Colloidal silica and method for producing same

Abstract

In the present invention, the amount of an alkoxysilane (for example, the total amount of tetraethyl orthosilicate and an alkoxysilane having an amino group) added in a core-particle shell-forming reaction is 200 times or more by mole relative to the amount of a basic catalyst present in a shell-forming reaction solution. According to the present invention, it is possible to provide a colloidal silica in which a silicon group having an amino group has been introduced into the interior of a particle, the colloidal silica containing core-shell silica particles having a silanol group density of 4.0 particles / nm2 or less, and having a small content of microparticles.

Description

Technical Field

[0001] The present invention relates to colloidal silicon dioxide and a method for producing the same. Background Art

[0002] Silica particles are used as abrasives for chemical polishing (CMP) of semiconductor substrates, fillers for resins, coatings for optical materials, additives for printing toner resin particles, cosmetic materials, etc. In order to improve the dispersion stability of the particles and give the particles properties corresponding to the use, the introduction of functional groups into the particles is widely used. One of these treatments is silane coupling treatment. In the silane coupling treatment, a typical example is to introduce an alkoxysilane having a functional group, such as Z-Si(OD) 3 [Wherein, Z represents a functional group and D represents an alkyl group] As a silane coupling agent, the alkoxy group of alkoxysilane reacts with the OH group on the particle surface (typically a dehydration condensation reaction) to form "Z-Si-O-particles", thereby introducing the functional group Z into the silica particles. By introducing the functional group (sometimes also referred to as modification), the silica particles are given properties corresponding to the functional group possessed by the introduced silane group. For example, when an amino group is introduced, the surface potential of the particles increases, and the pH region showing a positive potential expands.

[0003] As a method for introducing amino groups into silica particles, there is known a method for producing colloidal silica in which a liquid obtained by mixing tetraalkoxysilane and a silane coupling agent having amino groups is added to core particles to form a shell, thereby producing core-shell silica particles into which amino groups are introduced (Patent Document 1).

[0004] In addition, there is known a method for producing colloidal silica containing silica particles having an average primary particle size of 33 nm or more by adding an organic solvent to the reaction solution during the shell-forming reaction (Patent Document 2).

[0005] Furthermore, there are also known methods for producing colloidal silica under the condition that the alcohol concentration in the reaction liquid of the silica particle synthesis reaction is high (Patent Documents 3 to 6).

[0006] Furthermore, when a large number of fine particles are generated in the stage of forming a shell on the core particle, the removal of these fine particles becomes complicated.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2016-008157

[0010] Patent Document 2: International Publication No. 2020 / 179556

[0011] Patent Document 3: Japanese Patent Application Publication No. 2018-048042

[0012] Patent Document 4: Japanese Patent Application Publication No. 2016-094619

[0013] Patent Document 5: Japanese Patent Application Laid-Open No. 01-145317

[0014] Patent Document 6: Japanese Patent Application Laid-Open No. 62-072514

[0015] Patent Document 7: International Publication No. 2008 / 123373

[0016] Patent Document 8: Japanese Patent Application Publication No. 2006-231436

[0017] Non-patent literature

[0018] Non-patent document 1: Kazunori Hirabayashi and Atsuki Mori, Organic Chemistry of Siloxanes and Silanols, Journal of the Japanese Society of Synthetic Organic Chemistry, 2000, vol. 58, No. 10, pp. 926-933 Summary of the invention

[0019] Problems to be solved by the invention

[0020] The inventors of the present invention have confirmed that in the method for producing colloidal silica described in Patent Document 1, a large amount of fine particles, ie, particles having a smaller particle size than the core particles, are generated in the stage of forming a shell on the core particles (Comparative Example 1 of the present application).

[0021] In addition, although Patent Document 2 produces colloidal silica in which the ratio of the number of silica particles with an equivalent circular diameter of less than 20 nm is less than 15%, this effect is obtained by making the reaction liquid contain a certain amount of organic solvent (such as methanol) during the shell formation reaction. Moreover, Patent Document 2 does not provide any suggestion that the number of microparticles generated can be reduced by making the ratio of the amount of alkoxysilane added during the shell formation reaction greater than the amount of alkaline catalyst during the shell formation reaction. Moreover, in Patent Document 2, amino groups are introduced by adding alkoxysilanes having amino groups after the shell is formed.

[0022] In addition, in Patent Documents 3 to 6, since a reaction system with a high concentration of organic solvent (alcohol) in the mixed solution of the particle synthesis reaction is used, it is inferred that the density of silanol groups on the particle surface is high, and the inventors of the present invention have also confirmed that the density of silanol groups is high (Comparative Example 3 of the present application). Due to the high density of silanol groups, the following problems may occur: silanol groups become unstable ("2. Silanol" on page 928 of Non-Patent Document 1); it is difficult to form dense particles with high true density (Patent Document 7, paragraphs 0008 to 0011); there is a tendency to combine with the polar groups of the polishing pad and cause scaling of the polishing pad (Patent Document 8, paragraphs 0010 to 0015).

[0023] Therefore, an object of the present invention is to provide colloidal silica containing core-shell type silica particles having a silyl group having an amino group introduced inside the particles, particularly inside the shell, and having a low content of fine particles.

[0024] An object of the present invention is to reduce fine particles generated during shell formation reaction in the production of colloidal silica comprising core-shell type silica particles having amino-containing silyl groups introduced into the interior of the particles, particularly into the shell.

[0025] Methods for solving problems

[0026] The inventors of the present invention have discovered that by increasing the amount of alkoxysilane (e.g., the total amount of tetramethyl orthosilicate and alkoxysilane having an amino group) added in the reaction of forming a shell on the core particle by 200 times or more in molar ratio relative to the amount of the alkaline catalyst (e.g., the amount of 3-ethoxypropylamine) present in the shell forming reaction liquid, the amount of fine particles generated in the shell forming reaction can be reduced without increasing the silanol group density of the generated core-shell type silica particles, thereby completing the present invention.

[0027] Representatively, the present invention is described as follows.

[0028] Item 1.

[0029] A colloidal silica having silyl groups having amino groups introduced into the interior of the particles.

[0030] The ratio of the number of microparticles contained in the colloidal silica to the number of all particles is less than 5%.

[0031] The density of silanol groups on the surface of the colloidal silica particles is 4.0 / nm. 2 the following.

[0032] Item 2.

[0033] The colloidal silica as described in Item 1 has a true density of 1.90 or more.

[0034] Item 3.

[0035] A method for producing colloidal silica, wherein the colloidal silica is colloidal silica in which a silyl group having an amino group is introduced into the interior of the particles, the method comprising the step of reacting an alkoxysilane having an amino group and an alkoxysilane not having an amino group in a core particle in the presence of an alkaline catalyst to form a shell, wherein the total amount of the alkoxysilane added during the shell formation reaction is 200 times or more in molar ratio relative to the amount of the alkaline catalyst present in the reaction system during the shell formation reaction.

