Colloidal silica and method for producing same

Abstract

Provided are colloidal silica having reduced microparticles and a method for producing the same. And colloidal silica, in which the number distribution ratio of fine particles having a particle diameter of 50% or less of the particle diameter median value is 1% or less on the basis of the equivalent circle diameter (Heywood diameter) obtained by image analysis using an electron microscope. Furthermore, a method for producing the colloidal silica, in which a hydrolyzable organic silicate ester is supplied to a reaction solution containing a hydrolysis catalyst containing a mixture of one or more organic amines selected from the group consisting of organic amines and the reaction is carried out, is a method for producing the colloidal silica, said method comprising: supplying a hydrolyzable organic silicate ester to a reaction solution containing a hydrolysis catalyst containing a mixture of one or more organic amines selected from the group consisting of organic amines; the supply port of the easily hydrolyzable organic silicate ester is immersed in the reaction liquid surface to supply the reaction liquid.

Description

Technical Field

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

[0002] As methods for industrially producing high-purity colloidal silica, a method of ion-exchanging an aqueous sodium silicate solution, a method of thermally decomposing silicon tetrachloride, a method of hydrolyzing an organic silicate in a water-alcohol mixed solvent in the presence of an acid catalyst or an alkali catalyst, and the like have been proposed and implemented. However, since high-purity substances can be used as the organic silicate, catalyst, solvent, etc. used in the reaction, the method of hydrolyzing the organic silicate is suitable as a method for producing high-purity colloidal silica with extremely few impurities derived from these raw materials, especially a low content of metal impurities. So far, several methods related to the hydrolysis of the organic silicate have been proposed.

[0003] Among them, with regard to colloidal silica used in various applications, especially colloidal silica used in the field of abrasives for semiconductor wafers, with the high integration of current LSIs, various types of metal wiring, oxide films, etc. exist on a single wafer. In addition, each semiconductor wafer needs to be suitable for its own polishing performance, so colloidal silica with subtly different compositions and properties is required.

[0004] In addition, for colloidal silica used in applications such as hard coating agents, adhesives for ceramic applications, chromic acid-based metal surface treatment agents, and foundation improvement injection agents, which are not suitable even if they contain only a small amount of alkali metal impurities, acidic colloidal silica is required, and several methods for producing such acidic colloidal silica are known.

[0005] For example, Patent Document 1 discloses a method in which an alkaline silica sol containing an aluminum compound is first prepared, and then the alkaline silica sol containing the aluminum compound is treated with a cation exchange resin to dealkalize, thereby producing an acidic silica sol. Patent Document 2 discloses a method in which an alkali aluminate aqueous solution is added to a silica sol having a particle size of 4 to 30 and a pH of 2 to 9 to make Al 2 O 3 / SiO 2 The molar ratio is set to 0.0006 to 0.004, and then the mixture is contacted with an ion exchange resin to produce a stable acidic silica sol having a pH of 2 to 5 and a particle size of 4 to 30.

[0006] Furthermore, Patent Document 3 discloses a method in which colloidal silica obtained by hydrolyzing and condensing a hydrolyzable silicon compound is modified with a modifier such as a silane coupling agent to produce high-purity modified colloidal silica, wherein the modified colloidal silica does not aggregate or gel even in an acidic dispersion medium, can be dispersed stably for a long period of time, and has an extremely low content of metal impurities.

[0007] However, in the methods described in Patent Documents 1 and 2, it is necessary to prepare an alkaline silica sol containing an aluminum compound and then treat it with an ion exchange resin for dealkalization. Therefore, in addition to the increase in production cost, there are also problems such as contamination caused by the ion exchange resin itself and limitation of ion removal during ion exchange. In addition, in the method described in Patent Document 3, in addition to the surface of the obtained colloidal silica being modified with a modifier and sometimes not suitable for the desired use, there is also the problem of contamination from the modifier.

[0008] Therefore, in order to solve such a problem, the present inventors have studied a method that does not require special post-treatment such as acid treatment, ion exchange treatment, and further modification treatment, and can easily produce colloidal silica having prescribed properties such as spherical colloidal silica, which has an extremely low content of metal impurities including alkali metals, and has an average particle size in the range of 5 to 500 nm, a standard deviation of 20 or less, and a polydispersity index of 0.15 or less, as determined by particle size distribution analysis using an electron microscope. As a result, the present inventors have proposed a method that can easily produce neutral colloidal silica having a pH of 5 to 8 by using an easily hydrolyzable organic silicate having a fast hydrolysis rate and using a specific hydrolysis catalyst as a hydrolysis catalyst, adding the hydrolysis catalyst so that the ratio of the hydrolysis catalyst (A) to the silica (B) {catalyst residual molar ratio (A / B)} in the reaction mixture at least at the end of the reaction becomes a prescribed value or less, and reacting the hydrolysis catalyst (Patent Document 4).

[0009] In the above-mentioned conventional production method of the present inventors, it is necessary to supply the easily hydrolyzable organic silicate, which is the raw material of the silica source, to a reaction liquid containing water and a hydrolysis catalyst at a predetermined temperature to react. Usually, in order to reliably supply the silica source (to make it difficult for the silica source to come into contact with water and the catalyst near the nozzle and to cause side reactions), the supply port is arranged at a height as far away from the reaction liquid surface as possible, and the silica source is supplied and charged from the middle of the air (hereinafter sometimes referred to as "charge-in-the-air", etc.).

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Publication No. 4-55126

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 6-199515

[0014] Patent Document 3: Japanese Patent Application Publication No. 2005-162533

[0015] Patent Document 4: Japanese Patent Application Publication No. 2007-153732

[0016] Patent Document 5: Japanese Patent Application Publication No. 2020-073445

[0017] Patent Document 6: Japanese Patent Application Publication No. 2021-116209 Summary of the invention

[0018] Problems to be solved by the invention

[0019] However, if the silica source is added from the air as in the conventional method, in the case of a particularly volatile silica source, a lot of the silica source will fly around from the supply port and the reaction liquid surface. As for the silica source that flies around, for example, it adheres to the wall surface in the reaction container, which becomes a cause of contamination, and also leads to a reduction in yield, etc. However, the inventors of the present invention have conducted in-depth research and confirmed the following disadvantages: such a scattered silica source contacts with water droplets attached to the surrounding walls, etc., and a side reaction occurs to generate undesirable colloidal silica particles. Moreover, it has been confirmed that: if the colloidal silica particles generated by such a side reaction fall into the reaction liquid together with the water droplets, it usually becomes a product mixed with colloidal silica particles (hereinafter including particles and particles defined based on the image analysis described later, sometimes collectively referred to as "particles") that have grown particles in a different behavior from the target reaction. Furthermore, when such colloidal silica mixed with particles is used as seed particles to grow the particles to obtain colloidal silica with a larger particle size, undesirable particles are also contained in the same proportion. Such colloidal silica mixed with undesirable particles and having inconsistent particle sizes may also cause disadvantages such as unevenness in applications such as grinding and micro-machining.

[0020] Therefore, the present inventors conducted intensive research to solve the problems in such conventional methods and found that by improving the method of supplying a silica source to a reaction solution, colloidal silica with a reduced proportion of microparticles can be obtained, the yield can be improved, side reactions and contamination in the reaction vessel can be reduced, and the load of maintenance such as cleaning can be reduced, thereby completing the present invention.

[0021] Therefore, an object of the present invention is to provide colloidal silica having a reduced proportion of fine particles and a method for producing the same.

[0022] It should be noted that there are also several reports on colloidal silica with reduced particles (for example, Patent Document 5 and Patent Document 6), and Patent Document 5 relates to modified colloidal silica. In addition, in Patent Document 6, the definition of particles is unclear, and the actual proportion of particles is about 2 to 4 area%, and the reduction of particles is not necessarily sufficient.

[0023] Means for solving problems

[0024] That is, the gist of the present invention is as follows.

[0025] (1) Colloidal silica characterized in that the number distribution ratio of fine particles having a particle size of 50% or less of the median particle size based on an equivalent circle diameter (Heywood diameter) obtained by image analysis using an electron microscope is 1% or less.

[0026] (2) The colloidal silica according to (1), characterized in that it is based on image analysis using a scanning electron microscope (SEM) and a scanning transmission electron microscope (STEM).

[0027] (3) An abrasive comprising the colloidal silica according to (1) or (2).

[0028] (4) A method for producing colloidal silica, comprising supplying a readily hydrolyzable organic silicate to a reaction liquid containing a hydrolysis catalyst containing one or a mixture of two or more selected from organic amines and causing them to react, wherein the supply is carried out in a state where a supply port of the readily hydrolyzable organic silicate is immersed in the surface of the reaction liquid.

