Hexagonal boron nitride powder, method for producing the same, and cosmetic and method for producing the same

Abstract

The present application provides a hexagonal boron nitride powder, comprising secondary particles formed by agglomeration of primary particles of hexagonal boron nitride, wherein, when a particle diameter at which an accumulated value from a small particle diameter reaches 50% of the total in a cumulative distribution of volume-based particle diameters measured by a laser diffraction scattering method is defined as D50, a ratio of D50 to a BET specific surface area is 5 μg / m2 or more.

Description

Technical Field

[0001] This disclosure relates to hexagonal boron nitride powder and its manufacturing method, as well as cosmetics and their manufacturing method. Background Technology

[0002] Boron nitride possesses lubricating properties, high thermal conductivity, and insulation properties, and is widely used in solid lubricants, mold release agents, fillers for resins and rubbers, raw materials for cosmetics (also known as cosmetics), and heat-resistant insulating sintered bodies.

[0003] The functions of hexagonal boron nitride powder incorporated into cosmetics include improving the smoothness, spreadability, and opacity of cosmetics, as well as imparting gloss. In particular, because hexagonal boron nitride powder has superior smoothness compared to talc powder and mica powder, which have similar functions, it is widely used in cosmetics requiring excellent smoothness. Patent Document 1 proposes setting the average particle size and maximum particle size within a specified range to improve the smoothness of hexagonal boron nitride powder.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-165241 Summary of the Invention

[0007] To meet consumers' increasing demands for cosmetics, the properties of raw materials used in cosmetics are also required to be further improved. For example, raw materials used in foundations are considered to need to have better spreadability. Improving spreadability by allowing the powder to swell to a certain extent is effective.

[0008] This disclosure provides a hexagonal boron nitride powder capable of manufacturing cosmetics with excellent spreadability, and a method for manufacturing the same. Furthermore, this disclosure provides cosmetics with excellent spreadability achieved through the use of the aforementioned hexagonal boron nitride powder, and a method for manufacturing the same.

[0009] [Methods for solving the problem]

[0010] One aspect of the disclosed hexagonal boron nitride powder comprises secondary particles formed by the aggregation of primary particles of hexagonal boron nitride. In the cumulative distribution of volume-based particle size determined by laser diffraction scattering, when the particle size at which the cumulative value starting from the smallest particle size reaches 50% is defined as D50, the ratio of D50 to BET specific surface area is 5 μg / m or more.

[0011] The BET specific surface area of ​​the aforementioned hexagonal boron nitride powder mainly depends on the particle size of the primary particles. On the other hand, D50 mainly depends on the particle size of the secondary particles formed by the aggregation of these primary particles. Therefore, the ratio of D50 to BET specific surface area can be said to be related to the size of the secondary particles relative to the primary particles, and the proportion of the secondary particles relative to the total size of the aforementioned hexagonal boron nitride powder. Because the aforementioned hexagonal boron nitride powder has a ratio of 5 μg / m or more, the proportion of secondary particles formed by the aggregation of primary particles and / or the size of the secondary particles relative to the primary particles can be increased. The secondary particles have larger internal voids than the primary particles. Therefore, the hexagonal boron nitride powder containing these secondary particles becomes swollen and has a fluffy appearance. When this hexagonal boron nitride powder is applied, the aggregated secondary particles are broken down while being applied. Therefore, it has excellent spreadability. This type of hexagonal boron nitride powder is suitable for use as a raw material in cosmetics.

[0012] The BET specific surface area of ​​the above-mentioned hexagonal boron nitride powder is preferably less than 3m². 2 / g. As a result, the particle size of the primary particles increases, which can significantly improve smoothness.

[0013] The D50 of the aforementioned hexagonal boron nitride powder is preferably 12 μm or greater. This type of hexagonal boron nitride powder exhibits superior ductility.

[0014] The aforementioned hexagonal boron nitride powder can be used as a raw material in cosmetics. Because of its excellent ductility, the hexagonal boron nitride powder is suitable for use as a raw material in cosmetics.