[0036] Effects of the Invention

[0037] The present invention can provide a colloidal silica having a silanol group density of 4.0 / nm. 2 The following core-shell silica particles have a small content of fine particles, and a silyl group having an amino group is introduced inside the particles, particularly inside the shell.

[0038] According to the present invention, there is provided a method for producing colloidal silica, wherein the total amount of alkoxysilane added during the shell forming reaction is 200 times or more in molar ratio relative to the amount of the basic catalyst present in the reaction system during the shell forming reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a SEM image of the colloidal silica obtained in the final step of Example 1.

[0040] Figure 2 This is a SEM image of the colloidal silica obtained in the final step of Comparative Example 1.

[0041] Figure 3 This is a SEM image of methanol-dispersed colloidal silica obtained by the silica particle synthesis reaction of Comparative Example 3.

[0042] Figure 4 This is a SEM image of the water-dispersed colloidal silica obtained in the final step of Comparative Example 3.

[0043] Figure 5 This is a graph showing the results of measuring the zeta potential of the colloidal silica of Examples 1 to 4 and Comparative Example 1. The horizontal axis represents pH, and the vertical axis represents zeta potential (mV). DETAILED DESCRIPTION

[0044] In this specification, unless otherwise specified, "inside the particle" means "inside the particle or inside the shell constituting the particle". For example, the expression inside the silica particle means inside the silica particle or inside the shell constituting the silica particle. The colloidal silica of the present invention comprises core-shell silica particles into which silane groups containing amino groups are introduced inside the particles, the content of microparticles is low, and the density of silanol groups in the silica particles is low. Therefore, it has the advantages that the density of unstable silanol groups is not too high, dense particles with high true density are formed, and scaling of the polishing pad can be suppressed.

[0045] In the method for producing colloidal silica of the present invention, the amount of alkoxysilane added during the reaction of forming a shell on the core particle is 200 times or more in molar ratio relative to the amount of the alkaline catalyst (e.g., the amount of 3-ethoxypropylamine) present in the shell formation reaction liquid. Therefore, the amount of fine particles generated in the shell formation reaction can be reduced without increasing the silanol group density of the generated core-shell silica particles.

[0046] 1. Colloidal Silica

[0047] The colloidal silica of the present invention has amino groups introduced into the silica particles contained in the colloidal silica. In particular, amino groups are distributed throughout the shell of the core-shell type particles contained in the colloidal silica. In addition, the ratio of the number of microparticles contained in the colloidal silica to the number of all particles is less than 5%. Moreover, the density of silanol groups on the surface of the core-shell type silica particles contained in the colloidal silica is 4.0 / nm. 2 the following.

[0048] Typically, the colloidal silica of the present invention is produced by the production method of the present invention, but may also be produced by other methods.

[0049] The concentration of the silica particles in the colloidal silica of the present invention can be appropriately selected by a person skilled in the art according to the application of the colloidal silica, the expected storage time, etc., and can be, for example, 1 to 50% by mass.

[0050] Tiny particles

[0051] Microparticles refer to particles having a particle size of 75% or less relative to the average elliptical minor diameter of silica particles in the SEM image of colloidal silica. In the present invention, the ratio of the number of microparticles contained in the colloidal silica to the number of particles is less than 5.0%, preferably less than 4.0%, more preferably less than 3.0%, and further preferably less than 2.0%. Although the ratio is preferably lower, it can also be 0.01% or more and less than 5.0%, 0.01 to 3.0%, 0.01 to 2.0%, etc. The number ratio of microparticles contained in the colloidal silica can be determined by the method described in the examples.

[0052] Silanol group density

[0053] The density of silanol groups on the surface of silica particles contained in colloidal silica can be 4.0 / nm 2 Below, preferably 3.5 / nm 2 Less than, more preferably 3.0 / nm 2 Below. Moreover, it can be 1.0 / nm 2 Above, preferably 1.2 / nm 2 More preferably, 1.4 / nm 2 When the silanol group density is greater than or equal to these values, the hydrophobicity of the colloidal silica does not become too high, and thus the stability in water is high.

[0054] The silanol group density can be 1.0 to 4.0 per nm. 2 , 1.0~3.5 / nm 2 , 1.0~3.0 / nm 2 , 1.2~4.0 / nm 2 , 1.2~3.5 / nm 2 , 1.2~3.0 / nm 2 , 1.4~4.0 / nm 2 , 1.4~3.5 / nm 2 , 1.4~3.0 / nm 2 The silanol group density can be determined by the Sears method described in GW Sears, Jr., "Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide", Analytical Chemistry, 28 (12), 1981 (1956). More specifically, the silanol group density can be determined by the following formula using a 1 mass % silica dispersion and titrating it with a 0.1 mol / L sodium hydroxide aqueous solution in the Sears method.

[0055] ρ=(a×f×6022)÷(c×S)

[0056] In the above formula, ρ represents the silanol group density (number / nm 2 ), a represents the amount of 0.1 mol / L sodium hydroxide aqueous solution with a pH of 4 to 9 (mL), f represents the factor of 0.1 mol / L sodium hydroxide aqueous solution, c represents the mass of silica particles (g), S represents the BET specific surface area (m 2 / g).

[0057] Average primary particle size

[0058] The average primary particle size of the silica particles contained in the colloidal silica is not particularly limited and can be appropriately selected according to the purpose, for example, 1 nm or more, preferably 2 nm or more, and, for example, 350 nm or less, preferably 150 nm or less, more preferably 120 nm or less, and further preferably 100 nm or less. The average primary particle size of the silica particles 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, 2 nm to 100 nm. The average primary particle size can be determined by the method described in the examples.

[0059] Average secondary particle size

[0060] The average secondary particle size of the silica particles contained in the colloidal silica is not particularly limited and can be appropriately selected according to the application, and can be, for example, 1 nm to 500 nm, 2 nm to 300 nm, and preferably 3 nm to 250 nm. The average secondary particle size can be determined by the method described in the Examples.

[0061] Association ratio

[0062] The association ratio of the silica particles contained in the colloidal silica is expressed as the average secondary particle size / average primary particle size, which is typically less than 5.0, preferably less than 4.0, more preferably less than 3.5, and further preferably less than 3.0. Moreover, for example, it is more than 1.0, preferably more than 1.3, and more preferably more than 1.5. When the association ratio is within the above range, it is easy to suppress the occurrence of damage on the grinding surface when the particles are used as abrasives of the grinding agent, and it is easy to increase the grinding speed compared to the true spherical type. In addition, the association ratio can be set to 1.0-5.0, 1.3-5.0, 1.5-5.0, 1.0-4.0, 1.3-4.0, 1.5-4.0, 1.0-3.5, 1.3-3.5, 1.5-3.5, 1.0-3.0, 1.3-3.0, 1.5-3.0, etc.

