Colloidal silicon oxide

Abstract

The present invention provides colloidal silica containing silica particles with excellent density and excellent maintenance of surface irregularity under alkaline conditions, and a method for manufacturing the colloidal silica. The present invention provides a colloidal silicon oxide, which is a colloidal silicon oxide containing silicon oxide particles, characterized in that: (1) the content of metallic impurities in the aforementioned colloidal silicon oxide, as measured by an atomic absorption spectrometer, is less than 1 ppm, and the metallic impurities are sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, or cobalt; (2) the surface roughness (B1 / S1) of the silicon oxide particles is 1.1 or more, which is calculated by dividing the BET specific surface area (B1) measured by the following BET specific surface area measurement method by the specific surface area (S1) calculated by the following SEM minor axis; (3) the reduction rate of the specific surface area of ​​the aforementioned silicon oxide particles during heat treatment under alkaline conditions is less than 15.0%.

Description

Technical Field

[0001] This invention relates to colloidal silicon oxide and its manufacturing method, and more particularly to colloidal silicon oxide containing silicon oxide particles having an uneven surface shape and its manufacturing method. Prior Technology

[0002] Colloidal silica disperses silica microparticles in media such as water. Besides being used as a property modifier in fields such as paper, fiber, and steel, it is also used as an abrasive for electronic materials such as semiconductor wafers. For this application, the silica particles dispersed in colloidal silica require high purity and density.

[0003] As a method for manufacturing colloidal silica that can meet the above requirements, for example, a method for manufacturing aqueous silica sol in which alkyl silicates are added to a reaction medium with an alkaline concentration within a specific range has been disclosed (for example, see Patent Document 1).

[0004] However, the manufacturing method described in Patent Document 1 does not address the shape of the spherical particles or silicon oxide particles being manufactured.

[0005] A method for manufacturing colloidal silica containing silica particles with small protrusions on their particle surfaces has been disclosed, using quaternary ammonium salts or the like as hydrolysis catalysts (for example, see Patent Document 2). Colloidal silica is a deformed silica particle with protrusions or the like on its surface, and as an abrasive, it exhibits higher abrasiveness. [Previous Technical Documents] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-316407 [Patent Document 2] Japanese Patent Application Publication No. 2007-153732 Summary of the Invention

[0007] [The problem the invention aims to solve] The inventors have discovered that the colloidal silicon oxide manufactured by the manufacturing method described in Patent Document 2 has a problem that it cannot maintain the surface unevenness under alkaline conditions.

[0008] Through dedicated research, the inventors have successfully manufactured colloidal silicon oxide containing silicon oxide particles that maintain excellent surface texture even under alkaline conditions. Furthermore, this colloidal silicon oxide is suitable for use as an abrasive, and considering its ability to effectively solve the aforementioned problems, the present invention was thus completed.

[0009] The purpose of this invention is to provide a colloidal silica containing silica particles with excellent density and excellent maintenance of surface irregularity even under alkaline conditions, and a method for manufacturing the colloidal silica. [Methods used to solve problems]

[0010] Through repeated and dedicated research in order to achieve the above-mentioned objective, the inventors discovered that the above-mentioned objective can be achieved by using colloidal silica containing silica particles with an uneven surface shape, the alkoxy content of the silica particles being within a specific range, and the silica particles exhibiting a specific range of specific surface area reduction rate when heated under alkaline conditions, thus completing the present invention.

[0011] That is, the present invention relates to the following colloidal silicon oxide and its manufacturing method. 1. A colloidal silicon oxide, comprising silicon oxide particles having an uneven surface, characterized in that, (1) The alkoxy group content of the aforementioned silicon oxide particles is above 1000 ppm. (2) The specific surface area of ​​the aforementioned silicon oxide particles is reduced by less than 15.0% when heated under alkaline conditions. 2. The colloidal silicon oxide as described in item 1, wherein the true specific gravity of the aforementioned silicon oxide particles is 1.95 or higher. 3. The colloidal silicon oxide as described in item 1 or 2, wherein the aforementioned silicon oxide particles contain at least 5 μmol of at least one amine selected from the group consisting of primary amines, secondary amines and tertiary amines (but excluding hydroxyl groups as substituents) per 1 g of silicon oxide particles. 4. A method for manufacturing colloidal silicon oxide, comprising colloidal silicon oxide containing silicon oxide particles with uneven surface shapes, characterized by the following steps in sequence: (1) Step 1: Preparing a mother liquor containing an alkaline catalyst and water; (2) Step 2, which involves adding alkoxysilane to the aforementioned mother liquor to prepare a seed particle dispersion; and (3) Step 3, in which water, alkaline catalyst, and alkoxysilane are added to the aforementioned seed particle dispersion. The aforementioned alkaline catalyst is selected from at least one amine selected from the group comprising primary, secondary, and tertiary amines (except for hydroxyl groups as substituents). In step 3 above, the molar ratio (s3 / c3) between the amount of alkoxysilane added s3 (mol) and the amount of alkaline catalyst added c3 (mol) is greater than 185 and less than 400. [Effects of the Invention]

[0012] The colloidal silicon oxide of the present invention contains silicon oxide particles with excellent density and excellent maintenance of surface irregularity under alkaline conditions. Furthermore, the colloidal silicon oxide manufacturing method of the present invention can produce this colloidal silicon oxide. Simple Explanation of the Diagram

[0013] Figure 1 is an SEM image of the colloidal silica particles produced in Example 2. Implementation

[0014] [The form in which the invention is carried out] The colloidal silicon oxide and its manufacturing method of the present invention will be described in detail below.

[0015] The colloidal silicon oxide of the present invention exhibits high abrasiveness because it contains silicon oxide particles with an uneven surface. Furthermore, the colloidal silicon oxide of the present invention has a high alkoxy content of 1000 ppm or more in the silicon oxide particles, thus suppressing surface defects on substrates and other materials being polished. Moreover, the colloidal silicon oxide of the present invention exhibits excellent surface unevenness maintenance under alkaline conditions because the specific surface area reduction rate of the silicon oxide particles during heat treatment under alkaline conditions is less than 15.0%, maintaining high abrasiveness even under alkaline conditions. Furthermore, in the method for manufacturing colloidal silica of the present invention, as an alkaline catalyst, at least one amine selected from the group comprising primary amines, secondary amines and tertiary amines (but hydroxyl groups are excluded as substituents) is used, and the molar ratio (s3 / c3) of the amount of alkoxysilane added in step 3 to the amount of alkaline catalyst added c3 (mol) is set within a specific range to carry out the sol-gel reaction. In this way, colloidal silica with few metal impurities can be manufactured, which has excellent surface irregularity maintenance under alkaline conditions and can maintain high abrasiveness even under alkaline conditions.

