Zinc oxide particles

Abstract

The purpose of the present invention is to provide zinc oxide particles that are larger than nano-sized particles and have excellent ultraviolet shielding properties. This invention provides zinc oxide particles, configured so that when 200 zinc oxide particles are observed in a SEM image, using a scanning electron microscope (SEM), and the maximum inscribed circle of a particle is measured as the particle diameter, the zinc oxide particles have a median value (D50) of 100 nm or more, D10 in a particle size distribution obtained by analyzing the SEM image is 55-80 nm, and the value of D90 / D50 is 1.80 or less.

Description

Zinc oxide particles

[0001] The present invention relates to zinc oxide particles.

[0002] Zinc oxide has the effect of shielding ultraviolet rays without transmitting them, and is incorporated into cosmetics such as sunscreen as an ultraviolet ray shielding agent. Generally, it is known that the smaller the particles of zinc oxide, the larger the specific surface area and the higher the ultraviolet ray shielding ability. As a raw material for cosmetics, mainly nano-sized particles are used. In recent years, concerns have been raised about the harmfulness of nanomaterials to organisms and the environment, and zinc oxide is no exception. In the EU, stricter regulations are imposed on nano-sized zinc oxide incorporated into cosmetics than on non-nano-sized zinc oxide. Among consumers, there is also a movement to avoid nano-sized zinc oxide. Therefore, non-nano-sized particles larger than the nano-size are demanded by cosmetics manufacturers targeting the EU market and other markets as raw materials for cosmetics and the like.

[0003] Regarding non-nano-sized zinc oxide, Patent Document 1 discloses a composition: a water-soluble or water-insoluble carrier; and zinc oxide particles dispersed in the carrier, wherein the zinc oxide particles substantially do not have particles having a primary particle size smaller than 100 nm as measured by a transmission electron microscope. Patent Document 2 discloses a wide-spectrum UV light protection composition comprising mesoporous zinc oxide aggregates having an average aggregate size of at least 0.8 microns and dispersed in a dispersion medium (carrier), and being transparent to visible light. Patent Document 3 discloses a sunscreen cosmetic containing zinc oxide fine particles, wherein 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] Also, regarding a method for producing zinc oxide powder, Patent Document 4 discloses a method for producing high-purity nano zinc oxide powder including a step of charging basic zinc carbonate (ZnCO ３ ·Zn(OH) ２ ) into a rotary incinerator and firing it.

[0005] Japanese Patent Publication No. 2012-511499, Japanese Patent Publication No. 2011-509940, Japanese Patent Publication No. 2010-275223, Korean Published Patent No. 10-2020-0044485

[0006] As mentioned above, although various compositions containing non-nanosized zinc oxide have been disclosed, there is a problem in that increasing the size of the zinc oxide particles reduces the UV shielding ability.

[0007] In view of the above situation, the present invention aims to provide zinc oxide particles that are larger than nano-size but have excellent ultraviolet shielding ability.

[0008] The inventors investigated zinc oxide particles larger than nanosize and found that zinc oxide particles observed using a scanning electron microscope (SEM) in SEM images, where the median particle size (D50) and particle size distributions D10 and D90 / D50 measured by a predetermined method were below a predetermined range, exhibited excellent ultraviolet shielding ability despite being larger than nanosize, thus completing the present invention.

[0009] The present invention includes the following zinc oxide particles, etc.: [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 median value (D50) is 100 nm or more, the D10 of the particle size distribution obtained by analysis of the SEM image is 55 to 80 nm, and the D90 / D50 value is 1.80 or less. [2] Zinc oxide particles as described in [1] above, in which the d50 of the particle size distribution measured by a laser diffraction / scattering particle size distribution analyzer is 100 nm or more. [3] A specific surface area of ​​3.5 to 6.0 m² ２ Zinc oxide particles as described in [1] or [2] above, wherein the amount is / g. [4] A method for producing zinc oxide particles as described in [1] to [3] above, wherein the production method includes a step of calcining basic zinc carbonate at 570 to 700°C. [5] A cosmetic composition containing zinc oxide particles as described in any of [1] to [3] above.

