Colloidal silicon dioxide and methods for its production

Abstract

One object of the present invention is the provision of colloidal silicon dioxide in which a silyl group with one or more amino groups is introduced into the interior of the particles and in which the content of fine particles is low. Another object of the present invention is to reduce fine particles that arise in a shell formation reaction during the production of colloidal silicon dioxide containing core-shell silicon dioxide particles into which a silyl group with one or more amino groups is introduced into the interior of the particles. The present invention provides colloidal silicon dioxide in which a silyl group with one or more amino groups is introduced into the interior of the particles, wherein the proportion of the number of fine particles contained in the colloidal silicon dioxide is less than 5%, based on the total number of particles, and The density of silanol groups on the surface of the particles of colloidal silicon dioxide is 4.0 groups / nm². 2 or less.

Description

Technical field

[0001] The present invention relates to colloidal silicon dioxide and a method for its production. Technical background

[0002] Silicon dioxide particles are used, for example, as abrasive grains for chemical polishing (CMP) of semiconductor substrates and the like, as fillers for resins, colorants for optical materials, external additives for printer toner resin particles, and cosmetic materials. Treatment to introduce functional groups into particles is widely used, for example, to improve the dispersion stability of the particles and to impart properties to the particles that suit their intended use. Silane coupling treatment is one such treatment. Typically, in silane coupling treatment, an alkoxysilane with a functional group, such as Z-Si(OD)3, where Z is a functional group and D is an alkyl group, is used as the silane coupling agent.The alkoxy group of the alkoxysilane reacts with OH groups on the surface of the particles (typically via a dehydration-condensation reaction) to form "Z-Si-O particles," introducing the functional group Z into the silicon dioxide particles. The introduction of the functional group (sometimes referred to as "denaturation") imparts properties to the silicon dioxide particles corresponding to the introduced silyl functional group. For example, the introduction of amino groups increases the surface potential of the particles and expands the pH region that exhibits a positive potential.

[0003] A method for introducing amino groups into silicon dioxide particles is known which includes the addition of a liquid obtained by mixing tetraalkoxysilane and a silane adhesive with one or more amino groups to core particles to form shells, thereby producing colloidal silicon dioxide containing core-shell silicon dioxide particles into which the amino groups are introduced (PTL 1).

[0004] A process is known which involves the addition of an organic solvent to a reaction liquid in a shell formation reaction, whereby colloidal silicon dioxide is produced which contains silicon dioxide particles with an average primary particle size of 33 nm or more (PTL 2).

[0005] A process is known in which colloidal silicon dioxide is produced under conditions where the alcohol concentration in a reaction liquid is high in a silicon dioxide particle synthesis reaction (PTL 3 to 6).

[0006] If a large number of fine particles are formed during the shell formation stage on the nucleus particles, the removal of the fine particles becomes complicated. List of citations from patent literature PTL 1: JP 2016-008157 A PTL 2: WO 2020 / 179556 PTL 3: JP 2018-048042 A PTL 4: JP 2016-094619 A PTL 5: JP H01-145317 A PTL 6: JP S62-072514 A PTL 7: WO 2008 / 123373 PTL 8: JP 2006-231436 A Non-patent literature

[0007] NPL 1: Kazunori HIRABAYASHI and Atsunori MORI, “Organic Chemistry of Siloxane and Silanol,” Journal of Synthetic Organic Chemistry, Japan, 2000, Vol. 58, No. 10, pp. 926-933 Brief description of the invention: Technical problem

[0008] The inventor of the present invention has confirmed that in the process for producing colloidal silicon dioxide described in PTL 1, a large number of fine particles, i.e. particles with particle sizes smaller than those of the core particles, are produced during the stage of shell formation on the core particles (Comparative Example 1 of this application).

[0009] In PTL 2, colloidal silicon dioxide is produced in which the proportion of silicon dioxide particles with a circular equivalent diameter of less than 20 nm is less than 15%. This effect is achieved by including an organic solvent (e.g., methanol) at a concentration equal to or higher than a specific concentration in a reaction liquid during the shell formation reaction. Furthermore, PTL 2 does not teach that the number of fine particles produced can be reduced by increasing the proportion of alkoxysilane added to the shell formation reaction relative to the amount of alkaline catalyst added. Additionally, in PTL 2, one or more amino groups are introduced by adding an alkoxysilane containing one or more amino groups after shell formation.

[0010] In PTL 3 to 6, it is assumed that the density of silanol groups on the particle surface is high due to the use of a reaction system in which the concentration of an organic solvent (alcohol) in a mixed liquid is high in a particle synthesis reaction, and the inventor of the present invention has confirmed that the density of silanol groups is indeed high (Comparative Example 3 of this application). The high density of silanol groups can cause problems such as the instability of silanol groups (Section "2. Silanol" on p. 928 of PTL 1), difficulties in forming dense particles with a high true density (paragraphs 0008 to 0011 of PTL 7), and a tendency to bind to polar groups of a polishing pad and cause clogging of the polishing pad (paragraphs 0010 to 0015 of PTL 8).

[0011] Consequently, it is an object of the present invention to provide colloidal silicon dioxide containing core-shell silicon dioxide particles in which a silyl group with one or more amino groups is introduced into the interior of the particles, in particular in the shells, and in which the content of fine particles is low.

[0012] One object of the present invention is to reduce the fine particles that are formed during the shell formation reaction in the production of core-shell silicon dioxide particles containing colloidal silicon dioxide, in which a silyl group with one or more amino groups is introduced into the particles, in particular into the shells. Solution to the problem

[0013] The inventor of the present invention has found that the quantity of fine particles produced in the shell formation reaction can be reduced without increasing the density of the silanol groups of the resulting core-shell silicon dioxide particles by reducing the amount of alkoxysilane (e.g., the total amount of tetramethyl orthosilicate and the amount of alkoxysilane with one or more amino groups) added to the shell formation reaction on the core particles by a factor of 200 or more in relation to the molar ratio to the amount of an alkaline catalyst (e.g., the amount of 3-ethoxypropylamine) present in a shell formation reaction liquid, and has carried out the present invention.

[0014] The typical subject matter of the present invention is as follows. Point 1.

[0015] Colloidal silicon dioxide in which a silyl group is introduced into the interior of particles with one or more amino groups, wherein the proportion of the number of fine particles contained in the colloidal silicon dioxide is less than 5%, based on the total number of particles, and The density of silanol groups on the surface of the particles of colloidal silicon dioxide is 4.0 groups / nm². 2 or less. Point 2.

[0016] The colloidal silicon dioxide according to point 1, where the true density is 1.90 or more. Point 3.

[0017] A process for the production of colloidal silicon dioxide, in which a silyl group with one or more amino groups is introduced into the interior of the particles, comprising: a step in which an alkoxysilane with one or more amino groups and an alkoxysilane without an amino group are reacted with core particles in the presence of an alkaline catalyst to form shells, wherein the total amount of alkoxysilanes added in a shell formation reaction is 200 times or more, based on the molar ratio to the amount of alkaline catalyst present in a reaction system during the shell formation reaction. Advantageous effects of the invention

[0018] The present invention can provide colloidal silicon dioxide comprising core-shell silicon dioxide particles with a density of silanol groups of 4.0 groups / nm³. 2or less and which has a low content of fine particles, and into which a silyl group with one or more amino groups within the particles, especially within the shells, is introduced.