[0029] (5) The method for producing colloidal silica according to (4), wherein the length of the supply port of the readily hydrolyzable organic silicate immersed in the reaction liquid surface is at least 3 times the outer diameter of the supply port.

[0030] (6) The method for producing colloidal silica according to (4) or (5), wherein the easily hydrolyzable organic silicate is supplied together with an inert gas.

[0031] (7) The method for producing colloidal silica according to (6), wherein a flow rate (L) of the inert gas relative to a supply amount (kg) of the readily hydrolyzable organic silicate is 1 to 10000 L / kg.

[0032] (8) The method for producing colloidal silica according to (4) or (5), characterized in that, as a means for supplying the readily hydrolyzable organic silicate, a nozzle having an inner and outer double tube structure including an outer tube and an inner tube inserted into the outer tube is used, and while the readily hydrolyzable organic silicate is supplied to the inner tube, an inert gas is supplied to the outer tube.

[0033] (9) The method for producing colloidal silica according to (8), wherein a ratio O / I of an inner diameter (O) of an outer tube for supplying an inert gas to an outer diameter (I) of an inner tube for supplying the readily hydrolyzable organic silicate is 2 to 7.

[0034] (10) The method for producing colloidal silica according to (8), characterized in that the difference in length between the inner tube for supplying the easily hydrolyzable organic silicate and the outer tube for supplying the inert gas (outer tube - inner tube) is greater than the outer diameter of the outer tube and greater than 1 times and less than 10 times the outer diameter of the outer tube.

[0035] (11) The method for producing colloidal silica according to (4) or (5), wherein the easily hydrolyzable organic silicate is trimethyl silicate, tetramethyl silicate, triethyl silicate, or methyl trimethyl silicate.

[0036] (12) The method for producing colloidal silica according to (4) or (5), wherein the organic amine is one or a mixture of two or more selected from quaternary ammonium amines, tertiary amines, secondary amines and primary amines, and carbonates, bicarbonates and silicates thereof.

[0037] (13) The method for producing colloidal silica according to (6), characterized in that the inert gas is nitrogen, argon and / or helium.

[0038] (14) A method for producing colloidal silica, characterized in that after producing colloidal silica by the method according to (4) or (5), the colloidal silica is used as seed particles, and an easily hydrolyzable organic silicate is supplied to a reaction solution containing the seed particles and the hydrolysis catalyst to react, thereby producing grown colloidal silica having a particle size that is grown.

[0039] (15) A method for producing colloidal silica according to (14), characterized in that seed particles of colloidal silica having a particle size median value of 30 nm or less based on an equivalent circle diameter obtained by image analysis using an electron microscope are used, and the concentration of the silica component in the reaction system is set to 13% by mass or less to carry out the reaction, thereby producing grown colloidal silica having a particle size median value greater than 30 nm and less than 1 mm.

[0040] Effects of the Invention

[0041] According to the present invention, colloidal silica with reduced particles can be obtained. In addition, the yield can also be improved, the side reactions and pollution in the reaction vessel can be reduced, and the load of maintenance such as cleaning can also be reduced. Furthermore, the homogenization of particle size can be achieved, so for example, it is also helpful for the efficiency of grinding and micro-processing, and the manufacture of large particles (grown particles) with uniform particle size. The colloidal silica of the present invention is suitable for purposes such as abrasives (silicon wafers, hard disks, etc.), coating agents (glasses, displays, building materials, paper, etc.), adhesives (ceramics, catalysts, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram illustrating a reaction vessel and a double tube structure used therein.

[0043] Figure 2 STEM (a) and SEM (b) images of the colloidal silica obtained in Example 1 are shown (magnification 100,000).

[0044] Figure 3 The STEM analysis image (c) and the particle size distribution (d) of the colloidal silica obtained in Example 1 are shown.

[0045] Figure 4 STEM (a) and SEM (b) images of the colloidal silica obtained in Example 2 are shown (magnification 100,000).

[0046] Figure 5 The STEM analysis image (c) and particle size distribution (d) of the colloidal silica obtained in Example 2 are shown.

[0047] Figure 6 STEM (a) and SEM (b) images of the colloidal silica obtained in Example 3 are shown (magnification 50,000).

[0048] Figure 7 The STEM analysis image (c) and particle size distribution (d) of the colloidal silica obtained in Example 3 are shown.

[0049] Figure 8 STEM (a) and SEM (b) images of the colloidal silica obtained in Comparative Example 1 are shown (magnification: 100,000).

[0050] Fig. 9 The STEM analysis image (c) and the particle size distribution (d) of the colloidal silica obtained in Comparative Example 1 are shown.

[0051] Fig.10 STEM (a) and SEM (b) images of the colloidal silica obtained in Comparative Example 2 are shown (magnification: 100,000).

[0052] Fig.11 The STEM analysis image (c) and the particle size distribution (d) of the colloidal silica obtained in Comparative Example 2 are shown.

[0053] Fig.12 STEM (a) and SEM (b) images of the colloidal silica obtained in Comparative Example 3 are shown (magnification 50,000).

[0054] Fig.13 The STEM analysis image (c) and the particle size distribution (d) of the colloidal silica obtained in Comparative Example 3 are shown.

[0055] Fig.14 STEM (a) and SEM (b) images of the colloidal silica obtained in Example 10 are shown (magnification 100,000).

[0056] Fig.15 The STEM analysis image (c) and the particle size distribution (d) of the colloidal silica obtained in Example 10 are shown.

[0057] Fig.16 STEM (a) and SEM (b) images of the colloidal silica obtained in Comparative Example 4 are shown (magnification: 100,000).

[0058] Fig.17 The STEM analysis image (c) and the particle size distribution (d) of the colloidal silica obtained in Comparative Example 4 are shown. DETAILED DESCRIPTION

[0059] <Colloidal Silica>

[0060] As described above, the colloidal silica of the present invention has a particle size distribution ratio of 1% or less having a particle size of 50% or less of the median particle size based on an equivalent circle diameter obtained by image analysis using an electron microscope. Preferably, the particle size distribution ratio is 0.5% or less, and more preferably, the particle size distribution ratio can be close to 0%.

[0061] The equivalent circle diameter is also called Heywood diameter, which can be obtained according to JIS Z 8827-1:2008 particle size analysis-image analysis method. When measuring particles of various shapes such as particles with uneven surfaces and particles that are aggregated and shrunk on the particle surface of colloidal silica, there are problems such as errors that are easily generated during manual measurement and the time required for measurement. Therefore, by using the equivalent circle diameter based on such standardization, the amount of particles present can be objectively evaluated, which is preferred.

[0062] As the electron microscope used, as long as it is possible to obtain an image that can be applied to the measurement and analysis of the equivalent circular diameter, there is no restriction, for example, known electron microscopes such as scanning electron microscopes (SEM), transmission electron microscopes (TEM), scanning transmission electron microscopes (STEM) can be used without restriction. Preferably, SEM or TEM is used in conjunction with STEM, and more preferably, SEM and STEM can be used in conjunction. In the analysis of particles, the black part of the particle and the white part outside the particle are divided into binary values, and the particle is determined. For example, when the concave-convex particle is observed using SEM, the concave-convex part on the particle becomes black and white, so there is a tendency to be difficult to determine the boundary of the particle. Therefore, the observation of the white and black using TEM and STEM without producing concave-convex becomes necessary, but when only using TEM to observe, it tends to be difficult to judge whether it is a particle formed by the aggregation of particles or just particles overlapping each other and looking like a particle, so the image of SEM and STEM is taken and analyzed simultaneously and the shape of the particle can be accurately captured, and a more accurate equivalent circular diameter is measured.

[0063] Specifically, the STEM image is imported into any image analysis software used in the embodiment, the area of ​​the particle is measured, and the result is imported into the calculation software, compared with the SEM image taken at the same time, the overlapping particle data is removed, and the diameter calculated by the area of ​​the remaining particles is set to the equivalent circle diameter. After the equivalent circle diameters of all particles are added up, the particle size median is obtained from the particle size distribution (that is, the accumulation of the number (frequency) from the small particle side is just 50% of the particle size). Then, the particles with a particle size of less than 50% of the particle size median are defined as "microparticles" in the present invention, and the proportion of the number of the microparticles in all particles is obtained as the number distribution ratio. For example, when the total number of particles is 500, the particle size of the 250th particle accumulated from the small particle side becomes the particle size median, and if the particle size median is, for example, 30nm, particles with a particle size of less than half (15nm) thereof become "microparticles". The fact that the number distribution ratio of the particles of 15 nm or less is 1% or less means that the number of particles is 5 or less because the total number of particles is 500.

