JP2015193505A - Silicon oxide-coated zinc oxide and production method thereof, silicon oxide-coated zinc oxide-containing composition, and cosmetic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide silicon oxide-coated zinc oxide which can suppress elution of a zinc ion from a zinc oxide particle, and to provide a production method of the silicon oxide-coated zinc oxide, a silicon oxide-coated zinc oxide-containing composition, and a cosmetic.SOLUTION: The silicon oxide-coated zinc oxide of the present invention is obtained by coating the surface of the zinc oxide particle with a silicon oxide film. The zinc oxide particle has the average particle diameter larger than 50 nm and equal to or smaller than 500 nm. When the existence ratio of the silicon in the silicon oxide film in a Qenvironment is defined as Qand the existence ratio of the silicon in a Qenvironment is defined as Q, Q+Q≥0.6 and Q/(Q+Q)≥0.5 are satisfied. A decomposition rate of Brilliant Blue is 3% or lower when the decomposition thereof is caused by photocatalytic activity of the zinc oxide particle.

Description

  The present invention relates to a silicon oxide-coated zinc oxide, a method for producing the same, a silicon oxide-coated zinc oxide-containing composition, and a cosmetic, and more particularly, a lotion, a sunscreen gel, an emulsion, a cream, The present invention relates to a silicon oxide-coated zinc oxide suitable for use in foundations, lipsticks, blushers, eye shadows, and the like, a production method thereof, a silicon oxide-coated zinc oxide-containing composition, and a cosmetic.

Ultraviolet rays cause deterioration of many substances such as resin and rubber, and it is said that it can cause not only suntan and sunburn but also aging and skin cancer. Therefore, ultraviolet shielding agents are widely used in the fields of films, paints, cosmetics and the like.
As the ultraviolet shielding agent, an organic ultraviolet shielding agent such as benzophenone, methoxycinnamic acid or dibenzoylmethane, or an inorganic ultraviolet shielding agent such as zinc oxide or titanium oxide is generally used.

Organic UV screening agents may be deteriorated by heat or long-term UV irradiation, and a single organic UV screening agent alone cannot absorb a wide range of UV rays. There are problems such as the need to use a combination of various organic ultraviolet screening agents.
On the other hand, the inorganic ultraviolet shielding agent shields ultraviolet rays due to the effect of absorbing ultraviolet rays having a wavelength corresponding to the band gap of the inorganic particles contained therein and the scattering caused by the refractive index of the inorganic particles. There is no deterioration due to ultraviolet irradiation for a long time, excellent weather resistance, heat resistance, etc., and there is an advantage that ultraviolet rays in a wide wavelength region can be shielded.
By the way, even in the inorganic ultraviolet shielding agent having such advantages, it scatters not only ultraviolet rays but also visible light. Therefore, when a large amount of such inorganic ultraviolet shielding agents are blended into cosmetics, it becomes white. Therefore, in order to cope with such a problem, an inorganic ultraviolet shielding agent is appropriately used in combination with an organic ultraviolet shielding agent.

In general, titanium oxide, zinc oxide or the like is used as the inorganic ultraviolet shielding agent. In particular, zinc oxide can shield ultraviolet rays in a wide wavelength range from the UV-A region (320 nm to 400 nm) to the UV-B region (280 nm to 320 nm).
For example, when the photocatalytic activity for oxidizing a substance in contact with the particle surface is compared between zinc oxide and titanium oxide, zinc oxide is much lower. Moreover, since the refractive index of zinc oxide is 2.0 and lower than the refractive index of titanium oxide 2.7, when it is made into nanoparticles, it has excellent transparency. Therefore, zinc oxide has attracted attention as an ultraviolet shielding agent.

On the other hand, since zinc is an amphoteric element, its oxide zinc oxide is easily dissolved in acids and alkalis, and is also soluble in water and releases zinc ions, which is stable. It makes the sex insufficient.
Further, with respect to the photocatalytic activity, zinc oxide is very low as compared with titanium oxide, but it is desirable to suppress it. For example, when zinc oxide is nanoparticulated so that the average particle diameter is 50 nm or less, the photocatalytic activity is increased because the specific surface area is increased.
Thus, in zinc oxide particles, the release of zinc ions and high photocatalytic activity are particularly significant problems.

In addition, water-based cosmetics are not particularly sticky as compared with oil-based cosmetics and provide a smooth feeling of use, so that they are particularly used in recent years as various cosmetics such as sunscreens, emulsions and creams. When zinc oxide is used in these water-based cosmetics, the eluted zinc ions react with water-soluble polymers such as organic UV-screening agents and thickeners, resulting in reduced performance, discoloration, and viscosity as cosmetics. There is a possibility that problems such as increase / decrease will occur, and thus there is a problem that the degree of freedom of prescription is limited.
For example, when carbomer (carboxyvinyl polymer), which is widely used as a thickener, is used in combination with zinc oxide, the gel structure of the carbomer is destroyed by the reaction between the eluted zinc ions and the carboxylate group (COO ⁻ ) of the carbomer. There is a problem that the viscosity is lowered.

Thus, in order to solve the problems of zinc oxide, various types of zinc oxide coated with an inorganic oxide have been proposed.
For example, a method of obtaining silica-coated zinc oxide by adding zinc oxide in a sodium silicate aqueous solution to make it in a suspended state and maintaining the hydrogen ion index (pH) at about 7 has been proposed (Patent Document). 1).
In addition, by contacting zinc oxide as a raw material with a silica coating-forming composition containing silicic acid containing no organic group and halogen or a precursor capable of producing silicic acid, water, an alkali, and an organic solvent, a photocatalyst is obtained. There has been proposed a method for obtaining silica-coated zinc oxide free from weathering deterioration due to action (Patent Document 2).
In addition, zinc oxide powder is coated in a non-vapor state with at least one of organopolysiloxanes and silicone compounds (excluding silane compounds), and then fired at a temperature of 600 to 950 ° C. in an oxidizing atmosphere. Thus, a method for obtaining an activity-suppressed zinc oxide powder coated with silicon oxide has been proposed (Patent Document 3).

Japanese Patent No. 2851885 Japanese Patent No. 4582439 Japanese Patent No. 3187440

However, in the methods described in Patent Documents 1 to 3, since the zinc ion elution is not studied at all, the zinc ions are released from the zinc oxide even if the zinc oxide is coated with silica. There is a problem that it is difficult to sufficiently suppress the above.
In order to obtain a highly transparent cosmetic, zinc oxide having an average particle size of 50 nm or less is preferably used. When the average particle size of zinc oxide is reduced to 50 nm or less, the average particle size exceeds 50 nm. Compared with zinc oxide particles, there is a problem that the ultraviolet light scattering effect is reduced and the shielding ability of long-wavelength side, particularly long-wavelength ultraviolet light (UV-A) is inferior.

  The present invention has been made in view of the above circumstances, and is capable of suppressing elution of zinc ions from zinc oxide particles, a method for producing the same, and a silicon oxide-coated zinc oxide-containing composition. The object is to provide goods and cosmetics.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have made a silicon oxide-coated zinc oxide obtained by coating the surface of zinc oxide particles having an average particle diameter of more than 50 nm and 500 nm or less with a silicon oxide film. for, when the existence ratio in ^Q 3, ^{Q 4} environment of the presence ratio in ^{Q 3} environments of silicon oxide, silicon in the coating film was ^{Q 4, Q 3 + Q 4} ≧ 0.6 and ^{Q 4 / (Q 3 + Q} 4) If it is ≧ 0.5 and the decomposition rate of brilliant blue generated by the photocatalytic activity of zinc oxide particles is 3% or less, this silicon oxide film can prevent elution of zinc ions from the zinc oxide particles. If this silicon oxide-coated zinc oxide is applied to cosmetics, the UV shielding function will be improved, transparency will be improved, and problems arising from zinc ion elution will be solved. It is is found that has led to the completion of the present invention.

That is, the silicon oxide-coated zinc oxide of the present invention is a silicon oxide-coated zinc oxide formed by coating the surface of zinc oxide particles with a silicon oxide film, and the average particle diameter of the zinc oxide particles is more than 50 nm and 500 nm or less. , and the when the existence ratio in ^{Q 3} environment of silicon of the silicon oxide in the film were the presence ratio in ^Q 3, ^{Q 4} environment ^{Q 4, Q 3 + Q 4} ≧ 0.6 and ^Q 4 / ^(Q 3 + ^{Q 4} ) ≧ 0.5, and the degradation rate of brilliant blue produced by the photocatalytic activity of the zinc oxide particles is 3% or less.

It is preferable that the content rate of the said zinc oxide particle is 50 to 99 mass%.
When the silicon oxide-coated zinc oxide is immersed in an aqueous solution having a hydrogen ion index of 5 so as to be 0.05% by mass, the elution rate of zinc eluted in the aqueous solution is preferably 20% by mass or less.

  In the method for producing silicon oxide-coated zinc oxide according to the present invention, surface-modified zinc oxide particles are suspended in a solvent to form a surface-modified zinc oxide suspension, Any one or two or more of alkoxysilanes and oligomers of 10 or less alkoxysilanes, a catalyst, and water are allowed to react, and then the resulting reaction product is 150 ° C. or higher and lower than 600 ° C. It heat-processes at the temperature of.

  The silicon oxide-coated zinc oxide-containing composition of the present invention comprises the silicon oxide-coated zinc oxide of the present invention and a solvent.

  The cosmetic of the present invention is characterized by containing either or both of the silicon oxide-coated zinc oxide of the present invention and the silicon oxide-coated zinc oxide-containing composition of the present invention in a base.

According to the silicon oxide-coated zinc oxide of the present invention, the surface of zinc oxide particles is coated with a silicon oxide film, and the average particle diameter of the zinc oxide particles is more than 50 nm and not more than 500 nm. when the existence ratio in Q ³ environment and the existence ratio in ^Q 3, ^{Q 4} environment ^{Q 4,} and ^Q 3 + Q ⁴ ≧ 0.6 and ^{Q 4 / (Q 3 + Q} 4) ≧ 0.5, further, the Since the decomposition rate of brilliant blue generated by the photocatalytic activity of the zinc oxide particles was set to 3% or less, the surface of the zinc oxide particles was uniformly covered with a dense silicon oxide film, so that zinc ions were removed from the zinc oxide particles. Elution to the direction can be suppressed. Therefore, when this silicon oxide-coated zinc oxide is applied to cosmetics, it is possible to suppress deterioration in performance as cosmetics due to elution of zinc ions, discoloration, increase / decrease in viscosity, and the like.

