JP3496858B2 - Method for producing ultrafine zinc oxide - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing ultrafine zinc oxide excellent in ultraviolet ray shielding property and visible light transmitting property, and more specifically, it is incorporated into resin products, cosmetics, paints, inks and the like. The present invention relates to a method for producing ultrafine zinc oxide suitable for use, which is excellent in ultraviolet ray shielding property and visible light transmittance, or a method for producing coated ultrafine zinc oxide which is excellent in storage stability and dispersibility on it. .

[0002]

2. Description of the Related Art Ultraviolet rays, especially ultraviolet rays having a wavelength of 300 to 400 nm, cause a sunburn phenomenon on the skin,
It causes blackening and inflammation. In addition, this ultraviolet light decomposes the matrix resin and fats and oils contained in resin products, cosmetics, paints, inks, etc., and also decomposes and discolors pigments, or oxidizes fats and oils and fragrances, causing deterioration and odor. Sometimes you can

Therefore, it has been attempted to use an ultraviolet shielding agent to solve these problems. Heretofore, ultrafine titanium oxide has been known as this ultraviolet shielding agent.
Although titanium oxide has an excellent shielding effect in the ultraviolet region, it has a refractive index (2.6%) in the visible region.
1-2.90, rutile type has a refractive index of zinc oxide (2.0
0 to 2.02), the transmittance is poor. Therefore, when this titanium oxide is mixed with a transparent material such as resin products, paints, and cosmetics, an opaque white color is exhibited. In addition to the zinc oxide, it has a drawback that the matrix is easily deteriorated by the irradiation of ultraviolet rays.

It has also been reported that ultrafine zinc oxide is used as another shielding agent. That is, Japanese Patent Laid-Open No. 2-2
JP08369 proposes to use zinc oxide having a specific surface area of 25 m ² / g, which is obtained by oxidizing metal zinc vapor by blowing air, as a UV shielding agent. Reference is made to the transmittance in the light ray region. However, since such a manufacturing method requires high temperature, ultrafine zinc oxide cannot be easily and inexpensively produced, and even when such ultrafine zinc oxide is used, it is possible to shield in the ultraviolet region. The effect and the transmittance in the visible light region were not always satisfactory.

On the other hand, Japanese Patent Laid-Open No. 62-275182 describes an ultraviolet shielding agent composed of a complex oxide of a metal such as aluminum or iron and zinc. By using these ultraviolet ray shielding agents, excellent shielding ability against ultraviolet rays and high transmittance for visible rays can be obtained. However, although these ultraviolet ray shielding agents initially have excellent ultraviolet ray shielding ability and high visible ray transmittance, they have the problem that these characteristics deteriorate over time and storage stability is poor. Therefore, this ultraviolet blocking agent cannot be used for a long period of time, and has a problem that it is not practical.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to have excellent shielding ability against ultraviolet rays and high visible rays. Ultra-fine zinc oxide having a well-balanced transmittance and having these characteristics not deteriorated with time, preferably having a specific surface area (in this specification, the specific surface area is a value measured by the BET method) of 30 to 100 m.
An object of the present invention is to provide a production method capable of easily and inexpensively producing ultrafine zinc oxide of ² / g. Another object of the present invention is to have an excellent shielding ability against ultraviolet rays, a well-balanced high transmittance to visible rays, and further, these characteristics are not deteriorated with time, and particularly excellent in storage stability and dispersibility. Another object of the present invention is to provide a method capable of easily and inexpensively producing ultrafine zinc oxide.

[0007]

As a result of various studies for achieving the above-mentioned object, the present inventor has found that a zinc salt aqueous solution and an alkaline aqueous solution are continuously stirred at a specific rotation speed in a reaction tank at high speed. The above object is achieved by reacting under specific conditions, filtering and washing the neutralized product generated by the reaction, then drying and calcining, and further treating the produced zinc oxide with a silicone oil or a fatty acid. As a result, it was found that ultrafine zinc oxide having excellent storage stability and dispersibility can be obtained, and the present invention was completed. That is, according to the method for producing ultrafine zinc oxide of the present invention, the zinc salt aqueous solution and the alkaline aqueous solution are added in a zinc: alkali equivalent ratio of 1: 1 to 1: 3.
The reaction mixture is charged into the reaction tank continuously and semi-continuously at different amounts and at the same time.
It is characterized in that the neutralized product produced in the reaction is continuously or semi-continuously taken out of the reaction tank by high-speed stirring at a rotation speed of 0 to 20,000 rpm, and then filtered, washed, then dried and calcined.

