JPH11193354A - Silica-coated zinc oxide particle, its preparation, and composition containing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain silica-coated zinc oxide particles improved in chemical resistance, dispersibility, ultraviolet screening effect, transparency, and safety by surface-coating zinc oxide with silica to lower the photocatalytic activity of the zinc oxide. SOLUTION: A dispersion is obtained by dispersing zinc oxide in a 1-5C alcohol containing 5-100 wt.%, based on the zinc oxide, dispersant selected among ethylcellulose, polyvinyl butyral resins, polyvinyl alcohol resins, acrylic resins, phosphoric ester activators, and unsaturated carboxylic acids. An alkoxysilane, an alkylalkoxysilane or an oligomer thereof is added to the dispersion and hydrolyzed in the presence of a catalyst to surface-coat the zinc oxide with 5-100 wt.%, based on the weight of the zinc oxide, silica. The obtained silica-coated zinc oxide particles comprise at least 90 wt.% particles having a particle diameter of 0.1-9.0 μm and have a mean article diameter of 0.5-5.0 μm. The hydrolysis catalyst is exemplified by hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, oxalic acid, ammonia water, or ammonium hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technical field of ultraviolet shielding using zinc oxide.

[0002]

2. Description of the Related Art Ultraviolet rays are known to have an adverse effect on the skin.
320nm ultraviolet light causes inflammation such as erythema blister,
It is known that ultraviolet light in a wavelength range of 320 to 400 nm called UVA promotes melanin production and causes browning of the skin. As a countermeasure against such adverse effects of ultraviolet rays on the skin, various types of sunscreen cosmetics have been conventionally known. Components for preventing ultraviolet rays that have been used in these cosmetics can be broadly classified into organic and inorganic ultraviolet shielding agents.

[0003] Organic UV screening agents have excellent light absorption properties and are relatively easy to form fine particles. However, they have poor light resistance as compared with inorganic UV screening agents and cannot stably maintain UV screening performance over a long period of time. Had a problem. In addition, it has been pointed out that repeated contact of cosmetics containing this with the skin may cause allergic symptoms. There is a problem in terms of.

On the other hand, metal oxides are used for inorganic materials, and they are excellent in light resistance and safety for human bodies. However, since the particle diameter is generally larger than that of an organic type, the surface area per volume is small, and accordingly, the absorption capacity for ultraviolet rays is also reduced. Therefore, in order to enhance the ultraviolet shielding effect, a large amount must be blended and the light scattering ability of the compound itself must also be used together, and as a result, the light transmittance in the visible region is reduced and the transparent region is not sufficiently transparent. There was a problem.

[0005] As an inorganic ultraviolet shielding material, titanium oxide is generally most often used, but it has a problem in transparency in the visible region and has a fatal effect that it has no absorption in the UVA region. With disadvantages.

[0006] Zinc oxide has a function of shielding ultraviolet rays, and, in comparison with titanium oxide, particularly has a U-size of 320 nm or more.
It has an absorption band in the VA region and is excellent in transparency in the visible region. This is also an inorganic metal oxide which is excellent in light resistance and safety for the human body and is preferable as an ultraviolet shielding material.

[0007] However, since zinc oxide itself is an n-type semiconductor and has photocatalytic activity, the photocatalytic activity becomes extremely strong when it is micronized, and when it is formulated as a cosmetic or resin composition for preventing ultraviolet rays. In addition, there is a problem that it acts on other compounding components to induce phenomena such as decomposition and alteration.

[0008] In consideration of the efficient use of zinc oxide as an ultraviolet shielding agent, it is better to make the particle size smaller optically. If zinc oxide is made finer, the absorption having a peak in the ultraviolet region increases as the surface area increases, and the influence of scattering that hinders the transparency of the visible region decreases. In other words, the finer particles increase the ultraviolet shielding power and also increase the transparency of the visible portion, so that optical characteristics more suitable as an ultraviolet shielding agent can be obtained.

