Surface-treated silica powder

Abstract

The surface-treated silica powder according to the present invention contains silica particles surface-treated with a silane coupling agent, has a hydrophobization degree of 20% or more, and is configured such that C (mass%) represents the carbon content of the surface-treated silica powder, and C represents the carbon content of the surface-treated silica powder. When S (m < 2 > / g) is the specific surface area of the surface-treated silica powder as measured by a BET single-point method by nitrogen adsorption, C and S satisfy 0.025 < = C / S < = 0.070.

Description

Technical Field

[0001] The invention relates to surface-treated silicon dioxide powder. Background Art

[0002] Various developments have been made on surface-treated silica powders. For example, the technology described in Patent Document 1 is known as such a technology.

[0003] Patent Document 1 states that the specific surface area is 10 to 150 m 2 / g of surface-treated silica particles (claim 1 of Patent Document 1). The surface-treated silica particles of Test Example 1 of the Examples of the document were surface-treated with 3-methacryloxypropyltrimethoxysilane, showing a specific surface area of 43 m 2 / g, and the carbon content was 0.9 mass%.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-111474 Summary of the Invention

[0007] However, as a result of investigations by the present inventors, it has been found that the surface-treated silica particles described in Patent Document 1 have room for improvement in terms of the fluidity of a dispersion containing the particles.

[0008] As a result of further studies, the present inventors have found that the fluidity of a dispersion containing a surface-treated silica powder can be improved by appropriately controlling both the hydrophobization degree and the carbon content.

[0009] Based on this understanding, further in-depth research resulted in the discovery that, by using the degree of hydrophobization and carbon content / specific surface area as two indicators and setting both indicators above specified values, the fluidity of a dispersion containing surface-treated silica powder can be improved, leading to the completion of the present invention.

[0010] According to one embodiment of the present invention, the following surface-treated silica powder is provided.

[0011] 1. A surface-treated silica powder comprising silica particles surface-treated with a silane coupling agent, wherein:

[0012] The hydrophobization degree of the surface-treated silica powder determined according to the following step A is 20% or more, and the composition is:

[0013] The carbon content of the surface-treated silica powder determined in the following step B is defined as C (mass %), and the specific surface area of the surface-treated silica powder measured by the BET single-point method based on nitrogen adsorption is defined as S (m 2 / g), C and S satisfy 0.025≤C / S≤0.070.

[0014] (Step A)

[0015] The surface-treated silica powder was stored in an atmosphere at 20° C. and 23% RH for 7 days to prepare a sample.

[0016] A stirring bar was placed in the flask, 50 ml of ion-exchanged water at a liquid temperature of 25° C. was measured, and 0.2 g of a sample was lightly floated on the water surface.

[0017] Keep the stirrer rotating and slowly add methanol dropwise to prevent methanol from directly contacting the sample.

[0018] The amount of methanol when all samples settled from the water surface was measured, and the degree of hydrophobization (%) was calculated according to the following formula.

[0019] Hydrophobization degree (%) = [[amount of methanol added (mL)] / [amount of ion exchange water 50 mL + amount of methanol added (mL)]] × 100

[0020] (Step B)

[0021] 3 g of the surface-treated silica powder was added to 37 g of acetone and stirred for 30 minutes. The slurry was then centrifuged at 3500 rpm for 10 minutes to separate the surface-treated silica powder and acetone, and the acetone supernatant was discarded. This acetone washing operation was repeated twice, and the slurry was dried at 120°C for 2 hours.

[0022] The carbon content (mass %) in 0.3 g of the washed surface-treated silica powder was measured using a carbon / sulfur simultaneous analyzer and quantified using a calibration curve method.

[0023] 2. The surface-treated silica powder according to 1., wherein

[0024] In the volume frequency particle size distribution of the surface-treated silica powder measured by a laser diffraction scattering method, D50 is 1 μm or more and 30 μm or less, where D50 is the particle size at which the cumulative value from the smaller particle size becomes 50%.

[0025] 3. The surface-treated silica powder according to 1. or 2., wherein

[0026] In the volume frequency particle size distribution of the surface-treated silica powder measured by a laser diffraction scattering method, when the particle sizes at which the cumulative values from the smaller particle size side become 10%, 50%, and 90% are respectively defined as D10, D50, and D90, (D90-D10) / D50 is greater than or equal to 0.3 and less than or equal to 7.5.

