TW202304808A - Hexagonal boron nitride powder and method for producing same, and cosmetic material and method for producing same - Google Patents

Abstract

An object of the invention is to provide a hexagonal boron nitride powder containing secondary particles formed by the aggregation of primary particles of hexagonal boron nitride, wherein in a cumulative volume-based particle size distribution measured by a laser diffraction and scattering method, if the particle diameter at a cumulative 50% from the small particle diameter side is deemed D50, then the ratio of D50 relative to the BET specific surface area is 5 [µg/m] or greater.

Description

Hexagonal boron nitride powder and manufacturing method thereof, and cosmetics and manufacturing method thereof

This disclosure relates to hexagonal boron nitride powder and its manufacturing method, and cosmetics and its manufacturing method.

Boron nitride has lubricity, high thermal conductivity, and insulation properties, and is used in solid lubricants, mold release agents, resin and rubber fillers, raw materials for cosmetics (also called cosmetics), and heat-resistant It is used in a wide range of applications such as insulating sintered compacts.

The functions of the hexagonal boron nitride powder blended into cosmetics include improving the smoothness, spreadability, and hiding properties of cosmetics, and imparting gloss. In particular, since hexagonal boron nitride powder is superior in smoothness compared to talc powder and mica powder having the same function, it is generally used in cosmetics requiring excellent smoothness. Patent Document 1 proposes that in order to improve the smoothness of hexagonal boron nitride powder, the average particle size and the maximum particle size fall within a predetermined numerical range. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2018-165241

[Problem to be Solved by the Invention]

In order to respond to the high level of customer demand for cosmetics, the characteristics of raw materials used in cosmetics are also required to be further improved. For example, raw materials used in foundation etc. are considered to have more excellent ductility. In order to improve ductility, it is considered effective to swell the powder to some extent.

The present disclosure provides hexagonal boron nitride powder capable of producing cosmetics having excellent ductility and a method for producing the same. Also, the present disclosure provides a cosmetic having excellent ductility by using the above-mentioned hexagonal boron nitride powder and a method for producing the same. [Means to solve the problem]

The hexagonal boron nitride powder of one aspect of this disclosure includes the secondary particles formed by the aggregation of the primary particles of hexagonal boron nitride, and the cumulative distribution of the volume-based particle diameter measured by the laser diffraction scattering method In , when the particle diameter at which the cumulative value from the small particle diameter reaches 50% of the total is D50, the ratio of D50 to the BET specific surface area is 5 μg/m or more.

The BET specific surface area of the above-mentioned hexagonal boron nitride powder mainly depends on the particle size of the primary particles of the hexagonal boron nitride powder. On the other hand, D50 mainly depends on the particle diameter of the secondary particles formed by the aggregation of the primary particles. Therefore, the ratio of D50 to the BET specific surface area can be said to be related to the size of the secondary particles to the primary particles and the ratio of the secondary particles to the entire hexagonal boron nitride powder. Since the ratio of the hexagonal boron nitride powder is 5 μg/m or more, the ratio of secondary particles formed by aggregation of primary particles and/or the size of secondary particles relative to primary particles can be increased. The secondary particles have larger voids in the particles than the primary particles. Therefore, the hexagonal boron nitride powder containing such secondary particles becomes swollen and has a fluffy appearance. If this hexagonal boron nitride powder is spread, the agglomerated secondary particles will be spread while being destroyed. Therefore, ductility is excellent. This hexagonal boron nitride powder is suitable as a raw material for cosmetics.

The BET specific surface area of the hexagonal boron nitride powder is preferably less than 3 m ² /g. Thereby, the particle diameter of primary particle becomes large, and smoothness can fully be improved.

The D50 of the above-mentioned hexagonal boron nitride powder is preferably 12 μm or more. This kind of hexagonal boron nitride powder has more excellent ductility.

The aforementioned hexagonal boron nitride powder can be used as a raw material for cosmetics. The above-mentioned hexagonal boron nitride powder is suitable as a raw material for cosmetics because of its excellent ductility.