[0015] One method for manufacturing hexagonal boron nitride powder disclosed herein comprises the following steps: a calcination step in which a mixed powder containing hexagonal boron nitride and an additive is calcined in a gaseous environment of an inert gas, ammonia, or a mixture thereof at a temperature of 1600°C or higher and less than 1900°C to obtain a calcined product containing hexagonal boron nitride with higher crystallinity than that in the mixed powder; a refining step in which the calcined product is pulverized, washed, and dried to obtain a dry powder; and an annealing step in which the dry powder is annealed in a gaseous environment of an inert gas, ammonia, or a mixture thereof at a temperature of 1900 to 2100°C; and an annealing step in which the dry powder is heated at a heating rate of 5°C / min or higher, and the heating time at 1900 to 2100°C is less than 2 hours.

[0016] The above manufacturing method obtains a calcined product containing highly crystalline hexagonal boron nitride by calcining at a temperature of 1700°C or higher but lower than 1900°C using additives. By pulverizing and cleaning this calcined product, residual additives are reduced, thus suppressing grain growth during subsequent annealing. Furthermore, because the calcined product containing crystallized hexagonal boron nitride is annealed under predetermined conditions after drying, the grain growth of primary hexagonal boron nitride particles is suppressed, while primary particles agglomerate, promoting the formation of secondary particles. Therefore, the proportion of secondary particles and / or the size of secondary particles relative to primary particles can be increased.

[0017] Secondary particles have larger internal voids than primary particles. Therefore, hexagonal boron nitride powder containing these secondary particles swells up, giving it a fluffy appearance. When this hexagonal boron nitride powder is applied, the agglomerated secondary particles are broken down while being spread. Therefore, according to the above manufacturing method, hexagonal boron nitride powder with excellent ductility can be produced. This hexagonal boron nitride powder is suitable for use as a raw material in cosmetics.

[0018] The above manufacturing method may include a pre-calcination step before the calcination step: raw material powders containing boron-containing compounds and nitrogen-containing compounds are calcined in an inert gas, ammonia, or a mixture thereof at 600–1300°C to obtain a pre-calcined product containing hexagonal boron nitride with low crystallinity. Furthermore, the mixed powder in the calcination step may include the pre-calcined product and additives. In this way, by performing pre-calcination at a lower temperature than the calcination step, grain growth is suppressed, making it easier to obtain primary particles that readily form secondary particles that contribute to improved ductility.

[0019] The hexagonal boron nitride powder obtained in the annealing process of the above manufacturing method has a particle size distribution of 50% when the cumulative value from the smallest particle size reaches 50% of the total particle size, and the ratio of D50 to BET specific surface area is 5 μg / m or more.

[0020] One aspect of the cosmetic disclosed herein comprises the aforementioned hexagonal boron nitride powder. The hexagonal boron nitride powder exhibits excellent spreadability upon application. Therefore, cosmetics comprising this hexagonal boron nitride powder possess excellent spreadability.

[0021] One aspect of the cosmetic manufacturing method disclosed herein involves using hexagonal boron nitride powder obtained by any of the aforementioned manufacturing methods as a raw material. The hexagonal boron nitride powder obtained by the aforementioned manufacturing methods exhibits excellent spreadability upon application. Therefore, cosmetics manufactured using this hexagonal boron nitride powder as a raw material possess excellent spreadability.

[0022] According to this disclosure, a hexagonal boron nitride powder capable of manufacturing cosmetics with excellent spreadability and a method thereof are provided. Furthermore, according to this disclosure, a cosmetic with excellent spreadability achieved by using the aforementioned hexagonal boron nitride powder and a method thereof are provided. Detailed Implementation

[0023] The following describes embodiments of this disclosure. However, the following embodiments are illustrative and do not represent a limitation of this disclosure to the following content.

[0024] Secondary particles formed by the aggregation of primary particles containing hexagonal boron nitride, when the cumulative distribution of volume-based particle size determined by laser diffraction scattering is defined as the particle size at which the cumulative value from the smallest particle size reaches 50% of the total, have a D50 ratio to BET specific surface area of ​​5 μg / m or higher. This ratio (D50 / BET) can be 6 μg / m or higher, or 7 μg / m or higher. Therefore, the size and proportion of secondary particles can be increased, further improving ductility.

