JP7204732B2 - Hexagonal boron nitride powder, method for producing hexagonal boron nitride powder for cosmetics, and cosmetics - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to boron nitride powder, a method for producing boron nitride powder, and a cosmetic containing boron nitride powder.

Hexagonal boron nitride has a layered structure similar to that of graphite, and is excellent in properties such as lubricity, thermal conductivity, insulation, chemical stability, and thermal shock resistance. Taking advantage of these properties, hexagonal boron nitride is applied to cosmetic raw materials (also called cosmetic raw materials), solid lubricants and release agents, fillers for resins and rubbers, heat-resistant insulating sintered bodies, etc. It is

For example, Patent Document 1 proposes a boron nitride powder for cosmetics. The purpose of adding hexagonal boron nitride powder to cosmetics is to impart, for example, slipperiness, spreadability, glossiness, and the like. In particular, improvement of slipperiness is an important factor for cosmetics. The lubricity of hexagonal boron nitride powder is superior to that of talc and mica powders, which have similar functions.

However, for cosmetics, it cannot be unambiguously said that the higher the smoothness, the better the tactile sensation. For example, when boron nitride powder is blended into a cosmetic that has a "moist" or "slimy" feel to improve the slipperiness, if the slipperiness is increased too much, the "moist" or "slimy" feel is lost. put away. As a cosmetic, it is necessary to have a tactile feel while maintaining appropriate slipperiness. However, no boron nitride powder has been found that is useful for producing a cosmetic composition that satisfies both moderate slipperiness and tactile sensation.

MIU (mean coefficient of friction) is a method for quantifying slipperiness of cosmetics. MIU indicates that the smaller the value, the more excellent the slipperiness of the cosmetic. Moreover, there is MMD (variation in mean friction coefficient) as a method of quantifying the roughness of cosmetics. MMD indicates that the smaller the value, the smaller the roughness of the cosmetic.

It is known that even if the substance is the same, if the shape such as the particle size is different, the tactile sensation will be different (for example, Non-Patent Document 1). Therefore, as a method for adjusting the texture of cosmetics, a method of controlling the slipperiness and roughness of cosmetics by using boron nitride powder obtained by adjusting the particle size by pulverizing boron nitride as a cosmetic raw material is conceivable. . However, boron nitride has the problem that eluted boron (a boron compound soluble in water), which is irritating to the skin, is generated from new particle surfaces generated by pulverization.

From the viewpoint of safety and sanitation, the standards of raw materials for cosmetics are stipulated in the Standards for Quasi-drug Raw Materials 2006. In the above standards, when boron nitride is brought into contact with water in a predetermined procedure, the permissible amount of eluted boron is defined as 20 μg or less per 1 g of boron nitride (i.e., 20 ppm or less per 1 g). there is When boron nitride with an eluted boron amount exceeding the above range is used as a cosmetic raw material, the obtained cosmetic is highly irritating to the skin, which is undesirable. As described above, the method of adjusting the particle size simply by pulverizing boron nitride can lead to an increase in the amount of eluted boron. Therefore, the obtained boron nitride powder may not be desirable as a raw material for cosmetics.

The eluted boron is contained in raw materials and sintering aids remaining when boron nitride is produced, or is generated by hydrolysis of boron nitride during measurement of the amount of eluted boron. Various means of reducing leached boron have been disclosed. Patent Document 2 discloses a method in which hexagonal boron nitride is stirred and washed in a water-soluble organic solvent such as a lower alcohol or acetone, an aqueous solution thereof, or an aqueous surfactant solution, and dried in a low-temperature, low-oxygen atmosphere. there is

Japanese Patent Application Laid-Open No. 2015-140337 JP-A-63-33312

Shinichi Watanabe, "Recognition and Language Evaluation of Particle Groups by Tactile Sensation", Journal of the Japan Society for Precision Engineering, 2005, vol. 71, No. 11, p. 1421

It would be useful to have a boron nitride powder that can provide a cosmetic that has excellent tactile sensations such as "moisturizing" and "slimy" while maintaining appropriate slipperiness.

An object of the present disclosure is to provide a boron nitride powder suitable for cosmetic raw materials and a method for producing the boron nitride powder. Another object of the present disclosure is to provide a cosmetic that has moderate slipperiness and reduced irritation to the skin.

One aspect of the present disclosure includes particles of at least one of primary particles and agglomerated particles of primary particles, the amount of eluted boron is 20 ppm or less per 1 g, the average particle diameter is 2.5 to 7.0 μm, and is 36 μm or more A boron nitride powder is provided in which the content of the particles having a particle diameter of is 10.0% by volume or less.

The boron nitride powder has a low content of agglomerated particles and relatively large primary particles, has an average particle size within a predetermined range, and has a low eluted boron content, and is therefore useful as a raw material for cosmetics. .

The boron nitride powder may have a specific surface area of 3.0 to 12.0 m ² /g.

The boron nitride powder may have an average friction coefficient of 0.7 to 1.2 as measured by a friction tester.

The boron nitride powder may have an average friction coefficient variation of 0.015 or less as measured by a friction tester.

The boron nitride powder may have an aspect ratio of 8 to 23 in primary particles of boron nitride.

