Graphitic carbon nitride with metal oxide and production process thereof

Abstract

To provide a process for efficiently producing graphitic carbon nitride, which is suitable in cosmetic use.SOLUTION: The present invention mainly relates to a process for preparing graphitic carbon nitride, comprising a step of heating at least one precursor compound with at least one metal oxide particle. The present invention also relates to a mixture product prepared by the process according to the present invention, comprising the graphitic carbon nitride and the metal oxide particle.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention mainly relates to a method for preparing graphitic carbon nitride, particularly a method for preparing a mixture of graphitic carbon nitride and metal oxide.

Background Art

[0002] The UV protection effect is one of the important elements for cosmetics. Graphitic carbon nitride is an inorganic compound and is known to exhibit UV absorption characteristics. Regarding the technology for manufacturing carbon nitride materials, several documents have been published so far.

[0003] For example, JP2020-152609A discloses a method for producing graphitic carbon nitride with a higher yield and lower cost, and provides a novel graphitic carbon nitride.

[0004] Makeup compositions are used to impart a desired color appearance to keratinous substances, such as the skin, particularly the facial skin. The development of a new and efficient production method of graphitic carbon nitride as an environmentally friendly UV absorption material is required.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

[0007] An object of the present invention is to provide a method for efficiently producing graphitic carbon nitride, which is suitable for cosmetic use. [Means for Solving the Problems]

[0008] The above object of the present invention can be achieved by a method for preparing graphitic carbon nitride, which includes a step of heating at least one precursor compound together with at least one metal oxide particle.

[0009] The precursor compound may be selected from urea, thiourea, melamine, guanidine, arginine, cyanamide, dicyandiamide, and salts thereof, and combinations thereof.

[0010] The metal oxide particles may be selected from silica (SiO2), zeolite, and aluminum oxide (Al2O3) particles, and mixtures and composites thereof.

[0011] The metal oxide particles may have an average particle size in the range of 0.01 to 30 μm, preferably 0.05 to 20 μm.

[0012] The mass ratio of the precursor compound to the metal oxide particles may be in the range of 1:99 to 99:1, preferably 1:49 to 49:1, more preferably 1:24 to 24:1, still more preferably 1:9 to 9:1, and particularly 1:5 to 5:1.

[0013] Heating can be carried out at at least 450 °C for a period of at least 1 minute.

[0014] Heating can be carried out in the presence of oxygen-containing species such as O2 (especially together with an oxygen flux) and / or moisture.

[0015] The method can include an additional preheating step for the precursor compound or metal oxide particles, or both the precursor compound and the metal oxide particles.

[0016] Graphitic carbon nitride can have a porous structure.

[0017] The present invention also relates to a mixed product prepared by the method according to the invention, comprising graphitic carbon nitride and metal oxide particles.

[0018] The mass ratio of graphitic carbon nitride to metal oxide particles in the product can range from 1:99 to 99:1, preferably from 1:49 to 49:1, more preferably from 1:24 to 24:1, even more preferably from 1:9 to 9:1, and particularly from 1:5 to 5:1.

[0019] The mixed product can have an onset absorption edge value in the range of 390 to 430 nm, preferably 395 to 420 nm.

[0020] The present invention also relates to the use of the mixed product according to the invention as a UV absorber.

[0021] The present invention also relates to a composition, preferably a keratinous substance, such as a cosmetic composition for the skin, comprising the mixed product according to the invention.

[0022] The composition can be a sunscreen composition.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0024] As a result of intensive studies, the present inventors have surprisingly found that by heating a precursor compound together with metal oxide particles, graphitic carbon nitride having at least one heptazine unit can be efficiently produced, and that the product is suitable for cosmetic use, thus completing the present invention.

[0025] Accordingly, the present invention mainly relates to a method for preparing graphitic carbon nitride, which includes a step of heating a precursor compound together with metal oxide particles.

