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

Abstract

The hexagonal boron nitride powder of the present disclosure contains secondary particles formed by agglomeration of primary particles of hexagonal boron nitride, and when the cumulative distribution of particle diameters on a volume basis measured by a laser diffraction scattering method is such that the particle diameters at which the cumulative values from small particle diameters reach 10%, 50%, and 90% of the total are D10, D50, and D90, respectively, the D50 is 3 to 30 μm, and the D90 / D10 is 4.0 or greater.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a hexagonal boron nitride powder and a method for producing the same, and a cosmetic and a method for producing the same. BACKGROUND

[0002] Hexagonal boron nitride has lubricity, high thermal conductivity, and insulation, and is used for a wide variety of applications such as solid lubricants, release agents, filling materials for resins and rubbers, raw materials for cosmetics (also referred to as makeup materials), and insulating sintered bodies having heat resistance.

[0003] As the function of the hexagonal boron nitride powder incorporated into the cosmetic, there can be mentioned improvement in the slipperiness, extensibility, and hiding property of the cosmetic, and impartation of glossiness, and the like. In particular, the hexagonal boron nitride powder is excellent in slipperiness compared to talc powder and mica powder having the same function, and thus can be widely used for cosmetics requiring excellent slipperiness. In Patent Literature 1, in order to improve the slipperiness of the hexagonal boron nitride powder, it is proposed to make the average particle diameter and the maximum particle diameter fall within a prescribed numerical range.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2018-165241 SUMMARY

[0007] In order to cope with the high levelization of the level of requirements of customers for cosmetics, it is required that the properties of raw materials for cosmetics are further improved. For example, it is considered that raw materials for foundations and the like need to have further excellent extensibility. In order to improve the extensibility, it is considered to be effective to make the powder somewhat volumetrically increase.

[0008] The present disclosure provides a hexagonal boron nitride powder capable of producing a cosmetic excellent in extensibility and a method for producing the same. In addition, the present disclosure provides a cosmetic excellent in extensibility by using the above hexagonal boron nitride powder and a method for producing the same.

[0009] The hexagonal boron nitride powder of one aspect of the present disclosure contains secondary particles formed by agglomeration of primary particles of hexagonal boron nitride, and when particle diameters at which cumulative values from a small particle diameter reach 10%, 50%, and 90% of the whole in a cumulative distribution of particle diameters on a volume basis measured by a laser diffraction scattering method are set to D10, D50, and D90, respectively, the D50 is 3 to 30 μm, and the D90 / D10 is 4.0 or more.

[0010] The hexagonal boron nitride powder described above has a D50 of 3 to 30 μm, and thus contains primary particles having a size suitable for extensibility. Thus, since the primary particles have a size suitable for extensibility and the D90 / D10 is also large, the volume ratio of secondary particles formed by agglomeration of the primary particles can be increased. The secondary particles have a larger void within the particle than the primary particles. Thus, the volume of the hexagonal boron nitride powder having a large volume ratio of secondary particles increases, and has a fluffy appearance. If such a hexagonal boron nitride powder is spread out, the secondary particles formed by agglomeration are broken while being spread out. Thus, the extensibility is excellent. Such a hexagonal boron nitride powder is suitable for use as a raw material for a cosmetic.

[0011] The D90 / D50 of the hexagonal boron nitride powder described above can be 1.7 or more. Thus, the ratio of secondary particles can be further increased, and the effect of the secondary particles on the improvement of extensibility at the time of spreading can be further improved. Thus, a hexagonal boron nitride powder having further excellent extensibility can be produced.

[0012] The D90 of the hexagonal boron nitride powder described above can be 50 μm or less. Thus, the formation of coarse particles by excessive agglomeration of primary particles can be reduced, and the roughness can be reduced when used as a raw material for a cosmetic.

[0013] The hexagonal boron nitride powder described above can be used as a raw material for a cosmetic. The hexagonal boron nitride powder described above has excellent extensibility, and thus is suitable for use as a raw material for a cosmetic.