[0063] Mean ellipse minor diameter

[0064] The average elliptical minor diameter of the silica particles contained in the colloidal silica is not particularly limited and can be appropriately selected according to the purpose, for example, more than 1 nm, preferably more than 2 nm, and, for example, less than 350 nm, preferably less than 150 nm, more preferably less than 120 nm, and further preferably less than 100 nm. The average elliptical minor diameter 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, 2 nm to 100 nm. The average elliptical minor diameter can be determined by the method described in the examples.

[0065] Aspect Ratio

[0066] The aspect ratio of the silica particles contained in the colloidal silica can be, for example, 1.0 to 5.0, 1.0 to 3.0, preferably 1.2 to 2.5. When the aspect ratio is within the above range, it is easy to suppress the occurrence of damage on the grinding surface when the particles are used as abrasives of abrasives, and it is easy to increase the grinding speed compared to a true spherical type. The aspect ratio can be determined by the method described in the embodiments.

[0067] Surface roughness

[0068] The surface roughness of the silica particles contained in the colloidal silica can be set to, for example, 1.0 to 2.0, 1.0 to 1.8, and preferably 1.1 to 1.7. When the surface roughness is within the above range, it is advantageous in terms of polishing performance. The surface roughness can be determined by the method described in the examples.

[0069] True density

[0070] The true density of the silicon dioxide particles contained in the colloidal silica is, for example, more than 1.60, more than 1.70, preferably more than 1.90, more preferably more than 2.00, and, for example, less than 2.30. The true density can be set to 1.60-2.30, 1.70-2.30, 1.90-2.30, 2.00-2.30, etc. When the true density is within the above range, when the particles are used as abrasives of abrasives, it is easy to improve the mechanical grinding action and grinding speed of the particles. The true density can be determined by the method described in the embodiments.

[0071] Amino groups introduced into silica particles

[0072] The amino group introduced into the silica particles contained in the colloidal silica can be a group introduced into the silica by treating the silica with an alkoxysilane having an amino group. Representatively, it refers to a state in which a silyl group having an amino group is bound to the inside of the silica particles by a covalent bond (preferably a siloxane bond). In addition to a covalent bond, it can also be bound by an ionic bond, a hydrogen bond, a chemical adsorption, a physical adsorption, etc. In addition, the silyl group having an amino group can also be bound to the surface of the silica particles in the same manner. Therefore, in addition to containing a silyl group having an amino group inside the silica particles, the silica particles can also contain a silyl group having an amino group on the particle surface. In such an embodiment, the silica particles contained in the colloidal silica of the present invention are silica particles in which a silyl group having an amino group shown in the general formula (1) is bound to the inside of the silica particles by a covalent bond (preferably a siloxane bond).

[0073] -Si(X) n (L-NH 2 ) p (1)

[0074] [In the formula, X is the same or different and is a hydroxyl group, a hydrolyzable substituent, a non-hydrolyzable substituent, a bond to Si of another silyl group via -O-, or a bond to a silicon atom inside a silica particle via -O-, n is 0, 1 or 2, p is an integer from 1 to 3, n+p=3, and L is a linking group.]

[0075] For example, the silyl group allows Si in the silyl group to bond to the silicon atom inside the silica particle via -O-. Si in the silyl group may have 1, 2 or 3 such bonds via -O-.

[0076] A silyl group having an amino group represented by the general formula (1)

[0077] When there is only one bond between Si in the silyl group represented by the general formula (1) and the silicon atom inside the silica particle via -O-, -Si in the silyl group is bonded to the silicon atom inside the silica particle via -O- (siloxane bond). That is, Si is bonded to the inside of the silica particle via "Si*-O-Si(X) n -" (Si* is a silicon atom inside the silica particle, X is the same or different and is a hydroxyl group, a hydrolyzable substituent, a non-hydrolyzable substituent, or a bond to Si of another silyl group via -O-, and n is 0, 1 or 2).

[0078] When there are two such bonds, one X is "bonded to the silicon atom inside the silica particle via -O-". That is, Si in the silyl group and the silicon atom inside the silica particle are bonded in the form of "Si*-O-Si(X) 2 (OSi**) 1 -" (Si* and X are the same as above, Si** is a silicon atom inside the silica particle different from Si*).

[0079] When there are three such bonds, two Xs are "bonded to the silicon atom inside the silica particle via -O-". That is, Si in the silyl group and the silicon atom inside the silica particle are bonded via "Si*-O-Si(X) 1 (OSi**) 1 (OSi***) 1 -" (Si*, Si** and X are the same as above, Si*** is a silicon atom inside a particle different from Si* and Si**).

[0080] In the silyl group represented by the general formula (1), X is the same or different and is a hydroxyl group, a hydrolyzable substituent, a non-hydrolyzable substituent, a bond to Si of another silyl group via -O-, or a bond to a silicon atom inside the silica particle via -O-.

[0081] 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 the amino group is based on the degree of hydrolysis when the amino group is introduced, for example, it is not hydrolyzed and remains as a hydrolyzable group, or is hydrolyzed to form a hydroxyl group, or is hydrolyzed to form a hydroxyl group and further condensed with other hydroxyl 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 further preferably a methoxy group or an ethoxy group.

[0082] In X, the non-hydrolyzable substituent is a group that is not hydrolyzed in an aqueous system, that is, 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 further preferably a methyl group or an ethyl group.

[0083] 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) in the silica particles and Si in the silyl group present nearby via an oxygen atom, forming a Si-O-Si structure.

[0084] In X, the bond to the silicon atom inside the silica particle via -O- is the bond between Si in the silyl group and the silica particle, forming a Si-O-Si** structure or a Si-O-Si*** structure (Si** and Si*** are silicon atoms inside the silica particle, as described above). The details of this bond are as described above.

[0085] In one embodiment, X is preferably the same or different and is a bond to a silicon atom inside the silica particle via -O-, a bond to Si of a nearby silyl group via an oxygen atom, a hydroxyl group, a methoxy group, an ethoxy group, or a methyl group.

[0086] In the silyl group represented by the general formula (1), n ​​is 0, 1 or 2.

[0087] In the silyl group represented by the general formula (1), L is a linking group. Typically, the linking group is a group corresponding to the group formed between Si in the alkoxysilane having an amino group used when the amino group is introduced and the nitrogen atom constituting the amino group. That is, the linking group is a group linking Si in the silyl group and the nitrogen atom constituting the amino group in the alkoxysilane having an amino group used when the amino group is introduced. The linking group is, for example, a linear or branched C1-C18 alkylene group.

[0088] As a straight-chain or branched C1-C18 alkylene group, for example, methylene, ethylene, propylene, butylene, hexylene, decylene, octadecylene, etc. The branched chain in the branched alkylene group is, for example, a C1-C3 alkyl group. It should be noted that the branched chain refers to an alkyl group bonded to a carbon atom constituting the main chain in the case where the main chain in the branched alkylene group is a linear hydrocarbon chain connecting a carbon atom bonded to Si and a nitrogen atom constituting an amino group.

