Surface-modified silica particles and method for producing surface-modified silica particles

Abstract

Surface-modified inorganic oxide particles characterized in that, in diffuse reflectance measurement using an ultraviolet-visible spectrophotometer, the amount of by-products calculated by the following formula (1): amount of by-products = B / A(1) is 0.17 or less, where A is the K / S value obtained using a Kubelka-Munk function based on the diffuse reflectance at the peak top position of a diffuse reflectance peak having a peak top in the range of 270 to 320 nm, and B is the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at a position of 500 nm.The present invention can provide inorganic oxide particles that can minimize thickening of resin compositions when kneaded with resins.

Description

[Technical Field]

[0001] The present invention relates to a method for producing surface-modified inorganic oxide particles and surface-modified silica particles. [Background technology]

[0002] Silica particles have been used as a filler for insulating materials. In this case, the silica particles are kneaded and dispersed in a resin to prepare a resin composition, and the resulting resin composition is then molded into a product shape to produce a resin material.

[0003] Here, conventional silica particles increase the viscosity of a resin composition when kneaded into the resin, but if the content of silica particles in the resin becomes too high, the viscosity of the resin composition increases too much, resulting in a decrease in the dispersibility of the silica particles in the resin.

[0004] Therefore, as a technology for suppressing thickening of a resin composition, Patent Document 1 discloses hollow silica particles having an outer shell portion that forms an internal space, the outer shell portion being composed of a component containing silica, and the surface of the hollow silica particles being surface-treated with a nitrogen-containing silane coupling agent.

[0005] Patent Document 2 also discloses a surface treatment method for silica particles, which includes a surface treatment step of treating the surface of silica particles with a silane coupling agent and an organosilazane in a liquid medium containing water, wherein the silane coupling agent has three alkoxy groups and a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group, and the molar ratio of the silane coupling agent to the organosilazane is silane coupling agent:organosilazane = 1:2 to 1:10. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-83736 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-213736 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when preparing a resin composition containing silica particles, the techniques of either Patent Document 1 or Patent Document 2 were used, and the suppression of thickening of the resin composition was insufficient.

[0008] Furthermore, when inorganic oxide particles, not limited to silica particles, are used as a filler for a resin material, the problem of thickening of the resin composition similarly occurs in the preparation of a resin composition containing the inorganic oxide particles.

[0009] Therefore, an object of the present invention is to provide inorganic oxide particles that can minimize the increase in viscosity of a resin composition when kneaded with the resin. [Means for solving the problem]

[0010] The above problems are solved by the present invention described below. That is, the present invention (1) provides a method for measuring diffuse reflectance using an ultraviolet-visible spectrophotometer, in which the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at the peak top position of a diffuse reflectance peak having a peak top in the range of 270 to 320 nm is A, and the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at a position of 500 nm is B, and the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at a position of 500 nm is B, and the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at a position of 500 nm is A, and the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at a position of 500 nm is B ... Amount of by-product = B / A (1) The present invention provides surface-modified inorganic oxide particles characterized in that the amount of by-products determined by the above formula (1) is 0.17 or less.

[0011] The present invention (2) also provides surface-modified inorganic oxide particles (1) characterized in that the average value of the cut length mean diameter in scanning electron microscope (SEM) observation is 0.10 to 1.0 μm.

[0012] In addition, the present invention (3) is characterized in that the particle density measured by the nitrogen gas substitution method is 0.70 to 1.20 g / cm 3 The present invention provides surface-modified inorganic oxide particles according to (1) or (2), characterized in that:

[0013] The present invention (4) also provides a method for producing silane coupling agent-treated silica particles by adding a silane coupling agent to a dispersion of raw silica particles in a solvent, thereby surface-treating the raw silica particles with the silane coupling agent; a second step of adding organosilazane to a dispersion of the silane coupling agent-treated silica particles in a solvent to surface-treat the silane coupling agent-treated silica particles with the organosilazane, thereby obtaining surface-modified silica particles; and the addition rate of the organosilazane per 1.0 g of the raw silica particles is 0.0020 mol / min / g or less; The present invention provides a method for producing surface-modified silica particles, characterized by the above. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide inorganic oxide particles that can minimize the increase in viscosity of a resin composition when kneaded with the resin. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an analysis chart of the surface-modified silica particles of Example 2 obtained by an ultraviolet-visible spectrophotometer. DETAILED DESCRIPTION OF THE INVENTION

[0016] In diffuse reflectance measurement using an ultraviolet-visible spectrophotometer, the surface-modified inorganic oxide particles of the present invention satisfy the following formula (1), where A is the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at the peak top position of a diffuse reflectance peak having a peak top in the range of 270 to 320 nm, and B is the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at a position of 500 nm: Amount of by-product = B / A (1) The surface-modified inorganic oxide particles are characterized in that the amount of by-products determined by the above formula is 0.17 or less.

[0017] The surface-modified inorganic oxide particles of the present invention are not particularly limited, and examples thereof include silica, magnesium oxide, zinc oxide, lead oxide, aluminum oxide (alumina), tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, tin oxide, titanium oxide (titania), niobium oxide, molybdenum oxide, and vanadium oxide, the particle surfaces of which are surface-modified with a silane coupling agent and an organosilazane. The surface-modified inorganic oxide particles of the present invention may be either solid or hollow. That is, the surface-modified inorganic oxide particles of the present invention may or may not have a hollow inside. The surface-modified inorganic oxide particles of the present invention may also be porous.

[0018] The surface-modified inorganic oxide particles of the present invention are represented by the following general formula (2): Si(OR 1 ) (4-n) R 2 n (2) (In the formula, R 1 are alkyl groups and may be the same or different. 2 represents a phenyl group, a functional group containing a phenyl group, or a linear or branched alkyl group having a phenyl group or a functional group containing a phenyl group, and may be the same or different. n is 1 or 2. Preferably, the inorganic oxide particles are surface-modified with a silane coupling agent represented by the following formula (I) and an organosilazane.

[0019] In general formula (2), R 1 R is an alkyl group, preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 1 When there are multiple, they may be the same or different. In general formula (2), R 1 Specifically, is a methyl group, an ethyl group, a propyl group, an isobutyl group, a butyl group, a pentyl group, or a hexyl group.

[0020] R 2 is a phenyl group (C6H5-), a functional group containing a phenyl group, or a linear or branched alkyl group having a phenyl group or a functional group to which a phenyl group is bonded. 2 R is a phenyl group, a functional group containing a phenyl group, a linear or branched alkyl group to which a phenyl group is bonded, or a linear or branched alkyl group to which a functional group containing a phenyl group is bonded. The number of carbon atoms in the linear or branched alkyl group is preferably 1 to 8, more preferably 1 to 4, and even more preferably 1 to 3. 2 When there are multiple, they may be the same or different. R 2 As the alkyl group, an N-phenylamino group (C6H5-NH-), a phenyl group (C6H5), or an N-phenylaminopropyl group (C6H5-NH-C3H6-) is preferred.

[0021] n is 1 or 2, preferably 1.

[0022] Examples of the silane coupling agent represented by the general formula (2) include N-phenyl-3-aminopropyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and phenyltriethoxysilane. The silane coupling agent represented by the general formula (2) may be used alone or in combination of two or more kinds.

[0023] Preferred organosilazanes include tetramethyldisilazane, hexamethyldisilazane, and pentamethyldisilazane, and more preferably hexamethyldisilazane. The organosilazanes may be used alone or in combination of two or more.

