Hollow silica particles

Abstract

One aspect of the present invention provides hollow silica particles having both workability and functionality, the hollow silica particles being suppressed in viscosity increase after being kneaded in a resin, and having high strength. One aspect of the present invention relates to hollow silica particles having one or more peaks in the range of 0.1 [mu] m to 0.5 [mu] m and one or more peaks in the range of more than 0.5 [mu] m to 5.0 [mu] m in the particle size distribution in terms of volume distribution as measured by a laser diffraction scattering method, the hollow silica particles having a particle size distribution in terms of volume distribution as measured by a laser diffraction scattering method, the particle size distribution being in the range of 0.1 [mu] m to 0.5 [mu] m and the particle size distribution being in the range of more than 0.5 [mu] m to 5.0 [mu] m. Particles at a peak side of 0.1 [mu] m to 0.5 [mu] m account for 60 vol% or more; the hollow silica particles have a maximum particle diameter (D100) of 10 [mu] m or less; the apparent density A of the particles before being kneaded with the resin and the apparent density B of the particles after being kneaded with the resin satisfy 0.8 < (A / B).

Description

Technical Field

[0001] This invention relates to tiny hollow silica particles that exhibit minimal viscosity increase and high strength when mixed with resin. Background Technology

[0002] Hollow silica particles have a lower specific gravity than solid silica particles and, due to their hollow shape, possess characteristics such as low dielectric constant, low dielectric loss tangent, and low pyroelectricity. Therefore, by incorporating hollow silica particles into resins, the resins can be made lighter, have a lower dielectric constant, a lower dielectric loss tangent, and improved thermal insulation, leading to their wide range of applications. Specifically, reports have described hollow silica particles with a uniform particle size distribution that improves filling performance (see Patent Document 1), and hollow particles with a multi-peaked particle size distribution containing two or more peaks that achieve both tightness and strength (see Patent Document 2).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-203115

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-172474 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Regarding the hollow silica particles with a uniform particle size distribution described in Patent Document 1, the viscosity of the resin composition increases when mixed with resin, resulting in operational problems. Furthermore, regarding the multi-peaked hollow silica particles described in Patent Document 2, their larger particle size makes it difficult to fill the fine spaces in the resin when mixed, thus limiting their applicability. Moreover, generally, to exhibit the functionality of hollow silica particles after mixing with resin, a balance between particle strength and porosity is required. However, as tiny hollow silica particles, their particle size is small relative to the shell thickness; if the shell thickness is changed to improve particle strength, the impact on porosity increases. Therefore, in tiny hollow silica particles, it is desirable to maintain the hollow structure without changing the shell thickness.

[0009] Based on the above background, the purpose of this invention is to provide a hollow silica particle that can balance operability and function, wherein the viscosity increase is suppressed and the strength is high after the hollow silica particle is mixed with resin.

[0010] means for solving problems

[0011] In order to solve the above problems, the inventors conducted in-depth research and found that by producing multi-peaked hollow silica particles with a maximum particle size below a specified value, hollow silica particles with suppressed viscosity increase and high strength can be obtained after being mixed with resin.

[0012] Specifically, one aspect of the present invention relates to hollow silica particles having at least one peak in the range of 0.1 μm to 0.5 μm and at least one peak in the range of greater than 0.5 μm to 5.0 μm in a particle size distribution calculated by volume distribution according to laser diffraction scattering, wherein, calculated by volume distribution, particles on the peak side of 0.1 μm to 0.5 μm account for at least 60% by volume; the maximum particle size (D100) of the hollow silica particles is 10 μm or less; and the apparent density A of the hollow silica particles before being mixed with resin and the apparent density B of the hollow silica particles after being mixed with resin satisfy 0.8 < (A / B).

[0013] Invention Effects

[0014] According to the present invention, a hollow silica particle that combines operability and functionality can be provided, wherein the viscosity increase is suppressed and the strength is high after the hollow silica particle is compounded with resin. Detailed Implementation

[0015] The specific embodiments of the present invention will now be described in detail. However, the present invention is not limited to the embodiments described below.