[0019] The present invention can provide a process for the production of colloidal silicon dioxide in which the total amount of alkoxysilane added in the shell formation reaction is 200 times or more, expressed as a molar ratio in relation to the amount of alkaline catalyst present in the reaction system in the shell formation reaction. Brief description of the drawings Fig. Figure 1 is a SEM image of colloidal silicon dioxide obtained in the last stage of Example 1. Fig. Figure 2 is a SEM image of colloidal silicon dioxide obtained in the last stage of comparison example 1. Fig.Figure 3 is a SEM image of colloidal silicon dioxide dispersed in methanol, obtained in the silicon dioxide particle synthesis reaction of Comparative Example 3. Fig. Figure 4 is a SEM image of colloidal silicon dioxide dispersed in water, obtained in the last stage of Comparative Example 3. Fig. Figure 5 is a diagram showing the results of the zeta potential measurement of colloidal silicon dioxide of examples 1 to 4 and comparison example 1, where the horizontal axis represents the pH value and the vertical axis represents the zeta potential (mV). Description of the embodiments

[0020] In this description, unless otherwise specified, the expression "within a particle" means "within a particle or within a shell forming the particle." For example, the expression "within a silicon dioxide particle" means the interior of the silicon dioxide particle or the interior of a shell forming the silicon dioxide particle. The colloidal silicon dioxide of the present invention is a colloidal silicon dioxide containing core-shell silicon dioxide particles into which a silyl group with one or more amino groups is introduced, exhibiting a low content of fine particles and a low density of silanol groups on the silicon dioxide particles.Therefore, the colloidal silicon dioxide of the present invention is advantageous insofar as the density of the unstable silanol groups is not excessively high, dense particles with a high true density are obtained, and the clogging of a polishing pad, for example, can be suppressed.

[0021] According to the process for producing colloidal silicon dioxide of the present invention, the amount of alkoxysilane added in a shell formation reaction on core particles is adjusted to 200 times or more in relation to the molar ratio to the amount of an alkaline catalyst (e.g. the amount of 3-ethoxypropylamine) present in a shell formation reaction liquid, and therefore the amount of fine particles produced in the shell formation reaction can be reduced without increasing the density of the silanol groups on the core-shell silicon dioxide particles to be produced. 1. Colloidal silicon dioxide

[0022] The colloidal silicon dioxide of the present invention has amino groups introduced into the interior of the silicon dioxide particles contained in the colloidal silicon dioxide. In particular, the amino groups are distributed throughout the interior of the shells of the core-shell particles contained in the colloidal silicon dioxide. The proportion of fine particles contained in the colloidal silicon dioxide is less than 5%, based on the total number of particles. The density of silanol groups on the surfaces of the core-shell silicon dioxide particles contained in the colloidal silicon dioxide is 4.0 groups / nm². 2 or less.

[0023] The colloidal silicon dioxide of the present invention is usually produced according to the inventive method, but can also be produced according to other methods.

[0024] The concentration of silicon dioxide particles in the colloidal silicon dioxide of the present invention can be selected by a person skilled in the art depending on the intended use, the planned storage period and the like of the colloidal silicon dioxide, but can, for example, be set to 1 to 50 percent by mass. fine particles

[0025] The term "fine particles" refers to particles with a particle size that is 75% or less of the average elliptical minor axis of the silicon dioxide particles in a SEM image of the colloidal silicon dioxide. In the present invention, the proportion of fine particles contained in the colloidal silicon dioxide can be less than 5.0%, preferably 4.0% or less, more preferably 3.0% or less, and even more preferably 2.0% or less, based on the total number of particles. Although the lower the proportion, the better, it can also be 0.01% or more and less than 5.0%, 0.01% to 3.0%, 0.01% to 2.0%, or the like. The proportion of fine particles contained in the colloidal silicon dioxide can be determined by the method described in the examples. Density of silanol groups

[0026] The density of silanol groups on the surfaces of the silicon dioxide particles contained in the colloidal silicon dioxide can be 4.0 groups / nm². 2 or less, preferably 3.5 groups / nm 2 or less and preferably 3.0 groups / nm 2 or less. The density of the silanol groups can be 1.0 groups / nm³. 2 or more, preferably 1.2 groups / nm 2 or more and preferably 1.4 groups / nm 2 or more. If the density of the silanol groups is equal to or greater than these values, the hydrophobicity of the colloidal silicon dioxide is not excessively high and therefore its stability in water is high.

[0027] The density of the silanol groups can range from 1.0 to 4.0 groups / nm³. 2 , 1.0 to 3.5 groups / nm 2 , 1.0 to 3.0 groups / nm 2 , 1.2 to 4.0 groups / nm 2 , 1.2 to 3.5 groups / nm 2 , 1.2 to 3.0 groups / nm 2 , 1.4 to 4.0 groups / nm 2, 1.4 to 3.5 groups / nm 2 , 1.4 to 3.0 groups / nm 2 or the like. The density of the silanol groups can be determined by the Sears method, described in G.W. Sears, Jr., "Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide," Analytical Chemistry, 28 (12), 1981 (1956). More precisely, the density of the silanol groups can be determined by titration with a 0.1 mol / L aqueous sodium hydroxide solution using a 1 wt% silicon dioxide dispersion according to the Sears method, using the following formula: ρ=(a×f×6022) / (c×S).

[0028] In the formula above, ρ represents the density of silanol groups (number of silanol groups / nm³). 2), a for the droplet quantity of the 0.1 mol / l aqueous sodium hydroxide solution with a pH of 4 to 9 (ml), f for the factor of the 0.1 mol / l aqueous sodium hydroxide solution, c for the mass of the silicon dioxide particles (g) and S for the specific BET surface area (m²) 2 / G). Average primary particle size

[0029] The average primary particle size of the silicon dioxide particles contained in the colloidal silicon dioxide is not particularly restricted and can be selected according to the intended use; for example, it may be 1 nm or more, and preferably 2 nm or more, and 350 nm or less, preferably 150 nm or less, more preferably 120 nm or less, and even more preferably 100 nm or less. The average primary particle size of the silicon dioxide particles may be 1 nm to 350 nm, 1 nm to 150 nm, 1 nm to 120 nm, 1 nm to 100 nm, 2 nm to 350 nm, 2 nm to 150 nm, 2 nm to 120 nm, or 2 nm to 100 nm. The average primary particle size is determined according to the method described in the examples. Average secondary particle size

[0030] The average size of the secondary particles contained in the colloidal silicon dioxide is not particularly restricted and can be freely chosen depending on the intended use; for example, it can range from 1 nm to 500 nm and from 2 nm to 300 nm, and is preferably 3 nm to 250 nm. The average size of the secondary particles is determined according to the method described in the examples. Aggregation ratio

[0031] The aggregation ratio of the silicon dioxide particles contained in the colloidal silicon dioxide is represented by the average secondary particle size / average primary particle size and is typically 5.0 or less, preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.0 or less. An aggregation ratio of, for example, 1.0 or more, preferably 1.3 or more, and more preferably 1.5 or more, makes it easy to suppress the occurrence of scratches on the polishing surface when the particles are used as abrasive grains in abrasives and makes it easy to improve the polishing rate compared to that of spherical particles.The aggregation ratio can be, for example, 1.0 to 5.0, 1.3 to 5.0, 1.5 to 5.0, 1.0 to 4.0, 1.3 to 4.0, 1.5 to 4.0, 1.0 to 3.5, 1.3 to 3.5, 1.5 to 3.5, 1.0 to 3.0, 1.3 to 3.0, 1.5 to 3.0 or the like. Average ellipse minor axis

[0032] The average elliptical minor axis of the silicon dioxide particles contained in the colloidal silicon dioxide is not particularly restricted and can be selected according to the intended use, e.g., 1 nm or more, e.g., preferably 2 nm or more and 350 nm or less, preferably 150 nm or less, more preferably 120 nm or less, and even more preferably 100 nm or less. The average elliptical minor axis can be 1 nm to 350 nm, 1 nm to 150 nm, 1 nm to 120 nm, 1 nm to 100 nm, 2 nm to 350 nm, 2 nm to 150 nm, 2 nm to 120 nm, or 2 nm to 100 nm. The average elliptical minor axis is determined according to the method described in the examples. Length-width ratio

