Precipitation process silica and composition including the same and production method for precipitation process silica

Abstract

To provide: precipitation process silica which exhibits a polishing property excellent in terms of polishing speed and smoothness of a polished surface and a composition including the precipitation process silica; and a production method for the precipitation process silica.SOLUTION: A precipitation process silica has a total pore volume as measured by a mercury intrusion technique of 2.50 cm3 / g or more, a BET specific surface area of 15 to 35 m2 / g, a volume-average particle diameter D500min in a particle diameter distribution in slurry including 4 mass% of the precipitation process silica of 2.0 to 25 μm, and a percentage particle diameter change A of 0.50 to 0.90 calculated by the following formula: percentage particle diameter change A=(D500min-D505min) / D500min; where the volume-average particle diameter D505min is a volume-average particle diameter in the particle diameter distribution in the slurry including 4 mass% of the precipitation process silica subjected to 5 minute sonication.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to precipitated silica and compositions containing same, as well as a method for making precipitated silica. [Background technology]

[0002] Precipitated silica is generally used as a reinforcing filler for rubber, and is also widely used as a polishing compound (abrasive) for various polishing applications including mechanical polishing and toothpaste, as a cosmetic compound, as a matting agent for paints or inks, and as a paper coating agent.

[0003] For example, for abrasive applications and thermal paper coating applications, precipitated silicas have low BET surface areas (e.g., 100 m 2 / g or less).

[0004] Patent Document 1 relates to particulate amorphous silica (precipitated silica) for thermal paper. The particulate amorphous silica described in Patent Document 1 has a particle size distribution of secondary particles in which particles of 4 μm or less account for 90% by weight or more of the total when measured by centrifugal sedimentation, and further has a particle size distribution of 10 to 100 μm. 2 / g and a bulk density of 0.14 to 0.30 g / cc.

[0005] Patent Document 2 describes a sintered body having a BET specific surface area of ​​40 to 120 m 2

[0003] Patent Document 2 describes a polishing slurry containing silica with a specific surface area of ​​0.15g / g. Patent Document 2 teaches that an increase in particle abrasiveness is strongly correlated with a decrease in particle surface area as determined by N2 adsorption (BET) method. Therefore, it is expected that in polishing applications, the smaller the BET specific surface area of ​​precipitated silica, the better the abrasiveness.

[0006] Patent Document 3 relates to a slurry of hydrous silicic acid (precipitated silica) used as an abrasive, an additive for film or resin coating, and a matting agent for paint or ink. The slurry described in Patent Document 3 has a BET specific surface area of ​​10 to 35 m 2 / g, and has a volume average particle size (D50) of 0.4 to 0.9 μm as measured by laser diffraction, and a particle size (D90) of 90% of the bottom volume integrated cumulative value in the particle size distribution as measured by laser diffraction is 1.0 to 5.0 μm.

[0007] When precipitated silica, which has a low BET specific surface area, is used as a polishing compound, the polishing rate is fast, but the polished surface tends to be rough. Therefore, in the polishing process for substrates such as silicon wafers and glass, it is common to perform primary polishing using precipitated silica, followed by intermediate polishing such as secondary and tertiary polishing as necessary, and then final polishing using colloidal silica.

[0008] As mentioned above, colloidal silica has traditionally been used for final polishing. For example, Patent Document 4 discloses colloidal silica with a primary particle size of 10 to 100 nm as an abrasive for glass substrates. Patent Document 4 further describes that this colloidal silica can be used to perform precise polishing.

[0009] It should be noted that precipitated silica and colloidal silica as polishing compounds are completely different materials with different purposes and properties due to differences in their structures. Precipitated silica is a silica aggregate with an aggregated particle structure, while colloidal silica is a monodispersed silica particle that is not aggregated. Polishing using colloidal silica can produce a precise, smooth surface, but is characterized by a slow polishing rate, including the bearing effect. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 59-22794 [Patent Document 2] Special Publication No. 2002-527599 [Patent Document 3] Patent Publication No. 2021-59462 [Patent Document 4] Japanese Patent Application Publication No. 2017-124954 Summary of the Invention [Problem to be solved by the invention]

[0011] When the precipitated silica described in Patent Documents 1 and 2 is used as a polishing compound to polish a substrate, there is an advantage in that the polishing rate can be increased, but the polished surface becomes rough, causing irregularities on the surface, and further, abrasion marks (marks left when two objects rub against or come into contact with each other) may appear on the polished surface.

[0012] The slurry described in Patent Document 3 has a BET specific surface area of ​​35 m 2 / g or less and contains precipitated silica with a volume average particle size controlled to 0.4 to 0.9 μm, and therefore exhibits improved polishing properties compared to Patent Documents 1 and 2, but polishing properties that can further improve the smoothness of the polished surface are desired.

[0013] As mentioned above, colloidal silica is an excellent polishing compound for the final polishing, but due to its slow removal rate, it cannot be said to be a polishing compound suitable for the initial polishing of the polishing process.

[0014] The present invention has been made in view of the above problems, and has as its object to provide precipitated silica which exhibits excellent polishing properties in terms of polishing rate and smoothness of polished surface.

[0015] In another aspect, the present invention provides a composition comprising the above-described precipitated silica.

[0016] In another aspect, the present invention provides a method for producing the precipitated silica. [Means for solving the problem]

[0017] The above-mentioned problems have been solved by the fact that precipitated silica has a low BET specific surface area, an average particle size within a specific range, and a structure that is moderately easy to disintegrate. Specifically, the above-mentioned problems have been solved by the invention of [1] below, and preferably by the invention of [2] and subsequent inventions. [1] 2.50 cm measured by mercury porosimetry 3 / g or more total pore volume, 15~35m 2 / g BET specific surface area, The volume average particle diameter D50 of 2.0 to 25 μm in the particle size distribution obtained by measuring a slurry of precipitated silica prepared at 4 mass% without ultrasonic treatment using a laser diffraction particle size distribution analyzer. 0min , and Volume average particle size D50 0min and D50 5min A particle size change rate A of 0.50 to 0.90 calculated by the following formula 1 based on the above Precipitated silica having: Formula 1: Particle size change rate A = (D50 0min -D50 5min ) / D50 0min Here, the volume average particle diameter D50 5min is the volume average particle diameter in the particle size distribution obtained by subjecting 50 mL of a 4% by mass precipitated silica slurry to ultrasonic treatment for 5 minutes using an ultrasonic homogenizer with an output of 140 W, and then measuring the slurry with a laser diffraction particle size distribution analyzer. [2] Volume average particle size D50 5min and D50 10min The precipitated silica according to [1], having a particle size change rate B of 0.40 or less, calculated by the following formula 2 based on: Formula 2: Particle size change rate B = (D50 5min -D50 10min ) / D50 5min Here, the volume average particle diameter D50 10minis the volume average particle diameter in the particle size distribution obtained by subjecting 50 mL of a 4% by mass precipitated silica slurry to ultrasonic treatment for 10 minutes using an ultrasonic homogenizer with an output of 140 W, and then measuring the slurry with a laser diffraction particle size distribution analyzer. [3] Volume average particle size D50: 1.0 to 15 μm 5min The precipitated silica according to [1] or [2], having [4] The precipitated silica according to any one of [1] to [3], which has an apparent density of 80 to 180 g / L. [5] A 4% by weight slurry of precipitated silica without ultrasonic treatment has a pH of 5.5 to 8.5; and The filtrate of the slurry has an electrical conductivity of less than 1,000 μS / cm. The precipitated silica according to any one of [1] to [4]. [6] The precipitated silica according to any one of [1] to [5], which is used as a polishing compounding agent, a cosmetic compounding agent, or a matting agent for paints or inks. [7] Volume average particle size D50 5min and D50 10min The particle size change rate B is 0.40 or less, calculated by the following formula 2 based on Formula 2: Particle size change rate B = (D50 5min -D50 10min ) / D50 5min Here, the volume average particle diameter D50 10min is the volume average particle diameter in the particle size distribution obtained by subjecting 50 mL of a 4% by mass precipitated silica slurry to ultrasonic treatment for 10 minutes using an ultrasonic homogenizer with an output of 140 W, and then measuring the slurry using a laser diffraction particle size distribution analyzer. Volume average particle size D50: 1.0 to 15 μm 5min and It has an apparent density of 80 to 180 g / L. A slurry of precipitated silica prepared at 4% by mass without ultrasonic treatment has a pH of 5.5 to 8.5; the filtrate of the slurry has an electrical conductivity of less than 1,000 μS / cm; and The precipitated silica according to [1] is used as a polishing compounding agent, a cosmetic compounding agent, or a matting agent for paints or inks. [8] A polishing composition comprising the precipitated silica according to any one of [1] to [7]. [9] A cosmetic product comprising the precipitated silica according to any one of [1] to [7].

