JP2002060724A - Ultrasonic light-screening agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic light-screening agent which has a high screening effect in the UVB and UVA regions of ultrasonic light, is chemically stable and has good dispersibility. SOLUTION: This ultraviolet light-screening agent 50 characterized by covering the surfaces of agglomerate-like secondary particles 20 comprising the aggregates of primary cerium oxide particles with at least one metal compound 30 selected from the hydrate or anhydride of a metal hydroxide or a salt thereof. The ultrasonic-shielding agent 60 characterized by further applying a hydrophobization treatment using an organic hydrophobizing agent 40 to the primary coating films comprising the metal compound 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet ray shielding agent which is obtained by modifying the structure and surface of cerium oxide having an excellent effect of preventing ultraviolet rays, suppressing aggregation of particles and catalytic activity, and further improving yellowness.

[0002]

2. Description of the Related Art In recent years, the influence of ultraviolet rays on skin has been widely recognized due to an increase in solar ultraviolet rays due to destruction of the ozone layer and an increase in awareness of prevention of skin cancer. As a result, the function of an ultraviolet shielding agent as sun care for protecting the skin from the harm of ultraviolet rays has been attracting attention.

[0003] In general, ultraviolet shielding agents used in cosmetics are roughly classified into two types: an organic ultraviolet absorbing agent and an ultraviolet scattering agent comprising an inorganic metal oxide. Organic ultraviolet absorbers have a covalent double bond in the molecule, and when the electron energy level in the molecule rises due to ultraviolet light and enters an excited state, it immediately emits heat, phosphorescence, and fluorescence, and returns to the ground state. UV light is absorbed by converting it into another energy.

On the other hand, inorganic ultraviolet scattering agents, such as metal oxides represented by titanium oxide, block ultraviolet rays by an effect of scattering ultraviolet rays with a high refractive index and absorption by transition between band gaps.

[0005] In general, organic ultraviolet absorbers have better ultraviolet shielding properties and visible light transparency than inorganic ultraviolet scattering agents, but have a problem in the persistence of the ultraviolet shielding effect. Further, the organic UV absorber is chemically unstable because it is deteriorated by ultraviolet rays. Furthermore, when used as cosmetics, many of them cause irritation to the skin and allergic reactions, and there are restrictions on use and restrictions on the amount used.

[0006] On the other hand, inorganic ultraviolet scattering agents are less likely to be modified by ultraviolet rays and are stable, so that the use of inorganic ultraviolet scattering agents has been increasingly required.

[0007] Normally, titanium oxide is used as an inorganic ultraviolet scattering agent. This titanium oxide has an excellent shielding ability in the UVB region (290 to 320 nm), further has excellent photochemical stability, and has an ultraviolet shielding effect. Sustainability is also good.

However, conventionally used titanium oxide has a UVA region reaching the dermis (320 to 400).
nm) is not sufficient, and a particle diameter having a larger refractive index is employed. Therefore, titanium oxide having this particle diameter has a high refractive index even at a visible light wavelength (400 to 800 nm). As a result, there is a problem that the transparency of visible light is poor, and whitening of the skin occurs during makeup.
Therefore, in order to improve the visible light transparency, titanium oxide particles were made finer, but as the particles became finer, the cohesive force became stronger, causing a rough feeling during use or lowering the visible light transparency. There was a problem of doing.

On the other hand, although zinc oxide has a lower shielding effect than titanium oxide, zinc oxide is excellent not only in the UVB region but also in the UVA region, and can be made into ultrafine particles. In addition, the transparency of visible light is high, and in recent years, ultrafine particles of zinc oxide instead of titanium oxide have been widely used as an ultraviolet scattering agent.
However, for example, in order to secure an SPF index showing a protective effect of UVB ultraviolet rays in cosmetics, a larger amount of the compounding agent than titanium oxide is required, and there is a problem that the feeling of use is lowered and the cost is increased.