[0026] The inventors of the present invention have discovered that the production of graphitic carbon nitride results in graphitic carbon nitride having improved whiteness.

[0027] Therefore, the method according to the present invention can produce graphitic carbon nitride having improved whiteness.

[0028] Hereinafter, the present invention will be described in detail.

[0029] [Method] The present invention relates to a method for preparing graphitic carbon nitride, which includes a step of heating at least one precursor compound together with at least one metal oxide particle.

[0030] In the term "graphitic" in graphitic carbon nitride, it here means that the carbon nitride has a planar graphite-like structure. Thus, the graphitic carbon nitride of the present invention may have a layered structure or a sheet structure. Graphitic carbon nitride is generally solid at room temperature and is in powder form.

[0031] The graphitic carbon nitride of the present invention may contain at least one heptazine unit. As used herein, a heptazine unit means a hetero-condensed ring consisting of three hetero-rings composed of C atoms and N atoms, represented by C6N7. Thus, the graphitic carbon nitride of the present invention may have a monolayer structure mainly composed of heptazine. The graphitic carbon nitride of the present invention may contain at least one heptazine unit, at least one triazine unit, and combinations thereof. The presence of the heptazine unit can be determined by X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance spectroscopy (NMR) analysis.

[0032] The graphitic carbon nitride of the present invention may have a porous structure. More specifically, the graphitic carbon nitride of the present invention may have a nanoporous structure. The pores may exist on the layered structure of the graphitic carbon nitride between the heptazine unit and the triazine unit.

[0033] The graphitic carbon nitride of the present invention can exhibit UV absorption characteristics. Preferably, the graphitic carbon nitride has an absorption effect on both the UV-B and UV-A regions. UV-B here means ultraviolet rays having wavelengths between 280 and 320 nm. UV-A here means ultraviolet rays having wavelengths between 320 and 400 nm. The absorption curve in the range of ultraviolet and visible light can be measured, for example, by ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy.

[0034] The method according to the present invention includes a step of heating at least one precursor compound together with at least one metal oxide particle. Accordingly, the method according to the present invention includes a step of heating a mixture of at least one precursor compound and at least one metal oxide particle.

[0035] One kind of precursor compound may be used as a raw material for graphitic carbon nitride, or two or more kinds of precursor compounds may be used in combination.

[0036] The precursor compound can be selected from precursors known to those skilled in the art, such as urea, thiourea, melamine, guanidine, arginine, cyanamide, dicyandiamide, and salts thereof, and combinations thereof (Chem. Rev. 2016, 116, 7159 - 7329, Ong, W.J.; Tan, L.L.; Ng, Y.H.; Yong, S.T.; Chai, S.P., Catalysts 2019, 9(10), 805, Seong Jun Mun and Soo - Jin Park; https: / / doi.org / 10.3390 / catal9100805). Preferably, the precursor compound is selected from urea, melamine, guanidine, arginine, and salts thereof and combinations thereof.

[0037] The salt of the precursor compound is not particularly limited, and examples thereof include salts with inorganic acids such as carbonic acid and hydrochloric acid.

[0038] In a preferred embodiment of the present invention, only one kind of precursor compound is used.

[0039] In this method, at least one precursor compound is heated together with at least one metal oxide particle. The metal oxide particles are selected from silica (SiO2), zeolite, aluminum oxide (Al2O3) particles, and mixtures thereof, and preferably can be selected from silica (SiO2) and zeolite. One type of metal oxide particle may be used, or two or more types of metal oxide particles may be used in combination. The metal oxide particles can act as a catalyst for the synthesis of graphitic carbon nitride.

[0040] The metal oxide particles can have an average particle size of 0.01 μm or more, preferably 0.05 μm or more, and / or 30 μm or less, preferably 25 μm or less, more preferably 20 μm or less. As used herein, the term "average particle size" can represent the volume-average size mean diameter (D50) given by the statistical particle size distribution for half of the population. For example, the average particle size can be measured by a laser diffraction particle size distribution analyzer, such as Mastersizer 2000 from Malvern Corp.