[0027] 4. The surface-treated silicon dioxide powder according to any one of 1. to 3., wherein

[0028] The specific surface area of the surface-treated silicon dioxide powder measured by the BET single-point method based on nitrogen adsorption was 1.0 m 2 / g or above and 12.0m 2 / g or less.

[0029] 5. The surface-treated silicon dioxide powder according to any one of 1. to 4., wherein

[0030] The average sphericity is 0.80 or more.

[0031] 6. The surface-treated silicon dioxide powder according to any one of 1. to 5., wherein

[0032] The silane coupling agent includes a silane compound having one or more functional groups selected from the group consisting of epoxy, methacrylic, acrylic, amino, vinyl, alkyl, and phenyl groups.

[0033] 7. The surface-treated silicon dioxide powder according to any one of 1. to 6., wherein

[0034] The evaluation sample was configured such that the thixotropic ratio measured under the following conditions was 0.021 or more.

[0035] (condition)

[0036] 50% by volume of the surface-treated silica powder and 50% by volume of a liquid silicone resin (DOWSIL SE1885A) were mixed to obtain an evaluation sample.

[0037] The obtained evaluation sample was measured using a rheometer equipped with a conical cone head (3 degrees) at 30°C with a viscosity of η1 when measured at a shear rate of 1 [1 / s] and a viscosity of η when measured at a shear rate of 100 [1 / s]. 100 When η 100 / η1 to calculate the above thixotropic ratio.

[0038] According to the present invention, there is provided a surface-treated silica powder having excellent dispersion fluidity. DETAILED DESCRIPTION

[0039] The surface-treated silica powder according to this embodiment will be described.

[0040] The surface-treated silica powder of this embodiment comprises silica particles surface-treated with a silane coupling agent, has a hydrophobization degree of 20% or more, and is configured such that, assuming the carbon content of the surface-treated silica powder is C (mass %), the specific surface area of the surface-treated silica powder measured by the BET single-point method is S (m 2 / g), C and S satisfy 0.025≤C / S≤0.070.

[0041] According to the present inventors' findings, the stability of surface modification using a silane coupling agent can be appropriately evaluated by using two indicators: the degree of hydrophobization of the surface-treated silica powder and the carbon content (C) / specific surface area (S) of the surface-treated silica powder after washing. Further research revealed that by setting the two indicators, the degree of hydrophobization and C / S, above the lower limits, the fluidity of a dispersion containing the surface-treated silica powder can be improved.

[0042] The lower limit of the hydrophobization degree of the surface-treated silica powder is 20% or more, preferably 35% or more, and more preferably 50% or more. This can improve the fluidity of the dispersion.

[0043] The upper limit of the hydrophobization degree of the surface-treated silica powder is, for example, 80% or less, preferably 75% or less, and more preferably 70% or less. This can improve the aggregation of the surface-treated silica particles.

[0044] The hydrophobization degree of the surface-treated silica powder was determined according to the following procedure A.

[0045] (Step A)

[0046] The surface-treated silica powder was stored in an atmosphere at 20° C. and 23% RH for 7 days to prepare a sample.

[0047] A stirring bar was placed in the flask, 50 ml of ion-exchanged water having a liquid temperature of 25° C. was measured, and 0.2 g of a sample was lightly floated on the water surface.

[0048] Keep the stirrer rotating and slowly add methanol dropwise to prevent methanol from directly contacting the sample.

[0049] The amount of methanol when all samples settled from the water surface was measured, and the degree of hydrophobization (%) was calculated according to the following formula.

[0050] Hydrophobization degree (%) = [[amount of methanol added (mL)] / [amount of ion exchange water 50 mL + amount of methanol added (mL)]] × 100

[0051] Furthermore, the lower limit of the C / S is 0.025 or more, preferably 0.030 or more, and more preferably 0.035 or more. This can improve the fluidity of the dispersion.

[0052] The upper limit of the C / S is, for example, 0.070 or less, preferably 0.065 or less, and more preferably 0.060 or less. This can improve the compatibility of the surface-treated silica powder with the resin.

[0053] The carbon content (C) of the surface-treated silica powder is determined according to the following procedure B.

