JP2022102438A - Silica powder and use thereof, and method for producing silica powder - Google Patents

Abstract

To provide a novel silica powder having high safety, small apparent density and high concealing property.SOLUTION: A silica powder contains a plurality of voids having a length of a long axis of 200 nm or more and 3 μm or less inside the powder, and a value of {oil absorption amount (cm3/100 g)/100}/pore volume (cm3/g) is 1.5 or more.SELECTED DRAWING: None

Description

The present invention relates to silica particles and their uses, and a method for producing silica particles.

Particulate silica is used in various fields as a catalyst, a desiccant, an abrasive, a resin filler, a raw material for cosmetics, and the like. The types of silica particles include silica having continuous mesh-like fine pores inside one particle (porous silica), silica having a structure having one hollow portion inside one particle (hollow silica), and the like. There is silica (solid silica) that has substantially no voids inside the particles, and it is used properly according to each application.

For example, Patent Document 1 proposes a spherical metal oxide powder having excellent heat insulating properties and reduced bulk density, which is used as a core material for a vacuum heat insulating material, various filling applications, additive applications, cosmetic applications, and the like. It is stated that. Patent Document 1 exemplifies silica as a metal oxide. The metal oxide powder contains spherical independent particles as a main component, and has a specific surface area of 400 m ² / g or more and 1000 m ² / g or less by the BET method, and BJH. It is characterized in that the pore volume according to the method is 2 mL / g or more and 8 mL / g or less, and the oil absorption amount is 250 mL / 100 g or more.

Further, Patent Document 2 proposes a method for producing hollow particles composed of a dense silica shell, and the hollow particles of the dense silica have a BET specific surface area of about 15 to 800 m ² / g and 500 ml or more per 100 g of silica. It is described that the DOP oil absorption amount and the shell thickness of about 2 to 10 nm or less are shown. Patent Document 2 describes that such hollow particles of dense silica can be used as a hollow filler or an absorbent.

Further, Patent Document 3 describes a method for producing spherical porous inorganic particles capable of reflecting light in the visible light region, and producing porous inorganic particles containing macropores of 50 nm or more. Is described. Patent Document 3 describes that porous inorganic particles can be applied to various fields such as photonic crystals, UV reflective substances, and CO ₂ adsorbents.

International Publication No. 2012/147812 Special Table 2000-500113 Gazette Japanese Patent Publication No. 2020-525375

Inorganic white pigments used in cosmetics have the hiding property of the base as one of the required properties. In recent years, in order to improve the texture of the skin, there has been a demand for an inorganic white pigment having a good feel, high safety, and high concealing property.
Titanium dioxide, which is known as an inorganic white pigment with high concealing properties, has a large particle density and is heavy, so it feels bad, may be a carcinogen, and has a photocatalytic action, which may damage the skin surface. There are drawbacks.

On the other hand, silica particles are expected to be applied to cosmetics because they can adjust the particle size and particle density and are highly safe. However, the conventional silica particles do not have sufficient concealing property of the base, and further improvement is desired.

Therefore, it is an object of the present invention to provide novel silica particles having high safety, low apparent density, and high concealment.

As a result of studies in view of the above problems, the present inventors have found that the above problems can be solved by silica particles containing a plurality of voids having a major axis length of 200 nm or more inside the particles, and have completed the present invention. rice field.

The present invention relates to the following <1> to <12>.
<1> A plurality of voids having a major axis length of 200 nm or more and 3 μm or less are contained inside the particles, and the value of {oil absorption (cm ^{3/100 g) / 100} / pore volume (cm 3 /} g) is 1. .Silica particles that are greater than or equal to 5.
<2> The silica particles according to <1>, wherein the average circularity is 0.80 or more.
<3> The silica particles according to <1> or <2>, which have a hydrophilic surface.
<4> The silica particles according to any one of <1> to <3>, wherein the 50% particle size (D ₅₀ ) in the cumulative particle size distribution based on the volume of the silica particles is 3 to 500 μm.
<5> The silica particle according to any one of <1> to <4>, wherein the pore volume is less than 2.0 cm ³ / g.
<6> The silica particles according to any one of <1> to <5>, wherein the particle strength is 1 MPa or more.
<7> When a reddish brown iron (III) oxide powder having an a ^* value of 14 or more and 15 or less in the L ^* a ^* b ^* color system is mixed with the silica particles at a ratio of 30% by mass to obtain a mixed powder. The silica particles according to any one of <1> to <6>, wherein the a ^* value of the mixed powder is 6.0 or less.
<8> A white pigment containing the silica particles according to any one of <1> to <7>.
<9> A cosmetic product containing the silica particles according to any one of <1> to <7>.
<10> A method for producing silica particles, in which silica is precipitated after atomizing an aqueous sodium silicate solution containing template particles, the template particles are removed, and the silica from which the template particles have been removed is washed and dried.
<11> The dispersion phase is a mixture of template particles mixed in an aqueous sodium silicate solution, the organic phase containing a surfactant is used as a continuous phase, and the dispersed phase and the continuous phase are mixed and emulsified by stirring, and the dispersion is performed. An emulsion in which the phase is dropletized is obtained, the emulsion is gelled to obtain a silica slurry containing silica containing the template particles, and an acid is added to the silica slurry to remove the template particles. , A method for producing silica particles, wherein the silica from which the template particles have been removed is washed and dried.
<12> The method for producing silica particles according to <10> or <11>, wherein the template particles are at least one selected from the group consisting of magnesium hydroxide, magnesium carbonate, calcium hydroxide and calcium carbonate. ..

Since the silica particles of the present invention contain a plurality of voids having a major axis length of 200 nm or more and 3 μm or less inside the particles, the apparent density is reduced, so that the silica particles are light particles. In addition, the scattering surface of light in the visible light region (400 to 800 nm) increases, and the scattering property of the particles is improved, so that the particles have high concealing properties. Moreover, since it is composed of silica, it is highly safe. Therefore, it can be suitably used for cosmetics, and when it is used for cosmetics, it has a high concealing property of the base and an excellent shielding power against the skin.

