JP2000319128A - Modified silica-coated metal oxide, method for producing the same, and composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated metal oxide powder having a high ultraviolet ray shielding effect, no photocatalytic activity, easy dispersion in a fluid medium, excellent dispersion fluidity, and long-term dispersion stability. And a method for producing the powder. Kind Code: A1 A coated metal oxide powder having high ultraviolet shielding effect, no photocatalytic activity, easy dispersion in a fluid medium, excellent fluidity of the dispersion, and long-term dispersion stability, and a composition containing the same. And a method for producing the powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique of shielding ultraviolet rays using metal oxide particles and an application field thereof.

[0002]

2. Description of the Related Art Fine particles of metal oxides such as zinc oxide and titanium oxide have preferable ultraviolet shielding ability, but also have photocatalytic activity, so that cosmetics, paints, adhesives, resin molded articles, etc. In addition, there is a difficulty in that these components act under light irradiation to induce undesired phenomena such as decomposition and alteration. The present inventors have searched for a method of eliminating the photocatalytic activity while maintaining the ultraviolet shielding ability of zinc oxide, and found that in some cases, the object can be achieved by coating the surface with a silica layer. 9-370
No. 480. That is, the surface of the zinc oxide particles is coated with a silica-based material in an amount of 5% by weight or more and 100% by weight or less of zinc oxide, and 90% by weight or more of the coated particles have a particle size of 0.1 μm or more and 9.0 μm or less, The diameter is 0.
Surface-coated zinc oxide particles having a particle size of 5 μm or more and 5.0 μm or less, a composition in which the particles are blended in a cosmetic or the like, and a method of silica coating, wherein a zinc oxide is prepared by using a dispersant in an organic dispersion medium. Dispersing the particles, causing a sol-gel reaction of the tetraalkoxysilane or the alkylalkoxysilane and / or a low polymer thereof in the dispersion,
A method was proposed in which the particles were heated after separation to complete the gelation reaction and pulverized to obtain predetermined silica-coated zinc oxide particles.

[0003] However, from the results of studies of compositions in which the silica-coated zinc oxide particles of the above-mentioned proposals are blended with various substances, the uniform dispersibility of the silica-coated zinc oxide particles in a flowable state of the blended composition is not necessarily long. Due to the lack of securement and the internal structure of the coated zinc oxide particles,
It has been found that not only the ultraviolet ray shielding effect but also the dispersion stability, and particularly the cosmetics, have an influence on the fluidity and the feeling of use such as the tactile sensation. It turned out that the situation was exactly the same in the case of titanium oxide particles and the like which were subsequently studied.

[0004]

SUMMARY OF THE INVENTION The long-term dispersion stability of coated metal oxide particles in a blended composition, the fluidity, the feeling of use including touch, etc., while blocking the photocatalytic activity, while having a high ultraviolet shielding effect, are provided. To improve. Fine particles of metal oxides such as zinc oxide and titanium oxide have a preferable ultraviolet shielding ability, but also have a photocatalytic activity, so that when mixed in cosmetics, paints, adhesives, resin molded products, etc. There has been a problem in that these components act under irradiation to induce undesirable phenomena such as decomposition and alteration. We have:
A method for eliminating the photocatalytic activity while maintaining the ultraviolet shielding ability of zinc oxide has been sought, and it has been found that the object can sometimes be achieved by coating the surface with a silica layer, which is disclosed in Japanese Patent Application No. 9-370480. As suggested. That is,
The zinc oxide particles have a surface of 5% by weight or more of zinc oxide.
0% by weight or less of a silica-based material, and 90% by weight or more of the coated particles have a particle diameter of 0.1 μm or more and 9.0 μm or less, and an average particle diameter of 0.5 μm or more and 5.0 μm or less. A zinc oxide particle, a composition in which the particle is blended in a cosmetic or the like, and a method of silica coating, in which a zinc oxide particle is dispersed using a dispersant in an organic dispersion medium to form a tetraalkoxysilane or an alkylalkoxysilane. And / or a method of subjecting the low polymer to a sol-gel reaction in this dispersion system, separating and heating the particles to complete the gelation reaction, and pulverizing the particles to obtain predetermined silica-coated zinc oxide particles. .

[0005]

Means for Solving the Problems The object was solved by improving the coating material and the coating method. And the inner layer of the coating layer is substantially silica, and the outer layer is substantially alkyl-modified silica, and the surface-coated metal oxide particles are aggregated secondary particles of ultra-fine primary particles having an average particle size of 0.1 μm or less. The present inventors have found that a modified silica-coated metal oxide particle characterized by being a particle achieves the object, and has reached the present invention.

The details of the present invention will be described below. In the present invention, the metal oxide particles have an ultraviolet shielding effect,
The particles are selected from the group consisting of zinc oxide, titanium oxide, cerium oxide, and zirconium oxide. In each case,
Minor elements or metal oxides, such as iron, nickel, cobalt, zirconium, barium, silicon, etc., as trace impurities, such as 1% by weight or less, as impurities during production or as a result of surface treatment added or modified. May be contained. One example is titanium oxide doped with iron or iron oxide to enhance the ultraviolet shielding effect.

As is well known, the metal oxide particles of the present invention are composed of ultrafine primary particles having an average particle size of 0.1 μm or less, which has a high ultraviolet ray shielding effect, and are transparent to the naked eye in cosmetics and other uses. It is preferable because of high performance. However, in such ultra-fine particles, in production and use,
Often difficult to handle. Practically, it is convenient for handling that the ultrafine primary particles are agglomerated secondary particles having an average particle size of 0.5 μm or more and 5.0 μm or less. In this case, since the size of the primary particles is maintained, the ultraviolet ray shielding effect remains high. When such secondary particles are surface-coated with a silica-based material, if they are stably dispersed in a blended composition while blocking photocatalytic activity, they can be effectively used for various applications. The present inventors have proposed a technique for realizing this in the prior application. But,
In subsequent studies, when such surface-coated particles are used by being dispersed in a hydrophobic liquid medium or a medium containing the same, higher dispersion stability may be desired, and in particular, powder or In some cases, liquid cosmetics may give dissatisfaction with the tactile sensation and feeling of use that there is no roughening, and in that case, the oil absorption of the coated powder is usually large, and the oil component and the coated powder during the production of the cosmetic It was found that there was a problem that the fluidity when mixing was poor and kneading was difficult, and that the amount of the coated powder for increasing the ultraviolet shielding effect could not be increased.

