Boron nitride powder and cosmetic composition

Abstract

To provide a boron nitride powder that has excellent uniformity when used as a cosmetic. [Solution] In a dynamic fluidity test conducted using a powder rheometer at a blade rotation speed of 100 mm / s, the flowability energy is measured seven times, and when the ratio (1FE / 7FE) of the flowability energy of the first measurement (1FE) to the flowability energy of the seventh measurement (7FE) is defined as SI, the boron nitride powder has an SI of 0.85 to 1.15.

Description

[Technical Field]

[0001] The present invention relates to a boron nitride powder and a cosmetic composition. [Background technology]

[0002] Boron nitride powder has lubricity, high thermal conductivity, and insulating properties, and is used in a variety of applications, such as solid lubricants, release agents, fillers for resins and rubbers, raw materials for cosmetics, and heat-resistant insulating sintered bodies. Boron nitride powder has the functions of improving the slipperiness, spreadability, hiding power, etc. of cosmetics, as well as imparting gloss, etc. to cosmetics.

[0003] For example, Patent Document 1 discloses that a hexagonal boron nitride powder for cosmetics contains primary particles of hexagonal boron nitride, the primary particles having an aspect ratio of 25 or less, and an oil absorption of 50 to 90 mL / 100 g, and when used as a cosmetic, the powder has excellent spreadability and provides a cosmetic layer with excellent transparency and luster. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 224674 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when cosmetics containing boron nitride powder are used multiple times, variations in spreadability and feel can occur with each use, and there is a demand for improved uniformity (stability).

[0006] An object of the present invention is to provide a boron nitride powder that exhibits excellent uniformity when used as a cosmetic, and a cosmetic composition containing the boron nitride powder. [Means for solving the problem]

[0007] The present invention includes the following embodiments.

[0008] [1] A boron nitride powder in which the flowability energy is measured seven times in a dynamic fluidity test conducted using a powder rheometer at a blade rotation speed of 100 mm / s, and the SI is the ratio (1FE / 7FE) of the flowability energy of the first measurement (1FE) to the flowability energy of the seventh measurement (7FE), and the SI is 0.85 to 1.15.

[0009] [2] The boron nitride powder according to [1], wherein all seven measured values ​​of the flowability energy are within the range of 0 to 20 mJ.

[0010] [3] Using the powder rheometer, the angle of internal friction (AIF) is measured in a shear test performed under a pre-compression consolidation pressure of 1 to 15 kPa in accordance with ASTM D7891; and When the wall friction angle (WFA) was measured in a wall friction test using the powder rheometer under a pre-compression consolidation pressure of 1 to 15 kPa in accordance with ASTM D7891, except that artificial leather was attached to the surface of a circular disk, The boron nitride powder according to [1] or [2], wherein the ratio (AIF / WFA) of the angle of internal friction (AIF) to the angle of wall friction (WFA) is 0.5 to 1.5.

[0011] [4] The boron nitride powder according to [3], wherein the angle of internal friction (AIF) is 15° to 35°.

[0012] [5] The boron nitride powder according to [3] or [4], wherein the wall friction angle (WFA) is 10° to 30°.

[0013] [6] The boron nitride powder according to any one of [1] to [5], wherein the average crushing strength of 20 boron nitride particles having a particle diameter in the range of 63 to 106 μm in the boron nitride powder is 3 MPa or less.

[0014] [7] The boron nitride powder according to any one of [1] to [6], wherein when the boron nitride powder is passed through a standard sieve with a mesh size of 106 μm, the amount of boron nitride powder remaining on the standard sieve is 10 mass % or less of the total amount.

[0015] [8] A cosmetic composition comprising the boron nitride powder according to any one of [1] to [7]. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a boron nitride powder that exhibits excellent uniformity when used as a cosmetic, and a cosmetic composition containing the boron nitride powder. DETAILED DESCRIPTION OF THE INVENTION

[0017] [Boron nitride powder] The boron nitride powder according to this embodiment has an SI of 0.85 to 1.15 when the flowability energy is measured seven times in a dynamic flowability test using a powder rheometer (for example, product name: "Powder Rheometer FT4", manufactured by Malvern Panalytical) at a blade rotation speed of 100 mm / s, and the ratio (1FE / 7FE) of the flowability energy of the first measurement (1FE) to the flowability energy of the seventh measurement (7FE) is taken as SI.