Therefore, in recent years, cerium oxide, which has an ultraviolet shielding effect almost the same as that of conventional titanium oxide and can be made finer, has attracted attention. JP-A-1-190626 proposes a cosmetic comprising at least 0.1% by weight of cerium oxide and / or cerium oxide as ceric oxide.

However, the cosmetic containing this cerium oxide efficiently blocks ultraviolet rays in the range of 290 to 370 nm, but has an insufficient ultraviolet ray shielding effect at 370 nm or more.

Therefore, Japanese Patent Application Laid-Open No. 10-226518 proposes a cerium oxide powder which is effective for shielding in the UVA region, and this cerium oxide is fired at 700 ° C. or more in an oxidizing atmosphere. It is a white cerium oxide powder having a yellowness YI of 20 or less. Also, Japanese Patent Application Laid-Open No. H11-228135 discloses that 370 nm
A cerium oxide powder having a high shielding effect against the above ultraviolet rays has been proposed.

[0013]

However, any of the above-mentioned cerium oxides, for example, reacts with some organic compounds in cosmetics and discolors the cosmetics because their catalytic activities are not sufficiently suppressed. Or there was a possibility of coloring.

On the other hand, in recent years, there has been a tendency to prefer thin makeup, in other words, natural makeup, except for a very small portion of the scene, from thick makeup that can be firmly applied. In such a natural makeup orientation, for example, transparency is required even for sunscreen. Therefore, a demand for a highly transparent ultraviolet ray shielding agent is increasing.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to sufficiently suppress the catalytic activity of cerium oxide, improve the cohesiveness of cerium oxide powder, and provide excellent ultraviolet shielding properties and transparency. It is to provide an inorganic ultraviolet scattering agent having:

[0016]

Means for Solving the Problems In order to solve the above problems, the ultraviolet shielding agent according to the present invention has the following features.

(1) The surface of the coagulated secondary particles composed of an aggregate of primary particles of cerium oxide is selected from a metal compound comprising a hydroxide or an anhydride of a metal hydroxide or a salt thereof. Treated with at least one or more metal compounds.

By using cerium oxide as secondary particles as compared with the primary particles of cerium oxide, the scattering properties can be improved. Further, by forming the coagulated secondary particles, the cohesiveness is improved and the dispersion stability is also improved. Also,
By coating the coagulated secondary particles of cerium oxide with the above-mentioned metal compound, the catalytic activity of cerium oxide can be suppressed. Further, the uncoated cerium oxide usually shows yellow. Therefore, by covering the surface with the above-mentioned metal compound, the yellowness can be improved and yellowness can be suppressed. Thereby, even when cerium oxide is contained, cosmetics and paints having a wide range of colors, particularly cosmetics and paints having high whiteness, can be easily prepared.

(2) In the ultraviolet shielding agent according to the above (1), the agglomerated secondary particles are strawberry-shaped secondary particles and are substantially spherical.

Since the coagulated secondary particles are strawberry-shaped,
Agglomeration of particles is three-dimensionally suppressed. On the other hand, since the secondary particles are generally spherical, even if they are in the shape of a strawberry, the secondary particles have a smaller surface area per volume than other shapes, and as a result, it is possible to prevent the above-mentioned metal compound from remaining uncoated portions. As a result, it is possible to suppress, for example, oxidation of a compounded fat or oil component or a higher alcohol in a cosmetic or coloring due to deterioration due to catalytic activity of cerium oxide exposed in an uncoated portion.

(3) In the ultraviolet ray shielding agent according to the above (1) or (2), the coagulated secondary particles surface-coated with the metal compound are further subjected to a hydrophobic treatment with an organic hydrophobizing agent. .

2 coated with the above metal compound
By further coating the secondary particles with an organic hydrophobizing agent, sufficient water repellency and oil repellency can be obtained, for example, in oily cosmetics and paints.

(4) The cosmetic according to the present invention comprises the above (1)
To (3).