[0033] The length-to-width ratio of the silicon dioxide particles contained in the colloidal silicon dioxide can be adjusted to 1.0 to 5.0 or 1.0 to 3.0, and is preferably, for example, 1.2 to 2.5. A length-to-width ratio within the aforementioned range makes it easy to suppress the occurrence of scratches on the polishing surface when the particles are used as abrasive grains in abrasives, and makes it easy to improve the polishing rate compared to that of spherical particles. The length-to-width ratio is determined according to the method described in the examples. Surface roughness

[0034] The surface roughness of the silicon dioxide particles contained in the colloidal silicon dioxide can be adjusted to 1.0 to 2.0 or 1.0 to 1.8, and preferably to 1.1 to 1.7. A surface roughness within the aforementioned ranges is advantageous for polishing performance. The surface roughness is determined according to the method described in the examples. True density

[0035] The true density of the silicon dioxide particles contained in the colloidal silicon dioxide is 1.60 or more, or 1.70 or more, and preferably 1.90 or more, and more preferably, for example, 2.00 or more, and for example, 2.30 or less. The true density can be adjusted to 1.60 to 2.30, 1.70 to 2.30, 1.90 to 2.30, 2.00 to 2.30, or the like. A true density within the aforementioned ranges makes it easy to improve the mechanical polishing effect and polishing rate when the particles are used as abrasive grains in abrasives. The true density is determined according to the method described in the examples. Amino group introduced into silicon dioxide particles

[0036] The amino group introduced into the silicon dioxide particle contained in the colloidal silicon dioxide can be a group introduced by treating the silicon dioxide with an alkoxysilane containing one or more amino groups. Typically, the introduction refers to a state in which a silyl group with one or more amino groups is bound to the interior of the silicon dioxide particle by a covalent bond (preferably a siloxane bond), and may be additionally bound by an ionic bond, a hydrogen bond, chemical adsorption, physical adsorption, or the like. The silyl group with one or more amino groups can similarly be bound to the surface of a silicon dioxide particle. The silyl group with one or more amino groups is therefore located within the interior of the silicon dioxide particle.Furthermore, the silicon dioxide particle can have the silyl group with one or more amino groups on the particle surface. In one embodiment, the silicon dioxide particle contained in the colloidal silicon dioxide of the present invention is a silicon dioxide particle in which a silyl group with one or more amino groups is bonded to the interior of the silicon dioxide particle by a covalent bond (preferably a siloxane bond), represented by the general formula (1):. -Si(X) n (L-NH2) p (1)

[0037] In the formula above, the X's are either the same or different and each represents a hydroxyl group, a hydrolyzable substituent, a non-hydrolyzable substituent, a bond to Si of another silyl group via -O-, or a bond to the silicon atom inside the silicon dioxide particle via -O-. n is 0, 1, or 2, p is an integer from 1 to 3 (n + p = 3), and L is a linkage group. For example, in the silyl group above, the Si in the silyl group is covalently bonded to the silicon atom inside the silicon dioxide particle via -O-. The Si in the silyl group above can have 1, 2, or 3 bonds via -O-. Silyl group with one or more amino groups, represented by the general formula (1)

[0038] If the number of -O- bonds between Si in the silyl group represented by general formula (1) and the silicon atom in the interior of the silicon dioxide particle is one, then -Si in the silyl group is bonded to the silicon atom in the interior of the silicon dioxide particle by -O- (siloxane bonding). More precisely, Si and the interior of the silicon dioxide particle are bonded in the form represented by "Si*-O-Si(X)n-", where Si* is the silicon atom in the interior of the silicon dioxide particle, the Xs are the same or different and each represents a hydroxyl group, a hydrolyzable substituent, a non-hydrolyzable substituent, or a bond to Si of another silyl group by -O-, and n is 0, 1, or 2.

[0039] If the number of bonds is two, one of the X is “a bond to the silicon atom inside the silicon dioxide particle by -O-”. More precisely, Si in the silyl group and the silicon atom inside the silicon dioxide particle are bonded in the form represented by “Si*-O-Si(X)2(OSi**)1-”, where Si* and X are the same as above and Si** is the silicon atom inside the silicon dioxide particle, which is different from Si*.

[0040] If the number of bonds is three, the two Xs are "bonds to the silicon atom inside the silicon dioxide particle by -O-". More precisely, Si in the silyl group and the silicon atom inside the silicon dioxide particle are bonded in the form represented by "Si*-O-Si(X)1(OSi**)1(OSi***)1-", where Si*, Si** and X are the same as above and Si*** is the silicon atom inside the particle, which is different from Si* and Si**.

[0041] In the silyl group represented by the general formula (1), the X are the same or different and each represents a hydroxyl group, a hydrolyzable substituent, a non-hydrolyzable substituent, a bond to the Si of another silyl group via -O- or a bond to the silicon atom in the interior of the silicon dioxide particle via -O-.

[0042] In X, the hydrolyzable substituent is a group that can be hydrolyzed in an aqueous system to form a Si-OH group. The hydrolyzable group in the alkoxysilane used for the introduction of one or more amino groups either remains a hydrolyzable group without being hydrolyzed, is hydrolyzed to a hydroxyl group, or is hydrolyzed to a hydroxyl group and then, for example, further condensed with another hydroxyl group, depending on the degree of hydrolysis, e.g., upon the introduction of one or more amino groups. The hydrolyzable substituent is, for example, an alkoxy group, preferably a linear or branched C1-C6 alkoxy group, more preferably a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, or a tert-butoxy group, and even more preferably a methoxy group or an ethoxy group.

[0043] In X, the non-hydrolyzable substituent is a group that is not hydrolyzed in an aqueous system, i.e., a group that does not form a Si-OH group. The non-hydrolyzable substituent is, for example, an alkyl group, preferably a linear or branched C1-C6 alkyl group, more preferably a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, or a tert-butyl group, and even more preferably a methyl group or an ethyl group.

[0044] In X, the bond to Si of another silyl group via -O- is a bond (siloxane bond) between Si in the silyl group represented by the general formula (1) and Si in a silyl group that is present near Si in the silyl group represented by the general formula (1), via an oxygen atom in the silicon dioxide particle and forms the Si-O-Si structure.

[0045] In X, the bond to the silicon atom inside the silicon dioxide particle via -O- is a bond between Si in the silyl group and the silicon dioxide particle, forming the Si-O-Si** structure or the Si-O-Si*** structure, where Si** and Si*** are silicon atoms inside the silicon dioxide particle and are as described above. The details of this bond are as described above.

[0046] In one embodiment, Xs are preferably the same or different and each represents a bond to the silicon atom in the interior of the silicon dioxide particle via -O-, a bond to Si of a silyl group present near the silyl group represented by the general formula (1), via an oxygen atom, a hydroxy group, a methoxy group, an ethoxy group or a methyl group.

[0047] In the silyl group, which is represented by the general formula (1), n ​​is 0, 1 or 2.

[0048] In the silyl group, represented by the general formula (1), L is a bonding group. The bonding group typically corresponds to a group located between Si and a nitrogen atom forming an amino group in the alkoxysilane, which contains one or more amino groups used in the introduction of one or more amino groups. More precisely, the bonding group connects Si in the silyl group to the nitrogen atom forming an amino group in the alkoxysilane, which contains one or more amino groups used in the introduction of one or more amino groups. The bonding group is, for example, a linear or branched C1-C18 alkylene group.

