JP2008285406A - Silica spherical particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica spherical particle containing substantially no organic component, free from forming firm aggregation and capable of being easily dispersed in a resin, and the like, as submicron particles having uniform particle-size distribution. <P>SOLUTION: The silica spherical particle has 0.1-0.5 μm average particle diameter in an aqueous dispersion state and ≤26% particle size distribution coefficient S calculated by formula (I): S(%)=(particle diameter standard deviation/average particle diameter)×100 in the particle diameter range and satisfies formula (II): S(%)=aX+b, wherein X represents an average particle diameter (μm), a represents -10 to -6 and b represents 15-27. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to silica spherical particles. More specifically, the present invention relates to a spherical silica particle that is useful as a filler for electronic materials and that can be easily dispersed as submicron particles having a uniform particle size distribution in a resin or the like without having strong aggregation.

  Conventionally, metal oxide particles such as silica, titania, and alumina having an average particle diameter of 1 μm or less and a uniform particle size distribution are known to be useful as various fillers and abrasives. Then, there are many uses as a filler for electronic materials. In this field, there is a demand for particles for fillers having a particularly uniform particle size distribution due to the finer and more precise electronic components.

  Although metal oxide particles having an average particle size of 1 μm or less and a uniform particle size have existed so far, it is not easy to produce industrially.

  For example, it is possible to coarsely pulverize a natural mineral lump and further finely pulverize it into fine particles to obtain submicron particles. However, mixing of unpulverized material is unavoidable, and the particle size distribution becomes wide.

  A sol-gel method is known as a method for producing metal oxide fine particles. In this sol-gel method, a hydrolyzable metal compound is generally hydrolyzed in an aqueous medium containing alcohol and / or water, and the produced metal oxide particles have a desired size. And dispersed in an aqueous medium. In this state, the particles may be single particles of primary particles, or some particles may be aggregated. Particularly in the case of particles of 1 μm or less, the tendency to agglomerate is prominent and tends to agglomerate firmly.

  The hydrolyzed solution thus obtained is concentrated and dried to remove the solvent to obtain particle powder. In this drying treatment, a strong attractive force usually acts between the particles to cause secondary aggregation, and it is very difficult to unravel this aggregation. The above dry powder is again dispersed in a solvent and subjected to ultrasonic treatment, etc. to remove the settled particles, remove the supernatant, and obtain only particles having the desired particle diameter. It is difficult to cope with industrial scale.

  That is, so-called sub-micron metal oxide particles whose primary particle size has been strongly agglomerated (including primary agglomeration) once and whose particle diameter is 1 μm or less are agglomerated again in post-treatment such as conventional ultrasonic treatment. Is very difficult to solve. Further, if the primary particles have relatively small secondary agglomeration force with a particle size of 1 μm or more, for example, when used as a filler for a resin, a problem is caused by a share by kneading at the time of kneading into the resin. In some cases, submicron particles with a primary particle size of 1 μm or less are difficult to disaggregate due to the share at the time of kneading, and the metal oxide particles of the filler are not uniformly dispersed in the resin. Invite the situation. As a result, a desired filler addition effect cannot be obtained.

  On the other hand, as a method for solving such a problem, in order to reduce secondary aggregation, the particles are concentrated in a state where the particles are dispersed in the hydrolysis treatment liquid, and a dispersant such as ethylene glycol is added in the middle of the particles. A means for reducing the attractive force between particles generated on the surface may be used. It is possible to increase the particle size by hydrolyzing the hydrolyzable metal compound again using the concentrated liquid containing dispersed particles obtained here as a seed particle liquid. In this case, build-up is performed to a desired size by adding a dispersant such as ethylene glycol again at the time of concentration of the hydrolysis treatment liquid, and finally dry particles are obtained by solvent removal. In addition, attempts have been made to suppress secondary aggregation during drying by containing or coating an organic component such as a dispersant. Even with this method, submicron particles having a uniform particle size distribution can be obtained industrially. However, the particles obtained by such a method are unavoidable that organic components such as ethylene glycol used during the build-up remain inside or on the surface. The use in the affected area may cause a problem due to decomposition of the organic matter by the heat. Therefore, the actual situation is that the usage is very limited.