[0014] The production method of the hexagonal boron nitride powder of one aspect of the present disclosure has the following steps: a calcination step of calcining a raw material powder containing a powder of a compound containing boron and a powder of a compound containing nitrogen at 600 to 1300°C in an atmosphere of a non-active gas, ammonia gas, or a mixed gas thereof to obtain a calcination product containing hexagonal boron nitride; a calcination step of calcining a mixed powder containing the calcination product and an additive at 1900 to 2100°C in an atmosphere of a non-active gas, ammonia gas, or a mixed gas thereof to obtain a calcination product containing hexagonal boron nitride having higher crystallinity than the hexagonal boron nitride in the calcination product described above; a purification step of washing and drying the calcination product to obtain a dried powder; an annealing step of annealing the dried powder at 1900 to 2100°C in an atmosphere of a non-active gas, ammonia gas, or a mixed gas thereof to obtain a heat-treated product containing secondary particles formed by agglomeration of primary particles of hexagonal boron nitride; and a deagglomeration step of deagglomerating the heat-treated product to obtain a hexagonal boron nitride powder containing the secondary particles described above.

[0015] The manufacturing method described above can form primary particles of hexagonal boron nitride having a small particle diameter and high crystallinity by having a pre-burning step in which burning is performed at a lower temperature than the burning step, and a burning step in which burning is performed using an auxiliary agent. Then, the auxiliary agent and the like remaining in the burned product are reduced by the purification step, and the crystal grain growth in the subsequent annealing step can be suppressed. By performing the disintegration step after the annealing step, the secondary particles formed by the aggregation of the primary particles can be disintegrated into secondary particles having a moderate size while maintaining the aggregation of the primary particles.

[0016] The hexagonal boron nitride powder obtained in this manner can increase the volume ratio of the secondary particles formed by the aggregation of the primary particles. The secondary particles have a large void within the particle compared to the primary particles. Therefore, the volume of the hexagonal boron nitride powder having a large volume ratio of secondary particles increases, and has a fluffy appearance. If such a hexagonal boron nitride powder is spread out, the secondary particles formed by the aggregation are broken while being spread out. Therefore, the extensibility is excellent. Such a hexagonal boron nitride powder is suitable for use as a raw material for a cosmetic.

[0017] The hexagonal boron nitride powder obtained in the disintegration step of the manufacturing method described above has a cumulative distribution of the volume-based particle diameter measured by the laser diffraction scattering method, and when the particle diameters at which the cumulative values from the small particle diameter reach 10%, 50%, and 90% of the entire cumulative distribution are set as D10, D50, and D90, respectively, the D50 is 3 to 30 μm, and the D90 / D10 can be 4.0 or more.

[0018] The cosmetic of one aspect of the present disclosure contains the hexagonal boron nitride powder described above. The hexagonal boron nitride powder described above has excellent extensibility when spread out. Therefore, the cosmetic containing such a hexagonal boron nitride powder has excellent extensibility.

[0019] The manufacturing method of the cosmetic of one aspect of the present disclosure uses the hexagonal boron nitride powder obtained by any of the manufacturing methods described above as a raw material to manufacture a cosmetic. The hexagonal boron nitride powder obtained by the manufacturing method described above has excellent extensibility when spread out. Therefore, the cosmetic manufactured using such a hexagonal boron nitride powder as a raw material has excellent extensibility.

[0020] According to the present disclosure, it is possible to provide a hexagonal boron nitride powder and a manufacturing method thereof that can manufacture a cosmetic having excellent extensibility. In addition, according to the present disclosure, it is possible to provide a cosmetic and a manufacturing method thereof having excellent extensibility by using the hexagonal boron nitride powder described above. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a graph showing the cumulative distribution of the volume-based particle diameter measured by the laser diffraction scattering method. DETAILED DESCRIPTION

[0022] The following describes embodiments of the present disclosure. However, the following embodiments are examples for illustrating the present disclosure, and are not intended to limit the present disclosure to the following.

[0023] The secondary particles formed by agglomeration of the primary particles containing hexagonal boron nitride, when the particle diameters at which the cumulative values from the small particle diameter reach 10%, 50%, and 90% of the entire cumulative distribution of the particle diameters on a volume basis measured by the laser diffraction scattering method are set as D10, D50, and D90, respectively, D50 is 3 to 30 μm, and D90 / D10 is 4.0 or more.

[0024] D10, D50, and D90 of the present disclosure are measured by a commercially available laser diffraction particle size distribution measuring device. The size relationship of D10, D50, and D90 has a relationship of D10 < D50 < D90. From the viewpoint of further improving the slipperiness when used as a raw material for a cosmetic, D50 can be 5 μm or more, or 7 μm or more. From the viewpoint of reducing the appearance of glare when used as a raw material for a cosmetic, D50 can be 25 μm or less, or 20 μm or less.