[0024] In diffuse reflectance measurement using an ultraviolet-visible spectrophotometer, the surface-modified inorganic oxide particles of the present invention satisfy the following formula (1), where A is the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at the peak top position of a diffuse reflectance peak having a peak top in the range of 270 to 320 nm, and B is the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at a position of 500 nm: Amount of by-product = B / A (1) The amount of by-products calculated by formula (1) is 0.000 to 0.17, preferably 0.005 to 0.17, more preferably 0.010 to 0.16, and more preferably 0.015 to 0.15. When the amount of by-products calculated by formula (1) is within the above range, the inorganic oxide particles can be kneaded with a resin to minimize thickening. The amount of by-products calculated by formula (1) is preferably 0.000. In diffuse reflectance measurements using a UV-visible spectrophotometer, the diffuse reflectance peak with a peak top in the range of 270 to 320 nm is due to the normal reaction of the silane coupling agent during surface treatment, while the absorption at 500 nm is due to by-products derived from the silane coupling agent. Therefore, the smaller the value of the by-product amount calculated by Equation (1), the more the silane coupling agent is coated on the silica surface. Furthermore, by keeping the value of the by-product amount calculated by Equation (1) within the above range, the inorganic oxide particles can be obtained with minimal viscosity increase when kneaded into a resin, resulting in high dispersibility of the inorganic oxide particles in the resin. On the other hand, if the value of the by-product amount calculated by Equation (1) exceeds the above range, the inorganic oxide particles will thicken too much when kneaded into a resin.

[0025] The amount of by-products calculated by the formula (1) in the present invention can be calculated by the following procedure. First, the diffuse reflectance of the surface-modified inorganic oxide particles to be measured is measured using a UV-visible spectrophotometer when the particles are irradiated with light in the UV to visible region, at least in the range of 190 to 900 nm. Next, the diffuse reflectance at the peak top position of the diffuse reflectance peak having a peak top in the range of 270 to 320 nm is extracted from the measurement results, and the Kubelka-Munk function:

[0026]

number

[0027] (where R∞ is the diffuse reflectance of the object to be measured when the diffuse reflectance of the barium sulfate standard plate is taken as 100%), and the K / S value is calculated and obtained as value A. In addition, the diffuse reflectance at a position of 500 nm is extracted, and based on that diffuse reflectance, the K / S value is calculated using the Kubelka-Munk function and obtained as value B. Next, the following formula (1): Amount of by-product = B / A (1) Substitute the obtained A and B values ​​into to calculate the amount of by-products.

[0028] The surface-modified inorganic oxide particles of the present invention preferably have an average value of a cut length mean diameter in scanning electron microscope (SEM) of 0.10 to 1.0 μm, more preferably 0.20 to 0.90 μm, and even more preferably 0.30 to 0.90 μm. When the surface-modified inorganic oxide particles have an average value of a cut length mean diameter in scanning electron microscope (SEM) in the above range, they have excellent dispersibility in resins when used as resin-added fillers, etc.

[0029] The CV value of the cut length mean diameter of the surface-modified inorganic oxide particles of the present invention in scanning electron microscope (SEM) observation is preferably 0.1 to 10%, more preferably 0.1 to 9%, even more preferably 0.1 to 8%, and most preferably 0.1 to 7%.

[0030] In the present invention, the average value of the mean diameter at cut length in scanning electron microscope (SEM) observation of the surface-modified inorganic oxide particles, the raw silica particles described below, and the organic polymer particles is determined by measuring the mean diameter at cut length of 100 particles randomly selected in the SEM image obtained by using a scanning electron microscope (SEM) at an accelerating voltage of 15 kV, and averaging the values ​​of the obtained 100 mean diameters at cut length. In the present invention, the CV value of the mean diameter at break in scanning electron microscopy (SEM) of the surface-modified inorganic oxide particles, raw silica particles, and organic polymer particles is a value calculated by measuring the mean diameter at break of 100 particles selected at random in an SEM image obtained by SEM observation at an accelerating voltage of 15 kV, determining the average and standard deviation of the mean diameters at break from the obtained 100 particles, and then using the formula "CV value of mean diameter at break (%) = (standard deviation / mean value) × 100".

[0031] The surface-modified inorganic oxide particles of the present invention may be either hollow or non-hollow. When the surface-modified inorganic oxide particles of the present invention are hollow particles, the particle density of the surface-modified inorganic oxide particles of the present invention measured by a nitrogen gas substitution method is preferably 0.70 to 1.20 g / cm. 3 , more preferably 0.80 to 1.20 g / cm 3 , more preferably 0.80 to 1.10 g / cm 3 , more preferably 0.85 to 1.10 g / cm 3 is. When the surface-modified inorganic oxide particles of the present invention are solid particles, the particle density measured by the nitrogen gas substitution method is preferably 1.50 to 3.00 g / cm 3 , more preferably 1.50 to 2.70 g / cm 3 , more preferably 1.50 to 2.50 g / cm 3is. As the surface-modified inorganic oxide particles of the present invention, hollow surface-modified inorganic oxide particles have a lower dielectric constant than non-hollow particles, and are therefore preferred as fillers for insulating materials.

[0032] Furthermore, when the surface-modified inorganic oxide particles of the present invention are hollow particles, the porosity based on the theoretical density of the material of the surface-modified inorganic oxide particles of the present invention is preferably 30 to 99%, more preferably 35 to 90%, more preferably 40 to 85%, and even more preferably 40 to 80%. When the porosity of the hollow particles is within the above range, surface-modified inorganic oxide particles with a low dielectric constant can be obtained.

[0033] In the present invention, the porosity based on the theoretical density of the material of the surface-modified inorganic oxide particles (the inorganic oxide constituting the surface-modified inorganic oxide particles) is calculated by the following formula (3): Porosity (%) = (1 - (particle density measured by nitrogen gas substitution method (g / cm 3 ) / Theoretical density of material (g / cm 3 )))×100 (3) This is the value obtained by The theoretical density (g / cm 3 ) is the density of the material itself that forms the surface-modified inorganic oxide particles to be measured, and can be found in chemical handbooks, etc. Theoretical density is the true density, which does not include surface pores or internal voids, and is calculated from the volume occupied by the material itself. If the material is silica, the theoretical density is 2.2 g / cm 3 In this case, when the surface-modified inorganic oxide particles are a mixture of particles made of a plurality of materials, the theoretical density is calculated from the theoretical density of each material contained in the mixture and the volume ratio of each material.

[0034] The moisture content of the surface-modified inorganic oxide particles of the present invention is preferably 0.10% by mass or less, more preferably 0.09% by mass or less, more preferably 0.08% by mass or less, and more preferably 0.07% by mass or less. Having a moisture content within the above range indicates that the silica surface is modified with a silane coupling agent and an organosilazane. In the present invention, the moisture content of the surface-modified inorganic oxide particles of the present invention is a value measured by drying the particles at 120°C in a vacuum dryer for 2 hours or more, sampling 0.1 g of powder, and measuring the moisture content using a Karl Fischer moisture meter (MKA-610, manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0035] The surface-modified inorganic oxide particles of the present invention can minimize thickening of a resin composition when kneaded with the resin, and therefore have high dispersibility in the resin, thereby improving the performance of a resin material containing the surface-modified inorganic oxide particles of the present invention as a filler.