[0049] The linear or branched C1-C18 alkylene group is, for example, a methylene group, an ethylene group, a propylene group, a butylene group, a hexylene group, a decylene group, or an octadecylene group. A branched chain within the branched alkylene group is a C1-C3 alkylene group. The branched chain refers to an alkyl group bonded to a carbon atom that forms a main chain within the branched alkylene group, where the main chain is a linear hydrocarbon chain connecting the carbon atom bonded to silicon and the nitrogen atom that forms the amino group.

[0050] The linear or branched C1-C18 alkylene group can have one substituent. The substituent is, for example, an alkenyl group (e.g., a vinyl group or allyl group) or an alkynyl group. The substituents can be used singly or in a combination of two or more types. The number of substituents can be, for example, 0, 1, 2, or 3.

[0051] The linear or branched C1-C18 alkylene group can contain an oxygen atom (-O-), a nitrogen atom (-N-), or a sulfur atom (-S-) at the end of the alkylene chain or at any position within the chain. If these heteroatoms are present in the branched C1-C18 alkylene group, they can be found in the main chain or in the branched chain. If the nitrogen atom is present at the end of the alkylene chain or within the chain, it can be -NH- or substituted with a substituent. In this case, the substituent is either a methyl group or an ethyl group. The total number of oxygen atoms, nitrogen atoms, and sulfur atoms present at the end of the alkylene chain and within the chain is not particularly limited.

[0052] In one embodiment, L is preferably *-(CH2)3-O-CH2-, *-(CH2)2-O-CH2-, *-(CH2)3-O-(CH2)2-, *-(CH2)2-, *-(CH2)3-, *-(CH2)6-, *-(CH2)8-, *-(CH2)3-NH-CH2- or *-(CH2)3-NH-(CH2)2-, and is preferably *-(CH2)3-O-CH2-, *-(CH2)3-, *-(CH2)8- or *-(CH2)3-NH-(CH2)2- with regard to the easy availability of a silane adhesion agent as a starting material and the low steric hindrance. The asterisk (*) represents the Si(X) side. n .

[0053] The silyl group represented by the general formula (1) is preferably a group represented by one of the following formulas, since the alkoxysilane with one or more amino groups is readily available as a raw material. In the following formulas, Xs are the same as above: -Si(X)2(-(CH2)3-NH2)1, -Si(X)2(-(CH2)3-NH-(CH2)2-NH2)1.

[0054] The colloidal silicon dioxide of the present invention can be used as a physical property improver, for example, in the fields of paper, textiles, and iron and steel. Furthermore, the colloidal silicon dioxide of the present invention can also be used as an abrasive for chemical-mechanical polishing (CMP), silicon wafer polishing, and glass polishing. The colloidal silicon dioxide according to the present invention can also be used as an additive for fillers, as an external additive for toners, and the like, by drying it into a powder.

[0055] The abrasive containing the colloidal silicon dioxide can also be part of the present invention. The colloidal silicon dioxide of the present invention has a reduced content of fine particles and can therefore be suitablely used as an abrasive for chemical-mechanical polishing, in particular as an abrasive for the chemical-mechanical polishing of semiconductor wafers. 2. Process for the production of colloidal silicon dioxide

[0056] A process for producing colloidal silicon dioxide containing core-shell silicon dioxide particles into which amino groups are introduced is known, wherein the process includes a step in which an alkoxysilane with one or more amino groups and an alkoxysilane without an amino group are reacted with core particles in the presence of an alkaline catalyst to form shells on the core particles (shell formation step). The process for producing colloidal silicon dioxide according to the present invention is such that, in the shell formation step, the total amount of alkoxysilanes added in the shell formation reaction is adjusted to 200 times or more, expressed as a molar ratio, relative to the amount of alkaline catalyst present in the reaction system during the shell formation reaction.The inventive process for producing colloidal silicon dioxide can reduce the formation of fine particles without increasing the density of the silanol groups.

[0057] The process for producing the colloidal silicon dioxide of the present invention is suitable for producing the colloidal silicon dioxide described above of the present invention. Methods for producing nuclear particles

[0058] The nuclei can be produced by conventionally known methods for producing nuclei from colloidal silicon dioxide, and the process is not particularly restricted. Nuclei can be produced, for example, by: (1) preparing a mixed liquid containing an alkaline catalyst and water (step 1); (2) adding alkoxysilane to the mixed liquid prepared in step 1 to produce a mixed liquid (step 2); and (3) adding an alkaline catalyst to the mixed liquid prepared in step 2 to produce silicon dioxide particles (step 3).

[0059] The process for preparing the mixed liquid containing an alkaline catalyst and water is not particularly limited, and the alkaline catalyst can be added to the water and stirred according to conventional methods. The pH of the mixed liquid is not particularly limited and is preferably 9.0 or higher and more preferably 9.5 or higher.

[0060] In the process for the production of colloidal silicon dioxide, the alkaline catalyst is not particularly restricted and may be at least one amine selected from the group consisting of ammonia, primary amines, secondary amines and tertiary amines, and preferably an amine represented by the general formula (2) below: NR a R b R c (2).

[0061] In the above formula, R a , R b and R cThey may be the same or different and each represents a possibly substituted C1-C12 alkyl group or a hydrogen atom.

[0062] R a , R b and R c They can be the same or different. R a , R b and R c They can be linear or branched.

[0063] The number of carbon atoms in a linear or branched alkyl group can be 1 to 12, preferably 1 to 8, and more preferably 1 to 6. The linear alkyl groups include, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and the like.The branched alkyl groups include, for example, an isopropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,1-dimethylbutyl group, a 1,1-dimethylbutyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,2-dimethylbutyl group, a 2,3-dimethylbutyl group, a 1-methyl-1-ethylpropyl group, a 2-methyl-2-ethylpropyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-ethylhexyl group, a 2-ethylhexyl group, A 3-ethylhexyl group, a 4-ethylhexyl group, a 5-ethylhexyl group, and the like. Preferred linear or branched alkyl groups are an n-propyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, and the like.

[0064] In R a , Rb and R cIn the general formula (2) above, the alkyl groups may be substituted. The number of substituents may be, for example, 0, 1, 2, 3, 4, or the like, preferably 0, 1, or 2, and more preferably 0 or 1. An alkyl group with 0 substituents means an unsubstituted alkyl group. Examples of substituents include alkoxy groups with 1 to 3 carbon atoms (e.g., a methoxy group, an ethoxy group, a propoxy group, and an isopropoxy group), amino groups, primary amino groups substituted with linear alkyl groups having 1 to 4 carbon atoms, amino groups di-substituted with linear alkyl groups having 1 to 4 carbon atoms (e.g., a dimethylamino group and a di-n-butylamino group), unsubstituted amino groups, and the like. However, a hydroxyl group is excluded from the list of substituents. In alkyl groups with a large number of substituents, the substituents can be the same or different.

[0065] In one embodiment, R a , R b and R c same or different and each represent an unsubstituted linear or branched C1-C12 alkyl group, a linear or branched C1-C12 alkyl group substituted with an alkoxy group, or a hydrogen atom.

[0066] In another embodiment, R a , R b and R c same or different and each represent an unsubstituted linear or branched C1-C8 alkyl group, a linear or branched C1-C8 alkyl group substituted with a C1-C3 alkoxy group, or a hydrogen atom.

[0067] In another embodiment, R a , R b and R csame or different and each represent an unsubstituted linear or branched C1-C6 alkyl group, a linear or branched C1-C6 alkyl group substituted with a C1-C3 alkoxy group, or a hydrogen atom.