[0025] D90 can be 50 μm or less, 45 μm or less, or 40 μm or less. Thereby, the coarse particles formed by excessive agglomeration of the primary particles can be reduced, and the roughness when used as a raw material for a cosmetic can be reduced. From the viewpoint of further improving the spreadability, D90 can be 18 μm or more, or 19 μm or more. An example of the range of D90 can be 18 to 50 μm.

[0026] D10 can be 2 μm or more, or 3 μm or more. Thereby, the spreadability can be further improved. D10 can be 10 μm or less, or 8 μm or less. Thereby, the appearance of glare when used as a raw material for a cosmetic can be reduced. An example of the range of D10 can be 2 to 10 μm. D10, D50, and D90 can be adjusted, for example, by the particle size distribution of the raw material powder, the pre-burning temperature and the pre-burning time, the calcination temperature and the calcination time, and the annealing temperature and the annealing time.

[0027] D90 / D10 can be 4.5 or more, can be 5.0 or more, or can be 6.0 or more. By thus increasing D90 / D10, the ratio and size of secondary particles to primary particles can be sufficiently increased. As a result, the voids contained in the secondary particles become more numerous and the appearance further becomes fluffy, and the ductility at the time of spreading can be further improved. From the viewpoint of reducing manufacturing costs, the upper limit of D90 / D10 can be 10 or can be 8.0. D90 / D10 can be adjusted, for example, by changing the calcination temperature and calcination time of the calcination process, and the annealing temperature and annealing time of the annealing process. An example of the range of D90 / D10 can be 4.0 to 10.

[0028] D90 / D50 can be 1.7 or more, can be 1.8 or more, or can be 2.0 or more. As a result, the ratio of secondary particles can be further increased and the effect of improving the ductility at the time of spreading by the secondary particles can be further increased. Thus, a hexagonal boron nitride powder having further excellent ductility can be produced. From the viewpoint of reducing manufacturing costs, the upper limit of D90 / D50 can be 6.0 or can be 4.0. D90 / D50 can be adjusted, for example, by changing the annealing temperature and annealing time of the annealing process. An example of the range of D90 / D50 can be 1.7 to 6.0.

[0029] D50 / D10 can be 4.0 or less, can be 3.0 or less, or can be 2.8 or less. As a result, the deviation of the particle diameter of primary particles can be reduced and the hiding property can be sufficiently improved. From the viewpoint of reducing manufacturing costs, the lower limit of D50 / D10 can be 1.5 or more or can be 2.0 or more. D50 / D10 can be adjusted, for example, by changing the calcination time of the calcination process. An example of the range of D50 / D10 can be 1.5 to 4.0.

[0030] The bulk density of the hexagonal boron nitride powder can be 0.45 g / cm 3 Hereinafter, the bulk density can be 0.41 g / cm 3 Hereinafter, the bulk density can be 0.35 g / cm 3 Hereinafter, the bulk density can be 0.35 g / cm. By having such a low bulk density, a hexagonal boron nitride powder having a further fluffy appearance can be produced. The bulk density can be measured in accordance with "Method for measuring the bulk density of fine ceramic powder" of JIS R1628-1997.

[0031] The hexagonal boron nitride powder of the present embodiment has primary particles having a size suitable for extensibility, and a large D90 / D10, and thus can increase the volume ratio of secondary particles formed by aggregation of the primary particles. The secondary particles have a larger void within the particle than the primary particles. Thus, the hexagonal boron nitride powder containing a large amount of secondary particles has a large volume and has a fluffy appearance. If such a hexagonal boron nitride powder is spread, the secondary particles formed by aggregation are broken while being spread. Thus, the extensibility is excellent. Such a hexagonal boron nitride powder is suitable for use as a raw material for a cosmetic. That is, the present disclosure can also provide a use method using the hexagonal boron nitride powder as a raw material for a cosmetic.

[0032] The cosmetic of one embodiment contains the above-described hexagonal boron nitride powder. Thus, the extensibility of the cosmetic containing the hexagonal boron nitride powder is excellent. As the cosmetic, for example, there can be mentioned foundation (powder, liquid foundation, cream foundation), face powder, highlighter, eye shadow, eyeliner, nail polish, lipstick, blush, mascara, and the like. Among these, the hexagonal boron nitride powder is particularly well suited for foundation and eye shadow. The content of the hexagonal boron nitride powder in the cosmetic is, for example, 0.1 to 70% by mass. The cosmetic can be manufactured by a known method. The manufacturing method of the cosmetic, for example, has a step of compounding and mixing the hexagonal boron nitride powder with other raw materials.