[0016] The hollow silica particles of the present invention are as follows: A hollow silica particle, in a particle size distribution calculated according to volume distribution by laser diffraction scattering, has one or more peaks in the range of 0.1 μm or more and 0.5 μm or less, and one or more peaks in the range of greater than 0.5 μm or 5.0 μm or less, wherein, calculated according to volume distribution, particles on the peak side of 0.1 μm or more and 0.5 μm or less account for 60% or more of the particle size; the maximum particle size (D100) of the hollow silica particles is 10 μm or less; the apparent density A of the hollow silica particles before mixing with resin and the apparent density B of the hollow silica particles after mixing with resin satisfy 0.8 < (A / B).

[0017] In the particle size distribution converted from volume distribution, peaks existing in the range of 0.1 μm and 0.5 μm are preferably located at 0.2 to 0.48 μm, more preferably at 0.3 to 0.45 μm. Furthermore, peaks existing in the range of greater than 0.5 μm and 5.0 μm are preferably located at 0.8 to 4 μm, more preferably at 1 to 3 μm. As hollow silica particles having such a multi-peaked particle size distribution, the viscosity increase is smaller when mixed with resin, and the difference between the apparent density of the hollow silica particles after mixing with resin and the apparent density of the hollow silica particles before mixing with resin is smaller. Although the reason is not yet clear, it is speculated that the presence of peaks in the range of 0.1 μm and 0.5 μm disperses the pressure during mixing with resin, thereby increasing the overall strength of the hollow silica particles. Furthermore, the presence of peaks in the range greater than 0.5 μm and less than 5.0 μm suppresses the viscosity increase of the hollow silica particles as a whole. Based on these reasons, it is possible to suppress the overall viscosity increase of the resin composition and improve its strength.

[0018] Furthermore, when peaks are present below 0.1 μm, the viscosity of the resin composition increases significantly after mixing with the resin, and the porosity inside the hollow silica particles decreases, which is not ideal. When peaks are present in the range exceeding 5 μm, it is difficult for the resin composition to penetrate into the fine gaps, which is also not ideal.

[0019] Regarding the particle size distribution of the hollow silica particles of the present invention, in the particle size distribution calculated based on volume distribution according to laser diffraction scattering method, particles on the peak side in the range of 0.1 μm or more and 0.5 μm or less account for more than 60% by volume. Particle size distribution refers to the volume frequency of the detected particles measured for each particle size. Therefore, when a particle size is selected, if the volume frequency of the selected particle size is compared with the volume frequencies of the particle sizes measured before and after it, and the volume frequency of the selected particle size is greater than the volume frequencies of the particle sizes measured before and after it, it can be determined that the selected particle size has a peak. Based on this, since the peak positions of the measured particle size distribution can be determined, the positions of the largest peak in the range of 0.1 μm or more and 0.5 μm or less, and the positions of the smallest peak in the range of greater than 0.5 μm and 5.0 μm or less, can be determined. Then, the particle size with the smallest volume frequency among the determined peaks is set as the boundary value. The term "particles with peaks between 0.1 μm and 0.5 μm" refers to the cumulative value of the volumetric frequency of particles with a diameter between 0 μm and the boundary value.

[0020] If the value of particles on the peak side located in the range of 0.1 μm to 0.5 μm is less than 60% by volume, it is difficult for the resin composition to penetrate into the fine gaps, which is not ideal. Furthermore, by reducing this value to a certain extent, the functionality resulting from the multi-peaked particle size distribution can be further improved, and the viscosity after mixing with the resin can be further improved. From the above balance point of view, 60 to 95% by volume is preferred, more preferably 65 to 90% by volume, and particularly preferably 70 to 85% by volume.

[0021] Furthermore, considering the filling properties when the resin composition penetrates into fine gaps, the maximum particle size (D100) of the hollow silica particles of the present invention is 10 μm or less, preferably 9 μm or less. For example, the maximum particle size (D100) of the hollow silica particles can be measured by the method described in the examples.