As a result of investigations to improve the above difficulties, the object of the present invention is achieved by coating the metal oxide particles with a silica-based material on the outer layer with an alkyl-modified silica coating and the inner layer with a silica coating. And arrived at the present invention. When the entire layer or outer layer of the coating is silica, in the above-described dispersion, fluidity, and feeling of use, when the entire layer is coated with an alkyl-modified silica, the blocking of photocatalytic activity may be insufficient and unsatisfactory. In addition, when the entire layer corresponds to an intermediate composition between the silica coating and the alkyl-modified silica coating, the partial alkyl-modified silica coating is not satisfactory in the sealing of the photocatalytic activity and also in the dispersion and the fluidity and the feeling upon use described above. It turned out to be.

From the above, one of the features of the present invention is that
The metal oxide particles are surface-coated with two layers, the inner layer being coated with silica and the outer layer being coated with alkyl-modified silica. Such a coating, for example, performs a sol-gel reaction of tetraalkoxysilane in a liquid medium in which metal oxide particles are dispersed to form a silica layer, and then performs a sol-gel reaction of alkyl-modified alkoxysilane. This can be realized by forming an alkyl-modified silica layer. The coating amount of the present invention is such that the silica layer and the alkyl-modified silica layer have a weight ratio of 20 to 80:80 to 20 in a weight ratio of 5% to 100% by weight of the original metal oxide particles. You can achieve your goals. If the coating amount is small, the effect is less, and if the coating amount is too large, the effect is saturated and is meaningless. In order to surely achieve the object of the present invention in various uses, the coating amount is preferably in the range of 20% by weight to 60% by weight. Since the silica layer and the alkyl-modified silica layer have different portions in their effects, the ratio may be selected within the above range according to the application.

As one of the methods for producing the coated particles of the present invention, a sol-gel reaction can be applied. The sol-gel reaction can produce various products by devising the type of starting materials and the reaction method. The basic principles and application examples are described in "Sol-Gel Science" by Saio Sakuhana (198).
Published on July 5, 2008, published by Agne Shofusha). In the sol-gel reaction of tetraalkoxysilane applied in the present invention, the alkoxysilane is hydrolyzed in a liquid medium in the presence of water to generate Si-OH groups, which condense to form Si-O-Si groups. Form. In the intermediate stage of the condensation reaction, the reactant becomes a sol, and as the condensation further proceeds, the fraction of Si—O—Si groups increases to form a solid gel, that is, silica. In the sol state, if powder particles coexist in the system, the sol is adsorbed on the powder surface if the surface characteristics and the progress speed of the sol-gel reaction are appropriate, and gelation proceeds there. If the adsorption of the sol to the powder surface does not occur, the surface of the powder cannot be coated, and even if the gelation reaction is too fast to realize the process of adsorbing the gel, the surface coating is substantially impossible. Fortunately, the surface of the metal oxide particles of the present invention is suitable for adsorbing sols and depositing gels. Therefore, if the dispersion state of the metal oxide particles and the speed of the sol-gel reaction can be appropriately selected, the object of the present invention can be achieved. Alkyl-modified alkoxysilane R '<SUB> x </ SUB> Si (OR) <SUB> 4-
When the number x of the alkyl group R 'is less than 2, x follows the same process as above to form an alkyl-modified silica.

The tetraalkoxysilane used as a starting material for coating the inner layer in the production method of the present invention is a compound represented by the following general formula. Si (OR) <SUB> 4 </ SUB> wherein R is C1-3 alkyl. R in the above formula is methyl, ethyl, propyl, or isopropyl, which can be carried out even when it is a higher alkyl, but is unsuitable due to low reactivity. The compound may contain the tetraalkoxysilane defined by the above formula, or a low polymer thereof, or all may be a low polymer. R is C1
Any of the alkyls may be used, but if it is strong, ethyl is preferred because the reaction rate is moderate and it is easy to control the coating so that coating can be performed more uniformly, that is, tetraethoxysilane. However, there is no significant difference in C1-3 alkyl.

The alkyl-modified alkoxysilane used as a starting material for coating the outer layer in the production method of the present invention is a compound represented by the following general formula. R '<sub> x </ sub> Si (OR) <sub> 4-x </ sub>: wherein R and R' are the same or different and are C1-3 alkyl. In the compounds of the above formula, x is 1, where x is 2
Are mixed and the total average value is less than 2. It also includes the case where some or all of these are low polymers. When R or R 'is higher alkyl, it is unsuitable for the same reason as in the preceding paragraph. Note that R '
May be various perfluoro groups. However, for the purpose of the present invention, it is disadvantageous to economy and corresponds to excessive quality.

In the present invention, a sol-gel reaction is applied as a coating method of metal oxide particles. The reaction is carried out so that a tetraalkoxysilane or an alkyl-modified alkoxysilane as a starting material can be dissolved to form a uniform coating. A mixture of water and a water-soluble organic solvent is used as a medium. On the other hand, since metal oxide particles are insoluble, they cannot be uniformly coated unless they are kept in a good dispersion state. Even if a large number of primary particles cover the aggregated coarse particles, the sealing of the photocatalytic activity becomes an unsatisfactory level, and the powder is not suitable for powder. Before use, the metal oxide particles contain a large number of coarse secondary particles in which a large number of primary particles are aggregated, and this is crushed and dispersed in a medium that can be used as a sol-gel reaction medium in the presence of a dispersant. Need to be done. The secondary particles dispersed along with the progress of the sol-gel reaction are inevitably bound by the sol-gel reaction while being coated, so that the particles to be used for the reaction are preferably initially dispersed with a submicron particle size. The dispersant must have a dispersing ability that does not cause aggregation or sedimentation of the metal oxide particles themselves other than the unavoidable bonds at least until the end of the sol-gel reaction. In addition, the material must not excessively accelerate or suppress the sol-gel reaction. When the dispersant satisfies such performances, the coated particles have secondary particles having 90% by weight or more of particles having a particle diameter of 0.1 μm to 9.0 μm and an average particle diameter of 0.5 μm to 5.0 μm. It can be.