One aspect of the present disclosure is that the raw material powder containing the first boron nitride and a sintering aid is fired under conditions of 1600 to 1900 ° C. to obtain a second boron nitride having a higher crystallinity than the first boron nitride. At least one selected from the group consisting of a step of obtaining boron nitride, a step of pulverizing the second boron nitride to obtain a pulverized product, and an organic solvent, an aqueous solution containing an acidic substance, and an aqueous solution containing an organic solvent. and obtaining a boron nitride powder by washing the pulverized material depending on the seed, wherein the content of the sintering aid is Provided is a method for producing boron nitride powder, which is 0.9 to 20 parts by mass.

Since the above production method has a step of washing with a predetermined solution after pulverizing the second boron nitride having a high degree of crystallinity, it is possible to produce a boron nitride powder with a reduced amount of eluted boron. Such boron nitride powder is useful as a raw material for cosmetics.

In the above production method, the amount of eluted boron in the boron nitride powder may be 20 ppm or less per 1 g.

In the above production method, the boron nitride powder contains at least one of primary particles and agglomerated primary particles, has an average particle size of 2.5 to 7.0 μm, and has a particle size of 36 μm or more. The content of particles may be 10.0% by volume or less.

In the above manufacturing method, the boron nitride powder may have a specific surface area of 3.0 to 12.0 m ² /g.

One aspect of the present disclosure provides a cosmetic containing the boron nitride powder described above.

Since the cosmetic contains the above-described boron nitride powder, it has moderate slipperiness and reduced skin irritation.

The inventors of the present invention have found that boron nitride powder having a certain particle size range has tactile sensations such as "moist" and "slimy" while maintaining suitable slipperiness. That is, one aspect of the present disclosure is that the content of primary particles or aggregated particles of 36 μm or more is 10.0% by volume or less, the specific surface area is 3.0 to 12.0 m ² /g, and the average particle diameter is 2.5 Provided is a hexagonal boron nitride powder characterized by having a particle diameter of up to 7.0 μm and an eluted boron amount of 20 ppm or less. In addition, one aspect of the present disclosure is that the value of MIU (average coefficient of friction) measured with a friction tester is 0.7 to 1.2, and the value of MMD (variation of average coefficient of friction) is 0.015 or less. A hexagonal boron nitride powder characterized by: Furthermore, one aspect of the present disclosure provides a hexagonal boron nitride powder characterized by an aspect ratio of 8-23.

According to the present disclosure, it is possible to provide a boron nitride powder suitable for cosmetic raw materials and a method for producing the boron nitride powder. According to the present disclosure, it is also possible to provide a cosmetic that has moderate slipperiness and reduced irritation to the skin.

According to the present disclosure, it is possible to provide boron nitride that exhibits a tactile sensation such as "moist" or "slimy" and is useful as a raw material for cosmetics. According to the present disclosure, it is possible to provide an excellent cosmetic containing the boron nitride powder.

Embodiments of the present disclosure will be described below. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

The boron nitride powder of the present disclosure has an eluted boron amount of 20 ppm or less per 1 g, and is useful as a cosmetic raw material. That is, a boron nitride powder having an eluted boron amount of 20 ppm or less per 1 g can be called a cosmetic boron nitride powder. Boron nitride has a cubic crystal structure, a hexagonal crystal structure, and the like, and the hexagonal crystal structure is preferable from the viewpoint of excellent slipperiness.

<Boron nitride powder>
An embodiment of the boron nitride powder contains at least one of primary particles and agglomerated particles of the primary particles, the amount of eluted boron is 20 ppm or less per 1 g, the average particle size is 2.5 to 7.0 μm, The content of the particles having a particle diameter of 36 μm or more is 10.0% by volume or less.

The boron nitride powder according to the present disclosure has, for example, a content of primary particles of 36 μm or more or aggregated particles of 10.0% by volume or less, a specific surface area of 3.0 to 12.0 m ² /g, and an average particle diameter of 2 0.5 to 7 μm, an MIU value of 0.7 to 1.2, and an MMD value of 0.015 or less as measured by a friction tester.

A more detailed description for implementing the hexagonal boron nitride powder according to the present disclosure is provided below.

<Amount of eluted boron>
The amount of eluted boron in the boron nitride powder is 20 ppm or less per 1 g of the boron nitride powder. The eluted boron amount of the boron nitride powder may be, for example, 18 ppm or less, 15 ppm or less, or 10 ppm or less per 1 g of the boron nitride powder. By reducing the amount of eluted boron in the boron nitride powder, irritation to the skin can be reduced, making it more useful as a cosmetic raw material. As used herein, the term "dissolved boron amount" means a value measured in accordance with the Standards for Quasi-drug Ingredients 2006.

<Average particle size>
The average particle size of the boron nitride powder is 2.5-7.0 μm. The average particle size of the boron nitride powder is preferably 3.0-6.0 μm, more preferably 4.0-5.0 μm. If the average particle size of the boron nitride powder is less than 2.5 µm, the lubricating property is insufficient. When the average particle size of the boron nitride powder exceeds 7.0 µm, the slipperiness is too high, and the "moist" and "slimy" feel of the cosmetic may be impaired. When the average particle size of the boron nitride powder exceeds 7.0 μm, the appearance of the boron nitride powder becomes more glaring, which is not preferable as a raw material for cosmetics.