[0018] In the dynamic fluidity test, a blade is rotated and moved vertically through the powder. A vertical load and rotational torque are generated on the blade, and the fluidity energy is calculated based on these. The fluidity energy serves as an indicator of the powder's fluidity. When the fluidity energy is measured seven times, the more consistent the measured values, the more stable the powder's fluidity is. The inventors have found that when the ratio (1FE / 7FE) of the fluidity energy of the first measurement (1FE) to the fluidity energy of the seventh measurement (7FE) is defined as SI, a value of 0.85 to 1.15 indicates high uniformity (stability) and consistent spread and usability even when the boron nitride powder is used multiple times as a cosmetic. The SI value may be 0.9 to 1.1 or 0.95 to 1.05. The SI can be measured specifically by the method described in the Examples below. The SI value can be controlled by adjusting conditions such as the temperature of the mixed solution in the raw material production process described below. Specifically, when the temperature of the mixed liquid is increased, the SI value tends to approach 1. On the other hand, when the temperature of the mixed liquid is decreased, the SI value tends to deviate from 1.

[0019] It is preferable that all seven measured values ​​of the fluidity energy measured in the dynamic fluidity test are within the range of 0 to 20 mJ. When all seven measured values ​​are within the range of 0 to 20 mJ, even when the boron nitride powder is used multiple times as a cosmetic, the uniformity (stability) is high for each use, and consistent and superior spreadability and usability can be achieved. All seven measured values ​​may be within the range of 5 to 18 mJ, or may be within the range of 8 to 15 mJ. The seven measured values ​​can be controlled by adjusting conditions such as the pressure in the annealing step described below. Specifically, when the pressure in the annealing step is lowered, the seven measured values ​​tend to increase overall. On the other hand, when the pressure in the annealing step is increased, the seven measured values ​​tend to decrease overall. Furthermore, when the temperature rise rate in the annealing step is slowed, the seven measured values ​​tend to have less variation.

[0020] The boron nitride powder according to this embodiment preferably has a ratio (AIF / WFA) of the angle of internal friction (AIF) to the angle of wall friction (WFA). The angle of internal friction (AIF) is measured by a shear test using a powder rheometer (e.g., product name: "Powder Rheometer FT4" manufactured by Malvern Panalytical) in accordance with ASTM D7891, under a pre-load consolidation pressure of 1 to 15 kPa. The angle of wall friction (WFA) is measured by a wall friction test using the powder rheometer in accordance with ASTM D7891, under a pre-load consolidation pressure of 1 to 15 kPa, except that artificial leather (e.g., product name: "Suprale" manufactured by Idemitsu Technofine Co., Ltd.) is attached to the surface of a circular disk. The angle of internal friction (AIF) and the angle of wall friction (WFA) can be measured specifically by the method described in the Examples below.

[0021] The angle of internal friction (AIF) is an index that expresses the friction between boron nitride particles as an angle. A smaller value for the angle of internal friction (AIF) reduces the friction between particles, which in turn reduces the adhesive force between particles, and is thought to improve spreadability when used as a cosmetic. On the other hand, the angle of wall friction (WFA) is an index that expresses the friction between boron nitride particles and a disk surface as an angle. Because artificial leather is attached to the disk surface in the wall friction test, the value of the angle of wall friction (WFA) is thought to indicate the physical grip between the boron nitride particles and the skin, i.e., the feel when used. The inventors have discovered that boron nitride powders with a ratio (AIF / WFA) of the angle of internal friction (AIF) to the angle of wall friction (WFA) in the range of 0.5 to 1.5 can achieve both excellent spreadability and a moderate feel when used as a cosmetic. The ratio (AIF / WFA) of the angle of internal friction (AIF) to the angle of wall friction (WFA) may be 0.6 to 1.4, 0.7 to 1.3, or 0.8 to 1.2.

[0022] The internal friction angle (AIF) is preferably 15° to 35°. When the internal friction angle (AIF) is 15° or more, it is possible to prevent the composition from collapsing when used as a cosmetic. Furthermore, when the internal friction angle (AIF) is 35° or less, it is possible to exhibit superior spreadability when used as a cosmetic. The internal friction angle (AIF) may be 17° to 33°, 21° to 32°, or 23° to 30°. The value of the internal friction angle (AIF) can be controlled by adjusting the conditions of the baking step, which will be described later. Specifically, when the baking temperature is lowered, the value of the internal friction angle (AIF) tends to increase. On the other hand, when the baking temperature is increased, the value of the internal friction angle (AIF) tends to decrease.

[0023] The wall friction angle (WFA) is preferably 10° to 30°. A wall friction angle (WFA) of 10° or more ensures sufficient physical grip between the boron nitride particles and the skin, resulting in an improved feel when used as a cosmetic. A wall friction angle (WFA) of 30° or less can prevent excessive grip between the boron nitride particles and the skin, resulting in an improved feel when used as a cosmetic. The wall friction angle (WFA) may be 15° to 30°, 20° to 29°, or 25° to 28°. The wall friction angle (WFA) value can be controlled by adjusting the conditions of the annealing step, which will be described later. Specifically, a lower annealing temperature tends to increase the wall friction angle (WFA). On the other hand, a higher annealing temperature tends to decrease the wall friction angle (WFA).