[10] [1] - [7] A paint or ink containing the precipitated silica according to any one of the above items.

[11] A method for producing precipitated silica according to any one of [1] to [7], (A) Prepare an aqueous solution of alkali silicate at 80 to 95°C in a container equipped with a solution circulation line. (B) while stirring the solution in the container and circulating it through a circulation line, an aqueous alkali silicate solution having an SiO concentration of 10.0 to 15.0 mass % and dilute sulfuric acid of 1.0 to 10.0 mass % are simultaneously added to the solution in the container under conditions where the volume ratio of the aqueous alkali silicate solution to the dilute sulfuric acid is 1:0.5 to 1:10, thereby generating a reaction product in the solution in the container; (C) After the simultaneous addition is completed, acid is added to stop the formation of the reaction product; (D) separating the reaction product from the reaction solution in the vessel by solid-liquid separation to obtain the precipitated silica; A manufacturing method comprising:

[12] The method of manufacturing according to

[11] , wherein the simultaneous addition in step (B) is carried out for 450 to 750 minutes.

[13] The solution circulation is carried out in a container with a volume of Xm 3 0.3X~0.7Xm 3 The method according to

[11] or

[12] , wherein the method is carried out at a flow rate of 1000 kJ / min.

[14] The method according to any one of

[11] to

[13] , wherein the aqueous alkali silicate solution used for simultaneous addition has a Na2O concentration of 3.1 to 5.0 mass % and a SiO2 / Na2O molar ratio of 3.0 to 3.5. [Effects of the Invention]

[0018] According to the present invention, precipitated silica is obtained which exhibits excellent polishing properties in terms of polishing rate and smoothness of polished surface.

[0019] In another aspect, the present invention provides a composition comprising the above-described precipitated silica.

[0020] In another aspect, the present invention allows for the production of the precipitated silica described above. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a particle size distribution diagram of the precipitated silica of Example 1. [Figure 2] FIG. 2 is a particle size distribution diagram of the precipitated silica of Comparative Example 2. [Figure 3] FIG. 3 is a SEM photograph of the precipitated silica of Example 1 at (a) 10,000x and (b) 50,000x magnification. [Figure 4] FIG. 4 shows SEM photographs of the precipitated silica of Example 2 at (a) 10,000x and (b) 50,000x magnification. [Figure 5] FIG. 5 is a SEM photograph of the precipitated silica of Comparative Example 1 at (a) 10,000x magnification and (b) 50,000x magnification. [Figure 6] FIG. 6 is a set of SEM photographs of the precipitated silica of Comparative Example 2 at (a) 10,000x magnification and (b) 50,000x magnification. [Figure 7] FIG. 7 is a SEM photograph of the precipitated silica of Comparative Example 4 at (a) 10,000x magnification and (b) 50,000x magnification. [Figure 8] FIG. 8 is an image of the surface roughness of the ABS plate after evaluation of polishability using the precipitated silica of Example 1. [Figure 9]FIG. 9 is an image of the surface roughness of an ABS plate after evaluation of polishability using precipitated silica of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0022] [Precipitated silica] The precipitated silica of the present invention is 2.50 cm measured by mercury porosimetry 3 / g or more total pore volume, 15~35m 2 / g BET specific surface area, The volume average particle diameter D50 of 2.0 to 25 μm in the particle size distribution obtained by measuring a slurry of precipitated silica prepared at 4 mass% without ultrasonic treatment using a laser diffraction particle size distribution analyzer. 0min , and Volume average particle size D50 0min and D50 5min A particle size change rate A of 0.50 to 0.90 calculated by the following formula 1 based on the above It has. Formula 1: Particle size change rate A = (D50 0min -D50 5min ) / D50 0min Here, the volume average particle diameter D50 5min is the volume average particle diameter in the particle size distribution obtained by subjecting 50 mL of a 4% by mass precipitated silica slurry to ultrasonic treatment for 5 minutes using an ultrasonic homogenizer with an output of 140 W, and then measuring the slurry with a laser diffraction particle size distribution analyzer.

[0023] 1. Effect of precipitated silica as a polishing compound The precipitated silica of the present invention, having the above-described constitution, exhibits excellent polishing properties in terms of polishing rate and smoothness of polished surface. Without intending to be bound by theory, the reason for this is presumed to be as follows.

[0024] Conventional precipitated silica with a low BET specific surface area is composed of relatively large silica aggregates. During industrial polishing processes, the size of the aggregates creates a moderate resistance between the aggregates and the substrate surface, ensuring sufficient abrasive force and achieving a high polishing rate. Regarding the inability of conventional precipitated silica to achieve sufficient polishing surface smoothness, the inventors conducted detailed investigations into the polishing action of precipitated silica and found that the internal cohesive force (bonding between primary particles) of the aggregates of conventional precipitated silica is strong, resulting in excessive hardness and the formation of abrasion marks. For example, when conventional precipitated silica used as a polishing compound was observed with a scanning electron microscope (SEM), it was found that the primary particles were tightly adhered to each other in the form of massive aggregates, and that some aggregates had sharp edges on the fracture surface formed by grinding.

[0025] In contrast, the precipitated silica of the present invention is an aggregate having a relatively large volume average particle size and an aggregate structure that is moderately easy to disintegrate. It is believed that the precipitated silica of the present invention, due to its relatively large volume average particle size, generates a moderate resistance between the silica and the substrate surface during the polishing process, thereby achieving a sufficient polishing rate. In addition, the precipitated silica of the present invention has an aggregate structure that is moderately easy to disintegrate, which allows it to disintegrate moderately during the polishing process, thereby preventing excessive force from being applied to the polishing surface. Furthermore, due to its disintegrability, the precipitated silica of the present invention becomes an aggregate of a size suitable for smoothing the substrate surface at the end of the polishing process, which is similar to the situation when finish polishing is performed with colloidal silica having a small particle size. As a result, it is believed that the precipitated silica of the present invention can improve the smoothness of the substrate surface.

[0026] Generally, industrial polishing processes involve multiple steps, such as primary polishing and secondary polishing, to finish the surface of a substrate smoothly. This is because polishing that emphasizes polishing speed gradually shifts to polishing that emphasizes smoothness. By using the precipitated silica of the present invention, both polishing speed and smoothness can be achieved, so that the number of steps in the polishing process can be reduced.

[0027] Industrial polishing processes include lapping, buffing, and grinding stone polishing, and the precipitated silica of the present invention can be used for any of these polishing processes. In particular, the precipitated silica of the present invention can be suitably used in buffing or lapping as a powder or slurry. The object to be polished is not particularly limited, and known substrates such as metal substrates, silicon wafers, and glass substrates can be used. The precipitated silica of the present invention can also be used in combination with chemical agents to form slurries for CMP polishing.

[0028] Furthermore, the precipitated silica of the present invention can be suitably used not only as an industrial polishing compounding agent but also as a polishing compounding agent for dentifrices (toothpaste compounding agents). The precipitated silica of the present invention has few bonding sites (necking sites) between primary particles, and the spherical shape of the primary particles is largely maintained (see Figures 3 and 4, described below). In other words, the precipitated silica of the present invention is an aggregate containing many spherical primary particles (rounded surfaces) and having an aggregate structure that is moderately easy to disintegrate. It is believed that such an aggregate structure prevents excessive stress on the teeth, allowing stains to be removed without damaging the enamel or gums.

[0029] The precipitated silica of this invention can be used in place of or in addition to existing polishing formulations.

[0030] The precipitated silica of the present invention can be incorporated into various types of dentifrices, such as paste, gel, and liquid types.

[0031] 2. Further benefits of precipitated silica The present inventors have unexpectedly found that the precipitated silica of the present invention also exhibits excellent effects as a cosmetic formulation and matting agent.

[0032] (1) Cosmetic compounding agents The precipitated silica of the present invention has been found to have a moist feel and to have the property of adequately adhering to the skin. Cosmetics may contain silica of about 0.1 to 50 μm in size to adjust the properties of the cosmetics, such as adhesion to the skin, feel, and color (see, for example, JP-A-07-258030). Because the precipitated silica of the present invention has a moist feel, it can be used as a feel-improving agent for cosmetics.

[0033] Furthermore, it has been found that the precipitated silica of the present invention also has the property of adequately adhering to the skin, which is an extremely useful feature as a cosmetic ingredient in that it supports the adhesion and staying power of cosmetics on the skin and prevents makeup from coming off.

[0034] The reason why the precipitated silica of the present invention has a moist feel and adhesiveness is not clear, but it is presumed that it is compatible with the skin due to, for example, an appropriate total pore volume, BET specific surface area, and disintegrability of the aggregated structure.

