Zinc oxide particles

Abstract

The present invention provides zinc oxide particles that are larger than nano-size, have low ultraviolet absorption, and high whiteness. [Solution] Zinc oxide particles in which the D1 of the particle size distribution, when measured using a scanning electron microscope (SEM) with the maximum inscribed circle as the particle diameter for 200 particles observed in the SEM image, is 100 nm or more, and the whiteness measured by a colorimeter (Konica Minolta: CR-5) is 90.0 or more.

Description

[Technical Field]

[0001] This invention relates to zinc oxide particles. [Background technology]

[0002] White pigments for cosmetics are used as base pigments when mixed with other pigments to form cosmetic compositions, and zinc oxide and titanium dioxide are commonly used. Zinc oxide and titanium dioxide have high opacity due to their refractive index, and because larger particles appear white when applied, combining them with nanoparticles or other fine particles allows for transparency and creates a natural white appearance. However, in recent years, concerns have begun to arise regarding the harmful effects of nanomaterials on living organisms and the environment, and there are movements in various countries around the world to regulate the use of nano-sized zinc oxide as a cosmetic ingredient. Therefore, there is a demand for non-nanosized particles, which are larger than nanosized particles, to be used as cosmetic ingredients and other materials, as they can produce a moderate, natural whiteness.

[0003] Regarding non-nano-sized zinc oxide, Patent Document 1 discloses a composition comprising a water-soluble or water-insoluble carrier and zinc oxide particles dispersed in the carrier, wherein the zinc oxide particles substantially do not contain any particles with a primary particle size smaller than 100 nm as measured by transmission electron microscopy. Patent Document 2 discloses a broad-spectrum UV light protection composition characterized by comprising mesoporous zinc oxide aggregates dispersed in a dispersion medium (carrier) having an average aggregate size of at least 0.8 microns, and being transparent to visible light. Patent Document 3 discloses a sunscreen cosmetic containing zinc oxide fine particles, characterized in that the primary particle diameter of 90% or more of the zinc oxide fine particles is 0.1 μm or more and 0.4 μm or less.

[0004] Furthermore, regarding a method for producing zinc oxide powder, Patent Document 4 discloses a method for producing high-purity nano zinc oxide powder, which includes a step of feeding basic zinc carbonate (ZnCO3·Zn(OH)2) into a rotary incinerator and calcining it. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 2012-511499 [Patent Document 2] Special Publication No. 2011-509940 [Patent Document 3] Japanese Patent Publication No. 2010-275223 [Patent Document 4] Korean Published Patent Publication No. 10-2020-0044485 [Overview of the project] [Problems that the invention aims to solve]

[0006] While not as much as titanium dioxide, zinc oxide, especially in its finer particles, tends to absorb ultraviolet light and generate a large amount of radicals. These radicals can react with other substances in cosmetic formulations, potentially causing them to change or degrade. As mentioned above, various compositions containing non-nanosized zinc oxide have been disclosed, but the zinc oxide described in Patent Documents 1 to 3 is either highly absorbent of ultraviolet light or used in sunscreens, and does not have high whiteness as a white pigment. Therefore, there was room to develop zinc oxide particles that are larger than nanosize, have low ultraviolet light absorption, and high whiteness.

[0007] In view of the above situation, the present invention aims to provide zinc oxide particles that are larger than nano-size, have low ultraviolet absorption, and have high whiteness. [Means for solving the problem]

[0008] The present inventors conducted studies on zinc oxide larger than nano-size, and found that, among predetermined zinc oxide particles in SEM images observed using a scanning electron microscope (SEM), zinc oxide particles having a particle size distribution D1 measured by a predetermined method and a whiteness of not less than predetermined values are larger than nano-size and have a low ultraviolet absorption amount, and thus completed the present invention.

