KR100611647B1 - Silica coating method of TiO2 as ultraviolet shielding material to prevent photocatalytic activity and to disperse at solution - Google Patents

Abstract

The present invention suppresses the clouding phenomenon, which is a problem of titanium dioxide used as a sunscreen, improves the transparency and skin texture due to the entanglement of particles, improves the dispersibility in the solvent as well as block photocatalytic activity, After controlling the size of TiO ₂ for the trouble suppression of, it relates to the synthesis of titanium dioxide nanocomposites coated with silica, a stable oxide by the sol-gel method.

Sunscreen, titanium dioxide, silica, coating

Description

 Silica coating method of TiO2 as ultraviolet shielding material to prevent photocatalytic activity and to disperse at solution}

In general, ultraviolet rays are classified according to the length of the wavelength and the effect on the human body, and when they are irradiated excessively, it is known to cause various diseases and cancers. Ultraviolet rays are long-wave ultraviolet rays (UV-A), which lead to premature aging and blackening of the skin, and medium-wave ultraviolet rays (UV-B) that make the skin red, creating a sun burn, causing strong inflammation or creating blisters. It is divided into short-wave ultraviolet (UV-C), which is not transmitted to the ground by absorption by the ozone layer or by light that destroys life directly. In the past, long-wavelength ultraviolet light was welcomed because of its high effectiveness in treating inflammation, but it has recently been pointed out as a target for promoting skin aging due to degeneration of proteins in the dermis, capillary expansion, and destruction of hexane (DNA).

Meanwhile, the medium wavelength ultraviolet rays, which are mostly absorbed by the epidermal part of the skin, are called harmful ultraviolet rays because they act rapidly on the epidermis and cause burns. The long-wave UV rays come into contact with the skin all year round, but there is no self-awareness, and the skin grows old without you knowing it.

In ultraviolet cosmetics, inorganic ultraviolet scattering agents, organic ultraviolet absorbers and the like are used as sunscreens. Organic UV absorbers mainly absorb medium wavelength UV rays, while inorganic UV absorbers mainly scatter long wavelength UV rays. UV absorbers protect the skin by absorbing ultraviolet light and changing it into energy such as reverse, vibration, fluorescence, and radicals. In contrast, the ultraviolet scattering agent blocks the ultraviolet rays by the refractive index of the light of the inorganic pigment. Inorganic pigments have recently been spotlighted because they are relatively safe for the skin, but they have many problems in whitening and applicability to the skin when used excessively. In particular, clouding suppression is recognized as the most important part of the quality requirements for sunscreen cosmetics.

Inorganic ultraviolet scattering agents include metal oxides such as titanium dioxide, zinc oxide, and cerium oxide, and composites thereof. Titanium dioxide and zinc oxide are in the spotlight. Studies on the anti-burn cosmetics by these physical sunscreens include iron oxides, titanium dioxide, WO 93-11742 using zinc oxide and EP 55-9319, US 52-50289 using titanium dioxide and the like. As described above, titanium dioxide, which has the highest scattering effect and is chemically stable among metal oxides, is mainly used. Titanium dioxide is used as a raw material for cosmetics, but there are some problems.

First, there are problems of the touch surface (stiffness, poor applicationability) and the finish surface (white floating phenomenon) caused by the high compounding of the inorganic powder. In addition, in order to block ultraviolet rays, it is necessary to disperse the primary particles of the titanium fine particle inorganic powders and to stabilize them.

When this dispersion is stable, the uniformity of the ultraviolet scattering agent can be achieved when applied to the skin. The second deteriorates other raw materials of cosmetics because of its activity as a photocatalyst. Third, because it blocks even the visible light region, whitening occurs when used in cosmetics. Fourth, titanium dioxide nanoparticles act as phototoxic cells that affect intracellular hexane (DNA) when exposed to sunlight.

Titanium dioxide has a photocatalytic property, and when it receives light, it forms radicals and causes oxidation. On the other hand, due to the physical properties of white and excellent chemical properties of UV protection, the cosmetic industry has been used as a sunscreen and white pigment. However, there have been limitations in its use due to the cloudiness and photocatalytic properties. Thus, as a result of intensive studies on maximizing the sunscreen effect without increasing the cloudiness, the tetraethylorthosilicate is hydrolyzed and the surface is treated with acid. There is a technical problem in manufacturing an improved nanocomposite having a UV protection function by coating on titanium and photocatalytic phenomenon and phase separation.