However, since zinc metal is an amphoteric metal, zinc oxide is chemically vulnerable to acids and alkalis. In particular, if the surface area is increased by forming fine particles, the particle surface is easily attacked by chemicals. When the surface of zinc oxide is attacked by chemicals, reagglomeration occurs, and as a result, the particle size becomes large or the zinc oxide deteriorates to adversely affect other components, and its use has been a problem. Also, when surface treatment is performed on zinc oxide, treatment involving a large pH change cannot be performed due to lack of chemical resistance.

[0010] Further, when zinc oxide is blended into a milky lotion or cream as a cosmetic, the zinc oxide reacts with anionic residues such as thickeners and emulsifiers contained in the raw materials. As an example, it is known that a zinc salt crystal is formed by reacting with a higher fatty acid frequently used as a cosmetic material. By blending zinc oxide, it is possible to maintain a stable composition of the cosmetic, and thus maintain the quality. The problem of not being able to remain has significantly narrowed the scope of application of zinc oxide in the cosmetics field.

The inorganic ultraviolet shielding material has a large specific gravity, so that it is difficult to stably maintain a dispersed state. Even if the particle diameter can be temporarily reduced during the dispersion process, it is re-agglomerated due to overdispersion. Or a hard cake due to sedimentation. For example, when a cosmetic containing this is used, the transparency is significantly impaired, and there is also a problem that the skin becomes pale and dull and the product value as a cosmetic is impaired. There was also a need for the development of technologies that would facilitate this.

[0012] As described above, zinc oxide particles have favorable characteristics and have various difficulties, so that there are many restrictions on their practical use.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to reduce the photocatalytic activity of zinc oxide, improve the chemical resistance, and improve the dispersibility of zinc oxide. It is an object of the present invention to provide a material having both transparency and safety without impairing the high ultraviolet shielding effect of zinc oxide by the application.

[0014]

The object of the present invention is to solve the problem by coating the surface of zinc oxide with silica. Hereinafter, the present invention will be described in more detail.

The silica-coated zinc oxide particles of the present invention are realized by, for example, silica coating by a sol-gel method. As a method for obtaining an amorphous metal oxide such as glass at a low temperature, a sol-gel method has been well known. (See "Sol-Gel Method Science," by Agne Shofusha, 1988, by Sakubana Mio.) In the sol-gel method, a solution of a metal compound is first hydrolyzed and polycondensed to form a sol. Further proceeding the reaction as a gel,
By heating this gel, a solid of a metal oxide is obtained. The best known starting metal compounds are metal alkoxides. A general process of forming a silica glass film by a sol-gel method will be described below.

When an alkoxide of silicon as a metal compound, for example, tetraethoxysilane, is used, the alkoxide is dissolved in a solvent such as an alcohol, and a catalyst is added. Then, one-dimensional polymer particles are formed by polymerization of the hydrolyzate to form a so-called sol. Furthermore, clusters formed by collecting some particles in the sol grow as the hydrolysis / polymerization reaction proceeds, so that the sol viscosity gradually increases, and finally the solution becomes a gel. The glass gel film thus obtained is baked to evaporate the solvent and promote the polymerization of the unreacted portion to form a strong glass thin film. Glass thin film according to the present invention,
A glass thin film formed at a low temperature in the above-mentioned sol-gel method. In this case, the glass refers to an amorphous metal oxide.

The above is a general method of producing a glass gel thin film by the sol-gel method. It is assumed that a silica-coated gel thin film is formed on the surface of fine particles by using this method, and zinc oxide is coated with the above silica thin film. By performing the treatment, the surface of the zinc oxide does not come into direct contact with other materials, the adverse effect due to the interaction with the surrounding materials is suppressed, and the application range of the zinc oxide as an ultraviolet shielding material can be expected to be expanded.