[0035] The type of cosmetic product is not particularly limited. The precipitated silica of the present invention can be blended into conventionally known cosmetics, such as solid cosmetics such as foundations and liquid cosmetics such as sunscreens. In particular, the precipitated silica of the present invention not only improves the feel of the skin, but also has an excellent soft-focus effect that fills in wrinkles and other irregularities on the skin surface, making the skin look beautiful, making it useful as an ingredient in foundations.

[0036] The precipitated silica of the present invention can be used in place of or in addition to existing cosmetic formulations.

[0037] (2) Matting agents for paints or inks The precipitated silica of the present invention maintains a constant particle size and exhibits a sufficient matting effect, so it can also be used as a matting agent for paints or inks. The type of paint or ink is not particularly limited. The precipitated silica of the present invention can be blended with various types of known paints or inks, whether solvent-based or water-based.

[0038] The precipitated silica of the present invention can be used in place of or in addition to existing matting agents.

[0039] 3. Composition of precipitated silica The precipitated silica of the present invention has a pore size of 2.50 cm as measured by mercury porosimetry. 3 The precipitated silica of the present invention has a total pore volume of 2.50 cm3 or more. The total pore volume represents the total volume of pores in the precipitated silica and is a property related to the structural strength of the precipitated silica. Therefore, the total pore volume is one index of the collapsibility (collapseability) of the precipitated silica. The precipitated silica of the present invention has a total pore volume of 2.50 cm3 or more. 3 / g or more, it has an agglomerated structure that disintegrates moderately, and when used as a polishing compound, it does not roughen the polished surface and is less likely to leave scratches. For cosmetic applications, it is recommended that the total pore volume be 2.50 cm3 or more. 3 / g or more, it is easy to obtain a moist feel and adhesion. For paint and ink applications, a total pore volume of 2.50 cm 3 / g or more, a sufficient matte effect is easily obtained.

[0040] The precipitated silica of the present invention preferably has a total pore volume of 2.60 cm 3 / g or more, and more preferably 2.70 cm 3 / g or more, more preferably 2.80 cm 3 The total pore volume of the precipitated silica of the present invention is, for example, 4.00 cm3 / g or more, from the viewpoint of easily obtaining a suitable structural strength, easily obtaining a moist feel and adhesion, or easily obtaining a sufficient matte effect. 3 / g or less, preferably 3.80 cm 3 / g or less, and more preferably 3.70 cm 3 / g or less, and more preferably 3.60 cm 3 / g or less.

[0041] The precipitated silica of the present invention has a particle size of 15 to 35 m 2 / g. BET specific surface area is 15m 2 / g or more, the bonding between primary particles in the precipitated silica is suppressed. When the bonding between primary particles is suppressed, the precipitated silica becomes more easily disintegrated, and the particle size becomes smaller during the polishing process, so scratches are less likely to occur on the polished surface of the substrate. In addition, when the BET specific surface area is 15m 2 It is difficult to reduce the BET specific surface area to less than 35 m / g. 2 For cosmetic applications, a BET specific surface area of ​​15 to 35 m 2 / g range, it is easy to obtain a moist feel and adhesion. For paint and ink applications, a BET specific surface area of ​​15 to 35 m 2 / g, a sufficient matte effect is easily obtained.

[0042] The BET specific surface area is preferably 16 to 30 m 2 / g, and more preferably 17 to 26m 2 / g.

[0043] The precipitated silica of the present invention has a volume average particle diameter D50 of 2.0 to 25 μm in the particle size distribution obtained by measuring a slurry of precipitated silica prepared to 4 mass % without ultrasonic treatment using a laser diffraction particle size distribution analyzer. 0min Water is used as the solvent for the slurry. D50 0min When the D50 is 2.0 μm or more, the silica particles do not become monodispersed like colloidal silica, but become aggregates of a moderate size, thereby achieving a sufficient removal rate. 0min By keeping the particle size at 25 μm or less, scratches on the object to be polished due to coarse particles can be suppressed. 0min When the particle size is in the range of 2.0 to 25 μm, it is easy to obtain a moist feel and adhesion. For paint and ink applications, D50 0min When the particle size is in the range of 2.0 to 25 μm, a sufficient matte effect is easily obtained.

[0044] D50 0min is preferably 5.0 to 20 μm, and more preferably 10 to 15 μm.

[0045] The precipitated silica of the present invention has a volume average particle diameter D50 0min and D50 5min The particle size change rate A is calculated by Equation 1 based on the above and is 0.50 to 0.90. The particle size change rate A represents the rate of change in the volume average particle size before and after ultrasonic treatment when 50 mL of a 4% by mass slurry of precipitated silica is ultrasonicated for 5 minutes using an ultrasonic homogenizer with an output of 140 W. The particle size change rate A indicates the extent to which the particle size is reduced by the collapse of precipitated silica when an external force is applied to the precipitated silica, and is therefore one index of the disintegrability of precipitated silica. The larger the particle size change rate A, the more easily the precipitated silica disintegrates.

[0046] A particle size change rate A of 0.90 or less prevents excessive disintegration of precipitated silica, allowing appropriate particle size to be maintained for various applications, and in particular, sufficient polishing speed can be achieved in polishing applications. A particle size change rate A of 0.50 or more ensures that precipitated silica has adequate disintegrability, making it easy to adjust the particle size to suit various applications, and in particular, in polishing applications, a sufficiently smooth polished surface can be obtained. In cosmetics, a particle size change rate A in the range of 0.50 to 0.90 tends to provide a moist feel and adhesion. In paint and ink applications, a particle size change rate A in the range of 0.50 to 0.90 tends to provide a sufficient matte effect.

[0047] The particle size change rate A is preferably 0.55 to 0.85, and more preferably 0.60 to 0.80.

[0048] Volume average particle size D50 5min D50 is preferably 1.0 to 15 μm. 5min By keeping the D50 in the range of 1.0 to 15 μm, it becomes easier to adjust the particle size to suit various applications, and in particular, in polishing applications, it becomes easier to obtain a sufficiently smooth polished surface. 5min The thickness is more preferably 1.5 to 10 μm, and further preferably 2.0 to 5 μm.

[0049] The precipitated silica of the present invention has a volume average particle diameter D50 5min and D50 10min It is preferable that the particle diameter change rate B calculated by the following formula 2 based on the above formula is 0.40 or less. Formula 2: Particle size change rate B = (D50 5min -D50 10min ) / D50 5min Here, the volume average particle diameter D50 10min is the volume average particle diameter in the particle size distribution obtained by subjecting 50 mL of a 4% by mass precipitated silica slurry to ultrasonic treatment for 10 minutes using an ultrasonic homogenizer with an output of 140 W, and then measuring the slurry with a laser diffraction particle size distribution analyzer.

[0050] The particle size change rate B is a parameter that indicates the difference in volume average particle size of precipitated silica when subjected to short-term and long-term external force (ultrasound). The larger the particle size change rate B, the more the precipitated silica disintegrates and the smaller the volume average particle size when subjected to continuous external force. Conversely, the smaller the particle size change rate B, the more likely it is that disintegration will stop at a certain point and a constant volume average particle size will be maintained even when subjected to continuous external force. A particle size change rate B of 0.40 or less suppresses excessive disintegration of precipitated silica, maintaining an appropriate particle size for various applications, and achieving sufficient polishing speed, particularly in polishing applications. In cosmetic applications, a particle size change rate B of 0.40 or less tends to provide a moist feel and adhesion. In paint and ink applications, a particle size change rate B of 0.40 or less tends to provide a sufficient matte effect.

[0051] The particle size change rate B is preferably 0.35 or less, and more preferably 0.30 or less. The lower limit of the particle size change rate B is not particularly limited and may be zero, or may be, for example, 0.01 or more, 0.05 or more, or 0.1 or more.

[0052] Volume average particle size D50 10minD50 is preferably 1.0 to 15 μm. 10min By keeping the D50 in the range of 1.0 to 15 μm, it becomes easier to adjust the particle size to suit various applications, and in particular, in polishing applications, it becomes easier to obtain a sufficiently smooth polished surface. 10min The thickness is more preferably 1.5 to 10 μm, and further preferably 2.0 to 5 μm.

[0053] The precipitated silica of the present invention preferably has an apparent density of 80 to 180 g / L. This makes it easier to adjust the particle size to suit various applications, and in polishing applications in particular, makes it easier to obtain a sufficiently smooth polished surface. The apparent density is more preferably 100 to 175 g / L, and even more preferably 120 to 170 g / L.

[0054] For the precipitated silica of the present invention, a slurry of precipitated silica prepared to 4% by mass without ultrasonic treatment preferably has a pH of 5.5 to 8.5. This makes it easier to prepare slurries or compositions suitable for various applications, and in polishing applications in particular, it becomes easier to obtain a sufficiently smooth polished surface. The pH of the slurry is more preferably 6.0 to 8.0, and even more preferably 6.5 to 7.5.