[0009] The present invention includes the following zinc oxide particles and the like. [1] Zinc oxide particles, wherein D1 of the particle size distribution obtained when measuring the maximum inscribed circle as the particle diameter for 200 particles in an SEM image observed using a scanning electron microscope (SEM) is 100 nm or more, and the whiteness measured by a color difference meter (manufactured by Konica Minolta, Inc.: CR-5) is 90.0 or more. [2] L measured by a color difference meter (manufactured by Konica Minolta, Inc.: CR-5) * a * b * b value in the color system * is 2.0 or more, the zinc oxide particles according to [1] above. [3] The specific surface area is 0.1 to 2.0 m 2 / g, the zinc oxide particles according to [1] or [2] above. [4] A method for producing the zinc oxide particles according to [1] or [2] above, wherein the production method comprises a step of calcining basic zinc carbonate at 750 to 950°C, the method for producing zinc oxide particles. [5] A cosmetic comprising the zinc oxide particles according to [1] or [2] above. [Advantageous Effects of Invention]

[0010] The zinc oxide particles of the present invention are larger than nano-size, have a low ultraviolet absorption amount and high whiteness, and thus can be suitably used for cosmetics and the like. [Brief Description of Drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the particle size distribution obtained by analysis of an SEM image of the zinc oxide particles obtained in Example 1. [Figure 2] This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles obtained in Example 2. [Figure 3] This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles obtained in Example 3. [Figure 4] This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles obtained in Comparative Example 1. [Figure 5] This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles obtained in Comparative Example 2. [Figure 6] This figure shows the particle size distribution obtained by analyzing the SEM images of zinc oxide particles obtained in Comparative Example 3. [Figure 7] This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles obtained in Comparative Example 4. [Figure 8] This figure shows the particle size distribution obtained by analyzing the SEM images of titanium dioxide particles obtained in Comparative Example 5. [Figure 9] This figure shows the particle size distribution obtained by laser diffraction of zinc oxide particles from Example 1 and Comparative Examples 2-4, and titanium oxide particles from Comparative Example 5. [Figure 10] This figure shows the spectra of the total light transmittance at wavelengths of 300-400 nm for dispersions prepared using zinc oxide particles from Example 1 and Comparative Examples 2-4. [Figure 11] This figure shows the parallel transmittance spectra at wavelengths of 400-800 nm of dispersions prepared using zinc oxide particles from Example 1 and Comparative Examples 2-4. [Modes for carrying out the invention]

[0012] The following describes preferred embodiments of the present invention in detail, but the present invention is not limited to the following description and can be modified and applied as appropriate without altering the essence of the invention.

[0013] 1. Zinc oxide particles The zinc oxide particles of the present invention have a D10 particle size distribution of 100 nm or more when the maximum inscribed circle is measured as the particle diameter for 200 particles in an SEM image observed using a scanning electron microscope (SEM), and have a whiteness of 90.0 or more as measured by a colorimeter (manufactured by Konica Minolta, Inc.: CR-5). The zinc oxide particles of the present invention have low ultraviolet absorption and high whiteness, and thus can be suitably used in cosmetics and the like containing components that are vulnerable to radicals. The particle size distribution in the analysis of the above SEM image can be measured by the method described in the Examples.

[0014] The zinc oxide particles of the present invention only need to have a whiteness (WI) of 90.0 or more as measured by a colorimeter (manufactured by Konica Minolta, Inc.: CR-5), but the whiteness is preferably 92 or more, more preferably 93 or more, and still more preferably 95 or more.

[0015] The zinc oxide particles of the present invention have an L value measured by a colorimeter (manufactured by Konica Minolta, Inc.: CR-5) * a * b * value in the b color system * is preferably 2.0 or more. This results in a slightly yellowish white, so that a more natural whiteness can be achieved for cosmetics. The above b * value is more preferably 5.0 or more, and still more preferably 7.0 or more. The above b * value is also preferably 10.0 or less.

[0016] The zinc oxide particles of the present invention have an L value measured by a colorimeter (manufactured by Konica Minolta, Inc.: CR-5) * a * b * L value in the L * a*b* color system is not particularly limited, but is preferably 90.0 or more. It is more preferably 92.0 or more, and still more preferably 95.0 or more.

[0017] The zinc oxide particles of the present invention have an L value measured by a colorimeter (manufactured by Konica Minolta, Inc.: CR-5)* a * b * a in color system * The value is not particularly limited, but is preferably between -3.50 and -0.50. More preferably between -3.0 and -0.75.