[0064] In addition, as far as the colloidal silica of the present invention is concerned, as long as the particles as described above are in a predetermined number distribution ratio, they can have any shape and characteristics according to the use, purpose, etc. In particular, as far as the colloidal silica obtained in the present invention is concerned, as shown in the attached figure described later, there are a large number of irregular small protrusions on the surface of the particles, and the particles as a whole have a shape like a candy candy. The SEM average particle size obtained by measuring the arithmetic average of the particle image obtained by SEM observation is large, but the BET specific surface area is large. In addition, it has a high particle density (true specific gravity) measured by the liquid phase replacement method, in other words, a high hardness, and has an excellent polishing speed, which is suitable for CMP abrasives. For example, in the case of colloidal silica used in the field of abrasives for semiconductor wafers, preferably, the median value of the particle size based on the equivalent circle diameter obtained by image analysis using an electron microscope is 5 to 500 nm, and more preferably in the range of 30 to 300 nm. If small particle size products are to be manufactured, small particles are difficult to produce.

[0065] It should be noted that the shape of the particles of colloidal silica can be made into a monodisperse sphere (spherical product) or a shape in which the particles are aggregated together (aggregate product) according to the feed composition, etc. For example, by increasing the amount of catalyst and relatively slowly introducing the organic silicate as the raw material of silica into the reaction field, the organic silicate is rapidly and evenly hydrolyzed and grows gently, so that the particles grow slowly while maintaining a spherical state, and a spherical product can be made. In addition, for example, by reducing the amount of catalyst and relatively quickly introducing the organic silicate as the raw material of silica into the reaction field, the organic silicate is unevenly hydrolyzed, and thus acts like an adhesive between particles, and as a result, an aggregate product in which particles aggregate can be made.

[0066] The colloidal silica of the present invention preferably has a viscosity of 1 to 100 mPa·s, more preferably 1 to 20 mPa·s. The colloidal silica preferably has a BET particle size (nm) of 10 nm to 500 nm, more preferably 18 nm to 200 nm.

[0067] The colloidal silica of the present invention may be a monodisperse spherical product as described above, or may be an aggregated product (cocoon-shaped, chain-shaped, branched) having a shape that appears to be a plurality of particles two-dimensionally or three-dimensionally combined as observed by an electron microscope.

[0068] The colloidal silica of the present invention has the above-mentioned properties and is therefore suitable for use in, for example, abrasives (silicon wafers, hard disks, etc.), coating agents (glasses, displays, building materials, paper, etc.), adhesives (ceramics, catalysts, etc.), and the like.

[0069] <Method for producing colloidal silicon dioxide>

[0070] As described above, the colloidal silica of the present invention is obtained by supplying a readily hydrolyzable organic silicate to a reaction solution containing a hydrolysis catalyst containing one or a mixture of two or more selected from organic amines to carry out a hydrolysis reaction.

[0071] First, in the manufacturing method of the present invention, as described above, it is important to prevent the scattering of the easily hydrolyzable organic silicate (hereinafter sometimes referred to as "silica source") that serves as the silica source during supply, to prevent the scattering to the surroundings of the wall surface in the reaction container, to prevent the occurrence of side reactions, and to suppress the generation of microparticles. As described above, although the principle of the generation of microparticles is not necessarily clear, it is speculated that if the scattered silica source scatters to the surroundings of the wall surface in the reaction container, it contacts with water droplets attached to the surrounding wall surface, etc., and a side reaction occurs, thereby generating colloidal silica microparticles. If such side reaction products fall into the reaction solution together with the water droplets, colloidal silica microparticles that grow particles in a different behavior from the usual target reaction are generated.

[0072] Therefore, in the manufacturing method of the present invention, the supply port for supplying the silica source to the reaction liquid is supplied in a state immersed in the reaction liquid surface. In this way, by immersing the supply port in the reaction liquid surface, the silica source is supplied (discharged) in the reaction liquid, so that the scattering of the silica source at the supply port and the reaction liquid surface can be prevented as much as possible compared with the air input. At this time, with respect to the degree of immersion of the supply port, it is preferably immersed in a sufficient length so that the silica source supplied (discharged) from the supply port does not fly out of the reaction liquid surface. Preferably, the length of the immersed supply port can be made more than 3 times the outer diameter of the supply port (the outer diameter of the outer tube in the case of using a nozzle with a double tube structure described later). The upper limit of the length of the immersed supply port can be determined by considering the contact with other equipment (such as a stirrer, the wall surface of the reaction vessel, the bottom surface, etc.), and preferably, it can be a length that does not contact the bottom surface inside the reaction vessel. It should be noted that, as long as the purpose of the present invention is not impaired, the supply port can be used without restriction in any known shape or size, and can be a commonly used nozzle or tube with a circular or rectangular discharge portion. There is no restriction on the outer diameter of the supply port, and it can usually be set to about 1 mm to 100 mm. In addition, regarding the reaction container for carrying out the reaction, a reaction container with any known shape or size can also be used without restriction.

[0073] In order to allow the silica source supplied from the supply port to fully undergo a hydrolysis reaction with the reaction liquid in a reaction container, etc., it is preferred to impart a stirring power sufficient to stir the reaction liquid, preferably such that the power per unit liter of the stirred liquid (unit: Watt (W) / L) is 0.05 to 0.5 W / L, more preferably 0.09 to 0.2 W / L.

[0074] In addition, when the silica source is supplied (discharged) while the supply port is immersed in the reaction solution, it is preferably accompanied by a means for promoting or assisting the supply (discharge) of the silica source. As such means, for example, the use of an inert gas; the use of a neutral gas that does not react with the silica source, water, or a catalyst, etc., more preferably, by setting the supply port for supplying the inert gas together with the supply port for the silica source or setting it separately, an inert gas can be used to promote or assist the supply (discharge) of the silica source into the reaction solution. Inert gases such as nitrogen, argon, and helium can be used appropriately according to the purpose. By being accompanied by such means, problems such as retention near the supply port of the supplied silica source and blockage caused by side reactions will not occur, and the hydrolysis reaction can be fully carried out, so it is preferred.

[0075] When the inert gas is used, the amount of the inert gas supplied is preferably set according to the degree of promoting or assisting the supply of the silica source into the reaction solution so as to minimize the ejection of the silica source from the solution due to excessive gas flow rate. For example, the gas volume (L) per unit mass (kg) of the supplied silica source is preferably 1 to 10000 L / kg, and more preferably 10 to 1000 L / kg.

[0076] In order to more reliably supply the silica source to the reaction solution, from the perspective of reliability and efficiency of the supply, a preferred embodiment is: as a means of supplying the silica source, a nozzle having an inner and outer double tube structure including an outer tube and an inner tube inserted into the outer tube is used, and the silica source or inert gas is supplied from each tube. In this case, in order to suppress the scattering of the silica source from the supply port, it is preferred to flow the silica source in the inner tube and flow the inert gas in the outer tube. With regard to such a double tube structure, for example, it is possible to Figure 1 The embodiment shown in the example can be used without limitation as long as it is a nozzle having a known double tube structure. In this case, the pipeline can be multiple as long as it includes at least a double tube for supplying a silica source and an inert gas.

[0077] As for the diameter of the tubes through which the various substances flow using the nozzle having such a double tube structure, it is preferred that the ratio O / I of the inner diameter (O) of the outer tube for supplying the inert gas relative to the outer diameter (I) of the inner tube for supplying the silica source is 1 to 10. More preferably, O / I can be 2 to 7. This is because by setting such an O / I ratio, the supply effect and efficiency of the inert gas from the outer tube are improved, and it is possible to suppress stagnation and clogging near the supply port of the silica source, which tends to achieve a more reliable supply of the silica source.

[0078] The inner diameter of each tube can be appropriately set according to the scale, supply amount, flow rate, etc. during production. The outer diameter (I) of the inner tube for supplying the silica source can be generally set to 5 to 96 mm, more preferably 4 to 99 mm. The inner diameter (O) of the outer tube for supplying the inert gas can be generally set to 4 to 99 mm, more preferably 6 to 98 mm.