[0054] (Step B)

[0055] 3 g of surface-treated silica powder was added to 37 g of acetone and stirred for 30 minutes. The slurry was then centrifuged at 3500 rpm for 10 minutes to separate the surface-treated silica powder and acetone, and the acetone supernatant was discarded. This acetone washing operation was repeated twice, and the slurry was dried at 120°C for 2 hours.

[0056] The carbon content (mass %) in 0.3 g of the washed surface-treated silica powder was measured using a carbon / sulfur simultaneous analyzer and quantified using a calibration curve method.

[0057] The upper limit of the carbon content (C) of the surface-treated silica powder is, for example, 0.4 mass % or less, preferably 0.3 mass % or less, and more preferably 0.2 mass % or less.

[0058] On the other hand, the lower limit of the carbon content (C) of the surface-treated silica powder is, for example, 0.09 mass % or more, preferably 0.10 mass % or more, and more preferably 0.11 mass % or more.

[0059] The lower limit of the specific surface area (S) of the surface-treated silica powder measured by the BET single-point method based on nitrogen adsorption is, for example, 1.0 m 2 / g or more, preferably 2.5m 2 / g or more, more preferably 2.9m 2 Thereby, the amount of the resin added can be increased, and the thermal expansion coefficient of the resin composition can be suppressed.

[0060] The upper limit of the specific surface area (S) of the surface-treated silica powder is, for example, 12.0 m 2 / g or less, preferably 8.5m 2 / g or less, more preferably 7.0m 2 This can suppress aggregation of the filler.

[0061] The BET single-point method based on nitrogen adsorption can be performed using a specific surface area measuring device (e.g., manufactured by Yuasa Ionics Co., Ltd., device name: MONOSORB), using nitrogen as the adsorption gas and helium as the carrier gas, and drying and degassing 1 g of the sample at 300°C for 15 minutes before measurement.

[0062] In the volume frequency particle size distribution of the surface-treated silica powder measured by the laser diffraction scattering method, the particle size at which the cumulative value from the smaller particle size side becomes 10% is designated as D10, the particle size at which the cumulative value becomes 50% is designated as D50, and the particle size at which the cumulative value becomes 90% is designated as D90.

[0063] The lower limit of D50 is, for example, 1 μm or more, preferably 4 μm or more, and more preferably 8 μm or more. This can improve the filling property of the resin.

[0064] The upper limit of D50 is, for example, 30 μm or less, preferably 20 μm or less, and more preferably 15 μm or less. This can reduce the amount of coarse particles and make the sheet thickness thinner when the resin composition is molded into a sheet.

[0065] The lower limit of (D90-D10) / D50 is, for example, 0.3 or more, preferably 0.7 or more, and more preferably 1.0 or more. This can reduce the amount of coarse particles and make the sheet thickness thinner when the resin composition is molded into a sheet.

[0066] The upper limit of (D90-D10) / D50 is, for example, 7.5 or less, preferably 7.0 or less, and more preferably 6.5 or less. This can further improve the fluidity of the resin composition.

[0067] The lower limit of the average sphericity of the surface-treated silica powder is, for example, 0.80 or more, preferably 0.85 or more, and more preferably 0.90 or more. This can further improve the fluidity of the resin composition.

[0068] The upper limit of the average sphericity of the surface-treated silica powder is not particularly limited, and may be, for example, 0.99 or less.

[0069] The surface-treated silica powder may be configured so that the thixotropic ratio of an evaluation sample measured under the following conditions is 0.021 or more.

[0070] The lower limit of the thixotropic ratio is, for example, 0.021 or more, preferably 0.030 or more, and more preferably 0.040 or more. This can reduce sedimentation of the filler in the resin.

[0071] The upper limit of the thixotropic ratio is, for example, 0.50 or less, preferably 0.40 or less, and more preferably 0.30 or less. This can further improve the fluidity of the resin composition.

[0072] (Measurement Conditions for Thixotropic Ratio of Evaluation Samples)

[0073] The above-mentioned evaluation sample was obtained by mixing 50 volume % of surface-treated silica powder and 50 volume % of liquid silicone resin (DOWSIL SE 1885A).