[0024] The average crushing strength of 20 boron nitride particles having a particle size in the range of 63 to 106 μm in the boron nitride powder according to this embodiment is preferably 3 MPa or less. Having an average crushing strength of 3 MPa or less can suppress the feeling of unevenness when used as a cosmetic. The average crushing strength may be 2.5 MPa or less, or may be 2 MPa or less. The lower limit of the range of the average crushing strength is not particularly limited, but may be, for example, 0.1 MPa or more, 0.5 MPa or more, or 0.8 MPa or more. The average crushing strength can be measured specifically by the method described in the Examples below. The average crushing strength can be controlled by adjusting the conditions, such as the sieve conditions, for the mixture containing the calcined product in the firing step described below. Specifically, the average crushing strength tends to decrease when the mesh size of the sieve is reduced.

[0025] When the boron nitride powder according to this embodiment is sieved through a standard sieve with a mesh size of 106 μm, the amount of boron nitride powder remaining on the standard sieve is preferably 10% by mass or less of the total. Because the width of a fingerprint is approximately 106 μm, if the particle size of the boron nitride powder is smaller than this, the boron nitride powder is less likely to feel rough on the fingertips when used as a cosmetic. In particular, by keeping the amount of boron nitride powder remaining on the standard sieve to 10% by mass or less of the total, the roughness can be sufficiently reduced when the boron nitride powder is used as a cosmetic, resulting in a smooth feel when used. The amount of boron nitride powder remaining on the standard sieve may be 7% by mass or less of the total, 5% by mass or less, or even 3% by mass or less. Since the amount of boron nitride powder remaining on the standard sieve is preferably as small as possible, the lower limit of the range is not particularly limited, but may be, for example, 0.1% by mass or more. The amount of boron nitride powder remaining on the standard sieve can be specifically measured by the method described in the Examples below. The amount of boron nitride powder remaining on the standard sieve can be controlled by adjusting the conditions for pulverizing the fired product in the refining step described below. Specifically, when pulverizing the fired product, narrowing the gap between the upper and lower mills of the stone mill (glow mill) or increasing the rotation speed tends to reduce the amount of boron nitride powder remaining on the standard sieve.

[0026] [Manufacturing method of boron nitride powder] The method for producing the boron nitride powder according to this embodiment is not particularly limited as long as the resulting boron nitride powder has the above-described properties. The boron nitride powder according to this embodiment can be produced, for example, by the method shown below.

[0027] Specifically, the method for producing boron nitride powder according to this embodiment includes the steps of: heating and mixing a raw material composition containing a boron-containing compound including boric acid and a nitrogen-containing compound including melamine with water to obtain a mixed liquid; drying the mixed liquid to obtain a raw material (hereinafter also referred to as the "raw material production step"); firing the raw material at 600 to 1300°C in an atmosphere containing at least one of an inert gas and ammonia gas to obtain a calcined product containing at least one of low-crystalline boron nitride and amorphous boron nitride (hereinafter also referred to as the "calcination step"); and mixing the calcined product with an auxiliary, followed by The method includes the steps of pulverizing the mixture, sieving the mixture, and firing the resulting mixed powder at a temperature of 1500 to 1750°C in an atmosphere containing at least one of an inert gas and ammonia gas to obtain a fired product (hereinafter also referred to as the "firing process"); pulverizing, washing, and drying the fired product to obtain a dry powder (hereinafter also referred to as the "purification process"); and heating and pressurizing the dry powder at a temperature of 2100°C or higher and a pressure of 0.5 MPa or higher in an atmosphere containing at least one of an inert gas and ammonia gas (hereinafter also referred to as the "annealing process").

[0028] The firing step may be repeated multiple times (hereinafter, these steps will be referred to as the "first firing step," the "second firing step," etc., respectively). When the firing step is repeated multiple times, the fired product obtained in each firing step may be pulverized. By pulverizing the fired product, the melamine and other components in the raw material composition can be sufficiently consumed in the second firing step and subsequent firing steps.

[0029] (Raw material manufacturing process) In the raw material production process, a raw material composition containing a boron-containing compound including boric acid and a nitrogen-containing compound including melamine is heated and mixed with water to obtain a mixed liquid, and the mixed liquid is dried to obtain a raw material. The boron-containing compound is a compound having a boron atom as a constituent element. The boron-containing compound may further contain, in addition to boric acid, for example, boron oxide and borax. The nitrogen-containing compound is a compound having a nitrogen atom as a constituent element and may be an organic compound. The nitrogen-containing compound may further contain, in addition to melamine, for example, dicyandiamide and urea. The raw material composition may contain components other than the compounds. For example, the raw material composition may contain carbonates such as lithium carbonate and sodium carbonate as a calcination aid. The raw material composition may also contain a reducing substance such as carbon.