FIG. 1 shows a scanning electron microscope image (SEM image) of the fractured surface of the silica particles obtained in Example 4. FIG. 2 shows a scanning electron microscope image (SEM image) of the silica particles obtained in Example 4.

Hereinafter, the present invention will be described, but the present invention is not limited by the examples in the following description.

<Silica particles>
The silica particles of the present invention contain a plurality of voids having a major axis length of 200 nm or more and 3 μm or less inside the particles, and {oil absorption (cm ^{3/100 g) / 100} / pore volume (cm 3 /} g). The value of is 1.5 or more. The presence of voids inside the silica particles can be confirmed, for example, by observing the cross section of the particles with a scanning electron microscope (SEM).

The length of the major axis of the void is determined, for example, by photographing the fractured surface of the silica particles with an SEM and measuring the longest distance of the opening of the void in the SEM photograph.

The silica particles of the present invention contain a plurality of voids having a major axis length of 200 nm or more and 3 μm or less. Since visible light is diffused at the interface between silica and air, light is likely to be scattered if there are voids inside the silica particles, but light is not scattered if the voids are too small. By including a void having a major axis length of 200 nm or more, light scattering can be caused. Further, in consideration of the size of the silica particles that can be manufactured, the length of the major axis shall be 3 μm or less.
The length of the major axis of the void inside the particle is 200 nm or more, preferably 300 nm or more, more preferably 400 nm or more, 3 μm or less, preferably 2 μm or less, and more preferably 1 μm or less.

Since visible light is scattered at the interface between silica and air, the more interfaces there are, the more visible light can be scattered, and the concealment property is improved. Therefore, the scattering property of visible light is improved by having a plurality of voids having a major axis length of 200 nm or more and 3 μm or less inside the silica particles.
The number of voids having a major axis length of 200 nm or more and 3 μm or less may be two or more in one particle, depending on the size (particle size) of the silica particles and the size of the voids (length of the major axis). It can be adjusted as appropriate.

In the present invention, the pore volume of the silica particles is preferably less than 2.0 cm ³ / g. Here, the pore volume means a pore volume derived from a pore having a pore diameter of 1 to 100 nm. The apparent particle density is reduced by having pores (voids) having a pore diameter of 1 to 100 nm around voids having a major axis length of 200 nm or more and 3 μm or less. That is, the silica particles become light particles and the feel is improved, and even if the liquid is sucked, the air phase of large voids is maintained, so that the concealing property can be maintained. If the pore volume is too large, the particle strength may decrease and the use is limited. Therefore, it is preferably less than 2.0 cm ³ / g.
The pore volume is more preferably 1.9 cm ³ / g or less, further preferably 1.8 cm ³ / g or less, and particularly preferably 1.7 cm ³ / g or less. The lower limit of the pore volume of the silica particles is not particularly limited, but when the silica particles are unbaked products, it is preferably 0.9 cm ³ / g or more, more preferably 0.95 cm ³ / g or more, and 1 More preferably, it is 0.0 cm ³ / g or more.

When the silica particles are fired products, the pores (voids) having a pore diameter of 1 to 100 nm can be shrunk by firing to reduce the pore volume to 0.3 cm ³ / g or less. When the number of pores is small, it is difficult for the liquid to permeate into the voids having a major axis length of 200 nm or more and 3 μm or less, and the lightness and concealing property of the silica particles can be maintained.

The pore volume can be calculated by using the BJH method by the nitrogen adsorption method.

The silica particles preferably have an oil absorption of 30 to 500 cm / ^3/100 g. When the oil absorption amount is 30 cm ^3/100 g or more, the apparent density can be reduced to make light particles, and high concealment can be maintained even if some sebum is absorbed, so that it can be suitably used for cosmetics and oil absorption. When the amount is 500 cm ^3/100 g or less, high particle strength can be maintained.
The oil absorption amount is more preferably 50 cm ^3/100 g or more, further preferably 100 cm ^3/100 g or more, particularly preferably 250 cm ^3/100 g or more, and even more preferably 450 cm ^3/100 g or less, 400 cm ³ / 100 g or less is more preferable, and 350 cm ^3/100 g or less is particularly preferable.

The oil absorption amount can be measured according to JIS K 5101. Specifically, boiled flaxseed oil is added to the sample while kneading until the whole sample becomes a mass. The oil absorption amount is expressed by the volume of boiled flax oil per 100 g of the sample when the whole sample is agglomerated. Hereinafter, the amount of oil absorbed by this measuring method is simply referred to as the amount of oil absorbed.

In the present invention, silica represented by {oil absorption (cm ^{3/100 g) / 100} / pore volume (cm 3 /} g) (hereinafter referred to as "(oil absorption / 100) / pore volume"). The oil absorption amount with respect to the pore volume per 1 g of particles is 1.5 or more. When the ratio of (oil absorption / 100) to the pore volume is larger than 1, it means that there are many voids that can scatter visible light inside the particles. When the value of (oil absorption / 100) / pore volume is 1.5 or more, it indicates that there are particularly many voids in which visible light can be scattered inside the particle, so that visible light is scattered on the particle surface. The number increases, and sufficient concealment can be obtained.
The value of (oil absorption / 100) / pore volume is 1.5 or more, preferably 1.6 or more, more preferably 2.0 or more, and is not particularly limited as long as it does not affect the particle strength. , 500 or less is preferable.

The silica particles of the present invention preferably have a specific surface area of 1 m ² / g or more, which is obtained based on the nitrogen adsorption method. When the specific surface area is 1 m ² / g or more, the active sites can be increased when used as a catalyst carrier.
The specific surface area is more preferably 10 m ² / g or more, further preferably 50 m ² / g or more, particularly preferably 100 m ² / g or more, and the upper limit is not particularly limited.