  Accordingly, there has been a demand for metal oxide submicron particles which do not contain extra organic components and have little aggregation.

  Under such circumstances, the present invention is substantially free of organic components useful as a filler for electronic materials, has no strong aggregation, and is a submicron particle having a uniform particle size distribution in a resin or the like. It is an object to provide spherical silica particles that can be easily dispersed.

  As a result of intensive studies to develop silica spherical particles having the above-mentioned properties, the present inventors have concentrated, dried, calcined the particle-dispersed reaction liquid obtained by the sol-gel method, and further wet-pulverized it. It discovered that the silica spherical particle which has a desired property was obtained by processing and drying, and came to complete this invention based on this knowledge.

That is, the present invention
(1) In the water dispersion state, the average particle size is in the range of 0.1 to 0.5 μm, and the formula (I) in the particle size region
S (%) = (standard deviation of particle diameter / average particle diameter) × 100 (I)
And the particle size dispersion coefficient S calculated by the formula (II) is 26% or less,
S (%) = aX + b (II)
[However, X is an average particle diameter (micrometer) and is 0.1-0.5, a is the number of -10--6, b is the number of 15-27. ]
And (2) the spherical silica particles described in the above item (1), which are formed by a sol-gel method.

  According to the present invention, silica that is useful as a filler for electronic materials, substantially free of organic components, has no strong aggregation, and can be easily dispersed as submicron particles having a uniform particle size distribution in a resin or the like. Spherical particles can be provided.

The spherical silica particles of the present invention have an average particle diameter in the range of 0.1 to 0.5 μm in the water dispersion state, and the formula (I) in the particle diameter region.
S (%) = (standard deviation of particle diameter / average particle diameter) × 100 (I)
And the particle size dispersion coefficient S calculated by the formula (II) is 26% or less,
S (%) = aX + b (II)
[However, X is an average particle diameter (micrometer) and is 0.1-0.5, a is the number of -10--6, b is the number of 15-27. ]
The particles satisfy the relationship.

The average particle size and standard deviation in the water dispersion state are values measured by the following method.
<Method for measuring average particle size and standard deviation of silica particles in water dispersion>
0.1 g of a sample is added to 50 ml of water and dispersed with an ultrasonic homogenizer with an output of 150 W for 10 minutes to prepare an aqueous dispersion of silica particles. Next, using a particle size analyzer (“MICROTRACK UPA” manufactured by Nikkiso Co., Ltd.), the particle size distribution of the silica particles in the aqueous dispersion is measured, and the average particle size and standard deviation are obtained.

  In the water dispersion state, the silica spherical particles satisfying the relational expressions (I) and (II) are particles having an average particle diameter of submicron and uniform particle diameter in the water dispersion state. Since silica particles do not have a strong aggregate, they can be easily dispersed in a resin or the like using a general kneader.

  The silica spherical particles of the present invention having the above properties can be efficiently produced by the method of the present invention described below.

  In the method for producing silica spherical particles of the present invention, the reaction solution containing silica particles obtained by the sol-gel method is concentrated, dried and fired, and then the fired powder containing agglomerates of primary particles is subjected to a wet solution. Silica spherical particles having the desired properties are obtained by crushing and then drying.

Examples of the reaction liquid containing silica particles obtained by the sol-gel method include, for example, the general formula (III)
MRn (III)
(In the formula, M represents a silicon atom, R represents a hydrolyzable group, n represents a valence of the silicon atom M, and a plurality of R may be the same or different.)
What was obtained by hydrolyzing the hydrolysable silicon compound represented by these can be mentioned preferably.

  In the general formula (III), the hydrolyzable group represented by R is not particularly limited as long as it is a group bonded to the silicon atom M and hydrolyzed. For example, a hydroxyl group, an alkoxyl group, an isocyanate group A halogen atom such as a chlorine atom, an oxyhalogen group, an acetylacetonate group, and the like. Among these, an alkoxyl group, particularly a lower alkoxyl group having 1 to 4 carbon atoms is preferable.

