JPWO2018096876A1 - Sol-gel silica powder and method for producing the same - Google Patents

Abstract

Provided is a sol-gel silica powder which can obtain high fluidity without lowering the productivity and yield of a target product even when blended in a resin composition for electronic materials. The sol-gel silica powder of the present invention has an average particle size of from 0.5 μm to 2.0 μm by a laser diffraction scattering method, a coefficient of variation indicating the spread of the particle size distribution is 40% or less, and 5% by mass in water. The amount of the residual amount on the screen when the amount is screened by a wet sieving method using an electroformed screen having a mesh size of 5 μm is reduced to 10 ppm or less in a dispersion dispersed by ultrasonic waves under conditions of an output of 40 W and an irradiation time of 10 minutes. It is a sol-gel silica powder characterized by

Description

  The present invention relates to a sol-gel silica powder that can be suitably used as a filler for semiconductor sealing materials, liquid crystal sealants, films and the like. Specifically, the present invention relates to a sol-gel silica powder with a very small amount of coarse particles.

  Silica powder is blended as a filler in various resin compositions for electronic materials such as semiconductor sealing materials and liquid crystal sealants, and for film production.

  Among these, with semiconductor encapsulants, with the rapid progress of miniaturization, thinning, and high-density mounting of devices, the gap between the element and the substrate has progressed, further increasing the thermal conductivity, low thermal expansion, and high Formability is required, and the silica powder is required to be highly filled. On the other hand, the low viscosity of the resin composition filled with silica powder is also required, and there is an increasing demand for silica powder that does not contain coarse particles and is excellent in monodispersity.

  Conventionally, as a method for producing silica having high monodispersity, silicon alkoxide such as tetraethoxysilane as a raw material is supplied into a reaction solution containing a hydrolysis catalyst, water and an organic solvent, and hydrolysis and polycondensation are performed. There is a so-called sol-gel method. In this method, it is known that the particle size and the particle size distribution can be controlled to some extent by controlling the reaction conditions for carrying out the reaction.

  In Patent Document 1, by adjusting the reaction conditions in the sol-gel method, the particle size and particle size distribution are controlled, and the generation of coarse particles such as adhesion particles and aggregates is suppressed, and the monodispersibility is good. A method for producing silica is described.

  In the silica particle dispersion obtained by the sol-gel method, the silica particles are highly dispersed as fine primary particles, and substantially no agglomerates are seen. However, when taking it out as a dry powder, a step of solid-liquid separation of the sol-gel silica from the dispersion, a step of drying, or a step of firing as necessary is necessary. Agglomerated aggregates are formed. And it is difficult to crush what was aggregated firmly to primary particles, and as a result, coarse particles increase.

  Thus, when coarse particles are present in the silica powder in this way, in the resin composition containing this, the coarse particles inhibit the smooth flow of the resin and lower the fluidity when melted. As a result, in the production of a molded product such as a film, a pattern of traces of the molten resin flowing on the surface, a so-called “flow mark” is generated. Further, even when the semiconductor sealing material or the liquid crystal sealant is made of a resin composition having low fluidity such that a flow mark is generated, the gap penetration into a narrow gap is not sufficient, and clogging between wirings is caused. Is also likely to occur.

  From these, in Cited Document 2, by adding a coagulant composed of a specific compound to the silica particle dispersion obtained by the sol-gel method, in the post-process, without causing a strong agglomerate, It is described that it can be produced as a gentle aggregate, and this can be easily pulverized to primary particles by the share of the disperser when it is dispersed in the resin. That is, according to this method, if the sol-gel method is controlled as described above so as to be excellent in monodispersibility of silica, the aggregates produced in the subsequent step can be regenerated into primary particles by a simple crushing treatment. Therefore, the silica powder does not substantially contain coarse particles. That is, it is possible to obtain a silica powder in which coarse particles having a particle diameter exceeding 5 μm are not detected by measurement by a general-purpose particle size distribution measurement method, specifically, a laser diffraction scattering method.

JP 2013-193950 A JP 2012-6823 A

  However, even if such silica powder containing substantially no agglomerates as coarse particles is used, the effect of improving the fluidity as a filler for the resin is actually not satisfied one step at a time. In particular, when it is used as a filler for a resin composition for electronic materials such as the semiconductor sealing material and the liquid crystal sealant, the recent progress in downsizing, thinning, and high-density mounting of semiconductor devices described above. Thus, the problems of gap penetration into narrow gaps and clogging between narrowed wirings have become apparent year after year, and further improvements have been desired.

  From the above, it has been a major challenge to develop a sol-gel silica powder that can achieve high fluidity without reducing the productivity and yield of the target product even when blended with the resin composition for electronic materials. .

  The present inventors have intensively studied to solve the above problems. As a result, in the sol-gel method, silica synthesis was carried out by controlling so as to be excellent in monodispersity as described above, and a specific flocculant was added to the obtained silica particle dispersion to obtain a laser diffraction scattering method. Even when a sol-gel silica powder with reduced coarse particles as agglomerates is obtained, the wet sieving method (which has higher detection sensitivity than the laser diffraction scattering method) As a result, it was found that there was a significant amount of residue on the screen. Then, the present inventors have found out that the coarse particles are an impediment to obtaining the high fluidity required for the filler of the resin composition for electronic materials.

  As a result of further investigation, the coarse particles are mainly aggregated primary particles that are inevitably generated during the synthesis of silica by the sol-gel method, not aggregates generated in the subsequent steps such as the drying step. It was found that the coarse independent primary particles can be efficiently removed by wet filtration of the resulting silica particle dispersion after synthesizing the silica by the sol-gel method, and a novel sol-gel silica powder in which the above problems have been solved is obtained. I came to propose.

  That is, the sol-gel silica powder of the present invention has an average particle size of 0.05 μm or more and 2.0 μm or less by a laser diffraction scattering method, a coefficient of variation indicating the spread of the particle size distribution is 40% or less, In the dispersion liquid in which the amount of 5% by mass was dispersed by ultrasonic waves under the conditions of an output of 40 W and an irradiation time of 10 minutes, the residue on the screen when sieved by a wet sieving method using an electroformed sieve having an opening of 5 μm A sol-gel silica powder characterized in that the amount is 10 ppm or less.

  The sol-gel silica powder of the present invention has an average particle size of 0.05 μm or more and 2.0 μm or less by laser diffraction scattering method, and has a detection sensitivity higher than that of the laser diffraction scattering method as a particle size distribution measurement method ( The residual amount on the screen with a mesh sieve having an opening of 5 μm is also substantially reduced (10 ppm or less). Therefore, a resin composition containing this is highly excellent in fluidity at the time of melting. For this reason, in the production of a molded product such as a film, the generation of flow marks is suppressed.

  And when it is used for filling resin compositions for electronic materials such as semiconductor encapsulants and liquid crystal sealants, it is highly superior in gap penetration into narrow gaps and prevents clogging between narrowed wirings. It is highly superior in nature. As a result, the productivity and yield of the target electronic material member are improved, which is extremely useful.

(Embodiment)
The sol-gel silica powder of this embodiment is a sol-gel method, that is, a silicon alkoxide as a raw material in a reaction medium is hydrolyzed and polycondensed to form a silica sol, which is gelled, and then generated solid content. Is a silica powder obtained by taking out and drying. In the present embodiment, the silica powder obtained by drying can be fired as necessary. In general, silica particles obtained by a sol-gel method are independent spherical particles having a sphericity of 0.9 or more.

  The sol-gel silica powder of the present embodiment preferably has an average particle size of 0.05 μm or more and 2.0 μm or less, more preferably 0.1 μm or more and 1.5 μm or less by a laser diffraction scattering method. When it is larger than the above range, it becomes difficult to accurately reduce the agglomerates in the subsequent process, and the size is not suitable for filling the resin composition for electronic materials. In general, particles having a small particle size and a large specific surface area tend to aggregate. When the average particle size is smaller than the above range, it is difficult to suppress the formation of aggregates, and the generated aggregates are crushed. It is difficult to do and causes coarse grains. In addition, such a small particle size increases in viscosity and decreases in fluidity when filled in a resin or the like.

  In addition, the sol-gel silica powder of this embodiment is a dispersion liquid in which an amount of 5% by mass of silica powder in water is dispersed by ultrasonic waves under the conditions of an output of 40 W and an irradiation time of 10 minutes. The remaining amount on the screen when sieving by wet sieving using an artificial sieve is 10 ppm or less, and preferably 5 ppm or less. The sol-gel silica powder of the present embodiment is obtained by a manufacturing method described later, and even if individual silica particles are aggregated, since they are aggregates of weak force, simple crushing treatment Can be solved well. Therefore, in the 5% by mass dispersion of the silica powder, the weak agglomerates can be pulverized into primary particles by ultrasonic dispersion at an output of 40 W and an irradiation time of 10 minutes. It means that it can be solved well by the share of the disperser when it is dispersed in a solvent.

