Precipitated silica having low bet specific surface area, composition including same, and method for producing precipitated silica

Abstract

A precipitated silica having a low BET specific surface area according to the present invention has a total pore volume of 2.50 cm3 / g or more as measured by mercury porosimetry, a BET specific surface area of 15-35 m2 / g, a volume average particle diameter D500min of 2.0-25 μm in a particle size distribution of a slurry having 4 mass% of the precipitated silica, and a particle diameter change rate A of 0.50-0.90 as calculated by the following formula. Particle diameter change rate A = (D500min - D505min) / D500min. In the formula, the volume average particle diameter D505min is the volume average particle diameter in a particle size distribution when a ultrasonic treatment has been performed on the slurry having 4 mass% of the precipitated silica for 5 minutes. The precipitated silica according to the present invention exhibits excellent polishing properties in terms of polishing speed and smoothness of the polishing surface. The present invention further relates to a composition including the precipitated silica and a method for producing the precipitated silica.

Description

Precipitated silica having a low BET specific surface area, composition containing the same, and method for producing the precipitated silica

[0001] The present invention relates to precipitated silica, compositions containing the same, and a method for producing precipitated silica. CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Japanese Patent Application No. 2024-089838, filed June 3, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] In general, precipitated silica is used as a reinforcing filler for rubber, but it is also widely used as a matting agent for paints and inks, a polishing compounding agent (abrasive) for various polishing applications including mechanical polishing and toothpaste, a cosmetic compounding agent, and a paper coating agent.

[0003] For example, for abrasive applications and thermal paper coating applications, precipitated silicas have low BET specific 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 as 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 discloses a sintered body having a BET specific surface area of ​​40 to 120 m ２ The patent document 2 describes a polishing slurry containing silica with a content of N / g. ２ It is taught that there is a strong correlation between the specific surface area of ​​the particles as determined by the adsorption method (BET method). From this, it is expected that the smaller the BET specific surface area of ​​precipitated silica, the better the abrasive properties will be in polishing applications.

[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, a volume average particle size (D50) measured by a laser diffraction method of 0.4 to 0.9 μm, and a particle size (D90) of 90% of the bottom cumulative volume in the particle size distribution measured by the laser diffraction method of 1.0 to 5.0 μm.

[0007] When precipitated silica with a low BET specific surface area is used as a polishing compound, the polishing rate is high, but the polished surface tends to be rough. Therefore, in the polishing process of 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.

[0010] Patent Document 1: JP 59-22794 A Patent Document 2: JP 2002-527599 A Patent Document 3: JP 2021-59462 A Patent Document 4: JP 2017-124954 A The entire disclosures of Patent Documents 1 to 4 are incorporated herein by reference.

[0011] When the precipitated silica described in Patent Documents 1 and 2 is used as a polishing compounding agent 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 objects rub against or come into contact with each other) may be formed 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 controlled to a volume average particle size of 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.

[0017] The above-mentioned problem has 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 problem has been solved by the invention of [1] below, preferably by the inventions of [2] and later. [1] The above-mentioned problem has been solved by the invention of [1] below, preferably by the inventions of [2] and later. ３ / g or more total pore volume, 15 to 35 m ２ / g BET specific surface area, and 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 , and volume average particle diameter D50 ０ｍｉｎ and D50 ５ｍｉｎA precipitated silica having a particle size change rate A of 0.50 to 0.90, calculated by the following formula 1 based on the particle size change rate A: Formula 1: Particle size change rate A = (D50 ０ｍｉｎ -D50 ５ｍｉｎ ) / D50 ０ｍｉｎ Here, the volume average particle diameter D50 ５ｍｉｎ [2] Volume average particle diameter D50 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 analyzer. 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 the 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 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. [3] Volume average particle diameter D50 of 1.0 to 15 μm ５ｍｉｎ [4] The precipitated silica according to any one of [1] to [3], having an apparent density of 80 to 180 g / L. [5] The precipitated silica according to any one of [1] to [4], wherein a slurry of the precipitated silica prepared to a concentration of 4% by mass 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. [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 diameter D50 ５ｍｉｎ and D50 １０ｍｉｎ The particle diameter change rate B is 0.40 or less, calculated by the following formula 2 based on the above formula: ５ｍｉｎ -D50 １０ｍｉｎ ) / D50５ｍｉｎ Here, the volume average particle diameter D50 １０ｍｉｎ is a volume average particle diameter D50 of 1.0 to 15 μm in the particle size distribution obtained by subjecting 50 mL of a slurry containing 4% by mass of 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. ５ｍｉｎ The precipitated silica according to [1], which has an apparent density of 80 to 180 g / L, a slurry of the precipitated silica prepared to a concentration of 4% by mass without ultrasonic treatment has a pH of 5.5 to 8.5, and a filtrate of the slurry has an electrical conductivity of less than 1,000 μS / cm, and 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 comprising the precipitated silica according to any one of [1] to [7].

