JPH06145645A - Ultraviolet ray blocking agent and its production - Google Patents

Abstract

PURPOSE:To obtain an ultraviolet ray blocking agent excellent in transparency, stability and resistance to heat and chemicals, useful for coatings, etc., by dripping an aqueous cerium salt solution, under specified conditions, onto a specific aqueous pigment dispersion to cover the pigment with the resulting deposit followed by adding a silicate solution to the aqueous system to cover the pigment with the resulting deposit and then subjecting to baking. CONSTITUTION:An aqueous cerium salt solution such as of cerium sulfate is dripped, under heating, onto an aqueous dispersion of flaky pigment about 1.5-1.6 in refractive index selected from mica, talc, sericite, etc., at such an amount as to be 1-30wt.% in terms of CeO2 based on the pigment followed by adjusting the pH value of the aqueous system to 7-9 to deposit an insoluble compound such as cerium oxide on the pigment to cover the pigment with the cerium oxide. Then, a silicate solution such as of sodium silicate is added, under heating, to the aqueous dispersion to deposit amorphous silica on the pigment and cover it with the amorphous silica, followed by baking the resultant pigment at pref. 500 deg.C, thus obtaining the objective ultraviolet ray blocking agent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an inorganic ultraviolet blocking agent and a method for producing the same.

[0002]

2. Description of the Related Art It is widely known that ultraviolet rays have a strong effect on the living body, cause various changes in the skin, and deteriorate plastics. Therefore, in order to avoid this effect, various organic ultraviolet absorbers and inorganic ultraviolet blockers have been conventionally developed. Salicylic acid-based, benzophenone-based, benzotriazol-based, and cyanoacrylate-based UV absorbers have been used, and inorganic UV-blockers used include titanium oxide, zinc oxide, talc, kaolin, and iron oxide.

Organic UV absorbers have been used widely because they have the characteristic of being colorless and transparent when blended into plastics and cosmetics, but recently their safety has been a problem due to their toxicity, and their use is limited. Came to be. Among the inorganic ultraviolet blockers, titanium oxide is non-toxic, but it has the disadvantage that it cannot be used for those requiring transparency because it has a large hiding power, and zinc oxide and the like are mixed in plastics and cosmetics. Its catalytic action may limit its use because it may deteriorate the plastic or damage the skin.

Therefore, when blended into plastics, fibers, cosmetics, etc., it is desired to develop an inorganic ultraviolet blocking agent which is colorless and transparent, has good dispersibility, is nontoxic and does not show a catalytic action, and is heat and chemical resistant. Was there.

[0005]

In view of such circumstances, the present invention has heat resistance and chemical resistance and can block mid-ultraviolet rays and near-ultraviolet rays at the same time, and can be incorporated into plastics, fibers, paints, cosmetics, etc. It is an object of the present invention to provide an inorganic ultraviolet blocking agent that can effectively prevent harmful effects.

[0006]

The above problems are solved by the present invention. That is, in the ultraviolet blocking agent of the present invention, the surface of a flaky pigment selected from mica, talc, sericite having a refractive index of about 1.5 to 1.6 is coated with an insoluble cerium compound and amorphous silica. It is characterized by being a fired product of particles.

Further, in the present invention, 1 to 30% by weight of CeO ₂ as an aqueous solution of cerium salt is added dropwise to an aqueous dispersion of the flaky pigment under heating to adjust the pH to 7 to 9. Then, an insoluble cerium compound is deposited on the surface of the pigment to obtain a cerium-coated pigment, and then this aqueous dispersion is prepared.
The present invention proposes a method for producing an ultraviolet blocking agent, which comprises adding a silicate solution under heating to deposit and coat amorphous silica on the surface of the pigment, and then firing.

The present invention will be described in more detail below. As a result of various studies, the present inventors have conducted various studies on materials that have no toxicity or catalytic action and have good dispersibility and transparency when blended into plastics, fibers, paints, cosmetics and the like.
It has been found that inorganic pigments having a refractive index of about 5 to 1.6, particularly flaky pigments such as mica, talc and sericite are suitable.