  In the 5% by mass ultrasonic dispersion of the silica powder, when the remaining amount on the screen of the 5 μm mesh sieve exceeds the above range, the fluidity of the resin composition containing this decreases, When used for a semiconductor encapsulant or a liquid crystal sealant, the gap permeability of the resin composition due to coarse particles deteriorates, and clogging between wirings cannot be suppressed.

  Furthermore, for the same reason, the residual amount on the screen when sieving by the wet sieving method using an electroformed sieve having a mesh size of 3 μm is preferably 10 ppm or less, and more preferably 5 ppm or less.

  In the present embodiment, the above-mentioned electrogenic sieve is not particularly limited, and specifically, an electrogenic sieve manufactured by Iida Seisakusho may be mentioned. The above-mentioned electrogenic sieve is made of nickel steel, and since an organic solvent containing alcohol cannot be used, water is used as a medium.

  In addition, the said residual amount on a screen is a value at the time of screening 20g or more of sol-gel silica powder as a sample amount. When sieving, the 5 mass% ultrasonic dispersion liquid can be prepared at one time or can be prepared by dividing. Specifically, 20 g of sol-gel silica powder is measured in one container, water is added so that the amount of silica is 5% by mass, and then ultrasonic waves with an output of 40 W may be irradiated for 10 minutes. 5 g may be measured in four containers, and after adding water so that the amount of silica becomes 5% by mass, ultrasonic waves with an output of 40 W may be irradiated for 10 minutes. In the sieving, the temperature of the 5% by mass ultrasonic dispersion is 20 to 40 ° C.

  In general, as a method for quantifying the content of coarse particles, particle size distribution measurement by laser diffraction scattering method, SEM observation and the like can be mentioned. In the SEM observation, since there is a limit to the number of particles that can enter a single field of view, it is inefficient to observe and quantify coarse particles on the order of several ppm. In the particle size distribution measurement by the laser diffraction / scattering method, there is a limit to the amount of silica in the sample used for measurement in order to avoid multiple scattering. Further, the measurement method has a detection level of about a percent as described in JP-A-2008-19157, and the detection sensitivity is low. For example, as in this embodiment, a small amount of particles exceeding 5 μm in silica fine particles is used. Not suitable for quantification. Specifically, as shown in the examples, even when coarse particles are not detected by performing particle size distribution measurement by laser diffraction scattering method, the coarse particles detected when quantified by the wet sieving method using the electrode sieve In the present application, the presence of such coarse particles reduces the fluidity of the resin composition, and is a factor that hinders yield improvement in semiconductor sealing materials and liquid crystal sealant applications. It has been determined.

  In the sol-gel silica powder of the present embodiment, the coefficient of variation, which is one of the indexes indicating the spread of the particle size distribution, is 40% or less, preferably 25% or less, and more preferably 20% or less. The coefficient of variation is a value obtained by dividing the standard deviation by the average value. Here, the coefficient of variation is calculated using the standard deviation and average value of the measured particle diameter. If the coefficient of variation exceeds the above range, the particle size distribution becomes broad, and fine particles increase when compared with powders having the same average particle size. As described above, the increase in fine particles leads to an increase in viscosity when filled in a resin or the like. Generally, the variation coefficient in sol-gel silica is 10% or more. The coefficient of variation can be measured by a laser diffraction scattering method.

Sol-gel silica powder of the present embodiment, the silanol groups of the silica particle surface is preferably 5 or / nm ² or less. The smaller the amount of silanol groups, the better, since it is possible to suppress moisture absorption during storage, but it is usually 1 / nm ² or more.

The sol-gel silica powder of this embodiment preferably has an α dose of 0.002 c / cm ² · h or less. It is known that when the α dose is large, when this is used for filling the resin composition for electronic materials, it causes soft error factors such as reversal of accumulated charge in the memory cell. As miniaturization, high integration, and 3D mounting of semiconductor packages progress, the influence of alpha rays derived from fillers is increasing, and low alpha dose fillers are required.

  Uranium (U), thorium (Th), and the like are listed as impurities that emit α rays. In the sol-gel silica powder of this embodiment, the U content and the Th content are preferably 0.1 ppb or less. It is more preferably 0.05 ppb or less, and particularly preferably 0.02 ppb or less. The uranium and thorium quantification method is a value measured by ICP mass spectrometry, and the lower limit of detection is 0.01 ppb.

  Furthermore, the sol-gel silica powder of this embodiment has an Fe content of 10 ppm or less, an Al content of 10 ppm or less, an Na content of 5 ppm or less, a K content of 5 ppm or less, and a chloride ion content of 1 ppm or less. It is preferable. Furthermore, it is preferable that the Ca content is 5 ppm or less, the Cr content is 5 ppm or less, the Ni content is 5 ppm or less, and the Ti content is 5 ppm or less. The amount of impurities contained in the sol-gel silica powder of the present embodiment is in the above range is that when used as a filler for a semiconductor encapsulant, a short circuit between metal wirings or corrosion of metal wirings caused by silica particles This is preferable in that it can be reduced. The impurity quantification method is a value measured by ion chromatography for chloride ions, and a value measured by ICP emission analysis for elements other than chloride ions.

  Of the above impurities, uranium (U), thorium (Th), derived from raw materials and contained, Fe, Al, Cr, Ni, Ti not only from the raw materials, but also from reaction vessels, piping, crushers, etc. Those derived from wear powder are also included. Na, K, Ca, and chloride ions are often derived from the atmosphere.

  Since the sol-gel silica powder of this embodiment does not contain coarse particles and is excellent in fluidity when filled into a resin, it is particularly suitable for use as a semiconductor encapsulant or liquid crystal sealant for filling into a resin composition for electronic materials. It can be used suitably. Furthermore, the property that the resin composition is excellent in fluidity at the time of melting and hardly causes a flow mark in the molded product can be suitably used for various molded product applications including film applications.

  The kind of resin which mix | blends sol gel silica powder is not specifically limited. The type of the resin may be appropriately selected depending on the desired application, and examples thereof include an epoxy resin, an acrylic resin, a silicone resin, and an olefin resin.

  For example, epoxy resin, acrylic resin, silicone resin and the like are preferable for semiconductor encapsulant use and liquid crystal sealant use. For film applications, olefin resins (polypropylene, polyethylene, polystyrene, etc.) are preferred.

  In the resin composition, the filling amount of the sol-gel silica powder may be appropriately adjusted according to its use and purpose. Specifically, when used for semiconductor encapsulant applications, the range is 65 to 900 parts by mass with respect to 100 parts by mass of resin, and when used for liquid crystal sealant applications, 1 to 40 parts by mass with respect to 100 parts by mass of resin. When using for a range and a film use, it is preferable that it is the range of 0.01-1 mass part with respect to 100 mass parts of resin. In addition to the sol-gel silica powder of this embodiment, another filler may be included.

  Furthermore, since the sol-gel silica powder of this embodiment does not contain coarse particles, it can be suitably used as a toner filler.

<< Method for producing sol-gel silica powder >>
The sol-gel silica powder of this embodiment is not limited to a specific method as long as the stipulated requirements are satisfied by the sol-gel method, and any method may be used. Here, in the sol-gel method, silicon alkoxide is hydrolyzed and polycondensed in a reaction medium comprising water containing a catalyst and an organic solvent to form a silica sol, which is gelled, and then generated solid. It means a method of taking a minute and drying to obtain silica powder. In the present embodiment, the silica powder obtained by drying can be fired as necessary.

  If the suitable manufacturing method of the sol-gel silica powder of this embodiment is shown, the silica particle dispersion liquid with the average particle diameter of 0.05 micrometer or more and 2.0 micrometers or less by the laser diffraction scattering method manufactured by the sol-gel method will be 5 micrometers of openings. After wet filtration with the following filter medium, a coagulant composed of at least one compound selected from the group consisting of carbon dioxide, ammonium carbonate, ammonium hydrogen carbonate and ammonium carbamate is added to coagulate the silica particles. The silica particles are solid-liquid separated from the coagulated liquid and dried. Hereinafter, this manufacturing method will be described.

<Silicon alkoxide>
As a silicon alkoxide used in the manufacturing method of this embodiment, if it is a compound used for manufacture of the silica particle by reaction of a sol-gel method, it will not restrict | limit in particular and can be used.

  In the present embodiment, examples of silicon alkoxide (alkoxysilane) include methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane. Among these, methyltrimethoxysilane, tetramethoxysilane, and tetraethoxysilane are more preferable because they are easily available industrially and are easy to handle. These silicon alkoxides may be used alone or in combination of two or more.

  Furthermore, in order to obtain the above-mentioned sol-gel silica powder with reduced impurities, it is preferable to use a silicon alkoxide having a high purity. Specifically, when obtaining a sol-gel silica powder having a U content and a Th content of 0.1 ppb or less using tetramethoxysilane as a raw material silicon alkoxide, the U content and the Th content are each 0.2 ppb or less. Tetramethoxysilane is preferably used.

  In order to obtain high-purity silicon alkoxide, the raw material can be purified in advance by distillation or the like.

  When the silicon alkoxide is liquid at normal temperature and pressure, it may be used as it is, or may be diluted with an organic solvent described later. When the silicon alkoxide is solid at normal temperature and pressure, it can be used by being dissolved or dispersed in an organic solvent.