[0089] The linear or branched C1-C18 alkylene group may have a substituent. The substituent is, for example, an alkenyl group (e.g., a vinyl group, an allyl group) or an alkynyl group. The substituent may be one or more than one. The number of substituents may be, for example, 0, 1, 2, or 3.

[0090] A straight-chain or branched C1-C18 alkylene group may 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 in the alkylene chain. When these heteroatoms are contained in a branched C1-C18 alkylene group, they may be contained in the main chain or in the branched chain. In addition, when a nitrogen atom is contained in the end of the alkylene chain or in the alkylene chain, it may be -NH-, and the nitrogen atom may be substituted by a substituent. As the substituent in this case, methyl and ethyl can be listed. There is no particular limitation on the total number of oxygen atoms, nitrogen atoms and sulfur atoms contained in the end of the alkylene chain and the alkylene chain.

[0091] In one embodiment, L is preferably *-(CH 2 ) 3 -O-CH 2 -、*-(CH 2 ) 2 -O-CH 2 -、*-(CH 2 ) 3 -O-(CH 2 ) 2 -、*-(CH 2 ) 2 -、*-(CH 2 ) 3 -、*-(CH 2 ) 6 -、*-(CH 2 ) 8 -、*-(CH 2 ) 3 -NH-CH 2 -、*-(CH 2 ) 3 -NH-(CH 2 ) 2 In view of the easy availability of the raw material silane coupling agent and the small steric hindrance, *-(CH 2 ) 3 -O-CH 2 -、*-(CH 2 ) 3 -、*-(CH 2 ) 8 -、*-(CH 2 ) 3 -NH-(CH 2 ) 2 -. It should be noted that * represents Si(X) n side.

[0092] The silyl group represented by the general formula (1) is preferably a group represented by any of the following formulae from the viewpoint of easy availability of an alkoxysilane having an amino group as a raw material. In the following formulae, X is the same as described above.

[0093] -Si(X) 2 (-(CH 2 ) 3 -NH 2 ) 1

[0094] -Si(X) 2 (-(CH 2 ) 3 -NH-(CH 2 ) 2 -NH 2 ) 1

[0095] The colloidal silica of the present invention can be used as a crop quality improver in the fields of paper, fiber, steel, etc., and can also be used as an abrasive in chemical mechanical polishing (CMP), silicon wafer polishing, glass polishing, etc. In addition, by drying and making it into powder, it can also be used as a filler additive, a carbon powder admixture, etc.

[0096] In addition, an abrasive containing the colloidal silica described above can also be one of the present invention. Since the colloidal silica of the present invention has a reduced content of fine particles, it can be suitably used as an abrasive for chemical mechanical polishing, especially an abrasive for chemical mechanical polishing of semiconductor wafers.

[0097] 2. Method for producing colloidal silicon dioxide

[0098] The following method for manufacturing colloidal silica containing core-shell silica particles into which amino groups are introduced is known: an alkoxysilane having an amino group and an alkoxysilane not having an amino group are reacted on a core particle in the presence of an alkaline catalyst, and a shell is formed on the core particle (shell forming step). In the method for manufacturing colloidal silica of the present invention, in the shell forming step, the total amount of alkoxysilane added during the shell forming reaction is more than 200 times in molar ratio relative to the amount of alkaline catalyst present in the reaction system during the shell forming reaction. According to the method for manufacturing colloidal silica of the present invention, the generation of microparticles can be reduced without increasing the density of silanol groups.

[0099] The method for producing colloidal silica of the present invention is suitable for producing the colloidal silica of the present invention described above.

[0100] Method for manufacturing core particles

[0101] The core particles can be produced by a conventionally known method for producing core particles of colloidal silica, and the method is not particularly limited. For example, the core particles can be produced by (1) preparing a mixed solution containing an alkaline catalyst and water (step 1); (2) adding an alkoxysilane to the mixed solution prepared in step 1 to prepare a mixed solution (step 2); and (3) adding an alkaline catalyst to the mixed solution prepared in step 2 to prepare silica particles (step 3).

[0102] The method for preparing the mixed solution containing the alkaline catalyst and water is not particularly limited, and the alkaline catalyst can be added to water by a conventionally known method and stirred. The pH of the mixed solution is not particularly limited, but is preferably 9.0 or higher, and more preferably 9.5 or higher.

[0103] In the method for producing colloidal silica, the basic catalyst is not particularly limited and may be at least one amine selected from ammonia, primary amines, secondary amines and tertiary amines, and is preferably an amine represented by the following general formula (2).

[0104] NR a R b R c (2)

[0105] [Where R a , R b , R c The same or different, and represent an optionally substituted C1-C12 alkyl group or a hydrogen atom.]

[0106] R a , R b and R c Can be the same or different. a , R b and R c It may be either linear or branched.

[0107] The carbon number of the linear or branched alkyl group may be 1 to 12, preferably 1 to 8, and more preferably 1 to 6. Examples of the linear alkyl group include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl groups. Examples of the branched alkyl group include isopropyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 1-methyl-1-ethylpropyl, 2-methyl-2-ethylpropyl, 1-ethylbutyl, 2-ethylbutyl, 1-ethylhexyl, 2-ethylhexyl, 3-ethylhexyl, 4-ethylhexyl, and 5-ethylhexyl. Preferred linear or branched alkyl groups include n-propyl, n-hexyl, 2-ethylhexyl, and n-octyl.

[0108] In the above general formula (2), R a , R b and R c The alkyl group in may be substituted. The number of substituents may be, for example, 0, 1, 2, 3, 4, etc., preferably 0, 1 or 2, and more preferably 0 or 1. It should be noted that an alkyl group having 0 substituents refers to an unsubstituted alkyl group. As substituents, for example, alkoxy groups having 1 to 3 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy), amino groups, primary amino groups substituted with straight-chain alkyl groups having 1 to 4 carbon atoms, amino groups disubstituted with straight-chain alkyl groups having 1 to 4 carbon atoms (e.g., dimethylamino, di-n-butylamino, etc.), unsubstituted amino groups, etc. may be cited. Among them, as substituents, hydroxyl groups are not included. In an alkyl group having multiple substituents, the substituents may be the same or different.

[0109] In one embodiment, R a , R b and R c The same or different groups represent an unsubstituted linear or branched C1-C12 alkyl group, an alkoxy-substituted linear or branched C1-C12 alkyl group, or a hydrogen atom.

[0110] Additionally, in another embodiment, R a , R b and R c The same or different groups 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.

[0111] Additionally, in another embodiment, R a , Rb and R c The same or different groups 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.

[0112] In one embodiment, R a , R b and R c Two of them are hydrogen atoms, and the remaining one represents an unsubstituted straight-chain or branched C1-C12 alkyl group or a straight-chain or branched C1-C12 alkyl group substituted with an alkoxy group.