[0068] In one embodiment, two of the residues R a , R b and R c The hydrogen atoms and the remaining residue is an unsubstituted linear or branched C1-C12 alkyl group or a linear or branched C1-C12 alkyl group substituted with an alkoxy group.

[0069] In another embodiment, two of the residues R a , R b and R c The hydrogen atoms and the remaining residue is an unsubstituted linear or branched C1-C8 alkyl group or a linear or branched C1-C8 alkyl group substituted with a C1-C3 alkoxy group.

[0070] In another embodiment, two of the residues Ra , R b and R c The hydrogen atoms and the remaining residue is an unsubstituted linear or branched C1-C6 alkyl group or a linear or branched C1-C6 alkyl group substituted with a C1-C3 alkoxy group.

[0071] In another embodiment, R a , R b and R c all for hydrogen atoms.

[0072] The alkaline catalyst contains at least one selected from the group consisting of ammonia, 3-ethoxypropylamine, pentylamine, hexylamine, dipropylamine and triethylamine.

[0073] Among the aforementioned, ammonia, 3-ethoxypropylamine, dipropylamine, and triethylamine are preferred. To further improve the storage stability of the colloidal silicon dioxide, 3-ethoxypropylamine is preferred.

[0074] The alkaline catalysts can be used individually or in a combination of two or more types. The amines described above for colloidal silicon dioxide can be used as alkaline catalysts. Shell formation step

[0075] The shell formation step on the nucleus particle involves a shell formation reaction and includes the addition of alkoxysilane to form the shell. The total amount of alkoxysilane added in the shell formation reaction is set at 200 times or more in relation to the molar ratio to the amount of alkaline catalyst present in the reaction system.

[0076] The shell can be formed by adding alkoxysilane to nucleic particles dispersed in a mixed liquid of water and the alkaline catalyst to initiate a reaction. The alkaline catalyst can be added in this step to adjust its quantity. The nucleic particles used in shell formation are preferably dispersed in the mixed liquid of water and alkaline catalyst.

[0077] The shell formation step can be step (a) of mixing the nucleus particles, the alkaline catalyst and the alkoxysilane, for example, in any order, in the presence or absence of water and / or an organic solvent.

[0078] In the shell formation step and in step (a), a mixture is prepared by mixing the core particles, the alkaline catalyst, and the alkoxysilane in any order in the presence or absence of water and / or an organic solvent. Stirring can be carried out at any stage before, during, or after mixing. The stirring method is not particularly restricted. Alkaline catalyst

[0079] The alkaline catalysts described in the preceding process for the production of nuclear particles can be used as the alkaline catalyst. In the shell formation reaction, the amount (molar amount) of the alkaline catalyst present in the reaction system is adjusted to one part 200 or less of the total molar amount of the alkoxysilane added in the shell formation reaction. The alkaline catalyst can be added in the shell formation reaction provided that the amount is in the range of one part 200 or less of the total molar amount of the alkoxysilane. The amount (molar amount) of the alkaline catalyst present in the shell formation reaction system is preferably one part 200 or less, and more preferably one part greater than 250 or less, of the total molar amount of the alkoxysilane added in the shell formation reaction.The amount of alkaline catalyst present in the shell-forming reaction system can be 1 / 5000 to 1 / 200, 1 / 4000 to 1 / 200, 1 / 3000 to 1 / 200, 1 / 5000 to 1 / 250, 1 / 4000 to 1 / 250, or 1 / 3000 to 1 / 250 of the total molar amount of alkoxysilane added in the shell-forming reaction. A quantity of alkaline catalyst present in the shell-forming reaction system within the aforementioned ranges allows for more effective suppression of fine particle formation.

[0080] The manufacturing process of the present invention is a process for producing colloidal silicon dioxide in which a silyl group with one or more amino groups is introduced into the particles, and therefore the alkoxysilane with one or more amino groups and the alkoxysilane without an amino group can be used in the shell formation step.

[0081] In the shell formation step, the total amount of alkoxysilanes added in the shell formation reaction (the total amount of the alkoxysilane with one or more amino groups and the amount of the alkoxysilane without an amino group) is 200 times or more, and preferably 250 times or more, based on the molar ratio to the amount of alkaline catalyst present in the shell formation reaction system. The total amount of alkoxysilanes added can be 200 to 5000 times, 200 to 4000 times, 200 to 3000 times, 250 to 4000 times, and 250 to 3000 times, respectively, based on the amount of alkaline catalyst present in the shell formation reaction system. The total amount of alkoxysilanes added in the shell formation reaction, which falls within the aforementioned ranges, makes it possible to suppress the formation of fine particles more effectively.

[0082] In the shell formation reaction, the total amount of alkoxysilanes to be added is not particularly limited, provided that the colloidal silicon dioxide of the present invention is obtained, and is preferably 0.5 molar amount or more, more preferably 0.5 to 200 molar amount and even more preferably 0.5 to 120 molar amount per molar amount of the core particles.

[0083] The amount of alkoxysilane with one or more amino groups in the alkoxysilane added during the shell formation step is not particularly limited, provided that the colloidal silicon dioxide of the present invention is obtained, and is preferably 0.1 to 10 mol% and more preferably 0.2 to 5 mol%, based on the total amount (100 mol%) of the alkoxysilane. Alkoxysilane with one or more amino groups

[0084] The alkoxysilane with one or more amino groups is not particularly limited and the alkoxysilane represented by the general formula (3) below is, for example, usable: Si(OR e ) m (R f ) o (L-NH2) q (3)

[0085] In the formula above, R represents e represents an alkyl group, L represents a bonding group, m is an integer from 1 to 3, o is an integer from 0 to 2, q is an integer from 1 to 3 and m + o + q = 4.

[0086] R eThe choice of alkyl group is not particularly restricted in that it is a linear or branched C1-C8 alkyl group, more preferably a linear C1-C8 alkyl group, and even more preferably a linear C1-C4 alkyl group. Specific examples of the alkyl group are a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, and the like, with a methyl group and an ethyl group being preferred.

[0087] R fThe choice of alkyl group is not particularly restricted in that it is a linear or branched C1-C8 alkyl group, more preferably a linear C1-C8 alkyl group, and even more preferably a linear C1-C4 alkyl group. Specific examples of the alkyl group are a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, and the like, with a methyl group and an ethyl group being preferred.

[0088] L is a bonding group and corresponds to the bonding group in the silyl group with one or more amino groups represented by the general formula (1) above. Therefore, unless otherwise stated, the above description for L in the silyl group with one or more amino groups represented by general formula (1) applies to L in general formula (3).

[0089] The alkoxysilane with one or more amino groups comprises aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, (aminoethyl)aminopropyltrimethoxysilane, (aminoethyl)aminopropyltriethoxysilane, aminopropylmethyldiethoxysilane, (aminoethyl)aminopropylmethyldimethoxysilane, aminobutyltriethoxysilane and the like, wherein aminopropyltrimethoxysilane, aminopropyltriethoxysilane and (aminoethyl)aminopropyltriethoxysilane are preferred.

[0090] Alkoxysilanes with one or more amino groups can be used individually or in combination with other types. They can be added all at once or in several portions (e.g., two or three times). Alkoxysilane without amino group

[0091] The alkoxysilane lacking an amino group is not particularly limited and contains alkoxysilane of the following general formula (4A): Si(OR d )4 (4A), where R d represents an alkyl group or an alkoxysilane of the general formula (4B) below: Si(OR g ) t (R h ) u (4B), where R g represents an alkyl group, R h represents an alkyl group, t is an integer from 1 to 3, u is an integer from 1 to 3 and t + u = 4.