[10] A paint or ink comprising the precipitated silica according to any one of [1] to [7].

[11] A method for producing the precipitated silica according to any one of [1] to [7], comprising the steps of: (A) preparing an aqueous alkali silicate solution at 80 to 95°C in a vessel equipped with a solution circulation line; (B) adding 10.0 to 15.0 mass% of SiO to the vessel while stirring and circulating the solution in the vessel through the circulation line; ２ (C) adding an acid after the simultaneous addition is completed to stop the production of the reaction product, and (D) separating the reaction product from the reaction solution in the vessel by solid-liquid separation to obtain the precipitated silica.

[12] A production method according to

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

[13] A method according to

[11] , wherein the reaction solution is circulated at a volume of X m ３ 0.3X to 0.7Xm ３

[14] The method according to

[11] or

[12] , wherein the aqueous alkali silicate solution used for simultaneous addition is a solution containing 3.1 to 5.0 mass % of Na ２O concentration and SiO of 3.0 to 3.5 ２ / Na ２ The method according to any one of

[11] to

[13] , wherein the molar ratio of 1 to 2 is 0.

[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.

[0021] Figure 1 is a particle size distribution diagram for the precipitated silica of Example 1. Figure 2 is a particle size distribution diagram for the precipitated silica of Comparative Example 2. Figure 3 is a SEM photograph of the precipitated silica of Example 1 at (a) 10,000x magnification and (b) 50,000x magnification. Figure 4 is a SEM photograph of the precipitated silica of Example 2 at (a) 10,000x magnification and (b) 50,000x magnification. Figure 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 is a SEM photograph of the precipitated silica of Comparative Example 2 at (a) 10,000x magnification and (b) 50,000x magnification. Figure 7 is a SEM photograph of the precipitated silica of Comparative Example 4 at (a) 10,000x magnification and (b) 50,000x magnification. Fig. 8 is an observation image of the surface roughness of an ABS plate after polishing evaluation using the precipitated silica of Example 1. Fig. 9 is an observation image of the surface roughness of an ABS plate after polishing evaluation using the precipitated silica of Comparative Example 2.

[0022] [Precipitated Silica] The precipitated silica of the present invention has a surface roughness of 2.50 cm as measured by mercury intrusion porosimetry. ３ / g or more total pore volume, 15 to 35 m ２ / g BET specific surface area, and 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 , and volume average particle diameter D50 ０ｍｉｎ and D50 ５ｍｉｎThe particle diameter change rate A is 0.50 to 0.90, calculated by the following formula 1 based on the above formula. Formula 1: Particle diameter 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.

[0023] 1. Effect of Precipitated Silica as a Polishing Compound The precipitated silica of the present invention, having the above-mentioned constitution, exhibits excellent polishing properties in terms of the polishing rate and the smoothness of the 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, and during industrial polishing processes, the size of the aggregates creates a moderate resistance between the aggregates and the substrate surface, ensuring the force required to scrape the substrate surface and achieving a high polishing rate. Regarding the inability of conventional precipitated silica to achieve sufficient smoothness on the polished surface, the inventors have 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, making the aggregates too hard, resulting in the formation of abrasion marks. For example, when conventional precipitated silica used as a polishing compound is observed with a scanning electron microscope (SEM), it is found that the primary particles are tightly adhered to each other in the form of massive aggregates, and that the edges of the fracture surfaces formed by grinding of some aggregates are sharp.