[0055] For the precipitated silica of the present invention, the filtrate of a slurry of precipitated silica prepared at 4% by mass without ultrasonic treatment preferably has an electrical conductivity of less than 1,000 μS / cm. This makes it easier to prepare slurries or compositions suitable for various applications, and in polishing applications in particular, it is easier to obtain a sufficiently smooth polished surface. The electrical conductivity of the filtrate of the slurry is more preferably less than 800 μS / cm, and even more preferably less than 500 μS / cm. The lower limit of the electrical conductivity is not particularly limited, and may be 5 μS / cm or more, or 10 μS / cm or more.

[0056] Like conventional precipitated silica, the precipitated silica of the present invention may contain impurities within an acceptable range depending on the application. The amount of impurities is preferably low, for example, 1% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less. In particular, when used in dentifrice or cosmetics, the precipitated silica of the present invention is preferably free of heavy metals and the number of bacteria contained therein is preferably adjusted to a predetermined value or less. Heavy metals can be suppressed, for example, by selecting raw materials that do not contain them. Bacteria can be suppressed by using sterilized water when producing the precipitated silica, or by sterilizing the precipitated silica by adjusting the temperature during the drying process to a range that provides sterilization.

[0057] [Usage and applications of precipitated silica] The precipitated silica of the present invention can be subjected to a surface treatment as needed to modify the surface. In particular, when used in dentifrice or cosmetics, the precipitated silica can be surface-treated with a suitable treating agent that imparts compatibility with medicinal ingredients. The surface treatment can be appropriately selected from known methods.

[0058] When the final product is required to be blended into a liquid, such as a slurry, the precipitated silica of the present invention can be used as a slurry in which the precipitated silica is dispersed in water or a polar solvent. Examples of polar solvents include alcohols such as ethanol and ketones such as acetone, and additives such as salts and surfactants can also be added.

[0059] As described above, the precipitated silica of the present invention exhibits excellent polishing properties in terms of polishing rate and smoothness of polished surface, and therefore can be used as a polishing compound.

[0060] In another application, the precipitated silica of the present invention can be used as a cosmetic ingredient because it has a moist feel and good adhesion to the skin.

[0061] Regarding another application, the precipitated silica of the present invention exhibits sufficient matting effect that it can be used as a matting agent for paints or inks.

[0062] [Composition containing precipitated silica] In another aspect, the present invention is a polishing composition, a cosmetic, or a paint or ink containing the above-described precipitated silica.

[0063] The polishing composition of the present invention can be produced by adding the precipitated silica of the present invention as a polishing compounding agent to a known polishing composition, and can be used in the same way as known polishing compositions.Since the polishing composition of the present invention contains the above-mentioned precipitated silica of the present invention, it shows excellent polishing properties in terms of polishing rate and smoothness of polished surface.

[0064] The cosmetic product of the present invention can be produced by adding the precipitated silica of the present invention as a cosmetic ingredient to a known cosmetic product, and can be used in the same manner as a known cosmetic product. Because the cosmetic product of the present invention contains the above-mentioned precipitated silica of the present invention, it exhibits a moist feel to the touch and sufficient adhesion to the skin.

[0065] The paint or ink of the present invention can be produced by adding the precipitated silica of the present invention as a matting agent to a known paint or ink, and can be used in the same manner as a known paint or ink. The paint or ink of the present invention exhibits a sufficient matting effect because it contains the above-mentioned precipitated silica of the present invention.

[0066] [Precipitated silica manufacturing method] The precipitated silica of the present invention can be produced by the production method of the present invention described below. (A) Prepare an aqueous solution of alkali silicate at 80 to 95°C in a container equipped with a solution circulation line. (B) while stirring the solution in the container and circulating it through a circulation line, an aqueous alkali silicate solution having an SiO concentration of 10.0 to 15.0 mass % and dilute sulfuric acid of 1.0 to 10.0 mass % are simultaneously added to the solution in the container under conditions where the volume ratio of the aqueous alkali silicate solution to the dilute sulfuric acid is 1:0.5 to 1:10, thereby generating a reaction product in the solution in the container; (C) After the simultaneous addition is completed, acid is added to stop the formation of the reaction product; (D) Separating the reaction product from the reaction solution in the vessel by solid-liquid separation to obtain the precipitated silica of the present invention.

[0067] Generally, precipitated silica is synthesized by neutralizing an aqueous solution of an alkali metal silicate such as sodium silicate (alkali silicate aqueous solution) with a mineral acid such as sulfuric acid while stirring at 60-95°C. During the synthesis process, seed particles (primary particles) precipitate, which aggregate and grow further to become precipitated silica. The BET specific surface area is 60m 2 However, if the particle diameter is about 1 / g or more, the primary particles can be identified as independent particles. 2 When the primary particles are grown to a particle size of less than about 1 / g, the necking portion also grows, and the precipitated silica eventually becomes a mass-like aggregate in which the primary particles are strongly aggregated to the extent that they cannot be clearly distinguished.

[0068] Therefore, ingenuity is required to synthesize the precipitated silica of the present invention with a suitable disintegration property. Generally, the production method of the present invention involves adding an aqueous alkali silicate solution and sulfuric acid, each adjusted to a low concentration, to a reaction solution over a long period of time. In this way, the neutralization reaction of the aqueous alkali silicate solution and sulfuric acid proceeds slowly, resulting in the slow growth of primary particles, which grow larger while maintaining their spherical shape.

[0069] In addition, to further suppress the growth of necking, the production method of the present invention includes circulating the reaction solution using a circulation line installed in the vessel during the addition of the alkali silicate aqueous solution and sulfuric acid (during the neutralization reaction) in addition to the stirring operation, thereby wet-pulverizing the precipitated silica in the reaction solution during the neutralization reaction and further suppressing the aggregation of primary particles.

[0070] The manufacturing method of the present invention allows primary particles to grow slowly while suppressing aggregation of the primary particles, so that the BET specific surface area is 35 m 2 Even if the primary particles are grown to a particle size of 1 / g or less, precipitated silica having a suitable disintegrability can be obtained. The precipitated silica of the present invention cannot be synthesized without carrying out such an ingenious neutralization reaction.

[0071] Process (A) Step (A) is a step of preparing an aqueous alkali silicate solution at 80 to 95°C in a vessel equipped with a solution circulation line.

[0072] The aqueous alkali silicate solution at 80 to 95°C is the base solution for the neutralization reaction. The temperature is preferably 85 to 94°C, more preferably 87 to 93°C.

[0073] The SiO2 concentration of the alkali silicate aqueous solution prepared in the container is preferably low, for example, 5.0% by mass or less. This allows the primary particles to grow more slowly. This SiO2 concentration is preferably 1.0% by mass or less, more preferably 0.5% by mass or less. The alkali metal oxide concentration of the alkali silicate aqueous solution prepared in the container is preferably low, for example, 1.0% by mass or less. This allows the primary particles to grow more slowly. This alkali metal oxide concentration is preferably 0.5% by mass or less, more preferably 0.1% by mass or less.

[0074] The aqueous alkali silicate solution prepared in the vessel preferably has a lower SiO2 concentration and a lower alkali metal oxide concentration than the aqueous alkali silicate solution added in step (B). Furthermore, the aqueous alkali silicate solution prepared in step (A) is preferably a sodium silicate solution, and preferably has a lower SiO2 concentration and a lower Na2O concentration than the aqueous sodium silicate solution added in step (B).

[0075] Process (B) Step (B) is a step of simultaneously adding an aqueous alkali silicate solution having an SiO2 concentration of 10.0 to 15.0 mass % and dilute sulfuric acid of 1.0 to 10.0 mass % to the solution in the container under conditions where the volume ratio of the aqueous alkali silicate solution to the dilute sulfuric acid is 1:0.5 to 1:10 while stirring the solution in the container and circulating it through a circulation line, thereby producing a reaction product in the solution in the container.

[0076] Stirring conditions can be adjusted as appropriate. Stirring can be carried out using a stirring rod or stirring blade at a peripheral speed of 0.5 to 3.5 m / s, preferably 0.8 to 3.0 m / s.

[0077] The circulation line is not particularly limited as long as it can wet-pulverize precipitated silica while circulating the solution. The circulation line may be a simple circulation line that pumps the solution from the container and simply returns it to the container, or a combined circulation line that pumps the solution from the container to an external mill and returns the solution processed in the external mill to the container. As a simple circulation line, a turbine pump or a centrifugal pump is preferred. The external mill included in the combined circulation line is not particularly limited, and a known wet mill can be used. The outlet for the return solution from the circulation line may be above the liquid level of the solution in the container or may be submerged in the liquid. From the viewpoint of promoting wet-pulverization, it is preferable that the outlet for the return solution from the circulation line be above the liquid level of the solution in the container. The size of the container is not particularly limited, and a container with a capacity according to the desired production amount can be used.