  According to the method for producing silicon oxide-coated zinc oxide of the present invention, surface-modified zinc oxide particles are suspended in a solvent to form a surface-modified zinc oxide suspension, and then the surface-modified zinc oxide suspension In addition, any one or two or more of alkoxysilane and oligomers of 10-mer or less alkoxysilane, a catalyst, and water are allowed to react with each other, and then the resulting reaction product is heated to 150 ° C. or higher and 600 ° C. Since the heat treatment is performed at a temperature lower than 0 ° C., the surface of the zinc oxide particles can be uniformly covered with a dense silicon oxide film. Therefore, silicon oxide-coated zinc oxide that can suppress elution of zinc ions from the zinc oxide particles can be produced.

  According to the silicon oxide-coated zinc oxide-containing composition of the present invention, since the silicon oxide-coated zinc oxide of the present invention and a solvent are contained, the zinc element contained in this silicon oxide-coated zinc oxide is externally converted as zinc ions. It is possible to suppress elution. Accordingly, it is possible to suppress deterioration in performance as a composition due to elution of zinc ions, discoloration, increase and decrease in viscosity, and the like.

  According to the cosmetic of the present invention, since either or both of the silicon oxide-coated zinc oxide of the present invention and the silicon oxide-coated zinc oxide-containing composition of the present invention are contained in the base, these silicon oxide-coated oxides It can suppress that the zinc element contained in any one or both among zinc and a silicon oxide covering zinc oxide containing composition elutes in a base as zinc ion. Accordingly, it is possible to suppress deterioration in performance as a cosmetic due to elution of zinc ions, discoloration, increase / decrease in viscosity, and the like.

It is a figure which shows the NMR spectrum of the silicon oxide covering zinc oxide of Example 2 of this invention. It is a figure which shows the time-dependent change of the viscosity in 40 degreeC of each of the silicon oxide covering zinc oxide containing composition of Example 5 of this invention, and the carbomer aqueous solution of the comparative example 5. FIG.

The form for implementing the silicon oxide coating zinc oxide of this invention, its manufacturing method, a silicon oxide coating zinc oxide containing composition, and cosmetics is demonstrated.
The following embodiments are specifically described for better understanding of the gist of the invention, and do not limit the present invention unless otherwise specified.

[Silicon oxide coated zinc oxide]
The silicon oxide-coated zinc oxide according to one embodiment of the present invention is a silicon oxide-coated zinc oxide obtained by coating the surface of zinc oxide particles with a silicon oxide film, and the average particle diameter of the zinc oxide particles is more than 50 nm and 500 nm. or less, when the abundance ratio of the presence ratio in ^{Q 3} environments of silicon of the silicon oxide in the coating film in ^Q 3, ^{Q 4} environment was ^{Q 4, Q 3 + Q 4} ≧ 0.6 and ^Q 4 / ^{(Q 3} + Q ⁴ ) ≧ 0.5, and the degradation rate of brilliant blue produced by the photocatalytic activity of the zinc oxide particles is 3% or less.

  The content of zinc oxide particles in the silicon oxide-coated zinc oxide is preferably 50% by mass or more and 99% by mass or less. Here, when the content of zinc oxide particles in the silicon oxide-coated zinc oxide is less than 50% by mass, a desired ultraviolet shielding effect cannot be obtained. On the other hand, when the content of zinc oxide particles exceeds 99% by mass, the ratio of zinc oxide particles in the silicon oxide-coated zinc oxide becomes too high. As a result, the surface of the zinc oxide particles cannot be sufficiently covered with the silicon oxide film, which is not preferable.

The average particle diameter of the silicon oxide-coated zinc oxide is preferably more than 50 nm and not more than 2000 nm, more preferably not less than 100 nm and not more than 500 nm, still more preferably not less than 200 nm and not more than 300 nm.
Here, the reason why the average particle size of the silicon oxide-coated zinc oxide is limited to the above range is that when the average particle size is 50 nm or less, the particle size of the zinc oxide to be contained also becomes small, and the scattering in the ultraviolet region on the long wavelength side On the other hand, if it exceeds 2000 nm, when this silicon oxide-coated zinc oxide is used for cosmetics or the like, there is a possibility that squeaks or the like may occur and the usability may deteriorate. It is.

The “average particle size” as used herein refers to the silicon oxide-coated zinc oxide when the silicon oxide-coated zinc oxide is observed using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). It is a numerical value obtained by selecting a predetermined number, for example, 200 or 100, measuring the longest straight line portion (maximum major axis) of each of these silicon oxide-coated zinc oxides, and weighted averaging these measured values.
Here, when the silicon oxide-coated zinc oxide is aggregated, the aggregated particle diameter of the aggregate is not measured, but the silicon oxide-coated zinc oxide particles constituting the aggregate (primary A predetermined number of particles are measured to obtain an average particle diameter.

When this silicon oxide-coated zinc oxide is immersed in an aqueous solution having a hydrogen ion index (pH) of 5 so as to be 0.05% by mass for 1 hour, the dissolution rate of zinc eluted in this aqueous solution is 20% by mass or less. It is preferably 10% by mass or less, more preferably 5% by mass or less.
Here, the reason for setting the elution rate of zinc to 20% by mass or less is that when the elution rate of zinc exceeds 20% by mass, the stability of the silicon oxide-coated zinc oxide itself is lowered, and this silicon oxide-coated zinc oxide is applied as a makeup. When applied to cosmetics, the eluted zinc ions react with water-soluble polymers such as organic UV-screening agents and thickeners, causing deterioration in performance as cosmetics, discoloration, increase / decrease in viscosity, etc. This is because it is not preferable.

In this silicon oxide-coated zinc oxide, the brilliant blue decomposition rate generated by the photocatalytic activity of the zinc oxide particles is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less.
Here, the reason why the degradation rate of brilliant blue generated by the photocatalytic activity of the zinc oxide particles is 3% or less is that if the degradation rate of the brilliant blue is 3% or less, the photocatalytic activity of the zinc oxide particles is suppressed. This is because the uniformity of the silicon oxide film covering the zinc oxide particles is also high.
In addition, when the decomposition rate of brilliant blue exceeds 3%, the photocatalytic activity of the zinc oxide particles is not suppressed, so that the surface of the zinc oxide particles is partially covered with the silicon oxide film. The uniformity of the silicon coating will be low.

The method for measuring the degradation rate of this brilliant blue is as follows.
First, a brilliant blue aqueous solution prepared with a predetermined content (for example, 5 ppm) of brilliant blue is prepared, a predetermined amount is collected from this brilliant blue aqueous solution into a screw tube, and this brilliant blue aqueous solution is converted into zinc oxide in terms of zinc oxide. A silicon oxide-coated zinc oxide having a mass of 1% by mass of the liquid is added and ultrasonically dispersed to prepare a suspension. Next, the suspension is irradiated with ultraviolet rays having a predetermined wavelength from a predetermined distance (for example, 10 cm) for a predetermined time (for example, 6 hours).
As the ultraviolet irradiation lamp, for example, a sterilization lamp GL20 (wavelength 253.7 nm, ultraviolet output 7.5 W: manufactured by Toshiba Corporation) can be used.

Next, a supernatant is collected from the suspension irradiated with the ultraviolet rays, and the absorbance spectrum of each of the above-mentioned brilliant blue aqueous solution and the supernatant is measured by an atomic absorption photometry method. The decomposition rate D of brilliant blue is calculated by equation (1).
D = (A0−A1) / A0 (1)
(However, A0 is the absorbance at the absorption maximum wavelength (630 nm) of the absorbance spectrum of the brilliant blue aqueous solution (5 ppm), and A1 is the absorbance at the absorption maximum wavelength of the absorbance spectrum of the supernatant.)

  Here, as a specific example of the method for measuring the brilliant blue decomposition rate, the brilliant blue decomposition rate of zinc oxide (average particle size 35 nm; manufactured by Sumitomo Osaka Cement) was measured and found to be 90%. This shows that the decomposition rate of brilliant blue increases when zinc oxide has photocatalytic activity.

This silicon oxide-coated zinc oxide may be obtained by surface-treating the surface with a silicone resin.
This silicon oxide-coated zinc oxide is further surface-treated with a silicone resin, so that the affinity to the oil phase, particularly silicone oil, is increased. Therefore, the water-in-oil type (W / O type) or the oil-in-water type is used. Formulation of (O / W) into a cosmetic becomes easier.
That is, a water-in-oil type (W / O type) is obtained by blending silicon oxide-coated zinc oxide surface-treated with a silicone resin into an oil phase to form a water-in-oil or oil-in-water cosmetic. Alternatively, elution of zinc ions in an oil-in-water (O / W) cosmetic can be suppressed.

  The type of silicone resin used for the surface treatment is not particularly limited as long as it can be used as a cosmetic. Examples of such silicone resins include methyl hydrogen polysiloxane, dimethyl polysiloxane, methicone, hydrogen dimethicone, triethoxysilylethyl polydimethylsiloxyethyl dimethicone, triethoxysilylethyl polydimethylsiloxyethylhexyl dimethicone, (acrylates / acrylic acid (Tridecyl / triethoxysilylpropyl methacrylate / dimethicone methacrylate) copolymer, triethoxycaprylylsilane and the like. These may be used singly, a mixture of two or more of these may be used, or a copolymer thereof may be used.

  When the surface of this silicon oxide-coated zinc oxide is further surface-treated with a silicone resin, the surface treatment amount of the silicone resin in this surface treatment depends on the oil phase used in the water-in-oil type or oil-in-water type cosmetic. For example, it is preferably 1% by mass or more and 20% by mass or less, and more preferably 3% by mass or more and 10% by mass or less with respect to the total mass of the silicon oxide-coated zinc oxide.

