JP6022302B2 - Dry silica fine particles - Google Patents

Description

  The present invention relates to a novel dry silica that can be suitably used as a filler for a resin composition used for a semiconductor encapsulant or the like, or as an external additive for an electrophotographic toner.

Dry silica fine particles having a specific surface area of 20 to 60 m ² / g are expected to be used as fillers added to semiconductor encapsulants and semiconductor mounting adhesives and as external additives for electrophotographic toner particles.

That is, in recent years, with the downsizing and thinning of semiconductor devices, the particle size of fillers added to semiconductor encapsulants and semiconductor mounting adhesives, which are epoxy resin compositions, tends to decrease, and the specific surface area. Silica fine particles having a diameter of 20 to 60 m ² / g and a primary particle diameter of about 50 to 150 nm are preferably used (see Patent Document 1).

The progress of miniaturization and thinning of semiconductor devices is rapid, and in applications where emphasis is placed on moldability, an epoxy resin composition using dry silica fine particles having an existing specific surface area of 20 to 60 m ² / g as a filler Viscosity was high, causing problems.

On the other hand, when dry silica fine particles having a specific surface area of 20 to 60 m ² / g are used as an external additive for toner particles for electrophotography, they do not embed in the toner resin particles even for long-term use. It is known that the property can be imparted to toner particles (see Patent Document 1).

  The external additive for toner particles for electrophotography is required to have a property of being well dispersed in a desired particle size.

For this reason, it is a silica fine particle which has a specific surface area of 20 to 60 m ² / g and a primary particle diameter of about 50 to 150 nm, and the resin composition when filled with an epoxy resin rather than the existing dry silica fine particles of the same size A product having a low viscosity and a property of being well dispersed in a desired particle size has been demanded.

JP 2008-19157 A

Therefore, the object of the present invention is to provide excellent dispersion characteristics that can be easily dispersed to the primary particle size than the existing dry silica fine particles having the specific surface area in the range of ²⁰ to 60 m ² / g. Thus, the present invention provides a dry silica fine particle useful as a resin filler for a resin or a dry silica fine particle for a toner.

  In order to solve the above problems, the present inventor has conducted intensive studies on dry silica fine particles produced by combustion of a silicon compound and growing and aggregating in and near a flame. By adjusting not only the flame conditions but also the cooling conditions, the present inventors have succeeded in obtaining dry silica fine particles that have achieved the above object, and have completed the present invention.

That is, the present invention is a dry silica fine particle obtained by combustion of a silicon compound, which satisfies the following conditions.
(1) The BET specific surface area is 20 to 60 m ² / g.
_{(2) 100 × D CS /} D USAXS is 100 to 110.
Here, D _CS is the median diameter of the weight-based particle size distribution of wherein the drying type silica fine particles by centrifugal sedimentation, D _USAXS is volume-based median diameter of particle size distribution of wherein the drying type silica fine particles with ultra-small angle X-ray scattering method.

  In the dry silica fine particles of the present invention, it is preferable that the water content measured by the loss on drying method at 130 ° C. is 0.5% by mass or less, and that the silicon compound is siloxane, particularly cyclic siloxane. is there.

  In the present invention, the particle size distribution by the centrifugal sedimentation method described above is a weight-based particle size distribution of dispersed particles obtained by dispersing the dry silica fine particles in water at an output of 20 W at a concentration of 1.5% by mass and a dispersion time of 3 minutes. is there. As an example of the particle size distribution measuring machine of the centrifugal sedimentation method, CPS Instruments Inc. Examples thereof include a disk centrifugal particle size distribution measuring apparatus DC24000.

  The particle size distribution by the ultra-small angle X-ray scattering method of the present invention is as follows. The ultra-small angle X of an aqueous suspension obtained by dispersing the dry silica fine particles in water at a concentration of 1.5% by mass with an output of 20 W and a dispersion time of 3 minutes. This is a volume-based particle size distribution obtained by a spectrum fitting operation assuming a gamma distribution as a volume-based particle size distribution and a spherical shape as a particle shape. In the ultra-small angle X-ray scattering method, a particle size distribution with respect to primary particles, not dispersed particles, is obtained. For the particle size distribution measurement of the ultra-small angle X-ray scattering method, Rigaku's fully automatic horizontal multi-purpose X-ray diffractometer SmartLab is used, and the transmission method small-angle scattering of the ultra-small angle X-ray scattering specification is applied as the optical system. A technique for analyzing the particle size distribution with the analysis software NANO-Solver manufactured by Rigaku can be mentioned.