The band gap energy of cerium oxide is 3.1 eV, while the band gap energy of rutile type titanium oxide as an ultraviolet ray shielding agent is 3.0 eV.
V and zinc oxide are 3.4 eV. This indicates that cerium oxide has a higher UVA and UBV shielding effect than zinc oxide. Furthermore, while the refractive index of cerium oxide is 2.1, the refractive index of rutile-type titanium oxide is 2.7, which indicates that cerium oxide has excellent transparency. In addition, cerium oxide
Secondary particles improve dispersion stability, and further coat the surface to suppress the catalytic activity, so it has better chemical stability than before, and is the same as before even if the amount of UV scattering agent added by cerium oxide is reduced A degree of shielding effect can be obtained.

(5) The coating material according to the present invention comprises the above (1)
To (3).

Like the cosmetic of the above (4), by containing the ultraviolet shielding agent of the present invention, it is superior in chemical stability as compared with the conventional one, and the same as the conventional one even if the addition amount of the ultraviolet scattering agent by cerium oxide is reduced. Can obtain a degree of shielding effect,
Transparency is improved.

(6) The plastics composition according to the present invention contains the ultraviolet shielding agent according to any one of the above (1) to (3).

Like the cosmetic of the above (4), by containing the ultraviolet ray shielding agent of the present invention, it has excellent chemical stability as compared with the conventional one, and is the same as the conventional one even if the addition amount of the ultraviolet scattering agent by cerium oxide is reduced. Can obtain a degree of shielding effect,
Transparency is improved.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described. The ultraviolet shielding agent of the present invention will be described with reference to FIG.

The diameter of the primary particles 10 of cerium oxide in the present embodiment is preferably 10 to 50 nm. When the primary particle diameter is less than 10 nm, it becomes difficult to form the strawberry-like agglomerate secondary particles 20 as described later, and the particle diameter becomes small, so that the ultraviolet ray shielding effect may be insufficient. There is. On the other hand, when the diameter of the primary particles 10 exceeds 50 nm, the diameter of the obtained secondary particles 20 is too large, and the effective number of particles dispersed per unit area for protecting ultraviolet rays is insufficient. The shielding effect may be insufficient.

Further, the secondary particles 20 of cerium oxide in the present embodiment are formed by agglomerating the primary particles 10 and have a so-called strawberry-like form. The secondary particles 20 can be prepared, for example, by firing the primary particles 10 at a high temperature (about 600 to 1000 ° C.). The diameter of the secondary particles is preferably from 50 to 700 nm, more preferably from 100 to 400 nm. When the secondary particle diameter is less than 50 nm, the ratio of transmitting ultraviolet rays increases due to the small particle diameter, and the shielding effect may be insufficient. On the other hand, when the secondary particle diameter exceeds 700 nm, the number of effective particles distributed per unit area for protecting ultraviolet rays is insufficient, and the shielding effect may be insufficient.

The crystallite size of cerium oxide is 7
-60 nm (70-600 Å), more preferably 18-45 nm (180-4).
50 angstroms). When the crystallite size is less than 7 nm, the crystallinity is not sufficient. On the other hand, when the crystallite size exceeds 60 nm, crystals grow too much, and in all cases, the ability to block ultraviolet rays is not sufficient.

As the raw material powder of cerium oxide used in the present embodiment, those produced by various methods can be used. Examples of the production method include a hydrothermal method, an alkoxide method, a gas phase method, and a firing method. And the like. The above-mentioned hydrothermal method is performed by adding a base such as ammonia water to a cerium salt aqueous solution to neutralize the precipitate, depositing a precipitate, adding an oxidizing agent, and heating and crystallizing in a pressure vessel such as an autoclave. And cerium oxide. The alkoxide method is a method of obtaining a cerium oxide by hydrolyzing an alcohol solution of a cerium alkoxide compound.
Further, the gas phase method is a method in which cerium oxide powder is instantaneously melted in ultra-high temperature using high frequency induction thermal plasma to obtain cerium oxide powder. Further, in the firing method, a cerium organic compound such as cerium carbonate or cerium oxalate is fired, carbonate groups or oxalate groups are skipped, and the obtained fired powder is dry-ground by a jet mill or the like, or a ball mill, an attritor mill, This is a method in which fine cerium oxide is obtained by wet grinding using a bead mill or the like.