[0113] In another embodiment, R a , R b and R c Two of them are hydrogen atoms, and the remaining one represents an unsubstituted straight-chain or branched C1-C8 alkyl group or a straight-chain or branched C1-C8 alkyl group substituted with a C1-C3 alkoxy group.

[0114] Additionally, in another embodiment, R a , R b and R c Two of them are hydrogen atoms, and the remaining one represents an unsubstituted straight-chain or branched C1-C6 alkyl group or a straight-chain or branched C1-C6 alkyl group substituted with a C1-C3 alkoxy group.

[0115] Additionally, in another embodiment, R a , R b and R c Both represent hydrogen atoms.

[0116] Examples of the basic catalyst include at least one selected from the group consisting of ammonia, 3-ethoxypropylamine, pentylamine, hexylamine, dipropylamine, and triethylamine.

[0117] Among these, ammonia, 3-ethoxypropylamine, dipropylamine, and triethylamine are more preferred. Furthermore, in order to further improve the storage stability of colloidal silica, 3-ethoxypropylamine is preferred.

[0118] The basic catalyst may be used alone or in combination of two or more. As the basic catalyst, the amines described above for the colloidal silica may be used.

[0119] Shell forming process

[0120] The step of forming a shell on the core particle includes a shell forming reaction, and alkoxysilane is added for forming the shell. The total amount of alkoxysilane added in the shell forming reaction is 200 times or more in molar ratio relative to the amount of the basic catalyst present in the reaction system during the shell forming reaction.

[0121] The shell can be formed by adding alkoxysilane to the core particles dispersed in a mixture of water and an alkaline catalyst for reaction. In this step, an alkaline catalyst can also be added to adjust the amount of the alkaline catalyst. Preferably, the core particles used in the shell forming step are dispersed in a mixture of water and an alkaline catalyst.

[0122] The shell forming step may be, for example, a step (a) of mixing the core particles, the basic catalyst, and the alkoxysilane in any order in the presence or absence of water and / or an organic solvent.

[0123] In the shell forming step and step (a), the core particles, the basic catalyst and the alkoxysilane are mixed in any order to prepare a mixture in the presence or absence of water and / or an organic solvent. Stirring can be performed at any stage before, during or after mixing. The stirring method is not particularly limited.

[0124] Basic catalyst

[0125] As an alkaline catalyst, the alkaline catalyst described in the manufacturing method of the above-mentioned core particles can be used. In the shell formation reaction, the amount (molar amount) of the alkaline catalyst present in the reaction system is set to less than 1 / 200 of the total molar amount of the alkoxysilane added in the shell formation reaction system. As long as it is an amount within the range of less than 1 / 200, an alkaline catalyst can be added to the shell formation reaction. The amount (molar amount) of the alkaline catalyst present in the shell formation reaction system is preferably less than 1 / 200 of the total molar amount of the alkoxysilane added in the shell formation reaction system, and more preferably less than 1 / 250. The amount of alkaline catalyst present in the shell formation 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, 1 / 3000 to 1 / 250. By making the amount of alkaline catalyst present in the shell formation reaction system within the above range, the generation of fine particles can be more effectively suppressed.

[0126] The production method of the present invention is a method for producing colloidal silica having silyl groups having amino groups introduced into particles, and therefore, an alkoxysilane having amino groups and an alkoxysilane not having amino groups are used in the shell forming step.

[0127] In the shell formation step, the total amount of alkoxysilane added in the shell formation reaction (the total amount of alkoxysilane with amino group and alkoxysilane without amino group) is 200 times or more, preferably 250 times or more in molar ratio relative to the amount of the alkaline catalyst present in the reaction system during the shell formation reaction. The total amount of alkoxysilane added may also be 200 to 5000 times, 200 to 4000 times, 200 to 3000 times, 250 to 4000 times, or 250 to 3000 times. By making the total amount of alkoxysilane added in the shell formation reaction within the above range, the generation of fine particles can be more effectively suppressed.

[0128] In the shell forming reaction, the total amount of alkoxysilane added is not particularly limited as long as the colloidal silica of the present invention can be obtained, but is preferably 0.5 mol, more preferably 0.5 to 200 mol, and even more preferably 0.5 to 120 mol per 1 mol of the core particles.

[0129] The amount of the alkoxysilane having an amino group in the alkoxysilane added in the shell forming step is not particularly limited as long as the colloidal silica of the present invention can be obtained, but is preferably 0.1 to 10 mol %, more preferably 0.2 to 5 mol %, based on 100 mol % of the total amount of the alkoxysilane.

[0130] Alkoxysilane with amino group

[0131] The alkoxysilane having an amino group is not particularly limited, and for example, an alkoxysilane represented by the following general formula (3) can be used:

[0132] Si(OR e ) m (R f ) o (L-NH 2 ) q (3)

[0133] [Where R e represents an alkyl group, L represents a linking group, m is an integer of 1 to 3, o is an integer of 0 to 2, q is an integer of 1 to 3, and m+o+q=4.]

[0134] R e As long as it is an alkyl group, there is no particular limitation, but it is preferably a linear or branched C1-C8 alkyl group, more preferably a linear C1-C8 alkyl group, and further preferably a linear C1-C4 alkyl group. Specific examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, etc., and preferably methyl and ethyl.

[0135] R fAs long as it is an alkyl group, there is no particular limitation, but it is preferably a linear or branched C1-C8 alkyl group, more preferably a linear C1-C8 alkyl group, and further preferably a linear C1-C4 alkyl group. Specific examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, etc., and preferably methyl and ethyl.

[0136] L is a linking group, which corresponds to the linking group in the silyl group having an amino group represented by the general formula (1). Therefore, unless otherwise specified, the above description of L in the silyl group having an amino group represented by the general formula (1) can be applied to L in the general formula (3).

[0137] Examples of the alkoxysilane having an amino group include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, (aminoethyl)aminopropyltrimethoxysilane, (aminoethyl)aminopropyltriethoxysilane, aminopropylmethyldiethoxysilane, (aminoethyl)aminopropylmethyldimethoxysilane, and aminobutyltriethoxysilane. Preferred are aminopropyltrimethoxysilane, aminopropyltriethoxysilane, and (aminoethyl)aminopropyltriethoxysilane.

[0138] The alkoxysilane having an amino group may be used alone or in combination of two or more thereof. In addition, the alkoxysilane having an amino group may be added in full at once or in divided portions (eg, 2 or 3 times).

[0139] Alkoxysilane without amino group

[0140] The alkoxysilane not having an amino group is not particularly limited, and examples thereof include alkoxysilanes represented by the following general formula (4A) and alkoxysilanes represented by the following general formula (4B).

[0141] Si(OR d ) 4 (4A)

[0142] [Where R d represents an alkyl group.]