[0036] The degree of viscosity increase of the resin composition when the surface-modified inorganic oxide particles are kneaded into the resin can be determined by the following method. First, 0.6 g of the surface-modified inorganic oxide particles of the present invention and 2.4 g of 2,2-bis(4-glycidyloxyphenyl)propane were weighed out and mixed using a planetary mixer / defoamer at 2000 rpm for 5 minutes at 25°C, followed by degassing at 2000 rpm for 5 minutes at 25°C. Next, the viscosity of the resulting mixture was measured using a cone-plate viscometer with a spindle at 25°C and a shear force of 20 rpm. The surface-modified inorganic oxide particles of the present invention have a viscosity measured by the above method of 26,000 mPa·s or less, preferably 25,800 mPa·s or less.

[0037] The surface-modified inorganic oxide particles of the present invention are suitable for use as a filler for resin materials. The use of hollow silica particles in sealing materials, insulating films, and the like used in electronic materials such as printed wiring boards and package substrates can lead to poor workability, poor injection and poor wetting and spreading, and can cause poor electrical properties and malfunctions in the electronic materials. Therefore, the surface-modified inorganic oxide particles of the present invention, which are hollow silica particles, are suitable as fillers that do not thicken resin compositions and have excellent electrical properties.

[0038] The method for producing the surface-modified inorganic oxide particles of the present invention is not particularly limited.

[0039] A method for producing surface-modified silica particles of the present invention, in which the inorganic oxide is silica, will be described below. The method for producing surface-modified silica particles of the present invention includes a first step of adding a silane coupling agent to a dispersion of raw silica particles dispersed in a solvent, thereby surface-treating the raw silica particles with the silane coupling agent to obtain silane coupling agent-treated silica particles; a second step of adding organosilazane to a dispersion of the silane coupling agent-treated silica particles in a solvent to surface-treat the silane coupling agent-treated silica particles with the organosilazane, thereby obtaining surface-modified silica particles; and the addition rate of the organosilazane per 1.0 g of the raw silica particles is 0.0020 mol / min / g or less; The method for producing surface-modified silica particles is characterized by the following.

[0040] The first step in the method for producing surface-modified silica particles of the present invention is a step of adding a silane coupling agent to a dispersion in which raw silica particles are dispersed in a solvent, thereby surface-treating the raw silica particles with the silane coupling agent and obtaining silane coupling agent-treated silica particles.

[0041] The raw silica particles in the first step are particles to be surface-modified, and are not particularly limited as long as they are silica particles that can be surface-treated with a silane coupling agent and an organosilazane.In addition, the raw silica particles can be either solid particles or hollow particles.That is, the raw silica particles can be particles that have hollows formed inside the particles, or particles that do not have hollows formed inside the particles.The raw silica particles are not particularly limited by the method used to produce them.

[0042] The average value of the mean diameter along cut length of the raw silica particles as observed under a scanning electron microscope (SEM) is preferably 0.10 to 1.0 μm, more preferably 0.20 to 1.0 μm, and even more preferably 0.30 to 0.90 μm.

[0043] The CV value of the mean diameter along cut length of the raw silica particles observed under a scanning electron microscope (SEM) is preferably 0.1 to 10%, more preferably 0.1 to 9%, even more preferably 0.1 to 8%, and most preferably 0.1 to 7%.

[0044] The BET specific surface area of ​​the raw silica particles is preferably 1 to 100 g / m 2 , more preferably 1 to 90 g / m 2 , more preferably 1 to 80 g / m 2 , more preferably 1 to 70 g / m 2 is.

[0045] The raw silica particles include particles having a hollow inside and particles having no hollow inside. When the raw silica particles are hollow silica particles, the particle density measured by the nitrogen gas substitution method is preferably 0.70 to 1.20 g / cm. 3 , more preferably 0.80 to 1.20 g / cm 3 , more preferably 0.80 to 1.10 g / cm 3 , more preferably 0.85 to 1.10 g / cm 3 is. In addition, when the raw silica particles are solid silica particles, the particle density measured by the nitrogen gas substitution method is preferably 1.50 to 3.00 g / cm 3, more preferably 1.50 to 2.70 g / cm 3 , more preferably 1.50 to 2.50 g / cm 3 is.

[0046] The silane coupling agent used in the first step is not particularly limited as long as it can bond to the surface of the raw silica particles. Examples of the silane coupling agent include phenyltrimethoxysilane, diphenyldimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. Among these, the silane coupling agent is preferably a compound represented by the following general formula (2): Si(OR 1 ) (4-n) R 2 n (2) (In the formula, R 1 are alkyl groups and may be the same or different. 2 represents a phenyl group, a functional group containing a phenyl group, or a linear or branched alkyl group having a phenyl group or a functional group containing a phenyl group, and may be the same or different. n is 1 or 2. The silane coupling agent represented by general formula (2) relating to the silane coupling agent used in the first step is the same as the silane coupling agent represented by general formula (2) relating to the surface-modified inorganic oxide particles of the present invention. The silane coupling agent may be used alone or in combination of two or more kinds.

[0047] In the first step, a silane coupling agent is added to a dispersion liquid (hereinafter referred to as dispersion liquid A) in which raw silica particles are dispersed in a solvent.

[0048] Examples of the solvent in which the raw silica particles are dispersed include water and hydrophilic solvents. Examples of hydrophilic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol (IPA), ethylene glycol, propylene glycol, and 1,4-butanediol; ketones such as acetone and methyl ethyl ketone; and esters such as ethyl acetate. Examples of hydrophilic solvents include alcohols, and more preferably methanol, ethanol, and isopropanol. These solvents may be used alone or in combination (blended) of two or more.

[0049] When a mixed solvent of water and a hydrophilic organic solvent is used as the solvent, the mass ratio of the hydrophilic organic solvent (e.g., methanol) to water is not particularly limited, but the hydrophilic organic solvent:water (mass ratio) is preferably 90:10 to 10:90. By setting the mass ratio of the hydrophilic organic solvent to water in the mixed solvent within the above range, the surface treatment of the silica particles can be performed satisfactorily.

[0050] In the first step, the surface area of ​​the raw silica particles is 1 m 2 The amount of silane coupling agent added per unit area is preferably 2.0×10 -6 mol / m 2 Over 1.0 x 10 -3 mol / m 2 Less than or equal to 2.5 × 10 -6 mol / m 2 Over 5.0 x 10 -4 mol / m 2 Less than or equal to 2.7 × 10 -6 mol / m 2 Over 1.0 x 10 -4 mol / m 2 Less than or equal to 3.0 × 10 -6 mol / m 2 Over 5.0 x 10 -5 mol / m 2 The surface area of ​​the raw silica particles is 1 m 2By adding the silane coupling agent in an amount within the above range, it is possible to obtain surface-modified silica particles that have high dispersibility in resins and that can minimize thickening when kneaded with resins. 2 The amount of silane coupling agent added per unit is calculated by multiplying the specific surface area of ​​the raw silica particles by 1 (m 2 / g), the amount of raw silica particles used is y1 (g), and the amount of silane coupling agent added is z1 (mol). 2 The value is calculated by the formula "Amount of silane coupling agent added per unit = z1 / (x1 × y1)".

[0051] In the first step, the content of raw silica particles in dispersion A (dispersion before adding the silane coupling agent) in which raw silica particles are dispersed in a solvent is preferably 1 to 50 mass%, more preferably 3 to 45 mass%, even more preferably 5 to 40 mass%, and most preferably 5 to 35 mass%. By having the content of raw silica particles in dispersion A of raw silica particles within the above range, surface-modified silica particles can be obtained with excellent productivity while preventing particle aggregation.