In the method for producing coated ultrafine zinc oxide of the present invention, the zinc salt aqueous solution and the alkaline aqueous solution are separately and separately in such a ratio that the zinc: alkali equivalent ratio is 1: 1 to 1: 3. At the same time, the reaction vessel is continuously or semi-continuously charged, the reaction vessel is continuously stirred at a high rotation speed of 2000 to 20000 rpm, and the neutralization product generated in the reaction is continuously or semi-continuously. Remove from reaction tank, then filter,
It is characterized in that it is washed, then dried and calcined, and then surface-treated with silicone oil or fatty acid.

The manufacturing method of the present invention will be specifically described below. The zinc salt aqueous solution used in the present invention can be prepared by dissolving zinc sulfate, zinc chloride, zinc nitrate and the like in water. The aqueous solution may optionally contain a small amount of acid. The aqueous alkali solution used in the present invention is an aqueous solution of an alkali metal hydroxide, an aqueous solution of an alkali metal carbonate, an aqueous solution of an alkali metal oxalate, or the like. As the above zinc salt and alkali, commercially available products can be used as they are.

In the present invention, these zinc salt aqueous solutions are preferably used at a concentration of 0.01 to 10 M (molar concentration, mol / l) to achieve better production efficiency and to achieve a narrower particle size distribution. In order to obtain the finer zinc oxide that it has, it is more preferable to use it at a concentration of 1 to 5 M, and to use the alkaline aqueous solution at a concentration of preferably 0.01 to 10 M, to achieve better production efficiency and In order to obtain finer zinc oxide having a narrow particle size distribution, it is more preferably used in a concentration of 0.1 to 10M. When the concentration of the aqueous solution of zinc salt and alkali is less than 0.01, the production efficiency tends to decrease, and when it exceeds 10 M, the zinc oxide particles produced tend to be coarsened, and ultrafine particles can be obtained. Tends to be difficult.

In the present invention, the zinc salt aqueous solution and the alkaline aqueous solution are separately and simultaneously prepared by using a pump whose flow rate can be adjusted so that the equivalent ratio of zinc: alkali is 1: 1 to 1: 3. Charge the reaction vessel continuously or semi-continuously. When the equivalent ratio of zinc: alkali charged into the reaction tank is larger than 1: 1; that is, when the amount of zinc is larger than the equivalent, the particles of zinc oxide tend to become coarse and ultrafine particles may be obtained. It is not preferable because it tends to be difficult. Further, if the equivalent ratio of zinc: alkali is smaller than 1: 3, that is, if the amount of zinc is smaller than one third of the equivalent, the production efficiency tends to decrease, which is not preferable.

In the present invention, the zinc salt aqueous solution and the alkaline aqueous solution are separately and simultaneously charged into the reaction tank, so that the reaction temperature and pH are maintained at substantially constant values.
In the present invention, the zinc salt aqueous solution and the alkaline aqueous solution are continuously charged so that the equivalent ratio of zinc: alkali is 1: 1 to 1: 3 as long as they are separately and simultaneously charged into the reaction tank. It may be charged and continuously taken out, or a fixed amount (for example, half amount) of the neutralized product-containing dispersion liquid in the reaction vessel is taken out, and after taking-out is stopped, the zinc salt aqueous solution and the alkaline aqueous solution are mixed with zinc: alkali. Equivalent ratio of 1: 1 to
Separately and simultaneously, at a ratio of 1: 3, the reaction solution is gradually and additionally charged until a predetermined amount is reached, and after a predetermined time, a certain amount of the neutralized product-containing dispersion liquid in the reaction tank is taken out. This may be repeated, that is, semi-continuously. By carrying out semi-continuously in this way, there is no risk that unreacted zinc salt will be taken out together when the neutralized product-containing dispersion liquid is taken out from the reaction tank, and therefore, the product particles will be coarse after being taken out. There is no danger of becoming

In the reaction tank, a neutralization product is deposited by the neutralization reaction. At this time, in order to obtain ultrafine zinc oxide, high-speed stirring is indispensable.
Perform high speed uniform stirring at 0 rpm. The neutralized product precipitated by the neutralization reaction is instantly diffused by such high speed stirring, coarsening of particles is suppressed, and ultrafine particles are promoted. If the stirring speed is less than 2000 rpm, the particles grow faster and the ratio of coarse particles increases.
It becomes difficult to obtain the desired ultrafine particles. Also, 20
If it is faster than 000 rpm, the flow of the reaction solution will be separated from the stirring blade and the stirring effect will be reduced.
There is no point in being faster than. Such stirring may be performed by an impeller mill or an in-line mixer, for example.