[0030] In the raw material composition, the blending ratio of the boron-containing compound and the nitrogen-containing compound can be adjusted based on the molar ratio of boron atoms to nitrogen atoms. For example, the blending ratio may be such that the ratio of boron atoms to nitrogen atoms is 2:8 to 8:2, or 2.5:7.5 to 7.5:2.5. The raw material composition is heated and mixed with water to obtain a mixed liquid. The temperature of the mixed liquid during mixing is preferably 50°C or higher, more preferably 80°C or higher. The resulting mixed liquid is dried to remove water, thereby obtaining the raw material.

[0031] (Pre-firing process) In the calcination step, the raw materials are fired at 600 to 1300°C in an atmosphere containing at least one of an inert gas and ammonia gas to obtain a calcined product containing at least one of low-crystalline boron nitride and amorphous boron nitride. The calcination step is carried out in an atmosphere containing at least one of an inert gas and ammonia gas. Examples of inert gases include nitrogen gas and rare gases. Examples of rare gases include helium gas and argon gas. The calcination step may also be carried out in a mixed gas atmosphere containing an inert gas and ammonia gas. The calcination temperature may be, for example, 600 to 1300°C, 800 to 1200°C, or 900 to 1100°C. The calcination time may be, for example, 0.5 to 5.0 hours, or 1.0 to 4.0 hours. The calcined product obtained by calcination contains at least one of low-crystalline boron nitride and amorphous boron nitride, and may further contain hexagonal boron nitride. In the calcination step, the reaction of boron nitride proceeds at a lower temperature than in the firing step described below.

[0032] (Firing process) In the firing step, the calcined product and auxiliary agents are mixed, then pulverized and sieved, and the resulting mixed powder is fired at a temperature of 1500 to 1750°C in an atmosphere containing at least one of an inert gas and ammonia gas to obtain a fired product. In the firing step, in the presence of the auxiliary agents, the raw material composition is sufficiently consumed while the production and crystallization of boron nitride proceeds. This increases the crystallinity of the boron nitride contained in the calcined product, allowing it to form hexagonal boron nitride.

[0033] First, the calcined product is mixed with an auxiliary. Examples of the auxiliary include borates such as sodium borate, and carbonates such as sodium carbonate, calcium carbonate, and lithium carbonate. The auxiliary preferably contains sodium carbonate. The amount of the auxiliary blended per 100 parts by mass of the calcined product containing boron nitride can be 2 parts by mass or more but less than 20 parts by mass, or may be 3 to 10 parts by mass, or 3 to 7 parts by mass. The resulting mixture may further contain boric acid. After pulverizing the resulting mixture, coarse particles are removed using a sieve. The sieve opening is, for example, preferably 1 mm or less, more preferably 800 μm or less, even more preferably 500 μm or less, and particularly preferably 200 μm or less. The lower limit of the sieve opening range is not particularly limited, but can be, for example, 50 μm or more.

[0034] In the firing step, the mixed powder is fired, for example, using an electric furnace or the like, to obtain a fired product. The firing step is carried out in an atmosphere containing at least one of an inert gas and ammonia gas. Examples of inert gases include nitrogen gas and rare gases. Rare gases may be, for example, helium gas and argon gas. The firing step may also be carried out in a mixed gas atmosphere containing an inert gas and ammonia gas. The firing temperature is preferably 1500 to 1750°C, more preferably 1550 to 1750°C, and even more preferably 1600 to 1750°C. The firing time may be, for example, 0.5 to 5 hours, or 1 to 4 hours. In this specification, the terms firing time, heating time, calcination time, etc. refer to the time (retention time) during which the temperature of the ambient environment of the object is maintained at a predetermined temperature after it has reached that temperature.

[0035] (purification process) In the purification step, the fired product obtained in the firing step is pulverized, washed, and dried to obtain a dry powder. The fired product can be pulverized using, for example, a pulverizer. As the pulverizer, for example, a stone mill pulverizer (glow mill) or the like may be used. As the stone mill pulverizer, for example, one that can adjust the particle size of the pulverized product by adjusting the gap between the upper and lower mills can be suitably used. The gap between the mills may be, for example, 50 to 400 μm or 150 to 300 μm. Furthermore, the rotation speed of the stone mill pulverizer is preferably 200 to 1000 rpm, and more preferably 500 to 700 rpm.