The manufacturing method of the hexagonal boron nitride powder in one aspect of the present disclosure has the following steps: a calcination step, the mixed powder containing the hexagonal boron nitride and additives is placed in an inert gas, ammonia gas or their mixed gas Calcining at a temperature above 1600°C and not reaching 1900°C in a gas environment to obtain a calcined product containing hexagonal boron nitride with higher crystallinity than the hexagonal boron nitride in the mixed powder; refining step, the calcined product crushing, washing, and drying to obtain a dry powder; and an annealing step, annealing the dry powder at a temperature of 1900-2100°C in an inert gas, ammonia gas, or their mixed gas environment; the annealing step is The dry powder is heated at a heating rate of 5°C/minute or more, and the heating time at 1900-2100°C is less than 2 hours.

In the above production method, a calcined product including hexagonal boron nitride with high crystallinity can be obtained by calcining at a temperature of 1700° C. to less than 1900° C. using an auxiliary agent. By crushing and washing the calcined product, the remaining additives and the like are reduced, and the growth of crystal grains during subsequent annealing can be suppressed. Also, since the calcined product containing crystallized hexagonal boron nitride is annealed under predetermined conditions after drying, the grain growth of the primary particles of hexagonal boron nitride can be suppressed, and at the same time, the primary particles can be aggregated to promote secondary crystallization. The formation of secondary particles. Therefore, the ratio of the secondary particles and/or the size of the secondary particles relative to the primary particles can be increased.

The secondary particles have larger voids in the particles than the primary particles. Therefore, the hexagonal boron nitride powder containing such secondary particles becomes swollen and has a fluffy appearance. If this hexagonal boron nitride powder is spread, the agglomerated secondary particles will be spread while being destroyed. Therefore, according to the above production method, hexagonal boron nitride powder excellent in ductility can be produced. This hexagonal boron nitride powder is suitable as a raw material for cosmetics.

The above-mentioned production method may have a pre-calcination step before the calcination step: the raw material powder containing the powder of the boron-containing compound and the powder of the nitrogen-containing compound is heated in an atmosphere of inert gas, ammonia gas or their mixed gas at 600~1300 It is calcined under the condition of ℃ to obtain a calcined product containing hexagonal boron nitride with low crystallinity. Also, the mixed powder in the calcining step may contain calcined materials and additives. Thus, by pre-firing at a temperature lower than that of the calcination step, grain growth is suppressed, and it becomes easy to obtain primary particles that easily form secondary particles that contribute to improvement in ductility.

For the hexagonal boron nitride powder obtained in the annealing step of the above-mentioned production method, in the cumulative distribution of the volume-based particle diameter measured by the laser diffraction scattering method, the cumulative value starting from the small particle diameter will reach 50% of the total When the particle diameter at the time is D50, the ratio of D50 to the BET specific surface area is 5 μg/m or more.

The cosmetic material in one aspect of the present disclosure contains the above-mentioned hexagonal boron nitride powder. The above-mentioned hexagonal boron nitride powder has excellent ductility when spread. Therefore, cosmetics containing such hexagonal boron nitride powder have excellent ductility.

The method for producing cosmetics according to one aspect of this disclosure is to use the hexagonal boron nitride powder obtained in any of the above-mentioned production methods as a raw material to produce cosmetics. The hexagonal boron nitride powder obtained by the above manufacturing method has excellent ductility when spread. Therefore, the cosmetics manufactured using this hexagonal boron nitride powder as a raw material have excellent ductility. [Effect of Invention]

According to the present disclosure, it is possible to provide hexagonal boron nitride powder capable of producing cosmetics having excellent ductility and a method for producing the same. Also, according to the present disclosure, a cosmetic having excellent ductility by using the above-mentioned hexagonal boron nitride powder and a method for producing the same can be provided.

Embodiments of the present disclosure will be described below. However, the following embodiments are examples for explaining the present disclosure, and do not mean that the present disclosure is limited to the following contents.

Secondary particles formed by agglomeration of primary particles including hexagonal boron nitride, in the cumulative distribution of volume-based particle sizes measured by the laser diffraction scattering method, the cumulative value starting from the small particle size reaches all 50 When the particle diameter at % is D50, the ratio of D50 to the BET specific surface area is 5 μg/m or more. This ratio (D50/BET) may be 6 μg/m or more, and may be 7 μg/m or more. Thereby, the size and proportion of the secondary particles will be increased, and the ductility can be further improved.