[0033] The manufacturing method of the hexagonal boron nitride powder of one embodiment has the following steps: a calcination step of calcining a raw material powder containing a powder of a compound containing boron and a powder of a compound containing nitrogen at 600 to 1300°C in an atmosphere of a non-active gas, ammonia gas, or a mixed gas thereof to obtain a calcination product containing hexagonal boron nitride; a calcination step of calcining a mixed powder containing hexagonal boron nitride and an auxiliary at 1900 to 2100°C in an atmosphere of a non-active gas, ammonia gas, or a mixed gas thereof to obtain a calcination product containing hexagonal boron nitride having higher crystallinity than the hexagonal boron nitride in the mixed powder; a purification step of washing and drying the calcination product to obtain a dried powder; an annealing step of annealing the dried powder at 1900 to 2100°C in an atmosphere of a non-active gas, ammonia gas, or a mixed gas thereof to obtain a heat-treated product containing secondary particles formed by aggregation of primary particles of hexagonal boron nitride; and a deagglomeration step of deagglomerating the heat-treated product to obtain a hexagonal boron nitride powder containing secondary particles.

[0034] As the compound containing boron, boric acid, boron oxide, borax, and the like can be given. As the compound containing nitrogen, dicyanamide, melamine, and urea can be given. The molar ratio of boron atoms to nitrogen atoms in the raw material powder containing the powder of the compound containing boron and the powder of the compound containing nitrogen can be boron atoms : nitrogen atoms = 2 : 8 to 8 : 2, or 3 : 7 to 7 : 3. The raw material powder can contain components other than the above-mentioned compounds. For example, carbonates such as lithium carbonate and sodium carbonate can be contained as a pre-sintering aid. In addition, a reducing substance such as carbon can be contained.

[0035] The raw material powder containing the above-mentioned components is pre-sintered in a non-active atmosphere such as nitrogen, helium, or argon, in an ammonia atmosphere, or in a mixed atmosphere obtained by mixing them, using, for example, an electric furnace. The pre-sintering temperature can be 600 to 1300°C, can be 800 to 1200°C, or can be 900 to 1100°C. The pre-sintering time can be, for example, 0.5 to 5 hours, or can be 1 to 4 hours.

[0036] The pre-sintered product obtained by pre-sintering contains at least one selected from the group consisting of low-crystalline hexagonal boron nitride and amorphous hexagonal boron nitride. The pre-sintering process performs the reaction of boron nitride at a lower temperature than the calcination process described later. Therefore, the grain growth can be suppressed, and the particle size of primary particles in the finally obtained boron nitride powder can be reduced.

[0037] Next, the obtained pre-sintered product is mixed with an aid, and a mixed powder is obtained. As the aid, borates such as sodium borate, and carbonates such as sodium carbonate, calcium carbonate, and lithium carbonate can be given. The mixing amount of the aid can be 2 to 20 parts by mass, or can be 2 to 8 parts by mass, with respect to 100 parts by mass of the pre-sintered product containing hexagonal boron nitride. Such a mixed powder is calcined in a non-active atmosphere such as nitrogen, helium, or argon, in an ammonia atmosphere, or in a mixed atmosphere containing them, for example, in an electric furnace.

[0038] In the calcination process, the generation and crystallization of boron nitride are performed in the presence of the aid. Thereby, the crystallinity of boron nitride contained in the pre-sintered product can be improved. The calcination temperature is 1900 to 2100°C. The calcination temperature can also be 1950 to 2050°C. The calcination time can be, for example, 0.5 to 5 hours, or can be 1 to 4 hours.

[0039] If the calcination temperature becomes too low, there is a tendency that hexagonal boron nitride secondary particles are not sufficiently generated. If the volume ratio of the secondary particles becomes small, there is a tendency that the slip property is reduced when used as a raw material for a cosmetic. The same tendency is also observed when the calcination time becomes too short. On the other hand, if the calcination temperature becomes too high, the crystalline growth and agglomeration of hexagonal boron nitride are excessively performed, and there is a tendency that the glare is intensified when used as a raw material for a cosmetic.