From the above viewpoints, a search was made for a dispersant effective for the present invention. As a result, an alkanolamine salt of an acrylic polymer obtained by copolymerizing acrylic acid and / or methacrylic acid, N-vinylpyrrolidone-N, N-dialkyl Aminoalkyl acrylate copolymer, N-vinylpyrrolidone-N, N-dialkylaminoalkyl acrylate copolymer dialkyl sulfate, N-vinylpyrrolidone vinyl acetate copolymer, polyvinyl butyral, methyl vinyl ether-dialkyl maleate copolymer It has been found that one or more polymer dispersants selected from the group consisting of Substances having strong acidity or alkalinity are not suitable because the sol-gel reaction is not excessively accelerated or completed, and polyvinyl alcohol or ethylcellulose cannot exert a dispersing power in the system of the present invention even at neutrality. No effective substance was found for compounds known as surfactants and likely to have dispersing power, for example, various derivatives of polyoxyethylene. The dispersant varies depending on the type of the inorganic powder to be coated and the composition of the coating reaction medium that is the dispersion medium,
The purpose can be achieved by using the inorganic powder in a range of about 0.5% by weight or more and about 30% by weight or less based on the weight of the inorganic powder. In dispersing the inorganic powder to be subjected to the coating reaction, a wet dispersion method known in the art can be applied.

As has been found in the course of the search for the dispersant described in the preceding paragraph, in the method of the present invention, a mixture of water and a water-soluble organic solvent is used as a reaction medium. The lower aliphatic monohydric alcohols are preferred solvents because they sufficiently exhibit the dispersing ability of the dispersant, and also have good particle size and tactile sensation of the coated particles. Water-soluble organic solvents such as tetrahydrofuran and aliphatic ketones can be used, but the dispersing power is weak and the properties of the coated particles are inferior to those of the alcohol. Thus, a feature of the method of the present invention is the combination of the use of a specific dispersant and a water-soluble organic solvent. The amount of water used is
The amount required to hydrolyze all the alkoxy groups of the alkoxysilanes used for the coating reaction is essential, and the appropriate dispersion state of the inorganic powder is ensured in combination with the water-soluble organic solvent in the presence of the dispersant. The amount used is such that a smooth reaction proceeds. Generally speaking, 1.5 times the theoretical amount required for hydrolysis
A range of double to 15 times weight is appropriate. The amount of the water-soluble organic solvent used is an amount that ensures an appropriate dispersion state of the inorganic powder in combination with water in the presence of the dispersant, and allows a smooth reaction to proceed. It is used in the range of 1.0 to 15 times the weight. However, the total amount of water and water-soluble organic solvent used is preferably in the range of 3 to 20 times by weight of the inorganic powder. It is possible to select the water or a part of the water-soluble organic solvent to be used as the dispersion medium.

The sol-gel reaction in the method of the present invention uses a catalyst. Various acids and bases are known as reaction catalysts. However, with an acid catalyst such as hydrochloric acid or acetic acid, it is possible to coat the surface of the powder, but because of the inability to form a dense coating, the sealing of the photocatalytic activity is insufficient, and the degree of reaction of the raw material alkoxysilane is insufficient. In the sol-gel reaction of the alkyl-modified alkoxysilane coated on the outer layer, the reaction-promoting effect is low and there is a problem in the economics of the coating treatment. Even with basic catalysts, bases such as potassium hydroxide and ammonia have too high a catalytic activity, so that many sols, which are intermediates of the sol-gel reaction, gel themselves before coating the powder, producing The product is unsuitable because it is a mixture of a coated powder having a smaller coating amount than expected and a gel of silica or modified silica. Aliphatic amines are not as pronounced as ammonia, but the sol itself gels and the conversion of the starting alkoxysilane to the surface coating is poor. Attempts to improve the conversion by lowering the concentration of these basic catalysts,
Satisfactory improvements could not be achieved, only a noticeable decrease in the reaction rate. As a result of searching for a catalyst that can avoid such difficulties, it has been found that in the surface coating method of the present invention, alkanolamines represented by the following general formula are effective and appropriate catalysts. R <SUB> 3-x </ SUB> N (R'OH) <SUB> x </ SUB>: wherein R is hydrogen or alkyl, R 'is alkylene, x is 1,
It is either 2 or 3. In the method of the present invention, a mixed solution of water and a water-soluble organic solvent, particularly a lower aliphatic alcohol is used as a reaction medium, so that alkanolamine is uniformly dissolved in the reaction medium, and is used by selecting one having an appropriate catalytic activity. I do. Although it depends on the mixing ratio of water and the water-soluble organic solvent in the reaction medium and the value of x in the above formula, when the alkyl or alkylene of the above formula has 4 or more carbon atoms, the solubility and the catalytic activity are lowered, so that it is inappropriate. is there. Therefore, R is hydrogen or alkyl having 1 to 3 carbons,
R ′ is preferably used by selecting from alkylenes having 1 to 3 carbon atoms. When the value of x is 1, 2, 3, ie, mono,
Both di- and trialkanolamines can be used, and although there is a difference in their reaction accelerating properties, the desired coating of the present invention can be achieved by selecting the amount of the di- or trialkanolamine used. That is, the sol-gel reaction can be controlled and moderately promptly proceeded, and the entire amount of the sol can be formed into a coated gel on the powder surface. Further, these catalysts are effective for both inner layer coating and outer layer coating, and can be used commonly for both processes. These points were a great difference from the above-mentioned bases such as potassium hydroxide, ammonia or aliphatic amines.