[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 (dentifrice 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 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 Effects of Precipitated Silica The present inventors have unexpectedly discovered 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 for the purpose of adjusting the properties of the cosmetic, 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 an agent for improving the feel of cosmetics.

[0033] The adhesiveness to the skin is an extremely useful feature for cosmetic ingredients in that it supports the adhesion and retention 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, a BET specific surface area, and the 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 Agent 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. Constitution of Precipitated Silica The precipitated silica of the present invention has a particle size of 2.50 cm as measured by mercury intrusion 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 of the indicators 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 appropriately, and when used as a polishing compounding agent, the polished surface does not become rough and scratches are unlikely to occur. For cosmetic applications, ３ / g or more, a moist feel and adhesion are likely to be obtained. ３ When the content is in the range of 1 / 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 cm３ / g or more, more preferably 2.70 cm ３ / g or more, and more preferably 2.80 cm ３ The total pore volume of the precipitated silica of the present invention is, for example, 4.00 cm3 from the viewpoint of easily obtaining an appropriate 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 15 m 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 that scratches are less likely to occur on the polished surface of the substrate. In addition, when the BET specific surface area is 15 m ２ It is difficult to make the BET specific surface area less than 35 m / g. ２ For cosmetic applications, a BET specific surface area of ​​15 to 35 m is required. ２ For paint and ink applications, a BET specific surface area of ​​15 to 35 m ２ When the content is in the range of / 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 26 m 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 a concentration of 4 mass % without ultrasonic treatment using a laser diffraction particle size distribution analyzer. ０ｍｉｎ Water is used as the solvent for the slurry.０ｍｉｎ When the D50 is 2.0 μm or more, the silica particles do not become monodispersed as in colloidal silica, but become aggregates of a suitable size, thereby achieving a sufficient removal rate. ０ｍｉｎ By keeping the D50 at 25 μm or less, it is possible to prevent scratches on the object to be polished caused by coarse particles. 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. 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, 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 0.50 to 0.90, calculated by Equation 1 based on the above. The particle size change rate A represents the rate of change in volume average particle size before and after ultrasonic treatment when 50 mL of a 4 mass % precipitated silica slurry is subjected to ultrasonic treatment 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 the precipitated silica when an external force is applied to the precipitated silica, and is therefore one index of the disintegrability of the precipitated silica. The larger the particle size change rate A, the more easily the precipitated silica is disintegrated.

[0046] By having a particle size change rate A of 0.90 or less, excessive disintegration of the precipitated silica can be suppressed, allowing the appropriate particle size to be maintained for various applications, and in particular, in polishing applications, a sufficient polishing rate can be obtained. By having a particle size change rate A of 0.50 or more, the precipitated silica has appropriate 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 cosmetic applications, 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 diameter D50 ５ｍｉｎ 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 is more preferably 1.5 to 10 μm, and even more 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 is 0.40 or less, as calculated by the following formula 2 based on the above formula: Formula 2: Particle diameter 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.