The specific surface area can be calculated using the BET theory after obtaining an adsorption isotherm by the nitrogen adsorption method.

The shape of the silica particles of the present invention is not particularly limited, but is preferably spherical. When the shape of the silica particles is spherical, a smooth feeling of use can be obtained when they come into contact with the skin, which is suitable for cosmetic applications. Further, even in a catalyst carrier application, particularly a catalyst carrier application for polyolefin production, spherical particles are required because polymer particles having the same shape as that of the catalyst carrier are generated. Further, spherical particles are preferable from the viewpoint of filling property.

The silica particles of the present invention preferably have an average circularity of 0.80 or more. When the average circularity is 0.80 or more, the shape of the particles becomes close to a spherical shape, so that the particles can be suitably used for various purposes.
The average circularity of the silica particles is more preferably 0.90 or more, further preferably 0.95 or more. The upper limit of the circularity is not particularly limited, and is most preferably 1.

For the circularity, the area and perimeter of the particles obtained from the image obtained by a particle image analysis device (for example, Morphology 4 manufactured by Malvern Co., Ltd.) are obtained using the image analysis software attached to the above device, and are applied to the following formula. Can be calculated. The average circularity is the average value of 30,000 particles.
Circularity = Circumferential length of circles with equal projected area / Circumferential length of circles with equal projected area: Circumferential length of circles with equal projected area: When a certain particle is observed from directly above, the area of the shadow of the particle reflected on the lower plane is obtained. Calculate a circle equal to the area and length of the outline of the circle Particle circumference: Length of the outline of the shadow of the particle reflected on the plane below when the particle is observed from directly above

The 50% particle size (D ₅₀ ) in the cumulative particle size distribution based on the volume of the silica particles is preferably 3 to 500 μm. When the silica particles of the present invention are obtained, it is difficult to produce silica particles having a 50% particle diameter (D ₅₀ ) of less than 3 μm, and if the particle size exceeds 500 μm, the usage is limited, and the silica particles are used, for example, for cosmetics. In some cases, the particles are too large and the feeling of use may be deteriorated, so that the size is preferably 500 μm or less. It is preferable that the 50% particle diameter (D ₅₀ ) is in the above range because it can be used in various fields.
The 50% particle size (D ₅₀ ) is more preferably 5 μm or more, further preferably 10 μm or more, particularly preferably 20 μm or more, still more preferably 300 μm or less, further preferably 100 μm or less, and further preferably 50 μm or less. Is particularly preferable.

For the 50% particle diameter (D ₅₀ ), 30,000 particles having a circularity of 0.90 or more were measured using a particle image analysis device (for example, Morphology 4 manufactured by Malvern), and the 50% volume conversion particle diameter was obtained. Can be calculated as.

Further, the silica particles of the present invention preferably have a particle strength of 1 MPa or more. When the particle strength is 1 MPa or more, the particles have a strength that does not easily collapse, so that they can be applied to various uses.
The particle strength is more preferably 1.5 MPa or more, further preferably 2.0 MPa or more, particularly preferably 2.5 MPa or more, and the upper limit is not particularly limited.

The strength of the silica particles can be measured using a microcompression tester (for example, MCT-510 manufactured by Shimadzu Corporation). In the present invention, the particle strength is determined by measuring the compressive strength of 40 silica particles and averaging them.

The silica particles of the present invention preferably have a hydrophilic surface. When the surface of the particles is hydrophilic, the silica particles have little or no organic components, so that they have no adverse effect on the environment and can be used in various fields.

The hydrophilicity of the surface of the particles can be confirmed by a dispersion test in water. For example, 5 g of silica particle powder is added to 100 g of water, and the mixture is uniformly stirred and then allowed to stand for 24 hours. After 24 hours, 90% or more of the silica particles are submerged in water, and the silica particles are hydrophilic. Judge that there is. The ratio of the settled silica particles is calculated from the mass of the obtained silica particles obtained by collecting and drying the settled particles after allowing them to stand for 24 hours.

Further, the silica particles of the present invention are reddish brown iron (III) oxide powder having an L ^* a ^* b ^* color system a ^* value of 14 or more and 15 or less (for example, manufactured by Kanto Chemical Co., Ltd., deer special grade). ) Are mixed at a ratio of 30% by mass to obtain a mixed powder, and the a ^* value of the mixed powder is preferably 6.0 or less. The L ^* a ^* b ^* color system was standardized by the International Commission on Illumination (CIE) in 1976.

With the above measurement method, the shielding property of silica particles can be evaluated. When the a ^* value is 6.0 or less, it can be evaluated that the light scattering property is high and the shielding power is excellent.
The a ^* value is more preferably 5.0 or less, further preferably 4.5 or less, particularly preferably 4.0 or less, and the smaller the a ^* value is, the more preferable, so the lower limit is 0. Is preferable.

The a ^* value of the powder can be measured using, for example, a spectrocolor difference meter (for example, SE7700 manufactured by Nippon Denshoku Industries Co., Ltd.). In the measurement with the spectrocolor difference meter, the mixed powder is charged so as to have a thickness of 7.5 mm or more and measured.

<Manufacturing method of silica particles>
The silica particles of the present invention are formed by droplet-dropping an aqueous sodium silicate solution containing template particles and then precipitating silica to prepare spherical silica particles containing the template particles, and the obtained spherical silica particles containing the template particles. Obtained by removing the template particles from.
For example, the method is as follows.

In the first method for producing silica particles of the present invention, a mixed solution in which template particles are mixed in an aqueous sodium silicate solution is used as a dispersed phase, and an organic phase containing a surfactant is used as a continuous phase, and the dispersed phase and the continuous phase are used. To obtain an emulsified solution in which the dispersed phase is droplets (step (1-1)), the emulsion is gelled to precipitate silica, and spherical silica containing the template particles is obtained. (Step (1-2)), acid is added to the silica slurry to remove the template particles (step (1-3)), and the silica from which the template particles have been removed is washed. And dry (step (1-4)).