The dry silica fine particles of the present invention have an excellent dispersion performance that is substantially dispersed to the level of primary particles even though the BET specific surface area is 20 to 60 m ² / g. Viscosity characteristics that enable fine molding of the composition can be imparted, and it is extremely useful as a resin filler.

  In addition, since the dry silica fine particles of the present invention have the above-mentioned extremely excellent dispersion performance, the target particle size on the toner resin particles is not varied in the external addition / mixing step in the production of electrophotographic toner without variation due to prescription. To be distributed. For this reason, the effect which can provide the stable fluidity | liquidity to a toner product is exhibited. Therefore, it is extremely useful as an external additive for an electrophotographic toner.

The dry silica fine particles of the present invention are silica fine particles produced by burning a silicon compound and growing and agglomerating in a flame and in the vicinity of the flame, so-called “dry method”. (1) BET specific surface area of 20 while in the range of ~60m ² / g,
(2) It has the characteristic of being particularly excellent in dispersion performance.

The characteristic (2) excellent in the dispersibility is specified by 100 × D _CS / D _USAXS being 100 to 110. Here, D _CS is the median diameter of the weight-based particle size distribution of wherein the drying type silica fine particles by centrifugal sedimentation, D _USAXS is volume-based median diameter of particle size distribution of wherein the drying type silica fine particles with ultra-small angle X-ray scattering method.

Thus, dry silica particles having a specific surface area in the range of ²⁰ to 60 m ² / g and having the dispersion performance shown in the characteristic (2) are not conventionally produced, and the present invention Is provided for the first time. That is, the dry silica fine particles of the present invention represented by the characteristic (2) have almost no agglomerated particles formed by partial fusion based on chemical bonds between primary particles or strong physical interparticle forces. It means not existing. On the other hand, dry silica fine particles produced by conventional methods are formed by partial fusion based on chemical bonding between primary particles or formation of agglomerated particles by strong interparticle force due to differences in the production methods described below. As a result, the dry silica fine particles obtained greatly exceed the range indicated by the characteristic (2), and the effects of the present invention cannot be sufficiently exhibited.

  The dry silica fine particles of the present invention are suitably used in any application as a filler for resin compositions requiring fine molding and as an external additive for electrophotographic toner because of having the above properties. The

That is, the dry-type silica fine particles of the present invention enable fine molding of a resin composition as a resin filler when the BET specific surface area is within the above range. In addition, sufficient strength can be imparted to the cured composition that is the composition after molding and curing of the resin composition. In addition, when applied as an external toner additive for electrophotography, the toner resin particles have stable adhesion without being embedded or dropped. In consideration of the improvement in transfer rate during image formation, the BET specific surface area is more preferably 25 to 35 m ² / g.

In the dry silica fine particles of the present invention, 100 × D _CS / D _USAXS shown in the characteristic (2) is 100 to 110. This means that silica fine particles composed of primary particles are dispersed to the level of primary particles. It has excellent dispersion performance. Incidentally, D _CS is the median diameter of the weight-based particle size distribution of wherein the drying type silica fine particles by centrifugal sedimentation, D _USAXS is volume-based median diameter of particle size distribution of wherein the drying type silica fine particles with ultra-small angle X-ray scattering method. As described later, the particle size distribution of the centrifugal sedimentation method represents the particle size distribution of dispersed particles dispersed in the medium, and the particle size distribution of the ultra-small angle X-ray scattering method represents the particle size distribution of primary particles. Therefore, 100 × D _CS / D _USAXS means a value obtained by multiplying the median diameter of the dispersed particles by the median diameter of the primary particles multiplied by 100, and expresses the dispersion characteristics of the silica fine particles.

  When the dry silica fine particles having the characteristic (2) are used as a resin filler, the dry silica fine particles substantially act as primary particles that are spatially uniform and do not have a specific structure in the resin. The obtained resin composition has low viscosity characteristics necessary for fine molding. In addition, there is an advantage that it is possible to effectively prevent the formation of agglomerated particles in the resin, and the agglomerated particles dam the fine mold portion in the fine molding by the generation of the agglomerated particles, thereby effectively preventing the molding. .

