JP6691410B2 - Silica particles containing ethylenic double bond and method for producing the same - Google Patents

Description

  The present invention relates to ethylenic double bond-containing silica particles and a method for producing the same.

  Since silica particles are excellent in strength and heat resistance, for example, anti-blocking agents and slipperiness-imparting agents for various films such as polyester films, polyimide films and fluororesin films; in-plane spacers for liquid crystal display elements, liquid crystal display elements Sealer spacers, EL display element spacers, touch panel spacers, spacers such as gap retainers between various substrates such as ceramics and plastics; semiconductor sealants, liquid crystal sealants, LED light emitting element sealants, etc. Are widely used for various electronic component sealing agents; light diffusing agents used for light diffusing films, light diffusing plates, light guide plates, antiglare films, etc .; cosmetic additives such as white extender pigments; dental materials.

  It is known that the surface of silica particles is surface-treated with a silane coupling agent as an effective means for enhancing the dispersibility of silica particles in resins and various media. For example, in Patent Documents 1 and 2, calcined silica particles are known. And the silane coupling agent are mixed and stirred while heat treatment is performed. In Patent Documents 3 and 4, silica powder and a silane coupling agent are stirred in a stirrer to perform heat treatment.

JP, 2008-137854, A International Publication No. 2015/119283 Japanese Patent Laid-Open No. 6-100313 JP, 2001-188109, A

  However, as described in Patent Documents 1 and 2, when silica particles are treated with a silane coupling agent having an ethylenic double bond while stirring, agglomeration occurs, and after the treatment with the silane coupling agent, crushing is performed. Sometimes it was necessary to classify. Further, as described in Patent Documents 3 and 4, when the silica particles and the silane coupling agent are mixed and then directly heat-treated, the silica particles may aggregate. The present invention has been made in view of such circumstances, and an object thereof is to provide a production method capable of suppressing the aggregation of silica particles even when treated with a silane coupling agent having an ethylenic double bond. .

  The present inventors have conducted extensive studies to solve the above problems. As a result, in order to suppress the agglomeration of silica particles, it is generally desirable to stir during the treatment of the silane coupling agent, and the silane coupling agent contains an ethylenic double bond. In some cases, it was found that the stirring promotes the polymerization of the ethylenic double bond and causes aggregation. Then, when heating the mixture of the silica particles and the silane coupling agent, if the heating conditions are uneven, local overheating occurs, and it was found that this local overheating is the cause of aggregation. . Furthermore, if the silica particles and the silane coupling agent are mixed and heated under a condition that enables uniform heating and in a stationary state, heat treatment can be performed uniformly without stirring. It is possible to prevent local overheating, and as a result, surprisingly, polymerization of the silane coupling agent is suppressed more than when stirring is performed, and aggregation of the obtained ethylenic double bond-containing silica particles is prevented. The present invention has been completed by finding that it can be suppressed.

［式中、Ｒ¹は、水素原子又はメチル基を表す。Ｒ²は、−Ｓｉ（Ｒ³）₂−、−ＣＯ−、−ＣＨ₂−又はフェニレン基を表す。Ｒ³は、同一でも異なっていてもよく、ハロゲン原子、アルキル基又はアルコキシ基を表す。＊は結合手を表す。］
［７］下記測定方法により求められる凝集物の含有割合が１０，０００ｐｐｍ（質量基準）以下である［６］に記載のシリカ粒子。
［測定方法］
シリカ粒子１０ｇと、水９０ｇと、界面活性剤としてのドデシルベンゼンスルホン酸ナトリウム２ｇを、３００秒間以上超音波分散させて得られた分散液を、２５±３℃において、目開き２０μｍの篩に通した場合に篩上に残るシリカ粒子の質量をＷ（ｇ）としたとき、下記式で求められる値を凝集物の含有割合とする。
凝集物の含有割合（ｐｐｍ）＝（Ｗ（ｇ）／１０（ｇ））×１０⁶ That is, the present invention includes the following inventions.
[1] Ethylenic double bond including a step of preparing a mixture containing silica particles and an silane coupling agent containing an ethylenic double bond, and a step of heating the mixture to a temperature of 100 ° C. or higher in a stationary state Method for producing contained silica particles.
[2] The production method according to [1], which comprises a step of housing the mixture in a container having a horizontal surface as a bottom surface before allowing the mixture to stand.
[3] The manufacturing method according to [1] or [2], wherein the heating temperature is 150 ° C. or lower.
[4] The production method according to any one of [1] to [3], wherein the ethylenic double bond-containing silane coupling agent is a (meth) acryloyl group-containing silane coupling agent.
[5] The production method according to any one of [1] to [4], wherein the amount of the ethylenic double bond-containing silane coupling agent is 1 time or more the theoretical coating amount represented by the following formula.
Theoretical coverage (g) = mass of silica particles (g) × specific surface area of silica particles (g / m ² ) / minimum coating area of ethylenic double bond-containing silane coupling agent (m ² / g)
[6] An ethylenic double bond-containing silica particle, wherein the number (1) and number of the (meth) acryloyl group represented by the following formula (A1) when the organic group on the surface of the silica particle is measured by solid state ¹³ C-NMR. For the sum (I _A ) of the integrated values of the peaks assigned to the ^two carbons (C ¹ and C ² ),
The ratio of the integrated values of the peaks assigned to the carbons (C ³ and C ⁴ ) of the number 3 and the number 4 of the oligomerized (meth) acryloyl group represented by the following formula (B1) to the total I _B (I _B / I Silica particles containing ethylenic double bond, wherein _A ) is 0.1 or less.

[In the formula, R ¹ represents a hydrogen atom or a methyl group. R ^{2 _{is, -Si (R 3) 2 -}} , - CO -, - represents a or a phenylene group - CH _2. R ^{3 s} may be the same or different and each represents a halogen atom, an alkyl group or an alkoxy group. * Represents a bond. ]
[7] The silica particles according to [6], wherein the content of aggregates determined by the following measurement method is 10,000 ppm (mass basis) or less.
[Measuring method]
The dispersion obtained by ultrasonically dispersing 10 g of silica particles, 90 g of water, and 2 g of sodium dodecylbenzenesulfonate as a surfactant for 300 seconds or longer was passed through a sieve having an opening of 20 μm at 25 ± 3 ° C. When the mass of the silica particles remaining on the sieve in this case is W (g), the value obtained by the following formula is the content ratio of the aggregate.
Aggregate content ratio (ppm) = (W (g) / 10 (g)) × 10 ⁶

  In the production method of the present invention, the silica particles and the ethylenic double bond-containing silane coupling agent are mixed and the mixture is heated to a temperature of 100 ° C. or higher in a stationary state. Aggregation of the bond-containing silica particles can be suppressed.

The production method of the present invention is a step of preparing a mixture containing silica particles and an ethylenic double bond-containing silane coupling agent (hereinafter, may be simply referred to as “double bond-containing silane coupling agent”) (mixing step) ), And a step of heating the mixture to a temperature of 100 ° C. or higher in a stationary state (heating step). As a result, even when a silane coupling agent having a double bond is used, as a result of suppressing the polymerization of the double bond contained in the silane coupling agent, aggregation is suppressed and crushing and classification are not performed. Both can produce ethylenic double bond-containing silica particles with less aggregates.
The components and functional groups exemplified below can be used alone or in combination.

