Hexagonal boron nitride powder and its manufacturing method

Abstract

To provide hexagonal boron nitride powder having good moistness and high spreadability.SOLUTION: Provided is hexagonal boron nitride powder with a ratio of a maximum torque T1 to a minimum torque T2 (T1 / T2) of 1.8 or more and a dynamic friction coefficient of 0.50 or less. The maximum torque T1 is given, in a dibutyl phthalate (DBP) drop amount / torque curve obtained from a torque change at the time dibutyl phthalate is added to hexagonal boron nitride powder at an oil absorption of 70 ml / 100 g or more and at a temperature of 20°C and from an amount of DBP added, when dibutyl phthalate in a range of 40 ml / 100 g to 70 ml / 100 g is added to the hexagonal boron nitride powder. The minimum torque T2 is given, in the dibutyl phthalate (DBP) drop amount / torque curve, when dibutyl phthalate in a range of 70 ml / 100 g to X ml / 100 g is added to the hexagonal boron nitride powder (where X is an amount of dibutyl phthalate added when the torque is at a maximum point when X is in a range of 70 ml / 100 g to 130 ml / 100 g).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a novel hexagonal boron nitride powder and a method for producing the same. More specifically, the present invention provides a hexagonal boron nitride powder that exhibits both good spreadability and moist feeling when incorporated into powder cosmetics. [Background technology]

[0002] In cosmetics such as powder foundation, emphasis is placed on spreadability, lubricity, transparency, heat dissipation (cooling sensation), and moisturizing sensation. Various powder base materials are blended into cosmetics, and they are often selected with the above physical properties in mind. Regarding moisturizing sensation, it is important to increase wettability while suppressing slipperiness (spreadability) to an appropriate value. It is known that lowering the dynamic friction coefficient in order to increase slipperiness does not result in a highly moisturizing sensation (Patent Document 1, Non-Patent Document 1).

[0003] Hexagonal boron nitride powder is a white pigment with a hexagonal layer structure, and is widely used as a powder base material in cosmetics due to its excellent spreadability, lubricity, transparency, and heat dissipation (cool feeling). In Patent Document 1, the dynamic friction coefficient of the hexagonal boron nitride powder is adjusted to an appropriate value to obtain a highly moist feeling. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2019 / 172440 [Non-patent literature]

[0005] [Non-Patent Document 1] Bulletin of the Chemical Society of Japan,2020,93,399-405 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, hexagonal boron nitride powders used as powder base materials for cosmetics are required to have properties such as spreadability, lubricity, transparency, heat dissipation, and moist feel. However, if the dynamic friction coefficient is reduced to improve spreadability, a high level of moist feel cannot be obtained. Therefore, the hexagonal boron nitride powder of Patent Document 1 has a good moist feel but does not have high spreadability. In view of these circumstances, the present invention aims to provide a hexagonal boron nitride powder that has a good moist feel and high spreadability. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have discovered that by wet-grinding nitride powder synthesized by a reduction-nitriding method under specific conditions, a hexagonal boron nitride powder can be obtained that has a low coefficient of dynamic friction and exhibits a DBP drop amount-torque curve that exhibits a different behavior from conventional DBP drop amount-torque curves obtained by a method conforming to JIS K6217-4. Furthermore, they have discovered that when this hexagonal boron nitride powder is blended into cosmetics, the resulting cosmetics have excellent moisturizing properties and spreadability, leading to the completion of the present invention.

[0008] That is, the present invention provides a hexagonal boron nitride powder having an oil absorption of 70 ml / 100 g or more, characterized in that, in a DBP dropping amount-torque curve obtained from the torque change when dibutyl phthalate (DBP) is added to the hexagonal boron nitride powder at a temperature of 20°C and the amount of dibutyl phthalate added, the ratio (T1 / T2) of the maximum torque T1 in a range where 40 ml / 100 g to 70 ml / 100 g of dibutyl phthalate is added to the hexagonal boron nitride powder to the minimum torque T2 in a range where 70 ml / 100 g to X ml / 100 g of dibutyl phthalate is added to the hexagonal boron nitride powder (where X is the amount of dibutyl phthalate added at the point where the torque is maximum in the range of 70 ml / 100 g to 130 ml / 100 g) is 1.8 or more, and the kinetic friction coefficient is 0.50 or less.

[0009] The hexagonal boron nitride powder preferably has an average particle size of 3.0 to 20.0 μm and an aspect ratio of 7.0 to 18.0.

[0010] The hexagonal boron nitride powder is preferably used in cosmetics. Another embodiment of the present invention is a powder foundation containing the hexagonal boron nitride powder and an oil component, wherein the content of the oil component is 40 to 70 parts by volume per 100 parts by mass of the hexagonal boron nitride powder.

[0011] Furthermore, one embodiment of the present invention is a method for producing hexagonal boron nitride powder, comprising: a reduction-nitriding step of heating a raw material powder containing an oxygen-containing boron compound, an oxygen-containing alkaline earth metal compound, and a carbon source, wherein the atomic ratio (B / C) of the boron atoms (B) of the oxygen-containing boron compound to the carbon atoms (C) of the carbon source is 0.80 to 2.00, and the molar ratio (MO / BO) of the oxygen-containing alkaline earth metal compound (MO; M is an alkaline earth metal) to the oxygen-containing boron compound, calculated as oxide, is 0.002 to 0.12, to 1780°C or higher in a nitrogen atmosphere to obtain nitrided powder; and a wet-crushing step of wet-crushing the nitrided powder in a wet rotary disk mill under conditions of a slurry concentration of 5% by volume or more and a disk clearance of 35 μm or more. [Effects of the Invention]