[0022] Regarding the hollow silica particles of the present invention, even after being mixed with resin, the shell of the hollow silica particles will not crack, and the resin will not penetrate into the pores; that is, the hollow shape can be maintained, which is preferable. Specifically, the apparent density (A) of the hollow silica particles before being mixed with resin is compared with the apparent density (B) of the hollow silica particles calculated from the apparent density of the composition after being mixed with resin, and the density difference (A / B) is greater than 0.8, that is, 0.8 < (A / B). The more hollow silica particles that can maintain the hollow shape are present, the more the characteristics derived from the hollow shape are exhibited; therefore, 0.85 < (A / B) is preferable, and 0.9 < (A / B) is more preferable.

[0023] The hollow silica particles of this invention, due to their characteristics, can reduce the dielectric constant and dielectric loss tangent compared to solid silica particles.

[0024] The dielectric constant of the hollow silica particles is preferably 2.0 or less at a frequency of 10 GHz, more preferably 1.8 or less, and even more preferably 1.7 or less.

[0025] The dielectric loss tangent of the hollow silica particles is preferably 0.003 or less, more preferably 0.002 or less, and even more preferably 0.001 or less at a frequency of 10 GHz.

[0026] In addition, the dielectric constant and dielectric loss tangent can be measured using methods such as the cavity resonator method.

[0027] The hollow silica particles of the present invention exhibit excellent strength due to their characteristics. The particle strength of the hollow silica particles is preferably 50 MPa or more, more preferably 55 MPa or more. Furthermore, the particle strength can be measured using the method described in the examples.

[0028] As for the hollow silica particles of the present invention, there are no particular limitations as long as they meet the above characteristics. For example, they can be manufactured by the sol-gel method.

[0029] Although the hollow silica particles of the present invention have a multi-peaked particle size distribution, hollow silica particles manufactured individually can be mixed, or hollow silica particles with a multi-peaked particle size distribution can be manufactured in one step. Furthermore, the particle size distribution can be adjusted by applying a grading operation to the manufactured particles.

[0030] The hollow silica particles of the present invention are particles having internal pores and a shell portion that separates the pores from the outside, which is different from porous silica.

[0031] As can be understood from the above description, the present invention includes the following aspects [1] to [3].

[0032] Aspect [1]: A hollow silica particle having at least one peak in the range of 0.1 μm or more and 0.5 μm or less, and at least one peak in the range of greater than 0.5 μm and 5.0 μm or less, as measured by laser diffraction scattering, wherein the hollow silica particle is characterized in that, as measured by volume distribution, the particles on the peak side of 0.1 μm or more and 0.5 μm or less are at least 60% by volume; the maximum particle size (D100) of the hollow silica particle is at least 10 μm; and the apparent density A of the hollow silica particle before being mixed with resin and the apparent density B of the hollow silica particle after being mixed with resin satisfy 0.8 < (A / B).

[0033] Aspect [2]: The hollow silica particles according to aspect [1], wherein the dielectric constant is 2.0 or less and the dielectric loss tangent is 0.003 or less.

[0034] Aspect [3]: Hollow silica particles according to aspect [1] or [2], wherein the particle strength is 50 MPa or more.

[0035] Example

[0036] <Preparation of hollow silica particles with more than one peak at 0.1–0.5 μm>

[0037] (1) Hollow silica particles A1

[0038] Solution A was prepared by adding 100g of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Wako Grade I), 1.7g of dodecyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry), and 1g of dodecane (manufactured by Fujifilm Wako Pure Chemical Industries) to a 500mL flask and stirring. Solution B was prepared by adding 300g of water and 0.825g of 25% tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries) to a 500mL flask and stirring.

[0039] Solution A was stirred at 25°C while solution B was added, followed by 1.7 g of tetramethoxysilane (Domo Chemicals), and stirred at 25°C for 5 hours. The resulting hollow silica particle precursor dispersion was filtered through 5C filter paper and washed three times with water to recover the hollow silica particle precursor.

[0040] The recovered hollow silica particle precursor was dried at 100°C for 12 hours using a constant temperature, air-blown dryer (Sanyo, convection oven) to obtain a white powder form of hollow silica particle precursor.

