JPH0710538A - Flake-like zinc oxide material and method for producing the same - Google Patents

Abstract

PURPOSE:To provide a flaky zinc oxide-based material excellent in mechanical strength of the flakes and having UV shielding ability in the entire UV region including UVA and UVB. CONSTITUTION:This flaky zinc oxide-based material contains metal atoms of Ti, Si, Al and Zr by 0.2-1.0mol per 1mol Zn atom and has 0.8-70mum average size of the flakes, 0.1-3mum average thickness and 3-100 aspect ratio.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flaky zinc oxide material and a method for producing the same. The flaky zinc oxide substance is particularly useful as a filler for cosmetic raw materials and various industrial substances because it is excellent in a wide range of ultraviolet ray shielding effect, hiding power and flaky strength.

[0002]

2. Description of the Related Art Titanium oxide, iron oxide, zinc oxide and the like have been known as inorganic compounds having an ultraviolet shielding ability. If these fine particles are used, good ultraviolet ray shielding ability is exhibited, but since they are easily aggregated due to the fine particles, when compounded in a cosmetic composition, the spreadability and usability are poor, and there is a problem such as no elongation when blended with a paint. Have. In order to solve these problems, flaky titanium oxide (JP-A-60-
No. 176906) and fine-grain silica-dispersed flaky titanium oxide (Japanese Patent Laid-Open No. 64-9803), and the like, their ultraviolet shielding ability is UVB (290-320 n).
It is limited to the area of m). Recently UVA (320-40
0 nm) weakens the elasticity of the skin and gives rise to aging skin, and therefore it is strongly desired to shield not only the UVB region but also the UVA region.

On the other hand, as a method for producing flaky zinc oxide, Japanese Patent Publication No. 55-25133 discloses "basic sulfuric acid for precipitating crystals in an acidic region by catalytically absorbing ammonia gas in an acidic aqueous solution containing zinc sulfate. A method for producing a zinc plate crystal is taught, and a plate-shaped zinc oxide powder is described as a white pigment for this use. However, the disclosed sizes have particle sizes up to several hundred μm,
The thickness is several μm or more, and the concealed area per unit weight is low, and therefore the ultraviolet ray shielding ability is also low. In addition, when a thin piece having a thickness of 0.5 μm or less is produced by the above method, the mechanical strength is low, and when it is used for cosmetics, for example, it has a shape when kneaded with other raw materials constituting the cosmetics. Causing a collapse,
Excellent UV shielding ability cannot be expected.

[0004]

In view of the above circumstances, the inventors of the present invention have found that the present invention is a thin flaky sheet having excellent visible light transmittance and ultraviolet ray shielding ability, particularly ultraviolet ray shielding ability in the UVA region, and excellent mechanical strength. As a result of extensive studies to obtain zinc oxide powder, a specific metal alkoxide and a zinc salt are mixed at a specific ratio, and when thinned, dried and fired, a flaky zinc oxide substance satisfying all the above properties is obtained. They have found that they can be obtained and have completed the present invention.

[0005]

That is, according to the present invention, T
0.2 mol to 1.0 mol of metal atoms of i, Si, Al and Zr are contained per mol of Zn atom, and the average size of the flakes is 0.8 μm to 70 μm, and the average thickness is 0.1.
Another object is to provide a flaky zinc oxide material characterized by having a thickness of 3 to 3 μm and an aspect ratio of 3 to 100.

The present invention also relates to a zinc salt and Ti, Si, Al.
And a mixed solution of a metal alkoxide of at least one metal selected from the group consisting of Zr are applied on a smooth surface to form a coating film, and the coating medium is removed by volatilization and gelation of the dispersion medium of the coating film. Another object of the present invention is to provide a method for producing a flaky zinc oxide material, which comprises solidifying and volumetrically shrinking a film to form a flaky material, and peeling the flaky material from the smooth surface and baking the flaky material.

The present invention will be described in more detail below. The flaky zinc oxide material of the present invention contains Ti, Si, Al and Zr metal atoms in an amount of 0.2 mol to 1 mol per Zn atom.
Contains 1.0 mol and the average size of the flakes is 0.8μ
m to 70 μm, the average thickness is 0.1 μm to 3 μm, and the aspect ratio is 3 to 100.

Ti, Si, Al per mol of Zn atom
The metal atom of Zr and Zr is 0.2 mol to 1.0 mol, and more preferably 0.3 mol to 0.7 mol. Zn atom 1
If the metal atom content is less than 0.2 mol per mol, the strength of the flaky zinc oxide material obtained is low and it is difficult to maintain the shape during use.
The shielding ability in the A region is poor.

The zinc salt used in the production of the flaky zinc oxide substance of the present invention may be either an inorganic salt or an organic salt, and examples thereof include zinc chloride, zinc sulfate, zinc nitrate, zinc salicylate and naphthene. Examples thereof include zinc acidate, zinc octylate and zinc acetate.

