Method for producing modified colloidal silica, modified colloidal silica, and colloidal silica modifying agent

Abstract

This invention provides a novel method for producing colloidal silica that can reliably and uniformly perform modification using a modifying agent. [Solution] The method includes the steps of: first dendriming a colloidal silica modifier, which has a higher hydrolysis reaction activity than the silica matrix raw material, with tetramethoxysilane; and adding an activated silicic acid solution prepared from a mixture of the silica matrix raw material and the dendrimerized colloidal silica modifier to colloidal silica to form a coating layer on the surface of the silica fine particles.

Description

Technical Field

[0001] The present invention relates to a method for producing novel colloidal silica, modified colloidal silica, and a colloidal silica modifier.

Background Art

[0002] Colloidal silica is one in which silica fine particles are uniformly dispersed in a dispersion medium (e.g., water). Colloidal silica is used, for example, as a material for a polishing agent for mirror polishing of a silicon wafer, and also as a material for a polishing agent for CMP (chemical mechanical polishing) in a wiring manufacturing process of an integrated circuit in a semiconductor manufacturing process. Depending on the characteristics required for its applications, research on colloidal silica having various surface characteristics has been advanced. As a result, aluminum-modified colloidal silica, titanium-modified colloidal silica, silane coupling agent-modified colloidal silica, etc. have become known. Among the modified colloidal silicas, for example, aluminum-modified silica becomes a colloidal silica that is stable in a wider pH range compared to colloidal silica.

[0003] In addition, there is aluminum-modified colloidal silica in which aluminum anions are incorporated into a silica skeleton by modifying water glass method colloidal silica using sodium aluminate (Patent Document 1). However, the aluminum-modified colloidal silica of Patent Document 1 contains sodium ions in the raw material sodium aluminate and water glass method colloidal silica, and there is a problem in its application to uses in a semiconductor manufacturing process where the mixing of alkali metals is avoided.

[0004] There is a method for producing aluminum-modified colloidal silica and its manufacturing method (Patent Document 2) that involves adding high-purity colloidal silica, free from metal impurities, obtained by the alkoxide method, i.e., the Stoeber method (see Non-Patent Document 1), which involves hydrolysis and condensation of alkoxysilane and water, to an aqueous aluminate solution prepared by dissolving metallic aluminum powder or an aluminum compound in an aqueous tetramethylammonium hydroxide (TMAH) solution. According to Patent Document 2, it is possible to produce high-purity aluminum-modified colloidal silica with suppressed contamination of metal impurities such as sodium ions by using aluminate TMAH salt. However, when sodium aluminate is used in the aqueous aluminate solution, contamination of sodium ions is unavoidable, and there are limitations to the removal of sodium ions by cation exchange resin treatment after the production of aluminum-modified colloidal silica. Furthermore, even when sodium-free aluminate TMAH salt is used as the aqueous aluminate solution, purification by distillation is not possible, limiting the ability to achieve high purity.

[0005] As described above, while aluminum-modified colloidal silica can be purified to a high degree by distillation, there is no known modification method for obtaining aluminum-modified colloidal silica using aluminum alkoxide, which has very high hydrolysis reaction activity.

[0006] Regarding titanium-modified colloidal silica, there is a titanium-modified colloidal silica prepared using a method similar to the Stöber method, by adding a small amount of titanium isopropoxide (TIPD) to tetramethyl orthosilicate (also known as tetramethyl orthosilicate, TMOS) (Patent Document 3). Patent Document 3 shows that it exhibits zeta potential behavior similar to aluminum-modified colloidal silica. However, the hydrolysis reaction activity of TMOS and TIPD is significantly different, and a portion of TIPD is further... The process of methoxylation, which involves highly hydrolytic reaction activity, has not been taken into consideration, and in practice, there are concerns that a stable quality product may not be obtained.

[0007] As described above, no technology is known that takes into account the differences in hydrolysis reaction activity between TIPD and the silica matrix, such as TMOS or TEOS, for titanium-modified colloidal silica.

[0008] Regarding metal alkoxides, complex alkoxides that can be purified by distillation are known. For example, M[Al(OiPr)4] n Examples include (when M is Fe; n=3, when M is Mn, Co, Ni, Cu; n=2) (Non-Patent Document 2), Mg[Al(OiPr)4]2 (Patent Document 4), and Ba[Ti(OiPr)4]2 (Patent Document 5). While these complex alkoxides are known to be applied to the preparation of ceramic powders, their application to modified colloidal silica has not been investigated.

[0009] Regarding silane coupling agents, there is a method (Patent Document 6) in which a silane coupling agent is mixed with a silica matrix raw material such as TMOS or tetraethyl orthosilicate (TEOS), and alkyl groups such as phenyl groups, methyl groups, and 3-aminopropyl groups are introduced into the silica skeleton by a method similar to the Stöber process to control the true specific gravity of silica particles. However, this method is not intended to obtain modified colloidal silica.

[0010] As described above, regarding modification using silane coupling agents such as 3-aminopropyltrimethoxysilane (3APTMS), no techniques are known that take into account the differences in hydrolysis reaction activity between these agents and the silica matrix, such as TMOS and TEOS.

[0011] Regarding 3APTMS, one of the silane coupling agents, Patent Document 7 discloses a method of directly adding 3APTMS to colloidal silica to introduce amino groups to the surface of colloidal silica particles. However, paragraph

[0016] of Patent Document 8 states that this method has a problem with shelf life. It is not guaranteed that the aminosilane is bound to the surface of the colloidal silica particles, and there are concerns that it may be attached by weak forces such as van der Waals forces or electrostatic forces. Furthermore, paragraph

[0009] of Patent Document 9 points out that when a small amount of 3APTMS is mixed with TMOS and particle growth is carried out in a high-temperature aqueous solvent as disclosed in Patent Document 10, the problem of fine particles being generated is pointed out, and it is disclosed that this can be improved by limiting the amount of amine catalyst added. This problem is also thought to be influenced by the significant difference in hydrolysis reaction activity between TMOS and 3APTMS.

[0012] Silane coupling agents like 3APTMS are primarily intended for surface treatment of powders such as silica, employing mechanochemical methods to chemically bond to the powder surface and enhance affinity with organic matrices such as resins and rubbers. However, mechanochemical methods cannot be applied to the modification of colloidal silica particle surfaces; the only option was to simply add the agent and let the process unfold. Simple addition could lead to reactions between silane coupling agents, potentially resulting in substances like silsesquioxane. Therefore, it remains unclear whether modification has occurred while the silane coupling agent is firmly bonded to the silica skeleton of the colloidal silica particles, or whether modification has occurred at all.

[0013] Furthermore, in the method of mixing the silane coupling agent with TMOS and adding it at high temperature, since it is added as a monomer, even if the temperature is lowered somewhat, the vapor pressure does not become zero, raising concerns about gas-phase reactions due to volatilization. In fact, in the method of reacting in an aqueous solvent disclosed in Patent Document 10, the reaction is carried out at a relatively high temperature, so there are no problems with ethyl silicate or silicate oligomers, which have high boiling points, but when using TMOS, which is inexpensive but has a low boiling point, there are concerns about decomposition in the gas phase due to volatilization. There is a concern. This is because alkyl silicates are immediately hydrolyzed and disappear under acidic conditions, whereas they do not disappear immediately under basic conditions. This phenomenon is described by the inventors in Non-Patent Documents 3 and 4) Chapter 1, Section 1.1, on page 8, which summarize past literature. A similar description is also found on page 29 of Non-Patent Document 5. Specifically, in the case of ammonia catalysts, it is stated that in the case of TMOS, half of the TMOS remains even when the entire gel has formed, which is a well-known phenomenon among sol-gel researchers. In the case of TEOS, it is stated that the entire amount disappears before the entire gel has formed, indicating that TMOS is significantly more likely to leave unreacted material.

[0014] Because unreacted TMOS remains and volatilizes at high temperatures, it is impossible to rule out the possibility that small amounts of particles generated in an uncontrolled state due to gas-phase decomposition may exist. If a low-boiling point amine with vapor pressure at the reaction temperature is used as the basic catalyst, the basic catalyst will also volatilize, further promoting the gas-phase reaction.