  Silica particles are often used as resin fillers, etc. Among the hydrolyzable silicon compounds represented by the general formula (III), examples of silicon compounds used as raw materials for particles include tetramethoxysilane, Examples include tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, and tetra-tert-butoxysilane. In the present invention, the hydrolyzable silicon compound represented by the general formula (III) may be used alone or in combination of two or more.

  In the method for producing silica spherical particles of the present invention, the method for preparing a reaction solution containing silica particles by hydrolyzing the hydrolyzable silicon compound represented by the general formula (III) is not particularly limited. In addition, a conventionally known method can be used. For example, the hydrolyzable silicon compound is hydrolyzed in an aqueous medium such as water and / or alcohol, optionally in the presence of a hydrolysis catalyst such as a base catalyst or an acid catalyst, thereby containing a reaction liquid containing silica particles. Can be prepared. At this time, if silica particles having a desired particle diameter are obtained by one hydrolysis reaction, the reaction solution can be supplied to the next step as it is.

  In addition, when silica particles having a desired particle size cannot be obtained, the silica particles are used as seed particles, and the operation of further performing a hydrolysis reaction is repeated once or more to grow the particles to a desired particle size, The reaction liquid containing the grown particles can be supplied to the next step.

  In the method for producing the spherical silica particles of the present invention, the reaction solution containing the silica particles thus obtained is concentrated, dried, and further baked according to a conventional method. Since the fired powder obtained in this way contains agglomerates of primary particles, the fired powder is subjected to a wet crushing treatment.

  In general, as a means for crushing agglomerates, a crusher is used as a typical example. Many pulverizers have been put to practical use.

  Among them, the dry pulverizer jet mill feeds the pulverized material into the jet stream and breaks it down by the collision force between the particles. Although it is suitable for crushing to particles of 1 μm or more, a dry classifier is required because of the inclusion of uncrushed aggregates. Examples of such a dry pulverizer jet mill include a Hosokawa micron counter jet mill.

  Even when a dry classifier is used, it is difficult to extract only particles having a particle size of, for example, about 0.2 μm at the current classification level. In addition, depending on the powder to be handled, adhesion may be strong and classification may not be possible. Therefore, dry pulverizers are not suitable for crushing to submicron particles.

On the other hand, in the wet pulverizer, a high-pressure jet water flow collision type and a bead mill type, which are mainly performed conventionally, are well known. The former type of high-pressure jet water flow collision type is a method in which crushing is caused by collision of slurry liquid containing agglomerates from two nozzles facing each other. In the case of this method, if the primary particle diameter is about 0.5 μm or more, the aggregate is crushed. However, when the primary particle size is about 0.2 μm, the cohesive force is strong and not crushed. Therefore, it is unsuitable for crushing aggregates of about 0.2 μm. Further, when used as a crusher, an apparatus having an output of 196 N / mm ² or more is required, which is large and expensive.

Selection of the model is important for the bead mill type pulverizer of the wet pulverizer.
When the cylinder of the cylindrical portion is long in the horizontal horizontal bead mill, the slurry liquid to be crushed is easily divided into a reservoir portion such as a corner in the apparatus and a portion that can pass linearly, and thus a difference in residence time occurs. For this reason, the particles obtained were sufficiently disintegrated particles, particles that were too stressed and the spherical shape was broken, and solid agglomerates that were insufficiently disintegrated and remained agglomerated. This leads to an unfavorable situation such as being divided into particles. And processing time becomes a delicate adjustment and becomes an important factor. When the particle size distribution of the slurry liquid obtained here is measured, it tends to be a broad curve.

  For these reasons, in the method for producing silica spherical particles of the present invention, it is preferable to use a wet bead mill type pulverizer for crushing the calcined powder, and the wet bead mill type pulverizer is a cylinder. In the shape of the cylindrical pulverization chamber, the ratio of the length of the slurry inflow direction / the length of the slurry liquid in the outflow direction is preferably 1.0 or less, more preferably 0.7 or less. Are preferred. FIG. 1 is a diagram for explaining the shape of a cylindrical pulverization chamber inside a wet bead mill pulverizer. In this figure, the length of the slurry liquid in the cylindrical pulverization chamber 1 in the inflow direction (length of the cylindrical portion) Is A, and the length of the slurry liquid in the outflow direction (body diameter) is B. Therefore, A / B is preferably 1 or less, more preferably 0.7 or less.