[0025] The aforementioned ratio (D50 / BET) can be less than 30 μg / m or less than 20 μg / m. This reduces the grainy feel when used as a raw material in cosmetics. Examples of the aforementioned ratio (D50 / BET) range include 5 μg / m or more but less than 30 μg / m, and 7 μg / m or more but less than 20 μg / m.

[0026] The D50 disclosed herein was measured using a commercially available laser diffraction particle size distribution measuring device. From the viewpoint of further improving smoothness when used as a raw material in cosmetics, D50 can be 12 μm or more, or 14 μm or more. From the viewpoint of reducing gloss on the appearance when used as a raw material in cosmetics, D50 can be 30 μm or less, or 25 μm or less, or 20 μm or less. D50 can be adjusted by, for example, the particle size distribution of the raw material powder, pre-calcination temperature and time, calcination temperature and time, annealing temperature and time, and heating rate. For example, the range of D50 can be 12 to 30 μm.

[0027] BET specific surface area is a value measured using nitrogen as the adsorbent gas and a commercially available specific surface area measuring device. BET specific surface area can be less than 3 m². 2 / g, or less than 2.5m 2 / g. Therefore, in addition to improved ductility, it also significantly enhances smoothness. The specific surface area of ​​BET can be 0.5m². 2 / g or more, or 1m 2 / g or higher. This improves adhesion to skin and wrinkles. For example, the BET specific surface area can range from 0.5 to 3m².2 / g.

[0028] The bulk density of hexagonal boron nitride powder can be 0.47 g / cm³. 3 The following can be 0.43 g / cm³ 3 The following value can also be 0.37 g / cm³. 3 The following describes how a hexagonal boron nitride powder with a more porous appearance can be produced by achieving such a low bulk density. The determination can be performed according to JIS R1628-1997, "Method for Determination of Bulk Density of Precision Ceramic Powders".

[0029] According to this embodiment, the proportion of secondary particles and / or the size of secondary particles relative to primary particles in the hexagonal boron nitride powder can be increased. Secondary particles create larger internal voids compared to primary particles. Therefore, the hexagonal boron nitride powder containing these secondary particles becomes swollen and has a fluffy appearance. When this hexagonal boron nitride powder is applied, the agglomerated secondary particles are broken down while being applied, resulting in excellent spreadability. This hexagonal boron nitride powder is suitable for use as a raw material in cosmetics. That is, this disclosure also provides a method of using hexagonal boron nitride as a raw material in cosmetics.

[0030] One embodiment of the cosmetic contains the aforementioned hexagonal boron nitride powder. Therefore, cosmetics containing this hexagonal boron nitride powder exhibit excellent spreadability. Examples of cosmetics include foundations (powder foundations, liquid foundations, cream foundations), setting powders, highlighting makeup, eyeshadows, eyeliners, nail polishes, lipsticks, blushes, and mascaras. Among these, hexagonal boron nitride powder is particularly well-suited for use in foundations and liquid eyeshadows. The content of hexagonal boron nitride powder in the cosmetic is, for example, 0.1% to 70% by mass. The cosmetic can be manufactured using known methods. For example, a method for manufacturing cosmetics includes a step of mixing hexagonal boron nitride powder with other raw materials.

[0031] One embodiment of the method for manufacturing hexagonal boron nitride powder includes the following steps: a pre-calcination step, in which raw material powder containing a boron compound and a nitrogen compound is calcined in an inert gas, ammonia, or a mixture thereof at a temperature of 600 to 1300°C to obtain a pre-calcined product containing hexagonal boron nitride; a calcination step, in which a mixed powder containing hexagonal boron nitride and an additive is calcined in an inert gas, ammonia, or a mixture thereof at a temperature of 1600°C or higher and less than 1900°C to obtain a calcined product containing hexagonal boron nitride with higher crystallinity than the hexagonal boron nitride in the mixed powder; a refining step, in which the calcined product is pulverized, washed, and dried to obtain a dry powder; and an annealing step, in which the dry powder is annealed in an inert gas environment such as nitrogen, helium, or argon at a temperature of 1900 to 2100°C.