[0050] The particle size change rate B is a parameter that indicates the difference in the volume average particle size of precipitated silica when an external force (ultrasound) is applied to the precipitated silica over a short and long period of time. The larger the particle size change rate B, the more the precipitated silica disintegrates when an external force is continuously applied, resulting in a smaller volume average particle size. Conversely, the smaller the particle size change rate B, the more likely it is that the disintegration will stop at a certain point and a constant volume average particle size will be maintained even when an external force is continuously applied to the precipitated silica. By keeping the particle size change rate B at 0.40 or less, excessive disintegration of the precipitated silica can be suppressed, allowing appropriate particle size to be maintained in various applications, and in particular, sufficient polishing speed can be achieved in polishing applications. In cosmetic applications, a particle size change rate B of 0.40 or less can more easily achieve a moist feel and adhesion. In paint and ink applications, a particle size change rate B of 0.40 or less can more easily achieve 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 diameter D50 １０ｍｉｎ 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 is more preferably 1.5 to 10 μm, and even more 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 a concentration of 4% by weight 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 is 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 to 4% by mass without ultrasonic treatment preferably has an electrical conductivity of less than 1,000 μS / cm. This makes it easier to prepare a slurry or composition 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] [Methods of Use 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] The precipitated silica of the present invention exhibits excellent polishing properties in terms of polishing rate and smoothness of the polished surface, and can therefore be used as a polishing compound.

[0059] When used as a polishing compound, the precipitated silica of the present invention can be dispersed in a solvent such as water to form a slurry, which can also contain additives such as salts and surfactants.

[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] [Compositions Containing Precipitated Silica] In another aspect, the present invention is a polishing composition, a cosmetic, or a paint or ink containing the above-mentioned 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] [Method for Producing Precipitated Silica] The precipitated silica of the present invention can be produced by the production method of the present invention described below. The method for producing precipitated silica of the present invention comprises the steps of: (A) preparing an aqueous alkali silicate solution at 80 to 95°C in a vessel equipped with a solution circulation line; (B) adding 10.0 to 15.0 mass% of SiO to the aqueous alkali silicate solution while stirring the solution in the vessel and circulating it through the circulation line; ２ (C) simultaneously adding an aqueous alkali silicate solution having a concentration of 1.0 to 10.0 mass % and dilute sulfuric acid of 1.0 to 10.0 mass % to a solution in a vessel 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 vessel; (C) after completion of the simultaneous addition, adding an acid to stop the generation of the reaction product; and (D) separating the reaction product from the reaction solution in the vessel by solid-liquid separation, thereby obtaining the precipitated silica of the present invention.

[0067] In general, 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 to 95°C. During the synthesis process, seed particles (primary particles) precipitate, which aggregate and grow further to become precipitated silica. 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 diameter of less than about 1 / g, the necking between the primary particles 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, in order to further suppress the growth of necking between primary particles, 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. As a result, the precipitated silica agglomerated particles (or agglomerates, etc.) in the reaction solution are wet-pulverized during the neutralization reaction, and the aggregation of primary particles is further suppressed.

[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] Step (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] SiO of the alkali silicate aqueous solution prepared in the container ２ The concentration is preferably low, for example, 5.0 mass % or less, which allows the primary particles to grow more slowly. ２ The 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. The 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 has a low SiO content compared to the aqueous alkali silicate solution added in step (B). ２Furthermore, the aqueous alkali silicate solution prepared in step (A) is preferably an aqueous sodium silicate solution, and has a lower SiO concentration than the aqueous sodium silicate solution added in step (B). ２ Concentration and low Na ２ It is preferable that the concentration of 0 is 0.

[0075] Step (B) In step (B), 10.0 to 15.0 mass % of SiO is added to the solution in the container while stirring the solution and circulating it through the circulation line. ２ and 1.0 to 10.0 mass % dilute sulfuric acid are simultaneously added to a solution in a 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.

[0076] The 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 reaction liquid. The circulation line may be a simple circulation line that pumps the reaction liquid from the container and simply returns it to the container, or a combined circulation line that pumps the reaction liquid from the container to an external grinder and returns the reaction liquid treated in the external grinder to the container. As a simple circulation line, a turbine pump or a centrifugal pump is preferred. The external grinder included in the combined circulation line is not particularly limited, and a known wet grinder can be used. The outlet for the returned reaction liquid from the circulation line may be above the liquid level of the reaction liquid 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 returned reaction liquid from the circulation line be above the liquid level of the reaction liquid 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 reaction solution is circulated at a rate of X m ３ 0.3X to 0.7Xm ３It is preferable to carry out the circulation at a flow rate of 0.35X to 0.65X m / min. This can further suppress the aggregation of primary particles. ３ / min, and more preferably 0.37X to 0.60X m ３ / min.