[0018] In the zinc oxide particles of the present invention, the above-mentioned D1 may be 100 nm or more, but is preferably 101 to 300 nm, and more preferably 120 to 270 nm.

[0019] The D10 in the zinc oxide particles of the present invention is not particularly limited, but is preferably 150 to 525 nm, more preferably 175 to 500 nm, and even more preferably 200 to 475 nm.

[0020] The D90 / D50 ratio in the zinc oxide particles of the present invention is not particularly limited, but is preferably 2.0 or less, and more preferably 1.8 or less. The D90 / D50 ratio is also preferably 1.2 or more.

[0021] The zinc oxide particles of the present invention preferably have a particle size distribution d50 of 100 nm or more, as measured by a laser diffraction / scattering particle size distribution analyzer. More preferably, it is 101 to 300 nm, and even more preferably 120 to 270 nm. The above d50 can be measured by the method described in the example.

[0022] The zinc oxide particles of the present invention have a specific surface area of ​​0.1 to 2.0 m². 2 It is preferable that the concentration is / g. More preferably 0.15 to 1.75 m 2 The concentration is / g, and more preferably 0.2 to 1.5m 2 It is / g. The specific surface area of ​​zinc oxide particles can be measured by the method described in the examples.

[0023] The shape of the zinc oxide particles of the present invention is not particularly limited, but examples include spherical, rod-shaped, needle-shaped, spindle-shaped, plate-shaped, and the like.

[0024] The zinc oxide particles of the present invention may be surface-treated from the viewpoint of dispersibility and other factors. The surface treatment agent used in the above surface treatment is not particularly limited, but examples include organosilicon compounds and fatty acids. Examples of the organosilicon compounds mentioned above include organopolysiloxanes such as dimethylpolysiloxane, methylhydrogenpolysiloxane, hydrogen dimethicone, methylphenyl silicone, amino-modified silicone, triethoxysilylethyl polydimethylsiloxyethyl dimethicone, and triethoxysilylethyl polydimethylsiloxyethyl hexyl dimethicone; and alkylsilanes such as triethoxycaprylylsilane, trimethoxycaprylylsilane, and decyltriethoxysilane.

[0025] Examples of the above fatty acids include saturated fatty acids with 10 to 30 carbon atoms, such as stearic acid, myristic acid, lauric acid, and palmitic acid, and unsaturated fatty acids with 10 to 30 carbon atoms, such as oleic acid.

[0026] The amount of the above surface treatment agent used is not particularly limited, but it is preferably 0.3 to 10.0% by mass relative to 100% by mass of zinc oxide. More preferably it is 0.5 to 5.0% by mass, and even more preferably 0.8 to 3.0% by mass.

[0027] 2. Method for producing zinc oxide particles The method for producing the zinc oxide particles of the present invention is not particularly limited, but for example, a method including the step of calcining basic zinc carbonate at 750 to 950°C can be used. The present invention relates to a method for producing zinc oxide particles, the production method comprising a step of calcining basic zinc carbonate at 750 to 950°C.

[0028] The firing temperature in the above firing process may be 750 to 950°C, but is preferably 780 to 920°C, and more preferably 800 to 900°C.

[0029] The firing time in the above firing process is not particularly limited, but is preferably 1 to 10 hours, and more preferably 2 to 6 hours.

[0030] The atmosphere during the firing process described above is not particularly limited, but firing in an air atmosphere is preferable.

[0031] The above-described method for producing zinc oxide particles may include other steps besides the calcination step. Other steps include crushing the calcined zinc oxide, washing the calcined zinc oxide powder, drying the washed zinc oxide powder, and classifying the particles according to their size.

[0032] The above method for producing zinc oxide particles preferably includes a step of classifying the zinc oxide obtained in the above calcination step. There are no particular restrictions on the classification method described above, but one example is classification by sieving. Examples of classification by sieving include wet classification and dry classification.

[0033] 3. Cosmetics The zinc oxide particles of the present invention are larger than nano-size, have low ultraviolet absorption, and high whiteness, making them suitable for use as a compounding agent in cosmetics and other products containing radical-sensitive components. Cosmetics containing the above zinc oxide particles are also one of the present inventions.