The double bond-containing silane coupling agent may be one having an ethylenic double bond, more preferably a (meth) acryloyl group, and further preferably an acryloyl group.
The silane coupling agent generally has a group in which a hydrolyzable group is bonded to a silicon atom (hydrolyzable silicon group), and the hydrolyzable group includes a hydrogen atom and a halogen atom such as a chlorine atom. Atom; hydroxyl group; alkoxy group having 1 to 4 carbon atoms; acyloxy group having 2 to 5 carbon atoms and the like.

  Specific examples of the double bond-containing silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinyltrichlorosilane, vinyldichloromethylsilane and p-styryl. Vinyl group-containing silane coupling agents such as trimethoxysilane, p-styryltriethoxysilane, p-styrylmethyldimethoxysilane, p-styrylmethyldiethoxysilane; 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltri Methacryloyl group-containing silane coupling agents such as ethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane; 3-acryloxypropyltrimethoxy Acryloyl group-containing silane coupling agents such as orchid, 3-acryloxypropyltriethoxysilane, 3-acryloxypropylmethyldimethoxysilane, and 3-acryloxypropylmethyldiethoxysilane; and (meth) acryloyl group-containing silanes. Coupling agents are preferred, and acryloyl group-containing silane coupling agents are particularly preferred.

The amount of the double bond-containing silane coupling agent is preferably 1 time or more, more preferably 1.0 time or more, further preferably 1.5 times or more, of the theoretical coating amount represented by the following formula. It is more preferably 1.8 times or more, preferably 5 times or less, more preferably 4 times or less, and further preferably 3 times or less.
Theoretical coverage (g) = mass of silica particles (g) × specific surface area of silica particles (g / m ² ) / minimum coating area of silane coupling agent (m ² / g)
However, the minimum coverage area of the silane coupling agent is a value obtained by the following formula.
Minimum coating area (m ² /g)=(6.02×10 ²³ × 13 × 10 ⁻²⁰ ) / molecular weight of silane coupling agent

  According to the production method of the present invention, since the polymerization of the ethylenic double bond of the double bond-containing silane coupling agent can be suppressed, the ethylenic double bond-containing silica obtained can be obtained even if the amount of the silane coupling agent is increased. It is easy to suppress the aggregation of particles.

In addition to the double bond-containing silane coupling agent, the mixture may contain another silane coupling agent.
Other silane coupling agents include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, and tetraalkoxysilanes such as dimethoxydiethoxysilane; methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, Alkyl group-containing alkoxysilanes such as dimethyldiethoxysilane, trimethylmethoxysilane, and trimethylethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane Glycidyl group-containing alkoxysilanes such as; 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane and other halogenated alkyl group-containing alkoxysilanes Mercapto group-containing alkoxysilane such as 3-mercaptopropyltrimethoxysilane; amino group-containing alkoxysilane such as 3- (2-aminoethylamino) propyltrimethoxysilane; phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxy Aryl group-containing alkoxysilanes such as silane and diphenyldiethoxysilane; methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, chlorosilanes such as methyldiphenylchlorosilane; tetraacetoxysilane, methyltriacetoxysilane, phenyl Acyl triacetoxysilane, dimethyldiacetoxysilane, diphenyldiacetoxysilane, trimethylacetoxysilane, etc. Shishiran; dimethylsilane diol, diphenylsilane diol, hydroxy silane such as trimethyl silanol, and the like.

  Double bond-containing silane coupling agent contained in the mixture and other silane coupling agents used as necessary (hereinafter, these are collectively referred to as “silane coupling agent”) in 100% by mass. The silane coupling agent content is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more.

  When mixing the silica particles and the silane coupling agent, a diluent (alcohol, diol) may be further used. By using the diluent, it becomes easy to enhance the uniformity of coating with the silane coupling agent, and it is possible to further suppress aggregation of the obtained double bond-containing silica particles. Examples of the alcohols include methanol, ethanol, propanol, isopropyl alcohol, n-butyl alcohol, t-butyl alcohol, pentyl alcohol and the like, and examples of the diols include ethylene glycol, propylene glycol, 1,4-butanediol and the like. Is mentioned. Among them, alcohols are preferable, and alcohols corresponding to the alkoxy group of the silane coupling agent (alcohols having a hydrogen atom bonded to the alkoxy group) are particularly preferable. Water may coexist when the silica particles and the silane coupling agent are mixed.

  The amount of the diluent is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, and 200 parts by mass with respect to 100 parts by mass in total of the silane coupling agent. The amount is preferably the following, more preferably 150 parts by mass or less, and further preferably 120 parts by mass or less. The more diluent, the easier it is to coat the silane coupling agent uniformly, and the less diluent, the faster the coating speed.

  The silane coupling agent and the diluent used as necessary can be mixed with the silica particles in an appropriate order, and at least a part thereof, preferably all of them are mixed in advance to prepare a premix, and then the silica particles are mixed. It is preferable to mix with. At the time of mixing, the premix may be added to the silica particles, the silica particles may be added to the premix, or the premix is preferably added to the silica particles. Examples of the method for adding the preliminary mixture include dropping and spraying, and spraying is preferable.

When the silica particles and the silane coupling agent are mixed to prepare the above mixture, a blade type mixer (preferably a Henschel mixer) can be preferably used.
The temperature of the mixture when preparing the mixture is less than 100 ° C, preferably 60 ° C or less, more preferably 40 ° C or less, preferably 0 ° C or more, more preferably 10 ° C or more.
Further, the mixing time is preferably 30 minutes or more, more preferably 60 minutes or more, preferably 200 minutes or less, more preferably 120 minutes or less, further preferably 100 minutes or less.

  Subsequently, it is preferable to store the obtained mixture in a container whose bottom surface is a horizontal surface. When the bottom surface of the storage container is a horizontal surface, the thickness of the mixture can be easily made uniform, so that the heat treatment can be uniformly performed without stirring during the heat treatment, and further local overheating can be easily prevented.

  The maximum thickness of the contained mixture is preferably 100 mm or less, more preferably 70 mm or less, even more preferably 50 mm or less, preferably 1 mm or more, and more preferably 5 mm or more. The smaller the maximum thickness of the mixture, the easier the uniform heating conditions of the mixture.

The ratio of the weight of the mixture to the contact area of the mixture and the container (weight of the mixture / contact area of the mixture and the container) is preferably 100 kg / m ² or less, more preferably 70 kg / m ^2. Or less, more preferably 60 kg / m ² or less. By setting the ratio (weight of the mixture / contact area of the mixture and the container) within this range, it becomes easy to make the heating conditions uniform.
Furthermore, the ratio of the weight of the mixture to the cross-sectional area of the storage container (meaning the average value of the cross-sectional area in the horizontal direction with the bottom surface) (weight of the mixture / cross-sectional area of the storage container) is 120 kg / m ² or less. Is preferred, more preferably 100 kg / m ² or less, and even more preferably 70 kg / m ² or less. When the ratio (weight of the mixture / cross-sectional area of the container) is within this range, it becomes easy to make the heating conditions uniform.

