dimethoxydiethoxysilane. Examples thereof include a silane having four alkyloxy groups having a value of about 1 to 4. Further, as the alkoxysilane having an alkoxy group and an unsubstituted alkyl group as the substituent of the silicon atom, a trifunctional alkoxysilane such as methyltrimethoxysilane and methyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane and the like. Bifunctional alkoxysilane; monofunctional alkoxysilane such as trimethylmethoxysilane and trimethylethoxysilane; and the like. Further, as the alkoxysilane having an alkoxy group and a substituted alkyl group as the substituent of the silicon atom, the chloroalkyl group-containing alkoxysilane such as 3-chloropropylmethyldimethoxysilane and 3-chloropropyltrimethoxysilane; vinyltrimethoxysilane. , Vinyl group-containing alkoxysilanes such as vinyltriethoxysilane; aromatic group-containing alkoxysilanes such as phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane; 3-glycidoxypropyltrimethoxysilane, Glycidyl group-containing alkoxysilanes such as 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane; mercapto group-containing alkoxysilanes such as 3-mercaptopropyltrimethoxysilane; 3-aminopropyltrimethoxysilane , 3- (2-Aminoethylamino) propyltrimethoxysilane and other amino group-containing alkoxysilanes; and the like.

Among them, 1 to 4 functional alkoxysilanes are preferable, 3 to 4 functional alkoxysilanes are more preferable, and tetrafunctional alkoxysilanes are even more preferable. The larger the functional number (the number of alkoxy groups) of the alkoxysilane, the less likely it is that impurities will be mixed into the obtained silica calcined body. Of the alkoxysilanes used in the calcined silica, the tetrafunctional alkoxysilane (preferably tetramethoxysilane, tetraethoxysilane) is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 98% by mass. % Or more, and the upper limit is 100% by mass. From the viewpoint of reactivity, the alkoxy group preferably has 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 to 2 carbon atoms. That is, the alkoxysilane particularly preferably used for the silica particles of the present invention is a silane having four alkyloxy groups having about 1 to 4 carbon atoms, such as tetramethoxysilane and tetraethoxysilane.

In the reaction solution for hydrolyzing and condensing alkoxysilane, the concentration of alkoxysilane is preferably 0.05 mmol / g or more, more preferably 0.1 mmol / g or more, still more preferably 1 mmol / g or more. The upper limit is not particularly limited, but is preferably 3 mmol / g or less, for example. When the concentration of alkoxysilane in the reaction solution is in this range, the reaction rate can be easily controlled and the particle size can be made uniform.

The concentration of water in the reaction solution is preferably 2 mmol / g to 25 mmol / g. However, since the amount of water changes due to the hydrolysis / condensation of alkoxysilane, the amount at the time of preparation (before the start of hydrolysis / condensation) is used as a reference. The molar ratio of water to alkoxysilane (water / alkoxysilane) is preferably 3 to 20, more preferably 4 to 10. When the molar ratio of water to alkoxysilane is in this range, the silanol groups remaining inside the silica particles are likely to be reduced.

Examples of the basic catalyst include ammonia, amines having an H ⁺ adduct pKa of more than 7.5, and a quaternary ammonium compound. Examples of the ammonia include ammonia; an ammonia generating agent such as urea; and the like. Examples of the amines include aliphatic amines such as methylamine, ethylamine, propylamine, n-butylamine, dimethylamine, dibutylamine, trimethylamine and tributylamine; alicyclic amines such as cyclohexylamine; aromatics such as benzylamine. Group amines; alkanol amines such as monoethanolamines, diethanolamines, triethanolamines; and the like. Examples of the quaternary ammonium compound include tetramethylammonium hydroxide and tetrabutylammonium hydroxide.

As the basic catalyst, ammonia and amines having an H ⁺ adduct pKa of more than 7.5 are preferable from the viewpoint of easy control of the particle size. Further, from the viewpoint of increasing the purity of the obtained silica particles, it is preferable that the catalyst is easy to remove from the silica, and specifically, ammonia and an aliphatic amine are more preferable. Further, from the viewpoint of having both a catalytic effect and ease of removal, ammonia is preferable, and ammonia is particularly preferable.

The concentration of the basic catalyst in the reaction solution is preferably 0.8 mmol / g to 2 mmol / g. The total mass ratio of the basic catalyst, the basic catalyst, and water (basic catalyst / (basic catalyst + water)) is preferably 0.1 or more, more preferably 0.2 or more. It is preferably 0.4 or less, and more preferably 0.32 or less.