[0079] SiO of the aqueous alkali silicate solution added in step (B) ２ The concentration is 10.0 to 15.0 mass %, which allows the primary particles to grow slowly. ２ The concentration is preferably 10.0 to 14.5% by mass, and more preferably 10.0 to 14.0% by mass.

[0080] The alkali metal oxide concentration of the aqueous alkali silicate solution added in step (B) can be adjusted as appropriate. The alkali metal oxide concentration is preferably 3.1 to 5.0 mass %, more preferably 3.5 to 4.5 mass %. The SiO ２ The molar ratio of alkali metal oxide to alkali silicate can be adjusted as appropriate. 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 an aqueous sodium silicate solution. In this case, the Na ２ The O concentration can be adjusted as appropriate. ２ The O concentration is preferably 3.1 to 5.0 mass %, more preferably 3.5 to 4.5 mass %. ２ / Na ２ The molar ratio of O can be appropriately adjusted and 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, more preferably 4.0 to 7.0% by mass.

[0082] The volume ratio of the aqueous alkali silicate solution to dilute sulfuric acid when adding the material is 1:0.5 to 1:10. This allows the 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 material is not particularly limited. For example, when a 240 L reaction vessel is used as in Example 1 and the amount of liquid at the end of the neutralization reaction is assumed to be 120 to 220 L, the flow rate of the aqueous alkali silicate solution is ２ / Na ２ When the O 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 is 50 to 180 mL / min (58 to 207 g / min). From the viewpoint of growing the primary particles more slowly, the flow rate of the aqueous alkali silicate solution is preferably small, 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] Step (C) In step (C), after the simultaneous addition is completed, an acid is added to terminate the production of the reaction product. When the pH of the reaction solution in the vessel reaches an acidic range (e.g., 3 or less), the neutralization reaction of the alkali silicate aqueous solution and dilute sulfuric acid is terminated, and the production of the reaction product is also terminated.

[0088] Step (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 grinding is also preferred. Dry grinding can be carried out using a known grinding device 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 aqueous alkali silicate solution used as the raw material for the precipitated silica of the present invention is generally derived from silica sand, but from the viewpoint of the SDGs, the aqueous alkali silicate 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 on the emission of nanomaterials. Since the precipitated silica produced by the production 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.

[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 (cm) measured by mercury porosimetry ３ / g) The sample was loaded into a mercury porosimeter (model: PASCAL140, manufactured by ThermoQuest), and the pore volume distribution in the range of pore radius 1,600 to 62,000 nm (1.6 to 62 μm) was measured while increasing the pressure from 10 kPa to 400 kPa. Subsequently, the sample after the above measurement was loaded into a mercury porosimeter (model: PASCAL440, manufactured by ThermoQuest), and the pore volume distribution in the range of pore radius 3.6 to 6,400 nm was measured while increasing the pressure from 100 kPa to 200 MPa. The results of each measurement were integrated using the attached software to determine the pore volume distribution in the range of pore radius 3.6 nm to 62 μm, and the pore volume in that 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 single-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 diameter D50 ０ｍｉｎ(μm) 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 a precipitated silica slurry. The particle size distribution of the precipitated silica in the slurry that had not been subjected to ultrasonic treatment was measured using a laser diffraction particle size distribution analyzer (model: SYNC30, manufactured by Microtrac Bell Co., Ltd.), and the particle size (median diameter) at which the volumetric value in the particle size distribution accounts for 50% of the total was defined 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: Sonfier 250D, manufactured by Branson). The particle size distribution of the precipitated silica in the slurry that had been subjected to 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] 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 diameter change rate A was calculated according to the following formula 1. Formula 1: Particle diameter change rate A = (D50 ０ｍｉｎ -D50 ５ｍｉｎ ) / D50 ０ｍｉｎ