[0015] In addition, when the reaction is carried out at a consistently high pH, ​​there is a concern about gas-phase reactions, as well as the problem of residual "unreacted material." That is, because the reaction is carried out under consistently high pH basic conditions, "unreacted material" that has not fully converted into silica remains, which is thought to be related to the residual TMOS in basic conditions as described above. Patent document 11 states that methoxy groups remain in colloidal silica particles prepared by the method described in patent document 10. Here, the coefficient obtained by dividing the methoxy group content by the primary particle diameter is used as the main parameter. A simple comparison using the methoxy group content before dividing by the primary particle diameter yields the following results. Specifically, depending on the basicity strength of the amine, the amount of residual methoxy groups decreased in the following order: 13,130 ppm (TMAH, Comparative Example 2) > 9,338 ppm to 10,943 ppm (3-EOPA, Examples 1 and 2) > 6,544 ppm (TEA, Example 7), and 6,510 ppm (DPA, Example 6). This indicates that TMAH, which is highly basic and does not experience a concentration decrease due to volatilization, is the most likely to retain methoxy groups, meaning that a large amount of "unreacted material" remains, which is consistent with the above description.

[0016] On the other hand, in Patent Document 11, it was confirmed that in Comparative Example 1, which followed the method of Patent Document 12, the amount of residual methoxy groups was small. However, under the conditions described, an activated silicic acid solution with a silica concentration of 9 wt% was used, and more than 40 wt% methanol was included, so despite the conditions being such that methoxy groups tend to remain, the amount was as low as 6,660 ppm. This also demonstrates that methoxy groups tend to remain when hydrolysis is performed only on the basic side.

[0017] To address "unreacted substances," volatile amines like ammonia can be removed by volatilization, while other substances can be treated by neutralization, ion exchange, or other methods to lower the pH. As described later, when aluminum-modified colloidal silica is prepared using colloidal silica prepared by the method of Patent Document 10 as a raw material, a product with extremely poor filterability is obtained. However, this problem was resolved by first lowering the pH by ion exchange. This is thought to be because the "unreacted substances" disappeared due to the decrease in pH. Therefore, it is thought that when this type of colloidal silica is used under acidic conditions such as cation sols, problems due to unreacted substances will not occur.

[0018] The issue of "unreacted material" also applies to the Stöber process, but Non-Patent Document 1 describes the preparation of micron-sized particles, which can be separated by filtration, thus avoiding the problem. On the other hand, in the case of colloidal silica that cannot be separated by filtration, this problem can be avoided by removing volatile ammonia and lowering the pH during the water displacement operation from methanol to water solvent in order to change from a methanol dispersion to an aqueous dispersion. The existence of "unreacted material" is not mentioned in Patent Document 10, and it appears that those involved with colloidal silica are not aware of its existence. There's a possibility they're not there. [Prior art documents] [Patent Documents]

[0019] [Patent Document 1] U.S. Patent No. 2892797 [Patent Document 2] Patent No. 5221517 specification [Patent Document 3] Patent No. 4819322 specification [Patent Document 4] U.S. Patent No. 3761500 [Patent Document 5] Patent No. 3526886 specification [Patent Document 6] Special Publication No. 05-004325 [Patent Document 7] Patent No. 4577755 specification [Patent Document 8] International Publication No. 2015 / 200660

Patent Document 9

Patent Document 10

Patent Document 11

Patent Document 12

Non-Patent Document

[0020]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0021] In the CMP (Chemical Mechanical Polishing) process in the wiring manufacturing process of integrated circuits in the semiconductor manufacturing process, colloidal silica having various surface characteristics is required as a polishing agent material. From the perspective of sol-gel technology engineers, the present invention aims to propose a novel method for manufacturing colloidal silica, modified colloidal silica, and a colloidal silica modifier that can avoid the incorporation of sodium ions and can surely and uniformly perform the modification with a modifier.

[0022] Specifically, the objective is to provide modified colloidal silica in which the modifying agent is reliably incorporated into the silica matrix by suppressing the hydrolysis reaction activity of aluminum isopropoxide (AIPD), which has extremely strong hydrolysis reaction activity, and a silane coupling agent represented by the general formula RSi(OR)3, by dendrimerizing them, thereby increasing reaction selectivity. [Means for solving the problem]

[0023] The present invention provides a method for producing modified colloidal silica, comprising the steps of: first dendrimerizing a colloidal silica modifying agent, which has a higher hydrolysis reaction activity than the silica matrix raw material, with tetramethoxysilane; and adding an activated silicic acid solution containing the silica matrix raw material and the dendrimerized colloidal silica modifying agent to colloidal silica to form a coating layer on the surface of silica microparticles by hydrolysis. Silica matrix raw materials include, for example, methyl orthosilicate and ethyl orthosilicate. Lower alkyl silicates such as propyl orthosilicate and butyl orthosilicate, or mixed silicates or oligomers thereof, are preferably used. However, in the pretreatment step of metal alkoxides, if methyl orthosilicate is used, for example, an alcohol exchange reaction may occur with aluminum alkoxide, potentially generating aluminum methoxide which is insoluble in organic solvents. Therefore, alkyl silicates with 2 to 4 carbon atoms in the alkyl group are particularly preferred. The colloidal silica modifier may be any one alkoxide selected from aluminum alkoxide, titanium alkoxide, or distillable complex alkoxide, or it may be a silane coupling agent having the structural formula RSi(OMe)3 (wherein R is at least one group selected from the group consisting of an alkyl group which may have substituents, a vinyl group, an epoxy group, a styryl group, a methacrylic group, an acrylic group, an amino group, an isocyanurate group, a ureido group, a mercapto group, an isocyanate group, an acid anhydride group, a carbonyl group, an aryl group, an ether group, and an unsaturated aliphatic residue).

[0024] Examples of metal alkoxides include aluminum propoxide, aluminum isobutoxide, aluminum n-butoxide, aluminum sec-butoxide, or mixed alkoxides thereof, TIPD, titanium n-butoxide, titanium isobutoxide, titanium tertiary butoxide, zirconium isopropoxide, zirconium butoxide, and as complex alkoxides, examples of metal alkoxides soluble in organic solvents such as Co[Al(Oi-Pr)4]2 and Mg[Al(Oi-Pr)4]2.

[0025] Examples of silane coupling agents include 3APTMS. Numerous silane coupling agents represented by RSi(OMe)3 are commercially available. For example, methyltrimethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, p-styryltrimethoxysilane, N-phenyl-3-aminotrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-[methoxy(polyethyleneoxy) 9-12 Examples include propyltrimethoxysilane and (3-trimethoxysilylpropyl) succinic anhydride.

[0026] The modified colloidal silica of the present invention is aluminum-modified colloidal silica, comprising an aluminum-modified coating layer on the surface of the silica fine particles of colloidal silica, wherein the sodium ion content of the coating layer is 1 wt ppm or less.

[0027] Furthermore, the colloidal silica modifier of the present invention is dendrimerized with tetramethoxysilane. [Effects of the Invention]

[0028] According to the present invention, by dendrimerizing the hydrolysis reaction activity of metal alkoxides and silane coupling agents to suppress the reaction and enhance reaction selectivity, it is possible to propose a novel modified colloidal silica, a method for producing the same, and a colloidal silica modifying agent in which the modifying agent is reliably incorporated into the silica matrix. Furthermore, it is possible to propose a novel modified colloidal silica, a method for producing the same, and a colloidal silica modifying agent that can obtain a stable modification effect. [Brief explanation of the drawing]

[0029] [Figure 1] This graph shows the change in moisture content over time during the dendrimerization of Al-TEOS and 3APTMS. [Figure 2] This is a schematic diagram of a gas-phase water hydrolysis apparatus. [Figure 3] This is a schematic diagram of an industrial gas-phase water hydrolysis apparatus. [Figure 4] This is a schematic diagram of an experimental cooling feed tube. [Figure 5] This is a schematic diagram of the cooling feed tube of the actual device. [Figure 6] This photograph illustrates the clarity of the activated silica solution. [Figure 7] This graph shows the measurement results of the zeta potential of aluminum-modified colloidal silica. [Figure 8] This is an FE-SEM image of aluminum-modified colloidal silica. [Figure 9] This is a photograph showing the turbidity of the activated silica solution in the comparative example. [Figure 10] This photograph shows the blockage at the tip of the nozzle used to inject water-containing nitrogen gas. [Figure 11] This graph shows the time-dependent changes in moisture content during the TEOS conversion of TIPD. [Figure 12] This chart shows the IR spectrum of Ti-TEOS. [Figure 13] This graph shows the change in moisture content over time during the dendrimerization of Ti-TEOS. [Figure 14]This graph shows the measurement results of the zeta potential of titanium-modified colloidal silica. [Figure 15] This graph shows the zeta potential measurement results for Example 3 and Comparative Example 2. [Figure 16] This is a scattering intensity distribution diagram when measuring the secondary particle size of titanium-modified colloidal silica. [Figure 17] This is an FE-SEM image of titanium-modified colloidal silica. [Modes for carrying out the invention]

[0030] The following describes in more detail embodiments of the method for producing modified colloidal silica, modified colloidal silica, and colloidal silica modifying agent of the present invention.