[0036] The particle size can be adjusted by pulverizing the fired product. Adjusting the particle size can improve the efficiency of the subsequent annealing step. The pulverized product obtained by pulverizing the fired product may contain impurities other than boron nitride. Therefore, a treatment to reduce the impurities (purification treatment) may be carried out before the annealing step. Examples of impurities include remaining raw materials and auxiliary agents, as well as water-soluble boron compounds. The purification treatment can reduce the amount of such impurities, for example, by washing. After washing, the product is subjected to solid-liquid separation and drying to obtain a dry powder.

[0037] Examples of cleaning solutions used for cleaning include aqueous solutions containing acidic substances, organic solvents, and mixtures of organic solvents and water. Water with an electrical conductivity of 1 mS / m or less may be used to prevent secondary contamination with impurities. Examples of aqueous solutions containing acidic substances include inorganic acids such as hydrochloric acid and nitric acid. Examples of organic solvents include water-soluble organic solvents such as methanol, ethanol, propanol, isopropyl alcohol, and acetone. There are no particular limitations on the cleaning method; for example, the pulverized material may be immersed in a cleaning solution and stirred for cleaning, or the pulverized material may be sprayed with the cleaning solution for cleaning.

[0038] After the washing is completed, the washing liquid can be subjected to solid-liquid separation using decantation, a suction filter, a pressure filter, a rotary filter, a sedimentation separator, or a combination thereof. The separated solids can be dried in a conventional dryer to obtain a dry powder. Examples of the dryer include a tray dryer, a fluidized bed dryer, a spray dryer, a rotary dryer, a belt dryer, and combinations thereof. After drying, classification using a sieve, for example, may be performed to remove coarse particles.

[0039] (Annealing process) In the annealing step, the dried powder obtained in the purification step is heated and pressurized at a temperature of 2100°C or higher and a pressure of 0.5 MPa or higher in an atmosphere containing at least one of an inert gas and ammonia gas. In the annealing step, the dried powder can be heated and pressurized using, for example, an electric furnace. The annealing step is performed in an atmosphere containing at least one of an inert gas and ammonia gas. Examples of inert gases include nitrogen gas and rare gases. Examples of rare gases include helium gas and argon gas. The temperature of the heating and pressurizing step in the annealing step is preferably 2100°C or higher, more preferably 2200°C or higher. The temperature of the heating and pressurizing step in the annealing step may be 2500°C or lower, or may be 2400°C or lower. The pressure of the heating and pressurizing step in the annealing step is preferably 0.5 MPa or higher, more preferably 0.8 MPa or higher. The pressure of the heating and pressurizing step in the annealing step may be 2 MPa or lower, or may be 1.5 MPa or lower. The duration of the heat and pressure treatment in the annealing step can be, for example, 0.5 to 5.0 hours, or 1.0 to 4.0 hours. The obtained powder is pulverized and then sieved to remove coarse particles. The sieve opening is, for example, preferably 800 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less. The lower limit of the sieve opening range is not particularly limited, but can be, for example, 50 μm or more.

[0040] [Cosmetic composition] The cosmetic composition according to this embodiment contains the boron nitride powder according to this embodiment. Because the cosmetic composition according to this embodiment contains the boron nitride powder according to this embodiment, even when used multiple times, it has high uniformity (stability) each time and can exhibit consistent spreadability and usability. In the cosmetic composition according to this embodiment, the boron nitride powder according to this embodiment functions as an extender pigment. That is, the boron nitride powder according to this embodiment can be a cosmetic extender pigment.

[0041] Examples of cosmetic compositions include foundations (powder foundations, liquid foundations, cream foundations), face powders, point makeup, eye shadows, eyeliners, nail polishes, lipsticks, blushers, and mascaras. Among these, the boron nitride powder according to this embodiment is particularly well suited for foundations and eye shadows. The content of the boron nitride powder in the cosmetic composition may be, for example, 0.1 to 70% by mass. The cosmetic composition can be produced by a known method. The method for producing the cosmetic composition includes, for example, a step of blending and mixing the boron nitride powder according to this embodiment with other raw materials. [Example]

[0042] The following examples illustrate the present invention in more detail, but are not intended to limit the scope of the present invention. Regarding boron nitride powder, the flowability energy and SI, angle of internal friction (AIF), angle of wall friction (WFA), average crushing strength, and amount of boron nitride powder remaining on a standard sieve were measured using the following methods. Regarding cosmetic compositions containing boron nitride powder, the uniformity, spreadability, and usability were evaluated using the following methods.