The "average particle size" as used herein means a value measured based on particle size distribution measurement by a laser diffraction scattering method, and is a particle size with a cumulative value of 50% in a volume-based cumulative particle size distribution. In general, the average particle size may vary depending on the measurement method. In this specification, 60 mg of boron nitride powder and 2 mL of hexametaphosphoric acid aqueous solution (concentration: 20% by mass) are added to 200 mL of water, and a homogenizer is used at 300 W. It is a value measured by a particle size distribution measuring device, using a dispersion liquid prepared by dispersing for 180 seconds at an output and using the dispersion liquid as a measurement object.

<Content of primary particles or aggregated particles of 36 µm or more>
The boron nitride powder contains at least one of primary particles and aggregated particles of the primary particles, and has a particle size of 36 μm or more (e.g., primary particles with a particle size of 36 μm or more, aggregated particles with a particle size of 36 μm or more etc.) is 10.0% by volume or less. The content of the particles having a particle diameter of 36 μm or more in the boron nitride powder is 10.0% by volume or less, so that the boron nitride powder has excellent slipperiness. Cosmetics containing the boron nitride powder roughness can be sufficiently reduced. The content of the particles having a particle diameter of 36 μm or more in the boron nitride powder is, for example, 6.0% by volume or less, 5.0% by volume or less, 4.0% by volume or less, 3.0% by volume or less, 1 0.5% by volume or less, 1.0% by volume or less, or 0.5% by volume or less. When the content of the particles having a particle diameter of 36 μm or more in the boron nitride powder is within the above range, the tactile sensation such as “moist” and “slimy” of the boron nitride powder can be improved. In consideration of ease of manufacture, the above content may be 0.001% by volume or more, or 0.01% by volume or more.

As a result of intensive studies on a method for synthesizing hexagonal boron nitride powder that has excellent tactile sensations such as "moist" and "slimy" while maintaining slipperiness in the range of pressure applied to the skin in cosmetics, we found that hexagonal boron nitride powder It was found that a hexagonal boron nitride powder having excellent tactile sensation can be obtained by setting the content of primary particles of 36 μm or more or aggregated particles contained in the powder to 10.0% by volume or less. The content of primary particles of 36 μm or more or aggregated particles contained in the hexagonal boron nitride powder is 10.0% by volume or less, preferably 5.0% by volume or less, and more preferably 1.0% by volume or less. is. When the content of primary particles of 36 μm or more in the hexagonal boron nitride powder, or the content of aggregated particles exceeds 10.0% by volume, there is variation in slipperiness when applying the hexagonal boron nitride powder, and the applied hexagonal crystal Asperities may occur in the film of boron nitride powder. That is, if the content of primary particles of 36 μm or more or aggregated particles in the hexagonal boron nitride powder exceeds 10.0% by volume, the MMD increases, resulting in increased "roughness", which is not suitable as a cosmetic raw material. .

In the present disclosure, the content of particles having a particle diameter of 36 μm or more, primary particles of 36 μm or more, or agglomerated particles means values measured based on particle size distribution measurement by a laser diffraction scattering method. For example, the content of primary particles with a particle size of 36 μm or more is the volume ratio of primary particles with a particle size of more than 36 μm in the volume-based cumulative particle size distribution. Specifically, to 200 mL of water, 60 mg of boron nitride powder and 2 mL of hexametaphosphoric acid aqueous solution (concentration: 20% by mass) are added to prepare a mixed liquid, and the mixed liquid is measured by a particle size distribution analyzer. , the cumulative particle size distribution can be measured to determine the content. The mixed solution is subjected to particle size distribution measurement without being subjected to ultrasonic dispersion treatment or the like. Here, the reason why ultrasonic dispersion treatment is not performed is that when ultrasonic dispersion treatment is performed, coarse powder contained in the boron nitride powder is pulverized by ultrasonic waves. This is because it becomes impossible to accurately measure the content of the above-mentioned particles having the above-mentioned particles, the content of primary particles of 36 μm or more in the boron nitride powder, or the content of agglomerated particles.

<Specific surface area>
The specific surface area of boron nitride is preferably 3.0 to 12.0 m ² /g, more preferably 4.0 to 10.0 m ² /g. By setting the specific surface area of boron nitride to 3.0 m ² /g or more, excellent hiding power (covering power) is obtained. By setting the specific surface area of boron nitride to 3.0 m ² /g or more, it is possible to make the slipperiness moderate and suppress the deterioration of the tactile sensations such as "moist" and "slimy". Further, by setting the specific surface area of boron nitride to 3.0 m ² /g or more, glare in the appearance of the boron nitride powder can be suppressed, making it more suitable as a raw material for cosmetics. By setting the specific surface area of boron nitride to 12.0 m ² /g or less, it is possible to suppress deterioration of coating spreadability (extendability) and hiding power, and to suppress an increase in the amount of eluted boron.

The term "specific surface area" as used herein means a value calculated by the BET one-point method using a commercially available measuring device utilizing gas adsorption phenomenon.

<Aspect ratio>
The primary particles of hexagonal boron nitride are so-called "scale-shaped" particles. The aspect ratio of the primary particles of hexagonal boron nitride is preferably 8-23, more preferably 8-20. By setting the aspect ratio of the primary particles of hexagonal boron nitride to 8 or more, the thickness of the primary particles of hexagonal boron nitride can be made sufficiently thin, the slip property can be further improved, and the hiding power (cover force) can also be excellent. By setting the aspect ratio of the primary particles of hexagonal boron nitride to 23 or less, the thickness of the primary particles of hexagonal boron nitride can be made appropriate, and cracking or chipping of the primary particles can be suppressed. , the increase in the amount of eluted boron can be further suppressed.