[0078] In step (B) of the production method of the present invention, the solution is circulated in a vessel having a volume of Xm3 0.3X~0.7Xm 3 It is preferable to carry out the circulation at a flow rate of 0.35X to 0.65X m / min. This makes it possible to further suppress the aggregation of primary particles. 3 / min, more preferably 0.37X to 0.60X m 3 / min.

[0079] The SiO2 concentration of the aqueous alkali silicate solution added in step (B) is 10.0 to 15.0 mass%. This allows primary particles to grow slowly. The SiO2 concentration is preferably 10.0 to 14.5 mass%, more preferably 10.0 to 14.0 mass%.

[0080] The alkali metal oxide concentration of the aqueous alkali silicate solution added in step (B) can be adjusted as needed. The alkali metal oxide concentration is preferably 3.1 to 5.0 mass%, more preferably 3.5 to 4.5 mass%. The SiO2 / alkali metal oxide molar ratio of the aqueous alkali silicate solution added in step (B) can be adjusted as needed. This molar ratio is preferably 3.0 to 3.5, more preferably 3.1 to 3.3. The aqueous alkali silicate solution added in step (B) is preferably a sodium silicate solution. In this case, the Na2O concentration of the sodium silicate solution can be adjusted as needed. The Na2O concentration is preferably 3.1 to 5.0 mass%, more preferably 3.5 to 4.5 mass%. The SiO2 / Na2O molar ratio of the aqueous sodium silicate solution can be adjusted as needed. This molar ratio is preferably 3.0 to 3.5, more preferably 3.1 to 3.3.

[0081] The concentration of the diluted sulfuric acid added in step (B) is 1.0 to 10.0% by mass. This allows the primary particles to grow slowly. The concentration of the diluted sulfuric acid is preferably 3.0 to 8.0% by mass, and more preferably 4.0 to 7.0% by mass.

[0082] The volume ratio of the alkali silicate aqueous solution to dilute sulfuric acid when adding the materials is 1:0.5 to 1:10. This allows primary particles to grow slowly. This volume ratio is preferably 1:0.8 to 1:5.0, and more preferably 1:1.0 to 1:3.0.

[0083] The flow rate of the aqueous alkali silicate solution when adding the materials is not particularly limited, and for example, assuming a 240 L reaction vessel as in Example 1 and a liquid volume of 120 to 220 L at the end of the neutralization reaction, the flow rate is 50 to 180 mL / min (58 to 207 g / min) when the SiO2 / Na2O molar ratio is 3.2 and the volume ratio of the aqueous alkali silicate solution to dilute sulfuric acid is 1:1.4. The flow rate of the aqueous alkali silicate solution is preferably low from the viewpoint of growing primary particles more slowly, and is preferably 50 to 150 mL / min (58 to 173 g / min), and more preferably 50 to 130 mL / min (58 to 150 g / min).

[0084] The time for simultaneous addition in step (B) is not particularly limited and can be adjusted appropriately, and is, for example, 450 to 750 minutes, 480 to 750 minutes, or 500 to 750 minutes.

[0085] The method for adding the aqueous alkali silicate solution and dilute sulfuric acid is not particularly limited, and may be a method of adding them at equal intervals, or a method of adding them in multiple divided doses in amounts greater than the case of continuous addition. The term "simultaneous" when adding the aqueous alkali silicate solution and dilute sulfuric acid means that the addition periods of each material sufficiently overlap with each other, and the addition times of each material do not necessarily have to be simultaneous for each actual addition operation.

[0086] When the aqueous alkali silicate solution and dilute sulfuric acid are simultaneously added to the aqueous alkali silicate solution in the container, a neutralization reaction occurs between the aqueous alkali silicate solution and the dilute sulfuric acid, producing a reaction product in the aqueous alkali silicate solution in the container.

[0087] Process (C) In step (C), after the simultaneous addition is completed, an acid is added to stop the formation of the reaction product. When the pH of the solution in the vessel reaches an acidic range (for example, 3 or less), the neutralization reaction of the alkali silicate aqueous solution and dilute sulfuric acid stops, and the formation of the reaction product also stops.

[0088] Process (D) Step (D) is a step of separating the reaction product from the reaction liquid in the vessel by solid-liquid separation to obtain the above-mentioned precipitated silica of the present invention.

[0089] The method of solid-liquid separation is not particularly limited, and known methods can be used. Solid-liquid separation can be performed using a general solid-liquid separation device. Solid-liquid separation may be performed only once, or may be performed multiple times from the viewpoint of removing more foreign matter.

[0090] The solid-liquid separation is preferably carried out using a filtration device, which may be appropriately selected from known devices such as Nutsche type, belt filter type, and drum filter type filtration devices belonging to vacuum filtration, filter presses and sealed multistage filters belonging to pressure filtration, and centrifugal separators belonging to heavy pressure filtration.

[0091] After solid-liquid separation, the resulting reaction product (silica cake) is preferably washed with water and dried. By washing the reaction product with water, salts by-produced in the neutralization reaction remaining in the reaction product can be removed. Drying can be carried out using a known dryer such as a static dryer, a fluidized bed dryer, or a spray dryer. Dry pulverization is also preferred. Dry pulverization can be carried out using a known pulverizer such as a pin mill or a jet mill. If necessary, the reaction product can be classified using a classification device such as an air classifier to adjust the particle size.

[0092] In recent years, with the establishment of Sustainable Development Goals (SDGs), there has been a demand for the realization of a sustainable and regenerative society in order to protect the global environment. The alkali silicate aqueous solution used as the raw material for the precipitated silica of the present invention is generally derived from silica sand, but from the perspective of the SDGs, the alkali silicate aqueous solution used as the raw material in the present invention may be produced from a renewable raw material such as rice husk ash.

[0093] Furthermore, as part of sustainable chemical substance management, there are regulations regarding the emission of nanomaterials. However, since the precipitated silica produced by the manufacturing method of the present invention has a primary particle size of 100 nm or more, it does not fall under these regulations and can be used without safety concerns. [Example]

[0094] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, and processing procedures shown in the examples can be appropriately changed within the scope of solving the problems of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[0095] [Measurement of physical properties of precipitated silica] Total pore volume by mercury porosimetry (cm 3 / g) The sample was loaded into a mercury porosimeter (model: PASCAL 140, manufactured by ThermoQuest) and the pore volume distribution was measured for a pore radius range of 1,600 to 62,000 nm (1.6 to 62 μm) while increasing the pressure from 10 kPa to 400 kPa. The sample after the above measurements was then loaded into a mercury porosimeter (model: PASCAL 440, manufactured by ThermoQuest) and the pore volume distribution was measured for a pore radius range of 3.6 to 6,400 nm while increasing the pressure from 100 kPa to 200 MPa. The measurement results were integrated using the accompanying software to determine the pore volume distribution for a pore radius range of 3.6 nm to 62 μm, and the pore volume within this range was integrated to obtain the total pore volume.

[0096] ●BET specific surface area (m 2 / g) The BET specific surface area was measured by the one-point method using a fully automatic specific surface area measuring device (type: Macsorb (registered trademark) HM model-1201, manufactured by Mountec Co., Ltd.).

[0097] ●Volume average particle size D50 0min (μm) Precipitated silica was added to pure water to a concentration of 4% by mass and stirred thoroughly with a magnetic stirrer to prepare a precipitated silica slurry. The particle size distribution of the precipitated silica in this non-ultrasonicated slurry was measured using a laser diffraction particle size distribution analyzer (model: SYNC30, manufactured by Microtrac-Bell). The particle size (median diameter) at which the volumetric value accounts for 50% of the total was determined as D50. 0min was obtained as.

[0098] Particle size change rate A First, the volume average particle size D50 5min was determined by the following procedure. Precipitated silica was added to pure water to a concentration of 4% by mass, and the mixture was thoroughly stirred with a magnetic stirrer to prepare 50 mL of precipitated silica slurry. The slurry was then subjected to ultrasonic treatment at an output of 140 W for 5 minutes using an ultrasonic homogenizer (model: Sonfier250D, manufactured by Branson). The particle size distribution of the precipitated silica in the slurry that had been subjected to this ultrasonic treatment was measured using a laser diffraction particle size distribution analyzer (model: SYNC30, manufactured by Microtrac-Bell). The particle size (median diameter) at which the volumetric value in the particle size distribution accounted for 50% of the total was determined as D50. 5min was obtained as.