[0016] 1. Colloidal silicon oxide The colloidal silicon oxide of the present invention is a colloidal silicon oxide containing silicon oxide particles with an uneven surface, characterized in that (1) the content of alkoxy groups in the aforementioned silicon oxide particles is 1000 ppm or more, and (2) the specific surface area of ​​the aforementioned silicon oxide particles decreases by 15.0% or less when subjected to heat treatment under alkaline conditions.

[0017] In this specification, the term "surface unevenness" of silicon oxide particles refers to the shape of tiny protrusions on the surface of silicon oxide particles, giving them a shape similar to konpeito (Japanese sugar candy). This surface unevenness can be defined by the range of surface roughness (B1 / S1) calculated by dividing the BET specific surface area (B1) by the specific surface area (S1) calculated from the SEM minor axis. Furthermore, the specific surface area (S1) can be obtained by setting the true specific gravity of silicon oxide to 2.2 and converting it to the value of 2727 / SEM minor axis (nm). The surface roughness (B1 / S1) is preferably 1.1 or higher, more preferably 1.4 or higher, and preferably 2.0 or lower, more preferably 1.8 or lower.

[0018] The alkoxy group content of the aforementioned silica particles is 1000 ppm or more. If the alkoxy group content is less than 1000 ppm, the abrasiveness of the colloidal silica of the present invention decreases, and defects on the surface of the workpiece cannot be suppressed. The aforementioned alkoxy group content is preferably 4000 ppm or more, more preferably 5000 ppm or more. Furthermore, the aforementioned alkoxy group content is preferably 45000 ppm or less, more preferably 40000 ppm or less. By setting the upper limit of the alkoxy group content within the above range, the abrasiveness of the colloidal silica of the present invention is further improved.

[0019] In addition, the content of the above-mentioned alkoxy groups can be determined by the following methods.

[0020] (Alkyl group content (ppm)) After centrifuging the colloidal silica at 215,000 G for 90 minutes, the supernatant was discarded, and the solid component was vacuum dried at 60°C for 90 minutes. 0.50 g of the resulting dried silica was weighed and placed in 50 ml of 1 M sodium hydroxide aqueous solution. The solution was heated at 50°C for 24 hours while stirring to dissolve the silica. The silica solution was analyzed by gas chromatography to determine the alcohol content and calculate the amount of alkoxy groups per 1 g of silica. A flame ionization detector (FID) was used for the gas chromatography. The gas chromatography analysis was performed in accordance with JIS K0114.

[0021] (BET specific surface area (m2 / g)) Colloidal silicon oxide was pre-dried on a hot plate and then heat-treated at 800°C for 1 hour to prepare a sample for analysis. The prepared sample was then analyzed by nitrogen adsorption method (BET method).

[0022] (Average primary particle size (nm)) The true specific gravity of silica was set to 2.2. The value of 2727 / BET specific surface area (m2 / g) was converted from the BET specific surface area measurement value mentioned above and used as the average primary particle size (nm) of silica particles in colloidal silica.

[0023] The specific surface area reduction rate of the aforementioned silicon oxide particles during heat treatment under alkaline conditions is 15.0% or less. If the specific surface area reduction rate is greater than 15.0%, the alkali resistance of the protrusions decreases, and the surface irregularity of the silicon oxide particles under alkaline conditions is reduced, making it impossible to maintain grindability under alkaline conditions. The specific surface area reduction rate is preferably 14.5% or less, more preferably 14.3% or less. Furthermore, the lower limit of the specific surface area reduction rate is not particularly limited; approximately 0.1% is sufficient.

[0024] Furthermore, the reduction rate of the above-mentioned specific surface area was determined by the following measurement method. (Rate of decrease in specific surface area) 3-Ethoxypropylamine was added to 800g of colloidal silica to adjust the pH to 9.9-10.3. The colloidal silica was then placed in a flask equipped with a reflux tube and heated under reflux for 3 hours for alkali treatment. The pH of the alkali-treated colloidal silica was adjusted to 7.6-7.8, and the BET specific surface area was measured according to the method described above. The reduction rate of specific surface area was calculated using the following formula based on the BET specific surface area before and after alkali treatment. The rate of decrease in specific surface area (%) = (BET specific surface area before alkali treatment - BET specific surface area after alkali treatment) / BET specific surface area before alkali treatment × 100

[0025] The silicon oxide particles preferably have a true specific gravity of 1.95 or higher. A true specific gravity of 1.95 or higher further enhances the hardness of the silicon oxide particles and improves the abrasiveness of the colloidal silicon oxide. The true specific gravity of the silicon oxide particles is more preferably 2.00 or higher, and even more preferably 2.10 or higher. Furthermore, the aforementioned true specific gravity is preferably 2.20 or lower, and even more preferably 2.16 or lower.

[0026] The true specific gravity of the aforementioned silica particles can be determined by a liquid-phase substitution method using ethanol after drying colloidal silica on a hot plate at 150°C and holding it in a furnace at 300°C for 1 hour.

[0027] The aforementioned silicon oxide particles preferably contain at least one amine selected from the group consisting of primary, secondary, and tertiary amines. The amine is not particularly limited and is represented by the following general formula (X). NRaRbRc (X) (In the formula, Ra, Rb, and Rc represent alkyl groups with 1 to 12 carbon atoms that can be substituted, or hydrogen atoms. However, this excludes the case where Ra, Rb, and Rc are all hydrogen atoms, i.e., ammonia.) Ra, Rb, and Rc can be the same or different. Ra, Rb, and Rc can be any of the following: linear, branched, or cyclic.

[0028] The number of carbon atoms in the straight-chain or branched alkyl group can be 1 to 12, preferably 1 to 8, and more preferably 1 to 6. Examples of straight-chain alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, etc. Examples of branched alkyl groups 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. Preferably, straight-chain or branched alkyl groups include n-propyl, n-hexyl, 2-ethylhexyl, and n-octyl.

[0029] The cyclic alkyl group may have 3 to 12 carbon atoms, preferably 3 to 6. Examples of cyclic alkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Cyclohexyl is preferred.