The aspect ratio of a primary particle is represented by the ratio ((major axis)/(minor axis)) of the longest portion (major axis) and the shortest portion (minor axis) of the particle. Since the primary particles of hexagonal boron nitride are so-called "scale-shaped" particles, the thickness of the scale particles is the shortest (minor axis). The term "aspect ratio" as used herein means a value obtained by actually measuring and calculating the major diameter and thickness of a particle from a cross-sectional photographic image of a primary particle of hexagonal boron nitride. That is, the aspect ratio of the primary particles of hexagonal boron nitride is represented by the ratio of (length)/(thickness) of the primary particles of hexagonal boron nitride.

When measuring the aspect ratio of "scale-shaped" particles such as hexagonal boron nitride, for example, a method of directly analyzing a particle image taken by an electron microscope is prone to errors (e.g., the primary particles are tilted error occurs), making accurate measurement difficult. Therefore, the aspect ratio of hexagonal boron nitride in this specification is measured according to the method described below. 3 g of boron nitride powder is molded into a disk shape (diameter: 30 mmφ) at a pressure of 5 MPa using a press molding machine (for example, manufactured by Rigaku Co., Ltd., product name: BRE-32), and the resulting molded body is molded into a resin. (eg, GATAN, trade name: G2 epoxy), and then milling the cross section in the direction parallel to the direction in which the pressure is applied to prepare a sample in which the cross section of the boron nitride particles is exposed. Since the primary particles of boron nitride are oriented in one direction by press molding, measurement errors due to inclination of the primary particles can be suppressed. This cross section is photographed with a scanning electron microscope (for example, manufactured by JEOL Ltd., trade name: JSM-6010LA), and the obtained particle image is analyzed by image analysis software (for example, Mountec Co., trade name: Mac-View). ). Next, the long side (corresponding to the particle long diameter) and the short side (corresponding to the particle thickness and particle short diameter) of the rectangular particles were measured from the obtained photograph, and the ratio of the long diameter to the short diameter (long diameter/short diameter) was calculated. Measurements are performed on 100 arbitrarily selected primary particles. A cumulative distribution is created based on the obtained ratios of the major diameters and the minor diameters, and the ratio of the major diameters and the minor diameters corresponding to 95% of the cumulative distribution is obtained and taken as the aspect ratio.

<MIU (average friction coefficient), MMD (change in average friction coefficient)>
MIU (mean coefficient of friction) is a method for quantifying slipperiness of cosmetics. MIU indicates that the smaller the value, the more excellent the slipperiness of the cosmetic. Moreover, there is MMD (variation in mean friction coefficient) as a method of quantifying the roughness of cosmetics. MMD indicates that the smaller the value, the smaller the roughness of the cosmetic.

The MIU of the boron nitride powder is preferably 0.7-1.2, more preferably 0.8-1.1. By setting the MIU of the boron nitride powder to 1.2 or less, it is possible to further improve the lubricity of the boron nitride. By setting the MIU of the boron nitride powder to 0.7 or more, it is possible to improve the tactile sensation of boron nitride such as “moist” and “slimy”.

The MMD of the boron nitride powder is preferably 0.015 or less, more preferably 0.010 or less. By setting the MMD of the boron nitride powder to 0.015 or less, it is possible to suppress the roughness of the obtained cosmetic and improve the usability of the obtained cosmetic. In consideration of ease of manufacture, etc., the MMD of the boron nitride powder may be 0.00001 or more, or 0.0001 or more.

The boron nitride powder may have an MIU (mean friction coefficient) value of 0.7 to 1.2 and an MMD (mean friction coefficient variation) value of 0.015 or less.

"MIU (average coefficient of friction)" and "MMD (variation of average coefficient of friction)" in the present specification are measured using a friction tester (manufactured by Kato Tech Co., Ltd., trade name: KES-SE). is a number. Specifically, 0.8 g of boron nitride powder is placed on artificial leather (manufactured by Idemitsu Techno Fine Co., Ltd., trade name: Suprale PBZ13001 BK) that looks like skin, and the sensor part of the friction tester is placed on it. (10 mm square silicon) can be applied to measure MIU and MMD. The measurement conditions of the friction tester are sensitivity: H, test table moving speed: 1 mm/sec, and static load: 25 gf. The measurement is performed 5 times, and the average values obtained for the 3rd to 5th times are used as the MIU and MMD of the boron nitride powder.

<Method for producing boron nitride powder>
In one embodiment of the method for producing a boron nitride powder, the raw material powder containing the first boron nitride and a sintering aid is fired under conditions of 1600 to 1900 ° C. The degree of crystallinity is higher than that of the first boron nitride. A step of obtaining a high second boron nitride (hereinafter also referred to as a firing step), a step of pulverizing the second boron nitride to obtain a pulverized product (hereinafter also referred to as a pulverizing step), an organic solvent, an acidic substance and a step of obtaining boron nitride powder by washing the pulverized material with at least one selected from the group consisting of an aqueous solution containing and an aqueous solution containing an organic solvent (hereinafter also referred to as a washing step). In the method for producing boron nitride powder, the content of the sintering aid is 0.9 to 20 parts by mass with respect to 100 parts by mass of the first boron nitride in the raw material powder.