[0012] The hexagonal boron nitride powder of the present invention makes it possible to provide cosmetics that are excellent in both spreadability and moist feeling. For example, in the past, it was difficult to achieve both spreadability and moist feeling with hexagonal boron nitride powder, so attempts to achieve both of these physical properties were made by adjusting the type and amount of other ingredients, such as silicone resin. However, by using the hexagonal boron nitride powder of the present invention, restrictions on the blending of other ingredients are reduced, allowing for greater freedom in cosmetic design. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a graph showing a DBP dropping amount-torque curve of the hexagonal boron nitride powder of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Hexagonal boron nitride powder> The hexagonal boron nitride powder of the present invention has an oil absorption of 70 ml / 100 g or more, and is characterized in that, in a DBP addition amount-torque curve obtained from the torque change when dibutyl phthalate is added to the hexagonal boron nitride powder at a temperature of 20°C and the amount of dibutyl phthalate added, the ratio (T1 / T2) of the maximum torque T1 in a range where 40 ml / 100 g to 70 ml / 100 g of DBP is added to the hexagonal boron nitride powder to the minimum torque T2 in a range where 70 ml / 100 g to X ml / 100 g of dibutyl phthalate is added to the hexagonal boron nitride powder (where X is the amount of dibutyl phthalate added at the point where the torque is maximum in the range of 70 ml / 100 g to 130 ml / 100 g) is 1.8 or more, and the dynamic friction coefficient is 0.50 or less.

[0015] When the T1 / T2 ratio is 1.8 or more, it becomes possible to impart a highly moist feeling to cosmetics containing the hexagonal boron nitride powder. Although the reason for this is not clear, the present inventors believe it to be as follows.

[0016] Specifically, cosmetics such as powder foundation contain an oil component and a powder component such as hexagonal boron nitride, and the typical blend ratio is about 40 ml to 70 ml of oil component per 100 g of hexagonal boron nitride powder. When this cosmetic is applied to the skin, the cosmetic mixes with the oil (sebum) on the skin, increasing the amount of oil component relative to the hexagonal boron nitride powder. The behavior of the hexagonal boron nitride powder in the cosmetic immediately after application to the skin can be evaluated by torque within a range of 40 ml / 100 g to 70 ml / 100 g of DBP added to the hexagonal boron nitride powder. A large torque within this range, i.e., a large T1, is presumed to indicate poor wettability immediately after application to the skin. Furthermore, a T1 / T2 ratio of 1.8 or greater is presumed to mean that when the cosmetic mixes with sebum after application to the skin, a significant decrease in torque occurs, meaning that moisturization improves after the cosmetic is applied to the skin. It is presumed that the moisturization sensation is due to a change in moisturization after application, which causes the user of the cosmetic to feel a strong influence of moisturization, increasing the contribution of moisturization to the moisturization sensation and relatively reducing the influence of slipperiness, resulting in a high moisturization sensation while maintaining high slipperiness. On the other hand, typical hexagonal boron nitride powders with a low T1 / T2 ratio do not exhibit this change in wettability, and therefore have a relatively small influence of wettability. It is presumed that unless slipperiness is appropriately controlled, a high moisturization sensation cannot be achieved.

[0017] The T1 / T2 ratio is preferably 2.0 or more, and more preferably 2.3 or more. There are no particular limitations on the upper limit of the T1 / T2 ratio, but if this value is too high, the change when the sebum and the cosmetic mix may be drastic, making the makeup more likely to come off, so the T1 / T2 ratio is preferably 4.0 or less, and more preferably 3.5 or less.

[0018] The T1 value of the hexagonal boron nitride powder of the present invention is not particularly limited, but is generally 0.05 Nm or more, particularly 0.10 Nm or more, and 0.40 Nm or less, particularly 0.30 Nm or less. The oil absorption of the hexagonal boron nitride powder of the present invention is 70 ml / 100 g or more. This allows for the provision of a feel suitable for use in cosmetics. The oil absorption is preferably 80 ml / 100 g or more. The upper limit of the oil absorption is not particularly limited, but is generally 130 ml / 100 g or less, particularly 120 ml / 100 g or less. The oil absorption can be measured by the method described in the Examples.

[0019] The hexagonal boron nitride powder of the present invention has a dynamic friction coefficient of 0.50 or less. The smaller the dynamic friction coefficient, the better the spreadability of the cosmetic. The dynamic friction coefficient is preferably 0.45 or less, and more preferably 0.40 or less. The dynamic friction coefficient can be measured by the method described in the examples.

[0020] The hexagonal boron nitride powder of the present invention preferably has an average particle size of 3.0 to 20.0 μm, more preferably 5.0 to 12.0 μm, and even more preferably 6.0 to 10.0 μm. If the average particle size is less than 3.0 μm, the adhesive force between particles will be too strong, which may result in reduced spreadability when applied to the skin and spread. If the average particle size is more than 20.0 μm, the adhesive force between particles will be too weak, which may result in reduced smoothness and a powdery or dry feel.

[0021] The aspect ratio of the hexagonal boron nitride powder of the present invention is preferably 7.0 to 18.0, and more preferably 8.0 to 15.0. By having an aspect ratio within the above range, when applied to the skin, it becomes easy to spread with good spreadability while suppressing glare. If the aspect ratio is less than 7.0, there is a risk of resistance occurring during application and reduced spreadability. On the other hand, if the aspect ratio exceeds 18.0, there is a risk of glare occurring after application.

[0022] The tapped bulk density of the hexagonal boron nitride powder of the present invention is preferably 0.20 to 0.50 g / ml, and more preferably 0.25 to 0.45 g / ml. A tapped bulk density within the above range improves handling and facilitates processing and mixing into cosmetics and the like.

[0023] The hexagonal boron nitride powder of the present invention preferably has an eluted boron content of 20 ppm or less. The eluted boron content can be measured by the method specified in the Quasi-drug Ingredients Standards 2006.