In the second production method, a mixed solution of a sodium silicate aqueous solution containing template particles and an acid is sprayed in a short time before silica is precipitated, atomized in air, and then silica is precipitated. (Step (2-1)), the template particles were removed from the silica containing the template particles (step (2-2)), and the silica from which the template particles were removed was obtained. Includes washing and drying (steps (2-3)).

(First manufacturing method)
In the step (1-1) in the first production method, a mixed solution in which template particles are mixed in an aqueous sodium silicate solution is used as a dispersed phase, an organic phase containing a surfactant is used as a continuous phase, and a dispersed phase and a continuous phase are used. Mix and stir to obtain an emulsion.
By stirring and emulsifying the dispersed phase and the continuous phase, a water-in-oil (W / O) emulsion (emulsified liquid) can be obtained. In the continuous phase, the dispersed phase becomes droplets, and the droplets are in a state where template particles are present in the droplets of the sodium silicate aqueous solution.

As the template particles used for the dispersed phase, a substance that does not dissolve in the aqueous sodium silicate solution and is soluble in acid is used. Examples of the template particles include magnesium hydroxide, magnesium carbonate, calcium hydroxide, calcium carbonate and the like, and these may be used alone or in combination of two or more. Among them, at least one selected from the group consisting of magnesium hydroxide and magnesium carbonate is preferable from the viewpoint that template particles can be dissolved and removed using sulfuric acid. Sulfuric acid is a non-volatile acid and is preferable from the volatile acids such as hydrochloric acid, nitric acid and hydrofluoric acid from the viewpoint of safety and equipment protection.

Since the size of the template particles affects the size of the voids inside the particles of the obtained silica particles, the template particles of a desired size may be used. Specifically, it is preferable to use template particles having a 50% particle diameter (D ₅₀ ) of the particles in the range of 200 nm to 3 μm, more preferably 300 nm to 2 μm, and even more preferably 400 nm to 1 μm.

The sodium silicate aqueous solution preferably has a silicic acid component in the range of 3 to 35% by mass in terms of the SiO ₂ concentration converted to SiO ₂ . Since the silicic acid component in the sodium silicate aqueous solution is mainly contained in the form of SiO ₂ , it is expressed as the SiO ₂ concentration converted to SiO ₂ .
When the concentration of the silicic acid component in the sodium silicate aqueous solution is within the above range, silica particles can be produced with high production efficiency.
The concentration of the silicic acid component in the sodium silicate aqueous solution is more preferably 5% by mass or more, still more preferably 7% by mass or more, from the viewpoint of obtaining particles having high productivity and high sphericalness. 10% by mass or more is particularly preferable. Further, from the viewpoint that particles having a small particle size can be easily obtained, it is more preferably 30% by mass or less, further preferably 25% by mass or less, and particularly preferably 20% by mass or less.

The ratio of silicic acid to sodium in the sodium silicate aqueous solution is preferably 2 to 4 in SiO ₂ / Na ₂ O (molar ratio). Sodium silicate aqueous solution having SiO ₂ / Na ₂ O (molar ratio) in the above range is easily available. For example, No. 3 sodium silicate (manufactured by AGC SI Tech Co., Ltd., SiO ₂ / Na ₂ O = 3), 2 No. sodium silicate (manufactured by AGC SI Tech Co., Ltd., SiO ₂ / Na ₂ O = 2.5), No. 1 sodium silicate (manufactured by AGC SI Tech Co., Ltd., SiO ₂ / Na ₂ O = 2) and the like can be mentioned. ..

The template particles are preferably mixed in an aqueous sodium silicate solution in the range of 1 to 35% by mass. If the amount of template particles used is too small, it may not be possible to enclose a plurality of voids with a major axis length of 200 nm or more and 3 μm or less per particle, and if it is too large, the voids inside the silica particles become too large and the particles. The strength may be low.
The amount of the template particles used is more preferably 5 to 33% by mass, further preferably 10 to 31% by mass, and particularly preferably 15 to 30% by mass in the sodium silicate aqueous solution.

The sodium silicate aqueous solution may optionally contain other components. As other components, for example, sodium chloride, sodium sulfate, potassium chloride, potassium sulfate and the like can be used for the purpose of adjusting the pore size distribution.

The organic phase used for the continuous phase is preferably one having low solubility in an aqueous sodium silicate solution, and more preferably one having no solubility.
Examples of the organic liquid constituting the organic phase include saturated linear hydrocarbons having 9 to 12 carbon atoms such as n-nonane, n-decane, n-undecane, and n-dodecane, isononane, isodecane, isoundecane, and isododecane. Saturated branched chain hydrocarbons with 9 to 12 carbon atoms, n-hexane, isohexane, n-heptane, isoheptane, n-octene, isooctene and other aliphatic hydrocarbons with 6 to 8 carbon atoms, cyclopentane, cyclohexane, cyclohexene and the like. Alicyclic hydrocarbons with 1 to 8 carbon atoms, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, propylbenzene, cumene, mesitylene, tetraline, ethers such as propyl ether and isopropyl ether, ethyl acetate , Acetate-n-propyl, isopropyl acetate, acetic acid-n-petit, isobutyl acetate, acetic acid-n-amyl, isoamyl acetate, butyl lactate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyric acid. Examples thereof include esters such as butyl and fluorine-containing compounds such as 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.
These may be used individually by 1 type and may be used in combination of 2 or more type. Among them, saturated linear hydrocarbons having 9 to 12 carbon atoms such as n-decane, n-nonane, n-dodecane, and n-undecane, and saturated branched hydrocarbons such as isononane, isodecane, isoundecane, and isododecane are preferable.