In order to produce the silica-coated zinc oxide of the present invention, it is necessary to use the silica-coated zinc oxide dispersed in order to control an appropriate particle diameter. In order to disperse zinc oxide in an appropriate size in alcohol, a dispersant for stabilizing the dispersion must be used. As the dispersant, a dispersant that can uniformly disperse zinc oxide even in the presence of a metal alkoxide or a catalyst must be selected so as not to hinder the surface treatment by the sol-gel method.

Therefore, the search for a dispersant capable of uniformly dispersing even in a metal alkoxide solution was advanced. As a means for dispersing zinc oxide, it is soluble in alcohol, compatible with metal alkoxide, and adsorbed on zinc oxide. It has been found that an excellent dispersion can be obtained by using a substance exhibiting a dispersing power after the above.

As a result of various searches for dispersants, silica-coated zinc oxide of stable quality was obtained by the following. 1. Ethyl cellulose. For example, Etocel 7 manufactured by Dow Chemical Co., Ltd. 2. Polyvinyl butyral resin. For example, S-LEC BL- manufactured by Sekisui Jushi Chemical Co., Ltd.
One. 3. Polyvinyl alcohol resin. For example, Goseilan L-03 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
01. 4. acrylic resin. For example, Hitec 532 manufactured by Shellac Japan Co., Ltd. 5. Phosphate activator. For example, Descall A-200 manufactured by Asahi Denka Kogyo KK 6. Unsaturated polycarboxylic acids. For example, BIC 104S manufactured by BIC Chemie.

Due to problems such as poor dispersion in the reaction solution and inhibition of silica film formation, no other dispersant other than those mentioned above was found to be effective in treating the zinc oxide with the silica film in this method.

The amount of the dispersant added is preferably 5 to 100% by weight based on zinc oxide.

The metal alkoxide is generally M (O
R) _n . Here, M is a metal element, OR is an alkoxyl group, and n is the oxidation number of the metal. As a metal alkoxide used as a precursor of silica to be coated in the present invention, Si (OR) ₄ is used.
_{4 '-n Si (OR) n} (R'; alkyl group) alone or in combination, can be used for purposes such as improving the water repellency.

In addition, Zn, Ti, Al, F other than Si
A metal alkoxide composed of e, Co, Ni, or the like can be mixed with a Si alkoxide for the purpose. For example, it is beneficial to mix Ti or Zn when adjusting the refractive index, Zr when strength or alkali resistance needs to be improved, and alkoxide such as Ni when further improving weather resistance. .

Further, Si (OR) ₄ used in the present invention.
And R and R ′ of R ′ _4-n Si (OR) _n are as follows:
Generally, an alkyl group having 1 to 12 carbon atoms or a fluoroalkyl group in which a hydrogen atom of the alkyl group is substituted with a fluorine atom is desirable. Further, as the alcohol for dissolving the metal alkoxide, the viscosity of the alcohol solution increases with the increase in the number of carbon atoms. Therefore, the alcohol may be appropriately selected in consideration of this point. Generally usable alcohols include those having 1 to 5 carbon atoms.

Examples of the acid used as a hydrolysis catalyst include hydrochloric acid, nitric acid, sulfuric acid, carbonic acid, phosphoric acid and organic acids such as formic acid, acetic acid, oxalic acid and citric acid. Examples of the alkali include amines such as aqueous ammonia, ammonium hydroxide, ammonium bicarbonate, monoethanolamine, diethanolamine, and triethanolamine. Furthermore, as alkali neutralized salts of quaternary ammonium, for example, lauryl trimethyl ammonium hydroxide is also effective.

The silica-coated zinc oxide particles of the present invention can be realized by forming a silica-coated film in a zinc oxide dispersion using the above-mentioned sol-gel method. The silica coating film formed on the zinc oxide surface is an inorganic material containing SiO ₂ as a main component, and has a function as a protective film against zinc oxide. That is, by coating the zinc oxide particles with silica, the chemical resistance, which was a weak point of zinc oxide, can be improved. At the same time, since other substances cannot contact the zinc oxide surface, it is possible to prevent adverse effects on other components due to photocatalytic activity.