Hereinafter, each component of the silicon oxide-coated zinc oxide of this embodiment will be described in detail.
"Zinc oxide particles"
The average particle diameter of the zinc oxide particles is more than 50 nm and 500 nm or less, preferably 100 nm or more and 400 nm or less, more preferably 200 nm or more and 300 nm or less.

Here, the reason why the average particle diameter of the zinc oxide particles is limited to the above range will be described below.
Scattering by zinc oxide results in Rayleigh scattering when the particle diameter of zinc oxide is sufficiently smaller than the wavelength, that is, when α << 1 in the following formula (2), generally α <0.4. If the diameter is larger than that, Mie scattering occurs. Therefore, in order to obtain the effect of Rayleigh scattering in the ultraviolet region, particularly in the UV-A region (320 nm to 400 nm), which has a longer wavelength, a particle diameter exceeding 50 nm is preferable.
α = π · D / λ (2)
(Where α is the particle size parameter, D is the particle size, and λ is the wavelength.)

Therefore, when the average particle diameter of zinc oxide is 50 nm or less, as described above, Rayleigh scattering is inferior in scattering efficiency to Mie scattering, and the scattering effect may not be sufficiently obtained.
On the other hand, if the average particle size of zinc oxide exceeds 500 nm, the average particle size of silicon oxide-coated zinc oxide also increases, and when silicon oxide-coated zinc oxide is used in cosmetics, the transparency and usability in the visible light region are increased. There is a risk of damage.
The average particle diameter of the zinc oxide particles is determined by the same method as that for the silicon oxide-coated zinc oxide described above, that is, when the zinc oxide particles are observed using a transmission electron microscope (TEM) or the like. A predetermined number, for example, 200 or 100 zinc particles can be selected, the longest straight portion (maximum major axis) of each of these zinc oxide particles can be measured, and the measured values can be obtained by weighted averaging.

  The method for synthesizing zinc oxide particles is not particularly limited as long as it is a method capable of synthesizing zinc oxide particles having an average particle diameter of more than 50 nm and 500 nm or less. For example, the French method (indirect method), the United States Examples include a dry method such as a method (direct method) or a wet method such as a German method.

"Silicon oxide coating"
The silicon oxide film is, when the existence ratio in ^Q 3, ^{Q 4} environment of the presence ratio in ^{Q 3} Environment "silicon will be described later was ^{Q 4, Q 3 + Q 4} ≧ 0.6 and ^{Q 4 / (Q 3 + Q} 4 The degree of condensation is high enough to satisfy “) ≧ 0.5”, and the degree of uniformity is higher as the decomposition rate of brilliant blue generated by the photocatalytic activity of the zinc oxide particles is 3% or less, and is not particularly limited.
Regarding the degree of condensation of silicon oxide, a silicon oxide-coated zinc oxide was measured for its NMR spectrum by solid ²⁹ Si MAS-nuclear magnetic resonance (NMR) spectroscopy. From the peak area ratio of this NMR spectrum, Q ⁰ , Q ¹ , Q ² , Q ³ , and Q ⁴ can be easily known by measuring the area ratio of signals attributed to each environment.

Here, Q ⁿ (n = 0 to 4) is the number of oxygen atoms bonded to two Si atoms in the oxygen atoms of the SiO ₄ tetrahedron unit, which is a constituent unit of silicon oxide, that is, two Si atoms. It is a chemical structure that depends on
These ^{Q 0, Q 1, Q 2} , Q 3, Q 4 area ratio of the signal to be attributed to each ^environment, referred to as ^{Q 0, Q 1, Q 2} , Q 3, Q 4. However, Q ⁰ + Q ¹ + Q ² + Q ³ + Q ⁴ = 1.

When the existence ratio in ^{Q 3} environments of silicon of the silicon oxide in the coating film was abundance in ^Q 3, ^{Q 4} environment ^{Q 4, Q 3 + Q 4} ≧ 0.6 and ^{Q 4 / (Q 3 + Q} 4) ≧ 0.5.
Here, although Q ³ + Q ⁴ ≧ 0.6 is satisfied, Q ⁴ / (Q ³ + Q ⁴ ) is less than 0.5 (Q ⁴ / (Q ³ + Q ⁴ ) <0.5), or Although Q ⁴ / (Q ³ + Q ⁴ ) ≧ 0.5 is satisfied, when Q ³ + Q ⁴ is less than 0.6 (Q ³ + Q ⁴ <0.6), the silicon oxide in the silicon oxide film Condensation does not proceed sufficiently, and therefore a dense film cannot be obtained. As a result, there is a possibility that the effect of suppressing the elution of zinc ions of silicon oxide-coated zinc oxide may not be obtained, which is not preferable.

The uniformity of the silicon oxide film can be evaluated by the decomposition rate of brilliant blue generated by the photocatalytic activity of the zinc oxide particles described above.
Here, if the decomposition rate of brilliant blue is 3% or less, the photocatalytic activity of the zinc oxide particles is suppressed, so the uniformity of the silicon oxide film covering the zinc oxide particles is also high. .
On the other hand, when the brilliant blue decomposition rate exceeds 3%, the photocatalytic activity of the zinc oxide particles is not suppressed, and the surface of the zinc oxide particles is partially covered with the silicon oxide film. The uniformity of the silicon coating will be low.

[Method for producing silicon oxide-coated zinc oxide]
The method for producing the silicon oxide-coated zinc oxide of the present embodiment comprises a surface-modified zinc oxide suspension preparation step in which surface-modified zinc oxide is suspended in a solvent to form a surface-modified zinc oxide suspension, A reaction step of reacting the surface-modified zinc oxide suspension with any one or more of alkoxysilanes and oligomers of 10-mer or less alkoxysilane, a catalyst, and water; And a heat treatment step of heat-treating the reaction product at a temperature of 150 ° C. or more and less than 600 ° C.

Here, the surface-modified zinc oxide is zinc oxide coated with a flexible silicon oxide layer that can easily coat the zinc oxide particles uniformly.
The silicon oxide layer having flexibility may be a composite oxide of silicon oxide and metal oxide containing 20% by mass or less of metal oxide such as aluminum oxide and titanium oxide in terms of oxide.

The surface-modified zinc oxide used here can be produced as follows.
Using an alkali metal silicate aqueous solution, the surface of zinc oxide particles having an average particle diameter of more than 50 nm and 500 nm or less is 1% by mass or more and 45% by mass or less in terms of silicon oxide with respect to the zinc oxide particles. A silicon oxide layer is formed to form surface-modified zinc oxide.

Here, the alkali metal silicate aqueous solution is an aqueous solution in which an alkali metal silicate is dissolved in an aqueous solvent, and this aqueous solvent is a solvent containing 50% by mass or more of water.
The solvent other than water is not limited in any way, but polar solvents such as water-soluble monohydric alcohols and polyhydric alcohols are preferable in consideration of compatibility with water.
Although it does not specifically limit as alkali metal silicate, 1 type or 2 types selected from the group of orthosilicate sodium salt, orthosilicate potassium salt, metasilicate sodium salt, metasilicate potassium salt, sodium silicate A mixture of the above can be used.

Here, first, an alkali metal silicate aqueous salt solution having an amount capable of forming a silicon oxide layer of 1% by mass or more and 45% by mass or less in terms of silicon oxide with respect to zinc oxide particles is prepared. Zinc oxide particles having an average particle diameter of more than 50 nm and 500 nm or less are added to the alkali metal salt water-based solution and stirred to obtain a suspension containing zinc oxide particles.
When a water-soluble compound of aluminum or titanium such as sodium aluminate, aluminum nitrate, aluminum sulfate, or titanyl sulfate coexists in this alkali metal silicate aqueous solution, aluminum oxide, titanium oxide, or the like is contained in the silicon oxide layer. Can do.

Next, an acid such as hydrochloric acid is added to the zinc oxide particle-containing suspension to adjust the hydrogen ion index (pH) of the zinc oxide particle-containing suspension to 6 to 9, and the mixture is allowed to stand.
Although reaction temperature is not specifically limited, 40 degreeC or more and 100 degrees C or less are preferable and 50 degreeC or more and 70 degrees C or less are more preferable on the relationship of the precipitation rate of a silicon oxide.
As a result, silicon oxide is deposited on the surface of the zinc oxide particles contained in the suspension, and a surface-modified zinc oxide having a silicon oxide layer formed on the surface is obtained.

Next, this suspension is subjected to solid-liquid separation, and the obtained solid is washed with a solvent such as water, and water is removed for the next step. The method for removing the moisture is not particularly limited, but it is usually preferable to dry at a temperature of 100 ° C. or higher. Moreover, when removing at the low temperature of 80 degrees C or less, reduced pressure drying is preferable.
Thus, you may add a heat processing process to the dried material obtained by removing the water | moisture content.

"Surface modification process for surface-modified zinc oxide"
In this step, the surface-modified zinc oxide is suspended in a solvent to form a surface-modified zinc oxide suspension.
Here, the solvent for suspending the surface-modified zinc oxide may be any solvent that can suspend the surface-modified zinc oxide, and is not particularly limited. In addition to water, methanol, ethanol, 1- Alcohols such as propanol, 2-propanol, 1-butanol, 2-butanol, and octanol; esters such as ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone; Diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, die Ethers such as glycol monoethyl ether are preferably used.

Also, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetyl acetone, cyclohexanone, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, amides such as dimethylformamide, N, N-dimethylacetoacetamide, N-methylpyrrolidone Are also preferably used.
These solvents may be used alone or in combination of two or more.

  The content of the surface-modified zinc oxide in the surface-modified zinc oxide suspension is preferably 1% by mass to 80% by mass, more preferably 20% by mass to 70% by mass, and even more preferably 30% by mass. % To 60% by mass.

  Here, the reason why the content of the surface modified zinc oxide in the surface modified zinc oxide suspension is 1% by mass or more and 80% by mass or less is that when the content of the surface modified zinc oxide is less than 1% by mass, It is necessary to remove a large amount of solvent as compared with the content of the surface-modified zinc oxide in the suspension, which may increase the cost. On the other hand, if the content exceeds 80% by mass, the viscosity of the suspension increases (thickens), the dispersion stability of the surface-modified zinc oxide decreases, and the surface-modified zinc oxide may easily settle. is there.