[0079] Furthermore, in the case of such an embodiment, it is preferred that the length of the outer tube through which the inert gas flows is greater than the length of the inner tube through which the silica source flows. This is because the supply effect and efficiency of the inert gas from the outer tube are improved, and retention and blockage near the supply port of the silica source can be suppressed, which tends to enable a more reliable supply of the silica source. Preferably, the difference in length between the inner tube for supplying the silica source and the outer tube for supplying the inert gas (length of the outer tube - length of the inner tube) may be greater than the outer diameter of the outer tube and greater than 0.5 times and less than 20 times the outer diameter of the outer tube, and more preferably may be greater than 1 times and less than 10 times the outer diameter of the outer tube. With respect to the difference in length, if Figure 1 As shown, it can be obtained from the difference in length near the supply ports of the two.

[0080] The silica source used in the present invention is an easily hydrolyzable organosilicate with a fast hydrolysis rate. The so-called easily hydrolyzable organosilicate refers to an organosilicate that is subjected to a hydrolysis reaction of 10 g of the organosilicate and 100 g of pure water containing impurities of 0.1 ppb or less at 25° C. under stirring, and the hydrolysis reaction is completed within 1 hour. As such an easily hydrolyzable organosilicate, specifically, trimethyl silicate (hydrolysis reaction time until the hydrolysis reaction is completed: 3 minutes), tetramethyl silicate (hydrolysis reaction time: 5 minutes), triethyl silicate (hydrolysis reaction time: 5 minutes), methyltrimethyl silicate (hydrolysis reaction time: 7 minutes), etc. can be cited. As for tetraethyl silicate and organosilicates having a larger number of carbon atoms than tetraethyl silicate, they have a slow hydrolysis rate and are easily gelled (the hydrolysis reaction time is all: more than 24 hours), and are therefore not suitable as the organosilicate used in the method of the present invention.

[0081] In addition, in the present invention, there is no restriction on the organic amines used as hydrolysis catalysts, and one or a mixture of two or more thereof selected from quaternary ammoniums, tertiary amines, secondary amines and primary amines and their carbonates, bicarbonates and silicates can be widely used. Among them, for example, regarding quaternary ammoniums, for example, quaternary ammoniums such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), trimethylethylammonium hydroxide, trimethylethanolammonium hydroxide (choline), triethylethanolammonium hydroxide, tetrapropylammonium hydroxide, butylammonium hydroxide, and their carbonates, bicarbonates and silicates can be listed. Since the hydrolysis reaction preferably has a relatively high pH, ​​tetramethylammonium hydroxide (TMAH), choline, or tetraethylammonium hydroxide (TEAH) is preferably used.

[0082] In addition, the primary amines, secondary amines, and tertiary amines of the organic amines used as the hydrolysis catalyst are also not limited, and examples thereof include amino alcohols, morpholines, piperazines, aliphatic amines, aliphatic ether amines, etc. Among them, as for the amino alcohols, various amino alcohols can be used, including ethanolamine derivatives, and ethanolamine derivatives are preferred, and examples thereof include monoethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-di-n-butylethanolamine, N-(β-aminoethyl)ethanolamine, N-methylethanolamine, N-methyldiethanolamine, N-ethylethanolamine, N-n-butylethanolamine, N-n-butyldiethanolamine, N-tert-butylethanolamine, and N-tert-butyldiethanolamine.

[0083] Furthermore, as for the morpholines of the organic amines used as the hydrolysis catalyst, various morpholine derivatives can be used, and preferably morpholine, N-methylmorpholine, N-ethylmorpholine, etc. can be listed. In addition, as for the piperazines of the organic amines used as the hydrolysis catalyst, various piperazine derivatives can be used, and preferably piperazine, hydroxyethylpiperazine, etc. can be listed. In addition, as for the aliphatic amines and aliphatic ether amines of the organic amines used as the hydrolysis catalyst, as the aliphatic amines, preferably alkylamines having 1 to 8 carbon atoms such as triethylamine, dipropylamine, pentylamine, hexylamine, heptylamine, octylamine, etc. can be listed. In addition, as the aliphatic ether amines, preferably aliphatic ether amines having 1 to 8 carbon atoms such as 2-methoxyethylamine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-propoxypropylamine, 3-isopropoxypropylamine, 3-butoxypropylamine, etc. can be listed.

[0084] The organic amines used as the hydrolysis catalyst may be used alone or in combination of two or more thereof as necessary.

[0085] As mentioned above, the reaction solution in the present invention must contain a silica source and a hydrolysis catalyst. In addition, water, alcohols, aldehydes, ketones, surfactants, etc. can be used. Preferably, the total amount of the silica source, the hydrolysis catalyst, and water is preferably 90% by mass or more. More preferably, they are 95% by mass or more.

[0086] In the present invention, in the mixture after the reaction of the silica source and the hydrolysis catalyst (hereinafter sometimes referred to as "reaction mixture"), or the reaction mixture after the alcohol removal and dispersion stabilization treatment using an acid (hereinafter sometimes referred to as "reaction concentrate") described later, the hydrolysis catalyst can be added to the reaction system so that the ratio of the hydrolysis catalyst (A) to the silica (B) {catalyst residual molar ratio (A / B)} is preferably 0.012 or less, more preferably in the range of 0.00035 to 0.012, and further preferably in the range of 0.0035 to 0.011, and the hydrolysis reaction is carried out. In this way, the pH of the reaction mixture and the reaction concentrate can be rationalized, and thickening and gelation can be suppressed, so it is preferred.

[0087] There is no particular limitation on the method for achieving such a catalyst residual molar ratio, and examples thereof include: a method in which a silica source calculated so that the catalyst residual molar ratio (A / B) finally becomes within the aforementioned range is continuously or intermittently introduced into a reaction vessel containing water and a hydrolysis catalyst (A); a method in which a hydrolysis catalyst and a silica source calculated so that the catalyst residual molar ratio finally becomes within the aforementioned range is continuously or intermittently introduced into a reaction vessel containing only water; a method in which a hydrolysis catalyst and a silica source calculated so that the catalyst residual molar ratio finally becomes within the aforementioned range is continuously or intermittently introduced into a reaction vessel containing water and a small amount of a hydrolysis catalyst (A), etc.

[0088] In addition, seeds of colloidal silica having particle growth properties may be introduced into the reaction system of the hydrolysis reaction prior to the hydrolysis reaction of the silica source, and the silica source and the hydrolysis catalyst may be slowly added into the reaction system so that the catalyst residual molar ratio (A / B) is within the above-mentioned range. This enables the production of colloidal silica of uniform particles, and is therefore preferred.

[0089] Furthermore, in the present invention, it is preferred that the silica source, hydrolysis catalyst, and water used as raw materials for the hydrolysis reaction be high-purity substances having a metal impurity content of preferably 1 ppm or less, more preferably 0.01 ppm or less, so that a high-purity colloidal silica dispersion having a low metal impurity content can be easily produced. That is, the obtained colloidal silica dispersion also preferably satisfies the range of the metal impurity content, and more preferably, the metal impurity content is 0.0001 ppm or less.

[0090] In the present invention, after the reaction of the readily hydrolyzable organic silicate with the hydrolysis catalyst, the alcohol generated by the hydrolyzable organic silicate is preferably removed. There is no particular limitation on the method of such alcohol removal treatment, and for example, a method of distilling the alcohol by heating using an apparatus equipped with a distillation tube having a condenser can be cited. By performing such an alcohol removal treatment, there is no need to consider the alcohol resistance of the materials used in the subsequent steps, and since the highly volatile alcohol disappears, it is preferred in terms of stabilization of the concentration of colloidal silica.

[0091] Next, the reaction mixture after the alcohol removal treatment is preferably dispersed and stabilized using an acid. As such a dispersion and stabilization treatment, a carbon dioxide blowing method of blowing carbon dioxide or an acid solution adding method of adding an acid solution under stirring is performed. In addition to performing either the carbon dioxide blowing method or the acid solution adding method, these methods may be used in combination. In any case, during the dispersion and stabilization treatment, the reaction mixture needs to be maintained in a stirred state by bubbling, stirring, and the like using carbon dioxide.

[0092] When the dispersion stabilization treatment is carried out by adopting the carbon dioxide blowing method, the carbon dioxide blown into the reaction mixture may be 100 volume % carbon dioxide, or may be inert gas diluted carbon dioxide diluted to about 0.1 volume % with an inert gas such as nitrogen, or may be air. Preferably, it may be 100 volume % carbon dioxide or 1 volume % or more of inert gas diluted carbon dioxide.