[0024] <Method for producing hexagonal boron nitride powder> The hexagonal boron nitride powder of the present invention can be easily obtained by a production method in which nitride powder obtained by a reduction-nitridation method under specific conditions is subjected to wet-pulverization under specific conditions. Specifically, the hexagonal boron nitride powder can be easily produced by a production method including: a reduction-nitridation step in which a raw material powder containing an oxygen-containing boron compound, an oxygen-containing alkaline earth metal compound, and a carbon source is heated to 1780°C or higher in a nitrogen atmosphere to obtain nitride powder; the raw material powder has an atomic ratio (B / C) of the boron atoms (B) of the oxygen-containing boron compound to the carbon atoms (C) of the carbon source of 0.80 to 2.00, and a molar ratio (MO / BO) of the oxygen-containing alkaline earth metal compound (MO; M is an alkaline earth metal) to the oxygen-containing boron compound, calculated as oxide, of 0.002 to 0.12; and a wet-pulverization step in which the nitride powder is wet-pulverized in a wet rotary disk mill under conditions of a slurry concentration of 5% by volume or more and a disk clearance of 35 μm or more.

[0025] While the reason why the hexagonal boron nitride powder of the present invention can be obtained by the above-described production method is unclear, the inventors speculate as follows. Generally, when producing hexagonal boron nitride powder, nitride powder containing a large amount of agglomerates is first obtained. When a large amount of agglomerates is present in hexagonal boron nitride powder, the powder has poor ductility and high oil absorption. Therefore, even when the DBP dripping amount is in the range of 70 ml to 100 ml, the torque is large, resulting in a high T2 value, making it difficult to achieve a T1 / T2 ratio of 1.8 or greater. Therefore, to obtain the hexagonal boron nitride powder of the present invention, the nitride powder must be appropriately crushed. However, typical crushing processes can result in an increase in fine powder and peeling of the individual particle surfaces, making it difficult to maintain a low coefficient of dynamic friction. Furthermore, re-agglomeration of the fine powder can make it difficult to achieve a T1 / T2 ratio of 1.8 or greater. On the other hand, the boron nitride powder obtained by the reduction-nitridation reaction has relatively few agglomerates, and the agglomerates that do form are brittle and easily crumbled. Therefore, wet crushing under the above conditions, which is a relatively gentle crushing method, is presumably capable of adequately crushing the nitride powder while suppressing the generation of fine powder and peeling of the individual particle surfaces, thereby making it possible to obtain hexagonal boron nitride powder with excellent slip properties and a T1 / T2 ratio of 1.8 or greater.

[0026] In the reduction-nitridation step in the method for producing hexagonal boron nitride powder of the present invention, a raw material powder containing an oxygen-containing boron compound, an oxygen-containing alkaline earth metal compound, and a carbon source is heat-treated in a nitrogen atmosphere to obtain nitride powder.

[0027] Examples of the oxygen-containing boron compound include diboron trioxide (boron oxide), diboron dioxide, tetraboron trioxide, metaboric acid, perboric acid, and orthoboric acid. Generally, boric acid and boron oxide, which are readily available, are preferably used. The average particle size of the oxygen-containing boron compound is not particularly limited, but from the viewpoints of operability and reactivity, it is preferably 30 to 800 μm, and more preferably 100 to 500 μm. An average particle size of more than 30 μm reduces hygroscopicity and facilitates handling. A particle size of 800 μm or less can prevent uneven distribution of raw material components, making it easier to control the reaction.

[0028] The oxygen-containing alkaline earth metal compound is added as a reaction aid to promote the reaction, and examples thereof include magnesium oxide, calcium oxide, barium oxide, magnesium carbonate, calcium carbonate, barium carbonate, magnesium bicarbonate, calcium bicarbonate, and barium bicarbonate. The oxygen-containing alkaline earth metal compound is preferably a carbonate of an alkaline earth metal. By using a carbonate, carbon dioxide gas is generated during the reaction process, creating pores within the raw material powder mixture, facilitating the penetration of nitrogen gas. Similarly, by using a carbonate, pores are created within the raw material powder, allowing bubbles to enter between the individual particles generated by nitriding, suppressing the formation of agglomerates, and further reducing the density of the generated agglomerates themselves, making them more brittle and fragile.

[0029] Examples of the carbon source include carbon black, activated carbon, nanocarbon, graphite, carbon fiber, etc. Generally, carbon black is used because it is easily available and inexpensive.

[0030] The molar ratio (MO / BO) of the oxygen-containing alkaline earth metal compound to the oxygen-containing boron compound in the raw material powder is 0.002 to 0.12, and more preferably 0.01 to 0.10. If this molar ratio exceeds 0.12, the hexagonal boron nitride obtained by the reaction tends to grow excessively, making it difficult to control the particle size and aspect ratio. If it is less than 0.002, the reaction is not promoted, and there is a risk of increasing fine powder significantly smaller than the desired particle size.

[0031] The atomic ratio (B / C) of the boron atoms (B) of the oxygen-containing boron compound to the carbon atoms (C) of the carbon source in the mixed powder is 0.80 to 2.00, and more preferably 0.90 to 1.20. By setting the B / C ratio to 0.80 to 2.00, the reaction can be completed efficiently without reducing the yield of boron nitride. If the B / C ratio is less than 0.80, there is a high possibility that unreacted carbon source will remain, although this depends on the temperature distribution during nitriding and the degree of segregation of the raw materials. As a result, the purity of the resulting boron nitride powder may decrease. If the B / C ratio exceeds 2.00, the boron source will be in large excess relative to the carbon source (reducing agent), and unreacted boron source will remain in the nitrided powder obtained after the reaction, which is disadvantageous in terms of cost.

[0032] The raw material powder can be obtained by weighing out and mixing the oxygen-containing boron compound, oxygen-containing alkaline earth metal compound, and carbon source in predetermined amounts. The mixing method is not particularly limited as long as it can uniformly disperse the components, and can be carried out using a general mixer such as a vibration mill, a bead mill, a ball mill, or a mixer.

[0033] The raw material powder is heated in a nitrogen atmosphere to react, and simultaneously a reduction-nitridation reaction that enhances the crystallinity of the boron nitride is carried out, thereby obtaining nitride powder. The heating temperature is not particularly limited as long as it is 1780°C or higher. However, it is preferable to gradually increase the temperature to the maximum temperature in each temperature range during the reaction and firing processes, and then maintain the temperature. The heating temperature during the reaction process is preferably in the range of 1400°C to 1650°C, more preferably in the range of 1450°C to 1600°C. By maintaining the heating temperature within this range during the reaction process, the reaction can proceed efficiently while suppressing volatilization of the raw materials. The heating temperature during the firing process is preferably in the range of 1780°C to 2000°C, more preferably in the range of 1800°C to 1900°C. By maintaining the heating temperature within this range during the firing process, it is possible to enhance crystallinity while controlling the particle size and aspect ratio to be within the above range.