Bottom area of the container is preferably at 0.001 m ² or more, more preferably 0.01 m ² or more, further preferably 0.05 m ² or more, preferably 6 m ² or less, more preferably It is 1 m ² or less, more preferably 0.5 m ² or less.
The minor axis of the bottom surface of the container is preferably 200 cm or less, more preferably 120 cm or less, further preferably 70 cm or less, preferably 2 cm or more, more preferably 10 cm or more, further preferably 15 cm or more. is there.
The major axis of the bottom surface of the container is, for example, preferably 300 cm or less, more preferably 150 cm or less, 100 cm, preferably 5 cm or more, more preferably 15 cm or more, still more preferably 20 cm or more.
Further, the ratio of the major axis to the minor axis (major axis / minor axis) of the bottom surface of the container is preferably 1 or more, more preferably 1.2 or more, for example, 2 or less, and more preferably. It may be 1.7 or less.
The major axis of the bottom surface of the container means the length of the longest part of the bottom surface of the container, and the minor axis means the length of the longest part in the direction orthogonal to the major axis.

Further, from the viewpoint of making the heating conditions of the mixture uniform, it is preferable that the upper surface of the contained mixture is a horizontal surface.
The bottom shape of the storage container may be any shape having an area, and among them, it is preferably a polygon, an ellipse, and a circle, and more preferably a polygon (preferably a quadrangle (rectangle or square)). The bottom surface of the storage container being horizontal means that the bottom surface of the storage container does not have a convex portion such as a stirring blade and the entire bottom surface is flat.

The bottom surface may be provided with irregularities having a height difference of preferably 5 cm or less, more preferably 3 cm or less, and further preferably 1 cm or less.
Further, the bottom face may be provided with a curved surface portion having a curvature of preferably 10 m ^-1 or less, more preferably 1 m ^-1 or less, and further preferably 0.1 m ^-1 or less.
Further, the bottom surface may be provided with an inclined portion having an angle (tilt angle) with the horizontal plane of 10 ° or less, more preferably 5 ° or less, and further preferably 3 ° or less.
Even if the bottom surface of the container is provided with the unevenness, the curved surface portion, or the inclined portion in the above range, it is included in the horizontal surface in the present invention.

Next, the mixture (which may be contained in a container whose bottom surface is a horizontal surface if necessary) is heated to a temperature of 100 ° C. or higher in a stationary state. If the mixture is heated in a state where it is left still so that the heating conditions are uniform, it is possible to obtain the result of suppressing the polymerization of the double bond of the double bond-containing silane coupling agent, probably because the reaction is easily controlled. Aggregation of double bond-containing silica particles can be suppressed.
The state in which the mixture is left standing means that no stress such as shear stress or compressive stress is applied to the mixture.

The heating temperature is preferably 105 ° C or higher, more preferably 110 ° C or higher, preferably 150 ° C or lower, more preferably 130 ° C or lower, and further preferably 120 ° C or lower. The heating temperature may be constant or fluctuating. The heating temperature means the temperature inside the mixture.
The heating time is, for example, preferably 10 minutes to 5 hours, and more preferably 30 minutes to 2 hours. In addition, in the heating step, the heating time means a time when the heating temperature is within the above range.

Further, in the manufacturing method of the present invention, it is preferable to perform blast drying. The air velocity in the case of blowing and drying is preferably 0.1 m / s or more, more preferably 0.5 m / s or more, and preferably 10 m / s or less, more preferably 5 m / s or less, More preferably, it is 3 m / s or less.
In the production method of the present invention, since the mixture is heated while being left stationary, the heating efficiency is high, and the reaction between the silica particles and the silane coupling agent can be sufficiently advanced within the above heating temperature and heating time range.

The heating method may be any method as long as it can be performed while the silica particles are allowed to stand, and either ventilation heating or radiation heating may be used. As the heating device, a tray heating device and a conveyor heating device are preferable, and a tray heating device is more preferable.
The heating step can be performed under atmospheric pressure.

  The double bond-containing silica particles obtained by the above-mentioned production method are suppressed in agglomeration, and have a small amount of agglomerates even without crushing and classification. Specifically, even in double bond-containing silica particles that have not undergone crushing / classification, the content ratio of aggregates determined by the following measurement method is preferably 20,000 ppm (mass standard) or less, and more preferably It is 15,000 ppm (mass standard) or less, more preferably 10,000 ppm (mass standard) or less, and the smaller the content ratio of the aggregate is, the more preferable, for example, 100 ppm (mass standard) or more, further 500 ppm (mass standard) or more. Is also allowed.

[Measuring method]
The dispersion obtained by ultrasonically dispersing 10 g of silica particles, 90 g of water, and 2 g of sodium dodecylbenzenesulfonate as a surfactant for 300 seconds or longer was passed through a sieve having an opening of 20 μm at 25 ± 3 ° C. When the mass of the silica particles remaining on the sieve in this case is W (g), the value obtained by the following formula is the content ratio of the aggregate.
Aggregate content ratio (ppm) = (W (g) / 10 (g)) × 10 ⁶

When an ethylenic double bond-containing silane coupling agent is used as the silane coupling agent, when the obtained ethylenic double bond-containing silica particles are subjected to solid state ¹³ C-NMR to measure the organic groups on the silica particle surface, In the following formula (B1) with respect to the total (I _A ) of the integrated values of the peaks belonging to the carbons (C ¹ and C ² ) of the number 1 and number 2 of the ethylenic double bond represented by the following formula (A1) The ratio (IB / IA) of the peaks assigned to the carbons (C ³ and C ⁴ ) of the oligomerized ethylenic double bond shown in the numbers 3 and 4 to the total I _B (I _B / I _A ) is 0. It is preferably less than or equal to 1. The ratio (I _B / I _A) is more preferably 0.05 or less, more preferably 0.01 or less.

[In the formula, R ¹ represents a hydrogen atom or a methyl group. R ^{2 _{is, -Si (R 3) 2 -}} , - CO -, - represents a or a phenylene group - CH _2. R ^{3 s} may be the same or different and each represents a halogen atom, an alkyl group or an alkoxy group. * Represents a bond. ]

Examples of the halogen atom represented by R ³ include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and preferably a chlorine atom.
Examples of the alkyl group represented by R ³ include an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group and a propyl group, and preferably a methyl group.
Examples of the alkoxy group represented by R ³ include an alkoxy group having 1 to 3 carbon atoms such as a methoxy group, an ethoxy group and a propoxy group, and preferably a methoxy group or an ethoxy group.

The peaks attributed to C ¹ and C ² are usually observed around a chemical shift (δ) of 110 to 140 ppm, and the peaks attributed to C ³ and C ⁴ are usually a chemical shift (δ) of 20 to 50 ppm. Observed in the vicinity.

In particular, when a (meth) acryloyl group-containing silane coupling agent is used as the silane coupling agent, when the obtained (meth) acryloyl group-containing silica particles are subjected to solid state ¹³ C-NMR to measure the organic groups on the surface of the silica particles, The (meth) acryloyl group represented by the formula (A2) below is assigned to the integrated values of the peaks assigned to the carbons (C ⁶ and C ⁷ ) of the numbers 6 and 7 and the carbon (C ⁵ ) of the number 5. The integral of the peaks assigned to the carbons (C ⁹ and C ¹⁰ ) of the oligomerized (meth) acryloyl groups represented by the following formula (B2), which are represented by the following formula (B2), with respect to the total (I _C ) of the integrated values of the peaks. It is preferable that the ratio (I _D / I _C ) of the total I _D between the value and the integrated value of the peak attributed to the carbon (C ⁸ ) of No. 8 is 0.1 or less. The ratio (I _D / I _C) is more preferably 0.05 or less, more preferably 0.01 or less.