[0093] Moreover, regarding the treatment conditions during the carbon dioxide blowing method, since carbon dioxide blowing itself has a stirring effect, carbon dioxide can usually be introduced into the reaction mixture at a rate of preferably greater than 0 mL / min and less than 100000 mL / min, more preferably greater than 1 mL / min and less than 10000 mL / min, under stirring at a temperature higher than 0°C and less than 100°C, preferably greater than 5°C and less than 80°C.

[0094] In addition, when the dispersion stabilization treatment is carried out by the acid solution addition method, as the acid solution used, it is preferred to use an acid aqueous solution with a concentration of 20 wt % or less, which is a mixture of one or more selected from a carbonic acid aqueous solution, a dilute inorganic acid aqueous solution with a concentration of 20 wt % or less, and a dilute organic acid aqueous solution with a concentration of 20 wt % or less, and is preferably a mixture of one or more selected from a dilute inorganic acid aqueous solution with a concentration of 10 wt % or less and a dilute organic acid aqueous solution with a concentration of 10 wt % or less. Specifically, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid and phosphoric acid, and organic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylvaleric acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid and hydroxyethanesulfonic acid can be mentioned, and they can be appropriately selected according to the application and the like.

[0095] Regarding the treatment conditions during the method of adding the acid aqueous solution, the acid solution can be added in an amount generally in the range of 0.0001 mol to 10 mol, preferably 0.001 mol to 1 mol, based on acid, with stirring generally at 1 rpm to 3000 rpm, preferably 10 rpm to 1000 rpm, and generally at a temperature generally at 0°C to 100°C, preferably 5°C to 80°C.

[0096] The reaction mixture (reaction concentrate) subjected to dispersion and stabilization treatment by the method of the present invention has a silica concentration of 10% to 40% by mass and a pH of 6.0 to 8.1, which is almost able to maintain the pH value before the dispersion and stabilization treatment. In addition, the reaction mixture generally exhibits excellent dispersion stability for several weeks or even years without the occurrence of two-layer separation.

[0097] In the present invention, colloidal silica with reduced particles can be obtained as described above. Depending on the application, the obtained colloidal silica is used as seed particles, and a silica source is supplied to a reaction solution containing the seed particles and the hydrolysis catalyst to react, thereby producing grown colloidal silica with a grown particle size. In particular, when colloidal silica with a median particle size greater than 30 nm is to be obtained, the proportion of particles tends to increase significantly with conventional methods. Therefore, colloidal silica obtained by the means of supplying (discharging) the silica source in the liquid as described above is used as a seed particle, and the particles are grown, thereby obtaining colloidal silica with reduced particles and a relatively large particle size.

[0098] Regarding the growth colloidal silica for growing particles, it can be appropriately set and implemented in a manner to achieve its particle size according to the purpose and purpose. For example, as described above, it is preferred to use seed particles of colloidal silica with a particle size median value of less than 30nm based on the equivalent circle diameter obtained by image analysis using an electron microscope to manufacture growth colloidal silica with a particle size median value exceeding 30nm. There is no restriction on the particle size after growth, and it is preferably a particle size of about 1mm that can be stirred with a stirring force that does not cause the particles to settle and fog during stirring.

[0099] When the particles are grown, if the temperature of the reaction solution is high, the alcohol generated during hydrolysis tends to boil if the silica concentration in the reaction system increases, so it is preferred to react so that the silica concentration is 13% by mass or less. The so-called silica concentration is as defined in the examples.

[0100] Example

[0101] Hereinafter, preferred embodiments of the present invention will be specifically described based on Examples and Comparative Examples.

[0102] [Example 1]

[0103] In the mixer, temperature sensor, heating steam pipe, cooling water pipe, exhaust pipe, and Figure 1 In a 1000 liter (L) stainless steel reaction vessel with a double-tube organosilicate introduction tube of the structure illustrated in the example, 542.58 kg of pure water with a metal impurity content of less than 0.1 ppb and 0.58 kg of triethanolamine (bp: 361°C) with a metal impurity content of less than 10 ppb were placed. The double tube had an outer diameter of 25.4 mm, an inner diameter of 22 mm, and a length of 723 mm in the kettle, while the outer diameter of the inner tube was 6.35 mm, an inner diameter of 3.5 mm, and a length of 553 mm in the kettle. At this time, it was confirmed that the double-tube organosilicate introduction tube was immersed in the liquid for a length of 20 cm from the liquid surface to the liquid under stirring.

[0104] After confirmation, the liquid temperature in the reaction vessel was maintained at 80°C using steam and cooling water, while 236.84 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was flowed on the inner tube side of the double tube, and 0.5 L / min of nitrogen was flowed on the outer tube side, and it was continuously supplied for 6 hours under stirring. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. It was confirmed that the nozzle after the reaction was completed was not blocked by silicon dioxide.

[0105] Then, the temperature in the reaction vessel was lowered to 40°C to obtain a reaction product. In addition, the reaction product was transferred to a 500L stainless steel distillation vessel and a 500L stainless steel intermediate vessel, which included a stirrer, a temperature sensor, a pressure sensor, a liquid level control sensor, a heating steam pipe, a cooling water pipe, and an 800L stainless steel condenser with a distillate receiver connected to an exhaust pipe, and a sample was taken in the middle to analyze the solid content. Then, the system was depressurized to -73kPa with a vacuum pump, heated, and the evaporated gas was cooled with a condenser and distilled off to the distillate receiver. Every time the liquid in the distillation vessel decreased, the reaction crude product was supplied from the intermediate tank. After the reaction crude product was exhausted from the intermediate tank, 125.2kg of pure water was supplied to replace the solvent with water to obtain concentrated 20% colloidal silica.

[0106] Carbon dioxide was blown into the concentrate at 1.2 L / min for 10 minutes to disperse and stabilize the concentrate. Figures 2-3 Electron microscope observation was performed in this way to confirm that the particles were spherical particles with uniform particle size and protrusions. Image analysis was performed according to the steps described below, and the equivalent circle diameter was measured. The median particle size was obtained from the particle size distribution, and the number distribution ratio of the particles was calculated. The results are shown in Table 1. In addition, the metal impurity content was less than 0.1 ppb.

[0107] [Example 2]

[0108] 542.57 kg of pure water with a metal impurity content of 0.1 ppb or less and 0.58 kg of triethanolamine (bp: 361°C) with a metal impurity content of 10 ppb or less were loaded into the same apparatus as in Example 1. At this time, it was confirmed that the double-tube organosilicate introduction tube was immersed for 20 cm from the liquid surface to the liquid under stirring.

[0109] After confirmation, the liquid temperature in the reaction vessel was maintained at 70°C using steam and cooling water, while 236.85 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was flowed on the inner tube side of the double tube, and 0.5 L / min of nitrogen was flowed on the outer tube side, and it was continuously supplied for 6 hours under stirring. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. It was confirmed that the nozzle after the reaction was completed was not blocked by silicon dioxide.

[0110] Then, the temperature in the reaction container was lowered to 40°C, and 22.68 kg of the reaction product was added as seed particles, 526.17 kg of pure water with a metal impurity content of 0.1 ppb or less, and 1.40 kg of triethanolamine (bp: 361°C) with a metal impurity content of 10 ppb or less. At this time, it was confirmed that the double-tube organosilicate introduction tube was immersed in the liquid for 20 cm from the liquid surface to the liquid under stirring.

[0111] After confirmation, while the liquid temperature in the reaction container was maintained at 80°C using steam and cooling water, 229.75 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of 10 ppb or less was flowed on the inner tube side of the double tube, and 0.5 L / min of nitrogen was flowed on the outer tube side, and the supply was continuously supplied for 6 hours under stirring. Similarly, the supply pressure of the silicon dioxide source did not change and was 0 MPa, and the nozzle was not clogged after the reaction was completed.

[0112] Then, the temperature in the reaction vessel was lowered to 40°C, and the reaction vessel was transferred to a 500L stainless steel distillation vessel and a 500L stainless steel intermediate vessel, which were equipped with a stirrer, a temperature sensor, a pressure sensor, a liquid level control sensor, a heating steam pipe, a cooling water pipe, and an 800L stainless steel condenser with a distillate receiver connected to an exhaust pipe. Samples were taken during the process and the solid content was analyzed. Then, the system was depressurized to -73kPa with a vacuum pump, heated, and the evaporated gas was cooled with a condenser and distilled off to the distillate receiver. Every time the liquid in the distillation vessel decreased, the crude reaction product was supplied from the intermediate tank. After the crude reaction product was exhausted from the intermediate tank, 125.2kg of pure water was supplied to replace the solvent with water, thereby obtaining concentrated 20% colloidal silica.