[0041] The metal oxide particles can have an average particle size in the range of 0.01 to 30 μm, preferably 0.05 to 25 μm.

[0042] In one embodiment of the present invention, the metal oxide particles are porous. In this embodiment, the pore diameter of the metal oxide particles is not particularly limited, but can be in the range of 0.3 nm to 1 nm.

[0043] The mass ratio of the precursor compound to the metal oxide particles is not particularly limited. For example, the mass ratio of the precursor compound to the metal oxide particles can be in the range of 1:99 to 99:1, preferably 1:49 to 49:1, more preferably 1:24 to 24:1, even more preferably 1:9 to 9:1, particularly 1:5 to 5:1.

[0044] The method according to the present invention includes a step of heating a mixture of at least one precursor compound and at least one metal oxide particle.

[0045] The heating temperature can be at least 450 °C. Preferably, the heating is carried out at 500 °C or higher, more preferably 525 °C or higher, and can be 800 °C or lower.

[0046] The heating period can be at least 1 minute. Preferably, the heating period is at least 10 minutes, more preferably at least 20 minutes, and / or within 30 hours, more preferably within 25 hours.

[0047] The heating can be carried out in air, in a noble gas such as argon or helium, or in an inert gas such as nitrogen. In a preferred embodiment of the present invention, the heating is carried out in air or in argon. In a preferred embodiment, the heating is carried out in the presence of oxygen, for example, in air.

[0048] In a preferred embodiment, the heating process can be carried out in the presence of an oxygen-containing species, such as O2, moisture, O3, atomic O, and / or ionic oxygen, as an oxidizing agent. Without wishing to be bound by theory, it is considered that when the heating is carried out in the presence of an oxygen-containing species, more porous graphite-like carbon nitride can be obtained. In a preferred embodiment, the heating is carried out in air, or in a noble gas or inert gas containing an oxygen-containing species.

[0049] In a preferred embodiment, in addition to oxygen in the air, the heating process is carried out in the presence of an oxygen-containing species, such as O2, moisture, ozone O3, atomic O and / or ionic oxygen, as an oxidizing agent.

[0050] In a preferred embodiment, the heating process is carried out in the presence of O2, which is an oxygen-containing species, particularly an oxygen flux, and / or moisture. The term "oxygen flux" can mean an oxygen flow in this specification.

[0051] Preferably, the oxidizing agent used during the heating process is in gaseous form.

[0052] According to one embodiment, the oxygen source is neither derived from permanganate nor from hydrogen peroxide.

[0053] In one embodiment of the present invention, the heating process includes at least two heating steps at the same or different temperatures. In other words, the heating process may include a preheating step before the heating step described above.

[0054] The preheating step can be applied to the precursor compound or metal oxide particles, or both the precursor compound and metal oxide particles.

[0055] The preheating temperature can be at least 200°C. Preferably, the preheating is carried out at 250°C or higher, more preferably 275°C or higher, and can be 800°C or lower.

[0056] The preheating period can be at least 5 minutes. Preferably, the preheating period is at least 10 minutes, more preferably at least 20 minutes, and / or within 30 hours, more preferably within 25 hours.

[0057] The preheating can be carried out in air, a noble gas such as argon or helium, or an inert gas such as nitrogen. In a preferred embodiment of the present invention, the preheating is carried out in air or argon. In a preferred embodiment, the heating process is carried out in the presence of oxygen, for example, in air.

[0058] In one embodiment of the present invention, the cooling step exists during the heating step. Thus, in one embodiment, the cooling step is included between the first heating step and the second heating step. The temperature of the cooling step is not particularly limited. For example, the temperature is cooled to room temperature (about 25°C). The period of the cooling step is not particularly limited. For example, it is about 1 minute to 24 hours.