Further, since cerium oxide has an ultraviolet ray blocking property, it is used to enhance the ultraviolet ray blocking effect by being contained in a lens of glasses, glass or the like. A chromatic inorganic pigment such as yellow lead and a water-soluble substance such as cerium nitrate are used. It is also known to improve the light resistance (UV resistance) by causing a cerium salt to act on the surface of the flakes. The present invention was successfully achieved by depositing a particulate pigment with an ultraviolet-blocking cerium compound by deposition.

To carry out the method of the present invention, a flake pigment selected from mica, talc, sericite or the like having a refractive index of about 1.5 to 1.6 is used as a starting material, and this is used as a dispersion machine or a dispersion machine. An aqueous dispersion is prepared using an emulsifier, and an aqueous cerium salt solution such as cerium chloride, cerium nitrate or cerium sulfate is added dropwise while heating at 60 ° C. or higher, preferably 80 ° C.
In this case, the dropping amount is appropriately 1 to 30% by weight as CeO _{2 with} respect to the flake pigment.

Then, phosphoric acid, phosphate solution, polyphosphoric acid solution, polyphosphate solution, carbonate solution such as sodium carbonate, oxalic acid, oxalate solution, aqueous ammonia, alkali hydroxide solution such as sodium hydroxide. After the addition of at least one of the above, the pH of the solution is adjusted to about 7 to 9, the insoluble cerium compound is deposited on the surface of the flaky pigment to form a coating layer. This is filtered, washed with water, dried and crushed to obtain a flaky cerium-coated pigment.

The cerium-coated pigment is dispersed in water using a disperser or an emulsifier. In this case, the pigment concentration of the dispersion liquid is appropriately 40% by weight or less for reasons of dispersibility. Next, the silicate solution is added to the aqueous dispersion while heating and stirring at 60 ° C. or higher, preferably 80 ° C. As the silicate, in addition to an inorganic salt such as sodium silicate, an organic silicate such as ethyl orthosilicate may be used.

By adding the silicate, amorphous silica is deposited on the particle surfaces of the flaky cerium-coated pigment. The amount of deposition is appropriately in the range of 2 to 40% by weight based on the flaky pigment coated with an insoluble cerium compound as SiO ₂ . At the same time, add mineral acids such as sulfuric acid and nitric acid,
After the addition of the silicate, the total amount of mineral acid is added to bring the pH of the solution to 9-11. When stirring is continued for further 30 minutes or more and neutralized with a mineral acid, amorphous silica is deposited on the surface of the pigment particles and the coating is completed. Therefore, if filtered, washed with water, dried and crushed, flaky cerium- A silica-coated pigment is obtained.

FIG. 1 shows a flaky cerium-silica-coated talc pigment (CeO ₂ coating amount 1) obtained by the above method.
0 wt%, SiO ₂ coating amount 18 wt%),
5 shows the results of measuring the light transmittance of five types of samples ,, and, where is unbaked, is 150 ° C.,
Is the result of measuring the light transmittance when fired at 200 ° C., at 500 ° C., and at 1000 ° C. for 2 hours.

From this figure, from the unfired to 200
Cerium-silica coated pigment below 300C is 300-400n
In the region of m, almost no ultraviolet blocking effect is exhibited, but it is shown that the ultraviolet blocking effect occurs when firing as in and of the present invention. It was also found that the effect of blocking ultraviolet rays can be obtained by coating silica after firing.

The light transmittance in this case is 0.5 for the sample pigment.
0.4 ml of castor oil was added to g to add a flavor-maler (5
(0 rotation), and after further adding 6 ml of clear lacquer and kneading, this kneading liquid was applied to a transparent quartz plate to a thickness of 35 μm, and a spectrophotometer (UV-2200 manufactured by Shimadzu Corporation) was applied.
Type).

By the above-mentioned and, the ultraviolet blocking agent of the present invention having transparency can be obtained. In this method, the coating amount of CeO ₂ is set to 10 to 30% by weight. Blocking effect is not effective, 30
This is because the transparency when blended in plastics and cosmetics is reduced when the content is more than 10% by weight. This relationship is clear from FIG. FIG. 2 shows the results of examining the transparency of the talc pigment calcined at 500 ° C. for 2 hours from the wavelength and the light transmittance. The CeO ₂ coating amount was set to 0, ₂ , 10, 30% by weight. The transparency of the types of samples, and, is shown.