[0074] The obtained evaluation sample was measured using a rheometer equipped with a conical cone head (3 degrees) (Model: Modular Compact Rheometer MCR 102, manufactured by Anton Paar). The viscosity when measured at a shear rate of 1 [1 / s] at 30°C was defined as η1, and the viscosity when measured at a shear rate of 100 [1 / s] was defined as η. 100 When η 100 / η1 to calculate the above thixotropic ratio.

[0075] In this embodiment, the hydrophobization degree and carbon content can be controlled by, for example, appropriately selecting a method for preparing the raw silica powder, a method for surface treatment of the raw silica powder, etc. Among these, factors for setting the hydrophobization degree and carbon content to a desired numerical range include, for example, appropriately adjusting the specific surface area of the raw silica powder; subjecting the raw silica powder to a water retention treatment so that the amount of physically adsorbed water per unit specific surface area becomes relatively high depending on the type of silane coupling agent; and maintaining the raw silica powder mixed with the silane coupling agent after the water retention treatment for a predetermined period of time.

[0076] The silica powder only needs to contain silicon dioxide (SiO 2 ) as a main component.

[0077] The main component means that, in terms of mass, silicon dioxide (SiO 2 ) is contained in the total amount of the silicon dioxide powder, for example, at least 50%, preferably at least 80%, and more preferably at least 90%.

[0078] The silicon dioxide powder contains either or both of an amorphous substance and a crystalline substance.

[0079] Regarding silica powder, the amorphous rate measured, for example, by the following method is preferably 95% or more, more preferably 97% or more. Regarding the amorphous rate, a powder X-ray diffraction apparatus (for example, a trade name "Model MiniFlex" manufactured by Rigaku Corporation) is used to perform X-ray diffraction analysis in the range of 26° to 27.5° of 2θ of CuKα rays, and the intensity ratio of the specific diffraction peak is used for measurement. In the case of siliceous powder, crystalline silica has a main peak at 26.7°, but no peak exists in amorphous silica. If amorphous silica and crystalline silica are mixed, a peak height of 26.7° corresponding to the proportion of crystalline silica can be obtained. Therefore, the crystalline silica mixing ratio is calculated based on the ratio of the sample's X-ray intensity to the X-ray intensity of the crystalline silica standard sample (X-ray diffraction intensity of the sample / X-ray diffraction intensity of the crystalline silica), and the amorphous ratio is calculated according to the formula: Amorphous ratio (%) = (1-Crystalline silica mixing ratio) × 100.

[0080] As the silane coupling agent, for example, a silane coupling agent containing a silane compound having one or two or more functional groups selected from the group consisting of an epoxy group, a methacrylic group, an acrylic group, an amino group, a vinyl group, an alkyl group, a phenyl group, a mercapto group, a styryl group, an acid anhydride group, a urea group, an isocyanurate group, and an isocyanate group can be used. Preferably, a silane coupling agent containing a silane compound having one or two or more functional groups selected from the group consisting of an epoxy group, a methacrylic group, an acrylic group, an amino group, a vinyl group, an alkyl group, and a phenyl group can be used.

[0081] The silane compound has one or more hydrolyzable groups in addition to the functional group in the molecule.

[0082] As the hydrolyzable group, for example, an alkoxy group such as a methoxy group and an ethoxy group can be used.

[0083] The alkoxy groups are hydrolyzed to form silanol groups, which chemically react with OH groups (reaction sites) present on the surface of the silica particles, thereby chemically bonding the silane coupling agent to the surface of the silica particles.

[0084] Furthermore, the surface-treated silica powder has a silane coupling agent chemically and / or physically bonded to the surface of the silica particles.

[0085] Examples of the silane compound having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0086] Examples of the silane compound having a methacrylic group include 3-methacryloxypropyltrimethoxysilane, 8-methacryloxyoctyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0087] Examples of the silane compound having an acrylic group include 3-acryloyloxypropyltrimethoxysilane.

[0088] Examples of the silane compound having an amino group include N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and the hydrochloride of N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane.

[0089] Examples of the silane compound having a vinyl group include vinyltrimethoxysilane, 7-octenyltrimethoxysilane, and vinyltriethoxysilane.

[0090] Examples of the silane compound having an alkyl group include hexyltrimethoxysilane, octyltriethoxysilane, and decyltrimethoxysilane.

[0091] Examples of the silane compound having a phenyl group include phenyltrimethoxysilane and trimethoxy(2-phenylethyl)silane.