[0113] Carbon dioxide was blown into the concentrate at 1.2 L / min for 10 minutes to disperse and stabilize the concentrate. Figures 4-5 Electron microscope observation was performed in this way to confirm that the particles were spherical particles with uniform particle size and protrusions. Image analysis was performed according to the steps described below, and the equivalent circle diameter was measured. The median particle size was obtained from the particle size distribution, and the number distribution ratio of the particles was calculated. The results are shown in Table 1. In addition, the metal impurity content was less than 0.1 ppb.

[0114] [Example 3]

[0115] In the same apparatus as in Example 1, 108.41 kg of the product obtained in Example 1 was loaded as seed particles, 467.71 kg of pure water having a metal impurity content of 0.1 ppb or less, and 1.34 kg of triethanolamine (bp: 361° C.) having a metal impurity content of 10 ppb or less. At this time, it was confirmed that the double-tube organosilicate introduction tube was immersed in the liquid for a length of 20 cm from the liquid surface to the liquid under stirring.

[0116] After confirmation, the liquid temperature in the reaction vessel was maintained at 80°C using steam and cooling water, while 204.32 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was flowed on the inner tube side of the double tube, and 0.5 L / min of nitrogen was flowed on the outer tube side, and it was continuously supplied for 6 hours under stirring. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. It was confirmed that the nozzle after the reaction was completed was not blocked by silicon dioxide.

[0117] Then, the temperature in the reaction vessel was lowered to 40°C, and the reaction vessel was transferred to a 500L stainless steel distillation vessel and a 500L stainless steel intermediate vessel, which were equipped with a stirrer, a temperature sensor, a pressure sensor, a liquid level control sensor, a heating steam pipe, a cooling water pipe, and an 800L stainless steel condenser with a distillate receiver connected to an exhaust pipe. Samples were taken during the process and the solid content was analyzed. Then, the system was depressurized to -73kPa with a vacuum pump, heated, and the evaporated gas was cooled with a condenser and distilled off to the distillate receiver. Every time the liquid in the distillation vessel decreased, the crude reaction product was supplied from the intermediate tank. After the crude reaction product was exhausted from the intermediate tank, 125.2kg of pure water was supplied to replace the solvent with water, thereby obtaining concentrated 20% colloidal silica.

[0118] Carbon dioxide was blown into the concentrate at 1.2 L / min for 10 minutes to disperse and stabilize the concentrate. Figures 6-7 Electron microscope observation was performed in this way to confirm that the particles were spherical particles with uniform particle size and protrusions. Image analysis was performed according to the steps described below, and the equivalent circle diameter was measured. The median particle size was obtained from the particle size distribution, and the number distribution ratio of the particles was calculated. The results are shown in Table 1. In addition, the metal impurity content was less than 0.1 ppb.

[0119] [Example 4]

[0120] The same apparatus as in Example 2 was used, except that the nitrogen flow rate was 1 L / min and the same double tube as in Example 2 was used, and the reaction was carried out in the same manner as in Example 2. During the reaction, the supply pressure of the silica source did not change and was 0 MPa, and the reaction was able to be completed. After the reaction, it was confirmed that the nozzle was not clogged with silica.

[0121] [Comparative Example 1]

[0122] 542.58 kg of pure water with a metal impurity content of 0.1 ppb or less and 0.58 kg of triethanolamine (bp: 361° C.) with a metal impurity content of 10 ppb or less were charged into the same apparatus as in Example 1, except that a single-tube introduction tube for supplying organosilicate (silica source) was used instead of the double tube used in Example 1. At this time, it was confirmed that the single-tube introduction tube for organosilicate was not at a level below the liquid surface even if all the organosilicate was charged under stirring.

[0123] After confirmation, the liquid temperature in the reaction vessel was maintained at 80°C using steam and cooling water, and 236.84 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was flowed in a single tube and continuously supplied for 6 hours under stirring. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. After the reaction was completed, the nozzle was confirmed to be free of blockage by silicon dioxide.

[0124] Then, the temperature in the reaction vessel was lowered to 40°C to obtain a reaction product. In addition, the reaction product was transferred to a 500L stainless steel distillation vessel and a 500L stainless steel intermediate vessel, which included a stirrer, a temperature sensor, a pressure sensor, a liquid level control sensor, a heating steam pipe, a cooling water pipe, and an 800L stainless steel condenser with a distillate receiver connected to an exhaust pipe, and a sample was taken in the middle to analyze the solid content. Then, the system was depressurized to -73kPa with a vacuum pump, heated, and the evaporated gas was cooled with a condenser and distilled off to the distillate receiver. Every time the liquid in the distillation vessel decreased, the reaction crude product was supplied from the intermediate tank. After the reaction crude product was exhausted from the intermediate tank, 125.2kg of pure water was supplied to replace the solvent with water to obtain concentrated 20% colloidal silica.

[0125] Carbon dioxide was blown into the concentrate at 1.2 L / min for 10 minutes to disperse and stabilize the concentrate. Figures 8-9 Electron microscope observation was performed in this way to confirm that the particle size was uneven and the particles were spherical particles with protrusions. Image analysis was performed according to the steps described below, and the equivalent circle diameter was measured. The median particle size was obtained from the particle size distribution, and the number distribution ratio of the particles was calculated. The results are shown in Table 1.

[0126] [Comparative Example 2]

[0127] 542.57 kg of pure water with a metal impurity content of 0.1 ppb or less and 0.58 kg of triethanolamine (bp: 361° C.) with a metal impurity content of 10 ppb or less were charged into the same apparatus as in Example 1, except that a single-tube introduction tube for supplying organosilicate (silica source) was used instead of the double tube used in Example 1. At this time, it was confirmed that the single-tube introduction tube for organosilicate was not at a level below the liquid surface even if all the organosilicate was charged under stirring.

[0128] After confirmation, 236.85 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was continuously supplied for 6 hours under stirring while the liquid temperature in the reaction container was maintained at 70°C using steam and cooling water. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. It was confirmed that the nozzle after the reaction was completed was not clogged with silicon dioxide.

[0129] Then, the temperature in the reaction container was lowered to 40°C, and 22.68 kg of the reaction product was added as seed particles, 526.17 kg of pure water with a metal impurity content of 0.1 ppb or less, and 1.40 kg of triethanolamine (bp: 361°C) with a metal impurity content of 10 ppb or less. At this time, it was confirmed that the single-tube organosilicate introduction tube was not at a liquid level even if all the organosilicate was added under stirring.

[0130] After confirmation, 229.75 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was continuously supplied for 6 hours under stirring while the liquid temperature in the reaction container was maintained at 80°C using steam and cooling water. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. It was confirmed that the nozzle after the reaction was completed was not clogged with silicon dioxide.

[0131] Then, the temperature in the reaction vessel was lowered to 40°C, and the reaction vessel was transferred to a 500L stainless steel distillation vessel and a 500L stainless steel intermediate vessel, which were equipped with a stirrer, a temperature sensor, a pressure sensor, a liquid level control sensor, a heating steam pipe, a cooling water pipe, and an 800L stainless steel condenser with a distillate receiver connected to an exhaust pipe. Samples were taken during the process and the solid content was analyzed. Then, the system was depressurized to -73kPa with a vacuum pump, heated, and the evaporated gas was cooled with a condenser and distilled off to the distillate receiver. Every time the liquid in the distillation vessel decreased, the crude reaction product was supplied from the intermediate tank. After the crude reaction product was exhausted from the intermediate tank, 125.2kg of pure water was supplied to replace the solvent with water, thereby obtaining concentrated 20% colloidal silica.

[0132] Carbon dioxide was blown into the concentrate at 1.2 L / min for 10 minutes to disperse and stabilize the concentrate. Figures 10-11 Electron microscope observation was performed in this way to confirm that the particle size was uneven and the particles were spherical particles with protrusions. Image analysis was performed according to the steps described below, and the equivalent circle diameter was measured. The median particle size was obtained from the particle size distribution, and the number distribution ratio of the particles was calculated. The results are shown in Table 1.

[0133] [Comparative Example 3]

[0134] In the same apparatus as in Example 1, 108.41 kg of the product obtained in Comparative Example 1 as a seed, 467.71 kg of pure water having a metal impurity content of 0.1 ppb or less, and 1.34 kg of triethanolamine (bp: 361° C.) having a metal impurity content of 10 ppb or less were charged, except that a single-tube introduction tube for supplying organosilicate (silica source) was used instead of the double tube used in Example 1. At this time, it was confirmed that the single-tube introduction tube for organosilicate was not at a level below the liquid level even if all the organosilicate was charged under stirring.