[0143] Si(OR g ) t (R h ) u (4B)

[0144] [Where R g represents an alkyl group, R h represents an alkyl group, t is an integer of 1 to 3, u is an integer of 1 to 3, and t+u=4.]

[0145] In the above general formula (4A), R d R represents an alkyl group.d As long as it is an alkyl group, there is no particular limitation, and it is preferably a linear or branched C1-C8 alkyl group, more preferably a linear C1-C8 alkyl group, and further preferably a linear C1-C4 alkyl group. Specific examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, and the like. As the alkoxysilane represented by the general formula (4A), R d Tetramethoxysilane (also known as tetramethyl orthosilicate), R d Ethyl tetraethoxysilane (also known as tetraethyl orthosilicate), R d isopropyl tetraisopropoxysilane, more preferably R d Tetramethoxysilane is methyl, R d The ethyl group is tetraethoxysilane, and more preferably tetramethoxysilane.

[0146] In the above general formula (4B), R g and R h The same or different, represents an alkyl group. g and R h As long as it is an alkyl group, there is no particular limitation, and preferably a linear or branched C1-C8 alkyl group, more preferably a linear C1-C8 alkyl group, and further preferably a linear C1-C4 alkyl group. As the above-mentioned alkyl group, specific examples include methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, etc., preferably methyl, ethyl, n-propyl, and more preferably methyl, ethyl. As the alkoxysilane represented by the above-mentioned general formula (4B), more preferably methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, ethyltrimethoxysilane, diethyldimethoxysilane, ethyltriethoxysilane, diethyldiethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane.

[0147] The alkoxysilane having no amino group may be used alone or in combination of two or more thereof. In addition, the alkoxysilane having no amino group may be added in its entirety at once or in divided portions (eg, 2 or 3 times).

[0148] The alkoxysilane having an amino group and the alkoxysilane not having an amino group may be derivatives. As the derivative of the alkoxysilane, there can be exemplified low condensation products obtained by partial hydrolysis of the alkoxysilane having an amino group and the alkoxysilane not having an amino group.

[0149] The alkoxysilane having an amino group and the alkoxysilane not having an amino group may be added separately or may be mixed and added.

[0150] medium

[0151] The shell formation step can be carried out in the presence or absence of water and / or an organic solvent (hereinafter sometimes referred to as a medium). It is advantageous to carry out the process in the presence of a medium in terms of suppressing agglomeration, and is therefore preferred. When a medium is used, the amount of the medium used is not particularly limited as long as the shell formation can be carried out.

[0152] As the medium, water alone or water and an organic solvent are preferably used. The use of water can improve the reactivity of alkoxysilane, so it is preferred. As the organic solvent, there is no particular limitation as long as the colloidal silica of the present invention can be obtained, for example, alcohols such as methanol, ethanol, and 2-propanol, preferably methanol and ethanol.

[0153] Regarding the ratio of water to the organic solvent, relative to the total of 100 parts by mass of water and the organic solvent, for example, the ratio of water is 30 parts by mass or more, preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and for example, the ratio of water is 100 parts by mass or less, preferably 95 parts by mass or less. Regarding the ratio of water to the organic solvent, relative to the total of 100 parts by mass of water and the organic solvent, for example, the ratio 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, 50 to 95 parts by mass. By making the use ratio of water high, there is an advantage in terms of manufacturing cost.

[0154] In one embodiment, after adding a required amount of a basic catalyst to water containing the core particles, alkoxysilane is added and heated to form a shell. When the water containing the core particles contains a required amount of a basic catalyst, it is not necessary to add a basic catalyst.

[0155] In the shell forming reaction, the time required for adding the alkoxysilane is not particularly limited as long as the colloidal silica of the present invention can be obtained.

[0156] The temperature of the reaction solution in the shell formation reaction is not particularly limited as long as the colloidal silica of the present invention can be obtained, but is preferably 70°C or more, more preferably 75°C or more. When the lower limit of the temperature of the mixed solution is within the above range, gelation is not easy during the reaction. In addition, the temperature of the mixed solution is preferably 95°C or less, more preferably 90°C or less. When the upper limit of the temperature of the mixed solution is within the above range, alkoxysilane is not easy to vaporize. The temperature of the reaction solution can be 70-95°C, 75-95°C, 70-90°C, 75-90°C.

[0157] The colloidal silica obtained in the shell forming step can be concentrated or diluted as needed, for example, the silica particle concentration can be set to 1 to 50% by mass. The concentration method is not particularly limited, and the concentration can be carried out by a conventionally known method. As such a concentration method, for example, a method of heating and concentrating at a temperature of about 65 to 100° C. can be cited.

[0158] In addition, when an organic solvent is used as a medium, the colloidal silica obtained in the shell formation process contains an organic solvent such as alcohol. Therefore, the organic solvent can also be distilled from the colloidal silica to the outside of the system. There is no particular limitation on the method for distilling the organic solvent to the outside of the system. For example, a method can be cited in which pure water is added dropwise while heating the colloidal silica to keep the capacity constant, thereby replacing the dispersion medium with pure water. In addition, as other methods, there can be cited: a method in which the colloidal silica is precipitated and separated, or separated from the solvent by centrifugation, and then dispersed in water; a method in which the organic solvent is removed by ultrafiltration while adding pure water to replace the solvent with water, etc.

[0159] Example

[0160] Hereinafter, although embodiment of the present invention is specifically described with reference to Examples etc., the present invention is not limited thereto.

[0161] Example 1

[0162] Manufacturing of core particles

[0163] (Process 1)

[0164] 7500 g of pure water as a solvent was placed in a flask, and 0.7737 g of 3-ethoxypropylamine as a basic catalyst was added to prepare a mixed solution. The pH of the mixed solution was 10.7. Since the 0.7737 g of 3-ethoxypropylamine was used for the synthesis of the core particles, it was not included in the amount of the basic catalyst used for the shell formation.

[0165] (Process 2)

[0166] After the mixed solution was heated to an internal temperature of 85° C., the temperature was adjusted so as not to fluctuate, and 2740 g of tetramethyl orthosilicate (TMOS) was injected into the mixed solution at a constant rate over 60 minutes. After the injection, the mixture was stirred for 60 minutes to prepare a mixed solution.

[0167] (Process 3)

[0168] 10.0 g of 3-ethoxypropylamine (3-EOPA) was added to the mixed solution to prepare colloidal silica (10250.8 g of dispersion containing core particles). The silica concentration of the colloidal silica was 10.5% by mass, and the secondary particle size of the silica particles in the colloidal silica was 36 nm.

[0169] Shell formation

[0170] (Process 4)

[0171] In a flask, 5882 g of pure water as a solvent and 2604 g of the dispersion containing core particles prepared in step 3 (containing 2.540 g (0.02462 mol) of 3-EOPA added in step 3) were added and mixed to prepare a mixed solution. In this step, 3-ethoxypropylamine as a basic catalyst was not added.