[0099] And, the volume average particle diameter D50 when ultrasonic treatment is not performed 0min and volume average particle diameter D50 when ultrasonic treatment was performed for 5 minutes 5min Based on this, the particle size change rate A was calculated according to the following formula 1. Formula 1: Particle size change rate A = (D50 0min -D50 5min ) / D50 0min

[0100] Particle size change rate B First, the volume average particle size D50 10min was determined by the following procedure. Precipitated silica was added to pure water to a concentration of 4% by mass, and the mixture was thoroughly stirred with a magnetic stirrer to prepare 50 mL of precipitated silica slurry. The slurry was then subjected to ultrasonic treatment for 10 minutes at an output of 140 W using an ultrasonic homogenizer (model: Sonfier250D, manufactured by Branson). The particle size distribution of the precipitated silica in the slurry that had been subjected to this ultrasonic treatment was measured using a laser diffraction particle size distribution analyzer (model: SYNC30, manufactured by Microtrac-Bell). The particle size (median diameter) at which the volumetric value in the particle size distribution accounted for 50% of the total was determined as D50. 10min was obtained as.

[0101] The volume average particle diameter D50 after 5 minutes of ultrasonic treatment 5min and volume average particle diameter D50 when ultrasonic treatment was performed for 10 minutes 10min Based on this, the particle size change rate B was calculated according to the following formula 2. Formula 2: Particle size change rate B = (D50 5min -D50 10min ) / D50 5min

[0102] ●Apparent density (g / L) Apparent density was measured according to the apparent density measurement method specified in JIS K 5101-12-1:2004 (Test methods for pigments - Part 12: Apparent density or apparent specific volume - Section 1: Static method). A dedicated measuring device (0.5 mm mesh sieve, funnel, 30 mL cylindrical receiver, receiver stand, and funnel stand) was used. The sample was dropped from the sieve into the funnel with a brush, and the pile of sample that had accumulated in the receiver was scraped off with a spatula, after which the mass (g) of the sample was measured. The apparent density was calculated based on the mass of the sample using Equation 3. Formula 3: Apparent density (g / L) = (mass of sample / 30) x 1000

[0103] ● Slurry pH The pH of a slurry prepared by dissolving precipitated silica in pure water at a concentration of 4% by mass was measured using a commercially available glass electrode pH meter (Model: F-53, manufactured by Horiba, Ltd.) in accordance with JIS K 5101-17-2:2004 (Test methods for pigments - Part 17: pH value - Section 2: Room temperature extraction method).

[0104] ●Electrical conductivity (μS / cm) 4 g of precipitated silica was added to 50 mL of distilled water and mixed thoroughly. The mixture was then boiled for 5 minutes. After boiling, the total volume of the mixture was adjusted to 100 mL using distilled water, and the mixture was filtered to obtain a filtrate. The electrical conductivity of the filtrate was measured using an electrical conductivity meter (Model: CM30R, manufactured by Toa DKK Co., Ltd.).

[0105] ●Abrasiveness evaluation 10 g of precipitated silica was added to 30 g of distilled water placed in a 100 mL disposable cup, and the solution was stirred at 1,500 rpm for 5 minutes using a high-speed mixer (model: Lavorution, manufactured by Primix Corporation) to obtain a silica dispersion. Then, 40 g of a 14% by mass PVA solution was added to the silica dispersion, and the mixture was stirred again at 700 rpm for 10 minutes, taking care not to generate bubbles. The silica dispersion was applied to fine paper (OK Prince fine paper, basis weight 130 g / m) using a No. 40 bar coater. 2 The coating was applied to a sheet of high-quality paper (Oji Paper Co., Ltd.), which was then fixed to a wooden board and dried at 120°C for 5 minutes to obtain coated paper. A 20 mm x 60 mm test piece was cut from the coated paper. The test piece was placed in a Gakushin-type abrasion fastness tester (model: AB-301, Tester Sangyo Co., Ltd.) and run back and forth 50 times at a load of 500 gf on an ABS plate (70 mm x 150 mm, black, Coating Tester Co., Ltd.).

[0106] <Amount of polishing (polishing speed)> The amount of abrasion powder from the ABS plate adhering to the coated paper was visually confirmed, and the amount of abrasion (abrasion rate) was evaluated according to the following three levels. A: Large amount of polishing (fast polishing speed) B: Medium amount of polishing C: Almost no polishing (slow polishing speed)

[0107] <Surface roughness> Surface roughness was measured in accordance with JIS B 0601:1994 (Surface texture according to geometric product specifications (GPS): profile curve method - terms, definitions, and surface texture parameters). Using an ultra-depth profile measuring microscope (model: VK8500; manufactured by Keyence Corporation), the polished ABS plate surface was observed at 50x magnification, and the arithmetic mean roughness (Ra) and maximum height (Ry) values ​​were measured at five locations within a 300 μm × 300 μm area, and the measured values ​​were averaged. The mean Ra and Ry values ​​were each evaluated using the following three-level scale. The smaller the mean Ra and Ry values, the smoother the polished surface. ·Evaluation of average Ra value A: Less than 1.10 μm B: 1.10 μm or more and less than 1.60 μm C: 1.60μm or more Evaluation of the average Ry value A: Less than 15.00 μm B: 15.00 μm or more and less than 25.00 μm C:25.00μm or more

[0108] <Overall evaluation of abrasiveness> Based on the evaluation results of the three items of the polishing amount, the average Ra value, and the average Ry value, the polishing properties were evaluated comprehensively according to the following criteria. Good: There are two or more items with an A rating and no items with a C rating. Bad: Other than the above.

[0109] ●Evaluation of texture A small amount of sample powder of precipitated silica, the moisture content of which had been adjusted to 6% or less, was taken and applied to the back of the hand with the fingers, and the feel of the powder was evaluated according to the following criteria. Good: Moist to the touch and adhesive. Bad: The above tactile sensation is not obtained.

[0110] Evaluation of matte finish 2 g of precipitated silica was added to 20 g of distilled water placed in a 100 mL disposable cup, and the solution was stirred at 1,500 rpm for 1 minute using a high-speed mixer (model: Lavortion, manufactured by Primix Corporation) to obtain a silica dispersion. The silica dispersion was then added to 100 g of a commercially available water-based paint (product name: Asuka II, manufactured by Kansai Paint Co., Ltd.) placed in a 200 mL disposable cup, and the solution was stirred at 1,500 rpm for 20 minutes to obtain a paint sample for evaluation.

[0111] <Glossiness (60° gloss value)> The coating sample was applied to the surface of an ABS plate (100 mm × 200 mm, black, manufactured by Coating Tester Co., Ltd.) using a No. 30 bar coater to form a coating film, which was then dried at 80°C for 30 minutes. The 60° gloss value was measured using a gloss meter (model: VG7000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0112] <Dispersion> The degree of dispersion was measured in accordance with the dispersion measurement method (4.7.1 Distribution diagram method) of JIS K 5400 (general coating test method). The distribution density of the "particles" was measured using a grind meter (particle gauge, for 0-100 μm, 10 μm increments, manufactured by Taiyu Kizai Co., Ltd.), and the scale (boundary line) where densely packed "particles" began to appear was read. The lower the evaluation value, the better the dispersibility.

[0113] <Overall evaluation of matte finish> Based on the evaluation results of two items, glossiness (60° gloss value) and dispersibility, matte properties were comprehensively evaluated according to the following criteria. Good: Glossiness is less than 50 and dispersion is less than 60 μm. Bad: Other than the above.

[0114] [Example 1] The precipitated silica was produced in a 240 L (X = 0.24 m) reactor equipped with an agitator and an external circulation device. 3The experiment was carried out using a steam-heated stainless steel vessel (12.8 mass %), with constant stirring inside the vessel. The sodium silicate aqueous solution used in the following explanation was No. 3 sodium silicate solution with an SiO2 concentration of 12.8 mass %, an Na2O concentration of 4.0 mass %, and an SiO2 / Na2O molar ratio of 3.2, and the dilute sulfuric acid used in the following explanation was 5.0 mass % sulfuric acid.

[0115] A sodium silicate aqueous solution was added to 30.0 kg of water placed in a container to adjust the pH to 10.5, and the solution was heated to 90°C. At this time, the SiO2 concentration in the solution in the container was 0.1 mass% and the alkali metal oxide concentration was 0.03 mass%. While maintaining the solution temperature at 90°C, 71.1 kg of sodium silicate aqueous solution and dilute sulfuric acid were added simultaneously to the solution over 630 minutes, producing a reaction product through a neutralization reaction between the sodium silicate and dilute sulfuric acid. The volume ratio of the sodium silicate aqueous solution to dilute sulfuric acid during the simultaneous addition was 1:1.4. The flow rate of the sodium silicate aqueous solution was approximately 98 mL / min (113 g / min). During the neutralization reaction, a centrifugal pump (model: HCS419, manufactured by Honda Kiko Co., Ltd.) was used as an external circulation device to circulate the sodium silicate solution at 0.10 m 3 / min(0.4Xm 3 The solution was constantly circulated at a flow rate of 1 / min. After the simultaneous addition was completed, further dilute sulfuric acid was added until the pH reached 3, thereby terminating the neutralization reaction and halting the production of the reaction product. The reaction product was then filtered using a filter press and washed with water to obtain a silica cake.