  Further, according to the characteristic (2), when the dry silica fine particles are used as an electrophotographic toner external additive, the toner is dispersed with a desired particle size on the toner resin particles, so that the toner having stable fluidity is imparted. Demonstrates the effect of being a product.

  Other characteristics of the dry silica fine particles of the present invention are not particularly limited as long as they have the above-mentioned characteristics. For example, the moisture content measured by the loss on drying method at 130 ° C. is 0.5 mass. % Or less, it is possible to suppress the formation of strong agglomerated particles over time due to the adsorbed moisture of the silica fine particles, so that the above-mentioned superiority can be maintained even after long-term storage, which is a more preferable form.

  The dry silica fine particles of the present invention may be treated on the surface of the silica fine particles with a treatment agent selected from at least one selected from the group consisting of silylating agents, silicone oils, siloxanes and fatty acids depending on the application.

  Specific silylating agents include tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltri Methoxysilane, i-butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyl Diethoxysilane, i-butyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycine Sidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ Alkoxysilanes such as-(2-aminoethyl) aminopropyltrimethoxysilane and γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexabutyldi Examples thereof include silazanes such as silazane, hexapentyldisilazane, hexahexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, and dimethyltetravinyldisilazane.

  Silicone oils include dimethyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, alkyl modified silicone oil, carboxylic acid modified silicone oil, fatty acid modified silicone oil, polyether modified silicone oil, alkoxy modified silicone oil, carbinol modified. Examples include silicone oil, amino-modified silicone oil, and terminal reactive silicone oil.

  Examples of siloxanes include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, and octamethyltrisiloxane.

  As fatty acids, long-chain fatty acids such as undecyl acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, valmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, arachidonic acid, etc. Is mentioned.

(Method for producing dry silica fine particles)
The dry silica fine particles of the present invention are obtained by a combustion reaction of a silicon compound. In obtaining the dry silica fine particles of the present invention, it is necessary for the flame due to the combustion reaction of the silicon compound to have a maximum temperature exceeding the melting point of silica (about 2000 K) and a steep temperature gradient during cooling. .

  The dry silica fine particles of the present invention are preferably produced using a burner having a concentric multiple tube structure. Hereinafter, the case where a concentric quadruple burner is used will be described in detail as a typical example.

  This concentric quadruple burner has a central tube, a first annular tube is disposed on the outer periphery of the central tube, a second annular tube is disposed on the outer periphery of the first annular tube, and a third annular tube is disposed on the outer periphery of the second annular tube. A burner with a tube.

  A silicon compound vaporized as a silica source and oxygen are mixed and introduced into the central tube in advance. At this time, an inert gas such as nitrogen may also be mixed. Further, when silica fine particles are generated by a hydrolysis reaction of a silicon compound, a fuel that generates water vapor when reacted with oxygen, such as hydrogen and hydrocarbons, is mixed and mixed.

  In addition, a fuel for forming an auxiliary flame, such as hydrogen or hydrocarbon, is introduced into the first annular pipe. At this time, an inert gas such as nitrogen may be mixed and introduced. Furthermore, oxygen may be mixed together.

  Further, oxygen for forming an auxiliary flame is introduced into the second annular pipe. At this time, an inert gas such as nitrogen may be mixed and mixed.

  Furthermore, a mixed gas of an inert gas such as oxygen and nitrogen is introduced into the third annular tube. Since air introduction is easy, air introduction is a preferred mode.

  The characteristics of dry silica fine particles obtained by forming, growing and agglomerating in the flame and in the vicinity of the flame very strongly reflect the temperature history experienced by the silica fine particles.

  In the method for producing dry silica fine particles of the present invention, it is essential that the maximum flame temperature exceeds the melting point of silica. When the maximum flame temperature is lower than the melting point of silica, the dispersion performance is remarkably deteriorated, making it impossible to obtain the dry silica fine particles of the present invention.