The specific amine used to easily increase the particle size of silica particles to nano-size and to increase its density (density) is an amine as a base contained in colloidal silica for pH control described above. Examples thereof include amines similar to those exemplified, and the preferred range thereof is the same as that of amines as a base contained in colloidal silica for pH control.

The concentration of the specific amine in the reaction solution is preferably 0.01 mmol / g to 1 mmol / g. The mass ratio of the specific amine to the basic catalyst (specific amine / basic catalyst) is preferably 0.1 or more, more preferably 0.2 or more, and 1.0 or less. It is preferably 0.7 or less, and more preferably 0.7 or less.

When hydrolyzing and condensing alkoxysilane, a diluent may be further coexisted. By containing a diluent, the hydrophobic alkoxysilane and water can be easily mixed, the progress of hydrolysis / condensation of the alkoxysilane can be made uniform in the reaction solution, and the obtained silica particles can be mixed. Dispersibility is improved. Examples of the diluent include monools such as methanol, ethanol, propanol, isopropyl alcohol, n-butyl alcohol, t-butyl alcohol and pentyl alcohol; diols such as ethylene glycol, propylene glycol and 1,4-butanediol; etc. A water-soluble organic solvent typified by alcohols in the above is preferable.

In the reaction solution, the diluent is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 55% by mass or more, preferably 80% by mass or less, and more preferably 70% by mass. It is mass% or less, more preferably 65 mass% or less.
The diluent is preferably 120 parts by mass or more, more preferably 150 parts by mass or more, and more preferably 500 parts by mass or less with respect to 100 parts by mass of the total of alkoxysilane and water. It is preferably 300 parts by mass or less, more preferably 250 parts by mass or less.
The larger the amount of the diluent, the easier it is to make the progress of the reaction uniform, and the smaller the amount of the diluent, the higher the reaction rate. However, since the amount of alcohol changes due to the hydrolysis / condensation of alkoxysilane, the amount of the diluent is based on the amount at the time of charging (before the start of hydrolysis / condensation).

Ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; paraffins such as isooctane and cyclohexane; ethers such as dioxane and diethyl ether; aromatic hydrocarbons such as benzene and toluene; etc. A hydrophobic organic solvent may be contained. When these hydrophobic organic solvents are used, a surfactant may be added to improve the dispersibility.

Each of the above components may be mixed in an appropriate order, but for example, a premixed solution in which at least a part of each of the above components (for example, water, a basic catalyst, a specific amine, a diluent, etc.) is mixed in advance is prepared. After preparation, it may be mixed with alkoxysilane. The alkoxysilane may be mixed with the diluent in advance and then mixed with the premixture.

When hydrolyzing and condensing alkoxysilane, the reaction temperature is preferably 0 to 100 ° C, more preferably 20 to 70 ° C, still more preferably 20 to 55 ° C. The duration of hydrolysis / condensation is preferably 30 minutes to 100 hours, more preferably 1 to 20 hours, and even more preferably 2 to 10 hours.

The reaction mixture (liquid) containing the silica particles obtained as described above may be used as it is as the colloidal silica of the present invention, or may be subjected to solvent substitution to obtain the colloidal silica of the present invention. In addition, if necessary, after that, concentration / purification by filtration (extreme filtration, etc.), dilution, solvent substitution (ether-based solvent, ketone-based solvent, hydrocarbon-based solvent, halogenated hydrocarbon-based solvent, etc. It is also preferable to use an organic solvent such as an ester solvent), and by doing so, an organic solvent dispersion of silica particles can be obtained.

The procedure for ultra-filtering the colloidal silica of the present invention and substituting it with an organic solvent is as follows, for example. First, the colloidal silica of the present invention is filtered through an ultrafiltration membrane. By ultrafiltration, the base contained for the above-mentioned pH control and the basic catalyst can be removed. At this time, water or an alcohol solvent may be added and the solvent may be replaced while performing ultrafiltration. Next, colloidal silica after ultrafiltration (the solvent at this time may be a solvent at the time of synthesizing silica particles or a solvent substituted at the time of ultrafiltration) is treated with a cation exchange resin. By treating with a cation exchange resin, the basic catalyst adsorbed on the particle surface can be removed. Subsequently, it is replaced with an organic solvent different from the solvent of the colloidal silica (for example, at least one selected from an ether solvent, a ketone solvent, a hydrocarbon solvent, a halogenated hydrocarbon solvent, and an ester solvent). Therefore, an organic solvent dispersion of silica particles in which silica particles are dispersed in the organic solvent can be obtained. For the substitution with the organic solvent, a part of the solvent of the colloidal silica may be substituted or the whole may be substituted. The solvent of colloidal silica to be substituted is preferably removed by solid-liquid separation means such as centrifugation or distilling off the solvent.