The above-mentioned ratio (D50/BET) may be less than 30 μg/m or less than 20 μg/m. Thereby, graininess when used as a raw material of cosmetics can be reduced. An example of the range of the above-mentioned ratio (D50/BET) may be 5 μg/m or more and less than 30 μg/m, and may be 7 μg/m or more and less than 20 μg/m.

The D50 disclosed herein is measured with a commercially available laser diffraction particle size distribution measuring device. From the viewpoint of further improving smoothness when used as a raw material for cosmetics, D50 may be 12 μm or more, or may be 14 μm or more. From the viewpoint of reducing glossiness in appearance when used as a raw material of cosmetics, D50 may be 30 μm or less, 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, calcining temperature and calcining time, calcining temperature and calcining time, annealing temperature and annealing time, and heating rate. As an example of the range of D50, it can be 12-30 micrometers.

The BET specific surface area is a value measured using a commercially available specific surface area measuring device using nitrogen gas as an adsorption gas. The BET specific surface area may be less than 3 m ² /g or less than 2.5 m ² /g. Thereby, in addition to ductility, smoothness can be fully improved. The BET specific surface area may be not less than 0.5 m ² /g, or not less than 1 m ² /g. Thereby, the adhesion to skin and wrinkles can be improved. As an example of the range of the BET specific surface area, it may be 0.5 to 3 m ² /g.

The bulk density of the hexagonal boron nitride powder can be less than 0.47g/cm ³ , less than 0.43cm ³ , or less than 0.37cm ³ . By having such a low bulk density, hexagonal boron nitride powders can be made with a bulkier appearance. It can be measured in accordance with JIS R1628-1997 "Measurement method of bulk density of fine ceramic powder".

According to this embodiment, the ratio of the secondary particles in the hexagonal boron nitride powder and/or the size of the secondary particles relative to the primary particles can be increased. The secondary particles can make the voids in the particles larger than the primary particles. Therefore, the hexagonal boron nitride powder containing such secondary particles becomes swollen and has a fluffy appearance. If this hexagonal boron nitride powder is spread, the agglomerated secondary particles will be spread while being destroyed. Therefore, ductility is excellent. Such hexagonal boron nitride powder is suitable as a raw material for cosmetics. That is, the present disclosure can also provide a method of using hexagonal boron nitride as a raw material for cosmetics.

A cosmetic according to one embodiment contains the above-mentioned hexagonal boron nitride powder. Therefore, cosmetics containing this hexagonal boron nitride powder have excellent ductility. Cosmetics include, for example, foundation (powder foundation, liquid foundation, cream foundation), face powder, accent makeup, eye shadow, eyeliner, nail polish, lipstick, blush, and mascara. Among these, hexagonal boron nitride powder is particularly suitable for use in foundations and liquid eye shadows. The content of the hexagonal boron nitride powder in the cosmetic is, for example, 0.1 to 70% by mass. Cosmetics can be produced by known methods. The method for producing cosmetics includes, for example, a step of blending and mixing hexagonal boron nitride powder and other raw materials.

A method for producing hexagonal boron nitride powder in one embodiment includes the following steps: a pre-calcination step, where the raw material powders containing boron-containing compound powder and nitrogen-containing compound powder are placed in an inert gas, ammonia gas or their mixed gas Calcined under the condition of 600~1300℃ in the gas environment to obtain the calcined product containing hexagonal boron nitride; in the calcining step, the mixed powder containing hexagonal boron nitride and additives is inert gas, ammonia or Calcining their mixed gas at a temperature above 1600°C and not exceeding 1900°C to obtain a calcined product containing hexagonal boron nitride with higher crystallinity than the hexagonal boron nitride in the mixed powder; In the refining step, the calcined product is crushed, washed, and dried to obtain a dry powder; in the annealing step, the dry powder is annealed at a temperature of 1900-2100°C in an inert gas environment such as nitrogen, helium, or argon.