[0116] The obtained silica cake was slurried with water, and the slurry was spray-dried using a disk-type spray dryer (model: Spray Dryer AN-40R, manufactured by Ashizawa Niro Atomizer Co., Ltd.) to produce silica particles. The silica particles were then pulverized in a jet mill (model: PJM-100NP, manufactured by Nippon Pneumatic Mfg. Co., Ltd.) at a feed rate of 12±1 g / min and a pressure of 0.3 MPa to obtain precipitated silica. The volume average particle diameter D50 of the precipitated silica was 0min was 9.53 μm.

[0117] [Example 2] Precipitated silica was produced in the same manner as in Example 1, except that the flow rates of the aqueous sodium silicate solution and the diluted sulfuric acid were adjusted so that the simultaneous addition time was extended to 700 minutes. The flow rate of the aqueous sodium silicate solution was approximately 89 mL / min (102 g / min). The volume average particle diameter D50 of the precipitated silica 0min was 11.23 μm.

[0118] [Example 3] Precipitated silica was produced in the same manner as in Example 1, except that the flow rates of the aqueous sodium silicate solution and the diluted sulfuric acid were adjusted so that the simultaneous addition time was shortened to 540 minutes. The flow rate of the aqueous sodium silicate solution was approximately 115 mL / min (132 g / min). The volume average particle diameter D50 of the precipitated silica 0min was 12.11 μm.

[0119] [Example 4] Precipitated silica was produced in the same manner as in Example 1, except that the pulverization was carried out using a jet mill at a pressure of 0.5 MPa. The volume average particle diameter D50 of the precipitated silica 0min was 5.06 μm.

[0120] [Example 5] Precipitated silica was produced in the same manner as in Example 1, except that the pulverization was carried out using a jet mill at a pressure of 0.1 MPa. The volume average particle diameter D50 of the precipitated silica 0min was 21.89 μm.

[0121] [Comparative Example 1] Based on the method for producing hydrous silicic acid (b) in Patent Document 3, a BET specific surface area of ​​30 m 2 Precipitated silica with a solubility of 0.1g or less was produced. Comparative Example 1 differs from Example 1 in that the concentration of dilute sulfuric acid is relatively high at 9.0% by mass and the solution is not circulated by an external circulation device during the reaction. The vessel, aqueous sodium silicate solution, and apparatus are the same as those described in Example 1.

[0122] A sodium silicate aqueous solution was added to 36.8 kg of water in a vessel to adjust the pH to 10.5, and the solution was heated to 90°C. At this time, the SiO2 concentration in the vessel was 0.1% by mass, and the alkali metal oxide concentration was 0.03% by mass. While maintaining the solution temperature at 90°C, 87.3 kg of sodium silicate aqueous solution and dilute sulfuric acid (concentration: 9.0% by mass) were simultaneously added to the solution over 585 minutes to produce a reaction product through a neutralization reaction between the sodium silicate and dilute sulfuric acid. The volume ratio of the sodium silicate aqueous solution to dilute sulfuric acid during the simultaneous addition was 1:0.8. The flow rate of the sodium silicate aqueous solution was approximately 130 mL / min (149 g / min). The solution was not circulated during the neutralization reaction. After the simultaneous addition was completed, further dilute sulfuric acid was added until the pH reached 3, thereby terminating the neutralization reaction and stopping the production of the reaction product. The resulting reaction product was then filtered through a filter press and washed with water to obtain a silica cake. The same procedure as in Example 1 was then used to obtain precipitated silica. Precipitated silica volume average particle size D50 0min was 10.74 μm.

[0123] Comparative Example 2 Comparative Example 2 is an example of producing precipitated silica with a low BET specific surface area in a short time according to a conventional method. The vessel, aqueous sodium silicate solution, and apparatus are the same as those described in Example 1.

[0124] A 0.20 mol / L sodium sulfate solution (56.6 kg) was placed in a vessel, and a sodium silicate solution was added to adjust the pH to 10.5. The solution was then heated to 90°C. At this time, the SiO concentration in the vessel was 0.4% by mass, and the alkali metal oxide concentration was 0.13% by mass. While maintaining the solution temperature at 90°C, 116.17 kg of sodium silicate solution and concentrated sulfuric acid (concentration: 95.0% by mass) were simultaneously added to the solution over 120 minutes to neutralize the sodium silicate and concentrated sulfuric acid, producing a reaction product. The volume ratio of the sodium silicate solution to concentrated sulfuric acid during the simultaneous addition was 1:0.04. The flow rate of the sodium silicate solution was approximately 843 mL / min (970 g / min). The solution was not circulated during the neutralization reaction. After the simultaneous addition, additional concentrated sulfuric acid was added until the pH reached 3, terminating the neutralization reaction and stopping the production of the reaction product. The resulting reaction product was then filtered through a filter press and washed with water to obtain a silica cake. Thereafter, precipitated silica was obtained in the same manner as in Example 1. Volume average particle diameter D50 of precipitated silica 0min was 14.96 μm.

[0125] Comparative Example 3 With reference to the manufacturing method of Example 3 of Patent Document 1, a BET specific surface area of ​​35 m 2 / g or less. However, the production method of Comparative Example 3 was carried out using 9 times the amounts used in Example 3 of Patent Document 1. The vessels and apparatus were the same as those described in Example 1.

[0126] 81 L (86.7 kg) of 10.0 wt% aqueous sodium chloride solution and 81 L (86.7 kg) of 10.0 wt% aqueous sodium sulfate solution were mixed and heated to 85°C. 32.4 L (41.80 kg) of No. 3 sodium silicate solution (SiO concentration: 22.0 wt%, NaO concentration: 7.0 wt%) and approximately 32.4 L (35.32 kg) of 14.0 wt% sulfuric acid were added simultaneously over 60 minutes. The volume ratio of the sodium silicate aqueous solution to sulfuric acid during the simultaneous addition was 1:1.0. The flow rate of the sodium silicate aqueous solution was approximately 540 mL / min (697 g / min). The solution was not circulated during the neutralization reaction. After the simultaneous addition, sulfuric acid was further added until the pH reached 3, thereby terminating the neutralization reaction and halting the formation of the reaction product. The resulting reaction product was then filtered through a filter press and washed with water to obtain a silica cake. The same procedure as in Example 1 was then used to obtain precipitated silica. Precipitated silica volume average particle size D50 0min was 15.03 μm.

[0127] Comparative Example 4 Nipsil E-743, a commercially available precipitated silica (volume average particle size D50 0min 3.45 μm, manufactured by Tosoh Silica Corporation) was used.

[0128] [result] The results of Examples 1 to 5 and Comparative Examples 1 to 4 are shown in Tables 1 and 2 below and in FIGS.

[0129] [Table 1]

[0130] [Table 2]

[0131] [Explanation and discussion of results] Figures 1 and 2 are particle size distribution diagrams of the precipitated silica of Example 1 and Comparative Example 2, respectively. As can be seen from Figures 1 and 2, the precipitated silica disintegrates when subjected to external force (ultrasound) in the slurry, and the particle size distribution shifts toward smaller diameters. However, the amount of shift differs significantly between Example 1 and Comparative Example 2. The particle size distribution of the precipitated silica of Example 1 shifts significantly after 5 minutes of ultrasonic treatment (Figure 1), whereas the particle size distribution of Comparative Example 2 shifts very little (Figure 2). Thus, from the results of particle size distribution and particle size change rate A, it was confirmed that the precipitated silica of Example 1 has relatively large particle sizes in the initial stage and disintegrates appropriately when a certain external force is applied.

[0132] In addition, as can be seen from Figure 1, the precipitated silica of Example 1 shows a small shift in particle size distribution when ultrasonic treatment is performed for 5 minutes and 10 minutes, and particle size change rate B is smaller than particle size change rate A. Thus, from the results of particle size distribution and particle size change rate B, it was confirmed that the precipitated silica of Example 1 disintegrates appropriately when a certain external force is applied, but maintains a certain degree of particle size even when an external force is continuously applied.

[0133] The moderate disintegrability of the precipitated silica of the present invention is a characteristic imparted by the production method of the present invention, in which the concentrations of the alkali silicate aqueous solution and sulfuric acid added simultaneously are reduced, the sodium silicate aqueous solution and sulfuric acid are added slowly, and the solution in the container is circulated during the simultaneous addition. It is believed that the moderate disintegrability of the precipitated silica was imparted by reducing the concentrations of the alkali silicate aqueous solution and sulfuric acid added simultaneously and slowly growing the primary particles of the precipitated silica, and by circulating the solution, suppressing aggregation of the primary particles. In contrast, Comparative Example 1 is an example in which solution circulation was not performed, and Comparative Examples 2 and 3 are examples in which solution circulation was not performed, the sulfuric acid concentration was high, and the sodium silicate aqueous solution and sulfuric acid were added simultaneously at a high speed. It is believed that in the precipitated silica of Comparative Examples 1 to 3, the primary particles grew in an aggregated state, resulting in the formation of aggregates in which the primary particles were strongly bonded.