Examples of the ether-based solvent include aliphatic hydrocarbon ether-based solvents such as diethyl ether, dipropyl ether, diisopropyl ether, and dibutyl ether; butylphenyl ether, pentylphenyl ether, methoxytoluene, benzylethyl ether, diphenyl ether, dibenzyl ether, and the like. Aromatic hydrocarbon ether-based solvents; cyclic ether-based solvents such as propylene oxide, furan, and tetrahydrofuran; 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl Polyether-based solvents such as ether, diethylene glycol dibutyl ether, and glycerin ether; and the like can be mentioned.

Examples of the ketone solvent include acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, 2-hexanone, methyl isobutyl ketone, 2-heptanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, and acetophenone.

Examples of the hydrocarbon solvent include saturated aliphatic hydrocarbon solvents such as hexane, heptane and octane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, mesitylene, naphthalene, cyclohexylbenzene and diethylbenzene; cyclopentane. , Saturated alicyclic hydrocarbon solvents such as methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane; and the like.

Examples of the halogenated hydrocarbon solvent include chlorinated aliphatic hydrocarbon solvents such as methyl chloride, dichloromethane, chloroform, carbon tetrachloride and ethyl chloride; and halogenated aromatic hydrocarbons such as chlorobenzene, fluorobenzene and hexafluorobenzene. System solvent; and the like.

Examples of the ester-based solvent include formic acid ester-based solvents such as methyl formate, ethyl formate, propyl formate, butyl formate, isobutyl formate, and pentyl formate; methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, and 3-methoxybutyl. Acetate, sec-hexyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, benzyl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, 2-phenoxyethyl acetate, ethylene glycol Acetic acid ester-based solvents such as monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, methyl acetoacetate, ethyl acetate, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid; propionic acid Propinone acid ester-based solvents such as methyl, ethyl propionate, butyl propionate, isopentyl propionate; γ-butyrolactone: ethylene glycol monoacetate; ethylene diacetate; ethylene glycol ester; diethylene glycol monoacetate; diethyl carbonate, ethylene carbonate, propylene carbonate And the like; lactic acid esters such as ethyl acetate; and the like.

Further, the silica particles obtained as described above may be surface-treated by contacting them with a surface treatment agent at an appropriate stage, for example, after obtaining a reaction mixture (liquid) containing the silica particles. Colloidal silica containing silica particles is also included in the colloidal silica of the present invention. As the surface treatment agent, the above-mentioned various surface treatment agents can be appropriately used.

The amount of the surface treatment agent is preferably 0.1 part by mass or more, more preferably 1 part by mass or more, still more preferably 10 parts by mass or more, and preferably 1000 parts by mass or less with respect to 100 parts by mass of the silica particles. It is more preferably 500 parts by mass or less, still more preferably 100 parts by mass or less.

The colloidal silica of the present invention or an organic solvent dispersion of silica particles obtained from the colloidal silica of the present invention can be used for modifying a resin molded body by mixing with a resin, a resin raw material, or the like, for example, a resin molded body. It can be used to improve properties such as strength, hardness, heat resistance, and insulation of silica. Examples of the resin product modified by such colloidal silica include adhesive materials, dental materials, optical members, coating materials (for hard coats and antiglares), nanocomposite materials and the like. Moreover, since the colloidal silica of the present invention is also excellent in hardness, it is also excellent as an abrasive.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples as well as the present invention, and appropriate modifications are made to the extent that it can meet the purposes of the preceding and the following. Of course, it is possible to carry out, and all of them are included in the technical scope of the present invention.

The measurement method and evaluation method in each example are as follows.

[Measurement of pH]
The pH of the colloidal silica (alcoholic solution suspension) obtained in each example was measured using a pH composite meter PC700 manufactured by Nikko Hansen Co., Ltd.

[Measurement of contents of Al, Na, K, Fe, Ca, Mg, Zn, Ni, Co, Cr, and U]
Colloidal silica was added and mixed with a mixed solution of hydrofluoric acid and nitric acid, and nitric acid and hydrogen peroxide solution were sequentially added to the mixed solution to prepare a measurement sample solution having a total volume of 50 mL. This measurement sample solution was measured using a high-frequency plasma emission spectrophotometer (Agient 8800; manufactured by Agilent Technologies, etc.), and Al, Na, K, Fe, Ca, Mg, Zn, Ni, Co, Cr in colloidal silica. , And the content of U were calculated.

