JP2001058821A - Zinc oxide particle having suppressed surface activity, its production and utilization thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a zinc oxide particle having the suppressed surface activity and capable of imparting safe and effective ultraviolet screening properties (especially ultraviolet screening properties in a long wavelength region) to products in a wide field such as resin molded products, coating materials or cosmetics and to provide a method for producing the zinc oxide particle. SOLUTION: This zinc oxide particle has a coating layer comprising zinc silicate in an amount within the range of 0.5-50 wt.% expressed in terms of the zinc silicate (zinc orthosilicate or Zn2SiO4) based on the zinc oxide on the surface thereof. Iron or cobalt can especially be converted into a solid solution with the zinc oxide and the coating layer comprising the zinc silicate can be formed on the surface thereof to thereby impart effective screening properties even for ultraviolet rays in a long wavelength region while suppressing the surface activity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has a coating layer made of zinc silicate on the surface, has a greatly suppressed surface activity, and has an ultraviolet light including a long wavelength region of around 400 nm. The present invention relates to zinc oxide particles having excellent shielding properties and excellent transparency, and to their production and use.

[0002]

2. Description of the Related Art In recent years, due to the partial destruction of the ozone layer, the absolute amount of ultraviolet rays reaching the surface of the earth has increased, and with this, interest in protecting the human body from ultraviolet rays has increased. As already known, ultraviolet rays reaching the ground surface include those in the B region of 290 to 320 nm and 320 ultraviolet rays.
There is an A region in the range of 400 nm, and in recent years, there has been a particular interest in protecting not only the B region but also the longer region A from ultraviolet rays.

[0003] Conventionally, organic ultraviolet absorbers have been widely used for films, paints, sunscreen cosmetics and the like.
However, in the field of resin moldings and paints such as films, with the passage of time, a phenomenon in which the compounded organic ultraviolet absorber migrates to the surface layer of the film or coating, so-called bleed-out, There is a problem that the ultraviolet absorber is photolyzed and the ultraviolet shielding effect is deteriorated.

Further, conventional organic ultraviolet absorbers have a problem in skin irritation in the cosmetics field.
Since the ultraviolet absorption wavelength of the organic ultraviolet absorber is limited to a specific region, in recent years, there has been a strong demand for a material capable of blocking ultraviolet light of a wide range of wavelengths.

On the other hand, inorganic ultraviolet absorbers have been widely used, and among them, ultrafine rutile type titanium oxide has been widely used in the fields of paints and cosmetics. However, rutile-type titanium oxide has a large refractive index (2.7), and therefore has a strong hiding power despite being ultra-fine particles. Thus, when blended in a resin molded product or paint, the transparency is insufficient. In addition, when sunscreen cosmetics containing ultrafine rutile titanium oxide are applied to the skin, the ultrafine rutile titanium oxide strongly scatters blue light, often giving a pale tint, making the skin unhealthy. There is also a problem to show.
Furthermore, the shielding property against ultraviolet rays in the region A is insufficient.

In view of this, a composite oxide of Ti, Si and Fe has been proposed as titanium oxide having an excellent shielding property against ultraviolet rays in the region A (Japanese Patent Application Laid-Open No. 9-30933). Further, an ultrafine iron-containing titanium oxide rutile-type titanium oxide has been proposed as a useful product for sunscreen cosmetics while suppressing the bluish color tone (JP-A-5-330825). However, these still have insufficient ultraviolet ray shielding ability in the region A and have a large refractive index, so that they tend to conceal the underlayer. When there is blended, there is a problem that transparency is further reduced.

On the other hand, ultrafine zinc oxide has a sharp absorption edge at an ultraviolet wavelength of 380 nm, and not only region B but also region A
It has the property of being able to block most of the UV light in the region, and has a small refractive index (2.0), so it is very transparent. It is getting attention. Conventionally, it is mainly used in the field of cosmetics, but because of its excellent properties, it is being used not only in the field of cosmetics but also in various fields.

However, at the same time, conventionally known ultrafine zinc oxide, when used as an ultraviolet absorber,
Until now, various problems have been pointed out. For example, when blended with a thermoplastic resin such as polyethylene terephthalate or polycarbonate, there is a problem that the ultrafine zinc oxide accelerates the decomposition of these resins and significantly impairs the moldability. Further, when ultrafine zinc oxide is added to the coating, there is a problem that the zinc oxide reacts with the resin binder, and the coating thickens with time and gels.

Furthermore, when a resin molded product or a coating film containing conventionally known ultrafine zinc oxide is exposed outdoors, there is a problem that the zinc oxide particles photocatalytically oxidize and decompose the resin in the vicinity thereof. Also, in cosmetics, the generation of active oxygen by the photocatalytic activity is concerned.

[0010] Furthermore, zinc oxide originally has the property of being dissolved in a trace amount of water, and the physiological action of the eluted zinc ion has been used as an astringent in the cosmetics field for a long time. In addition, the chemical reactivity of producing metal soaps by reacting with fatty acids absorbs sebum secreted from the skin, improves makeup durability, and is used as a deodorant effect to absorb body odor components. There is also.

However, these physiological activities and chemical reactivity tend to be further enhanced by making zinc oxide ultrafine, and from the viewpoint of safety against skin tissues, it is necessary to suppress the activity of the particle surface. Have been.

Therefore, the present inventors have proposed that the surface of zinc oxide particles be surface-treated with high-density silica or the like in order to suppress such intrinsic surface activity of zinc oxide (Japanese Patent Laid-Open Publication No. Hei 11-1999). -336316). However, such a technique called surface treatment or coating basically forms a coating layer made of a hydrated oxide such as silica or alumina on the surface of zinc oxide particles, and is therefore molded at a high temperature. In high temperature baking type paints such as powder paints, pre-coated metals, etc. that manufacture and apply resin molded products, there is a problem that the resin and paints deteriorate in moldability due to such a coating layer made of hydrated oxide. is there.

Furthermore, zinc oxide particles coated with these hydrated oxides have a fatal defect of promoting hydrolysis of polyethylene terephthalate or polycarbonate resin.

In addition, in a food packaging film, it is necessary to shield ultraviolet rays up to around 400 nm depending on the content thereof. Is required not to transmit light having a wavelength up to 400 nm or more. However, ultrafine zinc oxide alone has a property of 380 n
m or more cannot be blocked.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems in zinc oxide particles, particularly in ultrafine zinc oxide, and has been made in consideration of the above various problems in conventional ultrafine zinc oxide. Without any problems, resin particles, paints, cosmetics, and other products in a wide range of fields, which can provide safe and effective ultraviolet shielding properties, suppressed surface activity zinc oxide particles, preferably ultrafine zinc oxide, It is an object of the present invention to provide a manufacturing method thereof.

Another object of the present invention is to provide uses of such zinc oxide particles, particularly resin molded articles, paints and cosmetics. Still another object of the present invention is to provide ultrafine zinc oxide which can effectively block ultraviolet rays in a long wavelength region around 400 nm.

[0017]

According to the present invention, zinc oxide particles having reduced surface activity according to the present invention have a surface in which zinc oxide is converted to zinc silicate (zinc orthosilicate, Zn ₂ SiO ₄ ).
It has a coating layer of zinc silicate in the range of 0.5 to 50% by weight, preferably 1 to 15% by weight.

In the present invention, "in terms of zinc silicate"
Then, this zinc silicate is a zinc orthosilicate (Z
n ₂ SiO ₄ ).

In the present invention, as a raw material (starting material) of the zinc oxide particles, in addition to the zinc oxide particles themselves, a water-insoluble zinc compound which can be converted to zinc oxide by heating in air (specific examples) Will be described later.)
Or, especially, while iron or cobalt is dissolved in solid solution,
In the case of obtaining zinc oxide particles having a coating layer made of zinc silicate on the surface, a water-soluble salt that produces the above-mentioned water-insoluble zinc compound by neutralizing with a neutralizing agent (specific examples will be described later) is used. be able to. In such a case, when "to zinc oxide" is referred to, in the present invention, it is formed from the water-insoluble zinc compound or the water-soluble zinc salt used as a starting material for zinc oxide. (Strictly speaking, stoichiometric) shall mean "relative to zinc oxide."

The zinc oxide particles with reduced such surface activity, the aqueous suspension of particles of the water-insoluble zinc compounds, each of the aqueous solution of zinc silicate of a water-soluble silicate and a water-soluble zinc salt (Zn ₂ Stoichiometric ratio to form SiO ₄ ), and
Zinc silicate (Zn ₂ SiO ₄ ) conversion to zinc oxide
After adding an amount in the range of 0.5 to 50% by weight, washing with water, drying, and then heating to a temperature in the range of 300 to 1200 ° C. to form zinc oxide particles, It can be obtained by forming a coating layer made of zinc acid.

As the water-insoluble zinc compound, for example, zinc oxide, zinc hydroxide, zinc carbonate, basic zinc carbonate, zinc sulfide or zinc oxalate is used.