[0059] The method according to the present invention can produce graphitic carbon nitride in an improved yield. For example, the method according to the present invention can produce graphitic carbon nitride in a mass yield of 6% or more, preferably 7% or more, more preferably 8% or more.

[0060] [Mixed product] The present invention also relates to a mixed product prepared by the method according to the present invention.

[0061] The product of the present invention contains graphitic carbon nitride and metal oxide particles. Therefore, the product of the present invention is a mixture of graphitic carbon nitride and metal oxide particles. The same description regarding graphitic carbon nitride and metal oxide particles can be applied to the description of the product here.

[0062] The mass ratio of graphitic carbon nitride to metal oxide particles in the product is not particularly limited. For example, the mass ratio of graphitic carbon nitride to metal oxide particles in the product can be in the range of 1:99 to 99:1, preferably 1:49 to 49:1, more preferably 1:24 to 24:1, even more preferably 1:9 to 9:1, particularly 1:5 to 5:1.

[0063] The mixed product of the present invention can exhibit UV absorption characteristics due to the presence of graphitic carbon nitride. Preferably, the mixed product has an absorption effect on both the UV-B and UV-A ray regions.

[0064] The UV absorption characteristics of the mixed product of the present invention can be represented by the onset absorption edge value (nm). The onset absorption edge value can be defined as the wavelength (nm) at the intersection of a straight line drawn to fit the region where the absorbance curve rapidly decreases from the short wavelength side of the absorbance curve and a straight line drawn to fit the absorbance curve in the wavelength range of 500 to 550 nm.

[0065] Example 1 in FIG. 2 shows an example where the onset absorption characteristic is 400 nm, which is the wavelength at the intersection of (1) a straight line drawn to fit the region where the absorbance curve rapidly decreases from the short-wavelength side of the absorbance curve, and (2) a straight line drawn to fit the absorbance curve in a specific wavelength range between 500 and 550 nm where the absorbance curve always remains low. The absorption curve in the ultraviolet and visible light ranges can be measured, for example, by ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy.

[0066] The inventors of the present invention surprisingly discovered that the hybrid product of the present invention can exhibit a lower onset absorption end value than a product manufactured without metal oxide particles. The lower the onset absorption end value, the less color the product has, and the less color the material has, the more improved whiteness can be shown. Therefore, the hybrid product of the present invention is versatilely applicable to various uses, especially in cosmetics.

[0067] The hybrid product of the present invention can have an onset absorption end value of 390 nm or more, preferably 395 nm or more, and generally 430 nm or less, preferably 420 nm or less.

[0068] The graphitic carbon nitride of the present invention can have an onset absorption end value in the range of 390 to 430 nm, preferably 395 to 420 nm.

[0069] [Use] The present invention also relates to the use of the hybrid product of the present invention as a UV absorber. For example, the UV absorber of the present invention can be used in paints, in coatings, especially as a filler for plastics, and in cosmetics. The UV absorber can be a UVA absorber and / or a UVB absorber.

[0070] Since the hybrid product of the present invention has sufficient UV absorption characteristics and less color, it is very useful for various products that require UV protection.

[0071] [Composition] The present invention also relates to a composition comprising the hybrid product of the present invention. Preferably, the composition according to the present invention is a cosmetic composition, in particular a cosmetic composition for keratinous substances, such as for the skin. In a preferred embodiment, the composition according to the present invention is a sunscreen composition.

[0072] Keratinous substances here mean substances containing keratin as a main component, examples of which include skin, scalp, nails, lips, hair, etc., preferably skin.

[0073] Since the hybrid product of the present invention can exhibit sufficient UV absorption properties and less color, the cosmetic composition according to the present invention can provide sufficient UV protection to keratinous substances without changing the color tone.

[0074] Details of the composition for use according to the present invention are described in the section entitled [Method] above.