[0100] Particle size change rate B First, the volume average particle size D50 １０ｍｉｎwas 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 using an ultrasonic homogenizer (model: Sonfier 250D, manufactured by Branson) at an output of 140 W for 10 minutes. 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), and the particle diameter (median diameter) at which the volumetric value in the particle size distribution accounted for 50% of the total was defined 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 diameter change rate B was calculated according to the following formula 2. Formula 2: Particle diameter change rate B = (D50 ５ｍｉｎ -D50 １０ｍｉｎ ) / D50 ５ｍｉｎ

[0102] Apparent density (g / L) The apparent density was measured in accordance with 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 (a sieve with 0.5 mm openings, a funnel, a 30 mL cylindrical receiver, a receiver stand, and a 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. Equation 3: Apparent density (g / L) = (mass of sample / 30) x 1000

[0103] The pH of a slurry prepared by adding precipitated silica to 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 Corporation).

[0105] Evaluation of abrasiveness 30 g of distilled water was placed in a 100 mL disposable cup, and 10 g of precipitated silica was added thereto. The mixture was stirred at 1,500 rpm for 5 minutes using a high-speed mixer (model: Lavorution, manufactured by Primix Corporation) to obtain a silica slurry. Then, 40 g of a 14 mass % PVA solution was added to the silica slurry, and the mixture was stirred again at 700 rpm for 10 minutes, taking care not to generate bubbles. The silica slurry was coated on 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 fine paper (Oji Paper Co., Ltd.), the fine paper was 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 out from the coated paper. The test piece was placed in a Gakushin-type abrasion fastness tester (model: AB-301, Tester Sangyo Co., Ltd.), and the test piece was run back and forth 50 times under a load of 500 gf on an ABS plate (70 mm x 150 mm, black, Coating Tester Co., Ltd.).

[0106] <Amount of abrasion (abrasion rate)> 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 using the following three levels: A: Large amount of abrasion (fast abrasion rate) B: Medium amount of abrasion C: Almost no abrasion (slow abrasion rate)

[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 a magnification of 50 times, and the arithmetic mean roughness Ra value and maximum height Ry value within an area of ​​300 μm × 300 μm were measured at five locations, and the measured values ​​were averaged. The mean Ra value and mean Ry value were each evaluated using the following three-level scale. The smaller the mean Ra value and mean Ry value, 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: 1.60 μm or more Evaluation of average Ry value: A: Less than 15.00 μm B: 15.00 μm or more and less than 25.00 μm C: 25.00 μm or more

[0108] <Overall Evaluation of Abrasiveness> Based on the evaluation results of three items, namely, the amount of polishing, the average Ra value, and the average Ry value, the abrasiveness was evaluated comprehensively according to the following criteria: Good: Two or more items rated A and no items rated C. 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 texture was evaluated according to the following criteria: Good: Moist texture and adhesiveness. Bad: The above-mentioned texture was not obtained.

[0110] Evaluation of matt property 20 g of distilled water was placed in a 100 mL disposable cup, and 2 g of precipitated silica was added thereto, and the mixture was stirred at 1,500 rpm for 1 minute using a high-speed mixer (model: Lavortion, manufactured by Primix Corporation) to obtain a silica slurry. The silica slurry was 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 mixture was stirred at 1,500 rpm for 20 minutes to obtain a paint sample for evaluation.

[0111] <Gloss (60° Gloss Value)> The above 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, and the coating film was 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 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 to 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 Property> Based on the evaluation results of two items, glossiness (60° gloss value) and dispersibility, matte property was evaluated comprehensively according to the following criteria: Good: glossiness less than 50 and dispersibility less than 60 μm. Bad: other than the above.

[0114] [Example 1] Precipitated silica was produced in a 240 L (X=0.24 m) reactor equipped with a stirrer and an external circulation device. ３ The sodium silicate aqueous solution in the following description was prepared by using a steam-heated stainless steel vessel (size: 1000 ml, capacity: 2000 ml) with constant stirring. ２ Concentration 12.8% by mass, Na ２ O concentration 4.0% by mass, SiO ２ / Na ２ No. 3 sodium silicate having an O molar ratio of 3.2 was used, and 5.0 wt % sulfuric acid was used as the dilute sulfuric acid in the following description.