[0172] (Process 5)

[0173] After heating the mixed solution prepared in step 4 to 80°C, 1872.3 g (12.3000 mol) of tetramethyl orthosilicate and 16.3 g (0.0909 mol) of 3-aminopropyltrimethoxysilane (3-APTMS) were injected at a constant rate over 180 minutes while adjusting the temperature so that the liquid temperature did not change. After the injection, the liquid temperature was maintained at 80°C for 15 minutes to form a shell to obtain a colloidal silica dispersion containing core-shell silica particles. The total amount of alkoxysilane added in the shell formation reaction was 503 times the amount of the alkaline catalyst in terms of molar ratio (= (12.3000 + 0.0909) / 0.02462).

[0174] Concentration, water replacement

[0175] (Process 6)

[0176] 900 g of the colloidal silica dispersion obtained in step 5 was collected as the mother liquid amount and 900 g as the feed amount, and the colloidal silica dispersion was fed while maintaining the volume at a constant level under normal pressure, and heated and concentrated until the silica concentration reached about 20% by mass. Next, in order to remove methanol from the system by distillation, 670 mL of pure water was added dropwise while maintaining the volume at a constant level to replace the dispersion medium, thereby preparing water-dispersed colloidal silica.

[0177] The obtained colloidal silica was observed by the SEM image analysis method described later. As a result, there were few fine particles ( Figure 1 ).

[0178] Example 2

[0179] Water-dispersed colloidal silica was prepared in the same manner as in Example 1 except that 2.536 g of 3-ethoxypropylamine was added as a basic catalyst in step 4 of Example 1. The total amount of alkoxysilane added in the shell forming reaction was 252 times the amount of the basic catalyst in terms of molar ratio.

[0180] Comparative Example 1

[0181] This example is equivalent to Example 1 described in Japanese Patent Application Laid-Open No. 2016-008157.

[0182] A water-dispersed colloidal silica was prepared in the same manner as in Example 1 except that 10.144 g of 3-ethoxypropylamine was added as a basic catalyst in step 4 of Example 1. The pH of the mixed solution obtained in step 4 was 10. The total amount of alkoxysilane added in the shell formation reaction was 101 times the amount of the basic catalyst in terms of molar ratio.

[0183] The obtained colloidal silica ( Figure 2 ), the results show that the colloidal silica of Comparative Example 1 (average ellipse minor axis 27nm) and the colloidal silica of Example 1 (average ellipse minor axis 27nm) ( Figure 1 ), there are obviously more tiny particles with a particle size of less than 20nm (27nm×0.75=20nm).

[0184] Example 3

[0185] Water-dispersed colloidal silica was prepared in the same manner as in Example 1 except that the following steps 4 and 5 were performed instead of steps 4 and 5 of Example 1. The total amount of alkoxysilane added in the shell forming reaction was 1007 times the amount of the basic catalyst in terms of molar ratio.

[0186] (Process 4)

[0187] In a flask, 6061 g of pure water, 930 g of methanol, 581 g of the dispersion containing the core particles prepared in step 3 of Example 1, and 0.789 g of 3-ethoxypropylamine (3-EOPA) were added and mixed to prepare a mixed solution.

[0188] (Process 5)

[0189] After the mixed solution prepared in step 4 was heated to 80°C, a mixed solution of 2000 g of tetramethyl orthosilicate, 800 g of methanol, and 17.4 g of 3-aminopropyltrimethoxysilane was injected at a constant rate over 360 minutes while adjusting the temperature so that the liquid temperature did not fluctuate. After the injection, the liquid temperature was maintained at 80°C for 15 minutes to obtain a colloidal silica dispersion containing core-shell silica particles.

[0190] Example 4

[0191] Water-dispersed colloidal silica was prepared in the same manner as in Example 3 except that the amount of 3-ethoxypropylamine used was changed to 2.144 g in step 4 of Example 3. The total amount of alkoxysilane added in the shell forming reaction was 504 times the amount of the basic catalyst in terms of molar ratio.

[0192] Comparative Example 2

[0193] Water-dispersed colloidal silica was prepared in the same manner as in Example 3 except that the amount of 3-ethoxypropylamine used as the basic catalyst was changed to 8.761 g in step 4 of Example 3. The total amount of alkoxysilane added in the shell forming reaction was 146 times the amount of the basic catalyst in terms of molar ratio.

[0194] Comparative Example 3

[0195] This example is equivalent to Example 2 described in Japanese Patent Application Publication No. 2018-048042.

[0196] At room temperature and pressure, 1316 g of tetramethyl orthosilicate, 13.333 g of 3-aminopropyltriethoxysilane and 352 g of methanol were mixed to prepare a composition.

[0197] 805 g of aqueous ammonia solution (28% by mass), 1298 g of water and 10417 g of methanol were added to the reaction vessel, and the above composition was slowly added over 30 minutes while stirring at 200 rpm at 35°C to prepare a colloidal silica dispersion. The obtained colloidal silica (colloidal silica after the shell formation reaction) was observed by the SEM image analysis method described later, and it was found that there were a lot of tiny particles ( Figure 3 ).

[0198] Next, the same method as step 6 of Example 1 was followed except that the amount of mother liquor was set to 800 g, the amount of feed was set to 1800 g, and the amount of pure water used to replace methanol was set to 1200 ml to prepare water-dispersed colloidal silica. The total amount of alkoxysilane added in the particle synthesis reaction was 0.658 times the amount of the alkaline catalyst in terms of molar ratio. The obtained water-dispersed colloidal silica was observed by SEM. As a result, the microparticles ( Figure 3 ) is reduced by the intake of silica particles ( Figure 4 ).

[0199] The conditions of the shell formation reaction of Examples 1 to 4 and Comparative Examples 1 to 2 and the physical properties of the particles after the shell formation reaction are shown in Table 1, and the corresponding contents of Comparative Example 3 are shown in Table 2. The physical properties of the water-dispersed colloidal silica prepared in the above Examples and Comparative Examples were measured by the methods described below, and the results are shown in Table 3.

[0200] [Table 1]

[0201]

[0202] [Table 2]

[0203]

[0204] [Table 3]

[0205] Particle properties unit Example 1 Example 2 Comparative Example 1 Example 3 Example 4 Comparative Example 2 Comparative Example 3 BET surface area <![CDATA[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 Association ratio - 2.4 2.3 2.4 1.9 1.9 1.9 1.6 Mean minor axis of the ellipse nm 27 27 27 47 48 45 38 75% diameter of the minor axis of the mean ellipse nm 20 20 20 35 36 34 29 The proportion of small particles ％ 0.4 1.8 6.7 1.4 1.6 10.9 1.1 Aspect 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 Silanol group density <![CDATA[per / 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

[0206] Zeta Potential of Colloidal Silica

[0207] In order to confirm that the silica particles contained amino groups, the zeta potential of the silica particles was measured. The results are shown in Tables 4 and Figure 5 . The Zeta potential of Comparative Example 1 of the present application is equivalent to that of Example 1 of Patent Document 1 (Japanese Patent Publication No. 2016-008157). The Zeta potential of Examples 1 to 4 of the present application at pH 2 is about 25 mV, which is equivalent to Comparative Example 1 of the present application. On the other hand, in Comparative Example 1 described in Japanese Patent Publication No. 2016-008157, which contains amino groups only on the surface of the particles, the Zeta potential at pH 2 is as high as about 45 mV. Based on these results, it can be confirmed that the silica particles in the colloidal silica of Examples 1 to 4 of the present application have amino groups and silanol groups mixed on the surface.