[0031] Regarding cases where the colloidal silica modifier is an aluminum alkoxide, AIPD is described in Japanese Patent No. 4303049. However, Japanese Patent No. 4303049 is a technology relating to granular synthetic silica as a raw material for quartz glass, and no technology relating to modified colloidal silica is known. The present invention provides a novel method for producing modified colloidal silica using AIPD.

[0032] Furthermore, the present invention relates to cases where the colloidal silica modifying agent is a titanium alkoxide or a silane coupling agent, and provides a novel method for producing modified colloidal silica that can more reliably and uniformly modify colloidal silica using TIPD or a silane coupling agent.

[0033] The present invention provides a method for producing modified colloidal silica, in which the hydrolysis reaction activity of a colloidal silica modifying agent, which has high hydrolysis reaction activity, can be suppressed by dendrimerizing it with TMOS beforehand.

[0034] Furthermore, the present invention aims to provide novel aluminum-modified colloidal silica, titanium-modified colloidal silica with more uniform and reliable incorporation into the silica framework, and silane coupling agent-modified silica, all obtained by the manufacturing method of the present invention.

[0035] The present invention provides a method for producing modified colloidal silica, comprising the steps of: first dendrimerizing a colloidal silica modifying agent, which has a higher hydrolysis reaction activity than the silica matrix raw material, with tetramethoxysilane; and adding an activated silicic acid solution containing the silica matrix raw material and the dendrimerized colloidal silica modifying agent to colloidal silica to form a coating layer on the surface of silica microparticles by hydrolysis.

[0036] As a specific example of modified colloidal silica, in the following embodiment, aluminum-modified colloidal silica This document describes colloidal silica, titanium-modified colloidal silica, zirconium-modified colloidal silica, composite metal-modified colloidal silica, and silane coupling agent-modified colloidal silica.

[0037] [Colloidal silica modifier] Examples of aluminum modifiers for aluminum-modified colloidal silica include AIPD and Al-TEOS. Examples of metal alkoxide modifiers for titanium-modified colloidal silica include TIPD, titanium-n-butoxide, titanium-isobutoxide, titanium-tertiary butoxide, and Ti-TEOS. Examples of zirconium modifying agents for zirconium-modified colloidal silica include zirconium isopropoxide, zirconium n-butoxide, and zirconium isobutoxide. Examples of composite metal modifiers for composite metal-modified colloidal silica include composite alkoxides such as Co[Al(Oi-Pr)4]2 and Mg[Al(Oi-Pr)4]2.

[0038] Regarding silane coupling agents for silane-modified colloidal silica, some have higher hydrolysis activity than TMOS, and such silane coupling agents with higher hydrolysis activity than TMOS are applicable in the present invention. 3APTMS is an example. To confirm that a silane coupling agent has higher hydrolysis activity than TMOS, hydrolysis is performed by adding gas-phase water, and those that show a change in moisture content as shown in Figure 1 (described later) are targeted.

[0039] These exemplified colloidal silica modifiers exhibit higher hydrolysis reaction activity than TMOS, which is used as a silica matrix raw material. Therefore, in this invention, the colloidal silica modifier is pre-dendrimerized with tetramethoxysilane to suppress its hydrolysis reaction activity.

[0040] [Preliminary processing] If the aluminum modifier is Al-TEOS, it can be used directly for the dendrimerization described later. If the aluminum modifier is AIPD, it is preferable to perform a preliminary treatment before the dendrimerization described later, in which the AIPD is chemically reacted to form tris(triethoxysilyloxy)aluminum (Al-TEOS).

[0041] This preliminary treatment can be carried out according to the procedure described by the present inventor in Japanese Patent No. 4303049. In a specific example, the preliminary treatment can be performed by uniformly mixing AIPD as an aluminum alkoxide and ethyl orthosilicate as an alkyl silicate in a solvent capable of dissolving both, introducing 2 to 4 equivalent amounts of water relative to AIPD over 5 to 20 hours until the ethyl orthosilicate disappears to induce a hydrolysis reaction, and then removing the solvent. In such a preliminary treatment, as described in paragraph

[0012] of Japanese Patent No. 4303049, TMOS cannot be used as the alkyl silicate because transesterification will occur.

[0042] The preliminary hydrolysis reaction is carried out using a hydrophilic solvent such as isopropyl alcohol (IPA). However, methanol cannot be used for the reasons mentioned above. Other hydrophilic solvents such as alcohols, ketones, dioxanes, and aprotic hydrophilic solvents like THF may also be used. IPA is preferred.

[0043] The hydrophilic solvent must be dehydrated to a moisture content of 300 ppm or less, preferably 200 ppm or less. The amount of hydrophilic solvent added is not particularly limited, as long as it can absorb the moisture added in the gas phase and perform its function as a hydrolysis solvent. Generally, it should be the same amount as or less than the amount of TMOS. Preferably, the amount should be at least twice the amount.

[0044] In the aforementioned Patent No. 4303049 specification, a gas chromatograph was used to monitor the progress of triethoxysilyloxylation, but there were problems such as the residue of non-volatile substances in the column and the time required for measurement. Therefore, in the preliminary treatment, it is preferable to monitor the amount of water in the reaction solution with a Karl Fischer moisture meter rather than a gas chromatograph. During hydrolysis with gas-phase water addition, the water content remains at several hundred ppm, but when the hydrolytic active groups disappear, it rises to more than 1,000 ppm. The preparation of Al-TEOS is considered complete when this rapid increase in water content is confirmed.

[0045] Figure 2 shows an illustration of hydrolysis by adding gas-phase water. As shown in Figure 2, pressurized air or nitrogen gas is blown into pure water heated to 60°C to hydrate it, and the water is then transported in the gas phase. Diluting water with a solvent requires a large amount of solvent, and there is a risk that water molecules are clustered together by hydrogen bonding, so a gas-phase method that can transport water at the single-molecule level is desirable. For industrial implementation, it is conceivable to apply a gas-liquid contact operation (humidification operation) using a packed column as shown in Figure 3.

[0046] Next, regarding the case of a titanium modifier, if the titanium modifier is Ti-TEOS, it can be directly subjected to the dendrimerization described later. If the titanium modifier is TIPD, it is preferable to perform a preliminary treatment before the dendrimerization described later, in which the TIPD is chemically reacted to form tris(triethoxysilyloxy)titanium (Ti-TEOS).

[0047] Pre-treatment of TIPD can be carried out using the same procedure as for AIPD described above. However, TIPD differs from AIPD in that it is preferable to add a strong anhydride to the hydrolysis reaction solution. Examples of strong anhydrides include concentrated sulfuric acid and concentrated nitric acid. If a strong anhydride is not added, a white gel forms at the tip of the water-containing gas injection nozzle, causing blockage. This is thought to be because TIPD does not have the strong Lewis acidity found in AIPD. Therefore, the inventors considered it necessary to add a catalyst separately and attempted to add concentrated sulfuric acid that does not contain water. As a result, it has been confirmed that the problem of white solid adhesion and blockage at the tip of the water-containing gas injection nozzle has been resolved. The formation of the white gel is thought to be due to the reaction shown in the following equation not occurring properly. TIFF2026116086000002.tif51148 In other words, when concentrated sulfuric acid is not added, it is thought that the reaction that produces titanium hydroxide, which is insoluble in organic solvents, takes precedence.

[0048] Next, regarding the zirconium modifier and the Al-Co composite metal modifier, with regard to zirconium butoxide and Al-Co composite alkoxide, even with the addition of a strong anhydride, a white solid adheres to the tip of the water-gas injection nozzle, causing the nozzle to become clogged. This problem has not yet been resolved. However, by improving the contact method with water-containing gas, it is possible to perform pretreatment following the same procedure as for aluminum modifiers and titanium modifiers. It's promising.