[In the formula, R ⁴ represents a hydrogen atom or a methyl group. * Represents a bond. ]

The peak attributed to C ⁵ is usually observed near the chemical shift (δ) of 160 to 170 ppm, and the peaks attributed to C ⁶ and C ⁷ are usually observed near the chemical shift (δ) of 120 to 140 ppm. The peak attributed to C ⁸ is usually observed around a chemical shift (δ) of 170 to 180 ppm, and the peaks attributed to C ⁹ and C ¹⁰ are usually observed near a chemical shift (δ) of 30 to 50 ppm. To be observed.

  The coverage of the double bond-containing silica particles with the silane coupling agent is 0.1 or more when evaluated by the molar ratio of carbon atoms and silicon atoms (C / Si ratio) measured by X-ray photoelectron spectroscopy. It is preferably 0.2 or more, more preferably 0.5 or more. The higher the C / Si ratio, the more preferable, but it may be 15 or less, for example. By increasing the C / Si ratio, dispersibility in an organic solvent can be improved. The C / Si ratio can be evaluated based on the C / Si ratio on the silica particle surface by measuring the abundance ratio (mol%) of C and Si atoms by X-ray photoelectron spectroscopy (XPS).

The double bond-containing silica particles of the present invention have few aggregates even if they are not crushed / classified, so that the mixing of iron components due to crushing / classification is suppressed. Therefore, the content of iron contained in the double bond-containing silica particles is preferably 20 ppm or less, more preferably 10 ppm or less, further preferably 2 ppm or less, and particularly preferably 1 ppm or less.
The iron content can be measured, for example, by a high frequency plasma emission spectroscopic analysis method (ICP method).

  The average primary particle diameter of the double bond-containing silica particles of the present invention is preferably 5 μm or less, more preferably 3 μm or less, still more preferably 2 μm or less, particularly preferably 1 μm or less, for example, 0 on a number basis. It may be 0.001 μm or more, preferably 0.005 μm or more, more preferably 0.01 μm or more, still more preferably 0.03 μm or more, even more preferably 0.05 μm or more, and particularly preferably 0.07 μm or more. May be.

The coefficient of variation of the particle size of the double bond-containing silica particles is preferably 30% or less, more preferably 20% or less, still more preferably 16% or less, and the smaller, the more preferable. % Or more is also acceptable.
The coefficient of variation of the particle size can be calculated based on the following formula using the primary average particle size (number basis) and the standard deviation of the primary average particle size.
Coefficient of variation (%) = (standard deviation of primary average particle diameter / primary average particle diameter (number basis)) × 100

  The primary average particle diameter (number basis) of double bond-containing silica particles is a measurement in which the number of silica particles included in one visual field of the double bond-containing silica particles sampled is 2,000 to 3,000. It can be obtained as an average value of the primary particle diameters of all the particles included in the scanning electron microscope image in the scanning electron microscope image of 5 or more visual fields obtained by observing with a scanning electron microscope at a magnification.

The silica particles used in the production method of the present invention may be particles formed of a siloxane skeleton (Si-O-Si), for example, particles having a silica content of 90% by mass or more. The silica content is preferably 95% by mass or more, more preferably 99% by mass or more.
The silica content can be determined by subtracting the sum of the content (percentage) of components other than the Si component in the calcined silica particles from 100. Components other than the Si component are Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Ge, K, La, Mg, Mn, Mo, Nb. , Nd, Ni, Na, P, Pb, Pd, Pt, Sb, Sc, Se, Sn, Sr, Ta, Te, Ti, Tl, V, Zn, Zr and Y are meant. The content of each element is a content value as an elemental element obtained by ICP emission spectroscopic analysis of JIS K 0116.

  The siloxane bond rate in the silica particles is preferably 60% or more, more preferably 65% or more, further preferably 68% or more, even more preferably 70% or more, particularly preferably 72% or more, and preferably 90% or more. % Or less, more preferably 80% or less, further preferably 76% or less, and particularly preferably 74% or less.

The siloxane bond ratio in the silica particles is obtained by measuring the silica particles with a ²⁹ Si-solid state NMR apparatus (for example, AVANCE400 manufactured by BRUKER), and measuring the area of all signals in the range of chemical shift (δ) −130 ppm to −80 ppm. When set to 100%, the ratio of the area of the signal having a peak at the chemical shift (δ) -111.4 ppm can be obtained as the siloxane bond rate.

The amount of silanol groups per unit surface area in the silica particles is preferably 0.010 mmol / m ² or more, more preferably 0.020 mmol / m ² or more, still more preferably 0.025 mmol / m ² or more, is preferably 0.065 mmol / m ² or less, more preferably 0.060 mmol / m ² or less, more preferably 0.055 mmol / m ^2, particularly preferably not more than 0.050 mmol / m ^2.

  Further, the silanol group concentration (mmol / g) on the surface of the silica particles is, for example, preferably 0.01 mmol / g or more, more preferably 0.05 mmol / g or more, and 0.60 mmol / g or less, more preferably It is preferably 0.50 mmol / g or less.

The amount of silanol groups per unit surface area can be determined by dividing the concentration of silanol groups on the surface of silica particles (mmol / g) by the specific surface area of particles (m ² / g). The concentration of silanol groups on the surface of the silica particles is determined by fully drying the amorphous silica particles under predetermined conditions (for example, pressure 6.6 kPa or less, temperature 120 ° C., 1 hour or more), and then in a solvent (eg dioxane). It can be determined by a method of quantifying the concentration of silanol groups (lithium aluminum hydride method) by reacting with lithium aluminum hydride in (1) and measuring the amount of hydrogen generated.

Furthermore, the specific surface area of the silica particles is preferably 1~300m ² / g, more preferably 2~200m ² / g, more preferably from 3~150m ² / g.

  Further, it is preferable that the silica particles have a reduced content of metals as impurities (transition metals such as Fe; alkali metals such as Na; alkaline earth metals such as Ca; etc.). The content of is preferably 0.1% by mass or less in the silica particles, more preferably 0.01% by mass or less, and further preferably 0.001% by mass or less.

  The primary average particle diameter of the silica particles is preferably 5 μm or less on the number basis, more preferably 3 μm or less, further preferably 2 μm or less, particularly preferably 1 μm or less, for example 0.001 μm or more. Well, preferably 0.01 μm or more, more preferably 0.03 μm or more, still more preferably 0.05 μm or more, still more preferably 0.07 μm or more. The primary average particle size (number basis) of the silica particles is a scanning type in which arbitrarily collected double bond-containing silica particles are measured at a measurement magnification such that the number of silica particles included in one visual field is 2,000 to 3,000. It can be obtained as an average value of the primary particle diameters of all the particles included in the scanning electron microscope image in the obtained scanning electron microscope image of five or more visual fields obtained by observing with an electron microscope.