[0034] The retention time during the reaction process is preferably 1 to 8 hours, more preferably 2 to 6 hours. If the retention time during the reaction process is too short, there is a risk that unreacted raw materials will remain, and if it is too long, productivity will decrease. The retention time during the firing process is preferably 1 to 5 hours, more preferably 2 to 4 hours. If the retention time during the firing process is too short, particle growth will be insufficient, resulting in reduced crystallinity and making particle size control difficult, and if it is too long, productivity will decrease.

[0035] The reaction atmosphere is not limited as long as it is a nitrogen atmosphere, and may be under pressure or normal pressure, or may be under flow.

[0036] The manner in which the raw material mixture is heated is not particularly limited as long as contact between the nitrogen gas and the raw material mixture is not prevented. For example, the raw material mixture may be filled into a carbon container, a boron nitride-coated carbon container, a boron nitride sintered container, or the like, and then placed in a graphite Tammann furnace.

[0037] The hexagonal boron nitride powder of the present invention can be obtained by wet-pulverizing the nitride powder using a wet rotary disk mill. Wet-pulverization using a wet rotary disk mill is a method in which a slurry of nitride powder is poured between disks rotating at high speed, and pulverization is carried out by shear force, making it possible to pulverize agglomerates while suppressing the increase in fine powder and peeling of the surfaces of individual particles. An example of a wet rotary disk mill is the Disparizer (manufactured by Shinto Kogyo Co., Ltd.).

[0038] Wet disintegration using a wet rotary disk mill can be performed by feeding a slurry of nitride powder into the wet rotary disk mill. The solvent for the slurry is not particularly limited as long as it can uniformly disperse the nitride powder, but water is generally used. The slurry concentration is adjusted so that the nitride powder is 5% by volume or more in the slurry. This allows for sufficient disintegration and makes it possible to adjust T1 / T2 to 1.8 or more. If the slurry concentration is less than 5% by volume, agglomerates cannot be sufficiently disintegrated, and the T2 value increases, which may result in a low T1 / T2 value, and the remaining agglomerates tend to increase the dynamic friction coefficient.

[0039] There is no particular upper limit to the slurry concentration, but if the concentration is too high there is a risk of individual particles being damaged, so the nitride powder is preferably 20% by volume or less, and more preferably 10% by volume or less, of the slurry.

[0040] The gap between the discs (disc clearance) in wet disintegration is 35 μm or more. If the disc clearance is too narrow, fine powder will be generated due to damage to individual particles, and the surface of the individual particles will peel off. The disc clearance is preferably 40 μm or more. If the disc clearance is too large, agglomerations may not be efficiently disintegrated, so the disc clearance is preferably 120 μm or less, more preferably 90 μm or less, and even more preferably 60 μm or less.

[0041] The rotation speed of the disk is not particularly limited, but is generally 8000 rpm to 12000 rpm.

[0042] In wet crushing, the crushed product is obtained as a slurry of hexagonal boron nitride powder and solvent, and a drying process is carried out to remove the solvent from this slurry. There are no particular restrictions on the drying conditions, but in order to efficiently proceed with drying while suppressing hydrolysis of hexagonal boron nitride, it is preferable to filter the product to a moisture content of about 30%, and then heat it at 80°C to 280°C (preferably 120°C to 220°C) in a reduced pressure atmosphere (preferably 10 kPa to 80 kPa).

[0043] The nitride powder obtained in the reduction-nitridation step contains by-products such as alkali metal salts and oxygen-containing boron compounds, and it is preferable to wash the nitride powder with an acid to remove these by-products. This facilitates the production of high-purity hexagonal boron nitride powder that is particularly suitable for cosmetic applications. The acid used for washing is not particularly limited, and examples include hydrochloric acid, sulfuric acid, nitric acid, and acetic acid. The washing method is not particularly limited, and an example is a method in which 50 to 200 parts by weight of concentrated hydrochloric acid (37% hydrogen chloride aqueous solution) and 200 to 500 parts by weight of pure water are mixed with 100 parts by weight of nitride powder to form a hydrochloric acid slurry, which is then stirred for at least 6 hours.

[0044] After washing with acid, it is preferable to wash with pure water to remove the acid. The method of washing with pure water is not particularly limited as long as it can remove the acid. For example, the acid slurry is filtered to remove the solvent, and then pure water is added to make an aqueous slurry. This operation is repeated until the aqueous slurry shows a pH in the range of 6.0 to 7.0.

[0045] The washing step may be carried out before or after the wet-crushing step, but is preferably carried out before the wet-crushing step in terms of ease of crushing, etc. When the washing step is carried out before the wet-crushing step, the nitride powder may be dried after the washing step and then a slurry for wet-crushing may be prepared, but it is not always necessary to completely remove the solvent used in the washing step, and the solvent for the wet-crushing step may be added after removing some of the solvent used in the washing step by filtration or the like to prepare a slurry for the wet-crushing step.

[0046] In the production method of the present invention, classification may be carried out after the wet-crushing step. The classification method is not particularly limited, and examples thereof include classification using a vibrating sieve, an air classifier, a cyclone, a wet sieve, etc.

[0047] <Uses of hexagonal boron nitride powder> The hexagonal boron nitride powder of the present invention is preferably used for cosmetics, such as powder foundation, solid foundation, cream foundation, face powder, face color, sunscreen powder, etc. It is particularly suitable for powder foundation containing 40 to 70 parts by volume of an oil component per 100 parts by mass of hexagonal boron nitride powder.

[0048] <Cosmetics> One embodiment of the present invention is a cosmetic, particularly a powder foundation, which contains the hexagonal boron nitride powder and an oil component, in which the content of the oil component is 40 to 70 parts by volume per 100 parts by mass of the hexagonal boron nitride powder.

