Colloidal silica and method for producing the same

Abstract

The present invention aims to provide a colloidal silica containing silica particles having a proper true specific gravity, a high aggregation ratio, and a high alkoxyl group content at a high purity, and a production method capable of easily producing the colloidal silica and reducing the production cost. The present invention relates to a colloidal silica characterized in that the silica particles contained in the above colloidal silica have an average primary particle diameter of 33 nm or more, an aggregation ratio of 1.2 or more, a true specific gravity of 1.95 or more, contain 1000 mass ppm or more of an alkoxyl group per 1 g of the silica particles, have a proportion of the number of silica particles having a circular equivalent diameter of less than 20 nm of less than 15%, and contain 5 μmol or more of a primary amine per 1 g of the silica particles.

Description

[0001] This application is a divisional application of the same patent application, filed on February 26, 2020, with application number 202080018899.3. Technical Field

[0002] This invention relates to colloidal silica and its manufacturing method, and particularly to colloidal silica containing silica particles with an average primary particle size of 33 nm or more, an aggregation ratio of 1.2 or more, a true specific gravity of 1.95 or more, and containing alkoxy groups, and its manufacturing method. Background Technology

[0003] Colloidal silica is formed by dispersing silica particles in a medium such as water. Besides its use 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 colloidal silica used in these applications, high specific gravity and high aggregation of the silica particles are required.

[0004] As a method for manufacturing colloidal silica that can meet the above requirements, for example, a method is disclosed in which a hydrolysate obtained by hydrolyzing alkoxysilane is added to a mother liquor containing an alkaline catalyst or the like (for example, see Patent Document 1).

[0005] However, according to the manufacturing method described in Patent Document 1, after preparing a hydrolysate obtained by temporarily hydrolyzing an alkoxysilane, adding the hydrolysate to the mother liquor can produce particles with high true specific gravity and density. However, due to the excessively high true specific gravity, there is a problem of increased surface defects (such as scratches) on the substrate or other material being ground. In addition, the manufacturing process becomes lengthy and multi-stage, resulting in complexity and high cost.

[0006] In addition, a method for manufacturing colloidal silica is disclosed that involves adding alkoxysilanes to a mother liquor without hydrolysis (for example, see Patent Document 2).

[0007] However, Patent Document 2 does not describe a method for manufacturing silica particles with high aggregation ratio and high true specific gravity. The colloidal silica obtained by the manufacturing method described in Patent Document 2 is difficult to achieve high abrasiveness, and there is room for further exploration regarding the improvement of abrasiveness.

[0008] Therefore, it is desirable to develop colloidal silica with excellent abrasive properties, and it is desirable to develop a manufacturing method that can easily produce the colloidal silica and reduce manufacturing costs.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: International Publication No. 2010 / 035613

[0012] Patent Document 2: Japanese Patent Application Publication No. 2016-008157 Summary of the Invention

[0013] The technical problem that the invention aims to solve

[0014] The object of the present invention is to provide a colloidal silica containing silica particles comprising alkoxy groups and having an appropriate true gravity, and a manufacturing method that enables the colloidal silica to be easily manufactured and reduces manufacturing costs.

[0015] Technical solutions for solving technical problems

[0016] To achieve the above objectives, the inventors of this invention conducted repeated and meticulous research, and as a result discovered that the following colloidal silica can achieve the above objectives, thereby completing this invention. The colloidal silica contains silica particles with an average primary particle size of 33 nm or more, an aggregation ratio of 1.2 or more, a true specific gravity of 1.95 or more, containing 1000 ppm or more of alkoxy groups per 1g of silica particles, having a proportion of silica particles with a spherical equivalent diameter of less than 20 nm of less than 15%, and containing 5 μmol or more of primary amines per 1g of silica particles.

[0017] The following are representative examples of the present invention.

[0018] Item 1. A colloidal silica, wherein,

[0019] The colloidal silica contained in the above-mentioned silica particles has an average primary particle size of 33 nm or more, an aggregation ratio of 1.2 or more, and a true specific gravity of 1.95 or more.

[0020] Each 1g of silica particles contains more than 1000 ppm of alkoxy groups by mass.

[0021] The proportion of silica particles with a spherical equivalent diameter of less than 20 nm is less than 15%.

[0022] Each 1g of silica particles contains more than 5μmol of primary amine.

[0023] Item 2. According to the colloidal silica described in Item 1, wherein,

[0024] The true specific gravity of the aforementioned silica particles is between 1.95 and 2.20.

[0025] Item 3. Colloidal silica as described in Item 1 or 2, wherein,

[0026] The surface of the aforementioned silica particles has organic functional groups represented by the following general formula (1).

[0027] -(CH2) n -R 3 (1)

[0028] (In equation (1), n ​​represents any integer greater than or equal to 0, R) 3 (Indicates any functional group.) Item 4. According to the colloidal silicon dioxide described in any one of items 1 to 3, wherein,

[0029] The surface of the aforementioned silica particles has cationic organic functional groups.

[0030] Item 5. According to the colloidal silica described in Item 4, wherein,

[0031] The surface of the aforementioned silica particles contains amino groups.

[0032] Item 6. Colloidal silica as described in any one of items 1 to 3, wherein,

[0033] The surface of the aforementioned silica particles has anionic organic functional groups.

[0034] Item 7. According to the colloidal silica described in Item 6, wherein,

[0035] The surface of the aforementioned silica particles contains sulfonyl groups.

[0036] Item 8. A method for manufacturing colloidal silica, comprising, in sequence:

[0037] (1) Step 1: Preparation of mother liquor containing alkaline catalyst and water;

[0038] (2) Step 2: Adding alkoxysilane to the above mother liquor to prepare a mixture;

[0039] (3) Step 3, which involves adding an alkaline catalyst to the above mixture to prepare a seed particle dispersion; and

[0040] (4) Step 4, in which water and organic solvent are added to the above-mentioned particle dispersion, followed by the addition of alkoxysilane.

[0041] The above-mentioned alkaline catalyst is a primary amine.

[0042] Item 9. According to the manufacturing method described in Item 8, wherein,

[0043] Between steps 3 and 4 mentioned above, there is step 3.5.

[0044] (3.5) Add water to the seed particle dispersion obtained in step 3, and then add alkoxysilane to prepare the seed particle dispersion.

[0045] Invention Effects

[0046] The colloidal silica of the present invention contains silica particles with an average primary particle size of 33 nm or more, a high aggregation ratio, a suitable true specific gravity, and a high alkoxy content. The proportion of silica particles with a spherical equivalent diameter of less than 20 nm is less than 15%, and it contains primary amines. Therefore, when used as an abrasive, it can exhibit high grinding speed and low defect rate. In addition, the method for manufacturing the colloidal silica of the present invention allows for easy production of this colloidal silica and reduces manufacturing costs. Attached Figure Description

[0047] Figure 1 This is a graph showing the measurement results of the zeta potential of colloidal silica obtained in Examples 1, 6 and 7.

[0048] Figure 2 This is a graph showing the XPS analysis results of the colloidal silica obtained in Example 6.

[0049] Figure 3 This is a graph showing the XPS analysis results of the colloidal silica obtained in Example 7. Detailed Implementation

[0050] The colloidal silica and its manufacturing method of the present invention will be described in detail below.

[0051] In the colloidal silica of the present invention, the silica particles have an average primary particle size of 33 nm or more, an aggregation ratio of 1.2 or more, a true specific gravity of 1.95 or more, and the proportion of silica particles with a spherical equivalent diameter of less than 20 nm is less than 15%, thus exhibiting excellent abrasiveness. Furthermore, the colloidal silica of the present invention has a high alkoxy content in its silica particles, thereby reducing surface defects (e.g., scratches) on substrates and the like that being abraded. Additionally, the colloidal silica of the present invention may also contain irregularly shaped silica particles.

[0052] Furthermore, in the manufacturing method of the present invention, a mother liquor containing an alkaline catalyst and water is prepared in step 1, and an alkoxysilane is added to the mother liquor in step 2 to prepare a mixed liquid. Therefore, it is not necessary to hydrolyze the alkoxysilane to temporarily prepare an aqueous silicic acid solution and then add that liquid to the mother liquor. Thus, it is possible to easily manufacture colloidal silica containing silica particles with a high aggregation ratio, appropriate true specific gravity, high alkoxy content, containing primary amines, and a proportion of silica particles with a spherical equivalent diameter of less than 20 nm of less than 15%. Moreover, the manufacturing method of the present invention has fewer steps, thus reducing manufacturing costs. Furthermore, in the manufacturing method of the present invention, alkoxysilane is added to the mother liquor containing an alkaline catalyst and water obtained in step 1 in step 2, and then an alkaline catalyst is further added in step 3 to prepare seed particles. Therefore, the seed particles are easily deformed. The seed particles are grown in step 4. Therefore, it is possible to easily manufacture colloidal silica containing silica particles with high purity and excellent grindability. The silica particles have an average primary particle size of 33 nm or more, an aggregation ratio of 1.2 or more, a true specific gravity of 1.95 or more, contain alkoxy groups of 1000 ppm by mass or more per 1g of silica particles, the proportion of silica particles with a spherical equivalent diameter of less than 20 nm is less than 15%, and contain 5 μmol or more of primary amine per 1g of silica particles.