[0030] In the general formula (X) above, Ra, Rb, and Rc, the alkyl group can be substituted. The number of substituents can be, for example, 0, 1, 2, 3, or 4, preferably 0, 1, or 2, and more preferably 0 or 1. Furthermore, an alkyl group with 0 substituents refers to an unsubstituted alkyl group. Examples of substituents include alkoxy groups with 1 to 3 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy), amino groups, primary amino groups substituted with a straight-chain alkyl group with 1 to 4 carbon atoms, amino groups disubstituted with a straight-chain alkyl group with 1 to 4 carbon atoms (e.g., dimethylamino, di-n-butylamino, etc.), and unsubstituted amino groups. However, hydroxyl groups are excluded as substituents. In alkyl groups having a plurality of substituents, the substituents can be the same or different.

[0031] In the above general formula (X), Ra, Rb, and Rc are linear or branched alkyl groups having 1 to 8 carbon atoms (preferably 1 to 6 carbon atoms). Furthermore, Ra, Rb, and Rc are linear or branched alkyl groups having 1 to 8 carbon atoms (preferably 1 to 6 carbon atoms) that can be substituted with an alkoxy group having 1 to 3 carbon atoms.

[0032] Furthermore, Ra, Rb, and Rc may also be unsubstituted. Preferably, Ra, Rb, and Rc are unsubstituted straight-chain or branched alkyl groups having 1 to 12 carbon atoms, or straight-chain or branched alkyl groups having 1 to 12 carbon atoms substituted with alkoxy groups.

[0033] As the aforementioned amine, examples include at least one amine selected from the group consisting of aliphatic ether amines such as 3-ethoxypropylamine, 2-methoxyethylamine, 2-2-ethoxyethylamine, 3-methoxypropylamine, 3-propoxypropylamine, 3-isopropoxypropylamine, 3-butoxypropylamine, 3-isobutoxypropylamine, 3-(2-ethylhexyloxy)propylamine, and 3-(2-methoxyethoxy)propylamine, as well as aliphatic amines such as pentylamine, hexylamine, dipropylamine, and triethylamine. Among these, from the viewpoint of further increasing the content of silicon oxide particles that exhibit excellent surface irregularity under alkaline conditions, aliphatic ether amines are preferred, and 3-ethoxypropylamine is more preferred.

[0034] The above-mentioned amines can be used alone or in combination of two or more.

[0035] The content of at least one amine selected from the group comprising primary, secondary, and tertiary amines (excluding hydroxyl groups as substituents) in the silica particles is preferably 5 μmol or more per 1 g of silica particles, more preferably 10 μmol or more per 1 g of silica particles. By setting the lower limit of the above-mentioned amine content within the above-mentioned range, the content of silica particles with excellent surface roughness maintenance under alkaline conditions in colloidal silica is further increased, and colloidal silica exhibits more sufficient abrasiveness. Furthermore, the above-mentioned amine content is preferably 100 μmol or less per 1 g of silica particles, more preferably 90 μmol or less per 1 g of silica particles. By setting the upper limit of the above-mentioned amine content within the above-mentioned range, silica particles with surface roughness become easier to generate.

[0036] Furthermore, the amine content mentioned above can be determined by the following method: After centrifuging colloidal silica at 215000G for 90 minutes, the supernatant is discarded, and the solid component is vacuum dried at 60°C for 90 minutes. 0.50 g of the obtained silica dry solids is weighed and placed in 50 ml of 1M sodium hydroxide aqueous solution. While stirring, the solution is heated at 50°C for 24 hours to dissolve the silica. The silica solution is then analyzed by ion chromatography to determine the amine content. The ion chromatography analysis is performed according to JIS K0127.

[0037] The boiling point of the aforementioned amine is preferably 85°C or higher, and more preferably 90°C or higher. By limiting the lower limit of the boiling point to the above range, vaporization during the reaction is further suppressed, making it suitable for use as a catalyst. Furthermore, the boiling point is preferably 500°C or lower, and more preferably 300°C or lower.

[0038] The colloidal silicon oxide of the present invention preferably comprises at least 20% silicon oxide particles with surface irregularities in any field of view observed by a scanning electron microscope at 200,000x magnification, and more preferably at least 30%. If the lower limit of the content of the aforementioned silicon oxide particles is within the above range, the grindability of the colloidal silicon oxide is further improved. The upper limit of the content is not particularly limited and may be 100% or 70%.

[0039] In this specification, the content of the aforementioned silicon oxide particles with uneven surface shapes can be determined by the following method: The particles with uneven surface shapes are counted from the number of particles observed by a scanning electron microscope (SEM) at any field of view magnified 200,000 times, and the proportion of these particles is taken as the content (%).

[0040] The SEM short axis of the silica particles in the colloidal silica is preferably 8 nm or more, and more preferably 15 nm or more. By setting the lower limit of the SEM short axis of the silica particles within the above range, the abrasiveness of the colloidal silica of the present invention is further improved. Furthermore, the SEM short axis of the silica particles is preferably 100 nm or less, and more preferably 80 nm or less. By setting the upper limit of the SEM short axis of the silica particles within the above range, damage to the workpiece is further reduced.

[0041] Furthermore, the aforementioned SEM minor axis can be determined using the following method: Images of silicon oxide particles taken by a scanning electron microscope are analyzed using image analysis software (WinRoof2015, manufactured by Mitani Corporation) to measure the elliptic approximation and minor axis of 1000 particles respectively. The frequency distribution of the number of minor axes is obtained, and the minor axis of the ellipse with the frequency of 50% is taken as the SEM minor axis (nm).

[0042] The average secondary particle size of the silica particles in the colloidal silica is preferably 8 nm or more, and more preferably 15 nm or more. By setting the lower limit of the average secondary particle size of the silica particles within the above range, the abrasiveness of the colloidal silica of the present invention is further improved. Furthermore, the average secondary particle size of the silica particles is preferably 400 nm or less, and more preferably 300 nm or less. By setting the upper limit of the average secondary particle size of the silica particles within the above range, damage to the workpiece is further reduced.

[0043] In this specification, the average secondary particle size of the silica particles in the aforementioned colloidal silica can be determined by the following method. Specifically, as a sample for dynamic light scattering, colloidal silica was prepared by adding it to a 0.3% by weight citric acid aqueous solution and homogenizing it. Using this sample, the secondary particle size was determined by dynamic light scattering (ELSZ-2000S, manufactured by Otsuka Electronics Co., Ltd.).

[0044] The aspect ratio of the silicon oxide particles in the colloidal silicon oxide is preferably 1.0 or higher, and more preferably 1.1 or higher. By setting the lower limit of the aspect ratio within the above range, the abrasiveness is further improved. Furthermore, the aspect ratio of the silicon oxide particles is preferably 4.0 or lower, and more preferably 3.0 or lower. By setting the lower limit of the aspect ratio within the above range, damage to the workpiece is further suppressed.