[0208] [Table 4]

[0209] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Zeta potential at pH 2 ﹢25mV ﹢25mV ﹢21mV ﹢27mV ﹢26mV Zeta potential at pH 3 ﹢26mV ﹢26mV ﹢31mV ﹢31mV ﹢27mV Zeta potential at pH 4 ﹢24mV ﹢21mV ﹢25mV ﹢25mV ﹢25mV Zeta potential at pH 5 ﹢17mV ﹢16mV ﹢12mV ﹢15mV ﹢14mV Zeta potential at pH 7 -23mV -27mV -29mV -26mV -19mV Zeta potential at pH 9 -46mV -44mV -51mV -49mV -60mV

[0210] Methods for determining physical properties

[0211] The physical property values ​​and the like in Table 3 were determined as follows.

[0212] 1. BET specific surface area and average primary particle size

[0213] After drying the colloidal silica on a hot plate, heat treatment was performed at 800°C for 1 hour to prepare a sample for measurement. The BET specific surface area (m 2 / g).

[0214] The true density of silica was set to 2.2, and the measured value of the BET specific surface area was converted into 2727 / BET specific surface area (m 2 The value of 100 μg / g) was taken as the average primary particle size (nm) of the silica particles in the colloidal silica.

[0215] 2. Average secondary particle size

[0216] As a measurement sample, colloidal silica was added to a 0.3 wt% citric acid aqueous solution and homogenized. Using this measurement sample, the secondary particle size of silica particles in the colloidal silica was measured by a dynamic light scattering method (ELSZ-2000S manufactured by Otsuka Electronics Co., Ltd.).

[0217] 3. Association ratio

[0218] The association ratio of the silica particles in the colloidal silica is obtained by calculating the average secondary particle size / average primary particle size of the silica particles in the colloidal silica.

[0219] 4. Analysis of SEM Images

[0220] 4-1. Preparation of samples for SEM observation

[0221] A liquid containing 7.5 mL of methanol, 1.5 mL of water, 1 mL of 0.01 M HCl, 5 μL of colloidal silica with a silica concentration of 20%, or 10 μL of a reaction solution with a silica concentration of 7 to 12% after the shell formation reaction was added dropwise to the sample stage and dried. When preparing the above-mentioned mixed solution, the amount of the dispersion containing the silica particles can be increased or decreased so that the silica concentration after dilution and mixing becomes 0.007 to 0.012% by mass. The sample stage is assembled to a scanning electron microscope (SEM) and the SEM image is taken. The white scale shown at the bottom of the SEM image represents a length of 100 nm.

[0222] 4-2. Mean ellipse minor axis

[0223] The image of the silica particles taken by the scanning electron microscope was fitted with an ellipse using image analysis software ("Win Roof 2015" manufactured by Mitani Shoji Co., Ltd.), and the major and minor axes of the ellipse were measured. The minor axes of the ellipses of all the particles in the SEM image were averaged to calculate the average minor axis of the ellipse (nm).

[0224] 4-3. Ratio of the number of tiny particles

[0225] The particles with a particle size of 75% or less of the minor axis of the average ellipse obtained by ellipse fitting in 4-2 above were defined as microparticles, and the number of all particles and microparticles in the SEM image were counted. The ratio of the number of microparticles to the number of all particles ((number of microparticles / total number of particles)×100(%)) was calculated.

[0226] 4-4. Aspect ratio

[0227] The ellipse major-minor axis ratio (ellipse major axis / ellipse minor axis) of each particle was calculated based on the ellipse major axis and ellipse minor axis obtained by ellipse fitting in 4-2 above, and the average value thereof was taken as the aspect ratio.

[0228] 5. Surface roughness

[0229] The surface roughness is calculated by dividing the BET specific surface area (Bl) by the specific surface area (S1) calculated based on the average ellipse minor axis (B1 / S1). It should be noted that the specific surface area (S1) is obtained by setting the true density of silica to 2.2 and converting the value of 2727 / average ellipse minor axis (nm).

[0230] 6.Silanol group density

[0231] The silanol group density of silica particles is obtained by the Sears method. The Sears method is implemented with reference to the record of GW Sears, Jr., "Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide", Analytical Chemistry, 28 (12), 1981 (1956). In the measurement, a 1% by mass silica dispersion is used and titrated with a 0.1 mol / L sodium hydroxide aqueous solution, and the silanol group density is calculated based on the following formula.

[0232] ρ=(a×f×6022)÷(c×S)

[0233] In the above formula, ρ represents the silanol group density (number / nm 2 ), a represents the amount of 0.1 mol / L sodium hydroxide aqueous solution with a pH of 4 to 9 (mL), f represents the factor of 0.1 mol / L sodium hydroxide aqueous solution, c represents the mass of silica particles (g), S represents the BET specific surface area (m 2 / g).

[0234] 7. True density

[0235] The true density was measured by a method in which colloidal silica was dried on a hot plate at 150° C., heat-treated at 300° C. for 1 hour, and then measured by a liquid phase replacement method using ethanol.

[0236] 8. Zeta potential

[0237] Colloidal silica was diluted with a 10 mM sodium chloride aqueous solution to a silica concentration of 1 mass %, and the zeta potential was measured using ELS-Z manufactured by Otsuka Electronics Co., Ltd.

Claims

1. A colloidal silicon dioxide, characterized in that: It is colloidal silica with silyl groups having amino groups introduced into the particles. The ratio of the number of microparticles contained in the colloidal silica to the number of all particles is less than 5%. The silanol group density on the surface of the colloidal silica particles is 4.0 / nm 2 the following.

2. The colloidal silicon dioxide according to claim 1, characterized in that: The true density is above 1.

90.

3. A method for producing colloidal silicon dioxide, characterized in that: The colloidal silica is a colloidal silica in which a silyl group having an amino group is introduced into the interior of the particles. The manufacturing method includes a step of reacting an alkoxysilane having an amino group and an alkoxysilane not having an amino group in a core particle in the presence of a basic catalyst to form a shell, wherein the total amount of the alkoxysilane added during the shell formation reaction is 200 times or more in molar ratio relative to the amount of the basic catalyst present in the reaction system during the shell formation reaction.

Images