[0053] 1. Colloidal silica

[0054] The colloidal silica of the present invention is characterized in that it comprises silica particles having an average primary particle size of 33 nm or more, an aggregation ratio of 1.2 or more, a true specific gravity of 1.95 or more, containing 1000 ppm or more alkoxy groups per 1g of silica particles, having a proportion of silica particles with a spherical equivalent diameter of less than 20 nm of less than 15%, and containing 5 μmol or more of a primary amine per 1g of silica particles.

[0055] The average primary particle size of the silica particles in the colloidal silica is preferably 33 nm or more, more preferably 38 nm or more. If the lower limit of the average primary particle size of the silica particles is within the above range, the abrasiveness of the colloidal silica of the present invention is further improved. In addition, the average primary particle size of the silica particles is preferably 200 nm or less, more preferably 100 nm or less. If the upper limit of the average primary particle size of the silica particles is within the above range, the occurrence of damage to the workpiece can be further reduced.

[0056] In this specification, the average primary particle size of the silica particles in the colloidal silica described above can be determined by the following method. Specifically, the colloidal silica is pre-dried on a hot plate and then heat-treated at 800°C for 1 hour to prepare a sample for testing. The BET specific surface area is then measured using the prepared sample. The true specific gravity of silica is set to 2.2, and the conversion is 2727 / BET specific surface area (m²). 2 The value of ( / g) is used as the average primary particle size (nm) of silica particles in colloidal silica.

[0057] The average secondary particle size of the silica particles in the colloidal silica is preferably 40 nm or more, more preferably 50 nm or more, and even more preferably 60 nm or more. If the lower limit of the average secondary particle size of the silica particles is 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, more preferably 300 nm or less. By ensuring that the upper limit of the average secondary particle size of the silica particles is within the above range, damage to the workpiece can be further reduced.

[0058] In this specification, the average secondary particle size of the silica particles in the colloidal silica described above can be determined by the following method. Specifically, a sample is prepared by adding colloidal silica to a 0.3% by weight citric acid aqueous solution and homogenizing it, as a sample for dynamic light scattering. Using this sample, the secondary particle size is determined by dynamic light scattering (ELSZ-2000S manufactured by Otsuka Electronics Co., Ltd.).

[0059] The aggregation ratio of silica particles in the colloidal silica is preferably 1.2 or more, more preferably 1.4 or more, even more preferably 1.5 or more, and particularly preferably 1.8 or more. If the lower limit of the aggregation ratio of silica particles is within the above range, the abrasiveness of the colloidal silica of the present invention is further improved. Furthermore, the aggregation ratio of silica particles is preferably 5.5 or less, more preferably 5.0 or less. If the upper limit of the aggregation ratio of silica particles is within the above range, the occurrence of damage to the workpiece is further reduced.

[0060] In this specification, the aggregation ratio of silica particles in the colloidal silica is a value obtained by calculating the average secondary particle size / average primary particle size of the silica particles in the colloidal silica.

[0061] The amount of alkoxy groups contained in the silica particles is preferably 1000 ppm by mass or more, more preferably 2500 ppm by mass or more, and even more preferably 4000 ppm by mass or more per 1g of silica particles. If the lower limit of the alkoxy group content is within the above range, the occurrence of damage to the workpiece is further reduced. In addition, the amount of alkoxy groups contained in the silica particles is preferably 15000 ppm by mass or less, more preferably 12000 ppm by mass or less, and even more preferably 10000 ppm by mass or less. If the upper limit of the alkoxy group content is within the above range, the abrasiveness of the colloidal silica of the present invention is further improved.

[0062] The alkoxy content was determined as follows: Colloidal silica was centrifuged at 215000 G for 90 minutes, the supernatant was discarded, and the solid component was vacuum dried at 60°C for 90 minutes. 0.5 g of the dried silica was weighed and added to 50 ml of 1M sodium hydroxide aqueous solution. The solution was heated at 50°C for 24 hours while stirring to dissolve the silica. The dissolved silica was analyzed by gas chromatography to determine the alcohol content, which was then used as the alkoxy content. A flame ionization detector (FID) was used for the gas chromatography. Gas chromatographic analysis was performed according to JIS K0114.

[0063] The proportion of silica particles with a spherical equivalent diameter of less than 20 nm in the colloidal silica of the present invention is preferably less than 15% of the total number of silica particles, more preferably less than 10%. If the upper limit of the proportion of silica particles with a spherical equivalent diameter of less than 20 nm is within the above range, the number of small particles is reduced, and the abrasiveness of the colloidal silica of the present invention is further improved.

[0064] The proportion of silica particles with a spherical equivalent diameter less than 20 nm can be determined using the following method: 100 primary particles in colloidal silica are observed using a scanning electron microscope (SEM, 50,000x magnification). The number of primary particles with a spherical equivalent diameter less than 20 nm is determined by image analysis, and the proportion of this number to the number of primary particles with a spherical equivalent diameter determined by SEM is expressed as a percentage.

[0065] The colloidal silica of the present invention preferably contains primary amines in its silica particles. The primary amine is not particularly limited, but is preferably an amine represented by the following general formula (2).

[0066] NH2-R 1 (2)

[0067] (where R is in the formula) 1 This refers to alkyl groups with 1 to 12 carbon atoms that can be substituted.

[0068] In the above general formula (2), R 1 This refers to an alkyl group having 1 to 12 carbon atoms that can be substituted. The alkyl group can be straight-chain, branched, or cyclic.

[0069] The number of carbon atoms in a 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, and octyl. 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. Preferred straight-chain or branched alkyl groups include n-propyl, n-hexyl, 2-ethylhexyl, and n-octyl.

[0070] The cyclic alkyl group can 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 a preferred cyclic alkyl group.

[0071] In the above general formula (2), R 1 In this alkyl group, the alkyl group can be substituted. The number of substituents can be, for example, 0, 1, 2, 3, 4, etc., preferably 0, 1, or 2, more preferably 0 or 1. An alkyl group with 0 substituents refers to an unsubstituted alkyl group. Examples of substituents include alkoxy groups having 1 to 3 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy). Hydroxyl groups and unsubstituted amino groups are excluded. In alkyl groups having multiple substituents, the substituents can be the same or different.

[0072] In one implementation, R in the above general formula (2) 1 It is a straight-chain or branched alkyl group with 1 to 8 carbon atoms (preferably 1 to 6 carbon atoms) that can be substituted. Alternatively, in another embodiment, the R... 1 It is a straight-chain or branched alkyl group with 1 to 8 carbon atoms (preferably 1 to 6 carbon atoms) that can be replaced by an alkoxy group with 1 to 3 carbon atoms.

[0073] In one embodiment, the primary amine is at least one amine selected from 3-ethoxypropylamine, pentylamine, hexylamine, and cyclohexylamine. Among these amines, 3-ethoxypropylamine is preferred from the viewpoint of easily deforming silica particles.

[0074] Primary amines can be used alone or in combination with two or more.

[0075] Regarding the content of primary amine in silica particles, it is preferably 5 μmol or more per 1g of silica particles, more preferably 10 μmol, and even more preferably 20 μmol or more. If the lower limit of the primary amine content is within the above range, particle size control becomes easier. Furthermore, regarding the content of primary amine in silica particles, it is preferably 100 μmol or less per 1g of silica particles, more preferably 90 μmol or less. By keeping the upper limit of the primary amine content within the above range, silica particles can be easily shaped into irregular shapes.

[0076] The content of primary amines can be determined by the following method: Colloidal silica is centrifuged at 215000 G for 90 minutes, the supernatant is discarded, and the solid component is vacuum dried at 60°C for 90 minutes. 0.5 g of the dried silica curd is weighed and added to 50 ml of 1M sodium hydroxide aqueous solution. The solution is heated at 50°C for 24 hours while stirring to dissolve the silica. The amine content is determined by analyzing the silica solution using ion chromatography. Ion chromatography analysis is performed according to JIS K0127.

[0077] The boiling point of the primary amine is preferably 85°C or higher, more preferably 90°C or higher. If the boiling point is within the above range, the reaction temperature is higher, which can suppress vaporization during the reaction. In addition, the boiling point is preferably 500°C or lower, more preferably 300°C or lower.