[0049] The content of the hexagonal boron nitride powder in the entire cosmetic is not particularly limited, but is preferably 1% by mass to 30% by mass, and more preferably 10% by mass to 25% by mass. By blending the hexagonal boron nitride powder in the cosmetic within the above range, the effects of improving the spreadability and moist feeling of the cosmetic are more easily felt.

[0050] As the oil agent, any oil agent that is generally blended into cosmetics can be used without any particular limitation, and examples thereof include hydrocarbons, oils and fats, waxes, hardened oils, ester oils, fatty acids, higher alcohols, silicone oils, fluorine-based oils, lanolin derivatives, and the like, regardless of their origin (e.g., animal oil, vegetable oil, synthetic oil) and their properties (e.g., solid oil, semi-solid oil, liquid oil, volatile oil, etc.). Specifically, hydrocarbons such as liquid paraffin, squalane, petrolatum, polyisobutylene, polybutene, paraffin wax, ceresin wax, microcrystalline wax, Japan wax, montan wax, and Fishertrops wax; oils and fats such as olive oil, castor oil, jojoba oil, mink oil, and macadamia nut oil; waxes such as beeswax, lanolin, carnauba wax, candelilla wax, and glabra; cetyl isooctanoate, isopropyl myristate, isopropyl palmitate, octyldodecyl myristate, glyceryl trioctanoate, diglyceryl diisostearate, diglyceryl triisostearate, glyceryl tribehenate, pentaerythritol rosinate, neopentyl glycol dioctanoate, cholesterol fatty acid esters, di(cholesteryl, behenyl, octyldodecyl) N-lauroyl-L-glutamate, methoxysilane, Examples of the surfactant include esters such as ethylhexyl arsenate; fatty acids such as stearic acid, lauric acid, myristic acid, behenic acid, isostearic acid, oleic acid, rosin acid, and 12-hydroxystearic acid; higher alcohols such as stearyl alcohol, cetyl alcohol, lauryl alcohol, oleyl alcohol, isostearyl alcohol, and behenyl alcohol; silicones such as low-polymerization dimethylpolysiloxane, high-polymerization dimethylpolysiloxane, methylphenylpolysiloxane, decamethylcyclopentasiloxane, octamethylcyclotetrasiloxane, and fluorine-modified silicone; fluorine-based oils and fats such as perfluoropolyether, perfluorodecane, perfluorooctane, and perfluorooctyltriethoxysilane; and lanolin derivatives such as lanolin, lanolin acetate, lanolin fatty acid isopropyl, and lanolin alcohol. These can be used alone or in combination.

[0051] The cosmetic preparation may contain other known ingredients in addition to the hexagonal boron nitride powder and oil, such as hexagonal boron nitride powder (pigments, etc.), aqueous ingredients, surfactants, gelling agents, film-forming agents, UV absorbers, moisturizers, antioxidants, preservatives, vitamins, anti-inflammatory agents, herbal medicines, chelating agents, fragrances, and cosmetic ingredients. [Example]

[0052] Examples will be described below to specifically explain the present invention, but the present invention is not limited to these examples. Measurements of each item in the examples and comparative examples were carried out by the following methods.

[0053] (1) DBP Drop Amount-Torque Curve Measurements were performed on hexagonal boron nitride powder in accordance with JIS-K6217-4, and a DBP drop amount-torque curve was obtained, with the horizontal axis representing the DBP drop amount (ml / 100g) and the vertical axis representing torque (Nm). Specifically, 15 g of hexagonal boron nitride powder was placed in a 70 mL mixing chamber, and DBP was added dropwise at 4.0 mL / min while stirring with a rotor at 125 rpm. The torque was measured over time, and the measurement was terminated when the drop amount reached 20 mL. A DBP drop amount-torque curve was created from the measurement results. Measurements were performed using an oil absorption analyzer S-500 (manufactured by Asahi Research Institute, Ltd.).

[0054] (2) Oil absorption amount The maximum torque value of the DBP dropping amount-torque curve obtained by the above method (1) was designated as T3, and the DBP dropping amount at 70% of the torque value of T3 was designated as the oil absorption amount. Note that, if there are multiple DBP dropping amounts that result in 70% of the torque value of T3 within a range smaller than the DBP dropping amount at T3 on the DBP dropping amount-torque curve, the largest value among them was designated as the oil absorption amount.

[0055] (3) Torque ratio (T1 / T2) In the DBP addition amount-torque curve obtained by the above method (1), the maximum torque value in the DBP addition amount range of 40 ml / 100 g to 70 ml / 100 g (the range in which 40 ml / 100 g to 70 ml / 100 g of DBP was added to the hexagonal boron nitride powder) was defined as T1, and the minimum torque value in the DBP addition amount range of 70 ml / 100 g to X ml / 100 g (the range in which 70 ml / 100 g to X ml / 100 g of DBP was added to the hexagonal boron nitride powder) was defined as T2, and the torque ratio (T1 / T2) was calculated using this value. X is the amount of dibutyl phthalate added at the point where the torque is maximum in the range of 70 ml / 100 g to 130 ml / 100 g.

[0056] (4) Average particle size (D50) of hexagonal boron nitride powder Measurements were performed by the laser diffraction method using a laser diffraction / scattering particle size analyzer MT3000 (manufactured by Microtrac Bell Co., Ltd.) Specifically, 0.1 g of hexagonal boron nitride powder was placed in a mixing vessel attached to the analyzer filled with 50 cc of ethanol, and the sample was ultrasonically dispersed for 20 seconds at an output of 40 W. The volume-based average particle size (D50) was calculated using this sample.

[0057] (5) Tapped bulk density of hexagonal boron nitride powder The tapped bulk density (g / cm) was measured using a tapped densityr KYT-5000 (manufactured by Seishin Enterprises). 3 ) was measured.