As the alkanolamine which can be suitably used as a catalyst for the sol-gel reaction in the method of the present invention,
Monoethanolamine, diethanolamine, triethanolamine, dimethylmonoethanolamine, monomethyldiethanolamine, diethylmonoethanolamine, monoethyldiethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, dimethylmonopropanolamine, monoethyldipropanolamine, etc. Examples thereof include diethanolamine, monomethyldiethanolamine,
Monoethyldiethanolamine and the like are preferable because a coated powder having an excellent tactile sensation can be obtained. The amount of the catalyst to be used is in the range of 5% by weight or more and 30% by weight or less based on the total weight of the alkoxysilanes used from the viewpoints of easy control of the coating reaction, touch feeling of the formed coated powder, and the like. Preferably, the range of 10% by weight or more and 25% by weight or less is particularly suitable.

In coating the inner layer of the inorganic powder in the present invention, first, an inorganic powder and a dispersant are added to a part of a mixture of water and a water-soluble organic solvent, and the inorganic powder is applied by a known method. A dispersion liquid of an inorganic powder is prepared by pulverizing and dispersing to an appropriate particle size. It is convenient that the liquid of the dispersion medium has the same composition ratio as that of the medium for the sol-gel reaction, but this is not always necessary and a composition ratio suitable for dispersion may be used. A dispersion of tetraalkoxysilane and inorganic powder is added to a mixed solution of water and a water-soluble organic solvent in a reaction vessel with stirring, and mixed. When the catalyst is added and stirring is continued, hydrolysis and condensation of the tetraalkoxysilane proceed, and the viscosity of the system increases with the formation of the sol. In the steps up to this point, the reaction temperature is 10 to 3
It is preferable to set the room temperature to 0 ° C. This is to avoid the formation of a gel not involved in the coating. The dispersion of the inorganic powder may be added not at the beginning but at the stage of sol formation. Then, when the temperature is raised to accelerate the gelation reaction and the reflux heating is continued at 60 to 90 ° C., the gelation reaction proceeds while the reaction intermediate is deposited on the surface of the inorganic powder particles, and the viscosity of the system decreases. When the alkyl-modified alkoxysilane is directly added to the reaction system after the inner layer coating is completed, hydrolysis and condensation of the alkyl-modified alkoxysilane occur, and gelation occurs while depositing on the inner layer surface of the inorganic powder particles through gel formation. The reaction proceeds to complete the outer layer coating reaction. In the first half of the outer layer coating reaction, unlike the first half of the inner layer coating performed at room temperature, a temperature higher than room temperature is possible. The reaction product is separated by filtration, and the remaining catalyst and dispersant are washed with a mixed solution of water and a water-soluble organic solvent or a single substance thereof, and
Heat drying at about 20 to 160 ° C. is performed and then lightly pulverized using a device such as a pin mill or an atomizer to obtain a coated powder intended for the present invention. The reaction yield of the alkoxysilanes on the coated powder is almost consistent with the calculated value that they were converted to silica or modified silica. Probably due to the presence of -OH or -OR groups which are unreacted ends and the trace amount of residual dispersant, the yield is often 0 to the calculated value of 0.
4% excess. It is conceivable that these are reduced by firing at a high temperature, but at such a temperature, it is unlikely that the denatured silica in the outer layer deteriorates, and thus firing is not necessary.

The characteristics of the coated particles of the present invention will be apparent from the following examples. That is, when the zinc oxide powder is added to the liquid stearic acid at room temperature and stirred, the two react immediately and solidify into a metal soap, but in the zinc oxide powder coated with two layers of the present invention, this is not the case. It is suppressed. When a single-layer coating with silica or an alkyl-modified silica equivalent to the coating weight of the two-layer coating is performed, there is an inhibitory effect, but it is far from the two-layer coating of the present invention. In addition, the dye-containing coating film undergoes fading of the dye under irradiation of light, particularly ultraviolet light, so that zinc oxide or titanium oxide having an ultraviolet shielding ability is present in the coating film in order to improve the dye fading. The discoloration of the dye is accelerated contrary to expectation due to the photocatalytic activity of titanium oxide and titanium oxide, but the discoloration of the dye is suppressed in the case of the coated zinc oxide powder or titanium oxide powder of the present invention. In any case, the effect is small when the coating amount is small, and the effect is obvious when the coating amount is moderate or higher. Furthermore, when dispersing the two-layer coated zinc oxide powder or titanium oxide of the present invention in a medium, it is easier to achieve uniform dispersion than in the case of simple single-layer coating, and the dispersion medium is in a liquid state. When dispersed even after dispersion, the uniform dispersion is stably maintained for a longer period of time, excellent in fluidity, and the spreadability of the cosmetic in a liquid or powdery cosmetic is good, and the roughness of the coated particles is rough. This is remarkable in that a good tactile sensation and a feeling of use, such as no touch, are obtained.

The coated metal oxide powder of the present invention has a high ultraviolet shielding effect, has a blocked photocatalytic activity, is easily dispersed in a fluid medium, and has a high fluidity when the composition is in a liquid state. Because it is excellent, to utilize its properties, including the application to the cosmetics, polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, polycarbonate resin, urethane resin, alkyd resin, epoxy resin, melamine resin and their Application to various resin molded products exemplified by copolymer resins, application to paints and adhesives using those resins or low polymerization products is possible,
Moreover, the present invention can be applied to the case where they contain additives such as dyes, pigments, organic ultraviolet absorbers and plasticizers.