[0078] The colloidal silica of the present invention preferably has a true specific gravity of 1.95 or more, more preferably 2.00 or more. If the lower limit of the true specific gravity is within the above range, the abrasiveness of the colloidal silica of the present invention is further improved. In addition, the true specific gravity is preferably 2.20 or less, more preferably 2.16 or less. If the upper limit of the true specific gravity is within the above range, the occurrence of damage to the workpiece being abraded is further reduced. The true specific gravity can be measured by a method in which the sample is dried and cured on a hot plate at 150°C, kept in an oven at 300°C for 1 hour, and then measured using a liquid-phase displacement method with ethanol.

[0079] The preferred density of silanol groups in colloidal silica particles is 1.9 groups / nm. 2 The above is preferred to be 2.0 units / nm. 2 The above is further optimized to 2.1 units / nm.2 The above applies. If the lower limit of the silanol group density is within the above range, damage to the workpiece being ground will be further reduced. Furthermore, a silanol group density of 5.0 groups / nm is preferred. 2 Below, 4.5 units / nm is preferred. 2 The following is a further preferred value of 3.4 units / nm. 2 The following applies. 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. The silanol group density of the silica particles in the colloidal silica can be obtained by the Sears method. The Sears 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% 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.

[0080] ρ=(a×f×6022)÷(c×S)

[0081] In the above formula, ρ represents the density of silanol groups (numbers / nm). 2 a: Volume (mL) of 0.1 mol / L sodium hydroxide aqueous solution at pH 4-9, f: Factor of 0.1 mol / L sodium hydroxide aqueous solution, c: Mass of silica particles (g), S: BET specific surface area (m²) 2 / g).

[0082] The colloidal silica of this invention can be used as a crop modifier in fields such as paper, fiber, and steel, and can also be used as an abrasive for electronic materials such as semiconductor wafers. Furthermore, by drying it into a powder, it can be used as a filler additive, a toner additive, etc.

[0083] The silica particles in colloidal silica preferably have organic functional groups on their surface represented by the following general formula (1).

[0084] -(CH2) n -R 3 (1)

[0085] By having an organic functional group represented by the above general formula (1), the aggregation of colloidal silica can be further suppressed. In addition, by having an organic functional group represented by the above general formula (1), for example, as an abrasive, the abrasive properties can be adjusted by utilizing electrostatic attraction or repulsion with the abrasive object; as a filler, when added to a polymer resin, the dispersibility can be improved, and the interaction with other substances can be adjusted.

[0086] In the above general formula (1), n ​​represents any integer greater than or equal to 0. n is preferably an integer greater than or equal to 1. In addition, n is preferably an integer less than or equal to 20, more preferably an integer less than or equal to 12, even more preferably an integer less than or equal to 6, and particularly preferably an integer less than or equal to 4.

[0087] In the above general formula (1), R 3 Represents any functional group. As R 3 There are no particular limitations as long as it is a functional group; examples include cationic, anionic, polar, and nonpolar functional groups. The colloidal silica of the present invention preferably has cationic, anionic, polar, and nonpolar organic functional groups on the surface of the silica particles, and more preferably has cationic and anionic organic functional groups.

[0088] As a cationic organic functional group, there are no particular limitations; examples include amino groups.

[0089] As an anionic organic functional group, there are no particular limitations; examples include sulfonyl and carboxyl groups. Among them, sulfonyl is preferred.

[0090] There are no particular limitations on whether a group is a polar or nonpolar organic functional group; examples include: methyl, ethyl, propyl, hexyl, decyl, dodecyl, octadecyl, vinyl, epoxy, methacrylate, acrylic, etc.

[0091] Furthermore, it can be confirmed by the following XPS measurements and zeta potential measurements that the surface of silica particles in colloidal silica is endowed with organic functional groups represented by the above general formula (1).

[0092] (XPS measurement)

[0093] Colloidal silica was centrifuged at 5°C and 77,000 G for 90 minutes. The resulting precipitate was dried at 60°C for 12 hours, then ground using a mortar and pestle, and dried under reduced pressure at 60°C for 2 hours to prepare a dried powder.

[0094] XPS was used to analyze the prepared dried powder and confirm the peaks of organic functional groups originating from the particle surface.

[0095] (ζ-potential measurement)

[0096] The zeta potential is measured using devices that utilize the principles of electrophoretic light scattering, colloidal vibration current method, electroacoustic method, and ultrasonic attenuation method.

[0097] 2. Method for manufacturing colloidal silica

[0098] The method for manufacturing colloidal silica of the present invention comprises, in sequence:

[0099] (1) Step 1: Preparation of mother liquor containing alkaline catalyst and water;

[0100] (2) Step 2: Adding alkoxysilane to the above mother liquor to prepare a mixture;

[0101] (3) Step 3, which involves adding an alkaline catalyst to the above mixture to prepare a seed particle dispersion; and

[0102] (4) Step 4, in which water and organic solvent are added to the above-mentioned particle dispersion, followed by the addition of alkoxysilane.

[0103] The above-mentioned alkaline catalyst is a primary amine.

[0104] (Process 1)

[0105] Step 1 is the process of preparing a mother liquor containing an alkaline catalyst and water.

[0106] The alkaline catalyst can be a primary amine. The amine described in the section on colloidal silica can be used as this amine.

[0107] The amine content in the mother liquor is preferably 0.30 mmol / kg or more, more preferably 0.50 mmol / kg or more. If the lower limit of the amine content is within the above range, particle size control becomes easier. Furthermore, the amine content in the mother liquor is preferably 20.0 mmol / kg or less, more preferably 15.0 mmol / kg or less. With the upper limit of the amine content within the above range, silica particles are easily shaped.

[0108] There are no particular limitations on the method for preparing the mother liquor; it is sufficient to add an alkaline catalyst to water and stir according to existing known methods.

[0109] The pH of the mother liquor is not particularly limited, but is preferably 9.5 or higher, more preferably 10.0 or higher. If the lower limit of the pH of the mother liquor is within the above range, it becomes easier to control the particle size. In addition, the pH of the mother liquor is preferably 12.0 or lower, more preferably 11.5 or lower. If the upper limit of the pH of the mother liquor is within the above range, the silica particles are more likely to become irregularly shaped.

[0110] (Process 2)

[0111] Step 2 is the process of adding alkoxysilane to the mother liquor to prepare a mixture.

[0112] As an alkoxysilane, there is no particular limitation, and examples of alkoxysilanes represented by the following general formula (3) can be given.

[0113] Si(OR 2 )4(3)

[0114] (where R is in the formula) 2 (Indicates an alkyl group.)

[0115] In the above general formula (3), R 2 Indicates an alkyl group. R 2 There is no particular limitation 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-mentioned alkyl groups include: methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, etc. As for the alkoxysilane represented by the above general formula (3), R is preferred. 2 Methyl tetramethoxysilane (tetramethyl orthosilicate), R 2 Ethyl tetraethoxysilane (tetraethyl orthosilicate), R 2 It is an isopropyl tetraisopropoxysilane, more preferably R 2 Methyl tetramethoxysilane, R 2 It is a tetraethoxysilane of ethyl group, and more preferably a tetramethoxysilane.

[0116] Alkoxysilanes can be used alone or in combination with two or more. Furthermore, alkoxysilanes can be added in full at once or in several portions (e.g., two, three, etc.).

[0117] The amount of alkoxysilane added in step 2 is not particularly limited. The molar ratio (s2 / c1) of the amount of alkoxysilane added in step 2 (s2, mol) to the amount of alkaline catalyst in the mother liquor (c1, mol) is preferably 10 or more, more preferably 100 or more, and even more preferably 150 or more. With the lower limit of s2 / c1 within the above range, the seed particles become more easily deformed. Furthermore, s2 / c1 is preferably 8500 or less, more preferably 8000 or less. If the upper limit of s2 / c1 is within the above range, gelation is less likely during the reaction.

[0118] The time required to add the alkoxysilane is preferably 5 minutes or more, more preferably 10 minutes or more. By keeping the lower limit of the addition time within this range, gelation is less likely to occur during the reaction. Furthermore, the time required to add the alkoxysilane is preferably 1000 minutes or less, more preferably 600 minutes or less. If the upper limit of the addition time is within this range, productivity is further improved, and manufacturing costs can be further suppressed.

[0119] The pH of the mixture is preferably 8.5 or lower, more preferably 8.0 or lower. If the upper limit of the pH of the mixture is within the above range, the seed particles become more prone to deformability. Furthermore, the pH of the mixture is preferably 4.5 or higher, more preferably 4.9 or higher. If the lower limit of the pH of the mixture is within the above range, gelation is less likely.