[0049] For the aluminum and titanium modifiers that have been converted to TEOS through preliminary treatment, the resulting Al-TEOS and Ti-TEOS can be stably stored for a long period of time as intermediates by adding TEOS equivalent to twice the amount of remaining water, and then distilling off the solvent at atmospheric pressure and then under reduced pressure.

[0050] Furthermore, since the silane coupling agent has no problems with miscibility with TMOS and its hydrolysis reaction activity is significantly lower than that of metal alkoxides, there is no need to perform pretreatment to convert it to TEOS, and the dendrimerization described below can be carried out directly.

[0051] [Dendrimerization] The aluminum modifier is prepared by dendrimerization at room temperature using a gas-phase water addition hydrolysis method with methanol as the solvent, using Al-TEOS prepared by pretreatment or Al-TEOS as an aluminum modifier and an excess amount of TMOS. Dendrimerization can suppress the hydrolysis reaction activity of the aluminum modifier. TIFF2026116086000003.tif87153

[0052] Here, a dendrimer is a dendritic polymer that has a structure in which it branches regularly from a central point. The amount of TMOS to be added during dendrimerization should be determined by considering the aluminum concentration in the aluminum-modified coating layer formed on the surface of colloidal silica. Specifically, for aluminum, 9 moles or more should be added per mole of Al-TEOS, depending on the number of active groups bonded. More preferably, 27 moles or more. On the other hand, Al-TEOS also has a hydrolysis catalytic function due to Lewis acidity, and if the amount added is too small, hydrolysis-dendrimerization will not proceed. Adding acid separately can also be considered, but if the amount is too small, the modification effect will decrease, so the amount of TMOS should be 200 moles or less, more preferably 150 moles or less, per mole of Al-TEOS.

[0053] The hydrolysis process during dendrimerization using gas-phase water addition was monitored with a Karl Fischer moisture meter, and the process continued until a rapid increase in water concentration was observed from the steady state. An example of the change in water content over time during hydrolysis is shown in Figure 1. In the dendrimerization experiment shown in Figure 1, a rapid increase in water concentration was observed after approximately 24 hours of gas-phase water addition hydrolysis. This indicates that the group with high hydrolysis activity was trimethoxysilyloxylated, suppressing the hydrolysis reactivity.

[0054] Next, regarding the dendrimerization of the titanium modifier, the titanium modifier is dendrimerized at room temperature using a gas-phase water addition hydrolysis method with methanol as the solvent, using Ti-TEOS or Ti-TEOS as a titanium modifier prepared by pretreatment and an excess amount of TMOS, similar to the aluminum modifier described above. Dendrimerization can suppress the hydrolysis reaction activity of the titanium modifier. However, the dendrimerization of the titanium modifier differs from that of aluminum in that an acid catalyst must be added, as shown in the examples described later. Suitable acid catalysts include concentrated sulfuric acid and concentrated nitric acid, and anhydrous is preferable. Organic acids may also be used. TIFF2026116086000004.tif104164

[0055] Next, regarding the dendrimerization of zirconium modifiers and Al-Co composite metal modifiers, as mentioned above, currently, TEOS formation is not possible in the preliminary treatment due to nozzle clogging problems. However, if the nozzle clogging problem can be resolved and TEOS formation can be achieved in the preliminary treatment, it is expected that dendrimerization will be possible in the same way as with aluminum and titanium modifiers.

[0056] Next, regarding the dendrimerization of silane coupling agents, unlike the aluminum modifier AIPD and the titanium modifier TIPD, the silane coupling agent 3APTMS can be directly dendrimed with TMOS without pretreatment. Similar to AIPD and TIPD, methanol solvent can be used for dendrimerization. Dendrimerization is carried out in a hydrophilic solvent by neutralizing the amino group with an equivalent amount of concentrated sulfuric acid, and then adding more concentrated sulfuric acid to create acidic conditions. Without neutralization, hydrolysis occurs under basic conditions. In the case of basic hydrolysis, as described on page 8 of Chapter 1, Section 1.1 of "Technical Issues and Countermeasures of the Sol-Gel Method" (IPC, edited and authored by Masayuki Yamane, published March 1990) (Non-Patent Literature 4), which the inventors compiled from literature search results, dehydration condensation occurs between silanol groups, leading to macromolecule formation, gelation, and turbidity. Therefore, for dendrimerization, after neutralization and further acidification, hydrolysis is carried out in a hydrophilic solvent with gas-phase water in the presence of an excess amount of TMOS, causing the reaction shown in the following equation to occur and dendrimerization is achieved (3APTMSTMOS dendrimer). TIFF2026116086000005.tif105149

[0057] Here too, the hydrophilic solvent used, such as methanol, must be anhydrous. The water content should be 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. If there is too much water, hydrolysis of 3APTMS in its basic state will occur when the solvent is added, leading to macromolecularization and resulting in a cloudy state.

[0058] Subsequently, a predetermined amount of TMOS is added. The amount of TMOS to add is determined considering the amount to be denatured. Specifically, for every mole of 3APTMS, 3 moles or more, more preferably 9 moles or more, of TMOS should be added. There is no particular upper limit, but if too much TMOS is added, the denaturation effect by the amino group will decrease, so it should be 200 moles or less, more preferably 100 moles or less, for every mole of 3APTMS.

[0059] As mentioned earlier, AIPD and TIPD can be isolated and stored for a long time in their dendrimer state. However, in the case of the silane coupling agent 3APTMS, the ammonium ion treatment with an anion exchange resin to return it to the amine state for isolation causes gelation. This is thought to be because the small amount of remaining silanol group condenses when it transitions to a basic state. Therefore, in the case of 3APTMS, it is necessary to proceed to the next stage of active silicic acid preparation while the ammonium ion is still present.

[0060] [Preparation of activated silica solution] An activated silica solution is prepared from a dendrimerized modifying agent. The activated silica solution is used to create a modified coating layer on the surface of colloidal silica colloidal microparticles.

[0061] For the aluminum modifier AIPD, the dendrimerization described above was performed to bring it to a state close to the hydrolysis rate of TMOS. Water was then directly added while controlling the temperature to prepare an activated silicic acid solution. For example, a 30°C water bath can be used for temperature control, and a tube pump can be used for water addition. The resulting activated silicic acid solution is clear. In one example of experimental results, the pH after water addition was 2.96.

[0062] As mentioned above, in the case of the aluminum modifier AIPD, acid addition is not necessary. Similarly, in the case of the titanium modifier TIPD, acid addition is not necessarily required, but in the case of the silane coupling agent 3APTMS, acid addition is necessary as shown in the examples described later. Except for the addition of acid, the activated silicic acid solution is prepared by the same procedure as when using AIPD.

[0063] [Modification of colloidal silica] The colloidal silica, which is the raw material for modified colloidal silica, is treated by adding an amine to adjust the pH to 8 or higher, preferably 9 or higher. The silica concentration is also set to 20 wt% or less, preferably 15 wt% or less, taking into consideration a more uniform reaction.

[0064] Colloidal silica, the raw material, is charged into a reactor capable of reflux and distillation. The colloidal silica used as the raw material is not particularly limited, but if high purity is required, colloidal silica prepared by the water glass method containing sodium ions is undesirable. Furthermore, colloidal silica obtained by the method of directly feeding TMOS into a high-temperature basic aqueous solvent, as disclosed in Japanese Patent Application Publication No. 6-316407 (Patent Document 10), is prepared at a consistently high pH and therefore contains "unreacted material" that has not been completely converted into silica. As a result, it may significantly reduce the filterability of the resulting modified colloidal silica and is therefore undesirable. Preferably, high-purity Stöber colloidal silica, or colloidal silica disclosed by the present inventors in International Publication No. 2008 / 123373 and International Publication No. 2010 / 035613 (Patent Document 12), is preferred.

[0065] The colloidal silica raw material is heated to a boil, and the activated silicic acid solution described above is fed in at a low speed. Activated silicic acid is unstable, and after hydrolysis, it needs to be cooled to prevent deterioration. In previous patent applications, the inventors have also stated that modified colloidal silica is prepared every 3 hours. Care must be taken to avoid heating the activated silicic acid to high temperatures as much as possible until just before adding it to the boiling reaction vessel. Exposure to high temperatures promotes condensation and reduces the number of silanol groups. For this purpose, the experiment was conducted by creating a cooling feed tube as shown in Figure 4 and cooling the activated silicic acid aqueous solution to the end of the feed. Similar measures should be taken in actual apparatus to ensure that the activated silicic acid aqueous solution is fed in a more stable state. In actual apparatus, for example, a feed structure like that shown in Figure 5 can be used.