In this specification, low crystallinity is also referred to as "low crystallinity". That is, the first boron nitride can also be said to be low-crystalline boron nitride. "Crystallinity" as used herein means a value measured by a wide-angle X-ray scattering method. More specifically, wide-angle X-ray scattering measurement is performed on the first boron nitride or the second boron nitride, and a one-dimensional profile (diffraction data) is created from the measurement results using data analysis software. Based on the descriptive data, the degree of crystallinity (%) was calculated from the following formula.

Crystallinity (%) = [Peak area indicating crystalline region/(Peak area indicating crystalline region + Peak area indicating amorphous region)] × 100

The temperature in the firing step is 1600-1900°C, preferably 1700-1900°C, more preferably 1700-1800°C. By setting the temperature in the firing step to 1600° C. or higher, the degree of crystallinity in the first boron nitride can be improved, and the second boron nitride having a higher degree of crystallinity can be prepared. By increasing the degree of crystallinity of the second boron nitride, the obtained boron nitride powder has improved lubricating properties and an increase in the amount of eluted boron can be suppressed, making it more suitable as a cosmetic raw material. . By setting the temperature in the firing step to 1900° C. or less, the degree of crystallinity of the second boron nitride can be moderated, the appearance of the obtained boron nitride powder can be suppressed, and the appearance of the obtained boron nitride powder can be suppressed. can be made suitable.

The firing step may be performed under an inert gas atmosphere or an ammonia gas atmosphere. Examples of inert gas atmospheres include nitrogen, helium, and argon.

In the above production method, the amount of eluted boron in the boron nitride powder may be 20 ppm or less per 1 g. In the above production method, the boron nitride powder contains at least one of primary particles and agglomerated primary particles, has an average particle size of 2.5 to 7.0 μm, and has a particle size of 36 μm or more. The content of particles may be 10.0% by volume or less. In the above manufacturing method, the boron nitride powder may have a specific surface area of 3.0 to 12.0 m ² /g.

As an embodiment of the method for producing hexagonal boron nitride powder, for example, a mixed powder containing low-crystalline hexagonal boron nitride powder and 0.9 to 20 parts by mass of sintering aid powder is heated to a maximum temperature of 1600 to 1900. A step of obtaining hexagonal boron nitride by firing under firing conditions of ° C., pulverizing the obtained hexagonal boron nitride with a jet mill or a glow mill, and mixing an aqueous solution containing an acidic substance, an organic solvent, and an organic solvent and water. A manufacturing method including the step of washing with at least one of the mixed liquids to manufacture the hexagonal boron nitride powder described above can be mentioned.

The method for producing the boron nitride powder includes a step of preparing a first boron nitride and a step of preparing a second boron nitride instead of the step of firing the raw material powder containing the first boron nitride. good too. Further, in the method for producing the hexagonal boron nitride, instead of the step of obtaining hexagonal boron nitride by firing the low-crystalline hexagonal boron nitride powder, the step of preparing low-crystalline hexagonal boron nitride and the production of hexagonal boron nitride You may have a process of obtaining.

Examples of the method for producing boron nitride powder include a powder of a compound containing boron and a powder of a compound containing nitrogen (hereinafter, the compound containing boron and the compound containing nitrogen are sometimes collectively referred to as "starting materials") and , a sintering aid powder that promotes the conversion of starting materials such as alkali metal compounds and / or alkaline earth metals into hexagonal boron nitride during firing, and a mixed powder containing nitrogen, helium, argon, etc. and/or in an ammonia atmosphere at 600 to 1300 ° C. (first firing conditions) to obtain low-crystalline hexagonal boron nitride, and the obtained low-crystalline hexagonal nitride Boron is further fired in an inert atmosphere such as nitrogen, helium, argon, etc. and/or in an ammonia atmosphere at 1500 to 2200 ° C. (second firing conditions) to obtain hexagonal boron nitride; and a step of removing impurities by washing the hexagonal boron nitride with a cleaning solution and then drying. The above-mentioned mixed powder may contain other components than the starting material and the sintering aid, if necessary, without departing from the purpose of the present disclosure. Other components include, for example, simple substances and compounds. Here, the sintering aid may be blended with the mixed powder, or may be blended with the low-crystalline hexagonal boron nitride.

The compound containing boron preferably includes, for example, boric acid, boron oxide, borax, etc., and more preferably includes boric acid. The nitrogen-containing compound preferably includes, for example, cyandiamide, melamine, urea, etc., and more preferably includes melamine.

The molar ratio of boron atoms and nitrogen atoms contained in the starting material need not necessarily be fixed at 5:5. The molar ratio of boron atoms and nitrogen atoms can be appropriately changed, preferably in the range of 2:8 to 8:2, more preferably in the range of 3:7 to 7:3, depending on the reactivity and yield. is. The various compounds used as starting materials for producing the first boron nitride or low-crystalline hexagonal boron nitride need not be limited to one type, and multiple types of compounds can be used at the same time. .

Preferred sintering aids include oxides or carbonates of alkali metals such as lithium, sodium and potassium, and oxides or carbonates of alkaline earth metals such as calcium and strontium. can. The content of the sintering aid is preferably 0.9 parts by mass or more with respect to 100 parts by mass of boron nitride, 100 parts by mass of the first boron nitride, or 100 parts by mass of low-crystalline hexagonal boron nitride in the mixed powder. It is 20.0 mass parts or less. In addition, it is not necessary to limit the various compounds used as sintering aids to one type, and a plurality of types of compounds may be used at the same time.