In order to obtain the zinc oxide particles according to the present invention in which iron or cobalt is dissolved, in the above-mentioned method, the water-soluble silicate and the water-soluble silicate are formed in a stoichiometric ratio to form zinc silicate (Zn ₂ SiO ₄ ). Before adding each aqueous solution of the zinc salt to the aqueous suspension of the water-insoluble zinc compound particles, a predetermined amount of hydrous iron oxide or hydrous cobalt oxide is previously deposited on the surface of the zinc compound particles with respect to zinc oxide. Then, aqueous solutions of a water-soluble silicate and a water-soluble zinc salt are added to such a suspension in a stoichiometric ratio to form zinc silicate (Zn ₂ SiO ₄ ), followed by washing with water and drying. And 300-12
What is necessary is just to heat to the temperature of 00 degreeC. By such a method, the zinc compound particles are converted into zinc oxide particles, that is, zinc oxide particles are generated from the zinc compound particles, and iron or cobalt is solid-dissolved in the zinc oxide particles. A zinc silicate layer is formed on the surface of the particles.

Here, usually, in order to make iron or cobalt form a solid solution in the crystal of the zinc oxide particles, several hundred degrees Celsius, preferably,
Heating and firing at a high temperature of 600 to 1000 ° C. are required. However, if the zinc oxide particles are fired at such a high temperature, the particles grow remarkably, and particles having high transparency cannot be obtained. However, according to the present invention, since zinc oxide particles have a coating layer made of zinc silicate on the surface thereof, even if fired at a high temperature as described above, sintering of the particles hardly occurs. Ultra fine particles can be obtained.

In addition to the above, in the range of 0.5 to 50% by weight of zinc silicate (Zn ₂ SiO ₄ ) based on zinc oxide, on the surface of zinc oxide in which iron or cobalt may be dissolved. A first coating layer made of zinc silicate, and further, 0.5 to 30% by weight of zinc oxide in terms of oxide based on zinc oxide
Provided is a zinc oxide particle having a reduced surface activity and having a second coating layer made of an oxide of at least one element selected from the group consisting of Al, Ti, Zr, Sn, Sb and a rare earth element. .

[0025] Such zinc oxide particles are prepared by preparing zinc oxide particles having a coating layer of zinc silicate on the surface of zinc oxide particles in which iron or cobalt may be dissolved. After adding an aqueous solution of a water-soluble compound of at least one element selected from the group consisting of aluminum, silicon, tin, zirconium, antimony and rare earths to an aqueous suspension of zinc oxide particles, using an acid or alkali as a neutralizing agent In addition, it can be obtained by neutralizing a water-soluble compound of the above element and precipitating it on the surface of the zinc oxide particles to form a second coating layer made of an oxide of the above element.

The above-described zinc oxide particles according to the present invention may be further treated with an organosilicon compound, a higher fatty acid, a higher fatty acid ester, metal soap, a polyhydric alcohol or an alkanolamine, if necessary.

The zinc oxide particles according to the present invention have the following characteristics:
Preferably, it has an average particle size of 0.15 μm or less.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION The zinc oxide particles used as a raw material in the present invention are obtained by evaporating and oxidizing an electric zinc ingot, or neutralizing an aqueous solution of a water-soluble salt such as zinc sulfate or zinc chloride. There is no particular limitation, such as those obtained by calcining the resulting zinc hydroxide, zinc carbonate, basic zinc carbonate, zinc sulfide, zinc oxalate, etc., and any of them may be used.

In the present invention, the zinc oxide particles used as a raw material preferably have high transparency, and accordingly, the average primary particle diameter is preferably 0.15 μm or less. When the average primary particle size is larger than 0.15 μm, the hiding power is large. For example, when blended in films, paints, cosmetics, and the like, their transparency is lowered and whitened. However, in the present invention, if necessary, zinc oxide particles having an average primary particle diameter of more than 0.15 μm may be used as a raw material. The lower limit of the average primary particle diameter of the zinc oxide particles used as a raw material is not particularly limited, but is usually 0.01 μm. Here, the average primary particle diameter is defined as a diameter in a certain direction (a so-called FERET diameter) in a field of view of 100,000 times that of a transmission electron microscope.

The zinc oxide particles with suppressed surface activity according to the present invention have zinc silicate (Zn
₂ SiO ₄₎ 0.5 to 50 wt% in terms of, preferably 1
It has a coating layer of zinc silicate in the range of １５15% by weight. When the proportion of zinc silicate in the zinc oxide particles according to the present invention is less than 0.5% by weight in terms of zinc silicate (Zn ₂ SiO ₄ ), the surface activity originally possessed by zinc oxide can be sufficiently suppressed. On the other hand, when it is more than 50% by weight, the inherent ultraviolet shielding effect of zinc oxide is significantly reduced.

The zinc oxide particles according to the present invention are prepared by forming aqueous solutions of a water-soluble silicate and a water-soluble zinc salt into an aqueous suspension of raw material zinc oxide particles to form zinc silicate (Zn ₂ SiO ₄ ). After adding an amount in the stoichiometric ratio and in the range of 0.5 to 50% by weight in terms of zinc silicate (Zn ₂ SiO ₄ ) with respect to the zinc oxide, washing with water, drying, and
It can be obtained by heating to a temperature in the range of 1200 ° C. to form zinc oxide particles and forming a zinc silicate layer on the surface of the particles.

To explain this method in more detail, in order to prepare an aqueous suspension of the zinc oxide particles, it is preferable to suspend the zinc oxide particles sufficiently pulverized by a pulverizer such as a sand mill in water. Here, the concentration of the zinc oxide particles in the suspension is preferably in the range of 50 to 250 g / L. However, in the present invention, the preparation of the aqueous suspension of zinc oxide particles and the concentration of zinc oxide particles in the suspension are not limited to the above examples.

Next, an aqueous solution of a water-soluble silicate and an aqueous solution of a water-soluble zinc salt are added to the aqueous suspension of zinc oxide particles thus obtained to form zinc silicate (Zn ₂ SiO ₄ ). In a stoichiometric ratio, zinc silicate (Z
n ₂ SiO ₄ ) in the range of 0.5 to 50% by weight. At this time, if necessary, a neutralizing agent may be added to adjust the pH.

As the water-soluble silicate, alkali metal silicates such as sodium silicate, potassium silicate and the like are preferably used. As the water-soluble zinc salt, inorganic acids such as zinc sulfate and zinc chloride are used. Salts are preferably used, but are not limited thereto. Here, when adding the aqueous solution of the water-soluble silicate and the aqueous solution of the water-soluble zinc salt to the suspension of the zinc oxide particles, either of them may be added first, or both may be added simultaneously.

According to the invention, the zinc oxide particles are separated from the suspension thus obtained, washed and, if necessary, dried, and then, for example, in an oxidizing atmosphere such as air. Below, heating and baking to a temperature in the range of 300 to 1200 ° C., followed by dry pulverization with a suitable pulverizer such as a hammer mill, an edge runner mill, a jet mill, etc. Zinc oxide particles according to the invention having a coating layer of .15 μm zinc silicate can be obtained.

When firing the zinc oxide particles thus obtained, if the firing temperature is lower than 300 ° C., it is not preferable because the hydrous zinc silicate remains on the zinc oxide particles. When the value exceeds, the particles grow extremely large and zinc oxide particles having high transparency cannot be obtained. Preferably, the firing temperature is in the range of 500-1100C, most preferably in the range of 600-1000C.

In addition to the above-mentioned method, a water-soluble silicate is added to the aqueous suspension of the water-insoluble zinc compound particles, and then a neutralizing agent is added. By baking, a coating layer made of zinc silicate can be formed on the surface of the zinc compound particles.

As described above, since the zinc oxide particles according to the present invention have a coating layer made of zinc silicate on the surface thereof, when dispersed in an appropriate medium, the coating layer made of zinc silicate becomes zinc oxide. By completely isolating the particles from the medium, for example, it is possible to significantly suppress zinc oxide's inherent properties such as solubility in water and chemical reactivity with fatty acids and the like. Can be suppressed.

Water-insoluble zinc compounds which can be converted to zinc oxide by heating in air, such as zinc hydroxide, zinc carbonate, basic zinc carbonate, zinc sulfide, zinc oxalate, etc. Can be used as a raw material instead of zinc oxide. That is, instead of the zinc oxide particles, such water-insoluble zinc compound particles are used, and as described above, the aqueous solutions of the water-soluble silicic acid and the water-soluble zinc salt are converted to zinc silicate (Zn ₂ SiO ₄ ). The stoichiometric ratio to form and the zinc silicate (Zn
₂ SiO ₄ ), added in an amount in the range of 0.5 to 50% by weight, washed with water, dried, and then heated to a temperature in the range of 300 to 1200 ° C. to convert the zinc compound particles into zinc oxide particles. And a coating layer made of zinc silicate is formed on the surface.

Further, according to the present invention, iron is solid-dissolved in zinc oxide in a range of 0.1 to 20% by weight in terms of iron, and the surface thereof has zinc silicate to zinc oxide. (Z
0.5 to 50% by weight in terms of n ₂ SiO ₄ ), preferably
Iron-dissolved zinc oxide particles having a coating layer of zinc silicate in the range of 1 to 15% by weight are provided.