  Further, the variation coefficient of the particle diameter of the silica particles is preferably 30% or less, more preferably 20% or less, further preferably 15% or less, and the smaller the more preferable, for example, 0.1% or more. Is also acceptable.

  The content of coarse particles in the silica particles is preferably 0.05% by mass or less, more preferably 0.02% by mass or less, still more preferably 0.01% by mass or less, and particularly preferably 0.1% by mass or less. The content is 005% by mass or less, and from the viewpoint of dispersibility in the resin or the resin raw material, the smaller the content of the coarse particles is, the more preferable. The content of coarse particles is a value obtained by dividing the mass of silica particles remaining on the sieve when the silica particles are sieved through a sieve having an opening of 20 μm by the total mass of the silica particles used for the measurement.

  The silica particles are usually solid particles, and the shape thereof may be, for example, spherical, spheroidal, etc., but spherical is preferable, and true spherical is particularly preferable. The ratio of the minor axis to the major axis of the particle diameter (minor axis / major axis) is preferably 0.90 or more, more preferably 0.92 or more, still more preferably 0.95 or more, and particularly preferably 0.98 or more. Is.

  The silica particle dispersion can be produced, for example, by hydrolyzing and condensing a hydrolyzable silicon compound to obtain wet silica particles, and drying the wet silica particles. The dried silica particles obtained are preferably further calcined before being subjected to the production method of the present invention.

  As the hydrolyzable silicon compound (hereinafter, may be simply referred to as “silicon compound”), the same compounds as those mentioned as the double bond-containing silane coupling agent and other silane coupling agents may be used. It can be used, tetraalkoxysilane or an alkyl group-containing alkoxysilane is preferable, tetraalkoxysilane is more preferable, and tetramethoxysilane or tetraethoxysilane is particularly preferable. The higher the number of functional groups of alkoxysilane (the number of alkoxy groups) contained in one molecule, the more difficult it is for impurities to be mixed into the obtained silica particles. Of the silicon compounds used, tetraalkoxysilane (preferably tetramethoxysilane, tetraethoxysilane) is preferably 90 mass% or more, more preferably 95 mass% or more, further preferably 98 mass% or more, The upper limit is 100% by mass.

  In the reaction liquid for hydrolyzing and condensing the silicon compound, the concentration of the silicon compound is preferably 0.05 mmol / g or more, more preferably 0.1 mmol / g or more, and the upper limit is not particularly limited. It is preferably 3 mmol / g or less, more preferably 1 mmol / g or less. When the concentration of the silicon compound in the reaction solution is within this range, the reaction rate can be easily controlled and the particle size can be made uniform.

  In addition, the concentration of water in the reaction liquid is preferably 1 mmol / g or more, more preferably 1.5 mmol / g or more, and preferably 25 mmol / g or less, more preferably 15 mmol / g. Or less, more preferably 10 mmol / g or less. However, since the amount of water changes due to hydrolysis / condensation of the silicon compound, the amount at the time of charging (before the start of hydrolysis / condensation) is used as the standard. The molar ratio of water to the silicon compound (water / silicon compound) is preferably 2 or more, more preferably 4 or more, preferably 20 or less, and more preferably 15 or less.

  When hydrolyzing and condensing the silicon compound, it is preferable to coexist with a catalyst. The silicon compound can be hydrolyzed and condensed even in the absence of a catalyst, but by using the catalyst, the reaction can be easily controlled and the particle size and the residual amount of silanol groups can be adjusted. The catalyst is preferably a basic catalyst from the viewpoint of increasing the reaction rate, and examples of the basic catalyst include ammonia, amines, quaternary ammonium compounds and the like. Examples of the ammonia include ammonia; an ammonia generator such as urea; and the like. Examples of the amines include aliphatic amines such as methylamine, ethylamine, propylamine, n-butylamine, dimethylamine, dibutylamine, trimethylamine, and tributylamine; alicyclic amines such as cyclohexylamine; fragrances such as benzylamine. Group amines; alkanolamines such as monoethanolamine, diethanolamine and triethanolamine; and the like. Examples of the quaternary ammonium compound include tetramethylammonium hydroxide and tetramethylammonium chloride.

  Of these, ammonias and amines are preferable from the viewpoint of easy control of particle size. Further, from the viewpoint of increasing the purity of the obtained silica particles, a catalyst that can be easily removed from the silica is preferable, and specifically, ammonias and amines are preferable, and ammonia and aliphatic amines are more preferable. Further, from the viewpoint of having both a catalytic effect and easy removal, ammonia is preferable, and ammonia is particularly preferable.

  The concentration of the catalyst in the reaction solution is preferably 0.8 mmol / g to 9.4 mmol / g. The mass ratio of the catalyst to the total of the catalyst and water (catalyst / (catalyst + water)) is preferably 0.1 or more, more preferably 0.2 or more and 0.4 or less. Is preferable, and 0.32 or less is more preferable.

Furthermore, when the silicon compound is hydrolyzed / condensed, it is preferable to coexist with a reaction diluent. By containing a reaction diluent, the hydrophobic silicon compound and water can be easily mixed, and the progress of hydrolysis and condensation of the silicon compound can be made uniform in the reaction solution, and the resulting uncalcined product can be obtained. The dispersibility of silica is improved. As the reaction diluent, a suitable water-soluble organic solvent can be used, alcohols and diols are preferable, and alcohols are preferable.
The reaction diluent is preferably 150 parts by mass or more, more preferably 200 parts by mass or more, and preferably 2500 parts by mass or less, more preferably 100 parts by mass with respect to the total of 100 parts by mass of the silicon compound and water. Is 1000 parts by mass or less, more preferably 500 parts by mass or less.
The larger the amount of the diluent, the easier it is to make the degree of reaction uniform, and the smaller the amount of the diluent, the higher the reaction rate.

  In addition, the reaction liquid contains ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; paraffins such as isooctane and cyclohexane; ethers such as dioxane and diethyl ether; aromatic hydrocarbons such as benzene and toluene. A hydrophobic organic solvent such as; may be contained. When using these hydrophobic organic solvents, a surfactant may be added to improve dispersibility.

  Although the above components may be mixed in an appropriate order, for example, a pre-mixed solution for preparing silica particles is prepared by previously mixing at least a part of each component (for example, water, catalyst, diluent, etc.). Then, it may be mixed with a silicon compound. Further, it is preferable to add the silicon compound to the preliminary mixture for preparing silica particles, and the addition method may be batch addition or sequential addition (continuous addition or intermittent addition), but it is preferable to add sequentially. The silicon compound may be premixed with the diluent and then mixed with the premix.

  When hydrolyzing and condensing the silicon compound, the reaction temperature is preferably 0 to 100 ° C, more preferably 10 to 60 ° C, and further preferably 10 to 40 ° C. The duration of hydrolysis / condensation is preferably 30 minutes to 100 hours, more preferably 50 minutes to 20 hours, still more preferably 1 to 10 hours.

  Dry silica particles can be obtained by drying the wet silica particles obtained as described above. The wet silica particles may be separated from the reaction solution by filtration, centrifugation, solvent evaporation (concentration) or the like from the viewpoint of suppressing agglomeration and sticking during drying. It is preferable to set. Further, the reaction solution may be filtered with a filter before separating the wet silica particles from the reaction solution.