[0058] (6) Aspect ratio of hexagonal boron nitride powder 10 parts by mass of hexagonal boron nitride powder was dispersed in 100 parts by mass of epoxy resin (EA E-30CL, manufactured by Henkel), and the resulting resin composition was degassed under reduced pressure, then poured into a 10 mm square, 1 mm thick mold and cured at a temperature of 70°C. The cured resin composition was then removed from the mold and polished to achieve equilibrium on both sides. One of the surfaces perpendicular to the thickness direction of the resin composition was then cross-sectionally milled at its center, and the milled surface was imaged using an SEM at a magnification of 2500. One hundred hexagonal boron nitride particles were randomly selected from the image, and their long sides (major axis) and short sides (thickness) were measured. The average values ​​were defined as the average major axis (μm) and average thickness (μm), respectively. Furthermore, the value obtained by dividing the average major axis by the average thickness was defined as the aspect ratio (average major axis / average thickness).

[0059] (7) Coefficient of kinetic friction (MIU) Measurements were taken using a friction tester KES-SE (manufactured by Kato Tech Co., Ltd.). Specifically, 0.8 g of hexagonal boron nitride powder was placed on artificial leather Supprale PBZ13001 BK (manufactured by Idemitsu Technofine Co., Ltd.), and the sensor part (10 mm square silicon) of the friction tester was placed on top of it to measure. The measurement conditions were sensitivity H, test table movement speed 1 mm / sec, static load 25 gf, and measurements were taken three times, with the average value being taken as MIU.

[0060] Example 1 400 g of boron oxide, 150 g of carbon black, and 50 g of calcium carbonate were mixed using a mixer. This mixture was heated to 1500 °C at a rate of 5 °C / min in a nitrogen gas atmosphere using a graphite Tammann furnace and held at 1500 °C for 2 hours. After holding at 1500 °C, the temperature was raised to 1850 °C at a rate of 3 °C / min and held at 1850 °C for 2 hours to obtain nitride powder by reduction-nitridation. The obtained nitride powder was then placed in a polyethylene container, and 250 g of nitride powder was mixed with 250 g of hydrochloric acid (37% by mass) and 750 g of pure water to prepare an acid slurry. The mixture was then stirred for 15 hours for acid washing. After washing, the acid slurry was filtered using a Buchner funnel, and pure water was added in an amount 10 times (by mass) or more of the nitride powder to prepare a water slurry. The mixture was then dehydrated by suction filtration until the moisture content of the nitride powder was 40% or less. Purified water was then added to make a nitride powder concentration of 8% by volume to form a water slurry, which was then wet-crushed using a wet rotary disk mill (disparizer) at a disk rotation speed of 12,000 rpm and a disk clearance of 50 μm. The water slurry after wet-crushing was dehydrated by suction filtration to a moisture content of 40% or less, and then vacuum-dried by heating at 200°C for 15 hours under a reduced pressure of 30 kPaA. The dried powder was classified using a vertical vibration sieve with 45 μm openings to obtain white hexagonal boron nitride powder. The production conditions and the evaluation results of the resulting hexagonal boron nitride powder are shown in Table 1. The obtained DBP dropping amount-torque curve is shown in Figure 1. The DBP dropping amount-torque curve for the hexagonal boron nitride powder of the present invention has a peak in the DBP dropping amount range of 40 ml / 100 g to 70 ml / 100 g and a valley between 70 ml and 70 ml / 100 g, and exhibits a higher T1 / T2 value than conventional hexagonal boron nitride powder.

[0061] (Examples 2 to 5, Comparative Examples 2 to 4, 6) Hexagonal boron nitride powder was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in Table 1. The production conditions and the evaluation results of the obtained hexagonal boron nitride powder are shown in Table 1.

[0062] (Comparative Example 1) 400 g of boron oxide, 150 g of carbon black, and 50 g of calcium carbonate were mixed using a mixer. This mixture was heated to 1500°C at a rate of 5°C / min in a nitrogen gas atmosphere using a graphite Tammann furnace and held at 1500°C for 2 hours. After holding at 1500°C, the temperature was raised to 1850°C at a rate of 3°C / min and held at 1850°C for 2 hours to obtain nitrided powder by reduction-nitridation. The obtained nitrided powder was then placed in a polyethylene container, and 250 g of nitrided powder was mixed with 250 g of hydrochloric acid (37% by mass) and 750 g of pure water to prepare an acid slurry. This slurry was then stirred for 15 hours for acid washing. After washing, the acid slurry was filtered using a Buchner funnel, and then pure water in an amount 10 times (by mass) or more the nitride powder was added to form a water slurry. The nitride powder was then dehydrated by suction filtration until its moisture content was 40% or less, and then vacuum dried by heating at 200°C for 15 hours under a reduced pressure of 30 kPaA. The dried powder was classified using a vertical vibration type vibrating sieve with 45 μm openings to obtain white hexagonal boron nitride powder. The production conditions and the evaluation results of the resulting hexagonal boron nitride powder are shown in Table 1.

[0063] (Comparative Example 5) 400 g of boron oxide, 150 g of carbon black, and 50 g of calcium carbonate were mixed using a mixer stirrer. This mixture was heated to 1500°C at a rate of 5°C / min in a nitrogen gas atmosphere using a graphite Tammann furnace and held at 1500°C for 2 hours. After holding at 1500°C, the temperature was raised to 1850°C at a rate of 3°C / min and held at 1850°C for 2 hours to obtain nitride powder. The obtained nitride powder was then placed in a polyethylene container, and 250 g of the nitride powder was mixed with 250 g of hydrochloric acid (37% by mass) and 750 g of pure water to prepare an acid slurry, which was then stirred for 15 hours for acid washing. After washing, the acid slurry was filtered using a Buchner funnel, and then pure water (at least 10 times the amount by mass of the nitride powder) was added to form a water slurry. The nitride powder was then dehydrated by suction filtration to a moisture content of 40% or less, and then heated at 200°C for 15 hours under a reduced pressure of 30 kPaA for vacuum drying. Dry crushing was then performed using a stone mill (mass colloider) with a disk clearance of 10 μm and a rotation speed of 2000 rpm. The powder was then classified using a vertical vibration sieve with 45 μm openings to obtain white hexagonal boron nitride powder. The production conditions and the evaluation results of the resulting hexagonal boron nitride powder are shown in Table 1.