[0120] The temperature of the mixture in step 2 is preferably 70°C or higher, more preferably 75°C or higher. If the lower limit of the temperature of the mixture is within the above range, gelation is less likely to occur during the reaction. Furthermore, the temperature of the mixture is preferably 95°C or lower, more preferably 90°C or lower. If the upper limit of the temperature of the mixture is within the above range, the vaporization of alkoxysilanes is more easily suppressed.

[0121] (Process 3)

[0122] Step 3 is the process of adding an alkaline catalyst to the mixture to prepare a seed particle dispersion.

[0123] The time from the end of the addition of alkoxysilane to the start of the addition of alkaline catalyst in step 3 (hereinafter referred to as "curing time") is preferably 0 minutes to 1500 minutes. The irregularity can be controlled by adjusting the curing time. If the curing time is within the above range, productivity can be ensured and silica particles with the desired aggregation ratio can be obtained.

[0124] The temperature of the mixture during maturation is preferably 70°C or higher, more preferably 75°C or higher. If the lower limit of this temperature is within the above range, the particle size is easily controlled. Furthermore, this temperature is preferably 95°C or lower, more preferably 90°C or lower. If the upper limit of this temperature is within the above range, gelation is less likely.

[0125] The alkaline catalyst is a primary amine, and it can be substituted. The amine described in the section on colloidal silica above can be used as this amine. Furthermore, the alkaline catalyst used in step 3 can be the same as or different from the alkaline catalyst used in step 1.

[0126] The amount of alkaline catalyst added in step 3 is not particularly limited. The molar ratio (s2 / c3) of the amount of alkoxysilane added in step 2 (s2, mol) to the amount of alkaline catalyst added in step 3 (c3, mol) is preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less. By keeping the upper limit of s2 / c3 within the above range, it is easier to control the primary particle size of silica particles. In addition, s2 / c3 is preferably 30 or more, more preferably 35 or more. By keeping the lower limit of s2 / c3 within the above range, gelation is further suppressed. Furthermore, the alkaline catalyst can be added in its entirety at once, or it can be added in several installments (e.g., 2 installments, 3 installments, etc.).

[0127] In addition, in step 3, the alkaline catalyst can be added as a diluted solution after being diluted with a solvent such as water.

[0128] The pH of the seed particle dispersion is preferably 8.0 or higher, more preferably 8.5 or higher. If the lower limit of the pH of the seed particle dispersion is within the above range, gelation is not easy. Furthermore, the pH of the seed particle dispersion is preferably 12.0 or lower, more preferably 11.0 or lower. If the upper limit of the pH of the seed particle dispersion is within the above range, silica is difficult to dissolve.

[0129] There are no particular limitations on the temperature of the seed particle dispersion when adding the alkaline catalyst in step 3. This temperature is preferably 70°C or higher, more preferably 75°C or higher. If the lower limit of this temperature is within the above range, the particle size is easily controlled. Furthermore, this temperature is preferably 95°C or lower, more preferably 90°C or lower. If the upper limit of this temperature is within the above range, gelation is less likely.

[0130] (Step 4)

[0131] Step 4 involves adding water and an organic solvent to the particle dispersion, followed by the addition of an alkoxysilane. Optionally, an alkaline catalyst may be further added in step 4.

[0132] The particle dispersion can be the dispersion obtained from step 3 above, or it can be the dispersion obtained from step 3.5 described later.

[0133] Regarding the amount of water added in step 4, the amount of seed particles in the seed particle dispersion is set to 1 part by mass, preferably 10 parts by mass or more, and more preferably 15 parts by mass or more. If the lower limit of the amount of water added is within the above range, the generation of new nuclei can be suppressed, thereby promoting the growth of seed particles and further increasing the average secondary particle size of silica particles. In addition, if the amount of seed particles in the seed particle dispersion is set to 1 part by mass, the amount of water added is preferably 250 parts by mass or less, more preferably 220 parts by mass or less. If the upper limit of the amount of water added is within the above range, the seed particles grow more easily. Furthermore, the water can be added all at once or in several portions (e.g., 2 times, 3 times, etc.).

[0134] As the organic solvent in step 4, hydrophilic organic solvents can be used, specifically including alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, and 1,4-butanediol, ketones such as acetone and methyl ethyl ketone, and esters such as ethyl acetate. The organic solvent can be used alone or in mixtures of two or more. Furthermore, the organic solvent can be added in its entirety at once or in several portions (e.g., two, three, etc.).

[0135] In particular, alcohols are preferably used in this invention, more preferably methanol, ethanol, or isopropanol, and even more preferably methanol or ethanol, with methanol being especially preferred. This is because alcohols are easily replaced by water through heating and distillation during the water displacement process described later.

[0136] Furthermore, it is even more preferable to use an alcohol that is the same as the alcohol generated by the hydrolysis of the alkoxysilane as the organic solvent. For example, when tetramethyl orthosilicate is used as the alkoxysilane, methanol is generated in the reaction system by the hydrolysis of this silicate ester, so methanol is also used as the organic solvent. As a result, the solvent can be easily recovered and reused.

[0137] Regarding the amount of organic solvent added in step 4, the amount of seed particles in the seed particle dispersion is set to 1 part by mass, preferably 0.3 parts by mass or more, and more preferably 0.5 parts by mass or more. If the lower limit of the amount of organic solvent added is within the above range, the generation of new core particles can be suppressed, thereby promoting the growth of seed particles and further increasing the average primary particle size of silica particles. Furthermore, if the amount of seed particles in the seed particle dispersion is set to 1 part by mass, the amount of organic solvent added is preferably 55.0 parts by mass or less, more preferably 50.0 parts by mass or less. If the upper limit of the amount of organic solvent added is within the above range, the decrease in true specific gravity can be suppressed.

[0138] As the alkoxysilane in step 4, in addition to the tetraalkoxysilane without organic functional groups described in step 2 above, i.e. the alkoxysilane represented by the above general formula (3), an alkoxysilane with organic functional groups may also be used.

[0139] Examples of alkoxysilanes having organic functional groups include those represented by the following general formulas (4) and (5).

[0140] (OR 2 )3Si[(CH2) n -R 3 (4)

[0141] (OR 2 )2Si[(CH2) n -R 3 [(CH2)] n -R 4 (5)

[0142] In the above general formulas (4) and (5), R 2 R is the same as the general formula (3) above. 2 Similarly defined groups, R 3 and R 4 The same or different is R with respect to the above general formula (1). 3The same group is defined, and n is an integer defined in the same way as n in the above general formula (1).

[0143] Specifically, examples of alkoxysilanes represented by the above general formulas (4) or (5) include: methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, phenyltrimethoxysilane, benzyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, diethoxymethylphenylsilane, allyltriethoxysilane, vinyltriethoxysilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. Alkoxysilanes, such as oxysilanes, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-sulfopropyltrimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, etc., which have one or more organic functional groups in their molecules; and chlorosilanes such as trimethylchlorosilane and diethyldichlorosilane.

[0144] In step 4, alkoxysilanes can be used alone or in combination of two or more. The amount of alkoxysilane with organic functional groups added is preferably 0.0004 to 0.03 molar times, more preferably 0.001 to 0.03 molar times, relative to the amount of alkoxysilane added as represented by the above general formula (3). If the proportion of alkoxysilane added as represented by the above general formula (3) is too small, fewer organic functional groups will be introduced into the particles, potentially failing to impart the desired properties. If the proportion of alkoxysilane with organic functional groups added is too large, it may lead to an increase in secondary particle size, the formation of aggregates, or gelation.

[0145] Furthermore, when adding the alkoxysilane in step 4, it can be diluted with an organic solvent beforehand before addition. As the organic solvent in step 4, a hydrophilic organic solvent can be used; specifically, examples include alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, and 1,4-butanediol, ketones such as acetone and methyl ethyl ketone, and esters such as ethyl acetate. The organic solvent can be used alone or in mixtures of two or more. Particularly in this invention, from the perspective of industrial availability, alcohols are preferred, more preferably methanol or ethanol, and even more preferably methanol. This is because alcohols can be easily replaced by water through heating and distillation during water displacement. Furthermore, as the organic solvent, it is more preferable to use the same alcohol as the alcohol generated by the hydrolysis of alkyl silicate esters. For example, when tetramethyl orthosilicate is used as the alkoxysilane, methanol is generated in the reaction system through the hydrolysis of this silicate ester; therefore, methanol is also used as the organic solvent. This allows for easy recovery and reuse of the solvent.

[0146] In step 4, the amount of organic solvent added is preferably 0 to 3 times the total amount of alkoxysilane added, more preferably 0 to 1.5 times the total amount added. If the amount of organic solvent added is within the above range, the decrease in true specific gravity can be suppressed.