In the iron-dissolved zinc oxide particles, the amount of iron dissolved in the zinc oxide is 0.1 to 0.1 in terms of iron with respect to the zinc oxide.
The range is 20% by weight, preferably 0.5 to 15% by weight, particularly preferably 1 to 10% by weight. As described above, by dissolving iron in zinc oxide, it is possible to obtain zinc oxide ultrafine particles that effectively shield ultraviolet rays in a long wavelength region as long as 400 nm. By blending this in a cosmetic, it is possible to obtain a cosmetic that does not cause an undesired reaction with other components, does not cause generation of active oxygen, and can obtain a finish with a white skin feeling without any whiteness.

When the amount of iron dissolved in zinc oxide is less than 0.1% by weight in terms of iron, the effect of shielding ultraviolet rays in the region A having a wavelength longer than 380 nm is insufficient, and on the other hand, 20% by weight. If the amount is larger than the above, a part of the iron is separated from the zinc oxide without being dissolved in the zinc oxide, and presents a problem such as color separation at the time of blending into the paint or the emulsion.

According to the present invention, such iron-dissolved zinc oxide particles are added to an aqueous suspension of zinc oxide particles in an aqueous solution of a water-soluble iron salt in an amount of 0.1 to 20% by weight of iron based on zinc oxide. Is added, a neutralizing agent is added to form an iron oxide-containing layer on the surface of the zinc oxide particles, and then, as described above, to an aqueous suspension containing such zinc oxide particles, in a stoichiometric ratio of the respective aqueous solutions of a water-soluble silicate and a water-soluble zinc salt to form zinc silicate (Zn ₂ SiO _4), and, zinc silicate to oxidation zinc (Zn ₂ SiO ₄₎ in terms After adding an amount in the range of 0.5 to 50% by weight, washing with water and drying, and then heating to a temperature in the range of 300 to 1200 ° C. to dissolve iron in the zinc oxide particles, By forming a coating layer made of zinc silicate on the substrate.

According to the present invention, in order to deposit the iron oxide hydroxide on the zinc oxide particles, for example, an aqueous suspension of the zinc oxide particles is used in an amount of 0.1 to 20% by weight in terms of iron with respect to zinc oxide.
After the addition of the water-soluble iron salt, a neutralizing agent may be added to neutralize the suspension. As the water-soluble iron salt, for example,
Ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous nitrate, ferric nitrate and the like are preferably used, but are not limited thereto. The neutralizing agent is not particularly limited, but sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like are preferably used.

After preparing an aqueous suspension of zinc oxide particles having an iron oxide hydroxide layer on the surface, a water-soluble silicate aqueous solution and a water-soluble zinc salt aqueous solution are added thereto as described above. At a stoichiometric ratio to form zinc silicate (Zn ₂ SiO ₄ ), and with zinc oxide to zinc silicate (Zn ₂ S)
After adding an amount in the range of 0.5 to 50% by weight in terms of iO ₄ ), washing with water, drying, and then 300 to 1200 ° C., preferably 500 to 1100 ° C., and most preferably 600
Heating, baking, and pulverizing at a temperature in the range of -1000 ° C can yield iron-dissolved zinc oxide particles having a coating layer made of zinc silicate having an average particle size of 0.01 to 0.15 µm.

However, according to the present invention, without using zinc oxide particles, by heating in air, such as zinc hydroxide, zinc carbonate, basic zinc carbonate, zinc sulfide, zinc oxalate, etc. An aqueous suspension is prepared using particles of a water-insoluble zinc compound that can be converted to zinc oxide, and the aqueous suspension is added to zinc oxide in an amount of 0.1 in terms of iron with respect to zinc oxide.
The water-insoluble zinc compound is added to the suspension to adjust the pH of the suspension to a range of 6.0 to 9.0. After depositing hydrous iron oxide on the surface of the particles, and then adding each aqueous solution of a water-soluble silicate and a water-soluble zinc salt to such an aqueous suspension of zinc compound particles as described above. , Washing, drying and heating to form zinc oxide particles, dissolving iron in the particles, and forming a coating layer made of zinc silicate on the surface thereof, the zinc oxide particles according to the present invention. Can be obtained.

Further, according to the present invention, a mixture of an aqueous solution of a water-soluble zinc salt and an aqueous solution of a water-soluble iron salt is prepared, and a neutralizing agent is added thereto, and zinc hydroxide, zinc carbonate, basic carbonate is prepared. A water-insoluble iron compound (eg, hydrous iron oxide) is co-precipitated with a water-insoluble zinc compound (eg, zinc hydroxide) such as zinc, zinc sulfide, and zinc oxalate, and the particles of the coprecipitate thus obtained are obtained. Is treated as described above to form a solid solution of iron in the generated zinc oxide particles, and also by forming a coating layer made of zinc silicate on the surface, to obtain iron-dissolved zinc oxide particles of the present invention. be able to.

As described above, the zinc oxide particles according to the present invention having the coating layer made of zinc silicate on the surface of the zinc oxide particles in which iron is dissolved, are excellent in the ability to shield ultraviolet rays in the A region of 380 nm or more. Compositions such as zinc oxide particles dispersed in a medium, such as cosmetics and paints, the coating layer made of zinc silicate completely separates the zinc oxide particles from the medium, for example, pure water The solubility in water and the reactivity with other components can be significantly suppressed, and the photocatalytic activity can be almost completely suppressed.

Further, according to the present invention, cobalt is 0.5 to 30 in terms of cobalt oxide (CoO) relative to zinc oxide.
%, Preferably 1 to 25% by weight, particularly preferably 3 to 20% by weight, and zinc silicate (Zn ₂ Si
O ₄ ) 0.5 to 50% by weight, preferably 1 to 15%
Cobalt-dissolved zinc oxide particles having a coating layer comprising zinc silicate in the range of weight percent are provided.

[0050] Such cobalt solid solution zinc oxide particles are also
It can be obtained in the same manner as the iron-dissolved zinc oxide particles described above. That is, the cobalt-solid-dissolved zinc oxide particles are added to the aqueous suspension of zinc oxide particles by adding cobalt oxide (C
After adding an aqueous solution of 0.5 to 30% by weight of a water-soluble cobalt salt in terms of oO), a neutralizing agent was added to form a hydrous cobalt oxide layer on the surface of the zinc oxide particles. In this manner, the aqueous suspension containing the zinc oxide particles is mixed with the aqueous solutions of the water-soluble silicate and the water-soluble zinc salt in a stoichiometric ratio to form zinc silicate (Zn ₂ SiO ₄ ). And zinc oxide (Zn ₂ Si)
O ₄₎ was added to an amount ranging from 0.5 to 50 wt% in terms of
Rinsing with water, drying, and then 300 to 1200 ° C, preferably 500 to 1100 ° C, most preferably 600 to 1100C.
It can be obtained by heating to a temperature in the range of 000 ° C. to form a solid solution of cobalt in the zinc oxide particles and to form a coating layer made of zinc silicate on the surface.

According to the present invention, for depositing the hydrated cobalt oxide on the zinc oxide particles, for example, an aqueous suspension of the zinc oxide particles may be coated with cobalt oxide (Co) over zinc oxide.
O) After adding 0.5 to 30% by weight of a water-soluble cobalt salt in terms of iron, a neutralizing agent may be added to neutralize the suspension. As the water-soluble cobalt salt, for example, cobalt chloride, cobalt sulfate, cobalt nitrate and the like are preferably used, but not limited thereto. The neutralizing agent is not particularly limited, but sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like are preferably used.

After preparing an aqueous suspension of zinc oxide particles having a hydrous cobalt oxide layer on the surface, a water-soluble silicate aqueous solution and a water-soluble zinc salt aqueous solution are added thereto as described above. After adding at a stoichiometric ratio to form zinc oxide (Zn ₂ SiO ₄ ), wash with water, dry,
It can be obtained by heating to a temperature in the range of 0 to 1200 ° C. to form a solid solution of cobalt in the zinc oxide particles and to form a zinc silicate layer on the surface thereof.

However, according to the present invention, without using zinc oxide particles, by heating such as zinc hydroxide, zinc carbonate, basic zinc carbonate, zinc sulfide, zinc oxalate, etc. An aqueous suspension is prepared using particles of a water-insoluble zinc compound that can be converted, and the aqueous suspension is added to cobalt oxide (Co
O) After adding a water-soluble cobalt salt so as to be 0.5 to 30% by weight in terms of conversion, a neutralizing agent is added, and the pH of the suspension is adjusted.
Was adjusted to the range of 6.0 to 9.0 to deposit cobalt hydroxide hydrate on the surface of the water-insoluble zinc compound particles,
As described above, to the aqueous suspension of such zinc compound particles, after adding each aqueous solution of a water-soluble silicate and a water-soluble zinc salt, washing with water, drying and heating, the zinc oxide particles The solid solution of cobalt and the formation of a coating layer made of zinc silicate on the surface can also provide the cobalt-dissolved zinc oxide particles according to the present invention.