Hereinafter, the present invention will be described in more detail with reference to examples. All parts in Examples and Comparative Examples are parts by weight. The particle size of the secondary particles of the coated powder was measured by dispersing the powder in liquid paraffin and using a laser diffraction type particle size distribution analyzer. Evaluation of dispersion stability is performed by dispersing the powder in a hydrophobic liquid, sealing the container in a transparent container, standing at room temperature, and visually determining whether sedimentation of the powder occurs with time. The sample was allowed to stand in a constant temperature dryer at 50 ° C. for one day, and then was repeatedly allowed to stand at room temperature for one day.

[0022]

Example 1 240 parts of ultrafine zinc oxide aggregate powder having an average primary particle diameter of 35 nm was mixed with isopropanolamine salt of acrylic acid-modified acrylic resin (degree of neutralization: 75%) as a dispersant. 96 parts of a 0% ethanol solution,
The mixture was charged into a bead mill together with 464 parts of an equal weight mixture of isopropanol and water as a medium, and the zinc oxide powder was dispersed while being ground. Liquid dropping device, reflux condenser,
In a reactor having a stirrer and an external heating device, 177 parts of tetraethoxysilane and 140 parts of isopropanol were charged, and 400 parts of the zinc oxide dispersion was added dropwise over 10 minutes while stirring at room temperature, followed by stirring for a while. Subsequently, a uniform dispersion was obtained. Then, 36 parts of diethanolamine and 2 parts of water
A catalyst solution consisting of 00 parts was added dropwise over 30 minutes while stirring at room temperature, and while the stirring was continued for another 40 minutes, the viscosity of the system increased and sol formation of silane proceeded. The reaction temperature was increased and maintained at 80 ° C. by external heating. During 30 minutes, the sol was gelled while adsorbing on the zinc oxide powder, and the viscosity of the system was reduced. When a reaction reagent consisting of 33 parts of monomethyltrimethoxysilane and 20 parts of isopropanol was added and stirring was continued at 80 ° C. for 60 minutes, the viscosity of the system increased halfway and then decreased again, so the reaction was terminated. After cooling, the reaction product was filtered and washed with water to remove the solvent, dispersant and catalyst. After drying at 120 ° C., the yield of the coated powder was 188.0 parts. This is a weight of 186., assuming that all of the silanes were converted to silica and methyl-modified silica and coated with zinc oxide.
Substantially equal to 3 parts. Therefore, the composition of the coating powder is calculated to be 64.5% by weight of zinc oxide, 27.0% by weight of silica, 8.5% by weight of methyl-modified silica, and the ratio of the coating layer is 35.5% by weight. The obtained coated powder was pulverized for 20 seconds using an impact pulverizer. The particle size of the coated powder after pulverization is distributed between 0.5 and 8 μm, and the average particle size is 2.5 μm.
m. As a result of observation with an electron microscope, these had a particle size of 30.
It was a coating of secondary particles that were aggregates of original primary particles of ~ 50 nm.

[0023]

Comparative Example 1 A sol-gel reaction was carried out in the same manner as in Example 1, except that the outer layer was not coated with monomethyltrimethoxysilane, but tetraethoxysilane was increased only in the inner layer coating reaction. The coating is quantitative, 65.0% by weight zinc oxide,
A silica-coated zinc oxide of 35.0% by weight of silica was obtained. The particle size and particle size distribution after pulverization were the same as in Example 1.

[0024]

Comparative Example 2 A sol-gel reaction was carried out in the same manner as in Example 1, except that the inner layer was not coated with tetraethoxysilane, but monomethyltrimethoxysilane was increased under the reaction conditions for the inner layer. The coating was quantitative, giving a methyl-modified silica-coated zinc oxide of 66.0% by weight of zinc oxide and 34.0% by weight of methyl-modified silica. The particle size and particle size distribution after pulverization were the same as in Example 1.

[0025]

Example 2 1.15 parts of the crushed coated zinc oxide powder obtained in Example 1 was dispersed in 100 parts of castor oil with a homomixer, placed in a 0.1 mm thick quartz cell, and transmitted with ultraviolet light by an ultraviolet spectrophotometer. When the ratio was measured, the absorbance at a wavelength of 375 nm was scaled out at 1.0.

[0026]

Comparative Example 3 A test similar to that of Example 2 was performed using the ground coated zinc oxide powder obtained in Comparative Examples 1 and 2, and similar results were obtained. The absorbance of the original uncoated zinc oxide powder was 0.54. The reason why the absorbance of the uncoated zinc oxide is low is that sufficient dispersion cannot be performed by the homomixer.

[0027]

Example 3 Three parts of the pulverized coated zinc oxide obtained in Example 1 was added to 10 parts of oleic acid and stirred. 48
Oleic acid was still in a liquid state after an hour.

[0028]

Comparative Example 4 For comparison with Example 2, an experiment was carried out in the same manner as in Example 3 using the crushed silica-only coated zinc oxide obtained in Comparative Example 1, and oleic acid was solidified after 10 hours. . In the case of the zinc oxide coated with only the methyl-modified silica obtained in Comparative Example 2, oleic acid solidified after 1 hour. Incidentally, in the case of zinc oxide which was not coated, it was solidified immediately after being charged.

[0029]

Example 4 In 100 parts of acrylic clear lacquer, 0.6 part of oil red 6B as a dye was dissolved, and 5 parts of the ground coated zinc oxide obtained in Example 1 was added and dispersed to prepare a paint. Painted thick tinplate. After exposure to sunlight outdoors for two days, the color difference (ΔE) measured to determine the degree of fading of the dye was 0.40.

[0030]

[Comparative Example 5] For comparison with Example 4, when the same experiment as in Example 4 was carried out using uncoated zinc oxide, the color difference was 5.98, and the dye was remarkably faded. Incidentally, the color difference in the case of only the dye without adding the coated zinc oxide is 0.4.
It was 5.