[0092] In the above general formula (4A), R represents d represents an alkyl group. R dis not particularly restricted in that it is an alkyl group, and is preferably a linear or branched C1-C8 alkyl group, more preferably a linear C1-C8 alkyl group, and even more preferably a linear C1-C4 alkyl group. Specific examples of the alkyl group are a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, and the like. The alkoxysilane represented by the above general formula (4A) is preferably tetramethoxysilane (also known as tetramethyl orthosilicate), in which R d a methyl group, tetraethoxysilane (also known as tetraethyl orthosilicate), in which R d an ethyl group, or tetraisopropoxysilane, in which R d an isopropyl group, preferably tetramethoxysilane, in which R d a methyl group, or tetraethoxysilane, in which R dan ethyl group, and even more preferably tetramethoxysilane.

[0093] In the above general formula (4B), R g and R h They are the same or different and each represents an alkyl group. R g and R h are not particularly restricted in that R g and R hThe alkyl groups are preferably linear or branched C1-C8 alkyl groups, more preferably linear C1-C8 alkyl groups, and even more preferably linear C1-C4 alkyl groups. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, and the like, wherein a methyl group, an ethyl group, and an n-propyl group are preferred, and a methyl group and an ethyl group are even more preferred. The alkoxysilane represented by the above general formula (4B) is more preferably methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, ethyltrimethoxysilane, diethyldimethoxysilane, ethyltriethoxysilane, diethyldiethoxysilane, n-propyltrimethoxysilane, and n-propyltriethoxysilane.

[0094] The alkoxysilanes without an amino group can be used individually or in combination with two or more types. The alkoxysilane without an amino group can be added all at once or in several portions (e.g., two or three times).

[0095] Alkoxysilanes with one or more amino groups and alkoxysilanes without amino groups can be derivatives. Examples of alkoxysilane derivatives are low condensates obtained by partial hydrolysis of alkoxysilanes with one or more amino groups and alkoxysilanes without amino groups.

[0096] The alkoxysilane with one or more amino groups and the alkoxysilane without an amino group can be added separately or together. medium

[0097] The shell formation step can be carried out in the presence or absence of water and / or an organic solvent (hereinafter sometimes simply referred to as the "medium"). To suppress aggregation, it is advantageous and preferred to carry out the shell formation step in the presence of a medium. If a medium is used, the amount of medium used is not particularly limited as far as the shell formation is concerned.

[0098] The medium is preferably water alone or a combination of water and an organic solvent. The use of water improves the reactivity of the alkoxysilane and is therefore preferred. The organic solvent is not particularly restricted, provided that the colloidal silicon dioxide of the present invention is obtained. Examples include alcohols such as methanol, ethanol, and 2-propanol, with methanol and ethanol being preferred. The ratio of water to the organic solvent is such that the amount of water is, for example, 30 parts by mass or more, preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, and also such that the amount of water is, for example, 100 parts by mass or less, and preferably 95 parts by mass or less, based on 100 parts by mass of the total amount of water and organic solvent.The ratio of water to organic solvent can also be such that, for example, the amount of water is 30 to 100 parts by mass, 40 to 100 parts by mass, 50 to 100 parts by mass, 30 to 95 parts by mass, 40 to 95 parts by mass, and 50 to 95 parts by mass, based on 100 parts by mass of the total amount of water and organic solvent. Using a higher proportion of water is advantageous for production costs.

[0099] In one embodiment, the required amount of alkaline catalyst is added to the water containing the nuclei, and then the alkoxysilane is added and heated to form the shells. If the water containing the nuclei already contains the required amount of alkaline catalyst, the addition of the alkaline catalyst is unnecessary.

[0100] In the shell formation reaction, the time required for the addition of the alkoxysilane is not particularly limited, provided that the colloidal silicon dioxide of the present invention is obtained.

[0101] The temperature of the reaction liquid in the shell formation reaction is not particularly restricted, provided the colloidal silicon dioxide of the present invention is obtained, and is preferably 70°C or higher and more preferably 75°C or higher. A lower limit of the temperature of the mixed liquid within the aforementioned ranges hinders gelation of the reaction. The temperature of the mixed liquid is preferably 95°C or less and more preferably 90°C or less. An upper limit of the temperature of the mixed liquid within the aforementioned ranges hinders the evaporation of the alkoxysilane. The temperature of the reaction liquid can be 70 to 95°C, 75 to 95°C, 70 to 90°C, or 75 to 90°C.

[0102] The colloidal silicon dioxide obtained during the shell formation step can be concentrated or diluted as required, and the concentration of silicon dioxide particles can be adjusted, for example, to 1 to 50 percent by mass. The concentration process is not particularly limited, and the colloidal silicon dioxide can be concentrated using conventionally known methods. One such concentration method involves, for example, heating and concentrating the colloidal silicon dioxide at a temperature of approximately 65 to 100°C.

[0103] When an organic solvent is used as the medium, the colloidal silicon dioxide obtained in the shell formation step contains the organic solvent, such as alcohol. Therefore, the organic solvent can be distilled out of the system. The method for distilling off the organic solvent from the system is not particularly limited and involves adding pure water dropwise to the colloidal silicon dioxide while heating the colloidal silicon dioxide and keeping the volume constant, thereby replacing the dispersion medium with the pure water.Examples of other methods include a process in which the colloidal silicon dioxide is separated by precipitation or separated from a solvent by centrifugation or the like and then redispersed in water, or a process in which pure water is added while the organic solvent is removed by ultrafiltration and the solvent is replaced by the water. Examples

[0104] The present invention is described below, in particular by way of examples; however, the present invention is not limited thereto. Example 1: Production of nuclear particles Step 1

[0105] 7500 g of pure water were placed in a flask as a solvent, and 0.7737 g of 3-ethoxypropylamine was added as an alkaline catalyst to prepare a mixed liquid. The pH of the mixed liquid was 10.7. The 0.7737 g of 3-ethoxypropylamine is used in the synthesis of the nuclei and is therefore not included in the amount of alkaline catalyst used for shell formation. Step 2

[0106] The mixed liquid was heated until the internal temperature reached 85°C, and 2740 g of tetramethyl orthosilicate (TMOS) were poured into the mixed liquid at a constant rate over 60 minutes, while the temperature was adjusted to maintain a stable internal temperature. After the pouring was complete, the resulting mixed liquid was stirred for 60 minutes to ensure a homogeneous mixture. Step 3

[0107] 10.0 g of 3-ethoxypropylamine (3-EOPA) were added to the mixed liquid to produce colloidal silicon dioxide (dispersion containing nucleated particles; 10250.8 g). The colloidal silicon dioxide had a silicon dioxide concentration of 10.5% by mass, and the secondary particle size of the silicon dioxide particles in the colloidal silicon dioxide was 36 nm. Shell formation Step 4

[0108] 5882 g of pure water as solvent and 2604 g of the dispersion containing nuclear particles prepared in step 3 (with 2.540 g (0.02462 mol) of the 3-EOPA added in step 3) were placed in a flask and mixed to produce a mixed liquid. The 3-ethoxypropylamine was not added as an alkaline catalyst in this step. Step 5

[0109] The mixed liquid prepared in step 4 was heated to 80°C, and a mixture of 1872.3 g (12.3000 mol) of tetramethyl orthosilicate and 16.3 g (0.0909 mol) of 3-aminopropyltrimethoxysilane (3-APTMS) was poured at a constant rate for 180 minutes while maintaining a stable temperature. After pouring, the liquid temperature was held at 80°C for 15 minutes, and shells formed, yielding a colloidal silicon dioxide dispersion containing core-shell silicon dioxide particles. The total amount of alkoxysilanes added in the shell formation reaction was 503 times the molar ratio of the amount of alkaline catalyst (= (12.3000 + 0.0909) / 0.02462). Concentration and water replacement Step 6

[0110] The colloidal silicon dioxide dispersion obtained in step 5 was collected in a starting volume of 900 g and a feed volume of 900 g. The colloidal silicon dioxide dispersion was fed under normal pressure at constant volume, and the resulting colloidal silicon dioxide dispersion was heated and concentrated until the silicon dioxide concentration reached approximately 20% by mass. To distill off the methanol from the system, 670 ml of pure water were then added dropwise at constant volume to replace the dispersion medium, producing colloidal silicon dioxide dispersed in water.

