Dimethicone-treated zinc oxide powder and composition containing dimethicone-treated zinc oxide powder

Abstract

Provided is a dimethicone-treated zinc oxide powder which is highly water repellent and dispersible in an oil agent and which can be used to prepare a cosmetic material with excellent ultraviolet ray shielding capability and visible light transmittance. Also provided is a composition containing the dimethicone-treated zinc oxide powder.　The dimethicone-treated zinc oxide powder according to the present invention is obtained as a result of treating a zinc oxide powder with dimethicone, and is characterized as follows. The ratio Tt550 / Tt370 of the transmittance Tt550 of light having a wavelength of 550 nm to the transmittance Tt370 of light having a wavelength of 370 nm, where transmittance is determined using a spectral transmittance curve measured using a specific dispersion coating film, is 10 or more. In a specific acid resistance test, the pH is 6.5 or less. Alternatively, the particle size at cumulative 90% in a volume-based particle size distribution measured by dynamic light scattering is 550 nm or less. The composition according to the present invention is characterized in that the dimethicone-treated zinc oxide powder according to the present invention is blended with an oil agent.

Description

Dimethicone-treated zinc oxide powder and composition containing said dimethicone-treated zinc oxide powder

[0001] The present invention relates to a dimethicone-treated zinc oxide powder that can be used to prepare cosmetics having excellent ultraviolet shielding ability and visible light transmittance, and that has high water repellency and dispersibility in oils, and to a composition containing the dimethicone-treated zinc oxide powder.

[0002] In order to impart a desired UV protection effect to cosmetics, metal oxide powders having UV protection effect, such as zinc oxide powder and titanium oxide powder, are blended in. In particular, zinc oxide powder is widely blended in sunscreen cosmetics because it has a high protection effect against long-wavelength ultraviolet rays (UV-A) with wavelengths of 320 to 400 nm, which cause wrinkles and sagging of the skin, and also has high visible light transmittance.

[0003] Many of the metal oxide powders incorporated into cosmetics are surface-treated with surface treatment agents such as dimethicone, hydrogen dimethicone, and triethoxycaprylylsilane in order to suppress secondary aggregation and improve dispersibility in oils and cosmetic durability (Patent Documents 1 and 2, etc.).

[0004] JP 11-302015 A JP 2018-12679 A

[0005] In recent years, environmental pollution caused by microplastics has become a concern, and there is a demand for safer materials with less environmental impact. Dimethicone is a stable substance without any chemically reactive groups, and expectations are growing for it to be a highly safe material. However, because dimethicone is a stable substance without any chemically reactive groups, it has been difficult to achieve uniform and strong bonding with the particle surface of metal oxide powders when used as a surface treatment agent for metal oxide powders. For this reason, metal oxide powders surface-treated with conventional dimethicone do not necessarily have sufficient water repellency or dispersibility in oils, and further improvements are needed in terms of UV protection and visible light transparency when incorporated into cosmetics.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dimethicone-treated zinc oxide powder that can be used to prepare cosmetics having excellent ultraviolet shielding ability and visible light transmittance, and that has high water repellency and dispersibility in oils, and a composition containing the dimethicone-treated zinc oxide powder.

[0007] The dimethicone-treated zinc oxide powder of the present invention is obtained by treating zinc oxide powder with dimethicone, and is characterized in that the ratio of Tt550 / Tt370, the transmittance of light having a wavelength of 550 nm (Tt550) to Tt370, the transmittance of light having a wavelength of 370 nm (Tt370), as determined using a spectral transmittance curve measured by the following measurement method (A), is 10 or more, and that the pH is 6.5 or less in the following acid resistance test (B).

[0008] <Measurement Method (A)> (1) In an environment of 25°C, 10 g of dimethicone-treated zinc oxide powder, 34 g of cyclopentasiloxane, 5 g of liquid paraffin, and 5 g of PEG-9 dimethicone are mixed using a disper mixer at 3000 rpm for 10 minutes to prepare a dispersion. (2) A mixture of 32 g of ion-exchanged water and 14 g of butylene glycol is prepared. (3) While stirring the dispersion prepared in (1) using a disper mixer at 3000 rpm, the mixture prepared in (2) is added to the dispersion, and the mixture is further mixed using a disper mixer at 3000 rpm for 5 minutes to prepare a sample solution. (4) The sample solution obtained in (3) is applied to a polypropylene film using an automatic bar coater equipped with a wire bar (No. 6) to form a coating film. (5) The total light transmittance of the coating film formed in (4) is measured within 1 minute using a spectrophotometer in an environment of 25° C. to obtain a spectral transmittance curve.

[0009] <Acid Resistance Test (B)> (i) In an environment of 25°C, 12.5 g of methanol and 12.5 g of ion-exchanged water are placed in a container, and 0.25 g of dimethicone-treated zinc oxide powder is added to the container while stirring. (ii) One minute after adding the dimethicone-treated zinc oxide powder to the solution of (i), 50 g of sulfuric acid at pH 3 is added over 10 minutes, and the pH of the solution after the addition of sulfuric acid is measured.