  Even when a wet type bead mill type pulverizer whose shape is in the above range is used, the shape of the cylindrical pulverization chamber is easily divided into a part where the slurry liquid to be crushed can pass linearly with a reservoir part such as a corner in the apparatus. However, since the length of the slurry liquid inflow direction (the length of the cylindrical portion) is short, there is no influence of the corner portion, and there is no difference in the residence time. Furthermore, the degree of progress of crushing and the prevention of particle cracking are controlled by bead diameter (media diameter), separator clearance, and processing time. And even if processing time progress exceeded about 20% compared with the target time, it turned out that there is no quality change (particle cracking).

  The media diameter is selected as needed, but is selected according to the size of the primary particle diameter. As a typical example, when the primary particle diameter is 1.0 μm or less and about 0.4 μm or more, about 0.3 mm of media is used, and when it is less than about 0.4 μm, about 0.2 mm of media is used. Easy to obtain particles.

  In the method for producing the spherical silica particles of the present invention, the fired powder is subjected to wet crushing treatment and then dried according to a conventional method, so that it does not contain strong agglomerates and has the desired properties. A powder composed of silica spherical particles is obtained.

  Next, an example of the method for producing the spherical silica particles of the present invention will be described.

  First, an aqueous medium containing a hydrolysis catalyst is prepared. As the aqueous medium, water or a mixture of water and a water-miscible organic solvent can be used. Here, examples of the water-miscible organic solvent include lower alcohols such as methanol, ethanol, propanol and butanol, and ketones such as acetone. These may be mixed with water alone or in combination of two or more with water. As the hydrolysis catalyst, ammonia and / or an amine are preferably used. Preferred examples of the amine include monomethylamine, dimethylamine, monoethylamine, diethylamine, and ethylenediamine. Ammonia and amine may be used alone or in combination of two or more. However, ammonia is preferred because it is less toxic, easy to remove, and inexpensive.

  Next, the aqueous medium containing the hydrolysis catalyst is stirred and the hydrolyzable silicon compound, preferably tetraalkoxysilane, is continuously added dropwise to the hydrolysis while maintaining the temperature at about 0 to 50 ° C. , To form silica particles. At this time, it is desirable to drop the silicon compound so that the concentration is preferably 20% by weight or less, more preferably 5 to 15% by weight. Although there is no restriction | limiting in particular about dripping time, Usually, it is about 0.5 to 5 hours.

  When the silica particles thus obtained have a desired particle size, the reaction solution is directly supplied to the concentration and drying step. If the desired particle size is not reached, volatile organic components such as alcohol, ammonia and amine in the reaction solution are distilled off to obtain an aqueous dispersion of silica seed particles. Used for growth reaction.

  To the aqueous medium containing the hydrolysis catalyst, the above silica seed particle aqueous dispersion is added and stirred, and while maintaining the temperature at 0 to 50 ° C., the same raw material hydrolyzable silicon compound is continuously added dropwise. Then, hydrolysis and condensation reactions are performed to grow silica seed particles to obtain a reaction liquid containing silica particles having a desired particle size.

  Next, the reaction liquid containing the silica particles is concentrated and dried by a conventional method using, for example, a vibration drier to obtain a dry powder composed of silica particles. The dried powder is further fired at a temperature of about 700 to 900 ° C. in a gas atmosphere containing oxygen to obtain a fired silica particle powder. Furthermore, since the calcined silica particle powder thus obtained contains a lump in which primary particles are aggregated, wet crushing is performed using a wet bead mill type pulverizer as described above. Silica spherical particles having desired properties can be obtained by drying the aqueous dispersion of silica particles obtained by this wet crushing treatment according to a conventional method.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Example 1
(1) Production of seed particles A 100-liter reaction vessel equipped with a stirrer is set in a thermostatic bath, and 37 kg of methanol, 26 kg of 25 wt% ammonia water and 23 kg of water are added and heated to 30 ° C. while mixing with a stirrer. did. Next, 5.8 kg of tetraethoxysilane was continuously added at a rate of 50 g / min while stirring the mixed solution. After the addition, methanol and ammonia were removed by a rotary evaporator to obtain an aqueous dispersion of silica seed particles. The average particle diameter of the silica seed particles measured by scanning electron microscope (SEM) was 0.14 μm.