Examples

[0075] The present invention will be described in more detail by way of examples. However, these examples should not be construed as limiting the scope of the present invention.

[0076] [Preparation] (Example 1) 0.6 g of urea was preheated in air at 300 °C for 1 hour. The preheated urea was mixed with 2.4 g of zeolite (HS-642, powder, sodium mordenite, FUJIFILM Wako Chemical Corporation, crystal size: 0.1 μm × 0.5 μm, average particle size: 12 μm, pore opening: 0.7 nm), and the mixture was heated in air at 550 °C for 1 hour to produce a mixture of graphite-like carbon nitride and zeolite.

[0077] (Comparative Example 1) 3 g of urea was preheated in air at 300 °C for 1 hour. The preheated urea alone was heated in air at 550 °C for 1 hour to produce graphite-like carbon nitride alone.

[0078] (Example 2) A mixture of 10 g of urea and 3 g of silica (average particle size: 5 μm) was heated in air at 600 °C for 2 hours to produce a mixture of graphitic carbon nitride and silica.

[0079] (Example 3) 3 g of silica (average particle size: 5 μm) was preheated in air at 600 °C for 2 hours. The preheated silica was mixed with 10 g of urea, and the mixture was heated in air at 600 °C for 2 hours to produce a mixture of graphitic carbon nitride and silica.

[0080] (Comparative Example 2) 10 g of urea was heated in air at 600 °C for 2 hours to produce pure graphitic carbon nitride.

[0081] (Example 4) 3 g of silica (average particle size: 5 μm) was preheated in air at 600 °C for 2 hours. The preheated silica was mixed with 10 g of urea, and the mixture was heated in air at 300 °C for 4 hours and then at 600 °C for 2 hours to produce a mixture of graphitic carbon nitride and silica.

[0082] (Comparative Example 3) 10 g of urea was heated in air at 300 °C for 4 hours and then at 600 °C for 2 hours to produce pure graphitic carbon nitride.

[0083] [Evaluation] The following evaluations were performed on the obtained powder samples.

[0084] (Yield) In each of the methods, the yield of the obtained graphitic carbon nitride was calculated by measuring the mass of the product.

[0085] (Morphology Analysis) The IR spectrum of the produced powder was obtained using the attenuated total reflection (ATR) method. According to Nan Liu et al. (ACS Omega, 2020, 5, 12557~12567), the peak assigned to the heptazine unit is 804 cm -1appears at a wavenumber higher than that of the triazine unit (814 cm for melamine -1 , 808 cm for melem -1 ).

[0086] Figure 1 shows the IR spectra of the product according to Example 4 and the product according to Comparative Example 3. The spectrum of the product according to Example 1 shows peaks derived from the structures of graphitic carbon nitride and silica.

[0087] Also, according to morphological analysis, it was confirmed that all of the graphitic carbon nitrides produced in the examples contained heptazine units.

[0088] (UV absorption / diffuse transmission characteristics) The light absorption performance of the powder sample in the wavelength range of ultraviolet and visible light was evaluated using ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (UV2500PC, Shimadzu Corporation) combined with an integrating sphere.

[0089] The UV-vis absorption spectrum of the powder sample suspended in water in a fine quartz cell (2-sided transparent, 2 mm (optical path length) × 10 mm × H45 mm, Tokyo Garasu Kikai Co., Ltd.) was collected using a UV-visible spectrophotometer (V750, Jasco Inc.) combined with an integrating sphere. Before measurement, the suspension was sonicated using an ultrasonic cleaner (ASU-3M, AS ONE Corporation).

[0090] The onset absorption edge value was estimated from the UV-vis diffuse reflectance spectrum of each sample.

[0091] Figure 2 shows a comparison of the UV-vis absorption spectral curves between Example 1 and Comparative Example 1. Example 1 shows a lower onset absorption edge value than Comparative Example 1, suggesting that the powder obtained by Example 1 shows less color than Comparative Example 1.