[0052] In the first step, a silane coupling agent is added to a dispersion (dispersion A) in which raw silica particles are dispersed in a solvent, and the silane coupling agent is reacted with the raw silica particles. When the raw silica particles are surface-treated with the silane coupling agent, the reaction temperature is preferably 30 to 100° C., more preferably 55 to 100° C., more preferably 60 to 95° C., and even more preferably 60 to 90° C. The reaction time is not particularly limited, but is preferably 0.5 to 10 hours.

[0053] Then, by carrying out the first step, the surfaces of the raw silica particles are surface-treated with a silane coupling agent to obtain silane coupling agent-treated silica particles. In the first step, the silane coupling agent-treated silica particles are obtained in the form of a dispersion liquid (hereinafter referred to as dispersion liquid B) in which the silane coupling agent-treated silica particles are dispersed in a solvent.

[0054] The second step in the method for producing surface-modified silica particles of the present invention is a step of adding organosilazane to dispersion B of silane coupling agent-treated silica particles obtained by carrying out the first step, i.e., dispersion B in which silane coupling agent-treated silica particles are dispersed in a solvent, thereby surface-treating the silane coupling agent-treated silica particles with organosilazane and obtaining surface-modified silica particles.

[0055] The organosilazane used in the second step is not particularly limited as long as it can react with the bonding groups on the surface of the silane coupling agent-treated silica particles, and examples thereof include hexamethyldisilazane, tetramethyldisilazane, and pentamethyldisilazane. The organosilazanes may be used alone or in combination of two or more.

[0056] In the second step, the surface area of ​​the raw silica particles is 1 m 2 The amount of organosilazane added per unit is preferably 5.0×10 -5 mol / m 2 Over 1.0 x 10 -2 mol / m 2 Less than or equal to 8.0 × 10 -5 mol / m 2 Over 5.0 x 10 -3 mol / m 2 or less, more preferably 1.0 × 10 -4 mol / m 2 Over 1.0 x 10 -3 mol / m 2 or less, more preferably 1.0 × 10 -4 mol / m 2 Over 5.0 x 10 -4 mol / m 2 The surface area of ​​the raw silica particles is 1 m 2 By adding an organosilazane in the amount per unit area within the above range, it is possible to obtain surface-modified silica particles that are highly dispersible in resins and that can minimize thickening when kneaded with resins. 2 The amount of organosilazane added per unit is calculated by multiplying the specific surface area of ​​the raw silica particles by 2 (m2 / g), the amount of raw silica particles used is y2 (g), and the amount of organosilazane added is z2 (mol). 2 The amount of organosilazane added per unit of polymer is calculated as follows: z2 / (x2 × y2).

[0057] In the second step, the addition rate of organosilazane per 1.0 g of raw silica particles is 0.0020 mol / min / g or less, preferably 0.0015 mol / min / g or less, more preferably 0.0010 mol / min / g or less, and more preferably 0.0008 mol / min / g or less. By adding organosilazane per 1.0 g of raw silica particles within the above range, surface-modified silica particles can be obtained that are highly dispersible in resin and that can minimize thickening when kneaded into resin. On the other hand, if the addition rate of organosilazane per 1.0 g of raw silica particles exceeds the above range, surface-modified silica particles that significantly increase in viscosity when kneaded into resin will be produced. Furthermore, from the viewpoint of production efficiency, the lower limit of the addition rate of organosilazane per 1.0 g of raw silica particles is preferably 0.000001 mol / min / g or more, more preferably 0.000005 mol / min / g or more. The addition rate of organosilazane per 1.0 g of raw silica particles is a value calculated as "addition rate of organosilazane per 1.0 g of raw silica particles = x3 / y3", where x3 (mol / min) is the addition rate of organosilazane to dispersion B and y3 (g) is the amount of raw silica particles used.

[0058] The molar ratio of the amount of silane coupling agent added in the first step to the amount of organosilazane added in the second step (organosilazane / silane coupling agent) is preferably 1 to 100, more preferably 3 to 95, more preferably 5 to 90, and more preferably 10 to 85.

[0059] In the second step, the content of the silane coupling agent-treated silica particles in dispersion B, in which the silane coupling agent-treated silica particles are dispersed in a solvent, is preferably 1 to 50 mass%, preferably 3 to 45 mass%, more preferably 3 to 40 mass%, and most preferably 3 to 35 mass%. By having the content of the silane coupling agent-treated silica particles in dispersion B of the silane coupling agent-treated silica particles within the above range, surface-modified silica particles can be obtained with excellent productivity while preventing particle aggregation.

[0060] In the second step, organosilazane is added to dispersion B in which silane coupling agent-treated silica particles are dispersed in a solvent, and the organosilazane is reacted with the silane coupling agent-treated silica particles. When the silane coupling agent-treated silica particles are surface-treated with organosilazane, heating is preferably performed, and the reaction temperature is preferably 30 to 100° C., more preferably 35 to 90° C., more preferably 40 to 90° C., and more preferably 50 to 80° C. The reaction time is not particularly limited, but is preferably 0.5 to 10 hours.

[0061] The time from the completion of the addition of the silane coupling agent to the dispersion liquid A in which the raw silica particles are dispersed in the first step to the start of the addition of the organosilazane in the second step is preferably 0.5 to 10 hours, preferably 0.5 to 8 hours, and preferably 0.5 to 6 hours.

[0062] Then, by carrying out the second step, surface-modified silica particles in which the surfaces of the silane coupling agent-treated silica particles are surface-treated with organosilazane, i.e., surface-modified silica particles whose surfaces are modified with a silane coupling agent and an organosilazane, are obtained.

[0063] The surface-modified silica particles obtained by carrying out the second step are appropriately subjected to washing, solvent substitution, filtration, drying, etc. to obtain powdery surface-modified silica particles.

[0064] Next, a method for producing raw silica particles used in the first step of the method for producing surface-modified silica particles of the present invention will be described.

[0065] The method for producing hollow silica particles used as raw silica particles includes the steps of: preparing organic polymer particles by polymerizing an organic monomer in a solution containing an organic monomer, a dispersant, a solvent, and a polymerization initiator; a core-shell particle forming step of adding one or more of tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof, and a basic catalyst to the organic polymer particles, and stirring the mixture to react with the one or more of tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof, to form core-shell particles having a core made of an organic polymer particle and a shell covering the organic polymer particle and made of a hydrolysis and condensation product of the tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof; a calcination step of calcining the core-shell particles at 350 to 1500°C, or alternatively, first heating the core-shell particles at 350 to 1200°C to thermally decompose the organic polymer particles, and then calcining the particles at 350 to 1500°C to obtain hollow silica particles; The method for producing hollow silica particles is characterized by having the following:

[0066] The method for producing hollow silica particles includes an organic polymer particle preparation step, a core-shell particle formation step, and a firing step.

[0067] The organic polymer particle preparation step is a step of obtaining organic polymer particles by carrying out a polymerization reaction of an organic monomer in a solution containing an organic monomer, a dispersant, a solvent, and a polymerization initiator.

[0068] The organic monomer used in the organic polymer particle preparation step is not particularly limited as long as it can produce organic polymer particles by polymerization. The organic monomer is preferably an organic monomer that can form organic polymer particles that are easily burned away by thermal decomposition after forming a shell. Examples of the organic monomer include styrene for producing polystyrene particles and methyl (meth)acrylate for producing polymethyl (meth)acrylate (PMMA) particles (note that methyl (meth)acrylate is a general term for methyl methacrylate and methyl acrylate). Styrene is preferred. Furthermore, by copolymerizing styrene together with alkyl(meth)acrylate or other copolymerizable monomers as organic monomers, polystyrene particles containing structural units derived from hydrophobic monomers such as alkyl(meth)acrylate or other copolymerizable monomer structural units can be obtained.