(2) Production of calcined silica particles A 100-liter reaction vessel equipped with a stirrer is set in a thermostatic bath, 20 kg of methanol, 15 kg of 25 wt% ammonia water and 1.6 kg of water are added, and further obtained in (1) above. 10 kg of the resulting silica seed particle aqueous dispersion (average particle size 0.14 μm, weight concentration 9%) was added to obtain a seed particle dispersion. This dispersion was heated to 30 ° C., and while stirring, 36 kg of tetraethoxysilane was continuously added at a rate of 100 g / min to carry out a hydrolytic condensation reaction to grow silica seed particles. The silica particles produced by this growth reaction were spherical particles having an average particle size of 0.23 μm (SEM measurement) and a very narrow particle size distribution.
15 kg of nylon balls (25 mmφ) for crushing in a vibration dryer (“VHS-30 type” manufactured by Chuo Processing Machine) with an internal capacity of 50 liters and an actual capacity of 27 liters equipped with a water-sealed vacuum pump, condenser and heating jacket Then, 25 liters out of 100 liters of the aqueous dispersion of silica particles obtained above were placed in the dryer, and the concentration operation was started under a reduced pressure condition of 53 MPa while heating the dryer body to 105 ° C. When the amount of liquid in the vibration dryer was concentrated to 15 liters, 10 liters of silica dispersion was further introduced into the dryer to perform concentration operation. By repeating such concentration operation, the total amount of the aqueous dispersion was concentrated to 15 liters 4 hours after the silica particle aqueous dispersion was first introduced. Next, 10 liters of pure water was poured into 15 liters of concentrated liquid in the dryer, and further concentration operation was performed to complete hydrolysis of unreacted tetraethoxysilane while removing alcohol and ammonia. After the injection of pure water is completed, moisture is removed by applying a concentration operation for another hour while applying vibration by a vibration force of 5.1 kN to the vibration dryer to obtain powdered silica particles. It was. Subsequently, the silica particles were dried at 105 ° C. for 3 hours.
Silica particles after drying are put in an alumina crucible and set in an electric furnace, heated in an oxygen stream from room temperature to 800 ° C. over 3 hours, held at this temperature for 9 hours, and then brought to room temperature over 3 hours. The temperature was lowered to obtain calcined silica particles.

(3) Production of target silica particles 2 kg of the fired silica particles obtained in the above (2) and 1.5 kg of pure water were placed in a 5-liter beaker (made of polyethylene) and dispersed using a spatula.
In the fired silica particles, there are many agglomerates formed at the time of drying or firing, and crushing with the SC mill may clog the screen, so we decided to perform preliminary crushing. .

As a preliminary crusher, Mitsui Mine Attritor NS-1 type was used. This attritor was previously filled with 12 kg of 5 mmφ zirconia beads. The dispersed silica particle aqueous dispersion was placed in an attritor and dispersed at 300 rpm for 30 minutes. Similarly, 2 kg of calcined silica particles and 1.5 kg of pure water were placed in a 5 liter hand-held beaker (made of polyethylene) and dispersed using a spatula. This dispersed silica particle aqueous dispersion was placed in an attritor and dispersed at 300 rpm for 30 minutes. Again, 2 kg of the fired silica particles and 1.5 kg of water were placed in a 5 liter hand-held beaker (made of polyethylene) and dispersed using a spatula. This dispersed silica particle aqueous dispersion was placed in an attritor and dispersed at 192 rpm for 30 minutes. Thus, preliminary crushing was performed three times, and a total of about 10.5 kg of a dispersion having a weight concentration of 57.1% was obtained.
The dispersion obtained here was used as a raw material for a wet crusher (“SC Mill 100 type” manufactured by Mitsui Mine).