[0147] There is no particular limitation on the amount of alkoxysilane of general formula (3) added in step 4. The molar ratio (s4 / sp4) of the amount of alkoxysilane of general formula (3) added in step 4 to the amount of seed particles in the seed particle dispersion (sp4 / sp4) is preferably 3 or more. If the lower limit of the amount of alkoxysilane added is within the above range, colloidal silica can be obtained more efficiently. In addition, s4 / sp4 is preferably 30 or less, more preferably 26 or less. If the upper limit of the amount of alkoxysilane added is within the above range, it is difficult to generate new core particles during the reaction, and the growth of the main particles can be promoted. The above molar ratio is a value specified with the molecular weight of the seed particles set to 60.08 g / mol.

[0148] The time required to add the alkoxysilane in step 4 is preferably 5 minutes or more, more preferably 10 minutes or more. If the lower limit of the addition time is within the above range, gelation is less likely to occur during the reaction. Furthermore, the time required to add the alkoxysilane is preferably 1000 minutes or less, more preferably 600 minutes or less. If the upper limit of the addition time is within the above range, productivity is improved, and manufacturing costs can be controlled.

[0149] The pH of the seed particle dispersion when adding alkoxysilane in step 4 is preferably 12.0 or lower, more preferably 11.5 or lower. If the upper limit of the pH is within the above range, the silica particles are not easily dissolved. Furthermore, the pH of the seed particle dispersion when adding alkoxysilane is preferably 7.0 or higher, more preferably 7.5 or higher. If the lower limit of the pH is within the above range, gelation is not easy. Additionally, to maintain the pH within the above range, an alkaline catalyst can be added when adding alkoxysilane.

[0150] The temperature of the seed particle dispersion when adding alkoxysilane in step 4 is preferably 70°C or higher, more preferably 75°C or higher. If the lower limit of the temperature is within the above range, gelation is not easy during the reaction. Furthermore, the temperature of the seed particle dispersion when adding alkoxysilane is preferably 90°C or lower, more preferably 85°C or lower. If the upper limit of the temperature is within the above range, alkoxysilane is not easy to vaporize.

[0151] A basic catalyst can also be added in step 4. Adding a basic catalyst allows the pH of the reaction system to be adjusted to the desired range. Furthermore, adding a basic catalyst makes it difficult for new nuclei to form during the reaction, which is advantageous from the viewpoint of promoting host particle growth. The basic catalyst in step 4 is a primary amine. The amine described in the section on colloidal silica can be used as this amine. Additionally, the basic catalyst used in step 4 can be the same as or different from the basic catalyst used in steps 1 or 3.

[0152] In step 4, the alkaline catalyst is added such that the pH of the seed particle dispersion at the time of alkoxysilane addition is preferably 7.0–12.0, more preferably 7.5–11.5. The alkaline catalyst can be added in its entirety at once or in several portions (e.g., 2, 3, etc.). The addition of the alkaline catalyst is usually carried out during and / or before the addition of the alkoxysilane, but it can also be carried out after the addition of the alkoxysilane, provided that the pH of the reaction system at the time of alkoxysilane addition is within the aforementioned range. Furthermore, when the alkaline catalyst is added in several portions (e.g., 2, 3, etc.), it can be added at two or more times selected from simultaneously with the addition of the alkoxysilane, before the addition, and after the addition.

[0153] (Process 3.5)

[0154] The method for manufacturing colloidal silica of the present invention may further include step 3.5 after step 3 and before step 4, in which water is added to the seed particle dispersion obtained in step 3, followed by the addition of an alkoxysilane to prepare the seed particle dispersion. Optionally, an alkaline catalyst and / or an organic solvent may be further added in step 3.5. The seed particle dispersion prepared in step 3.5 can be supplied to step 4. By including step 3.5, the growth of seed particles can be promoted, further increasing the primary particle size.

[0155] Regarding the amount of water added in step 3.5, the amount of seed particles in the seed particle dispersion is set to 1 part by mass, preferably 10 parts by mass or more, and more preferably 15 parts by mass or more. If the lower limit of the amount of water added is within the above range, the generation of new nuclei can be suppressed, and as a result, the growth of seed particles can be promoted, and the average secondary particle size of silica particles can be further increased. In addition, if the amount of seed particles in the seed particle dispersion is set to 1 part by mass, the amount of water added is preferably 250 parts by mass or less, and more preferably 220 parts by mass or less. If the upper limit of the amount of water added is within the above range, the seed particles grow more easily. In addition, the water can be added all at once, or it can be added in several times (e.g., 2 times, 3 times, etc.).

[0156] In step 3.5, an organic solvent may be added to the seed particle dispersion. The organic solvent is preferably added to the seed particle dispersion before the addition of the alkoxysilane. Alternatively, the organic solvent may be added in its entirety at once, or in several portions (e.g., two, three, etc.).

[0157] As the organic solvent in step 3.5, the organic solvent described in step 4 above can be used. Furthermore, the organic solvent used in step 3.5 can be the same as or different from the organic solvent used in step 4.

[0158] Regarding the amount of organic solvent added in step 3.5, the amount of seed particles in the seed particle dispersion is set to 1 part by mass, preferably 0.3 parts by mass or more, and more preferably 0.5 parts by mass or more. If the lower limit of the amount of organic solvent added is within the above range, the generation of new core particles can be suppressed, thereby promoting the growth of seed particles and further increasing the average primary particle size of silica particles. Furthermore, if the amount of seed particles in the seed particle dispersion is set to 1 part by mass, the amount of organic solvent added is preferably 55.0 parts by mass or less, more preferably 50.0 parts by mass or less. If the upper limit of the amount of organic solvent added is within the above range, the decrease in true specific gravity can be suppressed.

[0159] In step 3.5, alkoxysilanes can be used alone or in combination with two or more. Furthermore, alkoxysilanes can be added in their entirety at once or in several portions (e.g., two, three, etc.). Alternatively, when adding alkoxysilanes in step 3.5, they can be diluted with an organic solvent beforehand.

[0160] As the alkoxysilane in step 3.5, the alkoxysilane described in step 4 above can be used. Furthermore, the alkoxysilane used in step 3.5 can be the same as or different from the alkoxysilane used in steps 2 or 4.

[0161] There is no particular limitation on the amount of alkoxysilane added in step 3.5, but the molar ratio (s3.5 / sp3.5) of the amount of alkoxysilane added in step 3.5 to the amount of seed particles in the seed particle dispersion is preferably 3 or more. If the lower limit of the amount of alkoxysilane added is within the above range, colloidal silica can be obtained more efficiently. In addition, s3.5 / sp3.5 is preferably 30 or less, more preferably 26 or less. If the upper limit of the amount of alkoxysilane added is within the above range, it is difficult to generate new core particles during the reaction, and the growth of the host particles can be promoted.

[0162] The time required to add the alkoxysilane in step 3.5 is preferably 5 minutes or more, more preferably 10 minutes or more. If the lower limit of the addition time is within the above range, gelation is less likely to occur during the reaction. Furthermore, the time required to add the alkoxysilane is preferably 1000 minutes or less, more preferably 600 minutes or less. If the upper limit of the addition time is within the above range, productivity is improved, and manufacturing costs can be controlled.

[0163] In step 3.5, the pH of the seed particle dispersion when adding alkoxysilane is preferably 12.0 or lower, more preferably 11.5 or lower. If the upper limit of the pH is within the above range, the silica particles are difficult to dissolve. Furthermore, the pH of the seed particle dispersion when adding alkoxysilane is preferably 7.0 or higher, more preferably 7.5 or higher. If the lower limit of the pH is within the above range, gelation is difficult. Additionally, to maintain the pH within the above range, an alkaline catalyst can be added when adding alkoxysilane.

[0164] In step 3.5, the temperature of the seed particle dispersion when adding alkoxysilane is preferably 70°C or higher, more preferably 75°C or higher. If the lower limit of the temperature of the seed particle dispersion is within the above range, gelation is not easy. Furthermore, the temperature of the seed particle dispersion is preferably 90°C or lower, more preferably 85°C or lower. If the upper limit of the temperature of the seed particle dispersion is within the above range, alkoxysilane is not easy to vaporize.

[0165] In step 3.5, an alkaline catalyst can also be added to the seed particle dispersion. Adding an alkaline catalyst allows the pH of the reaction system to be adjusted to the desired range. Furthermore, adding an alkaline catalyst makes it difficult for new core particles to form during the reaction, which is advantageous from the viewpoint of promoting the growth of the host particles. The alkaline catalyst in step 3.5 is a primary amine. The amine described above in the section on colloidal silica can be used as this amine. Additionally, the alkaline catalyst used in step 3.5 can be the same as or different from the alkaline catalyst used in steps 1, 3, or 4.