The flash point of the organic liquid constituting the organic phase is preferably 20 to 80 ° C, more preferably 30 to 60 ° C. In addition, nonflammable or flame-retardant organic liquids are preferable.
When saturated hydrocarbons with a flash point of less than 20 ° C are used as organic liquids, the flash point is low, so measures for fire protection and work environment are required. When the flash point of the organic liquid is 20 ° C. or higher, the fire resistance can be improved and the working environment can be improved. On the other hand, when the temperature is 80 ° C. or lower, sufficient volatility can be obtained and it is possible to prevent the organic liquid from adhering to and mixing with the silica particles when the silica particles are recovered from the organic phase.

A surfactant is added to the organic phase as an emulsifier. Examples of the surfactant include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants and the like.

Examples of the anionic surfactant include sodium fatty acid, alkyl sulfate, alkylbenzene sulfonate, alkyl phosphate and the like.
Examples of the cationic surfactant include an alkyltrimethylammonium salt, a dialkyldimethylammonium salt, an alkylbenzyldimethylammonium salt and the like.
Examples of the amphoteric tenside agent include alkyldimethylamine oxide and alkylcarboxybetaine.
Examples of the nonionic surfactant include polyethylene glycol fatty acid ester, polypropylene glycol fatty acid ester, polyethylene glycol alkyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether and the like. Can be mentioned.
These surfactants may be used alone or in combination of two or more. Of these, sorbitan fatty acid esters such as sorbitan monooleate, sorbitan dioleate, and sorbitan trioleate are preferable.

The amount of the surfactant used depends on conditions such as the type of the surfactant, HLB (Hydrophile-lipophilic interface) which is an index showing the degree of hydrophilicity or hydrophobicity of the surfactant, and the particle size of the target silica particles. It can be selected as appropriate. Specifically, it is preferably contained in the organic phase in the range of 0.1 to 5.0% by mass, more preferably 0.1 to 3.0% by mass, and further preferably 0.1 to 1.0% by mass. preferable.
When the content of the surfactant is 0.1% by mass or more in the organic phase, it can be uniformly emulsified and the emulsion can be further stabilized. On the other hand, when it is 5.0% by mass or less, it is possible to prevent the surfactant from adhering to and mixing with the silica particles which are the final products. When the viscosity of the dispersed phase is low, it is preferable that the concentration of the surfactant is lower in order to emulsify uniformly.

The emulsion is obtained by adding a dispersed phase to a continuous phase and stirring the mixture. The dispersed phase is preferably added while stirring the continuous phase.
As the stirring method, a conventionally known method can be used, and an emulsifying device such as a homogenizer, a homomixer, a colloid mill, an ultrasonic emulsifier, or a homodisper can be used.

For example, when emulsifying using a homogenizer, the mixture may be agitated and emulsified under emulsification conditions so that a target droplet diameter can be obtained.

For example, when emulsifying using a homomixer, the mixture may be agitated and emulsified at a speed of 1,000 to 24,000 rpm for 1 to 10 minutes.

The liquid temperature at the time of stirring emulsification is preferably 10 to 40 ° C, more preferably 10 to 35 ° C, and even more preferably 10 to 30 ° C.

In the step (1-2), the emulsified liquid emulsified in the step (1-1) is gelled to precipitate silica, and a silica slurry containing silica containing template particles is obtained.
As a method of gelling, for example, addition of an acid under stirring can be mentioned. As a result, the pH of the sodium silicate aqueous solution is lowered, and the primary particles of silica are precipitated. Since the precipitated primary particles aggregate, silica secondary particles containing the template particles are generated. The conditions for adding the acid may be such that spherical particles are obtained at the end of gelation and the pH of the aqueous phase after the two-phase separation is near neutral, preferably pH 7 to 10.

As the acid to be used, either an inorganic acid or an organic acid may be used, and inorganic acids such as sulfuric acid, hydrochloric acid and carbonic acid are more preferable, and carbon dioxide gas is most preferable because of ease of operation.

Since the reaction solution is separated into an aqueous phase and an oil phase in which silica containing the template particles is precipitated, the oil phase is removed to obtain a silica slurry.
The oil phase can be removed by a conventionally known method, and examples thereof include decantation, vacuum filtration, pressure filtration, membrane separation, and centrifugation.

In the step (1-3), an acid is added to the silica slurry obtained in the step (1-2) to remove the template particles.

Examples of the acid that can be used include inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid, organic acids such as acetic acid, perchloric acid, hydrobromic acid, trichloroacetic acid, dichloroacetic acid, methanesulfonic acid and benzenesulfonic acid. .. Above all, it is preferable to use sulfuric acid from the viewpoint of safety and equipment protection.

The acid is preferably added until the pH of the silica slurry is 3 or less. As a result, the template particles are dissolved and removed from the silica, and voids derived from the template particles are formed inside the silica particles.
The pH is preferably 1.5 to 2.5, more preferably 1.5 to 2.0.

In step (1-4), the silica from which the template particles have been removed is washed and dried.
Examples of the cleaning liquid for cleaning silica include water; an organic solvent such as ethanol, acetone, and diethyl ether.

The temperature of the cleaning liquid is preferably 10 to 100 ° C, more preferably 20 to 90 ° C, still more preferably 30 to 80 ° C.

After the silica is thoroughly washed, it is dried. Drying may be carried out by a conventionally known method. Examples of the drying method include vacuum drying, natural drying, warm air drying and the like, and for example, a spray dryer, an air flow dryer, a shelf dryer, a vacuum dryer, a kiln and the like can be used.

As the drying conditions, it is sufficient that the cleaning liquid can be removed and dried, and the drying may be appropriately adjusted according to the drying method to be adopted.

(Second manufacturing method)
In the step (2-1) in the second production method, a mixed solution of a sodium silicate aqueous solution containing template particles and an acid was sprayed for a short time before silica was precipitated, and droplets were formed in the air. Later, silica is precipitated to obtain spherical silica containing template particles.