[0092] Next, a method for producing the surface-treated silica powder will be described.

[0093] One example of a method for producing surface-treated silica powder includes the step of contacting silica powder with a silane coupling agent to perform surface treatment for reacting the silane coupling agent with the surface of silica particles, thereby obtaining the surface-treated silica powder.

[0094] Regarding the raw material silica powder, silica powder produced by any method can be used, for example: silica powder obtained by putting powder obtained by crushing silica stone, silica sand, crystal, etc. into flame, high-temperature plasma and spheroidizing; silica powder obtained by synthesizing and spheroidizing silica powder by gas phase hydrolysis of silicon tetrachloride, and silica powder obtained by using the same as a raw material and subjecting it to calcination, flame spraying and spheroidization; silica powder obtained by synthesizing and spheroidizing silica powder in gas phase or liquid phase using metallic silicon or alkoxysilane as starting materials, and further subjecting it to calcination, flame spraying and spheroidization, etc.

[0095] As a method for surface treatment with a silane coupling agent, known techniques such as a dry method and a wet method can be employed, but the dry method is preferably employed.

[0096] The dry method is not particularly limited as long as it is a method of contacting a silane coupling agent with solid spherical silica powder (raw material), and a known method can be employed. Examples thereof include stirring methods with shearing force, mixing methods using a ball mill, a mixer, etc. Here, the solid state refers to a state in which the raw silica powder is not dispersed in a dispersion medium.

[0097] Furthermore, during the treatment with the silane coupling agent, an acidic substance and a basic substance may coexist.

[0098] As an example of a method for producing surface-treated silica powder, a silane coupling agent may be brought into contact with silica powder having an OH group density derived from physically adsorbed water of, for example, 7.0 groups / nm, as determined by the following procedure: 2 Above, preferably 8.0 / nm 2 More than 9.0 / nm 2 above.

[0099] (step)

[0100] The amount of water (ppm) generated by the silica powder (raw material) before the surface treatment until the temperature reached 200° C. was measured by the Karl Fischer method, and this amount was defined as the amount of physically adsorbed water.

[0101] The number of OH groups was calculated from the amount of physically adsorbed water obtained, and the number was divided by the specific surface area of the silica powder measured by the BET single-point method based on nitrogen adsorption to calculate the OH group density (number / nm) derived from physically adsorbed water. 2 ).

[0102] As an example of a method for producing the surface-treated silica powder, a water retention treatment may be performed in which the silica powder (raw material) is brought into contact with water before the silane coupling agent is brought into contact.

[0103] The lower limit of the amount of water added is, for example, 0.1% by mass or more, preferably 0.25% by mass or more, and more preferably 0.5% by mass or more relative to 100% by mass of the silica powder. This can increase the OH group density derived from physically adsorbed water in the silica powder.

[0104] The upper limit of the amount of water added is, for example, 3.0 mass% or less, preferably 2.0 mass% or less, and more preferably 1.5 mass% or less relative to 100 mass% of the silica powder.

[0105] Next, the dispersion according to this embodiment will be described.

[0106] The dispersion of this embodiment contains the surface-treated silica powder and a solvent.

[0107] Examples of the solvent include water, organic solvents, and resins. By using water and / or an organic solvent as the solvent, a slurry can be formed, and by using a resin, a resin composition can be formed.

[0108] A composition obtained by blending the surface-treated silica powder of the present invention into a resin composition can be suitably used as a resin molding material (dispersion).

[0109] The resin composition contains a resin, a known resin additive, and the like in addition to the surface-treated silica powder of the present invention.

[0110] In the resin composition, the surface-treated silica powder can be used alone or mixed with other fillers. The resin composition can contain 10 to 99% by mass of the surface-treated silica powder, or 10 to 99% by mass of a mixed inorganic powder containing the surface-treated silica powder and other fillers. Furthermore, the content of the other fillers in the mixed inorganic powder can be, for example, 1 to 20% by mass or 3 to 15% by mass relative to 100% by mass of the surface-treated silica powder.

[0111] In addition, in this specification, unless otherwise specified, "to" means that the upper limit and the lower limit are included.

[0112] Examples of the other fillers include particles of unsurface-treated silica (crystalline silica, fused silica, etc.) other than the surface-treated silica powder, alumina, titania, silicon nitride, aluminum nitride, silicon carbide, talc, and calcium carbonate.