  In the method for producing dry silica fine particles of the present invention, if the temperature gradient during cooling described later is the same, the BET specific surface area decreases as the maximum flame temperature increases. By utilizing this, the maximum temperature of the flame may be appropriately adjusted so that dry silica fine particles having a desired BET specific surface area can be obtained, but the viscosity at the time of liquid melting of the silica fine particles decreases with temperature. For the purpose of preventing fusion, the higher the maximum temperature of the flame, the better. The maximum temperature of the flame is preferably 3000K or higher, and more preferably 4500K or higher.

  In order to obtain the dry silica fine particles of the present invention, as described below, it is particularly important to adjust to a flame having a steep temperature gradient at the time of cooling according to the amount of heat.

  Due to the steep temperature gradient during cooling, the time to the temperature at which the aggregation of the silica fine particles is completed can be shortened. That is, the residence time of the aggregated region of the silica fine particles can be shortened. For this reason, partial fusion based on chemical bonds between primary particles or aggregation due to strong physical interparticle force can be prevented in the agglomerated region, and the agglomeration of the formed silica fine particles is weak and the agglomerated particle diameter is also small. . As a result, the silica fine particles exhibit easily dispersed characteristics and excellent dispersion characteristics.

  The specific adjustment of the flame temperature distribution is carried out by adjusting the introduction composition of the central tube, the size of the central tube, the size of the third annular tube, and the outlet flow velocity of the third annular tube.

  The maximum flame temperature is determined by the composition introduced in the central tube. The maximum temperature of the flame is preferably monitored at the adiabatic flame temperature that can be calculated from the introduced composition. In the application of this supervision method, it is essential to select a composition in which the reaction is completed only by chemical components introduced into the central tube, that is, a composition in which no unreacted silicon compound and fuel remain. For example, when only a silicon compound and oxygen are introduced into the central tube, it is essential that the amount of oxygen introduced is equal to or greater than the amount of oxygen necessary for the introduced silicon compound to completely burn.

  In the calculation of the adiabatic flame temperature, the thermodynamic property value may be referred to “JANAF Thermochemical Tables SECOND EDITION”, Horikoshi Research Institute (1975) or the like. As the specific heat necessary for calculating the adiabatic flame temperature, a value of 2000 K corresponding to the melting point of silica may be used.

  The steep temperature gradient according to the amount of heat is such that the cooling factor defined by (heat amount) x (flame cooling rate) is 8 kcal / ms x K / ms or more, the introduction composition of the center tube, the size of the center tube, This is done by adjusting the size of the third annular tube and the outlet flow velocity of the third annular tube.

  The amount of heat can be obtained by adding the sensible heat of the center tube introduction gas temperature to the combustion heat amount of the silicon compound.

The flame cooling rate will be described in detail below.
The flame cooling rate ΔT / Δt can be calculated as follows.

Here, T _a is the maximum temperature of the flame is determined as the adiabatic flame temperature. T _m is 2000K as the melting point of silica. _Tb means the ambient gas temperature, but the gas temperature of the third annular tube may be used, and when the gas of the third annular tube is introduced at room temperature, it may be 298K. k _B is the Boltzmann constant (1.38 × 10 ⁻²³ J / K). μ _STD is the viscosity of the central tube gas at 298 K. When only a silicon compound, oxygen and nitrogen are introduced into the central tube, 18 × 10 ⁻⁶ Pa · s corresponding to the viscosity of air may be used. T _STD is 298K. V _STD is the volume in terms of 298K of the gas flowing per unit time after the central tube gas burns. W is the amount of silica produced per unit time. ρ is the true density of silica and may be 2200 kg / m ³ . S is the BET specific surface area of the produced silica. D ₀ is the particle diameter before growth immediately after the production of silica produced by the combustion reaction, and may be 5 nm.
In the above formula, the silica fine particles perform Brownian motion in and near the flame, and the flame attenuates spatially as an exponential function by exchanging heat with the gas introduced into the third annular tube. Growth occurs at 2000K or higher, and does not grow at a temperature lower than 2000K, and is an equation constructed to form aggregated particles.

  The cooling factor increases by increasing the amount of silicon compound, decreasing the size of the central tube, increasing the size of the third annular tube, and increasing the outlet flow velocity of the third annular tube. The cooling factor may be appropriately adjusted so as to fall within the above-mentioned range while confirming the BET specific surface area of the obtained dry silica fine particles.