[0031]

Example 5 0.5 parts of Parsol A, a dibenzoylmethane ultraviolet absorber, was dissolved in 100 parts of liquid paraffin, and 1 part of the pulverized coated zinc oxide obtained in Example 1 was added and dispersed. Irradiated with a low pressure mercury lamp for 1 hour. Then, the coated zinc oxide was removed by a high-speed centrifuge, and the ultraviolet absorption spectrum of the supernatant was observed.
The absorbance at 40 nm was equal to the unirradiated state of the subject.

[0032]

Comparative Example 6 For comparison with Example 5, in an experiment similar to that of Example 5 using uncoated original zinc oxide, the absorbance was reduced by 60% as compared with the case where no irradiation was performed, and most of pulsol A was decomposed. I was

[0033]

Example 6 When the crushed coated zinc oxide powder obtained in Example 1 was sprayed on a water surface, it floated without settling. One week later, it remained floating.

[0034]

Comparative Example 7 For the purpose of comparison with Example 6, the same experiment as in Example 6 was performed on the ground silica-coated zinc oxide powder obtained in Comparative Example 1 and the powder settled.
The pulverized zinc oxide powder coated with methyl-modified silica alone obtained in Comparative Example 2 floated without settling. The original uncoated zinc oxide powder settled.

[0035]

Example 7 Three parts of the pulverized coated zinc oxide powder obtained in Example 1 were kneaded with 10 parts each of castor oil, liquid paraffin, and squalane to form a paste. All the pastes were excellent in fluidity, and when the stick immersed in the paste was picked up on the paste, the paste flowed down naturally like a continuous string. The powder was found to be familiar with these hydrophobic substances.

[0036]

Comparative Example 8 For the purpose of comparison with Example 7, the same experiment as in Example 7 was performed using the ground zinc-modified silica powder coated with methyl-modified silica alone obtained in Comparative Example 2. Although the same behavior was exhibited, the pulverized coated zinc oxide powder obtained in Comparative Example 1 and the original uncoated zinc oxide powder did not draw continuous yarn in any case,
It ruptured in a lump and fell with a feeling of dents and did not have fluidity.

[0037]

Example 8 Three parts of the ground coated zinc oxide powder obtained in Example 1 was mixed with 100 parts each of castor oil and liquid paraffin.
Each part was separately dispersed using a homomixer, and both were subjected to a three-month normal temperature dispersion stability test and an eight-cycle accelerated dispersion stability test. In each case, a good dispersion state was maintained, and no sedimentation or aggregation of the powder was observed.

[0038]

Comparative Example 9 For the purpose of comparison with Example 8, the same experiment as in Example 8 was performed using the ground zinc-modified zinc oxide powder coated with methyl-modified silica alone obtained in Comparative Example 2. The behavior was the same as that of Example 8, but in the case of the ground coated zinc oxide powder obtained in Comparative Example 1, the powder was dispersed after about one month in the room temperature dispersion stability test and at the end of 4 cycles in the accelerated dispersion stability test. A part of the body settled and a thin layer of clear supernatant was observed. In each case, the uncoated zinc oxide powder ensured coagulation and sedimentation of the powder on the second day in the room temperature dispersion stability test and at the end of one cycle in the accelerated dispersion stability test, and further worsened thereafter.

[0039]

Example 9 Using the coated powder of the present invention, an O / W emulsion type foundation was prepared with the following composition. That is, the composition was as follows: 5.6 parts of the crushed coated zinc oxide powder obtained in Example 1 as powder, 3.0 parts of talc, 0.5 parts of red iron oxide
Parts, 0.5 parts of bentonite as an aqueous phase, 0.9 parts of polyoxyethylene sorbitan monostearate, 1.0 part of triethanolamine, 10.0 parts of propylene glycol
Parts, purified water 56.4 parts, stearic acid 3.0 as oil phase
Parts, isohexadecyl alcohol 7.0 parts, glycerin monostearate 2.0 parts, liquid lanolin 2.0 parts, liquid paraffin 8.0 parts, preservative 0.05 parts, fragrance 0.0
5 parts. The preparation procedure was as follows: first, bentonite was dispersed in propylene glycol, and the purified water and then the remaining aqueous components were sequentially added, and the aqueous phase was uniformly mixed with a homomixer at 70 ° C., and the powder components previously mixed were stirred. It was added and dispersed below. At this time, the coated zinc oxide powder was easily and quickly dispersed. Further, the oil phase was added while hot and emulsified and dispersed. After cooling, a fragrance was added. The obtained foundation had good lubricity and tactile sensation during makeup, showed a good finish with transparency, and had a high UV shielding effect. When subjected to an accelerated dispersion stability test, no phase separation or sedimentation or aggregation of the coated zinc oxide powder was observed after 45 cycles.

[0040]

Comparative Example 10 For comparison with Example 9, the same experiment as in Example 9 was performed using the crushed silica-only-coated zinc oxide powder obtained in Comparative Example 1. Compared with the case of Example 9, when the powder component was added and dispersed, the stirring time in the homomixer to reach the uniform dispersion required an extra 50%, and the obtained cosmetic felt a little rough in makeup. In terms of growth, it needed to be improved one step now. No sedimentation or aggregation of the coated zinc oxide powder was observed after 45 cycles in the accelerated dispersion stability test.

[0041]

Example 10 45.0 parts of the pulverized coated zinc oxide powder obtained in Example 1, 44.9 parts of talc, starch of 2.10 parts.
0 parts, 3.0 parts of magnesium stearate, 3.0 parts of liquid paraffin, 2.0 parts of isopropyl myristate, 0.05 parts of preservatives, and 0.05 parts of fragrance are uniformly mixed. Excluded and compression molded into middle plate. The obtained powder foundation had good lubricity and tactile sensation during makeup, showed a good finish with transparency, and had a high ultraviolet shielding effect.

[0042]

Comparative Example 11 Comparative Example 1 was used for comparison with Example 10.
The same experiment as in Example 10 was performed using the crushed silica-only coated zinc oxide powder obtained in the above. The obtained cosmetic was inferior to the case of Example 10 in that it felt a little rough during makeup and that it spread.