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 atom to nitrogen atom in the raw material powder containing boron-containing compound powder and nitrogen-containing compound powder can be boron atom: nitrogen atom = 2:8~8:2, or 3:7~7 :3. The raw material powder may contain components other than the above compounds. For example, carbonates such as lithium carbonate and sodium carbonate may be contained as auxiliary agents for calcining. In addition, reducing substances such as carbon may be contained.

The raw material powder containing the above components is pre-fired in an inert gas environment such as nitrogen, helium, or argon, ammonia gas, or a mixed gas environment obtained by using, for example, an electric furnace. The calcining temperature can be 600~1300℃, 800~1200℃, or 900~1100℃. The pre-burning time may be, for example, 0.5 to 5 hours, or 1 to 4 hours.

The calcined product obtained by calcining includes at least one selected from the group consisting of low-crystalline hexagonal boron nitride and amorphous hexagonal boron nitride. The pre-calcination step allows the reaction of boron nitride to proceed at a lower temperature than the calcination step described below. Therefore, crystal grain growth can be suppressed, and the particle size of a primary particle in the finally obtained boron nitride powder can be reduced.

Then, the obtained calcined product is blended and mixed with additives to obtain a mixed powder. Examples of auxiliary agents include borates such as sodium borate, and carbonates such as sodium carbonate, calcium carbonate, and lithium carbonate. With respect to 100 parts by mass of the calcined material containing hexagonal boron nitride, the blending amount of the auxiliary agent may be 2-20 parts by mass, or 2-8 parts by mass. The mixed powder is calcined in an electric furnace, for example, in an inert gas atmosphere such as nitrogen, helium, or argon, in an ammonia gas atmosphere, or in a mixed gas atmosphere containing them.

The calcining step is to carry out the formation and crystallization of boron nitride in the presence of auxiliary agents. Thereby, the crystallinity of boron nitride contained in the calcined product can be improved. The calcination temperature is 1600°C or higher and less than 1900°C. The calcination temperature may be 1650~1850°C, or 1650~1750°C. The calcination time may be, for example, 0.5 to 5 hours, or 1 to 4 hours.

If the calcination temperature is too low, it tends to become difficult to sufficiently generate secondary particles of hexagonal boron nitride. When the size and/or ratio of the secondary particles are reduced, smoothness tends to decrease when used as a raw material for cosmetics. There is also a similar tendency when the calcination time becomes too short. On the other hand, if the calcination temperature becomes too high, the crystal growth and aggregation of hexagonal boron nitride will proceed excessively, and the luster will tend to become stronger when used as a raw material for cosmetics.

The calcined product obtained in the calcining step sometimes contains impurities other than hexagonal boron nitride. Impurities include, for example, residual additives and water-soluble boron compounds. In the refining step, such impurities can be reduced by washing. After washing, solid-liquid separation was performed and dried to obtain a dry powder. Examples of the cleaning solution used for cleaning include water, an aqueous solution containing an acidic substance, an organic solvent, a mixed solution 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 may 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. The cleaning method is not particularly limited. For example, the calcined object may be immersed in a cleaning solution to be stirred for cleaning, or may be washed by spraying a cleaning solution on the calcined object.

After the cleaning is finished, decantation, suction filter, pressure filter, rotary filter, sedimentation separator, or a combination of them can be used to separate the cleaning solution from solid to liquid. The separated solid component can be dried with a general dryer to obtain a dry powder. Examples of the dryer include shed dryers, fluidized bed dryers, spray dryers, rotary dryers, belt dryers, and combinations thereof. After drying, in order to remove coarse particles, it may be classified by, for example, a sieve.

In the annealing step, use an electric furnace to heat the dry powder at 1900~2100°C in an inert gas environment such as nitrogen, helium, or argon, in an ammonia gas environment, or a mixture of them. heating. The annealing temperature may be 1950° C. or higher in consideration of sufficiently aggregating the primary particles. In addition, the annealing temperature may be 2050° C. or lower from the viewpoint of suppressing grain growth of primary particles. In the annealing step, since the heating is performed at the same temperature as in the calcination step, secondary particles formed by agglomeration of primary particles can be sufficiently formed.