The raw material powder described above may contain other components in addition to the first boron nitride and the sintering aid. Moreover, the mixed powder described above may contain components other than the starting material and the sintering aid. Examples of the other components include simple substances and compounds. More specifically, the simple substance and the compound include reducing substances such as carbon.

The maximum temperature for firing the mixed powder is preferably in the range of 600° C. to 1300° C., more preferably in the range of 800° C. to 1200° C. under the first firing conditions. By setting the maximum temperature in the first firing condition to 600 ° C. or higher, it is possible to promote conversion from the mixed powder to low-crystalline hexagonal boron nitride, and unreacted starting materials in the mixed powder (for example, containing boron compound, etc.) can be reduced. By setting the maximum temperature in the first firing conditions to 600°C or higher, grain growth and crystallization are promoted, and the resulting boron nitride powder can be further improved in slipperiness, making it more suitable as a raw material for cosmetics. . By setting the maximum temperature in the first firing condition to 1300 ° C. or less, it is possible to suppress the reduction of oxides such as B ₂ O ₃ and sintering aids that contribute to the formation of hexagonal boron nitride, and grains It can promote growth and crystallization, and can improve the lubricity of the resulting boron nitride powder. By setting the maximum temperature under the first firing conditions to 1300° C. or less, it is possible to suppress an increase in the amount of eluted boron in the boron nitride powder, making it more suitable as a cosmetic raw material.

The maximum temperature when firing the low-crystalline hexagonal boron nitride is preferably in the range of 1600 to 1900°C, more preferably in the range of 1700 to 1800°C under the second firing conditions. If the maximum firing temperature is less than 1600° C., the conversion from low-crystalline hexagonal boron nitride to hexagonal boron nitride will be difficult to proceed, and grain growth and crystallization will be suppressed, resulting in a decrease in slipperiness and an amount of eluted boron. It is not suitable as a raw material for cosmetics because of the increase in If the maximum baking temperature exceeds 1900° C., the crystal growth of hexagonal boron nitride proceeds too much, and when used as a raw material for cosmetics, the appearance becomes more glaring, which is not practically preferable.

The firing temperature of the hexagonal boron nitride powder may be kept constant or may be changed continuously or discontinuously. There is no limit to the heating rate during heating and the cooling rate during cooling.

Under the first firing conditions, if the firing time is too short, the conversion to low-crystal hexagonal boron nitride will be difficult to proceed, and the residual amount of the starting materials (for example, compounds containing boron, etc.) will increase, resulting in , grain growth and crystallization can be suppressed. Therefore, the time for firing the mixed powder (firing time) is preferably 0.5 hours or longer, and more preferably 1 hour or longer.

Under the second firing conditions, if the firing time is too short, the firing will be insufficient, and grain growth and crystallization can be suppressed. Therefore, the time for firing the low-crystalline hexagonal boron nitride is preferably 2 hours or longer, more preferably 4 hours or longer.

There are no particular restrictions on the container for storing the mixed powder, the low-crystalline hexagonal boron nitride, etc., and the equipment for firing (for example, a heating device, etc.). For the container, for example, a container made of hexagonal boron nitride can be used. As the heating device, for example, a firing furnace using an electric heater can be used.

The method for producing the hexagonal boron powder described above includes heating, cooling, humidification, drying, and washing within the scope of the purpose of the present disclosure, from the preparation of the mixed powder to the end of the firing of the mixed powder. You may further have the process of adding operation.

Since the second boron nitride and the hexagonal boron nitride are generally taken out in the form of block-shaped solids, they are pulverized. By pulverizing, the average particle size and the like can be adjusted. For example, by pulverizing the second boron nitride or the hexagonal boron nitride, the content of primary particles of 36 μm or more or aggregated particles is reduced to 10.0% by volume or less, and the average particle diameter is 2.5 A hexagonal boron nitride powder that is ˜7.0 μm can be obtained. Examples of pulverizers include glow mills and jet mills. Depending on the pulverizer and the pulverization conditions, the obtained hexagonal boron nitride may become fine, and the amount of eluted boron may exceed 20 ppm. For example, when a jet mill is used to pulverize the second boron nitride or the hexagonal boron nitride, the feed amount can be increased and the pulverization pressure can be set to a moderately low condition. By setting the conditions as described above, the average particle size of the obtained boron nitride powder can be made appropriate, and an increase in the amount of eluted boron can be suppressed. In addition, in the above-described method for producing boron nitride powder, etc., the amount of eluted boron can be reduced by the washing step described later.

The pulverized hexagonal boron nitride powder may contain impurities other than hexagonal boron nitride and water-soluble boron compounds (hereinafter collectively referred to as “impurities, etc.”). Therefore, the hexagonal boron nitride powder of the present disclosure can be finally obtained by removing impurities and the like by washing with a washing liquid, followed by solid-liquid separation and drying.

The cleaning liquid used herein is desirably an aqueous solution containing an acidic substance, an organic solvent, or a mixed liquid of an organic solvent and water. Examples of acidic substances include inorganic acids such as hydrochloric acid and nitric acid. As the organic solvent, for example, water-soluble organic solvents such as methanol, ethanol, propanol, isopropyl alcohol and acetone can be preferably used.

Water having an electric conductivity of 1 mS/m or less can be used as a diluent for solid-liquid separation after washing from the viewpoint of avoiding secondary contamination of impurities. The amount of the diluent used for solid-liquid separation should be small from the viewpoint of cost and waste liquid treatment, but if it is too small, impurities etc. will remain in the hexagonal boron nitride powder, so dilution per 1 kg of boron nitride The liquid volume is, for example, preferably 300 times or less, more preferably 250 times or less, and still more preferably 200 times or less.