[0043] [Measurement of physical properties of boron nitride powder] (Measurement of fluid energy and SI) The flowability energy and SI of boron nitride powder were measured using a powder rheometer (product name: "Powder Rheometer FT4" manufactured by Malvern Panalytical) in a dynamic flow test conducted at a blade rotation speed of 100 mm / s. Specifically, the measurements were performed according to the "Stability + Flow Rate Change Test" section of the Powder Rheometer FT4's simple operating instructions. First, select "Standard Test Programs," "Stability + Variable Flow Rate," and select the vessel size (25 mm). After preparing the included blade and vessel, place the empty vessel in the measurement section and select "Tare Empty Vessel." After placing the sample into the vessel, select "Record Sample Mass." After attaching the blade to the instrument and entering the sample name and other information, select "Start Test." After conditioning, open the "Leveling Assembly" to level the sample, close the vessel, return it to its original position, and select "OK." After the measurement, the flowability energy was calculated through data analysis. The flowability energy was measured seven times for the same sample. The ratio (1FE / 7FE) of the fluidity energy at the first measurement (1FE) to the fluidity energy at the seventh measurement (7FE) was calculated and used as SI.

[0044] (Measurement of the angle of internal friction (AIF)) The angle of internal friction (AIF) of boron nitride powder was measured using a powder rheometer (product name: "Powder Rheometer FT4" manufactured by Malvern Panalytical) in accordance with ASTM D7891, using a shear test performed under a pre-compression consolidation pressure of 1 to 15 kPa. Specifically, measurements were performed according to the "Shear Test" section of the Powder Rheometer FT4's simple operation manual. First, select "Standard Test Programs," "Shear Cell," and then select the container size (25 mm) and pre-compression consolidation pressure (1 to 15 kPa). Note that when selecting the pre-compression consolidation pressure (1 to 15 kPa), the pre-compression consolidation pressure fluctuates within the range of 1 to 15 kPa during measurement. After preparing the included blade and container, place the empty container in the measurement section and select "Tare Empty Vessel." After placing the sample in the container, select "Record Sample Mass." After attaching the blade to the instrument and entering the sample name and other information, select "Start Test." After conditioning, the blade was replaced with a "Vented Piston" and "OK" was selected. After compacting the measurement sample, the funnel was removed and "OK" was selected. The measurement sample was leveled, the "Vented Piston" was replaced with a "Shear Cell" and "OK" was selected. After the measurement, the angle of internal friction (AIF) was calculated by data analysis.

[0045] (Wall Friction Angle (WFA) measurement) The wall friction angle (WFA) of boron nitride powder was measured using a powder rheometer (product name: "Powder Rheometer FT4" manufactured by Malvern Panalytical) under a pre-load consolidation pressure of 1 to 15 kPa. The wall friction test was performed according to ASTM D7891, except that artificial leather (product name: "Suprale" manufactured by Idemitsu Technofine Co., Ltd.) was attached to the surface of a circular disk. Specifically, measurements were performed according to the "Wall Friction Test" section of the Powder Rheometer FT4's simplified operating instructions. First, select "Standard Test Programs," then "Wall Friction," then select the container size (25 mm) and pre-load consolidation pressure (1 to 15 kPa). Note that when selecting the pre-load consolidation pressure (1 to 15 kPa), the pre-load consolidation pressure fluctuates within the range of 1 to 15 kPa during measurement. After preparing the included blade and container, place the empty container in the measurement section and select "Tare Empty Vessel." After placing the measurement sample into the container, select "Record Sample Mass." After attaching the blade to the device and entering the sample name, etc., select "Start Test." After conditioning, replace the blade with the "Vented Piston" and select "OK." After consolidating the measurement sample, remove the funnel and select "OK." After leveling the measurement sample, replace the "Vented Piston" with the "Wall Friction Head" and select "OK." After measurement, the wall friction angle (WFA) was calculated by data analysis.

[0046] (Measurement of average crushing strength) The average value of the crushing strength of 20 boron nitride particles in a boron nitride powder having a particle size in the range of 63 to 106 μm was measured and calculated by the following method. First, 20 boron nitride particles to be measured, each having a particle size in the range of 63 to 106 μm, were randomly selected from the boron nitride powder by observing with a microscope camera. The crushing strength of these 20 boron nitride particles was measured in accordance with JIS R 1639-5:2007. The measuring device used was a microcompression tester (product name: "MCT-211", manufactured by Shimadzu Corporation). The crushing strength σ (unit: MPa) of each boron nitride particle was calculated using the dimensionless number α (= 2.48), which varies depending on the position within the particle, the crushing test force P (unit: N), and the average particle size d (unit: μm), as follows: σ = α × P / (π × d 2 The crushing strength was measured for 20 boron nitride particles, and the average value was calculated.