[0066] In actual equipment feed tubes, it is possible to tapere the tube to concentrate the water condensed on the surface of the cooling feed tube at the nozzle tip, thereby diluting the activated silicic acid aqueous solution with the condensed water inside the reaction vessel and minimizing the deterioration of the activated silicic acid. Attention must also be paid to the formation and adhesion of silica on the internal surface of the preparation tank where the activated silica aqueous solution is prepared. In other words, care must be taken to suppress the drying of exposed surfaces as much as possible and prevent silica formation on the inner surface of the reaction tank. For example, it is preferable to feed the tank while blowing in moisture-saturated nitrogen. Completely dry nitrogen should be avoided as it will dry and solidify the activated silica that has adhered to the surface. Furthermore, it is preferable to promptly clean the inner wall after the feeding is complete. The amount of activated silicic acid solution to be added should be determined according to the thickness of the modified coating layer formed on the surface of the silica nanoparticles of colloidal silica. This can be calculated from the silica content in the activated silicic acid, based on the primary particle size of the colloidal silica raw material.

[0067] The activated silica solution contains dendrimerized modifying agents (aluminum modifying agent, titanium modifying agent, silane coupling agent, etc.), TMOS which can serve as a silica matrix raw material, and water. When the activated silica solution is fed, a condensation reaction occurs on the surface of the colloidal silica colloidal particles due to silanol groups, generating a modified coating layer.

[0068] After feeding the activated silica solution, continue reflux for about 30 minutes to complete the reaction. Afterward, if necessary, the methanol introduced from the activated silica solution may be replaced with water. Subsequently, the solution is concentrated to the desired silica concentration. Concentration can be performed by distilling off water by boiling or by membrane concentration using an ultrafiltration membrane. Since the activated silicic acid solution is prepared in an acidic environment, there are no "unreacted substances," making membrane concentration technology applicable. In conventional colloidal silica production methods, including the Stöber method, which contain "unreacted substances," unreacted alkyl silicates tend to remain in the reaction mixture during hydrolysis of alkyl silicates under basic conditions, and this is especially true when TMAH is used, which can lead to gelation in membrane concentration methods. In this respect, the present invention, which prepares the activated silicic acid solution in an acidic environment, is advantageous.

[0069] After concentrating and adjusting to the desired silica concentration, the coarse particles are finally removed by filtration to obtain a modified colloidal silica product.

[0070] The aluminum-modified colloidal silica of the present invention has an aluminum-modified coating layer on the surface of the silica nanoparticles of colloidal silica, and since sodium aluminate is not used in the manufacturing process, the sodium ion content in this coating layer is low, less than 1 wt ppm.

[0071] The colloidal silica modifying agent of the present invention is a colloidal silica modifying agent dendrimerized with tetramethoxysilane, and is, for example, a modifying agent that has undergone dendrimerization in the method for producing modified colloidal silica described above. [Examples]

[0072] (Example 1) Example 1 is an example of the production of modified colloidal silica using AIPD as the aluminum modifier. ·AIPD raw material preparation A 500ml three-necked flask was fitted with a metal-aluminum packed column, a Liebig condenser for IPA reflux, a liquid paraffin-packed trap for monitoring hydrogen generation, and a magnetic stirrer. A tray was placed at the bottom of the column, and 25g of metal-aluminum shot was packed into it.

[0073] 320g of IPA and a magnetic stirrer were placed in a flask and stirred. An aluminum-packed column was set up, and about one micro-spatulaful of iodine was dropped onto the top of the aluminum. A Liebig container was set up, and the column was heated with stirring using a mantle heater to create an IPA flux state. As the iodine dissolved, the aluminum surface was activated, and hydrogen generation began. The hydrogen generation state was confirmed by the bubble state of the liquid paraffin in the trap. The reaction was carried out until all the aluminum packed in the column had reacted, fallen to the bottom, and hydrogen production ceased.

[0074] • AIPD distillation and purification After the synthesis reaction was complete, a T-shaped tube, a Liebig column, and an adapter were attached, and IPA was removed by atmospheric distillation. 297.83 g of IPA was removed at an outflow temperature of 83°C. Next, the Liebig column was replaced with a column wrapped around a thermostat-equipped ribbon heater, and the adapter was replaced with a bifurcated adapter, and vacuum distillation was performed. After taking a small amount of the pre-distillate, the process was switched to the main distillate and collected in a 300 ml round-bottom flask. Since the distillate is prone to crystallization, it was heated to its melting point of approximately 140°C using a ribbon heater to prevent solidification. The pressure was reduced to -0.86 MPa, and the main distillate was collected until the bottom temperature reached 154.6°C. The yield was 148.0 g, and the yield percentage was 77 wt%.

[0075] [Preparation] (TEOSization (Al-TEOS preparation)) A 2L separable container was fitted with a 5cm rugby ball-shaped stirring bar, a water-containing air inlet tube, and an exhaust tube, and the above-mentioned distilled and purified AIPD 44.63g (0.22 mol) and TEOS 163g (0. 78 moles of AIPD were added, along with 820g of IPA (commercial reagent grade). The required amount of AIPD was left in the round-bottom flask containing the distillation distillate, and a portion of the IPA was added to homogenize it before being placed in a separable flask. TEOS from Colcoat was used.

[0076] Air was supplied from a compressor, and the amount of air blown in was controlled by adjusting the release amount with a needle valve, with a rotor meter measuring 200 ml / min. The compound to be produced is given by the following formula: TIFF2026116086000006.tif42142 (In the above formula, R represents an ethyl group or an isopropyl group (partially substituted with isopropyl by transesterification).)

[0077] During the blowing process, the moisture content in the reaction solution was checked occasionally using a Karl Fischer moisture meter. The moisture content during blowing was several hundred ppm. Once the reaction was complete and the AIPD had fully reacted, excess water remained, and the process was terminated when the moisture concentration reached approximately 0.1 wt% (1,000 ppm). No solid deposits adhered to or blocked the blowing nozzle during the blowing of the moistened air.

[0078] After blowing was complete, excess moisture can reduce shelf life, so to be safe, TEOS was added as a dehydrating agent, approximately twice the number of moles of water content. Since the water content was 0.074 mol, 31.0 g (0.149 mol) of TEOS was added.

[0079] After hydrolysis with gas-phase water, the IPA-EtOH mixture was removed by distillation, and the solvent alcohol was removed by raising the bottom temperature to approximately 140°C. The bottom residue was collected as the target product, Al-TEOS. Since it is sensitive to moisture, it was handled in a glove bag and transferred to a storage container. In a sealed state, it did not gel and could be stored stably for a long period of time. The yield was 154.0 g, and the Al content was calculated to be 3.85 wt%.

[0080] [Dendrimer formation by TMOS] 97.4g of TMOS and 3.1g of the above Al-TEOS were weighed into a 1L separable flask containing a 5cm rugby ball-shaped magnetic stirring bar. The lid of the three-necked separable flask was set, and the flask was immersed in a water bath heated to 30°C. Methanol (120 ppm water) was added using a dropping funnel under stirring.

[0081] Air from a compressor was drawn at a rate of approximately 200 ml / min using a rotometer, passed through a gas wash bottle containing pure water immersed in a 60°C water bath to become humidified air, and then passed through a gas filter and trap tube before being bubbled into a 2 L separable flask under agitation. Since continuous processing for about 24 hours was required, bubbling was continued overnight. During the process, the change in moisture content in the system was measured using a Karl Fischer moisture meter while the process continued. The lower part of the graph in Figure 1 shows the change in moisture content during Al-TEOS dendrimerization. The resulting dendrimer solution is referred to as the pretreatment solution.

[0082] [Preparation of activated silica solution] The obtained pretreatment solution (267.7g) was placed in a 1L separator containing a 5cm rugby ball-shaped stirring bar. The solution was placed in a Bull flask and immersed in a 30°C water bath. 218.3 g of pure water was added using a tube pump at a rate of 3.6 ml / min over 1 hour under stirring. The resulting activated silicic acid solution had a pH of 2.96 (at 17.1°C). The low pH is thought to be due to the Lewis acidity of aluminum. The resulting activated silicate aqueous solution was clear, as shown in Figure 6.