  The SC mill was filled with 440 g of 0.2 mmφ zirconia beads. The silica particle aqueous dispersion preliminarily crushed with an attritor was put into an SC mill, and the operation was started at a rotational speed of 1800 rpm. After 1 hour from the start of operation, the particle size distribution was confirmed, and after confirming that it was sufficiently crushed, about 10 kg of silica particle aqueous dispersion was taken out into a polyethylene container. The particle size distribution was confirmed using a laser diffraction particle size distribution analyzer “SALD-2000J” manufactured by Shimadzu Corporation. Note that sample preparation was performed only by ultrasonic dispersion incorporated in the apparatus, without performing ultrasonic homogenizer irradiation which is usually performed by preliminary dispersion. The refractive index used for the measurement was set to 1.60-0.10i.

Next, the silica particle aqueous dispersion obtained by the SC mill was concentrated and dried.
Put the total amount of 10 kg of the silica particle aqueous dispersion obtained above into a concentrating dryer Bravo (Shinko Invest "Type IV") with an internal volume of 47 liters and a heating capacity of 30 liters equipped with a heating jacket. The bottom agitation was stirred at 90 rpm and further rotated with a side cutter at 1670 rpm. The dryer main body was sucked with a blower while being heated to 105 ° C. with steam, and the concentration operation was started. The silica particle aqueous dispersion in Bravo changed from liquid to powder after 1 hour. At this time, the rotational speed of the side cutter was further increased to 3000 rpm. Further, after the silica particles were dried at 105 ° C. for 3 hours, the dryer was stopped and taken out.

  The silica particles thus obtained were measured for particle distribution in an aqueous dispersion state with a particle size analyzer “Microtrac UPA” (manufactured by Nikkiso Co., Ltd.) according to the method described in the specification text. The particles had a particle size distribution of 2 μm, a particle size dispersion coefficient S of 13.2%, and satisfying the condition of the formula (II).

Example 2
(1) Production of seed particles In the same manner as in Example 1 (1), an aqueous dispersion of silica seed particles was obtained. The average particle size of the seed particles measured by scanning electron microscope was 0.14 μm.

(2) Production of calcined silica particles A 100-liter reaction vessel equipped with a stirrer is set in a thermostatic bath, 32 kg of methanol, 21 kg of aqueous ammonia and 9 kg of water are added, and the water of silica seed particles obtained in (1) above is further added. 1.6 kg of a dispersion (average particle size 0.14 μm, weight concentration 9%) was added to obtain a seed particle dispersion. This dispersion was heated to 30 ° C., and while stirring, 36 kg of tetraethoxysilane was continuously added at a rate of 100 g / min to carry out a hydrolytic condensation reaction to grow silica seed particles. The silica particles produced by this growth reaction had a mean particle size of 0.47 μm (SEM measurement) and were spherical particles with a very narrow particle size distribution.
Thereafter, the same operation as in Example 1 (2) was performed to obtain calcined silica particles.

(3) Manufacture of the target silica particle Using the baked silica particle obtained by said (2), operation similar to Example 1 (3) was performed, and the target silica particle was obtained.
The silica particles thus obtained were measured for particle size distribution in an aqueous dispersion state with a particle size analyzer “Microtrac UPA” (manufactured by Nikkiso Co., Ltd.) by the method described in the specification text. The particles had a particle size distribution of 5 μm, a particle size dispersion coefficient S of 18.0% and a particle size distribution satisfying the condition of the formula (II).

Comparative Example 1
In Example 1, the calcined silica particles obtained in (2), that is, the silica particles not subjected to the production process of (3) were used as the particles of Comparative Example 1.
This particle tried to measure the average particle size and particle size dispersion coefficient S in the water dispersion state with a particle size analyzer “Microtrac UPA” (manufactured by Nikkiso Co., Ltd.). Since it is larger than the micron particle size range, measurement was impossible. In the test examples described later, the average particle diameter measured with a laser diffraction particle size distribution meter was 8.520 μm.

Test example 1
For the silica particles obtained in Example 1 and Comparative Example 1, the dispersibility in water, the particle size distribution of the silica particles in the aqueous dispersion, and the dispersion state were examined as follows.
(1) Dispersibility in water 0.1 g of sample is placed in 50 ml of water and dispersed by an ultrasonic homogenizer (output: 150 W), so that the sample of Example 1 and the sample of Comparative Example 1 are dispersed in water. As a result, the sample of Example 1 was 10 minutes, while the sample of Comparative Example 1 was 20 minutes.