[0040] The calcined product obtained in the calcining step contains, in addition to hexagonal boron nitride, sometimes impurities. As the impurities, there are, for example, residual auxiliary agents and water-soluble boron compounds. In the purification step, such impurities are reduced by washing. After washing, solid-liquid separation is performed and drying is performed to obtain a dry powder. As the washing liquid for washing, there are, for example, water, an aqueous solution containing an acidic substance, an organic solvent, a mixture of an organic solvent and water, and the like. From the viewpoint of avoiding secondary mixing of impurities, water having a conductivity of 1 mS / m or less can be used. As the acidic substance, there are, for example, inorganic acids such as hydrochloric acid and nitric acid. As the organic solvent, there are, for example, water-soluble organic solvents such as methanol, ethanol, propanol, isopropanol, and acetone. The method of washing is not particularly limited, and, for example, the calcined product can be immersed in the washing liquid and stirred to perform washing, or the washing liquid can be sprayed on the calcined product to perform washing.

[0041] After the completion of washing, the washing liquid can be separated from the solid by using a decanter, a suction filter, a pressure filter, a rotary filter, a sedimentation separator, or a device obtained by combining these. The separated solid can be dried by using a general dryer to obtain a dry powder. The dryer is, for example, a shelf dryer, a fluidized bed dryer, a spray dryer, a rotary dryer, a belt dryer, or a combination thereof. After drying, classification by using a sieve can be performed in order to remove coarse particles.

[0042] In the annealing step, the dry powder is heated to 1900 to 2100°C in a non-active atmosphere such as nitrogen, helium, or argon, an ammonia atmosphere, or a mixed atmosphere obtained by mixing these, by using, for example, an electric furnace. From the viewpoint of sufficiently agglomerating primary particles, the annealing temperature can be 1950°C or higher. In addition, from the viewpoint of suppressing the grain growth of primary particles, the annealing temperature can be 2050°C or lower. In the annealing step, since heating is performed to the same temperature as in the calcining step, a heat-treated product containing secondary particles obtained by agglomerating primary particles can be obtained. From the viewpoint of sufficiently reducing the oxygen content and suppressing the growth of particles, the annealing time is, for example, 0.5 to 5 hours, or 1 to 4 hours.

[0043] In the disintegration step, the heat-treated product obtained in the annealing step is disintegrated. The disintegration step is preferably performed by a method that gives an impact to the extent that the agglomerated secondary particles are broken. From such a viewpoint, the disintegration step preferably uses a homogenizer that gives ultrasonic vibration to the heat-treated product dispersed in a solvent. As the solvent, the solvents exemplified as the washing liquid of the purification step can be used. By such a disintegration step, coarse particles can be reduced, and secondary particles that give a fluffy feel can be sufficiently left. In addition, washing of impurities remaining in the heat-treated product can be smoothly performed.

[0044] The value of D90 / D10 of the hexagonal boron nitride powder can be adjusted by the disintegration time of the homogenizer after the annealing process. Specifically, if the disintegration time is increased, the value of D90 / D10 becomes smaller. On the other hand, if the disintegration time is shortened, the value of D90 / D10 becomes larger. In this way, by adjusting the disintegration time of the homogenizer in the disintegration process after the annealing process and the like, the value of D90 / D10 can be adjusted to the desired range.

[0045] In this way, the above-described hexagonal boron nitride powder can be obtained. In the above-described production method, the description of the embodiments of the hexagonal boron nitride powder can be applied.

[0046] The above describes several embodiments of the present disclosure, but the present disclosure is not limited at all by the above-described embodiments.

[0047] Example

[0048] The content of the present disclosure is described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0049] (Example 1)

[0050] [Production of hexagonal boron nitride powder]

[0051] <Pre-burning process>

[0052] A mixture of 100.0 g of boric acid powder (purity 99.8 mass% or more, manufactured by Kanto Chemical Co., Inc.) and 90.0 g of melamine powder (purity 99.0 mass% or more, manufactured by Wako Pure Chemical Industries, Ltd.) was obtained by mixing them with an alumina mortar for 10 minutes. The dried mixture was put into a container made of hexagonal boron nitride and placed in an electric furnace. While nitrogen gas was circulated in the electric furnace, the temperature was increased from room temperature to 1000°C at a rate of 10°C / minute. After being kept at 1000°C for 2 hours, the heating was stopped and the temperature was naturally cooled. The electric furnace was opened when the temperature became 100°C or less. In this way, a pre-burner containing low-crystalline hexagonal boron nitride was obtained.