[0115] A sodium silicate aqueous solution was added to 30.0 kg of water placed in a container so that the pH was 10.5, and the solution was heated to 90°C. ２The concentration was 0.1% by mass, and the alkali metal oxide concentration was 0.03% by mass. While maintaining the solution temperature at 90°C, 71.1 kg of the sodium silicate aqueous solution and dilute sulfuric acid were simultaneously added to the vessel over 630 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 1:1.4. 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.), which was an external circulation device, was used to circulate the sodium silicate aqueous solution at a rate of 0.10 m ３ / min (0.4Xm ３ The reaction solution was constantly circulated at a flow rate of 1 / min. After the simultaneous addition was completed, dilute sulfuric acid was further added until the pH reached 3, thereby completing the neutralization reaction and terminating 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] Water was added to the obtained silica cake to form a slurry, 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.) under conditions of 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 dilute 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 about 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 dilute 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 about 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] A hydrous silicate (b) having a BET specific surface area of ​​30 m was prepared by referring to the method for producing hydrous silicate (b) described in Patent Document 3. ２ / g or less precipitated silica was produced. Comparative Example 1 differs from Example 1 in that the concentration of dilute sulfuric acid is relatively high at 9.0 mass % and the reaction solution is not circulated by an external circulation device during the reaction. The vessel, aqueous sodium silicate solution, and device are the same as those described in Example 1.

[0122] A sodium silicate aqueous solution was added to 36.8 kg of water placed in a container so that the pH was 10.5, and the solution was heated to 90°C. ２The concentration 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 aqueous sodium silicate solution and dilute sulfuric acid (concentration 9.0% by mass) were simultaneously added to the vessel 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 aqueous sodium silicate solution to the dilute sulfuric acid during the simultaneous addition was 1:0.8. The flow rate of the aqueous sodium silicate solution was approximately 130 mL / min (149 g / min). The reaction 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. The volume average particle diameter D50 of the precipitated silica was 0.03% by mass. ０ｍｉｎ was 10.74 μm.

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

[0124] A sodium silicate aqueous solution was added to 56.6 kg of a 0.20 mol / L sodium sulfate aqueous solution placed in a container so that the pH was 10.5, and the solution was heated to 90°C. ２ The concentration 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 aqueous sodium silicate solution and concentrated sulfuric acid (concentration 95.0% by mass) were simultaneously added to the vessel over 120 minutes to produce a reaction product through a neutralization reaction between the sodium silicate and concentrated sulfuric acid. The volume ratio of the aqueous sodium silicate solution to concentrated sulfuric acid during the simultaneous addition was 1:0.04. The flow rate of the aqueous sodium silicate solution was approximately 843 mL / min (970 g / min). The reaction solution was not circulated during the neutralization reaction. After the simultaneous addition was completed, concentrated sulfuric acid was further 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. The volume average particle diameter D50 of the precipitated silica was 0.04.０ｍｉｎ was 14.96 μm.

[0125] [Comparative Example 3] A sintered body having a BET specific surface area of ​​35 m was prepared by referring to the manufacturing method of Example 3 of Patent Document 1. 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 vessel and apparatus were the same as those described in Example 1.

[0126] 81 L (86.7 kg) of 10.0 mass % aqueous sodium chloride solution and 81 L (86.7 kg) of 10.0 mass % aqueous sodium sulfate solution were mixed and heated to 85°C. Into the solution, No. 3 sodium silicate (SiO ２ Concentration 22.0% by mass, Na ２ 32.4 L (41.80 kg) of 14.0 mass% sulfuric acid (O concentration 7.0 mass%) and approximately 32.4 L (35.32 kg) of 14.0 mass% sulfuric acid were added simultaneously over 60 minutes. The volume ratio of the aqueous sodium silicate solution to sulfuric acid during the simultaneous addition was 1:1.0. The flow rate of the aqueous sodium silicate solution was approximately 540 mL / min (697 g / min). The reaction solution was not circulated during the neutralization reaction. After the simultaneous addition was completed, sulfuric acid was further 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 using a filter press and washed with water to obtain a silica cake. Subsequently, precipitated silica was obtained in the same manner as in Example 1. The volume average particle diameter D50 of the precipitated silica was ０ｍｉｎ was 15.03 μm.