[0045] In this specification, the aspect ratio of the silicon oxide particles in the aforementioned colloidal silicon oxide can be determined by the following method. Specifically, images of the silicon oxide particles taken with a scanning electron microscope are analyzed using image analysis software (WinRoof2015, manufactured by Mitani Corporation) to measure the elliptic approximation, major axis, and minor axis of each of 1000 particles. The ratio of the major and minor axes of the ellipse (major axis / minor axis) of each particle is calculated, and the average value is taken as the aspect ratio.

[0046] The colloidal silicon oxide of the present invention preferably contains less than 1 ppm of metallic impurities such as sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt. Because the content of metallic impurities is less than 1 ppm, it can be suitable for use in grinding electronic materials and the like.

[0047] In this specification, the content of the aforementioned metallic impurities is the value determined using an atomic absorption spectrometer.

[0048] The association ratio of silicon oxide particles in the colloidal silicon oxide is preferably 1.5 or higher, and more preferably 1.7 or higher. By setting the lower limit of the silicon oxide particle association ratio within the above range, the abrasiveness of the colloidal silicon oxide of the present invention is further improved. Furthermore, the association ratio of silicon oxide particles is preferably 5.5 or lower, and more preferably 5.0 or lower. By setting the upper limit of the silicon oxide particle association ratio within the above range, damage to the workpiece is further reduced.

[0049] In this specification, the aggregation ratio of silica particles in the above-mentioned colloidal silica is obtained by calculating the average secondary particle size / average primary particle size of the silica particles in the colloidal silica.

[0050] The density of silanol groups in the colloidal silica particles is preferably 1.5 particles / nm² or more, and more preferably 1.6 particles / nm² or more. If the lower limit of the silanol group density is within the above range, damage to the workpiece is further reduced. Furthermore, the silanol density of the silica particles is preferably 5.0 particles / nm² or less, and more preferably 4.0 particles / nm² or less. If the upper limit of the silanol group density is within the above range, the abrasiveness of the colloidal silica of the present invention is further improved.

[0051] Furthermore, the silanol group density of silica particles in colloidal silica can be determined using the Sears method. The Sears method is performed with reference to the description in GWSears, Jr., “Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide”, Analytical Chemistry, 28(12), 1981 (1956). In the determination, a 1 wt% silica dispersion was titrated with a 0.1 mol / L sodium hydroxide aqueous solution, and the silanol group density was calculated based on the following formula. ρ = (a × f × 6022) ÷ (c × S) In the above formula, ρ: density of silanol groups (units / nm2), a: drop volume of 0.1mol / L sodium hydroxide aqueous solution at pH 4~9 (mL), f: factor of 0.1mol / L sodium hydroxide aqueous solution, c: mass of silicon oxide particles (g), and S: BET specific surface area (m2 / g).

[0052] 2. Manufacturing method of colloidal silicon oxide The present invention discloses a method for manufacturing colloidal silicon oxide, which comprises silicon oxide particles having an uneven surface, and includes the following steps in sequence. (1) Step 1: Preparing a mother liquor containing an alkaline catalyst and water; (2) Step 2, which involves adding alkoxysilane to the aforementioned mother liquor to prepare a seed particle dispersion; and (3) Step 3, in which water, alkaline catalyst, and alkoxysilane are added to the aforementioned seed particle dispersion. The aforementioned alkaline catalyst is selected from at least one amine selected from the group comprising primary, secondary, and tertiary amines (except for hydroxyl groups as substituents). In step 3 above, the molar ratio (s3 / c3) between the amount of alkoxysilane added s3 (mol) and the amount of alkaline catalyst added c3 (mol) is greater than 185 and less than 400.

[0053] (Step 1) Step 1 is the step of preparing a mother liquor containing an alkaline catalyst and water.

[0054] The alkaline catalyst is selected from at least one amine selected from the group comprising primary, secondary, and tertiary amines (excluding hydroxyl groups as substituents). As long as the amine is the same as that described in the above description of colloidal silicon oxide, it is acceptable to use it.

[0055] The amine content in the mother liquor is preferably 0.30 mmol / kg or more, and more preferably 0.50 mmol / kg or more. By keeping the lower limit of the amine content within this range, particle size becomes easier to control. Furthermore, the amine content in the mother liquor is preferably 20.0 mmol / kg or less, and more preferably 15.0 mmol / kg or less. By keeping the amine content within this range, gelation is less likely during the reaction.

[0056] The method for preparing the mother liquor is not particularly limited; it is sufficient to add an alkaline catalyst to water using conventional methods and stir.

[0057] The pH of the mother liquor is not specifically limited, but is preferably 9.5 or higher, and more preferably 10.0 or higher. By limiting the lower limit of the mother liquor pH to the above range, particle size is more easily controlled. Furthermore, the pH of the mother liquor is preferably 12.0 or lower, and more preferably 11.5 or lower. By limiting the upper limit of the mother liquor pH to the above range, the average secondary particle size of silica particles with uneven surface shapes is more easily controlled, and the aggregation of seed particles in the seed particle dispersion obtained in step 2 (described later) is suppressed, further improving the storage stability of colloidal silica.

[0058] (Step 2) Step 2 is the step of adding alkoxysilane to the above mother liquor to prepare a seed particle dispersion.

[0059] As alkoxysilanes, they are not specifically limited, and examples of alkoxysilanes represented by the following general formula (2) can be listed. Si(OR1)4 (2) (In the formula, R1 represents an alkyl group).

[0060] In the above general formula (2), R1 represents an alkyl group. R1 is not particularly limited as long as it is an alkyl group, but it is preferably a lower alkyl group having 1 to 8 carbon atoms, and more preferably a lower alkyl group having 1 to 4 carbon atoms. Specifically, examples of the above alkyl group include methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, etc. As an alkoxysilane represented by the above general formula (2), it is preferably a tetramethoxysilane (tetramethyl n-silate) with R1 being methyl, a tetraethoxysilane (tetraethyl n-silate) with R1 being ethyl, a tetraisopropoxysilane with R1 being isopropyl, more preferably a tetramethoxysilane with R1 being methyl, a tetraethoxysilane with R1 being ethyl, and even more preferably a tetramethoxysilane.

[0061] The alkoxysilane represented by the above general formula (2) can be a derivative. Examples of such derivatives include low-condensity condensates obtained by partially hydrolyzing the alkoxysilane represented by the above general formula (2).