In order to suppress grain growth and excessive aggregation of primary particles, the time for heating at a temperature of 1900 to 2100° C. in the annealing step is 2 hours or less, and may be 1 hour or less. On the other hand, from the viewpoint of forming sufficient secondary particles, the time for heating at a temperature of 1900 to 2100° C. in the annealing step may be 0.5 hour or more.

In the annealing step, the dry powder is heated at a temperature increase rate of 5° C./minute or more. By heating at such a heating rate, grain growth of primary particles and excessive aggregation of primary particles can be suppressed. In addition, the temperature increase rate can be obtained by dividing the temperature difference (temperature increase range) between the temperature at the start of the temperature increase and 1900°C by the time required to reach 1900°C from the start of the temperature increase. The upper limit of the above-mentioned temperature increase rate may be, for example, 15° C./min.

In this way, the above-mentioned hexagonal boron nitride powder can be obtained. In the above-mentioned production method, the description regarding the embodiment of the hexagonal boron nitride powder can be applied. The manufacturing method of the hexagonal boron nitride powder is not limited to the above-mentioned embodiments. For example, the annealing step may be repeated multiple times. In addition, after the annealing step, a disintegration step of disintegrating the hexagonal boron nitride powder may be performed to such an extent that the secondary particles are not destroyed by using a homogenizer to which ultrasonic vibration is applied, or the like.

As mentioned above, some embodiments of the present disclosure have been described, but the present disclosure is not limited to the above-mentioned embodiments at all. [Example]

The contents of the present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited by the following examples.

(Example 1) [Preparation of hexagonal boron nitride powder] ＜Pre-burning step＞ 100.0 g of boric acid powder (purity: 99.8% by mass or more, manufactured by Kanto Chemical Co., Ltd.) and 90.0 g of melamine powder (purity: 99.0% by mass or more, manufactured by Wako Pure Chemical Industries, Ltd.) were mixed for 10 minutes using an alumina mortar to obtain a mixed raw material . The dried mixed raw material was put into a container made of hexagonal boron nitride, and placed in an electric furnace. While flowing nitrogen gas into the electric furnace, the temperature was raised from room temperature to 1000°C at a rate of 10°C/min. After maintaining at 1000° C. for 2 hours, heating was terminated and natural cooling was performed. The electric furnace was turned on at the point when the temperature became below 100°C. In this way, a calcined product containing hexagonal boron nitride with low crystallinity is obtained.

＜Calcination step＞ Add 3.0 g of sodium carbonate (purity: 99.5% by mass or more) as an auxiliary agent to 100.0 g of calcined material, and mix for 10 minutes using an alumina mortar. The mixture was placed in the electric furnace mentioned above. While flowing nitrogen gas into the electric furnace, the temperature was raised from room temperature to 1700°C at a rate of 10°C/min. After maintaining the calcination temperature of 1700° C. for 4 hours, the heating was terminated and natural cooling was performed. The electric furnace was turned on at the point when the temperature became below 100°C. The obtained calcined product was collected and pulverized in an alumina mortar for 3 minutes to obtain a coarse powder of hexagonal boron nitride.

＜Refinement process＞ In order to remove impurities contained in the coarse powder of hexagonal boron nitride, 30 g of the coarse powder was poured into 500 g of dilute nitric acid (nitric acid concentration: 5% by mass), and stirred at room temperature for 60 minutes. After stirring, the solid-liquid separation was carried out by suction filtration, and the water was replaced (conductivity 1 mS/m) to wash until the filtrate became neutral. After washing, it was dried at 120° C. for 3 hours using a drier to obtain a dry powder. Coarse particles were removed from the obtained dry powder using an ultrasonic vibrating sieve (KFS-1000, manufactured by Kowa Kogyo Co., Ltd., with a mesh size of 250 μm).

＜Annealing step＞ The dry powder after removal of coarse grains was arranged in the above-mentioned electric furnace. While flowing nitrogen gas into the electric furnace, the temperature was raised from room temperature to 2000° C. at a rate of 5° C./min. After maintaining at 2000° C. for 2 hours, heating was terminated and natural cooling was performed. The electric furnace was turned on at the point when the temperature became below 100°C.