[0034] The cosmetic composition of the present invention is not particularly limited, but examples include foundation, makeup base, eyeshadow, blush, mascara, lipstick, sunscreen, etc. The cosmetic composition of the present invention can be in any form, such as oil-based cosmetic composition, water-based cosmetic composition, O / W type cosmetic composition, or W / O type cosmetic composition. Among these, it can be used particularly suitably in makeup cosmetics such as foundation, makeup base, and eyeshadow.

[0035] The cosmetic of the present invention may contain any optional aqueous component or oily component that can be used in the cosmetic field, in addition to the zinc oxide particles of the present invention. The above-mentioned aqueous components and oily components are not particularly limited, and examples thereof include oils, surfactants, humectants, higher alcohols, sequestering agents, natural and synthetic polymers, water-soluble and oil-soluble polymers, ultraviolet shielding agents, various extracts, inorganic and organic pigments, various powders such as inorganic and organic clay minerals, inorganic and organic pigments treated with metal soap or treated with silicone, colorants such as organic dyes, preservatives, antioxidants, pigments, thickeners, pH adjusters, perfumes, cooling sensates, antiperspirants, bactericides, skin activators, and the like. One or more of these components can be arbitrarily blended to produce the target cosmetic by a conventionally commonly used method. The blending amount of these optional components is not particularly limited as long as it does not impair the effects of the present invention. [EXAMPLES]

[0036] Specific examples are given below to describe the present invention in detail, but the present invention is not limited to only these examples. Unless otherwise specified, "%" and "wt%" mean "% by weight (mass%)". The methods for measuring each physical property are as follows.

[0037] <Analysis of SEM Image> Using a scanning electron microscope (JEM-7000F, manufactured by JEOL Ltd.), the maximum inscribed circles of at least 200 particles in SEM images randomly observed at an acceleration voltage of 15 kV were measured, and the obtained value was taken as the particle diameter.

[0038] <Average Particle Diameter d50 Measured by Laser Diffraction / Scattering Particle Size Distribution Analyzer> Measurement was carried out using a laser diffraction / scattering particle size distribution analyzer Microtrac sync (manufactured by Microtrac Inc.), and in the volume-based particle size distribution curve, the particle diameter value at which the cumulative value reaches 50% was taken as the average particle diameter d50. The measurement conditions are shown below. Dispersion medium: 0.025 mass % sodium hexametaphosphate aqueous solution (for products with untreated surface) Isopropyl alcohol (for products with treated surface) Measurement upper limit: 2000μm Measurement lower limit: 0.021μm Particle refractive index: 2.03 Particle shape: non-spherical Solvent refractive index: 1.33 (0.025% by mass sodium hexametaphosphate aqueous solution) 1.38 (Isopropyl alcohol)

[0039] <Specific surface area> The values ​​were measured using the BET flow method (single-point method) with an automatic BET specific surface area measuring device MacsorbModel HM-1220 (manufactured by Mounttech), after degassing by holding at 130°C for 20 minutes and then flowing a mixed gas of 30% nitrogen and 70% helium through it.

[0040] Example 1 500 g of basic zinc carbonate was weighed and packed into an alumina sagger. The mixture was heated to 800°C at a rate of 100°C / hour under an atmospheric environment, maintained at that temperature for 2 hours, and then cooled at a rate of 100°C / hour. The d50 of the raw material, basic zinc carbonate, determined by laser diffraction was 3.519 μm, and its specific surface area was 47.3 m². 2 It is / g.

[0041] Example 2 500 g of basic zinc carbonate was weighed and packed into an alumina sagger. The mixture was heated to 800°C at a rate of 100°C / hour under an atmospheric environment, maintained at that temperature for 5 hours, and then cooled at a rate of 100°C / hour.

[0042] Example 3 500 g of basic zinc carbonate was weighed and packed into an alumina sagger. The mixture was heated to 900°C at a rate of 100°C / hour under an atmospheric environment, maintained at that temperature for 2 hours, and then cooled at a rate of 100°C / hour.