[0053] <Calcination process>

[0054] To 100.0 g of the pre-burner, 3.0 g of sodium carbonate (purity 99.5 mass% or more) as an auxiliary agent was added, and mixed with an alumina mortar for 10 minutes. The mixture was placed in the above-described electric furnace. While nitrogen gas was circulated in the electric furnace, the temperature was increased from room temperature to 2000°C at a rate of 10°C / minute. After being kept at a calcination temperature of 2000°C for 4 hours, the heating was stopped and the temperature was naturally cooled. The electric furnace was opened when the temperature became 100°C or less. The obtained calcinates were recovered and pulverized with an alumina mortar for 3 minutes to obtain a crude powder of hexagonal boron nitride.

[0055] <purification step>

[0056] To remove impurities contained in the coarse powder of hexagonal boron nitride, 30 g of the coarse powder was put in 500 g of dilute nitric acid (nitric acid concentration: 5 mass%) and stirred at room temperature for 60 minutes. After the stirring, solid-liquid separation was performed by suction filtration, and washing was performed with water (conductivity: 1 mS / m) until the filtrate became neutral. After the washing, the obtained dry powder was dried using a drying machine at 120°C for 3 hours.

[0057] <annealing step>

[0058] The dry powder after the removal of coarse particles was placed in the above-mentioned electric furnace. While nitrogen was circulated in the electric furnace, the temperature was increased from room temperature to 2000°C at a rate of 10°C / minute. After the temperature was maintained at 2000°C for 4 hours, the heating was stopped and the electric furnace was naturally cooled. The electric furnace was opened when the temperature became 100°C or less. The obtained calcined product was recovered to obtain a coarse powder of hexagonal boron nitride powder.

[0059] <deagglomeration step>

[0060] 30 g of the coarse powder of hexagonal boron nitride obtained in the annealing step was put in 300 ml of water, and ultrasonic dispersion was performed using a homogenizer (manufactured by SONIC & MATERIALS, INC., trade name: VC505) at 500 W and 20 kHz for 5 minutes. After the ultrasonic dispersion, to remove impurities contained in the coarse powder, 500 g of dilute nitric acid (nitric acid concentration: 5 mass%) was added, and the mixture was stirred at room temperature for 60 minutes. After the stirring, solid-liquid separation was performed by suction filtration, and washing was performed with water (conductivity: 1 mS / m) until the filtrate became neutral. After the washing, the obtained dry powder was dried using a drying machine at 120°C for 3 hours. Coarse particles were removed from the obtained dry powder using an ultrasonic vibrating sieve (manufactured by KOSHO KOGYO CO., LTD., trade name: KFS-1000, mesh size: 250 μm). This was used as the hexagonal boron nitride powder of Example 1.

[0061] [Evaluation of hexagonal boron nitride powder]

[0062] [Measurement of particle size distribution]

[0063] The particle size distribution of the hexagonal boron nitride powder prepared in Example 1 was measured using a laser diffraction type particle size distribution measuring device (manufactured by NIKKISO CO., LTD., device name: MT3300EX) on a volume basis. Figure 1 is a graph showing the cumulative distribution of the particle size on a volume basis obtained by the measurement. Figure 1In the cumulative distribution shown, the particle diameters at which the cumulative values from the small particle diameters reach 10%, 50%, and 90% of the entire body are set as D10, D50, and D90, respectively, and the values of D10, D50, and D90 are shown in Table 2. The values of D90 / D10, D90 / D50, and D50 / D10 are also shown in Table 2.

[0064] <Assessment of Spreading>

[0065] Hexagonal boron nitride powder 0.2 g was placed on one end of an artificial skin (length x width = 10 mm x 50 mm). The hexagonal boron nitride powder was extended in the longitudinal direction using a doctor blade in a manner such that the hexagonal boron nitride powder was spread on the surface of the artificial skin. Image analysis was performed using a commercially available image analysis software (WinROOF), and the proportion of the spread area of the hexagonal boron nitride powder with respect to the total area of the artificial skin was calculated. The greater the area proportion, the more excellent the spreading. The assessment criteria for the spreading were based on the area proportion, as shown in Table 1. The results of the assessment of the spreading are shown in Table 2.