[0041] The obtained white powder was heated to 1000°C at a rate of 1°C / min using an electric furnace (Yamato Scientific, FO810), and sintered at 1000°C for 10 hours to obtain hollow silica particles A1 with a peak position of 0.4 μm in the particle size distribution.

[0042] (2) Hollow silica particles A2

[0043] Solution A was prepared by adding 100g of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Wako Grade I), 0.9g of dodecyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry), and 0.5g of dodecane (manufactured by Fujifilm Wako Pure Chemical Industries) to a 500mL flask and stirring. Solution B was prepared by adding 300g of water and 0.413g of a 25% tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries) to a 500mL flask and stirring.

[0044] Solution A was stirred at 25°C while solution B was added, followed by 0.9 g of tetramethoxysilane (Domo Chemicals), and stirred at 25°C for 5 hours. The resulting hollow silica particle precursor dispersion was filtered through 5C filter paper and washed three times with water to recover the hollow silica particle precursor.

[0045] The recovered hollow silica particle precursor was dried at 100°C for 12 hours using a constant temperature, air-blown dryer (Sanyo, convection oven) to obtain a white powder form of hollow silica particle precursor.

[0046] The obtained white powder was heated to 1000°C at a rate of 1°C / min using an electric furnace (Yamato Scientific, FO810), and sintered at 1000°C for 10 hours to obtain hollow silica particles A2 with a peak position of 0.2 μm in the particle size distribution.

[0047] (3) Hollow silica particles A3

[0048] Solution A was prepared by adding 100g of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Wako Grade I), 1.4g of dodecyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry), and 0.8g of dodecane (manufactured by Fujifilm Wako Pure Chemical Industries) to a 500mL flask and stirring. Solution B was prepared by adding 300g of water and 0.620g of 25% tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries) to a 500mL flask and stirring.

[0049] Solution A was stirred at 25°C while solution B was added, followed by 1.4 g of tetramethoxysilane (Domo Chemicals), and stirred at 25°C for 5 hours. The resulting hollow silica particle precursor dispersion was filtered through 5C filter paper and washed three times with water to recover the hollow silica particle precursor.

[0050] The recovered hollow silica particle precursor was dried at 100°C for 12 hours using a constant temperature, air-blown dryer (Sanyo, convection oven) to obtain a white powder form of hollow silica particle precursor.

[0051] The obtained white powder was heated to 1000°C at a rate of 1°C / min using an electric furnace (Yamato Scientific, FO810), and sintered at 1000°C for 10 hours to obtain hollow silica particles A3 with a peak position of 0.3 μm in the particle size distribution.

[0052] <Preparation of hollow silica particles with more than one peak at 0.5–5 μm>

[0053] (1) Hollow silica particles B1

[0054] In a 200 mL flask, 1.3 g of hydroxypropyl cellulose (Sigma-Aldrich, average molecular weight approximately 370,000) was added to 86 g of 1-octanol (pure chemical preparation, reagent grade). The solution was heated to 80 °C and stirred for 4 hours. Then, the temperature was lowered to 40 °C, and 2.7 g of sorbitan monooleate (Sigma-Aldrich, Span 80) was added to prepare solution A.

[0055] Additionally, in a 20 mL beaker, 0.6 g of polyethylene glycol (pure chemical preparation, polyethylene glycol 20000) and 0.5 g of polyethylene glycol dehydrated sorbitol monolaurate (Sigma-Aldrich preparation, Tween 20) were added to 8.1 g of water and stirred for 20 minutes. Then, 0.8 g of 25% ammonia (Fujifilm Wako Pure Chemical Preparation, Wako Grade 1) was added, thereby preparing solution B.

[0056] Then, while stirring solution A (temperature set at 40°C), solution B was added, and stirring was continued for 1 hour to prepare solution C.

[0057] Then, while stirring solution C, 20g of tetraethoxysilane (manufactured by Fujifilm and Kagaku Pure Chemicals, Kagaku Grade Tetraethyl Orthosilicate) was added, and the mixture was stirred for 14 hours to obtain a hollow silica particle precursor dispersion. The hollow silica particle precursor dispersion was filtered using 5C filter paper and washed three times with ethanol (manufactured by Fujifilm and Kagaku Pure Chemicals, Kagaku Grade 1) to recover the hollow silica particle precursor.