Next, the metal compound 30 covering the surface of the secondary particles 20 of cerium oxide is a hydrate or an anhydride of a metal hydroxide or a salt thereof, for example, aluminum, magnesium, silicon, or the like. Hydrates or anhydrides of zirconium or barium hydroxides or salts thereof may be mentioned.

The metal compound 30 is composed of cerium oxide 10
1.0 to 70% by weight, preferably 5.
It is coated in the range of 0 to 60% by weight, more preferably 8 to 30% by weight. 1.0% by weight of metal compound
If it is less than 10%, it is difficult to suppress the catalytic activity of cerium oxide due to the presence of an uncoated portion. On the other hand, when the coating amount of the metal compound exceeds 70% by weight, the bulk increases, the number of particles per unit area decreases, and the ultraviolet shielding function decreases.

The method for coating the surface of the secondary particles 20 used in the present embodiment is, for example, an aqueous solution of aluminum chloride, sodium aluminate, aluminum sulfate, sodium silicate, magnesium chloride, magnesium sulfate, zirconium oxychloride, titanium tetrachloride or the like. Is added to the cerium oxide powder slurry, the metal salt is adsorbed on the surface of the cerium oxide powder, and then an acid or alkali solution is added to hydrolyze or substitute the metal salt adsorbed on the cerium oxide surface. To precipitate metal hydroxide or its hydrate or anhydride on the surface of cerium oxide.

Alternatively, cerium oxide can be coated by using a coupling agent. For example, when a silane coupling agent is used, an alkoxy group bonded to a silicon atom is hydrolyzed by moisture on the surface of the cerium oxide powder, and the coupling agent coats the surface of the cerium oxide powder. Thereafter, the other organic functional group bonded to silicon but not to cerium oxide is skipped by heat treatment to form a silica layer on the surface of the cerium oxide powder. The silane coupling agent is preferably an alkoxysilane. Examples of the alkoxysilane include dimethyldimethoxysilane, monomethyltrimethoxysilane, tetramethoxysilane, diethyldimethoxysilane, monoethyltrimethoxysilane, diethyldiethoxysilane, and monoethyltrimethoxysilane. Ethoxysilane, tetraethoxysilane and the like can be mentioned. This alkoxysilane is
It is used by dissolving it in an appropriate amount in an organic solvent. As the organic solvent, methyl alcohol, ethyl alcohol and the like are preferable.

Further, in this embodiment, if necessary,
The surface of the primary coated cerium oxide secondary particles whose surface is coated with the metal compound 30 may be further subjected to a hydrophobic treatment with an organic hydrophobizing agent 40 to apply a secondary coating to the cerium oxide. By performing the hydrophobic treatment in this manner, the final product has sufficient water repellency and oil repellency. Examples of the organic hydrophobizing agent include, but are not limited to, silicone compounds, fluorine compounds, vegetable oils, animal oils, fatty acid metal salts, and the like. Examples of the silicone compound include dimethylpolysiloxane, cyclic dimethylpolysiloxane, and methylhydrogenpolysiloxane. Examples of the fluorine compound include perfluoropolyether, perfluoroalkyl-modified silicone, fluorocarbon, perfluoroalkylsilane, and perfluoroalkylphosphate ester salt.

The coating amount of the above-mentioned hydrophobizing agent varies depending on its type, but is preferably 0.1 to 40% by weight, more preferably 0.5 to 20% by weight, based on 100% by weight of the cerium oxide powder. Range. When the coating amount of the hydrophobizing agent is less than 0.1% by weight, sufficient water repellency and oil repellency cannot be obtained. On the other hand, when the coating amount of the hydrophobizing agent exceeds 40% by weight, for example, in the case of cosmetics, the feeling of use is impaired.