[0010] Another embodiment of the dimethicone-treated zinc oxide powder of the present invention is a zinc oxide powder that has been treated with dimethicone, and is characterized in that the cumulative 90% particle diameter in the volume-based particle size distribution measured by dynamic light scattering is 550 nm or less.

[0011] Furthermore, another embodiment of the dimethicone-treated zinc oxide powder of the present invention is characterized in that the zinc oxide powder is treated with the dimethicone by kneading the zinc oxide powder and dimethicone using a continuous injection mixer.

[0012] The composition of the present invention is characterized by comprising the dimethicone-treated zinc oxide powder of the present invention and an oil agent.

[0013] According to the present invention, it is possible to provide a dimethicone-treated zinc oxide powder that can be used to prepare cosmetics having excellent ultraviolet shielding ability and visible light transmittance, and that has high water repellency and dispersibility in oils, and a composition containing the dimethicone-treated zinc oxide powder.

[0014] <Dimethicone-Treated Zinc Oxide Powder> When treating zinc oxide powder with dimethicone, as described above, dimethicone cannot react with zinc oxide, so for example, it cannot adhere well to the surface of the zinc oxide powder, or the dimethicone adhering to the zinc oxide powder is likely to detach from the zinc oxide powder during the production of the cosmetic or during use of the cosmetic. Therefore, even if an attempt is made to disperse the dimethicone-treated zinc oxide powder in a composition such as a cosmetic containing an oil agent, the oil dispersibility improving effect of the dimethicone treatment is not fully exerted, and the dimethicone-treated zinc oxide powder cannot be dispersed well, and in cosmetics containing the dimethicone-treated zinc oxide powder, the effect of the dimethicone-treated zinc oxide powder may not be fully ensured.

[0015] The present inventors have conducted extensive research into methods for treating zinc oxide powder with dimethicone, and have found that when zinc oxide powder and dimethicone are kneaded using a continuous jet mixer (flow jet mixer), the effects of the dimethicone treatment are significantly exhibited in the resulting dimethicone-treated zinc oxide powder, ensuring high water repellency and improving dispersibility in oil agents.

[0016] The reason for this is unclear, but is presumed to be as follows. When treating zinc oxide powder with dimethicone, a common method is to mix the zinc oxide powder and dimethicone in a batch mixer such as a Henschel mixer or blender. When zinc oxide powder and dimethicone are mixed in a batch mixer, a large amount of zinc oxide powder and a large amount of dimethicone are mixed in a relatively large space, making it difficult to adhere dimethicone to the surface of the zinc oxide powder with high uniformity. For example, the zinc oxide powder may aggregate, resulting in a low dimethicone content in that area, or conversely, zinc oxide powder with a very high dimethicone content may be produced. The dimethicone-treated zinc oxide powder obtained in this manner has significantly different affinity for oils in different areas. Therefore, when blended into cosmetics containing oils, the dimethicone-treated zinc oxide powder is likely to undergo uneven dispersion. Furthermore, in areas with a particularly high dimethicone content, dimethicone is likely to detach from the zinc oxide powder, further amplifying this uneven dispersion. In such cosmetic compositions, in areas where the amount of dimethicone-treated zinc oxide powder dispersed is small, the functions of the zinc oxide powder (for example, ultraviolet blocking function) are not fully exhibited.

[0017] In contrast, a continuous injection mixer is a device that continuously mixes and discharges raw materials supplied in small amounts. When zinc oxide powder and dimethicone are mixed using this, a small amount of zinc oxide powder and dimethicone are mixed in a very small area with high shear force compared to when a batch mixer is used. Therefore, dimethicone-treated zinc oxide powder can be continuously obtained while improving the uniformity of the amount of dimethicone attached to each particle of zinc oxide powder. The dimethicone-treated zinc oxide powder obtained in this way has a high uniformity of affinity to oils at each location, so even when incorporated into a composition containing an oil, dispersion irregularities are unlikely to occur. In addition, since there are few locations where a large amount of dimethicone is attached, dimethicone is unlikely to detach from the zinc oxide powder, which is thought to suppress the occurrence of dispersion irregularities.

[0018] Dimethicone-treated zinc oxide powder obtained by kneading zinc oxide powder and dimethicone using a continuous injection mixer has high water repellency due to the action of dimethicone, and can be well dispersed in oil agents in compositions such as cosmetics containing oil agents. Therefore, in addition to being able to exhibit good ultraviolet shielding function, the powder is unlikely to impede the transmission of visible light, which can also improve the visible light transmittance of the composition, making it easy to prepare a highly transparent composition.

[0019] When dimethicone-treated zinc oxide powder is obtained by kneading zinc oxide powder and dimethicone using a continuous injection mixer, it is difficult to specify, for example, the state of adhesion of dimethicone to the zinc oxide powder (such as the uniformity of the amount of adhesion). However, dimethicone-treated zinc oxide powder obtained by such a method will have, for example, the following characteristic (I) or satisfy the physical property (II).