Stable operation is possible by precipitating the neutralization product by the neutralization reaction under the above-mentioned conditions, the quality is stable even in the case of mass production, and the specific surface area is 30 to 30. An ultrafine zinc oxide of 100 m ² / g is obtained. In the continuous or semi-continuous operation as described above, the neutralized product-containing dispersion liquid is gradually or continuously taken out, for example, from the lower part of the reaction vessel. The taken-out neutralized product-containing dispersion is subjected to solid-liquid separation, filtration, washing and drying, and further 300 to 1000 ° C., preferably 350 to 70.
In the temperature range of 0 ℃, under atmospheric pressure or reduced pressure (10mmHg
The following) is performed for 2 to 3 hours.

The ultrafine zinc oxide obtained in this way has a very active surface, so that it improves storage stability and dispersibility, and also when used in a resin product, paint, cosmetic or the like matrix or other For the purpose of preventing the reaction with the additive, the surface treatment can be carried out with silicone oil or fatty acid, if desired. As a concrete treatment method, silicone oil or fatty acid is dissolved in an organic solvent such as alcohols such as methanol or ethanol, or ketones such as acetone or methyl ethyl ketone, and zinc oxide is directly immersed in this solution, or is oxidized. It can be carried out by spraying zinc. After performing such processing, 80
Re-dry the zinc oxide at ~ 150 ° C.

Examples of the silicone oil which can be used for the surface treatment include dimethyl silicone oil, methylphenyl silicone oil, cyclic silicone oil, polyether silicone oil, modified silicone oil and methylhydrogen silicone oil. Examples of the fatty acid include saturated fatty acids such as n-decanoic acid, caprylic acid, lauric acid, stearic acid, behenic acid and palmitic acid, and unsaturated fatty acids such as linoleic acid, linoleic acid and oleic acid. The processing amount (coating amount) of these silicone oils and fatty acids is preferably such that the amount is 0.05 to 10% by weight based on the weight of zinc oxide.

The ultrafine zinc oxide obtained by the production method of the present invention has an excellent ultraviolet shielding effect, has a high transmittance in the visible light region, and the surface-treated coated ultrafine zinc oxide is a resin product. It does not react with the matrix or additives when blended in paints, cosmetics, etc., and also improves storage stability and dispersibility, and has an excellent UV shielding effect and high transmittance in the visible light region for a long time. It can be maintained throughout.

[0018]

EXAMPLES The present invention will be specifically described below based on examples. Example 1 A 3M zinc chloride aqueous solution and a 1M sodium carbonate aqueous solution were prepared. The zinc chloride aqueous solution and the sodium carbonate aqueous solution were separately and continuously fed into the reaction tank by adjusting the flow rate with a pump capable of adjusting the flow rate so that the zinc: alkali equivalent ratio was 1: 2. 60 with impeller mill
The neutralized product was deposited by high-speed stirring at a rotation speed of 00 rpm. During this time, no particular heating was performed and the pH was maintained at 6-8. Further, the same amount as the liquid fed to the reaction tank was continuously taken out from the reaction tank. Filtration and washing of the neutralized product-containing dispersion were repeated until the filtrate conductivity became 200 μs / cm or less, and the obtained cake was dried at 150 ° C. Then, it was fired in air at 400 ° C. for 3 hours to obtain ultrafine zinc oxide having a specific surface area of 50 m ² / g.

30 wt% of this zinc oxide powder was blended with a polyester resin, dispersed with glass beads for 1.5 hours with a paint shaker, coated on an OHP sheet with a bar coater, and dried at 70-80 ° C. A transparent coating film was obtained. When the transmittance of the obtained transparent coating film in the visible light region (400 to 700 nm) was measured with a turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd., it was 92%. Similarly, when the transmittance in the ultraviolet region (380 nm) was measured with a Hitachi spectrophotometer, it was 6%. The visible light transmittance of the transparent coating film obtained in the same manner as above except that the zinc oxide powder was not added was measured to be 98%. Further, the ultraviolet transmittance was similarly measured and found to be 98%.