[0062] The alkoxysilanes shown in the above general formula (2) can be used alone or in combination of two or more.

[0063] The amount of alkoxysilane represented by the above general formula (2) added to the particle dispersion is not particularly limited. The molar ratio (s2 / c1) of the amount of alkoxysilane added s2 (mol) in step 2 to the amount of alkaline catalyst c1 (mol) in the mother liquor is preferably 10 or more, more preferably 100 or more, and even more preferably 150 or more. By setting the lower limit of s2 / c1 to the above range, the content of silicon oxide particles in colloidal silicon oxide is further increased. Furthermore, s2 / c1 is preferably 8500 or less, more preferably 8000 or less. By setting the upper limit of s2 / c1 to the above range, gelation is difficult during the reaction.

[0064] In step 2, the addition time of the alkoxysilane is preferably 5 minutes or more, and more preferably 10 minutes or more. By limiting the addition time to the above range, gelation is less likely to occur during the reaction. Furthermore, the addition time of the alkoxysilane is preferably less than 1000 minutes, and more preferably less than 600 minutes. If the upper limit of the addition time is within the above range, productivity is further improved, and manufacturing costs can be further controlled.

[0065] The pH of the seed particle dispersion is preferably 8.5 or lower, and more preferably 8.0 or lower. By setting the upper limit of the pH of the seed particle dispersion within this range, it becomes easier to form silicon oxide particles with an uneven surface. Furthermore, the pH of the seed particle dispersion is preferably 4.5 or higher, and more preferably 4.9 or higher. By setting the lower limit of the pH of the seed particle dispersion within this range, gelation is further suppressed.

[0066] In step 2, the temperature of the seed particle dispersion is preferably 70°C or higher, and more preferably 75°C or higher. By limiting the temperature of the seed particle dispersion to the above range, gelation during the reaction is further suppressed. Furthermore, the temperature of the seed particle dispersion is preferably 95°C or lower, and more preferably 90°C or lower. By limiting the temperature of the seed particle dispersion to the above range, the vaporization of the alkoxysilane is further suppressed.

[0067] (Step 3) Step 3 involves adding water, an alkaline catalyst, and an alkoxysilane to the particle dispersion.

[0068] The alkaline catalyst is selected from at least one amine from the group comprising primary, secondary, and tertiary amines (excluding hydroxyl groups as substituents). As the amine, it may be the same as the amine described in the above description of colloidal silicon oxide. Furthermore, the alkaline catalyst used in step 3 may be the same as or different from the alkaline catalyst used in step 1.

[0069] In step 3, silica particles with an uneven surface are formed in colloidal silica. While the exact mechanism is not yet clear, it is presumed to be as follows: In step 3, the pH of the seed particle dispersion decreases due to the addition of alkoxysilanes. In the reaction that forms silica particles in step 3, under alkaline and higher pH conditions, it is believed that new seed particles will not be generated; instead, the alkoxysilanes are consumed through the simple growth of silica particles, and silica particles with an uneven surface cannot be formed. Conversely, if the pH gradually decreases and the seed particle dispersion becomes weakly alkaline, it is predicted that the condensation rate of the alkoxysilane hydrolysate increases, and the embryo, the precursor of the seed particles, becomes less likely to dissolve, thus new seed particles are formed. Furthermore, if the pH decreases to around neutral, it is believed that the seed particles generated in the weakly alkaline environment will combine with the seed particles already present from step 2, forming an uneven surface on the particle surface. Therefore, it is believed that the manufacturing method of the present invention can be used to manufacture colloidal silicon oxide with surface irregularities.

[0070] Due to the anticipated mechanism of action described above, in step 3, the pH of the particle dispersion is preferably decreased while being controlled at an appropriate pH from strongly alkaline to near neutral. Therefore, as the alkaline catalyst used in step 3, alkaline catalysts that maintain a high pH or whose pH decreases rapidly are not suitable; rather, alkaline catalysts with buffering capacity that gradually decrease while being controlled within an appropriate pH range are suitable.

[0071] Based on the above-described mechanism, since the pKa value, which represents the physical properties of an acid or base, is the central value of the buffer zone, it becomes the benchmark in step 3 for determining whether a substance possesses a buffering energy that gradually decreases while being controlled within an appropriate pH range. That is, the alkaline catalyst used in step 3 is preferably an amine represented by the above general formula (X) with a pKa value of 8.5 or higher and less than 11, and more preferably an amine represented by the above general formula (X) with a pKa value of 9 or higher and less than 10.

[0072] Furthermore, as amines represented by the above general formula (X) and their pKa values, among aliphatic ether amines, 3-ethoxypropylamine (9.79), 2-methoxyethylamine (9.89), 3-methoxypropylamine (9.73), 3-propoxypropylamine (9.78), 3-isopropoxypropylamine (9.82), and 3-butoxypropylamine (9.77). Also, among aliphatic amines, pentylamine (10.63), hexylamine (10.56), dipropylamine (10.91), and triethylamine (10.75).

[0073] The alkoxysilane used in step 3 is not particularly limited and may be the same as that described in step 2 above. The alkoxysilane used in step 3 may be the same as or different from that used in step 2, but it is preferred to be the same as that used in step 2.

[0074] In step 3, the molar ratio (s3 / c3) of the amount of alkoxysilane added (s3, mol) to the amount of alkaline catalyst added (c3, mol) is greater than 185. Because the lower limit of s3 / c3 is greater than 185, it becomes easier to form a surface irregularity. Preferably, s3 / c3 is 200 or higher, more preferably 220 or higher. Furthermore, the aforementioned s3 / c3 is 400 or lower. Because s3 / c3 is 400 or lower, gelation of colloidal silica is further suppressed. Preferably, s3 / c3 is 380 or lower, more preferably 350 or lower.

[0075] In step 3, in addition to the water, alkaline catalyst and alkoxysilane mentioned above, alcohol may also be added to the particle dispersion.

[0076] The alcohol is not particularly limited as long as it is soluble in water, but it is preferred to be the same alcohol as the alcohol produced as a byproduct of the hydrolysis of the alkoxysilane. For example, methanol is preferred when the alkoxysilane is tetramethyl n-silate, and ethanol is preferred when the alkoxysilane is tetraethyl n-silate.

[0077] In step 3, relative to 100% by mass of the mixture of the mixed seed particle dispersion, water, alkaline catalyst, and alcohol, the alcohol content is preferably 25% by mass or less, and more preferably 20% by mass or less. By setting the upper limit of the alcohol content to the above range, it becomes easier to raise the temperature of the mixture in step 3. Furthermore, the lower limit of the alcohol content is not particularly limited and can be 0% by mass or 2% by mass.

[0078] The amount of alkoxysilane added in step 3 is not specifically limited. The molar ratio (s3 / sp3) between the amount of alkoxysilane added (s3, mol) in step 3 and the amount of seed particles (sp3, mol) in the mixture of seed particle dispersion, water, alkaline catalyst, and alcohol is preferably 0 or higher and 30 or lower. By limiting the s3 / sp3 ratio to this range, it is difficult for new nuclei to form during the reaction, thus further promoting the growth of the host particle. Furthermore, the above molar ratio is defined with the molecular weight of the seed particles set at 60.08 g / mol.

[0079] The temperature of the mixture in step 3 is preferably above 70°C, and more preferably above 75°C. By setting the lower limit of the mixture temperature within this range, gelation during the reaction is further suppressed. Furthermore, the temperature of the mixture is preferably below 95°C, and more preferably below 90°C. By setting the upper limit of the temperature of the seed particle dispersion within this range, the vaporization of the alkoxysilane is further suppressed.

[0080] In step 3, the addition time of the alkoxysilane is preferably 5 minutes or more, and more preferably 10 minutes or more. By limiting the addition time to the above range, gelation is less likely to occur during the reaction. Furthermore, the addition time of the alkoxysilane is preferably less than 1000 minutes, and more preferably less than 600 minutes. If the upper limit of the addition time is within the above range, productivity is further improved, and manufacturing costs can be further controlled.

[0081] The colloidal silicon oxide of the present invention can be manufactured using the manufacturing method described above.

[0082] The pH of colloidal silica is preferably below 11.0, and more preferably below 10.0. By maintaining the upper limit of the pH in this range, the dissolution of silica particles is further inhibited. Furthermore, the pH of colloidal silica is preferably above 5.8, and more preferably above 6.0. By maintaining the lower limit of the pH in this range, gelation is further inhibited.

[0083] The method for manufacturing colloidal silicon oxide of the present invention may further include a step of concentrating the colloidal silicon oxide after step 3 described above. The concentration method is not particularly limited and can be carried out using conventionally known methods. Examples of such concentration methods include, for instance, concentration by heating at a temperature of approximately 65 to 100°C.

[0084] The concentration of silica particles in the concentrated colloidal silica is not particularly limited, but it is preferably about 1 to 50% by mass when the colloidal silica is 100% by mass.

[0085] The method for manufacturing colloidal silica of the present invention, after step 3 described above, may further include a step of externally distilling away the methanol byproduct produced during the reaction. The method for externally distilling away the methanol is not particularly limited; examples include heating the colloidal silica while dripping pure water to maintain a constant volume, thereby replacing the dispersion medium with pure water. Another example is redispersing the colloidal silica in water after separating it from the solvent through precipitation, separation, centrifugation, etc.

[0086] The colloidal silicon oxide of the present invention, and the colloidal silicon oxide manufactured by the manufacturing method of the present invention, can be used in various applications such as abrasives and paper coating agents. Abrasives containing the above-mentioned colloidal silicon oxide are also part of the present invention. The colloidal silicon oxide of the present invention is of high purity because it can reduce the content of metallic impurities such as sodium to less than 1 ppm, making it particularly suitable for use as an abrasive in the chemical mechanical polishing of semiconductor wafers. [Example]

[0087] The present invention will be specifically described below by disclosing embodiments, etc., but the present invention is not limited to the embodiments.

[0088] Example 1 (Step 1) In a flask, add 6767g of pure water as a solvent and 6.98g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst to prepare a mother liquor. The pH of the mother liquor is 11.0. (Step 2) After heating the mother liquor to an internal temperature of 80°C, the temperature of 2472g of tetramethyl orthosilicate was adjusted in the mother liquor without changing the internal temperature, and the drop was carried out at a constant rate for 210 minutes to prepare a seed particle dispersion. (Step 3) In a flask, add 5704 g of pure water as a solvent, 6.50 g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst, and 1075 g of the seed particle dispersion prepared in Step 2. Then, heat to an internal temperature of 80°C, and adjust the temperature of 2397 g of tetramethyl orthosilicate while maintaining a constant internal temperature, allowing for a constant-rate dropwise addition over 180 minutes. After the dropwise addition is complete, maintain stirring for 15 minutes to prepare a colloidal silica dispersion. Next, at atmospheric pressure, use 800 mL of the colloidal silica dispersion as a baseline and concentrate by heating until the silica concentration reaches 20 wt%. Then, to remove the methanol byproduct of the reaction through external distillation, while maintaining a constant volume, use 500 mL of pure water instead of the dispersion medium to prepare colloidal silica.

[0089] Furthermore, in Example 1, the molar ratio (s3 / c3) of the amount of alkoxysilane (tetramethyl orthosilicate) added in step 3 to the amount of alkaline catalyst (3-ethoxypropylamine) added is 250.

[0090] Example 2 (Step 1) In a flask, add 6767g of pure water as a solvent and 10.47g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst to prepare a mother liquor. The pH of the mother liquor is 11.3. (Step 2) After heating the mother liquor to an internal temperature of 85°C, the temperature of 2472g of tetramethyl orthosilicate was adjusted in the mother liquor without changing the internal temperature, and the drop was carried out at a constant rate for 210 minutes to prepare a seed particle dispersion. (Step 3) In a flask, add 5704g of pure water as a solvent, 6.50g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst, 242g of methanol, and 667g of the seed particle dispersion prepared in Step 2. Then, heat to an internal temperature of 80°C, and adjust the temperature of 2397g of tetramethyl orthosilicate while maintaining a constant internal temperature, allowing for a constant-rate dropwise addition over 180 minutes. After the dropwise addition is complete, maintain stirring for 15 minutes to prepare a colloidal silica dispersion. Next, at atmospheric pressure, use 9000mL of the colloidal silica dispersion as a baseline and heat to concentrate until the silica concentration reaches 20wt%. Then, to remove the methanol byproduct of the reaction through external distillation, while maintaining a constant volume, replace the dispersion medium with 5680mL of pure water to prepare colloidal silica.

[0091] Furthermore, in Example 2, the molar ratio (s3 / c3) of the amount of alkoxysilane (tetramethyl orthosilicate) added in step 3 to the amount of alkaline catalyst (3-ethoxypropylamine) added is 250.