Further, according to the present invention, the cobalt-dissolved zinc oxide particles may be prepared by mixing a water-soluble zinc salt and a water-soluble cobalt salt aqueous solution with a neutralizing agent, preferably in a pH range of 6.0 to 9.0. To prepare an aqueous suspension containing particles of a co-precipitate of a water-insoluble zinc compound (e.g., zinc hydroxide) and a water-insoluble cobalt compound (e.g., hydrous cobalt oxide), as described above. After the respective aqueous solutions of the water-soluble silicate and the water-soluble zinc salt are added in a stoichiometric ratio to form zinc silicate (Zn ₂ SiO ₄ ), washing and drying are performed, and then 300 to 1200 ° C. To obtain a solid solution of cobalt in the generated zinc oxide particles and to form a coating layer made of zinc silicate on the surface.

In the cobalt solid solution zinc oxide particles according to the present invention, when the amount of cobalt solid solution is less than 0.5% by weight in terms of cobalt oxide (CoO) with respect to zinc oxide, 3
When there is almost no shielding effect against ultraviolet rays in a long wavelength region of 80 to 420 nm, and when the content is more than 30% by weight, the transmittance of visible light, that is, the transparency is significantly reduced.

The cobalt-dissolved zinc oxide particles according to the present invention not only have an excellent ability to shield ultraviolet rays in the long wavelength region of 380 to 420 nm, but also disperse them in a medium to form a composition such as a cosmetic or paint. In this case, the coating layer made of zinc silicate on the surface completely separates the cobalt-containing zinc oxide particles from the medium, and therefore, for example, significantly improves the solubility in pure water and the reactivity with other components. The photocatalytic activity can be almost completely suppressed.

The zinc oxide particles according to the present invention obtained as described above have an average primary particle diameter of 0.1 to ensure high transparency, including those in which iron or cobalt is dissolved. It is preferably 15 μm or less. However, particles having an average primary particle size larger than 0.15 μm may be used depending on the application. The lower limit of the average primary particle diameter of the zinc oxide particles according to the present invention is not particularly limited, but is usually 0.01 μm.

According to the present invention, the zinc oxide particles having the first coating layer made of zinc silicate on the zinc oxide particles, in which iron or cobalt may be dissolved, are further provided thereon.
It may have a second coating layer made of an oxide of at least one element selected from the group consisting of aluminum, silicon, tin, zirconium, antimony and rare earths. Here, the second coating layer has a thickness of 0.5 with respect to zinc oxide.
-30% by weight, particularly preferably 2-15% by weight.
Is preferable. Examples of the rare earth element include yttrium, lanthanum, cerium, neodymium, and the like.

The zinc oxide particles according to the present invention having such a second coating layer are prepared, for example, by preparing zinc oxide particles having a coating layer made of zinc silicate on the surface as described above, and then adding the zinc oxide particles to water. To prepare an aqueous suspension,
After adding an aqueous solution of a water-soluble compound of the above element to this suspension, an acid or alkali is added as a neutralizing agent to neutralize the water-soluble compound of the above element and precipitate on the surface of the zinc oxide particles, Such zinc oxide particles can be obtained by separating, and, if necessary, drying and firing.

Examples of the water-soluble compound of aluminum include aluminum nitrate, aluminum sulfate, and sodium aluminate. Examples of the water-soluble compound of silicon include sodium silicate. , Tin chloride, as a water-soluble compound of zirconium, for example, zirconium nitrate, zirconium sulfate, etc., as a water-soluble compound of antimony, for example, antimony chloride, etc., as a water-soluble compound of a rare earth element, for example, And cerium nitrate.

In the preparation of the zinc oxide particles having the second coating layer according to the present invention, an acid or an alkali is used as the neutralizing agent.
Sulfuric acid, inorganic acids such as hydrochloric acid, acetic acid, organic acids such as oxalic acid are preferably used, while as the alkali, for example,
Sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like are preferably used.

When forming a second coating layer made of an oxide of the above element on the surface of zinc oxide particles having a first coating layer made of zinc silicate, the second coating layer made of an oxide of two or more kinds of elements is used. When forming the coating layer, a coating layer composed of an oxide of a plurality of elements may be formed at a time using an aqueous solution of a water-soluble compound of a plurality of elements. It is preferable to form a second coating layer in multiple layers by sequentially forming a coating layer of the oxide one by one using an aqueous solution. In particular, when forming a coating layer containing aluminum oxide as the second coating layer, it is desirable to form the coating layer made of aluminum oxide last. Further, according to the present invention, in order to enhance dispersibility in a resin molded product, cosmetic oil or the like, after forming a first coating layer made of zinc silicate on the surface of zinc oxide particles, After forming the coating layer, such zinc oxide particles may be surface-treated with a surface treatment agent selected from an organosilicon compound, a polyhydric alcohol and an alkanolamine. Such a surface treatment agent is usually in a range of 1 to 20% by weight based on zinc oxide, and preferably,
It is used in the range of 1 to 10% by weight.

Examples of the organosilicon compound include, for example,
Examples include organopolysiloxanes such as methylhydrogenpolysiloxane and dimethylpolysiloxane, and silane coupling agents such as triethoxyvinylsilane and diphenyldimethoxysilane. Examples of polyhydric alcohols include trimethylolethane and trimethylolpropane. And pentaerythritol. Examples of the alkanolamine include, for example, diethanolamine, dipropanolamine, triethanolamine, and tripropanolamine. When the treatment amount with such a surface treating agent is less than 1% by weight based on zinc oxide, the effect of improving the dispersibility of the zinc oxide particles according to the present invention is poor. It is economically disadvantageous because the sex is saturated.

Further, according to the present invention, after the first coating layer made of zinc silicate is formed on the surface of the zinc oxide particles, or after the second coating layer is formed, such zinc oxide particles are formed. C10 to C30 higher fatty acids such as lauric acid, stearic acid and palmitic acid, for example, alkyl esters of these higher fatty acids such as octyl palmitate, for example, these higher fatty acids such as aluminum stearate and aluminum laurate Surface treatment with a metal salt of, for example, metal soap. Metal species constituting metal soap are not limited to aluminum, for example,
Examples thereof include lithium, magnesium, calcium, strontium, barium, zinc, aluminum, and tin.

As described above, when the second coating is formed with a surface treating agent such as a higher fatty acid, a higher fatty acid ester, or metal soap, the amount thereof is usually 1 to 20 with respect to zinc oxide. % By weight, preferably from 1 to 1%.
The range is 0% by weight.

When the amount of treatment with the surface treating agent is less than 1% by weight based on zinc oxide, the effect of improving the dispersibility of the zinc oxide particles according to the present invention is poor.
If it exceeds 0% by weight, the dispersibility will be saturated, which is economically disadvantageous.

The surface treatment with such a surface treatment agent is as follows.
It can be obtained by mixing a predetermined amount of a surface treatment agent with the zinc oxide particles having the first (and second) coating layer and pulverizing the mixture. Alternatively, the zinc oxide particles having the first (and second) coating layer may be pulverized and then mixed with a surface treating agent. Furthermore, after suspending the zinc oxide particles having the first (and second) coating layer in an appropriate medium, for example, water, alcohol, ether, or the like, a surface treatment agent is added to the suspension, It can also be obtained by stirring, fractionating, drying and pulverizing, or by evaporating to dryness and pulverizing.

Since the zinc oxide particles according to the present invention have a coating layer made of zinc silicate on the surface thereof, they do not promote the decomposition of thermoplastic resins such as polyethylene terephthalate and polycarbonate, and are suitably used for these resins. In addition, it can be suitably used for other various resin products. Further, since the solubility in pure water or sulfuric acid is extremely low and the photocatalytic activity is extremely suppressed, it can be used for paints in a wide range of fields including outdoor applications where acid rain resistance is a concern.

The zinc oxide particles according to the present invention have
It can be blended with the resin composition or the coating composition in the range of 80% by weight.

When using zinc oxide in cosmetics, the production of active oxygen due to the photocatalytic activity of zinc oxide must be suppressed in order to protect the human body. Active oxygen is also known to be generated by ultraviolet light. Active oxygen includes superoxide, hydrogen peroxide, hydroxyl radical, singlet oxygen, etc., lipids, sugars, proteins,
It is said that DNA and the like are attacked to cause lipid peroxidation, protein denaturation, DNA damage, enzyme inhibition and the like, and as a result, to induce or promote various diseases such as skin cancer and skin photoaging.

Therefore, in order to protect the human body from skin disorders, not only the generation of active oxygen due to ultraviolet rays but also the suppression of the intrinsic photocatalytic ability of zinc oxide is a major factor.

Here, according to the present invention, in addition to the inherent ultraviolet shielding performance of zinc oxide, by dissolving iron or cobalt in zinc oxide, a long-wavelength A around 400 nm can be obtained.
In addition to being able to shield the UV rays in the area and thus not only protect the human body from active oxygen generated by the UV rays, the coating made of inert zinc silicate crystals on the surface makes the zinc oxide particles In addition, it can be effectively used for a sunscreen cosmetic because it is effectively isolated from active oxygen due to the intrinsic photocatalytic function of zinc oxide.

The zinc oxide particles according to the present invention have
It can be blended with cosmetics in the range of 80% by weight.