[0058] The recovered hollow silica particle precursor was dried at 130°C for 12 hours using a constant temperature, air-blown dryer (Sanyo, convection oven) to obtain a white powder form of hollow silica particle precursor.

[0059] The obtained white powder was heated to 1000°C at a rate of 100°C / hour using an electric furnace (Yamato Scientific, FO810), and sintered at 1000°C for 10 hours to obtain hollow silica particles B1 with a peak position of 1.7 μm in the particle size distribution.

[0060] (2) Hollow silica particles B2

[0061] In a 200 mL flask, 1.3 g of hydroxypropyl cellulose (Sigma-Aldrich, average molecular weight approximately 370,000) was added to 86 g of 1-octanol (pure chemical preparation, reagent grade). The solution was heated to 80 °C and stirred for 4 hours. Then, the temperature was lowered to 40 °C, and 1.5 g of sorbitan monooleate (Sigma-Aldrich, Span 80) was added to prepare solution A.

[0062] Additionally, in a 20 mL beaker, 0.6 g of polyethylene glycol (pure chemical preparation, polyethylene glycol 20000) and 0.3 g of polyethylene glycol dehydrated sorbitol monolaurate (Sigma-Aldrich preparation, Tween 20) were added to 8.1 g of water and stirred for 20 minutes. Then, 0.8 g of 25% ammonia (Fujifilm Wako Pure Chemical Preparation, Wako Grade 1) was added, thereby preparing solution B.

[0063] Then, while stirring solution A (temperature set at 40°C), solution B was added, and stirring was continued for 1 hour to prepare solution C.

[0064] Then, while stirring solution C, 20g of tetraethoxysilane (manufactured by Fujifilm and Kagaku Pure Chemicals, Kagaku Grade Tetraethyl Orthosilicate) was added, and the mixture was stirred for 14 hours to obtain a hollow silica particle precursor dispersion. The hollow silica particle precursor dispersion was filtered using 5C filter paper and washed three times with ethanol (manufactured by Fujifilm and Kagaku Pure Chemicals, Kagaku Grade 1) to recover the hollow silica particle precursor.

[0065] The recovered hollow silica particle precursor was dried at 130°C for 12 hours using a constant temperature, air-blown dryer (Sanyo, convection oven) to obtain a white powder form of hollow silica particle precursor.

[0066] The obtained white powder was heated to 1000°C at a rate of 100°C / hour using an electric furnace (Yamato Scientific, FO810), and sintered at 1000°C for 10 hours to obtain hollow silica particles B2 with a peak position of 3.0 μm in the particle size distribution.

[0067] (3) Hollow silica particles B3

[0068] In a 200 mL flask, 1.3 g of hydroxypropyl cellulose (Sigma-Aldrich, average molecular weight approximately 370,000) was added to 86 g of 1-octanol (pure chemical preparation, reagent grade). The solution was heated to 80 °C and stirred for 4 hours. Then, the solution temperature was lowered to 40 °C, and 1.0 g of sorbitan monooleate (Sigma-Aldrich, Span 80) was added to prepare solution A.

[0069] Additionally, in a 20 mL beaker, 0.6 g of polyethylene glycol (pure chemical preparation, polyethylene glycol 20000) and 0.2 g of polyethylene glycol dehydrated sorbitol monolaurate (Sigma-Aldrich preparation, Tween 20) were added to 8.1 g of water and stirred for 20 minutes. Then, 0.8 g of 25% ammonia (Fujifilm Wako Pure Chemical Preparation, Wako Grade 1) was added, thereby preparing solution B.

[0070] Then, while stirring solution A (temperature set at 40°C), solution B was added, and stirring was continued for 1 hour to prepare solution C.