[0047] (Measurement of the amount of boron nitride powder remaining on the standard sieve) A mixed solution was obtained by stirring 10 g of boron nitride powder, 50 mL of ethanol, and 50 mL of water for 3 minutes. The mixed solution was placed on a standard sieve with a mesh size of 106 μm, and the standard sieve was vibrated using a wet sieving machine (product name: "VBL-FU", manufactured by Hosokawa Micron) while pouring 10 L of water over it. The vibration conditions were 100% amplitude and 5 minutes. The boron nitride powder remaining on the standard sieve was dried at 120°C for 10 hours and its mass was measured. The ratio of the mass of the boron nitride powder remaining on the standard sieve to the mass (10 g) of the boron nitride powder initially added was calculated.

[0048] [Evaluation of cosmetic compositions] (uniformity) The uniformity of cosmetic compositions containing boron nitride powder was evaluated using the following method. A panel of 20 experts in cosmetic evaluation used the prepared cosmetic compositions, and they conducted a sensory evaluation of the uniformity. If less than 30% of the panelists felt that the uniformity was good, the rating was "X", if 30% or more but less than 60% felt that the uniformity was good, the rating was "△", if 60% or more but less than 80% felt that the uniformity was good, the rating was "○", and if 80% or more felt that the uniformity was good, the rating was "◎".

[0049] (Extensibility) The spreadability of cosmetic compositions containing boron nitride powder was evaluated by the following method. A panel of 20 experts in cosmetic evaluation used the prepared cosmetic compositions, and they performed a sensory evaluation of the spreadability. If less than 30% of the panelists felt that the spreadability was good, the rating was "X", if 30% or more but less than 60% felt that the spreadability was good, the rating was "△", if 60% or more but less than 80% felt that the spreadability was good, the rating was "○", and if 80% or more felt that the spreadability was good, the rating was "◎".

[0050] (Feeling of use) The usability of a cosmetic composition containing boron nitride powder was evaluated using the following method. A panel of 20 experts in cosmetic evaluation used the prepared cosmetic composition, and a sensory evaluation of the usability was conducted. If less than 30% of the panelists felt that the usability was good, the rating was "X", if 30% or more but less than 60% felt that the usability was good, the rating was "△", if 60% or more but less than 80% felt that the usability was good, the rating was "○", and if 80% or more felt that the usability was good, the rating was "◎".

[0051] [Example 1] (Preparation of Boron Nitride Powder) <Raw material manufacturing process> 65.0 g of boric acid powder (purity: 99.8% by mass or more, manufactured by Kanto Chemical Co., Ltd.), 35.0 g of melamine powder (purity: 99.0% by mass or more, manufactured by Wako Pure Chemical Industries, Ltd.), and water were mixed and stirred at 80° C. for 10 minutes to obtain a mixed liquid. The mixed liquid was dried to obtain a raw material.

[0052] <Pre-firing process> The raw materials were placed in a hexagonal boron nitride container and placed in an electric furnace. While circulating nitrogen gas through the electric furnace, the temperature was increased from room temperature to 1000°C at a rate of 10°C / min. After holding at 1000°C for 2 hours, heating was stopped and the material was allowed to cool naturally. When the temperature dropped below 100°C, the electric furnace was opened. In this way, a calcined product containing low-crystalline boron nitride was obtained.

[0053] <Firing process> 5.0 g of sodium carbonate (purity: 99.5% by mass or higher) was added as an auxiliary agent to 100.0 g of the calcined product, and the mixture was mixed in an alumina mortar for 10 minutes and sieved using a 106 μm mesh sieve. The mixed powder that passed through the sieve was placed in the electric furnace. While circulating nitrogen gas through the electric furnace, the temperature was increased from room temperature to 1700°C at a rate of 10°C / min. After maintaining the firing temperature of 1700°C for 4 hours, heating was stopped and the mixture was allowed to cool naturally. When the temperature reached 100°C or below, the electric furnace was opened to obtain a fired product.

[0054] <Purification process> The fired material was pulverized at 600 rpm using a glow mill with a mill gap adjusted to 200 μm to obtain a coarse powder containing boron nitride. To reduce impurities contained in the coarse powder, 30 g of the coarse powder was added to 500 g of diluted nitric acid (nitric acid concentration: 5% by mass) and stirred at room temperature for 60 minutes. After stirring, the solid-liquid separation was performed by suction filtration, and the filtrate was washed with water (water with an electrical conductivity of 1 mS / m) until it became neutral. After washing, the product was dried in a dryer at 120°C for 3 hours to obtain a dry powder.

[0055] <Annealing process> The dried powder was placed in the electric furnace. The temperature in the electric furnace was increased from room temperature to 2100°C at a rate of 5°C / min under a nitrogen gas atmosphere of 0.8 MPa. After holding at 2100°C for 4 hours, heating was stopped and the material was allowed to cool naturally. When the temperature reached 100°C or below, the electric furnace was opened. The obtained powder was collected and crushed using a bench jet mill. Furthermore, coarse powder was removed using an ultrasonic vibration sieve (product name: "KFS-10000", manufactured by Kowa Kogyosho Co., Ltd., mesh size 250 μm), and boron nitride powder was obtained.