Further, the obtained silica-coated zinc oxide can be adjusted to a desired particle size by a conventionally known pulverization or classification technique, if necessary.

The silica coating amount of the present invention is in the range of 5 to 100% by weight based on zinc oxide. When the amount of the silica coating is 5% by weight or less, the effect of dispersion is not exhibited because the coating amount is not sufficient, and a sufficient ultraviolet light shielding effect cannot be obtained.
Furthermore, it was not effective in suppressing the photocatalytic activity. Even when the silica coating amount exceeds 100% by weight, the amount of silica with respect to zinc oxide is too large, so that the ultraviolet ray shielding effect in the UVA region decreases. Further, since the characteristic of silica that the amount of oil absorption is high appears strongly, it is difficult to disperse and mix the silica at a high concentration with respect to a substrate or the like. In addition, it has been found that, when formulated as a cosmetic, it gives a rough sensation on the skin, which causes a problem of deterioration in the feeling upon use.

The particle diameter of the silica-coated zinc oxide in the present invention is such that most of the particles are in the range of 0.1 μm to 9.0 μm and the average particle diameter is 0.5 μm to 5.0 μm. Should be within range. With such silica-coated zinc oxide, not only good ultraviolet shielding ability can be obtained, but also the above-mentioned disadvantages of uncoated zinc oxide can be overcome.

In the case of particles having a particle size of less than 0.1 μm, the dispersion efficiency for producing the particles becomes extremely poor, and the effect of shielding ultraviolet rays is not improved as compared with the energy for dispersion. As the number of particles exceeding 0.0 μ increases, the light absorption characteristics deteriorate. However, the inclusion of this type of particles is permissible as long as the amount is small, so that it is sufficiently practicable if the particles having a particle size of less than 0.1 μm and the particles having a particle size of more than 9.0 μm are 10% by weight or less. is there.

If the average particle size is less than 0.5 μm, the dispersion efficiency for producing the particles becomes extremely poor. Further, if the average particle size exceeds 5.0 μ, the transparency and the effect of shielding ultraviolet rays are deteriorated.

The silica-coated zinc oxide having such a particle size distribution can be easily realized by selecting the manufacturing process conditions, particularly the conditions for dispersing the zinc oxide.

When the zinc oxide according to the present invention is blended as a cosmetic, the zinc oxide is encapsulated in the silica coating film, so that the zinc oxide does not directly touch other materials or skin in the blend. For this reason, against other ingredients and skin in the formulation,
Without causing chemical reaction due to pH or photocatalytic activity,
Conventionally, there is no danger of skin irritation or the like caused by a substance resulting from a chemical reaction caused by uncoated zinc oxide. Also, since the ability to adapt to pH changes can be improved,
Combinations that are not possible with conventional zinc oxide are now possible.

Further, when the zinc oxide according to the present invention is used as a cosmetic, since the silica coating film is transparent and has a high oil absorption, the performance of the cosmetic such as dullness and sinking of color due to the wetting of sweat and sebum is reduced. Impaired color change is less likely to appear.

Further, the zinc oxide according to the present invention can be blended as a resin composition such as a paint, an adhesive or a resin molded product. Since the silica-coated zinc oxide resin composition has reduced photocatalytic activity of untreated zinc oxide,
Does not adversely affect surrounding materials such as resins and colorants. Accordingly, the range of application of zinc oxide can be expanded, and paints, adhesives, and resin molded products having excellent ultraviolet shielding ability can be obtained.

The following are examples of the resin used in the resin composition. For example, coatings include alkyd resins, acrylic resins, epoxy resins, urethane resins, etc., adhesives include melamine resins, phenolic resins, epoxy resins, etc., and resin-formed products such as polyethylene, polyvinyl chloride, and polystyrene. , Polypropylene and the like.