[0111] The observation of the obtained colloidal silicon dioxide by a subsequently described SEM image analysis method showed that only a few fine particles were found ( Fig. 1). Example 2

[0112] Water-dispersed colloidal silicon dioxide was prepared in the same manner as in Example 1, except that 2.536 g of 3-ethoxypropylamine were added as an alkaline catalyst in step 4 of Example 1. The total amount of alkoxysilanes added in the shell formation reaction was 252 times the molar ratio of the amount of alkaline catalyst. Comparative example 1

[0113] This example corresponds to Example 1 described in JP 2016-008157 A.

[0114] Water-dispersed colloidal silicon dioxide was prepared in the same manner as in Example 1, except that 10.144 g of 3-ethoxypropylamine was added as an alkaline catalyst in step 4 of Example 1. The mixed liquid obtained in step 4 had a pH of 10. The total amount of alkoxysilanes added in the shell formation reaction was 101 times the molar ratio of the amount of alkaline catalyst.

[0115] The observation of the resulting colloidal silicon dioxide dispersed in water using the SEM image analysis method described later ( Fig. 2) showed that the colloidal silicon dioxide (average ellipse secondary axis of 27 nm) of comparison example 1 compared to the number of fine particles of the colloidal silicon dioxide (average ellipse secondary axis of 27 nm) ( Fig.1) of example 1 clearly contains a larger number of fine particles with a particle size of 20 nm (27 nm × 0.75 = 20 nm) or less. Example 3

[0116] The water-dispersed colloidal silicon dioxide was prepared in the same manner as in Example 1, except that steps 4 and 5 below were performed instead of steps 4 and 5 of Example 1. The total amount of alkoxysilanes added in the shell formation reaction was 1007 times the molar ratio of the amount of alkaline catalyst. Step 4

[0117] 6061 g of pure water, 930 g of methanol, 581 g of the dispersion containing nucleic particles prepared in step 3 of Example 1, and 0.789 g of 3-ethoxypropylamine (3-EOPA) were placed in a flask and mixed to produce a mixed liquid. Step 5

[0118] The mixed liquid prepared in step 4 was heated to 80°C, and then a mixed liquid consisting of 2000 g tetramethyl orthosilicate, 800 g methanol, and 17.4 g 3-aminopropyltrimethoxysilane was poured into it at a constant rate over 360 minutes, while the temperature was adjusted to maintain a stable liquid temperature. After completion of the pouring, the liquid temperature was held at 80°C for 15 minutes to obtain a colloidal silicon dioxide dispersion containing core-shell silicon dioxide particles. Example 4

[0119] Water-dispersed colloidal silicon dioxide was prepared in the same manner as in Example 3, except that the amount of 3-ethoxypropylamine used in step 4 of Example 3 was changed to 2.144 g. The total amount of alkoxysilanes added in the shell formation reaction was 504 times the molar ratio with respect to the amount of alkaline catalyst. Comparison example 2

[0120] Water-dispersed colloidal silicon dioxide was prepared in the same manner as in Example 3, except that the amount of 3-ethoxypropylamine used in step 4 of Example 3 was changed to 8.761 g. The total amount of alkoxysilanes added in the shell formation reaction was 146 times the molar ratio of the amount of alkaline catalyst. Comparison example 3

[0121] This example corresponds to Example 2 described in JP 2018-048042 A.

[0122] At normal temperature and pressure, 1316 g of tetramethyl orthosilicate, 13.333 g of 3-aminopropyltriethoxysilane and 352 g of methanol were mixed to obtain a composition.

[0123] A reaction vessel was charged with 805 g of aqueous ammonia solution (28 wt%), 1298 g of water, and 10417 g of methanol, followed by stirring at 35°C and 200 rpm. The aforementioned composition was then added stepwise over 30 minutes to produce a colloidal silicon dioxide dispersion. Observation of the resulting colloidal silicon dioxide (colloidal silicon dioxide after the shell formation reaction) by the SEM image analysis method described later showed that an excessive number of fine particles were found. Fig. 3).

[0124] Next, colloidal silicon dioxide dispersed in water was prepared in the same manner as in step 6 of Example 1, except that the base amount was adjusted to 800 g, the input amount to 1800 g, and the amount of pure water, replacing methanol, to 1200 ml. The total amount of alkoxysilanes added in the particle synthesis reaction was 0.658 times the molar ratio of the amount of alkaline catalyst. SEM observation of the resulting colloidal silicon dioxide dispersed in water showed that the fine particles observed after the particle synthesis reaction ( Fig. 3) were absorbed into the silicon dioxide particles and decreased ( Fig. 4).

[0125] The reaction conditions for the shell formation reaction and the physical properties of the particles after the shell formation reaction of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Table 1, and those of Comparative Example 3 are shown in Table 2. The physical properties, for example, of the colloidal silicon dioxide dispersed in water, prepared in each of the examples and comparative examples above, were measured by the methods described below, and the results are shown in Table 3.

[0095] Table 2 Particle synthesis reaction conditions or physical properties of the particles Unit See example 3 Reaction conditions molar ratio of alkoxysilane / alkaline catalyst - 0,658 Methanol concentration in the mixed liquid before the addition of alkoxysilane % by weight 83 Physical properties of the particles after the reaction Average ellipse minor axis nm Not measurable due to the many fine particles 75% of the diameter of the average ellipse's minor axis nm Proportion of the number of fine particles % Table 3 Physical properties of particles Unit Example 1 Example 2 See example 1 Example 3 Example 4 See example 2 See example 3 specific BET surface m 2 / g 115 115 115 69 69 68 81 Average primary particle size nm 23,7 23,7 23,7 39,6 39,7 40,1 33,5 Average secondary particle size nm 58 56 56 77 76 76 53 Aggregation ratio - 2,4 2,3 2,4 1,9 1,9 1,9 1,6 Average ellipse minor axis nm 27 27 27 47 48 45 38 75% of the diameter of the average ellipse's minor axis nm 20 20 20 35 36 34 29 Proportion of the number of fine particles % 0,4 1,8 6,7 1,4 1,6 10,9 1,1 Length-width ratio - 1,8 1,7 1,8 1,5 1,4 1,4 1,3 Surface roughness - 1,1 1,1 1,1 1,2 1,2 1,1 1,1 Density of silanol groups Groups / nm 2 1,8 1,7 1,7 2,8 2,8 2,1 6,1 True density - 2,10 2,10 2,10 2,07 2,06 2,06 1,87 Zeta potential of colloidal silicon dioxide