[0083] [Modification of colloidal silica (coating with an aluminum-containing layer)] In a 2L separable flask equipped with a Dean-Stark type drain adapter connected to a stirrer and a Liebig condenser, 667g of colloidal silica (primary particle size: 18.3nm, secondary particle size: 29.7nm, silica content 20wt%) and 700g of pure water were charged, and 3g of 1N-TMAH was added. The pH was 8.74 (20.2℃). This was used as the mother liquor.

[0084] To this, the prepared activated silica aqueous solution was added at a rate of 2.7 ml / min over 3 hours under mother liquor flux. The liquid level was kept constant by draining from the Dean-Stark adapter. During the addition process, the pH was checked every 30 minutes, and 1 g of 1N-TMAH was added to maintain the pH at 8-8.5 or higher.

[0085] After the addition was complete, the silica concentration was adjusted by adding pure water and performing water displacement until the liquid temperature reached 100°C. Finally, the mixture was filtered through a 3 μm membrane filter. The obtained aluminum-modified colloidal silica had a primary particle size of 19.8 nm and a secondary particle size of 32.4 nm. The thickness of the aluminum-containing layer (coating layer) was 0.75 nm. The calculated aluminum content in the aluminum-containing layer was 0.3 wt%, which was 430 ppm relative to the total silica content.

[0086] When the amount of aluminum in the supernatant obtained by ultracentrifugation of the resulting aluminum-modified colloidal silica at 97,500 rpm for 30 minutes was measured by ICP-AES, it was below the detection limit. This suggests that the entire amount of aluminum was stably incorporated into the colloidal silica framework, and there were no aluminum-containing particles released from the colloidal silica.

[0087] Figure 7 shows the zeta potential measurement results of the obtained aluminum-modified colloidal silica. From Figure 7, a decrease in zeta potential was confirmed due to aluminum modification. This is thought to be because the incorporation of aluminum anions resulted in the formation of an anionic sol, as described in U.S. Patent No. 2,892,797 (Patent Document 3). Figure 8 shows a post-FE-SEM image of aluminum-modified colloidal silica.

[0088] (Comparative Example 1) In Example 1, Al-TEOS obtained by the AIPD raw material preparation, AIPD distillation purification, and pretreatment was mixed with TMOS without dendrimerization with TMOS, and methanol was added to the solution. Water was then directly added to this solution to prepare an activated silicic acid solution. The resulting activated silicic acid aqueous solution was cloudy, as shown in Figure 9, indicating that Al-TEOS underwent preferential hydrolysis, and a uniform activated silicic acid aqueous solution was not obtained.

[0089] (Example 2) Example 2 is an example of the production of modified colloidal silica using TIPD as the titanium modifier. [Preparation] (TEOS conversion of TIPD (Al-TEOS preparation)) In a 1L three-necked flask containing a 5mm rugby ball-shaped magnetic stirrer, 420g of commercially available Ti(Oi-Pr) (0.07mol, molecular weight 284.215, Ti: 47.867) was pre-treated in approximately 500ml (approximately 400g) of IPA solvent with 70g of TEOS (0.34mol, molecular weight 208.33) in the same manner as in Example 1, and then converted to TEOS by hydrolysis with gas-phase water.

[0090] During the TEOS conversion of this titanium modifier, unlike the TEOS conversion of the aluminum modifier in Example 1, a problem arose where a white solid adhered to the tip of the water-containing nitrogen gas injection nozzle, as shown in Figure 10, causing frequent blockages and preventing the continuation of gas-phase water hydrolysis. This was thought to be due to the fact that TIPD does not possess the strong Lewis acidity of AIPD. Therefore, when 0.2 g of anhydrous concentrated sulfuric acid was added and TEOS conversion was performed, the above problem was resolved. Under these conditions with added anhydrous concentrated sulfuric acid, it was confirmed that TEOS conversion proceeded similarly to that of AIPD in Example 1. In other words, it was found that when the titanium modifier is TIPD, a sulfuric acid catalyst is required in this pretreatment step.

[0091] Figure 11 shows a graph of the moisture content change over time during the preliminary treatment. The graph in Figure 11 shows that the moisture content did not reach a steady state and continued to rise. This is thought to be because the reaction scale is smaller than that of AIPD, and the amount of moisture delivered at 200 ml / min is not sufficient to react with the amount of TIPD added. Due to the scale of the rotometer, the supply rate could not be reduced, so when the moisture content rose, the experiment was interrupted and continued while waiting for the moisture content to return to a steady state. After 24 hours, the blowing rate was adjusted to 100 ml / min, the lowest setting on the rotometer. The point marked with an "x" in Figure 11 is thought to be the steady state of moisture content. After 32 hours, the rise in steady state moisture content was confirmed, and the TEOS conversion was completed.

[0092] After confirming the increase in moisture content, the mixture was refluxed for one hour. As shown by the triangles in Figure 11, 600 ppm of moisture remained even after reflux, confirming that the highly hydrolytically active portion had disappeared. The solvent was then removed under atmospheric pressure until the flask temperature reached 141°C, and the liquid remaining at the bottom was identified as Ti-TEOS. The yield was 72.4 g, and the titanium content was calculated to be 4.63 wt%. Ti-TEOS could be stored for a long period in a sealed state. The IR spectrum of the obtained Ti-TEOS is shown in Figure 12.

[0093] The Ti-O-Si bond is 920 cm².-1 (Nogami et al., Journal of the Ceramics Association 85 [2]) It is recorded as 1977 (59), and was confirmed as a weak peak in Figure 12. 1040cm -1 The strong peaks in the vicinity are thought to be Si-OC bonds.

[0094] [Dendrimer formation by TMOS] In a 1L three-necked flask containing a 5mm rugby-type magnetic stirrer, 6.62g of the obtained Ti-TEOS and 97.4g (0.64mol) of TMOS were added, along with 420g of methanol (439ppm water content) as the solvent and 0.1g of concentrated sulfuric acid as the acid catalyst.

[0095] Using the same method as described in Example 1 for dendrimerization, hydrated nitrogen gas was blown in at 200 ml / min. Since an increase in moisture content was observed, the flow rate was changed to 100 ml / min, and gas-phase water hydrolysis was performed. Figure 13 shows the change in moisture content over time during gas-phase water hydrolysis. As Figure 13 shows an increase in moisture content over time, concentrated sulfuric acid was added twice at 0.2 g each. A steady state was reached at approximately 700 ppm of moisture, confirming that stable dendrimerization occurred. Therefore, it was confirmed that 0.5 g of concentrated sulfuric acid needs to be added in this formulation.

[0096] Subsequently, hydrolysis with gas-phase water at a rate of 100 ml / min was continued until a rapid increase in moisture content was observed. After approximately 48 hours of hydrolysis with gas-phase water, a rapid increase in moisture content was confirmed, and the dendrimerization process was terminated. The added acid was removed with 10 g (12 ml) of anion exchange resin (1.2 eq. / L). The addition of water during hydrolysis increased the acid strength, raising concerns about the decomposition of the Si-O-Ti bond. This solution was used as the pretreatment solution.

[0097] [Preparation of activated silica solution] Half of the obtained pretreatment solution (239.3g) was placed in a three-necked flask containing a 5mm rugby ball-shaped magnetic stirrer, immersed in a water bath heated to 30°C, and hydrolyzed by adding 200g of water at a rate of 3.6ml / min while stirring. Unlike the case of AIPD, slight turbidity occurred upon water addition. Since dendrimerization by TMOS had been performed, it was decided to proceed directly to the next denaturation stage for confirmation.

[0098] [Modification of colloidal silica] In a 2L four-necked flask similar to that used in Example 1, 500g of colloidal silica (primary particle size 23.3nm, secondary particle size 28.1nm, silica content 21.9wt%) was mixed with 700g of pure water and 9g of 1N-TMAH to prepare the mother liquor. The mixture was brought to a boil in an oil bath, and the prepared activated silicic acid solution was added at a rate of 2ml / min, with 1g of 1N-TMAH added every 30 minutes to maintain the pH of the mother liquor above 8.

[0099] After the addition of the activated silica solution was complete, water displacement was performed by adding pure water at a rate of 2 ml / min until the liquid temperature reached the boiling point of water. After the water displacement was complete, the solution was concentrated to a silica concentration of approximately 20 wt%. The obtained titanium-modified colloidal silica was stable, with a primary particle size of 22.9 nm and a secondary particle size of 27.6 nm, and contained approximately 1,200 ppm of titanium relative to the silica (calculated value). Within the coating layer, it contained 1.66% titanium relative to the silica.