As a method of suspending the surface-modified zinc oxide in a solvent, water or an organic solvent is used by using a known suspension method in order to prevent the surface-modified zinc oxide from being coated in the aggregated state. Suspend in solvent. As a suspension technique, for example, a bead mill using a medium such as zirconia beads, a ball mill, a homogenizer, a disper, a stirrer, or the like is preferably used.
The time required for the suspension treatment may be sufficient as long as the surface-modified zinc oxide is uniformly suspended in the solvent.
In this case, you may add a dispersing agent as needed.

"Reaction process"
To the surface-modified zinc oxide suspension, one or more of alkoxysilane and an oligomer of alkoxysilane of 10-mer or less, a catalyst and water are added, and 30 minutes or more and 24 hours are added. This is a step of stirring and reacting.
Here, the reason for limiting to alkoxysilane and oligomers of 10-mer or less alkoxysilane is to obtain a dense silicon oxide film having a high degree of condensation of silicon oxide.
Here, when alkali metal silicate or trialkoxysilane is used instead of alkoxysilane, it is difficult to improve the degree of condensation of silicon oxide in the silicon oxide film, and a dense silicon oxide film can be obtained. It is not preferable because it cannot be done.

  Also, the reason for limiting the alkoxysilane oligomer to an alkoxysilane oligomer of 10-mer or less is that the distance between the oligomers is likely to increase as the oligomer chain length increases. This is because even if heat treatment is performed after coating, the silicon oxide in the coating does not sufficiently condense, and thus a dense silicon oxide coating cannot be obtained, and the desired elution suppression effect may not be obtained. .

As said alkoxysilane, tetraalkoxysilane is preferable, and as said oligomer of 10 mer or less alkoxysilane, oligomer of tetramer or less tetramer is preferable.
This tetraalkoxysilane has the following general formula (3)
Si (OR) ₄ ...... (3)
(However, R is an alkoxyl group (RO group), and all of these four alkoxyl groups (RO groups) may be the same or partially or completely different). Is done. These alkoxyl groups preferably have 1 to 8 carbon atoms.

Examples of such tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetra n-propoxysilane, tetraisopropoxysilane, tetra n-butoxysilane, tetraisobutoxysilane, tetrasec-butoxysilane, tetra-t-butoxysilane. , Tetraphenoxysilane, monoethoxytrimethoxysilane, monobutoxytrimethoxysilane, monopentoxytrimethoxysilane, monohexoxytrimethoxysilane, dimethoxydiethoxysilane, dimethoxydibutoxysilane and the like.
Among these, tetramethoxysilane and tetraethoxysilane can be suitably used because they contain a large amount of Si and are easy to control the concentration when dispersed in a solvent and have high hydrolysis / condensation reactivity. .
These tetraalkoxysilanes may be used alone or in combination of two or more.

Further, the tetraalkoxysilane oligomer of the 10-mer or less can be obtained by adding water to one or more tetraalkoxysilane monomers and hydrolyzing and condensing to some extent.
Such tetraalkoxysilane oligomers are MKC silicate MS51 (manufactured by Mitsubishi Chemical Corporation), methyl silicate 51 (average tetramer), methyl silicate 53A (average heptamer), ethyl silicate 40 (average 5 quantities). ), Ethyl silicate 48 (average 10-mer) (above, manufactured by Colecoat Co., Ltd.) and the like.

  Any one or two or more of the tetraalkoxysilanes and tetraalkoxysilane oligomers of 10-mer or less are converted into surface-modified oxide in a surface-modified zinc oxide suspension when converted to silicon oxide. It is preferable to add so that it may become 2 mass% or more and 45 mass% or less with respect to zinc.

The catalyst is added for the purpose of accelerating the hydrolysis or polycondensation reaction of tetraalkoxysilane and an oligomer of tetraalkoxysilane of 10-mer or less. As such a catalyst, a known acid catalyst or basic catalyst can be used (see Sakuo Sakuo, “Science of Sol-Gel Method”, Agne Jofusha, Chapter 9 (p154-p173)).
Examples of the acid catalyst include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; organic acids such as formic acid, acetic acid, oxalic acid, lactic acid and tartaric acid. Among these, inorganic acids, particularly hydrochloric acid are preferred. Can be used. Moreover, said acid catalyst may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of this basic catalyst include sodium hydroxide, potassium hydroxide, lithium hydroxide, cerium hydroxide, barium hydroxide, calcium hydroxide, pyridine, pyrrole, piperazine, pyrrolidine, piperidine, picoline, ammonia, methylamine, Ethylamine, propylamine, butylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, monoethanolamine, diethanolamine, dimethylmonoethanolamine, monomethyldiethanolamine, triethanolamine, diaza Bicyclooctane, diazabicyclononane, diazabicycloundecene, urea, tetramethylammonium hydroxide, tetraethylan Pyridinium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, choline, and the like.
Among these, ammonia, organic amines, and ammonium hydroxides can be preferably used. These basic catalysts may be used alone or in combination of two or more.

The reaction temperature is not particularly limited as long as the hydrolysis or polycondensation reaction of the tetraalkoxysilane and the tetraalkoxysilane oligomer of 10-mer or less proceeds rapidly, but preferably 0 ° C or more and 100 ° C or less, More preferably, they are 20 degreeC or more and 80 degrees C or less, More preferably, they are 40 degreeC or more and 60 degrees C or less.
Water is added in an amount that is at least the amount necessary to hydrolyze any one or more of tetraalkoxysilane and tetraalkoxysilane oligomers of 10-mer or less, that is, an amount that provides a hydrolysis rate of 100% or more. do it.

As a result, a reaction liquid in which any one or two or more hydrolysis reactions proceed among the alkoxysilanes and oligomers of the alkoxysilanes in 10-mer or less and the condensation reaction also proceeds is obtained.
A solid reaction product is obtained by solid-liquid separation of the reaction solution by atmospheric pressure filtration, vacuum filtration, pressure filtration, centrifugation, or the like.

"Heat treatment process"
In this step, the reactant is heat-treated at a temperature of 150 ° C. or higher and lower than 600 ° C.
In order to promote the densification of the silicon oxide film, the heat treatment of the reaction product is more preferably 250 ° C. or more and less than 600 ° C., more preferably 300 ° C. or more and 500 ° C. or less.
Here, the reason why the heat treatment temperature is limited to 150 ° C. or more and less than 600 ° C. is that if it is less than 150 ° C., a sufficiently condensed dense silicon oxide film cannot be obtained, and as a result, zinc ions are eluted from the zinc oxide particles. This is because the effect of suppressing this may not be sufficiently obtained. On the other hand, at 600 ° C. or higher, the silicon oxide-coated zinc oxide on which the silicon oxide film is formed binds to form coarse particles, or the zinc oxide grows. As a result, cosmetics containing the silicon oxide-coated zinc oxide are blended. This is because there is a possibility that sufficient transparency cannot be obtained in the visible light region.

  This heat treatment step may be repeated a plurality of times at a predetermined temperature within this temperature range as long as the heat treatment temperature is in a temperature range of 150 ° C. or more and less than 600 ° C., or a plurality of times at different temperatures within this temperature range. You may go.

When the surface of the silicon oxide-coated zinc oxide thus obtained is further surface-treated with a silicone resin, the silicon oxide-coated zinc oxide after the heat treatment step and the silicone resin are directly mixed (dry treatment method). Alternatively, a known method such as a method of dispersing the silicon oxide-coated zinc oxide after the heat treatment step in a solvent containing a silicone resin, then removing the solvent, and then performing a heat treatment (wet treatment method) may be used. it can.
When the silicon oxide-coated zinc oxide after the heat treatment step is dispersed in a solvent containing a silicone resin, the content of the silicon oxide-coated zinc oxide is 10% by mass or more and 40% by mass or less in the solvent containing the silicone resin, preferably It is preferable to mix so that it may become 25 to 35 mass%. By mixing in this range, production efficiency can be improved.

The heat treatment when the surface treatment is performed with the silicone resin is preferably performed at 100 ° C. or more and 300 ° C. or less. By performing the heat treatment in this range, the surface of the silicon oxide-coated zinc oxide can be surface-treated with a silicone resin, and thermal decomposition of the silicone resin and crystal growth of zinc oxide can be suppressed.
As described above, the silicon oxide-coated zinc oxide of this embodiment can be produced.

[Silicon oxide-coated zinc oxide-containing composition]
The silicon oxide-coated zinc oxide-containing composition of the present embodiment contains the above silicon oxide-coated zinc oxide and a solvent.

The average particle diameter of the silicon oxide-coated zinc oxide is preferably more than 50 nm and not more than 2000 nm, more preferably not less than 100 nm and not more than 500 nm, still more preferably not less than 200 nm and not more than 300 nm.
Here, the reason why the average particle size of the silicon oxide-coated zinc oxide is limited to the above range is that when the average particle size is 50 nm or less, the particle size of the zinc oxide to be contained also becomes small, and the scattering in the ultraviolet region on the long wavelength side On the other hand, if it exceeds 2000 nm, when this silicon oxide zinc oxide is used in cosmetics or the like, there is a risk that squeaks may occur and the usability may deteriorate. is there.

The average dispersed particle diameter of the silicon oxide-coated zinc oxide in the silicon oxide-coated zinc oxide-containing composition is preferably 60 nm or more and 10 μm or less, more preferably 80 nm or more and 7 μm or less, more preferably 100 nm or more and 5 μm. It is as follows.
Here, the reason why the above range is preferable is that if the average dispersed particle size is less than 60 nm, it is not preferable because scattering in the ultraviolet region on the long wavelength side may be relatively small, whereas the average dispersed particle size exceeds 10 μm. And, when the silicon oxide coating-containing composition is blended in cosmetics, the transparency may be lowered, which is not preferable.