[0020] (I) The ratio of Tt550 / Tt370, the transmittance of light having a wavelength of 550 nm (Tt550) to Tt370, the transmittance of light having a wavelength of 370 nm, determined using a spectral transmittance curve measured by the following measurement method (A), is 10 or more, and the pH is 6.5 or less in the following acid resistance test (B).

[0021] <Measurement Method (A)> (1) In an environment of 25°C, 10 g of dimethicone-treated zinc oxide powder, 34 g of cyclopentasiloxane, 5 g of liquid paraffin, and 5 g of PEG-9 dimethicone are mixed using a disper mixer at 3000 rpm for 10 minutes to prepare a dispersion. (2) A mixture of 32 g of ion-exchanged water and 14 g of butylene glycol is prepared. (3) While stirring the dispersion prepared in (1) using a disper mixer at 3000 rpm, the mixture prepared in (2) is added to the dispersion, and the mixture is further mixed using a disper mixer at 3000 rpm for 5 minutes to prepare a sample solution. (4) The sample solution obtained in (3) is applied to a polypropylene film using an automatic bar coater equipped with a wire bar (No. 6) to form a coating film. (5) Within 1 minute after formation in (4), the total light transmittance of the coating film [the coating film in a wet state (containing the liquid components of the sample liquid)] is measured using a spectrophotometer in an environment of 25°C, and a spectral transmittance curve is obtained.

[0022] In measuring the values ​​shown in the examples below, a "Plain OPP Sheet #40" manufactured by Mitsui Chemicals Tohcello Co., Ltd. was used as the polypropylene film (4), and an "IMC-7000" manufactured by Imoto Machinery Co., Ltd. was used as the automatic bar coater. The coating speed of the automatic bar coater was set as follows: SPEED CONTROL: 15

[0023] The spectrophotometer used in (5) was a Hitachi High-Technologies Corporation "U-4100" (using an integrating sphere). The conditions for measurement using the spectrophotometer were as follows: Scan speed: 300 nm / min, Sampling interval: 2 nm, Measurement wavelength: 250 to 700 nm.

[0024] <Acid Resistance Test (B)> (i) In an environment of 25°C, 12.5 g of methanol and 12.5 g of ion-exchanged water are placed in a container, and 0.25 g of dimethicone-treated zinc oxide powder is added thereto while stirring (for example, using a stirrer). (ii) One minute after adding the dimethicone-treated zinc oxide powder to the solution of (i), 50 g of sulfuric acid at pH 3 is added over 10 minutes, and the pH of the solution after the addition of sulfuric acid is measured.

[0025] The above-mentioned measurement method (A) evaluates the balance between the UV-shielding ability and visible light transmittance of the dimethicone-treated zinc oxide powder when the dimethicone-treated zinc oxide powder is dispersed in a water-in-oil emulsion (in the oil phase) of a specific composition and exhibited in a coating film of this emulsion. A Tt550 / Tt370 value of 10 or more in the above-mentioned measurement method (A) indicates that the dimethicone-treated zinc oxide powder has high water repellency and excellent dispersibility in oil agents, and therefore can exhibit excellent UV-shielding ability and visible light transmittance in a composition containing oil agents. In the case of dimethicone-treated zinc oxide powder with poor dispersibility in oil agents, dispersion irregularities of the dimethicone-treated zinc oxide powder occur in the emulsion, resulting in areas where sufficient UV-shielding ability cannot be exhibited (areas with high UV transmittance), resulting in a large Tt370 and making it impossible to achieve the above-mentioned large Tt550 / Tt370 value.

[0026] In the dimethicone-treated zinc oxide powder, the Tt550 / Tt370 value in the above measurement method (A) is preferably not less than 11. In addition, in the dimethicone-treated zinc oxide powder, the upper limit of the Tt550 / Tt370 value in the above measurement method (A) is not particularly limited, but is usually not more than 20.

[0027] Furthermore, in the acid resistance test (B), for example, when dimethicone is unevenly attached to the zinc oxide powder, the exposed parts of the zinc oxide powder have low water repellency, so that the test solution containing sulfuric acid easily adheres to them, and zinc oxide dissolves from these exposed parts into the test solution, raising the pH of the test solution. On the other hand, when dimethicone is attached to the zinc oxide powder with high uniformity, the water repellency of the dimethicone-treated zinc oxide powder is high, and as a result, acid resistance is improved, so that the pH of the test solution can be maintained low. In the case of a dimethicone-treated zinc oxide powder obtained by kneading zinc oxide powder and dimethicone using a continuous injection mixer, dimethicone is attached to the zinc oxide powder with high uniformity, so that the pH can be kept at 6.5 or less in the acid resistance test (B).

[0028] The dimethicone-treated zinc oxide powder more preferably has a pH of 6.3 or less in the acid resistance test (B). Although there is no particular restriction on the lower limit of the pH in the acid resistance test (B), the pH is usually 5 or more.