[0010] The zinc oxide particles of the present invention, while being larger than nano-size, exhibit excellent ultraviolet shielding ability, making them suitable for use in cosmetics and the like.

[0011] This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles obtained in Example 1. This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles obtained in Example 2. This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles obtained in Example 3. This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles obtained in Comparative Example 1. This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles in Comparative Example 2. This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles in Comparative Example 3. This figure shows the particle size distribution obtained by analyzing SEM images of zinc oxide particles in Comparative Example 4. This figure shows the particle size distribution obtained by laser diffraction of zinc oxide particles in Examples 1-3 and Comparative Examples 1-4. This figure shows the particle size distribution obtained by laser diffraction of the raw material, basic zinc carbonate. This figure shows the spectrum of total light transmittance at wavelengths of 300-400 nm of dispersions prepared using zinc oxide particles in Examples 1-3 and Comparative Examples 1-4. This figure shows the parallel transmittance spectra at wavelengths of 400 to 800 nm of dispersions prepared using zinc oxide particles from Examples 1 to 3 and Comparative Examples 1 to 4.

[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 median value (D50) 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 the D10 of the particle size distribution obtained by analysis of the SEM image is 55 to 80 nm, and the D90 / D50 value is 1.80 or less. If there are many coarse particles in the zinc oxide particles, the amount of ultraviolet absorption decreases and it is also unfavorable in terms of ultraviolet scattering, but the zinc oxide particles of the present invention have fewer coarse particles because the D50, D10, and D90 / D50 values ​​are within the above range, and therefore have excellent ultraviolet shielding ability despite being larger than nano-size particles. The particle diameter and particle size distribution in the analysis of the above SEM image can be measured by the method described in the examples.

[0014] In the zinc oxide particles of the present invention, the D50 value may be 100 nm or greater, but is preferably 100 to 125 nm, and more preferably 101 to 115 nm.

[0015] In the zinc oxide particles of the present invention, the above-mentioned D10 may be 55 to 80 nm, but is preferably 60 to 75 nm.

[0016] The D90 / D50 ratio in the zinc oxide particles of the present invention may be 1.80 or less, but is preferably 1.65 or less. Furthermore, it is preferable that the D90 / D50 ratio is 1.20 or more.

[0017] 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 100 to 125 nm, and even more preferably 101 to 115 nm. The above d50 can be measured by the method described in the examples.

[0018] The zinc oxide particles of the present invention have a specific surface area of ​​3.5 to 6.0 m². ２ It is preferable that the amount is / g. This results in zinc oxide particles having superior ultraviolet shielding ability. The specific surface area is more preferably 4.0 to 6.0 m². ２ The value is / g. The specific surface area of ​​zinc oxide particles can be measured by the method described in the examples.

[0019] 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.

[0020] 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 for the above surface treatment is not particularly limited, but examples include organosilicon compounds and fatty acids. Examples of the above organosilicon compounds include organopolysiloxanes such as dimethylpolysiloxane, methylhydrogenpolysiloxane, hydrogen dimethicone, methylphenyl silicone, amino-modified silicone, triethoxysilylethyl polydimethylsiloxyethyl dimethicone, and triethoxysilylethyl polydimethylsiloxyethylhexyl dimethicone; and alkylsilanes such as triethoxycaprylylsilane, trimethoxycaprylylsilane, and decyltriethoxysilane.

[0021] 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.

[0022] The amount of the above surface treatment agent used is not particularly limited, but it is preferably 0.3 to 10% by mass based on 100% by mass of zinc oxide. More preferably it is 0.5 to 5% by mass, and even more preferably 0.8 to 3% by mass.

[0023] 2. Method for Producing Zinc Oxide Particles The method for producing zinc oxide particles according to the present invention is not particularly limited, but for example, a method including a step of calcining basic zinc carbonate at 570 to 700°C can be used. The present invention is a method for producing the above-mentioned zinc oxide particles, and the production method is also a method for producing zinc oxide particles that includes a step of calcining basic zinc carbonate at 570 to 700°C.

[0024] The firing temperature in the above firing process may be 570 to 700°C, but is preferably 580 to 690°C, and more preferably 600 to 680°C.