<Basic catalyst>
In the production of silica particles by the sol-gel method, an appropriate catalyst is preferably used. In the sol-gel method, an acidic catalyst may be used, but a basic catalyst is used in the present embodiment in that it is easy to obtain spherical particles having a uniform particle diameter. However, in the sol-gel method, particle growth is often performed after preliminary hydrolysis is first performed under an acidic catalyst, but in this embodiment, the use of an acidic catalyst during preliminary hydrolysis is excluded as described above. Instead, any method that uses a basic catalyst at the time of particle growth may be used.

  As the basic catalyst used in the present embodiment, any known basic catalyst used for the production of silica particles by a sol-gel method reaction can be suitably used.

  Examples of such basic catalysts include amine compounds and alkali metal hydroxides. In particular, it is preferable to use an amine compound from the viewpoint that the amount of impurities containing a metal other than the metal element constituting the target silica particles is small and high-purity silica particles can be obtained. Examples of such amine compounds include ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, dimethylamine, and trimethylamine. Among these, it is particularly preferable to use ammonia because it is highly volatile and easy to remove, and the reaction rate of the sol-gel method is high.

  These basic catalysts can be used alone or in combination of two or more.

  As the above basic catalyst, an industrially available one can be used as it is (as it is in a commercially available form), or it is used after being diluted with water or an organic solvent such as ammonia water. You can also. In particular, it is preferable to use the aqueous solution in which the basic catalyst is diluted with water and the concentration is adjusted as necessary, in terms of easy control of the reaction progress rate. The concentration in the case of using an aqueous solution as the basic catalyst is preferably in the range of 1 to 30% by mass because it is easily available industrially and the concentration can be easily adjusted.

  The proportion of the basic catalyst used may be appropriately determined in consideration of the reaction rate of hydrolysis and polycondensation reaction of silicon alkoxide. As a use ratio of the basic catalyst, the amount of the basic catalyst in the reaction solution is preferably 0.1 to 60% by mass, and 0.5 to 40% by mass with respect to the mass of the silicon alkoxide to be used. It is more preferable to use in the range of%.

<Solvent>
In this embodiment, the solvent used for the hydrolysis and polycondensation reaction of the silicon alkoxide is preferably a polar solvent. Here, the polar solvent is an organic solvent that dissolves 10 g or more of water per 100 g under normal temperature and normal pressure, or water. A plurality of organic solvents other than water may be mixed and used. In this case, the mixture of the organic solvents only needs to satisfy the above requirements.

  Examples of the organic solvent that is a polar solvent other than water include alcohols such as methanol, ethanol, isopropyl alcohol, and butanol; ethers such as tetrahydrofuran and dioxane; amide compounds such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. be able to.

  Since alcohol is a by-product during the reaction of the sol-gel method, it is unnecessary to use alcohol such as methanol, ethanol, isopropyl alcohol, butanol among the above in the silica particle dispersion after the reaction. This is particularly preferable from the viewpoint of suppressing the mixing of impurities and the point that it can be easily removed by heating.

  The organic solvent and water can be used alone or as a mixture of two or more solvents.

  The use ratio of the organic solvent or water may be appropriately determined according to the desired value of the particle size of the target silica particles and the concentration of the silica particles in the silica particle dispersion after the reaction of the sol-gel method. For example, when alcohol is used as the organic solvent, the proportion of alcohol in the mass (100% by mass) of the silica particle dispersion obtained by the sol-gel reaction is preferably 10 to 90% by mass, more preferably 15 to It is used so that it may become the range of 80 mass%.

  Water is essential for the reaction of the sol-gel method (for this reason, a polar solvent that dissolves water as described above is used). When the basic catalyst is added as an aqueous solution or when water is used as part or all of the solvent, it is not necessary to add water separately to the reaction solution. However, in other cases, it is necessary to add water necessary for the sol-gel reaction separately.

  The use ratio of water is appropriately adjusted and selected according to the particle size of the silica particles to be produced. If the proportion of water used is too small, the reaction rate becomes slow. Conversely, if too much water is used, it takes a long time for drying (solvent removal). Therefore, the proportion of water used is selected in consideration of both of these requirements. The ratio of water used is preferably in the range of 2 to 50% by mass and preferably in the range of 5 to 40% by mass with respect to the total mass of the silica dispersion obtained by the sol-gel method reaction. More preferred.

  Water may be used as a part or all of the reaction solvent, and may be added to the reaction solution after preparing all reaction raw materials other than water. However, in order to advance the reaction of the sol-gel method quickly and stably, it is preferable to use water as a part of the solvent, that is, to use a mixture of water and an organic solvent as the solvent. The term “water” as used herein includes a case where water is added along with the addition of a basic catalyst.

<Reactor>
The reactor used in this embodiment is not particularly limited as long as it is a reactor having a stirrer. As the agitator blades of the agitator, known ones can be used without any particular limitation. However, representative examples include a tilted paddle blade, a turbine blade, three retreat blades, an anchor blade, a full zone blade, and a twin star blade. , Max blend wings and the like.

  In addition, the reactor having such a stirrer is particularly limited to a hemispherical or flat-bottomed or round-bottomed cylindrical reactor, and further a baffle plate installed in these reactors. Can be used without Also, the material of the reactor is not particularly limited, and those made of glass, metal such as stainless steel (including those coated with glass or resin), or resin can be used. In order to obtain the above-described sol-gel silica powder with reduced impurities, a material having excellent wear resistance is preferable.

  Although the stirring efficiency of the reactor used in this embodiment is not particularly limited, the dimensionless mixing time nθm (where n is the stirring blade rotation speed (1 / s)), which is an index of the stirring efficiency of the reactor. , Θm is desirably a reactor having a mixing time (s) of 100 or less. By setting the dimensionless mixing time nθm within the above range, the reaction solution during the reaction can be kept uniform, and a sol-gel silica powder with a more uniform particle size and a narrow particle size distribution can be obtained.

  Generally, the range of the stirring efficiency of the reactor generally corresponds to the stirring efficiency of a reactor that handles a reaction liquid of 50 L or more in industrial implementation described later.

  The dimensionless mixing time nθm means the product of the stirring blade rotation speed n (1 / s) and the mixing time θm (s). If the stirring Reynolds number is constant, it is unambiguous regardless of the scale of the reactor. It is a very useful index for showing the stirring efficiency. Θm generally means the time until the tracer substance is uniformly mixed. The mixing time θm is the shape of the reactor, the presence / absence of a baffle plate and its arrangement, the type and rotation of the stirring blades, and the like. It is influenced by the number and viscoelastic properties of the liquid to be mixed.

  When the dimensionless mixing time nθm is lower than 55, the stirring efficiency of the reactor is high, the reaction liquid can be sufficiently stirred, and adhesion particles and agglomerates are not easily generated. When nθm is 55 to 100, the generation of adhesion particles and aggregates can be suppressed by supplying the silicon alkoxide solution into the reaction solution at a discharge linear velocity of 30 mm / s to 1000 mm / s. On the other hand, when the dimensionless mixing time nθm exceeds 100, the stirring efficiency of the reactor becomes extremely low, the mixing is insufficient, the reaction solution becomes non-uniform, and many adhesion particles and agglomerates are easily generated.

<Reaction conditions>
The hydrolysis and polycondensation reaction (sol-gel method reaction) in the present embodiment is usually performed in the presence of a basic catalyst as described above. Known conditions can be adopted as the reaction conditions, and the contact method between the silicon alkoxide and the basic catalyst is not particularly limited, and has a desired particle size distribution in consideration of the configuration of the reactor and the reaction scale. What is necessary is just to select and determine suitably so that a silica powder may be obtained.

  An example of the reaction method of the sol-gel method is specifically shown as follows, for example.

  Examples include a method in which water, a polar solvent other than water (organic solvent), and a basic catalyst are charged into a reaction vessel, and a silicon alkoxide (or an organic solvent solution of silicon alkoxide) and an aqueous solution of a basic catalyst are added simultaneously. it can. According to this method, spherical silica particles having good reaction efficiency and uniform particle diameter can be produced efficiently and with good reproducibility, which is preferable. In this case, for example, after adding a part of silicon alkoxide first, the remaining silicon alkoxide and the basic catalyst can be added simultaneously. When two or more silicon alkoxides are used in combination, they may be mixed and added at the same time, or each may be added sequentially.

  The silicon alkoxide and the basic catalyst are preferably added dropwise to the reaction solution. Here, dripping in the liquid means that the tip of the dripping port is immersed in the reaction liquid when the above raw material is dropped into the reaction liquid. Furthermore, it is desirable that the position of the tip of the dropping port is a position where stirring is sufficiently performed, such as in the vicinity of the stirring blade, and the dripping material can quickly diffuse into the reaction solution.