[0126] To confirm the presence of amino groups in the silicon dioxide particles, the zeta potential of the silicon dioxide particles was measured. The results are shown in Table 4 and Fig.Figure 5 illustrates this. The zeta potential of the comparison example in this application corresponded to that of Example 1 from PTL 1 (JP 2016-008157 A). The zeta potentials at pH 2 of Examples 1 to 4 were all approximately 25 mV, all corresponding to that of Comparison Example 1 of this application. In Comparison Example 1 described in JP 2016-008157 A, which contains only amino groups on the particle surface, the zeta potential at pH 2 is even approximately 45 mV. From these findings, it can be confirmed that the silicon dioxide particles in the colloidal silicon dioxide of each of Examples 1 to 4 of this application exhibit both the silanol groups and the amino groups on their surfaces. Table 4 Example 1 Example 2 Example 3 Example 4 See example 1 Zeta potential at a pH of 2 +25 mV +25 mV +21 mV +27 mV +26 mV Zeta potential at a pH of 3 +26 mV +26 mV +31 mV +31 mV +27 mV Zeta potential at a pH of 4 +24 mV +21 mV +25 mV +25 mV +25 mV Zeta potential at a pH of 5 +17 mV +16 mV +12 mV +15 mV +14 mV Zeta potential at a pH of 7 -23 mV -27 mV -29 mV -26 mV -19 mV Zeta potential at a pH of 9 -46 mV -44 mV -51 mV -49 mV -60 mV Methods for determining physical properties

[0127] The physical properties, for example in Table 3, were determined as follows. 1. Specific BET surface area and average primary particle size

[0128] The colloidal silicon dioxide was dried on a hot plate and then heat-treated for 1 hour at 800°C to produce a measurement sample. The specific BET surface area (m²) of the produced measurement sample was then determined. 2 / g) measured using a nitrogen gas adsorption method (BET method).

[0129] The average primary particle size (nm) of the silicon dioxide particles in the colloidal silicon dioxide was determined by converting the specific surface area (m²) value of 2727 / BET. 2 / g) determined from the above-mentioned measurements of the specific BET surface area, assuming the actual specific weight of silicon dioxide to be 2.2. 2. Average secondary particle size

[0130] Colloidal silicon dioxide was added to a 0.3 wt% aqueous citric acid solution and homogenized to prepare a sample. This sample was then used to measure the secondary particle size of the silicon dioxide particles in the colloidal silicon dioxide by dynamic light scattering (ELSZ-2000S, manufactured by Otsuka Electronics Co., Ltd.). 3. Aggregation ratio

[0131] The aggregation ratio of the silicon dioxide particles of the colloidal silicon dioxide was determined by calculating the average secondary particle size / average primary particle size of the silicon dioxide particles of the colloidal silicon dioxide. 4. Analysis of the SEM image 4-1. Preparation of the sample for SEM observation

[0132] Ten microliters of a liquid obtained by mixing 7.5 ml methanol, 1.5 ml water, 1 ml 0.01 M HCl, and 5 µl colloidal silicon dioxide with a silicon dioxide concentration of 20%, or a reaction liquid with a silicon dioxide concentration after the shell formation reaction of 7 to 12%, were placed dropwise onto a sample stage and dried. In preparing the aforementioned mixed liquid, the amount of the dispersion containing silicon dioxide particles can be increased or decreased so that the silicon dioxide concentration after dilution and mixing is 0.007 to 0.012% by mass. This sample stage is placed in a scanning electron microscope (SEM), and an SEM image is acquired. The white bar at the bottom of the SEM image indicates a length of 100 nm. 4-2. Average ellipse minor axis

[0133] The scanning electron microscope image of the silicon dioxide particles was used to decompose 1000 particles into ellipses using image analysis software (WinRoof 2015, manufactured by Mitani Corporation), and the major and minor axes of each ellipse were measured. The minor axes of the ellipses of all particles in the SEM image were averaged to calculate the average ellipse minor axis (nm). 4-3. Proportion of the number of fine particles

[0134] Particles with a particle size of 75% or less with respect to the average ellipse minor axis determined by the ellipse approximation in Section 4-2 above were defined as fine particles, and the total number of particles and the number of fine particles in the SEM image were counted. The ratio between the number of fine particles and the total number of particles was calculated ((number of fine particles / total number of particles) x 100 (%)). 4-4. Length-to-width ratio

[0135] The ratio between the major axis of the ellipse and the minor axis of the ellipse (major axis of the ellipse / minor axis of the ellipse) of each particle was calculated from the major axis of the ellipse and the minor axis of the ellipse obtained by the ellipse approximation in the preceding section 4-2, and the average value was defined as the length-width ratio. 5. Surface roughness

[0136] The value (B1 / S1), obtained by dividing the specific BET surface area (B1) by the specific surface area (S1) calculated using the average ellipse minor axis, was defined as the surface roughness. The specific surface area (S1) was determined by converting the value 2727 / average ellipse minor axis (nm) using the actual specific gravity of silicon dioxide, which is 2.2. 6. Density of the silanol groups

[0137] The density of the silanol groups of the silicon dioxide particles was measured using the Sears method. The Sears method was performed according to the description in G.W. Sears, Jr., “Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide”, Analytical Chemistry, 28 (12), 1981 (1956). For the measurement, the titration was carried out with a 0.1 mol / L aqueous sodium hydroxide solution using a 1 wt% silicon dioxide dispersion, and the density of the silanol groups was calculated using the following formula: ρ=(a×f×6022) / (c×S).

[0138] In the formula above, ρ represents the density of the silanol groups (groups / nm³). 2), a for the droplet quantity of the 0.1 mol / l aqueous sodium hydroxide solution with a pH of 4 to 9 (ml), f for the factor of the 0.1 mol / l aqueous sodium hydroxide solution, c for the mass of the silicon dioxide particles (g) and S for the specific BET surface area (m²) 2 / G). 7. True Density

[0139] The colloidal silicon dioxide was dried on a 150°C hot plate and then heat-treated for 1 hour at 300°C. The true density was then measured using a liquid phase shift method with ethanol. 8. Zeta potential

[0140] The colloidal silicon dioxide was diluted with a 10 mM aqueous sodium chloride solution so that the silicon dioxide concentration was 1 mass percent, and the zeta potential was measured using an ELS-Z manufactured by Otsuka Electronics Co., Ltd. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2016-008157 A [0006, 0113, 0126] JP 2018-048042 A [0006, 0121] JP 2016-094619 A

[0006] JP H01-145317 A

[0006] JP S62-072514 A

[0006] WO 2008 / 123373

[0006] JP 2006-231436 A

[0006] Cited non-patent literature

[0000] Kazunori HIRABAYASHI und Atsunori MORI, „Organic Chemistry of Siloxane and Silanol“ (Organische Chemie von Siloxan und Silanol), Journal of Synthetic Organic Chemistry, Japan, 2000, Bd. 58, Nr. 10, S. 926-933

[0007] G. W. Sears, Jr. „Determination of Specific Surface Area of Colloidal Silica by Titration with Sodium Hydroxide“, Analytical Chemistry, 28 (12), 1981 (1956

[0027] G. W. Sears, Jr., „Determination of Specific Surface Area of Colloidal Silica by Titration with Sodium Hydroxide“, Analytical Chemistry, 28 (12), 1981 (1956

[0137]

Claims

[1] Colloidal silicon dioxide in which a silyl group with one or more amino groups is introduced into the interior of the particles, wherein the proportion of the number of fine particles contained in the colloidal silicon dioxide is less than 5% based on the total number of particles, and the density of silanol groups on the surface of the colloidal silicon dioxide particles is 4.0 groups / nm 2 or less. [2] Colloidal silica according to claim 1, wherein the true density is 1.90 or more. [3] A process for producing colloidal silicon dioxide, in which a silyl group having one or more amino groups is introduced into the interior of the particles, the process comprising: Allowing an alkoxysilane having one or more groups and an alkoxysilane without an amino group to react with core particles in the presence of an alkaline catalyst to form shells, wherein the total amount of alkoxysilanes added in a shell formation reaction is 200 times or more, based on the molar ratio, to the amount of alkaline catalyst present in a reaction system in the shell formation reaction.

Images