The coating amount of SiO ₂ is set to 2 to 40% by weight because when it is 2% by weight or less, a dense coating of amorphous silica cannot be obtained and the protective action is poor, and when it is 40% by weight or more, it is free. This is because the amorphous silica deposits and impairs the dispersibility.

FIG. 3 shows that when the CeO ₂ coating amount is 10% by weight, S
₂ shows the results of examining the ultraviolet blocking effect from the relationship between the light transmittance and the wavelength of two types of talc pigment samples A and B having an iO ₂ coating amount of 0 and 18% by weight, which were baked at 500 ° C. for 2 hours. From this, the effect of blocking the ultraviolet rays by the SiO ₂ coating of the present invention is clear.

FIG. 4 shows a conventional talc pigment UV-screening agent (CeO ₂ coating amount 10% by weight, SiO ₂ coating amount 18% by weight) of the present invention as a sample C, and a conventional organic UV-screening agent (absorber, stabilizer). Is a specific amount), E is fine particle zinc oxide, F is fine particle titanium oxide, and G is a particle without a blocking agent. The results are shown in FIG. The ultraviolet blocking effect is slightly inferior to that of fine particle titanium oxide or fine particle zinc oxide, but is superior to that of organic type. Further, it can be seen that the light transmittance in the region of 400 to 800 nm is slightly inferior to that of the organic system, but is superior to that of titanium and fine particle zinc oxide, and has sufficient transparency.

[0021]

【Example】

Example 1 500 g of talc was dispersed in 10 liters of pure water, and then dispersed with a Despamill (manufactured by Hosokawa Micron) for 1 hour. While heating and stirring this dispersion at 80 ° C., 264 g of an aqueous cerium nitrate solution (CeO ₂ content 19% by weight, insoluble cerium compound deposition amount CeO ₂ of 10% by weight) was added dropwise. Then, a sodium hydroxide solution is added to neutralize the pH of the solution to 7 to 9, and cerium hydroxide is deposited on the surface of talc to form a coating layer. This was filtered, washed with water, dried and pulverized to obtain a flaky cerium-coated talc pigment.

The cerium-coated talc pigment is dispersed in 10 liters of pure water and then dispersed in a despamill for 1 hour. While heating and stirring the dispersion at 80 ° C. or higher, 348 g of sodium silicate No. 3 (SiO ₂ content 28.5% by weight, amorphous silica deposit amount SiO ₂ 18% by weight) is added. At this time, dilute sulfuric acid was also added to maintain the pH of the solution at 9 to 11, and stirring was continued for 1 hour, and then the pH was adjusted to 6 to 8 with sulfuric acid.
And This was filtered, washed with water, dried and pulverized to obtain a flaky cerium-silica-coated talc pigment. Next, the cerium-silica-coated talc pigment was added at a temperature of 500 ° C. to 2
After firing for an hour, the ultraviolet blocking agent (Ce of the present invention shown in FIG.
O ₂ 10 wt% -SiO ₂ 18 wt%) was obtained.

Example 2 500 g of mica was dispersed in 10 liters of pure water, and then dispersed for 1 hour with a Despamill (manufactured by Hosokawa Micron). While heating and stirring this dispersion at 80 ° C., 527 g of an aqueous cerium nitrate solution (CeO ₂ content 19% by weight, insoluble cerium compound deposition amount CeO ₂ of 20% by weight) was added dropwise. Subsequently, sodium carbonate solution was added to adjust the pH of the solution to 7
Neutralize to -9 to deposit cerium hydroxide on the surface of mica to form a coating layer. This was filtered, washed with water, dried and pulverized to obtain a flaky cerium-coated mica pigment.

Next, this cerium-coated mica pigment is dispersed in 10 liters of pure water and then dispersed in a despamill for 1 hour. No. 3 sodium silicate (SiO ₂ content 28.5% by weight, amorphous silica deposit amount 32% by weight as SiO ₂ content) 674 while heating and stirring this dispersion liquid at 80 ° C. or higher
g is added. At this time, dilute sulfuric acid was also added to adjust the pH of the solution to 9
Keep at ~ 11 and continue stirring for 1 hour, then pour with sulfuric acid.
H was set to 6-8.