[0166] In step 3.5, the alkaline catalyst is added such that the pH of the reaction system at which the alkoxysilane is added is preferably 7.0 to 12.0, more preferably 7.5 to 11.5. The alkaline catalyst can be added in its entirety at once, or in several portions (e.g., 2, 3, etc.). The addition of the alkaline catalyst is usually performed at the time of and / or before the addition of the alkoxysilane, but it can also be performed after the addition of the alkoxysilane, provided that the pH of the reaction system at the time of the alkoxysilane addition is within the aforementioned range. Furthermore, when the alkaline catalyst is added in several portions (e.g., 2, 3, etc.), it can be added at two or more times selected from simultaneously with the addition of the alkoxysilane, before its addition, and after its addition.

[0167] Furthermore, the method for manufacturing colloidal silica of the present invention may further include a step of concentrating the colloidal silica after step 4 described above. There are no particular limitations on the concentration method, and concentration can be performed according to currently known methods. Examples of such concentration methods include heating at a temperature of approximately 65–100°C and concentrating by ultrafiltration.

[0168] There is no particular limitation on the concentration of silica particles in the concentrated colloidal silica. When the colloidal silica is set to 100% by mass, it is preferably about 1 to 50% by mass.

[0169] In the method for manufacturing colloidal silica of the present invention, the colloidal silica obtained in step 4 or 5 contains an alcohol generated as a byproduct during the reaction and an organic solvent added in steps 3.5, 4, or 5. Therefore, a step of removing the organic solvent from the system by distillation can be included after step 4 or 5, or the above-mentioned concentration step of colloidal silica. There are no particular limitations on the method for removing the organic solvent by distillation; for example, a method in which pure water is added dropwise while heating the colloidal silica to maintain a constant volume, thereby replacing the dispersion medium with pure water. Other methods include: separating the colloidal silica from the solvent by precipitation, centrifugation, etc., and then redispersing it in water; and a method of replacing the solvent with water by ultrafiltration.

[0170] (Step 5)

[0171] In the case where the colloidal silica of the present invention has an organic functional group represented by the above general formula (1), the method for manufacturing the colloidal silica of the present invention may further include a step 5 of adding an alkoxysilane having an organic functional group after the above step 4.

[0172] In step 5, as an alkoxysilane having an organic functional group, an alkoxysilane having an organic functional group represented by the above general formula (4) or (5) can be used.

[0173] In step 5, if the organic functional group is a cationic organic functional group, examples of alkoxysilanes having a cationic functional group include aminopropyltrimethoxysilane, (aminoethyl)aminopropyltrimethoxysilane, (aminoethyl)aminopropyltriethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, and aminobutyltriethoxysilane.

[0174] When the organic functional group is a cationic organic functional group, the amount of alkoxysilane with an organic functional group added in step 5 is not particularly limited. The amount is preferably 0.5 to 350 μmol per gram of the solid content of the colloidal silica before adding the alkoxysilane, more preferably 5.5 to 170 μmol. By keeping the lower limit of the amount of alkoxysilane with an organic functional group within the above range, the modification of the colloidal silica becomes more complete, and modified colloidal silica that can be dispersed stably for a longer period can be obtained. Furthermore, because the positive charge of the colloidal silica increases under acidic conditions, the electrostatic attraction and repulsion with the object being ground can be further increased. By keeping the upper limit of the amount of alkoxysilane with an organic functional group within the above range, the increase in secondary particle size, the formation of aggregates, and gelation can be further suppressed.

[0175] In step 5, when the organic functional group is an anionic organic functional group, particularly a sulfonyl group, for example, as an alkoxysilane with an organic functional group, it is preferable to have an organic functional group that can be chemically converted into a sulfonyl group. Examples of such organic functional group alkoxysilanes include: 1) alkoxysilanes with an organic functional group that can be converted into a sulfonyl ester group by hydrolysis; and 2) alkoxysilanes with an organic functional group that can be converted into a sulfonyl mercapto group and / or a sulfide group by oxidation. Furthermore, since the sulfonic acid modification of the colloidal silica surface is carried out in solution, the latter type of alkoxysilane with an organic functional group having a mercapto group and / or a sulfide group is preferred to improve the modification efficiency.

[0176] Examples of alkoxysilanes with an organic functional group, such as 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane, are alkoxysilanes with a thiol group.

[0177] Examples of alkoxysilanes with organic functional groups, such as bis(3-triethoxysilylpropyl) disulfide, are thioether groups.

[0178] When the organic functional group is an anionic organic functional group, particularly a sulfonyl group, the amount of alkoxysilane with an organic functional group used in step 5 is not particularly limited. It is preferably 0.5 to 350 μmol, more preferably 5.5 to 170 μmol, relative to 1 g of the solid content of colloidal silica after adding the alkoxysilane with an organic functional group. By keeping the lower limit of the amount of alkoxysilane with an organic functional group within the above range, the zeta potential under acidic conditions is further stabilized. By keeping the upper limit of the amount of alkoxysilane with an organic functional group within the above range, the increase in secondary particle size, the formation of aggregates, and gelation can be further suppressed.

[0179] As a method for oxidizing the mercapto and thioether groups modified on the surface of silica particles, methods using oxidizing agents can be cited. Examples include nitric acid, hydrogen peroxide, oxygen, ozone, organic peracids (percarboxylic acids), bromine, hypochlorite, potassium permanganate, and chromic acid. Among these oxidizing agents, hydrogen peroxide and organic peracids (peracetic acid, perbenzoic acid, etc.) are preferred from the perspective of ease of handling and good oxidation yield. Furthermore, considering reaction byproducts, hydrogen peroxide is the most preferred.

[0180] Regarding the amount of oxidant added, it is preferably 3 to 100 moles of alkoxysilanes with organic functional groups. There is no particular upper limit to the amount of oxidant added, but approximately 50 moles is more preferred. Furthermore, regarding colloidal silica and alkoxysilanes with organic functional groups, they possess stable structures in oxidation reactions, except for those oxidized (converted) to sulfonyl functional groups, thus suppressing byproducts.

[0181] In step 5, the temperature at which the alkoxysilane with organic functional groups is added is not limited, but room temperature (approximately 20°C) to the boiling point is preferred. The reaction time is also not limited, but is preferably 10 minutes to 10 hours, more preferably 30 minutes to 2 hours. The pH at the time of addition is also not limited, but is preferably 3 or higher and 11 or lower. Maintaining the pH within the above range further promotes the reaction between the alkoxysilane with organic functional groups and the silica surface, and further inhibits the self-condensation of the alkoxysilanes with organic functional groups. Furthermore, only a small amount of acidic or alkaline substances are added to adjust the pH, ensuring stable silica particle retention.

[0182] Alkoxysilanes with organic functional groups are preferably diluted with an organic solvent before being added to colloidal silica. By using alkoxysilanes with organic functional groups diluted with an organic solvent, the increase in secondary particle size and the formation of aggregates can be suppressed. There are no particular limitations on the dilution of alkoxysilanes with organic functional groups with an organic solvent, as long as the proportion of alkoxysilanes with organic functional groups is 0.1 to 100% by mass, preferably 1 to 100% by mass.

[0183] There are no particular limitations on the organic solvent used, but hydrophilic organic solvents are preferred, such as methanol, ethanol, isopropanol, butanol and other lower alcohols.

[0184] The colloidal silica 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. This content of less than 1 ppm of metallic impurities makes it suitable for grinding electronic materials and the like.

[0185] The colloidal silica of the present invention, and the colloidal silica obtained by the manufacturing method of the present invention, can be used for various applications such as abrasives and paper coating agents. Abrasives containing the above-mentioned colloidal silica are also one aspect of the present invention. In the colloidal silica of the present invention, regarding silica particles, the average primary particle size is 33 nm or more, the aggregation ratio is 1.2 or more, the true specific gravity is 1.95 or more, the alkoxy content is high, the proportion of particles with a spherical equivalent diameter of less than 20 nm is less than 15%, and it contains primary amines, which enables the content of metallic impurities such as sodium to be less than 1 ppm, thus achieving high purity. Therefore, it is particularly suitable for use as an abrasive for chemical mechanical polishing of semiconductor wafers.

[0186] Example

[0187] The present invention will now be described in detail with reference to embodiments, etc., but the present invention is not limited to these embodiments.

[0188] Example 1

[0189] (Step 1) Add 7500g of pure water to a flask as a solvent, and add 0.38685g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst to prepare the mother liquor. The pH of the mother liquor is 10.2.

[0190] (Step 2) After heating the mother liquor to an internal temperature of 85°C, while adjusting the temperature without changing the internal temperature, 2740g of tetramethyl orthosilicate is added dropwise at a constant rate over 120 minutes to prepare a mixed solution.