＜Shredding steps＞ 30 g of the obtained coarse powder of hexagonal boron nitride was poured into 300 ml of water, and ultrasonic dispersion was performed for 5 minutes at 500 W and 20 kHz using a homogenizer (manufactured by SONIC & MATERIALS, INC., trade name: VC505). Thereafter, the dispersion liquid was filtered to separate the solid content and dried. Coarse particles were removed from the obtained dry powder using an ultrasonic vibrating sieve (manufactured by Kowa Kogyo Co., Ltd., KFS-1000, mesh 250 μm), and the hexagonal boron nitride powder of Example 1 was obtained.

[Evaluation of hexagonal boron nitride powder] ＜Measurement of Particle Size Distribution＞ The volume-based particle size distribution of the hexagonal boron nitride powder prepared in Example 1 was measured using a laser diffraction particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., device name: MT3300EX). In the volume-based cumulative distribution of particle diameters, the particle diameter (D50) at which the cumulative value from the small particle diameter reaches 50% of the total is calculated. The results are shown in Table 2.

＜Measurement of specific surface area (N)＞ The BET specific surface area of the hexagonal boron nitride powder produced in Example 1 was measured by the BET one-point method using a specific surface area measuring device (manufactured by Yuasa IONICS, device name: MONOSORB). Nitrogen was used as the adsorption gas and helium was used as the carrier gas. Measurement was performed after drying and degassing 1 g of the sample at 300° C. for 15 minutes. The measurement results are shown in Table 2. Also, in Table 2, the ratio of D50 to the BET specific surface area is shown in the column of "D50/BET".

＜Evaluation of ductility＞ 0.2 g of hexagonal boron nitride powder was carried on one end of the artificial skin (length×width=10 mm×50 mm). The hexagonal boron nitride powder is spread along the longitudinal direction by using a spatula to coat the hexagonal boron nitride powder on the surface of the artificial skin. Image analysis was performed using a commercially available image analysis software (WinROOF), and the ratio of the coated area of the hexagonal boron nitride powder to the total area of the artificial skin was obtained. The larger this area ratio is, the more excellent the ductility is. The evaluation criteria of ductility are as shown in Table 1 based on the area ratio. The results of ductility evaluation are shown in Table 2.

[Table 1] Area ratio determination above 95 very good More than 80% and less than 95% good More than 70% and less than 80% passable More than 60% and less than 70% ordinary More than 40% and less than 60% Difference Less than 40% very bad

(Example 2) Hexagonal boron nitride powder was prepared in the same manner as in Example 1 except that the heating time at 2000° C. in the annealing step was set to 1 hour. Also, in the same manner as in Example 1, various measurements and evaluations of the hexagonal boron nitride powder were implemented. The results are shown in Table 2.

(Example 3) Hexagonal boron nitride powder was prepared in the same manner as in Example 1, except that the rate of temperature increase from room temperature to 2000° C. in the annealing step was set to 10° C./minute. Also, in the same manner as in Example 1, various measurements and evaluations of the hexagonal boron nitride powder were implemented. The results are shown in Table 2.

(Example 4) Add 3.0 g of sodium carbonate (purity of 99.5% by mass or more) as an auxiliary agent to the dried mixed raw material, and perform the calcining step instead of the pre-calcination step, and manufacture hexagonal crystals in the same manner as in Example 1 Boron nitride powder. Also, in the same manner as in Example 1, various measurements and evaluations of the hexagonal boron nitride powder were implemented. The results are shown in Table 2.

(comparative example 1) The annealing step of Example 1 was not performed, and the dry powder obtained by removing coarse particles in the refining step was used as the hexagonal boron nitride powder of Comparative Example 1. In the same manner as in Example 1, various measurements and evaluations of the hexagonal boron nitride powder were carried out. The results are shown in Table 2.