[0113] Regarding the average particle size of other fillers, for example, fillers having an average particle size of about 2 to 100 μm are used, and there are no particular restrictions on the particle size composition and shape.

[0114] Examples of the resin include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamide-imides, polyetherimides and other polyamides, polyesters such as polybutylene terephthalate and polyethylene terephthalate, polyphenylene sulfide, wholly aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylate rubber-styrene) resins, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins, acrylic resins, etc. These resins may be used alone or in combination of two or more.

[0115] The embodiments of the present invention have been described above, but these are merely examples of the present invention, and various structures other than the above can be adopted. Furthermore, the present invention is not limited to the above embodiments, and modifications and improvements within the scope of achieving the purpose of the present invention are included in the present invention.

[0116] Example

[0117] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited at all by the description of these Examples.

[0118] <Manufacturing of surface-treated silica powder>

[0119] (Examples 1 to 7)

[0120] Silica powder was prepared having the specific surface area shown in Table 1. The prepared silica powder was stored in a container at a temperature of 30° C. and a humidity of 80% for 72 hours (water retention treatment).

[0121] Next, under atmospheric pressure, a temperature of 25°C, and a humidity of 65%, a silane coupling agent (KBM-503, a methacrylic acid group-containing silane coupling agent manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the water-retention treated silica powder, and the mixture was mixed. The mixture was then allowed to stand for 30 days under the same environmental conditions (surface treatment). The surface-treated silica powder was recovered 30 days after the addition of the coupling agent.

[0122] (Comparative Examples 1 to 4)

[0123] The prepared silica powder having the specific surface area shown in Table 1 was not subjected to the aforementioned water retention treatment, but was dried in a dryer at a temperature of 150 to 200°C (however, in Comparative Examples 1 to 3, the drying time was adjusted). Surface treatment was then performed in the same manner as in Example 1, and the surface-treated silica powder was recovered 30 days after the addition of the coupling agent.

[0124] (Examples 8 to 12)

[0125] To the silica powder obtained in Comparative Example 3 after drying and before surface treatment, water in the amount shown in Table 1 was added to 100% by mass of the silica powder shown in Table 1, and the mixture was mixed (water retention treatment). Surface treatment was then performed in the same manner as in Example 1, and the surface-treated silica powder was recovered 30 days after the addition of the coupling agent.

[0126] (Example 13)

[0127] The surface-treated silica powder was recovered 30 days after the addition of the coupling agent in the same manner as in Example 8 except that the silane coupling agent was changed to an alkyl group-containing silane coupling agent (KBM-3083).

[0128] (Example 14)

[0129] The surface-treated silica powder was recovered 30 days after the addition of the coupling agent in the same manner as in Example 8 except that the silane coupling agent was changed to a phenylamino group-containing silane coupling agent (KBM-573).

[0130] [Table 1]

[0131]

[0132] Silica powder (raw material) before surface treatment or surface-treated silica powder 30 days after addition of a coupling agent was used as a sample, and the following items were evaluated.

[0133] <Specific surface area>

[0134] The specific surface area of the powders was determined by the BET single-point method based on nitrogen adsorption.

[0135] Specifically, a specific surface area measuring apparatus (manufactured by Yuasa Ionics Co., Ltd., apparatus name: MONOSORB) was used, and 1 g of a sample was dried and degassed at 300° C. for 15 minutes using nitrogen as the adsorption gas and helium as the carrier gas.

[0136] Furthermore, it was confirmed that the specific surface area of the surface-treated silica powder of each example was the same value as that of the silica powder used as the raw material.

[0137] <Particle size>

[0138] The volume frequency particle size distribution of the powder was determined using a particle size distribution analyzer (MT-3300EXII, manufactured by Microtrac BEL Corporation) using a wet laser diffraction scattering method. Water was used as the solvent, and as a pretreatment, a homogenizer was used at an output of 200 W for 1 minute to disperse the powder in the solvent. The resulting dispersion was used as the measurement target. Based on the obtained volume frequency particle size distribution, the particle size (DX) at which the cumulative value, calculated from the smallest particle size, reached X% was calculated.