In order to achieve the above object, the inventors of the present invention are the first improvement, which is coated with silica, which has good durability, dispersibility, heat resistance and light weight, and prevents photolysis of organic substances by inhibiting radical generation and dispersibility in oil and moisture. Synthesis was performed for improved and improved textures. Second, in order to reduce the cloudiness and improve the transparency, the average diameter of TiO ₂ was reduced to 100 nm or less. The reduction of the particle diameter increases the surface area can be expected to improve the UV blocking effect.

The method for preparing silica-coated titanium dioxide composite powder according to the present invention is:

Acid treatment of titanium dioxide nanoparticles with hydrochloric acid solution: commercially available Degussa P-25 (the composition ratio of analyte and rutile is 7: 3). After mixing nanoparticles with 0.1M HCl After sonication for 1 hour, the mixture was stirred for 6 hours. Centrifuge for 30 minutes in a centrifuge of 10000 rpm or higher. After washing three times in alcohol such as ethanol or methanol and centrifuged for 30 minutes at 10000 rpm or more. This is a process for dehydrating the surface of titanium dioxide, and keep the dehydrated titanium dioxide in Chloroform to prevent moisture.

Example 1

The nanoparticles dehydrated through the above process were used as seeds to synthesize composite nanoparticles coated with silica on the surface of titanium dioxide using a phase transfer reaction.

Degussa P-25 acid treated with hydrochloric acid mentioned above is dispersed in Chloroform and sonicated for 1 hour at room temperature to minimize entanglement of titanium dioxide particles.

Tetraethylorthosilicate (purity 98%, Aldrich Chemical Company) and H ₂ O are synthesized in ethanol solution at room temperature. At this time, pH was adjusted using ammonia water as a basic catalyst to accelerate the hydrolysis of Tetraethylorthosilicate. After mixing the prepared solutions together, acetone was added at room temperature, stirred for 2 hours, and filtered. After drying the filtered slurry for 24 hours in a dryer of 60 ℃ or more, high temperature treatment at 800 ℃ for 1 hour to stabilize the phase of the silica coated on the titanium dioxide surface. At the time of synthesis, the molar ratio of titanium dioxide and tetraethylorthosilicate is 0.4: 0.6, and it blocks light as much as possible. Through this process, composite nanoparticles with silica coated on the surface of nanoparticles of titanium dioxide with 10-15 nm thickness were synthesized.

Comparative Example 1

Silica-coated titanium dioxide nanoparticles were synthesized in the same manner as in Example 1 by using a molar ratio of tetraethylorthosilicate and titanium dioxide as 0: 1.

Comparative Example 2

Silica-coated titanium dioxide nanoparticles were synthesized in the same manner as in Example 1 using the molar ratio of tetraethylorthosilicate and titanium dioxide to 0.2: 0.8.

Comparative Example 3

Silica-coated titanium dioxide nanoparticles were synthesized in the same manner as in Example 1 using the molar ratio of tetraethylorthosilicate and titanium dioxide to 0.4: 0.6.

Comparative Example 4

Silica-coated titanium dioxide nanoparticles were synthesized in the same manner as in Example 1 using a molar ratio of tetraethylorthosilicate and titanium dioxide at 0.5: 0.5.

Comparative Example 5

Silica-coated titanium dioxide nanoparticles were synthesized in the same manner as in Example 1 using a molar ratio of tetraethylorthosilicate and titanium dioxide of 0.8: 0.2.

Test Example 1

TEM and EDS were measured to measure the structure and coating thickness of the particles of silica coated titanium dioxide prepared by the method described above.

In Figure 1 (a) shows the titanium dioxide nanoparticles before coating with silica and (b) shows the titanium dioxide nanoparticles after coating with silica. A comparison of the above photographs shows that the titanium dioxide nanoparticles are surrounded by an amorphous SiO ₂ layer. The thickness of the amorphous SiO ₂ layer is 10-15 nm and the average diameter of the coated particles is 40-50 nm.