[0069] The dispersant used in the organic polymer particle preparation step is not particularly limited as long as it can produce organic polymer particles. Examples of dispersants include polyvinylpyrrolidone (PVP), hydroxypropyl cellulose (HPC), polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene glycol (PPG), polypropylene oxide (PPO), collagen, and polysaccharides (gum arabic). When the organic polymer particles are polystyrene particles, the use of polyvinylpyrrolidone or hydroxypropyl cellulose as a dispersant can suppress aggregation of the polystyrene particles, thereby suppressing aggregation of the core-shell particles obtained in the core-shell particle formation step. The dispersant may be used alone or in combination (mixture) of two or more types.

[0070] Examples of the solvent used in the organic polymer particle preparation process include water and hydrophilic organic solvents. Examples of hydrophilic organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, and 1,4-butanediol; ketones such as acetone and methyl ethyl ketone; and esters such as ethyl acetate. The hydrophilic organic solvent is preferably an alcohol, and more preferably methanol, ethanol, or isopropanol. The solvent may be used alone or in combination (mixture) of two or more. The solvent is preferably water or a mixed solvent of water and methanol. Organic polymer particles with a narrow particle size distribution can be obtained by using a mixed solvent of water and methanol. When a mixed solvent of water and methanol is used, the mass ratio of water to methanol (water:methanol) is preferably 5:95 to 50:50, more preferably 8:92 to 40:60, and more preferably 10:90 to 30:70. By setting the mass ratio of water to methanol within the above range, organic polymer particles having a narrow particle size distribution can be obtained, and the particle size distribution of the core-shell particles obtained in the core-shell particle forming step can be narrowed.

[0071] The polymerization initiator used in the organic polymer particle preparation process is not particularly limited as long as it can produce organic polymer particles. Examples of polymerization initiators include peroxides such as inorganic peroxides and organic peroxides, organic initiators such as azo compounds, and redox agents. Organic peroxides are represented by the general formula RO-OR, where R is an acyl group, an alkyl group, a ketone group, or the like. Azo compounds are represented by the general formula A-CN=NC-A, where A is an amidine group, a cyano group, a carboxyl group, or the like. Examples of the polymerization initiator include benzoyl peroxide, 2,2'-azobis(isobutylamidine) dihydrochloride (AIBA), 4,4'-azobis-4-cyanovaleric acid, and azobisisobutyronitrile (AIBN), of which 2,2'-azobis(isobutylamidine) dihydrochloride (AIBA) and 4,4'-azobis-4-cyanovaleric acid are preferred, and 2,2'-azobis(isobutylamidine) dihydrochloride (AIBA) is more preferred. The polymerization initiator may be used alone or in combination (mixture) of two or more types.

[0072] In the organic polymer particle preparation process, the concentration of the organic monomer in the solution at the start of the polymerization reaction is not particularly limited. The concentration of the organic monomer at the start of the polymerization reaction is preferably 0.1 to 20 mass % relative to the solution, and more preferably 0.2 to 11 mass %. By keeping the organic monomer concentration at the start of the polymerization reaction within the above range, the average value of the cut length mean diameter of the hollow silica particles in the final product can be well controlled.

[0073] In the organic polymer particle preparation step, the amount of dispersant used is preferably 0.01 to 100% by mass, more preferably 0.05 to 100% by mass, based on the organic monomer. By using the dispersant in this range, aggregation of the organic polymer particles can be suppressed, and aggregation of the core-shell particles obtained in the core-shell particle formation step can be suppressed.

[0074] In the organic polymer particle preparation step, the concentration of the dispersant in the solution is not particularly limited. The concentration of the dispersant is preferably 0.01 to 10% by mass, more preferably 0.1 to 7% by mass, relative to the solution. By setting the dispersant concentration within the above range, aggregation of the organic polymer particles can be suppressed, and aggregation of the core-shell particles obtained in the core-shell particle formation step can be suppressed.

[0075] In the organic polymer particle preparation step, the amount of polymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.05 to 10% by mass, based on the organic monomer. By using the polymerization initiator in this range, the average value of the cut length mean diameter of the hollow inorganic particles in the final product can be well controlled.

[0076] In the organic polymer particle preparation step, the concentration of the polymerization initiator in the solution is not particularly limited. The concentration of the polymerization initiator is preferably 0.01 to 1 mass% relative to the solution. By setting the concentration of the polymerization initiator within the above range, the average value of the cut length mean diameter of the hollow inorganic particles in the final product can be well controlled.

[0077] In the organic polymer particle preparation step, a polymerization reaction of the organic monomer is carried out in a solution containing an organic monomer, a dispersant, a solvent, and a polymerization initiator, preferably while mixing and stirring the solution.

[0078] The reaction temperature during the polymerization reaction in the organic polymer particle preparation step is not particularly limited, but is preferably 30°C or higher and below the boiling point of the solvent, and more preferably 40 to 90°C and below the boiling point of the solvent. By setting the reaction temperature of the polymerization reaction within the above range, the solvent does not evaporate and the polymerization reaction can proceed smoothly. The reaction time of the polymerization reaction is not particularly limited, but is preferably 1 minute to 12 hours, and more preferably 10 minutes to 10 hours. By setting the reaction time of the polymerization reaction within the above range, the polymerization reaction can proceed smoothly.

[0079] In the core-shell particle formation step, the compounds that undergo hydrolysis and condensation reaction are one or more of tetraalkoxysilane or its derivatives, trialkoxysilane or its derivatives, and metal alkoxide or its derivatives. Among these, tetraalkoxysilane is preferred because it can form a smooth and dense silica shell.

[0080] The tetraalkoxysilane is preferably represented by the following general formula (4): Si(OR 1 )4(4) Examples of tetraalkoxysilanes include those represented by the following formula: In general formula (4), R 1 are alkyl groups, preferably alkyl groups having 1 to 8 carbon atoms, more preferably alkyl groups having 1 to 4 carbon atoms, and more preferably alkyl groups having 1 to 3 carbon atoms, and may be the same or different. In general formula (4), R 1 Specifically, is a methyl group, an ethyl group, a propyl group, an isobutyl group, a butyl group, a pentyl group, or a hexyl group. In general formula (4), R 1 Tetramethoxysilane (TMOS), where R is a methyl group 1 Tetraethoxysilane (TEOS), in which the alkyl group is an ethyl group, is preferred in that it can produce silica well and a dense shell can be obtained. Tetraalkoxysilane derivatives are those in which part of the molecular structure of tetraalkoxysilane is replaced with another atomic group. The tetraalkoxysilane or its derivative may be used alone or in combination of two or more kinds.

[0081] The trialkoxysilane preferably has the general formula (5): Si(OR 1 )3R 2 (5) Examples of the trialkoxysilane include trialkoxysilanes represented by the following formula: In general formula (5), R 1 is R in the general formula (4). 1 is the same as: In general formula (5), R 2 are hydrogen or an alkyl group, preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and may be the same or different. A trialkoxysilane derivative is one in which part of the molecular structure of trialkoxysilane is replaced with another atomic group. The trialkoxysilane or its derivative may be used alone or in combination of two or more kinds.

[0082] The metal alkoxide is not particularly limited, and preferred examples of the metal alkoxide include aluminum alkoxide, titanium alkoxide, and zirconium alkoxide. The metal alkoxides may be used alone or in combination of two or more. A metal alkoxide derivative is a metal alkoxide in which a part of the molecular structure of the metal alkoxide is replaced with another atomic group.