[0025] The firing time in the above firing process is not particularly limited, but is preferably 1 to 5 hours, and more preferably 2 to 4 hours.

[0026] The atmosphere during the firing process described above is not particularly limited, but firing in an air atmosphere is preferable.

[0027] 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.

[0028] The above method for producing zinc oxide particles preferably includes a step of classifying the zinc oxide obtained in the calcination step. The classification method is not particularly limited, but for example, classification by sieving can be used. Examples of classification by sieving include wet classification and dry classification.

[0029] 3. Cosmetics The zinc oxide particles of the present invention, while not nanoparticles, have excellent UV shielding properties and can therefore be suitably used as a component in cosmetics. Cosmetics containing the above zinc oxide particles are also one of the present inventions.

[0030] 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, aqueous 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 sunscreen, foundation, makeup base, and eyeshadow.

[0031] The cosmetic composition of the present invention may contain, in addition to the zinc oxide particles of the present invention, any aqueous and oily components that can be used in the field of cosmetics. The aqueous and oily components are not particularly limited and include, for example, oils, surfactants, humectants, higher alcohols, metal ion chelating agents, natural and synthetic polymers, water-soluble and oil-soluble polymers, UV shielding agents, various extracts, inorganic and organic pigments, various powders such as inorganic and organic clay minerals, colorants such as inorganic and organic pigments treated with metal soap or silicone, organic dyes, preservatives, antioxidants, pigments, thickeners, pH adjusters, fragrances, cooling agents, antiperspirants, bactericides, skin activators, etc. One or more of these can be optionally blended to produce the desired cosmetic composition by commonly used methods. The amount of these optional components blended is not particularly limited as long as it does not impair the effects of the present invention.

[0032] Specific examples are given below to illustrate the present invention in detail, but the present invention is not limited to these examples. Unless otherwise specified, "%" and "wt%" mean "weight percent (mass percent)". The measurement methods for each physical property are as follows.

[0033] <Analysis of SEM Images> Using a scanning electron microscope (JEM-7000F, manufactured by JEOL), the maximum inscribed circle of the smallest 200 particles in the SEM images, which were randomly observed at an accelerating voltage of 15 kV, was measured and defined as the particle diameter.

[0034] <Average particle diameter d50 measured by laser diffraction / scattering particle size distribution analyzer> The average particle diameter d50 was measured using a Microtrac sync laser diffraction / scattering particle size distribution analyzer (manufactured by Microtrac). The particle size value at which the cumulative value on the volume-based particle size distribution curve reaches 50% was defined as the average particle diameter d50. The measurement conditions are as follows: Dispersion medium: 0.025 mass% sodium hexametaphosphate aqueous solution (zinc oxide without surface treatment) Isopropyl alcohol (zinc oxide with surface treatment) Upper measurement limit: 2000 μm Lower measurement limit: 0.021 μm Particle refractive index: 2.03 Particle shape: Non-spherical Solvent refractive index: 1.33 (0.025 mass% sodium hexametaphosphate aqueous solution) 1.38 (isopropyl alcohol)

[0035] <Specific Surface Area> Measured by the BET flow method (one-point method) using an automatic BET specific surface area measuring device, Macsorb Model HM-1220 (manufactured by Mounttech Co., Ltd.), after degassing by holding at 130°C for 20 minutes and flowing a mixed gas of 30% nitrogen and 70% helium.

[0036] Example 1 Weighed 500 g of basic zinc carbonate and filled it into an alumina crucible. Heated it to 600°C at a rate of 100°C / hour in an air atmosphere, held it for 2 hours as it was, and then cooled it at a rate of 100°C / hour. The d50 of the starting basic zinc carbonate by laser diffraction was 3.519 μm, and the specific surface area was 47.3 m ２ / g.

[0037] Example 2 Weighed 500 g of basic zinc carbonate and filled it into an alumina crucible. Heated it to 620°C at a rate of 100°C / hour in an air atmosphere, held it for 2 hours as it was, and then cooled it at a rate of 100°C / hour.