When drying is performed after solid-liquid separation after washing, the method of solid-liquid separation is not particularly limited. can be used.

There is no particular limitation on the drying method of the hexagonal boron nitride powder after solid-liquid separation. Examples of drying equipment that can be used are tray dryers, fluid bed dryers, spray dryers, rotary dryers, belt dryers, or combinations thereof. The ambient temperature in the dryer is preferably 30 to 300°C, more preferably 30 to 200°C.

Washing, solid-liquid separation, and drying may each be performed once, or may be performed multiple times by combining the same method or different methods.

<Cosmetics Containing Boron Nitride Powder, Cosmetics Containing Hexagonal Boron Nitride Powder>
The above-described boron nitride powder and hexagonal boron nitride powder are suitable for cosmetics and can be used as raw materials for cosmetics. One embodiment of the cosmetic contains the boron nitride powder described above.

Another aspect of the present disclosure is a cosmetic containing the hexagonal boron nitride powder described above. Examples of cosmetics include foundation (powder foundation, liquid foundation, cream foundation), face powder, point makeup, eye shadow, eyeliner, nail polish, lipstick, blush, and mascara. The cosmetic of the present disclosure is particularly well suited for foundation and eye shadow among the above cosmetics.

The content of the boron nitride powder in the cosmetic may be, for example, 0.1 to 70% by mass based on the total amount of the cosmetic. A suitable blending ratio of the hexagonal boron nitride powder described above to the cosmetic is 0.1 to 70% by mass.

Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. Also, the descriptions of the above-described embodiments can be applied to each other.

Hereinafter, the present disclosure will be described more specifically with reference to examples and comparative examples. Table 1 shows a summary of the examples, and Table 2 shows the comparative examples. However, the present disclosure is not limited to the following examples.

<Example 1>
As starting materials, 200 g of boric acid powder (manufactured by Kanto Chemical Co., Ltd., purity: 99.8% by mass or more) and 180 g of melamine powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.0% by mass or more) were used. It was weighed and mixed for 10 minutes using an alumina mortar. Put the prepared powder mixture (mixed powder) in a thermo-hygrostat (manufactured by ADVANTEC, trade name: AGX-225), humidify at temperature: 80 ° C., relative humidity: 95% for 1 hour, then at 120 ° C. for 1 hour. Time dried.

The powder mixture after drying is placed in a hexagonal boron nitride container (inner volume: 1.4 L), and the container is placed in an electric furnace with a furnace interior volume of 16 L (manufactured by Tokai Konetsu Kogyo Co., Ltd., product name: TV -200). Then, while supplying nitrogen gas into the furnace chamber at a flow rate of 16 L/min (volume at 25° C.), the temperature was raised from room temperature at a rate of 10° C./min and held at 1000° C. for 2 hours. After that, the heating was stopped and the mixture was allowed to cool naturally. When the temperature in the furnace chamber dropped to 100° C. or less, the electric furnace was opened to collect the low-crystalline boron nitride (before pulverization).

10 parts by mass of sodium carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 99.5% by mass or more) is blended with 100 parts by mass of the obtained low-crystalline hexagonal boron nitride powder, and an alumina mortar is added. was mixed for 10 minutes and then placed in the electric furnace described above. Then, while supplying nitrogen gas into the furnace chamber at a flow rate of 16 L/min (volume at 25°C), the temperature was raised at a rate of 10°C/min to reach the maximum firing temperature of 1750°C. After that, the temperature was maintained for 4 hours (firing step). After that, the heating was stopped and the mixture was allowed to cool naturally. When the temperature dropped to 100° C. or less, the electric furnace was opened to recover the hexagonal boron nitride (before pulverization).

The obtained hexagonal boron nitride (before pulverization) was pulverized with a jet mill (manufactured by Seishin Enterprise Co., Ltd., trade name: STJ-200) to obtain hexagonal boron nitride powder. In the jet mill, hexagonal boron nitride was supplied into the mill at a feed rate of 10 kg/hour, the treatment was performed at a pulverization pressure of 0.7 MPa, and pulverized hexagonal boron nitride powder was recovered from the bag filter.

In order to remove impurities contained in the hexagonal boron nitride powder obtained by pulverization as described above, 20 L of 67% by mass diluted nitric acid and 390 L of water are mixed with 40 kg of hexagonal boron nitride. and washed with agitation for 60 minutes at room temperature. After that, solid-liquid separation is performed by a continuous pressure filtration device (manufactured by Hiroshima Metal & Machinery Co., Ltd., product name: RF-2.5), and before the solid-liquid separation is completely completed, per 1 kg of hexagonal boron nitride An additional 275 times of water was added for dilution. Solid-liquid separation was then completed. The powder after solid-liquid separation was dried at 170° C. for 12 hours in a dryer to obtain hexagonal boron nitride powder (boron nitride powder) of Example 1.

<Examples 2 to 5, Comparative Example 1>
Hexagonal crystals of Examples 2 to 5 and Comparative Example 1 were prepared in the same manner as in Example 1 except that the feed amount and pulverization pressure of the jet mill were changed to the feed amounts and pulverization pressures shown in Tables 1 and 2. A boron nitride powder was produced.