[0074]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples. In the following Examples and Comparative Examples, unless otherwise specified, the ultrafine zinc oxide used as the raw material zinc oxide particles had an average primary particle diameter of 0.06 μm obtained by evaporating and oxidizing an electro-zinc ingot. Ultrafine zinc oxide (FINEX-25 manufactured by Sakai Chemical Industry Co., Ltd.).

Example 1 An aqueous suspension of ultrafine zinc oxide (ZnO concentration 100 g /
L), at 60 ° C. under stirring, an aqueous solution of sodium silicate (1.3% by weight as SiO _{2 with} respect to ultrafine zinc oxide) and an aqueous solution of zinc sulfate (Z
3.7% by weight as nO). Then, the pH of this suspension was adjusted to 7.5 using an aqueous sodium hydroxide solution,
Aged for 30 minutes. This suspension was cooled to room temperature, filtered, washed with water, and then dried by heating at 120 ° C. for 5 hours in air. The obtained dried product is dried in air at 800 ° C. for 60 minutes.
After baking for 2 minutes, it is pulverized by a jet mill, and zinc oxide ultrafine particles having a coating layer of zinc silicate (5% by weight based on zinc oxide in terms of zinc silicate (Zn ₂ SiO ₄ )) on the surface of zinc oxide particles. A powder was obtained.

Example 2 An aqueous suspension of ultrafine zinc oxide (ZnO concentration 100 g /
L) except that an aqueous solution of sodium silicate (4.0% by weight as SiO _{2 with} respect to ultrafine zinc oxide) and an aqueous solution of zinc sulfate (11.0% by weight as ZnO with respect to ultrafine zinc oxide) were added to L). In the same manner as in Example 1, the surface of the zinc oxide particles was 15% by weight with respect to zinc oxide in terms of zinc silicate.
Ultrafine zinc oxide powder having a coating layer made of zinc silicate (Zn ₂ SiO ₄ ) was obtained.

Example 3 Aqueous suspension of basic zinc carbonate (ZnO concentration 100 g /
L), at 60 ° C. with stirring, an aqueous solution of sodium silicate (1.3% by weight as SiO _{2 with} respect to zinc oxide) and an aqueous solution of zinc sulfate (3.7% by weight as ZnO with respect to zinc oxide). added. Next, the pH of this suspension was adjusted to 7.5 using an aqueous solution of sodium hydroxide, and the suspension was aged for 30 minutes. This suspension was cooled to room temperature, filtered, washed with water, and then dried by heating at 120 ° C. for 5 hours in air. After baking the obtained dried product in air at 800 ° C. for 60 minutes,
Ultra-fine zinc oxide particles having a coating layer composed of 5% by weight of zinc silicate based on zinc oxide in terms of zinc silicate (Zn ₂ SiO ₄ ) on the surface thereof, while being subjected to jet mill pulverization to generate zinc oxide particles. A powder was obtained.

Example 4 An aqueous suspension of ultrafine zinc oxide (ZnO concentration 100 g /
L), at 60 ° C. under stirring, an aqueous solution of sodium silicate (1.3% by weight as SiO _{2 with} respect to ultrafine zinc oxide) and an aqueous solution of zinc sulfate (Z
3.7% by weight as nO). Then, the pH of this suspension was adjusted to 7.5 using an aqueous sodium hydroxide solution,
Aged for 30 minutes. This suspension was cooled to room temperature, filtered, washed with water, and then dried by heating at 120 ° C. for 5 hours in air.

The dried product thus obtained is put in the air,
After baking at 800 ° C. for 60 minutes, the mixture was pulverized by a hammer mill, dispersed in water so that the ZnO concentration became 100 g / L, and pulverized by a sand mill to prepare an aqueous suspension of ultrafine zinc oxide.

While the suspension is being well stirred, bring the suspension to 60 ° C.
The temperature is raised and the zinc oxide is_TwoO _Three3% by weight
Aqueous solution of sodium aluminate was added and aged for 10 minutes
Thereafter, the suspension was neutralized to pH 7.0 using sulfuric acid. 30 minutes
Aging and then the suspension thus obtained is filtered.
After being washed with water, it was dried by heating at 120 ° C. for 5 hours.

The dried product thus obtained is pulverized by a jet mill to form a coating layer comprising 5% by weight of zinc silicate in terms of zinc silicate on the surface of zinc oxide particles. Further, on the outside thereof, Al ₂ O ₃
A second consisting of 3% by weight of hydrous aluminum oxide
Ultrafine zinc oxide powder having a coating layer of

Example 5 While stirring the zinc oxide ultrafine particle powder obtained in Example 1 in a super mixer, 3% by weight based on zinc oxide was added thereto.
Of methyl oxide polysiloxane (Silicone Oil KF-99, manufactured by Shin-Etsu Chemical Co., Ltd.) was sprayed to obtain ultrafine zinc oxide particles treated with methyl hydrogen polysiloxane.

Comparative Example 1 An aqueous suspension of ultrafine zinc oxide (ZnO concentration 100 g /
L), at 60 ° C. under stirring, with respect to zinc oxide,
A 5.0% by weight aqueous sodium silicate solution as iO ₂ was added. Next, the pH of this suspension was adjusted to 7.5 using sulfuric acid, and the suspension was aged for 30 minutes. After cooling such a suspension to room temperature, filtering and washing with water, the suspension was heated at 120 ° C. for 5 hours in air.
Heat and dry. The obtained dried product was pulverized by a jet mill to obtain ultrafine zinc oxide powder having a coating layer composed of 5% by weight of SiO _{2 in} terms of SiO _{2 on} the surface of zinc oxide particles.

Comparative Example 2 Ultrafine zinc oxide powder (FINEX manufactured by Sakai Chemical Industry Co., Ltd.)
-25) itself was used as a zinc oxide particle as a comparative example.

The following Examples 1 to 5 and Comparative Examples 1 and 2
Various tests were carried out to examine the structure and properties of the ultrafine zinc oxide powder obtained by the above method.

Test 1 (Identification of zinc silicate layer by X-ray diffraction method) Measurement range 2θ
FIG. 1 shows an X-ray diffraction chart of the zinc oxide ultrafine particle powder according to Example 1 in which the angle is in the range of 20 ° to 60 °. For comparison, the X-ray of the ultrafine zinc oxide powder itself according to Comparative Example 2 was used for comparison. FIG. 2 shows the diffraction chart. The ultrafine zinc oxide particles obtained in Example 1 had β-
It has a diffraction peak of Zn ₂ SiO ₄ . The ultrafine zinc oxide powder according to Example 3 also had the same X-ray diffraction pattern.

Test 2 The ultrafine zinc oxide particles obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were purified water and pH at 25 ° C.
The solubility of zinc oxide in the aqueous sulfuric acid solution (0.0005% by weight sulfuric acid aqueous solution) was measured by atomic absorption spectrometry. Table 1 shows the results. The ultrafine zinc oxide particles obtained in Example 5 were excluded from the present test because they were water-repellent. As is clear from Table 1, the ultrafine zinc oxide particles according to the present invention have extremely low solubility in pure water and aqueous sulfuric acid.

[0088]

[Table 1]

Test 3 The reactivity of the ultrafine zinc oxide particles obtained in Examples 1 to 3 and Comparative Examples 1 and 2 to fatty acids was examined. 3 g of ultrafine zinc oxide powder and 27 g of oleic acid (Kanto Chemical Co., Ltd. (special grade reagent)) were sufficiently mixed at room temperature to prepare a suspension, and the suspension was heated at 120 ° C. with warm air. In a dryer, add zinc oxide to oleic acid (melting point 24
C) to produce zinc oleate (melting point 78 ° C.) in an atmosphere of 120 ° C.

As a result, the zinc oxide ultrafine particles according to Comparative Examples 1 and 2 all reacted with oleic acid under the above conditions to form zinc oleate. Solution. On the contrary,
The ultrafine zinc oxide particles according to Examples 1 to 3 did not substantially react with oleic acid and remained unreacted, and thus the suspension remained. Therefore, it is shown that the zinc oxide ultrafine particle powder according to the present invention effectively suppresses the reaction with the fatty acid.

Test 4 Using the ultrafine zinc oxide particles obtained in Examples 1 to 4 and Comparative Examples 1 and 2, a water-soluble acrylic polymer having a carboxyl group (an acrylic acid-alkyl acrylate copolymer (Carbohydrate manufactured by Goodrich Co.) Paul 934))
The reactivity to was examined.

The above water-soluble polymer was dissolved in water to prepare an aqueous solution, and the aqueous solution was adjusted to pH 6.
By adjusting to 5, an aqueous gel containing 0.2% by weight of the water-soluble polymer was prepared. Ultrafine zinc oxide powder at a concentration of 12% by weight was added to the aqueous gel of the water-soluble polymer, and the mixture was stirred at 5000 rpm for 5 minutes using a homomixer.
The slurry thus obtained was placed in a thermostat maintained at 38 ° C., and allowed to stand for 7 days.
5 ° C., B-type viscometer). Table 2 shows the results.
The ultrafine zinc oxide particles obtained in Example 5 were excluded from the present test because they were water-repellent.