[0071] Then, while stirring solution C, 20g of tetraethoxysilane (manufactured by Fujifilm and Kagaku Pure Chemicals, Kagaku Grade Tetraethyl Orthosilicate) was added, and the mixture was stirred for 14 hours to obtain a hollow silica particle precursor dispersion. The hollow silica particle precursor dispersion was filtered using 5C filter paper and washed three times with ethanol (manufactured by Fujifilm and Kagaku Pure Chemicals, Kagaku Grade 1) to recover the hollow silica particle precursor.

[0072] The recovered hollow silica particle precursor was dried at 130°C for 12 hours using a constant temperature, air-blown dryer (Sanyo, convection oven) to obtain a white powder form of hollow silica particle precursor.

[0073] The obtained white powder was heated to 1000°C at a rate of 100°C / hour using an electric furnace (Yamato Scientific, FO810), and sintered at 1000°C for 10 hours to obtain hollow silica particles B3 with a peak value of 4.6 μm in the particle size distribution.

[0074] The evaluation methods for the various physical properties of hollow silica particles are as follows.

[0075] (1) Particle size distribution based on volume reference using laser diffraction scattering method

[0076] 0.1 g of hollow silica particles were weighed into a 50 mL glass bottle using an electronic balance. 40 mL of ethanol was added, and the particles were dispersed using an ultrasonic homogenizer (BRANSON Sonifier 250) at 60 W for 2 minutes. The volumetric reference modulus (most common particle size) (μm) and the maximum particle size (D100) (μm) were then measured using a laser diffraction particle size distribution measurement device (Beckman Coulter LS13320). At this point, the refractive index of the dispersion medium was 1.36, and the refractive index of the measured material was 1.45. The maximum particle size (D100) was the largest particle size detected by the laser diffraction particle size distribution measurement device used.

[0077] (2) Apparent density of hollow silica particles before being mixed with resin

[0078] Hollow silica particles, dried under reduced pressure at 110°C for 24 hours, were weighed into a 10ml sample container until a unit of 0.001g was reached. Next, the sample container was placed in the measuring chamber of a dry automatic densitometer (Shimadzu AccuPyc1330), and the particle density was measured at a measuring temperature of 25°C while nitrogen gas was flowing into the measuring chamber. In the above-mentioned dry automatic densitometer, when the mass of the powder to be measured is entered, the particle density is expressed in g / cm³.3 The unit is displayed to the 5th decimal place, in g / cm. 3 The value obtained by rounding the particle density to the second decimal place.

[0079] (3) Particle strength

[0080] Hollow silica particles were dispersed in ethanol at a concentration of 0.02% by mass. One drop was placed on the lower pressure plate of a micro compression testing machine (Shimadzu MZCT-W510-J) and allowed to dry. A load was applied to one particle on the lower pressure plate using an upper pressure fitting (flat fitting, diamond) with a diameter of 20 μm, and the deformation of the particle was automatically measured. The test force P (N) at particle fracture and the measured particle diameter Z (mm) were used for measurement. Five particles were randomly selected and measured using the microscope provided with the testing machine. The average value was used to calculate the particle strength (MPa) using the following formula.

[0081] Particle strength (MPa) = 2.8 × P ÷ π ÷ Z 2

[0082] The subsequent analysis was performed on the resin composition prepared by the method described in the examples. Furthermore, the resin and curing agent in the resin composition were reacted after mixing to become a single resin. Regarding the resin and curing agent, the resin to curing agent composition ratio was set to 71:29 for mixing, the cured composition was measured, and its value was used.

[0083] (4) Viscosity measurement

[0084] Viscosity was measured using 0.2 g of the resin composition and a rheometer (HAAKEMARS40, Thermo Fisher Scientific). The measurement was performed at 25°C using a C35 / 1 sensor (cone-plate type, 35 mm diameter, 1° angle, titanium material) at a shear rate of 1 s. -1 The value at time.

[0085] (5) Measurement of dielectric constant and dielectric loss tangent

[0086] The resin composition was poured into a SUS mold with a thickness of 0.4 mm, a short side of 60 mm, and a long side of 70 mm. It was heated at 80°C for 1 hour in a controlled-air thermostat (Yamato Scientific, DNK302), followed by heating at 120°C for 3 hours. The dielectric constant and dielectric loss tangent of the cured resin composition were measured using a network analyzer (Keysight Technologies, N5209A). Measurements were also performed at a frequency of 10 GHz.