Next, a method for hydrophobizing the surface of cerium oxide powder which has been subjected to a primary coating treatment with the above metal compound will be described.

When the hydrophobizing treatment is a silicone treatment, the above-mentioned silicone compound is dissolved in a solvent, added to and mixed with the surface-coated cerium oxide powder, and then the solvent is removed. A secondary silicone film is formed on the surface of the cerium powder.

When the hydrophobic treatment is a fluorine compound,
The above-mentioned fluorine compound, for example, a perfluoroalkyl phosphate diethanolamine salt [having a structural formula (CF
_{2m + 1} CF _2m CH ₂ CH ₂ O) _n PO [O (NH ₂
CH ₂ CH _{2 OH) 2]} is a _3-n, where, m =. 6 to
18, 2>n> 1] aqueous solution is added to and mixed with the primary coated cerium oxide powder, an acid is further added to lower the pH to 3 or less, and a fluorine compound such as perfluoroalkylphosphoric acid is coated on the powder surface. Precipitate. The powder having the fluorine compound precipitated on the surface is filtered, washed with water, and dried to obtain a cerium oxide powder which is secondarily coated with the fluorine compound.

The ultraviolet shielding cosmetic of the present embodiment may be prepared by adding the above-mentioned ultraviolet shielding agent to, for example, a basic cosmetic such as cream, lotion, lotion, milky lotion, and foundation, whitening, lipstick, blusher, eye shadow and the like. It can be obtained by adding an appropriate amount to a finish cosmetic or a cosmetic such as a hair lotion such as a set lotion, a hair cream or a pomade.

Further, the coating material for ultraviolet shielding according to the present embodiment can be obtained by blending the above-mentioned ultraviolet shielding agent in various paints in appropriate amounts. Examples of the paint include a paint for automotive coating, a paint for a house outdoor wall, a conductive paint, a magnetic paint and the like.

In the plastics composition for shielding ultraviolet rays of the present embodiment, the above-mentioned ultraviolet shielding agent may be used, for example, vinyl chloride resin, ABS resin, polyethylene, polypropylene, vinylidene chloride, polystyrene, polycarbonate, nylon, EVA resin. , Polyacetal resin, polyamide resin, phenol resin, melamine resin, acrylic resin, polyester resin, urea resin, silicone resin,
It can be obtained by adding an appropriate amount to a synthetic resin such as a fluororesin.

[0046]

Next, the present invention will be described with reference to examples.
The present invention is not limited by the embodiments described here.

Hereinafter, a production example of cerium oxide will be described.

[Preparation Example 1] In 150 ml of 1.6 mol / l cerium nitrate (Ce (NO ₃ ) ₃ ) aqueous solution, 31
After adding 19.7 g of a 1% by weight aqueous hydrogen peroxide solution, pure water was added to bring the total volume to 200 ml. On the other hand, water was added to 28% by weight aqueous ammonia to dilute to 10% by weight. This was added dropwise little by little and stirred to precipitate cerium oxide-containing gel. Next, the precipitated gel was heated in a pressure reactor at 150 ° C. for 24 hours to obtain a slurry. Then, it was washed by filtration and dried under reduced pressure. This powder was placed in an alumina crucible, heated in an electric furnace at a rate of 5 ° C./min in air, kept at 1000 ° C. for 3 hours, and fired. Then, the mixture was pulverized and dispersed in a bead mill, filtered and dried under reduced pressure to obtain a cerium oxide powder. This cerium oxide powder was a secondary particle having a diameter of 100 nm and a crystallite size of 44 nm (440 angstroms).