[0139] <Average sphericity>

[0140] Regarding the average sphericity of the powder, the particle image obtained by photographing with a stereo microscope (for example, the model "SMZ-10" manufactured by Nikon Corporation), a scanning electron microscope, etc. is read into an image analysis device (for example, manufactured by Nippon Avionics Co., Ltd.), and measured in the following manner. That is, the projected area (A) and the perimeter (PM) of the particle are measured from the photograph. If the area of the perfect circle corresponding to the perimeter (PM) is set to (B), the roundness of the particle can be expressed as A / B. Therefore, if it is assumed that a perfect circle with the same perimeter as the perimeter (PM) of the sample particle is used, PM = 2πr, B = πr 2 , so B = π × (PM / 2π) 2 The sphericity of each particle can be calculated as Sphericity = A / B = A × 4π / (PM) 2 The circularity of any 200 particles thus obtained is determined, and the average value thereof is defined as the average sphericity.

[0141] The average sphericity of the silicon dioxide powder of Example 1 was 0.90.

[0142] Furthermore, it was confirmed that the average sphericity of the surface-treated silica powder of each example was substantially the same as that of the silica powder used as the raw material.

[0143] <Water content>

[0144] The water content in the silica powder was measured by the Karl Fischer method.

[0145] Specifically, using a trace moisture measuring device (manufactured by Mitsubishi Chemical Corporation, model CA-05), the powder was placed in a quartz tube in a moisture vaporization mechanism. While being heated from room temperature to 900°C using an electric heater, dehydrated argon gas was supplied as a carrier gas. Water vapor volatilized from the powder surface was introduced into the moisture measuring mechanism, and the moisture content was measured.

[0146] The moisture generated until the heating temperature of the electric heater reaches 200°C is regarded as physically adsorbed water, the moisture generated until the temperature exceeds 200°C and reaches 550°C is regarded as water derived from hydrogen-bonded OH groups, and the moisture generated until the temperature exceeds 550°C and reaches 900°C is regarded as water generated by dehydration condensation of isolated OH groups.

[0147] OH group density

[0148] The OH group density was calculated according to the following formula.

[0149] OH group density (number / nm 2 )=0.0668×P / Q

[0150] In the above formula, P (ppm) is the moisture content of the powder measured by the Karl Fischer method in the above <Moisture Content>, and Q (ppm) is the moisture content of the powder measured by the Karl Fischer method in the above <Moisture Content>. 2 / g) is the specific surface area of the powder measured by the BET single-point method based on nitrogen adsorption in the above <Specific surface area>.

[0151] Table 1 shows the values of the OH group density derived from physically adsorbed water.

[0152] <Hydrophobicity>

[0153] The surface-treated silica powder was stored in an atmosphere at 20° C. and 23% RH for 7 days to prepare a sample.

[0154] A stirring bar was placed in the flask, 50 ml of ion-exchanged water at a liquid temperature of 25° C. was measured, and 0.2 g of a sample was lightly floated on the water surface.

[0155] The stirring bar was rotated and methanol was slowly added dropwise to prevent methanol from directly contacting the sample.

[0156] The amount of methanol when all samples settled from the water surface was measured, and the degree of hydrophobization (%) was calculated according to the following formula.

[0157] Hydrophobization degree (%) = [[amount of methanol added (mL)] / [amount of ion exchange water 50 mL + amount of methanol added (mL)]] × 100

[0158] Carbon content

[0159] 3 g of surface-treated silica powder was added to 37 g of acetone and stirred for 30 minutes to obtain a slurry. The slurry was then centrifuged at 3500 rpm for 10 minutes to separate the surface-treated silica powder and acetone, and the acetone supernatant was discarded. This acetone washing operation was repeated twice, and the mixture was dried at 120°C for 2 hours.

[0160] The carbon content (mass %) in 0.3 g of the washed surface-treated silica powder was measured using a carbon / sulfur simultaneous analyzer "CS-444LS" (manufactured by LECO Corporation) and quantified using a calibration curve method.

[0161] Viscosity

[0162] An evaluation sample was obtained by mixing 50 volume % of surface-treated silica powder and 50 volume % of a liquid silicone resin (DOWSIL SE 1885A).