[0038]

EXAMPLES Next, the present invention will be described specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 100.0 g of zinc oxide, 15.0 g of ethylcellulose (Ethocel 7, manufactured by Dow Chemical Co., Ltd.) and 285.0 g of isopropyl alcohol were mixed, and subjected to a dispersion treatment using a disperser for 30 minutes. A 25% zinc oxide dispersion was prepared.

Next, 170.0 g of tetraethoxysilane
(Containing 50.0 g as SiO ₂ ), 250.0 g of isopropyl alcohol, 2.0 g of ammonia water, all of the above zinc oxide dispersions, and 250.0 g of water were sequentially added and mixed, and the alkoxide was hydrolyzed at 80 ° C. The stirring was continued until the reaction was completed to fix the silica layer on the zinc oxide surface.

Next, the mixture was filtered, washed well with alcohol and water, dried, and then crushed by a pulverizer to obtain a silica coating amount of 49% by weight, an average particle size of 2.5 μm, a particle size of less than 0.1 μm, A silica-coated zinc oxide having a content of more than 0.0 μm and 2% by weight or less was obtained. The particle size distribution is measured using a laser diffraction particle size distribution analyzer (SALD-1 manufactured by Shimadzu Corporation).
100).

Example 2 170.0 g of the tetraethoxysilane of Example 1 was added to 10
0.0 g, and newly added methyltrimethoxysilane.
0 g (containing 20.5 g as MeSiO _1.5 ) was added at the same time as tetraethoxysilane, and zinc oxide was treated in the same manner as in Example 1 to obtain silica-coated zinc oxide having the same silica coating amount and particle size. Obtained.

Example 3 0.5 g of the silica-coated zinc oxide of Example 1 and 99.5 g of castor oil as a dispersion medium were dispersed in a homomixer for 15 minutes to obtain a slurry of silica-coated zinc oxide.

The slurry was placed in a 0.1 mm quartz cell, and the light transmittance was measured with a spectrophotometer (Ubest manufactured by JASCO Corporation).
-30), the result of FIG. 1 was obtained.

Example 4 In place of 0.5 g of the silica-coated zinc oxide of Example 3, 0.5 g of the silica-coated zinc oxide of Example 2 was used. A slurry of silica-coated zinc oxide was prepared by the method of Example 3, and the light transmittance was measured. The result of FIG. 2 was obtained.

Comparative Example 1 An untreated zinc oxide slurry was prepared in the same manner as in Example 3, except that 0.5 g of zinc oxide without silica coating was used instead of 0.5 g of silica-coated zinc oxide of Example 3. When the light transmittance was measured, the result of FIG. 3 was obtained.

From Examples 3, 4 and Comparative Example 1, it was confirmed that the silica-coated zinc oxide had a higher ultraviolet shielding ability than the untreated zinc oxide, and the visible portion was more transparent. Was done. This indicates that the dispersion state of the silica-coated zinc oxide is stabilized as compared with the untreated product, and that it has better suitability as an ultraviolet shielding agent.

Example 5 The silica-coated zinc oxide of Example 1 was replaced with the dye Oil Red.
A paint was prepared by mixing with the 6B acrylic resin solution, and the paint was applied on an aluminum plate with a 10 mil doctor blade, the coated plate was exposed outdoors for 5 days, and the color difference of the coated plate after exposure was measured.

Example 6 Instead of the silica-coated zinc oxide of Example 1, the silica-coated zinc oxide of Example 2 was used to perform outdoor exposure for 5 days in the same manner as in Example 5, and the color difference of the coated plate after the exposure was measured. It was measured.

Comparative Example 2 In place of the silica-coated zinc oxide of Example 1, zinc oxide not treated by this method was used and exposed outdoors for 5 days in the same manner as in Example 5. The color difference was measured.

Comparative Example 3 The silica-coated zinc oxide of Example 1 was removed, and outdoor exposure was performed for 5 days in the same manner as in Example 5, and the color difference of the coated plate after the exposure was measured.

Example 5, Example 6, Comparative Example 2, Comparative Example 3
Table 1 summarizes the results.