[0100] When the obtained titanium-modified colloidal silica was ultracentrifuged at 97,500 rpm for 30 minutes, the amount of titanium in the supernatant was measured by ICP-AES and was below the detection limit, suggesting that all of the titanium was incorporated into the colloidal silica framework. Figure 14 shows the zeta potential measurement results for the obtained titanium-modified colloidal silica.

[0101] Titanium, like silicon, is tetravalent and is not thought to be anionized like aluminum. Therefore, although the zeta potential does not decrease as much as with aluminum, the isoelectric point is shifted to a lower pH side than the isoelectric point of the raw material colloidal silica shown in Figure 7, indicating that some kind of change has occurred in the surface state of the colloidal silica.

[0102] In Japanese Patent No. 4819322 (Patent Document 3), a low zeta potential is observed even in the low pH range, similar to aluminum modification. However, as mentioned above, titanium is tetravalent, like silicon, and therefore does not form anions like trivalent aluminum. Consequently, it is expected to exhibit zeta potential behavior similar to that of unmodified colloidal silica. The chart in Figure 12 corresponds to this, indicating that the titanium atoms are incorporated into the silica skeleton. In the method described in Japanese Patent No. 4819322 (Patent Document 3), it is highly likely that the titanium atoms are not incorporated into the silica skeleton.

[0103] (Example 3) Example 3 is an example of the production of modified colloidal silica using zirconium butoxide as the zirconium modifier.

[0104] In Example 2, instead of TIPD, we attempted TEOS conversion using zirconium-normal butoxide (Zr(On-Bu)4). Similar to TIPD, the hydrated nitrogen gas injection nozzle turned white, suggesting that TEOS conversion was not progressing. We checked the effect of adding concentrated sulfuric acid, but it did not resolve as with TIPD, and it was confirmed that the hydrolysis rate of zirconium butoxide was fast, and it became insoluble in the solvent before TEOS conversion could occur. Therefore, at present, zirconium-modified colloidal silica cannot be obtained. However, if the whitening of the hydrated nitrogen gas injection nozzle can be addressed and TEOS conversion can proceed, then according to the present invention, It is expected that aruconium-modified colloidal silica will be obtained.

[0105] (Example 4) Example 4 is an example of the production of modified colloidal silica using a Co-Al complex alkoxide as the complex metal modifier.

[0106] Co[Al(Oi-Pr)4]2, which can be purified by distillation, was synthesized according to SYNTH. REACT. INORG. MET.-ORG. CHEM., 9(1), 79-88 (1979) (Non-Patent Literature 2). In Example 3, TEOSization was attempted using Co[Al(Oi-Pr)4]2 instead of zirconium butoxide. Similar to Example 3, a white solid adhered to the blowing nozzle and this could not be resolved by adding concentrated sulfuric acid. Therefore, at present, modified colloidal silica using Co-Al complex alkoxide cannot be obtained. However, if the whitening of the hydrated nitrogen gas blowing nozzle can be addressed and TEOSization can proceed, it is expected that modified colloidal silica using Co-Al complex alkoxide can be obtained according to the present invention.

[0107] (Example 5) Example 5 is an example of the production of colloidal silica modified with 3APTMS, a silane coupling agent.

[0108] [TEOS conversion] In the case of 3APTMS, even if transesterification occurs with TMOS, it does not pose a problem because both are methoxy groups. Therefore, TEOSization by pretreatment is not necessary. Thus, we will start with dendrimerization with TMOS as described below.

[0109] [Dendrimer formation by TMOS] 438g of methanol, 0.62g (6.32 mmol) of concentrated sulfuric acid, 2.28g (12.72 mmol, 2 mol% relative to TMOS) of 3APTMS, and 97.4g (639.9 mmol) of TMOS were charged into a 2L separable flask equipped with a magnetic stirrer.

[0110] In the same manner as in Example 1, a humidified gas was passed through the 2L separable flask at a rate of 200 ml / min under stirring. This process was carried out day and night, and the moisture content of the reaction solution was monitored using a Karl Fischer moisture meter. As shown in the moisture content graph in Figure 1, the process was terminated when a rapid increase in moisture content was observed, and this was referred to as the pre-treatment solution.

[0111] [Preparation of activated silicate aqueous solution] Half of the obtained pretreatment solution was placed in a 2 L separable flask equipped with a 5 cm rugby ball-shaped magnetic stirrer, 300 μl of 50 wt% sulfuric acid was added, and the flask was immersed in a water bath set to 30°C. 378 g of pure water was then added to this solution at a rate of 6.3 ml / min over 1 hour with stirring to prepare an activated silicic acid solution containing ammonium groups. The pH was 2.76 (at 14.1°C).

[0112] [Modification of colloidal silica (amine modification)] A 2L separable flask equipped with a Dean-Stark adapter with a Liebig fitting and a 5cm rugby ball-shaped magnetic stirrer was used to prepare the mother liquor by charging 600g of colloidal silica (primary particle size: 18.3nm, secondary particle size: 29.7nm, silica content 20wt%), 700g of pure water, and 10g of 1N-TMAH. The pH was 9.53 (at 22.2℃).

[0113] Add 2.7 ml / min of ammonium-containing activated silica solution to the boiling, fluxed mother liquor. The mixture was fed to form a coating layer. During the process, 3g of 1N-TMAH was added every 30 minutes to maintain the pH at approximately 9.

[0114] After the addition of the activated silicic acid solution was complete, 467 g of pure water was fed at the same rate to perform water displacement. The final pH was 9.33 (23.5°C). After water displacement, the mixture was cooled and filtered through a 3 μm membrane filter. The primary particle size was 25.0 nm and the secondary particle size was 32.3 nm.

[0115] (Comparative Example 2) In the colloidal silica modification process using 3APTMS, a silane coupling agent, as described in Example 5, we confirmed the case where dendrimerization was not performed.

[0116] 0.5785 g (3.23 mmol, 1 mol% relative to TMOS) of 3APTMS (molecular weight: 179.29) was diluted with 57.4 g of methanol. 3.18 g of 1N nitric acid (0.2 g as HNO3, 3.17 mmol) was added to 526.4 g of pure water to prepare nitric acid water. The resulting nitric acid water was reacted dropwise with the methanol dilution of 3APTMS in a 30°C water bath under stirring for 5 minutes to protonate it and obtain the ammonium ion state.

[0117] To this aqueous solution, 48.7 g (319.9 mmol) of TMOS, which had been preheated to 30°C, was added, and hydrolysis was carried out for 1 hour to prepare an aqueous solution of activated silicic acid containing ammonium groups with a silica content of 3.3 wt%. The pH was 3.75 (at 20.4°C).

[0118] A 2L separable flask equipped with a Dean-Stark adapter with a Liebig fitting and a 5cm rugby ball-shaped magnetic stirrer was used as the mother liquor by adding 600g of raw material colloidal silica (primary particle size: 18.3nm, secondary particle size: 29.7nm, silica content 20wt%), 700g of pure water, and 3g of 1N-TMAH as seed particles.

[0119] An activated silica aqueous solution was added to the mother liquor, which had been brought to a boiling flux state, at a rate of 2.7 ml / min to coat the surface of the seed particles. Every 30 minutes, 2 g of 1N-TMAH1 was added to maintain the pH at around 8.

[0120] After the addition of the activated silicate aqueous solution was complete, water displacement was performed at the same rate while feeding 547g of pure water, and the temperature was changed from 98°C to 99.5°C. After water displacement, the mixture was cooled and filtered through a 3μm membrane filter. The primary particle size was 23.0nm and the secondary particle size was 32.5nm.

[0121] Figure 15 shows the zeta potential measurement results for silane coupling agent-modified colloidal silica in Example 3 and Comparative Example 2. Comparative Example 2 shows a higher positive potential in the acidic range than Example 3. In Comparative Example 2, since it is not dendrimerized, the silane coupling agent may simply be adsorbed onto the colloidal silica surface, whereas in Example 3, the amino group is reliably incorporated into the silica skeleton, resulting in a decrease in potential. Furthermore, the significantly more rapid rise around pH 6.6 in Example 3 compared to Comparative Example 2 is also thought to be related to the incorporation into the skeleton. In other words, observing the differences in zeta potential behavior described above is a useful method for distinguishing between products manufactured using conventional methods and products produced using the dendrimerization method described in this patent.

[0122] The methods for producing modified colloidal silica and the modified colloidal silica described in Examples 1 to 5 above will now be explained, along with their functions and effects.