The silicon oxide-coated zinc oxide content in the silicon oxide-coated zinc oxide-containing composition may be appropriately adjusted in order to obtain the desired ultraviolet shielding performance, and is not particularly limited, but is preferably 1% by mass or more And it is 80 mass% or less, More preferably, it is 20 mass% or more and 70 mass% or less, More preferably, it is 30 mass% or more and 60 mass% or less.
Here, the reason why the content of the silicon oxide-coated zinc oxide is 1% by mass or more and 80% by mass or less is that when the content of the silicon oxide-coated zinc oxide is less than 1% by mass, the composition has a sufficient ultraviolet shielding function. Therefore, it is necessary to add a large amount of the composition in order to show a desired ultraviolet shielding function when this composition is blended with cosmetics, etc., and the production cost is high. This is not preferable. On the other hand, if the content exceeds 80% by mass, the viscosity of the composition is increased, the dispersion stability of the silicon oxide-coated zinc oxide is lowered, and the silicon oxide-coated zinc oxide is liable to settle, which is not preferable.

The solvent is not particularly limited as long as it can disperse the silicon oxide-coated zinc oxide, and examples thereof include water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, Alcohols such as 2-butanol, octanol, glycerin;
Esters such as ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, γ-butyrolactone;
Ethers such as diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, diethylene glycol monoethyl ether;
Are preferably used.

In addition, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetyl acetone, cyclohexanone;
Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene;
Cyclic hydrocarbons such as cyclohexane;
Amides such as dimethylformamide, N, N-dimethylacetoacetamide, N-methylpyrrolidone;
Linear polysiloxanes such as dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane;
Are also preferably used.

And cyclic polysiloxanes such as octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexanesiloxane;
Modified polysiloxanes such as amino-modified polysiloxane, polyether-modified polysiloxane, alkyl-modified polysiloxane, and fluorine-modified polysiloxane;
Are also preferably used.
These solvents may be used alone or in combination of two or more.

  The silicon oxide-coated zinc oxide-containing composition of the present embodiment may contain commonly used additives such as a dispersant, a stabilizer, a water-soluble binder, and a thickener as long as the properties are not impaired.

  Dispersants include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, silane coupling agents such as organoalkoxysilanes and organochlorosilanes, polyether-modified silicones, amino-modified silicones, etc. The modified silicone is preferably used. The type and amount of these dispersants may be appropriately selected depending on the particle diameter of the silicon oxide-coated zinc oxide and the type of the desired dispersion medium, and only one type of the above dispersants may be used, or two or more types may be used. May be used in combination.

  As the water-soluble binder, polyvinyl alcohol (PVA), polyvinyl pyrrolidone, hydroxycellulose, polyacrylic acid, or the like can be used.

As the thickener, when this silicon oxide-coated zinc oxide-containing composition is applied to cosmetics, it is not particularly limited as long as it is a thickener usable for cosmetics. For example, natural water-soluble polymers such as gelatin, casein, collagen, hyaluronic acid, albumin, starch, methylcellulose, ethylcellulose, methylhydroxypropylcellulose, carboxymethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, sodium carboxymethylcellulose, propylene glycol alginate Semi-synthetic polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, carbomer (carboxyvinyl polymer), synthetic polymers such as polyacrylate and polyethylene oxide, inorganic minerals such as bentonite, laponite and hectorite are preferably used. These thickeners may be used alone or in combination of two or more.
Among these thickeners, a synthetic polymer is preferable, and a carbomer is more preferable.

Here, when carbomer is used as the thickener, the content of carbomer in the silicon oxide-coated zinc oxide-containing composition is preferably 0.01% by mass or more and 10% by mass or less, and 0.01% by mass. More preferably, the content is 3% by mass or less.
If the carbomer content in the silicon oxide-coated zinc oxide-containing composition is less than 0.01% by mass, the thickening effect may not be obtained. On the other hand, the carbomer content is 10% by mass. If it exceeds, the viscosity will become too high, and when applied to cosmetics, the riding on the skin when spread and applied to the skin will worsen, causing problems such as reduced usability, It is not preferable from the viewpoint.

The hydrogen ion index (pH) in the silicon oxide-coated zinc oxide-containing composition when carbomer is used as the thickener is preferably 5 or more and 10 or less, more preferably 6 or more and 10 or less, and 7 or more and 9 or less. Is more preferable.
By setting the pH of the silicon oxide-coated zinc oxide-containing composition within the above range, changes with time such as viscosity can be suppressed.

The above carbomer (carboxyvinyl polymer) is widely used as a thickener for water-based cosmetics, but it thickens (gels) using the interaction between carboxyl groups or between carboxylate groups. In the presence of zinc ions, the network structure of the carbomer is destroyed and the viscosity cannot be kept constant. Therefore, when several mass% of zinc oxide is mixed with the carbomer aqueous solution whose viscosity has been adjusted, the viscosity reduction proceeds within a few hours.
Even in the case of using zinc oxide coated with an inorganic oxide or resin to suppress surface activity, in many cases, the viscosity reduction or phase separation proceeds within a few hours to a few days. Therefore, when carbomer and zinc oxide are used in combination, it becomes a problem to suppress or reduce a decrease in viscosity of a mixture containing them.

In addition, when zinc oxide, which is coated with a conventional inorganic oxide or resin and suppresses surface activity, is used to suppress the decrease in viscosity of the carbomer aqueous solution, the viscosity decrease after a certain period of time often occurs rather than the initial viscosity decrease. It becomes a big problem.
The initial decrease in viscosity can be dealt with by adjusting the viscosity of the carbomer aqueous solution to a high value in advance, but if the viscosity changes in the medium to long term after a certain period of time, the properties of the cosmetics change at the distribution stage. However, the stability over time is impaired. In particular, zinc oxide surface-treated with an inorganic oxide or a resin has a certain elution suppressing effect, and thus there is a possibility that zinc ions are gradually eluted over a medium to long term.
Conventionally, there are few reports on the viscosity change of a composition containing a carbomer, and even if there is a report example, suppression has been confirmed only up to a viscosity change over time of about 7 days at room temperature.

  The silicon oxide-coated zinc oxide-containing composition of the present embodiment uses silicon oxide-coated zinc oxide, which has a higher zinc elution suppression effect than zinc oxide coated with conventional inorganic oxides and resins. Even when a carbomer is used as a sticking agent, a decrease in viscosity with time is small, and therefore a composition having excellent quality stability over a long period of time can be obtained.

In the silicon oxide-coated zinc oxide-containing composition of the present embodiment, the viscosity after 300 hours when stored at 40 ° C., for example, under accelerated conditions that promote chemical reaction, is the viscosity after the initial viscosity reduction, for example, after 15 hours. The value divided by the viscosity is preferably 0.8 or more and 1.2 or less.
Thus, by setting the value obtained by dividing the viscosity after 300 hours under the accelerating condition by the viscosity after the decrease in the initial viscosity within the above range, the viscosity of the silicon oxide-coated zinc oxide-containing composition can be maintained over the medium to long term. It can be maintained and has excellent stability over time.

When the silicon oxide-coated zinc oxide-containing composition of the present embodiment has a silicon oxide-coated zinc oxide content of 15% by mass and this composition is a coating having a thickness of 32 μm, the transmittance for light having a wavelength of 450 nm is: 50% or more is preferable, 60% or more is more preferable, and 70% or more is more preferable.
This transmittance is obtained by coating a silicon oxide-coated zinc oxide-containing composition containing 15% by mass of silicon oxide-coated zinc oxide on a quartz substrate with a bar coater to form a coating film having a thickness of 32 μm. The spectral transmittance of the film can be determined by measuring with a SPF analyzer UV-1000S (manufactured by Labsphere).

The method for producing the silicon oxide-coated zinc oxide-containing composition of the present embodiment is not particularly limited as long as the silicon oxide-coated zinc oxide can be dispersed in the solvent.
As such a dispersion method, a known dispersion method can be used. For example, besides a stirrer, a bead mill using zirconia beads, a ball mill, a homogenizer, an ultrasonic disperser, a kneader, a three-roll mill, a rotation / revolution mixer, and the like are preferably used.
The time required for the dispersion treatment may be a time sufficient to uniformly disperse the silicon oxide-coated zinc oxide in the solvent.

  Next, as a specific example of the silicon oxide-coated zinc oxide-containing composition of the present embodiment, (1) a silicon oxide-coated zinc oxide-containing silicone in which silicon oxide-coated zinc oxide is dispersed in a silicone resin that is a water-insoluble dispersion medium The resin-based composition and (2) the silicon oxide-coated zinc oxide-containing aqueous composition in which silicon oxide-coated zinc oxide is dispersed in water will be described.

"Silicon resin-based zinc oxide-containing silicone resin composition"
This silicon oxide-coated zinc oxide-containing silicone resin-based composition is a silicone resin-based composition obtained by dispersing the above-described silicon oxide-coated zinc oxide in a silicone resin, and the content of this silicon oxide-coated zinc oxide is 1 mass. % Or more and 80% by mass or less, more preferably 20% by mass or more and 70% by mass or less, and further preferably 30% by mass or more and 60% by mass or less.

The average particle size of the silicon oxide-coated zinc oxide used in this silicon oxide-coated zinc oxide-containing silicone resin-based composition is preferably more than 50 nm and not more than 2000 nm, more preferably not less than 100 nm and not more than 500 nm, still more preferably 200 nm or more and 300 nm or less.
The average dispersed particle size of the silicon oxide-coated zinc oxide in this silicon oxide-coated zinc oxide-containing silicone resin composition is preferably 60 nm or more and 10 μm or less, more preferably 80 nm or more and 7 μm or less, and further preferably 100 nm or more and 5 μm or less. preferable.
In this embodiment, it is more preferable to use silicon oxide-coated zinc oxide surface-treated with silicone.

The silicone resin is not particularly limited as long as it is used in cosmetics. For example, a cyclic silicone resin or a linear silicone resin can be used.
Examples of such silicone resins include chain siloxanes such as dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, and methylhydrogenpolysiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and decamethylpentasiloxane. And cyclic siloxanes such as decamethylcyclopentasiloxane, dodecamethylcyclohexanesiloxane, and tetramethyltetrahydrogenpolysiloxane, modified silicones such as amino-modified silicone, polyether-modified silicone, and alkyl-modified silicone, and methyltrimethicone.
These silicone resins may be used alone or in combination of two or more.

This silicon oxide-coated zinc oxide-containing silicone resin-based composition may contain a dispersant.
Examples of the dispersant include modified silicones such as polyether-modified silicone, polyglycerin-modified silicone, amino-modified silicone, phenyl-modified silicone, alkyl-modified silicone, carbinol-modified silicone, and dimethylsilicone;
Surfactants such as anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants;
Silane coupling agents such as organoalkoxysilanes and organochlorosilanes;
Etc.
These dispersants may be used alone or in combination of two or more.