  The addition time of silicon alkoxide and basic catalyst (the time from the start of addition to the end of addition) is a very important factor in producing particles having a narrow particle size distribution. If this addition time is too short, the particle size distribution range tends to be widened. Conversely, if it is too long, stable particle growth cannot be achieved. Therefore, in order to obtain silica particles with a narrow particle size distribution width and uniform particle size, it is necessary to select and employ an addition time suitable for the growth of the particles. In particular, in order to produce sol-gel silica particles having good monodispersity, it is preferable to supply a raw material such as silicon alkoxide at a discharge linear velocity of 30 mm / s to 1000 mm / s. From such a viewpoint, the addition time is preferably in the range of 0.2 to 8 hours per desired particle diameter of 100 nm.

  The reaction temperature is not particularly limited as long as the reaction of the sol-gel method proceeds promptly according to the type of raw material used, and can be appropriately selected according to the particle size of the target silica particles. Good. When silica particles having an average particle diameter of 0.05 to 2 μm are obtained, the reaction temperature may be appropriately selected within the range of −10 to 60 ° C.

  In order to advance the reaction of the sol-gel method with certainty, after the dropping of the silicon alkoxide and the basic catalyst is completed, ripening (a period of time is required until the next step) may be performed. In this case, the aging temperature is preferably about the same as the reaction temperature, that is, −10 to 60 ° C., and the aging time is preferably 0.25 to 5 hours.

  In order to obtain silica particles having a desired particle size, a method such as adding silicon alkoxide and a basic catalyst again after aging to grow the particle size of the silica particles may be used.

<Silica particle dispersion>
By the method described above, a silica particle dispersion liquid having an average particle diameter of 0.05 to 2.0 μm by a laser diffraction / scattering method manufactured by a sol-gel method is obtained. In this dispersion, the silica particles are present in a dispersed state in a mixed solvent composed of the polar solvent used and an alcohol generated by hydrolysis of silicon alkoxide.

  In the above dispersion, the silica particles are well monodispersed without substantially forming adhesion particles or agglomerates, but due to local excessive reaction progress, coarse independent primary particles (particle size exceeding 5 μm) Hereinafter, this is abbreviated as “coarse independent primary particles”). Specifically, coarse independent primary particles are contained in an amount of about 15 to 1000 ppm with respect to the silica particles, and if they remain in the final silica powder as described above, there is a problem of a decrease in fluidity of the resin composition. cause.

  When the ratio of the silica particles contained in the silica dispersion is too large, the viscosity of the dispersion becomes high and handling becomes difficult. On the other hand, if the proportion of silica particles in the dispersion is too small, the amount of silica particles obtained in one reaction is reduced, which is uneconomical. From such a viewpoint, the concentration of the silica particles in the obtained silica particle dispersion is preferably 1 to 40% by mass, and particularly preferably 2 to 25% by mass. Therefore, it is preferable to adjust the use amount of a polar solvent, particularly a polar solvent other than water, so that the concentration of the silica particles is adjusted to the above range. If there are too many silica particles in the dispersion obtained by the sol-gel reaction and handling is difficult, etc., before the dispersion filtration step described below, or as necessary It is preferable to adjust the concentration by adding a polar solvent before the surface treatment step.

<Filtration process>
In the method of this embodiment, the silica particle dispersion obtained after the sol-gel reaction is filtered by a wet method to remove the coarse independent primary particles contained therein. That is, by filtering the silica dispersion, if the coarse independent primary particles, further adhesion particles and agglomerates are generated on the filter medium together with the reaction residue and the like, these are also separated.

  As a filter medium, a filter having a mesh opening of 5 μm or less can be used without particular limitation, and a filter having a mesh opening of 3 μm or less can be preferably used. If the aperture is too small, not only will the filterability be reduced, but the average particle size of the silica particles to be filtered will also vary from the above range, so depending on the average particle size of the target powder, The lower limit is usually 1 μm.

  The material of the filter is not particularly limited, and examples thereof include resin (polypropylene, PTFE, etc.) and metal. From the viewpoint of preventing metal impurities from mixing, it is preferable to use a resin filter.

  As a method of removing coarse independent primary particles, there is a method of obtaining a sol-gel silica powder and then sieving it by a dry method as a final step. However, if these coarse particles of several μm size are removed with a dry sieve, clogging will occur. It is difficult to carry out industrially due to poor efficiency.

  Moreover, although the method of disperse | distributing a sol-gel silica powder to a solvent again to make a dispersion liquid and performing wet filtration is also mentioned, In this case, it will pass through the process of collect | recovering silica particles and drying again. In the sol-gel method, in the step of solid-liquid separation, the step of drying, or the step of firing as necessary, agglomerates in which silica particles are strongly agglomerated are easily produced, and the production of the agglomerates is suppressed, In order to easily recover the solid content from the dispersion by filtration, it is necessary to provide a coagulation step described later again. In any case, it is complicated, and increasing the number of processes in this way not only increases the risk of contamination from the environment, but also affects productivity, which is not efficient.

<Surface treatment process>
In producing the sol-gel silica powder of this embodiment, at least one surface treatment selected from the group consisting of a silicone oil, a silane coupling agent, and a silazane is used as a dispersion before coagulating a silica particle dispersion described later. An agent may be added to perform surface treatment.

  By performing the surface treatment, the solid-liquid separation step described later can be performed efficiently. Moreover, since it can suppress the production | generation of a firm aggregate at the time of drying, the obtained silica particle can be used for various uses, without performing a special crushing process.

  The surface treatment process may be performed before the coagulation process in the dispersion after the sol-gel reaction, and may be either before or after the filtration process of the dispersion, but is dispersed in that the coarse independent primary particles are accurately reduced. It is preferable to carry out before the liquid filtration step. By doing so, agglomerates and surface treatment agent residues generated during the surface treatment in the step can also be removed in the dispersion filtration step.

  As the silicone oil, known silicone oils usually used for the surface treatment of silica particles can be used without particular limitation, and can be appropriately selected according to the required performance of the surface-treated silica particles. , Use it.

  Specific examples of the silicone oil include, for example, dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, alkyl-modified silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, Examples thereof include methacryl-modified silicone oil, polyether-modified silicone oil, and fluorine-modified silicone oil.

  The usage ratio of the silicone oil is not particularly limited, but if it is too small, the surface treatment becomes insufficient, and if it is too large, the post-treatment is complicated, so 0.05 to 80 parts by mass with respect to 100 parts by mass of the silica particles to be used. Part, preferably 0.1 to 60 parts by mass.

  As the silane coupling agent, a known silane coupling agent usually used for surface treatment can be used without particular limitation, and is appropriately selected according to the performance of the surface-treated silica particles required. And use it.

  Specific examples of the silane coupling agent include, for example, methyltrimethoxysilane, methyltriethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloyloxy. Propyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-acryloyloxytrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane N-phenyl-3-aminopropyltrimethoxysilane, N, N-dimethyl-3-aminopropyltrimethoxysilane, N, N-diethyl-3-aminopropyltrimethoxysilane, 4-styryltrimethoxysilane, etc. Can be mentioned.

  The use ratio of the silane coupling agent is not particularly limited. However, if the amount is too small, the surface treatment becomes insufficient, and if the amount is too large, the post-treatment becomes complicated. It is preferable to set it as a mass part, and it is more preferable to set it as 0.1-40 mass parts.

  As said silazane, the well-known silazane normally used for surface treatment can be used without a restriction | limiting in particular.

  Specific examples of silazane include tetramethyldisilazane, hexamethyldisilazane, heptamethyldisilazane, and the like. Among the above, hexamethyldisilazane is preferably used because of its good reactivity and good handling.

  The amount of silazane used is not particularly limited, but if it is too small, the surface treatment becomes insufficient, and if it is too large, the post-treatment becomes complicated, so 0.1 to 150 masses with respect to 100 mass parts of silica particles to be used. Part, preferably 1 to 120 parts by mass.

  Said surface treating agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  Among the surface treatment agents as described above, it is preferable to use at least one selected from the group consisting of a silane coupling agent and a silazane because the fluidity of the obtained surface-treated silica particles is good, and silazane is used. More preferably.

  The method for adding the surface treatment agent is not particularly limited. When the surface treating agent is a liquid having a low viscosity at normal temperature and pressure, it may be dropped into the dispersion. When the surface treatment agent is a high-viscosity liquid or solid, it can be added in the same manner as in the case of a low-viscosity liquid after it is added to an appropriate organic solvent to form a solution or dispersion. As an organic solvent used here, the same thing as the said polar solvent can be mentioned. Furthermore, when the surface treatment agent is in a gaseous state, it can be added by blowing it into the liquid so as to form a fine foam.

  The treatment temperature when performing the surface treatment may be determined in consideration of the reactivity of the surface treatment agent to be used. However, if the treatment temperature is too low, the reaction proceeds slowly, and if too high, the operation is complicated. It is preferable to set it as 10-100 degreeC, and it is more preferable to set it as 20-80 degreeC.

  The treatment time for performing the surface treatment is not particularly limited, and may be determined in consideration of the reactivity of the surface treatment agent to be used. Considering both sufficient progress of the surface treatment reaction and shortening the process time, the treatment time is preferably 0.1 to 48 hours, more preferably 0.5 to 24 hours.