Samples from Example 1 and Comparative Example 1 to Comparative Example 4 prepared by the present invention were measured for the energy dispersion spectrum (EDX) to confirm the compositional analogy. As shown in Comparative Example 3 in Table 1, since the molar ratio of silica and titanium dioxide was mixed at a molar ratio of 0.4: 0.6, the molar ratio of silica and titanium dioxide was almost unchanged.

Test Example 2

The chemical bonding of the particle surface to the titanium dioxide nanocomposites coated with silica was measured via FT-IR. In FIG. 2, (a) is an FT-IR graph for pure titanium dioxide, and (b) is an FT-IR graph of silica coated titanium dioxide nanocomposites prepared in Example 1. FIG. Through the above two graphs, the peaks of Ti-O for titanium dioxide were wide in the range of 600-900 cm ^-1 in (a) and (b), and the peaks of Si-O for silica only in (b). Peaks for and Ti-O-Si can be seen as 1000-1200 cm ^-1 , 950cm ^-1 , respectively. To further confirm these results, an X-ray photoelectron spectroscope (XPS) was measured. XPS is a device that analyzes the elements and their chemical composition on the surface by measuring binding energy according to chemical environment. As can be seen in FIG. 3, the 528.1 eV and 530.3 eV peaks of the silica-coated titanium dioxide prepared in Example 1 were +0.5 eV and + compared to 527.6 eV and 529.9 eV of pure titanium dioxide. It can be seen that it is shifted by 0.4 eV. In addition, in the graph of Ti 2p in FIG. 3, 456.2 eV of pure titanium dioxide and 456.6 eV of titanium dioxide coated with silica prepared in Example 1 were shifted by +0.4 eV. Si has a higher electronegativity compared to Ti. If there is a large electronegativity around Ti atoms, the shielding effect is reduced due to the decrease of the electron density, so that the electrons are attracted to the nucleus and the binding energy increases. This fact confirms that silica is bound to the surface of titanium dioxide particles.

Test Example 3

Samples from Example 1 and Comparative Example 1 to Comparative 5 were each heat-treated at 500 ° C. to 1000 ° C. for 1 hour.

Figure 4 is a graph of XRD (X-ray powder diffraction) observed the phase change after the heat treatment to increase the stability of the silica coated on the titanium dioxide particle surface. The comparison of the two graphs shows that the pure titanium dioxide uncoated had a phase change from anatase to rutile after heat treatment above 900 ℃, but the titanium dioxide coated with silica showed no phase change even after high temperature treatment. It can be seen that this is due to the heat resistance of silica. 5 is a graph illustrating the phase change when the high temperature treatment time is changed at a constant temperature. The results of this experiment also confirmed that the silica-coated titanium dioxide did not occur phase change even after high temperature treatment for a long time.

Test Example 4

Titanium dioxide has a large blocking effect on the UV-B (290-320 nm) region, which causes erythema of the skin. The UV-vis λ _max of the titanium dioxide coated with silica prepared according to Example 1 was 260-330 nm, compared to that of FIG. 6, even if coated with silica, the UV-B blocking ability of titanium dioxide. It can be seen that is maintained, and can be seen to be blocked more extensively than UV-B.

The photocatalytic activity of titanium dioxide was measured through the color change of the organic material. Titanium dioxide has the ability to decompose organic matter due to its photocatalytic properties, which can also be used for oil spills from seawater. In the manufacture after the titanium dioxide and the titanium dioxide untreated surface coated with a high temperature-treated silica at 800 ℃ each Rhodamine B (Rhodamine B was used to this experiment are reddish-violet a substance according to the molar ratio λ _max is 543 nm It was prepared by stirring in an aqueous solution containing (in 0.01 g + 1.0 x 10 ^-5 M Rhodamine B 100 ml).

The mixed solution prepared as described above was irradiated with a 300 W Xe lamp for 30 minutes to check the presence or absence of organic matter through UV. Figure 7 shows the UV absorbance of the light irradiation time between the titanium dioxide coated with silica and pure titanium dioxide at 543 nm over time. (If the intensity of the lamp is weak, you can measure it with more time.) As can be seen from FIG. 7, it can be seen that as time passes, organic matter is decomposed by pure titanium dioxide and disappeared. However, Rhodamine B in the silica-coated titanium dioxide nanocomposite particles remains in half. Figure 7 shows the change in photocatalytic effect after silica coating, and after coating with silica it can be seen that the effect of photocatalytic activity is blocked.