[0029] (II) The particle diameter (D90) of the cumulative 90% of the particle size distribution on a volume basis, as measured by dynamic light scattering, is 550 nm or less.

[0030] In dimethicone-treated zinc oxide powder, when dimethicone is unevenly attached to zinc oxide powder, the primary particle of dimethicone-treated zinc oxide powder itself becomes coarse, and dimethicone-treated zinc oxide powder is likely to aggregate and produce coarse secondary particles, so that the value of D90 becomes large.On the other hand, when dimethicone is attached to zinc oxide powder with high uniformity, the particle size of the primary particle of dimethicone-treated zinc oxide powder does not become too large from the particle size of original zinc oxide powder, and furthermore, the aggregation of primary particles (coarsening of secondary particles) is suppressed.Therefore, if the dimethicone-treated zinc oxide powder obtained by kneading zinc oxide powder and dimethicone using continuous injection mixer, dimethicone is attached to zinc oxide powder with high uniformity, so that D90 satisfies the above-mentioned value.

[0031] In the dimethicone-treated zinc oxide powder satisfying the physical property (II), it is preferable that D90 is 500 nm or less. In the dimethicone-treated zinc oxide powder satisfying the physical property (II), the lower limit of D90 is not particularly limited, but it is usually 250 nm or more.

[0032] In addition, in the dimethicone-treated zinc oxide powder satisfying the physical property (II), the cumulative 50% particle diameter (D50) in the volume-based particle size distribution measured by dynamic light scattering is preferably 450 nm or less, more preferably 400 nm or less. In the dimethicone-treated zinc oxide powder satisfying the physical property (II), the lower limit of the D50 value is not particularly limited, but is usually 150 nm or more.

[0033] Furthermore, in the dimethicone-treated zinc oxide powder satisfying the physical property (II), the cumulative 10% particle diameter (D10) in the volume-based particle size distribution measured by dynamic light scattering is preferably 400 nm or less, more preferably 350 nm or less. In the dimethicone-treated zinc oxide powder satisfying the physical property (II), the lower limit of the D10 value is not particularly limited, but is usually 100 nm or more.

[0034] The specific methods for measuring D10, D50, and D90 shown in the Examples below are as follows. In an environment of 25°C, 20.0 g of dimethicone-treated zinc oxide powder was added to a mixed solvent of 79.0 g of dimethicone (KF-96A-6cs, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sorbitan sesquiisostearate (NIKKOL SI-15RV, manufactured by Nikko Chemicals Co., Ltd.), and the mixture was mixed for 10 minutes at 3,000 rpm using a disper. 1 mL of the resulting dispersion was diluted with 99 mL of dimethicone (KF-96A-6cs, manufactured by Shin-Etsu Chemical Co., Ltd.), and the mixture was mixed for 2 minutes at 1,500 rpm using a disper to obtain a sample solution. The measurement is carried out for 60 seconds in an environment of 25° C. using a concentrated particle size analyzer (FPAR-1000 manufactured by Otsuka Electronics Co., Ltd.), and D10, D50 and D90 of the volume distribution are obtained.

[0035] Also, in the dimethicone-treated zinc oxide powder having the characteristic (I), D90 is preferably 550 nm or less, more preferably 500 nm or less, and usually 250 nm or more. Furthermore, in the dimethicone-treated zinc oxide powder having the characteristic (I), D50 is preferably 450 nm or less, more preferably 400 nm or less, and usually 150 nm or more. Also, in the dimethicone-treated zinc oxide powder having the characteristic (I), D10 is preferably 400 nm or less, more preferably 350 nm or less, and usually 100 nm or more.

[0036] In the dimethicone-treated zinc oxide powder having the characteristic (I), the dimethicone-treated zinc oxide powder satisfying the physical property (II), and the dimethicone-treated zinc oxide powder obtained by kneading zinc oxide powder and dimethicone using a continuous injection mixer, the specific surface area is 10 m ２ / g or more, and ２ / g or more is more preferable, and 40m ２ / g or less, and ２ / g or less is more preferable. Dimethicone-treated zinc oxide powder having such a specific surface area exhibits a better balance between ultraviolet blocking ability and visible light transmittance, for example.

[0037] The specific surface area of ​​the dimethicone-treated zinc oxide powder referred to in this specification and the zinc oxide powder used as a substrate, which will be described later, is measured using a fully automatic specific surface area measuring device (for example, "Macsorb HM model-1208" manufactured by Mountech Co., Ltd.) using nitrogen (N ２ ) and measured by the BET method.

[0038] The dimethicone-treated zinc oxide powder having the above-mentioned specific surface area can be obtained by kneading zinc oxide powder having the average particle size described below with dimethicone using a continuous injection mixer.

[0039] Next, matters common to the dimethicone-treated zinc oxide powder having the characteristic (I) and the dimethicone-treated zinc oxide powder satisfying the physical properties (II) will be described.