The amount of the dispersant added is preferably in the range of 1% by mass to 50% by mass with respect to the mass of the silicon oxide-coated zinc oxide in the silicon oxide-coated zinc oxide-containing silicone resin composition.
By adjusting the addition amount of the dispersant within the above range, even when this silicon oxide-coated zinc oxide-containing silicone resin composition is used alone or when directly mixed with cosmetics, Transparency can be sufficiently ensured when spread and coated on.
Further, natural oil, humectant, thickener, fragrance, preservative and the like may be further mixed with the silicon oxide-coated zinc oxide-containing silicone resin-based composition as long as the characteristics are not impaired.

This silicon oxide-coated zinc oxide-containing silicone resin composition may be emulsified with an aqueous component as an oil phase to form an emulsion composition.
The oil phase preferably contains at least one of a higher alcohol and a higher fatty acid, and more preferably contains both. By containing these components in the oil phase, the firmness and moisturizing feeling are improved, and the sustainability of these effects is improved.

  The higher alcohol is not particularly limited as long as it is used as a cosmetic. For example, capryl alcohol, lauryl alcohol, stearyl alcohol, oleyl alcohol, myristyl alcohol, cetyl alcohol, cholesterol, phytosterol and the like are preferably used. These may be used alone or in combination of two or more.

As the higher fatty acid, a saturated or unsaturated fatty acid having 12 to 24 carbon atoms is preferably used. For example, myristic acid, palmitic acid, stearic acid, isostearic acid, linoleic acid, arachidonic acid and the like are preferably used. These may be used alone or in combination of two or more.
In this oil phase, oil-soluble preservatives, ultraviolet absorbers, oil-soluble drugs, oil-soluble pigments, oil-soluble proteins, vegetable oils, animal oils and the like may be appropriately mixed as necessary.

The method for producing the silicon oxide-coated zinc oxide-containing silicone resin composition is not particularly limited as long as the silicon oxide-coated zinc oxide can be dispersed in the silicone resin.
As such a dispersion method, a known dispersion device can be used. As such a dispersing device, for example, a stirrer, a bead mill, a ball mill, a homogenizer, an ultrasonic disperser, a kneader, a three-roll mill, a rotation / revolution mixer, and the like are preferably used.
The time required for the dispersion treatment may be a time sufficient for the silicon oxide-coated zinc oxide to be uniformly dispersed in the silicone resin.

"Aqueous composition containing zinc oxide coated zinc oxide"
This silicon oxide-coated zinc oxide-containing aqueous composition is an aqueous composition obtained by dispersing the above-mentioned silicon oxide-coated zinc oxide in an aqueous dispersion medium containing alcohols, and the content ratio of this silicon oxide-coated zinc oxide is 1 It is contained in an amount of not less than 80% by mass and not more than 80% by mass, more preferably not less than 20% by mass and not more than 70% by mass, more preferably not less than 30% by mass and not more than 60% by mass. And it is an aqueous composition containing 20 mass% or less.

The average particle diameter of the silicon oxide-coated zinc oxide used in the silicon oxide-coated zinc oxide-containing aqueous composition is preferably more than 50 nm and not more than 2000 nm, more preferably not less than 100 nm and not more than 500 nm, and still more preferably not less than 200 nm. And it is 300 nm or less.
The average dispersed particle size of the silicon oxide-coated zinc oxide in the silicon oxide-coated zinc oxide-containing aqueous composition is preferably 60 nm or more and 10 μm or less, more preferably 80 nm or more and 7 μm or less, and further preferably 100 nm or more and 5 μm or less.

  Here, the aqueous dispersion medium containing alcohols is a dispersion medium containing alcohols and water. Examples of alcohols include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, octanol, Examples thereof include monohydric alcohols or polyhydric alcohols having 1 to 6 carbon atoms such as glycerin, 1,3-butylene glycol, propylene glycol, and sorbitol. Of these, monohydric alcohols, particularly ethanol, are preferred.

When this aqueous composition is composed of the above-described silicon oxide-coated zinc oxide and an aqueous dispersion medium containing alcohols, the alcohol content is preferably 5% by mass or more and 20% by mass or less, more preferably It is 10 mass% or more and 20 mass% or less.
In particular, when the alcohol content is 10% by mass or more and 20% by mass or less, the dispersibility and stability over time of the aqueous composition of the silicon oxide-coated zinc oxide can be improved.

  In this silicon oxide-coated zinc oxide-containing aqueous composition, the water-soluble polymer is further contained in an amount of 0.001% by mass to 10% by mass, more preferably 0.005% by mass and 5% by mass, and still more preferably 0%. It is good also as containing 0.01 mass% or more and 3 mass% or less. In this case, it is necessary to adjust the content of each component so that the total content of each of the silicon oxide-coated zinc oxide, the aqueous dispersion medium containing alcohols, and the water-soluble polymer does not exceed 100% by mass.

When applying this silicon oxide-coated zinc oxide-containing aqueous composition to cosmetics, the water-soluble polymer contained in this aqueous composition is not particularly limited as long as it can be used for cosmetics, Gum arabic, sodium alginate, casein, carrageenan, galactan, carboxyvinyl polymer, carboxymethylcellulose, sodium carboxymethylcellulose, carboxymethyl starch, agar, xanthan gum, quince seed, guar gum, collagen, gelatin, cellulose, dextran, dextrin, tragacanth gum, hydroxyethylcellulose , Hydroxypropylcellulose, sodium hyaluronate pectin, pullulan, methylcellulose, methylhydroxypropylcellulose and the like. These water-soluble polymers may be used alone or in combination of two or more.
This water-soluble polymer has a role as a dispersant and a viscosity modifier, and when added to the aqueous composition, the dispersibility and temporal stability of the silicon oxide-coated zinc oxide in the aqueous composition are also improved.

When the aqueous composition contains a water-soluble polymer, the content of the alcohol is preferably 5% by mass or more and 20% by mass or less, more preferably 15% by mass or more and 20% by mass or less.
Here, the reason why the content of the alcohol in the case where the water-based composition includes a water-soluble polymer is 5% by mass or more and 20% by mass or less is that the content of the alcohol is less than 5% by mass. Since the amount is too small, the water-soluble polymer cannot uniformly infiltrate into the alcohols and swells non-uniformly with moisture. As a result, the dispersibility of the silicon oxide-coated zinc oxide is reduced, making it difficult to handle. Furthermore, since the temporal stability of the aqueous composition is lowered, it is not preferable.
On the other hand, when the content exceeds 20% by mass, the viscosity of the entire aqueous composition is increased, the dispersion stability of the silicon oxide-coated zinc oxide is decreased, and the temporal stability of the aqueous composition is also decreased. .

In this silicon oxide-coated zinc oxide-containing aqueous composition, the above-mentioned silicon oxide-coated zinc oxide is mixed with an aqueous dispersion medium containing alcohols or an aqueous dispersion medium containing alcohols and a water-soluble polymer, and then water is added. It can be obtained by mixing and dispersing. The amount of water may be appropriately adjusted, but considering the dispersion stability and aging stability of the silicon oxide-coated zinc oxide, a range of 15% by mass to 94% by mass is preferable.
By adjusting the amount of water in the above range, it can be used alone or mixed with cosmetics, and it can be sufficiently coated with the silicon oxide coating to ensure sufficient transparency when applied to the skin. A zinc-containing aqueous composition is obtained.
The silicon oxide-coated zinc oxide-containing aqueous composition may be used as an aqueous composition and an emulsified composition mixed with an oil phase.

[Cosmetics]
The cosmetic of this embodiment contains either or both of the silicon oxide-coated zinc oxide and the silicon oxide-coated zinc oxide-containing composition in the base.
When this silicon oxide-coated zinc oxide is used for ultraviolet shielding applications, the silicon oxide-coated zinc oxide preferably has an average particle diameter of more than 50 nm and not more than 2000 nm.

  Further, even when this silicon oxide-coated zinc oxide-containing composition is used for ultraviolet shielding applications, the average particle size of the silicon oxide-coated zinc oxide contained in the silicon oxide-coated zinc oxide-containing composition is more than 50 nm and not more than 2000 nm. It is preferable that it is 100 nm or more and 500 nm or less, more preferably 200 nm or more and 300 nm or less.

  The average dispersed particle size of the silicon oxide-coated zinc oxide in the cosmetic is preferably 60 nm or more and 10 μm or less, more preferably 80 nm or more and 7 μm or less, and further preferably 100 nm or more and 5 μm or less.

  The content of the silicon oxide-coated zinc oxide contained in the cosmetic using either one or both of the silicon oxide-coated zinc oxide and the silicon oxide-coated zinc oxide-containing composition may be appropriately adjusted. It is preferable to contain 1 mass% or more and 60 mass% or less with respect to the mass of the whole material. By containing the silicon oxide-coated zinc oxide within the above range, a sufficient transparency can be ensured, and there can be obtained a cosmetic having no rough feeling and having an excellent feeling of use.

The cosmetic of the present embodiment contains additives generally used in cosmetics, such as organic UV screening agents, inorganic UV screening agents, whitening agents, and the like within a range that does not impair the effects of the present invention. It may be.
Examples of the organic ultraviolet screening agent include anthranilates, cinnamic acid derivatives, salicylic acid derivatives, camphor derivatives, benzophenone derivatives, β, β'-diphenyl acrylate derivatives, benzotriazole derivatives, benzalmalonate derivatives, Benzimidazole derivatives, imidazolines, bisbenzoazolyl derivatives, p-aminobenzoic acid (PABA) derivatives, methylenebis (hydroxyphenylbenzotriazole) derivatives, etc., and one or more selected from these groups It can be selected and used.

  In addition, examples of the inorganic ultraviolet shielding agent include oxides other than zinc oxide, such as titanium oxide and cerium oxide, and one or more of these groups can be appropriately selected and used.