[0134] The degree of aggregation of primary particles can be confirmed by SEM photographs. Figures 3 and 4 are SEM photographs of the precipitated silicas of Examples 1 and 2 (without ultrasonic treatment) at (a) 10,000x magnification and (b) 50,000x magnification, respectively. Figures 5 and 6 are SEM photographs of the precipitated silicas of Comparative Examples 1 and 2 (without ultrasonic treatment) at (a) 10,000x magnification and (b) 50,000x magnification, respectively. The precipitated silica of the present invention shown in Figures 3 and 4 has little necking between primary particles, so that the spherical shape of the primary particles can be seen in many areas, while the precipitated silica of the comparative example shown in Figures 5 and 6 has many necking between primary particles, and in some areas the spherical shape of the primary particles is barely visible. This shows that differences in aggregate structure result in differences in disintegration properties.

[0135] As described above, the precipitated silica of Examples 1 to 5 all had a particle size of 2.50 cm 3 / g or more, total pore volume 15-35m 2 / g BET specific surface area, volume average particle diameter D50 of 2.0 to 25 μm 0min and a particle size change rate A of 0.50 to 0.90. The precipitated silicas of Examples 1 to 5 all achieved a sufficient polishing amount and provided an improved polished surface, and as a result, had sufficient polishing properties.

[0136] Regarding the evaluation of polishing properties, specifically, the polishing amounts in Examples 1 to 5 were equal to or greater than those of conventional precipitated silica having a low BET specific surface area (e.g., Comparative Examples 1 to 3), and the polished surfaces had improved properties and were smoother than those of conventional precipitated silica having a low BET specific surface area (Table 2, Figures 8 and 9). This result is presumably due to the moderate disintegrability of the precipitated silica of the present invention. That is, at the start of the polishing process, the precipitated silica of the present invention has a relatively large particle size, resulting in a large polishing amount (fast polishing rate), and as the polishing process progresses, the precipitated silica gradually disintegrates, and by the end of the polishing process, the precipitated silica has reached a size suitable for polishing the surface to a smooth finish.

[0137] In contrast, in Comparative Examples 1 to 3, which had a small total pore volume and a small particle size change rate A, a smooth polished surface was not obtained, and in Comparative Example 4, which had a large BET specific surface area, a sufficient amount of polishing was not obtained.

[0138] Furthermore, the precipitated silica of the present invention unexpectedly has excellent feel and matte properties.

[0139] In the evaluation of the texture, the precipitated silicas of Examples 1 to 5 had a moist feeling and high adhesion to the skin, resulting in an extremely good texture. The precipitated silica of the present invention is grown slowly, so there is little necking between particles, and the primary particles are spherical (see Figures 1 and 2), which is thought to also contribute to the improved texture.

[0140] In the paint evaluation, the precipitated silica of Examples 1 to 5 exhibited excellent matting properties and did not impair the design properties due to the absence of coarse particles of 60 μm or more.

[0141] In contrast, Comparative Examples 1 to 3, in which the primary particles were strongly aggregated, did not have the desired feel and matte finish. Comparative Example 4, in which the BET specific surface area was large, had sufficient matte finish, but did not have the desired feel.

[0142] In summary, the precipitated silica of the present invention has a low BET specific surface area and moderate disintegrability, and therefore can be suitably used as a polishing compounding agent that can achieve both high removal rate and smoothness. The precipitated silica of the present invention has an excellent tactile feel (moist feeling and adhesion to skin), and therefore can be suitably used as a cosmetic compounding agent. Furthermore, the precipitated silica of the present invention has excellent matting properties, and therefore can be suitably used as a matting agent for paints or inks.

Claims

1. 2.50 cm measured by mercury porosimetry 3 / g or more total pore volume, 15 to 35 m 2 / g BET specific surface area, A slurry of precipitated silica prepared to 4% by mass without ultrasonic treatment was measured using a laser diffraction particle size distribution analyzer, and the volume average particle diameter D50 of 2.0 to 25 μm was measured. 0min , and Volume average particle diameter D50 0min and D50 5min A particle size change rate A of 0.50 to 0.90 calculated by the following formula 1 based on Precipitated silica having: Formula 1: Particle size change rate A = (D50 0min -D50 5min ) / D50 0min Here, the volume average particle diameter D50 5min is the volume average particle diameter in the particle size distribution obtained by subjecting 50 mL of a slurry containing 4 mass % precipitated silica to ultrasonic treatment for 5 minutes using an ultrasonic homogenizer with an output of 140 W, and then measuring the slurry using a laser diffraction particle size distribution measuring device.

2. Volume average particle diameter D50 5min and D50 10min 2. The precipitated silica according to claim 1, wherein the particle size change rate B is 0.40 or less, as calculated by the following formula 2 based on: Formula 2: Particle size change rate B = (D50 5min -D50 10min ) / D50 5min Here, the volume average particle diameter D50 10min is the volume average particle diameter in the particle size distribution obtained by subjecting 50 mL of a slurry containing 4 mass % precipitated silica to ultrasonic treatment for 10 minutes using an ultrasonic homogenizer with an output of 140 W, and then measuring the slurry using a laser diffraction particle size distribution measuring device.

3. Volume average particle diameter D50 of 1.0 to 15 μm 5min 3. The precipitated silica according to claim 1, wherein

4. 3. The precipitated silica according to claim 1, having an apparent density of 80 to 180 g / L.

5. A 4% by weight slurry of precipitated silica prepared without ultrasonic treatment has a pH of 5.5 to 8.5; and The filtrate of the slurry has an electrical conductivity of less than 1,000 μS / cm.

3. The precipitated silica according to claim 1 or 2.

6. 3. The precipitated silica of claim 1, which is used as a polishing compounding agent, a cosmetic compounding agent, or a matting agent for paints or inks.

7. Volume average particle diameter D50 5min and D50 10min The particle size change rate B is 0.40 or less, calculated by the following formula 2 based on Formula 2: Particle size change rate B = (D50 5min -D50 10min ) / D50 5min Here, the volume average particle diameter D50 10min is the volume average particle diameter in the particle size distribution obtained by subjecting 50 mL of a slurry containing 4 mass % precipitated silica to ultrasonic treatment for 10 minutes using an ultrasonic homogenizer with an output of 140 W and then measuring the slurry using a laser diffraction particle size distribution measuring device. Volume average particle diameter D50 of 1.0 to 15 μm 5min and having an apparent density of 80 to 180 g / L; A slurry of precipitated silica prepared at 4% by weight without ultrasonic treatment has a pH of 5.5 to 8.5; the filtrate of the slurry has an electrical conductivity of less than 1,000 μS / cm; and 2. The precipitated silica of claim 1 used as a polishing compound, a cosmetic compound, or a matting agent for paints or inks.

8. A polishing composition comprising the precipitated silica according to claim 1 or 2.

9. A cosmetic product comprising the precipitated silica according to claim 1 or 2.

10. A paint or ink containing the precipitated silica according to claim 1 or 2.

11. 10. A method for producing the precipitated silica of claim 1, comprising: (A) preparing an aqueous alkali silicate solution at 80 to 95°C in a container equipped with a solution circulation line; (B) While stirring the solution in the container and circulating it through the circulation line, add 10.0 to 15.0 mass % of SiO 2 an aqueous alkali silicate solution having a concentration of 1.0 to 10.0 mass % and dilute sulfuric acid having a concentration of 1.0 to 10.0 mass % are simultaneously added to the solution in the container under the condition that the volume ratio of the aqueous alkali silicate solution to the dilute sulfuric acid is 1:0.5 to 1:10, thereby generating a reactant in the solution in the container; (C) After the simultaneous addition is completed, an acid is added to stop the formation of the reaction product; (D) separating the reaction product from the reaction solution in the vessel by solid-liquid separation to obtain the precipitated silica; A manufacturing method comprising:

12. The method of claim 11, wherein the simultaneous addition in step (B) is carried out for 450 to 750 minutes.

13. The solution circulation is carried out in a container with a volume of Xm. 3 0.3X to 0.7Xm 3 The method according to claim 11 or 12, wherein the method is carried out at a flow rate of 1 / min.

14. The aqueous alkali silicate solution to be added simultaneously contains 3.1 to 5.0 mass % of Na 2 O concentration and SiO of 3.0 to 3.5 2 / Na 2 13. The method of claim 11 or 12, wherein the molar ratio of 1:1 is 0.

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