[0093]

[Table 2]

As is clear from Table 2, the zinc oxide ultrafine powder according to the present invention hardly reacts with the above-mentioned polymer, so that the aqueous gel of the polymer retains its gel structure. The gel retained a high viscosity over time. On the other hand, both the zinc oxide ultrafine particles according to Comparative Example 1 and the zinc oxide ultrafine particles according to Comparative Example 2 having no coating layer react with the carboxyl groups of the polymer to change the gel structure of the polymer. It is thought that this was due to deterioration, but the viscosity significantly decreased with time.

Test 5 With respect to the ultrafine zinc oxide particles obtained in Examples 1 to 3 and Comparative Examples 1 and 2, the suitability for blending with a resin was evaluated.

3 g of ultrafine zinc oxide powder and polyethylene terephthalate resin powder (TR-4550 manufactured by Teijin Limited)
BH) was mixed well at room temperature with 15 g at 120 ° C.
After drying for a time, a sample was prepared using a melt indexer (Model C5059D, manufactured by Toyo Seiki Seisaku-sho, Ltd.).
It was extruded with a piston at a load of 875 g while maintaining the ambient temperature at 260 ° C. The extrusion weight per 10 minutes was calculated based on the time required for the extrusion and the extrusion weight at that time, and each was defined as the fluidity of the sample. Table 3 shows the results.

[0097]

[Table 3]

As is apparent from Table 3, the ultrafine zinc oxide powder according to Comparative Example 1 has a coating layer made of hydrated silicon oxide, and therefore, the crystal of the hydrated silicon oxide was obtained at an ambient temperature of 260 ° C. It is shown that the water hydrolyzed the polyethylene terephthalate resin, resulting in a liquid having a very low viscosity. Comparative Example 2
Also, the zinc oxide ultrafine particle powder according to the present invention has a tendency to decompose the polyethylene terephthalate resin, since it is higher than the melt flow rate of the resin alone.

On the other hand, since the zinc oxide ultrafine powder according to the present invention has a coating layer made of zinc silicate having no crystallization water on the surface, the polyethylene terephthalate resin can be used even at an ambient temperature of 260 ° C. Does not cause hydrolysis. Therefore, the zinc oxide ultrafine particle powder according to the present invention can be used as an ultraviolet ray shielding agent by kneading it into a polyethylene terephthalate resin without any problem of hydrolysis of the resin.

Test 6 The ultrafine zinc oxide particles obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were evaluated for the ability to block ultraviolet light and the transparency to visible light.

1.5 g of ultrafine zinc oxide powder was added to 7.9 g of squalane (manufactured by Nikko Chemicals Co., Ltd.) and 0.6 g of surfactant (Span 80 manufactured by Kao Corporation), and a paint shaker (manufactured by Red Devil Co., Ltd.) was added. After dispersing it in a vehicle using a No. 5410) to form a coating, this was coated on a polyethylene terephthalate film with a bar coater # 6.
A test piece was used.

Using a visible / ultraviolet spectrophotometer (V-550, manufactured by JASCO Corporation), the ultraviolet shielding ability in the A region at a wavelength of 350 nm and the transparency of visible light at a wavelength of 550 nm were evaluated. Table 4 shows the results.

[0103]

[Table 4]

The ultrafine zinc oxide powder according to the present invention has a high-density coating layer made of zinc silicate, but the ultraviolet shielding property and visible light transparency inherent in the ultrafine zinc oxide are not impaired at all, and are excellent. It has excellent ultraviolet shielding ability and high visible light transparency.

Example 6 Aqueous suspension of ultrafine zinc oxide (ZnO concentration 100 g /
To L), an aqueous ferrous sulfate solution (4% by weight in terms of iron based on ultrafine zinc oxide) and an aqueous sodium hydroxide solution were simultaneously added over 60 minutes while stirring at room temperature. During this time,
The pH of the suspension was maintained at 9. After aging for 30 minutes, the obtained aqueous suspension was heated to 60 ° C., and an aqueous sodium silicate solution (1.3% by weight as SiO _{2 with} respect to ultrafine zinc oxide) and an aqueous zinc sulfate solution (super 3.7% by weight of ZnO based on the fine zinc oxide) was added.

Next, the pH of the aqueous suspension was adjusted to 7.5 using an aqueous solution of sodium hydroxide, and the mixture was aged for 30 minutes. This suspension was cooled to room temperature, filtered, washed with water, and dried by heating at 120 ° C. for 5 hours in the air.
The obtained dried product is calcined in air at 900 ° C. for 60 minutes, and then pulverized by a jet mill to obtain a solid solution of 4% by weight of iron in zinc oxide with respect to zinc oxide. Zinc silicate (Zn ₂ SiO ₄ ) against zinc oxide on the surface
Ultra-fine powder of iron-dissolved zinc oxide having a coating layer composed of 5.0% by weight of zinc silicate was obtained.

Example 7 An aqueous suspension of ultrafine zinc oxide (ZnO concentration 100 g /
L) in an aqueous solution of ferrous sulfate (8 in iron equivalent to zinc oxide)
8% by weight of iron with respect to zinc oxide in solid solution with zinc oxide, and a silica Ultrafine powder of iron-dissolved zinc oxide having a coating layer composed of 5.0% by weight of zinc silicate in terms of zinc oxide (Zn ₂ SiO ₄ ) was obtained.

Example 8 An aqueous zinc sulfate solution (100 g / L ZnO concentration) was mixed with an aqueous solution of ferrous sulfate at 4% by weight based on zinc oxide in terms of iron, and the pH of the resulting mixed aqueous solution was adjusted to an aqueous sodium carbonate solution. And 9 was used. After aging for 30 minutes, the resulting aqueous suspension was stirred at 60 ° C. at 60 ° C. with an aqueous solution of sodium silicate (1.3% by weight as SiO _{2 based on} zinc oxide) and an aqueous solution of zinc sulfate (based on zinc oxide). (3.7% by weight as ZnO).

Next, the pH of this suspension was adjusted to 7.5 using an aqueous sodium hydroxide solution, and the suspension was aged for 30 minutes. This suspension was cooled to room temperature, filtered, washed with water, and dried by heating at 120 ° C. for 5 hours in the air. The obtained dried product is baked at 800 ° C. for 60 minutes in the air, and then pulverized by a jet mill to produce zinc oxide.
% Of iron is dissolved in solid solution, and 5.0% of zinc oxide (Zn ₂ SiO ₄ ) is converted to zinc oxide on the particle surface.
An iron-dissolved zinc oxide ultrafine particle powder having a coating layer composed of zinc silicate by weight was obtained.

Example 9 The dried product obtained in the same manner as in Example 6 was dried in air at 800
After baking at 60 ° C. for 60 minutes, the mixture is crushed with a hammer mill and dispersed in water so that the zinc oxide concentration becomes 100 g / L.
The mixture was pulverized with a sand mill to prepare an aqueous suspension of iron-dissolved ultrafine zinc oxide. The suspension was heated to 60 ° C. with stirring, and a 3% by weight aqueous solution of sodium aluminate in terms of Al ₂ O ₃ was added to zinc oxide, and the mixture was aged for 10 minutes.
Neutralized to pH 7.0 with sulfuric acid.

After aging for 30 minutes, the resulting suspension was filtered, washed with water, and dried by heating at 120 ° C. for 5 hours. The obtained dried product is pulverized by a jet mill, and 8% by weight of iron in terms of iron with respect to zinc oxide is dissolved in the zinc oxide, and zinc silicate (Zn ₂ Si
O ₄₎ having a coating layer comprising 5.0 wt% of zinc silicate in terms of further, Al relative to zinc oxide on the outside of the coating layer
Ultrafine iron-dissolved zinc oxide powder having a second coating layer composed of 3% by weight of hydrous aluminum oxide in terms of ₂ O ₃ was obtained.

Comparative Example 3 A mixed powder comprising 92 parts by weight of ultrafine zinc oxide and 8 parts by weight of ultrafine iron oxide (FRO-3 manufactured by Sakai Chemical Industry Co., Ltd.) having an average particle diameter of 0.03 μm was prepared. Comparative Example 4 Ultrafine zinc oxide powder (FINEX manufactured by Sakai Chemical Industry Co., Ltd.)
-25) itself was used as a zinc oxide particle as a comparative example.

Hereinafter, Examples 6 to 9 and Comparative Examples 3 and 4 will be described.
Various tests were carried out to examine the structure and properties of the ultrafine zinc oxide powder obtained by the above method.

Test 7 (Identification of Zinc Silicate Layer by X-ray Diffraction Method) The iron-dissolved zinc oxide ultrafine particles obtained in Examples 6 and 8 were both zinc oxide ultrafine particles obtained in Example 1. The powder shows substantially the same X-ray diffraction pattern as the powder, with β-
It has a diffraction peak of Zn ₂ SiO ₄ .