As an example, 100 kg / h of vaporized octamethylcyclotetrasiloxane is mixed with oxygen 121 Nm ³ / h and nitrogen 121 Nm ³ / h, and this is introduced into a burner central tube at 473 K, and octamethylcyclotetrasiloxane is introduced under atmospheric pressure. Assuming a case where dry silica fine particles having a BET specific surface area of 40 m ² / g = 4 × 10 ⁴ m ² / kg are obtained by burning siloxane, the cooling factor at this time is calculated. The gas temperature of the third annular tube is 298K. Nm ³ represents a gas amount in terms of a temperature of 273 K and 1 atm.

By calculating the composition of the post-combustion, silica 80.92kg / h, carbon dioxide 60.42Nm ³ / h, steam 90.63Nm ³ / h, oxygen 0.16 nm ³ / h, a nitrogen 121Nm ³ / h.
From the above composition, the amount of gas flowing per unit time after the center tube gas burns is as follows in terms of 298K.

  If 6063 kcal / kg (value at 298 K) is used as the combustion heat of octamethylcyclotetrasiloxane, the combustion heat is calculated as follows.

6063 × 1000 kcal / h = 606.3 million kcal / h
Further, the specific heat of the component after combustion is a value at 2000 K, silica 0.34 kcal / kg / K, carbon dioxide 0.64 kcal / Nm ³ / K, water vapor 0.55 kcal / Nm ³ / K, oxygen 0.40 kcal / If Nm ³ / K and nitrogen 0.38 kcal / Nm ³ / K are used, the heat capacity per unit time can be obtained as follows.

  Moreover, sensible heat is calculated | required as follows.

162 × (473-298) kcal / h = 284,000 kcal / h
Accordingly, the amount of heat is calculated as follows.

Adiabatic flame temperature is
^{298 + 63.5 × 10 4/162} = 4218K
Is calculated.

  The flame cooling rate can be calculated by substituting numerical values obtained by reversing the above equation.

  From the above results, the cooling factor defined by (calorie) × (flame cooling rate) is obtained as follows.

In the present invention, as the silicon compound, those which are gaseous or liquid at normal temperature are used without any particular limitation. For example, cyclic siloxanes such as octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane, chain siloxanes such as hexamethyldisiloxane, alkoxysilanes such as tetramethoxysilane and tetraethoxysilane, trichlorosilane and tetrachlorosilane Chlorosilanes can be used as silicon compounds.
Use of siloxanes and alkoxysilanes that do not contain chlorine as the silicon compound is preferable because high purity dry silica fine particles with significantly reduced chlorine as an impurity can be obtained.

  In siloxanes and alkoxysilanes, siloxanes have fewer carbon atoms per silicon atom than alkoxysilanes, so it is difficult to cause poor combustion such as generation of carbon and to make the flame uniform. As compounds, siloxanes are the preferred form, and cyclic siloxane is the most preferred form.

  The dry silica fine particles of the present invention can be obtained by generating, growing and agglomerating in and near the flame, but the recovery can be performed by filtering with a metal filter, ceramic filter, back filter, etc., or by centrifugal separation with a cyclone, etc. It is done by separating and collecting.

  Examples and comparative examples are shown to specifically describe the present invention, but the present invention is not limited to these examples.

  In addition, various physical property measurements in the following examples and comparative examples are based on the following methods.

(1) BET specific surface area It measured by the nitrogen adsorption BET 1-point method using the specific surface area measuring device SA-1000 made by Shibata Rika.

(2) Absorbance (Preparation of measurement sample)
A silica suspension having a silica concentration of 1.5% by mass as a measurement sample was prepared as follows.
0.3 g of silica and 20 ml of distilled water are placed in a glass sample tube bottle (manufactured by ASONE, inner volume 30 ml, outer diameter about 28 mm), and an ultrasonic cell crusher (BRANSON Sonifier II Model 250D, probe: 1. A sample tube bottle with a sample is placed so that the bottom surface of the 4 inch probe tip is 15 mm below the water surface, and silica fine particles are dispersed in distilled water under the conditions of an output of 20 W and a dispersion time of 3 minutes. A 5% by weight aqueous suspension was prepared.
(Absorbance measurement)
Using a spectrophotometer V-530 manufactured by JASCO Corporation, the absorbance of an aqueous suspension having a silica concentration of 1.5 mass% with respect to light having a wavelength of 700 nm was measured. The measurement sample cell used was a synthetic quartz cell (5-sided transparent, 10 × 10 × 45H) manufactured by Tokyo Glass Instruments.