<Coagulation process>
In the method of this embodiment, coagulation is performed after the dispersion is filtered.

  The coagulation step is performed in a state where a coagulant composed of at least one compound selected from the group consisting of carbon dioxide, ammonium carbonate, ammonium hydrogen carbonate and ammonium carbamate is added to the dispersion. By adding a coagulant as described above to the dispersion, weak aggregates of silica particles are formed in the dispersion. This agglomerate can be stably present in the dispersion due to the presence of the coagulant or derivative thereof present in the dispersion, and therefore can be easily recovered by filtration.

  Although a technique for forming an aggregate of silica particles by adding a metal salt to a dispersion of silica particles is known, according to this method, for example, when sodium salt, potassium salt, or the like is used, these are added to the obtained silica particles. There is a possibility that a metal element component constituting the salt of the product is mixed, and a cleaning (purification) operation for removing this is necessary, which is industrially disadvantageous. In addition, the cohesiveness becomes strong, and there is a possibility that the sol-gel silica powder may remain as coarse particles without being broken into primary particles by a simple crushing treatment.

  On the other hand, since the coagulant used in the present embodiment is easily decomposed and removed by slight heating, there is an advantage that high-purity silica particles can be easily produced. According to the method of the present embodiment, for example, the content ratio of sodium element in the obtained silica particles can be 100 ppm or less, and more preferably 10 ppm or less.

  The use ratio and addition method of the coagulant can be set as follows according to the type of coagulant used. The use ratio of the coagulant is set by considering the balance between the degree of formation of weak aggregates of silica particles in the dispersion and the waste of using an excessively large amount of raw material. The mass of the silica particles as a reference for the use ratio of the coagulant in the following is a conversion value when it is assumed that the silicon alkoxide used is all hydrolyzed and polycondensed to form silica particles.

  When carbon dioxide is used as the coagulant, the use ratio is preferably 0.005 parts by mass or more with respect to 100 parts by mass of silica particles contained in the dispersion, It is more preferable to set it as a mass part. The more preferable usage rate of carbon dioxide when the surface treatment is not performed on the silica particles is 0.05 parts by mass or more and 0.05 to 300 parts by mass with respect to 100 parts by mass of the silica particles. Particularly preferred is 0.25 to 200 parts by mass. On the other hand, the more preferable usage rate of carbon dioxide in the case where the surface treatment is performed on the silica particles is 15 parts by mass or more with respect to 100 parts by mass of the silica particles, and particularly preferably 15 to 300 parts by mass, It is especially preferable to set it as 17-200 mass parts.

  Examples of the method of adding carbon dioxide include a method of blowing into a dispersion in a gaseous state, a method of adding in a solid state (dry ice), etc., but adding in a solid state is easy to operate. Therefore, it is preferable.

  When ammonium carbonate, ammonium hydrogen carbonate or ammonium carbamate is used as the coagulant, the proportion used is 0.001 part by mass or more with respect to 100 parts by mass of silica particles contained in the dispersion. Is preferable, and 0.001 to 80 parts by mass is more preferable. In the case where the surface treatment is not performed on the silica particles, a more preferable usage ratio of ammonium carbonate, ammonium hydrogen carbonate or ammonium carbamate is 0.001 to 15 parts by mass with respect to 100 parts by mass of the silica particles. It is especially preferable to set it as 001-10 mass parts. On the other hand, the more preferable usage rate of ammonium carbonate, ammonium hydrogen carbonate or ammonium carbamate when surface treatment is performed on silica particles is 15 parts by mass or more with respect to 100 parts by mass of silica particles, and 15 to 80 masses. Part of which is particularly preferably 17 to 60 parts by weight, and more preferably 20 to 50 parts by weight.

  Ammonium carbonate, ammonium hydrogen carbonate or ammonium carbamate may be added in a solid state or in a solution state dissolved in a suitable solvent. The solvent used in the case of adding these in a solution state is not particularly limited as long as it dissolves them, but water is used from the viewpoint of high dissolving ability and easy removal after filtration. It is preferable to use it. The concentration of the ammonium carbonate, ammonium hydrogen carbonate or ammonium carbamate solution is not particularly limited as long as they are in a range in which they can be dissolved. However, if the concentration is too low, the amount of the solution used increases, which is uneconomical. %, Preferably 5 to 12% by mass.

  The coagulant may be used alone or in combination of two or more.

  In particular, a mixture of ammonium hydrogen carbonate and ammonium carbamate, which is commercially available as so-called “ammonium carbonate”, can be used as it is or as a solution in an appropriate solvent. In this case, the total use ratio of ammonium hydrogen carbonate and ammonium carbamate, the type of solvent used when adding this as a solution, and the concentration of the solution are ammonium carbonate, ammonium hydrogen carbonate or ammonium carbamate. As described above.

  As the coagulant in this embodiment, it is preferable to use at least one selected from the group consisting of ammonium hydrogen carbonate and ammonium carbamate, more preferably ammonium hydrogen carbonate, and particularly ammonium hydrogen carbonate in an aqueous solution. It is preferable to add as.

  The pH of the silica particle dispersion at the time of adding the coagulant is set by selecting a pH region in which the coagulant does not undesirably decompose in the dispersion and the effects of this embodiment can be effectively exhibited. It is desirable. From such a viewpoint, the pH of the dispersion is preferably in the alkaline region, more preferably 9 or more.

  The temperature of the silica particle dispersion when adding the coagulant is desirably set by selecting a temperature at which weak aggregates of silica particles generated by the addition of the coagulant can stably exist. From such a viewpoint, the temperature of the dispersion liquid is preferably −10 to 60 ° C., more preferably 10 to 40 ° C., which is the same as the reaction temperature in the sol-gel reaction.

  It is preferable to perform aging after the addition of the coagulant, that is, to leave a certain interval before filtration in the next step. By aging after the addition of the coagulant, formation of the above-mentioned weak aggregates of silica particles is promoted, which is preferable. A longer aging time is better, but too long is uneconomical. On the other hand, if the aging time is too short, the formation of weak aggregates of silica particles becomes insufficient. Therefore, the aging time is preferably 0.5 to 72 hours, particularly preferably 1 to 48 hours. The temperature of the dispersion during the aging is not particularly limited, and can be carried out in the same temperature range as the preferred temperature during the addition of the coagulant, if it is carried out at the same temperature as when the coagulant was added. It ’s enough.

<Separation process>
The next step in the method of this embodiment is a separation step in which the silica particles are recovered by filtration from the dispersion after adding the coagulant and preferably aging as described above.

  Silica particles in which weak aggregates are formed by the addition of the coagulant can be easily recovered by separating the solid and liquid as a filtrate by filtration. The filtration method is not particularly limited, and known methods such as vacuum filtration, pressure filtration, and centrifugal filtration can be applied.

  The filter paper, filter, filter cloth, etc. (hereinafter collectively referred to as “filter paper”) used for filtration can be used without particular limitation as long as they are industrially available. What is necessary is just to select suitably according to the scale of an apparatus (filter). According to the present embodiment, since the primary particles are weakly aggregated by the addition of the coagulant, the pore diameter of the filter paper or the like may be much larger than the primary particle diameter. In the case of 01 to 5 μm silica particles, for example, a pore diameter of about 5 μm is sufficient. As described above, since the filter paper or the like has a large hole diameter, it can be quickly filtered.

  The silica particles are recovered as a cake by filtration.

  When an aqueous ammonium hydrogen carbonate solution was used as a coagulant in the above coagulation step, the resulting cake was used in a sol-gel reaction by rinsing with an appropriate solvent such as water or alcohol. The solvent, the basic catalyst, and the unreacted surface treatment agent can be decomposed or removed.

<Drying process>
Next, the silica particles recovered by the separation step are dried in this step.

  In the present embodiment, when the cake of silica particles recovered as described above is dried at a temperature of 35 ° C. or higher, the disintegration property is further improved. Therefore, the drying temperature in the drying process of the present embodiment is preferably set to a temperature of 35 ° C. or higher. By heating at this temperature, the coagulant remaining in the cake without being removed by the above filtration, rinsing or the like can be easily removed by thermal decomposition. This is also one of the great advantages of this embodiment.

  The drying method is not particularly limited, and a known method such as blow drying or drying under reduced pressure can be employed. However, as a result of studies by the present inventors, it has become clear that drying under reduced pressure tends to be more easily crushed than drying under atmospheric pressure, and therefore it is preferable to employ reduced-pressure drying. .

  Increasing the temperature during drying is advantageous from the viewpoint of the decomposition efficiency of the coagulant and silica particles that are more easily crushed. However, if the drying temperature is too high, aggregates may be generated due to reactive substituents introduced on the surface of the silica particles by the surface treatment, which is not preferable. Therefore, in order to balance the above, the drying temperature is preferably 35 to 200 ° C, more preferably 50 to 200 ° C, particularly preferably 80 to 200 ° C, and 120 to 200 ° C. It is particularly preferable that

  The drying time is not particularly limited, but the silica particles can be sufficiently dried by setting the drying time to about 2 to 48 hours.