[0092] Figure 3 shows the UV-vis absorption spectrum curve measured for the mixed product according to Example 4 in the form of a 0.1 mass% aqueous suspension.

[0093] The results are summarized in Table 1 below.

[0094]

Table 1

[0095] As can be seen from the results in Table 1, the methods according to Examples 1 to 4 were able to produce graphitic carbon nitride in a higher yield. Therefore, the method according to the present invention was able to efficiently produce graphitic carbon nitride. In addition, the mixed product produced according to Example 1 showed a lower onset absorption edge value than Comparative Example 1, suggesting that the mixed product according to Example 1 had less color. A lower onset absorption edge value suggests that the product according to the present invention exhibits improved whiteness.

[0096] Therefore, the method according to the present invention is very useful for the production of graphitic carbon nitride, and the product prepared by the method of the present invention can provide sufficient UV protection to keratinous substances without a change in color tone. Thus, it can be concluded that the method is very useful for various products that require UV protection, particularly cosmetics.

Claims

1. A method for preparing graphitic carbon nitride, the method comprising a step of heating at least one precursor compound together with at least one metal oxide particle.

2. The method according to claim 1, wherein the precursor compound is selected from urea, thiourea, melamine, guanidine, arginine, cyanamide, dicyandiamide, and salts thereof, and combinations thereof.

3. The metal oxide particles are silica (SiO 2 ), zeolite, aluminum oxide (Al 2 O 3 3. The method of claim 1 or 2, wherein the hydroxyl group is selected from the group consisting of hydroxyl groups, ...

4. The method according to any one of claims 1 to 3, wherein the metal oxide particles have an average particle size in the range of 0.01 to 30 μm, preferably 0.05 to 20 μm.

5. The method according to any one of claims 1 to 4, wherein the mass ratio of the precursor compound to the metal oxide particles is in the range of 1:99 to 99:1, preferably 1:49 to 49:1, more preferably 1:24 to 24:1, even more preferably 1:9 to 9:1, particularly 1:5 to 5:

1.

6. The method according to any one of claims 1 to 5, wherein the heating is carried out at at least 450 °C for a period of at least 1 minute.

7. The heating is carried out in the presence of an oxygen-containing species as an oxidizing agent, such as O 2 , moisture, O 3 , atomic O and / or ionic oxygen, preferably, the oxidizing agent used during the heating step is in gaseous form, more preferably, the oxygen-containing species is neither derived from permanganate nor from hydrogen peroxide, the method according to any one of claims 1 to 6.

8. The method according to any one of claims 1 to 7, comprising an additional preheating step for the precursor compound or the metal oxide particles, or both the precursor compound and the metal oxide particles.

9. The method according to any one of claims 1 to 8, wherein the graphitic carbon nitride has a porous structure.

10. A mixed product prepared by the method according to any one of claims 1 to 9, comprising graphitic carbon nitride and metal oxide particles.

11. The mixed product according to claim 10, wherein the mass ratio of the graphitic carbon nitride to the metal oxide particles is in the range of 1:99 to 99:1, preferably 1:49 to 49:1, more preferably 1:24 to 24:1, even more preferably 1:9 to 9:1, particularly 1:5 to 5:

1.

12. The mixed product according to claim 10 or 11, having an onset absorption edge value in the range of 390 to 430 nm, preferably 395 to 420 nm.

13. Use of the mixed product according to claim 10 or 11 as a paint active substance, a pigment, in particular a filler for plastics or a cosmetic active substance.

14. Use of the mixed product according to claim 10 or 11 as a UV absorber.

15. A composition comprising the graphitic carbon nitride as defined in claim 14, water and / or at least one organic medium.

16. A composition, preferably a keratinous substance, such as a cosmetic composition for the skin, comprising the hybrid product according to claim 10 or 11.

17. The composition according to claim 16, which is a sunscreen composition.

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