[Production Example 2] In 150 ml of a 1.6 mol / l cerium nitrate (Ce (NO ₃ ) ₃ ) aqueous solution, 31
After adding 19.7 g of a 1% by weight aqueous hydrogen peroxide solution, pure water was added to bring the total volume to 200 ml. On the other hand, water was added to 28% by weight aqueous ammonia to dilute to 10% by weight. This was added dropwise little by little and stirred to precipitate cerium oxide-containing gel. Next, the precipitated gel was heated in a pressure reactor at 110 ° C. for 10 hours to obtain a slurry. Thereafter, the mixture was filtered, washed, pulverized and dispersed in a bead mill, filtered, and dried under reduced pressure to obtain a cerium oxide powder. This cerium oxide powder is a primary particle having a diameter of 8 nm and a crystallite size of 3 n.
m (30 angstroms).

Next, the cerium oxide produced according to the above production example was evaluated for its ultraviolet protection properties. The evaluation method is described below.

[Evaluation Method] (1) Particle Size: Transmission Electron Microscope (JEM, JEM
The powder was observed at −2000 FX2) and expressed as an average particle size.

(2) Crystallite size: The cubic diffraction pattern of cerium oxide was measured, and the Sherler equation was calculated from the half-value width of 28.6 ° (lattice constant: 3.1234 Å) showing the strongest peak. Calculated using

(3) UV protection: 2.5% by weight of cerium oxide powder was added to water, and a dispersant (Chukyo Yushi,
"D-305") is added at 3% to the powder. This slurry was dispersed in a bead mill to form a sample. The dispersed sample was sandwiched between quartz cells to a thickness of 15 μm, and the spectral transmittance (%) was measured using a spectrophotometer (UV-3100PC, Shimadzu Corporation) using water as a reference material. It measured using.

[0054]

[Table 1] From the above, it can be seen that the cerium oxide of the secondary particles is superior to the cerium oxide of the primary particles in ultraviolet ray protection performance, particularly in the UVA region.

Next, the cerium oxide powder which has been subjected to the primary coating with the above-mentioned metal compound and the secondary coating with the use of the hydrophobizing agent, the cerium oxide powder which has been subjected to the primary coating with the above-mentioned metal compound, and only the hydrophobizing agent A cerium oxide powder coated with was prepared.

Example 1 15 g of aluminum chloride was dissolved in 1000 ml of water, and 100 g of the cerium oxide of Production Example 1 was added to this solution, and the mixture was stirred and uniformly dispersed. To this is added 10% sodium hydroxide with stirring to bring the pH to 9. After stirring for 1 hour, the mixture was filtered, washed with water and dried. Then, xylene 5 was added to 100 g of the powder.
0 g and 10 g of methyl hydrogen polysiloxane are added and mixed with a mixer. The powder was air-dried to volatilize xylene. Further, baking was performed at 140 ° C. for 2 hours to obtain a powder coated with silicone.

Example 2 The same aluminum treatment as in Example 1 was performed using the cerium oxide of Production Example 1. 400 ml of water was added to 100 g of this powder, and 35 g of a 17% aqueous solution of the above-mentioned perfluoroalkylphosphate diethanolamine salt was further added thereto, followed by stirring at 40 ° C.
Next, 1N hydrochloric acid was added to lower the pH to 3 or less,
Perfluoroalkyl phosphoric acid was deposited on the powder surface.
This powder was filtered, washed with water, and stirred to obtain a powder coated with a fluorine compound.

Example 3 The same treatment as in Example 1 was performed using 14.6 g of magnesium chloride instead of aluminum chloride. Using 100 g of this powder, the same treatment as in Example 1 was further performed to obtain a silicone-coated powder.

Example 4 The same magnesium treatment as in Example 3 was performed. Using 100 g of this powder, the same treatment as in Example 2 was further performed to obtain a powder coated with a fluorine compound.

Example 5 A silane compound (product name: KBM-3103C, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 50 g of methanol.
5 g of decyltrimethoxysilane). To this solution, 100 g of the cerium oxide of Production Example 1 is added, and the mixture is stirred and homogeneously mixed. The solvent of the resulting mixture is removed with a hot air drier. Using 100 g of this powder, Example 1
Was carried out in the same manner as described above to obtain a silicone-coated powder.

Example 6 The same silica treatment as in Example 5 was performed. Using 100 g of this powder, the same treatment as in Example 2 was further performed to obtain a powder coated with a fluorine compound.