(2) Particle size distribution of silica particles in aqueous dispersion Laser dispersion particle size distribution measuring machine ("SALD-2000J" manufactured by Shimadzu Corporation) was used for the aqueous dispersion of silica particles of Example 1 and Comparative Example 1 obtained in (1) above. The particle size distribution was measured over a wide particle size range. The result of Example 1 is shown in FIG. 2, and the result of Comparative Example 1 is shown in FIG. Moreover, the particle size distribution in the submicron particle diameter region was measured using a particle size analyzer ("Microtrac UPA" manufactured by Nikkiso Co., Ltd.). The result of Example 1 is shown in FIG. In Comparative Example 1, measurement was impossible.

  In the particle size distribution in the wide particle diameter range by the laser diffraction particle size distribution analyzer, as can be seen from FIGS. 2 and 3, in Example 1, the average value is about 0.2 μm, and 0.07 to 0.4 μm. In Comparative Example 1, the average value is about 8.5 μm and is distributed between 1 and 50 μm.

  In addition, in the particle size distribution in the submicron particle diameter range by the particle size analyzer, as can be seen from FIG. 4, in Example 1, when the median diameter is 0.2 μm, the distribution is within ± 0.1 μm. The particle size dispersion coefficient is 13.2%, and the particle diameters are very uniform. On the other hand, in Comparative Example 1, the particle size area was large and measurement was impossible.

(3) Dispersion State in Aqueous Dispersion Regarding the silica particle aqueous dispersions of Example 1 and Comparative Example 1 obtained in (1) above, the dispersion state of the silica particles was observed by SEM. FIG. 5 shows an SEM photograph of Example 1, and FIG. 6 shows an SEM photograph of Comparative Example 1. 5 and 6, (a) shows the case where the shooting magnification is 5000 times, and (b) shows the case where the shooting magnification is 15000 times.
From these figures, it can be seen that there is no aggregate in Example 1, but there is a large aggregate that can be observed in Comparative Example 1.

From the above evaluation results, it can be proved that there is a large difference in dispersibility between Example 1 and Comparative Example 1.
In the water dispersion state of the present invention, it is presumed that even when submicron particles having a uniform particle size are kneaded into a resin, they are easily dispersed into primary particle states due to the shear effect.

  According to the present invention, silica that is useful as a filler for electronic materials, substantially free of organic components, has no strong aggregation, and can be easily dispersed as submicron particles having a uniform particle size distribution in a resin or the like. Spherical particles can be obtained.

It is a diagram for explaining the shape of a cylindrical pulverizing chamber portion of wet-type bead mill pulverizer. It is the particle size distribution figure measured about the aqueous dispersion liquid of the silica particle obtained in Example 1 in the wide particle diameter range using the laser diffraction particle size distribution measuring machine. It is the particle size distribution figure measured about the aqueous dispersion liquid of the silica particle obtained by the comparative example 1 in the wide particle diameter range using the laser diffraction particle size distribution measuring machine. It is the particle size distribution figure measured about the aqueous dispersion liquid of the silica particle obtained in Example 1 in the submicron particle diameter area using the particle size analyzer. 3 is a SEM photograph showing the water dispersion state of the silica particles obtained in Example 1. FIG. 4 is a SEM photograph showing the water dispersion state of silica particles obtained in Comparative Example 1. FIG.

Explanation of symbols

  1 Cylindrical grinding chamber

Claims (2)

In the water dispersion state, the average particle size is in the range of 0.1 to 0.5 μm, and the formula (I) in the particle size region
S (%) = (standard deviation of particle diameter / average particle diameter) × 100 (I)
And the particle size dispersion coefficient S calculated by the formula (II) is 26% or less,
S (%) = aX + b (II)
[However, X is an average particle diameter (micrometer) and is 0.1-0.5, a is the number of -10--6, b is the number of 15-27. ]
Silica spherical particles characterized by satisfying the relationship:   The spherical silica particles according to claim 1, which are formed by a sol-gel method.