[0163] The obtained evaluation samples were measured at 30°C using a rheometer equipped with a conical cone head (3 degrees) (Model: Modular Compact Rheometer MCR 102, manufactured by Anton Paar). The viscosity at a shear rate of 1 [1 / s] (η1), the viscosity at a shear rate of 100 [1 / s] (η 100 ). And, according to η 100 / η1 to calculate the thixotropic ratio.

[0164] Good: Since the viscosity in the low shear region is low, the fluidity of the dispersion is judged to be good.

[0165] Poor: The dispersion was judged to have poor fluidity due to high viscosity or solidification in the low shear region.

[0166] The surface-treated silica powders of Examples 1 to 14 showed excellent fluidity in the dispersion as compared to Comparative Examples 1 to 4.

[0167] This application claims priority based on Japanese patent application No. 2022-212398, filed on December 28, 2022, the disclosure of which is incorporated herein in its entirety.

Claims

1. A surface-treated silica powder comprising silica particles surface-treated with a silane coupling agent, wherein: The hydrophobization degree of the surface-treated silica powder determined according to the following step A is 20% or more, and the composition is: The carbon content of the surface-treated silica powder determined in the following step B is defined as C (mass %), and the specific surface area of the surface-treated silica powder measured by the BET single-point method based on nitrogen adsorption is defined as S (m 2 / g), C and S satisfy 0.025≤C / S≤0.070, Step A: The surface-treated silica powder was stored in an atmosphere at 20° C. and 23% RH for 7 days to prepare a sample. Place a stirring bar in the flask, measure 50 ml of ion exchange water at 25°C, and gently float 0.2 g of the sample on the water surface. Make the stirrer rotate and slowly add methanol dropwise to prevent methanol from directly contacting the sample. The amount of methanol when all samples settled from the water surface was measured, and the hydrophobicity (%) was calculated according to the following formula: Hydrophobization degree (%) = [[amount of methanol added (mL)] / [amount of ion exchange water 50 mL + amount of methanol added (mL)]] × 100 Step B: 3 g of the surface-treated silica powder was added to 37 g of acetone and stirred for 30 minutes. The slurry was then centrifuged at 3500 rpm for 10 minutes to separate the surface-treated silica powder and acetone. The acetone supernatant was discarded. This acetone-based washing operation was repeated twice, and the mixture was dried at 120° C. for 2 hours. The carbon content (mass %) in 0.3 g of the washed surface-treated silica powder was measured using a carbon / sulfur simultaneous analyzer and quantified using a calibration curve method.

2. The surface-treated silica powder according to claim 1, wherein In the volume frequency particle size distribution of the surface-treated silica powder measured by a laser diffraction scattering method, D50 is 1 μm or more and 30 μm or less, where D50 is the particle size at which the cumulative value from the smaller particle size becomes 50%.

3. The surface-treated silica powder according to claim 1 or 2, wherein In the volume frequency particle size distribution of the surface-treated silica powder measured by a laser diffraction scattering method, when the particle sizes at which the cumulative values from the smaller particle size side become 10%, 50%, and 90% are respectively defined as D10, D50, and D90, (D90-D10) / D50 is greater than or equal to 0.3 and less than or equal to 7.

5.

4. The surface-treated silica powder according to claim 1 or 2, wherein The specific surface area of the surface-treated silicon dioxide powder measured by the BET single-point method based on nitrogen adsorption was 1.0 m 2 / g or above and 12.0m 2 / g or less.

5. The surface-treated silica powder according to claim 1 or 2, wherein The average sphericity is 0.80 or more.

6. The surface-treated silica powder according to claim 1 or 2, wherein The silane coupling agent includes a silane compound having one or more functional groups selected from the group consisting of epoxy, methacrylic, acrylic, amino, vinyl, alkyl, and phenyl groups.

7. The surface-treated silica powder according to claim 1 or 2, wherein The composition is such that the thixotropic ratio of the evaluation sample measured under the following conditions is 0.021 or more, condition: 50% by volume of the surface-treated silica powder and 50% by volume of liquid silicone resin DOWSIL SE1885A were mixed to obtain an evaluation sample. The obtained evaluation sample was measured using a rheometer equipped with a conical cone head with a cone angle of 3 degrees at 30°C. The viscosity when measured at a shear rate of 1 [1 / s] was defined as η1, and the viscosity when measured at a shear rate of 100 [1 / s] was defined as η 100 When η 100 The thixotropic ratio is calculated from η / η1.

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