[0083] Examples of the solvent used in the core-shell particle formation step include water or a hydrophilic organic solvent. By using water as the solvent, core-shell particles can be formed inexpensively and safely. Preferred examples of the hydrophilic organic solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, and 1,4-butanediol; ketones such as acetone and methyl ethyl ketone; and esters such as ethyl acetate. Preferred examples of the hydrophilic organic solvent include alcohols, and more preferably methanol, ethanol, and isopropanol. The solvent may be used alone or in combination (mixture) of two or more. Examples of the solvent include water and a mixed solvent of water and a hydrophilic organic solvent (e.g., methanol). In the mixed solvent, which is preferably a mixed solvent of water and a hydrophilic organic solvent (e.g., methanol), the mass ratio of the hydrophilic organic solvent (e.g., methanol) to water is not particularly limited. When a mixed solvent of water and methanol is used, the mass ratio of the hydrophilic organic solvent to water is preferably 50:50 to 95:5, and more preferably 60:40 to 95:5. By setting the mass ratio of the hydrophilic organic solvent to water in the mixed solvent within the above range, core-shell particles with a narrow particle size distribution can be obtained.

[0084] The basic catalyst used in the core-shell particle formation step is not particularly limited. As the basic catalyst, an organic base catalyst not containing a metal component or an inorganic catalyst not containing a metal component is preferred in that it can prevent the inclusion of metal impurities. Preferred examples of the organic base catalyst include nitrogen-containing organic base catalysts such as ethylenediamine, diethylenetriamine, triethylenetetraamine, urea, ethanolamine, tetramethylammonium hydroxide (TMAH), tetramethylguanidine, and basic amino acids. A preferred example of the inorganic base catalyst is aqueous ammonia. The basic catalyst may be used alone or in combination of two or more kinds.

[0085] In the core-shell particle forming step, one or more of tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof, and a basic catalyst are added to organic polymer particles dispersed in a solvent.

[0086] In this case, the concentration of the organic polymer particles in the dispersion of the organic polymer particles is preferably 0.01 to 50% by mass, more preferably 0.01 to 20% by mass, based on the dispersion of the organic polymer particles. The amount of one or more of tetraalkoxysilane or its derivative, trialkoxysilane or its derivative, and metal alkoxide or its derivative added is preferably 100 to 600 mass %, more preferably 100 to 500 mass %, based on the organic polymer particles. The amount of the basic catalyst added is preferably 0.1 to 100% by mass, more preferably 1 to 90% by mass, based on one or more of tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof. When two or more of tetraalkoxysilane or its derivative, trialkoxysilane or its derivative, and metal alkoxide or its derivative are added, the above-mentioned amount added refers to the total amount added.

[0087] In the core-shell particle formation step, one or more of tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof, and a basic catalyst are added to the organic polymer particles dispersed in a solvent, and the mixture is stirred to carry out a hydrolysis and condensation reaction of one or more of tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof, thereby producing a hydrolysis and condensation product of one or more of tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof on the surface of the organic polymer particles, and the organic polymer particles are coated with the hydrolysis and condensation product of one or more of tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof, thereby forming core-shell particles.

[0088] The reaction temperature in the core-shell particle formation step is not particularly limited, but is preferably 5 to 200° C., and more preferably 5 to 150° C. By setting the reaction temperature in the core-shell particle formation step within the above range, the solvent does not evaporate and the reaction can proceed smoothly. The reaction time in the core-shell particle forming step is not particularly limited, but is preferably 1 to 1200 minutes, and more preferably 1 to 600 minutes. By setting the reaction time in the core-shell particle forming step within the above range, shell coating can proceed smoothly.

[0089] The core-shell particle formation process can produce core-shell particles having a core made of an organic polymer particle and a shell covering the organic polymer particle and made of a hydrolysis and condensation product of one or more of tetraalkoxysilane or a derivative thereof, trialkoxysilane or a derivative thereof, and metal alkoxide or a derivative thereof.

[0090] The core-shell particles obtained through the core-shell particle forming step are appropriately subjected to washing, solvent substitution, filtration, drying, etc. to obtain powdery core-shell particles.

[0091] The calcination step is a step of obtaining hollow silica particles by calcining the core-shell particles at 350 to 1500° C., or by first heating the core-shell particles at 350 to 1200° C. to pyrolyze the organic polymer particles, and then calcining at 350 to 1500° C. That is, the calcination step can be performed in two ways: (i) calcining the core-shell particles obtained by the core-shell particle-forming step at 350 to 1500° C. without pyrolysis, or (ii) calcining the core-shell particles obtained by the core-shell particle-forming step at 350 to 1500° C. after pyrolysis.

[0092] When thermal decomposition is performed prior to the firing step, the core-shell particles obtained by the core-shell particle formation step are heated at 350 to 1200°C in the thermal decomposition step to thermally decompose the organic polymer particles within the core-shell particles and remove the organic polymer particles. The heating temperature for thermal decomposition is more preferably 400 to 800°C, and even more preferably 450 to 700°C. The heating time for thermal decomposition is 1 to 12 hours, and preferably 2 to 10 hours. The atmosphere during thermal decomposition is preferably an inert gas such as argon gas, helium gas, CO2 gas, or nitrogen gas, or a water vapor (HO) atmosphere.

[0093] When core-shell particles are thermally decomposed in air, the organic polymer in the core rapidly decomposes and gasifies (cracked gas). This rapid generation of cracked gas can lead to fires in the electric furnace, or the cracked gas can pass through the shell of the silica particles and escape, creating holes in the shell. For this reason, the cracking is preferably carried out under low-oxygen conditions. For example, a method of preventing the generation of cracked gas is employed by filling the heating furnace with an inert gas (argon gas, helium gas, CO2 gas, nitrogen gas) or water vapor (HO) and carrying out the cracking.

[0094] In the calcination step, (i) the core-shell particles obtained by the core-shell particle-forming step, or (ii) the core-shell particles obtained by the core-shell particle-forming step are subjected to a thermal decomposition treatment to pyrolyze the organic polymer particles within the core-shell particles, and the resulting particles are calcined at 350 to 1500°C to obtain hollow silica particles. The calcination temperature is more preferably 400 to 1200°C, and even more preferably 600 to 1100°C, and the calcination time is 1 to 10 hours, and preferably 3 to 10 hours. The calcination atmosphere is preferably an oxidizing gas atmosphere such as air or oxygen gas.

[0095] By carrying out the calcination step of the form (i) or (ii), the organic polymer particles inside the core-shell particles are removed, and sintering of the particles can be suppressed, resulting in hollow silica particles with fewer cracks in the silica shell and high porosity. Calcination can increase the strength of the hollow silica particles, suppress moisture adsorption, and reduce the water absorption rate and dielectric loss tangent.

[0096] The heating device used in the firing step is not particularly limited as long as it can heat to a desired temperature in a desired atmosphere. The heating device may be a batch type or a continuous type. The heating method may be electric or gas. Examples include a muffle furnace, a rotary kiln, and a mesh belt kiln.

[0097] Then, by carrying out the calcination process, the organic polymer particles inside the core-shell particles are removed, and the hydrolysis and dehydration of one or more of the tetraalkoxysilane or its derivative, trialkoxysilane or its derivative, and metal alkoxide or its derivative that form the outer shell layer proceeds, resulting in hollow silica particles.