[0064] (Comparative Example 7) 300 g of boric acid and 270 g of melamine were mixed and filled into a covered graphite crucible. The mixture was heated in a graphite Tammann furnace under a nitrogen gas atmosphere at 1000 °C for 8 hours to obtain low-crystalline nitride powder. 100 g of calcium carbonate was added to the obtained low-crystalline nitride powder, mixed and ground in a ball mill, and then heated in a graphite Tammann furnace under a nitrogen atmosphere at 1900 °C for 6 hours to obtain nitride powder by the melamine method. The obtained nitride powder was then placed in a polyethylene container. 120 g of the nitride powder was mixed with 120 g of hydrochloric acid (37% by mass) and 360 g of pure water to prepare an acid slurry, which was then stirred for 15 hours for acid washing. After washing, the acid slurry was filtered using a Buchner funnel, and pure water was added in an amount 10 times (by mass) or more of the nitride powder to form a water slurry. The nitride powder was then dehydrated by suction filtration to a moisture content of 40% or less. Purified water was then added to make a 10% by volume nitride powder concentration to form a water slurry, which was then wet-crushed using a wet rotary disk mill (disparizer) at a disk rotation speed of 12,000 rpm and a disk clearance of 40 μm. The wet-crushed water slurry was dehydrated by suction filtration to a moisture content of 40% or less, and then vacuum-dried by heating at 200°C for 15 hours under a reduced pressure of 30 kPaA. The dried powder was classified using a vertical vibration sieve with 45 μm openings to obtain white hexagonal boron nitride powder. The production conditions and the evaluation results of the resulting hexagonal boron nitride powder are shown in Table 2.

[0065] (Comparative Example 8) 300 g of boric acid and 270 g of melamine were mixed and filled into a lidded graphite crucible. The mixture was heated in a graphite Tammann furnace under a nitrogen gas atmosphere at 1000°C for 8 hours to obtain a low-crystalline nitride powder. 100 g of calcium carbonate was added to the obtained low-crystalline nitride powder, and the mixture was mixed and pulverized in a ball mill. The mixture was then heated in a graphite Tammann furnace under a nitrogen atmosphere at 1900°C for 6 hours to obtain a nitride powder by the melamine method. The obtained nitride powder was then placed in a polyethylene container, and 120 g of the nitride powder was mixed with 120 g of hydrochloric acid (37% by mass) and 360 g of pure water to prepare an acid slurry. The mixture was then stirred for 15 hours for acid washing. After washing, the acid slurry was filtered using a Buchner funnel, and then pure water in an amount 10 times (by mass) or more of the nitride powder was added to form a water slurry. The nitride powder was then dehydrated by suction filtration until its moisture content was 40% or less, and then dried under reduced pressure at 200°C for 15 hours at a reduced pressure of 30 kPaA. The dried powder was classified using a vertical vibration type vibrating sieve with 45 μm openings to obtain white hexagonal boron nitride powder. The production conditions and the evaluation results of the resulting hexagonal boron nitride powder are shown in Table 2.

[0066] (Comparative Example 9) 300 g of boric acid and 270 g of melamine were mixed and filled into a lidded graphite crucible. The mixture was heated in a graphite Tammann furnace under a nitrogen gas atmosphere at 1000°C for 8 hours to obtain a low-crystalline nitride powder. 100 g of calcium carbonate was added to the obtained low-crystalline nitride powder, and the mixture was mixed and pulverized in a ball mill. The mixture was then heated in a graphite Tammann furnace under a nitrogen atmosphere at 1900°C for 6 hours to obtain a nitride powder by the melamine method. The obtained nitride powder was then placed in a polyethylene container, and 120 g of the nitride powder was mixed with 120 g of hydrochloric acid (37% by mass) and 360 g of pure water to prepare an acid slurry. The mixture was then stirred for 15 hours for acid washing. After washing, the acid slurry was filtered using a Buchner funnel, and then pure water (at least 10 times the amount by mass of the nitride powder) was added to form a water slurry. The nitride powder was then dehydrated by suction filtration to a moisture content of 40% or less, and then heated at 200°C for 15 hours under a reduced pressure of 30 kPaA for vacuum drying. Dry crushing was then performed using a stone mill (mass colloider) with a disk clearance of 10 μm and a rotation speed of 2000 rpm. The powder was then classified using a vertical vibration type vibrating sieve with 45 μm openings to obtain white hexagonal boron nitride powder. The production conditions and the evaluation results of the resulting hexagonal boron nitride powder are shown in Table 2.

[0067] Furthermore, a foundation was prepared with the following composition using the hexagonal boron nitride powders obtained in Examples 1 to 5 and Comparative Examples 1 to 9. In this foundation, ethylhexyl methoxycinnamate and perfluorooctyltriethoxysilane correspond to the oil components, and the total amount of these is 55 parts by mass (51 parts by volume) per 100 parts by mass of the hexagonal boron nitride powder.

[0068] Hexagonal boron nitride powder 20.0 mass% Mica 15.0% by mass Synthetic phlogopite 12.0% by mass Ethylhexyl methoxycinnamate 8.0% by mass (Vinyl dimethicone / methicone silsesquioxane) crosspolymer 8.0% by mass (Diphenyl Dimethicone / Vinyl Diphenyl Dimethicone / Silsesquioxane crosspolymer 8.0% by mass Nylon 12 3.0% by mass Silica 3.0% by mass Talc 3.0% by mass Acrylates crosspolymer 3.0% by mass Perfluorooctyltriethoxysilane 3.0% by mass Zinc oxide 3.0% by mass Polymethyl methacrylate polymer 3.0% by mass Silicone-treated red iron oxide (red iron oxide) 1.0% by mass Silicone-treated yellow iron oxide 0.6% by mass Silicone-treated black iron oxide 0.4% by mass Silicone-treated titanium dioxide 6.0% by mass

[0069] The spreadability and moisturizing feel of the foundation obtained with the above formulation were evaluated by 20 expert panelists. If less than 30% of the panelists felt it was good, they were rated as X, if 30% or more but less than 60% felt it was good, they were rated as △, if 60% or more but less than 80% felt it was ○, and if 80% or more felt it was ◎. The evaluation results are shown in Tables 1 and 2.