As the template particles, a substance that is the same as the first production method and is not soluble in an aqueous sodium silicate solution and is soluble in an acid is used. Examples of the template particles include magnesium hydroxide, magnesium carbonate, calcium hydroxide, calcium carbonate and the like, and these may be used alone or in combination of two or more. Among them, at least one selected from the group consisting of magnesium hydroxide and magnesium carbonate is preferable from the viewpoint that template particles can be dissolved and removed using sulfuric acid. Sulfuric acid is a non-volatile acid and is preferable from the volatile acids such as hydrochloric acid, nitric acid and hydrofluoric acid from the viewpoint of safety and equipment protection.

The size of the template particles is the same as that of the first manufacturing method, and template particles having a desired size may be used. Specifically, it is preferable to use template particles having a 50% particle diameter (D ₅₀ ) of the particles in the range of 200 nm to 3 μm, more preferably 300 nm to 2 μm, and even more preferably 400 nm to 1 μm.

As the sodium silicate aqueous solution, the same one as in the first production method can be used, and it is preferable that the silicic acid component is in the range of 3 to 35% by mass in the SiO ₂ concentration converted to SiO ₂ .
When the concentration of the silicic acid component in the sodium silicate aqueous solution is within the above range, silica particles can be produced with high production efficiency.
The concentration of the silicic acid component in the sodium silicate aqueous solution is more preferably 5% by mass or more, still more preferably 7% by mass or more, from the viewpoint of obtaining particles having high productivity and high sphericalness. 10% by mass or more is particularly preferable. Further, from the viewpoint that particles having a small particle size can be easily obtained, it is more preferably 30% by mass or less, further preferably 25% by mass or less, and particularly preferably 20% by mass or less.

The ratio of silicic acid to sodium in the sodium silicate aqueous solution is preferably 2 to 4 in SiO ₂ / Na ₂ O (molar ratio). As the SiO ₂ / Na ₂ O (molar ratio) is in the above range, the above-mentioned commercially available product can be easily obtained.

The template particles are preferably mixed in an aqueous sodium silicate solution in the range of 1 to 35% by mass. If the amount of template particles used is too small, it may not be possible to enclose a plurality of voids with a major axis length of 200 nm or more and 3 μm or less per particle, and if it is too large, the voids inside the silica particles become too large and the particles. The strength may be low.
The amount of the template particles used is more preferably 5 to 33% by mass, further preferably 10 to 31% by mass, and particularly preferably 15 to 30% by mass in the sodium silicate aqueous solution.

The sodium silicate aqueous solution may optionally contain other components. As other components, for example, sodium chloride, sodium sulfate, potassium chloride, potassium sulfate and the like can be used for the purpose of adjusting the pore size distribution.

As the acid, either an inorganic acid or an organic acid may be used. Of these, inorganic acids such as sulfuric acid, hydrochloric acid, and carbonic acid are more preferable.

The acid to be mixed with the sodium silicate aqueous solution containing the template particles is added to the sodium silicate aqueous solution containing the template particles so that the pH of the aqueous solution is near neutral, preferably 7 to 10.

In the second production method, the mixed solution of the sodium silicate aqueous solution containing the template particles and the acid is sprayed in a short time before the silica precipitates. Examples of the method of spraying the mixed liquid in a short time to form droplets include a spraying method, ultrasonic atomization, and a method of colliding a large droplet with a high-speed fluid to atomize the mixed liquid.

Examples of the method for precipitating silica after forming droplets include lengthening the residence time in air, raising the temperature to dry the silica, and spraying the silica into an acid gas.

As a result, spherical silica containing template particles can be obtained.

Next, an acid is added to the spherical silica particles encapsulating the template particles to remove the template particles (step 2-2).

The acids that can be used are the same as in the first production method, and are, for example, inorganic acids such as sulfuric acid, hydrochloric acid, and nitrate, acetic acid, perchloric acid, hydrobromic acid, trichloroacetic acid, dichloroacetic acid, methanesulfonic acid, and benzene. Examples thereof include organic acids such as sulfonic acid. Above all, it is preferable to use sulfuric acid from the viewpoint of safety and equipment protection.

The acid is preferably added until the pH of the silica slurry is 3 or less. As a result, the template particles are dissolved and removed from the silica, and voids derived from the template particles are formed inside the silica particles.
The pH is preferably 1.5 to 2.5, more preferably 1.5 to 2.0.

In the next step, the silica from which the template particles have been removed is washed and dried (step 2-3).

Examples of the cleaning liquid for cleaning silica include water; an organic solvent such as ethanol, acetone, and diethyl ether.

The temperature of the cleaning liquid is preferably 10 to 100 ° C, more preferably 20 to 90 ° C, still more preferably 30 to 80 ° C.

After the silica is thoroughly washed, it is dried. The drying is the same as the first production method, and may be performed by a conventionally known method. Examples of the drying method include vacuum drying, natural drying, warm air drying and the like, and for example, a spray dryer, an air flow dryer, a shelf dryer, a vacuum dryer, a kiln and the like can be used.

As the drying conditions, it is sufficient that the cleaning liquid can be removed and dried, and the drying may be appropriately adjusted according to the drying method to be adopted.

The production method of the present invention may further include a step of calcining the silica particles obtained in the steps of the first production method (1-4) and the second production method (2-3). By firing the silica particles, the strength of the silica particles can be increased. The silica particles after firing are all amorphous.

The temperature at which the silica particles are fired is preferably 800 ° C. or higher, more preferably 850 ° C. or higher, and even more preferably 900 ° C. or higher, from the viewpoint of increasing the particle strength. Further, from the viewpoint of leaving voids of 200 nm or more in the particles, preventing the formation of crystalline silica, and preventing the fusion of the particles, the temperature is preferably 1100 ° C. or lower.