[0092] Comparative Example 1 (Step 1) In a flask, add 7500g of pure water as a solvent and 1.35g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst to prepare a mother liquor. The pH of the mother liquor is 10.3. (Step 2) After heating the mother liquor to an internal temperature of 85°C, the temperature of 2740g of tetramethyl orthosilicate was adjusted in the mother liquor without changing the internal temperature, and the mixture was dropped at a constant rate for 60 minutes and stirred for 15 minutes to prepare a seed particle dispersion. (Step 3) Add 50g of 3-ethoxypropylamine (3-EOPA) to the seed particle dispersion as an alkaline catalyst to prepare a mixture. In another flask, add 5379g of pure water as a solvent, and add 2382g of the above mixture of 3-ethoxypropylamine and seed particle dispersion. Then, heat to an internal temperature of 80°C, and adjust the temperature by adding 1712.5g of tetramethyl orthosilicate at a constant rate over 180 minutes without changing the internal temperature. After the addition is complete, maintain stirring for 15 minutes to prepare a colloidal silica dispersion. Next, at atmospheric pressure, take 800mL of the colloidal silica dispersion as a base volume and heat to concentrate until the silica concentration reaches 20wt%. Then, in order to remove the methanol byproduct produced during the reaction by external distillation, while maintaining a constant volume, use 500mL of pure water to replace the dispersion medium to prepare colloidal silica. No surface irregularities were formed in the obtained particles.

[0093] Furthermore, in Comparative Example 1, the molar ratio (s3 / c3) of the amount of alkoxysilane (tetramethyl orthosilicate) added in step 3 to the amount of alkaline catalyst (3-ethoxypropylamine) added was 100.

[0094] Comparative Example 2 (Step 1) In a flask, add 9492g of pure water as a solvent and 3.28g of triethanolamine (TEA) as an alkaline catalyst to prepare a mother liquor. The pH of the mother liquor is 9.4. (Step 2) After heating the mother liquor to an internal temperature of 80°C, the temperature of 1704g of tetramethyl silicate was adjusted in the mother liquor while maintaining a constant internal temperature, and the mixture was dropped at a constant rate over a period of 180 minutes. After the supply of tetramethyl silicate to the reaction vessel was completed, the reaction liquid in the reaction vessel was heated to distill methanol from the distillation tube with a capacitor, and the reaction liquid prepared under the same conditions was fed into the reaction vessel for concentration to prepare a seed particle dispersion with a silica concentration of 12.2wt%. (Step 3) In a flask, 5582 g of pure water as a solvent, 9.43 g of triethanolamine (TEA) as an alkaline catalyst, and 857 g of the seed particle dispersion prepared in Step 2 were added. Next, the mixture was heated to an internal temperature of 80°C, and the temperature of 3878 g of tetramethyl orthosilicate was adjusted while maintaining a constant internal temperature, with a constant-rate dropwise addition over 180 minutes. After the dropwise addition was completed, stirring was maintained for 15 minutes to prepare a colloidal silica dispersion. Then, under normal pressure, 4500 mL of the colloidal silica dispersion was used as a baseline and heated to concentrate until the silica concentration reached 20 wt%. Next, to remove the methanol byproduct of the reaction through external distillation, while maintaining a constant volume, 5680 mL of pure water was used instead of the dispersion medium to prepare colloidal silica.

[0095] Furthermore, in Comparative Example 2, the molar ratio (s3 / c3) of the amount of alkoxysilane (tetramethyl orthosilicate) added in step 3 to the amount of alkaline catalyst (triethanolamine) added (s3 / c3) was 403.

[0096] The properties of the colloidal silicon oxides of the embodiments and comparative examples obtained as described above were evaluated by the following methods.

[0097] (Alkyl group content (ppm)) After centrifuging the colloidal silica at 215,000 G for 90 minutes, the supernatant was discarded, and the solid component was vacuum dried at 60°C for 90 minutes. 0.50 g of the resulting dried silica was weighed and placed in 50 ml of 1M sodium hydroxide aqueous solution. The solution was heated at 50°C for 24 hours with stirring to dissolve the silica. The silica solution was analyzed by gas chromatography to determine the alcohol content, which was used as the alkoxy group content. A flame ionization detector (FID) was used for the gas chromatography. The gas chromatography analysis was performed in accordance with JIS K0114.

[0098] (BET specific surface area (m2 / g)) The sample for measurement was prepared by pre-drying colloidal silicon oxide on a hot plate and then heat-treating it at 800°C for 1 hour. The BET specific surface area was determined using the prepared sample by the nitrogen adsorption method (BET method). Nitrogen adsorption method Pretreatment unit: BELPREP-vacII (manufactured by MicrotracBEL Corporation) Pretreatment method: Vacuum degassing at 120℃ for 8 hours. Measuring apparatus: BELSORP-miniII (manufactured by MicrotracBEL Corporation) Measurement method: The adsorption isotherm caused by nitrogen was measured using the constant volume method. Measurement conditions: Adsorption temperature 77 K; adsorbate nitrogen; measured saturated vapor pressure; adsorbate profile 0.162 nm²; equilibrium waiting time (the waiting time after reaching adsorption equilibrium (the pressure change at the moment of adsorption-desorption becomes below a specified value) 500 sec The specific surface area is calculated using the BET method based on the measurement results.

[0099] (Average primary particle size (nm)) The true specific gravity of silica was set to 2.2. The value of 2727 / BET specific surface area (m2 / g) was converted from the BET specific surface area measurement value mentioned above and used as the average primary particle size (nm) of silica particles in colloidal silica.

[0100] (Average secondary particle size) As a sample for dynamic light scattering, colloidal silicon oxide was added to a 0.3% by weight citric acid aqueous solution and homogenized. Using this sample, the average secondary particle size was determined by dynamic light scattering (ELSZ-2000S, manufactured by Otsuka Electronics Co., Ltd.).

[0101] (Rate of decrease in specific surface area) 3-Ethoxypropylamine was added to 800g of colloidal silica to adjust the pH to 9.9-10.3. The colloidal silica was then placed in a flask equipped with a reflux tube and heated under reflux for 3 hours for alkali treatment. The pH of the alkali-treated colloidal silica was adjusted to 7.6-7.8, and the BET specific surface area was measured according to the method described above. Based on the BET specific surface area before and after alkali treatment, the reduction rate of specific surface area was calculated using the following formula. The rate of decrease in specific surface area (%) = (BET specific surface area before alkali treatment - BET specific surface area after alkali treatment) / BET specific surface area before alkali treatment × 100

[0102] (Short axis of SEM) Images of silicon oxide particles taken by scanning electron microscopy were analyzed using image analysis software (WinRoof2015, manufactured by Mitani Corporation) to measure the minor axis of 1000 elliptical approximation particles. The frequency distribution of the number of minor axes was obtained, and the minor axis with the frequency of 50% was taken as the SEM minor axis (nm).