This cosmetic comprises any one or both of the above-mentioned silicon oxide-coated zinc oxide and the above-mentioned silicon oxide-coated zinc oxide-containing composition in a base such as an emulsion, cream, foundation, lipstick, blusher, and eye shadow. It can be obtained by blending as usual.
Furthermore, one or both of the above-mentioned silicon oxide-coated zinc oxide and the above-mentioned silicon oxide-coated zinc oxide-containing composition are added to water-based cosmetics such as lotions and sunscreen gels, which have been difficult to formulate conventionally. By doing so, it is possible to obtain a water-based cosmetic excellent in ultraviolet shielding ability, transparency and feeling of use.

  Furthermore, by using this cosmetic as a cosmetic ingredient, it is possible to provide various cosmetics such as skin care cosmetics, makeup cosmetics, and body care cosmetics that are excellent in ultraviolet shielding ability, transparency, and feeling of use. In particular, it is suitable for sunscreens and the like of body care cosmetics that require ultraviolet shielding ability.

As described above, according to the silicon oxide-coated zinc oxide of the present embodiment, the surface of the zinc oxide particles is coated with a dense silicon oxide film, and the average particle diameter of the zinc oxide particles is set to more than 50 nm and not more than 500 nm. when the presence ratio of the presence ratio in ^{Q 3} environments of silicon of the silicon oxide in the coating film in ^Q 3, ^{Q 4} environment was ^{Q 4, Q 3 + Q 4} ≧ 0.6 and ^{Q 4 / (Q 3 + Q} 4) Since ≧ 0.5, and the decomposition rate of brilliant blue generated by the photocatalytic activity of the zinc oxide particles was 3% or less, the surface of the zinc oxide particles was uniformly covered with a dense silicon oxide film. It can suppress that zinc ion elutes outward from this zinc oxide particle. Therefore, when this silicon oxide-coated zinc oxide is applied to cosmetics, it is possible to suppress deterioration in performance as cosmetics due to elution of zinc ions, discoloration, increase / decrease in viscosity, and the like.

  According to the method for producing silicon oxide-coated zinc oxide of the present embodiment, the surface of zinc oxide particles having an average particle diameter of more than 50 nm and 500 nm or less is added to the zinc oxide particles using an alkali metal silicate aqueous solution. On the other hand, a silicon oxide layer of 1% by mass or more and 45% by mass or less in terms of silicon oxide is formed to form surface modified zinc oxide, and then this surface modified zinc oxide is suspended in a solvent to perform surface modified oxidation. Then, one or more of alkoxysilane and an oligomer of alkoxysilane of 10-mer or less, a catalyst, and water are added to the surface-modified zinc oxide suspension. Then, the obtained reaction product is heat-treated at a temperature of 150 ° C. or higher and lower than 600 ° C., so that the surface of the zinc oxide particles can be uniformly covered with a dense silicon oxide film. Therefore, silicon oxide-coated zinc oxide that can suppress elution of zinc ions from the zinc oxide particles can be produced.

According to the silicon oxide-coated zinc oxide-containing composition of the present embodiment, since the silicon oxide-coated zinc oxide of the present embodiment and the solvent were contained, the zinc element contained in the silicon oxide-coated zinc oxide was converted into zinc ions. Elution to the outside can be suppressed. Accordingly, it is possible to suppress deterioration in performance as a composition due to elution of zinc ions, discoloration, increase and decrease in viscosity, and the like.
In this silicon oxide-coated zinc oxide-containing composition, since elution of zinc ions is suppressed, an aqueous dispersion, an oil-in-water (O / W type) dispersion, and a water-in-oil (W / O type) dispersion It can be suitably used for cosmetics such as multilayer type (W / O / W type or O / W / O type) dispersions, particularly sunscreens. Moreover, when it applies to resin films, such as polyester and polyamide, it can be used suitably also as an ultraviolet shielding agent of a resin film.
Furthermore, since this silicon oxide-coated zinc oxide-containing composition can be mixed with a carbomer or a carbomer aqueous solution, it is possible to provide a water-soluble composition or a water-insoluble composition excellent in feeling of use.

  According to the cosmetic of this embodiment, since either or both of the silicon oxide-coated zinc oxide of this embodiment and the silicon oxide-coated zinc oxide-containing composition of this embodiment are contained in the base, these oxidations are performed. It can suppress that the zinc element contained in any one or both among a silicon covering zinc oxide and a silicon oxide covering zinc oxide containing composition elutes in a base as zinc ion. Accordingly, it is possible to suppress deterioration in performance as a cosmetic due to elution of zinc ions, discoloration, increase / decrease in viscosity, and the like.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.
Here, (1) silicon oxide-coated zinc oxide and (2) silicon oxide-coated zinc oxide-containing composition will be described with reference to examples and comparative examples.

(1) Silicon oxide-coated zinc oxide [Example 1]
Zinc oxide particles (average particle size 250 nm; manufactured by Sumitomo Osaka Cement) and water were mixed and then ultrasonically dispersed to prepare a zinc oxide aqueous suspension having a zinc oxide content of 20 mass%.
Next, this zinc oxide aqueous suspension is added to a 15 mass% sodium silicate aqueous solution in terms of silicon oxide based on the mass of zinc oxide particles in the zinc oxide aqueous suspension, and the suspension is vigorously stirred. It was.

  Subsequently, after heating this suspension to 60 degreeC, dilute hydrochloric acid was added gradually to this suspension, and it adjusted so that pH might be set to 6.5-7. Thereafter, the suspension was allowed to stand for 2 hours, the suspension was subjected to solid-liquid separation, and the resulting solid was washed with water. This solid was heat-treated at 150 ° C. for 1 hour to prepare surface-modified zinc oxide A.

Next, the surface-modified zinc oxide A and 2-propanol are mixed and then ultrasonically dispersed to prepare a surface-modified zinc oxide A2-propanol suspension having a surface-modified zinc oxide A content of 10% by mass. did.
Subsequently, this surface-modified zinc oxide A2-propanol suspension was heated to 60 ° C., and while stirring, ammonia water and water were added to adjust the pH to 10-11. Further, a tetramethoxysilane (TMOS) 2-propanol solution was slowly added dropwise, and stirring was continued for 6 hours for reaction.
The dripping amount of this tetramethoxysilane was 15 mass% with respect to zinc oxide in terms of silicon oxide. Moreover, water was 120 mass% of tetramethoxysilane.

  After the reaction, solid-liquid separation was performed by centrifugation, and the resulting solid reaction product was heat-treated at 150 ° C. for 12 hours to obtain silicon oxide-coated zinc oxide A of Example 1.

[Example 2]
Silicon oxide-coated zinc oxide A obtained according to Example 1 was heat-treated at 500 ° C. for 2 hours to obtain silicon oxide-coated zinc oxide B of Example 2.

[Example 3]
Example 1 except that the aqueous zinc oxide suspension of Example 1 was added to a 5 mass% sodium silicate aqueous solution in terms of silicon oxide based on the mass of the zinc oxide particles in the aqueous zinc oxide suspension. In the same manner as described above, surface-modified zinc oxide C of Example 3 was obtained.
Next, the surface-modified zinc oxide C and 2-propanol are mixed and then ultrasonically dispersed to prepare a surface-modified zinc oxide C2-propanol suspension having a surface-modified zinc oxide C content of 10% by mass. did.

Next, this surface-modified zinc oxide C2-propanol suspension was heated to 60 ° C., and while stirring, ammonia water and water were added to adjust the pH to 10-11. Further, a tetramethoxysilane (TMOS) 2-propanol solution was slowly added dropwise, and stirring was continued for 6 hours for reaction.
The amount of tetramethoxysilane added was 5% by mass with respect to zinc oxide in terms of silicon oxide. Moreover, water was 120 mass% of tetramethoxysilane.
After the reaction, solid-liquid separation was performed by centrifugation, and the obtained solid reaction product was heat-treated at 150 ° C. for 12 hours to obtain silicon oxide-coated zinc oxide C of Example 3.

[Example 4]
Silicon oxide-coated zinc oxide C obtained according to Example 3 was heat-treated at 500 ° C. for 2 hours to obtain silicon oxide-coated zinc oxide D of Example 4.

[Comparative Example 1]
Zinc oxide particles (average particle size 250 nm; manufactured by Sumitomo Osaka Cement) and water were mixed and then ultrasonically dispersed to prepare a zinc oxide aqueous suspension having a zinc oxide content of 20 mass%.
Next, this zinc oxide aqueous suspension is added to a 15 mass% sodium silicate aqueous solution in terms of silicon oxide based on the mass of zinc oxide particles in the zinc oxide aqueous suspension, and the suspension is vigorously stirred. It was.

  Subsequently, after heating this suspension to 60 degreeC, dilute hydrochloric acid was added gradually to this suspension, and it adjusted so that pH might be set to 6.5-7. After that, the mixture was allowed to stand for 2 hours, this suspension was subjected to solid-liquid separation, and the resulting solid was washed with water. This solid was heat treated at 150 ° C. for 12 hours to obtain surface-modified zinc oxide E of Comparative Example 1.

[Comparative Example 2]
Surface-modified zinc oxide E obtained according to Comparative Example 1 was heat-treated at 500 ° C. for 2 hours to obtain surface-modified zinc oxide F of Comparative Example 2.

[Evaluation]
Each of the silicon oxide-coated zinc oxide of Examples 1 to 4 and the surface-modified zinc oxide of Comparative Examples 1 and 2 were evaluated. The evaluation items are as follows.
(1) Average particle diameter Silicon oxide-coated zinc oxide (or surface-modified zinc oxide) is observed using a transmission electron microscope (TEM), and 200 particles are selected. These silicon oxide-coated zinc oxide (or surface-modified oxide) Zinc) Each longest straight portion (maximum major axis) was measured, and these measured values were calculated by weighted averaging.

(2) Infrared spectroscopy (IR)
IR evaluation of silicon oxide-coated zinc oxide (or surface-modified zinc oxide) was performed by KBr method using JASCO FT / IR-670 Plus (manufactured by JASCO). Here, “1000” indicates that an absorption band derived from Si—O—Si stretching and an absorption band derived from zinc oxide are observed in 1000 to 1200 cm ⁻¹ and 400 to 600 cm ⁻¹ , respectively. The case where either one or both were not observed was designated as “x”.