(3) Particle size distribution by centrifugal sedimentation (Preparation of measurement sample)
The absorbance was exactly the same as the measurement sample.
(Particle size distribution measurement)
CPS Instruments Inc. The weight-based particle size distribution was measured using a disk centrifugal particle size distribution measuring apparatus (DC24000). The measurement conditions were a rotational speed of 18000 rpm, a temperature of 32 ° C., and a true silica density of 2.2 g / cm ³ .

  The median diameter was calculated from the obtained weight-based particle size distribution.

(4) Particle size distribution by ultra-small angle X-ray scattering (Preparation of measurement sample)
The sample was exactly the same as the measurement sample in the absorbance and the particle size distribution by centrifugal sedimentation.
(Ultra-small angle X-ray scattering measurement)
In order to obtain an ultra-small-angle X-ray scattering spectrum, the transmission method small-angle scattering of the ultra-small-angle X-ray scattering specification is applied as an optical system to Rigaku's fully automatic horizontal multi-purpose X-ray diffractometer SmartLab, and the ultra-small angle X of the measurement sample is applied. The line scattering spectrum was measured. The wavelength of X-ray was 0.154187 nm. As the holder, a sample holder for small-angle transmission with a spacer of 1 mm was used, and the incident side and the scattering side of the sample were sandwiched between polyimide films (Kapton films). The detector was a scintillation counter.
(Calculation of particle size distribution)
The sample was subjected to spectral fitting using the Rigaku analysis software NANO-Solver, and the sample was obtained as a volume-based particle size distribution. . In spectral fitting, the fitting target angle range was determined using the Bragg equation and the X-ray wavelength so that the fitting target particle size range was 0.3 × average particle size to 3 × average particle size. That was a fitting target angle range as ^{sin -1} {X-ray wavelength / (6 × average particle diameter)} ~sin ^-1 {X-ray wavelength /(0.6× average particle diameter)}.

(5) Water content The water content was measured by the loss on drying method at 130 ° C.

(6) Thickening index (Preparation of epoxy resin composition)
42.84 g of Toto Kasei epoxy resin ZX-1059 was weighed and 28.56 g of silica was added thereto. Then, using a planetary mixer AR-500 manufactured by Sinky Corporation, the mixture was stirred for 8 minutes at a rotational speed of 1000 rpm and then degassed for 2 minutes at a rotational speed of 2000 rpm to obtain an epoxy resin composition. Then, the resin composition was left still for 1 hour or more in a 25 degreeC thermostat.
(Viscosity of epoxy resin composition)
The resin composition was taken out from the thermostatic bath at 25 ° C., and the viscosity was measured at a shear rate of 10 s ⁻¹ using a rheometer Rheo Stress RS600 manufactured by Haake. The measurement temperature is 25 ° C., the sensor used is C35 / 1 (cone plate type diameter 35 mm, angle 1 degree, material titanium), and the viscosity value after maintaining the state of shear rate 10 s ⁻¹ for 3 minutes is epoxy. The viscosity of the resin composition was used.
(Viscosity of epoxy resin)
The viscosity of the epoxy resin ZX-1059 manufactured by Tohto Kasei Co., Ltd. was measured at a shear rate of 10 s ⁻¹ using a rheometer Rheo Stress RS600 manufactured by Haake. The measurement temperature is 25 ° C., the sensor used is C35 / 1 (cone plate type diameter 35 mm, angle 1 degree, material titanium), and the viscosity value after maintaining the state of shear rate 10 s ⁻¹ for 3 minutes is epoxy. The viscosity of the resin was used.
(Thickening index)
The thickening index [g ² / m ⁴ ] was determined by the following formula.

Thickening index [g ² / m ⁴ ] = (η · η ₀ ⁻¹ · S ⁻² ) × 100
Here, η is the viscosity [Pa · s] of the resin composition, η ₀ is the viscosity [Pa · s] of the resin, and S is the BET specific surface area [m ² / g].