[0070] [Table 1]

[0071] [Table 2]

[0072] The evaluation results showed that the hexagonal boron nitride powders of Examples 1 to 5, which were produced by a production method including a reduction-nitriding step of heating a raw material powder containing an oxygen-containing boron compound, an oxygen-containing alkaline earth metal compound, and a carbon source, wherein the atomic ratio (B / C) of the boron atoms (B) of the oxygen-containing boron compound to the carbon atoms (C) of the carbon source was 0.80 to 2.00, and the molar ratio (MO / BO) of the oxygen-containing alkaline earth metal compound (MO; M is an alkaline earth metal) to the oxygen-containing boron compound, calculated as oxide, was 0.002 to 0.12, to 1780°C or higher in a nitrogen atmosphere to obtain nitrided powder, and a wet-crushing step of wet-crushing the nitrided powder in a wet rotary disk mill under conditions of a slurry concentration of 5% by volume or higher and a disk clearance of 35 μm or higher, all had a T1 / T2 of 1.8 or higher and a dynamic friction coefficient of 0.50 or lower. In sensory evaluation, foundations containing these hexagonal boron nitride powders exhibited good spreadability and a moist feel. Furthermore, for all hexagonal boron nitride powders, T1 was between 0.10 Nm and 0.30 Nm.

[0073] On the other hand, in Comparative Example 1, in which the wet disintegration step was not carried out, aggregation remained, resulting in a T1 / T2 ratio of less than 1.8 and a dynamic friction coefficient of more than 0.50. Furthermore, the foundation containing this compound was unable to achieve good spreadability and a moist feel.

[0074] Although a wet crushing step was carried out, Comparative Example 2, in which the disc clearance was less than 35 μm, had a T1 / T2 ratio of less than 1.8, and the foundation containing this product was unable to achieve a good moist feeling.

[0075] In Comparative Example 3, where a wet crushing step was carried out and the slurry concentration was less than 5% by volume, the coefficient of dynamic friction was high, and the foundation containing this compound was unable to achieve good spreadability and a moist feel.

[0076] In Comparative Example 4, where the MO / BO ratio in the reduction-nitridation step was greater than 0.12, the particles grew and the aspect ratio became smaller, and the foundation containing this compound was unable to achieve good spreadability.

[0077] In Comparative Example 5, which was dry-crushed without a wet-crushing step, the T1 / T2 ratio was less than 1.8. This is thought to be because the amount of fine powder increased due to the insufficient gentle crushing, causing re-agglomeration. Furthermore, the foundation containing this compound was unable to achieve a good moist feeling.

[0078] In Comparative Example 6, in which the temperature during the reduction-nitridation reaction was less than 1780°C, particle growth was insufficient and the dynamic friction coefficient could not be reduced to 0.50 or less, and the foundation containing this compound was unable to achieve good spreadability.

[0079] Comparative Example 8, which was produced by the melamine method rather than the reduction-nitridation reaction, had many hard agglomerates, and it was not possible to achieve a T1 / T2 of 1.8 or more and a dynamic friction coefficient of 0.50 or less. Comparative Example 7, which was wet-disintegrated, also failed to break down the agglomerates, resulting in a similar result. Foundations incorporating these ingredients failed to achieve good spreadability and a moist feel. Comparative Example 9, which was dry-disintegrated, was able to disintegrate the agglomerates, thereby achieving a dynamic friction coefficient of 0.50 or less, but it was not possible to achieve a T1 / T2 of 1.8 or more, and the foundations incorporating this ingredient failed to achieve a good moist feel.

Claims

1. Hexagonal boron nitride powder having an oil absorption of 70 ml / 100 g or more, in a DBP dropping amount-torque curve obtained from the torque change when dibutyl phthalate is added to hexagonal boron nitride powder at a temperature of 20°C and the amount of dibutyl phthalate (DBP) added, the ratio (T1 / T2) of the maximum torque value T1 in a range where 40 ml / 100 g to 70 ml / 100 g of dibutyl phthalate is added to the hexagonal boron nitride powder to the minimum torque value T2 in a range where 70 ml / 100 g to X ml / 100 g of dibutyl phthalate is added to the hexagonal boron nitride powder (where X is the amount of dibutyl phthalate added at the point where the torque is maximum in the range of 70 ml / 100 g to 130 ml / 100 g) is added to the hexagonal boron nitride powder is 1.8 or more, The dynamic friction coefficient is 0.50 or less. Hexagonal boron nitride powder.

2. 2. The hexagonal boron nitride powder according to claim 1, having an average particle size of 3.0 to 20.0 μm and an aspect ratio of 7.0 to 18.

0.

3. 3. The hexagonal boron nitride powder according to claim 1 or 2, which is for use in cosmetics.

4. A powder foundation comprising the hexagonal boron nitride powder according to claim 3 and an oil component, wherein the content of the oil component per 100 parts by mass of the hexagonal boron nitride powder is 40 to 70 parts by volume.

5. The method for producing hexagonal boron nitride powder includes a reduction-nitriding step of heating a raw material powder containing an oxygen-containing boron compound, an oxygen-containing alkaline earth metal compound, and a carbon source, wherein the atomic ratio (B / C) of the boron atoms (B) of the oxygen-containing boron compound to the carbon atoms (C) of the carbon source is 0.80 to 2.00, and the molar ratio (MO / BO) of the oxygen-containing alkaline earth metal compound (MO; M is an alkaline earth metal) to the oxygen-containing boron compound is 0.002 to 0.12, calculated as oxides, to 1780°C or higher in a nitrogen atmosphere to obtain nitrided powder, and a wet-crushing step of wet-crushing the nitrided powder using a wet rotary disk mill under conditions of a slurry concentration of 5% by volume or more and a disk clearance of 35 μm or more.

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