[0032] Examples of boron-containing compounds include boric acid, boron oxide, and borax. Examples of nitrogen-containing compounds include dicyandiamine, melamine, and urea. The molar ratio of boron atoms to nitrogen atoms in the raw material powder containing the boron-containing compound powder and the nitrogen-containing compound powder can be 2:8 to 8:2 or 3:7 to 7:3. The raw material powder may also contain components other than the above-mentioned compounds. For example, it may contain carbonates such as lithium carbonate and sodium carbonate, which are used as pre-calcination aids. In addition, it may contain reducing substances such as carbon.

[0033] The raw material powder containing the above-mentioned components is pre-fired in an inert gas environment such as nitrogen, helium, or argon, an ammonia gas environment, or a mixed gas environment composed of these gases, using, for example, an electric furnace. The pre-fired temperature can be 600–1300°C, 800–1200°C, or 900–1100°C. The pre-fired time can be, for example, 0.5–5 hours or 1–4 hours.

[0034] The pre-calcined product obtained by pre-calcination includes at least one selected from the group consisting of low-crystallinity hexagonal boron nitride and amorphous hexagonal boron nitride. The pre-calcination process is carried out at a lower temperature than the calcination process described below to cause the reaction of boron nitride. Therefore, grain growth can be suppressed, and the particle size of primary particles in the final boron nitride powder can be reduced.

[0035] The obtained pre-calcined material is then mixed with additives to obtain a mixed powder. Examples of additives include borates such as sodium borate, and carbonates such as sodium carbonate, calcium carbonate, and lithium carbonate. The amount of additive can be 2 to 20 parts by mass, or 2 to 8 parts by mass, relative to 100 parts by mass of the pre-calcined material containing hexagonal boron nitride. This mixed powder is then calcined in, for example, an electric furnace in an inert gas environment such as nitrogen, helium, or argon, an ammonia gas environment, or a mixed gas environment containing them.

[0036] The calcination process involves the formation and crystallization of boron nitride in the presence of additives. This improves the crystallinity of the boron nitride contained in the pre-calcined material. The calcination temperature is above 1600℃ and below 1900℃. This calcination temperature can be 1650–1850℃ or 1650–1750℃. The calcination time can be, for example, 0.5–5 hours or 1–4 hours.

[0037] If the calcination temperature is too low, it tends to become difficult to fully generate secondary particles of hexagonal boron nitride. If the size and / or proportion of these secondary particles decrease, the smoothness of the material tends to decrease when used as a cosmetic ingredient. The same tendency occurs when the calcination time is too short. On the other hand, if the calcination temperature is too high, the crystal growth and aggregation of hexagonal boron nitride will occur excessively, resulting in a tendency for the material to have a stronger shine when used as a cosmetic ingredient.

[0038] The calcined product obtained in the calcination process sometimes contains impurities in addition to hexagonal boron nitride. Examples of impurities include residual additives and water-soluble boron compounds. These impurities can be reduced by washing during the refining process. After washing, solid-liquid separation is performed, followed by drying to obtain a dry powder. Examples of washing solutions include water, aqueous solutions containing acidic substances, organic solvents, and mixtures of organic solvents and water. To avoid secondary contamination of impurities, water with a conductivity of less than 1 mS / m can be used. Examples of 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, isopropanol, and acetone. There are no particular limitations on the washing method; for example, the calcined product can be immersed in the washing solution and stirred, or the washing solution can be sprayed onto the calcined product.

[0039] After cleaning is completed, the cleaning solution can be separated into solid and liquid components using a decanter, vacuum filter, pressure filter, rotary filter, sedimentation separator, or a combination thereof. The separated solid components can be dried using a conventional dryer to obtain a dry powder. Examples of dryers include rack dryers, fluidized bed dryers, spray dryers, rotary dryers, belt dryers, and combinations thereof. After drying, to remove coarse particles, grading can be performed using, for example, sieving.