[0103] Aspect Ratio Images of silicon oxide particles taken by a scanning electron microscope were analyzed using image analysis software (WinRoof2015, manufactured by Mitani Corporation) to measure the major and minor axes of ellipses for 1000 elliptical approximate particles. The ratio of the major to minor axis of the ellipse (major axis / minor axis) of each particle was calculated, and the average value was used as the aspect ratio.

[0104] (Surface roughness) Divide the BET specific surface area (B1) by the specific surface area (S1) calculated from the SEM minor axis, and use the calculated (B1 / S1) as the surface roughness. In addition, the specific surface area (S1) is obtained by setting the true specific gravity of silicon oxide to 2.2 and converting it to the value of 2727 / SEM minor axis (nm).

[0105] (True specific gravity) After the sample is dried on a hot plate at 150°C, it is kept in an oven at 300°C for 1 hour. The true specific gravity is then determined by a liquid-phase substitution method using ethanol.

[0106] (Amine content) After centrifuging the colloidal silica at 215,000 G for 90 minutes, the supernatant was discarded, and the solid component was vacuum dried at 60°C for 90 minutes. 0.50 g of the resulting dried silica was weighed and placed in 50 ml of 1 M sodium hydroxide aqueous solution. The solution was heated at 50°C for 24 hours with stirring to dissolve the silica. The silica solution was analyzed by ion chromatography to determine the amine content. The ion chromatography analysis was performed according to JIS K0127.

[0107] (Silanol group density) The silanol density of silicon oxide particles can be determined by the Syres method. The Syres method is performed according to the description in GWSears, Jr., “Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide”, Analytical Chemistry, 28(12), 1981(1956). In the determination, a 1 wt% silicon oxide dispersion was titrated with a 0.1 mol / L sodium hydroxide aqueous solution, and the silanol density was calculated based on the following formula. ρ = (a × f × 6022) ÷ (c × S) In the above formula, ρ: density of silanol groups (units / nm2), a: drop volume of 0.1mol / L sodium hydroxide aqueous solution at pH 4~9 (mL), f: factor of 0.1mol / L sodium hydroxide aqueous solution, c: mass of silicon oxide particles (g), and S: BET specific surface area (m2 / g).

[0108] (Content of metallic impurities) The content of metallic impurities was determined using an atomic absorption spectrometer. The total content of sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt in colloidal silicon oxide was taken as the content of metallic impurities.

[0109] [Table 1] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Alkyl group content (ppm) 18109 7281 10569 8692 Average primary particle size (nm) 28.0 26.8 22.1 28.7 Reduction rate of specific surface area (%) 8.1 14.3 2.9 15.2 Alkali catalyst 3-EOPA 3-EOPA 3-EOPA TEA s3 / c3 (The amount of alkoxysilane added in step 3 is s3 (mol)) / Amount of alkaline catalyst added in step 3, c3 (mol) 250 250 100 403 s2 / c1 (The amount of alkoxysilane added in step 2 is s2 (mol)) The amount of alkaline catalyst in step 2 is c1 (mol). 240 160 1376 509 SEM short axis (nm) 39 42 twenty two 45 Aspect Ratio 1.2 1.3 1.4 1.3 Surface roughness 1.4 1.6 1.0 1.6 True specific gravity 2.11 2.11 2.15 2.07 Amine content (μmol / g) 58.2 58.2 54.3 ※1 Average secondary particle size (nm) 44.6 52.8 38.6 50.9 Aggregation ratio (Average secondary particle size / Average primary particle size) 1.6 2.0 1.7 1.8 Silane alcohol group density (units / nm2) 2.5 2.6 1.7 3.5 Silicon oxide particles with uneven surface shapes Content (%) 91 100 0 79 Content of metallic impurities (ppm) 0.02 0.1 0.03 0.1

[0110] ※1: In Comparative Example 2, no amine content was detected because no amine selected from the group containing primary amines, secondary amines and tertiary amines (but, as a substituent, hydroxyl groups were excluded).

Claims

1. A colloidal silicon oxide, comprising silicon oxide particles, characterized in that: (1) the content of metallic impurities in the colloidal silicon oxide, as determined by atomic absorption spectrometry, is less than 1 ppm, wherein the metallic impurities are sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, or cobalt; (2) the surface roughness (B1 / S1) of the silicon oxide particles is 1.1 or more, which is calculated by dividing the BET specific surface area (B1) determined by the BET specific surface area determination method described below by the specific surface area (S1) calculated by the minor axis of the SEM described below; (3) the reduction rate of the specific surface area of ​​the silicon oxide particles, as determined by the following method, is less than 15.0% when the particles are heated under alkaline conditions; (method for determining the reduction rate of specific surface area) Add 3-ethoxypropylamine to 800g of colloidal silica to adjust the pH to 9.9–10.3; place the colloidal silica in a flask equipped with a reflux tube and heat it, maintaining reflux for 3 hours for alkali treatment; adjust the pH of the alkali-treated colloidal silica to 7.6–7.8, and measure the BET specific surface area according to the following method; calculate the reduction rate of specific surface area based on the BET specific surface area before and after alkali treatment using the following formula: Reduction rate of specific surface area (%) = (BET specific surface area before alkali treatment - BET specific surface area after alkali treatment) / BET specific surface area before alkali treatment × 100 (Method for determining BET specific surface area). After pre-drying the colloidal silica on a hot plate, heat-treat it at 800°C for 1 hour to prepare a sample for testing; measure the prepared sample using the nitrogen adsorption method (BET method). (Method for determining specific surface area (S1) calculated from SEM minor axis) Images of silicon oxide particles taken by scanning electron microscopes were analyzed using image analysis software (WinRoof2015 manufactured by Mitani Corporation) to measure the elliptic approximation and minor axis of ellipse for 1000 particles respectively; the frequency distribution of the number of minor axes of ellipse was obtained, and the minor axis of ellipse with the frequency of 50% was taken as the SEM minor axis (nm); by setting the true specific gravity of silicon oxide to 2.2, the value of 2727 / SEM minor axis (nm) was converted to obtain the specific surface area (S1) calculated from the SEM minor axis.

Images