  In this embodiment, it is also possible to continuously remove the dispersion medium from the silica particle dispersion liquid through concentration and drying. For example, silica particles from which the dispersion medium has been removed from the silica particle dispersion can be obtained directly by performing a method of volatilizing the dispersion medium by heating concentration or vacuum concentration of the silica particle dispersion. In this case, when removing the dispersion medium by heating, the salt derived from the specific coagulant may be lost. In such a case, the specific coagulant is added to the concentrate of the silica dispersion during concentration and drying. May be added as appropriate so that the salt does not disappear in the concentrate.

  In the present embodiment, the silica particles obtained by the above method are obtained as a dry powder in the form of an aggregate in which individual particles are aggregated with a weak force. And the silica particle which does not produce | generate the agglomerate which is difficult to crush, and is excellent in the dispersibility which can be easily crushed. Without any special crushing treatment, it can be easily crushed and dispersed uniformly in the resin or solvent due to the share of the disperser when it is dispersed in the resin or solvent. Even in the measurement of the remaining amount on the screen by the wet sieving method using an electroforming screen, the silica powder is easily crushed by a dispersion treatment by ultrasonic irradiation with an output of about 40 W for 10 minutes in a 5 mass% aqueous solution of silica powder.

<Baking process>
In the dried silica particles, the dispersion medium absorbed in the particles is not completely removed, silanol groups remain, and pores exist. In order to remove the dispersion medium in the particles to a high degree and crush silanol groups to obtain solid silica, it is preferable to further perform a firing treatment depending on the application. That is, the silica particles treated in the firing step are preferable not only because the amount of silanol groups on the particle surface is reduced, but also from the point that the dispersion medium remaining in the particles is removed. When the solvent remaining in the particles is used as a resin filler, when heated, bubbles and the like are generated, causing a decrease in yield. In particular, it becomes prominent in semiconductor sealing material applications and liquid crystal sealant applications having a high filling rate. Therefore, it is preferable to provide the said process especially in manufacture of the silica particle used for a semiconductor sealing material use or a liquid-crystal sealing agent use.

  If the calcination temperature during the calcination treatment is too low, it is difficult to remove the dispersion medium component, and if it is too high, silica particles are fused, so that the calcination temperature is preferably 300 to 1300 ° C, more preferably 600 to 1200 ° C. .

  The firing time is not particularly limited as long as the remaining dispersion medium is removed, but if it is too long, the productivity is lowered. Therefore, after raising the temperature to the intended firing temperature, 0.5 to 48 hours, more preferably It is sufficient to hold and calcinate for 2 to 24 hours.

  The atmosphere at the time of firing is not particularly limited, and can be performed under an inert gas such as argon or nitrogen, or in an air atmosphere.

  The silica particles obtained from the firing step are also obtained as a dry powder in the form of an aggregate in which individual particles are aggregated with a weak force as described above.

<< Silica particles >>
The sol-gel silica powder of the present embodiment produced as described above does not contain coarse independent primary particles excessively grown at the time of synthesis or agglomerates in which the particles are strongly aggregated, and the silica powder 5 mass% ultrasonic dispersion liquid In (output 40 W, irradiation time 10 minutes), the residual amount on the screen when sieving by the wet sieving method using an electroformed sieve having an opening of 5 μm is 10 ppm or less.

  In this embodiment, the sol-gel silica powder can be used for various applications without performing a special crushing treatment. However, in order to further reduce the agglomerates according to the purpose, a known solution is used. It is also possible to use after crushing by crushing means. By performing the crushing treatment, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm can be reduced to 5 ppm or less.

  Examples of known crushing means include a ball mill and a jet mill. In addition, when using in a resin or solvent without using a known crushing means, by using a high shear disperser, the particles can be crushed simultaneously with the dispersion in the resin or solvent. It can be carried out.

  Hereinafter, although an example of this embodiment is given and explained concretely, the present invention is not restricted at all by these examples.

  Hereinafter, evaluation methods of physical properties used for evaluation in Examples and Comparative Examples are as follows.

(Remaining amount on sieve by wet sieving method using electroformed sieve)
The measurement samples were prepared by weighing 5 g of sol-gel silica powder (20 g in total) in four 200 mL resin cups with an electronic balance, and adding 95 ml of distilled water. Each sample was dispersed under the condition of 40 W for 10 minutes using an ultrasonic homogenizer (manufactured by BRANSON, Sonifier 250), and then the entire amount (20 g for sol-gel silica powder) was opened at 5 μm square holes or 3 μm square holes. Wet sieving was carried out using an electroformed sieve (manufactured by Iida Seisakusho, φ75 mm × 40 mmH), and the residue on the sieve mesh was quantified.

(Average particle size, coefficient of variation, and coarse particle amount of 5 μm or more in the laser diffraction scattering method)
About 0.1 g of sol-gel silica powder is weighed on a 50 mL glass bottle with an electronic balance, about 40 ml of distilled water is added, and dispersed using an ultrasonic homogenizer (BRANSON, Sonifier 250) under the conditions of 40 W and 10 minutes. The average particle size (μm) and coefficient of variation of the sol-gel silica powder were measured with a laser diffraction scattering method particle size distribution measuring device (LS-230, manufactured by Beckman Coulter, Inc.). The average particle diameter (μm) here means a volume-based cumulative 50% diameter (μm).

  Moreover, the presence or absence of a signal of 5 μm or more was confirmed for coarse particles of 5 μm or more in the laser diffraction scattering method.

(Sphericity)
The shape of the silica particles was observed with SEM (manufactured by JEOL Datum, JSM-6060), and the sphericity was determined. Specifically, 1000 or more silica particles were observed, and the sphericity of each particle was measured using an image processing program (Soft Imaging System GmbH, AnalySIS), and the average was obtained. The sphericity was calculated by the following formula.
Sphericality = 4π × (area) / (perimeter) ²
(Α dose)
The α dose was measured using a low-level α ray measuring device (LACS-4000M, manufactured by Sumika Chemical Analysis Center). The measurement was performed with a sample area of 1000 cm ² .

(Amount of metal impurities)
U and Th: The sol-gel silica powder was dissolved by heating with hydrofluoric acid (a mixed solution of hydrofluoric acid and nitric acid 5: 1), and the residue was measured by ICP mass spectrometry (Agilent Technology, Agilent 4500).

  Fe, Al, Na, K, Ca, Cr, Ni, Ti: Sol-gel silica powder was dissolved by heating with hydrofluoric acid, and the residue was measured by an ICP emission analysis method (manufactured by Thermo Scientific, iCAP 6500 DUO).

Cl ⁻ : sol-gel silica powder is mixed with ultrapure water and heat-treated under pressure. The Cl ⁻ concentration in the solution after treatment was measured by an ion chromatograph method (ICS-2100, manufactured by Nippon Dionex).

(Measurement of specific surface area)
Using a specific surface area measuring device SA-1000 manufactured by Shibata Kagaku Kikai Kogyo Co., Ltd., the BET one-point method based on the amount of nitrogen adsorption was used.

(Silanol group amount on the surface)
The sample was left in an atmosphere of 25 ° C. and 80% relative humidity for 45 days, and then the sample was dried at 120 ° C. for 12 hours. This material was dispersed in a methanol solvent, and the moisture content was measured using a Karl Fischer moisture meter MKS-210 manufactured by Kyoto Electronics Industry Co., Ltd. As a titration reagent, “HYDRANAL COMPOSITE 5K” (manufactured by Riedel-deHaen) was used.

The amount of surface silanol groups was calculated from the water content measured by the above method and the specific surface area according to the following formula.
Surface silanol groups (number ^/ nm 2) = 668.9 × water content (mass%) ÷ specific surface area ^(m 2 / g)
(Flow mark)
25 g of sol-gel silica fine powder was added to 25 g of bisphenol A + F type mixed epoxy resin (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., ZX-1059) and kneaded by hand. The kneaded resin composition was preliminarily kneaded with a rotating / revolving mixer (manufactured by THINKY, Awatori Netaro AR-500) (kneading: 1000 rpm, 8 minutes, defoaming: 2000 rpm, 2 minutes). The pre-kneaded resin composition was kneaded using three rolls (manufactured by IMEX, BR-150HCV roll diameter φ63.5). The kneading conditions were such that the kneading temperature was room temperature, the distance between rolls was 20 μm, and the number of kneading was 5 times.

  Two glass sheets were stacked in advance so as to have a gap of 30 μm and heated to 100 ° C., and the prepared kneaded resin composition was subjected to a high temperature penetration test. Observation was made until the kneaded resin composition reached 20 mm or until the penetration stopped, and the presence or absence of a flow mark was visually evaluated.

(Coarse amount of 5 μm and 3 μm or more in the Coulter counter method)
Prepare five 50 mL glass bottles, weigh about 0.1 g of sol-gel silica powder with an electronic balance, add about 40 ml of distilled water, and use an ultrasonic homogenizer (manufactured by BRANSON, Sonifier 250) for 40 W for 10 minutes. The sample was dispersed under the conditions of The particle diameter of the sol-gel silica powder in each sample was measured using a Coulter counter (manufactured by Beckman Coulter, Multisizer 3) with an aperture diameter of 30 μm. At this time, the number of measurement at one time is about 50,000, the measurement is performed five times, the total number of measurements (about 250,000) is measured, the number of particles having a particle size of 5 μm or more, and the particle size of 3 μm or more The number of particles was calculated, and the amount of each coarse particle (ppm) relative to the total number measured.