  In order to dry the wet silica particles, it is preferable to adopt, for example, a gas stream drying method. In the air flow drying method, the wet silica particles being dried are dispersed by the air flow or collide with the inner wall of the drying device, so that the agglomeration of the silica particles can be suppressed while drying. When the reaction liquid (concentrated liquid) is dried by the airflow drying method, either a direct heating method (method using a heated airflow) or an indirect heating method (heating the heat transfer plate of the dryer (preferably the inner wall of the dryer)) May be selected. When the direct heating method is adopted, the high temperature airflow generated from the hot air generation furnace etc. contacts the reaction solution (concentrate) to evaporate the solvent and dry the wet silica particles, and at the same time, the high temperature airflow causes the wet silica particles to dry. The particles are crushed and the agglomeration of the dried silica particles can be suppressed. Further, when the indirect heating method is adopted, the reaction liquid (concentrated liquid) is heated through the heat transfer plate (preferably the inner wall) to evaporate the solvent and dry the wet silica particles, and at the same time, to introduce them from the outside. The wet silica particles being dried are disintegrated by the airflow or the airflow circulating inside, and the agglomeration of the dry silica particles is suppressed. Among them, the indirect heating method is preferable.

  The drying device may have a tubular structure, a container structure such as a can, or a structure in which a drying tube and a drying container are combined. From the viewpoint of improving the disintegration property of the wet silica particles during drying and suppressing the agglomeration of the dry silica particles, a structure having a tubular heat transfer plate (preferably an inner wall) (hereinafter referred to as a drying tube) is used as a drying device. It is preferable. In particular, it is more preferable that the drying tube is capable of evacuating from the bent portion side (outlet side) while supplying the reaction liquid (concentrated liquid) from the linear portion side (inlet side).

  The inner diameter of the drying tube is preferably 6 mm or more, more preferably 7 mm or more, further preferably 8 mm or more, and preferably 20 mm or less. The total length of the drying tube is preferably 800 mm or more and 9600 mm or less.

  The drying temperature is preferably 150 to 200 ° C. The drying temperature means the temperature of the air flow in the case of the direct heating method, and the temperature of the drying tube in the case of the indirect heating method. The pressure (degree of reduced pressure) during drying is preferably 30 to 300 torr, and more preferably 40 to 250 torr.

  As an apparatus capable of drying by the air flow drying method (indirect heating method), an instantaneous vacuum drying apparatus "Cracks System 8B type" (manufactured by Hosokawa Micron Corporation) can be mentioned.

The water content after leaving the obtained dried silica particles for 24 hours in an atmosphere having a temperature of 30 ° C. and a relative humidity of 90% is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably It is 15% by mass or less, particularly preferably 10% by mass or less, and may be, for example, 0.05% by mass or more, and further 0.1% by mass or more.
The water content can be measured by the following measuring method. That is, 5 g of dried silica particles are placed on a watch glass having a diameter of 10 cm and spread evenly and thinly. Then, it is left for 24 hours in an atmosphere of a temperature of 30 ° C. and a relative humidity of 90%. The water content of the silica after standing can be measured by the Karl Fischer method to obtain the water content.

  By calcining the dried silica particles, the silica particles of the present invention can be obtained. The firing temperature is 800 to 1200 ° C, preferably 900 to 1100 ° C. The calcination facilitates reduction of the silanol groups remaining in the silica particles.

  Examples of the atmosphere during firing include an oxidizing atmosphere such as air and nitrogen-oxygen mixed gas; an inert atmosphere such as nitrogen gas, argon gas, and helium gas; and the like, and an oxidizing atmosphere is preferable. This facilitates removal of silanol groups, alkoxy groups and the like.

  It is not necessary to perform dry pulverization after firing, but dry pulverization may be performed if necessary. The dry pulverization conditions may be the same as those of the dry pulverization before firing.

  The ethylenic double bond-containing silica particles obtained by the production method of the present invention are coated with a silane coupling agent while suppressing aggregation, and have good dispersibility in a resin. Therefore, for example, polyester film, polyimide film, anti-blocking agent for various films such as fluororesin film and slipperiness imparting agent; in-plane spacer for liquid crystal display element, seal part spacer for liquid crystal display element, spacer for EL display element, Spacers for touch panels, spacers for holding gaps between various substrates such as ceramics and plastics; sealing materials for semiconductors, liquid crystal sealing materials, sealing materials for LED light emitting elements, etc .; It can be applied to light diffusing agents such as films, light diffusing plates, light guide plates and antiglare films; cosmetic additives such as white extender pigments; dental materials. In particular, it is useful as a filler for various electronic component sealing materials such as semiconductor sealing materials, liquid crystal sealing agents, and LED light emitting element sealing materials.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples as well as the present invention, and may be appropriately modified within a range compatible with the gist of the preceding and the following. Of course, it is possible to carry out, and all of them are included in the technical scope of the present invention.
In the following, "parts" means "parts by mass" and "%" means "% by mass" unless otherwise specified.

<Solid ¹³ C-NMR spectrum>
Solid-state ¹³ C-NMR measurement was performed under the following conditions using "AVANCE400" manufactured by BRUKER. Then, the following formula (A1) peaks (chemical shifts (δ): 110~140ppm) attributed to the carbon C ¹ and C ² of the No. 1 and No. 2 acryloyl groups, expressed by the sum of the integrated value of (I _A) , And the integrated value of the peaks (chemical shift (δ): 20 to 50 ppm) belonging to carbons C ³ and C ⁴ of the oligomerized (meth) acryloyl groups represented by the following formula (B1). The total I _B was obtained and the ratio (I _B / I _A ) was calculated.

［式中、Ｒ¹は水素原子を表す。Ｒ²は、−ＣＯ−を表す。＊は結合手を表す。］

[In the formula, R ¹ represents a hydrogen atom. R ² represents a -CO-. * Represents a bond. ]

Similarly, an integrated value of peaks (chemical shift (δ): 120 to 140 ppm) assigned to carbons C ⁶ and C ⁷ of Nos. 6 and 7 of the acryloyl group represented by the following formula (A2) and No. 5 of The sum (I _C ) of the peaks (chemical shift (δ): 160 to 170 ppm) belonging to carbon C ⁵ and the oligomerization (meth) acryloyl group number 9 represented by the following formula (B2) and Integrated values of peaks (chemical shift (δ): 30 to 50 ppm) assigned to carbons C ⁹ and C ¹⁰ of No. 10 and peaks assigned to carbon C ^{8 of} number 8 (chemical shift (δ): 170 to The total I _D of the integrated values of 180 ppm) was obtained, and the ratio (I _D / I _C ) was calculated.