Example 2 A 3M aqueous solution of zinc sulfate and a 1M aqueous solution of sodium carbonate were prepared. The zinc chloride aqueous solution and the sodium carbonate aqueous solution were separately and continuously fed into the reaction tank by adjusting the flow rate with a pump capable of adjusting the flow rate so that the zinc: alkali equivalent ratio was 1: 2. 60 with impeller mill
The neutralized product was deposited by high-speed stirring at a rotation speed of 00 rpm. During this time, no particular heating was performed and the pH was maintained at 6-8. Further, the same amount as the liquid fed to the reaction tank was continuously taken out from the reaction tank. Filtration and washing of the neutralized product-containing dispersion were repeated until the filtrate conductivity became 200 μs / cm or less, and the obtained cake was dried at 150 ° C. Then, it was baked in air at 400 ° C. for 3 hours to obtain ultrafine zinc oxide having a specific surface area of 65 m ² / g.

30% by weight of this zinc oxide powder was mixed with a polyester resin, dispersed with glass beads for 1.5 hours with a paint shaker, coated on an OHP sheet with a bar coater, and dried at 70-80 ° C. A transparent coating film was obtained. The visible light transmittance of the obtained transparent coating film was measured in the same manner as in Example 1, and it was 93%.
Also, the ultraviolet transmittance was similarly measured and found to be 5%.

Example 3 A 3M zinc chloride aqueous solution and a 1M sodium oxalate aqueous solution were prepared. The zinc chloride aqueous solution and the sodium carbonate aqueous solution were separately and continuously fed into the reaction tank by adjusting the flow rate with a pump capable of adjusting the flow rate so that the zinc: alkali equivalent ratio was 1: 2. The neutralized product was deposited by high-speed stirring with an impeller mill at a rotation speed of 6000 rpm. During this period, no particular heating was performed, and the pH was 6 to 8
Maintained at. Further, the same amount as the liquid fed to the reaction tank was continuously taken out from the reaction tank. Filtration of the neutralized product-containing dispersion,
The washing was repeated until the conductivity of the filtrate became 200 μs / cm or less, and the obtained cake was dried at 150 ° C. Then, it was fired in air at 400 ° C. for 3 hours to obtain ultrafine zinc oxide having a specific surface area of 100 m ² / g.

30 wt% of this zinc oxide powder was blended with a polyester resin, dispersed with glass beads by a paint shaker for 1.5 hours, applied to an OHP sheet with a bar coater, and dried at 70-80 ° C. A transparent coating film was obtained. The transparent coating film thus obtained was measured by a turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd.
The transmittance of 0 to 700 nm) was measured and found to be 94%. Similarly, the transmittance in the ultraviolet region (380 nm) was measured by a spectrophotometer manufactured by Hitachi, Ltd., and it was 4%.

Example 4 The method described in Example 1 was carried out semi-continuously. That is, half of the neutralized product-containing dispersion liquid in the reaction tank was taken out, and after the taking-out was stopped, the equivalence ratio of zinc: alkali was adjusted by a pump capable of adjusting the flow rates of the 3M zinc chloride aqueous solution and the 1M sodium carbonate aqueous solution. The flow rate was adjusted so that it became 1: 2, and they were separately and simultaneously continuously fed to the reaction tank until a predetermined amount was reached, and the inside of the reaction tank was 6000 with an impeller mill.
The neutralized product was precipitated by high-speed stirring at a rotation speed of rpm, and half an amount of the neutralized product-containing dispersion liquid in the reaction tank was taken out 2 minutes after stopping the feeding to the reaction tank. During this time, no particular heating was performed and the pH was maintained at 6-8. This operation was repeated. The ultrafine zinc oxide obtained was the same as that obtained in Example 1.

Example 5 The zinc oxide ultrafine powder obtained in Example 1 was surface-treated with silicone oil. That is, a silicone oil DC-3PA (purity 10%) for paint addition manufactured by Toray Dow Corning Co., Ltd. was used as the silicone oil, and 135 g of this silicone oil was added to 5 liters of toluene and stirred for 5 minutes, A toluene solution was prepared. 2.7 Kg of the zinc oxide ultrafine powder obtained in Example 1 was added to this solution, and the mixture was further stirred for 30 minutes. It was found that the powder obtained by filtering and drying at 120 ° C. was water repellent and was sufficiently covered with silicone oil. Further, the coating amount of silicone oil was 0.
It was 5% by weight.