[0087] Then, the physical properties of the hollow silica particles are calculated using the Bruggeman formula shown below.

[0088] [Mathematical Formula 1]

[0089]

[0090] In addition, in the formula, Φa represents the volume fraction of resin and curing agent in the resin composition, Φb represents the volume fraction of hollow silica particles in the resin composition, εa represents the dielectric constant of resin and curing agent, εb represents the dielectric constant of hollow silica particles, and εc represents the dielectric constant of the resin composition.

[0091] (6) Apparent density of hollow silica particles after being mixed with resin

[0092] The resin composition was poured into a Teflon (registered trademark) mold with a thickness of 5 mm, a short side of 10 mm, and a long side of 15 mm. The mold was then heated at 80°C for 1 hour in a controlled-air thermostat (Yamato Scientific, DNK302), followed by heating at 120°C for 3 hours. The density of the cured resin composition was measured using a high-precision electronic hydrometer (ALFA MIRAGE, SD-200L).

[0093] The apparent density of the hollow silica particles after being mixed with the resin was calculated based on the true density of the epoxy resin and curing agent used, as well as the composition ratio of the resin composition. Furthermore, the true density of the resin and curing agent was 1.18 g / cm³. 3 .

[0094] The apparent density of hollow silica particles after being mixed with resin = the composition ratio of hollow silica particles ÷ {(1 ÷ measured value) - (total composition ratio of resin and curing agent ÷ 1.18)}

[0095] Table 1

[0096]

[0097] Table 2

[0098]

[0099]

[0100] (Examples 1-8, Comparative Examples 1 and 2)

[0101] Following the proportions listed in Tables 1 and 2, 5.0 g of hollow silica particles A and B, 10.7 g of bisphenol F epoxy resin (manufactured by Nippon Steel Chemical Materials, YDF-8170), and 4.3 g of curing agent (manufactured by Nippon Kayaku, KAYAHARD AA) were manually stirred. Then, the resin composition was pre-mixed using a rotary mixer (THINKY, defoaming Rentaro, AR-500) (mixing: 1000 rpm, 8 minutes; defoaming: 2000 rpm, 2 minutes). The pre-mixed resin composition was stored in a constant temperature water bath at 25°C, and then processed using a three-roll mill (AIMEX Corporation, BR-150HCV, roller diameter...). The resin composition was then mixed. The mixing conditions were 25°C, 20 μm roller spacing, and 8 mixing cycles. The resulting resin composition was defoamed for 30 minutes under reduced pressure using a vacuum pump (Sato Vacuum TSW-150). The results are shown in Tables 1 and 2.

[0102] As shown in Tables 1 and 2, the resin compositions of Examples 1 to 8 containing the hollow silica particles of the present invention have lower viscosity and higher strength, resulting in smaller density differences, and also exhibiting low values ​​for dielectric constant and dielectric loss tangent. In Comparative Example 1, however, the viscosity of the resin composition was too high to be measured.

Claims

1. A type of hollow silica particle, in a particle size distribution calculated based on volume distribution according to laser diffraction scattering, having one or more peaks in the range of 0.1 μm to 0.5 μm, and having one or more peaks in the range of greater than 0.5 μm to 5.0 μm. The hollow silica particles are characterized by the following: Based on volume distribution conversion, particles located on the peak side between 0.1 μm and 0.5 μm account for more than 60% by volume; The maximum particle size (D100) of hollow silica particles is less than 10 μm; The apparent density A of the hollow silica particles before being mixed with the resin and the apparent density B of the hollow silica particles after being mixed with the resin satisfy 0.8 < (A / B).

2. The hollow silica particles according to claim 1, wherein, The dielectric constant is below 2.0, and the dielectric loss tangent is below 0.

003.

3. The hollow silica particles according to claim 1 or 2, wherein, The particle strength is above 50 MPa.

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