[0135] After confirmation, 204.32 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was continuously supplied for 6 hours under stirring while the liquid temperature in the reaction container was maintained at 80°C using steam and cooling water. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. It was confirmed that the nozzle after the reaction was completed was not clogged with silicon dioxide.

[0136] Then, the temperature in the reaction vessel was lowered to 40°C, and the reaction vessel was transferred to a 500L stainless steel distillation vessel and a 500L stainless steel intermediate vessel, which were equipped with a stirrer, a temperature sensor, a pressure sensor, a liquid level control sensor, a heating steam pipe, a cooling water pipe, and an 800L stainless steel condenser with a distillate receiver connected to an exhaust pipe. Samples were taken during the process and the solid content was analyzed. Then, the system was depressurized to -73kPa with a vacuum pump, heated, and the evaporated gas was cooled with a condenser and distilled off to the distillate receiver. Every time the liquid in the distillation vessel decreased, the crude reaction product was supplied from the intermediate tank. After the crude reaction product was exhausted from the intermediate tank, 125.2kg of pure water was supplied to replace the solvent with water, thereby obtaining concentrated 20% colloidal silica.

[0137] The reaction, distillation and dispersion stabilization treatment were carried out using the same apparatus as in Example 1, except that the organosilicate introduction tube was provided with a length that allowed the introduction of the organosilicate from outside the liquid to proceed even after the introduction of the organosilicate was completed, and nitrogen was not introduced. Figures 12-13 By performing electron microscope observation in this manner, it was confirmed that the particles were spherical particles having uneven particle diameters and protrusions.

[0138] [Example 5]

[0139] The same apparatus as in Example 2 was used to carry out the reaction in the same manner as in Example 2, except that the inner tube of the double tube of the apparatus in Example 2 had an outer diameter of 6.35 mm, an inner diameter of 3.5 mm, and an inner length of 703 mm, and the same solvent, i.e., pure water and catalyst, as in Example 2 were charged, and the nitrogen flow rate was 4 L / min. During the reaction, the supply pressure of the silica source changed to 0.08 MPa. After the completion of the reaction, the nozzle was checked and clogging of silica was found.

[0140] [Example 6]

[0141] The same apparatus as in Example 2 was used to carry out the reaction in the same manner as in Example 2, except that the outer tube side of the double tube of the apparatus in Example 2 had an outer diameter of 12.7 mm, an inner diameter of 10 mm, and an inner length of 723 mm, and the same solvent, i.e., pure water and catalyst, as in Example 2 were charged, and the nitrogen flow rate was 4 L / min. During the reaction, the supply pressure of the silica source changed to 0.08 MPa. After the completion, the nozzle was checked and clogging of silica was found.

[0142] [Example 7]

[0143] The double tube of the apparatus of Example 2 was set to have an outer diameter of 12.7 mm, an inner diameter of 10 mm, and a length of 723 mm in the kettle on the outer tube side, and an outer diameter of 6.35 mm, an inner diameter of 3.5 mm, and a length of 703 mm in the kettle on the inner tube side. The same solvent as in Example 2, i.e., pure water and a catalyst, were loaded, and the same apparatus as in Example 2 was used. The nitrogen flow rate was set to 0.5 L / min in the same manner as in Example 2, and the reaction was carried out. During the reaction, the supply pressure of the silica source changed to 0.04 MPa, and after the completion of the reaction, the nozzle was checked and clogging of silica was found.

[0144] [Example 8]

[0145] The double tube of the apparatus of Example 2 was set to an outer diameter of 12.7 mm, an inner diameter of 10 mm, and a length of 723 mm in the kettle on the outer tube side, and an outer diameter of 6.35 mm, an inner diameter of 3.5 mm, and a length of 703 mm in the kettle on the inner tube side. The same solvent as in Example 2, i.e., pure water and a catalyst, were loaded, and the same apparatus as in Example 2 was used to carry out the reaction at a nitrogen flow rate of 1 L / min. During the reaction, the supply pressure of the silica source changed to 0.02 MPa. After the completion, the nozzle was checked and clogging of silica was found.

[0146] [Example 9]

[0147] The double tube of the apparatus of Example 2 was set to have an outer diameter of 12.7 mm, an inner diameter of 10 mm, and a length of 723 mm in the kettle on the outer tube side, and an outer diameter of 6.35 mm, an inner diameter of 3.5 mm, and a length of 703 mm in the kettle on the inner tube side. The same solvent as in Example 2, i.e., pure water and a catalyst, were loaded, and the same apparatus as in Example 2 was used to carry out the reaction at a nitrogen flow rate of 4 L / min. During the reaction, the supply pressure of the silica source changed by 0.02 MPa. After the completion, the nozzle was checked and clogging of silica was found.

[0148] [Example 10]

[0149] In the mixer, temperature sensor, heating steam pipe, cooling water pipe, exhaust pipe, and Figure 1 In a 1000 liter (L) stainless steel reaction container with a double-tube organosilicate introduction tube of the structure illustrated in the example, 542.70 kg of pure water with a metal impurity content of less than 0.1 ppb and 0.4015 kg of 3-ethoxypropylamine (bp: 137°C) with a metal impurity content of less than 10 ppb were placed. The double tube had an outer diameter of 25.4 mm, an inner diameter of 22 mm, and a length of 723 mm in the kettle, while the outer diameter of the inner tube was 6.35 mm, an inner diameter of 3.5 mm, and a length of 553 mm in the kettle. At this time, it was confirmed that the double-tube organosilicate introduction tube was immersed in the liquid for a length of 20 cm from the liquid surface to the liquid under stirring.

[0150] After confirmation, the liquid temperature in the reaction vessel was maintained at 80°C using steam and cooling water, while 236.90 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was flowed on the inner tube side of the double tube, and 0.5 L / min of nitrogen was flowed on the outer tube side, and it was continuously supplied for 6 hours under stirring. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. It was confirmed that the nozzle after the reaction was completed was not blocked by silicon dioxide.

[0151] Then, the temperature in the reaction container was lowered to 40°C to obtain a reaction product. In addition, the reaction product was transferred to a 500L stainless steel distillation container and a 500L stainless steel intermediate container including a stirrer, a temperature sensor, a pressure sensor, a liquid level control sensor, a heating steam pipe, a cooling water pipe, and an 800L stainless steel condenser with a distillate receiver connected to an exhaust pipe, and a sample was taken in the middle to analyze the solid content. Then, the evaporated gas was cooled with a condenser and distilled off to the distillate receiver. Every time the liquid in the distillation container decreased, the reaction crude product was supplied from the intermediate tank. After the reaction crude product was exhausted from the intermediate tank, 125.2kg of pure water was supplied to replace the solvent with water to obtain concentrated 20% colloidal silica.

[0152] Carbon dioxide was blown into the concentrate at 1.2 L / min for 10 minutes to disperse and stabilize the concentrate. Figures 14-15 Electron microscope observation was performed in this way to confirm that the particles were spherical particles with uniform particle size and protrusions. Image analysis was performed according to the steps described below, and the equivalent circle diameter was measured. The median particle size was obtained from the particle size distribution, and the number distribution ratio of the particles was calculated. The results are shown in Table 1. In addition, the metal impurity content was less than 0.1 ppb.

[0153] [Comparative Example 4]

[0154] In the same apparatus as in Example 1, 542.70 kg of pure water having a metal impurity content of 0.1 ppb or less and 0.4015 kg of 3-ethoxypropylamine (bp: 137° C.) having a metal impurity content of 10 ppb or less were charged, except that a single-tube introduction tube for supplying organosilicate (silica source) was used instead of the double tube used in Example 1. At this time, it was confirmed that the single-tube introduction tube for organosilicate was not at a level below the liquid surface even if all the organosilicate was charged under stirring.

[0155] After confirmation, 236.9 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was continuously supplied for 6 hours under stirring while the liquid temperature in the reaction container was maintained at 70°C using steam and cooling water. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. It was confirmed that the nozzle after the reaction was completed was not clogged with silicon dioxide.

[0156] Then, the temperature in the reaction container was lowered to 40°C, and 103.24 kg of the reaction product was added as seed particles, 471.66 kg of pure water with a metal impurity content of 0.1 ppb or less, and 0.929 kg of 3-ethoxypropylamine (bp: 137°C) with a metal impurity content of 10 ppb or less. At this time, it was confirmed that the single-tube organosilicate introduction tube was not at a liquid level even if all the organosilicate was added under stirring.