Examples 1-5, Comparative Examples 1-9
Octamethylcyclotetrasiloxane was burned with a concentric quadruple burner to produce dry silica fine particles. Hereinafter, octamethylcyclotetrasiloxane is referred to as a raw material.

  After mixing the vaporized raw material, oxygen and nitrogen, they were introduced into the burner center tube at 473K. Further, hydrogen and nitrogen were mixed and introduced into a first annular tube disposed on the outer periphery of the central tube, and oxygen was introduced into a second annular tube disposed on the outer periphery of the first annular tube. Further, air was introduced at 298K into the third annular tube disposed on the outer periphery of the second annular tube.

  The obtained dry silica fine particles were collected with a metal filter, and the BET specific surface area, absorbance, particle size distribution by centrifugal sedimentation method, particle size distribution by ultra-small angle X-ray scattering, water content, and thickening index were measured. It was confirmed that the moisture content of the dry silica fine particles of Examples 1 to 5 and Comparative Examples 1 to 9 was 0.5% by mass or less. Table 1 shows the production conditions and silica characteristics of Examples 1 to 5, Table 2 shows the production conditions and silica characteristics of Comparative Examples 1 to 5, and Table 3 shows the production conditions and silica characteristics of Comparative Examples 6 to 9.

The oxygen ratios in Tables 1 to 3 are (number of moles of oxygen introduced into the central tube) / (16 × number of moles of raw material introduced into the central tube), and the oxygen concentration is (oxygen introduced into the central tube). Number of moles) / (number of moles of oxygen introduced into the central tube + number of moles of nitrogen introduced into the central tube). R _SFL is (number of moles of hydrogen introduced into the first annular tube) / (32 × number of moles of raw material introduced into the center tube), and R _cmbts is (number of moles of oxygen introduced into the second annular tube). / (16 × number of moles of raw material introduced into the central tube). Further, D _CS median diameter of the weight-based particle size distribution by centrifugal sedimentation method, D _USAXS the volume-based median diameter of particle size distribution by ultra-small angle X-ray scattering method, a geometric standard deviation of σg weight based particle size distribution by centrifugal sedimentation method Represent.

In the calculation of the adiabatic flame temperature, which is the maximum temperature of the flame, and the cooling factor, the combustion heat of octamethylcyclotetrasiloxane is 6063 kcal / kg (value at 298 K), the specific heat is silica 0.34 kcal / kg / K, carbon dioxide 0 .64 kcal / Nm ³ / K, water vapor 0.55 kcal / Nm ³ / K, oxygen 0.40 kcal / Nm ³ / K, nitrogen 0.38 kcal / Nm ³ / K.

  Moreover, the same burner was used in Examples 1-3 and Comparative Examples 1-3. In Example 4 and Comparative Examples 4 to 7, the central tube, the first annular tube, and the second annular tube were the same as in Example 1, and the third annular tube used a burner having a diameter 1.8 times larger than that in Example 1. . Further, in Example 5, the central tube, the first annular tube, and the second annular tube were the same as in Example 1, and the third annular tube was a burner having a diameter 2.5 times larger than that in Example 1. In Comparative Examples 8 to 9, the center tube diameter is 1/2 of Example 1, the clearance (space) of the first annular tube and the sectional area of the second annular tube are the same as those of Example 1, and the third annular tube The outer diameter used was 1.1 times that of Example 1.

  Further, the viscosity of the epoxy resin measured for obtaining the thickening index was 2.22 Pa · s.

  Tables 1 to 3 show that the examples have a smaller thickening effect by removing the influence of the specific surface area than the comparative examples, that is, show low viscosity characteristics.

Claims (2)

Dry silica fine particles characterized by satisfying the following conditions.
(1) The BET specific surface area is 20 to 60 m ² / g.
_{(2) 100 × D CS /} D USAXS is 100 to 110.
Here, D _CS is the median diameter of the weight-based particle size distribution of wherein the drying type silica fine particles by centrifugal sedimentation, D _USAXS is volume-based median diameter of particle size distribution of wherein the drying type silica fine particles with ultra-small angle X-ray scattering method.   The dry silica fine particles according to claim 1, wherein the moisture content measured by a loss on drying method at 130 ° C is 0.5% by mass or less.