Test 8 In the same manner as in Test 3, each of the iron-dissolved ultrafine zinc oxide particles obtained in Examples 6 and 7 was mixed with oleic acid at room temperature to prepare a suspension. , But
The iron-dissolved zinc oxide ultrafine particles did not substantially react with oleic acid, remained unreacted, and thus remained in suspension.

Test 9 The iron-dissolved zinc oxide ultrafine particles obtained in Examples 6 to 9 and Comparative Examples 3 and 4 were examined for the ultraviolet ray shielding effect in the region A and the transparency of visible light.

Iron-dissolved zinc oxide ultrafine powder (2 g), room temperature drying type acrylic resin (D-Nippon Ink Chemical Industry Co., Ltd. A-
132, a solid content of 50% by weight) and a solvent were treated with a paint shaker (Model 5410, manufactured by Red Devil Co.) to obtain a dispersion of the iron-dissolved zinc oxide ultrafine particles.
Thereafter, 12 g of a room-temperature-dry type acrylic resin was further added thereto, mixed well, and dispersion-stabilized to prepare a paint containing 20% by weight of iron-dissolved zinc oxide ultrafine particles. This was applied on a polyethylene terephthalate film with a bar coater # 10 and dried at room temperature for 4 hours to obtain a test piece.

Using a spectrophotometer (Model V-550, manufactured by JASCO Corporation), the transmittance of ultraviolet light in the region A at wavelengths of 350 nm and 385 nm and the light transmittance in the visible region at 550 nm were measured. The region was evaluated for its ability to block ultraviolet light and its transparency to visible light. Table 5 shows the results.

[0119]

[Table 5]

As is clear from Table 5, the ultrafine iron-dissolved zinc oxide particles according to the present invention have a low transmittance of ultraviolet light in the region A, and the ultraviolet light in a longer wavelength region than 380 nm, which is the original absorption edge of zinc oxide. The shielding effect on the screen is improved. Further, the transparency is almost the same as that of the ultrafine zinc oxide particles of Comparative Example 4.

Test 10 The iron-dissolved ultrafine zinc oxide particles obtained in Examples 6 to 9 and Comparative Examples 3 and 4 were treated in the same manner as in Test 2.
Pure water at 25 ° C. and a sulfuric acid acid solution of pH 4 (0.00
(A 05% by weight aqueous sulfuric acid solution). Table 6 shows the results. As is evident from Table 6, the iron-dissolved ultrafine zinc oxide particles according to the present invention have extremely low solubility in water and aqueous sulfuric acid.

[0122]

[Table 6]

Test 11 A paint containing the iron-dissolved zinc oxide ultrafine particles obtained in Examples 6 to 9 and Comparative Examples 3 and 4 was prepared, and its weather resistance was examined by an outdoor exposure test.

4 g of iron-dissolved zinc oxide ultrafine particles powder, a room temperature drying type acrylic resin (D-Nippon Ink Chemical Industry Co., Ltd.
470, a solid content of 70% by weight) and a solvent were treated with a paint shaker (Model 5410 manufactured by Red Devil Co.) to obtain a dispersion of the iron-dissolved zinc oxide ultrafine particles.
Thereafter, 45 g of a room-temperature-dry type acrylic resin and 0.3 g of a curing agent were further added thereto, mixed well, and dispersed and stabilized.
A paint containing 10% by weight of iron-dissolved zinc oxide ultrafine particles was prepared. This was applied on a polyethylene terephthalate film with a bar coater # 10 and dried at room temperature for 4 hours to obtain a test piece.

The paint was 23 cm long, 10 cm wide, and had a thickness of 23 cm.
The coating was applied uniformly to a 1.4 cm cedar board at a coating amount of 54 g / cm ² without returning the brush vertically. Thereafter, after drying at room temperature for 3 days, the film was exposed for 120 days under the condition of a south-facing elevation angle of 45 °. Using a color difference meter (SM-5, manufactured by Suga Test Instruments Co., Ltd.), the L, a, and b values of the Hunter color system were measured, and the color difference ΔE before and after exposure was calculated based on the values. The smaller this value is, the better the weather resistance is.

[0126]

[Table 7]

As is clear from Table 7, Comparative Examples 3 and 4
According to the paint using zinc oxide according to the present invention, the discoloration of the coated surface is large, whereas the iron-dissolved zinc oxide according to the present invention suppresses the discoloration and is excellent in the effect of protecting the substrate.

Example 10 An aqueous solution of cobalt sulfate (12% by weight based on ultrafine zinc oxide in terms of cobalt oxide (CoO)) and water were added to ultrafine zinc oxide (ZnO concentration 100 g / L) at room temperature with stirring. An aqueous sodium oxide solution was added simultaneously over 60 minutes. During this time, the pH of the suspension was maintained at 8. After aging for 30 minutes, the obtained aqueous suspension was heated to 60 ° C., and a 2.4% by weight aqueous solution of sodium silicate as SiO _{2 with} respect to zinc oxide was added. A 6.5% by weight aqueous zinc sulfate solution was added as zinc (ZnO).

Next, the pH of this suspension was adjusted to 7.5 using an aqueous sodium hydroxide solution, and the suspension was aged for 30 minutes. The suspension thus obtained was cooled to room temperature, filtered,
After washing with water, it was dried by heating at 120 ° C. for 5 hours in the air. The obtained dried product is baked at 900 ° C. for 60 minutes in the air, and then pulverized by a jet mill, and 12% by weight of cobalt in terms of cobalt oxide (CoO) with respect to zinc oxide forms a solid solution in zinc oxide. In addition, an ultrafine cobalt solid solution zinc oxide powder having a coating layer of 8.9% zinc silicate in terms of zinc oxide (Zn ₂ SiO ₄ ) with respect to zinc oxide on the surface thereof was obtained.

Example 11 A 12% by weight aqueous solution of cobaltous sulfate in terms of cobalt oxide (CoO) was mixed with an aqueous solution of zinc sulfate (100 g / L of ZnO) with respect to zinc oxide. After an aqueous sodium solution was added to pH 8 over 60 minutes, the mixture was aged for 30 minutes. Next, the resulting aqueous suspension was heated to 60 ° C., and SiO ₂ was added to zinc oxide.
Then, a 2.4% by weight aqueous solution of sodium silicate was added, and then a 6.5% by weight aqueous solution of zinc sulfate as zinc oxide (ZnO) was added to zinc oxide.

Next, the aqueous suspension thus obtained is
PH adjusted to 7.5 by adding aqueous sodium hydroxide solution
And aged for 30 minutes. The suspension thus obtained
Is cooled to room temperature, filtered, washed with water, and then at 120 ° C for 5 hours.
During the heating, it was dried by heating. The obtained dried product is in air at 900 ° C.
After calcination for 60 minutes in a jet mill,
12% by weight of cobalt oxide (CoO) based on lead
Cobalt is dissolved in zinc oxide and its surface
Zinc silicate (Zn)_TwoSiO _Four) Conversion
With a coating consisting of 8.9% zinc silicate
Solid solution zinc oxide ultrafine powder was obtained.

Example 12 A dried product obtained in the same manner as in Example 11 was dried at 800 ° C. for 6 hours.
After baking for 0 minutes, the mixture is coarsely crushed by a hammer mill, dispersed in water so as to have a zinc oxide (ZnO) concentration of 100 g / L, and crushed by a sand mill to obtain an aqueous suspension of ultrafine zinc oxide solid solution zinc oxide. Prepared.

The temperature of the suspension was raised to 60 ° C. with stirring, a 3% by weight aqueous solution of sodium aluminate in terms of Al ₂ O ₃ was added to zinc oxide, the mixture was aged for 10 minutes, and sulfuric acid was added. , PH 7.0. After aging for 30 minutes, the resulting suspension was filtered, washed with water, and dried by heating at 120 ° C. for 5 hours. The obtained dried product is pulverized by a jet mill to form a solid solution in cobalt zinc oxide of 12% by weight in terms of cobalt oxide (CoO) with respect to zinc oxide. It has a coating layer composed of 8.9% by weight of zinc silicate in terms of zinc (Zn ₂ SiO ₄ ), and further, outside the coating layer, a water content of 3% by weight in terms of Al ₂ O _{3 with} respect to zinc oxide. Ultrafine cobalt solid solution zinc oxide powder having a second coating layer made of aluminum oxide was obtained.

Comparative Example 5 A 12% by weight aqueous solution of cobaltous sulfate in terms of cobalt oxide (CoO) with respect to zinc oxide was mixed with an aqueous solution of zinc sulfate (100 g / L of ZnO), and an aqueous solution of sodium carbonate was added. The pH was set to 8. After aging for 30 minutes, the mixture was filtered, washed with water, heated at 120 ° C. for 5 hours, and dried. After baking the obtained dried product at 400 ° C. for 60 minutes,
Jet mill pulverization was performed to obtain zinc oxide ultrafine powder in which 12% by weight of cobalt was converted to cobalt oxide (CoO) as a solid solution with respect to zinc oxide.

Comparative Example 6 Ultrafine zinc oxide powder (FINEX manufactured by Sakai Chemical Industry Co., Ltd.)
-25) itself was used as a zinc oxide particle as a comparative example.