<Examples 6-7, Comparative Examples 2-3>
Same as Example 1 except that the mass ratio of the sintering aid to 100 parts by mass of the low-crystalline hexagonal boron nitride was changed to the ratio shown in Tables 1 and 2 (the content of the sintering aid was changed). Then, hexagonal boron nitride powders of Examples 6-7 and Comparative Examples 2-3 were produced.

<Examples 8-9, Comparative Examples 4-5>
Hexagonal boron nitride of Examples 8 and 9 and Comparative Examples 4 and 5 in the same manner as in Example 1 except that the maximum firing temperature was changed from 1750 ° C. to the temperatures shown in Tables 1 and 2. A powder was produced.

<Examples 10-11, Comparative Examples 6-7>
Hexagonal boron nitride powders of Examples 10 to 11 and Comparative Examples 6 to 7 were prepared in the same manner as in Example 1 except that the grinding conditions or washing conditions were changed to the conditions shown in Tables 1 and 2. .

In Example 10, 40 kg of hexagonal boron nitride obtained by pulverization was mixed with 10 L of ethanol and 390 L of water. It was subjected to solid-liquid separation, diluted with 275 times as much water as 1 kg of hexagonal boron nitride, and washed. The powder after washing and solid-liquid separation was dried at 70° C. for 12 hours to obtain hexagonal boron nitride powder.

In Example 11, Glow Mill (manufactured by Seishin Enterprise Co., Ltd., trade name: STJ-200) was used as a pulverizer under conditions of a gap of 5 μm and a rotation speed of 1200 rpm to pulverize hexagonal boron nitride (before pulverization). , washed and dried in the same manner as in Example 1 to obtain a hexagonal boron nitride powder.

In Comparative Example 7, 40 kg of hexagonal boron nitride (before pulverization) was mixed with 390 L of water, and the mixture was stirred and washed at room temperature for 60 minutes. After that, solid-liquid separation was performed by a continuous pressurized filtration device, and 275 times as much water was added to 1 kg of hexagonal boron nitride to dilute and further washed. The powder after washing and solid-liquid separation was dried at 70° C. for 12 hours to obtain hexagonal boron nitride powder.

<Measurement of Average Particle Size of Hexagonal Boron Nitride Powder (Boron Nitride Powder), Content of Particles of 36 μm or More, Specific Surface Area, and Aspect Ratio of Primary Particles>
Regarding the hexagonal boron nitride powders obtained in Examples 1 to 11 and Comparative Examples 1 to 7, the content of particles having an average particle diameter of 36 μm or more (described in Tables 1 and 2 as “amount of particles of 36 μm or more”) , specific surface area, and aspect ratio of primary particles (described as “aspect ratio” in Tables 1 and 2) were measured.

<Evaluation of hexagonal boron nitride powder (boron nitride powder)>
The hexagonal boron nitride powders obtained in Examples 1 to 11 and Comparative Examples 1 to 7 were evaluated for the amount of eluted boron, MIU (average friction coefficient) and MMD (variation in average friction coefficient). The results are shown in Tables 1 and 2.

According to the present disclosure, there is provided a hexagonal boron nitride powder that is superior in tactile sensation such as “moist” and “slimy” in the range of pressure required as a cosmetic compared to the past, and a cosmetic containing the hexagonal boron nitride powder. can. The boron nitride powder of the present disclosure is suitably used as a raw material for cosmetics such as foundations and eye shadows.

Claims (8)

At least one particle of primary particles and aggregated particles of primary particles,
The amount of eluted boron is 20 ppm or less per 1 g,
The primary particles have an aspect ratio of 8 to 23,
an average particle size of 2.5 to 7.0 μm,
A hexagonal boron nitride powder, wherein the content of the particles having a particle diameter of 36 μm or more is 10.0% by volume or less. The hexagonal boron nitride powder according to claim 1, having a specific surface area of 3.0-12.0 m ² /g. 3. The hexagonal boron nitride powder according to claim 1, which has an average friction coefficient of 0.7 to 1.2 as measured by a friction tester. 4. The hexagonal boron nitride powder according to any one of claims 1 to 3, wherein the variation of the average coefficient of friction measured with a friction tester is 0.015 or less. obtaining a second boron nitride having a higher degree of crystallinity than the first boron nitride by firing a raw material powder containing the first boron nitride and a sintering aid under conditions of 1600 to 1900° C.;
pulverizing the second boron nitride to obtain a pulverized product;
obtaining hexagonal boron nitride powder by washing the pulverized material with at least one selected from the group consisting of an organic solvent, an aqueous solution containing an acidic substance, and an aqueous solution containing an organic solvent;
The content of the sintering aid is 0.9 to 20 parts by mass with respect to 100 parts by mass of the first boron nitride in the raw material powder,
The hexagonal boron nitride powder contains at least one of primary particles and agglomerated primary particles, has an average particle size of 2.5 to 7.0 μm, and contains the particles having a particle size of 36 μm or more. A method for producing hexagonal boron nitride powder for cosmetics , wherein the amount is 10.0% by volume or less . 6. The method according to claim 5 , wherein the hexagonal boron nitride powder has an eluted boron amount of 20 ppm or less per 1 g. The production method according to claim 5 or 6 , wherein the hexagonal boron nitride powder has a specific surface area of 3.0 to 12.0 m ² /g. A cosmetic containing the hexagonal boron nitride powder according to any one of claims 1 to 4 .