Regarding the TEM diameter, DLS diameter, and true density of the silica particles in colloidal silica, the colloidal silica (alcoholic solution suspension) obtained in each example is heated on a hot plate heated to 150 ° C. for 6 hours. Then, powdered silica particles were obtained, and the obtained silica particles were measured by the following method.

[Measurement of Arithmetic Mean Particle Diameter (TEM Diameter) Obtained Based on Transmission Electron Micrograph]
The TEM diameter of the silica particles was measured by observing with a transmission electron microscope (H-7650, manufactured by Hitachi High Technology). The particles were observed at a magnification of 200,000 times, the major axis (length in the major axis direction) of each particle was measured for any 100 particles, and the average value (arithmetic mean value) based on the number was calculated.

[Measurement of average particle size (DLS diameter) based on dynamic light scattering method]
The particle size measured with a concentrated particle size analyzer (manufactured by Otsuka Electronics Co., Ltd., FPAR1000, laser light wavelength: 650 nm) was defined as the DLS diameter. As a sample for measurement by the dynamic light scattering method, a silica particle dispersion (methanol dispersion having a silica particle concentration of 9% by mass) was used.

[Measurement of true density of silica particles]
The true density of the silica fine particles was measured by a dry true density meter (Accupic II 1340-TC-10CC manufactured by Shimadzu Corporation) using nitrogen gas.

Example 1
To a 20 L SUS container equipped with a stirrer, a dropping port and a thermometer, add 8120 g of methanol, 1426 g of water, 846 g of 25% ammonia water and 90 g of 1-methylimidazole, and stir for 30 minutes to obtain a uniform solution. Got While stirring the mixed solution and adjusting the liquid temperature to 49 to 51 ° C., 2840 g of tetramethyl orthosilicate (TMS) was added dropwise from the dropping port over 1 hour. After completion of the dropping, hydrolysis was continued for 1 hour to obtain an alcoholic solution suspension (coloidal silica) (1) of silica fine particles. When the alcoholic solution suspension (1) was allowed to stand at 25 ° C. for 2 weeks and then visually observed, neither aggregation nor thickening was observed.

Example 2
An alcoholic solution suspension (2) of silica fine particles was obtained in the same manner as in Example 1 except that 90 g of 1-methylimidazole used in Example 1 was changed to 90 g of imidazole. When the alcoholic solution suspension (2) was allowed to stand at 25 ° C. for 2 weeks and then visually observed, neither aggregation nor thickening was observed.

Example 3
An alcoholic solution suspension (3) of silica fine particles was obtained in the same manner as in Example 1 except that 90 g of 1-methylimidazole used in Example 1 was changed to 90 g of thiazolidine.

Example 4
An alcoholic solution suspension (4) of silica fine particles was obtained in the same manner as in Example 1 except that 90 g of 1-methylimidazole used in Example 1 was changed to 90 g of pyridine. When the alcoholic solution suspension (4) was allowed to stand at 25 ° C. for 2 weeks and then visually observed, neither aggregation nor thickening was observed.

Example 5
An alcoholic solution suspension (5) of silica fine particles was obtained in the same manner as in Example 1 except that 90 g of 1-methylimidazole used in Example 1 was changed to 90 g of tetrahydroquinoline. When the alcoholic solution suspension (5) was allowed to stand at 25 ° C. for 2 weeks and then visually observed, neither aggregation nor thickening was observed.

Example 6
An alcoholic solution suspension (6) of silica fine particles was obtained in the same manner as in Example 1 except that 90 g of 1-methylimidazole used in Example 1 was changed to 90 g of quinoline. When the alcoholic solution suspension (6) was allowed to stand at 25 ° C. for 2 weeks and then visually observed, neither aggregation nor thickening was observed.

Example 7
An alcoholic solution suspension (7) of silica fine particles was obtained in the same manner as in Example 1 except that 90 g of 1-methylimidazole used in Example 1 was changed to 90 g of indoline. The alcoholic solution suspension (7) was allowed to stand at 25 ° C. for 2 weeks and then visually observed. Although no thickening was observed, visual aggregation was observed.

Example 8
An alcoholic solution suspension (8) of silica fine particles was obtained in the same manner as in Example 1 except that 90 g of 1-methylimidazole used in Example 1 was changed to 90 g of aniline. The alcoholic solution suspension (8) was allowed to stand at 25 ° C. for 2 weeks and then visually observed. Although no thickening was observed, visual aggregation was observed.

Example 9
An alcoholic solution suspension (9) of silica fine particles was obtained in the same manner as in Example 1 except that 90 g of 1-methylimidazole used in Example 1 was changed to 90 g of dimethylaminoacetonitrile.