[0191] (Step 3) After stirring for 60 minutes, add 50.124 g of 3-ethoxypropylamine (3-EOPA) to the mixture to prepare a seed particle dispersion. The pH of the seed particle dispersion is 10.3.

[0192] (Step 4) In another flask, add 6061g of pure water, 930g of methanol, 581g of the seed particle dispersion, and 8.761g of 3-ethoxypropylamine (3-EOPA). Then, heat to an internal temperature of 80°C, and while maintaining a constant internal temperature, add 2000g of tetramethyl orthosilicate dropwise over a constant rate for 360 minutes. After the addition is complete, stir for 15 minutes to prepare colloidal silica. Next, take 800mL of colloidal silica as a baseline under normal pressure, and while maintaining a constant volume, feed the colloidal silica to concentrate it until the silica concentration reaches 20% by mass. Then, to remove methanol by distillation, while maintaining a constant volume, replace the dispersion medium with 500mL of pure water to prepare colloidal silica. The physical properties of the obtained colloidal silica are shown in Table 1, and the zeta potential is expressed as follows: Figure 1 middle.

[0193] Example 2

[0194] 6103 g of pure water was added to a flask as a solvent, along with 1142 g of methanol, 296 g of the particle dispersion from Example 1 (as the core silica particles), and 10.148 g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst. The mixture was then heated to an internal temperature of 80°C, and tetramethyl orthosilicate was added dropwise at a constant rate over 360 minutes while maintaining a constant internal temperature. After the addition was complete, the mixture was stirred for 15 minutes to prepare colloidal silica. 800 mL of the obtained colloidal silica was taken as a baseline at atmospheric pressure, and the volume was kept constant while feeding the colloidal silica to concentrate it until the silica concentration reached 20% by mass. Next, to remove methanol by distillation, the dispersion medium was replaced with 500 mL of pure water while maintaining a constant volume to prepare colloidal silica. The properties of the obtained colloidal silica are shown in Table 1.

[0195] Example 3

[0196] (Step 1) Add 6250g of pure water to a flask as a solvent and add 0.32238g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst to prepare the mother liquor. The pH of the mother liquor is 10.2.

[0197] (Step 2) After heating the mother liquor to an internal temperature of 80°C, while adjusting the temperature without changing the internal temperature, 3107.9g of tetramethyl orthosilicate is added dropwise to the mother liquor at a constant rate over a period of 100 minutes to prepare a mixed solution.

[0198] (Step 3) After stirring for 15 minutes, add 56.8680 g of 3-ethoxypropylamine (3-EOPA) to the mixture to prepare a seed particle dispersion. The pH of the seed particle dispersion is 10.3.

[0199] (Step 3.5) In another flask, add 5840g of pure water and 1921g of the seed particle dispersion. Then, heat to an internal temperature of 80°C, and while maintaining this temperature, add 2000g of tetramethyl orthosilicate dropwise at a constant rate over 360 minutes. After the addition is complete, stir for 15 minutes. Next, add 36.6280g of 3-ethoxypropylamine (3-EOPA) to prepare the seed particle dispersion. The pH of this particle dispersion is 10.3.

[0200] (Step 4) In another flask, add 4719g of pure water, 665g of methanol, and 2366g of the particle dispersion obtained in Step 3.5, which will serve as the core silica particles. Then, heat to an internal temperature of 80°C, and while maintaining a constant internal temperature, add 2000g of tetramethyl orthosilicate dropwise over a constant rate for 360 minutes. After the addition is complete, stir for 15 minutes to prepare colloidal silica. Next, take 2600mL of colloidal silica as a baseline at atmospheric pressure, and while maintaining a constant volume, feed the colloidal silica to concentrate it by heating until the silica concentration reaches 20% by mass. Then, to remove methanol from the system by distillation, while maintaining a constant volume, replace the dispersion medium with 2000mL of pure water to prepare colloidal silica. The physical properties of the obtained colloidal silica are shown in Table 1.

[0201] Example 4

[0202] (Step 1) Add 6250g of pure water to a flask as a solvent, and add 0.32240g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst to prepare the mother liquor. The pH of the mother liquor is 10.2.

[0203] (Step 2) After heating the mother liquor to an internal temperature of 80°C, while adjusting the temperature without changing the internal temperature, 3729.5g of tetramethyl orthosilicate is added dropwise to the mother liquor at a constant rate over a period of 120 minutes to prepare a mixed solution.

[0204] (Step 3) Over a period of 30 minutes, 68.0110 g of 3-ethoxypropylamine (3-EOPA) was diluted with pure water to a concentration of 20% by mass to prepare a seed particle dispersion. The pH of the seed particle dispersion was 10.4.

[0205] (Step 3.5) In another flask, add 5989 g of pure water and 1761 g of the seed particle dispersion. Then, heat to an internal temperature of 80°C, and while maintaining this temperature, add 2000 g of tetramethyl orthosilicate dropwise at a constant rate over 360 minutes. After the addition is complete, stir for 15 minutes. Next, add 10.0010 g of 3-ethoxypropylamine (3-EOPA) to prepare the seed particle dispersion. The pH of this seed particle dispersion is 10.3.

[0206] (Step 4) In another flask, add 4389 g of pure water, 1005 g of methanol, 2356 g of the particle dispersion obtained in Step 3.5 (which serves as the core silica particles), and 6.432 g of 3-ethoxypropylamine (3-EOPA). Then, heat to an internal temperature of 80°C, and while maintaining a constant internal temperature, add 2000 g of tetramethyl orthosilicate dropwise over a constant rate for 360 minutes. After the addition is complete, stir for 15 minutes to prepare colloidal silica. Next, take 2700 mL of colloidal silica as a baseline at atmospheric pressure, and while maintaining a constant volume, feed the colloidal silica to concentrate it by heating until the silica concentration reaches 20% by mass. Then, to remove methanol from the system by distillation, while maintaining a constant volume, replace the dispersion medium with 1350 mL of pure water to prepare colloidal silica. The physical properties of the obtained colloidal silica are shown in Table 1.

[0207] Example 5

[0208] (Step 1) Add 7500g of pure water to a flask as a solvent, and add 0.62300g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst to prepare the mother liquor. The pH of the mother liquor is 10.4.

[0209] (Step 2) After heating the mother liquor to an internal temperature of 85°C, while adjusting the temperature without changing the internal temperature, 2740g of tetramethyl orthosilicate is added dropwise to the mother liquor at a constant rate over a period of 120 minutes to prepare a mixed solution.

[0210] (Step 3) After stirring for 60 minutes, add 50.124 g of 3-ethoxypropylamine (3-EOPA) to the mixture to prepare a seed particle dispersion. The pH of the seed particle dispersion is 10.3.

[0211] (Step 4) In another flask, add 6061g of pure water, 930g of methanol, 581g of the seed particle dispersion, and 8.761g of 3-ethoxypropylamine (3-EOPA). Then, heat to an internal temperature of 80°C, and while maintaining a constant internal temperature, add 2000g of tetramethyl orthosilicate dropwise over a constant rate for 360 minutes. After the addition is complete, stir for 15 minutes to prepare colloidal silica. Next, take 800mL of colloidal silica as a baseline under normal pressure, and while maintaining a constant volume, feed the colloidal silica to concentrate it until the silica concentration reaches 20% by mass. Then, to remove methanol from the system by distillation, while maintaining a constant volume, replace the dispersion medium with 500mL of pure water to prepare colloidal silica. The physical properties of the obtained colloidal silica are shown in Table 1.

[0212] Example 6

[0213] Colloidal silica (silica concentration 20% by mass) was prepared in the same manner as in Example 1.

[0214] (Step 5)

[0215] 0.7 g of 3-ethoxypropylamine (3-EOPA) was added to 750 g of the prepared colloidal silica to adjust the pH to 9. A mixture of 0.7 g of 3-aminopropyltrimethoxysilane and 74.1 g of methanol was then added at room temperature. Next, to remove the methanol from the liquid by distillation, while maintaining a constant volume, 200 mL of pure water was used to displace the dispersion medium, thus preparing colloidal silica with cationic organic functional groups modified on the surface of the silica particles. The zeta potential of the obtained colloidal silica is expressed as follows: Figure 1 middle.

[0216] Example 7

[0217] Colloidal silica (silica concentration 20% by mass) was prepared in the same manner as in Example 1.