Further, the firing time is preferably 1 hour or longer, more preferably 2 hours or longer, still more preferably 3 hours or longer, from the viewpoint of increasing the particle strength. Further, from the viewpoints of leaving voids of 200 nm or more in the particles, preventing the formation of crystalline silica, and preventing fusion of the particles, 6 hours or less is preferable, 5 hours or less is more preferable, and 4 hours or less is further preferable. ..

<Use of silica particles>
The silica particles of the present invention can be used as materials in various fields. For example, cosmetic applications, catalyst-supporting applications, heat insulating materials, and the like can be mentioned.

In cosmetic applications, it is characterized by its high concealing property with dry powder, so it can be expected to improve its performance as a cosmetic material that can be used in the dry powder state, such as finishing powder, loose foundation, and pressed foundation. Since it has relatively small voids around the silica particles of the present invention, it is also excellent in concealing property in the presence of sweat and sebum. Further, since the silica particles of the present invention have a high porosity and become light particles, they can be expected to be used for mascara, which requires lightness, and to have a new feel due to the added lightness. It can also be used as a white pigment because it scatters visible light.

In catalyst-supporting applications, when polymer polymerization is carried out while disintegrating the carrier, it also leads to easy disintegration and the reaction rate can be improved.

Further, in the use of a heat insulating material, since the silica particles of the present invention have a high porosity, high heat insulating performance can be expected.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In the following description, the same components are used.
Further, Examples 1 to 5 are Examples, Examples 6 to 8 are Comparative Examples, and Example 9 is iron oxide (III) used in the test.

(Example 1)
As a dispersed phase, No. 3 sodium silicate (made by AGC Si-Tech Co., Ltd., aqueous sodium silicate solution, SiO ₂ / Na ₂ O (molar ratio) = 3) is diluted with distilled water to adjust the SiO ₂ concentration to 24% by mass. A slurry obtained by stirring and mixing magnesium hydroxide as template particles (Magnes X-6F, 50% particle diameter 0.8 μm, manufactured by Kamishima Chemical Industry Co., Ltd.) was used.
As a continuous phase, 0.7% by mass of sorbitan monooleate (manufactured by Sanyo Chemical Industries, Ltd., Ionet S80) was previously dissolved in n-decane (manufactured by Tosoh Corporation, HC _- 250, C 10H ₂₂ ) as a surfactant. Was used.
While stirring the continuous phase surfactant-containing n-decane with a homogenizer (Microtech Nithion Co., Ltd., Hiscotron, generator shaft NS-30UG / 20P), add the dispersed phase magnesium hydroxide-containing sodium silicate slurry. The mixture was stirred and emulsified at 8,000 rpm for 5 minutes.
Silica was precipitated by blowing carbon dioxide gas at a rate of 1.0 L / min for 20 minutes while stirring the obtained emulsion with a three-one motor. Then, while stirring the aqueous phase containing silica gel obtained by removing the oil phase at room temperature, sulfuric acid was added until the pH reached 2, and the template was removed. The slurry after removing the template was filtered and washed with warm water and dried with a spray dryer (Mini Spray Dryer B290, manufactured by Nippon Buch Co., Ltd.) to obtain silica particles of Example 1.

(Example 2)
The silica particles obtained in Example 1 were heated to 1050 ° C. at a heating rate of 5 ° C./min and calcined for 4 hours. Then, the silica particles of Example 2 were obtained by cooling to room temperature.

(Example 3)
The silica particles obtained in Example 1 were heated to 1100 ° C. at a heating rate of 5 ° C./min and calcined for 4 hours. Then, the silica particles of Example 3 were obtained by cooling to room temperature.

(Example 4)
Silica particles of Example 4 were obtained in the same manner as in Example 1 except that magnesium carbonate (Magthermo MS-S, manufactured by Konoshima Chemical Co., Ltd., 50% particle diameter 1.5 μm) was used as the template particles.

(Example 5)
The silica particles obtained in Example 4 were heated to 1000 ° C. at a heating rate of 5 ° C./min and calcined for 4 hours. Then, the silica particles of Example 5 were obtained by cooling to room temperature.

(Example 6)
"Sunsphere H-121" manufactured by AGC Si-Tech Co., Ltd., which is a commercially available porous silica, was used.

(Example 7)
"Sunsphere H-122" manufactured by AGC Si-Tech Co., Ltd., which is a commercially available porous silica, was used.

A commercially available non-porous silica "Sunsphere NP-100" manufactured by AGC Si-Tech Co., Ltd. was used.

(Example 9)
Commercially available iron (III) oxide powder (manufactured by Kanto Chemical Co., Inc., deer special grade, reddish brown powder) was used.

For the silica particles of Examples 1 to 8, the physical properties of the silica particles were measured according to the following. The results are shown in Table 1. Example 9 is a material used for chromaticity evaluation.

<Size and number of voids inside particles>
After intentionally breaking the particles by sandwiching the powder of silica particles between two slide glasses and grinding them, the split cross section of the particles is divided using a desktop scanning electron microscope (JCM-7000, manufactured by JEOL Ltd.). Observed. The length of the long axis at the opening of the void was measured, and it was confirmed whether or not there were a plurality of voids of 200 nm or more and 3 μm or less. The case where there were a plurality of voids of 200 nm or more and 3 μm or less was evaluated as “presence”, and the case where there were no voids of 200 nm or more and 3 μm or less or one was evaluated as “absence”.
For the silica particles of Example 4, an SEM photograph of a fractured surface is shown in FIG. 1, and an SEM photograph of the appearance is shown in FIG.