[0040] In the annealing process, the dried powder is heated at 1900–2100°C in an inert gas environment such as nitrogen, helium, or argon, an ammonia gas environment, or a mixture of these gases, using, for example, an electric furnace. This annealing temperature can be 1950°C or higher, considering the need for sufficient agglomeration of primary particles. Alternatively, considering the need to suppress the growth of primary particle grains, the annealing temperature can be 2050°C or lower. Because the annealing process involves heating at the same temperature as the calcination process, secondary particles formed from the agglomeration of primary particles can be sufficiently formed.

[0041] To suppress primary grain growth and excessive agglomeration, the heating time at 1900–2100°C during the annealing process is 2 hours or less, or even 1 hour or less. On the other hand, considering the formation of sufficient secondary grains, the heating time at 1900–2100°C during the annealing process can be 0.5 hours or more.

[0042] In the annealing process, the dried powder is heated at a rate of 5°C / min or higher. This heating rate suppresses the growth of primary particles and excessive agglomeration of primary particles. Furthermore, the heating rate can be obtained by dividing the temperature difference (heating amplitude) between the initial temperature and 1900°C by the time required to reach 1900°C from the initial temperature. An upper limit for this heating rate can be, for example, 15°C / min.

[0043] In this way, the aforementioned hexagonal boron nitride powder can be obtained. The description of embodiments for manufacturing hexagonal boron nitride powder is applicable to the above manufacturing method. The manufacturing method of hexagonal boron nitride powder is not limited to the above embodiments. For example, the annealing process can be repeated multiple times. Alternatively, after the annealing process, a homogenizer or similar device capable of applying ultrasonic vibration can be used to perform a pyrolysis process that pyrolyzes the hexagonal boron nitride powder to a degree that does not damage secondary particles.

[0044] The above describes several embodiments of this disclosure, but this disclosure is not limited to the above embodiments at all.

[0045] Example

[0046] The present disclosure will be described in more detail with reference to the embodiments and comparative examples, but the present disclosure is not limited to the following embodiments.

[0047] (Example 1)

[0048] [Preparation of hexagonal boron nitride powder]

[0049] <Pre-firing process>

[0050] A mixed raw material was obtained by mixing 100.0 g of boric acid powder (purity ≥ 99.8% by mass, manufactured by Kanto Chemical Co., Ltd.) and 90.0 g of melamine powder (purity ≥ 99.0% by mass, manufactured by Wako Pure Chemical Co., Ltd.) for 10 minutes using an alumina mortar. The dried mixed raw material was then placed in a container made of hexagonal boron nitride and placed in an electric furnace. While circulating nitrogen gas within the furnace, the temperature was increased from room temperature to 1000°C at a rate of 10°C / min. After maintaining the temperature at 1000°C for 2 hours, heating was stopped and the material was allowed to cool naturally. The furnace was then turned on when the temperature dropped below 100°C. This process yielded a pre-calcined product containing low-crystallinity hexagonal boron nitride.

[0051] <Calcination Process>

[0052] 3.0 g of sodium carbonate (purity ≥ 99.5% by mass) as an auxiliary agent was added to 100.0 g of the pre-calcined material, and mixed for 10 minutes using an alumina mortar. The mixture was placed in the aforementioned electric furnace. While circulating nitrogen gas in the furnace, the temperature was increased from room temperature to 1700°C at a rate of 10°C / min. After maintaining the calcination temperature at 1700°C for 4 hours, heating was stopped and the material was allowed to cool naturally. The furnace was turned on when the temperature dropped below 100°C. The obtained calcined material was recovered and pulverized in an alumina mortar for 3 minutes to obtain coarse hexagonal boron nitride powder.

[0053] <Refining Process>

[0054] To remove impurities from the coarse hexagonal boron nitride powder, 30g of the powder was added to 500g of dilute nitric acid (nitric acid concentration: 5% by mass) and stirred at room temperature for 60 minutes. After stirring, solid-liquid separation was performed by vacuum filtration, and the powder was washed with water (conductivity 1 mS / m) until the filtrate became neutral. After washing, the powder was dried at 120°C for 3 hours using a dryer to obtain a dry powder. Coarse particles were removed from the obtained dry powder using an ultrasonic vibrating sieve (KFS-1000, manufactured by Xinghe Industrial Co., Ltd., 250μm mesh).