Example 1
Using a reactor with a Max Blend blade (blade diameter 345 mm) in a jacketed glass-lined reactor (inner diameter 1200 mm) with an internal volume of 1000 L, methanol 75 kg, isopropanol 30 kg and aqueous ammonia (25 mass%) as reaction media 25 kg was charged (reaction medium amount: 150 L), the reaction temperature was set to 40 ° C., and the mixture was stirred at 52 rpm. Then, a mixture of 3.0 kg of tetraethoxysilane, 7.0 kg of methanol, and 2.0 kg of isopropanol as raw materials was added to the reaction medium to prepare silica seed particles. Next, 350 kg of tetramethoxysilane and 100 kg of methanol were fed into the reaction medium at a discharge linear velocity of 51 mm / s, and 150 kg of ammonia water (25% by mass) was simultaneously fed at a rate of 0.8 kg / min. Silica particles were grown and synthesized. The dimensionless mixing time nθm at this time was 78.

  After the supply was completed, stirring was continued for 1 hour, and then the silica particle dispersion was subjected to wet filtration using a polypropylene filtration filter having an opening of 3 μm to remove coarse particles. Thereafter, 3 kg of dry ice was added and left for 20 hours. After 20 hours, the sol-gel silica particles had settled, and after using a quantitative filter paper (retained particle size of 6 μm) and solid-liquid separation, a concentrate of 190 kg (silica concentration 74 mass%) was obtained. The filtrate was transparent and no filtrate leakage was observed. Furthermore, it dried under reduced pressure at 100 degreeC for 15 hours, and obtained 132 kg of sol-gel silica powder. Subsequently, baking was performed at 800 ° C. for 10 hours in an air atmosphere. There was no appearance of sintering after firing, and 124 kg of sol-gel silica powder was obtained.

  The obtained sol-gel silica powder had an average particle diameter of 0.74 μm, a coefficient of variation of 20.7% and a sphericity of 0.96, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was 5 ppm and 6 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was less than 4 ppm and 8 ppm.

α dose is 0.002 c / cm ² · h, metal impurity amount is 0.02 ppb for U, 0.02 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.2 ppm for Na, and 0 for K 0.0 ppm, Ca was 0.1 ppm, Cr was 0.0 ppm, Ni was 0.0 ppm, Ti was 0.0 ppm, and Cl ⁻ was 0.0 ppm. The specific surface area was 4 m ² / g, the surface silanol group amount was 3 / nm ² , and no flow mark was observed.

Example 2
The sol-gel silica powder obtained in Example 1 was crushed using a jet mill. The obtained sol-gel silica powder had an average particle size of 0.73 μm, a coefficient of variation of 19.1% and a sphericity of 0.96, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was both less than 5 ppm (less than the lower limit of determination). The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was less than 4 ppm.

α dose is 0.002c / cm ² · h, metal impurity amount is 0.02ppb for U, 0.02ppb for Th, 0.4ppm for Fe, 2.1ppm for Al, 0.2ppm for Na, K is 0 0.0 ppm, Ca was 0.1 ppm, Cr was 0.0 ppm, Ni was 0.1 ppm, Ti was 0.0 ppm, and Cl ⁻ was 0.0 ppm. The specific surface area was 4 m ² / g, the surface silanol group amount was 3 / nm ² , and no flow mark was observed.

Example 3
The sol-gel silica powder obtained in Example 1 was crushed using a ball mill. The obtained sol-gel silica powder had an average particle size of 0.74 μm, a coefficient of variation of 21.6% and a sphericity of 0.95, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was both less than 5 ppm (less than the lower limit of determination). The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was less than 4 ppm.

α dose is 0.002 c / cm ² · h, metal impurity amount is 0.02 ppb for U, 0.02 ppb for Th, 0.2 ppm for Fe, 0.4 ppm for Al, 0.2 ppm for Na, and 0 for K 0.1 ppm, Ca 0.1 ppm, Cr 0.0 ppm, Ni 0.1 ppm, Ti 0.0 ppm, and Cl ⁻ were 0.1 ppm. The specific surface area was 4 m ² / g, the surface silanol group amount was 3 / nm ² , and no flow mark was observed.

Example 4
In Example 1, the raw material discharge linear velocity was changed to 263 mm / s. Otherwise, sol-gel silica particles were synthesized and evaluated in the same manner as in Example 1. The sol-gel silica powder obtained after firing was 122 kg.

  The obtained sol-gel silica powder had an average particle diameter of 0.75 μm, a coefficient of variation of 20.3%, a sphericity of 0.97, and no coarse particles of 5 μm or more were detected in the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was less than 5 ppm (less than the lower limit of determination) and 6 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was less than 4 ppm and 8 ppm.

α dose is 0.001 c / cm ² · h, metal impurity amount is 0.02 ppb for U, 0.01 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.1 ppm for Na, 0 for K 0.0 ppm, Ca was 0.1 ppm, Cr was 0.0 ppm, Ni was 0.0 ppm, Ti was 0.0 ppm, and Cl ⁻ was 0.1 ppm. The specific surface area was 4 m ² / g, the surface silanol group amount was 3 / nm ² , and no flow mark was observed.

Example 5
In Example 1, the dry ice was changed to 3 kg of ammonium bicarbonate. Otherwise, sol-gel silica particles were synthesized and evaluated in the same manner as in Example 1. The sol-gel silica powder obtained after firing was 122 kg.

  The obtained sol-gel silica powder had an average particle size of 0.72 μm, a coefficient of variation of 18.1% and a sphericity of 0.97, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was 5 ppm and 6 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was 5 ppm and 8 ppm.

The α dose is 0.001 c / cm ² · h, and the metal impurity amount is 0.01 ppb for U, 0.01 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.1 ppm for Na, and 0 for K. 0.1 ppm, Ca 0.1 ppm, Cr 0.0 ppm, Ni 0.0 ppm, Ti 0.0 ppm, and Cl ⁻ were 0.0 ppm. The specific surface area was 4 m ² / g, the surface silanol group amount was 3 / nm ² , and no flow mark was observed.

Example 6
In Example 1, the raw material after producing silica seed particles was changed to 90 kg of tetramethoxysilane, 25 kg of methanol, and 40 kg of aqueous ammonia (25% by mass). Otherwise, sol-gel silica particles were synthesized and evaluated in the same manner as in Example 1. The sol-gel silica powder obtained after firing was 35 kg.

  The obtained sol-gel silica powder had an average particle size of 0.43 μm, a coefficient of variation of 14.8%, a sphericity of 0.98, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was both less than 5 ppm (less than the lower limit of determination). The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was less than 4 ppm.

The alpha dose is 0.002 c / cm ² · h, and the amount of metal impurities is 0.01 ppb for U, 0.01 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.1 ppm for Na, and 0 for K 0.0 ppm, Ca was 0.1 ppm, Cr was 0.0 ppm, Ni was 0.0 ppm, Ti was 0.0 ppm, and Cl ⁻ was 0.0 ppm. The specific surface area was 7 m ² / g, the amount of surface silanol groups was 3 / nm ² , and no flow mark was observed.

Example 7
In Example 1, the reactor was changed to 4000 L, and the raw material after producing silica seed particles was changed to 1750 kg of tetramethoxysilane, 500 kg of methanol, and 750 kg of aqueous ammonia (25% by mass). Otherwise, sol-gel silica particles were synthesized and evaluated in the same manner as in Example 1. The sol-gel silica powder obtained after firing was 674 kg.

  The obtained sol-gel silica powder had an average particle size of 1.14 μm, a coefficient of variation of 22.4% and a sphericity of 0.96, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the screen by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was 6 ppm and 8 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was 8 ppm and 12 ppm.

α dose is 0.001c / cm ² · h, metal impurity amount is 0.01ppb for U, 0.02ppb for Th, 0.1ppm for Fe, 0.1ppm for Al, 0.2ppm for Na, K for 0 0.1 ppm, Ca 0.1 ppm, Cr 0.0 ppm, Ni 0.0 ppm, Ti 0.0 ppm, and Cl ⁻ were 0.0 ppm. The specific surface area was 3 m ² / g, the surface silanol group amount was 3 / nm ² , and no flow mark was observed.

Example 8
In Example 1, the reactor was changed to 10000 L, and the raw material after producing silica seed particles was changed to 4200 kg of tetramethoxysilane, 1200 kg of methanol, and 1800 kg of aqueous ammonia (25 mass%). Otherwise, sol-gel silica particles were synthesized and evaluated in the same manner as in Example 1. The sol-gel silica powder obtained after firing was 1608 kg.

  The obtained sol-gel silica powder had an average particle size of 1.54 μm, a coefficient of variation of 24.3%, a sphericity of 0.96, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was 8 ppm and 10 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was 8 ppm and 16 ppm.