[0056] The obtained boron nitride powder was subjected to measurements of the angle of internal friction (AIF), angle of wall friction (WFA), average crushing strength, amount of boron nitride powder remaining on the standard sieve, as well as flowability energy and SI using the methods described above. The results are shown in Table 1. In Table 1, the range of flowability energy is shown as the minimum and maximum values ​​of seven measurements.

[0057] (Preparation of cosmetic composition) Using the obtained boron nitride powder, a cosmetic composition was prepared in the following blending ratio. Boron nitride 20.0 mass% Mica 15.0% by mass Synthetic phlogopite 12.0% by mass Ethylhexyl methoxycinnamate 8.0% by mass (Vinyl dimethicone / methicone silsesquioxane) crosspolymer 8.0% by mass (Diphenyl dimethicone / vinyl diphenyl dimethicone / silsesquioxane) crosspolymer 8.0% by mass Nylon 12 3.0% by mass Silica 3.0% by mass Talc 3.0% by mass Acrylates crosspolymer 3.0% by mass Perfluorooctyltriethoxysilane 3.0% by mass Zinc oxide 3.0% by mass Polymethyl methacrylate polymer 3.0% by mass Silicone-treated red iron oxide (red iron oxide) 1.0% by mass Silicone-treated yellow iron oxide 0.6% by mass Silicone-treated black iron oxide 0.4% by mass Silicone-treated titanium dioxide 6.0% by mass

[0058] The obtained cosmetic compositions were evaluated for uniformity, spreadability, and feel in use by the methods described above. The results are shown in Table 1.

[0059] [Example 2] A boron nitride powder and a cosmetic composition were prepared and evaluated in the same manner as in Example 1, except that the firing temperature in the firing step was changed to 1850° C. The results are shown in Table 1.

[0060] [Example 3] A boron nitride powder and a cosmetic composition were prepared and evaluated in the same manner as in Example 1, except that the mesh size of the sieve used for the mixture of the calcined product and auxiliary agents in the firing step was changed to 500 μm. The results are shown in Table 1.

[0061] [Example 4] Except for changing the sieve mesh size of the ultrasonic vibration sieve used in the annealing step to 106 μm, a boron nitride powder and a cosmetic composition were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0062] [Comparative Example 1] A boron nitride powder and a cosmetic composition were prepared and evaluated in the same manner as in Example 1, except that the temperature of the mixed liquid during stirring and mixing in the raw material production process was changed to 30°C. The results are shown in Table 1.

[0063] Comparative Example 2 A boron nitride powder and a cosmetic composition were prepared and evaluated in the same manner as in Example 1, except that in the raw material production process, dry mixing was used instead of wet mixing when stirring and mixing. The results are shown in Table 1.

[0064] [Table 1]

Claims

1. A boron nitride powder in which the flowability energy is measured seven times in a dynamic fluidity test conducted using a powder rheometer at a blade rotation speed of 100 mm / s, and the SI is the ratio (1FE / 7FE) of the flowability energy of the first measurement (1FE) to the flowability energy of the seventh measurement (7FE), where SI is the ratio.

2. 2. The boron nitride powder of claim 1, wherein all seven measurements of the flowability energy are within the range of 0 to 20 mJ.

3. Using the powder rheometer, the angle of internal friction (AIF) is measured in a shear test performed under a pre-compression consolidation pressure of 1 to 15 kPa in accordance with ASTM D7891; and When the wall friction angle (WFA) was measured in a wall friction test using the powder rheometer under a pre-compression consolidation pressure of 1 to 15 kPa in accordance with ASTM D7891, except that artificial leather was attached to the surface of a circular disk, 3. The boron nitride powder according to claim 1, wherein the ratio (AIF / WFA) of the angle of internal friction (AIF) to the angle of wall friction (WFA) is 0.5 to 1.

5.

4. 4. The boron nitride powder according to claim 3, wherein the angle of internal friction (AIF) is between 15° and 35°.

5. 5. The boron nitride powder according to claim 3, wherein the wall friction angle (WFA) is between 10° and 30°.

6. 6. The boron nitride powder according to claim 1, wherein an average value of the crushing strength of 20 boron nitride particles having a particle diameter in the range of 63 to 106 μm in the boron nitride powder is 3 MPa or less.

7. 7. The boron nitride powder according to claim 1, wherein when the boron nitride powder is sieved through a standard sieve having a mesh size of 106 μm, the amount of the boron nitride powder remaining on the standard sieve is 10 mass% or less of the total boron nitride powder.

8. A cosmetic composition comprising the boron nitride powder according to any one of claims 1 to 7.

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