<Average circularity>
The circularity is calculated by calculating the area and perimeter of particles of an image obtained by a particle image analysis device (for example, Morphology 4 manufactured by Malvern) using the image analysis software attached to the above device and applying it to the following formula. did. The average circularity of 30,000 silica particles was calculated and used as the average circularity.
Circularity = Circumferential length of circles with equal projected area / Circumferential length of circles with equal projected area: Circumferential length of circles with equal projected area: When a certain particle is observed from directly above, the area of the shadow of the particle reflected on the lower plane is obtained. Calculate a circle equal to the area and length of the outline of the circle Particle circumference: Length of the outline of the shadow of the particle reflected on the plane below when the particle is observed from directly above

<50% particle size (D ₅₀ ) (μm)>
The 50% particle diameter (D ₅₀ ) was calculated as a 50% volume-equivalent particle diameter by measuring 30,000 particles having a circularity of 0.90 or more from a particle image analyzer (Morphilogi 4 manufactured by Malvern).

<Specific surface area (m ² / g)>
The specific surface area was measured by the BET method using an automatic specific surface area / pore distribution measuring device (Tristar II 3020 series manufactured by Shimadzu Corporation) at a relative pressure of 0 to 0.99 by the nitrogen adsorption method. I asked for it.

<Pore volume (cm ³ / g)>
The pore volume was measured at a relative pressure of 0 to 0.99 by the nitrogen adsorption method using an automatic specific surface area / pore distribution measuring device (Tristar II 3020 series manufactured by Shimadzu Corporation) in the same manner as the specific surface area. Was analyzed and obtained by the BJH method.

<Oil absorption (cm ³ / 100g)>
The oil absorption was measured according to JIS K 5101.
Boiled flax oil was added to the sample while kneading until the entire silica particles of the sample became a mass, and the volume of the boiled flax oil per 100 g of the sample when the entire sample became a mass was determined.

<Particle strength (MPa)>
The particle strength was determined by measuring the compressive strength of 40 silica particles per sample using a micro-compression tester (MCT-510, manufactured by Shimadzu Corporation) and calculating the average value.

<Nature of particle surface>
To 100 g of water, 5 g of silica particle powder was added, and the mixture was uniformly stirred and then allowed to stand for 24 hours. After 24 hours, 90% or more of the silica particles were submerged in water, and the silica particles were judged to be hydrophilic and evaluated as "yes". Those in which the amount of silica particles settled after 24 hours was less than 90% were evaluated as hydrophilic "none". The ratio of the settled silica particles was calculated from the mass of the obtained silica particles obtained by collecting and drying the settled particles after allowing them to stand for 24 hours.

<a ^* value, L * value, WB value ^(-)>
The iron (III) oxide powder (a ^* value: 14.9) of Example 9 was added to the powder of silica particles at a ratio of 30% by weight and mixed well to obtain a mixed powder. The mixed powder was put into a round cell for measurement (diameter 35 mm × height 15 mm) so as to have a bulk of more than half, and measured using a spectrocolor difference meter (SE7700, manufactured by Nippon Denshoku Industries Co., Ltd.).
The ^* value indicates the strength of the tint, the larger the + side, the stronger the redness, the larger the-side, the stronger the greenishness, and when it is 6.0 or less, the tint (redness) of iron oxide (III) is strong. It can be judged that it is suppressed. The L ^* value indicates the brightness of the color. The larger the value, the brighter the color, and the smaller the value, the darker the color. The WB value indicates the degree of whiteness, and the larger it is, the whiter it is, and the smaller it is, the blacker it is.

The silica particles of Examples 1 to 5 had a plurality of voids of 200 nm or more and 3 μm or less inside the particles, and the value of (oil absorption / 100) / pore volume was 1.5 or more. As can be seen from Table 1, in the evaluation using the silica particles of Examples 1 to 5, the a ^* value by the chromaticity evaluation was 6.0 or less, and the redness of iron (III) oxide was suppressed. It was found that the silica particles of Examples 1 to 5 have higher visible light scattering properties than the silica particles of Examples 6 to 8 and are excellent in shielding property of the substrate.

Claims (12)

Multiple voids with a major axis length of 200 nm or more and 3 μm or less are included inside the particles, and the value of {oil absorption (cm ^{3/100 g) / 100} / pore volume (cm 3 /} g) is 1.5 or more. Silica particles that are. The silica particles according to claim 1, wherein the silica particles have an average circularity of 0.80 or more. The silica particles according to claim 1 or 2, wherein the surface is hydrophilic. The silica particles according to any one of claims 1 to 3, wherein the 50% particle size (D ₅₀ ) in the cumulative particle size distribution based on the volume of the silica particles is 3 to 500 μm. The silica particle according to any one of claims 1 to 4, wherein the pore volume is less than 2.0 cm ³ / g. The silica particle according to any one of claims 1 to 5, wherein the particle strength is 1 MPa or more. When a reddish brown iron (III) oxide powder having an L ^* a ^* b ^* color system a ^* value of 14 or more and 15 or less was mixed with the silica particles at a ratio of 30% by mass to obtain a mixed powder, the mixture was obtained. The silica particle according to any one of claims 1 to 6, wherein the a ^* value of the powder is 6.0 or less. A white pigment containing silica particles according to any one of claims 1 to 7. A cosmetic product containing the silica particles according to any one of claims 1 to 7. A method for producing silica particles, wherein silica is precipitated after atomizing an aqueous sodium silicate solution containing template particles, the template particles are removed, and the silica from which the template particles have been removed is washed and dried. A mixed solution of template particles mixed in an aqueous sodium silicate solution is used as a dispersed phase, an organic phase containing a surfactant is used as a continuous phase, and the dispersed phase and the continuous phase are mixed and emulsified by stirring, and the dispersed phase is liquid. A dropleted emulsion is obtained, the emulsion is gelled to obtain a silica slurry containing silica containing the template particles, an acid is added to the silica slurry to remove the template particles, and the template is removed. A method for producing silica particles, in which the silica from which the particles have been removed is washed and dried. The method for producing silica particles according to claim 10 or 11, wherein the template particles are at least one selected from the group consisting of magnesium hydroxide, magnesium carbonate, calcium hydroxide and calcium carbonate.

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