The alpha dose is 0.001 c / cm ² · h, and the amount of metal impurities is 0.01 ppb for U, 0.01 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.2 ppm for Na, and 0 for K 0.0 ppm, Ca was 0.1 ppm, Cr was 0.0 ppm, Ni was 0.0 ppm, Ti was 0.0 ppm, and Cl ⁻ was 0.1 ppm. The specific surface area was 2 m ² / g, the amount of surface silanol groups was 3 / nm ² , and no flow mark was observed.

Example 9
In Example 1, the firing step was not performed.

  The obtained sol-gel silica powder had an average particle size of 0.82 μm, a coefficient of variation of 21.4%, and a sphericity of 0.97, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was 5 ppm and 5 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was 4 ppm and 12 ppm.

α dose is 0.001 c / cm ² · h, metal impurity amount is 0.01 ppb for U, 0.02 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.3 ppm for Na, 0 for K 0.1 ppm, Ca 0.1 ppm, Cr 0.0 ppm, Ni 0.0 ppm, Ti 0.0 ppm, and Cl ⁻ were 0.0 ppm. The specific surface area was 5 m ² / g, the surface silanol group amount was 15 / nm ² , and no flow mark was observed.

Comparative Example 1
In Example 1, solid-liquid separation was performed immediately after the synthesis of sol-gel silica without adding dry ice. Otherwise, sol-gel silica particles were synthesized and evaluated in the same manner as in Example 1. The filtrate was cloudy and a high concentration sol-gel silica dispersion flowed out. Furthermore, it dried under reduced pressure at 100 degreeC for 15 hours, and obtained 43 kg of sol-gel silica powder. Subsequently, baking was performed at 800 ° C. for 10 hours in an air atmosphere. After firing, it was sintered to form hard agglomerated particles, and 38 kg of sol-gel silica powder was obtained.

  The obtained sol-gel silica powder had an average particle size of 0.94 μm, a coefficient of variation of 34.2% and a sphericity of 0.82, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was 80 ppm and 2400 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was 120 ppm and 2600 ppm.

α dose is 0.002 c / cm ² · h, metal impurity amount is 0.02 ppb for U, 0.02 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.2 ppm for Na, and 0 for K .0ppm, Ca is 0.1 ppm, Cr is 0.0 ppm, Ni is 0.0 ppm, Ti is 0.0 ppm, Cl ^- was 0.1 ppm. A specific surface area of 4 m ² / g, a surface silanol group amount of 3 / nm ² , and a flow mark were observed.

Comparative Example 2
In Example 1, the dispersion was not filtered. Otherwise, sol-gel silica particles were synthesized and evaluated in the same manner as in Example 1. The sol-gel silica powder obtained after firing was 120 kg.

  The obtained sol-gel silica powder had an average particle size of 0.75 μm, a coefficient of variation of 22.4% and a sphericity of 0.96, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amounts on the screen by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm were 20 ppm and 210 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was 25 ppm and 240 ppm.

The alpha dose is 0.002 c / cm ² · h, and the amount of metal impurities is 0.02 ppb for U, 0.01 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.1 ppm for Na, and 0 for K 0.0 ppm, Ca was 0.1 ppm, Cr was 0.0 ppm, Ni was 0.0 ppm, Ti was 0.0 ppm, and Cl ⁻ was 0.0 ppm. A specific surface area of 4 m ² / g, a surface silanol group amount of 3 / nm ² , and a flow mark were observed.

Comparative Example 3
In Example 6, solid ice was separated immediately after the synthesis of sol-gel silica without adding dry ice. Otherwise, sol-gel silica particles were synthesized and evaluated in the same manner as in Example 6. The filtrate was cloudy and a high concentration sol-gel silica dispersion flowed out. Furthermore, it dried under reduced pressure at 100 degreeC for 15 hours, and obtained 13 kg of sol-gel silica powder. Subsequently, baking was performed at 800 ° C. for 10 hours in an air atmosphere. After firing, it was sintered to form hard agglomerated particles, and 11 kg of sol-gel silica powder was obtained.

  The obtained sol-gel silica powder had an average particle diameter of 0.68 μm, a coefficient of variation of 36.7%, and a sphericity of 0.81, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was 260 ppm and 8900 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was 240 ppm and 10400 ppm.

The α dose is 0.001 c / cm ² · h, and the metal impurity amount is 0.01 ppb for U, 0.01 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.1 ppm for Na, and 0 for K. 0.1 ppm, Ca 0.1 ppm, Cr 0.0 ppm, Ni 0.0 ppm, Ti 0.0 ppm, and Cl ⁻ were 0.0 ppm. A specific surface area of ^7m 2 / g, surface silanol group amount three / nm ^2, also flow marks were observed.

Comparative Example 4
In Example 6, the dispersion was not filtered. Otherwise, sol-gel silica particles were synthesized and evaluated in the same manner as in Example 6. The sol-gel silica powder obtained after firing was 34 kg.

  The obtained sol-gel silica powder had an average particle size of 0.44 μm, a coefficient of variation of 15.2%, a sphericity of 0.98, and no coarse particles of 5 μm or more were detected by the laser diffraction scattering method. Moreover, the residual amount on the sieve by the wet sieving method using an electroformed sieve having an opening of 5 μm and an opening of 3 μm was 15 ppm and 200 ppm, respectively. The amount of coarse particles of 5 μm and 3 μm or more in the Coulter counter method was 20 ppm and 200 ppm.

The alpha dose is 0.002 c / cm ² · h, and the amount of metal impurities is 0.01 ppb for U, 0.01 ppb for Th, 0.1 ppm for Fe, 0.1 ppm for Al, 0.1 ppm for Na, and 0 for K .0ppm, Ca is 0.1 ppm, Cr is 0.0 ppm, Ni is 0.0 ppm, Ti is 0.0 ppm, Cl ^- was 0.0 ppm. A specific surface area of 7 m ² / g, a surface silanol group amount of 3 / nm ² , and a flow mark were observed.

（その他の実施形態）
上述の実施形態は本願発明の例示であって、本願発明はこれらの例に限定されず、これらの例に周知技術や慣用技術、公知技術を組み合わせたり、一部置き換えたりしてもよい。また当業者であれば容易に思いつく改変発明も本願発明に含まれる。

(Other embodiments)
The above-described embodiment is an exemplification of the present invention, and the present invention is not limited to these examples, and these examples may be combined or partially replaced with known techniques, common techniques, and known techniques. Also, modified inventions easily conceived by those skilled in the art are included in the present invention.

Claims (11)

The average particle size by laser diffraction scattering method is 0.05 μm or more and 2.0 μm or less, and the coefficient of variation indicating the spread of the particle size distribution is 40% or less,
In a dispersion in which an amount of 5% by mass in water was dispersed by ultrasonic waves under the conditions of an output of 40 W and an irradiation time of 10 minutes, when sieving by a wet sieving method using an electroforming sieve having an opening of 5 μm A sol-gel silica powder characterized by having a residual amount on a sieve of 10 ppm or less.   2. The sol-gel silica powder according to claim 1, wherein the residual amount on a sieve by a wet sieving method using an electroformed sieve having an opening of 3 μm is 10 ppm or less. The sol-gel silica powder according to claim 1 or 2, wherein the amount of silanol groups on the surface is 5 / nm ² or less. The sol-gel silica powder according to any one of claims 1 to 3, wherein the α dose is 0.002 c / cm ² · h or less.   The sol-gel silica powder according to any one of claims 1 to 4, wherein the U content is 0.1 ppb or less and the Th content is 0.1 ppb or less.   The Fe content is 10 ppm or less, the Al content is 10 ppm or less, the Na content is 5 ppm or less, the K content is 5 ppm or less, and the chloride ion content is 1 ppm or less. The sol-gel silica powder according to any one of the above.   The sol gel according to any one of claims 1 to 6, wherein the Ca content is 5 ppm or less, the Cr content is 5 ppm or less, the Ni content is 5 ppm or less, and the Ti content is 5 ppm or less. Silica powder. A production method for producing the sol-gel silica powder according to claim 1,
A dispersion preparing step of preparing a silica particle dispersion liquid in which silica particles having an average particle diameter of 0.05 μm or more and 2.0 μm or less by laser diffraction scattering method are dispersed in water by a sol-gel method;
A filtration step of wet-filtering the silica particle dispersion with a filter medium having an opening of 5 μm or less;
A coagulation step of coagulating the silica particles by adding a coagulant composed of at least one compound selected from the group consisting of carbon dioxide, ammonium carbonate, ammonium hydrogen carbonate and ammonium carbamate to the filtrate;
A separation step of separating the silica particles from the coagulation liquid;
A drying step of drying the separated silica particles. A method for producing a sol-gel silica powder.   Furthermore, the manufacturing method of the sol-gel silica powder of Claim 8 including the baking process which bakes the said silica particle.   A resin composition in which the sol-gel silica powder according to any one of claims 1 to 7 is dispersed.   The filler for semiconductor sealing materials consisting of the sol-gel silica powder of any one of Claim 1 to 7.