[0055] Annealing process

[0056] The dried powder, after removing coarse particles, was placed in the aforementioned electric furnace. While circulating nitrogen gas within the furnace, the temperature was increased from room temperature to 2000°C at a rate of 5°C / min. After maintaining the temperature at 2000°C for 2 hours, heating was stopped, and the furnace was allowed to cool naturally. The furnace was then turned on when the temperature dropped below 100°C.

[0057] <Pyrolysis Process>

[0058] 30g of the obtained coarse hexagonal boron nitride powder was added to 300ml of water and ultrasonically dispersed for 5 minutes using a homogenizer (SONIC & MATERIALS, INC., trade name: VC505) at 500W and 20kHz. The dispersion was then filtered to separate the solid components and dried. Coarse particles were removed from the dried powder using an ultrasonic vibrating sieve (Kōwa Industrial Co., Ltd., KFS-1000, 250μm mesh) to obtain the hexagonal boron nitride powder of Example 1.

[0059] [Evaluation of Hexagonal Boron Nitride Powder]

[0060] <Determination of Particle Size Distribution>

[0061] The volumetric particle size distribution of the hexagonal boron nitride powder prepared in Example 1 was determined using a laser diffraction particle size distribution measuring apparatus (manufactured by Nikkiso Corporation, apparatus name: MT3300EX). The particle size (D50) at which the cumulative value from the smallest particle size reaches 50% of the total volumetric particle size distribution was calculated. The results are shown in Table 2.

[0062] <Determination of specific surface area (N)>

[0063] The BET specific surface area of ​​the hexagonal boron nitride powder prepared in Example 1 was determined using a specific surface area measuring apparatus (manufactured by YUASA IONICS, apparatus name: MONOSORB) via the BET single-point method. Nitrogen was used as the adsorbent gas and helium as the carrier gas. 1 g of the sample was dried and degassed at 300°C for 15 minutes before measurement. The results are shown in Table 2. In Table 2, the ratio of D50 to BET specific surface area is shown in the "D50 / BET" field.

[0064] <Evaluation of Extensibility>

[0065] 0.2g of hexagonal boron nitride powder was placed on one end of an artificial skin (10mm x 50mm). The hexagonal boron nitride powder was spread longitudinally using a spatula to coat the surface of the artificial skin. Image analysis was performed using commercially available image analysis software (WinROOF) to determine the ratio of the coated area of ​​the hexagonal boron nitride powder to the total area of ​​the artificial skin. A larger ratio indicates better spreadability. The evaluation criteria for spreadability, based on the area ratio, are shown in Table 1. The evaluation results for spreadability are shown in Table 2.

[0066] [Table 1]

[0067] Area ratio determination More than 95% very good More than 80% but less than 95% good More than 70% but less than 80% acceptable More than 60% but less than 70% ordinary More than 40% but less than 60% Difference Less than 40% Very bad

[0068] (Example 2)

[0069] The annealing process was carried out at 2000°C for 1 hour, and the rest of the process was the same as in Example 1 to prepare hexagonal boron nitride powder. Furthermore, all measurements and evaluations of the hexagonal boron nitride powder were performed in the same manner as in Example 1. The results are shown in Table 2.

[0070] (Example 3)

[0071] The heating rate from room temperature to 2000°C in the annealing process was set to 10°C / min, and hexagonal boron nitride powder was prepared in the same manner as in Example 1. Furthermore, all measurements and evaluations of the hexagonal boron nitride powder were performed in the same manner as in Example 1. The results are shown in Table 2.

[0072] (Example 4)

[0073] 3.0 g of sodium carbonate (purity ≥ 99.5% by mass) was added to the dried mixed raw materials as an additive. The calcination process was performed without pre-calcination, and hexagonal boron nitride powder was produced in the same manner as in Example 1. Furthermore, all measurements and evaluations of the hexagonal boron nitride powder were performed in the same manner as in Example 1. The results are shown in Table 2.