Further, the metals are Ti, Si, Al and Zr.
As the metal alkoxides consisting of one selected from the group consisting of, alkoxides with alcohols having 1 to 17 carbon atoms, particularly industrially methoxy, ethoxy, tetra-
i-Propoxy, tetra-n-butoxy, tetrakis (2-ethylhexoxy), tetrastearoxy and the like can be used, and among them, methoxy and tetra-i-propoxy are preferable from the economical aspect.

As a solvent for a mixed solution of a zinc salt and a metal alkoxide consisting of at least one metal selected from the group consisting of Ti, Si, Al and Zr, as long as it can dissolve both the zinc salt and the alkoxide. Good, but 70-150 in terms of workability in liquid film formation and evaporation removal
A solvent having a boiling point range of about 0 ° C. is preferable. As such an organic solvent, for example, hydrocarbons such as toluene, xylene, heptane, and cyclohexane, alcohols such as ethanol, propanol, and butanol can be used alone, or a mixture thereof can be used. Industrially, if the same alcohol as the alkoxide is used, it is advantageous that the recovered solvent need not be separated and purified.

The supporting substrate for forming the liquid film may be a flat plate, but a drum flaker or a belt-shaped endless plate is used for continuous production on an industrial scale. The material of the base material is glass, metals such as chromium and nickel, ceramics such as alumina and tungsten carbide,
Resins such as unsaturated polyester and Teflon can be used. When selecting these materials, it is not unambiguous due to the peelability of the formed thin film, the peeling means, and the physical properties of the raw materials used, but generally, a metal drum, an alumina spray drum if chemical resistance and wear resistance are important. Is preferred.

The liquid film formed on the substrate is subjected to heat treatment to evaporate and remove the solvent from the liquid film. The solvent may be removed from the liquid film by evaporation by heating the support substrate from the inside, blowing hot air onto the surface of the liquid film, or a combination of these, but excessive heating causes boiling of the solvent to form flakes. Therefore, the heating is not more than the boiling point of the solvent composition constituting the liquid film, and when using warm air, the amount of the blowing air may be carried out in an amount such that the liquid film surface does not impair the smoothness. It is preferable for obtaining a thin piece.

The liquid film on the supporting substrate after the solvent is removed by heating is
Then, it is forcibly hydrolyzed by humidified air such as steam to form a solid film on the supporting substrate. With the progress of hydrolysis, the formed solid film shrinks in volume and cracks in the thin film, resulting in thinning.

As a method for peeling the flaky material formed on the supporting base material from the base material, a mechanical scraping method such as a scraper is usually adopted. Peeling by vibration or the like, and further, when the base material is flexible, a method of bending and peeling the base material may be mentioned. The release material is then about 500 ° C. to about 750.
C., preferably at a temperature of about 550.degree. C. to about 700.degree. C. for about 1 hour or more. The flaky zinc oxide material after firing is
As is, or if necessary, neutralization treatment, pulverization, and sieving are performed to adjust to a desired shape.

The shape of the flaky zinc oxide material obtained in the present invention has an average size of 0.8 to 70 μm, an average thickness of 0.1 to 3 μm, and an aspect ratio (size / thickness) of about 3. ~ About 100 are manufactured.

[0017]

INDUSTRIAL APPLICABILITY As described above in detail, the flaky zinc oxide material obtained according to the present invention is used not only in the UVB region but also in the UV region.
It also has an excellent UV shielding ability in the A region, and 0.5 g of flaky zinc oxide powder was added to 100 ml of a 0.2% sodium hexametaphosphate aqueous solution to homogenize (US-300.
T: Ultrasonic disperser / made by Leeds & Northlap Co., Ltd., and dispersed by Microtrac MKII (made by Leeds & Northlap Co.) for 1 minute and 10 minutes, respectively. The strength of the flakes obtained by measuring (average particle diameter of flakes after dispersion treatment for 10 minutes / average particle diameter of flakes after dispersion treatment for 1 minute) × 100 (%) is the conventionally known neutralization precipitation method. Although the flaky zinc oxide obtained in 1 is less than 50%, it has an excellent mechanical strength of 60% or more. When the flaky zinc oxide substance is applied to a cosmetic such as a foundation, Is
It is possible to provide a make-up cosmetic excellent in spreadability, adhesiveness and tactile feel, which cannot be obtained with conventional particulate zinc oxide, and not only as a cosmetic but also as a paint, a resin filler, etc. Its industrial value is enormous.

[0018]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In addition,
The evaluation method of the UVA shielding ability in the present invention is carried out by adding flake-like zinc oxide substance to silicone oil in an amount of 15% by weight and mixing them well, and then drawing a film on a polypropylene film to a thickness of 25 μm using an auto applicator, The absorbance of this was measured with an ultraviolet-visible spectrophotometer U-2000 manufactured by Hitachi Ltd., and the absorption wavelength edge of ultraviolet rays was obtained.