This was filtered, washed with water, dried and pulverized to obtain a flaky cerium-silica-coated mica pigment. Next, the cerium-silica-coated mica pigment was treated at a temperature of 90
CeO ₂ 20 wt% -SiO ₂ by firing at 0 ° C. for 2 hours
32% by weight of UV blocker was obtained. This ultraviolet blocking agent also had a sufficient ultraviolet blocking effect and light transmittance as in the previous example.

[0026]

The ultraviolet blocking agent of the present invention is particularly useful for UV-B.
It has an excellent effect of blocking ultraviolet rays in the vicinity, has no toxicity or catalytic action, and has excellent heat resistance and chemical resistance. Further, when it is blended with plastics, fibers, paints, cosmetics, etc., it is expected to be applied in a wide range of fields in the future because it is colorless and transparent and dispersible.

[Brief description of drawings]

FIG. 1 is a graph showing an ultraviolet blocking effect of an ultraviolet blocking agent containing the present invention depending on firing conditions.

FIG. 2 is a graph showing the relationship between CeO ₂ coating amount and transparency of an ultraviolet blocking agent containing the present invention.

FIG. 3 is a graph showing a SiO ₂ coating amount and an ultraviolet blocking effect of an ultraviolet blocking agent including the present invention.

[Explanation of Codes] Unfired, 150 ° C. fired, 200 ° C. fired, 500
℃ firing, 1000 ℃ firing. No CeO ₂ coating, coating amount-2% by weight, 10% by weight 30% by weight. A, Si
No O ₂ coating, coating amount-B 18% by weight, C, present invention,
D, conventional organic UV absorber, G, no blocking agent added,
E, fine particle zinc oxide, F, fine particle titanium oxide

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[Procedure amendment]

[Submission date] July 16, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Added

[Correction content]

[Brief description of drawings]

FIG. 1 is a graph showing an ultraviolet blocking effect of an ultraviolet blocking agent containing the present invention depending on firing conditions.

FIG. 2 is a graph showing the relationship between CeO ₂ coating amount and transparency of an ultraviolet blocking agent containing the present invention.

FIG. 3 is a graph showing the SiO ₂ coating amount and ultraviolet blocking effect of the ultraviolet blocking agent containing the present invention.

FIG. 4 is a graph showing the ultraviolet blocking effect between the ultraviolet blocking agent C obtained in Example 1 of the present invention and a conventional product.

Claims (6)

[Claims] 1. A calcined product of particles obtained by coating the surface of a flaky pigment selected from mica, talc, sericite, etc. having a refractive index of about 1.5 to 1.6 with an insoluble cerium compound and amorphous silica. An ultraviolet blocker characterized by being present. 2. The insoluble cerium compound is cerium oxide,
The ultraviolet blocking agent according to claim 1, which is selected from cerium hydroxide, cerium phosphate, cerium polyphosphate, cerium carbonate, cerium oxalate and the like. 3. The coating amount of the insoluble cerium compound is CeO 2.
_2. The ultraviolet blocking agent according to claim 1, which is 1 to 30% by weight based on the flaky pigment as ₂ . 4. The ultraviolet blocking agent according to claim 1, wherein the coating amount of the amorphous silica is ₂ to 40% by weight based on the flaky pigment coated with an insoluble cerium compound as SiO ₂ . 5. An aqueous dispersion of a flaky pigment selected from mica, talc, sericite, etc., having a refractive index of about 1.5 to 1.6, and an aqueous cerium salt solution is added to the pigment in a C solution under heating.
1 to 30% by weight of eO ₂ was added dropwise, the pH was adjusted to 7 to 9 to deposit and coat an insoluble cerium compound on the surface of the pigment, and then a silicate solution was added to the aqueous dispersion under heating. A method for producing an ultraviolet blocking agent, comprising depositing amorphous silica on the surface of the pigment by depositing and then firing. 6. The method for producing an ultraviolet blocking agent according to claim 5, wherein the baking temperature is 200 ° C. to 1000 ° C., preferably 500 ° C.