Example 7 15 g of aluminum chloride was dissolved in 1000 ml of water, and 100 g of cerium oxide of Production Example 1 was added to this solution, and the mixture was stirred and uniformly dispersed. To this is added 10% sodium hydroxide with stirring to bring the pH to 9. After stirring for 1 hour, the mixture was filtered, washed with water, dried, and baked at 140 ° C. for 2 hours to obtain aluminum oxide-treated powder.

Example 8 The same treatment as in Example 7 was carried out except that 14.6 g of magnesium chloride was used instead of aluminum chloride to obtain a magnesium oxide-treated powder.

Example 9 A silane compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBM-3103C) was added to 50 g of methanol.
5 g of decyltrimethoxysilane). To this solution, 100 g of the cerium oxide of Production Example 1 is added, and the mixture is stirred and homogeneously mixed. The solvent of the obtained mixture was removed with a hot air drier to obtain a silica-coated powder.

Comparative Example 1 An uncoated powder of cerium oxide produced in Production Example 1.

Next, the photocatalytic activities of the ultraviolet shielding agents of Examples 1 to 9 and Comparative Example 1 were evaluated. The evaluation method is described below.

[Evaluation Method] Photocatalytic activity: Journal of the Society of Color Materials, 61 (12), 665 (19)
Photocatalytic activity was measured by the autoxidation method of tetralin / formic acid described in 88). 0.2 g of a sample is added to tetralin, and the mixture is stirred with a stirrer while maintaining the temperature at 40 ° C. Irradiate from above with a 2500 LX mercury lamp for 30 minutes.
The intensity of the photocatalytic activity was measured by measuring the amount of oxygen consumed by the decomposition of tetralin by irradiation as the decrease in oxygen partial pressure. Therefore, the lower the oxygen consumption, the lower the photocatalytic activity.

[0068]

[Table 2] From Table 2 above, it can be seen that the photocatalytic activity can be suppressed by the coating treatment.

Next, the SPF of cerium oxide and zinc oxide
The test evaluation results are shown below.

[Preparation of Sample] (1) As the cerium oxide powder, the cerium oxide of Production Example 1 was taken as 100% by weight, and this cerium oxide powder was coated with 10% by weight of silica with the silane compound described in the above Example. Further, a cerium oxide powder which was secondarily coated with 5% by weight of silicone using the silicone compound described in the above example was used. A 25% mixed emulsion of cerium oxide subjected to the secondary coating treatment was prepared.

(2) Zinc oxide ultrafine powder (Sumitomo Osaka Cement, trade name: ZnO-350) is 100% by weight, and zinc oxide fine powder is primarily coated with silicone 6% by weight with the silicone compound described in the above embodiment. The treated zinc oxide powder was used. This primary coating-treated 25% zinc oxide emulsion was prepared.

[Evaluation Method] SP
F measuring device (OPTOMETRICS SPF-290
(Analyzer). Table 3 shows the results.

[0073]

[Table 3] From Table 3, it can be seen that cerium oxide has a remarkable SPF effect as compared with zinc oxide even with the same blending amount.

Next, the relationship between the amount of silica treatment for cerium oxide and the catalytic activity will be described with reference to Table 4.

[Evaluation Method] For the samples to be evaluated, cerium oxide powder which had been subjected to a primary silica coating treatment at the ratios shown in Table 4 was used. Then, 1% by weight of the primary coated cerium oxide powder was added to an isoprene glycol solution containing 0.1% by weight of methyl paraben, and the mixture was stirred.
After a minute, the color of the solution was measured. The higher the numerical value of the yellowness YI, the stronger the yellowness, indicating that methyl paraben in the solution is chemically reacted by the catalytic activity of cerium oxide.

[0076]

[Table 4]

Here, the yellowness refers to JIS K710.
3 refers to the degree of yellowness used to evaluate the discoloration of the plastic to yellow in the weather (light) resistance test of the plastic described in No. 3, and is an SM color computer SM- manufactured by Suga Test Instruments Co., Ltd.
After using the tristimulus values X, Y, and Z of the sample using the type 4, it is determined by the following equation.

[0078]

## EQU00001 ## YI = 100.times. (1.28X-1.06Z) / Y The yellowness YI indicates the degree to which the hue departs from colorless or white in the yellow direction, and is displayed as a positive value. The larger the positive value, the stronger the yellow tint. If the yellowness YI is a negative value, it indicates that the hue shifts to the blue direction.

Further, the dispersion stability will be described below. [Evaluation method] 1 g of a sample was added to 50 ml of liquid paraffin, subjected to ultrasonic dispersion, allowed to stand for about 12 hours, and measured from the settling volume (= (settled body height) / (total height)). , And dispersibility were evaluated. Those with poor dispersibility settle quickly so as to behave like apparently large particles, form a bulky precipitate, and have a large sedimentation volume. On the other hand, those having good dispersibility have many dispersion stabilizations in the liquid, so that they are densely clogged even if they settle. Therefore, the sedimentation volume is small. From the above, it can be determined that those having a large sedimentation volume have poor dispersibility, and those having a small sedimentation volume have good dispersibility.

As a result of the experiment, the sedimentation volume of untreated cerium oxide (Comparative Example 1 above) was 16/45, while the sedimentation volume of secondary-coated cerium oxide (Example 5 above). The volume is 6/45, and the dispersion stability is sufficiently improved.

[0081]

As described above, according to the ultraviolet shielding agent of the present invention, ultraviolet shielding can be performed with a small amount of the compounding agent. Furthermore, since it is stable in dispersion and high in chemical stability, it can be blended in a wide range of fields such as cosmetics, paints and plastics compositions, and can effectively protect ultraviolet rays.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a method for producing an ultraviolet shielding agent of the present invention.

FIG. 2 is a transmission electron micrograph showing the structure of secondary particles of cerium oxide in the present invention. FIG. 2B shows the uncoated secondary particles, and FIG. 2A is an enlarged photograph of the uncoated secondary particles.

FIG. 3 is a transmission electron micrograph showing the structure of secondary coated cerium oxide in the present invention. FIGS. 3 (a) and 3 (b) each show a case where a silica coating is applied onto a silica coating.

[Explanation of symbols]

10 primary particles, 20 secondary particles, 30 metal compounds,
40 Organic hydrophobizing agents, 50, 60 UV screening agents.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 101/00 C08L 101/00 C09D 5/32 C09D 5/32 201/00 201/00 F-term (Reference) 4C083 AB211 AB212 CC05 CC12 CC19 CC31 EE17 FF01 4G076 AA02 AB02 BF02 BF05 CA03 CA05 DA16 DA30 4J002 AA001 BB031 BB061 BB121 BC031 BD041 BD101 BD121 BG041 BN151 CB001 CC001 CC181 CF001 CG001 FB013 012 001 001 HA376 HA456 JC25 JC31 JC32 KA14 KA15 KA20 NA01 NA19

Claims (6)

[Claims] 1. The surface of a coagulated secondary particle composed of an aggregate of primary particles of cerium oxide has at least a metal compound selected from metal hydroxides or hydrates or anhydrides of salts thereof. An ultraviolet ray shielding agent, which is treated with one or more metal compounds. 2. The ultraviolet shielding agent according to claim 1, wherein the agglomerated secondary particles are strawberry-shaped secondary particles and are substantially spherical. 3. The ultraviolet shielding agent according to claim 1, wherein the agglomerated secondary particles surface-coated with the metal compound are further subjected to a hydrophobic treatment with an organic hydrophobizing agent. Characteristic UV screening agent. 4. A cosmetic comprising the ultraviolet screening agent according to claim 1. 5. A coating material comprising the ultraviolet screening agent according to claim 1. Description: 6. A plastics composition comprising the ultraviolet shielding agent according to claim 1.