[0098] The hollow silica particles obtained as described above may be further subjected to a shell coating step and / or a hydrophobic treatment. Alternatively, the hollow silica particles may be crushed by a conventionally known crushing method.

[0099] The manufacturing method of the solid silica particles that are used as raw silica particles is not particularly limited.As the manufacturing method of solid silica particles, there can be mentioned the manufacturing method of conventional silica particles, for example, the manufacturing method of alkoxysilane by hydrolysis and dehydration condensation to obtain silica sol (the method of synthesizing silica particles by alkoxide method), as well as the manufacturing method of sodium silicate by ion exchange to prepare activated silicic acid, and then condense silicic acid species under basic conditions to obtain silica sol.

[0100] Furthermore, the surface-modified inorganic oxide particles of the present invention can be produced by using, instead of the raw silica particles used in the method for producing surface-modified silica particles of the present invention, metal oxide particles whose particle surfaces can be surface-modified by a silane coupling agent and an organosilazane upon reaction with the silane coupling agent and the organosilazane, such as metal oxide particles of aluminum, titanium, zirconium, etc.

[0101] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples shown below. [Example]

[0102] Example 1 <Organic polymer particle preparation process> First, 200 parts by mass of ultrapure water and 799 parts by mass of methanol were poured into a flask, and the mixture was heated to an internal temperature of 55°C while stirring at 250 rpm in a nitrogen atmosphere. Next, 100 parts by mass of styrene monomer (organic monomer) and 40 parts by mass of a 5% by mass aqueous solution of AIBA (2,2'-azobis(isobutylamidine) dihydrochloride) dissolved in ultrapure water were added, and a polymerization reaction was carried out at 55°C for 3 hours. Subsequently, a PVP (polyvinylpyrrolidone, Daiichi Kogyo Co., Ltd. Pitzcol K-60L) methanol aqueous solution (10 parts by mass of PVP, 152 parts by mass of methanol, 38 parts by mass of water) was added, and the temperature was further increased and heated under reflux for 3 hours to produce a polystyrene particle reaction solution. The polystyrene particle reaction solution was heated with a mantle heater to replace with methanol, and the reaction was completed when the internal temperature reached 70°C. Polystyrene particles, which are organic polymer particles, were prepared in methanol to obtain a polystyrene particle dispersion.

[0103] <Core-shell particle formation process> Liquid A was prepared by mixing 100 parts by mass of TMOS (tetramethoxysilane) and 198 parts by mass of methanol. Furthermore, the polystyrene particle dispersion liquid produced above, ultrapure water as a solvent, and a 25 mass % ammonia aqueous solution (basic catalyst) containing methanol were added to a flask to prepare liquid B. Polystyrene 27 parts by mass Ultrapure water 132 parts by mass Methanol 660 parts by mass 25% by weight ammonia aqueous solution 71 parts by weight While maintaining the temperature of solution B at 30°C and stirring at 250 rpm, solution A was added over 4 hours. Core-shell particles having polystyrene particles as cores and silica-based shells covering the polystyrene particles were formed in the solution, thereby preparing a core-shell particle dispersion. The aqueous dispersion of core-shell particles obtained above was dried on a hot plate at a temperature of 130° C. to obtain a powder of core-shell particles.

[0104] <Firing process> The resulting core-shell particle powder was then subjected to pyrolysis at a temperature of 500° C. for 4 hours. Next, the mixture was calcined at 1050° C. for 3 hours to remove the polystyrene particles, and then crushed to produce a powder of hollow silica particles.

[0105] <First process, second process> 100 parts by mass of the hollow silica particles obtained above as raw silica particles, 1031 parts by mass of ultrapure water, 688 parts by mass of IPA (isopropanol), and 1 part by mass of N-phenyl-3-aminopropyltrimethoxysilane (KBM-573, manufactured by Shin-Etsu Chemical Co., Ltd.) (trialkoxysilane) were mixed in a flask, stirred, and heated at 75°C for 1 hour to obtain hollow silica particles treated with a silane coupling agent. Next, 32 parts by weight of hexamethyldisilazane (HMDS) (SZ-31, manufactured by Shin-Etsu Chemical Co., Ltd.) (organosilazane) was added dropwise at a rate of 0.07 mol / min / 100 parts by weight per 100 parts by weight of the raw material hollow silica particles (addition rate: 0.0007 mol / min / g per 1.0 g of hollow silica), and the mixture was heated for another 2 hours. The mixture was then dried on a hot plate at 130°C for at least 2 hours to obtain surface-modified hollow silica particles.

[0106] Example 2 The same method as in Example 1 was carried out in the first and second steps, except that 2 parts by mass of N-phenyl-3-aminopropyltrimethoxysilane was mixed instead of 1 part by mass of N-phenyl-3-aminopropyltrimethoxysilane.

[0107] Example 3 The same method as in Example 1 was carried out, except that in the first and second steps, instead of mixing 1 part by mass of N-phenyl-3-aminopropyltrimethoxysilane, 5 parts by mass of N-phenyl-3-aminopropyltrimethoxysilane was mixed.

[0108] Example 4 <Organic polymer particle preparation process> First, 171 parts by mass of ultrapure water and 698 parts by mass of methanol were poured into a flask, and the mixture was heated to an internal temperature of 55°C while stirring at 250 rpm in a nitrogen atmosphere. Next, 100 parts by mass of styrene monomer (organic monomer) and 38 parts by mass of a 5% by mass aqueous solution of AIBA (2,2'-azobis(isobutylamidine) dihydrochloride) dissolved in ultrapure water were added, and a polymerization reaction was carried out at 55°C for 3 hours. Subsequently, a PVP (polyvinylpyrrolidone, Pitzcol K-60L manufactured by Daiichi Kogyo Co., Ltd.) methanol aqueous solution (15 parts by mass of PVP, 211 parts by mass of methanol, 63 parts by mass of ultrapure water) was added, and the temperature was further increased and the mixture was heated under reflux for 3 hours to produce a polystyrene particle reaction solution. The polystyrene particle reaction solution was heated with a mantle heater to replace the methanol, and the reaction was completed when the internal temperature reached 70°C. Polystyrene particles, which are organic polymer particles, were prepared in methanol to obtain a polystyrene particle dispersion.

[0109] <Core-shell particle formation process> Liquid A was prepared by mixing 100 parts by mass of TMOS (tetramethoxysilane) and 200 parts by mass of methanol. Furthermore, ultrapure water, methanol, and a 25% by mass aqueous ammonia solution (basic catalyst) were added to the flask as a solvent for the polystyrene particle dispersion liquid produced above to prepare liquid B. Polystyrene 29 parts by mass Ultrapure water 29 parts by mass Methanol 732 parts by mass 25% by mass ammonia aqueous solution 151 parts by mass While maintaining the temperature of Solution B at 30°C and stirring at 250 rpm, Solution A was added over 6 hours. Core-shell particles having polystyrene particles as cores and silica-based shells covering the polystyrene particles were formed in the solution, thereby preparing a core-shell particle dispersion. The firing step was carried out in the same manner as in Example 1.