(3) Condensation degree of silicon oxide The silicon oxide-coated zinc oxide (or surface-modified zinc oxide) was measured for its NMR spectrum by solid ²⁹ Si MAS-nuclear magnetic resonance (NMR) spectroscopy, and the peak area ratio of this NMR spectrum. ^{Q 0, Q 1, Q 2} , Q 3, Q 4 area ratio of the signal to be attributed to each environment ^{Q 0, Q 1, Q 2} , Q 3, Q 4 is calculated, then, the silicon oxide film from (or surface modified film) and the value of ^Q 3 + ^{Q 4} when the abundance ratio was ^{Q 4} of the presence ratio in ^{Q 3} environments of silicon in the ^Q 3, ^{Q 4 environments, Q 4 / (Q 3 +} Q 4 ) Was calculated.

Here, the actual NMR spectrum measurement data Q ^{d is} subjected to waveform separation so as to fit the measurement data Q ^d to be Q ² , Q ³ , and Q ⁴ .
Furthermore, FIG. 1 shows an NMR spectrum of the silicon oxide-coated zinc oxide of Example 2 as an example of the NMR spectrum.
In Figure 1, NMR spectrum shown in ^{Q t} in the figure is obtained by summing the NMR spectrum ^{Q 2,} Q 3, ^{Q 4,} which are waveform separation, is represented by a smooth curve. This NMR spectrum Q ^t was in good agreement with the measurement data Q ^d including actual noise.

(4) Zinc dissolution rate Silicon oxide-coated zinc oxide (or surface-modified zinc oxide) is added to a buffer solution of pH = 5 so as to be 0.05% by mass, and then stirred and dispersed for 1 hour. Solid-liquid separation was performed, and the zinc concentration in the liquid phase was measured with an ICP emission spectrometer.
And the ratio of zinc ion (mol) eluted in said liquid phase among zinc content (mol) in silicon oxide covering zinc oxide (or surface modification zinc oxide) was made into the zinc elution rate (%).
The buffer solution of pH = 5 was prepared by mixing 500 ml of a 0.1 M potassium hydrogen phthalate aqueous solution and 226 ml of a 0.1 M sodium hydroxide aqueous solution, and then adding water to make a total volume of 1000 ml.

(5) Decomposition rate of brilliant blue A brilliant blue aqueous solution in which the content of brilliant blue was adjusted to 5 ppm was prepared, and 0.15 g of silicon oxide-coated zinc oxide (or surface modification) in terms of zinc oxide was added to 15 g of this brilliant blue aqueous solution. (Zinc oxide) was introduced and ultrasonically dispersed to prepare a suspension. The suspension was irradiated with an ultraviolet lamp (center wavelength: 254 nm) at an irradiation distance of 10 cm for 6 hours, and then the supernatant was collected. .
Next, the absorption spectrum of each of the above brilliant blue aqueous solution and the supernatant was measured by atomic absorption spectrophotometry, and the degradation rate D of brilliant blue was calculated by the above-described equation (1) using these measured values.

Tables 1 and 2 show the raw material components and the evaluation results of the silicon oxide-coated zinc oxide of Examples 1 to 4 and the surface-modified zinc oxide of Comparative Examples 1 and 2, respectively.
Table 2 shows the measurement results of the zinc elution rate and the brilliant blue decomposition rate of the zinc oxide particles (average particle size 250 nm; manufactured by Sumitomo Osaka Cement) used in Example 1 as Comparative Example 3.

According to Tables 1 and 2, the silicon oxide-coated zinc oxides of Examples 1 to 4 are Q ³ + Q ⁴ ≧ 0.6 and Q ⁴ / (Q as compared with the surface-modified zinc oxides of Comparative Examples 1 and 2. When Q ³ + Q ⁴ ) ≧ 0.5 and the decomposition rate of brilliant blue is 3% or less, a dense and uniform silicon oxide film is formed on the surface of the zinc oxide particles, and the zinc elution rate can be reduced. It was confirmed that it was possible.

(2) Silicon oxide-coated zinc oxide-containing composition [Example 5]
Carbomer Ultrez 10 (manufactured by Nikko Chemicals Co., Ltd.) 1.5 g was dissolved in pure water, then 10% by mass aqueous sodium hydroxide solution was added dropwise to adjust the pH, and 1.5% by mass of carbomer was contained and the pH was 7.5. A carbomer aqueous solution was prepared.
Next, the carbomer aqueous solution and the silicon oxide-coated zinc oxide B obtained according to Example 2 were mixed at a mass ratio of 95: 5, and then stirred, and the silicon oxide-coated zinc oxide-containing composition of Example 5 was mixed. I got a thing.

The viscosity of this composition was 10.4 Pa · s as a result of measurement using a viscometer BII viscometer (manufactured by Toki Sangyo Co., Ltd.) at 20 ° C. and 30 rpm.
A predetermined amount was collected from this composition, and the collected sample was kept at 40 ° C. using a thermostatic bath, and the viscosity was measured at 20 ° C. and 30 rpm every predetermined time. The measurement result of this viscosity is shown in FIG.

[Comparative Example 4]
The oxidation of Comparative Example 4 was performed in accordance with Example 5 except that zinc oxide particles (average particle size 250 nm; manufactured by Sumitomo Osaka Cement) were used instead of using the silicon oxide-coated zinc oxide obtained according to Example 1. A zinc-containing composition was obtained.
The viscosity of this composition was measured according to Example 5 and found to be 2.4 Pa · s.

[Comparative Example 5]
Carbomer Ultrez 10 (manufactured by Nikko Chemicals Co., Ltd.) 1.5 g was dissolved in pure water, then 10% by mass aqueous sodium hydroxide solution was added dropwise to adjust the pH, and 1.5% by mass of carbomer was contained and the pH was 7.5. A carbomer aqueous solution was prepared.
Next, the carbomer aqueous solution and pure water were mixed at a mass ratio of 95: 5 and then stirred to obtain a carbomer aqueous solution of Comparative Example 5.

Next, the viscosity of the carbomer aqueous solution was measured according to Example 5, and as a result, it was 9.5 Pa · s.
A predetermined amount was collected from the carbomer aqueous solution, and the collected sample was kept at 40 ° C. using a thermostatic bath, and the viscosity was measured at 20 ° C. and 30 rpm every predetermined time. The measurement result of this viscosity is shown in FIG.

According to the above results, the zinc oxide-coated zinc oxide-containing composition of Example 5 has a sufficiently suppressed zinc elution rate, and the viscosity decreases until about 15 hours after the composition is produced. It was confirmed that the subsequent viscosity was constant and the decrease in viscosity was suppressed.
In addition, the viscosity became a little lower at first due to the change with time, but after a certain time or more, the viscosity after that became almost constant, and it was confirmed that the decrease in viscosity was suppressed.

On the other hand, the composition of Comparative Example 4 was confirmed to have a high zinc elution rate because the surface of zinc oxide was not coated with a silicon oxide film, and that the viscosity immediately decreased after the composition was prepared. .
In Comparative Example 5, since the carbomer aqueous solution did not contain zinc oxide, it was not affected by heating and holding at 40 ° C., and the viscosity was constant at about 10 Pa · s.

In the silicon oxide-coated zinc oxide of the present invention, the average particle diameter of the zinc oxide particles in the silicon oxide-coated zinc oxide obtained by coating the surface of the zinc oxide particles with a dense silicon oxide film is more than 50 nm and not more than 500 nm. when the existence ratio in ^{Q 3} environments of silicon in the silicon film was the presence ratio in ^Q 3, ^{Q 4} environment ^{Q 4, Q 3 + Q 4} ≧ 0.6 and ^{Q 4 / (Q 3 + Q} 4) ≧ 0. 5 and the decomposition rate of the brilliant blue generated by the photocatalytic activity of the zinc oxide particles is set to 3% or less, the surface of the zinc oxide particles is uniformly covered with a dense silicon oxide film. Zinc ions can be prevented from leaching out of the particles, and therefore, when this silicon oxide-coated zinc oxide is applied to cosmetics, Because it can suppress degradation of cosmetic performance, discoloration, increase / decrease in viscosity, etc. due to elution, UV shielding ability is required, not to mention application to cosmetics with excellent usability, and other than cosmetics In the case of using in this field, the range of selection of the dispersant and resin is widened, the degree of freedom of design blending of paints and the like can be increased, and its industrial value is great.

Claims (6)

A silicon oxide-coated zinc oxide obtained by coating the surface of zinc oxide particles with a silicon oxide film,
The average particle diameter of the zinc oxide particles is more than 50 nm and not more than 500 nm,
Wherein when the presence ratio in ^{Q 3} environments of silicon oxide, silicon in the film was the presence ratio in ^Q 3, ^{Q 4} environment ^{Q 4, Q 3 + Q 4} ≧ 0.6 and ^{Q 4 / (Q 3 + Q} 4) ≧ 0.5,
A silicon oxide-coated zinc oxide, wherein the decomposition rate of brilliant blue produced by the photocatalytic activity of the zinc oxide particles is 3% or less.   The silicon oxide-coated zinc oxide according to claim 1, wherein the content of the zinc oxide particles is 50% by mass or more and 99% by mass or less.   When the silicon oxide-coated zinc oxide is immersed in an aqueous solution having a hydrogen ion index of 5 so as to be 0.05% by mass, the elution rate of zinc eluted in the aqueous solution is 20% by mass or less. The silicon oxide-coated zinc oxide according to claim 1 or 2. Surface-modified zinc oxide particles are suspended in a solvent to form a surface-modified zinc oxide suspension,
Next, this surface-modified zinc oxide suspension is reacted by adding one or more of alkoxysilane and an oligomer of alkoxysilane of 10-mer or less, a catalyst, and water,
Next, a method for producing silicon oxide-coated zinc oxide, wherein the obtained reaction product is heat-treated at a temperature of 150 ° C. or higher and lower than 600 ° C.   A silicon oxide-coated zinc oxide-containing composition comprising the silicon oxide-coated zinc oxide according to any one of claims 1 to 3 and a solvent.   It contains either or both of the silicon oxide-coated zinc oxide according to any one of claims 1 to 3 and the silicon oxide-coated zinc oxide-containing composition according to claim 5 in a base. And cosmetics.

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