Test Example 5

Dispersion stability of titanium dioxide coated with silica was measured using a Zeta pontential analyzer with pH.

The low absolute value of the zeta potential indicates the colloidal instability (agglomeration), while the high absolute value of 30 mV indicates a stable dispersion. After the pH adjustment of the prepared silica coated titanium dioxide, pure titanium dioxide and pure silica with 0.1 M NH ₄ OH and 0.1 M HCl, when measuring Zeta potential, as shown in FIG. 8 and Table 2, pure dioxide at pH 7 The Zeta potential of titanium was -26.25 mV, and the Zeta potential of silica-coated titanium dioxide nanocomposites was -47.46 mV, which is similar to that of pure silica (-51.17 mV) and the dispersion stability was improved.

1A and 1B show TEM images before and after coating with silica of titanium dioxide nanoparticles.

2 is a comparative graph of FT-IR of particles synthesized in Example 1 and pure titanium dioxide.

3A and 3B are comparative graphs of O 1s and Ti 2p in XPS of the particles synthesized in Example 1 and pure titanium dioxide.

4A to 4F are XRD patterns of titanium dioxide coated with silica synthesized in Example 1 and the temperatures of Comparative Examples 1 to 5, respectively.

5 is a phase change graph when the high temperature treatment time is changed at a constant temperature.

FIG. 6 is a graph of UV absorbance of titanium dioxide coated with silica synthesized in Example 1 and pure titanium dioxide. FIG.

FIG. 7 is a graph of UV absorbance versus light irradiation time of Example 1 and pure titanium dioxide at 543 nm. FIG.

8 is a Zeta potential difference graph according to pH of titanium dioxide coated with silica synthesized in Example 1, pure titanium dioxide, and pure silica.

Table 1 shows the nanocomposite particle composition analysis (atomic%) according to the molar ratio of tetraethylorthosilicate and titanium dioxide by EDX.

Table 2 is a numerical table of Zeta potential differences between titanium dioxide coated with silica prepared in Example 1, pure titanium dioxide and pure silica.

As described above, the titanium dioxide coated with silica prepared according to the present invention has excellent UV blocking ability and transparency, and can be expressed naturally.Trouble with the skin and deterioration of the product due to deterioration of photocatalytic activity by silica It can be suppressed and used for makeup products, sun protection products and the like.

Claims (5)

Acid treating the titanium dioxide nanoparticles with a hydrochloric acid solution; Commercially available Degussa P-25 (the composition ratio of anatase and rutile is 7: 3). The nanoparticles are mixed with 0.1M HCl, sonicated for 1 hour, and then stirred for 6 hours; After centrifugation for 30 minutes in a centrifuge of 10000 rpm or more, washing with at least three times in alcohol such as ethanol or methanol to dehydrate the surface of the titanium dioxide and then centrifuging for 30 minutes at 10000 rpm or more; And Store dehydrated titanium dioxide in chloroform to prevent moisture from entering. Method of producing a cosmetic composition for UV protection, characterized in that a simple pre-treatment process of the titanium dioxide nanoparticles before coating with silica as described above. The composite nanoparticles according to claim 1, wherein the silica prepared by hydrolysis of tetraethylorthosilicate using pretreated titanium dioxide nanoparticles as a seed and the composite nanoparticles coated with silica on the titanium dioxide surface by using a phase transfer reaction between an aqueous solution and a CHCl ₃ organic solution How to manufacture. The method of claim 2, wherein the pH of the mixed solution is adjusted to between 7 and 8 using ammonia water, which is a basic catalyst for further accelerating the hydrolysis of Tetraethylorthosilicate. The method of claim 2, wherein the titanium dioxide coated with silica is treated at a high temperature at 800 ℃ to increase the coating stability of the silica. The method for preparing a cosmetic composition for protecting sunscreen according to claim 2, wherein the composite nanoparticles have an average particle size of 40-50 nm with silica coated on the surface of the nanoparticles of titanium dioxide with a thickness of 10-15 nm. Fig. 1 a

Fig 1 b

 2

3 a

3 b

4a

4b

4c

4d

4e

4f

5

6

7

8

Table 1 TABLE 2