[0040] The zinc oxide powder (zinc oxide powder treated with dimethicone) used as the base material can be appropriately selected from a variety of physical properties depending on the requirements of the composition, such as a cosmetic, to which the dimethicone-treated zinc oxide powder is blended, and for example, from the viewpoint of imparting a good UV protection effect to the cosmetic, the average particle diameter (average primary particle diameter) is preferably 5 nm or more, more preferably 10 nm or more, and preferably 200 nm or less, and more preferably 150 nm or less. The average particle diameter of the zinc oxide powder referred to here is the number-average particle diameter of the Heywood diameter (diameter equivalent to a circle with a projected area) of 500 or more zinc oxide particles, obtained by analyzing zinc oxide powder photographed with a transmission electron microscope using the image analysis particle size distribution measurement software "Mac-View."

[0041] In addition, the zinc oxide powder used as the base material has a specific surface area of ​​25 m2 or less, from the viewpoint of imparting a better ultraviolet protection effect to the cosmetic. ２ / g or more, and ２ / g or more is more preferable, and 65m ２ / g or less, and ２ It is more preferable that the SiO2 content is 1 / g or less.

[0042] Furthermore, the zinc oxide powder used as the base material may be surface-treated with an inorganic compound such as silica before being treated with dimethicone.

[0043] The dimethicone used as the treating agent for the dimethicone-treated zinc oxide powder of the present invention preferably has a viscosity of 10 to 3,500 mPa·s at 25° C. as measured at 6 rpm with a Brookfield viscometer. Dimethicone having such a viscosity enables the zinc oxide powder to be treated more uniformly.

[0044] The amount of dimethicone to be treated (amount attached to the zinc oxide powder) is preferably 3 to 10% by mass when the total amount of the zinc oxide powder as the base material and dimethicone is taken as 100% by mass.

[0045] When treating zinc oxide powder with dimethicone, as described above, the zinc oxide powder and dimethicone can be kneaded using a continuous injection mixer.The zinc oxide powder can be fed into the continuous injection mixer using, for example, a feeder, and the dimethicone can be fed using, for example, a metering pump.By adjusting the balance of these feeding speeds, the amount of dimethicone treated in the finally obtained dimethicone-treated zinc oxide powder (the amount of dimethicone in the total amount of zinc oxide powder and dimethicone) can be adjusted.The stirring conditions (kneading conditions) of the continuous injection mixer for kneading these can be appropriately set.

[0046] <Composition> The composition of the present invention contains the dimethicone-treated zinc oxide powder of the present invention and an oil agent. The form of the composition of the present invention can be, for example, an oil-in-water emulsion, a water-in-oil emulsion, or an oil dispersion, and can be selected depending on the intended use.

[0047] The composition of the present invention can be embodied as a composition for various applications to which compositions containing inorganic oxide powders such as zinc oxide powder are applied, and typical applications include cosmetics (sunscreen, foundation, emulsion, skin cream, etc.). When the composition of the present invention is used for cosmetics, the composition of the present invention itself can be embodied as a cosmetic (cosmetic composition), or can be embodied as a raw material composition for cosmetics (a composition containing some of the raw materials used in cosmetics).

[0048] The dimethicone-treated zinc oxide powder of the present invention can be used to prepare a composition having excellent ultraviolet shielding ability and visible light transmittance, but the composition of the present invention also includes embodiments in which the transparency is not high due to the influence of components other than the dimethicone-treated zinc oxide powder.

[0049] Examples of oils that can be incorporated into the composition include silicone oils, hydrocarbons, higher fatty acids, higher alcohols, oils and fats, waxes, and ester oils. The composition can contain one or more of these oils. The amount of oil in the composition varies depending on the form and application of the composition, but is typically 20 to 80% by mass.

[0050] When the composition is an oil-in-water emulsion or a water-in-oil emulsion, water is blended into the composition, and an aqueous thickener may also be blended in. For example, when the composition is used in cosmetics such as sunscreens, it is preferable to blend in an aqueous thickener.

[0051] Examples of aqueous thickeners include those containing at least one of a carboxyl group, a carboxylate group (a salt of a carboxyl group), a sulfonic acid group, and a sulfonate group (a salt of a sulfonic acid group) in the molecule. More specifically, examples include copolymers (synthetic polymers) such as (sodium acrylate / sodium acryloyldimethyltaurate) copolymer, (hydroxyethyl acrylate / sodium acryloyldimethyltaurate) copolymer, (ammonium acryloyldimethyltaurate / vinylpyrrolidone) copolymer, (dimethylacrylamide / sodium acryloyldimethyltaurate) crosspolymer, and carboxyvinyl polymer; copolymers (natural polysaccharides) such as xanthan gum and carrageenan; and other polymers. Hydroxypropyl methylcellulose stearoxy ether can also be used as an aqueous thickener. The above composition may contain only one of the aqueous thickeners exemplified here, or two or more of them.