［式中、Ｒ⁴は、水素原子を表す。＊は結合手を表す。］

[In the formula, R ⁴ represents a hydrogen atom. * Represents a bond. ]

< ¹³ C-NMR measurement conditions>
Device: BRAKER's "AVANCE400"
Sample tube: 7 mm diameter Made of zirconia Rotation speed: 6 kHz
Observation nucleus: ¹³ C
Observation nuclear resonance frequency: 100.625 MHz
Pulse Program: CP / MAS (Cross Polarization Method)
Contact time: 2 ms Repetition time: 10 seconds Accumulation count: 8192 times Observation temperature: room temperature Chemical shift value of reference substance: Glycine (carbonyl peak 176.03 ppm) External reference

<Content ratio of aggregate>
The content of aggregates contained in the silica particles was determined by the following measuring method. That is, a mixture formed by adding 10 g of silica particles, 90 g of water, and 2 g of sodium dodecylbenzenesulfonate as a surfactant to form a dispersion liquid by ultrasonically dispersing for 1 hour, and then at 25 ± 3 ° C. The dispersion is passed through a sieve (metal mesh (JIS standard)) having a diameter of 75 mm × height of 20 mm and an opening of 20 μm and dried at 110 ° C. for 1 hour, and then the mass of aggregates not passing through the net is W (g). The value obtained by the following formula was defined as the content ratio of the aggregate. The lower limit of detection of the content ratio of aggregates was 10 ppm.
Aggregate content ratio (ppm) = (W (g) / 10 (g)) × 10 ⁶
In the examples and comparative examples shown below, the content of the aggregate was an average value when the number of measurements was 10.

<Primary average particle size, coefficient of variation and number ratio of coarse particles>
The arbitrarily-collected silica particles were observed at five different locations using a scanning electron microscope at a measurement magnification such that the number of silica particles contained in one visual field was 2,000 to 3,000. At this time, the primary particle diameter of 2,000 silica particles contained in each of the obtained five-field scanning electron microscope images was measured with a caliper, and the number average of all of them was taken as the primary average particle diameter. Further, the coefficient of variation of the primary particle diameter was calculated based on the following formula using the primary average particle diameter and the standard deviation of the primary particle diameter.
Coefficient of variation (%) = (standard deviation of primary particle size / primary average particle size) × 100

<Measurement of water content>
5 g of dried silica particles were further placed on a watch having a diameter of 10 cm and spread uniformly and thinly. Then, it was left for 24 hours in an atmosphere of a temperature of 30 ° C. and a relative humidity of 90%. The water content of the silica after standing was measured by the Karl Fischer method to obtain the water content.

<Measurement of silica content>
The silica content was determined by subtracting the sum of the content (percentage) of components other than the Si component in the calcined silica particles from 100. Components other than the Si component are Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Ge, K, La, Mg, Mn, Mo, Nb. , Nd, Ni, Na, P, Pb, Pd, Pt, Sb, Sc, Se, Sn, Sr, Ta, Te, Ti, Tl, V, Zn, Zr and Y are meant. The content of each element is a content value as an elemental element obtained by ICP emission spectroscopic analysis of JIS K 0116.

[Example 1]
A 200 L reactor equipped with a stirrer, a dropping device and a thermometer was charged with 67.54 kg of methyl alcohol and 26.33 kg of 28 mass% ammonia water (water and catalyst), and the liquid temperature was 33 ± 3 while stirring. The temperature was adjusted to 0.5 ° C. On the other hand, a solution prepared by dissolving 13.45 kg of tetramethoxysilane in 5.59 kg of methyl alcohol was charged into the dropping device. While maintaining the liquid temperature in the reactor at 33 ± 0.5 ° C., the solution was dropped from the dropping device over 1 hour, and after the dropping was completed, stirring was performed for 1 hour while keeping the liquid temperature at the temperature. Thus, the tetramethoxysilane was hydrolyzed and condensed to obtain a dispersion liquid containing the silica particle precursor.

  Dry silica particles were obtained by subjecting the dispersion to airflow drying with an instantaneous vacuum evaporator. As an instantaneous vacuum evaporator, a cracks system 8B type (manufactured by Hosokawa Micron Co., Ltd.) was used. As the drying conditions, a heating tube temperature of 175 ° C. and a pressure reduction degree of 200 torr (27 kPa) were adopted. The instantaneous vacuum evaporator comprises a stainless steel pipe having an inner diameter of 8 mm and a length of 9 m covered with a jacket to which heated steam is supplied, and a supply unit for supplying a dispersion liquid containing a silica particle precursor to one end of the steel pipe. A powder collection chamber in a depressurized state, which is connected to the other end of the steel pipe and is provided with a bag filter for separating powder and vapor. In the steel pipe, the dispersion liquid containing the silica particle precursor supplied from the supply unit is indirectly heated, the solvent is evaporated, and the air is created by depressurizing the powder collection side, thereby producing silica. Dispersion of the dispersion liquid containing the particle precursor and crushing of the silica particle precursor are promoted. The powder is transferred in the steel pipe by the air flow created by depressurizing the powder collecting side, and is collected by the bag filter. After passing through the bag filter, the vapor is condensed and then discharged to the outside of the apparatus.

  The obtained dried silica particles were put into a crucible, calcined at 1050 ° C. for 1 hour using an electric furnace, cooled, and then crushed with a crusher to obtain calcined silica particles. The firing temperature is a value obtained by measuring the ambient temperature in the electric furnace. The silica content of the obtained calcined silica was 99.9%.

5 kg of the calcined silica particles (specific surface area 20 m ² / g) were charged into a Henschel mixer (FM20J type manufactured by Mitsui Mining Co., Ltd.) having a capacity of 20 L equipped with a heating jacket. The Henschel mixer is equipped with a container for containing the mixture and a rotary shaft with stirring blades at the bottom of the container, and a plate-shaped blade installed along the wall surface as a device for scraping off wall surface deposits. The attached rotating shaft is installed on the upper surface of the container. While stirring the calcined silica particles, at room temperature (about 25 ° C.), 3-acryloxypropyltrimethoxysilane (KBM-5103 manufactured by Shin-Etsu Chemical Co., Ltd., a minimum coating area 333 m ² / g) 600 g was added dropwise and mixed with a solution prepared by dissolving 250 g of methyl alcohol. Incidentally, 600 g of 3-acryloxypropyltrimethoxysilane corresponds to 2.0 times the theoretical coating amount of the silane coupling agent with respect to 5 kg of the calcined silica particles (specific surface area 20 m ² / g).

  Then, the obtained mixture was transferred to a tray and adjusted so that the maximum thickness of the mixture was 20 mm and the upper surface of the mixture was a horizontal surface. The bottom surface of the tray was a horizontal surface, and the bottom surface was rectangular (long diameter 35 cm, short diameter 25 cm). Further, this tray was housed in a tray dryer (“PV-212” manufactured by Espec Co., Ltd.), heated to 120 ° C. under atmospheric pressure over about 1 hour, and held at 120 ° C. for 1 hour to perform heat treatment. I went. The wind speed during drying was 1.5 m / s. The temperature value of 120 ° C. is a value obtained by measuring the temperature in the mixture of the pyrogenic silica and the silane coupling agent. The heat treatment was performed while the mixture of the calcined silica particles and the silane coupling agent was allowed to stand.

[Example 2]
In Example 1, the maximum thickness of the mixture was set to 40 mm instead of 20 mm, the tray containing the mixture was heated to 120 ° C. under atmospheric pressure over about 1 hour, and held at 120 ° C. for 1 hour to be heated. Instead of performing the treatment, an ethylenic double bond was prepared in the same manner as in Example 1 except that the temperature was raised to 110 ° C. over about 1 hour under atmospheric pressure and the heating treatment was performed at 110 ° C. for 1 hour. Obtained silica particles were obtained.