[0218] (Step 5)

[0219] 0.8 g of 3-ethoxypropylamine (3-EOPA) was added to 830 g of the prepared colloidal silica to adjust the pH to 9. Next, 9.9 g of 3-mercaptopropyltrimethoxysilane was added, followed by 21.1 g of 30% hydrogen peroxide solution. Then, to remove methanol from the liquid by distillation, while maintaining a constant volume, the dispersion medium was replaced with 200 mL of pure water, and the mixture was heated under reflux for 3 hours to prepare colloidal silica with anionic organic functional groups modified on the surface of the silica particles. The zeta potential of the obtained colloidal silica is expressed as... Figure 1 middle.

[0220] Comparative Example 1

[0221] To prepare a mother liquor, 0.151 g of a 25% tetramethylammonium hydroxide (TMAH) aqueous solution was added to 1732 g of water and stirred. The mother liquor was then heated to reflux. Separately, tetramethyl orthosilicate was hydrolyzed to prepare a 9% silicic acid aqueous solution. Under reflux, 346.5 g of the silicic acid aqueous solution was added dropwise to the mother liquor over 3 hours, followed by reflux for 30 minutes. Then, 1.26 g of the 25% tetramethylammonium hydroxide (TMAH) aqueous solution was added dropwise to prepare a seed particle dispersion. Next, 2910 g of water was added to the seed particle dispersion, and the mixture was stirred and heated to reflux. Then, while adding 500 g of the 9% silicic acid aqueous solution and 1.21 g of the 25% tetramethylammonium hydroxide (TMAH) aqueous solution dropwise over 2.5 hours, 600 g of a mixture of water and methanol was extracted. This operation was repeated 26 times to prepare colloidal silica. The properties of the obtained colloidal silica are shown in Table 1. No primary amines were detected in the colloidal silica obtained in Comparative Example 1.

[0222] Comparative Example 2

[0223] 0.365 g of a 25% tetramethylammonium hydroxide (TMAH) aqueous solution was added to 2000 g of water and stirred to prepare a mother liquor, which was then heated to 80°C. While maintaining the temperature of the mother liquor at 80°C, 228 g of tetramethyl orthosilicate was added dropwise over 3 hours. Immediately afterwards, 2.92 g of the 25% tetramethylammonium hydroxide (TMAH) aqueous solution was added. While maintaining the temperature at 80°C, 228 g of tetramethyl orthosilicate and 3.19 g of the 25% tetramethylammonium hydroxide (TMAH) aqueous solution were added dropwise over 3 hours. This operation was repeated four times to prepare colloidal silica. The physical properties of the obtained colloidal silica are shown in Table 1. Compared with Examples 1-4, the colloidal silica obtained from Comparative Example 2 had a lower aggregation ratio of silica particles, and no primary amines were detected.

[0224] Comparative Example 3

[0225] The effect of adding methanol was evaluated. 6991 g of pure water was added to a flask as a solvent, along with 581 g of the particle dispersion from Example 1 (which forms the core particles) and 8.761 g of 3-ethoxypropylamine (3-EOPA) as an alkaline catalyst, to prepare a mother liquor. The pH of the mother liquor was 10.2. The mother liquor was heated to an internal temperature of 80°C, and while maintaining this temperature, 2000 g of tetramethyl orthosilicate was added dropwise at a constant rate over 360 minutes. After the addition was complete, the mixture was stirred for 15 minutes to prepare a mixture. No growth of the main particles was observed in Comparative Example 3. This was because methanol was not added to the mother liquor, thus failing to inhibit the formation of new core particles (small particles), thereby hindering the growth of the main particles. The physical properties of the obtained colloidal silica are shown in Table 1.

[0226] The properties of the colloidal silica of the examples and comparative examples obtained as described above were evaluated according to the following methods.

[0227] (Average primary particle size)

[0228] Colloidal silica was pre-dried on a hot plate and then heat-treated at 800°C for 1 hour to prepare the sample for measurement. The BET specific surface area was measured using the prepared sample. The true specific gravity of silica was set to 2.2, and the ratio of 2727 / BET specific surface area (m²) was calculated. 2 The value of ( / g) is used as the average primary particle size (nm) of silica particles in colloidal silica.

[0229] (Average secondary particle size)

[0230] As a sample for dynamic light scattering, a sample was prepared by adding colloidal silica to a 0.3% by weight citric acid aqueous solution and homogenizing it. Using this sample, the average secondary particle size was determined by dynamic light scattering (ELSZ-2000S manufactured by Otsuka Electronics Co., Ltd.).

[0231] (clustering ratio)

[0232] The aggregation ratio is calculated based on the average secondary particle size / average primary particle size.

[0233] (True specific gravity)

[0234] After the sample was dried and cured on a hot plate at 150°C, it was kept in an oven at 300°C for 1 hour. The true specific gravity was then determined by a liquid-phase displacement method using ethanol.

[0235] (Amine content)

[0236] After centrifuging the colloidal silica at 215000 G for 90 minutes, the supernatant was discarded, and the solid component was vacuum dried at 60°C for 90 minutes. 0.5 g of the dried silica curd was weighed and added to 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 ion chromatography to determine the amine content. Ion chromatography analysis was performed according to JIS K0127.

[0237] (Alkoxy content)

[0238] After centrifuging the colloidal silica at 215000 G for 90 minutes, the supernatant was discarded, and the solid component was vacuum dried at 60°C for 90 minutes. 0.5 g of the dried silica curd was weighed and added to 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, which was then used as the alkoxy group content. A flame ionization detector (FID) was used in the gas chromatography. Gas chromatographic analysis was performed according to JIS K0114.

[0239] (The proportion of particles with a spherical equivalent diameter of less than 20 nm)

[0240] One hundred primary particles were observed using a scanning electron microscope (SEM, 50,000x magnification). The number of primary particles with a circular equivalent diameter less than 20 nm was determined by image analysis. The percentage of these particles relative to the number of primary particles with a circular equivalent diameter determined by SEM was expressed as a percentage. Particles with a circular equivalent diameter less than 20 nm were rated as "○", and particles with a circular equivalent diameter greater than 20 nm were rated as "×".

[0241] (Silanol group density)

[0242] The silanol group density of silica particles in colloidal silica can be determined using the Sears method. The Sears 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% silica dispersion was titrated with a 0.1 mol / L aqueous sodium hydroxide solution, and the silanol group density was calculated based on the following formula.

[0243] ρ=(a×f×6022)÷(c×S)

[0244] In the above formula, ρ represents the density of silanol groups (numbers / nm). 2 a: Volume (mL) of 0.1 mol / L sodium hydroxide aqueous solution at pH 4-9, f: Factor of 0.1 mol / L sodium hydroxide aqueous solution, c: Mass of silica particles (g), S: BET specific surface area (m²) 2 / g).

[0245] [Table 1]

[0246]

[0247] The zeta potential and XPS of the colloidal silica obtained in Examples 1, 6 and 7 were determined by the following methods.

[0248] (ζ-potential measurement)

[0249] The zeta potential of colloidal silica was measured using a measuring device that utilizes ultrasonic attenuation.

[0250] (XPS measurement)

[0251] Colloidal silica was centrifuged at 5°C and 77,000 G for 90 minutes. The resulting precipitate was dried at 60°C for 12 hours, then ground using a mortar and pestle, and dried under reduced pressure at 60°C for 2 hours to prepare a dried powder.

[0252] The dried powder was analyzed by XPS to confirm the peaks of organic functional groups originating from the particle surface.

[0253] The results of the zeta potential measurements of colloidal silica obtained from Examples 1, 6, and 7 are expressed as follows: Figure 1 In addition, the XPS analysis results of the colloidal silica obtained in Example 6 are presented in [the table / section]. Figure 2 The XPS analysis results of the colloidal silica obtained in Example 7 are presented below. Figure 3 middle.

[0254] exist Figure 1 In this study, the zeta potential of the colloidal silica obtained in Example 6 shifted positively compared to that obtained in Example 1. In particular, the isoelectric point of Example 6 reached 5 or higher. Figure 2 N atoms were detected in the XPS measurements, indicating that the surface of the silica particles was endowed with amino groups as cationic functional groups.

[0255] In addition, Figure 1In this study, the zeta potential of the colloidal silica obtained in Example 7 shifted negatively compared to that obtained in Example 1. Specifically, the zeta potential of Example 7 was negative across the entire pH range of 3–9. Figure 3 S atoms were detected in the XPS measurements, indicating that the surface of the silica particles was endowed with sulfonyl groups as anionic functional groups.

Claims

1. A colloidal silica, characterized in that, The colloidal silica contains silica particles with an average primary particle size of 33 nm to 200 nm, an aggregation ratio of 1.2 to 5.5, and a silanol group density of 1.9 particles / nm. 2 Above 5.0 units / nm 2 the following, Each 1g of silica particles contains alkoxy groups at a concentration of 1000 ppm to 15000 ppm by mass. The proportion of silica particles with a spherical equivalent diameter of less than 20 nm is less than 15%.

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