[0052] When water is added to the composition, the amount of water added varies depending on the form and use of the composition, but is usually 40 to 80% by mass.

[0053] When the composition contains an aqueous thickener, the amount of the thickener is, for example, 0.1 to 2.0% by mass.

[0054] The amount of dimethicone-treated zinc oxide powder in the composition may be any amount that can sufficiently ensure the functions of the dimethicone-treated zinc oxide powder (for example, ultraviolet shielding ability), and is, for example, 2 to 30% by mass.

[0055] When the composition is an oil-in-water emulsion or a water-in-oil emulsion, it is preferable to incorporate a surfactant to maintain a stable emulsified state. Examples of surfactants include various surfactants (cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants) that are incorporated into emulsions such as ordinary cosmetics. When the dimethicone-treated zinc oxide powder is incorporated into the composition to stabilize the emulsified state of the composition, the amount of the dimethicone-treated zinc oxide powder incorporated in the composition may be any amount that can maintain the stable emulsified state, and is, for example, 0.5 to 5% by mass.

[0056] In addition to the various components exemplified above, the composition may contain various components required depending on the intended use of the composition, etc. For example, when the composition is used in a cosmetic product, components to be contained therein include a moisturizer (such as a polyhydric alcohol), a lower alcohol, a preservative, a pH adjuster, etc.

[0057] The composition can be prepared by mixing the dimethicone-treated zinc oxide powder, the oil agent, and other components used as needed using a known method appropriate for the form of the composition.

[0058] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0059] <Preparation of Dimethicone-Treated Zinc Oxide Powder> (Example 1) Zinc oxide powder having an average primary particle size of 15 nm (manufactured by Teika Corporation: MZ-700) and dimethicone (viscosity at 25°C: 1080 mPa s) were supplied to a continuous injection mixer (flow jet mixer; manufactured by Koken Powtex Corporation: MW-F-200-S) at rates of 92.5 g / min and 7.5 g / min, respectively, and kneaded at a stirring speed of 3600 rpm. The resulting kneaded mixture was placed in a dryer and dried at 170°C for 2 hours, and then pulverized using a jet mill (manufactured by Seishin Enterprises) to obtain dimethicone-treated zinc oxide powder.

[0060] (Example 2) A dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 1, except that the zinc oxide powder was changed to one having an average primary particle diameter of 25 nm (manufactured by Teika Corporation: MZ-500) and the supply rates of the zinc oxide powder and dimethicone to the continuous injection mixer were changed to 95.0 g / min and 5.0 g / min, respectively.

[0061] (Example 3) Dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 2, except that the supply rates of zinc oxide powder and dimethicone to the continuous injection mixer were changed to 93.0 g / min and 7.0 g / min, respectively.

[0062] (Example 4) Dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 2, except that the supply rates of zinc oxide powder and dimethicone to the continuous injection mixer were changed to 91.0 g / min and 9.0 g / min, respectively.

[0063] Example 5 A dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 1, except that the zinc oxide powder was changed to one having an average primary particle diameter of 35 nm (manufactured by Teika Corporation: MZ-300) and the supply rates of the zinc oxide powder and dimethicone to the continuous injection mixer were changed to 97.0 g / min and 3.0 g / min, respectively.

[0064] (Example 6) A dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 5, except that dimethicone having a viscosity of 3080 mPa·s at 25°C was used, and the supply rates of the zinc oxide powder and dimethicone to the continuous injection mixer were changed to 96.0 g / min and 4.0 g / min, respectively.

[0065] Example 7 Dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 6, except that dimethicone having a viscosity of 1080 mPa·s at 25°C was used.

[0066] Example 8 Dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 6, except that dimethicone having a viscosity at 25°C of 100 mPa·s was used.

[0067] Example 9 Dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 6, except that dimethicone having a viscosity of 20 mPa·s at 25°C was used.

[0068] (Example 10) Dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 5, except that the supply rates of zinc oxide powder and dimethicone to the continuous injection mixer were changed to 95.0 g / min and 5.0 g / min, respectively.

[0069] (Example 11) Dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 5, except that the supply rates of zinc oxide powder and dimethicone to the continuous injection mixer were changed to 93.0 g / min and 7.0 g / min, respectively.

[0070] (Example 12) A dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 5, except that the supply rates of the zinc oxide powder and dimethicone to the continuous injection mixer were changed to 90.0 g / min and 10.0 g / min, respectively.

[0071] Example 13 947 g of zinc oxide powder (MZ-500 manufactured by Teika Corporation) having an average primary particle size of 25 nm, 182 g of tetraethyl orthosilicate (KBE-04 manufactured by Shin-Etsu Chemical Co., Ltd.), and 3,000 g of isopropyl alcohol were mixed and crushed using a sand grinder mill (manufactured by Shinmaru Enterprises Co., Ltd.), and the isopropyl alcohol was then removed by distillation under reduced pressure. The resulting treated product was placed in a dryer and dried at 105°C for 2 hours to obtain hydrous silica-treated zinc oxide powder.