Example 1 Tetra-i-propoxy titanium (manufactured by Nippon Soda Co., Ltd.) was added to a solution of 15 g of zinc acetate dihydrate (manufactured by Wako Pure Chemical Industries, Ltd.), 48 g of methanol and 2 g of water.
An undiluted stock solution was prepared by adding so that the molar ratio of / Zn was 0.4. This stock solution was spread on a rotating chrome-plated drum having a diameter of 15 cm and a width of 15 cm heated at 90 ° C. through a rubber roll to form a liquid film, and then the solvent was removed by evaporation, followed by contact with steam. Partial hydrolysis occurred. The liquid film changed to a solid state and cracked as the hydrolysis proceeded to form flakes. Then, the flakes on the drum were scraped off with a scraping blade, and then the flaking stock solution was spread again on the surface of the drum to continuously manufacture flakes. The flaky material thus obtained was calcined in an electric furnace at a temperature of 660 ° C. for 1 hour to obtain a flaky zinc oxide material having an average size of 5 μm and an average thickness of 0.5 μm. This product has an ultraviolet absorption wavelength edge of 383
nm and the flake strength was 68%.

Example 2 The amount of tetra-i-propoxytitanium added was changed to Ti / Zn.
A flaky zinc oxide material was produced in the same manner as in Example 1 except that the molar ratio of was adjusted to 0.26. The obtained flaky zinc oxide material has an average size of 4 μm and an average thickness of 0.4 μm, and has an ultraviolet absorption wavelength end of 378 n.
In m, the flake strength was 65%.

Example 3 Instead of tetra-i-propoxytitanium, tri-i-
A flaky zinc oxide material was produced in the same manner as in Example 1 except that propoxy aluminum (manufactured by Wako Pure Chemical Industries, Ltd.) was used. The obtained flaky zinc oxide material has an average size of 5.5 μm and an average thickness of 0.5 μm,
The absorption wavelength edge of ultraviolet rays is 380 nm, and the slice intensity is 71%.
Met.

Comparative Example 1 The amount of tetra-i-propoxytitanium added was Ti / Zn.
A flaky zinc oxide material was produced in the same manner as in Example 1 except that the molar ratio of was adjusted to 2.0. The obtained flaky zinc oxide material has an average size of 5 μm and an average thickness of 0.5 μm, and has an ultraviolet absorption wavelength edge of 330 n.
In m, the thin piece strength was 70%.

Comparative Example 2 The amount of tetra-i-propoxytitanium added was Ti / Zn.
Example 1 except that the molar ratio of was 0.12.
A flaky zinc oxide material was produced in the same manner as in. The obtained flaky zinc oxide material was broken into powder after firing and did not maintain the flaky shape.

Comparative Example 3 2 parts of 55 g of zinc sulfate heptahydrate (manufactured by Wako Pure Chemical Industries, Ltd.)
Dissolve in 00 ml of water, raise the temperature to 80 ° C. with stirring, contact this solution with nitrogen gas containing 0.1% ammonia on the liquid surface, absorb it, and neutralize while maintaining the pH value of the solution at 5. The reaction was carried out. The obtained slurry was filtered, washed, and dried at a temperature of 110 ° C. to obtain plate-like basic zinc sulfate. Then, this powder in air,
Heat treatment was performed at 950 ° C. for 1 hour to produce flaky zinc oxide. The obtained flaky zinc oxide has an average size of 18
The average thickness was 0.5 μm, the ultraviolet absorption wavelength edge was 383 nm, and the flake strength was 45%.

Claims (4)

[Claims] 1. A metal atom of Ti, Si, Al and Zr is contained in an amount of 0.2 mol to 1.0 mol per mol of Zn atom, and the average size of the flakes is 0.8 μm to 70 μm.
Average thickness is 0.1 μm to 3 μm, aspect ratio is 3 to
A flaky zinc oxide material characterized by being 100. 2. The strength of a thin piece measured by the following method is 60.
The flaky zinc oxide material according to claim 1, which is at least%. Flake strength measurement method: Flake-shaped zinc oxide powder to be measured 0.5 g
0.2% sodium hexametaphosphate aqueous solution 100m
Disperse in 1 with a homogenizer and use Microtrac MKII
Dispersion treatment was carried out for 1 minute and 10 minutes respectively, and then the average particle diameter of the flakes after the treatment was measured ((average particle diameter of flakes after 10 minutes dispersion treatment / average particle diameter of flakes after 1 minute dispersion treatment). ) × 100 (%) to obtain the strength of the flakes. 3. A smooth surface is coated with a mixed solution of a zinc salt and a metal alkoxide consisting of at least one metal selected from the group consisting of Ti, Si, Al and Zr to form a coating film. A flaky zinc oxide characterized in that the coating film is solidified and volumetrically contracted by volatilization removal and gelation of a dispersion medium of the film to form a flaky substance, and the flaky substance is peeled from the smooth surface and then baked. Of producing high quality substances. 4. The obtained flaky material is Ti, Si, Al.
And 0.2 to 1.0 mol of Zr metal atom per mol of Zn atom, and the average size of the flakes is 0.
8 μm to 70 μm, average thickness is 0.1 μm to 3 μm,
An aspect ratio is 3-100, The manufacturing method of the flaky zinc oxide material of Claim 3 characterized by the above-mentioned.