[0043] Comparative Example 1 500 g of basic zinc carbonate was weighed and packed into an alumina sagger. The mixture was heated to 1000°C at a rate of 100°C / hour under an atmospheric environment, maintained at that temperature for 10 hours, and then cooled at a rate of 100°C / hour.

[0044] Table 1 shows the physical properties of the zinc oxide particles of Examples 1-3 and Comparative Example 1, as well as the properties of fine zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.) as Comparative Example 2, ultrafine zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., FINEX-30) as Comparative Example 3, one type of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.) as Comparative Example 4, and titanium oxide (manufactured by Sakai Chemical Industry Co., Ltd., MKR-1S) as Comparative Example 5. Furthermore, Figures 1-8 show the particle size distribution obtained by analyzing SEM images of zinc oxide particles from Examples 1-3 and Comparative Examples 1-4, and titanium oxide particles from Comparative Example 5. Figure 9 shows the particle size distribution obtained by laser diffraction of zinc oxide particles from Example 1 and Comparative Examples 2-4, and titanium oxide particles from Comparative Example 5.

[0045] [Table 1]

[0046] <Whiteness> The sample was placed to the brim in a Φ30mm glass petri dish, and the whiteness was measured using a colorimeter (Konica Minolta CR-5). The results are shown in Table 2.

[0047] [Table 2]

[0048] <Ultraviolet shielding ability and transparency> 2 g of zinc oxide particles, 10 g of acrylic polyol resin, 5 g of xylene, 5 g of butyl acetate, and 38 g of 1.5 mmφ glass beads from Example 1 and Comparative Examples 2-4 were placed in a 75 ml mayonnaise bottle and shaken for 90 minutes using a paint shaker to obtain a dispersion. The obtained dispersion was coated onto a glass slide with a bar coater #6, and the total light transmittance at wavelengths of 300-400 nm was measured using a spectrophotometer. The results are shown in Figure 10. Furthermore, the parallel transmittance of the glass slides coated with the above dispersion was measured at wavelengths of 400 to 800 nm, and the results are shown in Figure 11. Regarding UV shielding ability, Figure 10 shows that the zinc oxide particles of Example 1 have a higher total light transmittance at wavelengths of 300-380 nm and a lower amount of UV absorption than Comparative Examples 2-4. Furthermore, regarding transparency, Figure 11 shows that Example 1 has lower parallel transmittance and higher coverage in the visible light region than Comparative Examples 2-4. Although total light transmittance and parallel transmittance were not measured for Examples 2 and 3, considering the results of Example 1, the particle size distribution in Figures 2 and 3, and common technical knowledge, it is presumed that these particles also have low ultraviolet absorption and low transparency in the visible light region.

[0049] From the results in Tables 1 and 2 and Figure 10, it was confirmed that zinc oxide particles whose particle size distribution D1 and whiteness, measured by a predetermined method using a scanning electron microscope (SEM), were above a predetermined value were larger than nano-size particles and had low ultraviolet absorption. Furthermore, the zinc oxide particles of Examples 1-3 are L * a * b * b in the color system * It has a high value and produces a slightly yellowish-white color, which allows it to create a more natural whiteness when used in cosmetics.

Claims

1. Zinc oxide particles in which, when 200 particles in an SEM image observed using a scanning electron microscope (SEM) are measured with the maximum inscribed circle as the particle diameter, the D1 of the particle size distribution is 100 nm or more, and the whiteness measured by a colorimeter (Konica Minolta: CR-5) is 90.0 or more.

2. L measured by a colorimeter (Konica Minolta: CR-5) ＊ a ＊ b ＊ b in the color system ＊ The zinc oxide particles according to claim 1, wherein the value is 2.0 or greater.

3. Specific surface area of ​​0.1 to 2.0 m² ２ Zinc oxide particles according to claim 1 or 2, wherein the particle size is / g.

4. A method for producing zinc oxide particles according to claim 1 or 2, The manufacturing method is a method for producing zinc oxide particles, comprising the step of calcining basic zinc carbonate at 750 to 950°C.

5. A cosmetic composition comprising zinc oxide particles as described in claim 1 or 2.

Images