(comparative example 2) Hexagonal boron nitride powder was prepared in the same manner as in Example 1 except that the rate of temperature increase from room temperature to 2000° C. in the annealing step was set to 2° C./minute. Also, in the same manner as in Example 1, various measurements and evaluations of the hexagonal boron nitride powder were implemented. The results are shown in Table 2.

[Table 2] D50 (μm) BET specific surface area [m ² /g] D50/BET [μg/m] Extensibility Example 1 20.8 2.7 7.7 very good Example 2 25.9 2.9 8.9 very good Example 3 14.8 2.3 6.4 good Example 4 18.0 3.5 5.1 passable Comparative example 1 11.9 5.4 2.2 very bad Comparative example 2 10.3 2.1 4.9 very bad

Examples 1 to 4 all contain secondary particles formed by agglomeration of primary particles. Compared with Comparative Examples 1 and 2, the values of D50/BET in Examples 1 to 4 are larger and have a fluffy appearance. Therefore, Examples 1 to 4 have more excellent ductility than Comparative Examples 1 and 2 because they contain more secondary particles that contribute to the improvement of ductility. The D50 of Example 1 is smaller than that of Example 2. This is considered to be due to the fact that the grain growth of the primary particles progressed and the aggregation was dispersed because the annealing time in Example 1 was long. It is considered that if the annealing time is made longer than that of Example 1, the influence on the grain growth of the primary particles disappears, aggregation proceeds, and D50 increases. [industrial availability]

According to the present disclosure, there are provided hexagonal boron nitride powders capable of producing cosmetics having excellent ductility and a method for producing the same. Also, there are provided cosmetics having excellent ductility by using the above-mentioned hexagonal boron nitride powder and a method for producing the same.

Claims (9)

A hexagonal crystal boron nitride powder, comprising secondary particles formed by agglomeration of primary particles of hexagonal crystal boron nitride, In the cumulative distribution of volume-based particle diameters measured by the laser diffraction scattering method, when the particle diameter at which the cumulative value from the small particle diameter reaches 50% of the total is D50, the ratio of D50 to the BET specific surface area The ratio is above 5μg/m. The hexagonal boron nitride powder according to Claim 1, wherein the BET specific surface area is less than 3m ² /g. The hexagonal boron nitride powder according to claim 1 or 2, wherein D50 is 12 μm or more. For example, the hexagonal boron nitride powder of claim 1 or 2 is used as a raw material for cosmetics. A method for manufacturing hexagonal boron nitride powder, comprising the following steps: The calcination step is to calcine the mixed powder containing hexagonal boron nitride and additives in the gas environment of inert gas, ammonia gas or their mixed gas at a temperature above 1600°C and below 1900°C to obtain Calcined hexagonal boron nitride in mixed powder with higher crystallinity; a refining step of pulverizing, washing, and drying the calcined product to obtain a dry powder; and annealing step, the dry powder is annealed at 1900~2100°C in an inert gas, ammonia gas or their mixed gas atmosphere; In the annealing step, the dry powder is heated at a heating rate of 5°C/minute or more, and the heating time at 1900-2100°C is 2 hours or less. The method for manufacturing hexagonal boron nitride powder as claimed in item 5 further includes: In the pre-calcination step, the raw material powder containing boron-containing compound powder and nitrogen-containing compound powder is calcined at 600-1300°C in an inert gas, ammonia gas or their mixed gas atmosphere to obtain hexagonal crystal Calcined boron nitride, And the mixed powder in the calcining step includes the calcined product and the auxiliary agent. The method for manufacturing hexagonal boron nitride powder as claimed in claim 5 or 6, wherein, In the hexagonal boron nitride powder obtained in the annealing step, in the cumulative distribution of the volume-based particle diameter measured by the laser diffraction scattering method, the cumulative value from the small particle diameter reaches the particle size when the cumulative value reaches 50% of the total. When the diameter is D50, the ratio of D50 to the BET specific surface area is 5 μg/m or more. A cosmetic comprising the hexagonal boron nitride powder according to any one of Claims 1 to 4. A method for producing cosmetics, which uses the hexagonal boron nitride powder obtained according to the method for producing hexagonal boron nitride powder according to any one of Claims 5 to 7 as a raw material to produce cosmetics.