[Comparative Example 1]
5 kg of the calcined silica particles (specific surface area 20 m ² / g) obtained in Example 1 were charged into a 20 L Henschel mixer (FM20J type manufactured by Mitsui Mining Co., Ltd.) equipped with a heating jacket. The Henschel mixer is equipped with a container for containing the mixture and a rotary shaft with stirring blades at the bottom of the container, and a plate-shaped blade installed along the wall surface as a device for scraping off wall surface deposits. The attached rotating shaft is installed on the upper surface of the container. While stirring the calcined silica particles, at room temperature (about 25 ° C.), 3-acryloxypropyltrimethoxysilane which is a silane coupling agent (KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd., minimum coating area 333 m ² / g) 600 g was added dropwise and mixed with a solution prepared by dissolving 250 g of methyl alcohol. Incidentally, 600 g of 3-acryloxypropyltrimethoxysilane corresponds to 2.0 times the theoretical coating amount of the silane coupling agent with respect to 5 kg of the calcined silica particles (specific surface area 20 m ² / g). After that, the mixture of the calcined silica particles and the silane coupling agent was heated to 120 ° C. over about 1 hour and kept at 120 ° C. for 3 hours for heat treatment. The temperature value of 120 ° C. is a value obtained by measuring the temperature in the mixture of the pyrogenic silica and the silane coupling agent. The heat treatment was performed while mixing and stirring the mixture of the calcined silica particles and the silane coupling agent. In the heat treatment, the scraping device was constantly rotated in the direction opposite to the stirring blade to scrape off the deposits on the wall surface. Further, it was also appropriate to scrape off the adhered material on the wall surface using a spatula.

[Comparative example 2]
5 kg of the calcined silica particles (specific surface area 20 m ² / g) obtained in Example 1 were charged into a 20 L Henschel mixer (FM20J type manufactured by Mitsui Mining Co., Ltd.) equipped with a heating jacket. The Henschel mixer is equipped with a container for containing the mixture and a rotary shaft with stirring blades at the bottom of the container, and a plate-shaped blade installed along the wall surface as a device for scraping off wall surface deposits. The attached rotating shaft is installed on the upper surface of the container. While stirring the calcined silica particles, at room temperature (about 25 ° C.), 3-acryloxypropyltrimethoxysilane which is a silane coupling agent (KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd., minimum coating area 333 m ² / g) 600 g was added dropwise and mixed with a solution prepared by dissolving 250 g of methyl alcohol. 250 g of 3-acryloxypropyltrimethoxysilane corresponds to 2.0 times the theoretical coverage of the silane coupling agent. Then, the mixture of the calcined silica particles and the silane coupling agent was heated to 120 ° C. over about 1 hour and kept at 120 ° C. for 1 hour for heat treatment. The temperature value of 120 ° C. is a value obtained by measuring the temperature in the mixture of the pyrogenic silica and the silane coupling agent. The heat treatment was performed while mixing and stirring the mixture of the calcined silica particles and the silane coupling agent. In the heat treatment, the scraping device was constantly rotated in the direction opposite to the stirring blade to scrape off the deposits on the wall surface. Further, it was also appropriate to scrape off the adhered material on the wall surface using a spatula.

By the primary average particle diameter of the silica particles containing ethylenic double bond obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the coefficient of variation of the primary particle diameter, the content ratio of aggregates, the water content and ¹³ C-NMR. determined ratio (I _B / I _a), shown in Table 1 (I _D / I _C).

  As shown in Table 1, silica particles and an acryloyl group-containing silane coupling agent were mixed, the mixture was placed in a container having a horizontal surface as a bottom surface, and the mixture was allowed to stand at a temperature of 110 ° C or 120 ° C. In Examples 1 and 2 heated to 0 ° C., the content ratio of aggregates was suppressed even without crushing and classification. On the other hand, in Comparative Examples 1 and 2 in which the mixture of the silica particles and the acryloyl group-containing silane coupling agent was heated with stirring, it was confirmed that the ethylenic double bond-containing silica particles were aggregated.

  The ethylenic double bond-containing silica particles obtained by the production method of the present invention are coated with a silane coupling agent while suppressing aggregation, and have good dispersibility in a resin. Therefore, for example, polyester film, polyimide film, anti-blocking agent and slippery agent for various films such as fluororesin film; in-plane spacer for liquid crystal display element, seal part spacer for liquid crystal display element, spacer for EL display element, Spacers for touch panels, spacers for holding gaps between various substrates such as ceramics and plastics; sealants for semiconductors, sealants for liquid crystals, sealants for LED light emitting elements, etc .; various electronic component sealants; light diffusion It can be applied to light diffusing agents such as films, light diffusing plates, light guide plates and antiglare films; cosmetic additives such as white extender pigments; dental materials. In particular, it is useful as a filler for various electronic component sealing agents such as semiconductor sealing agents, liquid crystal sealing agents, and LED light emitting element sealing agents.

Claims (6)

Preparing a mixture comprising silica particles and (meth) acryloyl group-containing silane coupling agent, and a step of heating above a temperature 100 ° C. in a state of standing the mixture (meth) acryloyl group-containing silica particles Manufacturing method.   The manufacturing method according to claim 1, further comprising a step of housing the mixture in a container having a horizontal surface as a bottom surface before allowing the mixture to stand.   The manufacturing method according to claim 1, wherein the heating temperature is 150 ° C. or lower. The amount of (meth) acryloyl group-containing silane coupling agent, the manufacturing method according to any one of claims 1 to 3 to 1 times the theoretical coverage represented by the following formula.
Theoretical coverage (g) = mass of silica particles (g) × specific surface area of silica particles (g / m ² ) / minimum coating area of ( meth) acryloyl group- containing silane coupling agent (m ² / g) (Meth) an acryloyl group-containing pyrogenic silica particles, a solid ¹³ C-NMR as measured organic groups of the silica particle surface, expressed by the following formula (A2) (meth) numbers 6 and No. 7 acryloyl groups With respect to the sum ( I _c ) of the integrated value of the peaks assigned to carbon ( C ⁶ and C ⁷ ) and the integrated value of the peaks assigned to carbon (C ⁵ ) of No. 5 ,
Integral values of peaks assigned to carbons ( C ⁹ and C ¹⁰ ) of numbers 9 and 10 of the oligomerized (meth) acryloyl group represented by the following formula ( B2 ) and carbons of number 8 (C ⁸ ). The (meth) acryloyl group- containing calcined silica particles having a ratio ( I _D / I _C ) of the total I _{D to} the integrated value of the generated peaks of 0.1 or less.

[In the formula, R ⁴ represents a hydrogen atom or a methyl group. * Represents a bond. ] The silica particles according to claim 5 , wherein the content ratio of the aggregates determined by the following measurement method is 10,000 ppm (mass basis) or less.
[Measuring method]
The dispersion obtained by ultrasonically dispersing 10 g of silica particles, 90 g of water, and 2 g of sodium dodecylbenzenesulfonate as a surfactant for 300 seconds or longer was passed through a sieve having an opening of 20 μm at 25 ± 3 ° C. When the mass of the silica particles remaining on the sieve in this case is W (g), the value obtained by the following formula is the content ratio of the aggregate.
Aggregate content ratio (ppm) = (W (g) / 10 (g)) × 10 ⁶