[0066] [Table 1]

[0067] Area ratio Determination 95% or more Very good 80% or more and less than 95% Good 60% or more and less than 80% Common 40% or more and less than 60% Poor Less than 40% Very poor

[0068] (Example 2)

[0069] The heating temperature of the annealing step was set to 2050°C, and hexagonal boron nitride powder was produced in the same manner as in Example 1 except for this. Then, each measurement and assessment of the hexagonal boron nitride powder were performed in the same manner as in Example 1. The results are shown in Table 2 and Table 2. Figure 1

[0070] (Example 3)

[0071] The holding time of the annealing step was set to 5 hours, and hexagonal boron nitride powder was produced in the same manner as in Example 1 except for this. Then, each measurement and assessment of the hexagonal boron nitride powder were performed in the same manner as in Example 1. The results are shown in Table 2 and Table 2. Figure 1

[0072] (Example 4)

[0073] The time of the homogenizer in the disintegration step was changed to 8 minutes, and hexagonal boron nitride powder was produced in the same manner as in Example 1 except for this. Then, each measurement and assessment 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] The heating temperature of the annealing step was set to 1700°C, and hexagonal boron nitride powder was produced in the same manner as in Example 1 except for this. Each measurement and assessment of the hexagonal boron nitride powder were performed in the same manner as in Example 1. The results are shown in Table 2.​​Figure 1 and shown in Table 2.

[0076] [Table 2]

[0077]

[0078] Examples 1 to 4 each contain secondary particles formed by aggregation of primary particles. Examples 1 to 4 have a large value of D90 / D10 and have an appearance with a fluffy feeling, as compared with Comparative Example 1. Thus, Examples 1 to 4 contain a large amount of secondary particles, as compared with Comparative Example 1, and exhibit excellent extensibility. The hexagonal boron nitride powder of Example 1, which has the largest degree of aggregation, has the most excellent extensibility.

[0079] Industrial applicability

[0080] According to the present disclosure, it is possible to provide a hexagonal boron nitride powder capable of manufacturing a cosmetic having excellent extensibility and a manufacturing method thereof. In addition, it is possible to provide a cosmetic having excellent extensibility by using the above hexagonal boron nitride powder and a manufacturing method thereof.

Claims

1. A hexagonal boron nitride powder for use as a raw material for cosmetics, wherein the hexagonal boron nitride powder comprises secondary particles formed by agglomeration of primary particles of hexagonal boron nitride. In the cumulative distribution of volume-based particle sizes measured by the laser diffraction scattering method, the particle sizes at which the cumulative values ​​from the smallest particle size reach 10%, 50%, and 90% of the total are defined as D10, D50, and D90, respectively. D50 is 3 to 30 μm. D90 / D10 is 5.0 or more.

2. The hexagonal boron nitride powder according to claim 1, wherein D90 / D50 is 1.7 or above.

3. The hexagonal boron nitride powder according to claim 1 or 2, wherein D90 is 50 μm or less.

4. A method for producing hexagonal boron nitride powder, wherein the hexagonal boron nitride powder is used as a raw material for cosmetics, the method comprising the following steps: In the calcining step, raw material powders containing a powder of a compound containing boron and a powder of a compound containing nitrogen are calcined at 600 to 1300° C. in an atmosphere of an inert gas, ammonia, or a mixed gas thereof to obtain a calcined product containing hexagonal boron nitride. a calcining step of calcining the mixed powder comprising the calcined product and the auxiliary agent at 1900-2100° C. in an atmosphere of an inert gas, ammonia gas, or a mixed gas thereof to obtain a calcined product comprising hexagonal boron nitride having higher crystallinity than the hexagonal boron nitride in the calcined product; Purification step, washing and drying the calcined product to obtain dry powder, an annealing step of annealing the dry powder at 1900-2100° C. in an atmosphere of an inert gas, ammonia, or a mixed gas thereof to obtain a heat-treated product comprising secondary particles formed by aggregation of primary particles of hexagonal boron nitride; and a crushing step of crushing the heat-treated product to obtain hexagonal boron nitride powder containing the secondary particles; In the cumulative distribution of the volume-based particle size of the hexagonal boron nitride powder obtained in the crushing process measured by the laser diffraction scattering method, when the particle sizes when the cumulative values ​​from the small particle size reach 10%, 50% and 90% of the total are respectively set as D10, D50 and D90, D50 is 3 to 30 μm, and D90 / D10 is greater than 5.

0. A cosmetic comprising the hexagonal boron nitride powder according to any one of claims 1 to 3.

6. A method for producing a cosmetic, comprising using the hexagonal boron nitride powder obtained by the method according to claim 4 as a raw material.

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