[0110] <First process, second process> 100 parts by mass of the hollow silica particles obtained above as raw silica particles, 789 parts by mass of ultrapure water, 526 parts by mass of IPA (isopropanol), and 1 part by mass of N-phenyl-3-aminopropyltrimethoxysilane (KBM-573, manufactured by Shin-Etsu Chemical Co., Ltd.) (trialkoxysilane) were mixed in a flask, stirred, and heated at 75°C for 1 hour to obtain hollow silica particles treated with a silane coupling agent. Next, 24 parts by weight of hexamethyldisilazane (HMDS) (SZ-31, manufactured by Shin-Etsu Chemical Co., Ltd.) (organosilazane) was added dropwise at a rate of 0.07 mol / min / 100 parts by weight per 100 parts by weight of the raw material hollow silica particles (addition rate: 0.0007 mol / min / g per 1.0 g of hollow silica), and the mixture was heated for another 2 hours. The mixture was then dried on a hot plate at 130°C for at least 2 hours to obtain surface-modified hollow silica particles.

[0111] (Comparative Example 1) In the first and second steps, the same method as in Example 2 was used, except that 31.6 parts by mass of hexamethyldisilazane was added dropwise at a rate of 0.40 mol / min / 100 parts by mass per 100 parts by mass of hollow silica, which is the raw silica particles (addition rate per 1.0 g of hollow silica: 0.0040 mol / min / g).

[0112] (Comparative Example 2) The same method as in Example 4 was used, except that in the first and second steps, 23.6 parts by mass of hexamethyldisilazane was added dropwise at a rate of 0.40 mol / min / 100 parts by mass per 100 parts by mass of hollow silica, which is the raw silica particles (addition rate per 1.0 g of hollow silica: 0.0040 mol / min / g).

[0113] The obtained hollow silica particles were analyzed and evaluated by the following methods, and the results are shown in Table 1.

[0114] <Measurement of the amount of by-products> 0.6 g of the surface-modified hollow silica particles to be measured was irradiated with light of wavelengths of 190 to 900 nm using an ultraviolet-visible spectrophotometer (Shimadzu Corporation, UV-2600, integrating sphere ISR-2600PLUS) and the diffuse reflectance was measured using barium sulfate as a standard plate, with the standard plate being set at 100%. Next, the diffuse reflectance at the peak top position of the diffuse reflectance peak having a peak top in the range of 270 to 320 nm is extracted from the measurement results, and the Kubelka-Munk function:

[0115]

number

[0116] (where R∞ is the diffuse reflectance of the object to be measured when the diffuse reflectance of the barium sulfate standard plate is taken as 100%), and the K / S value was calculated and obtained as value A. In addition, the diffuse reflectance at a position of 500 nm was extracted, and based on that diffuse reflectance, the K / S value was calculated using the Kubelka-Munk function and obtained as value B. Next, the following formula (1): Amount of by-product = B / A (1) The amount of by-products was calculated by substituting the determined A and B values ​​into FIG. 1 shows a chart obtained by a UV-visible spectrophotometer.

[0117] <Measurement of average cutting length diameter and CV value> The surface-modified hollow silica particles or hollow silica particles to be measured were photographed using a scanning electron microscope (SEM, JSM-7900F, manufactured by JEOL Ltd.) at an accelerating voltage of 15 kV to obtain SEM images. Next, 100 particles were randomly selected from the obtained SEM images, and the mean diameter along the cut length of each particle was measured. The average value of the mean diameter along the cut length of the 100 particles was calculated. Image analysis was performed using the image analysis and measurement software WinROOF. In addition, the average and standard deviation of the average cut length diameters of 100 randomly selected samples obtained above were determined, and the CV value was then calculated using the formula "CV value (%) = (standard deviation / average value) × 100".

[0118] <Particle density measurement by nitrogen gas substitution method> The particle density of 0.2 g of the surface-modified hollow silica particles or hollow silica particles to be measured was measured using a nitrogen gas pycnometer (Ultrapyc 5000 Micro, manufactured by Anton Paar Japan Co., Ltd.).

[0119] <Porosity measurement> The particle density measured with the nitrogen gas pycnometer was used to calculate the particle density using the following formula. Porosity (%) = (1 - (particle density measured by nitrogen gas pycnometer (g / cm 3 ) / Theoretical density of material (g / cm 3 )))×100 (3) The theoretical density is the density of the silica that forms the surface-modified silica particles to be measured. Refer to a chemical handbook or other sources and use a value of 2.2 g / cm. 3 The value of was used.

[0120] <Measurement of moisture content> After drying in a vacuum dryer at 120°C for 2 hours or more, 0.1 g of powder was sampled and the amount of water (% by mass) generated by heating at 200°C was measured using a coulometric Karl Fischer moisture meter. The measured amount of water was taken as the water content.

[0121] <Viscosity measurement> Weighed 0.6 g of surface-modified hollow silica particles to be measured and 2.4 g of 2,2-bis(4-glycidyloxyphenyl) propane (manufactured by Tokyo Chemical Industry Co., Ltd.), used a planetary stirring and defoaming device MAZERUSTAR (manufactured by Kurashiki Boseki Co., Ltd.), mixed them at 25 °C and 2000 rpm for 5 minutes, and defoamed them at 25 °C and 2000 rpm for 5 minutes. Next, for the obtained mixture, using a cone plate type viscometer DV-1MCP (manufactured by Eihiro Seiki Co., Ltd.), with a spindle, the viscosity when applying a shear force of 20 rpm at 25 °C was measured.

[0122] <Measurement of BET specific surface area> The powder of the hollow silica particles to be measured was dried under reduced pressure at 300 °C for 7 hours or more, and the BET specific surface area was measured by the nitrogen adsorption method.

[0123] [Table 1]

[0124] ·Silica content in dispersion A: The content of the raw silica particles in dispersion A (dispersion A before adding the silane coupling agent) in which the raw silica particles are dispersed ·Silica 1m 2 CA addition amount per unit area: The addition amount of the silane coupling agent per 1 m 2 of the surface area of the raw hollow silica particles ·Reaction temperature of CA: The reaction temperature of the silane coupling agent ·Silica 1m 2 Organosilazane addition amount per unit area: The addition amount of organosilazane per 1 m 2 of the surface area of the raw hollow silica particles ·Organosilazane addition rate per gram of silica: The addition rate of organosilazane per 1.0 g of the raw hollow silica particles ·Measurement of diffuse reflectance by UV-Vis: Measurement of diffuse reflectance by an ultraviolet-visible spectrophotometer

Claims

1. Surface-modified silica particles, the surfaces of which are surface-modified with N-phenyl-3-aminopropyltrimethoxysilane and organosilazane, In diffuse reflectance measurement using an ultraviolet-visible spectrophotometer, when the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at the peak top position of a diffuse reflectance peak having a peak top in the range of 270 to 320 nm is A, and the K / S value obtained using the Kubelka-Munk function based on the diffuse reflectance at a position of 500 nm is B, the following formula (1) can be used: Amount of by-product = B / A (1) The amount of by-products calculated by is 0.17 or less, The particle density measured by a nitrogen gas substitution method is 0.70 to 1.20 g / cm 3 ; The surface-modified silica particles are characterized by:

2. 2. The surface-modified silica particles according to claim 1, wherein the average value of the cut length mean diameter in scanning electron microscope (SEM) observation is 0.10 to 1.0 μm.

3. a first step of adding a silane coupling agent to a dispersion of raw silica particles dispersed in a solvent, thereby surface-treating the raw silica particles with the silane coupling agent to obtain silane coupling agent-treated silica particles; a second step of adding organosilazane to a dispersion of the silane coupling agent-treated silica particles in a solvent to surface-treat the silane coupling agent-treated silica particles with the organosilazane, thereby obtaining surface-modified silica particles; and the addition rate of the organosilazane per 1.0 g of the raw silica particles is 0.0020 mol / min / g or less; A method for producing surface-modified silica particles, characterized by:

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