Example 10
An alcoholic solution suspension (10) of silica fine particles was obtained in the same manner as in Example 1 except that 90 g of 1-methylimidazole used in Example 1 was changed to acetohydrazide.

Example 11
An alcoholic solution suspension (11) of silica fine particles was obtained in the same manner except that 2840 g of tetramethyl orthosilicate (TMS) used in Example 1 was changed to 2840 g of tetraethyl orthosilicate (TEOS). When the alcoholic solution suspension (11) was allowed to stand at 25 ° C. for 2 weeks and then visually observed, neither aggregation nor thickening was observed.

Comparative Example 1
(Adjustment of hydrolyzed solution)
342.0 g of tetramethyl orthosilicate (TMS) was weighed in a four-necked flask (capacity 2 L), and the temperature was adjusted to 10 ° C. This TMOS was added to 1158.0 g of pure water whose temperature had been adjusted to 10 ° C. in advance under stirring. The solution temperature was maintained at 10 ± 2 ° C. for 1 hour to prepare a TMOS hydrolyzed solution (active silicic acid aqueous solution) having a silica content of 9% by mass.

(Particle synthesis)
9000 g of pure water, TMAH (tetramethylammonium hydroxy) in a four-necked flask (10 L) equipped with a thermometer, a Dimroth condenser, a distilling head with a thermometer for checking steam temperature, an active silica acid aqueous solution feed tube, and a stirrer. D) was added in an amount of 5.6 mmol to prepare a mother liquor. The pH of the mother liquor was 10.84. This was heated, and when it was in a reflux state, feeding of the active silicic acid aqueous solution was started. The addition rate was 5.0 mL / min (3.6 g silica / hour / kg mother liquor). After that, a 1N-TMAH aqueous solution was added every hour so as to maintain pH 8. When 3 hours had passed after the start of the feed, the mixture was replaced with the prepared active silicic acid aqueous solution and the addition was continued, and the feed was carried out for a total of 18 hours to obtain an aqueous solution suspension of silica fine particles.

Table 1 shows the measurement results of Examples 1 to 11 and Comparative Example 1.

As a result of measuring the pH of the alcoholic solution suspensions (1) to (11) in Examples 1 to 11, all of them were 9.0 or more, and among the alcoholic solution suspensions (1) to (11). The metal content of Na, K, Al, Fe, Ca, Mg, Zn, Ni, Co, Cr and U was less than 1 ppm. Further, the pH of the aqueous suspension suspension of the silica fine particles in Comparative Example 1 was 8.

In Examples 1 to 11, colloidal silica containing silica particles having high purity (Al concentration of 500 ppm or less) and high strength (true density of 1.90 g / cm ³ or more) could be obtained. On the other hand, in Comparative Example 1, the amine in the preferable production method was not used, and the result was that the true density was inferior.

Claims (9)

It contains silica particles having an arithmetic average particle diameter of 100 nm or less, a dispersion medium, and hydrogen , which are determined based on a transmission electron micrograph, and the true density of the silica particles is 1.90 g / cm ³ or more, and the pH is 9. Colloidal silica having 0 or more, an Al concentration of 500 ppm (mass basis) or less, and a pKa of the H ⁺ adduct of the amine of 7.5 or less. The colloidal silica according to claim 1 , wherein the amine is a compound that does not contain a hydroxyl group and an ether bond. The colloidal silica according to claim 1 or 2 , wherein the dispersion medium is water or a mixed solvent of water and an alcohol-based solvent. The colloidal silica according to any one of claims 1 to 3 , wherein the silica particles are surface-treated. The colloidal silica according to any one of claims 1 to 4 , wherein the coefficient of variation of the particle size of the silica particles obtained based on a transmission electron micrograph is 20% or less. The colloidal silica according to any one of claims 1 to 5 , wherein the Na concentration is 200 ppm (mass standard) or less and the Fe concentration is 50 ppm (mass standard) or less. The colloidal silica according to any one of claims 1 to 6 , wherein the Na concentration is 5 ppm (mass standard) or less and the K concentration is 5 ppm (mass standard) or less. The colloidal silica according to any one of claims 1 to 7 is filtered through an ultrafiltration membrane, subsequently treated with a cation exchange resin, and then replaced with an organic solvent different from the solvent of the colloidal silica. A method for producing an organic solvent dispersion of silica particles. The production method according to claim 8 , wherein the organic solvent is at least one selected from an ether solvent, a ketone solvent, a hydrocarbon solvent, a halogenated hydrocarbon solvent, and an ester solvent.