[0072] Dimethicone-treated zinc oxide powder was prepared in the same manner as in Example 2, except that this hydrous silica-treated zinc oxide powder was used in place of zinc oxide powder.

[0073] Comparative Example 1 92.5 g of zinc oxide powder (MZ-700 manufactured by Teika Corporation) having an average primary particle size of 15 nm and 7.5 g of dimethicone (having a viscosity of 1080 mPa s at 25°C) were mixed and stirred for 20 minutes using a bench blender. The resulting mixture was placed in a dryer and dried at 170°C for 2 hours, and then pulverized using a jet mill (manufactured by Seishin Enterprises) to obtain dimethicone-treated zinc oxide powder.

[0074] (Comparative Example 2) Dimethicone-treated zinc oxide powder was prepared in the same manner as in Comparative Example 1, except that 93.0 g of zinc oxide powder (MZ-500 manufactured by Teika Corporation) having an average primary particle size of 25 nm and 7.0 g of dimethicone (having a viscosity of 1080 mPa·s at 25°C) were used.

[0075] (Comparative Example 3) Dimethicone-treated zinc oxide powder was prepared in the same manner as in Comparative Example 1, except that 95.0 g of zinc oxide powder (MZ-300 manufactured by Teika Corporation) having an average primary particle size of 35 nm and 5.0 g of dimethicone (having a viscosity of 1080 mPa·s at 25°C) were used.

[0076] Details of the dimethicone-treated zinc oxide powders of Examples 1 to 13 and Comparative Examples 1 to 3 are shown in Tables 1 and 2. Note that the "treatment amount of dimethicone" in Table 1 means the amount of dimethicone when the total of the zinc oxide powder as the base material in the dimethicone-treated zinc oxide powder and dimethicone is taken as 100% by mass. Furthermore, in the "treatment method" in Table 1, "continuous" means that the zinc oxide powder and dimethicone were kneaded using a continuous injection mixer, and "batch" means that the zinc oxide powder and dimethicone were mixed using a bench blender.

[0077]

[0078]

[0079] As shown in Tables 1 and 2, the dimethicone-treated zinc oxide powders of Examples 1 to 13 obtained through a process of kneading zinc oxide powder and dimethicone using a continuous injection mixer exhibited good Tt550 / Tr370 values ​​and pH values ​​in the acid resistance test, and also had small D90. That is, in the dimethicone-treated zinc oxide powders of Examples 1 to 13, dimethicone could be adhered to the zinc oxide powder with high uniformity, thereby achieving good properties.

[0080] In contrast, the dimethicone-treated zinc oxide powders of Comparative Examples 1 to 3, which were obtained by mixing zinc oxide powder and dimethicone in a batch process, did not allow dimethicone to be adhered to the zinc oxide powder with high uniformity, and therefore had low Tt550 / Tr370 values, high pH in the acid resistance test, and very large D90.

[0081] <Preparation of Cosmetic Compositions (Oil-in-Water Emulsions)> (Examples 14 to 26, Comparative Examples 4 to 6) The cosmetic compositions of Examples 14 to 26 and Comparative Examples 4 to 6 were prepared by blending the components shown in Tables 3 and 4 in the proportions shown in Tables 3 and 4.

[0082] The state of each cosmetic composition immediately after preparation was observed using an optical microscope at 450x magnification. All cosmetic compositions were found to be oil-in-water emulsions, and the emulsification state was evaluated at this time. When no oil droplets in the field of view exceeded 200 μm in size, the emulsion was rated as good (◯), and when oil droplets exceeding 200 μm were found, the emulsion was rated as poor (×).

[0083] These results are also shown in Tables 3 and 4. In Tables 3 and 4, the blending amount of each component is shown in % so that the total cosmetic composition is 100%, but the % is always % by mass, and the % indication is omitted in these tables, and only the numerical value indicating the blending amount is shown.

[0084]

[0085]

[0086] As shown in Tables 3 and 4, in the cosmetic compositions of Examples 14 to 26 prepared using the dimethicone-treated zinc oxide powders of Examples 1 to 13, the dimethicone-treated zinc oxide powders had high water repellency due to the action of dimethicone, and the dispersibility of the dimethicone-treated zinc oxide powder in the oil phase was good, so the size of the oil droplets was kept small and the emulsification state was good. In contrast, in the cosmetic compositions of Comparative Examples 4 to 6 prepared using the dimethicone-treated zinc oxide powders of Comparative Examples 1 to 3, the dispersibility of the dimethicone-treated zinc oxide powder in the oil phase was low, so the oil droplets were large and the emulsification state was poor.

[0087] As described above, the dimethicone-treated zinc oxide powders of Examples 1 to 13 have good Tt550 / Tr370 values, and therefore the cosmetic compositions of Examples 14 to 26 using these powders have good ultraviolet screening ability and visible light transmittance.