Test 12 (Identification of Zinc Silicate Layer by X-Ray Diffraction Method) The ultra-fine zinc solid oxide powder obtained in Examples 10 and 11 was substantially the same as the ultra-fine zinc oxide powder obtained in Example 1. Shows the same X-ray diffraction pattern, and β-Zn around 22 ° and 26 °.
_It has a diffraction peak of ₂ SiO ₄ .

Test 13 In the same manner as in Test 3, the cobalt-dissolved ultrafine zinc oxide particles obtained in Examples 10 and 11 were mixed with oleic acid at room temperature to prepare a suspension. Although retained, the iron-dissolved zinc oxide ultrafine particles did not substantially react with oleic acid and remained unreacted, and thus remained in suspension.

Test 14 With respect to the ultra-fine particles of the cobalt-dissolved zinc oxide obtained in Examples 10 to 12 and Comparative Examples 5 and 6, the effect of shielding ultraviolet light in the region A and the transparency of visible light were examined.

2 g of ultra-fine cobalt solid solution zinc oxide powder,
Room temperature drying type acrylic resin (Dainippon Ink and Chemicals Co., Ltd.)
A-132, solid content 50% by weight) and a solvent were treated with a paint shaker (Model 5410, manufactured by Red Devil Co., Ltd.) to obtain a dispersion of the above-mentioned ultra-fine particles of cobalt solid solution zinc oxide. Then, a room temperature drying type acrylic resin 12
g was further added, mixed well, and dispersion-stabilized to prepare a coating material containing 20% by weight of cobalt solid solution ultrafine zinc oxide powder. This was applied on a polyethylene terephthalate film with a bar coater # 10 and dried at room temperature for 4 hours to obtain a test piece.

Using a spectrophotometer (Model V-550, manufactured by JASCO Corporation), the transmittance of ultraviolet light in the A region at wavelengths of 350 nm and 385 nm and the transmittance of light in the visible region at 550 nm were measured. A-area UV shielding ability and transparency were evaluated. Further, the total transmittance in the measurement range of 250 to 800 nm was measured. The results are shown in Table 8 and FIG.

[0141]

[Table 8]

As apparent from Table 8 and FIG. 3, the ultrafine particles of the cobalt-dissolved zinc oxide according to the present invention have an extremely low transmittance in the ultraviolet region A, particularly near 400 nm, and are the original absorption edges of zinc oxide. The effect of blocking ultraviolet rays in a wavelength region longer than 380 nm is improved. Also, transparency,
It is almost the same as the ultrafine zinc oxide of Comparative Example 6.

Test 15 The cobalt solid solution zinc oxide ultrafine particles obtained in Examples 8 and 9 and Comparative Examples 4 and 5 were treated in the same manner as in Test 3 with pure water at 25 ° C. and a sulfuric acid solution (pH 0 The solubility of zinc oxide in .0005% by weight sulfuric acid aqueous solution) was measured. Table 9 shows the results. As is evident from Table 9, the ultra-fine cobalt solid solution zinc oxide powder according to the present invention has remarkably low solubility in water and an aqueous sulfuric acid solution.

[0144]

[Table 9]

[0145]

As described above, the zinc oxide particles according to the present invention have a coating layer made of zinc silicate on the surface.
While having excellent ultraviolet shielding ability and high visible light transparency, the intrinsic surface activity of zinc oxide is suppressed, and therefore, the solubility in water and sulfuric acid aqueous solution is extremely small, and the photocatalytic function is also suppressed. Because of the resin, paint,
In various fields such as cosmetics, it can be suitably used as an ultraviolet shielding agent.

Further, according to the present invention, the zinc oxide particles having a coating layer made of zinc silicate on the surface and having solid solution of iron or cobalt have a longer wavelength than the ultraviolet shielding wavelength of the region A inherent to zinc oxide. Ultraviolet light, and has excellent transparency.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction chart of zinc oxide particles according to the present invention (Example 1).

FIG. 2 is an X-ray diffraction chart of zinc oxide ultrafine particle powder (Comparative Example 2).

FIG. 3 is a graph showing the light transmittance of ultrafine cobalt-dissolved zinc oxide particles according to the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 201/00 C09D 201/00 // A61K 7/42 A61K 7/42 C09K 3/00 104 C09K 3/00 104Z (72) Inventor Keita Kobayashi 110 Izumi-machi Shimokawa-shi Tajuku, Iwaki-shi, Fukushima Prefecture Inside the Onahama Plant of Sakai Chemical Industry Co., Ltd. Onahama Office

Claims (14)

[Claims] 1. A method according to claim 1, wherein the surface of the zinc oxide is zinc silicate (Zn).
₂ SiO ₄₎ Zinc oxide particles with reduced surface activity and having a coating layer made of zinc silicate in the range of 0.5 to 50 wt% in terms of. 2. The zinc oxide particles according to claim 1, wherein iron is dissolved in the zinc oxide in a range of 0.1 to 20% by weight. 3. Cobalt oxide (Co) is added to zinc oxide.
2. The zinc oxide particles according to claim 1, wherein the zinc oxide particles are dissolved in a range of 0.5 to 30% by weight in terms of O). 4. An organosilicon compound, a higher fatty acid, a higher fatty acid ester in the range of 1 to 20% by weight based on zinc oxide,
The zinc oxide particles according to any one of claims 1 to 3, further treated with metallic soap, polyhydric alcohol or alkanolamine. 5. The method according to claim 1, wherein the first coating layer made of zinc silicate is provided on the first coating layer.
A second oxide made of at least one element selected from the group consisting of Al, Ti, Zr, Sn, Sb and a rare earth element in an amount of 0.5 to 30% by weight in terms of oxide with respect to zinc oxide; The zinc oxide particles according to any one of claims 1 to 3, further comprising a coating layer. 6. An organosilicon compound, a higher fatty acid, a higher fatty acid ester in the range of 1 to 20% by weight based on zinc oxide,
The zinc oxide particles according to claim 5, further treated with metallic soap, polyhydric alcohol or alkanolamine. 7. The zinc oxide particles according to claim 1, having an average particle size of 0.15 μm or less. 8. The zinc oxide particles according to claim 1, having a solubility in pure water of 2 ppm or less as Zn and a solubility in a 0.0005% by weight aqueous sulfuric acid solution of 20 ppm or less as Zn. . 9. A resin composition comprising the zinc oxide particles according to claim 1 in a range of 1 to 80% by weight. 10. A coating composition comprising the zinc oxide particles according to claim 1 in an amount of 1 to 80% by weight. 11. A cosmetic comprising the zinc oxide particles according to claim 1 in an amount of 1 to 80% by weight. 12. An aqueous suspension of particles of a water-insoluble zinc compound is mixed with an aqueous solution of a water-soluble silicate and a water-soluble zinc salt in a stoichiometric ratio to form zinc silicate (Zn ₂ SiO ₄ ). And zinc oxide (Zn ₂ SiO)
₄ ) After adding an amount in the range of 0.5 to 50% by weight in conversion, washing with water, drying, and then heating to a temperature in the range of 300 to 1200 ° C. to generate zinc oxide particles, and The method for producing zinc oxide particles according to claim 1, wherein a coating layer made of zinc silicate is formed on the surface of the particles. 13. An iron-based amount of 0.1 to 20 times the weight of zinc oxide.
% Iron oxide hydroxide or Kovar oxide against zinc oxide
0.5 to 30% by weight of hydrated Kovar in terms of (COO)
After depositing it on the surface of the water-insoluble zinc compound particles.
Water-soluble silicate in aqueous suspension of zinc compound particles such as
And aqueous solutions of water-soluble zinc salts with zinc silicate (Zn
_TwoSiO_Four) To form a stoichiometric ratio and zinc oxide
Against zinc silicate (Zn_TwoSiO_Four0.5) in conversion
After adding an amount in the range of 0% by weight, washing with water, drying,
And heat to a temperature in the range of 300 to 1200 ° C. to oxidize
While generating zinc particles, the surface of the particles is silicic acid
Claims characterized in that a coating layer made of zinc is formed.
Item 4. The method for producing zinc oxide particles according to item 2 or 3. 14. An iron equivalent to a water-soluble zinc salt and zinc oxide.
An aqueous solution containing 0.1 to 20% by weight of a water-soluble iron salt, or
Is the equivalent of cobalt oxide to water-soluble zinc salt and zinc oxide.
Aqueous solution containing 0.5 to 30% by weight of a water-soluble cobalt salt
Add a neutralizing agent and remove the zinc and iron coprecipitate or zinc and iron
Prepare an aqueous suspension containing the coprecipitate of
Add the water-soluble silicate and water-soluble zinc salt
The solution was zinc silicate (Zn_TwoSiO_Four) To form stoichiometry
In a ratio and with zinc oxide to zinc silicate (Zn _TwoSi
O_Four) After adding the amount in the range of 0.5 to 50% by weight in conversion,
Rinse with water, dry, then heat in the range of 300-1200 ° C.
Heat to produce zinc oxide particles,
Solid solution of iron or cobalt in the particles and the surface
Characterized in that a coating layer made of zinc silicate is formed on
The method for producing zinc oxide particles according to claim 2.