[0038] Example 3 Triethoxycaprylylsilane (manufactured by Shin-Etsu Chemical Co., Ltd., AES-3038) was added to and mixed with the zinc oxide obtained in Example 1 at 1% by mass based on zinc oxide to obtain triethoxycaprylylsilane-treated zinc oxide.

[0039] Comparative Example 1 Weighed 500 g of basic zinc carbonate and filled it into an alumina crucible. Heated it to 500°C at a rate of 100°C / hour in an air atmosphere, held it for 5 hours as it was, and then cooled it at a rate of 100°C / hour.

[0040] The physical properties of the zinc oxide particles of Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 1. As Comparative Example 2, one type of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.) was used, as Comparative Example 3, fine zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.) was used, and as Comparative Example 4, ultrafine zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., FINEX-30) was used. Also, FIGS. 1 to 7 show the particle size distributions obtained by analyzing the SEM images of the zinc oxide particles of Examples 1 to 3 and Comparative Examples 1 to 4. FIG. 8 shows the particle size distributions obtained by laser diffraction of the zinc oxide particles of Examples 1 to 3 and Comparative Examples 1 to 4. FIG. 9 shows the particle size distribution obtained by laser diffraction of the starting basic zinc carbonate.

[0041]

[0042] <UV Blocking Ability> (Evaluation Method) 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 of Examples 1 to 3 and Comparative Examples 1 to 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 applied to a slide glass using a bar coater #6, and the total light transmittance at wavelengths of 300 to 400 nm was measured using a spectrophotometer, and the results are shown in FIG. 10. Also, for the slide glass coated with the above dispersion, the parallel transmittance at wavelengths of 400 to 800 nm was measured, and the results are shown in FIG. 11. Regarding the UV blocking ability, from FIG. 10, it can be seen that the non-nano-sized zinc oxide particles of Examples 1 to 3 have the same size as the zinc oxide of Comparative Example 2, but the total light transmittance at wavelengths of 300 to 400 nm is low, indicating excellent UV blocking ability. Regarding transparency, from FIG. 11, it can be seen that Examples 1 and 2 without surface treatment have a higher parallel transmittance at wavelengths of 400 to 800 nm than Comparative Example 2, indicating high transparency.

[0043] <Evaluation of SPF Value and Use Feeling in Powder Foundation> A powder foundation was prepared with the formulation described in Table 2. As Comparative Example 5, a powder foundation without zinc oxide was also prepared. The SPF value is an index indicating the UV prevention effect, and the higher the SPF value, the stronger the protective effect against ultraviolet B waves (UVB). (Evaluation Method) SPF value: The in vitro SPF value of the prepared powder foundation was measured using an SPF analyzer (UV-2000S, manufactured by Labsphere). Use feeling: Five monitors used the powder foundation, and the obtained sensations such as good elongation and no squeak were evaluated according to the following evaluation criteria. ◎: Very good. 〇: Good. △: Normal. ×: Poor use feeling.

[0044] The evaluation results of the SPF value and use feeling in the powder foundation are shown in Table 2.

[0045]

[0046] From the results in Table 1 and Figure 10, it was confirmed that zinc oxide particles with a median particle size (D50) and particle size distributions D10 and D90 / D50 within the specified range, measured by a predetermined method using a scanning electron microscope (SEM), exhibited excellent UV shielding ability despite being larger than nano-size particles. Furthermore, from the results in Table 2, it was confirmed that when zinc oxide particles with the above-mentioned D50, D10, and D90 / D50 within the specified range were used in foundation, they exhibited excellent UV shielding ability and also provided a superior user experience.

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 median value (D50) is 100 nm or more, the D10 of the particle size distribution obtained by analysis of the SEM image is 55 to 80 nm, and the D90 / D50 value is 1.80 or less.

2. Zinc oxide particles according to claim 1, wherein the d50 of the particle size distribution measured by a laser diffraction / scattering particle size distribution analyzer is 100 nm or more.

3. Specific surface area of ​​3.5 to 6.0 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 any one of claims 1 to 3, the method comprising the step of calcining basic zinc carbonate at 570 to 700°C.

5. A cosmetic composition comprising zinc oxide particles according to any one of claims 1 to 3.

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