[0123] The colloidal silica was modified by first reacting it with TMOS to form a dendrimer, thereby bringing the hydrolysis reaction activity of the modifying agent closer to that of TMOS, the silica matrix raw material.

[0124] Regarding the aluminum modification, measuring moisture content using a Karl Fischer moisture meter was an effective way to confirm the reaction progress of gas-phase water hydrolysis, and the completion of the reaction was clearly confirmed.

[0125] Furthermore, by further reacting Al-TEOS with TMOS to dendrimerize it, a homogeneous activated silicic acid solution could be prepared, yielding stable aluminum-modified colloidal silica free of sodium ions. The obtained aluminum-modified colloidal silica did not exhibit a decrease in zeta potential compared to that produced using sodium aluminate, but it had a negative zeta potential across almost the entire pH range. The reduced decrease in potential is thought to indicate that aluminum was reliably incorporated into the silica skeleton. This incorporation into the skeleton was also confirmed by checking whether aluminum in the ultracentrifugation supernatant could be detected by ICP-AES, which showed no detection (below the detection limit).

[0126] Japanese Patent Publication No. 2010-269985 describes a sulfonic acid-modified anionic sol having a negative zeta potential across the entire pH range. This anionic sol is prepared by modifying colloidal silica with a thiolsilane coupling agent and then oxidizing it with hydrogen peroxide. However, to completely oxidize the thiols, it is necessary to add an excess amount of hydrogen peroxide. Therefore, it is difficult to adjust the hydrogen peroxide content, which is affected by the hydrogen peroxide content in compositions used for metal polishing, making it difficult to use. However, the aluminum-modified colloidal silica according to the present invention does not require hydrogen peroxide in the manufacturing process, thus avoiding the problems associated with sulfonic acid-modified anionic sols.

[0127] Regarding titanium modification, it was confirmed that TEOS formation can be achieved by adding concentrated sulfuric acid, that dendrimer formation can be achieved similarly to aluminum, and that activated silicic acid solution preparation is possible. The required amount of sulfuric acid was also confirmed. Although slight turbidity was observed during the activated silicic acid solution preparation, no titanium was detected in the ultracentrifugation supernatant (below the ICP-AES detection limit), and there were no problems with the stability of the obtained titanium-modified colloidal silica, so it can be said that the objective was achieved. To avoid turbidity, it may be necessary to consider adding acid during the preparation of activated silicic acid. The aluminum modification proceeded smoothly due to the aluminum's own acid catalytic ability, but the titanium modification required searching for optimal reaction conditions. The experimental conditions for the aluminum modification happened to be ideal by chance.

[0128] We also investigated the cases where the modifying agent was zirconium butoxide and Co-Al complex alkoxide. These exhibited different hydrolysis characteristics, and at present, we were unable to obtain modified colloidal silica; however, future improvements to the manufacturing process are anticipated. Regarding complex alkoxides, only the case of Co-Al complex alkoxide was experimentally investigated and confirmed; therefore, the manufacturing method of this invention may be applicable to various other complex alkoxides.

[0129] Regarding 3APTMS as a silane coupling agent, experiments were conducted under acidified conditions by adding sulfuric acid, ammonium chloride, and further acidification, confirming that modified colloidal silica could be obtained. This was because stable dendrimerization was thought not to occur under basic conditions due to amines. The experimental results showed that, although not as high as AIPD, it had significantly higher hydrolysis reaction activity than TMOS, as shown in the graph in Figure 1, confirming the effectiveness of the dendrimerization method of the present invention. Gas-phase reactions can also be prevented, and a more uniform and stable modification effect can be expected.

[0130] 3APTMS is more difficult to handle than other silane coupling agents because it contains an amino group that catalyzes dehydration condensation reactions within its molecule. Therefore, the stability of extracting the dendrimer was lower compared to AIPD and TIPD. Gelation occurred when the ammonium salt was treated with an anion exchange resin to convert it back to an amine. It is believed that some other silane coupling agents can be isolated and stored as dendrimers.

[0131] If the modifying agent is a silane coupling agent, the manufacturing method according to the present invention involves more steps than simply adding it, making it less costly. However, if only surface modification is required, the amount used is small, and the cost increase is not expected to be significant.

[0132] By combining this with the true specific gravity control method disclosed in the aforementioned Patent No. 2002177 (Patent Document 6), the density of colloidal silica can be arbitrarily controlled, making it possible to perform fine adjustments to prevent scratch formation. The results of the denaturation experiment are summarized in Table 1.

[0133] [Table 1] The secondary particle size was measured using dynamic light scattering with an ELSZ-2000S manufactured by Otsuka Electronics Co., Ltd.

[0134] For TIPD only, a phenomenon was observed in which the particle size of the primary and secondary particles after modification became smaller compared to before modification. The scattering intensity distribution map during secondary particle size measurement is shown in Figure 16. No fine particles were detected in Figure 16. Therefore, further visual observation was performed using FE-SEM as shown in Figure 17. Figure 17(a) is an SEM image at a magnification of 20,000x, and Figure 17(b) is an SEM image at a magnification of 200,000x.

[0135] Figure 17 confirms that no microparticles released from the modified colloidal silica were observed at 20,000x and 200,000x magnification. The zeta potential measurement results associated with degeneration are summarized in Table 2.

[0136] [Table 2]

[0137] Table 2 confirms that the isoelectric point pH changes due to denaturation. Adjustment of the amount of denaturation, It is thought that further modifications can be made by combining denaturing agents, etc.

[0138] Finally, the effects of the present invention will be summarized based on the embodiments and examples. This invention discloses a method to mitigate the difference in reaction activity between a highly hydrolytically reactive modifying agent and TMOS, a silica matrix raw material, by pre-dendrimerizing the modified agent with TMOS using a gas-phase water addition hydrolysis method. This eliminates the possibility of direct reaction between modifying agents, improves reaction selectivity, and increases the number of anchor points that bond to the silica surface, thereby increasing the probability of bonding to the silica particle surface. As shown in the examples, in the case of metal modification, the absence of metal ions in the aqueous phase was confirmed by ICP-AES analysis. Similarly, although not confirmed by metal analysis, it is thought that a similar effect is achieved in modification with a silane coupling agent.

[0139] By combining this with the true specific gravity control method disclosed in the aforementioned Patent Document 6, the density of colloidal silica can be arbitrarily controlled while avoiding the formation of silsesquioxane, enabling fine-tuning to prevent scratch formation. By arbitrarily changing the amount of silane coupling agent, Si-R groups that are not susceptible to hydrolysis can be reliably incorporated. In contrast, the aforementioned Patent Document 11 attempts to achieve a similar objective by retaining methoxy groups, but does not disclose a control method for arbitrarily retaining methoxy groups.

[0140] Dendrimerization makes the volatile silane coupling agent non-volatile, thus avoiding the risk of gas-phase reactions at high temperatures. Furthermore, since the method of the present invention does not contain "unreacted material," it is possible to employ a membrane concentration method for concentration, which is advantageous in that it saves energy. This invention makes it possible to obtain aluminum-modified colloidal silica that does not contain sodium ions, which was previously unknown.

Claims

1. A process of pre-dendrimerizing a colloidal silica modifier, which has higher hydrolysis reaction activity than the silica matrix raw material, with tetramethoxysilane. A step of adding an activated silicic acid solution containing the silica matrix raw material and the dendrimerized colloidal silica modifier to colloidal silica to form a coating layer on the surface of silica microparticles by hydrolysis. A method for producing modified colloidal silica containing

2. The method for producing modified colloidal silica according to claim 1, wherein the colloidal silica modifying agent is an alkoxide selected from aluminum alkoxide, titanium alkoxide, and distillable complex alkoxide.

3. The colloidal silica modifier is RSi(OMe) ３ A method for producing modified colloidal silica according to claim 1, wherein the silane coupling agent has a structural formula consisting of an alkyl group, vinyl group, epoxy group, styryl group, methacrylic group, acrylic group, amino group, isocyanurate group, ureido group, mercapto group, isocyanate group, acid anhydride group, carbonyl group, aryl group, ether group, and unsaturated aliphatic residue, which may have substituents.

4. Aluminum-modified colloidal silica comprising an aluminum-modified coating layer on the surface of colloidal silica nanoparticles, wherein the sodium ion content of the coating layer is 1 wt ppm or less.

5. A colloidal silica modifier dendrimerized with tetramethoxysilane.

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