[0043]

Example 11 100 parts of polystyrene resin pellets and 2 parts of the pulverized coated zinc oxide powder obtained in Example 1 were mixed and extruded into a strand by a melt extruder. When the strand was cut into thin pieces and observed, the powder was uniformly dispersed in the strand.

[0044]

Comparative Example 12 Comparative Example 1 was used for comparison with Example 11.
When the same experiment as in Example 11 was performed using the crushed silica-only coated zinc oxide powder obtained in the above, the powder was substantially uniformly dispersed in the strand, but exceeded 10 μm in some places. Powder particles were observed. In addition, when the original uncoated zinc oxide powder was used, there were many powder particles exceeding 10 μm due to poor dispersion, and the amount of the powder varied in the direction in which the strands were extruded.

[0045]

Example 12 240 parts of an ultrafine zinc oxide aggregate powder having an average primary particle diameter of 35 nm was mixed with 35.0% of a dispersant N-vinylpyrrolidone-N, N-dialkylaminoalkyl acrylate copolymer. 96 parts of an ethanol solution,
The mixture was charged into a bead mill together with 464 parts of an equal weight mixture of isopropanol and water as a medium, and the zinc oxide powder was dispersed while being ground. 177 parts of tetraethoxysilane and 140 parts of isopropanol were charged into a reactor, and 400 parts of the above-mentioned zinc oxide dispersion was added dropwise over 10 minutes while stirring at room temperature, and stirring was continued for a while to obtain a uniform dispersion.
Then, a catalyst solution comprising 36 parts of monoethanolamine and 200 parts of water was added dropwise over 30 minutes while stirring at room temperature, and stirring was further continued for 40 minutes to advance sol formation. The reaction temperature was raised to 80 ° C. by external heating to gel the sol for 30 minutes. A reaction reagent consisting of 33 parts of monomethyltrimethoxysilane and 20 parts of isopropanol was added, and stirring was continued at 80 ° C. for 60 minutes to perform a sol-gel reaction. After cooling, the reaction product was filtered and washed with water to remove the solvent, dispersant and catalyst. After drying at 120 ° C., the yield of coated powder was 189.
5 copies. This is substantially equivalent to a weight of 186.3 parts assuming that the total amount of silanes has been converted to silica and methyl-modified silica and coated with zinc oxide. Therefore, the composition of the coating powder is calculated to be 64.5% by weight of zinc oxide, 27.0% by weight of silica, 8.5% by weight of methyl-modified silica, and the ratio of the coating layer is 35.5% by weight. The obtained coated powder was pulverized with an impact pulverizer for 20 seconds. The particle size of the coated powder after pulverization was distributed between 0.5 and 8 μm, and the average particle size was 2.8 μm. As a result of electron microscope observation,
These were coatings of secondary particles which were aggregates of the original primary particles with a particle size of 30 to 50 nm. Using the obtained crushed coated zinc oxide powder, an ultraviolet ray shielding test of Example 2, an oleic acid solidification test of Example 3, a fading test of a coating dye of Example 4, and a water surface floating test of Example 6 , A paste fluidity test of Example 7, an oil dispersion stability test of Example 8, an emulsified foundation trial production test of Example 9, a powder foundation trial production test of Example 10, and a resin melt kneading extrusion test of Example 11. When a test equivalent to each test was performed, the same preferable results as in the case of the pulverized coated zinc oxide powder obtained in Example 1 were obtained.

[0046]

Example 13 240 parts of ultrafine zinc oxide aggregate powder having an average primary particle diameter of 35 nm was mixed with 96 parts of a 15.0% ethanol solution of polyvinyl butyral as a dispersant, and ethanol and water as a medium. The mixture was charged into a bead mill together with 464 parts by weight of a weight mixture, and the zinc oxide powder was dispersed while being pulverized. In a reactor, tetraethoxysilane 169.
Five parts and 140 parts of isopropanol were charged, and 400 parts of the above zinc oxide dispersion was added dropwise over 10 minutes while stirring at room temperature, and stirring was continued for a while to obtain a uniform dispersion. Then, a catalyst solution comprising 36 parts of diethanolamine and 200 parts of water was added dropwise over 30 minutes while stirring at room temperature.
The stirring was continued for a minute to advance the sol formation. The reaction temperature was raised by external heating to gel the sol for 30 minutes. A reaction reagent consisting of 31.6 parts of monomethyltrimethoxysilane and 20 parts of ethanol was added, and stirring was further continued for 60 minutes to perform a sol-gel reaction. After cooling, the reaction product was separated by filtration and washed with ethanol or water to remove the solvent, dispersant and catalyst. After drying at 120 ° C., the yield of the coated powder was 182.5 parts. This is substantially equivalent to a weight of 181.8 parts assuming that the total amount of silanes has been converted to silica and methyl-modified silica and coated with zinc oxide. The composition of the coating powder was 66.0% by weight of zinc oxide, 25.9% by weight of silica, 8.1% by weight of methyl-modified silica, and the ratio of the coating layer was 34.0% by weight. The obtained coated powder was pulverized with an impact pulverizer for 20 seconds. The particle size of the coated powder after pulverization is 0.5
To 8 μm, and the average particle size was 2.5 μm. As a result of observation with an electron microscope, these have a particle size of 30 to 50 n.
m was a coating of secondary particles that were aggregates of primary particles. Using the obtained crushed coated zinc oxide powder, an ultraviolet ray shielding test of Example 2, an oleic acid solidification test of Example 3, a fading test of a coating dye of Example 4, and a water surface floating test of Example 6 Paste flowability test of Example 7, Example 8
The dispersion stability test in oil, the emulsified foundation trial production test in Example 9, the powder foundation trial production test in Example 10, and the resin melt kneading and extrusion test in Example 11 were performed. The same favorable results as in the case of the pulverized coated zinc oxide powder obtained in 1 were obtained.