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

[0128] [Results] The results of Examples 1 to 5 and Comparative Examples 1 to 4 are shown in Tables 1 and 2 below and in Figures 1 to 9.

[0129]

[0130]

[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 is significantly different 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), while 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 a relatively large particle size 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 the particle size change rate B is smaller than the 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 reaction solution in the vessel 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 adding the sodium silicate aqueous solution and sulfuric acid, which allowed the primary particles of the precipitated silica to grow slowly, and by circulating the reaction solution, which prevented the aggregation of the primary particles. In contrast, Comparative Example 1 is an example in which the reaction solution was not circulated, and Comparative Examples 2 and 3 are examples in which the reaction solution was not circulated, 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 the primary particles grew in an aggregated state in the precipitated silica of Comparative Examples 1 to 3, 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 silicas of the present invention shown in Figures 3 and 4 have little necking between primary particles, so that the spherical shape of the primary particles can be seen in many areas, whereas the precipitated silicas of the comparative examples shown in Figures 5 and 6 have 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 disintegrability.

[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 to 35 m 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 polished surface smoothly.

[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 the primary 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 silicas 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, and 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 , and volume average particle diameter D50 ０ｍｉｎ and D50 ５ｍｉｎ A precipitated silica having a particle size change rate A of 0.50 to 0.90, calculated by the following formula 1 based on the particle size change rate A: 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, having a particle size change rate B of 0.40 or less, calculated by the following formula 2 based on the following formula: 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. The precipitated silica according to claim 1 or 2, having an apparent density of 80 to 180 g / L.

5. The precipitated silica according to claim 1 or 2, wherein a 4% by mass slurry of the 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.

6. The precipitated silica according to claim 1 or 2, 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 diameter change rate B is 0.40 or less, calculated by the following formula 2 based on the above formula: ５ｍｉｎ -D50 １０ｍｉｎ ) / D50 ５ｍｉｎ Here, the volume average particle diameter D50 １０ｍｉｎ is a volume average particle diameter D50 of 1.0 to 15 μm in the particle size distribution obtained by subjecting 50 mL of a slurry containing 4% by mass of 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. ５ｍｉｎ 10. The precipitated silica of claim 1, wherein the precipitated silica has an apparent density of 80 to 180 g / L, a 4% by weight slurry of the precipitated silica prepared without ultrasonic treatment has a pH of 5.5 to 8.5, and a filtrate of the slurry has an electrical conductivity of less than 1,000 μS / cm.

11. The precipitated silica of claim 1, wherein the precipitated silica is used as a polishing compound, a cosmetic compound, or a matting agent for paints or inks.

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

9. A cosmetic product containing 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. A method for producing precipitated silica according to claim 1, comprising the steps of: (A) preparing an aqueous alkali silicate solution at 80 to 95°C in a vessel equipped with a solution circulation line; (B) stirring the solution in the vessel and circulating it through the circulation line while adding 10.0 to 15.0 mass% of SiO ２ (C) simultaneously adding an aqueous alkali silicate solution having a concentration of 0.01% by mass and 1.0 to 10.0% by mass of dilute sulfuric acid to a solution in a vessel 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 vessel; (C) after completion of the simultaneous addition, adding an acid to stop the generation of the reaction product; and (D) separating the reaction product from the reaction solution in the vessel by solid-liquid separation, thereby obtaining the precipitated silica.

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

13. The reaction solution is circulated in a vessel with a volume of X m 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 used for simultaneous addition contains 3.1 to 5.0 mass% 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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