[0088] The present invention can be implemented in other forms without departing from the spirit of the present invention. The embodiments disclosed in this application are merely examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the appended claims rather than the description in the above specification, and all modifications within the scope of the claims are included in the scope of the claims.

[0089] As described above, the composition of the present invention can be used for various purposes in which compositions containing inorganic oxide powders such as zinc oxide powder are used, but is particularly useful as cosmetics (sunscreen, foundation, emulsion, skin cream, etc.). In addition, the dimethicone-treated zinc oxide powder of the present invention can constitute the composition of the present invention.

Claims

1. Dimethicone-treated zinc oxide powder obtained by treating zinc oxide powder with dimethicone, characterized in that the ratio of the transmittance of light having a wavelength of 550 nm (Tt550) to the transmittance of light having a wavelength of 370 nm (Tt370), Tt550 / Tt370, as determined using a spectral transmittance curve measured by the following measurement method (A), is 10 or greater, and the pH is 6.5 or less in the following acid resistance test (B). <Measurement Method (A)> (1) In an environment of 25°C, 10 g of dimethicone-treated zinc oxide powder, 34 g of cyclopentasiloxane, 5 g of liquid paraffin, and 5 g of PEG-9 dimethicone are mixed using a disper at 3,000 rpm for 10 minutes to prepare a dispersion. (2) A mixture of 32 g of ion-exchanged water and 14 g of butylene glycol is prepared. (3) While stirring the dispersion prepared in (1) using a disper at 3000 rpm, the mixed solution prepared in (2) is added thereto, and further mixed using a disper at 3000 rpm for 5 minutes to prepare a sample solution. (4) The sample solution obtained in (3) is applied to a polypropylene film using an automatic bar coater equipped with a wire bar (No. 6) to form a coating film. (5) The total light transmittance of the coating film formed in (4) within 1 minute is measured using a spectrophotometer in an environment of 25°C to obtain a spectral transmittance curve. <Acid Resistance Test (B)> (i) In an environment of 25°C, 12.5 g of methanol and 12.5 g of ion-exchanged water are placed in a container, and 0.25 g of dimethicone-treated zinc oxide powder is added thereto while stirring. (ii) One minute after adding the dimethicone-treated zinc oxide powder to the solution (i), 50 g of sulfuric acid having a pH of 3 is added over 10 minutes, and the pH of the solution after the addition of sulfuric acid is measured.

2. Dimethicone-treated zinc oxide powder according to claim 1, wherein the cumulative particle size of 90% in the volume-based particle size distribution measured by dynamic light scattering is 550 nm or less.

3. Dimethicone-treated zinc oxide powder according to claim 2, wherein the cumulative 50% particle size in the volume-based particle size distribution measured by dynamic light scattering is 450 nm or less.

4. Dimethicone-treated zinc oxide powder according to claim 2 or 3, wherein the cumulative particle size of 10% in the volume-based particle size distribution measured by dynamic light scattering is 400 nm or less.

5. Dimethicone-treated zinc oxide powder obtained by treating zinc oxide powder with dimethicone, characterized in that the cumulative 90% particle diameter in the volume-based particle size distribution measured by dynamic light scattering is 550 nm or less.

6. Dimethicone-treated zinc oxide powder according to claim 5, wherein the cumulative 50% particle size in the volume-based particle size distribution measured by dynamic light scattering is 450 nm or less.

7. Dimethicone-treated zinc oxide powder according to claim 5 or 6, wherein the cumulative particle size of 10% in the volume-based particle size distribution measured by dynamic light scattering is 400 nm or less.

8. Dimethicone-treated zinc oxide powder, characterized in that the zinc oxide powder is treated with dimethicone by kneading the zinc oxide powder and dimethicone using a continuous injection mixer.

9. Specific surface area is 10 to 40 m ２ The dimethicone-treated zinc oxide powder according to any one of claims 1 to 8, wherein the dimethicone-treated zinc oxide powder has a molecular weight of 1000 or more and a molecular weight of 1000 or more.

10. A composition comprising the dimethicone-treated zinc oxide powder according to any one of claims 1 to 9 and an oil agent.

11. The composition according to claim 10, further comprising water and an aqueous thickener.

12. The composition according to claim 11, wherein the aqueous thickener contains in its molecule at least one group selected from the group consisting of a carboxyl group, a carboxylate group, a sulfonic acid group, and a sulfonate group.

13. The composition of claim 11, wherein the aqueous thickener is at least one copolymer selected from the group consisting of sodium acrylate / sodium acryloyldimethyltaurate copolymer, hydroxyethyl acrylate / sodium acryloyldimethyltaurate copolymer, ammonium acryloyldimethyltaurate / vinylpyrrolidone copolymer, dimethylacrylamide / sodium acryloyldimethyltaurate crosspolymer, carboxyvinyl polymer, hydroxypropyl methylcellulose stearoxy ether, xanthan gum, and carrageenan.

14. The composition according to any one of claims 10 to 13, which is used in cosmetics.

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