[0047]

Comparative Example 13 The method of Example 1 was repeated, except that the type of dispersant was changed to the Na salt of acrylic acid copolymerized acrylic resin.
Aggregation of the zinc oxide particles progressed during the sol-gel reaction, and silica gel was generated which was partially unrelated to the coating. Even after the pulverization, the powder was rough and rough, and had a rough touch. In the oleic acid solidification test, oleic acid solidified in 2 to 3 minutes.

[0048]

Comparative Example 14 The type of catalyst was changed from diethanolamine to ammonia, and 10.4 parts of 28% aqueous ammonia was replaced with 2 parts of ammonia.
The method of Example 1 was repeated using diluted with 00 parts of water. After the reaction, the filter paper was clogged, and the reaction product could not be separated by filtration. Observation of the solid content obtained by evaporation to dryness revealed that zinc oxide particles and silica gel particles were mixed. In the oleic acid solidification test using this powder, oleic acid solidified within one minute.

[0049]

Comparative Example 15 The method of Example 1 was repeated, except that the type of the catalyst was changed to triethylamine. Observation of the obtained powder showed that silica gel particles were mixed. In the oleic acid solidification test using this powder, oleic acid solidified in 5 to 6 minutes.

[0050]

Example 16 The method of Example 1 was repeated, except that the ultrafine zinc oxide in Example 1 was replaced with ultrafine titanium oxide having an average particle diameter of 40 nm. The sol-gel reaction proceeds quantitatively, with 64.5% by weight of titanium oxide, 27.0% by weight of silica, 8.5% by weight of methyl-modified silica, and the proportion of the coating layer is 35.5% by weight. The obtained coated powder was pulverized with an impact pulverizer for 20 seconds. The particle size of the coated powder after pulverization is 0.5
And 8 μm, and the average particle size was 2.8 μm. As a result of observation with an electron microscope, these particles have a particle size of 30 to 50 n.
m was a coating of secondary particles that were aggregates of primary particles. Using the obtained crushed coated titanium oxide powder,
A discoloration test of the coating film dye of Example 4, a water surface spray test of Example 6, a paste fluidity test of Example 7, a dispersion stability test in oil of Example 8, an emulsified foundation trial production test of Example 9, When the same tests as the powder foundation trial production test of Example 10 and the resin melt-kneading extrusion test of Example 11 were performed, the same preferable results as in the case of the pulverized coated zinc oxide powder obtained in Example 1 were obtained. I got the result.
In addition, the results of the comparative tests corresponding to the above tests showed that the single-layer coated titanium oxide powder was inferior to the single-layer coated zinc oxide powder, and the uncoated titanium oxide was the same inferior result as the uncoated zinc oxide. .

[0051]

Example 17 The method of Example 16 was repeated, except that the ultrafine particle titanium oxide in Example 16 was replaced with an iron-containing ultrafine particle titanium oxide having an average particle diameter of 40 nm in which a very small amount of iron was added to further enhance the ultraviolet shielding effect. Repeated. The properties of the powder obtained from the progress of the sol-gel reaction were the same as those in Example 16 except that the ultraviolet ray shielding effect was high.

Industrial Applicability The coated metal oxide powder of the present invention has a high ultraviolet shielding effect, has a blocked photocatalytic activity, is easily dispersed in a fluid medium, and the dispersed liquid has excellent fluidity. Moreover, because it has long-term dispersion stability, cosmetics,
It is useful when applied to paints, adhesives, resin molded products, and the like. Further, according to the method of the present invention, a useful coated metal oxide powder that satisfies the above-mentioned properties at the same time can be produced.

[Procedure amendment]

[Submission date] November 19, 1999 (1999.11.
19)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4C083 AA122 AB052 AB171 AB172 AB212 AB232 AB241 AB442 AC022 AC092 AC122 AC242 AC252 AC352 AC392 AC442 AC541 AC542 AC911 AC912 AD022 AD071 AD091 AD092 AD111 AD112 AD242 AD512 BB23 BB25 BB26 CC12 CC01 DD17 DD33 EE07 EE17 FF01

Claims (5)

[Claims] 1. Zinc oxide, titanium oxide, cerium oxide,
And the surface of particles selected from the group consisting of zirconium oxide is coated with a silica-based material in an amount of 5% by weight or more and 100% by weight or less of the metal oxide, and 90% by weight or more of the coated particles has a particle size of 0.1 μm or more and 9% or more. 0.0 μm or less and an average particle size of 0.
In the surface-coated metal oxide particles in the range of 5 μm or more and 5.0 μm or less, the inner layer of the coating layer is silica, the outer layer is alkyl-modified silica, and the surface-coated metal oxide particles have an average particle size of 0.1 μm. Modified silica-coated metal oxide particles, which are aggregated secondary particles of the following ultrafine primary particles. 2. A composition comprising the modified silica-coated metal oxide particles according to claim 1 incorporated in any one of a cosmetic, a paint, an adhesive, and a resin molded product. 3. Metal oxide particles are dispersed in an organic dispersion medium using a dispersant, and a tetraalkoxysilane is subjected to a sol-gel reaction in the dispersion, and then an alkylalkoxysilane is subjected to a sol-gel reaction in the dispersion. A method for producing modified silica-coated metal oxide particles, which is characterized by performing a gel reaction. 4. The method according to claim 3, wherein the dispersant is an alkanolamine salt of an acrylic acid and / or methacrylic acid copolymer, an N-vinylpyrrolidone-N, N-dialkylaminoalkyl acrylate copolymer, A polymer selected from the group consisting of dialkyl sulfates of vinylpyrrolidone-N, N-dialkylaminoalkylacrylate copolymer, N-vinylpyrrolidone vinyl acetate copolymer, polyvinyl butyral, and methyl vinyl ether-dialkyl maleate copolymer 4. The method according to claim 3, wherein the dispersant is one or more kinds. 5. The method according to claim 3, wherein an alkanolamine is used as a reaction catalyst.