[0157] After confirmation, 204.18 kg of tetramethyl silicate (silicon dioxide source; manufactured by Tama Chemical Industry Co., Ltd.) with a metal impurity content of less than 10 ppb was continuously supplied for 6 hours under stirring while the liquid temperature in the reaction container was maintained at 80°C using steam and cooling water. During this period, the supply pressure of the silicon dioxide source did not change and was 0 MPa. It was confirmed that the nozzle after the reaction was completed was not clogged with silicon dioxide.

[0158] Then, the temperature in the reaction vessel was lowered to 40°C, and the reaction vessel was transferred to a 500L stainless steel distillation vessel and a 500L stainless steel intermediate vessel, which included a stirrer, a temperature sensor, a pressure sensor, a liquid level control sensor, a heating steam pipe, a cooling water pipe, and an 800L stainless steel condenser with a distillate receiver connected to an exhaust pipe. Samples were taken in the middle and the solid content was analyzed. Then, the evaporated gas was cooled with a condenser and distilled off to the distillate receiver. Every time the liquid in the distillation vessel decreased, the crude reaction product was supplied from the intermediate tank. After the crude reaction product was exhausted from the intermediate tank, 125.2kg of pure water was supplied to replace the solvent with water to obtain concentrated 20% colloidal silica.

[0159] Carbon dioxide was blown into the concentrate at 1.2 L / min for 10 minutes to disperse and stabilize the concentrate. Figures 16-17 Electron microscope observation was performed in this way to confirm that the particle size was uneven and the particles were spherical particles with protrusions. Image analysis was performed according to the steps described below, and the equivalent circle diameter was measured. The median particle size was obtained from the particle size distribution, and the number distribution ratio of the particles was calculated. The results are shown in Table 1.

[0160] In addition, the physical properties and the like of the obtained colloidal silica were evaluated by the following methods.

[0161] (1) SEM observation:

[0162] Colloidal silica was diluted with water, placed on a sample stage of a silicon wafer, dried, and observed using an ultra-high resolution field emission scanning electron microscope SU9000 manufactured by Hitachi High-Tech. The observed images of Examples 1 to 3, 10, and Comparative Examples 1 to 4 are shown in FIG. Figure 2 , 4 , 6, 8, 10, 12, 14 and 16 (b).

[0163] (2) STEM observation:

[0164] Colloidal silica was diluted with water, placed on a TEM indicator film, dried, and observed using an ultra-high resolution field emission scanning electron microscope SU9000 manufactured by Hitachi High-Tech. The observed images (a) and analyzed images (c) of Examples 1 to 3, 10, and Comparative Examples 1 to 4 are shown in FIG. Figures 2 to 17 .

[0165] (3) Equivalent circle diameter, particle size median value:

[0166] The STEM image obtained in (2) is imported into the Image-Pro software of Hakuto Corporation, and the area of ​​the particles is measured. The result is imported into the calculation software and compared with the SEM image taken at the same time. The overlapping particle data is removed, and the diameter calculated from the area of ​​the remaining particles is taken as the equivalent circle diameter. The equivalent circle diameters of all particles other than those that have been removed are added up, and the particle size at which the accumulation of the frequency (number) is exactly 50% is calculated as the median particle size. Then, the particle size below 50% of the median particle size is regarded as a microparticle, and its number distribution ratio is calculated. The particle size distribution (d) of Examples 1 to 3, 10 and Comparative Examples 1 to 4 is shown in Figure 3 , 5 , 7, 9, 11, 13, 15 and 17.

[0167] (4) BET particle size: measured using NOVA4200e manufactured by Yuasa Ionics. The average particle size of the spherical colloidal silica particles constituting the colloidal silica particles is the specific surface area Sm measured by the nitrogen adsorption method (BET method). 2 / g, using D 2 =2720 / S.

[0168] (5) Zeta potential: Zeta potential was measured using a Zeta Probe Zeta potentiometer manufactured by Colloidal Dynamics, Inc., according to a method for measuring zeta potential in a high concentration colloidal solution (solutions having the silica concentrations after production shown in Tables 1 and 2) based on the theory of the ESA electroacoustic phenomenon.

[0169] (6) Average particle size (nm): The median value of the particle size distribution measured using a disc centrifugal particle size distribution measuring apparatus manufactured by CPS Instruments, USA, was defined as the average particle size (nm).

[0170] (7) Silica concentration: The residue obtained by evaporating the water content was defined as the silica concentration.

[0171] (8) pH, viscosity, and conductivity: measured at 25°C.

[0172] (9) Metal impurity content: An atomic absorption spectrophotometer was used to measure the metal impurities (the total of Na, Fe, Cu, Al, K, Cr, Ni, Pb, Mn, Mg, Zn and Ca) using a 50 g sample.

[0173] [Table 1]

[0174]

[0175] [Table 2]

[0176]

[0177] Description of Reference Numerals

[0178] 1...Inner tube, 2...Outer tube, 3...Introduction tube insertion port, 4...Introduction tube, 5...Reaction container, 6...Reaction liquid, 7...Agitator

Claims

1. Colloidal silicon dioxide, It is characterized in that Based on the Heywood diameter, which is an equivalent circle diameter obtained by image analysis using an electron microscope, the number distribution ratio of fine particles having a particle size that is 50% or less of the median particle size is 1% or less.

2. The colloidal silicon dioxide according to claim 1, It is characterized in that It is based on image analysis using scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM).

3. An abrasive comprising the colloidal silica according to claim 1 or 2.

4. A method for producing colloidal silica, comprising supplying a readily hydrolyzable organic silicate to a reaction solution containing a hydrolysis catalyst containing one or a mixture of two or more selected from organic amines and reacting the mixture to produce colloidal silica. It is characterized in that The supply of the easily hydrolyzable organic silicate is performed in a state where the supply port of the easily hydrolyzable organic silicate is immersed in the reaction liquid surface.

5. The method for producing colloidal silica according to claim 4, It is characterized in that The length of the supply port of the easily hydrolyzable organic silicate immersed in the reaction liquid surface is 3 times or more the outer diameter of the supply port.

6. The method for producing colloidal silica according to claim 4 or 5, It is characterized in that The easily hydrolyzable organic silicate is supplied together with an inert gas.

7. The method for producing colloidal silica according to claim 6, It is characterized in that The flow rate L of the inert gas relative to the supply amount kg of the easily hydrolyzable organic silicate is 1 to 10000 L / kg.

8. The method for producing colloidal silica according to claim 4 or 5, It is characterized in that As a means for supplying the readily hydrolyzable organic silicate, a nozzle having an inner-outer double tube structure including an outer tube and an inner tube inserted into the outer tube is used, and the readily hydrolyzable organic silicate is supplied to the inner tube while an inert gas is supplied to the outer tube.

9. The method for producing colloidal silica according to claim 8, It is characterized in that The ratio O / I of the inner diameter O of the outer tube for supplying the inert gas to the outer diameter I of the inner tube for supplying the easily hydrolyzable organic silicate is 2 to 7.

10. The method for producing colloidal silica according to claim 8, It is characterized in that The difference in length between the inner tube for supplying the easily hydrolyzable organic silicate and the outer tube for supplying the inert gas, i.e., outer tube-inner tube, is greater than or equal to the outer diameter of the outer tube and is 1 to 10 times greater than the outer diameter of the outer tube.

11. The method for producing colloidal silica according to claim 4 or 5, in, The easily hydrolyzable organic silicate is trimethyl silicate, tetramethyl silicate, triethyl silicate, or methyl trimethyl silicate.

12. The method for producing colloidal silica according to claim 4 or 5, in, The organic amine is one or a mixture of two or more selected from quaternary ammonium amines, tertiary amines, secondary amines and primary amines, and carbonates, hydrogen carbonates and silicates thereof.

13. The method for producing colloidal silica according to claim 6, It is characterized in that The inert gas is nitrogen, argon and / or helium.

14. A method for producing colloidal silicon dioxide, It is characterized in that After producing colloidal silica by the method according to claim 4 or 5, the colloidal silica is used as seed particles, and a readily hydrolyzable organic silicate is supplied to a reaction solution containing the seed particles and the hydrolysis catalyst to react, thereby producing grown colloidal silica having a grown particle size.

15. The method for producing colloidal silica according to claim 14, It is characterized in that Using seed particles of colloidal silica having a particle median value of 30 nm or less based on the equivalent circle diameter obtained by image analysis using an electron microscope, a reaction is performed with a silica component concentration in the reaction system being 13% by mass or less to produce grown colloidal silica having a particle median value exceeding 30 nm and being 1 mm or less.

Images