[0074] (Comparative Example 1)

[0075] Without performing the annealing process of Example 1, the dried powder obtained by removing coarse particles through a refining process was used as the hexagonal boron nitride powder of Comparative Example 1. The various measurements and evaluations of the hexagonal boron nitride powder were performed in the same manner as in Example 1. The results are shown in Table 2.

[0076] (Comparative Example 2)

[0077] The heating rate from room temperature to 2000°C in the annealing process was set to 2°C / min, and hexagonal boron nitride powder was prepared in the same manner as in Example 1. Furthermore, all measurements and evaluations of the hexagonal boron nitride powder were performed in the same manner as in Example 1. The results are shown in Table 2.

[0078] [Table 2]

[0079]

[0080] Examples 1-4 all contain secondary particles formed by the aggregation of primary particles. Compared to Comparative Examples 1 and 2, Examples 1-4 have larger D50 / BET values ​​and a fluffy appearance. Therefore, Examples 1-4 have superior ductility due to the presence of more secondary particles that contribute to improved ductility compared to Comparative Examples 1 and 2. The D50 of Example 1 is smaller than that of Example 2. This is because the annealing time in Example 1 is longer, causing the primary particles to grow and disperse. If the annealing time is extended further than that in Example 1, the effect of primary particle grain growth will disappear, and aggregation will occur, resulting in a larger D50.

[0081] [Industrial applicability]

[0082] According to this disclosure, a hexagonal boron nitride powder capable of manufacturing cosmetics with excellent spreadability is provided, as well as a method for manufacturing the same. Furthermore, a cosmetic exhibiting excellent spreadability using the aforementioned hexagonal boron nitride powder is provided, along with a method for manufacturing the same.

Claims

1. A hexagonal boron nitride powder, comprising secondary particles formed by the aggregation of primary hexagonal boron nitride particles. In the cumulative distribution of volume-based particle size determined by laser diffraction scattering, when the particle size at which the cumulative value from the smallest particle size reaches 50% is defined as D50, the ratio of D50 to BET specific surface area is greater than 5 μg / m². The specific surface area of ​​BET is 2.3 m². 2 / g or more and less than 3 m 2 / g, D50 is below 30μm, Furthermore, it is used as a raw material in cosmetics.

2. The hexagonal boron nitride powder as described in claim 1, wherein, D50 is above 12μm.

3. A method for manufacturing hexagonal boron nitride powder, comprising the following steps: The calcination process involves calcining a mixed powder containing hexagonal boron nitride and additives in a gaseous environment of inactive gas, ammonia, or a mixture thereof at a temperature above 1600°C and below 1900°C to obtain a calcined product containing hexagonal boron nitride with higher crystallinity than the hexagonal boron nitride in the mixed powder. The refining process involves pulverizing, washing, and drying the calcined material to obtain a dry powder. The annealing process involves annealing the dried powder in a gaseous environment of inactive gas, ammonia, or a mixture thereof at a temperature of 1900-2100°C. In the annealing process, the dried powder is heated at a rate of 5°C / min or higher, and the heating time at 1900~2100°C is less than 2 hours.

4. The method for manufacturing hexagonal boron nitride powder as described in claim 3, further comprising the following steps prior to the calcination step: The pre-calcination process involves calcining raw material powders containing boron compounds and nitrogen compounds in an inert gas, ammonia, or a mixture thereof at 600–1300°C to obtain a pre-calcined product containing hexagonal boron nitride. in, The mixed powder in the calcination process comprises the pre-calcined material and the additives.

5. The method for manufacturing hexagonal boron nitride powder as described in claim 3 or 4, wherein, In the hexagonal boron nitride powder obtained in the annealing process, when the cumulative distribution of the volume reference particle size determined by laser diffraction scattering method is defined as the particle size at which the cumulative value starting from the smallest particle size reaches 50% of the total, the ratio of D50 to BET specific surface area is 5 μg / m or more.

6. A cosmetic product comprising the hexagonal boron nitride powder as described in claim 1 or 2.

7. A method for manufacturing a cosmetic, using hexagonal boron nitride powder obtained by the manufacturing method according to any one of claims 3 to 5 as a raw material to manufacture the cosmetic.

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