Table 1: Color difference after outdoor exposure

Although the above results were obtained, the color difference ΔE indicates the degree of color change before and after exposure, and the larger the value, the larger the color difference between the coated plate before and after exposure. . This change in color is due to the fading of the dye due to outdoor exposure.Therefore, the fact that the degree of fading of the contained zinc oxide is greater than that of the absence of the zinc oxide is due to the effect of the photocatalytic activity of the zinc oxide. Responsible.

From Table 1, the degree of deterioration of the dye due to the photocatalytic activity is considerable for untreated zinc oxide, but not so much for the silica-coated zinc oxides of Examples 5 and 6. Since there is not much difference from Comparative Example 3 in which zinc oxide is not added, it is shown that the photocatalytic activity of zinc oxide can be suppressed by the silica coating of the present method.

Example 7 1.0 g of the silica-coated zinc oxide of Example 1 and 99 g of liquid paraffin as a dispersing medium were added to 80 g of 1.5 mm glass beads, dispersed by a paint conditioner (manufactured by Red Devil Co.), and dispersed for 5 minutes. 30 minutes later, 60 minutes later 3
The transmittance at 70 nm was measured.

Example 8 Using the silica-coated zinc oxide of Example 2, dispersion was measured in the same manner as in Example 7, and the measurement was performed.

Comparative Example 4 Untreated zinc oxide was dispersed and measured in the same manner as in Example 7.

Table 2 summarizes the results of Examples 7, 8, and Comparative Example 4. Table 2: Transmittance at 370 nm

From the above results, Examples 7 and 8 are superior in the ultraviolet shielding power than the initial stage of dispersion, but Comparative Example 4 has a low ultraviolet shielding capability in the initial stage of dispersion and silica coating is obtained even after dispersion for 60 minutes. Not as good as processed. this is,
This shows that the dispersibility was improved by the silica coating treatment.

Example 9 25 g of the silica-coated zinc oxide of Example 1 and 75 oleic acid
g was weighed, mixed and stirred for 5 minutes, and the state was observed.

Example 10 25 g of the silica-coated zinc oxide of Example 2 and 75 oleic acid
g was weighed, mixed and stirred for 5 minutes, and the state was observed.

Comparative Example 5 25 g of untreated zinc oxide and 75 g of oleic acid were weighed, mixed and stirred for 5 minutes, and the state was observed.

In the silica-coated zinc oxide of Examples 9 and 10, no change was observed during mixing and over time.
In the untreated zinc oxide of Comparative Example 5, as soon as it was mixed, it was coagulated and solidified by reaction with oleic acid.

It is known that untreated zinc oxide reacts with higher fatty acids to form a zinc salt. In Comparative Example 5, a salt is formed simultaneously with mixing with oleic acid, causing coagulation and solidification. Chemical resistance was improved by the silica coating of this method, and stable zinc oxide could be obtained even when mixed with oleic acid.

Example 11 A powder foundation was prepared using the silica-coated zinc oxide of Example 1 with the following composition.

The silica-coated zinc oxide of Example 1 40.0 parts by weight Talc 44.9 Titanium oxide 5.0 Starch 2.0 Magnesium stearate 3.0 Liquid paraffin 3.0 Isopropyl myristate 2.0 Preservatives 05 Fragrance 0.05

The talc and the pigment component are mixed in a blender. The remaining powder is added thereto, mixed well, and then a binder and a preservative are added. After the color is adjusted, the fragrance is sprayed and uniformly mixed. This is pulverized by a pulverizer and then compression-molded into a middle plate through a sieve.

Example 12 A powder foundation was prepared by the method of Example 11 using the silica-coated zinc oxide of Example 2 instead of the silica-coated zinc oxide of Example 1.

Comparative Example 6 Powder foundation was prepared by using untreated zinc oxide in place of the silica-coated zinc oxide of Example 1.
Created by

In Comparative Example 6, a natural finish feeling could not be obtained because the cosmetic film was bluish or white. In contrast, Embodiments 11 and 12 according to the present invention
Was transparent, had a good finish, and had an excellent ultraviolet shielding effect.

Example 13 An O / W emulsified foundation was prepared using the silica-coated zinc oxide of Example 1 in the following formulation.

Powders Silica-coated zinc oxide of Example 1 5.0 parts by weight Talc 3.0 Bengala 0.5 Titanium oxide 0.6 Water phase Bentonite 0.5 Polyoxyethylene sorbitan monostearate 0.9 Triethanolamine 1.0 Propylene glycol 10.0 Purified water 56.4 Oil phase Stearic acid 3.0 Isohexadecyl alcohol 7.0 Glycerin monostearate 2.0 Liquid lanolin 2.0 Liquid paraffin 8.0 Preservatives 0.05 Perfume 0.05

Propylene glycol in which bentonite, which is an aqueous thickener, is dispersed is added to purified water, homogenized at 70 ° C., and the remaining aqueous components are added and sufficiently stirred. The powder portion sufficiently mixed and pulverized is added thereto with stirring, and treated at 70 ° C. with a homomixer. Next 70
The oil phase heated and dissolved at ~ 80 ° C is gradually added, and homomixed at 70 ° C. This is cooled with stirring and 45
Add perfume at ℃ and cool to room temperature.

Example 14 An O / W emulsion type foundation was prepared by the method of Example 13 using the silica-coated zinc oxide of Example 2 instead of the silica-coated zinc oxide of Example 1.

Comparative Example 7 An O / W emulsified foundation was prepared by using untreated zinc oxide in place of the silica-coated zinc oxide of Example 1.
3 was prepared.

In Comparative Example 7, a natural finished feeling could not be obtained because blushiness and whitening occurred in the decorative film. In contrast, Embodiments 13 and 14 according to the present invention
Was transparent, had a good finish, and had an excellent ultraviolet shielding effect.

[0078]

The silica-coated zinc oxide of the present invention has an excellent shielding effect in the ultraviolet region with high transparency in the visible region, is safe, has excellent chemical resistance, and has a reduced photocatalytic activity. Further, resin compositions and cosmetics such as paints, adhesives, and molding materials containing the silica-coated zinc oxide of the present invention,
It shows an excellent ultraviolet blocking effect and does not impair transparency by zinc oxide.

[Brief description of the drawings]

FIG. 1 is a curve diagram showing the relationship between light transmittance and wavelength in silica-coated zinc oxide of Example 3.

FIG. 2 is a curve diagram showing the relationship between light transmittance and wavelength in silica-coated zinc oxide of Example 4.

FIG. 3 is a curve diagram showing a relationship between light transmittance and wavelength in silica-coated zinc oxide of Comparative Example 1.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C09D 7/12 C09D 7/12 Z C09J 11/04 C09J 11/04 (72) Inventor Kazuo Sakai 2-23-2 Obana, Kawanishi-shi, Hyogo Prefecture (72) Inventor Tsutomu Ueda 2-23-2 Obana, Kawanishi-shi, Hyogo Inside Fuji Color Machine Co., Ltd.

Claims (4)

[Claims] 1. A zinc oxide particle whose surface is coated with 5% by weight to 100% by weight of silica based on the weight of zinc oxide, and 90% by weight or more of the coated particle has a particle size of 0.1 μm.
Not less than 9.0 μm, and the average particle size is not less than 0.5 μm and 5.0.
The silica-coated zinc oxide particles are in the range of μ or less. 2. A composition comprising the cosmetic and the silica-coated zinc oxide particles according to claim 1 incorporated therein. 3. A composition comprising the silica-coated zinc oxide particles according to claim 1 incorporated into any one of a paint, an adhesive and a resin molded product. 4. A method of dispersing zinc oxide particles in an organic dispersion medium using a dispersant, and subjecting the alkoxysilane or alkylalkoxysilane or a low polymer thereof to a gelling reaction in the dispersion. A method for producing silica-coated zinc oxide particles.