30% by weight of this surface-treated zinc oxide powder was blended with a polyester resin, dispersed together with glass beads for 1.5 hours with a paint shaker, applied to an OHP sheet with a bar coater, and 70 to 80 ° C. And dried to obtain a transparent coating film. The visible light transmittance of the obtained transparent coating film was measured in the same manner as in Example 1. The result was 90.
%Met. Further, the ultraviolet transmittance was similarly measured and found to be 6%. Further, the transparent coating film was subjected to an environment resistance acceleration test for 240 hours under the conditions of a temperature of 40 ° C. and a relative humidity of 90%, and then the visible light transmittance was measured in the same manner as in Example 1 to find that it was 90%. there were. Further, the ultraviolet transmittance was measured and found to be 6%.

Example 6 Zinc oxide was surface-treated in the same manner as in Example 5 except that 300 g of n-decanoic acid and 30 L of methyl alcohol were used in place of 135 g of silicone oil and 5 L of toluene used in Example 4. And a transparent coating film was prepared. When the visible light transmittance of this transparent coating film was measured in the same manner as in Example 1, it was 92%. Also, when the ultraviolet transmittance was measured in the same manner, it was 6%.
Met. The temperature of this transparent coating film is 40
After performing an environment resistance acceleration test for 240 hours under conditions of ° C and relative humidity of 90%, the visible light transmittance was measured in the same manner as in Example 1, and it was 90%. Further, the ultraviolet transmittance was measured and found to be 7%.

Example 7 300 g of n-decanoic acid used in Example 6 was mixed with lauric acid 3
A surface-treated zinc oxide powder was obtained in the same manner as in Example 6 except that the amount was changed to 00 g, and a transparent coating film was prepared. When the visible light transmittance of this transparent coating film was measured in the same manner as in Example 1, it was 92%. Further, the ultraviolet transmittance was similarly measured and found to be 6%. Also,
About this transparent coating film, temperature 40 ℃, relative humidity 90%
After conducting the environment-resistant accelerated test for 240 hours under the condition of 1, the visible light transmittance was measured in the same manner as in Example 1,
It was 90%. Further, the ultraviolet transmittance was measured and found to be 8%.

[0029]

INDUSTRIAL APPLICABILITY As described above, according to the production method of the present invention, ultrafine zinc oxide can be obtained stably and uniformly on an industrial scale, and these ultrafine zinc oxide have excellent shielding ability against ultraviolet rays and Also, it has a high transmittance for visible light in a well-balanced manner, and when it is surface-treated, the storage stability is further improved, and these characteristics are maintained for a long period of time. Also, resin products, paints,
It does not react with the matrix or the like even when incorporated into cosmetics or the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08K 9/04 C08K 9/04 9/06 9/06 C09C 1/04 C09C 1/04 C09D 5/00 C09D 5/00 Z 7 / 12 7/12 Z C09K 3/00 104 C09K 3/00 104Z (58) Fields investigated (Int.Cl. ⁷ , DB name) C01G 1/00-23/08 A61K 7/00 A61K 7/02 A61K 7 / 42 C08K 3/22 C08K 9/04 C08K 9/06 C09C 1/04 C09D 5/00 C09D 7/12 C09K 3/00 104

Claims (3)

(57) [Claims] 1. A zinc salt aqueous solution and an alkaline aqueous solution are zinc:
Alkali equivalent ratios of 1: 1 to 1: 3 are separately and simultaneously charged into the reaction tank continuously or semi-continuously, and the reaction tank is continuously 2,000 to 20,000 rp.
Ultra-fine zinc oxide characterized by high-speed stirring at a rotation speed of m, the neutralization product generated in the reaction being continuously or semi-continuously taken out of the reaction vessel, followed by filtration, washing, drying and calcination. Manufacturing method. 2. The method according to claim 1, wherein ultrafine zinc oxide having a specific surface area of 30 to 100 m ² / g is produced. 3. A zinc salt aqueous solution and an alkaline aqueous solution are used as zinc:
Alkali equivalent ratios of 1: 1 to 1: 3 are separately and simultaneously charged into the reaction tank continuously or semi-continuously, and the reaction tank is continuously 2,000 to 20,000 rp.
Highly stirred at a rotation speed of m, the neutralization product generated by the reaction is continuously or semi-continuously taken out of the reaction tank, and then filtered, washed, dried and calcined, and then surface-treated with silicone oil or fatty acid. A method for producing a coated ultrafine zinc oxide, comprising: