JP7107901B2 - Boron nitride powder for cosmetics and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a boron nitride powder used for cosmetics and a method for producing the same.

Boron nitride powder is a white extender pigment with a hexagonal layered crystal structure and is excellent in covering power, transparency, spreadability, adhesion and lubricity.・It is used as a powder base material for cosmetics such as make-up cosmetics for the purpose of filling.

The feeling of use (feeling) of a cosmetic as a powdery base material varies depending on the shape of the powder, such as spherical or plate-like, particle size, hardness, surface condition, etc., and the shape of the powder, etc. is controlled. By this, it is known that a boron nitride powder having excellent physical properties such as lubricity, whiteness, hydrolysis resistance, spreadability, and adhesion, which is preferable as a powder base material for cosmetics, can be obtained (for example, See Patent Documents 1 to 4).

Here, powder composed of particles having a particle diameter of about several μm to several tens of μm generally has cohesion, and when the cohesion is high, the powder tends to clump, so lubricity, In order to improve spreadability, adhesiveness, etc., the lower the cohesion, the better. In addition, the presence of aggregates also poses a problem of poor touch.
In the prior art, processing such as pulverization, pulverization, and dispersion is essential in order to reduce cohesiveness, so there is a problem of high production costs.
In terms of covering power, transparency, spreadability, and adhesion, the most preferred boron nitride powder for cosmetics has an average length of 3 to 7 μm and an average aspect ratio of 6 to 15. In the reductive nitriding method, it is possible to obtain boron nitride having an average major diameter of 8 to 12 μm even if it contains agglomerates or few aggregates, and a boron nitride powder with few aggregates and an average major diameter of 3 to 7 μm is obtained. was difficult.

JP 2019-043792 A Japanese Patent Application Laid-Open No. 2004-035273 JP-A-63-274603 JP 2012-176910 A

In view of the above circumstances, an object of the present invention is to provide a cosmetic boron nitride powder having low cohesiveness and an average length suitable for cosmetic use. Another object of the present invention is to provide a manufacturing method capable of manufacturing the boron nitride powder for cosmetics at a low cost.

The present invention is a boron nitride powder having a median diameter (D1) measured by a laser diffraction scattering method in the range of 4 to 30 μm, an average major axis in the range of 3 to 7 μm, and an average aspect ratio in the range of 6 to 15, Provided is a cosmetic boron nitride powder characterized by having a median diameter (D2) in the range of 4 to 10 μm when ultrasonically dispersed in ethanol at an output of 25 W for 1200 seconds.

Further, the present invention provides a step of preparing a raw material mixture containing a compound serving as a carbon source together with an oxygen-containing boron compound and an oxygen-containing alkaline earth metal compound;
a reaction step of heating the raw material mixture in a nitrogen atmosphere for reduction nitriding;
a cleaning step of acid-cleaning the reaction product containing boron nitride obtained in the reaction step;
In a method for producing a boron nitride powder comprising
The raw material mixture has a B/C atomic ratio of 0.80 to 2.00, and contains an oxygen-containing alkaline earth metal compound (MO; M is an alkaline earth metal) and an oxygen-containing boron compound (B ₂ O ₃ ) and the molar ratio (MO/B ₂ O ₃ ) is set to 0.12 or less,
The boron nitride powder for cosmetics, wherein in the reaction step, the reaction conditions are adjusted so that the molar ratio of M/B ₂ O ₃ in the reaction product is 0.1 to 0.7, and the reductive nitriding reaction is performed. to provide a method of manufacturing

Since the boron nitride powder for cosmetics of the present invention has an average major diameter and an aspect ratio suitable for cosmetics, it is excellent in covering power, transparency, spreadability, and adhesion, and is suitable as a boron nitride powder for cosmetics. there is In addition, since it has few aggregates and is soft, it feels good on the skin when used in cosmetics.

The present invention is a boron nitride powder having a median diameter (D1) measured by a laser diffraction scattering method in the range of 4 to 30 μm, an average major axis in the range of 3 to 7 μm, and an average aspect ratio in the range of 6 to 15, It is a cosmetic boron nitride powder having a median diameter (D2) in the range of 4 to 10 μm when ultrasonically dispersed in ethanol at an output of 25 W for 1200 seconds.

Here, the median diameter (D1) measured by the laser diffraction scattering method is measured by the laser diffraction scattering method using ethanol as a dispersion medium and using boron nitride powder as a sample that has not been subjected to any treatment after production. In the cumulative particle size distribution graph of the case (the vertical axis is the cumulative rate of particle volume from 0 to 100%, and the horizontal axis is an upward-sloping graph representing the particle size), the particle size at a cumulative rate of 50% is shown. Generally, it is also expressed as d50, which means the average particle size of the boron nitride powder containing aggregates.
If the median diameter (D1) is larger than the above range, the product will feel rough when applied to the skin, and lubricity, spreadability, adhesion, etc. will be reduced. On the other hand, when the median diameter (D1) is smaller than the above range, the average length becomes smaller than 3 μm, resulting in deterioration of covering power, transparency, spreadability and adhesiveness.

In addition, the average length indicates the average length of the long side of the boron nitride particles when the cross section of the epoxy resin in which the boron nitride powder is dispersed is milled and the processed surface is photographed by SEM, and the average aspect ratio is the average value of the aspect ratio, which is a numerical value obtained by dividing the long side (long diameter) of the particles by the short side (thickness) of each particle, and the boron nitride powder has a micron-order size. It is meant to be flaky.

Then, the median diameter (D2) when ultrasonically dispersed in ethanol at an output of 25 W for 1200 seconds was obtained by using an ultrasonic homogenizer and performing ultrasonic dispersion treatment under the above conditions. indicates the median diameter measured in , and means the average particle diameter of the boron nitride powder in which some/or all of the aggregates are destroyed by ultrasonic dispersion treatment.
The smaller the median diameter (D2), the softer the aggregate. Agglomerates are less likely to remain in cosmetic products, and even if a small amount of aggregates remain in the product, they are easily broken when applied to the skin, resulting in excellent lubricity, spreadability, adhesion, and the like.
In addition, it is common to measure the particle size distribution after performing ultrasonic dispersion treatment for 1200 seconds at an output of 100 W of a homogenizer. inadequate to assess

Therefore, the present invention is composed of flake particles with an average major axis of 3 to 7 μm, completely dispersed in the absence of agglomerates, or almost completely dispersed with very little force if agglomerates are present. It is a boron nitride powder for cosmetics that is in a state.

Furthermore, in the present invention, the boron nitride powder can be produced by one heat treatment from the starting material using the specific reduction nitriding method, and after the production of the boron nitride powder, pulverization is performed to reduce cohesion. Since there is no need to perform treatments such as pulverization, dispersion, etc., the boron nitride powder for cosmetics can be produced at low cost.

Hexagonal boron nitride (hereinafter also referred to as “h-BN”) can be produced by the reductive nitriding method, for example, as follows. That is, an oxygen-containing boron compound such as boron oxide (B ₂ O ₃ ) is used as a boron source, and a mixed powder of this oxygen-containing boron compound powder, carbon powder, and an auxiliary agent is used as a reaction raw material in a nitriding reaction furnace. , nitrogen is supplied to obtain h-BN by reduction and nitridation of the oxygen-containing boron compound.

The above reaction is represented by the following formula, and generally proceeds at 1200° C. or higher.
B2O3+ _{3C + N2} →2BN+3CO
It is generally preferred that the above reaction proceed at a temperature of 1550° C. or less. If 5% by mass or more of carbon remains at a temperature of 1550° C. or higher, black impurities such as CaB ₆ are generated, which is not preferable. For example, it is preferable to allow the reaction to proceed sufficiently by holding at a temperature of about 1500° C. for 2 to 10 hours.

After the above reaction, the inside of the nitriding reactor is generally kept at a temperature of 1700 to 2000° C., preferably 1750 to 1900° C., so that BN crystal growth proceeds. If this temperature is too low, the particles will not grow to a suitable average major axis for cosmetics, and if the temperature in the nitriding reactor is higher than necessary, the average major axis will become too large.

Further, the oxygen-containing alkaline earth metal compound as an auxiliary agent in the reaction raw material is used to promote the above crystal growth. can be used. Boron oxide ( _{B.sub.2O.sub.3} ) is usually added excessively for reduction nitridation, and a _two -component liquid phase ( _{B.sub.2O.sub.3} --CaO) forms at the stage of crystal growth at 1700.degree. C. to _2000.degree . Crystal growth proceeds in this liquid phase. Here, when the Ca concentration in the liquid phase is too high, not only does the length of the h-BN become too large, but there is also the problem of promoting aggregation of particles. Therefore, in order to obtain the h-BN of the present invention, it is necessary to keep this Ca concentration low, and as a means of controlling the Ca concentration in the liquid phase, the ratio of the boron source, the carbon source and the auxiliary agent in the raw material and a method of controlling the volatilization amount of the liquid phase.

The ratio of the boron source and the carbon source in the reaction raw materials is set so that the B/C atomic ratio is in the range of 0.80 to 2.00, especially 0.80 to 1.20. If the atomic ratio (B/C) is smaller than the above range, the concentration of Ca in the liquid phase becomes high, the major axis of h-BN becomes larger than intended, and aggregation may become hard. On the other hand, if it is larger than the above range, the ratio of unreacted B ₂ O ₃ becomes too excessive, and the yield of boron nitride with respect to the amount of charged raw materials is remarkably lowered, resulting in lowered productivity.
Further, the ratio of the auxiliary agent and the boron-containing compound is such that the molar ratio (MO/B ₂ O ₃ ) of the oxygen-containing alkaline earth metal compound and the oxygen-containing boron compound in terms of oxide is 0.12 or less, particularly 0. 0.10 or less is preferable. If this molar ratio exceeds this range, the major axis of h-BN tends to be larger than intended. In addition, there is no lower limit to the molar ratio, but if it is completely 0, crystallization will not be promoted, and there is a possibility that fine powder that is significantly smaller than the desired major axis will increase. .002.

Here, the liquid phase gradually volatilizes during the reaction process, but since B ₂ O ₃ volatilizes more easily than CaO, the Ca concentration in the liquid phase increases as the volatilization progresses. going to rise. Therefore, in order to control the length of h-BN, it is necessary to control the volatilization amount of the liquid phase.
In the reaction step, the inside of the nitriding reactor is a nitrogen atmosphere at atmospheric pressure, and nitrogen gas is generally supplied and exhausted at a flow rate of 0.1 to 10 L/hr per 1 L of the volume of the nitriding reactor. As the flow rate of the gas increases, the liquid phase becomes more likely to volatilize, so the major axis of h-BN tends to increase. Therefore, in order to obtain boron nitride powder having an average length of 3 to 7 μm, it is preferable to lower the flow rate of nitrogen gas. However, the volatilization amount of the liquid phase also greatly depends on the structure inside the reactor. Therefore, although the preferred nitrogen gas flow rate is not particularly limited, it is generally preferred to be 0.1 to 3 L/hr per 1 L volume of the nitriding reactor.
The molar ratio (M/B ₂ O ₃ ) between the alkaline earth metal (M) contained in the boron nitride powder obtained in the reaction step and the unreacted B ₂ O ₃ is 0.1 to 0.7. is preferably If this molar ratio is larger than the range, it means that the Ca concentration in the liquid phase has increased by the end of the reaction step, and the major axis of h-BN tends to be larger than intended. On the other hand, if the molar ratio is smaller than the above range, it means that the Ca concentration in the liquid phase during the reaction step is too low, and there is a possibility that fine powder having a remarkably smaller diameter than the intended major axis will increase.

The molar ratio (M/B ₂ O ₃ ) of alkaline earth metal (M) and unreacted B ₂ O ₃ was obtained by adding the boron nitride powder obtained in the reaction step to an aqueous sulfuric acid solution and eluting it into the aqueous sulfuric acid solution. The concentration (ppm) of M and B was quantified by ICP emission spectrometry and converted into a molar ratio (M/B ₂ O ₃ ).
Next, the boron nitride powders other than those used for analysis of the molar ratio (M/B ₂ O ₃ ) are washed with an acid to remove by-products contained in the boron nitride powders. For example, it is put into a container made of polyethylene, an aqueous solution of hydrochloric acid (10% by weight HCl) is added in an amount ten times that of boron nitride, and the mixture is stirred at a rotation speed of 300 rpm for 15 hours.
After the acid wash, the acid is filtered. The acid-washed boron nitride is then dispersed in the acid used and pure water from a colleague and filtered again. Further, washing with pure water and filtration are repeated until the filtrate becomes neutral.
After washing with pure water, the obtained powder is dried in the air at 50 to 250° C. or under reduced pressure to obtain a highly pure boron nitride powder.

In the present invention, the oxygen-containing boron compound is not particularly limited, but examples include boric acid, boric anhydride, metaboric acid, perboric acid, hypoboric acid, sodium tetraborate, sodium perborate, and the like. can be used. Boric acid, which is generally easily available, is preferably used.

In the present invention, the carbon source is not particularly limited, and examples include amorphous carbon such as carbon black, activated carbon and carbon fiber, crystalline carbon such as diamond, graphite and nanocarbon, Pyrolytic carbon or the like obtained by pyrolyzing a polymer can be used. Inexpensive carbon black is generally used.

In the present invention, the oxygen-containing alkaline earth metal compound is not particularly limited, but examples include magnesium oxide, calcium oxide, magnesium carbonate, calcium carbonate, magnesium hydrogen carbonate, calcium hydrogen carbonate, magnesium hydroxide, water Calcium oxide, magnesium nitrate, calcium nitrate, magnesium sulfate, calcium sulfate, magnesium phosphate, calcium phosphate, magnesium oxalate, calcium oxalate, etc. can be used, and two or more of these can be mixed and used.

The mixing for preparing the mixed powder, which is the reaction raw material, is not particularly limited as long as each component is uniformly mixed, and is performed using a mixing device such as a vibration mill, a ball mill, and a drum mixer vibration stirrer. .

In the present invention, the nitrogen atmosphere can be formed by known means. The gas to be used is not particularly limited as long as it can give nitrogen to boron in the nitriding reaction, and nitrogen gas and ammonia gas can also be used. , argon, helium, and other non-oxidizing gases can also be used.

In the present invention, the reduction-nitridation reaction step can be performed using a known apparatus capable of controlling the reaction atmosphere. For example, an atmosphere-controlled high-temperature furnace in which heat treatment is performed by high-frequency induction heating or heater heating can be used. In addition to batch furnaces, continuous furnaces such as pusher-type tunnel furnaces and vertical reaction furnaces can also be used.

In the present invention, nitric acid, sulfuric acid, acetic acid, etc. can also be used as the acid used for acid cleaning in addition to hydrochloric acid.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1
<Preparation of Raw Material Mixture and Reductive Nitriding Reaction Step>
70 g of boron oxide, 30 g of carbon black and 10 g of calcium carbonate were mixed in a ball mill. Using a graphite Tammann furnace, the mixture was heated to 1500° C. at 15° C./min under a nitrogen gas atmosphere and held at 1500° C. for 6 hours. After holding at 1500° C., the temperature was raised to 1800° C. at a rate of 15° C./min, held at 1800° C. for 2 hours, and subjected to reductive nitriding treatment.
Here, since the molecular weights of boron oxide, carbon black, and calcium carbonate are 69.6, 12.0, and 100.1, respectively, the number of moles in the raw material mixture is 1.01 (70/69.6=1 .01) mol, 2.50 (30/12.0 = 2.50) mol, 0.10 (10/100.1 = 0.10) mol, and the B/C atomic ratio is 0.81 (1 .01×2/2.5=0.81), and the molar ratio (CaO/B ₂ O ₃ ) is calculated to be 0.10 (0.10/1.01=0.10).

<Ca/B ₂ O ₃ measurement after reduction nitridation reaction step>
Put 50 g of a sulfuric acid aqueous solution prepared by dissolving 2 g of concentrated sulfuric acid in 48 g of ultrapure water into a 50 cc screw tube bottle, add 1 g of boron nitride powder before acid cleaning, and mix with a mixing rotor (FLMX-T6-5 manufactured by AS ONE Corporation, rotation speed 70 rpm). The boron nitride suspension after stirring for 24 h was filtered through a 0.45 μm membrane filter, and calcium (Ca) and boron (B) contained in the filtrate were quantified by ICP emission spectrometry. Furthermore, the obtained concentration (ppm) of each component was converted into a molar ratio (Ca/B ₂ O ₃ ).

<Washing process including acid cleaning and drying>
Next, the rest of the boron nitride powder was put into a polyethylene container, an aqueous solution of hydrochloric acid (10% by weight HCl) in an amount ten times that of the boron nitride was added, and the mixture was stirred at 300 rpm for 15 hours. After the acid washing, the acid is filtered, and after washing again with pure water having a specific resistance of 1 MΩ cm at 25 ° C., which is 300 times the amount of the charged boron nitride, the water content in the powder after filtering by suction filtration. Dehydration was carried out until the percent was 50 wt% or less. After washing with pure water, the obtained powder was dried under reduced pressure at 200° C. for 15 hours under a pressure of 1 kPaA to obtain a highly pure boron nitride powder.

<Measurement of average length, average thickness and aspect ratio of boron nitride powder>
10 parts by mass of the obtained 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. It was poured into a mold and cured at a temperature of 70°C.
Next, the cured resin composition is extracted from the mold, and after both surfaces are polished so that they are parallel, one of the surfaces perpendicular to the thickness direction of the resin composition is subjected to cross-sectional milling at the center. After processing, an image of the processed surface was taken by SEM at a magnification of 2500 times. Randomly select 100 boron nitride particles from the resulting image, measure the long side (= major diameter) and short side (= thickness) of the particles in consideration of the magnification, and calculate each average value as the average major diameter (μm), average thickness (μm), and the value obtained by dividing the average length by the average thickness was defined as the aspect ratio (average length/average thickness).

<Measurement of median diameter (D1)>
0.3 g of the obtained boron nitride powder was placed in 50 cc of ethanol, and the boron nitride suspension after light stirring was measured using a laser diffraction/scattering particle size distribution analyzer (LA-950V2 manufactured by HORIBA) to determine the particle size distribution. was measured to obtain the average particle size (D50) (μm).

<Measurement of median diameter (D2)>
0.3 g of the obtained boron nitride powder was put into a screw tube bottle with a volume of 100 cc and a diameter of 4 cm together with 50 cc of ethanol. Using a laser diffraction/scattering particle size distribution analyzer (LA-950V2 manufactured by HORIBA), the particle size distribution of the boron nitride suspension after being subjected to ultrasonic waves at an output of 25 W for 20 minutes was measured, and the average particle size The diameter (D50) (μm) was determined.

<Preparation and evaluation of powder foundation>
Using the obtained boron nitride powder, a powder foundation was prepared in the following proportions. The obtained powder foundation was subjected to sensory evaluation by 20 expert panelists in terms of coverage, transparency, spreadability, adhesion, and skin feel. The case where less than 30% of the panelists felt good was evaluated as x, the case where 30% or more and less than 60% was Δ, the case where 60% or more and less than 80% was ◯, and the case where 80% or more was ⊚.

Hexagonal boron nitride powder 20.0% by 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
Silicon-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 oxide 6.0% by mass

Examples 2-4, Comparative Examples 1-4
By changing the B/C atomic ratio, CaO/B ₂ O ₃ molar ratio, nitrogen flow rate, and maximum temperature of the raw material mixture of Example 1, boron nitride powders of Examples 2 to 4 and Comparative Examples 1 to 4 were produced. did. Table 1 shows the production conditions and evaluation results of each boron nitride.

The boron nitride powders of Examples 1 to 4 were produced so that the Ca/B ₂ O ₃ molar ratio in the reaction product was 0.1 to 0.7, and the median diameter (D1) was 4 to 30 μm. , a boron nitride powder having a median diameter (D2) of 4 to 10 μm is obtained. That is, these boron nitride powders have small agglomerates and are soft to the touch. Further, the boron nitride powder has an average length of 3 to 7 μm and an average aspect ratio of 6 to 15, and is excellent in covering power, transparency, spreadability and adhesion, and is suitable as a boron nitride powder for cosmetics.

Moreover, since the boron nitride powder for cosmetics can be produced at low cost, it is industrially extremely useful.

Claims (2)

Boron nitride having a median diameter (D1) measured by a laser diffraction scattering method in the range of 21 to 30 μm, an average length of 3 to 7 μm, an average thickness of more than 0.5 μm, and an average aspect ratio in the range of 6 to 15 . 1. A boron nitride powder for cosmetics, characterized in that the powder has a median diameter (D2) in the range of 4 to 10 μm when ultrasonically dispersed in ethanol at an output of 25 W for 1200 seconds. A step of preparing a raw material mixture containing boron oxide as an oxygen-containing boron compound and one or both of calcium carbonate and calcium oxide as an oxygen-containing alkaline earth metal compound and carbon black as a compound serving as a carbon source;
a reaction step of heating the raw material mixture in a nitrogen atmosphere for reduction nitriding;
a cleaning step of acid-cleaning the reaction product containing boron nitride obtained in the reaction step;
In a method for producing a boron nitride powder comprising
The raw material mixture has a B/C atomic ratio of 0.80 to 2.00, and contains an oxygen-containing alkaline earth metal compound (MO; M is an alkaline earth metal) and an oxygen-containing boron compound (B ₂ O ₃ ) and the molar ratio (MO/B ₂ O ₃ ) is set to 0.12 or less,
2. The cosmetic according to claim 1, wherein in the reaction step, the reaction conditions are adjusted so that the M/B ₂ O ₃ molar ratio in the reaction product is 0.1 to 0.7, and the reductive nitriding reaction is performed. A method for producing raw boron nitride powder.